Vortex dynamics and Lagrangian statistics in a model for active turbulence

TL;DR

This paper investigates active turbulence in cellular suspensions using a generalized Navier-Stokes model, analyzing velocity statistics and vortex dynamics to understand its scale-dependent features and statistical nature.

Contribution

It provides a detailed statistical analysis of active turbulence, including two-point velocity statistics and vortex dynamics, extending previous models with new insights into large-scale behavior.

Findings

Large-scale active turbulence exhibits near-Gaussian velocity statistics.

Two-point velocity correlations reveal scale-dependent features.

Vortex dynamics analysis enhances understanding of turbulence structure.

Abstract

Cellular suspensions such as dense bacterial flows exhibit a turbulence-like phase under certain conditions. We study this phenomenon of "active turbulence" statistically by using numerical tools. Following Wensink et al. [Proc. Natl. Acad. Sci. U.S.A. 109, 14308 (2012)], we model active turbulence by means of a generalized Navier-Stokes equation. Two-point velocity statistics of active turbulence, both in the Eulerian and the Lagrangian frame, is explored. We characterize the scale-dependent features of two-point statistics in this system. Furthermore, we extend this statistical study with measurements of vortex dynamics in this system. Our observations suggest that the large-scale statistics of active turbulence is close to Gaussian with sub-Gaussian tails.