如何模拟有柔性触感的雪花？

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采用通用界面模型计算复杂三维雪花生长有可能为其他树状材料的模拟提供帮助。当雪晶种子穿过大气不断捕获水分子时，雪晶体通过初始种子向外扩展而使水分子凝固。虽然大多数模拟方法都将这种雪晶不断增长的界面视为一个敏感的界面，但法国鲁昂大学的Gilles Demange及其同事却用可变换的模拟方法获得非常实用的结果。他们用相场模型方法，将雪花表面表示为冰和水蒸气混合的可移动薄层，用新的表面张力函数来表示各向异性的结晶。该方法包括了模拟三维晶面的特殊算法，能使模型复制出基本的雪花形态，并可对各种气象条件下云中的冰水含量进行预测。该文近期发表于npj Computational Materials 3:15 (2017); doi:10.1038/s41524-017-0015-1，英文标题与摘要如下，点击阅读原文可以自由下载论文PDF。

原文链接：
http://www.nature.com/articles/s41524-017-0015-1

A phase field model for snow crystal growth in three dimensions

Gilles Demange, Helena Zapolsky, Renaud Patte & Marc Brunel

Snowflake growth provides a fascinating example of spontaneous pattern formation in nature. Attempts to understand this phenomenon have led to important insights in non-equilibrium dynamics observed in various active scientific fields, ranging from pattern formation in physical and chemical systems, to self-assembly problems in biology. Yet, very few models currently succeed in reproducing the diversity of snowflake forms in three dimensions, and the link between model parameters and thermodynamic quantities is not established. Here, we report a modified phase field model that describes the subtlety of the ice vapour phase transition, through anisotropic water molecules attachment and condensation, surface diffusion, and strong anisotropic surface tension, that guarantee the anisotropy, faceting and dendritic growth of snowflakes. We demonstrate that this model reproduces the growth dynamics of the most challenging morphologies of snowflakes from the Nakaya diagram. We find that the growth dynamics of snow crystals matches the selection theory, consistently with previous experimental observations.

原文链接：
http://www.nature.com/articles/s41524-017-0015-1

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