基于相场法的不同过冷度冰枝生长形态及速率模拟

The Simulation of the Velocity and Morphology of Ice Dendrite Growth Using Phase Field Method Under Different Supercooling

针对目前实验与理论研究只给出过冷度0~20K范围内的结冰规律,远低于飞机结冰过冷度范围0~40K的问题,采用适合大过冷度结晶模拟的扩散界面相场方法,并考虑冰枝各向异性和热扰动,重点研究了过冷度20~40K范围内的冰枝生长速度、形貌和尖端半径等特征.通过分析给出了过冷度20K以上的冰枝生长速度规律,发现其斜率显著高于现有0~20K范围的结果.这是由于在过冷度20K左右尖端曲率的增大使热扩散长度出现了非线性的快速减小,从而促进了热扩散,同时尖端曲率的增大使得动力学过冷度明显增加,两者共同导致冰枝生长随过冷度加速增长.通过获得的冰生长速度规律分析飞机表面结冰溢流问题发现,在20K以上过冷度及大水含量条件下,结冰溢流距离对水含量十分敏感,在上述条件下结冰速度快和强溢流的异常结冰特征可能同时出现.

At present,the study only discusses the icing law between supercooling 0—20 K,which is half of the icing range of flight.To solve this problem,a diffusive interface phase field method which is suitable for large supercooling simulation of crystal is adopted,and anisotropy and thermal disturbance are considered.The characteristics of growth speed,morphology and tip radius in the supercooling range of20—40 Kare quite concerned.The analysis of ice growth law shows its slope is significantly higher than the existing data of 0—20 K.This is due to the increase of the tip's curvature,which has a rapid decrease of thermal diffusion length,and promotes the thermal diffusion,and the increasing of curvature leading to the dynamic supercooling.Both of them lead to the increase of ice growth rate with supercooling.Using the ice growth law obtained to analyze the runback icing in aircraft,it is found that the ice runback distance is sensitive to the liquid water content(LWC)when the supercooling is larger than 20 Kand the LWC is large.Under this condition,the abnormal icing characteristics of fast growth and severe runback may occur simultaneously.