Gyrotactic swimmers in turbulence: shape effects and role of the large-scale flow

Abstract

We study the dynamics and the statistics of dilute suspensions of gyrotactic swimmers, a model for many aquatic motile microorganisms. By means of extensive numerical simulations of the Navier-Stokes equations at different Reynolds numbers, we investigate preferential sampling and small scale clustering as a function of the swimming (stability and speed) and shape parameters, considering in particular the limits of spherical and rod-like particles. While spherical swimmers preferentially sample local downwelling flow, for elongated swimmers we observe a transition from downwelling to upwelling regions at sufficiently high swimming speed. The spatial distribution of both spherical and elongated swimmers is found to be fractal at small scales in a wide range of swimming parameters. The direct comparison between the different shapes shows that spherical swimmers are more clusterized at small stability and speed numbers, while for large values of the parameters elongated cells concentrate more. The relevance of our results for phytoplankton swimming in the ocean is briefly discussed.

11 pages, 5 figures

References in corpus (5)

• Physics of Microswimmers - Single Particle Motion and Collective Behavior
• Gravitaxis of asymmetric self-propelled colloidal particles
• Biased swimming cells do not disperse in pipes as tracers: a population model based on microscale behaviour
• Gyrotactic trapping in laminar and turbulent Kolmogorov flow
• Phototactic Clustering of Swimming Micro-organisms in a Turbulent Velocity Field

Cited by in corpus (4)

• Gyrotactic phytoplankton in laminar and turbulent flows: a dynamical systems approach
• Bacteria hinder large-scale transport and enhance small-scale mixing in time-periodic flows
• Turbulence induces clustering and segregation of non-motile, buoyancy-regulating phytoplankton
• Accumulation and alignment of elongated gyrotactic swimmers in turbulence