This thesis aims at presenting the Discrete Vortex Method (DVM) as a tool to determine the flow field and associated wind loads over structures. Two structures are considered: the first is a surface-mounted prism and is used to simulate wind loads over low-rise structures. The second is a bridge section with attached flaps that can be oriented to vary the moment coefficient. Advantages and disadvantages of using DVM for these applications are discussed. For the surface-mounted prism, the results show that the developed code correctly predicts the flow separation around the corners. As for the surface pressures, it is concluded that parallel processing, which could be easily implemented for DVM, should be used to correctly predict surface pressures and their variations. This is due to the required slow time advancement of the computations. The results on attaching flaps to bridge sections yield required orientations to minimize moments under different angles of attack. / Master of Science

Long span bridges are susceptible to wind. Hence it is important to study their wind-induced vibrations to avoid any probable structural failures. In this thesis, the results of an experimental and computational investigation of the aerodynamic characteristics of trapezoid bridge deck cross-sections with three different aspect ratios (10, 12 and 15) and four different side angles (75&ordm / , 60 &ordm / , 45 &ordm / and 30 &ordm / ) are analyzed and presented. The flow around rigid fixed bridge deck models is investigated to obtain the relevant aerodynamic coefficients and the vortex shedding frequency and Strouhal number. Two dimensional unsteady Reynolds Averaged Navier-Stokes equations are solved using commercial CFD software at different Reynolds numbers. The numerical results are compared with the experimental data obtained by testing the model bridge decks geometries in a low speed wind tunnel. The results of this study demonstrate that the models aerodynamic parameters except their lift coefficient are almost dependent on the aspect ratio. In addition, the influence of side angle on all aerodynamic parameters has to be taken in account.

Dans l’environnement concurrentiel d’aujourd’hui, la mondialisation des marchés et les enjeux socio-écologiques du développement durable représentent des défis majeurs pour l’industrie automobile. Afin de relever ces défis, les entreprises doivent investir dans des outils de développent plus performants. Pour améliorer la performance d’un moteur thermique en termes de consommation et d’émissions une compréhension enrichie de la boucle d’air autour du moteur et de l’interaction entre ses composants est indispensable Cette thèse suit deux axes de recherche dans ce contexte. Dans un premier temps, les problèmes liés à la modélisation d’une boucle d’air globale sont traités. En particulier, sont modélisés le débit d’air entre les différents sous-systèmes, la combustion en fonction du degré vilebrequin, la pulsation du débit et de la pression et l’estimation de la force aérodynamique sur les vannes des turbocompresseurs à géométrie variable (TGV). Cette étude de modélisation détaillée à été utilisée pour mettre en place un simulateur de la boucle d’air, qui prend en compte ces interactions et qui peut prédire l’influence des sous-systèmes sur la boucle globale. En suite, l’effort de notre recherche a été consacré à la modélisation des actionneurs mécatroniques de la boucle d’air et de leur comportement non linéaire dû au frottement, aux variations de la température, etc. Un modèle dynamique non linéaire à été développé et intégré dans le simulateur. Ce modèle peut être adapté aux plusieurs types d’actionneurs commerciaux. Le simulateur complet à été implémenté sous AMESim pour les modèles du moteur et de la boucle d’air, et sous Simulink pour le contrôle. Les modèles ont été paramétrées selon les spécifications d’un moteur commercial et le simulateur à été validé expérimentalement. Finalement, des lois de commande robustes ont été étudiées pour le contrôle en position (contrôle locale) des actionneurs. Un contrôleur adaptatif à été développé pour garantir la performance des actionneurs malgré des changements dans le frottement, ainsi que dans la charge externe. La performance de toutes les méthodes étudiées, a été validée expérimentalement. / Today’s globally competitive market and its associated environmental and social issues of sustainable development are major challenges for the automobile industry. To meet them, the industry needs to invest in high performance development tools. For improving engine performance in terms of consumption and emission, the interactions between the subsystems of the engine air-path need to be understood. This thesis followed two major axes of research in this context. First, the problems related to the modeling of the global air-path system were studied, which include the airflow characteristics between the different subsystems of the air-path, high frequency combustion modeling and pulsating airflow, and estimation of the exhaust aerodynamic force on the vanes of variable geometry turbochargers (VGT). The detailed modeling study was used for developing an engine air-path simulator, which takes into account these interactions and predicts the influence of subsystems on the global air-path. The second axis of research was focused on modeling of mechatronic actuators of the air-path, taking into account their nonlinear behavior due to friction and changes in operating conditions. A generic nonlinear dynamic model was developed and included in the simulator. This model can be adapted to most commercial actuators. The complete simulator has been implemented using AMESim for engine and air-path modeling, and Simulink for control. It has been parameterized according to the specifications of a commercial diesel engine and validated against experimental data. Finally, robust local controllers were studied for actuator position control, aimed at guaranteeing the performance of the actuators under parametric uncertainty and external disturbances. An advanced controller was developed, which adapts to changes in friction characteristics of the actuator and external load changes. The performance of all controllers has been demonstrated experimentally.

Today's globally competitive market and its associated environmental and social issues of sustainable development are major challenges for the automobile industry. To meet them, the industry needs to invest in high performance development tools. For improving engine performance in terms of consumption and emission, the interactions between the subsystems of the engine air-path need to be understood. This thesis followed two major axes of research in this context. First, the problems related to the modeling of the global air-path system were studied, which include the airflow characteristics between the different subsystems of the air-path, high frequency combustion modeling and pulsating airflow, and estimation of the exhaust aerodynamic force on the vanes of variable geometry turbochargers (VGT). The detailed modeling study was used for developing an engine air-path simulator, which takes into account these interactions and predicts the influence of subsystems on the global air-path. The second axis of research was focused on modeling of mechatronic actuators of the air-path, taking into account their nonlinear behavior due to friction and changes in operating conditions. A generic nonlinear dynamic model was developed and included in the simulator. This model can be adapted to most commercial actuators. The complete simulator has been implemented using AMESim for engine and air-path modeling, and Simulink for control. It has been parameterized according to the specifications of a commercial diesel engine and validated against experimental data. Finally, robust local controllers were studied for actuator position control, aimed at guaranteeing the performance of the actuators under parametric uncertainty and external disturbances. An advanced controller was developed, which adapts to changes in friction characteristics of the actuator and external load changes. The performance of all controllers has been demonstrated experimentally.