Hydrodynamic interaction of a self-propelling particle with a wall: Comparison between an active Janus particle and a squirmer model

TL;DR

This study compares the hydrodynamic interactions of active Janus particles and squirmers near a wall using simulations, revealing similarities in far-field behavior but key differences in near-field interactions and trapping tendencies.

Contribution

The paper introduces a computational model for active Janus particles and compares their near-wall hydrodynamics to squirmers, highlighting differences in trapping behavior and near-field effects.

Findings

Janus particles and squirmers have similar far-field hydrodynamics.

Active Janus particles are more prone to surface trapping than squirmers.

Velocity parallel to the surface scales linearly with the squirming parameter |0;

Abstract

Using lattice Boltzmann simulations we study the hydrodynamics of an active spherical particle near a no-slip wall. We develop a computational model for an active Janus particle, by considering different and independent mobilities on the two hemispheres and compare the behaviour to a standard squirmer model.We show that the topology of the far-field hydrodynamic nature of the active Janus particle is similar to the standard squirmer model, but in the near-field the hydrodynamics differ. In order to study how the near-field effects affect the interaction between the particle and a flat wall, we compare the behaviour of a Janus swimmer and a squirmer near a no-slip surface via extensive numerical simulations. Our results show generally a good agreement between these two models, but they reveal some key differences especially with low magnitudes of the squirming parameter $\beta$. Notably the affinity of the particles to be trapped at a surface is increased for the active Janus particles when compared to standard squirmers. Finally we find that when the particle is trapped on the surface, the velocity parallel to the surface exceeds the bulk swimming speed and scales linearly with $|\beta|$.