A Supersonic Cavity Flow And The Aerodynamic Noise Control

The open straight cavity flow exhibits intensely self-sustained oscillation at the free-stream Mach number of 1.5.This transient characteristic stimulates violent pressure fluctuation which contains broad band noise and multiple order cavity tones.In order to improve the understanding of the shear layer transport processes and frequency characteristic,LES was used in numerical simulation of the flow field,,Dynamic Mode Decomposition(DMD)were conducted to analyze this phenomenon.The results show that DMD is able to extract the main dynamic features and high-order modes from original flow field,which will provide serviceable information of flow configuration with different frequency.Through the DMD aided analysis techniques,the cavity tones self-sustained oscillations with different frequencies and broad band noise of the supersonic open straight cavity flow have been considered.the conclusions shows that the cavity tones self-sustained oscillations with different orders were cause by the impingement of Entrainment waves on the back wall of the cavity,and the impingement of the shear layer on the tail edge of the cavity gave rise to the broad band noise which in the high frequency region.Meanwhile,the analogue property between the shock waves and the Entrainment waves was discussed.In the end,two passive control scheme have been conducted to suppress the aerodynamic noise of supersonic open straight cavity flow.The plan A: through installing the pressure pipeline to decrease the intensity of feedback acoustic waves.Thereby,suppressing the sound pressure level inside cavity.The plan B: the guide vane which was make up by a supersonic airfoil was installed near the leading edge of the cavity.Through deflecting the supersonic free-stream to change the flow behavior into analogously transitional cavity flow.On account of the existent of impingement shock wave at the middle region of the cavity,it obstruct the feedback loop of the feedback acoustic waves,and effectively suppressed the sound pressure level inside cavity as well.