Experimental investigation of 3D acoustic receptivity of an airfoil boundary layer due to surface vibrations

The receptivity was investigated in two general cases: in 'plus-regimes' when the TS-waves were excited at combination frequencies fTS+=fac+fv and in 'minus-regimes' when the excitation occurred at frequencies fTS−=fac−fv. The complex (amplitude and phase) receptivity coefficients are obtained experimentally as functions of the spanwise wavenumber (and the wave propagation angle) for three different frequency ratios K and also for several TS-wave frequencies at fixed values of K. The obtained vibro-acoustic receptivity coefficients are compared with the acoustic-roughness receptivity coefficients (i.e. for K=0) found in previous experiments and DNS.