Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China.
Langmuir. 2013 Apr 30;29(17):5160-6. doi: 10.1021/la400187c. Epub 2013 Apr 17.
Quantitative correlation between critical air velocity and roughness of microstructured surface has still not been established systematically until the present; the dynamics of water droplet detachment by air flow from micropillar-like superhydrophobic surfaces is investigated by combining experiments and simulation comparisons. Experimental evidence demonstrates that the onset of water droplet detachment from horizontal micropillar-like superhydrophobic surfaces under air flow always starts with detachment of the rear contact lines of the droplets from the pillar tops, which exhibits a similar dynamic mechanism for water droplet motion under a gravity field. On the basis of theoretical analysis and numerical simulation, an explicit analytical model is proposed for investigating the detaching mechanism, in which the critical air velocity can be fully determined by several intrinsic parameters: water-solid interface area fraction, droplet volume, and Young's contact angle. This model gives predictions of the critical detachment velocity of air flow that agree well with the experimental measurements.
定量关联空气临界速度和微结构表面粗糙度的问题至今尚未得到系统地建立；本文通过实验和模拟对比，研究了空气流从类 micropillar 超疏水表面脱离液滴的动力学过程。实验证据表明，空气流作用下水平类 micropillar 超疏水表面液滴的脱离起始于液滴后接触线从支柱顶端开始脱离，这表现出与重力场下液滴运动类似的动力学机制。基于理论分析和数值模拟，提出了一个明确的分析模型来研究脱离机制，其中临界空气速度可以完全由几个内在参数来确定：水-固界面面积分数、液滴体积和杨氏接触角。该模型给出了空气临界脱离速度的预测值，与实验测量值吻合较好。
