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Purely elastic shear flow instabilities : linear stability, coherent states and direct numerical simulationsSearle, Toby William January 2017 (has links)
Recently, a new kind of turbulence has been discovered in the flow of concentrated polymer melts and solutions. These flows, known as purely elastic flows, become unstable when the elastic forces are stronger than the viscous forces. This contrasts with Newtonian turbulence, a more familiar regime where the fluid inertia dominates. While there is little understanding of purely elastic turbulence, there is a well-established dynamical systems approach to the transition from laminar flow to Newtonian turbulence. In this project, I apply this approach to purely elastic flows. Laminar flows are characterised by ordered, locally-parallel streamlines of fluid, with only diffusive mixing perpendicular to the flow direction. In contrast, turbulent flows are in a state of continuous instability: tiny differences in the location of fluid elements upstream make a large difference to their later locations downstream. The emerging understanding of the transition from a laminar to turbulent flow is in terms of exact coherent structures (ECS) — patterns of the flow that occur near to the transition to turbulence. The problem I address in this thesis is how to predict when a purely elastic flow will become unstable and when it will transition to turbulence. I consider a variety of flows and examine the purely elastic instabilities that arise. This prepares the ground for the identification of a three-dimensional steady state solution to the equations, corresponding to an exact coherent structure. I have organised my research primarily around obtaining a purely elastic exact coherent structure, however, solving this problem requires a very accurate prediction of the exact solution to the equations of motion. In Chapter 2 I start from a Newtonian ECS (travelling wave solutions in two-dimensional flow) and attempt to connect it to the purely elastic regime. Although I found no such connection, the results corroborate other evidence on the effect of elasticity on travelling waves in Poiseuille flow. The Newtonian plane Couette ECS is sustained by the Kelvin-Helmholtz instability. I discover a purely elastic counterpart of this mechanism in Chapter 3, and explore the non-linear evolution of this instability in Chapter 4. In Chapter 5 I turn to a slightly different problem, a (previously unexplained) instability in a purely elastic oscillatory shear flow. My numerical analysis supports the experimental evidence for instability of this flow, and relates it to the instability described in Chapter 3. In Chapter 6 I discover a self-sustaining flow, and discuss how it may lead to a purely elastic 3D exact coherent structure.
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Adult children of divorce : patterns of organisation characterising committed relationshipsFulford, Claire Natalie 06 1900 (has links)
This study aims to present an alternative framework with which to view the phenomenon of parental divorce and its perceived consequences for adult children of divorce in committed relationships. Research done within the traditional Newtonian framework is reviewed and its limitations explicated. The epistemological presuppositions of the new epistemology are presented along with their implications for conducting research. The importance of description as research methodology is emphasised. Written descriptions from various adult children of divorce are presented. Metadescriptions, by the author, are presented. These metadescriptions, based on the presuppositions of the new epistemology, highlight the value of describing the patterns of organisation which characterise the committed relationships of adult children of divorce. It is concluded that an alternative approach, based on the new epistemology, enlarges our understanding of the adult child of divorce within the context of a committed relationship. / Psychology / M.A. (Psychology)
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Analyse locale et globale de l'hydrodynamique et du transfert de matière dans des fluides à rhéologie complexe caractéristiques des milieux de fermentation / Local and global study of hydrodynamic and mass transfer in stirred vessels with non Newtonian model fluidsGabelle, Jean-christophe 05 September 2012 (has links)
La production d’éthanol à partir de biomasse lignocellulosique est reconnue comme une des voies possibles de réduction des émissions de gaz à effet de serre et de remplacement partiel des énergies fossiles. Pour être compétitif, la production d'enzymes à bas coûts est nécessaire. Ces enzymes sont produites par le champignon filamenteux Trichoderma reesei, qui présente, à forte concentration, un comportement fortement rhéofluidifiant pouvant entrainer des limitations de mélange et de transfert de matière lors du changement d'échelle. Dans ce travail, il est proposé de compléter les données de la littérature concernant le temps de mélange, la puissance dissipée et le transfert de matière gaz-liquide (global et local) par des mesures à plusieurs échelles dans des fluides modèles de rhéologie similaire aux milieux biologiques visés. Les modèles et corrélations développés qui en résultent sont directement exploitables pour le design des fermenteurs industriels. Afin d’étudier plus en détail le mélange, le taux de cisaillement et la turbulence, une étude par PIV a été menée sur des milieux transparents. La caractérisation fine de l'hydrodynamique repose sur la dissociation des différentes composantes du mouvement à l’aide de la POD. L'évolution des grandeurs mesurées avec les conditions opératoires permet de fournir des indications précieuses pour l'extrapolation des fermenteurs mettant en œuvre des micro-organismes potentiellement sensibles au cisaillement / Ethanol made from cellulosic biomass is recognized as a promising substitute for fossil fuel and thus as a way to reduce greenhouse gas emissions. To be competitive, low cost cellulosic enzymes produced by the filamentous fungus Trichoderma reesei are required. At high biomass concentration, the culture broth becomes so highly shear-thinning that mixing and mass transfer limitations may be encountered when the process is scaled up.In this study, we propose to complete data available in the literature for mixing times, power draw, and mass transfer (local and global) with measurements at several scales in model fluids (shear thinning) that mimic the rheology of biological media. Models and correlations that derive from this work can be used directly for industrial fermentor design. In order to study mixing, local shear rate and turbulence in detail, PIV is performed in transparent model fluids. The refined hydrodynamic characterisation relies on the dissociation of instantaneous velocity by means of the POD method. The change of key parameters with operating conditions gives relevant information for the scale-up of shear-sensitive micro-organisms.
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Extension de la méthode LS-STAG de type frontière immergée/cut-cell aux géométries 3D extrudées : applications aux écoulements newtoniens et non newtoniens / Extension of the LS-STAG immersed boundary/cut-cell method to 3D extruded geometries : Application to Newtonian and non-Newtonian flowsNikfarjam, Farhad 23 March 2018 (has links)
La méthode LS-STAG est une méthode de type frontière immergée/cut-cell pour le calcul d’écoulements visqueux incompressibles qui est basée sur la méthode MAC pour grilles cartésiennes décalées, où la frontière irrégulière est nettement représentée par sa fonction level-set, résultant en un gain significatif en ressources informatiques par rapport aux codes MFN commerciaux utilisant des maillages qui épousent la géométrie. La version 2D est maintenant bien établie et ce manuscrit présente son extension aux géométries 3D avec une symétrie translationnelle dans la direction z (configurations extrudées 3D). Cette étape intermédiaire sera considérée comme la clé de voûte du solveur 3D complet, puisque les problèmes de discrétisation et d’implémentation sur les machines à mémoire distribuée sont abordés à ce stade de développement. La méthode LS-STAG est ensuite appliquée à divers écoulements newtoniens et non-newtoniens dans des géométries extrudées 3D (conduite axisymétrique, cylindre circulaire, conduite cylindrique avec élargissement brusque, etc.) pour lesquels des résultats de références et des données expérimentales sont disponibles. Le but de ces investigations est d’évaluer la précision de la méthode LS-STAG, d’évaluer la polyvalence de la méthode pour les applications d’écoulement dans différents régimes (fluides newtoniens et rhéofluidifiants, écoulement laminaires stationnaires et instationnaires, écoulements granulaires) et de comparer ses performances avec de méthodes numériques bien établies (méthodes non structurées et de frontières immergées) / The LS-STAG method is an immersed boundary/cut-cell method for viscous incompressible flows based on the staggered MAC arrangement for Cartesian grids where the irregular boundary is sharply represented by its level-set function. This approach results in a significant gain in computer resources compared to commercial body-fitted CFD codes. The 2D version of LS-STAG method is now well-established and this manuscript presents its extension to 3D geometries with translational symmetry in the z direction (3D extruded configurations). This intermediate step will be regarded as the milestone for the full 3D solver, since both discretization and implementation issues on distributed memory machines are tackled at this stage of development. The LS-STAG method is then applied to Newtonian and non-Newtonian flows in 3D extruded geometries (axisymmetric pipe, circular cylinder, duct with an abrupt expansion, etc.) for which benchmark results and experimental data are available. The purpose of these investigations is to evaluate the accuracy of LS-STAG method, to assess the versatility of method for flow applications at various regimes (Newtonian and shear-thinning fluids, steady and unsteady laminar to turbulent flows, granular flows) and to compare its performance with well-established numerical methods (body-fitted and immersed boundary methods)
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Desenvolvimento e caracterização de sistemas líquido-cristalinos para aplicação tópica de metotrexato: estudos de liberação, retenção e permeação in vitroVon Zuben, Eliete de Souza [UNESP] 27 June 2012 (has links) (PDF)
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000693706.pdf: 2880957 bytes, checksum: 43d4b15dffaa346d602b5f57917996d4 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Amplamente utilizado no tratamento de vários tipos de câncer e na psoríase, o metotrexato (MTX) é um quimioterápico, estruturalmente análogo do ácido fólico, que apesar de sua eficácia apresenta uma série de efeitos adversos, sendo a hepatotoxicidade o mais grave. Atualmente os sistemas nanoestruturados líquido-cristalinos de fase lamelar estão sendo utilizados como dispositivos para liberação modificada de fármacos, sendo vantajosos na liberação tópica de várias substâncias, conforme suas características de interação com o estrato córneo e as outras camadas da pele, evitando assim efeitos adversos sistêmicos. Os objetivos deste trabalho foram desenvolver sistemas nanoestruturados líquido-cristalinos de fase lamelar, acrescidos de MTX, caracteriza-los do ponto de vista físico, realizar a análise estrutural das formulações, através de microscopia de luz polarizada (MLP), espalhamento de raios-X a baixo ângulo (SAXS) e suas propriedades reológicas, executar os testes de estabilidade preliminar (TEP) das formulações, validar o método analítico para a quantificação de MTX por CLAE e executar ensaios de liberação, permeação e retenção in vitro. As formulações preparadas a partir da mistura do poliéter funcional siloxano (Dow Corning® 5329) como tensoativo, com silicone fluido de co-polímero glicol (Dow Corning® 193C) como fase oleosa titulados em fase aquosa, composta por tampão fosfato de potássio monobásico 0,01M pH 7,4, apresentaram fases líquido-cristalinas do tipo lamelar, confirmados pelos ensaios de MLP e SAXS. Os TEPs evidenciaram que as formulações A, B e C mantiveram-se estáveis durante o período do estudo. Os estudos do comportamento reológico das formulações apresentaram-se como fluidos pseudoplásticos não–newtonianos tixotrópicos ... / Widely used in the treatment of some types of cancer, the methotrexate (MTX) is a chemotherapeutic, structurally analog of the folic acid, although its effectiveness, presents a series of adverse effect, being the most serious hepatotoxicity. Currently, the liquid crystal lamellar phase is being used of devices for modified release of drug demonstrated to be advantageous in the release topic of some substances, given to the characteristics of interaction with the stratum corneun and other layers of the skin, avoiding systemic adverse effects. The aims of this research had been to develop and to characterize liquid crystalline nanostructure systems of lamellar phase, increased of MTX of the physical point of view, also carry through the structural analysis of the formulations through by polarized light microscopy (PLM), small-angle X-ray scattering (SAXS) and rheological properties. Perform stability studies of the chosen formulations, validate the analytical method of quantification of MTX for High Performance Liquid Chromatography (HPLC) and carry through release assay, cutaneous permeation and skin retention in vitro for the chosen formulations. The formulations prepared by the mixture of polyether functional siloxane as surfactant, with silicone polyether copolymer as oily phase and phosphate buffer 0,01M pH 7,4 as aqueous phase demonstrating lamellar liquid-crystalline phases, confirmed by assays of PLM and SAXS. The stability studies showed that formulations A, B and C remained stable throughout the period of the study. The study of the rheological behavior of the formulations presented as not Newtonian pseudoplastic fluid and thixotropic ...
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Non-Newtonian Flow Modelling Through A Venturi Flume / Modélisation d'écoulements non newtoniens le long de canaux VenturiMouzouri, Miloud 07 November 2016 (has links)
Lors d’une opération de forage, un certain nombre d’événements imprévus par rapport à l’écoulement du fluide de forage dans le puits, peuvent se produire assez rapidement. Des exemples de tels événements sont les afflux de pétrole ("kick") ainsi que les pertes de boue dans la formation. Un "kick" qui augmente en intensité peut entraîner, par ce que l’on nomme, un "blowout" (par exemple l’incident Deepwater Horizon en 2010). Les pertes et les gains sont habituellement détectés en contrôlant l’équilibre de la boue de forage dans le puits, en particulier en contrôlant le débit sortant du puits et en le comparant au débit entrant induit par les pompes. La plupart des méthodes de surveillance, de l’écoulement du puits en cours de forage, est d’utiliser un simple "paddle" (capteur qui mesure la hauteur du fluide de forage avec l’inclinaison d’une pagaie) dans la ligne d’écoulement de retour, ou d’utiliser un débitmètre de Coriolis (débitmètre connu pour sa précision, mais coûteux et nécessite une installation complexe en ajoutant un "by-pass"). Il y a un besoin évident d’un nouveau débitmètre précis, mais facile à installer et peu coûteux. Le canal Venturi a été utilisé comme débitmètre pendant des années dans l’industrie des eaux. Il apparaît comme une solution peu chère mais précise pour mesurer des débits importants. Beaucoup de personnes ont travaillé sur cette solution pour améliorer sa précision et élargir son champ d’application. Ils ont développé des modèles, sur la base d’un processus d’étalonnage, permettant de relier la hauteur en amont au débit. Cela signifie que les modèles actuels, comme ISO NORM 4359 [1], peuvent être uniquement utilisés pour l’écoulement d’eau et pour une géométrie bien spécifique. Comme nous le savons, les boues ont des comportement non- Newtonien, et donc ces modèles établis ne peuvent pas être utilisés avec ce type de fluides. Pour notre application, la forme trapézoïdale apparaît comme un bon compromis entre la précision et la portée des mesures de débit. Ainsi, nous avons développé un modèle capable de calculer le débit en prenant en compte les propriétés du fluide ainsi que les paramètres géométriques du canal. Ce modèle a été simplifié sous forme 1D en utilisant la théorie des eaux peux profondes, et a été complété par un modèle de friction tenant en compte de la variation des propriétés des fluides et de la géométrie du canal. Ce modèle a été validé par une série d’expériences avec les deux types de fluides: Newtonien et non-Newtonien, où nous avons mesuré le débit et la hauteur de l’écoulement à différents endroits le long du canal Venturi. Nous avons également réalisé des simulations 3D, en simulant des écoulements Newtoniens et non- Newtonien le long du canal. Pour généraliser cette étude, cette démarche a été étendue à une autre forme de Venturi plus adapté à un certain design de plate-forme pétrolière. Les corrélations et les modèles développés et validés expérimentalement au cours de cette étude peuvent être utilisés pour étendre l’utilisation des canaux Venturi à tous les fluides Newtonien mais aussi non-Newtonien. Il est maintenant l’occasion pour les industries de proposer une solution, peu chère mais précise pour mesurer les débits dans des canaux ouverts et pour tous types de fluides. / During a drilling operation, a certain number of unexpected events, related to the flow of drilling fluid in the well, may happen rather quickly. Examples of such events are formation fluid influx (kick) and mud loss to the formation. An uncontrolled kick that increases in intensity may result in what is known as a blowout (e.g. the Deepwater Horizon incident in 2010). Influxes and kicks are traditionally detected by monitoring the drilling mud balance in the well, in particular, by monitoring the flow out the well and comparing it to the incoming flow induced by the pumps. Most methods of monitoring the flow out of the well while drilling consists in using a simple paddle (sensor that measures the height of drilling fluid with the inclination of a paddle) in the return flow line, or in using a Coriolis flow meter (flow meter known for its accuracy but expensive and requires a complex installation by adding a bypass). There is a clear need of a new accurate flow meter, but easy to install and inexpensive. The Venturi flume has been used as flow meter for years in water industry. It appears as a cheap but accurate solution to measure large flow rates. Many people have worked on this solution to improve its accuracy and to expand its scope. They have developed models, based on a calibration process, to relate the upstream height to the flow rate. This means that current models, as ISO NORM 4359 [1], can be used only for water flow and specific geometry. As known, muds have non-Newtonian behavior and water models cannot be used with this kind of fluids. For our application, trapezoidal shape appears as a good compromise between accuracy and range of flow rate measurements. Thus, we built a model able to compute the flow rate with taking into account fluid properties and geometrical parameters. This model is simplified in 1D form by using the Shallow Water theory, and completed by a friction model taking into account the variation of fluid properties and geometry along the open channel. It have been validated by series of experiments with both Newtonian and non-Newtonian fluids, where we measured the flow rate and heights of the flow at different locations along the trapezoidal Venturi flume. It have been also completed by 3D CFD which has been simulated both Newtonian and non-Newtonian flows along the flume. To generalized this study, the work was extended to another shape of Venturi more suited to some rig design. The correlations and models developed and experimentally validated during this research can be used to extend the use of Venturi flume flow meters for any fluids : Newtonian and non- Newtonian. It is an opportunity for industries to propose a cheap but accurate solution to measure flow rates in open channels with any kind of fluids.
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Análise e implementação de modelos não newtonianos no sistema FreeFlow-2D / Analysis and implementation of non-Newtonian models in FreeFlow-2D system.Ricardo da Silva Siquieri 26 April 2002 (has links)
O presente trabalho consiste em uma extensão do sistema FreeFlow-2D para simular escoamentos de fluidos não newtonianos bidimensionais com superfí cies livres, onde o fluido é descrito pelos modelos de Cross ou o modelo ``power-law\'\'. O método numérico empregado é o método GENSMAC. As equações governantes são aproximadas pelo método de diferenças finitas em uma malha deslocada e partículas marcadoras são utilizadas para a visualização do escoamento e localização da superfície livre. Resultados numéricos são apresentados. Em particular, a presente implementação é validada comparando-se a solução numérica com uma solução analítica / This work presents an extention of the Freeflow-2D system to non-Newtonian free surface flows. The governing equations are solved by the finite difference method on a staggered grid. Marker particles are used to describe the fluid providing the location and the visualization of the free surface. The methodology employed is based on the GENSMAC method. The fluid is modelled by the Cross and power-law models. Numerical examples are presented. The code is validated by making a comparison between analytical and numerical solutions
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Simulation à l’échelle microscopique et analyse macroscopique de l’imprégnation d’un matériau composite par un fluide chargé en particules / Microscopic simulation and macroscopic analysis of impregnation process of composite material by a concentrated suspensionDugois, Kévin 13 February 2017 (has links)
Dans le but d’améliorer le comportement thermo-mécanique des aubes de turbine présentes dans les moteurs d’avion développés par SAFRAN, il est nécessaire de mettre au point un nouveau matériau composite. Le procédé de fabrication de ce matériau est complexe et requiert une densification par voie liquide divisée en deux étapes. Cette thèse s’intéresse à la modélisation numérique de la première étape appelée Slurry Cast/APS.Celle-ci consiste en l’injection et le confinement, dans la préforme fibreuse, de particules préalablement mises en suspension. Pour cela, nous avons développé à l’échelle des fibres,un modèle qui utilise les équations de Navier-Stokes incompressibles et monophasiques ,l’équation de Phillips [Phillips et al., 1992] et une loi rhéologique [Krieger, 1972]. Après validation des résultats numériques par comparaison avec des résultats expérimentaux [Hampton et al., 1997] et théoriques [Belfort et al., 1994], le modèle est utilisé pour simuler l’écoulement autour de géométries de tissage proches du matériau étudié. / In order to improve thermo-mechanical behavior of tubine blades in SAFRAN engines plane, a new composite material is necessary. The manufacturing process to obtain this composite is intricate and requires a two steps fluid densification process. This thesis focuses on numerical simulation of the first one called Slurry Cats/APS. In this step, suspended particles are introducted and captured in the reinforcement. For that purpose,we carry out a model at fiber scale, using Navier-Stokes equations in incompressible and monophasic formulation, Phillips equations [Phillips et al., 1992] and a rheological law [Krieger, 1972]. After validation step consisting in a comparison of computational results with experiments [Hampton et al., 1997] and theorical law [Belfort et al., 1994], this model has been used to simulate flow around geometries similar to those encountered in our composite material.
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A Numerical Study of Droplet Dynamics in Viscoelastic FlowsArun, Dalal Swapnil January 2016 (has links) (PDF)
The polymers are integral part of vast number of products used in day to day life due to their anomalous viscoelastic behaviour. The remarkable flow behaviour exhibited by the polymeric fluids including rod climbing, extrudate swell, tube-less siphon, viscoelastic jet, elastic recoil and sharkskin instability is attributed to the complex microstructures in the polymeric liquids that arise due to the interactions of long chain polymer molecules with each other and with the surrounding fluid particles. The significance of polymer in transportation, packaging, pharmaceutical, chemical, biomedical, textiles, food and polymer processing industries highlights the requirement to comprehend the complex rheology of polymeric fluids.
First, we investigate the flow features exhibited by different shear thinning vis-coelastic fluids in rectangular cavities over a wide range of depth to width ratio. We have developed a viscoelastic flow solver in order to perform numerical simulations of highly elastic flow of viscoelastic fluids. In particular, we discuss the simulations of flows of constant viscosity Boger and shear thinning viscoelastic fluids in the complex flow problems using different constitutive equations. The effects of elasticity and inertia on the flow behaviour of two shear thinning vis-coelastic fluids modeled using Giesekus and linear PTT constitutive equations in rectangular cavities is studied. The size of the primary eddies and critical aspect ratio over which the corner eddies merge to yield a second primary eddy in deep cavities is discussed. We demonstrate that the flow in the shallow and deep cavities can be characterized using Weissenberg number, defined based on the shear rate, and Deborah number, specified based on the convective time scale, respectively. The study of flow in driven cavities is important in understanding of the mixing process during synthesis of blends and composites.
Next, we study two phase polymeric flow in confined geometries. Nowadays, polymer processing industries prefer to develop newer polymer with the desired material properties mechanically by mixing and blending of different polymer components instead of chemically synthesizing fresh polymer. The microstructure of blends and emulsions following drop deformation, breakup and coalescence during mixing determines its macroscopic interfacial rheology. We developed a two phase viscoelastic flow solver using volume conserving sharp interface volume-of-fluid (VOF) method for studying the dynamics of single droplet subjected to the complex flow fields.
We investigated the effects of drop and matrix viscoelasticity on the motion and deformation of a droplet suspended in a fully developed channel flow. The flow behaviour exhibited by Newtonian-Newtonian, viscoelastic-Newtonian, Newtonian-viscoelastic and viscoelastic-viscoelastic drop-matrix systems is presented. The difference in the drop dynamics due to presence of constant viscosity Boger fluid and shear thinning viscoelastic fluid is represented using FENE-CR and linear PTT constitutive equations, respectively. The presence of shear thinning viscoelastic fluid either in the drop or the matrix phase suppresses the drop deformation due to stronger influence of matrix viscoelasticity as compared to the drop elasticity. The shear thinning viscoelastic drop-matrix system further restricts the drop deformation and it displays non-monotonic de-formation. The constant viscosity Boger fluid droplet curbs the drop deformation and exhibits flow dynamics identical to the shear thinning viscoelastic droplet, thus indicating that the nature of the drop viscoelasticity has little influence on the flow behaviour. The matrix viscoelasticity due to Boger fluid increases drop deformation and displays non-monotonic deformation. The drop deformation is further enhanced in the case of Boger fluid in viscoelastic drop-matrix system. Interestingly, the pressure drop due to the presence of viscoelastic drop in a Newtonian matrix is lower than the single phase flow of Newtonian fluid. We also discuss the effects of inertia, surface tension, drop to matrix viscosity ratio and the drop size on these drop-matrix systems.
Finally, we investigate the emulsion rheology by studying the motion of a droplet in the square lid driven cavity flow. The viscoelastic effects due to constant viscosity Boger fluid and shear thinning viscoelastic fluid are illustrated using FENECR and Giesekus rheological relations, respectively. The presence of viscoelasticity either in drop or matrix phase boosts the drop deformation with the drop viscoelasticity displaying intense deformation. The drop dynamics due to the droplet viscoelasticity is observed to be independent of the nature of vis-coelastic fluid. The shear thinning viscoelastic matrix has a stronger influence on the drop deformation and orientation compared to the Boger fluid matrix. The different blood components, cells and many materials of industrial importance are viscoelastic in nature. Thus, the present study has significant applications in medical diagnostics, drug delivery, manufacturing and processing industries, study of biological flows, pharmaceutical research and development of lab-on-chip devices.
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Simulação de escoamento de fluidos em superfícies definidas por pontos não organizados / Fluid flow simulation in surfaces defined by non-organized pointsKémelli Campanharo Estacio 24 October 2008 (has links)
Atualmente diversos produtos são fabricados por meio de injeção de polímeros, num processo denominado moldagem por injeção: material fundido é injetado em um molde no qual resfria e endurece. Contudo, ao contrário de outros processos de produção, a qualidade da peça criada por meio de moldagem por injeção não depende apenas do material e da sua forma geométrica, mas também da maneira na qual o material é processado durante a moldagem. Por esse motivo, o uso de modelagem matemática e simulações numéricas tem aumentado consideravelmente como maneira de auxiliar o processo de produção e tem-se tornado uma ferramenta indispensável. Desta forma, este projeto tem o propósito de simular o escoamento de fluidos durante a fase de preenchimento do processo de moldagem por injeção, utilizando o modelo 21/2-dimensional, composto por uma equação bidimensional para a pressão, conhecida como equação de Hele-Shaw, e uma equação tridimensional para a temperatura do fluido. Um modelo bidimensional para a temperatura é também desenvolvido e apresentado. Este projeto de doutorado propõe duas estratégias numéricas para a solução da equação de Hele-Shaw. A primeira delas é baseada em uma formulação euleriana do método Smoothed Particle Hydrodynamics, onde os pontos utilizados na discretização não se movem, e não há utilização de malhas. A segunda estratégia é baseada na criação de malhas dinamicamente construídas na região do molde que já encontra-se parcialmente cheio de fluido e subseqüente aplicação do método Control Volume Finite Element Method. Uma estratégia dinâmica do método semi lagrangeano é apresentada e aplicada à solução da equação bidimensional da temperatura. O projeto também pretende investigar três novas abordagens para o tratamento da superfície livre. Duas delas são baseadas na técnica Volume of Fluid e uma delas é uma adaptação meshless do método Front-Tracking. O comportamento não newtoniano do fluido é caracterizado por uma família de modelos de viscosidade. Testes numéricos indicando a confiabilidade das metodologias propostas são conduzidos / Currently, several plastic products are manufactured by polymer injection, in a process named injection molding: molten material is injected into a thin mold where it cools and solidifies. However, unlike other manufacturing processes, the quality of injection-molded parts depends not only on the material and shape of the part, but also on how the material is processed throughout the molding. For this reason, the use of mathematical modelling and numerical simulations has been increasing in order to assist in the manufacturing process, and it has become an essential tool. Therefore, this Sc.D. project has the purpose of simulating the fluid flow during the filling stage of the injection molding process, using the 21/2-dimensional model, compounded by a two-dimensional equation for the pressure field (also known as Hele-Shaw equation) and a three-dimensional equation for the temperature of the fluid. A simpler two-dimensional model for the temperature field is also derived and presented. This project proposes two novel numerical strategies for the solution of Hele-Shaw equation. The first one is based on an Eulerian formulation of the Smoothed Particle Hydrodynamics method, where the particles used in the discretization do not move along as the simulation evolves, thereby avoing the use of meshes. In the second strategy, local active dual patches are constructed on-the-fly for each active point to form a dynamic virtual mesh of active elements that evolves with the moving interface, then the Control Volume Finite Element Method is applied for the pressure field approximation. A dynamic approach of the semi-Lagrangian scheme is applied to the solution of the two-dimensional temperature equation. The project also assesses three new approaches for the treatment of the free surface of the fluid flow. Two of them are based on the Volume of Fluid technique and one of them is a meshless adaptation of the Front-Tracking method. The non-Newtonian behavior is characterized by a family of generalized viscosity models. Supporting numerical tests and performance studies, which assess the accuracy and the reliability of the proposed methodologies, are conducted
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