# Orienting field effects on the flow of an active nematic liquid crystal in a channel

## TL;DR

This paper studies how an external field affects the flow and orientation of an active nematic liquid crystal in a channel, focusing on dynamic responses and steady states.

## Contribution

The study introduces a mathematical model showing how activity can influence the kickback effect in active nematics.

## Key findings

- High activity in contractile agents can reduce or eliminate the kickback effect after field switch-off.
- Activity and orienting field parameters define a region where kickback occurs.
- The model reveals nontrivial steady-state solutions influenced by activity.

## Abstract

We examine the influence of an external orienting field on the director orientation and fluid flow of an active nematic liquid crystal confined in a channel, subject to infinite anchoring of the director and no-slip conditions at the channel walls. A mathematical model based on the Ericksen–Leslie dynamic equations for nematic liquid crystals is employed, with an additional active stress tensor accounting for the activity of the fluid. By solving the fully coupled nonlinear equations numerically, we investigate the dynamic response and the steady state of the active nematic when an orienting field is switched on. The dynamic behaviour when an orienting field is switched off is also examined, with our model demonstrating how the activity of the liquid crystal can enhance or hinder the classically observed kickback immediately after switch-off and generate nontrivial steady-state solutions. Specifically, we find that kickback, which can delay relaxation of the system to a steady state, can be made less pronounced, and eventually completely avoided, for contractile agents with a high activity parameter, even with a high magnitude orienting field value.

Region of kickback effect in the space of activity and orienting field parameters - increased contractile behaviour will delay kickback to higher orienting field values