"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:5cfe9305-304f-4b9e-8bf0-2ba7cad59e86","http://resolver.tudelft.nl/uuid:5cfe9305-304f-4b9e-8bf0-2ba7cad59e86","Turbulent channel flow with stable stratification beyond the Oberbeck-Boussinesq assumptions: A DNS study","Kotturshettar, Sanath (TU Delft Mechanical, Maritime and Materials Engineering; TU Delft Process and Energy)","Pecnik, Rene (mentor); Costa, Pedro (mentor); Peeters, J.W.R. (graduation committee); Weymouth, Gabriel D. (graduation committee); Delft University of Technology (degree granting institution)","2023","Stratified turbulent flows abound in environmental and industrial settings. Examples are atmospheric boundary layer flows, the transport of nutrients and organisms and the mixing of heat and salinity in the oceans, fluid flow in heat exchangers, and the transport of reactants and products in chemical reactions. These examples and many others consider stratified wall-bounded turbulence, in which the creation of turbulence by mechanical processes contends with its dissipation due to buoyancy effects. These flows are said to be stably stratified as these are inherently stable flows and are averse to mixing. The buoyancy effects alter the structure of the flow, and consequently the dynamics of mass, heat, and momentum transport. As density fluctuations become more severe, the Oberbeck-Boussinesq approximation becomes inaccurate and the resulting dynamics are not correctly predicted. In the current work, we developed and validated a numerical solver for direct numerical simulations (DNS) of turbulent flows featuring strong property variations. More precisely, we solve the Navier-Stokes equations in the limit of vanishing Mach number (so-called low-Mach number limit), with the fluid density given by the ideal gas law, and the dynamic viscosity and thermal conductivity also expressed as functions of temperature.
Our numerical solver is used to study stably-stratified turbulent channel flow under non-Oberbeck-Boussinesq conditions. The simulations are carried out at friction Reynolds number of 180, Prandtl number of 0.71, and friction Richardson number of the O(10). These non-dimensional numbers are the governing parameters and are defined based on the prescribed pressure drop and properties of the fluid at the reference temperature. Stratification is achieved by imposing constant temperature boundary conditions, with a high upper-to-lower wall temperature ratio (larger than 2), resulting in strong density variations in the flow. We will vary the temperature ratios and adjust gravity to maintain a similar Richardson number between cases, thereby isolating the effects of strong property variations in the flow dynamics. We will analyze the dynamics of heat and momentum transport under strong stratification for these conditions, also in light of DNS data of the same system under the Oberbeck-Boussinesq regime.
The present research work has been motivated by an unintuitive strengthening of the streamwise-elongated coherent structures of the atmospheric boundary layer (ABL), observed by Jayaraman & Brasseur (2021), for a certain range of weakly unstable thermal stratification conditions. Such observation evinced the existence of a sweet-spot where the large-scale streamwise-oriented counter-rotating vortical structures, characteristic of any turbulent boundary layer, were able to strengthen themselves by collecting small-scale thermal plumes, eventually creating the so-called large-scale atmospheric rolls. The importance of these findings lies in the fact that large-scale atmospheric rolls are known to be one of the most important structures when it comes to vertical transport of momentum and scalars (i.e. pollutants) in the ABL.
Following from this observation, we hypothesize that the counter-rotating roll structures behind a high-rise building could potentially exhibit a similar behaviour and strengthen themselves under weakly unstable thermal stratification conditions by collecting small-scale thermal plumes. If this was the case, it would enhance large-scale vertical mixing which could be beneficial for street canyon ventilation, reducing urban pollution levels. Therefore, the importance of studying the evolution of the roll structures behind a high-rise building under different thermal stratification conditions becomes evident.
In this regard, the present work has focused on the study of the roll structures behind a high-rise building under different thermal stratification conditions, by means of wall-resolved Large-Eddy Simulations (LES) using the Nek5000 Spectral Element Method (SEM) code. The present work has succeeded in providing a qualitative proof of concept of the presented hypothesis, proving that the rolls behind a surface-mounted cube (model for a high-rise building) under weakly unstable thermal stratification conditions do strengthen themselves in a similar manner as observed by Jayaraman & Brasseur (2021) for the ABL. Moreover, a reliable LES numerical model for simulating flow past a surface-mounted cube (high-rise building) has been built and thoroughly validated against DNS data, tuning the optimal mesh, and simulation and filtering settings.
32 = 7.9 μm) has been investigated experimentally under vibration of varying conditions. X-ray imaging was carried out to directly capture the temporal evolution of system hydrodynamics, and identify in-situ powder stratification, bubbling and channel formation. The study demonstrates that vibration effectively collapses gas channels, yet facilitates powder stratification and compaction, therefore developing three distinctive flow regions inside the bed with different fluidization states. Consequently, common measurements, such as pressure drop and bed expansion, tend to overestimate the improvement. In addition, increasing frequency, from 10 Hz to 30 Hz, is observed to increase the number of bubbles by 60 %, whereas a large amplitude (e.g., 2 mm) leads to a 10 % compaction in the top flow region.","Assistance; Gas channel; Scale-up; Stratification; Vibration","en","journal article","","","","","","","","","","","ChemE/Product and Process Engineering","","",""
"uuid:1f670359-539d-4a09-9186-bbbe8f696e13","http://resolver.tudelft.nl/uuid:1f670359-539d-4a09-9186-bbbe8f696e13","Efficient Shapley Value Approximation Methods: for Cost Redistribution in Energy Communities","Cremers, Sho (TU Delft Electrical Engineering, Mathematics and Computer Science)","Robu, Valentin (mentor); la Poutré, J.A. (graduation committee); de Weerdt, M.M. (graduation committee); Delft University of Technology (degree granting institution)","2022","With the emergence of energy communities, where a number of prosumers (consumers with their own energy generation) invest in shared renewable generation capacity and battery storage, the issue of fair allocation of benefits and costs has become increasingly important. The Shapley value, a solution concept in cooperative game theory initially proposed by Nobel prize-winning economist Lloyd Shapley, has attracted increasing interest for redistribution in energy settings. However, due to its high time complexity, it is intractable beyond communities of a few dozen prosumers. This study proposes a new deterministic method for approximating the Shapley value in realistic community energy settings and compares its performance with existing methods. To provide a benchmark for the comparisons of these methods, we also design a novel method to compute the exact Shapley value for communities of up to several hundred agents by clustering consumers into a smaller number of demand profiles. Experimental analyses with large-scale case studies of a community of up to 200 household consumers in the UK show that the newly proposed method can achieve very close redistribution to the exact Shapley values but at a much lower (and practically feasible) computation cost. Furthermore, it performed similarly to the probabilistic, state-of-the-art approximation method while having smaller time complexity as well as other desirable characteristics for cost redistribution in energy communities.","Energy Community; Shared assets; Shapley value; Approximation algorithms; Smart grid; Stratification; Cost allocation","en","master thesis","","","","","","","","","","","","","",""
"uuid:5cd38c3b-f0f5-405f-9f9f-02512ebb77dd","http://resolver.tudelft.nl/uuid:5cd38c3b-f0f5-405f-9f9f-02512ebb77dd","The Changjiang Estuary: A highly turbid estuary in transition","Lin, J. (TU Delft Coastal Engineering)","Wang, Zhengbing (promotor); He, Qing (promotor); van Prooijen, Bram (promotor); Delft University of Technology (degree granting institution)","2022","Estuaries are the core area of land-sea interactions and have significant ecological and economic value. In estuaries, hydrodynamics and sediment dynamics are the crucial processes governing geomorphology, navigability, and primary production. Since the turn of the 20th century, increased human activities (e.g., damming, dredging, and reclamation) have subjected estuaries to significant pressure and prompted changes in hydrodynamics and sediment dynamics. Some estuaries, for example, experienced a transition from low- to hyper-turbidity after channel deepening. This transition is particularly common in tide-dominated estuaries such as the Ems and Loire estuaries. However, the reactions of estuaries with a high runoff (such as the Changjiang/Yangtze Estuary) are unclear, and the transition and underlying processes of such estuaries are further complicated by declined fluvial sediment supply. By integrating acoustic and optical sensors, this PhD dissertation developed a wide-range and high-precision sediment concentration observation system to monitor high sediment concentrations in the Changjiang Estuary. Over the past three decades, observations revealed a transition in suspended sediment concentrations, with increasing concentrations near the bed and decreasing concentrations near the water surface. The drag reduction induced by suspended sediment was assessed by a bottom-mounted tripod system. Moreover, this dissertation clarified the mechanism controlling the formation of concentrated benthic suspensions, namely the positive feedback between stratification, turbulence damping, and hindered setting. The comparison between sediment transport processes before and after the Deep Waterway Project reveals that estuarine circulation is the primary force driving sediment import from the sea, whereas tidal pumping results in the along-estuary extension of the estuarine turbidity maximum zone. These findings enhance our knowledge of the response of estuarine hydrodynamics and sediment dynamics to human interventions and provide a theoretical basis for the effective management of estuarine systems.","Sediment concentration; Human interventions; Drag reduction; Turbulence damping; Density stratification; Estuarine circulation; Tidal pumping","en","doctoral thesis","","978-94-6458-315-1","","","","","","","","","Coastal Engineering","","",""
"uuid:dad02812-79f6-468e-9c99-433274e53b78","http://resolver.tudelft.nl/uuid:dad02812-79f6-468e-9c99-433274e53b78","Numerical analysis of effects of fins and conductive walls on heat transfer in side heated cavities — Onset of three-Dimensional phenomena in natural convection","Vesper, J.E. (TU Delft ChemE/Transport Phenomena; TU Delft J.M. Burgers Center for Fluid Mechanics); Tietjen, Sebastian C. (Student TU Delft); Chakkingal, M. (TU Delft ChemE/Transport Phenomena; TU Delft J.M. Burgers Center for Fluid Mechanics); Kenjeres, S. (TU Delft ChemE/Transport Phenomena; TU Delft J.M. Burgers Center for Fluid Mechanics)","","2022","In the present study, we analyse individual and combined effects of conductive horizontal walls and conductive fins on the natural convection of air in side heated cavities (SHC). The flow and heat transfer are studied for Rayleigh numbers in the range of 104−−109: Direct Numerical Simulation (DNS) is conducted for the lower and Large Eddy Simulation (LES) for the higher Rayleigh numbers (>108). Thermally conductive walls destabilize the flow yielding an earlier transition to turbulence and expedite the decay in boundary layer thickness with increase in Rayleigh number. The preheating/precooling along the conductive walls reduces the actual heat transfer at the vertical walls. Above the fin, instabilities are only marginally enhanced for adiabatic horizontal walls, whereas for conductive horizontal walls, plumes erupt from the fin. This localized Rayleigh-Bénard-like effect triggers 3D instabilities in the entire flow field and yields a steeper slope in Nusselt-Rayleigh diagram. The presence of a fin increases the integral heat transfer by 18% for adiabatic and 21% for conductive horizontal walls. We show that 2D and 3D simulations are similar for the smooth cases (i.e., without fin), but differ by 4% and 13% for the adiabatic and conductive fin cases respectively. The local heat transfer characteristics even deviates up to 50%, therefore a 2D simplification should be avoided.","Conductive walls; Differentially heated cavity; Finned cavity; Heat transfer; Instabilities; Natural convection; Side heated cavity; Stratification","en","journal article","","","","","","","","","","","ChemE/Transport Phenomena","","",""
"uuid:9abdf46f-9833-45ba-ab22-abba8e716735","http://resolver.tudelft.nl/uuid:9abdf46f-9833-45ba-ab22-abba8e716735","The spatial and temporal behaviour of stratification in the Fehmarnbelt strait: An analysis on when and where bi-directional plume spread due to stratification can occur during dredging activities in the Fehmarnbelt","Nanninga, Stefanie (TU Delft Civil Engineering & Geosciences)","Pietrzak, J.D. (mentor); de Boer, Gerben (mentor); van Miltenburg, E.M.L (mentor); Tuinhof, T.J. (mentor); Wegman, T.M. (mentor); Delft University of Technology (degree granting institution)","2021","The amount of suspended sediment spill released during dredging activities in the Fehmarnbelt strait is monitored along the excavated trench to prevent negative effects on local ecology. Stratification due to the interaction of saline water from the North Sea and fresh water from the Baltic Sea forces bi-directional flow of the layer above and below the density gradient, causing bi-directional spread of the dredging plume perpendicular to the trench as well. During such an event, monitoring on both sides of the trench is required. By mapping out the spatial and temporal behaviour of stratification, a prediction can be given on where and when measuring on both sides of the trench will be needed to include the baroclinic effect. Figures created with monitoring data show that the density profile is influenced by the salinity, rather than the temperature. Therefore, stratification predominantly depends on the in and outflow of water with respect to the Baltic Sea. The figures also show a larger density gradient during out than inflow. It can also be observed that where the water depth is restricted to 10 meters, wind and bottom friction mix the entire water column. Therefore, stratification occurs predominantly during outflow in sections deeper than 10 meters, indicating the need for monitoring the bi-directional plume spread during such circumstances. Whether stratification occurs during inflow in sections deeper than 10 meters likely depends on the duration and strength
of the wind forcing and the initial strength of the density gradient prior to the inflow event. Further analysis should be done to confirm this. Signs of Ekman transport, return flows and the deflection of the currents towards deeper water can also be observed in the measurement figures. Since these processes affect the plume spread direction, additional research can be done on the behaviour of the current direction in the Fehmarnbelt.","Stratification; Sediment; Dredging; Oceanography; Baltic Sea","en","student report","","","","","","","","2023-11-05","","","","Civil Engineering | Environmental Engineering","Fehmarnbelt fixed link","54.568302, 11.275126"
"uuid:79cd9834-63a7-40f4-a43c-05d005c2f48f","http://resolver.tudelft.nl/uuid:79cd9834-63a7-40f4-a43c-05d005c2f48f","Assessment of future stratification induced by opening of Haringvliet sluices","Binsma, Jouke (TU Delft Civil Engineering and Geosciences)","Pietrzak, J.D. (mentor); Katsman, C.A. (graduation committee); Aarninkhof, S.G.J. (graduation committee); Delft University of Technology (degree granting institution)","2021","class=""MsoNormal"">Key points:- Pre-closure salinity intrusion into Haringvliet-Hollands Diep is known to have reached Biesbosch National Park at flood tide. Post-Delta21 salinity intrusion is projected to be less extensive than pre-closure. Maximum intrusion is estimated to reach the westernmost Moerdijk ports mainly due to diminished tidal flow at the estuary mouth.- Freshwater intake in the Haringvliet is projected to be compromised for the majority of the year whereas freshwater intake in Hollands Diep is compromised during prolonged drought.- Salinity outwash from the Haringvliet on ebb tide is projected to be poor under both drought and normal conditions due to widespread salinity diffusion in lateral and vertical directions on flood tide. The Delta21 framework, in which this study is positioned, aims at increased flood safety and ecological restoration of the Haringvliet, a former estuary in the Dutch southwestern delta that has been closed as part of the Delta works. To achieve this, Delta21 proposes to reopen the Haringvliet freshwater basin to tidal effects in an attempt to restore its estuarine character. Implementation of Delta21 introduces the risk of compromising agricultural and industrial activities around the Haringvliet-Hollands Diep by reintroducing salinity and tidal movement in the basin. The central problem lies in quantifying the extent and stability of the expected periodic salt intrusion post-Delta21. This has been done by projecting a geographical bandwidth of salinity intrusion patterns depending on the severity of SLR (2020-2100) and low-to-mean Rhine-Meuse discharges (in 2100 CE) using a numerical model. Mitigation strategies are then recommended based on these numerical results. The OSR-HV model (owner: Port of Rotterdam) is used to run predictive scenarios of salinity intrusion for the lower reaches of the Rhine-Meuse basin. OSR-HV runs in TRIWAQ (Rijkswaterstaat), which is 3D numerical modelling software that employs coupled hydrodynamics and constituent transport thereby resolving salinity transport. An upper-end critical scenario consists of a Rhine (Lobith) discharge averaging 1000 m3/s for 31 days combined with 85cm SLR in 2100. This resulted in an intrusion pattern reaching the westernmost port of Moerdijk in Hollands Diep. Results show that the basin geometry, possibly nudged by Coriolis deflection, initially causes a preferential path of salinity intrusion along the southern bank of the Haringvliet. Lateral and vertical mixing is extensive in the western part of Haringvliet which is thought to be a combined effect of weakened tidal flow at the estuary mouth and robust and erratic geometry of the basin. Further up-estuary, the historical flood-ebb tidal channel structures is the main transporter of salinity. The Haringvliet shows distinctly different estuarine behaviour compared to the neighbouring Rotterdam Waterways where stratification is more stable, causing less up-estuary diffusion. The relative robustness of the Haringvliet and mild freshwater forcing give rise to extensive 3D mixing which subsequently limits the maximum horizontal excursion of salinity. Salinity intrusion into the Old Meuse is observed to aggravate upon opening of the Haringvliet sluices due to flow reversal in Spui which connects Haringvliet with the Rotterdam Waterways. This effect can even result in salt intrusion from the Rotterdam Waterways via Old Meuse and Spui back into the Haringvliet, causing a secondary spike in salinity on ebb tide there. Finally, height-limitation of the Haringvliet sluice gates is somewhat effective in countering horizontal excursion of salinity but runaway diffusion in the Haringvliet results in similar salinity profiles compared to full opening of the sluice gates. A shipping channel that crosses the current Haringvliet front delta is included in Delta21. This deep feature promotes advection of salt through the Haringvliet sluices. Subsequent diffusion patterns cause for poor washout of salinity from the basin upon ebb tide. Limiting the depth of this channel is recommended if salt intrusion is to be reduced. Full opening of the Haringvliet sluices furthermore causes approx. 0.50m lowering of Mean Low Water (MLW) near Moerdijk which affects busy shipping routes between Rotterdam-Moerdijk-Scheldt. Partial reduction of the conveying area of the Haringvliet sluices may be used to suppress the tidal wave penetration into Haringvliet-Hollands Diep. Significant gain in ecological value is likely post-Delta21 due to addition of approx. 1900 ha of intertidal areas and a 40 km salinity gradient (excl. front delta). Ample recommendations on further research have been made in this exploratory study. It is recommended to further study the effects of Delta21 interventions on macro hydrodynamics of the Dutch coastal shelf. The interconnected nature of the region requires a larger modelling domain to prevent the occurrence of non-physical effects obtained from the current numerical schematization. Furthermore, hydrological relations and bathymetry were generated from 2020 data. It is therefore recommended to precede the assessment of salinity intrusion into the Haringvliet with numerical projections on change to these environmental factors. Lastly, significant gain in accuracy may be obtained from applying spatially varying temperature and wind to the domain to better replicate baroclinic flows and turbulent mixing.","Haringvliet; Salt Intrusion; DELTA21; Climate projections; Stratification","en","master thesis","","","","","","","","","","","","","DELTA21","51.832729, 4.049717"
"uuid:53e2e57a-87eb-493d-ab63-3559ecb447a4","http://resolver.tudelft.nl/uuid:53e2e57a-87eb-493d-ab63-3559ecb447a4","Graphene-based newtonian nanoliquid flows over an inclined permeable moving cylinder due to thermal stratification","Ghani, Siti Nur Ainsyah (University of Malaya); Yarmand, H. (TU Delft Human-Robot Interaction); Noor, Noor Fadiya Mohd (University of Malaya)","","2021","Heat flux enhancement due to utilization of graphene, graphene nanoplatelets, and graphene oxides in water/ethylene-glycol based nanofluids over an inclined permeable cylinder is focused in the present study. The governing PDE are reformulated into non-linear ODE by applying similarity expressions. A shooting procedure is opted to reformulate the equations into boundary value problems which are solved by employing a numerical finite difference code in MATLAB. The effects of constructive parameters toward the model on non-dimensional velocity and temperature dissemination, reduced skin friction coefficient and reduced Nusselt number are graphically reported and discussed in details. It is observed that by increasing the thermal stratification and inclination angle, the temperature profile and Nusselt number for the selected nanofluids will be decreased.","graphene; graphene nanoplatelets; graphene oxides; heterogeneous; inclined cylinder; nanofluid; thermal stratification","en","journal article","","","","","","","","","","","Human-Robot Interaction","","",""
"uuid:687f4d25-2b04-4c26-b927-20af2d262ab0","http://resolver.tudelft.nl/uuid:687f4d25-2b04-4c26-b927-20af2d262ab0","The hydrodynamics of an eco-innovative sediment reuse project in the Rotterdam Waterway: Gaining insight into the physics and the predictive capability of two operational hydrodynamic models","Geraeds, Marlein (TU Delft Civil Engineering & Geosciences)","Pietrzak, J.D. (mentor); Kirichek, Alex (graduation committee); Hulsen, Lambèr (mentor); Chassagne, C. (graduation committee); de Vries, S. (graduation committee); Delft University of Technology (degree granting institution)","2020","Phenomena like sea level rise, global warming and erosion together contribute to increasing flood risk in vulnerable coastal areas. As this flood risk increases, initiatives to mitigate the effects of climate change in the coastal zone are also increasingly sought. During recent years, the view that these measures should be circular has gained significant momentum. In line with this, the idea that sediment should not be treated as waste, but as a valuable product in a circular economy has been widely accepted. Within this theme, the sediment uses as resources in circular and in territorial economies (SURICATES) was created to develop and execute eco-innovative solutions for the reuse of sediments in Western Europe. As a part of SURICATES, over the course of a nine week pilot, a total of 500 tonnes of sediment was reallocated in a designated area in the Rotterdam Waterway, with the expectation that this sediment would be transported out of the Rhine-Meuse estuary into the North Sea. The SURICATES project is one of the first real large-scale efforts to reuse sediment for economic as well as ecosystem services. Effective implementation of the SURICATES project, however, requires a thorough understanding of the governing physical processes impacting the distribution of the deposited sediment locally. Furthermore, to assess the feasibility of similar future applications, efficient modelling of the pilot project is necessary. The work presented here aims to elucidate the hydrodynamic processes that are governing in the Rotterdam Waterway, within the framework of the SURICATES pilot project, and assess the reproducibility of these processes by (two) predictive models that are currently operational at the Port of Rotterdam. A special 6-hour monitoring survey was set up to measure salinities, velocities, temperature, and suspended particulate matter (SPM) along a transect crossing the reallocation location. In combination with a literature review, this dataset provides the basis for research into the predictive capabilities of two currently operational hydrodynamic models. Analysis of this dataset reveals the dominant terms in the momentum balance, the influence of Coriolis, the occurrence of internal waves, and the effect that all these mechanisms may have on the SPM distribution around the reallocation location. When the system dynamics are elucidated, the model performance of the two hydrodynamic models is assessed—both quantitatively and qualitatively. It is also investigated whether phase shifts are introduced in the models. It is found that the primary hydrodynamic processes in the Rotterdam Waterway are related to the barotropic tidal asymmetry imposed at the river mouth, the tidal excursion of the salt wedge, baroclinic exchange flow processes, and turbulence damping at the pycnocline. Turbulence damping at the pycnocline generally poses an upper limit to the (re)distribution of SPM over the water column, although field data suggests that this damping may not be sufficient to counteract diffusion processes locally. This effect occurs under certain forcing conditions and during low water slack. Furthermore, an internal Froude number analysis provides evidence for the possible generation of internal waves in one of the river’s bends. The evaluated models, however, are not capable of reproducing all of these hydrodynamic processes adequately. Although both models adequately reproduce water levels and the vertical velocity structure, they have difficulties predicting the pycnocline height. Additionally, it is found that both models introduce a small phase shift in the velocity and salinity prediction. The research presented here is a contribution to the understanding of the governing hydrodynamic processes in the Rotterdam Waterway, and the effect that (in)accurate modelling of these processes may have on future studies. Recommendations following from this research could improve future modelling practices.","Hydrodynamic modelling; SIMONA; Stratification; Port of Rotterdam; SURICATES; Rotterdam Waterway; Sediment reuse; Eco-innovation","en","master thesis","","","","","","","","","","","","Civil Engineering | Hydraulic Engineering","","51.928149, 4.225140"
"uuid:546e1a84-71b0-4ffb-98fc-137477914bcf","http://resolver.tudelft.nl/uuid:546e1a84-71b0-4ffb-98fc-137477914bcf","Sediment traps: for reducing maintenance dredging costs in the port of Rotterdam","Tempel, Auke (TU Delft Civil Engineering and Geosciences; TU Delft Rivers, Ports, Waterways and Dredging Engineering)","van Koningsveld, Mark (mentor); Pietrzak, Julie (graduation committee); Kirichek, Alex (graduation committee); Chassagne, Claire (graduation committee); Hulsen, Lambèr (mentor); Delft University of Technology (degree granting institution)","2019","Regular maintainance dredging is a large expense to the Port of Rotterdam, therefore the installation of sediment traps is considered. By increasing the bathymetry locally, an increase of local accumulation is expected and a decrease deeper in the harbour basin. This thesis describes the functioning of sediment traps in a stratified tidally energetic estuary, where sediment is supplied by the river and sea. A numerical 2DV representation is set up for the Botlek Harbour with the hydrostatic Delft3D software. A calculated salinity time-series by Operationeel Stromingsmodel Rotterdam (OSR) is combined with a measured water level time series for the same time period to describe the hydrodynamic boundary conditions. Simulations are done with a variable and constant Suspended Particulate Matter (SPM) time series boundary conditions, that were generated based on the measurements of De Nijs (2012). Flow expansion caused by the sediment trap reduces the flow velocity, but increases the turbulent kinetic energy locally. A reduction of bed shear stress is observed in the trap, except near the edges where an increase is observed. Density currents caused by salinity differences govern the vertical flow velocity distributions, while tidal filling causes the net exchange. The depth of the trap plays a significant role in the internal flow characteristics. The sediment trap changes the properties of the internal flow, which may change the hydraulic state of the flow, i.e. from supercritical to subcritical, resulting in large instabilities and even an internal hydraulic jump. Shallow sediment traps result in less frequent internal hydraulic jump and weaker jumps compared to deeper sediment traps. To investigate the dominant mechanism for the trapping of sediment in the sediment trap, a distinction is made between an erosion and a fluid mud scenario. The erosion scenario shows the largest agreement with the survey data, i.e. maintenance dredging data and Echosounder multibeam surveys, but contribute only marginally to the trapping of sediment. The fluid mud scenario yields the largest contribution to the trapping of sediment. The decreased amounts of accumulated sediment in the basin for substantial to lots of fluid mud behaviour may vary between 10% and 14%, depending on how this fluid mud behaviour is modelled. Various shapes have been tested on erosion and fluid mud scenarios. Both for erosion and fluid mud a more extreme choice of parameters might yield also more extreme results, this is however not considered realistic. The creation of an overdepth has shown to result in a marginal improvement in the capturing of sediment in an environment where erosion is important. A regular sediment trap decreases accumulation in the harbour basins by 2%. A trap twice as shallow increases this amount to 4%, but deepening the trap further may even enhance accumulation in the basins. A shorter or longer trap did not improve the situation. Installation of a sill did however result in a decrease of 6% compared to the situation without trap. It is concluded that this effect can be largely contributed to the internal flow properties and the presence of internal hydraulic jumps. The presence of an overdepth results in a significant improvement in the capturing of fluid mud flow. For the trapping of fluid mud flow, an overdepth results in 6% less sediment in the harbour basins no matter the depth or shape of the trap. The length of the trap did influence the accumulation in the basins. A trap twice as short shows an increase of 4 % of accumulation in the basins compared to a regular trap. A trap twice as long or installation of a sill results in similar accumulation in the harbour basins as a regular trap. For fluid mud flows, any type of overdepth decreases accumulation of sediment considerably. The amount of overdepth or the shape does not influence this. The length of the trap should be sufficient. A trap that is too short results in an increase of accumulation in the basins. For environments where erosion is important, only shallow sediment traps have proven to reduce accumulation in the basins. Traps that are too deep actually increase accumulation in the basins. A sill has proven to be the best measure for both mechanisms. If overdepth is desirable for navigation a shallow sediment trap is advised. This leads to a reduction of accumulation in the harbour basins for both erosion and fluid mud scenarios.","Sediment traps; Siltation traps; Supercritical; Stratification; Stratified; Harbour siltation","en","master thesis","","","","","","","","","","","","Civil Engineering | Hydraulic Engineering","",""
"uuid:1b91c352-0544-4744-9023-4efbcfd8bdd7","http://resolver.tudelft.nl/uuid:1b91c352-0544-4744-9023-4efbcfd8bdd7","Machine Learning Revealing Insights into Soil Stratification: An Application for Dikes and Dams","Leunge, Laurens (TU Delft Civil Engineering and Geosciences)","Kok, Matthijs (graduation committee); Jorissen, Richard (graduation committee); Vardon, Phil (graduation committee); Coelho, Bruno Zauda (mentor); Klerk, Wouter Jan (mentor); Delft University of Technology (degree granting institution)","2019","In the Netherlands, robust dike and dam design is a major concern in the context of flood defence. Due to heterogeneity of the subsoil on which these structures are founded, the validity range of in situ tests decreases drastically. Consequently, large uncertainties regarding spatial variation of soil stratification and soil layer parameters are incorporated in the cross-sectional reliability requirements, resulting in conservative designs. This thesis presents a Machine Learning application, which, by learning locally measured information and analysing high spatial resolution surface settlement data, can provide insights into spatial variation of soil stratification. Through the analysis of these insights, the uncertainties regarding spatial variability in cross-sectional reliability requirements can be reduced, which leads to less conservatism in dike and dam construction.","Machine Learning; Support Vector Machines; Soil Stratification; Dike; Dam","en","master thesis","","","","","","","","","","","","Civil Engineering","",""
"uuid:b98e7799-c0d3-42ca-8c9c-70ee64bf059a","http://resolver.tudelft.nl/uuid:b98e7799-c0d3-42ca-8c9c-70ee64bf059a","Effects of a stratified tidal flow on the morphodynamics","Meirelles, Saulo (TU Delft Coastal Engineering)","Stive, M.J.F. (promotor); Reniers, A.J.H.M. (promotor); Pietrzak, J.D. (promotor); Delft University of Technology (degree granting institution)","2019","This thesis examines the effects of the stratified tidal flow on the morphodynamics of the Dutch inner shelf. The south portion of the Dutch inner shelf is strongly influenced by the Rhine River ROFI (Region Of Freshwater Influence), which is generated by the discharge from the Rhine River through the Rotterdam waterways. Under stratified conditions, the three-dimensional structure of the tidal currents develops a strong cross-shore shear so that the bottom and surface currents become 180deg out of phase. The sheared flow created by stratification operates in the inner shelf and nearshore zones so that the flow asymmetries imparted by stratification are expected to impact the morphodynamics, however the role of the stratified tidal flow on the morphodynamics along the Dutch coast has been often neglected or oversimplified. In this context, this thesis aims to provide new insights on how the stratified tidal flow dictates the morphodynamics outside the surfzone.
In the south portion of the Dutch coast is located the Sand Engine, a 21.5 million m3 experimental mega-nourishment that was built in 2011. This intervention created a discontinuity in the previous straight sandy coastline, altering the local hydrodynamics in a region that is influenced by the Rhine River ROFI. Estimates of the centrifugal acceleration directly after construction of the Sand Engine showed that its curved shape impacted the cross-shore flow, suggesting that the Sand Engine might have played a role in controlling the cross-shore exchange currents during the first three years after the completion of the nourishment. Presently, the curvature effects are minute owned to the morphodynamic evolution of the Sand Engine. Observations document the development of strong baroclinic-induced cross-shore exchange currents dictated by the intrusion of the river plume fronts as well as the classic tidal straining which are found to extend further into the nearshore (from 12 to 6 m depth), otherwise believed to be a mixed zone.
In the inner shelf, shoaling waves are as effective in mobilizing sediment as the other co-existing flows. The influence of stratification on the hydrodynamics is translated into near-bed shear velocity in the layer immediately above the sea floor. The tide-induced bed shear stress is able to periodically agitate the bed near the peaks of flood and ebb cycles mostly during spring tides. Results from observations suggested that, under stratified conditions, relatively high values of bed shear stress are sustained for a prolonged period of time. The results also revealed that the non-tidal flow, such as the wind-induced flow, plays a role in controlling the bed mobility. However, wave-induced bed shear stress in general does not set sediment in motion during fair weather conditions and thus the stirring role of the waves is mostly important during storms.
The co-exiting near-bed flows in the inner shelf are responsible for moulding the seafloor so that the resulting types of bedforms can reveal important information on the hydrodynamic forcings that dictate the sediment mobility. Observations showed that 56% of the ripples in the Dutch inner shelf are classified as current ripples. Wave ripples occur only during storm conditions, comprising 3%. The frequency of occurrence of transitional bed types composes 23% and poorly developed ripples is found to develop mostly during neap tides making up 15% of the observed bed types. The feedback of the different types of bedforms on the overlying boundary layer plays a fundamental role in the dynamics of the sediment load.
The morphological response of the bed to the stratified and non-stratified tidal flow leads to differentiations of the ripple migration as well as the sediment transport modes (bedload and suspended load). The bedforms at the measurement site are strongly controlled by tides so that their behavior exhibits not only a spring-neap signature, but also a distinct semi-diurnal fluctuation. Under the influence of the Rhine ROFI, the bedform mean dimensions (ripple height and wavelength) are reduced, indicating that their development is affected by the stratified tidal flow. In the absence of (ambient) stratification, the tidal current ripples are more developed, attaining relatively larger dimensions. The net alongshore bedload transport is south-directed, whereas the net alongshore suspended load is north-directed regardless of stratification. Moreover, the net alongshore bedload transport is higher during stratified conditions but the net alongshore suspended transport is smaller. Regarding the cross-shore sediment transport, the findings show that ambient stratification promotes onshore-directed bed- and suspended load net transport. The gross suspended transport rates are 10 times greater than the gross bedload transport rates.","stratification; bedforms; sediment transport","en","doctoral thesis","","","","","","","","","","","Coastal Engineering","","",""
"uuid:874636af-ca58-42fc-804c-1c84a4a92aeb","http://resolver.tudelft.nl/uuid:874636af-ca58-42fc-804c-1c84a4a92aeb","Offshore Energy Hub Island in the North Sea: The development of a hydrodynamic model to explore the ecological feasibility","Groot, Jeffrey (TU Delft Civil Engineering and Geosciences; TU Delft Hydraulic Engineering)","Aarninkhof, Stefan (mentor); Katsman, Caroline (graduation committee); Hoekstra, Roderik (graduation committee); Zijl, Firmijn (graduation committee); van Duren, Luca (graduation committee); Delft University of Technology (degree granting institution)","2018","To combat the emission of greenhouse gasses and the corresponding climate change, emission reduction goals have been established in the recent Paris Agreement. In order to meet these reduction goals and minimise the global average temperature increase, implementation of renewable energy sources is critical. Wind energy is one of the fastest growing renewable energy sources in the European Union, since Europe has the largest offshore wind energy capacity with its shallow shelf sea: the North Sea.
Over the last twenty years, the wind energy capacity has increased significantly to become the current second highest power generation form of the European Union. The downside to offshore wind energy however, are the high costs that come with its generation. Cable losses of alternating currents between the wind turbines and the shore become increasingly high, as the distances towards the shore increment. For long distances, this inefficiency becomes unacceptable and conversion to a direct current is deemed necessary.
A recently presented concept that aims to reduce the costs of offshore wind energy, is the concept of a large scale roll-out of interlinked offshore turbines, coordinated at an European level, including a so-called hub island. This artificial island facilitates converters, as well as a home base for engineers and large scale power storage. Technically, no big problems are expected with the construction of such artificial island. The major reason that could stop the hub island concept, is resistance from environmental organisations.
To predict ecological repercussions of an artificial island, the impact on hydrodynamic parameters most important to the bottom of the marine food chain are explored. The primary producers represent this foundation of the food chain, and are most affected by the island through changes in water stratification and residual currents. These parameters highly influence the light and nutrient availability, thereby regulating the primary production dynamics of the ecosystem.
By developing and applying the Three Dimensional Dutch Continental Shelf Flexible Mesh (3D DCSM-FM) model, the impact of an artificial island on the stratification and residual currents is explored for five case studies. Each case study comprises a 6km$^2$ cylindrical island, for different North Sea locations with distinct hydrodynamic properties.
The implementation of an artificial island alters residual currents up to 10km from its position. The location determines the impact pattern, but influences remain local without any large scale North Sea impacts. Since changes in nutrient availability are only expected for large scale residual current impacts, no significant alterations in primary production dynamics are to be expected.
The impact on stratification however, can have a significant influence on the dynamics of primary production. The originally well-mixed areas remain mostly unchanged, while islands in the more stratified regions can cause significant changes in absolute stratification up to 20km from the banks, and alterations in regimes or the seasonal onset timing up to 2.5km. The location and its hydrodynamic properties are paramount to the type of expected stratification impact, and proves to be an important design parameter for ecology around an offshore energy hub island in the North Sea.
4 +/L and no COD) achieved nitrogen loading rates of 0.8 g N-NH4 +/(L·d) during partial nitritation. The switch between nitrite-oxidizing bacteria (NOB) repression and NOB proliferation was observed when ammonium concentrations in the reactor were below 2–5 mg N-NH4 +/L for DO concentrations lower than 4 mg O2/L at 20 °C. Nitrospira spp. were detected to be the dominant NOB population during the entire reactor operation, whereas Nitrobacter spp. were found to be increasing in numbers over time. Stratification of the granule structure, with ammonia-oxidizing bacteria (AOB) occupying the outer shell, was found to be highly important in the repression of NOB in the long term. The pH gradient in the granule, containing a pH difference of ca. 0.4 between the granule surface and the granule centre, creates a decreasing gradient of ammonia towards the centre of the granule. Higher residual ammonium concentration enhances the ammonium oxidation rate of those cells located further away from the granule surface, where the competition for oxygen between AOB and NOB is more important, and it contributes to the stratification of both populations in the biofilm.","Mainstream conditions; Nitrobacter; Nitrospira; pH gradient; Stratification","en","journal article","","","","","","Accepted Author Manuscript","","2017-04-11","","","BT/Environmental Biotechnology","","",""
"uuid:9f032a7a-89b8-4669-b6b2-4843315cae06","http://resolver.tudelft.nl/uuid:9f032a7a-89b8-4669-b6b2-4843315cae06","Impact Assessment of the Rhine ROFI on the Annual Cross-shore Sand Transport","Waagmeester, N.C.D.","Stive, M.J.F. (mentor); Pietrzak, J.D. (mentor); Luijendijk, A.P. (mentor); Meirelles, S. (mentor); Henriquez, M. (mentor); Rijnsburger, S. (mentor)","2015","Using D-Flow Flexible Mesh numerical software to simulate the region of freshwater influence of the Rhine in front of the Dutch coast to assess the influence of stratification on the near-bottom velocities and the related cross shore sand transport.","DFlow; Rhine ROFI; stratification; cross-shore velocities; Rhine; sand transport; Delft3D; Flexible Mesh; fresh water","en","master thesis","","","","","","","","2020-06-18","Civil Engineering and Geosciences","Hydraulic Engineering","","Coastal Engineering","",""
"uuid:5824c0b7-a680-4657-a686-b01f37fbfcf4","http://resolver.tudelft.nl/uuid:5824c0b7-a680-4657-a686-b01f37fbfcf4","Multiscale physical processes of fine sediment in an estuary","Wan, Y.","Roelvink, J.A. (promotor)","2015","This study presented in this book investigates micro- and macro- scale physical processes of a large-scale fine sediment estuarine system with a moderate tidal range as well as a highly seasonal-varying freshwater inflow. Based on a series measured, experimented and modeled results, the research highlights that (i) along-channel fresh-salt gradient near an estuarine turbidity maximum zone is a key parameter controlling local density stratification and sedimentation in the channel; (ii) the salinity-induced baroclinic pressure gradient forces are a major factor impacting internal velocity and suspended sediment concentration (SSC) structures; (iii) vertical profiles of current, salinity and SSC within a river plume are dependent on a correct prediction of the development of turbulence; (iv) both suspended particulate matter availability and local residual flow regime are of critical importance for trapping probability of sediment and the occurrence of fluid mud; (v) river discharge impacts the horizontal and vertical distribution of residual current; (vi) seasonally varying wind effect alters the residual currents near the riverine limit; (vii) seasonally varying mean sea level and wind climate jointly shape the saltwater intrusion length near the estuarine front.","fine sediment; settling velocity; stratification; flocculation; Yangtze Estuary; turbulence damping","en","doctoral thesis","CRC Press/Balkema","","","","","","","2015-05-15","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:51454527-14fa-447c-9ff7-11c64aa73150","http://resolver.tudelft.nl/uuid:51454527-14fa-447c-9ff7-11c64aa73150","The influence of an obstacle on flow and pollutant dispersion in neutral and stable boundary layers","Tomas, J.M.; Pourquie, M.J.B.M.; Jonker, H.J.J.","","2015","Predicting pollutant dispersion in urban environments requires accurate treatment of obstacle geometry, inflow turbulence and temperature differences. This paper considers both the influence of thermal stratification and the presence of a single obstacle on pollutant dispersion in turbulent boundary layers (TBLs). Turbulent flow over a fence with line sources of pollutant in its vicinity is simulated by means of Large-Eddy Simulations. Separate ‘driver’ simulations are done to generate the inflow TBL for several levels of stratification. Using these inflow TBLs the flow development and pollutant dispersion behind the fence, up to 100 fence heights, h, is investigated. It is shown that the decay of velocity and temperature deficit is independent of stability, while the decay of Reynolds stress and concentration excess decreases with increasing stability. For neutral cases the influence of the obstacle is gone after approximately 75h, while for stable cases near the ground the flow is still accelerated compared to the undisturbed case. The fence does cause a local reduction of stratification and thereby increased pollutant dispersion. However, neglecting the effect of buoyancy results in an underestimation of pollutant concentration by a factor 2.5 at 75h downstream of the emission source for the most stable case.","stratification; boundary layer; obstacle; pollutant dispersion; turbulence; wake","en","journal article","Elsevier","","","","","","","","Mechanical, Maritime and Materials Engineering","Process and Energy","","","",""
"uuid:d54c7b9e-e86a-43e3-ac54-bde997bf128c","http://resolver.tudelft.nl/uuid:d54c7b9e-e86a-43e3-ac54-bde997bf128c","Linear stability analysis reveals exclusion zone for sliding bed transport","Talmon, A.M.","","2015","A bend or any another pipe component disturbs solids transport in pipes. Longitudinal pressure profiles downstream of such a component may show a stationary transient harmonic wave, as revealed by a recent settling slurry laboratory experiment. Therefore the fundamental transient response of the two-layer model for fully stratified flow is investigated as a first approach. A linear stability analysis of the sliding bed configuration is conducted. No stationary transient harmonic waves are found in this analysis, but adaptation lengths for exponential recovery are quantified. An example calculation is given for a 0.1 m diameter pipeline. Also consequences for long stretches of pipe line emerged. A so far undiscovered exclusion zone is found in the I-V diagram. This exclusion zone is situated adjacent to the deposit limit velocity locus curve. This simplified physical system reveals that flow velocities should be taken about 10% greater than the calculated maximum deposit limit velocity for stable converging flow.","stratification; hydrotransport; transients; bed layer","en","journal article","De Gruyter Open","","","","","","","","Mechanical, Maritime and Materials Engineering","Marine and Transport Technology","","","",""
"uuid:1bad7611-59ee-49d1-bf41-220612dfa298","http://resolver.tudelft.nl/uuid:1bad7611-59ee-49d1-bf41-220612dfa298","Numerical analysis of stratification and destratification processes in a tidally energetic inlet with an ebb tidal delta","Purkiani, K.; Becherer, J.; Flöser, G.; Gräwe, U.; Mohrholz, V.; Schuttelaars, H.M.; Burchard, H.","","2015","Stratification and destratification processes in a tidally energetic, weakly stratified inlet in the Wadden Sea (south eastern North Sea) are investigated in this modeling study. Observations of current velocity and vertical density structure show strain-induced periodic stratification for the southern shoal of the tidal channel. In contrast to this, in the nearby central region of the channel, increased stratification is already observed directly after full flood. To investigate the processes leading to this different behavior, a nested model system using GETM is set up and successfully validated against field data. The simulated density development along a cross section that includes both stations shows that cross-channel stratification is strongly increasing during flood, such that available potential energy is released in the deeper part of the channel during flood. An analysis of the potential energy anomaly budget confirms that the early onset of vertical stratification during flood at the deeper station is mainly controlled by the stratifying cross-channel straining of the density field. In contrast to this, in the shallow part of the channel, the relatively weak cross-channel straining is balanced by along-channel straining and vertical mixing. An idealized analytical model confirms the following hypothesis: The laterally convergent flood current advecting laterally stratified water masses from the shallow and wide ebb tidal delta to the deep and narrow tidal channel has the tendency to substantially increase cross-channel density gradients in the tidal channel. This process leads to stratification during flood.","tidal channel; tidal straining; lateral circulation; Wadden Sea; numerical modeling; stratification","en","journal article","American Geophysical Union","","","","","","","2015-07-21","Electrical Engineering, Mathematics and Computer Science","Delft Institute of Applied Mathematics","","","",""
"uuid:251b4a5a-2823-4a2b-aa4a-1a2f52bc9272","http://resolver.tudelft.nl/uuid:251b4a5a-2823-4a2b-aa4a-1a2f52bc9272","Turbulence modelling in environmental flows: Improving the numerical accuracy of the k-epsilon model by a mathematical transformation","Dijkstra, Y.M.","Pietrzak, J.D. (mentor); Schuttelaars, H.M. (mentor); Uittenbogaard, R.E. (mentor); Van Kester, J.A.T.M. (mentor)","2014","Numerical modelling for environmental flow applications, such as for rivers, lakes, estuaries and coastal flows, faces a trade-off between the numerical accuracy and the required computation time. This trade-off results in grids which typically contain 10 to 100 layers in the vertical direction. Such a grid resolution poses severe limitations to the numerical accuracy of the model. The turbulence model determines a significant part of this accuracy. This research therefore investigates an unexplored method of using transformations to improve the numerical accuracy of two-equation turbulence models at a low resolution. The k-epsilon model is used as starting point for this method. The equation for epsilon is transformed to equations for omega and tau. This results in three turbulence models, the k-epsilon, k-omega and k-tau models, which are physically equivalent, but possess different numerical properties. This research identifies these different numerical properties in order to explain when and why a certain transformation is beneficial to the numerical accuracy. The three turbulence models are tested in six cases of homogeneous and stratified flows in a one-dimensional vertical (1DV) numerical model, which is representative for the implementation in the 3D simulation system Delft 3D-FLOW. It is shown that the k-tau model yields more accurate results than the k-epsilon and k-omega models in boundary friction dominated flows, such as those found in rivers, partially stratified estuaries and along the coast. This improved performance is explained from the profile of tau, which is linear near the frictional boundary and therefore accurately approximated on a low resolution grid. The profiles of epsilon and omega are hyperbolic near the frictional boundary and therefore not accurately represented on such a grid. The boundary condition for tau is well-posed, while no natural boundary conditions for epsilon and omega exist. Dirichlet boundary conditions for epsilon and omega are therefore inaccurate. The Neumann boundary condition is found to be the most accurate alternative boundary condition for epsilon and omega. An adjusted Dirichlet conditions used in Delft 3D-FLOW improves on the result of the ordinary Dirchlet condition, but shows bad convergence behaviour, with results being significantly worse at 100 vertical layers than at 10 vertical layers. A new adjusted Dirichlet condition is developed, which has better convergence behaviour, but is still somewhat worse than the Neumann condition. The k-tau and k-omega models contain a number of diffusive terms, the implementation of which may introduce numerical diffusion in the model. Some of these diffusive terms are essential to the stability of the model. Others are optional. It is argued that the choice whether or not to include such optional diffusive terms should be based on both physical and numerical arguments, because the numerical diffusion associated with the implementation of the terms may have a significant desired or undesired effects on the model results. It is found in the cases in this research that convergence of the turbulence models with increasing grid resolution is typically found between 100 and 1000 grid cells in the vertical direction. One case of temperature modelling of a lake has been tested in which convergence did not occur up to 2000 grid cells. So converged results are generally beyond the range of generally used vertical resolution in 3D models. Within the feasible range of 10 to 100 layers it is found that the results of the turbulence models do not necessarily become more accurate if higher resolution grids are used. So monotonous convergence of the turbulence models is not guaranteed.","turbulence modelling; numerical accuracy; stratification; k-epsilon model; k-tau model; convergence","en","master thesis","","","","","","","","2015-11-06","Civil Engineering and Geosciences","Hydraulic Engineering","","Environmental Fluid Mechanics","",""
"uuid:78f0fde9-0412-44f9-92fd-89ed993a4694","http://resolver.tudelft.nl/uuid:78f0fde9-0412-44f9-92fd-89ed993a4694","Stratification and mixing in the Rhine region of fresh water influence; Analysing two parallel transects","Rijnsburger, S.","Pietrzak, J.D. (mentor)","2014","The Rhine River and the Meuse River discharge into the southern North Sea, and form the Rhine Region of Fresh Water Influence (ROFI) in front of the Dutch coast. A complex hydrodynamic system is generated, dominated by mixing from strong tides, wind and waves and the stratifying influence of the freshwater and solar heating. This influences the distribution and dynamics of fine sediments. A proper understanding of the system is required to evaluate the effects of human interferences, such as the dredging for Maasvlakte 2. Previous years more insight is gained into the interaction between the tide and the stratification by numerical modelling (de Boer, et al., 2008). Furthermore, various measurement campaigns are carried out to determine the effect of dredging activities for Maasvlakte 2. This Master Thesis presents the analysis of a unique in-situ dataset focused on the different cross- and alongshore processes which induce the onset and breakdown of stratification. The aim of this study is to gain more insight into the complex four dimensional nature of the Rhine ROFI, in order to generate a better understanding of the behaviour of Suspended Particluate Matter (SPM). In October 2011 the Port of Rotterdam Authority (PoR) and NIOZ (Royal Netherlands Institute for Sea Research) sailed simultaneously on two parallel cross-shore transects in order to conduct measurements, one near Egmond and one near Wijk aan Zee. Salinity, temperature, SPM and velocities were measured. The advantage of measuring along two transects is the extra dimension in alongshore direction. Therefore, a dataset is obtained allowing analysis in four dimensions. In the previous years the four dimensional nature of the ROFI has only been studied with numerical modelling. However, data analysis was only performed with data from a single mooring or a single transect, both of which do not give spatial information in cross- and alongshore direction. The contribution of alongshore advection and straining is investigated with a simplified form of the three-dimensional Potential Energy Anomaly Equation (PEA) (de Boer, et al., 2008), influenced by wind, waves and tide. Tidal analysis is used to investigate the presence of ellipses, which indicate the presence of the plume. After analysis it has become clear that the Northern transect is far more stratified than the expected. It was anticipated that the waters this far north were well-mixed. Instead it is shown that the Northern transect is even more stratified than the Southern transect. The simplified three-dimensional Potential Energy Anomaly analysis shows that cross-shore straining is the dominant process inducing stratification and mixing. Although the other cross- and alongshore processes are also observed and these prove significant as well. However, the alongshore advection works different than expected; it enhances stratification during ebb instead of during flood. This is the result of the more stratified Northern transect in comparison with the more homogeneous Southern transect. Tidal ellipses are observed in front of the coast. The ellipses show that the state of the water column is spring-like, stratification is yet observed. Using two vessels to obtain information in four dimensions is on the verge of what is currently possible with the ships available to the Dutch community. This first measurement in four dimensions with two vessels and using the three-dimensional Potential Energy Anomaly Equation has led to more insights. This study highlights the dynamic and unpredictable behaviour of the Rhine ROFI, as the measurements have led to surprising outcomes.","stratification; Rhine Region of Freshwater Influence","en","master thesis","","","","","","","","2015-05-16","Civil Engineering and Geosciences","Hydraulic Engineering","","Environmental Fluid Mechanics","",""
"uuid:3ad16a88-ab3c-474b-8823-a13d975d678b","http://resolver.tudelft.nl/uuid:3ad16a88-ab3c-474b-8823-a13d975d678b","Thermal stratification within urban street canyons: SARA3DCLIMAT flow simulations","Meyer, M.P.","Kenjeres, S. (mentor); Kleijn, C.R. (mentor); De Roode, S.R. (mentor); Schrijvers, P.J.C. (mentor)","2014","For this study, Urban Heat Island (UHI) consequential urban atmospheric thermally stratified buoyancy influences were investigated, utilising an in-house Computational Fluid Dynamic (CFD) modelling code, SARA3DCLIMAT. The code is based on transient-Reynolds Averaged Navier-Stokes (T-RANS) and hybrid Large Eddy Simulation (LES)/T-RANS methods, with modification to dissipation coefficient to the turbulent kinetic energy dissipation conservation equation. For the study, it was hypothesised that SARA3DCLIMAT would be capable of accurately predicting thermally stable and unstable stratified turbulent urban atmospheric buoyancy flows.","thermal stratification; urban atmospheric flow; turbulent Prandtl number","en","master thesis","","","","","","","","","Applied Sciences","Chemical Engeneering","","Transport Phenomena","",""
"uuid:e37a8243-fcc4-4384-b88b-54140f35313c","http://resolver.tudelft.nl/uuid:e37a8243-fcc4-4384-b88b-54140f35313c","Quantification of Imaging Biomarkers For Cardiovascular Disease in CT(A)","Shahzad, R.","Van Vliet, L.J. (promotor); Niessen, W.J. (promotor); Van Walsum, T. (promotor)","2013","For better management of cardiovascular disease, it is of utmost importance to categorize the subjects into different risk groups. This categorization can be made based on cardiovascular risk factors including the family history of the subject. Imaging techniques play an increasing role in order to assess ardiovascular risk factors. In this thesis we set out to develop and evaluate automatic techniques for the extraction of quantitative imaging biomarkers for coronary artery disease (CAD). One of the important cardiovascular risk factor is the presence of calcium in the arteries. We presented an automatic method that can compute the amount of calcium scores for the whole heart as well as for each of the coronary arteries from CT data. The system also categorizes patients into different risk groups. This vessel specific calcium lesion information can be used for treatment planning and assessing progression of CAD in follow up studies. The possibility to assign calcium to individual coronary arteries was possible owing to the ’Coronary Density Estimate’. The second imaging biomarker is epicardial fat volume. We resent a method that can accurately quantify the amount of epicardial fat volume. It was demonstrated that the method performs as good as the manual observers, hence has great potential to be used in daily clinical practice. In a clinical study on 2298 subjects it was demonstrated that indeed larger volumes of epicardial fat volumes were related to larger volumes of calcified lesions in the various vessel beds. The potential of this biomarker will need to be established in multiple larger studies. The third imaging biomarker in CAD considered in this thesis is coronary artery stenosis grade. Accurate detection and quantification of coronary stenoses is of great importance, as this information is very important for the clinician in order to make accurate treatment selection and planning. We investigated the ability of detecting and quantifying coronary stenoses from CTA data. We demonstrated that the vessel lumen can be segmented with a precision similar to the human observers, but that it is still a challenge to be able to distinguish between significant and non-significant lesions. Quantitative imaging biomarkers in CAD may provide both anatomical and functional information, and are often obtained from different imaging modalities. An important subject with respect to treatment planning is therefore the ability to combine information from different modalities in an integrated display. The SMARTVis system was introduced to fuse anatomical information from CTA scans and functional information from SPECT-MPI into one display. The integrated visualization proposed in the SMARTVis system enables a one-stop-shop visual exploration of cardiac anatomical and functional data, to maximally exploit the complementary information of multiple imaging modalities. It has been confirmed that such comprehensive visualizations allow to effectively relate perfusion defects and coronary lesions, and that fused integrated analysis leads to a more accurate diagnosis. Automatic image processing plays an increasingly important role. Not only to extract relevant quantitative imaging biomarkers from CT imaging data, but also establish with what accuracy they can be assessed. For a number of relevant cardiovascular quantitative imaging biomarkers, this thesis has provided the required methodology.","Cardiovascular; Image Processing; Image Segmentation; Image Registration; Risk Stratification","en","doctoral thesis","","","","","","","","","Applied Sciences","Imaging Science & Technology","","","",""
"uuid:40962f3b-3ffe-4d39-bca6-30b4d9f27ffc","http://resolver.tudelft.nl/uuid:40962f3b-3ffe-4d39-bca6-30b4d9f27ffc","A numerical study of mixing and stratification dynamics in the Ria de Arousa estuary (nw Spain) during summer","Bermudez, M.; Pietrzak, J.D.; Cea, L.; Puertas, J.; Stelling, G.S.; De Boer, G.J.","","2013","In this paper we explore the role of the river run-off, the tidal regime and the local winds in the dynamics of the Ria de Arousa estuary during the summer period, using for that purpose the numerical model Delft3D. First of all, a simulation under real hydrological and meteorological conditions is conducted in order to validate the ability of the model to reproduce measured salinity and temperature profiles. Subsequently, a series of simulations considering simplified meteorological input data and river discharge conditions are carried out in order to study the sensitivity of stratification conditions in the estuary to the various external forcings of the model. The results are analyzed using potential energy anomaly arguments, which allow quantifying and ranking the contribution of the different processes to the stratification of the estuarine system.","Ria de Arousa estuary; 3D numerical model; potential energy anomaly; mixing and stratification","en","conference paper","Bordeaux University","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:03f71917-061e-4ffb-82ee-9b71d09878ac","http://resolver.tudelft.nl/uuid:03f71917-061e-4ffb-82ee-9b71d09878ac","RESTRATIFICATION IN HYDRAULIC TRANSPORT: IS IT A BEND EFFECT?","Talmon, A.M.","van Rhee, C. (advisor)","2013","","hydraulic transport; stratification; ERT; hydraulic gradient","","conference paper","","","","","","","","indefinite","Mechanical, Maritime and Materials Engineering","Marine and Transport Technology","Offshore and Dredging Engineering","","",""
"uuid:fb0ec18d-dcfd-468d-af4a-45bfb02cac1c","http://resolver.tudelft.nl/uuid:fb0ec18d-dcfd-468d-af4a-45bfb02cac1c","On sedimentation processes in a stratified estuarine system","De Nijs, M.A.J.","Stelling, G.S. (promotor); Pietrzak, J.D. (promotor)","2012","","tidally energetic stratified estuary; salt wedge; estuarine turbidity maximum; harbour siltation; Port of Rotterdam; Rotterdam Waterway; Botlek Harbour; baroclinicity; salinity stratification; turbulence damping; transport of SPM; trapping of SPM; total turbulent energy; countergradient buoyancy fluxes; Turbulent Prandtl number; energetic turbulent structures; convective motions","en","doctoral thesis","","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:c5c07865-be69-4db2-91e6-f675411a4136","http://resolver.tudelft.nl/uuid:c5c07865-be69-4db2-91e6-f675411a4136","On the interaction between tides and stratification in the Rhine Region of Freshwater Influence","De Boer, G.J.","Stelling, G.S. (promotor); Pietrzak, J.D. (promotor)","2009","","southern north sea; semi-diurnal tides; advection and strain induced periodic stratification; rofi; river plume; baroclinic numerical model delft3d; coastal upwelling; tidal straining; tidal ellipses; knmi noaa sst satellite imagery; potential energy anomaly equation","en","doctoral thesis","","","","","","","","","Civil Engineering and Geosciences","","","","",""
"uuid:f6e4cdab-a155-423e-9f58-de90cad514f9","http://resolver.tudelft.nl/uuid:f6e4cdab-a155-423e-9f58-de90cad514f9","A first validation of BLOOM for species groups","Wesenbeeck, B.K. van","","2007","","fytoplankton; phytoplankton; algenbloei; algal blooms; tweedimensionale modellen; two-dimensional models; driedimensionale modellen; three-dimensional models; validatie; validation; gelaagdheid; stratification","en","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:b4c9740a-dcd5-4364-a6d3-ad13553f887b","http://resolver.tudelft.nl/uuid:b4c9740a-dcd5-4364-a6d3-ad13553f887b","Hydraulic roughness in sediment-laden flow","Lely, M.S.","Stive, M.J.F. (mentor); Winterwerp, J.C. (mentor); Wang, Z.B. (mentor); Van Maren, D.S. (mentor)","2007","Most estuarine, and some coastal, areas are characterised by large amounts of fine-grained cohesive and non-cohesive sediments. At sufficiently high concentrations, sediment transport in suspension may significantly influence the hydrodynamics. In sediment-laden flow with concentrations of approximately, stratification may occur due to a vertical gradient of sediment concentration. In a stratified flow, turbulence is damped due to buoyancy destruction. According to many reports in literature buoyancy destruction results in a decrease of effective hydraulic roughness. Furthermore, the sediment induced stratification causes an appreciable modification of the vertical profiles of velocity, vertical eddy viscosity and shear stresses (e.g. Winterwerp [2001])). Considering the propagation of a tidal wave in estuaries, the decrease of roughness results in an increase of the depth-averaged velocity and an increase of tidal amplitudes of the water level. When modelling flow behaviour in estuarine and coastal environments, vertical gradients of horizontal velocity and sediment and salt concentration in stratified systems can only be simulated with three dimensional numerical modelling. However a full three dimensional model is not always practical. The wide shallow domains that occur in civil engineering practice make depth-averaged simulation often necessary in view of the computational demands. However no theoretically accepted, justifiable parameterisation for effective hydraulic roughness in turbulent sediment-laden flow exists to date. Therefore the effect of suspended sediment on tidal propagation in estuaries is not accounted for in 2Dh modelling. This makes 2Dh modelling intrinsically less accurate than 3D. In case the flow contains an appreciable amount of suspended sediment it is difficult to reliably predict flow behaviour in estuaries through 2Dh modelling. In depth-averaged equations solved in 2Dh models, the bottom shear stress is explicitly prescribed using a friction coefficient. The reduction of hydraulic roughness due to stratification can in this case effectively be accounted for by alteration of the friction coefficient. By applying theories commonly used for stratified flow in the earth's atmosphere and taking into account the free surface effects, a depth-averaged friction law was derived This friction law is validated by numerical experiments with the 1DV POINT MODEL. These numerical experiments show that the buoyancy effect is small compared to the integral effect of sediment in nature that is reported in literature. To further evaluate the depth-averaged roughness parameterisation it is applied to a numerical model of the Yangtze Estuary (China). Calibration shows that the bottom of the Yangtze Estuary is very smooth even without the buoyancy effect, and that the buoyancy effect decreases the effective roughness further. For the Yangtze Estuary the buoyancy effect is properly simulated by the depth-averaged roughness parameterisation. Through the parameterisation the effective Chézy coefficient is increased from for clear water to for flow conditions commonly found in the Yangtze Estuary. Thereby the sediment-induced error in 2Dh modelling is reduced by approximately 75%. From this it is concluded that 2Dh modelling becomes more accurate through application of the roughness parameterisation. Several other issues can be done that might increase the reliability of 2Dh models even more. For example it is recommended to implement the roughness parameterisation in the numerical code of DELFT3D-FLOW, so that the effective hydraulic roughness is continuously updated with feedback to hydrodynamics and sediment transport.","sediment; stratification; flow; buoyancy; turbulence","en","master thesis","TU Delft, Civil Engineering and Geosciences, Hydraulic Engineering","","","","","","","","Civil Engineering and Geosciences","","","","",""
"uuid:955c212d-49aa-4c2c-a1a1-1cb2775cffda","http://resolver.tudelft.nl/uuid:955c212d-49aa-4c2c-a1a1-1cb2775cffda","Unsteady separated fluid flows around a sphere in the wide range of the Reynolds and Froude numbers","Gushchin, V.A.; Matyushin, P.V.","","2006","The homogeneous (1 < Re < 5000000) and stratified (0.004 < Fr < 1, 10 < Re < 1000) viscous incompressible fluid flows around a sphere have been investigated by means of the direct numerical simulation (DNS) and the visualization of the vortex structures in the wake. In case of the homogeneous fluid at 200 < Re < 1000 the detailed formation mechanisms of vortices (FMV) in the sphere wake have been described for the different unsteady periodical flow regimes (270 < Re < 290, 290 < Re < 320, 320 < Re < 400, 400 < Re < 700 and Re > 700) and the six basic FMV have been selected; at 290 < Re < 320 a new flow regime has been discovered; at 50000 < Re < 5000000 the preliminary results are presented. The following six basic FMV work during the period in the different parts of the flow: 1) in the recirculation zone a new vortex ring (or semi-ring) is generated near the sphere surface due to the Kelvin-Helmholtz instability (1k), the two vortex filaments connected with a new vortex ring are formed (1f), the main vortex ring is displaced closer to the sphere surface (1d); 2) the side parts of the vortex envelope (surrounding the recirculation zone) are stretched downstream (2s), the top or bottom edge of the vortex envelope is rolling up cylindrically and detached (2t/b); 3) in the outer flow the head of the vortex loop (facing upwards (t) or downwards (b)) is generated (3t/b). In case of the stratified fluid the four different flow regimes have been simulated (0.004 < Fr < 1, 10 < Re < 1000); for the first time the complex 3D vortex structures of these flows have been shown; the high gradient sheets of density have been observed near the poles of the resting sphere and the moving sphere (Fr < 0.02). For DNS the explicit numerical method SMIF-MERANGE (second-order accuracy in space, minimum scheme viscosity and dispersion, monotonous) has been used. For the visualization of the vortex structures in the sphere wake the isosurfaces of the imaginary part of the complex-conjugate eigen-values of the velocity gradient tensor have been used.","stratification; formation mechanisms of vortices; incompressible fluid; numerical simulation; sphere wake; visualization","en","conference paper","","","","","","","","","","","","","",""
"uuid:e37ff3e5-8f2d-4800-82e8-f5bd7286dc1a","http://resolver.tudelft.nl/uuid:e37ff3e5-8f2d-4800-82e8-f5bd7286dc1a","Stratification effects by fine suspended sediment at low, medium, and very high concentrations","Winterwerp, J.C.","","2006","This paper describes results of the second part of a study on stratification effects by cohesive and noncohesive sediment. Winterwerp (2001) applied classical stratified flow theory implemented in a one-dimensional vertical numerical model (the 1DV POINT MODEL), showing that sediment-induced stratification effects may occur at already fairly small suspended sediment concentrations (i.e., a few 100 mg/L). We also discussed a basic difference between the behavior of cohesive and noncohesive sediment, which emerges as a result of the large water content of mud flocs. In this paper we elaborate further on the hydrodynamic description of the transport of fine suspended sediment by analyzing field and laboratory observations over a very large range of concentrations. We propose a sediment stability diagram to explain some features of hyperconcentrated flows, such as those observed in the Yellow River. We show that the behavior of hyperconcentrated flows is affected largely by hindered settling effects reducing the energy required to keep the sediment in suspension. The hydrodynamic description of sediment transport is used to predict capacity conditions as a function of a dimensionless stream power, i.e., U3/hgWs. This prediction agrees favorably with observations reported in literature covering four orders of magnitude in suspended sediment concentration.","stratification; fine sediment; stability diagram","en","journal article","American Geophysical Union","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:0e08fd45-5a6f-43ab-baea-839e1762fb84","http://resolver.tudelft.nl/uuid:0e08fd45-5a6f-43ab-baea-839e1762fb84","Modelonderzoek naar de effectiviteit van een doorlaatmiddel van de waterkwaliteit van het Veerse Meer","Nolte, A.J.; Bijvelds, M.D.J.P.","","2000","","waterkwaliteitsmodellen; water quality models; gelaagdheid; stratification; doorlaatmiddel; outlet; Veerse Meer","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:53c10550-4d5b-47ef-af38-04097a1c5ada","http://resolver.tudelft.nl/uuid:53c10550-4d5b-47ef-af38-04097a1c5ada","North Sea temperature modelling with SST forcing","Goede, E.D. de","","1999","","zeewatertemperatuur; seawater temperature; temperatuurmeting; temperature measurement; gelaagdheid; stratification; North Sea","en","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:10d41bf5-0c3b-4a7b-afa9-098272168991","http://resolver.tudelft.nl/uuid:10d41bf5-0c3b-4a7b-afa9-098272168991","Toepassing GEM Veerse Meer","Smits, J.G.C.; Blauw, A.N.; Nolte, A.J.","","1998","","modelijking; model calibration; ecologische modellen; ecological models; nutrienten; nutrients; gelaagdheid; stratification; waterkwaliteit; water quality; Veerse Meer","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:d2054a22-b384-41d4-9b16-96362fb65ae1","http://resolver.tudelft.nl/uuid:d2054a22-b384-41d4-9b16-96362fb65ae1","Onderzoek naar thermocliene effecten op de Noordzee","Kester, J.A.T.M. van; Uittenbogaard, R.E.; Goede, E.D. de","","1997","","North Sea; thermische gelaagdheid; thermal stratification; stromingsmodellen; flow models; stoftransport; mass transport","en","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:63a0ccd5-368a-48a8-b01f-16fffe3c59f7","http://resolver.tudelft.nl/uuid:63a0ccd5-368a-48a8-b01f-16fffe3c59f7","The importance of internal waves for mixing in a stratified estuarine tidal flow","Uittenbogaard, R.E.; Imberger, J.","","1993","","interne golven; internal waves; getijstromen; tidal currents; estuaria; estuaries; menging; mixing; dichtheidsstroming; density induced flow; gelaagdheid; stratification; turbulentie; turbulence; Rotterdamse Waterweg","en","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:56497ce4-a6c1-4b7a-bbe3-f93315d61c52","http://resolver.tudelft.nl/uuid:56497ce4-a6c1-4b7a-bbe3-f93315d61c52","On Internal Waves in a Density-Stratified Estuary","Kranenburg, C.","","1991","In this article some field observations, made in recent years, of internal wave motions in a density-stratified estuary are presented, In order to facilitate the appreciation of the results, and to make some quantitative comparisons, the relevant theory is also summarized. Furthermore, the origins of stratification in estuaries is briefly discussed.","density-stratified; estuary; internal waves; stratification; field observations","en","report","TU Delft, Department of Hydraulic Engineering","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:d1b96073-8736-4279-bbc2-53fabbc288bd","http://resolver.tudelft.nl/uuid:d1b96073-8736-4279-bbc2-53fabbc288bd","Interaction of Water Waves with a Density-Stratified Fluid in a Rectangular Trench","Ting, F.C.K.","Raichlen, F. (contributor); W.M. Keck Laboratory of Hydraulics and Water Resources","1989","The interaction of normally incident time-periodic water waves with a density-stratified fluid in a rectangular trench is studied experimentally and theoretically; the fluid outside the trench is homogeneous. This investigation has focused on the excitation of internal waves in the trench by surface waves, and the effects of the internal oscillations on the waves on the free surface. The study shows that, when the frequency of the incoming surface waves corresponds to the natural frequency of oscillation of the internal waves in the trench, the amplitude of the internal waves becomes large compared to the amplitude of the surface waves. The effects of the internal waves on the surface waves were very small in the experiments. A two-layer model and a three-layer model are developed and applied to a particular constant-depth channel and trench configuration used in the experiments. The two-layer model is also applied to a rectangular trench in an infinite region. These models treat steady-state wave motions of infinitesimal amplitude for all ranges of fluid depth relative to the wavelength of the surface waves, and include a vigorous treatment of the effects of energy dissipation in the laminar boundary layers adjacent to the solid surfaces and at the density interface. In the two-layer model the stratified fluid in the trench is represented by two homogeneous fluids of different densities; in the three-layer model these two fluids are separated in between by a transition region of linear density variation. Fresh water and salt water were used to model density stratification in the experiments. The effects of surface wave amplitude and density distribution on the internal motion in the trench were investigated for small density differences compared to the density of water. A new technique using a scanning laser beam and detector system was developed to measure internal wave amplitudes. Satisfactory agreement with the theoretical predictions was obtained. The effects of nonlinearity and viscous dissipation on the internal motions were more pronounced when the depth of the heavier fluid was small compared to the wavelength of the internal waves in the trench. For a trench in an infinite region, the two-layer model also predicts that large surface wave reflections occur when the trench is ""at internal resonance,"" and a significant portion of the incident wave energy can be dissipated within the trench. The investigation has provided insight with regard to both the dynamics of wave-trench interaction and the design of navigation channels in density-stratified fluids for reducing the potential of wave-induced internal resonance.","wave interaction; density-stratified fluid; wave amplitudes; internal resonance; density stratification","en","report","California Institute of Technology","","","","","","","","","","","","",""
"uuid:3e53bc4e-4ccf-4497-a2d5-c829a8f4e103","http://resolver.tudelft.nl/uuid:3e53bc4e-4ccf-4497-a2d5-c829a8f4e103","Internal lee waves in a turbulent two-layer flow","Pietrzak, J.; Kranenburg, C.; Abraham, G.","","1988","","turbulentie; turbulence; gelaagdheid; stratification; dichtheidsstroming; density induced flow","en","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:bb37f312-de0b-42b1-aae2-d36500d404df","http://resolver.tudelft.nl/uuid:bb37f312-de0b-42b1-aae2-d36500d404df","Zout-zoetproblematiek kompartimentering Oosterschelde: Interimrapport produktiefase","","Deltares","1985","","gelaagdheid; Oosterschelde; salinity; stratification; zoutgehalte","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:1cc9886b-23c8-43e3-bc3c-728375ba9966","http://resolver.tudelft.nl/uuid:1cc9886b-23c8-43e3-bc3c-728375ba9966","A k-Model for Stably Stratified Nearly Horizontal Turbulent Flows","Kranenburg, C.","","1985","A k-model is formulated that consists of the turbulent kinetic energy equation and an algebraic expression for the mixing length taking into account the influence of stratification. Applicability of the model is restricted to shallow, nearly horizontal flows. For local-equilibrium flows the model reduces to the well-known mixing-length hypothesis including a damping function depending on the gradient Richardson number. The model is applied to stratified turbulent Poiseuille flow between two parallel plates.","k-model; turbulence; turbulent kinetic energy equation; mixing length; stratification; horizontal flows; Poiseuille flow","en","report","TU Delft, Department of Hydraulic Engineering","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:5e8c78b0-ab9f-4546-8acd-acaf6253ccf8","http://resolver.tudelft.nl/uuid:5e8c78b0-ab9f-4546-8acd-acaf6253ccf8","Verificatie van numeriek 2D (vertikaal)-model DISTRO aan getijgootmetingen: Verslag wiskundig onderzoek","Karelse, M.","Deltares","1981","","calibration; dispersie; dispersion; gelaagdheid; ijking; numerical modelling; numerieke modellen; stratification; turbulence models; turbulentiemodellen","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:75d4c1c5-1de6-440f-8725-e521644ff465","http://resolver.tudelft.nl/uuid:75d4c1c5-1de6-440f-8725-e521644ff465","Principe-onderzoek stratificatie in diepe putten","Winterwerp, J.C.","","1979","","gelaagdheid; stratification; thermische gelaagdheid; thermal stratification","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:bd24b7d6-cbef-4c19-8571-82043ef662f5","http://resolver.tudelft.nl/uuid:bd24b7d6-cbef-4c19-8571-82043ef662f5","Zoutindringing achter schutsluizen: Getijgootonderzoek en wiskundig modelonderzoek (expliciet model)","Roelfzema, A.","Deltares","1979","","gelaagdheid; locks; modelling; modelonderzoek; numerical modelling; numerieke modellen; salt water intrusion; schutsluizen; stratification; zoutwaterindringing","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:020a6dae-c9b0-4094-8235-99ae059949d2","http://resolver.tudelft.nl/uuid:020a6dae-c9b0-4094-8235-99ae059949d2","Lake destratification induced by local air injection","Kranenburg, C.","","1979","Mathematical and physical modelling makes possible quantitative predictions regarding the destratification process brought about by the local injection of air at the bottom of a thermally stratified lake or reservoir. The mathematical model developed distinguishes between a near field and a far field. Mixing of epilimnion water and hypolimnion water takes place in the near field. The mixing water is accumulated in the far field as an interlayer between epilimnion and hypolimnion. The influence of wind on the destratification process is not considered. To account for the relatively large azimuthal velocities observed under prototype conditions the influence of the Coriolis force is examined in detail. Interfacial and bottom friction is incorporated in the theory through an Ekman model. The theory compares well with laboratory experiments and reasonably well with prototype destratification experiments, although further measurements ~n nature are desirable. The Coriolis force is found to considerably decrease the rate of destratification, but this effect is partly suppressed by friction.","stratification; temperture effect; air bubbles","en","report","Delft University of Technology","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:672b0fcb-8784-430c-904a-5fc53e8866af","http://resolver.tudelft.nl/uuid:672b0fcb-8784-430c-904a-5fc53e8866af","On the destratification of lakes and reservoirs using bubble columns","Kranenburg, C.","","1978","The aim of this research project was (i) to obtain an understanding of the destratification process caused by the local injection of air at the bottom of a thermally stratified lake or reservoir, and (ii) to make possible quantitative predictions of the rate of destratification in a given situation. To this end a mathematical model was set up, and experiments in a laboratory model and in nature were made. The situation considered in the theory was relatively simple: the initial stratification was schematized as a two-layer system at rest in a constant-depth reservoir; wind and insolation during air injection were disregarded. The mathematical model distinguishes between a near field and a far field. The near field theory is taken from research carried out elsewhere. The far field is modelled as a three-layer system, since the water mixed in the near field forms an interlayer between the original epilimnion and hypolimnion. Turbulent exchange of mass and heat between the layers is disregarded, although this is not correct in some cases (appendices III and IV). The Coriolis force and the inertial terms are included in the layer model. Coupling conditions between near field and far field can be derived by considering the transition between the two zones as an ""internal weir"".","stratification; stratified flow; air bubbles","en","report","Delft University of Technology","","","","","","","","Civil Engineering and Geosciences","Hydraulic Engineering","","","",""
"uuid:41949c21-678d-46a1-bfed-3a805ecc5d0c","http://resolver.tudelft.nl/uuid:41949c21-678d-46a1-bfed-3a805ecc5d0c","Wind effect on the distribution of velocity and temperature in stratified enclosed systems","Delvigne, G.A.L.","","1978","","thermische gelaagdheid; thermal stratification; stroming in gesloten leidingen; closed conduit flow","en","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:1467ea2c-a544-4831-bfec-3ac7be0c11ae","http://resolver.tudelft.nl/uuid:1467ea2c-a544-4831-bfec-3ac7be0c11ae","On the magnitude of interfacial shear of subcritical stratified flows: Report on analysis of literature data","Abraham, G.; Karelse, M.; Os, A.G. van","","1977","","dichtheidsstroming; density induced flow; gelaagdheid; stratification; interne golven; internal waves","en","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:b7c5980b-9888-4552-b854-10f979dd9947","http://resolver.tudelft.nl/uuid:b7c5980b-9888-4552-b854-10f979dd9947","Oceanografische omstandigheden in het zeegebied nabij Texel","Visser, M.P.","Rijkswaterstaat","1977","Complex oceanographic circumstances are often found near the island of Texel. Generally, large variations occur in the water density (salinity, temperature), both in horizontal and in vertical direction, and in the course of time. Current velocity and direction are often depth dependent. Interaction between one aspect and the other is not yet clear. The so-called Texel section (fig. 4) has been sampled for over fourty times during the period 1964-1969. Situations with no density gradients at all, or with gradients only in horizontal or vertical direction, are shown in fig. 6. The mean situation is shown schematically in fig. 8. It has been found that vertical stratification is dependent on tidal phase to a minor degree only (fig. 9). However, a strong connection was found between existence or absence of vertical density stratification in the water, and occurrence of strong winds (table V). The latter can almost prevent such a stratification near Texel for a period of 25 -.42 days afterwards. These figures agree well with the average time freshwater takes between its leaving the Rhine estuary and its arrival near Texel.","tidal currents; waddenzee; stratification","nl","report","KNMI","","","","","","","","","","","","",""
"uuid:57f3b4fb-ef09-455f-b451-7987335758b8","http://resolver.tudelft.nl/uuid:57f3b4fb-ef09-455f-b451-7987335758b8","Programma voor getijgootonderzoek","Karelse, M.","Deltares","1976","","density induced flow; dichtheidsstroming; gelaagdheid; menging; mixing; numerical modelling; numerieke modellen; stratification","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:6070e0e8-19f5-4aa1-83b3-b7760cd87e20","http://resolver.tudelft.nl/uuid:6070e0e8-19f5-4aa1-83b3-b7760cd87e20","Berekening van thermische stratificatie bij variabele weersomstandigheden Oostvoornsemeer 1972, 1974","Verhagen, J.H.G.","Deltares","1976","","diffusie; diffusion; ecological research; ecologisch onderzoek; thermal stratification; thermische gelaagdheid; Zuid-Holland","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:2eb76bac-d48c-4f1b-a47c-7db476bab2ec","http://resolver.tudelft.nl/uuid:2eb76bac-d48c-4f1b-a47c-7db476bab2ec","Diep water langs de noordkust van Zuid-Amerika","Van Bennekom, A.J.; Tijssen, S.B.; Van der Veen, K.; Visser, M.P.","Rijkswaterstaat","1976","Results of CICAR-investigations off the northern Southamerican coast during autumn 1970 and spring 1971 are given, concerning the water below the 10oC-isotherm. Topographies of the sigma rt =27.3 and 27-4 surfaces indicate a motion of the Subantarctic Intermediate Water mass along the continental rise. This motion being far from regular gives an indication of meandering along the boundary of an ocean current. The Upper and Middle Northatlantic Deepwater are clearly distinguishable by their characteristics, i.e. salinity and oxygen maxima. It is possible for some of the deepest reaching stations to make a distinction in the bottom water between water of Arctic and of Antarctic origin. Extrapolation yields an antarctic bottom water contribution of about 40%, being in good agreement with literature.","Amazone; oceanographic observations; ocean current; stratification","nl","report","KNMI","","","","","","","","","","","","",""
"uuid:e7e9d9e5-81f6-4c1f-ae7e-41d1f8abccbe","http://resolver.tudelft.nl/uuid:e7e9d9e5-81f6-4c1f-ae7e-41d1f8abccbe","Invloed van de Amazone rivierafvoer op de westelijk tropische Atlantische Oceaan","Van der Veen, K.; Van Bennekom, A.J.; Tijssen, S.B.","Rijkswaterstaat","1976","Observations were made of temperature, salinity, currents and meteorology in the ocean off the northern coast of South America, during autumn 1970 and spring 1971. The observed salinity distributions in the surface layer reflect the seasonal variation in the trade winds. Besides, very strong vertical current shear waS found over the layer between surface and halocline. A rough estimate for the horizontal lateral exchange-coefficient is 1. 4 to 2 X_ 105 m2 s-1 being of the same order of magnitude as the values reported for the Gulf Stream. Large scale movements of the water have been traced by drift bottle experiments; recoveries were reported from the northern coast of South America, from Central America and from North America. An estimate is made of the fresh water flux of the Amazon that passes along the coast. There are no indications to conclude to an intermittent fresh water flow.","Amazone; river discharge; stratification; ocean currents","nl","report","KNMI","","","","","","","","","","","","",""
"uuid:f7878a7c-b77f-404a-b419-75bca8369890","http://resolver.tudelft.nl/uuid:f7878a7c-b77f-404a-b419-75bca8369890","Momentum and mass transfer in stratified flows","Karelse, M.; Vreugdenhil, C.B.; Delvigne, G.A.L.; Breusers, H.N.C.","","1974","","dichtheidsstroming; density induced flow; gelaagdheid; stratification","en","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:83789064-f68e-4277-8381-9cedc8f2f14d","http://resolver.tudelft.nl/uuid:83789064-f68e-4277-8381-9cedc8f2f14d","Verticale diffusie coëfficiënten, berekend volgens de methode Lerman - Stiller: Brielse Gat 1972","Verboom, G.K.","Deltares","1974","","diffusie; diffusion; ecological research; ecologisch onderzoek; thermal stratification; thermische gelaagdheid; Zeeland","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:3efb9b47-4827-46ae-90da-6ddd0cbba1ce","http://resolver.tudelft.nl/uuid:3efb9b47-4827-46ae-90da-6ddd0cbba1ce","Een berekeningsmethode van thermische gelaagdheid bij variabele wind en instraling","Verhagen, J.H.G.","","1974","","thermische gelaagdheid; thermal stratification; opwaaiing; wind set up","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:642bbb62-4794-43ae-b507-5a25bec3e7f6","http://resolver.tudelft.nl/uuid:642bbb62-4794-43ae-b507-5a25bec3e7f6","Reproductie zouttoestand getijrivieren (XXVI): Zoutvangonderzoek in de getijgoot","Karelse, M.","Deltares","1974","","density induced flow; dichtheidsstroming; gelaagdheid; getijmodellen; luchtbelschermen; pneumatic barriers; salt water intrusion; stratification; tidal models; zoutwaterindringing","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:7a24c7dc-8b81-4506-9d33-02de2dcd6e27","http://resolver.tudelft.nl/uuid:7a24c7dc-8b81-4506-9d33-02de2dcd6e27","Computational methods for the vertical distribution of flow in shallow water","Breusers, H.N.C.","Deltares","1973","","computational models; gelaagdheid; ondiep water; ondiepwatervergelijkingen; rekenmodellen; shallow water; shallow water equations; stratification","en","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:72de9cc3-a15c-4aa9-a8f1-07478632a458","http://resolver.tudelft.nl/uuid:72de9cc3-a15c-4aa9-a8f1-07478632a458","Reproductie zouttoestand getijrivieren (XXIV, deel 1): Aanvullend schaalonderzoek (proeven met gemengde en gelaagde omstandigheden)","Mazijk, A. van","Deltares","1973","","current velocity measurement; density induced flow; density measurement; dichtheidsmeting; dichtheidsstroming; estuaria; estuaries; gelaagdheid; getijmodellen; menging; mixing; Rotterdamse Waterweg; salt water intrusion; stratification; stroomsnelheidsmeting; tidal models; water level measurement; waterstandmeting; zoutwaterindringing","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:b6bc16a0-0ace-4894-8c06-c29bfb8b5d0a","http://resolver.tudelft.nl/uuid:b6bc16a0-0ace-4894-8c06-c29bfb8b5d0a","Reproductie zouttoestand getijrivieren (XXIV, deel 5): Aanvullend schaalonderzoek (proeven met gemengde en gelaagde omstandigheden) : resultaten proef T 203","Mazijk, A. van","Deltares","1973","","current velocity measurement; density induced flow; density measurement; dichtheidsmeting; dichtheidsstroming; estuaria; estuaries; gelaagdheid; getijmodellen; menging; mixing; Rotterdamse Waterweg; salt water intrusion; stratification; stroomsnelheidsmeting; tidal models; water level measurement; waterstandmeting; zoutwaterindringing","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:2927460d-548e-479a-aed1-4edfcbcf6833","http://resolver.tudelft.nl/uuid:2927460d-548e-479a-aed1-4edfcbcf6833","Reproductie zouttoestand getijrivieren (XXIV, deel 3): Aanvullend schaalonderzoek (proeven met gemengde en gelaagde omstandigheden): resultaten proef T 199","Mazijk, A. van","Deltares","1973","","current velocity measurement; density induced flow; density measurement; dichtheidsmeting; dichtheidsstroming; estuaria; estuaries; gelaagdheid; getijmodellen; menging; mixing; Rotterdamse Waterweg; salt water intrusion; stratification; stroomsnelheidsmeting; tidal models; water level measurement; waterstandmeting; zoutwaterindringing","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:c9e9e369-25a8-4a3a-8ff5-3fed101a2e5f","http://resolver.tudelft.nl/uuid:c9e9e369-25a8-4a3a-8ff5-3fed101a2e5f","Reproductie zouttoestand getijrivieren (XXIV, deel 6): Aanvullend schaalonderzoek (proeven met gemengde en gelaagde omstandigheden): resultaten proef T 204","Mazijk, A. van","Deltares","1973","","current velocity measurement; density induced flow; density measurement; dichtheidsmeting; dichtheidsstroming; estuaria; estuaries; gelaagdheid; getijmodellen; menging; mixing; Rotterdamse Waterweg; salt water intrusion; stratification; stroomsnelheidsmeting; tidal models; water level measurement; waterstandmeting; zoutwaterindringing","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:201b6394-7875-4570-b1b5-a35c2161c4aa","http://resolver.tudelft.nl/uuid:201b6394-7875-4570-b1b5-a35c2161c4aa","Reproductie zouttoestand getijrivieren (XXIV, deel 4): Aanvullend schaalonderzoek (proeven met gemengde en gelaagde omstandigheden): resultaten proef T 202","Mazijk, A. van","Deltares","1973","","current velocity measurement; density induced flow; density measurement; dichtheidsmeting; dichtheidsstroming; estuaria; estuaries; gelaagdheid; getijmodellen; menging; mixing; Rotterdamse Waterweg; salt water intrusion; stratification; stroomsnelheidsmeting; tidal models; water level measurement; waterstandmeting; zoutwaterindringing","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:1a93b45f-1b5a-4d98-b835-638d9c73357a","http://resolver.tudelft.nl/uuid:1a93b45f-1b5a-4d98-b835-638d9c73357a","Reproductie zouttoestand getijrivieren (XXIV, deel 2): Aanvullend schaalonderzoek (proeven met gemengde en gelaagde omstandigheden) : resultaten proef T 197","Mazijk, A. van","Deltares","1973","","current velocity measurement; density induced flow; density measurement; dichtheidsmeting; dichtheidsstroming; estuaria; estuaries; gelaagdheid; getijmodellen; menging; mixing; Rotterdamse Waterweg; salt water intrusion; stratification; stroomsnelheidsmeting; tidal models; water level measurement; waterstandmeting; zoutwaterindringing","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:d25d9128-7cdf-41b7-b0f5-62308345f7c7","http://resolver.tudelft.nl/uuid:d25d9128-7cdf-41b7-b0f5-62308345f7c7","Reproductie zouttoestand getijrivieren (XXIV, deel 7): Aanvullend schaalonderzoek (proeven met gemengde en gelaagde omstandigheden): resultaten proef T 205","Mazijk, A. van","Deltares","1973","","current velocity measurement; density induced flow; density measurement; dichtheidsmeting; dichtheidsstroming; estuaria; estuaries; gelaagdheid; getijmodellen; menging; mixing; Rotterdamse Waterweg; salt water intrusion; stratification; stroomsnelheidsmeting; tidal models; water level measurement; waterstandmeting; zoutwaterindringing","nl","report","Deltares (WL)","","","","","","","","","","","","",""
"uuid:ea14a108-82b9-4849-b601-e135dde8b321","http://resolver.tudelft.nl/uuid:ea14a108-82b9-4849-b601-e135dde8b321","Diffusive Properties of Interfacial Layers","Sjöberg, A.","TU Delft","1967","The vertical stability of submerged sewage fields is a matter of great importance in Sweden where the coastal waters are strongly stratified. The diffusive properties of interfacial layers are therefore discussed and the experimental results of different authors are compared.","density stratification; diffusion; vertical stability; sewage fields; interfacial layers","en","report","Chalmers University of Technology","","","","","","","","","","","","",""