Experimental investigation of self-oscillation feedback flow field structure and flow induced aeroacoustics for an open cavity in low speed wind tunnel

To investigate the noise issue caused by open-cavity self-sustained oscillations, flow over a rectangular cavity with a length-to-depth ratio of 2 at Mach numbers of 0.10, 0.15,0.20, and 0.25 was experimentally studied in a 0.55 m × 0.40 m aeroacoustics wind tunnel.Further, the velocity field and self-sustained oscillation were studied. High-frequency particle image velocimetry was employed to visualise the flow-field structure and analyse the path of the acoustic and pressure waves. The acoustic self-sustaining oscillation modes and duct modes were investigated by testing the far field and the fluctuating wall pressure. Moreover, the characteristics of the correlation between the wall pressure and the acoustic performance were discussed. The results demonstrated that apart from the main vortex structure, shear vortices at the leading edge and crash vortices at the trailing edge were observed. Furthermore, around the frequencies of 875 Hz, 1288 Hz, 1875 Hz, and 2050 Hz, an evident tonal noise, induced by the cavity oscillation, could be detected. In addition, the wall pressure strongly correlated with the far-field noise, and the tone appeared at the same frequencies where the peaks occurred in the wall pressure spectra.