Study of Transonic Tone in Supersonic Nozzle

The present paper describes experimental and numerical works to investigate noise phenomenon in supersonic flow that is discharged from a convergent-divergent nozzle. The noise phenomenon of flow is generated by an emission of 'transonic tones'. The results of obtaining show that the frequency of a transonic tone that differs from the frequency of a screech tone due to the shock-cell structures in a jet, and originates in the shock wave in the nozzle increases in proportion to the nozzle pressure ratio. The transonic tone of high-order has the directivity in the direction of the flow. As for the frequency of the transonic tone, the separated zone was calculated by using a simple flow model by whom the propagate perturbation was considered. The calculation results by the model were corresponding to the present experimental results well.