Villa Fabio, Marengo Marco, De Coninck Joël
University of Mons, Laboratory of Surface and Interfacial Physics (LPSI), 19 avenue Maistriau, 7000, Mons, BE, Belgium.
University of Brighton, School of Computing, Engineering and Mathematics, Lewes Road, BN2 4GJ, Brighton, UK.
Sci Rep. 2018 Apr 25;8(1):6549. doi: 10.1038/s41598-018-24828-8.
The measurement of the equilibrium contact angle (ECA) of a weakly evaporating sessile drop becomes very challenging when the temperatures are higher than ambient temperature. Since the ECA is a critical input parameter for numerical simulations of diabatic processes, it is relevant to know the variation of the ECA with the fluid and wall temperatures. Several research groups have studied the effect of temperature on ECA either experimentally, with direct measures, or numerically, using molecular dynamic simulations. However, there is some disagreement between the authors. In this paper two possible theoretical models are presented, describing how the ECA varies with the surface temperature. These two models (called Decreasing Trend Model and Unsymmetrical Trend Model, respectively) are compared with experimental measurements. Within the experimental errors, the equilibrium contact angle shows a decrease with increasing surface temperatures on the hydrophilic surface. Conversely the ECA appears approximately constant on hydrophobic surfaces for increasing wall temperatures. The two conclusions for practical applications for weakly evaporating conditions are that (i) the higher the ECA, the smaller is the effect of the surface temperature, (ii) a good evaluation of the decrease of the ECA with the surface temperature can be obtained by the proposed DTM approach.
当温度高于环境温度时，测量弱蒸发静滴的平衡接触角（ECA）变得极具挑战性。由于ECA是绝热过程数值模拟的关键输入参数，了解ECA随流体和壁面温度的变化情况很有必要。几个研究小组已经通过实验（直接测量）或数值模拟（使用分子动力学模拟）研究了温度对ECA的影响。然而，作者之间存在一些分歧。本文提出了两种可能的理论模型，描述了ECA如何随表面温度变化。将这两种模型（分别称为下降趋势模型和不对称趋势模型）与实验测量结果进行了比较。在实验误差范围内，亲水性表面上的平衡接触角随表面温度升高而减小。相反，在疏水性表面上，随着壁面温度升高，ECA似乎近似恒定。对于弱蒸发条件的实际应用，两个结论是：（i）ECA越高，表面温度的影响越小；（ii）通过所提出的DTM方法可以很好地评估ECA随表面温度的降低情况。
