Acoustic near- to far-field characteristics of nozzle radiation through plug flow jets

Gabard, G., Tester, B.J. and De Mercato, L. (2007) Acoustic near- to far-field characteristics of nozzle radiation through plug flow jets. 13th AIAA/CEAS Aeroacoustics Conference (28th AIAA Aeroacoustics Conference), , Rome, Italy. 20 - 22 May 2007. 13 pp .

Abstract

This paper reports a theoretical and numerical study of the radiation of sound through jet exhausts. It focuses on the transition from near field to far field by considering the features of the near field solution and how these features translate to the far field. The main finding of this work is the importance (in some cases) of lateral waves radiating from the jet. While the presence of lateral waves has long been recognized, there has been no systematic investigation of the practical consequences of these waves in the prediction of sound propagation through jet mixing layers. The physical mechanisms involved in the generation of these waves are presented as well as the conditions under which they become significant. This paper also discusses the validity of the far-field approximation when lateral waves are present. It is shown that the standard far-field asymptotic can be improved by adding a correction term which accounts for the presence of the lateral waves.

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