Issue
EPL
Volume 83, Number 3, August 2008
Article Number 34006
Number of page(s) 6
Section Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics
DOI http://dx.doi.org/10.1209/0295-5075/83/34006
Published online 23 July 2008
EPL, 83 (2008) 34006
DOI: 10.1209/0295-5075/83/34006

Dumb-bell swimmers

G. P. Alexander and J. M. Yeomans

Rudolf Peierls Centre for Theoretical Physics, University of Oxford - 1 Keble Road, Oxford, OX1 3NP, England, UK, EU

g.alexander1@physics.ox.ac.uk

received 6 May 2008; accepted in final form 17 June 2008; published August 2008
published online 23 July 2008

Abstract
We investigate the way in which oscillating dumb-bells, a simple microscopic model of apolar swimmers, move at low Reynold's number. In accordance with Purcell's Scallop Theorem a single dumb-bell cannot swim because its stroke is reciprocal in time. However the motion of two or more dumb-bells, with mutual phase differences, is not time reversal invariant, and hence swimming is possible. We use analytical and numerical solutions of the Stokes equations to calculate the hydrodynamic interaction between two dumb-bell swimmers and to discuss their relative motion. The cooperative effect of interactions between swimmers is explored by considering first regular, and then random arrays of dumb-bells. We find that a square array acts as a micropump. The long-time behaviour of suspensions of dumb-bells is investigated and compared to that of model polar swimmers.

PACS
47.63.Gd - Swimming microorganisms.
47.63.mf - Low-Reynolds-number motions.

© EPLA 2008