Dissertations / Theses on the topic 'Three-dimensional modelling'
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Kay, Gillian Evelyn. "Three-dimensional modelling of metal evaporated tape." Thesis, University of Central Lancashire, 1999. http://clok.uclan.ac.uk/20078/.
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As developments in magnetic recording increase, the demands for high density recording media continue to rise. One particular medium developed towards meeting these needs is the commercially successftil metal evaporated (ME) tape. To provide a deeper understanding of the magnetic processes occurring in recording media, theoretical studies are carried out to complement experimental observations. Therefore, this thesis is concerned with developing a micromagnetic model to simulate the magnetic behaviour of ME tape. ME tape consists of bundles of granular columns which are tilted towards the film normal. The morphology of the film influences the magnetic behaviour and a 3D model is developed in this thesis to represent the columnar structure and the granular nature of ME tape. A Monte Carlo algorithm, consisting of a 'move and grow' procedure, is developed to generate an irregular system of spherical grains whose radii were generated from a log-normal distribution. This structure provides the foundation for modelling columns of ME tape. Initially an isolated column of ME tape was investigated. Grains were considered to be single domain and the dynamic process of the magnetic moments was explored by the Landau-Lifschitz equation. The model demonstrated that as the strength of the exchange coupling parameter increased, then moments which were strongly coupled resisted large negative fields and square hysteresis loops with a high coercivity were produced. Reversal of the moments was observed to be initiated at the ends of a column and then propagated throughout the column. This was attributed to large demagnetising fields and was particularly evident in the model with aligned easy axes. If the easy axes were randomiy orientated then more disorder was present in the model and moments rotated incoherently. This produced hysteresis loops that were less square than those of the aligned model. The results also showed how the microstructure influenced the reversal processes. Simulations on assemblies of interacting columns of ME tape highlighted that, when exchange coupling was weak, moments reversed incoherently throughout the structure. However, increasing the strength of the exchange coupling caused a high degree of cooperative reversal to occur in individual columns. As moments reverse their direction they initially relax towards the long axis of a column due to column demagnetising effects. The model demonstrates that as moments reverse there is a changing balance between magnetostatic (demagnetising) and exchange interactions within and between columns. The model was considered to be a good representation of ME tape, and the results obtained not only complement previous studies but provide a deeper understanding of the reversal processes occurring both within and between columns of ME tape.
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Cachola, Danny G. "Modelling and animating three-dimensional articulate figures." Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/25851.
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This thesis describes an animation extension to a high-level graphical programming language which provides constructs for the definition, manipulation, and external representation of three-dimensional articulate figures and and their associated movements. The extension permits the definition of models consisting of segments and joints and the specification of each model's motion at a high level of abstraction. The relationship of the extension with respect to the host language is discussed and a general description of the animation language's design and implementation is given. The modelling and motion constructs are discussed and examples of the constructs are presented. It is concluded that high level animation permits the implementation of sophisticated application programs that are easy to read and understand.Science, Faculty of
Computer Science, Department of
Graduate
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Burrows, Justin. "Vector modelling three-dimensional engineering surface topography." Thesis, Brunel University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286805.
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Tung, D.-K. "A knowledge-based three-dimensional modelling system." Thesis, Swansea University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.639269.
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As manufacturers strive towards high-quality production, automated industrial inspection is a potent resource in the design of cost-effective systems which can ensure that products meet all their design specifications. However, in reality, only in well-controlled applications are economically usable systems being taken into daily use. Where such systems are being used, they are seen to be primarily addressing 2-dimensional inspection problems. This is not surprising, given the highly complex problems which must be dealt with in practical, real-world environments. However, there is an urgent need to move towards acceptable machine-vision systems which not only can operate in industrial environments, but also offer the benefits of 3-dimensional visual representation - so vital in any real inspection situation. A fundamental aspect of any inspection system is the development of inspection models - to be used in subsequent inspection procedures. The generation of these models is a non-trivial task, and one which is increasingly being seen to be best done using operator assistance - as shown, for example, in the work of Chen [34]. However, most current work in such model generation has been tackled in the 2-D arena. This thesis addresses the problem of providing high-quality, visually meaningful, representations of 3-dimensional bodies, drawing information from 2 simple, but industrially-rugged, 2-dimensional images, and using operator assistance to determine the final models. When combined, the resulting 3-dimensional representation provides a valuable reference to an object's total physical structure. The models themselves allow for accurate inspection of the objects' physical parameters.
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Faraz, A. "Three dimensional force modelling for milling operations." Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381031.
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Haidekker, Andras. "Radiation modelling in complex three dimensional enclosures." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1991. http://theses.uqac.ca.
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Kleinermann, Frederic. "Three dimensional modelling of Electrical Impedance Tomography." Thesis, University of Salford, 2000. http://usir.salford.ac.uk/43047/.
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Electrical Impedance Tomography (ElT) is an emerging imaging technique with applications in the medical field and in the field of industrial process tomography (lPT). Until recently, data acquisition and image reconstruction schemes have been constructed with the assumption that the object being imaged is two-dimensional. In recent years, some research groups have started to address the third dimensional aspects of ElT by both building three dimensional enabled data acquisition systems and solving the three dimensional Forward Problem numerically since this allows the possibility of modelling complex shapes. However, solving the Forward Problem analytically is still very attractive as an analytical solution does not depend on the way the domain has been meshed. Furthermore, if dynamic images are reconstructed which are less sensitive to the model of the electrodes employed, the shape of the object being imaged and the position of the electrodes, an analytical solution to the Forward Problem can be used to reconstruct dynamic three dimensional images. This thesis will start by describing how a full analytical solution for a finite right circular cylinder (which approximately models the human thorax) on which two electrodes have been placed, is derived. It will be shown that the analytical solution has two different forms. Results will be presented detailing the convergence performance of the two different forms as well as comparisons between the analytical solution and experimentally obtained data. Finally three dimensional images reconstructed using these methods will be presented. In order to better approximate the shape of the human thorax, the above work has been extended to provide an analytical solution for an elliptical cylinder and this is presented in this thesis for the first time together with some simulation results. Today in Multi-frequency Electrical Impedance Tomography (MEIT), new hardware for recording measurements operating above 1MHz is now available. This high operating frequency raises the question of the validity of the employed quasi-static conditions used in the associated Forward Problem modelling. It is important to be able to determine when the quasi-static conditions fail and to investigate the differences between a solution to the Forward Problem based on quasi-static conditions and the one based on non quasistatic conditions at these frequencies. This thesis details the derivation of a new analytical solution based on non quasi-static conditions for a finite right circular cylinder having two electrodes placed on its boundary. Some comparisons between the new analytical solution and data obtained from in-vitro experiments will be presented in this thesis. A comparison between the new analytical solution and the analytical solution derived earlier in this thesis (which is based on quasi-static conditions) is also conducted. Whilst these results are preliminary results, they reveal that for situations associated with imaging the human thorax the quasi-static assumption appear violated when most modern MEIT systems are employed. This frequency dependent three dimensional analytical Forward Problem work has wide ranging implications for the future of MEIT. The thesis will conclude with some initial thoughts on how to incorporate anisotropy into three dimensional Forward Problem solutions.
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Barnett, Nicholas David. "Measurement and modelling of three dimensional scapulohumeral kinematics." Thesis, University of Newcastle upon Tyne, 1996. http://hdl.handle.net/10443/3588.
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The term scapulohumeral rhythm is commonly used to describe the two dimensional rotation of the scapula accompanying motion of the arm. Despite the development of a variety of measurement techniques, including radiography, goniometry and three dimensional digitisation, the complete three dimensional kinematics of the scapula have never been presented. Nor have the effects of arm motions outside elevation in the coronal, sagittal or scapula planes been considered. Employing the Isotrak®" electromagnetic measurement system, this study has developed and validated a new method to simultaneously measure the three dimensional kinematics of the scapula and humerus. Euler angle rotations of the· scapu·lawere defined in a sequence approximately analogous to clinical definitions. For the first time, the three dimensional displacements of the scapula have also been determined. 950/0 confidence intervals for lateral rotation of the scapula during humeral elevation in the coronal plane have been calculated at under 4°, Significantly smaller than those presented by previous authors. A mathematical model of three dimensional scapulohumeral kinematics has been developed, capable of predicting the position and orientation of the scapula for a given orientation of the humerus over a wide range of humeral motion. Using this model system, the effects of humeral azimuth, elevation and rotation on the kinematics of the scapula have been investigated. Humeral elevation was seen to have the largest effect, causing the scapula to rotate laterally, retract and tip backwards. Humeral azimuth. has no noticeable effect on the lateral rotation of the scapula, although it causes the scapula to retract, and to tip backwards slightly. Rotation of the humerus has littre effect on the kinematics of the scapula. However, when approaching maximal internal rotation, the ligaments around the glenohumeral joint impose a kinematic constraint on the scapula, resulting in elevation of the scapula upon the thoracic cage.
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Sides, Edmund John. "Modelling three-dimensional geological discontinuities for mineral evaluation." Thesis, Imperial College London, 1992. http://hdl.handle.net/10044/1/8809.
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Hodgetts, David. "Three dimensional numerical modelling of continental lithosphere deformation." Thesis, Keele University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295800.
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Ghosh, Tushar Kanti. "Three dimensional modelling and optimisation of multistage collectors." Thesis, Lancaster University, 2002. http://eprints.lancs.ac.uk/76623/.
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Multistage collectors are commonly used in travelling wave tubes (TWTs), klystrons, gyrotrons and inductive output tubes (IOTs). A dc beam transfers some of its energy to the input RF wave during its travel through the interaction circuit. The purpose of a collector is to recover most of the remaining dc power from the spent beam and thereby increase both the collector and the overall efficiency. Secondary electrons play a detrimental role in collector performance. Use of the asymmetric collector geometries and application of a magnetic field in the collector region have proved to be effective in recapturing the secondaries. A fully three-dimensional simulator LKOBRA (MF) – the mainframe version of Lancaster KOBRA, has been developed at Lancaster University; this is capable of simulating multistage collectors including the effects of secondary electron emission and magnetic field. It is based on KOBRA3-INP1 but has been modified and improved together with the pre- and post-processors of the package. Efficiency is an important parameter in space applications of microwave tubes so it is always desirable to optimise the collector performance to maximise the overall tube efficiency. As a first step the potentials at the collector electrodes are optimised to achieve the maximum possible theoretical efficiency. A computer code based on the well-known enumerative technique has been developed for this purpose. In the next step the geometry of the collector electrodes is optimised using an automated design package that is based on a genetic algorithm. The genetic algorithm creates a new geometry through a search procedure that works from a population of possible geometries. A new set of geometries is generated using three basic operators namely reproduction, crossover and mutation. The collector efficiency is used as the fitness parameter in the genetic algorithm that produces a new population of geometries. This package has been used to optimise the efficiency of a 4-stage symmetric collector and a 2-stage asymmetric collector.
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Bateman, William John Douglas. "A numerical investigation of three dimensional extreme water waves." Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326278.
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Shepherd, James Robert. "Modelling ocean circulation with large-scale semi-geostrophic equations." Thesis, Imperial College London, 1999. http://hdl.handle.net/10044/1/51559.
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The Large-scale Semi-Geostrophic Equations (LSGE, Salmon[73]) are three-dimensional equations valid for an ocean with a rigid lid and length scales much greater than the internal deformation radius (about 40km). In this thesis I reduce the LSGE to a pair of two-dimensional equations via the ansatz that the temperature is independent of the vertical co-ordinate. I refer to these as the Depth-Independent-Temperature (DIT) equations. Whilst this is regarded as a paradigm for the entire ocean, the reduction is similar in spirit to that utilised by many authors for modelling the mixed layer of the ocean. The equations of this thesis differ from the work of such mixed layer models because they involve no ad hoc vertical averaging and so solutions to these equations are also solutions to the full three-dimensional LSGE. The DIT are arguably the simplest equations for ocean circulation to include the effects of inertia, topography and baroclinicity. The DIT are studied both analytically and numerically. It is shown that the model exhibits baroclinic instabilities and analogies are drawn with classical Rayleigh-Benard convection. It is shown that both viscosity and thermal diffusivity are required to avert an ultra-violet catastrophe. Numerical simulations of turbulence demonstrate that the long-time behaviour resembles barotropic flow and that the temperature is reduced to the role of a passive tracer unless large-scale thermal structure is imposed externally on the flow. One of the advantages of the current model over the more widely used quasi-geostrophic models is that there is no restriction on the vertical extent of the bottom topography. This allows the simulation of idealised oceanic basin circulations in which the depth of the ocean vanishes smoothly at boundaries. These ocean simulations are used to study the sensitivity of the model to the Rossby Number, Ekman Number and forcing parameters. Comparison of a barotropic and a DIT ocean reveals the influence of baroclinicity in the latter model. Characteristic features of the Gulf Stream such as meandering, recirculation gyres and the shedding of warm and cold core rings are reproduced by the DIT model and the simple nature of the equations permits an interpretation of these features.
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Hoven, Lisa Emilie. "Three-dimensional numerical modelling of sediments in water reservoirs." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for vann- og miljøteknikk, 2010. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-12623.
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Many places in the world the rivers transport a lot of sediments. When these sediments enter slow flowing areas like a water reservoir, the sediments are deposited. This leads to a reduction in the volume of the reservoir. The object of this project is to do three-dimensional numerical modelling of sediments in a water reservoir in using the SSIIM model. The chosen reservoir is the Angostura reservoir in Costa Rica. This reservoir has significant sediment problems and is flushed two times per year. Both the deposition of sediments and the flushing of the reservoir should be modelled. SSIIM is a computational fluid dynamics program tailor-made for hydraulic engineering. The program can model sediment transport in a reservoir with a movable bed and varying water level, because of this it is suited to model both sediment deposition and reservoir flushing. An unstructured grid with about 27 000 cells is made for the Angostura reservoir. This grid is used for all the simulations and for an analysis of the volume development of the reservoir. The Angostura reservoir was put into operation in year 2000. The yearly inflow of sediments is estimated to be 1.5 million tonnes, this sediment inflow led to a reduction in the reservoir volume. Data from bathymetric surveys has been used as input data for SSIIM, to analyse the volume development of the reservoir. After six years of operation the reservoir had lost almost 30% of its volume. At this time it was decided to do two yearly flushings instead of one as had been done up to this time. After this the volume has remained quite stable with only a slight decrease. The Angostura reservoir is flushed in September and in November every year. Three main simulations have been carried out: simulation of sediment deposition from November until September, simulation of the September flushing, and simulation of the November flushing. After countless tests, the algorithms and parameters giving solutions as close to the measured data as possible, is found. There are still many uncertainties concerning both input data and algorithms used. Further work on the model is therefore recommended. The model successfully simulates deposition and flushing of the reservoir. With further testing and development the model can be used to predict the future volume development of the Angostura reservoir.
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Jeffrey, Stuart. "Three dimensional modelling of Scottish early medieval sculpted stones." Thesis, Connect to electronic version, 2003. http://ads.ahds.ac.uk/catalogue/library/theses/jeffrey%5F2004/index.cfm.
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Thesis (Ph. D.)--University of Glasgow, 2003.Accompanied by CD-ROM. Ph. D. thesis submitted to the Department of Archaeology, University of Glasgow, 2003. Includes bibliographical references. Print version also available.
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Nizam. "Numerical modelling of three-dimensional wave induced nearshore current." Thesis, Imperial College London, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285609.
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Ratcliffe, Jonathan Albert. "Three dimensional cell reconstructions for morphological analysis and modelling." Thesis, University of Nottingham, 2011. http://eprints.nottingham.ac.uk/28689/.
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It is highly desirable to devise a systematic approach to predict cell – material interactions, especially for novel biomaterial surfaces, and to further understanding in the complex area of attachment and spreading. The aim of this research was to produce a new method of studying morphology in real time, whereby data from live spreading cells can be collected for mathematical modelling. There is an abundance of models for sub-cellular elements, however, there are few calibrated models of whole cells; in particular, three-dimensional models predicting attachment, spreading and cell morphology have yet to be produced. Live HOS cells were imaged using LavaCell membrane stain and CLSM every 5 min for a period of 75 min in this study, capturing sufficient detail to produce three dimensional representations of cells during initial attachment and spreading. In order for the contact line to be measured, the interface between the cell membrane and the substrate had to be imaged in sufficient resolution for accurate measurements of the angles to be made. An image processing algorithm developed using Matlab was able to detect the edge of cells in the CLSM z-stack optical sections. These were then used to create contour plots onto which a surface representing the cell membrane could be added. These reconstructions of cells can be easily manipulated to enable the dynamic contact line of attaching cells to be measured for a model based on two-phase poroviscous flow equations. The three dimensional representations not only showed the changing morphology of spreading cells, but gave data on contact radius and area, contact angle and cell height. The main modelling prediction is a near contact line law, which is given by; Θ3 - Φ3 = 3 µ(n)ln(R/λ) (3nV - J(V,n,... )) γ where Θ is the dynamic contact angle (which remains to be determined by experimental means as the cell is spreading), Φ is the static contact angle, n the network density at the contact-line, J is the mass transfer rate from G- to F-actin at contact line and V equals the outward normal velocity of contact line. Once the method had been developed for glass surfaces, the influence on attachment and spreading of various material substrate and protein conditioning layers was investigated. This was achieved by using transparent thin film coated surfaces of titanium nitride and titanium oxide and pre-coating glass with fibronectin and albumin respectively. Three dimensional representations showed the ability to reproduce the different cell response to each surface and gave comparable morphologies to cells fixed for SEM and immunocytochemical staining.
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Kerr, Malcolm James. "Interactive garment design using three-dimensional surface modelling tehniques." Thesis, Queen's University Belfast, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292543.
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Lattuada, Roberto. "A triangulation based approach to three dimensional geoscientific modelling." Thesis, Birkbeck (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312757.
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Johns, David Philip. "A three-dimensional frequency-domain transmission-line modelling method." Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318645.
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Park, Soojin. "Modelling soil-landform continuum on a three-dimensional hillslope." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.670238.
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Taylor, Richard. "Finite element modelling of three dimensional fluid-structure interaction." Thesis, Swansea University, 2013. https://cronfa.swan.ac.uk/Record/cronfa42308.
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This work is focused on the numerical modelling of fluid-structure interaction in three dimensions. Both internal and external laminar flow around flexible bodies are considered. The fluid flow simulated is based on the incompressible Navier-Stokes equations and the general focus is on laminar Newtonian flow. The streamline upwind/ pressure stabilising Petrov-Galerkin (SUPG/PSPG) method is employed to achieve a stable low order finite element discretisation of the fluid, while the solid is discretised spatially by a standard Galerkin finite element approach. The behavior of the solid is governed by Neo-Hooke elasticity. For temporal discretisation the discrete implicit generalised-alpha method is employed for both the fluid and the solid domains. The motion of the fluid mesh is solved using an arbitrary Lagrangian-Eulerian (ALE) scheme employing a nonlinear pseudo-elastic mesh update method. The fluid-solid interface is modelled using a finite element interpolation method that allows for non-matching meshes and satisfies the required conservation laws. The resulting sets of fully implicit strongly coupled nonlinear equations are then decomposed into a general framework consisting of fluid, interface and solid domains. These equations are then solved using different solution techniques consisting of strongly coupled monolithic Newton and block Gauss-Seidel methods as well as a weakly coupled novel staggered scheme. These solvers are employed to solve a number of three dimensional numerical examples consisting of: External flow: o a soft elastic beam fixed at both ends o a thin cantilever plate.
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Wang, Lei Carleton University Dissertation Engineering Mechanical. "Tire modelling using a three-dimensional finite element method." Ottawa, 1990.
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Bricis, Anne. "Three dimensional simulation of cloth drape." Thesis, Loughborough University, 1995. https://dspace.lboro.ac.uk/2134/6932.
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Research has been carried out in the study of cloth modelling over many decades. The more recent arrival of computers however has meant that the necessary complex calculations can be performed quicker and that visual display of the results is more realistic than for the earlier models. Today's textile and garment designers are happy to use the latest two dimensional design and display technology to create designs and experiment with patterns and colours. The computer is seen as an additional tool that performs some of the more tedious jobs such as re-drawing, re-colouring and pattern sizing. Designers have the ability and experience to visualise their ideas without the need for photo reality. However the real garment must be created when promoting these ideas to potential customers. Three dimensional computer visualisation of a garment can remove the need to create the garment until after the customer has placed an order. As well as reducing costs in the fashion industry, realistic three dimensional cloth animation has benefits for the computer games and film industries. This thesis describes the development of a realistic cloth drape model. The system uses the Finite Element Method for the draping equations and graphics routines to enhance the visual display. During the research the problem of collision detection and response involving dynamic models has been tackled and a unique collision detection method has been developed. This method has proved very accurate in the simulation of cloth drape over a body model and is also described in the thesis. Three dimensional design and display are seen as the next logical steps to current two dimensional practices in the textiles industry. This thesis outlines current and previous cloth modelling studies carried out by other research groups. It goes on to provide a full description of the drape method that has been developed during this research period.
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Krasnovyd, Vanessa. "The importance of 3D modelling." Thesis, Дніпровський національний університет залізничного транспорту імені академіка В. Лазаряна, 2019. https://er.knutd.edu.ua/handle/123456789/14701.
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The work deals with 3D modelling as the technique which is used to create a 3D representation of any surface or object. The 3D modelling process creates a digital object that is capable of becoming fully animated, making it an important process for special effects and character animation.У роботі розглядається 3D-моделювання як техніка, яка використовується для створення 3D-зображення будь-якої поверхні чи об'єкта. Процес 3D-моделювання створює цифровий об’єкт, який здатний стати повністю анімованим, що робить його важливим процесом для спеціальних ефектів та анімації персонажів.
Работа посвящена трехмерному моделированию как технике, которая используется для создания трехмерного представления любой поверхности или объекта. Процесс трехмерного моделирования создает цифровой объект, который способен стать полностью анимированным, что делает его важным процессом для специальных эффектов и анимации персонажей.
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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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Costa, Rui Carlos Faria Gameiro da. "Three-dimensional modelling of cohesive sediment transport in estuarine environments." Thesis, University of Liverpool, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262293.
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Campos, Antonio Guilherme Rocha. "Three-dimensional digital waveguide mesh modelling for room acoustic simulation." Thesis, University of York, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.423754.
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Stockley, Edward William. "Three-dimensional reconstruction and electronic modelling of CA1 hippocampal neurones." Thesis, University of Southampton, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295927.
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Willman, E. J. "Three dimensional finite element modelling of liquid crystal electro-hydrodynamics." Thesis, University College London (University of London), 2009. http://discovery.ucl.ac.uk/16162/.
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Liquid crystals (LC) are used in new applications of increasing complexity and smaller dimensions. This includes complicated electrode patterns and devices incorporating three dimensional geometric shapes, e.g. grating surfaces and colloidal dispersions. In these cases, defects in the liquid crystal director field often play an important part in the operation of the device. Modelling of these devices not only allows for a faster and cheaper means of optimising the design, but sometimes also provides information that would be difficult to obtain experimentally. As device dimensions shrink and complex geometries are introduced, one and two dimensional approximations become increasingly inaccurate. For this reason, a three dimensional finite element computer model for calculating the liquid crystal electro-hydrodynamics is programmed. The program uses the Q-tensor description allowing for variations in the liquid crystal order and is capable of accurately modelling defects in the director field. The aligning effect solid surfaces has on liquid crystals, known as anchoring, is essential to the operation of nearly all LC devices. A simplifying assumption often made in LC modelling is that of strong anchoring (the LC orientation is fixed at the LC- solid surface interface). However, in small scale structures with high electric fields and curved surfaces this assumption is often not accurate. A general expression that can be used to represent various weak anchoring types in the Landau-de Gennes theory is introduced. It is shown how experimentally measurable values can be assigned to the coefficients of the expression. Using the Q-tensor model incorporating the weak anchoring expression, the operation of the Post Aligned Bistable Nematic (PABN) device is modelled. Two stable states, one of higher and the other of lower director tilt angle, are identified. Then, the switching dynamics between these two states is simulated.
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Young, Grace C. "Three-dimensional modelling of coral reefs for structural complexity analysis." Thesis, University of Oxford, 2017. http://ora.ox.ac.uk/objects/uuid:cde6d4fd-a2a6-4d31-b37c-adca785dc614.
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Coral reefs are some of Earth's most biodiverse and economically valuable ecosystems. Simultaneously they are among the most threatened by anthropogenic factors including global climate change. Their unique three-dimensional (3D) structural complexity is part of what enables them to provide their ecosystem services. It strongly affects species richness, abundance, and other indicators of ecosystem health. This thesis explores the relationship between coral reef 3D structural complexity and ecosystem features. It has developed a new, low-cost method for creating and analysing photogrammetric 3D models of shallow reefs from diver-held camera footage. 3D models are analysed at scales 1-175 cm in terms of point-to-point distances, linear rugosity (R), fractal dimension (D), and vector dispersion (1/k). The 3D models' accuracy and precision were determined by comparisons with ground truths. The 3D models have root mean square errors of 1.35-1.48 cm in the X, Y and Z dimensions. Values of R from the 3D models were 86.8% accurate compared to in-situ chain-and-tape measurements. Values of D and 1/k were 86.9-99.6% accurate compared with ground truths from 3D printed objects modelled underwater. Data collected around Utila, Bay Islands, Honduras in the Caribbean showed that 3D metrics automatically calculated from the 3D models had the same predictive power for fish abundance and diversity as the more traditional Habitat Assessment Score (HAS). Like HAS, the 3D metrics explained 12-34% of variation in the fish data. A controlled experiment furthermore tested how 1/k affected sessile epibenthic organism settlement around Utila after one year. Results from approximately 200 3D printed recruitment tiles showed that 1/k significantly affected algae settlement, but not coral spat, polychaete, sponge, or bryozoan settlement. The results suggested that the surfaces of artificial reefs can be designed to minimise algal recruitment and that the availability of sheltered, reef-facing area influences epibenthic settlement more strongly than 1/k at the 1 cm scale. Finally, a convolutional neural network (CNN) learned patterns between the 3D models and fish data with just 85 data points. The CNN is a promising approach for analysing larger data sets without 3D metrics. We suggest 3D models become a standard approach for measuring reef structural complexity. Not only can they explain as much variation in fish abundance and diversity as traditional measurements, but also they can nondestructively produce a variety of 3D metrics at numerous spatial scales and keep a permanent record of reef structure over time.
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Vieira, da Silva Nuno Miguel. "Three-dimensional modelling and inversion of controlled source electromagnetic data." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/9120.
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The marine Controlled Source Electromagnetic (CSEM) method is an important and almost self-contained discipline in the toolkit of methods used by geophysicists for probing the earth. It has increasingly attracted attention from industry during the past decade due to its potential in detecting valuable natural resources such as oil and gas. A method for three-dimensional CSEM modelling in the frequency domain is presented. The electric field is decomposed in primary and secondary components, as this leads to a more stable solution near the source position. The primary field is computed using a resistivity model for which a closed form of solution exists, for example a homogeneous or layered resistivity model. The secondary electric field is computed by discretizing a second order partial differential equation for the electric field, also referred in the literature as the vector Helmholtz equation, using the edge finite element method. A range of methods for the solution of the linear system derived from the edge finite element discretization are investigated. The magnetic field is computed subsequently, from the solution for the electric field, using a local finite difference approximation of Faraday’s law and an interpolation method. Tests, that compare the solution obtained using the presented method with the solution computed using alternative codes for 1D and 3D synthetic models, show that the implemented approach is suitable for CSEM forward modelling and is an alternative to existing codes. An algorithm for 3D inversion of CSEM data in the frequency domain was developed and implemented. The inverse problem is solved using the L-BFGS method and is regularized with a smoothing constraint. The inversion algorithm uses the presented forward modelling scheme for the computation of the field responses and the adjoint field for the computation of the gradient of the misfit function. The presented algorithm was tested for a synthetic example, showing that it is capable of reconstructing a resistivity model which fits the synthetic data and is close to the original resistivity model in the least-squares sense. Inversion of CSEM data is known to lead to images with low spatial resolution. It is well known that integration with complementary data sets mitigates this problem. It is presented an algorithm for the integration of an acoustic velocity model, which is known a priori, in the inversion scheme. The algorithm was tested in a synthetic example and the results demonstrate that the presented methodology is promising for the improvement of resistivity models obtained from CSEM data.
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Dongre, Arundhati. "Modelling lymphangioleiomyomatosis (LAM) using two-dimensional and three-dimensional in vitro co-culture systems." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/50037/.
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Background: Lymphangioleiomyomatosis (LAM) is a rare progressive neoplastic cystic lung disease that primarily affects women of child bearing age leading to lung destruction, respiratory failure and death. Thought to be a consequence of dysregulated protease expression, cells of unknown origin accumulate in the lung, often forming clusters or nodules of cells with both melanocytic and smooth muscle properties. Some of these cells, known as LAM cells, have bi-allelic mutations in TSC2 resulting in constitutive mTOR activation. However LAM nodules are heterogeneous structures and genotyping analyses suggest that cells without LOH for TSC2 including wild-type fibroblasts are also common within LAM nodules. Hypotheses and aims: We hypothesise that LAM cells recruit wild-type fibroblasts and modify their properties to generate a permissive microenvironment, akin to a tumour stroma including the production and activation of matrix-degrading proteases which contribute to the destruction of the lung parenchyma. This study has therefore deigned in vitro co-culture models with an aim to study the expression patterns and activation of proteases in a LAM lung leading to matrix destruction. Another aim was also to characterise transcriptional differences normal human lung fibroblasts (NHLFs) and LAM-associated fibroblasts (LAFs) and to investigate changes in their gene expression when cultured together with a model LAM cell line, 621-101 angiomyolipoma cells which were derived from a LAM patient and have bi-allelic loss of TSC2. Methods: In vitro 2-dimensional (2D) and 3-dimensionalD (3D) co-culture models were designed and validated using fibroblasts characterised and isolated from 4 LAM lung donors, now termed LAFs, and 621-101 cells. The 3D extracellular matrix (ECM) incorporated the two cell types in a 10:1 ratio embedded in a basement membrane extract (BME) mimicking the lung matrix. An organotypic spheroid model was also developed incorporating both cell types thereby mimicking a LAM nodule. 6 LAM lung and 3 normal lung tissue donors were screened for candidate proteases in LAM pathology using qRT-PCR and identified upregulated proteases which may contribute to a role in LAM pathology. These findings were verified in the 2D and 3D in vitro models as well as ex vivo tissue using a variety of immunostaining techniques, activity assays and ELISA. Lastly, commercially bought NHLF (n=3) and LAF (n=3) were cultured in the presence or absence of 621-101 cells in the 2D Boyden chamber co-culture model. LAF and NHLF RNA was analysed using Affymetrix Human Genome U133 Plus 2.0 Arrays and Genomics Suite and Pathway (Partek). Findings were validated by multiplex assay and immunohistochemistry in 2D and 3D in vitro models and tissue respectively. Inflammatory cell migration and function was examined in co-culture model and LAM tissue. Results: The 3D BME model showed that TSC2-/- 621-101 cells and fibroblasts spontaneously form aggregates and clump together akin to a LAM nodule. The two cell types exhibited strong heterotypic cell-cell adhesive forces and resulted in strictly spherical spheroids. The 3D models designed all showed expression of markers of LAM nodules thereby representing LAM nodules in a dish. Of 30 proteases screened, cathepsin K gene expression was increased almost 15-fold in LAM lung compared to normal tissue and was also found to be elevated in 3D BME model. Cathepsin K in LAM tissue was expressed in the LAM nodules associated with cysts and was expressed exclusively by fibroblasts in the 3D spheroid model. As cathepsin K requires low pH for activity it was determined if LAFs and TSC2-/- cells can acidify the extracellular space. TSC2-/- cells but not LAFs decreased extracellular pH, over 24 hours and pH values < 7 were associated with increased cathepsin K activity in co-cultures. TSC2-/- cells expressed membrane transporters associated with extra-cellular acidification and inhibitors of the sodium bicarbonate co-transporters, carbonic anhydrases and mTOR reduced the pH gradient and decreased CTSK activity in co-cultures. Transcriptomic analysis using the 2D co-culture model showed 148 genes were significantly altered in both NHLF and LAF by 621-101 cells. Soluble factors from 621-101 cells induce pro-inflammatory transcriptional changes in both NHLFs and LAFs and pathway analysis showed enhanced chemokine signalling which highlighted stimulation of mainly the C-X-C motif chemokines and chemokine receptor signalling. The analysis identified 6 C-X-C motif chemokines all possessing a cognate receptor. The gene and protein expression of these chemokines was validated in the in vitro models and in ex vivo LAM lung tissue. Conclusions: The in vitro models are versatile and mimic the LAM lung nodule and environment. A potent matrix degrading protease possibly playing a role in LAM has been identified and using the in vitro models a possible mechanism of activation of CTSK resulting from a synergistic relationship between TSC2-/- cells and LAFs has been demonstrated. Also, soluble factors from the TSC2-/- LAM cell line elicit changes in gene expression in co-cultured fibroblasts. Chemokine signalling is associated with cell migration; elevated chemokine expression may be associated with the recruitment of inflammatory cells to the LAM nodule. The identification of these mechanisms and pathways opens up new avenues for therapeutic interventions in LAM.
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Ghodoosipour, Behnaz. "Three dimensional groundwater modeling in Laxemar-Simepevarp guaternary deposits." Thesis, KTH, Mark- och vattenteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-171841.
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Groundwater is one of the main sources of drinking water in Sweden. Groundwater fluctuations and the detection of flow direction is of significant environmental importance especially when there is a risk for transport of contaminations. The Swedish Nuclear Fuel and Waste Management Company (SKB) has done detailed geotechnical investigations at two potential sites for a final nuclear waste deposition. This report presents the results from groundwater modeling in quaternary deposits in one of these sites. A steady state three dimensional groundwater model was developed for a 71 km2 large area in the Laxemar-Simpevarp, 320 km south of Stockholm close to the nuclear power plant Simpevarp. For this purpose, the Groundwater Modelling System (GMS) was used. The model uses finite difference method to solve the partial differential equation for the water movement with constant density through porous medium. The main objectives were to predict the groundwater heads and the flow directions, and to study the water balance. A conceptual model approach was used by creating five heterogynous soil and rock layers. GIS (Geographic Information System) was used to create top and bottom elevation of the layers by interpolating the GIS data. The model was calibrated using observation data in groundwater monitoring wells and the optimum values for recharge and hydraulic values were found. The numerical simulation was done for two different grid sizes (511×316 m2 and 255×158 m2) referred to coarse and fine grid model respectively. Results from the multilayer model showed flow towards the sea and in the quaternary deposits but not in high elevated rocks. The water balance in the multilayer model was satisfied in both grid sizes. The 3D groundwater model GMS was successfully applied to the large Laxemar-Simpevarp region. The choice of grid size was studied and better agreements between observed and simulated groundwater heads were found in the finer grid model. Large simulation errors in some of the observation wells can indicate GMS model’s weakness in modelling thin soil layers and large variance in topography.
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Planitz, Brigit Maria. "A correspondence framework for surface matching algorithms." Queensland University of Technology, 2004. http://eprints.qut.edu.au/16001/.
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Computer vision tasks such as three dimensional (3D) registration, 3D modelling, and 3D object recognition are becoming more and more useful in industry, and have application such as reverse CAD engineering, and robot navigation. Each of these applications use correspondence algorithms as part of their processes. Correspondence algorithms are required to compute accurate mappings between artificial surfaces that represent actual objects or scenes. In industry, inaccurate correspondence is related to factors such as expenses in time and labour, and also safety. Therefore, it is essential to select an appropriate correspondence algorithm for a given surface matching task. However, current research in the area of surface correspondence is hampered by an abundance of applications specific algorithms, and no uniform terminology of consistent model for selecting and/or comparing algorithms. This dissertation presents a correspondence framework for surface matching algorithms. The framework is a conceptual model that is implementable. It is designed to assist in the analysis, comparison, development, and implementation of correspondence algorithms, which are essential tasks when selecting or creating an algorithm for a particular application. The primary contribution of the thesis is the correspondence framework presented as a conceptual model for surface matching algorithms. The model provides a systematic method for analysing, comparing, and developing algorithms. The dissertation demonstrates that by dividing correspondence computation into five stages: region definition, feature extraction, feature representation, local matching, and global matching, the task becomes smaller and more manageable. It also shows that the same stages of different algorithms are directly comparable. Furthermore, novel algorithms can be created by simply connecting compatible stages of different algorithms. Finally, new ideas can be synthesised by creating only the stages to be tested, without developing a while new correspondence algorithm. The secondary contribution that is outlined is the correspondence framework presented as a software design tool for surface matching algorithms. The framework is shown to reduce the complexity of implementing existing algorithms within the framework. This is done by encoding algorithms in a stage-wise procedure, whereby an algorithm is separated into the five stages of the framework. The software design tool is shown to validate the integrity of restructuring existing algorithms within it, and also provide an efficient basis for creating new algorithms. The third contribution that is made is the specification of a quality metric for algorithms comparison. The metric is used to assess the accuracy of the outcomes of a number of correspondence algorithms, which are used to match a wide variety of input surface pairs. The metric is used to demonstrate that each algorithm is application specific, and highlight the types of surfaces that can be matched by each algorithm. Thus, it is shown that algorithms that are implemented within the framework can be selected for particular surface correspondence tasks. The final contribution made is this dissertation is the expansion of the correspondence framework beyond the surface matching domain. The correspondence framework is maintained in its original form, and is used for image matching algorithms. Existing algorithms from three image matching applications are implemented and modified using the framework. It is shown how the framework provides a consistent means and uniform terminology for developing both surface and image matching algorithms. In summary, this thesis presents a correspondence framework for surface matching algorithms. The framework is general, encompassing a comprehensive set of algorithms, and flexible, expanding beyond surface matching to major image matching applications.
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Planitz, Birgit. "A correspondence framework for surface matching algorithms." Thesis, Queensland University of Technology, 2004. https://eprints.qut.edu.au/16001/1/Brigit_Planitz_Thesis.pdf.
Full textAbstract:
Computer vision tasks such as three dimensional (3D) registration, 3D modelling, and 3D object recognition are becoming more and more useful in industry, and have application such as reverse CAD engineering, and robot navigation. Each of these applications use correspondence algorithms as part of their processes. Correspondence algorithms are required to compute accurate mappings between artificial surfaces that represent actual objects or scenes. In industry, inaccurate correspondence is related to factors such as expenses in time and labour, and also safety. Therefore, it is essential to select an appropriate correspondence algorithm for a given surface matching task. However, current research in the area of surface correspondence is hampered by an abundance of applications specific algorithms, and no uniform terminology of consistent model for selecting and/or comparing algorithms.
This dissertation presents a correspondence framework for surface matching algorithms. The framework is a conceptual model that is implementable. It is designed to assist in the analysis, comparison, development, and implementation of correspondence algorithms, which are essential tasks when selecting or creating an algorithm for a particular application.
The primary contribution of the thesis is the correspondence framework presented as a conceptual model for surface matching algorithms. The model provides a systematic method for analysing, comparing, and developing algorithms. The dissertation demonstrates that by dividing correspondence computation into five stages: region definition, feature extraction, feature representation, local matching, and global matching, the task becomes smaller and more manageable. It also shows that the same stages of different algorithms are directly comparable. Furthermore, novel algorithms can be created by simply connecting compatible stages of different algorithms. Finally, new ideas can be synthesised by creating only the stages to be tested, without developing a while new correspondence algorithm.
The secondary contribution that is outlined is the correspondence framework presented as a software design tool for surface matching algorithms. The framework is shown to reduce the complexity of implementing existing algorithms within the framework. This is done by encoding algorithms in a stage-wise procedure, whereby an algorithm is separated into the five stages of the framework. The software design tool is shown to validate the integrity of restructuring existing algorithms within it, and also provide an efficient basis for creating new algorithms.
The third contribution that is made is the specification of a quality metric for algorithms comparison. The metric is used to assess the accuracy of the outcomes of a number of correspondence algorithms, which are used to match a wide variety of input surface pairs. The metric is used to demonstrate that each algorithm is application specific, and highlight the types of surfaces that can be matched by each algorithm. Thus, it is shown that algorithms that are implemented within the framework can be selected for particular surface correspondence tasks.
The final contribution made is this dissertation is the expansion of the correspondence framework beyond the surface matching domain. The correspondence framework is maintained in its original form, and is used for image matching algorithms. Existing algorithms from three image matching applications are implemented and modified using the framework. It is shown how the framework provides a consistent means and uniform terminology for developing both surface and image matching algorithms.
In summary, this thesis presents a correspondence framework for surface matching algorithms. The framework is general, encompassing a comprehensive set of algorithms, and flexible, expanding beyond surface matching to major image matching applications.
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Ou, Jianhua. "Three-dimensional numerical modelling of interaction between soil and pore fluid." Thesis, University of Birmingham, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.578082.
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Boukanga, Noel Rupert Thierry. "Three dimensional modelling of generalized Newtonian fluids in domains including obstructions." Thesis, Loughborough University, 2010. https://dspace.lboro.ac.uk/2134/6936.
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Three dimensional flow regimes are encountered in many types of industrial flow processes such as filtration, mixing, reaction engineering, polymerization and polymer forming as well as environmental systems. Thus, the analyses of phenomena involved fluid flow are of great importance and have been subject of numerous ongoing research projects. The analysis of these important phenomena can be conducted in laboratory through experiments or simply by using the emerging computational fluid dynamics (CFD) techniques. But when dealing with three dimensional fluid flow problems, the complexities encountered make the analysis via the traditional experimental techniques a daunting task. For this reason, researchers often prefer to use the CFD techniques which with some care taken, often produce accurate and stable results while maintaining cost as low as possible. Many CFD codes have been developed and tested in the past decades and the results have been successful and thus encouraging researchers to develop new codes and/or improve existing codes for the solutions of real world problems. In this present project, CFD techniques are used to simulate the fluid flow phenomena of interest by solving the flow governing equations numerically through the use of a personal computer. The aim of this present research is to develop a robust and reliable technique which includes a novel aspect for the solution of three dimensional generalized Newtonian fluids in domains including obstructions, and this must be done bearing in mind that both accuracy and cost efficiency have to be achieved. To this end, the finite element method (FEM) is chosen as the CFD computational method. There are many existing FEM techniques namely the streamline upwind Petrov-Galerkin methods, the streamline diffusion methods, the Taylor-Galerkin methods, among others. But after a thorough analysis of the physical conditions (geometries, governing equations, boundary conditions, assumptions …) of the fluid flow problems to be solve in this project, the appropriate scheme chosen is the UVWP family of the mixed finite element methods. It is scheme originally developed to solve two dimensional fluid flow problems but since the scheme produced accurate and stable results for two dimensional problems, then attempt is made in this present study to develop a new version of the UVWP scheme for the numerical analysis of three dimensional fluid flow problems. But, after some initial results obtained using the developed three dimensional scheme, investigations were made during the course of this study on how to speed up solutions' convergence without affecting the cost efficiency of the scheme. The outcomes of these investigations yield to the development of a novel scheme named the modified three dimensional UVWP scheme. Thus a computer model based on these two numerical schemes (UVWP and the Modified UVWP) is developed, tested, and validated through some benchmark problems, and then the model is used to solve some complicated tests problems in this study. Results obtained are accurate, and stable, moreover, the cost efficiency of the computer model must be mentioned because all the simulations carried out are done using a simple personal computer.
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Qian, Aiguo, and 乾愛國. "Three-dimensional modelling of hydrodynamics and tidal flushing in Deep Bay." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B29799004.
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Richards, Andrew John. "An integrated approach to three-dimensional computer modelling of sedimentary basins." Thesis, Keele University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311738.
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Parkin, Geoffrey. "A three-dimensional variably-saturated subsurface modelling system for river basins." Thesis, University of Newcastle upon Tyne, 1996. http://hdl.handle.net/10443/3161.
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There are many circumstances where lateral flows in the upper soil layers above the regional groundwater table are important for hillslope and catchment hydrology, and in particular for the transport of contaminants. Perched water tables frequently occur in Quaternary drift sequences, reducing rates of recharge to the underlying aquifers and altering contaminant migration pathways; recent experimental and modelling studies have demonstrated the potential importance of lateral flows in the unsaturated zone, even in homogeneous soils; and lateral interflow at the hillslope scale, and its role in generating storm runoff, is the subject of intense current debate amongst hydrologists. A numerical model for simulating transient three-dimensional variably-saturated flow in complex aquifer systems (the Variably-Saturated Subsurface flow, or VSS, model), capable of representing these conditions, is presented in this thesis. The VSS model is based on the extended Richards equation for saturated as well as unsaturated conditions, and also includes capabilities for modelling surface-subsurface interactions, stream-aquifer interactions, prescribed head and flow boundary conditions, plant and well abstractions, and spring discharges. A simple but novel approach is taken to solving the three-dimensional non-linear Richards equation on a flexible-geometry finite-difference mesh, using Newton-Raphson iteration and an adaptive convergence algorithm. The VSS model is implemented as a module of the catchment flow and transport modelling system, SHETRAN. The reliability of the full SHETRAN modelling system is demonstrated using verification and validation tests, including comparisons against analytical solutions for simple cases, and simulations of storm runoff in a small Mediterranean catchment. Simulations of flow and contaminant transport in complex sequences of Quaternary drift deposits demonstrate the full capabilities of the modelling system under real-world conditions.
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Li, Xiaorong. "Three-dimensional modelling of tidal stream energy extraction for impact assessment." Thesis, University of Liverpool, 2016. http://livrepository.liverpool.ac.uk/3006766/.
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This research is themed around development of a tidal turbine simulation platform based on a three-dimensional oceanographic numerical modellling environment; more specifically, parameterization of effects of tidal turbine on flow current, turbulence, waves and sediment transport. In this context, the author adopts concepts in the current module, the turbulent module, the wave module and the sediment transport module of Finite-Volume, primitive equation Commmunity Ocean Model (FVCOM) to simulate the effects of tidal turbines. The retarding force concept is employed in the current module, working as an additional body force exerted on the water to simulate the turbine induced water deceleration. Three terms are added into the MY-2.5 turbulence closure to model turbine related turbulence generation, dissipation and turbulence length-scale interference. The built-in feature 'OBSTACLE' of the wave module is used to simulate the reduction of wave height caused by the turbine. The enhanced sediment suspension due to the turbine in motion is represented by an additional bottom shear stress term, entraining an extra portion of sediment particles from the bed into the water. Due to the fact that the bedload sediment transport module of FVCOM is not fully developed, it is not considered in this research; development of such a module is beyond the scope of this project. Coefficients of the turbine simulation terms are calibrated based on experimental data collected in the 'Total Environment Simulator laboratory flume' at the University of Hull, in which a prototype experiment was conducted. Small scale simulations carried out using ANSYS FLUENT also provided complementary calibration data. An idealized water channel model with mesh resolution fined down to the size of the simulated turbine is built to carry out the coefficient calibration. In general, the developed turbine simulation platform is capable of predicting reliable flow velocity, turbulent level, wave height and suspended sediment transport in the far wake region of the turbine, given proper values assigned to the relating coefficients. In addition, preliminary sensitivity tests are carried out to investigate the impact of these coefficients to the model's overall prediction to reveal the model's application range. Upon the satisfactory choices of the coefficients, the platform is applied to a 15m scale idealized single turbine case as well as a regional scale case based on the realistic hydrodynamics off the Anglesey coast, north-west of Wales. A series of single turbine tests are carried out with and without the turbine implementations, i.e. the coefficients represent turbine effects being switched on and off, in order to reveal the differences between the baseline case (no turbine) and case with turbine effects. Under realistic natural tidal and wave conditions, the Anglesey coast case showcases impact from a large scale turbine farm to both local and regional processes.
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Lum, Kah-Wai. "Three-dimensional computational modelling of a polymer electrolyte membrane fuel cell." Thesis, Loughborough University, 2003. https://dspace.lboro.ac.uk/2134/35974.
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The replacement of internal combustion engines used for transportation by polymer electrolyte membrane fuel cells (PEMFCs) is one goal of the future since they are clean, quiet, energy efficient and capable of quick start-up. At present, fuel cells are receiving much attention at both fundamental research, and technology development levels, but cost is the main factor that hinders the commercialisation of PEMFCs. In order to reduce cost, a better, fundamental description of fuel cell operation than is presently available is required. The operation of PEMFCs simultaneously involves electrochemical reactions, current distribution, fluid mechanics, multicomponent multiphase mixtures, and heat transfer processes. It is important to have a comprehensive mathematical model to provide improved understanding of the interactions between various electrochemical and transport phenomena in PEMFCs in order to aid in the design and optimisation of fuel cells. This thesis describes research at developing such a comprehensive model.
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Ferrer, Albero Ana. "Three-dimensional Multiscale Modelling and Simulation of Atria and Torso Electrophysiology." Doctoral thesis, Universitat Politècnica de València, 2017. http://hdl.handle.net/10251/88402.
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A better understanding of the electrical activity of the heart under physiological and pathological conditions has always been key for clinicians and researchers. Over the last years, the information in the P-wave signals has been extensively analysed to un-cover the mechanisms underlying atrial arrhythmias by localizing ectopic foci or high-frequency rotors. However, the relationship between the activation of the different areas of the atria and the characteristics of the P-wave signals or body surface poten-tial maps are still far from being completely understood. Multiscale anatomical and functional models of the heart are a new technological framework that can enable the investigation of the heart as a complex system.
This thesis is centred in the construction of a multiscale framework that allows the realistic simulation of atrial and torso electrophysiology and integrates all the anatom-ical and functional descriptions described in the literature. The construction of such model involves the development of heterogeneous cellular and tissue electrophysiolo-gy models fitted to empirical data. It also requires an accurate 3D representation of the atrial anatomy, including tissue fibre arrangement, and preferential conduction axes. This multiscale model aims to reproduce faithfully the activation of the atria under physiological and pathological conditions. We use the model for two main applica-tions. First, to study the relationship between atrial activation and surface signals in sinus rhythm. This study should reveal the best places for recording P-waves signals in the torso, and which are the regions of the atria that make the most significant contri-bution to the body surface potential maps and determine the main P-wave characteris-tics. Second, to spatially cluster and classify ectopic atrial foci into clearly differenti-ated atrial regions by using the body surface P-wave integral map (BSPiM) as a bi-omarker. We develop a machine-learning pipeline trained from simulations obtained from the atria-torso model aiming to validate whether ectopic foci with similar BSPiM naturally cluster into differentiated non-intersected atrial regions, and whether new BSPiM could be correctly classified with high accuracy.En la actualidad, una mejor compresión de la actividad eléctrica del corazón en condi-ciones fisiológicas y patológicas es clave para médicos e investigadores. A lo largo de los últimos años, la información derivada de la onda P se ha utilizado para intentar descubrir los mecanismos subyacentes a las arritmias auriculares mediante la localiza-ción de focos ectópicos y rotores de alta frecuencia. Sin embargo, la relación entre la activación de distintas regiones auriculares y las características tanto de las ondas P como de la distribución de potencial en la superficie del torso está lejos de entenderse completamente. Los modelos cardíacos funcionales y anatómicos son una nueva he-rramienta que puede facilitar la investigación relativa al corazón entendido como sis-tema complejo. La presente tesis se centra en la construcción de un modelo multiescala para la simula-ción realista de la electrofisiología cardíaca tanto a nivel auricular como de torso, integrando toda la información anatómica y funcional disponible en la literatura. La construcción de este modelo implica el desarrollo, en base a datos experimentales, de modelos electrofisiológicos heterogéneos tanto celulares como tisulares. Así mismo, es imprescindible una representación tridimensional precisa de la anatomía auricular, incluyendo la dirección de fibras y los haces de conducción preferentes. Este modelo multiescala busca reproducir fielmente la activación auricular en condiciones fisiológi-cas y patológicas. Su uso se ha centrado fundamentalmente en dos aplicaciones. En primer lugar, estudiar la relación entre la activación auricular en ritmo sinusal y las señales en la superficie del torso. Este estudio busca definir la mejor ubicación para el registro de las ondas P en el torso así como determinar aquellas regiones auriculares que contribuyen fundamentalmente a la formación y distribución de potenciales super-ficiales así como a las características de las ondas P. En segundo lugar, agrupar y cla-sificar espacialmente los focos ectópicos en regiones auriculares claramente diferen-ciables empleando como biomarcador los mapas superficiales de integral de la onda P (BSPiM). Se ha desarrollado para ello una metodología de aprendizaje automático en la que las simulaciones obtenidas con el modelo multiescala aurícula-torso sirven de entrenamiento, permitiendo validar si los focos ectópicos cuyos BSPiMs son similares se agrupan de forma natural en regiones auriculares no intersectadas y si BSPiMs nue-vos podrían ser clasificados prospectivamente con gran precisión.
Avui en dia, una millor comprenssió de l'activitat elèctrica del cor en condicions fisio-lògiques i patològiques és clau per a metges i investigadors. Al llarg dels últims anys, la informació derivada de l'ona P s'ha utilitzat per intentar descobrir els mecanismes subjacents a les arítmies auriculars mitjançant la localització de focus ectòpics i rotors d'alta freqüència. No obstant això, la relació entre l'activació de diferents regions auri-culars i les característiques tant de les ones P com de la distribució de potencial en la superfície del tors està lluny d'entendre's completament. Els models cardíacs funcionals i anatòmics són una nova eina que pot facilitar la recerca relativa al cor entès com a sistema complex. La present tesi es centra en la construcció d'un model multiescala per a la simulació realista de la electrofisiologia cardíaca tant a nivell auricular com de tors, integrant tota la informació anatòmica i funcional disponible en la literatura. La construcció d'aquest model implica el desenvolupament, sobre la base de dades experimentals, de models electrofisiològics heterogenis, tant cel·lulars com tissulars. Així mateix, és imprescindible una representació tridimensional precisa de l'anatomia auricular, in-cloent la direcció de fibres i els feixos de conducció preferents. Aquest model multies-cala busca reproduir fidelment l'activació auricular en condicions fisiològiques i pa-tològiques. El seu ús s'ha centrat fonamentalment en dues aplicacions. En primer lloc, estudiar la relació entre l'activació auricular en ritme sinusal i els senyals en la superfí-cie del tors. A més a més, amb aquest estudi també es busca definir la millor ubicació per al registre de les ones P en el tors, així com, determinar aquelles regions auriculars que contribueixen fonamentalment a la formació i distribució de potencials superfi-cials a l'hora que es caracteritzen les ones P. En segon lloc, agrupar i classificar espa-cialment els focus ectòpics en regions auriculars clarament diferenciables emprant com a biomarcador els mapes superficials d'integral de l'ona P (BSPiM). És per això que s'ha desenvolupat una metodologia d'aprenentatge automàtic en la qual les simulacions obtingudes amb el model multiescala aurícula-tors serveixen d'entrenament, la qual cosa permet validar si els focus ectòpics, llurs BSPiMs són similars, s'agrupen de for-ma natural en regions auriculars no intersectades i si BSPiMs nous podrien ser classifi-cats de manera prospectiva amb precisió.
Ferrer Albero, A. (2017). Three-dimensional Multiscale Modelling and Simulation of Atria and Torso Electrophysiology [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/88402
TESIS
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Lindkvist, Gaute. "Indirect boundary element methods for modelling bubbles under three dimensional deformation." Thesis, Deaprtment of Engineering Systems and Management, 2009. http://hdl.handle.net/1826/3098.
Full textAbstract:
The nonlinear behaviour of gas and vapour bubbles is a complex phenomenon
which plays a signi cant role in many natural and man-made processes.
For example, bubbles excited by an acoustic eld play important roles in
lithotripsy, drug delivery, ultrasonic imaging, surface cleaning and give rise
to the phenomenon of sonoluminescence (light emission from a bubble excited
by sound). In such contexts, the oscillation of even a single bubble is not
yet fully understood, let alone the behaviour of multiple bubbles interacting
with each other. An essential part of understanding such problems is un-
derstanding the complex and sometimes unpredictable coupling between the
oscillation of the bubble volume and the bubble shape, a problem requiring
experimental research, theoretical work and numerical studies.
In this Thesis we focus on numerical simulation of a single gas bubble
oscillating in a free liquid. Previously, such numerical simulations have al-
most exclusively assumed axisymmetry and small amplitude oscillations. To
avoid these assumptions we build upon and extend previous boundary ele-
ment methods used for three dimensional simulations of other bubble prob-
lems. We use high order elements and parallel processing to yield an indirect
boundary element method capable of capturing ne surface e ects on three
dimensional bubbles subjected to surface tension, over extended periods of
time.
We validate the method against the classical Rayleigh-Plesset equation
for spherical oscillation problems before validating the indirect boundary el-
ement method and the method used by Shaw (2006), against each other, on
several small amplitude axisymmetric oscillation problems. We then proceed
to study near-resonant non-axisymmetric shape oscillations of order 2 and 4
and the e ect these oscillations have on higher order modes, with a level of
detail we believe has not been achieved in a non-axisymmetric study before.
We also con rm some predictions made by Pozrikidis' on resonant interac-
tions between the second order modes and the volume mode in addition.
Finally we study the spherical instability of a bubble trapped in a uniform
acoustic eld, demonstrating, as expected, that instabilities show up in all
resonant shape modes, including non-axisymmetric ones.
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Islam, Mohammad Saidul. "Three-dimensional modelling of particulate deposition in the human respiratory tract." Thesis, Queensland University of Technology, 2018. https://eprints.qut.edu.au/115472/1/115472_9028200_mohammad_saidul_islam_thesis.pdf.
Full textAbstract:
This study is the first-ever approach to simulate particulate matter transport and deposition in the terminal bronchioles of the 17-generation, whole lung model by considering a possible entire branching pattern. The anatomically explicit, digital 17-generation conduit model is generated from the high-resolution CT data. A comprehensive size- and shape-specific particle transport and deposition study is performed for different physical conditions and finds a new deposition pattern for a realistic anatomical model. The present findings would potentially help the targeted drug delivery system design and increase the efficiency of the drug delivery to the specific positions in the pulmonary airways.
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Mantle, Emma Jane. "An evaluation of 3D building modelling and visualisation packages for enhancing public participation within the planning process." Thesis, University of South Wales, 2007. https://pure.southwales.ac.uk/en/studentthesis/an-evaluation-of-3d-building-modelling-and-visualisation-packages-for-enhancing-public-participation-within-the-planning-process(9e7f4a54-2fde-4723-ada8-17412b5f9efe).html.
Full textAbstract:
This thesis will look at the importance of 3D Visualization within the planning process and addresses the issue of improving public participation within urban regeneration. The main aim of this research is therefore to discover what type of model the public require in terms of understanding future developments, which may in turn help them engage in the planning process. In order to achieve the main aim several other aims need to be established, such as; identifying the capacity of the profession in Wales to deliver 3D models of urban environments, evaluating software solutions to create 3D models of urban environments, and to explore emerging techniques that might contribute to the efficiency and economy of producing models of urban environments. These aims were realised through conducting surveys which targeted the Building Design Profession (BDP) and established which software packages were being used and for what purpose. A second survey was also conducted by means of an exhibition, which aimed to establish what the public require in regards to being presented with proposed developments. Other aims were realized through conducting trials. These examined the usability of different 3D CAD packages and the possibility of integrating CAD data with GIS, and how it could be used to quicken the modeling process. Results from these trials showed that through the use of workarounds there are possibilities of integrating CAD and GIS data. The research reported here indicates that members of the public have trouble understanding 2D Plans and Elevations and the data consistently demonstrates that more than 40% of participants chose 3D technology as a more understandable method of being shown future developments. The results from the two surveys show that although the majority (42.4%) of participants selected 3D technology as their preferred option, only 28% of participating Building Design Professionals in Wales use 3D computer packages, albeit not for presenting propose urban regeneration projects to the public. From the outset of this research the purpose has been to evaluate whether public participation will be increased if 3D technologies are provided to showcase proposed developments. The more efficient the modelling process, the more feasible and likely it will be that 3D CAD will one day be a paramount tool within the Planning Process. Numerous techniques were included to examine this efficiency.
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Sawadogo, Ousmane. "Coupled fully three-dimensional mathematical modelling of sediment deposition and erosion in reservoirs." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/96707.
Full textAbstract:
Thesis (PhD)--Stellenbosch University, 2015.ENGLISH ABSTRACT: The investigation of reservoir sedimentation has become an important and valuable research topic in engineering practice. Sediment deposition in reservoirs can affect ood levels, drainage for agriculture land, pumpstation and hydropower operation and navigation. An extensive review of the technical literature pertaining to suspended sediment transports as well as deposited sediment ushing from reservoirs has shown that most studies on sediment are still based on empirical formulas and experimental work, despite the availability of sophisticated computers. This is because sediment transport and particularly sediment deposition and erosion are complex processes, that involve the interaction of many physical factors which are not easily modelled numerically. In addition, most of the existing three-dimensional numerical models are not coupled hydrodynamic and sediment transport models. They first simulate the velocity field and water depth and then the concentration and bed change are calculated. Furthermore, they are not fully three-dimensional models for using layer-averaged approaches in conjunction with Saint-Venant equations. The key objective of the present research was to develop a coupled fully three-dimensional (3D) numerical model based on Navier-Stokes equations which includes both the sediment transport component and hydrodynamic parameters. In this regard, a physical model was set up in a laboratory ume in order to investigate the bottom outlet sediment ushing under pressure in a controlled environment. The proposed coupled fully 3D numerical model was used to simulate the experimental tests. Results from these simulations were in good agreement with the measurements. The geometric features of the scour hole (temporal and spatial hole development) upstream of the bottom outlet were reasonably well predicted compared to the experimental data. Furthermore, the velocity field upstream of the bottom outlet was in good agreement with measurements. The proposed numerical model can be considered reliable provided that the model is correctly set up to reflect the condition of a particular case study. Finally, the coupled fully 3D numerical model for turbulent suspended sediment transport in reservoirs was validated against a range of typical reservoir sediment transport and deposition laboratory flume cases. The proposed suspended sediment transport model successfully predicted both sediment deposition and entrainment processes and therefore, it can be used for turbulent suspended sediment transport assessments in reservoirs.
AFRIKAANSE OPSOMMING: Die ondersoek van damtoeslikking het 'n belangrike navorsing onderwerp in ingenieurswese praktyk geword. Sedimentdeponering in damme kan vloed vlakke, dreinering van landbo grond sowel as pompstasie en hidrokrag werking en navigasie benvloed. 'n Omvattende ontleding van die tegniese literatuur met betrekking tot gesuspendeerde sedimentvervoer asook die spoel van gedeponeerde sediment uit reservoirs het getoon dat die meeste studies oor sediment steeds op empiriese formules en eksperimentele werk gebaseer is, ten spyte van die beskikbaarheid van gesofistikeerde rekenaars. Dit is omdat sedimentvervoer en veral sedimentafsetting en -erosie komplekse prosesse is, wat die interaksie van baie fisiese faktore behels en nie moeiteloos numeries gemodelleer kan word nie. Daarbenewens, in die meeste van die bestaande drie -dimensionele numeriese modelle is die hidrodinamika en sedimentvervoer modelle nie gekoppel nie. Die numeriese modelle simuleer eerstens die snelheid veld en waterdiepte en dan word die sedimentkonsentrasie en bedverandering bereken. Verder is die bestaande modelle nie ten volle driedimensioneel nie, en gebruik laag-gemiddelde benadering in samewerking met Saint- Venant vergelykings. Die hoofdoelwit van die huidige navorsing was om 'n gekoppelde volle drie -dimensionele (3D) numeriese model gebaseer op Navier -Stokes-vergelykings wat beide die sediment vervoer komponent en hidrodinamiese parameters insluit, te ontwikkel. In hierdie verband is 'n fisiese model opgestel in 'n laboratorium kanaal om die bodem uitlaat spoel van sediment onder druk in 'n beheerde omgewing te ondersoek. Die voorgestelde gekoppelde 3D numeriese model is gebruik om die eksperimentele toetse na te boots. Resultate van hierdie simulasies het goed ooreengestem met die metings. Die geometriese eienskappe van die erosie gat (tyd en ruimtelike gatontwikkeling) stroomop van die bodemuitlaat was redelik goed voorspel vergeleke met die eksperimentele data. Verder is die snelheid veld stroomop van die bodem uitlaat ook goed voorspel. Die voorgestelde numeriese model kan beskou word as betroubaar met die wete dat die model korrek opgestel is om die toestand van 'n bepaalde gevallestudie te weerspiel. Ten slotte, is n gekoppelde 3D numeriese model vir turbulente gesuspendeerde sediment vervoer in reservoirs ontwikkel en getoets teen 'n reeks laboratorium kanaal eksperimente. Die voorgestelde gesuspendeerde sediment vervoer model voorspel suksesvol beide die sediment afsetting- en erosieprosesse en daarom kan dit gebruik word vir die simulasie van turbulente gesuspendeerde sediment vervoer in damme.
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Cleak, James Gilbert Edwin. "Validation of viscous, three-dimensional flow calculations in an axial turbine cascade." Thesis, Durham University, 1989. http://etheses.dur.ac.uk/6429/.
Full textAbstract:
This thesis presents a detailed investigation of the capability of a modern three-dimensional Navier-Stokes solver to predict the secondary flows and losses in a linear cascade of high turning turbine rotor blades. Three codes were initially tested, to permit selection of the best of the available numerical solvers for this case. This program was then tested in more detail. Results showed that although very accurate prediction of the effects of inviscid fluid mechanics is now possible, the Reynolds stress modelling can have profound effects upon the quality of the solutions obtained. Solutions using two different calculation meshes, have shown that the results are not significantly grid dependent. The flowfield of the cascade was traversed with hot-wires to obtain measurements of the turbulent Reynolds stresses. A turbulence generating grid was placed upstream of the cascade, to produce a more realistic inlet turbulence intensity. Results showed that regions of high turbulent kinetic energy are associated with regions of high total pressure loss. Calculation of eddy viscosities from the Reynolds stresses showed that downstream of the -cascade the eddy viscosity is fairly isotropic. Evaluation of terms in the kinetic energy equation, also indicated that both the normal and shear Reynolds stresses are important as loss producing mechanisms in the downstream flow. The experimental Reynolds stresses have been compared with those calculated from the eddy viscosity and velocity fields of Navier-Stokes predictions using a mixing length turbulence model, a one equation model, and K - ϵ model. It was found that in the separated, shear flows, agreement was poor, although the K - ϵ model performed best. Further experimental work is suggested to obtain data with which to determine the accuracy of the models within the blade and endwall boundary layers.
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Hess, Victor George. "Three-dimensional mathematical model of a high temperature polymer electrolyte membrane fuel cell." Doctoral thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/24481.
Full textAbstract:
Polymer electrolyte fuel cells are regarded as one of the most promising alternatives to the depleting and high pollutant fossil fuel energy sources. High temperature Polymer electrolyte fuel cells are especially suitable for stationary power applications. However, the length scale of a PEM fuel cells main components range from the micro over the meso to the macro level, and the time scales of various transport processes range from milliseconds up to a few hours. This combination of various spatial and temporal scales makes it extremely challenging to conduct in-situ measurements or other observations through experimental means. Thus, numerical simulation becomes a very important tool to help understand the underlying electrochemical dynamics and transient transport phenomena within PEM fuel cells. In this thesis research a comprehensive, three- dimensional mathematical model is developed which accounts for the convective and diffusive gas flow in the gas channel, multi-component diffusion in the porous backing layer, electrochemical reactions in the catalyst layers, as well as flow of charge and heat through the solid media. The governing equations which mathematically describe these transport processes, are discretized and solved using the finite-volume based software, Ansys FLUENT, with its in-built CFD-solvers. To handle the significant non-linearity stemming from these transport phenomena, a set of numerical under-relaxation schemes are developed using the programming language C++. Good convergence is achieved with these schemes, though the model is based on a serpentine single-channel flow approach. The model results are validated against experimental results and good agreement is achieved. The result shows that the activation overpotential is the greatest cause of voltage loss in a high temperature PEM fuel cell. The degree of oxygen depletion in the catalyst layer, under the ribs, is identified and quantified for a given set of input parameters. This factor is followed by membrane resistance to protonic migration. The model can thus be suitable applied as a tool to predict cell performance. The results also show that performance is influenced by not just one, but a combination of inter-related factors, thus temperature increases, and flow rate changes will only be effective if simultaneously, the concentration of inlet oxygen, and the mobility of proton-ions in the membrane is increased. Not only does the model results verify these phenomena, but provide a quantitative output for any given set of input parameters. It can therefore be suitably applied as an optimisation tool in high temperature PEM fuel cell design.