Study on Coalescence Characteristics and Mechanisms of Salt-laden Droplets Under Electric-magnetic Coupling Field

Abstract Electric-magnetic coupling dehydration technology is a novel method that can significantly improve the efficiency of water-oil separation in water-in-oil (W/O) emulsions. However, the electric-magnetic coupling mechanisms and its influence on droplet coalescence have not been understood from a microscopic perspective, which has become a bottleneck restricting the progress of this technology. In this study, the high-speed microscopic experiment and molecular dynamics (MD) simulation were combined to study the kinetic properties of droplets coalescence under an electric-magnetic coupling field, and the potential mechanisms of electric-magnetic coupling field strengthening droplet coalescence were articulated from the perspective of salt ions migration and energy evolution. The results show that the experiment and simulation have excellent qualitative consistency. As water molecules polarise and migrate, the contact interface between adjacent droplets forms a cone tip during the approach process. The contact point of the droplet forms hydrogen bonds due to the mutual attraction of water molecules, which are then transformed into a continuously expanding liquid bridge. The salt ions in the droplet undergo migration deflection by the electric-magnetic coupling effect, which may affect the surface charge distribution of the droplets. During the process of droplet coalescence, strong electrostatic attraction occurs between molecules, leading to a significant increase in coulomb potential and dominating the overall potential energy variation. However, excessively small molecular spacing induces exchange repulsion, thereby reducing the van der Waals potential. The study results are of guiding significance for sounding droplet dynamics theory and guiding the research and development of electric-magnetic dehydration equipment.