Roughness element induced hypersonic boundary layer transition on a flat plate is investigated using infrared thermography at Ma = 5 and 6 flow condition. Surface Stanton number is acquired to analyze the effect of roughness element shape and height on the transition process. The correlation between the vortex structure induced by roughness element and the wall heat streaks is established. The results indicate that higher roughness element would induce stronger streamwise heat flux streaks, lead to transition advance in streamwise centerline and increase the width of spanwise wake. Moreover, for low roughness element, the effect of the shape is not obvious, and the height plays a leading role in the transition; for tall roughness element, the effect on accelerating transition for the diamond roughness element is the best, the square is the worst, and the shape plays a leading role in the transition.

中文翻译：

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孤立粗糙元引起的高超声速边界层转变的红外热成像

在 Ma = 5 和 6 流动条件下，使用红外热成像研究了粗糙元诱导的平板上的高超声速边界层转变。获取Surface Stanton数，分析粗糙元形状和高度对过渡过程的影响。建立了粗糙元引起的涡流结构与壁面热条纹的相关性。结果表明，较高的粗糙度元素会导致更强的流向热通量条纹，导致流向中心线的过渡提前并增加展向尾流的宽度。而且，对于低粗糙度元素，形状效果不明显，过渡起主导作用；对于高粗糙度元素，金刚石粗糙度元素的加速过渡效果最好，正方形最差，