相场法模拟冰晶生长的参数优化

Optimization of correlative parameters in numerical simulation of ice crystal growth by phase-field

水溶液冻结过程生成的冰晶是低温保存中造成细胞损伤的主要原因.研究如何降低冰晶形成和生长过程对细胞伤害的方法,是低温生物研究的重要课题.本文采用国内外描述相变微观结构的相场模型,将体系视为水和溶质二元系统,研究了界面厚度尺度、各向异性强度和过冷度对结晶过程冰晶生长的影响.结果表明：界面厚度影响模拟结果,为了获得可靠的计算结果,界面厚度参数取值为3.00 dx；各向异性系数大小对冰晶形貌有很大影响,取值越大,冰晶的二次分枝越发达,且尖端速度波动的幅值越大,各向异性系数取值范围0.010～0.025；过冷度明显影响冰晶的生长和形貌,过冷度大,冰晶生长速度加快,二次分枝发达,形貌变化较大,固相率也随之变大.参数优化结果为：界面厚度尺度等于3.00 dx,各向异性系数等于0.023,过冷度等于20 K 的模拟结果与低温显微镜下观察到的冰晶生长形貌试验结果相吻合.

The main cause of cell damage in aqueous solution was ice crystals generated by low temperature preservation.It is an important topic for low temperature biology research to study how to reduce the cell damage from ice crystal formation and growth.In order to investigate the influence on correlative parameters such as interface thickness,anisotropic and degree of supercooling,by regarding system as water and solute in binary system,the phase-field model theory which had been widely used in the phase transition of the microscopic structure at home and abroad was employed to stimulate the ice growth process.The results showed that the interface thickness had influence on the simulation results.It should be taken a reasonable value of 3.00 dx to get reliable cal-culation results.The anisotropic coefficient had a great influence on the crystal morphology.When it became bigger, the secondary dendritic branches of ice crystals were better-developed and the fluctuation amplitude of tip growth speed would be intensified ranging from 0.010 to 0.025.The degree of supercooling significantly affected the growth and morphology of the ice crystals.The growth speed of ice crystal would increase by the larger degree of supercooling and the secondary dendritic branches of ice crystals were better-developed,the morphology and the solid fraction would have greater change too.The conclusion of the optimization results of the interface thickness was 3.00 dx,the anisotropic coefficient was 0.023 and super-cooling degree was 20 K.It would validate the simulation results coincided well with the experiment.