Study on transonic tone in an axisymmetric supersonic nozzle

This paper describes experimental and numerical works to investigate noise phenomenon in supersonic flow discharged from a convergent-divergent nozzle. The noise phenomenon of flow is generated by an emission of 'transonic tones'. The results obtained 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 high-order transonic tone has the directivity in the direction of the flow. As for the transonic tone's frequency, the separated zone was calculated by using a simple flow model considering the propagating perturbation. The results of the model corresponded to the results of this experiment well.