Molecular dynamic simulations of systems undergoing shear

Abstract

Non-equilibrium molecular dynamics have been used to simulate, at a molecular level, fluids undergoing planar Couette flow. The results give a microscopic picture of the processes involved in viscoelasticity, shear dilatancy, shear birefringence, normal stress effects and shear thinning behavior. The calculations prove that shear dilatant fluids are not necessarily shear thickening. The results also suggest that the constitutive relations governing non-Newtonian behavior are non-analytic functions of strain rate. The calculations have led directly to the development of non-linear irreversible thermodynamics. This generalization of thermodynamics provides a macroscopic understanding of such processes as shear induced phase changes and the relation of shear dilatancy to shear induced energy changes.