Giant vortex dynamics in confined active turbulence

TL;DR

This paper presents numerical evidence of a novel stable giant vortex state in confined active turbulence, where dense bacterial suspensions self-organize into a large, ordered vortex structure breaking angular momentum symmetry.

Contribution

The study introduces a new stable vortex state in confined active turbulence, supported by numerical simulations of the Toner-Tu-Swift-Hohenberg model, with analytical and experimental scale estimates.

Findings

Formation of a stable, giant vortex in confined active turbulence.

Radial velocity profile matches analytical predictions.

Presence of boundary-adjacent vorticity streaks.

Abstract

We report the numerical evidence of a new state of active turbulence in confined domains. By means of extensive numerical simulations of the Toner-Tu-Swift-Hohenberg model for dense bacterial suspensions in circular geometry, we discover the formation a stable, ordered state in which the angular momentum symmetry is broken. This is achieved by self-organization of a turbulent-like flow into a single, giant vortex of the size of the domain. The giant vortex is surrounded by an annular region close to the boundary, characterized by small-scale, radial vorticity streaks. The average radial velocity profile of the vortex is found to be in agreement with a simple analytical prediction. We also provide an estimate of the temporal and spatial scales of a suitable experimental setup comparable with our numerical findings.