Determination of Noise Sources within a high-speed Jet via Simultaneous Acoustic Measurements and real-time Flow Visualization,”

Abstract

Much of the work in the field of jet aeroacoustics has focused on how to model noise sources without sufficient knowledge on what exactly constitutes a noise source. Further, the acoustics of a jet are often analyzed without any regard for the dynamic features of the noise producing events. The work presented in this paper examines the dynamic far field acoustic signature of an ideally expanded, Mach 1.3, high Reynolds number jet, and then attempts to relate outstanding features of the acoustic signature to interactions between large-scale structures within the jet mixing layer. A four-microphone array was used to determine the origin of individual sound pressure events while movies of the flow were taken simultaneously with a pulse burst laser/high speed camera system. Two different noise generation mechanisms have been observed and are presented here. The first involves the formation of large structures within the mixing layer via structure rollup, while the other mechanism involves the strong interaction between structures within the two sides of the mixing layer