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| Coalescence Process of Droplets on DecimillimeterScaled Grooved Surfaces |
| HU Haibao1,HE Qiang1,HUANG Suhe1,XUE Qunji2,DU Xiangdang1 |
| (1. College of Marine, Northwestern Polytechnical University, Xi’an 710072, China;
2. Ningbo Key Laboratory of Marine Protection Materials, Ningbo Institute of Materials Technology
and Engineering, Chinese Academy of Sciences, Ningbo 315201, Zhejiang, China) |
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Abstract Abstract： This paper investigated the coalescence of two droplets on decimillimeterscaled grooved surfaces by using a highspeed camera and compared the coalescence process of isometric/anisometric droplets on parallel/vertical grooved surfaces. During the experiment, a syringe needle was inserted from the bottom of the substrates in order to obtain a horizontal coalescence of a preplaced static droplet and a slowly growing quasistatic droplet. The results show that the whole coalescence process can be divided into the coalesce process and the oscillation process. When the droplets are isometric, on parallel grooved surfaces, due to the guiding effect of grooves, they oscillate sharply by the direction of grooves, accompanied by reciprocating contact line. On vertical grooved surfaces, limited by the energy barrier of vertical grooves, the oscillation of droplet is weaker and the contact line is almost fixed, while the vertical amplitude of oscillation is distinct. Different phenomena are observed when the droplets are anisometric: the smaller droplet is attracted to the other side, resulting in an asymmetrical coalescence process. Besides, the height of liquid bridge, the lasting time of coalescence and the length of contact line increase as the overall volume of the two droplets increases.
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Received: 13 January 2015
Published: 29 February 2016
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