5 × 5棒束的直接数值模拟
Towards Direct Numerical Simulation of a 5x5 Rod Bundle
摘要：
棒束流在轻水反应堆和先进反应堆概念的核工程中是普遍存在的。与正则通道流不同，棒束中的流呈现出一些独特的特征，特别是由于不均匀的截面，其可以呈现不同的湍流局部条件以及外部流的局部效应特征。尽管普遍存在的棒束流和几十年的实验和数值知识在这一领域中获得的，有没有公开可用的直接数值模拟（DNS）的多针棒束流与传热。一个多针DNS研究是非常有价值的，因为它将允许在存在热传递的各种湍流模型的可靠性进行评估，以及允许更深入地了解流动物理。我们目前的工作DNS的流动在一个正方形的5x 5棒束代表轻水堆燃料。我们考虑标准配置以及配置的中心销被替换为一个指导顶针。我们在STAR-CCM+中进行模拟以设计数值DNS，这将使用开源谱元素代码Nek 5000进行。还在Nek 5000中进行了大涡模拟，以确认分辨率要求是否充分。我们比较了STAR-CCM+和Nek 5000的结果，在宽间隙中显示出非常好的一致性，在窄间隙中存在较大的差异。特别是，在LES中的边缘子通道中可以看到间隙涡街的证据，但STAR-CCM+没有预测到。
英文摘要：
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, there are no publicly available direct numerical simulations (DNS) of the flow in multiple pin rod bundles with heat transfer. A multiple pin DNS study is of great value as it would allow for assessment of the reliability of various turbulence models in the presence of heat transfer, as well as allow for a deeper understanding of the flow physics. We present work towards DNS of the flow in a square 5x5 rod bundle representative of LWR fuel. We consider standard configurations as well as configurations where the central pin is replaced with a guide thimble. We perform simulations in STAR-CCM+ to design the numerical DNS, which is to be conducted using the open source spectral element code Nek5000. Large Eddy Simulations are also performed in Nek5000 to confirm that the resolution requirements are adequate. We compare results from STAR-CCM+ and Nek5000, which show very good agreement in the wide gaps with larger discrepancies in the narrow gaps. In particular, evidence of a gap vortex street is seen in the edge subchannels in LES but is not predicted by STAR-CCM+.
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