Research on the displacement resonance frequency of water droplets in oil under AC electric fields

Appropriate electrical parameters are crucial for efficient dehydration. At the resonance frequency, the weakened interfacial film is prone to rupture, promoting droplet aggregation and enhancing dehydration efficiency. However, the theoretical mechanism of droplet resonance remains unclear. To elucidate the dynamic response mechanism of droplets in oil under an AC electric field, this paper analyzes the force on droplets under the electric field, deduces the frequency conditions for displacement resonance and velocity resonance, and explores the effects of droplet particle size, oil viscosity, interfacial tension, and electric field strength on the resonance frequency under the vertical electrodes. Results reveal a critical frequency that maximizes droplet deformation. Droplets experience electric, drag, and internal forces, and the resonance frequency is determined by the difference between the intrinsic frequency ( ω 0 ) and oil damping. The resonance frequency decreases by about 0.99 times when the droplet radius increases by 1.6 times. The maximum deformation reaches 0.14 at an interfacial tension of 4.9 mN·m −1 . At resonance, the droplet deformation stabilizes at a high value of 0.0498 when the viscosity is 100 mPa·s, whereas viscosities above a critical value induce delayed deformation and lower stabilized values. Higher voltages accelerate deformation. These findings provide a theoretical basis for optimizing electrical parameters and improving dehydration efficiency in water-in-oil emulsions.