| 论文简介 |
The dynamics of an initially-ellipsoidal compound capsule in a simple shear flow is investigated numerically using a three-dimensional front-tracking finite-difference model. Membrane bending resistance is included basing on Helfrich’s energy function besides the resistances against shear deformation and area dilatation govern by Skalak et al.’s constitutive law. In this paper, we focus specifically on how the presence of spherical inner capsule and its size affect the characteristics and transition of various dynamical states of nonspherical compound capsules (i.e., the outer capsule). Significant differences in the dynamical characteristics are observed between compound capsules and homogeneous capsules in both qualitative and quantitative terms. We find the transition from swinging to tumbling can occur at vanishing viscosity mismatch with only increasing inner capsule size to a critical value, no matter whether the compound capsule is initially prolate or oblate. Besides, for compound capsules with viscosity mismatch, the critical viscosity ratio for the swinging-to-tumbling transition remarkably decreases with increasing inner capsule size. These results identify that the inner capsule size is another important governing parameter of compound capsule dynamics besides capillary number, aspect ratio and viscosity ratio that have been identified for homogeneous capsules. Besides, we discuss the mechanisms underlying the effects of the inner capsule on the compound capsule dynamics from the viewpoint of the effective viscosity of internal fluid, and find that the effects of the inner capsule on compound capsule dynamics are qualitatively similar to increasing internal viscosity to homogeneous capsule dynamics. However, in quantitative terms, the compound capsule cannot be viewed as a homogeneous capsule with higher viscosity as strong inhomogeneity in fluid stress distribution is induced by the inner membrane. |
(创新港)
