Abstract Natural circulation, which is employed in the design of a small modular reactor, influences the removal of decay heat from the upper header of a pressure vessel under severe accident conditions. This phenomenon has been emphasized for a better understanding of passive safety systems. In this paper, a Reynolds-averaged turbulence model is used to simulate turbulent natural convection in a rectangular enclosure with a curved surface heated from below. The simulation results are first compared with the Direct Numerical Simulation (DNS) of a differential heated cavity obtained from the literature. A good agreement demonstrated the ability of the employed computational fluid dynamics (CFD) approach to predict turbulent natural convection flow and its induced heat transfer. Consequently, the turbulent natural convection formed in a rectangular enclosure heated by a curved surface was investigated. The ensemble average was employed to evaluate the local Nusselt number distribution quantitatively as well as the velocity and temperature distributions. Their dependency was also evaluated based on a systematic CFD simulation that covers a wide range of Rayleigh numbers. Least square regression analysis was employed to propose a correlation to predict the averaged Nusselt number as a function of the Rayleigh number. The influence of the thermal boundary conditions and the discrete heater was also determined.

中文翻译：

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从下方加热的曲面外壳中湍流自然对流的数值模拟

摘要 小型模块化反应堆设计中采用的自然循环会影响严重事故条件下压力容器上部集管的衰变热的去除。强调这种现象是为了更好地理解被动安全系统。在本文中，雷诺平均湍流模型用于模拟具有从下方加热的曲面的矩形外壳中的湍流自然对流。首先将模拟结果与从文献中获得的差动加热腔的直接数值模拟 (DNS) 进行比较。良好的一致性证明了所采用的计算流体动力学 (CFD) 方法预测湍流自然对流及其诱导传热的能力。最后，研究了在由曲面加热的矩形外壳中形成的湍流自然对流。集合平均值用于定量评估局部努塞尔数分布以及速度和温度分布。它们的依赖性还基于涵盖广泛瑞利数的系统 CFD 模拟进行了评估。最小二乘回归分析被用来提出相关性来预测作为瑞利数的函数的平均努塞尔数。还确定了热边界条件和离散加热器的影响。它们的依赖性还基于涵盖广泛瑞利数的系统 CFD 模拟进行了评估。最小二乘回归分析被用来提出相关性来预测作为瑞利数的函数的平均努塞尔数。还确定了热边界条件和离散加热器的影响。它们的依赖性还基于涵盖广泛瑞利数的系统 CFD 模拟进行了评估。最小二乘回归分析被用来提出相关性来预测作为瑞利数的函数的平均努塞尔数。还确定了热边界条件和离散加热器的影响。