Sound generated by fluid-structure interactions

Abstract

A tutorial summary is given of the theory of aerodynamic sound with special reference to the generation of sound by flow interacting with rigid and elastic structures. Lighthill's acoustic analogy and the theory of vortex sound are discussed. Several applications of the theory are described that exemplify the considerable progress that has been made in the analytical treatment of flow generated sound at low Mach numbers, including the use of the compact acoustic Green's function to estimate fluid-structure interaction noise when one or more pertinent source dimensions are small compared to the acoustic wavelength. The need to take proper account of additional sources formed by vortex shedding during an interaction is emphasized, and illustrated by the example of blade-vortex interaction noise. The modification caused by surface compliance of the efficiency of sound production by an adjacent flow is discussed by reference to simple analytical models involving vortex flow near the edge of an elastic plate, and over a surface inhomogeneity on a large plate.