J. Phys. II France
Volume 7, Numéro 10, October 1997
Page(s) 1533 - 1540
DOI: 10.1051/jp2:1997201
J. Phys. II France 7 (1997) 1533-1540

The Lift on a Tank-Treading Ellipsoidal Cell in a Shear Flow

Piero Olla

ISIAtA-CNR, Universitá di Lecce, 73100 Lecce Italy

(Received 25 October 1996, revised 22 April 1997, accepted 9 June 1997)

The lift on a strongly non-spherical vesicle in a bounded shear flow is studied in the case the membrane moves with a velocity, which is a linear function of the coordinates. The magnitude of the induced drift is calculated as a function of the axes lengths, of the distance from the wall, and of the ratio of the cell to the solvent viscosity. It appears that the main mechanism for lift, in the presence of tank-treading motions, is the fixed orientation of the vesicle with respect to the flow. Tank-treading vesicles in suspensions, flowing through narrow gaps under small Reynolds number conditions: ${\rm Re} = Lv/\nu < 1$ (with L the gap width, v the flow velocity and $\nu$ the viscosity) migrate away from the walls, with a velocity that is ${\cal O}({\rm Re}^{-1})$ larger than predicted by inertia.

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