Lattice Boltzmann modeling of droplet condensation on superhydrophobic nanoarrays
Lattice Boltzmann modeling of droplet condensation on superhydrophobic nanoarrays
复制标题
超疏水纳米阵列上液滴凝结的格子玻尔兹曼模型
作者：
Zhang Qingyu;Sun Dongke;Zhang Youfa;Zhu Mingfang
采用多相、多组分格子Boltzmann（LB）模型模拟了超疏水纳米阵列上液滴的成核和生长。三个典型的优先形核模式的冷凝液滴观察通过LB模拟与不同的几何参数的纳米阵列，这被发现影响纳米结构表面的润湿性能显着。在纳米阵列的柱的顶部处成核（顶部成核）或在纳米阵列的上部柱间空间中成核（侧面成核）的液滴将产生非润湿Cassie状态，而在纳米阵列的柱之间的底部拐角处成核（底部成核）的液滴产生润湿Wenzel状态。分析了不同位置处液滴压力随时间的变化规律，揭示了不同成核方式下液滴生长的物理机制。结果表明，具有较高的柱和高的柱高与柱间空间（H/S）的比率的纳米结构有利于产生顶部和侧面成核模式。具有各种几何构型的纳米结构上的冷凝液滴的模拟润湿状态与实验观察相当好地比较。纳米阵列的几何参数和冷凝液滴的优先成核模式之间建立的关系提供了指导的纳米阵列的设计与理想的抗冷凝超疏水性能。
Droplet nucleation and growth on superhydrophobic nanoarrays is simulated by employing a multiphase, multicomponent lattice Boltzmann (LB) model. Three typical preferential nucleation modes of condensate droplets are observed through LB simulations with various geometrical parameters of nanoarrays, which are found to influence the wetting properties of nanostructured surfaces significantly. The droplets nucleated at the top of posts (top nucleation) or in the upside interpost space of nanoarrays (side nucleation) will generate a nonwetting Cassie state, while the ones nucleated at the bottom corners between the posts of nanoarrays (bottom nucleation) produce a wetting Wenzel state. The simulated time evolutions of droplet pressures at different locations are analyzed, which offers insight into the underlying physics governing the motion of droplets growing from different nucleation modes. It is demonstrated that the nanostructures with taller posts and a high ratio of post height to interpost space (H/S) are beneficial to produce the top- and side-nucleation modes. The simulated wetting states of condensate droplets on the nanostructures, having various geometrical configurations, compare reasonably well with experimental observations. The established relationship between the geometrical parameters of nanoarrays and the preferential nucleation modes of condensate droplets provides guidance for the design of nanoarrays with desirable anticondensation superhydrophobic properties.