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Vibration and Aeroelasticity of Advanced Aircraft Wings Modeled as Thin-Walled Beams--Dynamics, Stability and ControlQin, Zhanming 17 October 2001 (has links)
Based on a refined analytical anisotropic thin-walled beam model, aeroelastic instability, dynamic aeroelastic response, active/passive aeroelastic control of advanced aircraft wings modeled as thin-walled beams are systematically addressed. The refined thin-walled beam model is based on an existing framework of the thin-walled beam model and a couple of non-classical effects that are usually also important are incorporated and the model herein developed is validated against the available experimental, Finite Element Anaylsis (FEA), Dynamic Finite Element (DFE), and other analytical predictions. The concept of indicial functions is used to develop unsteady aerodynamic model, which broadly encompasses the cases of incompressible, compressible subsonic, compressible supersonic and hypersonic flows. State-space conversion of the indicial function based unsteady aerodynamic model is also developed. Based on the piezoelectric material technology, a worst case control strategy based on the minimax theory towards the control of aeroelastic systems is further developed. Shunt damping within the aeroelastic tailoring environment is also investigated. The major part of this dissertation is organized in the form of self-contained chapters, each of which corresponds to a paper that has been or will be submitted to a journal for publication. In order to fullfil the requirement of having a continuous presentation of the topics, each chapter starts with the purely structural models and is gradually integrated with the involved interactive field disciplines. / Ph. D.
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Simulation numérique de jets liquides cisaillés par une phase rapide : dynamique de battement à grande échelle et intéraction avec les structures tourbillonnaires / Numerical simulation of liquid jets sheared by a high-speed stream : flapping dynamics and interaction with vortical structuresOdier, Nicolas 18 December 2014 (has links)
L'injection d'un mélange carburant/comburant dans une chambre de combustion d'un turboréacteur ou d'un moteur-fusée fait intervenir un jet liquide, cisaillé par un gaz rapide. Le jet liquide peut être sous certaines conditions sujet à un phénomène de battement à grande échelle. Ce phénomène, dont les mécanismes de base sont aujourd'hui mal connus, peut avoir des conséquences importantes sur la combustion. Nous réalisons dans ce travail une étude numérique de jets liquides cisaillés par une phase rapide, en portant une attention particulière à l'étude de l'interaction entre les structures tourbillonnaires de la phase rapide et le jet liquide. Une nappe liquide plane cisaillée de part et d'autre par une phase rapide est analysée dans un premier temps . Les mécanismes de déstabilisation de cette nappe liquide sont étudiés, ainsi que le contrôle passif du phénomène de battement. Des jets liquides coaxiaux, cisaillés par une couronne de phase rapide, sont ensuite analysés. Les mécanismes de déstabilisation à grande échelle sont étudiés, ainsi que le contrôle passif et actif de cette déstabilisation. La simulation d'une configuration d'écoulement réaliste eau/air est enfin réalisée, en interaction avec les expérimentateurs du LEGI. Une attention particulière est portée à l'écoulement se produisant au sein de la buse d'injection. / Fuel injection in an aircraft engine or in a rocket engine involves a liquid jet sheared by a high-velocity gas. The liquid jet can display, under some specific conditions, a flapping motion. This flapping motion, the basic mechanisms of which are still poorly understood, can significantly impact the combustion process. We perform in this work a numerical study of liquid jets interacting with a high-speed stream and focus on the interactions between the vortical structures in this high-speed stream and the liquid jet. A plane liquid jet surrounded by two high-speed streams is first analysed. The mechanisms leading to the flapping motion are studied, as well as the passive control of this instability. A liquid coaxial jet, sheared by an annular high speed stream, is next analysed. The mechanisms leading to the flapping motion are also analysed, as well as passive and active strategies for controlling this instability. Finally, we perform simulations of an experimental set-up studied at LEGI, focusing on the flow inside the nozzle.
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