  The dynamics of a shock wave impinging on a transitional high-enthalpy
boundary layer out of thermochemical equilibrium is investigated for the first
time by means of a direct numerical simulation. The freestream Mach number is
equal to 9 and the oblique shock impinges with a cooled flat-plate boundary
layer with an angle of 10{\deg}, generating a reversal flow region. In
conjunction with freestream disturbances, the shock impingement triggers a
transition to a fully turbulent regime shortly downstream of the interaction
region. Accordingly, wall properties emphasize the presence of a laminar
region, a recirculation bubble, a transitional zone and fully turbulent region.
The breakdown to turbulence is characterized by an anomalous increase of skin
friction and wall heat flux, due to the particular shock pattern. At the
considered thermodynamic conditions the flow is found to be in a state of
thermal non-equilibrium throughout, with non-equilibrium effects enhanced and
sustained by the shock-induced laminar/turbulent transition, while chemical
activity is almost negligible due to wall cooling. In the interaction region,
relaxation towards thermal equilibrium is delayed and the fluctuating values of
the rototranslational and the vibrational temperatures strongly differ, despite
the strong wall-cooling. The fully turbulent portion exhibits evolutions of
streamwise velocity, Reynolds stresses and turbulent Mach number in good
accordance with previous results for highly-compressible cooled-wall boundary
layers in thermal nonequilibrium, with turbulent motions sustaining thermal
nonequilibrium. Nevertheless, the vibrational energy is found to contribute
little to the total wall heat flux.
