摘要
反应堆严重事故模拟中涉及大量含有自由界面或组分界面的多相流动,不具有拓扑结构的粒子法在这类流动的模拟中有其独特的优势。本文在移动粒子半隐式(MPS)法的基础上开发了适用于多边形壁面的粒子分裂模型。针对多粒径模拟及多边形壁面的特殊性,对粒子有效半径、数密度、梯度算子模型、拉普拉斯算子模型和表面粒子识别模型等进行改进,并对分裂过程进行简要阐述。将改进后的MPS法运用于无挡板及有挡板的溃坝实验模拟计算。计算结果表明,采用多边形壁面的粒子分裂模型对复杂自由液面捕捉清晰,且计算时间仅为传统MPS法的18.75%,但监测点的压力波动较大。改进后的模型在保证准确性和精度的同时提高了计算效率,为进一步计算三维相变传热奠定基础。
Simulation of severe accident in nuclear reactor involves multiphase flow phenomena containing free surface or component interfaces.The moving particle semi-implicit(MPS)method waiving the topological mesh has been extensively employed for multiphase simulation.However,the uniform-size particle used in the traditional MPS method cannot provide high enough spatial resolution in the region of interest,e.g.,near the phase interfaces,since utilization of uniform-size fine particle significantly raises the computation cost.Meanwhile,a large number of wall particles are utilized to model the wall boundary,which remarkably increases the computation resource.In order to improve the computation efficiency and accuracy,the particle splitting algorithm is implemented along with the polygon wall boundary.Utilization of particle splitting in the specified region refines simulation of flow with complex free surfaces.The polygon wall model eliminates the wall particle.In the model,the wall effect is modelled based on a flat wall scenario where the contribution of the wall to the particle number density is estimated as a function of wall distance.The zero-pressure gradient at the wall is realized with the virtual mirror particles about the wall.In order to facilitate the implementation of particle splitting algorithm and polygon wall model,several basic models of the MPS method were modified,including particle effective radius,particle number density,gradient operator model,Laplace operator model,and free surface identification model.For algorithm verification,the static pressure of water column was simulated with the improved MPS method.The discrepancy between the pressure at the monitoring point and the theoretical value is 6.25%.Then the baffle-free dam-break flow was simulated.The simulation is in good agreement with the experiment,which indicates that the particle splitting algorithm has little effect on the flow pattern.In the simulation of dam-break with baffles,the free surface motion can be replicated with the modified MPS method.The modified method predicts appreciably larger pressure fluctuation range than the traditional MPS method,which should be improved in the future.The splitting model can reduce the computation time by about 55%,while the polygon wall can reduce the computation time by around 62.5%.Combining both of the models,the computation time can be reduced by over 80%.Hence,the particle splitting model together with polygon wall boundary can improve local resolution and computational efficiency in the same time,which solidates a foundation for the particle merging calculation,three-dimensional calculation,and phase change heat transfer calculation.
作者
张静
熊进标
ZHANG Jing;XIONG Jinbiao(School of Nuclear Science and Engineering,Shanghai Jiao Tong University,Shanghai 200240,China)
出处
《原子能科学技术》
EI
CAS
CSCD
北大核心
2022年第6期1138-1146,共9页
Atomic Energy Science and Technology
关键词
移动粒子半隐式法
多边形壁面
粒子分裂
溃坝
moving particle semi-implicit method
polygon wall
particle splitting
dam-break
