L'allumage d'un moteur fusée cryotechnique (carburants liquides) est une phase critique. La moindre anomalie dans la procédure d'allumage peut conduire à la destruction du lanceur. L'objectif de cette thèse est de développer une méthodologie s'appuyant sur la simulation aux grandes échelles (LES) pour étudier les phénomènes physiques impliqués dans un tel allumage. L'intérêt de la méthode LES est de pouvoir capturer les couplages instationnaires entre la turbulence, les processus diphasiques et la cinétique chimique. L'outil numérique est tout d'abord validé sur des cas académiques et expérimentaux, puis appliqué à un moteur fusée réel. Une approche graduelle est employée : les différents cas de validation présentent une complexité croissante, permettant d'isoler les processus physiques principaux. Ce travail de recherche montre que l'approche de la simulation aux grandes échelles, dans un contexte de calcul massivement parallèle, peut être utilisée pour étudier la séquence complète d'allumage dans un moteur fusée réel. / The ignition of a cryogenic rocket engine (liquid propellants) is a critical phase. The slightest anomaly in the ignition sequence can lead to the destruction of the entire launcher. The objective of this research work is to set a methodology based on the Large Eddy Simulation (LES) approach, to study the different physical phenomena involved in such ignition transient. The LES method can capture the unsteady processes such as turbulence, two-phase flow physics and chemical kinetics. The numerical tool is first validated in academic and experimental cases, and then applied to a real rocket engine. A gradual approach is employed : the complexity is increased between each validation case, so as to identify the main physical processes. This research work shows that the LES approach, in the context of massively parallel computing, can be used to study the whole ignition sequence of a real cryogenic rocket engine.

Pour effectuer des simulations d'écoulement diphasique dans les réservoirs fracturés, l'usage des modèles DFM entraîne des temps de calculs exorbitants. L'une des solutions envisageables est le recours aux modèles double milieu. Ces modèles nécessitent la détermination des dimensions du bloc équivalent et la mise à l'échelle des paramètres d'écoulement monophasique et diphasique. Concernant les paramètres d'écoulement monophasique, des méthodes de mise à l'échelle existantes ont déjà fait leur preuve. En contrepartie la mise à l'échelle des paramètres d'écoulement diphasique reste un sujet ouvert nécessitant l'identification de la nature des forces (capillaires, gravitaires ou visqueuses) contrôlant l'écoulement dans le réservoir. Dans le cadre de cette thèse, les formulations mathématiques et les modèles numériques liées à la simulation de type DFM et double milieu ont été explorés. Une étude bibliographique portant sur les méthodes existantes de mise à l'échelle a été développée. Une nouvelle méthode de détermination des dimensions du bloc équivalent (méthode OBS) a été mise en place. Une analyse dimensionnelle servant à identifier la nature des échanges matrice-fractures (capillaire ou visqueuses) lors d'un écoulement diphasique eau-huile, sans gravité, a été mise en place. Le nombre capillaire dérivé a été testé. Enfin, une méthodologie de mise l'échelle des paramètres équivalents double milieu a été mise en place. Cette méthodologie traite le cas d'un écoulement diphasique dans les réservoirs fracturés ayant un milieu matriciel hétérogène dans un contexte d'échanges matrice-fractures dominés par les effets visqueux. / In order to carry-out two phase flow simulations within naturally fractured reservoirs, using DFM models results in huge computational costs. Using dual medium models is one of the available alternative solutions. These models require identifying the equivalent bloc dimensions and upscaling single phase and two phase flow parameters. Available upcaling methods related to single phase parameters reached maturity. Otherwise, upscaling two phase flow parameters is still an open research topic requiring identifying the type of the forces controlling flow in the fractured reservoir (gravity, capillary forces, and viscous forces). During this PhD work, mathematical and numerical models related to DFM and dual medium simulations were explored. A study of the state of the art related to upscaling methods was done. A new and original method allowing determining the dual medium equivalent bloc dimensions (OBS method) was settled down. A dimensional analysis aiming at identifying the type of the forces controlling matrix-fracture exchanges (capillarity, viscous forces) in a water-oil two phase flow within naturally fractured reservoirs without gravity was settled down. The derived capillary number was tested. Finally, an equivalent two phase flow parameters upscaling workflow was also settled down. This workflow treats the particular case of a two phase flow in naturally fractured reservoirs with an heterogeneous matrix medium in a context of matrix-fracture exchanges ruled by viscous forces.

Gas-liquid annular two phase flow in pipes is important in the oil and gas, nuclear and the process industries. It has been identified as one of the most frequently encountered flow regimes and many models (empirical and theoretical) for the film flow and droplet behaviour for example have been developed since the 1950s. However, the behaviour in large pipes (those with diameter greater than 100 mm) has not been fully explored. As a result, the two- phase flow characteristics, data, and models specifically for such pipes are scarce or non-existent such that those from smaller pipes are extrapolated for use in design and operation. Many authors have cautioned against this approach since multiphase pipe flow behaviour is different between small and large pipes. For instance the typical slug flows seem not to occur in vertical upwards flows when the pipe diameter exceeds 100 mm. It is therefore imperative that theoretical models and empirical correlations for such large diameter pipes are specifically developed.

The geological repository for final storage of spent nuclear fuel, envisioned by the Swedish Nuclear Fuel and Management Company (SKB), relies on several barriers: copper canisters deposited in holes in the floor of underground tunnels in deep bedrock, embedded in a buffer of compacted bentonite. The initially unsaturated buffer would take up water from the surrounding rock mass and swell to seal any potential gap. This initial two-phase (gas and liquid) regime with two components (air and water) may impact the final density, swelling pressure and biogeochemical conditions in the buffer. A main objective of this work is to identify factors and mechanisms that govern deposition hole inflow and bentonite wetting under the prevailing two-phase flow conditions in sparsely fractured bedrock. For this purpose, we use the numerical code TOUGH2 to perform two-phase flow simulations, conditioned by a companion field experiment (the Bentonite Rock Interaction Experiment or BRIE) performed in a 417 m deep tunnel of the Äspö Hard Rock Laboratory in southeastern Sweden. The models predict a significant de-saturation of the rock wall, which was confirmed by field data. To predict the early buffer wetting rates and patterns, the position of local flowing fractures and estimates of local rock matrix permeability appear more important than the total open hole groundwater inflow. A global sensitivity analysis showed that the buffer wetting time and the persistence of unsaturated conditions over extended periods of time in the rock depend primarily on the local fracture positions, rock matrix permeability, ventilation conditions in the tunnel and pressure far in the rock. Dismantling photographs from BRIE were used to reconstruct a fine-scale snapshot of saturation at the bentonite/rock interface, showing tremendous spatial variability. The high level of heterogeneity in the rock generates complex two-phase flow phenomena (air trapping, dissolution), which need to be accounted for in buffer design and rock suitability criteria. In particular, results suggest that uncertainties regarding two-phase flow behavior are relatively high close to residual air saturation, which may also have important implications for other applications involving two-phase flows, such as geological storage of carbon dioxide. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 4: Manuscript.</p>

Lorsqu'un verre libère trop rapidement le gaz qu'il contient, la disparition des arômes véhiculés par la bulle est soudaine et irrémédiable. Ainsi, la connaissance des mécanismes physiques à l'origine de la libération du CO2 dans un verre de champagne doit permettre de mener à une forme de verre propice à un épanouissement des arômes et à une effervescence durable. La contribution des processus convectifs de brassage du vin sur la désorption du CO2 demeure assez mal connue. Pour approfondir notre compréhension de ces aspects, nous analysons les processus de libération du dioxyde de carbone au cours d'une dégustation. La démarche adoptée dans cette thèse consiste à étudier les mécanismes de transferts de masse (nucléation, diffusion, évaporation) entre les phases liquide et gazeuse. Par le biais de méthodes expérimentales (tomographie laser, PIV, thermographie IR) et numérique (code CFD), nous réalisons le suivi de l'évolution instationnaire de l'écoulement diphasique dans un verre de champagne. Nous mettons en évidence un écoulement complexe, composé de multiples instabilités hydrodynamiques. Les résultats montrent également que la libération du CO2 dépend intimement de la forme du verre et de la température de service du vin. En mettant en évidence le rôle de la forme du verre sur la libération du CO2, ces travaux ont permis d'améliorer la connaissance des paramètres qui affectent ou favorisent l'effervescence au cours d'une dégustation. Ces conclusions devront être confirmées par un panel de dégustation pour montrer que la libération des arômes est étroitement liée à la forme du verre qui reçoit le vin. / When a glass releases too quickly his dissolved gas, the loss of the aromas carried by the bubbles is sudden and irreversible. So, the knowledge of the physical mechanisms at the origin of CO2 release in a glass of champagne should lead to a glass shape conducive to aromas development and at a sustainable effervescence.The contribution of mechanisms of admixture of the wine on the CO2 desorption in a glass of champagne remains still unknown. To deepen our understanding of these aspects, we analyze the carbon dioxide release processes in tasting conditions. The approach adopted in this thesis consists in studying the mass transfer mechanisms (nucleation, diffusion, evaporation) between the liquid and gaseous phase. By experimental (laser tomography, PIV, IR thermography) and numerical ways (CFD), we follow the unsteady evolution of the two phase flow in a champagne glass. We highlight a complex flow, composed of multiple hydrodynamic instabilities. The results show also that the CO2 release strongly depends on the glass shape and on the wine temperature.By highlighting the glass shape on the carbon dioxide release, these works allowed to improve the parameters knowledge which affect or favor the effervescence process in tasting conditions. These conclusions must be confirmed by a tasting panel to show that the aromas release is closely related to the glass shape.

Orientador: Eugênio Spanó Rosa / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-18T15:26:34Z (GMT). No. of bitstreams: 1 Lima_LuizEduardoMelo_D.pdf: 3018902 bytes, checksum: ac45ca48369c0c21398892fa2f7de5ac (MD5) Previous issue date: 2011 / Resumo: Escoamentos gás-líquido são frequentemente encontrados na natureza, bem como em diversas aplicações industriais. Na área de produção de petróleo, por exemplo, em sistemas de elevação natural ou artificial (gas-lift contínuo ou intermitente), gás e óleo escoam simultaneamente em tubulações. A previsão de escoamentos gás-líquido torna-se necessária à viabilidade técnica-econômica de muitos processos industriais, por exemplo, na indústria de petróleo devido ao aumento do consumo mundial de combustíveis e a descoberta de novos campos petrolíferos. Em escoamentos gáslíquido, as fases se distribuem espacialmente e temporalmente ao longo da tubulação dependendo das vazões, propriedades físicas das fases e das características da tubulação, entre outros parâmetros. A combinação destes fatores gera diversos padrões de escoamento gás-líquido que podem ser agrupados em três classes principais: disperso, separado e intermitente. Os principais objetivos deste trabalho são o desenvolvimento e a análise de uma modelagem unidimensional em regime permanente, baseada no modelo de mistura, que permita a simulação de escoamentos isotérmicos gás-líquido em tubulações com seção transversal circular constante, considerando a fenomenologia envolvida nestes escoamentos. Dentre as contribuições obtidas com a realização deste trabalho destacam-se: a identificação das vantagens e limitações do modelo; as análises de suas formulações, dos parâmetros de fechamento e de sensibilidade às variáveis relacionadas aos padrões; a proposição de um método de solução para um modelo fenomenológico de força de atrito na parede, aplicável aos diversos padrões de escoamento gás-líquido. Os resultados do modelo de mistura foram comparados contra dados experimentais do gradiente de pressão de escoamento nos padrões disperso, separado e intermitente, em diversas inclinações de tubo. Além disto, foram realizadas análises envolvendo transição de padrão de escoamento num tubo vertical. Os resultados obtidos demonstraram que o modelo de mistura captura de forma satisfatória o gradiente de pressão para os diversos padrões de escoamento gás-líquido, num único algoritmo de integração / Abstract: Gas-liquid flows are often found in nature as well as in various industrial applications. In the oil production, for example, in natural or artificial lift systems (continuous or intermittent gas-lift), gas and oil flow simultaneously in pipes. The prediction of gas-liquid behavior becomes necessary for technical and economic viability of many industrial processes, for example, the oil industry due to the increase of world oil consumption and the discovery of new oilfields. In gas-liquid flow, the phases are distributed spatially and temporally along the pipe depending on the flow rate, phase's physical properties and pipe characteristics, among other parameters. The combination of these factors creates different gas-liquid flow patterns that can be grouped into three main classes: dispersed, separated and intermittent. The main objectives of this work are the development and analysis of a steady one-dimensional modeling, based on the mixture model, which allows the simulation of isothermal gas-liquid flow in pipes with constant circular cross section, considering the phenomenology involved in these flows. Among the contributions obtained in this work stand out: to identify the advantages and limitations of the model; the analysis of their formulations, closing parameters and sensibility to variables related to the patterns; to propose a solution method for a phenomenological model of the wall friction force, applied to the different gas-liquid flow patterns. The mixture model results were compared against pressure gradient experimental data from flow in the dispersed, separated and intermittent patterns, in different pipe inclinations. In addition, it was performed an analysis of the flow pattern transition in a vertical pipe. The results showed that the mixture model captures satisfactorily the pressure gradient for different gas-liquid flow patterns, in a single integration algorithm / Doutorado / Termica e Fluidos / Doutor em Engenharia Mecânica

O ambiente Antártico é caracterizado por condições ambientais restritivas de clima, hábitat e biogeografia. Neste sentido, o objetivo deste estudo foi avaliar a diversidade de leveduras em amostras marinhas e terrestres do ambiente Antártico, além da prospecção de lipases que atuem em processos que requerem baixas e moderadas temperaturas. De acordo com os resultados obtidos, 97 leveduras foram recuperadas por semeadura em meio de cultura PDA e YMA a partir de diferentes amostras coletadas na OPERANTAR XXVIII (verão 2010), das quais foram identificados 12 gêneros e 21 espécies. Destas, 45 apresentaram atividade de lipase e duas foram selecionadas para o ensaio de otimização da produção enzimática: C. laurentii L59 e L. scotti L117. A extração de lipase de L. scottii L117 foi avaliada por Sistema de Duas fases Aquosas e o sistema micelar utilizando TX-114 foi o mais eficiente para purificação parcial desta enzima. Por fim, a avaliação da diversidade das 405 leveduras isoladas de macroalgas e liquens (coletadas na OPERANTAR XXXII no verão de 2013) revelou a ocorrência de 24 taxons de leveduras a partir das amostras de macroalgas e 18 taxons a partir das amostras de liquens, sendo apenas cinco espécies comuns a estes dois substratos. / The Antarctic continent is characterized by restrictive environmental conditions of climate, habitats and biogeography. In this sense, the objective of this study was to evaluate the diversity of yeasts in marine and terrestrial samples of the Antarctic environments, as well as the propspecting of lipases that can act in proceses that require low and moderate temperatures. According to the results, 97 yeasts were recovered from different samples collected in OPERANTAR XXVIII (summer 2010), representing 21 different species. Among them, 45 showed lipase activity and two were selected for the optimization of enzyme production: C. laurentii L59 and L. scotti L117. Extraction of L. scottii L117 lipase was assessed by Aqueous Two-Phase System and the micellar system TX-114 was the most efficient for partial enzyme purification. Finally, the diversity evaluation of 405 isolates from seaweeds and lichens (collected in XXXII OPERANTAR, summer of 2013) revealed the occurrence of 24 taxa from macroalgae samples and 18 taxa from lichens samples, being only five substrates common to these two substrata.

Les écoulements diphasiques dans les centrales de type réacteur à eau pressurisée appartiennent à des régimes très variés allant du faible nombre de Mach jusqu'aux ondes de chocs. Calculer des solutions approchées précises de ces écoulements peut s'avérer délicat dans certains régimes. On s'intéresse dans cette thèse à la conception et à l'étude de méthodes numériques robustes et stables à grand pas de temps, capables de calculer des solutions approchées précises quel que soit le régime d'écoulement, y compris sur maillage grossier. Une stratégie pour construire de tels schémas consiste à : utiliser un schéma semi implicite basé sur un splitting d’opérateurs pour séparer la résolution approchée des phénomènes rapides de celles des phénomènes lents ; corriger les flux numériques afin d’améliorer la précision du schéma dans certains régimes. Deux approches sont utilisées pour analyser la capacité du schéma numérique à gérer plusieurs régimes d'écoulement. L’approche des schémas asymptotic preserving est utilisée pour traiter le système de la dynamique des gaz avec termes sources raides. On utilise ensuite la notion de schéma tout-régime pour le système de la dynamique des gaz et les systèmes diphasiques homogénéisés HRM et HEM à bas nombre de Mach. Des propriétés garantissant la stabilité et la robustesse des schémas ont été obtenues, et en particulier des inégalités d'entropie discrètes. L'implémentation de ces méthodes a permis de mener des expériences numériques en 1D et 2D sur maillage non structuré qui confirment le gain en précision et en temps de calcul des schémas asymptotic preserving et tout-régime ainsi construits par rapport à des schémas numériques classiques. / Two-phase flows in Pressurized Water Reactors belong to a wide range of Mach number flows. Computing accurate approximate solutions of those flows may be challenging from a numerical point of view as classical finite volume methods are too diffusive in the low Mach regime. In this thesis, we are interested in designing and studying some robust numerical schemes that are stable for large time steps and accurate even on coarse meshes for a wide range of flow regimes. An important feature is the strategy to construct those schemes. We use a mixed implicit-explicit strategy based on an operator splitting to solve fast and slow phenomena separately. Then, we introduce a modification of a Suliciu type relaxation scheme to improve the accuracy of the numerical scheme in some regime of interest. Two approaches have been used to assess the ability of our numerical schemes to deal with a wide range of flow regimes. The first approach, based on the asymptotic preserving property, has been used for the gas dynamics equations with stiff source terms. The second approach, based on the all-regime property, has been used for the gas dynamics equations and the homogeneous two-phase flows models HRM and HEM in the low Mach regime. We obtained some robustness and stability properties for our numerical schemes. In particular, some discrete entropy inequalities are shown. Numerical evidences, in 1D and in 2D on unstructured meshes, assess the gain in term of accuracy and CPU time of those asymptotic preserving and all-regime numerical schemes in comparison with classical finite volume methods.

[pt] Escoamentos intermitentes gás-líquido são encontrados em diversas aplicações de engenharia, como em linhas de produção de petróleo e em sistemas de refrigeração de reatores nucleares. O conhecimento detalhado deste padrão de escoamento é indispensável para a construção de modelos matemáticos representativos deste fenômeno físico complexo. No presente trabalho, foi desenvolvido um estudo experimental com o objetivo de fornecer informações que possibilitem a melhoria dos modelos existentes para o escoamento bifásico intermitente em duto horizontal. A técnica de velocimetria por imagem de partículas estereoscópica (SPIV) de alta frequência foi empregada, em conjunto com a técnica de fluorescência induzida por laser (LIF), permitindo a obtenção de campos de velocidade na região do pistão de líquido, a jusante da bolha alongada, e na região do filme líquido, a montante da bolha. O arranjo experimental possibilitou a medição das três componentes do vetor velocidade do escoamento bifásico água-glicerina e ar na seção transversal de uma tubulação horizontal de 40mm de diâmetro interno. Os resultados obtidos, originais na literatura, mostraram a evolução detalhada das três componentes dos campos médios do vetor velocidade ao longo da passagem da bolha alongada durante o escoamento intermitente. / [en] Gas-liquid intermittent flows can be found in many engineering applications, such as oil production lines and nuclear reactors cooling systems. The detailed knowledge of this flow pattern is necessary for the development of accurate mathematical models of this complex phenomenon. In this work, an experimental study was developed with the goal to provide data that could be used to improve the existing models for two-phase intermittent flow in horizontal pipes. The high-frequency stereoscopic particle image velocimetry (SPIV) technique was employed along with the laser induced fluorescence (LIF) technique, allowing the measurement of velocity fields in the liquid slug, downstream of the elongated bubble, and in the liquid film, upstream of the elongated bubble. The experimental arrangement allowed the measurement of the three components of the velocity vector in an intermittent two-phase water-glycerine and air flow, in a transversal sections of a 40mm internal diameter horizontal pipe. The results obtained revealed original detailed information on the evolution of the three components of the averaged velocity field associated with the passage of the elongated bubble characteristic of the intermittent flow.

<div>As space exploration continues to accelerate, various cooling applications follow suit. Refrigeration and freezing of biological samples, astronaut food as well as electronics cooling and air-conditioning are necessary and demand increased capacity. In the past, these demands have been met by thermoelectric cooling or cryogenic cycles, which are easily adapted to a microgravity environment but have a relatively low efficiency in the refrigeration and freezing temperature range. A number of studies have investigated the development of higher efficiency vapor compression cycles for spacecraft, which would have the benefit of a smaller mass penalty due to the reduced power consumption. Despite notable research efforts during the 1990s, the number of vapor compression coolers that have operated in microgravity until today is small and their performance was insufficient to provide confidence into the technology for microgravity applications. Related experimental research has decreased since the 2000s.<br></div><div><br></div><div>For this dissertation, all vapor compression cycles (VCC) that have operated in microgravity according to the open literature were reviewed with their applications, compressor types and reported issues. Suggested design tools were summarized with a focus on gravity independence criteria for two-phase flow. For the most effective increase of the technology readiness level, simple but systematic experiments regarding the stability of VCCs against orientation and gravity changes were prioritized in this dissertation. An important goal of the research was the continuous operation and start-up of vapor compression cycles on parabolic flights, experiments that have not been reported in the open literature. Two separate test stands were built and flown on four parabolic flights, totaling 122 parabolas for each experiment.<br></div><div><br></div><div>The parabolic flight experiments were prepared with extensive ground-based testing. Multiple anomalies were encountered during the pursuit of continuous vapor compression cycle operation through a rotation of 360 degrees, including liquid flooding of the compressor. Systematic inclination testing was conducted with two different cycle configurations and a wide range of operating conditions. A strong correlation was found between the relative stability of the heat source heat transfer rate and the refrigerant mass flux for an inclination procedure with angle changes once every 2 minutes.<br></div><div><br></div><div>The parabolic flights exposed the test stand to quickly alternating hyper and microgravity. The evaporation temperature reacted to the different gravity levels with fluctuations that stretched on average 2.2 K from the maximum to minimum temperature measured during one set of parabolas. Changes of the evaporator inlet flow regime as a function of gravity were observed visually and the low-side pressure and mass flow rate sometimes oscillated in microgravity. The cycle responses induced by ground-based inclination testing were typically stronger than changes caused by the parabolic flight maneuvers for relatively low mass flow rates. Overall, the parabolic flight maneuvers were not detrimental to the cycle operation. <br></div><div><br></div><div>The second test stand was dedicated to liquid flooding observations at cycle start-up. Different flow regimes were observed in microgravity during testing with a transparent evaporator but the absence of gravity did not significantly alter the general time-based flooding quantifiers.<br></div><div><br></div><div>Design recommendations are drawn from the research where possible and summarized at the end of the dissertation. Selected data, code, pictures and videos were released together with this dissertation(Brendel, 2021)<br></div>