Abstract

The simulation of fluid flow over solid surfaces is important in many applications, for example, in automotive applications where good visibility and the performance of external sensors are essential. Multiphase CFD simulation methods such as level set or coupled level set–volume of fluid typically require a validated dynamic contact angle model as a function of capillary number to accurately resolve the near wall behaviour. This paper explores an experimental approach to identify a suitable contact angle model for pure and contaminated water on glass and painted surfaces. Applying image processing methods to high-resolution digital images of droplets descending flat plate samples of the required surfaces, the dynamic advancing and receding contact angles and capillary number are determined. Cox–Voinov, de Gennes and Yokoi models are parameterised from the experimental data, and the Yokoi model is shown to be the most suited to these surface/fluid combinations where hysteresis is significant. A multiphase simulation implementing the Yokoi model demonstrates good correlation for the Bond number between simulation and experiment.

Graphic abstract

中文翻译：

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用于汽车外部水管理的接触角测量

摘要

在许多应用中，例如在汽车应用中，良好的可视性和外部传感器的性能至关重要，因此，模拟在固体表面上流动的流体非常重要。多相CFD模拟方法（例如液位或耦合液位-体积）通常需要经过验证的动态接触角模型作为毛细管数的函数，才能准确解决近壁行为。本文探索了一种实验方法，以确定玻璃和喷漆表面上纯净水和污染水的合适接触角模型。将图像处理方法应用于从所需表面的平板样本下降的液滴的高分辨率数字图像中，确定动态前进和后退接触角以及毛细管数。考克斯·沃伊诺夫，de Gennes和Yokoi模型是从实验数据中参数化的，并且Yokoi模型显示出最适用于这些具有明显滞后作用的表面/流体组合。实施Yokoi模型的多阶段仿真表明，仿真和实验之间的键数具有良好的相关性。

图形摘要