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Tank Treading and Unbinding of Deformable Vesicles in Shear Flow: Determination of the Lift Force

2002; American Physical Society; Volume: 88; Issue: 6 Linguagem: Inglês

10.1103/physrevlett.88.068103

1092-0145

Manouk Abkarian, C. Lartigue, Annie Viallat,

Fluid Dynamics and Turbulent Flows

Deformation and tank-treading motion of flaccid vesicles in a linear shear flow close to a wall are quantitatively studied by light microscopy. Velocities of bounded vesicles obey Goldman's law established for rigid spheres. A progressive tilt and a transition of unbinding of vesicles are evidenced upon increasing the shear rate, gamma;. These observations disclose the existence of a viscous lift force, F(l), depending on the viscosity eta of the fluid, the radius R of the vesicle, its distance h from the substrate, and a monotonous decreasing function f(1-v) of the reduced volume v, in the following manner: F(l) = eta(gamma)(R(3)/h)f(1-v). This relation is valid for vesicles both close to and farther from the substrate.