Confined active nematic flow in cylindrical capillaries

TL;DR

This study uses numerical modeling to explore how active nematic fluids flow within cylindrical capillaries, revealing complex flow patterns, defect-driven pumping, and the impact of activity level and boundary conditions on flow dimensionality.

Contribution

It introduces a detailed numerical analysis of active nematic flow in confined cylindrical geometries, highlighting defect dynamics and flow dimensionality effects.

Findings

Active flow occurs along the capillary axis and within the plane, forming radial vortices.

Topological defects act as local pumps driving the flow.

Flow dimensionality increases with activity, with defects escaping into the third dimension.

Abstract

We use numerical modelling to study the flow patterns of an active nematic confined in a cylindrical capillary, considering both planar and homeotropic boundary conditions. We find that active flow emerges not only along the capillary axis but also within the plane of the capillary, where radial vortices are formed. If topological defects are imposed by the boundary conditions, they act as local pumps driving the flow. At higher activity we demonstrate escape of the active defects and flow into the third dimension, indicating the importance of dimensionality in active materials. We argue that measuring the magnitude of the active flow as a function of the capillary radius allows determination of a value for the activity coefficient.