Impact of surface physisorption on gas scattering dynamics

Engineering flow systems operating under low pressures and/or at the micro/nano scale generally include a physically adsorbed gas layer next to surface. In this paper, we develop scattering kernel that accounts for effect of adsorption, arising from van der Waals interactions, on dynamics molecules impinging solid smooth surfaces. limit bulk density, surface adsorption becomes negligible and recovers consistently Cercignani–Lampis model, which best describes molecular collisions with clean, high dense forms its presence is picked up by Maxwell model complete diffuse reflection, better captures multiple suffered molecules. A weight coefficient based Langmuir isotherm incorporated into modelling handle transition between these two limiting conditions densities. The proposed validated against high-fidelity simulations are performed variety gas–surface combinations layers different It shown very well patterns beams velocities surfaces, as momentum energy accommodation coefficients in entire range explored conditions.