Abstract
In this study, the oscillation phenomena of underexpanded jet were discussed. The jet becomes underexpanded when the pressure ratio exceeds the critical value across the convergent nozzle discharging it. The jet is not uniform because of the presence of the expansion wave, the compression wave and the shock wave formed in it. In the jet boundary, many vortices are generated by the shearing stress between the supersonic flow of jet and still atmosphere The interaction of vortices and jet is closely related to the strong acoustic noise radiating from such flow field. In this experiment, in order to measure the behavior of jet, the flow field was visualized and the photograpbs were analyzed, and furthermore, the acoustic noise was measured.
