Influence of the cavity flexible bottom wall on the self-sustaining oscillation mode

Fluid-structure interaction in a cavity affects self-sustained oscillatory flow and noise. The noise and flow field characteristics of cavities with different flexible bottom walls are investigated in a low-speed wind tunnel. The experimental tests include near-field and far-field noise, and the velocity of the shear layer. The elastic modes were varied using different thicknesses of bottom plates so that the cavity self-sustained oscillatory modes interacted with different elastic modes. The noise results of the flexible cavity measured in the experiment are coupled to both acoustic resonance modes and elastic modes. The results show that the coupling of the self-sustained oscillatory and elastic modes increases the sound pressure level of the mode. The flexible wall affects the velocity spectral characteristics of the shear layer as well as the far-field noise, but does not change the vortex-convection velocity dimensionless parameter κ. When the Rossiter mode is coupled to both acoustic resonance and elastic modes, the excitation of the two coupled modes is characterized by alternating excitation. Finally, the coupled mode frequencies of the elastic and Rossiter modes are accurately predicted based on the calculation of the phase delay term.