Eur. Phys. J. E (2017) 40: 95
https://doi.org/10.1140/epje/i2017-11586-4

Regular Article

Do hydrodynamically assisted binary collisions lead to orientational ordering of microswimmers?

¹ Mathematics for Advanced Materials-OIL, AIST-Tohoku University, 980-8577, Sendai, Japan
² Department of Chemical Engineering, Kyoto University, 615-8510, Kyoto, Japan
³ Institute of Industrial Science, The University of Tokyo, 153-8505, Tokyo, Japan

^* e-mail: oyama@cheme.kyoto-u.ac.jp

Received: 15 February 2017
Accepted: 23 October 2017
Published online: 8 November 2017

Abstract

We have investigated the onset of collective motion in systems of model microswimmers, by performing a comprehensive analysis of the binary collision dynamics using three-dimensional direct numerical simulations (DNS) with hydrodynamic interactions. From this data, we have constructed a simplified binary collision model (BCM) which accurately reproduces the collective behavior obtained from the DNS for most cases. Thus, we show that global alignment can mostly arise solely from binary collisions. Although the agreement between both models (DNS and BCM) is not perfect, the parameter range in which notable differences appear is also that for which strong density fluctuations are present in the system (where pseudo-sound mound can be observed (N. Oyama et al., Phys. Rev. E 93, 043114 (2016))).