Dynamic modes of microcapsules in steady shear flow: Effects of bending and shear elasticities

作者：Noguchi Hiroshi^*

来源：Physical Review E, 2010, 81(5): 056319.

DOI：10.1103/PhysRevE.81.056319

The dynamics of microcapsules in steady shear flow were studied using a theoretical approach based on three variables: the Taylor deformation parameter alpha(D), the inclination angle theta, and the phase angle phi of the membrane rotation. It is found that the dynamic phase diagram shows a remarkable change with an increase in the ratio of the membrane shear and bending elasticities. A fluid vesicle (no shear elasticity) exhibits three dynamic modes: (i) tank treading at low viscosity eta(in) of internal fluid (alpha(D) and theta relaxes to constant values), (ii) tumbling (TB) at high eta(in) (theta rotates), and (iii) swinging (SW) at middle eta(in) and high shear rates (gamma) over dot. (theta oscillates). All of three modes are accompanied by a membrane (phi) rotation. For microcapsules with low shear elasticity, the TB phase with no phi rotation and the coexistence phase of SW and TB motions are induced by the energy barrier of phi rotation. Synchronization of phi rotation with TB rotation or SW oscillation occurs with integer ratios of rotational frequencies. At high shear elasticity, where a saddle point in the energy potential disappears, intermediate phases vanish and either phi or theta rotation occurs. This phase behavior agrees with recent simulation results of microcapsules with low bending elasticity.

• 出版日期2010-5