Hypothesis

Computer fluid dynamics simulations of dynamic wetting are often performed using a slip model on the substrate. In previous studies, the generalized Navier boundary condition (GNBC) has shown promising results and could help clear the gap between molecular and continuum scales, but lacks quantitative comparisons to experiments. We seek to investigate the dependence between the contact-line velocity and the slip length in a GNBC, by confronting numerical simulations to experimental data.

Experiments

The physical properties of a molten polymer (polyethylene glycol) were assessed thoroughly. Its dynamic contact angle on a cellulosic substrate was measured carefully using the Wilhelmy method. The experiment was reproduced in a finite elements model using a GNBC. It was repeated for capillary numbers between 10⁻⁶ and 10⁻¹, and slip lengths ranging from 1 μm to 1 mm.

Findings

A realistic value of the slip length was selected by matching the dynamic contact angles issued from numerical simulations and their experimental counterparts. The slip length behavior as a function of contact line velocity displayed a clear transition. The model also reproduced a dynamic wetting transition between frictional and viscous dissipations, which seems to be linked to an increasing difference between microscopic and macroscopic contact angles.

中文翻译：

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广义Navier边界条件的动态润湿中的滑移跃迁

假设

动态润湿的计算机流体动力学模拟通常是使用基底上的滑动模型进行的。在先前的研究中，广义的Navier边界条件（GNBC）已显示出令人鼓舞的结果，可以帮助消除分子尺度和连续尺度之间的差距，但缺乏与实验的定量比较。我们试图通过面对数值模拟实验数据来研究GNBC中接触线速度和滑动长度之间的依赖性。

实验

彻底评估了熔融聚合物（聚乙二醇）的物理性能。使用Wilhelmy方法仔细测量其在纤维素基质上的动态接触角。实验是使用GNBC在有限元模型中复制的。重复10 ^-6至10 ^-1之间的毛细管数，滑移长度范围为1μm至1 mm。

发现

通过匹配由数值模拟和它们的实验对应物发出的动态接触角来选择滑移长度的实际值。滑移长度行为作为接触线速度的函数显示出明显的过渡。该模型还再现了摩擦耗散和粘性耗散之间的动态润湿过渡，这似乎与微观和宏观接触角之间的差异越来越大有关。