Abstract Melt drop collision is an important phenomenon in the circumstance of pressure wave propagation during fuel–coolant interaction (FCI). The deformation and fragmentation of melt drops can increase the contact area with coolant, and as a result will affect the heat transfer and melt oxidation. In this study, a numerical model was established by considering surface tension and validated with the experimental results that were obtained from water droplet collision in gaseous environment. Then, the head-on collision of two UO2 melt drops in water pool was investigated at different Weber numbers, and the melt morphology, contact area, and the number and size distribution of children droplets were analyzed. The results show that interfacial waves and wrinkles could be clearly observed on the melt film, and the finger structures presented at the rim of melt film and finally separated into children melt droplets. The increase of fuel–coolant contact area could be divided into the inducements by deformation and fragmentation. The melt deformation only had influence to the area increase at intermediate process but no effect to that at steady state. By contrast, the final fuel–coolant contact area was determined by the intensity of melt fragmentation. The size distribution of melt children droplets was like an off-centered normal distribution, where the maximum number of children droplets existed in the size range of 0.03

中文翻译：

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核反应堆严重事故FCI熔滴碰撞及水力碎裂数值研究

摘要 熔滴碰撞是燃料-冷却剂相互作用（FCI）过程中压力波传播环境中的一种重要现象。熔滴的变形和碎裂会增加与冷却剂的接触面积，从而影响传热和熔体氧化。在这项研究中，通过考虑表面张力建立了数值模型，并通过气态环境中水滴碰撞的实验结果进行了验证。然后，研究了不同韦伯数下两个UO2熔体液滴在水池中的正面碰撞，分析了熔体形态、接触面积以及子液滴的数量和尺寸分布。结果表明，在熔膜上可以清楚地观察到界面波和皱纹，指状结构出现在熔膜边缘，最后分离成儿童熔滴。燃料-冷却剂接触面积的增加可分为变形和破碎的诱因。熔体变形只对中间过程的面积增加有影响，而对稳态时的面积增加没有影响。相比之下，最终的燃料-冷却剂接触面积由熔体破碎的强度决定。熔融儿童液滴的尺寸分布类似于偏心正态分布，其中儿童液滴的最大数量存在于0.03的尺寸范围内 熔体变形只对中间过程的面积增加有影响，而对稳态时的面积增加没有影响。相比之下，最终的燃料-冷却剂接触面积由熔体破碎的强度决定。熔融儿童液滴的尺寸分布类似于偏心正态分布，其中儿童液滴的最大数量存在于0.03的尺寸范围内 熔体变形只对中间过程的面积增加有影响，而对稳态时的面积增加没有影响。相比之下，最终的燃料-冷却剂接触面积由熔体破碎的强度决定。熔融儿童液滴的尺寸分布类似于偏心正态分布，其中儿童液滴的最大数量存在于0.03的尺寸范围内