Skip to Main content Skip to Navigation
Journal articles

Thermochemical non-equilibrium effects in turbulent hypersonic boundary layers

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

https://hal.archives-ouvertes.fr/hal-03661004
Contributor : Compte De Service Administrateur Ensam Connect in order to contact the contributor
Submitted on : Friday, May 6, 2022 - 2:43:34 PM
Last modification on : Wednesday, May 18, 2022 - 12:21:40 PM

File

DynFluid_JFM_2022_PASSIATORE.p...
Files produced by the author(s)

Identifiers

Citation

Donatella Passiatore, Luca Sciacovelli, Paola Cinnella, Pascazio Giuseppe. Thermochemical non-equilibrium effects in turbulent hypersonic boundary layers. Journal of Fluid Mechanics, Cambridge University Press (CUP), 2022, ⟨10.1017/jfm.2022.283⟩. ⟨hal-03661004⟩

Share

Metrics

Record views

7

Files downloads

2