The response of a laminar boundary layer to sound and wall vibration

An experimental analysis of the interaction of sound and plate vibration with a laminar boundary layer is presented. The two excitations generate disturbances at the leading edge of the plate which develop into Tollmien-Schlichting (TS) waves in the quasi-parallel region of the boundary layer. It is demonstrated that the TS wave and the sound wave coexist independently in this region, as predicted by the linear theory. A TS wave generated by a vibrating ribbon is shown to superimpose linearly with the sound-generated TS wave. Plate vibration is used to successfully cancel a sound-excited TS wave.