4 research outputs found
The role of tank-treading motions in the transverse migration of a spheroidal vesicle in a shear flow
The behavior of a spheroidal vesicle, in a plane shear flow bounded from one
side by a wall, is analysed when the distance from the wall is much larger than
the spheroid radius. It is found that tank treading motions produce a
transverse drift away from the wall, proportional to the spheroid eccentricity
and the inverse square of the distance from the wall. This drift is independent
of inertia, and is completely determined by the characteristics of the vesicle
membrane. The relative strength of the contribution to drift from tank-treading
motions and from the presence of inertial corrections, is discussed.Comment: 16 pages, 1 figure, Latex. To appear on J. Phys. A (Math. Gen.
Influence of shear flow on vesicles near a wall: a numerical study
We describe the dynamics of three-dimensional fluid vesicles in steady shear
flow in the vicinity of a wall. This is analyzed numerically at low Reynolds
numbers using a boundary element method. The area-incompressible vesicle
exhibits bending elasticity. Forces due to adhesion or gravity oppose the
hydrodynamic lift force driving the vesicle away from a wall. We investigate
three cases. First, a neutrally buoyant vesicle is placed in the vicinity of a
wall which acts only as a geometrical constraint. We find that the lift
velocity is linearly proportional to shear rate and decreases with increasing
distance between the vesicle and the wall. Second, with a vesicle filled with a
denser fluid, we find a stationary hovering state. We present an estimate of
the viscous lift force which seems to agree with recent experiments of Lorz et
al. [Europhys. Lett., vol. 51, 468 (2000)]. Third, if the wall exerts an
additional adhesive force, we investigate the dynamical unbinding transition
which occurs at an adhesion strength linearly proportional to the shear rate.Comment: 17 pages (incl. 10 figures), RevTeX (figures in PostScript