A Fundamental Study on the Clarification and Control of Supersonic Boundary Layer Transition

为了阐明超声速边界层跃迁的机理，我们利用校准的定量纹影光学系统、皮托管、热线和DNS对沿矩形截面的小隧道喷嘴壁面的超声速边界层进行了研究，重点寻找控制跃迁的非线性扰动。结果清楚地表明，本研究中检测的过渡与亚音速情况相同，最初由低速条纹和流向涡控制，可以导致湍流斑的形成。此外，我们还获得了超声速边界层转捩的数值数据和知识，如转捩雷诺数，它不仅对转捩预测很重要，而且对层流控制也很重要。

In order to clarify the mechanism for supersonic boundary layer transition, we examine a supersonic boundary layer along a small tunnel nozzle wall with rectangular cross section using calibrated quantitative schlieren optical system, Pitot-tube, hot-wire and DNS with focusing efforts on finding non-linear disturbances governing the transition. The results clearly show that the transition examined in this study is the same as the subsonic case initially governed by low-speed streaks and streamwise vortices which can lead to the formation of turbulent spots. Also, we obtain useful numerical data and knowledge on the supersonic boundary layer transition, such as transition Reynolds number which is important not only for the transition prediction but for the laminar flow control.