Deformation and motion behavior of droplets in a non-uniform electric field

Abstract

The deformation and motion behaviors of droplets under electric field are important research tasks regarding the mechanisms of emulsion electric dehydration. In order to study the dehydration characteristics of droplets under a non-uniform electric field, the simulation model of droplets under a non-uniform electric field was established using the phase field method, based on Cahn-Hilliard formulation. During the process of droplet deformation and motion the distribution regularities of the charge density and Maxwell force on the droplet surface were simulated, based on the method of flow field coupled electric field. The respective influences of electric field intensity and droplet diameter on the deformation degree and motion behaviors of the droplets were also studied. The phenomena of droplet movement behavior were observed and recorded by high-speed camera. The experimental results show that the distribution of polarization charges was asymmetrical on the droplet surface under the non-uniform electric field, increasing from the center to both ends of the water droplets. The values of polarization charge and Maxwell stress at one of droplets' end surface closed to the electric field concentrated area were the largest. The higher electric field intensity or larger droplet diameter could lead to larger deformation degree of the droplets and faster speed of droplet movement to the concentrated electric field. Under excessively high electric field intensity, the droplets will be easily ruptured and the dehydration rate will decrease.