Wall-Resolved Large-Eddy Simulations of Transitional Supersonic Boundary Layers Over Sinusoidal Roughness Elements

We investigate the use of high-fidelity numerical simulations to analyze skin friction and heat flux in hypersonic boundary layers developing over a blunt-body geometry with distributed surface roughness. Wall-Resolved Large Eddy Simulations (WRLES) are performed for a Mach 5.9 freestream over walls embedded with roughness elements of varying heights and wavelengths, and the results are compared against a baseline smooth-wall configuration. The influence of both roughness height and wavelength on the onset and progression of transition is systematically examined, with particular attention to their effects on surface heat flux and skin friction coefficients. Our findings also provide some insight into the mechanisms by which surface roughness triggers and sustains transition in high-speed blunt-body flows. This study contributes to the ongoing development of predictive tools for hypersonic aerothermodynamics and serves as a foundation for future high-fidelity strategies applicable to transitional flows with roughness and mean curvature. The results demonstrate that increasing roughness height and reducing roughness wavelength promote earlier boundary layer transition, with evidence from skin friction coefficient, wall heat flux, and turbulence statistics.