Gas physisorption impact on prolate dust in free-molecule flows: A static study

Abstract

Gas–solid coupling systems operating at low pressure or the micro/nanoscale generally exist in nature and industrial manufacture. Although the gas-scattering model has been widely used to study this problem on the dust surface, the consideration of gas physisorption was often neglected in previous applications of gas–surface scattering models. Therefore, this study aims to investigate the distribution of gas physisorption on the dust surface and assess its impact on the static force experienced by nonspherical dust in free-molecule flows. In this study, the prolate dust spinning around its minor axis is considered and the in-house direct simulation Monte Carlo code is used. Results show that gas physisorption on prolate dust is influenced by changes in gas number densities, Mach number, and dust shape. Furthermore, the gas physisorption enhances the gas–dust coupling for dust with a smooth surface at low gas pressure, attributed to the increasing ratio of Maxwell diffuse scattering of gas molecules on the gas-adsorbed part of the surface. Hence, gas physisorption was suggested as a potential factor for gas–dust coupling at low gas pressure.