All good things come in threes - Three beads learn to swim with lattice Boltzmann and a rigid body solver

TL;DR

This paper presents a coupled simulation framework combining lattice Boltzmann and rigid body physics to study low Reynolds number propulsion of three-bead devices, revealing effects of design asymmetry on efficiency.

Contribution

It introduces a novel coupled simulation approach for analyzing self-propulsion of multi-body devices in fluid environments.

Findings

Propulsion velocity matches theoretical predictions for three-sphere devices.

Design asymmetry significantly impacts propulsion efficiency.

Capsule replacements alter propulsion dynamics compared to spheres.

Abstract

We simulate the self-propulsion of devices in a fluid in the regime of low Reynolds numbers. Each device consists of three bodies (spheres or capsules) connected with two damped harmonic springs. Sinusoidal driving forces compress the springs which are resolved within a rigid body physics engine. The latter is consistently coupled to a 3D lattice Boltzmann framework for the fluid dynamics. In simulations of three-sphere devices, we find that the propulsion velocity agrees well with theoretical predictions. In simulations where some or all spheres are replaced by capsules, we find that the asymmetry of the design strongly affects the propelling efficiency.