Tesi: "Hydrodynamic modelling"

7

Haq, Rafiq Ul. "The hydrodynamic modelling of an evolving sea." Thesis, London Metropolitan University, 1985. http://repository.londonmet.ac.uk/3318/.

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A model of a changing tidal regime in an evolving shallow sea such as the ancient North Sea is developed and solved analytically as a generalization of Taylor's problem. Characteristic scales and coefficients are treated as functions of historical time. The z dependency, dissipative and non-linear terms are effectively separated from the governing equations by the use of a Latta expansion. A composite solution is found which takes account of each of these features. A Green's function technique is used to calculate the effects of friction. A sloping bed topography is simulated by a horizontally varying eddy viscosity.

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8

van, 't Hoff J. "Hydrodynamic modelling of the Oscillating Wave Surge Converter." Thesis, Queen's University Belfast, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.517034.

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9

Engström, Jens. "Hydrodynamic Modelling for a Point Absorbing Wave Energy Converter." Doctoral thesis, Uppsala universitet, Elektricitetslära, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-160319.

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Surface gravity waves in the world’s oceans contain a renewable source of free power on the order of terawatts that has to this date not been commercially utilized. The division of Electricity at Uppsala University is developing a technology to harvest this energy. The technology is a point absorber type wave energy converter based on a direct-driven linear generator placed on the sea bed connected via a line to a buoy on the surface. The work in this thesis is focused mainly on the energy transport of ocean waves and on increasing the transfer of energy from the waves to the generator and load. Potential linear wave theory is used to describe the ocean waves and to derive the hydrodynamic forces that are exerted on the buoy. Expressions for the energy transport in polychromatic waves travelling over waters of finite depth are derived and extracted from measured time series of wave elevation collected at the Lysekil test site. The results are compared to existing solutions that uses the simpler deep water approximation. A Two-Body system wave energy converter model tuned to resonance in Swedish west coast sea states is developed based on the Lysekil project concept. The first indicative results are derived by using a linear resistive load. The concept is further extended by a coupled hydrodynamic and electromagnetic model with two more realistic non-linear load conditions. Results show that the use of the deep water approximation gives a too low energy transport in the time averaged as well as in the total instantaneous energy transport. Around the resonance frequency, a Two-Body System gives a power capture ratio of up to 80 percent. For more energetic sea states the power capture ratio decreases rapidly, indicating a smoother power output. The currents in the generator when using the Two-Body system is shown to be more evenly distributed compared to the conventional system, indicating a better utilization of the electrical equipment. Although the resonant nature of the system makes it sensitive to the shape of the wave spectrum, results indicate a threefold increase in annual power production compared to the conventional system.

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10

Crooks, David Joel. "Nonlinear hydrodynamic modelling of an oscillating wave surge converter." Thesis, Queen's University Belfast, 2017. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.725744.

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This study develops further the conceptual model of Oscillating Wave Surge Converter (OWSC) hydrodynamics and improves the representation of hydrodynamic torques in the device's nonlinear time domain numerical model. Wave excitation torque tests were used to evaluate how the wave excitation torque experienced by a static OWSC varies with wave period and amplitude for a range of OWSC pitch angles. Forced oscillation tests were used to evaluate how the radiation torque experienced by an OWSC, due to its motion through still water, varies with oscillation period, oscillation amplitude and angular velocity. A third set of experiments, in which the restoring moment of buoyancy was augmented with mechanical springs, referred to as buoyancy simulation tests, demonstrated how modifications to the static torque of the system influences OWSC motion, The experiments validated and identified the limits of linear hydrodynamic coefficients obtained using Boundary Element Method (BEM) codes. Numerical methods were evaluated on their ability to improve the representation of the measured torques not estimated by the BEM codes. The wave excitation and buoyancy simulation tests were performed in 4.5m and 16m wide wave tanks at Queen's University Belfast (QUB). This presented the unique opportunity to observe how wave tank characteristics can influence experimental measurements. The buoyancy simulation tests also calibrated and validated an enhanced nonlinear time domain numerical model. The enhanced nonlinear time domain numerical model contained the numerical methods that were found to improve the estimates of the wave excitation and radiation torques measured during the wave excitation torque and buoyancy simulation tests. The enhanced nonlinear time domain numerical model contained a pitch angle dependent wave excitation torque, a nonlinear state-space approach to modelling radiation torque, an empirically developed drag torque term and an analytically derived nonlinear hydrostatic torque.

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11

Sarjamee, Samieh. "Numerical Modelling of Extreme Hydrodynamic Loading on Coastal Structures." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/35124.

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Natural disasters usually occur without any warning. They can leave trail of destruction and cause much tragedy. We are at a time when we witness fast technological advances; hence, we need to apply the force of scientific advancements to decrease economic losses and the number of human deaths. Tsunami is one of the extreme environmental events that leaves nothing but a path of death and destruction, and as a result, it is essential to understand this phenomenon and identify the mitigation strategies. Several mitigation strategies have been proposed so far; however, more investigations are still required to achieve an acceptable solution. Researchers around the world are studying different aspects of this phenomenon. One of the proposed solutions that has received much attention is designing tsunami-resistant structures which can withstand the force of a tsunami bore. Various studies have been done so far to understand the base shear force of tsunami bore on structures. The focus of this thesis is to improve and better understand the characteristics of the tsunami base shear forces on structures. Hence, in this thesis, two numerical studies were proposed and performed with the main goal of estimating the total tsunami forces on structure under two different conditions. Those include structures with various cross sections, as well as positioning a mitigation wall at an appropriate location relative to the structure. The first study focused on developing a numerical model to study the relationship between tsunami forces and the geometry of the structure. The main goal of this study was to define a numerical model capable of simulating this case precisely. To ensure the accuracy of the model, a comparison was carried out between the results of the numerical model and experimental test performed at the NRC-CHC (National Research Council- Canadian Hydraulics Center) laboratory in Ottawa, Canada and Université Catholique de Louvain (UCL), Belgium, which revealed a very good agreement between the results of the experimental test and numerical model. Further, the validated model was applied to investigate the tsunami force on structures with various cross sections. The second study focus was on developing a numerical model for understanding the role of mitigation wall (a novel idea proposed as a mitigation strategy by the second author of technical paper 2) on reducing the exerted force of tsunami on structures. After developing various models and applying several turbulence models, a valuable result was obtained which demonstrated that a Large Eddy Simulation (LES) model seems to be an excellent approach for predicting the tsunami forces on the structure with a mitigation wall in the direction of the flow. The results of this study will be used to better estimate the tsunami forces exerted on coastal structures which will light the path to the main goal of designing tsunami resistant-structures.

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12

Westwater, David. "Modelling hydrodynamic and shallow water processes over vegetated floodplains." Thesis, Cardiff University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391534.

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13

Whittaker, Peter. "Modelling the hydrodynamic drag force of flexible riparian woodland." Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/62503/.

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In this thesis, two practical models for predicting the drag force exerted on flexible riparian vegetation under hydrodynamic loading have been developed. The models were formulated based on the results of a unique experimental data set that consisted of high resolution force-velocity and physical property measurements for twenty-one full-scale riparian trees, in both foliated and defoliated conditions. One of the models has then been used to numerically simulate the impact of riparian woodland on the flooding characteristics of a mid-catchment river site. Analysis of photographs and video footage of the trees from the experimental study during drag force testing allowed the frontal projected area to be determined, both in still air and as a function of flow velocity. The observed reductions in projected area and drag coe�cient with velocity were normalized using the projected area in still air to provide an empirical relationship between the ‘rigid’ drag coe�cient and area Reynolds number. The resulting drag force predictions were found to be accurate when properly calibrated against the vegetation under consideration. A second, more physically based model to predict the reconfiguration of flexible vegetation has been developed based on dimensional analysis of the relevant parameters, including flexural rigidity. The model utilizes a novel vegetative Cauchy number to determine the extent of the reconfiguration and has been shown to be more accurate than two existing drag force models. The model has also been validated against independent drag force data, demonstrating that it is applicable to vegetation of di�ering scale, morphology and flexibility. Serial and parallel optimizations of an existing two-dimensional hydrodynamic modelling code have enabled detailed numerical simulations of extreme flood events to be undertaken for a mid-catchment river site in Somerset, UK. The results indicated that riparian vegetation has a minimal impact on the downstream flooding characteristics, at least for the small site investigated herein. Significant reductions in key flow properties, namely velocity and bed shear stress, were however observed within the vegetated areas.

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14

Harris, John M. "Modelling random wave boundary layers." Thesis, University of Liverpool, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366399.

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15

Setegn, Shimelis Gebriye. "Modelling Hydrological and Hydrodynamic Processes in Lake Tana Basin, Ethiopia." Doctoral thesis, KTH, Vattendragsteknik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-12024.

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Lake Tana Basin is of significant importance to Ethiopia concerning water resources aspects and the ecological balance of the area. The growing high demands in utilizing the high potentials of water resource of the Lake to its maximal limit, pictures a disturbing future for the Lake. The objective of this study was to assess the influence of topography, soil, land use and climatic varia-bility on the hydrological and hydrodynamic processes of the Lake Tana Basin. The physically based SWAT model was successfully calibrated and validated for flow and sediment yield. Se-quential uncertainty fitting (SUFI-2), parameter solution (ParaSol) and generalized likelihood un-certainty estimation (GLUE) calibration and uncertainty analysis methods were compared and used for the set-up of the SWAT model. There is a good agreement between the measured and simulated flows and sediment yields. SWAT and GIS based decision support system that uses multi-criteria evaluation (MCE) was used to identify the most vulnerable areas to soil erosion in the basin. The results indicated that 12 to 30.5% of the watershed is high erosion potential. Pro-jected changes in precipitation and temperature in the basin for two seasons were analyzed using outputs from fifteen global climate models (GCMs). A historical-modification procedure was used to downscale large scale outputs from GCM models to watershed-scale climate data. The results showed significant changes in streamflow and other hydrological parameters in the period between 2045-2100. SWAT was combined with a three dimensional hydrodynamic model, GEMSS to investigate the flow structure, stratification, the flushing time, lake water balance and finally the Lake‘s water level response to planned water removal. We have found an alarming and dramatic fall of the water levels in Lake Tana as response to the planned water withdrawal. The combination of the two models can be used as a decision support tools to better understand and manage land and water resources in watersheds and waterbodies. The study showed that the Lake Tana Basin may experience a negative change in water balance in the forthcoming decades due to climate change as well as over abstraction of water resources. QC 20100720

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16

Henshaw, M. J. deC. "Computer modelling of hydrodynamic instability in spherical laser accelerated targets." Thesis, University of Hull, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280834.

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17

Melville, Guy T. "Hydrodynamic and economic modelling of tidal current energy conversion systems." Thesis, Robert Gordon University, 2008. http://hdl.handle.net/10059/695.

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This thesis examines the contribution of computational modelling to the development of the tidal current energy industry, against the background of increasing commercial, government, academic and public interest. It does this through the practical application of a number of computational techniques in the areas of: 1. Tidal current analysis and prediction 2. Hydrodynamic flow modelling 3. Tidal resource analysis 4. Optimised economic modelling Appropriate survey set-up is essential in gathering data. Given this, processing the data using velocity profiles; statistical techniques; and harmonic analysis can produce valuable data for site development, device design and grid management. This work developed the application of a directional and time-dependent power coefficient and demonstrates its importance in resource evaluation from tidal flow data. It further concludes that hydrodynamic flow modelling of sites prior to development is important in determining suitable sites, given the scarcity of tidal information in the areas suitable for tidal developments. The same scarcity of data, in terms of boundary conditions, interior validation points and depth does limit the accuracy of such models. The work demonstrates that using differing resource analyses can obtain dramatically different results; and develops a correlation relating energy extraction to developed energy extraction using a one dimensional channel model. In doing so it concludes that energy resource estimates may be reduced from contemporary estimates. Overall, computational modelling of tidal current energy conversion systems can have a significant contribution to their design and site development. The most significant capital costs arise from installation, decommissioning and the turbine itself, however significant reduction in the cost of energy production can result from correct placement, array size and component selection This work contributes to knowledge in a number of areas, namely: 1. It is the first published work on survey data analysis prior to deployment of a large-scale prototype tidal current energy conversion system; 2. At the time that the work was carried out, it was the first published work considering the use of the least-squared harmonic method for prediction of energy output from a tidal current energy device; 3. It is the first work to propose a directional power coefficient in the process of resource analysis for a tidal current energy conversion system; 4. The work on economic modelling was the first to produce an optimised economic model for tidal current energy conversion systems (TCECS); 5. It is the first work to use an optimised economic model for TCECSs to demonstrate the effect of device placement on the cost of energy produced; 6. It is the first work to use an optimised economic model for TCECSs to demonstrate that the cost of energy for TCECSs is minimised by maximising the rated power, given no topographical impedence; 7. It proposes a method to determine the energy resource available including energy extraction.

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18

Kulkarni, A. "Three dimensional hydrodynamic modelling of combined free/porous flow regimes." Thesis, Loughborough University, 2008. https://dspace.lboro.ac.uk/2134/13001.

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In the present scenario, as advances in research, technology and engineering application have been on a rise , thus persuading researchers and engineers to employ new computer modelling techniques for the design and analysis, mainly due to time, environmental and economic constraints. Moreover it also forms a basis for any observed anomalies, when comparing with the simulated and experimental results and taking steps to develop optimum design strategies. The present research work deals with the development of novel ftlter designs when employed in aeronautical hydraulic systems. These pleated cartridge ftlters would be fabricated using eco-friendly fIltering media supported by unconventional disposable or reusable solid components. The primary focus of the present research work to develop a robust cost-effective simulating tools for simulating the results in the hydrodynamic behaviour of the fluid in pleated cartridge ftlters. As observed in any ftltration process, it comprises of two flow regimes namely free flow and porous flow regimes. For over five decades, it had been a subject of intense research and investigation for researchers, scientist and engineers to resolve some of the critical and vital issues related to filtration process. The main problems, when compared to others, that are associated with such processes are the free/porous interfacial constraints along with boundary conditions and their mathematical representation with respect to the industrial applications. A three dimensional model has been developed to represent the momentum and mass conservation for creeping incompressible flow in coupled free/porous flow regimes. In order to take into consideration the rheological behaviour of the fluid, power law model has been included, which forms the constitutive equation, and the viscosity of the fluid has been updated for the highly viscous specially formulated hydraulic fluid. For any numerical technique of analysis, on vital aspect is the boundary conditions that are imposed on the surface/volume/edge of the domain under consideration. The free (Stokes) and porous flow (Darey) regimes have been linked and solved in conjunction with continuity equations on a perturbed continuity scheme based on the standard Galerkin weighted residual finite element method. The perturb continuity UVWP finite element scheme is based On the equal order interpolation approximations and the discretized working equations are then transformed into the local coordinate system using iso-parametric mapping. The elements used are linear (8 nodded) hexahedral elements. The integrals in the elemental stiffness equations were calculated using Gauss-Legendre quadrature. After evaluation of the members of the elemental stiffness matrix, they are assembled over the common nodes in the computational grid to obtain a system of algebraic equations. After substituting the boundary conditions, the system becomes determinate and the algebraic equations can be solved using a frontal solution method. The described simulations are carried out using an in-house developed lnte! Visual FORTRAN code. The time stepping technique used here is second order Taylor-Galerkin method. The concept of compression permeability model developed by Nassehi et aL Nassehi et aL, 2005J ( developed for two dimensional case and now extended to three dimensional case) has been used to into the flow model to take into account the effects arising due to the mtration area loss in pleated cartridge filters and degree or extent of compression of the fUter medium. Significant over-use of media material or the need for changes to the geometric or mechanical design can be identified using the procedures described.

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19

Allsop, Steven Christopher. "Hydrodynamic modelling for structural analysis of tidal stream turbine blades." Thesis, University of Exeter, 2018. http://hdl.handle.net/10871/33219.

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The predictable nature of the tides offers a regular, reliable source of renewable energy that can be harnessed using tidal stream turbines (TSTs). The UK's practically extractable tidal stream energy resource has the potential to supply around 7 % of the country's annual electricity demand. As of 2016, the world's first commercial scale arrays have been deployed around the UK and France. The harsh nature of the marine operating environment poses a number of engineering challenges, where the optimal turbine design solution remains under investigation. In this thesis, a numerical model is developed to assess the power production and hydrodynamic behaviour of horizontal axis tidal turbines. The developed model builds upon well established and computationally efficient Blade Element Momentum Theory (BEMT) method for modern three-bladed wind turbines. The main novel contribution of this thesis is extending the application to an alternative design of a ducted, high solidity and open centre TST. A validation study using measurements from multiple different scale model experimental tank tests has proven the applicability of the model and suitability of the imposed correction factors. The analytical modifications to account for ducted flow were subsequently indirectly verified, where predictions of turbine power and axial thrust forces under optimal operating speeds were within 2 % of those using more advanced computational fluid dynamics (CFD) methods. This thesis presents a commercial application case of two turbines designed by OpenHydro, examining the BEMT performance with a sophisticated blade resolved CFD study. A comparison of results finds that the model is capable of predicting the average peak power to within 12 %, however it under predicts thrust levels by an average of 35 %. This study concludes that the model is applicable to ducted turbine configurations, but is limited in capturing the complex flow interactions towards the open centre, which requires further investigation. The computational efficiency of the newly developed model allowed a structural analysis of the composite blades, thus demonstrating it is suitable to effectively evaluate engineering applications. Stresses are seen to be dominated by flap-wise bending moments, which peak at the mid-length of the blade. This tool will further enable EDF to perform third party assessments of the different turbine designs, to aid decision making for future projects.

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20

Larsen, Genevieve Ruth. "Modelling hydrodynamic processes within Pumicestone Passage, Northern Moreton Bay, Queensland." Thesis, Queensland University of Technology, 2007. https://eprints.qut.edu.au/16634/1/Genevieve_Larsen_Thesis.pdf.

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Estuaries can be considered as vital natural resources and are unique ecosystems at the interface between terrestrial and marine environments. The increase of population density centred on these coastal features and associated anthropogenic activities such as trade, industry, agriculture and recreation can adversely affect these sensitive environments. The Pumicestone Passage, located in northern Moreton Bay, Australia, is one such estuarine environment where there are concerns about degradation of water quality resulting from rapid land use change. These changes are both immediate to the Passage and within its wider catchment. Of notable concern are the outbreaks of Lyngbya (a toxic blue-green algae) in the Passage itself and near its interface with Deception Bay to the south. Other factors of concern are increased suspended and dissolved loads, and maintenance of ecosystem integrity. In this study, numerical modelling, graphical methods and water surface elevation and current velocity parameter calculations are used to describe hydrological processes in the Pumicestone Passage. A hydrodynamic model is developed using the modelling software SMS and RMA2 as a foundation for future hydrodynamic and water quality modelling. In addition, observed data are used to interpret general hydrodynamic behaviour in the passage, and determine various parameters for use in model development and calibration. Tidal prediction is also discussed and used for model calibration. To support the modelling and for preliminary interpretation of hydrodynamic processes within the Passage, measurements were made in the field of (a) water surface elevation variation at 17 sites; (b) tidal current velocities in four of the tributary creeks and at the northern boundary; (c) volumetric flow rates at two cross-sections within the Passage; and (d) cross-sectional bathymetry at sites where tidal current velocities were measured in the creeks. In general, examination of the observational data reveals a number of important processes in the Pumicestone Passage. Almost all sites within Pumicestone Passage and its tributaries are flood dominant indicating that tidal storage and bottom friction effects are significant. Mesotidal ranges occur at sites close to the southern boundary of the passage, however, bottom friction greatly reduces the tidal response at the remaining sites which results in microtidal ranges. The influence of both the southern and northern tides can be seen in the deformation of tidal waveforms in the central passage. Extensive intertidal areas at and inside the northern inlet to the Passage markedly reduce tidal ranges in the northern estuary and its tributary creeks. Issues involved in hydrodynamic model development and performance are discussed. Overall, model results for the southern estuary have satisfactory correlation with observed data whereas model results for the northern estuary are less satisfactory. In addition, water surface elevation variation model results are generally more accurate than tidal current velocity model results. Reasons for the differences between model and observed values are considered and possible solutions given. Factors discussed relate to boundary condition locations, resolution of bathymetric and geographical data, mesh development methods and parameter assignment.

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21

Larsen, Genevieve Ruth. "Modelling hydrodynamic processes within Pumicestone Passage, Northern Moreton Bay, Queensland." Queensland University of Technology, 2007. http://eprints.qut.edu.au/16634/.

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Abstract (sommario):

Estuaries can be considered as vital natural resources and are unique ecosystems at the interface between terrestrial and marine environments. The increase of population density centred on these coastal features and associated anthropogenic activities such as trade, industry, agriculture and recreation can adversely affect these sensitive environments. The Pumicestone Passage, located in northern Moreton Bay, Australia, is one such estuarine environment where there are concerns about degradation of water quality resulting from rapid land use change. These changes are both immediate to the Passage and within its wider catchment. Of notable concern are the outbreaks of Lyngbya (a toxic blue-green algae) in the Passage itself and near its interface with Deception Bay to the south. Other factors of concern are increased suspended and dissolved loads, and maintenance of ecosystem integrity. In this study, numerical modelling, graphical methods and water surface elevation and current velocity parameter calculations are used to describe hydrological processes in the Pumicestone Passage. A hydrodynamic model is developed using the modelling software SMS and RMA2 as a foundation for future hydrodynamic and water quality modelling. In addition, observed data are used to interpret general hydrodynamic behaviour in the passage, and determine various parameters for use in model development and calibration. Tidal prediction is also discussed and used for model calibration. To support the modelling and for preliminary interpretation of hydrodynamic processes within the Passage, measurements were made in the field of (a) water surface elevation variation at 17 sites; (b) tidal current velocities in four of the tributary creeks and at the northern boundary; (c) volumetric flow rates at two cross-sections within the Passage; and (d) cross-sectional bathymetry at sites where tidal current velocities were measured in the creeks. In general, examination of the observational data reveals a number of important processes in the Pumicestone Passage. Almost all sites within Pumicestone Passage and its tributaries are flood dominant indicating that tidal storage and bottom friction effects are significant. Mesotidal ranges occur at sites close to the southern boundary of the passage, however, bottom friction greatly reduces the tidal response at the remaining sites which results in microtidal ranges. The influence of both the southern and northern tides can be seen in the deformation of tidal waveforms in the central passage. Extensive intertidal areas at and inside the northern inlet to the Passage markedly reduce tidal ranges in the northern estuary and its tributary creeks. Issues involved in hydrodynamic model development and performance are discussed. Overall, model results for the southern estuary have satisfactory correlation with observed data whereas model results for the northern estuary are less satisfactory. In addition, water surface elevation variation model results are generally more accurate than tidal current velocity model results. Reasons for the differences between model and observed values are considered and possible solutions given. Factors discussed relate to boundary condition locations, resolution of bathymetric and geographical data, mesh development methods and parameter assignment.

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22

Forth, Shaun Anthony. "Morphological and hydrodynamic instabilities in undirectional alloy solidification." Thesis, University of Bristol, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292481.

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23

Suckling, H. "Modelling of hydrodynamic effects and optimization of energy benefit in tidal power schemes." Thesis, University of the West of England, Bristol, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233602.

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Energy Benefit in Tidal Power Schemes' by Helen Suckling Abstract Predictions of energy output from a barrage in the Severn Estuary can be made by using a mathematical model describing the operation of the barrage linked to one of tidal flow. Estimates of the likely energy production from such a barrage have been made using a flat surface model of the estuary which incorporates real machinery operating characteristics. The flow through the barrage can be controlled optimally in order to obtain the greatest amount of energy from the tides. The energy predictions made by using the flat surface model are examined using a hydrodynamic model of flow in the estuary. A simple one-dimensional hydrodynamic model of the tidal flow in the Severn Estuary is presented. The area of the estuary under consideration is that which lies between approximately Berkeley in Gloucestershire and 11 fracombe on the North Devon coast. The only open boundary is assumed to be the seaward boundary. No account is taken of flow into the estuary from rivers. Finite amplitude shallow water wave equations, together with a representation of bottom friction, are used to describe the tidal behaviour in the estuary. The crosssectional topography of the estuary is assumed to be a rectangle. The boundary conditions are that there is no flow through the landward boundary and the water level at the seaward boundary is a known function of time. The equations are solved numerically as a system of ordinary differential equations. A simple Runge-Kutta method is used. The mqdel is used to obtain predictions of the level and time of high and low tide at certain points along the estuary. The results are compared with those obtained by using another, but more complex, onedimensional model. In the region of computation, the accuracy of the results of the two models are comparable. The effect of varying both the coefficient of friction and the form of the friction term is examined. The effect of linearizing the governing equations is also studied. A model of a tidal power barrage, sited between Weston-super-Mare and Cardiff, is then incorporated into the hydrodynamic model. The operation 'of the barrage is determined by using an open loop control, obtained by using a flat surface model of the estuary. The extent to which hydrodynamic effects may modify the energy predictions made by the flat surface are examined. variation of the time at which generation is allowed to start is found to affect the amount of energy predicted by the hydrodynamic model. The costate equations, which are necessary for the solution of the optimal control problem are derived, but the solution of these equations is not presented

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24

Semuwemba, James. "Modelling tracer breakthrough curves to determine stream reaeration and hydrodynamic properties." Thesis, Queen's University Belfast, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.580085.

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This study investigates and applies robust modelling techniques for analysis of tracer concentration versus time curves (so-called breakthrough curves; BTCs) for the direct (gas) tracer technique in an attempt to quantify more accurately both the reaeration coefficient (K2) and other hydrodynamic parameters with associated uncertainties. Three issues related to the Peak, Modified Peak and Area methods (the standard methods in literature) used to compute K2 from tracer BTCs have been addressed. (a) The three methods rely on the presumption that transport is prescribed by the Advection-Dispersion Model (ADM), which is not always true for natural rivers, thus estimated K2 might be in error (the magnitude of which is not yet known). (b) Although K2 is computed, important hydrodynamic parameters characterising advection, dispersion and transient storage, which determine rates of spreading of solutes and pollutants are not. (c) Uncertainty in K2 has not been quantified, yet this is a critical requirement for stochastic water quality modelling. This study addresses these issues. To address issue (a), the three standard methods are appraised using 800 tracer BTCs simulated for hypothetical rivers both with and without transient storage. The former was achieved using the Transient Storage Model (TSM) and the latter using the ADM. The error in K2 computed with each method was quantified. To address issue (b), a global inverse modelling routine is introduced and tested using perfect and noisy synthetic BTCs. The inversion routine is used to compute both K2 and hydrodynamic parameters for two reaches of the River Lagan in Northern Ireland using real data from 33 tracer tests. In order to address issue (c), both the Linear Approximation method and the Metropolis Hastings (MH) algorithm (a Markov Chain Monte Carlo sampler) are used to compute linear and nonlinear parameter uncertainties, respectively. The MH algorithm, thought to be applied here for the first time in tracer studies, gives posterior distributions both for K2 and key hydrodynamic parameters. A Gelman statistic indicated that the MH algorithm converges to stationary posterior distributions both for synthetic and real data. This study shows, for BTCs described by the TSM (as evidenced by "tailing" of most tracer BTCs in natural rivers), none of the three standard methods gives reliable values of K» Errors in K2 reach 80% for noise-free data; .noise in data exacerbates the errors and leads to inconsistencies in K2 from these methods. For perfect synthetic BTCs, the global inversion routine returned the true hydrodynamic parameters and K2, although this proved impossible for noisy BTCs; but the posterior distributions encompass the true parameter values, highlighting the importance of estimating parameter uncertainty. For the River Lagan, the modelling revealed that transport in the reaches is influenced by transient storage due to stagnant zones, the cross section area of which accounts for 18-60% of that of the main channel. Posterior distributions show non-uniqueness mainly for the exchange coefficient and area of storage zones for some tests. For tests where all parameters are unique, parameter values are comparable with those in literature. More importantly values of the cross section area of the main channel are comparable with those measured physically. Values of K2 at 20°C (K2(20)= 6 - 45 d-I) are comparable with those in literature for similar rivers and show a positive trend with volumetric flow and mean velocity. Linear uncertainty (13-31% of K2(20)) is not equal to the nonlinear uncertainty (16-44% of K2(20)) implying fallibility of the Linear Approximation method despite it requiring minimal computational resources. The uncertainty analysis of dissolved oxygen predictions using a QUAL2Kw model demonstrates the relevance of an accurate K2 and its uncertainty to water quality modelling. It justifies the case for routine use of robust modelling methods to compute K2 and its uncertainty.

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25

Zainy, Mohammed. "Hydrodynamic modelling of cerebrospinal fluid motion within the human ventricular system." Thesis, Nottingham Trent University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272855.

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26

Wang, Xio Shan. "Hydrodynamic behaviour and coal combustion modelling of a circulating fluidised bed." Thesis, University of Leeds, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303327.

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27

Bhinder, Majid. "3D non-linear numerical hydrodynamic modelling of floating wave energy converters." Ecole centrale de Nantes, 2013. http://www.theses.fr/2013ECDN0028.

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Dans cette thèse, on cherche à quantifier l’impact des effets d’origine visqueuse sur la dynamique et la production d’énergie des systèmes houlomoteurs. A l’heure actuelle, l’état de l’art pour évaluer la production d’énergie des houlomoteurs repose sur des approches en théorie linéarisée des écoulements potentiels (codes BEM) car la CFD (Computational Fluid Dynamics) est encore trop coûteuse en terme de temps de calcul. Cependant, l’approche potentielle est limité par les hypothèses de linéarité sur laquelle elle repose. Ces limitations doivent être comprises et des améliorations apportées. En particulier, une piste d’amélioration est l’ajout de correction visqueuse via l’ajout de terme quadratique à la Morison dans l’équation du mouvement. Cette correction dépend d’un coefficient de trainée qui doit être estimé avant de pouvoir réaliser la simulation. Une possibilité est d’interpoler la valeur de ce coefficient à partir des données expérimentales que l’on peut trouver dans la littérature, ou bien utiliser la CFD. Dans ce travail, on s’est intéressé à la faisabilité de cette seconde approche. Deux houlomoteurs académiques ont été modélisés. Le premier est une bouée pilonnante de forme cylindrique, à bouchains vifs. Le second est un volet oscillant en cavalement. Des calculs CFD des efforts exercés sur ces géométries ont été réalisés dans un écoulement oscillant. L’effort mesuré est lissé conformément à la formule de Morison en utilisant la méthode des moindres carrés pour déterminer les coefficients de trainée et de masse d’eau ajoutée. Ensuite, le coefficient de trainée est implémentée dans l’équation du mouvement du houlomoteur correspondant. L’absorption d’énergie avec et sans la prise en compte des effets visqueux est alors évaluée, qui met en évidence l’importance de leur prise en compte The impact of the viscous and vortex forces in the context of floating wave energy devices has been studied in this work. At present the state of the art tools to assess the efficiency of the WECs (Wave Energy Converters) comprise the BEM (boundary element method) codes based on the potential linear approach whereas CFD (computational fluid dynamics) is still considered to be computationally expensive. However the former has its limits regarding linearity restrictions and hence needs further inspections and improvements. A possibility for improvement is to account for viscous damping via additional Morison-like quadratic damping term. The intensity of this additional damping term depends on a coefficient which needs to be estimated prior to the calculations. One can interpolate this coefficient from the many previously published experimental results or imagine using CFD. In this study, the applicability of the latter option is investigated for WEC application. Two generic devices such as a heaving cylinder with sharp corners and a surging flap type WEC are considered. CFD computations of the forces on the buoy in an oscillatory flow are performed. This CFD-force is then fitted by the Morison’s equation using least square approach, which gives estimation of the viscous damping coefficient. This coefficient is implemented in the equation of motion of the WEC. The energy absorption with and without taking into account the viscous damping is then derived, which shows the importance of its appropriate modelling

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28

Vallet, Alexandra. "Hydrodynamic modelling of the shock ignition scheme for inertial confinement fusion." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0214/document.

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Le schéma d'allumage par choc pour la fusion par confinement inertiel utilise une impulsion laser intense à la fin d'une phase d'assemblage de combustible. Les paramètres clefs de ce schéma sont la génération d'une haute pression d'ablation, l'amplification de la pression du choc généré par un facteur supérieur à cent et le couplage du choc avec le point chaud de la cible. Dans cette thèse, de nouveaux modèles semi-analytiques sont développés afin de décrire le choc d'allumage depuis sa génération jusqu'à l'allumage du combustible. Tout d'abord, un choc sphérique convergent dans le coeur pré-chauffé de la cible est décrit. Le modèle est obtenu par perturbation de la solution auto-semblable de Guderley en tenant compte du nombre de Mach du choc élevé mais fini. La correction d'ordre un tient compte de l'effet de la force du choc. Un critère d'allumage analytique est exprimé en fonction de la densité surfacique du point chaud et de la pression du choc d'allumage. Le seuil d'allumage est plus élevé pour un nombre de Mach faible. Il est montré que la pression minimale du choc, lorsqu'il entre dans le coeur de la cible, est de 20Gbar. La dynamique du choc dans la coquille en implosion est ensuite analysée. Le choc se propage dans un milieu non inertiel avec un fort gradient de pression et une augmentation temporelle générale de la pression. La pression du choc est amplifiée plus encore durant la collision avec une onde de choc divergente provenant de la phase d'assemblage. Les modèles analytiques développés permettent une description de la pression et de la force du choc dans une simulation typique de l'allumage par choc. Il est démontré que, dans le cas d'une cible HiPER, une pression initiale du choc de l'ordre de 300 Mbar dans la zone d'ablation est nécessaire. Il est proposé une analyse des expériences sur la génération de chocs forts avec l'installation laser OMEGA. Il est montré qu'une pression du choc proche de 300Mbar est atteinte près de la zone d'ablation avec une intensité laser absorbée de l'ordre de 2 X 10(15) W.cm-2 et une longueur d'onde de 351 nm. Cette valeur de la pression est deux fois plus importante que la valeur attendue en considérant une absorption collisionnelle de l'énergie laser. Cette importante différence est expliquée par la contribution d'électrons supra-thermiques générés durant l'interaction laser/plasma dans la couronne. Les modèles analytiques proposés permettent une optimisation de l'allumage par choc lorsque les paramètres de la phase d'assemblage, sont pris en compte. Les diverses approches analytiques, numériques et expérimentales sont cohérentes entre-elles The shock ignition concept in inertial confinement fusion uses an intense power spike at the end of an assembly laser pulse. the key feature of shock ignition are the generation of a high ablation pressure, the shock pressure amplification by at least a factor of a hundred in the cold fuel shell and the shock coupling to the hot-spot. in this theses, new semi-analytical hydrodynamic models are developed to describe the ignitor shock from its generation up to the moment of fuel ignition. A model is developed to describe a spherical concerging shock wave in a pre-heated hotspot. The self-similar solution developed by Guderley is perturbed over the shock Mach number Ms >>1. The first order correction accounts for the effects of the shock strength. An analytical ignition criterion is defined in terms of the shock strength ans th hot-spot areal density. The ignition threshold is higher when the initial Mach number of the shock is lower. A minimal shock pressure of 20 Gbar is needed when it enters the hot-spot. The shock dynamics in the imploding shell is the analyzed. The shock is propagating into a non inertial medium with a high radial pressure gradient and an averall pressure increase with time. The collision with a returning shock coming from the assembly phase enhances further the ignitor shock pressure. The analytica theory allows to des cribe the shock pressure and strength evolution in a typical shock ignition implosion. It is demonstrated that, in the case of the HiPER target design, a generation shock pressure near the ablation zone on the order of 300-400 Mbar is needed. An analysis of experiments on the strong shock generation performed on the OMEGA laser facility is presented. It is sown that a shock presssure close to 300 Mbar near the ablation zone has been reached with an absorbed laser intensity up to 2 x 10(15) W:cm-2 and a laser wavelength of 351 nm. This value is two times higher than the one expected from collisional laser absorption only. That significant pressure enhancement is explained by contribution of hot-electrons generated by non-linear laser/plasma interaction in the corona. The proposed analytical models allow to optimize the shock ignition scheme, including the inuence of the implosion parameters. Analytical, numerical and experimental results are mutualy consistent

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29

Angelotti, de ponte rodrigues Natalia. "Open water swimming : Monitoring and hydrodynamic modelling for sanitary conditions assessment." Electronic Thesis or Diss., Marne-la-vallée, ENPC, 2023. http://www.theses.fr/2023ENPC0046.

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La baignade en eau libre connait un fort engouement, notamment en milieu urbain où les canicules estivales sont de plus en plus fréquentes. Pour éviter les risques sanitaires, le suivi d’indicateurs de micro-organismes pathogènes, les bactéries indicatrices fécales (BIF) telles que E. coli, est nécessaire. Les résultats des méthodes de référence en laboratoire sont obtenus au mieux en 24h.Pour qu’une baignade soit ouverte au public, les concentrations de BIF doivent être inférieures à des seuils réglementaires. En cours d'eau, ces conditions peuvent être estimées à partir de mesures en un point amont, défini en tenant compte du temps de transfert vers la baignade et du temps de réponse de la mesure des BIF. Le temps de transfert change en fonction du débit et de la stratification thermique. Ces variations peuvent être calculées par des modèles hydrodynamiques, également utiles pour estimer la distribution spatiotemporelle des BIF. Afin de proposer un système de suivi et de prévision de la qualité microbiologique d’une zone de baignade, deux axes de recherche ont été développés: (1) la mise en œuvre d'un modèle hydrodynamique 3D pour calculer les champs de vitesses et la température de l'eau et (2) la définition d'un proxy des BIF pour une évaluation rapide de la qualité microbiologique de l'eau. Les objectifs spécifiques du doctorat sont les suivants:-Mise en œuvre du modèle hydrodynamique, TELEMAC-3D, couplé au module thermique WAQTEL;-Conception et déploiement d’un système de mesure de terrain;-Étude de l’influence de la stratification thermique sur la distribution spatiotemporelle des BIF;-Identification d’un indicateur des BIF de mesure rapide. Le site d’étude, le bassin de La Villette, est situé à Paris (France). Il se compose d'un canal en amont (25 m de large, 800 m de long) et d'un bassin en aval (70m de large, 700m de long, 3m de profondeur). Le débit moyen est d'environ 2.1m³/s. Le système de suivi se compose de deux points de mesure situés à 1000m en amont de la zone de baignade et en aval, à proximité de la baignade. Sur les deux sites, la température de l'eau est mesurée à trois profondeurs et la conductivité électrique à mi- profondeur (pas de temps 10 min).Du printemps à l’automne, une stratification thermique de la colonne d'eau, interrompue la nuit a été mesurée. Les données de conductivité aux deux points de suivi ont permis d'estimer le temps de transfert d’un traceur passif, qui varie de 6h30 à 24h.Pour connaitre leur niveau en temps réel, la relation entre BIF et fluorescence de la matière organique dissoute (MOD) a été étudiée. La spectroscopie de fluorescence combinée à la modélisation PARAFAC a été utilisée pour caractériser la MOD et l'activité microbiologique dans 5 sites en région parisienne. Les résultats ont montré une forte présence d'un composant protéique dans les échantillons de contamination microbienne plus élevée. Une relation a été établie entre ce composant et les BIF. Pour une prévision à court terme (3 jours), une relation entre BIF et données hydrométéorologiques (débit, pluie et durée de temps sec) a été étudiée. À La Villette, une relation entre E. coli et la pluie mesurée en amont, entre 1 et 3 jours avant le jour d'intérêt, a été trouvée. Les mesures ont été utilisées comme données d'entrée du modèle et pour sa validation, la concentration des BIF étant estimée à partir des relations établies entre fluorescence et données de pluie. Les résultats du modèle hydro-microbiologique ont été comparés aux mesures. L'alternance de stratification thermique et mélange observée a été correctement reproduite. Son effet sur la distribution spatiale d'E. coli a été mis en évidence. La variation de la conductivité a été bien simulée. Les temps de transfert, correctement estimés, peuvent être appliqués à d'autres traceurs passifs. Ce travail met en évidence la pertinence d'un modèle hydrodynamique 3D pour évaluer le transport des contaminants et les conditions sanitaires dans un cours d’eau Swimming in open water has become very popular, particularly in urban areas where summer heatwaves are increasingly frequent. To control sanitary risks, the monitoring of indicators of pathogenic microorganisms, namely faecal indicator bacteria (FIB), such as E. coli is required. Reference laboratory methods take at least 24h to provide results.For opening a bathing area to the public, FIB concentrations must meet the regulatory limits. In watercourses, this condition can be estimated from measurements at an upstream point, defined to take into account the transfer time to the bathing area and the response time of the FIB measurement.The transfer time is affected by flowrate and thermal stratification. Variations in current velocity can be computed using hydrodynamic models, which are also useful to estimate the FIB spatiotemporal distributionIn order to propose a system for monitoring and forecasting the microbiological quality of bathing areas, two research lines have been developed: (1) the implementation of a 3D hydrodynamic model to compute the velocity field and the water temperature and (2) the definition of a FIB proxy for faster microbiological water quality assessment.The specific objectives of the PhD thesis are as follows:- To implement the 3D hydrodynamic model TELEMAC-3D, coupled with the WAQTEL thermal module;- To design and install a monitoring system to obtain field data that can be used for input and validation of the hydrodynamic model;- To investigate the influence of thermal stratification on the spatiotemporal distribution of faecal contamination;- To identify a fast-measuring indicator of FIB.The study site, La Villette basin, is located in Paris (France). It consists of a canal upstream (25m wide, 800m long), and a basin downstream (70m wide, 700m long, 3m deep). The average discharge is around 2.1m³.s-1.The installed fully autonomous monitoring system consists of two monitoring points located: (1) 1000m upstream of the bathing area and (2) downstream, close to the bathing area. At both sites, water temperature is measured at three depths, and electrical conductivity at mid-depth, with a 10 min time step.From spring to mid-autumn, the data showed a daily thermal stratification of the water column, breaking up at night. Conductivity data allowed to estimate the transfer time between both monitoring points. The values varied from 6h30 to more than 24h.To obtain real-time information on FIB level, the relationship between FIB and the fluorescence of dissolved organic matter (FDOM) was investigated. Fluorescence spectroscopy combined with PARAFAC modelling was used to characterize DOM and microbiological activity in five watercourses in the Paris metropolitan region. The results showed a higher presence of a protein-like component in samples with higher microbial contamination. A relationship was established between this component and FIB.For a short-term (3 days) FIB level forecast, a relationship between FIB and hydro-meteorological data (discharge, rainfall and dry weather duration) was investigated. In La Villette basin, a relationship between E. coli and the precipitation measured upstream, between one and three days before the day of interest, was found.The in-situ measured values were used as model input and for validation. The FIB concentration was derived from FDOM data and from hydro-meteorological data using the established relationships.The results of the 3D hydro-microbiological model were compared to field data. The observed alternation of thermal stratification and mixing was correctly reproduced. Its effect on E. coli spatial distribution was highlighted. The conductivity variation was well simulated. The transfer time between the two measuring points was correctly estimated and can be applied to other passive tracers.This work highlights the relevance of a 3D hydrodynamic model for assessing contaminant transport and sanitary conditions in a river area of interest

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30

Chen, Yiping. "Numerical modelling of solute transport processes using higher order accurate finite difference schemes : numerical treatment of flooding and drying in tidal flow simulations and higher order accurate finite difference modelling of the advection diffusion equation for solute transport predictions." Thesis, University of Bradford, 1992. http://hdl.handle.net/10454/4344.

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The modelling of the processes of advection and dispersion-diffusion is the most crucial factor in solute transport simulations. It is generally appreciated that the first order upwind difference scheme gives rise to excessive numerical diffusion, whereas the conventional second order central difference scheme exhibits severe oscillations for advection dominated transport, especially in regions of high solute gradients or discontinuities. Higher order schemes have therefore become increasingly used for improved accuracy and for reducing grid scale oscillations. Two such schemes are the QUICK (Quadratic Upwind Interpolation for Convective Kinematics) and TOASOD (Third Order Advection Second Order Diffusion) schemes, which are similar in formulation but different in accuracy, with the two schemes being second and third order accurate in space respectively for finite difference models. These two schemes can be written in various finite difference forms for transient solute transport models, with the different representations having different numerical properties and computational efficiencies. Although these two schemes are advectively (or convectively) stable, it has been shown that the originally proposed explicit QUICK and TOASOD schemes become numerically unstable for the case of pure advection. The stability constraints have been established for each scheme representation based upon the von Neumann stability analysis. All the derived schemes have been tested for various initial solute distributions and for a number of continuous discharge cases, with both constant and time varying velocity fields. The 1-D QUICKEST (QUICK with Estimated Streaming Term) scheme is third order accurate both in time and space. It has been shown analytically and numerically that a previously derived quasi 2-D explicit QUICKEST scheme, with a reduced accuracy in time, is unstable for the case of pure advection. The modified 2-D explicit QUICKEST, ADI-TOASOD and ADI-QUICK schemes have been developed herein and proved to be numerically stable, with the bility sta- region of each derived 2-D scheme having also been established. All these derived 2-D schemesh ave been tested in a 2-D domain for various initial solute distributions with both uniform and rotational flow fields. They were further tested for a number of 2-D continuous discharge cases, with the corresponding exact solutions having also been derived herein. All the numerical tests in both the 1-D and 2-D cases were compared with the corresponding exact solutions and the results obtained using various other difference schemes, with the higher order schemes generally producing more accurate predictions, except for the characteristic based schemes which failed to conserve mass for the 2-D rotational flow tests. The ADI-TOASOD scheme has also been applied to two water quality studies in the U. K., simulating nitrate and faecal coliform distributions respectively, with the results showing a marked improvement in comparison with the results obtained by the second order central difference scheme. Details are also given of a refined numerical representation of flooding and drying of tidal flood plains for hydrodynamic modelling, with the results showing considerable improvements in comparison with a number of existing models and in good agreement with the field measured data in a natural harbour study.

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31

Phelps, Jack. "Modelling hydrodynamic transport and larval dispersal in North-East Atlantic Shelf seas." Thesis, University of Liverpool, 2015. http://livrepository.liverpool.ac.uk/2026939/.

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This thesis presents a series of numerical modelling studies into hydrodynamic transport and larval dispersal. The initial investigation seeks to evaluate retention timescales in Liverpool Bay. The flushing time and residence time are equal to 136 days and 103 days respectively, however small concentrations of seawater are retained over several years due to vigorous tidal mixing. The age distribution is shown to be highly variable and dependent upon tracer input duration, however salinity can be used to estimate the mean age, which is not directly observable in practice. Chapters 3, 4 and 5 all focus upon the dispersal of meroplanktonic larvae and aim to determine how larval behaviour affects their transport. Vertical migration is a significant influence upon larval dispersal within each case study, although the effect of this behaviour is conditional upon local hydrodynamic conditions. For example diel vertical migration promotes dispersal in the western Irish Sea, however the identical swimming pattern facilitates local retention in the eastern Irish Sea. The ecological implications of these findings are discussed. This thesis concludes with an investigation into the impact of large CO2 leakages on the marine carbonate system at potential carbon sequestration sites in the North Sea. Perturbations to seawater pH are found to vary according to the rate, duration and location of CO2 input. The northern North Sea is particularly vulnerable to large perturbations ( > 1 pH units) during the summer months, as the strong seasonal thermocline suppresses CO2 outgasing.

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32

McEwan, Robert. "Interdisciplinary study of hydrodynamic and biogeochemical processes of a large-scale river plume." Thesis, University of Plymouth, 2013. http://hdl.handle.net/10026.1/1551.

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This research has utilised the Massachusetts Institute of Technology gen- eral circulation model (MITgcm) along with observations taken as part of the River In uences on Shelf Ecosystems (RISE) study to investigate the dynamic processes associated with the Columbia River plume at different temporal and spatial scales. Firstly, a high resolution ( x= y=25 m) investigation of the near-field plume was undertaken using the fully non-hydrostatic mode of the MITgcm. This resulted in the reproduction of a detailed inner plume as well as a series of radiated internal waves. In addition to first mode internal waves, second order waves were radiated from the plume boundary when propagation ve- locity becomes sub-critical. Third mode internal waves were also observed, trapped at the plume head. The fine plume structure produced revealed sec- ondary fronts within the plume that also generated internal waves. These features increase the mixing occurring inside the plume, resulting in greater entrainment of underlying waters into the plume. The use of Lagrangian drifters within the model produced detailed results of the recirculation tak- ing place within the emerging plume and how this recirculation changes with depth. This has implications for the near-field recirculation of biologically important solutes present in the plume waters. A second coarser resolution horizontal grid ( x= y=500 m) was imple- mented to investigate the processes of the large-scale plume with the addi- tion of wind forcing. Experiments with both simplified and realistic wind scenarios were carried out and comparisons with in-situ data were made. This revealed the dominance of wind effects on the outer plume and tidal effects on the inner plume. In the simplified wind cases, the classical the- ory of plume propagation under the action of upwelling and downwelling favourable winds was recreated. For the case of realistic winds, there was some success in reproducing a hindcast of the plume location. Tracer fields were used to represent nutrient concentrations based on observed data. Whilst these results showed variations from observations, they did allow a spatially and temporally complete view to be taken of nutrient distribu- tion in the region.

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33

Goodhue, Nigel David. "Hydrodynamic and water quality modelling of the lower Kaituna River and Maketu Estuary /." The University of Waikato, 2007. http://hdl.handle.net/10289/2375.

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The Maketu Estuary is a shallow intertidal estuary (2.3 km2) located in the Bay of Plenty, North Island, New Zealand. The Kaituna River contributes the largest freshwater flow into the estuary through control gates. Lake Rotoiti and indirectly Lake Rotorua supply the base flow to the Kaituna River, with tributaries along the 50 km reach also significantly contributing to the flow. Water quality within the river is affected by elevated nutrients, faecal coliforms, high oxygen demand and algae concentrations derived from the lakes as well as contributions from tributaries and industrial and urban discharge. Through the use of a coupled hydrodynamic-biogeochemical numerical model ELCOM-CAEDYM, this study aims to examine the nutrient, phytoplankton and hydrodynamics of the Maketu Estuary and lower Kaituna River. Water quality and hydrodynamic measurements were sourced from Environment Bay of Plenty's data archives as well as a number of instrument deployments to collect water velocity, tidal elevation and salinity and temperature measurements during the course of this study. Included in the field work was a survey of the lower river and estuary bathymetry. Model simulations predicted that the maximum residence time in the Maketu Estuary is 1.5 days, occurring in the inner western region. Residence time in the lower river (mouth to 8.5 km upstream) is in the order of hours although some variations were predicted near the river mouth. Growth rates of four phytoplankton groups where assessed over a 15 day period in January 2004. In the Kaituna River ELCOM-CAEDYM predicted that the community growth rates were small with the exception of a slight increase in biomass of the two freshwater groups in a semi-detached river bend. The increase in the loop was correlated with an increase of residence time. In the estuary, marine diatoms showed the highest growth rates in the western region which is expected to relate to retention time and available nutrients. Dinoflagellates showed the smallest variation in predicted growth rates, most likely due to their broad salinity tolerance. The two freshwater species showed a reduction in abundance when mixed with marine water. A principle limiting factor to phytoplankton growth in both the river and estuary is the low residence time. A number of scenarios were simulated in the river and estuary by altering the forcing conditions in the model. A simulation of the increased nutrient load associated with the Rotoiti diversion wall revealed that phytoplankton growth in the river and estuary will not be significantly affected. Because of the close proximity of the control gates to the river mouth, a proportion of water drawn through the structure can be marine. By opening the old river channel, model simulations predicted that a reduction in salinity would be possible, however the outcome of complete freshwater is probably not achievable. Increasing the discharge volume from the river into the estuary was also simulated. The results indicated that increasing the freshwater inflow at Fords Cut would reduce the salinity in the estuary while increasing the net (residual) flow towards the estuary mouth. Increasing the flow would also result in a greater range of salinity in regions of the estuary. Changing the inflow location to the historic Papahikahawai Channel also affected the salinity in the estuary. The most significant effect of an inflow at this location was a reduction of the residual currents in the western region of the estuary.

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34

Jennings, Christopher Ashley. "Radiation transport effects in wire array Z pinches and magneto-hydrodynamic modelling techniques." Thesis, Imperial College London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.423270.

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35

Roc, Thomas. "Numerical modelling for hydrodynamic impact and power assessments of tidal current turbine arrays." Thesis, University of Plymouth, 2013. http://hdl.handle.net/10026.1/1557.

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Channel constrictions in which strong currents are mainly driven by tidal processes represent sites with high potential for harvesting renewable and predictable tidal stream energy. Tidal Current Turbines (TCTs) deployed in arrays appear to be the most promising solution to efficiently capturing this carbon neutral energy resource. However to ensure the sustainable character of such projects, the balance between power extraction maximization and environmental impact minimization must be found so that device layout optimization takes into account environmental considerations. This is particularly appropriate since both resource and impact assessments go intrinsically hand in hand. The present method proposes the use and adaptation of ocean circulation models as an assessment tool framework for tidal current turbine (TCT) array-layout optimization. By adapting both momentum and turbulence transport equations of an existing model, the present TCT representation method is proposed to extend the actuator disc concept to 3-D large scale ocean circulation models. Through the reproduction of physical experiments to reasonable accuracy, grid and time dependency tests and an up-scaling exercise, this method has shown its numerical validity as well as its ability to simulate accurately both momentum and turbulent turbine-induced perturbations in the wake. These capabilities are demonstrated for standalone devices and device arrays, and are achieved with a relatively short period of computation time. Consequently the present TCT representation method is a very promising basis for the development of a TCT array layout optimization tool. By applying this TCT representation method to realistic cases, its capability is demonstrated for power capture assessment and prediction of hydrodynamic interactions as would be required during the layout deployment optimization process. Tidal energy has seen considerable development over the last decade and the first commercial deployments are likely to take place within the next 5 years. It is hoped that this new tool and the numerical approaches described herein will contribute to the development of TCT array power plants around the world.

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36

Gardano, Paola. "Modelling of hydrodynamic forces acting on the human arm during front crawl stroke." Thesis, Queen Mary, University of London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.504543.

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Propuisive force generated by swimmers' hand/forearm is the key factor determining performances in human competitive swimming. This work analysed the propulsion given by swimmer's arm performing front crawl stroke by using two complimentary methods: experimental tests and computational methods. The experimental part of the project aimed to derive both appropriate input and validation data from wind tunnel experiments on two models of human arm in order to obtain Drag and Lift values and related pressure distribution. However, due to the limitations in the experimental methods in terms of added terms, numerical approach becomes an invaluable tool in such simulations. The most prominent approach is the Computational Fluid Dynamics (CFD). The main results reported that the Drag was the one that contributes more for the proplllsioD An important and innovative element that has been analysed in this work is the special consideration to the dynamic of structures surrounded by water in term of induced acceleration and production of extra force on the structure in addition to the fluid-dynamic drag force. These results pointed out that the acceleration of hand/arm provides more propulsion to swimmers, confirming that some unsteady mechanism must be present in swimming propulsion. Another important aspect of this work has been focusing on the real swimmer stroke trajectory, as a three dimensional approach, by recording a competitive swimmer during training with three underwater cameras and by analysing the swimmer arm movement performing stroke. Drag and Lift forces have been calculated and the results obtained showed a lower profile for both forces, compared to those ones obtained in a configuration with straight or fixed elbow angle (20 analysis). This innovative and original approach to the study of swimming made these results more reliable for a complete, comprehensive and reliable analysis.

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37

Gao, Guanghai. "Numerical modelling of hydrodynamic and sediment-bacteria interaction processes in estuarine and coastal waters." Thesis, Cardiff University, 2008. http://orca.cf.ac.uk/54738/.

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A study has been undertaken to investigate and improve the representation and modelling of a range of various hydrodynamic, biochemical and sediment transport processes relating to the transport of enteric bacteria organisms in estuarine waters. In this study a relatively simple turbulence model was first further investigated to predict the complex three-dimensional flow structure in a flume with vegetation. The main purpose of this part of the study was to try and acquire accurate velocity profiles of complex flows without the need for a more advanced two-equation turbulence model, requiring values for a number of unknown coefficients and extra computing cost. The results showed that the simple two layer mixing length model was capable of giving more accurate complex velocity profile predictions, with the advantage of requiring limited coefficient data. Formulations developed through earlier studies for dynamic decay rates were then refined and included in the numerical model. The model predictions were tested against field data, with good agreement being obtained. Further refinements to the representation of the transport of bacteria through the flow field were included in the model by the novel addition of the interaction of bacteria with the sediments by partitioning the total bacteria into their free-living and attached phases using a dynamic partitioning ratio. This ratio was related to the suspended sediment concentrations. The novel method used in this study was to include the re-suspension and deposition of the absorbed bacteria with the sediments and this approach has been tested against analytical solutions for steady uniform flow conditions, and published field and experimental data. The model was then applied to the Severn Estuary. After calibration against available data sets the model was then run for different scenarios to investigate the effects of different hydro-environmental conditions on the bacteria distributions in the Severn Estuary. The model was finally used to investigate the impact of the proposed Cardiff-Weston tidal barrage on the hydrodynamic, the sediment transport and bacterial processes within the Severn Estuary. The results showed that the barrage would reduce the currents, as well as significantly reducing the suspended sediment concentrations and bacteria concentration levels in the estuary.

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38

Hornung, Ralf. "Numerical modelling of stratification in Lake Constance with the 1-D hydrodynamic model DYRESM." [S.l. : s.n.], 2002. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB10361133.

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39

Moore, Rowena Deborah. "Hydrodynamic and Morphometric Modelling of a Macro-Tidal Estuary : The Dee Estuary of NW England." Thesis, University of Liverpool, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.511030.

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40

Arnau, Notari María Rosario. "Hydrodynamic and biochemical Computational Fluid Dynamic modelling of full-scale anaerobic digesters for wastewater treatment." Doctoral thesis, Universitat Jaume I, 2022. http://dx.doi.org/10.6035/14107.2022.234094.

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Anaerobic digestion is one of the most widely used biological treatments for the stabilisation of sewage sludge, but the effectiveness of the process depends on good mixing. The Computational Fluid Dynamics (CFD) technique allows analysing the mixing and hydrodynamics, so it has been widely used to study anaerobic digestion. In this thesis, hydrodynamics in full-scale digesters have been studied by means of CFD models, evaluating their mixing systems by means of different scenarios according to mixing and design parameters and dead volumes. In a second part, a new CFD solver was developed to couple a biological model with hydrodynamics and applied to a laboratory and a full-scale digester. The last part was devoted to evaluate the hydrodynamic behaviour of biogas bubbles in anaerobic sludge, so that local mixing by biogas bubbles in anaerobic digesters was evaluated. Future work needs to focus on experimental measurements and new two-phase CFD models. Programa de Doctorat en Tecnologies Industrials i Materials

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41

Justice, Brad L. "Modelling of Calcium Carbonate Precipitation in Natural Karst Environments Under Hydrodynamic and Chemical Kinetic Control." University of Akron / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=akron1145310619.

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42

Mahrabian, Mozaffar Ali. "Experimental, theoretical and computational modelling of flow in corrugated channels to investigate thermal and hydrodynamic characteristics of plate heat exchangers." Thesis, University of Bristol, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387964.

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43

Marshall, Miles Ramsvik. "Spatial variablity and pesticide leaching : measurement and modelling the hydrodynamic aspects of pesticide leaching in soils." Thesis, University of Reading, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402812.

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44

Appelgren, Patrik. "Experiments with and modelling of explosively driven mangetic flux compression generators." Licentiate thesis, KTH, Rymd- och plasmafysik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9638.

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This thesis presents work performed on explosively driven magnetic flux compression generators. This kind of devices converts the chemically stored energy in a high explosive into electromagnetic energy in the form of a powerful current pulse. The high energy density of the high explosives makes flux compression generators attractive as compact power sources. In order to study these devices a generator was designed at FOI in the mid-90ies. Two generators remained unused and became available for this licentiate work. The thesis reports experiments with, and simulations of, the operation of the two remaining generators. The aim was to fully understand the performance of the generator design and be able to accurately simulate its behaviour. The generators were improved and fitted with various types of diagnostics to monitor the generator operation. Two experiments were performed of which the first generator was operated well below its current capability limits while the second was stressed far above its limits. Since the generator generates a rapidly increasing current, a current measurement is the most important diagnostic revealing the current amplification of the generator and its overall performance. Further it is important to measure the timing of various events in the generator. With a common time reference it is possible to combine data from different probes and extract interesting information which cannot be directly obtained with a single measurement. Two types of numerical simulations have been performed: Hydrodynamic simulations of the high explosive interaction with the armature were used to verify the measured armature dynamics. A zero-dimensional code was used to perform circuit simulations of the generator. The model takes into account the inductance reduction due to the compression of the generator as well as the change in conductivity due to heating of the conductors in the generators. QC 20101103

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45

Ekwall, Jakob, and Julian Kolesnik Lindgren. "Hydrodynamic Modelling of the Nanjing Reach in the Yangtze River. : Managing the impact of Three Gorges dam." Thesis, KTH, Industriell ekologi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-149945.

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Due to the impoundment of the Three Gorges Dam a decrease in sediment flow has been a major factor for erosion on the riverbed further downstream in the Yangtze River. This rapport studies the water flow conditions in the Nanjing reach. It also examines the effect of building a diversion dike at the head of the reach as a measure to redistribute some of the water flow to the northern branch. This branch suffers from a declining water flow, largely as a consequence from the erosion in the southern branch. By constructing a numerical model model with the software SMS, the current conditions of the reach were simulated. The simulated diversion dike having best effect on diverting water was able to improve the split ratio with 4.3 percentage points.

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46

Blackman, David Rhys. "Kinetic-hydrodynamic modelling of short-pulse Doppler-shift spectroscopy experiments, and resistive filamentation of fast-electron transport." Thesis, University of York, 2017. http://etheses.whiterose.ac.uk/18765/.

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Three pump-3ω-probe Doppler-shift spectroscopy experiments are presented along with both 1D radiation-hydrodynamics modelling (HYADES) and 1D three-stage modelling process involving: HYADES radiation-hydrodynamics pre-pulse calculations; EPOCH kinetic particle-in-cell main-pulse calculation initialised from HYADES result; followed by hydrodynamic calculations, initialised from EPOCH result, of the evolution after the main-pulse. These investigations are aimed at exploring the formation of shocks at the front surface of targets after interaction with an ultra-short (30 fs), ultra-intense (10^18 W/cm^2 ) laser pulse. To this end a 3ω-probe is delayed then reflected from a 3ω critical surface on the front surface to obtain a temporal profile of the velocity of this surface. Two investigations use identical polished crown glass targets, but are performed with lasers systems with different contrast ratios (10^5 and 10^7 ). HYADES simulations match experimental results for the high contrast experiments except at early times. HYADES simulations of low contrast experiments do not agree. The three-step modelling process shows good agreement with experimental results in both cases, though with some adjustment to the pre-plasma scale-length for the low contrast case. The third Doppler-spectroscopy experiment uses a low density (over-dense) foam target with identical setup to high-contrast case described. Experimental results show a similar magnitude Doppler-shift evolution as in low-contrast case. HYADES simulations show similarities to experimental results but not overall trend. The three-step modelling process shows that the experimental response may be due to post-soliton formation as a result of SRS or photon acceleration plasma instabilities. This is supported by an additional 2D EPOCH simulation. A fourth theoretical investigation is presented into the transport of fast electrons produced 10^19−20 W/cm^2 laser pulses using the hybrid code ZEPHYROS. A low resistivity (< 5 µωm) at low temperatures (1 eV) is found to be of critical importance to suppressing filamentation of electron beams through low-Z targets.

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47

Iyalla, Ibiyekariwaripiribo. "Computational fluid dynamics modelling of pipeline on-bottom stability." Thesis, Robert Gordon University, 2017. http://hdl.handle.net/10059/2721.

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Subsea pipelines are subjected to wave and steady current loads which cause pipeline stability problems. Current knowledge and understanding on the pipeline on-bottom stability is based on the research programmes from the 1980’s such as the Pipeline Stability Design Project (PIPESTAB) and American Gas Association (AGA) in Joint Industry Project. These projects have mainly provided information regarding hydrodynamic loads on pipeline and soil resistance in isolation. In reality, the pipeline stability problem is much more complex involving hydrodynamic loadings, pipeline response, soil resistance, embedment and pipe-soil-fluid interaction. In this thesis Computational Fluid Dynamics (CFD) modelling is used to investigate and establish the interrelationship between fluid (hydrodynamics), pipe (subsea pipeline), and soil (seabed). The effect of soil types, soil resistance, soil porosity and soil unit weight on embedment was examined. The overall pipeline stability alongside pipeline diameter and weight and hydrodynamic effect on both soil (resulting in scouring) and pipeline was also investigated. The use of CFD provided a better understanding of the complex physical processes of fluid-pipe-soil interaction. The results show that the magnitude of passive resistance is on the average eight times that of lateral resistance. Thus passive resistance is of greater significance for subsea pipeline stability design hence the reason why Coulomb’s friction theory is considered as conservative for stability design analysis, as it ignores passive resistance and underestimates lateral resistance. Previous works (such as that carried out by Lyons and DNV) concluded that soil resistance should be determined by considering Coulomb’s friction based on lateral resistance and passive resistance due to pipeline embedment, but the significance of passive resistance in pipeline stability and its variation in sand and clay soils have not be established as shown in this thesis. The results for soil porosity show that increase in pipeline stability with increasing porosity is due to increased soil liquefaction which increases soil resistance. The pipe-soil interaction model by Wagner et al. established the effect of soil porosity on lateral soil resistance but did not attribute it to soil liquefaction. Results showed that the effect of pipeline diameter and weight vary with soil type; for sand, pipeline diameter showed a greater influence on embedment with a 110% increase in embedment (considering combined effect of diameter and weight) and a 65% decrease in embedment when normalised with diameter. While pipeline weight showed a greater influence on embedment in clay with a 410% increase. The work of Gao et al. did not completely establish the combined effect of pipeline diameter and weight and soil type on stability. Results also show that pipeline instability is due to a combination of pipeline displacement due to vortex shedding and scouring effect with increasing velocity. As scoring progresses, maximum embedment is reached at the point of highest velocity. The conclusion of this thesis is that designing for optimum subsea pipeline stability without adopting an overly conservative approach requires taking into consideration the following; combined effect of hydrodynamics of fluid flow on soil type and properties, and the pipeline, and the resultant scour effect leading to pipeline embedment. These results were validated against previous experimental and analytical work of Gao et al, Brennodden et al and Griffiths.

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48

Snyman, Jasper Lodewyk. "Modelling of the heliosphere and cosmic ray transport / Jasper L. Snyman." Thesis, North-West University, 2007. http://hdl.handle.net/10394/1814.

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49

Inga, Juan Ricardo. "Hydrodynamic studies and reactor modelling of a three phase slurry reactor in Fischer Tropsch application / Juan Ricardo Inga." Thesis, Potchefstroom University for Christian Higher Education, 1992. http://hdl.handle.net/10394/9611.

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In this .study the hydrodynamic characteristics of the slurry bed reactor was investigated. This study was aimed to the under" standing of the important parameters that describe the hydrodynamic regime and their quantification. In order to determine the relevant parameters the use of a theoretical model was necessary. This model should include all the hydrodynamic parameters in form of correlations. A sensitivity study was done and the parameters which have great impact were determined. An extensive literature review was done in order to gather the experience of previous investigations. Unfortunately all the experience was obtained in a different hydrodynamic regime and therefore the published results could not be used directly in our study. Hydrodynamic test were performed in the works pilot plant at the operating conditions. Unlike a laboratory, the instrumentation used was the one use in commercial reactors with the commercially acceptable range of accuracy. A mass balance was done around the reactor to ensure that the data was sound. Heat balance was also performed and the study of the heat transfer coefficient was performed. Although this was beyond the scope of this study was here included due to its importance in the design of slurry bed reactors. An existing computer model was adapted for the churn-turbulent regime and the hydrodynamic parameters were implemented. This reactor model was coupled with flashes subroutines in order to have a complete reactor train. This computer model was used for the design of the Slurry Bed Commercial Reactor to be commissioned on 1993 at Sasol One. Thesis (MIng (Chemies))--PU for CHE, 1993

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50

Boye, Brian A. "Integrated modelling of hydrodynamic processes, faecal indicator organisms and related parameters with Improved accuracy using parallel (GPU) computing." Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/60096/.

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Environmental problems and issues are not limited by artificial boundaries created by man. Usually there are different teams or individuals working on the catchments, estuaries, rivers and coastal basins in different countries using different parameters and formulations for various processes. However, the system is a natural one and as such no boundaries exist. When a rain drop of water moves from a catchment to a stream, river or estuary and to the sea, it does not know at any stage whether it is in the catchment, river, estuary or sea. In recent years there has been growing concern about the impact of diffuse source pollution on river, estuarine and coastal water quality and particularly with regard to non-compliance of bathing waters. Hydro-environmental impact assessment modelling studies are generally regarded as having several fundamental shortcomings in model simulations, which can lead to erroneous environmental impact assessment outcomes. These shortcomings were addressed in this project and included: 1. Applying a Cloud to Coast (C2C) approach to modelling flow and solute transport processes in river, estuarine and coastal waters; 2. Improving the computational linking of catchment, river and estuarine-coastal models; 3. Improving the kinetic decay process representation in deterministic models, to include the impacts of salinity, solar irradiance, turbidity and temperature, and; 4. Using parallel (GPU based) computing to enhance the computational speed in executing bathing water quality models. In this research study, the Ribble Estuary and Fylde Coast model was refined to more accurately predict bathing water quality and use parameters which give a better representation of the existing physical and bio-chemical processes. A Cloud to Coast (C2C) approach to modelling was implemented by using common input parameters and formulations in both the 1-D and 2-D domains of the Ribble Estuary and Fylde Coast model. An empirical formulation linking the mortality (decay) rate of bacterial water quality indicators to environmental conditions such as solar irradiation, turbidity, temperature and salinity was added to the numerical code. The linked boundary between the 1-D and 2-D domains of the numerical model was improved by removing the large overlapped linked region. An existing numerical code was rewritten to take advantage of the parallel computing capability of the Graphics Processing Unit (GPU). This was tested on the Ribble Estuary and the Thames Estuary model. Thames Estuary models of varying mesh density were prepared in this research study using lots of bathymetric data (over 80 million points) and tested on the GPU. This research study improved the ability to predict bathing water quality accurately by introducing more realistic representation of environmental conditions and using parallel computing. This improved the ability to carry real time forecasting of bathing water quality and hence prevent failure to meet the requirements of the EU Bathing Water Directive.

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Tesi sul tema "Hydrodynamic modelling"

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