Asymmetric rheological behaviors of double-emulsion globules with asymmetric internal structures in modest extensional flows

The oriented shift and inverse of double-emulsion globules containing two inner droplets with different sizes and locations in modest extensional flows are investigated numerically in this paper through a boundary element method. The asymmetric layout of daughter droplets leads to the asymmetric inner flow field and pressure field inside the globule, which causes its asymmetric rheological behaviors. The direction of shift is determined not only by the size ratio rR2/rL2 and the location ratio dR/dL of two inner droplets, but also by some flow factors such as the capillary number Ca. There is a critical capillary number Cac as a function of rR2/rL2 and dR/dL, beyond which the globule will move to the right, otherwise, it will shift to the opposite direction.