Motion of an oblate capsule in simple shear flow

Abstract eng:
The present study is focused on the dynamics of non-spherical liquid-core capsules in simple shear flow. The objective is to determine the stability of the equilibrium configurations of oblate capsules. To solve the fluid-structure interaction problem, we use a numerical model coupling a finite element method for the capsule deformation with a boundary integral method for the internal and external flows. The equilibrium motions are found to be independent of the capsule initial inclination and to depend only on the capillary number Ca and inner-toouter viscosity ratio λ. For λ =1, the tumbling and swinging regimes are found to be stable only until Ca ~ 0.9. Above, the capsule follows an out of plane motion which converges towards the rolling motion for Ca > 1.2. For λ > 4, only tumbling is stable at low Ca and rolling at higher Ca.

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