Passive Hypersonic Boundary Layer Transition Control Using Ultrasonically Absorptive Carbon-Carbon Ceramic with Random Microstructure

Kurzfassung

For the first time the influence of ultrasonically absorptive carbon-carbon material on hypersonic laminar to turbulent boundary-layer transition was investigated experimentally. A 7° half-angle blunted cone with a nose radius of 2.5 mm and a total length of 1077 mm was tested at zero angle of attack in the High Enthalpy Shock Tunnel Göttingen (HEG) of the German Aerospace Center (DLR) at Mach 7.5. One third of the model surface in circumferential direction was equipped with a in-house manufactured ultrasonically absorptive carbon-carbon material with random microstructure for passive transition control. The remaining model surface consisted of polished steel and served as reference surface. The study revealed a clear damping of the second-mode instabilities and a delay of boundary layer transition along the ultrasonically absorptive carbon-carbon insert.