Experimental Investigation of Woven Thermal Protection System Material Roughness Effects on Transition Onset and Turbulent Heating Augmentation at Mach 6

An experimental investigation of woven thermal protection system material surface roughness effects on boundary-layer transition and turbulent heating has been performed at hypersonic test conditions. Two representative entry vehicle geometries, a sphere-cone aeroshell and a spherical-cap aeroshell, were considered. Cast ceramic models of each geometry were fabricated with surface textures that simulated a woven thermal protection material and aeroheating and boundary-layer transition onset data were obtained on these models using global phosphor thermography. Wind tunnel testing was performed at Mach 6 over a range of Reynolds numbers sufficient to produce laminar, transitional, and turbulent flow. The experimental heating and boundary-layer transition data are presented herein, as are comparisons to laminar and turbulent smooth-wall heat transfer distributions from computational flow field simulations. The boundary-layer transition data were found to correlate with a functional representation developed in prior roughness studies. However, a shift in the correlation curve indicates the need for a comprehensive analysis of roughness-height definitions for the current woven roughness data, as well as the sand-grain and hexcomb roughness datasets from which the correlation was developed.