高超声速边界层Görtler涡及其控制研究

The boundary layer flow at the concave surface generates pressure compression and high lift, it has significant influence to the success of hypersonic flight. How the hypersonic boundary layer evolving on the concave surface depends very much on the evolution of the Görtler vortices that usually exist at the concave surfaces. The objective of the present proposal is to elucidate the flow mechanisms of the receptivity, spatial development and the secondary instability of the Görtler modes in the hypersonic boundary layer flows. Particularly, the effects of Mach number and wall temperature on the hypersonic Görtler instability will be explored in detail. This study will also propose the control strategies for the Görtler instability. ..The secondary instability of the Görtler vortex will be the research focal point. In low-speed case, the wavelength of the Görtler vortex from the primary instability often determines the sinuous or varicose form of disturbances in the secondary instability. This work will highlight the main causes affecting the disturbance forms in hypersonic boundary layer flows...Görtler vortices are often deemed as to enhance transition from laminar to turbulent flows. Control of the Görtler vortices is controlling the flow transition. Through the investigation of the Görtler vortices on the first and second instability modes in the hypersonic boundary layer and the relationship between Görtler vortices and the boundary-layer streaks, this proposal will attempt to put forward the control methodologies enhancing or damping flow transition.

凹形压缩面上的高超声速边界层的演化（如失稳、转捩等）对高超声速飞行的成败与否起着十分关键的作用。在凹面高超声速边界层的失稳、转捩过程中，Görtler涡如何演化是核心。本项目拟开展研究的目标是，获得高超声速边界层Görtler模态的感受性、空间发展和二次失稳的演化机理，探究Ma数、壁温等因素对上述过程的影响，进而提出相应的Görtler失稳转捩的控制方法。研究将重点探讨Görtler涡的二次失稳导致的转捩。在低速条件下，一次失稳时的Görtler涡的波长往往决定二次失稳过程中出现sinuous或varicose形式的扰动。研究将揭示高超声速边界层二次失稳的类型、其本质特性以及关键的影响因素。控制Görtler涡即控制流动转捩。研究将通过对Görtler涡对高超声速边界层失稳的第一、第二模态不同的影响，以及Görtler涡与边界层条带之间的关系，提出Görtler失稳转捩的控制方法。

高速层流-湍流转捩极大地影响飞行器气动力与气动热的分布。在高速流动中，失稳、转捩以及控制十分复杂，目前国际国内对于高速转捩的机理仍没有定论。Görtler涡广泛存在于带有曲率的边界层流动中，在飞行器外形设计中不可避免。但现有对于Görtler涡诱导转捩的研究仅处于起步阶段，针对Görtler涡转捩问题，项目组首次系统性的研究了Görtler涡的二次失稳，分析了压缩性对于Görtler模态的影响，揭示了不同影响因素下Görtler条带二次失稳的机理。进一步地，项目组发明了一种基于条带及Görtler模态的转捩控制方法，独创性地为粗糙单元强制转捩装置提供了一种定量的设计方案，在理论及数值实验中获得了理想的控制效果。项目组的工作成功解决了实际工程中出现的问题，并推动了高速流动转捩理论的发展。