Dynamic wetting failure in curtain coating: Comparison of model predictions and experimental observations
Dynamic wetting failure in curtain coating: Comparison of model predictions and experimental observations
复制标题
幕涂中的动态润湿失效：模型预测与实验观察的比较
DOI：
10.1016/j.ces.2018.11.015
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发表时间：
2019
影响因子：
4.7
通讯作者：
Satish Kumar
中科院分区：
文献类型：
--
作者：
Chen;M. Carvalho;Satish Kumar
在这项工作中，使用我们之前工作中开发的流体动力学模型研究了帘式涂层几何结构中牛顿液体的动态润湿失效（Liu 等人，2016b）。该模型用于预测润湿失败的发生，帘幕高度与之前的实验设置一致。在模型中，纳维滑移边界条件和恒定接触角用于描述动态接触线（DCL）。采用伽辽金有限元法求解控制方程，并确定发生润湿失效的临界基材速度。构建了涂层窗口的边界，该边界概述了不同液幕流速的临界基材速度。将模型预测与 Blake 等人报告的先前实验观察结果进行比较。 （1999）和马斯顿等人。 （2009）。该模型再现了当液体流速增加时临界速度的非单调行为。当不存在表面活性剂时，我们的结果表明，实验观察结果在很大程度上可以用一个模型来解释，该模型在 DCL（纳维滑移和恒定接触角）处使用最简单的边界条件，并考虑那里的空气应力以准确计算界面形状。当存在表面活性剂时，我们的结果表明平衡表面张力的降低可能不是导致涂层窗口形状变化的唯一机制。尤其是，马兰戈尼压力可能发挥重要作用。
In this work dynamic wetting failure of Newtonian liquids in a curtain coating geometry is studied using a hydrodynamic model developed in our prior work (Liu et al., 2016b). The model is used to predict the onset of wetting failure with curtain heights consistent with prior experimental setups. In the model, a Navier-slip boundary condition and constant contact angle are used to describe the dynamic contact line (DCL). The governing equations are solved with the Galerkin finite-element method and the critical substrate speed is identified at which wetting failure occurs. A boundary of a coating window is constructed which outlines the critical substrate speed for different flow rates of the liquid curtain. The model predictions are compared with prior experimental observations reported by Blake et al. (1999) and Marston et al. (2009). The model reproduces the non-monotonic behavior of the critical speed as the liquid flow rate increases. When surfactants are absent, our results suggest that the experimental observations can largely be explained with a model that uses the simplest boundary conditions at the DCL (Navier-slip and constant contact angle) and accounts for the air stresses there to accurately calculate interface shapes. When surfactants are present, our results suggest that a decrease in the equilibrium surface tension may not be the only mechanism responsible for changes in the shape of the coating window. In particular, Marangoni stresses may play an important role.