Wang Heping, Li Xiaoguang, Li Yanggui, Geng Xingguo
Functional Soft Matter & Materials Group, Key Laboratory of Space Applied Physics and Chemistry of Ministry of Education, School of Science, Northwestern Polytechnical University, Xi'an 710129, China.
Functional Soft Matter & Materials Group, Key Laboratory of Space Applied Physics and Chemistry of Ministry of Education, School of Science, Northwestern Polytechnical University, Xi'an 710129, China.
Ultrason Sonochem. 2017 May;36:101-111. doi: 10.1016/j.ultsonch.2016.11.012. Epub 2016 Nov 10.
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.
本文采用格子玻尔兹曼方法，对超声场中油水分离及油滴聚并进行了探索。通过超声行波和驻波进行模拟，以强化油的分离并捕获油滴。重点研究了驻波场中超声辐照对水包油乳液性质的影响，如油滴半径、形态以及相分离的生长动力学。在420kHz的情况下，施加超声场辐照水包油乳液以使油滴絮凝；在2MHz和10MHz的情况下，分别得到更大的分散油滴和连续相。经过几个周期后，分离出的相开始沿声传播方向上升。超声作用下絮凝物的上升速率明显大于原始乳液中油滴的上升速率，这表明超声辐照在分离过程中使油滴数量迅速增加。分离程度也随着频率或辐照时间的增加而显著提高。通过球平均结构因子以及油相和乳液相的比例，对超声相分离生长动力学的数据进行重新整理并绘制成图。分析得出了两个不同的时间阶段：旋节线分解阶段和畴生长阶段，这进一步量化了形态学结果。这些数值结果为设定超声场中水包油乳液分离的最佳条件提供了指导。
