Supersonic Jet Noise Control via Trailing Edge Modifications

초록

Various experimental data, including mixing areas, cross correlation factors, surface flow patterns on nozzle walls, and far field noise, was used to draw a noise control mechanism of a supersonic jet noise. In the unexpanded case, mixing of the jet air with ambient air was significantly enhanced as presented before, and mixing noise was also dramatically reduced. Screech tones, in the overexpanded case, were effectively suppressed by trailing edge modifications although mixing enhancement was not noticeable. From mixing and noise performance of nozzles with modified trailing edges, enhancing mixing through streamwise vortices is an effective way to reduce mixing noise in the underexpanded flow regime. However, screech tones in the overexpanded flow regime is well controoled or suppressed by making shock cells and spanwise large scale structures irregular and/or less organized.