This thesis investigates three problems in the general area of environmental fluid mechanics. The first two problems are related to liquid or gas flow through clay-water suspensions, with relevance for the underground storage of radioactive waste and also for understanding the mechanism of eruption in mud volcanoes. The third problem centres on the different problem of mixing in a turbulent buoyant plume. First, the injection of gas and water from a central source into a two-dimensional layer of clay confined between two circular horizontal plates is investigated. This provides a model of the potential pressurisation and failure of the seal rock around a radioactive waste repository as may arise if gas is continuously generated in the repository. As the gas injection pressure is gradually increased the cell walls deform and the clay moves radially outwards. However, at a critical radius, the liquid-clay interface becomes unstable and a series of channels propagate through the clay. When one of the channels reaches the edge of the domain the gas escapes and the pressure is released. As a result, the domain relaxes by elastic deformation and the clay seals the channel. In this way, continuous fluid injection leads to episodic release of gas from the cell. The second problem concerns the flow of mud along a vertical conduit driven by the combined effect of reservoir pressure and buoyancy associated with the gas injected at the base of the conduit. This represents an analogue model of the eruption of a mud volcano, in which mud rises from a deep reservoir to the surface. I find that the pressure associated with the reservoir and any buoyancy force produced by the migration of gas from deep in the reservoir to the surface leads to a continuous eruption if the net pressure is greater than the yield stress of the clay. If the reservoir pressure falls during such an event, the eruption will eventually stop, once the pressure reaches a dynamic yield stress condition. Only later, if the reservoir pressure increases to the static yield stress of the clay will the eruption start again, and this can lead to a series of eruption cycles which depend on the non-Newtonian rheology of the clay. In contrast, if this pressure is smaller than the yield stress of the clay, a series of episodic gas burst events can occur until the conduit is cleared of mud. The third problem relates to the mixing in a turbulent buoyant plume. Through a series of new experiments and some complementary theoretical modelling I show that the mixing in a turbulent plume is strongly affected by the eddies and leads to significant longitudinal dispersion in the flow. The implications of the modelling for determining the residence time distribution of the fluid in the plume is discussed.

Magnetic resonance (MR) is a highly versatile technique with great potential for use in industrial applications; from the in situ study of unit operations to the optimisation of product properties. This thesis, concerned with the latter, is divided into two parts. Firstly, dynamic MR is applied to characterise the flow behaviour, or rheology, of process fluids. Such characterisation is typically performed using conventional rheometry methods operating offline, with an online, or inline, method sought for process control and optimisation. Until recently, MR was an unlikely choice for this application due to the requirement of high-field MR hardware. However, recent developments in low-field MR hardware mean that the potential of MR in such applications can now be realised. Since the implementation of MR flow imaging is challenging on low-field MR hardware, two new approaches to MR rheometry are described using pulsed field gradient (PFG) MR. A cumulant analysis of the PFG MR signal is first used to characterise the rheology of model power-law fluids, namely xanthan gum-in-water solutions, accurate to within 5% of conventional rheometry, the data being acquired in only 6% of the time required when using MR flow imaging. The second approach utilises a Bayesian analysis of the PFG MR signal to characterise the rheology of model Herschel--Bulkley fluids, namely Carbopol 940-in-water solutions; data are acquired in only 12% of the time required for analysis using MR flow imaging. The suitability of the Bayesian MR approach to study process fluids is demonstrated through experimental study on an alumina-in-acetic acid slurry used by Johnson Matthey. Secondly, MR imaging is used to provide insights into the origins and mechanisms of colloidal gel collapse. Many industrial products are colloidal gels, a space-spanning network of attractive particles with a yield stress. Colloidal gels are, however, known to undergo gravitational collapse after a latency period, thus limiting the shelf-life of products. This remains poorly understood, with a more detailed understanding of both fundamental interest and practical importance. To this end, MR imaging is applied offline to investigate the phase behaviour of colloidal gels. In particular, a comparison of the simulated and experimental phase diagrams suggests gravitational gel collapse to be gravity-driven. Furthermore, measurement of the colloid volume fraction using MR imaging indicates the formation of clusters of colloids at the top of the samples. Whether such clusters initiate gravitational gel collapse is yield stress-dependent; the gravitational stress exerted by a cluster must be sufficient to yield the colloidal gel.

Nas pesquisas que buscam a inserção da História e Filosofia da Ciência no Ensino de Física aparecem dois papeis principais para a Filosofia, a saber, o de atuar como estratégia didática para a compreensão conceitual e o de ser necessária para a compreensão da Natureza da Ciência. Com respeito ao primeiro, investigamos se a Filosofia pode ser mais do que apenas uma estratégia e passar a contribuir de maneira essencial, uma vez que identificamos nas propostas mencionadas que elas não trouxeram um modo de compreensão diferente dos que antes se criticava. Começamos analisando as relações entre Física e Filosofia e encontramos que o pensamento físico possui intersecções constitutivas com o pensamento filosófico, tanto na atribuição de significações, ao conectar as teorias formalizadas com o mundo físico, quanto na crítica de suas próprias teorias. Em seguida, exploramos a concepção de compreensão na Filosofia da Linguagem tardia de Wittgenstein. Para ele, a compreensão de um conceito não está em processos ou estados mentais, mas sim nos usos que fazemos das palavras em diferentes contextos, fundamentadas em uma normatividade presente na própria linguagem. O pensamento filosófico, como parte desta normatividade é também condição para a compreensão e formação de conceitos físicos em um grau suficiente para permitir a autonomia do sujeito. Exemplificamos nossa defesa a partir de um estudo teórico da mecânica newtoniana, explorando as questões metafísicas relacionadas ao problema do espaço e do movimento e através da análise de discussões entre professores em formação inicial, procurando observar o papel dos pressupostos filosóficos para a significação. Concluímos que, sem eles, havia grandes lacunas de significação que eram preenchidas por conceitos pertencentes a contextos não físicos, além de que a mecânica clássica era sinônima de um conjunto de pressupostos para a resolução de exercícios. Estes permitiram que os futuros professores fizessem descrições, deduções e classificações de fenômenos físicos, mas apenas em conjunto com as proposições filosóficas, passaram a permitir um grau mais alto de compreensão, bem como a formação de novas habilidades, tais como a elaboração de hipóteses, argumentações, deduções e críticas. / Most proposals that advocate the inclusion of history and philosophy of science in physics curriculum award two main roles to philosophy: as a teaching strategy for conceptual understanding and as a method to understand the Nature of Science. With respect to the first role, we inquire whether philosophy can be more than just a teaching strategy and to contribute in an essential way instead, as we find that the above-mentioned proposals do not yield better results in terms of conceptual understanding then the methods criticized by them. We begin by analysing the relationship between physics and philosophy and we find that physical thinking has constitutive intersections with philosophical thought, so much in assigning meanings in order to connect formalized theories to the world as in the criticism of its own theories. Then we explore the conception of understanding in the philosophy of language of the late Wittgenstein. For him, understanding of a concept is not a mental process or state, but it rather consists in the use we make of the words in different contexts, based on the normativity present in language itself. Philosophical thought, as a part of this normativity is also a condition for the comprehension and development of physicals concepts in a level sufficient for the subject\'s autonomy. We exemplify our conclusions in theoretical study of newtonian mechanics, exploring the metaphysical questions related to the problem of space and movement and analyzing discussions among teachers in initial training, trying to observe the role of philosophical assumptions in shaping meanings. We conclude that, without them, there were great significance gaps, which were filled with concepts belonging to non-physical contexts, and that classical mechanics was synonymous to a set of assumptions for solving exercises. These assumptions enabled the prospective teachers to make descriptions, deductions and classifications of physical phenomena, but only together with philosophical propositions, did they increased the degree of understanding and enable formation of new skills, such as development of hypothesis, argumentation and criticism.

Made available in DSpace on 2014-06-11T19:23:39Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-12-02Bitstream added on 2014-06-13T18:50:59Z : No. of bitstreams: 1 leite_lob_me_ilha.pdf: 7876959 bytes, checksum: 679218273f75952f4df0237622251b57 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Rompimentos de Barreira são fenômenos caracterizados por um campo de escoamento inicialmente represado e submetido nos instantes subseqüentes a uma liberação abrupta. Diversos modelos matemáticos e leis de comportamento reológico podem ser associados a este problema e cada um deles deve ser estudado e compreendido de maneira a predizer, a partir de testes físicos e numéricos, sua adequação à descrição da evolução espaço-temporal de frentes resultantes deste fenômeno, tipo ruptura de barragem, retendo água , rejeitos ou materiais de reologia complexa. O desenvolvimento de técnicas analíticas possibilitou entender de maneira impar o desenvolvimento desses fenômenos, porém, a difícil obtenção de dados que alcançassem consonância com aqueles obtidos experimentalmente, demonstrava a fragilidade desse tipo de análise perante a descrição de sistemas dinâmicos complexos. Sendo assim, optou-se pela tentativa de recriar estes fenômenos a partir de técnicas que utilizassem a manipulação de equações governantes completas. Sistemas contínuos podem ser analisados através de aproximações discretas, resultando em valores realísticos, muito próximos aos obtidos experimentalmente, e a capacidade computacional atual, permite diminuir sensivelmente os erros envolvidos, aumentando cada vez mais a consistência física destes métodos. Neste trabalho utilizou-se o software comercial ANSYS-CFX para simular os fenômenos de ruptura de barreira, configurando a reologia de dois materiais, o Carbopol 940 representando um material de reologia complexa (Herschel-Bulkley) e o Glicerol (Newtoniano), esses dados foram então confrontados com os obtidos experimentalmente através de um modelo em escala reduzida. Campos de velocidade, pressão e evolução temporal das frentes foram analisadas, verificando-se valores com grande consonância entre numérico e experimental, mostrando uma grande consistência física dos métodos utilizados / The Dam Break problem is a phenomenon characterized by a flow field initially dammed and submitted in the subsequent moments of an abrupt release. Various mathematical models and laws of rheological behavior may be associated with this type of problem and each must be studied and understood in order to predict from physical and numerical tests the temporal evolution of their fronts resulting from this phenomenon, type Dan Break problems, retaining water or rheology complex materials. The development of analytical techniques enabled the understanding the development of these phenomena, however, the difficulty to obtain a reach agreement data with those obtained experimentally, showed the fragility of this type of analysis to the description of complex dynamic systems. But, it was decided by attempt of recreate these phenomena from techniques that use the manipulation of complete government equations. Continuous systems can be analyzed by discrete approximations, leading to realistic values, very close to those obtained experimentally, and current computational capacity, enables to reduce the errors involved significantly, increasing the consistency of these physical methods. This work used the commercial software ANSYSCFX to simulate the phenomena of breaking the barrier, setting the rheology of two materials, the Carbopol 940 representing a material of complex rheology (Herschel-Bulkley) and glycerol (Newtonian), these data were then compared with those obtained experimentally using a model in scale. Fields of velocity, pressure and temporal evolution of the fronts were analyzed. Found very similar values between numerical and experimental simulations, showing the physical consistency of the methods used

Submitted by Vasti Diniz (vastijpa@hotmail.com) on 2017-09-13T13:50:59Z No. of bitstreams: 1 arquivototal.pdf: 2320909 bytes, checksum: 25cc6b6504385f6f69412717c2952be1 (MD5) / Made available in DSpace on 2017-09-13T13:50:59Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2320909 bytes, checksum: 25cc6b6504385f6f69412717c2952be1 (MD5) Previous issue date: 2016-07-29 / We considered the discrete approach to Newtonian cosmology presented by Ellis and Gibbons in a recent paper, and generalize this to the continuum limit. The results are obtained using the Newton's laws for particles interacting gravitationally, which are moving homothetically, with with their comoving positions constituting a central configuration. It requines no use of the fluid mechanics, but just a correspondence between the quantities which appear in the approach of Ellis and Gibbons and their generalizations for a system with high density, but with a finite number of particles. The solutions of the equation for the scale factor are presented, taking into account the presence of a term associated with the cosmological cons­tant. We briefly present the relativistic cosmology and compare with Newtonian cosmology. / Consideramos a formulagao discreta da cosmologia Newtoniana adotada por Ellis e Gibbons, em artigo recente, e fazemos uma generalizagao para o limite do continuo. Os resultados sao obtidos com o use das leis de Newton para particulas que interagem gravitacionalmente, que se movem homoteticamente, com suas coordenadas comOveis constituindo-se uma con­figuragao central. Nao foi necessario o use da mecanica dos fluidos, mas tao somente, uma correspondencia direta entre as grandezas discretas da formulagao de Ellis e Gibbons e suas generalizagoes para um sistema muito denso, com um nilmero finito de particulas. Sao apresentadas solugoes da equagao para o fator de escala, considerando a presenga do termo associado a constante cosmolOgica. E feita uma breve apresentagao da cosmologia Einstei­niana e uma comparagao com a cosmologia Newtoniana.

Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2011. / Despite the extensive research work carried out on flow through short square-edged orifice plates over the last century (e.g. Johansen, 1930; Benedict, 1977; Alvi et al., 1978; Swamee, 2005; ESDU, 2007), gaps in the engineering data still exist for certain ranges of flow conditions and geometries. The majority of data available in the literature are for Newtonian fluids in the turbulent flow regime (ESDU, 2007). Insufficient data have been observed for the orifice with pipe diameter ratio, β = 0.2, in the laminar flow regime. There are no experimental data for β = 0.3 and 0.57. The objective of this thesis was to conduct wide-ranging experimental studies of the flow in orifice plates, which included those geometrical configurations, by measuring pressure loss coefficients and discharge coefficients across the orifice plates using both Newtonian fluids and non-Newtonian fluids in both laminar and turbulent flow regimes. The test work was conducted on the valve test rig at the Cape Peninsula University of Technology. Four classical circular short square-edged orifice plates having, β = 0.2, 0.3, 0.57 and 0.7, were tested. In addition, two generation 0 Von Koch orifice plates (Von Koch, 1904), with equivalent cross sectional area were also tested for β = 0.57. Water was used as Newtonian fluid to obtain turbulent regime data and also for calibration purposes to ensure measurement accuracy and carboxymethyl cellulose, bentonite and kaolin slurries were used at different concentrations to obtain laminar and transitional loss coefficient data. The hydraulic grade line method was used to evaluate pressure loss coefficients (Edwards et al., 1985), while the flange tap arrangement method was used to determine the discharge coefficients (ESDU, 2007). A tube viscometer with three different pipe diameters was used to obtain the rheological properties of the fluids. The results for each test are presented in the form of pressure loss coefficient (kor) and discharge coefficient (Cd) against pipe Reynolds number (Re)

Thesis (DTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2013 / The flow of reactive viscous fluids in porous media presents a theoretically challenging problem and has a broad range of scientific, technological and engineering applications. Real life areas where such flow systems are encountered include drying of food, geothermal energy extraction, nuclear waste disposal, the flow of heat and fluid inside human organs, insulation of buildings, groundwater movement, oil and gas production, astrophysical plasmas, magnetohydrodynamic (MHD) pumps and generators, metal extraction and granulation of metals, aerospace and ship propulsion and automobile exhaust systems. The reactions within such flow systems are inherently exothermic. It is in this view that we carry out studies of thermal effects and thermal stability criteria for unsteady flows of reactive variable viscosity non-Newtonian fluids through saturated porous media. The study focuses on non-Newtonian fluids mainly because the majority of industrial fluids exhibit non-Newtonian character. Particular focus will be on fluids of the differential type exemplified by third grade fluid. Both analytical and numerical techniques were employed to solve the nonlinear partial differential equations that were derived from the conservation principles, namely the principles of conservation of mass, momentum and energy balance. Graphical representations were adopted in trying to explain the response of solutions to various flow parameter variations. In chapter 1 we defined important terms and expressions, laid down a summary of important applications, carried out literature survey, stated the statement of the problem, the aims and objectives of the study as well as an outline of the envisaged research methodology. Chapter 2 focuses on the derivations of the fundamental equations that derive the flow system. These are the continuity equation, the momentum equation and the energy equation. In chapter 3 we computationally investigated the unsteady flow of a reactive temperature dependent viscosity third grade fluid through a porous saturated medium with asymmetric convective boundary conditions. The response of velocity and temperature fields to each of the various flow parameters was analysed and interpreted. A transient increase in both the velocity and temperature profiles with an increase in the reaction strength, viscous heating and fluid viscosity parameter was observed. On the other hand, a transient decrease in the field properties was observed with increase in non-Newtonian character and the porous medium shape parameter. The reaction was noticed to blow-up if, depending on other flow parameters, the reaction strength is not carefully controlled.

O estudo do comportamento reológico de fluidos não Newtonianos tem grande importância em diversas áreas da engenharia. O aumento na demanda destes fluidos por exemplo, no uso doméstico, pessoal e em processos químicos acarreta em dificuldades que vão desde o processo de sua mistura ao seu manuseio. Dentre os fluidos não Newtonianos estão os viscoelásticos, os quais exibem deformação aparente quando os níveis de tensões são inferiores ao limite de escoamento do material e, dentro desta classe, alguns ainda podem apresentam comportamento elástico quando submetidos à baixa taxa de cisalhamento. Juntamente com os efeitos elasto-viscoplásticos, os materiais podem apresentar comportamento tixotrópico, onde devido as tensões sua reestruturação não é instantânea. Na presente Tese, fez-se um estudo numérico a fim de analisar o problema especifico de escoamentos de fluidos elasto-viscoplásticos com comportamento tixotrópico em uma expansão planar abrupta na razão de aspecto 4 : 1. O modelo mecânico aplicado consiste de uma equação viscoelástica para o campo de tensões, uma evolutiva para o parâmetro de estrutura do material, bem como as equações de conservação de massa e momento. O modelo mecânico aplicado mostrou-se capaz de prever o comportamento tixotrópico. A aproximação numérica do modelo aplicado foi feita através do método estabilizado de elementos finitos, especificamente o método Galerkin Mínimos-Quadrados (GLS), o qual foi implementado no código de elementos finitos para fluidos não Newtonianos em desenvolvimento no Laboratório de Mecânica dos Fluidos Aplicada e Computacional (LAMAC) da Universidade Federal do Rio Grande do Sul. Os fenômenos reológicos presentes no problema foram analisados a partir da influência da cinemática do escoamento, da elasticidade e da tixotropia, no nível de estruturação do material, na posição e tamanho das regiões não escoadas e na deformação elástica do material. Os resultados mostraram-se satisfatórios, pois condizem com os apresentados na literatura, apontando a boa predição do modelo mecânico aplicado bem como a robustez de sua implementação computacional. / The rheological behavior of non-Newtonian uids study is of great then importance in many areas of engineering. The increase in demand of these uids - for example, domestic use, personal and processes chemical - causes di culties ranging from the process of mixing it to handling. Among the non-Newtonian uids are viscoelastic, which exhibit apparent deformation when stress levels are lower than the yield limit of the material and, within this class, some still have elastic behavior when subjected to low shear rates. Together with the elastic-viscoplastic e ects, materials may exhibit thixotropic behavior, ie, due the restructuring strain is not instantaneous. In this thesis was made a numerical study to simulate the speci c problem of ow of elastic-viscoplastic uids with thixotropic behavior in abrupt planar expansion { common geometry in industrial systems associated with elastic-viscoplastic uids, whose ratio the aspect is 4:1. The mechanical behavior of most of these structured materials, are highly non-Newtonian, with this, there is need to make them more pseudoplastic, causing undesirable behaviors such as thixotropic which is a phenomenon somewhat characterized and modeled in the literature. The mechanical model applied is able to predict thixotropic behavior and is composed of a viscoelastic equation for the stress eld and an evolutionary to the material structure parameter in addition to the mass and momentum conservation equations. This mechanical model is approximated by a stabilized nite element model, called the Galerkin method of least squares (GLS). In order to study the rheological phenomena present in the problem is analyzed the in uence of the ow kinematics, elasticity and thixotropy in the level of structure of the material, in position and size of unyielded regions and the elastic deformation of the material. The results were satisfactory, since the the study of intensity the U the results agree with those reported in the literature pointing to good prediction of the mechanical model applied well as the hardiness of their computational implementation.The results of the elasticity showed quite spectacular behavior of unyielded regions of the material since for high values of relaxation time, the unyielded region of channel larger has the form of " ngers"because of the high exibility of the material along the line of symmetry of the channel. The results of the analysis of the elastic deformation show, that model correctly dosing the elasticity in the unyielded regions. The thixotropic e ects reported a slower structuring of the material with increasing characteristic time, in response to strain change caused by the expansion, results indicate that for high values of relaxation time, higher the distance between the unyielded regions of smaller channel and larger.

La contraction périodique du coeur est à l’origine de l’onde de pouls qui, de part son interaction avec les artères élastiques, le sang et le réseau artériel lui-même, devient le signal observé quotidiennement par les médecins. Cette dynamique ondulatoire est d’une importance primordiale dans la compréhension de la genèse de nombreuses maladies cardiovasculaires. En effet, ce sont souvent des facteurs hémodynamiques qui sont à l’origine de la croissance de ces pathologies. Malheureusement, les mesures non-invasives et l’imagerie médicale sont souvent insuffisantes pour appréhender la complexité des écoulements sanguins. La simulation numérique est donc en plein essor car celle-ci permet d’obtenir des données précises dans des régions vasculaires difficiles d’accès. Bien que les modèles sanguins tridimensionnels soient très précis et permettent de reproduire fidèlement la géométrie vasculaire, leur coût, à la fois numérique et paramétrique, est trop important pour que ceux-ci soient utilisés dans de grands réseaux vasculaires. Nous avons donc choisi d’utiliser des modèles simplifiés qui permettent d’accéder à cette dynamique de réseau si importante. Premièrement, nous nous sommes intéressés aux modèles unidimensionnels et nous avons développé de nouvelles approches permettant de prendre en compte l’aspect non-Newtonien du sang et la viscoélasticité des parois artérielles. Secondement, nous avons proposé un modèle bidimensionnel, que nous avons utilisé pour simuler l’écoulement dans des sténoses et anévrismes. Finalement, nous avons utilisé ces modèles pour décrire l’écoulement du sang dans de grands réseaux artériels et pour optimiser un pontage extracorporel. / Every cardiac cycle, the heart contracts and ejects blood into the vascular network. This periodic inflow translates into the propagation of a pulse wave, which, through interactions with the elastic arterial wall, the blood and the complex arterial network, shapes itself into the pulsatile signal clinicians observe on a daily basis. Understanding these complex wave propagation dynamics is of great clinical relevance as large arteries are a breeding ground for many common cardiovascular pathologies which are often triggered by hemodynamical factors. Unfortunately, hemodynamics in large arteries are too complex to be apprehended using only non-invasive measurements and medical imaging techniques. Patient-specific numerical simulations of blood flow have therefore been developed to provide clinicians with valuable insights on pathogenesis and the outcome of surgeries. As three-dimensional models are usually used only in small portions of the cardiovascular system due to their high modeling and computational costs, we have used reduced-order models to reproduce complex wave propagation behaviors in large networks of arteries. We have first focused on one-dimensional models for blood flow and developed novel approaches that take into account the non-Newtonian behavior of blood and the viscoelastic response of the arterial wall. Next, we have proposed a fluid-structure interaction twodimensional blood flow model to capture the complex flow patterns in stenoses and aneurysms unavailable to classical one-dimensional models. Finally, we have applied these models to compute the flow in large arterial networks and to predict the outcome of bypass surgeries.

O estudo do comportamento reológico de fluidos não Newtonianos tem grande importância em diversas áreas da engenharia. O aumento na demanda destes fluidos por exemplo, no uso doméstico, pessoal e em processos químicos acarreta em dificuldades que vão desde o processo de sua mistura ao seu manuseio. Dentre os fluidos não Newtonianos estão os viscoelásticos, os quais exibem deformação aparente quando os níveis de tensões são inferiores ao limite de escoamento do material e, dentro desta classe, alguns ainda podem apresentam comportamento elástico quando submetidos à baixa taxa de cisalhamento. Juntamente com os efeitos elasto-viscoplásticos, os materiais podem apresentar comportamento tixotrópico, onde devido as tensões sua reestruturação não é instantânea. Na presente Tese, fez-se um estudo numérico a fim de analisar o problema especifico de escoamentos de fluidos elasto-viscoplásticos com comportamento tixotrópico em uma expansão planar abrupta na razão de aspecto 4 : 1. O modelo mecânico aplicado consiste de uma equação viscoelástica para o campo de tensões, uma evolutiva para o parâmetro de estrutura do material, bem como as equações de conservação de massa e momento. O modelo mecânico aplicado mostrou-se capaz de prever o comportamento tixotrópico. A aproximação numérica do modelo aplicado foi feita através do método estabilizado de elementos finitos, especificamente o método Galerkin Mínimos-Quadrados (GLS), o qual foi implementado no código de elementos finitos para fluidos não Newtonianos em desenvolvimento no Laboratório de Mecânica dos Fluidos Aplicada e Computacional (LAMAC) da Universidade Federal do Rio Grande do Sul. Os fenômenos reológicos presentes no problema foram analisados a partir da influência da cinemática do escoamento, da elasticidade e da tixotropia, no nível de estruturação do material, na posição e tamanho das regiões não escoadas e na deformação elástica do material. Os resultados mostraram-se satisfatórios, pois condizem com os apresentados na literatura, apontando a boa predição do modelo mecânico aplicado bem como a robustez de sua implementação computacional. / The rheological behavior of non-Newtonian uids study is of great then importance in many areas of engineering. The increase in demand of these uids - for example, domestic use, personal and processes chemical - causes di culties ranging from the process of mixing it to handling. Among the non-Newtonian uids are viscoelastic, which exhibit apparent deformation when stress levels are lower than the yield limit of the material and, within this class, some still have elastic behavior when subjected to low shear rates. Together with the elastic-viscoplastic e ects, materials may exhibit thixotropic behavior, ie, due the restructuring strain is not instantaneous. In this thesis was made a numerical study to simulate the speci c problem of ow of elastic-viscoplastic uids with thixotropic behavior in abrupt planar expansion { common geometry in industrial systems associated with elastic-viscoplastic uids, whose ratio the aspect is 4:1. The mechanical behavior of most of these structured materials, are highly non-Newtonian, with this, there is need to make them more pseudoplastic, causing undesirable behaviors such as thixotropic which is a phenomenon somewhat characterized and modeled in the literature. The mechanical model applied is able to predict thixotropic behavior and is composed of a viscoelastic equation for the stress eld and an evolutionary to the material structure parameter in addition to the mass and momentum conservation equations. This mechanical model is approximated by a stabilized nite element model, called the Galerkin method of least squares (GLS). In order to study the rheological phenomena present in the problem is analyzed the in uence of the ow kinematics, elasticity and thixotropy in the level of structure of the material, in position and size of unyielded regions and the elastic deformation of the material. The results were satisfactory, since the the study of intensity the U the results agree with those reported in the literature pointing to good prediction of the mechanical model applied well as the hardiness of their computational implementation.The results of the elasticity showed quite spectacular behavior of unyielded regions of the material since for high values of relaxation time, the unyielded region of channel larger has the form of " ngers"because of the high exibility of the material along the line of symmetry of the channel. The results of the analysis of the elastic deformation show, that model correctly dosing the elasticity in the unyielded regions. The thixotropic e ects reported a slower structuring of the material with increasing characteristic time, in response to strain change caused by the expansion, results indicate that for high values of relaxation time, higher the distance between the unyielded regions of smaller channel and larger.