Oblique viscous–inviscid free interaction on the lee-side of an inclined slab delta in hypersonic flow

Near wakes and cross-flow separation in hypersonic flows have important implications for the effective design and engineering of next-generation flight vehicles, reentry capsules, and propulsion systems. The present work utilizes numerical simulations of a Mach 10 slab delta at a moderate angle of attack in adiabatic, cold wall, and slip wall flow in order to reconcile the cross-flow vortex formation with free-interaction processes observed on primitive shapes and capsules. Validation of the simulation methodology is performed by comparing with experimental data from the literature for pressure and Stanton number distributions. First, the work shows that a boundary layer separation is not required to form a cross-flow recirculation flow pattern. This indicates that the flow reversal leading to the rotating flow is related to gasdynamic phenomena, rather than being a result of boundary layer separation alone. Subsequently, simulation results are used to examine the mechanisms of viscous–inviscid interaction leading to separation. The work demonstrates that despite substantially changing pressure and local skin friction along the delta wing, the separation process obeys a nearly self-similar free-interaction process over a large portion of the body. A free-interaction parameter modified to account for the momentum balance in the direction of the leading edge is presented and demonstrates the predictability of this interaction at various stations along the delta. These results and observations demonstrate that past work on near-wake free interactions is more general than previously shown and confirms and builds on early work in the literature.