Passive hypersonic boundary layer control by means of ultrasonically absorptive carbon-carbon ceramics: Investigations of different boundary conditions

Kurzfassung

The influence of carbon fiber reinforced carbon ceramic (C/C) surfaces on hypersonic boundary layer instabilities is analysed numerically using the stability code NOLOT, NOn-Local Transition analysis code, of the German Aerospace Center (DLR). Experimental investigations in the DLR High Enthalpy Shock Tunnel Göttingen, HEG, show that C/C surfaces can be utilized to damp acoustic second mode instabilities, which results in a delay of boundary layer transition onset. The investigated geometry is a blunt 7° half-angle cone model with a nose radius of 2.5 mm and a total length of about 1 m. One-third of the metallic model surface in circumferential direction was replaced by C/C ceramics. In this paper different approaches for the formulation of the boundary conditions in NOLOT, modeling the acoustic damping properties of the C/C material, are analysed and compared with the experimental results.