抄録
The effects of nozzle geometry on the acoustic waves from Mach 1.9 supersonic jet are experimentally investigated. PIV and microphone measurements are conducted to analyze the relationship between flows and acoustic waves. In this study, three different nozzles of conical nozzle, convergent-divergent nozzle (C-D) nozzle, and tab C-D nozzle in which tab is attached in nozzle inlet to generate disturbance are considered. Three noise sources are identified. Conical nozzle case shows screech and broad band shock noise spectra because of the existence of strong shock train in flow. For the other two cases (C-D nozzle and tab nozzle), there are not clear shock associated noise spectra due to nearly ideally expanded condition by the nozzle geometries so that turbulent mixing noise should be dominant. Tab nozzle case shows higher frequency acoustic spectra than that of C-D case. This is because inflow become turbulent flow from the very beginning by the existence of tab so that smaller scale turbulence is generated.
