Numerical assessment of the scattering of acoustic waves by turbulent structures

The scattering of harmonic sound waves by a single vortex is studied to provide someinsight into the more complex problem of sound scattering by a turbulent layer. Twodifferent methods are used to model the scattering by a steady vortex or by a vortexconvected in a uniform mean flow. The first method is based on the linearized Eulerequations in the frequency domain and is used to study the scattering by a steady vortex.The speed of this method allows to perform a study of the spatial scattering of a planewave over a wide range of frequencies, where analytical models previously developed arerestricted either to low or high frequencies. The second method uses a finite differencesolver, also based on the linearized Euler equations but in the time domain. This methodis used to study the scattering by a vortex convected in a uniform mean fow, where aspectral scattering occurs in addition to the spatial scattering. A parametric study isrealized, focusing on four parameters including the source frequency and the convection velocity. The spectra deduced from this study show a pattern similar to the haystackingobserved in existing studies of the scattering by a turbulent shear layer. Some of the trends deduced from the parametric study are also in agreement with these previous observations. Thus, the detailled study of the scattering by a single eddy is able to provide further understanding of the turbulence scattering.