It is well known that hypersonic boundary-layer transition is sensitive to a surface roughness since the roughness may either trigger an early transition or delay the transition. Hypersonic transition is still poorly understood as there are a very limited number of studies in the literature. In the present work, we conduct a computational study on the transition process of a hypersonic Mach 6 flow over a flat plate with a gap. An implicit large eddy simulation approach based on the flux reconstruction/correction procedure via a reconstruction method is used to investigate the interaction between the hypersonic boundary layer and a gap. Flow structures with and without the gap are compared to analyze the local skin friction coefficient overshoots before and after the gap. Two inlet angles of attack are investigated. The evolution of the skin friction coefficient shows that the gap has a very limited influence on the oblique transition at a zero angle of attack. In contrast, the gap can trigger an early transition at a negative angle of attack. In this case, the transverse feedback mechanism is believed to be the main cause, which amplifies the broadband instability waves.

中文翻译：

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通过 6 马赫的斜击穿引起的间隙诱导转变

众所周知，高超声速边界层过渡对表面粗糙度很敏感，因为粗糙度可能会触发早期过渡或延迟过渡。高超声速过渡仍然知之甚少，因为文献中的研究数量非常有限。在目前的工作中，我们对具有间隙的平板上的高超音速 6 马赫流的过渡过程进行了计算研究。基于通量重建/校正程序的隐式大涡模拟方法通过重建方法用于研究高超声速边界层和间隙之间的相互作用。比较有和没有间隙的流动结构，以分析间隙前后的局部皮肤摩擦系数超调。研究了两个入口攻角。蒙皮摩擦系数的演变表明，间隙对零攻角的倾斜过渡的影响非常有限。相比之下，间隙可以在负迎角下触发早期过渡。在这种情况下，横向反馈机制被认为是放大宽带不稳定波的主要原因。