Mitigating Density Fluctuations in Particle-based Active Nematic Simulations

TL;DR

This paper improves particle-based simulations of active nematic fluids by introducing three new activity formulations that significantly reduce density fluctuations, enabling more accurate modeling of active matter with inclusions.

Contribution

The authors develop three novel activity formulations within the Active-Nematic Multi-Particle Collision Dynamics algorithm to mitigate density fluctuations in active nematic simulations.

Findings

Density fluctuations are reduced to passive levels.

Active turbulence regime is increased four-fold.

The method remains faithful to active nematic phenomenology.

Abstract

Understanding active matter has led to new perspectives on biophysics and non-equilibrium dynamics. However, the development of numerical tools for simulating active fluids capable of incorporating non-trivial boundaries or inclusions has lagged behind. Active particle-based methods, which typically excel at this, suffer from large density fluctuations that affect the dynamics of inclusions. To this end, we advance the Active-Nematic Multi-Particle Collision Dynamics algorithm, a particle-based method for simulating active nematics, by addressing the large density fluctuations that arise from activity. This paper introduces three novel activity formulations that mitigate the coupling between activity and local density. Local density fluctuations are decreased to a level comparable to the passive limit while retaining the phenomenology of active nematics and increasing the active turbulence regime four-fold. These developments extend the technique into a flexible tool for modeling active systems, including solutes and inclusions, with broad applications for the study of biophysical systems.