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Topology optimization method applied to design channels considering non-newtonian fluid flow. / Método de otimização topológica aplicado ao projeto de canais considerando escoamento de fluídos não-newtonianos.Jacqueline de Miranda Kian 19 October 2017 (has links)
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.
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Modelagem e investigação numérica de escoamentos de fluidos estruturados tixotrópicosFonseca, Cleiton Elsner da January 2013 (has links)
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.
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Escoamento de fluidos complexos e transporte de partÃculas em geometrias irregulares. / Complex fluid flows and particle transport in irregular geometries.Apiano Ferreira de Morais Neto 14 April 2011 (has links)
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.
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[pt] ESCOAMENTO DE FLUIDOS NÃO NEWTONIANOS ATRAVÉS DE CANAIS CONVERGENTES-DIVERGENTES / [en] FLOW OF NON-NEWTONIAN FLUIDS THROUGH CONVERGING-DIVERGING CHANNELSMAURICIO LANE 23 December 2005 (has links)
[pt] Neste trabalho foi analisado o escoamento de fluidos não
Newtonianos através de canais
axisimétricos convergentes divergentes. A solução da
conservação de massa e de
conservação de momento foi obtida numericamente via
volumes finitos utilizando o
programa de computador Fluent. A equação constitutiva de
fluidos Newtonianos
generalizados foi utilizada para modelar o comportamento
não Newtoniano, utilizando a
equação constitucional de Shunk-Scriven para cálculo da
viscosidade, que assume como
sendo a média geométrica ponderada pelo classificador de
escoamento R entre a
viscosidade de cisalhamento e a viscosidade de extensão.
Os resultados de perda de
pressão e vazão são comparados com os resultados
calculados pela relação simplificada
proposta por Souza Mendes e Naccache, 2002 entre a perda
de carga e vazão de fluidos
viscoelásticos fluindo através do meio poroso, para
analisar a sua performance. / [en] In this work, the flow of non-Newtonian fluids through
axisimmetric convergingdiverging
channels is analyzed. The solution of mass and momentum
conservation
equations is obtained numerically via finite volume
technique using the Fluent software.
The Generalized Newtonian Fluid constitutive equation was
used to model the non-
Newtonian fluid behavior, using the Shunk-Scriven model
for the viscosity, where a
weighted geometric mean by the flow classifier R between
shear and extensional
viscosities is assumed. The results of pressure drop and
flow rate are compared to the
ones predicted by a previously proposed simplified
relation (Souza Mendes and
Naccache, 2002) between pressure drop and flow rate, for
viscoelastic fluids flow
through porous media, in order to analyze its performance.
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Laminar heat transfer to Newtonian and Non-Newtonian fluids in tubes. Temperature and velocity profiles were determined experimentally for heating and cooling of Newtonian and non-Newtonian fluids in tubes and the results compared with theoretical predictions incorporating a temperature-dependent viscosity.Pavlovska-Popovska, Frederika January 1975 (has links)
This thesis is concerned with a theoretical and experimental
study of the hydrodynamics and heat transfer characteristics
of viscous fluids flowing in tubes under laminar conditions.
Particular attention has been given to the effects of the rheological
properties and their variation with temperature. A review of
problems of this type showed that in spite of the many potential
applications of the results in a wide range of industries
the subject had not been well developed and further work is justified in order to fill some of the gaps in our knowledge.
The early part of the thesis considers the justification of the
work in this way and sets down the scope and objectives. A computer progracune was then developed to allow the
governing equations of the problem to be solved numerically to
give the velocity and temperature profiles and pressure drop for
both heating and cooling conditions. The results were also
presented in the form of Nusselt numbers as a function of the
Graetz numberp since this form is useful for engineering design
purposes. The validity of the predictions were then checked by a
programme of experimental work. Temperature and velocity profiles
have been measured in order to provide a more severe test of the
theory than could be imposed by the measurement of overall heat
transfer rates. A combined thermocouple probe/Pitot tube was
developed to allow simultaneous measurements of velocity and
temperature to be made. A Newtonian oil and two non-Newtonian
Carbopol solutions were studied. This is the first time that
velocity and temperature profiles have been measured for non-Newtonian
fluids in this type of situation. The results of the work heve shown that
(a) the velocity and temperature profiles and pressure
drops are greatly affected by the temperature dependence
of the rheological properties and since real viscous
fluids are normally very temperature-sensitive it is
important that this effect is properly taken into
account.
(b) the engineering design correlations commonly used for
the prediction of heat transfer coefficients can be
seriously in error, especially for cooling conditions
and when non-Nevitonian fluids are being considered.
(c) a mathematical model can be developed which accurately
describes all the phenomena and gives predictions which
are very close to those observed experimentally. An important objective was to develop more accurate engineering
design correlations for non-isothermal pressure drop and heat
transfer rates. / University of Bradford
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Physics-based Modeling Techniques for Analysis and Design of Advanced Suspension Systems with Experimental ValidationFarjoud, Alireza 31 January 2011 (has links)
This research undertakes the problem of vibration control of vehicular and structural systems using intelligent materials and controllable devices. Advanced modeling tools validated with experimental test data are developed to help with understanding the fundamentals as well as advanced and novel applications of smart and conventional suspension systems.
The project can be divided into two major parts. The first part is focused on development of novel smart suspensions using Magneto-Rheological (MR) fluids in unique configurations in order to improve efficiency, controllability, and safety of today's vehicles. In this part of the research, attention is paid to fundamentals as well as advanced applications of MR technology. Extensive rheological studies, both theoretical and experimental, are performed to understand the basic behaviors of MR fluids as complex non-Newtonian fluids in novel applications. Using the knowledge obtained from fundamental studies of MR fluids, unique application concepts are investigated that lead to design, development, and experimental testing of two new classes of smart devices: MR Hybrid Dampers and MR Squeeze Mounts. Multiple generations of these devices are built and tested as proof of concept prototypes. Advanced physics-based mathematical models are developed for these devices. Experimental test data are used to validate the models and great agreement is obtained. The models are used as design tools at preliminary as well as detailed design stages of device development. The significant finding in this part of the research is that MR fluids can deliver a much larger window of controllable force in squeeze mode compared to shear and valve modes which can be used in various applications.
The second part of the research is devoted to the development of innovative design tools for suspension design and tuning. Various components of suspension systems are studied and modeled using a new physics-based modeling approach. The component of main interest is the shim stack assembly in hydraulic dampers which is modeled using energy and variational methods. A major finding is that the shims should be modeled individually in order to represent the sliding effects properly when the shim stack is deflected. Next, the individual component models are integrated into a full suspension model. This model is then used as a tool for suspension design, synthesis, and tuning. Using this design tool, suspension engineers in manufacturing companies and other industrial sections can easily perform parametric studies without the need to carry out time consuming and expensive field and laboratory tests. / Ph. D.
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Shear-induced microstructure in hollow fiber membrane dopesPeterson, Emily Cassidy 13 January 2014 (has links)
Hollow fiber membranes offer the opportunity to dramatically reduce the energy required to perform gas separations in the chemical industry. The membranes are fabricated from highly non-Newtonian precursor materials, including concentrated polymer solutions that sometimes also contain dispersed particles. These materials are susceptible to shear-induced microstructural changes during processing, which can affect the characteristics of the resulting membrane. This thesis explores several shear-related effects using materials and flow conditions that are relevant for fiber spinning. The findings are discussed as they relate to membrane processing, and also from the standpoint of enhancing our fundamental understanding of the underlying phenomena.
First, the effect of shear on polymeric dope solutions was investigated. Shear-induced demixing—a phenomenon not previously studied in membrane materials—was found to occur in membrane dopes. Phase separation experiments also showed that shear-induced demixing promotes macrovoid formation. The demixing process was found to depend not only on the instantaneous shear conditions, but also on the shear history of the solution. This suggests that low-shear flow processes that occur in the upstream tubing and channels used for fiber spinning can affect macrovoid formation.
The effect of viscoelastic media on dispersed particles was also explored. Shear-small-angle light scattering results showed that particles suspended in membrane dope solutions formed aggregated, vorticity-oriented structures when shear rates in the shear-thinning regime of the polymer solution were applied. Shear rates well below the shear-thinning regime did not produce any structure. In fact, the application of a Newtonian shear rate to a sample already containing the vorticity structure caused the sample to return to isotropy. Measurements using a highly elastic, constant-viscosity Boger fluid showed that strong normal forces alone are not sufficient to form the vorticity structures, but that shear thinning is also required.
Lastly, a study was conducted examining cross-stream migration of particles dispersed in viscoelastic media. Fluids exhibiting varying degrees of shear thinning and normal forces were found to have different effects on the particle distribution along the shear gradient axis in Poiseuille flow. Shear thinning was found to promote migration toward the channel center, while normal stresses tended to cause migration toward the channel walls.
In addition to hollow fiber spinning, many other industrially relevant applications involve polymer solutions and suspensions of particles in viscoelastic media. Often, the properties and performance of the material depend strongly on the internal microstructure. The results from the research described in this thesis can be used to guide the design of materials and processing conditions, so that the desired microstructural characteristics can be achieved.
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Three dimensional modelling of generalized Newtonian fluids in domains including obstructionsBoukanga, Noel Rupert Thierry January 2010 (has links)
Three dimensional flow regimes are encountered in many types of industrial flow processes such as filtration, mixing, reaction engineering, polymerization and polymer forming as well as environmental systems. Thus, the analyses of phenomena involved fluid flow are of great importance and have been subject of numerous ongoing research projects. The analysis of these important phenomena can be conducted in laboratory through experiments or simply by using the emerging computational fluid dynamics (CFD) techniques. But when dealing with three dimensional fluid flow problems, the complexities encountered make the analysis via the traditional experimental techniques a daunting task. For this reason, researchers often prefer to use the CFD techniques which with some care taken, often produce accurate and stable results while maintaining cost as low as possible. Many CFD codes have been developed and tested in the past decades and the results have been successful and thus encouraging researchers to develop new codes and/or improve existing codes for the solutions of real world problems. In this present project, CFD techniques are used to simulate the fluid flow phenomena of interest by solving the flow governing equations numerically through the use of a personal computer. The aim of this present research is to develop a robust and reliable technique which includes a novel aspect for the solution of three dimensional generalized Newtonian fluids in domains including obstructions, and this must be done bearing in mind that both accuracy and cost efficiency have to be achieved. To this end, the finite element method (FEM) is chosen as the CFD computational method. There are many existing FEM techniques namely the streamline upwind Petrov-Galerkin methods, the streamline diffusion methods, the Taylor-Galerkin methods, among others. But after a thorough analysis of the physical conditions (geometries, governing equations, boundary conditions, assumptions …) of the fluid flow problems to be solve in this project, the appropriate scheme chosen is the UVWP family of the mixed finite element methods. It is scheme originally developed to solve two dimensional fluid flow problems but since the scheme produced accurate and stable results for two dimensional problems, then attempt is made in this present study to develop a new version of the UVWP scheme for the numerical analysis of three dimensional fluid flow problems. But, after some initial results obtained using the developed three dimensional scheme, investigations were made during the course of this study on how to speed up solutions' convergence without affecting the cost efficiency of the scheme. The outcomes of these investigations yield to the development of a novel scheme named the modified three dimensional UVWP scheme. Thus a computer model based on these two numerical schemes (UVWP and the Modified UVWP) is developed, tested, and validated through some benchmark problems, and then the model is used to solve some complicated tests problems in this study. Results obtained are accurate, and stable, moreover, the cost efficiency of the computer model must be mentioned because all the simulations carried out are done using a simple personal computer.
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Aproximação numérica de escoamento de fluidos power-law utilizando o código livre MFIXSiqueira, Eduardo Schnurr 31 January 2013 (has links)
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Previous issue date: 2013-01-31 / Nenhuma / Fluidos não-Newtonianos apresentam relação não linear entre a tensão de cisalhamento e a taxa de cisalhamento, ou seja, sua viscosidade não é constante. Eles estão presentes na natureza (sangue, lamas, areia movediça), assim como em muitos produtos industriais classificam-se nesta categoria, tais como produtos alimentícios (iogurtes, queijos cremosos, doces de frutas, chocolate ), tintas, borrachas, polímeros fundidos, soluções poliméricas, adesivos e gomas. Nos casos em que a viscosidade diminui com aumento da taxa de cisalhamento, os fluidos são classificados como pseudoplásticos; os que apresentam comportamento inverso são classificados como dilatantes. O modelo Power-Law é utilizado em engenharia para modelar ambos os comportamentos. Computational Fluid Dynamics - CFD (Dinâmica dos Fluidos Computacional) é uma ferramenta utilizada na simulação numérica de escoamentos de fluidos Newtonianos e não-Newtonianos. Inúmeros códigos comerciais e livres são utilizados atualmente, dentre eles o código livre e aberto Multiphase Flow with Interphase Exchanges (MFIX), o qual foi desenvolvido visando a simulação numérica de escoamentos multifásicos reativos do tipo sólido-gás em leitos fluidizados. O objetivo do presente trabalho é implementar no MFIX o modelo Power-Law, validar a modificação e realizar um estudo de caso utilizando o modelo. Com a implementação de um modelo não-Newtoniano ao código, pretende-se abrir caminho para a simulação de escoamentos multifásicos do tipo sólido-líquido não-Newtoniano, bem como aumentar a potencialidade do código, a fim de se estudar casos monofásicos de escoamentos de fluidos não-Newtonianos sujeitos à transferência de calor. O modelo implementado foi validado através da comparação com resultados da literatura para o escoamento em uma cavidade. Posteriormente, foram realizadas simulações do escoamento não isotérmico e isotérmico em torno de um prisma de seção quadrada imerso em um canal. Foram variados os parâmetros número de Prandtl, índice do modelo Power-Law e razão de bloqueio. Verificou-se que o número de Nusselt tem influência direta e é fortemente influenciado pela razão de bloqueio e inversamente, com pouca intensidade, pelo índice Power-Law. O número de Prandtl também influenciou diretamente no número de Nusselt e demonstrou que, quanto maior o seu valor, mais acentuada fica a variação do número de Nusselt em função da razão de bloqueio. / Non-Newtonian fluids exhibit nonlinear relationship between the shear stress and the shear rate, that is, its viscosity is not constant. They are present in nature (blood, sludge) as well as many industrial products are classified in this category, such as food products (yoghurt, soft cheeses, jams, chocolate), paints, rubber, polymer melts, polymer solutions, adhesives and gums. In cases where viscosity decreases with increasing shear rate, the fluids are classified as shear-thinning, while the opposite behavior is classified as shear-thickening. The Power-Law model is used in engineering to model both behaviors. Computational Fluid Dynamics - CFD is a tool used in the numerical simulation of Newtonian and non-Newtonian fluid flow. Numerous free and commercial codes are used today, including the free and open source Multiphase Flow with Interphase Exchanges (MFIX), which was developed to the numerical simulation of multiphase (fluid-solid) and reactive flows. The goal of this work is to implement the Power-Law model in MFIX, validate the implementation and conduct a case study using the model implemented. With the implementation of a non-Newtonian model to the code, a new possibility for the simulation of multiphase flows of solid-non-Newtonian liquids is opened, as well as there is an increase in the capability of the code regarding the study of single-phase fluid flows of Non-Newtonian fluids subject to heat transfer. The model was implemented and validated by comparison with literature results for the flow in a lid driven cavity. Subsequently, simulations were carried out concerning isothermal and non-isothermal flows around a square cylinder immersed in a channel. Parameters of analyses consisted of Prandtl number, Power-Law index and blockage ratio, for a fixed Reynolds number. It was found that the Nusselt number is strongly influenced by the blockage ratio and decreases with the increase of the Power-Law index. The Prandtl number also directly influences the process. With its increase, the dependence of the Nusselt number with the blockage ratio is more pronounced.
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Análise fatorial de fluido viscoplástico dependente da temperatura através de um método estabilizado de elementos finitosTeles, Márcio Lembi 16 September 2016 (has links)
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Previous issue date: 2016-09-16 / Nenhuma / Este trabalho apresenta uma análise fatorial, através de fluidodinâmica computacional, do escoamento e transferência de calor para fluidos viscoplásticos a partir de um cilindro confinado entre paredes paralelas. Considera-se que as propriedades reológicas sensíveis à temperatura, o que acopla os problemas térmico e fluidodinâmico de forma bilateral. Foi desenvolvida uma formulação baseada no método estabilizado de elementos finitos Galerkin Mínimos Quadrados (GLS – Galerkin Leart-Squares) para a aproximação de escoamentos não newtonianos com transferência de calor e propriedades reológicas termodependentes. Esta formulação foi implementada em um código computacional próprio. Para a modelagem das tensões viscosa, foi utilizado um modelo de líquido newtoniano generalizado, com função viscosidade dada pelo modelo de Herschel-Bulkley regularizado conforme Papanastasiou e propriedades termodependentes – a tensão inicial de escoamento e o índice de consistência. Os resultados numéricos foram investigados utilizando os adimensionais: número de Reynolds (Re), número de Herschel-Bulkley (Hb), número de Prandtl (Pr), índice de potência (n) e coeficientes de dependência térmica (a* e b*). Foi realizado um planejamento experimental fatorial completo 2K, com objetivo de avaliar a influência destes parâmetros na taxa de transferência de calor, através do número de Nusselt (Nu), e na perda de carga localizada devido à obstrução do canal pelo cilindro. / This paper presents a factor analysis using computational fluid dynamics, flow and heat transfer for viscoplastic fluids from a cylinder confined between parallel walls. It is considered that the rheological properties sensitive to temperature, which couples the thermal and fluid dynamic problems bilaterally. It was developed a formulation based on stabilized finite element method Galerkin Least Squares (GLS - Galerkin Leart-Squares) for approaching non-Newtonian flow with heat transfer and rheological properties dependent terms. This formulation has been implemented in a proper computer code. For the modeling of viscous stresses, a generalized Newtonian fluid model was used, with viscosity function given by the Herschel-Bulkley regularized model as Papanastasiou and properties dependent terms – the initial yield stress and consistency index. The numerical results were investigated using the dimensionless: Reynolds number (Re), Herschel-Bulkley number (Hb), Prandtl number (Pr), potency index (n) and temperature dependence coefficients (a* and b*). It conducted a full factorial experimental design 2K, with objective to evaluate the influence of these parameters on the heat transfer rate, through the Nusselt number (Nu), and localized head loss due to the cylinder by duct obstruction.
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