5×5棒束CFD模拟计算域和网格标准

Standards for Grid and Zone in Simulation of Flow in 5 × 5 Pins Assembly

采用不可压N-S方程、标准k-ε湍流模型、SIMPLE算法,对某压水堆的两跨距5×5燃料组件的水循环区域流动进行数值分析.对比流道横截面上的压降、速度及其横向分量的相对误差,得到计算域的进出口段长度、网格形式、网格尺寸的选取标准.结果显示：计算域的进口段、出口段长度不宜过短或过长,分别为2.0倍、2.3～2.8倍格架中心距长度;格架区宜采用非结构蜂窝网格,光棒区宜采用结构网格;格架区网格尺寸可取0.3 mm,最大不宜超过0.35 mm,而结构网格横向尺寸可取0.3 mm～0.5 mm,纵向稀疏比应小于1.5为宜.满足上述标准,数值分析能保证较高的可信度,同时保持可接受的计算量.

To obtain reasonable scales and grid requirements of computational zone,water flow in 5 × 5 fuel pins assembly was simulated adopting incompressible N-S equations,standard k-ε turbulent model and SIMPLE algorithm. By comparing pressure drop,velocity and its vertical component at different planes perpendicular to fuel pins,with relative error smaller than 5%,conclusions were obtained. Length of inlet part and outlet part of computational domain should be about 2. 0 times and 2. 3-2. 8 times of space between two spacer. Polyhedral mesh should be adopted and its scale should be smaller than 0. 35 mm in zone between spacer as smooth pin zone adopt structured grid with 0. 3 mm-0. 5 mm dimension.