Influence of wall riblets on diffuser flow

Diffuser flows have been investigated with different riblet combinations both experimentally and numerically. Wall pressures and velocity profiles have been measured throughout a large working domain. In addition numerical calculations have been performed by accounting for the strong coupling between the inviscid core flow and the viscous boundary layer flows by using a simple model based on the negative roughness for the riblet walls.Nomenclature c_f skin friction coefficient - p local static pressure - x streamwise distance - y distance normal to the wall - u friction velocity - A diffuser cross section - H shape factor - U_e fluid velocity in inviscid flow - W₁ inlet height of the diffuser - * boundary layer displacement thickness - density of working fluidInstitut de Machines Hydrauliques et de Mecanique des Fluides