Weady Scott, Tong Joshua, Zidovska Alexandra, Ristroph Leif
Applied Math Lab, Courant Institute, New York University, New York, New York 10012, USA.
Department of Physics, New York University, New York, New York 10003, USA.
Phys Rev Lett. 2022 Jan 28;128(4):044502. doi: 10.1103/PhysRevLett.128.044502.
We report on the shape dynamics of ice suspended in cold fresh water and subject to the natural convective flows generated during melting. Experiments reveal shape motifs for increasing far-field temperature: Sharp pinnacles directed downward at low temperatures, scalloped waves for intermediate temperatures between 5 °C and 7 °C, and upward pointing pinnacles at higher temperatures. Phase-field simulations reproduce these morphologies, which are closely linked to the anomalous density-temperature profile of liquid water. Boundary layer flows yield pinnacles that sharpen with accelerating growth of tip curvature while scallops emerge from a Kelvin-Helmholtz-like instability caused by counterflowing currents that roll up to form vortex arrays. By linking the molecular-scale effects underlying water's density anomaly to the macroscale flows that imprint the surface, these results show that the morphology of melted ice is a sensitive indicator of ambient temperature.
我们报告了悬浮在冷淡水中并受到融化过程中产生的自然对流影响的冰的形状动力学。实验揭示了随着远场温度升高的形状特征：低温时向下的尖锐尖顶，5°C至7°C之间的中间温度时的扇形波，以及高温时向上的尖顶。相场模拟再现了这些形态，它们与液态水异常的密度-温度分布密切相关。边界层流动产生的尖顶随着尖端曲率加速增长而变尖锐，而扇贝状形态则源于由反向流动形成涡旋阵列的开尔文-亥姆霍兹型不稳定性。通过将水密度异常背后的分子尺度效应与印刻在表面的宏观尺度流动联系起来，这些结果表明融化冰的形态是环境温度的敏感指标。
