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

为了弄清超音速边界层转变的机理，我们用定标的定量纹影光学系统、皮托管、热线和直接数值模拟方法研究了矩形截面隧道喷管壁上的超音速边界层，重点研究了影响边界层转变的非线性扰动。结果清楚地表明，本文所研究的转变与最初由低速条纹和流向涡控制的亚音速情况相同，这些低速条纹和流向涡会导致湍流斑点的形成。此外，我们还获得了关于超音速边界层过渡的有用的数值数据和知识，如过渡雷诺数，这不仅对过渡预测很重要，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.