Hybrid CFD–DSMC for Multiscale Rarefied Gas Flows

Hybrid CFD–DSMC: An Efficient Framework for Multiscale Rarefied Flow Simulation

Multiscale rarefied gas flows often include both continuum and rarefied regions, making it impossible for a single method to capture the entire physics efficiently. Computational Fluid Dynamics (CFD) is accurate and cost-effective in near-continuum regimes, while the Direct Simulation Monte Carlo (DSMC) method provides fidelity in rarefied regimes but at high computational expense. The hybrid CFD–DSMC framework combines the strengths of both approaches by decomposing the flow domain and exchanging flux information across the continuum–rarefied interface. This enables efficient and robust prediction of flows spanning a wide range of Knudsen numbers. Such hybrid methods are particularly valuable for hypersonic reentry flows, launch vehicle plumes, and spacecraft aerothermodynamics, where multiscale effects play a critical role in system design and mission performance.

Plume–Surface Interaction in Lunar Landing

During lunar landing, rocket exhaust plumes directly interact with the regolith surface, creating a complex multiphase flow environment. The high-speed jet induces dust erosion, particle entrainment, and plume–dust interactions, which can obscure sensors, damage lander hardware, and pose risks to nearby infrastructure. We employ multiphysics CFD and DSMC simulations to capture gas expansion, dust entrainment, and gas–particle coupling under rarefied and low-gravity conditions. By resolving both the plume flowfield and dust particle dynamics, this framework provides predictive insight into erosion rates, dust cloud evolution, and visibility hazards. Such simulations are critical for the safe design of next-generation lunar landers, surface habitats, and exploration missions.