Numerical Simulation Study of Oil-Water Emulsion Separation in an Ultrasonic Field: Effect of Coupling between Acoustic and Flow Field Parameters

In this study, the separation and coalescence of oil-in-water emulsions are explored in an ultrasonic field using the lattice Boltzmann method. By simulating the propagation of ultrasonic waves, this study focuses on examining the effects of acoustic wave frequency, the ratio of oil to water components, and the aspect ratio of the boundary on the emulsification and separation processes of oil-water mixtures. The following conclusions are drawn.(1) Frequency affects the speed of oil droplet separation, leading to an increase in droplet size over time. Larger droplets are found near the source, while smaller droplets are distributed throughout the wave web.(2) As the boundary aspect ratio increases, the emulsification efficiency of the droplets weakens, and the system takes longer to stabilize.(3) Emulsions with a higher component of oil can better resist acoustic waves.(4) At the same acoustic frequency, longer wavelength ultrasonic fields promote the formation of uniformly distributed, smaller oil droplets, which is beneficial to the storage of emulsions. These numerical simulation results offer insights for optimizing conditions for oil-in-water separation and serve as a numerical reference for the study of oil-in-water emulsion separation in ultrasonic environments.