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首页> 外文期刊>International Journal of Heat and Mass Transfer >Numerical stability analyses of upward flow of supercritical water in a vertical pipe
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Numerical stability analyses of upward flow of supercritical water in a vertical pipe

机译：竖管中超临界水向上流动的数值稳定性分析

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摘要

A numerical study is performed for 2-D axisymmetric turbulent flow of supercritical water flowing upward in a vertical pipe with constant applied wall heat flux. This study uses Computational Fluid Dynamics (CFD) to analyze supercritical flow instability in a vertical heated channel. The governing equations are solved using two RANS models in the CFD code ANSYS CFX v14.5. Analyses of static and oscillatory flow instabilities are performed using the standard k-ε model with a scalable wall-function and the k-ω-based SST model. The instability threshold results of the CFD code are compared with 1-D non-linear code predictions. Also, criteria for approximating the thresholds of static and oscillatory instabilities based on steady-state results are assessed and discussed. The effect of changing the turbulent Prandtl number (Pr_t) on the instability threshold is also examined. It was observed that the instability threshold results obtained using the k-ε and the SST models are similar. Also, the results of the CFD and 1-D codes are different due mainly to the different pressure drop predictions between the two methodologies. Comparisons of instability threshold predictions between CFD and 1-D codes showed smaller differences for static instabilities and greater differences for oscillatory instabilities. In addition, approximating the flow instability threshold by the criteria proposed generally holds true for a CFD solution. Results also indicate that the value of Pr_t does not have a noticeable effect on the instability threshold for the cases examined in the present study.
机译：对在恒定壁热通量下垂直管道中向上流动的超临界水的二维轴对称湍流进行了数值研究。这项研究使用计算流体动力学（CFD）分析垂直加热通道中的超临界流动不稳定性。控制方程使用CFD代码ANSYS CFX v14.5中的两个RANS模型求解。使用具有可扩展壁函数的标准k-ε模型和基于k-ω的SST模型，进行静态和振荡流动不稳定性的分析。将CFD代码的不稳定性阈值结果与一维非线性代码预测进行比较。同样，评估和讨论了基于稳态结果近似静态和振荡不稳定性阈值的标准。还检查了湍流普朗特数（Pr_t）对不稳定性阈值的影响。观察到，使用k-ε和SST模型获得的不稳定性阈值结果相似。同样，CFD和一维代码的结果也不同，这主要是由于两种方法之间的压降预测不同。 CFD和一维代码之间的不稳定性阈值预测比较表明，静态不稳定性差异较小，而振荡不稳定性差异较大。此外，对于CFD解决方案，按建议的标准近似流动不稳定性阈值通常适用。结果还表明，对于本研究中检查的病例，Pr_t的值对不稳定性阈值没有显着影响。

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