LAUSR

We investigate the transition in Mach 6 boundary layers over a heated wall by magenta using the Mach 6 wind tunnel at Peking University and using visualization, focused laser differential interferometry, infrared imaging, and numerical simulation. The model's wall-temperature ratio Tw/T0 (where Tw and T0 are the wall and total temperature, respectively) can be controlled to vary from 0.66 to 1.77. The results show that increasing Tw/T0 initially delays but then promotes the transition to turbulence with the reversal point near Tw/T0≈1. In contrast with the cooled-wall condition ( Tw/T0 1). Ultrafast visualization and Lagrangian tracking indicate that wave packets play a dominant role in producing turbulence, which is similar to the soliton-like coherent structure detected in low-speed boundary layers.