Acoustic excitation of Tollmien-Schlichting waves in a laminar boundary layer
Abstract
Acoustic plane waves were shown to excite Tollmien-Schlichting (T-S) waves in a flat plate laminar boundary layer. The level of excitation depended on the frequency and the acoustic angle of incidence. Two distinct regions of excitation were observed, near the leading edge and downstream in the parallel flow region. An existing theory which modeled the interaction in the second region was extended to include arbitrary angles of incidence. Measurements of the cross power spectra of the sound and T-S waves were made in a low turbulence anechoic wind tunnel. This receptivity of the boundary layer to acoustic disturbances caused a forward shift in the transition point. A sound pressure level of 121 dB moved the transition point forward from a Reynolds number of 1.7 x 10 to the 6th to 1.3 x 10 to the 6th power.
- Publication:
-
NASA STI/Recon Technical Report N
- Pub Date:
- March 1987
- Bibcode:
- 1987STIN...8728862B
- Keywords:
-
- Acoustic Excitation;
- Laminar Boundary Layer;
- Plane Waves;
- Tollmien-Schlichting Waves;
- Anechoic Chambers;
- Angles (Geometry);
- Incidence;
- Leading Edges;
- Parallel Flow;
- Power Spectra;
- Sound Pressure;
- Transition Points;
- Turbulence;
- Wind Tunnel Tests;
- Fluid Mechanics and Heat Transfer