Regensburg 2019 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 64: Active Matter III (joint session BP/CPP/DY)
CPP 64.4: Talk
Friday, April 5, 2019, 10:15–10:30, H11
Simple Swimmers Reverse Direction near a Surface — •Michael Kuron1, Philipp Stärk1, Joost de Graaf2, and Christian Holm1 — 1Institut für Computerphysik, Universität Stuttgart, Deutschland — 2Institute for Theoretical Physics, Universiteit Utrecht, Nederland
The motion of a microswimmer can change substantially in the presence of a surface. Sperm are known to move in circular trajectories near a wall, paramecia move in sinusoidal trajectories through a tube, and chemical swimmers can orbit around spherical obstacles. Spherical squirmers are one of the simplest model microswimmers, commonly defined by the first two Legendre modes of their surface slip velocity. In this talk, we use the squirmer to numerically investigate the effect of the environmental geometry. We discuss how the transition between scattering and orbiting/hovering depends on the strength of the squirmer’s hydrodynamic dipole moment. Interestingly, we observe cases where the squirmer orbits/hovers along a surface in a direction opposite to that observed in bulk. This effect is present both in a far-field theoretical model and our lattice Boltzmann calculations, which accurately account for the near-field flow. These results extend the understanding of the effect of geometry on microswimmer motion and show the importance of finite swimmer size and associated near-field effects.