Clustering instability of focused swimmers


Type
Article
Change log
Authors
Nadal, F 
Abstract

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.

Description
Keywords
cond-mat.soft, cond-mat.soft, physics.bio-ph, physics.flu-dyn
Journal Title
Europhysics Letters
Conference Name
Journal ISSN
0295-5075
1286-4854
Volume Title
116
Publisher
IOP Publishing
Sponsorship
European Research Council (682754)
This work was funded in part by the European Union through a Marie Curie CIG Grant and an ERC consol- idator grant to EL.