Suppression of Pressure Oscillations for Supersonic Cavity Flow with Passive Control

Large eddy simulation (LES) for a supersonic Mach 1.8 flow past 2D cavities with/without passive control is carried out to investigate the characteristics of oscillations, and the dynamic mode decomposition (DMD) is used to identify the dominant flow structures with pertinent frequencies. A passive control by substituting the cavity trailing edge with a quarter-circle is studied. The pressure field for the dominant dynamic mode becomes more uniform, the intensity of fluctuations in the shear-layer is reduced, and the wavelength of the shear-layer vortices is significantly shortened under control. It is found that the dominant oscillation frequency of the cavity corresponds to the third Rossiter mode, which is significantly increased after control. The amplitude of the pressure oscillations in the cavity shifts to lower level. The sound pressure level (SPL) can even be reduced by approximate 10dB. The oscillation mechanism illustrated by the DMD remains the same after passive control. Overall, the oscillations of the cavity flow are closely linked with the shear-layer instability, which is suppressed by the current control technique.