Stress Tensors of Multiparticle Collision Dynamics Fluids

TL;DR

This paper derives stress tensors for multiparticle collision dynamics fluids, providing analytical and simulation results for shear viscosity and stress fluctuations in various boundary conditions.

Contribution

It introduces new expressions for stress tensors in multiparticle collision dynamics, including confined and particle-embedded systems, and validates them through simulations.

Findings

Analytical expressions for shear viscosity are derived.

Simulations show good agreement with analytical viscosity.

Stress fluctuations vary with boundary conditions and system configurations.

Abstract

Stress tensors are derived for the multiparticle collision dynamics algorithm, a particle-based mesoscale simulation method for fluctuating fluids, resembling those of atomistic or molecular systems. Systems with periodic boundary conditions as well as fluids confined in a slit are considered. For every case, two equivalent expressions for the tensor are provided, the internal stress tensor, which involves all degrees of freedom of a system, and the external stress, which only includes the interactions with the confining surfaces. In addition, stress tensors for a system with embedded particles are determined. Based on the derived stress tensors, analytical expressions are calculated for the shear viscosity. Simulations illustrate the difference in fluctuations between the various derived expressions and yield very good agreement between the numerical results and the analytically derived expression for the viscosity.