Force calculation on walls and embedded particles in multiparticle collision dynamics simulations

TL;DR

This paper presents a method for calculating forces on walls and particles in multiparticle collision dynamics simulations, demonstrating accurate friction measurements and analyzing size effects in confined geometries.

Contribution

It introduces a no-slip boundary condition implementation that accurately computes forces without detailed velocity or stress profiles, and examines hydrodynamic size effects in slit geometries.

Findings

Enhanced Enskog friction observed with no-slip boundaries

Friction depends on system size differently in slit geometries

Method accurately measures forces without detailed fluid profiling

Abstract

Colloidal solutions posses a wide range of time and length scales, so that it is unfeasible to keep track of all of them within a single simulation. As a consequence some form of coarse-graining must be applied. In this work we use the Multi-Particle Collision Dynamics scheme. We describe a particular implementation of no-slip boundary conditions upon a solid surface, capable of providing correct force s on the solid bypassing the calculation of the velocity profile or the stre ss tensor in the fluid near the surface. As an application we measure the friction on a spherical particle, when it is placed in a bulk fluid and when it is confined in a slit. We show that the implementation of the no-slip boundary conditions leads to an enhanced Ensko g friction, which can be understood analytically. Because of the long-range nature of hydrodynamic interactions, the Stokes friction obtained from the simulations is sensitive of the simulation box size. We address this topic for the slit geometry, showing that that the dependence on the system size differs very much from what is expected in a 3D system, where periodic boundary conditions are used in all directions.