Future advanced air vehicles demonstrate a development trend towards high-speed flight in low-altitude airspace so that boundary layers over the aircraft high Mach numbers, high Reynolds numbers, and high total enthalpy feature. Higher Reynolds numbers lead to the boundary layer transition from laminar to turbulent states. The high-temperature environment, induced by the compression of intense shock waves, results in a thermochemical non-equilibrium state encompassing the effects of vibration excitation, dissociation, and ionization that invalidate the perfect gas assumption. The deeply intertwined high-temperature and high-Reynolds-number effects give rise to the high-temperature turbulence, which introduces novel flow physics including the disturbances evolution and multiscale flow structures in high-enthalpy boundary layers, gas-solid multiphase reactions under high-temperature and strong disturbances, as well as plasma turbulence in extremely high-temperature environments. This study provides a comprehensive overview of the research progress and current status regarding high-temperature turbulence mechanisms, prediction, and experimental measurements. Furthermore, it outlines the future research directions that deserve attention.

When flying at extremely high Mach numbers at low and medium altitudes, the new hypersonic vehicles will encounter a complicated flow environment, i.e. the coupling between turbulence and chemical non-equilibrium. However, there are only very few related studies so far. In this work, direct numerical simulations (DNS) were performed for the high-temperature and non-equilibrium turbulent boundary layer after the leading shock of a cone using two different gas models, i.e. the calorically perfect gas model and the chemical non-equilibrium gas model. The Walz equation, the strong Reynolds analogy (SRA) relation, the turbulent kinetic energy production-dissipation mechanism and the compressibility effects were compared and analyzed. The results show that the weak compressibility hypothesis still holds in the chemical non-equilibrium turbulent boundary layer. When using the relation between the non-dimensional recovery enthalpy and the velocity, effects of the Mach number, the chemical reaction, etc. can be eliminated, and the prediction agrees well with the DNS result. GHSRA (Generalized Huang’s SRA) is appropriate to describe the relation between the temperature fluctuation and the velocity fluctuation. The ‘semi-local’ scaling can collapse the distribution profiles of the turbulent kinetic energy budgets under different flow conditions. The compressibility effect caused by the chemical non-equilibrium and the high Mach number is limited.