This is a companion paper to a previous study of hypersonic boundary layer transition over a concave wall [Huang et al., “Inner structures of Görtler streaks,” Phys. Fluids 33, 034116 (2021)]. Experiments are performed in a Mach 6.5 quiet wind tunnel using CO₂-enhanced filtered Rayleigh scattering flow visualization, PCB fast-response pressure sensors, and a high-frequency Schlieren technique to investigate naturally developing Görtler streaks. This is the first time that naturally developing Görtler streaks have been visualized using the Rayleigh scattering technique in a hypersonic flow. The results show that three-dimensional waves can be clearly visualized inside the Görtler streaks. More importantly, these waves are amplified owing to Görtler instability, contributing to the formation of Görtler streaks and mushroom-like structures. Thus, the three-dimensional waves can be considered to be basic structures inside Görtler streaks and to play a crucial role in boundary layer transition.

中文翻译：

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自然发展的 Görtler 条纹的早期演变

这是先前对凹壁上高超声速边界层过渡研究的配套论文 [Huang et al. ，“Görtler 条纹的内部结构”，Phys。流体33 , 034116 (2021)]。使用 CO ₂在 6.5 马赫的安静风洞中进行实验- 增强的滤波瑞利散射流可视化、PCB 快速响应压力传感器和用于研究自然发展的 Görtler 条纹的高频纹影技术。这是第一次在高超声速流动中使用瑞利散射技术对自然发展的 Görtler 条纹进行可视化。结果表明，在 Görtler 条纹内部可以清楚地看到三维波。更重要的是，由于 Görtler 不稳定性，这些波被放大，导致 Görtler 条纹和蘑菇状结构的形成。因此，三维波可以被认为是 Görtler 条纹内部的基本结构，并且在边界层转变中起着至关重要的作用。