This research is situated in the field of Computational AeroAcoustics (CAA). The thesis focuses on the computation of the aerodynamic noise generated by turbulent flows around wing, fan, or propeller airfoils. The computation of the noise radiated from a device is the first step for designers to understand the acoustical characteristics and to determine the noise sources in order to modify the design toward having acoustically efficient products. As a case study, the broadband or trailing-edge noise emanating from a CD (Controlled-Diffusion) airfoil, belonging to a fan is studied. The hybrid methods of aeroacoustic are applied to simulate and predict the radiated noise. The necessary tools were researched and developed. The hybrid methods consist in two steps simulations, where the determination of the aerodynamic field is decoupled from the computation of the acoustic waves propagation to the far field, so the first part of this thesis is devoted to an aerodynamic study of the considered airfoil. In this part of the thesis, a complete aerodynamic study has been performed. Some aspects have been developed in the used in-house solver SFELES, including the implementation of a new SGS model, a new outlet boundary condition and a new transient format which is used to extract the noise sources to be exported to the acoustic solver, ACTRAN. The second part of this thesis is concerned with the aeroacoustic study where four methods have been applied, among them two are integral formulations and the two others are partial-differential equations. The first method applied is Amiet’s theory, implemented in Matlab, based on the wall-pressure spectrum extracted in a point near the trailing edge. The second method is Curle’s formulation. It is applied proposing two approaches; the first approach is the implementation of the volume and surface integrals in SFELES to be calculated simultaneously with the flow in order to avoid the storage of noise sources which requires a huge space. In the second approach, the fluctuating aerodynamic forces, already obtained during the aerodynamics simulation, are used to compute the noise considering just the surface sources. Finally, Lighthil and Möhring analogies have been applied via the acoustic solver ACTRAN using sources extracted via SFELES. Maps of the radiated noise are demonstrated for several frequencies. The refraction effects of the mean flow have been studied. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

In this dissertation, we are concerned with the numerical simulation for flows of electrically conducting fluids exposed to an external magnetic field (also known as magnetohydrodynamics or in short MHD). The aim of the present dissertation is twofold. First, the in-house CFD hydrodynamic solver SFELES is extended to MHD problems. Second, MHD turbulence is studied in the simple configuration of a MHD pipe flow within an external transverse magnetic field. Chapter 2 of this dissertation aims at reminding the physical equations that govern incompressible MHD problems. Two equivalent formulations are put forward in the particular case of quasi-static MHD. Chapter 3 is devoted to the detailed development of the hybrid spectral - stabilized finite element methods for quasi-static MHD problems. The extension of SFELES is made for both Cartesian and axisymmetric systems of coordinates. The short chapter 4 follows to provide the performances of SFELES executed by several processes in a parallel environment. The addition of a parallel direct solver is studied in regards with the memory and time requirements. The extension of SFELES is then validated in chapter 5 with test cases of increasing complexity. For this purpose, laminar flows with an existing analytical-asymptotic solution are considered. The subject of chapter 6 is the MHD turbulent pipe flow within an external transverse and uniform magnetic field. The results are partially compared with the corresponding hydrodynamic flow and with a few data available in the literature. / Le thème de cette thèse de doctorat est la simulation numérique d'écoulements de fluides conducteurs d'électricité qui sont exposés à un champ magnétique extérieur (également connu sous le nom de magnétohydrodynamique ou encore MHD). L'objectif de ce travail est double. Premièrement, le code CFD maison SFELES est étendu aux problèmes MHD. Deuxièmement, la turbulence MHD est étudiée dans la configuration de l'écoulement en conduite cylindrique à l'intérieur d'un champ magnétique transverse. Le chapitre 2 de cette thèse a pour but de rappeler les équations qui gouvernent les problèmes de MHD incompressible. Deux formulations équivalente sont mises en évidence dans le cas particulier de la MHD quasi-statique. Le chapitre 3 est dévoué au développement détaillé des méthodes spectrale - éléments finis pour la MHD quasi-statique. L'extension de SFELES est réalisée dans les systèmes de coordonnées cartésiennes et axisymétriques. Le court chapitre 4 suit pour fournir les performances de SFELES exécuté sur plusieurs processeurs dans un environnement parallèle. L'ajout d'un solveur parallèle direct est étudié en ce qui concerne les demandes en temps et mémoire. L'extension de SFELES est alors validée dans le chapitre 5 avec des cas d'étude de complexité croissante. Dans ce but, des écoulements laminaires avec solution théorique-asymptotique sont envisagés. Le sujet du chapitre 6 est l'écoulement MHD turbulent en conduite cylindrique à l'intérieur d'un champ magnétique transverse et uniforme. Les résultats sont partiellement comparés avec l'écoulement hydrodynamique correspondant et avec des données disponibles dans la littérature. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished