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Dissertations / Theses on the topic 'Lid-Driven-Cavity Flow'
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Gürcan, Fuat. "Flow bifurcations in rectangular, lid-driven, cavity flows." Thesis, University of Leeds, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425523.
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Benson, John D. "Transition to a time periodic flow in a through-flow lid-driven cavity." Thesis, Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/18179.
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Hussain, Amer. "A Numerical Study of Compressible Lid Driven Cavity Flow with a Moving Boundary." ScholarWorks@UNO, 2016. http://scholarworks.uno.edu/td/2155.
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A two-dimensional (2-D), mathematical model is adopted to investigate the development of circulation patterns for compressible, laminar, and shear driven flow inside a rectangular cavity. The bottom of the cavity is free to move at a specified speed and the aspect ratio of the cavity is changed from 1.0 to 1.5. The vertical sides and the bottom of the cavity are assumed insulated. The cavity is filled with a compressible fluid with Prandtl number, Pr =1. The governing equations are solved numerically using the commercial Computational Fluid Dynamics (CFD) package ANSYS FLUENT 2015 and compared with the results for the primitive variables of the problem obtained using in house CFD code based on Coupled Modified Strongly Implicit Procedure (CMSIP). The simulations are carried out for the unsteady, lid driven cavity flow problem with moving boundary (bottom) for different Reynolds number, Mach numbers, bottom velocities and high initial pressure and temperature.
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Lemée, Thomas. "Shear-flow instabilities in closed flow." Thesis, Paris 11, 2013. http://www.theses.fr/2013PA112038.
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Cette étude se concentre sur la compréhension de la physique des instabilités dans différents écoulements de cisaillement, particulièrement la cavité entraînée et la cavité thermocapillaire, où l'écoulement d'un fluide incompressible est assuré soit par le mouvement d’une ou plusieurs parois, soit par des contraintes d’origine thermique.Un code spectral a été validé sur le cas très étudié de la cavité entrainée par une paroi mobile. Il est démontré dans ce cas que l'écoulement transit d'un régime stationnaire à un instationnaire au-delà d'une valeur critique du nombre de Reynolds. Ce travail est le premier à donner une interprétation physique de l'évolution non monotonique du nombre de Reynolds critique en fonction du facteur d'aspect. Lorsque le fluide est entraîné par deux parois mobiles, la cavité entraînée possède un plan de symétrie particulièrement sensible. Des solutions asymétriques peuvent être observés en plus de la solution symétrique au-dessus d'une certaine valeur du nombre de Reynolds. La transition oscillatoire entre la solution symétrique et les solutions asymétriques est expliquée physiquement par les forces en compétition. Dans le cas asymétrique, l'évolution de la topologie permet à l'écoulement de rester stationnaire avec l'augmentation du nombre de Reynolds. Lorsque l'équilibre est perdu une instabilité se manifeste par l'apparition d'un régime oscillatoire dans l'écoulement asymétrique.Dans une cavité thermocapillaire rectangulaire avec une surface libre, Smith et Davis prévoient deux types d'instabilités convectives thermiques: des rouleaux longitudinaux stationnaires et des ondes hydrothermales instationnaires. L'apparition de ses instabilités a été mis en évidence à plusieurs reprises expérimentalement et numériquement. Alors que les applications impliquent souvent plus d'une surface libre, il semble qu'il y ait peu de connaissances sur l'écoulement thermocapillaire entraînée avec deux surfaces libres. Un film liquide libre soumis à des contraintes thermocapillaires possède un plan de symétrie particulier comme dans le cas de la cavité entrainée par deux parois mobiles. Une étude de stabilité linéaire avec deux profils de vitesse pour le film liquide libre est présentée avec différents nombres de Prandtl. Au-delà d'un nombre de Marangoni critique, il est découvert que ces états de base sont sensibles à quatre types d'instabilités convectives thermiques qui peuvent conserver ou briser la symétrie du système. Les mécanismes qui permettent de prédire ces instabilités sont également découverts et interpréter en fonction de la valeur du nombre de Prandtl du fluide. La comparaison avec les travaux de Smith et Davis est faite. Une simulation numérique directe permet de valider les résultats obtenus avec l'étude de stabilité de linéaireThis study focuses on the understanding of the physics of different instabilities in driven cavities, specifically the lid-driven cavity and the thermocapillarity driven cavity where flow in an incompressible fluid is driven either due to one or many moving walls or due to surface stresses that appear from surface tension gradients caused by thermal gradients. A spectral code is benchmarked on the well-studied case of the lid-cavity driven by one moving wall. In this case, It is shown that the flow transit form a steady regime to unsteady regime beyond a critical value of the Reynolds number. This work is the first to give a physical interpretation of the non-monotonic evolution of the critical Reynolds number versus the size of the cavity. When the fluid is driven by two facing walls moving in the same direction, the cavity possesses a plane of symmetry particularly sensitive. Thus, asymmetrical solutions can be observed in addition to the symmetrical solution above a certain value of the Reynolds number. The oscillatory transition between the symmetric solution and asymmetric solutions is explained physically by the forces in competition. In the asymmetric case, the change of the topology allows the flow to remain steady with increasing the Reynolds number. When the equilibrium is lost, an instability manifests by the appearance of an oscillatory regime in the asymmetric flow. In a rectangular cavity thermocapillary with a free surface, Smith and Davis found two types of thermal convective instabilities: steady longitudinal rolls and unsteady hydrothermal waves. The appearance of its instability has been highlighted repeatedly experimentally and numerically. While applications often involve more than a free surface, it seems that there is little knowledge about the thermocapillary driven flow with two free surfaces. A free liquid film possesses a particular plane of symmetry as in the case of the two-sided lid-driven cavity. A linear stability analysis for the free liquid film with two velocity profiles is presented with various Prandtl numbers. Beyond a critical Marangoni number, it is observed that these basic states are sensitive to four types of thermal convective instabilities, which can keep or break the symmetry of the system. Mechanisms that predict these instabilities are discovered and interpreted according to the value of the Prandtl number of the fluid. Comparison with the work of Smith and Davis is made. A direct numerical simulation is done to validate the results obtained with the linear stability analysis
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Xu, Ying. "TWO-DIMENSIONAL SIMULATION OF SOLIDIFICATION IN FLOW FIELD USING PHASE-FIELD MODEL|MULTISCALE METHOD IMPLEMENTATION." Lexington, Ky. : [University of Kentucky Libraries], 2006. http://lib.uky.edu/ETD/ukymeen2006d00524/YingXu_Dissertation_2006.pdf.
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Thesis (Ph. D.)--University of Kentucky, 2006.Title from document title page (viewed on January 25, 2007). Document formatted into pages; contains: xiii, 162 p. : ill. (some col.). Includes abstract and vita. Includes bibliographical references (p. 151-157).
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Kumar, Pankaj. "Chaos in Pulsed Laminar Flow." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/39260.
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Fluid mixing is a challenging problem in laminar flow systems. Chaotic advection can play an important role in enhancing mixing in such flow. In this thesis, different approaches are used to enhance fluid mixing in two laminar flow systems. In the first system, chaos is generated in a flow between two closely spaced parallel circular plates by pulsed operation of fluid extraction and reinjection through singularities in the domain. A singularity through which fluid is injected (or extracted) is called a source (or a sink). In a bounded domain, one source and one sink with equal strength operate together as a source-sink pair to conserve the fluid volume. Fluid flow between two closely spaced parallel plates is modeled as Hele-Shaw flow with the depth averaged velocity proportional to the gradient of the pressure. So, with the depth-averaged velocity, the flow between the parallel plates can effectively be modeled as two-dimensional potential flow.
This thesis discusses pulsed source-sink systems with two source-sink pairs operating alternately to generate zig-zag trajectories of fluid particles in the domain. For reinjection purpose, fluid extracted through a sink-type singularity can either be relocated to a source-type one, or the same sink-type singularity can be activated as a source to reinject it without relocation. Relocation
of fluid can be accomplished using either â first out first inâ or â last out first inâ scheme. Both relocation methods add delay to the pulse time of the system. This thesis analyzes mixing in pulsed source-sink systems both with and without fluid relocation. It is shown that a pulsed source-sink system with â first out first inâ scheme generates comparatively complex fluid flow than pulsed source-sink systems with â last out first inâ scheme. It is also shown that a pulsed source-sink system without fluid relocation can generate complex fluid flow.
In the second system, mixing and transport is analyzed in a two-dimensional Stokes flow system. Appropriate periodic motions of three rods or periodic points in a two-dimensional flow are determined using the Thurston-Nielsen Classification Theorem (TNCT), which also predicts a lower bound on the complexity generated in the fluid flow. This thesis extends the TNCT -based framework by demonstrating that, in a perturbed system with no lower order fixed points, almost invariant sets are natural objects on which to apply the TNCT. In addition, a method is presented to compute line stretching by tracking appropriate motion of finite size rods. This method accounts for the effect of the rod size in computing the complexity generated in the fluid flow. The last section verifies the existence of almost invariant sets in a two-dimensional flow at finite Reynolds number. The almost invariant set structures move with appropriate periodic motion validating the application of the TNCT to predict a lower bound on the complexity generated in the fluid flow.Ph. D.
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Bergamo, Leandro Fernandes. "Instabilidade hidrodinâmica linear do escoamento compressível em uma cavidade." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/18/18148/tde-28052014-164324/.
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Os mecanismos de instabilidade hidrodinâmica têm um papel importante no processo da transição do escoamento de laminar para turbulento. A análise da instabilidade hidrodinâmica em uma cavidade com tampa deslizante foi realizada através da decomposição em modos globais (biglobal) para avaliar o efeito da compressibilidade neste fenômeno. O escoamento base foi obtido através de simulação numérica direta (DNS). Para tal, foi desenvolvido um código DNS compressível com discretização espacial por diferenças finitas compactas de alta resolução espectral e capacidade de processamento paralelo, com um método de decomposição de domínio que mantém a precisão das diferenças finitas compactas. O escoamento base é usado para montar o problema de autovalor oriundo das equações de Navier-Stokes linearizadas para a perturbação, discretizadas por diferenças finitas explícitas. O uso de diferenças finitas em conjunto com a implementação em matrizes esparsas reduz sensivelmente o uso de memória. Através do algoritmo de Arnoldi, a ordem do problema de autovalor é reduzida e os autovalores de interesse são recuperados. Os resultados indicam o efeito estabilizante da compressibilidade nos modos dominantes da cavidade e revelam modos inerentes ao escoamento compressível, para os quais a compressibilidade tem efeito desestabilizante. Dentre estes modos compressíveis, estão presentes modos de propagação sonora em dutos e modos relacionados à geração de som na cavidade.Hydrodynamic instability mechanisms play an important role in laminar to turbulent transition. Hydrodynamic instability analysis of a lid-driven cavity flow was performed by global mode decomposition (biglobal) to evaluate compressibility effects on this phenomenon. The basic flow was calculated by direct numerical simulation (DNS). A compressible DNS code was developed with spectral-like compact finite difference spatial discretization. The code allows parallel processing with a domain decomposition method that preserves the compact finite difference accuracy. The basic flow is used to form the eigenvalue problem associated to the linear Navier- Stokes equations for the perturbation, which were discretized by an explicit finite difference scheme. The combination of sparse matrix techniques and finite difference discretization leads to a significant memory reduction. The order of the eigenvalue problem was reduced using the Arnoldi algorithm and the eigenvalues of interest were calculated. Results show the stabilizing effect of compressibility on the leading modes and reveal some modes intrinsic to compressible flow, for which compressibility has a destabilizing effect. Among these compressible modes, there are some related to sound propagation in ducts and to sound generation inside the cavity.
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Santos, Daniel Dall'Onder dos. "Modelagem mecânica e investigação numérica de escoamentos de fluidos SMD empregando um método multi-campos de galerkin mínimos-quadrados." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2010. http://hdl.handle.net/10183/27259.
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A maioria dos líquidos encontrados na natureza são não-Newtonianos e o estudo do seu comportamento tem uma importância significante em diferentes áreas da engenharia. Entre eles, uma larga classe de materiais que exibem pequena ou nenhuma deformação quando sujeitos a um nível de tensões inferiores a uma tensão limite de escoamento – chamado de comportamento viscoplástico. A presente Dissertação tem como objetivo o estudo numérico de escoamentos bidimensionais em regime permanente de fluidos viscoplásticos não-lineares em uma cavidade forçada. O modelo mecânico é definido pelas equações de conservação de massa e de balanço de momentum acopladas ao modelo viscoplástico recentemente introduzido por Souza Mendes e Dutra – SMD – e é aproximado por um método de elementos finitos multi-campos estabilizado baseado na metodologia de Galerkin mínimos-quadrados que possui como variáveis primais os campos de tensão-extra, velocidade e pressão. As condições de compatibilidade entre os subespaços de elementos finitos para tensão-extra-velocidade e velocidade-pressão são violadas, permitindo assim a utilização de interpolações de igual ordem. O método estabilizado foi implementado no código de elementos finitos para fluidos não-Newtonianos em desenvolvimento no Laboratório de Mecânica dos Fluidos Aplicada e Computacional (LAMAC) da UFRGS. Em diversos trabalhos encontrados na literatura, a superfície de escoamento do material é definida como a região onde o módulo da tensão-extra é igual à tensão limite de escoamento. É mostrado nesta Dissertação que esta metodologia pode conduzir à alguns erros, dado ao grande aumento experimentado pela taxa de cisalhamento em uma pequena faixa de tensões próximas à tensão limite de escoamento. Assim, foi adotada outra metodologia, definindo a superfície de escoamento como a linha onde a taxa de cisalhamento é igual a um valor dado pela relação de parâmetros reológicos do fluido, especificamente a tensão limite de escoamento e a viscosidade Newtoniana para baixas taxas de cisalhamento. Nas simulações numéricas realizadas, o número de salto, J, o coeficiente de power-law, n, e a vazão adimensional, U*, são variados de forma a avaliar de que modo influenciam na dinâmica de escoamentos viscoplásticos. Os resultados obtidos estão de acordo com a literatura e atestam a estabilidade da formulação empregada.Non-Newtonian fluids are the majority of liquids found on the nature and the study of their behavior has a significant importance on different areas of engineering. Among them, there is a wide class of materials that exhibits little or no deformation when subjected to a stress level behind an apparent yield stress – called the viscoplastic behavior. The present thesis aimed to a numerical study of two dimensional steady state laminar flows of non-linear viscoplastic fluids in a lid-driven cavity. The mechanical model was defined by the mass conservation and momentum balance equations coupled to the recently introduced Souza Mendes and Dutra – SMD – viscoplastic model and has been approximated by a stabilized multi-field finite element method based on the Galerkin least-squares methodology, having as primal variables the extra-stress, velocity and pressure fields. In this way, the compatibility conditions between the extra-stressvelocity and pressure-velocity (Babuška-Brezzi condition) finite element subspaces are violated, allowing to use equal-order finite element interpolations. The stabilized method has been implemented in the finite element code for non-Newtonian fluids under development at the Laboratory of Applied and Computational Fluid Mechanics (LAMAC) of UFRGS. In several works found on the literature, the yield surface of the material is defined as the region where the stress modulus is equal to the yield stress. Is shown in this work that this methodology can lead to some errors, due to the large strain rate increasing in a small range of values of stress on the vicinity of the yield stress. Therefore, it was adopted another approach, defining the yield surface as the line where the strain rate is equal to a value given by the relation of the rheological parameters of the fluid, namely the yield stress and the viscosity at low shear rates. In the performed numerical simulations, the jump number, J, the the power-law coefficient, n,and the non-dimensional flow rate, U*, are ranged in order to evaluate how they the influence on the viscoplastic fluid dynamics have been investigated. All results found were in accordance with the affine literature and attests the good stability features of the formulation.
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Loiseau, Jean-Christophe. "Dynamics and global stability analysis of three-dimensional flows." Thesis, Paris, ENSAM, 2014. http://www.theses.fr/2014ENAM0016/document.
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Comprendre, prédire et finalement retarder la transition vers la turbulence dans les écoulements sont d'importants problèmes posés aux scientifiques depuis les travaux pionniers d'Osborne Reynolds en 1883. Ces questions ont été principalement adressées à l'aide de la théorie des instabilités hydrodynamiques. A cause des ressources informatiques limitées, les analyses de stabilité linéaire reposent essentiellement sur d'importantes hypothèses simplificatrices telles que celle d'un écoulement parallèle. Dans ce cadre, connu sous le nom de stabilité locale, seule la stabilité d'écoulement ayant un fort intérêt académique mais relativement peu d'applications pratiques a pu être étudiée. Néanmoins, au cours de la décennie passée, l'hypothèse d'écoulement parallèle a été relaxée au profit de celle d'un écoulement bidimensionnel conduisant alors à ce que l'on appelle la stabilité globale. Ce nouveau cadre permet alors d'étudier les mécanismes d'instabilité et de transition ayant lieu au sein d'écoulements plus réalistes. Plus particulièrement, la stabilité d'écoulements fortement non-parallèles pouvant présenter des décollements massifs, une caractéristique fréquente dans les écoulements d'intérêt industriel, peut maintenant être étudiée. De plus, avec l'accroissement constant des moyens de calcul et le développement de nouveaux algorithmes de recherche de valeurs propres itératifs, il est aujourd'hui possible d'étudier la stabilité d'écoulements pleinement tridimensionnels pour lesquels aucune hypothèse simplificatrice n'est alors nécessaire. Dans la continuité des travaux présentés par Bagheri et al. en 2008, le but de la présente thèse est de développer les outils nécessaires à l'analyse de la stabilité d'écoulements 3D. Trois écoulements ont été choisis afin d'illustrer les nouvelles capacités de compréhension apportées par l'analyse de la stabilité globale appliquée à des écoulements tridimensionnels réels : i) l'écoulement au sein d'une cavité entraînée 3D, ii) l'écoulement se développant dans un tuyau sténosé, et enfin iii) l'écoulement de couche limite se développant au passage d'une rugosité cylindrique montée sur une plaque plane. Chacun de ces écoulements a différentes applications pratiques allant d'un intérêt purement académique à une application biomédicale et aérodynamique. Ce choix d'écoulements nous permet également d'illustrer les différents aspects des outils développés au cours de cette thèse ainsi que les limitations qui leur sont inhérentesUnderstanding, predicting and eventually delaying transition to turbulence in fluid flows have been challenging issues for scientists ever since the pioneering work of Osborne Reynolds in 1883. These problems have mostly been addressed using the hydrodynamic linear stability theory. Yet, due to limited computational resources, linear stability analyses have essentially relied until recently on strong simplification hypotheses such as the “parallel flow” assumption. In this framework, known as “local stability theory”, only the stability of flows with strong academic interest but limited practical applications can be investigated. However, over the course of the past decade, simplification hypotheses have been relaxed from the “parallel flow” assumption to a two-dimensionality assumption of the flow resulting in what is now known as the “global stability theory”. This new framework allows one to investigate the instability and transition mechanisms taking place in more realistic flows. More particularly, the stability of strongly non-parallel flows exhibiting separation, a common feature of numerous flows of practical interest, can now be studied. Moreover, with the continuous increase of computational power available and the development of new iterative eigenvalue algorithms, investigating the global stability of fully three-dimensional flows, for which no simplification hypothesis is necessary, is now feasible. Following the work presented in 2008 by Bagheri et al., the aim of the present thesis is thus to develop the tools mandatory to investigate the stability of 3D flows. Three flow configurations have been chosen to illustrate the new investigation capabilities brought by global stability theory when it is applied to realistic three-dimensional flows: i) the flow within a cuboid lid-driven cavity, ii) the flow within an asymmetric stenotic pipe and iii) the boundary layer flow developing over a cylindrical roughness element mounted on a flat plate. Each of these flows have different practical applications ranging from purely academic interests to biomedical and aerodynamical applications. They also allow us to put in the limelight different aspects and possible limitations of the various tools developed during this PhD thesis
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Furtado, Giovanni Minervino. "Modelagem mecânica e numérica da influência dos efeitos viscosos e elásticos nos escoamentos de materiais elasto-viscoplásticos." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2016. http://hdl.handle.net/10183/134937.
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Esta dissertação investiga numericamente a influência dos efeitos viscosos e elásticos em escoamentos de materiais viscoplásticos no interior de uma cavidade dirigida. O modelo mecânico empregado é constituído pelas equações de conservação de massa e pelo princípio da quantidade de movimento linear, para fluidos incompressíveis, acoplado à equação constitutiva. Esta equação modifica o modelo viscoelástico de Oldroyd-B de modo a acomodar que os tempos de relaxação e retardo do material, bem como sua viscosidade viscoplástica, dependam das mudanças de sua microestrutura. A aproximação numérica do modelo emprega o método multi-campos de Galerkin mínimos-quadrados em termos do tensor de tensão extra, do vetor velocidade e do campo de pressão. Os resultados objetivam a determinção do tamanho e localização das regiões aparentemente não-escoadas do material, bem como sua deformação elástica, intensidade de tensão, e a sua vorticidade no interior da cavidade. Os resultados claramente indicam que o padrão do escoamento é fortemente influenciado pela variação dos efeitos elásticos (variação do tempo de relaxação adimensional, θ0 * ), viscosos (variação do índice de power-law, n) e cinemáticos (variação da velocidade adimensional, U* , do escoamento) no interior da cavidade.This dissertation investigated numerically the influence of viscous and elastic effects on flows of viscoplastic materials within a lid-driven cavity. The mechanical model used is made up of mass and momentum balance equations, coupled with the constitutive equation. This equation modifies the viscoelastic Oldroyd-B model to accommodate both relaxation and retardation times, and viscosity function, dependent on the microstructure changes. Numerical approximations of the model make use a three-field Galerkin least squares method in terms of the extra stress tensor, velocity vector and pressure field. Computations focus on the determination of the size and position of apparently unyielded regions as well as the elastic deformation, stress intensity, and the vorticity within of the cavity. Results clearly indicate that the flow pattern is strongly influenced by the elastic (variation of the dimensionless relaxation time, θ0 * ), viscous (variation of the power-law index, n) and kinematic (variation of the dimensionless flow velocity, U* ) effects within the cavity.
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Pokorný, Jan. "Numerická simulace proudění nestlačitelných kapalin metodou spektrálních prvků." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2008. http://www.nusl.cz/ntk/nusl-228180.
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Tato diplomová práce prezentuje metodu spektrálních prvků. Tato metoda je použita k řešení stacionárního 2-D laminárního proudění Newtonovské nestlačitelné tekutiny. Proudění je popsáno stacionarní Navier-Stokesovou rovnicí. Dohromady s okrajovou pod- mínkou tvoří Navier-Stokesův problém. Na slabou formulaci této úlohy je aplikována metoda spektrálních prvků. Touto discretizací se získá soustava nelineárních rovnic. K obrdžení lineární soustavy je použita Newtonova iterační metoda. Podorobný algorit- mus tvoří jádro Navier-Stokeseva solveru, který je naprogramován v Matlabu. Na závěr jsou pomocí tohoto solveru řešeny dva příklady: proudění v kavitě a obtékání válce. Přík- lady jsou řešeny pro různé Reynoldsovy čísla. První od 1 do 1000 a druhý od 1 do 100.
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Talpaert, Arthur. "Direct Numerical Simulation of bubbles with Adaptive Mesh Refinement with Distributed Algorithms." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX016/document.
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Ce travail de thèse présente l'implémentation de la simulation d'écoulements diphasiques dans des conditions de réacteurs nucléaires à caloporteur eau, à l'échelle de bulles individuelles. Pour ce faire, nous étudions plusieurs modèles d'écoulements thermohydrauliques et nous focalisons sur une technique de capture d'interface mince entre phases liquide et vapeur. Nous passons ainsi en revue quelques techniques possibles de maillage adaptatif (AMR) et nous fournissons des outils algorithmiques et informatiques adaptés à l'AMR par patchs dont l'objectif localement la précision dans des régions d'intérêt. Plus précisément, nous introduisons un algorithme de génération de patchs conçu dans l'optique du calcul parallèle équilibré. Cette approche nous permet de capturer finement des changements situés à l'interface, comme nous le montrons pour des cas tests d'advection ainsi que pour des modèles avec couplage hyperbolique-elliptique. Les calculs que nous présentons incluent également la simulation du système de Navier-Stokes incompressible qui modélise la déformation de l'interface entre deux fluides non-misciblesThis PhD work presents the implementation of the simulation of two-phase flows in conditions of water-cooled nuclear reactors, at the scale of individual bubbles. To achieve that, we study several models for Thermal-Hydraulic flows and we focus on a technique for the capture of the thin interface between liquid and vapour phases. We thus review some possible techniques for Adaptive Mesh Refinement (AMR) and provide algorithmic and computational tools adapted to patch-based AMR, which aim is to locally improve the precision in regions of interest. More precisely, we introduce a patch-covering algorithm designed with balanced parallel computing in mind. This approach lets us finely capture changes located at the interface, as we show for advection test cases as well as for models with hyperbolic-elliptic coupling. The computations we present also include the simulation of the incompressible Navier-Stokes system, which models the shape changes of the interface between two non-miscible fluids
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Fenzi, Robin. "Numerical simulations of viscoelastic tridimensional lid-driven cavity flows." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
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Much is known about the dynamics of viscous Newtonian fluids in the classical “lid driven cavity” problem. However, little is known about the corresponding motion of viscoelastic fluids. The aim of this work is to study qualitatively and quantitatively the dynamics of viscoelastic flows for three different Deborah numbers in a tridimensional cavity. The so called “log-conformation formulation” made available by rheoTool for the OpenFOAM software is used to research the onset of elastic instabilities as an effect of viscoelasticity. The results obtained are presented through flow visualization and stress profiles. The symmetry observed in the velocity field of viscous Newtonian cavity flows at negligible Reynolds number is broken. The primary vortex centre shift progressively upstream with increasing Deborah number. The flow remains stable and two-dimensional with increasing Deborah number and no elastic instabilities appear. Upon the cessation of the moving wall motion, a pronounced elastic recoil is observed which leads to a rapid reversal in the recirculation direction. The elastic recoil subsequently decays through viscous dissipative effects.
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Corrêa, Laís. "Simulação de grandes escalas de escoamentos turbulentos com filtragem temporal via método de volumes finitos." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/55/55134/tde-27092016-161820/.
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Este trabalho tem como principal objetivo o desenvolvimento de um método numérico para simulação das grandes escalas de escoamentos turbulentos tridimensionais utilizando uma modelagem de turbulência baseada em filtragem temporal (denominada TLES - Temporal Large Eddy Simulation). O método desenvolvido combina discretizações temporais com ordem de mínima precisão 2 (Adams-Bashforth, QUICK, Runge-Kutta), um método de projeção de ordem 2, com discretizações espaciais também de ordem 2 obtidas pelo método de volumes finitos. Esta metodologia foi empregada na simulação de problemas teste turbulentos como o canal e a cavidade impulsionada, sendo este último resultado simulado pela primeira vez com modelagem TLES. Os resultados mostram uma excelente concordância quando comparado com resultados de simulações diretas (DNS) e dados experimentais, superando resultados clássicos obtidos com formulação LES com filtragem espacial.The main objective of this work is to develop a numerical method for large eddy simulation of tridimensional turbulent flows using a model based on temporal filtering (TLES - Temporal Large Eddy Simulation). The developed method combines at least 2nd order temporal discretizations (Adams-Bashforth, QUICK, Runge-Kutta), a 2nd order projection method, and 2nd order spatial discretizations obtained by the finite volume method. This methodology was employed to the simulation of turbulent benchmark problems such as channel and lid-driven cavity flows. The latter is simulated for the first time using a TLES turbulence modelling. Results show excellent agreement when compared to Direct Numerical Simulations (DNS) and experimental data, with better results than classical results produced by standard LES formulation with spatial filtering.
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Brynjell-Rahkola, Mattias. "Global stability analysis of three-dimensional boundary layer flows." Licentiate thesis, KTH, Stabilitet, Transition, Kontroll, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-175353.
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This thesis considers the stability and transition of incompressible boundary layers. In particular, the Falkner–Skan–Cooke boundary layer subject to a cylindrical surface roughness, and the Blasius boundary layer with applied localized suction are investigated. These flows are of great importance within the aviation industry, feature complex transition scenarios, and are strongly three-dimensional in nature. Consequently, no assumptions regarding homogeneity in any of the spatial directions are possible, and the stability of the flow is governed by an extensive three-dimensional eigenvalue problem. The stability of these flows is addressed by high-order direct numerical simulations using the spectral element method, in combination with a Krylov subspace projection method. Such techniques target the long-term behavior of the flow and can provide lower limits beyond which transition is unavoidable. The origin of the instabilities, as well as the mechanisms leading to transition in the aforementioned cases are studied and the findings are reported. Additionally, a novel method for computing the optimal forcing of a dynamical system is developed. This type of analysis provides valuable information about the frequencies and structures that cause the largest energy amplification in the system. The method is based on the inverse power method, and is discussed in the context of the one-dimensional Ginzburg–Landau equation and a two-dimensional flow case governed by the Navier–Stokes equations.QC 20151015
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Loy, Kak Choon. "Efficient Semi-Implicit Time-Stepping Schemes for Incompressible Flows." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/36442.
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The development of numerical methods for the incompressible Navier-Stokes equations received much attention in the past 50 years. Finite element methods emerged given their robustness and reliability. In our work, we choose the P2-P1 finite element for space approximation which gives 2nd-order accuracy for velocity and 1st-order accuracy for pressure. Our research focuses on the development of several high-order semi-implicit time-stepping methods to compute unsteady flows. The methods investigated include backward difference formulae (SBDF) and defect correction strategy (DC). Using the defect correction strategy, we investigate two variants, the first one being based on high-order artificial compressibility and bootstrapping strategy proposed by Guermond and Minev (GM) and the other being a combination of GM methods with sequential regularization method (GM-SRM). Both GM and GM-SRM methods avoid solving saddle point problems as for SBDF and DC methods. This approach reduces the complexity of the linear systems at the expense that many smaller linear systems need to be solved. Next, we proposed several numerical improvements in terms of better approximations of the nonlinear advection term and high-order initialization for all methods. To further minimize the complexity of the resulting linear systems, we developed several new variants of grad-div splitting algorithms besides the one studied by Guermond and Minev. Splitting algorithm allows us to handle larger flow problems. We showed that our new methods are capable of reproducing flow characteristics (e.g., lift and drag parameters and Strouhal numbers) published in the literature for 2D lid-driven cavity and 2D flow around the cylinder. SBDF methods with grad-div stabilization terms are found to be very stable, accurate and efficient when computing flows with high Reynolds numbers. Lastly, we showcased the robustness of our methods to carry 3D computations.
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Brynjell-Rahkola, Mattias. "Studies on instability and optimal forcing of incompressible flows." Doctoral thesis, KTH, Stabilitet, Transition, Kontroll, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-218172.
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This thesis considers the hydrodynamic instability and optimal forcing of a number of incompressible flow cases. In the first part, the instabilities of three problems that are of great interest in energy and aerospace applications are studied, namely a Blasius boundary layer subject to localized wall-suction, a Falkner–Skan–Cooke boundary layer with a localized surface roughness, and a pair of helical vortices. The two boundary layer flows are studied through spectral element simulations and eigenvalue computations, which enable their long-term behavior as well as the mechanisms causing transition to be determined. The emergence of transition in these cases is found to originate from a linear flow instability, but whereas the onset of this instability in the Blasius flow can be associated with a localized region in the vicinity of the suction orifice, the instability in the Falkner–Skan–Cooke flow involves the entire flow field. Due to this difference, the results of the eigenvalue analysis in the former case are found to be robust with respect to numerical parameters and domain size, whereas the results in the latter case exhibit an extreme sensitivity that prevents domain independent critical parameters from being determined. The instability of the two helices is primarily addressed through experiments and analytic theory. It is shown that the well known pairing instability of neighboring vortex filaments is responsible for transition, and careful measurements enable growth rates of the instabilities to be obtained that are in close agreement with theoretical predictions. Using the experimental baseflow data, a successful attempt is subsequently also made to reproduce this experiment numerically. In the second part of the thesis, a novel method for computing the optimal forcing of a dynamical system is developed. The method is based on an application of the inverse power method preconditioned by the Laplace preconditioner to the direct and adjoint resolvent operators. The method is analyzed for the Ginzburg–Landau equation and afterwards the Navier–Stokes equations, where it is implemented in the spectral element method and validated on the two-dimensional lid-driven cavity flow and the flow around a cylinder.QC 20171124
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Akin, Ayhan. "Development Of A Laminar Navier-stokes Solver For Incompressible Flows Using Structured Grids." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607206/index.pdf.
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A method to solve the Navier-Stokes equations for incompressible viscous flows is proposed. This method is SIMPLE (Semi-Implicit Method for Pressure Linked Equations) algorithm to iteratively solve the two-dimensional laminar steady momentum equations and based upon finite volume method on staggered grids. Numerical tests are performed on several cases of the flow in the lid-driven cavity, as well as of the flow after a backward-facing step with SIMPLE and SIMPLER (SIMPLE Revised) methods. Finally, results are compared qualitatively and quantitatively with numerical and experimental results available in the literature for different Reynolds numbers to validate the methods.
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Jheng, CI-YOU, and 鄭啟佑. "Three-Dimensional Flow Structure Analysis of Two-Sided Lid-Driven Cavity." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/84437669575670625774.
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碩士國立臺灣海洋大學
輪機工程系
98
In this study, numerical simulation for three-dimensional incompressible viscous fluid in a rectangular container by two parallel and opposite direction driven is investigated. The numerical results are independently verified by experiments and grid independent tests, and analyzed the rectangular container inside the vortex generated. The numerical results are divided two parts. The first part, a rectangular container with (SAR=6.55 and AR=2),is observed the vortex generated by increases Reynolds number from Re=100 to Re=1200.The results have shown that, two significant main parallel vortex corelines formed in the longitudinal direction in low Reynolds number. As Re≦250, the vortex structure is formed in the z axis parallel to the two vortex structure. As Re = 275,flow eddy divides the entire rectangular into three zones. As Reynolds number is between 300 and 1200, eddy regions are divided into four zones. The second part, Reynolds number is fixed as Re = 800 and aspect ratio is AR = 2, spanwise aspect ratios SAR are changed from 1 to 6.The phoenomenon of the vortex flow in this rectangular container structure is obsered.The results shown when spanwise aspect ratio is SAR<2.25, a single zone of the vortex structure is formed. As the spanwise aspect ratio increases, the rectangular container gradually forms a instable wavy vortex coreline. The original single vortex block is split into two, three or four zone as the spanwise aspect ratios are changed.
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WANG, JIAN-SHENG, and 王建升. "Flow field and mass(heat)transfer in a lid-driven open cavity flow." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/31552637485361400019.
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Shuen-Jong, Tsorng. "Three-dimensional particle paths in a lid-driven cavity flow: experiments and analysis." 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-0407200613490500.
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Tsorng, Shuen-Jong, and 欉順忠. "Three-dimensional particle paths in a lid-driven cavity flow: experiments and analysis." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/58870469735998663320.
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博士國立臺灣大學
土木工程學研究所
94
Experiments and analysis are performed to character three-dimensional particle paths in a lid-driven cavity. Two types of particles with various diameters and experimental methods are utilized in this thesis. Illuminated micro-particles and artificial long exposure techniques visualize two-dimensional flow field. Stereo image methods measure three-dimensional macro-particle positions and Kalman filter efficiently attenuates measurement errors. To complement of experiments, analysis of velocity fields from three-dimensional Navier-Stokes equations in velocity-vorticity formulation solved by finite difference method extract details of flow structures and these computations stand for motions of fluid-particles. Stereo tracking experiments delineate macro-particle shuttling to and fro from side wall to centre plane in spiral way in cavity flow. Mutual comparisons of trajectories and velocities for fluid- (passive tracers), micro- and macro-particles are carried out in Lagrangian and Eulerian viewpoints to highlight similarities and discrepancies among them. There are two interesting phenomena: 1) macro-particle paths are only confined in primary eddy region even if trajectories and velocities of macro-particle matches computational fluid-particle results, whereas fluid- and micro-particles migrate to primary and corner vortices; 2) preferential paths of macro-particle approach to boundary walls while Re increasing. We afterward come up with some possible mechanisms to explain observations such as density mismatch, steric effect, inertia effect and particle rotation. After further examinations, density mismatch is excluded. The steric effect due to particle size gives an evident limitation for invasion of corner eddies through streamline corridors. Inertia effects contain the Reynolds number dependence of macro-particle trajectories and significant deviation of macro-particle rotation rate relative to fluid-particle.
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Sundaresan, Sundaram. "Clustered Grids And Mesh-Independence In Numerical Simulation Of 2-D Lid-Driven Cavity Flows." Thesis, 1996. http://etd.iisc.ernet.in/handle/2005/1578.
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Lin, Li-Song, and 林立松. "Predictions of flow instability in deep lid driven cavity flows using multiple relaxation time lattice Boltzmann method." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/45564528596322131040.
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博士國立清華大學
動力機械工程學系
103
The present study employs the multi relaxation time (MRT) lattice Boltzmann equation (LBE) to study the flow instability within lid driven cavity at different depth-width aspect ratios. The focuses are to examine the correlation between the depth-width aspect ratio and the transition Reynolds number, and to identify the oscillatory instability mechanism. Simulations were applied to two and three dimensional cavity flows at different depth aspect rations. For square and cubic cavity flows, the predicted results were validated with available benchmark solutions [48, 62, 63]. For two-dimensional flows, MRT LBE was used to compute flow fields at different Reynolds numbers (100 to 7500) and cavity depth aspect ratios (K) (1 to 4). It is found that the merger of the bottom corner vortices into a primary vortex (PV) and the reemergence of the corner vortices as the Reynolds number increases, are more evident for the deep cavity flows. When the depth aspect ratio is 4, four PVs were predicted by MRT model for Reynolds number beyond 1000, which were not captured by previous single relaxation time (SRT) BGK model. Present study also shows that with the increase of the cavity depths, the first Hopf bifurcation Reynolds number decreases. In addition, since MRT LBM is explicit, it is suitable for parallel computing. Graphical Processing Unit (GPU) is used to speed up the simulation for 2D flows, and the computing platform is NVIDIA TeslaTM C2050 GPU. In the present study, CPU and GPU comparisons performed have shown that the maximum GPU speedup is 20.4 times faster than its Intel CoreTM i7-920 CPU counterpart. MRT LBE was further adopted to simulate three dimensional cavity flows at various Reynolds numbers (100-1900) and depth aspect ratios (1-4). Compared to its 2D counterpart along the wall bisector, at high Reynolds number, the presence of secondary flows causes the dramatically different both on flow structure and velocity profile. Also, the critical Reynolds number (Recr) for the first Hopf bifurcation in 3D cavity was found to be much lower than its 2D cavity counterpart. For 3D cubic cavity, the Recr for the onset of first Hopf bifurcation is 1763.7, which is much lower than its square cavity counterpart at Recr ∼ 8300. The present result is consistent with the experimental result [63], where Recr locates in the range of (1700
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Tsai, Chih-Ching, and 蔡至清. "Advanced Study in the Effects of Aspect Ratio on Two-Sided Lid-Driven Cavity Flow." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/91595917658598252412.
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碩士國立中興大學
應用數學系所
99
The lid-driven cavity problem has been studied theoretically and experimentally for decades. In this study, the bifurcation phenomenon of rectangular two-sided liddriven cavity flow with various aspect ratios is explored via continuation method for the antiparallel motion and the parallel motion of two facing walls. For antiparallel motion, the upper and the bottom walls of the rectangular cavity move simultaneously in opposite directions with constant velocities while these two walls both move to the right for parallel motion. The antiparallel motion with aspect ratios from 1.0 to 2.0 and Reynolds numbers below 7500 and the parallel motion with aspect ratios from 0.54 to 1.0 and Reynolds numbers below 13000 are numerically simulated. Comprehensive bifurcation diagrams of the cavity flow for both cases are obtained and linear stability analysis is performed to identify the nature of the various flow solutions. Furthermore, five different types of stable flow patterns for antiparallel motion and two different types for parallel motion are identified, and some critical Reynolds numbers at which the solution curve bifurcates are predicted. The flow patterns are highly dependent upon the aspect ratio of the cavity and upon the velocities of the moving walls. Not only flow patterns but also bifurcation diagrams changes tremendously around certain critical aspect ratios. According to the values of aspect ratio, there are two types of bifurcation diagrams for antiparallel motion whereas for parallel motion, bifurcation diagrams can be classified into four categories. Meanwhile, the various existent regions of stable flow patterns for antiparallel and parallel motion are recognized.
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Yeh, Meng Kang, and 葉孟剛. "A numerical study on the vortical structures in a three-dimensional lid-driven cavity flow." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/87085687670186667672.
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碩士國立交通大學
土木工程系
91
To gain physical insights into the developing vortical structure in a three-dimensonal lid-driven cavity of square cross section (depth : width=1:1), we conduct a series of simulations with varied numerical grid resolutions and spanwise aspect ratios (SARs). The sensitivity of the simulated flows to the grid resolution is first examined by conducting numerical experiments for the cavity flow of SAR=3 with various grids of 42x63x42, 60x90x60 and 84x126x84. The impact of the SAR on the three-dimensional vortical structure is then examined for SAR=1, 2, 3 and 4 . The simulation results reveal that the initial end wall vortices depend only on the developing spanwise jet induced by the high-pressure, low-velocity flow region near the end wall. With the increases of the cavity span, more disturbances along the bottom occur, which consequently result in more Taylor-Gortler-like vortices.
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Chen, Chin-Lung, and 陳金龍. "Study of Periodic Flow Pattern and Convection Heat Transfer in a Lid-Driven Arc-Shape Cavity." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/64357277040749471796.
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博士大同大學
機械工程學系(所)
93
ABSTRACT Experimental and numerical study has been performed to investigate the combined effects of lid movement and buoyancy on flow pattern and heat transfer characteristics for the mixed convective flow inside an arc-shape cavity. The governing equations in terms of the stream function-vorticity formulation are solved by the finite-volume method coupled with a body-fitted coordinate transformation scheme. In experiments, steady-state temperature data are measured by K-type thermocouples, and the flow field is visualized by using kerosene smoke. The task of the present study includes the numerical and experimental investigation of (1) Natural convection heat transfer and flow pattern in the horizontal and the inclined cavities. (2) Steady mixed convection heat transfer and flow pattern in the horizontal cavities with a moving lid. (3) Unsteady (periodic) mixed convection heat transfer and flow pattern in the horizontal and the inclined cavities, particularly under the effects of irregular shape and lid oscillation. Results show that only when the inertial and buoyant forces are of approximately equal strength the periodic flow pattern can be observed. For an inertia-dominant or buoyancy-dominant situation, the periodic flow pattern is not visible. Flow pattern, friction factor, and Nusselt numbers are investigated in wide ranges of parameters. Close agreement in the comparison between the predicted and the visualized flow patterns has been found. In these above ranges of the parameters, two kinds of oscillatory flow pattern have been observed, namely, the traversing-periodic and the half-periodic patterns. Attention has been focused on the effects of the inclination effects on the occurrence of these two different oscillatory flow patterns. Meanwhile, periodic variation in the mixed convection heat transfer accompanying the oscillatory moving lid has also been studied, and the results for the local and the overall Nusselt numbers are presented. This report is also concerned with transient behavior of a buoyancy-induced periodic flow in different lid-driven cavities with different cross-sectional shapes. Periodic flow patterns and heat transfer characteristics for various geometries are predicted.
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Liang, Chen Ying, and 陳盈良. "Effect of Reynolds Number on the Vortical Structures in a Three-Dimensional, Lid-Driven Cavity Flow." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/09802035864914472348.
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碩士國立交通大學
土木工程系
90
Abstract The purpose of the present research is to investigate the effect of Reynolds number on the vortical structure in a three-dimensional cavity. This cavity flow is incompressible and it is stationary in the beginning. The primitive velocities and pressure in a set of incompressible continuity and Navier-Stokes equations are solved using the finite difference method. The velocity boundary conditions are no-slip and the pressure satisfies the Neumann boundary condition. By numerical computations, the plots of velocity vector, vorticity iso-line and vorticity iso-surface are illustrated. Then the effect of Reynolds number on the vortical structure variations and wavy disturbances in the spanwise direction are shown through these plots. The results of this study reveal that raising of the Reynolds number makes two-dimensional vortical structure will evolve into three-dimensional structure. As the Reynolds number reaches 1300, the three-dimensional vortical structure starts to exist obviously in the flow field. This flow is not a steady motion, and it will continue to become a turbulence flow with the increase of Reynolds numbers.
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Ho, Ping-Huan, and 何秉寰. "Using the Moving Particle Method With Eularian Mesh toSolve Lid-Driven Cavity Flow Problem in Stream Function-vorticity Formulation." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/55603312173627893916.
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碩士國立高雄海洋科技大學
輪機工程研究所
101
This study focused on applying the method of dual particles to solve the lid-driven cavity flow problem in stream function–vorticity formulation. The method of dual particles includes the Lagrangian particle which possesses the convection behavior, while another Eulerian particle does not have such flowing characteristic effect. Using the property of the Eulerian particle, a fixed grid framework can be constructed. This paper considered three different schemes to evaluate the diffusion effect occurring in Lagrangian particle. They are particle smoothing (PS), smoothing difference (SD) and local mesh (LM). The PS scheme is formulated by superimposing contribution from distributed particles; SD scheme by combining the PS and Taylor series analysis and LM is derived based on a referenced mesh. The numerical results obtained by using the dual particle method proposed in the present study of the lid-driven cavity flow problem for various Reynolds numbers indicated that the more accurate solutions are attained in the formulation of stream function-vorticity rather than the formulation in primitive variables, especially under very high Reynolds numbers. The resultant simulations are observed deviated from the reference data for coarse meshes, however, when fine meshes are adopted, the simulation results obtained are in good agreement with the literatures.
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Jheng, Jia-Bin, and 鄭嘉賓. "The Study of the Geometric Parameter Effects on Cavity Nanofluid Thermal and Flow Fields under the Action of Lid-Driven Velocity and Natural Convection." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/7h3627.
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碩士國立虎尾科技大學
車輛工程系碩士班
104
This research numerically explores the thermal and flow fields of a rectangular cavity filled with nanofluid under the combining action of lid-driven velocity and natural convection. The top surface and bottom surfaces are fixed in constant temperature and constant heat flux, respectively. The right and left sides are set in thermal insulation conditions. A second order up wind finite volume method is used to solve the continuity, momentum and energy equations. Different nanofluid volume fraction, baffle number, lid-driven velocity, baffle height and cavity height are assigned to investigate their effects on thermal and flow fields. Finally, the Taguchi method and response surface methodology are applied to obtain a set of optimal parameters and the result is show =5%, u=0.082m/sec, cavity height=1cm and baffle height=0.1cm to be the optimal ,parameter comsination among the ranges for different parameters in this study.
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LIU, CHIH-WEI, and 劉志偉. "Numerical Simulation of Lid-Driven Flows in a Hemispherical Cavity." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/9c8n5c.
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碩士逢甲大學
水利工程與資源保育學系
105
This thesis proposes a three-dimensional numerical model in the Cartesian coordinates system, by using the finite difference method to simulate the hemispherical cavity flow. The main difficulty is how to treat the solid boundary in orthogonal grid system. The simplified immersed boundary method and volume of solid method are applied to overcome the irregular solid boundary, and then it is not necessary to use the grid generation technique to deal with issues of complex flow field with solid interface. The numerical model to solve the three-dimensional Navier-Stokes equations is established to investigate the flow regimes in several different Reynolds number. The projection method is first employed to obtain the pressure Poisson equation such that the continuity equation can be satisfied. The pressure is solved directly by using fast Fourier transform method. The velocity can be solved then from the momentum equations by using the Adams-Bashforth scheme, and the virtual force of solid can be obtained to meet the solid boundary condition finally. The numerical flow visualization was carried out from the Tecplot 3D software. The effect of Reynolds number to the flow regimes is investigated. The preliminary results show that the critical Reynolds number is of 2450 in hemispherical cavity flow. The steady state solution can be obtained below this value of Reynolds number. The flow is shown as periodic or non-periodic unsteady solution while the Reynolds number greater than 2450.
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dong, Liu hwai, and 劉懷東. "The initial development and evolution of flows in a three-dimensional lid-driven cavity." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/34971932200495406966.
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碩士國立交通大學
土木工程系
90
Lid-driven flow in a rectangular cavity of span to width aspect ratio of 3：1 and depth to width aspect ratio of 1：1 is simulated numerically at Reynolds number 1500 to gain physical insight into the initial development of the three-dimensional perturbation and its subsequent evolution. The emphases are on the end-wall effect which causes the initial almost-two-dimensional flow to develop into a three-dimensional flow structure, and the evolution of such a flow structure into Taylor-Gortler-like（TGL） vortices distributing along the cavity span in planes perpendicular to the lid. It is found that spanwise jet flows and corner vortices form near the end walls immediately after the start of the motion of the lid. As time proceeds, the disturbed spanwise motions in the upstream area become more complex than those in the downstream area, and the circulating motions of fluid particles in the region near the symmetric plane are more active than those near the end walls. The axes of the TGL vortices are found to stretch along the streamlines of the primary recirculating flow.
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Liu, Wen-Hsiang, and 柳文祥. "The Effects of Aspect Ratio and Inclination Angle on the Characteristics of Heat Transfer in Lid-driven Cavity Flows." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/49365516826195172702.
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碩士中華大學
機械工程學系碩士班
98
Numerical simulations are performed to investigate the effects of aspect ratio (AR = 0.2、1、5), Richardson number (Ri = 0.01、1、100), and inclination angle ( 0°～90°) on the flow structures and heat transfer in a air-filled (Pr = 0.71), two-dimensional (2-D) cavity where the flow is induced by a shear force resulting from the motion of the cooled upper lid combined with buoyancy force due to bottom heating. The governing equations for the 2-D velocity and temperature fields are discretized spatially into a fourth-order accurate compact form. Numerical results indicate that among the three aspect ratios studied the increase of inclination angle does not affect the flow structures and heat transfer when the flow is in a forced convection dominated regime (Ri = 0.01). However, when the flow is in a pure natural convection dominated regime (Ri = 100), the increase of inclination angle enhances the heat transfer rate, especially for AR = 1 and 5. The maximum heat transfer rate occurs at 75° and Ri = 100. In addition, the flow changes from a stable, laminar regime to an unstable, chaos regime under certain inclination angles. At these conditions, the total kinetic energy appears to be in periodic or non-periodic oscillations.