AN EXPERIMENTAL-STUDY OF RECEPTIVITY OF ACOUSTIC-WAVES IN LAMINAR BOUNDARY-LAYERS

The receptivity of a laminar boundary layer developing on a flat plate was studied with two- and three-dimensional roughness elements. The l ayer was subjected to acoustic waves from speakers orientated perpendi cular to the surface of the plate. Visualization of the transition pat terns were obtained by heating temperature sensitive liquid crystals o n the plate and observing the cooling patterns associated with the dif ferent flow regimes. Hot-wire data showed that the most amplified Toll mien-Schlichting waves dominated the downstream growth when the roughn esses were placed within the linearly unstable regime. The receptivity depended upon the size and aspect ratio of the three-dimensional roug hness as predicted by Choudhari and Kerschen 1990.