Investigation of upstream moving pressure waves on a supercritical airfoil☆

The present work is a preliminary experimental and numerical investigation of wave processes taking place in the flow field on a supercritical airfoil in a defined Mach and Reynolds number range. These waves which originate near the trailing edge propagate upstream in the subsonic region and become apparently weak near the leading edge. Time-resolved pressure measurements performed, reveal the unsteady behaviour of these waves. The frequencies measured are in the order of kHz. The wave structures can also be seen on corresponding time-resolved shadowgraphs. Not yet fully understood, however, is the mechanism which generates the waves as well as their interaction with the boundary layer. Early numerical investigations show that the wave formation is coupled with a vortex formation in the boundary layer.