稠密栅元棒束内流动行为的CFD数值模拟

Flow Behavior Analysis in Tight Lattice Rod Bundle Using CFD Method

国内针对稠密栅元组件内流体的流动和传热特征展了大量的实验研究,但目前仍缺乏对稠密栅元通道内冷却剂流动特性的全面认识。本文对矩形和三角形稠密栅元通道内的空气湍流流动进行了数值研究。结合实验数据,系统地验证了涡粘性和雷诺应力两类湍流模型模拟稠密栅元内流动特征的适用范围。结果表明:SSG雷诺应力模型对流动有较好的模拟,但在棒壁窄缝处的计算结果与实验数据存在较大的差距;在y+<20时,SSG模型对近壁面区域网格的疏密不敏感;在y+较小时,二阶ω模型出现数值震荡。

Tight lattice rod bundles have been applied to reactors due to Its high conversion ratio, However, there still exists big deficiency in understanding of the coolant flow characteristics inside the sub-channels of tight lattices. This paper investigates the turbulence air flow behavior inside both square and triangular tight lattice. The validity of both eddy viscosity models and Reynolds stress models is assessed by comparing computational results with experimental data. The results show a reasonable prediction of the numerical analysis using the Reynolds stress model SSG, except for the flow behavior in the gap region between the rod and the wall. The SSG model is not sensitive to the mesh structure, in the case the size of the near wall meshes satisfies y^＋〈 20, while the secondary moment closure ω model shows numerical oscillation with fine mesh sizes.