Excitation of Instability Waves in the Supersonic Boundary Layer by Sound

Abstract

The receptivity of a supersonic boundary layer to acoustic waves is considered. To do so it is noted that sound waves and Tollmien-Schlichting waves in supersonic flow have similar parameters. This fact has two consequences: First, in parallel flow, the strong interaction of a sound wave with a critical layer (which is determined by the sound phase velocity) leads to strong oscillations in the boundary layer. Second, in nonparallel flow, the two parameters are indistinguishable. In consequence, oscillatory energy is transmitted from one kind of disturbance to the another. In the present work, these phenomena are illustrated by studying the interaction of sound waves with a supersonic boundary layer on a flat plate.