A model of hydrodynamic interaction between swimming bacteria

TL;DR

This paper models the hydrodynamic interactions between two swimming bacteria using a self-propelled dumbbell model, revealing how propulsion force positioning influences their alignment and interaction dynamics.

Contribution

It introduces a mathematical model for bacterial interactions that accounts for propulsion force placement, providing insights consistent with experimental observations.

Findings

Position of propulsion force affects bacterial alignment.

Dumbbell model predicts mutual alignment in converging bacteria.

Asymptotic expressions match experimental behaviors.

Abstract

We study the dynamics and interaction of two swimming bacteria, modeled by self-propelled dumbbell-type structures. We focus on alignment dynamics of a coplanar pair of elongated swimmers, which propel themselves either by pushing" or "pulling" both in three- and quasi-two-dimensional geometries of space. We derive asymptotic expressions for the dynamics of the pair, which, complemented by numerical experiments, indicate that the tendency of bacteria to swim in or swim off depends strongly on the position of the propulsion force. In particular, we observe that positioning of the effective propulsion force inside the dumbbell results in qualitative agreement with the dynamics observed in experiments, such as mutual alignment of converging bacteria.