Issue
EPL
Volume 83, Number 2, July 2008
Article Number 24002
Number of page(s) 6
Section Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics
DOI http://dx.doi.org/10.1209/0295-5075/83/24002
Published online 03 July 2008
EPL, 83 (2008) 24002
DOI: 10.1209/0295-5075/83/24002

Hydrodynamic lift of vesicles under shear flow in microgravity

N. Callens1, C. Minetti1, G. Coupier2, M.-A. Mader2, F. Dubois1, C. Misbah2 and T. Podgorski2

1  Microgravity Research Center, Université Libre de Bruxelles - 50 Av. F. Roosevelt, B-1050 Brussels, Belgium, EU
2  Laboratoire de Spectrométrie Physique, CNRS Université J. Fourier - Grenoble I, BP 87, 38402 Saint-Martin d'Hères, France, EU

thomas.podgorski@ujf-grenoble.fr

received 9 April 2008; accepted in final form 30 May 2008; published July 2008
published online 3 July 2008

Abstract
The dynamics of a vesicle suspension in a shear flow between parallel plates has been investigated under microgravity conditions, where vesicles are only submitted to hydrodynamic effects such as lift forces due to the presence of walls and drag forces. The temporal evolution of the spatial distribution of the vesicles has been recorded thanks to digital holographic microscopy, during parabolic flights and under normal gravity conditions. The collected data demonstrates that vesicles are pushed away from the walls with a lift velocity proportional to $\dot{\gamma} R^3/z^2 $, where $\dot{\gamma}
$ is the shear rate, R the vesicle radius and z its distance from the wall. This scaling as well as the dependence of the lift velocity upon the vesicle aspect ratio are consistent with the theoretical predictions by Olla (J. Phys. II, 7 (1997) 1533).

PACS
47.15.G- - Low-Reynolds-number (creeping) flows.
87.16.D- - Membranes, bilayers, and vesicles.
47.55.Kf - Particle-laden flows.

© EPLA 2008