Action of gas-permeable materials of varied porosity on the supersonic separated flow over a forward-facing step

Results of an experimental and numerical study of a supersonic flow over a model forward-facing step with a gas-permeable insert of variable porosity installed upstream of the step are reported. The free-stream Mach number was M = 2.0, 2.5, and 3.0, and the Reynolds number, Re = 5·10⁵. The gas-permeable insert was either a section of a perforated plate or a section of a highly porous permeable cellular material. The flow visualization performed using the shadow method, PIV, and a soot-oil film has shown that the characteristic size of the vortical flow region exhibited a profound decrease on increasing the insert porosity. In numerical calculations performed at high values of that po-rosity, data on the displacement of the recirculation flow region into the porous material were obtained.