Investigation on aerodynamic noise characteristics of cavity flow at high subsonic speeds

Aerodynamic noise characteristics of cavity flow at high subsonic speeds are investigated based on analysis of sound pressure level distributions on the cavity floor centerline and sound pressure frequency spectrum characteristics at different measurement positions. The cavity studied was with the length-to-depth ratios of 6, 10 and 15. The test was performed over a Mach number of 0.8 at a Reynolds number of 1.15×107 per meter with a boundary-layer thickness of approximately 0.034 m. The results indicate that SPL in the region upstream of the cavity rear-face is more than that in the region downstream of the cavity forward-face. Impingement of the shear-layer and the cavity floor disturbs the noise feedback mechanism from the cavity rear-face to forward-face for closed and transitional cavity, which causes an incurrence of self-sustained flow oscillations and peak frequencies of sound pressure. However, the shear-layer bridges open-cavity, which has no influence on the mechanism. The self-sustained flow oscillations and some peak frequencies of sound pressure occur inside the open cavity.