Measurement of Acoustic Receptivity at Leading Edges and Porous Strips

Abstract

The receptivity of a laminar boundary layer to acoustic disturbances in the vicinity of a leading edge and a narrow porous surface is investigated experimentally. The relative importance of the receptivity mechanisms is explored for leading edge and porous surface configurations. Several methods to decouple the acoustic and instability wave velocity perturbations are discussed, and consistent estimates of the Tollmien-Schlichting modes are achieved when the acoustic field is directly estimated from profiles of the total fluctuating velocity. A 24:1 leading edge produces negligible Tollmien-Schlichting response when interacting with symmetric acoustic disturbances and is used to confirm the porous-surface receptivity mechanism.