Retention Forces for Drops on Microstructured Superhydrophobic Surfaces
Retention Forces for Drops on Microstructured Superhydrophobic Surfaces
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DOI：
10.1021/acs.langmuir.2c02290
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发表时间：
2022-12-14
期刊：
影响因子：
3.9
通讯作者：
Iverson, Brian D.
中科院分区：
文献类型：
--
作者：
Humayun, Shaur;Maynes, R. Daniel;Iverson, Brian D.
准确的模型之间的保留力的下降和超疏水（SH）的表面上预测液滴动力学。这种保持力是，反过来，有用的模拟传热速率的SH表面上的滴状冷凝。液滴接触角分布和SH表面的底面积是预测固位力的重要因素。目前的工作措施的接触角分布和底面积形状的各种滴尺寸在很宽的范围内的固体分数为倾斜的微结构SH表面在点的下降出发。发现使用具有不同纵横比的两个椭圆可以很好地近似基底区域形状，并且发现接触角分布通过S形函数最佳拟合。在滚降角附近的倾斜处，发现固体分数接近1和接近0的表面的液滴基底面积接近圆形，而中间固体分数的表面上的液滴的基底面积偏离圆形行为。在这项工作中，最大前进和最小后退接触角被发现作为固体分数的函数，并用于计算保持力。然后使用接触角分布和底面积形状来计算液滴和SH表面之间的保持力。这些计算进行了比较，与测得的滴重量的组成部分平行于一个倾斜的表面上的平面进行验证。先前研究光滑表面的基底面积形状和接触角分布的保持力研究不适用于微结构SH表面。这项工作表明，使用S形接触角分布和修改的基础面积形状产生的保持力平均比以前报道的方法好50%。本研究中计算的光滑和SH表面的保持力用于建议不同固体分数表面的保持力因子值。
Accurate models of retention forces between drops and superhydrophobic (SH) surfaces are required to predict drop dynamics on the surface. This retention force is, in turn, useful in modeling heat transfer rates for dropwise condensation on a SH surface. Drop contact angle distribution and base area on SH surfaces are essential factors for predicting retention forces. The present work measures the contact angle distribution and base area shapes of various drop sizes over a wide range of solid fraction for inclined microstructured SH surfaces at the point of drop departure. Base area shape was found to be well approximated using two ellipses with different aspect ratios, and the contact angle distribution was found to be best fit by a sigmoid function. At an incline near the roll-off angle, drop base area for surfaces with solid fraction close to 1 and close to 0 were found to be nearly circular, whereas the base area of drops on surfaces with an intermediate solid fraction deviated from circular behavior. In this work, maximum advancing and minimum receding contact angles were found as a function of solid fraction and used to calculate retention forces. Contact angle distribution and base area shapes are then used to calculate retention forces between drops and SH surfaces. These calculations are compared with the component of measured drop weight acting parallel to the plane on a tilted surface for validation. Previous retention force studies that investigate base area shape and contact angle distribution for smooth surfaces are not applicable for microstructured SH surfaces. The work shows that using a sigmoid contact angle distribution and modified base area shape yields retention forces that are on average 50% better than previously reported methods. Retention forces for smooth and SH surfaces calculated in this study were used to suggest retention force factor values for varying solid fraction surfaces.