"uuid","repository link","title","author","contributor","publication year","abstract","subject topic","language","publication type","publisher","isbn","issn","patent","patent status","bibliographic note","access restriction","embargo date","faculty","department","research group","programme","project","coordinates"
"uuid:bfd0d299-b573-4a1d-aab8-a085d9284d87","http://resolver.tudelft.nl/uuid:bfd0d299-b573-4a1d-aab8-a085d9284d87","Blind Polarization Demultiplexing of Shaped QAM Signals Assisted by Temporal Correlations","Bajaj, V. (TU Delft Team Sander Wahls); Van de Plas, Raf (TU Delft Team Raf Van de Plas; VanderBilt University); Wahls, S. (Karlsruhe Institut für Technologie)","","2024","While probabilistic constellation shaping (PCS) enables rate and reach adaption with finer granularity [1] (Cho and Winzer, 2009), it imposes signal processing challenges at the receiver. Since the distribution of PCS-quadrature amplitude modulation (QAM) signals tends to be Gaussian, conventional blind polarization demultiplexing algorithms are not suitable for them [2] (Johnson et al., 1998). It is known that independently and identically distributed (iid) Gaussian signals, when mixed, cannot be recovered/separated from their mixture. For PCS-QAM signals, there are algorithms such as [3] and [4] Dris et al. (2019) and Athuraliya et al. (2004) which are designed by extending conventional blind algorithms used for uniform QAM signals. In these algorithms, an initialization point is obtained by processing only a part of the mixed signal, which have non-Gaussian statistics. In this article, we propose an alternative method wherein we add temporal correlations at the transmitter, which are subsequently exploited at the receiver in order to separate the polarizations. We will refer to the proposed method as frequency domain (FD) joint diagonalization (JD) probability aware-multi modulus algorithm (pr-MMA), and it is suited to channels with moderate polarization mode dispersion (PMD) effects. Furthermore, we extend our previously proposed JD-MMA [5] (Bajaj et al., 2022) by replacing the standard MMA with a pr-MMA, improving its performance. Both FDJD-pr-MMA and JD-pr-MMA are evaluated for a diverse range of PCS (entropy $\mathcal {H}$) of 64-QAM over a first-order PMD channel that is simulated in a proof-of-concept setup. A MMA initialized with a memoryless constant modulus algorithm (CMA) is used as a benchmark. We show that at a differential group delay (DGD) of 10% of symbol period T$_{\text{symb}}$ and 18 dB SNR/pol., JD-pr-MMA successfully demultiplexes the PCS signals, while CMA-MMA fails drastically. Furthermore, we demonstrate that the newly proposed FDJD-pr-MMA is robust against moderate PMD effects by evaluating it over a DGD of up to 40% of T$_{\text{symb}}$. Our results show that the proposed FDJD-pr-MMA successfully equalizes PMD channels with a DGD up to 20% of T$_{\text{symb}}$.","and optical fiber communication; Correlation; Demultiplexing; digital signal processing; Optical fiber dispersion; Polarization demultiplexing; probabilistic constellation shaping; Programmable logic arrays; Quadrature amplitude modulation; Signal processing algorithms; Symbols","en","journal article","","","","","","","","2024-03-14","","","Team Sander Wahls","","",""
"uuid:55c2d2db-32f7-4ad7-a51c-0af839d7efc0","http://resolver.tudelft.nl/uuid:55c2d2db-32f7-4ad7-a51c-0af839d7efc0","A generating absorbing boundary condition for simulating wave interaction with maritime structures in current or at forward speed","Chang, X. (Shanghai Ship and Shipping Research Institute Co.); Wellens, P.R. (TU Delft Ship Hydromechanics and Structures)","","2024","The lack of suitable boundary conditions in practical surface wave simulations with maritime structures in current or at forward speed may cause energy in the computational domain to accumulate due to spurious wave reflection. The common way to prevent wave reflection is to use passive wave absorbers, such as damping zones or relaxation zones, which requires larger domains at the cost of computational effort. Our goal is to derive a local generating absorbing boundary condition (GABC) for long-crested irregular waves on top of a mean flow, using the flow to model the forward speed of a structure such as a ship. Earlier work has demonstrated that a local GABC for free surface waves has a performance similar to passive wave absorbers, but at a reduced computational effort. New in the present work is that we extend, verify and validate the GABC in the presence of a nonzero mean flow. The GABC is designed to be accurate for a range of wave components in irregular sea states, with the resulting reflection coefficients for each component lower than a chosen value, say 5%. Having used potential flow theory for its derivation means that the boundary should not be placed at the exact location where wave breaking is expected, such as very close to the structure in the domain, or in the surf zone in coastal modeling. For the application with ships in this article that does not pose a limitation. The performance is demonstrated for a range of dimensionless wave number between 0 and 6. Such a boundary condition is obtained through a rational approximation of the linear dispersion relation with a mean flow, in combination with vertical derivatives of the solution variables along the boundary. Local linearization means that the GABC incorrectly considers bound, nonlinear wave components to be freely propagating wave components. Bound components, however, tend to have smaller amplitudes and do not appear to affect performance for the considered cases. Results of simulations with regular and irregular waves, on top of flows with different magnitudes and directions, are found to agree with the theory. The main source of differences is the implementation of the second derivate in the GABC near the free surface. Simulations of a Wigley hull at forward speed in irregular waves are compared to an experiment that was conducted specifically for validating the ABC. The data of the experiment are available as open data through doi: 10.4121/21320604. The comparison between simulation and experiment demonstrates that the GABC with a mean flow can be applied not only for theoretical simulations with propagating waves, but also for more practical applications with a structure in the domain.","Absorbing boundary condition; Combined waves and mean flow; Doppler shift; Volume of Fluid (VoF); Wave dispersion","en","journal article","","","","","","","","","","","Ship Hydromechanics and Structures","","",""
"uuid:10b92009-fa98-447a-bec1-5fa706f4d643","http://resolver.tudelft.nl/uuid:10b92009-fa98-447a-bec1-5fa706f4d643","Simulating decadal cross-shore dynamics at nourished coasts with Crocodile","Kettler, T.T. (TU Delft Coastal Engineering); de Schipper, M.A. (TU Delft Coastal Engineering); Luijendijk, Arjen (TU Delft Coastal Engineering; Deltares)","","2024","Projections of high rates of sea level rise have stimulated proposals for adaptation strategies with increasingly high nourishment volumes along sandy beaches. An underlying assumption is that coastal profiles respond rapidly to nourishments by redistributing sediments towards a (new) equilibrium shape. However, this perception may not be valid when high volumes of nourishment are applied, as the profile shape may then undergo significant deformation. Current state-of-the-art modelling techniques often concentrate on a single spatio-temporal scale, either lacking the necessary temporal horizon or failing to provide the required level of cross-shore detail. This article introduces Crocodile, a diffusion based cross-shore model designed to bridge the gap between short- and long-term nourishment modelling. The model simulates the effects of nourishment strategies on coastal volume, coastline position and beach width over a decadal timeframe. It incorporates different elements which compute cross-shore diffusion, sediment exchange with the dune and longshore sediment losses. To test the model performance, a series of idealized nourishment scenarios are examined, along with three case studies along the Dutch coast with different nourishment strategies over the past few decades. The modelled coastal volume, shoreline position and beach width strongly resemble the observations with only a 12% overestimation in profile volume and 13% underestimation in beach width. Averaged over selected periods of nourishment, trends and trend reversals between different strategies are well replicated with slight overestimation for coastal volume trends by 1.5m3/m/yr(10%), while beach width trends are underestimated by 0.2m/yr (15%). Given that the added nourishment volumes are typically in the order of 100m3/m, these model errors are considered sufficiently low to conclude that Crocodile effectively simulates variations in coastal volume, coastline position and beach width over a decadal timeframe in response to different nourishment strategies. Therefore, Crocodile can facilitate the evaluation of future nourishment strategies.","Cross-shore profile; Diffusion model; Nourishment strategies; Numerical modelling; Sand dispersion","en","journal article","","","","","","","","","","","Coastal Engineering","","",""
"uuid:17f3ad2c-bf95-4a4e-8f57-fa9c0d18e5f6","http://resolver.tudelft.nl/uuid:17f3ad2c-bf95-4a4e-8f57-fa9c0d18e5f6","Passive VLC: Spatial Color Channel Modulation through Dispersion of Light","Minderman, Björn (TU Delft Electrical Engineering, Mathematics and Computer Science; TU Delft Networked Systems)","Zuniga, Marco (mentor); Ghiasi, S.K. (mentor); Song, Q. (graduation committee); Delft University of Technology (degree granting institution)","2023","In the last decades our usage of the Radio Frequency (RF) spectrum has intensified a lot due to the increasing number of mobile devices. The spectrum is getting crowded and new communication alternatives might become necessary in the future. One such alternative is Visible Light Communication (VLC),which uses the visible light spectrum instead of RF. Passive VLC, in particular, combines this property with a low power usage, suited for battery powered devices. However, high data rates are lacking.
This thesis proposes a multi-channel passive VLC system, based on light dispersion principles, as a novel concept to try and enhance these data rates. Results of the system so far only show low data rates however, at a maximum of 4 bits per second. The low data rate in particular is caused by choice of transmitter and receiver, thereby limiting the bandwidth and the number of channels that can be created. Yet, the concept itself is still considered a valid and valuable approach, and higher data rates can be expected from future works.
In this thesis we will see exactly how we can go from light dispersion to creating a multi-channel passive VLC system. As we will see this requires an optical design, a transmitter and a receiver, all of which will be working together. Besides an evaluation of the performance it will give insight in challenges this concept faces and, also, what improvements might increase the system performance.","Passive VLC; Multi-Channel; Light Dispersion; Wavelength Modulation","en","master thesis","","","","","","","","","","","","Computer Engineering | Embedded Software","",""
"uuid:ab98e53a-5931-4b78-98ec-f0cb6df20986","http://resolver.tudelft.nl/uuid:ab98e53a-5931-4b78-98ec-f0cb6df20986","GSL-Bench: High Fidelity Gas Source Localization Benchmarking","Erwich, Hajo (TU Delft Aerospace Engineering)","de Croon, G.C.H.E. (mentor); Duisterhof, B.P. (graduation committee); Delft University of Technology (degree granting institution)","2023","Gas Source Localization (GSL) is a challenging field of research within the robotics community. Existing methods vary widely and each has its own strengths and weaknesses. Existing GSL evaluations vary in environment size, wind conditions, and gas simulation fidelity, thereby complicating objective comparison between algorithms. They also lack photo-realistic rendering for the integration of obstacle avoidance. In this paper, we propose GSL-Bench, a benchmarking suite to evaluate the performance of GSL algorithms. GSL-Bench features high-fidelity graphics and gas simulation. Realism is further increased by simulating relevant gas and wind sensors. Scene generation is simplified with the introduction of AutoGDM+, capable of procedural environment generation, CFD and particle-based gas dispersion simulation. To illustrate GSL-Bench's capabilities, three algorithms are compared in six warehouse settings of increasing complexity: E. Coli, dung beetle and a random walker. Our results demonstrate GSL-Bench's ability to provide valuable insights into algorithm performance.","gas sensing; benchmarking; simulation; source localization; gas dispersion; odour souce localization","en","master thesis","","","","","","https://sites.google.com/view/gslbench/ Website providing additional results and instructions","","","","","","Aerospace Engineering","",""
"uuid:746940e0-d51e-4a6d-92b9-40602ef452d8","http://resolver.tudelft.nl/uuid:746940e0-d51e-4a6d-92b9-40602ef452d8","Improving the recovery efficiency of the Aquifer Storage and Recovery system in Hoorn","Dirks, Dylan (TU Delft Civil Engineering & Geosciences)","Bakker, M. (mentor); Schoups, G.H.W. (graduation committee); des Tombe, B.F. (mentor); Delft University of Technology (degree granting institution)","2023","PWN is responsible for supplying sufficient quantities of high-quality water to its customers. The growing population and the effects of climate change, such as heat waves and droughts, are straining the capacity of the water supply network, especially during dry and warm periods when water demand increases. A significant portion of the drinking water is produced in Andijk. From there, the drinking water is transported to Hoorn, where it is further distributed to customers. The connection between Andijk and Hoorn is therefore crucial, and in the event of a pipeline failure due to a calamity or maintenance, capacity issues can arise. To maintain the redundancy of this connection and to smooth out the daily water demand and supply fluctuations, PWN is exploring the implementation of an Aquifer Storage and Recovery (ASR) system in Hoorn.
The ASR system in Hoorn faces strict requirements, which address the challenge of maintaining water quality standards and optimising recovery efficiency. These requirements must ensure that the extracted water remains suitable for consumption, with no more than 1% dilution with ambient groundwater. The objective of this study is to identify a method to improve the recovery efficiency of the ASR system in Hoorn. The ASR system operates by injecting drinking water into an aquifer during periods of water availability and recovering it when needed. Compared to installing a new pipeline, the ASR system offers a more cost-effective solution with additional benefits such as space efficiency and temperature stability. However, the ASR system in Hoorn faces challenges related to maintaining water quality standards and optimising recovery efficiency. Processes such as lateral flow, dispersion, and buoyancy affect the system’s performance, and a thorough understanding of these processes is crucial for accurately predicting recovery efficiency. A comprehensive analysis of a pilot ASR system in Hoorn was conducted by PWN to address these challenges. The pilot system consists of a single well where two pumps operate at two different filter depths in an aquifer. In the final layout of the ASR, additional wells are necessary to achieve the desired capacity.
A radially symmetric model was used to simulate groundwater flow, conservative solute transport, and heat transport. Due to the stringent water quality requirements, the radially symmetric model must accurately capture essential processes in an Aquifer Storage and Recovery (ASR) system, such as flow, dispersion, retardation, and buoyancy. The performance of a radial symmetric model in SEAWAT and MODFLOW 6 was assessed based on analytical methods and 3D models. Through this analysis, it was decided to utilise a radial symmetric model in SEAWAT due to the presence of numerical dispersion in a model using MODFLOW 6.
After this analysis, the model’s performance was tested against various measurements, including hydraulic head, temperature, and electrical conductivity. It is evident that the model effectively captures both solute transport and heat transport. Discrepancies between measurements and the model can be attributed to assumptions made during the study and uncertainties in the measured values. However, the presence of clay layers between the deep and shallow filters in the pumping well significantly contributes to local differences between the model and the measurements. The main reason for this difference is that these layers are not homogeneous throughout the depths, allowing water to flow between them. This heterogeneity cannot be simulated with a radially symmetric model. However, despite this heterogeneity, these clay layers consistently result in low recovery efficiency in the current system.
The objective of this study was to identify a method to improve the recovery efficiency of the ASR system in Hoorn. The current system has a recovery efficiency of about 30%. This can improved by implementing a check valve in the shallow filter of the pump well, with 60% to 65% of the filter dedicated to recovery to achieve a recovery efficiency of 80%. During the testing of this system, an injection period was followed by a recovery period with specific pumping rates. It took three cycles to achieve the desired recovery efficiency. It is important to note that these cycles did not include storage and rest phases. The system’s recovery efficiency may change when these phases are incorporated. However, an important assumption is that homogeneous layers are present. Heterogeneity of layers can lead to deviations from the modelled recovery efficiency. This research contributes to a better understanding of the pilot ASR system in Hoorn and provides insights into improving its recovery efficiency. With the lessons learned from this study,
PWN can assist in developing the final design for the ASR system. This design will involve multiple wells to meet the required capacity.","Aquifer Storage and Recovery; SEAWAT; Groundwater modelling; Distributed Temperature Sensing; Radial symmetric modelling; Advection; Dispersion; Buoyancy; Numerical Dispersion; Retardation; Solute Transport; Heat transport; Recovery efficiency","en","master thesis","","","","","","","","","","","","Water Management","","52.667297, 5.036507"
"uuid:a39973d6-f497-4857-9ee9-9ece204ec180","http://resolver.tudelft.nl/uuid:a39973d6-f497-4857-9ee9-9ece204ec180","Towards a Sustainable and Liveable Desakota: Designing for sustainable industry transition in the peri-urban territory of the Greater Bay Area","Liu, Shiru (TU Delft Architecture and the Built Environment; TU Delft Urbanism)","Wandl, Alex (mentor); Yu, Hsinko Cinco (graduation committee); Delft University of Technology (degree granting institution)","2023","This thesis explores spatial strategies for achieving sustainable industry transition in the dispersed urbanised areas of the Greater Bay Area (GBA) in China. Since 1978, urbanisation in the GBA has accelerated, significantly expanding beyond metropolitan regions. These dispersed areas, described as the Desakota by Terry McGee, encompass a patchwork landscape of urban and rural settlements, as well as industrial and agricultural lands. However, this region faces pressing issues, including unsustainable industrial activities, fragmented landscapes, inadequate public services, and a loss of identity. The existing urban-rural dichotomy planning system fails to address these challenges, leading to environmental degradation and a decline in quality of life. Therefore, there is an urgent need for a regional strategy to explore the potential for sustainable and liveable urbanisation in Desakota.
Hence, this thesis adopts the “Netzstadt” concept as a guiding methodology from a regional perspective. It leads to defining Desakota’s spatial and functional nodes and connections, identifying potential elements for sustainable industrial transformation, adapting structural features through reference projects, experimenting with a design project, and proposing an adapted planning system.
These assignments yield three significant outcomes. Firstly, the adapted structure plan proposes a decentralised development pattern of Desakota, envisioning a circular and symbiotic industry conversion, repurposing industrial redundancy for metropolitan publicness, and enhancing the green and public network. Secondly, a showcased design project incorporates industrial, open space, and residential elements, proposing a specific spatial morphology and physiological flow. It emphasises the local identity and demonstrates the importance of involving local actors in the transition. Thirdly, a more decentralised and flexible spatial planning system should be employed to materialise the proposed Desakota structure.
By implementing these strategies, the desakota of GBA can progress towards a sustainable and liveable future that integrates nature, supports diverse livelihoods and lifestyles, and optimises resource management. This thesis can also provide transferable knowledge to other similar dispersed areas on how the pattern, flow and policy could be synthesised into future urbanisation and contribute to ensuring the sustainable development of society and ecology.
The present research work has been motivated by an unintuitive strengthening of the streamwise-elongated coherent structures of the atmospheric boundary layer (ABL), observed by Jayaraman & Brasseur (2021), for a certain range of weakly unstable thermal stratification conditions. Such observation evinced the existence of a sweet-spot where the large-scale streamwise-oriented counter-rotating vortical structures, characteristic of any turbulent boundary layer, were able to strengthen themselves by collecting small-scale thermal plumes, eventually creating the so-called large-scale atmospheric rolls. The importance of these findings lies in the fact that large-scale atmospheric rolls are known to be one of the most important structures when it comes to vertical transport of momentum and scalars (i.e. pollutants) in the ABL.
Following from this observation, we hypothesize that the counter-rotating roll structures behind a high-rise building could potentially exhibit a similar behaviour and strengthen themselves under weakly unstable thermal stratification conditions by collecting small-scale thermal plumes. If this was the case, it would enhance large-scale vertical mixing which could be beneficial for street canyon ventilation, reducing urban pollution levels. Therefore, the importance of studying the evolution of the roll structures behind a high-rise building under different thermal stratification conditions becomes evident.
In this regard, the present work has focused on the study of the roll structures behind a high-rise building under different thermal stratification conditions, by means of wall-resolved Large-Eddy Simulations (LES) using the Nek5000 Spectral Element Method (SEM) code. The present work has succeeded in providing a qualitative proof of concept of the presented hypothesis, proving that the rolls behind a surface-mounted cube (model for a high-rise building) under weakly unstable thermal stratification conditions do strengthen themselves in a similar manner as observed by Jayaraman & Brasseur (2021) for the ABL. Moreover, a reliable LES numerical model for simulating flow past a surface-mounted cube (high-rise building) has been built and thoroughly validated against DNS data, tuning the optimal mesh, and simulation and filtering settings.
ventilation. Consequently, to limit the spread of the virus, researchers explored several indicators that, through different approaches, assess IAQ and ventilation performance in indoor spaces. This paper gives an overview of those indicators and assessment methods used to evaluate IAQ and ventilation regimes focusing specifically on airborne pathogens. This review considers studies from before and during the COVID-19 pandemic. The indicators found fit into three categories: dose, building, and occupant-related indicators. Studies exploring assessment methods found in this review are grouped according to their themes: aerosol dispersion, ventilation, infection risk, design parameters, and human behaviour. The review showed a need for a holistic definition for IAQ indicators that includes all indicators and a holistic approach of studying IAQ including all five themes.","indoor air quality; aerosol dispersion; ventilation; numerical modelling; computational fluid dynamics; assessment","en","abstract","","","","","","","","","","","Urban Data Science","","",""
"uuid:0311d2fc-4ef8-4066-839a-5f844c57517c","http://resolver.tudelft.nl/uuid:0311d2fc-4ef8-4066-839a-5f844c57517c","Radio Receiver with Internal Compression of Input Signals Using a Dispersive Delay Line with Bandpass Filters","Pantyeyev, Roman (National Aviation University); Ianovskyi, F. (TU Delft Atmospheric Remote Sensing; National Aviation University); Mykolushko, Andriy (National Aviation University); Shutko, Volodymyr (National Aviation University)","","2023","This article proposes a receiving device in which arbitrary input signals are subject to pre-detector processing for the subsequent implementation of the idea of compressing broadband modulated pulses with a matched filter to increase the signal-to-noise ratio and improve resolution. For this purpose, a model of a dispersive delay line is developed based on series-connected high-frequency time delay lines with taps in the form of bandpass filters, and analysis of this model is performed as a part of the radio receiving device with chirp signal compression. The article presents the mathematical description of the processes of formation and compression of chirp signals based on their matched filtering using the developed model and proposes the block diagram of a radio receiving device using the principle of compression of received signals. The proposed model can be implemented in devices for receiving unknown signals, in particular in passive radar. It also can be used for studying signal compression processes based on linear frequency modulation in traditional radar systems.","Bandpass Filter; Chirp Signal; Compressive Receiver; Dispersive Delay Line; Signal Compression","en","journal article","","","","","","","","","","","Atmospheric Remote Sensing","","",""
"uuid:cbb28343-d285-488f-ac0a-8426e2619a03","http://resolver.tudelft.nl/uuid:cbb28343-d285-488f-ac0a-8426e2619a03","Sonic assessment of physical ageing of plastic pipes","Makris, K. (TU Delft Sanitary Engineering); Langeveld, J.G. (TU Delft Sanitary Engineering; Partners4UrbanWater); Clemens-Meyer, François H.L.R. (Deltares; Norwegian University of Science and Technology (NTNU)); Watts, Joanna (University of Sheffield); Begum, Hasina (University of Sheffield); Horoshenkov, Kirill V. (University of Sheffield)","","2023","This article explores the potential of vibro-acoustics to detect physical ageing of plastic pipes. For this purpose, two different topics are combined: the ability of vibro-acoustics to estimate the storage modulus of a plastic pipe, and the sensitivity of the estimated storage modulus to changes due to ageing. Concerning the first topic, a vibro-acoustic method was applied to two water-filled HDPE pipes, one surrounded by air and another by sand. The excitation was achieved via an impact hammer and the propagating signal was recorded with the aid of hydrophones. Signal analysis led to the estimation of the axial wavenumber of the propagating axisymmetric fluid-borne wave. This value was used in the dispersion equation for the propagating mode to evaluate the storage modulus of the pipe material for a given experimental setup. Results revealed that the vibro-acoustic method gives consistent and reliable estimations of the storage modulus. Concerning the second topic, samples from two PVC pipes with an age difference of 41 years were subjected to dynamic mechanical analysis to study the behaviour of the storage modulus as a function of frequency. Results showed that it is feasible to distinguish discrepancies in the magnitude of the storage modulus due to ageing, provided that the measurement uncertainty is small. The uncertainty analysis highlighted the parameters that need to be more accurately known in order to lower the overall uncertainty of the estimated storage modulus when the proposed vibro-acoustic method is used. Irrespectively of the medium surrounding the pipe (air or soil), the distance between the points of the recording signals should be sufficiently long to measure the signal phase accurately. It was found that the accurate knowledge of the pipe's geometry, i.e. the wall thickness and internal radius, was more or equally important for controlling the overall uncertainty than that of the parameters of surrounding soil.","Acoustic waves; Ageing; Dispersion equation; Fluid-filled pipe; Storage modulus; Wave propagation","en","journal article","","","","","","","","","","","Sanitary Engineering","","",""
"uuid:a5053581-1f08-4762-8280-6da5a222f20b","http://resolver.tudelft.nl/uuid:a5053581-1f08-4762-8280-6da5a222f20b","Dispersed-ply design and optimization to improve the brittle flexural behaviour of composite laminates","Mouri Sardar Abadi, P. (IMDEA Materials Institute; Student TU Delft); Baluch, Abrar H. (IMDEA Materials Institute; Institute of Space Technology, Islamabad); Sebaey, T. A. (COINS Research Group, Prince Sultan University); Peeters, D.M.J. (TU Delft Aerospace Structures & Computational Mechanics); Barzegar, M. (IMDEA Materials Institute; University of Girona); Lopes, C. S. (IMDEA Materials Institute; Luxembourg Institute of Science and Technology)","","2023","This work aims to improve the flexural behaviour of unidirectional fibre-reinforced laminates by means of coupling an optimization procedure for quasi-isotropic configurations with the design space opened by dispersed-ply orientations. The design approach consists of finding suitable alternatives to traditional laminates (with fibre orientations limited to 0°, ±45∘, and 90°), while maintaining their stiffness characteristics. This strategy isolates the interlaminar response as the objective function that is optimized to improve their flexural behaviour. To this end, a modified Ant Colony Optimization was implemented and geared towards optimizing the interlaminar stress profile, allowing plies at every possible 5° orientation, with the ultimate goal of delaying delamination. To validate the approach, a traditional reference laminate and derived fully dispersed designs were experimentally tested. The correlated responses show that it was not possible to improve flexural resistance. However, the typical flexural brittleness of laminates can be modified into a pseudo-ductile behaviour.","Ant colony algorithm; Dispersed-ply laminates; Flexural behaviour; Optimization","en","journal article","","","","","","","","","","","Aerospace Structures & Computational Mechanics","","",""
"uuid:28dfab8f-40dd-4b41-9db8-3bc9427c12f8","http://resolver.tudelft.nl/uuid:28dfab8f-40dd-4b41-9db8-3bc9427c12f8","Effect of injection water ionic strength on estimating hydraulic parameters in a 3D sand tank using silica encapsulated magnetic DNA particles","Chakraborty, S. (Universiteit Utrecht); Elhaj, Rayan (IHE Delft Institute for Water Education); Foppen, J.W.A. (TU Delft Water Resources); Schijven, Jack (Universiteit Utrecht; Rijksinstituut voor Volksgezondheid en Milieu (RIVM))","","2023","We investigated the applicability of Silica encapsulated, superparamagnetic DNA particles (SiDNAmag) in determining aquifer hydraulic parameters at different ionic strengths (1 mM, 5 mM, and 20 mM phosphate buffer) of injection suspension. Thereto, in a homogeneous, unconsolidated sand tank we pulse - injected two uniquely sequenced SiDNAmag at two injection points. At 0.5 m and 0.8 m downstream from the injection points, we measured the concentration of SiDNAmags at three vertically distributed and two horizontally distributed sampling locations. We estimated the hydraulic parameter distributions from the SiDNAmag breakthrough curves through a Monte – Carlo approach and compared the parameter distributions with salt tracer breakthrough curves. Our results indicated that at all the ionic strengths, the times of peak concentrations, and the shapes of the breakthrough curves were similar to the salt tracer. As compared to the salt, a 1 – 3 log units reduction in the maximum effluent concentration of SiDNAmag was due to kinetic attachment. The attachment rate reduced from 1 mM to 5 mM phosphate buffer possibly due to competitive adsorption of phosphate onto the favourable attachment sites. SiDNAmag attachment rate further increased in 20 mM buffer suspension, possibly due to the compression of electric double layer and reduction in energy barrier for attachment. The parameter distributions of hydraulic conductivity (k), effective porosity (ne), longitudinal dispersivity (αL), vertical transverse dispersivity (αTV /αL) and horizontal transverse dispersivity (αTH /αL) estimated from the SiDNAmag and the salt tracer breakthrough curves were statistically similar. Our work contributes to the applicability of colloidal SiDNAmags for determining hydraulic parameters at different ionic strength conditions.","Colloids; Effective porosity; Hydraulic conductivity; Longitudinal dispersivity; Sand tank","en","journal article","","","","","","","","","","","Water Resources","","",""
"uuid:b19bab9d-f06c-41a2-a226-006734731494","http://resolver.tudelft.nl/uuid:b19bab9d-f06c-41a2-a226-006734731494","Testing a Thermal Dispersion-Based Upscaling Method for Geothermal Reservoir Simulation","van Nieuwkerk, Pelle (TU Delft Civil Engineering & Geosciences)","Rossen, W.R. (mentor); Daniilidis, Alexandros (mentor); Tang, J. (mentor); Delft University of Technology (degree granting institution)","2022","The United Nations’ Paris Agreement forces nations and industries to transition from conventional hydrocarbon-based energy sources to more sustainable and less-emitting alternatives such as geothermal energy. Geothermal doublets are used to provide a source of green heat to greenhouses and residential buildings. In industry, reservoir simulators are used to make predictions about the energy production and thermal lifetime of such a geothermal project; however they can be computational expensive. Upscaling approximates the expensive fine-grid simulation and reduces the necessary computational power, but is by definition not mathematically exact. This thesis tests a newly derived thermal dispersion-based upscaling method, referred to as Taylor-based upscaling, and compares it to conventional arithmetic upscaling and a reference fine-grid simulation. The upscaling methods are applied on reservoir descriptions from the Margretheholm-1A and the HON-GT-01 reservoirs, and simulations are done using Delft Advanced Research Terra Simulator (DARTS). The reservoirs are modelled as 2D layer-cake models in the form of a geothermal doublet with a fine longitudinal resolution, 1000 grid blocks between injector and producer, to minimize numerical dispersion. The results are presented as 2D-temperature profiles and breakthrough-curves. The deviations are quantified in the form of L2-norm calculations and by comparing the amount of days it takes for each upscaling method to reach a 1◦C or 5◦C drop in production temperature. The results show that arithmetic upscaling underestimates the spreading of the cold-temperature front leading to later breakthrough, whereas Taylor-based upscaling overestimates this spreading. For the Margretheholm-1A reservoir Taylor-based upscaling mimics the fine-grid reference simulation better compared to arithmetic upscaling, whereas arithmetic averaging performs better for the HON-GT-01 reservoir. Increasing the vertical thermal conductivity (kz ) leads to Taylor-based upscaling coming closer to the fine-grid reference simulation; however different reservoir descriptions require a different kz adjustment. In conclusion, the Taylor-based upscaling method does not outperform conventional arithmetic upscaling for all reservoir descriptions. Also, no universal rule was found for increasing the kz -value to improve the Taylor-based upscaling method.","Geothermal Energy; Reservoir Simulation; Upscaling; Thermal Dispersion","en","master thesis","","","","","","","","","","","","Applied Earth Sciences","",""
"uuid:79168434-0db1-4f29-9ad0-d5c9644594aa","http://resolver.tudelft.nl/uuid:79168434-0db1-4f29-9ad0-d5c9644594aa","Storage Performance Analyses of Underground Hydrogen Storage in Depleted Gas Reservoirs","Ocampo Mendoza, Alonso (TU Delft Civil Engineering & Geosciences)","Hajibeygi, H. (mentor); Geiger, S. (graduation committee); Boon, M.M. (graduation committee); Eikelenboom, Walter (graduation committee); Delft University of Technology (degree granting institution)","2022","Overcoming the intermittency problem of renewable energy is an issue that has to be addressed in order to achieve an efficient energy system. Hydrogen has been gaining interests, as green energy carrier, which is included in the energy transition plans of not only the Netherlands, but worldwide. Due to its physical characteristics, large scale storage of hydrogen requires volumes that can only be provided by porous media in the subsurface. Underground Hydrogen Storage (UHS) in depleted gas fields is a large scale storage possibility that is generating attention and increased research. However, it is currently in a Low Technology Readiness Level, meaning that more research, and especially field scale projects are necessary. There is very few literature that tries to use alternative gases as a cushion gas for a UHS. Therefore, this investigation is relevant for the future development of UHS. This investigation will use CMG GEM, a commercial compositional reservoir simulator to model the fluid interactions in the subsurface when hydrogen is stored in depleted gas fields. This will be done by means of a sensitivity analysis, where the hydrodynamic behaviour between hydrogen and possible alternative cushion gases, such as methane, carbon dioxide and nitrogen are studied. Apart from the technical analysis, a simplified economic evaluation is used to calculate a levelized cost to store hydrogen, which will allow for an economic optimized selection of cushion gases in an UHS. The two main constraints for an UHS system are the purity of the extracted hydrogen and the rate at which it is extracted from the subsurface. The results of this investigation show that the mixing of hydrogen with an alternative cushion gas will change drastically based on the degree of the reservoir heterogeneity and the location of the perforated interval. This ever-increasing mixing will have an effect on the capability of the system of delivering pure hydrogen for the expected time.
2). While street-level air quality model chains can predict concentration gradients at high spatial resolution, measurement campaigns lack the coverage and spatial density required to validate these gradients. Citizen science offers a tool to collect large-scale datasets, but it remains unclear to what extent such data can truly increase model performance. Here we use the passive sampler dataset collected within the large-scale citizen science campaign CurieuzeNeuzen to assess the integrated ATMO-Street street-level air quality model chain. The extensiveness of the dataset (20.000 sampling locations across the densely populated region Flanders, ∼1.5 data points per km2) allowed an in-depth model validation and optimization. We illustrate generic techniques and methods to assess and improve street-level air quality models, and show that considerable model improvement can be achieved, in particular with respect to the correct representation of the small-scale spatial variability of the NO2-concentrations. After model optimization, the model skill of the ATMO-Street chain significantly increased, passing the FAIRMODE model quality threshold, and thus substantiating its suitability for policy support. More generally, our results reveal how a “deep validation” based on extensive spatial data can substantially improve model performance, thus demonstrating how air quality modelling can benefit from one-off large-scale monitoring campaigns.","Air pollution; Citizen science; Dispersion modelling; FAIRMODE Model Quality Objective; Model optimization; Model validation; Semi-variogram analysis; Spatial variation; Street level modelling","en","journal article","","","","","","Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.","","2023-07-01","","","BT/Environmental Biotechnology","","",""
"uuid:60b9f1c9-ab1d-4e27-97f4-4a1177e95501","http://resolver.tudelft.nl/uuid:60b9f1c9-ab1d-4e27-97f4-4a1177e95501","TU Delft COVID-app: A tool to democratize CFD simulations for SARS-CoV-2 infection risk analysis","Engler Faleiros, D. (TU Delft Transport Engineering and Logistics); van den Bos, W. (TU Delft Transport Engineering and Logistics; SDC Verifier); Botto, L. (TU Delft Complex Fluid Processing); Scarano, F. (TU Delft Aerodynamics)","","2022","This work describes a modelling approach to SARS-CoV-2 dispersion based on experiments. The main goal is the development of an application integrated in Ansys Fluent to enable computational fluid dynamics (CFD) users to set up, in a relatively short time, complex simulations of virion-laden droplet dispersion for calculating the probability of SARS-CoV-2 infection in real life scenarios. The software application, referred to as TU Delft COVID-app, includes the modelling of human expiratory activities, unsteady and turbulent convection, droplet evaporation and thermal coupling. Data describing human expiratory activities have been obtained from selected studies involving measurements of the expelled droplets and the air flow during coughing, sneezing and breathing. Particle Image Velocimetry (PIV) measurements of the transient air flow expelled by a person while reciting a speech have been conducted with and without a surgical mask. The instantaneous velocity fields from PIV are used to determine the velocity flow rates used in the numerical simulations, while the average velocity fields are used for validation. Furthermore, the effect of surgical masks and N95 respirators on particle filtration and the probability of SARS-CoV-2 infection from a dose-response model have also been implemented in the application. Finally, the work includes a case-study of SARS-CoV-2 infection risk analysis during a conversation across a dining/meeting table that demonstrates the capability of the newly developed application.","Application; COVID-19 simulation; COVID-app; Infection probability; SARS-CoV-2 dispersion; Unsteady speaking","en","journal article","","","","","","","","","","","Transport Engineering and Logistics","","",""
"uuid:68302511-d4de-4148-8d21-0d7a104cb9f2","http://resolver.tudelft.nl/uuid:68302511-d4de-4148-8d21-0d7a104cb9f2","A rational hybrid RANS-LES model for CFD predictions of microclimate and environmental quality in real urban structures","Hadžiabdić, Muhamed (International University of Sarajevo); Hafizović, Mahir (International University of Sarajevo; Enova Consultants and Engineers, Sarajevo); Ničeno, Bojan (Paul Scherrer Institut); Hanjalic, K. (TU Delft ChemE/Transport Phenomena; University of Sarajevo)","","2022","We report on the application and comparative assessment of two rational turbulence modelling approaches for the computer simulation of air flow and pollutant dispersion in real urban environment: a stand-alone unsteady Reynolds-averaged Navier-Stokes eddy-viscosity model (URANS), and its blend with Large-eddy simulations (LES) in a hybrid mode (HRL). The elliptic-relaxation (k−ε)ζ−feddy-viscosity model was applied in both methods. The models, verified earlier in a range of engineering flows including heat transfer, were here validated in two environmental benchmark cases, a single building and an idealized urban settlement, both subjected to a steady wind. The velocity field and pollutant concentration are better predicted by the HRL method in both benchmarks. The HRL is then applied to predictions of air flow and spreading of pollutant from road traffic in downtown of a real city (Sarajevo) containing 100 realistic buildings. The simulations were performed with the in-house open-source CFD code T-Flows, specifically optimized for a fast and efficient high-quality unstructured meshing of the terrain orography and building configurations. The benchmark validations demonstrated that, compared with the standard k−ε, in typical urban applications with complex urban shapes and arrangements the accuracy and credibility of the predictions can substantially be improved by applying a physically sounder and yet still relatively simple ζ−f eddy-viscosity model that specifically accounts for the elliptic inviscid wall-blocking effects and near-wall stress anisotropy. The benchmarking also showed that still further improvements are achieved by using the HRL scheme which ensures a rational balance in capturing the important physics and the computational economy.","Hybrid RANS-LES; Pollutant dispersion; URANS; Urban environment; Urban wind flow","en","journal article","","","","","","Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.","","2023-07-01","","","ChemE/Transport Phenomena","","",""
"uuid:76ebe151-f25c-4d1f-8007-8cc48a62402a","http://resolver.tudelft.nl/uuid:76ebe151-f25c-4d1f-8007-8cc48a62402a","Weakly nonlinear waves in stratified shear flows","Geyer, A. (TU Delft Mathematical Physics); Quirchmayr, Ronald (University of Vienna)","","2022","We develop a Korteweg-De Vries (KdV) theory for weakly nonlinear waves in discontinuously stratified two-layer fluids with a generally prescribed rotational steady current. With the help of a classical asymptotic power series approach, these models are directly derived from the divergence-free incompressible Euler equations for unidirectional free surface and internal waves over a flat bed. Moreover, we derive a Burns condition for the determination of wave propagation speeds. Several examples of currents are given; explicit calculations of the corresponding propagation speeds and KdV coefficients are provided as well.","Burns condition; dispersion relation; internal waves; KdV equation; shear flow; stratified flows; vorticity; Weakly nonlinear waves","en","journal article","","","","","","","","","","","Mathematical Physics","","",""
"uuid:0aa74b23-7fad-41ca-ba40-55666836df52","http://resolver.tudelft.nl/uuid:0aa74b23-7fad-41ca-ba40-55666836df52","Dispersing and Sonoporating Biofilm-Associated Bacteria with Sonobactericide","Lattwein, K.R. (Erasmus MC); Beekers, Inés (Erasmus MC); Kouijzer, Joop J.P. (Erasmus MC); Leon-Grooters, Mariël (Erasmus MC); Langeveld, Simone A.G. (Erasmus MC); van Rooij, Tom (Erasmus MC); van der Steen, A.F.W. (TU Delft ImPhys/Medical Imaging; Erasmus MC); de Jong, N. (TU Delft ImPhys/Medical Imaging; Erasmus MC); van Wamel, Willem J.B. (Erasmus MC); Kooiman, Klazina (Erasmus MC)","","2022","Bacteria encased in a biofilm poses significant challenges to successful treatment, since both the immune system and antibiotics are ineffective. Sonobactericide, which uses ultrasound and microbubbles, is a potential new strategy for increasing antimicrobial effectiveness or directly killing bacteria. Several studies suggest that sonobactericide can lead to bacterial dispersion or sonoporation (i.e., cell membrane permeabilization); however, real-time observations distinguishing individual bacteria during and directly after insonification are missing. Therefore, in this study, we investigated, in real-time and at high-resolution, the effects of ultrasound-induced microbubble oscillation on Staphylococcus aureus biofilms, without or with an antibiotic (oxacillin, 1 µg/mL). Biofilms were exposed to ultrasound (2 MHz, 100–400 kPa, 100–1000 cycles, every second for 30 s) during time-lapse confocal microscopy recordings of 10 min. Bacterial responses were quantified using post hoc image analysis with particle counting. Bacterial dispersion was observed as the dominant effect over sonoporation, resulting from oscillating microbubbles. Increasing pressure and cycles both led to significantly more dispersion, with the highest pressure leading to the most biofilm removal (up to 83.7%). Antibiotic presence led to more variable treatment responses, yet did not significantly impact the therapeutic efficacy of sonobactericide, suggesting synergism is not an immediate effect. These findings elucidate the direct effects induced by sonobactericide to best utilize its potential as a biofilm treatment strategy.","antibiotic; bacteria; biofilm; dispersion; microbubble; sonobactericide; sonoporation; Staphylococcus aureus; ultrasound","en","journal article","","","","","","","","","","","ImPhys/Medical Imaging","","",""
"uuid:f203763d-a766-4dce-acc1-4ea0596774b9","http://resolver.tudelft.nl/uuid:f203763d-a766-4dce-acc1-4ea0596774b9","Influence of Wind on Subtidal Salt Intrusion and Stratification in Well-Mixed and Partially Stratified Estuaries","Jongbloed, Hendrik (Wageningen University & Research); Schuttelaars, H.M. (TU Delft Mathematical Physics); Dijkstra, Y.M. (TU Delft Mathematical Physics); Donkers, Paul B. (Student TU Delft); Hoitink, Antonius J.F. (Wageningen University & Research)","","2022","An idealized width-averaged model is employed to study the influence of wind stress on subtidal salt intrusion and stratification in well-mixed and partially stratified estuaries. We show that even in mild conditions, wind forcing can influence the estuarine salinity structure in a substantial way. By studying the role of wind forcing on dominant salt transport balances and associated salt transport regimes, we unify and clarify ambiguous observations from previous authors regarding the influence of wind stress: the response of the estuarine salinity structure to wind forcing is different depending on the underlying dominant salt transport balance, which in turn was found to determine whether wind-induced salinity shear, wind-induced modulation of the longitudinal salt distribution, or wind-induced mixing dominates. SIGNIFICANCE STATEMENT: The purpose of this idealized study is to better understand how wind influences the salinity distribution in estuaries on large time scales. This is important because a change in winds can move saline water further inland, threatening freshwater availability and the natural balance of delicate ecosystems. We clarify the sometimes ambiguous observations regarding the influence of wind on the salt distribution and highlight the importance of including average wind forcing in analyses of estuarine dynamics on large time scales.","Baroclinic flows; Dispersion; Estuaries; Idealized models; Wind stress","en","journal article","","","","","","Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.","","2023-07-01","","","Mathematical Physics","","",""
"uuid:00c13030-4327-49c1-a163-b237759445a6","http://resolver.tudelft.nl/uuid:00c13030-4327-49c1-a163-b237759445a6","Numerical and Experimental Study of Acoustic Emission Source Signal Reconstruction in Fibre-Reinforced Composite Panels","Huijer, A.J. (TU Delft Ship Hydromechanics and Structures); Kassapoglou, C. (TU Delft Aerospace Structures & Computational Mechanics); Pahlavan, Lotfollah (TU Delft Ship Hydromechanics and Structures)","Rizzo, Piervincenzo (editor); Milazzo, Alberto (editor)","2022","The recording and processing of acoustic emissions can be used to identify and localise damage mechanisms occurring in engineering structures. In plate-like structures, acoustic emissions propagate through the structure as guided waves. With a measurement location away from the source location, dispersion effects in the guided wave distort the acoustic emission signal. The distortion of the original signal hampers identification of damage mechanisms. This research describes and assesses a method to reconstruct the original acoustic emission signal using dispersion compensation. Simulations and experiments are performed involving thick glass-fibre reinforced plastic laminates. The signal reconstruction on the simulated data gives a reasonable representation of the simulated signal at the location of interest. In the experimental case, similarity slightly degrades. Deviation in arrival time between original measurement and reconstruction is attributed to a possible discrepancy in material properties in reality versus the properties used in the reconstruction.","Acoustic emission; Damage identification; Dispersion compensation; Fibre-reinforced plastics; Guided waves","en","conference paper","Springer","","","","","Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.","","2022-12-22","","","Aerospace Structures & Computational Mechanics","","",""
"uuid:b9fbf8e5-dc31-4da0-b560-79c05ebc00a2","http://resolver.tudelft.nl/uuid:b9fbf8e5-dc31-4da0-b560-79c05ebc00a2","On the powder metallurgy, additive manufacturing and welding of oxide dispersion strengthened Eurofer steel","Fu, J. (TU Delft Team Marcel Hermans)","Richardson, I.M. (promotor); Hermans, M.J.M. (promotor); Delft University of Technology (degree granting institution)","2021","Oxide dispersion strengthened (ODS) steels are promising candidates for use as structural materials in the next generation fission and fusion reactors. Compared to conventional ferritic or martensitic steels, ODS steels exhibit improved high-temperature creep properties and irradiation resistance. Favourable properties are mainly attributed to the fine grain features and the high number density of nanosized oxide particles in the steel matrix. These nanoparticles can act as pinning sites for dislocations and stable sinks for irradiation introduced defects, leading to significantly enhanced mechanical properties. In order to be employed in nuclear systems with large, complex structures, the fabrication and welding of ODS steels with reproducible and superior properties are inevitable and essential. However, after 10–20 years of studying since the emergence of ODS steels, these issues remain the major bottlenecks limiting further development. This thesis is concerned with ODS Eurofer steel, which is one of the representatives of ODS steels and has been the research focus in terms of promising nuclear materials within the European Union. With the aim to develop suitable and effective methods for the fabrication and welding of ODS Eurofer, the result of this study should help to extend the use of ODS steels in future nuclear applications.","Oxide dispersion strengthened steel; Microstructural analysis; Mechanical properties; Powder metallurgy; Additive manufacturing; Welding","en","doctoral thesis","","978-94-6423-565-4","","","","","","","","","Team Marcel Hermans","","",""
"uuid:5e2b222f-22b1-486d-99eb-34b8916bbaa7","http://resolver.tudelft.nl/uuid:5e2b222f-22b1-486d-99eb-34b8916bbaa7","Analysis of mixing during hydrogen storage in gas reservoirs: A reservoir simulation study","Terstappen, Robin (TU Delft Civil Engineering & Geosciences)","Bruhn, D.F. (mentor); Hajibeygi, H. (graduation committee); Eikelenboom, W. (mentor); Huijskes, Thijs (graduation committee); Delft University of Technology (degree granting institution)","2021","This thesis contributes to increasing the technology readiness level of hydrogen storage in gas reservoirs, which will be required when hydrogen has become a major energy carrier in the future Dutch energy system. It addresses the mixing processes with resident gases that occur during hydrogen storage operations in gas fields, and analyzes their implementation in a reservoir simulator. The CMG GEM reservoir simulator allows incorporation of mechanical dispersion and effective molecular diffusion into its simulations, while solving the advection dispersion transport equation fully implicitly, as well as gravitational segregation and other macro scale mixing phenomena. Mechanical dispersion is quantified by its main parameter dispersivity, for which a large uncertainty exists in the literature. Dispersivity represents pore scale fluid velocity differences caused by microscale heterogeneities in a porous medium. Due to the lack of adequate hydrogen dispersivity experiments, a range of dispersivity values is collected from literature on (groundwater) dispersivity experiments in sandstones. A sensitivity analysis is conducted, in which the influence of the different mixing processes on the mixing between working gas and cushion gas is analyzed. For this, a conceptual reservoir model (radial and homogeneous), with properties based on Dutch sandstone gas fields was built in CMG GEM. The effect of molecular diffusion on mixing proves to be negligible compared to mechanical dispersion at typical reservoir flow rates. Furthermore, the results of the simulations prove to be significantly influenced by numerical dispersion, which is a calculation error, dependent on grid size and time step. The effect of numerical dispersion compared to mechanical dispersion is quantitatively analyzed, after which various options are introduced to deal with numerical dispersion in a way that the physical processes are most realistically represented. The work in this thesis demonstrates the challenges of realistically implementing hydrogen storage mixing processes in a reservoir simulator, and should be regarded as a foundation for further research.","Hydrogen; Storage; mixing; dispersion; dispersivity; gas reservoirs; gravitational segregation; diffusion","en","master thesis","","","","","","","","","","","","Applied Earth Sciences","",""
"uuid:774ac341-d513-4b4c-870d-2c9e4f585b34","http://resolver.tudelft.nl/uuid:774ac341-d513-4b4c-870d-2c9e4f585b34","Dispersion and Heat Conduction in a Simplified Geothermal Doublet","Maat, Sander (TU Delft Civil Engineering and Geosciences)","Rossen, W.R. (mentor); Voskov, D.V. (mentor); Tang, J. (mentor); Wang, Y. (mentor); Delft University of Technology (degree granting institution)","2021","The goal of this study is to test out the accuracy of the upscaling approach (Jinyu Tang, 2021) for a geothermal doublet. This approach tries to simulate the physical thermal dispersion. When modeling in a geothermal reservoir it would be easy if a lot of layers can be upscaled. However, when doing upscaling one can not just take an average of the layer properties. This results in a very inaccurate representation of reality. That is where the upscaling comes in. First, some other points need to be considered. The reservoir is simulated in DARTS (Wang, Voskov, Khait, & Bruhn, 2020). This simulator uses numerical methods to model the reservoir. Before starting on modeling geothermal reservoirs first a 1D case is evaluated to check for numerical dispersion that comes into play. With that evaluation done the 2D cases were simulated. The full reservoir has 91 layers, these can be upscaled into 9 layers eventually. To start building up to that scenario first 2 other scenarios are evaluated. First, an upscaled section of the first block of upscaled layers is evaluated. This was originally 10 layers and now upscaled to one layer. This one layer was first simulated in a one grid simulation and then a single grid simulation. These results are compared to a simulation of the original layer properties and a simulation of an arithmetic average of the reservoir properties. This is also done on a second scenario with 2 upscaled groups and eventually the full 9 layer reservoir (originally 91 layers). With these scenarios evaluated the upscaling shows to give a better simulation of the reservoir compared to using an average for the layer properties. This is all compared with a simulation of the original layer properties.","Dispersion; Geothermal; Doublet; DARTS; Conduction; Heat","en","bachelor thesis","","","","","","","","","","","","","",""
"uuid:3bd817ad-792d-4279-8c8a-5b571466eada","http://resolver.tudelft.nl/uuid:3bd817ad-792d-4279-8c8a-5b571466eada","A New Dispersion Model to Control the Emission Levels in the Vicinity of Freeways","Damoiseaux, Michiel (TU Delft Mechanical, Maritime and Materials Engineering; TU Delft Delft Center for Systems and Control)","De Schutter, B.H.K. (mentor); Delft University of Technology (degree granting institution)","2021","One of the main sources of greenhouse gasses is the vast and still expanding road transport sector. The number of vehicles utilizing freeways increases every day, with more and more traffic jams as a result. Lately, the development of smart traffic management systems seems to be a way out and these systems are used extensively. In this thesis, smart traffic management systems are used to control a freeway network in order to achieve an optimal flow, as well as a minimal amount of emitted gasses, and to protect target areas in the vicinity of freeways from dispersed gasses. Smart traffic management systems use control measures such as ramp metering and variable speed limits. To control these measures in an optimal way, model predictive control is found to be a suitable control method. In order to simulate the behavior of freeway traffic and traffic emissions, a model predictive control scheme uses traffic models. The METANET traffic flow model and the VT-macro traffic emission model are suitable models for control purposes in traffic networks, and therefore, these are used in this work. In order to predict the amount of pollutant gasses distributed in the area downwind of the freeway, a third model has to be used. Multiple authors have proposed so-called dispersion models, but none is yet suitable for on-line control of freeway networks. This is due to high computational costs, the inapplicability in constantly changing traffic networks, or deviating purposes of models. This work proposes a new dispersion model that is able to model the distribution of pollutant gasses in the vicinity of a freeway and which is applicable in real-time traffic control. The proposed model, the line source Gaussian puff model, is an extension of the existing Gaussian puff model. The Gaussian puff model is suitable for the modelling of point sources such as industrial stacks. In this work, the Gaussian puff model is modified to make it suitable for the dispersion modelling of freeway sections. This is done by implementing line sources instead of point sources. The proposed model has a small normalized error such as the validation data set generated by a CFD model, implying a good performance. Compared to alternative models used in freeway traffic control, the new model has a smaller error. The LSGP model is used in a case study to get an understanding of what level of pollutant gasses can be averted to disperse to target areas. In this case study, an MPC scheme is used to control a freeway. The aim is to find an optimal situation where the flow of the freeway is optimal, the total amount of emitted gasses is minimal, and the concentration level in the target area is reduced. The results show that the new model is able to minimize the amount of pollutant gasses nearby a freeway with a low computational complexity in a model predictive control scheme.","Dispersion; Traffic control; Freeway Traffic Control; model predictive control","en","master thesis","","","","","","","","","","","","Mechanical Engineering | Systems and Control","",""
"uuid:4bd2437f-5940-4ee0-b18c-659d78264b6f","http://resolver.tudelft.nl/uuid:4bd2437f-5940-4ee0-b18c-659d78264b6f","A mean-squared-error condition for weighting ionospheric delays in GNSS baselines","Teunissen, P.J.G. (TU Delft Mathematical Geodesy and Positioning; University of Melbourne; Curtin University of Technology); Khodabandeh, A. (University of Melbourne)","","2021","Although ionosphere-weighted GNSS parameter estimation is a popular technique for strengthening estimator performance in the presence of ionospheric delays, no provable rules yet exist that specify the needed weighting in dependence on ionospheric circumstances. The goal of the present contribution is therefore to develop and present the ionospheric conditions that need to be satisfied in order for the ionosphere-weighted solution to be mean squared error (MSE) superior to the ionosphere-float solution. When satisfied, the presented conditions guarantee from an MSE performance view, when (a) the ionosphere-fixed solution can be used, (b) the ionosphere-float solution must be used, or (c) an ionosphere-weighted solution can be used.","Best linear unbiased estimator (BLUE); GNSS; Ionosphere fixed; Ionosphere float; Ionosphere weighted; Ionospheric dispersion; Mean squared error (MSE)","en","journal article","","","","","","","","","","","Mathematical Geodesy and Positioning","","",""
"uuid:2b85e496-a719-4aed-8b4a-d587ee38fd7e","http://resolver.tudelft.nl/uuid:2b85e496-a719-4aed-8b4a-d587ee38fd7e","Pollution and accuracy of solutions of the Helmholtz equation: A novel perspective from the eigenvalues","Dwarka, V.N.S.R. (TU Delft Numerical Analysis); Vuik, Cornelis (TU Delft Numerical Analysis)","","2021","In researching the Helmholtz equation, the focus has either been on the accuracy of the numerical solution (pollution) or the acceleration of the convergence of a preconditioned Krylov-based solver (scalability). While it is widely recognized that the convergence properties can be investigated by studying the eigenvalues, information from the eigenvalues is not used in studying the numerical dispersion which drives the pollution error. Our aim is to bring the topics of accuracy and scalability together for the first time; instead of approaching the pollution error in the conventional sense of being the result of a discrepancy between the exact and numerical wavenumber, we show that the dispersion which drives the pollution error can also be decomposed in terms of the eigenvectors and eigenvalues. Using these novel insights, we construct sharper upper bounds for the total error independent of the grid resolution. While the pollution error can be minimized in one-dimension by introducing a dispersion correction, the latter is not possible in higher dimensions, even for very simple model problems. For our model problem, a correction on the eigenvalues enables us to remove the pollution error and study it in full detail, both in one- and two-dimensions.","Helmholtz equation; Pollution; Numerical dispersion; Eigenvalues; FDM; FEM","en","journal article","","","","","","","","","","","Numerical Analysis","","",""
"uuid:e6720ff1-4ec1-4563-9d2e-c1337214dc62","http://resolver.tudelft.nl/uuid:e6720ff1-4ec1-4563-9d2e-c1337214dc62","Measurement of Pipe and Fluid Properties with a Matrix Array-based Ultrasonic Clamp-on Flow Meter","Massaad Mouawad, J.M. (TU Delft ImPhys/Medical Imaging); van Neer, P.L.M.J. (TU Delft ImPhys/Medical Imaging); van Willigen, D.M. (TU Delft Electronic Instrumentation); Sabbadini, A. (TU Delft ImPhys/Medical Imaging); de Jong, N. (TU Delft ImPhys/Medical Imaging); Pertijs, M.A.P. (TU Delft Electronic Instrumentation); Verweij, M.D. (TU Delft ImPhys/Medical Imaging)","","2021","Current ultrasonic clamp-on flow meters consist of a pair of single-element transducers that are carefully positioned before use. This positioning process consists of manually finding the distance between the transducer elements, along the pipe axis, for which maximum signal-to-noise ratio (SNR) is achieved. This distance depends on the sound speed, thickness, and diameter of the pipe and on the sound speed of the liquid. However, these parameters are either known with low accuracy or completely unknown during positioning, making it a manual and troublesome process. Furthermore, even when sensor positioning is done properly, uncertainty about the mentioned parameters, and therefore on the path of the acoustic beams, limits the final accuracy of flow measurements. In this research, we address these issues using an ultrasonic clamp-on flow meter consisting of two matrix arrays, which enables the measurement of pipe and liquid parameters by the flow meter itself. Automatic parameter extraction, combined with the beam-steering capabilities of transducer arrays, yields a sensor capable of compensating for pipe imperfections. Three parameter extraction procedures are presented. In contrast to similar literature, the procedures proposed here do not require that the medium be submerged nor do they require a priori information about it. First, axial Lamb waves are excited along the pipe wall and recorded with one of the arrays. A dispersion curve-fitting algorithm is used to extract bulk sound speeds and wall thickness of the pipe from the measured dispersion curves. Second, circumferential Lamb waves are excited, measured, and corrected for dispersion to extract the pipe diameter. Third, pulse-echo measurements provide the sound speed of the liquid. The effectiveness of the first two procedures has been evaluated using simulated and measured data of stainless steel and aluminum pipes, and the feasibility of the third procedure has been evaluated using simulated data.","Dispersion correction; Lamb waves; matrix transducer; parameter extraction; ultrasound flow meter","en","journal article","","","","","","Accepted Author Manuscript","","","","","ImPhys/Medical Imaging","","",""
"uuid:9de8ba77-e430-4513-a3f8-8e452cbdd41d","http://resolver.tudelft.nl/uuid:9de8ba77-e430-4513-a3f8-8e452cbdd41d","On the Potential of 3D Transdimensional Surface Wave Tomography for Geothermal Prospecting of the Reykjanes Peninsula","Rahimi Dalkhani, A. (TU Delft Applied Geophysics and Petrophysics); Zhang, Xin (University of Edinburgh); Weemstra, C. (TU Delft Applied Geophysics and Petrophysics; Royal Netherlands Meteorological Institute (KNMI))","","2021","Seismic travel time tomography using surface waves is an effective tool for three-dimensional crustal imaging. Historically, these surface waves are the result of active seismic sources or earthquakes. More recently, however, surface waves retrieved through the application of seismic interferometry have also been exploited. Conventionally, two-step inversion algorithms are employed to solve the tomographic inverse problem. That is, a first inversion results in frequency-dependent, two-dimensional maps of phase velocity, which then serve as input for a series of independent, one-dimensional frequency-to-depth inversions. As such, a set of localized depth-dependent velocity profiles are obtained at the surface points. Stitching these separate profiles together subsequently yields a three-dimensional velocity model. Relatively recently, a one-step three-dimensional non-linear tomographic algorithm has been proposed. The algorithm is rooted in a Bayesian framework using Markov chains with reversible jumps, and is referred to as transdimensional tomography. Specifically, the three-dimensional velocity field is parameterized by means of a polyhedral Voronoi tessellation. In this study, we investigate the potential of this algorithm for the purpose of recovering the three-dimensional surface-wave-velocity structure from ambient noise recorded on and around the Reykjanes Peninsula, southwest Iceland. To that end, we design a number of synthetic tests that take into account the station configuration of the Reykjanes seismic network. We find that the algorithm is able to recover the 3D velocity structure at various scales in areas where station density is high. In addition, we find that the standard deviation of the recovered velocities is low in those regions. At the same time, the velocity structure is less well recovered in parts of the peninsula sampled by fewer stations. This implies that the algorithm successfully adapts model resolution to the density of rays. It also adapts model resolution to the amount of noise in the travel times. Because the algorithm is computationally demanding, we modify the algorithm such that computational costs are reduced while sufficiently preserving non-linearity. We conclude that the algorithm can now be applied adequately to travel times extracted from station–station cross correlations by the Reykjanes seismic network.","seismic interferometry; transdimensional tomography; surface wave dispersion; probabilistic inversion; Markov chain Monte Carlo","en","journal article","","","","","","","","","","","Applied Geophysics and Petrophysics","","",""
"uuid:6e210eb5-a341-4384-acff-dbe3787fddcf","http://resolver.tudelft.nl/uuid:6e210eb5-a341-4384-acff-dbe3787fddcf","Investigating functional mix in Europe's dispersed urban areas","Wandl, Alex (TU Delft Environmental Technology and Design); Hausleitner, B. (TU Delft Urban Design)","","2021","A large proportion of European inhabitants live in dispersed urban settlements, much of which is labelled as sprawl, defined by monofunctional, low-density areas. However, there is increasing evidence that this may be an overly simplistic way of describing territories-in-between (TiB). This paper defines and maps functional mix in six dispersed urban areas across Europe, applying a method that goes beyond existing land-use-based mixed-use indicators but considers functional mixing on the parcel level. The paper uses data on the location of economic activities and the residential population. It concludes that, in eight cases from four European countries, mixed-use is widespread and that more than 65% of inhabited areas are mixed. Moreover, the paper relates functional mixing to specific settlement characteristics: permeability, grain size, centrality and accessibility, and connectivity. This demonstrates that functional mixing is not the result of local urban morphology or planning instruments, but of the multi-scalar qualities of a location. Therefore, there is a requirement to coordinate planning and design through different scales if mixed-use areas are to be seen as one strategy for achieving greater sustainability in the spatial development of dispersed areas.","dispersed urban development; Mixed-use; settlement characteristics; typology","en","journal article","","","","","","","","","","","Environmental Technology and Design","","",""
"uuid:178248b3-43e4-457a-b015-9c1378d8f0a2","http://resolver.tudelft.nl/uuid:178248b3-43e4-457a-b015-9c1378d8f0a2","Microstructure Study of Pulsed Laser Beam Welded Oxide Dispersion-Strengthened (ODS) Eurofer Steel","Fu, J. (TU Delft Team Marcel Hermans; FOM Institute DIFFER - Dutch Institute for Fundamental Energy Research); Richardson, I.M. (TU Delft Team Marcel Hermans); Hermans, M.J.M. (TU Delft Team Marcel Hermans)","","2021","Oxide dispersion-strengthened (ODS) Eurofer steel was laser welded using a short pulse duration and a designed pattern to minimise local heat accumulation. With a laser power of 2500 W and a duration of more than 3 ms, a full penetration can be obtained in a 1 mm thick plate. Material loss was observed in the fusion zone due to metal vaporisation, which can be fully compensated by the use of filler material. The solidified fusion zone consists of an elongated dual phase microstructure with a bimodal grain size distribution. Nano-oxide particles were found to be dispersed in the steel. Electron backscattered diffraction (EBSD) analysis shows that the microstructure of the heat-treated joint is recovered with substantially unaltered grain size and lower misorientations in different regions. The experimental results indicate that joints with fine grains and dispersed nano-oxide particles can be achieved via pulsed laser beam welding using filler material and post heat treatment.","oxide dispersion strengthened steel; ODS Eurofer; laser welding; microstructure; EBSD","en","journal article","","","","","","","","","","","Team Marcel Hermans","","",""
"uuid:b977743a-d7e7-4402-8ec4-ab490734cd62","http://resolver.tudelft.nl/uuid:b977743a-d7e7-4402-8ec4-ab490734cd62","Morphometric and Mechanical Analyses of Calcifications and Fibrous Plaque Tissue in Carotid Arteries for Plaque Rupture Risk Assessment","Gijsen, F.J.H. (TU Delft ChemE/Transport Phenomena; Erasmus MC); Vis, Bas (Erasmus MC; Student TU Delft); Barrett, Hilary E. (Erasmus MC); Zadpoor, A.A. (TU Delft Biomaterials & Tissue Biomechanics); Verhagen, Hence J. (Erasmus MC); Bos, Daniel (Erasmus MC); van der Steen, A.F.W. (Erasmus MC); Akyildiz, A.C. (TU Delft Medical Instruments & Bio-Inspired Technology; Erasmus MC)","","2021","Objective: Atherosclerotic plaque rupture in carotid arteries is a major source of cerebrovascular events. Calcifications are highly prevalent in carotid plaques, but their role in plaque rupture remains poorly understood. This work studied the morphometric features of calcifications in carotid plaques and their effect on the stress distribution in the fibrous plaque tissue at the calcification interface, as a potential source of plaque rupture and clinical events. Methods: A comprehensive morphometric analysis of 65 histology cross-sections from 16 carotid plaques was performed to identify the morphology (size and shape) and location of plaque calcifications, and the fibrous-tissue fiber organization around them. Calcification-specific finite element models were constructed to examine the fibrous plaque tissue stresses at the calcification interface. Statistical correlation analysis was performed to elucidate the impact of calcification morphology and fibrous tissue organization on interface stresses. Results: Hundred-seventy-one calcifications were identified on the histology cross-sections, which showed great variation in morphology. Four distinct patterns of fiber organization in the plaque tissue were observed around the calcification. They were termed as attached, pushed-aside, encircling and random patterns. The stress analyses showed that calcifications are correlated with high interface stresses, which might be comparable to or even above the plaque strength. The stress levels depended on the calcification morphology and fiber organization. Thicker calcification with a circumferential slender shape, located close to the lumen were correlated most prominently to high interface stresses. Conclusion: Depending on its morphology and the fiber organization around it, a calcification in an atherosclerotic plaque can act as a stress riser and cause high interface stresses. Significance: This study demonstrated the potential of calcifications in atherosclerotic plaques to cause elevated stresses in plaque tissue and provided a biomechanical explanation for the histopathological findings of calcification-associated plaque rupture.","Atherosclerosis; Carotid arteries; Histopathology; Morphology; Optical fiber dispersion; Organizations; Stress","en","journal article","","","","","","Accepted Author Manuscript","","","","","ChemE/Transport Phenomena","","",""
"uuid:eef4dcc4-57af-4e79-93a3-25c708db32d7","http://resolver.tudelft.nl/uuid:eef4dcc4-57af-4e79-93a3-25c708db32d7","Towards accuracy and scalability: Combining Isogeometric Analysis with deflation to obtain scalable convergence for the Helmholtz equation","Dwarka, V.N.S.R. (TU Delft Numerical Analysis); Tielen, R.P.W.M. (TU Delft Numerical Analysis); Möller, M. (TU Delft Numerical Analysis); Vuik, Cornelis (TU Delft Numerical Analysis)","","2021","Finding fast yet accurate numerical solutions to the Helmholtz equation remains a challenging task. The pollution error (i.e. the discrepancy between the numerical and analytical wave number k) requires the mesh resolution to be kept fine enough to obtain accurate solutions. A recent study showed that the use of Isogeometric Analysis (IgA) for the spatial discretization significantly reduces the pollution error. However, solving the resulting linear systems by means of a direct solver remains computationally expensive when large wave numbers or multiple dimensions are considered. An alternative lies in the use of (preconditioned) Krylov subspace methods. Recently, the use of the exact Complex Shifted Laplacian Preconditioner (CSLP) with a small complex shift has shown to lead to wave number independent convergence while obtaining more accurate numerical solutions using IgA. In this paper, we propose the use of deflation techniques combined with an approximated inverse of the CSLP using a geometric multigrid method. Numerical results obtained for one- and two-dimensional model problems, including constant and non-constant wave numbers, show scalable convergence with respect to the wave number and approximation order p of the spatial discretization. Furthermore, when kh is kept constant, the proposed approach leads to a significant reduction of the computational time compared to the use of the multigrid-approximated or exact inverse of the CSLP with a small shift, in particular for three-dimensional model problems.","Deflation; GMRES; Helmholtz; Isogeometric Analysis; Numerical dispersion; Pollution","en","journal article","","","","","","","","","","","Numerical Analysis","","",""
"uuid:932fb88a-6b18-4054-8a38-2b077bda49b5","http://resolver.tudelft.nl/uuid:932fb88a-6b18-4054-8a38-2b077bda49b5","Multimodal dispersive waves in a free rail: Numerical modeling and experimental investigation","Zhang, P. (TU Delft Railway Engineering); Li, S. (TU Delft Railway Engineering); Nunez, Alfredo (TU Delft Railway Engineering); Li, Z. (TU Delft Railway Engineering)","","2021","In this paper, we present a solution method based on finite element (FE) modeling to predict multimodal dispersive waves in a free rail. As well as the modal behaviors and wavenumber-frequency dispersion relations, the phase and group velocities of six types of propagative waves are also derived and discussed in detail in the frequency range of 0–5 kHz. To experimentally distinguish different types of wave modes, the operating deflection shape (ODS) measurement approach is employed in the laboratory. ODS is measured from the spatial distribution of imaginary parts of the FRFs. We also propose a synchronized multiple-acceleration wavelet (SMAW) approach to experimentally study the propagation and dispersion characteristics of waves in a free rail. The group velocities in the vertical, longitudinal and lateral directions are estimated from the wavelet power spectra (WPSs). The good agreement between the simulation and measurement in terms of mode shapes and ODSs, wavenumber-frequency dispersion curves, and group velocities indicates that the ODS and SMAW approaches are capable of distinguishing different wave modes and measuring wave propagation and dispersion characteristics. In situ experimental results further demonstrate the effectiveness of the ODS measurement for coupled modal identification and the SMAW approach for wave dispersion analysis of the rail in a field track.","Multimodal dispersive waves; Operating deflection shapes; Phase and group velocities; Synchronized multiple-acceleration wavelet","en","journal article","","","","","","","","","","","Railway Engineering","","",""
"uuid:c39bdb82-5c00-400d-a5b0-e79a9e938431","http://resolver.tudelft.nl/uuid:c39bdb82-5c00-400d-a5b0-e79a9e938431","Transport of silica encapsulated DNA microparticles in controlled instantaneous injection open channel experiments","Tang, Yuchen (TU Delft Water Resources); Foppen, J.W.A. (TU Delft Water Resources; IHE Delft Institute for Water Education); Bogaard, T.A. (TU Delft Water Resources)","","2021","Surface water tracing is a widely used technique to investigate in-stream mass transport including contaminant migration. Recently, a microparticle tracer was developed with unique synthetic DNA encapsulated in an environmentally-friendly silica coating (Si-DNA microparticle). Previous tracing applications of such tracers reported detection and quantification, but a massive loss of tracer mass. However, the transport behavior of these DNA-tagged microparticle tracers has not been rigorously quantified and compared with that of solute tracers. Therefore, we compared the transport behavior of Si-DNA microparticles to the behavior of solute NaCl in 6 different, environmentally representative water types using breakthrough curves (BTCs), obtained from laboratory open channel injection experiments, whereby no Si-DNA microparticle tracer mass was lost. Hereafter, we modelled the BTCs using a 1-D advection-dispersion model with one transient storage zone (OTIS) by calibrating the hydrodynamic dispersion coefficient D and a storage zone exchange rate coefficient. We concluded that the transport behavior of Si-DNA microparticles resembled that of NaCl in surface-water relevant conditions, evidenced by BTCs with a similar range of D; however, the Si-DNA microparticle had a more erratic BTC than its solute counterpart, whereby the scatter increased as a function of water quality complexity. The overall larger confidence interval of DSi-DNA was attributed to the discrete nature of colloidal particles with a certain particle size distribution and possibly minor shear-induced aggregations. This research established a solid methodological foundation for field application of Si-DNA microparticles in surface water tracing, providing insight in transport behavior of equivalent sized and mass particles in rivers.","DNA; Hydrodynamic dispersion; Microparticle tracers; Surface water","en","journal article","","","","","","","","","","","Water Resources","","",""
"uuid:3f153a7f-a1d3-4ead-be4b-34f188ccbfc8","http://resolver.tudelft.nl/uuid:3f153a7f-a1d3-4ead-be4b-34f188ccbfc8","Highly Efficient and Broadband Achromatic Transmission Metasurface to Refract and Focus in Microwave Region","Ji, W. (TU Delft ImPhys/Optics); Cai, Tong (Ningbo University; Zhejiang University); Xi, Z. (TU Delft ImPhys/Optics); Urbach, Paul (TU Delft ImPhys/Optics)","","2021","Achromatic devices have wide application prospects in radar and imaging fields. However, chromatic aberration and limited bandwidth restrict their development. Moreover, broadband and highly efficient achromatic devices working in transmission mode are still difficult to realize. In this paper, broadband highly efficient achromatic transmission in the microwave region by a metasurface is achieved. First, the ideal dispersion conditions of achromatic meta-atoms are given. Then, a polarization selective grating metasurface and a split ring slot metasurface are designed using the transfer matrix method and equivalent circuit theory, respectively. The former is used to control phase characteristics while the latter enables controlling dispersion. Phase and dispersion can be controlled independently by cascading them and any phase curve can be designed as is desired. In order to verify the strategy, an achromatic deflector and an achromatic lens are designed and samples are fabricated. The experimental results show that the deflector can realize achromatic refraction from 9.3 to 12.3 GHz with average efficiency 77.5% and the lens can realize achromatic focusing from 9.8 to 12.2 GHz with average efficiency 78.9%, respectively. The experimental results are in good agreement with theory. The findings provide valuable strategy for achromatic devices design, which can be widely applied.","achromatic; broadband; dispersion; metasurfaces","en","journal article","","","","","","","","","","","ImPhys/Optics","","",""
"uuid:4f39d3ef-3496-4ced-8da3-a7d21cf5e1ef","http://resolver.tudelft.nl/uuid:4f39d3ef-3496-4ced-8da3-a7d21cf5e1ef","A Study on Plume Dispersion Characteristics of Two Discrete Plume Stacks for Negative Temperature Gradient Conditions","Sivanandan, H. (TU Delft Flow Physics and Technology; Amrita School of Engineering, Coimbatore); Kishore, V. Ratna (Amrita School of Engineering, Coimbatore); Goel, Mukesh (Sheffield Hallam University); Asthana, Abhishek (Sheffield Hallam University)","","2021","The dispersion of air pollutants emitted from industries has been studied ever since the dawn of industrialisation. The present work focuses on investigating the effect of negative atmospheric temperature gradient and the plume stack orientation of two individual equal-height stacks on the vertical rise and dispersion of the plume. The study carried out upon three-stack layout configurations namely inline, 45° and non-inline, separated by an inter-stack distance of 12 times the exit chimney diameter (12 D) and 22 times the exit chimney diameter (22 D) in each case over the two temperature gradients of −0.2 K/100 m and −0.5 K/100 m. The turbulence is modelled using realisable k-ε model, a model used in the FLUENT flow solver. In the case of the inline configuration, the upwind plume shields its downwind counterpart, which in turn allows for higher plume rise at a given temperature gradient. The plume oscillates more in the case of inline than 45° and non-inline cases. Also, for a temperature gradient of −0.5 K/100 m, the plumes oscillate violently in the vertical direction, mainly because, with the initial rise of the plume, cold air from higher altitudes moves down and forms a layer of lower temperature closer to the ground. The present study is important to highlight the plume dispersion characteristics under negative temperature gradient conditions.","Negative temperature gradient; Numerical methods; Plume dispersion; Stack configuration; Unstable","en","journal article","","","","","","","","","","Flow Physics and Technology","","","",""
"uuid:2025fc04-5e7e-4509-8834-3eb3b19f1ae9","http://resolver.tudelft.nl/uuid:2025fc04-5e7e-4509-8834-3eb3b19f1ae9","Efficient two-layer non-hydrostatic wave model with accurate dispersive behaviour","de Ridder, M.P. (Deltares); Smit, Pieter B. (Sofar Ocean Technologies); van Dongeren, Ap R. (Deltares; IHE Delft Institute for Water Education); McCall, Robert T. (Deltares); Nederhoff, Kees (Deltares-USA); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics)","","2021","A 2-layer non-hydrostatic model with improved dispersive behaviour is presented. Due to the assumption of a constant non-hydrostatic pressure distribution in the lower layer, the dispersive behaviour is improved without much additional computational time. A comparison with linear wave theory showed that this 2-layer model gives a better result for the dispersion relation and shoaling of waves in intermediate water. This means that the 2-layer model is applicable in shallow and intermediate water depths (up to relative depths kh equals 4), whereas the 1-layer model is only applicable in shallow water depths (kh smaller than 1). Three laboratory experiments, including a fringing reef and a barred beach, were used to validate the presented mode for different hydrodynamic conditions. Based on these results, it can be concluded that the 2-layer model can be applied to accurately simulate the bulk wave height and spectral properties. The low frequency wave height, the setup and in particular the second order statistics contain more scatter, but the model accurately captured the general trend. Furthermore, the model showed good results for complex bathymetries in shallow to intermediate water.","Dispersive behaviour; Non-hydrostatic model; Wave modelling; XBeach","en","journal article","","","","","","Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.","","2021-05-05","","","Environmental Fluid Mechanics","","",""
"uuid:fc2b0218-5743-4050-9ea8-121820e07592","http://resolver.tudelft.nl/uuid:fc2b0218-5743-4050-9ea8-121820e07592","Characterisation of the influence of vanadium and tantalum on yttrium-based nano-oxides in ODS Eurofer steel","Fu, J. (TU Delft Team Marcel Hermans; DIFFER institute Eindhoven); Davis, T. P. (University of Oxford); Kumar, A. (TU Delft (OLD) MSE-3); Richardson, I.M. (TU Delft Team Marcel Hermans); Hermans, M.J.M. (TU Delft Team Marcel Hermans)","","2021","Oxide dispersion strengthened (ODS) steels are leading candidates for structural materials in nuclear fission and fusion power plants. Understanding the nature of nano-oxide particles in ODS steels is vital for a better control of the microstructure and mechanical properties to further their applications. In this study, electron microscopy and atom probe tomography (APT) have been used to investigate the nanocluster features in ODS Eurofer steel. With the addition of V and Ta in ODS Eurofer, the nanoclusters exhibit a higher number density with a decreased average diameter, indicating that V and Ta are beneficial for the formation of small clusters. Irrespective of the composition of the base material, the smaller particles have a variable stoichiometry while the larger particles are likely to have Y2O3 stoichiometry. The nanoclusters were found to have a core/shell structure, where Y, O and Ta are enriched in the core and Cr and V are predominant in the shell. The formation of the complex structure is possibly the result of a competing effect between Ta, Y, V and Cr binding with O. It is deduced that Ta tends to combine with O in the core (Y2O3) of the clusters due to a higher affinity, and pushes V and Cr to the surrounding shell during the formation of nanoclusters.","Atom probe tomography; Microstructure; Nanoclusters; ODS Eurofer; Oxide dispersion strengthened steel","en","journal article","","","","","","","","","","","Team Marcel Hermans","","",""
"uuid:92364ae0-3458-4bb3-b0e8-47bd8035c025","http://resolver.tudelft.nl/uuid:92364ae0-3458-4bb3-b0e8-47bd8035c025","CFD and EnKF coupling estimation of LNG leakage and dispersion","Wu, Jiansong (China University of Mining and Technology (Beijing)); Cai, Jitao (China University of Mining and Technology (Beijing)); Yuan, S. (TU Delft Safety and Security Science; China University of Mining and Technology (Beijing)); Zhang, Xiaole (ETH Zürich); Reniers, G.L.L.M.E. (TU Delft Safety and Security Science)","","2021","As a kind of clean fuel, increasing quantities of natural gas have been transported as liquefied natural gas (LNG) worldwide. The safety of LNG storage has gained the concerns from the public due to the potential severe consequences that may arise from LNG leakage. In this paper, a three-dimensional model with the combination of computational fluid dynamics (CFD) and the ensemble Kalman filter (EnKF) is proposed to predict LNG vapor dispersion and estimate the strength of the LNG leakage source. The LNG vapor dispersion CFD model is validated by the experimental data with good feasibility, and is further demonstrated with the reasonable modeling of the characteristics of the LNG vapor dispersion in a typical receiving terminal. The effectiveness of the proposed CFD and EnKF coupling model is evaluated and validated by a twin experiment. The results of the twin experiment indicate that the proposed CFD and EnKF coupling model allows the integration of observation data into the CFD simulations to enhance the prediction accuracy of the LNG vapor spatial-temporal distribution and thereby realizing a reasonable estimation of the LNG leakage velocity under complex environments. This study can provide technical supports for safety control, loss prevention and emergency response in case of LNG leakage accidents.","Computational fluid dynamics; Ensemble Kalman filter; LNG leakage; LNG receiving terminal; LNG vapor dispersion","en","journal article","","","","","","","","2024-03-30","","","Safety and Security Science","","",""
"uuid:608628bf-a1bc-45b3-9d06-574861b513ea","http://resolver.tudelft.nl/uuid:608628bf-a1bc-45b3-9d06-574861b513ea","Localised Corrosion Studies on FSW Al-Li alloys: Microstructure Effect","Garg, Vishant (TU Delft Mechanical, Maritime and Materials Engineering)","Gonzalez Garcia, Yaiza (mentor); Michailidou, Emina (graduation committee); Delft University of Technology (degree granting institution)","2020","Al-Li alloys were introduced for the use in aerospace applications due to its many advantages over steel such as its low density, good thermal and electrical conductivity and corrosion resistance of these alloys. The current generation of Al-Li alloys were developed to replace the currently used AA2024 alloy in commercial airframes, military and space applications. Traditional joining methods cannot be used to join dissimilar aluminium alloys. Thus, friction stir welding (FSW) was used to join the 2 dissimilar Al-Li alloys - AA2099 T83 and AA2060 T8E30 alloys. FSW causes several changes in the microstructure due to the rotational movement of the tool which results in localised plastic deformation and a thermal cycle in the alloys. This leads to 4 distinct zones in the alloys - the stir zone, thermo-mechanically affected zone, heat affected zone, and the base metal. The differences in microstructure is suggested to cause a change in the mechanical properties and localised corrosion behaviour of the alloys. In this work, the localised corrosion behaviour of the friction stir welded Al-Li alloys were investigated. The effect of FSW on the microstructure and corrosion behaviour was also studied. Microstructural characterisation was done for both the alloys and their respective weld zones. Coarse constituent particles were found in all weld zones with a decreasing trend in average size towards the weld centre. Strengthening precipitates such as the T_1 phase particles were observed on the grain boundaries of the alloys. This had a decreasing trend of distribution density towards the weld centre with virtually no precipitates in the SZ. In order to assess the corrosion performance potentiodynamic polarisation, open circuit potential, linear polarisation resistance, and immersion tests were deployed. Furthermore, scanning electron microscopy with energy dispersive X-ray spectroscopy was used to evaluate the morphology and chemical composition of the of the corroded surface. It was found that for the BM and HAZ regions of both alloys, the attack occurred mainly on the grain boundaries which were sites for the T_1 particles. These particles were suggested to be the controlling factor of localised corrosion behaviour in these regions due to their high electrochemical behaviour, which also resulted in almost no passivity in these regions. A large attack site was also observed on the surface of the matrix which was the site of hydrogen evolution during initial immersion time periods. Pits were also formed on the sites of coarse intermetallic particles. For the SZ regions the dominating attack was due to the coarse particles in the matrix. The effect of anodising the surface and sol-gel coating of the surface on the corrosion behaviour was determined in this project. It was found that the anodised layer did enhance the corrosion performance of the alloys. The SZ of the anodised sample was found to be most prone to corrosion compared to the anodised base metals. The sol-gel coating on the surface was also found to increase the corrosion resistance of the surface due to its self healing properties thus protecting the surface of the alloys.","Aluminium-Lithium alloys;; Corrosion;; AA2060 T8E30;; AA2099 T83;; Anodising;; Sol-gel coating; Hydrogen evolution;; energy dispersive X-ray spectroscopy;; Passivity;; Linear polarisation resistance;; Intergranular attack;; Scanning electron microscopy;; Friction stir welding;; Immersion tests;; Potentiodynamic polarisation;","en","master thesis","","","","","","","","","","","","Mechanical Engineering | Vehicle Engineering","",""
"uuid:53f44f30-f1f3-42ab-b4e8-17b3bc6e7ae2","http://resolver.tudelft.nl/uuid:53f44f30-f1f3-42ab-b4e8-17b3bc6e7ae2","Investigation of novel Cr6+-free anodising pre-treatments for enhanced corrosion protection of aluminium alloy 2024-T3","Nierijnck, Sven (TU Delft Mechanical, Maritime and Materials Engineering; TU Delft Materials Science and Engineering)","Mol, J.M.C. (mentor); Buijnsters, J.G. (graduation committee); Tiringer, U. (graduation committee); Delft University of Technology (degree granting institution)","2020","Hexavalent chromium has been the industry standard for corrosion protection for many years. Its unsurpassed active corrosion inhibiting capabilities, its incredible versatility and its economic benefits made it a popular all-rounder. Nowadays the widely known toxic and carcinogenic nature have restricted its use within the European Union. More and more research in the field of corrosion science has been focussing on finding safer alternatives, since hexavalent chromium was officially added the US annual report on carcinogens in the 1980s. Before it was used in almost every step of corrosion protective schemes consisting of a pre-treatment, a primer and a topcoat. In this work a novel approach to two industrial anodising pre-treatments (sulfuric acid anodising and tartaric sulfuric acid anodising) was investigated in order to improve the corrosion performance of the corrosion sensitive aluminium alloy 2024-T3. Both are currently used as alternatives to the historically often applied chromic acid anodising procedure, which contains hexavalent chromium compounds. In this work the effect of the anodising electrolyte viscosity, the anodising interelectrode distance and the addition of ceric sulphate to the anodising bath were investigated. Different fractions of ethylene glycol were used to vary the electrolyte viscosity. All anodising procedures used a fixed anodising voltage, temperature, acid concentration and agitation speed. These parameters were not changed. All samples were cleaned before anodising. In order to assess the corrosion performance linear sweep voltammetry, electrochemical impedance spectroscopy and immersion tests were deployed. Furthermore scanning electron microscopy with energy dispersive X-ray spectroscopy was used to evaluate the chemical composition of the anodised substrates.
It was found that an increase of the electrolyte viscosity results in a decrease of the anodising current density, which was related to a decrease in the overall thickness of the oxide layer created by the anodising process. The addition of 25 vol% ethylene glycol did not show any significant changes in corrosion performance although some indications of a slight improvement were found. Slightly smaller pores and a tighter barrier layer were proposed to be a possible explanation. A fraction of 75 vol% on the other hand dramatically deteriorated the corrosion performance, due to much slower oxide growth kinetics resulting in a much thinner oxide. The addition of ceric sulphate did not lead to any significant improvements in the corrosion performance for any of the tested procedures with one exception. The tartaric acid based procedure without ethylene glycol addition did show a significant improvement. Negatively charged complexes of cerium and tartaric acid compounds, which are supposed to be drawn towards the substrate during anodising, were proposed to be a possible explanation. The interelectrode distance did not show any significant differences except for the tartaric acid based procedure with ceric sulphate but without ethylene glycol addition. A higher electric field strength as a results of the smaller interelectrode distance was held responsible. The electric field strength should directly affect the amount of cerium complexes attracted towards the substrate, increasing the chance of cerium ending up as residues in the pores of the anodic oxide layer.","Anodising; Corrosion; Aluminium; AA2024-T3; Chromium-6; Chromic acid; Sulfuric acid; Tartaric acid; Ethylene glycol; Interelectrode distance; Inhibitor; Cerium; Linear sweep voltammetry; Electrochemical impedance spectroscopy; Scanning electron microscopy; Energy dispersive X-ray spectroscopy; Immersion tests","en","master thesis","","","","","","","","","","","","Materials Science and Engineering","",""
"uuid:58e77969-38ad-47d5-b41a-81c80e68c684","http://resolver.tudelft.nl/uuid:58e77969-38ad-47d5-b41a-81c80e68c684","Territories-in-between: A Cross-case Comparison of Dispersed Urban Development in Europe","Wandl, Alex (TU Delft Environmental Technology and Design)","Nadin, V. (promotor); Zonneveld, W.A.M. (promotor); Rooij, R.M. (copromotor); Delft University of Technology (degree granting institution)","2020","An increasing body of literature suggests that the conventional idea of a gradual transition in spatial structure from urban to rural does not reflect contemporary patterns of urban development and their potential for sustainable development. The research introduces the concept of territories-in-between (TiB) to address the issues surrounding the sustainability of dispersed urban development. A cross-case comparison research design was chosen to develop methods and principles that can be transferred to other geographical contexts. Ten cases in five countries were studied with the aim to answer the following questions:
What spatial structures characterise dispersed urban areas in Europe? Which morphological and functional structures of dispersed urban areas offer the potential for more sustainable development? If so, how can this potential be mapped and measured to inform regional planning and design? Are there similarities and dissimilarities concerning potentials of dispersed urban areas in different locations, planning cultures, topographies and histories? Do dispersed urban areas have distinct characteristics? In sum, the findings show that dispersed urban areas in Europe are quite distinct from urban and rural areas and that they share characteristics from one place to another. The research investigated three aspects of sustainable spatial development, the potential of multi-functionality, the provision of ecosystem services and the presence and potential for mixed-use.","dispersed urban development; Spatial planning; regional spatial analysis,; sprawl","en","doctoral thesis","A+BE | Architecture and the Built Environment","978-94-6366-244-4","","","","A+BE | Architecture and the Built Environment No 2 (2020)","","2020-06-30","","","Environmental Technology and Design","","",""
"uuid:cf6ce406-33a6-4f61-bc14-e2237693fc6d","http://resolver.tudelft.nl/uuid:cf6ce406-33a6-4f61-bc14-e2237693fc6d","Dispersion and Nonlinearity Identification for Single-Mode Fibers Using the Nonlinear Fourier Transform","de Koster, P.B.J. (TU Delft Team Sander Wahls); Wahls, S. (TU Delft Team Sander Wahls)","","2020","Efficient fiber-optic communication requires precise knowledge of the fiber coefficients, but these often change over time due to factors such as aging or bending. We propose a novel algorithm that identifies the average second-order dispersion and Kerr nonlinearity coefficient of a fiber, without employing any special training signals. Instead, ordinary input and output data recorded during normal operation is used. To the best of our knowledge, this is the first such algorithm. The algorithm is based on the nonlinear Fourier spectrum of the signal, which is known to evolve trivially as the signal propagates through an idealized model of the fiber. The algorithm varies the values of the fiber coefficients until the corresponding nonlinear Fourier spectrum at transmitter and receiver match optimally. We test the algorithm on simulated transmission data over a 1600 km link, and accurately identify the fiber coefficients. The identification algorithm is in particular well suited for providing a fiber model for nonlinear Fourier transform-based communication.","Chromatic dispersion; digital signal processing; fiber identification; fiber-optic communications; Kerr nonlinear effect; nonlinear Fourier transform","en","journal article","","","","","","Accepted Author Manuscript","","","","","Team Sander Wahls","","",""
"uuid:5651990b-6236-4840-a1aa-02f28c0a6ec5","http://resolver.tudelft.nl/uuid:5651990b-6236-4840-a1aa-02f28c0a6ec5","Descriptive Statistical Analysis of Frequency control-related variables of Nordic Power System","Acosta, Martha N. (Autonomous University of Nuevo León); Andrade, Manuel A. (Autonomous University of Nuevo León); Sanchez, Francisco (Loughborough University); Gonzalez-Longatt, Francisco (University of South-Eastern Norway); Rueda, José L. (TU Delft Intelligent Electrical Power Grids)","","2020","This paper presents a descriptive statistical analysis (DSA) of time-series of electro-mechanical quantities related to the frequency control (e.g. kinetic energy (KE), electrical frequency and power demand) of the Nordic power system (NPS). The idea of the DSA is to identify main observables features and patterns between these variables. Historical data publicly available has been used in this research paper; pre-processing included evaluating and identify missing data, and it filled by using the linear interpolation. The DSA uses descriptive statistical indicators to obtaining observable features. The dispersion analysis is used to observes how affects the KE to the electrical frequency. The data is grouped by weeks, days and hours, and its correlation coefficient was calculated. A correlation analysis between the KE and the power demand was computed, and the linear regression was used to construct a prediction model.","Correlation coefficients; Dispersion analysis; Patterns; Power system; Statistical analysis","en","conference paper","IEEE","","","","","Accepted author manuscript","","","","","Intelligent Electrical Power Grids","","",""
"uuid:9b3b0748-33fd-4afc-ad84-a26e14e15754","http://resolver.tudelft.nl/uuid:9b3b0748-33fd-4afc-ad84-a26e14e15754","A generating and absorbing boundary condition for dispersive waves in detailed simulations of free-surface flow interaction with marine structures","Wellens, P.R. (TU Delft Ship Hydromechanics and Structures); Borsboom, Mart (Deltares)","","2020","The boundaries of numerical domains for free-surface wave simulations with marine structures generate spurious wave reflection if no special measures are taken to prevent it. The common way to prevent reflection is to use dissipation zones at the cost of increased computational effort. On many occasions, the size of the dissipation area is considerably larger than the area of interest where wave interaction with the structure takes place. Our objective is to derive a local absorbing boundary condition that has equal performance to a dissipation zone with lower computational cost. The boundary condition is designed for irregular free-surface wave simulations in numerical methods that resolve the vertical dimension with multiple cells. It is for a range of phase velocities, meaning that the reflection coefficient per wave component is lower than a chosen value, say 2%, over a range of values for the dimensionless wave number kh. This is accomplished by extending the Sommerfeld boundary condition with an approximation of the linear dispersion relation in terms of kh, in combination with vertical derivatives of the solution variables. For this article, the boundary condition is extended with a non-zero right-hand side in order to prevent wave reflection, while, at the same time, at the same boundary, generating waves that propagate into the domain. Results of irregular wave simulations are shown to correspond to the analytical reflection coefficient for a range of wave numbers, and to have similar performance to a dissipation zone at a lower cost.","Boundary condition; Free surface waves; Volume-of-Fluid (VoF); Wave dispersion","en","journal article","","","","","","","","","","","Ship Hydromechanics and Structures","","",""
"uuid:22ae74db-7ede-4ceb-b109-db160fc74d92","http://resolver.tudelft.nl/uuid:22ae74db-7ede-4ceb-b109-db160fc74d92","Exact NFDM transmission in the presence of fiber-loss","Bajaj, V. (TU Delft Team Sander Wahls); Chimmalgi, S. (TU Delft Team Sander Wahls); Aref, Vahid (Nokia Bell Labs); Wahls, S. (TU Delft Team Sander Wahls)","","2020","Nonlinear frequency division multiplexing (NFDM) techniques encode information in the so-called nonlinear spectrum which is obtained from the nonlinear Fourier transform (NFT) of a signal. NFDM techniques so far have been applied to the nonlinear Schrödinger equation (NLSE) that models signal propagation in a lossless fiber. Conventionally, the true lossy NLSE is approximated by a lossless NLSE using the path-average approach which makes the propagation model suitable for NFDM. The error of the path-average approximation depends strongly on signal power, bandwidth and the span length. It can degrade the performance of NFDM systems and imposes challenges on designing high data rate NFDM systems. Previously, we proposed the idea of using dispersion decreasing fiber (DDF) for NFDM systems. These DDFs can be modeled by a NLSE with varying-parameters that can be solved with a specialized NFT without approximation errors. We have shown in simulations that complete nonlinearity mitigation can be achieved in lossy fibers by designing an NFDM system with DDF if a properly adapted NFT is used. We reported performance gains by avoiding the aforementioned path-average error in an NFDM system by modulating the discrete part of the nonlinear spectrum. In this paper, we extend the proposed idea to the modulation of continuous spectrum. We compare the performance of NFDM systems designed with dispersion decreasing fiber to that of systems designed with a standard fiber with the path-average model. Next to the conventional path-average model, we furthermore compare the proposed system with an optimized path-average model in which amplifier locations can be adapted. We quantify the improvement in the performance of NFDM systems that use DDF through numerical simulations.","Fiber-optic communication; nonlinear frequency division multiplexing; nonlinear Fourier transform; dispersion decreasing fiber","en","journal article","","","","","","","","","","","Team Sander Wahls","","",""
"uuid:03782203-f8f2-43c8-8ff3-8b40048d3ebe","http://resolver.tudelft.nl/uuid:03782203-f8f2-43c8-8ff3-8b40048d3ebe","Applicability study of pulsed laser beam welding on ferritic–martensitic ODS eurofer steel","Fu, J. (TU Delft (OLD) MSE-5); van Slingerland, J. (TU Delft (OLD) MSE-5; FOM Institute DIFFER - Dutch Institute for Fundamental Energy Research); Brouwer, J.C. (TU Delft (OLD) MSE-1); Bliznuk, Vitaliy (Universiteit Gent); Richardson, I.M. (TU Delft (OLD) MSE-5); Hermans, M.J.M. (TU Delft (OLD) MSE-5)","","2020","Pulsed laser beam welding was used successfully to join the oxide dispersion-strengthened (ODS) Eurofer steel. The joining was conducted with a laser power of 2500 W and a pulsed duration of 4 ms. With the filler material being used, a minor material loss and microvoids were observed in the joint. The microstructure of the fusion zone consists of dual phase elongated structures. The heat-affected zone has a width of around 0.06 mm with finer grains. The transmission electron microscopy observation reveals that nanoprecipitates are finely distributed in the fusion zone. The tensile strength, yield strength and elongation of the joint are slightly inferior to the base material. The fractography results reveal a typical ductile fracture. The experimental results indicate a reasonable joint from the perspective of both the microstructure and mechanical behaviour.","Electron microscopy; Laser welding; Mechanical properties; Microstructure; Oxide dispersion strengthened (ODS) alloy","en","journal article","","","","","","","","","","","(OLD) MSE-5","","",""
"uuid:1031e57f-0d9c-4d49-b766-e3a6b05045b4","http://resolver.tudelft.nl/uuid:1031e57f-0d9c-4d49-b766-e3a6b05045b4","Sub-nanoscale Surface Engineering of TiO2Nanoparticles by Molecular Layer Deposition of Poly(ethylene terephthalate) for Suppressing Photoactivity and Enhancing Dispersibility","La Zara, D. (TU Delft ChemE/Product and Process Engineering); Bailey, Maximilian R. (ETH Zürich; Student TU Delft); Hagedoorn, P.L. (TU Delft BT/Biocatalysis); Benz, D. (TU Delft ChemE/Product and Process Engineering); Quayle, Michael J. (AstraZeneca); Folestad, Staffan (AstraZeneca); van Ommen, J.R. (TU Delft ChemE/Product and Process Engineering)","","2020","In this work, we report molecular layer deposition (MLD) of ultrathin poly(ethylene terephthalate) (PET) films on gram-scale batches of ultrafine particles for the first time. TiO2 P25 nanoparticles (NPs) are coated up to 50 cycles in an atmospheric-pressure fluidized-bed reactor at 150 °C using terephthaloyl chloride and ethylene glycol as precursors. Ex-situ diffuse reflectance infrared Fourier transform spectroscopy, thermogravimetric analysis, and transmission electron microscopy show the linear growth at 0.05 nm/cycle of uniform and conformal PET films, which are unattainable with conventional wet-phase approaches. The sub-nanoscale and nanoscale PET films not only suppress the photocatalytic activity of TiO2 NPs by hindering the access of water and reactant molecules to the TiO2 surface but also improve the dispersibility of TiO2 NPs in both organic and aqueous media. Still, the bulk optical properties, electronic structure, and surface area of TiO2 are essentially unaffected by the MLD process. This study demonstrates the industrial relevance of MLD to simultaneously suppress the photoactivity and enhance the dispersibility of commercial TiO2 P25 nanopowders, which is crucial for their use for example as UV-screening agents in sunscreens and as white pigments in paints. Moreover, by rapidly modifying the surface properties of particles in a controlled manner at the sub-nanometer scale, particle MLD can serve many other applications ranging from nanofluids to emulsions to polymer nanocomposites.","improved dispersion; inorganic-organic nanocomposite; molecular layer deposition; organic coating; polyethylene terephthalate; sub-nanoscale; suppressed photoactivity; surface engineering; TiO","en","journal article","","","","","","","","","","","ChemE/Product and Process Engineering","","",""
"uuid:50c6b364-018b-4865-8bb4-06da70da518d","http://resolver.tudelft.nl/uuid:50c6b364-018b-4865-8bb4-06da70da518d","Microstructure characterisation and mechanical properties of ODS Eurofer steel subject to designed heat treatments","Fu, J. (TU Delft (OLD) MSE-5; Dutch Institute for Fundamental Energy Research); Brouwer, J.C. (TU Delft (OLD) MSE-1); Hendrikx, R.W.A. (TU Delft (OLD) MSE-1); Richardson, I.M. (TU Delft (OLD) MSE-5); Hermans, M.J.M. (TU Delft (OLD) MSE-5)","","2020","The present work deals with oxide dispersion strengthened (ODS) Eurofer steel fabricated by powder metallurgy involving mechanical alloying and spark plasma sintering. A heat treatment route including normalising and tempering was applied to the as-produced steel, based on differential scanning calorimetry (DSC) measurement. The microstructure was characterised by scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), electrolytic extraction, X-ray diffraction (XRD) and transmission electron microscopy (TEM). Thermodynamic calculations conducted using Thermo-Calc software were used to determine the precipitation conditions. The results show that the Vickers microhardness of the sample after the designed heat treatment is more uniform compared to the as-produced condition. A dual phase and bimodal microstructure is formed in the as-produced and tempered steels. M23C6 and M6C carbides were found in the as-produced sample while only M23C6 carbides were observed in the tempered sample. The carbides dissolve and reprecipitate during the heat treatment, preferably at the grain boundaries. Nanosized Y2O3 particles were found to be homogenously distributed in the steel matrix, which is crucial for the mechanical properties. The dislocation density in the material is decreased significantly after the normalising and tempering treatment. A yield strength model was developed that includes the strengthening contributions of solid solutes, grain size, dislocation density and nanoparticles. Good agreement is obtained between the experimentally measured and theoretically calculated strength of the as-produced and tempered steels.","Heat treatment; Microstructure; Oxide dispersion strengthened steels; Powder metallurgy; Yield strength modelling","en","journal article","","","","","","","","","","","(OLD) MSE-5","","",""
"uuid:ad06e3d5-3df1-433d-abbb-0fe46b8dc2bd","http://resolver.tudelft.nl/uuid:ad06e3d5-3df1-433d-abbb-0fe46b8dc2bd","Electron beam-induced deposition of platinum from Pt(CO)2Cl2 and Pt(CO)2Br2","Mahgoub, A.M.I.M. (TU Delft ImPhys/Microscopy Instrumentation & Techniques); Lu, Hang (University of Florida); Thorman, Rachel M. (Johns Hopkins University); Preradovic, Konstantin (University of Central Florida); Jurca, Titel (University of Central Florida); McElwee-White, Lisa (University of Florida); Fairbrother, Howard (Johns Hopkins University); Hagen, C.W. (TU Delft ImPhys/Microscopy Instrumentation & Techniques)","","2020","Two platinum precursors, Pt(CO)2Cl2 and Pt(CO)2Br2, were designed for focused electron beam-induced deposition (FEBID) with the aim of producing platinum deposits of higher purity than those deposited from commercially available precursors. In this work, we present the first deposition experiments in a scanning electron microscope (SEM), wherein series of pillars were successfully grown from both precursors. The growth of the pillars was studied as a function of the electron dose and compared to deposits grown from the commercially available precursor MeCpPtMe3. The composition of the deposits was determined using energy-dispersive X-ray spectroscopy (EDX) and compared to the composition of deposits from MeCpPtMe3, as well as deposits made in an ultrahigh-vacuum (UHV) environment. A slight increase in metal content and a higher growth rate are achieved in the SEM for deposits from Pt(CO)2Cl2 compared to MeCpPtMe3. However, deposits made from Pt(CO)2Br2 show slightly less metal content and a lower growth rate compared to MeCpPtMe3. With both Pt(CO)2Cl2 and Pt(CO)2Br2, a marked difference in composition was found between deposits made in the SEM and deposits made in UHV. In addition to Pt, the UHV deposits contained halogen species and little or no carbon, while the SEM deposits contained only small amounts of halogen species but high carbon content. Results from this study highlight the effect that deposition conditions can have on the composition of deposits created by FEBID.","energy-dispersive X-ray spectroscopy (EDX); focused electron beam-induced deposition (FEBID); nanofabrication; platinum precursors; scanning electron microscopy (SEM); thermogravimetric analysis (TGA)","en","journal article","","","","","","","","","","","ImPhys/Microscopy Instrumentation & Techniques","","",""
"uuid:7b59cbd4-7b00-4d3a-99d6-3fe9a5a53267","http://resolver.tudelft.nl/uuid:7b59cbd4-7b00-4d3a-99d6-3fe9a5a53267","Solid State Diffusion Bonding of ODS Eurofer Steel by Spark Plasma Sintering","Fu, J. (TU Delft (OLD) MSE-5; Dutch Institute for Fundamental Energy Research); Brouwer, J.C. (TU Delft (OLD) MSE-1); Richardson, I.M. (TU Delft (OLD) MSE-5); Hermans, M.J.M. (TU Delft (OLD) MSE-5)","","2020","Oxide dispersion strengthened (ODS) steels are considered to be one of the candidate structural materials for advanced nuclear applications due to their high elevated-temperature strength, corrosion resistance, and radiation tolerance. Joining of ODS steels by traditional fusion joining techniques is not applicable, because the melting process results in the coarsening of fine grains and agglomeration of nanosized oxide particles, and consequently a significant loss of strength. Spark plasma sintering (SPS) has recently been employed as a novel joining technique, which could be beneficial for joining ODS steels considering the solid state characteristic. A powder metallurgy prepared ODS Eurofer steel was successfully joined using SPS. The microstructure and mechanical properties of the joints were investigated. An almost defect-free joint was obtained at the selected processing condition. The tensile properties of the joints are comparable to the base material. Fracture analysis shows an intergranular fracture in the as-joined sample, while a ductile fracture with well-defined dimples is found in the tempered sample.","Joining; Mechanical properties; Oxide dispersion strengthened alloy; Spark plasma sintering","en","conference paper","Springer","","","","","Accepted Author Manuscript","","2021-02-12","","","(OLD) MSE-5","","",""
"uuid:67d131a5-e737-49ec-b863-7a76f6c43c2a","http://resolver.tudelft.nl/uuid:67d131a5-e737-49ec-b863-7a76f6c43c2a","Wave energy dissipation by a viscous surface layer: Effects on the shear diffusion of a mineral oil slick","Kuijpers, Ties (TU Delft Civil Engineering & Geosciences)","Reniers, A.J.H.M. (mentor); Uijttewaal, W.S.J. (graduation committee); Zijlema, M. (graduation committee); Ridderinkhof, Wim (graduation committee); Delft University of Technology (degree granting institution)","2019","Mineral oil spills at sea can have many negative consequences. For both preventive and responsive purposes, it is essential to accurately forecast oil spill evolution. Shear diffusion (in this context, i.e. the combined effect of vertical mixing and differentiated horizontal advection of mass) determines for a significant part the evolution of an oil spill. These processes are partially forced by waves. A viscous fluid layer attenuates the waves throughout the area the layer covers. In this thesis, surface oil slicks are modeled as a continuous viscous fluid layer. It is investigated to what extent the wave-forced shear diffusion of the oil is affected by the oil-induced attenuation of the waves. For this purpose, the spectral wave model SWAN is extended with a module for energy dissipation due to a viscous fluid layer. The stationary, 1D wave energy balance is solved for uniformly forced waves in deep water. A high cutoff frequency (5 Hz) is employed to include the wave frequencies at which the dissipation is active. Also, special attention is paid to the choice of the wind and whitecapping formulation. Simulations are performed in full factorial setup, varying wind speed, oil layer thickness and oil viscosity. The results are compared to a no-oil case. Based on the difference, functions are fitted for the reduction of two key wave properties: the whitecapping dissipation rate and the surface Stokes drift velocity. The reduction functions are included in the oil spill module of the particle tracking model OpenDrift, which is subsequently used to calculate oil spill evolution due to shear diffusion for 2DV cases. The results of oil spill simulations with and without the implemented reduction functions are compared. Idealized cases (only wave-forced) show that for sufficiently thick layers (h+ ≥ O{10^-3} m) of sufficiently viscous (ν+ ≥ O{10^-3} m^2/s) oil, the Stokes drift reduction can significantly affect the wave-driven evolution of an oil spill in two ways: the average forward transport is reduced and the skewness of the oil mass distribution is increased to ‘less negative’ or even positive values. If simple sheared wind drift and ambient vertical turbulence are added, however, the relative importance of these effects becomes smaller. In none of the cases, a difference is found for the distribution of the oil mass between surface and subsurface, which implies that the whitecapping reduction hardly affects the results. It is recommended that further effort is put into obtaining a detailed understanding of the (differentiated) forward transport of the surface and near-surface oil, so that wave and wind effects can be distinguished, and modeled independently, more accurately.","oil spill; mineral oil; shear diffusion; oil dispersion; Stokes drift; viscous wave attenuation; SWAN; OpenDrift","en","master thesis","","","","","","","","","","","","Civil Engineering | Hydraulic Engineering","",""
"uuid:fe4c033e-8ca8-4fef-99ba-49863e8a52a3","http://resolver.tudelft.nl/uuid:fe4c033e-8ca8-4fef-99ba-49863e8a52a3","Behaviour of ODS 12Cr steel under thermal treatment at micro and macro level: A positron annihilation and Vickers hardness study","Hoogenberg, Friso (TU Delft Applied Sciences; TU Delft RST/Neutron and Positron Methods in Materials)","Schut, H. (mentor); Marques Pereira, V. (mentor); Bouwman, W.G. (graduation committee); Delft University of Technology (degree granting institution)","2019","The behaviour of ODS 12Cr steel under thermal treatment is studied in this report at micro and macro level. ODS 12Cr steel is always in the ferrite phase and has a melting point at 1500 ºC. Before studying,
the retrieved samples were metallographically prepared in four steps: mounting, grinding, mechanically polishing and electrolytically polishing. A measurement was done to analyse the effect of electrolytically polishing on bulk S and W parameters. This showed that mechanically polishing with 0.04 μm alumina particles has the same effect as electrolytically polishing. Next, the alloy was studied with three different measurement techniques: positron annihilation Doppler broadening spectroscopy, Vickers hardness test and positron lifetime measurements. Before these measurements the samples were annealed at selected temperatures for 10 minutes and naturally cooled.
The Doppler broadening spectroscopy was done with the Variable Energy Positron beam (VEP) at the Reactor Institute Delft (RID). With this set-up the S and W parameter were measured at different im-
plantation energies and converging bulk values of them were determined. The results were fitted with VEPFIT. This measurement was done in the as received state and after annealing from 200 ºC up to
1300 ºC in steps of 100 ºC. The Vickers hardness test was done with a load of 0.3 kgf and in the same temperature range as the VEP measurements but with steps of 200 ºC. A lifetime spectrum was measured in the as received state with two sample sandwiching a 22Na source packed with kapton. The average lifetime was determined by fitting the spectrum with LT 9.2. This measurement was repeated
after annealing for 10 minutes from 200 ºC up to 700 ºC in steps of 100 ºC.
The three different measurement techniques show corresponding results. Up to annealing temperatures of 1000 ºC the results stay constant. The bulk S and W parameters are respectively 0.475 and 0.078.
The Vickers hardness stays at 395 HV and is comparable to literature values. The average lifetime is approximately 208 ps, which corresponds with defects with sizes comparable to or at least larger than
that of divacancies. At this temperatures most thermal vacancies are trapped by the nano-oxide particles and are not able to liberate themselves which causes the constant results. At higher temperatures (larger than 1100 ºC) the thermal vacancy concentration increases and the vacancies gain enough energy to be liberated. This causes, in combination with oxide particles clustering, more defects in the material and explains the increasing bulk S value for temperatures up from 1100 ºC. The high bulk S values, compared with an iron alloy with less chromium, can also originate from clustering of chromium atoms. The surface S parameters are also increased in this temperature domain due to the formation of an oxide layer which can be seen with the naked-eye. Finally, the hardness value decreases to 374 HV after annealing at 1200 ºC which is a significant decrease and indicates that the pinning of the nano-particles decreases, resulting in grains growing easier.","positron annihilation; Vickers hardness; positron lifetime; annealing; nuclear fusion; oxide dispersion strengthened ferritic steel; thermal treatment; micro level; macro level","en","bachelor thesis","","","","","","","","","","","","Applied Physics","",""
"uuid:d97b5fc4-43ab-4ed9-8712-7f6158509c80","http://resolver.tudelft.nl/uuid:d97b5fc4-43ab-4ed9-8712-7f6158509c80","Applications of an Embedded Seamless Hybrid RANS/LES Approach for Turbulent Dispersion over Complex Urban Areas","Kenjeres, S. (TU Delft ChemE/Transport Phenomena)","","2019","This work presents an application of a RANS/LES hybrid approach in simulating flows and turbulent dispersion in complex urban areas. It is demonstrated that the
hybrid approach correctly captures the time-dependent behavior of the wake regions behind buildings, resulting in improvements of the total turbulent kinetic energy and, consequently, the turbulent dispersion of pollutants.
The seamless variant of the hybrid RANS/LES approach proposed here, based on a dynamic evolution of the local interface zone, in combination with a generic-reaction set atmospheric chemistry model, proved to be numerically efficient and robust, and is recommended for future investigations of turbulent dispersion in real-scale city domains.
2 and CH4 in zeolite ITQ-29 is investigated. Pure component linear adsorption isotherms for CO2 and CH4 are predicted by fitting the theoretical breakthrough curves to the experimental ones. Henry coefficients obtained from our approach are in excellent agreement with those measured experimentally. A similar procedure is applied to predict the complete Langmuir adsorption isotherm from breakthrough curves at high pressures. The resulting adsorption isotherms are in very good agreement with those measured experimentally. In our model for transient adsorption, mass transfer from the gas phase to the adsorbed phase is considered using the Linear Driving Force model and dispersion of the gas phase in the packed bed is taken into account. IAST is used to compute the equilibrium loadings for a mixture of gases. The influence of the dispersion coefficient and the effective mass transfer coefficient on the shape of breakthrough curves is investigated and discussed. Rough estimations of these values are sufficient to predict adsorption isotherms from breakthrough curves.","Adsorption isotherm; breakthrough curve; Dispersion; Mass transfer","en","journal article","","","","","","Accepted Author Manuscript","","2020-11-10","","","Engineering Thermodynamics","","",""
"uuid:14f328ed-d0b6-4bc4-be31-f2c9c8a08231","http://resolver.tudelft.nl/uuid:14f328ed-d0b6-4bc4-be31-f2c9c8a08231","Observations of mixing and transport on a steep beach","Brown, Jenna A. (Naval Post Graduate School of Engineering and Applied Sciences); MacMahan, Jamie H. (Naval Post Graduate School of Engineering and Applied Sciences); Reniers, A.J.H.M. (TU Delft Environmental Fluid Mechanics; University of Miami); Thornton, Ed B. (Naval Post Graduate School of Engineering and Applied Sciences); Shanks, Alan L. (University of Oregon); Morgan, Steven G. (University of California); Gallagher, Edie L. (Franklin and Marshall College, Lancaster)","","2019","Surfzone mixing and transport on a sandy, steep (∼1/8 slope), reflective beach at Carmel River State Beach, California, are described for a range of wave and alongshore flow conditions. Depth-limited wave breaking occurred close to the shore due to the steepness of the beach, creating a narrow surf/swash zone (∼10 m wide). Fluorescent Rhodamine dye was released as a slug in the surfzone, and the temporal and spatial evolution was measured using in-situ dye sensors. Dye concentration measured as a function of time reveals sharp fronts that quickly decay resulting in narrow peaks near the dye release, which subsequently broaden and decrease in peak concentration with alongshore distance. The measurements indicate two stages of mixing and transport occur inside the surfzone on the steep beach. 1) In the near-field (<50 m downstream of the dye release location), the dye fully mixed throughout the water column after a few incident waves then continued to disperse in two dimensions, with both advection and diffusion processes being important. 2) In the far-field (>50 m downstream from the dye release location), the mass transport was dominated by advection. The distance to the far-field is much shorter in the alongshore on a steep beach compared with a dissipative beach. Estimates of cross-shore and alongshore diffusion coefficients (κ x , κ y ) were found to be similar in magnitude within the surfzone. Outside the surfzone in the far-field, the results suggest that the mixing processes are independent of those inside the surfzone. The mixing and transport of material observed on this steep beach are found to be analogous to that previously measured on dissipative beaches, however the diffusion coefficients within and outside the surfzone were found to be smaller on this steep beach.","Diffusion; Dispersion; Dye; Mass transport; Steep beach; Surfzone","en","journal article","","","","","","Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.","","2019-09-23","","","Environmental Fluid Mechanics","","",""
"uuid:b3360315-0766-4459-a472-27208130f632","http://resolver.tudelft.nl/uuid:b3360315-0766-4459-a472-27208130f632","Effect of mechanical alloying and spark plasma sintering on the microstructure and mechanical properties of ODS Eurofer","Fu, J. (TU Delft (OLD) MSE-5); Brouwer, J.C. (TU Delft (OLD) MSE-1); Richardson, I.M. (TU Delft (OLD) MSE-5); Hermans, M.J.M. (TU Delft (OLD) MSE-5)","","2019","Oxide dispersion strengthened (ODS)Eurofer steel was prepared via mechanical alloying (MA)and spark plasma sintering (SPS). Different combinations of MA and SPS parameters were adopted in order to optimise the fabrication process. The experimental results show that the sample milled for 30 h, sintered at 1373 K at a pressure of 60 MPa has the highest density and microhardness among all the results obtained. As-produced ODS Eurofer shows a bimodal microstructure with homogeneously dispersed nanoscale Y 2 O 3 , that is beneficial for the mechanical properties. The yield and tensile strengths are higher while the elongation is lower in the top and bottom surfaces compared to the middle area of the sample. This is due to the presence of a larger number of M 23 C 6 carbides, resulting from carbon diffusion from the mould material. As-produced samples were also subjected to a heat treatment. A good balance is achieved between the strength and ductility of the heat-treated material. Yielding properties comparable to hot isostatic pressing or hot extrusion as reported in the literature, the processing route presented by this study shows potential to produce high performance ODS Eurofer.","Mechanical properties; Microstructure; Oxide dispersion strengthened steel; Powder metallurgy; Spark plasma sintering","en","journal article","","","","","","","","","","","(OLD) MSE-5","","",""
"uuid:e2f116fb-5ce4-42d7-ba00-f10a11181bf5","http://resolver.tudelft.nl/uuid:e2f116fb-5ce4-42d7-ba00-f10a11181bf5","A dispersive homogenization model for composites and its RVE existence","Liu, Y. (TU Delft Applied Mechanics); van der Meer, F.P. (TU Delft Applied Mechanics); Sluys, Lambertus J. (TU Delft Materials- Mechanics- Management & Design)","","2019","An asymptotic homogenization model considering wave dispersion in composites is investigated. In this approach, the effect of the microstructure through heterogeneity-induced wave dispersion is characterised by an acceleration gradient term scaled by a “dispersion tensor”. This dispersion tensor is computed within a statistically equivalent representative volume element (RVE). One-dimensional and two-dimensional elastic wave propagation problems are studied. It is found that the dispersive multiscale model shows a considerable improvement over the non-dispersive model in capturing the dynamic response of heterogeneous materials. To test the existence of an RVE for a realistic microstructure for unidirectional fiber-reinforced composites, a statistics study is performed to calculate the homogenized properties with increasing microstructure size. It is found that the convergence of the dispersion tensor is sensitive to the spatial distribution pattern. A calibration study on a composite microstructure with realistic spatial distribution shows that convergence is found although only with a relatively large micromodel.","Composites; Homogenization; RVE; Spatial distribution; Wave dispersion","en","journal article","","","","","","","","","","Materials- Mechanics- Management & Design","Applied Mechanics","","",""
"uuid:9e5de706-0275-46b3-b074-aa291b9247d7","http://resolver.tudelft.nl/uuid:9e5de706-0275-46b3-b074-aa291b9247d7","Structure-activity relationships in metal organic framework derived mesoporous nitrogen-doped carbon containing atomically dispersed iron sites for CO2 electrochemical reduction","Sun, X. (TU Delft ChemE/Catalysis Engineering); Wang, R. (TU Delft ChemE/Catalysis Engineering); Ould-Chikh, Samy (King Abdullah University of Science and Technology); Osadchii, D. (TU Delft ChemE/Catalysis Engineering); Li, G. (TU Delft ChemE/Inorganic Systems Engineering; TU Delft ChemE/Catalysis Engineering); Aguilar, Antonio (Université Grenoble Alpes); Hazemann, Jean louis (Université Grenoble Alpes); Kapteijn, F. (TU Delft ChemE/Catalysis Engineering); Gascon, Jorge (TU Delft ChemE/Catalysis Engineering; King Abdullah University of Science and Technology)","","2019","Mesoporous nitrogen-doped carbon nanoparticles with atomically dispersed iron sites (named mesoNC-Fe) are synthesized via high-temperature pyrolysis of an Fe containing ZIF-8 MOF. Hydrolysis of tetramethyl orthosilicate (TMOS) in the MOF framework prior to pyrolysis plays an essential role in maintaining a high surface area during the formation of the carbon structure, impeding the formation of iron (oxide) nanoparticles. To gain inside on the nature of the resulting atomically dispersed Fe moieties, HERFD-XANES, EXAFS and valence-to-core X-ray emission spectroscopies have been used. The experimental spectra (both XAS and XES) combined with theoretical calculations suggest that iron has a coordination sphere including a porphyrinic environment and OH/H2O moieties responsible for the high activity in CO2 electroreduction. DFT calculations demonstrate that CO formation is favored in these structures because the free energy barriers of *COOH formation are decreased and the adsorption of *H is impeded. The combination of such a unique coordination environment with a high surface area in the carbon structure of mesoNC-Fe makes more active sites accessible during catalysis and promotes CO2 electroreduction.","Atomically dispersed sites; CO; Electroreduction; Iron","en","journal article","","","","","","Accepted Author Manuscript","","2021-09-25","","","ChemE/Catalysis Engineering","","",""
"uuid:a9ae953c-71ec-4974-b21e-838e9ac0f72d","http://resolver.tudelft.nl/uuid:a9ae953c-71ec-4974-b21e-838e9ac0f72d","River-induced anomalies in seasonal variation of traffic-emitted CO distribution over the City of Krasnoyarsk","Hrebtov, Michael (Russian Academy of Sciences); Hanjalic, K. (TU Delft ChemE/Transport Phenomena)","","2019","Seasonal variation of air quality in a city with a large river was investigated by means of numerical simulations of air movement and pollutant dispersion over inversion-capped diurnal cycles using a Reynolds-averaged Navier-Stokes (RANS) approach with algebraic turbulent flux model. The study accounts for the effects of urban heat island (UHI), terrain orography and high thermal inertia of the river body. The case mimics the real environment of the Krasnoyarsk region with the river Yenisei (Russia). Two scenarios were considered typical of the winter and summer seasons. The study is focused on the dynamics of dispersion of CO emanating mainly from road traffic, which remains fairly uniform throughout the year. The simulation starts from a mild low-altitude inversion with penetrative convection gradually developing over the daytime and attenuating during the night. The main difference between the two cases is in the temperature of the river surface relative to the ambient air. In winter, the non-freezing river acts as a source of positive thermal buoyancy, while in summer the cool river at the daytime acts in the opposite way, as a heat sink. The effect of the river-induced air circulation appears significant enough to account for the observed winter accumulation of the pollutant in the city center.","Atmospheric boundary layer; Diurnal convection; Pollutants dispersion; Reynolds-averaged Navier-Stokes modelling; Seasonal variation","en","journal article","","","","","","","","","","","ChemE/Transport Phenomena","","",""
"uuid:e3deaadb-0f89-43f0-8fa8-339fdfc9f538","http://resolver.tudelft.nl/uuid:e3deaadb-0f89-43f0-8fa8-339fdfc9f538","Nanoengineering of Crystal and Amorphous Surfaces of Pharmaceutical Particles for Biomedical Applications","Zhang, Di (AstraZeneca); La Zara, D. (TU Delft ChemE/Product and Process Engineering); Quayle, Michael J. (AstraZeneca); Petersson, Gunilla (AstraZeneca); van Ommen, J.R. (TU Delft ChemE/Product and Process Engineering); Folestad, Staffan","","2019","The morphology, size, and surface properties of pharmaceutical particles form an essential role in the therapeutic performance of active pharmaceutical ingredients (APIs) and excipients as constituents in various drug delivery systems and clinical applications. Recent advances in methods for surface modification, however, rely heavily on liquid-phase-based modification processes and afford limited control over the thickness and conformality of the coating. Atomic layer deposition (ALD), on the other hand, enables the formation of conformal nanoscale films on complex structures with thickness control on the molecular level, while maintaining the substrate particle size and morphology. Moreover, this enables nanoengineering of surfaces of pharmaceutical particles also in the dry state. Successful nanoengineeering of crystal and amorphous surfaces of pharmaceutical particles is demonstrated in this study whereby functional properties, such as dissolution and dispersibility, were tailored for drug delivery applications. This expands on our initial work on ALD of alumina on pharmaceutical particles within the lower micro- to higher nanosize ranges to here probe both crystalline and amorphous lactose substrate surfaces (d50 = 3.5 and 21 μm). In addition, both water and ozone coreactants were evaluated, the latter having not been evaluated previously for pharmaceutical particles. The deposition process is carried out at ambient conditions in a fluidized bed reactor for a low number of cycles (i.e., from 4 to 14). Improved dissolution and extended release were achieved by the ALD nanoengineering of both crystalline and amorphous surfaces. This novel concept opens up exciting opportunities to produce more complex materials and structures using temperature- and moisture-sensitive drugs, e.g., targeting and drug delivery opportunities, as well as delivering new functionalities for novel applications in the pharmaceutical, medical, biological, and advanced materials fields. The prospects for advancing inhaled drug delivery are exemplified by the ALD surface nanoengineering concept.","alumina; atomic layer deposition; improved dispersibility; lactose; pharmaceutical; powders; slowed dissolution; surface modification","en","journal article","","","","","","Accepted Author Manuscript","","2020-03-01","","","ChemE/Product and Process Engineering","","",""
"uuid:8a6e430a-eccf-4cd1-bb1e-0268fb624b7c","http://resolver.tudelft.nl/uuid:8a6e430a-eccf-4cd1-bb1e-0268fb624b7c","A non-collocated method to quantify plastic deformation caused by impact pile driving","Meijers, P.C. (TU Delft Offshore Engineering); Tsouvalas, A. (TU Delft Offshore Engineering); Metrikine, A. (TU Delft Offshore Engineering; TU Delft Engineering Structures)","","2018","The use of bolted connections between the tower and a support structure of an offshore wind turbine has created the need for a method to detect whether a monopile foundation plastically deforms during the installation procedure. Small permanent deformations are undesirable, not only because they can accelerate fatigue of the structure; but also because they can lead to misalignment between the tower and the foundation. Since direct measurements at the pile head are difficult to perform, a method based on non-collocated strain measurements is highly desirable. This paper proposes such a method. First, a physically non-linear one-dimensional model is proposed, which accounts for wave dispersion, effects that are relevant for large-diameter piles currently used by the industry. The proposed model, combined with an energy balance principle, gives an upper bound for the amount of plastic deformation caused by an impact load based on simple strain measurements. This is verified by a lab-scale experiment with a uni-axial stress state. Second, measurement data collected during pile driving of a large-diameter pile show that the proposed one-dimensional model, while able to predict the peak stresses, fails to accurately predict the full time history of the measured stress state. In contrast, an advanced model based on shell membrane theory is able to do that, showing that a bi-axial stress state is needed for these type of structures. This requires an extension of the theory for plasticity quantification presented in this paper.","Impact pile driving; Plastic deformation; Wave dispersion","en","journal article","","","","","","","","2020-08-25","","Engineering Structures","Offshore Engineering","","",""
"uuid:be0be1e4-b53b-4a90-99ab-d66c16a73f4b","http://resolver.tudelft.nl/uuid:be0be1e4-b53b-4a90-99ab-d66c16a73f4b","Dispersion Properties of Explicit Finite Element Methods for Wave Propagation Modelling on Tetrahedral Meshes","Geevers, S. (University of Twente); Mulder, W.A. (TU Delft Applied Geophysics and Petrophysics; Shell Global Solutions International B.V.); van der Vegt, J. J.W. (University of Twente)","","2018","We analyse the dispersion properties of two types of explicit finite element methods for modelling acoustic and elastic wave propagation on tetrahedral meshes, namely mass-lumped finite element methods and symmetric interior penalty discontinuous Galerkin methods, both combined with a suitable Lax–Wendroff time integration scheme. The dispersion properties are obtained semi-analytically using standard Fourier analysis. Based on the dispersion analysis, we give an indication of which method is the most efficient for a given accuracy, how many elements per wavelength are required for a given accuracy, and how sensitive the accuracy of the method is to poorly shaped elements.","Discontinuous Galerkin method; Dispersion analysis; Explicit finite element method; Mass lumping; Tetrahedral mesh; Wave equation","en","journal article","","","","","","","","","","","Applied Geophysics and Petrophysics","","",""
"uuid:9c84e607-89c4-49ac-ae9d-4448fb2706e5","http://resolver.tudelft.nl/uuid:9c84e607-89c4-49ac-ae9d-4448fb2706e5","Compliant Remote-Center-of-Motion Mechanism Optimized for Energy-Dispersive Spectroscopy","Janssen, Janeau (TU Delft Mechanical, Maritime and Materials Engineering; TU Delft Precision and Microsystems Engineering)","Herder, J.L. (graduation committee); Tolou, N. (mentor); Farhadi Machekposhti, D. (mentor); Ghatkesar, M.K. (graduation committee); Delft University of Technology (degree granting institution)","2018","In-situ sample holders with double-tilting capabilities are used to insert and position samples inside a transmission electron microscope for dynamic imaging. However, the performance of these sample holders, regarding energy-dispersive X-ray spectroscopy (EDS) analysis, is not on par with their single-tilt counterparts. By analyzing the EDS influences and the tilting mechanism of double-tilt sample holders, the need for a remote-center-of-motion (RCM) mechanism as a tilting mechanism is identified. Because existing RCM mechanism design strategies limit the design flexibility, a novel design strategy is developed. The novel strategy gives more flexibility in terms of the use of space, design for stiffness and it gives variable input/output link rotation ratio functionality. A compliant proof-of-principle mechanism, which is designed using the novel RCM mechanism design strategy, is manufactured to characterize the accuracy, force/displacement behavior and the input/output link rotation ratio. Analytical, numerical and experimental results are compared, and it can be concluded that the compliant RCM mechanism has potential to be used in double-tilt sample holders.","Classification; Compliant Mechanisms; Design strategy; energy-dispersive X-ray spectroscopy; kinematics; remote-center-of-motion; sample holder","en","master thesis","","","","","","","","2019-12-31","","","","Mechanical Engineering | Mechatronic System Design (MSD)","",""
"uuid:221b8af2-1413-4681-b65c-67a8c5b785b4","http://resolver.tudelft.nl/uuid:221b8af2-1413-4681-b65c-67a8c5b785b4","The suburban commons","Santilli, Virginia (TU Delft Architecture and the Built Environment)","Cavallo, R. (mentor); Read, S.A. (mentor); Jennen, P.H.M. (mentor); Delft University of Technology (degree granting institution)","2018","In European suburban areas, shopping centres are the main attractor, socially and commercially. Overcoming the scale of small town centres and providing a common regional place, these world interiors of capital are building a new territorial identity.
Nevertheless, today online shopping is denaturating shopping centres, turning them into entertaining centres.
The project deals with very different scales to envision a future scenario for the Western European dispersed city and to frame to future the role of the mall for these territories. The suburban commons proposes a mediation between the public, the private and the collective to imagine a new regional centre that breaks the sole commercial function and provides a place to gather, a space of appearance, linked to its territory. It imagines a sustainable, convivial scenario that rethinks the shopping centre and prepares the territory for a possible post-mall phase.","Dispersed city; Suburban; Shopping centre; Commons; Role of architect; Microstories","en","master thesis","","","","","","","","","","","","Architecture, Urbanism and Building Sciences | Explorelab","","45.572553, 11.933290"
"uuid:8ae6954d-10f2-408a-a53a-80f46ba232d8","http://resolver.tudelft.nl/uuid:8ae6954d-10f2-408a-a53a-80f46ba232d8","Evaluation of Micromixing Models for Turbulent Mixing in Supercritical Water","Koene, Michael (TU Delft Applied Sciences; TU Delft Electrical Engineering, Mathematics and Computer Science)","Roekaerts, Dirk (mentor); Heemink, Arnold (mentor); Pecnik, Rene (graduation committee); Redig, Frank (graduation committee); Delft University of Technology (degree granting institution)","2018","Hydrothermal flames have become a very important field of study, especially for supercritical water oxidation. In supercritical water oxidation hazardous, toxic or non-biodegradable aqueous organic waste water streams can be efficiently destructed. Supercritical water oxidation takes place in a aqueous environment above the supercritical point.
In the case of turbulent flow, micromixing models are needed.
In this work, three different mixing models are analysed in a hydrothermal flame environment. These models are Interaction by Exchange with the Mean, Coalescence/Dispersion and the Mapping Closure model. When the mixing is done around temperatures far below or far above the pseudocritical temperature all models gave the same evolution of average temperature. However when the mixing is done around the pseudocritical temperature the differences are large. The Mapping Closure model is best in agreement with the Navier-Stokes equations so it is advised to use that model when simulating mixing around the pseudocritical temperature.","Hydrothermal flames; supercritical water; micromixing; Interaction by exchange with the mean; Coalescence/Dispersion; Mapping Closure","en","bachelor thesis","","","","","","","","","","","","","",""
"uuid:9fa0bdd9-29b4-489c-9799-b86e07e92813","http://resolver.tudelft.nl/uuid:9fa0bdd9-29b4-489c-9799-b86e07e92813","Model Reduction of Wave Equations: Theory and applications in Forward modeling and Imaging","Zimmerling, J.T. (TU Delft Signal Processing Systems)","Urbach, Paul (promotor); Remis, R.F. (promotor); Delft University of Technology (degree granting institution)","2018","HoW do you look inside a box without opening it? How can we know whether or not a heart valve is functioning correctly without cutting a person open? Imaging – the art of seeing the unseeable. A CT-scan at the doctor’s office, crack detection in the wing of an airplane, and medical ultrasound are all examples of imaging techniques that allow us to inspect the interior of an object or person and enable us to observe features that are not directly visible to the naked eye. Science continuously improves upon existing imaging methods and occasionally invents new ones leading to improved image quality and faster image acquisition. Many imaging applications rely on acoustic, electromagnetic, or elastodynamic waves for imaging. These methods use waves to illuminate a penetrable object, and then forman image of its interior from measurements of transmitted or scattered waves. In such imaging problems efficient computation of wavefields in complex geometries is key. New mathematical methods and algorithms are needed to keep up with the demands of the imaging industry – advancements in the computer industry alone cannot respond to the shift towards larger domains, higher resolution, and larger data sets. This thesis is about reduced-order modeling of the equations that describe the dynamics of wave propagation. In reduced-order modeling, the aim is to systematically develop a small model that describes a complex system without losing information that is valuable for a specific application. Evaluating such a model is computationally much more efficient than direct evaluation of the unreduced system and in the context of imaging it can lighten the computational burden associated with imaging algorithms. The central question is, of course: How does one construct a model that describes the wave dynamics relevant to a particular application? Wave equations are partial differential equations that interrelate the spatial and temporal variations of a particular physical wavefield quantity. When we discretize such equations in space, sparse systems of equations with hundreds of thousands or even millions of unknowns are obtained. Via projection onto a small subspace such a largescale system can be reduced to a much smaller reduced system. The solution of this small system is called a reduced-order model. A properly constructed reduced-order model can be easily evaluated and gives an accurate wavefield description over a certain time or frequency interval or parameter range of interest. In this thesis, we discuss different choices for the subspaces that are used for projection in model-order reduction. In particular, we show which types of subspaces are effective for wavefields that are localized and highly resonant and how to efficiently generate such subspaces by exploiting certain symmetry properties of the wave equations. We illustrate the effectiveness of the resulting reduced-order models by computing optical wavefield responses in three-dimensional metallic nano-resonators. Not all wavefields are determined by a few resonances, of course. Waves can also travel over long distances without losing information; a property that is used by mobile phones every day. The reduction methods developed for resonating fields are not efficient for these types of propagation problems and require a different approach. In this thesis, we present a so-called phase-preconditioning reduction method, in which a specific subspace is generated that explicitly takes the large travel times of the waves into account. We demonstrate the effectiveness of this reduction approach using examples from geophysics, where waves with long travel times are frequently encountered or used to probe the subsurface of the Earth. Finally, we show how reduced-order modeling techniques can be incorporated into advanced nonlinear imaging algorithms. Here, we focus on an imaging application in geophysics, where the goal is to retrieve the conductivity tensor of a bounded anomaly located in the subsurface of the Earth, based on measured electromagnetic field data collected on a borehole axis. We demonstrate that the use of reduced-order models in a nonlinear optimization framework does indeed lead to significant computational savings without sacrificing the quality of imaging results. To illustrate the wide applicability of model-order reduction techniques in imaging, an additional example from nuclear geophysical imaging is also presented.","Maxwell Equations; Reduced-Order Modeling; Dispersive Media; Open Resonators; Krylov","en","doctoral thesis","","978-94-6186-927-2","","","","","","","","","Signal Processing Systems","","",""
"uuid:c151739e-716f-40e4-b1c7-66039ac7d643","http://resolver.tudelft.nl/uuid:c151739e-716f-40e4-b1c7-66039ac7d643","Data-driven hazardous gas dispersion modeling using the integration of particle filtering and error propagation detection","Zhu, Zhengqiu (National University of Defense Technology); Qiu, S. (TU Delft Web Information Systems; National University of Defense Technology); Chen, Bin (National University of Defense Technology); Wang, Rongxiao (National University of Defense Technology); Qiu, Xiaogang (National University of Defense Technology)","","2018","The accurate prediction of hazardous gas dispersion process is essential to air quality monitoring and the emergency management of contaminant gas leakage incidents in a chemical cluster. Conventional Gaussian-based dispersion models can seldom give accurate predictions due to inaccurate input parameters and the computational errors. In order to improve the prediction accuracy of a dispersion model, a data-driven air dispersion modeling method based on data assimilation is proposed by applying particle filter to Gaussian-based dispersion model. The core of the method is continually updating dispersion coefficients by assimilating observed data into the model during the calculation process. Another contribution of this paper is that error propagation detection rules are proposed to evaluate their effects since the measured and computational errors are inevitable. So environmental protection authorities can be informed to what extent the model output is of high confidence. To test the feasibility of our method, a numerical experiment utilizing the SF6 concentration data sampled from an Indianapolis field study is conducted. Results of accuracy analysis and error inspection imply that Gaussian dispersion models based on particle filtering and error propagation detection have better performance than traditional dispersion models in practice though sacrificing some computational efficiency.","Atmospheric dispersion; Data-driven modeling; Error propagation; Gaussian dispersion model; Particle filter; OA-Fund TU Delft","en","journal article","","","","","","","","","","","Web Information Systems","","",""
"uuid:c5ee953e-21c0-4dbd-b3d2-e51fd782e708","http://resolver.tudelft.nl/uuid:c5ee953e-21c0-4dbd-b3d2-e51fd782e708","Effects of a fence on pollutant dispersion in a boundary layer exposed to a rural-to-urban transition","Eisma, H.E. (TU Delft Fluid Mechanics); Tomas, J.M. (TU Delft Fluid Mechanics); Pourquie, M.J.B.M. (TU Delft Fluid Mechanics); Elsinga, G.E. (TU Delft Fluid Mechanics); Jonker, H.J.J. (TU Delft Atmospheric Physics); Westerweel, J. (TU Delft Fluid Mechanics)","","2018","Simultaneous particle-image velocimetry and laser-induced fluorescence combined with large-eddy simulations are used to investigate the flow and pollutant dispersion behaviour in a rural-to-urban roughness transition. The urban roughness is characterized by an array of cubical obstacles in an aligned arrangement. A plane fence is added one obstacle height h upstream of the urban roughness elements, with three different fence heights considered. A smooth-wall turbulent boundary layer with a depth of 10h is used as the approaching flow, and a passive tracer is released from a uniform line source 1h upstream of the fence. A shear layer is formed at the top of the fence, which increases in strength for the higher fence cases, resulting in a deeper internal boundary layer (IBL). It is found that the mean flow for the rural-to-urban transition can be described by means of a mixing-length model provided that the transitional effects are accounted for. The mixing-length formulation for sparse urban canopies, as found in the literature, is extended to take into account the blockage effect in dense canopies. Additionally, the average mean concentration field is found to scale with the IBL depth and the bulk velocity in the IBL.","Large-eddy simulation; Laser-induced fluorescence; Mixing-length model; Pollutant dispersion; Stereoscopic particle-image velocimetry","en","journal article","","","","","","","","","","","Fluid Mechanics","","",""
"uuid:09ffab37-9f0d-4156-852e-bb39948fc159","http://resolver.tudelft.nl/uuid:09ffab37-9f0d-4156-852e-bb39948fc159","Air pollutant sinks on noise barriers: Where do they perform the best?","Dash, A. (TU Delft Multi Phase Systems); Elsinga, G.E. (TU Delft Fluid Mechanics)","","2018","While laboratory experiments, numerical simulations as well as field tests have underlined the influence of noise barriers in dispersing vehicular emissions and reducing downwind peak concentrations, these pollutants still remain in the atmosphere. Artificial pollutant sinks (for example, particle capturing or toxic gas treating devices) installed on top of noise barriers can further alleviate this problem by eliminating the pollutants passing through it. However, it is not known how the installation of a semi-permeable pollutant sink affects the aerodynamics of the pollutants’ flow. By finding an optimal position and orientation for these sinks, the mass of the pollutants reaching the sink inlet can be maximized. Scaled down water tunnel experiments have been used to investigate the effectiveness of installing such a pollutant sink, of fixed dimensions, on top of a noise barrier adjacent to a highway. It is found that installing a sink is more beneficial on top of shorter barriers and that vertically elevating the sink, only slightly, can enhance its pollutant capturing performance. Using a sink in a ‘highway canyon’ (two noise barriers placed symmetrically with respect to the highway) must be done cautiously as there are several flow regimes observed, which are sensitive not only to the canyon aspect ratio (ratio between canyon width and height), but also to the presence/absence of the sink. The results here not only demonstrate the effectiveness of installing pollutant sinks on noise barriers, but also provide ballpark estimates on the optimal placement, orientation and performance of these devices, prior to field tests or even large-scale installation.","Air pollutant sinks; Highway canyon; Laboratory scale experiments; Noise barrier; Pollutant dispersion","en","journal article","","","","","","Accepted Author Manuscript","","2020-06-02","","","Multi Phase Systems","","",""
"uuid:a7a44200-864d-4d88-bb04-0a4224f9271e","http://resolver.tudelft.nl/uuid:a7a44200-864d-4d88-bb04-0a4224f9271e","Hazardous Source Estimation Using an Artificial Neural Network, Particle Swarm Optimization and a Simulated Annealing Algorithm","Wang, Rongxiao (National University of Defense Technology); Chen, B. (National University of Defense Technology); Qiu, S. (TU Delft Web Information Systems; National University of Defense Technology); Ma, Liang (National University of Defense Technology); Zhu, Zhengqiu (National University of Defense Technology); Wang, Yiping (Naval 902 Factory); Qiu, Xiaogang (National University of Defense Technology)","","2018","Locating and quantifying the emission source plays a significant role in the emergency management of hazardous gas leak accidents. Due to the lack of a desirable atmospheric dispersion model, current source estimation algorithms cannot meet the requirements of both accuracy and efficiency. In addition, the original optimization algorithm can hardly estimate the source accurately, because of the difficulty in balancing the local searching with the global searching. To deal with these problems, in this paper, a source estimation method is proposed using an artificial neural network (ANN), particle swarm optimization (PSO), and a simulated annealing algorithm (SA). This novel method uses numerous pre-determined scenarios to train the ANN, so that the ANN can predict dispersion accurately and efficiently. Further, the SA is applied in the PSO to improve the global searching ability. The proposed method is firstly tested by a numerical case study based on process hazard analysis software (PHAST), with analysis of receptor configuration and measurement noise. Then, the Indianapolis field case study is applied to verify the effectiveness of the proposed method in practice. Results demonstrate that the hybrid SAPSO algorithm coupled with the ANN prediction model has better performances than conventional methods in both numerical and field cases.","Artificial neural network; Atmospheric dispersion model; Particle swarm optimization; Simulated annealing algorithm; Source estimation","en","journal article","","","","","","","","","","","Web Information Systems","","",""
"uuid:e681175a-09f1-4ad3-a599-fd2cd876a9d7","http://resolver.tudelft.nl/uuid:e681175a-09f1-4ad3-a599-fd2cd876a9d7","Comparison of Machine Learning Models for Hazardous Gas Dispersion Prediction in Field Cases","Wang, Rongxiao (National University of Defense Technology); Chen, B. (National University of Defense Technology); Qiu, S. (TU Delft Web Information Systems; National University of Defense Technology); Zhu, Zhengqiu (National University of Defense Technology); Wang, Yiduo (National University of Defense Technology); Wang, Yiping (Naval 902 Factory); Qiu, Xiaogang (National University of Defense Technology)","","2018","Dispersion prediction plays a significant role in the management and emergency response to hazardous gas emissions and accidental leaks. Compared with conventional atmospheric dispersion models, machine leaning (ML) models have both high accuracy and efficiency in terms of prediction, especially in field cases. However, selection of model type and the inputs of the ML model are still essential problems. To address this issue, two ML models (i.e., the back propagation (BP) network and support vector regression (SVR) with different input selections (i.e., original monitoring parameters and integrated Gaussian parameters) are proposed in this paper. To compare the performances of presented ML models in field cases, these models are evaluated using the Prairie Grass and Indianapolis field data sets. The influence of the training set scale on the performances of ML models is analyzed as well. Results demonstrate that the integrated Gaussian parameters indeed improve the prediction accuracy in the Prairie Grass case. However, they do not make much difference in the Indianapolis case due to their inadaptability to the complex terrain conditions. In addition, it can be summarized that the SVR shows better generalization ability with relatively small training sets, but tends to under-fit the training data. In contrast, the BP network has a stronger fitting ability, but sometimes suffers from an over-fitting problem. As a result, the model and input selection presented in this paper will be of great help to environmental and public health protection in real applications.","Back propagation network; Field case; Hazardous gas dispersion prediction; Input selection; Support vector regression","en","journal article","","","","","","","","","","","Web Information Systems","","",""
"uuid:af9c1089-b779-47c0-b213-18ec64a7d155","http://resolver.tudelft.nl/uuid:af9c1089-b779-47c0-b213-18ec64a7d155","A data-driven approach for optimal design of integrated air quality monitoring network in a chemical cluster","Zhu, Zhengqiu (National University of Defense Technology); Chen, B. (National University of Defense Technology); Qiu, S. (TU Delft Web Information Systems); Wang, Rongxiao (National University of Defense Technology); Wang, Yiping (Naval 902 Factory); Ma, Liang (National University of Defense Technology); Qiu, Xiaogang (National University of Defense Technology)","","2018","The chemical industry is of paramount importance to the world economy and this industrial sector represents a substantial income source for developing countries. However, the chemical plants producing inside an industrial district pose a great threat to the surrounding atmospheric environment and human health. Therefore, designing an appropriate and available air quality monitoring network (AQMN) is essential for assessing the effectiveness of deployed pollution-controlling strategies and facilities. As monitoring facilities located at inappropriate sites would affect data validity, a two-stage data-driven approach constituted of a spatio-temporal technique (i.e. Bayesian maximum entropy) and a multi-objective optimization model (i.e. maximum concentration detection capability and maximum dosage detection capability) is proposed in this paper. The approach aims at optimizing the design of an AQMN formed by gas sensor modules. Owing to the lack of long-term measurement data, our developed atmospheric dispersion simulation system was employed to generate simulated data for the above method. Finally, an illustrative case study was implemented to illustrate the feasibility of the proposed approach, and results imply that this work is able to design an appropriate AQMN with acceptable accuracy and efficiency.","air quality monitoring network; atmospheric dispersion simulation system; Bayesian maximum entropy; multi-objective optimization model","en","journal article","","","","","","","","","","","Web Information Systems","","",""
"uuid:f0740b7d-1e09-4a4c-ae70-53b13affd231","http://resolver.tudelft.nl/uuid:f0740b7d-1e09-4a4c-ae70-53b13affd231","Analysis of the measured data of sediment nourishments in the Rhine River","Emmanouil, Antonis (TU Delft Civil Engineering and Geosciences; TU Delft Hydraulic Engineering)","Delft University of Technology (degree granting institution)","2017","Sediment nourishments have become an attractive alternative to hard measures in counteracting long-term river bed degradation. Due to the large degree of uncertainty concerning mixed sediment morphodynamics, river authorities conduct field studies to collect data that will help in the calibration of morphological models, eventually used to design effective mitigation measures.
In the present study, we analyse measured data from two field experiments in the Rhine river, that monitored the fate of the mixed-size nourished sediment. In the first study case, we analyse data from a 5 year monitoring campaign at the reach below the most downstream weir in the Rhine river. The sieving analyses of the soil samples collected from the bed of the study reach, reveal the concentrations of various tracer granite fractions at several vertical layers, lateral positions and cross sections along the streamwise direction. Second, we studied the early development of the nourishment pilot study initiated in 2016 at Lobith, a reach situated further downstream in the Rhine river. In spite of the early stage of the nourishment, due to intensive monitoring of the pilot, data are collected in dense time intervals by means of bed surveys, radioactivity measurements for the detection of tracer sediment as well as soil samples, revealing the initial morphodynamic trends in the study reach.
In both study cases we predominantly focus on the migration of nourished sediment in all directions and the main physical processes that regulate the feedback between flow and mixed sediment morphodynamics. We conclude that nourished sediment disperses along the streamwise direction, gets mixed into larger depths as it migrates downstream, but also follows certain paths along the mitigated meandering reaches. We found that especially vertical mixing of nourished sediment is a major control on its streamwise migration. Regarding certain of these aspects, the various grain size fractions of the nourished sediment were seen to behave differently. For example ner fractions
migrated downstream faster, but were also mixed in larger depths below Iffezheim. In the present study we assess the in influence of temporal and spatial flow variability, but also the inuence of small and large scale processes which are relevant in mixed sediment morphodynamics. The feedback between
ow and mixed sediment morphodynamics is key in explaining the main physical processes controlling the fate of nourished sediment, yet more work needs to be done to assess which are the dominant small and large scale physical mechanisms when mixed-size sediment feeding in lowland rivers is considered.
Scaled down experiments were performed in a water channel, housed in the Laboratory for Aero and Hydrodynamics at the Delft University of technology. Simultaneous measurements of the flow velocities and dye intensities in the symmetry-plane of the channel were made through planar Particle Image Velocimetry (PIV) and Planar Laser Induced Fluorescence (PLIF). A few flow configurations were studied by varying certain parameters. It was found that: (a) ESP installation is more beneficial on top of shorter sound barriers. (b) Slightly raising the ESP from the top of the sound barrier is advantageous. (c) Installation of ESPs in isolated highway canyons should be done with care, as several flow regimes are observed.
First order estimates on the aerodynamic efficiencies of the ESP were determined. This was accompanied by the identification of ESP performance trends that should serve as a guideline for the initial testing of the ESPs at full scale. The guidelines include the physical location and entrance orientation of the ESP. It is known that the collection efficiency of the ESP is a function of the incoming flow velocity. It is recommended that the entrance flow velocities reported here be used as an input for calculating the associated particle collection efficiency. Together, the collection and aerodynamic efficiencies can be used to estimate the overall efficiency of the ESP. If the overall efficiency satisfies a minimum desirable threshold, the field experiments yield promising results, the device clears safety requirements, and the benefits outweigh the costs, the ‘Open Air Line ESP’ can be installed along the highways en masse in the future.","Pollution dispersion; Scaled down experiments; Aerodynamics; Particle Image Velocimetry; Laser Induced Fluorescence; Particulate Matter; Air quality improvement; Electrostatic Precipitators; Sound barriers; Highways","en","master thesis","","","","","","","","","","","","","",""
"uuid:07a91b3a-7068-48fd-a74f-1f7906602832","http://resolver.tudelft.nl/uuid:07a91b3a-7068-48fd-a74f-1f7906602832","Dispersion in the Ayeyarwady: A description of the mixing of tracers in the area of the Ayeyarwady River- Chindwin River confluence","Bakker, Tije (TU Delft Civil Engineering and Geosciences; TU Delft Hydraulic Engineering)","Rutten, Martine (mentor); Sloff, Kees (mentor); Delft University of Technology (degree granting institution)","2017","The Ayeyarwady River (also called Irrawaddy River) is the most important river of Myanmar and due to the country’s rapid development it is expected to become even more important. The river flows roughly from north to south through Myanmar and is very dynamic and mostly unregulated. With a length of 2170 km and an over the year average (highly seasonally varying) discharge of 13’000 m3/s into the Andaman Sea (Bhardwaj, Owen, & Leinbach, 2012), the Ayeyarwady is one of the bigger rivers in Asia. To more than before take into account the interests of different stakeholders, as well as ecological aspects, sustainable management of the river is needed. Understanding the key aspects of the river flow can be a first step to sustainable river management (Richter et al., 2003). Pollution due to a large variety of activities of different nature make that water quality monitoring is of high importance (Thanda Thatoe Nwe Win, Bogaard, & Van de Giesen, 2015). For monitoring and modelling the water quality, information about the mixing of tracers trough the river is needed, which can be quantified with the use of dispersion coefficients. Little research has been done about the Ayeyarwady River in general considered its size and importance. Very limited data about the mixing of tracers and the parameters needed to estimate the mixing of tracers was available. This research focuses on the situation around the Ayeyarwady-Chindwin confluence in the first week of February 2017 (dry season). Hence, there is a very different situation during for example wet season. For the water quality, mainly the mixing in the longitudinal direction (direction of the main river flow) is of interest, which can be quantified by a longitudinal dispersion coefficient (Kx). First relevant parameters for estimating Kx were identified based on the theory. This appeared to be the discharge, roughness and bathymetry. Besides, Kx has to be calibrated by floater experiments. To get better insight into the magnitude of these parameters, flow velocity and depth measurements (needed for estimating the discharge, roughness and bathymetry) and floater experiments have been done during a week of fieldwork in the area. Due to loss, theft and destruction of floaters, less data was collected than planed. To get further insight in the mixing of tracers, a numerical model was made in the software Delft3D based on data collected during the fieldwork. Based on the combined results of the theory, measurements done during the fieldwork and the Delft3D model, it is expected that the magnitude of Kx in the Ayeyarwady River is somewhere in between 50-500 m2/s (best estimate: Kx~300 m2/s), although this has to be confirmed by further research. When the found value is compared with values found for other bigger rivers this value for Kx appears to be somewhat on the low side. From the Delft3D model runs follows that the longitudinal dispersion coefficient in the Chindwin River is higher than in the Ayeyarwady, possibly even a factor 10. Besides, insight in the effect of the different parameters on the dispersion was obtained, contributing to a better understanding of processes causing the mixing of tracers in the Ayeyarwady and Chindwin rivers. Estimating the highly sensitive longitudinal dispersion coefficient (Kx) appeared to be challenging, mostly due to the remote and highly dynamic character of the area. To make a better estimate of Kx, the uncertainty in the parameters needed (discharge, roughness, bathymetry and spreading of floaters for calibration) has to be reduced. Although some modelling options in Delft3D could be tried to narrow the range of these parameters, the best option to reduce this uncertainty is collecting more (high quality) data in the field.","Myanmar; Ayeyarwady River; Dispersion; Delft3D; Confluence","en","student report","","","","","","","","","","","","","","21.466510, 95.285375"
"uuid:27050a98-9c91-41f0-975a-c40535439caf","http://resolver.tudelft.nl/uuid:27050a98-9c91-41f0-975a-c40535439caf","Metropolitan Region Vienna-Bratislava, rethinking the dispersed territory in-between the two capital cities","Überbacher, A.","Nadin, V. (mentor); Wandl, A. (mentor); Viganó, P. (mentor)","2017","This thesis was written in the course of the European Postgraduate Master in Urbanism – Strategies and Design for Cities and Territories (EMU) at the Department of Urbanism in the Faculty of Architecture of the Delft University of Technology (TU Delft) in the Netherlands. The research analyses the spatial condition and the planning system in the dispersed territory between the two capital cities Vienna and Bratislava. Further, the thesis offers an alternative approach to guide the on-going urban transformation process in the dispersed territory between Vienna in Austria and Bratislava in Slovakia. In particular the work is dedicated to the question to what extend it is possible to foster more sustainability in the territory, while at the same time providing enough space for the growing population in the territory. The therefore established framework for a more sustainable region consists of a design research part on regional and local scale including a sustainable growth concept, and recommendations for the planning system. The proposal not only offers the opportunity to rethink the territory by using design as a research tool, but also combines this methodology with a reflection on the existing strategic planning in the territory and its output in space.","Vienna; Bratislava; dispersed territories; dispersion; Concept Horizontal Metropolis; urban sprawl; territory in-between; metropolitan territory Vienna-Bratislava; research based design; urbanism","en","master thesis","","","","","","","","2018-08-31","Architecture and The Built Environment","Urbanism","","European Postgraduate Master in Urbanism (EMU)","",""
"uuid:d7633f67-7686-46a3-abbc-ea6c25897fdc","http://resolver.tudelft.nl/uuid:d7633f67-7686-46a3-abbc-ea6c25897fdc","Spreading of polluted sediment around the U-864 wreck: Analyses of currents and sediment dispersal during installation of a capping layer using a fexible fallpipe vessel","van Miltenburg, Marlies (TU Delft Civil Engineering and Geosciences; TU Delft Hydraulic Engineering)","Pietrzak, J.D. (mentor); Chassagne, C. (graduation committee); Jommi, C. (graduation committee); de Boer, G.J. (graduation committee); Laugesen, Jens (graduation committee); Delft University of Technology (degree granting institution)","2017","Four kilometers west of the Norwegian island Fedje, mercury, leaking from the U-864 wreck, has highly polluted a seabed area of approximately 40 000 m2. The bow section of the wreck is located on a stability critical slope of 15 degrees. In 2016, Van Oord used a flexible fall pipe system to install a counter fill to stabilize the wreck and simultaneously cap a portion of the contaminated area. In the future, the Norwegian government plans to cap the complete area to prevent further dispersion of mercury. This research aims to gain more knowledge about the spreading of sediments during such an operation occurring under realistic hydrodynamic conditions. A more complete understanding of the process will allow for better risk assessment of future capping operations. To this end, the unique data set gathered during the counter fill project has been analyzed.
In order to predict extreme flow events, the bottom currents are decomposed. By decomposing the erratic velocity signal, tidal (25 %) and inter-tidal residual current (38 %) components are identified and understood. However, the driving force for the remaining intra-tidal part, which contains the highest current anomaly events, cannot be identified. Evidence is found for the occurrence of internal waves providing a possible explanation. Due to a lack of data, a quantitative prediction cannot be made. Consequently, the exact maximum currents at the site are unpredictable, but stayed below 0.4 m/s during the project.
During the installation work, high turbidity clouds have been measured. The origin is investigated by analyzing the particle size distribution and the mercury concentration of sediment samples; said samples are drawn from the capping material, the installed capping layer and sediment traps placed around the wreck. The findings indicate that the clouds are caused by a loss of clean material and are not from the contaminated seabed. This is supported by modeling the dispersal of clean particles from the flexible fall pipe. The promising results regarding the use of a flexible fall pipe for capping layer installation are not only applicable for the U-864 area but also for other polluted offshore areas.
pumped semiconductor materials. Such devices exploit the photoconductivity phenomenon to generate and radiate power over a broadband up to the THz frequencies. However, nowadays the use of photoconductive antennas are confined to niche short-range applications, because of the bottleneck of the low power emitted. Early in this research work, it was understood that such bottleneck came from the fact that there was not a clear description about the coupling between the photocondcutive source and the antenna. For this reason,
this work has been focused to develop a Thévenin or Norton equivalent circuit for the photoconductor generators of photoconductive antennas.
A Norton equivalent circuit for pulsed photoconductive antennas has been derived, starting by the electrodynamic model of the photogeneration of free carriers in laser pumped semiconductor material. Such equivalent circuit allows to maximize the radiated power as function of the geometry of the gap, the properties of the semiconductor material, and the features of the laser pump, providing a clear description of the coupling between the photoconductor generator and the antenna over the operative bandwidth.
An electromagnetic model of the quasi-optical (source-to-detector) channel, typically used for measuring power and spectrum radiated by photoconductive antennas, has been proposed. Such model jointly with the developed Norton equivalent circuit allows a complete characterization of the power budget from the source to the detector. Providing for the first time a complete description about the dispersion introduced by the quasi-optical channel on the energy spectrum radiated by photoconductive antennas. The entire proposed model (equivalent circuit and channel) has been validated by spectrum and power
measurements of photoconductive antenna prototypes.
The proposed equivalent circuit and the electromagnetic model of the quasi-optical channel provide a powerful engineering tool to design photoconductive antennas, opening the way for more standard engineering optimization of wide band laser pumped sources, resorting to the vast heritage of wide band microwave engineering tools that have been developed mostly for analyzing detectors in radiometric domains.
The radiation performances of logarithmic spiral antennas as feed of dense dielectric lenses has been intensively analyzed. The results of the investigation have demonstrated the presence of the leaky wave radiation, when the spiral antenna are printed at the air dielectric interface, leading to a design of a logarithmic spiral antenna lens antenna, which provides an high aperture efficiency over a decade frequency bandwidth. However, only using extremely thin substrate allows to feed this design with a planar feeding system without limiting the bandwidth. A new design of a logarithmic spiral lens antenna has been proposed for relaxing such limitation, introducing a small air gap between the spiral feed and the bottom lens interface, which enhances the leaky wave radiation. Such new design, coupled with a synthesized elliptical lens, achieves directive patterns without sidelobes over a decade frequency bandwidth. Moreover, the new spiral design can be used also as feed of a hemispherical lens with low extension height, when the dispersion of the radiated pulses has to be minimized.
A novel design for photoconductive sources has been proposed, aiming to increase dramatically the radiated power with respect to the current photoconductive antennas. The new source is based on the well established concept in the microwave community of connected array. Thanks to the intrinsic wide band behavior of the connected array, the proposed solution is able to radiate efficiently the wide band energy spectrum generated by the photoconductive source. Such design is suitable to be employed also as receiver of ultra-wide bandwidth radiation, increasing the sensitivity with respect to the current photoconductive receivers. In order to implement the design of the photoconductive connected array, an ad-hoc biasing network has been proposed, in order to properly bias all the array cells, preserving the connected structure of the elements. Moreover, a design of an optical system has been proposed, in order to optically excite all the elements of the photoconductive array coherently. Using the proposed Norton equivalent circuit for photoconductive generator, a photoconductive connected array generating an average power of 2.35mW over a bandwidth from 0.1THz − 0.4THz has been designed. A demonstrator of the proposed photoconductive source design is going to be realized, and a complete characterization of the prototype will be performed by means of power and spectrum measurements, proving the validity of the concept.","photoconductivity; photoconductive antenna; THz source; THz technology; equivalent circuit; dispersion; leaky wave antenna; lens antenna; ultra-wideband antenna; ultra-wideband array","en","doctoral thesis","","978-94-028-0657-1","","","","","","2018-09-01","","","Tera-Hertz Sensing","","",""
"uuid:6c109908-b188-47b7-8193-ba45ee9030c6","http://resolver.tudelft.nl/uuid:6c109908-b188-47b7-8193-ba45ee9030c6","The behaviour of parent and daughter nuclides in aerosols released in radiological dispersion events: a study of a SrTiO3 source","van Maris, V. R. (European Commission, Joint Research Centre (JRC), Directorate for Nuclear Safety and Security,); Naji, M. (European Commission, Joint Research Centre (JRC), Directorate for Nuclear Safety and Security,); Di Lemma, F.G. (TU Delft RST/Reactor Physics and Nuclear Materials; European Commission, Joint Research Centre (JRC), Directorate for Nuclear Safety and Security,); Colle, J-Y (European Commission, Joint Research Centre (JRC), Directorate for Nuclear Safety and Security,); Bykov, D. (TU Delft RST/Reactor Physics and Nuclear Materials); Konings, R. (TU Delft RST/Reactor Physics and Nuclear Materials; European Commission, Joint Research Centre (JRC), Directorate for Nuclear Safety and Security,)","","2017","During rapid high-temperature events, like a terrorist attack with radiological dispersal device, radiological material will be released into the environment. In these scenarios, the ratio between parent and daughter nuclides can be used for nuclear forensic investigations to determine the age of the used radioactive source. We have used fast laser heating to produce aerosols of a material often found in radioisotope thermoelectric generators. To investigate the behaviour of SrTiO3, we have recreated pure and mixed samples, mimicking several parent-to-daughter ratios. By combining scanning electron microscopy and energy-dispersive X-ray spectroscopy analysis with Raman spectroscopy, we were able to distinguish different elements and phases present in the aerosols. Two types of aerosols have been identified: individual aerosols from a few micrometre to a few tens of micrometre and agglomerates of smaller aerosols from a few hundred nanometre to a few micrometre. The bigger aerosols, formed from mechanically expelled liquefied material, showed a parent-to-daughter ratio that stays close to the value that would be anticipated by the initial composition of the material, but in the agglomerates, formed from vaporised material, the presence of the daughter elements reduces significantly due to differences in the condensation behaviour.","aerosol characterisation; nuclear forensics; radiological dispersal device; Raman spectroscopy; strontium titanate","en","journal article","","","","","","","","","","","RST/Reactor Physics and Nuclear Materials","","",""
"uuid:020e282d-2e6a-43ac-b76a-dcc280d9feeb","http://resolver.tudelft.nl/uuid:020e282d-2e6a-43ac-b76a-dcc280d9feeb","Pollutant dispersion in boundary layers exposed to rural-to-urban transitions: Varying the spanwise length scale of the roughness","Tomas, J.M. (TU Delft Fluid Mechanics); Eisma, H.E. (TU Delft Fluid Mechanics); Pourquie, M.J.B.M. (TU Delft Fluid Mechanics); Elsinga, G.E. (TU Delft Fluid Mechanics); Jonker, H.J.J. (TU Delft Atmospheric Physics); Westerweel, J. (TU Delft Fluid Mechanics)","","2017","Both large-eddy simulations (LES) and water-tunnel experiments, using simultaneous stereoscopic particle image velocimetry and laser-induced fluorescence, have been used to investigate pollutant dispersion mechanisms in regions where the surface changes from rural to urban roughness. The urban roughness was characterized by an array of rectangular obstacles in an in-line arrangement. The streamwise length scale of the roughness was kept constant, while the spanwise length scale was varied by varying the obstacle aspect ratio l / h between 1 and 8, where l is the spanwise dimension of the obstacles and h is the height of the obstacles. Additionally, the case of two-dimensional roughness (riblets) was considered in LES. A smooth-wall turbulent boundary layer of depth 10h was used as the approaching flow, and a line source of passive tracer was placed 2h upstream of the urban canopy. The experimental and numerical results show good agreement, while minor discrepancies are readily explained. It is found that for (Formula presented.) the drag induced by the urban canopy is largest of all considered cases, and is caused by a large-scale secondary flow. In addition, due to the roughness transition the vertical advective pollutant flux is the main ventilation mechanism in the first three streets. Furthermore, by means of linear stochastic estimation the mean flow structure is identified that is responsible for street-canyon ventilation for the sixth street and onwards. Moreover, it is shown that the vertical length scale of this structure increases with increasing aspect ratio of the obstacles in the canopy, while the streamwise length scale does not show a similar trend.","Large-eddy simulation; Laser-induced fluorescence; Pollutant dispersion; Roughness transition; Stereoscopic particle image velocimetry","en","journal article","","","","","","","","","","","Fluid Mechanics","","",""
"uuid:e27fb9ab-2a9f-4245-a6e8-ead0bc55f030","http://resolver.tudelft.nl/uuid:e27fb9ab-2a9f-4245-a6e8-ead0bc55f030","The Effect of Stress Wave Dispersion on the Drivability Analysis of Large-Diameter Monopiles","Meijers, P.C. (TU Delft Offshore Engineering); Tsouvalas, A. (TU Delft Offshore Engineering); Metrikine, A. (TU Delft Offshore Engineering; TU Delft Applied Mechanics)","Vestroni, Fabrizio (editor); Gattulli, Vincenzo (editor); Romeo, Francesco (editor)","2017","Due to the increasing need for energy from renewable resources, a large number of offshore wind farms are planned to be constructed in the near future. Despite the plethora of available foundation concepts for offshore wind turbines, the monopile foundation is the most widely adopted concept in practice. To predict the installation process for a monopile a so-called drivability study is performed. Such a study allows one to decide on a number of key parameters for the installation process, such as, the appropriate size of the hydraulic hammer, the number of hammer blows and energy input needed to reach the final penetration depth, and the induced stresses in the system. The latter is important for the prediction of the fatigue life of the pile.
Currently, drivability studies are based on one-dimensional wave equation models as first proposed by Smith in the 1950s. These models are valid as long as the diameter of the pile is small compared to the excited wavelengths in the structure due to the hammer impact. For large-diameter monopiles that are currently being used in the offshore wind industry, the latter condition is not met and the effect of stress wave dispersion can no longer be neglected.
In this paper the classical wave equation model is amended by an extra term which accounts for the lateral inertia of the cross-section, resulting in the so-called Rayleigh-Love rod theory. With this new model, a parametric study is performed in which the effect of stress wave dispersion on the induced stresses and the number of hammer blows needed to reach the final penetration depth are assessed. A comparison with the results obtained from the classical model is also included in order to define the applicability range of the models. It is shown that the effect of stress wave dispersion can not be neglected for a drivability study of large-diameter monopiles.","Monopile foundation; drivability study; lateral inertia; wave equation; stress wave dispersion; offshore wind energy","en","conference paper","","","","","","","","","","","Offshore Engineering","","",""
"uuid:18c7dbdd-563f-4821-8da3-7dd1a93288c1","http://resolver.tudelft.nl/uuid:18c7dbdd-563f-4821-8da3-7dd1a93288c1","Comparing the Landscape Fragmentation and Accessibility of Green Spaces in Territories-in-Between across Europe","Wandl, Alex (TU Delft Environmental Technology and Design)","","2017","To improve the positive effects provided by green spaces on human well-being in dispersed urban areas is a key challenge for sustainable spatial development in Europe. This article presents a methodology that allows for the comparison of the potential of green spaces in Territories-in-Between across Europe, in a way that crosses the fields of urban ecology and urbanism. The article adds to the existing knowledge and understanding of the relation between the spatial organisation of systems of green spaces and their accessibility to biodiversity and human well-being. Firstly, it adapts the fragmentation index in a way that it can be applied to the specific spatial characteristics of Territories-in-Between. Secondly, it combines the fragmentation index with an indicator for accessibility of green spaces, in order to integrate aspects of ecology, human well-being and the spatial heterogeneity of the relation between them. The methodology is applied to ten areas across western Europe in order to inform decision and policy makers including urban planners, designers and environmental agencies to be able to assess the potential of system of green spaces for biological diversity and human well-being in an integrated manner.","accessibility of green spaces; dispersed urban development; ecosystem services; landscape fragmentation; OA-Fund TU Delft","en","journal article","","","","","","","","","","","Environmental Technology and Design","","",""
"uuid:79807f70-fc08-4ab1-987d-01fb984aa0c0","http://resolver.tudelft.nl/uuid:79807f70-fc08-4ab1-987d-01fb984aa0c0","An absorbing boundary condition for free surface water waves","Duz, B. (TU Delft Ship Hydromechanics and Structures; Maritime Research Institute Netherlands (MARIN)); Borsboom, M.J.A. (Deltares); Veldman, A.E.P. (Rijksuniversiteit Groningen); Wellens, P.R. (TU Delft Ship Hydromechanics and Structures; Deltares); Huijsmans, R.H.M. (TU Delft Ship Hydromechanics and Structures)","","2017","In this paper, the use of an absorbing boundary condition (ABC) is investigated for the numerical simulation of free surface water waves. An enhanced type of an ABC based on the first- and second-order Higdon boundary conditions is presented. The numerical implementation of the ABC using a staggered grid arrangement is explained in detail. Numerical examples are provided to demonstrate the performance of the proposed boundary conditions.","Directional effects; Dispersive effects; Higdon boundary condition; Local absorbing boundary condition; Regular and irregular water waves","en","journal article","","","","","","Accepted Author Manuscript Part of special issue: Ninth International Conference on Computational Fluid Dynamics (ICCFD9)","","2019-09-05","","","Ship Hydromechanics and Structures","","",""
"uuid:13a312cd-6ece-43b2-89ea-74cd736d4b45","http://resolver.tudelft.nl/uuid:13a312cd-6ece-43b2-89ea-74cd736d4b45","Instability of the flow over a porous surface: Linear stability analysis","Ghosh, S.","Loiseau, J.Ch. (mentor); Brandt, L. (mentor); Breugem, W.P. (mentor)","2016","Direct numerical simulations of the fully developed turbulent flow through a porous channel show the appearance of short span-wise rollers at the fluid-porous interface along with the streaky structures of wall-bounded turbulence near the upper wall of the channel. The scope of the present research project is to investigate the instabilities in porous channel flow by means of local linear stability analysis in order to elucidate their physical origin and underlying mechanisms. The numerical approach for the problem consists of framing an eigenvalue problem using primitive variable approach to model the porous channel flows. The Volume Averaged Navier-Stokes (VANS) equations are used for modeling the flow through a porous channel with a porosity distribution function varying along the wall-normal direction separating the homogeneous fluid region and the homogeneous porous region by an interface region with smooth transition of porosity. The linearized VANS equations are discretized using 4th order dispersion-relation preserving finite-differences schemes, in order to reduce the computational resources in terms of memory and time. The modal stability analysis is performed to identify the linearly unstable region based on the critical flow parameters (critical Reynolds number and critical wavenumber). Reynold-Orr analysis is carried out to identify the contribution of different terms of the perturbation kinetic energy in the flow. A scaling approach is done to identify and distinguish between the different physical mechanisms governing the instabilities in the flow at different ranges of porosity. Non-modal analysis is carried out to understand the mechanism responsible for optimal energy amplification in the sub-critical regime and the wavenumbers over which maximum energy growth takes place. Non-modal analysis for turbulent porous channel flow is also carried out to get better insight into the underlying mechanisms governing the instabilities in the flow. It is seen that the 4th order dispersion relation preserving scheme is well able to capture the physics of the flow through porous channel. Initial analysis about the linearly unstable region shows that the Squire transformation holds for porous channel flows and hence the modal stability analysis is performed using two dimensional perturbations. The eigenspectrum and the shape of the eigenmode shows the evolution of viscid instability from fluid region at low values of porosity. At high values of porosity, the eigenmode shows strong flow reversal at the interface due to weakening of wall-blocking and wall induced viscous effects. Energy analysis shows the dominance of viscous dissipation at lower values of porosity while the porous dissipation becomes significant at higher values of porosity. The physical origin of the instability is identified by the scaling analysis. It is seen that at lower values of porosity, the instability stems from the viscous fluid region (TS instability) while the primary source of instability at higher values of porosity is a TS instability wave modified by the drag from porous region. Non-modal analysis shows the optimal mechanism of energy amplification over different ranges of porosity is the Lift-up effect due to the streaky structures. However the non-normal energy growth becomes insignificant at extremely high values of porosity. The turbulent flow analysis provides a better understanding of the perturbation kinetic energy gain as seen from the direct numerical simulations. The optimal mechanism responsible for the energy growth is due to the streaky structures for different values of porosity. However at extremely high values of porosity there is energy gain due to the span-wise rollers as well but energy gain due to streaks still dominates.","Resolvent norm; Porous channel flow; Volume-averaged Navier-Stokes; Dispersion relation preserving schemes; Local stability analysis; Modal stability; Reynolds-Orr analysis; Non-modal stability; Transient growth","en","master thesis","","","","","","","","","Mechanical, Maritime and Materials Engineering","Process and Energy","","","",""
"uuid:0043be29-6a88-419e-991d-2618f4f21c37","http://resolver.tudelft.nl/uuid:0043be29-6a88-419e-991d-2618f4f21c37","Dispersion and dynamically one-dimensional modeling of salt transport in estuaries","Daniëls, J.","Savenije, H.H.G. (mentor)","2016","An estuary forms the transition between the ocean/sea and a river. Within its boundaries salt and fresh water mix. Fresh water intake points may be located within the reach of salt intrusion. In order to justify political and managerial decisions it is thus necessary to understand and be able to predict the process of salt intrusion in estuaries. Within this thesis the one-dimensional modeling suite SOBEK is used to simulate salt intrusion in estuaries. Within SOBEK the one-dimensional continuity and momentum equations are used to describe hydrodynamics within the system. A state equation, relating salinity and density, is used to couple an advection-diffusion equation to the momentum equation. This advectiondiffusion equation can be used to describe salt transport and makes use of a dispersion coefficient. The dispersion coefficient should capture the mixing mechanisms taking place in an estuary. Mixing mechanisms in an estuary are induced by tidal forcing, river discharge or wind and the most dominant ones are gravitational circulation and tidal pumping. Recent validations of SOBEK have mainly focused on water levels and discharges, while less attention was payed to its capability to describe salt transport. The objective of this research is thus to obtain a better understanding of dynamic one-dimensional modeling of salt transport, validate the model and used dispersion coefficient, determine the applicability of the model and improve the dispersion coefficient based on the latest insights and recent developments. The study is performed using two data sets. One of which is a prismatic tidal flume experiment conducted in the 60’s at Delft Hydraulics. The other one is a data set considering worldwide measurements in convergent estuaries by Savenije and his students. The nature of the considered water bodies, tidal flume and real convergent estuaries, differs much and so do the results and conclusions regarding both data sets. The first analysis performed was testing the dispersion formulation based on the one derived by Thatcher and Harleman (1972) which is currently used in SOBEK. Based on validation results for both the tidal flume experiment and real convergent estuaries and an analysis of the dispersion relation, improvements to the dispersion formulation were formulated and tested in the second phase of this research. For example, simulations for the tidal flume test showed that the model was not capable of dealing with changes in bed roughness or water depth in the tidal flume and as such terms containing those characteristics were added to the dispersion formulation. In search of a better performing dispersion formula, the effect of the improvements to the dispersion formulation are tested. Individual adjustments were tested separately on the tidal flume simulations. More recent formulations derived by Savenije (2012), Kuijper and Van Rijn (2011), Gisen et al. (2015) and Zhang and Savenije (2016) are tested on the tidal flume experiment and/or real convergent estuaries . The dispersion formulations described by those researchers all contain one or more of the suggested improvements and together they contain all of the suggested improvements. For the tidal flume experiment model results using dispersion formulas derived by Thatcher and Harleman, Gisen and Kuijper and van Rijn are compared. For convergent estuaries simulations using dispersion formulas derived by Thatcher and Harleman, Gisen, Savenije, Kuijper and van Rijn and Zhang are compared. For the tidal flume experiment the dispersion formula derived by Kuijper and van Rijn clearly performed best. This formulation relates the dispersion coefficient to the maximum flood velocity in the estuary mouth, the water depth in the estuary mouth, the estuarine Richardson number1, the bed roughness and the relative salinity. Other formulas performed worse as they do not relate dispersion with the water depth in the estuary mouth or bed roughness. For the convergent estuaries none of the assessed dispersion formulations performed substantially better than the others as all of them result in strong correlation between measurements and simulations. However, the simulations using the dispersion formula’s described by Thatcher and Harleman (1972) and Gisen et al. (2015) are closer to the measurements than the other ones. The formulas described by Savenije, Kuijper and van Rijn and Zhang underestimated the salt intrusion and may potentially be improved by recalibrating the constant used. The dispersion formulation derived by Gisen is the simplest formulation, while it performs more or less equally well than the others. Here it is therefore suggested to continue with this dispersion formula. Gisen related dispersion at the inflection point to the maximum flood velocity, the tidal excursion and the estuarine Richardson number and used the relative salinity to convert this to dispersion along an estuary. Savenije and Kuijper and van Rijn additionally included terms relating dispersion to the estuary geometry and bed roughness, however this did not lead to better results. The formulation of Thatcher and Harleman uses the estuary length, instead of the tidal excursion, as a mixing length scale. This estuary length is not well defined and lacks a physical background regarding dispersive salt transport. Therefore the formulation derived by Thatcher and Harleman is not recommended.","(alluvial) estuaries; dispersion; tidal flume experiment; mixing processes; one-dimensional numerical modeling; salinity; salt intrusion; SOBEK","en","master thesis","","","","","","","","","Civil Engineering and Geosciences","Water Management","","NUS-TUD Double Degree Program Hydraulic Engineering and Water Resources Management","",""
"uuid:d2ed7adf-45fe-4fde-af60-14671b5319ea","http://resolver.tudelft.nl/uuid:d2ed7adf-45fe-4fde-af60-14671b5319ea","Spatio-Temporal Stability Analysis of Shear Flows: Using analytical and non-analytical approaches","Kumar, N.","Pinna, F. (mentor); Groot, K.J. (mentor); Pecnik, R. (mentor)","2016","A comprehensive understanding of the stability of shear flows is a fundamental problem in fluid mechanics and it has been a subject of both theoretical and practical interest in engineering research. A key aspect of these dynamic flows is the behaviour exhibited by the instabilities as it evolves from initial small perturbations of an equilibrium state, and may lead to fluctuations. In order to control these fluctuations, a study on the spatial and temporal evolution of the perturbations must be carried out. The objective of this thesis is to perform the spatio-temporal stability analysis on the plane, incompressible shear layers representing confined and unconfined shear flows. The analysis requires the estimation of the response of the flow to the initial perturbations for fixed values of relevant parameters. The numerical tools are developed for the low order piecewise linear profile approximations to the shear layers. The influence of typical flow features, like single and multiple shear dynamics, on the stability behaviour is studied and the convective/absolute instability boundary for various parameter combinations are identified. After validation for the analytical models, the numerical tools are extended to the non-analytical models. The analysis is then performed for higher order approximations of the experimental base flows in order to validate the results from the toolkit. A variation of the flow features and variables can change the stability behaviour of the shear flows. The single shear layer dynamics cannot contribute to absolute instability in the absence of a dispersive medium, like surface tension. The surface tension acts as a stabilising mechanism for perturbations of short wavelength. The multiple shear layer dynamics dictates that the unconfined jet or wake flow is more unstable than the single shear layer with equivalent parameter values, and that very high values of surface tension stabilises all perturbations. For confined jet or wake flows, the varicose mode perturbations are found to be highly absolutely unstable in the strongly confined dense inner flow limit. The temporal branches obtained from the toolkit match with the Linear Stability Theory (LST) results. This is a key result that allows the extension of the numerical tools developed for the low order analytical models to be applied to the non-analytical models obtained for higher order approximations of the experimental base flow.","instability; shear flow; dispersion relation; , local stability analysis; local stability analysis","en","master thesis","","","","","","","","","Mechanical, Maritime and Materials Engineering","Process and Energy","","","",""
"uuid:5b477bce-8716-45ea-968f-1a07f56bdefe","http://resolver.tudelft.nl/uuid:5b477bce-8716-45ea-968f-1a07f56bdefe","Radiation of Logarithmic Spiral Antennas in the Presence of Dense Dielectric Lenses","Garufo, A. (TU Delft Tera-Hertz Sensing); Llombart, Nuria (TU Delft Tera-Hertz Sensing); Neto, A. (TU Delft Tera-Hertz Sensing)","","2016","In this paper, the performance of logarithmic spiral antennas as feeds of dense dielectric lens are investigated in detail. The performances are evaluated in terms of clean symmetric radiation patterns, high polarization purity, antenna efficiency, and radiation dispersivity. A logarithmic spiral antenna placed in the dielectric-air interface can provide high aperture efficiencies over large bandwidths if coupled to a synthesized elliptical lens. The use of an air gap increases the directivity of the spiral radiation inside the dielectric allowing for lens directive patterns without sidelobes and reducing the dispersivity of the radiated pulse. The directivity enhancement of the fields inside the dielectric is validated by the measurement of a prototype. The highest frequency at which these antennas can be fed by a planar microstrip line is limited by the thickness of the microstrip substrate.","ultrawideband antenna; Dispersion; leaky-wave antenna; lens antenna; spiral antenna","en","journal article","","","","","","","","","","","Tera-Hertz Sensing","","",""
"uuid:7cd416b3-5f73-4fb7-ba6c-836b1dfb8091","http://resolver.tudelft.nl/uuid:7cd416b3-5f73-4fb7-ba6c-836b1dfb8091","A Quasi-Analytical Tool for the Characterization of Transmission Lines at High Frequencies","van Berkel, S.L. (TU Delft Tera-Hertz Sensing); Garufo, A. (TU Delft Tera-Hertz Sensing); Llombart, Nuria (TU Delft Tera-Hertz Sensing); Neto, A. (TU Delft Tera-Hertz Sensing)","","2016","In this article, we present a freely accessible software tool that allows for fast characterization of dynamic phenomena in a wide variety of transmission lines that include characteristic impedance, effective dielectric constant, and losses, such as radiation into space and surface waves. For printed transmission lines, the radiation effects are of particular importance when the transverse dimensions of the transmission lines become significant in terms of wavelength. Generally, dispersion and losses of the line due to these dynamic phenomena are predicted by full-wave simulations as quasi-static formula do not suffice. The presented software tool, freely downloaded from http://terahertz.tudelft.nl, is capable of accurately analyzing the most widely used transmission lines at high frequencies.","Power transmission lines; Software tools; Propagation losses; Surface waves; Dielectric losses; Dispersion; Coplanar waveguides","en","journal article","","","","","","","","","","","Tera-Hertz Sensing","","",""
"uuid:bb3e2fe0-dfc5-49b2-b816-e7339e0cd4b3","http://resolver.tudelft.nl/uuid:bb3e2fe0-dfc5-49b2-b816-e7339e0cd4b3","Dispersal and growth of bacteria","Gude, S.","Tans, S.J. (promotor); Shimizu, T.S. (promotor)","2016","Quantitative experiments with the ability to systematically probe the system under investigation are a key element to gain insight and understanding. We present a novel and simple technique enabling the maintenance and controlled perturbation of experimental conditions of microorganisms from bacteria to nematodes. Polyacrylamide-based devices are simple to fabricate from ingredients typically present in biolabs and are in addition biocompatible, permeable to small molecules and physically robust to even withstand adult C. elegans nematodes while keeping the study object within a confined region, e.g. the field of view of a microscope. Furthermore polyacrylamide gels can easily be combined with PDMS and microfluidics to continuously supply fresh nutrients and remove waste products. Beyond this rather technical work, we set out to chart the influence of spatial structure and dispersal on evolutionary dynamics. To our surprise we found that already one of the most basic experiments imaginable, mixing two genetically identical bacterial populations labeled with distinct fluorescent markers, yielded drastically altered population dynamics in spatial habitats compared to well-mixed conditions. Motile populations in spatial habitats are found to spontaneously segregate over a broad range of initial conditions. We were able to identify dispersal rate as a key determinate of spatial confinement.","dispersal; motility; growth; bacteria; species diversity; coexsitence; polyacrylamide; microfluidics; space; population dynamics","en","doctoral thesis","","","","","","","","2020-04-12","Applied Sciences","Kavli Institute of Nanoscience Delft","","","",""
"uuid:636ee0b2-ddf5-4e50-8874-be7f771816b7","http://resolver.tudelft.nl/uuid:636ee0b2-ddf5-4e50-8874-be7f771816b7","Characterization of aerosols from RDD surrogate compounds produced by fast thermal transients","Di Lemma, F.G. (TU Delft RST/Reactor Physics and Nuclear Materials; European Commission Joint Research Centre, Institute for Transuranium Elements Karlsruhe); Colle, Jean Yves (European Commission Joint Research Centre, Institute for Transuranium Elements Karlsruhe); Ernstberger, Markus (European Commission Joint Research Centre, Institute for Transuranium Elements Karlsruhe); Konings, R. (TU Delft RST/Reactor Physics and Nuclear Materials; European Commission Joint Research Centre, Institute for Transuranium Elements Karlsruhe)","","2016","Experimental tests have been performed to characterize the aerosols representative of radiological dispersion devices (RDDs, a.k.a. ""dirty bombs"") by applying to chosen surrogate compound rapid high temperature transients, vaporizing the sample and forming aerosols mainly by rapid cooling of the vapour. The materials, which were tested in their non-radioactive form, had been chosen from the radioactive sources widely used in industries and nuclear medicine applications, Co, CsCl, Ir and SrTiO3. Our analyses permitted the characterization of the inhalable fraction of the aerosols released, and the study of the influence of cladding materials on the aerosol release and on its characteristics.","aerosol characterization; experimental data; particle size; radioactivity; radiological dispersion devices; source term","en","journal article","","","","","","","","","","","RST/Reactor Physics and Nuclear Materials","","",""
"uuid:fa9179f7-85f1-4eda-86d8-033d66b11203","http://resolver.tudelft.nl/uuid:fa9179f7-85f1-4eda-86d8-033d66b11203","Stable Stratification Effects on Flow and Pollutant Dispersion in Boundary Layers Entering a Generic Urban Environment","Tomas, J.M.; Pourquie, M.J.B.M.; Jonker, H.J.J.","","2016","Large-eddy simulations (LES) are used to investigate the effect of stable stratification on rural-to-urban roughness transitions. Smooth-wall turbulent boundary layers are subjected to a generic urban roughness consisting of cubes in an in-line arrangement. Two line sources of pollutant are added to investigate the effect on pollutant dispersion. Firstly, the LES method is validated with data from wind-tunnel experiments on fully-developed flow over cubical roughness. Good agreement is found for the vertical profiles of the mean streamwise velocity component and mean Reynolds stress. Subsequently, roughness transition simulations are done for both neutral and stable conditions. Results are compared with fully-developed simulations with conventional double-periodic boundary conditions. In stable conditions, at the end of the domain the streamwise velocity component has not yet reached the fully-developed state even though the surface forces are nearly constant. Moreover, the internal boundary layer is shallower than in the neutral case. Furthermore, an investigation of the turbulence kinetic energy budget shows that the buoyancy destruction term is reduced in the internal boundary layer, above which it is equal to the undisturbed (smooth wall) value. In addition, in stable conditions pollutants emitted above the urban canopy enter the canopy farther downstream due to decreased vertical mixing. Pollutants emitted below the top of the urban canopy are 85 % higher in concentration in stable conditions mostly due to decreased advection. If this is taken into account concentrations remain 17 % greater in stable conditions due to less rapid internal boundary-layer growth. Finally, it is concluded that in the first seven streets the vertical advective pollutant flux is significant, in contrast to the fully-developed case.","boundary layer; large-eddy simulation; pollutant dispersion; roughness transition; stratification","en","journal article","Springer","","","","","","","","Mechanical, Maritime and Materials Engineering","Process and Energy","","","",""
"uuid:ab6c14c4-dacc-4c1f-a098-9df620ccbd62","http://resolver.tudelft.nl/uuid:ab6c14c4-dacc-4c1f-a098-9df620ccbd62","Nature’s Particulate Matter with and without Charge and Travelling","Ursem, W.N.J. (TU Delft BT/Botanical Garden Delft)","","2016","Natures and anthropogenic particulates can travel long distances on wind flows, but negative electrical charge due to friction can increase dispersion. Models for calculations of distance travelling of biological particulate matter with and without charge are never been calculated in a theoretical approach. Nor do we realize the fact that we can calculate actual distances if we take the charge on particles in account. Particles that travel through the air encounter friction. Friction can be described in two ways; either in a smooth constant way through the air with its viscous forces, or in a turbulent chaotic eddies and vortices and other flow instabilities. In case of only viscous forces are to be concerned, it can be described as a lower Reynolds number than one, while in all other setting it always must be described by Reynolds numbers larger than or equal to one. This article describes the calculated effects on particles, either in a low Reynolds number and thus as a Navier-Stokes equation or Stokes’ Law or, in case of non-laminar and complex forces in an equal or higher Reynolds number according to the third Law of Newton. In addition some striking examples of particle travelling are given with evidence of natural particulate matter long distance dispersion.","Natural Dispersion; Electrical Charge; Stokes; Newton","en","journal article","","","","","","","","","","","BT/Botanical Garden Delft","","",""
"uuid:191a7bc9-090e-47cd-b5eb-dd7782c50c22","http://resolver.tudelft.nl/uuid:191a7bc9-090e-47cd-b5eb-dd7782c50c22","Identification and Treatment of Erodible Clays in Dikes","Nagy, G.; Nagy, L.","","2015","When it comes to flood protection, the established method is to use impermeable material in dikes, to prevent seepage. This material is usually some kind of clay soil which is considered as impermeable and erosion-resistant. Dispite that, in many occasions not only seepage, but the failure of the dam occured due to surface erosion, because these kinds of irregular soils are barely investigated, and their presence are not considered during the phase of designing. In geotechnics these soils are called dispersive clays, and their greatest hazard is that they are not distinguishable at sight or by the standard geotechnical tests from the regular erosion-resistant clays, therfore many dams are built by these kind of materials, causing extra risk when it comes to evaluating the probability of failure. The reason for this kind of behavior can be found in the structure and the distribution of the clay minerals which are building up the soil. Based on earlier experiences and papers it is possible to reduce the magnitude of erosion by mixing the soil with slaked lime. First to evince the dispersive nature of the soils we developed a testing program. Therefore we collected samlpes from the Great Hungarian Plane, and identified them by the pinhole test after Sherard. If the soil was identified as a dispersive clay, slaked lime was mixed to it, and the test was performed again to see if the soil became less dispersive, therefore more erosion-resistant or not. The main goal was to find an optimal value of the added lime. The main chapters the paper present the background of the dispersive soils, and the mechanism of failure, the tunnel erosion. Shortly the laboratory testing methods are demonstrated, and the way feedback affects the further tests, and the results of the treatments, the changes of the degree of dispersion are shown.","dispersive clay; pinhole test; tunnel erosion; geotechnical risk","en","conference paper","","","","","","","","","","","","","",""
"uuid:8a736606-a00c-4618-9955-1ec44d87471e","http://resolver.tudelft.nl/uuid:8a736606-a00c-4618-9955-1ec44d87471e","Damage resistance of dispersed-ply laminates","Sardar Abadi, P.M.; Jeliazkov, M.; Sebaey, T.A.; Lopes, C.S.; Abdalla, M.M.; Peeters, D.M.J.","","2015","This paper presents the design procedure of a quasi-isotropic (QI) laminate employing dispersion of ply orientations. The goal is to improve damage resistance of a laminate under low velocity impact (LVI). The LVI is treated as a quasi-static loading and instead of a plate a laminated beam is considered. Therefore, this situation simplifies the problem to an interlaminar shear (ILS) test. Although the specimen might experience several failure mechanism, only delamination which influence the load carrying capability of it drastically under compression after impact (CAI) is considered here. By studying the interlaminar shear stresses through the thickness of the laminate, initiation of crack can be inspected in every layer using a quadratic initiation criterion (QIC). Finally, employing a modified ant colony optimization (ACO) algorithm (two-pheromone ACO algorithm) a fully dispersed QI laminate is designed. The domain of the orientation angles is between -85º to 90º with a 5º interval. The results showed that the interface angles does not present a decisive influence on the crack onset. On the other hand, the dispersion tends to have as large as possible angles near the middle of the laminate to minimize the maximum value of QIC, and some small angles in the outside to provide enough bending stiffness.","damage resistance; dispersed-ply laminates; optimization; ant colony algorithm","en","conference paper","ICCM","","","","","","","","Aerospace Engineering","Aerospace Structures & Materials","","","",""
"uuid:fe53a3da-fae6-4fc4-983e-00279068cdf0","http://resolver.tudelft.nl/uuid:fe53a3da-fae6-4fc4-983e-00279068cdf0","Modeling dispersion and mixing in EOR processes","Van El, W.A.","Rossen, W.R. (mentor); Heimovaara, T.J. (mentor); Hajibeygi, H. (mentor)","2015","“Dispersion” has two meanings in reservoir engineering: (1) the variety of arrival times at a production well for an injected tracer, which is mostly a function of heterogeneity of permeability in the reservoir, and (2) mixing of injected fluids in situ. It is very difficult to distinguish these two processes in situ, while the success of different processes depends on different aspects of dispersion. For instance: a geothermal producer depends on the arrival time of cold water, while low-salinity water and miscible-flood displacements are harmed by in situ mixing. Moreover, simulation studies need to contend with numerical dispersion, a purely artificial effect of numerical simulation. In this thesis we develop a first-order-accurate two-dimensional streamline-based simulator to model in-situ mixing of tracer particles. A coordinate transformation is performed from an (x,y) to an (x,?) domain, such that all streamlines are parallel, before applying the convection-diffusion equation. When using streamline methods, numerical dispersion mostly occurs in the longitudinal direction which effects particle distributions in the same way as longitudinal diffusion. Taylor (1953) described how the effect of transverse diffusion effects the distribution of particles more than longitudinal diffusion. The streamline model is used to simulate Taylor dispersion in a tube in order to study the effect of longitudinal numerical dispersion on the accuracy of the model. As predicted by (Taylor 1953), numerical dispersion is found to diminish in importance as higher transverse diffusion coefficients are introduced, increasing the accuracy of the model. This effect is further studied by comparing the first-order accurate model with a higher-order accurate model and analytical solutions. After establishing that the model works, it is compared to a particle-tracking simulator which is considered to be state-of-the-art. Particle-tracking simulators are free of numerical dispersion but cannot accurately model in-situ concentrations unless exceedingly large numbers of particles are included. Rather, they infer mixing has taken place from the variance of particles positions obtained from flow-reversal tests and assume part of this mixing has taken place in forward flow. The streamline-based model developed in this thesis shows similar results to the model developed by Berentsen et al. (2007) in the Taylor limit, but slightly different results in the convective limit and intermediate scenarios. The potential of the streamline-based simulator is shown by applying the model to a realistic, although only two-dimensional, scenario of a heterogeneous reservoir. Especially in the convective limit does the streamline based model show more accurate results than a conventional simulator. Finally, we apply the model to a situation which includes adsorption of particles by the solid phase. The adsorption and flow depend on local concentrations; a situation a particle-tracking model cannot easily model.","Taylor dispersion; mixing; streamline modeling","en","master thesis","","","","","","","","","Civil Engineering and Geosciences","Section Petroleum Engineering","","","",""
"uuid:51454527-14fa-447c-9ff7-11c64aa73150","http://resolver.tudelft.nl/uuid:51454527-14fa-447c-9ff7-11c64aa73150","The influence of an obstacle on flow and pollutant dispersion in neutral and stable boundary layers","Tomas, J.M.; Pourquie, M.J.B.M.; Jonker, H.J.J.","","2015","Predicting pollutant dispersion in urban environments requires accurate treatment of obstacle geometry, inflow turbulence and temperature differences. This paper considers both the influence of thermal stratification and the presence of a single obstacle on pollutant dispersion in turbulent boundary layers (TBLs). Turbulent flow over a fence with line sources of pollutant in its vicinity is simulated by means of Large-Eddy Simulations. Separate ‘driver’ simulations are done to generate the inflow TBL for several levels of stratification. Using these inflow TBLs the flow development and pollutant dispersion behind the fence, up to 100 fence heights, h, is investigated. It is shown that the decay of velocity and temperature deficit is independent of stability, while the decay of Reynolds stress and concentration excess decreases with increasing stability. For neutral cases the influence of the obstacle is gone after approximately 75h, while for stable cases near the ground the flow is still accelerated compared to the undisturbed case. The fence does cause a local reduction of stratification and thereby increased pollutant dispersion. However, neglecting the effect of buoyancy results in an underestimation of pollutant concentration by a factor 2.5 at 75h downstream of the emission source for the most stable case.","stratification; boundary layer; obstacle; pollutant dispersion; turbulence; wake","en","journal article","Elsevier","","","","","","","","Mechanical, Maritime and Materials Engineering","Process and Energy","","","",""
"uuid:a4260691-15fb-4035-ba94-50a4535ef63d","http://resolver.tudelft.nl/uuid:a4260691-15fb-4035-ba94-50a4535ef63d","Prediction in Ungauged Estuaries","Gisen, J.I.A.","Savenije, H.H.G. (promotor)","2015","Estuaries have been used for settlement by humans since 5000-9000 years ago [Day et al., 2012]. The calm environment and nutrient-rich soil encouraged the development of ports and agriculture. Over-development however has put estuaries in unhealthy condition, where the water is polluted (excessive nutrient or salt intrusion problem) and natural morphodynamic equilibrium is disturbed. This implies that the need for effective estuarine management is crucial. Unfortunately, most of the estuaries around the globe are still ungauged, limiting the understanding and knowledge of the underlying hydrological process. Hence, the aims of this study are to: 1) collect and reorganize the existing information available from various sources such as the literature, engineering reports, and open access databases shared by researchers and authorities; 2) conduct field surveys in 7 Malaysian estuaries to expand the database; and 3) develop predictive measures to estimate the two important calibration parameters in salt intrusion (the Van der Burgh and dispersion coefficients), the estuary depth, and the bankfull discharge. Data collection was carried out in 7 previously un-surveyed Malaysian estuaries during the dry season and near spring tide, from June to August 2012 and February to March 2013. Fundamental data such as cross-sectional area, water level, and salinity were surveyed, starting from the estuary mouth moving landward until a few kilometers beyond the salt intrusion limit. Subsequently, the fully analytical 1-D salt intrusion model of Savenije [1986] was tested on all the newly surveyed estuaries making used of the data collected. Here, the geometry was analyzed following a branched exponential function. The cross-sectional data were adjusted in reference to the mean tidal level. The results obtained from the salt intrusion model show that the model is capable of simulating the salinity distribution in comparison to the observed data. Although the existing predictive equations for the Van der Burgh and dispersion coefficients appeared reliable, there were still some issues to deal with. In this study, several modifications were made to improve the predictive equations. Geometry and salinity data of 30 estuaries worldwide including the newly surveyed were collected and re-analysed to create a consistence data base. Selection of data was made to ensure that only the reliable dataset was applied in the derivation of the predictive equations, using various combinations of dimensionless parameters. Moreover, the seaward boundary location was moved to the inflection point (determined by the geometry analysis) where the system becomes tide dominated. Another reason for shifting the boundary location was to eliminate the dilemma of the downstream boundary location. From analyses, it is found that the predictive coefficients are strongly related to the geometry, tidal strength, friction and the Canter-Cremers estuarine number. The new equation obtained for the dispersion is very satisfying and reliable. On the other hand, the correlation for the Van der Burgh coefficient is slightly lower, implying the equation has to be used with caution. Nevertheless, these predictive equations are adequate to be applied for obtaining a first order estimate of the salt intrusion. In cases where data are strictly limited, more parameters have to be predicted. In salt intrusion analysis, discharge data is crucial because the salt intrusion length is strongly dependent on the amount of river flow draining into the estuary. Apart from the discharge, the estuary depth is also an important parameter to determine the salt intrusion. Without an extensive filed survey, it is nearly impossible to obtain these parameters, especially the discharge. In this study, an effort has been made to find predictive measures that can be applied to estimate depth and discharge. This was done by relating the hydraulic geometry theory of river regime [Lacey, 1930] with the estuary depth estimated using the analytical tidal dynamics solutions of Savenije et al. [2008]. Subsequently, the relation was verified by linking the Canter-Cremers estuarine flood number for bankfull discharge at 1.5-years return period to the estuary shape (represented by the width ratio at the infection point and upstream boundary of the tidal limit). Results show that the relationship between the estuary depth and bankfull discharge can be expressed by a power function with an exponent near to 1/3, in agreement with Lacey’s theory. Furthermore, the results obtained from the Canter-Cremers flood number analysis imply that the estuary depth is determined by the bankfull discharge, while the width is determined by the tide. This analysis has demonstrated that the downstream hydraulic geometry theory can also be applied in the estuary region. In spite of the fact that predictive measures established are useful in making first order estimates of salt intrusion, they are still open for improvements. It is hope that in future more reliable data can be collected and used to strengthen the predictive methods.","alluvial estuary; Malaysian estuaries; salt intrusion; salinity; dispersion; bankfull discharge; geometry","en","doctoral thesis","","","","","","","","","Civil Engineering and Geosciences","Water Management","","","",""
"uuid:c616f3da-5ae9-4a92-b9d7-c435d3ad81b0","http://resolver.tudelft.nl/uuid:c616f3da-5ae9-4a92-b9d7-c435d3ad81b0","The influence of fractures on geothermal heat production in the Roer Valley Graben","Biemans, B.C.B.","Bruhn, D.F. (mentor); Nick, H.M. (mentor); Jansen, J.D. (mentor); Hagedoorn, S. (mentor)","2014","This thesis looks into the possibility to produce geothermal energy in the Roer Valley Graben. The locations in this area are limited due to the low permeability of the deep Triassic layers. Fractures can enhance the heat production by increasing the effective permeability and decrease the pressure that is needed to produce the heat. However, fractures can also decrease the lifetime of a reservoir due to early breakthrough of the cold water. The goal of this study is to explore the influence of fractures on geothermal heat production. Multiple 2D fracture patterns are modelled in a numerical finite element program and the fractures are represented as lower dimensional line elements. The breakthrough time is strongly influenced by the position of the horizontal fractures. A smaller spacing between the fractures decreases the breakthrough time and the breakthrough time is increased if the orientation of the doublet is not in line with the fractures. The vertical fractures also influence the breakthrough if the fractures are connected to horizontal fractures. The standard Advection-Diffusivity Equation (ADE), applied to an effective porous media, is fitted to the breakthrough curves of the numerical models by changing the apparent thermal dispersion. A different method, the Continuous Time Random Walk (CTRW) framework is also fitted to the numerical breakthrough curves. This framework, that is developed to describe solute transport, has five parameters that can be changed to create a fit. The global breakthrough curve is captured better by the CTRW, however the breakthrough is better described by the ADE. Both methods show similar results estimating the lifetime of the numerical model. To determine when the ADE is able to describe the breakthrough curve of a certain fracture model, the area of influence of the fracture model is plotted against the error between the numerical experiment and the ADE. If the area of influence of a fracture pattern is small, the ADE has trouble describing the breakthrough curve correctly. If the full width of the model is not covered by the area of influence, two cold fronts evolve, one through the fractures and one through the matrix. If the cold front of the matrix would arrive at the outlet before the cold fluid through the fractures has cooled down the outlet, the breakthrough curve could not be described by the ADE. If the fractures are placed in each other's area of influence the cold injected fluid can travel further because it is less retarded by the matrix, creating an even earlier breakthrough. I found that the area of influence also influences the apparent thermal dispersion. A negative relation could be constructed between the two parameters. The discussion about thermal dispersion and its dependency on Peclet is also addressed in this thesis. Different relations between Peclet and the apparent thermal dispersion are studied and the relations varied from a linear relation to a power law relation. I found that the three regimes that Detwiler (2000) constructed for solute longitudinal dispersion can also be constructed for the apparent thermal dispersion. For values of Pe smaller than 1, the apparent thermal dispersion has a very small negative to zero relation with Pe. For intermediate values of Pe (between 1 and 10) Peclet is linearly related to the apparent thermal dispersion and for larger values of Peclet a power law relation can be constructed. The power law and the additional thermal dispersion parameters are dependent of the subsurface parameters and the fracture pattern. The three regimes are constructed for a fracture/matrix permeability ratio between 8.000 and 8.000.000.","geothermal; heat transport; fracture; thermal transport; Roer Valley Graben; dispersion; energy; brabant; breakthrough; CTRW; Continous Time Random Walk","en","master thesis","","","","","","","","","Civil Engineering and Geosciences","Geoscience & Engineering","","","",""
"uuid:887b1d31-219c-4d3d-a87e-a987c0df8b0b","http://resolver.tudelft.nl/uuid:887b1d31-219c-4d3d-a87e-a987c0df8b0b","Soil properties from seismic intrinsic dispersion","Zhubayev, A.S.","Wapenaar, C.P.A. (promotor); Ghose, R. (promotor)","2014","Theoretical and experimental studies in the past have shown the sensitivity of seismic waves to soil/rock properties, such as composition, porosity, pore fluid, and permeability. However, quantitative characterization of these properties has remained challenging. In case of unconsolidated soils, the inherently loose and heterogeneous nature complicates the task of obtaining the in situ properties and spatial variations. In this thesis, we investigate the possibility of exploiting the information of seismic intrinsic dispersion in the low frequency band (10-200 Hz), which is relevant to onshore field data, in order to quantify these physical properties, with special focus on soil porosity and permeability. In situ values of these properties are crucial in many different projects. We first investigate the frequency-dependent seismic velocity and attenuation caused by inelastic losses at grain contacts and wave-induced fluid flow at different scales (from grain size to seismic wavelength), using the theory of poroelasticity first proposed by Biot and many subsequent extensions and modifications. Several pertinent models of poroelasticity are looked at in order to find out their applicability in explaining the observed seismic dispersion. The observed dispersion can vary greatly between various unconsolidated, fully-saturated soils. Further, we develop a stress-dependent Biot (SDB) model in order to study the behaviour of seismic waves propagating through a fully-saturated porous medium subjected to different stress conditions. This is achieved by combining the mechanics of granular soils with the effective-stress laws, finally coupling with Biot's theory. Careful analyses of the underlying soil/rock physics that relate geophysical observations to the physical properties reveal an interesting feature in the property domain among several different measurements. This is an extention to some recent work done by others. We have found that it is possible to find two or more measured quantities, showing contrasting (sometimes quasi-orthogonal) behaviour in the common parameter space, such that a combination of those measured quantities leads to a physics-based uniqueness in the property estimation. This quasi-orthogonality in the common property domain among different measured quantities is advantageously used for estimation of porosity, permeability, water saturation, and effective stress. Several numerical examples are presented where P- and S-wave velocity and attenuation are efficiently integrated in order to obtain soil properties. In addition to seismic waves, electromagnetic waves are briefly considered for extracting extra soil properties. In this research, considerable attention has been paid to the investigation of S waves travelling through a porous medium, since S waves have well-known significance in the context of shallow subsurface characterization. Twelve selected datasets of frequency-dependent S-wave velocity and attenuation from various soft-soil sites are used in this study. Data for fully-saturated, unconsolidated soils from land/onshore environment are only considered. It is found that the behaviour of seismic intrinsic dispersion can vary greatly with the soil-type. One of the main challenges in property estimation using intrinsic dispersion relates to reliable extraction of the information of intrinsic dispersion from the recorded seismic data. The difficulty lies in the quantification of scattering attenuation, the effect of which is always present in the recorded seismograms due to the wavelength-scale and smaller heterogeneities in the subsurface. Scattering has an absorption-like effect on the transmitted seismic energy. Accordingly, determining and subtracting the scattering attenuation from the total (or apparent) attenuation is critically important. We have discussed and successfully tested an approach, achieving this goal. Several shallow vertical seismic profiling (VSP) measurements are conducted in the field using a recently developed digital, array-seismic cone penetrometer (CPT) system. CPT provides information on cone-tip resistance, sleeve friction, and pore pressure, thus offering direct, additional knowledge on geological layering, that is used to calculate the scattering attenuation. To obtain the soil properties, an inversion algorithm is presented based on simulated annealing and the poroelasticity theory. We study the sensitivity of different parameters involved in the cost function to be minimized. The most and the least sensitive parameters are discriminated based on the eigenanalyses of the covariance matrix of the gradient of the cost function. The eigenvectors and the corresponding eigenvalues of the covariance matrix are used to navigate efficiently the search algorithm in the multidimensional space and find a relatively stable, global solution of the cost function. Finally, we apply the methodology developed in this research to a VSP dataset acquired in a layered sequence of siltstone, shale and sandstone. The porous sandstone contains hydrocarbon accumulations. The influence of fluid mobility (permeability-to-viscosity ratio) on the estimated P-wave intrinsic dispersion is distinctly observed. Using optimization by simulated annealing together with VSP and well-log measurements, the Biot and squirt flow (BISQ) model is found to provide one possible mechanism for the observed dispersion. The layer-specific fluid mobility values are estimated using our approach; they are found to be close to the independent measurements of mobility using Stoneley waves and from dynamic formation-tests carried out at the same borehole. The depth distribution of fluid mobility matches well between our estimate and the independent measurements. The methodology developed and the results obtained in this research pave the way to a new direction for in situ, quantitative soil/rock characterization using seismic waves.","seismic dispersion; poroelasticity; inversion","en","doctoral thesis","","","","","","","","","Civil Engineering and Geosciences","Geoscience & Engineering","","","",""
"uuid:578e1967-072f-4a5d-b9f6-dd27219eb988","http://resolver.tudelft.nl/uuid:578e1967-072f-4a5d-b9f6-dd27219eb988","Experimental Verification of Clogging within Vertical Transport Systems for the Deep Sea Mining Industry","Van Grunsven, F.","Talmon, A.M. (mentor); Van Rhee, C. (mentor); Van Wijk, J.M. (mentor); Van Prooijen, B.C. (mentor)","2014","This report concerns the experimental validation of recent numerical predictions of pipe blockage during the vertical hydraulic transport of ore for the deep sea mining industry. A hydraulic circuit, incorporating an 8.5 m riser pipe of 99.4 mm inner diameter, was built to identify and quantify the dominant transport mechanisms during conveying, merging and passing of two batches of solids. Experiments were conducted with single batches and various combinations of two batches, including two types of sand (0.39 mm and 1.05 mm), two types of gravel (6.34 mm and 11.20 mm) and Polystyrene granulate (2.80 mm). Experiments indicated a decreasing influence of axial dispersion for an increasing particle size and particle density. By measurement data analysis, it is proven that axial dispersion is negligible for coarser solids, implying a larger risk of concentration peaks during transport compared to recent numerical calculations which assumed Taylor dispersion. Experiments with two merging batches revealed the ability for sand to merge and pass the gravel, whereas polystyrene merges and fuses with the gravel leading to pipe blockage. This discrepancy is thought to originate from a specific solids diameter ratio between both batches. A relation is suggested between the occurrence of pipe blockage and Terzaghi’s filter rules. The report concludes that the volume fraction of solids can rise significantly during the merging process and that for certain solids combinations, the merging process can lead to blockage of the riser.","hydraulic vertical transport; deep sea mining; axial dispersion; pipe blockage","en","master thesis","","","","","","","","","Mechanical, Maritime and Materials Engineering","Maritime and Transport Technology","","Offshore and Dredging Engineering","",""
"uuid:adcff048-bcd4-480f-97ba-b1afed8d84be","http://resolver.tudelft.nl/uuid:adcff048-bcd4-480f-97ba-b1afed8d84be","Improving the predictive equation for dispersion in estuaries","Nijzink, R.C.","Savenije, H.H.G. (mentor); Kuijper, K. (mentor); Gisen, J.I.A. (mentor); Wang, Z.B. (mentor)","2013","Dispersion is often hard to incorporate in analytical salt intrusion models. The analytical models of Savenije (1986) and Kuijper & Van Rijn (2011) are quite similar and use a predictive equation for the dispersion in the estuary mouth. The biggest difference between the two models is the Van der Burgh K for which Kuijper and Van Rijn stated that it should be equal to 0.5. The main goal of this research is to improve the applicability of the analytical salt models. The two models were applied to 72 measurements in 27 estuaries. Both models gave reasonable results, but Savenije's model gave in general a slightly better fit. The differences were found in especially the tail of the curve, what indicates that K is probably not equal to 0.5. Linear regressions were carried out in order to derive new possible predictive equations for the dispersion coefficient. Several existing dimensionless ratios were combined in different regressions. Another regression technique, genetic programming, confirmed that a linear combination of the log of the dimensionless ratios is correct. The linear regressions were carried out for both models and for the estuary mouth and the inflection point, where the shape of the estuary changes. Many of the derived equations showed however more or less comparable results. The significance of the different terms was tested to see if each term contributed significantly. In this way it was already possible to reduce the number of possible new predictive equations. The same selection of equations was applied to the salt models. Eventually a choice of a new predictive equation was made based on the regressions, the local applications and the applications in the salt models. The horizontal to vertical tidal range and a friction term should be added to the Richardson number to get an improved predictive equation. The applicability of the analytical models will also increase by starting the calculation from the more clearly defined inflection point. A disadvantage of the new equation is especially the friction term, because friction is often not known a priori. The hydraulic model of Cai et al. (2012) was used to test if friction and depth could be estimated with just a minimum of information. It was possible to use these equations to make a ""quick and dirty"" estimate of these parameters. The new proposed approach is therefore as follows: - Determine the location of the inflection point based on information about the geometry - Estimate hydraulic parameters, also with help of the equations of Cai et al. (2012) - Determine the dispersion coefficient with the new predictive equations - Determine the salt distribution with the model of Savenije (1986) or Kuijper & Van Rijn (2011)","salt intrusion; dispersion; estuary","en","master thesis","","","","","","","","","Civil Engineering and Geosciences","Water Management","","Hydrology","",""
"uuid:73857c78-6e11-4dee-87ae-630fa6d8b63a","http://resolver.tudelft.nl/uuid:73857c78-6e11-4dee-87ae-630fa6d8b63a","Fluid mobility in reservoir rocks from integrated VSP and openhole data","Zhubayev, A.; Ghose, R.; Jihai, Y.; Jun, C.; Borodin, I.; Sanders, M.; Lim, T.K.; Menkiti, H.","","2013","In this study, we first estimate seismic velocity and attenuation dispersion from a comprehensive zero-offset vertical seismic profile (VSP) data acquired in China. These results, combined with openhole data acquired at the same location, provide experimental evidence that the seismic attenuation in rocks is dominated by a fluid-flow mechanism. The loss mechanism due to multiple scattering is found to be negligible. This implies that extraction of fluid mobility (permeability to viscosity ratio) in reservoir rocks using low frequency (10 to 150 Hz) seismic data should be possible. We present a methodology, based on poroelastic inversion using a rotated coordinate system and simulated annealing, to extract fluid mobility from combined VSP and openhole data. Finally, we compare layer-specific fluid mobility values, obtained using this approach, with independent fluid mobility measurements and estimates based on wireline openhole data.","VSP; attenuation; dispersion; permeability; reservoir characterization","en","journal article","Society of Exploration Geophysicists","","","","","","","","Civil Engineering and Geosciences","Geoscience & Engineering","","","",""
"uuid:45c7c7a0-dbaf-471f-9f81-576e789507ab","http://resolver.tudelft.nl/uuid:45c7c7a0-dbaf-471f-9f81-576e789507ab","Development of a methodology for the application of synthetic DNA in stream tracer injection experiments","Foppen, J.W.; Seopa, J.; Bakobie, N.; Bogaard, T.","","2013","Stream tracer injection experiments are useful for characterizing hydrological and biogeochemical processes in streams. We used nonconservative synthetic DNA and conservative NaCl in six instantaneous tracer injection experiments in streams in the Benelux. The main aim was to compare the performance of injected synthetic DNA tracer “T23” with NaCl. In all experiments, the shapes of the T23 and NaCl breakthrough curves (BTCs) were similar. Recovered T23 mass ranged from 2.9 to 52.6%, while recovered NaCl tracer mass ranged from 66.7% to complete mass recovery. In batch experiments, T23 decay was not detected. However, in those batches, we observed an unexplained initial T23 mass loss of 40–97%. In batches with sediment, T23 attachment rate coefficients ranged from close to zero to 0.2 hr?1. Advective and dispersive transport parameters of both NaCl and T23 fitted with STAMMT-L were similar. However, compared to T23, fitted storage zone areas of NaCl were 2–5 times larger, while storage zone exchange coefficients were two times larger. Fitted mass dilution factors of T23 ranged from 1.6 to 34.8. Together, these results pointed toward the disappearance of a part of the T23 mass due to both initial losses and attachment or sorption of T23 mass in those storage zone(s), while decay was not important. Our research demonstrated that artificial DNA can be a valuable tool to determine advective and dispersive transport in brooks, but not to assess solute mass exchange processes related to surface transient storage or hyporheic exchange.","synthetic DNA tracer; salt tracer; transient storage zone; longitudinal dispersion; STAMMT-L","en","journal article","American Geophysical Union","","","","","","","2014-03-04","Civil Engineering and Geosciences","Water Management","","","",""
"uuid:149aab88-19ad-4df6-a6a8-1179dc0861d7","http://resolver.tudelft.nl/uuid:149aab88-19ad-4df6-a6a8-1179dc0861d7","The effect of interface movement and viscosity variation on the stability of a diffusive interface between aqueous and gaseous CO2","Meulenbroek, B.J.; Farajzadeh, R.; Bruining, J.","","2013","Carbon dioxide injected in an aquifer rises quickly to the top of the reservoir and forms a gas cap from where it diffuses into the underlying water layer. Transfer of the CO2 to the aqueous phase below is enhanced due to the high density of the carbon dioxide containing aqueous phase. This paper investigates the behavior of the diffusive interface in an enclosed space in which initially the upper part is filled with pure carbon dioxide and the lower part with liquid. Our analysis differs from a conventional analysis as we take the movement of the diffusive interface due to mass transfer and the composition dependent viscosity in the aqueous phase into account. The same formalism can also be used to describe the situation when an oil layer is underlying the gas cap. Therefore we prefer to call the lower phase the liquid phase. In this paper we include these two effects into the stability analysis of a diffusive interface between CO2 and a liquid in the gravity field. We identify the relevant bifurcation parameter as q = ?Ra, where ? is the width of the interface. This implies the (well known) scaling of the critical time ?Ra?2 and wavelength ?Ra?1(The critical time tc and critical wavelength kc are defined as follows: ?(k) ? 0??t ? tc; equality only holds for t = tc and k = kc). Inclusion of the interface upward movement leads to earlier destabilization of the system. Increasing viscosity for increasing CO2 concentration stabilizes the system. The theoretical results are compared to bulk flow visual experiments using the Schlieren technique to follow finger development in aquifer sequestration of CO2. In the appendix, we include a detailed derivation of the dispersion relation ?(k) in the Hele-Shaw case [C. T. Tan and G. M. Homsy, Phys. Fluids 29, 3549–3556 (1986)]10.1063/1.865832 which is nowhere explicitly given.","bifurcation; carbon compounds; critical phenomena; diffusion; dispersion relations; flow instability; groundwater; inclusions; mass transfer; oils; reservoirs; two-phase flow; viscosity","en","journal article","American Institute of Physics","","","","","","","","Electrical Engineering, Mathematics and Computer Science","Delft Institute of Applied Mathematics","","","",""
"uuid:1440c86c-2e53-4a3c-a43c-77ef9b75fa82","http://resolver.tudelft.nl/uuid:1440c86c-2e53-4a3c-a43c-77ef9b75fa82","A new numerical model for simulating the propagation of and inundation by tsunami waves","Cui, H.","Stelling, G.S. (promotor); Pietrzak, J.D. (promotor)","2013","This thesis has involved the development of an unstructured grid ocean model, H2Ocean, with accurate flooding and drying algorithms for tsunami studies. The research is co-funded by the Alfred Wegener Institute (AWI) in Bremerhaven, Germany, as part of their contribution to the German-Indonesian Tsunami Early Warning System, which is installed in Jakarta, Indonesia. The objectives are to improve the capability of the model in handling the flooding and drying, and dispersion. Based on an unstructured mesh finite element model TsunAWI, a finite volume model H2Ocean has been developed. This model is an analogue of the P1NC- P1 finite element. In the successful applications of the model in simulations of the 2004 Indian Ocean Tsunami and the 2011 Japan Tsunami, excellent agreement have been achieved, when compared to both flooding data and measured run-up. The model is found to be an accurate and efficient model for tsunami simulations.","Tsunami modelling; flooding and drying; finite element model; finite volume model; dispersion; non-hydrostatic; 2004 Indian Ocean Tsunami; 2011 Japan Tsunami","en","doctoral thesis","VSSD","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:19b96d86-b170-4153-a5f2-a70a131fc98c","http://resolver.tudelft.nl/uuid:19b96d86-b170-4153-a5f2-a70a131fc98c","A Framework for Designing and Testing the Digital Signal Processing unit of a Pulsar Based Navigation System","Karunanithi, V.","Van der Meijs, N.P. (mentor); Van Leuken, T.G.R.M. (mentor)","2012","Navigation systems using pulsar signals have been of great interest ever since the discovery of pulsars in 1967 and various studies were carried out ever since to determine the feasibility of such systems. The successful working of a navigation system using pulsar would mean that spacecraft can maneuver through the deep space with very little help from earth. Another notable aspect of this navigation mechanism is that pulsar signals are available throughout the cosmos, so this sys- tem could be used for a wide range of orbital configurations such as Low Earth Orbits (LEO), Medium Earth Orbit (MEO), Geosta- tionary Orbits (GEO) and Interplanetary orbits enabling a universal navigation system. In this thesis, a software framework has been developed to replicate the environmental setup for a pulsar navigation system. This frame- work can be used to design a high level system design of the pulsar signal processing unit which will be a part of the navigation system. The framework can be used to generate pulsar templates as it can process the raw data from a receiver. The generated templates will be used in the final navigation system in the stages of correlation and detection. The software framework was developed using a very novel system design approach using SystemC-AMS, which consists of C++ classes that felicitate high level system design involving analog and mixed signals. The design approach, implementation, results and limitations of this framework is also presented. Based on the conclusions derived from the framework, a road-map is provided for future development.","Pulsar Navigation; Dispersion; Inter Stellar Medium (ISM); Fast Fourier Transform; Polyphase Filter Bank; SystemC; SystemC-AMS","en","master thesis","","","","","","","","","Electrical Engineering, Mathematics and Computer Science","Microelectronics & Computer Engineering","","Embedded Systems","",""
"uuid:e676256d-0428-45e6-bc12-b58697e9545e","http://resolver.tudelft.nl/uuid:e676256d-0428-45e6-bc12-b58697e9545e","Disperse or unite? A mathematical model of coordinated attack","Op den Kelder, J.M.","Fokkink, R.J. (mentor)","2012","Throughout the history of the western world a constant struggle has been taking place between governments and terrorist organisations. Game theory has proven helpful in enhancing our understanding of struggles between two players with opposing interests. The September 11 attacks on the USA in 2001 marked a profound strategic shift in the strategies employed: multiple bombings were carried out simultaneously by different groups with different targets. As such, the terrorist organisation responsible made the strategic decision to divide its resources between multiple targets. We study this decision-making process mathematically by introducing a new type of search game.","zero-sum game; minimax theorem; probability of dispersion","en","bachelor thesis","","","","","","","","2012-12-06","Electrical Engineering, Mathematics and Computer Science","Delft Institute of Applied Mathematics","","Applied Probability","",""
"uuid:68771b79-3b91-4ea1-815b-c76ccc5494b3","http://resolver.tudelft.nl/uuid:68771b79-3b91-4ea1-815b-c76ccc5494b3","Separating convection from diffusion in a model of dispersion in fluid injection in forward flow","Bouman, L.S.","Rossen, W.R. (mentor)","2012","Recent research (John et al., 2008) has shown that the usual way of measuring dispersion in flow through permeable layers doesn’t distinguish between dispersion caused by convective spreading and mixing. Dispersion is used to mean both the variation of arrival times of material at a well and the molecular mixing of components in a reservoir. John et al used flow reversal to distinguish between the two, and quantified dispersion using particle-tracking. To make it more clear, in this thesis the case with convection and diffusion is called “diffusion”, and the case with convective-flow only is called “convective-flow”. Comparing results of forward movement with the results of flow-reversing allows one to distinguish the effects of convection alone from convection and diffusion. John et al. came to the conclusion that the difference can be seen only in flow-reversal. They compared the positions of “diffusion” particles and the mean of the positions of the “convective-flow” particles. This is possible in a computer simulation, where diffusion can be excluded from the process. Part of the difficulty in distinguishing between convection and diffusion arises because convection alone gives rise to a variation of particle positions that on the large scale looks scattered and random. On the small scale the convection particles trace a surface that is deterministic, based on the distribution of permeability in the medium. We test whether it is possible to distinguish convection from diffusion if one compares the positions of ""diffusion"" particles to the surface of “convective-flow” particles rather than the mean position of the convective-flow particles. If such a difference could be found it would give more insight in the movement of particles during forward movement. To achieve this, one would have to interpolate the convection surface between the “convective-flow” particles. This was done in Matlab and the features of this surface were closely examined. I conclude that the amount of data (number of particles) was not sufficient to give an accurate representation of the features of this surface. Unfortunately I conclude that, with this amount of data, one cannot distinguish quantitatively between convection and diffusion in forward flow, because more data are needed to make a representative surface for the convection particles. The idea of plotting a surface to give a more accurate difference between diffusion and convection might in principle still work. To find out if it would really work, a larger amount of particles is needed to represent the convection surface.","dispersion; flow reversal; convection; diffusion","en","bachelor thesis","","","","","","","","","Civil Engineering and Geosciences","Geoscience & Engineering","","Section Petroleum Engineering","",""
"uuid:cb93d40a-1c98-4082-8ed7-676af0d1182e","http://resolver.tudelft.nl/uuid:cb93d40a-1c98-4082-8ed7-676af0d1182e","Electrophoretic mobility of latex nanospheres in electrolytes: Experimental challenges","Chassagne, C.; Ibanez Sanz, M.E.","","2012","The electrophoretic mobility of sulfate latex nanospheres (radius 300 ± 10 nm) was measured as a function of ionic strength for different salts. The results were obtained from two similar instruments (Malvern ZetaSizer 3000 HSa and Malvern ZetaSizer Nano) using the same dispersions, in the same conditions. The values predicted from the standard electro - kinetic model for constant surface charge were in good agreement with the data over a large range of ionic strength. The influence of the protocol used to fill the cells appears to be of importance between 1–10 mM of added monovalent salt. There, the capillary wall properties seem to influence the electrophoretic measurements, even at fast field reversal (FFR), where electroosmosis should be absent. We found that during a series of measurements with monovalent salts, it was best to fill the cell starting from high ionic strength and decreasing the ionic strength during the series. The measurements with divalent salts were not sensitive to the filling procedure.","colloidal dispersions; electrokinetics; electrophoresis; latex nanospheres; zeta potential","en","journal article","International Union of Pure and Applied Chemistry (IUPAC)","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:49f2ff3d-68ae-4f46-9424-5595e7505c87","http://resolver.tudelft.nl/uuid:49f2ff3d-68ae-4f46-9424-5595e7505c87","Monodisperse water microdroplets generated by electrohydrodynamic atomization in the simple-jet mode","Agostinho, L.L.F.; Yurteri, C.U.; Fuchs, E.C.; Marijnissen, J.C.M.","","2012","Experiments were conducted in order to investigate the influences of flow rate, applied voltage, and electric conductivity on droplet size and size distribution of water electrosprays in the simple-jet mode. The results show that the electric potential decreases significantly the relative standard deviation (RSD) of the spray size distribution, with the best result obtained for Weber number, We?=?3.3 (240?ml/h) when the RSD decreases from 0.50 at 0?kV to 0.18 at 5?kV. We conclude that simple-jet mode electrosprays are a good option for applications which require monodisperse micrometer droplets with high throughput.","disperse systems; drops; electrohydrodynamics; jets; sprays; two-phase flow","en","journal article","American Institute of Physics","","","","","","","","Applied Sciences","","","","",""
"uuid:6486e144-b176-47e9-bf2e-4c2c4438cf51","http://resolver.tudelft.nl/uuid:6486e144-b176-47e9-bf2e-4c2c4438cf51","Are stirring and sonication pre-dispersion methods equivalent for in vitro toxicology evaluation of SiC and TiC?","Mejia, J.; Valembois, V.; Piret, J.P.; Tichelaar, F.; Van Huis, M.; Masereel, B.; Toussaint, O.; Delhalle, J.; Mekhalif, Z.; Lucas, S.","","2012","The evolution of the particle size distribution and the surface composition of silicon carbide and titanium carbide nanoparticle (NP) dispersions were studied. The pre-dispersions were prepared using two commonly used protocols for dispersion: stirring and sonication. Two dispersants were investigated (water and Pluronic F108 1 %) at two stages: predispersion and during in vitro assays. Our data show that for each tested condition, different time-dependent results for the surface chemical composition as well as size and percentage of the agglomerates and the primary particles are observed. De-agglomeration and successive or simultaneous cleaning-wrapping cycles of the nanomaterial are observed and are related to the dispersion method and the medium as well as to the chemical stability of the NP surface. Biological response during in vitro assessment was also performed for one given pre-dispersion time condition and demonstrates that the preparation method significantly alters the results","SiC nanoparticles; TiC nanoparticles; particle size distribution; surface composition; protocol of dispersion; in vitro assays; effective dose; environmental and health effects","en","journal article","Springer","","","","","","","","Applied Sciences","Kavli Institute of NanoScience","","","",""
"uuid:b02e69f3-5a25-44a1-8785-7205e5502c5f","http://resolver.tudelft.nl/uuid:b02e69f3-5a25-44a1-8785-7205e5502c5f","Contrasting behavior between dispersive seismic velocity and attenuation: Advantages in subsoil characterization","Zhubayev, A.; Ghose, R.","","2012","A careful look into the pertinent models of poroelasticity reveals that in water-saturated sediments or soils, the seismic (P and S wave) velocity dispersion and attenuation in the low field-seismic frequency band (20–200 Hz) have a contrasting behavior in the porosity-permeability domain. Taking advantage of this nearly orthogonal behavior, a new approach has been proposed, which leads to unique estimates of both porosity and permeability simultaneously. Through realistic numerical tests, the effect of maximum frequency content in data and the integration of P and S waves on the accuracy and robustness of the estimates are demonstrated.","acoustic dispersion; acoustic wave velocity; elasticity; permeability; sediments; seismic waves; soil","en","journal article","Acoustical Society of America","","","","","","","2012-07-26","Civil Engineering and Geosciences","Geoscience & Engineering","","","",""
"uuid:ff8f30e1-1426-4df8-8665-2c48470e8634","http://resolver.tudelft.nl/uuid:ff8f30e1-1426-4df8-8665-2c48470e8634","Model-Based Traffic Control for Sustainable Mobility","Zegeye, S.K.","De Schutter, B. (promotor); Hellendoorn, J. (promotor)","2011","Computationally efficient dynamic fuel consumption, emissions, and dispersion of emissions models are developed. Fast and practically feasible model-based controller is proposed. Using the developed models, the controller steers the traffic flow in such a way that a balanced trade-off between the travel times, fuel consumption, and emissions (to a target zone) is achieved. Simulation-based case studies are used to compare and illustrate the models and control approaches proposed.","model-based control; MPC; parameterized MPC; RHPC; emissions; fuel consumption; emissions dispersion; sustainable mobility; traffic control","en","doctoral thesis","","","","","","","","2011-10-12","Mechanical, Maritime and Materials Engineering","Delft Center for Systems and Control","","","",""
"uuid:fff182ad-bec4-4481-a96a-e1eef3a75fbf","http://resolver.tudelft.nl/uuid:fff182ad-bec4-4481-a96a-e1eef3a75fbf","Computation of the Longitudinal and Transverse Dispersion Coefficient in an Adsorbing Porous Medium Using Homogenization","Bruining, J.; Darwish, M.; Rijnks, A.","","2011","This article compares for the first time, local longitudinal and transverse dispersion coefficients obtained by homogenization with experimental data of dispersion coefficients in porous media, using the correct porosity dependence. It is shown that the longitudinal dispersion coefficient can be reasonably represented by a simple periodic unit cell (PUC), which consists of a single sphere in a cube. We present a slightly modified and simplified approach to derive the homogenized equations,which emphasizes physical aspects of homogenization. Subsequently, we give full dimensional expressions for the dispersion tensor based on a comparison with the convective dispersion equation used for contaminant transport, inclusive the correct dependence on porosity. For the PUC of choice, the dispersion relations are identical to the relations obtained for periodic media.We show that commercial finite element software can be readily used to compute longitudinal and transverse dispersion coefficients in 2D and 3D. The 3D results are for the first time obtained at relevant Peclet numbers. There is good agreement for longitudinal dispersion. The computed transverse dispersion coefficients for a single sphere in a cube are much too low. The effect of adsorption on the dispersion coefficient is also studied. Adsorption does not affect the transverse dispersion coefficient. However, adsorption enhances the longitudinal dispersion coefficient in agreement with an analysis of homogenization applied to Taylor dispersion discussed in the literature.","homogenization; dispersion tensor; adsorption","en","journal article","Springer","","","","","","","","Civil Engineering and Geosciences","Geoscience & Engineering","","","",""
"uuid:650bf314-2543-41dc-a97b-23e0110ece25","http://resolver.tudelft.nl/uuid:650bf314-2543-41dc-a97b-23e0110ece25","Computation of the longitudinal and transverse dispersion coefficient in an adsorbing porous medium using homogenization","Bruining, H.; Darwish, M.; Rijnks, A.","","2011","This article compares for the first time, local longitudinal and transverse dispersion coefficients obtained by homogenization with experimental data of dispersion coefficients in porous media, using the correct porosity dependence. It is shown that the longitudinal dispersion coefficient can be reasonably represented by a simple periodic unit cell (PUC), which consists of a single sphere in a cube. We present a slightly modified and simplified approach to derive the homogenized equations,which emphasizes physical aspects of homogenization. Subsequently, we give full dimensional expressions for the dispersion tensor based on a comparison with the convective dispersion equation used for contaminant transport, inclusive the correct dependence on porosity. For the PUC of choice, the dispersion relations are identical to the relations obtained for periodic media.We show that commercial finite element software can be readily used to compute longitudinal and transverse dispersion coefficients in 2D and 3D. The 3D results are for the first time obtained at relevant Peclet numbers. There is good agreement for longitudinal dispersion. The computed transverse dispersion coefficients for a single sphere in a cube are much too low. The effect of adsorption on the dispersion coefficient is also studied. Adsorption does not affect the transverse dispersion coefficient. However, adsorption enhances the longitudinal dispersion coefficient in agreement with an analysis of homogenization applied to Taylor dispersion discussed in the literature.","homogenization; dispersion tensor; adsorption","en","journal article","Springer","","","","","","","","Civil Engineering and Geosciences","Geoscience & Engineering","","","",""
"uuid:080eb125-6477-45e0-9f0e-d8bb1621c977","http://resolver.tudelft.nl/uuid:080eb125-6477-45e0-9f0e-d8bb1621c977","Numerical study on dispersion of dilute glycerol-water mixtures in channel flow","Ruoff, M.C.","Berentsen, C.W.J. (mentor)","2011","In this work we developed a numerical model for channel flow on a pore or micro scale. A straight channel was simulated with a flow regime of Re=0.03 and Re=0.3 (comparable to typical fluid flow in petroleum reservoirs) to visualize the characteristics of flow and dispersion up to the Fickian limit. The objective of this study was to quantify the effect of the dilute assumption on the channel averaged longitudinal dispersion of glycerol in water flow and to qualitatively assess the specific contribution of the diffusion, viscosity and density of the solute. In all cases a mixture with a concentration of 200 mol/m3 solute was injected into the channel. The ideal tracer flow model was verified by comparing it to theory. A literature study on the properties of glycerol-water mixtures was done to incorporate the correct property behaviour for variable glycerol concentration. In addition, the creeping flow assumption was tested. Detailed analysis of the changes in flow velocity components and concentration distribution was performed. The dilute, non-dilute and creeping flow models have also been tested and analysed for a tenfold increased velocity. For the base model (with Re=0.03), diffusion showed to be the main contributor to a different dispersive behaviour, followed by viscosity and density respectively. Viscosity and density variability caused changes in the velocity profiles of the flow. Longitudinal dispersion appeared to be 0.35% higher when all variability was included, compared to an ideal tracer flow simulation. Higher flow velocity (Re=0.3) appears to increase the dispersion differences, mainly caused by viscosity variability.","dispersion; channel; glycerol; water; dilute; pore scale","en","master thesis","","","","","","","","","Civil Engineering and Geosciences","Section Petroleum Engineering","","","",""
"uuid:8ef5b075-b71f-4c24-a6cf-62650d08a970","http://resolver.tudelft.nl/uuid:8ef5b075-b71f-4c24-a6cf-62650d08a970","A unique growth mechanism of donut-shaped Mg–Al layered double hydroxides crystals revealed by AFM and STEM–EDX","Budhysutanto, W.N.; Van Den Bruele, F.J.; Rossenaar, B.D.; Van Agterveld, D.; Van Enckevort, W.J.P.; Kramer, H.J.M.","","2010","Donut-like crystals of Mg–Al layered double hydroxides (LDH) are synthesized using a hydrothermal method with microwave heating. This morphology provides enlargement of the specific surface area of the {h k 0} faces, needed for adsorption application. The growth mechanism for donut-shaped crystals is proposed on the basis of AFM and STEM–EDX images. The nucleation of Mg–Al LDH starts on the amorphous surface of spherical MgO particles, which have a much lower solubility compared to the aluminum trihydroxides at the synthesis pH (?11). The outgrowing nucleus provides re-entrant corners on both sides. These are preferential sites for the addition of new growth units, allowing lateral growth of the LDH crystal encircling the MgO particles. The dissolving MgO provides the supersaturation needed for growth and once it is depleted, a donut-like structure remains.","A1. atomic force microscopy; A1. scanning transmission electron; microscopyEnergy dispersive X-ray; spectroscopy; A2. hydrothermal crystal growth; B1. layered double hydroxides","en","journal article","Elsevier","","","","","","","","Mechanical, Maritime and Materials Engineering","Process and Energy","","","",""
"uuid:74f875f6-aae5-4189-a9f3-d4e0a736b995","http://resolver.tudelft.nl/uuid:74f875f6-aae5-4189-a9f3-d4e0a736b995","On wavemodes at the interface of a fluid and a fluid-saturated poroelastic solid","Van Dalen, K.N.; Drijkoningen, G.G.; Smeulders, D.M.J.","","2010","Pseudo interface waves can exist at the interface of a fluid and a fluid-saturated poroelastic solid. These waves are typically related to the pseudo-Rayleigh pole and the pseudo-Stoneley pole in the complex slowness plane. It is found that each of these two poles can contribute (as a residue) to a full transient wave motion when the corresponding Fourier integral is computed on the principal Riemann sheet. This contradicts the generally accepted explanation that a pseudo interface wave originates from a pole on a nonprincipal Riemann sheet. It is also shown that part of the physical properties of a pseudo interface wave can be captured by loop integrals along the branch cuts in the complex slowness plane. Moreover, it is observed that the pseudo-Stoneley pole is not always present on the principal Riemann sheet depending also on frequency rather than on the contrast in material parameters only. Finally, it is shown that two additional zeroes of the poroelastic Stoneley dispersion equation, which are comparable with the P-poles known in nonporous elastic solids, do have physical significance due to their residue contributions to a full point-force response.","dispersion (wave); elasticity; porosity; porous materials; Rayleigh waves; surface acoustic waves","en","journal article","Acoustical Society of America","","","","","","","2010-10-01","Civil Engineering and Geosciences","Geotechnology","","","",""
"uuid:21e2a318-b08d-4edb-bebf-fcc672b07c39","http://resolver.tudelft.nl/uuid:21e2a318-b08d-4edb-bebf-fcc672b07c39","Tracer Dispersion: The effect of gravity, inertia & diffusion on fluid flow simulations","Hustoft, L.","Berentsen, C. (mentor)","2010","This project focuses on developing a parallel Navier Stokes simulator capable of modeling single phase dispersion in porous media at the pore scale. Many different factors can contribute to dispersion on a pore scale and this study was limited to fluid flow related factors. The model, including convective motion and diffusive (Fickian) spreading, also incorporates the influences of gravity, inertia and viscous forces on the motion. The precise interaction between these forces and the way these interactions contribute to dispersion is not fully understood from a theoretical point of view. In order to gain insight into dispersion, pore scale simulations are performed in a domain consisting of a few grains. The primary objective of the project was to investigate whether the parallel computational power of NVidia graphics cards (GPUs) could be utilized to tackle the computational intensive Navier Stokes equations. Mainstream NVidia graphics cards (GPUs) appeared to be unable to model the system of equations due to hardware limitations and in addition a conventional parallel processor (CPU) code was developed. Based on a small sample of simulations, diffusion appears to be a significant factor controlling the distribution of the tracer. Inertia may also play a significant role, depending on the alignment relative to pore geometry and gravity. For the case we consider gravity appears to have the least influence on dispersion.","dispersion; tracer; simulation","en","master thesis","","","","","","","","","Civil Engineering and Geosciences","Section Petroleum Engineering","","","",""
"uuid:119ae503-ba03-4676-871a-960579903d1d","http://resolver.tudelft.nl/uuid:119ae503-ba03-4676-871a-960579903d1d","Seismoelectric reflection and transmission at a fluid/porous-medium interface","Schakel, M.D.; Smeulders, D.","","2010","The dispersion relation for seismoelectric wave propagation in poroelastic media is formulated in terms of effective densities comprising all viscous and electrokinetic coupling effects. Using Helmholtz decomposition, two seismoelectric conversion coefficients are derived, for an incident P-wave upon an interface between a compressible fluid and a poroelastic medium. These coefficients relate the incident P-wave to a reflected electromagnetic wave in the fluid, and a transmitted electromagnetic wave in the porous medium. The dependency on angle of incidence and frequency is computed. Using orthodox and interference fluxes, it is shown that energy conservation is satisfied. A sensitivity analysis indicates that electrolyte concentration, viscosity, and permeability highly influence seismoelectric conversion.","acoustic wave reflection; acoustic wave transmission; dispersion relations; elasticity; electrokinetic effects; electrolytes; electromagnetic wave transmission; Helmholtz equations; permeability; porosity; seismic waves; viscosity","en","journal article","Acoustical Society of America","","","","","","","","Civil Engineering and Geosciences","Geotechnology","","","",""
"uuid:dfc29462-9639-4eab-a0a9-d80569a7a311","http://resolver.tudelft.nl/uuid:dfc29462-9639-4eab-a0a9-d80569a7a311","Mean particle diameters: From statistical definition to physical understanding","Alderliesten, M.","Schmidt-Ott, A. (promotor)","2008","Mean particle diameters are important for the science of particulate systems. This thesis deals with a definition system for these mean diameters, called Moment-Ratio (M-R) definition system, and provides a general statistical and physical basis. Also, the current DIN/ISO definition system is discussed. Many types of mean diameters defined according to the M-R system are not merely statistical parameters, but quantities of physical relevance because of causal relationships with, e.g., physical product and process properties. The nomenclature of these mean diameters clearly conveys their physical meanings. Methods were developed to derive theoretically or select empirically the proper type of mean diameter describing a product or process property. Examples from the areas of evaporation, heat transfer, and turbulent two-phase flow, illustrate the theoretical approach. The empirical approach is illustrated by examples, mainly, from the areas of high shear granulation in detergent processing and pharmaceutics. An example from the foods area is concerned with a visual ranking of photographs of bubble size distributions of chocolate mousse samples. The selected type of mean bubble diameter suggests that our visual system, i.e., eyes + brain, has a logarithmic response.","particle; mean diameter; moment-ratio; dispersed phase; size distribution; evaporation; heat transfer; two-phase flow; granulation","en","doctoral thesis","","","","","","","","","Applied Sciences","","","","",""
"uuid:3f373fa6-1039-445a-927f-a4c7ccfbe346","http://resolver.tudelft.nl/uuid:3f373fa6-1039-445a-927f-a4c7ccfbe346","Laplacian Instability of Planar Streamer Ionization Fronts: An Example of Pulled Front Analysis","Derks, G.; Ebert, U.; Meulenbroek, B.","","2008","Streamer ionization fronts are pulled fronts that propagate into a linearly unstable state; the spatial decay of the initial condition of a planar front selects dynamically one specific long-time attractor out of a continuous family. A stability analysis for perturbations in the transverse direction has to take these features into account. In this paper we show how to apply the Evans function in a weighted space for this stability analysis. Zeros of the Evans function indicate the intersection of the stable and unstable manifolds; they are used to determine the eigenvalues. Within this Evans function framework, we define a numerical dynamical systems method for the calculation of the dispersion relation as an eigenvalue problem. We also derive dispersion curves for different values of the electron diffusion constant and of the electric field ahead of the front. Numerical solutions of the initial value problem confirm the eigenvalue calculations. The numerical work is complemented with an analysis of the Evans function leading to analytical expressions for the dispersion relation in the limit of small and large wave numbers. The paper concludes with a fit formula for intermediate wave numbers. This empirical fit supports the conjecture that the smallest unstable wave length of the Laplacian instability is proportional to the diffusion length that characterizes the leading edge of the pulled ionization front.","pulled front; stability analysis; streamer ionization front; dispersion relation; wave selection of Laplacian instability","en","journal article","Springer","","","","","","","","Electrical Engineering, Mathematics and Computer Science","Applied Mathematics","","","",""
"uuid:f845cc4e-5499-4dfe-bbb3-c28fbf525c54","http://resolver.tudelft.nl/uuid:f845cc4e-5499-4dfe-bbb3-c28fbf525c54","Near and intermediate fields of an ultrashort pulse transmitted through Young’s double-slit experiment","Nugrowati, A.M.; Pereira, S.F.; Van de Nes, A.S.","","2008","We present a systematic study of the transmitted field of an ultrashort pulse through Young’s double slit. We show how the spatial-temporal distribution of the field in the near and intermediate zone is affected by the input polarization state of the pulse. The analysis has been separated to study the dispersion, the diffraction and the interference effects individually. A combination of these effects provide the key to understand the temporal dependence of the field observed at various distinctive locations. A thorough understanding of the near- and intermediate-field distribution of a single- or double-slit for an ultrashort pulse can be exploited in many near-field applications, and tailored by tuning the width, thickness, and separation of the slits.","high-speed optical techniques; light diffraction; light interference; light polarisation; optical dispersion; spatiotemporal phenomena","en","journal article","American Physcial Society","","","","","","","","Applied Sciences","Imaging Science and Technology","","","",""
"uuid:85fdac44-ca9e-4421-b2e2-bb9b8ee509d8","http://resolver.tudelft.nl/uuid:85fdac44-ca9e-4421-b2e2-bb9b8ee509d8","The Einstein relation in quantum wires of III-V, ternary, and quaternary materials in the presence of light waves: Simplified theory, relative comparison, and suggestion for experimental determination","Ghatak, K.P.; Bhattacharya, S.; Bhowmik, S.; Benedictus, R.; Choudhury, S.","","2008","We study the Einstein relation for the diffusivity to mobility ratio (DMR) in quantum wires (QWs) of III-V, ternary, and quaternary materials in the presence of light waves, whose unperturbed energy band structures are defined by the three band model of Kane. It has been found, taking n-InAs, n-InSb, n-Hg1?xCdxTe, n-In1?xGaxAsyP1?y lattice matched to InP as examples, that the respective DMRs exhibit decreasing quantum step dependence with the increasing film thickness, decreasing electron statistics, increasing light intensity and wavelength, with different numerical values. The nature of the variations is totally band structure dependent and is influenced by the presence of the different energy band constants. The strong dependence of the DMR on both the light intensity and the wavelength reflects the direct signature of the light waves which is in contrast as compared to the corresponding QWs of the said materials in the absence of photoexcitation. The classical equation of the DMR in the absence of any field has been obtained as a special case of the present analysis under certain limiting conditions and this is the indirect test of the generalized formalism. We have suggested an experimental method of determining the DMR in QWs of degenerate materials having arbitrary dispersion laws and our results find six applications in the field of quantum effect devices.","band structure; cadmium compounds; carrier mobility; diffusion; dispersion relations; gallium arsenide; gallium compounds; III-V semiconductors; indium compounds; mercury compounds; semiconductor quantum wires; ternary semiconductors","en","journal article","American Institute of Physics","","","","","","","","Aerospace Engineering","Aerospace Materials & Manufacturing","","","",""
"uuid:43dae97c-431c-4ed3-8064-35686940a32a","http://resolver.tudelft.nl/uuid:43dae97c-431c-4ed3-8064-35686940a32a","Transport modelling in coastal waters using stochastic differential equations","Charles, W.M.","Heemink, A.W. (promotor)","2007","In this thesis, the particle model that takes into account the short term correlation behaviour of pollutants dispersion has been developed. An efficient particle model for sediment transport has been developed. We have modified the existing particle model by adding extra equations for the suspension using a probabilistic concepts (the Poisson distribution function) to determine the actual number of particles to suspend in each cell. The deposition is modelled by an exponential decaying ordinary differential equation. In order to get accurate results from Monte Carlo simulations of sediment transport, a large number of particles is often needed. However, computation time in a particle model increases linearly with the number of particles. Thus, we have developed a high performance particle model for sediment transport by considering three different sediment suspension methods. Parallel simulation experiments are performed in order to investigate the efficiency of these three methods. We conclude that the second method is the best method on distributed computing systems (e.g., a Beowulf cluster), whereas the third maintains the best load distribution. Using variable time stepping to integrate the particle track in this thesis, has also proved to be efficient.","Wiener process; dispersion coefficient; coloured noise forces; stochastic differential equation; lagrangian particle model; pollution; sediment transport; parallel processing; speed up; load balance; efficiency","en","doctoral thesis","","","","","","","","","Electrical Engineering, Mathematics and Computer Science","","","","",""
"uuid:3b5d5197-a8f5-4349-996a-a8fb932b8f79","http://resolver.tudelft.nl/uuid:3b5d5197-a8f5-4349-996a-a8fb932b8f79","Evaluation of a modified reynolds stress model for turbulent dispersed two-phase flows including two-way coupling","Beishuizen, N.A.; Naud, B.; Roekaerts, D.","","2007","","Turbulence; Two-way coupling; Dispersion model; Sprays; Multiphase flows","en","journal article","Springer","","","","","","","","Applied Sciences","","","","",""
"uuid:09d7710c-d990-45a3-983e-c18347a99c26","http://resolver.tudelft.nl/uuid:09d7710c-d990-45a3-983e-c18347a99c26","Upscaling, relaxation and reversibility of dispersive flow in stratified porous media","Berentsen, C.W.J.; Van Kruijsdijk, C.P.J.W.; Verlaan, M.L.","","2007","","Relaxation; Reversibility; Taylor dispersion; Non-Fickian dispersion; Upscaling; Tracer flow; Stratified flow","en","journal article","Springer","","","","","","","","Civil Engineering and Geosciences","","","","",""
"uuid:069e295d-1b04-4a58-8ba4-484e53f6757c","http://resolver.tudelft.nl/uuid:069e295d-1b04-4a58-8ba4-484e53f6757c","A task based design procedure and modelling approached for industrial crystallization processes","Menon, A.R.","Grievink, J. (promotor); Jansens, P.J. (promotor)","2006","A synthesis-based approach to the design of crystallizers and industrial crystallization processes is introduced in this thesis. An ontology for a task-based design procedure has been developed which breaks the crystallization process into a subset of basic functions (physical tasks) which transform the physical state of matter to a final desired state. These tasks are connected in a network to accomplish the transformation of the feed into the product within quality specifications. This approach can facilitate the creative process of arriving at novel crystallizer configurations, with the aim to reduce cost of resources and capital, and so arrive at process intensification. Experimental investigations into the effect of actuators on process dynamics and subsequent model validation and parameter estimation studies in fed-batch processes is also studied. The study reveals a significant influence of the actuators on the initial start-up and dynamic behavior of the process, especially the effect of the propeller frequency and the fines removal rate. Modelling of growth rate dispersion (using multi-dimensional population balance models) due to strain in secondary nuclei via attrition provides an interesting insight into the broadening of crystal size distribution and the healing of strained crystals. The sustained cyclic behavior observed in DTB crystallizers for the continuous crystallization of ammonium sulphate from water is captured very well using a two-population balance model approach. Here, secondary nucleation mechanisms with a strong dependency on supersaturation are studied and the nucleation bursts could exclusively be located into the boiling zone of the crystallizer using a compartmental modelling approach.","industrial crystallization; task based design; population balance; growth rate dispersion; sustained oscillatory behavior","en","doctoral thesis","","","","","","","","","Applied Sciences","","","","",""
"uuid:4a14da46-e4c3-444a-9bf4-60d193958cc0","http://resolver.tudelft.nl/uuid:4a14da46-e4c3-444a-9bf4-60d193958cc0","Multi-scale attenuation and dispersion in seismic transmission data","Filippidou, N.","Fokkema, J.T. (promotor)","2006","Abstract not available","attenuation; dispersion; wavelet transform; outcrop; multilayered; thin layers; multiples; seismic; geophysics; geology","en","doctoral thesis","","","","","","","","","Civil Engineering and Geosciences","","","","",""
"uuid:e529efdd-9446-49f2-91e5-a750150849cc","http://resolver.tudelft.nl/uuid:e529efdd-9446-49f2-91e5-a750150849cc","A Symmetry and Dispersion-Relation Preserving High-Order Scheme for Aeroacoustics and Aerodynamics","Kok, J.C.","","2006","A new high-order, finite-volume scheme is presented that preserves the symmetry property and the dispersion relation of the convective operator. The scheme is applied to large-eddy simulation of compressible, turbulent flow and to the solution of the linearized Euler equations for aeroacoustic applications. For large-eddy simulation, the discretization is based on the skew-symmetric form, which ensures that the kinetic energy is conserved by the convective operator. This property minimizes the interference of numerical errors with the subgrid-scale model and also enhances numerical stability. Low numerical dispersion is obtained by extending the dispersion-relation preserving scheme of Tam & Webb to finite-volume schemes. The proposed finite-volume scheme is unique in that it is truly fourth-order accurate, conservative, symmetry preserving and dispersion-relation preserving on non-uniform, curvilinear structured grids.","high-order discretization; skew-symmetric form; dispersion-relation preserving; computational aeroacoustics; compressible turbulence; large-eddy simulation","en","conference paper","","","","","","","","","","","","","",""
"uuid:9fdf2c8b-a627-41ae-affc-35d3111f4253","http://resolver.tudelft.nl/uuid:9fdf2c8b-a627-41ae-affc-35d3111f4253","An overview of numerical methods for acoustic wave propagation","Bailly, C.; Bogey, C.","","2006","This paper presents a short overview of recent developments of low-dispersive and low-dissipation finite-difference schemes as an alternative to more classical methods of applied mathematics. Needs of accurate and efficient numerical solvers in computational aeroacoustics have motivated these developements over the last two decades. Properties of the differencing methods are illustrated through theoretical analyses and numerical experiments.","finite-difference schemes; dispersion relation; acoustic propagation; Eulers equations; computational aeroacoustics","en","conference paper","","","","","","","","","","","","","",""
"uuid:b7515c97-65f5-4ab7-a275-026477c4279b","http://resolver.tudelft.nl/uuid:b7515c97-65f5-4ab7-a275-026477c4279b","Numerical study of aerosol dust behaviour in aspiration bunker","Logachev, K.I.; Puzanok, A.I.; Zorya, V.U.","","2006","The information concerning dispersed composition and concentration of dust particles which are caught by local exhausts is necessary for scientific proved choice of dust retaining devices. To receive this information it is necessary to apply the stochastic [1] and determinate methods [2]. The last ones are based on the studying of single dust particles behavior and on the determination of maximum diameter of the caught particles or on the composition of their bordering trajectories. The main objective of this scientific paper is to work out the methods of dispersed composition prediction and dust concentration in extracting local exhausts air in the areas of arbitrary geometry taking into account vortical transitional currents which occur as a result of abrupt modification of area configuration. The mentioned method is based on the introduction of finite number of different fractions dust particles into the stream at every design moment of definite time period and on the tracing of their behavior until they are caught or precipitated. The stream of air current is designed on the basis of the method of discontinuous vortexes. Vortical transitional currents are formed as a result of current isolation from sharp edges of area border, and also from smooth surface on the spot of tangential gear constituent change. The program of air- and coal currents calculation near the local exhausts of different kinds is worked out. The concentration calculation and the design of dispersed dust composition in aspirated air of rotating cylinder-exhaust placed in aspirated cover is carried out. The geometric and kinematics parameters at which the minimum carry-over of dust particles into aspiration net are revealed. The worked out computer program allows to determine the most optimum geometric and aerodynamic properties of local exhausts in aspiration system. The conducted researches of air- and coal currents of such program allowed to state the scheme of energy-efficient aspiration cover with the functions of dust precipitation chamber.","discrete vortex method; aspiration; concentration; dispersion composition","en","conference paper","","","","","","","","","","","","","",""
"uuid:1e51218d-fa17-42dd-afad-14f4092202e7","http://resolver.tudelft.nl/uuid:1e51218d-fa17-42dd-afad-14f4092202e7","Numerical study for accidental gas releases from high pressure pipelines","Novembre, N.; Podenzani, F.; Colombo, E.","","2006","This work concerns the analysis of consequences of gas releases from high pressure pipelines due to accidental events. This analysis has been performed using the CFD code Fluent. The first step of the work intended to evaluate the capability of Fluent to adequately simulate a supersonic underexpanded free jet. This validation has been based on small scale experimental data from literature. Methane jets from high pressure (from 10 to 250 barg), large diameter (0.5 m) pipelines have then been simulated. As second step of our analysis, a simplified model (based on works by Birch et al.) to handle the highly-compressible-fluid region of such kind of jets has been checked. Birch model resulted reliable once completed with two relations, one to evaluate the air entrainment and the other to compute the distance from the release point at which fluid catches up the atmospheric pressure.","free jet; methane release; high pressure; pipeline; accidental event; gas dispersion","en","conference paper","","","","","","","","","","","","","",""
"uuid:a2ccf690-71d9-4421-acc7-cbf6915ff0c4","http://resolver.tudelft.nl/uuid:a2ccf690-71d9-4421-acc7-cbf6915ff0c4","Numerical Dispersion of Gravity Waves","Schroeder, G.; Schlünzen, K.H.","","2006","In this work numerical dispersion relations for atmospheric gravity waves are experimentally analyzed using the anelastic mesoscale model METRAS. The dependency of the group velocity on grid size and advection scheme (central scheme (CDF) and methods based on the essentially non-oscillatory (ENO) method) is presented showing a retardation of the waves with coarser resolution. ENO can simulate smaller waves than CDF. When the grid spacing is discontinuous waves moving from the fine grid to the coarse grid are reflected due to numerical dispersion. A solution is presented to attenuate the reflected waves in order to avoid gravity waves being trapped within the domain of the fine grid. It is based on an internal sponge layer between coarse and fine grid with optimized damping coefficients depending on the local stratification. The method is successfully applied in an idealized two-dimensional test case with gravity waves of different wave lengths (relative to the resolution).","gravity waves; numerical dispersion; irregular grids","en","conference paper","","","","","","","","","","","","","",""
"uuid:1ac957e5-da9f-4da9-89a4-74e1a1d719d1","http://resolver.tudelft.nl/uuid:1ac957e5-da9f-4da9-89a4-74e1a1d719d1","Dispersive surface waves along partially saturated porous media","Chao, G.; Smeulders, D.M.J.; Van Dongen, M.E.H.","","2006","Numerical results for the velocity and attenuation of surface wave modes in fully permeable liquid/partially saturated porous solid plane interfaces are reported in a broadband of frequencies (100?Hz–1?MHz). A modified Biot theory of poromechanics is implemented which takes into account the interaction between the gas bubbles and both the liquid and the solid phases of the porous material through acoustic radiation and viscous and thermal dissipation. This model was previously verified by shock wave experiments. In the present paper this formulation is extended to account for grain compressibility. The dependence of the frequency-dependent velocities and attenuation coefficients of the surface modes on the gas saturation is studied. The results show a significant dependence of the velocities and attenuation of the pseudo-Stoneley wave and the pseudo-Rayleigh wave on the liquid saturation in the pores. Maximum values in the attenuation coefficient of the pseudo-Stoneley wave are obtained in the 10–20?kHz range of frequencies. The attenuation value and the characteristic frequency of this maximum depend on the liquid saturation. In the high-frequency limit, a transition is found between the pseudo-Stoneley wave and a true Stoneley mode. This transition occurs at a typical saturation below which the slow compressional wave propagates faster than the pseudo-Stoneley wave.","surface acoustic waves; acoustic wave absorption; acoustic wave propagation; acoustic wave velocity; acoustic dispersion; bubbles; porosity; porous materials","en","journal article","Acoustical Society of America","","","","","","","","Civil Engineering and Geosciences","Geotechnology","","","",""
"uuid:d83894b3-1056-448d-80f8-5b6a0a5eb304","http://resolver.tudelft.nl/uuid:d83894b3-1056-448d-80f8-5b6a0a5eb304","Shape characterization of concrete aggregate","Stroeven, P.; Hu, J.","","2006","As a composite material, the performance of concrete materials can be expected to depend on the properties of the interfaces between its two major components, aggregate and cement paste. The microstructure at the interfacial transition zone (ITZ) is assumed to be different from the bulk material. In general, properties of conventional concrete have been found favoured by optimum packing density of the aggregate. Particle size is a common denominator in such studies. Size segregation in the ITZ among the binder particles in the fresh state, observed in simulation studies by concurrent algorithm-based SPACE system, additionally governs density as well as physical bonding capacity inside these shell-like zones around aggregate particles. These characteristics have been demonstrated qualitatively pertaining also after maturation of the concrete. Such properties of the ITZs have direct impact on composite properties. Despite experimental approaches revealed effects of aggregate grain shape on different features of material structure (among which density), and as a consequence on mechanical properties, it is still an underrated factor in laboratory studies, probably due to the general feeling that a suitable methodology for shape characterization is not available. A scientific argument hindering progress is the interconnected nature of size and shape. Presently, a practical problem preventing shape effects to be emphasized is the limitation of most computer simulation systems in concrete technology to spherical particles. New developments at Delft University of Technology will make it possible in the near future to generate jammed states, or other high-density fresh particle mixtures of non-spherical particles, which thereupon can be subjected to hydration algorithms. This paper will sketch the outlines of a methodological approach for shape assessment of loose (non-embedded) aggregate grains, and demonstrate its use for two types of aggregate, allowing evaluation of usefulness of the various methods.","Concrete; Discrete Element Computer-simulation; Mathematical Morphology; Particle Dispersion; Porosity; Stereology","en","journal article","International Society for Stereology","","","","","","","","Civil Engineering and Geosciences","","","","",""
"uuid:fbdca278-d4a6-4faa-9c39-f10525f21655","http://resolver.tudelft.nl/uuid:fbdca278-d4a6-4faa-9c39-f10525f21655","Modern routes ro explore concrete's complex pore space","Stroeven, P.; Guo, Z.","","2006","This paper concentrates on discrete element computer-simulation of concrete. It is argued on the basis of stochastic heterogeneity theory that modern concurrent-algorithm-based systems should be employed for the assessment of pore characteristics underlying durability performance of cementitious materials. The SPACE system was developed at Delft University of Technology for producing realistic schematizations of realcrete for a wide range of other particle packing problems, involving aggregate and fresh cement, and for the purpose of exploring characteristics in the hardened state of concrete, including of the pore network structure because of obvious durability problems. Since structure-sensitive properties are involved, schematization of reality should explicitly deal with the configuration of the cement particles in the fresh state. The paper concentrates on the stereological and mathematical morphology operations executed to acquire information on particle size, global porosity, and on distribution of porosity and of the connected pore fraction as a result of the near neighbourhood of aggregate grains. Goal is to provide information obtained along different exploration routes of concretes pore space for setting up a pore network modelling approach. This type of methodological papers is scarce in concrete technology, if not missing at all. Technical publications that report on obtained results in our investigations are systematically referred to.","concrete; discrete element computer-simulation; mathematical morphology; particle dispersion; porosity; stereology","en","journal article","International Society for Stereology","","","","","","","","Civil Engineering and Geosciences","","","","",""
"uuid:85cef785-c17c-41d7-9a58-6a183c468523","http://resolver.tudelft.nl/uuid:85cef785-c17c-41d7-9a58-6a183c468523","Hydroelastic analysis of very large floating structures","Andrianov, A.O.I.","Hermans, A.J. (promotor)","2005","Due to the growth of their population, urban development and the corresponding expansion of land use, several countries have decided to build artificial islands in the sea to decrease the pressure on the heavily used land space. The reclamation of the land from the sea is already widely applied, however, there is also an attractive new alternative: construction of very large floating structures (VLFSs). VLFSs can and are already being used for storage facilities, industrial space, wind and solar power plants, bridges, ferry piers, docks, rescue bases, breakwaters, airports, entertainment facilities, military purposes, even habitation, and other purposes. They can be speedily constructed, exploited, and easily relocated, expanded, or removed. The subject of the dissertation is hydroelastic analysis of a very large floating structure, so the motion of a VLFS (modelled by an elastic plate) and its response to surface water waves. Several problems of the interaction between the VLFS and water waves are treated in the dissertation. The plate deflection, free-surface elevation, reflection and transmission of water waves are studied using different theories of applied mathematics, mechanics and hydrodynamics. New method for the hydroelastic analysis of the VLFSs, an integro-differential equation method, is proposed, justified, and applied in the dissertation. Also, the geometrical-optics approach, the ray method, and the Lindstedt method are used.\par An analytical solution and numerical results are derived for various shapes and dimensions of the floating plate and three different models of water depth. The problem background and introduction, literature survey and information on VLFSs are given in chapter 1. Chapter 2 describes the general theory, the basic equations and conditions, introduces and formulates particular problems considered, and proposes a method of solution. The problems for the following models and horizontal shapes of a very large floating platform are solved in chapters 3--7: a semi-infinite plate and a strip of infinite length, a circular plate, a ring-shaped plate, a quarter-infinite plate, and a plate of finite, but small, thickness. Analytical solutions together with representations and operations are described for specific cases. Numerical results are obtained for practically important and relevant situations.\par General conclusions, recommendations and a discussion on VLFSs in and of the future are given in chapter 8.","diffraction; dispersion relation; elastic plate; fluid-structure interaction; freesurface elevation; hydroelastic analysis; hydroelastic response; incident surface waves; initiated wave pattern; integro-differential equation; offshore structure; plate deflection; plate-water interaction; reflection; transmission; very large floating platform (VLFP); very large floating structure (VLFS); water depth","en","doctoral thesis","","","","","","","","","Electrical Engineering, Mathematics and Computer Science","","","","",""
"uuid:c01d1324-a6ac-442b-aeca-bd66c78a320a","http://resolver.tudelft.nl/uuid:c01d1324-a6ac-442b-aeca-bd66c78a320a","Parametrization of acoustic boundary absorption and dispersion properties in time-domain source/receiver reflection measurement","De Hoop, A.T.; Lam, C.H.; Kooij, B.J.","","2005","Closed-form analytic time-domain expressions are obtained for the acoustic pressure associated with the reflection of a monopole point-source excited impulsive acoustic wave by a planar boundary with absorptive and dispersive properties. The acoustic properties of the boundary are modeled as a local admittance transfer function between the normal component of the particle velocity and the acoustic pressure. The transfer function is to meet the conditions for linear, time-invariant, causal, passive behavior. A parametrization of the admittance function is put forward that has the property of showing up explicitly, and in a relatively simple manner, in the expression for the reflected acoustic pressure. The partial fraction representation of the complex frequency domain admittance is shown to have such a property. The result opens the possibility of constructing inversion algorithms that enable the extraction of the relevant parameters from the measured time traces of the acoustic pressure at different offsets, parallel as well as normal to the boundary, between source and receiver. Illustrative theoretical numerical examples are presented.","acoustic wave absorption; acoustic wave reflection; acoustic dispersion; transfer functions; acoustic intensity","en","journal article","Acoustical Society of America","","","","","","","","Electrical Engineering, Mathematics and Computer Science","Telecommunications","","","",""
"uuid:ad45c08f-974f-4e24-883d-431ad9b42392","http://resolver.tudelft.nl/uuid:ad45c08f-974f-4e24-883d-431ad9b42392","Analysis of physical mechanisms underlying density-dependent transport in porous media","Landman, A.J.","Hassanizadeh, S.M. (promotor)","2005","In this thesis, the interaction between (large) density gradients and flow and transport in porous media is studied. Large gradients in the density of groundwater exist for example near deep salt rock formations, which are considered as possible long-term storage sites for radioactive waste. Furthermore, density effects play a role in many other groundwater applications, such as salt water intrusion. Density gradients mainly affect the flow field and mass transport in two ways: by fluid volume changes (the compressibility effect) and by inducing gravity forces. The first part of the thesis deals with the compressibility effect, which is often disregarded. Contrary to the general belief, the (Oberbeck-)Boussinesq approximation is not consistent with the limit of infinitely small density variations, in which the gravity term disappears as well. In this thesis, limits are derived for which the compressibility effect can be neglected in comparison with the gravity effect. In addition, similarity solutions are presented for simultaneous heat and brine transport. For one-dimensional brine transport, approximate analytical solutions are derived that account for the density coupling between the fluid and salt mass balance. In the second part of the thesis, the effect of stabilizing gravity forces on hydrodynamic dispersion in a heterogeneous porous medium is investigated. High-accuracy numerical simulations are performed for multiple realizations of permeability fields with small-scale heterogeneities. Fresh water is displaced upward by denser brine. The reduction of the longitudinal dispersivity under the influence of density gradients is governed by the dimensionless gravity number. The numerical simulations show a large similarity to laboratory experiments in almost homogeneous porous media. Moreover, the ensemble-averaged simulation results are compared to predictions obtained with three different nonlinear dispersion models. One of these models is obtained by homogenization (a mathematical up-scaling technique) of the local scale brine transport equations. The main objective of the numerical experiments is to test and compare the different macroscopic dispersive transport models. Parameter dependencies are studied, and the applicability and limitations of the three different models are discussed.","density-dependent transport; porous media; hydrodynamic dispersion; boussinesq approximation; brine trasnport","en","doctoral thesis","","","","","","","","","Civil Engineering and Geosciences","","","","",""
"uuid:3c613301-54f1-4fe0-bfa4-9793fa751d5f","http://resolver.tudelft.nl/uuid:3c613301-54f1-4fe0-bfa4-9793fa751d5f","Correction of the phase retardation caused by intrinsic birefringence in deep UV lithography","Serebriakov, A.; Bociort, F.; Braat, J.","","2005","In the year 2001 it was reported that the birefringence induced by spatial dispersion (BISD), sometimes also called intrinsic birefringence, had been measured and calculated for fluorides CaF2 and BaF2 in the deep UV range. It was also shown that the magnitude of the BISD in these cubic crystals is sufficiently large to cause serious problems when using CaF2 for lithographic objectives at 157 nm and possibly also in the case of high numerical aperture immersion objectives at 193 nm. Nevertheless the single-crystal fluorides such as CaF2 are the only materials found with sufficient transmissivity at 157 nm and they are widely used at 193 nm for chromatic correction. The BISD-caused effects lead to the loss of the image contrast. In this work we discuss issues related to the design of optical systems considering the BISD effect. We focus on several approaches to the compensation of the BISD-related phase retardation and give examples of lithographic objectives with the compensated phase retardation","lithography; birefringence; spatial dispersion; phase retardation; optical system design","en","conference paper","SPIE","","","","","","","","Applied Sciences","Optics Research Groep","","","",""
"uuid:10486dfd-24f4-4044-bc1b-754dbc2bea70","http://resolver.tudelft.nl/uuid:10486dfd-24f4-4044-bc1b-754dbc2bea70","Scales and structures in bubbly flows. Experimental analysis of the flow in bubble columns and in bubbling fluidized beds","Groen, J.S.","Mudde, R.F. (promotor); Van den Akker, H.E.A. (promotor)","2004","In this project a detailed experimental analysis was performed of the dynamic flow field in bubbly flows, with the purpose of determining local hydrodynamics and scale effects. Measurements were done in gas-liquid systems (air-water bubble columns) and in gas-solid systems (air-sand bubbing fluidized beds) of different size. Amongst others with the help of lasers and glass fibres the behaviour was studied of single bubbles, bubble swarms and the continuous phase. These techniques were combined with advanced signal processing such as correlation analysis. A striking new phenomenon was the anisotropy or orientation dependence of experimental results. A detailed experimental study into the applicability of laser Doppler anemometry (LDA) in bubble columns showed that virtually only the liquid phase is recorded with LDA. The measurements show a pronouncedly turbulent flow field, but it is striking that this complex view can be characterized by a small number of fixed parameters. These parameters can also be used quite well for describing several physical phenomena and for scaling up these reactors.","bubble column; fluidized bed; bubbly flow; turbulence; laser doppler anemometry; glass fibre; coherent structures; dispersion; scale-up","en","doctoral thesis","","","","","","","","","Applied Sciences","","","","",""
"uuid:dfe1c9ee-2d1d-4ab3-a1ae-1c966b7ac4da","http://resolver.tudelft.nl/uuid:dfe1c9ee-2d1d-4ab3-a1ae-1c966b7ac4da","Photogeneration and dynamics of charge carriers in the conjugated polymer poly(3-hexylthiophene)","Dicker, G.","Siebbeles, L.D.A. (promotor)","2004","The conjugated polymer poly(3-hexylthiophene) is a promising candidate for applications in organic thin-film electronic and optoelectronic devices. This dissertation addresses fundamental issues regarding the photogeneration and recombination dynamics of charge carriers in this polymer. Measurements were carried out using an electrodeless, low-field microwave detection technique. With this technique, the intrinsic charge-carrier photogeneration and charge-transport properties of the material can be studied, in the absence of effects arising from electrode contacts and high electric fields, commonly present in conventional DC conductivity studies. The following issues are investigated: The quantum yield and wavelength dependence of photoelectron emission from the polymer surface. The wavelength dependence and activation energy of the quantum yield of charge carrier photogeneration within thin layers. The role of molecular order in the photogeneration of charge carriers. The effect of exciton annihilation on the photoconductance. The recombination dynamics of photogenerated charge carriers. The GHz charge carrier mobility and its activation energy. A generalized version of the stretched-exponential (Kohlrausch) decay law is derived, which provides an analytical description of the diffusive recombination of charge carriers.","photoconductivity; photoemission; disperse kinetics; thin film; flash-photolysis; pulse-radiolysis; microwave detection","en","doctoral thesis","Delft University Press","","","","","","","","Interfaculty Reactor Institute","","","","",""
"uuid:4c0701a8-a7cd-4b55-954a-b7b74fc95b2b","http://resolver.tudelft.nl/uuid:4c0701a8-a7cd-4b55-954a-b7b74fc95b2b","Dispersion resulting from wide passband shape in 50-GHz-spaced wavelength router","Gamet, J.; Pandraud, G.; Vonsovici, A.P.","","2004","","dispersion; integrated optics; multiplexers; silica; optical communications","en","journal article","SPIE","","","","","","","","Electrical Engineering, Mathematics and Computer Science","Electronic Instrumentation Laboratory","","","",""
"uuid:313027f3-71b7-4400-9ce3-0de86590952a","http://resolver.tudelft.nl/uuid:313027f3-71b7-4400-9ce3-0de86590952a","Upscaling of flow in porous media from a tracer perspective","Berentsen, C.W.J.","Van Kruijsdijk, C.P.J.W. (promotor)","2003","Most of our knowledge of flow in porous media is obtained at the pore and the macro scale. For reservoir scale modelling it is not practical to model the flow at these fine scales. Considering the usual objectives (e.g. large scale flow pattern and production forecast) it is undesirable to have to gather the tremendous amount of fine scale data that is required to model an entire reservoir. Moreover, present computational resources are simply not able to handle flow simulations of this size. Hence we resort to models that describe the essential physical behaviour in an averaged sense at the mega scale without modelling all finer scale details. Unfortunately, fine scale details are often correlated over large distances and appear to be part of the essential behaviour at a larger scale. As a consequence the reservoir scale flow is not just a function of some average properties of the finer scale structures. For these cases the scales in the problem are non-separable. The major challenge in upscaling is to account for this non-separability of scales. Going from single phase single component, via single phase multi component to multi phase fluid flow, upscaling becomes progressively more complex. In this Thesis we treat several aspects of upscaling of single and multi phase flow in porous media approached from a single phase context. Single phase upscaling The simplest flow type in porous media is single phase single component flow. For this type of flow the general assumption is that the upscaled megascopic pressure flux relation is the same as at the macro scale, namely Darcyâs law, albeit with effective coefficients. When the spatial length scales are non-separable the upscaled quantity depends on choices we make at the fine scale. As a consequence, single phase upscaling is mainly concerned with the proper estimation of the fine scale flux boundaries. In this thesis a method is developed that allows us to investigate the pressure and flux response of each individual flux boundary independent of the other boundaries. Fourier decomposition enables us further to investigate the effect of each individual frequency a flux boundary consists of. The major observation is that the significance of the flux response in the far field generally decreases with increasing frequency of the flux boundary that is applied. This does not generally hold for the pressure response; In case of long correlated streaks of especially low permeability the far field pressure response may be significantly larger than one would a priori expect. Upscaling of tracer dispersion At the next level of complexity we arrive at the upscaling of tracer dispersion. Traditionally dispersion has been modelled using Fickian models. However the Fickian approach does not satisfactorily explain all of the experimental observations. For instance the Fickian model cannot describe effective dispersion coefficients that vary with the Péclet number or with the length scale of observation. Moreover the Fickian description cannot account for the partial reversibility of dispersion when the flow direction is reversed. We focus on (Taylor) dispersion of a tracer released in a unidirectional velocity field belonging to a two dimensional (2D) porous medium. The tracer concentration is described by the two dimensional unidirectional classical convection dispersion equation (2D uCCDE), in which we initially restrict the small scale dispersive mechanisms to isotropic molecular diffusion. Our goal is to describe the (non-Fickian) evolution of the height averaged tracer concentration in time. The analysis starts with the relaxation concept; transverse diffusion causes the particle cloud to describe a transition from a correlated convective behaviour for short times towards uncorrelated Fickian behaviour for asymptotic long times. From a particle viewpoint this process describes the convergence of the velocity auto correlation function (VACF) of tracer particles to zero in time, as a result of the transverse displacement by diffusion. The correlation of the velocity of a particle in time results from the spatial correlation of the velocity field in the transverse direction and the limited (averaged) transverse displacement of particles by diffusion over short times. This relaxation process is characterised by a height averaged concentration profile that initially reflects the velocity profile and that converges in time towards a Gaussian profile typical for Fickian displacements. The corresponding spatial variance is initially proportional to t2 and becomes asymptotically with time proportional to t. The time that characterises this relaxation process is called the relaxation time. To analyse the model behaviour we transform the 2D uCCDE into an equivalent spectral representation using Fourier transformation. Each non-zero mode contributes to the mass balance of the height averaged concentration (zero-th mode) via a dispersive modal flux term. The evolution of each non-zero mode is described by a relaxation equation. It is characterised by a modal relaxation time that originates from the transverse molecular diffusion term in the 2D uCCDE. This modal relaxation time is proportional to the total height of the velocity field squared and decreases inversely proportional to the molecular diffusion and to the modal number squared. From the spectral representation we are able to derive the exact behaviour of the spatial moments belonging to the height averaged concentration. Moreover it forms the base of the upscaling approach we developed. To obtain the essential behaviour of the height averaged concentration, it is impractical to solve all modal equations. Hence we need to reduce the set of equations to a manageable size. A common approach is to describe the evolution of the dispersive Taylor flux as a single valued quantity. An important consequence of this approach is that the multi-scale character of the full model is lost. Classically this Taylor flux has been modelled in a Fickian way. However, such an approach ignores the relaxation process of the tracer and only covers the tracer behaviour for asymptotic long times. Here we follow the upscaling approach of Camacho. By summing all evolution equations of the modal fluxes, an approximate evolution equation of the Taylor flux is obtained. The result is a linear parabolic relaxation equation that is characterised by an approximate effective relaxation time and a closure term that accounts for all higher order modal interactions. Combining this equation with the mass balance for the averaged concentration results in the so-called c-J model. In case the spreading by diffusion in the longitudinal direction is negligible compared to the spreading induced by the velocity field, the c-J model simplifies to a generalised hyperbolic Telegraph equation. The c-J model describes the variance correctly in both the short and the long time limit. As it incorporates the relaxation process in a single scale sense, it is also able to show qualitatively the proper development of the variance for intermediate times. Quantitatively, we show that the c-J model improves significantly when scale separation is applied; The smaller Fourier scales that are relaxed with respect to the time scale of observation are described by a Fickian term and only the relaxation of the large(r) scales is modelled explicitly. In this way part of the multi scale character of the full model is again retrieved. Special attention is paid to the closure term in the c-J model that accounts for the modal interactions of the higher order concentration modes. As mentioned the multi scale character of the 2D uCCDE is lost by describing the dispersive flux as a single valued quantity. A consequence of this is that the c-J model is unable to show a sign change in the 3-rd moment that may occur in the full 2D model. To remedy this we consider alternative descriptions of the closure term in the upscaled model. We restrict our focus to the proper description of the third spatial moment and require that the present description of the mean and variance remains unaltered. Moment analysis demonstrates that the present form of the term that accounts for the modal interactions in the c-J modal is the only allowable linear form that does not affect the present description of the mean and variance. Alternatively, the coefficient in front of the closure term may be replaced by an empirical time varying function. The result describes qualitatively the proper behaviour of the 3-rd moment and is exact in the convective and dispersive limit. Overall it produces smaller errors in the 3-rd moment than the original c-J model while the lower moments remain unchanged. Until now we discussed the behaviour for particle distributions that are initially uniform over the height. Distributions that are initially non-uniform converge asymptotically in time towards a uniform distribution. This is shown by the convergence of the mean particle velocity towards the mean fluid velocity in time. Another consequence of non-uniform distributions is that the modal interactions of the higher order concentrations modes also affect the variance. Moreover, each moment is characterised by its ""own"" effective relaxation time. In general it is not longer adequate to describe the behaviour of the modal fluxes as a single valued quantity. We develop a truncation model in which, up to a separation scale, the evolution of each mode is modelled individually while the smaller scales are combined in an effective upper mode. The separation scale is determined such that the mean and variance are correctly described. The detail required in the truncation model increases as the initial distribution deviates more from uniformity and increases for decreasing observation times. However, even for quite small observation times, the truncation model is able to describe the proper behaviour with only little detail. We compare the 1D CCDE and the Telegraph model with the truncation method by means of the first two spatial moments. The CCDE ignores the relaxation process and only describes the behaviour of the mean and variance properly for asymptotic long times. For non-uniform initial particle distributions, the Telegraph equation describes both a relaxation of the mean and the variance with a single effective relaxation time. It is exact in the convective limit and describes the proper growth of the mean and variance in the long time limit. However, the shortcoming of the Telegraph model is that it cannot distinguish two distributions that have the same mean particle velocity and, as a consequence, it may produce large errors for intermediate times. Its applicability is therefore, similarly to the 1D CCDE, essentially restricted to uniform initial particle distributions. A second concept that is incorporated in the full physical model is reversibility of dispersion. When the flow direction is reversed a 'new' relaxation process is initiated similar to forward relaxation. However, the velocity of a particle after flow reversal is correlated in time to the velocity of that particle before reversal. This is again caused by the limited transverse particle displacement by diffusion over short times and the correlation of the velocity field in the transverse direction. As a consequence, we experience a demixing of the particle cloud as long as this velocity correlation dominates the particle behaviour. This is quantified by a temporary decrease of the variance. The major advantage of the c-J model over the 1D Fickian CCDE is demonstrated in these cases of partial reversibility of dispersion. While the Fickian model simply cannot handle a temporal decrease of the variance, the reversal behaviour is directly incorporated in c-J model via the relaxation time. The c-J model describes the (reversed flow) variance exactly in the convective and dispersive limit and gives a qualitatively correct picture for intermediate times. Applying scale separation further improves the quantitative description for intermediate times. So far the small scale mixing mechanism was restricted to isotropic diffusion. For flow in porous media this is too restrictive and we generalise it to a transverse varying dispersion. For unidirectional flow the microscopic dispersion in the transverse direction is commonly defined in an averaged sense at the macro scale as . This has as consequence that the relaxation mechanism turns from a time dependent mechanism for small Péclet number towards a space dependent relaxation mechanism for large Péclet number. For the spectral representation the extended dispersion has as major consequence that the relaxation times of the higher order modes are coupled. However, we have shown that by transformation of the modal concentrations we can obtain a set of modified modal equations that is of identical shape as the original set in which the modified relaxation times are again uncoupled. The transformation depends on the Péclet number. The advantage of the shape similarity is that, except for the modified coefficients, the mean and variance for uniform particle distributions are not altered and only one additional term shows up in the variance for non-uniform particle distributions. An upscale approach is followed similar to the diffusive case. The result is again a parabolic relaxation equation for the Taylor flux that is similar to the case of isotropic molecular diffusion. However, the effective relaxation time and modal interaction term are now functionally related to the Péclet number. In the diffusive limit the upscaled equation describes a relaxation in time identical to the isotropic case. For large Péclet numbers it describes a relaxation in space, similar to the full 2D model. We also investigate tracer dispersion in arbitrary velocity fields belonging to two dimensional porous media bounded in the y-direction. In these fields a second convergence mechanism may be present of which the variance of the height averaged concentration is initially proportional to t2 and which is linear in time for asymptotic long times. This mechanism, called convective convergence, takes place if the velocity field is second order stationary and if the velocity auto correlation function converges to zero sufficiently fast in time. As this mechanism is purely convective its dispersion is in principle fully reversible. In other words the spreading caused by the forward movement is completely cancelled when the flow is reversed and the flow time in both directions is equal. We investigate again if it is possible to describe the dispersive flux as a single valued quantity. Starting from the spectral equivalent of the two-dimensional convection diffusion equation, we follow an upscaling approach similar to the one discussed above. However, the spatial dependency of the velocity complicates matters considerably. Even for particle distributions that are initially uniform over the height, the modal interactions affect the lowest order derivatives in the equations of the dispersive flux and as a consequence the complete relaxation mechanism. The resulting model is of identical form as the c-J model but with coefficients that vary in space and are all functions of the velocity. If the velocity field is unidirectional the original c-J model is retrieved. In the absence of diffusion the equation is purely convective and is from a one-dimensional viewpoint able to demonstrate convective convergence and its reversibility. However, the present model has some severe (physical) shortcomings. Convective convergence in the sense of a single valued dispersive flux, requires that the relaxation time alters sign when the flow is reversed. A negative relaxation time is, similar to a negative dispersion coefficient hard to defend. Besides the relation between the upscaled coefficients and the original two dimensional field is (yet) unclear. Nevertheless, the present extension to arbitrary velocity field appears as a promising ansatz. The megascopic equations that we derive all appear to be of the same form, the c-J model, with the exception of the truncation model. The c-J model is also similar to recently developed macroscopic non-Fickian dispersion models. However the c-J model is a 1D model whereas the others are 3D. This similarity encouraged us to investigate if experimental results for macroscopic homogeneous media can be explained with this model. When a relaxation mechanism is present that works similarly to the combination of dispersion and diffusion, we show indeed that the c-J model may explain the variation of the effective dispersion coefficient as function of the Péclet number. It may also explain some experimental results concerning the reversibility of dispersion. However at present a clear mathematical link between the 1D c-J model and macroscopic homogeneous media is not yet established. Finally we establish a link between the relaxation process in the 2D uCCDE and Markovian Lagrangian theory. A Markovian model is presented in which we explicitly modelled the loss of velocity correlation of particles in time. A discrete velocity set represents the unidirectional velocity field of the full two-dimensional model. A large number of particles are redistributed over this set in time. If the magnitude of the small scale dispersion mechanisms in the full 2D model decreases the redistribution is such that the probability for a particle to keep the same velocity (auto correlation) increases. The model is constructed in such a way that any arbitrary initial particle distribution converges towards a uniform particle distribution in time. When the velocity auto correlation is uniform, the model shows relaxation behaviour that is essentially the same as the Telegraph equation. Moreover, in case there are only two velocities we proof that both models are identical upto second order accuracy in time. For a non-uniform velocity auto correlation, multi scale behaviour is demonstrated that is similar to the 2D uCCDE. By exploring a moment analysis from a Lagrangian viewpoint we derive analytical expressions for the mean, variance and third moment. More importantly, the Lagrangian viewpoint also enables us to explain the behaviour of the moments of the 2D uCCDE qualitatively. Especially the correlation structure of the velocity in time is visible from this point of view. Two phase flow upscaling This dissertation ends with upscaling of the more complex two phase flow type from a single phase context. In two phase flow in heterogeneous porous media, the important âconvectiveâ part may be divided in a single phase term and a two phase flow term. The first term captures the large scale permeability variations and is expressed in a Piston-Like (single phase) arrival time distribution. The second term captures the physics of multi-phase flow in porous media and is expressed in a relative permeability formulation. Here the overall convective two-phase model is approximated by convolution of the two terms. In order to quantify the effect of the fractional flow curves on production we defined a measure, based on the differences in period of production, that is relatively insensitive to the arrival time. For a number of two dimensional heterogeneous quarter five spot production scenarios and for four fractional flow curves, the two phase behaviour obtained by convolution is compared with the ârealâ two phase flow behaviour (fully 2D numerical solution). Most convolution results are at best in fair agreement with the full physics simulations. This can be attributed to the preferences in the flow direction resulting from total mobility near the fluid front. However, in our results the averaged error in the arrival time prediction of the watercut in the range 5-95% remains smaller than 20% and the error in the oil recovery remains within the 10% range (at 2.7 Pore Volumes injected). In summary, in an extremely fast way, convolution provides us a rough estimate of the full physics displacement.","porous media; upscaling; taylor dispersion; dispersion; reversibility; relaxation; single phase flow; two phase flow","en","doctoral thesis","DUP Science","","","","","","","","Civil Engineering and Geosciences","","","","",""
"uuid:74b0fb98-6f11-4a92-b2cb-fef46716ddc8","http://resolver.tudelft.nl/uuid:74b0fb98-6f11-4a92-b2cb-fef46716ddc8","Verspreiding van productiewater vanaf platforms in zee","Minns, A.W.","","2000","","boorplatforms; drilling platforms; oliewinning; oil production; gaswinning; gas production; afvalwaterverspreiding; waste water dispersion","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:abc7d4f0-68f2-42f5-9435-37722ad22cba","http://resolver.tudelft.nl/uuid:abc7d4f0-68f2-42f5-9435-37722ad22cba","Solitons and nonlinear dispersive waves","Sattinger, D.H.","TU Delft","1998","Description of a mathematical model to describe solitons in matlab.","soliton; dispersive wave; matlab","en","report","","","","","","","","","","","","","",""
"uuid:122992a9-c0c1-4e12-8e7b-c34c71436dff","http://resolver.tudelft.nl/uuid:122992a9-c0c1-4e12-8e7b-c34c71436dff","Verspreiding boorspecie Westerscheldetunnel bij storten in de Westerschelde","Vliet, F.W.J. van","","1997","","baggerspecie; dredge spoil; baggerspeciedepots; dredge spoil disposal sites; troebelheid; turbidity; Westerschelde; dispersie; dispersion","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:16c19819-ade3-46b6-b12d-28142fca4ba3","http://resolver.tudelft.nl/uuid:16c19819-ade3-46b6-b12d-28142fca4ba3","Measuring & modeling of concentrated settling suspensions using electrical impedance tomography","Grootveld, C.J.","Scarlett, B. (promotor); Van Weert, G. (promotor)","1996","","electrical impedance tomography; dispersion coefficients; concentration profiles; image reconstruction convection-dispersion equation","en","doctoral thesis","","","","","","","","","Applied Sciences","","","","",""
"uuid:734d4d63-dc5b-424d-a47e-0fabfc312c48","http://resolver.tudelft.nl/uuid:734d4d63-dc5b-424d-a47e-0fabfc312c48","Some observations on localisation in non-local and gradient damage models","Peerlings, R.H.J.; De Borst, R.; Brekelmans, W.A.M.; De Vree, J.H.P.; Spee, I.","","1996","","A0340K Waves and wave propagation: general mathematical aspects; A4620 Continuum mechanics; classical continuum descriptions; continuum; continuum damage; continuum mechanics; Damage; damage model; Deformation; degradation; dispersive wave propagation; finite element; finite element analysis; finite element simulation; finite element simulations; gradient approaches; gradient damage; gradient damage models; Loading; loading conditions; localisation; material degradation; mechanical; Model; MODELS; nonlocal damage models; one dimensional problem; Propagation; quasi static loading; quasistatic loading conditions; regularisation methods; Simulation; Softening; softening induced localisation; softening metallurgical; Wave propagation; Wave-propagation; Waves","en","journal article","Gauthier-Villars","","","","","","","","","","","","",""
"uuid:3b6c1408-7a9e-466c-b6da-ca2af978bdf4","http://resolver.tudelft.nl/uuid:3b6c1408-7a9e-466c-b6da-ca2af978bdf4","On gradient-enhanced damage and plasticity models for failure in quasi-brittle and frictional materials","De Borst, R.; Pamin, J.; Peerlings, R.H.J.; Sluys, L.J.","","1995","","Damage; dispersion; Failure; finite element; finite element simulation; finite element simulations; gradient enhanced damage; Localization; Model; MODELS; Plasticity; Simulation","en","journal article","Springer","","","","","","","","","","","","",""
"uuid:f7f2ff70-f4ee-4ad3-904f-6c6000cb8d6e","http://resolver.tudelft.nl/uuid:f7f2ff70-f4ee-4ad3-904f-6c6000cb8d6e","Hydraulic fracture characterization with dispersion measurements of seismic waves","Groenenboom, J.; Duijndam, A.J.W.; Fokkema, J.T.","","1995","","body waves elastic waves experimental studies geophysical methods hydraulic fracturing laboratory studies P waves rock mechanics seismic methods seismic waves theoretical studies ultrasonic methods wave dispersion 30 Engineering geology 20 Applied geophys","en","conference paper","Society of Exploration Geophysicists","","","","","","","","","","","","",""
"uuid:4d46f2cc-b19e-4554-a8c9-ac6cbd187ab9","http://resolver.tudelft.nl/uuid:4d46f2cc-b19e-4554-a8c9-ac6cbd187ab9","Experimental verification of stress-induced anisotropy","Cruts, H.M.A.; Groenenboom, J.; Duijndam, A.J.W.; Fokkema, J.T.","","1995","","anisotropy body waves deformation earthquakes elastic waves elastodynamic properties experimental studies laboratory studies propagation rock mechanics S waves seismic waves seismology stress transverse isotropy triaxial tests verification wave dispersion","en","conference paper","Society of Exploration Geophysicists","","","","","","","","","","","","",""
"uuid:d1451e17-e968-4175-bf8f-7080b3e88cf8","http://resolver.tudelft.nl/uuid:d1451e17-e968-4175-bf8f-7080b3e88cf8","Microstructure and properties of styrene acrylate polymer cement concrete","","","1995","The paper systematically describes the evolution of the microstructure of a styrene acrylate polymer cement concrete in relation to its mechanical properties and durability. The results presented and discussed at the present paper involve the interaction of the polymer dispersion with portland cement; the effect of the polymer modification on the hydration of cement; the evolution of the microstructure of polymer cement pastes at the early stage; the interface, pore structure, mechanical properties and freeze-thaw (F-T) resistance of polymer cement concrete (pee). The objective of this investigation is to arrive at a better understanding of the microstructure of pee and the way in which the microstructure develops. Furthermore, an attempt has been made to relate the micro-structure of concrete to its mechanical properties and durability aspects, such as F-T resistance.","microstructure; polymer dispersion; cement concrete; mechanical properties; freeze/thaw","en","journal article","Delft University of Technology","","","","","","","","Civil Engineering and Geosciences","","","","",""
"uuid:d292269c-4621-4e50-a9ce-f12cb2f11e9c","http://resolver.tudelft.nl/uuid:d292269c-4621-4e50-a9ce-f12cb2f11e9c","Image analysis of surf zone hydrodynamics","Redondo, J.M.; Rodriguez, A.; Bahia, E.; Falques, A.; Gracia, V.; Sanchez-Arcilla, A.; Stive, M.J.F.","","1994","","Hydrodynamics Image analysis Water waves Coastal zones Image recording Oceanography Surfaces Ocean currents Measurements Tracking position Surf zone hydrodynamics Digital image processing Video image recording Sea surfaces Longshore current Dispersion mea","en","conference paper","Ministerio de Educacion y Ciencia (Spain); Office of Naval Research; Generalitat de Catalunya; Japan Society of Civil Engineers; E.T.S. d'Enginyers de Camins; et al","","","","","","","","","","","","",""
"uuid:693de6a8-eefa-48d0-bb18-22ba61988e80","http://resolver.tudelft.nl/uuid:693de6a8-eefa-48d0-bb18-22ba61988e80","Analysis of the transport of a pollution cloud in the Upper-Rhine River between Lake of Constance","Van Kuik, C.A.; Van Mazijk, A.","","1994","In the one-dimensional 'Rhine Alarm Model' differences between the actual travel time of a pollution cloud, originating from an instantaneous release of an accidental spill, and the travel time, based on the flow velocity is represented by a lag coefficient. In the model this lag coefficient is defined by the relative difference between these two travel times. This paper presents the results of a study on the influence of tributaries and suppressed flow by weirs on the lag coefficient in general and on the influence of the River Aare and the suppressed flow by water power stations on this coefficient in the Upper-Rhine River between Lake of Constance and Basel especially. Also the influence of incompletely transversal mixing in the vicinity of the point of release at a river bank as a special case of a polluted tributary is discussed. In the study analytical and numerical approaches were applied. For the numerical approach a two-dimensional transport model of the ""Versuchsanstalt fUr Wasserbau (VAW)"" (Hydraulic Research Institute) of the ETH-Ziirich (Federal University of Technology of Zurich) was used. The main conclusion is that the behaviour of the lag coefficient along the Upper-Rhine River is strongly influenced by sudden increases of the flow velocity at power stations, due to the differences in waterdepth upstream and downstream of the station, and at the Aare-Rhine confluence, due to the large discharge ratio of these river branches. The outcome of these flow-velocity discontinuities is a relatively large negative value of the lag coefficient upstream of the discontinuity and a relatively large positive value downstream. This is because upstream of the discontinuity the transport velocity of the centroid of the pollution cloud is already influenced by the larger flow velocity downstream of the discontinuity as soon as the front of the cloud has passed the discontinuity. Downstream of the discontinuity the transport velocity of the centroid is still influenced by the smaller flow velocity upstream of the discontinuity as long as the tail of the cloud remains upstream of the discontinuity. Case studies on the Upper-Rhine River between Lake of Constance and Basel show good fits of the calibrated values of the lag coefficient in the Rhine Alarm Model with the results of the two-dimensional transport model.","dispersion; rivers","en","report","TU Delft","","","","","","","","Civil Engineering and Geosciences","","","","",""
"uuid:e78efc76-a631-45f2-aa76-6c91add2456e","http://resolver.tudelft.nl/uuid:e78efc76-a631-45f2-aa76-6c91add2456e","Fundamental issues in finite element analyses of localization of deformation","De Borst, R.; Sluys, L.J.; Muhlhaus, H.B.; Pamin, J.","","1993","","A0260 Numerical approximation and analysis; A4630 Mechanics of solids; Civil; continuum; continuum model; continuum models; Deformation; dispersion; Failure; finite element; finite element analyses; finite element analysis; Gradients; higher order deformation gradients; internal length scale; Localization; localization of deformation; mechanical; micropolar continuum models; Model; MODELS; Numerical simulation; numerical simulations; Numerical-simulation; Propagation; rate dependence; Simulation; size effect; Strain softening; Strain-softening; Wave propagation; Wave-propagation","en","journal article","","","","","","","","","","","","","",""
"uuid:235a09c8-18d9-411d-b97e-d85cba4d690f","http://resolver.tudelft.nl/uuid:235a09c8-18d9-411d-b97e-d85cba4d690f","A 3D particle model for transport problems in transformed coordinates","Dunsbergen, D.W.; Stelling, G.","","1993","In this report, transport problems are solved with a particle method that takes into account the Eulerian background flow field. Dispersion and other transport problems can be solved applying this model, as long as the corresponding transport process is formulated with a flux gradient relation, i.e., the advection-diffusion equation. The particle method has been made consistent with such a transport process. Since many 3D flow models are formulated in general coordinates, the 3D particle displacements are also given with respect to such a coordinate system. Analytical and numerical aspects of this particle method have been studied. The effectiveness of the method has been demonstrated with two academic test cases including streamlines in a recirculation zone and grid dependency in a discharge problem.","dispersion; mathematical modelling","en","report","TU Delft","","","","","","","","Civil Engineering and Geosciences","","","","",""
"uuid:dbc91ad6-555c-4cff-8507-9e2b68a983ec","http://resolver.tudelft.nl/uuid:dbc91ad6-555c-4cff-8507-9e2b68a983ec","Wave propagation, localization and dispersion in a gradient-dependent medium","Sluys, L.J.; De Borst, R.; Muhlhaus, H.B.","","1993","","A0230 Function theory, analysis; A4630J Viscoelasticity, plasticity, viscoplasticity, creep, and stress relaxation; A4630M Vibrations, aeroelasticity, hydroelasticity, mechanical waves, and shocks; Civil; continuum; continuum model; discretization; dispersion; dispersive wave propagation; energy dissipation; gradient dependent medium; grid lines; inelastic strain; initial value problem; initial value problems; internal length scale; Laplacian; Localization; localization zone; mechanical; Model; nonassociated flow; Plastic Flow; Preserves; Propagation; Softening; Strain; strain profiles; Strain softening; Strain-softening; two dimensional problems; Wave propagation; wave reflection; Wave-propagation","en","journal article","","","","","","","","","","","","","",""
"uuid:cac48afc-4496-43f3-bd0f-75c6185a5fc6","http://resolver.tudelft.nl/uuid:cac48afc-4496-43f3-bd0f-75c6185a5fc6","The method of characteristics applied to analyse 2DH models","Sloff, C.J.","","1992","To gain insight into the physical behaviour of 2D hydraulic models (mathematically formulated as a system of partial differential equations), the method of characteristics is used to analyse the propagation of physical meaningful disturbances. These disturbances propagate as wave fronts along bicharacteristics (rays) into the physical solution domain, while carrying the information from initial and boundary conditions. The method is applied to 2DH models for flow on a fixed and a 2DH two-layer model for turbidity currents in a reservoir. Introducing a point disturbance, circular shaped wave fronts develop related to water movement, and a star-shaped wave front related to disturbances in the mobile bed. A transversal wave front, related to vorticity, is formed in all models. An essential difference is shown in the propagation of the wave fronts for subcritical and supercritical flows. The characteristics have been used to define rules for imposing boundary conditions, and to find a stability condition for the two-layer 2D flow. The theory presented in this report is also applicable to other twodimensional engineering problems, and is important for imposing boundary conditions and for using the 2D numerical solution methods.","dispersion; mathematical modelling","en","report","TU Delft","","","","","","","","Civil Engineering and Geosciences","","","","",""
"uuid:ca687068-4639-4359-beec-8a357e48ca0a","http://resolver.tudelft.nl/uuid:ca687068-4639-4359-beec-8a357e48ca0a","Separation, dispersion, humidification and transport of fibres in a physical lung model","Stoelinga, M.A.; Marijnissen, J.C.M.; Bibo, B.H.; Prodi, V.","","1992","","Fibre separation; monodisperse fibres; fibre dispersion; fibre deposition; fibre transport; lung model","en","journal article","Elsevier","","","","","","","","","","","","",""
"uuid:fb69a757-f19e-4f98-b8a0-128a77dcb9f7","http://resolver.tudelft.nl/uuid:fb69a757-f19e-4f98-b8a0-128a77dcb9f7","Gebruikershandleiding MARS: Versie 1.0","Postma, L.; Gils, J.A.G. van; Hendriks, A.; Stralen, F.C. van","","1989","","simulatie; simulation; computerprogramma's; software; waterverontreiniging; water pollution; olieverontreiniging; oil pollution; afvalwaterverspreiding; waste water dispersion","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:08798beb-4b70-49e3-bb63-31500ab3eae2","http://resolver.tudelft.nl/uuid:08798beb-4b70-49e3-bb63-31500ab3eae2","Regeling stofstromen zout: Voorstel voor aanpassing en aanvulling modelinstrumentarium voor toxische stoffen","Pagee, J.A. van; Markus, A.A.","","1988","","North Sea; zeewaterkwaliteit; seawater quality; toxicologie; toxicology; dispersie; dispersion; zoutgehalte; salinity","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:f56e12d2-07f9-439f-b6a0-d8b076a7d0d2","http://resolver.tudelft.nl/uuid:f56e12d2-07f9-439f-b6a0-d8b076a7d0d2","A numerical wave model based on new equations of Boussinesq type which incorporate improved dispersion characteristics","Murray, R.","Battjes, J.A. (mentor); Madsen, P.A. (mentor); Abbott, M.B. (mentor)","1988","The Boussinesq equations are a modification of the long wave equations to make some allowance for the effects of the non-hydrostatic pressure in short waves, and are capable of describing the transformation of directional, irregular, nonlinear waves in relatively shallow water. This thesis introduces new equations of Boussinesq type in one and two horizontal dimensions that have greatly improved linear dispersion characteristics for water depths up to the 'deepwater limit', and which reduce to a classical form in shallow water. A finite difference model, based on a well-proven prototype which uses an implicit scheme and an alternating direction algorithm, has been developed in one dimension to solve the new equations. It is demonstrated tor linear waves that accurate results can be obtained with computational efficiency even when the spatial and temporal resolution of the waves is low.","Boussinesq; long wave equations; dispersion characteristics","en","master thesis","","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:a0ae89ba-6d64-4b09-aa8b-01f344830cb1","http://resolver.tudelft.nl/uuid:a0ae89ba-6d64-4b09-aa8b-01f344830cb1","Some properties of the Langevin model for dispersion","De Baas, A.F.","Nieuwstadt, F.T.M. (promotor); Schuurmans, C.J.E. (promotor)","1988","The Langevin Equation is used to describe dispersion of pollutants in the atmosphere. The theoretical background for the equation is discussed in length and a review on previous treatments and applications is given. It is shown that the Langevin equation can describe dispersion in complex circumstances. In particular the equation is applied to dispersion in a convective boundary layer, where it reproduced the measurements accurately. Two forms of the Langevin Equation, which have both been used in practical applications, are copared and it is concluded that in terms of their theoretical properties, they are not very different in spite of important differences in practical application.","dispersion; Langevin equation; boundary layer; air pollution","en","doctoral thesis","Riso National Laboratory","","","","","","","","Mechanical Maritime and Materials Engineering","","","","",""
"uuid:8b4bf992-e874-4251-a5e3-024725344f73","http://resolver.tudelft.nl/uuid:8b4bf992-e874-4251-a5e3-024725344f73","A discrete-time inverse scattering algorithm for plane wave incidence in a one-dimensional inhomogeneous acoustic medium","Leyds, F.B.; Fokkema, J.T.","","1988","","acoustical waves algorithms direct problem geophysical methods heterogeneous materials inverse problem models one dimensional models reflection methods seismic methods seismograms signal to noise ratio synthetic seismograms wave dispersion 20 Applied geop","en","journal article","","","","","","","","","","","","","",""
"uuid:4c251f10-35b1-46a8-961c-274cd1822a1b","http://resolver.tudelft.nl/uuid:4c251f10-35b1-46a8-961c-274cd1822a1b","Eddy simulation of two-dimensional dispersion","Van Dam, G.C.","Rijkswaterstaat","1987","This report presents a study on the behaviour of particle clouds in two-dimensional velocity fields. The results can be applied in a general way but are especially of interest for the dispersion of matter in surface waters of a large horizontal extent and relatively small depth or layer thickness. They may be somewhat more relevant to seas than to lakes, because at sea the energy supply feeding the velocity field contains an important constant component (of astronomical origin) so that the energy content (at various length scales) of the velocity field will not fluctuate as strongly as may be the case in lakes. Synthetic fields have been used of well defined spectral structure so that numerical experiments could be performed under controlled conditions, which is not possible in nature. By comparing the results with experiments and observations in the field, one obtains insight into natural conditions and prevailing mechanisms and how to model these adequately. Present computer facilities do not only enable these basic studies with synthetic fields of detailed spectral structure but also make it possible to supplement existing flow models with spectral modes which are not reproduced by the flow model while they are essential for proper modelling of dispersion. Sometimes simpler means to the same end with less computational effort are permissible although they remain inferior to the spectral approach.","eddy simulation; dispersion; diffusion","en","report","Rijkswaterstaat, RIKZ","","","","","","","","","","","","",""
"uuid:9a64053c-1170-41c5-aa0e-699160beeb62","http://resolver.tudelft.nl/uuid:9a64053c-1170-41c5-aa0e-699160beeb62","Invloed van in lengterichting geïntregeerde effecten op tijdsafhankelijke dispersiekoëfficiënt","Abraham, G.","","1986","","dispersie; dispersion","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:f75a8cb8-b0d1-4fa4-9114-59e876736ffc","http://resolver.tudelft.nl/uuid:f75a8cb8-b0d1-4fa4-9114-59e876736ffc","Dispersion of matter in homogeneous, time-dependent nearly-horizontal flows","Kalkwijk, J.P.Th.","","1986","","dispersion; water flow","en","report","TU Delft","","","","","","","","Civil Engineering and Geosciences","","","","",""
"uuid:34504cdd-1728-490b-9559-451f062e6345","http://resolver.tudelft.nl/uuid:34504cdd-1728-490b-9559-451f062e6345","Herkomst en transport van contaminanten op de Noordzee: Relatie tot de dumping van baggerspecie","Salomons, W.; Chardon, W.; Kerdijk, H.N.; Marquenie, J.W.","","1984","","zeewaterkwaliteit; seawater quality; baggerspeciedepots; dredge spoil disposal sites; afvalwaterverspreiding; waste water dispersion","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:7faea55b-2a80-42ae-90fc-8176be4b7073","http://resolver.tudelft.nl/uuid:7faea55b-2a80-42ae-90fc-8176be4b7073","Reststroomonderzoek in Oosterschelde-getijmodel","Karelse, M.","Deltares","1982","","afvalwaterverspreiding; numerical modelling; numerieke modellen; Oosterschelde; residual currents; reststromen; waste water dispersion; Zeeland","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:84cfca88-c246-4aae-bfaf-6c2d03d005c4","http://resolver.tudelft.nl/uuid:84cfca88-c246-4aae-bfaf-6c2d03d005c4","Principles of Mixing in Tidal Basins in the Netherlands","Dronkers, J.; Zimmerman, J.T.F.","Rijkswaterstaat","1981","Some fundamental notions related to the flushing of tidal basins are reviewed and some important mixing mechanics are discussed. It is shown that the characteristics of mixing and flushing in tidal basins can be described in various but connected ways, introducing the concepts of time scales and dispersion coefficients. For some simple geometrical configurations formulas for the computation of time scales and dispersion coefficients are given. For complex-shaped tidal bas ins field data are necessary in order to obtain quantitative information on time scales, dispersion coefficients or on the contribution of different mixing processes. The theoretical topics dealt with in this paper are illustrated by field data collected in some tidal basins in the Netherlands.","tidal basins; mixing; dispersion","en","report","Rijkswaterstaat, Deltadienst","","","","","","","","","","","","",""
"uuid:5e8c78b0-ab9f-4546-8acd-acaf6253ccf8","http://resolver.tudelft.nl/uuid:5e8c78b0-ab9f-4546-8acd-acaf6253ccf8","Verificatie van numeriek 2D (vertikaal)-model DISTRO aan getijgootmetingen: Verslag wiskundig onderzoek","Karelse, M.","Deltares","1981","","calibration; dispersie; dispersion; gelaagdheid; ijking; numerical modelling; numerieke modellen; stratification; turbulence models; turbulentiemodellen","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:601842cc-99a2-4aa4-bc26-710548c71c7b","http://resolver.tudelft.nl/uuid:601842cc-99a2-4aa4-bc26-710548c71c7b","Getijgootonderzoek: Invloed dwarsmiddeling op grootte van dispersietransporten in 2D (vertikaal)-beschrijving","Karelse, M.","Deltares","1981","","diffusiecoefficient; diffusivity; dispersie; dispersion; exchange flow; mass transport; numerical modelling; numerieke modellen; salt water intrusion; stoftransport; uitwisseling; zoutwaterindringing","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:b57b3597-81dd-42e8-ad10-29d84b5b98f9","http://resolver.tudelft.nl/uuid:b57b3597-81dd-42e8-ad10-29d84b5b98f9","Two-dirnensional Dispersion governed by Second Order Equatian","Soerjadi, R.","De Josselin de Jong, G. (mentor)","1981","The paper is dealing with dispersion, which is defined as the scattering of a particle cloud in space due to some stochastic spreading mechanisme In many cases such a process can be approximately described by a differential equation, sometimes called dispersion equation. This equation turns out to be a partial differential equation of infinite order with non-constant coefficients. For simple or simplified problems, in which the spreading mechanism is time and place independent, the equation possesses constant coefficients.","dispersion","en","master thesis","","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:6f95cd95-3a87-44df-a655-a8c8193cc4bd","http://resolver.tudelft.nl/uuid:6f95cd95-3a87-44df-a655-a8c8193cc4bd","Onderzoek naar de verspreidingsmechanismen in de Oosterschelde","Karelse, M.","Deltares","1980","","afvalwaterverspreiding; diffusie; diffusion; mass transport; Oosterschelde; stoftransport; waste water dispersion; Zeeland","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:ecd35cd9-648b-41f6-b136-b45624f82edc","http://resolver.tudelft.nl/uuid:ecd35cd9-648b-41f6-b136-b45624f82edc","Getijgootonderzoek: Onderzoek met bodemruwheid ter verifikatie van tweedimensionaal numeriek zoutindringingsmodel - deel B : zout-zoet proeven","Karelse, M.","Deltares","1979","","bed roughness; bodemruwheid; current velocity measurement; dispersie; dispersion; getijmodellen; numerical modelling; numerieke modellen; salt water intrusion; stroomsnelheidsmeting; tidal models; zoutwaterindringing","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:d5d9c6b8-d8da-4726-abdc-f43bb627b741","http://resolver.tudelft.nl/uuid:d5d9c6b8-d8da-4726-abdc-f43bb627b741","Getijgootonderzoek: Onderzoek met bodemruwheid ter verifikatie van tweedimensionaal numeriek zoutindringingsmodel - deel A : homogene proeven","Karelse, M.","Deltares","1979","","bed roughness; bodemruwheid; current velocity measurement; dispersie; dispersion; getijmodellen; numerical modelling; numerieke modellen; salt water intrusion; stroomsnelheidsmeting; tidal models; zoutwaterindringing","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:daa2996d-32d4-4cfe-8ce5-04b4ec9c5697","http://resolver.tudelft.nl/uuid:daa2996d-32d4-4cfe-8ce5-04b4ec9c5697","Getijgootonderzoek: Eendimensionale numerieke berekening van getijbeweging en zoutverdeling in de getijgoot","Karelse, M.","Deltares","1978","","dispersie; dispersion; numerical modelling; numerieke modellen","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:5c4cf9af-f0cc-4c25-8693-9881f14a74e5","http://resolver.tudelft.nl/uuid:5c4cf9af-f0cc-4c25-8693-9881f14a74e5","One-dimensional analysis of salinity intrusion in estuaries","Sanmuganathan, K.","TU Delft","1977","This report describes a mathematical model that was developed to predict salinity intrusion in estuaries as it is affected by control and abstraction of fresh water. The need for such a model, particularly for estuaries in tropical areas with large variations in fresh water flow, capable of giving satisfactory predictions of salinity movement from limited field data is brought out. The difficulties in using existing mathematical models for such purposes are discussed. The model outlined in this report overcomes these difficulties by relying on an approximate analytical solution of the unsteady one dimensional high water slack mass balance equation. The model relies on estimating the value of the longitudinal dispersion coefficient from field data obtained within a period of about six months. The predictions made for a continuous period of over two years for the Gambia estuary are shown to agree well with observations. The predictions made by the model for salinity movement under different fresh water abstraction and regulation patterns are also presented.","salinity; salt intrusion; density currents; longitudinal dispersion; mathematical model; Gambia estuary; diffusion","en","report","HR Wallingford","","","","","","","","","","","","OD",""
"uuid:7b4ce234-ea2f-4626-b374-01b35ed7b42f","http://resolver.tudelft.nl/uuid:7b4ce234-ea2f-4626-b374-01b35ed7b42f","Analysis of the NLR airports pollution dispersion model on sensitivity for meteorological parameters and on source modeling","Tiggelaar, J.J.","","1976","The NLR airports pollution dispersion model is analysed with regard to sensitivity for meteorological parameters and the modeling of the sources of pollution (i.e. airplanes). It is found that the weather resolution of the model is satisfactory in view of the present standards of meteorological measurement. Atmospheric stability (Pasquill class) turns out to he the parameter that influences the pollution dispersion most, especially through its influence on vertical dispersion rate. For long term prediction of pollution levels, where mean values of weather parameters are more accurately known, the meteorological modeling is most appropriate. To treat real airplanes, which do not emit continuously (e.g. if above the inversion layer, emitted pollution does not reach the ground), the Gaussian plume was modified into a ""cut-off plume"". Then modeling of the polluting airplanes by series of moving point sources, using the cut-off plume, was compared with modeling them by a line source representing their averaged emission. It turns out that deviations are important only in close vicinity of taxi- and flight tracks, e.g. on the airport itself. Thus for applications to the surroundings of airports, the line source modeling, present in the model, is adequate.","air pollution; meteorological parameters; mathematical models; air ports; air traffic; traffic; plumes; exhaust gases; dispersion; concentration (composition); normal density functions","en","report","Nationaal Lucht- en Ruimtevaartlaboratorium","","","","","","Campus only","","","","","","",""
"uuid:6ee3a436-7bf9-4cc5-b62b-dd8605d873f2","http://resolver.tudelft.nl/uuid:6ee3a436-7bf9-4cc5-b62b-dd8605d873f2","Verspreiding schutwater Kreekraksluizen in de kom van de Oosterschelde","Wijngaarden, N.J. van","Deltares","1976","","afvalwaterverspreiding; diffusie; diffusion; locks; Oosterschelde; schutsluizen; waste water dispersion; waterkwaliteit; water quality; Zeeland","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:a8f66d86-2d5d-4294-af89-419a70440e19","http://resolver.tudelft.nl/uuid:a8f66d86-2d5d-4294-af89-419a70440e19","Limitations of dispersion concept","Abraham, G.","","1974","","dispersie; dispersion; diffusie; diffusion","en","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:5e19e197-7162-41d8-8811-da492648e71d","http://resolver.tudelft.nl/uuid:5e19e197-7162-41d8-8811-da492648e71d","Diffusie in estuaria: Schaalonderzoek in protype en hydraulische modellen van het estuarium Brouwershavense Gat - Grevelingen","Eysink, W.D.","Deltares","1974","","afvalwaterverspreiding; Brouwershavense Gat; diffusie; diffusion; estuaria; estuaries; Grevelingen; tracers; tracers; waste water dispersion; Zeeland","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:1c32a6a7-02b6-497f-93d5-f82d1720066d","http://resolver.tudelft.nl/uuid:1c32a6a7-02b6-497f-93d5-f82d1720066d","RESIDENCE TIMES OF WATERS BEHIND BARRIER ISLANDS","Chiu, T.Y.; Van de Kreeke, J.; Dean, R.G.","Rijkswaterstaat","1970","This study pertains to lagoons connected to the ocean by narrow, constricted inlets. The purpose of the study is to evaluate the convective or non-dispersive transport in these lagoon systems. Equations describing the flow in the lagoon and in the inlets are derived. Because the convective transport results from the higher order (non-linear) terms in the equations, only third order terrms and higher are neglected. A numerical model is developed especially to compute the flow in water bodies connected to the ocean by inlets. The results of the study presented here are mainly based on theoretical considerations.","lagoons; constricted inlets; non-dispersive transport","en","report","College of Engineering University of Florida Gainesvilie, Florida","","","","","","","","","","","","KWP-collection",""
"uuid:65d1454c-e070-44f3-a28a-9c03cc9868ef","http://resolver.tudelft.nl/uuid:65d1454c-e070-44f3-a28a-9c03cc9868ef","Mean value and correlation problems connected with the motion of small particles suspended in a turbulent fluid","Tchen, C.M.","Burgers, J.M. (promotor)","1947","A theoretical treatment of diffusion as function of turbulence, by working out the dispersion of small particles in turbulent fluid. The method of Kolmogoroff is used to decribe the movement in a statistical ways","dispersion; diffusion; turbulence; Kolmogoroff","en","doctoral thesis","Martinus Nijhoff, The Hague","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""