Eur. Phys. J. E (2007) 22: 275-280
https://doi.org/10.1140/epje/e2007-00029-6

Regular Articles

On coupling between the orientation and the shape of a vesicle under a shear flow

¹ Laboratoire de Spectrométrie Physique, CNRS Université J. Fourier - Grenoble I, BP 87, 38402, Saint Martin d'Hères, France
² Laboratoire de Magnétisme et de la Physique des Hautes Énergies, Université Mohammed V, Faculté des Sciences, Avenue Ibn Battouta B.P., 1014, Rabat, Morocco

^* e-mail: thomas.podgorski@ujf-grenoble.fr

Received: 26 September 2006
Published online: 30 March 2007

Abstract

A simple 2D model of deformable vesicles tumbling in a shear under flow is introduced in order to account for the main qualitative features observed experimentally as shear rates are increased. The simplicity of the model allows for a full analytical tractability while retaining the essential physical ingredients. The model reveals that the main axes of the vesicle undergo oscillations which are coupled to the vesicle orientation in the flow. The model reproduces and sheds light on the main novel features reported in recent experiments [M. Mader et al., Eur. Phys. J. E. 19, 389 (2006)], namely that both coefficients A and B that enter the Keller-Skalak equation, dψ/dt = A+Bcos(2 ψ) (ψ is the vesicle orientation angle in the shear flow), undergo a collapse upon increasing shear rate.