Heng Li,Yafeng Zhang,Xing Shi Gu,Huimin Qi,Jiaxin Yu,Jian Zhuang
The variation of velocity field inside a droplet was investigated by particle image velocimetry when the droplet moved on a superhydrophobic surface. Results showed that shear stress increased with the increase of the motion velocity of droplet and droplet viscosity when the motion velocity of droplet increased from 0.3 to 1.1 mm/s and the droplet viscosity increased from 2.69 to 17.41 mPa·s. Moreover, friction force at liquid/solid interface was independent on droplet volume, viscosity and motion velocity on the superhydrophobic surface. It is indicated that the variation of velocity field and shear stress inside droplet was closely associated with the change of the influence depth and the center of mass inside the droplet caused by the substrate. The findings are helpful to understand the motion behaviors of a droplet on the superhydrophobic surface to reduce the energy dissipation when a droplet transport on the superhydrophobic surfaces.
Xin Huang,Limin He,Xiaoming Luo,Ke Xu,Yuling Lü,Donghai Yang
s The coalescence behaviors of two neutral droplets suspended in silicone oil under the alternating current (AC) and pulsed direct current (DC) electric fields are investigated by experiments and numerical simulations. The distribution evolutions of electric force and velocity field during the droplet coalescence under the AC and pulsed DC electric fields are analyzed. The relationship between electric field excitation and droplet interface response is illustrated. The equivalent response mechanism of droplets under the high-frequency AC and pulsed DC electric fields and under the DC electric fields is revealed. The relationship of droplet dynamic behaviors under the DC electric field and under the AC and pulsed DC electric fields are established. The critical electric field frequencies above which the shortest distance curves no longer change under the AC and pulsed DC electric fields are obtained. These new findings are significant for the optimization of electrostatic coalescence.
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