Effect of uneven wall blowing on hypersonic boundary-layer stability and transition

Abstract

The understanding of aerothermodynamics in complex multiphysics environments such as atmospheric entry is of vital importance for the design of optimized vehicles. A better insight into the interaction between the thermal protection system ablation and the flow’s stability and transition would significantly increase the available payload and reduce the overall mission costs. In order to improve the modeling of the effect of ablation-induced outgassing, a continuously blowing boundary condition for linear stability theory is developed and tested against existing homogeneous and porous conditions in cold wind-tunnel calorically perfect gas conditions. The new model predicts a substantially higher destabilization of the boundary layer than the classic one. An exhaustive parametric study addresses the effect of the most important parameters influencing the boundary condition characteristics. Porous layer stabilization/destabilization maps for different porous layers and flow conditions are built, serving as a starting point for a stabilizing-porous-coating design methodology. Previous controversial literature findings are clarified in the light of the current work, showing a consistent way of addressing similar future tests. The semiempirical eN method is used to predict the location of transition onset in noisy wind-tunnel conditions, obtaining substantially different predictions with different wall models.