Abstract
To obtain a better understanding of the coupling between external disturbances and excited instability waves, the receptivity to acoustic disturbances is studied experimentally for separated flows in the leading-edge region of a flat-plate airfoil. A linear stability calculation (with parallel flow assumption) is also made on the inflectional velocity distribution near the leading edge to clarify the receptivity through identifying the instability wave excited. The results show that the separated flow in the leading-edge region is highly receptive to external disturbances and develops the instability wave, whose amplitude (in terms of u-fluctuation) is proportional to and an order of magnitude larger than that of the external sound wave. It is also shown that the excited wave is, even in the vicinity of the leading edge, very close to the eigenmode calculated from the linear stability theory. The strong receptivity of the leading-edge-separated flow is emphasized through comparing with that in the flow without separation.
