Дисертації: "Fluid Dynamic Modeling"

1

Cardillo, Giulia. "Fluid Dynamic Modeling of Biological Fluids : From the Cerebrospinal Fluid to Blood Thrombosis." Thesis, Institut polytechnique de Paris, 2020. http://www.theses.fr/2020IPPAX110.

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Dans cette thèse, trois modèles mathématiques ont été proposés, avec l’objectif de modéliser autant d’aspects complexes de la biomédecine, dans lesquels la dynamique des fluides du système joue un rôle fondamental: i) les interactions fluide-structure entre la pulsatilité du liquide céphalo-rachidien et la moelle épinière (modélisation analytique); ii) dispersion efficace d’un médicament dans l’espace sous-arachnoïdien (modélisation numérique); et iii) la formation et l’évolution d’un thrombus au sein du système cardiovasculaire (modélisation numérique).Le liquide céphalorachidien est un fluide aqueux qui entoure le cerveau et la moelle épinière afin de les protéger. Une connaissance détaillée de la circulation du liquide céphalorachidien et de son interaction avec les tissus peut être importante dans l’étude de la pathogenèse de maladies neurologiques graves, telles que la syringomyélie, un trouble qui implique la formation de cavités remplies de liquide (seringues) dans la moelle épinière.Par ailleurs, dans certains cas, des analgésiques - ainsi que des médicaments pour le traitement de maladies graves telles que les tumeurs et les infections du liquide céphalorachidien - doivent être administrés directement dans le liquide céphalorachidien. L’importance de connaître et de décrire l’écoulement du liquide céphalorachidien, ses interactions avec les tissus environnants et les phénomènes de transport qui y sont liés devient claire. Dans ce contexte, nous avons proposé: un modèle capable de décrire les interactions du liquide céphalo-rachidien avec la moelle épinière, considérant cela, pour la première fois, comme un milieu poreux imprégné de différents fluides (sang capillaire et veineux et liquide céphalo-rachidien); et un modèle capable d’évaluer le transport d’un médicament dans l’espace sousarachnoïdien, une cavité annulaire remplie de liquide céphalo-rachidien qui entoure la moelle épinière.Avec le troisième modèle proposé, nous entrons dans le système cardiovasculaire.Dans le monde entière, les maladies cardiovasculaires sont la cause principale de mortalité. Parmi ceux-ci, nous trouvons la thrombose, une condition qui implique la formation d’un caillot à l’intérieur d’un vaisseau sanguin, qui peut causer sa occlusion. À cet égard, un modèle numérique a été développé qui étudie la formation et l’évolution des thrombus, en considérant simultanément les aspects chimico-biomécaniques et dynamiques des fluides du problème. Dans le modèle proposé pour la première fois, l'importance du rôle joué par les gradients de contrainte de cisaillement dans le processus de thrombogenèse est pris en compte.Les modèles sélectionnés ont fourni des résultats intéressants. Tout d’abord, l’étude des interactions fluide-structure entre le liquide céphalo-rachidien et la moelle épinière a mis en évidence es conditions pouvant induire l’apparition de la syringomyélie. Il a été observé comment la déviation des valeurs physiologiques du module d’Young de la moelle épinière, les pressions capillaires dans l’interface moelle-espace sousarachnoïdien et la perméabilité des compartiments capillaire et veineux, conduisent à la formation de seringues.Le modèle de calcul pour l’évaluation de la dispersion pharmacologique dans l’espace sousarachnoïdien a permis une estimation quantitatif de la diffusivité effective du médicament, une quantité qui peut aider à l’optimisation des protocoles d’injections intrathécales.Le modèle de thrombogenèse a fourni un instrument capable d’étudier quantitativement l’évolution des dépôts de plaquettes dans la circulation sanguine. En particulier, les résultats ont fourni des informations importantes sur la nécessité de considérer le rôle de l’activation mécanique et de l’agrégation des plaquettes aux côtés de la substance chimique
In the present thesis, three mathematical models are described. Three different biomedical issues, where fluid dynamical aspects are of paramount importance, are modeled: i) Fluid-structure interactions between cerebro-spinal fluid pulsatility and the spinal cord (analytical modeling); ii) Enhanced dispersion of a drug in the subarachnoid space (numerical modeling); and iii) Thrombus formation and evolution in the cardiovascular system (numerical modeling).The cerebrospinal fluid (CSF) is a liquid that surrounds and protects the brain and the spinal cord. Insights into the functioning of cerebrospinal fluid are expected to reveal the pathogenesis of severe neurological diseases, such as syringomyelia that involves the formation of fluid-filled cavities (syrinxes) in the spinal cord.Furthermore, in some cases, analgesic drugs -- as well drugs for treatments of serious diseases such as cancers and cerebrospinal fluid infections -- need to be delivered directly into the cerebrospinal fluid. This underscores the importance of knowing and describing cerebrospinal fluid flow, its interactions with the surrounding tissues and the transport phenomena related to it. In this framework, we have proposed: a model that describes the interactions of the cerebrospinal fluid with the spinal cord that is considered, for the first time, as a porous medium permeated by different fluids (capillary and venous blood and cerebrospinal fluid); and a model that evaluates drug transport within the cerebrospinal fluid-filled space around the spinal cord --namely the subarachnoid space--.The third model deals with the cardiovascular system. Cardiovascular diseases are the leading cause of death worldwide, among these diseases, thrombosis is a condition that involves the formation of a blood clot inside a blood vessel. A computational model that studies thrombus formation and evolution is developed, considering the chemical, bio-mechanical and fluid dynamical aspects of the problem in the same computational framework. In this model, the primary novelty is the introduction of the role of shear micro-gradients into the process of thrombogenesis.The developed models have provided several outcomes. First, the study of the fluid-structure interactions between cerebro-spinal fluid and the spinal cord has shed light on scenarios that may induce the occurrence of Syringomyelia. It was seen how the deviation from the physiological values of the Young modulus of the spinal cord, the capillary pressures at the SC-SAS interface and the permeability of blood networks can lead to syrinx formation.The computational model of the drug dispersion has allowed to quantitatively estimate the drug effective diffusivity, a feature that can aid the tuning of intrathecal delivery protocols.The comprehensive thrombus formation model has provided a quantification tool of the thrombotic deposition evolution in a blood vessel. In particular, the results have given insight into the importance of considering both mechanical and chemical activation and aggregation of platelets

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2

Kachani, Soulaymane, and Georgia Perakis. "Modeling Travel Times in Dynamic Transportation Networks; A Fluid Dynamics Approach." Massachusetts Institute of Technology, Operations Research Center, 2001. http://hdl.handle.net/1721.1/5224.

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In this paper, we take a fluid dynamics approach to determine the travel time in traversing a network's link. We propose a general model for travel time functions that utilizes fluid dynamics laws for compressible flow to capture a variety of flow patterns such as the formation and dissipation of queues, drivers' response to upstream congestion or decongestion and drivers' reaction time. We examine two variants of the model, in the case of separable velocity functions, which gives rise to two families of travel time functions for the problem; a polynomial and an exponential family. We analyze these travel time functions and examine several special cases. Our investigation also extends to the case of non-separable velocity functions starting with an analysis of the interaction between two links, and then extending it to the general case of acyclic networks.

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3

Clinkinbeard, Nicholus Ryan. "Computational fluid dynamic modeling of acoustic liquid manipulation." [Ames, Iowa : Iowa State University], 2006.

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4

Jupp, Laurence. "Dynamic modeling of complex fluids under flow." Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288304.

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5

Jacobsson, Krister. "Dynamic modeling of Internet congestion control." Doctoral thesis, Stockholm : Electrical Engineering, Elektrotekniska system, Kungliga Tekniska högskolan, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4708.

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6

Cortes, Capetillo Azael Jesus. "Computational fluid dynamic modeling of in-duct UV air sterilisation systems." Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/9591/.

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In-duct UVC air sterilisation is a technology that can help in the reduction and control of airborne diseases. Nevertheless, improvements in sterilisation performance efficiency are required for the technology to succeed in an increasingly restricted energy society. Computational fluid Dynamics (CFD) was used to systematically improve the performance of in-duct UVC air sterilisation systems. The Discrete Ordinates method (DO) was used to model lamp irradiation, and a user defined function (UDF) to model the injection of microorganisms inside the duct to then calculate the average UV dose of the system, with this it was possible to reproduce test results published by EPA. After the CFD model was validated, operation parameters such as wall reflectivity, lamp location, lamp position, air velocity and airflow patterns were analysed. It was found that accurate information of UVC susceptibility for microorganisms in air was essential for the correct modeling of UVC air sterilisation systems using CFD, and current available data contain considerable variations that needed to be analysed and interpreted in an appropriate manner. It was also found that the DO method was appropriate to model lamp irradiation and could account for reflectivity, and that CFD was robust enough to reproduce lab tests results. Moreover it was found that airflow patterns, and lamp location and position influenced the sterilisation performance of a UVC system. Results include a comprehensive list of microorganisms UVC susceptibilities in air (Chapter 3); a set of CFD models that can be used for validation or calibration for future studies and a confirmation that CFD is capable to model in-duct UVC air sterilisation systems (Chapter 5). Ultimately this research presents a series of conclusions that will help on the design of more efficient in-duct UVC air sterilisation systems.

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Surendran, Mahesh. "Computational Fluid Dynamic Modeling of Natural Convection in Vertically Heated Rods." DigitalCommons@USU, 2016. https://digitalcommons.usu.edu/etd/5168.

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Natural convection is a phenomenon that occurs in a wide range of applications such as cooling towers, air conditioners, and power plants. Natural convection may be used in decay heat removal systems such as spent fuel casks, where the higher reliability inherent of natural convection is more desirable than forced convection. Passive systems, such as natural convection, may provide better safety, and hence have received much attention recently. Cooling of spent fuel rods is conventionally done using water as the coolant. However, it involves contaminating the water with radiation from the fuel rods. Contamination becomes dangerous and difficult for humans to handle. Further, the recent nuclear tragedy in Fukushima, Japan has taught us the dangers of contamination of water with nuclear radiation. Natural convection can perhaps significantly reduce the risk since it is self-sufficient and does not rely on other secondary system such as a blower as in cases of forced convection. The Utah State University Experimental Fluid Dynamics lab has recently designed an experiment that models natural convection using heated rod bundles enclosed in a rectangular cavity. The data available from this experiment provides and opportunity to study and validate computational fluid dynamics(CFD)models. The validated CFD models can be used to study multiple configurations, boundary conditions, and changes in physics(natural and/or forced convection). The results are to be validated using experimental data such as the velocity field from particle image velocimetry (PIV), pressure drops across various sections of the geometry, and temperature distributions along the vertically heated rods. This research work involves modeling natural convection using two-layer turbulence models such as k - ε and RST (Reynolds stress transport) using both shear driven (Wolfstein) and buoyancy driven (Xu) near-wall formulations. The interpolation scheme employed is second-order upwinding using the general purpose code STAR-CCM+. The pressure velocity coupling is done using the SIMPLE method. It is ascertained that turbulence models with two-layer formulations are well suited for modeling natural convection. Further it is established that k - ε and Reynolds stress turbulence models with the buoyancy driven (Xu)formulation are able to accurately predict the flow rate and temperature distribution.

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Chakraborty, Sanjib. "Dynamic Modeling and Simulation of Digital Displacement Machine." Thesis, Linköpings universitet, Fluida och mekatroniska system, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-85277.

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Improved efficiency, better controllability and low noise are the most demanding features form a displacement machine now-a-days. Most of the conventional displacement machines are basically a reciprocating pumping element controlled by valve plates or with the help of check valve [1]. This kind of hydraulic machines loose efficiency dramatically at partial displacement because all of the pistons remain at high pressure at the cycle time and due to pressure inside the piston leakage and shear losses increases. One approach to improve the efficiency of the displacement machine can be controlling each hydraulic piston by using programmable faster valves called digital valve. As the total displacement will be controlled digitally, the total system is called Digital Displacement Technology. In digital displacement machine it is possible to disconnect some of the pistons from the load and the piston will connect only with the low pressure side, minimizing losses due to leakage and shear. As the valve will control directly with digital controller it will eliminate the necessity of servo-hydraulic control required by conventional systems. Digital valves can open fully and close again with the input signal within one revaluation of the shaft, so it gives better control to the pumping element results reduction in hysteresis and increase the linearity of the pumping element. In Digital Displacement machines by controlling the valves pistons are connected with the machine when pressure is equal, but in the traditional machines piston connection was pre-determined with the shaft angle. By doing the piston control efficiency of the machine will improve and the sound generates for the decompression flow will be reduced [17]. Also energy storage and recovery can be possible by using accumulator.

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Larsen, Joshua. "Pore Scale Computational Fluid Dynamic Modeling| Approaches for Permeability Modeling and Particle Tracking Using Lattice Boltzmann Methods." Thesis, The University of Arizona, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10978423.

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Knowledge of colloid mobility is important for understanding nutrient cycling, the transport of some contaminants, and for developing environmental remediation systems such as geologic filters. The interaction forces between colloids and soil materials are central to colloid transport and immobilization. These forces act at the microscale (nanometers to microns) and include: fluid drag (friction), Brownian motion, gravity and buoyancy, and fluid chemical forces (including DLVO and van der Waals mechanisms). Most vadose zone studies, however, consider colloids at the continuum scale in terms of solute transport mechanisms using parametrized forms of the advection-dispersion equation and absorption isotherms. A comprehensive, generally applicable, well-documented and publicly available framework for simulating colloids at the microscale is still lacking.

Colloid transport and mobility are mechanisms that fundamentally occur at the microscale. As such, representation of the pore-structure needs to be obtained that is meaningful for the pore-scale fluid flow field and colloid mobility (pore-scale colloidal force balances cause the colloidal transport field to be different from the fluid flow field). At the same time, the pore-structure needs to be relevant for continuum-scale experiments or simulations. There are two ways by which a pore-structure can be obtained: by direct three-dimensional imaging (typically with x-ray tomographic techniques) or by reconstruction techniques that yield a synthetic, but presumably representative, pore-structure. Both techniques are examined in this dissertation, but the synthetic route must be used if little micro-scale information is available.

This dissertation addresses three main objectives. In chapter 2 it addresses the relation between image quality obtained with two different x-ray tomography techniques (a synchrotron and an industrial scanner) and the obtained flow field. Chapter 3 discusses the development of the LB-Colloids software package, while chapter 4 applies the code to data obtained from a breakthrough experiment of nanoparticulate TiO₂.

In chapter 2, pore-scale flow fields for Berea sand stone and a macropore soil sample were obtained with lattice Boltzmann simulations which were volume-averaged to a sample-scale permeability and verified with an observed sample-scale permeability. In addition, the lattice Boltzmann simulations were verified with a Kozeny-Carman equation. Results indicate that the simulated flow field strongly depends on the quality of the x-ray tomographic imagery and the segmentation algorithm used to convert gray-scale tomography data into binary pore-structures. More complex or advanced segmentation algorithms do not necessarily produce better segmentations when dealing with ambiguous imagery. It was found that the KC equation provided a reliable initial assessment of error when predicting permeability and can be used as a quick evaluation of whether simulations of the micro-scale flow field should be pursued. In the context of this study, this chapter indicated that LB is able to generate relevant pore-scale flow fields that represent sample-scale permeabilities. However, because the remainder of the study was focused on the development of a pore-scale colloid mobility framework we decided to focus primarily on synthetically-generated pore-structures. This also allowed us to focus on actual mechanisms that were free of imaging and segmentation artifacts.

Chapter 3 discusses the development of the LB-Colloids package. This simulation framework is able to simulate large collections of individual colloids through pore representations and porous media. The general workflow for users is as follows: 1) Obtain a pore structure by tomographic imaging or by synthetic means. The latter can be accomplished though the included PSPHERE module which is able to generate a random porous medium using user-supplied porosity and particle size. 2) The pore-scale fluid flow field in the porous medium is generated with a lattice Boltzmann method and a user-specified body force that controls the volume averaged Darcy velocity. 3) Mobility and attachment/detachment of colloids is simulated by accounting of the force balance (fluid drag, Brownian motion, gravity and buoyancy forces, and fluid-chemical forces including DLVO and van der Waals mechanisms). Colloid mobility is carried out at a submicron to nanometer scale and requires grid refinement of the LB flow field. To speed up computations the fluid-chemical forces are precomputed for every grid cell.

Because of computational considerations, the LB-Colloids package is presently only able to deal with 2D representations of the porous medium. Code-development and testing (chapter 4) would have taken too long for a full 3D approach. The main draw-back of the 2D approach is that these cannot accurately represent 3D pore-structures. However, no fundamental “new” mechanisms are needed for a 3D approach and we expect that this can be easily built into the clean and well-documented LB-colloids code. The LB-Colloids framework is applied on data obtained from a break-through experiment of TiO₂ nanoparticles. (Abstract shortened by ProQuest.)

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Scharf, Frank H. "Fluid dynamic and kinetic modeling of the near cathode region in thermal plasmas." Berlin Logos-Verl, 2008. http://d-nb.info/994080492/04.

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11

Maggiolo, Dario. "Numerical modeling and fluid-dynamic optimisation of fuel cells and flow batteries systems." Doctoral thesis, Università degli studi di Padova, 2017. http://hdl.handle.net/11577/3424775.

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Nowadays, the energy challenge is one of the largest driving forces behind many research efforts. Future energy strategies include smart ways to store and convert energy on demand. On this exciting perspective, fuel cells and flow batteries play a key role, the former in converting energy into propulsion, the latter in storing renewable energy surplus. Nevertheless, some main technological issues still must be overcome, such as limited peak performances often caused by poor fluid-mechanic efficiency. The fluid-dynamic optimisation of fuel cells and flow batteries systems is the main aim of the present thesis work. To this end, the focus is set on studying liquid-vapour two-phase flows and dispersion dynamics in fibrous porous media, by means of Lattice-Boltzmann numerical models, in order to catch the effects of microscale phenomena on macroscale features of both technologies. Present findings offer new insights into understanding fundamental physical behaviours in fuel cells and flow batteries, and give a guideline for good and innovative design practice.
Al giorno d'oggi, la sfida energetica è una delle più importanti spinte alla ricerca scientifica. Le strategie energetiche future includono vie alternative ed efficienti per stoccare e convertire l'energia su richiesta. In questa prospettiva entusiasmante, le celle a combustibile e le batterie a flusso svolgono un ruolo chiave, le prime nella conversione dell'energia in propulsione, le seconde nello stoccaggio dei surplus derivanti da energia rinnovabile. Tuttavia, rimangono ancora da superare alcuni importanti aspetti tecnologici, come ad esempio le limitate prestazioni di picco spesso causate da una scarsa efficienza fluido-meccanica. L'obiettivo principale della presente tesi è l'ottimizzazione fluidodinamica delle celle a combustibile e delle batterie a flusso. A tal fine, la ricerca si focalizza sullo studio dei flussi bifase liquido-vapore e delle dinamiche di dispersione in mezzi porosi, mediante modelli numerici Lattice-Boltzmann, al fine di studiare gli effetti dei fenomeni microscopici sulle caratteristiche macroscopiche di entrambe le tecnologie. I risultati di questo studio forniscono nuove interpretazioni nella comprensione dei comportamenti fisici fondamentali nelle celle a combustibile e nelle batterie di flusso, ed offrono linee guida per una buona e innovativa pratica di progettazione.

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Keyhan, Hooman. "Fluid structure interaction (FSI) based wind load modeling for dynamic analysis of overhead transmission lines." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114457.

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Electricity is a crucial form of energy in our societies, and transmission lines are key elements to ensure the reliability of electric power grids. Continuity of service is the main preoccupation of electric utilities, and this continuity may be disrupted by a large variety of sources and accidents. Transmission lines, by their intrinsic topology, remain the grid components that are the most exposed to climatic sources of disruption.The most common and important source of dynamic loads on transmission lines results from wind effects on the towers and conductors. Conductors are particularly sensitive to wind effects as they are long and relatively flexible (compared to their supports) and are literally wind-catching structures in the power grid infrastructure. In cold climates, wind and ice have compounding effects on lines and give rise to the most severe design loading conditions. Therefore, accurate prediction of the wind pressure on overhead conductors is essential to conduct a reliable assessment of the line response, in terms of both electrical clearances and conductor loads transferred to supports. Spatial randomness of wind loads on overhead lines has already been addressed by stochastic analysis methods and is now taken into account in design with the use of so-called span factors. Further gains in wind load accuracy can be obtained by examining the physics of wind effects on conductors, in both non-iced and iced conditions, with improved predictions of lift and drag forces determined from fluid-structure interaction (FSI) analysis.The traditional design method to apply wind load on transmission lines is to convert the design wind speed to a static pressure through Bernoulli's equation where the pressure is proportional to the air density and the squared wind speed. In this approach the fluid-structure interaction of wind and line components is ignored: wind is considered as a quasi-static load on conductors and supports, while special instability effects due to particular wind conditions such as vortex shedding (Aeolian vibrations) and flutter (cable galloping) are accounted for separately with specific mitigation solutions if necessary.In gusty wind conditions with high turbulence intensity, conductors may experience large horizontal displacements that affect their surrounding wind flow. A physically accurate wind load evaluation on conductors is possible by computational wind-structure interaction analysis. To date, largely due to its high computational cost and the lack of experimental data to validate computational models, an advanced fluid-structure analysis framework for wind-cable interaction has not been developed. In this study a new approach based on FSI analysis to evaluate equivalent wind loads on conductors is developed. The first step in such an approach is accurate evaluation of wind pressure on conductor. For this purpose the FSI analysis is carried out in two dimensions where the detailed bare and iced conductor section geometry and surrounding air flow are modeled, considering a given incident wind speed. The conductor cross section is assumed to be supported on flexible supports to study the interaction between the conductor motion and the air flow. FSI analysis yields both the fluid and structure response. Of particular interest is the wind pressure field on the conductor section, which allows the computation of the resultant drag and lift forces. This process is repeated for several cross sections along the span and the resulting forces provide the effective span wise wind load distribution on the conductor. This wind loading is then used as input in a separate 3-D computational nonlinear dynamic analysis model to predict the line response. This dynamic analysis of the line section can be detailed to represent very realistic line sections including conductors, suspension links and supporting towers.
Nos sociétés sont fortement dépendantes de l'électricité, et il ne fait pas de doute que la fonctionnalité des lignes de transport est déterminante pour assurer la fiabilité des réseaux électriques modernes. En effet, la continuité de l'approvisionnement en électricité reste la préoccupation majeure de toutes les compagnies d'électricité, et cette continuité du service peut être compromise par une multitude d'incidents ou d'accidents sur l'ensemble du réseau. Parmi toutes les sources possibles de charges dynamiques sollicitant les lignes de transport, celles provenant des effets du vent sur les pylônes et les conducteurs restent les plus fréquentes. Les conducteurs de lignes sont particulièrement vulnérables aux effets du vent car les portées sont longues et flexibles (comparé aux pylônes) et leur présence physique dans le réseau en font des structures exposées à toutes les intempéries qui peuvent survenir sur le territoire couvert. Cette vulnérabilité est encore plus grande dans les climats nordiques où les effets combinés du givrage atmosphérique et du vent créent des scénarios de charges de conception parmi les plus critiques et donc susceptibles de contrôler la conception finale des lignes. Il nous apparaît donc essentiel de comprendre la dynamique des fluides des effets du vent pour prédire avec réalisme et un degré de précision raisonnable la pression du vent exercée sur les conducteurs. Une meilleure évaluation des charges dues au vent permettrait par le fait même des prédictions plus réalistes de la réponse des lignes aux charges de vent, non seulement en terme de déplacements et dégagements électriques mais aussi en terme des charges nettes transférées aux pylônes par les conducteurs. La nature aléatoire des effets du vent sur les conducteurs a déjà fait l'objet de nombreuses études scientifiques et les méthodes d'analyse stochastique modernes permettent de cerner la question : les méthodes de conception simplifiées qui sont suggérées dans les normes et guides tiennent compte de ces effets en utilisant un coefficient de portée global qui ajuste à la baisse les efforts calculés au pylône sous des charges supposées synchrones et uniformes le long des conducteurs. Cette recherche ne concerne pas cet aspect de la question. Nous croyons que des gains de précision appréciables dans la prédiction des charges de vent sur les lignes sont possibles par une meilleure modélisation de la physique des effets du vent sur les conducteurs, dans les conditions givrées ou non, en utilisant les techniques d'analyse qui tiennent compte des interactions dynamiques fluide-structure. Ces interactions sont ignorées dans les méthodes d'analyse conventionnelles qui consistent simplement à calculer une pression statique proportionnelle à la vitesse carrée du fluide selon l'équation classique de Bernoulli. Bien sûr, les concepteurs ne négligent pas la considération des vibrations éoliennes ou du galop des conducteurs, mais ces phénomènes sont traités séparément et n'influencent pas le calcul des charges sur les pylônes. Dans cette recherche, nous nous intéressons aux conditions de vent de rafale avec grande turbulence qui caractérisent les tempêtes de vent. Ces vents forts et turbulents créent de grands déplacements des conducteurs qui modifient les conditions d'écoulement d'air. Une évaluation plus précise de ces conditions est possible par analyse computationnelle des interactions vent-conducteur.Les bases théoriques de la physique des phénomènes en présence sont connues mais aucun cadre d'application numérique n'a été proposé jusqu'à maintenant, en partie à cause des coûts numériques élevés mais aussi dû au manque de données expérimentales pouvant valider ces modèles computationnels.Nous avons développé un tel cadre d'analyse computationnelle dans cette recherche et l'avons illustré dans un cycle complet, du calcul des charges au calcul de la réponse d'une section de ligne, avec plusieurs exemples pratiques à chacune des étapes de développement

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Garbe, C. S. [Verfasser], and Bernd [Akademischer Betreuer] Jähne. "Measuring and Modeling Fluid Dynamic Processes using Digital Image Sequence Analysis / C.S. Garbe ; Betreuer: Bernd Jähne." Heidelberg : Universitätsbibliothek Heidelberg, 2007. http://d-nb.info/118778723X/34.

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Garbe, C. S. Verfasser], and Bernd [Akademischer Betreuer] [Jähne. "Measuring and Modeling Fluid Dynamic Processes using Digital Image Sequence Analysis / C.S. Garbe ; Betreuer: Bernd Jähne." Heidelberg : Universitätsbibliothek Heidelberg, 2007. http://nbn-resolving.de/urn:nbn:de:bsz:16-heidok-197175.

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Besse, Grant A. "Analysis and Optimization of the Wave Suppression and Sediment Collection System| Performance Characterization, Sand Collection, Mathematical Modeling and Computational Fluid Dynamic Modeling." Thesis, University of Louisiana at Lafayette, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10163277.

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Minimizing coastal wetland loss is a high priority in coastal areas throughout the world. Commonly used protection methods are costly, and may have negative impacts on the surrounding areas. The Wave Suppression and Sediment Collection (WSSC) system is an alternative shoreline protection structure. Primary goals of this study are to evaluate the sediment collection performance of three WSSC units under different sand conditions, to determine the performance characteristics of the units in terms of energy coefficients, and to validate a Computational Fluid Dynamic (CFD) model to determine the parameters governing wave attenuation. Sand collection results showed the units collected a minimum of 25% more fine sand than coarse, and that collection was affected by pipe size and row location. A mass transfer model was developed to predict the collection rate of sands based on wave and sand characteristics. The model fit experimental data well, with R2 values over 0.84 for three units and two different sands. A mass transfer coefficient alpha (a) was used within the model to compare the actual sand collection to the predicted amount. Resulting alpha values showed that sediment collection efficiency is governed by open area and pipe location within the devices. Performance characterization showed the WSSC units have wave reflections of 0.45 to 0.80, wave transmissions ranging from 0.10 to 0.40, and wave energy dissipation between 0.50 and 0.90, depending upon the unit and wave conditions. The WSSC units reflect more wave energy and transmit less energy compared to other breakwaters. The CFD model was validated using experimental velocity measurements. Statistical tests showed model velocities were not significantly different from experimental data. Units were modeled parametrically using CFD. Results indicated that wave reduction could be increased by decreasing pipe diameter, reducing the face slope, or increasing the number of rows.

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16

Prosser, Daniel T. "Advanced computational techniques for unsteady aerodynamic-dynamic interactions of bluff bodies." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53899.

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Interactions between the aerodynamics and dynamics of bluff bodies are important in many engineering applications, including suspension bridges, tall buildings, oil platforms, wind turbine towers, air drops, and construction with cranes. In the rotorcraft field, bluff bodies are commonly suspended underneath the vehicle by tethers. This approach is often the only practical way to deliver a payload in a reasonable amount of time in disaster relief efforts, search-and-rescue operations, and military operations. However, currently a fundamental understanding of the aerodynamics of these bluff bodies is lacking, and accurate dynamic simulation models for predicting the safe flying speed are not available. In order to address these shortcomings, two main advancements are presented in this thesis. The aerodynamics of several three-dimensional canonical bluff bodies are examined over a range of Reynolds numbers representative of wind-tunnel-scale to full-scale models. Numerical experiments are utilized, with a focus on uncertainty analysis and validation of the computations. Mean and unsteady forces and moments for these bluff bodies have been evaluated, and empirical models of the shear layer characteristics have been extracted to quantify the behaviors and provide predictive capability. In addition, a physics-based reduced-order simulation model has been developed for bluff bodies. The physics-based approach is necessary to ensure that the predicted behavior of new configurations is accurate, and it is made possible by the breakthroughs in three-dimensional bluff body aerodynamics presented in this thesis. The integrated aerodynamic forces and moments and dynamic behavior predicted by model are extensively validated with data from wind tunnels, flight tests, and high-fidelity computations. Furthermore, successful stability predictions for tethered loads are demonstrated. The model is applicable to the simulation of any generic bluff body configuration, is readily extensible, and has low computational cost.

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17

Stamato, Marisa. "Modeling, characterization and microalgal cultivation in an airlift panel photobioreactors." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amslaurea.unibo.it/6038/.

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Microalgae cultures are attracting great attentions in many industrial applications. However, one of the technical challenges is to cut down the capital and operational costs of microalgae production systems, with special difficulty in reactor design and scale-up. The thesis work open with an overview on the microalgae cultures as a possible answer to solve some of the upcoming planet issues and their applications in several fields. After the work offers a general outline on the state of the art of microalgae culture systems, taking a special look to the enclosed photobioreactors (PBRs). The overall objective of this study is to advance the knowledge of PBRs design and lead to innovative large scale processes of microalgae cultivation. An airlift flat panel photobioreactor was designed, modeled and experimentally characterized. The gas holdup, liquid flow velocity and oxygen mass transfer of the reactor were experimentally determined and mathematically modeled, and the performance of the reactor was tested by cultivation of microalgae. The model predicted data correlated well with experimental data, and the high concentration of suspension cell culture could be achieved with controlled conditions. The reactor was inoculated with the algal strain Scenedesmus obliquus sp. first and with Chlorella sp. later and sparged with air. The reactor was operated in batch mode and daily monitored for pH, temperature, and biomass concentration and activity. The productivity of the novel device was determined, suggesting the proposed design can be effectively and economically used in carbon dioxide mitigation technologies and in the production of algal biomass for biofuel and other bioproducts. Those research results favored the possibility of scaling the reactor up into industrial scales based on the models employed, and the potential advantages and disadvantages were discussed for this novel industrial design.

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18

Zappone, Marco. "Computational Fluodynamics Modeling (CFD) of horizontal propane jet fires." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.

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With regard to pipeline transportation of hazardous material, the occurrence of a jet fire is one of the most common accidents in case of loss of containment. In light of this consideration, an appropriate estimation of the accident scenario is necessary to determine the magnitude of the risk and the required measures to avoid or mitigate the consequences. Computational Fluid Dynamics (CFD) represents a valid tool to be used in this framework, because of its capability to describe the evolution of the accident, considering the obstacles and the site-specific factors. In this work, the capability of FLACS CFD code to simulate a propane horizontal jet fire is analyzed and the code is validated against experimental data. The parameters used for the validation are the jet fire geometrical characteristics and the flame temperature. The assessment is performed comparing different numerical models available in FLACS code in order to define the most appropriate to describe horizontal jet-fires. Then, the accuracy of simulation results is assessed using statistical performance metric parameters. In conclusion, results show that the FLACS CFD code is able to describe the horizontal jet fire phenomena in good accordance with experimental data, even though with a slight overprediction. On this basis, an initial study of the model proposed to simulate horizontal jet fire impingement on a pipe is conducted, and the possibility to use Fire Dynamics Simulator (FDS) CFD code to simulate horizontal jet fire is explored.

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19

Fricke, Mathis [Verfasser], Dieter [Akademischer Betreuer] Bothe, Stefan [Akademischer Betreuer] Ulbrich, and Stéphane [Akademischer Betreuer] Zaleski. "Mathematical modeling and Volume-of-Fluid based simulation of dynamic wetting / Mathis Fricke ; Dieter Bothe, Stefan Ulbrich, Stéphane Zaleski." Darmstadt : Universitäts- und Landesbibliothek, 2021. http://d-nb.info/1225040795/34.

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20

Scholes, Daniel Burton. "Evaluation of the Aerodynamic Differences of a Balloon Shape and a Sphere Using Computational Fluid Dynamic Modeling in Fluent." DigitalCommons@USU, 2011. https://digitalcommons.usu.edu/etd/872.

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While tracking balloons for wind characterization, there was a question about the theoretical rise rate and corresponding coefficient of drag of a balloon shape as compared to a sphere. Since there are many studies published detailing the drag on spherical shapes, the question of whether or not a balloon can be treated as a sphere begged to be answered. In this study we apply Computational Fluid Dynamic (CFD) modeling to compare the aerodynamic behavior and drag of a sphere to that of a balloon as it moves through fluid at Reynolds numbers from 10,000 to 100,000. Fluent CFD models are created and used to estimate the coefficient of drag (Cd) vs. Reynolds number (Re) for a sphere and for a balloon shape. Details are given for the meshed model creation and the simulation methods. Sphere model results are compared to data provided in published literature. Sphere and balloon model results are compared to each other. The results of this study show that the drag on a balloon is not statistically different from a sphere. While there are differences in the flow characteristics over the two shapes, a spherical shape is a good approximation for a balloon shape.

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21

Hosseini, Kordkheili Seyed. "A new continuum based non-linear finite element formulation for modeling of dynamic response of deep water riser behavior." Thesis, Brunel University, 2009. http://bura.brunel.ac.uk/handle/2438/4068.

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The principal objective of this investigation is to develop a nonlinear continuum based finite element formulation to examine dynamic response of flexible riser structures with large displacement and large rotation. Updated Lagrangian incremental approach together with the 2nd Piola-Kirchhoff stress tensor and the Green-Lagrange strain tensor is employed to derive the nonlinear finite element formulation. The 2nd Piola-Kirchhoff stress and the Green-Lagrange strain tensors are energy conjugates. These two Lagrangian tensors are not affected by rigid body rotations. Thus, they are used to describe the equilibrium equation of the body independent of rigid rotations. While the current configuration in Updated Lagrangian incremental approach is unknown, the resulting equation becomes strongly nonlinear and has to be modified to a linearized form. The main contribution of this work is to obtain a modified linearization method during development of incremental Updated Lagrangian formulation for large displacement and large rotation analysis of riser structures. For this purpose, the Green-Lagrange strain and the 2nd Piola-Kirchhoff stress tensors are decomposed into two second-order six termed functions of through-thethickness parameters. This decomposition makes it possible to explicitly account for the nonlinearities in the direction along the riser thickness, as well. It is noted that using this linearization scheme avoids inaccuracies normally associated with other linearization schemes. The effects of buoyancy force, riser-seabed interaction as well as steady-state current loading are considered in the finite element solution for riser structure response. An efficient riser problem fluid-solid interaction Algorithm is also developed to maintain the quality of the mesh in the vicinity of the riser surface during riser and fluid mesh movements. To avoid distortions in the fluid mesh two different approaches are proposed to modify fluid mesh movement governing elasticity equation matrices values; 1) taking the element volume into account 2) taking both element volume and distance between riser centre and element centre into account. The formulation has been implemented in a nonlinear finite element code and the results are compared with those obtained from other schemes reported in the literature.

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22

Luzi, Giovanni [Verfasser], Antonio [Akademischer Betreuer] Delgado, and Philipp [Akademischer Betreuer] Epple. "Thermo-Fluid-Dynamic Modeling and Simulations of the Drawing Process of Photonic Crystal Fibers / Giovanni Luzi. Gutachter: Antonio Delgado ; Philipp Epple." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2014. http://d-nb.info/1075475686/34.

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23

Liu, Huolong. "Modeling and control of batch pulsed top-spray fluidized bed granulation." Thesis, De Montfort University, 2014. http://hdl.handle.net/2086/11006.

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In this thesis, a thorough study of the batch top-spray fluidized bed granulation was carried out including experimental study, population balance model (PBM), computational fluid dynamic (CFD) study and control strategy development. For the experimental study, the influence variables of pulsed frequency, binder spray rate and atomization pressure of a batch top-spray fluidized bed granulation process were studied using the Box-Behnken experimental design method. Different mathematical models were developed to predict the mean size of granules, yield, relative width of granule distribution, Hausner ratio and final granule moisture content. Validation experiments have shown the reliability and effectiveness of using the Box-Behnken experimental design method to study a fluidized bed granulation process. The one-dimensional population balance models (ODPBMs) have been developed to model a pulsed top-spray fluidized bed granulation, linking the operating factors of the pulsed frequency, the binder spray rate, and atomization air pressure with the granule properties to predict granule growth behavior at different operating conditions. A multi-stage open optimal control strategy based on the developed ODPBMs was proposed to reduce the model and process mismatch through adjusting the trajectory of the evolution of the granule size distribution at predefined sample intervals. The effectiveness of the proposed modeling and multi-stage open optimal control strategy has been validated by experimental and simulation tests. In addition, an Eulerian-Eulerian two-fluid model (EETFM) was developed to describe the gas-particle two-phase flow in the fluidized bed granulator. By computational fluid dynamic analysis, it has been proven that the fluidized bed granulation system is not homogeneous, based on which a two-compartmental population balance model (TCPBM) was developed to describe the particle growth in the fluidized bed granulation. Validation experiments have shown the effectiveness and superior accuracy of the TCPBM comparing with the ODPBM in predicting the final particle size distribution.

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24

Nastic, Aleksandra. "Cold Gas Dynamic Spray Impact: Metallic Bonding Pre-Requisites and Experimental Particle In-Flight Temperature Measurements." Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/42086.

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The impact phenomena of high velocity micron-size particles, although commonly considered and described as detrimental in numerous engineering applications, can be used in a beneficial way if properly understood and controlled. The Cold Gas Dynamic Spray (CGDS) process, known as a surface modification, repair and additive manufacturing process, relies on such high velocity impacts. In the process, solid particles are accelerated by a supersonic gas flow to velocities up to 1200 m/s and are simultaneously heated to temperatures lower than their melting point. When propelled under proper velocity and temperature, the particles can bond onto a target surface. This bonding is caused by the resulting interfacial deformation processes occurring at the contact interface. Hence, the process relies heavily on the gas/particle and particle/substrate interactions. Although numerous experimental and/or numerical studies have been performed to describe the phenomena occurring during particle flight and impact in the CGDS process, numerous phenomena remain poorly understood. First, the effect of substrate surface topographical condition on the particle deformation and ability to successfully adhere, i.e. atomically and/or mechanically, has not been thoroughly investigated such that its influence is not well understood. Another aspect of the process that is generating the largest gap between experimental and numerical studies in the field is the lack of particle in-flight temperature measurements. Obtaining such data has proven to be technically difficult. The challenges stem from the short particle flight time, low particle temperature and small particle size preventing the use of established thermal spray pyrometry equipment. Relatedly, lack of such measurements precludes a proper experimental study of the impact related phenomena at the particle/substrate interface. As a result, the effect of particle size dependent temperature on overall coating properties and atomic bonding relies currently on estimates. Finally, the effect of particle impact characteristics on interfacial phenomena, i.e. grain size and geometry, velocity/temperature, and oxide scale thickness, on adhesion and deformation upon single particle collision has also been scarcely studied for soft particle depositions on hard substrate. Hence, the current research work aims at studying fundamental aspects of particle/gas heat transfer and particle/substrate impact features in goals to improve the understanding of the CGDS process. Different surface preparation methods will be used to create various surface roughness and topographical features, to provide a clear understanding of the target surface state influence on coating formation and adhesion. Additionally, new equipment relying on novel technology, i.e. high-speed IR camera, will be utilized to obtain particle in-flight temperature readings with sequence recordings. Subsequently, the experimental particle in-flight temperature readings will be used to develop a computational fluid dynamics model in goals to validate currently used Nusselt number correlations and heat transfer equations. The particle size-dependent temperature effect on the particle’s elastic and plastic response to its impact with a targeted surface and its ability to successfully bond and form a coating will be studied experimentally. A thorough CFD numerical work, based on experimental findings, will be included to provide full impact characteristics (velocity, temperature, size and trajectory) of successfully deposited particles. Finally, the numerical results will be utilized in the ensuing study to correlate single particle deformation, adhesion and interfacial features to impact characteristics. A finite element model will be included to investigate the effect of particle size dependent temperature on single particle interfacial pressure, temperature and bonding ability.

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25

Livescu, Silviu. "Mathematical and numerical modeling of coating flows." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 3.48 Mb., 279 p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3221057.

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26

Ellam, Darren John. "Modelling smart fluid devices using computational fluid dynamics." Thesis, University of Sheffield, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398597.

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27

Hester, Eric William. "Modelling fluid-solid interactions." Thesis, The University of Sydney, 2021. https://hdl.handle.net/2123/25114.

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Fluid-solid interactions have wide-ranging implications for science, engineering, and the global climate. This thesis combines mathematical analysis, computational algorithms, and laboratory experiments to understand fluid-solid interactions, providing new insights on the influence of shape on iceberg melting, and mysterious boat drag in the dead-water effect. The discontinuous interfaces of fluid-solid interactions are challenging to simulate. We develop improved diffuse-domain methods that allow straightforward algorithms to simulate fluid-solid interactions. Diffuse-domain methods are simple to implement because they replace complicated boundary conditions with smooth source terms. But the smoothing induces a boundary layer of size ε between the fluid and solid. Previous diffuse-domain methods incurred errors of this size—corresponding to first order numerical accuracy. The first part of the thesis develops an asymptotic framework to derive second-order accurate diffuse-domain methods. In chapter 2, we exploit the signed distance function to simplify vector calculus around boundary layers in arbitrary smooth geometries. In chapter 3 we apply this machinery to optimise the volume-penalty method for fluid-solid interactions. In chapter 4 we then derive higher-order phase-field models for coupled melting, dissolution, and convection. We verify these corrections in extensive numerical benchmarks. We also explore techniques for fourth order convergence in ε using Richardson extrapolation, and spectral accuracy simulations via coordinate remapping. These improved methods provide powerful tools to simulate and understand real-world fluid-solid interactions. In chapter 5, we apply these methods to investigate how iceberg shape affects melting. Icebergs vary in shape and size, and iceberg melting determines their influence on the climate. Our laboratory experiments reveal previous models underestimate melting and ignore large differences between sides. The improved phase-field model reproduces experimental melt rates and explains observed patterns. Simulations show that non-uniform basal melt rates stem from upwelling during vortex generation. We outline the geophysical implications of our findings and discuss improvements to current melting parameterisations that account for iceberg geometry. Then in chapter 6, we use these techniques to examine the dead-water effect—extreme boat drag in density-stratified waters. Walfrid Ekman showed in 1904 that sub-surface internal waves cause dead water. Boats moving near the internal wave speed generate large internal waves which steal energy from the boat. We perform the first direct numerical simulation of dead water. In contrast to previous potential flow models, we find that vorticity generated throughout the domain plays an important role in the effect. The vorticity coalesces into large, previously unnoticed eddies. These robust eddies interfere with the boat-wave interaction, and may suggest new strategies to mitigate the effect.

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28

Wang, Chuanfeng. "Collective dynamics and control of a fleet of heterogeneous marine vehicles." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50336.

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Cooperative control enables combinations of sensor data from multiple autonomous underwater vehicles (AUVs) so that multiple AUVs can perform smarter behaviors than a single AUV. In addition, in some situations, a human-driven underwater vehicle (HUV) and a group of AUVs need to collaborate and preform formation behaviors. However, the collective dynamics of a fleet of heterogeneous underwater vehicles are more complex than the non-trivial single vehicle dynamics, resulting in challenges in analyzing the formation behaviors of a fleet of heterogeneous underwater vehicles. The research addressed in this dissertation investigates the collective dynamics and control of a fleet of heterogeneous underwater vehicles, including multi-AUV systems and systems comprised of an HUV and a group of AUVs (human-AUV systems). This investigation requires a mathematical motion model of an underwater vehicle. This dissertation presents a review of a six-degree-of-freedom (6DOF) motion model of a single AUV and proposes a method of identifying all parameters in the model based on computational fluid dynamics (CFD) calculations. Using the method, we build a 6DOF model of the EcoMapper and validate the model by field experiments. Based upon a generic 6DOF AUV model, we study the collective dynamics of a multi-AUV system and develop a method of decomposing the collective dynamics. After the collective dynamics decomposition, we propose a method of achieving orientation control for each AUV and formation control for the multi-AUV system. We extend the results and propose a cooperative control for a human-AUV system so that an HUV and a group of AUVs will form a desired formation while moving along a desired trajectory as a team. For the post-mission stage, we present a method of analyzing AUV survey data and apply this method to AUV measurement data collected from our field experiments carried out in Grand Isle, Louisiana in 2011, where AUVs were used to survey a lagoon, acquire bathymetric data, and measure the concentration of reminiscent crude oil in the water of the lagoon after the BP Deepwater Horizon oil spill in the Gulf of Mexico in 2010.

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29

Zitzmann, Tobias. "Adaptive modelling of dynamic conjugate heat transfer and air movement using computational fluid dynamics." Thesis, De Montfort University, 2007. http://hdl.handle.net/2086/4287.

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30

Hunsaker, Doug F. "Evaluation of an Incompressible Energy-Vorticity Turbulence Model for Fully Rough Pipe Flow." DigitalCommons@USU, 2011. https://digitalcommons.usu.edu/etd/1068.

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Traditional methods of closing the Boussinesq-based Reynolds-averaged Navier-Stokes equations are considered, and suggestions for improving two-equation turbulence models are made. The traditional smooth-wall boundary conditions are shown to be incorrect, and the correct boundary conditions are provided along with sample solutions to traditional models. The correct boundary condition at a smooth wall for dissipation-based turbulence models is that which forces both the turbulent kinetic energy and its first derivative to zero. Foundations for an energy-vorticity model suggested by Phillips are presented along with the near-smooth-wall behavior of the model. These results show that at a perfectly smooth wall, the turbulent kinetic energy may approach the wall at a higher order than is generally accepted. The foundations of this model are used in the development of a k-λ model for fully rough pipe flow. Closure coefficients for the model are developed through gradient-based optimization techniques. Results of the model are compared to results from the Wilcox 1998 and 2006 k-ω models as well as four eddy-viscosity models. The results show that the Phillips k-λ model is much more accurate than other models for predicting the relationship between Reynolds number and friction factor for fully rough pipe flow. However, the velocity profiles resulting from the model deviate noticeably from the law of the wall.

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31

Zhao, Kun. "Initial-boundary value problems in fluid dynamics modeling." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31778.

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Thesis (Ph.D)--Mathematics, Georgia Institute of Technology, 2010.
Committee Chair: Pan, Ronghua; Committee Member: Chow, Shui-Nee; Committee Member: Dieci, Luca; Committee Member: Gangbo, Wilfrid; Committee Member: Yeung, Pui-Kuen. Part of the SMARTech Electronic Thesis and Dissertation Collection.

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32

Jayaraman, Balaji. "Computational modeling of glow discharge-induced fluid dynamics." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0015702.

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33

Kardos, T. N. "Modelling Smoke Flow Using Computational Fluid Dynamics." University of Canterbury. Civil Engineering, 1996. http://hdl.handle.net/10092/8278.

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There have been a number of experimental investigations into the backdraft phenomena. A backdraft occurs in the event of a ventilation source being formed in a compartment, within which a fire has been burning for a sufficiently long enough time to form a deep layer of excess pyrolyzates. The source of fresh air will flow into the compartment in the form of a gravity current. It is the gravity current feature of backdrafts that this research project focuses on. Application of Computational Fluid Dynamics (CFD) to fire problems is expanding, including the development of specific programs for fire engineering applications. The experimental programme that was used in this research project highlights the difficulties of analysing fluid flows by using CFD simulations. The Flow3D program was used to obtain a more detailed understanding of the behaviour of a gravity current, allowing a detailed study of fluid dynamics which cannot be investigated experimentally. The simulations used two different vent configurations, with the CFD model being validated on the experimental results of salt water tank models. The simulations preformed compared well to the experimental data that was used for scaled salt water tank experiments.

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Hurst, Gareth Alan D. "Modelling and analysis of ophthalmic fluid dynamics." Thesis, University of Leeds, 2014. http://etheses.whiterose.ac.uk/7839/.

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Mathematical models and numerical methods are developed for analysing and simulating the spatio-temporal evolution of the tear film coating the anterior surface of the human eye during an interblink period. The novelty of the work is on two distinct fronts. • First, a systematic approach is taken to ensure that the (coupled) model evolution equations — one each for film thickness and lipid-surfactant concentration — arising from asymptotic thin-film approximations of the Navier-Stokes equations, are uniformly valid when realistic ophthalmic data are used in the parameterisation. In this way, the present model does not — as occurs in related literature — yield results that are in conflict with a priori approximation hypotheses. More specifically, novel results are obtained on the effects of substrate curvature by proposing a specific coordinate system in which: the influence of curvilinearity on the evolution of the tear film can be parameterised, and; the limiting case recovers the Cartesian models of related literature. Additionally, the evolution equations are developed using sophisticated bespoke computer-algebra (MAPLE) techniques that permit the correct a priori scalings — of the competing effects of gravity, inertia, evaporation and surface tension — that guarantee the above-mentioned uniform validity. A novel consideration of the physical viability of boundary conditions at three-phase contact line on the eyelid in the existing mathematical literature leads to the proposal, implementation and investigation of novel Neumann boundary conditions that are supported by the results of recent in vitro experimental work. • Second, bespoke spectral numerical methods are developed for solving the thinfilm approximations, yielding hitherto-unseen explicit formulæfor high-order Chebyshev differentiation matrices. Inherent errors are quantified, thereby yielding an explicit understanding of both the modelling limitations and the plausibility of results. A suite of post-processing tools is developed to negotiate the complexities of implementing the novel boundary conditions in a spectral environment. All numerical techniques are validated on test problems; a high degree of both accuracy and efficiency is demonstrated. An analysis is presented of the errors incurred in the numerical approximation of the (steep) film-profile gradients near the eyelids; the results of this error analysis prompt questions on the accuracy of many of the results of previously published models. Through the combination of new, uniformly valid, thin-film approximations and bespoke, fully validated numerical methods, the coupled evolution equations for the thin-film thickness and lipid surfactant concentration are solved with confidence that the results obtained are credible. The novel boundary conditions lead to results that predict behaviours of the tear film that, whilst unseen in all prior related mathematical literature, encouragingly align with in vivo experimental observations in the ophthalmic literature. As a result, a novel hypothesis is presented for the behaviour of the tear-film contact line, through which predictions are made regarding the development and treatment of dry-eye pathologies. Suggestions for future work conclude the thesis.

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35

Liu, Li. "Computational fluid dynamics modelling of complex fluid flow in stirred vessels." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/4753/.

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Fluid mixing in stirred vessels is widely encountered in a number of industries. In this work, different experimental techniques and the CFD modelling approach are used to measure the mixing of a wide range of fluids in stirred vessels. As the detailed validation is essential for CFD modelling, CFD predictions are compared in detail with different experimental measurements. The capability of CFD modelling of the 3D spatial distribution of velocity and solid concentration within opaque concentrated solid-liquid suspensions with the mean solid concentration up to 40 wt% is assessed by comparing with the experimental data obtained from positron emission particle tracking (PEPT) measurements. Because the impeller configuration is of significant importance to the flow pattern, the performance of different impellers for single-phase mixing of Newtonian and non-Newtonian fluids in stirred vessels is compared. CFD predictions of flow fields generated from different impellers are compared with those measured by the well-established particle image velocimetry (PIV) technique. The capability of CFD modelling of different mixing features of non-Newtonian fluids in stirred vessels are verified by comparing with experimental data obtained from PIV, PEPT, and planar laser induced fluorescence (PLIF) measurements.

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36

Abuhaiba, Mohammad. "Mathematical Modeling and Analysis of a Variable Displacement Hydraulic Bent Axis Pump Linked to High Pressure and Low Pressure Accumulators." Connect to full text in OhioLINK ETD Center, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1240528916.

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Dissertation (Ph.D.)--University of Toledo, 2009.
Typescript. "Submitted as partial fulfillment of the requirements for the Doctor of Philosophy degree in Mechanical Engineering." Bibliography: leaves 203-209.

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37

Vecina, Tanit-Daniel Jodar. "Investigação da camada limite atmosférica simulada em túnel de vento no topo de morros utilizando dinâmica dos fluídos computacional (CFD)." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/158347.

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O formato do perfil de velocidades do vento varia de acordo com as características locais da superfície terrestre e de rugosidade do terreno, parâmetros que definem o perfil da Camada-Limite Atmosférica (CLA). As características do escoamento do ar atmosférico sobre e ao redor de acidentes geográficos, tais como morros e colinas, são de grande interesse para aplicações relacionadas à Engenharia de Turbinas e Parques Eólicos. No topo de morros, ocorre a aceleração do vento, fenômeno que pode representar um fator decisivo para a instalação de aerogeradores. Este trabalho dedica-se ao estudo do comportamento da CLA como função da inclinação e rugosidade superficial da elevação, fazendo uso da Dinâmica de Fluidos Computacional (CFD) para construir perfis de velocidade do vento e de intensidade de turbulência. O problema de fechamento das Equações Médias de Reynolds (RANS) é contornado com o uso do modelo de turbulência k-ω SST; os resultados numéricos obtidos são comparados com dados experimentais medidos em túnel de vento sobre modelos em escala dos morros. São testados oito modelos de morros com declives que variam de 25° a 64° para dois tipos de categorias de terreno, em 2D e 3D, e são aplicados dois códigos analíticos para representar o perfil de velocidades de entrada. Resultados numéricos para os perfis de velocidade apresentam diferença inferior a 4% em relação aos respectivos dados obtidos experimentalmente. Os perfis de intensidade de turbulência apresentam diferença máxima na casa dos 7% em comparação aos dados experimentais, o que é explicado pelo fato de que não é possível inserir o perfil de entrada de intensidade de turbulência nas simulações numéricas. Em alternativa, foi usado um valor constante resultado da média dos valores dos perfis usados no túnel de vento. Os modelos de morro em 3D apresentam maior concordância nos resultados de velocidade que os modelos em 2D e que ademais quanto maior é a inclinação do morro maior é a concordância com as medições experimentais.
The shape of the wind velocity profile changes according to local features of terrain shape and roughness, which are parameters responsible for defining the Atmospheric Boundary Layer (ABL) profile. Air flow characteristics over and around landforms, such as hills, are of considerable importance for applications related to Wind Farm and Turbine Engineering. The air flow is accelerated on top of hills, which can represent a decisive factor for Wind Turbine placement choices. The present work focuses on the study of ABL behavior as a function of slope and surface roughness of hill-shaped landforms, using the Computational Fluid Dynamics (CFD) to build wind velocity and turbulent intensity profiles. Reynolds-Averaged Navier-Stokes (RANS) equations are closed using the SST k-ω turbulence model; numerical results are compared to experimental data measured in wind tunnel over scale models of the hills under consideration. Eight hill models with slopes varying from 25° to 64° were tested for two types of terrain categories in 2D and 3D, and two analytical codes are used to represent the inlet velocity profiles. Numerical results for the velocity profiles show differences under 4% when compared to their respective experimental data. Turbulent intensity profiles show maximum differences around 7% when compared to experimental data, this can be explained by not being possible to insert inlet turbulent intensity profiles in the simulations. Alternatively, constant values based on the averages of the turbulent intensity at the wind tunnel inlet were used. The 3D models present greater concordance in the speed results than the 2D models and that in addition the greater the slope of the hill, the greater the agreement with the experimental measurements.

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38

Leckenby, Robert James. "Dynamic characterisation and fluid flow modelling of fractured reservoirs." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.423031.

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39

Seddon, Caroline Michelle. "Modelling transient dynamic fluid-structure interaction in aerospace applications." Thesis, University of Salford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492434.

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Although significant progress has been made in the study of dynamic loading of aircraft structures, several areas have been identified that require further research. In particular, attention is drawn to problems involving transient, dynamic fluid-structure interaction, where fluids play an important role, heavily influencing the response of the structure to the applied dynamic load. In this work the use of existing numerical modelling techniques for the evaluation of such problems is investigated.

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40

Coroneo, Mirella <1982&gt. "Fluid dynamic analysis and modelling of industrial chemical equipment." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3256/1/Coroneo_Mirella_tesi.pdf.

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The research is aimed at contributing to the identification of reliable fully predictive Computational Fluid Dynamics (CFD) methods for the numerical simulation of equipment typically adopted in the chemical and process industries. The apparatuses selected for the investigation, specifically membrane modules, stirred vessels and fluidized beds, were characterized by a different and often complex fluid dynamic behaviour and in some cases the momentum transfer phenomena were coupled with mass transfer or multiphase interactions. Firs of all, a novel modelling approach based on CFD for the prediction of the gas separation process in membrane modules for hydrogen purification is developed. The reliability of the gas velocity field calculated numerically is assessed by comparison of the predictions with experimental velocity data collected by Particle Image Velocimetry, while the applicability of the model to properly predict the separation process under a wide range of operating conditions is assessed through a strict comparison with permeation experimental data. Then, the effect of numerical issues on the RANS-based predictions of single phase stirred tanks is analysed. The homogenisation process of a scalar tracer is also investigated and simulation results are compared to original passive tracer homogenisation curves determined with Planar Laser Induced Fluorescence. The capability of a CFD approach based on the solution of RANS equations is also investigated for describing the fluid dynamic characteristics of the dispersion of organics in water. Finally, an Eulerian-Eulerian fluid-dynamic model is used to simulate mono-disperse suspensions of Geldart A Group particles fluidized by a Newtonian incompressible fluid as well as binary segregating fluidized beds of particles differing in size and density. The results obtained under a number of different operating conditions are compared with literature experimental data and the effect of numerical uncertainties on axial segregation is also discussed.

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41

Coroneo, Mirella <1982&gt. "Fluid dynamic analysis and modelling of industrial chemical equipment." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3256/.

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The research is aimed at contributing to the identification of reliable fully predictive Computational Fluid Dynamics (CFD) methods for the numerical simulation of equipment typically adopted in the chemical and process industries. The apparatuses selected for the investigation, specifically membrane modules, stirred vessels and fluidized beds, were characterized by a different and often complex fluid dynamic behaviour and in some cases the momentum transfer phenomena were coupled with mass transfer or multiphase interactions. Firs of all, a novel modelling approach based on CFD for the prediction of the gas separation process in membrane modules for hydrogen purification is developed. The reliability of the gas velocity field calculated numerically is assessed by comparison of the predictions with experimental velocity data collected by Particle Image Velocimetry, while the applicability of the model to properly predict the separation process under a wide range of operating conditions is assessed through a strict comparison with permeation experimental data. Then, the effect of numerical issues on the RANS-based predictions of single phase stirred tanks is analysed. The homogenisation process of a scalar tracer is also investigated and simulation results are compared to original passive tracer homogenisation curves determined with Planar Laser Induced Fluorescence. The capability of a CFD approach based on the solution of RANS equations is also investigated for describing the fluid dynamic characteristics of the dispersion of organics in water. Finally, an Eulerian-Eulerian fluid-dynamic model is used to simulate mono-disperse suspensions of Geldart A Group particles fluidized by a Newtonian incompressible fluid as well as binary segregating fluidized beds of particles differing in size and density. The results obtained under a number of different operating conditions are compared with literature experimental data and the effect of numerical uncertainties on axial segregation is also discussed.

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42

Charmchi, Isar. "Computational Fluid Dynamics (CFD) Modeling of a Continuous Crystallizer." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.

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Crystallization is one of the most important separation and purification processes in chemical and especially in pharmaceutical industries. Currently most crystallization processes in the industry are based on batch crystallization; however, due to the variation of product quality per batch, efforts are made to move to continuous processes instead. In this respect, micro and meso scale reactors represents a promising technology due to enhanced heat and mass transfer rates, which, translated to particle generation, provide control of size, morphology, and composition. In this study, a meso-scale continuous crystallizer has been characterized and optimized. A stirred tubular continuous-crystallizer has been characterized and optimized in which the crystallization of active pharmaceutical ingredients (APIs) can be performed under controlled conditions. The crystallizer is formed by two tubes, one for nucleation and the other one for growth, in order to separate different phenomena to control better the process and hence the crystal size distribution. The optimized nucleation tube has a length of 35 cm and a diameter of 3 cm with a long axial blade across the tube with the length of 30 cm and 2.5 cm of diameter. The phenomena of mixing helps to achieve homogeneous supersaturation along the tube to prevent growth during the nucleation and enables narrow residence time distribution of the crystals in the tube with the help of gravity to achieve narrower crystal size distribution. Computational fluid dynamics (CFD) is used to optimize the process. CFD is the application of numerical methods to solve systems of partial differential equations related to fluid dynamics. The continuity and the momentum equations are the most commonly applied equations within CFD, and together they can be used to calculate the velocity and pressure distributions in a fluid.

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43

Kaggerud, Torbjørn Herder. "Modeling an EDC Cracker using Computational Fluid Dynamics (CFD)." Thesis, Norwegian University of Science and Technology, Department of Energy and Process Engineering, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9536.

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The process used by the Norwegian company Hydro for making Vinyl Chloride Monomer (VCM) from natural gas and sodium chloride has been studied. A three dimensional CFD model representing the firebox of the EDC cracker has been developed using the commercial CFD tool Fluent. Heat to the cracker is delivered by means of combustion of a fuel gas consisting of methane and hydrogen. In the developed CFD model used in this work, the combustion reaction itself is omitted, and heat is delivered by hot flue gas. With the combustion reaction left out, the only means of tuning the CFD model is through the flue gas inlet temperature. With the flue gas inlet temperature near the adiabatic flame temperature, the general temperature level of the EDC cracker was reported to be too high. The outer surface temperature of the coil was reported to be 3-400 K higher than what was expected. By increasing the mass flow of flue gas and decreasing the temperature, the net delivered heat to the firebox was maintained at the same level as the first case, but the temperature on the coil was reduced by 100-150 K. Further reductions in the flue gas inlet temperature and modifications in the mass flow of flue gas at the different burner rows, eventually gave temperature distributions along the reaction coil, and flue gas and refractory temperatures, that resemble those in the actual cracker. The one-dimensional reactor model for the cracking reaction represents the actual cracker in a satsifactorily manner. The cracking reaction was simulated using a simple, global reaction mechanism, thus only the main components of the process fluid, EDC, VCM and HCl, can be studied. The model is written in a way suitable for implementation of more detailed chemical reaction mechanisms. The largest deviation in temperature between measured and simulated data are about 5%. At the outlet the temperature of the process fluid is equal to the measured data. The conversion of EDC out of the firebox is assumed to be 50 wt-%, this value is met exactly by the model.

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44

Kellar, William Patrick. "Geometry modeling in computational fluid dynamics and design optimisation." Thesis, University of Cambridge, 2003. https://www.repository.cam.ac.uk/handle/1810/251878.

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45

Limache, Alejandro Cesar. "Aerodynamic Modeling Using Computational Fluid Dynamics and Sensitivity Equations." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/27033.

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A mathematical model for the determination of the aerodynamic forces acting on an aircraft is presented. The mathematical model is based on the generalization of the idea of aerodynamically steady motions. One important use of these results is the determination of steady (time-invariant) aerodynamic forces and moments. Such aerodynamic forces can be determined using computer simulation by determining numerically the associated steady flows around the aircraft when it is moving along such generalized steady trajectories. The method required the extension of standard (inertial) CFD formulations to general non-inertial reference frames. Generalized Navier-Stokes and Euler equations have been derived. The formulation is valid for all ranges of Mach numbers including transonic flow. The method was implemented numerically for the planar case using the generalized Euler equations. The developed computer codes can be used to obtain numerical flow solutions for airfoils moving in general steady motions (i.e. circular motions). From these numerical solutions it is possible to determine the variation of the lift, drag and pitching moment with respect to the pitch rate at different Mach numbers and angles of attack. One of the advantages of the mathematical model developed here is that the aerodynamic forces become well-defined functions of the motion variables (including angular rates). In particular, the stability derivatives are associated with partial derivatives of these functions. These stability derivatives can be computed using finite differences or the sensitivity equation method.
Ph. D.

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46

Hayden, Kevin. "Modeling of dynamical systems /." abstract and full text PDF (UNR users only), 2007. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1446796.

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Thesis (M.S.)--University of Nevada, Reno, 2007.
"May, 2007." Includes bibliographical references (leaves 128-129). Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2008]. 1 microfilm reel ; 35 mm. Online version available on the World Wide Web.

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47

Ji, Yingchun. "Computational fluid dynamics modelling of displacement natural ventilation." Thesis, De Montfort University, 2005. http://hdl.handle.net/2086/4951.

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Natural ventilation is widely recognised as contributing towards low-energy building design. The requirement to reduce energy usage in new buildings has rejuvenated interest in natural ventilation. This thesis deals with computer modelling of natural displacement ventilation driven either by buoyancy or buoyancy combined with wind forces. Two benchmarks have been developed using computational fluid dynamics (CFD) in order to evaluate the accuracy with which CFD is able to model natural displacement ventilation flow. The first benchmark considers the natural ventilation of a single ventilated space with high and low level openings connected to the exterior driven by combined forces of wind and buoyancy. The second benchmark considers natural ventilation flow in a single space connected to an atrium driven by pure buoyancy. Simulation results of key ventilation parameters (stratification depth, temperature gradient and ventilation flow rate) have been compared with analytical and experimental models and close agreements have been achieved. The two benchmarks are defined using the RNG k-epsilon turbulence model. A pressure boundary is applied onto the ventilation openings directly and a porous medium boundary is used to assist the development of the thermal plume. This method has proved to be robust and the close agreement between the three modelling techniques indicates that CFD is able to model natural ventilation flows in simple geometries with acceptable accuracy and reliability. Using the benchmarks the influences of key CFD modelling parameters and building design issues have been investigated. For example, representing openings, heat source representation, stack height, and air inlet strategies. Natural displacement ventilation of a multi-storey building comprising an atrium is also addressed. Simple analytical models have been developed to describe the key air flow features within the ventilation system.

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48

McClure, Dale David. "Modelling Bubble Column Bioreactors Using Computational Fluid Dynamics." Thesis, The University of Sydney, 2014. http://hdl.handle.net/2123/12058.

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Bubble columns are widely used in the bio-processing industry to perform large scale, aerobic fermentations. For this reason, there is a clear interest in optimising both the design and operation of such reactors. One cost-effective approach is the development of a Computational Fluid Dynamics (CFD) model of the process; the major advantage of this methodology being that it provides detailed information about the flow patterns within the column, knowledge which is difficult to experimentally obtain at an industrial scale. Such data are of particular value as it has been conjectured that poor distribution of nutrients leads to a reduction in the process yield. Hence, the aim of this work was the development of a CFD model capable of accurately describing flow in bubble columns operated in the industrially relevant heterogeneous flow regime (i.e. at superficial velocities greater than 0.1 m/s). In order to develop and validate such a model, it was necessary to obtain experimental data for both an air/water system as well as an air/fermentation media system, the latter being a topic rarely examined in the literature. Hence, a comprehensive experimental program was undertaken at both the bench-top (using a column 0.19 m in diameter and 1 m in height) and pilot-scales (using a column 0.39 m in diameter and 2 m in height). A comprehensive experimental dataset consisting of measurements of the mixing time, overall hold-up, bubble size distribution, as well as profiles of the local hold-up, liquid velocity and gas velocity was generated. Both experimental configurations were modelled using CFD; with the model predictions being in satisfactory agreement with the experimental data at both scales. The development of a predictive model capable of accurately describing the complex mixing patterns in bubble columns (both with and without the presence of surfactants) operating in the heterogeneous flow regime is seen as a key step in the design and optimisation of such systems.

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49

Morris, Paul. "Computational fluid dynamics modelling of coronary artery disease." Thesis, University of Sheffield, 2015. http://etheses.whiterose.ac.uk/11772/.

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Background Coronary artery disease (CAD) is the leading cause of death in the world. Physiological lesion assessment with indices such as fractional flow reserve (FFR) is now accepted as the invasive gold-standard for diagnosing the significance of CAD and for guiding treatment. Patients undergoing percutaneous coronary intervention (PCI) guided by FFR have better clinical outcomes than those undergoing standard assessment. Furthermore, FFR-guided PCI is associated with decreased stent implantation and reduced long-term cost. Only a minority of patients undergoing invasive coronary angiography are currently afforded these benefits due to a number of procedure, operator, and economic related factors. There may be additional benefits from combined pressure and flow measurement. There is therefore a need for a technology that delivers the benefits of physiological lesion assessment without the factors which limit use of the invasive technique. Hypothesis Computational fluid dynamics (CFD) modelling based upon invasive coronary angiographic images (ICA) can characterise and predict intracoronary physiology. Aims (i) To develop a CFD-based model capable of simulating and predicting clinically relevant intracoronary physiology and (ii) validate model performance using clinical data from patients with CAD. Methods A workflow, based upon 3-D CFD modelling, capable of predicting intracoronary pressure and ‘virtual’ FFR from ICA, was developed. The model was validated against in vivo clinical measurements in 35 unique arterial datasets. The model predicted physiological lesion significance with 97% overall accuracy. Computation was prolonged (>24hrs). Two novel methods for solving the 3-D CFD were therefore developed. These methods enabled accurate computation of results in clinically tractable timescales (<5mins), at least equivalent to invasive measurement. The critical influence of system boundary conditions was explored, characterised, and quantified. A novel approach to patient-specific tuning of the outlet boundary conditions was developed and evaluated. The workflow was adapted to compute the pressure-flow relationship from measured pressure boundary conditions within a fully patient-specific in silico model. Results were validated within a novel experimental flow circuit incorporating patient-specific 3-D printed coronary arterial phantom models. Conclusions It is possible to compute clinically relevant intracoronary physiology (pressure or flow) from ICA. Results can be generated in clinically tractable timescales. The CFD model can be tuned to individual patient characteristics. The developed tools may be commercially desirable. Prior to full clinical translation, the model must be evaluated in a clinical trial.

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Robertson, Guy Kinloch. "Labyrinth weir hydraulics : validation of CFD modelling." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86277.

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Thesis (MScEng)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: The use of computational fluid dynamics (CFD) as a design tool is becoming increasingly popular in the water resources field. This thesis aims to extend the knowledge of CFD and determine the usefulness of current CFD programs as a modelling tool. This thesis also seeks to determine the accuracy of CFD modelling when compared to physical modelling, the more established form of model testing. It is important that research is conducted on the validation of CFD because with an increase in computer power, processing speed and continual development in the programs used to generate the models, CFD could become an essential tool for the hydraulic engineer. A current key difficulty faced by CFD programs is the mapping of the free surface level of a body of fluid in a two-phase (water and air) flow condition. This is further complicated by the existence of three-dimensional flow over a labyrinth weir and a fluctuating nappe, which at times requires a free surface level to be mapped both above and below the nappe. This thesis begins by detailing the design methods and actual design of a typical labyrinth weir. It then describes the construction of a 1:20 scale physical model, testing procedures, goals, and the results of the physical model tests. Following the physical model study, the thesis discusses the development of a three-dimensional CFD model, designed in a way that matched the physical model. Simulation results obtained from the CFD model are then compared to those from the physical model study and the accuracy and suitability of CFD modelling as a design tool are evaluated. This evaluation considers the surcharge upstream of the weir and transient pressures on the weir. The thesis concludes with recommendations for further research in this field. The results achieved show that the CFD model was able to accurately map the movement of particles within the domain, to fully develop a flow profile, and to accurately predict the water surface level. The pressure readings obtained during CFD modelling were in the same order as those obtained during physical modelling. However, the CFD modelling pressure readings did not often accurately correspond with the physical modelling data, with the average error being 92%. These results indicate that there is still further development required in CFD before it can be relied upon as a design tool independent of other experimental methods. The difficulty and the length of time taken to generate the results also indicate that, at this stage and in this particular scenario, the engineer would be better served through the use of a physical model.
AFRIKAANSE OPSOMMING: Die gebruik van gerekenariseerde vloeidinamika (CFD) as ’n ontwerpinstrument het toenemend gewild begin raak op die gebied van waterhulpbronne. Die doel van hierdie verslag is om kennis van CFD uit te brei en die nut van huidige CFD-programme as ’n modelleringsinstrument te bepaal. Daar word voorts ook gepoog om die akkuraatheid van CFD-modellering te bepaal in vergelyking met fisiese modellering – die meer gevestigde vorm van modeltoetsing. Dit is noodsaaklik dat navorsing gedoen word oor die bekragtiging van CFD, want met ’n toename in rekenaarkrag, verwerkingsnelheid en deurlopende ontwikkeling in die programme wat gebruik word om die modelle te genereer, sal CFD ’n noodsaaklike instrument vir die hidroulika-ingenieur word. ’n Belangrike probleem wat CFD-programme tans inhou, is die kartering van die vry oppervlak van ’n liggaam vloeistof in ’n tweefasse vloeitoestand (water en lug). Dit word verder bemoeilik deur die bestaan van driedimensionele vloei oor ’n labirint-stuwal en ’n skommelende “nappe”, wat by tye vereis dat ’n vry oppervlak sowel bo as onder die “nappe” gekarteer met word. Die verslag begin met ’n uiteensetting van die ontwerpmetodes en fisiese ontwerp van ’n tipiese labirintstuwal. Die bou van ’n 1:20-skaal- fisiese model, toetsprosedures, doelwitte en die resultate van die toetse op die fisiese model word dan beskryf. Ná die studie van die fisiese model, word die ontwikkeling van ’n driedimensionele CFD-model bespreek, wat ontwerp is om by die fisiese model te pas. Die simulasie-resultate van die CFD-model word dan vergelyk met dié van die studie van die fisiese model en die akkuraatheid en geskiktheid van CFD-modellering as ’n ontwerpinstrument word geëvalueer. In hierdie evaluering word die opdamming stroomop van die stuwal en druk op die stuwal ondersoek. Die verslag word afgesluit met aanbevelings vir verdere navorsing op hierdie gebied. Die resultate toon dat die CFD-model die beweging van partikels in die domein akkuraat kon karteer ten einde ’n volledige vloeiprofiel te ontwikkel en die watervlak akkuraat te voorspel. Die drukke wat tydens CFD-modellering verkry is, stem egter nie ooreen met die lesings wat tydens fisiese modellering verkry is nie. Die gemiddelde fout is 92%. Hierdie resultate toon dat verdere ontwikkeling in CFD nodig is voordat daarop staat gemaak kan word as ’n ontwerpinstrument wat onafhanklik van ander eksperimentele metodes gebruik kan word. Die moeilikheidsgraad en die lang tydsduur betrokke by die generering van resultate is ook ’n aanduiding dat die gebruik van ’n fisiese model die ingenieur op hierdie stadium en in hierdie spesifieke scenario beter tot diens sal wees.

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