Noise from Fine-Scale Turbulence of Nonaxisymmetric Jets

Abstract

The noise from the fine-scale turbulence of high-speed nonaxisymmetric jets is considered. A prediction method is developed by extending the work of Tam and Auriault. A set of improved numerical boundary conditions for use in nonaxisymmetricjet mean flow and turbulence calculation is developed. These new boundary conditions allow the computation to be carried out in a smaller computation domain. It is known that nonaxisymmetric mean flow has a significant impact on the radiated noise spectrum and directivity through refraction. In the Tam and Auriault theory, this effect is accounted for by means of the adjoint Green's function. Here the adjoint Green's function method is extended to nonaxisymmetric mean flows. The adjoint Green's function is first recast into the solution of a sound scattering problem. The sound scattering problem is then solved computationally by computational aeroacoustics methods. Extensive comparisons between calculated and experimentally measured jet noise spectra are presented. They include both rectangular and elliptic jets at supersonic and subsonic Mach numbers