各向异性强度对冷冻浓缩过程冰晶生长影响的相场法模拟

针对各向异性参数与实际物性参数的关系无法用试验方法准确获得的问题,采用描述相变微观结构的相场模型,探讨各向异性强度对冰晶生长形貌和冰晶的溶质分布的影响,确定模型中各向异性强度系数的合理取值。结果表明:各向异性强度系数取值大小对冰晶的形貌有很大影响,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,但对冰晶大小影响不大;各向异性强度系数取值大小对冰晶的溶质分布也有较大影响,取值越大则冰晶前沿溶质越富集,溶质分布波动范围越大。各向异性强度系数取值范围为0.010~0.025时,模拟获得的形貌与低温显微镜下观察到的冰晶生长形貌试验结果较为吻合,能够较真实地反映冷冻浓缩过程冰晶生长形貌。

Phase-field simulation of ice crystal growth by anisotropy influence on freeze concentration process

In view of the relationship between anisotropic parameter and the physical parameters could not be accurately determined by the experimental methods,the phase-field model theory which had been widely used in the phase transition of the microscopic structure was employed in this research for the freeze concentration process analysis.The influence of anisotropic parameters on ice crystal growth morphology and solute distribution was investigated,and a reasonable value of anisotropic strength coefficient was estimated.Results showed that the anisotropic strength factor would have a great influence on the ice crystal morphology.The secondary branches of ice crystals would become more and more developed and tip speed fluctuation amplitude would increase with anisotropic strength coefficient increased,but it had little effect on ice crystal size.The anisotropic strength factor would also have a great influence on the solute distribution of ice crystals.The larger of the anisotropic strength factor,the more enrichment of the ice edge,and the larger range of the fluctuation.When the strength of anisotropic coefficient values range was between 0.010-0.025,the simulation results would coincide well with the ice crystal growth morphology test results observed by the low temperature microscope.