Roughness-Induced Laminar-Turbulent Transition in the Boundary Layer of a Capsule-Like Geometry at Mach 20 Including Non-equilibrium

Direct Numerical Simulations are performed to investigate the instability mechanisms in a capsule-like configuration with a rough wall under typical re-entry conditions. The growth of unstable crossflow-type modes induced by a patch of randomly distributed roughness is analyzed in both the linear and non-linear stages up to laminar-turbulent breakdown. At the considered conditions, molecular dissociation and non-equilibrium effects significantly change the temperature profiles of the capsule boundary layer and have a non-negligible effect on the stability properties of the roughness wake.