Determination of momentum accommodation coefficients and velocity distribution function for Noble gas-polymeric surface interactions using molecular dynamics simulation

摘要

Due to the momentum and energy exchange between the gas and solid surface molecules, by means of the accommodation coefficients in the Cercignani-Lampis-Lord (CLL) model, the velocity components used in the Direct Simulation Monte Carlo (DSMC) method can be studied more accurately. The coefficients can also be used in calculation of slip velocity, temperature jumping, drag force and shear stress. In the light of rising needs for polymers in industrial applications, the scattering behavior of noble gas molecules in their collision with a surface made of diglycidyl ether bisphenol A (DGEBA) epoxy resin, cured by tetrahydrophthalic anhydride (THPA) agent and reinforced by mull-layer graphite, was simulated and investigated by Molecular Dynamics (MD). The momentum and energy accommodation coefficients for gas-surface interactions were also calculated by MD simulation. The results indicated that temperature increase, change in the gas species, reduction in surface roughness, and increase in the Knudsen number (Kn) and the wall velocity could cause the accommodation coefficients to be less than one. Based on the scattering kernel of CLL boundary condition, a suitable distribution function for calculating the velocity components of noble gas molecules (e.g., argon molecules) after interaction with polymeric surface was proposed.