L'application de l'injection fluidique dans le divergent d’une tuyère axisymétrique supersonique pour dévier le vecteur poussée est une alternative attrayante aux systèmes classiques, puisqu’elle peut se substituer aux dispositifs mécaniques. Un tel concept de vectorisation est actuellement en cours d'application sur de récents avions de combat équipés de tuyères planes. La vectorisation fluidique peut trouver également son application dans les systèmes de contrôle d’altitude de satellites ; ce principe peut réduire le nombre de tuyères habituellement utilisées. L’un des objectifs principaux de ce travail consiste à analyser et étudier les différents phénomènes mis en jeu lors de l'injection d'un fluide secondaire dans le divergent de la tuyère. Partant de cette étude, un modèle analytique, basé sur le calcul d'un bilan complet de tous les efforts exercés sur les parois de la tuyère a été construit. Ce modèle permet de donner une estimation rapide de la déviation du vecteur-poussée. L'influence de certains paramètres sur cette déviation a été également abordée. Des calculs numériques ont été réalisés par la suite afin de valider ce modèle. Les résultats obtenus par notre modèle ont été par ailleurs comparés avec les données expérimentales disponibles dans la littérature. / Fluid injection application in the divergent of a supersonic axisymmetrical nozzle is an attractive way to produce vectored thrust since it can remove the need for complex mechanical devices. Such concept of thrust vectoring is currently applied for some recent jet-fighters with planar nozzles. However, fluidic thrust-vectoring may be interesting for satellite attitude control system; thrust-vectoring may reduce the number of nozzles usually used. One of the aims of this work is to analyse and study the numerous parameters concerned by the fluid secondary injection in the divergent nozzle. From this study, an analytical model, based on calculation of all efforts applied on the nozzle walls, is constructed. This model makes it possible to give a fast estimation of the thrust-vectoring. The effect of many parameters on the thrust vectoring was also studied. Extensive numerical calculations have been carried out thereafter to validate this model. The results obtained by our model were also compared to some existing experimental data which give a significant confidence of the model.

In this work, numerical simulations of flow separation control are performed. The sep-aration control technique studied is called 'synthetic jet actuation'. The developed code employs a cell centered finite volume scheme which handles viscous, steady and unsteady compressible turbulent flows. The pulsating zero mass jet flow is simulated by imposing a harmonically varying transpiration boundary condition on the airfoil's surface. Turbulence is modeled with the algebraic model of Baldwin and Lomax. The application of synthetic jet actuators is based in their ability to energize the boundary layer, thereby providing signifcant increase in the lift coefficient. This has been corroborated experimentally and it is corroborated numerically in this research. The performed numerical simulation investigates the flow over a NACA0015 air-foil. For this flow Re = 9??105 and the reduced frequency and momentum coefficient are F+ = 1:1 and C?? = 0:04 respectively. The oscillatory injection takes place at 12.27% chord from the leading edge. A maximum increase in the mean lift coefficient of 93% is predicted by the code. A discrepancy of approximately 10% is observed with corresponding experimental data from the literature. The general trend is, how-ever, well captured. The discrepancy is attributed to the modeling of the injection boundary condition and to the turbulence model.A sensitivity analysis of the lift coefficient to different values of the oscillation parameters is performed. It is concluded that tangential injection, F + ?? O(1) and the utilized grid resolution around the site of injection are optimal. Streamline fields ob-tained for different angles of injection are analyzed. Flow separation and attachment as functions of the injection angle and of the velocity of injection can be observed. It is finally concluded that a reliable numerical tool has been developed which can be utilized as a support tool in the optimization of the synthetic jet operation and in the modeling of its operation.

In this work, numerical simulations of flow separation control are performed. The sep-aration control technique studied is called 'synthetic jet actuation'. The developed code employs a cell centered finite volume scheme which handles viscous, steady and unsteady compressible turbulent flows. The pulsating zero mass jet flow is simulated by imposing a harmonically varying transpiration boundary condition on the airfoil's surface. Turbulence is modeled with the algebraic model of Baldwin and Lomax. The application of synthetic jet actuators is based in their ability to energize the boundary layer, thereby providing signifcant increase in the lift coefficient. This has been corroborated experimentally and it is corroborated numerically in this research. The performed numerical simulation investigates the flow over a NACA0015 air-foil. For this flow Re = 9??105 and the reduced frequency and momentum coefficient are F+ = 1:1 and C?? = 0:04 respectively. The oscillatory injection takes place at 12.27% chord from the leading edge. A maximum increase in the mean lift coefficient of 93% is predicted by the code. A discrepancy of approximately 10% is observed with corresponding experimental data from the literature. The general trend is, how-ever, well captured. The discrepancy is attributed to the modeling of the injection boundary condition and to the turbulence model.A sensitivity analysis of the lift coefficient to different values of the oscillation parameters is performed. It is concluded that tangential injection, F + ?? O(1) and the utilized grid resolution around the site of injection are optimal. Streamline fields ob-tained for different angles of injection are analyzed. Flow separation and attachment as functions of the injection angle and of the velocity of injection can be observed. It is finally concluded that a reliable numerical tool has been developed which can be utilized as a support tool in the optimization of the synthetic jet operation and in the modeling of its operation.

No description available.

The growing need for increased performance from gas turbines has fueled the drive to raise turbine inlet temperatures. This results in high thermal stresses especially along the first stage nozzle guide vane cascade as the hot combustion products exiting modern day gas turbine combustors generally reach temperatures that could endanger the structural stability of these vanes and greatly reduce the vane life. The highest heat transfer coefficients in the vane passage occurs near the endwall, particularly in the leading edge-endwall junction where vortical flows cause the flow of hotter fluid in the mainstream to mix with relatively lower temperature boundary layer fluid. This work documents the computational investigation of air injection at the end wall through a cylindrical hole placed upstream of the nozzle guide vane leading edge-end wall junction. The effect of the secondary jet on the formation of the leading edge horseshoe vortex and the consequent formation of the passage vortex has been studied. For the computations, the Reynolds averaged Navier–Stokes (RANS) equations were solved with the commercial software ANSYS Fluent using the SST k-ω model. Total pressure loss coefficient and kinetic energy loss Coefficient contour plots at the exit of the cascade to estimate the effect of the endwall fluid injection on loss profiles at the vane cascade exit. Swirling strength contours were plotted at several axial chord locations in order to track the path of the passage vortex in and downstream of the vane cascade. Two different hole-positions (located at 1 hole diameter and 2 hole diameters from the leading edge) along a plane parallel to the incident flow were considered in order to study the effect of the hole position with respect to the vane leading edge-endwall junction. Three different streamwise hole inclination angles with respect to the mainstream flow direction were studied to identify the best angle for the injection of fluid through the endwall. This angle was combined with five different compound angles (0°, 30°, 45°, 60° and 90°) in order to study the effect of varying the compound angle on the leading edge vortex and the passage vortex. Each of the above studies were conducted at two different injected fluid-to-mainstream mass flow ratios (0.5% and 1%) in order to study the effect of varying injected flow rate on the formation of the leading edge vortex and the vane passage vortex. From the results it was observed that suitable selection of the secondary injection mass flow rate, injection angle and hole-position caused an absence of the leading edge horseshoe vortex and delayed migration of the passage vortex across the guide vane passage. Heat Transfer studies were also conducted to observe the absence/weakening of the leading edge vortex and the delayed pitch-wise movement of the passage vortex. / Master of Science / Gas turbines are a kind of Internal Combustion engine that convert chemical energy to mechanical energy by way of burning an air-fuel mixture to cause turbine blades to spin and produce power. A typical gas turbine consists of a compressor which compresses the air intake into the combustion chamber, the combustion chamber in which energy is released from fuel by the combustion of the air-fuel mixture, and a turbine coupled to the compressor that is made to spin by the high pressure high temperature exhaust from the combustor. In order to increase the amount of power produced per unit (by weight or volume) of fuel consumed and increase the performance of the engine, the turbine inlet temperature i.e. the temperature of the hot gas products leaving the gas turbine combustor is increased by changing the fuel flow rate into the combustors and the amount of compression of the air entering the combustor. Consequently, the first component of the turbine, the nozzle guide vane faces high thermal loading which could structurally endanger vane life. The existence of complex secondary flows (leading edge vortex, passage vortex, corner vortices) near the junction of vane’s leading edge and the turbine endwall to which the vane is connected to causes increased heat transfer at this point as opposed to other points on the vane surface. The aim of this work is to study through computational simulations how injecting high momentum fluid (air) near the leading edge junction to observe any changes to the secondary flow near the endwall. The angle at which this fluid is injected and the rate of injection of this fluid are, among others, the parameters varied in this study. The flow near the leading edge and through the vane passage is visualized and the pressures at the inlet and outlet of the test domain measured at each step to compute parameters which decide how further studies are designed. The ultimate aim of this project is to identify if injecting fluid through the endwall would prove useful in reducing the vortical flows near the endwall (thereby reducing the thermal load on the endwall).

Comprendre et connaitre les propriétés physiques et le comportement mécanique de l'andésite est important pour des applications industrielles comme la géothermie ou le stockage de CO2 mais aussi pour comprendre différents processus naturels. Tout d'abord, les effets de la fissuration thermique sur les propriétés physiques et les processus de rupture de l'andésite ont été étudiés via des expériences triaxiales à taux de déformation constant et à température ambiante. Deuxièmement, nous avons effectué des recherches sur les effets de l'altération sur le comportement physique et la minéralogie. Enfin, une série d'expériences a été réalisée afin d'étudier l'effet de la variation de la pression du fluide i) sur le comportement mécanique des échantillons d'andésite et ii) sur les activités d'émissions acoustiques. / The physical properties and mechanical behavior of andesite are of interest in the context of geothermal reservoir, CO2 sequestration and for several natural processes. The effects of thermal crack damage on the physical properties and rupture processes of andesite were investigated under triaxial deformation at room temperature. Secondly we did research on the effect of alteration on physical behavior and mineralogy. At last a series of experiments were performed in order to investigate the effect of fluid pressure variation i) on the mechanical behavior of andesite samples and ii) on acoustic emissions activities

Integrated theoretical and experimental analysis is carried out in this work to investigate the fundamental failure mechanisms and flow patterns involved in the process of fluid injection into dense granular media. The experimental work is conducted with aqueous glycerin solutions, utilizing a novel setup based on a Hele-Shaw cell filled with dense dry sand. The two dimensional nature of the setup allows direct visualization and imaging analysis of the real-time fluid and grain kinematics. The experimental results reveal that the fluid flow patterns show a transition from simple radial flow to a ramified morphology while the granular media behaviors change from that of rigid porous media to localized failure that lead to development of fluid channels. Based on the failure/flow patterns, four distinct failure/flow regimes can be identified, namely, (i) a simple radial flow regime, (ii) an infiltration-dominated regime, (iii) a grain displacement-dominated regime, and (iv) a viscous fingering-dominated regime. These distinct failure/flow regimes emerge as a result of competition among various energy dissipation mechanisms, namely, viscous dissipation through infiltration, dissipation due to grain displacements, and viscous dissipation through flow in thin channels and can be classified based on the characteristic times associated with fluid injection, hydromechanical coupling and viscoelastoplasticity. The injection process is also analyzed numerically using the discrete element method (DEM) coupled with two fluid flow scheme, a fixed coarse grid scheme based on computational fluid dynamics (CFD) and a pore network modeling scheme. The numerical results from the two complementary methods reproduce phenomena consistent with the experimental observations and justify the concept of associating the displacement regimes with the partition among energy dissipation mechanisms. The research in this work, though fundamental in nature, will have direct impacts on many engineering problems in civil, environmental and petroleum engineering such as ground improvement, environmental remediation and reservoir stimulation.

Submitted by Marco Antonio Oliveira da Silva (maosilva@ipen.br) on 2016-08-26T11:43:46Z No. of bitstreams: 0 / Made available in DSpace on 2016-08-26T11:43:46Z (GMT). No. of bitstreams: 0 / O Ipen/Cnen-SP possui um Reator de Pesquisa(IEA-R1) em operação desde 1957. Ele utiliza água leve como blindagem, moderador e como fluido refrigerante, o volume desta piscina é de 273m3. Até 1995 a operação do Reator era descontinua, ou seja, operava diariamente sendo desligado no final do dia, a uma potência de 2,0 MW. A partir daquele ano, após algumas modificações de segurança, o Reator passou a operar de forma continua, ou seja, de segunda-feira a quarta-feira sem ser desligado, totalizando 64 horas semanais. A potência também foi aumentando até 4,5 MW em 2012. Em virtude dessas alterações, a saber, operação contínua e do aumento da potência, as doses dos trabalhadores aumentaram e por isso foram realizados vários estudos para diminui-las. Estudos demonstraram que uma das principais limitações para operação de um reator em potência elevada, provém das radiações gama emitidas pelo sódio-24. Outros elementos como magnésio-27, Alumínio-28, Argônio-51, contribuem de forma considerável para a atividade da água da piscina. A introdução de uma camada de água quente em sua superfície, estável e isenta de elementos radioativos com 1,5m a 2m de espessura constituiria uma blindagem às radiações provenientes dos elementos radioativos dissolvidos na água. Estudos de otimização provaram que a instalação da camada quente não era necessária para o regime e potência atual de operação do Reator, pois outros procedimentos adotados eram mais eficazes. A partir desta decisão o serviço de Proteção Radiológica do Reator IEA-R1, montou um programa de avaliação das doses para certificar-se de que elas se mantinham em valores razoáveis baseados em princípios estabelecidos em normas nacionais e internacionais. O intuito deste trabalho é realizar uma análise das doses individuais dos IOE (Individuo Ocupacionalmente Expostos), considerando as mudanças no regime de operação do Reator e sugerir opções de proteção e segurança, viáveis em primeira instância, para reduzir as doses analisadas, visando se chegar aos níveis de referencia de 3 mSv/ano adotados pela instalação em apreço. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP