Persistence in Active Turbulence

TL;DR

This paper investigates the persistence times of passive tracers in active turbulence, revealing Weibull and exponential distributions influenced by activity strength and linking persistence to topological field decorrelation and vortex turnover.

Contribution

It introduces a generalized hydrodynamic model to analyze persistence in active turbulence, highlighting differences from inertial turbulence and identifying key drivers of persistence.

Findings

Persistence time inside vortices follows a Weibull distribution influenced by activity.

In turbulent background, persistence time is exponentially distributed.

Persistence is driven by topological field decorrelation and vortex turnover time.

Abstract

Active fluids such as bacterial swarms, self-propelled colloids, and cell tissues can all display complex spatio-temporal vortices that are reminiscent of inertial turbulence. This emergent behavior despite the overdamped nature of these systems is the hallmark of active turbulence. In this letter, using a generalized hydrodynamic model, we present a study of the persistence problem in active turbulence. We report that the persistence time of passive tracers inside the coherent vortices follows a Weibull probability density whose shape and scale are decided by the strength of activity -- contrary to inertial turbulence that displays power-law statistics in this region. In the turbulent background, the persistence time is exponentially distributed that is remindful of inertial turbulence. Finally we show that the driver of persistence inside the coherent vortices is the temporal decorrelation of the topological field, whereas it is the vortex turnover time in the turbulent background.