Molecular Dynamics Study of the Coalescence Characteristics of Water-in-Oil Emulsions under the Action of Electric Field

Using molecular dynamics simulations, this study investigates the dynamic coalescence of water droplets in oil-in-water emulsions under the influence of electric fields, from a microscopic perspective. The effects of electric field strength, field type, droplet position, and ion concentration on coalescence were systematically analyzed. The results indicate that, under a direct current (DC) electric field, the condition of E = 0.03 V/Å is the most optimal for droplet coalescence among all tested DC field conditions. Under a rectangular alternating current (AC) electric field, the condition of E = 0.045 V/Å–80 ps yielded the best coalescence performance. Compared to the DC field, the rectangular AC field facilitates coalescence between droplets positioned at greater distances. Defining the contact time of droplets with an ion concentration of 40 N as t_40N, the corresponding contact times for other concentrations are denoted as t_0N, t_20Ν, and t_60N. The contact times under different ion concentrations follow the order: in the DC field, t_40N < t_20N < t_60N < t_0N, while in the rectangular AC field, t_20N < t_40N < t_0N < t_60N. For the same ion concentration, the time required to complete coalescence in the rectangular AC field is longer than in the DC field.