William C. Meecham
Dept. of Mech., Aerosp., and Nucl. Eng., Univ. of California, Los Angeles, CA 90024
Acoustic radiation from turbulent fluids, aeroacoustics, has been a major research area especially since the pioneering work of Lighthill. The fundamental mechanism of acoustic radiation from homogeneous turbulence has been discussed, using a similarity hypothesis [W. C. Meecham and G. W. Ford, J. Acoust. Soc. Am. 30, 318 (1958)]. This paper presents a new application of large eddy simulation (LES) techniques to the calculation of the acoustic far field produced by turbulent fluids. The acoustic radiation problem consists of two steps; in the first step one simulates homogeneous turbulent fields using LES; and in the second step one generates the far-field sound using Lighthill's analogy. It is found that the radiated power spectrum is proportional to (omega)[sup 4]M[sup 3], where M is the Mach number, at high frequencies as predicted in the early work. Other features of the sound field support the early theory. Similar calculations for jet noise will be discussed. Color computer graphics will be shown.