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Issue 41, 2017
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Collective sedimentation of squirmers under gravity

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Abstract

Active particles, which interact hydrodynamically, display a remarkable variety of emergent collective phenomena. We use squirmers to model spherical microswimmers and explore the collective behavior of thousands of them under the influence of strong gravity using the method of multi-particle collision dynamics for simulating fluid flow. The sedimentation profile depends on the ratio of swimming to sedimentation velocity as well as on the squirmer type. It shows closely packed squirmer layers at the bottom and a highly dynamic region with exponential density dependence towards the top. The mean vertical orientation of the squirmers strongly depends on height. For swimming velocities larger than the sedimentation velocity, squirmers show strong convection in the exponential region. We quantify the strength of convection and the extent of convection cells by the vertical current density and its current dipole, which are large for neutral squirmers as well as for weak pushers and pullers.

Graphical abstract: Collective sedimentation of squirmers under gravity

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Publication details

The article was received on 14 Jun 2017, accepted on 20 Aug 2017 and first published on 02 Oct 2017


Article type: Paper
DOI: 10.1039/C7SM01180F
Citation: Soft Matter, 2017,13, 7548-7555
  • Open access: Creative Commons BY-NC license
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    Collective sedimentation of squirmers under gravity

    J. Kuhr, J. Blaschke, F. Rühle and H. Stark, Soft Matter, 2017, 13, 7548
    DOI: 10.1039/C7SM01180F

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