VOF simulations of the contact angle dynamics during the drop spreading: Standard models and a new wetting force model
VOF simulations of the contact angle dynamics during the drop spreading: Standard models and a new wetting force model
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DOI：
10.1016/j.cis.2014.07.004
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发表时间：
2014-10-01
影响因子：
15.6
通讯作者：
Gavaises, Manolis
中科院分区：
文献类型：
--
作者：
Malgarinos, Ilias;Nikolopoulos, Nikolaos;Gavaises, Manolis
简介：在这项研究中，一种新的数值实现的液滴的粘附通常影响固体干燥表面。这种新方法的优点，大多数现有的模型相比，是动态接触角形成过程中的表面润湿过程中不插入作为边界条件，但推导出隐含的诱导流体流动特性（界面形状）和粘附物理的气体-液体-表面界面（三线），只从前进和后退的平衡接触角。这些角度是必需的，以定义润湿性能的液相时，与固体surface.Methodology相互作用：的物理模型被实现为一个源项的动量方程的Navier-Stokes CFD流求解器作为一个“粘附”的力量，其作用在三相接触线作为一个结果的液滴和固体基质之间的毛细相互作用。数值模拟通过考虑流体体积（VOF）方法和利用自动局部网格加密技术来捕获液-气界面运动，以提高感兴趣区域的预测精度，同时最小化界面的数值扩散。所提出的模型进行了验证，对以前报道的实验数据正常的水滴在干表面上的冲击在室温下。一个广泛的范围内的冲击速度，即韦伯数从低至0.2高达117，无论是亲水性（θ（adv）= 10度-70度）和疏水性（θ（adv）= 105度-120度）的表面，已被检查。预测包括除了液滴扩散动力学，动态接触角的估计，后者被发现在合理的协议对可用的实验measurement.Conclusion：因此得出结论，该模型的实施是一种有效的方法，用于克服需要一个预定义的动态接触角法，经常采用这种模拟的近似边界条件。显然，对于低We数冲击（We <（类似于）80）的情况，该模型在扩展阶段期间是最有影响的，因为对于高冲击速度，惯性在扩展的初始阶段中显著地超过毛细管力。(C)2014爱思唯尔有限公司版权所有。
Introduction: In this study,a novel numerical implementation for the adhesion of liquid droplets impacting normally on solid dry surfaces is presented. The advantage of this new approach, compared to the majority of existing models, is that the dynamic contact angle forming during the surface wetting process is not inserted as a boundary condition, but is derived implicitly by the induced fluid flow characteristics (interface shape) and the adhesion physics of the gas-liquid-surface interface (triple line), starting only from the advancing and receding equilibrium contact angles. These angles are required in order to define the wetting properties of liquid phases when interacting with a solid surface.Methodology: The physical model is implemented as a source term in the momentum equation of a Navier-Stokes CFD flow solver as an "adhesion-like" force which acts at the triple-phase contact line as a result of capillary interactions between the liquid drop and the solid substrate. The numerical simulations capture the liquid-air interface movement by considering the volume of fluid (VOF) method and utilizing an automatic local grid refinement technique in order to increase the accuracy of the predictions at the area of interest, and simultaneously minimize numerical diffusion of the interface.Results: The proposed model is validated against previously reported experimental data of normal impingement of water droplets on dry surfaces at room temperature. A wide range of impact velocities, i.e. Weber numbers from as low as 0.2 up to 117, both for hydrophilic (theta(adv) = 10 degrees-70 degrees) and hydrophobic (theta(adv) = 105 degrees-120 degrees) surfaces, has been examined. Predictions include in addition to droplet spreading dynamics, the estimation of the dynamic contact angle; the latter is found in reasonable agreement against available experimental measurements.Conclusion: It is thus concluded that the implementation of this model is an effective approach for overcoming the need of a pre-defined dynamic contact angle law, frequently adopted as an approximate boundary condition for such simulations. Clearly, this model is mostly influential during the spreading phase for the cases of low We number impacts (We < (similar to)80) since for high impact velocities, inertia dominates significantly over capillary forces in the initial phase of spreading. (C) 2014 Elsevier B.V. All rights reserved.