Thesis (MTech (Chemical Engineering))--Cape Peninsula University of Technology, 2013 / Centrifugal pumps are the most commonly used pumps in slurry transport systems. The design of pumping systems dealing with liquids more viscous than water requires a reliable method of pump performance prediction for the pump selection. For Newtonian fluids, the Hydraulic Institute method is well established, but there is no generally accepted method for non-Newtonian fluids. Many authors have fallen back on using the Hydraulic Institute method for non-Newtonian fluids. This requires a constant viscosity while non-Newtonian fluid viscosity varies with the shear rate. The question arises: What viscosity should be used in this method for non-Newtonian fluids? Two approaches have been developed: the use of a Bingham plastic viscosity made by Walker and Goulas (1984) and the use of the apparent viscosity calculated using an “equivalent hydraulic pipe” diameter, designed by Pullum et al. (2007). Previous results obtained from these two approaches are not in agreement. Therefore, the aim of this study is to explore a suitable procedure to determine a representative non-Newtonian viscosity to be used in the Hydraulic Institute method to predict the pump performance. To achieve this goal, a set of data was experimentally obtained and the existing data were reused. Test work was conducted using the pump test rig in the Flow Process Research Centre at the Cape Peninsula University of Technology. A Warman 4/3 pump was tested, using four concentrations of kaolin suspension and three concentrations of CMC solution. Five pump speeds were chosen to run these tests: 1200, 1400, 1600, 1800, and 2000 rpm. An additional data set obtained by testing two submersible centrifugal pumps with eight concentrations of sludge, in Stockholm, Sweden, was also analysed. These sets of data were analysed firstly according to the Walker and Goulas (1984) approach and secondly according to the Pullum et al. (2007) approach. The use of the apparent viscosity led to the better pump head prediction. The results of this prediction were close to those obtained in the Pullum et al. (2007) work, and even better in some cases. On the other hand, the use of the Bingham plastic viscosity showed better pump efficiency prediction, although the Walker and Goulas (1984) efficiency prediction range was achieved only for one pump out of five. The apparent viscosity reflected the non-Newtonian behaviour but it could not represent alone the non-Newtonian viscosity because of the poor efficiency predictions and the sensitivity of the Pullum et al. (2007) approach to a change in viscosity. From the results of this work, it is advisable that the pump performance prediction be done using both apparent and Bingham plastic viscosity, the apparent viscosity for the head prediction and the Bingham plastic viscosity for the efficiency prediction.

A dissertation submitted to the Faculty of Engineering, Cape Peninsula University of Technology, Cape Town, in partial fulfilment of the requirements for the MTech Degree in Mechanical Engineering 2012 / Flow features provide considerable guidance for the rational selection of techniques to predict hydraulic behaviour and for suitable operating conditions for pipelines. Traditionally, water was used to transport coarse particles, and it was necessary to operate at velocities at which the flow was turbulent in order to avoid blockage. Consequently the friction losses were too high for economic operation. In addition, wear on pipes, fittings and pumps presented serious problems. Nowadays, it is well established that it is possible to operate at very high solids concentration in a heavy vehicle (carrier fluid). Similar solids throughputs may be achieved at very much lower velocities by operating in the laminar flow regime. This results not only in lower power requirement, but it also reduces wear and water consumption. In spite of these potential benefits, only a few studies dealing with the transport of coarse particles in heavy media have been reported. Since the distinction between different flow patterns is of paramount importance for modelling purposes, as equations are flow pattern dependent, and given the importance of avoiding excessive wear of pipes at low and high velocities, the present work was carried out in the context of dense or non-Newtonian carrier fluid. This project comprised analysis of existing data acquired at the Flow Process and Rheology Centre of the Cape Peninsula University of Technology. Kaolin in the range of 6% to 15% volumetric concentration was used as a carrier fluid and coarse material in the range of 10% to 30% volumetric concentration was simulated by silica sand ranging in size from 1 mm to 3 mm. For the purpose of this study flow patterns derived from resistance curves for various mixtures, particle concentrations, particle grading and flow conditions were compared with “concentration profiles” and images obtained from electrical resistance tomography (ERT). It appeared from this work that the sand concentration does not change the flow pattern but increases or reduces the pressure gradients depending on the case. The concentration of kaolin carrier can change the flow patterns from layered to homogeneous flow, inducing an increase in total pressure gradients as it increases. Flow patterns obtained from ERT compared reasonably well with those derived from pressure gradients profiles. The transition velocities from layered to heterogeneous flow obtained from both methods were similar, especially for low and moderate carrier concentrations. As the kaolin carrier concentration or as the sand concentration increased it became more difficult to distinguish the transition velocity between heterogeneous and layered flow. More work is still needed to improve the ERT instrument and its image reconstruction software.

The increasing activity of oil and gas extraction in deep water has stimulated several studies to solve problems encountered in drilling wells. During the drilling operation, a fluid (drilling mud) is pumped through the column to the bottom, carrying to the surface the drill cuttings generated, through the annular space formed between the column and the borehole wall. In this type of flow may appear a kind of hydrodynamic instability characterized by the appearance of toroidal vortices. This type of instability (Taylor-Couette) may profoundly alter the pressure drop of the flow, the shear stress at the borehole wall and the ability of carrying the solids. Moreover, during the process of drilling a well it is necessary promotes the well cementing and coating to provide a mechanical support, as well as, to isolate it from different rock formations traversed. For this step to be successful, the drilling mud must be completely removed from the annular space, and this removal may be impaired in wells which have varying eccentricity along the tube. Due to high costs of correction transactions and loss of drilling time, it is crucial to predict the mud flow around the annular. The effects of this variation of the eccentricity have not been much discussed in the literature, and they may have great influence on the displacement of the mud in the annular space. As an initial phase of work, numerical simulations were performed to study the flow and the emergence of Taylor- Couette instabilities in a concentric annular section, in order to compare them with literature data. Numerical simulations were developed in annular periodic sections, concentric and eccentric (E = 0.5) in order to obtain average profiles of axial and tangential velocities using different turbulence models, aiming at a comparison of simulated results with experimental data from literature. Later, it was made an experimental study and simulation to assess the effect of internal axis rotation on the pressure drop in the flow of non-Newtonian fluids (aqueous solutions of xanthan gum and carboxymethyl cellulose with 0.2% by weight) in a section annular concentric and the other with fixed eccentricity (E = 0.75). Finally, it was elaborated an experimental design (3k) with four variables, such as, xanthan gum concentration (0.05%, 0.10% and 0.15% by weight), eccentricity (0.0, 0.23 and 0.46), fluid flow rate (5, 7 and 9 m3/h) and internal rotation axis (0, 100 and 200 rpm). Following this planning, experimental data of pressure drop were collected, as well as, numerical simulations (CFD) in periodic annular sections to get results of axial velocity, in order to evaluate the effect of variable eccentric rotation on the fluid dynamics of non-Newtonian flows in annular spaces. / A crescente atividade de extração de petróleo e gás em águas cada vez mais profundas tem impulsionando diversos estudos para solucionar problemas encontrados na perfuração de poços. Durante a operação de perfuração, um fluido (lama de perfuração) é bombeado através da coluna até o fundo do poço, retornando à superfície carreando os cascalhos gerados pela broca, passando pelo espaço anular formado entre a coluna e a parede do poço. Neste tipo de escoamento pode ocorrer um tipo de instabilidade hidrodinâmica caracterizada pelo aparecimento de vórtices toroidais. Este tipo de instabilidade (Taylor-Couette), pode alterar profundamente a perda de carga do escoamento, a tensão cisalhante na parede do poço e a capacidade de carreamento de cascalho. Além disto, durante o processo de perfuração de um poço é necessário promover o revestimento e a cimentação do poço para fornecer a sua sustentação mecânica, bem como, para isolá-lo das diferentes formações rochosas atravessadas. Para esta etapa ser bem sucedida, a lama de perfuração deve ser completamente removida do anular, sendo que, esta remoção pode ser prejudicada em poços que apresentem excentricidade variando ao longo do tubo. Devido aos altos custos das operações de correção e a perda de tempo de perfuração, é fundamental prever este deslocamento da lama ao redor do anular. Os efeitos desta variação da excentricidade ainda não foram muito abordados na literatura e podem apresentar grande influência no deslocamento da lama no espaço anular. Como etapa inicial do trabalho, foram realizadas simulações numéricas para estudar o escoamento com surgimento de instabilidades do tipo Taylor-Couette em uma seção anular concêntrica, com intuito de compará-las com trabalhos da literatura. Depois foram desenvolvidas simulações numéricas em seções anulares periódicas, concêntrica e excêntrica (E = 0,5), a fim de obter perfis médios de velocidades axial e tangencial usando diferentes modelos de turbulência, visando uma comparação dos resultados simulados com os dados experimentais da literatura. Posteriormente, foi feito um estudo experimental e de simulação para avaliar o efeito da rotação do eixo interno sobre a queda de pressão no escoamento de fluidos não-Newtonianos (soluções aquosas de Goma Xantana e de Carboximetilcelulose a 0,2% em peso) numa seção anular concêntrica e outra com excentricidade fixa (E = 0,75). Finalmente, elaborou-se um planejamento fatorial de experimentos do tipo 3k com quatro variáveis, tais como, concentração de Goma Xantana (0,05%, 0,10% e 0,15%), excentricidade (0,0; 0,23 e 0,46), vazão volumétrica (5, 7 e 9 m3/h) e rotação do eixo interno (0, 100 e 200 rpm). Seguindo este planejamento foram levantados dados experimentais de queda de pressão, bem como, simulações numéricas (CFD) em seções periódicas para obtenção de resultados de velocidade axial, com intuito de avaliar efeito do movimento de rotação excêntrica variável sobre a dinâmica do escoamento de fluidos não-Newtonianos em espaços anulares. / Doutor em Engenharia Química

Fluidos Não-newtonianos estão presentes em grande quantidade na natureza e em muitas aplicações industriais. Tais fluidos apresentam uma variedade de comportamentos específicos. Dentre eles podemos citar: elasticidade, plasticidade, viscosidade variando com a taxa de deformação, tixotropia. Esta tese de doutorado apresenta um recente modelo para Fluidos Estruturados Tixotrópicos (de Souza Mendes, 2009), no qual baseasse nas tradicionais equações de balanço de momentum e massa, em uma equação constitutiva de Maxwell-b modificada e uma equação de evolução para o nível de estrutura do material. Na equação constitutiva de Maxwell-b modificada, tempo de relaxação e viscosidade estrutural são funções da estrutura do material. A equação evolutiva para o parâmetro de estruturação prevê efeitos de tixotropia, dependentes do tempo de equilíbrio do material. As equações que constituem o modelo mecânico para Fluidos Estruturados Tixotrópicos são aproximadas numericamente através do Método de Elementos Finitos de Galerkin Mínimos-quadrados (GLS). Tal método adicionou termos dependentes de malha ao método clássico de Galerkin, de forma a aumentar a estabilidade da formulação original, proporcionando compatibilizar os sub-espaços de velocidade e pressão. São investigados escoamentos creeping flow de Fluidos Estruturados Tixotrópicos em dois problemas clássicos de engenharia: em torno de um cilindro confinado entre duas placas e em uma expansão planar abrupta. Parâmetros relevantes ao modelo são variados em faixas pertinentes ao problema físico simulado e os resultados demonstraram uma boa capacidade de previsão. / Non-Newtonian fluids are present in large quantities in nature and in many industrial applications. Such fluids exhibit a variety of specific behaviors. Among them we can mention: elasticity, plasticity, viscosity varying with the strain rate, thixotropy, etc. This thesis presents a new model for thixotropic Structured Fluids (de Souza Mendes, 2009), in which were a basis in traditional balance equations of mass and momentum, the constitutive equation of Maxwell-type and an evolution equation for the level structure of the material. In the modified constitutive equation of Maxwell-b, relaxation time and structural viscosity are functions of material structure. The structure parameter evolutive equation provides effects of thixotropy, dependent on the equilibration time of the material. The equations which constitute the mechanical model for Structured Thixotropic fluids are approximated numerically using the Galerkin Least-squares Finite Element Method (GLS). Such a method added mesh dependent terms to the classical method of Galerkin in order to increase the stability of the original formulation, providing compatibility between sub-spaces of velocity and pressure. Are investigated Structured Thixotropic Fluids creeping flow in two classical problems in engineering: around a cylinder confined between two plates and in a planar abrupt expansion. Relevant parameters to the model are varied in pertinent ranges to physical problem simulated and the results demonstrated a good predictive capability.

abstract: This dissertation describes Space Vector 1 and Space Vector 2, two video games that introduce Newtonian mechanics concepts. Space Vector 1 is a side-scrolling game, in which players choose to drop bombs or supplies. Players had to identify if the physics was correct during a mission, or they had to plot the trajectory of a falling object, which was then simulated. In Space Vector 2, players were given velocity and acceleration values and had to plot the trajectory of a spaceship across a grid, or players were given a trajectory of a spaceship on a grid and had to program the velocity and acceleration values to produce the trajectory. Space Vector 1 was evaluated with 65 college undergraduates. Space Vector 2 was evaluated with 18 high school students. All participants were given a subset of the Force Concept Inventory, a standard assessment tool in physics education, as a pretest and posttest. Space Vector 1 was evaluated with a single group pretest-posttest design. Space Vector 2 was evaluated with a 2 x 2 ANOVA, where the factors were game mechanic (prediction mechanic or programming mechanic) and bonus questions (bonus question after a mission or no bonus question). Bayesian statistical methods were used for the data analysis. The best estimate for the average change in test scores for Space Vector 1 was a score gain of 1.042 (95% Highest Density Interval (HDI) [0.613, 1.487]) with an effect size of 0.611 (95% HDI [0.327, 0.937]). The best estimate for the grand mean of change scores in Space Vector 2 was an increase of 0.78 (95% HDI [-0.3, 1.85]) with an effect size of 0.379 (95% HDI [-0.112, 0.905]). The prediction/no bonus question version produced the largest change in score, where the best estimate for the mean change score was an increase of 1.2. The estimation intervals for the Space Vector 2 results were wide, and all included zero as a credible value. / Dissertation/Thesis / Doctoral Dissertation Educational Technology 2014

The study of non-Newtonian flow is presents itself as relevant in bioengineering field, specially for design of devices that conduct blood, as arterial bypass grafts. Improvements in reducing energy dissipation and blood cell damage caused by artificial flows can be achieved by using numerical simulation and optimization methods. Thus, the present work proposes the study of design channels for steady, incompressible non-Newtonian flow, by using Topology Optimization Method based on the density method. The fluid flow is modeled with the Navier-Stokes equations coupled with Carreau-Yasuda constitutive equation for the dynamic viscosity to take into account the effects of the non-Newtonian blood properties. The Topology Optimization Method distributes regions of solid and fluid, given a volume constraint, within a specified domain in order to obtain a geometry and layout that minimizes energy dissipation, shear stress and vorticity by using the material pseudo-density as design variable. To apply this method to fluidic systems design, a fictional porous media based on Darcy equation is introduced. The flow model is implemented in its discrete form by using the Finite Element Method through the OpenSource platform FEniCS, applied to automate the solution of mathematical models based on differential equations. The optimization problem is solved by using the library DOLFIN-adjoint and IPOpt optimizer. Optimized topologies of channels for blood flow, focusing in arterial bypass grafts, are presented to illustrate the proposed method. / O estudo de escoamento de fluidos não-Newtonianos apresenta-se relevante no campo de bioengenharia, em especial no projeto de dispositivos para condução de sangue, como bypass arterial. Melhorias na redução de dissipação de energia e no dano às células sanguíneas causados por fluxos artificiais podem ser obtidas através do uso de técnicas de simulação e otimização numéricas. Deste modo, este trabalho propõe o estudo do projeto de canais para escoamentos incompressíveis em regime permanente de fluidos não-Newtonianos através do Método de Otimização Topológica baseado no método de densidade. O escoamento é modelado com as equações de Navier-Stokes acopladas com a equação constitutiva de Carreau-Yasuda para a viscosidade dinâmica, para que sejam considerados os efeitos das propriedades não-Newtonianas do sangue. O Método de Otimização Topológica distribui regiões de sólido e fluido, dada uma restrição de volume, dentro de um domínio especificado de modo a obter uma geometria e configuração que minimize a dissipação de energia, tensão de cisalhamento e vorticidade, utilizando a pseudo-densidade do material como variável de projeto. Para aplicar este método a sistemas fluidos, um meio poroso fictício, baseado na equação de Darcy, é introduzido. O modelo de escoamento é implementado em sua forma discreta utilizando o Método de Elementos Finitos através da plataforma OpenSource FEniCS, aplicada para automatizar a solução dos modelos matemáticos baseados em equações diferenciais, e o problema de otimização é resolvido utilizando a biblioteca DOLFIN-adjoint e otimizador IPOpt. Topologias otimizadas de canais para fluxo de sangue, com foco em bypass arterial, são apresentadas para ilustrar o método proposto.

O processamento térmico de alimentos visa garantir qualidade e inocuidade pela inativação de micro-organismos e enzimas. Geralmente ocorre sobreprocessamento, levando à perda de características nutricionais e sensoriais e à elevação de custos operacionais. Foi desenvolvida a modelagem matemática (modelos térmico, mássico, hidráulico e reativo) de um equipamento bitubular para o processamento térmico contínuo de um alimento líquido homogêneo em regime laminar difusivo, para determinação das distribuições de temperatura e letalidade. No modelo foram incorporados parâmetros para quantificar os efeitos das difusividades térmica e mássica efetivas na direção radial ao escoamento. O modelo contempla três seções: aquecimento; tubo de retenção e resfriamento, em que as seções de aquecimento e resfriamento são trocadores de calor modulares. Foram considerados os seguintes volumes de controle: alimento, tubo interno, fluido de utilidade, tubo externo, isolamento térmico e ar ambiente. Balanços diferenciais de energia e massa foram aplicados para modelar as trocas térmicas e a distribuição de micro-organismos, enzimas ou nutrientes. Condições de contorno foram aplicadas para manter a continuidade entre as seções e módulos. O modelo foi resolvido através do método de diferenças finitas, discretizando as componentes axiais e radiais. No estudo de caso foram feitas simulações para o processamento térmico de suco de amora, quantificando os efeitos dos parâmetros difusivos e das variáveis de processo sobre os atributos de qualidade nutricional (antocianina) e qualidade microbiológica (levedura). Na validação dos modelos térmico e mássico os efeitos de mistura e difusão na direção radial foram quantificados através do ajuste da condutividade térmica efetiva e número de Peclet modificado. Utilizou-se um pasteurizador em escala laboratorial e os fluidos: mistura glicerina/água 80% (newtoniano) e solução de CMC 1% (pseudoplástico) nas vazões de 10 a 50 L/h. Os resultados indicam que o modelo proposto representou satisfatoriamente as distribuições de temperaturas, letalidade e comportamento experimental com reduzida complexidade computacional. / The thermal processing ensures quality and safety by inactivation of micro-organisms and enzymes. Generally, over-processing occurs, resulting in sensorial and nutritional losses and operating costs increase. A mathematical model (thermal, mass, hydraulic and reactive) of a double-pipe pasteurizer has developed for the continuous thermal processing of a liquid food in laminar diffusive regime, to obtain the temperature and lethality distributions. Parameters to quantify the effects of thermal and mass effective diffusivities in the radial direction were incorporated in the model. The model comprises three zones: heating; holding tube and cooling, where the heating and cooling zones are modular double-pipe heat exchangers. The following control volumes were considered: food, inner tube, utility fluid, outer tube, thermal insulation and ambient air. Energy and mass differential balances were used for modeling the heat transfer and the destruction of micro-organisms, enzymes or nutrients. Boundary conditions were applied to maintain the continuity between zones and modules. The finite difference method was used to discretize the model in the axial and radial directions. A simulation study case for blueberry juice thermal processing was made, analyzing the effects of the diffusive parameters and processing variables of the thermal treatment in the nutritional quality (anthocyanin) and microbiological quality (yeasts) attributes. In the validations of the heat and mass models, the mixture and diffusive effects in the radial direction were quantified by adjusting the heat conductivity and the modified Peclet number. A laboratory scale pasteurizer was used with the following fluids: glycerin/water mixture 80% (newtonian) and CMC 1% solution (pseudoplastic) in flows rates between 10 and 50 L/h. The obtained results indicate that the proposed model successfully represented the temperature and lethality distributions and experimental behavior with reduced computational complexity.

Fluidos Não-newtonianos estão presentes em grande quantidade na natureza e em muitas aplicações industriais. Tais fluidos apresentam uma variedade de comportamentos específicos. Dentre eles podemos citar: elasticidade, plasticidade, viscosidade variando com a taxa de deformação, tixotropia. Esta tese de doutorado apresenta um recente modelo para Fluidos Estruturados Tixotrópicos (de Souza Mendes, 2009), no qual baseasse nas tradicionais equações de balanço de momentum e massa, em uma equação constitutiva de Maxwell-b modificada e uma equação de evolução para o nível de estrutura do material. Na equação constitutiva de Maxwell-b modificada, tempo de relaxação e viscosidade estrutural são funções da estrutura do material. A equação evolutiva para o parâmetro de estruturação prevê efeitos de tixotropia, dependentes do tempo de equilíbrio do material. As equações que constituem o modelo mecânico para Fluidos Estruturados Tixotrópicos são aproximadas numericamente através do Método de Elementos Finitos de Galerkin Mínimos-quadrados (GLS). Tal método adicionou termos dependentes de malha ao método clássico de Galerkin, de forma a aumentar a estabilidade da formulação original, proporcionando compatibilizar os sub-espaços de velocidade e pressão. São investigados escoamentos creeping flow de Fluidos Estruturados Tixotrópicos em dois problemas clássicos de engenharia: em torno de um cilindro confinado entre duas placas e em uma expansão planar abrupta. Parâmetros relevantes ao modelo são variados em faixas pertinentes ao problema físico simulado e os resultados demonstraram uma boa capacidade de previsão. / Non-Newtonian fluids are present in large quantities in nature and in many industrial applications. Such fluids exhibit a variety of specific behaviors. Among them we can mention: elasticity, plasticity, viscosity varying with the strain rate, thixotropy, etc. This thesis presents a new model for thixotropic Structured Fluids (de Souza Mendes, 2009), in which were a basis in traditional balance equations of mass and momentum, the constitutive equation of Maxwell-type and an evolution equation for the level structure of the material. In the modified constitutive equation of Maxwell-b, relaxation time and structural viscosity are functions of material structure. The structure parameter evolutive equation provides effects of thixotropy, dependent on the equilibration time of the material. The equations which constitute the mechanical model for Structured Thixotropic fluids are approximated numerically using the Galerkin Least-squares Finite Element Method (GLS). Such a method added mesh dependent terms to the classical method of Galerkin in order to increase the stability of the original formulation, providing compatibility between sub-spaces of velocity and pressure. Are investigated Structured Thixotropic Fluids creeping flow in two classical problems in engineering: around a cylinder confined between two plates and in a planar abrupt expansion. Relevant parameters to the model are varied in pertinent ranges to physical problem simulated and the results demonstrated a good predictive capability.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / Neste trabalho, foram estudados vÃrios tipos de escoamentos laminares de fluidos incompressÃveis Newtonianos e nÃo-Newtonianos. Isto foi feito atravÃs do estudo da interaÃÃo destes escoamentos com geometrias complexas atravÃs de modelagem computacional e da soluÃÃo numÃrica das equaÃÃes de conservaÃÃo do momento e continuidade de massa. Numa primeira etapa, a modelagem computacional de uma rede de poros foi usada para a gerar padrÃes de agregados granulares resultando de mecanismos de erosÃo-deposiÃÃo de grÃos leves. A geometria da rede de poros foi alterada dinamicamente de acordo com a transferÃncia de momento do escoamento para as partÃculas localizadas em cada vÃrtice da rede de poros. Os resultados mostraram que, para esse processo irreversÃvel, o modelo foi capaz de reproduzir padrÃes tÃpicos de processos de erosÃo bem-conhecidos. Numa segunda etapa, um separador de partÃculas semelhante à estrutura pulmonar foi proposto com base nas propriedades de escoamento em uma estrutura ramificada e nas propriedades de transporte inercial das partÃculas, quantificadas atravÃs do nÃmero de Stokes. Os resultados indicaram que a variaÃÃo dos parÃmetros de construÃÃo da estrutura ramificada leva a um regime eficiente do processo de separaÃÃo em um amplo espectro de valores do nÃmero de Stokes. Por Ãltimo, o escoamento de vÃrios fluidos nÃo-Newtonianos atravÃs de meios porosos desordenados em trÃs-dimensÃes foi estudado. Os resultados mostraram, para fluidos do tipo lei-de-potÃncia, que o escoamento pode ser descrito como uma curva universal se o nÃmero de Reynolds e a permeabilidade hidrÃulica forem redefinidos de maneira apropriada. Fluidos de Bingham tambÃm foram estudados atravÃs do modelo de Herschel-Bulkley. Neste caso, as simulaÃÃes revelaram que as interaÃÃes entre a geometria complexa do espaÃo poroso, as propriedades reolÃgicas do fluido e os efeitos inerciais do escoamento sÃo responsÃveis por uma melhora substancial da permeabilidade hidrÃulica do sistema em valores intermediÃrios do nÃmero de Reynolds. / In this work many types of incompressible laminar Newtonian and Non-Newtonian flows are studied. The interplay of these flows with complex geometries was investigated using computational modeling and numerical solution of the conservation of momentum and mass continuity equations. As a first step, the computational modeling of a network of pores was adopted to reveal the formation patterns caused by the mechanism of erosion-deposition of light grains. The geometry of the pore network was changed dynamically according to the flow momentum transfer for particles located on each vertex of the pore network. The results showed that, for this irreversible processes, the model is capable of reproducing patterns of formation of well-known erosion processes. In a second step, a particle separator inspired on the lung structure was proposed based on the flow properties in a branched structure and transport of inertial particles, quantified in terms of the Stokes number. The results indicated that the variation of construction parameters of the branched structure leads to an efficient design of the separation process in a wide range of values of the Stokes number. Finally, the flow of non-Newtonian fluids through three-dimensional disordered porous media has been studied. The results showed, for power-law fluids that the flow can de described as a universal curve if the Reynolds number and the hydraulic permeability are redefined properly. The flow of Bingham fluids was also studied using the model of Herschel-Bulkley. In this case, the simulations showed that the interaction between the complex geometry of the pore space, the rheological properties of the fluid and the inertial effects of the flow is responsible for a substantial improvement of the hydraulic permeability of the system at intermediate values of the Reynolds number.

Cette thèse est une contribution à la simulation numérique des transferts de quantité de mouvement et de chaleur dans les écoulements turbulents de fluides non-Newtoniens dans une conduite cylindrique fixe. La viscosité du fluide utilisé est décrite par la loi d'Ostwald de Waele. Deux modèles sous-mailles dans l'approche des simulations des grandes échelles ont été considérés : le modèle dynamique de Germano et al. (1991) et le modèle de Smagorinsky non-Newtonien. Ils sont utilisés pour décrire les mécanismes physiques mis en jeu dans les écoulements isothermes de ces fluides à rhéologie complexe. Les transferts thermiques sont simulés avec le modèle de Smagorinsky non-Newtonien. Ces derniers sont traités en deux parties. La première concerne les échanges de chaleur sans influence sur la distribution des vitesses. Il s'agit des écoulements non-thermo dépendants ou écoulements isothermes. La deuxième partie concerne la résolution des écoulements thermo dépendants qui mettent l'accent sur les modifications induites par le couplage vitesse-température. Les champs turbulents sont analysés statistiquement en moyennant dans le temps et dans l'espace (suivant les directions périodiques) les champs instantanés de vitesse et de température pour établir les profils moyens de vitesse et de température, les rms, la tension de Reynolds, les flux de chaleur, les moments d'ordre plus élevé (coefficients de dissymétrie et d'aplatissement), les pdf (fonction de densité de probabilté), les jpdf (fonction de densité de probabilité jointe), le coefficient de frottement, le nombre de Nusselt... Ces différentes grandeurs sont analysées en fonction des divers paramètres qui gouvernent le problème: les nombres de Reynolds et de Prandtl, l’indice d'écoulement et le nombre de Pearson / This thesis is a numerical contribution of momentum and heat transfer of turbulent pipe flows of non-Newtonian fluids. The apparent viscosity of the fluid is modelled by a power-law (Ostwald de Waele model). Two models subgrid of LES were considered: the dynamic model of Germano et al. (1991) and model Smagorinsky non-Newtonian. They are used to describe the physical mechanisms involved in the isothermal flow of these complex rheology fluids. Heat transfer are simulated with the model of non-Newtonian Smagorinsky. These are processed in two parts. The first concerns the heat exchange without affecting the velocity distribution. This is non-thermo dependent flow or isothermal flow. The second part concerns the resolution of thermo dependent flows that focus on changes induced by the temperature-velocity coupling. The turbulent fields are analyzed statistically by averaging over time and space (according to the periodic directions) the instantaneous field of velocity and temperature to establish the average profiles of velocity and temperature, the root mean square of turbulent fluctuations (rms), Reynolds stress, the heat flow, the moments of higher order (skewness and flatness), the pdf (probability density function), the jpdf (attached probability density function), the coefficient of friction, the number of Nusselt ... These differents variables are analyzed for various parameters governing the problem: the Reynolds and Prandtl flow index and the number of Pearson