ABSTRACT We presented both experimental and numerical studies on the freezing of impacting water droplets on a cold surface at different surface temperatures. The numerical model consists of two parts. The first one is to determine the temperature evolution of the droplet prior to the occurrence of freezing by solving the heat conduction equation, and the second one is to simulate the freezing process via an extended phase change model. Experiments were conducted to observe and record the freezing process. The droplet profile and the propagation of moving water–ice interface during freezing were obtained from image analysis. Based on the numerical pre-recalescence temperature of the droplet, the average initial ice fraction and local initial ice fraction were obtained. Then, both the two kinds of initial ice fractions were used to figure out the difference that they brought to the predicted freezing process. Through a comparison of the experimental observations and the numerical predictions, the freezing process predicted by using local initial ice fraction showed a better agreement with the experiment than using average initial ice fraction.

中文翻译：

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基于平均和局部初始冰分数的水滴冻结过程研究

摘要 我们介绍了在不同表面温度下撞击水滴在冷表面上冻结的实验和数值研究。数值模型由两部分组成。第一个是通过求解热传导方程来确定液滴在冻结发生之前的温度演变，第二个是通过扩展的相变模型来模拟冻结过程。进行实验以观察和记录冷冻过程。从图像分析获得液滴轮廓和冻结过程中移动的水-冰界面的传播。基于液滴的数值预再辉温度，获得平均初始冰分数和局部初始冰分数。然后，这两种初始冰部分都被用来计算它们给预测的冻结过程带来的差异。通过实验观察和数值预测的比较，使用局部初始冰分数预测的冻结过程比使用平均初始冰分数与实验显示出更好的一致性。