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Clustering instability of focused swimmers

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journal contribution
posted on 30.08.2018, 11:03 by Eric Jean-Marie Lauga, Francois NadalFrancois Nadal
One of the hallmarks of active matter is its rich nonlinear dynamics and instabilities. Recent numerical simulations of phototactic algae showed that a thin jet of swimmers, obtained from hydrodynamic focusing inside a Poiseuille flow, was unstable to longitudinal perturbations with swimmers dynamically clustering (Jibuti L. et al., Phys. Rev. E, 90, (2014) 063019). As a simple starting point to understand these instabilities, we consider in this paper an initially homogeneous one-dimensional line of aligned swimmers moving along the same direction, and characterise its instability using both a continuum framework and a discrete approach. In both cases, we show that hydrodynamic interactions between the swimmers lead to instabilities in density for which we compute the growth rate analytically. Lines of pusher-type swimmers are predicted to remain stable while lines of pullers (such as flagellated algae) are predicted to always be unstable.

Funding

This work was funded in part by the European Union through a Marie Curie CIG Grant and an ERC consolidator grant to EL.

History

School

  • Mechanical, Electrical and Manufacturing Engineering

Published in

EPL

Volume

116

Issue

6

Citation

LAUGA, E. and NADAL, F., 2017. Clustering instability of focused swimmers. EPL, 116 (6), 64004, doi: 10.1209/0295-5075/116/64004

Publisher

IOP Publishing © EPLA

Version

AM (Accepted Manuscript)

Publisher statement

This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/

Acceptance date

18/01/2017

Publication date

2017-02-09

Copyright date

2016

Notes

This article was published in the EPL Journal [©EPLA] and the definitive version is available at: https://doi.org/10.1209/0295-5075/116/64004

ISSN

0295-5075

eISSN

1286-4854

Language

en

Article number

64004

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