M2CRYO aims at providing accurate modeling tools for refueling of cryogenic propellants allowing to account for phase change phenomena in micro-gravity from small to large scales, by developing an innovative numerical solver for two-phase compressible flow and accurate closure models. Efficient human exploration missions will require refueling and depot capabilities in low gravity environment (Low Earth Orbit, Lagrange points or Moon orbits). The development of In Situ Resources Utilisation (ISRU) foresee the development of Moon-produced hydrogen, methane and oxygen, allowing the reutilization of hardware in orbit, reducing the upload mass requirements. This implies the transfer of cryogenic fluids in much larger quantities than any demonstrated technologies. Cryogenic refueling is a major challenge due to the fuel loss, phase change (boiling and cavitation) and sloshing phenomena. The main difficulty relies on the multi-scale nature of the problem, which is driven by small scales (nanometers to millimeters) but impact large tank scales (meters). The lack of understanding of fundamental mechanisms at the small scales, the absence of reliable experimental data and the low fidelity of global heat transfer correlations for large scales induce large wastes of propellants and uncertainties for the overall mission. Our project will overcome these problems. The novelty is the development of a solver for direct numerical simulation (DNS) of compressible two-phase flows with phase change that will permit for the first time to accurately describe phase change induced by pressure and temperature variations in real fluids, including complex thermodynamic effects and accounting for sub-grid scales (micro-region). The solver will be used to investigate single bubble cavitation in micro-gravity. Then, data-driven models for the phase change mass flow rate, based on DNS data, will be developed and used for large scale simulations while accounting for small scales driven mechanisms.
