The isoAdvector method for simulating deformation and breakup of multiple emulsion droplets responding to a DC electric field

Abstract

The droplet dynamic model under an electric field is established in this paper by coupling electric equations, multiphase flow equations, and isoAdvector interface capture method, accurately predicting the deformation and rupture characteristics of multiple emulsion droplets affected by an electric field. The evolutions of the flow field and electric field during the deformation and breakup processes of multiple emulsion droplets subjected to an electric field are elucidated and the effects of the electric capillary number Ca and the radius ratio R^∗ of the inner and outer droplets on the characteristics of droplet deformation and rupture are analyzed. The results show that in the silicone oil/water emulsion system, the inner droplet is difficult to induce charge since the electrostatic shielding effect of the outer droplet, and it has no impact on the equilibrium deformation of the outer droplet; whereas in the castor oil/silicone oil emulsion system, the charge is induced on the interfaces of both the internal and external droplets and the internal droplet has a remarkable impact on the equilibrium deformation of the external droplet. Furthermore, deformation-breakup phase diagrams of multiple emulsion droplets exposed to the electric field are obtained. As R^∗ increases, the Ca_c for droplet breakup decreases, indicating that the internal droplet intensifies the breakup of the external droplet. The results are significant for the promotion and application of electric field-driven droplet manipulation technology.