Local effective viscosity of gas in nano-scale channels

Abstract

The non-equilibrium molecular dynamics method is used in the present study to investigate the local effective viscosity in nano-scale shear-driven gas flows. The profiles of gas velocity and shear stress across the channel are sampled and the Newton law of viscosity is applied to obtain the local effective viscosity. By using this method, the profile of local effective viscosity across the channel is obtained. In the bulk region of the channel, the local effective viscosity agrees well with the experimental value. However, in the near wall region, the local effective viscosity deviates from experimental value. The wall influence depth decreases with the increase of gas density, and this depth is independent of channel height, temperature and shear velocity in the shear driven Couette flow. The wall influence depth is approximately twice of the mean free path.