Heat transfer effects and topology of the viscous interaction induced by surface protuberances in hypersonic flow

Abstract

Surface protuberances with a height of the order of the boundary layer thickness are frequently unavoidable in the design of hypersonic vehicles. These protuberances interfere with the flow and induce complex interactions which may lead to notable increases in the local surface heating rates and cause a significant damage to the vehicle. This computational and experimental study investigated hypersonic interference heating in the vicinity of simple surface protuberances. Perfect gas and Reynolds averaged Navier–Stokes simulations were carried out based on benchmark experimental cases using the compressible commercial code Cobalt. The freestream conditions were M∞ = 8.2 and Re∞/ m = 9.35 × 106. The investigated protuberances were three-dimensional compression corners with different deflection angles (30°, 60°, and 90°) and with a relatively low profile where the height was approximately the same as the local boundary layer thickness. A comparison between numerical and experimental data shows a reasonable agreement, although there are areas where there are notable differences between the predictions and measurements. In the low-deflection case (30°), good agreement is observed and the location of the hot spot is well predicted by the different turbulence models. In the higher deflection cases (60° and 90°), in which the incoming boundary layer is separated ahead of the protuberance, the maximum heating rates are reasonably well predicted by the shear stress transport and k–ω models, but systematically overpredicted by the Spalart–Allmaras model. In terms of flow structure, the simulations enable a good understanding of the flow topology, which is marked by the occurrence of junction and separation vortices to the sides and upstream of the protuberance.