Deformation of spherical compound capsules in simple shear flow
Release Time:2025-04-30
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- Date:
- 2025-04-30
- Title of Paper:
- Deformation of spherical compound capsules in simple shear flow
- Journal:
- Journal of Fluid Mechanics
- Summary:
- The deformation of a compound capsule (an elastic capsule with a smaller capsule inside) in a simple shear flow is studied by using three-dimensional numerical simulations based on a front tracking method. The inner and outer capsules are concentric and initially spherical. Skalak et al.’s constitutive law is employed for the mechanics of both the inner and outer membranes. Our results concerning the deformation of a homogeneous capsule (i.e., a capsule without the inner capsule) are quantitatively in agreement with the predictions by previous numerical simulations and perturbation theories. Compared to the homogeneous capsule, the compound capsule exhibits a smaller deformation. The deformation of the inner and outer capsules is both significantly affected by the capillary numbers of the inner and outer membranes and the volume ratio of the inner to the outer capsule. When the inner capsule is small, it presents smaller deformation than the outer capsule. However, when the inner capsule is sufficiently large, it can present larger deformation than the outer capsule, even if the inner membrane has a much lower capillary number than the outer membrane. The underlying mechanisms are discussed: (i) the inner capsule is deformed by a rotational flow with lower rate-of-strain rather than by the simple shear flow which deforms the outer capsule, thus the inner capsule exhibits smaller deformation; (ii) when the inner and outer membranes are sufficiently close (i.e., the inner capsule is sufficiently large), the hydrodynamic interaction between the two membranes becomes significant, which is found to inhibit the deformation of the outer capsule but promote the deformation of the inner capsule.
- Co-author:
- Luo Zhengyuan, He Long, Bai Bofeng*
- Volume:
- 775
- Page Number:
- 77-104
- Translation or Not:
- No
- Date of Publication:
- 2015-06-10
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