Stability analyses of hypersonic, conical flows with transpiration cooling

The influence of transpiration cooling on second modes is analyzed in the present study. The investigations are carried out on a 7° half angle, blunted cone with a nose radius of 5 mm. At a free stream Mach number of 7, various gas injection mass flow rates are applied. The goal is to have the cooling effect, without triggering the transition. Thus the investigations focused on low mass fluxes. As injection gas nitrogen is used. At the considered free stream conditions second modes are the dominant boundary-layer instabilities, which are consequently the focus of this study. The stability analyses are performed by the stability code NOLOT, NOnLOcal Transition analysis, of the German Aerospace Center (DLR). Beside the analyses of the influence of different mass injection on the frequencies and growth rates of the second modes and finally on the transition onset itself, different stability approaches are applied: Calculations based on Linear Stability Theory (LST) are compared against Parabolized-Stability-Equations (PSE) results. The numerical predictions are compared with experimental data, which were obtained in the DLR High Enthalpy Shock Tunnel G ̈ottingen (HEG)