Este trabalho aborda a utilização do método de Lattice Boltzmann como ferramenta de simulação para a área de dinâmica de fluidos. Além disso, apresenta o programa LBSim desenvolvido durante o período de pesquisa, construído para ser flexível e extensível (através do emprego de técnicas de orientação a objetos) e com uma interface gráfica mais amigável do que outros projetos semelhantes. Como resultado deste trabalho, o software LBSim implementa uma série de módulos diferentes que utilizam o método de Lattice Boltzmann como base, permitindo a simulação de casos monofásico, multifásico, multicomponente, com suporte à gravidade, meios porosos, difusão, transferência de calor e paredes deslizantes. / This work approaches the use of the Lattice Boltzmann method as a simulation tool for the fluid dynamics area. Beyond that, it presents the LBSim software, developed during the period of the research and built to be flexible and extensible (through the application of techniques of the object oriented paradigm) and with a graphical interface more friendly than other similar projects. As a result of this work, the LBSim software implements a series of different modules that uses the Lattice Boltzmann method as a base, allowing the simulations of the following cases: monophase, multiphase, multicomponent, with support of gravity, porous media, diffusion, heat transfer and moving walls.

Com o desenvolvimento para aeronaves de propulsores turbo-fan com elevada razão de derivação, componentes da estrutura do avião passaram a ter relevância na geração de ruído aerodinâmico, principalmente durante a aproximação e o pouso. Dentre esses componentes, o eslate se destaca por ser uma fonte que se estende ao longo de praticamente toda a envergadura da asa. Neste trabalho, simulações numéricas foram feitas no intuito de considerar configurações práticas nas análises do ruído aeroacústico gerado pelo eslate. Um código comercial baseado no Método Lattice-Boltzmann foi usado no cálculo do escoamento transiente em torno do aerofólio MD30P30N. O domínio computacional simulado imitou a configuração geométrica de um túnel de vento. Foi levado em consideração o efeito da presença de duas formas de excrescência que são comuns na cova do eslate de aeronaves comerciais. Uma delas foi um selo que fica posicionado na parede da cova e a outra, um tubo do sistema anti-gelo. Tanto o escoamento transiente na região da cova quanto as características do ruído aeroacústico propagado para o campo distante foram analisados. Uma metodologia que impõe condição de parede com escorregamento livre no es- late e elemento principal, permitindo assim uma redução do custo computacional, foi usada. A abordagem foi ainda testada para a condição de um aerofólio submetido a escoamento cruzado, simulando uma asa infinita com enflechamento. Também uma modificação na metodologia, para que ela possa ser empregada em aerofólios com elevados ângulos de ataque, foi proposta e testada. O código híbrido MSES foi usado para o cálculo da espessura de deslocamento na camada limite do aerofólio. A modificação na geometria baseada em \'delta\'* causou uma melhora da solução aeroacústica de uma simulação empregando paredes com escorregamento livre, tomando como base de comparação a solução com paredes sem escorregamento. Simulações com selo dentro da cova, perto do recolamento, mostraram que, em certas circunstâncias, há um bloqueio dos vórtices da camada de mistura, intensificando picos tonais no espectro do ruído. A variação da posição do selo mostrou um efeito significativo no ruído do eslate, de forma que um selo suficientemente afastado do recolamento modificou o espectro do ruído do eslate. Os resultados com o aerofólio enflechado indicam que, também neste caso, o ruído do eslate não depende diretamente da camada limite na cúspide, mas da circulação do aerofólio. Por sua vez, a presença do tubo na cova aumenta significativamente a intensidade do ruído de banda larga produzido pelo eslate. Em uma asa sem enflechamento, o tubo causa também um aumento substancial na intensidade de picos tonais de baixa frequência. / The development of high by-pass ratio turbo-fan engine turned the airframe noise into an important component in a commercial airplanes\' noise characteristics. Between the airframe noise sources the slat can be highlighted as it extends almost along the whole wing span. Numerical simulation was carried out in order to consider practical configuration in the aeroacoutic noise generated by the slat. The effects of two different excrescences, which are normally present in commercial airplanes\' slat cove, were taken into account. One of them was a seal attached to the cove wall and the outher one was a tube that compose the anti-icing system. Both unsteady flow in cove region and far-field noise characteristics were analysed. A methodology that impose free-slip wall boundary condition on slat and main element surfaces was employed, which allowed the reduction of computational requirements. This approach was also tested for airfoil with crossflow, which simulates an infinite swept wing. Also a modification of the methodology was proposed and tested to extend its application in high-lift airfoils under higher angle of attack. A commercial code based on the Lattice-Boltzmann Method was used to compute the unsteady flow over the MD30P30N airfoil. The simulated computational domain imitates the geometry of a wind tunnel. The hybrid Euler/IBL code MSES was employed to calculate the displacement thickness of the airfoil\'s boundary layers. The geometry modification based on \'delta\'* caused a improvement on the aeroacoustic solution of a free-slip simulation, the no-slip simulation results being taken as reference. Simulations of geometries with relatively small seal close to the reattachment point showed that a blockage of the mixing layer vortices hapens and tonal peaks are intensified in the far-field noise spectrum. The variation of the seal position showed a significant effect on the slat noise, so that a seal farther from the reattachment modified affected both the shape and intensity of the noise spectrum. Results with the swept airfoil indicates that, even in the presence of crossflow, the slat noise does not depend on the cusp boundary layer, namely it is more sensitive to the airfoil circulation. The tube crossing the slat cove augmented significantly the broadband noise generated by the slat. In an unswept wing it also caused a substantial increase in the low-frequency tonal peaks.

Por meio do método lattice Boltzmann (LBM), este projeto de pesquisa propõe a simulação computacional da extração dos compostos diterpênicos do café verde em sistemas com fluido pressurizado. Para isso foi adotado um modelo fenomenológico dinâmico e de primeira ordem quanto à dependência espacial. Usando a rede D1Q2, o LBM foi implementado com duas funções de distribuição de partículas, acompanhadas das respectivas funções de distribuição de equilíbrio. Cada função refere-se à concentração em uma dada fase (sólida e fluida). A previsão das curvas de rendimento pressupõe o conhecimento dos parâmetros do processo, tais como a difusividade mássica interna (intrapartícula), o coeficiente de partição volumétrica e a difusividade mássica axial. Para o devido ajuste destes parâmetros contra dados experimentais, foi desenvolvido um código computacional utilizando a técnica de gradiente descendente. Resultados numéricos das simulações foram comparados com dados experimentais e mostraram-se satisfatórios. Adicionalmente, foi realizada a análise da influência dos parâmetros supracitados mediante a criação de uma interface gráfica amigável para o código computacional original. Este projeto de pesquisa, além de fomentar a agregação de valor ao café, desenvolveu competências em modelagem e simulação de processos de extração de espécies químicas a partir de métodos numéricos. / Using the lattice Boltzmann method (LBM), this research project proposes a computer simulation of diterpene compounds extraction from green coffee beans in high pressure fluid systems. In order to do so, a dynamic phenomenological model with first-order spatial dependence was adopted. LBM was implemented on D1Q2 lattice, using two particle distribution functions, followed by the respective equilibrium distribution functions. Each function refers to the extract concentration in each phase, namely solid and fluid. Prediction of extract yield curves relies on process parameters such as internal (i.e., intraparticle) mass diffusivity, volumetric partition coefficient and axial mass diffusivity. Values of aforesaid parameters were fitted against experimental data via descendent gradient technique coupled to the LBM computer code and numerically simulated result were consistent. Besides modeling and simulation, this project performed the influence analysis of those process parameters. To this end, a user-friendly graphical interface for the original computer code was created. While fostering value to be added to coffee, this research project develops skills in modeling and simulation of chemical species extraction through numerical methods.

Por meio do método lattice Boltzmann (LBM), este projeto de pesquisa propõe a simulação computacional da extração dos compostos diterpênicos do café verde em sistemas com fluido pressurizado. Para isso foi adotado um modelo fenomenológico dinâmico e de primeira ordem quanto à dependência espacial. Usando a rede D1Q2, o LBM foi implementado com duas funções de distribuição de partículas, acompanhadas das respectivas funções de distribuição de equilíbrio. Cada função refere-se à concentração em uma dada fase (sólida e fluida). A previsão das curvas de rendimento pressupõe o conhecimento dos parâmetros do processo, tais como a difusividade mássica interna (intrapartícula), o coeficiente de partição volumétrica e a difusividade mássica axial. Para o devido ajuste destes parâmetros contra dados experimentais, foi desenvolvido um código computacional utilizando a técnica de gradiente descendente. Resultados numéricos das simulações foram comparados com dados experimentais e mostraram-se satisfatórios. Adicionalmente, foi realizada a análise da influência dos parâmetros supracitados mediante a criação de uma interface gráfica amigável para o código computacional original. Este projeto de pesquisa, além de fomentar a agregação de valor ao café, desenvolveu competências em modelagem e simulação de processos de extração de espécies químicas a partir de métodos numéricos. / Using the lattice Boltzmann method (LBM), this research project proposes a computer simulation of diterpene compounds extraction from green coffee beans in high pressure fluid systems. In order to do so, a dynamic phenomenological model with first-order spatial dependence was adopted. LBM was implemented on D1Q2 lattice, using two particle distribution functions, followed by the respective equilibrium distribution functions. Each function refers to the extract concentration in each phase, namely solid and fluid. Prediction of extract yield curves relies on process parameters such as internal (i.e., intraparticle) mass diffusivity, volumetric partition coefficient and axial mass diffusivity. Values of aforesaid parameters were fitted against experimental data via descendent gradient technique coupled to the LBM computer code and numerically simulated result were consistent. Besides modeling and simulation, this project performed the influence analysis of those process parameters. To this end, a user-friendly graphical interface for the original computer code was created. While fostering value to be added to coffee, this research project develops skills in modeling and simulation of chemical species extraction through numerical methods.

Les simulations numériques à l'échelle du pore sont fréquemment utilisées pour étudier le comportement des écoulements multiphasiques largement rencontrées dans phénomènes naturels et applications industrielles. Dans ce travail, la morphologie de structures liquides et l'action capillaire sont examinées à l'échelle des pores par la méthode de Boltzmann sur réseau (LBM) à plusieurs composants selon le modèle de Shan-Chen. Les résultats numériques obtenus sont en bon accord avec les solutions théoriques. Les simulations numériques sont étendues à microstructures complexes au-delà du régime pendulaire.La LBM a été utilisée pour modéliser l'écoulement multiphasique à travers un milieu poreux idéalisé dans des conditions de drainage primaire quasi-statique. Les simulations LBM ont fourni une excellente description du déplacement de l'interface fluide-fluide à travers les grains. Pendant le drainage, les simulations LBM sont capables de reproduire la déconnexion d'une phase dans le milieu granulaire sous la forme de ponts pendulaires ou structures liquides complexes. Malheureusement, le temps de calcul nécessaire pour ce type de simulations est assez élevé. Afin d’optimiser les ressources de calcul, nous présentons un modèle 2D (modèle Throat-Network) basé sur des solutions analytiques pour décrire l'écoulement biphasique à travers un ensemble de disques dans un temps de calcul très réduit, donc le modèle 2D est susceptible de remplacer les simulations LBM lorsque les ressources de calcul sont limitées. L'approche souligne l'importance de simuler le problème a l'échelle de la gorge du pore pour obtenir les relations volume - pression capillaire locales. Le modèle Throat-Network est un point de départ pour le modèle hybride proposé pour résoudre les problèmes en 3D. Le modèle hybride combine l’efficacité de l’approche réseau de pores et la précision du LBM à l’échelle des pores. Le modèle hybride est basé sur la décomposition de l’échantillon en petits sous-domaines, dans lesquels des simulations LBM sont effectuées pour déterminer les propriétés hydrostatiques principales (pression capillaire d'entrée, courbe de drainage primaire et morphologie du liquide pour chaque gorge du pore). Malgré la réduction significative des temps de calcul obtenus avec le modèle hybride, le temps n’est pas négligeable et les modélisations numériques d'échantillons de grandes tailles ne sont pas réalistes. Les approximations données par les méthodes Incircle et MS-P, qui prédisent les propriétés hydrostatiques, sont comparées à celles de LBM et du modèle hybride. / Numerical simulations at the pore scale are a way to study the behavior of multiphase flows encountered in many natural processes and industrial applications. In this work, liquid morphology and capillary action are examined at the pore-scale by means of the multicomponent Shan-Chen lattice Boltzmann method (LBM). The accuracy of the numerical model is first contrasted with theoretical solutions. The numerical results are extended to complex microstructures beyond the pendular regime.The LBM has been employed to simulate multiphase flow through idealized granular porous media under quasi-static primary drainage conditions. LBM simulations provide an excellent description of the fluid-fluid interface displacement through the grains. Additionally, the receding phase trapped in the granular media in form of pendular bridges or liquid clusters is well captured. Unfortunately, such simulations require a significant computation time. A 2D model (Throat-Network model) based on analytical solutions is proposed to mimic the multiphase flow with very reduced computation cost, therefore, suitable to replace LBM simulations when the computation resources are limited. The approach emphasizes the importance of simulating at the throat scale rather than the pore body scale in order to obtain the local capillary pressure - liquid content relationships. The Throat-Network model is a starting point for the a hybrid model proposed to solve 3D problems. The hybrid model combines the efficiency of the pore-network approach and the accuracy of the LBM at the pore scale to optimize the computational resources. The hybrid model is based on the decomposition of the granular assembly into small subsets, in which LBM simulations are performed to determine the main hydrostatic properties (entry capillary pressure, capillary pressure - liquid content relationship and liquid morphology for each pore throat). Despite the reduction of computation time, it is still not negligible and not affordable for large granular packings. Approximations by the Incircle and the MS-P method, which predict hydrostatic properties, are contrasted with the results provided by LBM and the hybrid model. Relatively accurate predictions are given by the approximations.

Helicopter performance is greatly influenced by its drag. Pylons, fuselage, landing gear, and especially the rotor hub of a helicopter experience large separated flow regions, even under steady level flight conditions the vehicle has been designed for, contributing to the helicopter drag. Several passive and active flow control concepts have been studied for reducing helicopter drag. While passive flow control methods reduce drag, they do so at one optimized design condition. Therefore, passive drag reduction methods may not work for helicopters that operate under widely varying flight conditions. Active flow control (AFC) methods overcome this disadvantage and consequently are widely being pursued. The present investigator has studied some of these AFC methods using computational fluid dynamics (CFD) techniques and has found synthetic (or pulsed) jets as one of the more effective drag reduction devices. Two bluff bodies, representative of helicopter components, have been studied and the mechanism behind drag reduction has been analyzed. It was found that the increase in momentum due to the jet, and a resultant reduction in the separated flow region, is the main reason for drag reduction in these configurations. In comparison with steady jets, synthetic jets were found to use less power for a greater drag reduction. The flow inside these synthetic jet devices is incompressible. It is computationally inefficient to use compressible flow solvers in incompressible regions. In such regions, using Lattice Boltzmann equations (LBE) is more suitable compared to solving the incompressible Navier-Stokes equations. The length scales close to the synthetic jet devices are very small. LBE may be used to better resolve these small length scale regions. However, using LBE throughout the whole domain would be computationally expensive since the grid spacing in the LBE solver has to be of the order of the mean free path. To address this need, a coupled Lattice Boltzmann-Navier-Stokes (LB-NS) methodology has been developed. The LBE solver has been successfully validated in a standalone manner for several benchmark cases. The solver has also been shown to be of second order accuracy. This LBE solver has been subsequently coupled with an existing Navier-Stokes (NS) solver. Validation of the coupled methodology has been done for analytical problems with known closed form solution. This LB-NS methodology is further used to simulate the flow past a cylinder where synthetic jet devices have been used to reduce drag. The LBE solver is used in the cavity of the synthetic jet nozzle while the NS solver is employed in the rest of the domain. The cylinder configuration was chosen to demonstrate drag reduction on helicopter hub shape geometries. Significant drag reduction is observed when synthetic jets are used, compared to the baseline no flow control case.

The Lattice-Boltzmann-model is analyzed with regard to application to numerical solution of flow acoustic problems. In the first part of this study the description of sound wave propagation by common variants of the Lattice-Boltzmann-model is examined by calculation of phase velocity and effective viscosity for sound waves. Schemes with nine velocities in two dimensions and nineteen velocities in three dimensions are considered. For each of these a single relaxation time model (LBGK-model) and a multiple relaxation time model (MRT) is investigated. All schemes exhibit an almost isotropic error in phase speed of sound waves. With a spatial resolution of 10 or 30 grid spacings per wavelength the deviation of phase speed is less than 1 % or 0.1 %, respectively. The dissipation of sound waves is not simulated correctly by LBGK-models since there the bulk viscosity is fixed to the shear viscosity. Apart from that there is only very little numerical dissipation. The dissipation error therefor is negligible in the audible frequency range in air as long as the simulation volumes do not become very large, i.e. much more than some hundred wavelengths. The MRT-models allow to adjust the bulk viscosity by a suitable choice of relaxation parameters. However, if the bulk viscosity is set to a realistic value, stability of the scheme requires free relaxation parameter values which are close to the relaxation parameters that determine the viscosities. Then the gain in stability of MRT-models compared to LBGK-models is lost to some extent. All schemes considered here are able to reproduce the effect of sound wave convection in homogeneous background flows. Although additional numerical errors arise in transport coefficients, the overall errors are of the same order of magnitude as in the case with zero background flow and are not critical in practical applications. In the second part of the work numerical experiments are described which demonstrate the coupling of the flow- and sound field. Three test cases are considered: Sound generation by a single vortex interaction with the leading edge of a semi-infinite flat plate, sound generation by a grazing flow over a partially covered cavity and instationary flow around a half-cylinder with an attached wedge tail. The first test case is simulated in two dimensions with a self-written program. The sound calculated directly is compared to prediction based on an acoustic analogy. The observed amplitudes of the radiated sound agree quantitatively well for all flow and eddy velocities considered here. This implies, that the coupling of the sound and flow field is correct. In the case of the cavity the flow is computed in two dimensions with a self-written program as well as in three dimensions with the commercially available program PowerFLOW. The simulated pressure fluctuations in the cavity are compared to results of a wind tunnel experiment. Good agreement between simulation and wind tunnel experiment is found. The instationary flow around a half cylinder with an attached wedge tail is simulated in three dimensions using PowerFLOW. The radiated sound cannot be captured with PowerFLOW because of insufficient quantization of fluid density. However, pressure fluctuations on the surface of the body exhibit good agreement with the result of a wind tunnel test. Summarizing the results of this work it can concluded, that the Lattice-Boltzmann-model is well suited to numerical solutions of flow acoustic problems.

Der ehemalige Salzbergbau im Raum Staßfurt führt seit dem 19. Jahrhundert zu Subrosion und teils bruchhaften Deformationen und damit verbundenen Senkungen und Vernässungen im Stadtgebiet. Im Rahmen eines Forschungsverbundvorhabens unter Federführung der BGR sollen in dieser Arbeit die grundlegenden strömungsdynamischen Prozesse im Salinar und Deckgebirge der betroffenen geologischen Formationen aufgeklärt werden. An Bohrkernen aus den entsprechenden Bereichen werden Durchflussexperimente durchgeführt und die Fluiddynamik im Inneren der Proben mittels Positronen-Emissions-Tomographie dreidimensional dargestellt. In Kooperation mit der Bundesanstalt für Materialforschung- und prüfung Berlin und dem Geologischen Institut der Johannes-Gutenberg Universität Mainz werden diese PET-Messungen der Fluiddynamik mit hochauflösenden computertomographischen Messungen der internen Struktur der Proben in Übereinstimmung gebracht. Die beobachteten Fließmuster sollen mittels einer Lattice-Boltzmann-Simulation nachvollzogen und dadurch das grundlegende Verständnis der Strömungsdynamik in diesen Gesteinen erweitert werden. Langfristig soll dies zu einer Verbesserung des Verständnisses der Grundwasserdynamik auf regionaler Ebene führen.

The characteristics of fibers suspensions depend on the properties of fibers, the suspending fluid, and fiber-fiber interactions. This thesis demonstrates the development and application of a novel coupled method (lattice Boltzmann and finite element methods) to investigate these relationships. Fibers are modeled as flexible rod particles which are simulated by the finite element method. The fluid flow that causes the fibers to deform is calculated by the lattice Boltzmann method. The method is extended from the two dimensional case to the three dimensional case. Results from simulation show the rigid fiber in simple shear flow produces a good agreement for orientation of a fiber relative to the theoretical study by Jeffery (1922). The flexible fiber exhibits an increase on the rotational period from the rigid fiber due to more deformation shape is revealed during rotation. The simulation technique demonstrates the ability to simulate fiber-fiber interactions to further study of relative viscosity of suspensions in shear flow. Simulation results show that fiber orientation and relative viscosity depend on the fiber characteristics (fiber aspect ratio, fiber flexibility, and volume fraction). The results are verified against known experimental measurements and theoretical results. The broad aim of this research is to better understand the behavior of fibers in fluid flow. It is hoped that future researchers may benefit from the new technique and algorithms developed here.

[Truncated abstract] The hydrodynamic forces on a marine pipeline and the local scour around it are the most serious and important issues in designing and maintaining pipelines. This thesis explores the vortex shedding phenomena for the flow over smooth surface and rough surface isolated cylinders. This thesis also explores the two-dimensional and three-dimensional scour process beneath offshore pipelines numerically. A series of numerical models are proposed in this dissertation for the prediction of flow characteristics and the time development of local scour around pipelines. All the models presented in this thesis are deliberately developed based on novel lattice Boltzmann method (LBM), because in recent years it has been considered as a serious alternative to standard computational fluid dynamics (CFD) as it is ideally suited to massively parallel computations. The lattice Boltzmann method is described in details to reveal how it recovers the Navier- Stokes equations. Various grid refinement schemes available in literature are discussed and a slightly modified new scheme is proposed to remove oscillatory solutions at high velocity change regime. The proposed scheme is then validated against bench mark tests for low Reynolds number flow. A turbulent model based on LBM is developed in order to predict the vortex shedding flow around an isolated square smooth surface cylinder. The various local and global flow parameters and structure of vortices are validated against experimental and numerical data available in literature. The model is then extended to investigate the vortex shedding flow over an isolated rough surface cylinder as it has an engineering significance in the design process of pipelines. The model is employed to investigate the influence of pipe roughness on various local and global parameters of flow. ... Significant part of this thesis is aimed at modelling flow and local scour around pipelines employing LBM and cellular automata (CA) methods. The erosion mechanism of the CA method available in literature for sand particles is improved by defining the threshold of sediment entrainment on bed in a similar manner to that employed in the traditional scour models. The predicted scour profiles for various incoming flow conditions are found to compare well with the experimental results reported in the literature. The existence of lee wake erosion due to continuous generation of vortex shedding in the lee of the pipelines is revealed. The time development of the maximum scour depth below the pipe is also found to be in good agreement with the experimental measurements reported in literature Finally, a three-dimensional flow and scour model is developed in order to explore the scour process beneath pipelines. It is revealed that the three-dimensionality effects are more pronounced near the span shoulder. On the other hand, there exists a two-dimensional scour regime in the vicinity of the middle section of the suspended pipe. It is found that the propagation speed of the scour hole in the sapnwise direction remains almost constant at all stages of scour process.