Aerodynamic Sound Generation by Turbulence in Shear Flows

Abstract

A comparative analysis of linear and nonlinear aerodynamic sound generation in two dimensional (2D) plane inviscid unbounded shear flow with uniform density, pressure and constant shear of velocity is presented. Self-consistent treatment of a linear aerodynamic sound generation and its interpretation are given in terms of modes with linear coupling induced by the non-normality of the flow. Perturbations of potential vorticity is identified as the only source of acoustic waves in the flow within the linear regime. Numerical simulation of a dynamics of the testing turbulent/stochastic perturbation embedded in the flow is presented. It was found that the linear aerodynamic sound dominates (up to large amplitudes of the turbulent perturbations) over the nonlinear one both at moderate and high shear rates.