Transport behavior of pressure-driven gas flow in a nanochannel and the variation of thermal accommodation coefficient

Abstract

A three-dimensional molecular dynamics simulation of a rarefied gas flow confined between two parallel solid walls has been carried out to study the gas transport behavior in nanoscale pressure-driven flows. To simulate the effects of pressure-driven flows in nanoscale systems; a reservoir is created at the beginning of the channel. A force, in the form of gravity, is applied to every gas molecule occupying a specific region in the reservoir thereby facilitating to establish a streamwise inhomogeneous flow in a finite length nanochannel. Further, the model is tested for its structural stability and steady-state characteristics. The flow characteristics are evaluated at various bins (A, B, C, and D) along the length of the channel. The presence of a pressure drop established along the length of the channel results in a significant variation of flow properties in the channel. The characteristics of the system are further studied using the spatial distribution of flow properties. To investigate the streamwise variation, thermal accommodation coefficients (TACs) at various sections of the channel are calculated. The results indicate that the TACs vary along the length. Further, the effect of pressure drop on TACs is also analysed. The effect of confinement is also studied with velocity autocorrelation function (VACF) and mean squared displacement (MSD). The effect of confinement is evident in the fluid region away from the wall too.