Computational analysis of the unsteady type IV shock interaction of blunt body flows

A thin-layer approximation to the two-dimensional Navier-Stokes equations, coupled with the total variation diminishing scheme, is used to examine a type IV shock interaction at Mach 8. The calculations reveal that the apparent unsteadiness of the type IV interaction is related to the formation and shedding of shear layers within the shock layer and acoustical feedback between the distorted bow shock arid the body. A Fourier analysis of the flowfield indicates that this shedding frequency is the same frequency associated with the motion of the supersonic jet. The effects of shock impingement angle and shock strength on the location and magnitude of the peak pressure are also studied and it is shown that changes in the impinging shock angle can strongly affect the peak surface pressure and the supersonic jet position. Further examination of the unsteady behavior of the interaction reveals that a small change in the impinging shock angle can change the flowfield from steady to unsteady.