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.

Transonic Moist Air Flow around a Circular Arc Blade with Bump

The unsteady phenomena in the transonic flow around airfoils are observed in the flow field of fan, compressor blades and butterfly valves, and this causes often serious problems such as aeroacoustic noise and the vibration. In recent years, the effect of bump wall on the flow field around an airfoil has been investigated experimentally and as a result, it was observed that the bump wall is effective for the control of shock wave on the airfoil. In the transonic or supersonic flow field, a rapid expansion of moist air or steam gives rise to non-equilibrium condensation. In the present study, the effect of non-equilibrium condensation of moist air on the self-excited shock wave oscillation around a circular arc blade with or without a bump on the blade was investigated numerically. The results showed that the non-equilibrium condensation significantly reduced the flow field unsteadiness such as root mean of pressure oscillation and frequency compared to the case without the non-equilibrium condensation.

Control of Transonic Flow Fields Using Local Occurrence of Non-Equilibrium Condensation

Control of supersonic flow fields with shock wave is important for some industrial fields. There are many studies for control of the supersonic flow fields using active or passive control. When non-equilibrium condensation occurs in a supersonic flow field, the flow is affected by latent heat released. Many studies for the condensation have been conducted and the characteristics have been almost clarified. Further, it was found that non-equilibrium condensation can control the flow field. In these studies, the condensation occurs across the passage of the flow field and it causes the total pressure loss in the flow field. However, local occurrence of non-equilibrium condensation in the flow field may change the characteristics of total pressure loss compared with that by the condensation across the passage of the nozzle and there are few for researches of locally occurred non-equilibrium condensation in supersonic flow field. The purpose in the present study is to clarify the effect of local occurrence of non-equilibrium condensation on the transonic flow field in a nozzle with a circular bump. As a result, local occurrence of non-equilibrium condensation reduced the shock strength and total pressure loss in the transonic flow field by flowing the moist air from trailing edge of the circular bump to the mainstream.