Experimental investigation of receptivity of a shear layer separating at a convex corner

Receptivity of a shear layer separating at a convex corner in the wall is examined experimentally. Acoustic forcing is applied to excite instability waves. Particular attention is focused on the comparison of receptivity coefficient between a sharp-edged corner and a rounded corner whose radius of curvature is 20 times the boundary-layer displacement thickness. The results clearly show that the receptivity coefficient is quite sensitive to the sharpness of the corner and that the amplitude of the excited instability wave is twice larger for the sharp corner compared with the rounded corner. The same dependency of the receptivity coefficient on the corner sharpness is verified by analyzing the shear layer response to wind-tunnel background noise without acoustic forcing.