PROGRESS IN THE RESEARCH OF HYPERSONIC AND HIGH­ENTHALPY BOUNDARY LAYER INSTABILITIES AND TRANSITION

Boundary layer transition from laminar to turbulence is of vital importance to the design of hypersonic vehicles. With continuous expansion of flight speed and altitude domains, the high-temperature gas effects in hypersonic high-enthalpy boundary layers invalidate the calorically perfect gas assumption. They can thus largely influence the flow transition process. Relevant research is multi-interdisciplinary and multi-physics coupling. In recent years, the hypersonic high-enthalpy boundary layer transition has received increasing interest worldwide owing to rapid development of vehicle design. Recent progress is reviewed in this article. Firstly, commonly used high-temperature gas models are introduced, especially the thermochemical non-equilibrium models. Then, the prevailing computational methods for high-enthalpy flows, including the shock-capturing, shock-fitting and boundary layer equation methods are introduced. The progress in experimental techniques for high-enthalpy wind tunnels and flight tests are also summarized. Afterward, the influences of high-temperature effects on the receptivity, modal growth, transient growth and nonlinear interactions in the transition process are reviewed. Here some phenomena has received wide interests that the third mode and the supersonic mode appear at relatively large growth rates in the streamwise instability. Finally, the progress is summarized, and future researches are briefly prospected.