Natural circulation is exploited in nuclear systems to passively remove power in case of accident scenarios. In this regard, the DYNASTY experimental facility at Politecnico di Milano has been setup to increase the knowledge on single-phase, buoyancy-driven systems in the presence of distributed heating. In this paper, the development of a computational fluid dynamics (CFD) model of DYNASTY is presented, focusing on the capability of CFD to assess the dynamic behavior of the facility. The large eddy simulation (LES) model takes into account both the fluid and the solid regions, with heat generation and 3D heat conduction resolved in the pipe walls. The study, conducted using OpenFOAM, shows (i) the capability of reproducing stable and unstable transients of DYNASTY, (ii) new observations on the features of flow reversals during unstable transients, (iii) the suitability and the advantages of LES for the prediction of the specific features of natural circulation systems.

在发生事故的情况下，核系统中利用自然循环来被动地切断电源。在这方面，米兰理工大学的DYNASTY实验设施已经建立，以在存在分布式供热的情况下增加对单相浮力驱动系统的了解。本文介绍了DYNASTY的计算流体动力学（CFD）模型的开发，重点是CFD评估设施动态行为的能力。大涡模拟（LES）模型同时考虑了流体和固体区域，并在管壁中解决了热量生成和3D导热问题。使用OpenFOAM进行的这项研究显示了（i）再现DYNASTY的稳定和不稳定瞬变的能力，（ii）关于不稳定瞬变期间流量逆转特征的新观察，