Effects of steps on the hypersonic boundary layer transition over a cone at 10° angle-of-attack

In a previous research on the hypersonic boundary layer transition over a sharp cone at 0 degrees angle-of-attack (AoA), we concluded the different effects of the forward-facing step (FFS) and the backward-facing step (BFS) on the transition [Xu et al., AIAA J. 59, 439-446 (2021)]. This further study intends to examine if the conclusion still maintains after changing the nose bluntness and the angle-of-attack of the cone. Experiments are conducted in a Mach 6 wind tunnel using nano-tracer-based planar laser scattering techniques, temperature sensitive paints, and high-frequency pressure sensors. The results show that although the FFS delays the boundary layer transition while the BFS promotes the transition at AoA = 0 degrees and at AoA = 10 degrees a completely different pattern is observed; the FFS significantly promotes the transition, while the effect of the BFS appears only weakly to advocate the transition. Noteworthy, the nose bluntness will not change the effects of the BFS/FFS on the transition. Published under an exclusive license by AIP Publishing.