初边值条件对二维通道内降膜流动行为影响的数值分析

Numerical analysis of the falling film flow behavior in the two-dimensional channel under different initial and boundary conditions

在压水堆核电站中,非能动安全壳冷却系统是比较重要的事故缓解措施,其中对水膜流动行为的研究至关重要。目前这些研究较少关注液膜波动现象,也很少考虑空气和水膜界面的剪切力。因此,采用Fluent VOF和k-ε模型对二维矩形通道内单侧水膜流动行为进行数值模拟,并考虑空气和水膜两相交界面的剪切力作用,讨论了液膜入口速度分布、液膜入口宽度、空气入口速度、液膜入口雷诺数以及空气流动方向等因素对液膜厚度沿流动方向变化的影响。模拟研究表明:液膜入口宽度,气体流动方向对液膜表面波动有影响,该表面波动现象与气液两相间的速度差有关,速度差越大,波动越大。在某些条件下,当前的数值模型可再现降膜流动的波动现象。

In the pressurized water reactor nuclear power plant,the passive containment cooling system is an important accident mitigation measure,and the research on the water film flow behavior is very important.At present,the liquid film fluctuation and the shear force at the interface between air and water film are rarely considered.Therefore,the VOF and k-εmodels of Fluent code are used in present study to simulate the flow behavior of unilateral water film in a twodimensional rectangular channel,considering the interface shear force.The influence of liquid film inlet width,air inlet velocity,liquid film inlet Reynolds number and air flow direction on the change of liquid film thickness along the flow direction is discussed.The simulation results show that the liquid film inlet width and the direction of gas flow have an effect on the phenomenon of liquid film surface fluctuation,and this phenomenon is related to the velocity difference between the gas and liquid phases.The larger the velocity difference is,the larger the fluctuation is.Under certain conditions,the current numerical model can reproduce fluctuations in falling film flow.