High-fidelity numerical simulations of transitional supersonic boundary layers over sinusoidal roughness elements

As space vehicles enter a planet’s atmosphere at hypersonic speeds, they decelerate due to increasing atmospheric density, leading to increased drag and heat flux on the surface. This heat flux causes the thermal protection system (TPS) to ablate, resulting in surface roughness elements whose sizes and shapes depend on flight conditions and TPS materials (Berry & Horvath, 2008). The surface roughness can disturb the mean flow, leading to a transitional boundary layer that adversely affects aerodynamic performance and structural integrity (Hollis, 2021). This study focuses on high-fidelity numerical simulations of transitional flow over a surface with sinusoidal roughness in both the streamwise and spanwise directions to predict friction and heat flux coefficients in a supersonic transitional boundary layer at Mach 3 and Re_Θ ≈ 5000 . Inspired by Muppidi & Mahesh (2012), we extend the surface roughness to the end of the domain and study the effects of varying the ratio of roughness height to boundary layer thickness, mean curvature mimicking blunt body reentry vehicles, and inflow conditions. This research aids in understanding transitional boundary layers due to surface roughness and helps improve the design and performance of the TPS in high-speed reentry vehicles.