Luo Shuang, Wang Jun, Li Zhigang
Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon 999077, Hong Kong.
Key Laboratory of Enhanced Heat Transfer and Energy Conservation, Ministry of Education, College of Environmental and Energy Engineering, Beijing University of Technology, Beijing 100124, P.R. China.
J Phys Chem B. 2020 May 7;124(18):3701-3708. doi: 10.1021/acs.jpcb.9b11209. Epub 2020 Mar 26.
Homogeneous ice nucleation involving a water flow is subject to shear, which may greatly affect the ice nucleation rate. In this work, we investigate the homogeneous ice nucleation rate under shear through molecular dynamics simulations. It is found that the ice nucleation rate changes nonlinearly with varying shear rates and reaches a maximum at an intermediate shear rate. Such a behavior is determined by two distinct effects of shear rates. On the one hand, shear increases the free energy barrier for the nucleation, which hinders the ice nucleation. On the other hand, shear enhances the diffusion of water molecules, assists the adsorption of water molecules on the ice nucleus, and consequently promotes the growth of ice nucleus. The latter effect dominates at low shear rates, while the former effect becomes significant at high shear rates. The competition between these two effects leads to a non-monotonic dependence of the ice nucleation rate on the shear rate.
涉及水流的均匀冰核形成会受到剪切力影响，这可能极大地影响冰核形成速率。在这项工作中，我们通过分子动力学模拟研究了剪切力作用下的均匀冰核形成速率。研究发现，冰核形成速率随剪切速率变化呈非线性变化，并在中间剪切速率下达到最大值。这种行为由剪切速率的两种不同效应决定。一方面，剪切增加了成核的自由能垒，阻碍了冰核形成。另一方面，剪切增强了水分子的扩散，有助于水分子在冰核上的吸附，从而促进冰核的生长。后一种效应在低剪切速率下占主导，而前一种效应在高剪切速率下变得显著。这两种效应之间的竞争导致冰核形成速率对剪切速率呈现非单调依赖性。
