竖壁降膜波动特性数值模拟研究

Numerical simulation for laminar wave characteristics of falling film flow

建立了竖直壁面降膜流动的二维几何模型,运用VOF方法对雷诺数200~1 000的降膜的波动特性进行了数值模拟。研究了液膜的波动特征、液膜流动方向的速度变化以及液体雷诺数对液膜波动的影响规律。结果表明:根据液膜的形态可以将流动区域分为入口区、发展区和稳定区三部分。入口区的液膜相对比较平滑,发展区的液膜表现为频率较高的小幅波动,稳定区的液膜波动幅度增加而频率减小;入口区的最大流速大于初始流速,发展区的最大流速在初始流速上下波动,而稳定区流速小于初始流速;随着液体雷诺数的增加,液膜厚度增加而波幅降低。

A physical model of falling film flow on two-dimensional vertical wall is established,and the laminar wave characteristics of falling film that the Reynolds number ranges from 200 to 1000 is simulated with the VOF method.The fluctuation characteristics of falling film,velocity change in the direction of flow and the influence of Reynolds number are studied.The results show that the flow region can be divided into three parts according to the shape of the falling film:entrance area,development area and stability area.The shape of the liquid film in the entrance area is relatively smooth,the liquid film in the development area starts to show small amplitude fluctuation with high frequency,and the fluctuation amplitude increases in the stable area while the fluctuation frequency decreases.The maximum velocity in the entrance area is greater than the initial velocity,the maximum velocity in the development area fluctuates across the initial velocity,and the velocity in the stability area is completely less than the initial velocity.With the increase of Reynolds number,the liquid film thickness increases and the fluctuation amplitude decreases.