Nous avons tou(te)s été témoins des nuages d'étourneaux dans le ciel ou de la formation de bancs de poissons dans l'océan. Ce type d'organisation chez les êtres vivant se produit aussi à des échelles parfois invisibles pour l'oeil humain: celles des micro-organismes. Les suspensions de micro-nageurs présentent une dynamique riche. Elles peuvent former des structures cohérentes résultant d'un mouvement collectif, mélanger le fluides environnant et/ou modifier ses propriétés rhéologiques. Leurs comportements peuvent jouer un rôle important dans la survie, l'équilibre des espèces, leur stratégie trophique et même pour la fertilité animale. La diversité des phénomènes observés résulte de l'interaction complexe entre mécanismes de nage, processus physiologiques, processus chimiques et interactions hydrodynamiques. Comprendre et maîtriser les mécanismes impliqués fait nécessairement appel la Mécanique des Fluides. Les études expérimentales permettent de mettre en exergue certains phénomènes et parfois de les expliquer. Cependant la modélisation s'avère indispensable. Or, inclure une description fine des mécanismes de nages dans une suspension contenant des milliers (voire des millions) d'individus, implique de considérer une vaste gamme d'échelles couplées (typiquement du micron 10^-6m au millimètre 10^-3m). Décrire une physique multi-échelles pour ce type problème reste un défi majeur pour la modélisation numérique actuelle. Ainsi, dans le cadre de cette thèse nous nous proposons d'apporter une contribution dans cette direction. Nous montrerons dans une premiere partie qu'il est possible de reproduire les mécanismes de nage de façon satisfaisante à l'échelle du micro-organisme avec des modèles de différentes complexités. Nous présenterons ensuite nos développements pour étendre ces modèles a l'échelle de la suspension. Nous montrerons comment inclure simultanément les effets Browniens qui agissent sur les plus petite particules (10^-6m). Enfin, nous exploiterons l'outil mis en place pour simuler des suspensions actives. Sa capacité à reproduire certains résultats de la littérature à précision égale, à moindre coût et à plus grande échelle, permet de combler le fossé entre modèles individuels, travaux expérimentaux et modèles continus issus de la théorie cinétique. Forts de cet outil, nous tenterons de répondre à deux questions ouvertes dans la littérature expérimentale : l'origine des corrélations d'orientation dans les suspensions de microgouttes auto-propulsées et les mécanismes en jeu dans la diffusion des particules Browniennes dans les suspensions actives. / We have all witnessed the flocking of starlings in the sky and the schools of fish that form in the ocean. This kind of organization of living creatures is not limited to those that we see, but also occurs for those that we don’t : swimming microorganisms. Suspen- sions of micro-swimmers exhibit a rich dynamics. Their behaviors can play an important role in the survival of the group, its development, the balance between species, their trophic strategies and even animal fertility. They can form coherent structures due to collective motion, mix the surrounding fluid or modify its rheological properties. Such diversity results from the complex interplay between swimming strategies, physiological processes, chemical reactions and hydrodynamic interactions. Fluid Mechanics is there- fore essential to understand and master the mechanisms involved in these phenomena. While experimental studies bring out new findings and, sometimes, provide physical ex- planations, modeling remains essential. Yet, including an accurate description of the micro-swimmers in a suspension containing thousands (nay millions) individuals, requires considering a wide range of coupled scales (from one micron 10^−6m to several millimeters 10^−3m). What happens on large scales depends on sophisticated mechanisms occurring two or three orders of magnitude below. Therefore, the multiscale modeling of such phenomena is still a major challenge for the state-of-the-art numerical methods. This thesis aims at providing a contribution in that direction. In a first part, we will show that reproducing swimming mechanisms at the scale of the micro-swimmer can be achieved with various models spanning different levels of complexity. We will then present our developments to incorporate these models in an efficient framework for large scale simulations. We will show how to simultaneously account for the Brownian motion of the smallest particles (10^−6m). Our code reproduces known results from the literature with the same accuracy, but at lower cost and at larger scales, thus bridging a gap between particle-based models, experiments and continuum formulations from kinetic theory. Using the capabilities afforded by our method, we eventually address two open problems in the experimental literature : the origins of orientational correla- tions between interacting self-propelled micro-droplets and the mechanisms at play in the nonlinear enhancement of Brownian particle diffusion in active suspensions.

La cathode creuse est un élément clef des propulseurs à plasma. Dans un propulseur à plasma, un gaz propulsif est ionisé dans un canal de décharge puis accéléré hors de celui-ci afin de créer la poussée. Dans le propulseur de Hall en particulier, l'ionisation du gaz est provoquée par l'injection dans le canal de décharge d'un intense courant électronique (de quelques ampères à plus d'une centaine d'ampères). L'élément chargé de fournir le courant électronique de la décharge, la cathode creuse, est crucial dans le fonctionnement du propulseur. Or, celle-ci est souvent idéalisée dans les modèles de propulseur et n'est que rarement étudiée pour sa physique propre. Pourtant, le développement de propulseurs de Hall de haute puissance, destinés à terme à équiper l'ensemble des missions spatiales, requiert la mise au point de cathodes capable de délivrer un fort courant (jusqu'à plus de 100 A) sur des durées de l'ordre de la dizaine de milliers d'heures. Or, la mise au point de nouvelles cathodes s'est révélée difficile en raison de l'absence de modèle susceptible de prédire a priori les performances d'une cathode en fonction de sa conception. On se propose ici de mettre en place un modèle prédictif de cathode creuse capable de retranscrire la physique du fonctionnement de la cathode. L'objectif in fine est bien sûr d'utiliser ce modèle afin de faire le lien entre la conception de la cathode et son fonctionnement dans le but de guider le développement de futures cathodes. On présentera tout d'abord brièvement le contexte d'application des cathodes creuses, et on donnera un rapide aperçu du principe de fonctionnement global de la cathode. Ensuite, après avoir effectué un tour d'horizon des différents modèles numériques de cathode creuse préexistants dans la littérature, on détaillera le modèle de la cathode développé ici, qui incorpore une description fluide du plasma, ainsi que des transferts thermiques aux parois, qui conditionnent en grande partie le bon fonctionnement de la cathode. Un soin particulier sera apporté à la validation des résultats de simulation vis-à-vis des mesures expérimentales disponibles dans la littérature, ce qui nous permettra de perfectionner certains points du modèle afin de mieux traduire la réalité physique. En particulier, une modélisation spécifique de la région de transition entre la décharge interne de la cathode et la plume du propulseur sera réalisée. Ce modèle permettra de mettre en évidence certains phénomènes d'instabilité du plasma spécifiques de cette décharge, qui ont été jusqu'ici observés expérimentalement mais jamais pleinement intégrés aux modèles de cathode creuse. A l'aide du modèle validé, on procèdera à l'analyse physique de l'ensemble des phénomènes qui gouvernent le fonctionnement d'une cathode particulière, la cathode NSTAR développée par la NASA au Jet Propulsion Laboratory. Ensuite, on s'appuiera sur le modèle numérique pour comprendre l'impact sur le fonctionnement de la cathode des choix de conception au travers d'une étude paramétrique autour de la cathode NSTAR. Les tendances dégagées nous permettront de formuler des recommandations quant au développement de cathodes de haute puissance. Enfin, dans le but d'illustrer la versatilité du modèle développé, le comportement d'une cathode creuse employant une géométrie alternative à la cathode NSTAR sera également présenté. / A hollow cathode is a critical component of plasma thrusters. In a plasma thruster, a propellant gas is ionized in a discharge chamber and accelerated out of it so as to generate thrust. In Hall thrusters in particular, the ionization of the gas is caused by an intense electron current (from a few to hundred amps) which flows through the discharge chamber. The hollow cathode is the device which is responsible for providing the discharge current. This key element is often idealized in thruster numerical models and its physical behavior is rarely studied for its own sake. Yet, developing high power Hall thrusters, designed to propel in the long run every type of space mission, requires new hollow cathodes able to supply an intense electron current (over 100 A) over a duration on the order of ten thousand hours. So far, designing new cathodes proved difficult because of the lack of model capable of predicting the performance of a cathode based on its design. In this work, we build up a predictive model of a hollow cathode capable of simulating the physics relevant to the operation of the cathode. In the end, we aim at using this model to associate design characteristics of the cathode to key aspects of the cathode performance during operation. Our goal with this model is to guide the development of future high power hollow cathodes. We will first briefly describe the range of application of hollow cathodes related to space propulsion. Then we will give a brief account of the working principles of the cathode and we will set the numerical models available in the literature prior to this one out. The numerical model developed in this work will then be described. It includes a fluid treatment of the plasma as well as an account of the heat fluxes to the walls which largely control the performance of the cathode. Simulation results will be thoroughly compared to experimental measurements available in the literature and specific aspects of the model will be refined to match up simulation results with the physical reality. For instance, a model that specifically represents the transition region between the internal plasma of the cathode and the plume of the cathode will be described. This model will enable us to highlight plasma instability phenomena which were so far observed experimentally, yet never properly included in hollow cathode models. Using the model just developed, we will analyze the physics of a particular hollow cathode which has been developed by NASA at the Jet Propulsion Laboratory, the NSTAR hollow cathode. Then, thanks to the numerical model, we will be able to carry out a parametric study revolving around the design of the NSTAR cathode. This will allow us to bring out the influence of the design on the cathode performance and we will eventually express recommendations regarding the design of future high power cathodes. To conclude, the versatility of the numerical model built up here will also be displayed through simulations of the behavior of a hollow cathode based on an alternate geometry.

O formato do perfil de velocidades do vento varia de acordo com as características locais da superfície terrestre e de rugosidade do terreno, parâmetros que definem o perfil da Camada-Limite Atmosférica (CLA). As características do escoamento do ar atmosférico sobre e ao redor de acidentes geográficos, tais como morros e colinas, são de grande interesse para aplicações relacionadas à Engenharia de Turbinas e Parques Eólicos. No topo de morros, ocorre a aceleração do vento, fenômeno que pode representar um fator decisivo para a instalação de aerogeradores. Este trabalho dedica-se ao estudo do comportamento da CLA como função da inclinação e rugosidade superficial da elevação, fazendo uso da Dinâmica de Fluidos Computacional (CFD) para construir perfis de velocidade do vento e de intensidade de turbulência. O problema de fechamento das Equações Médias de Reynolds (RANS) é contornado com o uso do modelo de turbulência k-ω SST; os resultados numéricos obtidos são comparados com dados experimentais medidos em túnel de vento sobre modelos em escala dos morros. São testados oito modelos de morros com declives que variam de 25° a 64° para dois tipos de categorias de terreno, em 2D e 3D, e são aplicados dois códigos analíticos para representar o perfil de velocidades de entrada. Resultados numéricos para os perfis de velocidade apresentam diferença inferior a 4% em relação aos respectivos dados obtidos experimentalmente. Os perfis de intensidade de turbulência apresentam diferença máxima na casa dos 7% em comparação aos dados experimentais, o que é explicado pelo fato de que não é possível inserir o perfil de entrada de intensidade de turbulência nas simulações numéricas. Em alternativa, foi usado um valor constante resultado da média dos valores dos perfis usados no túnel de vento. Os modelos de morro em 3D apresentam maior concordância nos resultados de velocidade que os modelos em 2D e que ademais quanto maior é a inclinação do morro maior é a concordância com as medições experimentais. / The shape of the wind velocity profile changes according to local features of terrain shape and roughness, which are parameters responsible for defining the Atmospheric Boundary Layer (ABL) profile. Air flow characteristics over and around landforms, such as hills, are of considerable importance for applications related to Wind Farm and Turbine Engineering. The air flow is accelerated on top of hills, which can represent a decisive factor for Wind Turbine placement choices. The present work focuses on the study of ABL behavior as a function of slope and surface roughness of hill-shaped landforms, using the Computational Fluid Dynamics (CFD) to build wind velocity and turbulent intensity profiles. Reynolds-Averaged Navier-Stokes (RANS) equations are closed using the SST k-ω turbulence model; numerical results are compared to experimental data measured in wind tunnel over scale models of the hills under consideration. Eight hill models with slopes varying from 25° to 64° were tested for two types of terrain categories in 2D and 3D, and two analytical codes are used to represent the inlet velocity profiles. Numerical results for the velocity profiles show differences under 4% when compared to their respective experimental data. Turbulent intensity profiles show maximum differences around 7% when compared to experimental data, this can be explained by not being possible to insert inlet turbulent intensity profiles in the simulations. Alternatively, constant values based on the averages of the turbulent intensity at the wind tunnel inlet were used. The 3D models present greater concordance in the speed results than the 2D models and that in addition the greater the slope of the hill, the greater the agreement with the experimental measurements.

As obras de engenharia atuais envolvem unidades estruturais de grande porte cujo projeto e execução devem ser cuidadosamente observados. Devido à complexidade das cargas e solicitações estruturais, as metodologias de projeto devem atender a necessidades específicas. A variabilidade geotécnica associada à diversidade de carregamentos, impõe a necessidade de desenvolvimento de metodologias aplicadas especificamente a projetos de fundações que serão sujeitas a carregamentos laterais, tais como pontes, obras portuárias, torres de linhas de transmissão, aerogeradores (onshore e offshore) e plataformas (offshore e nearshore) de exploração de petróleo e gás natural. Existem alguns métodos relatados na literatura geotécnica para projeto de fundações submetidas a esforços horizontais. Nenhum destes métodos considera uma solução baseada no simples reforço, através de técnicas de cimentação, dos solos na sua camada superficial, radial à estaca. Dessa forma, procura-se na presente pesquisa estudar o comportamento de fundações profundas com reforço do solo na sua camada superficial, sujeitas a carregamentos horizontais. São apresentadas diretrizes de projeto, estabelecendo-se ainda um modelo de previsão da capacidade de carga de fundações profundas submetidas a este tipo de carregamentos. Ensaios em campo experimental e simulações numéricas tridimensionais, usando o Método dos Elementos Finitos foram realizados, por forma a se obter uma melhor compreensão do comportamento de estacas carregadas lateralmente. Considerando o diâmetro da estaca (D) e a sua profundidade (L), no campo experimental, foram definidas razões L/D representando o comportamento de estacas rígidas e flexíveis. Diversos ensaios de carregamento horizontal foram realizados para estas relações L/D, em solo natural e com solo melhorado radial às estacas. As análises numéricas consistiram numa análise paramétrica onde foram variados parâmetros geométricos (da estaca e do solo tratado) e geotécnicos, necessários à caracterização dos materiais no modelo utilizado, o de Mohr-Coulomb. O modelo de previsão proposto foi obtido com base na análise dos resultados de simulações numéricas usando o software ABAQUS®, validados com provas de cargas no campo experimental. É também de salientar que nesta pesquisa apenas será considerada a ruptura geotécnica, pelo que é assumido que as estacas têm comportamento elástico. Do estudo realizado pode-se concluir que o uso de uma camada superficial de solo tratado radial à estaca melhora significativamente o desempenho do sistema, aumentando a sua capacidade de carga e diminuindo a sua deformação, mostrando ser uma ótima e promissora alternativa para fundações profundas sujeitas a carregamentos horizontais. / Current engineering works typically envolve large structural units whose design and implementation should be closely observed. Due to the complexity of the loads and structural needs, the design methodologies should comply specific requirements. The geotechnical variability combined with the loads diversity imposes the need to develop methodologies applied specifically to projects whose foundations will be laterally loaded, like bridges, harbors, transmission line towers, onshore and offshore wind turbines, among others. There are several methods reported in geotechnical literature to design piles that will be subjected to horizontal loads. However, none of these methods consider a solution based on a simple soil reinforcement using cementation techniques, in a superficial layer, radial to pile. The main goal of this research is to study the behavior of deep foundations with a reinforced soil system, subjected to lateral loads. Design guidelines are presented, leading to a model that predicts the ultimate load capacity of deep foundations subjected to these types of efforts. Field tests and tridimensional numerical simulations using the Finite Element Method were performed in order to achieve a better understanding of the behaviour of laterally loaded piles. Considering the pile diameter (D) and its depth (L), different L/D ratio were defined, corresponding to rigid and flexible piles. Using these L/D ratios, in both natural and reinforced soils, numerical and field tests were performed to provide experimental evidences of its behaviour. Numerical tests consisted in a parametric analysis where different geometric (pile and treated soil) and geotechnical parameters, necessaries to the Mohr-Coulomb model, have been modified. The proposed prediction model is based on the analysis of the numerical simulations results, using ABAQUS® software, validated with the field tests. It is important to point that in this study only geotechnical rupture is considered. Therefore it is assumed that piles have elastic behaviour. Has been concluded that the use of a superficial treated layer, radial to pile, considerably improves the system performance, increasing the lateral load capacity and decreasing their deformation, showing that this technique could be a promising solution to deep foundations subjected to horizontal loads.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Na avaliação da maturidade de horizontes geradores e da história térmica de uma bacia com registro de atividade magmática é preciso considerar o efeito térmico imposto pela intrusão de corpos ígneos, como diques e soleiras. Dessa maneira, foi realizada a análise numérica transiente, pelo método de diferenças finitas, do fluxo térmico por condução provocado pela intrusão das soleiras básicas cretáceas nos horizontes geradores do Membro Assistência, Formação Irati, Bacia do Paraná. Esta análise, por sua vez, viabilizou a modelagem do parâmetro de reflectância da vitrinita nos estratos de folhelhos adjacentes às soleiras. Para tanto, foram utilizados os dados de seção de três poços, os quais registram espessuras de soleiras de até 4 m, e um poço com uma soleira de 27 m de espessura. Os poços localizam-se na porção sudeste da bacia. Na simulação numérica, foi considerado o processo de solidificação do magma ou de cristalização das suas fases minerais. A modelagem de reflectância da vitrinita baseou-se em um modelo pré-concebido da história térmica da Formação Irati, sendo os resultados desta simulação de maturidade do querogênio obtidos através do uso do programa EASY%Ro. Considerando-se os erros embutidos no modelo numérico e na discretização da história térmica dos estratos estudados, foram obtidos valores modelados de reflectância da vitrinita similares aos valores medidos nos poços pelo método tradicional. Somente no caso da seção com a soleira de 27 m de espessura houve uma grande diferença entre estes valores. Contudo, o alto coeficiente de correlação (0,95) entre estes possibilita a correção do efeito da espessura da soleira em análises futuras. Assim, a análise numérica simulou o halo térmico da soleira, caracterizado, segundo os dados de modelagem de refletância da vitrinita, por uma faixa acima e abaixo da soleira com espessura equivalente à espessura da soleira encaixada nos estratos geradores da Formação Irati. Essa metodologia de avaliação propicia um estudo preditivo das condições de maturidade de horizontes geradores em bacias ou áreas com magmatismo intrusivo, nas quais as análises do parâmetro de reflectância da vitrinita sejam ausentes ou escassas. / To evaluate the thermal maturity and thermal history of source rocks in basins with magmatic activity it is important to consider the thermal effects imposed by igneous intrusions, such as sills and dykes. This work uses the finite difference method for such evaluation, with the transient numerical analysis of heat conduction from Cretaceous diabase sills intruded into the source rocks of the Assistência Member, Irati Formation, Paraná Basin. This analysis has permitted modeling vitrinite reflectance of the shale strata adjacent to the sills. The data of four wells are used from the southeastern portion of the basin, with diabase thicknesses, respectively, of 1m, 2 m, 4 m and 27 m. The numerical simulation includes the process of magma solidification or mineral phase crystallization. The vitrinite reflectance modeling followed a pre-established thermal history of the Irati Formation, using the EASY%Ro program to simulate kerogen maturity levels. Considering the errors built into the numerical model and the thermal history discretisation of studied strata, the acquired values of modeled vitrinite reflectance closely resembled well data analyzed by the traditional method. Major discrepancies were observed in the case of the well containing a sill 27 m thick, but even in this case the high correlation coefficient (0,95) between the measured and calculated values is expected to permit correction of the sill thickness effect in future studies. The numerical analysis correctly simulated the thermal halo induced by sill emplacement, enabling vitrinite reflectance modeling to characterize it as a zone extending both above and below the sill with thicknesses similar to that of the sills. This evaluation methodology contributes to a predictive study of the maturity conditions of source rocks within basins or areas with intrusive magmatism where analysis of the vitrinite reflectance parameter are sporadic or absent.

Diversos pesquisadores têm estudado o comportamento e o emprego de aduelas de concreto, que constituem as vigas segmentadas em sistemas estruturais, de maneira especial pontes e viadutos. Por esta razão, inúmeros trabalhos têm sido publicados nos últimos anos respaldados por testes experimentais e análises numéricas. O comportamento destas vigas contrasta com as clássicas vigas monolíticas em diversos aspectos, pois, a estrutura é composta de partes de elementos de concreto pré-moldado que, após serem posicionados no local definitivo, são protendidos. A protensão pode ser aderente ou não aderente. A principal vantagem deste sistema de construção é a rapidez e o alto controle de qualidade, por isso é largamente utilizado, havendo uma demanda de estudo de previsão do seu real comportamento No presente trabalho apresenta-se uma modelagem numérica via elementos finitos, para simular o comportamento de vigas compostas por aduelas justapostas sem material ligante entre as juntas. A protensão aplicada é aderente e a análise considera a não linearidade da região da junta. Assim sendo, o objetivo desta investigação é dar uma contribuição ao estudo do comportamento estrutural estático de vigas segmentadas, atentando para o comportamento das juntas, utilizando um programa comercial. Para o modelo são empregadas técnicas usuais de discretização, via método dos elementos finitos (MEF), por meio do programa de elementos finitos SAP2000[93]. O modelo proposto é constituído de elementos de placa próprios para concreto para representar a viga, a protensão é introduzida por meio de barras bidimensionais que transferem as tensões ao longo de seu comprimento e as juntas são implementadas utilizando elementos de contato. A analise é bidimensional e considera os efeitos das perdas de protensão. Este trabalho de pesquisa objetiva também o estudo de elementos de contato especialmente as características de deformação para esta ferramenta computacional. A definição dos parâmetros para o modelo foi feita com base em dados experimentais disponíveis na literatura. O modelo numérico foi calibrado e confrontado com resultados experimentais obtidos em ensaios de laboratório. / Several researchers have studied the behavior and the use of concrete staves, which are segmented beams in structural systems, especially bridges and overpasses, in civil engineering. For this reason, numerous studies have been published in recent years supported by experimental tests and numerical analyzes. The behavior of these beams in contrast to the conventional monolithic beams in different ways because the structure is composed of portions of pre-cast concrete elements which after being placed in situ are prestressed. The prestressing can be adhered or otherwise attached. The main advantage of this system of construction is speed and high quality control, so it is widely used; there is a demand forecast study their actual behavior. In this paper, we present a finite element model to simulate the behavior of composite beams prestressed by adherent with staves. Therefore, the objective of this research is to make a contribution to the study of static structural behavior of beams targeted observing the behavior of joints using a commercial program. For the model are employed standard techniques of discretization via the finite element method (FEM), using the finite element program SAP2000 [90]. The model is made of elements suitable for plaque to represent the actual beam, the prestressing is introduced by means of two-dimensional bar which transfer the stresses along its length and the joints are implemented using contact elements proposed by the program, called Link. The analysis is two dimensional and considers the effects of prestressing losses. This research also aims to study the contact elements especially the characteristics of deformation to this computational tool. The definition of parameters for the model was based on experimental data available in literature. The numerical model was calibrated and compared with experimental results obtained in laboratory trials.

Les géostructures énergétiques sont des ouvrages de génie civil qui intègrent un circuit de fluide caloporteur. Dans cette étude l’installation de circuits géothermiques dans des remblais est envisagé afin d’injecter ou d’extraire de la chaleur. Lors de la construction de ces remblais, deux paramètres sont à contrôler : la teneur en eau w (%) et la masse volumique sèche rd (Mg/m3). Ces deux paramètres ainsi que la nature du sol, le chargement appliqué et la variation cyclique de la température pourraient influencer la capacité de stockage et la stabilité du système. Après une partie synthétisant l’état de l’art sur ces thématiques, cette thèse comprend une partie expérimentale puis une partie numérique appliquée à un cas test de stockage. Dans la partie expérimentale, l’influence de la variation de température induite par l’échange thermique sur les propriétés thermiques et mécaniques du sol est étudiée. Pour cela des essais sont réalisés en laboratoire sur un limon du bassin parisien compacté et soumis à une gamme de variation de température de 20° à 50°C. Les effets de ces variations sur les paramètres mécaniques et les paramètres thermiques sont mesurés. Les résultats obtenus montrent une évolution des paramètres thermiques du matériau du côté sec de la courbe de compactage, particulièrement visible pour les températures importantes. La réversibilité de l’effet du chauffage est obtenue après plusieurs cycles de chauffage-refroidissement. Les propriétés mécaniques mesurées sont la résistance à la compression simple et les paramètres pressiométriques. Pour cela, des essais en laboratoire, à l’échelle métrique, sont réalisés. Un ramollissement du sol sous l’effet du chauffage et une rigidification sous l’effet des cycles thermiques sont constatés. Pour optimiser le système du stockage, une modélisation thermo-hydrique d’un remblai modèle réalisé avec le limon de Plaisir compacté légèrement du côté humide de l’optimum Proctor est effectuée. La comparaison des cas tests a permis de déterminer l’entraxe qui minimise l’interaction entre les sondes thermiques, ainsi que la distance optimale entre les dernières sondes et le pied de remblai. Les scenarii d’injection/extraction étudiés ont montré que le stockage de chaleur dans le remblai est faisable en choisissant un programme thermique adéquat pour l’exploitation du stockage. La mise en place de plusieurs lits de sondes thermiques et d’une isolation thermique sur la partie supérieure du remblai de stockage permet d’augmenter la capacité du remblai à accumuler de la chaleur dans le noyau à la fin de la période de relaxation. La simulation de ce scénario sur 10 ans avec la prise en compte des cycles de température, montre un réchauffement du remblai sur plusieurs années jusqu’à atteindre une évolution équilibrée au bout de la 7 ème année. Arrivé à cet état d’équilibre, l’évolution des températures est reproductible d’une année sur l’autre / Energy geostructures are civil engineering structures equipped with energy exchanger elements in order to store heat seasonally. The aim of this study is the use of compacted soil to store energy through installation of horizontal exchangers in an embankment. During the soil compaction, two parameters were controlled: the water content w and the dry density ρd. This parameters as well as the soil nature, the mechanical load path and the cyclic temperature variation may affect the storage capacity and the system stability. This work includes an experimental part and a modeling part. In the experimental part, the impact of the temperature variation is studied on the thermal and mechanical properties of the compacted soil. The Plaisir loam (PL) extracted from the Paris region was investigated through laboratory tests at a temperatures range of 20 to 50°C. The results showed that the thermal properties of the compacted soils increased on the dry side of the compaction curve. This evolution was clearly confirmed for higher temperatures. The application of cyclic temperature variations showed reversible evolutions in the thermal properties after one cycle. The results of unconfined compressive tests and pressuremeter tests showed that heating induces a softening of the material whereas several temperature cycles induce a stiffening of the material. Thereafter, a coupled thermo-hydraulic modeling of an embankment made of the compacted Plaisir loam is performed in order to optimize the storage system. The comparison of different modelling results, fixed the temperature sensors spacing that minimizes the interactions between them, and the optimal distance between the last sensors and the bottom of the slope. It is shown that if an appropriate thermal program is chosen, the heat storage in the embankment could be possible. A better efficiency of the storage capacity can be reached by introducing 3 temperature sensors rows in the storage and by covering the storage with a thermal insulation. The simulation of this scenario over 10 years including temperature cycles shows a heating of the embankment for several years, until to reach an equilibrium state after the 7th year

Made available in DSpace on 2014-06-11T19:32:17Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-05-22Bitstream added on 2014-06-13T18:43:28Z : No. of bitstreams: 1 romero_af_dr_rcla.pdf: 17670184 bytes, checksum: 06d42107402ca20faf754bc99cbfe1ea (MD5) / Agência Nacional do Petróleo, Gás Natural e Biocombustíveis (ANP) / Este trabalho apresenta Mapas de Vulnerabilidade Ambiental ao Óleo simulando um vazamento de óleo no fundeadouro do Porto de Santos, próximo ao litoral de Praia Grande. Foram também elaboradas Cartas de Sensibilidade Ambiental ao Óleo (SAO) para o trecho do litoral paulista entre os municípios de Praia Grande e Cananéia. A metodologia utilizada para elaboração das Cartas SAO é baseada nas normas do Ministério do Meio Ambiente e para a elaboração dos Mapas de Vulnerabilidade foi utilizado o modelo SIMAP, desenvolvido pela empresa ASA, capaz de representar a mancha de óleo na superfície do mar, na linha de costa e na coluna d’água. A área apresenta trechos com intenso uso turístico, principalmente nos meses de verão e áreas com ambientes naturais preservados, com destaque à presença do sistema estuarino-lagunar de Cananéia-Iguape e Unidades de Conservação, que conferem à área grande importância ecológica. As Carta SAO foram geradas nas escalas tática (1:150.000) e operacional (1:50.000 e 1:25.000) e os Mapas de Vulnerabilidade foram gerados em escalas entre 1:100.000 e 1:750.000, de forma a abranger toda a área da mancha de óleo. Os resultados confirmam a necessidade de avançar na abordagem da sensibilidade da costa ao óleo, incorporando às cartas SAO informações sobre a probabilidade das áreas serem atingidas, estimativas do tempo de contato na costa e informações sobre a área da mancha que tem potencial tóxico à biota. / This paper shows the Environmental Vulnerability Maps a simulated oil spill in the anchorage of the Santos port, close to Praia Grande shore. ESI Maps for the São Paulo shore between the municipalities of Praia Grande and Cananéia were also built. The methodology used to build ESI Maps is based on the Ministry of the Environment rules and for the construction of the Vulnerability charts used the SIMAP model, developed by the ASA. This is capable of modeling the oil spill on the surface of the sea, in the coast line and in the water column. The whole area shows intense tourist use, especially during the summer and areas with preserved natural environments include the presence of the estuarine-lagoon system of Cananéia-Iguape and Conservation Units that give the area great ecological importance. ESI Maps were generated in the tatic range (1:150.000) and operational (1:50.000 and 1:25.000) and the vulnerability maps were generated using 1:100.000 and 1:750.000 scales, to cover the entire area of oil stain. The results confirm the sensitivity of the coast to oil, use of the information above has been incorporated in the ESI Maps to estimate shore contact lead time and of the oil spill and this toxicity potential on the environment.

Les disques de débris orbitant dans l'environnement des étoiles proches constituent un indicateur très important des propriétés des systèmes planétaires extra-solaires. Depuis l'espace et au sol, les moyens observationnels actuels permettent de déterminer dans divers domaines de longueurs d'ondes les propriétés spatiales de ces disques et celles des grains de poussières circumstellaires. Cette thèse aborde le sujet de la modélisation des disques de débris, à partir de données fournies par de multiples instruments, en premier lieu les télescopes spatiaux Hubble et Herschel, et les interféromètres infrarouges du VLTI, CHARA, et KIN. Mes premiers projets ont pris place dans le cadre de deux programmes-clés de l'Observatoire Spatial Herschel dédiés à l'étude des disques circumstellaires autour des étoiles proches. Au sein du projet GASPS, j'ai obtenu des observations spectro-photométriques de HD 181327, une jeune étoile (12+8-4 millions d'années, Ma) de type solaire entourée d'un anneau de débris massif de 90 unités astronomique (UA) de rayon vu aussi en lumière diffusée par le télescope spatial Hubble. La bonne détermination de la géométrie de l'anneau permet de se concentrer sur la modélisation de la distribution spectrale d'énergie, afin de mieux caractériser les propriétés des poussières. J'ai utilisé le code de transfert radiatif GRaTer et démontré que le système héberge une population de planétésimaux glacés, qui pourrait représenter une source d'eau et de volatils susceptible d'être libérée sur des planètes telluriques encore en formation. Je discute quelques résultats additionnels obtenus avec Herschel à propos de disques de débris jeunes, notamment HD 32297, et d'analogues faibles de la Ceinture de Kuiper. Les disques exo-zodiacaux (exozodis), analogues du nuage Zodiacal du Système Solaire, représentent une contrepartie chaude (ou tiède) aux disques de débris, résidant proche de la zone habitable (moins de quelques unités astronomiques) et encore mal connue. Ils sont révélés par leur émission proche et moyen infrarouge et peuvent être étudiés avec la précision et la résolution requises grace à l'interférométrie optique. Dans le cas de l'étoile Beta Pictoris (12+8-4 Ma), dont le disque est vu par la tranche, une fraction significative du disque externe diffuse de la lumière vers le champ de vue des interféromètres ; une composante interne chaude doit tout de même être invoquée pour justifier de l'excès mesuré dans l'infrarouge proche. En m'appuyant sur l'exemple de l'étoile Véga (440±40 Ma), je présente la méthodologie employée et démontre que les exozodis chauds se caractérisent par une abondance de poussières sub-microniques, près de la distance de sublimation de l'étoile. D'un point de vue théorique, le mécanisme de production de ces petits grains non-liés est encore incompris. J'aborde plus en détails le cas du disque exozodiacal à deux composantes (chaude et tiède) de Fomalhaut (440±40 Ma). Je développe une nouvelle méthode de calcul des distances de sublimation et recense les processus variés qui peuvent affecter un grain de poussière afin de fournir un cadre pour l'interprétation : l'exozodi chaud à ~0.1 - 0.2 UA serait la signature indirecte d'une ceinture d'astéroïdes située à 2 UA à l'activité dynamique particulièrement intense. Finalement, je dresse un bilan des propriétés des disques de débris et de ce qu'ils peuvent nous apprendre quand on les compare au Système Solaire, et propose de futures directions de recherche pour explorer davantage les systèmes planétaires et leur dynamique. / Debris disks orbiting in the environment of nearby stars are a very important indicator of extrasolar planetary systems properties. From space and from the ground, current observational facilities enable a multi-wavelength determination of the disks structures and of the dust properties. This thesis addresses the topic of debris disks modelling, based on data from multiple instruments including first of all the Herschel and Hubble space telescopes, and the VLTI, CHARA and KIN infrared interferometers. My first research pro jects took place in the framework of two key programs from the Herschel Space Observatory dedicated to the study of circumstellar disks around nearby stars. As part of the GASPS pro ject, I obtained Herschel far-infrared spectro-photometric observations of HD 181327, a young (12+8−4 Myr) Sun-like star surrounded by a massive, 90 AU-wide debris belt, also imaged in scattered light by the Hubble Space Telescope. Proper determination of the belt geometry allows one to focus on modelling the dust properties. I used the GRaTer radiative transfer code to demonstrate that the system hosts a population of icy planetesimals that may be a source for the future delivery of water and volatiles onto forming terrestrial planets. I discuss additional results obtained with Herschel related to young debris disks, in particular HD 32297, and to faint Kuiper-Belt analogues. Exo-zodiacal disks (exozodis), those analogues to the Solar System Zodiacal cloud, represent a little known hot (or warm) counterpart of debris disks located close the habitable zone (inside of a few AUs). They are revealed by their near- to mid-infrared emission and can be assessed with the required accuracy and resolution with optical interferometers. In the case of the near edge-on star β Pictoris (12+8−4 Myr), I show that a significant fraction of the outer disk scatters light towards the small field-of-view of the interferometers; an inner hot component must nonetheless be invoked to explain the measured near-infrared excess. Based on the example of the star Vega (440 ± 40 Myr), I introduce a methodology to study inner dust disks and I show that hot exozodis are characterized by an abundance of submicron-sized grains, close to the star sublimation distance. From a theoretical point-of-view, the production mechanism for these small, unbound grains is not understood. I go into more details on the case of the Fomalhaut (440 ± 40 Ma) double-component (warm and hot) exozodiacal disk. I develop a new model for the calculation of the dust sublimation distances, and I address the various processes that can affect a dust grain in order to provide a framework for interpreting the exozodi: the hot exozodiacal disk may be the indirect signature of an asteroid belt with a particularly high dynamical activity. Lastly I draw up a summary of the properties of dusty debris disks and of what they can teach us when compared to the Solar System. I propose possible future research directions for further investigations of planetary systems and their dynamics.

[pt] Neste trabalho, apresenta-se um estudo dos processos de transporte e biodegradação do benzeno e da mistura benzeno/etanol em um solo contaminado, através de simulações em diferentes modelos. Nas simulações foi utilizado o programa de elementos finitos FEFLOW 6.1, para análise de fluxo e transporte de contaminantes. No estudo incorporou-se satisfatoriamente o modelo de reação cinético de Monod multiplicativo, para problemas de transporte de contaminantes, no módulo de reação definido pelo usuário (FEMATHED) do programa FEFLOW 6.1. Este modelo foi utilizado nas diversas simulações realizadas. Para encontrar os valores de parâmetros de Monod e da população bacteriana, simulou-se o comportamento de um bloco de solo in situ contaminado com benzeno usando dados experimentais publicado na dissertação de mestrado de Martins (2010). Como aplicação dos procedimentos estudados, foram simuladas duas colunas em PVC com amostras indeformadas de um solo residual (lisímetros), onde foi fornecida uma solução contaminante na direção vertical, contrário à gravidade, com a finalidade de avaliar ao longo da coluna, a biodegradação dos compostos de benzeno e a influência do etanol nesse processo. Além disso, avaliou-se o atraso da degradação do benzeno por causa da presença do etanol na zona saturada e pelo aumento de biomassa nos domínios simulados. O trabalho também mostra uma descrição do programa utilizado e sua formulação. Finalmente, apresenta-se, comentam-se os resultados e concluem-se a pesquisa. / [en] In this work was studied the transport and biodegradation processes of benzene and of the benzene/ethanol mixture in a contaminated soil using different simulation models. In the simulations, were used the finite element program called FEFLOW 6.1 for flow analysis and transport of contaminants. The study successfully incorporated the kinetic reaction model of multiplicative Monod, for contaminant transport problems, in a reaction module defined by the user (FEMATHED - FEFLOW 6.1). This model was applied in the simulations. To find the values of Monod parameters and bacterial population the behavior of an in situ benzene contaminated soil-block was simulated using experimental data published by Martins (2010). As an application of the studied procedures, two PVC columns filled with undisturbed residual soil were simulated (lysimeters). The lysimeters were vertically provided with a contaminant solution in the vertical direction opposite to gravity, in order to evaluate along the column, the biodegradation of benzene compounds and the influence of the ethanol in the process. In addition, was evaluated the delay of benzene degradation due to the presence of ethanol in the saturated zone and the increasing in biomass in the region of simulated model. This study also shows a description of the program used and its formulation. Finally, the results of the analyses and the incorporation of the model performed are presented, conclude and commented.