Dissertations / Theses: 'Fluid dynamics – Computer simulation'

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Zhang, Junfang. "Computer simulation of nanorheology for inhomogenous fluids." Australasian Digital Thesis Program, 2005. http://adt.lib.swin.edu.au/public/adt-VSWT20050620.095154.

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Thesis (PhD) - Swinburne University of Technology, School of Information Technology, Centre for Molecular Simulation - 2005.
A thesis submitted in fulfilment of requirements for the degree of Doctor of Philosophy, Centre for Molecular Simulation, School of Information Technology, Swinburne University of Technology - 2005. Typescript. Bibliography: p. 164-170.

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Andersson, Tomas. "Controlling the fluid dynamics : an analysis of the workflow of fluids." Thesis, University of Gävle, Department of Mathematics, Natural and Computer Sciences, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-155.

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A scene containing dynamic fluids can be created in a number of ways. There are two approaches that will highlight the problems and obstacles that might occur. Today’s leading fluid simulator, RealFlow, simulates the fluid dynamics. A comparison between the two approaches will be made and are analyzed. Through experimentation, one of the approaches fails to produce the set requirements in the experiment and furthermore the two approaches differ in efficiency.

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Barran, Brian Arthur. "View dependent fluid dynamics." Texas A&M University, 2006. http://hdl.handle.net/1969.1/3827.

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This thesis presents a method for simulating fluids on a view dependent grid structure to exploit level-of-detail with distance to the viewer. Current computer graphics techniques, such as the Stable Fluid and Particle Level Set methods, are modified to support a nonuniform simulation grid. In addition, infinite fluid boundary conditions are introduced that allow fluid to flow freely into or out of the simulation domain to achieve the effect of large, boundary free bodies of fluid. Finally, a physically based rendering method known as photon mapping is used in conjunction with ray tracing to generate realistic images of water with caustics. These methods were implemented as a C++ application framework capable of simulating and rendering fluid in a variety of user-defined coordinate systems.

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Greenwood, Shannon Thomas. "The incorporation of bubbles into a computer graphics fluid simulation." Thesis, Texas A&M University, 2003. http://hdl.handle.net/1969.1/2267.

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We present methods for incorporating bubbles into a photorealistc fluid simulation. Previous methods of fluid simulation in computer graphics do not include bubbles. Our system automatically creates bubbles, which are simulated on top of the fluid simulation. These bubbles are approximated by spheres and are rendered with the fluid to appear as one continuous surface. This enhances the overall realism of the appearance of a splashing fluid for computer graphics. Our methods leverage the particle level set representation of the fluid surface. We create bubbles from escaped marker particles from the outside to the inside. These marker particles might represent air that has been trapped within the fluid surface. Further, we detect when air is trapped in the fluid and create bubbles within this space. This gives the impression that the air pocket has become bubbles and is an inexpensive way to simulate the air trapped in air pockets. The results of the simulation are rendered with a raytracer that includes caustics. This allows the creation of photorealistic images. These images support our position that the simple addition of bubbles included in a fluid simulation creates results that are much more true to life.

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Wrenninge, Magnus. "Fluid Simulation for Visual Effects." Thesis, Linköping University, Department of Science and Technology, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2347.

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This thesis describes a system for dealing with free surface fluid simulations, and the components needed in order to construct such a system. It builds upon recent research, but in a computer graphics context the amount of available literature is limited and difficult to implement. Because of this, the text aims at providing a solid foundation of the mathematics needed, at explaining in greater detail the steps needed to solve the problem, and lastly at improving some aspects of the animation process as it has been described in earlier works.

The aim of the system itself is to provide visually plausible renditions of animated fluids in three dimensions in a manner that allows it to be usable in a visual effects production context.

The novel features described include a generalized interaction layer providing greater control to artists, a new way of dealing with moving objects that interact with the fluid and a method for adding source and drain capabilities.

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Woodburn, Peter. "Computational fluid dynamics simulation of fire-generated flows in tunnels and corridors." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282879.

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Thampy, Sajjit. "Feature tracking in two dimensional time varying datasets." Master's thesis, Mississippi State : Mississippi State University, 2003. http://library.msstate.edu/etd/show.asp?etd=etd-04082003-160214.

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Doddamani, Niranjana Sharma. "A hierarchy based interface for integration of scientific applications." Master's thesis, Mississippi State : Mississippi State University, 2003. http://library.msstate.edu/etd/show.asp?etd=etd-12032002-141349.

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Nelson, Christopher C. "Simulations of spatially evolving compressible turbulence using a local dynamic subgrid model." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/12002.

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Smith, Thomas M. "Unsteady simulations of turbulent premixed reacting flows." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/13097.

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Melek, Zeki. "Interactive simulation of fire, burn and decomposition." Texas A&M University, 2007. http://hdl.handle.net/1969.1/85805.

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This work presents an approach to effectively integrate into one unified modular fire simulation framework the major processes related to fire, namely: a burning process, chemical combustion, heat distribution, decomposition and deformation of burning solids, and rigid body simulation of the residue. Simulators for every stage are described, and the modular structure enables switching to different simulators if more accuracy or more interactivity is desired. A "Stable Fluids" based three gas system is used to model the combustion process, and the heat generated during the combustion is used to drive the flow of the hot air. Objects, if exposed to enough heat, ignite and start burning. The decomposition of the burning object is modeled as a level set method, driven by the pyrolysis process, where the burning object releases combustible gases. Secondary deformation effects, such as bending burning matches and crumpling burning paper, are modeled as a proxy based deformation. Physically based simulation, done at interactive rates, enables the user to ef- ficiently test different setups, as well as interact and change the conditions during the simulation. The graphics card is used to generate additional frames for real-time visualization. This work further proposes a method for controlling and directing high resolution simulations. An interactive coarse resolution simulation is provided to the user as a "preview" to control and achieve the desired simulation behavior. A higher resolution "final" simulation that creates all the fine scale behavior is matched to the preview simulation such that the preview and final simulations behave in a similar manner. In this dissertation, we highlighted a gap within the CG community for the simulation of fire. There has not previously been a physically based yet interactive simulation for fire. This dissertation describes a unified simulation framework for physically based simulation of fire and burning. Our results show that our implementation can model fire, objects catching fire, burning objects, decomposition of burning objects, and additional secondary deformations. The results are plausible even at interactive frame rates, and controllable.

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Fredriksson, Adam. "Visual Comparison of Lagrangian and Semi-Lagrangian fluid simulation." Thesis, Blekinge Tekniska Högskola, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-14838.

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Context. Fluid simulations are an important part for enhancing the visualization of games, movies and other graphical applications. Fluid simulations can be achieved in different type of context ranging between slow, high-quality simulations which is mainly used for movies, to fast lower-quality simulations which is primarily used for real-time applications such as games. Objectives. The goal was to compare the visual appearance of a Lagrangian method and a semiLagrangian method when it came to realistic appearance. Methods. Identical scenes of water being rendered are made for both the Lagrangian and the semiLagrangian algorithm. This is later measured by using a user study which will provide the result of which method that provides a more realistic appearance Results. The result of the tests showed that the visual realism between the semi-Lagrangian and Lagrangian were different depending on the scene environment. Conclusions. The conclusion of the data presented in the result yields that the Lagrangian and semiLagrangian looks very much alike and there is no real realistic difference between the methods, some scene yields a vast majority of votes in the favor of one method.

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Brown, Jason. "Computational fluid dynamics in an equation-based, acausal modeling environment." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37247.

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The practice of building simulation is split between domains such as energy, multizone airflow, computational fluid dynamics (CFD) airflow, and controls analysis, as well as between the tools which conduct these analyses. Previous work in the integration of these analyses and tools have focused on linking existing tools, written in algorithmic programming languages, together by interfacing them using coupling mechanisms implemented in algorithmic programming languages. This thesis takes a different approach, using the equation-based, object oriented modeling language Modelica to create models in different domains and interfaces between those models within a single framework which has benefits to the modeler/analyst in terms of both representation of physical processes and flexibility in modeling systems composed of many interacting components. Specifically, the simulation of airflows within buildings has historically been compartmentalized into distinct domains such as nodal network (multizone) simulations and CFD. Such airflow simulations are also often treated independently of building energy simulations (via heat transfer) despite their interrelation. Recent work has reported on combining these types of analyses by linking pre-existing simulation software together. Here a prototype CFD package of models is built in Modelica and coupled to models of conductive heat transfer and controls. Comparisons of results of simulations so constituted to analytical solutions and benchmark data available in the literature show good agreement, indicating the technical viability of this approach. Limitations include the absence of turbulence modeling and the lack of modeling features which improve computational efficiency, such as non-uniform grids.

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Jury, Simon Ian. "Computer simulation of complex fluids using dissipative particle dynamics." Thesis, University of Edinburgh, 1999. http://hdl.handle.net/1842/12323.

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A parallel code has been developed to implement the Dissipative Particle Dynamics (DPD) simulation algorithm. DPD is a particle based method which simulates the fluid at a mesoscopic scale. Since the DPD interactions are both soft (compared to the potentials used in molecular dynamics) and momentum conserving, DPD offers the possibility of reproducing hydrodynamic behaviour at large length and time scales. Other techniques for hydrodynamic flow simulation are reviewed before the DPD algorithm is presented together with some of the coding issues arising from using a parallel implementation. Equilibrium thermodynamics, as pertaining to phase separation, is presented, together with the scaling arguments used to derive growth laws for domain size. An in depth study of domain size scaling in three dimensional binary fluid phase separation has been completed. For an appropriate choice of parameters, domain growth is shown to enter a regime dominated by capillary and viscous forces. Qualitative analysis of interface maps and velocity fields reveal the Siggia mechanism for domain coarsening in operation. By performing simulations over two orders of magnitude in reduced length and reduced time units, a small yet significant breakdown of scaling is observed in the domain growth rate. Possible explanations for this breakdown are considered. By extending the code, we study a dense solution of an amphiphilic species focusing on the smectic mesophase. Results are presented for the formation of monodomain, bidomain and polydomain lamellar phases. Shearing is performed, using Lees Edwards boundary conditions, the effect of shear on the lamellar phase is examined. It is shown how, for certain concentrations and shear rates, a lamellar structure will tend to fold in upon itself, this is a possible first stage in onion formation.

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Marcelli, Gianluca, and g. marcelli@imperial ac uk. "The role of three-body interactions on the equilibrium and non-equilibrium properties of fluids from molecular simulation." Swinburne University of Technology. Centre for Molecular Simulation, 2001. http://adt.lib.swin.edu.au./public/adt-VSWT20060112.082425.

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The aim of this work is to use molecular simulation to investigate the role of three-body interatomic potentials in noble gas systems for two distinct phenomena: phase equilibria and shear flow. In particular we studied the vapour-liquid coexisting phase for pure systems (argon, krypton and xenon) and for an argon-krypton mixture, utilizing the technique called Monte Carlo Gibbs ensemble. We also studied the dependence of the shear viscosity, pressure and energy with the strain rate in planar Couette flow, using a non-equilibrium molecular simulation (NEMD) technique. The results we present in this work demonstrate that three-body interactions play an important role in the overall interatomic interactions of noble gases. This is demonstrated by the good agreement between our simulation results and the experimental data for both equilibrium and non-equilibrium systems. The good results for vapour-liquid coexisting phases encourage performing further computer simulations with realistic potentials. This may improve the prediction of quantities like critical temperature and density, in particular of substances for which these properties are difficult to obtain from experiment. We have demonstrated that use of accurate two- and three-body potentials for shearing liquid argon and xenon displays significant departure from the expected strain rate dependencies of the pressure, energy and shear viscosity. For the first time, the pressure is convincingly observed to vary linearly with an apparent analytic y2 dependence, in contrast to the predicted y3/2 dependence of mode -coupling theory. Our best extrapolation of the zero -shear viscosity for argon gives excellent agreement (within 1%) with the known experimental data. To the best of our knowledge, this the first time that such accuracy has been achieved with NEMD simulations. This encourages performing simulations with accurate potentials for transport properties.

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Lea, Jimmy Chemical Sciences &amp Engineering Faculty of Engineering UNSW. "The computational fluid dynamics analysis and optimisation of process vessels used in the manufacture of military propellants and high explosives." Publisher:University of New South Wales. Chemical Sciences & Engineering, 2007. http://handle.unsw.edu.au/1959.4/40560.

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This research focuses on the computational fluid dynamics modelling and simulation of the existing reactors and mixing tanks employed by the Australian Defence Industries to manufacture military propellants for gun projectiles and small rockets; high explosives for naval gun projectiles and aerial bombs. The main objective of this research is to gain a thorough understanding of these process vessels via research and to provide recommendations to improve their performance. Reactors and mixing tanks were chosen as the test unit operations because although they contribute significantly to the manufacturing process, reactors have frequently been poorly understood or in the case of mixing tanks, taken for granted. Consequently, there is a lack of comprehensive knowledge to support successful operations of these process vessels. In addition, this research also recommends using photocatalysis technology to destroy liquid wastes produced from such manufacturing activities. For each product, a full characterisation was provided that included detailed theoretical analyses that presents a unique insight into the hydrodynamics occurring in these process vessels. The credibility of theoretical predictions was demonstrated via qualitative and quantitative validation using particle image velocimetry. Results from characterisation showed that the reactors and mixing tanks employed in the manufacture of military propellants, high explosives or aerial bombs were operating at sub-optimum conditions. To tackle this shortcoming, four ideal geometrical configurations that promised optimum performance were proposed for each of the test studies. These included a designer reactor for the manufacture of military propellants and effective mixing tanks for suspending high explosive particles, blending different high explosives and for manufacturing aerial bombs. The correct implementation of these recommendations will provide an optimum operation that achieves high product throughput and concurrently reduces reject rate. Research was also conducted to formulate a set of multipurpose design guidelines for a suspension mixing tank. The design template created from the results will provide valuable information to researchers across industries in their quest to optimise any unit suspension mixing tank operated on the principle of mechanical agitation. Finally, modelling of reactive species was conducted on a laboratory-scale photoreactor, involving physical experiments to destroy toxic effluent aqueous phase.

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Myhrberg, Viktor. "Fluid Dynamics as a Foundation for Game Mechanics." Thesis, Uppsala universitet, Institutionen för speldesign, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-419539.

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This thesis investigates whether a game world based solely on fluid dynamics could be an interesting alternative to one based on rigid bodies by presenting a prototype to players where they can control the movement of a fluid. The players evaluate the prototype’s responsiveness, intuitiveness, visual appeal, immersion, and how well they think the fluid could represent ghosts, flocks, magic, and a platformer avatar by rating them vocally while playing. The fluid physics engine prototype is a simple grid-based one that utilizes the ideal gas law and pressure gradient force to calculate the flow between its cells. It is unstable and thus cannot handle too large time-steps. Therefore, simulating many cells (more than 10000 for two fluids) at the same is a slow process, and the prototype can only present a pixelated result. If a highresolution game is in general preferred by players, a computationally efficient solution could consist of utilizing shaders for cell blending. In the experiments, all categories except the platform avatar received positive evaluations despite the prototype’s early stage, which according to theories presented within Swink’s Game Feel (Swink, 2009) and the MDA framework (Hunicke et al., 2004) may indicate that a game based on a fluid physics engine like this one could be entertaining. The simulation could possibly be run as a separate system to add game mechanics to a game based on rigid bodies as well.

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Drewniak, Marta. "Computer Simulations of Dilute Polymer Solutions: Chain Overlaps and Entanglements." Thesis, University of North Texas, 1996. https://digital.library.unt.edu/ark:/67531/metadc278086/.

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Chain conformations and the presence of chain overlaps and entanglements in dilute polymer solutions have been analyzed. The fundamental problem of existence of chain overlaps in dilute solutions is related to the drag reduction phenomenon (DR). Even though DR occurs in solutions with the concentration of only few parts per million (ppm), some theories suggest that entanglements may play an important role in DR mechanism. Brownian dynamics technique have been used to perform simulations of dilute polymer solutions at rest and under shear flow. A measure of interchain contacts and two different measures of entanglements have been devised to evaluate the structure of polymer chains in solution. Simulation results have shown that overlaps and entanglements do exist in static dilute solutions as well as in solutions under shear flow. The effect of solution concentration, shear rate and molecular mass have been examined. In agreement with the solvation theory of DR mechanism, simulation results have demonstrated the importance of polymer + polymer interactions in dilute solutions.

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Jackson, Mark John Clinical School St Vincent's Hospital Faculty of Medicine UNSW. "A study of vein graft haemodynamics using computational fluid dynamics techniques." Awarded by:University of New South Wales, 2007. http://handle.unsw.edu.au/1959.4/38575.

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Atherosclerosis, the leading cause of mortality in Western societies, affects large elastic arteries, causing focal deposition of proliferative inflammatory and lipid-laden cells within the artery. Several risk factors have been causally implicated in the ???reaction to injury??? hypothesis first described by Ross in 1969. The ???injury??? sustained by endothelial cells may be either mechanical or chemical. Environmental factors have a role in the production of chemical agents that are injurious to the endothelium. Mechanical stresses such as wall tensile stress are proportional to systemic blood pressure and pulse pressure. Essentially, these systemic pressures are fairly evenly distributed throughout the circulation. However, atherosclerotic lesions characteristically occur at focal sites within the human vasculature; at or near bifurcations, within the ostia of branch arteries and at regions of marked or complex curvature, where local haemodynamic abnormalities occur. The most discussed haemodynamic factor seems to be low or highly oscillating wall shear stress which exists on the outer wall of bifurcations and on the inner aspect of curving vessels. The magnitude of these haemodynamic forces may not be great but the subtleties of their variable spatial distribution may help to explain the multifocal distribution of atherosclerotic plaques. With the altered haemodynamics there is endothelial injury and phenotypic changes in the endothelium result, which in turn lead to endothelial cell dysfunction. These haemodynamic variables are difficult to measure directly in vivo. In this work a novel model is developed utilising human autologous vein bypass grafts as a surrogate vessel for the observation of pathological structural changes in response to altered haemodynamics. The influence of haemodynamic factors (such as wall shear stress) in the remodeling of the vein graft wall and the pathogenesis of Myointimal Hyperplasia (MIH) and resultant wall thickening in femoral bypass grafts is analysed. The haemodynamic determinants of MIH (which have been established in many animal models) are similar to those implicated in atherosclerosis. The accelerated responses of the vein (Intimal hyperplasia develops much more rapidly than atherosclerotic lesions in native vessels) make it an ideal model to expediently examine the hypothesised relationships prospectively in an in vivo setting. Furthermore, the utilisation of in vivo data acquired from non-invasive diagnostic methods (such as Magnetic Resonance Angiography (MRA) and Duplex ultrasound) combined with the application of state-of-the-art Computational Fluid Dynamic (CFD) techniques makes the model essentially non-invasive. The following hypotheses are examined: 1) regions of Low shear and High tensile stress should develop disproportionately greater wall thickening, 2) regions of greater oscillatory blood flow should develop greater wall thickening, and 3) regions of lower wall shear should undergo inward (or negative) remodelling and result in a reduction in vessel calibre. The conclusions reached are that abnormal haemodynamic forces, namely low Time-averaged Wall Shear Stress, are associated with subsequent wall thickening. These positive findings have great relevance to the understanding of vein graft MIH and atherosclerosis. It was also evident that with non-invasive data and CFD techniques, some of the important haemodynamic factors are realistically quantifiable (albeit indirectly). The detection of parameters known to be causal in the development of graft intimal hyperplasia or other vascular pathology may improve ability to predict clinical problems. From a surgical perspective this might be employed to facilitate selection of at-risk grafts for more focused postoperative surveillance and reintervention. On a broader stage the utilisation of such analyses may be useful in predicting individuals at greater risk of developing atherosclerotic deposits, disease progression, and the likelihood of clinical events such as heart attack, stroke and threat of limb loss.

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Forrester, Alexander I. J. "Efficient global aerodynamic optimisation using expensive computational fluid dynamics simulations." Thesis, University of Southampton, 2004. https://eprints.soton.ac.uk/45902/.

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The expense of high fidelity computational fluid dynamics, in terms of time and amount of computing resources required, excludes such methods from the early stages of aircraft design. It is only in the early, conceptual, stage of aircraft development where a wide range of designs are considered and global, rather than local, optimisation can play a key role. This thesis deals with methods which may allow high cost computer simulations to be used within a global optimisation design process. The first half of the thesis concentrates on the use of surrogate modeling of the optimisation design space, which allows cheap approximations to be used in lieu of expensive computer simulations. The process is automated and present statistical methods are modified to accommodate problems associated with the simulation of fluid flow and uncertainty within an automated system. The re-interpolation of a regression model of noisy data is presented as a method of improving convergence towards a global optimum. The second half of the thesis develops methods of using partially converged computational fluid dynamics simulations within a surrogate modelling optimisation process. Significant time savings are made possible by reducing computational effort directed at producing a surrogate for regions of poor designs and concentrating resources on modelling regions of promising designs.

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Moreau, Filip. "Physics-Based, Real-Time Simulation of Fluid-Immersed Rigid Bodies." Thesis, Malmö universitet, Fakulteten för teknik och samhälle (TS), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-43343.

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Objects interacting with fluid are of high interest to visually present in three-dimensional applications, such as computer games and virtual environments. For presenting the interactions with high correctness, dynamic rigid body simulation may be used. This paper presents methods for efficient, physics-based real-time simulation of fluid-immersed rigid bodies, where the correctness of the simulation is maintained. Simulated forces include gravity, buoyancy, thrust, drag, and lift. To have the simulation run efficiently in real-time, discretization of the simulated rigid body is made by applying mentioned forces to a user-defined number of particles, sampled pseudo-randomly within the rigid body.

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Sjöstedt, Carl-Johan. "On the modular modelling for dynamical simulation with application to fluid systems." Licentiate thesis, KTH, Machine Design (Div.), 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-566.

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This licentiate thesis highlights some topics on modular modelling for dynamical simulation with application to fluid systems. The results are based on experience from the development of the fuel cell component simulation environment NFCCPP. The general application is cross-enterprise simulation of technical systems. There are four main topics: component definition including selection of interfaces, lumped modelling of fluid components, the use of dynamical equations to reduce simulation time in large systems and methods of to protect the intellectual property (IP) of a component.

An overview of different dynamical fluid simulation tools such as HOPSAN, MATLAB/Simulink and Easy5 is presented. Special focus is on interfaces, where different approaches for representing interfaces are presented using an illustrative example. Selecting interfaces is however not a separated task from how to set up and solve the underlying equations, which also is shown. Equations to model a lumped component are derived, to get a mathematical background to what problems there are to solve. These equations are derived especially to be applicable in block model software simulation tools such as MATLAB/Simulink. The equations are also compared with the bond-graph approach of representing dynamical systems. A twinscrew compressor is modelled in MATLAB/Simulink as an implementation of these equations. A method to decrease the simulation time in dynamical fluid system is also presented. The technique is to add virtual mass in the force equation to get a slower acceleration of the fluid. Using this slower response, it is possible to use larger time-steps when integrating the equations and thus the total simulation time can be reduced. The error introduced using this method is a modelling error in the time domain, and it is comparable with using unit transmission lines (UTL:s), as does HOPSAN.

The protection of the intellectual property (IP) of a component model is presented. The concept of clamping is thoroughly explained, as it often is overlooked in conventional IPprotection. Three concepts for code protection are presented: “Centralised simulation with remote user control”, “Localised simulation with simulation-time model usage control” and “Parallel distributed simulation”. The NFCCPP implementation of the concept “Localised simulation with simulation-time model usage control” is presented in more detail.

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Srinivasan, Raghavan. "CFD Heat Transfer Simulation of the Human Upper Respiratory Tract for Oronasal Breathing Condition." Thesis, North Dakota State University, 2011. https://hdl.handle.net/10365/29310.

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In this thesis. a three dimensional heat transfer model of heated airflow through the upper human respiratory tract consisting of nasal, oral, trachea, and the first two generations of bronchi is developed using computational fluid dynamics simulation software. Various studies have been carried out in the literature investigating the heat and mass transfer characteristics in the upper human respiratory tract, and the study focuses on assessing the injury taking place in the upper human respiratory tract and identifying acute tissue damage based on level of exposure. The model considered is for the simultaneous oronasal breathing during the inspiration phase with high volumetric flow rate of 90/liters minute and a surrounding air temperature of 100 degrees centigrade. The study of the heat and mass transfer, aerosol deposition and flow characteristics in the upper human respiratory tract using computational fluid mechanics simulation requires access to a two dimensional or three dimensional model for the human respiratory tract. Depicting an exact model is a complex task since it involves the prolonged use of imaging devices on the human body. Hence a three dimensional geometric representation of the human upper respiratory tract is developed consisting of nasal cavity, oral cavity, nasopharynx, pharynx, oropharynx, trachea and first two generations of the bronchi. The respiratory tract is modeled circular in cross-section and varying diameter for various portions as identified in this study. The dimensions are referenced from the literature herein. Based on the dimensions, a simplified model representing the human upper respiratory tract is generated.This model will be useful in studying the flow characteristics and could assist in treatment of injuries to the human respiratory tract as well as help optimize drug delivery mechanism and dosages. Also a methodology is proposed to measure the characteristic dimension of the human nasal and oral cavity at the inlet/outlet points which are classified as internal measurements.

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Tang, Hansong. "Numerical simulation of unsteady three dimensional incompressible flows in complex geometries." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/19324.

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Steiner, Thomas. "Dissipative particle dynamics simulation of microfluidic systems with fluid particle methods on high performance computers." Aachen Shaker, 2009. http://d-nb.info/995271100/04.

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Holladay, Seth R. "Optimized Simulation of Granular Materials." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3856.

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Visual effects for film and animation often require simulated granular materials, such as sand, wheat, or dirt, to meet a director's needs. Simulating granular materials can be time consuming, in both computation and labor, as these particulate materials have complex behavior and an enormous amount of small-scale detail. Furthermore, a single cubic meter of granular material, where each grain is a cubic millimeter, would contain a billion granules, and simulating all such interacting granules would take an impractical amount of time for productions. This calls for a simplified model for granular materials that retains high surface detail and granular behavior yet requires significantly less computational time. Our proposed method simulates a minimal number of individual granules while retaining particulate detail on the surface by supporting surface particles with simplified interior granular models. We introduce a multi-state model where, depending on the material state of the interior granules, we replace interior granules with a simplified simulation model for the state they are in and automate the transitions between those states. The majority of simulation time can thus be focused on visible portions of the material, reducing the time spent on non-visible portions, while maintaining the appearance and behavior of the mass as a whole.

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Fahey, Mark, and n/a. "Assessment of the suitability of CFD for product design by analysing complex flows around a domestic oven." University of Otago. Department of Design Studies, 2007. http://adt.otago.ac.nz./public/adt-NZDU20070417.111809.

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Competitive global markets are increasing the commercial pressure on manufacturing companies to develop better products in less time. To meet these demands, the appliance manufacturer, Fisher & Paykel, has considered the use of computer simulation of fluid flows to assist in product design. This technology, known as Computational Fluid Dynamics (CFD), has the potential to provide rewarding insight into the behaviour of designs involving fluids. However, the investment in CFD is not without risk. This thesis investigates the use of CFD in oven design expressly to evaluate the numerical accuracy and suitability of CFD in the context of oven product development. CFD was applied to four cases related to oven design, along with detailed experimental investigations, and resulted in a number of relevant findings. In a study of an impinging jet, the SST turbulence model was found to produce better results than the k-ε turbulence model. Measurements indicated that the flow was unsteady, but CFD struggled to reproduce this behaviour. The synergy between experimental and numerical techniques was highlighted in the simulation of a two-pane oven door, and resulted in temperatures on outer surface of the door predicted by CFD to within 2% of measured values. In the third study, a CFD simulation of a tangential fan failed to deliver acceptable steady-state results, however a transient simulation showed promise. The final case examined the flows through the door and cooling circuit of the Titan oven. Velocities predicted by CFD compared well against measurements in some regions, such as the potential core of the jet at the outlet vent, but other regions, such as entrained air, were poor. Temperatures were predicted to within an average of 2% of measured values. It is found that limited accuracy does not necessarily prevent CFD from delivering engineering value to the product development process. The engineering value delivered by CFD is instead more likely to be limited by the abilities of the user. Incompatibilities between CFD and the product development process can reduce the potential value of CFD but the effects can be minimised by appropriate management action. The benefits of CFD are therefore found to be sufficient to merit its use in the product development process, provided its integration into the organisation is managed effectively and the tool is used with discernment. Recommendations for achieving this are provided.

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Li, Xiaoyi. "Computational study of fluid particles dynamics of drops, rheology of emulsions and mechanics of biological cells /." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 283 p, 2007. http://proquest.umi.com/pqdweb?did=1362531671&sid=35&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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Wang, Huamin. "Practical water animation using physics." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31745.

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Thesis (Ph.D)--Computing, Georgia Institute of Technology, 2010.
Committee Chair: Greg Turk; Committee Member: C. Karen Liu; Committee Member: Irfan Essa; Committee Member: Jarek Rossignac; Committee Member: Peter J. Mucha. Part of the SMARTech Electronic Thesis and Dissertation Collection.

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Rahimian, Abtin. "Parallel algorithms for direct blood flow simulations." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/43611.

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Fluid mechanics of blood can be well approximated by a mixture model of a Newtonian fluid and deformable particles representing the red blood cells. Experimental and theoretical evidence suggests that the deformation and rheology of red blood cells is similar to that of phospholipid vesicles. Vesicles and red blood cells are both area preserving closed membranes that resist bending. Beyond red blood cells, vesicles can be used to investigate the behavior of cell membranes, intracellular organelles, and viral particles. Given the importance of vesicle flows, in this thesis we focus in efficient numerical methods for such problems: we present computationally scalable algorithms for the simulation of dilute suspension of deformable vesicles in two and three dimensions. Our method is based on the boundary integral formulation of Stokes flow. We present new schemes for simulating the three-dimensional hydrodynamic interactions of large number of vesicles with viscosity contrast. The algorithms incorporate a stable time-stepping scheme, high-order spatiotemporal discretizations, spectral preconditioners, and a reparametrization scheme capable of resolving extreme mesh distortions in dynamic simulations. The associated linear systems are solved in optimal time using spectral preconditioners. The highlights of our numerical scheme are that (i) the physics of vesicles is faithfully represented by using nonlinear solid mechanics to capture the deformations of each cell, (ii) the long-range, N-body, hydrodynamic interactions between vesicles are accurately resolved using the fast multipole method (FMM), and (iii) our time stepping scheme is unconditionally stable for the flow of single and multiple vesicles with viscosity contrast and its computational cost-per-simulation-unit-time is comparable to or less than that of an explicit scheme. We report scaling of our algorithms to simulations with millions of vesicles on thousands of computational cores.

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Frankfurt, Ricardo. "Simulação de transporte de massa de um soluto em meio poroso com auxílio do CFD (Computer Fluid Dynamics)." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-29012009-162554/.

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Com o avanço dos computadores pessoais, problemas técnicos complexos, antes restritos aos grandes centros de pesquisas internacionais, passam a ser acessíveis pelas mais diversas áreas do conhecimento, como as engenharias e em particular a Engenharia Química. Fenômenos físicos são representados matematicamente por equações diferenciais, que na maioria das vezes não possuem solução analítica possível. O CFD ( Computer Fluid Dynamics) é uma técnica numérica iterativa, que busca a solução destas equações diferenciais através da discretização do domínio estudado e das equações que governam o fenômeno envolvido. Neste trabalho, através de um software especialista de CFD, o ANSYS CFX 11.0, foi simulado o transporte de massa e momento de um soluto traçador, o Cloreto, presente no sal Cloreto de Sódio, em um meio poroso. Em seguida, os resultados desta simulação foram comparados e validados por um experimento de transporte de massa numa caixa de areia.
With the advance of the personal computers, complex technical problems, before restricted to the huge centers of international researches, have become more accessible by many areas of the knowledge, like the engineering and in particular the Chemical Engineering. Physical phenomena are represented mathematically by differentials equations, which most of the time do not have possible analytical solution. CFD (Computer Fluid Dynamics) is an iterative numeric technique, which search the solution of these differentials equations through both discretization of the studied domain and the equations that govern the involved phenomenon. In this work, through a CFD\'s specialist software, ANSYS CFX 11.0, it was simulated the mass and momentum transport of a solute tracer, Chloride, present in Sodium Chloride, in a porous media. After this, the simulations results were compared and validated in a mass transport experiment in a sand box.

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Wake, Amanda Kathleen. "Modeling Fluid Mechanics in Individual Human Carotid Arteries." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7562.

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In the interest of furthering the understanding of hemodynamics, this study has developed a method for modeling fluid mechanics behavior in individual human carotid arteries. A computational model was constructed from magnetic resonance (MR) data of a phantom carotid bifurcation model, and relevant flow conditions were simulated. Results were verified by comparison with previous in vitro experiments. The methodology was extended to create subject-specific carotid artery models from geometry data and fluid flow boundary conditions which were determined from MR and phase contrast MR (PCMR) scans of human subjects. The influence of subject-specific boundary conditions on the flow field was investigated by comparing a model based on measured velocity boundary conditions to a model based on the assumption of idealized velocity boundary conditions. It is shown that subject-specific velocity boundary conditions in combination with a subject-specific geometry and flow waveform influence fluid flow phenomena associated with plaque development. Comparing a model with idealized Womersley flow boundary conditions to a model with subject-specific velocity boundary conditions demonstrated the importance of employing inlet and flow division data obtained from individual subjects in order to predict accurate, clinically relevant, fluid flow phenomena such as low wall shear stress areas and negative axial velocity regions. This study also illustrates the influence of the bifurcation geometry, especially the flow divider position, with respect to the velocity distribution of the common carotid artery on the development of flow characteristics. Overall it is concluded that accurate geometry and velocity measurements are essential for modeling fluid mechanics in individual human carotid arteries for the purpose of understanding atherosclerosis in the carotid artery bifurcation.

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Awad, Mohammad Ali. "An investigation of flux-limiting and non-linear solution techniques for efficient simulation of transport in porous media." Thesis, Queensland University of Technology, 2000. https://eprints.qut.edu.au/37057/1/37057_Awad_2000.pdf.

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This thesis presents a comprehensive analysis of efficient computational techniques for simulating transport in porous media. The equations that govern the flow of liquids in porous media are ubiquitous in science and engineering. For example, the governing equations find application in fields as diverse as drying, ground water flow, contamination and petroleum reservoir engineering. Typically, the conservation laws that are encountered are highly non-linear and have steep fronts that require resolution in time. It is one of the aims of this work to analyse the use of higher order spatial weighting schemes and temporal methods for reducing numerical dispersion. Another important ingredient in the development of an efficient simulator is the treatment of the non-linear system that results from the discrete analogue of the conservation law. In this work, a vertex-centered finite volume method has been used for discretising a representative conservation law in one-dimension and three non-linear iterative methods, an inexact full Newton method, the modified Shamanskii method (referred as the Definitive method), and the globally convergent Newton method ( with line searching) will be scrutinised. The globally convergent Newton method will converge to a solution from almost any any starting point, or it will fail to do so in a well defined manner. The size of the Newton step used in this scheme is controlled to ensure that a sufficient decrease in the non-linear residual has been achieved before the new iterate is computed. In this sense, one can view the solution procedure as a minimisation of the sum of the squares of the coordinate functions. Two case studies have been chosen to highlight the performance of the chosen numerical techniques. At first, the focus will be on the accuracy and efficiency of the spatial weighting methods for a linear advection-dispersion equation and then, a two-phase flow problem will be analysed to gauge the performance of the non-linear solvers. In both cases, comparisons with exact solutions will be provided. One of the outcomes of this work highlights that flux limiting techniques, when used in conjunction with Crank Nicolson temporal weighting, are far more accurate and efficient than solution methods that use a first order upstream strategy. Furthermore, the flux limiter with the sensor based on the ratio of fluxes, when used in combination with the Definitive non-linear solution technique produced an efficient and accurate computational model for two-phase flow.

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Steiner, Thomas [Verfasser]. "Dissipative Particle Dynamics : Simulation of Microfluidic Systems With Fluid Particle Methods on High Performance Computers / Thomas Steiner." Aachen : Shaker, 2009. http://d-nb.info/1156518954/34.

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35

Blom, Andrej. "Comparing FumeFx with Autodesk Maya Dynamic System." Thesis, University of Gävle, Department of Mathematics, Natural and Computer Sciences, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-610.

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One of the main problem areas within computer graphics is simulating natural phenomena’s, working with fluid solvers, and particle systems. In the special effects industry, there is a demand for mimicking appearance of common special effect such as fire, smoke, and water. Autodesk Maya and FumeFx are used for exploring those methods in creating smoke and fire simulations and implementing those into a

large dynamic system, while researching the possibility to efficiently control and modify an entire dynamic system on a per object level. Final production renders results are from both Maya and FumeFx.

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Lundqvist, Viktor. "A smoothed particle hydrodynamic simulation utilizing the parallel processing capabilites of the GPUs." Thesis, Linköping University, Department of Science and Technology, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-21761.

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Simulating fluid behavior has proven to be a demanding challenge which requires complex computational models and highly efficient data structures. Smoothed Particle Hydrodynamics (SPH) is a particle based computational model used to simulate fluid behavior that has been found capable of producing convincing results. However, the SPH algorithm is computational heavy which makes it cumbersome to work with.

This master thesis describes how the SPH algorithm can be accelerated by utilizing the GPU’s computational resources. It describes a model for how to distribute the work load on the GPU and presents a suitable data structure. In addition, it proposes a method to represent and handle moving objects in the fluids surroundings. Finally, the performance gain due to the GPU is evaluated by comparing processing times with an identical implementation running solely on the CPU.

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Fimbres, Weihs Gustavo Adolfo UNESCO Centre for Membrane Science &amp Technology Faculty of Engineering UNSW. "Numerical simulation studies of mass transfer under steady and unsteady fluid flow in two- and three-dimensional spacer-filled channels." Publisher:University of New South Wales. UNESCO Centre for Membrane Science & Technology, 2008. http://handle.unsw.edu.au/1959.4/41453.

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Hollow fibre and spiral wound membrane (SWM) modules are the most common commercially available membrane modules. The latter dominate especially for RO, NF and UF and are the focus of this study. The main difficulty these types of modules face is concentration polarisation. In SWM modules, the spacer meshes that keep the membrane leaves apart also help reduce the effects of concentration polarisation. The spacer filaments act as flow obstructions, and thus encourage flow destabilisation and increase mass transfer enhancement. One of the detrimental aspects of the use of spacers is an increase of pressure losses in SWM modules. This study analyses the mechanisms that give rise to mass transfer enhancement in narrow spacer-filled channels, and investigates the relationship between flow destabilisation, energy losses and mass transfer. It shows that the regions of high mass transfer on the membrane surface correlate mainly with those regions where the fluid flow is towards the membrane. Based on the insights gained from this analysis, a series of multi-layer spacer designs are proposed and evaluated. In this thesis, a Computational Fluid Dynamics (CFD) model was used to simulate steady and unsteady flows with mass transfer in two- and three-dimensional narrow channels containing spacers. A solute with a Schmidt number of 600 dissolving from the wall and channel Reynolds numbers up to 1683 were considered. A fully-developed concentration profile boundary condition was utilised in order to reduce the computational costs of the simulations. Time averaging and Fourier analysis were performed to gain insight into the dynamics of the different flow regimes encountered, ranging from steady flow to vortex shedding behind the spacer filaments. The relationships between 3D flow effects, vortical flow, pressure drop and mass transfer enhancement were explored. Greater mass transfer enhancement was found for the 3D geometries modelled, when compared with 2D geometries, due to wall shear perpendicular to the bulk flow and streamwise vortices. Form drag was identified as the main component of energy loss for the flow conditions analysed. Implications for the design of improved spacer meshes, such as extra layers of spacer filaments to direct the bulk flow towards the membrane walls, and filament profiles to reduce form drag are discussed.

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Ertbruggen, Caroline van. "Study of aerosol transport and deposition in the lungs using computational fluid dynamics (CFD)." Doctoral thesis, Universite Libre de Bruxelles, 2005. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/211037.

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We have studied gas flow and particle deposition in a realistic three-dimensional model of the bronchial tree, extending from the trachea to the segmental bronchi (7th airway generation for the most distal ones) using Computational Fluid Dynamics (CFD). The model is based on the morphometrical data of Horsfield et al. [J. Appl. Physiol. 31: 207-217, 1971] and on bronchoscopic and CT images, which give the spatial 3D-orientation of the curved ducts. It incorporates realistic angles of successive branching planes. Steady inspiratory flow varying between 50cm³/s and 500cm³/s was simulated as well as deposition of spherical aerosol particles (1 to 7&
Doctorat en sciences appliquées
info:eu-repo/semantics/nonPublished

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39

Ha, Oai The. "Modeling and Numerical Investigation of Hot Gas Defrost on a Finned Tube Evaporator Using Computational Fluid Dynamics." DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/400.

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Defrosting in the refrigeration industry is used to remove the frost layer accumulated on the evaporators after a period of running time. It is one way to improve the energy efficiency of refrigeration systems. There are many studies about the defrosting process but none of them use computational fluid dynamics (CFD) simulation. The purpose of this thesis is (1) to develop a defrost model using the commercial CFD solver FLUENT to simulate numerically the melting of frost coupled with the heat and mass transfer taking place during defrosting, and (2) to investigate the thermal response of the evaporator and the defrost time for different hot gas temperatures and frost densities. A 3D geometry of a finned tube evaporator is developed and meshed using Gambit 2.4.6, while numerical computations were conducted using FLUENT 12.1. The solidification and melting model is used to simulate the melting of frost and the Volume of Fluid (VOF) model is used to render the surface between the frost and melted frost during defrosting. A user-defined-function in C programming language was written to model the frost evaporation and sublimation taking place on the free surface between frost and air. The model was run under different hot gas temperatures and frost densities and the results were analyzed to show the effects of these parameters on defrosting time, input energy and stored energy in the metal mass of the evaporator. The analyses demonstrate that an optimal hot gas temperature can be identified so that the defrosting process takes place at the shortest possible melting time and with the lowest possible input energy.

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Kim, Yootai. "Control of physics-based fluid animation using a velocity-matching method." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1149087881.

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Gempesaw, Daniel. "A multi-resolution discontinuous Galerkin method for rapid simulation of thermal systems." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42775.

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Efficient, accurate numerical simulation of coupled heat transfer and fluid dynamics systems continues to be a challenge. Direct numerical simulation (DNS) packages like FLU- ENT exist and are sufficient for design and predicting flow in a static system, but in larger systems where input parameters can change rapidly, the cost of DNS increases prohibitively. Major obstacles include handling the scales of the system accurately - some applications span multiple orders of magnitude in both the spatial and temporal dimensions, making an accurate simulation very costly. There is a need for a simulation method that returns accurate results of multi-scale systems in real time. To address these challenges, the Multi- Resolution Discontinuous Galerkin (MRDG) method has been shown to have advantages over other reduced order methods. Using multi-wavelets as the local approximation space provides an inherently efficient method of data compression, while the unique features of the Discontinuous Galerkin method make it well suited to composition with wavelet theory. This research further exhibits the viability of the MRDG as a new approach to efficient, accurate thermal system simulations. The development and execution of the algorithm will be detailed, and several examples of the utility of the MRDG will be included. Comparison between the MRDG and the "vanilla" DG method will also be featured as justification of the advantages of the MRDG method.

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Vantieghem, Stijn. "Numerical simulations of quasi-static magnetohydrodynamics using an unstructured finite volume solver: development and applications." Doctoral thesis, Universite Libre de Bruxelles, 2011. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209929.

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Dans cette dissertation, nous considérons l’écoulement des liquides conducteurs d’électricité dans un champ magnétique externe. De tels écoulements sont décrits par les équations de la magnétohydrodynamique (MHD) quasi-statique, et sont fréquemment rencontrés dans des applications pratiques. Il suit qu’il y a un intérêt fort pour des outils numérques qui peuvent simuler ces écoulements dans des géometries complexes.

La première partie de cette thèse (chapitres 2 et 3) est dédiée à la présentation de la machinerie numérique qui a été utilisée et implémentée afin de résoudre les équations de la MHD quasi-statistique (incompressible). Plus précisément, nous avons contribué au développement d’un solveur volumes finis non-structuré parallèle. La discussion sur ces méthodes est accompagnée d’une analyse numérique qui est aussi valable pour des mailles non-structurées. Dans le chapitre 3, nous vérifions notre implémentation par la simulation d’un certain nombre de cas tests avec un accent sur des écoulements dans un champ magnétique intense.

Dans la deuxième partie de cette thèse (chapitres 4-6), nous avons utilsé ce solveur pour étudier des écoulements MHD de proche paroi .La première géometrie considérée (chapitre 4) est celle d’une conduite circulaire infini d’axe à haut nombre de Hartmann. Nous avons investitgué la sensitivité des résultats numériques au schéma de discrétisation et à la topologie de la maille. Nos résultats permettent de caractériser in extenso l’écoulement MHD dans une conduite avec des bords bien conducteurs par moyen des lois d’échelle.

Le sujet du cinquième chapitre est l’écoulement dans une conduite toroïdale à section carée. Une étude du régime laminaire confirme une analyse asymptotique pour ce qui concerne les couches de cisaillement. Nous avons aussi effectué des simulations des écoulements turbulents afin d’évaluer l’effet d’un champ magnétique externe sur l’état des couches limites limites.

Finalement, dans le chapitre 6, nous investiguons l’écoulement MHD et dans un U-bend et dans un coude arrière. Nous expliquons comment générer une maille qui permet de toutes les couches de cisaillement à un coût computationelle acceptable. Nous comparons nos résultats aux solutions asymptotiques.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished

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43

Patel, Nayan V. "Simulation of Hydrodynamic Fragmentation from a Fundamental and an Engineering Perspective." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16225.

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Liquid fragmentation phenomenon is explored from both a fundamental (fully resolved) and an engineering (modeled) perspective. The dual objectives compliment each other by providing an avenue to gain further understanding into fundamental processes of atomization as well as to use the newly acquired knowledge to address practical concerns. A compressible five-equation interface model based on a Roe-type scheme for the simulation of material boundaries between immiscible fluids with arbitrary equation of state is developed and validated. The detailed simulation model accounts for surface-tension, viscous, and body-force effects, in addition to acoustic and convective transport. The material interfaces are considered as diffused zones and a mixture model is given for this transition region. The simulation methodology combines a high-resolution discontinuity capturing method with a low-dissipation central scheme resulting in a hybrid approach for the solution of time- and space-accurate interface problems. Several multi-dimensional test cases are considered over a wide range of physical situations involving capillary, viscosity, and gravity effects with simultaneous presence of large viscosity and density ratios. The model is shown to accurately capture interface dynamics as well as to deal with dynamic appearance and disappearance of material boundaries. Simulation of atomization processes and its interaction with the flow field in practical devices is the secondary objective of this study. Three modeling requirements are identified to perform Large-Eddy Simulation (LES) of spray combustion in engineering devices. In concurrence with these requirements, LES of an experimental liquid-fueled Lean Direct Injection (LDI) combustor is performed using a subgrid mixing and combustion model. This approach has no adjustable parameters and the entire flow-path through the inlet swirl vanes is resolved. The inclusion of the atomization aspects within LES eliminates the need to specify dispersed-phase size-velocity correlations at the inflow boundary. Kelvin-Helmholtz (or aerodynamic) breakup model by Reitz is adopted for the combustor simulation. Two simulations (with and without breakup) are performed and compared with measurements of Cai et al. Time-averaged velocity prediction comparison for both gas- and liquid-phase with available data show reasonable agreement. The major impact of breakup is on the fuel evaporation in the vicinity of the injector. Further downstream, a wide range of drop sizes are recovered by the breakup simulation and produces similar spray quality as in the no-breakup case.

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Thatte, Azam. "Multi-scale multi-physics model and hybrid computational framework for predicting dynamics of hydraulic rod seals." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37272.

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Rod seals are one of the most critical components of hydraulic systems. However, the fundamental physics of seal behavior is still poorly understood and the seal designers have virtually no analytical tools with which to predict the behavior of potential seal designs. In pursuit of a comprehensive physics based seal analysis/ design tool, in this work, a multi-scale multi-physics (MSMP) seal model is developed. The model solves the transient problem involving macro-scale viscoelastic deformation mechanics, macro-scale contact, micro-scale two phase fluid mechanics in the sealing zone, micro-scale asperity contact mechanics and micro-scale deformation mechanics of the sealing edge in a strongly coupled manner. The model takes into account surface roughness, mixed lubrication, cavitation and two phase flow, transient squeeze film effects and the dynamic operation as well as the effect of macro/micro/nano scale viscoelasticity. A hybrid finite element-finite volume-statistical computational framework is developed to solve the highly coupled multi-physics interactions of the MSMP model simultaneously. Surface characterization experiments are performed to extract the parameters like RMS roughness, asperity density, autocorrelation length and asperity radius needed by MSMP. To remove the high frequency noise without removing the high frequency real surface features, a wavelet transform based adaptive surface extraction method is implemented. Dynamic mechanical analysis (DMA) is performed to extract the macro-scale viscoelastic parameters of the seal. Through atomic force microscopy (AFM) experiments, the local micro/nano scale elastic moduli were found to be varying within two orders of magnitude higher than the bulk of the polymer. Significant differences in local stiffness, adhesion and the relaxation time scales of individual surface asperities were also observed. With the MSMP model, dynamic seal performance was analyzed. The results confirmed the mixed lubrication and the effect of surface roughness. Thicker fluid films during instroke and cavitation during the outstroke were found to be important for non-leakage. Seal behavior was a function of the complex dual dependence on the time varying sealed pressure and hydrodynamic effects. Viscoelasticity is seen to critically affect the leakage and friction characteristics. It produces thicker fluid films and produces a significant increase in Poiseuille component of flow during instroke. Ignoring viscoelasticity leads to under-prediction of the time required to reach the zero leakage state. Several high pressure - high frequency sealing applications were analyzed. In such applications, a new phenomenon of "secondary contact" was observed. Viscoelastic creep was seen to critically affect the contact pressure and hence the friction characteristics. In high frequency applications, viscoelasticity induced significant differences in Poiseuille flow and friction force from cycle to cycle. Cycle frequency was seen to play an important role in governing visco-elastohydrodynamics and the leakage of such seals. The seals need to be designed by considering the relationship between relaxation time scales of the polymer and the cycle frequencies. Study also revealed the presence of characteristics like "critical temperature" and "critical frequency". Using the multi-physics modeling capability of MSMP framework, several novel seal designs using smart materials like piezo-ceramic embedded polymers are proposed and analyzed. The MSMP computational framework developed here has a great potential to be used as a stand-alone seal design and analysis software in academic and industrial research.

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Donzis, Diego Aaron. "Scaling of turbulence and turbulent mixing using Terascale numerical simulations." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19794.

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Fundamental aspects of turbulence and turbulent mixing are investigated using direct numerical simulations (DNS) of stationary isotropic turbulence, with Taylor-scale Reynolds numbers ranging from 8 to 650 and Schmidt numbers from 1/8 to 1024. The primary emphasis is on important scaling issues that arise in the study of intermittency, mixing and turbulence under solid-body rotation. Simulations up to 2048^3 in size have been performed using large resource allocations on Terascale computers at leading supercomputing centers. Substantial efforts in algorithmic development have also been undertaken and resulted in a new code based on a two-dimensional domain decomposition which allows the use of very large number of processors.Benchmark tests indicate very good parallel performance for resolutions up to 4096^3 on up to 32768 processors. Investigation of intermittency through the statistics of dissipation and enstrophy in a series of simulations at the same Reynolds number but different resolution indicate that accurate results in high-order moments require a higher degree of fine-scale resolution than commonly practiced. At the highest Reynolds number in our simulations (400 and 650) dissipation and enstrophy exhibit extreme fluctuations of O(1000) the mean which have not been studied in the literature before and suggest a universal scaling of small scales. Simulations at Reynolds number of 650 on 2048^3 grids with scalars at Sc=1/8 and 1 have allowed us to obtain the clearest evidence of attainment of inertial-convective scaling in the scalar spectrum in numerical simulations to date whereas results at high Sc support k^{-1} viscous-convective scaling. Intermittency for scalars as measured by the tail of the PDF of scalar dissipation and moments of scalar gradient fluctuations is found to saturate at high Sc. Persistent departures from isotropy are observed as the Reynolds number increases. However, results suggest a return to isotropy at high Schmidt numbers, a tendency that appears to be stronger at high Reynolds numbers. The effects of the Coriolis force on turbulence under solid-body rotation are investigated using simulations on enlarged solution domains which reduce the effects of periodic boundary conditions.

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Svidrytski, Artur [Verfasser], and Ulrich [Akademischer Betreuer] Tallarek. "Study of random porous morphologies by means of statistical analysis and computer simulations of fluid dynamics / Artur Svidrytski ; Betreuer: Ulrich Tallarek." Marburg : Philipps-Universität Marburg, 2021. http://d-nb.info/1226287387/34.

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Makgata, Katlego Webster. "Computational analysis and optimisation of the inlet system of a high-performance rally engine." Diss., Pretoria : [s.n.], 2005. http://upetd.up.ac.za/thesis/available/etd-01242006-123639.

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Marano, Susan Aileen. "Smarticles: A Method for Identifying and Correcting Instability and Error Caused by Explicit Integration Techniques in Physically Based Simulations." DigitalCommons@CalPoly, 2014. https://digitalcommons.calpoly.edu/theses/1304.

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Using an explicit integration method in physically based animations has many advantages including conceptual and computational simplicity, however, it re- quires small time steps to ensure low numerical instability. Simulations with large numbers of individually interacting components such as cloth, hair, and fluid models, are limited by the sections of particles most susceptible to error. This results in the need for smaller time steps than required for the majority of the system. These sections can be diverse and dynamic, quickly changing in size and location based on forces in the system. Identifying and handling these trou- blesome sections could allow for a larger time step to be selected, while preventing a breakdown in the simulation. This thesis presents Smarticles (smart particles), a method of individually de- tecting particles exhibiting signs of instability and stabilizing them with minimal adverse effects to visual accuracy. As a result, higher levels of error introduced from large time steps can be tolerated with minimal overhead. Two separate approaches to Smarticles were implemented. They attempt to find oscillating particles by analyzing a particle’s (1) past behavior and (2) behavior with re- spect to its neighbors along a strand. Both versions of Smarticles attempt to correct unstable particles using velocity dampening. Smarticles was applied to a two dimensional hair simulation modeled as a continuum using smooth particle hydrodynamic. Hair strands are formed by linking particles together using one of two methods: position based dynamics or mass-spring forces. Both versions of Smarticles, as well as a control of normal particles, were directly compared and evaluated based on stability and visual fluidity. Hair particles were exposed to various forms of external forces under increasing time step lengths. Testing showed that both versions of Smarticles working together allowed an average increase of 18.62% in the time step length for hair linked with position based dynamics. In addition, Smarticles was able to significantly reduce visible instability at even larger time steps. While these results suggest Smarticles is successful, the method used to correct particle instability may jeopardize other important aspects of the simulation. A more accurate correction method would likely need to be developed to make Smarticles an advantageous method.

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Parisi, Valerio. "Large Eddy Simulation of a Stagnation Point Reverse Flow Combustor." Thesis, Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/13995.

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In this study, numerical simulations of a low emission lab-scale non-premixed combustor are conducted and analyzed. The objectives are to provide new insight into the physical phenomena in the SPRF (Stagnation Point Reverse Flow) combustor built in the Georgia Tech Combustion Lab, and to compare three Large Eddy Simulation (LES) combustion models (Eddy Break-Up [EBU], Steady Flamelet [SF] and Linear Eddy Model [LEM]) for non-premixed combustion. The nominal operating condition of the SPRF combustor achieves very low NOx and CO emissions by combining turbulent mixing of exhaust gases with preheated reactants and chemical kinetics. The SPRF numerical simulation focuses on capturing the complex interaction between turbulent mixing and heat release. LES simulations have been carried out for a non-reactive case in order to analyze the turbulent mixing inside the combustor. The LES results have been compared to PIV experimental data and the code has been validated. The dominating features of the operational mode of the SPRF combustor (dilution of hot products into reactants, pre-heating and pre-mixing) have been analyzed, and results from the EBU-LES, SF-LES and LEM-LES simulations have been compared. Analysis shows that the LEM-LES simulation achieves the best agreement with the observed flame structure and is the only model that captures the stabilization processes observed in the experiments. EBU-LES and SF-LES do not predict the correct flow pattern because of the inaccurate modeling of sub-grid scale mixing and turbulence-combustion interaction. Limitations of these two models for this type of combustor are discussed.

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Abbasi, Baharanchi Ahmadreza. "Development of a Two-Fluid Drag Law for Clustered Particles Using Direct Numerical Simulation and Validation through Experiments." FIU Digital Commons, 2015. http://digitalcommons.fiu.edu/etd/2489.

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This dissertation focused on development and utilization of numerical and experimental approaches to improve the CFD modeling of fluidization flow of cohesive micron size particles. The specific objectives of this research were: (1) Developing a cluster prediction mechanism applicable to Two-Fluid Modeling (TFM) of gas-solid systems (2) Developing more accurate drag models for Two-Fluid Modeling (TFM) of gas-solid fluidization flow with the presence of cohesive interparticle forces (3) using the developed model to explore the improvement of accuracy of TFM in simulation of fluidization flow of cohesive powders (4) Understanding the causes and influential factor which led to improvements and quantification of improvements (5) Gathering data from a fast fluidization flow and use these data for benchmark validations. Simulation results with two developed cluster-aware drag models showed that cluster prediction could effectively influence the results in both the first and second cluster-aware models. It was proven that improvement of accuracy of TFM modeling using three versions of the first hybrid model was significant and the best improvements were obtained by using the smallest values of the switch parameter which led to capturing the smallest chances of cluster prediction. In the case of the second hybrid model, dependence of critical model parameter on only Reynolds number led to the fact that improvement of accuracy was significant only in dense section of the fluidized bed. This finding may suggest that a more sophisticated particle resolved DNS model, which can span wide range of solid volume fraction, can be used in the formulation of the cluster-aware drag model. The results of experiment suing high speed imaging indicated the presence of particle clusters in the fluidization flow of FCC inside the riser of FIU-CFB facility. In addition, pressure data was successfully captured along the fluidization column of the facility and used as benchmark validation data for the second hybrid model developed in the present dissertation. It was shown the second hybrid model could predict the pressure data in the dense section of the fluidization column with better accuracy.

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Dissertations / Theses on the topic 'Fluid dynamics – Computer simulation'

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