Impingement of a supersonic underexpanded jet onto obstacles with different permeabilities

Results of an experimental study of the flow structure and characteristics of flow oscillations induced by impinging of a supersonic underexpanded jet onto obstacles made of permeable and impermeable materials are presented. Spectral characteristics of the acoustic field in the regime of unsteady interaction between the jet and the obstacle are determined. The influence of permeability of porous obstacles on these characteristics is identified.