Sound radiation from a vibrating body in relative motion with its surrounding medium

Abstract

As an extension of the authors' previous work [J. Acoust. Soc. Am. Suppl. 1 83, S77 (1988)], this paper considers sound radiation from a vibrating body in relative motion with its surrounding medium, namely, either a vibrating body radiating sound into a homogeneous inviscid fluid in uniform motion or a moving vibrating body radiating sound into a stationary inviscid fluid. The resulting sound fields in both cases can be expressed in terms of volume integrals and surface integrals based on the exact theory of Lighthill's acoustic analogy and generalized function theory. However, quantities involved in the volume integrals are not known a priori. Determination of these quantities is equivalent to solving an inhomogeneous wave equation governing the entire flow field, which is virtually impossible for most problems of interest. This paper shows that for a vibrating body in constant and rectilinear relative motion with its surrounding medium, the volume integrals can be transformed into surface integrals. Consequently, the acoustic field can be completely determined given the boundary conditions on the vibrating surface. The total radiated power is calculated and shown to be greatly enhanced by the Mach number. [Work supported in part by ONR, NSF, and Institute for Manufacturing Research at Wayne State University.]