Journal of Fluid Mechanics

Role of membrane viscosity in the orientation and deformation of a spherical capsule suspended in shear flow

D.  Barthes-Biesel a1 and H.  Sgaier a1
a1 Départment de Génie Biologique, Université de Technologie de Compiègne, B.P. 233, 60206 Compiègne, France

Article author query
barthes-biesel d   [Google Scholar] 
sgaier h   [Google Scholar] 


Red blood cells or artificial vesicles may be conveniently represented by capsules, i.e. liquid droplets surrounded by deformable membranes. The aim of this paper is to assess the importance of viscoelastic properties of the membrane on the motion of a capsule freely suspended in a viscous liquid subjected to shear flow. A regular perturbation solution of the general problem is obtained when the particle is initially spherical and undergoing small deformations. With a purely viscous membrane (infinite relaxation time) the capsule deforms into an ellipsoid and has a continuous flipping motion. When the membrane relaxation time is of the same order as the shear time, the particle reaches a steady ellipsoidal shape which is oriented with respect to streamlines at an angle that varies between 45° and 0°, and decreases with increasing shear rates. Furthermore it is predicted that the deformation reaches a maximum value, which is consistent with experimental observations of red blood cells.

(Published Online April 20 2006)
(Received October 31 1984)
(Revised April 9 1985)