Direct numerical simulation of the effects of Reynolds number in Mach 2.9 flows over an expansion–compression corner

Abstract

In order to investigate the characteristics of shock wave/boundary layer interaction and its variation with Reynolds number in expansion–compression corner flows, direct numerical simulations of Mach 2.9 expansion–compression corner flows at Reδref=12 000,22 000, and 43 000 were carried out. The λ type shock wave structure appears near the compression corner. Compared with the flat-compression corner wave system, the separation shock wave is weaker, and the reattachment shock wave is stronger. With the increase in the Reynolds number, the separation angle of the separation bubble decreases, the separation pressure rise decreases, and the reattachment pressure rise increases. The separation flow has the unsteady characteristics of low frequency, and the main frequency after nondimensionalized with separation length is St = 0.032. The pressure gradient is the main factor affecting the turbulence change at the expansion corner. With the increase in the Reynolds number, the absolute peak value of pressure gradient at the expansion corner increases, but the spatial range of pressure variation decreases. These two trends together lead to the insignificant change of turbulent energy at the expansion corner. At the compression corner, the main reason for the change of turbulent energy is the strong shear above the separation bubble, which shows a monotone change with the Reynolds number. The results show that the Reynolds number obviously affects the near-wall pressure distribution in the shock disturbance region in the expansion–compression corner flow. The turbulent energy distribution at the expansion corner and compression corner is also affected, but the influence laws are different due to different influence mechanisms.