A lattice Boltzmann model for squirmers

Michael Kuron*, Philipp Stärk, Christian Burkard, Joost De Graaf, Christian Holm

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

The squirmer is a simple yet instructive model for microswimmers, which employs an effective slip velocity on the surface of a spherical swimmer to describe its self-propulsion. We solve the hydrodynamic flow problem with the lattice Boltzmann (LB) method, which is well-suited for time-dependent problems involving complex boundary conditions. Incorporating the squirmer into LB is relatively straightforward, but requires an unexpectedly fine grid resolution to capture the physical flow fields and behaviors accurately. We demonstrate this using four basic hydrodynamic tests: two for the far-field flow - accuracy of the hydrodynamic moments and squirmer-squirmer interactions - and two that require the near field to be accurately resolved - a squirmer confined to a tube and one scattering off a spherical obstacle - which LB is capable of doing down to the grid resolution. We find good agreement with (numerical) results obtained using other hydrodynamic solvers in the same geometries and identify a minimum required resolution to achieve this reproduction. We discuss our algorithm in the context of other hydrodynamic solvers and present an outlook on its application to multi-squirmer problems.

Original languageEnglish
Article number144110
Number of pages8
JournalJournal of Chemical Physics
Volume150
Issue number14
DOIs
Publication statusPublished - 9 Apr 2019

Funding

We thank the Deutsche Forschungsgemeinschaft (DFG) for funding through the SPP 1726 “Microswimmers: from single particle motion to collective behavior” (Nos. HO1108/24-1 and HO1108/ 24-2). We are grateful to Alexander Chamolly for useful discussions and to Martin Bauer, Sebastian Eibl, Christian Godenschwa-ger, Christoph Rettinger, and Florian Schornbaum for developing waLBerla and supporting us in using and extending it.

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