Dissertations / Theses: 'Computational fluid dynamic'

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Da, Ronch Andrea. "On the calculation of dynamic derivatives using computational fluid dynamics." Thesis, University of Liverpool, 2012. http://livrepository.liverpool.ac.uk/5513/.

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In this thesis, the exploitation of computational fluid dynamics (CFD) methods for the flight dynamics of manoeuvring aircraft is investigated. It is demonstrated that CFD can now be used in a reasonably routine fashion to generate stability and control databases. Different strategies to create CFD-derived simulation models across the flight envelope are explored, ranging from combined low-fidelity/high-fidelity methods to reduced-order modelling. For the representation of the unsteady aerodynamic loads, a model based on aerodynamic derivatives is considered. Static contributions are obtained from steady-state CFD calculations in a routine manner. To more fully account for the aircraft motion, dynamic derivatives are used to update the steady-state predictions with additional contributions. These terms are extracted from small-amplitude oscillatory tests. The numerical simulation of the flow around a moving airframe for the prediction of dynamic derivatives is a computationally expensive task. Results presented are in good agreement with available experimental data for complex geometries. A generic fighter configuration and a transonic cruiser wind tunnel model are the test cases. In the presence of aerodynamic non-linearities, dynamic derivatives exhibit significant dependency on flow and motion parameters, which cannot be reconciled with the model formulation. An approach to evaluate the sensitivity of the non-linear flight simulation model to variations in dynamic derivatives is described. The use of reduced models, based on the manipulation of the full-order model to reduce the cost of calculations, is discussed for the fast prediction of dynamic derivatives. A linearized solution of the unsteady problem, with an attendant loss of generality, is inadequate for studies of flight dynamics because the aircraft may experience large excursions from the reference point. The harmonic balance technique, which approximates the flow solution in a Fourier series sense, retains a more general validity. The model truncation, resolving only a small subset of frequencies typically restricted to include one Fourier mode at the frequency at which dynamic derivatives are desired, provides accurate predictions over a range of two- and three-dimensional test cases. While retaining the high fidelity of the full-order model, the cost of calculations is a fraction of the cost for solving the original unsteady problem. An important consideration is the limitation of the conventional model based on aerodynamic derivatives when applied to conditions of practical interest (transonic speeds and high angles of attack). There is a definite need for models with more realism to be used in flight dynamics. To address this demand, various reduced models based on system-identification methods are investigated for a model case. A non-linear model based on aerodynamic derivatives, a multi-input discrete-time Volterra model, a surrogate-based recurrence-framework model, linear indicial functions and radial basis functions trained with neural networks are evaluated. For the flow conditions considered, predictions based on the conventional model are the least accurate. While requiring similar computational resources, improved predictions are achieved using the alternative models investigated. Furthermore, an approach for the automatic generation of aerodynamic tables using CFD is described. To efficiently reduce the number of high-fidelity (physics-based) analyses required, a kriging-based surrogate model is used. The framework is applied to a variety of test cases, and it is illustrated that the approach proposed can handle changes in aircraft geometry. The aerodynamic tables can also be used in real-time to fly the aircraft through the database. This is representative of the role played by CFD simulations and the potential impact that high-fidelity analyses might have to reduce overall costs and design cycle time.

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Hickerson, David A. "Computational Fluid Dynamic Study of Heaving-to." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/23766.

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This study looks at the fluid interactions from the wake of a sail boat performing the heaving-to storm tactic in heavy weather seas with the waves. This interaction causes the wave height in the wake to be reduced. The fluid flow in the top layer of the wave is seen to move with the wake as the hull drifts with the wind. This movement of the top layer of the wave provides a vertical momentum cancelation affect with the portion of the wave that it moves over reducing the wave height. STAR-CCM+ CFD software is used to perform the simulations of the steep waves with wavelength of 25 meters, 55 meters, and 67 meters. In the simulation, a propulsive force is used to simulate the wind force on the boat.
Master of Science

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Molale, Dimpho Millicent. "A computational evaluation of flow through porous media." Thesis, Link to the online version, 2007. http://hdl.handle.net/10019/686.

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Chambers, Steven B. "Investigation of combustive flows and dynamic meshing in computational fluid dynamics." Thesis, Texas A&M University, 2004. http://hdl.handle.net/1969.1/1324.

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Computational Fluid Dynamics (CFD) is a ﬁeld that is constantly advancing. Its advances in terms of capabilities are a result of new theories, faster computers, and new numerical methods. In this thesis, advances in the computational ﬂuid dynamic modeling of moving bodies and combustive ﬂows are investigated. Thus, the basic theory behind CFD is being extended to solve a new class of problems that are generally more complex. The ﬁrst chapter that investigates some of the results, chapter IV, discusses a technique developed to model unsteady aerodynamics with moving boundaries such as ﬂapping winged ﬂight. This will include mesh deformation and ﬂuid dynamics theory needed to solve such a complex system. Chapter V will examine the numerical modeling of a combustive ﬂow. A three dimensional single vane burner combustion chamber is numerically modeled. Species balance equations along with rates of reactions are introduced when modeling combustive ﬂows and these expressions are discussed. A reaction mechanism is validated for use with in situ reheat simulations. Chapter VI compares numerical results with a laminar methane ﬂame experiment to further investigate the capabilities of CFD to simulate a combustive ﬂow. A new method of examining a combustive ﬂow is introduced by looking at the solutions ability to satisfy the second law of thermodynamics. All laminar ﬂame simulations are found to be in violation of the entropy inequality.

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

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CARDILLO, GIULIA. "Fluid Dynamic Modeling of Biological Fluids: From the Cerebrospinal Fluid to Blood Thrombosis." Doctoral thesis, Politecnico di Torino, 2020. http://hdl.handle.net/11583/2845786.

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Mora, Acosta Josue. "Numerical algorithms for three dimensional computational fluid dynamic problems." Doctoral thesis, Universitat Politècnica de Catalunya, 2001. http://hdl.handle.net/10803/6685.

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The target of this work is to contribute to the enhancement of numerical methods for the simulation of complex thermal systems. Frequently, the factor that limits the accuracy of the simulations is the computing power: accurate simulations of complex devices require fine three-dimensional discretizations and the solution of large linear equation systems.
Their efficient solution is one of the central aspects of this work. Low-cost parallel computers, for instance, PC clusters, are used to do so. The main bottle-neck of these computers is the notwork, that is too slow compared with their floating-point performance.
Before considering linear solution algorithms, an overview of the mathematical models used and discretization techniques in staggered cartesian and cylindrical meshes is provided.
The governing Navier-Stokes equations are solved using an implicit finite control volume method. Pressure-velocity coupling is solved with segregated approaches such as SIMPLEC.
Different algorithms for the solution of the linear equation systems are reviewed: from incomplete factorizations such as MSIP, Krylov solvers such as BICGSTAB and GMRESR to acceleration techniques such as the Algebraic Multi Grid and the Multi Resolution Analysis with wavelts. Special attention is paid to preconditioned Krylov solvers for their application to parallel CFD problems.
The fundamentals of parallel computing in distributed memory computers as well as implemetation details of these algorithms in combination with the domain decomposition method are given. Two different distributed memory computers, a Cray T3E and a PC cluster are used for several performance measures, including network throughput, performance of algebraic subroutines that affect to the overall efficiency of algorithms, and the solver performance. These measures are addressed to show the capabilities and drawbacks of parallel solvers for several processors and their partitioning configurations for a problem model.
Finally, in order to illustrate the potential of the different techniques presented, a three-dimensional CFD problem is solved using a PC cluster. The numerical results obtained are validated by comparison with other authors. The speedup up to 12 processors is measured. An analysis of the computing time shows that, as expected, most of the computational effort is due to the pressure-correction equation,here solved with BiCGSTAB. The computing time algorithm , for different problem sizes, is compared with Schur-Complement and Multigrid.
El trabajo de tesis se centra en la solución numérica de las ecuaciones de navier-Stokes en regimen transitorio, tridimensional y laminar. Los algoritmos utilizados son del tipo segregado (SIMPLEC)y se basan en el uso de técnicas de volumenes finitos, con mallas estructurales del tipo staggered y discretizaciones temporales implícitas. En este contexto, el pricipal, problema son los elevados tiempos de cálculo de las simulaciones, que en buena parte se deben a la solución de los sistemas de ecuaciones lineales. Se hace una revisión de diferentes métodos utilizados típicamente en ordenadores secuenciales: GMRES, BICGSTAB, ACM, MSPIP.
A fin de reducir los tiempos de cálculo se emplean ordenadores paralelos de memoria distribuida, basados en la agrupacion de ordenadores personales convencionales (PC clusters). Por lo que respecta a la potencia de cálculo por procesador, estos sistemas son comparables a los ordenadores paralelos de memoria distribuida convencionales (como el Cray T3E) siendo, su principal problema la baja capacidad de comunicación (elevada latencia, bajo ancho de banda). Este punto condiciona toda la estrategia computacional, obligando a reducir al máximo el número y el tamaño de los mensajes intercambiados. Este aspecto se cuantifica detalladamente en la tesis, realizando medidas de tiempos de cálculo en ambos ordenadores para diversas operaciones críticas para los algoritmos lineales. Tambien se miden y comparan los tiempos de cálculo y speed ups obtenidos en la solución de los sistemas lineales con diferentes algoritmos paralelos (Jacobi, MSIP, GMRES, BICGSTAB) y para diferentes tamaños de malla.
Finalmente, se utilizan las técnicas anteriores para resolver el caso denominado driven cavity, en situacionies tridimensionales y con numeros de Reynolds de hasta 8000. Los resultados obtenidos se utilizan para validar los códigos desarrollados, en base a resultados de otros códigos y también se basa en la comparación con resultados experimentales procedentes de la bibliografía. Se utilizan hasta 12 procesadores, obteniendose spped ups de hasta 9.7 en el cluster de PCs. Se analizan los tiempos de cálculo de cada fase del código, señalandose areas para futuras mejoras. Se comparan los tiempos de cálculo con los algoritmos implementados en otros trabajos. La conclusión final es que los clusters de PCs son una plataforma de gran potencia en los cálculos de dinámica de fluidos computacional.

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Coppel, Anna Louise. "A computational fluid dynamic investigation of rowing oar blades." Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/793/.

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This thesis describes the application of computational fluid dynamics (CFD) to model the flow regime around rowing oar blades. The two phase flow that was present at the surface between the water and the air was also incorporated into the CFD model. Firstly, a quasi–static method was applied, whereby the blade was held at a discrete number of angles of attack to the oncoming flow. The performance of the model was assessed by applying it to four scaled oar blade designs and validating results against an experimental data set. The results were encouraging with lift and drag coefficients acting on the blades being well predicted throughout. The scope was extended to include full size oar blades of designs typically found in competition rowing. A second approach to investigating the flow around oar blades was also adopted, where instead of being held stationary, the blades moved in the fluid domain. The unsteady effects induced by this rotational motion were found to be substantial, with a 72% and 67% increase in the lift and drag coefficients respectively. Finally, through coupling the CFD predictions of oar blade force coefficients with a mathematical model of rowing, it was possible to determine the influence of oar blade design on rowing performance, and also use the mathematical model to further validate the CFD predictions against on–water data. The results provided an accurate assessment of boat performance during the rowing stroke.

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Irshad, Wahid. "Wind resource assessment : statistical and computational fluid-dynamic analysis." Thesis, Edinburgh Napier University, 2012. http://researchrepository.napier.ac.uk/Output/5329.

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Wind is an important source of renewable energy and is widely available, despite the changing condition. In recent years a growing number of manufacturers have produced small wind turbines suitable for utilisation by individual householders or small businesses. These systems are designed to install in towns or cities. This raises the question about the potential of wind energy resource in build-up areas. This thesis sets to investigate the wind energy resource implication in the build-up areas by understanding the wind climatology of urban areas. As well as the overall mean wind speed, knowledge of the wind speed distribution (due to the non-linear relationship between wind speed and wind power) and the wind-direction distribution for optimum turbine siting is required. Other areas that have been considered are short-duration fluctuations in both speed and direction as these can affect the efficiency of the turbine. The aims of this research are to study the local wind conditions and estimate the available wind resource for the wind-energy driven generation of electricity in Edinburgh by taking into account of its climate, wind data and topographical effects. To achieve these aims eleven years of Met office data was investigated in addition to analysis of the data collected from locally installed weather station. Diurnal effect on wind condition was studied and found to be more pronounced in Edinburgh's rural area than its urban conurbation. It was also found that the available wind energy in the urban area is 30% less than that of the rural area. Turbulence in wind speed and direction of flow was also investigated. Careful consideration of all the parameters defining and affecting the prevailing wind revealed the wind resource in Edinburgh's urban area to be insufficient for viable generation of wind energy through the available technology of micro WEC (wind energy converter) systems. A CFD analysis was also performed to determine wind resource differences because of different mounting locations of wind equipment over the building under consideration. As a part of the project, a commercially available wind turbine was installed and monitored to investigate its performance in urban area. The research study finally suggests that the available grid connected micro WEC system cannot provide a cost effective contribution to urban Edinburgh's renewable energy generation.

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Gao, Rui. "Computational Fluid Dynamic and Rotordynamic Study on the Labyrinth Seal." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/28134.

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The labyrinth seal is widely used in turbo machines to reduce leakage flow. The stability of the rotor is influenced by the labyrinth seal because of the driving forces generated in the seal. The working fluid usually has a circumferential velocity component before entering the seal; the ratio of circumferential velocity and shaft synchronous surface velocity is defined as pre-swirl rate. It has been observed that pre-swirl rate is an important factor affecting driving forces in the labyrinth seal thus affecting the stability of the rotor. Besides the pre-swirl, the eccentricity, the clearance, and the configuration of tooth locations are all factors affecting the rotordynamic properties of the labyrinth seal. So it is of interest to investigate the exact relationships between those factors and the sealâ s rotordynamic properties. In this research, three types of labyrinth seals have been modeled: the straight eye seal, the stepped eye seal, and the balance drum seal. For the straight eye seal, a series of models were built to study the influence of eccentricity and clearance. The other two seals each have only one model. All models were built with Solid Works and meshed with ANSYS-ICEM. Flows in those models were simulated by numerically solving the Reynolds-Averaged Navier-Stokes (RANS) equations in the ANSYS-CFX and then rotordynamic coefficients for each seal were calculated based on the numerical results. It had previously been very difficult to generate a pre-swirl rate higher than 60% in a numerical simulation. So three ways to create pre-swirl in ANSYS-CFX were studied and finally the method by specifying the inlet velocity ratio was employed. Numerical methods used in this research were introduced including the frame transfer, the k-Îµ turbulence model with curvature correction, and the scalable wall function. To obtain the optimal mesh and minimize the discretization error, a systematical grid study was conducted including grid independence studies and discretization error estimations. Some of the results were compared with previous bulk-flow or experimental results to validate the numerical model and method. The fluid field in the labyrinth seal must be analyzed before conducting rotordynamic analysis. The predicted pressure distributions and leakages were compared with bulk-flow results. A second small vortex at the downstream edge of each tooth was found in the straight eye seal. This has never been reported before and the discovery of this small vortex will help to improve seal designs in the future. The detailed flows in discharged region and in chambers were also discussed. Radial and tangential forces on the rotor were solved based on the fluid field results. It is shown that the traditional first-order rotordynamic model works well for low pre-swirl cases but does not accurately reflect the characteristics for high pre-swirl cases. For example compressor eye seals usually have pre-swirl rates bigger than 70% and the second order model is required. Thus a second-order model including inertia terms was built and applied to the rotordynamic analysis in this research. The influence of pre-swirl, eccentricity and clearance were studied using the straight eye seal model. The rotordynamic characteristics of the stepped eye seal and the balance drum seal were studied considering high pre-swirl rates. Some relationships between influencing factors and the four rotordynamic coefficients were concluded. The results also showed that for all the three seals higher pre-swirl leads to higher cross-coupled stiffness which is one of the main factors causing rotor instability. The rotor stability analysis was conducted to study the influence of drum balance seal on the stability. The rotor was designed with typical dimensions and natural frequencies for a centrifugal compressor rotor. The parameters for bearing and aerodynamic force were also set according to general case in compressors to minimize the effects from them. The result shows that the high pre-swirl rate in balance drum seal leads to rotor instability, which confirmed the significant effect of pre-swirl on the seal and the rotor system.
Ph. D.

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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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Heminger, Michael Alan. "Dynamic Grid Motion in a High-Order Computational Aeroacoustic Solver." University of Toledo / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1272550725.

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Robinson, Craig David. "Particle simulations on parallel computers with dynamic load balancing." Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269198.

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Rashid, Tariq Mahmood. "Computational modelling of dynamic wind effects relevant to compliant offshore structures." Thesis, University of Hertfordshire, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332219.

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Holmlund, Petter. "Computational fluid dynamic simulations of pulsatile flow in stenotic vessel models." Thesis, Umeå universitet, Institutionen för fysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-93007.

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Wilson, Paul. "Computational fluid dynamic investigation of blood flow through heart valve prostheses." Thesis, Nottingham Trent University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360773.

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Janyalertadun, Adun. "Computational fluid dynamic modelling of an inlet in a cross-flow." Thesis, University of Hertfordshire, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323460.

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Hedges, Collin R. "Computational fluid dynamic model of steam ingestion into a transonic compressor." Thesis, Monterey, Calif. : Naval Postgraduate School, 2009. http://edocs.nps.edu/npspubs/scholarly/theses/2009/Jun/09Jun%5FHedges.pdf.

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Thesis (M.S. in Mechanical Engiineering)--Naval Postgraduate School, June 2009.
Thesis Advisor(s): Gannon, Anthony J. "June 2009." Author(s) subject terms: Computational Fluid Dynamics, Transonic, Compressor, Steam Ingestion, Sanger Rotor. Description based on title screen as viewed on July 10, 2009. Includes bibliographical references (p. 61). Also available in print.

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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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Ang, Keng Cheng. "A computational fluid dynamic study of blood flow through stenosed arteries /." Title page, table of contents and summary only, 1996. http://web4.library.adelaide.edu.au/theses/09PH/09pha5808.pdf.

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Linton, Daniel. "A Hybrid Computational Fluid Dynamics Method for Unsteady Simulation of the Ship-Helicopter Dynamic Interface." Thesis, University of Sydney, 2020. https://hdl.handle.net/2123/22894.

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Helicopters operating from ships are exposed to turbulent airwakes which can determine ship-helicopter operating limits. During concurrent operations rotor-rotor interactions add to the complexity of the aerodynamics. Computational fluid dynamics solvers are able to predict these aerodynamics from first principles with the aid of turbulence-resolving approaches such as detached eddy simulation. Although it is possible to create body-fitted grids to resolve the rotor blades and move them, the fuselage, and the ship relative to one another, this is a computationally expensive and labour intensive method. To avoid this expense and while accurately predicting unsteady loading, a time accurate rotor model has been coupled to a Navier-Stokes solver by introducing momentum source terms to the governing equations. A novel coupling algorithm that accounts for the effects of unsteady aerodynamics as well as the induced velocity of the wake has been developed and validated. The coupled rotor model predicts performance, thrust and torque distributions, and unsteady aerodynamic loading of isolated and interacting rotors. A time accurate wake can also be generated by the model. The method requires far fewer grid points to resolve the rotor than a body-fitted grid and grids can be generated automatically. Navier-Stokes simulation of the ship airwake is a complex task and many of the parameters of importance for such simulations have been identified in the literature. A study of grid convergence of velocity spectra and analysis of finite sample error have been performed to add to this knowledge. A method for objectively assessing the finite sample error and determining the minimum sample time required to reach a certain error has been applied to ship airwake simulations for the first time and a minimum level of grid refinement for resolved velocity spectra suggested. The ship airwake and rotor model have been combined for ship-helicopter dynamic interface simulations of single helicopter operations and concurrent helicopter operations involving five rotors. These simulations demonstrate the ability of the method to predict the aerodynamic factors that influence ship-helicopter operating limits and, to the best of our knowledge, contain more vehicles than any previously published dynamic interface simulations.

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Watanawanavet, Somsak. "Optimization of a high-efficiency jet ejector by computational fluid dynamic software." Texas A&M University, 2005. http://hdl.handle.net/1969.1/2432.

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Research was performed to optimize high-efficiency jet ejector geometry (Holtzapple, 2001) by varying nozzle diameter ratios from 0.03 to 0.21, and motive velocities from Mach 0.39 to 1.97. The high-efficiency jet ejector was simulated by Fluent Computational Fluid Dynamics (CFD) software. A conventional finite-volume scheme was utilized to solve two-dimensional transport equations with the standard k-?? turbulence model (Kim et. al., 1999). In this study of a constant-area jet ejector, all parameters were expressed in dimensionless terms. The objective of this study was to investigate the optimum length, throat diameter, nozzle position, and inlet curvature of the convergence section. Also, the optimum compression ratio and efficiency were determined. By comparing simulation results to an experiment, CFD modeling has shown high-quality results. The overall deviation was 8.19%, thus confirming the model accuracy. Dimensionless analysis was performed to make the research results applicable to any fluid, operating pressure, and geometric scale. A multi-stage jet ejector system with a total 1.2 compression ratio was analyzed to present how the research results may be used to solve an actual design problem. The results from the optimization study indicate that the jet ejector efficiency improves significantly compared to a conventional jet-ejector design. In cases with a subsonic motive velocity, the efficiency of the jet ejector is greater than 90%. A high compression ratio can be achieved with a large nozzle diameter ratio. Dimensionless group analysis reveals that the research results are valid for any fluid, operating pressure, and geometric scale for a given motive-stream Mach number and Reynolds ratio between the motive and propelled streams. For a given Reynolds ratio and motivestream Mach number, the dimensionless outlet pressure and throat pressure are expressed as Cp and Cpm, respectively. A multi-stage jet ejector system with a total 1.2 compression ratio was analyzed based on the optimization results. The result indicates that the system requires a lot of high-pressure motive steam, which is uneconomic. A high-efficiency jet ejector with mixing vanes is proposed to reduce the motive-steam consumption and is recommended for further study.

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Bangalore, Ashok K. "Computational fluid dynamic studies of high lift rotor systems using distributed computing." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/12949.

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Bryan, Grant T. "EXPERIMENTAL AND COMPUTATIONAL FLUID DYNAMIC ANALYSIS OF AXIAL-FLOW HYDRODYNAMIC POWER TURBINE." Monterey, California. Naval Postgraduate School, 2013. http://hdl.handle.net/10945/32801.

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Thorough analysis of drag and power characteristics of hydrodynamic power turbines is necessary for the efficient extraction of energy available at sea. In an effort to obtain these characteristics for a three-bladed, axial-flow hydroturbine, used to provide electric power on small sailing vessels, a load cell and voltage measuring system was installed on a carriage in a towing tank for analysis across a speed range of 0.5 to 1.8 m/s. A high-speed camera was used to determine the precise carriage speed and the rotational speed of the turbine rotor. For validation of concept, two thin flat plates were analyzed using the same drag force measuring system in the tow tank to compare experimentally determined drag coefficients with known literature values. Results are shown for the drag force experienced by the flat plates and both the non-rotating and the rotating turbine configurations. Additional results are shown for the turbines power generation capabilities at rotational speeds between 90 and 500 RPMs. Using computational fluid dynamics for the rectangular flat plate and non-rotational turbine configuration, the experimental and computational results for the drag force characteristics were compared.

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Das, Sudhakar. "Computational fluid dynamic modelling of flow and combustion in spark ignition engines." Thesis, Loughborough University, 1996. https://dspace.lboro.ac.uk/2134/7327.

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The present work is based on the need for understanding the in-cylinder flow and its subsequent effects on combustion in a valved-two-stroke spark ignition engine with fuel injection using Computational Fluid Dynamics (CFD) and experimental techniques. In this context, the CFD code KIVA-II has been modified to model the two-stroke engine gas exchange and combustion processes. A 3-D Cartesian grid generation program for complex engine geometry has been added to the KIVA code which has been modified to include intake and exhaust flow processes with valves. New and improved sub models for wall jet interaction, mixing controlled combustion and one dimensional wave action have also been incorporated. The modified version of the program has been used to simulate a fuel injected two-stroke spark ignition engine and parametric studies have been undertaken. The simulated flow, combustion and exhaust emission characteristics over a wide range of operating conditions show the expected trends in behaviour observed in actual engines. In the second phase of this study, the air-assisted-fuel-injection (AAFI) process into a cylinder has been simulated with a high resolution computational grid. The simulation results are presented and compared with experimental data obtained using the Schlieren optical technique. An approximate method based on the conservation of mass, momentum and energy of the spray jet and using a comparatively coarse grid has been suggested for simulating the AAFI process. The simulation study predicts a high degree of atomisation of fuel spray with Sauter mean diameter around 10 μm even with moderate air and fuel pressures. The penetration and width of spray are simulated within 15% of the experimental values. In the last phase of this study, the flow and combustion processes have been studied for a four-stroke spark ignition engine with the AAFI process. The simulation results obtained using this approximate method have been validated with experimental data generated for the same engine configuration.

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Terzi, Antonia. "A combination of computational fluid dynamic methods for formula-1 aerodynamic analysis." Thesis, University of Exeter, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286545.

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DOMALAPALLY, PHANI KUMAR. "Computational Thermal Fluid Dynamic Analysis of Cooling Systems for Fusion Reactor Components." Doctoral thesis, Politecnico di Torino, 2013. http://hdl.handle.net/11583/2514474.

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In a fusion reactor during plasma operation, the heat loads on plasma facing components can be as high as 5 MW/m2 [1], which should be removed by a proper mechanism to prevent the damage of reactor components. In order to handle such high heat fluxes a suitable heat sink with proper thermal hydraulics is required. In the recent past several heat sinks have been proposed; among which the Hypervapotron heat sink, operating in the highly subcooled boiling regime, is considered as one of the potential candidates. In order to accurately predict the performance of the system, a thermal hydraulic analysis is required. This thesis employs a Computational Fluid Dynamic (CFD) approach to do the thermal hydraulic analysis of the subcooled flow boiling inside the Hypervapotron channel. For this purpose four boiling models are tested using two commercial CFD codes. The four boiling models tested are Rensselaer Polytechnic Institute (RPI) boiling model [2] available in ANSYS-FLUENT 13, Bergles-Rohsenow (BR) model [3] implemented as an external User Defined Function (UDF) in the FLUENT code, the Rohsenow boiling model [4] extended with the capability of transition to film boiling for high heat fluxes available in STAR-CCM+ 7.02, and finally Transition boiling model [4] available in STAR-CCM+ 7.02. These models are used to test the thermal performance of Hypervapotron using the experimental data (showing the variation of temperature with heat flux) obtained from the experiments conducted at Efremov Institute Russia and Joint European Torus United Kingdom. Simulations were conducted using the above mentioned boiling models, the obtained results were compared against the experimental data and also different boiling models are compared with each other whenever possible to test their applicability. From the simulations conducted on the Hypervapotron geometries it is found that the Transition boiling model can capture the thermal performance (in terms of tracing the experimental data) better than any other model both quantitatively and qualitatively, covering the different boiling regimes shown by the experiments ( that is no boiling, nucleate boiling and hard boiling regimes), than the other models.

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Goolcharan, John D. "Computational Fluid Dynamic analysis of Microbubble Drag Reduction Systems at High Reynolds Number." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/2542.

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Microbubble drag reduction (MBDR) is an effective method to improve the efficiency of fluid systems. MBDR is a field that has been extensively studied in the past, and experimental values of up to 80% to 90% drag reduction have been obtained. The effectiveness and simplicity of MBDR makes it a viable method for real world applications, particularly in naval applications where it can reduce the drag between the surface of ships and the surrounding water. A two dimensional single phase model was created in ANSYS Fluent to effectively model the behavior of bubble laden flow over a flat plate. This model was used to analyze the effectiveness of MBDR based on the following factors: Reynolds number, types of gas injected, upstream flow velocity, upstream fluid type, density ratio, flow rate of injected gas, using air as the upstream injected fluid.

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Franchetta, Matteo. "Experimental and transient computational fluid dynamic analysis of vehicle underhood in heat soak." Thesis, University College London (University of London), 2006. http://discovery.ucl.ac.uk/1444411/.

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Simulation-based analyses of underhood compartments are proving to be crucially important in a vehicle development program, reducing test work and time-to-market. While Computational Fluid Dynamics (CFD) simulations of steady forced flows have demonstrated reliable, studies of transient natural convective flows in engine compartments under thermal soak are not yet carried out due the high computing demands and lack of validated work. The present work assesses the practical feasibility of applying the CFD tool at the initial stage of a vehicle development programme for investigating the thermally-driven flow in an engine bay. A typical vehicle underhood was reproduced in half-scale for laboratory investigations. Surface temperatures of components, airflow patterns induced by the buoyant forces as well as the spatial distribution of the air temperature were measured under both steady and transient thermal conditions. Temperature mappings were obtained with thermocouples whereas airflow magnitudes and directions were determined with Particle Image Velocimetry (PIV) instrumentation. The detailed measurements were used as reference for validating the corresponding CFD simulations carried out with the software VECTIS. Experimental and numerical data correlated well in steady state, both quantitatively and qualitatively. A computation procedure that enables pseudo time-marching simulations to be performed with significantly reduced CPU time usage, in comparison to traditional fully-conservative transient simulations, was also developed. The methodology used a unique combination of CFD solver parameters to overcome the computationally challenging problem of solving for momentum transport in time-marching mode and for a long period of physical time. The procedure was successful in providing a detailed and time-accurate flow and thermal simulation of the underhood model during transient cooling. Such simulation would not have been practically feasible with a standard transient simulation. A reduction in CPU processing time in excess of 90% was achieved with good correlation between the CFD predictions and the experimental data.

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Fairman, Randall S. "Investigation into the discrepancies between computational fluid dynamic lift predictions and experimental results." 2002, 2002. http://hdl.handle.net/10945/11020.

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An analysis of current computational fluid dynamics capabilities in predicting mean lift forces for two dimensional foils is conducted. It is shown that both integral boundary layer theory and Reynolds Averaged Navier Stokes algorithms provide the same over-prediction of lift forces when properly converged. It is also shown that the over-prediction is insensitive to turbulence model details. Experimentation and computational fluid dynamics modeling show that discrete vortices are shed with significant sizes and distinct frequencies. These vortices are shown to result in significant cfd prediction errors when they are asymmetric in size or shape. Inaccuracies in flow predictions in the near wake appear to result in an effective change in the Kutta Condition due to pressure biasing associated with vortex asymmetry. The net result is a consistent overprediction of mean lift. Based on an analysis of over 1000 historical experiments an empirical model is developed to allow the error in predicted lift coefficient to be anticipated based on the local flow conditions at the trailing edge of the foil. A series of experiments are conducted and reported to test the accuracy of the empirical model. The result is a significant improvement in mean lift prediction and pressure profile for both RANS and IBLT.

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Collins, Kimberlee C. (Kimberlee Chiyoko). "Computational fluid dynamic (CFD) optimization of microfluidic mixing in a MEMS steam generator." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45770.

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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.
Includes bibliographical references (p. 23-24).
The challenge of achieving rapid mixing in microchannels is addressed through a computational fluid dynamics (CFD) study using the ADINA-F finite element program. The study is motivated by the need to design an adequate mixing chamber for aqueous chemical reactants in a micro steam generator. The study focuses on the geometric optimization of a static micromixer channel by considering the trade-off between mixing quality and pressure drop. Both zigzag and straight channels are evaluated, in addition to channels with differing amounts of added obstruction features. Due to computational limits, the numerical analysis is conducted in two dimensions. The results indicate that hydrodynamic focusing of the reactant at the inlet, in addition to the amount and density of added obstruction features, has the most significant impact on mixing efficiency and increased pressure drop. The study presents mixing quality and pressure drop trends that provide useful information for the micro steam generator mixing chamber design.
by Kimberlee C. Collons.
S.B.

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Johns, Adam Stephen. "Computational fluid dynamic modelling and optimisation of internal twist-drill coolant channel flow." Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/9288/.

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Due to the increasingly challenging thermal loads during drilling applications, coolant application is prevalent in twist-drill machining of metals. However, because the cutting zone is not directly observable, there is limited knowledge encompassing the distribution of coolant during the cutting process. This work looks to expand current knowledge of coolant delivery during the cutting process and inform future tool design through the application of numerical methods. This is implemented in the form of two numerical models: a through-tool model, which examines internal coolant flow and the second model which calculates coolant exit flow behaviour. The through-tool model employs a single phase model and is used to perform a parametric study which identifies the influence of each design parameter on the delivery of coolant. In addition to this metamodelling techniques are adopted to give a global overview of tool parameter effects on coolant delivery and to identify optimal channel configurations. The coolant exit flow model employs the Volume of Fluid method to simulate the multiphase exit flow of coolant and is validated against experimental data for a simplified case. This model was used to evaluate coolant exit flow for four different coolant channel configurations and study the influence of channel configuration parameters on domain flooding, surface wetting and flow field features.

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Van, Rooyen Jacobus A. "Computational fluid dynamic based optimisation of an industrial axial fan for rapid prototyping." Doctoral thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/24931.

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Axial air flow fans are widely used for air movement. In an increasingly international and competitive market, smaller fan companies find themselves in need of rapid preliminary design. This need is addressed in this study through the development of a first-revision, Computational Fluid Dynamics (CFD) based, optimisation tool which allows for rapid prototyping of a ducted axial fan. The result is an ElementalTM-based multi-disciplinary software tool, comprising 2D CFD, mesh movement, and constrained geometric optimisation. The analytical equation employed to represent the aerofoil significantly reduces the cost of the optimisation. A pseudo-3D fan model is generated by superimposing 2D CFD results. This is done without the general assumption of the free-vortex method, which is not a necessity for fan design and other velocity distributions may be used. For this purpose, an enhanced finite volume discretisation method was developed. A penalty function minimisation, by means of an unconstrained optimisation algorithm, is implemented thereafter. The primary objective is to deliver a specific fan static pressure rise, while optimising for fan static efficiency by means of altering the rotor blade geometry. The spherical quadratic steepest descent method is employed, which does not rely on any explicit line searches, as required by traditional steepest descent techniques. The rapid prototyping tool is finally applied to an under-performing base fan (Fan-D) which cannot meet a specified duty point. The resulting optimised fan (Fan-Optim) is manufactured and experimentally tested, in accordance with the ISO 5801 standard. The pseudo-3D model is proven to predict fan performance accurately at the target duty point, while capturing fan behaviour over a range of volumetric flow rates. The former is to within 13% of the fan static pressure rise and within 2.3% of fan static efficiency. While Fan-Optim meets the desired duty point within 2%, it offers a considerable improvement in fan static efficiency over Fan-D. Furthermore, an approximate 38% reduction in blade material is achieved as a secondary effect.

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Cossey, Aaron Mitchell. "Computational fluid dynamic analysis of the purification process of the neutrino detector KamLAND." Thesis, [Tuscaloosa, Ala. : University of Alabama Libraries], 2009. http://purl.lib.ua.edu/118.

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Jones, Cameron Christopher. "VALIDATION OF COMPUTATIONAL FLUID DYNAMIC SIMULATIONS OF MEMBRANE ARTIFICIAL LUNGS WITH X-RAY IMAGING." UKnowledge, 2012. http://uknowledge.uky.edu/cbme_etds/2.

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The functional performance of membrane oxygenators is directly related to the perfusion dynamics of blood flow through the fiber bundle. Non-uniform flow and design characteristics can limit gas exchange efficiency and influence susceptibility of thrombus development in the fiber membrane. Computational fluid dynamics (CFD) is a powerful tool for predicting properties of the flow field based on prescribed geometrical domains and boundary conditions. Validation of numerical results in membrane oxygenators has been predominantly based on experimental pressure measurements with little emphasis placed on confirmation of the velocity fields due to opacity of the fiber membrane and limitations of optical velocimetric methods. A novel approach was developed using biplane X-ray digital subtraction angiography to visualize flow through a commercial membrane artificial lung at 1–4.5 L/min. Permeability based on the coefficients of the Ergun equation, α and β, were experimentally determined to be 180 and 2.4, respectively, and the equivalent spherical diameter was shown to be approximately equal to the outer fiber diameter. For all flow rates tested, biplane image projections revealed non-uniform radial perfusion through the annular fiber bundle, yet without flow bias due to the axisymmetric position of the outlet. At 1 L/min, approximately 78.2% of the outward velocity component was in the radial (horizontal) plane verses 92.0% at 4.5 L/min. The CFD studies were unable to predict the non-radial component of the outward perfusion. Two-dimensional velocity fields were generated from the radiographs using a cross-correlation tracking algorithm and compared with analogous image planes from the CFD simulations. Velocities in the non-porous regions differed by an average of 11% versus the experimental values, but simulated velocities in the fiber bundle were on average 44% lower than experimental. A corrective factor reduced the average error differences in the porous medium to 6%. Finally, biplane image pairs were reconstructed to show 3-D transient perfusion through the device. The methods developed from this research provide tools for more accurate assessments of fluid flow through membrane oxygenators. By identifying non-invasive techniques to allow direct analysis of numerical and experimental velocity fields, researchers can better evaluate device performance of new prototype designs.

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Bezuidenhout, Johan Jacobus. "Computational fluid dynamic modelling of an electric smelting furnace in the platinum recovery process." Thesis, Stellenbosch : Stellenbosch University, 2008. http://hdl.handle.net/10019.1/2022.

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Thesis (MScEng (Process Engineering))--Stellenbosch University, 2008.
The electric smelting furnace is found at the heart of the platinum recovery process where the power input from the electrodes produces a complex interplay between heat transfer and fluid flow. A fundamental knowledge of the dynamic system hosted by the electric furnace is valuable for maintaining stable and optimum operation. However, describing the character of the system hosted by the electric furnace poses great difficulty due to its aggressive environment. A full-scale threedimensional Computational Fluid Dynamics (CFD) model was therefore developed for the circular, three-electrode Lonmin smelting furnace. The model was solved as time dependent to incorporate the effect of the three-phase AC current, which was supplied by means of volume sources representing the electrodes. The slag and matte layers were both modelled as fluid continuums in contact with each other through a dynamic interface made possible by the Volume of Fluid (VOF) multi-phase model. CO-gas bubbles forming at electrode surfaces and interacting with the surrounding fluid slag were modelled through the Discrete Phase Model (DPM). To account for the effect of concentrate melting, distinctive smelting zones were identified within the concentrate as assigned a portion of the melting heat based on the assumption of a radially decreasing smelting rate from the centre of the furnace. The tapping of slag and matte was neglected in the current modelling approach but compensation was made for the heating-up of descending material by means of an energy sink based on enthalpy differences. Model cases with and without CO-gas bubbles were investigated as well as the incorporation of a third phase between the slag and matte for representing the ‘mushy’ chromite/highly viscous slag commonly found in this region. These models were allowed to iterate until steady state conditions has been achieved, which for most of the cases involved several weeks of simulation time. The results that were obtained provided good insight into the electrical, heat and flow behaviour present within the molten bath. The current density profiles showed a large portion of the current to flow via the matte layer between the electrodes. Distributions for the electric potential and Joule heat within the melt was also developed and showed the highest power to be generated within the immediate vicinity of the electrodes and 98% of the resistive heat to be generated within the slag. Heat was found to be uniformly distributed due the slag layer being well mixed. The CO-gas bubbles was shown to be an important contributor to flow within the slag, resulting in a order of magnitude difference in average flow magnitude compared to the case where only natural buoyancy is at play. The highest flow activity was observed halfway between electrodes where the flow streams from the electrodes meet. Consequently, the highest temperatures are also observed in these regions. The temperature distribution within the matte and concentrate layers can be characterized as stratified. Low flow regions were identified within the matte and bottom slag layer which is where chromite and magnitite deposits are prone to accumulate. The model results were partially validated through good agreement to published results where actual measurements were done while also falling within the typical operating range for the actual furnace. The modelling of the electric furnace has been valuably furthered, however for complete confidence in the model results, further validation is strongly recommended.

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Bujalski, Jakub Michal. "Computational fluid dynamic modelling of stirred reactors : power, baffle stresses, mixing times and semi-batch precipitation." Thesis, University of Birmingham, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289683.

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A commercial CFD (Computational Fluid Dynamics) code CFX (version 4.2 to 4.4) from AEA Technologyl'' has been used to compute the fluid flow, power number, Po, the stresses on baffles, mixing time and a precipitation reaction in a mixing vessel. The impellers investigated were Rushton turbine and 4 or 6 blade 45° pitch blade turbine. The impeller generated flow was modelled primarily using the sliding mesh technique, with additional modelling using Multiple Frames of Reference (MFR) for the mixing time simulations. The Po was estimated from three different methods i.e. specific energy dissipation rate, ET, summation, torque acting on the impeller surfaces, POp(primary power number), and the reaction torque acting on the vessel walls and baffles, POs (the secondary power number). The Po from the summation of ET, was underpredicted as compared with experimental values in all the simulations by over 50%. The investigation of the calculated power numbers for the vessels found that the closest and most consistent values of Po compared to experimental results were obtained from the torque acting on the impeller surfaces, POp. The value of POs was found to be greatly dependent on the sliding mesh simulation parameters and an improvement in the POsprediction could be obtained by using a small time step. A further investigation lead to the computation of the tangential forces and subsequently the axial pressure distribution on the baffles. The baffle pressure distribution depends on the impeller type and its clearance and was better predicted for greater impeller clearances and for the radial flow impellers. The mixing times simulations were performed using a computational method analogous to the experimental method of probe responses. The system was in the high transitional flow regime (Re=8800) and a low Reynolds k-e turbulence model was used in the development of the flow field. The simulations were compared with experimental results (based on decolorisation technique) and to three different mixing time correlations giving mixing times at three different levels of homogenisation (i.e. 90%, 95% and 99%). Worryingly, the simulation results were found to depend on the radial feed position even though the experimental results suggest that it does not. At certain radial position, the simulated mixing time responses accurately predicted the mixing times from the experiments and empirical correlations. CFD based flow visualisation showed that the feed position influenced where the majority of the tracer was initially distributed. The further the radial position was from the axis of the impeller, the more the bulk of the tracer moved towards the low velocity region near the vessel walls, leading to an overestimate of the mixing time. The sliding mesh and MFR simulations of the velocity fields were used for the computation of the mixing time. The results were similar in each case. The precipitation modelling was achieved through the coupling of the CFD hydrodynamics and user defined precipitation model. This approach was able to predict the performance of a semi-batch process involving the precipitation of BaS04 with 270 s addition time. The results (i.e. mean crystal size (d[4,3]) and the particle size distributions) were compared with experimental results for a double feed precipitation reaction for a number of feed configurations and concentration ratios. Overall reasonable trends and agreement have been obtained for the modelled Po, mixing time and baffle stresses. The precipitation model was less successful and was very dependant on the different crystal shape factors used in the simulation model. Further experimental work is required in order to define this parameter accurately, especially as experiments have shown that it varies during the addition time.

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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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Hobbs, Andrew M. "Design and optimization of a vortex particle separator for a hot mix asphalt plant using computational fluid dynamics." Thesis, Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04192004-101304/unrestricted/hobbs%5Fandrew%5Fm%5F200312%5Fms.pdf.

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Sundararaj, Vivekanandhan. "Computational fluid dynamic analysis of unsteady compressible flow through a single cylinder internal combustion engine /." Available to subscribers only, 2006. http://proquest.umi.com/pqdweb?did=1240704871&sid=3&Fmt=2&clientId=1509&RQT=309&VName=PQD.

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Thesis (M.S.)--Southern Illinois University Carbondale, 2006.
"Department of Mechanical Engineering and Energy Processes." Includes bibliographical references (leaves 171-174). Also available online.

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

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

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Horin, Brett. "Applying Computational Fluid Dynamic Simulations and Predictive Models to Determine Control Schedules for Natural Ventilation." Thesis, Illinois Institute of Technology, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10843192.

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This thesis investigates natural ventilation in building design, culminating in a final project to design optimal ventilation in an underground parking garage. The aim of this research is to explore a method combining computational fluid dynamic (CFD) simulations with neural networks as a means of performing a robust, yet computationally inexpensive simulation. The final project has the objective of simulating an annual operation schedule for louvers at the openings of the garage to achieve a desired airflow rate. Concepts in computational design and building science are explored to fully capture how the geometric domain of architectural modeling can be expressed in computational parameters to successfully perform effective simulations. It was important to make these workflows accessible to architects, so common software in the architecture industry was used. The results of this project support a coupled approach of using CFD simulations and neural networks to predict airflow parameters of interest. Validation CFD simulation results were compared to the results using the neural network and they were in good agreement. Ultimately, this project proves that using this approach is a relatively computationally inexpensive alternative to solely using CFD simulations, making design optimization possible.

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El-Ibrahim, Salah Jamil Saleh. "Prediction of the effects of aerofoil surface irregularities at high subsonic speeds using the Viscous Garabedian and Korn (VKG) method." Thesis, University of Hertfordshire, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365928.

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45

Badioli, Rodolfo. "development of a computational fluid dynamic numerical model for the hydrodynamic forces evaluation on subsea structures." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.

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The aim of this master thesis is to simulate, in a multiphase environment (air and water), a free surface wave by making use of the computational fluid dynamics software “OpenFoam” and evaluate the hydrodynamic forces and physical parameters acting on subsea structures. It will be discussed how the hydrodynamic load and other physical parameters vary, according to water depth, when the action of waves and current act together and impact structures of different cross-sections and geometry that lie on the seabed. A comparison between the obtained software results and the analytical solutions will be presented to assess the reliability of “OpenFoam” and the model created for such a problem, trying to give an explanation of the fluid dynamics around the elements when running the simulations. In particular, starting from the multiphase solver “InterFoam”, will be shown how the “wave” tutorial case, available in “OpenFoam V5.0”, has been modified and adapted in order to implement objects on the seabed and eventually determine the hydrodynamic load on submerged structures. For the implemented elements, it will be examined the horizontal and the lift force, trying to verify and validate the model, making a comparison between the theoretical hydrodynamic load, available from the literature and the model post-processed outcomes, extrapolated by OpenFoam object functions. The evaluation of the force coefficients (Drag, Lift, Added Mass) will be also made on the same structures to see which level of influence certain parameters have to respect with others. It will also be presented the Morison’s theory for the evaluation of waves induced load that represents not only the theoretical load with which the model results have been compared to testify the project but it also plays the key role concept of all the following aspects.

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Dooley, Gregory M. "Ship airwakes in waves and motions and effects on helicopter operation." Thesis, University of Iowa, 2019. https://ir.uiowa.edu/etd/6727.

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This thesis focuses on the effects of wave-induced motions on the airwake of a ship and on the operation of a helicopter in the airwake. While the topic is broad, efforts are concentrated on understanding fundamentals of the ship’s airwake structure at varying Reynolds (Re) numbers without motions, using available experimental data for validation of the computational fluid dynamics (CFD) methodology used, and on studying the effects of waves and motions on the airwake of a ship and a helicopter operating above a ship’s flight deck in full-scale. The static ONR Tumblehome (ONRT) ship geometry with a solid boundary representative of the free surface is simulated at three different Re numbers, 3.2x104, 1x106, and 1.3x108. Validation is performed against experimental measurements at model-scale Re=1x106. Full-scale simulations of the ONRT are carried out in head winds and regular waves approximately equivalent to conditions seen at sea states 3 and 6. Effects of waves and motions are isolated for both sea states using simulations with combinations of waves and motions, waves and no motions, no waves with motions, and no motions or waves. A triple velocity decomposition is conducted in order to quantify changes in the airwake due to motions and waves. The operation of rotorcraft in the ONRT airwake is analyzed using one-way and two-way coupling approaches. The one-way coupling approach uses the velocity field data from the full-scale ONRT simulations and disk actuator theory to calculate thrust fluctuations for three different rotor sizes. The results of the one-way coupling approach show that the smallest rotor is much more affected by small scale turbulence, while small scale fluctuations are filtered out by larger rotor diameters. In the two-way coupling approach, a helicopter based on the Sikorsky SH-60 hovering above the flight deck is simulated, including explicitly moving grids to discretize the main rotor, tail rotor, and fuselage. This method captures the effects of the interaction between the rotor downwash and the ONRT airwake. The study shows that for the mild conditions of sea state 3 the motions have little effect on the airwake behavior. At sea state 6 the airwake behavior is significantly altered, which is reflected in the resulting forces on the helicopter body operating in this condition.

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Lam, Shang-king, and 林省京. "Computational fluid dynamic analyses of the endovascular stent-graft at the thoracic aorta with different biomechanical factors." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B41758031.

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Lam, Shang-king. "Computational fluid dynamic analyses of the endovascular stent-graft at the thoracic aorta with different biomechanical factors." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B41758031.

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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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Khodier, Mohanad A. "Weir-Baffled Culvert Hydrodynamics Evaluation for Fish Passage Using Particle Image Velocimetry and Computational Fluid Dynamic Techniques." DigitalCommons@USU, 2014. https://digitalcommons.usu.edu/etd/3078.

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Due to a recent increase in environmental awareness regarding fish passage through hydraulic constructions including culverts, an evaluation for the passage of wild brown trout through a weir-baffled prototype-scale culvert was performed under a variety of culvert slopes and discharge conditions. The influence of the sample fish population and the length of the individual fish on passage rates were investigated; the data showed that the brown trout fish passage sample size evaluated in this study (25 per test) was sufficiently large to minimize sample size dependency. Fish behavior while traversing the culvert was observed and reported, including resting/staging zone locations. Turbulent flow through weir baffled-culvert was also simulated numerically using three-dimensional numerical model employing the (k- �) model, Renormalized Group k-� model (RNG), and Large Eddy Simulation (LES) model. Experimental data measured with the Particle Image Velocimetry (PIV) were used to assess the accuracy and the applicability of these turbulence models in predicting the turbulent flow characteristics of the flow through a weir-baffled culvert at different spatial locations inside the culvert for variety of culvert slopes and flow rates. The influence of flow rates and culvert slopes on the forward velocities and reverse velocities was evaluated. It was noted that the influence of the flow rates on the flow velocities depends on the culvert slopes. Turbulent kinetic energy and flow direction effects on flow characteristic were also evaluated. Validation of Manning’s equation and Manning’s roughness coefficient for the tested culvert were reported.

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Dissertations / Theses on the topic 'Computational fluid dynamic'

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