Unsteady shock interactions on V-shaped blunt leading edges

Abstract

The unsteady dynamics of shock interactions on the crotch of two typical V-shaped blunt leading edges have been investigated numerically and experimentally with a freestream Mach number 6 for different ratios (R), defined as the rounding radius at the crotch to the blunt radius at the leading edge. The primary flow features observed in the shock tunnel experiments are reproduced by the large-eddy simulations. The time-averaged flow structures in the crotch are clearly shown as counterrotating vortices originating from the collision of jets near the stagnation point. These jets and vortices undergo unsteady motions coupled with the dynamics of shock interactions. Of great interest, two typical global oscillations, i.e., swing oscillation and arch-recover oscillation corresponding to the two values of R, are identified. The coherent structures of the oscillations are analyzed using the proper orthogonal decomposition technique. It is demonstrated that the swing oscillation and arch-recover oscillation are characterized by an antisymmetric pattern and a symmetrical pattern, respectively. These two oscillations are also characterized by the energetic middle-frequency components of the broadband wall pressure spectra. Two feedback models are proposed for the prediction of such middle-frequency components. The results show that the swing oscillation causes much more severe pressure load, and the local impingement of the transmitted shock on the crotch is responsible for the peak value of the pressure fluctuation. This study illustrates that the geometry of R has a key impact on the unsteady shock interactions and, therefore, should be considered critically in practical applications, such as the cowl lip of a hypersonic inward-turning inlet.