Supersonic and hypersonic boundary-layer flows

Supersonic and hypersonic numerical research activities of the "Lehrstuhl für Aerodynamik" at the Technische Universität München are presented in this paper. Based on the ADM (Approximate Deconvolution Method), LES simulations of a turbulent ramp flow with a subsequent decompression corner at M=2.95 are conducted (the Reynolds number based on the boundary-layer thickness at the inflow is or Re_δo = 63560 r = Re_θ = 4705). The results excellently compare with the experimental findings by Zheltovodov e t al. [27] and show the feasibility of such large-scale simulation albeit their large computer resource requirements. These simulations predict flow phenomena like the slow motion shock oscillations which can not be captured with RANS simulations. The skin friction, surface pressure and heat transfer can also be predicted correctly in contrast to RANS simulations. For the hypersonic research, flat-plate boundary layers are investigated to examine the influence of chemical and thermal non-equilibrium on laminar-turbulent transition with direct numerical simulations. This encompasses the modeling of the chemical reactions of dissociating gas and the variable thermodynamic properties which depend on species concentrations. A second temperature describing the vibrational degrees of freedom of the molecules involved is used to model the thermal non-equilibrium. The direct numerical simulations reveal a changing disturbance evolution for equilibrium and non-equilibrium calculations.