Experimental Study of Essentially Non-Stationary Acoustic Receptivity of a Boundary Layer on an Airfoil Due to Surface Non-Uniformities

摘要

The case when acoustic and surface vibrations have comparable frequencies has not been studied at all despite such situation seems very realizable at flight conditions. The important peculiarity of this receptivity mechanism is that both participating frequencies (f(sub ac) and f(sub v)), may lie in the range of stable frequencies and do not produce in the boundary layer any amplified perturbations but the resulting TS-wave may lie in the range of unstable frequencies and can provoke earlier transition. This work is intended to study systematically the vibration-acoustic mechanism of TS-wave production and to compare the obtained receptivity results with a roughness case.