Hypersonic Boundary-Layer Flow with an Obstacle in Thermochemical Equilibrium and Nonequilibrium

The hypersonic flow around a tip of a rocket-mounted Hypersonic Boundary-Layer Transition experiment has been simulated with direct numerical simulations. The numerical results reveal the local flow conditions at the location of a surface-mounted cuboid on the wedge-shaped geometry roughly 50 cm downstream of the leading edge for ideal-gas, chemical-equilibrium, and nonequilibrium conditions. The flow is subject to an oblique shock to deliver about at the boundary-layer edge at the cuboid depending on the gas model used. The flow around the object of about one-third of the boundary-layer thickness in height is influenced by the chemical modeling of the air, and reveals different wakes downstream of the cuboid. The details of the flow depending on the chemical model employed underline the necessity for nonequilibrium simulations under the conditions investigated. The laminar wake shows hot fluid being transported close to the surface through the trailing longitudinal vortices, increasing the heat flux at the wall for the chemically reacting cases, most notably for the nonequilibrium case, compared to an ideal-gas comparative case. Although the maximum temperature in the wake decreases for the chemically reacting flows, the location of the maximum moves closer to the wall amounting to a net increase in heat transfer.