【摘要】 利用发展起来的数值算法模拟了微尺度水滴在冷表面上的撞击冻结过程，采用格子玻尔兹曼通量求解器计算流场，应用相场方法追踪水气界面，基于焓模型确定冰水界面。通过与实验对比水滴在表面上撞击冻结过程中的外形，验证了数值方法的准确性与可靠性。本文研究水滴动态冻结过程时考虑了水滴尺度、撞击速度及冷板温度3个因素的影响。结果表明，水滴底部冻结限制了水滴在表面上铺展后的弹跳过程，可能形成帽子状的形态。水滴撞击速度增加，冰层在水滴径向上发展更快，水滴与表面间的传热增强。另外，温度控制着水滴中心的动力学过程，当表面温度更低，水滴可能会在中心出形成凹坑。通过对水滴内部温度分布情况分析可知，热流密度随着离冷表面距离的增加而降低。随着结冰增长，水滴轴线上逐渐降低的温度与冷表面温度呈非线性关系，表面温度越低，由于温差增加，冰层内部的无量纲温度变得越低。更多还原

【Abstract】 The impact and freezing of micro-sized droplets on cold surface is simulated by the developed numerical methods which couple the multiphase lattice Boltzmann flux solver to simulate the flow field, the phase field method to track the droplet-air interface, and the enthalpy model to determine the liquid-ice interface. The accuracy and reliability of the numerical method are validated by the comparison between the predicted morphology of the droplet impact and freezing on the surface and that from the experiment. The dynamic freezing process is investigated considering the effects of the droplet size, the impact velocity and the temperature of the cold surface. The results show that the freezing of the droplet bottom inhibits the rebound after the droplet spreading, and it may even form a hat-like shape. For the droplet with higher velocity, the ice develops faster in the radial direction and the heat transfer between the droplet and surface is enhanced. In addition, the temperature governs the dynamic behavior of the droplet center. When the surface is colder, it may form a crater in the center. The analysis on the temperature distribution inside the droplet shows that the heat flux decreases with the increasing distance to the cold surface. Moreover, with the ice growing, the decreased temperature in symmetric axis is not proportional to the surface temperature. The dimensionless temperature inside the ice becomes lower for the colder surface due to the increased temperature difference.更多还原