转捩预测是高超声速飞行器设计中面临的一个重要但尚未解决的问题。目前工程上应用最广泛的转捩预测方法用在高超声速边界层中并不成功。原因是，原有的方法没有考虑边界层内扰动波的产生机制，即边界层对外界扰动的感受性。没能给出一个物理意义明确、可由实验直接检验的转捩判据。而对高超声速边界层，缺乏足够的实验和经验去应对由这两个不足导致的不确定性。为此，本项目拟采用理论分析与数值计算相结合的方法，以高超声速平板、小钝头圆锥为研究对象，研究自由流中声波、涡波、熵波激发边界层内模态的机理，及边界层内不稳定波的激发机制。以期得到外界自由流扰动特性与边界层内主导转捩的不稳定波之间的定量关系，为发展可用于高超声速边界层中的转捩预测方法提供可靠的科学依据。

Transition prediction is an important but still unsolved problem facing the design of hypersonic flying vehicles. Up to now, the method of transition prediction, which is most widely used in engineering is unsuccessful for hypersonic boundary layers. The reason is that the traditional method does not consider the mechanism of how the disturbances in the boundary layer are generated, i.e. receptivity of boundary layer to external disturbances. And a transition criterion with a clear physical meaning, which can be verified directly by experiments, cannot be provided. For hypersonic boundary layers, there is no enough experiments and experience to make up for the uncertainty caused by the above drawbacks. Therefore, this project will perform both theoretical analysis and numerical simulation of hypersonic boundary layers on a flat plate or a cone with a small blunt nose. We will make investigations on the mechanism of how modal modes in the boundary layers are excited by acoustic, vorticity and entropy disturbances in free-stream, and how the unstable waves are generated in order to get the quantitative correlations between the characteristics of external disturbances and the dominated unstable waves in the boundary layers. It will provide reliable scientific foundations for developing a method of transition prediction which is applicable to hypersonic boundary layers.