Droplet condensation and jumping on structured superhydrophobic surfaces
Droplet condensation and jumping on structured superhydrophobic surfaces
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DOI：
10.1016/j.ijheatmasstransfer.2019.01.026
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发表时间：
2019-05
影响因子：
5.2
通讯作者：
Amir Ashrafi-Habibabadi;A. Moosavi
中科院分区：
文献类型：
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作者：
Amir Ashrafi-Habibabadi;A. Moosavi
首次采用二维双分布函数热格子Boltzmann方法研究了液滴在不同织构的疏水和超疏水表面上的成核、生长、聚结和跳跃的完整循环。首先，对光滑和粗糙表面上的液滴形核机理进行了详细的研究。结果表明，在完全光滑的表面上的冷凝冷却蒸汽层的不稳定性的存在。然而，在粗糙表面上和粗糙度附近观察到完全不同的机制，并且成核发生在粗糙度楔上。研究了在标称接触角θ a= 90°、120°、155°的不同织构表面上的冷凝现象。在所有这些表面上，据观察，对于小纹理的成核通常发生在结构楔附近。然而，增加纹理的高度将成核位点移位到结构的顶部，靠近结构边缘。液滴生长后，对于不同的接触角观察到不同的行为，即，形成Wenzel或悬浮液滴，并且液滴甚至跳出。此外，基于无量纲数的液滴跳跃进行了全面的研究，并提出了合理设计的纹理表面的方法。最后，使用混合纹理表面的好处和这些表面上的液滴跳跃的机制进行了解释。
A complete cycle of droplet nucleation, growth, coalescence and jumping on different textured hydrophobic and superhydrophobic surfaces is studied for the first time, using a 2-D double distribution function thermal lattice Boltzmann method. First, droplet nucleation mechanism on smooth and rough surfaces is studied in detail. The results reveal the presence of cooled vapor layer instability in the condensation on completely smooth surfaces. However, on the rough surfaces and near the roughness a completely different mechanism is observed and the nucleation occurs on the roughness wedges. Also, the condensation on different textured surfaces with nominal contact angles θ a= 90°, 120°, 155° is studied. On all these surfaces it is observed that for small textures the nucleation occurs normally near the structure wedges. However, increasing the height of the textures displaces the nucleation sites to the top of the structure, near the structure edge. After growing the droplets different behaviors are observed for different contact angles, ie, the Wenzel or suspended droplets are formed and the droplets even jump out. Moreover, based on the non-dimensional numbers a complete study of droplet jumping is carried out and a method for proper designing the textured surfaces is presented. Finally, the benefits of using hybrid textured surfaces and the mechanism of droplet jumping on these surfaces are explained.