Sound radiation from a turbulent boundary layer

Abstract

Sound radiation due to fluctuating viscous wall shear stresses in a plane turbulent boundary layer is investigated by a two-stage procedure using direct numerical simulation (DNS) databases for incompressible turbulent Poiseuille flow in a plane channel, at Reynolds numbers up to Reτ=1440. The power spectral density of radiated pressure and spectra of sound power per unit wall area are calculated in the low Mach number limit by substituting source terms obtained from DNS into a Ffowcs Williams–Hawkings wave equation and using a half-space Green function. The same DNS data are used to predict the spectrum of turbulent boundary layer noise measured in a diffuser downstream of a fully developed channel flow [Greshilov and Mironov, Sov. Phys. Acoust. 29, 275 (1983)]. The measured spectrum is ∼15dB higher at low frequencies, but converges with the prediction at high frequencies.