Yang Jiapei, Ma Xiao, Fei Linlin, Zhang Xiaoqing, Luo Kai H, Shuai Shijin
State Key Laboratory of Automotive Safety and Energy, School of Vehicle and Mobility, Tsinghua University, Beijing 100084, China.
Center for Combustion Energy, Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Energy and Power Engineering, Tsinghua University, Beijing 100084, China.
J Colloid Interface Sci. 2020 Apr 15;566:327-337. doi: 10.1016/j.jcis.2020.01.042. Epub 2020 Jan 21.
Contact angle hysteresis, defined as the difference between advancing and receding contact angles, is an important phenomenon in multiphase flow on a wetting surface. In this study, a modified pseudo-potential lattice Boltzmann (LB) multiphase model with tunable surface tension is proposed, which is further coupled with the geometrical formulation contact angle scheme to investigate the motion of droplets invoking the contact angle hysteresis. We focus on the dynamic behaviour of droplets driven by a body force at the Bond number ranging from 1 to 6, which is defined as the ratio of the body force to the capillary force. The droplet morphology change is examined by varying (i) the Bond number and (ii) the hysteresis window. Results show the droplet morphology evolution can be classified into different stages, including stretch, relaxation, and equilibrium. The droplet oscillation phenomenon at large Bond numbers at the equilibrium stage is observed for the first time. In addition, it is found that such oscillation can lead to the breakup and/or coalescence of droplets when the surface waves spread on the top of the droplet. Furthermore, there is slight oscillation of the normalized length, width and height at the equilibrium stage for the neutral hysteresis window while more dramatic oscillation will appear for the hydrophobic hysteresis window.
接触角滞后定义为前进接触角与后退接触角之差，是润湿表面多相流中的一个重要现象。在本研究中，提出了一种具有可调表面张力的改进伪势格子玻尔兹曼（LB）多相模型，并将其与几何公式接触角方案进一步耦合，以研究考虑接触角滞后的液滴运动。我们关注在邦德数从1到6范围内由体力驱动的液滴的动态行为，邦德数定义为体力与毛细力之比。通过改变（i）邦德数和（ii）滞后窗口来研究液滴形态变化。结果表明，液滴形态演变可分为不同阶段，包括拉伸、松弛和平衡。首次观察到平衡阶段大邦德数下的液滴振荡现象。此外，发现当表面波在液滴顶部传播时，这种振荡会导致液滴破裂和/或合并。此外，对于中性滞后窗口，平衡阶段归一化长度、宽度和高度存在轻微振荡，而对于疏水滞后窗口则会出现更剧烈的振荡。
