Dynamics of droplet formation with oscillation of meniscus in electric periodic dripping regime

• Published in: Experimental thermal and fluid science Vol. 120; p. 110250
• Main Authors: Wang, Zhentao, Zhang, Yaosheng, Wang, Qisi, Dong, Kai, Yang, Shiqi, Jiang, Yimin, Zheng, Jun, Li, Bin, Huo, Yuanping, Wang, Xiaoying, Wang, Junfeng, Tu, Jiyuan
• Format: Journal Article
• Language: English
• Published: Philadelphia Elsevier Inc 01.01.2021; Elsevier Science Ltd
• Subjects: Amplitude; Bond number; Digital cameras; Dripping dynamics; Droplet formation; Droplets; Electric field strength; Electric fields; Electric periodic dripping; Electric potential; Evolution; Flow rates; Flow velocity; Low flow; Nozzles; Oscillation frequency; Amplitude; Droplet formation; Dripping dynamics; Oscillation frequency; Electric periodic dripping
• ISSN: 0894-1777; 1879-2286
• DOI: 10.1016/j.expthermflusci.2020.110250

•The droplet formation in electric periodic dripping regime was visualized.•The oscillation of electrified meniscus was visualized and identified.•The characteristic frequency deceases with an increase in applied potential.•The amplitude increases as electric number increasing. The dynamics of droplets and oscillation of electrified meniscus at low flow rates in an external electric field were investigated. An electric field is created by nozzle-plated electrode. The evolution of droplet formation is recorded by a high-speed digital camera. Meanwhile, the time evolution of meniscus is also focused. The critical sizes of the droplet and liquid thread were used to characterize the dynamics of droplet formation and oscillation of the meniscus. The results showed that a droplet gradually originates from a hemispherical meniscus and changes from spherical to pear-shaped. A liquid thread connects the meniscus and primary droplet, and pinches off as time advances. The droplets diameter decreases as electric potential increasing and is dependent of capillary diameter, while usually independent of flow rates. The droplet limiting length decreases, while the liquid thread diameter increases as electric Bond number increasing. The period of detachment decreases with an increase in electric potential and strongly depends on flow rate. The meniscus usually oscillates when the primary droplet detaches. The oscillation frequency increases as electric field strength increasing and is substantially affected by flow rate. An approximate equation to predict the oscillation frequency was presented, where the electric potential was taken into account. The variation of the oscillation frequency is qualitatively good agreement with experimental work. The amplitude of oscillation (or displacement) is significantly affected by electric field and increases as electric Bond number increasing.