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Understanding the flow in stirred vessels can be useful for a wide number of industrial applications, like in mining, chemical and pharmaceutical processes. Remodeling and redesigning these processes may have a significant impact on the overall design characteristics, affecting directly product quality and maintenance costs. In most cases the flow around the rotating impeller blades interacting with stationary baffles can cause rapid changes of the flow characteristics, which lead to high levels of turbulence and higher shear rates. The flow is anisotropic and inhomogeneous over the entire volume. A better understanding and a detailed documentation of the turbulent flow field is needed in order to design stirred tanks that can meet the required operation conditions. This thesis describes efforts for accurate estimation of the velocity distribution and the turbulent characteristics (vorticity, turbulent kinetic energy, dissipation rate) in a cylindrical vessel agitated by a Rushton turbine (a disk with six flat blades) and in a tank typical of flotation cells. Results from simulations using FLUENT (a commercial CFD package) are compared with Time Resolved Digital Particle Image Velocimetry (DPIV) for baseline configurations in order to validate and verify the fidelity of the computations. Different turbulence models are used in this study in order to determine the most appropriate for the prediction of turbulent properties. Subsequently a parametric analysis of the flow characteristics as a function of the clearance height of the impeller from the vessel floor is performed for the Rushton tank as well as the flotation cell. Results are presented for both configurations along planes normal or parallel to the impeller axis, displaying velocity vector fields and contour plots of vorticity turbulent dissipation and others. Special attention is focused in the neighborhood of the impeller region and the radial jet generated there. This flow in this neighborhood involves even larger gradients and dissipation levels in tanks equipped with stators. The present results present useful information for the design of the stirring tanks and flotation cells, and provide some guidance on the use of the present tool in generating numerical solutions for such complex flow fields. / Master of Science

Les exploitant aériens cherchent à réduire toujours davantage le coût d'utilisation et d'opération de maintenance des hélicoptères ainsi qu'à limiter leur impact environnemental. Par conséquent, les motoristes tels que Safran Helicopter Engines doivent constamment améliorer les performances de leurs moteurs. Cette amélioration passe notamment par la réduction des consommations de carburants et d'huile de lubrification. La consommation d'huile est liée en grande partie à la formation d'un brouillard diphasique air-huile au sein des paliers de roulements des arbres du moteur. L'air est continûment évacué en transportant des inclusions d'huile vers l'extérieur. Pour limiter ces rejets d'huile, un séparateur en rotation est utilisé pour récupérer l'huile et évacuer l'air. Afin de prédire avec davantage de précision la consommation d'huile et les pertes de charges induites par le séparateur, la présente thèse développe une stratégie d'analyse des écoulements diphasiques au sein des séparateurs. Cette stratégie s'appuie en premier lieu sur des simulations numériques du brouillard d'huile basées sur une approche Euler-Lagrange. Ces simulations permettent d'une part d'analyser l'écoulement d'air et les pertes de charges du séparateur et d'autre part d'appréhender les mécanismes de la séparation de l'huile et d'analyser la consommation en fonction des conditions de fonctionnement. Parallèlement, grâce au financement du projet européen E-Break, un banc d'essais dégazeur a été conçu dans le cadre de cette thèse et réalisé à l'Université Libre de Bruxelles. Des analyses croisées entre essais et simulations permettent de valider la méthodologie de simulation. Cependant, si les pertes de charges sont correctement prédites par le calcul, des efforts supplémentaires sont nécessaires, aussi bien sur la précision des mesures que sur la modélisation de l'écoulement diphasique, pour assurer une prédiction satisfaisante de la consommation d'huile. / Air operators try to reduce ever more operation and maintenance costs of helicopters as well as to limit their environmental impact. Consequently, engine manufacturers such as Safran Helicopter Engines must constantly improve the performance level of the engines they develop. To achieve such an improvement, oil and kerosene consumption must be reduced. Oil consumption is mostly due the formation of an oil mist inside bearing chambers. As the air is continuously scavenged, it carries along oil droplets out of the engines. In order to limit the oil wastes, a separator is used which recovers oil drops carried by the owing air that is vented out. In order to predict with a better level of accuracy the oil consumption and the pressure losses induced by the separator, the present thesis develops a strategy to analyse the two-phase flow within the separator. This strategy relies in the first place on Euler-Lagrange numerical simulation of the oil mist which allow on the one hand to compute the turbulent air flow and the pressure drop induced by the separator and on the other hand to better understand the separation mechanisms and to predict the oil consumption for various operating conditions. Besides, thanks to the funding of the E-Break European project, a test bench has been designed in the framework of this PhD and set up at the Université Libre de Bruxelles. Cross comparisons between measurements and simulations allow validating the numerical methodology. However, even though pressure drops are correctly predicted by the simulation, improvements are still needed, regarding both the measurement accuracy and the two-phase numerical modelling, in order to provide a satisfactory prediction of the oil consumption.

La réfrigération magnétique est une technologie innovante de production de froid, qui peut remplacer la technique classique de compression-détente de fluides frigorigènes. Son principe est basé sur l'effet magnétocalorique qui se traduit par le refroidissement ou l'échauffement de certains matériaux sous l'action d'un champ magnétique. Ce travail de thèse s'est déroulé dans le cadre d'un projet « CARNOT Energies du futur » et s'oriente vers l'étude magnétothermique et fluidique de systèmes de réfrigération. Pour cela, un outil numérique a été développé à l'aide du logiciel FLUENT afin de décrire le comportement thermique de différents régénérateurs, cœur même des systèmes de RM. En parallèle, deux systèmes de réfrigération magnétique ont été développés et améliorés, chacun d'eux présentant des performances intéressantes. Ces résultats ont permis de comprendre et définir les facteurs les plus influents sur leurs performances, et en déduire ainsi leurs conditions de fonctionnement optimales / The magnetic refrigeration is an innovative technology of production of cold, which can replace the refrigerants classic compression-relaxation technique. Its principle is based on the magnetocaloric effect which leads to the cooling or the heating of certain materials under the effect of a magnetic field. This thesis work took place within the framework of a project named " CARNOT Energies of future", and turns to the magnetothermal and fluidic study of refrigeration systems. For that purpose, a digital tool was developed using the FLUENT software to describe the thermal behavior of various regenerators, heart of the MR systems. In parallel, two magnetic refrigeration systems were developed and improved, each of them bringing interesting performances. These results allowed to understand and to define the most influential factors on their performances, so as to deduct their optimal operating conditions.

Des travaux expérimentaux et théoriques ont été menés afin d’enrichir la connaissance et la compréhension du comportement en corrosion du carbure de silicium en présence de mélanges gazeux complexes à très hautes températures. A cette fin ont été mis au point deux nouvelles méthodes expérimentales basées sur le chauffage par effet Joule pour le suivi in-situ des cinétiques d’oxydation, ainsi qu’un modèle intégrant thermodynamique hétérogène et phénomènes de transport en phase gazeuse. Dans le domaine des hautes températures et des basses pressions partielles en espèces oxydantes, l’oxydation de SiC est dite « active » et se traduit par la formation de produits gazeux et la dégradation rapide du matériau associée à une cinétique limitée par le transport des espèces en phase gazeuse. Dans le domaine des basses températures et des hautes pressions partielles en espèces oxydantes, l’oxydation est dite « passive » et se traduit par la croissance d’une couche d’oxyde condensé SiO2 qui agit comme une barrière de diffusion vis-à-vis des espèces oxydantes, et dont la croissance fait intervenir une variété de phénomènes physico-chimiques qu’il a été nécessaire de découpler.Une attention particulière a été portée à l’étude de la transition entre les domaines de conditions correspondant à chacun de ces modes d’oxydation dans des mélanges simples et dans des mélanges complexes comportant deux espèces oxydantes différentes. Une analyse précise de plusieurs modèles de description théorique de cette transition active/passive a pu être réalisée en s’appuyant sur les nouveaux moyens numériques ainsi que sur les nouveaux éclairages relatifs aux mécanismes d’oxydation active et passive issus de cette étude et de la littérature. / Experimental and theoretical studies have been carried out in order to obtain further knowledge and understanding of the corrosion behavior of silicon carbide under complex gas mixtures at very high temperatures. To that purpose, two original experimental methods based on Joule-heating have been designed for the in-situ following of SiC oxidation kinetics, and a model accounting for both heterogeneous kinetics and gas-phase transport phenomena has been developed thanks to a finite volume method. At high temperatures and low oxidant partial pressure, oxidation of SiC is « active » and associated with the formation of gaseous products and high degradation rates of the original materials, the reaction being rate-determined by species transport through a gaseous boundary layer. At low temperatures and high oxidant partial pressures, oxidation is « passive » and associated with the growth of a condensed oxide scale acting as a protecting diffusion barrier. An analytical study has been conducted in order to try and isolate the effects of the various physical and chemical phenomena involved during this passive oxidation, such as different growth mechanisms, volatilization or bubble formation, and quantify how temperature and gas composition influence them.An experimental study of the active/passive transition in the oxidation of SiC has been conducted under gas mixtures including one or two different oxidant species. Numerical simulation tools as well as new insights on oxidation mechanisms were used to analyze different predictive models of the active/passive transition and evaluate and understand the differences between these theoretical results and the ones obtained experimentally.

Os idosos representam um grupo crescente na população e algumas alterações importantes de saúde dessa população advêm de acidentes vasculares cerebrais, que podem deixar sequelas como as afasias. A despeito de resultados positivos obtidos por áreas tradicionais do tratamento das afasias, analistas do comportamento têm desenvolvido procedimentos de ensino bem-sucedidos com populações clínicas de não idosos, empregando procedimentos de exclusão e de ensino de repertórios de discriminação condicional para formação de classes de equivalência entre estímulos verbais. Os objetivos gerais deste trabalho foram: a) verificar a efetividade de um procedimento de ensino por exclusão de substantivos e de verbos para afásicos fluentes e não fluentes, a partir do ensino de discriminações condicionais com estímulos auditivos e visuais, e b) verificar a emergência de repertórios não diretamente ensinados (relações transitivas entre estímulos, nomeação e leitura). Participaram do estudo 14 idosos com afasia. Foram conduzidos dois estudos, nos quais os participantes foram expostos às avaliações iniciais de repertório verbal e foram submetidos ao procedimento de ensino de relações entre palavras ditadas, figuras ou vídeos, e palavras impressas, com sondas posteriores de formação de equivalência, nomeação e leitura, além de pós-testes. Foi utilizado um delineamento de múltiplas sondagens. Resultados gerais indicaram que o procedimento foi efetivo para ensinar novas relações aos participantes, porém não foi suficiente para sustentar a formação de classes de equivalência entre estímulos para a maioria das relações ensinadas, e nem para a emergência de nomeação desses estímulos. Não houve diferenças entre a aprendizagem de substantivos e verbos. O procedimento estudado, com adaptações, pode ser uma alternativa terapêutica para recuperação de repertórios verbais em afásicos. / The elderly represents a growing group in the population and some important changes in the health of this population come from strokes, which can leave sequels such as aphasias. Despite positive results from traditional areas of aphasia treatment, behavioral analysts have developed successful teaching procedures with non-elderly clinical populations, employing exclusion procedures and teaching conditional discrimination to form equivalence classes between verbal stimuli. The general objectives were: a) to verify the effectiveness of a teaching by exclusion nouns and verbs for fluent and non-fluent aphasics, from teaching conditional discriminations with auditory and visual stimuli, and b) verify the emergence of repertoires not directly taught (transitive relations between stimuli, naming and reading). A total of 14 elderly people with aphasia participated in the study. Two studies were conducted, in which the participants were exposed to the initial verbal repertoire evaluations and were submitted to the procedure of teaching relationships between dictated words, figures or videos, and printed words, with subsequent probes of formation of equivalence, naming and reading, besides post-tests. A multiple probe design was used. Overall results indicate that the procedure was effective to teach new relationships to the participants, but it was not enough to sustain the formation of equivalence classes between stimuli for most of the relationships taught, and the emergence of naming these stimuli. There were no differences between the learning of nouns and verbs. The procedure studied, with adaptations, may be a therapeutic alternative for the recovery of verbal repertoires in aphasics.

Os idosos representam um grupo crescente na população e algumas alterações importantes de saúde dessa população advêm de acidentes vasculares cerebrais, que podem deixar sequelas como as afasias. A despeito de resultados positivos obtidos por áreas tradicionais do tratamento das afasias, analistas do comportamento têm desenvolvido procedimentos de ensino bem-sucedidos com populações clínicas de não idosos, empregando procedimentos de exclusão e de ensino de repertórios de discriminação condicional para formação de classes de equivalência entre estímulos verbais. Os objetivos gerais deste trabalho foram: a) verificar a efetividade de um procedimento de ensino por exclusão de substantivos e de verbos para afásicos fluentes e não fluentes, a partir do ensino de discriminações condicionais com estímulos auditivos e visuais, e b) verificar a emergência de repertórios não diretamente ensinados (relações transitivas entre estímulos, nomeação e leitura). Participaram do estudo 14 idosos com afasia. Foram conduzidos dois estudos, nos quais os participantes foram expostos às avaliações iniciais de repertório verbal e foram submetidos ao procedimento de ensino de relações entre palavras ditadas, figuras ou vídeos, e palavras impressas, com sondas posteriores de formação de equivalência, nomeação e leitura, além de pós-testes. Foi utilizado um delineamento de múltiplas sondagens. Resultados gerais indicaram que o procedimento foi efetivo para ensinar novas relações aos participantes, porém não foi suficiente para sustentar a formação de classes de equivalência entre estímulos para a maioria das relações ensinadas, e nem para a emergência de nomeação desses estímulos. Não houve diferenças entre a aprendizagem de substantivos e verbos. O procedimento estudado, com adaptações, pode ser uma alternativa terapêutica para recuperação de repertórios verbais em afásicos. / The elderly represents a growing group in the population and some important changes in the health of this population come from strokes, which can leave sequels such as aphasias. Despite positive results from traditional areas of aphasia treatment, behavioral analysts have developed successful teaching procedures with non-elderly clinical populations, employing exclusion procedures and teaching conditional discrimination to form equivalence classes between verbal stimuli. The general objectives were: a) to verify the effectiveness of a teaching by exclusion nouns and verbs for fluent and non-fluent aphasics, from teaching conditional discriminations with auditory and visual stimuli, and b) verify the emergence of repertoires not directly taught (transitive relations between stimuli, naming and reading). A total of 14 elderly people with aphasia participated in the study. Two studies were conducted, in which the participants were exposed to the initial verbal repertoire evaluations and were submitted to the procedure of teaching relationships between dictated words, figures or videos, and printed words, with subsequent probes of formation of equivalence, naming and reading, besides post-tests. A multiple probe design was used. Overall results indicate that the procedure was effective to teach new relationships to the participants, but it was not enough to sustain the formation of equivalence classes between stimuli for most of the relationships taught, and the emergence of naming these stimuli. There were no differences between the learning of nouns and verbs. The procedure studied, with adaptations, may be a therapeutic alternative for the recovery of verbal repertoires in aphasics.

This diploma thesis focuses on optimization of the flap for the ultralight aircraft Skyleader JA 600, which is produced by the Jihlavan s.r.o. company. Individual types of flaps used in ultralight aircrafts are described in the initial phase of the thesis. In addition, description of the plane of interest Skyleader has been conducted, while along with the basic characteristics the focus is mainly on its wing and flap. The thesis continues with detailed CFD method calibration task, which is mostly focused on the basic turbulent models comparison. The optimization task conducted within this diploma thesis includes CFD calculations to determine aerodynamic characteristics of the flap provided by Jihlavan company, and subsequent determination of its optimal position. An important part of this thesis is also evaluation of the load and strength of the flap in previously determined optimal position. At the end, the strength and fly tests of the flap in the new position are described.