Planar Couette Flow in a Single Gas

Abstract

In the three preceding chapters we have considered the properties of the uniform shear flow state (USF) far from equilibrium. As said in Section 2.1, this represents a prototype situation to unveil non-Newtonian features in a gas, obtain exact results, and test approximate theories. In addition, the USF is relatively easy to implement in simulations by means of (Lees–Edwards) periodic boundary conditions. As a counterpart, this state is an idealized version of a realistic shear flow problem since the gas is formally unbounded, the flow velocity profile is assumed to be strictly linear, and the density and temperature are spatially uniform. The price to be paid is that the temperature increases with time (due to viscous heating effects), unless an (artificial) thermostat force is applied.