Leading-edge bluntness effects on the hypersonic flow over the double wedge at multiple aft-wedge angles

The present numerical investigation focuses on the leading-edge bluntness effects on the double wedge with varied aft-wedge angles exposed to low enthalpy hypersonic free stream conditions. The bluntness ratio in this study varies, ranging from R/L-1 = 0 (sharp leading edge) to R/ L-1 = 0.577 (maximum allowable bluntness), along with the aft-wedge angle varying between theta(2) = 45 degrees and 60 degrees. Noticeably, even a small bluntness ratio can completely change the shock interaction pattern compared to its sharp geometrical counterpart due to a detached leading-edge shock, enlarged separation bubble, and location of various shock waves concerning it. Critical bluntness ratios exist for the low aft-wedge theta(2) = 45 degrees angle, but increasing the aft-wedge angle makes the flow field highly unsteady for some bluntness ratios. Nevertheless, these bluntness ratios for such double-wedge configurations are reported using the mean of separation bubble size. Moreover, this work unravels the cause of such unsteadiness for the unsteady flow fields using the spatial-temporal evolution of the wall pressure distribution and fast Fourier transform of the pressure fluctuation signal at the compression corner and supports the deduced observation with the help of energy-based proper orthogonal decomposition. The increased shock-boundary layer interaction strength moves the separation point upstream beyond the junction of cylindrical bluntness and inclined fore-wedge surface, accompanying sudden change in its direction of motion that perturbs the shear layer that set to a self-sustained, highly unsteady flow field.