一种稳定性增强及高精度数值方法在RELAP5中的实现与评价  

Implementation and assessment of a stability-enhancing and high-resolution numerical scheme in RELAP5

作　　者：李伟[1] 苏光辉[2] 秋穗正[2] 田文喜[2] 陈平[1] 李垣明[1] 

机构地区：[1]中国核动力研究设计院核反应堆系统设计技术重点实验室,成都610213 [2]西安交通大学核科学与技术学院,西安710049

出　　处：《核技术》2016年第11期67-73,共7页Nuclear Techniques

摘　　要：在计算稳定性的改进方面,修正RELAP5程序中的虚拟质量力(Virtual mass force)形式,同时添加了新的界面压力项(Interface pressure);在计算精度的改进方面,采用具有总变差减小(Total variation diminish,TVD)特点的高精度通量限制器(Flux limiter)方法取代RELAP5程序原本的一阶迎风方法来离散质量和能量守恒方程中的对流项。在模拟水平管道内空泡份额微扰随时间发展的数值实验中,相比改进前的RELAP5,改进后的RELAP5计算得到的微扰幅度并未增长;在模拟液相沉降的数值实验中,改进前的RELAP5程序计算得到了不真实的空泡份额分布,而改进后的RELAP5在不同的网格数量下能够得到收敛的稳定解。对Ransom水龙头数值实验和Marviken CFT 15大破口喷放实验的计算表明,改进后的具有二阶TVD格式的RELAP5程序能够得到更接近实验数据的计算结果。Background： RELAP5 has been widely used in the field of nuclear thermal-hydraulics and safety analysis. However, improvement issues in terms of numerical stability and accuracy exist due to its basic single-pressure two-fluid model. Purpose： This study aims to enhance the numerical stability and numerical accuracy of RELAP5 by modifying the mathematical structure of RELAP5 basic model. Methods： Firstly, the default mathematical expression of the virtual mass force was modified in the RELAP5 code. Secondly, an interface pressure term was incorporated in the code, and a total variation diminish （TVD）-type flux limiter method was implemented in the RELAP5 code in place of the default lst-order upwind scheme for the convective terms in mass and energy conversation equations. Results： In a numerical test where the evolvements of void fraction perturbation were concerned, the modified RELAP5 predicted no growth of the perturbation amplitude in contrast to a rapidly developing divergence for the default RELAP5. In addition, for the phase segmentation problem, convergence was accomplished on finer mesh by the modified RELAP5, while non-physical distribution of the void fraction was rendered by the default RELAP5 especially for finer mesh. When applied to the Ransom water faucet numerical test and Marviken CFT 15 experiments, the improved RELAP5 with 2nd-order of accuracy was more reliable in that thepredictions were closer to the experimental results. Conclusion： Compared with the original RELAP5, the modified or improved RELAP5 showed evident numerical stability and accuracy during the assessment in this work.

关 键 词：RELAP5 稳定性 精确性 双曲性 虚拟质量力 界面压力项 

分 类 号：TL33[核科学技术—核技术及应用]