An experimental study on the effects of Backward-Facing Step (BFS) shapes was conducted in the Ma6 hypersonic wind tunnel. The step shape was changed by installing different ramps in the step corner, including 10, 30, and 60 deg gibbous ramps and the original square step. The centerline heat flux distribution downstream of the step was measured by the Temperature-Sensitive Paints (TSP), and the flow structures across the step were visualized by Nano-tracer-based Planar Laser Scattering (NPLS) and schlieren techniques. The results revealed that the heat flux density was effectively reduced by shaping the step, among which the 30 deg ramp achieved the lowest heat flux amplitude. Meanwhile, the reattachment and transition positions of the 30 deg slope were obviously delayed. The reattachment position and reattachment shock angle of the 60 deg and gibbous ramps had no significant changes compared with that of the square step, but they could maintain a longer laminar flow after the reattachment, and its transition process was prolonged, whereas the instability of the boundary layer of 90 and 10 deg steps grew quickly after crossing the step. The average error percentage of heat flux measurement is about 16.8% through uncertainty analysis based on 3–5 repeated samples.

在 Ma6 高超声速风洞中对后向台阶 (BFS) 形状的影响进行了实验研究。通过在台阶拐角处安装不同的坡道来改变台阶形状，包括10度、30度和60度的凸形坡道和原来的方形台阶。台阶下游的中心线热通量分布由温度敏感涂料 (TSP) 测量，跨越台阶的流动结构由基于纳米示踪剂的平面激光散射 (NPLS) 和纹影技术可视化。结果表明，台阶成形有效地降低了热流密度，其中30度坡度达到了最低的热流幅值。同时，30度斜坡的再附着和过渡位置明显延迟。60°和凸形斜坡的重附位置和重附激波角与方形台阶相比无明显变化，但重附后仍能保持较长的层流，延长其过渡过程，而90 度和 10 度台阶的边界层在跨越台阶后迅速增长。通过基于 3-5 个重复样本的不确定性分析，热通量测量的平均误差百分比约为 16.8%。