Effect of small bluntness on the formation of Görtler vortices in a supersonic flow around a compression corner

The influence of small cylindrical bluntness of the leading edge of a flat plate on the formation of spatial structures in a nominally two-dimensional supersonic flow in a compression corner at the Mach number $\mathrm{M}_{\infty}\approx 8$ and a laminar state of the undisturbed boundary layer is studied by the method of temperature-sensitive paints. Streamwise vortices are found in the region of reattachment of the separated flow in a wide range of Reynolds numbers $(0.15\cdot10^6-2.55\cdot 10^6)$ for various angles of flow deflection and plate lengths. It is demonstrated that the existence of these vortices induces transverse oscillations of the heat transfer coefficient; the amplitude of these oscillations may reach $30\%$. The maximum Stanton numbers reaching $80\%$ are observed in the case with significant roughness of the leading edge of the flat plate. Both the maximum Stanton numbers in the reattachment region and the amplitude of transverse oscillations of the Stanton number induced by streamwise vortices are found to decrease significantly in the case of small bluntness of the leading edge. Solutions of three-dimensional Navier–Stokes equations are derived for some test conditions. The computed results are in good agreement with experimental data, which testifies to a significant stabilizing effect of small bluntness on the intensity of streamwise vortices.