Direct Simulation Monte Carlo Sensitivity Analysis at Super-Orbital Velocities

Designing efficient and robust hypersonic vehicles requires understanding a range of physical flow phenomena. However, many of the parameters used in computational modeling tools to describe these key phenomena are subject to uncertainties. This work uses a Direct Simulation Monte Carlo method coupled with uncertainty quantification tools to explore a wide range of flow regimes. The geometry considered is a slender 20 cm wedge with a 2.5 cm nose radius. Altitudes range from free molecular to transitional Knudsen numbers, and velocities range from approximately low Earth orbit to super-orbital. A detailed analysis is performed to compute the sensitivities and confidence intervals for convective heating and pressure. Results indicate the importance of the thermal accommodation coefficient of the wall and nitrogen dissociation reactions. Comparisons to analogous Navier-Stokes uncertainty quantification studies are presented for a transitional flow condition. These results inform how to quantify uncertainties in existing hypersonic modeling capabilities and how to best mitigate uncertainties in the future for a wide range of hypersonic flow conditions.