Concluding the Development of C/C-SiC Based Thermal Protection Material With Random Porosity for Hypersonic Transition Suppression

Abstract

The present work concludes the experimental and numerical efforts to develop a C/C-SiC based material for use as ultrasonically absorptive thermal protection to passively control hypersonic boundary layer transition. The study covers the design strategy including the linear stability analysis of the flow field at the test condition of interest, the homogeneous absorber theory for an initial absorber layout, the material design, the acoustic characterization of the C/C-SiC samples resulting from different manufacturing processes, the final tests in the High Enthalpy Shock Tunnel Göttingen (HEG) and the numerical prediction of the observed transition delay. The wind tunnel tests to validate the design approach are conducted on a 7 degree half angle cone with a large C/C-SiC insert tested at Mach 7.4 in the shock tunnel HEG. The change of second mode instability growth and its effect on the transition location are investigated by means of high speed Schlieren visualization and surface mounted transducers assessing the surface heat flux. Strong boundary layer transition delay on the porous surface was observed.