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arXiv · 1703.01892

The role of correlations in the collective behaviour of microswimmer suspensions

Joakim Stenhammar·Cesare Nardini·Rupert W. Nash·Davide Marenduzzo·Alexander Morozov
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Abstract

In this Letter, we study the collective behaviour of a large number of self-propelled microswimmers immersed in a fluid. Using unprecedently large-scale lattice Boltzmann simulations, we reproduce the transition to bacterial turbulence. We show that, even well below the transition, swimmers move in a correlated fashion that cannot be described by a mean-field approach. We develop a novel kinetic theory that captures these correlations and is non-perturbative in the swimmer density. To provide an experimentally accessible measure of correlations, we calculate the diffusivity of passive tracers and reveal its non-trivial density dependence. The theory is in quantitative agreement with the lattice Boltzmann simulations and captures the asymmetry between pusher and puller swimmers below the transition to turbulence.

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Joakim Stenhammar, Cesare Nardini, Rupert W. Nash, Davide Marenduzzo, Alexander Morozov. 2017-07-05. The role of correlations in the collective behaviour of microswimmer suspensions. https://doi.org/10.1103/physrevlett.119.028005

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