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Ostwald熟化~(ripening)是指局部热力学平衡状态下, 颗粒/液滴/汽泡系统为了减小界面能, 而自发地进行颗粒群尺度分布调整的过程, 具有重要研究价值. 针对目前数值模拟手段缺乏的现状, 本文采用格子Boltzmann方法, 对相变速率主控的二维蒸汽泡系统演化开展了数值模拟研究. 模拟结果与本文所推导的二维汽泡群演化标度律吻合较好, 证实了格子Boltzmann方法对复杂相变-物质输运过程捕捉的准确性. 研究同时表明, 蒸汽泡系统演化过程中物质输运为液相压力不平衡所驱动, 并且在小汽泡``溃灭''过程中水动力学作用会影响汽泡群半径分布函数的局部细节; 汽--液状态方程参数对熟化过程的影响效果分析显示, 汽液两相比内能差是驱动相变的核心要素, 此差异越大相变速率越快---该结论进一步诠释了化学势驱动熟化过程的物理图像.
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关键词:
- Ostwald熟化 /
- 格子Boltzmann方法 /
- 相变 /
- LSW理论
Ostwald ripening refers to a process of a particle/droplet/bubble system under thermal equilibrium state adjusting the size distribution spontaneously to reduce the total surface energy. With knowing lack in numerical studies, a lattice Boltzmann approach is used to simulate the ripening process of two dimensional vapour bubble cluster dominated by phase transition kinetics. By comparing the numerical results with the theoretical prediction derived in two dimensional space, it is shown that the lattice Boltzmann method is accurate in the simulations. The results also indicate that the mass transfer in liquid phase is driven by hydrodynamic pressure distribution and the hydrodynamic collapse of bubbles influences the size distribution function in small size region. The impact of the parameters of the equation of state of the material is studied further. A positive relation between phase transition speed and specific internal energy is proposed, which enhances the thermal fundamental of phase transition.-
Keywords:
- Ostwald ripening /
- lattice Boltzmann method /
- phase transition /
- LSW theory
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