Effects of nozzle trailing edges on acoustic field of supersonic rectangular jet

Acoustic measurements of a Mach 2, rectangular nozzle with modified trailing edges mere carried out using three microphones, placed 90 deg apart azimuthally in a plane normal to the jet axis. The measurements were obtained at three streamwise locations, with microphone angles of 90, 60, and 30 deg with respect to the jet centerline. The trailing-edge modified nozzles substantially reduced the turbulent mixing and broadband shock associated noise radiation by up to 12 dB for the underexpanded flow regime and up to 7 dB for the overexpanded condition. However, in some symmetric modifications, the very-high-frequency noise was increased for the overexpanded condition. Screech tones in the overexpanded how condition were either reduced or eliminated for asymmetric modifications, but amplified for symmetric modifications. The trailing-edge modifications were found to not significantly alter the noise field for the ideally expanded flow condition.