La méthode Smoothed Particle Hydrodynamics (SPH) est une méthode lagrangienne, sans maillage développée initialement pour des simulations de phénomènes astrophysiques. Depuis, elle a connu de nombreuses applications, notamment pour la simulation des écoulements des fluides. Contrairement aux méthodes utilisant un maillage, la méthode SPH peut gérer de manière naturelle et sans traitement spécifique les simulations des écoulements à sur- face libre et multiphasiques avec interface subissant de grandes déformations. Dans cette thèse, une modélisation SPH des écoulements des fluides multiphasiques a été réalisée en tenant compte de différentes complexités (écoulements à surface libre et multiphasiques interfacials) et de natures d'écoulement (si- mulation des fluides, des sols et les deux en interactions). Un modèle SPH faiblement compressible (WCSPH) a été proposé pour simuler les écoulements des fluides multiphasiques avec interface comprenant plus de deux phases de fluide. Ce modèle inclut le développement d’une nouvelle formulation de force de tension de surface en utilisant un opérateur SPH consistant de premier ordre. Une modification de condition généralisée aux parois solides a été apportée pour qu’elle soit appliquée sur les écoulements des fluides multiphasiques avec des rapports de densité et de viscosité élevés. Une nouvelle loi de comportement dépendant de la pression nommée RBMC-αμ ( Regularized Bingham Mohr Coulomb où αμ est un paramètre libre) a également été développée. Cette loi peut simuler les fluides (Newtonien, Binghamien), les sols (cohésif, frictionnel) et les deux en interactions. La loi précédente étant sensible à la pression, une extension du terme diffusif δ-SPH a été faite pour le cas des écoulements des fluides multiphasiques afin de réduire les oscillations de pression à haute fréquence qui sont dues à l’utilisation d’une équation d’état. La validation et l’application des modèles développés dans cette thèse sont montrées à travers plusieurs cas tests de difficulté croissante. / Smoothed Particle Hydrodynamics (SPH) is a Lagrangian gridless method developed initially to simulate astrophysical phenomena, and since it has been known for a large number of applications, especially for fluid flow simulations. Contrary to the grid-based method, the SPH method can handle free surface and interfacial fluid flow simulation including large deformations naturally and without the need for any specific treatment. In this thesis a SPH modeling of multiphase fluid flows has been achieved with consideration of different complexities ( free surface and interfacial fluid flows) and natures (simulation of fluids, soil and both in interactions). A consistent weakly compressible SPH model (WCSPH) has been proposed to simulate interfacial multiphase fluid flows with more than two fluid phases. This model includes a new expression of the surface tension force using a first order consistency SPH operator. A modification to the well known generalized wall boundary condition have been brought in order to be applied to multiphase fluid flow with large density and viscosity ratios. A new pressure-based constitutive law named RBMC-αμ (Regularized Bingham Mohr Coulomb with αμ is free parameter) has been developed in this thesis. This model can simulate fluids (Newtonian, Binghamton), soils (cohesive, frictional) and both in interactions. Because the previous model is pressure sensitive, an extension of δ-SPH diffusive term has been proposed for multiphase fluid flows to overcome the hight frequency pressure oscillations due to the determination of pressure from an equation of state. The validation and application of the developed models have been shown in this thesis through several test-cases of increasing difficulty.

In this thesis, a numerical method is developed for simulating non-isothermal multiphase flows, which are important in many technical applications such as crystal growth and welding. The method is based on the arbitrary Lagrangian Eulerian method of Li (2013). The interface is represented explicitly by mesh lines, and is tracked by an adaptive moving unstructured mesh. The $P2-P1d$ finite element method (FEM) is used for discretisation and the incompressible Navier-Stokes equations are solved by the uzawa method. Firstly, a thorough study is presented on the method's capability in numerically representing the force balance condition on the interface. An inaccurate representation of this condition induces the non-physical spurious currents, which degrade the simulation accuracy especially when the viscous damping is weak (small Ohnesorge number, $Oh$). For the example of a circular/spherical droplet, the interfacial tension and the associated pressure jump are exactly balanced numerically and thus the static Laplace solution exists in our method. The stability of this solution is examined numerically. The amplitude of the dimensionless spurious currents is found to be around $10^{−15}$ for $Oh \geq 10^{−3} $. Another benchmark test is the axisymmetric oscillation of a freesurface droplet/bubble. The simulation results are in good agreement with the analytical solution for $Oh = 10^{−3}$. This is by far the first successful simulation of droplet/bubble oscillation with such weak viscous damping and it demonstrates the ability of our method in simulating flows with strong capillary forces. Secondly, a numerical treatment of interface topology changes is incorporated into our method for studying problems with interface breakup. Thanks to the adaptive mesh generator, the thin region between the interface boundary and another boundary consists of one layer of elements. The interface topology change is performed once the minimum distance between the two boundaries falls below a pre-set scale $l_{breakup}$ . The numerical implementation is verified through two different examples: dripping faucet and droplet coalescence. Remarkably good agreement has been obtained with the experimental results. The simulation of the low Oh dripping problem shows both the accuracy and robustness of our method. The simulation of droplet coalescence demonstrates the great advantage of our method in solving problems with a large disparity in length scales. Finally, an FEM solver for temperature is developed and the non-isothermal effects are included in our method for the purpose of simulating non-isothermal multiphase flows. The modified method is validated to be accurate through three benchmark examples: natural convection in a cavity, thermocapillary convection of two layers, and droplet migration subject to a temperature gradient. Our method is then applied to investigate the liquid bridge breakup with thermocapillary effect. The non-isothermal liquid bridge breakup in the viscous and inertial regimes are studied. It has been found that the inertial regime breakup exhibits different pinchoff shapes as the Capillary number increases, and that the viscous regime breakup is accelerated by the thermocapillary motion.

Submitted by Silvana Teresinha Dornelles Studzinski (sstudzinski) on 2016-02-17T16:06:10Z No. of bitstreams: 1 Guilherme Alfredo Genehr_.pdf: 3248455 bytes, checksum: 2c7c7d772f1c7cc1743b696d11f69d05 (MD5) / Made available in DSpace on 2016-02-17T16:06:10Z (GMT). No. of bitstreams: 1 Guilherme Alfredo Genehr_.pdf: 3248455 bytes, checksum: 2c7c7d772f1c7cc1743b696d11f69d05 (MD5) Previous issue date: 2015-11-20 / UNISINOS - Universidade do Vale do Rio dos Sinos / Este trabalho apresenta a caracterização física de amostras de biomassas e inertes e a caracterização da fluidodinâmica de misturas binárias entre biomassa e areia, através da determinação das curvas de fluidização destas misturas. Como biomassa foram utilizadas casca de eucalipto (Eucalyptus) e casca de pinus (Pinus elliotti). Os experimentos foram realizados em um leito de bancada desenvolvido na Unisinos com diâmetro interno de 9,4 cm e 1,2 m de comprimento. A amostra de pinus possui um tamanho de partícula médio de 579,13 μm e a amostra de eucalipto um tamanho médio de partícula de 537,50 μm com massas específicas de 1,271 g/cm³ e 1,386 g/cm³ respectivamente. As misturas foram feitas com proporções entre 1,43% até 41,89% de massa de biomassa. Para os ensaios fluidodinâmicos foram determinadas as velocidades características inicial (ufi), aparente (ufa) e completa (ufc), além da velocidade de mínima fluidização (umf). Os métodos empregados foram o gráfico de queda de pressão em função da velocidade do gás e observações. As análises foram feitas com base na influência da natureza da biomassa, a fração de massa de biomassa contida na mistura e a comparação dos resultados experimentais em relação a correlação proposta na literatura. Os resultados mostraram que com o aumento da proporção de biomassa as velocidades características tendem a aumentar, com exceção das amostras de areia 01 com pinus. A correlação proposta pelos autores Paudel e Feng (2013) apresentou uma boa estimativa para a previsão da velocidade de mínima fluidização de misturas de biomassa e inerte com erros relativos médios absolutos de 12,70%, 31,90%, 140,33% e 19,10% para as misturas de areia 01 com eucalipto, areia 02 com eucalipto, areia 01 com pinus e areia 02 com pinus, respectivamente. / This paper presents the physical characterization of samples of biomass and inert and the characterization of fluid dynamics of binary mixtures of sand and biomass, by determining the fluidization curves from these mixtures. Eucalyptus bark (Eucalyptus) and pine bark (Pinus elliottii) were used as biomass. The experiments were performed in a bench bed developed at the Unisinos with an internal diameter of 94 cm and 1.2 m in length. The biomass samples have an average particle size of 579.13 μm for pine and 537.50 μm for eucalyptus with specific real mass of 1,271 g/cm³ and 1.386 g/cm³ respectively. The mixtures were prepared with proportions between 1.43% to 41.89% by weight of biomass. The initial (ufi), the apparent (ufa), the complete (ufc), and the minimum fluidization velocity (umf) were determined for fluid dynamic tests. The methods employed were the pressure drop graph as a function of gas velocity and observations. The analyzes have been performed concerning the influence of the nature of the biomass, the mass fraction of biomass contained in the mixture and comparison of the experimental results regarding the correlation proposed in the literature. The results showed that with the increase of the proportion of biomass characteristics speeds tend to increase, with the exception of the sand 01 with pine mixtures. The correlation proposed by the authors Paudel and Feng (2013) presented a good estimate for the prediction of the minimum fluidization velocity of mixtures of biomass and inert with absolute average relative errors of 12.70%, 31.90%, 140.33% and 19.10% for mixtures of sand 01 with eucalyptus, sand 02 with eucalyptus, sand 01 with pine and sand 02 with pine respectively.

Um modelo matemático multifásico para a solidificação equiaxial de ligas binárias capaz de prever o efeito de taxa de resfriamento e da concentração de soluto no tamanho médio final de grãos foi proposto no presente trabalho. O modelo matemático foi desenvolvido através do conceito de envelope envolvendo os grãos, utilizando as equações de conservação de energia, massa e espécies químicas. O modelo de nucleação utilizado possibilita que novos núcleos possam surgir durante todo o período de resfriamento. As equações diferenciais foram obtidas através de uma média volumétrica das equações de conservação em um volume elementar representativo contendo três \"pseudofases\": sólido, líquido interdendrítico e líquido extradendrítico. O efeito de algumas variáveis de processamento sobre o tamanho médio final de grão foi analisado. Os resultados do modelo proposto foram comparados com resultados de alguns modelos disponíveis na literatura. / A multiphase mathematical model for the equiaxed solidification of binary alloys was proposed in the present work to predict the effects of the cooling rate and the average solute concentration on the final average grain size. The mathematical model was based on the concept of the grain envelope and on the conservation of energy, mass and chemical species. A nucleation model was adopted to consider the nucleation of new grains during the whole solidification time. The differential equations were derived from the volume average of conservation equations within a representative elementary volume that consisted of three pseudophases: solid, interdendritic liquid, and extradendritic liquid. The effect of some processing variables on the final average grain size was studied. The results from the proposed model were compared with those available in the literature from other models.

A estimativa das taxas de coalescência em sistemas de fluxo multifásico é um factor chave para prever situações críticas , em que as fases começam a separar . Esta pode ser uma orientação para controlar a estabilidade da emulsão e para impedir a substituição desnecessária em processos em que são usados de óleo / água (O / A) dispersões . Estudos CFD apresentar alternativas atraentes para prever o aumento de tamanho de gota , devido a fenômenos de coalescência nos casos em que as emulsões fluem através de diferentes sistemas de circulação , e estão sujeitas a repentinas expansões e contrações . Neste estudo o comportamento de emulsões sob diferentes condições de fluxo foi investigada por acoplamento em equações de Navier Stokes com modelos de equilíbrio populacional e de gotículas de coalescência. Este estudo analisa os efeitos de coalescência em um sistema de O / A, quando as forças hidrodinâmicas promoverem eventos em que duas gotículas colidem para dar origem a novas gotículas. No estudo, o desempenho dos diferentes modelos de turbulência (K-, k-Q) é comparado a avaliar a sua influência sobre a interacção entre as fases. Diferentes algoritmos para acoplamento pressão-velocidade (PIMPLE, SIMPLEC, PIMPLEC) são avaliados também, uma vez que podem afetar os tempos computacionais e de convergência. O efeito das condições de fluxo e as propriedades de cada fase da distribuição de tamanho das gotículas é estudado para o fluxo de emulsões O / A numa tubagem com súbita alargamento. Os resultados permitem avaliar o efeito de coalescência e modelo de eficiência na média de gotículas de diâmetro Sauter. O desempenho de cada modelo em relação ao tempo computacional e a convergência é também discutida. / The estimation of coalescence rates in multiphase flow systems is a key factor to predict critical situations, in which phases start to separate. This can be a guideline to control emulsion stability and to prevent unnecessary replacement in processes where oil/water (O/W) dispersions are used. CFD studies exhibit attractive alternatives to predict the increase of droplet size due to coalescence phenomena in cases where emulsions flow through different circulation systems, and are subject to sudden expansions and contractions. In this study the behavior of emulsions under different flow conditions was investigated by coupling Navier Stokes equations with population balance and droplet coalescence models. This study analyzes coalescence effects in an O/W system, when hydrodynamic forces promote events in which two droplets collide to give rise to new droplets. In the study, the performance of different turbulence models (k-, k-) is compared by evaluating their influence on the interaction between phases. Different algorithms for pressure-velocity coupling (PIMPLE, SIMPLEC, PIMPLEC) are also evaluated, since they can affect computational times and convergence. The effect of flow conditions and properties of each phase on droplet size distribution is studied for the flow of O/W emulsions in a pipeline with sudden enlargement. The results enable to evaluate the effect of coalescence model and efficiency on the mean Sauter diameter of droplets. The performance of each model with respect to computational time and convergence is also discussed.

Transportation of unprocessed multiphase reservoir fluids from deep/ultra deep offshore through a long subsea tieback/pipeline is inevitable. This form of transportation is complex and requires accurate knowledge of critical transport velocity, flow pattern changes, phase velocity, pressure drop, particle drag & lift forces, sand/liquid/gas holdup, flow rate requirement and tieback sizing etc at the early design phase and during operation for process optimisation. This research investigated sand transport characteristics in multiphase, water‐oil‐gas‐sand flows in horizontal, inclined and vertical pipes. Two critical factors that influence the solid particle transport in the case of multiphase flow in pipes were identified; these are the transient phenomena of flow patterns and the characteristic drag & lift coefficients ( D C , L C ). Therefore, the equations for velocity profile were developed for key flow patterns such as dispersed bubble flow, stratified flow, slug flow and annular flow using a combination of analytical equations and numerical simulation tool (CFD). The existing correlations for D C & L C were modified with data acquired from multiphase experiment in order to account for different flow patterns. Minimum Transport Velocity (MTV) models for suspension and rolling were developed by combining the numerically developed particle velocity profile models with semi‐empirical models for solid particle transport. The models took into account the critical parameters that influence particle transport in pipe flow such as flow patterns and particle drag & lift coefficients, thus eliminate inaccuracies currently experienced with similar models in public domain. The predictions of the proposed MTV models for suspension and rolling in dispersed bubble, slug flow and annular flow show maximum average error margin of 12% when compared with experimental data. The improved models were validated using previously reported experimental data and were shown to have better predictions when compared with existing models in public domain. These models have the potential to solve the problems of pipe and equipment sizing, the risk of sand deposition and bed formation, elimination of costs of sand unloading, downtime and generally improve sand management strategies.

A indústria de petróleo e gás tem trabalhado para o desenvolvimento de métodos que permitam o monitoramento e controle da produção de fluidos nos poços. Para isso são desenvolvidos equipamentos específicos para medição de vazões. Este trabalho apresenta um sistema baseado em medidores de vazão por obstrução ou pressão diferencial (placas de orifício, bocais e Venturis) para determinação em linha de vazões de produção (óleo, gás e água) em poços de petróleo. A partir das equações de conservação da massa e do momento para escoamento unidimensional e considerando escoamento isotérmico com fases incompressíveis, sem mudança de fase, com fases líquidas homogeneizadas e com escorregamento constante entre as fases líquida e gasosa, é deduzida uma relação geral entre vazão mássica total e queda de pressão. Utilizando a correlação de Chisholm para o escorregamento, é realizada uma comparação entre os resultados obtidos com o modelo homogêneo e o modelo de escorregamento constante. Por meio de uma caracterização dos fluidos em produção em estado permanente e utilizando o modelo de black oil para o sistema óleo-gás, são determinadas as vazões de produção na condição de referência. São realizadas validações dos resultados do modelo com dados experimentais obtidos numa bancada experimental em Aracaju (Sergipe) e em poços de Urucu (Amazonas). A comparação com os resultados experimentais mostra que as predições feitas com o modelo de escorregamento podem ser consideradas satisfatórias, levando-se em conta que o modelo foi desenvolvido de maneira independente, sem parâmetros de ajuste dos dados experimentais. / The oil and gas industry has been working to develop methods to monitor and control the fluid production in the wells. For this purpose, specific equipments are developed for measuring stream flows. This work presents a system based on differential pressure (or obstruction) flow meters (orifice plates, Venturis and nozzles) for online determination of production flows (oil, gas and water) in oil wells. Starting from the mass and momentum conservation equations for one-dimensional, isothermal flow and considering incompressible phases without phase change, homogenized liquid phases and constant slip between gas and liquid phases, a general relationship between total mass flow and pressure drop is derived. Using Chisholmts correlation for the slip, a comparison is made between the results obtained with the homogeneous model and the constant slip model. Through a characterization of the production fluids in steady state and using the black oil model for the oil-gas system, the production flows are determined at the reference condition. A validation is made between results obtained with the model and experimental data obtained in a rig at Aracaju (Sergipe) and in wells at Urucu (Amazonas). The comparison with experimental results shows that the predictions made with the slip model may be considered satisfactory, taking into account that the model was developed independently, without parameters adjusted from the experimental data.

O presente trabalho tem como objetivo fundamental a construção de um sistema de identificação capaz de diagnosticar em tempo real as diferentes configurações de escoamentos bifásicos horizontais. É importante ressaltar que o desenvolvimento deste know-how é capital para a operação eficaz de instalações de manipulação e ou transporte de fluidos multifásicos, e representa, hoje, um dos grandes desafios nas indústrias do petróleo e termonuclear. O princípio de funcionamento do sistema proposto baseia-se nos sinais captados por um sensor de pressão flutuante de resposta rápida, e no seu pósprocessamento com auxílio da transformada de Gabor e de uma rede neural convenientemente treinada. A implementação é tal que a operação de diagnóstico pode ser feita on-line, desde a aquisição dos sinais até o pósprocessamento. Resultados experimentais foram obtidos no circuito experimental do NETeF - Núcleo de Engenharia Térmica e Fluidos da USP - Universidade de São Paulo, para uma secção de testes horizo ntal com 12 m de comprimento e diâmetro interno de 30 mm. Em específico foram ensaiados os seguintes padrões de escoamento ar-água: estratificado liso, ondulado, intermitente, anular e a bolhas. Os resultados mostram que, dependendo dos limites de detecção pré-estabelecidos, todos o principais padrões de escoamento bifásico horizontal são identificados corretamente. / The fundamental objective of this work is the construction of an identification system capable of diagnosing in real time different configurations of horizontal two-phase flow patterns. It is important to emphasize that the development of this know-how is capital to the efficient operation of facilities for manipulation and transportation of multiphase fluids, and represents, today, one of the most important challenges in the oil and thermonuclear industries. The working principle of the proposed system is based on the signals acquired by a rapid response fluctuating pressure sensor, and on its post processing through Gabor Transform and on a conveniently trained artificial neural network. The implementation is accomplished in way that the diagnosis operation is performed on-line, from signal acquisition to post-processing. Experimental results were obtained on the experimental circuit at NETeF - Núcleo de Engenharia Térmica e Fluidos of USP - Universidade de São Paulo, at São Carlos, using a horizontal test section, with 12 m length and 30 mm internal diameter. Experiments were done with the following air-water flow patterns: stratified smooth, wavy, intermittent, annular, and bubbly. Results show that, depending on the preset detection limits, all the main horizontal two phase flow patterns were correctly identified.

A indústria de petróleo e gás tem trabalhado para o desenvolvimento de métodos que permitam o monitoramento e controle da produção de fluidos nos poços. Para isso são desenvolvidos equipamentos específicos para medição de vazões. Este trabalho apresenta um sistema baseado em medidores de vazão por obstrução ou pressão diferencial (placas de orifício, bocais e Venturis) para determinação em linha de vazões de produção (óleo, gás e água) em poços de petróleo. A partir das equações de conservação da massa e do momento para escoamento unidimensional e considerando escoamento isotérmico com fases incompressíveis, sem mudança de fase, com fases líquidas homogeneizadas e com escorregamento constante entre as fases líquida e gasosa, é deduzida uma relação geral entre vazão mássica total e queda de pressão. Utilizando a correlação de Chisholm para o escorregamento, é realizada uma comparação entre os resultados obtidos com o modelo homogêneo e o modelo de escorregamento constante. Por meio de uma caracterização dos fluidos em produção em estado permanente e utilizando o modelo de black oil para o sistema óleo-gás, são determinadas as vazões de produção na condição de referência. São realizadas validações dos resultados do modelo com dados experimentais obtidos numa bancada experimental em Aracaju (Sergipe) e em poços de Urucu (Amazonas). A comparação com os resultados experimentais mostra que as predições feitas com o modelo de escorregamento podem ser consideradas satisfatórias, levando-se em conta que o modelo foi desenvolvido de maneira independente, sem parâmetros de ajuste dos dados experimentais. / The oil and gas industry has been working to develop methods to monitor and control the fluid production in the wells. For this purpose, specific equipments are developed for measuring stream flows. This work presents a system based on differential pressure (or obstruction) flow meters (orifice plates, Venturis and nozzles) for online determination of production flows (oil, gas and water) in oil wells. Starting from the mass and momentum conservation equations for one-dimensional, isothermal flow and considering incompressible phases without phase change, homogenized liquid phases and constant slip between gas and liquid phases, a general relationship between total mass flow and pressure drop is derived. Using Chisholmts correlation for the slip, a comparison is made between the results obtained with the homogeneous model and the constant slip model. Through a characterization of the production fluids in steady state and using the black oil model for the oil-gas system, the production flows are determined at the reference condition. A validation is made between results obtained with the model and experimental data obtained in a rig at Aracaju (Sergipe) and in wells at Urucu (Amazonas). The comparison with experimental results shows that the predictions made with the slip model may be considered satisfactory, taking into account that the model was developed independently, without parameters adjusted from the experimental data.

Escoamentos multifásicos estão presentes em diversas aplicações industriais, principalmente na indústria do petróleo. Um dos casos de aplicação, objeto de estudo desse trabalho, é a determinação da produção de poços de petróleo através de válvulas choke. É apresentada uma revisão dos efeitos físicos e do equacionamento adotado pelos principais modelos multifásicos existentes para tais válvulas. Um estudo de sensibilidade de tais efeitos físicos é realizado, analisando as possíveis alternativas para a diferença de velocidade entre as fases, o mecanismo adotado para a troca de calor entre as fases, a influência da energia cinética a montante da válvula, a influência da área efetiva da garganta e a metodologia de cálculo da recuperação de pressão a jusante da válvula. Conclui-se que dos diversos fatores que influenciam no cálculo da vazão mássica e da condição crítica, a área efetiva da garganta é um parâmetro importante e que é necessário uma maior investigação de como determinar tal parâmetro. / Multiphase flow are present in many industrial applications, mainly at the petroleum industry. One of these application cases, aim of this work study, is to determine a petroleum well production by the choke valves. It is presented a revision of the physical effects and for the adopted equation by the main existing multiphase models for such valves. A sensibility study of such physical effects is performed, analyzing the possible alternatives for the phases velocities difference, the adopted mechanism for the heat transfer between the phases, the upstream kinetic energy influence, the throat effective area influencie and the calculation methodology adopted for the valve downstream pressure recover. It is concluded that from many factors that influence in the mass flow and critical condition calculation, the throat effective area is a important parameter and it is necessary a deeper investigation in how to determine such parameter.