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1
Welsh, Stephanie. "Compressible Taylor-Couette flow." Thesis, University of Leeds, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.616475.
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Incompressible Taylor-Couette flow has been studied extensively over the years. However, the compressible system has been largely ignored with only a few notable studies. The present thesis aims to explore the compressible Taylor-Couette system for a large range of parameters. The compressible equations have been linearised and a spectral method was applied to solve the system using a MATLAB-routine. In Chapter 2, we discuss the analysis performed to solve the system and explain the basic concepts and phenomena we expect to find. We also explain the numerical methods used. Chapter 3 discusses the case in which the outer cylinder remains motionless. The most important parameters, the Mach and Prandtl number and the radius ratio, are varied. In Chapters 4 and 5, the same procedure is applied to the cases of the co- and counter-rotating cylinders, respectively.
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Blum, Kevin M. "Acoustically probed Taylor-Couette flow apparatus." Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/27925.
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Youd, Anthony John. "Bifurcations in forced Taylor-Couette flow." Thesis, University of Newcastle Upon Tyne, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420066.
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Åsén, Per-Olov. "Stability of plane Couette flow and pipe Poiseuille flow." Doctoral thesis, KTH, Numerisk Analys och Datalogi, NADA, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4368.
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This thesis concerns the stability of plane Couette flow and pipe Poiseuille flow in three space dimensions. The mathematical model for both flows is the incompressible Navier--Stokes equations. Both analytical and numerical techniques are used. We present new results for the resolvent corresponding to both flows. For plane Couette flow, analytical bounds on the resolvent have previously been derived in parts of the unstable half-plane. In the remaining part, only bounds based on numerical computations in an infinite parameter domain are available. Due to the need for truncation of this infinite parameter domain, these results are mathematically insufficient. We obtain a new analytical bound on the resolvent at s=0 in all but a compact subset of the parameter domain. This is done by deriving approximate solutions of the Orr--Sommerfeld equation and bounding the errors made by the approximations. In the remaining compact set, we use standard numerical techniques to obtain a bound. Hence, this part of the proof is not rigorous in the mathematical sense. In the thesis, we present a way of making also the numerical part of the proof rigorous. By using analytical techniques, we reduce the remaining compact subset of the parameter domain to a finite set of parameter values. In this set, we need to compute bounds on the solution of a boundary value problem. By using a validated numerical method, such bounds can be obtained. In the thesis, we investigate a validated numerical method for enclosing the solutions of boundary value problems. For pipe Poiseuille flow, only numerical bounds on the resolvent have previously been derived. We present analytical bounds in parts of the unstable half-plane. Also, we derive a bound on the resolvent for certain perturbations. Especially, the bound is valid for the perturbation which numerical computations indicate to be the perturbation which exhibits largest transient growth. The bound is valid in the entire unstable half-plane. We also investigate the stability of pipe Poiseuille flow by direct numerical simulations. Especially, we consider a disturbance which experiments have shown is efficient in triggering turbulence. The disturbance is in the form of blowing and suction in two small holes. Our results show the formation of hairpin vortices shortly after the disturbance. Initially, the hairpins form a localized packet of hairpins as they are advected downstream. After approximately $10$ pipe diameters from the disturbance origin, the flow becomes severely disordered. Our results show good agreement with the experimental results. In order to perform direct numerical simulations of disturbances which are highly localized in space, parallel computers must be used. Also, direct numerical simulations require the use of numerical methods of high order of accuracy. Many such methods have a global data dependency, making parallelization difficult. In this thesis, we also present the process of parallelizing a code for direct numerical simulations of pipe Poiseuille flow for a distributed memory computer.<br>QC 20100825
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Carnevali, Emanuele. "Simulation of a viscoelastic Taylor-Couette flow." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
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Since the early stages of Computational Rheology the Taylor-Couette geometry received a lot of attention from researchers, up to becoming one of the benchmark problem of viscoleastic flows. In particular, the circular bounding geometry, together with the shear driven characteristic, allowed to gain relevant insight about the relation between the distortion of polymer conformation, and the arise of elastic instabilities.
The present document has the purpose of presenting the thesis project results, concerning the numerical investigation of a Taylor-Couette geometry through the newly developed viscoelastic toolbox Rheotool of OpenFOAM.
The simulations have been performed for increasing values of Weissemberg number, with the aim of detecting the effect of polymer stretching on the arise and development of particular fluid dynamic structures; furthermore, to understand the effect of space refinement on motion evolution, three different meshes have been used, exploiting also a new available stabilization technique based on stress-velocity coupling to avoid numerical breakdown.
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Deguchi, Kengo. "Finite amplitude solutions in sliding Couette flow." 京都大学 (Kyoto University), 2013. http://hdl.handle.net/2433/174925.
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Pudjiono, Putut Irwan. "Protein precipitation in a Couette flow device." Thesis, University of Manchester, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357604.
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Willis, Ashley Phillip. "The hydromagnetic stability of Taylor Couette flow." Thesis, University of Newcastle Upon Tyne, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246621.
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MATUTTI, OSCAR CORONADO. "TAYLOR-COUETTE INSTABILITY IN VISCOPLASTIC FLUID FLOW." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2002. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=2814@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR<br>A superposição de um escoamento circular de Couette e um
fluxo com gradiente de pressão axial, através de um espaço
anular ocorre em muitas aplicações práticas, tais como:
reatores químicos catalíticos, filtros, extratores líquido-
líquido, mancais e o fluxo de retorno de lamas de
perfuração entre a coluna de perfuração rotatória e a
formação rochosa na perfuração de poços produtores de
petróleo e gás. As linhas de corrente curvadas do fluxo
circular de Couette podem causar uma instabilidade
centrífuga que produz vórtices toroidais, conhecidos como
vórtices de Taylor. A presença destes vórtices muda as
características hidrodinâmicas e a transferência de calor
no processo. Em conseqüência, é muito importante ser capaz
de prever o aparecimento da instabilidade. A maioria das
análises numéricas e experimentais disponíveis na
literatura são para fluidos Newtonianos e viscoelásticos
(soluções polimericas). Neste trabalho, o efeito das
propriedades viscoplásticas de suspensões de altas
concentrações neste tipo de escoamento e nas condições
críticas para o aparecimento de vórtices são determinadas
teoricamente através da solução das equações de
conservação. As equações diferenciais foram integradas pelo
método de elementos finitos-Galerkin e o sistema de
equações algébricas não lineares resultante foi resolvido
pelo método de Newton.<br>The superposition of a circular Couette flow and a pressure-
driven axial flow in an annulus occurs in many practical
applications, such as catalytic chemical reactors,
filtration devices, liquid-liquid extractors, journal
bearings, and the return flow of drilling mud between the
rotating drill string and the stationary wall in oil and
gas well drilling. The curved streamlines of the circular
Couette flow can cause a centrifugal instability leading to
toroidal vortices, well known as Taylor vortices. The
presence of these vortices changes the hydrodynamic and
heat transfer characteristics of the process. Therefore, it
is very important to be able to predict the onset of
instability. Most of the available theoretical and
experimental analyses are for Newtonian and viscoelastic
(polymeric solutions) liquids. In this work, the effect of
the viscoplastic properties of high concentration
suspensions on the onset of the Taylor vortices are
determined theoretically by solving the conservation
equations and searching the critical conditions. The
differential equations were solved by the Galerkin / finite
element method and the resulting set of non-linear
algebraic equations, by Newtons method.
10
Topayev, Sultan. "Taylor-Couette flow for shear-thinning fluids." Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0301.
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On s’intéresse aux instabilités secondaires dans un écoulement de Taylor-Couette en grand entrefer pour un fluide rhéofluidifiant. Des études théorique, expérimentale et numérique ont été mises en œuvre. D’un point de vue théorique, une analyse faiblement non linéaire a été développée en régime dit TVF (Taylor Vortex Flow) pour rendre compte des premiers effets de la non linéarité de la loi de comportement sur la structure de l’écoulement. Le comportement rhéologique du fluide est décrit par le modèle de Carreau. Des effets significatifs du caractère rhéofluidifiant ont été mis en évidence : Les rouleaux de Taylor ont une taille plus petite et sont écrasés contre le cylindre intérieur. Le jet radial sortant est plus fin et beaucoup plus intense que le jet radial entrant. Par conservation de débit, la zone de jet radial entrant est plus étendue. Ces modifications sont probablement à l’origine des instabilités des rouleaux de Taylor observées expérimentalement et numériquement. Le dispositif expérimental utilisé est constitué de deux cylindres coaxiaux, où le cylindre intérieur est en rotation et le cylindre extérieur est fixe. Le rapport des rayons est "eta = 0.4" et le rapport d’aspect "L = 32". Les fluides utilisés sont des solutions de xanthane à différentes concentrations ainsi qu’une solution de glycérole, comme fluide newtonien de référence. La structure de l’écoulement est déterminée par visualisation et par mesures de vitesse par PIV 2D. Pour la solution de glycérole, après la bifurcation primaire à "Re = Re_c", le régime TVF stationnaire reste stable jusqu’à pratiquement "7 Re_c". A partir de cette dernière valeur, les rouleaux de Taylor perdent leur stabilité vis-à-vis de perturbations azimutales. Dans le cas des solutions de xanthane, les valeurs du nombre de Reynolds à partir desquelles, les rouleaux de Taylor apparaissent sont en accord avec la théorie linéaire comme dans le cas Newtonien. En augmentant le nombre de Reynolds, les rouleaux de Taylor deviennent instables, mais cette-fois-ci vis-à vis de perturbations axiales. Ces instabilités peuvent être considérées comme des instabilités d’Eckhaus généralisées. Elles se caractérisent par un processus récurrent de création et d’appariement de rouleaux. L’augmentation du nombre de sites où se produit ce processus conduit à un écoulement chaotique (turbulence de phase). Il convient de noter que plus les effets rhéofluidifiants sont importants, et plus la gamme de Re où le régime TVF est stable, est réduite. Ces résultats ont été confirmés par une simulation numérique 2D des équations de conservation instationnaires, en utilisant le solveur de FreeFem++. Le cas des fluides rhéofluidifiants avec seuil de contrainte a été entamé , en se focalisant sur le cas particulier où il existe une zone non-cisaillée attachée au cylindre extérieur<br>This work deals with secondary instabilities in a Taylor-Couette flow with a wide gap in the case of shear-thinning fluids. Theoretical, experimental and numerical approaches are used. From theoretical point of view, a weakly nonlinear analysis has been done to account for the nonlinear effects of constitutive law on the flow structure of the Taylor Vortex Flow (TVF) regime. The shear-thinning behavior of the fluid are characterized by the Carreau model. Significant effects of shear-thinning have been demonstrated: Taylor vortices are smaller in size and shifted toward the inner cylinder. The radial outflow jet is thinner and stronger than the radial inflow jet. This asymmetry leads to an increase of the radial inflow zone. These changes in the flow structure are probably the origin of the secondary instabilities of Taylor vortices observed experimentally and numerically. The experimental setup consist of two coaxial cylinders where the inner cylinder is rotating and the outer one is at rest. The radius ratio is "eta = 0.4" and the aspect ratio is "L = 32". The fluids used are aqueous xanthan gum solutions at different concentrations and aqueous glycerol solution as a reference Newtonian fluid. The flow structure is analyzed through the visualization and by the 2D PIV velocity measurements. For the aqueous glycerol solution, once the primary bifurcation is reached at "Re = Re_c", the stationary TVF regime remains stable up to practically "Re = 7 Re_c". From this values the Taylor vortices lose its stability with respect to azimuthal disturbances. In the case of the aqueous xanthan gum solutions the values of the Reynolds number from which the Taylor vortices appear are in agreement with a linear theory as for the case of Newtonian fluid. By increasing the Reynolds number, the Taylor vortices become unstable, but with respect to axial disturbances. There instabilities can be considered as generalized Eckhaus instabilities. They are characterized by the continuous processes of creation and merging of vortices. The increase in the number of axial positions where these processes occur leads to the chaotic flow (phase turbulence). It should be noted that the stronger shear-thinning effects, the smaller the range of stable TVF regime. These results have been confirmed by a 2D numerical simulation of unsteady conservation equations, using PDE solver Freefem++. The case of shear-thinning with a stress-yield was started as well, focusing on the particular case when the unyielded zone is attached to the outer cylinder
11
Ebrinc, Ali Aslan. "High Speed Viscous Plane Couette-poiseuille Flow Stability." Phd thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/3/12604769/index.pdf.
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The linear stability of high speed-viscous plane Couette and Couette-Poiseuille flows are investigated numerically. The conservation equations along with Sutherland&<br>#65533<br>s viscosity law are studied using a second-order finite difference scheme. The basic velocity and temperature distributions are perturbed by a small-amplitude normalmode disturbance. The small-amplitude disturbance equations are solved numerically
using a global method using QZ algorithm to find all the eigenvalues at finite Reynolds numbers, and the incompressible limit of these equations is investigated for
Couette-Poiseuille flow. It is found that the instabilities occur, although the corresponding growth rates are often small. Two families of wave modes, Mode I (odd modes) and Mode II (even modes), were found to be unstable at finite Reynolds
numbers, where Mode II is the dominant instability among the unstable modes for plane Couette flow. The most unstable mode for plane Couette &<br>#65533<br>Poiseuille flow is Mode 0, which is not a member of the even modes. Both even and odd modes are acoustic modes created by acoustic reflections between a will and a relative sonic line. The necessary condition for the existence of such acoustic wave modes is that there is a region of locally supersonic mean flow relative to the phase speed of the instability wave. The effects of viscosity and compressibility are also investigated and shown to have a stabilizing role in all cases studied. Couette-Poiseuille flow stability is investigated in case of a choked channel flow,
where the maximum velocity in the channel corresponds to sonic velocity. Neutral stability contours were obtained for this flow as a function if the wave number,Reynolds number and the upper wall Mach number. The critical Reynolds number is found as 5718.338 for an upper wall Mach number of 0.0001, corresponding to the fully Poiseuille case.
12
Olvera, Cabrera Daniel. "Coherent structures in stably stratified plane couette flow." Thesis, University of Bristol, 2017. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.723480.
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Szklarski, Jacek T. "Helical magnetorotational instability in MHD Taylor-Couette flow." Phd thesis, kostenfrei, 2007. http://opus.kobv.de/ubp/volltexte/2008/1600/.
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Borrero, Daniel. "Subcritical Transition to Turbulence in Taylor-Couette Flow." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53140.
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Turbulence is ubiquitous in naturally-occurring and man-made flows. Despite its importance in scientific and engineering applications, the transition from smooth laminar flow to disorganized turbulent flow is poorly understood. In some cases, the transition can be understood in the context of linear stability theory, which predicts when the underlying laminar solution will become unstable as a parameter is varied. For a large class of flows, however, this approach fails spectacularly, with theory predicting that the laminar flow is stable but experiments and simulations showing the emergence of spatiotemporal complexity. In this dissertation, the direct or subcritical transition to turbulence in Taylor-Couette flow (i.e., the flow between independently rotating co-axial cylinders) is studied experimentally. Chapter 1 discusses different scenarios for the transition to turbulence and recent advances in understanding the subcritical transition within the framework of dynamical systems theory. Chapter 2 presents a comprehensive review of earlier investigations of linearly stable Taylor-Couette flow. Chapter 3 presents the first systematic study of long-lived super-transients in Taylor-Couette flow with the aim of determining the correct dynamical model for turbulent dynamics in the transitional regime. Chapter 4 presents the results of experiments regarding the stability of Taylor-Couette flow to finite-amplitude perturbations in the form of injection/suction of fluid from the test section. Chapter 5 presents numerical investigations of axisymmetric laminar states with realistic boundary conditions. Chapter 6 discusses in detail the implementation of time-resolved tomographic particle image
velocimetry (PIV) in the Taylor-Couette geometry and presents preliminary tomographic PIV measurements of the growth of turbulent spots from finite-amplitude perturbations. The main results are summarized in Chapter 7.
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Szemberg, O'Connor Teddy. "Bulk viscosity effects in compressible turbulent Couette flow." Thesis, Imperial College London, 2018. http://hdl.handle.net/10044/1/62657.
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This work investigates the effect of bulk viscosity in one-, two-, and three{dimensional compressible fows via direct numerical simulation. The role of bulk viscosity in compressible turbulence is of increasing importance due to three applications: spacecraft descending through the Martian atmosphere, the thermodynamic cycle of solar-thermal power plant, and carbon capture and storage compressors. All three rely on the accurate description of turbulence in carbon dioxide, a gas with a bulk-to-shear viscosity ratio three orders of magnitude larger than for air. In these applications, invoking Stokes's hypothesis is questioned as the divergence of velocity is non-zero, implying a significant difference between mechanical and thermodynamic pressures. Results of a constantly forced velocity perturbation follow the same trend as that predicted by Landau's acoustic absorption coeffcient for suffciently high Reynolds numbers. Below an optimum Reynolds number, the damping effectiveness reduces by a different mechanism to that of Landau. Maximum damping is achieved at an acoustic Reynolds number equal to unity. Two-dimensional decaying turbulence at the bulk-to-shear viscosity ratio of carbon dioxide demonstrates that the magnitude of the dilatational production term is greatly enhanced and is strongly biased to negative values, reducing the generation of velocity dilatation compared to the zero bulk viscosity case. Compressible Couette flow at two Reynolds numbers and two bulk-to-shear viscosity ratios show minimal changes to mean flow quantities and the main terms of interest in the turbulence kinetic energy budget. Instantaneous views of the dilatational velocity field show that an intermediate range of scales are damped in accordance with Landau's acoustic damping coeffcient. At small scales, however, damping reduces and turbulent patterns are preserved.
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Oglethorpe, Rosalind Leigh Frances. "Mixing in stably stratified turbulent Taylor-Couette flow." Thesis, University of Cambridge, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708399.
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Moore, Christine M. V. "Characterization of a Taylor-Couette vortex flow reactor." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/11654.
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Ebrinç, Ali Aslan. "High speed viscous plane couette-poiseuille flow stability." Ankara : METU, 2004. http://etd.lib.metu.edu.tr/upload/12604769/index.pdf.
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Zhang, Pu. "Simulations of nonlinear flow in spherical system." Thesis, University of Exeter, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248176.
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Peralta, Carlos Andrés. "Superfluid spherical Couette flow and rotational irregularities in pulsars /." Connect to thesis, 2006. http://eprints.unimelb.edu.au/archive/00003176.
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Lagha, Maher. "Modeling the transition to turbulence in plane Couette flow." Phd thesis, Ecole Polytechnique X, 2006. http://pastel.archives-ouvertes.fr/pastel-00675068.
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The Galerkin method is used to derive a realistic model of plane Couette flow in terms of partial differential equations governing the space-time dependence of the amplitude of a few cross-stream modes. Numerical simulations show that it reproduces the globally sub-critical behavior typical of this flow. In particular, the statistics of turbulent transients at decay from turbulent to laminar flow displays striking similarities with experimental findings.
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Ho, Wai-man, and 何慧敏. "A numerical study on turbulent oscillatory plane Couette flow." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B2977083X.
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Bock, Christopher Paul. "Particle separation through Taylor-Couette flow and dielectrophoretic trapping." Master's thesis, University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4625.
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As the world population approaches seven billion, a greater strain is put on the resources necessary to sustain life. One of the most basic and essential resources is water and while two thirds of the earth is covered by water, the majority is either salt water (oceans and seas) or it is too contaminated to drink. The purpose of this project is to develop a portable device capable of testing whether a specific source of water (i.e. lake, river, well ...) is potable. There are numerous filtration techniques that can remove contaminants and make even the dirtiest water clean enough for consumption but they are for the most part, very time consuming and immobile processes. The device is not a means of water purification but rather focuses on determining the content of the water and whether it is safe. Particles within the water are separated and trapped using a combination of a Taylor Couette fluid flow system and Dielectrophoretic electrodes. This paper explores Taylor Couette flow in a large gap and low aspect ratio system through theory and experimentation with early stage prototypes. Different inner cylinder radii, 2.12cm, 1.665cm and 1.075cm, were tested at different speeds approaching, at and passing the critical Taylor number, 3825, 4713 and 6923 respectively for each cylinder. Dielectrophoretic (DEP) electrodes were designed, fabricated, coated and tested using latex beads to determine the method of integrating them within the fluid flow system. Taylor Couette theory, in terms of the formation of vortices within the large gap, small aspect ratio system, was not validated during testing. The flow pattern generated was more akin to a chaotic circular Couette flow but still served to move the particles toward the outer wall. Fully integrated tests were run with limited success.; Recommendations were made to pursue both circular Couette flow as the basis for particle separation and dimensional changes in the setup to allow for the formation of Taylor vortices by increasing the radius ratio but still allowing for a larger volume of fluid.<br>ID: 028916599; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (M.S.M.E.)--University of Central Florida, 2010.; Includes bibliographical references (p. 108-109).<br>M.S.M.E.<br>Masters<br>Department of Mechanical, Materials and Aerospace Engineering<br>Engineering and Computer Science<br>Miniature Engineering Systems
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Adams, Matthew Michael. "Magnetic and acoustic investigations of turbulent spherical Couette flow." Thesis, University of Maryland, College Park, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10160544.
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<p> This dissertation describes experiments in spherical Couette devices, using both gas and liquid sodium. The experimental geometry is motivated by the Earth's outer core, the seat of the geodynamo, and consists of an outer spherical shell and an inner sphere, both of which can be rotated independently to drive a shear flow in the fluid lying between them. In the case of experiments with liquid sodium, we apply DC axial magnetic fields, with a dominant dipole or quadrupole component, to the system. We measure the magnetic field induced by the flow of liquid sodium using an external array of Hall effect magnetic field probes, as well as two probes inserted into the fluid volume. This gives information about possible velocity patterns present, and we extend previous work categorizing flow states, noting further information that can be extracted from the induced field measurements. The limitations due to a lack of direct velocity measurements prompted us to work on developing the technique of using acoustic modes to measure zonal flows. Using gas as the working fluid in our 60 cm diameter spherical Couette experiment, we identified acoustic modes of the container, and obtained excellent agreement with theoretical predictions. For the case of uniform rotation of the system, we compared the acoustic mode frequency splittings with theoretical predictions for solid body flow, and obtained excellent agreement. This gave us confidence in extending this work to the case of differential rotation, with a turbulent flow state. Using the measured splittings for this case, our colleagues performed an inversion to infer the pattern of zonal velocities within the flow, the first such inversion in a rotating laboratory experiment. This technique holds promise for use in liquid sodium experiments, for which zonal flow measurements have historically been challenging.</p>
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de, Oliveira Ebenezer. "Computations of the interface in two-fluid Couette flow." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1587032365434615.
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Liu, Tao. "Dynamics of turbulent structures in plane Couette-Poiseuille flow." Electronic Thesis or Diss., Université Paris Cité, 2022. https://wo.app.u-paris.fr/cgi-bin/WebObjects/TheseWeb.woa/wa/show?t=4350&f=40173.
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Dans cette thèse, nous étudions expérimentalement la dynamique des structures turbulentes omniprésentes dans les écoulements de cisaillement confinés par des parois : les « stries » et les « rouleaux ». L’interaction entre ces structures est responsable du processus d’auto-entretien (SSP) de la turbulence. Nous réalisons les expériences dans un canal Couette-Poiseuille plan dans lequel le fluide est entraîné par une membrane mobile latérale et relié à deux réservoirs de sorte que le flux moyen soit nul. Les stries et les rouleaux sont quantifiés par les composantes de vitesse dans la direction de l’écoulement (ux) et dans la direction transverse (uz) mesurées par un système PIV 2D2C et 2D3C. L’évolution des stries et des rouleaux est étudiée par un protocole de «trempe», c’est-à-dire la diminution brutale du nombre de Reynolds Re en partant d’un état totalement turbulent à un régime laminaire ou de transition. L’évolution au cours du processus de décroissance est caractérisée en calculant l’énergie cinétique et la fraction turbulente de la vitesse dans la direction de l’écoulement et dans la direction transverse. Nous montrons que la décroissance des rouleaux est plus rapide que celle des stries. Deux étapes peuvent être distinguées lors de la décroissance des stries. Au cours de la première étape de la décroissance, les rouleaux restants ralentissent la décroissance des stries. Ceci est cohérent avec le mécanisme de soulèvement ("lift-up"), c’est-à-dire la formation de stries par advection linéaire des rouleaux. Nous observons une décroissance exponentielle de l’énergie cinétique dans la direction transverse Ez et caractérisons son taux de décroissance Az qui évolue linéairement avec le nombre de Reynolds final Ref après trempe. Nous étudions également l’effet du bruit, qui est la perturbation générée par le cylindre d’entraînement de la membrane, sur la décroissance transitoire et le régime permanent. Le taux de décroissance de Ez est indépendant des niveaux de bruit. Nous utilisons la susceptibilité de Ez en régime permanent pour quantifier l’intensité du bruit. La susceptibilité maximale augmente lorsque le niveau de bruit diminue. Cette idée est validée par un modèle de 1D dérivé du modèle 1D de D. Barkley pour lequel le bruit en entrée est contrôlé. Nous étudions l’ondulation des stries avec des générateurs de vortex. Les stries sont générées par une paire de cylindres fixés sur la paroi fixe du canal (côté de l’écoulement de Poiseuille). L’évolution des stries devenant ondulées à partir d’un état rectiligne est caractérisée par les trois composantes de vitesse. Nous appliquons un filtre spatial pour séparer la partie droite et la partie ondulée des stries. Nos résultats montrent que l’apparition de la grande amplitude de la vitesse dans la direction transverse et de la vitesse normale à la paroi ondulée est corrélée à l’augmentation de l’ondulation des stries. Enfin, nous relions les mesures de visualisation de l’écoulement et les mesures de PIV dans des expériences de trempe en comparant les évolutions de la fraction turbulente Ft. La visualisation de la fraction turbulente de l’écoulement est obtenue par des méthodes de traitement d’image issues de la littérature. La fraction turbulente des mesures PIV est calculée en seuillant chaque composante de vitesse. La comparaison montre que le temps de décroissance mesuré par la visualisation de l’écoulement correspond à la décroissance des stries dans les mesures de PIV, pour une des méthodes d’analyse d’images testée<br>In this thesis we investigate experimentally the dynamics of the ubiquitous turbulent structures in wall-bounded shear flows: streamwise ’streaks’ and ’rolls’. The interaction between these structures is responsible for the self-sustaining process (SSP) of the turbulence. We carry out the experiments in a plane Couette-Poiseuille channel in which the flow is driven by one side moving belt and connected to two reservoirs so that the mean flux is zero. The streaks and rolls are quantified by the streamwise ux and spanwise uz velocity components measured by a 2D2C and 2D3C PIV system. The evolution of the streaks and rolls are studied by a ’quench’ protocol, i.e. decrease of the Reynolds number Re abruptly from a fully turbulent state to a laminar or transition regime. We use ux to present the streaks and the uz as a proxy of the rolls. The evolution during the decay process is characterized by the kinetic energy and the turbulent fraction of the streamwise and spanwise velocity, respectively. We show that the decay of the rolls is faster than the streaks. The streaks have two decay stages in the decay process. During the first stage of the decay, the remaining rolls slow down the decay of the streaks. This is consistent with the lift-up effect, i.e. the formation of streaks by linear advection of the rolls. We observe an exponential decay of the spanwise kinetic energy Ez and characterize its decay rate Az which scales linearly with the final Reynolds number Ref after quenching. We also study the noise effect, which is the disturbance generated by the belt driving cylinder, on the transient decay and the permanent regime. The decay rate of Ez is independent of the noise levels. We use the susceptibility of Ez in the permanent regime to quantify the noise intensity. The maximum susceptibility increases with the decrease of the noise levels. This idea is validated by a 1D map model derived from 1D Barkley model with well defined noise intensity, which can mimic the noise advected in the system. We study the waviness of streaks with vortex generators. The streaks are generated by a pair of cylinders attached on the fixed wall of the channel (Poiseuille flow side). The evolution of the streaks becoming wavy from a straight state is characterized by the three velocity components. We apply a spatial filter to separate the straight part and the wavy part of the flow. Our results shows that the appearance of the large amplitude spanwise and wavy wall-normal velocities is correlated to the increase of the waviness of the streaks. This scenario is consistent with the non-linear self-interactions step which induces streamwise dependent flow in self-sustaining process (SSP). The different cut-off wavelengths of the wavy streaks are investigated to show that the generation of the cross flow components is effective when the waviness is strong enough (small streamwise wavelenth). Finally, we link the PIV and flow visualization measurements in quench experiments by comparing the turbulent fraction Ft evolutions. The turbulent fraction of the flow visualization is obtained by image processing methods from the literature. However, the turbulent fraction from the PIV measurements is computed by thresholding each velocity component. The comparison shows the decay time measured by flow visualization corresponds to the decay of the streaks in PIV measurements, for one of the tested image processing method
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Sirisup, Sirod. "Linear stability of plane Couette flow at moderate Reynolds numbers." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq64453.pdf.
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Bourne, David. "The Taylor-Couette problem for flow in a deformable cylinder." College Park, Md. : University of Maryland, 2007. http://hdl.handle.net/1903/6893.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2007.<br>Thesis research directed by: Mathematics. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Liefvendahl, Mattias. "Stability results for viscous shock waves and plane Couette flow." Doctoral thesis, Stockholm, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3241.
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Wilson, Matthew Bernard. "Numerical study of plane couette flow in a rotating framework." Thesis, Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/17359.
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Bell, Martin Derek. "Ordering of particulate suspensions in Couette flow at moderate Reynolds numbers." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/28901.
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A remarkable ordering phenomenon has been seen to occur when a suspension of particles undergoes shear at particle Reynolds numbers of the order of or greater than one in the annular gap of a Couette type shearing device. This particulate ordering was observed and studied with both suspensions of rigid spheres and suspensions of polystyrene latex aggregates formed in the presence of shear within the gap. Each of these systems was studied under a variety of initial conditions in order to define the particular flow conditions required for particle alignment to occur. It was found that particulate ordering occurred under similar conditions to those used by Segré and Silberberg (35) to observe the "necklace formations" that formed within particulate suspensions flowing inside tubes. The separations between aligned particles was found to be strongly dependent on the particle Reynolds number and the ratio between the particle diameter and the width of the annular gap. An insight into the hydrodynamic interactions occurring was provided by the comparisons made between the ordered aggregates and the ordered rigid spheres under similar flow conditions.<br>Science, Faculty of<br>Chemistry, Department of<br>Graduate
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Zhang, Xiao-Ming. "Flow dynamics of time-dependent and viscoplastic fluids in couette gemoetry /." Title page, abstract and contents only, 1997. http://web4.library.adelaide.edu.au/theses/09PH/09phz63328.pdf.
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Brown, Jason Britton. "An experimental facility for the investigation of the flow in a circular-couette flow bioreactor." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/18174.
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Mehri, Rym. "Micro PIV and Numerical Investigation of a Micro-Couette Blood Flow." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/22916.
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The purpose of this thesis is to design a physical microchannel model for micro-Couette blood flow that provides constant and controlled conditions to study and analyze Red Blood Cell (RBC) aggregation. The innovation of this work is that the Couette blood flow is created by the motion of a second fluid with different properties, thereby entraining the blood. The experimental work is coupled with three-dimensional numerical simulations performed using a research Computational Fluid Dynamic (CFD) Solver, Nek5000, based on the spectral element method, while the experiments are conducted using a micro Particle Image Velocimetry (μPIV) system with a double frame CCD camera and an inverted laser imaging microscope. The design of the channel (150 × 33 μm and 170 × 64 μm microchannels) is based on several parameters determined numerically, such as the velocity and viscosity ratios and the degree of miscibility between the fluids, and the resulting configurations are fabricated in the laboratory using standard photolithography methods. The microchannel designed numerically is then tested experimentally, first, with a Newtonian fluid (glycerol), then with RBC suspensions to be compared to the simulations results. It was found that, numerically, using a velocity ratio of 4 between the two fluids, a third of the channel thickness corresponds to the blood layer. Within that range, it can be concluded, that the velocity profile of the blood layer is approximately linear as confirmed by experimental tests, resulting in the desired profile to study RBC aggregation in controlled conditions. The effect of several parameters, such as the hematocrit and the shear rate, on the RBC aggregates and the velocity profile is investigated, through experiments on the RBC suspensions.
The final goal of this research is to ensure the compatibility of the results between the experiments and the Newtonian numerical model for several ranges of shear rate with the future intention of finding an accurate method to be able to quantitatively analyze aggregates and determine the number of RBC in each aggregate depending on the flow conditions (the shear rate).
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Kirkconnell, Carl Scott. "Experiments on the stability characteristics of an unsteady circular couette flow." Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/16400.
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Harris, Derek. "A study of a nonlinear amplitude equation modelling spherical couette flow." Thesis, University of Exeter, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367377.
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Lyon, David J. "Couette flow measurement of equilibrium and energization charging in transformer insulation." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/112666.
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Martínez, Arias Borja. "Torque measurement in turbulent Couette-Taylor flows." Thesis, Le Havre, 2015. http://www.theses.fr/2015LEHA0004/document.
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L’écoulement entre deux cylindres coaxiaux, appelé l’écoulement de Couette-Taylor, a été étudié lorsque le cylindre intérieur tourne. Quatre dispositifs ont été utilisés avec différentes tailles d’entrefer. Les visualisations montrent l’évolution des motifs avec le nombre de Reynolds, Re. La variation du couple sur le cylindre intérieur a été déterminée en utilisant le pseudo-nombre de Nusselt, qui est une mesure du taux de dissipation d’énergie.Pour des faibles valeurs de Re, l’écoulement est laminaire et azimutal, et le couple est proportionnel à Re. Au-delà d’une valeur critique de Re, les rouleaux de Taylor apparaissent et la pente de variation du couple change brutalement. Pour de grandes valeurs de Re, les rouleaux deviennent turbulents et la pente du couple augmente à cause de la dissipation d’énergie turbulente. Le couple a été mesuré jusqu’à Re=45.000 et montre une dépendance avec le rapport de rayons des cylindres et du nombre de vortex. Avant le régime ultime de la turbulence, les états avec plus de rouleaux présentent un couple plus grand et la situation est inversée dans le régime ultime.Une étude du couple agissant sur le cylindre intérieur a été menée en présence d’un liquide viscoélastique contenant des polymères de grande masse molaire. En appliquant des cycles d’accélération-décélération de la rotation du cylindre intérieur, le couple présente une boucle d’hystérèse dont l’aire augmente avec la concentration de polymère. Les statistiques des fluctuations de la turbulence élastique ont été analysées. Le couple exercé par les vortex solitaires obtenus lors de la phase de décélération, avant la relaminarisation complète de l’écoulement, a été étudié<br>The flow between two concentric cylinders, i.e., the Couette-Taylor flow, has been investigated when only the inner cylinder rotates. Four set-ups have been employed with 4 values of the radius ratio. Flow visualisations have been performed to analyse the evolution of the flow patterns with the Reynolds number, Re. The variation of the torque acting on the inner cylinder with different parameters has been quantified using the pseudo-Nusselt number, which measures the rate of energy dissipation in the flow.At low Re, the flow is laminar and azimuthal, and the torque is proportional to Re. Above a critical value of Re, Taylor vortices emerge in the flow and the slope of the torque changes drastically. At high values of Re, the vortices become turbulent and the increase rate of torque is enhanced due to the energy dissipation of turbulence. The torque measured up to Re=45 000 depends on the radius ratio of the cylinders and on the number of vortices. Below the ultimate regime of turbulence, flows containing larger number of vortices exert larger levels of torque; above it, flows containing larger number of vortices exert lower levels of torque.A specific study of the torque exerted on the inner cylinder has been carried out with viscoelastic fluids made of large-weight-molecule polymers. If acceleration-deceleration cycles of the rotation of the inner cylinder are applied, the torque exhibits a hysteretic loop, which increases with the polymer concentration. The statistics of the elastic turbulence fluctuations have been analysed. A special focus was made on the torque induced by the solitary vortices obtained in the deceleration phase, before the flow relaminarisation
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Basik, Beata-Marie. "Direct simulation Monte Carlo model of a couette flow of granular materials." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60433.
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Since life-threatening natural phenomena, such as, snow avalanches and lava flows, and many industrial and agricultural material handling processes may be classified as granular flows, establishing constitutive relationships which model granular flow behaviour is of prime importance. While laboratory experiments attempting to support granular flow theory have been plagued by poor instrumentation, numerical simulations are becoming increasingly helpful in understanding the nature of these flows. The present investigation describes such a simulation developed within the framework of the Direct Simulation Monte Carlo model for rarefied gases presented in Bird (1976) and granular flow kinetic theory according to Lun, et al. (1984). More specifically, the model generates a Couette flow of smooth, inelastic, homogeneous, spherical granular particles. Two different boundary condition models are used to model the flow field's upper and lower boundaries: the Periodic Boundary Condition (PBC) model and the Finite Shear Layer (FSL) model. An essentially uniform shear flow with virtually no slip at the boundaries results from both boundary conditions. Stress and granular temperature results obtained with the PBC and FSL models for the lower range of solids fractions ($ nu < 0.3)$ compare very well with the Lun, et al. (1984) theory. At higher solids fractions, while the total stresses generated with both boundary models are in reasonable agreement with the latter theory and results from other numerical work, higher than expected streaming stresses appear to be compensating for lower than expected collisional stresses; as a result, granular temperature in this range of solids fractions proves to be higher than predicted.
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Salhi, Abdelaziz. "Etude de l'ecoulement couette poiseuille, liquide et liquide-gaz, dans un espace annulaire reduit." Nantes, 1986. http://www.theses.fr/1986NANT2066.
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Etude experimentale d'un ecoulement force dans un labyrinthe tournant. Interpretation des resultats en fonction des diverses compositions de regimes laminaire-turbulent-tourbillonnaire. Proposition d'une correlation semi-analytique. Essais en ecoulements diphasiques
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Johnson, Tyler Jay. "Drag measurements across patterned surfaces in a low Reynolds number Couette flow facility." Thesis, [Tuscaloosa, Ala. : University of Alabama Libraries], 2009. http://purl.lib.ua.edu/2128.
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Yim, Samson Sau Shun. "The effect of flow stability on residence time distribution of Newtonian and non-Newtonian liquids in couette flow." Thesis, University College London (University of London), 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264191.
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Dumas, Guy Leonard Anthony. "Study of spherical couette flow via 3-D spectral simulations : large and narrow-gap flows and their transitions /." Diss., Pasadena, Calif. : California Institute of Technology, 1991. http://resolver.caltech.edu/CaltechETD:etd-04162004-103555.
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Seyidoglu, Tijen. "Generalized Couette Flow Of A Herschel-bulkley Fluid Through Eccentric Annulus-an Approximate Solution." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/2/12607087/index.pdf.
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ABSTRACT
GENERALIZED COUETTE FLOW OF A
HERSCHEL - BULKLEY FLUID
THROUGH ECCENTRIC ANNULUS - AN APPROXIMATE SOLUTION
Seyidoglu, Tijen
M.S., Department of Chemical Engineering
Supervisor: ismail Tosun
Co-Supervisor: Ahmet N. Eraslan
January 2006, 134 pages
Generalized Couette flow of a Herschel-Bulkley fluid in an eccentric annulus is analyzed by approximating the flow geometry as a slit of variable height. Besides an imposed pressure gradient, one of the plates is considered non-stationary to take into account the axial and/or angular motion of the inner pipe in an eccentric annulus system.
Depending on the magnitude and the direction of the applied pressure gradient with respect to the plate velocity, three separate flow cases are studied in which the velocity reaches its maximum value either within the plug flow region or at the moving boundary. Velocity distributions are obtained for each case by solving the equations of continuity and motion. Volumetric flow rate expressions are obtained by integrating the velocity distribution over the cross-sectional area. At a given pressure gradient, the results indicate an increase in volumetric flow rate with an increase in eccentricity ratio. Criteria for each flow type is developed in terms of a dimensionless parameter &<br>#923<br>, which takes into account the ratio of the imposed pressure gradient to the plate velocity. Volumetric flow rate expressions for Newtonian, Bingham and power-law fluids are obtained by considering the limiting values of the fluid index and yield stress. The validity of the equations are checked by considering the slit height to be a constant, i.e., flow between parallel plates.
Surge/swab pressure calculations are carried out for Herschel-Bulkley, power-law and Bingham fluids and the results are expressed as a function of eccentricity ratio, radius ratio, fluid index and yield stress. The results indicate that when the fluid index and the eccentricity ratio are fixed, a slight increase in the radius ratio causes a tremendous increase in surge/swab pressure, especially for low values of fluid index. On the other hand, displacement of the inner pipe from a concentric position causes a decrease in swab/surge pressure when other parameters are held constant.
Comparison with the literature values reveals the fact that flow in an eccentric annulus can be modeled as flow between a slit of variable height as long as the radius ratio is greater than 0.5 and the eccentricity ratio is less than 0.3. The results for other values of radius ratio and eccentricity ratio can be used as initial guess values in carrying out numerical calculations.
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Bentley, David Christopher. "Localised solutions in the magnetorotational Taylor-Couette flow with a quartic marginal stability curve." Thesis, University of Leeds, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.590491.
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This thesis is motivated by the observation in the magnetorotational Taylor-Couette flow that, for certain configurations of an externally applied magnetic field, there is competition between two different wavelengths at the thresh• old of instability. Moreover, for a particular magnetic field configuration the two critical wavelengths coalesce, such that the marginal stability curve has a quartic minimum. By perturbing about this quartic minimum, we recover competition between two similar wavelengths. This competition suggests the possibility that the secondary flow may exhibit localised patches of Taylor vortices of one wavelength embedded in a background of Taylor vortices with the other wavelength. In this thesis we develop a model equation that displays qualitatively the aforementioned behaviour, based on the Swift- Hohenberg equation [75]. A weakly nonlinear analysis is performed, in the manner of the Ginzburg-Landau derivation from the Swift- Hohenberg equation [41]. The resultant amplitude equation is, under certain restrictions on the parameters, the complex SwiftHohenberg equation [32J. We next extend the recently developed [24] techniques for finding localised solutions of the Swift- Hohenberg equation to the model equation; in particular the use of a conserved quantity to identify the constituent wavelengths of the localised solutions, and numerical continuation to compute the bifurcation diagrams for the model equation. We also compute the normal form for the bifurcation at the quartic minimum, following the similar analysis of the Hamiltonian-Hopf bifurcation relevant to the Swift- Hohenberg equation. The extension does not carry forward the integrals we might expect, however. Finally, we present preliminary numerical simulations of the nonlinear Taylor-Couette system in the appropriate parameter regime. The derivation and analysis of the model equation in this thesis represents a significant advance in the development of a framework for understanding localised solutions consisting of regions of two similar wavelengths.
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Ali, M. A. "Thermal and MHD effects on the stability of Couette flow between two rotating cylinders." Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383882.
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Halcrow, Jonathan. "Charting the State Space of Plane Couette Flow: Equilibria, Relative Equilibria, and Heteroclinic Connections." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24724.
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Thesis (Ph.D.)--Physics, Georgia Institute of Technology, 2009.<br>Committee Chair: Cvitanovic, Predrag; Committee Member: Bracco, Annalisa; Committee Member: Dieci, Luca; Committee Member: Goldman, Daniel; Committee Member: Grigoriev, Roman
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Gaied, Lamia. "Influence de la rugosité de surfaces de parois sur les instabilités hydrodynamiques d'un écoulement de Couette-Taylor et de Couette-Taylor-Poiseuille." Thesis, Valenciennes, Université Polytechnique Hauts-de-France, 2020. http://www.theses.fr/2020UPHF0018.
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Ce travail porte sur l’étude numérique et expérimentale d’un écoulement de Couette-Taylor dans une géométrie à surfaces rugueuses, afin de détecter l’effet de la rugosité sur les instabilités hydrodynamiques. Dans un premier temps, nous avons effectué une étude de simulation numérique (CFD) 3D dans le cas d’un écoulement de Couette-Taylor sans débit axial, mais en utilisant plusieurs types de rugosités de surfaces : rugosité isotrope (micro-rugosité), rugosité anisotrope (macro-rugosité), variation de l’amplitude ainsi que le type de la macro-rugosité. Les résultats obtenus montrent bien l’effet de cette rugosité sur la restructuration de l’écoulement et le développement des instabilités hydrodynmiques. Dans un second temps, nous nous sommes intéressés à l’étude expérimentale des écoulements de Couette-Taylor-Poiseuille avec et sans débit axial en utilisant deux protocols (direct et inverse). En effet, la superposition d’un écoulement axial (Poiseuille) avec un écoulement de Couette-Taylor, peut avoir un effet important sur la réorganisation de l’hydrodynamique de base déjà connue et constituée de cellules de Taylor. Par conséquent, la présence d’un écoulement axial peut générer la formation de vortex ou leur brisure ou disparition, et peut déplacer ces derniers (vortex ou cellules de Taylor) dans la même direction ou la direction inverse de l’écoulement axial imposé. Expérimentalement, nous avons commencé par une étude qualitative en visualisant les instabilités hydrodynamiques grâce à des particules de kalliroscope. Par la suite, une étude quantitative utilisant la PIV et la polarographie a été effectuée afin de caractériser les régimes d’écoulement des premières instabilités (TVF, WVF, MWVF et TN) en présence ou non d’un débit axial. La méthode polarographique, au moyen de sondes simples circulaires, a été alors utilisée pour quantifier le gradient pariétal de vitesse local et instanané. La PIV a permis d’étudier les régimes WVF, MWVF et turbulent. Différents critères de détection de tourbillons (la vorticité ω et le critère Q) ont été alors développés et utilisés pour bien identifier les structures tourbillonnaires<br>This work deals with a numerical and experimental study of the Couette-Taylor flow where the geometry contains rough surfaces, in order to detect the effect of these irregularities on the hydrodynamic instabilities. Firstly, we carried out a 3D mumerical simulation study (CFD) in the case of a Couette-Taylor flow without axial flow, but using several types of surface roughness: isotropic roughness (micro-roughness), anisotropic roughness (macro-roughness) and variation of the amplitude as well as the type of macro-roughness. The obtained results clearly show the effect of this roughness on the reorganization of the flow and the development of the hydrodynamic instabilities. Secondly, we were interested to carry out an experimental study of Couette-Taylor-Poiseuille flows, with and without axial flow by using two protocols (direct and reverse). Indeed, the superposition of an axial flow (Poiseuille) with a Couette-Taylor flow can have a significant effect on the reorganization of the basic and already known hydrodynamic instabilities, constituted by Taylor cells. Therefore, the presence of an axial flow can generate the development of vortices or their breakup or disappearance, and can move the Taylor vortices in the same direction or the opposite direction of the imposed axial flow. Experimentally, we started with a qualitative study by visualizing the hydrodynamic instabilities thanks to kalliroscope particles. Thereafter, a quantitative study using PIV and polarography was carried out in order to characterize the flow regimes of the first instabilities (TVF, WVF, MWVF and TN) with or without axial flow. The polarographic method, using simple circular probes, was then used to quantify the local and instantaneous wall shear stress. The PIV allowed to study the WVF, MWVF and turbulent regimes. Different vortices’ detection criteria (vorticity ω and Q criterion) were then developed and used to correctly identify the turbulent structures
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El, Anadouli Mohamed. "Étude des instabilités imparfaites de Couette-Taylor." Vandoeuvre-les-Nancy, INPL, 1994. http://www.theses.fr/1994INPL117N.
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Ce mémoire est consacré à l'étude des instabilités imparfaites de l'écoulement de Couette-Taylor en géométrie fine et à faible vitesse de rotation. Dans le premier chapitre, nous effectuons l'analyse de la stabilité linéaire pour différents rapports de rayons qui définit les paramètres critiques de l'écoulement. Pour tenir compte des effets de bords nous recourrons à l'analyse quasi-linéaire. Ces effets se traduisent par la présence du terme quadratique dans l'équation de ginzburg-landau. Ceci fait l'objet de notre deuxième chapitre. Le troisième chapitre est consacré à la description de la méthode des éléments finis ainsi qu'à la méthode de résolution de notre système (variante d'algorithme d'Uzawa). Dans le quatrième chapitre, nous retrouvons les résultats de la simulation pour quelques rapports d'aspect avec le cylindre extérieur tournant ou fixe. Nous retrouvons également une comparaison qualitative simulation-visualisation expérimentale. Enfin, le dernier chapitre est consacré à la comparaison entre les résultats de la simulation numérique et les résultats de la théorie quasi-linéaire. Nous finissons par une approche numérique de la solution de base en géométrie fine
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Skufca, Joseph D. "Understanding a chaotic saddle with focus on a 9-variable model of Planar Couette flow." College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/2897.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2005.<br>Thesis research directed by: Applied Mathematics Program. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.