TIP SPLITTING IN DENDRITIC GROWTH OF ICE CRYSTALS
TIP SPLITTING IN DENDRITIC GROWTH OF ICE CRYSTALS
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DOI：
10.1103/physreva.44.3782
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发表时间：
1991-09-15
影响因子：
2.9
通讯作者：
GILL, WN
中科院分区：
文献类型：
--
作者：
KOO, KK;ANANTH, R;GILL, WN
在 0.035 < DELTA-T < 1.0 K 范围内的小过冷度下，研究了在静态超纯水中垂直向上生长的冰晶。在低于 0.35 K 的过冷度下，枝晶尖端分裂，尖端半径 R2 下降，因为从基面看去，两个尖端取代了一个尖端。然而，发现枝晶边缘平面的生长速度和尖端半径与时间无关，并且不受基面形态不稳定性的影响。相反，当过冷度大于 0.35 K 时，尖端似乎以不变的形状生长。观察到与固体冰处于平衡状态的水滴的形状接近圆盘。从这些液滴的形状来看，椭圆形边缘平面的表面能各向异性估计约为 30%，而尽管冰具有六边形结构，但发现底面与圆形没有区别。我们推测，冰树突中的尖端分裂可能是由于基面缺乏各向异性和自然对流之间的耦合而引起的形态不稳定性，这在小 DELTA-T 时变得显着。
Ice crystals growing vertically upwards in quiescent ultrapure water have been investigated at small subcoolings in the range of 0.035 < DELTA-T < 1.0 K. At subcooling less than 0.35 K, dendritic tips split and the tip radius R2 drops because two tips replace one when viewed from the basal plane. The growth velocity and the tip radius of the edge plane of the dendrite, however, are found to remain independent of time and unaffected by the morphological instabilities in the basal plane. In contrast, when the subcooling is greater than 0.35 K, the tips seem to grow with an invariant shape. The shape of drops of water that are in equilibrium with solid ice is observed to be close to a circular disk. From the shape of these drops, the anisotropy of the surface energy in the edge plane, which is an ellipse, is estimated to be about 30%, while the basal plane is found to be indistinguishable from a circle, despite the hexagonal structure of ice. We speculate here that tip splitting in ice dendrites may be a morphological instability caused by the coupling between lack of anisotropy in the basal plane and natural convection, which becomes significant at small DELTA-T.