Ein neues, verallgemeinertes Modell für Blasenkoaleszenz und –zerfall wurde entwickelt. Es basiert auf physikalischen Überlegungen und berücksichtigt verschiedene Mechanismen, die zu Blasenkoaleszenz und –zerfall führen können. In einer ausführlichen Literaturrecherche wurden zunächst die verfügbaren Modelle zusammengestellt und analysiert. Es zeigte sich, dass viele widersprüchliche Modelle veröffentlicht wurden. Keins dieser Modelle erlaubt die Vorhersage der Entwicklung der Blasengrößenverteilungen entlang einer Rohrströmung für einen breiten Bereich an Kombinationen von Volumenströmen der Gas- und der Flüssigphase. Das neue Modell wurde ausführlich in einem vereinfachten Testsolver untersucht. Dieser erfasst zwar nicht alle Einzelheiten einer sich entlang des Rohres entwickelten Strömungen, erlaubt aber im Gegensatz zu den CFD-Simulationen eine Vielzahl von Variationsrechnungen zur Untersuchung des Einflusses einzelner Größen und Modelle. Koaleszenz und Zerfall kann nicht getrennt von anderen Phänomenen und Modellen, die diese widerspiegeln, betrachtet werden. Es bestehen enge Wechselwirkungen mit der Turbulenz der Flüssigphase und dem Impulsaustausch zwischen den Phasen. Da die Dissipationsrate der turbulenten kinetischen Energie ein direkter Eingangsparameter für das neue Modell ist, wurde die Turbulenzmodellierung besonders genau untersucht. Zur Validierung des Modells wurde eine TOPFLOW-Experimentalserie zur Luft-Wasser-Strömungen in einem 8 m langen DN200-Rohr genutzt. Die Daten zeichnen sich durch eine hohe Qualität aus und wurden im Rahmen des TOPFLOW-IIVorhabens mit dem Ziel eine Grundlage für die hier vorgestellten Arbeiten zu liefern, gewonnen. Die Vorhersage der Entwicklung der Blasengrößenverteilung entlang des Rohrs konnte im Vergleich zu den bisherigen Standardmodellen für Blasenkoaleszenz und -zerfall in CFX deutlich verbessert werden. Einige quantitative Abweichungen bleiben aber bestehen. Die vollständigen Modellgleichungen sowie eine Implementierung über „User-FORTRAN“ in CFX stehen zur Verfügung und können für weitere Arbeiten zur Simulation polydisperser Blasenströmungen genutzt werden.

Em algumas capitais da costa do nordeste do Brasil, a verticalização de áreas de orla marítima representa uma barreira em potencial contra a passagem da ventilação natural ao interior destas cidades. Na cidade de São Luís/MA, inicia-se um processo de verticalização nas proximidades da Avenida Litorânea, localizada na praia do Calhau, com 5,3km de extensão. Esta pesquisa tem o objetivo de investigar a relação entre esta iminente verticalização e a ventilação natural. Para isto, foram construídos cinco diferentes cenários de verticalização neste bairro, variando-se o gabarito, os afastamentos laterais e a tipologia dos edifícios propostos, em lotes voltados para a avenida mencionada. Em seguida, estes cenários foram simulados no Ansys CFX Software e comparados com a situação atual. Foram monitorados 24 pontos distribuídos em seis quadras, observando-se a influência de cada cenário sugerido nos padrões de velocidade e direção do vento e pressão no nível do pedestre. Concluiu-se que os cenários de verticalização propostos influenciam significativamente nos padrões do vento. Portanto, este trabalho traz uma grande contribuição para o planejamento urbano de São Luís, auxiliando o planejador na pré-determinação dos impactos de novos edifícios nos padrões de ventilação natural em áreas de orla já ocupadas. / In some of the coastal capitals of the Brazilian northeast states, the building verticalization of seaside areas represents a potential barrier to the air flow through the built environment, towards the inner city areas. In São Luís, capital of the state of Maranhão (MA), the verticalization process has begun along Litorânea Avenue, which is a 5,3km long street located in Calhaus Beach district. In this context, the objective of this research work is to investigate the relationship between this imminent verticalization and the natural ventilation. In order to fulfill such objective, there were created five different fictional scenarios of verticalization among the sites placed in Litorânea Avenue, which were gathered according to the height, distances between buildings and buildings typology. These scenarios were simulated in Ansys CFX Software and compared with the areas current situation. Along six blocks of the avenue, 24 points were distributed and monitored, observing the influence of each proposed scenario in the wind velocity and direction patterns, also considering the pressure in the pedestrian level. As a conclusion to this study, the pointed scenarios of verticalization have proved to result in significant influence in the wind pattern, distinguished from each other. Contributing to the urban planning of the city of São Luís, this research anticipates the impact of new buildings in the air flow of already occupied seaside areas.

Em algumas capitais da costa do nordeste do Brasil, a verticalização de áreas de orla marítima representa uma barreira em potencial contra a passagem da ventilação natural ao interior destas cidades. Na cidade de São Luís/MA, inicia-se um processo de verticalização nas proximidades da Avenida Litorânea, localizada na praia do Calhau, com 5,3km de extensão. Esta pesquisa tem o objetivo de investigar a relação entre esta iminente verticalização e a ventilação natural. Para isto, foram construídos cinco diferentes cenários de verticalização neste bairro, variando-se o gabarito, os afastamentos laterais e a tipologia dos edifícios propostos, em lotes voltados para a avenida mencionada. Em seguida, estes cenários foram simulados no Ansys CFX Software e comparados com a situação atual. Foram monitorados 24 pontos distribuídos em seis quadras, observando-se a influência de cada cenário sugerido nos padrões de velocidade e direção do vento e pressão no nível do pedestre. Concluiu-se que os cenários de verticalização propostos influenciam significativamente nos padrões do vento. Portanto, este trabalho traz uma grande contribuição para o planejamento urbano de São Luís, auxiliando o planejador na pré-determinação dos impactos de novos edifícios nos padrões de ventilação natural em áreas de orla já ocupadas. / In some of the coastal capitals of the Brazilian northeast states, the building verticalization of seaside areas represents a potential barrier to the air flow through the built environment, towards the inner city areas. In São Luís, capital of the state of Maranhão (MA), the verticalization process has begun along Litorânea Avenue, which is a 5,3km long street located in Calhaus Beach district. In this context, the objective of this research work is to investigate the relationship between this imminent verticalization and the natural ventilation. In order to fulfill such objective, there were created five different fictional scenarios of verticalization among the sites placed in Litorânea Avenue, which were gathered according to the height, distances between buildings and buildings typology. These scenarios were simulated in Ansys CFX Software and compared with the areas current situation. Along six blocks of the avenue, 24 points were distributed and monitored, observing the influence of each proposed scenario in the wind velocity and direction patterns, also considering the pressure in the pedestrian level. As a conclusion to this study, the pointed scenarios of verticalization have proved to result in significant influence in the wind pattern, distinguished from each other. Contributing to the urban planning of the city of São Luís, this research anticipates the impact of new buildings in the air flow of already occupied seaside areas.

This research presents an analysis of multiphase flow classified as dispersed solid and characterized by solid - gaseous medium granular mineral materials (silica) in a transport process in a discharge chute. The device is subsequently inserted into the tubular chamber with a rotatable differential pressure and temperature, to drag the mineral in the discharge chute which carries the flow direction of the mineral two exit points for the process. The objective of this work is to analyze the behavior of the material in the original geometry of the discharge chute, identifying flow paths, pressure loss and velocity discharge and subsequently propose a modified geometry permits to make a comparison between them, applying dynamic computational fluid. This study and simulation of the behavior of the scale models were developed considering the physical and chemical characteristics of the material as well as process data, generating information for creating the models, processing, and post -analysis simulation in CFX 12.0 software. The results of the simulations by comparison between the original geometry of the discharge chute and the modified geometry showed considerable variations in pressure drop, reduced velocities, and also the discharge points of sedimentation of the material due to better flow characteristics. The study leads to the conclusion that the modification made and simulated by CFD between geometries, has resulted in pressure discharge velocities in the gas phase and the solid phase decreases, and an improvement in the flow path which reduces wear and lessens sedimentation of material inside the machine. / Esta pesquisa apresenta uma análise de escoamento multifásico classificado como disperso contínuo e caracterizado pelo meio sólido-gasoso de material mineral granulado (sílica) em um processo de transporte em uma calha de descarga. O equipamento esta inserido posteriormente a uma câmara tubular rotativa com diferencial de pressão e temperatura, para o arraste do mineral na calha de descarga, que realiza o direcionamento do fluxo mineral por dois pontos de saída para o processo. O objetivo deste trabalho é realizar a análise do comportamento do material na geometria original da calha de descarga, identificando as trajetórias de fluxo, perda de pressão e velocidade de descarga e posteriormente propor uma geometria modificada permitindo a realização de uma comparação entre ambas, aplicando dinâmica dos fluidos computacional. O estudo e simulação do comportamento dos modelos foram desenvolvidos em escala, considerando as características físicas e químicas do material assim como dados de processo, gerando informações para criação dos modelos, processamento, simulação e pós-análise no software CFX 12.0. Os resultados obtidos pela comparação das simulações entre a geometria original da calha de descarga e a geometria modificada mostraram variações consideráveis de perda de pressão, redução das velocidades de descarga e também dos pontos de sedimentação do material devido a melhores características de escoamento. A pesquisa permite concluir que a modificação realizada e simulada por meio de CFD entre as geometrias, resultou em reduções de pressão, velocidades de descarga na fase gasosa e na fase sólida, além de uma melhoria na trajetória de fluxo o que reduz o desgaste e diminui sedimentação de material no interior do equipamento.

This project uses CFD analysis to make design choices for a facility to test flow accelerated lead corrosion erosion of steel samples. Two conceptual designs are considered and compared through mechanical and physical criteria. The first design uses steel samples on stationary plates next to rotating discs. The second design has the steel samples on the rotating disc. The first design is considered unfeasible due to high pressure gradients in the system and a high power requirement from the motor. The second design removes the issue of high pressure gradients and can decrease the motor requirements. This design is selected for further analysis and discussion of manufacturing. / Detta projekt använder CFD-analys för att göra designval för en anläggning för att testa flödesaccelererad blykorrosionserosion av stålprover. Två konceptuella konstruktioner beaktas och jämförs genom mekaniska och fysiska kriterier. Den första designen använder stålprover på stationära plattor bredvid roterande skivor. Den andra designen har stålproverna på den roterande skivan. Den första konstruktionen anses vara ogenomförbar på grund av höga tryckgradienter i systemet och ett högt effektbehov från motorn. Den andra designen tar bort problemet med höga tryckgradienter och kan minska motorkraven. Denna design är vald för vidare analys och diskussion om tillverkning.

In this work, a new approach to optimize facility layout for toxic release, fire and explosion scenarios is presented. By integrating a risk analysis in the optimization formulation, safer assignments for facility layout and siting have been obtained. Accompanying with the economical concepts used in a plant layout, the new model considers the cost of willing to avoid a fatality, i.e. the potential injury cost due to accidents associated with toxic release near residential areas. For fire and explosion scenarios, the building or equipment damage cost replaces the potential injury cost. Two different approaches have been proposed to optimize the total cost related with layout. In the first phase using continuous-plane approach, the overall problem was initially modeled as a disjunctive program where the coordinates of each facility and cost-related variables are the main unknowns. Then, the convex hull approach was used to reformulate the problem as a Mixed Integer Non-Linear Program (MINLP) that identifies potential layouts by minimizing overall costs. This approach gives the coordinates of each facility in a continuous plane, and estimates for the total length of pipes, the land area, and the selection of safety devices. Finally, the 3D-computational fluid dynamics (CFD) was used to compare the difference between the initial layout and the final layout in order to see how obstacles and separation distances affect the dispersion or overpressures of affected facilities. One of the CFD programs, ANSYS CFX was employed for the dispersion study and Flame Acceleration Simulator (FLACS) for the fires and explosions. In the second phase for fire and explosion scenarios, the study is focused on finding an optimal placement for hazardous facilities and other process plant buildings using the optimization theory and mapping risks on the given land in order to calculate risk in financial terms. The given land is divided in a square grid of which the sides have a certain size and in which each square acquires a risk-score. These risk-scores such as the probability of structural damage are to be multiplied by prices of potential facilities which would be built on the grid. Finally this will give us the financial risk. Accompanying the suggested safety concepts, the new model takes into account construction and operational costs. The overall cost of locations is a function of piping cost, management cost, protection device cost, and financial risk. This approach gives the coordinates of the best location of each facility in a 2-D plane, and estimates the total piping length. Once the final layout is obtained, the CFD code, FLACS is used to simulate and consider obstacle effects in 3-D space. The outcome of this study will be useful in assisting the selection of location for process plant buildings and risk management.

<p>Three-dimensional turbulent flow in a cylindrical hydrocyclone is considered and studied by means of computational fluid dynamics using software packages CFX and Fluent. The aim has been to identify the methods that can be used for accurate simulation of the flow in three-dimensional configurations in hydrocyclones at high swirl numbers.</p><p>As a starting point, swirling pipe flows created by tangential inlets, where detailed experimental data were available in literature, were considered. It was found that the velocity profiles for the flow with a swirl number of 2.67 could be predicted accurately using a Reynolds stress model and an accurate numerical discretization on a fine-enough mesh. At a higher swirl number, 7.84, under-prediction in the tangential velocity profiles was observed; however the prediction of the axial velocity profiles was satisfactory. The validated methods were then used to simulate the flow in a cylindrical hydrocyclone at a swirl number as large as 21. The calculated tangential velocity profiles were compared against experimental data measured with a pitometer. Acceptable agreements were recorded except near the geometric axis of the cyclone. Due to the lack of the aircore in the numerical model, disagreements near the axis of the cyclone could be expected to some extent.</p><p>Numerical experiments performed in the present work indicated that the RNG k-ε model is not likely to be capable to predict highly swirling flows accurately and a Reynolds stress model is required. For three-dimensional models, where the computing capacity and the available memory set strong restrictions on the computational mesh, optimizing the maximum mesh resolution available play an important role on the accuracy and stability of the solution procedure. The most stable results in the present study were found using the Reynolds stress model proposed by Launder et al. on an as regular and structured mesh as possible using a higher order discretization scheme in Fluent. Therefore, the meshing capabilities of the pre-processor, the available turbulence models and the accuracy of the numerical methods must be considered in parallel. Acceptable results were also generated using the Baseline Reynolds stress model implemented in CFX, however, only with a transient procedure which was likely to be more time-consuming.</p><p>Present simulations present a complex flow structure in the cylindrical cyclone with a double axial flow reversal. The effect of such a flow pattern on the fractionation of the fibres with small differences in density needs to be investigated in future studies.</p>

Vertical up-flow of supercritical fluid in the subchannel of a heated rod bundle was numerically simulated using the Computational Fluid Dynamics (CFD) codes ANSYS CFX and ANSYS FLUENT. A total of seven cases from three different sets of experiments were simulated. Three-dimensional steady-state predictions of fluid velocity, pressure, and temperature were made using five versions of two-equation RANS turbulence models with accompanying wall treatments. In addition, the temperature distribution in a solid region comprising a heater and sheathing was also computed in some cases. The k-epsilon turbulence model, implemented using CFX and scalable wall functions, provided the numerical results that have the smallest overall deviation from experimental results for three of the seven cases, and predicts the experimental data of the remaining four cases reasonably well, unlike other turbulence models that severely over-predict the experimental data for wall surface temperature. / February 2016

Submitted by Lucienne Costa (lucienneferreira@ufcg.edu.br) on 2018-04-04T20:52:13Z No. of bitstreams: 1 JÉSSICA BARBOSA DA SILVA DO NASCIMENTO - DISSERTAÇÃO (PPGEM) 2017.pdf: 5634263 bytes, checksum: 929da71867fefc79201bbfa0a102a100 (MD5) / Made available in DSpace on 2018-04-04T20:52:13Z (GMT). No. of bitstreams: 1 JÉSSICA BARBOSA DA SILVA DO NASCIMENTO - DISSERTAÇÃO (PPGEM) 2017.pdf: 5634263 bytes, checksum: 929da71867fefc79201bbfa0a102a100 (MD5) Previous issue date: 2017-08-17 / Capes / Os separadores são equipamentos utilizados no processamento primário da indústria do petróleo com o objetivo de separar a mistura multifásica proveniente dos poços produtores. O trabalho avaliou o efeito dos dispositivos internos do vaso separador sobre a dinâmica do escoamento no processo de separação gás/óleo. Foi definido uma modelagem matemática com base na dinâmica de fluidos computacional (CFD) do separador horizontal bifásico. Adotou-se a abordagem Euleriana-Euleriana, considerando o modelo de mistura, disponibilizado no software Ansys CFX 15.0. O domínio consiste em um separador horizontal cilíndrico constituído de uma placa porosa que o divide em duas regiões: a região de separação primária, contendo três dispositivos internos (um defletor e duas chicanas) e a região de decantação. Foi gerada uma malha numérica empregando elementos tetraédricos, para a discretização das equações de conservação de massa, momento linear e de turbulência k padrão usando o método dos volumes finitos. Assumiu-se o escoamento em regimes permanente e transiente, isotérmico, com propriedades dos fluidos constantes e das forças interfaciais foram consideradas apenas as forças de arraste. Os resultados dos campos vetoriais de velocidade, assim como a fração volumétrica das fases indicam que a dinâmica do escoamento é fortemente dependente dos dispositivos internos. Na região de separação primária observou-se um alto nível de mistura causada pela turbulência gerada pelo impacto dos fluidos sobre a placa defletora posicionada imediatamente após a seção de entrada. A placa porosa possibilitou uma redução da turbulência dos fluidos, causada pela resistência do meio poroso ao escoamento. / The separators are equipments used in the primary processing of the petroleum industry to separate the multiphase mixture from the producing wells. The work evaluated the effect of the internal devices of the separator vessel on the flow dynamics in the gas/oil separation process. A mathematical model was defined based on computational fluid dynamics (CFD) of the horizontal two-phase separator. The Eulerian-Eulerian approach was adopted, considering the mixture model, available in Ansys CFX 15.0 software. The domain consists of a horizontal cylindrical separator consisting of a porous plate that divides it in to two regions: the primary separation, containing three internal devices (one deflector plate and two baffles) and the settling region. A numerical grid was generated employing tetrahedral elements, for the discretization of the mass conservation, linear momentum and k standard turbulence equations using the finite volume method. Isothermal flow with constant fluid properties in both steady state and transient regimes were assumed, and, from the interfacial forces, only the drag forces were considered. The velocity vector field results as well as the volumetric fraction of the phases indicate that the flow dynamics are strongly dependent on the internal devices. In the primary separation region, a high-level of mixing was observed due to the turbulence generated by the impact of the fluids on a deflector plate positioned immediately after the inlet section. The porous plate allowed a reduction of the turbulence of the fluids, caused by the resistance of the porous medium to the flow.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-09-03T20:13:43Z No. of bitstreams: 1 FABIANA PIMENTEL MACÊDO FARIAS - TESE PPGEP 2006..pdf: 6819431 bytes, checksum: 61825d33b2b61b2732d80e7e82b96b05 (MD5) / Made available in DSpace on 2018-09-03T20:13:43Z (GMT). No. of bitstreams: 1 FABIANA PIMENTEL MACÊDO FARIAS - TESE PPGEP 2006..pdf: 6819431 bytes, checksum: 61825d33b2b61b2732d80e7e82b96b05 (MD5) Previous issue date: 2006-04-19 / Os ciclones são equipamentos utilizados em processos químicos, em diversas operações unitárias, com o objetivo de promover a separação de sólido e/ou líquido de uma corrente gasosa e secar sólidos. Neste sentido, o presente trabalho propõe um estudo teórico da termofluidodinâmica de um ciclone como secador. O modelo matemático considera escoamento tri-dimensional, turbulento e estacionário para a fase gasosa, e o modelo Lagrangeano para as partículas. As equações diferenciais que representam o fenômeno físico foram resolvidas numericamente pelo método dos volumes finitos, com esquema de interpolação UPWIND para os termos convectivos e o algoritmo SIMPLEC para o acoplamento pressão-velocidade. Como aplicação, a metodologia foi usada para predizer a secagem do bagaço de cana-de-açúcar em um ciclone. As simulações foram realizadas utilizando o código computacional CFX-3D. Resultados do teor de umidade, temperatura e variações dimensionais da partícula, distribuição de velocidade, pressão e temperatura do ar de secagem, para diversas condições do ar, geometria do ciclone e velocidade inicial da partícula são apresentados e analisados. Constatou-se o caráter tridimensional do escoamento gás-partícula no interior do ciclone com presenças de regiões de zonas de recirculação e de inversão de fluxo, apresentando razoável concordância com os dados experimentais. Verificou-se que a cinética de secagem, o aquecimento e o tempo de residência das partículas são afetadas pelas condições do ar de secagem e geometria do ciclone, e quando comparadas com dados experimentais apresentaram boa aproximação. O ciclone com seção de entrada quadrada se mostrou mais eficiente, do ponto de vista de secagem, quando comparados com os dutos de seção retangulares vertical e horizontal. / Cyclones are equipments very used in chemical processes, in several units operations. Their aim is to promote the solid and/or a liquid separation from a gas stream and dry solids. In this sense, the present work proposes a theoretical study of thermal fluid dynamics of a cyclone as dryer. The mathematical model considers three-dimensional, turbulent and stationary flow for gas phase, and Lagrange model for particles. The governing equations were solved numerically with the finite-volumes method, using UPWIND interpolation scheme for convective terms and algorithm SIMPLEC for pressure-velocity coupling. As an application, the methodology was used to predict the sugar cane bagasse drying in a cyclone. Simulations had been carried out using the computational code CFX-3D. Results of the moisture content, temperature and dimensional variations of the particles and velocity, pressure and temperature distributions of the air drying, to several air conditions, shape of the cyclone and initial velocity of particle is presented and analyzed. Three-dimensional gas-particle flow, recirculation zones and inversion flow were verified inside the cyclone. Numerical data fitted well experimental ones. It was verified that the kinetic drying, temperature and residence time of the particles were affected by air drying conditions and cyclone geometry. Cyclone with square inlet section were more efficient to dry than cyclone with vertical and horizontal rectangular section duct.