Numerical Simulation Study of Droplet Impact Process on Free Liquid Surface
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摘要: 稳压器的雾化和喷淋对核动力设备的安全运行有着十分重要的作用。研究喷淋液滴撞击稳压器自由液面的过程可以从单个液滴撞击液面入手，揭示其基本规律和现象，从而为稳压器喷淋中液滴连续撞击液面的研究提供理论基础。对基于Fluent的DPM-to-VOF（DTV）方法进行了数值模拟和分析。通过流体体积分数方法（VOF）验证了DTV方法的准确性，系统研究了不同直径和不同初速度液滴对液坑和液柱主要尺寸的影响规律，并详细揭示了液面波动的演变过程，对液膜波动细节进行了精确捕捉。研究表明，增大液滴直径或增加液滴速度会加剧液面的干扰，导致液坑尺寸增大、液柱高度增加，可能产生一次液滴和二次液滴；同时，对不同工况下的流动分布情况进行了综合分析，发现在大韦伯数（We） 和小弗劳德数（Fr）区域，液面干扰较为显著，定量分析了HK/d0、LK/d0和HZ/d0随We和Fr的变化规律，为理解和优化稳压器喷淋过程提供了重要的理论基础。
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关键词:
- DPM-TO-VOF(DTV) /
- 液滴撞击 /
- 液坑液柱演变 /
- 液面波动
Abstract: Atomization and spraying of pressurizer are crucial for safely operation of nuclear power equipment. Study on the process of spray droplets impacting the free surface of the pressurizer can start from the impact of single droplet on the liquid surface, revealing fundamental patterns and phenomena. This provides a theoretical foundation for study on the continuous impact of droplets on the liquid surface during pressurizer spraying. Numerical simulations and analyses were conducted using Fluent's DPM-to-VOF (DTV) method. The accuracy of the DTV method was validated using the Volume of FluiD (VOF) approach. The study systematically investigated the influence of droplet diameter and initial velocity on the main dimensions of liquid pits and columns. It comprehensively revealed evolution process of liquid surface fluctuation, accurately captured details of liquid film fluctuation. Results indicate that increasing droplet diameter or velocity intensifies surface disturbances, resulting in larger pit sizes, taller columns, and potential occurrences of primary and secondary droplets. In addition, a comprehensive analysis of flow distributions under various conditions revealed significant surface disturbances in regions of high Weber and low Froude numbers. Quantitative analyses of $ H_{\mathrm{K}}/d_0 $, $ L\mathrm{_K}/d_0 $, and $ H\mathrm{_Z}/d_0 $ variations with $ We $ and $ Fr $ provide an improtant theoretical basis for understanding and optimizing pressurizer spraying process. -
图 2 DTV方法模拟撞击过程液滴演变过程
Figure 2. Evolution Process of Droplets during Simulated Impacts by the DTV Method
图 3 DTV方法和VOF方法模拟结果比较
X—验证模型纵截面的横坐标；H—液膜位置，其中H=0为液面的初始位置。
Figure 3. Comparison of DTV and VOF Simulation Results
图 4 液滴坍塌开始时DTV方法和VOF方法的差异
Figure 4. Difference between the DTV and VOF at the Onset of Droplet Collapse
图 8 不同直径液滴撞击液膜演变的图像
Figure 8. Evolution Images of Droplets of Different Diameters Impacting the Liquid Film
图 10 不同速度液滴撞击液膜演变的图像
Figure 10. Evolution Images of Droplets of Different Velocities Impacting the Liquid Film
图 11 液滴撞击的流动分类图像
图中方块颜色代表液面流动形态；方块中数字黑色代表We、蓝色代表Fr。
Figure 11. Flow Classification Images of Droplet Impacts
图 12 监测点纵坐标h随时间的变化曲线
Figure 12. Variation Curve of the Vertical Coordinates at the Monitoring Points with Time
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