Influences of Oblique Surface Corrugation on Boundary-Layer Instability

The influence of surface corrugation on the growth of Tollmien–Schlichting (TS) waves was examined experimentally in a zero-pressure-gradient boundary layer. Corrugations with various oblique angles were considered to see how the growth of two-dimensional (2D) TS waves was affected by the angle of surface corrugation. The results clearly showed that as the oblique angle increased, the destabilizing effect (which was pronounced for the 2D corrugation) gradually weakened and that when the corrugation direction was normal to the TS wave, the corrugation little influenced the growth of 2D TS wave though the wave underwent a spanwise distortion corresponding to the corrugation.