Book Description

This report summarizes major theoretical aerodynamic and acoustic developments and experimental findings aimed at providing a better understanding and a detailed mathematical specification of the noise-producing sources of simple exhaust jets. A review is given of calculation procedures for shock wave structure and flow field properties of simple circular jets. Results of new theoretical acoustic developments illustrating the influence of a jet's mean flow shrouding on jet acoustic radiation for unheated and heated jets are outlined. Additional discussions of interesting insights regarding the classical turbulent mixing theory of jet noise and the aeroacoustic formulations for a jet's orderly structure are given. Summaries of a series of high velocity, high temperature velocity field measurements using a General Electric developed laser velocimeter are discussed, and the application of the velocimeter for performing turbulence spectra and in-jet to far-field cross-correlation type measurements is reviewed. Key experiments illustrating the influence of swirl and combustion roughness on jet noise generation/reduction are presented. Results of high velocity and high temperature refraction experiments are also discussed, as well as discussions concerning jet flow amplifying effects of injected low frequency noise. Additionally, suggestions concerning shock-related noise as related to full-size engines are given. And finally, recommendations for future investigations are given. (Author).