# Particle-resolved lattice Boltzmann simulations of 3-dimensional active turbulence

## TL;DR

This paper uses large-scale particle-resolved lattice Boltzmann simulations to study active turbulence in suspensions of microswimmers, revealing how collective chaotic flows emerge and evolve with swimmer density.

## Contribution

It provides the first large-scale simulations of active turbulence with detailed hydrodynamic interactions, validating analytical predictions and exploring transition behavior at high densities.

## Key findings

- Transition to turbulence occurs at predicted densities.
- Flow length- and timescales increase steeply near transition.
- Simulation results agree with analytical predictions in dilute limit.

## Abstract

Collective behaviour in suspensions of microswimmers is often dominated by the impact of long-ranged hydrodynamic interactions. These phenomena include active turbulence, where suspensions of pusher bacteria at sufficient densities exhibit large-scale, chaotic flows. To study this collective phenomenon, we use large-scale (up to $N=3\times 10^6$) particle-resolved lattice Boltzmann simulations of model microswimmers described by extended stresslets. Such system sizes enable us to obtain quantitative information about both the transition to active turbulence and characteristic features of the turbulent state itself. In the dilute limit, we test analytical predictions for a number of static and dynamic properties against our simulation results. For higher swimmer densities, where swimmer-swimmer interactions become significant, we numerically show that the length- and timescales of the turbulent flows increase steeply near the predicted finite-system transition density.