Numerical analysis of supersonic flows over an aft-ramped open-mode cavity

The characteristics of supersonic cavity flows were investigated using large eddy simulation together with the acoustic analogy method. A fifth-order hybrid compact-weighted essentially non-oscillatory scheme was applied to calculate the convective flux, and a sixth-order compact scheme was used for the viscous flux. Farassat's Formula 1A was used to solve the Ffowcs William-Hawkings equations to obtain the far-field acoustic pressure fluctuations. The effects of cavity configuration and flow Mach number on the pressure waves generated by the interaction of shear vortices and cavity were compared. The ramped rear-step of the cavity can increase the more-organized level of flow coherent structures, and decrease the static pressure distribution on the cavity bottom-wall. The attenuation of the interactions between the shear layer vortex and the aft-ramped wall of the cavity can reduce the feedback of pressure waves upstream. The energy of the main frequency significantly decreases for the far-field acoustics in the upstream flow over the ramped rear-step cavity. Thus, the effectiveness of noise reduction by the rear-ramp is considerable for the area upstream of the cavity for the present conditions, but it is not the case opposite to and downstream of the cavity. The present conclusions are valuable for evaluating the performance of noise suppression by cavities embedded in supersonic inflows in engineering applications.