Thermochemical non-equilibrium effects in turbulent hypersonic boundary layers

A hypersonic, spatially evolving turbulent boundary layer at Mach 12.48 with a cooled wall is analysed by means of direct numerical simulations. At the selected conditions, massive kinetic-to-internal energy conversion triggers thermal and chemical non-equilibrium phenomena. Air assumed to behave as five-species reacting mixture, two-temperature model adopted account for vibrational non-equilibrium. Wall cooling partly counteracts effects friction heating, temperature rise in excites modes while inducing mild dissociation oxygen. Vibrational mostly driven molecular nitrogen, characterized slower relaxation rates than other molecules mixture. The results reveal that sustained mixing: sweep ejection events efficiently redistribute gas, contributing generation vibrationally under-excited state close wall, an over-excited outer region layer. tight coupling between turbulence quantified defining interaction indicator. modelling strategy flux proposed, based on definition Prandtl number. validity strong Reynolds analogy under also evaluated. Strong compressibility promote translational–vibrational exchange, but no preferential correlation was detected expansions/compressions over-/under-excitation, opposed what has been observed unconfined configurations.