棒束通道单相流数值方法应用特性

Application characteristics of single-phase numerical treatments for rod bundle

摘要:

为改善压水堆棒束通道单相流与传热的数值计算效率和精度,在不同工况下对无格架四通道及带交混翼格架的5×5棒束通道模型进行数值模拟．采用高质量壁面函数网格和低雷诺数网格,从传热(Nusselt数)及流动(二次流,湍流强度)两方面对不同湍流模型、近壁面处理和近壁面网格的应用特性进行了综合评估．分析表明,Nusselt数受湍流模型及近壁面处理的影响均较大,二次流和湍流强度则主要受湍流模型的影响．雷诺应力模型(RSM)相比于两方程涡黏模型能更准确地预测无格架通道中的二次流,但在格架下游二者无明显差异．所有模型中只有SST k-ω模型结合不同近壁面网格均表现良好．工程计算中使用SST模型加壁面函数网格的方法能同时保证计算效率和精度,数值研究则推荐采用SST模型加低雷诺数网格．

Abstract:

To improve the efficiency and accuracy of numerical simulation of single-phase flow and heat transfer in Pressurized Water Reactor (PWR) rod bundle, simulations were performed in two computational models of four-subchannel without spacer and 5×5 rod bundle with a mixing vane spacer under different working conditions. The different turbulence models, near-wall treatments and near-wall mesh generation strategies were comprehensively evaluated from two aspects of heat transfer (Nusselt number) and fluid flow (Secondary flow, turbulence intensity) by using high quality wall-function mesh and low-Reynolds-number mesh. Analysis shows that the numerical results of Nusselt number were seriously affected by both of the turbulence model and near-wall treatment, while secondary flow and turbulence intensity were mainly influenced by turbulence model. The Reynolds Stress Model (RSM) could predict the secondary flow field in bare rod bundle better than eddy viscosity models, and there was no significant difference for calculating the secondary flow field downstream of the mixing vane spacer grid. Among all turbulence models, only the SST k-ω model behaved well even combined with different type of near-wall meshes. Using the SST model with wall-function mesh for engineering computation can provide both the efficiency and accuracy of simulation, and the SST model combined with low-Reynolds-number mesh is recommended for numerical research.