Conditions aux limites dans un gaz raréfié: loi de réflexion à la paroi, saut de température, vitesse de glissement, couche de Knudsen Boundary conditions in rarefied gas flows: scattering kernal, temperature jump, slip velocity, Knudsen layer problem

This thesis deals with the problem of gas/wall interaction and boundary conditions in rarefied gas flows. Recent developments in microsystems and atmospheric re-entry flight let appear new flow fields where boundary conditions are very important. These boundary conditions should be basically derived from gas kinetic theory. During this thesis, we developed a model of kinetic boundary conditions for unstructured and structured molecules gas flows in the gas surface interaction topic. The proposed kinetic boundary conditions were based on some mathematical integral formulations of the problem, supported by phenomenological descriptions. Then, the kinetic boundary conditions were used to describe hydrodynamic boundary conditions through the problem of temperature jump and slip velocity at the solid body. The Knudsen layer (which is a thin layer close to the wall) is also briefly described. Finally, the proposed kinetic boundary conditions are used in drag coefficient calculations, for higher altitude hypersonic flows in the free molecular regime, and in some particular flow predictions. Comparisons are made with other models and experiments