"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:a370be10-b49d-4f4d-a074-39f464c3d8f9","http://resolver.tudelft.nl/uuid:a370be10-b49d-4f4d-a074-39f464c3d8f9","Optimizing the configuration of tidal turbines in storm surge barriers","Verbeek, Merel C. (TU Delft Environmental Fluid Mechanics)","Uijttewaal, W.S.J. (promotor); Labeur, R.J. (copromotor); Delft University of Technology (degree granting institution)","2023","The flow between bridge piers and through storm surge barriers and barrages is an untapped and promising source of water energy. This energy can be harvested with tidal or hydro turbines. In 2015, five turbines with a total capacity of 1.2 MW were retrofit in a flow opening of the Eastern Scheldt storm surge barrier (the Netherlands). These turbines form world's first commercial-scale tidal fence. However, there is still a major challenge to optimize the configuration of these turbines based on their energy yield and their possible environmental effects to the hinter-lying estuary.
This thesis presents a model tool to optimize the energy yield and impact on the environment of installing turbines in flood defences by altering the turbine placing. Mapping out the effects of turbines on the flow is the central question. To answer this question, this research consists of three parts: (1) measuring the field situation, (2) testing a turbine in the laboratory and (3) setting up an analytical model that is coupled to a regional flow model.
In the first part of this study (1), unique, high-resolution data of the flow through the Eastern Scheldt storm surge barrier and around the turbines were investigated. In particular, for the first time in the literature, commercial-scale turbines are used to determine the effect of tidal turbines on the water flow. The power output of the turbines is also quantified. The data is used to derive an analytical model of the flow around a turbine in a barrier. This model can calculate the power of tidal turbines and the resistance of the barrier and turbine for different forms of the installation and variable strength of the external flow.
In the second part of this study (2), these insights were refined in laboratory tests, in which the configuration of the turbine and barrier was varied. This method is more representative of real turbines because it has a larger scale factor (1:9) than is usual in the literature. The tests show that the generated power strongly depends on the position of the turbine relative to the barrier. The data also show that the combined resistance of a barrier and turbine is lower than the sum of the individual resistances. These outcomes are used to successfully validate the previously developed analytical model.
In the last part of this study (3), the developed analytical model was implemented in a larger-scale numerical flow model. In this larger-scale model, the small-scale flow around a barrier with turbines is linked in an efficient way to the large-scale water movement in a tidal basin. This makes it possible to optimize existing or new tidal power stations, both at the level of the entire barrier and at that of a single flow opening. The impact on the environment can therefore be determined with the model, even more accurately than was previously possible.
The research in this thesis shows that the effect of the turbines on the flow at a larger distance is smaller than previously thought. This offers the possibility, for example, to install more turbines and harvest more energy without exceeding the acceptable environmental impact (e.g. ecological effects). This study has contributed to confidence in the technical and economic feasibility of turbine installations that can be built in hydraulic engineering works in the Dutch Delta. The developed calculation tool is freely available to investigate energy yield and environmental effects of tidal energy projects worldwide.","tidal energy; hydrodynamics; modelling","en","doctoral thesis","","978-94-6483-182-5","","","","","","","","","Environmental Fluid Mechanics","","",""
"uuid:d4c0062c-9191-40e4-805a-72fe7afde7bd","http://resolver.tudelft.nl/uuid:d4c0062c-9191-40e4-805a-72fe7afde7bd","Chenier Dynamics","Tas, S.A.J. (TU Delft Environmental Fluid Mechanics)","Reniers, A.J.H.M. (promotor); Delft University of Technology (degree granting institution)","2022","Over the last decades, mangrove forests have suffered immense and rapid losses worldwide. In recognition of their important socio-economic and environmental functions, many attempts have been made to both protect the remaining mangrove coastlines and restore eroding sites. Unfortunately, many rehabilitation attempts have failed, lacking a thorough system understanding of mangrove-mud coasts.
Some mangrove-mud coasts are protected on their seaward side by sandy ridges (called `cheniers'). They protect against wave attack and can help to protect vulnerable mangrove-mud coastlines. In order to sustainably restore mangrove coasts, chenier dynamics need to be understood at the temporal and spatial scales relevant for mangrove establishment (daily to yearly variability driven by waves and tides). This dissertation aims to advance our understanding of chenier dynamics within the context of an eroding mangrove-mud coast. The severely eroded coastline of Demak, Indonesia, is used as a case study.
We started with a field campaign in Demak, observing the cross-shore dynamics of a single chenier. The observations revealed that cheniers can be very dynamic in relatively calm conditions. Using velocity moments as a proxy for the sediment transport, we have explored the role of tides and waves in the observed chenier dynamics. Tides drive the chenier landward, especially when the water depth over the chenier crest is low (high crest level relative to mean sea level). Waves only generate substantial sediment transport when the chenier is submerged. Overall, the cross-shore chenier dynamics are very sensitive to the timing of tides and waves: most transport takes place when high water levels coincide with (relatively) high waves.
While our observations showed the chenier to be highly dynamic in the short term, satellite images reveal that over longer timescales the position of the chenier remains more or less stable within the intertidal zone. This is in contrast to cheniers described in literature, which only migrate landward until they reach a stable position above tidal influences. We have developed an idealised chenier model to explore this dynamically stable position. The model simulates cross-shore chenier dynamics under daily wave and tidal influences and is able to predict both onshore and offshore migration. Onshore migration is mainly driven by wave action, while offshore migration is induced by a tidal phase lag or storms. This phase lag is caused by drowning of the coastal plain due to subsidence. For certain combinations of waves and tides, the model predicts a dynamically stable chenier. In the absence of a phase lag and storm season effect, the model yields a `classic' stable chenier that welds onto the shoreline by onshore migration.
We used Delft3D to explore the formation of cheniers through wave winnowing (the sorting of sand and mud by waves). We have identified three phases of chenier development: (1) a winnowing phase, during which mud is washed out of the seabed initially consisting of a mixture of sand and mud, (2) a sand transport phase, when the sand in the upper layer is transported onshore, and (3) a crest formation phase, during which a chenier crest rapidly develops at the landward limit of onshore sediment transport. The main mechanism driving onshore sand transport is wave asymmetry. During calm conditions, sand transport takes place within a narrow band limiting the volume of sand delivered nearshore, and therefore no chenier develops. In contrast, average storm conditions mobilise sufficient sand for a crest to develop. Our results thus reveal that chenier formation through wave winnowing does not require extreme storm conditions. Our study also shows that chenier formation through wave winnowing is a relatively slow process, with the largest time scales associated with the the first two phases of chenier development: winnowing and sand transport.
Overall, this dissertation contributes to our understanding of cross-shore chenier dynamics. While very dynamic in the short term, cheniers can maintain a stable position in the intertidal zone for certain combinations of waves and tides. As such, they can contribute to mangrove rehabilitation by creating windows of opportunity for mangrove establishment. Due to its rapid subsidence rates, the coast of Demak provides an analogue for a global drowning of coastlines under anticipated accelerated sea level rise. In fact, cheniers may form a natural defense mechanism of drowning coastal plains. As a result, small changes to the coastal plain (e.g. constructing a dike) could have a significant impact, disturbing the chenier dynamics and interrupting their negative feedback on coastal erosion. This work has illustrated the complexity and interconnectedness of coastal systems, a crucial notion in designing successful protection strategies for mangrove-mud coasts.","chenier; morphodynamics; modelling; sediment transport; mangroves","en","doctoral thesis","","978-94-6366-576-6","","","","","","","","","Environmental Fluid Mechanics","","",""
"uuid:d1d741d9-3022-40dd-a464-3c07052f209e","http://resolver.tudelft.nl/uuid:d1d741d9-3022-40dd-a464-3c07052f209e","Computational Design of High Temperature Alloys","Yu, H. (TU Delft Novel Aerospace Materials)","Xu, W. (promotor); van der Zwaag, S. (promotor); Delft University of Technology (degree granting institution)","2019","The development in computational simulation techniques has brought significant progress in the realization of computational alloy design. The advantages are most significant when developing novel materials of which the research & development cycles are particularly time and energy (and hence cost) consuming, such as high-temperature alloys. In our former research, a computational alloy design approach coupling thermodynamics, kinetics, metal physics and genetic algorithm has been developed. By applying this new approach, novel heat resistant steels have been successfully designed with different microstructural features, which manage to nicely outperform existing commercial alloys. In this thesis, we follow the same approach while more focus has been given on adjusting the alloying level of different elements to solve specific issues, such as the high cost issue caused by a high Cobalt level, and the high microstructural instability caused by a high Chromium concentration. Extended application has been made to design novel heat resistant steels by introducing the concept of self-healing mechanisms. The creep damage (grain boundary cavities) of newly-developed steels during service are expected to be automatically filled by the special-designed Laves phase of which their formation kinetics was adjusted.","Computational design; heat resistant steels; Ni superalloys; modelling; Thermodynamics; kinetics","en","doctoral thesis","","978-94-028-1832-1","","","","","","2020-11-01","","","Novel Aerospace Materials","","",""
"uuid:2a13956c-e2d3-4641-b79d-db8c62fb65b9","http://resolver.tudelft.nl/uuid:2a13956c-e2d3-4641-b79d-db8c62fb65b9","Towards intrinsically safe microstructures in resistant spot welded advanced and ultra high strength automotive steels","Eftekharimilani, P. (TU Delft (OLD) MSE-5)","Hermans, M.J.M. (promotor); Richardson, I.M. (promotor); Delft University of Technology (degree granting institution)","2019","The potential for weight reduction, ease of manufacturing and improved crashworthiness makes advanced and ultra high strength steels attractive for automotive applications. Resistance spot welding is by far the most widely used joining method in the automotive industry due to the high operating speeds, the reliability of the process and the suitability for automation. Safe microstructures in resistance spot welds in AHSS and UHSS have to be assured to promote acceptance of these steels in the automotive industry. However, the higher alloying contents of AHSS/UHSS steels limit their weldability and unfavourable modes of weld failure are frequently observed. The main aim of this research is to identify and understand the unfavourable failure of the AHSS welds and to modify the microstructure and thus the mechanical response of the welds. In this PhD thesis the results of alternative welding schedules to modify the microstructure and mechanical performance of the AHSS resistance spot welds are reported. The effects of a paint bake cycle on the microstructure of the welds have also been investigated and the predominant mechanisms involved were studied. The residual stress within these welds were measured and simulated to facilitate the residual stress prediction before welding. Double pulse resistance spot welding with different second pulse current levels was applied to improve the microstructure of the weld edge. The second current pulse equal to the first pulse anneals the weld edge and modifies the weld edge microstructure. Microstructural analysis was performed using optical microscopy, scanning electron microscope, electron probe microanalysis (EPMA) and electron back scattered diffraction (EBSD). The double pulse weld showed a reduction in segregation of alloying elements such as phosphorous and a change in grain morphology from dendritic to a more equi-axed shape and smaller grain size. The results obtained from the mechanical testing i.e. cross tension strength test (CTS) and tensile shear strength test (TSS) showed enhanced cross-tension strength and energy absorption capability of the weld for the double pulse welds.","Resistance spot welding; Advanced high strength steels (AHSS); Microstructure analysis; Steels; EPMA; EBSD analysis; Mechanical properties; TEM study; Phase transformations; residual stress; modelling; Automotive","en","doctoral thesis","","978-94-6380-515-5","","","","","","","","","(OLD) MSE-5","","",""
"uuid:7be51192-65f2-47c4-a1ca-9f15bab12dbc","http://resolver.tudelft.nl/uuid:7be51192-65f2-47c4-a1ca-9f15bab12dbc","Characterising Angular Accelerometers using a Two-Axis Motion Simulator","Jatiningrum, D. (TU Delft Control & Simulation)","Mulder, Max (promotor); de Visser, C.C. (copromotor); Delft University of Technology (degree granting institution)","2018","Fault-Tolerant Flight Control (FTFC) systems reconfigure aircraft flight control laws to help restore a controlled flight and preserve acceptable performance under systemfaults. A typical approach to achieve fault tolerance is using inertial sensor measurementswhich can provide robustness to abrupt changes in the aircraft dynamics. This method does not rely on an accurate and full aerodynamic model, but only requires an estimate of the control effectiveness and an additional reconfiguration mechanism to the control laws such as switching, model following, matching, and adaptive compensation. With the inertial sensor being at the very heart of the control laws, to have proven and well-understood sensors is essential to increase the operational performance of a post-failure aircraft. Recent developments lead to FTFC systems that require angular acceleration feedback, which with the current conventional Inertial Measurement Unit (IMU) is obtained by taking the first derivative of the angular rates measured by gyroscopes. Because differentiation commonly intensifies noise and incurs a delay, a direct measurement of angular acceleration is anticipated to enhance the quality of the feedback signal. However, angular accelerometers are currently not part of the commercial aircraft system, which prompts the need to understand their characteristics. This thesis aims to investigate how an angular accelerometer can be evaluated and calibrated in a systematic fashion.","angular accelerometer; calibration; novel inertial sensor; modelling; motion simulator; frequency response; axis alignment","en","doctoral thesis","","978-94-6186-968-5","","","","","","","","","Control & Simulation","","",""
"uuid:ef6aa135-0ef3-42d5-b2a7-d270f36529ad","http://resolver.tudelft.nl/uuid:ef6aa135-0ef3-42d5-b2a7-d270f36529ad","Resistance Spot Welding of Advanced High Strength Steels","Den Uijl, N.J.","Richardson, I.M. (promotor)","2015","The introduction of advanced high strengths steels enabled automotive manufacturers to simultaneously reduce weight and increase safety of vehicles. However issues were reported concerning the weldability of these steels. These issues concerned both the manufacturability as well as the performance of resistance spot welded joints. The manufacturability addresses the ability to produce joints in an industrial set up, especially the welding range and the electrode lifetime. The performance includes the post weld hardness and the failure mode of resistance spot welded joints. Both aspects are addressed in the dissertation using experimental data and software to model and simulate welding processes.","welding; Resistance Spot Welding; modelling; post weld hardness; advanced high strength steels","en","doctoral thesis","","","","","","","","","Mechanical, Maritime and Materials Engineering","Materials Science & Engineering","","","",""
"uuid:cfe95bfa-4a52-48a1-9368-b0f66d89d980","http://resolver.tudelft.nl/uuid:cfe95bfa-4a52-48a1-9368-b0f66d89d980","Emissions of methane and nitrous oxide from full-scale municipal wastewater treatment plants","Daelman, M.R.J.","Van Loosdrecht, M.C.M. (promotor); Volcke, E.I.P. (promotor)","2014","Since 1750, the year that commonly marks the start of the Industrial Revolution, the atmospheric concentrations of carbon dioxide, methane and nitrous oxide have risen about 40 %, 150 % and 20 %, respectively, above the pre-industrial levels due to human activity (IPCC (2013) Climate Change 2013: The Physical Science Basis. Working Group I Contribution to the IPCC 5th Assessment Report, IPCC, Cambridge, United Kingdom and New York, NY, USA). These elevated greenhouse gas concentrations are held responsible for climate change, which has detrimental effects on the global ecosystem. The treatment of municipal wastewater entails the emission of greenhouse gases. The emission of carbon dioxide and the extent to which it contributes to the increased atmospheric greenhouse gas concentrations is well understood. The origins of methane and nitrous oxide, both potent greenhouse gases with a global warming potential of respectively 34 and 298 CO2 equivalents over a 100 year time horizon, are far less understood. This lack of insight hampers the mitigation of these emissions. The present thesis discusses the emission of nitrous oxide and methane from municipal wastewater treatment plants. The final goal is to come up with guidelines to mitigate these emissions in order to decrease the climate footprint of wastewater treatment. This requires insight into the extent of the emissions and into the relationships between the emissions on the one hand and the plant’s operational conditions on the other hand. This work fulfils the need for decent emission data by providing long-term, online emission data from a covered wastewater treatment plant that resulted in the most precise and accurate emission estimate from a full-scale plant to date. Given the importance of reliable data, particular attention is paid to sampling techniques (dissolved methane) and sampling strategies (nitrous oxide).","greenhouse gas; wastewater treatment; monitoring; modelling","en","doctoral thesis","","","","","","","","","Applied Sciences","Biotechnology","","","",""
"uuid:f8cd8841-7f88-4c29-86a5-2a1c58021d96","http://resolver.tudelft.nl/uuid:f8cd8841-7f88-4c29-86a5-2a1c58021d96","DEM-CFD Modelling of the ironmaking blast furnace","Adema, A.T.","Boom, R. (promotor)","2014","","blast furnace; solid flow; gas flow; modelling; coupled DEM-CFD; cohesive zone","en","doctoral thesis","","","","","","","","","Mechanical, Maritime and Materials Engineering","Materials Science & Engineering","","","",""
"uuid:f9ec2a55-a7af-49ec-9e24-db866776a96f","http://resolver.tudelft.nl/uuid:f9ec2a55-a7af-49ec-9e24-db866776a96f","Computational modelling of pattern formation by myxobacteria","Janulevicius, A.","Van Loosdrecht, M. (promotor)","2014","Myxobacteria are social bacteria that are remarkable for their complex life cycle. In vegetative state, when nutrients are available, myxobacteria cooperatively swarm on a solid surface and feed. When exposed to starvation conditions, myxobacteria exhibit multicellular morphogenesis: 10^5-10^6 cells aggregate to form a fruiting body. Due to their unique life cycle, myxobacteria often serve as relatively simple model organism to study multicellular development and morphogenesis. Myxobacteria cells glide on a substratum, periodically reversing direction and interact with surrounding cells of a swarm. During developmental process, myxobacteria cells often form various patterns: clusters of cells, domains of aligned cells, circular aggregates and streams of cells traveling into the aggregates. The goal of the thesis was to formulate a computationally efficient mechanical mass-spring model of a myxobacterium cell and study the importance of mechanical interactions between cells for the pattern formation in myxobacteria populations. In Chapter 2, a basic model was formulated and it was investigated how cell flexibility affects cell alignment in the population in two-dimensions. The model was formulated in terms of experimentally measurable mechanical parameters, such as engine force, bending stiffness, and drag coefficient. It was shown, that a population of rigid cells can align well due to mechanical interactions between cells, but that cell flexibility impedes the alignment. Theoretical estimations of cell flexibility suggest that myxobacteria cells could be too flexible for the population to align due to mechanical interactions. Therefore, in Chapter 3 lateral restriction of cell movement due to contact with the substratum was introduced in the model. It was shown that lateral restriction can increase the ability of a population of flexible cells to align. In Chapter 4 it was studied how reversal period of cells affects population movement patterns. The results indicate that short reversal period results in domains of aligned cells, whereas long reversal period produces cell clusters. Furthermore, the model reveals that in densely packed populations, non-reversing cells can sort themselves due to mechanical interactions to produce streams of cells that travel in the same direction. Chapter 5 introduces short-range guidance forces between the trailing pole of one myxobacterium and the leading pole of another and investigates the resulting patterns. It is shown that certain types of short-range guiding interactions can explain the formation of circular aggregates. In Chapter 6, the model is extended to three-dimensions and simulation outcome is compared with the results obtained in the previous chapters. The three-dimensional model shows that guiding interactions as in Chapter 5 can initiate the formation of unstable mounds. Finally, the thesis Outlook discusses a series of directions in which the current model can be extended to further understand the importance of mechanical interactions between gliding cells on the development of myxobacteria.","myxobacteria; modelling","en","doctoral thesis","","","","","","","","","Applied Sciences","Biotechnology","","","",""
"uuid:596899e4-94d7-4d47-b3cf-126fbe6c1de3","http://resolver.tudelft.nl/uuid:596899e4-94d7-4d47-b3cf-126fbe6c1de3","Shipping and shipbuilding scenario evaluations through integration of maritime and macroeconomic models","Pruyn, J.F.J.","Nienhuis, U. (promotor); Meersman, H. (promotor); Van de Voorde, E. (promotor)","2013","This research focusses on the use of consistent scenarios to help ship owners, banks and other parties with an interest the maritime business get a better grip on the future. Three levels of detail can be distinguished for the maritime industry. The macroeconomic level is the highest and focusses on the behaviour of countries and the trade between them. The next level is that of the maritime markets, newbuilding, secondhand sales, scrapping and trading. The last level is at company level, optimizing the assignment of vessels. While for each level models exists in many shapes and forms. The strength of this thesis is to combine the latest ideas and techniques into one single model spanning all three levels. It creates a much more consistent picture of the effects of a scenario on the future and many different scenarios can be tested. Also the effect of a set of scenarios on the profitability of a vessel can be investigated. The downside is the amount of data required for such a model, as well as the fact that mistakes (in this data) are carried over within the model. The model now available is a good first attempt at such a model. Some simple scenarios were able to demonstrate realistic, but counterintuitive behaviour, that would have been missed with a less complex model. This supports the notion that such a model is necessary for understanding the complex nature of the maritime economy.","shipping; maritime; economics; scenario analysis; modelling; newbuilding; secondhand; scrapping; ordering; allocation of world fleet; trade flow; demand; supply; GAM; multi-country","en","doctoral thesis","","","","","","","","2013-12-11","Mechanical, Maritime and Materials Engineering","Marine & Transport Technology","","","",""
"uuid:339d5c2a-6889-4002-b02d-0283c97f1610","http://resolver.tudelft.nl/uuid:339d5c2a-6889-4002-b02d-0283c97f1610","Thermostatistical theory of plastic deformation in metals","Galindo Nava, E.I.","Sietsma, J. (promotor); Rivera Diaz-del-Castillo, P.E.J. (promotor)","2013","This work aims to describe plastic deformation and microstructure evolution of metals at various scales in terms of dislocation behaviour. The theory is based on statistical thermodynamics, where the entropy is proposed to incorporate the possible paths for dislocation motion. Other than estimating the velocity gradients a dislocation may reach, the number of possible paths (configurations) that are favourable in terms of free energy at a given temperature and strain rate are considered in the entropy. It is demonstrated that the entropy features strongly in plasticity: 1) Its description supplies a physical foundation to the Kocks–Mecking formulation across the scales at a variety of deformation conditions for FCC, BCC and HCP metals, by identifying the activation energy for dislocation annihilation. 2) The transitions from low, medium and high temperature dislocation annihilation mechanisms are physically explained. 3) It aids in describing the conditions for the formation of dislocation cells and their average size, as well as the work hardening behaviour at large strains in FCC and BCC metals. 4) Deformation twinning in HCP, FCC and nano–twinned copper can be described. 5) The transition tempera- tures where different twin modes predominate in HCP metals are predicted. 6) The dynamic recrystallisation behaviour in pure and multicomponent FCC systems can be described; the critical conditions for recrystallisation occurrence are obtained in terms of alloy’s composition and deformation parameters. 7) Solid solution effects in work hardening can be identified. All these results allow to describe various plasticity phenomena in terms of a single parameter: the average dislocation density.","dislocation theory; statistical thermodynamics; plastic deformation; modelling; dynamic recovery; dynamic recrystallization","en","doctoral thesis","","","","","","","","","Mechanical, Maritime and Materials Engineering","Materials Science and Engineering","","","",""
"uuid:f3ba6eb1-bccc-4999-a667-6ee92b65161d","http://resolver.tudelft.nl/uuid:f3ba6eb1-bccc-4999-a667-6ee92b65161d","Unstructured Orthogonal Meshes for Modeling Coastal and Ocean Flows","Kleptsova, O.","Pietrzak, J.D. (promotor); Stelling, G.S. (promotor)","2013","In this thesis a z?layer unstructured C-grid finite volume hydrostatic model is presented. An efficient and highly scalable implicit technique for the solution of the free surface equation is combined with an Eulerian approach for the advection of momentum. A consistent velocity reconstruc- tion procedure which not only satisfies the continuity law but also guarantees the discrete kinetic energy conservation is presented. It is shown that an ac- curate velocity reconstruction procedure is of crucial importance not only for discretization of the Coriolis term, but also for the correct advection of mo- mentum, especially in the multilayer case. Unlike other z?layer models the method presented here ensures that the staircase representation of bathymetry and free surface has no influence on the vertical structure of the flow. The method is therefore guaranteed to be strictly momentum conservative, also in the layers containing the free surface and bed. A number of test cases are presented to show that the model is able to accu- rately simulate Coriolis dominated flows and flooding and drying processes both in the depth-averaged case and in the presence of multiple z?layers. A simulation of the 2004 Indian Ocean tsunami is used to evaluate the ability of the method to simulate fast propagating tsunami waves and detailed inundation processes. Results obtained using two different rupture models are compared to the tide gauge arrival times, satellite altimetry data and the inundation ob- servations in the Banda Aceh area. The comparison is used not only to assess the quality of the underlying rupture models but also to determine the value of the available data sources for such an assessment. Preliminary results of the unstructured grid fine resolution tidal model the southern North Sea including the Rhine-Scheldt Delta region are presented. The model is able to correctly reproduce the essential characteristics of the M2 tide, as well as of the most important nonlinear shallow water overtides M4 or M6. The simulated velocity field was used to evaluate the Simpson- Hunter stratification parameter, the variability of frontal positions due to tidal advection and spring-neap adjustment.","shallow-water equations; modelling; unstructured mesh","en","doctoral thesis","","","","","","","","2013-04-26","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:163507af-96df-4804-ad19-2147921b6cbc","http://resolver.tudelft.nl/uuid:163507af-96df-4804-ad19-2147921b6cbc","Multi-class continuum traffic flow models: Analysis and simulation methods","Van Wageningen-Kessels, F.L.M.","Hoogendoorn, S.P. (promotor); Vuik, C. (promotor)","2013","How to model and simulate traffic flow including different vehicles such as cars and trucks? This dissertation answers this question by analyzing existing models and simulation methods and by developing new ones. The new model (Fastlane) describes traffic as a continuum flow while accounting for different types of vehicles. It is reformulated in Lagrangian coordinates. Using the reformulation, mathematical properties of the model are analyzed and efficient simulation methods are developed.","traffic flow; modelling; simulation; multi-class; traffic","en","doctoral thesis","TRAIL","","","","","","","","Civil Engineering and Geosciences","Transport & Planning","","","",""
"uuid:e613a11d-65bd-4ce0-bbb9-6821cc455de3","http://resolver.tudelft.nl/uuid:e613a11d-65bd-4ce0-bbb9-6821cc455de3","Dynamics of Energy System Behaviour and Emissions of Trailing Suction Hopper Dredgers","Shi, W.","Stapersma, D. (promotor)","2013","Reducing fuel consumption from dredge vessels is always one of the priorities of the ship builder and the dredge contractor. In addition there is an increased awareness worldwide regarding exhaust emissions. CO2, NOx and SOx currently are or will in future be regulated strictly by international legislation and local authorities. Looking at a dredge cycle of a Trailing Suction Hopper Dredger (TSHD), every stage is far from stationary and in fact the dynamic variations are very severe.. Its performance is strongly influenced by weather condition, hydrological condition, river/sea bed profiles, soil types and characteristics, discharge method and discharge pipeline configuration. Although, nowadays, sophisticated automation is employed on subsystems for optimizing the dredging process, the dredger is still mainly under control of operators. The knowledge, the skill, the attitude of the dredge operators determine the performance of a TSHD and make it even more dynamic. In order to reduce fuel consumption and exhaust emissions, the impact from said dynamics need to be taken into account. This research is therefore conducted in order to know, capture, understand and be able to predict the behaviour of the energy system of a TSHD under dynamic load. Comprehensive onboard measurements have been executed to collect real time data on the energy system behaviour and exhaust emissions. After post-processing, consisting of signal synchronization, correction of the NOx-sensor time lag, filtering, signal organization and unit conversion, the results are presented the very first time. It is observed that, at constant nominal engine speed transient loads push the fuel consumption, air consumption and NOx emission away from the stationary lines. However seen at a larger time scale (in the order of stages per dredging cycle), the effects from transient loads are neutralized. The most important conclusion is: that in terms of total fuel consumption and total exhaust emissions, a dynamic loading of the energy system is not resulting in a penalty. Nonlinear time domain simulation models of a TSHD energy system (for dredging and sailing) are built in Matlab/Simulink®. The main system components and their dynamics are included, which makes the scope of the simulation models wide enough to cover all required energy systems. By means of matching and validation, the precision of the simulation models is ensured on both component and system level. Most of the components are modelled based on first principle concepts. They provide the required level of detail for understanding the system behaviour and emissions. In addition, the simulation models are well structured, providing easy removal of non-needed components, addition of new components and improvement of existing components. Through onboard measurements and simulation models, the dynamics of the behaviour of energy systems and in particular the emissions of a TSHD was thoroughly investigated in the time domain. Using normalization and linearization, the response of the energy systems to external disturbances and control commands are also investigated in the frequency domain. The linear model requires only a limited number of normalized derivatives and time constants and they are relatively independent of physical dimensions of the components. In a block diagram as presented in the thesis it can be easily traced how the disturbances propagate through the energy system and the sensitivities of involved parameters can be judged. The linear model has several advantages when compared to the nonlinear model. In the first place a linear model is generic. Further the required normalized derivatives and time constants can often easily be estimated beforehand, also because their first principle origin is made explicit. So this makes it possible that the order of magnitude of the frequency bands of any system can be grasped, even before there is an actual design. Finally the dynamic response can be explored using classical control methods. This would be useful in deciding whether a control system is needed and to determine what kind of control strategy would be effective. In summary, the three approaches (onboard measurement, non-linear simulation model and linear model) presented in this thesis provide an exclusive database and practical tools to know, to capture, to understand and to be able to predict the behaviour of the energy system and emissions of a TSHD. By further development, such as: measurement from more vessels, extending the scope of the model, increasing the precision of the model and increasing the level of details of the model, these methods can eventually be used for optimizing the design of a TSHD and reducing operational cost (fuel and emissions).","dynamic behaviour; emissions; energy system; onboard measurement; modelling","en","doctoral thesis","VSSD","","","","","","","","Mechanical, Maritime and Materials Engineering","MTT-SPDO","","","",""
"uuid:81b7a378-fe87-4a43-8f34-3134d5fa0433","http://resolver.tudelft.nl/uuid:81b7a378-fe87-4a43-8f34-3134d5fa0433","Understanding socio-technical change: A system-network-agent approach","Chiong Meza, C.M.","Weijnen, M.P.C. (promotor); Dijkema, G.P.J. (promotor)","2012","Transitions are processes of change that have always occurred in society: for example, the production of goods changed from handcraft to machine-made. In recent years, these transitions attract more and more attention, mainly because societies now wish to actively bring about certain changes, such as the reduction of the use of fossil fuels – the so-called energy transition. This raises several questions, such as: how do ‘transitions’ evolve and to what extent can the course of such a process be influenced? This PhD thesis tries to improve the understanding of those transitions that have both a social and a technological aspect. This thesis presents a method of analysis with which these processes of socio-technical change can be captured in their full breadth and be modelled, which can serve as a basis for the simulation of a transition. Central to this approach is that we analyse the dynamics of the entire system, of the individual actors and of the actor networks at the same time as well as the interactions between these levels. This is the ‘System-Network-Agent approach’ that is proposed in this thesis. This method of analysis was applied in two in-depth case studies: about the transition in Brazil towards the use of bio-ethanol as car fuel, and the transition in the Netherlands towards a supply-chain approach for the treatment of household waste. Several lessons can be learned from these case studies. First, government can affect a transition, but not effect it. Government can try to start a transition process, but it depends on many other circumstances and actors – which cannot be controlled by government – whether the desired change is actually achieved. Moreover, both case studies show that a hierarchical government with a clear policy focus is more effective in bringing about changes than a government that keeps all options open and seeks to reach social consensus first. For example, the most significant change concerning the treatment of household waste in the last century in the Netherlands occurred during the German occupation in World War II. Drastic events, such as a crisis or very high oil prices, play an important role in transitions. They can be an incentive for the development of alternatives to the current practice or help to align the preferences of different actors. As such, drastic events can provide a window of opportunity in a transition, but they could also hinder such a process. From the case studies we conclude that the system, network and agent levels are all needed in a transition. A ‘top-down transition’ needs bottom-up acceptance, whereas a ‘bottom-up transition’ will not succeed if it is blocked from the top. The proposed ‘System-Network-Agent approach’ has proven to be a powerful tool to capture exactly those interdependencies, as this thesis shows.","transitions; socio-technical systems; modelling","en","doctoral thesis","Next Generation Infrastructures Foundation","","","","","","","2012-06-01","Technology, Policy and Management","Infrastructure Systems & Services","","","",""
"uuid:30858e82-68cc-497f-baf2-aae1f59c222f","http://resolver.tudelft.nl/uuid:30858e82-68cc-497f-baf2-aae1f59c222f","Fast Frequency and Time Domain Integral Equation Modelling for Marine CSEM Applications","Moradi Tehrani, A.","Slob, E.C. (promotor)","2012","In this study we developed algorithms for fast frequency and time domain integral equation modelling for marine controlled-source electromagnetic (CSEM) applications. Solutions of integral equations for CSEM applications in a three-layered earth with an assumed reservoirs is examined using the conjugate gradient fast Fourier transformation (CG-FFT) method, which is used as a reference. For 3D configurations fast computational methods are relevant for both forward and inverse modelling studies. The Born approximation, extended Born approximation, and iterative extended Born approximation are implemented and compared with the full solution of the CG-FFT, even with a reservoir consisting of two separated compartments. We also showed that the approximate results are accurate at the receiver level, which is usually the sea bottom, and inside the reservoir. This iterative method is suitable as a modelling algorithm for solving the inverse scattering problem as well. These methods are based on an electric field domain integral equation formulation. With the help of this method sensitivity analysis using 3D modelling is possible in a timely manner, which is vital for CSEM applications. Our modelling studies investigate to which extent the iterative extended Born approximation method is fast and accurate for forward modelling and could be used for inverse modelling. Sensitivity analysis as a function of the source position and different reservoir sizes validates the accuracy of the iterative extended Born approximation. We also looked into the question in what model configurations two-and-a-half dimensional modelling is a good modelling choice for three-dimensional reservoir response to the diffusive EM field. It is investigated how the accuracy of 2.5D modelling compares with 3D modelling depending on the configurations. Because 2.5D modelling is much faster than 3D modelling, proper use of 2.5D CSEM modelling provides sensitivity analysis of subsurface parameters for many different scenarios in a limited amount of time. Depending on size and depth of the target, hydrocarbon thickness, and extension in cross-line dimension, the required frequency content of the emitted diffusive field and the number of offsets must be determined to assess if the target can be detected. At this stage a decision can be made on whether or not the target reservoir is detectable. From here an optimum survey can be designed based on the forward modelling results. Similarly, in this way the detectability from time-lapse monitoring data of changes in the reservoir due to production can be assessed. Finally we investigated how frequency-domain data can be efficiently transformed to the time-domain. CSEM methods are generally divided into frequency-domain electromagnetic (FDEM) and time-domain (transient) electromagnetic (TDEM) methods, depending on the waveform of the transmitted electrical current. We compared a quasi-analytical method to transform frequency-domain CSEM data back to the time-domain with a numerical transformation. The quasi-analytical method exploits the fact that the kernel of the integral equation has a known behavior as a function of frequency and that the solution to the integral equation can be written as a sum of repeated applications of the kernel to the incident field. A set of expansion functions is found, which have analytically known time domain counterparts, which need only a limited number of frequency values for the transformation back to time. We compared this quasi-analytical method, coined the Diffusive Expansion Method in CSEM applications with two other numerical methods, Gaver-Stehfest method and an optimized form of the fast Fourier transformation method where the data is required at an minimum number of discrete frequency values such that the data at intermediate frequency values can be accurately obtained by interpolation. We found that the Diffusion Expansion Method is a good candidate for CSEM frequency-to-time conversion of data for any kind of subsurface model and survey configuration.","integral equation; CSEM; modelling","en","doctoral thesis","","","","","","","","","Civil Engineering and Geosciences","Geoscience & Engineering","","","",""
"uuid:38b0eaef-2d37-4145-9ea8-545faf1a7c07","http://resolver.tudelft.nl/uuid:38b0eaef-2d37-4145-9ea8-545faf1a7c07","Transportation Modelling for Regional Evacuations","Pel, A.J.","Hoogendoorn, S.P. (promotor)","2011","Regional evacuation planning is complex and timely. These planning studies can be assisted by a transportation model. In this thesis, we investigate the requirements for such a model, and develop, implement, and test a new model, called EVAQ, which meets these requirements. Two case studies show how EVAQ can be used to assess the success and robustness of an existing evacuation plan, as well as design an optimal plan anticipating uncertainty in traveller compliance behaviour. The analyses yield a number of practical recommendations to improve evacuation planning.","travel behaviour; evacuation; modelling; planning","en","doctoral thesis","TRAIL Research School","","","","","","","","Civil Engineering and Geosciences","Transport and Planning","","","",""
"uuid:24c3f698-376a-43c0-8240-bb278fa01433","http://resolver.tudelft.nl/uuid:24c3f698-376a-43c0-8240-bb278fa01433","Microstructure and transport phenomena in visco-elastic modelling of hardening cementitious materials","Van der Ham, H.W.M.","Van Breugel, K. (promotor); Koenders, E.A.B. (promotor)","2011","Since the durability depends, among other things, on the quality of the concrete and presence of cracks, it is necessary to calculate the probability of cracking in hardening concrete as reliable as possible in case of durability predictions. In this thesis, it is investigated how the accuracy of stress prediction in hardening concrete can be improved by a more detailed description of microstructural and transport phenomen. First it is described how hydration of cement and the microstructural development can be described. Two basically different models for cement hydration are explained, which introduced the possibility to couple results and information from the simulations with accurately property development of hardening concrete (strength, stiffness, porosity), however, the relation between visco-elastic behavior of hardening concrete and the microstructural development is still under development. Some history of development of visco-elastic models is presented, from which it turned out that there is a need for a step forward in understanding and explicit modeling of visco-elastic behavior of hardening concrete, by taking into account the microstructural development of hardening cement paste and moisture movements in order to make stress predictions in hardening concrete elements more accurate and reliable. The moisture state is modeled explicitly in the solidification theory by including hollow permeable shells in a microstructural hydration model. A hollow shell, or annular space, is defined as the zone between an anhydrous cement grain and the gel shell. This space is filled with water. The Shell Deformation Model (SDM) as developed in this thesis relates the time dependent deformations of a loaded cement paste to the transport of load bearing water inside the shell of cement gel to the capillary pores. The model assumes equal time dependent deformations for cement paste loaded in tension and compression. From the simulated results, it turned out that the fineness of cement does not influence the visco-elastic behavior of hardening concrete. In order to obtain reliable and accurate results from the proposed model, the moisture state in the capillary pores is considered accurately. For this purpose, moisture movements are modeled at microlevel. Due to the inhomogeneous distribution of cement particles in the cement paste between the aggregates, pressure differences exist between water in the pores of cement paste located near the aggregates and the water in the pores of cement paste in-between the aggregates. A model is developed which describe pressure driven moisture movements based on the conservation of volume. The influence of capillary water transport on visco-elastic behaviour of hardening cement paste is studied. Taking those movements into account, an influence up to 8% on the visco-elastic behaviour is observed. The differences are bigger for higher water/cement ratio’s and arise earlier for higher Blaine values of the used cement. As a first validation of the proposed model, two test series are performed. First test serie contains sustained loading experiments. The results are used to study the influence of the cement fineness and to study the influence of the load sign. Result of this program is that no influence on the visco-elastic behaviour can be ascribed to both parameters. Second test serie contains degree of restraint experiments to validate the Shell Deformation Model. For three mixtures with different cement finenesses, it turned out that stress predictions are predicted more accurate by using the proposed Shell Deformation Model (SDM) compared to a model previously proposed.","hardening concrete; modelling; visco-elastic behaviour; moisture transport","en","doctoral thesis","","","","","","","","","Civil Engineering and Geosciences","Design & Construction","","","",""
"uuid:17c4311d-a706-4253-bdd5-c832456918b1","http://resolver.tudelft.nl/uuid:17c4311d-a706-4253-bdd5-c832456918b1","Quantitative Seismic Amplitude Analysis","Dey, A.K.","Gisolf, A. (promotor)","2011","The Seismic Value Chain quantifies the cyclic interaction between seismic acquisition, imaging and reservoir characterization. Modern seismic innovation to address the global imbalance in hydrocarbon supply and demand requires such cyclic interaction of both feed-forward and feed-back processes. Currently, the seismic value chain paradigm is in a feed-forward mode. Modern seismic data now have the potential to yield the best images in terms of spatial resolution, amplitude accuracy, and increased illumination in terms of offset and azimuth. Today’s challenge lies with reservoir characterisation. An immediate requirement is extracting quantitative rock properties information from these improved data-sets and images, to move from a, geophysically based, smooth elastic characterisation of reservoirs towards a geologically accessible, blocky layer-based rock properties parameterisation. Currently reservoir characterization does not fully exploit the wide-angle information present in seismic data. This is primarily due to the fact that the current paradigm for analysing reflectivities is at odds with the assumptions made for standard seismic data processing. The current practice of using single interface models to calculate reflectivities in a long-offset layered earth is inconsistent with the assumed time invariant convolution data model for seismic. The interplay of the modelling and inversion enables a better seismic characterisation of the reservoir by moving away from traditional band-limited, smooth, elastic attributes and towards obtaining high resolution, blocky, rock properties that correlate better to well measurements. A new layered earth forward model is developed that preserves linearity at large ray-parameter and handles kinematic wave-field effects at their proper scale. This full linearisation of the elastic property contrasts for successive layers means partitioning the compressional wave and shear wave velocity fields into two fundamental scales: a kinematic scale that governs wave-field propagation effects and a dynamic scale that governs wave-field scattering effects. The proposed layered-earth forward model recognizes the physics of seismic wave propagation, in addition to wave-field scattering, and allows for a more complete exploitation of the information available in the pre-critical seismic amplitudes. Following the extension to a layered earth, in so far as to be physically meaningful, a second step in quantitative seismic amplitude analysis is taken. Leveraging the knowledge gained from the forward analysis, a methodology to extract quantitative layer properties from the acquired seismic data is developed and creates a framework which furthers the use of seismic data in quantitative hydrocarbon reservoir characterization and management. Data kernels built with these new forward models combines with the imposition of non-quadratic regularisation (in the vertical direction) on the least-squares solution to deliver reliable broadband reservoir rock properties estimates from pre-stack seismic amplitudes. The analysis goes on to show that converted wave inversion delivers better estimates of parameters that suffer in the compressional wave inversion alone. Furthermore, considering both wave-modes simultaneously improves both the problem conditioning and the parameter estimates. The final thrust of the inversion analysis takes the theoretical inversion development and applies it to create a novel and practical method to infer sparse, high-resolution/well-resolved, rock properties from pre-stack compressional wave seismic amplitude data. Evolving from current industry standard techniques for linear inversion, the method is an extension of the solution to the classical damped least-squares problem. The final deliverable is a pre-conditioned conjugate gradient algorithm that performs broad-band, minimum structure, least-squares inversion of pre-stack seismic field data. The outcome of the inversion demonstrates that the proposed method successfully identifies the reservoir and its properties at a significantly higher resolution than is currently available with most standard, commercial, techniques and that the results are more geologically plausible. The overall message is that sparse, well-resolved, seismic reservoir characterization is possible from field acquired pre-stack seismic amplitude data.","quantitative; seismic; amplitude; interpretation; reservoir; characterisation; forward; modelling; sparse; inversion","en","doctoral thesis","","","","","","","","","Applied Sciences","Imaging Science & Technology","","","",""
"uuid:ef6df5cc-ac64-4b33-bc05-3d6a0b98727d","http://resolver.tudelft.nl/uuid:ef6df5cc-ac64-4b33-bc05-3d6a0b98727d","Analyzing Transition Dynamics: The Actor-Option Framework for Modelling Socio-Technical Systems","Yücel, G.","Thissen, W.A.H. (promotor)","2010","Transition can be characterized as long-term structural changes in the societal systems, through which the way these systems function change significantly. Both the scope and extent of change, and the nature of the societal systems make transition processes a complex dynamic phenomena to understand. This study explores both methodological and conceptual issues in order to contribute to the ways transitions are analyzed. On the methodological frontier, the book investigates different forms of simulation-supported analysis. On the conceptual frontier, the study focuses on structural and behavioral similarities among socio-technical systems in order to develop a general modelling framework that can serve as a conceptual basis for simulation-supported analyses. Additional to introducing the developed framework, i.e. the actor-option framework, the book also presents a set of modelling studies that are based on the actor-option framework. Besides two simulation-supported analyses on historical transitions in the British naval transportation and the Dutch waste management systems, the third modelling study focuses on plausible transition trajectories for the Dutch electricity supply system.","socio-technical systems; transitions; simulation; modelling; actor-option framework","en","doctoral thesis","","","","","","","","","Technology, Policy and Management","Policy Analysis","","","",""
"uuid:99bea5ae-a78b-4965-84c4-2230f7f364c3","http://resolver.tudelft.nl/uuid:99bea5ae-a78b-4965-84c4-2230f7f364c3","Micromilling of hardened tool steels","Li, P.","Munnig Schmidt, R.H. (promotor)","2009","Miniaturized parts are increasingly demanded in different fields like medical, transportation, environmental, and communication industries. In order to manufacture these parts in an economical way, mass replication methods, such as micro injection molding, have to be applied. Currently, Electro Discharge Machining (EDM) process is mainly used to manufacture the needed moulds for micro injection molding in industries. In order to achieve the final shape, several electrodes have to be made by milling with different levels of geometrical accuracy. Besides, the material removal rate of EDM is relatively low. This results in a long throughput-time and high manufacturing cost. Therefore, industries are looking for alternative technologies to overcome these drawbacks; micromilling is one of the promising technologies. The advantages of the micromilling technology include the applicability of a broad range of materials including hardened tool steels, the capability of manufacturing three dimensional geometries, accurate machining of complex features, and it is economical for small and medium lot sizes, etc. However, although micromilling in principle is a good alternative for the EDM process, it is found in research that some challenges have to be overcome before this technology is ready to be adopted in industrial applications. The literature survey shows that the fundamental micro cutting mechanism has been well investigated and understood through the study of micro orthogonal cutting and ultraprecision machining. Issues related to the application of micromilling have however not yet been well studied. Besides, inconsistent observations are commonly seen in literature. This is because observed results in micromilling are highly dependent on the experimental conditions. Based on the literature survey and initial micromilling tests, the general goal of this research has been defined as to develop and describe a reliable micromilling process for precision machining of hardened tool steels. It was decided to first improve lives of micro endmills to achieve a reliable cutting, and then to improve the performance of the process through process planning. In this research, experiments were mainly done with Ø 0.5 mm square endmills on hardened tool steels (AISI H11, H13, etc.). Experimental investigations were done to identify the main problems in micromilling. It was observed that the used commercial micro tools suffered severe wear, the tool life was too short to conduct a successful task, and the workpiece quality was not achieving the requirements. Investigations were conducted to understand tool wear types and mechanism. The factors which influence the tool performance were analyzed. It was found that the geometry of commercial tools is mainly derived from macro endmills, with which the cutting edge corners have the highest stress level. The machining parameters and tool paths are two factors that have significant effect on the tool performance; however, there was no good method available for the planning of the micromilling process. The geometry of micro endmills was studied theoretically by means of analytical modeling and FEA method. Having understood the relationship between geometrical features of the cutting tool and their influence on the tool performance (stiffness and strength of the cutting edge corners), the geometry of the micro endmill can be designed specifically for a given application to achieve the desired performance. This method was demonstrated by designing the micro square endmill especially for hard milling applications. The newly designed tools were manufactured and validated through experiments in comparison with the commercial tools. The experimental results have shown that the new designs have improved the tool performance as expected. The planning of the micromilling process has been divided into two parts. In the first part, design of experiments has been used to understand the relationship between input variables (machining parameters and tool paths) and process response (tool wear and surface finish). With this method, the significant variables can be identified by means of ANOVA analysis, and the cutting conditions can be planned accordingly to optimize the process output. For example, to have a long tool life is important for the roughing operation, and to achieve a good surface finish is of interest for the finishing operation. In the second part of the process planning, a knowledge-based method is used to plan cutting conditions for the machining of micro features with high aspect ratios. The selection of machining parameters was done by means of a force model, which describes the relation between machining parameters and average forces. The tool paths were tested by a FEM model. An improved tool path was proposed to overcome the disadvantage of the conventional tool path. Experiments were done with conditions chosen by the theoretical analysis, and the results proved the validity of the developed method. Micro ribs with aspect ratios higher than 50 could be machined successfully.","micromachining; micromilling; design; experimentation; modelling","en","doctoral thesis","","","","","","","","2009-10-22","Mechanical, Maritime and Materials Engineering","Precision and Microsystems Engineering","","","",""
"uuid:c4fc894f-aee4-466b-8811-7427ccebf697","http://resolver.tudelft.nl/uuid:c4fc894f-aee4-466b-8811-7427ccebf697","Hybrid models for hydrological forecasting: Integration of data-driven and conceptual modelling techniques","Corzo Perez, G.A.","Solomatine, D.P. (promotor)","2009","This book presents the investigation of different architectures of integrating hydrological knowledge and models with data-driven models for the purpose of hydrological flow forecasting. The models resulting from such integration are referred to as hybrid models. The book addresses the following topics: A classification of different hybrid modelling approaches in the context of flow forecasting. The methodological development and application of modular models based on clustering and baseflow empirical formulations. The integration of hydrological conceptual models with neural network error corrector models and the use of committee models for daily streamflow forecasting. The application of modular modelling and fuzzy committee models to the problem of downscaling weather information for hydrological forecasting.","Delft Cluster; CT04.30; veiligheid tegen overstromingen; safety against floods; CT04.33.11; consequences and societal acceptance of floods; hybrid models; hydrological; forecasting; hybrid; modelling","en","doctoral thesis","CRC Press/Balkema","","","","","","","","Civil Engineering and Geosciences","Watermanagement","","","",""
"uuid:fc4d865d-1ed7-409e-83ba-6270dacdec67","http://resolver.tudelft.nl/uuid:fc4d865d-1ed7-409e-83ba-6270dacdec67","Model-Based Control of Drinking-Water Treatment Plants","Van Schagen, K.M.","Babuska, R. (promotor); Rietveld, L.C. (promotor)","2009","The drinking water in the Netherlands is of high quality and the production cost is low. This is the result of extensive research in the past decades to innovate and optimise the treatment processes. The processes are monitored and operated by motivated and skilled operators and process technologists, which leads to an operator-dependent, subjective, variable and possibly suboptimal operation of the treatment plants. Furthermore, the extensive automation of the treatment plants reduces the possible operator attention to the individual process units. The use of mathematical process models might solve these problems. This thesis focuses on the application of models in model-based monitoring, optimisation and control of drinking-water treatment plants, with the Weesperkarspel treatment plant of Waternet as a case study. To shift the operation of drinking water treatment plants from experience driven to knowledge based, a model-based approach is shown to be effective. Models are successfully used in plant analysis and basic control design, resulting in the successful implementation of new basic control for the softening reactors at the Weesperkarspel plant. Model-based monitoring schemes abstract relevant information from the large amount of data and the schemes estimate the current state of the processes. Model-based control uses the monitored process state to dynamically optimise the treatment without introducing new disturbances in the treatment plant. Model-based optimisation gives the process technologist the possibility to improve treatment operation without disrupting the full-scale plant.","drinking water; control; modelling","en","doctoral thesis","","","","","","","","","Mechanical, Maritime and Materials Engineering","Delft Center for Systems and Control","","","",""
"uuid:7e6f97a1-89a4-4376-bd1f-9f1ce69278dd","http://resolver.tudelft.nl/uuid:7e6f97a1-89a4-4376-bd1f-9f1ce69278dd","Analysis and modelling of river meandering","Crosato, A.","De Vriend, H.J. (promotor)","2008","This thesis examines the morphological changes of non-tidal meandering rivers at the spatial scale of several meanders. With this purpose, a physics-based mathematical model, MIANDRAS, has been developed for the simulation of the medium-term to long-term evolution of meandering rivers. Application to several real rivers shows that MIANDRAS can properly simulate both equilibrium river bed topography and planimetric changes. Three models of different complexity can be obtained by applying different degrees of simplification to the equations. These models, along with experimental tests and field data, constitute the tools for several analyses. At conditions of initiation of meandering, it is found that river bends can migrate upstream and downstream. This depends on meander wave length and width-to-depth ratio, irrespective of whether the parameters are in the subresonant or the superresonant range. Varying lag distances between flow velocity and bed topography are found to offer an explanation why local channel migration rates reach a maximum at a certain bend sharpness, in addition to previous explanations based on flow separation. A new method has been developed to calculate the number of bars in a river channel with given width. It predicts successfully whether reducing or enlarging the river width would lead to meandering or braiding. Channel migration coefficients are demonstrated to depend not only on physical properties of the eroding bank, but also on physical properties of the accreting bank and the numerical scheme. Moreover, they need to account for overbank flows. Model results and a re-examination of experimental observations suggest that intrinsic initiation of meandering is not necessarily related to steady bars due to a permanent upstream disturbance. They may also be related to a steady bed deformation due to small quickly-varying periodic or random disturbances, for instance due to the presence of migrating alternate bars. The latter finding still requires further confirmation.","river morphology; river meandering; bank erosion; bank accretion; modelling","en","doctoral thesis","IOS Press","","","","","","","","Civil Engineering and Geosciences","","","","",""
"uuid:d8aeddfe-892e-4b95-9cce-7cbbdb3797cc","http://resolver.tudelft.nl/uuid:d8aeddfe-892e-4b95-9cce-7cbbdb3797cc","Expecting the unexpected: A study of interactive driving behaviour at intersections","Houtenbos, M.","Hale, A.R. (promotor); Wieringa, P.A. (promotor)","2008","Given the high number of encounters in traffic and the low number of accidents in which these result, it can be concluded that road users are quite good at interacting safely. To achieve a better understanding of this interactive behaviour, this thesis focused on road users' expectancies. In an explorative study, the aspects road users mention in their expectancies of interaction situations in traffic were studied. The mentioned aspects were distinguished into three categories: references to 1) right of way, 2) other road users and 3) the location of other road users (past, present and future). Subsequently, two experiments were conducted using linked driving simulators, which allowed for the study of interaction behaviour between two real people, rather than between a real and a pre-programmed road user. In the experiments, participants were confronted with expected and unexpected behaviour of a road user coming from an intersecting road. Additionally. in the second experiment, the interaction space was increased (by adjusting the infrastructure and providing information). The results showed that participants tended to take right of way when they were entitled to it, but also when they were confronted with another road user slowing down. Unexpected behaviour does not necessarily lead to a critically unsafe situation. The available interaction space is initially used to safely settle the interaction situation; additional interaction space is used to increase efficiency. It can be concluded that car drivers are quite capable of dealing with situations in which the behaviour of other car drivers is in conflict with the priority regulation if the interaction space allows for it.","traffic psychology; expectancy; interaction behaviour; adas; modelling; traffic; driving","en","doctoral thesis","TRAIL Research School","","","","","","","","Trail","","","","",""
"uuid:d50848b4-cd08-4482-a824-7d51700be44e","http://resolver.tudelft.nl/uuid:d50848b4-cd08-4482-a824-7d51700be44e","Integrated modeling of ozonation for optimization of drinking water treatment","van der Helm, A.W.C.","van Dijk, J.C. (promotor)","2007","Drinking water treatment plants automation becomes more sophisticated, more on-line monitoring systems become available and integration of modeling environments with control systems becomes easier. This gives possibilities for model-based optimization. In operation of drinking water treatment plants, the processes are usually optimized individually on the basis of ""rules of thumb"" and operator knowledge and experience. However, changes in operational conditions of individual processes can affect subsequent processes and an optimal operation, which can include a number of water quality parameters, costs and environmental impact is different for every operator. Improvement of the operation of a drinking water treatment plant is possible by using an integrated model of the entire water treatment plant as an instrument for operational support and for process control. For this purpose, it is important that explicit objectives are defined for the operation. From the research it is concluded that the objective for integrated optimization of the operation of drinking water treatment should be the improvement of water quality and not a priori reduction of environmental impact or costs. In the research an integrated model for ozonation, including ozone decay, bromate formation, assimilable organic carbon (AOC) formation, E. coli disinfection, CT and decrease in UV absorbance at 254 nm (UVA254) is developed. With the model, different control strategies for ozonation are assessed. The research also describes a newly developed design for ozone installations, the dissolved ozone plug flow reactor, (DOPFR) and the effect of character and removal of natural organic matter (NOM) prior to ozonation. The research was carried out as part of the project Promicit, a cooperation of Waternet, Delft University of Technology, DHV B.V. and ABB B.V. and was subsidized by SenterNovem, agency of the Dutch Ministry of Economic Affairs. Part of the experiments was performed in cooperation with Kiwa Water Research.","modeling; modelling; integrated; ozonation; optimization; drinking water; drinking water treatment; bromate; natural organic matter; nom; disinfection; assimilable organic carbon; aoc; life cycle assessment; lca; bottled water","en","doctoral thesis","Water Management Academic Press","","","","","","","","Civil Engineering and Geosciences","","","","",""
"uuid:56110b93-6c6e-4594-b771-b08bfa56001c","http://resolver.tudelft.nl/uuid:56110b93-6c6e-4594-b771-b08bfa56001c","Physically-based modelling of material response to welding","Thiessen, R.G.","Richardson, I.M. (promotor); Sietsma, J. (promotor)","2006","Abstract not available","modelling; welding; phase-field; phase transformations; nucleation; steel","en","doctoral thesis","","","","","","","","","Mechanical Maritime and Materials Engineering","","","","",""
"uuid:769ccdf5-5f90-4f66-a1ba-fa3a09c38ccf","http://resolver.tudelft.nl/uuid:769ccdf5-5f90-4f66-a1ba-fa3a09c38ccf","Space charge accumulation in polymeric high voltage DC cable systems","Bodega, R.","Smit, J.J. (promotor)","2006","One of the intrinsic properties of the polymeric high voltage (HV) direct current (DC) cable insulation is the accumulation of electrostatic charges. Accumulated charges distort the initial Laplacian distribution of the electric field, leading to a local field enhancement that may cause insulation degradation and premature breakdown of the system. The general objective of the present study is to obtain a better understanding of the major factors that control the space charge processes in polymeric HVDC cable systems. In order to achieve this goal, two main factors of influence have been investigated. 1) Cable accessories, i.e. cable joints and cable terminations, are considered to be the weakest part of a cable system, because of the presence of a dielectric interface between the cable insulation and that of the accessory. This thesis aims at a better knowledge of the polarization phenomena occurring at dielectric interfaces. To that purpose, an accurate methodology has been developed for the experimental study of the space charge behavior at the dielectric interface. The pulsed electro-acoustic (PEA) method for the measurement of space charge has been reviewed in case of dielectric interfaces. Secondly, space charge accumulation has been experimentally observed at the dielectric interfaces of different test specimens. 2) Across the insulation of HVDC cable systems a temperature drop is present when the cable carries a current. This thesis aims to provide a better understanding about the mechanisms responsible for space charge accumulation when a temperature drop is present across the insulation of the cable system. To that purpose, a physical model has been developed for the prediction of space charge dynamics and electric field in loaded HVDC cable systems. The physical model has been validated by means of laboratory investigation.","space charge; hvdc; dc; cable; cable system; xlpe; pea; pulsed electroacoustic method; temperature gradient; dielectric; dielectric material; modelling","en","doctoral thesis","","","","","","","","","Electrical Engineering, Mathematics and Computer Science","","","","",""
"uuid:a23ba934-3b4a-476e-a781-798723a74056","http://resolver.tudelft.nl/uuid:a23ba934-3b4a-476e-a781-798723a74056","Aerobic granular sludge: Scaling up a new technology","De Kreuk, M.K.","Van Loosdrecht, M.C.M. (promotor)","2006","Most conventional wastewater treatment plants need a large surface area for the treatment of their sewage. This is due to the open structure of the biomass used to convert the polluting components in wastewater. Because of the flocculated growth, sludge concentrations in reaction tanks are low and settling times need to be long in order to keep the biomass in the system. This Ph.D. thesis describes the development of a new compact aerobic granular sludge technology, in which the biomass is grown in compact granular structures. The main advantage of this compact growth structure is the higher biomass concentrations that van be reached and that all processes, needed for the treatment of wastewater, can be performed in one (discontinuously operated) reactor. Therefore, 80% less area and 30% less energy is required for the treatment of the wastewater. This process is unique, since by the natural composition of the aerobic granular sludge, combined with different diffusion limitations, all processes for the conversion of the polluting agents can occur in the same granule simultaneously. In the laboratory, biological removal efficiencies of 100% COD (acetate), 94% phosphate and 94% nitrogen (of which full-nitrification) were measured. During the Ph.D. a large-scale design has been made by the engineers of the Dutch consultancy firm DHV. Bottlenecks from practice were translated to scientific research and the results of the research could directly be used in the design. Different bottlenecks that were studied in the laboratory scale research were the influence on conversions and granule morphology of i) the way of influent dosing, ii) the use of a bubble column or airlift (influence of high local shear forces), iii) influence of temperature, iv) type of wastewater. A model for aerobic granular sludge has been developed as well, in order to study the sensitivity of different process parameters on conversion rates and efficiencies. This fast procedure for developing innovations led to a successful pilot scale study at sewage treatment plant Ede, The Netherlands and to the market introduction of this new technology by DHV under the name of NeredaTM.","wastewater treatment; sewage; nutrient removal; modelling; biological phosphate removal; nitrification; denitrification; aerobic granular sludge; activated sludge","en","doctoral thesis","","","","","","","","","Applied Sciences","","","","",""
"uuid:a0116113-5b85-4afd-b8d7-cdd976e82aac","http://resolver.tudelft.nl/uuid:a0116113-5b85-4afd-b8d7-cdd976e82aac","Smoothie: A model for linearity optimization of FET devices in RF applications","Cuoco, V.","Burghartz, J.N. (promotor); De Vreede, L.C.N. (promotor)","2006","","database; modelling; LDMOSFET; VDMOSFET; pHEMT; HBT; linearity; rotation; smoothing splines; isothermal measurements; high-order derivates; extraction of parasitic components; extraction of thermal networks; electro-thermal effects","en","doctoral thesis","","","","","","","","","Electrical Engineering, Mathematics and Computer Science","","","","",""
"uuid:7c08c409-18ad-47d4-8bfe-e141c946f2d6","http://resolver.tudelft.nl/uuid:7c08c409-18ad-47d4-8bfe-e141c946f2d6","Modelling of flow phenomena during DC casting","Zuidema, J.","Katgerman, L. (promotor)","2005","Modelling of Flow Phenomena during DC Casting Jan Zuidema The production of aluminium ingots, by semi-continuous casting, is a complex process. DC Casting stands for direct chill casting. During this process liquid aluminium transforms to solid aluminium while cooling down. This is not an instantaneous transformation, but occurs in temperature interval. In the casting process the latent heat is moved away by convection and conduction. A number of problems may occur during solidification, because the solidification rate is rather high. The difference in density between liquid and solid aluminium is 7% and because of that solidification porosities may form during solidification when transport of liquid metal is insufficient. If besides this also high enough thermal stresses are present, cracks may be induced from these pores. The cracks, that originate during the solidification of the metal are called hot cracks. This in contradiction with cold cracks. These are formed due to high stress levels in the already solidified aluminium. What happens from the moment that the casting process is started? This is one of the questions that is treated in this thesis. To be able to describe the DC Casting process, it is necessary to have a good model that describes the phenomena at hand adequately and that also enables to do predictions on process changes. The model, that is used , is based on the differential equations that describe the heat- and fluid dynamics transport. In chapter 2 a description of the model is given. Numerical methods for solving these equations are also given there. Without validation, a model is of little use. Model validation can be performed using various methods during DC Casting experiments. Temperature recordings enable to follow the evolution of the temperature during the casting- and solidification process in some important positions. Because part of the heat transport in the DC Casting process is convection driven, it is also important to find information on the flow pattern and velocities in the liquid aluminium. Various methods to evaluate velocities in liquid metals are described in chapter 2. Based on their use for measuring the molten aluminium velocity during DC Casting, a ranking of the methods is made. Good boundary conditions are essential for reliable predictions of the behaviour of aluminium during the mould filling and subsequent solidification. In chapter 3 the determination of the most important boundary conditions is described. Those boundary conditions determine the amount of heat transport in that area of the system, where the heat transfer to the surroundings is the largest. Through sophisticated experiments the heat transfer from a plate of aluminium to (boiling) water could be predicted. This heat transfer model enables the prediction of temperatures close to the surface of the solidifying aluminium. By instrumentation of the experimental casting facility with thermocouples, the temperature close to the surface of the ingot could be measured as function of time. Calculations using the casting- and solidification model with the constant heat transfer coefficients, and calculations with the new model for water cooling were performed. This showed, that in the first centimetres from the surface of the ingot the new model gives a better description of the experiment. Further away from the surface towards the centre of the billet, the constant heat transfer coefficient model is just as good as the new model. The best method to measure liquid metal velocities during DC Casting is a method that is based on magnetic induction. The sensor to measure velocities is based on a ferro magnet, surrounded by a conduction tube with spot-welded thermocouples. Between two opposing thermocouples an inductive voltage is measured, which is proportional with the velocity of the surrounding medium. To test this method, a prototype of this sensor was constructed. In chapter 4 this sensor is described. The sensor was firstly tested in a water setup. Because the electrical conductivity of the water was several orders of magnitude less than that of liquid metals, this gave an unsatisfactory result. It was decided to perform fluid flow experiments in liquid tin. From these experiments results were obtained which gave a velocity dependent signal for the probe output. Unfortunately, electro-magnetical shielding from the surroundings was not good enough. This prevented to quantitatively test the sensor. In chapter 5 the start-up phase of the casting is covered. In the first part of this chapter, a calculation described in the literature was repeated, using the casting- and solidification model. This showed that, due to lack of published data, more validation was necessary to fully validate the model. With the aid of the experimental casting facility, a number of casting experiments were conducted. The experiments were recorded with a video camera and the temperature during casting was recorded by thermocouples at a number of locations in the ingot. The experiments served as the basis for a number of calculations with the casting- and solidification model. A conclusion, that could be drawn from the combination of the results of the casting experiments and the calculations , was that the description of the inlet of the mould in the model as an jet of aluminium was a good description of reality during the first tenths of seconds of the process. From the moment that the aluminium melt level is overflowing the inlet level, the jet description is not accurate anymore and should be replaced with a filling over the complete width of the mould. During casting, unwanted inclusions are filtered from the liquid aluminium by degassers and filters, before the casting table is reached. In order to comply with the increasing demands for the quality of cast products, an additional method to filter out particles from the launder system was evaluated. This is the subject of chapter 6. Manipulation of the flow pattern enables to create wakes, where particles can settle. Two dimensional calculations of the flow pattern in the mould with special flow modifiers, show that this settling is possible in theory. However, it is more likely, that transient velocity fluctuations prevent the settling of particles. To create a better method for settling of unwanted inclusions, a cyclone was designed, which enables the separation of particles 20 micrometers in diameter from a stream of liquid aluminium. The cyclone was used in a series of calculations with the fluid-flow and solidification model. The outcome of these calculations has resulted in a patent for this type of cyclone. Validation measurements using a water model of the cyclone have confirmed the working of the cyclone in separation of denser particles out of a slow flowing medium. The velocity of the particles was therefore tracked using a laser and camera set-up. The laser exposed a two-dimensional area of the water model. By auto-correlation of two subsequent images, it was possible to extract the particulate rate in this area. Velocity patterns indicated, that particles had a tendency of settling down in the lower part of the cyclone. Because there was no possibility to count all particles going in and out of the system, no quantitative comparison with the model was possible.","casting; modelling; aluminum; cyclone; velocity probe","en","doctoral thesis","","","","","","","","","Design, Engineering and Production","","","","",""
"uuid:3ae428c7-0441-4187-9f78-fad4be2c20a9","http://resolver.tudelft.nl/uuid:3ae428c7-0441-4187-9f78-fad4be2c20a9","Osmosis in groundwater: Chemical and electrical extensions to Darcy's Law","Bader, S.","Hassanizadeh, S.M. (promotor)","2005","In problems of groundwater flow and solute transport in clayey soils subject to salt concentration gradients, chemical and electro-osmosis can be too important to disregard, as is commonly done in geohydrology. In this thesis, we consider the quantification of these couple effects to be able to simulate experiments and natural situations involving possible chemically and electrically driven water flow. Because clay can act as a semi-permeable membrane, groundwater flow in clay layers may be driven by osmosis. This can be mathematically accounted for by extending Darcys law with a term related to a salt concentration difference. Also, electrical potential differences may induce water flow, in which case we speak of electro-osmosis. In this work, the incorporation of these processes in existing groundwater models has been thoroughly investigated. The relevant processes and corresponding coefficients have been reviewed and we have suggested some improvements. The equations are used to model lab and field experiments and it is shown how to obtain numerical and analytical solutions for these equations. Some mathematical properties of the model equations are studied and some existing numerical codes for groundwater flow are extended with chemical and electro-osmosis. An important result is derived when membrane potential is coupled to chemical osmosis. It is shown how an experiment that is shorted can be modeled and how measurements of parameters such as permeability should be corrected for electrical effects.","chemical osmosis; electro-osmosis; membrane potential; modelling","en","doctoral thesis","Ponsen and Looijen","","","","","","","","","","","","",""
"uuid:38aa1c82-f543-42e9-b55c-f0a1b51c0214","http://resolver.tudelft.nl/uuid:38aa1c82-f543-42e9-b55c-f0a1b51c0214","Microchemistry in aluminium sheet production","Lok, Z.J.","Van der Zwaag, S. (promotor)","2005","The production of aluminium sheet alloys from as-cast ingots is a complex process, involving several rolling operations in combination with various thermal heat treatments. Through their influence on the alloy microchemistry and microstructure, these thermomechanical treatments are all aimed at controlling the final material properties. In addition, microchemistry and microstructure also affect each others development, which makes their control during industrial processing a rather complex issue. For this reason an EU-supported project under the name VIR[*], was started in March 2000, in which several European aluminium producers and research institutes co-operated in developing physically based models for the microchemistry and microstructure evolution during industrial processing of non heat-treatable aluminium alloys. The present PhD-research is part of the VIR[*] results and focusses at the influence of microstructure on the Mn precipitation in a commercial Al-Mn-Fe-Si alloy (AA3103). Firstly, several techniques for measuring the concentration of aluminium alloying elements in solid solution, are evaluated. Measurement of the thermoelectric power (TEP) proves to be the most reliable technique. As opposed to electrical resistivity and microprobe analysis, its signal is hardly influenced by alloy features other than solute atoms (e.g. precipitates). It is also shown that by combining TEP and resistivity, it is possible to independently measure the Fe and Si solute levels in a commercial Al-Fe-Si alloy. Subsequently, commercial AA3103 was solutionised, hot rolled and annealed under laboratory conditions. TEP measurements show that the precipitation of solute Mn slows down significantly as the material recrystallises. It is assumed that a large difference in Mn diffusivity between the deformed and undeformed microstructure is responsible for this effect. This observation serves as basis for a quantitative precipitation model that is also able to include the effects of an evolving microstructure. Finally, the predictive power of the precipitation model is tested. After coupling with a VIR[*] microstructure model, the microchemistry predictions are compared with measurments on AA3103 samples taken from various stages of the industrial processing route. It shows that, although not always quantitatively accurate, the measured microchemical trends are well reproduced.","aluminium alloys; solutes; precipitation; deformation; modelling","en","doctoral thesis","","","","","","","","","Aerospace Engineering","","","","",""
"uuid:4f4e110a-a1ea-4d51-b645-3c9c58c67c92","http://resolver.tudelft.nl/uuid:4f4e110a-a1ea-4d51-b645-3c9c58c67c92","Improving operation of drinking water treatment through modelling","Rietveld, L.C.","Van Dijk, J.C. (promotor); Haarhoff, J. (promotor)","2005","","modelling; drinking water; operation; simulation; ozonation; activated carbon filtration; softening","en","doctoral thesis","","","","","","","","","Civil Engineering and Geosciences","","","","",""
"uuid:e0d5af2b-7bf6-4cd8-9a22-aac3f8d112fe","http://resolver.tudelft.nl/uuid:e0d5af2b-7bf6-4cd8-9a22-aac3f8d112fe","Theoretical and practical aspects of modelling activated sludge processes","Meijer, S.C.F.","Van Loosdrecht, M.C.M. (promotor); Heijnen, J.J. (promotor)","2004","This thesis describes the full-scale validation and calibration of a integrated metabolic activated sludge model for biological phosphorus removal. In chapters 1 and 2 the metabolic model is described, in chapters 3 to 6 the model is tested and in chapters 7 and 8 the model is put into practice. Chapter 1 is a general introduction to this research. Chapter 2 is a more specific introduction to the metabolic biological phosphorus removal (BioP) model. The goal of this introduction is to obtain a better understanding of the stoichiometric and kinetic structure of the metabolic model and the role of the storage polymers glycogen, poly-phosphate and PHB. In chapters 3 and 4, the model is validated at full-scale conditions. Chapter 3 describes the simulation of a full-scale nutrient removing WWTP at steady state conditions. In chapter 4, the start-up of a full-scale WWTP is simulated. Under start-up conditions model kinetics can be tested more extensively than is possible at steady state conditions. In chapter 5, a method presented for data evaluation, reconciliation and model calibration. The method is tested in a full-scale simulation study. In chapter 6, all previous modelling experiences with the metabolic BioP model are evaluated. The adapted model is tested on the basis of several lab-scale experiments. The updated version of the integrated model is presented in appendix III. In chapters 7 and 8, the model is put into practice. In a case study, a process control based on the oxidation reduction potential was evaluated. On the basis of a literature study, in chapter 7 the physical meaning of measuring the oxidation reduction potential in activated sludge is discussed. In chapter 8, it is demonstrated how the model can be used for (ORP related) process control and control design.","modelling; activated sludge; biological; wastewater treatment process; biological phosphorus removal; orp control; calibration; data evaluation","en","doctoral thesis","","","","","","","","","Applied Sciences","","","","",""
"uuid:f1489e9e-d50b-49f9-8e66-3c35c03eae3b","http://resolver.tudelft.nl/uuid:f1489e9e-d50b-49f9-8e66-3c35c03eae3b","Advanced energy analysis of high temperature fuel cell systems","De Groot, A.","Kouffeld, R.W.J. (promotor); Veringa, H.J. (promotor)","2004","In this thesis the performance of high temperature fuel cell systems is studied using a new method of exergy analysis. The thesis consists of three parts: ⢠In the first part a new analysis method is developed, which not only considers the total exergy losses in a unit operation, but which distinguishes between different types of exergy losses; ⢠The second part describes the development of a fuel cell model. A detailed model is used to determine the relevant aspects of the performance of the fuel cell. Using this knowledge, a simpler model for the off-design performance of a fuel cell is designed for the system calculations. ⢠In the last part the advanced exergy analysis method is used to compare different high temperature fuel cell system configurations. The focus is on understanding the effect of changes in the conceptual design on the performance of the system. The value of the exergy analysis method is discussed and the main factors influencing the system efficiency are identified. The fuel cell is a single component in a complex system. As this study, and earlier studies on fuel cell systems show, th design of the fuel cell system largely determines the efficiency of the system. To achieve a high efficiency a high degree of integration is necessary. But a high degree of integration generally tends to make optimisation of systems difficult. The focus of this thesis is therefore on: ⢠Identifying how the interaction between subsystems in the fuel cell system affects straight-forward optimisation; ⢠Identifying how exergy analysis can be used in the optimisation process.","fuel cells; modelling; exergy analysis; flow sheeting; system analysis","en","doctoral thesis","The Energy research Centre of the Netherlands (ECN)","","","","","","","","Applied Sciences","","","","",""
"uuid:6a2b93f3-4ef4-4363-8b2f-440e0a6d01e1","http://resolver.tudelft.nl/uuid:6a2b93f3-4ef4-4363-8b2f-440e0a6d01e1","Charge transport in disordered organic field-effect transistors","Meijer, E.J.","Klapwijk, T.M. (promotor)","2003","In this thesis we study charge transport in organic semiconductors. We do this by focusing on the physical characterization of disordered organic field-effect transistors. It will be made clear that the disorder in the polymer films is crucial for the interpretation of the data. The field-effect transistor geometry allows variation of the charge carrier density in the semiconductor, without the presence of counter ions. Therefore, the transistor allows a rather clean study of the charge transport in organic semiconductors as a function of the charge carrier density and temperature. In the experiments we find that the organic transistors are in several respects not comparable to silicon MOSFETs. Therefore, in this thesis we redefine and re-evaluate basic transistor parameters, such as the threshold voltage, the field-effect mobility, the contact resistance and the dopant density. Subsequently, we study the charge transport as a function of charge density, temperature and electric field, giving insight into the charge transport mechanism. Based on our observations we propose as the main charge transport mechanism: multiphonon hopping of polaronic charge carriers in a Gaussian density of states. We investigate the electrical stability of the polymer layer in metal-insulator-semiconductor diodes, where we determine and analyse the dopant density changes as a function of oxygen and light exposure. The presence of contact resistances in the transistors is addressed by analysing the scaling behavior of the electrical characteristics as a function of the transistor channel length, and an empirical relation between the contact resistance and the charge carrier mobility in the polymer layer is observed. Finally, we discuss why typically only unipolar transistor behavior is observed experimentally, and we demonstrate ambipolar transistor behavior in organic field-effect transistors based on blends of organic semiconductors and on low band gap organic semiconductors.","organic semiconductor; field-effect transistor; charge transport; modelling; polymers","en","doctoral thesis","Optima Grafische Communicatie, Rotterdam","","","","","","","","Applied Sciences","","","","",""
"uuid:e7a8d441-fc9e-441a-b3c9-4104ed48cf84","http://resolver.tudelft.nl/uuid:e7a8d441-fc9e-441a-b3c9-4104ed48cf84","A Design Procedure and Predictive Models for Solution Crystallisation Processes","Bermingham, S.K.","Grievink, J. (promotor)","2003","","crystallisation; design; modelling","en","doctoral thesis","Delft University Press","","","","","","","","Applied Sciences","","","","",""
"uuid:eafae9f0-990b-423a-83c8-4b36fd5c1359","http://resolver.tudelft.nl/uuid:eafae9f0-990b-423a-83c8-4b36fd5c1359","Innovative High Temperature Fuel Cell systems","Au, Siu Fai","De Wit, J.H.W. (promotor); Kouffeld, R.W.J. (promotor); Hemmes, K. (promotor)","2003","The world's energy consumption is growing extremely rapidly. Fuel cell systems are of interest by researchers and industry as the more efficient alternative to conventional thermal systems for power generation. The principle of fuel cell conversion does not involve thermal combustion and hence in theory fuel cell systems can be far more efficient than thermal power systems. This advantage is only partly utilized in present fuel cell pilot plants and additional optimization is needed. The complexity of fuel cell systems makes the optimization process anything but simple. This thesis presents the results of studies to understand the complex interactions between the different segments of a fuel cell system, and it presents additional insights into the fundamental aspects of the fuel cell conversions. Theories are presented and tested in practical situations with the objective of generating innovative ideas for future high temperature fuel cell systems.","fuel cells; modelling; flowsheet calculations","en","doctoral thesis","Delft University Press","","","","","","","","Applied Sciences","","","","",""
"uuid:1dbcb7fb-3f8f-466b-8517-b2235ad4912f","http://resolver.tudelft.nl/uuid:1dbcb7fb-3f8f-466b-8517-b2235ad4912f","Simulation of Volume Changes in Hardening Cement-Based Materials","Koenders, E.A.B.","Walraven, J.C. (promotor)","1997","","cement hydration; modelling; volume changes; pore structure","en","doctoral thesis","Delft University Press","","","","","","","","Civil Engineering and Geosciences","","","","",""
"uuid:21a2ba8f-1997-45c9-a227-bbb2c21dc232","http://resolver.tudelft.nl/uuid:21a2ba8f-1997-45c9-a227-bbb2c21dc232","Impact of sea level rise on groundwater flow regimes: A sensitivity analysis for the Netherlands","Oude Essink, G.H.P.","Van Dam, J.C. (promotor)","1996","","sea level rise; the Netherlands; groundwater flow; modelling","en","doctoral thesis","","","","","","","","","Civil Engineering and Geosciences","","","","",""
"uuid:c31f2eed-a7cd-4be2-9159-453b36cbefdc","http://resolver.tudelft.nl/uuid:c31f2eed-a7cd-4be2-9159-453b36cbefdc","Quaestor: Expert governed parametric model assembling","van Hees, M.T.","","1996","","parametric; modelling","","doctoral thesis","","","","","","","","indefinite","Mechanical, Maritime and Materials Engineering","Marine and Transport Technology","Ship Design, Production and Operation","","",""
"uuid:31b51067-f361-4acf-9272-7358200ef66b","http://resolver.tudelft.nl/uuid:31b51067-f361-4acf-9272-7358200ef66b","Te economic value of CAD systems to structural design and construction; a modelling approach","Chandansingh, R.A.","Vos, Ch.J. (promotor)","1995","","modelling; cost-effects; CAD systems","en","doctoral thesis","","","","","","","","","Civil Engineering and Geosciences","","","","",""
"uuid:44236190-814d-4c8f-91a9-2d5b7ae073b4","http://resolver.tudelft.nl/uuid:44236190-814d-4c8f-91a9-2d5b7ae073b4","Process Development of Thermal HydroDechlorination","ten Kate, A.J.B.","van den Bleek, C.M. (promotor); van den Berg, P.J. (promotor)","1993","","chlorinated waste treatment; process development; modelling","en","doctoral thesis","Delft University Press","","","","","","","","Applied Sciences","","","","",""
"uuid:325d4d7e-621c-41b1-b42d-2b50b4f576d4","http://resolver.tudelft.nl/uuid:325d4d7e-621c-41b1-b42d-2b50b4f576d4","Modelling of NOx Formation in a High Temperature Gas-Fired Furnace","Koster, C.L.","Hoogendoorn, C.J. (promotor)","1993","","combustion; NOx formation; modelling","en","doctoral thesis","Delft University Press","","","","","","","","Applied Sciences","","","","",""
"uuid:d68e5e1c-d1e1-4e90-9861-1867a7073067","http://resolver.tudelft.nl/uuid:d68e5e1c-d1e1-4e90-9861-1867a7073067","Dynamic modelling and robust control of a wind energy conversion system","Steinbuch, M.","Bosgra, O.H. (promotor)","1989","The application of wind energy conversion systems for the production of electrical energy requires a cheap and reliable operation. Especially at high wind velocities fluctuations from the wind field result in large mechanical loads of the wind turbine. Also fluctuations in the grid voltage may yield large dynamic excitations. In order to realize a long lifetime and a reliable operation active control systems are necessary. The main goal of the study described in this thesis is to develop an approach for the design of a high performance control system for a wind turbine with variable speed. The wind turbine system under investigation has a three-bladed rotor which is connected to the generator by a transmission. The electrical conversion system consists of a synchronous generator with a rectifier, direct current transmission and an inverter. The manipulable inputs are the pitch angle of the turbine blades, the field voltage of the generator and the delay angle of the rectifier. Both the generator speed and the direct current are being measured. The control design problem at full load is to minimize fluctuations in speed and current while reducing the mechanical (fatigue) loads. The feedback system should realize this without excessive use of the input variables and must also be simple to implement. I In order to be able to design a high performance control system a high quality dynamic model is required. Much attention has been given to the. modelling of the electrical conversion system. The switching of the thyristors of the rectifier bridge results in periodic behaviour at a high frequency. In order to design a control system an averaged model has been derived through the application of Floquet theory for periodic systems. The properties of the aerodynamic transfer and of the drive train only have been approximately modelled. Deviations of these nominal models from the real system are accounted for using norm-bounded uncertainty models. Using the nominal model and the uncertainty models the control system design has been carried out. The control design problem can suitably be handled by the Linear Quadratic design method. However, instead of using the standard solution with observers, in this study the optimization theory has been applied with respect to a predefined structure of the feedback law. In this approach the order and structure of the controller can be selected as part of the problem formulation. The application to the wind turbine system shows that a high performance control system can be obtained using a relatively simple, low order multivariable feedback law. The use of frequency weighting effectively reduces the role of mechanical parasitic dynamics. Application of the multi-model principle in combination with LQ optimization theory provides a way to synthesize controllers which are robust for large (aerodynamic) changes in operating conditions. A quantitative robustness analysis shows how the design parameters of the feedback law can be adapted in order to enhance the robustness of the controller. The approach taken, involving extensive modelling combined with uncertainty models and with the use of optimization theory and robustness analysis, has been shown to result in a high performance control system. Its main characteristic is the integrated approach of the control problem, with combined control action via the mechanics and the electrical conversion system. It is recommended to apply this integrated approach also to other types of wind turbine systems.","wind energy conversion system; modelling; robust control.","en","doctoral thesis","","","","","","","","","Mechanical Maritime and Materials Engineering","","","","",""