A new state-of-the-art CFD solver capable of simulating a broad range of complex engineering flows at real-life Reynolds numbers is developed. The method solves the three-dimensional incompressible unsteady Reynolds-averaged Navier-Stokes (URANS) equations closed with statistical turbulence models. Three such models are incorporated in the solver: the standard k - e model with wall functions, the Spalart-Allmaras model and the detached-eddy simulation (DES) model. The numerical solver employs domain decomposition with structured Chimera overset grids to handle complex, multi-connected geometries. The governing equations are discretized with second order accuracy schemes both in space and time. The capabilities and versatility of the numerical method are demonstrated by applying it to simulate two widely different flow problems: a) flow past a geometrical complex array of multiple bridge piers mounted both on a natural river reach and on a flat bed experimental flume; and b) flow in mechanical, bileaflet, prosthetic heart valve with the leaflets fixed in the fully-open position. Overset grid systems with several millions of grid nodes are used and grid-refinement and other numerical dependency studies are carried out to explore the sensitivity of the computed solutions to various numerical parameters. For all simulated cases, large-scale unsteadiness appears naturally as a result of excited mean-flow instabilities and the computed mean flowfields are shown to be in good quantitative agreement with experimental measurements. By analyzing the instantaneous flowfields numerous novel insights into the physics of both flow cases are obtained and discussed extensively. The results of this thesis demonstrate the potential of the new method as a powerful simulation tool for a broad range of cross-disciplinary engineering flow problems and underscore the need for physics-based numerical modeling by integrating CFD with laboratory experimentation.

L'approche la plus courante en Mécanique des Fluides Numérique pour réaliser les simulations d'écoulement cardiovasculaire consiste à utiliser des méthodes numériques Body-fitted. Ces méthodes ont permis d'obtenir des simulations d'écoulement sanguin dans les artères qui sont précises et utiles. Toutefois, la génération du maillage body-fitted est une tâche qui demande beaucoup de temps et d'expertise à l'utilisateur.Les méthodes de Frontières Immergées sont des méthodes numériques alternatives qui ont l'avantage d'être plus simples d'emploi car elles ne requièrent aucune tâche de maillage de la part de l'utilisateur. Le travail présenté ici vise à évaluer le potentiel d'un méthode de Frontières Immergées à réaliser des simulations d'écoulement cardiovasculaire.Ce travail s'attache, dans un premier temps, à décrire les capacités de cette méthode numérique à rendre compte de l'imperméabilité et de la mobilité des parois sur des cas relativement simples mais représentatifs d'écoulements cardiovasculaires. Ensuite, des applications de la méthode à des cas d'écoulement cardiovasculaire plus complexes sont montrées. Il s'agira d'abord d'une simulation de l'écoulement dans un modèle rigide d'artère aorte. Puis, la simulation d'un écoulement à l'intérieur d'un ventricule cardiaque à paroi mobile sera montrée. / The most common approach in Computational Fluid Dynamics(CFD) for simulating blood flow into vessel is to make use of a body-fitted me-thod. This approach has lead to accurate and useful simulations of blood flowinto arteries. However, generation of the body-fitted grid is time consuming andrequires from the user an engineering knowledge.The Immersed Boundary Method has emerged as an alternate method whichdoes not require from the user any grid generation task. Simulations are done on astructured Cartesian grid which can be automatically generated. Here we addressthe question of the capability of an Immersed Boundary Method to cope withcardiovascular flow simulations.In particular, we assess the impermeable and moving properties of the wallwhen using the Immersed Boundary Method on simple but relevant vascular flowcases. Then, we show more complex and realistic cardiovascular flow simulations.The first application consists of blood flow simulation inside an aorta cross model.Then, the simulation of blood flow inside a cardiac ventricle with moving wall isshown.