2D and 3D Dense-Fluid Shear Flows via Nonequilibrium Molecular Dynamics. Comparison of Time-and-Space-Averaged Tensor Temperature and Normal Stresses from Doll's, Sllod, and Boundary-Driven Shear Algorithms

摘要

Homogeneous shear flows (with constant strainrate du/dy) are generated withthe Doll's and Sllod algorithms and compared to corresponding inhomogeneousboundary-driven flows. We use one-, two-, and three-dimensional smooth-particleweight functions for computing instantaneous spatial averages. The nonlinearstress differences are small, but significant, in both two and three spacedimensions. In homogeneous systems the sign and magnitude of the shearplanestress difference, P(xx) - P(yy), depend on both the thermostat type and thechosen shearflow algorithm. The Doll's and Sllod algorithms predict oppositesigns for this stress difference, with the Sllod approach definitely wrong, butsomewhat closer to the (boundary-driven) truth. Neither of the homogeneousshear algorithms predicts the correct ordering of the kinetic temperatures,T(xx) > T(zz) > T(yy).