Rod bundle flows are prevalent in nuclear engineering for both light water reactors (LWR) and advanced reactor concepts. Unlike canonical channel flow, the flow in rod bundles presents some unique characteristics, notably due to the inhomogeneous cross section which can present different local conditions of turbulence as well as localized effects characteristic of external flows. Despite the ubiquity of rod-bundle flows and the decades of experimental and numerical knowledge acquired in this field, high-fidelity datasets of multiple-pin configurations are still relatively sparse due to the computational cost involved in generating them at relevant Reynolds numbers. These datasets are of great value as they allow for assessment of the reliability of various turbulence models, as well as allow for a deeper understanding of the flow physics. We present Large Eddy Simulations (LES) of the flow at Reynolds number 19,000 in a square 5 × 5 rod bundle representative of LWR fuel generated by the flow solver Nek5000. We consider standard configurations as well as configurations where the central pin is replaced with a control rod guide thimble, and analyze the flow fields in detail. The accuracy of the LES of the base 5 × 5 configuration is established by comparing against Direct Numerical Simulation (DNS) results. We compare the LES results from Nek5000 with an advanced Reynolds Stress model from STAR-CCM+, which shows good agreement in the wide gaps with larger discrepancies in the narrow gaps. In particular, evidence of gap vortex streets and changes in the turbulence structure are seen in the edge subchannels and in the narrow thimble gaps in LES, but are not predicted by STAR-CCM+.

棒束流在轻水反应堆 (LWR) 和先进反应堆概念的核工程中很普遍。与经典通道流不同，棒束中的流动具有一些独特的特征，特别是由于不均匀的横截面可以呈现不同的局部湍流条件以及外部流动的局部效应特征。尽管棒束流无处不在，并且在该领域获得了数十年的实验和数值知识，但由于在相关雷诺数下生成它们所涉及的计算成本，多针配置的高保真数据集仍然相对稀疏。这些数据集非常有价值，因为它们允许评估各种湍流模型的可靠性，并允许更深入地了解流动物理。我们在代表由流动求解器 Nek5000 生成的 LWR 燃料的方形 5 × 5 棒束中呈现雷诺数为 19,000 的流动的大涡模拟 (LES)。我们考虑标准配置以及中心销替换为控制杆导向套管的配置，并详细分析流场。基本 5 × 5 配置的 LES 精度是通过与直接数值模拟 (DNS) 结果进行比较来确定的。我们将来自 Nek5000 的 LES 结果与来自 STAR-CCM+ 的高级雷诺应力模型进行比较，该模型在宽间隙中表现出良好的一致性，在窄间隙中具有较大的差异。特别是，在边缘子通道和 LES 的狭窄顶针间隙中可以看到间隙涡街和湍流结构变化的证据，但 STAR-CCM+ 没有预测到。