The rheology of gases. A molecular-dynamics study

Abstract

Non-equilibrium molecular dynamics, NEMD, computer simulation is used to characterise and understand the nature of shear thinning in the gas phase. An extensive series of calculations is used to provide simple expressions which represent the effect of shear rate on the shear viscosity, the cartesian components of the self-diffusion coefficient and normal pressure differences for the dilute Lennard-Jones (LJ) fluid. The temperature range considered was T^*= 1.5–10 and the density range was mainly less than ρ^*= 0.1. Shear thinning in the gaseous phase is associated with a distortion of the Maxwell–Boltzmann velocity distribution. A shear-induced clustering of molecules is also observed at ρ= 0.01.