Clustering of gyrotactic microorganisms in turbulent flows

TL;DR

This paper investigates how gyrotactic microorganisms cluster in turbulent flows, revealing that their behavior mimics tracers in a compressible flow, leading to multi-fractal clustering patterns.

Contribution

It demonstrates that gyrotactic microorganisms exhibit multi-fractal clustering in turbulence due to effective compressibility effects.

Findings

Gyrotactic cells behave like tracers in a compressible flow.

Clustering exhibits multi-fractal characteristics.

Effective compressibility depends on fluid acceleration relative to gravity.

Abstract

We study the spatial distribution of gyrotactic microorganisms transported by a three-dimensional turbulent flow generated by direct numerical simulations. We find that gyrotaxis combines with turbulent fluctuations to produce small scales (multi-)fractal clustering. We explain this result by showing that gyrotactic swimming cells behave like tracers in a compressible flow. The effective compressibility is derived in the limits of fluid acceleration much larger and smaller than the gravity.