Abstract Prediction and analysis of coolant flow and mixing problems in the reactor pressure vessel (RPV) are some of the most critical studies to ensure system safety and balance of nuclear power plant. The flow mixing problem in the reactor primary system with complicated interior structure is a large domain three-dimensional problem. In this paper, we investigated the performance of utilizing multiple RANS models (MRANS) coupling method in the computational fluid dynamics (CFD) code ANSYS FLUENT to study flow mixing. Based on the domain decomposition technique, the 2-equation and 7-equation RANS models were coupled and applied to simulate the flow mixing phenomenon in the Rossendorf Coolant Mixing Model (ROCOM) test facility. First, a CFD model of ROCOM was developed, and the explicit domain decomposition coupling simulation was achieved with a user-defined Python control program. To ensure the best CFD model was utilized, three different turbulence models and varying resolution grids were used for turbulence model feasibility analysis and grid sensitivity testing. Then the applicability of MRANS coupling method was evaluated by comparing the results from the MRANS simulations with those obtained from flow mixing experiments. In addition, single and MRANS model simulation results were compared. Results show good agreements between the MRANS coupling simulations and the experimental data. Compared with overall simulations by single RANS models, the MRANS coupling method also have superior performance in accuracy and efficiency for the CFD simulation study of mixing phenomena in the reactor primary coolant system.

中文翻译：

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多RANS模型耦合模拟流动混合实验研究

摘要 反应堆压力容器（RPV）中冷却剂流动和混合问题的预测和分析是确保核电厂系统安全和平衡的最关键的研究之一。内部结构复杂的反应器主系统中的流动混合问题是一个大域三维问题。在本文中，我们研究了在计算流体动力学 (CFD) 代码 ANSYS FLUENT 中利用多 RANS 模型 (MRANS) 耦合方法研究流动混合的性能。基于域分解技术，将 2 方程和 7 方程 RANS 模型耦合并应用于模拟罗森多夫冷却剂混合模型 (ROCOM) 测试设施中的流动混合现象。首先，开发了ROCOM的CFD模型，并通过用户定义的 Python 控制程序实现了显式域分解耦合模拟。为确保使用最佳 CFD 模型，三种不同的湍流模型和不同分辨率的网格用于湍流模型可行性分析和网格敏感性测试。然后通过比较 MRANS 模拟的结果与流动混合实验获得的结果来评估 MRANS 耦合方法的适用性。此外，还比较了单一模型和 MRANS 模型的仿真结果。结果表明 MRANS 耦合模拟与实验数据之间具有良好的一致性。与单个 RANS 模型的整体模拟相比，