Duality of the vortex structure arising in a supersonic viscous gas flow past a plate and a blunt-fin body junction

The results of a numerical solution of the problem of supersonic flow past an elongate blunt-fin body mounted on a plate with developing laminar boundary layer are presented. The calculations cover flow cases with the freestream Mach number equal to 6.7 and two different Reynolds numbers: $\operatorname{Re}$ = 1.25 $\times$ 10$^4$ and 1.56 $\times$ 10$^4$. The structure of the horseshoe vortices arising in the body leading-edge region is analyzed. It has been revealed that, for both $\operatorname{Re}$ values, there are two stable solutions that correspond to different metastable states of the flow. The solutions differ in the number of vortices forming in the separation region and its length. In the smaller Reynolds number case, both solutions are steady-state, whereas in case of a larger $\operatorname{Re}$ value one of them remains steady-state, and the other one becomes quasi-periodic.