Abstract In the present work, different closure relations in the one-dimensional Two-Fluid Model were investigated in order to assess the effect on the numerical simulation of vertical annular flows, including the formation and propagation of waves at the gas-liquid interface. Different interfacial friction formulations, momentum flux parameters and dynamic pressure terms were employed. The conservation equations were discretized and solved within the finite volume framework, with a first order time discretization, a second order TVD and first order Upwind schemes for the convective term. A rigorous mesh sensitivity analysis was performed, showing the advantages and shortcomings of each discretization scheme, as well as the impact of closure formulations and their importance for better physical representativeness and well-posedness. Flow and wave parameters were obtained with the different approaches for various test cases taken from the literature. A sensitivity analysis was performed with varying momentum flux parameter values, interfacial friction factors and dynamic pressure expressions. Liquid film thickness, pressure-drop and wave characteristics results were systematically compared to experimental data. Predictions for pressure gradient and mean liquid holdup with the best set of closures presented an average error of 9% and 22%. Comparison of the wave characteristics, given by the group speed and frequency with available measured values has shown that the model is capable to simulate the qualitative features of wave formation and propagation in vertical annular flow with a reasonable quantitative agreement, given the complexity of the physical phenomena involved. However, while it has been shown through the sensitivity analysis that the closure relations investigated here have an important effect on quantities of interest in annular flows, in particular that a momentum flux parameter value larger than unit seems beneficial, further investigations are suggested for a wider range of conditions, providing a robust physical support for the generalization of the closure model formulations.

中文翻译：

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用双流体模型评估垂直环流数值预测的闭合关系

摘要 在目前的工作中，研究了一维二维流体模型中的不同闭合关系，以评估对垂直环形流数值模拟的影响，包括气液界面波的形成和传播。采用了不同的界面摩擦公式、动量通量参数和动态压力项。在有限体积框架内对守恒方程进行离散化和求解，对流项采用一阶时间离散化、二阶 TVD 和一阶迎风方案。进行了严格的网格敏感性分析，显示了每个离散化方案的优点和缺点，以及闭合公式的影响及其对更好的物理代表性和适定性的重要性。流动和波浪参数是通过从文献中提取的各种测试案例的不同方法获得的。使用不同的动量通量参数值、界面摩擦系数和动态压力表达式进行敏感性分析。液膜厚度、压降和波特性结果与实验数据进行了系统比较。使用最佳封闭装置对压力梯度和平均液体滞留量的预测呈现出 9% 和 22% 的平均误差。由群速度和频率给出的波浪特征与可用测量值的比较表明，考虑到物理的复杂性，该模型能够以合理的定量一致性模拟垂直环形流中波浪形成和传播的定性特征。涉及的现象。