Relevance of angular momentum conservation in mesoscale hydrodynamics simulations

TL;DR

This paper investigates how violating angular momentum conservation in mesoscale hydrodynamics simulations affects flow behavior, revealing non-physical torques and velocity discrepancies that align with theoretical predictions.

Contribution

It demonstrates the impact of angular momentum non-conservation in particle-based simulations and quantifies its effects on flow and polymer dynamics.

Findings

Non-physical torques observed in eccentric Couette flows.

Incorrect angular velocities in polymer-solvent simulations.

Results agree with macroscopic stress tensor theory.

Abstract

The angular momentum is conserved in fluids with a few exceptions such as ferrofluids. However it can be violated locally in fluid simulations to reduce computational costs. The effects of this violation are investigated using a particle-based simulation method, multi-particle collision dynamics, which can switch on or off angular-momentum conservation. To this end, we study circular Couette flows between concentric and eccentric cylinders, where non-physical torques due to the lack of the angular-momentum conservation are found whereas the velocity field is not affected. In addition, in simulations of fluids with different viscosities in contact and star polymers in solvent, incorrect angular velocities occur. These results quantitatively agree with the theoretical predictions based on the macroscopic stress tensor.