Nonlinear dynamics and rheology of active fluids: simulations in two dimensions

TL;DR

This paper presents simulations of two-dimensional active fluids, revealing complex flow patterns such as stationary, oscillatory, or chaotic states, and explores their effects on rheology under various boundary conditions.

Contribution

It introduces a 2D continuum model simulation of active fluids, showing the emergence of complex flow behaviors beyond 1D predictions.

Findings

Steady shear bands are replaced by complex flow patterns in 2D.

Flow patterns can be stationary, oscillatory, or chaotic.

Time-averaged rheology is affected by these flow states.

Abstract

We report simulations of a continuum model for (apolar, flow aligning) active fluids in two dimensions. Both free and anchored boundary conditions are considered, at parallel confining walls that are either static or moving at fixed relative velocity. We focus on extensile materials and find that steady shear bands, previously shown to arise ubiquitously in 1D for the active nematic phase at small (or indeed zero) shear rate, are generally replaced in 2D by more complex flow patterns that can be stationary, oscillatory, or apparently chaotic. The consequences of these flow patterns for time-averaged steady-state rheology are examined.