Simulation of morphology for oil droplets in aqueous solution controlled by electric fields.

This study investigate the morphology of oil-in-water at high density ratio controlled by electric field. We incorporated the electric field into the Lattice Boltzmann method (LBM). The focus is on the modified lattice Boltzmann color gradient model simulate the evolution of the oil-in-water and analyze the relation between morphologies and electric field parameters. The results show that the stretching, merging and even breaking can be regulated by electric field strength, conductivity, dielectric constant, oil-water density ratio and droplet radius. Simulation results showed that the larger dielectric constant resulted in the smaller deformation, and the larger conductivity related to the greater deformation. Meanwhile, the larger radius droplet is easier to deform and break, and the higher density droplet is less likely to break. And this paper also gives the morphology of the stretching and destabilization of the droplets at each stage. These results are in good agreement with the relevant theoretical and experimental results.

Simulation of phase separation with large component ratio for oil-in-water emulsion in ultrasound field.

This paper presents an exploration for separation of oil-in-water and coalescence of oil droplets in ultrasound field via lattice Boltzmann method. Simulations were conducted by the ultrasound traveling and standing waves to enhance oil separation and trap oil droplets. The focus was to the effect of ultrasound irradiation on oil-in-water emulsion properties in the standing wave field, such as oil drop radius, morphology and growth kinetics of phase separation. Ultrasound fields were applied to irradiate the oil-in-water emulsion for getting flocculation of the oil droplets in 420kHz case, and larger dispersed oil droplets and continuous phases in 2MHz and 10MHz cases, respectively. The separated phases started to rise along the direction of sound propagation after several periods. The rising rate of the flocks was significantly greater in ultrasound case than that of oil droplets in the original emulsion, indicating that ultrasound irradiation caused a rapid increase of oil droplet quantity in the progress of the separation. The separation degree was also significantly improved with increasing frequency or irradiation time. The dataset was rearranged for growth kinetics of ultrasonic phase separation in a plot by spherically averaged structure factor and the ratio of oil and emulsion phases. The analyses recovered the two different temporal regimes: the spinodal decomposition and domain growth stages, which further quantified the morphology results. These numerical results provide guidance for setting the optimum condition for the separation of oil-in-water emulsion in the ultrasound field.