Molecular dynamics insights into reflected gas behavior in rarefied flows: Effects of gas-surface interaction strength and surface conditions

Q Miao and LQ Li and X Yu and JL Wu and M Fang, SURFACES AND INTERFACES, 71, 106884 (2025).

DOI: 10.1016/j.surfin.2025.106884

The interaction between air and the surface is essential for accurately predicting aerodynamic characteristics in rarefied regimes. This research utilized molecular dynamics (MD) simulations to delve into the dynamic mechanisms underlying the reflection of rarefied gases on solid surfaces. Specifically, the effects of gas-surface interactions (GSI) strength, surface temperature and roughness on gas reflection characteristics have been explored. The results reveal that the adsorption and reflection behavior of gases vary significantly at different incident velocities. At low incident velocities, gas adsorption is obviously influenced by the GSI strength, following a Boltzmann distribution; while at high incoming velocities, gas adsorption is almost negligible. Furthermore, at low incident velocities, the reflection velocity of gas satisfies different scaling laws with changes in GSI strength, and different GSI strength leads to distinct temperature-dependent alternations in the gas reflection velocity, but the energy accommodation coefficient (EAC) exhibits the same exponential decay with temperature; at high incident velocities, both gas reflection velocity and EAC change linearly with GSI strength and surface temperature. Besides, surface roughness induces a power-law decay in reflection velocity under all incident velocities, the power- law exponent increases as incident velocity rises.

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