Les mélanges multiphasiques en déséquilibre de vitesse sont habituellement modélisés à l'aide d'un modèle à 6 ou 7 équations (Baer and Nunziato, 1986). Ces modèles sont très efficaces pour traiter des mélanges avec effets d'interpénétration. Ils peuvent aussi être utilisés pour traiter des problèmes à interface dans lesquels il est nécessaire de respecter les conditions d'interface (continuité de la vitesse normale et de la pression). Ceci est réalisé à l'aide de solveurs de relaxation mécanique (Saurel and Abgrall, 1999). Une autre méthode consiste à utiliser un modèle à une vitesse et une pression (Kapila et al., 2001). Cependant, de nombreuses applications font intervenir des interfaces instables entre fluides. On traite habituellement ces zones de mélanges turbulents en utilisant un modèle à une vitesse et en résolvant spatialement les diverses instabilités. Dans de nombreuses applications cela devient impossible en raison du trop grand nombre de « jets » et de « bulles ». De plus, on rencontre des difficultés numériques y compris pour le calcul d'une instabilité isolée (Liska and Wendroff, 2004). Dans ce manuscrit, nous abordons le problème de la modélisation des zones de mélange avec des modèles multiphasiques. Cela pose un sérieux problème de modélisation pour des écoulements évoluant d'une situation où l'interface est bien définie (une seule vitesse) vers une configuration de mélange de fluides à plusieurs vitesses. Cette question a été abordée par Besnard and Harlow (1988), Youngs et al. (1989), Chen et al. (1996), Glimm et al. (1999), Saurel et al. (2003) par exemple. / Multiphase mixtures with velocity disequilibrium are usually modelled with 6 or 7 equations models (Baer and Nunziato, 1986). These models are very efficient to model mixtures with velocity drift effects. They can also be used to model interfacial flows where the respect of interface conditions (continuous normal velocity and pressure) is mandatory. Such aim is usually achieved with the help of stiff mechanical relaxation solvers (Saurel and Abgrall, 1999). Another option is to use single pressure and single velocity models (Kapila et al., 2001). However, many applications involve unstable fluid-fluid interfaces for which flow conditions range from well separated fluids to fully mixed ones. The usual way to deal with these turbulent mixing zones is to use a single velocity flow model and to resolve spatially the various instabilities. However, spatial resolution of these instabilities in many applications is impossible as too many ‘jets' and ‘bubbles' are present. Also, numerical difficulties and large inaccuracies are present even for an isolated instability computation (Liska and Wendroff, 2004). In this work, we address the issue of mixing zone modelling with multiphase flow models. This poses the serious difficulty of model derivation for flows conditions ranging from well defined interfaces (single velocity) to fluid mixtures evolving with several velocities. This issue has been addressed by Besnard and Harlow (1988), Youngs et al. (1989), Chen et al. (1996), Glimm et al. (1999), Saurel et al. (2003) to cite a few. In Saurel et al. (2010) an extension of the Kapila et al. (2001) model was done to deal with permeation effects through material interfaces.

[pt] Sistemas de escoamento multifásico se formam ao longo de um poço de produção de petróleo. A análise do comportamento do escoamento através da coluna de produção é realizada com o apoio de ferramentas computacionais e é essencial para o projeto e operação de um sistema de produção de petróleo. Os simuladores comerciais disponíveis para esse tipo de análise exigem aquisição de licença, cujo custo é elevado, restringindo seu uso às grandes companhias petrolíferas e aos renomados institutos de pesquisa. Além disso, esses programas não permitem a visualização da metodologia utilizada para o tratamento do problema físico e para a solução numérica empregada, e nem a alteração de parâmetros internos, tornando seu uso restrito a certas classes de problemas. Apesar da grande demanda e utilidade desse tipo de software ainda há poucos trabalhos desenvolvidos nessa área. Esta pesquisa tem como objetivo apresentar o desenvolvimento de um simulador de escoamento multifásico simplificado e aberto, com aplicação na otimização da produção de óleo e gás. Dentre as aplicações do programa podemos citar a obtenção das curvas de gradiente de pressão e a otimização de gás-lift. Um estudo paramétrico foi conduzido, mostrando a influência de parâmetros como, por exemplo, o diâmetro da tubulação. Os resultados obtidos foram comparados com a literatura e são fisicamente coerentes. Sendo assim, o programa desenvolvido mostra-se promissor. / [en] Multiphase flow systems are formed along an oil production well. The analysis of the flow behavior through the production column is performed with the aid of computational tools, and is very important to the design and optimization of the oil well production operation. In general, the commercial softwares available to analyze this process are very expensive, which restrict its use to some particular companies. In addition, the methodology used to analyze the physical problem, and the numerical solution are fixed and closed, which restrict its use to certain classes of problems, since it is not possible to change or improve the numerical solution. Despite the great demand and use of this kind of software, there are few researches in this area. This research aims to present the development of a simplified multiphase flow simulator open to public, with application to the optimization of oil and gas production wells. Among the applications are the plot of pressure-distribution curves and the optimization of gas-lift. A parametric study is performed, showing the influence of some governing parameters, such as tubing diameter, in the production flow rate. The results obtained were compared with pertinent literature and are physically reasonable, showing that the software developed is promising.

[pt] Dentre os custos considerados na explotação de um campo de petróleo, os de perfuração constituem uma parcela significativa do total. Dentro deste cenário, devemos estar atentos à remoção dos cascalhos gerados pela perfuração, também referido como limpeza de poços. Esta operação é, ainda hoje, um tema crítico na perfuração de poços de alta inclinação, pois os cascalhos que se depositam devido à ação da gravidade, formam um leito no interior do espaço anular formado entre a coluna de perfuração e o revestimento. Quando este leito ocupa grande parte do espaço anular, ele é responsável por diversos problemas na perfuração, como por exemplo, desgaste prematuro da broca, baixas taxas de penetração, fraturamento da formação, torques e arrastes excessivos na coluna de perfuração, prisão da coluna de perfuração, interrupção da circulação de fluido, aumento da pressão no anular, etc. Se esta situação não for tratada adequadamente, o problema pode provocar a perda do poço. A tese propõe uma modelagem para o escoamento multifásico na perfuração de poços de petróleo, capaz de avaliar a formação do leito de cascalhos e prever oscilações de pressões no anular decorrentes do escoamento. O modelo adotado é o de duas camadas, onde o espaço anular é dividido em duas regiões: leito e suspensão. O leito (Região 1) é formado pelos cascalhos que se sedimentam devido ao efeito gravitacional enquanto a suspensão (Região 2) é a porção do anular acima do leito depositado, formada pelo fluido de perfuração e os cascalhos transportados. As equações que constituem o modelo implementado são dadas pelas equações de conservação de massa para os sólidos e para o líquido e as equações de conservação de quantidade de movimento para o leito e para a suspensão. O método dos volumes finitos foi utilizado para a discretização das equações diferenciais juntamente com o método de Newton para a solução do sistema não-linear de equações. A solução é dada através das seguintes variáveis: altura do leito, velocidade dos sólidos no leito e na suspensão, velocidade do fluido no leito e na suspensão, pressão no anular e concentração de sólidos no anular. Exemplos de aplicação da metodologia são apresentados e mostram o comportamento das variáveis envolvidas ao longo do tempo. Os exemplos mostram a eficácia da metodologia para simular operações de perfuração, em especial, a limpeza de poço. / [en] Among the costs considered on an oil field exploration, the drilling process related ones constitute a significant share. Consequently, the focus on the removal of cuttings generated by the drilling process, or the hole cleaning operation, is essential. This operation remains a critical issue in the drilling of high inclination-wells, since the cuttings tend to deposit themselves due to gravity´s action, forming a bed in the annular space formed between the drill string and the casing. When this bed takes a sizable fraction of the annular space, it becomes responsible for many problems that appear on the drilling stage, such as premature bit´s exhaustion, low rates of penetration, formation fracture, excessive torque and drag on the drillstring, stuck pipe, fluid flow interruption, etc. If this situation is not treated properly, it may cause the loss of the well. This present thesis proposes a model for multiphase flow in the wellbore drilling, capable of evaluating the formation of the cuttings´ bed and to predict oscillations of pressures in annulus due to the flow. A two-layer model is adopted, where the annular space is divided in two regions: bed and suspension. The bed (Region 1) is formed by the cuttings, which were deposited due to the action of gravitational force, while the suspension (Region 2) is the portion of the annular above the deposited bed, formed by the drilling fluid and cuttings. The constitutive equations of the aforementioned model are given by the equations of mass conservation for solids and liquids and the momentum conservation equations for the bed and the suspension. The finite volumes method was used to turn the differentials equations into discrete ones, while the Newton´s method was applied for the solution of the nonlinear system of equations. The solution is given through the following variables: bed height, solid velocity and fluid velocity both in bed and suspension, annular pressure and solid concentration in the annular. Examples of application of the methodology are presented, showing the behavior of the involved variables through time. The examples show the efficacy of the methodology to simulate drilling operations, in special hole cleaning ones.

Afin de prédire l’évolution de la composition chimique du laitier dans différents procédés sidérurgiques, un modèle CFD a été développé. Les coefficients de transfert de masse sont estimés à partir des modèles basés sur les paramètres physico-chimiques et hydrodynamiques, comme par exemple la diffusivité des espèces chimiques et la divergence de l’interface. Ces modèles ont été développé pour la prédiction du transfert gaz-liquide où le les nombres de Schmidt (Sc=ν⁄D) sont relativement faible (Sc≈200). Par contre, les procédés industriels ont un nombre de Sc considérablement plus importante, de l’ordre de 103 à 104. Pour évaluer la pertinence de ces modèles, l’hydrodynamique au voisinage d’une interface liquide-liquide a été étudiée. Un modèle CFD et des mesures par l’anémométrie laser (LDA) ont été utilisés pour calculer et valider les champs de vitesse d’une maquette à eau d’une lingotière de coulée continue (CC).Le modèle de transfert de masse d’une lingotière de coulée continu industriel nous a montré que les coefficients de transfert de masse ne sont pas distribués de manière homogène, et les propriétés physiques du laitier ne doivent pas y être non plus. Cette distribution non-homogène a été confirmée par des essais physiques. Les écoulements calculés numériquement ont été utilisé pour prédire les coefficients de transfert de masse entre les deux phases liquide. Ces paramètres seront utilisés comme donnée d’entré pour un modèle de thermodynamique afin de prédire l’évolution de la composition chimique du laitier. / In order to characterize the mass transfer coefficients (MTC) of different species across liquid steel/slag interface, a multiphase Computational Fluid Dynamic (CFD) model was developed. MTC’s are estimated from models based on physicochemical and hydrodynamic parameters, such as mass diffusivity, interface shear and divergence strength. These models were developed for gas-liquid interactions with relative low Schmidt (Sc=ν⁄D) numbers (Sc≈200). However, the industrial processes involve mass transfer of chemical species with Sc number ranging from 103 to 104. To evaluate the applicability of these existing models, the fluid flow in the vicinity of a liquid/liquid interface is investigated. Computational Fluid Dynamic (CFD) and Laser Doppler Anemometry (LDA) were used to calculate and measure the velocity field on a continuous casting (CC) water model configuration. The work provides new insights and original measures to understand the fluid flow near liquid-liquid interfaces.The mass transfer model of an industrial continuous casting mold showed that the mass transfer coefficients are not homogeneously distributed, and slag properties should follow this trend. This non-homogeneity was confirmed by physical experiments performed with a water model of a CC configuration and its CFD representation. The calculated flow was used to predict the MTC and the interface area between phases, since the interface is constantly moving. These parameters will be the input of thermodynamic models to predict slag composition and viscosity. This methodology is currently under validation, and it will also be applied to improve steel plant performance in the desulphurization process.

L'objectif de cette thèse est de contribuer au développement et à la validation d'outils numériques permettant la Simulation aux Grandes Echelles (SGE) de l'allumage d'un écoulement turbulent diphasique dans une chambre de combustion. Pour ce faire, une méthode de dépôt d'énergie modélisant l'apport d'énergie lié au claquage de la bougie d'allumage a été implémentée dans la chaîne de calcul CEDRE. Cette méthode a été validée sur une simulation de l'allumage d'un écoulement laminaire purement gazeux d'air et de propane. Une SGE de l'écoulement d'air du MERCATO a été effectué à l'aide du solveur Navier-Stokes CHARME de CEDRE. Cette simulation reproduit fidèlement l'écoulement turbulent non-réactif dans la chambre de combustion. Une méthode d'injection simplifiée FIMUR a été ajoutée au solveur lagrangien SPARTE de CEDRE. Dans cette méthode, des gouttes sont injectées directement au nez de l'injecteur avec une distribution de vitesse et de taille imposée. Une SGE de l'écoulement turbulent diphasique dispersé non-réactif dans la chambre MERCATO a ensuite été réalisée avec cette méthode. La comparaison des champs particulaires moyens de vitesse et de taille obtenus par simulation numérique avec les données expérimentales est satisfaisante. Enfin, des SGE de l'allumage de la chambre MERCATO ont été effectuées à partir du champ diphasique non-réactif simulé et de la méthode de dépôt d'énergie développée. Selon l'instant du dépôt d'énergie, les simulations conduisent à des allumages réussis ou ratés. La propagation de la flamme dans la chambre pour un allumage réussi a fait l'objet d'une analyse détaillée pour tenter de déterminer les principaux facteurs l'influençant. / The goal of this thesis is to contribute to the development and validation of numerical tools for the Large Eddy Simulation (LES) of the ignition of a turbulent multiphase flow in a combustion chamber. An energy deposition method that models the energy supplied by the spark plug to the flow was implemented in the CEDRE code. This method was validated on a simulation of the ignition of a purely gaseous laminar propane-air flow. Then, a LES of the non-reacting gas flow in the monosector combustor MERCATO was performed with the Navier-Stokes solver CHARME of the CEDRE code. The comparison between simulations and experiments demonstrates that the main flow field features are well reproduced. In order to simulate the non-reacting dispersed two-phase flow of the same configuration, a simplified injection method called FIMUR was implemented in the Lagrangian solver SPARTE of the CEDRE code. In this method, droplets are injected directly at the tip of the injector with velocities deduced from experimental correlations while the size distribution is directly obtained from experimental data. The comparison of the mean droplet velocity and diameter fields in the vicinity of the injector between simulations and experiments appears satisfactory. Finally, LES's of the ignition of the MERCATO were performed using the non-reacting two-phase flow simulations and the aformentioned energy deposition method. Depending on the instant of energy deposition, the simulations lead to successful or failed ignitions. The flame propagation in a successful ignition was analysed in order to attempt to determine the physical phenomena at play and to better understand them.

Ce travail est une investigation expérimentale de l’hydrodynamique, du transfert massique et du mélange induit par un panache de bulles dans des milieux de différentes viscosités. Dans l’industrie on est souvent confronté à des problèmes de transfert et de mélange d’une phase liquide et d’une phase gazeuse afin de provoquer des réactions chimiques ou biochimiques. La plupart du temps on utilise des colonnes à bulles, simple à mettre en œuvre, pour ce type de procédé. Mais il existe d’autres situations adaptées aux très grands volumes comme par exemple les bassins d’aération de traitement des eaux ou les méthaniseurs. Dans ce cas de figure, la répartition des injecteurs de gaz doit être adaptée aux dimensions du bassin et contribuer au mélange du liquide. Ceci est autant plus vrai pour le bioréacteur de méthanisation où l’état du liquide change en continu pendant la fermentation. Cependant, il y a un manque d'informations concernant l'hydrodynamique induit par l'injection de gaz en milieu visqueux. Afin de mieux comprendre l'écoulement, le transfert massique et finalement le mélange dans ces situations, il a été décidé d’étudier le cas d'un panache de bulles, généré par un seul injecteur dans des liquides de différentes viscosités. Pour cela des expériences ont été effectuées dans deux types de colonne à bulles avec injection centrale. Un grand nombre de méthodes métrologiques tel que la PIV, l’ombroscopie, différents capteurs etc. ont été utilisés. Une attention particulière a été donnée aux fluctuations à différentes échelles induit par le mouvement oscillatoire du panache de bulles. / This work is an experimental investigation on hydrodynamics, mass transfer and mixing induced by a bubble plume. In chemical engineering, people are often confronted to mixing problems of liquid and gas to create chemical or biochemical reactions. Most of the time, bubble column of big height compared to its diameter are used for such kind or processes.But there are also situations using large scale reactors like tanks for methanization or wastewater treatment. In such configurations, spargers must be adapted to reactor dimensions and fluid properties. This particularly important for methanization reactors since fluid properties are changing continuously during the fermentation. In order to understand hydrodynamics, mass transfer and mixing it is easier to study one single bubble swarm, or so called bubble plume, first.Different experiments were figured out in two different columns types. First one is a pseudo two dimensional column (6cm * 35 cm * 130cm ) allowing the application of optical metrological methods. Hence, the gas phase was studied via shadowgraphy and the liquid phase via PIV. Plus, light intensity measurements after dye injection were done. Besides, pressure sensors and oxygen probes were used.In this way, one could study the oscillating behavior, the corresponding characteristic frequency, mass transfer and mixing time scales. In order to analyze fluid properties, a copolymer called Breox was used. Plus, two different spargers generating different bubble shapes and sizes were applied to estimate their impact. Additional experiments in a cylindrical bubble column were performed at the HDZR in Germany. The same fluids and the same spargers were used to compare results from both geometries. Due to the difficulty to apply optical methods, a Wire-Mesh system recently developed at the HZDR was used to follow the bubble plume movement. Finally, first CFD simulations showing encouraging results are presented at the end of the manuscript.

abstract: The understanding of multiphase fluid flow in porous media is of great importance in many fields such as enhanced oil recovery, hydrology, CO2 sequestration, contaminants cleanup, and natural gas production from hydrate bearing sediments. In this study, first, the water retention curve (WRC) and relative permeability in hydrate bearing sediments are explored to obtain fitting parameters for semi-empirical equations. Second, immiscible fluid invasion into porous media is investigated to identify fluid displacement pattern and displacement efficiency that are affected by pore size distribution and connectivity. Finally, fluid flow through granular media is studied to obtain fluid-particle interaction. This study utilizes the combined techniques of discrete element method simulation, micro-focus X-ray computed tomography (CT), pore-network model simulation algorithms for gas invasion, gas expansion, and relative permeability calculation, transparent micromodels, and water retention curve measurement equipment modified for hydrate-bearing sediments. In addition, a photoelastic disk set-up is fabricated and the image processing technique to correlate the force chain to the applied contact forces is developed. The results show that the gas entry pressure and the capillary pressure increase with increasing hydrate saturation. Fitting parameters are suggested for different hydrate saturation conditions and morphologies. And, a new model for immiscible fluid invasion and displacement is suggested in which the boundaries of displacement patterns depend on the pore size distribution and connectivity. Finally, the fluid-particle interaction study shows that the fluid flow increases the contact forces between photoelastic disks in parallel direction with the fluid flow. / Dissertation/Thesis / Doctoral Dissertation Civil and Environmental Engineering 2016

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No. of bitstreams: 1 TeseGHJ.pdf: 12148265 bytes, checksum: 1180759f1c9f8691c3ce486239959cf5 (MD5) Previous issue date: 2016-03-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / The development of the design of chemical processes has received increasing improvement, incorporating sophisticated mathematical models, which allowed better simulation of its real behavior. Distillation is one of the most important and used separation techniques of components at industrial level, applied in a wide range of processes and its perfect working and optimization are economically crucial factors. Its great importance is due to the capacity of purify components of a mixture using the volatility difference among them as driving force. However, this technique represents 40% of the total energy consumption of an industrial facility. Some of models used for this, such as the models based on equilibrium and non-equilibrium stage concepts, usually provide useful results, but consider empirically many of the fluid dynamics phenomena by assuming a perfect mixture in each phase. Due to the development of the Information Technology (IT), in the numerical methods and improvement in models of multiphase flows, the investigation of complex turbulent flow problems is possible. One way to investigate these problems is to use the Computational Fluid Dynamics (CFD) tecniques. Therefore, it was adopted for this study a CFD model, with the main objective of evaluating the transport phenomena for the isothermal (water-air) and non-isothermal (ethanol-water) flows through the CFD techniques to simulate a distillation sieve tray. The proposed models had the following characteristics in common in the modeling: heterogeneous, three-dimensional, shear stress transport as turbulence model, and Eulerian-Eulerian approach at 1 atm. The continuity and momentum conservation equations were used to describe the isotherm model and for non-isothermal model it was added the energy and chemical species conservations equations. The simulated sieve trays geometries were based on experimental work of Solari e Bell (1986), to which it were observed the influence of the inlet downcomer presence or not on sieve tray. The results for isotherm flow showed the velocity profiles, the volume fractions, and clear liquid height under the influence of the inlet downcomer. For the non-isotherm flow, the results showed moreover the hydraulic parameters, the temperature profiles and ethanol mass fractions for vapor flow rates. Thus, the simulations of the isothermal system indicated a strong influence of the liquid velocity profile for the domain with downcomer inlet. In the non-isothermal system it was possible to determine the separation efficiency, which varied with the vapor flow rates on the sieve tray. The proposed methodology in this work proved to be appropriate and the computational fluid dynamics techniques presented to be an important tool in the design and optimization of sieve trays. / O desenvolvimento de projetos de processos químicos tem recebido aperfeiçoamento cada vez maior, incorporando modelos matemáticos mais sofisticados, os quais possibilitam uma maior aproximação do seu comportamento real. A destilação é uma das mais importantes técnicas de separação de componentes empregada a nível industrial nos mais diversos processos e o seu perfeito funcionamento e otimização são fatores economicamente cruciais. Sua importância dá-se na capacidade de separar os componentes de uma mistura utilizando a diferença de volatilidade entre eles como força motriz. Entretanto, trata-se de uma técnica que representa cerca de 40% da energia consumida em uma planta industrial. Alguns modelos utilizados nesses dispositivos, tais como os modelos baseados em conceitos de estágios de equilíbrio e não-equilíbrio, geralmente fornecem resultados úteis, mas consideram empiricamente muitos fenômenos fluidodinâmicos e assumem uma mistura perfeita em cada fase. Com o avanço da Tecnologia de Informação (TI), dos métodos numéricos e aperfeiçoamento em modelos de fluxos multifásicos, é possível a investigação de problemas complexos de escoamentos turbulentos. Uma das formas de investigar esses problemas é a aplicação das técnicas da Fluidodinâmica Computacional (CFD). Dessa maneira, foi adotado para o presente trabalho um modelo de CFD, tendo como objetivo principal a avaliar os fenômenos de transportes para os escoamentos isotérmico (água-ar) e não isotérmico (etanol-água) através das técnicas de CFD na simulação de um prato perfurado de destilação. Os modelos propostos, possuem em geral, as seguintes características em comum: modelo heterogêneo, tridimensional, modelo de turbulência shear stress transport e abordagem Euleriana-Euleriana a 1 atm. As equações da continuidade e de conservação da quantidade de movimento foram empregadas no modelo isotérmico e para o modelo não isotérmico foram adicionadas as equações de conservações de energia e das espécies químicas. Os domínios computacionais foram baseados no trabalho de Solari e Bell (1986), onde foram observados a influência da presença ou não do downcomer de entrada no prato perfurado. Os resultados para o escoamento isotérmico mostraram os perfis de velocidades de líquido, as frações volumétricas e a altura de líquido claro sob a influência do downcomer de entrada. Para o escoamento não isotérmico, os resultados mostraram, além dos parâmetros hidráulicos, os perfis de temperatura e das frações mássicas de etanol para várias vazões de vapor. Assim, as simulações do sistema isotérmico indicaram uma forte influência do perfil de velocidade de líquido na entrada prato para o domínio com downcomer. No sistema não isotérmico foi possível determinar a eficiência de separação, a qual variou com a vazão de vapor no prato. A metodologia proposta neste trabalho foi adequada para aplicações em internos de coluna de destilação, mostrando-se uma ferramenta viável e importante no desenvolvimento e otimização de pratos perfurados.

In the present work, the flow behavior of an oil-in-water emulsion around and inside the measurement chamber of an in-line optical sensor probe is studied. The emulsion consists of a metalworking fluid, with oil droplets diameter ranging from 100 nanometers to 100 micrometers. The design of the UV-Vis light spectrometer probe is in accordance with the concept proposed in the research project named EPM (Emulsion Process Monitor in Metalworking Processes), carried out within the scope of the BRAGECRIM program between the University of São Paulo and the University of Bremen. This study is based on the numerical simulation of the interactions between the emulsion and the measurement system using computational fluid dynamic techniques, and is aimed at evaluating the effects of the probe geometry, its position relative to the flow field, and fluid properties on the expected spectrometer readings. Such effects are correlated with changes in droplet concentration and or droplet size segregation inside the measurement chamber of the optical probe, which can cause changes in the scattered light intensity readings. Segregation effects due to flow disturbances around the probe can be neglected under normal measurement conditions, with the probe facing the slit area inlet against the flow stream. Based on the simulation results, even if the probe is misplaced, the effect on the measurements is still insignificant. In-situ measurements carried out in a laboratory set up installed in the injection tube of a drilling machine support the simulation results, since no segregation effect related to the measurement system was observed. In addition to the study, the possibility of bacteria attachment on the internal glass walls of the probe was evaluated and it was found that when the flow velocity is large enough to produce a wall shear stress of about 3-5 Pa the bacterial contamination may be avoided. Changes in the probe geometry are proposed in order to attain an isokinetic condition for the flow around and inside the probe, resulting in a higher wall shear stress for lower inlet flow velocities. An additional study was performed using a tracking particle model to understand the relevance of the individual particles behavior under different flow conditions. The results do not indicate any significant effect on the measurements inside the probe, although additional studies should be carried out in this topic by considering a population balance model for the oil droplets. / O presente trabalho tem como objetivo o estudo do comportamento do escoamento de uma emulsão do tipo óleo - em água que flui no interior de câmara/duto de medição e que tem como obstáculo em seu caminho uma sonda de um sensor óptico, sensor óptico este que deve avaliar em tempo real a estabilidade da emulsão onde está inserido. A emulsão é constituída por um fluido de corte para usinagem, com gotículas de óleo de diâmetro variando de 100 nanômetros para 100 micrometros. A sonda utilizada junto ao espectrômetro de luz UV- Vis está de acordo com o conceito proposto no projeto de pesquisa chamado EPM (Emulsion Process Monitor in Metalworking Fluid), realizado no âmbito do programa BRAGECRIM entre a Universidade de São Paulo e a Universidade de Bremen. Este estudo baseia-se na simulação numérica das interações entre a emulsão e o sistema de medição proposto, utilizando técnicas de Fluido Dinâmica Computacional (CFD), e tem por objetivo avaliar os efeitos da geometria da sonda, a sua posição em relação ao campo do escoamento, e propriedades do fluido, em especial as propriedades a serem medidas pelo espectrômetro. Tais efeitos estão correlacionadas com alterações na concentração de gotas e a segregação ou o tamanho das gotas dentro da câmara de medição da sonda óptica, o que pode causar mudanças nas leituras de intensidade de luz difusa. Efeitos de segregação devido a perturbações do escoamento em torno da sonda podem ser negligenciados, em condições normais de medição, com a sonda voltada para frente e sua área de entrada contra a corrente do escoamento. Com base nos resultados de simulação, mesmo que a sonda seja deslocada, o efeito sobre as medições ainda é insignificante. Medições foram efetuadas em laboratório e também foram realizadas medições in-situ utilizando um adaptador de medição acoplado diretamente no tubo de injeção de fluido de corte da máquina de perfuração, estes testes foram feitos para de validar os resultados obtidos por simulação, uma vez que não se observou qualquer efeito de segregação relacionada com o sistema de medição. Além disso, foi acrescentada ao estudo, a possibilidade de fixação de bactérias nas paredes de vidro internas da sonda e verificou-se que quando a velocidade de escoamento é suficientemente grande para produzir uma tensão de cisalhamento de cerca de 3-5 Pa a fixação de bacteriana pode ser evitado. Aproveitando os resultados do estudo para prevenção de contaminação por bactéria, mudanças na geometria da sonda foram propostas a fim de atingir uma condição isocinética para o escoamento ao redor e dentro da sonda, resultando em uma maior tensão de cisalhamento para baixas velocidades de fluxo de entrada. Por fim um estudo adicional foi realizado utilizando um modelo de rastreamento de partículas para compreender a relevância do comportamento individual de cada partícula no escoamento da emulsão. Os resultados não indicam qualquer efeito significativo sobre as medições no interior da sonda, embora estudos adicionais devem ser realizados neste tópico, considerando um modelo de balanço populacional para as gotículas de óleo.

Orientador: Milton Mori / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-10T00:06:10Z (GMT). No. of bitstreams: 1 Marini_Fabio_M.pdf: 5333553 bytes, checksum: 72ac631f4271ce7c21408f1eb72ddb1c (MD5) Previous issue date: 2008 / Resumo: Os leitos fluidizados são amplamente utilizados em muitas operações nas indústrias químicas, agrícolas, bioquímicas, de geração de energia e em especial petroquímicas. Com o aumento na disponibilidade de computadores, a aplicação de modelos matemáticos para predizer o comportamento de um leito fluidizado segue a mesma tendência, e vários modelos têm sido propostos. Neste trabalho foi abordada a modelagem matemática de simulação de um leito fluidizado. O modelo empregado é baseado na descrição euleriana (contínuo) de ambas as fases, e consiste num conjunto de equações de conservação de massa e momento para cada uma destas. Neste modelo estão contempladas a turbulência (modelo k-epsilon) e mistura multifásica. Para descrever o comportamento das muitas partículas em um contínuo foi utilizada a teoria cinética do escoamento granular, que vem se tornando uma aproximação típica para executar simulações eulerianas. A teoria cinética do escoamento granular é baseada na teoria cinética dos gases. Na teoria cinética do escoamento granular, as interações na fase particulada são levadas em conta, pela contribuição das colisões entre as partículas. Nesta teoria, as colisões são o principal mecanismo de transporte nas propriedades da fase particulada. A geometria e a malha numérica foram geradas utilizando o software ANSYS ICEM CFD. O conjunto de equações diferenciais parciais foi discretizado e resolvido utilizando o software ANSYS CFX 10. A KTGF foi implementada em subrotinas Fortran externas ao código comercial. Os resultados obtidos com as simulações foram por fim validados com os dados experimentais encontrados em SAMUELSBERG e HJERTAGER (1996) / Abstract: Fluidized beds are widely used in many operations in chemical, metallurgical, energy generation and specially in petrochemical industries. With the increase in the availability of computers, the application of mathematical models to predict the behavior of a fluidized bed follows the same trend, and several models have been proposed. In this work, it has been studied mathematical modelling for the fluidized bed simulation. The model utilized is based in the Eulerian (continuum) description for both phases, and is composed of a set of mass conservation and momentum equations, for each phase. In this model are contemplated turbulence (k-epsilon model) and multifasic mixture. To describe the behavior of the several particles in a continuum, it has been used the kinetic theory of granular flow, that is becoming a typical approach to perform eulerian simulations. The kinetic theory of granular flow is based in the kinetic theory of gases. In the kinetic theory of granular flow, the interactions in the particulate phase are taking in account, by the contribution of the colisions between the particles. In this theory, collisions are the main mecanism of transport in the properties of the particulate phase. The geometry and numerical mesh were generated usins ANSYS ICEM CFD software. The set of partial differential equations was discretized and solved using ANSYS CFX 10 software. The KTGF was implemented by Fortran subroutines apart from the commercial code. The results achieved with simulations were validated with experimental data found in SAMUELSBERG and HJERTAGER (1996) / Mestrado / Desenvolvimento de Processos Químicos / Mestre em Engenharia Química