High-Fidelity Gas and Granular Flow Physics Models for Rocket Exhaust Interaction with Lunar Soil

Current modeling of Lunar and Martian soil erosion and debris transport caused by rocket plume impingement lacks essential physics from the peculiar granular characteristics of highly irregular regolith particles. Current granular mechanics models are based on mono-disperse spherical particles empiricism unsuitable for capturing the poly-disperse irregularly shaped grain mechanics. CFDRC and the University of Florida successfully demonstrated a novel approach in Phase I to develop granular mechanics constitutive models through innovative Discrete Element Methods emulating non-spherical, jagged particles constructed as clusters of linked/overlapping spheres. This first principle modeling captures the fundamental relationship between particle shape and particle-phase stress, cohesion, and particle flow kinetics. In Phase II, detailed regolith granular flow constituent models will be derived with these methods. An Eulerian granular phase model with the resulting constitutive models will be implemented in the Unified Flow Solver (UFS) simulation framework developed by CFDRC and UF for lunar debris transport and applied in Eulerian multi-phase gas-regolith interaction simulations. Surface stresses from turbulent jet plume scouring and regolith roughness that amplify erosion mechanisms will be captured using a Reynolds Stress Turbulence model. The integrated UFS simulation tool will be validated against erosion and cratering experiments with sand, lunar/Mars simulants, and reduced gravity effects. The technology will be applied for Moon/Mars landing crater formation and debris transport predictions. This high-fidelity simulation capability will be essential for predicting regolith dust and debris transport and for developing mitigation measures.