Eur. Phys. J. E (2014) 37: 60
https://doi.org/10.1140/epje/i2014-14060-y

Regular Article

Rotational propulsion enabled by inertia

¹ Commissariat à l’Energie Atomique, 33114, Le Barp, France
² Department of Mechanical and Aerospace Engineering, Princeton University, 08544-5263, Princeton, NJ, USA
³ Linné Flow Center, KTH Mechanics, S-100 44, Stockholm, Sweden
⁴ Laboratory of Fluid Mechanics and Instabilities, EPFL, CH1015, Lausanne, Switzerland
⁵ Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Center for Mathematical Sciences, Wilberforce Road, CB3 0WA, Cambridge, UK

^* e-mail: francois.nadal33@gmail.com
^** e-mail: e.lauga@damtp.cam.ac.uk

Received: 19 December 2013
Revised: 10 June 2014
Accepted: 13 June 2014
Published online: 21 July 2014

Abstract

The fluid mechanics of small-scale locomotion has recently attracted considerable attention, due to its importance in cell motility and the design of artificial micro-swimmers for biomedical applications. Most studies on the topic consider the ideal limit of zero Reynolds number. In this paper, we investigate a simple propulsion mechanism --an up-down asymmetric dumbbell rotating about its axis of symmetry-- unable to propel in the absence of inertia in a Newtonian fluid. Inertial forces lead to continuous propulsion for all finite values of the Reynolds number. We study computationally its propulsive characteristics as well as analytically in the small-Reynolds-number limit. We also derive the optimal dumbbell geometry. The direction of propulsion enabled by inertia is opposite to that induced by viscoelasticity.