自然循环中冷凝液滴自由表面识别的改进

自然循环过冷沸腾过程是第3代核电站非能动安全性的基础，该过程中冷凝液滴的传热计算对核电站的安全性具有重要意义。本研究采用移动粒子半隐式（MPS）方法对该过程进行模拟。为了对该过程中冷凝液滴传热传质界面的识别进行改进和优化，提出一种基于全局扫描的自由表面识别方案，将该方案以及其他3种典型的自由表面识别方案应用于冷凝液滴撞击液面问题。结果表明：采用粒子数密度法的自由表面识别方案、采用法向量扫描的自由表面识别方案和采用弧度法的自由表面识别方案皆因其方法本身的缺陷而无法精确地对液滴自由表面进行识别；而采用全局扫描的自由表面识别方案，能克服上述方法的缺陷，准确地对自由表面粒子进行识别，且其求解得到的压力场与物理实际最为接近。这种新型的基于全局扫描的自由表面识别方案为今后计算冷凝液滴交界面处传热传质问题打下了良好的基础。

Improvement of Free-surface Detection Method of Condensate Droplet in Natural Circulation

Subcooled boiling process in natural circulation is the basis of safety of third generation nuclear power plant. Moving particle semi-implicit method was employed to simulate this process. In order to improve the surface detection method of condensate droplet, a new global scanning free-surface detection method was proposed. This new free-surface detection method and other typical free-surface detection methods were applied to the simulation of condensate drop impact on wet surface. The results demonstrate that the free-surface detection method based on particle number density, the free-surface detection method based on normal vector and the free-surface detection method based on arc method lead to mislabeled boundary particles due to their defects. The new free-surface detection method overcomes the above defects and detects the free-surface particles accurately. At the same time, the pressure distribution calculated by this new free-surface particles detection method is more close to the physical result. This new free-surface particles detection method has important implications for interfacial heat and mass transfer calculation of condensate droplet.