基于一维漂移流模型的并联矩形双通道密度波流动不稳定性数值模拟

Numerical Simulation on Density Wave Oscillation in Parallel Twin Rectangular Channels Based on One-dimensional Drift Flux Model

基于一维漂移流模型构建了并联矩形双通道密度波流动不稳定性数学模型。模型中采用Zuber推荐的经验关系式计算两相流体空泡份额,采用Chisholm关系式和中国核动力研究设计院自拟关系式计算两相流体的摩擦压降。求解过程中将质量方程、能量方程与动量方程解耦,并在计算域内沿流动方向依次求解方程组。计算过程中,首先开展稳态计算,在稳态解的基础上,通过添加流量或功率扰动,诱发流体周期性振荡,通过辨识瞬态计算中得到的流量振荡模式来获得流动不稳定边界。采用数值计算获得的密度波脉动图像与实验中观察到的密度波脉动现象的特征基本一致。最后,针对16组典型实验工况开展数值模拟,结果表明,大部分工况下计算不稳定界限热流密度与实验值的相对偏差小于±20%。

A mathematical model was proposed for the density wave oscillation in parallel twin rectangular channels based on one-dimensional drift flux model in this paper.In the model,an empirical correlation recommended by Zuber was applied to calculate the void fraction of two-phase flow.Chisholm correlation and the correlation developed by NPIC were used for the prediction of the frictional pressure drop of two-phase flow.During the process of solving,mass,momentum and energy balance equations were decoupled and solved along the flow direction successively in the whole computational domain.The steady state calculation was made at first,then the periodical oscillation of flow was induced by adding small flow rate or heating power disturbance to the steady state solution.The flow instability boundary can be obtained by checking the oscillation mode in transient calculation.The calculation results indicate that the flow oscillationsobtained through simulation have the same characteristics as those observed in the experiment.At last,the simulation were made for sixteen typical cases chosen from the experiment,and the results indicate that the relative differences between the calculated flow instability boundary heat flux and the corresponding experimental data are no more than ±20%for most part of cases.