﻿ 初边值条件对二维通道内降膜流动行为影响的数值分析
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 应用科技  2020, Vol. 47 Issue (2): 85-92  DOI: 10.11991/yykj.201905008 0

### 引用本文

DU Kashuai, HU Po, HU Zhen, et al. Numerical analysis of the falling film flow behavior in the two-dimensional channel under different initial and boundary conditions[J]. Applied Science and Technology, 2020, 47(2): 85-92. DOI: 10.11991/yykj.201905008.

### 文章历史

Numerical analysis of the falling film flow behavior in the two-dimensional channel under different initial and boundary conditions
DU Kashuai, HU Po, HU Zhen, ZHAI Shuwei
School of Nuclear Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
Abstract: 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-ε models of Fluent code are used in present study to simulate the flow behavior of unilateral water film in a two-dimensional 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.
Keywords: two-dimensional channel    falling film flow    the shear force at the interface between air and water film    the surface fluctuation of liquid film    initial and boundary condition    liquid film thickness    numerical analysis    user-defined function (UDF)

1 模型及求解方法 1.1 物理对象描述

 $\delta = {(0.75)^{{1 / 3}}}{({{{\nu ^2}} / g})^{{1 / 3}}}R{e^{{1 / 3}}}$ (1)

1.2 数值求解

 ${\tau _i}{\rm{ = }}0.5f{\rho _{\rm{g}}}u_{\rm{g}}^2$ (2)

 $f = 0.005(1 + 300{\delta / {{D_h}}})$
 $f{\rm{ = }}0.079R{e_{\rm{g}}}^{ - 0.25}\left[ {1 + 115{{\left( {{\delta ^*}} \right)}^N}} \right]$

 ${U_{\rm{l}}} = \frac{{g{\delta ^2}}}{\nu }\left[ {\frac{x}{\delta } - \frac{1}{2}{{\left( {\frac{x}{\delta }} \right)}^2}} \right] + \frac{{{\tau _{\rm{i}}}}}{\mu }x$ (3)

 $\overline \delta {\rm{ = }}\frac{1}{n}\sum\limits_{i{\rm{ = }}1}^n {{\delta _i}}$ (4)

1.3 网格无关性分析及数值模型验证

2 模拟结果与分析 2.1 入口速度分布影响

2.2 液膜入口宽度的影响

2.3 空气入口流速及液膜入口雷诺数的影响

2.4 气体流动方向的影响

3 结论

1）速度分布对液膜厚度沿流动方向的影响主要是通过液膜入口质量流量变化来反映的。对于瞬态流动模拟来说，可用入口准对数速度分布来减少常规均匀分布中流动发展所需的模拟时间。当入口质量流量比较小时，速度分布的影响可以忽略。随着液膜入口流量增加，准对数分布条件下的液膜波动现象比均匀分布条件下显著。

2）液膜在较大的入口宽度下呈现出向壁面法向上的堆积，使液膜增厚，所受黏性力增大；而在较小的入口宽度下表现出沿通道长度方向上的铺展流动，液膜减薄，流速加快，导致液面波动增强。

3）在空气和水膜并流流动条件下，液膜表面波动现象跟气液两相间的速度差有关，两相间速度差越大，液膜表面波动越剧烈。在液膜入口速度分布为对数分布和准对数分布条件下，气液波动界面剪切力作用引起液膜入口质量流量的增加对平均液膜厚度的影响较大。

4）气体流动方向对液膜厚度沿流动方向的变化趋势影响较大。在并流条件下，重力和界面剪切力合力大于壁面黏性力，导致液膜做加速运动，液膜减薄；而在逆流条件下，壁面黏性力和界面剪切力的合力大于重力，导致液膜做减速运动，液膜增厚。

 [1] 韦胜杰, 宋建, 胡珀, 等. 竖壁冷态降液膜流动统计特性实验研究[J]. 原子能科学技术, 2012, 46(6): 674-678. (0) [2] 宋建, 胡珀, 韦胜杰, 等. 竖直平板降水膜表面波波动特性实验研究[J]. 原子能科学技术, 2012, 46(6): 679-683. (0) [3] 袁猛, 胡剑光, 陈剑佩, 等. 微结构壁面降膜波动的统计特性[J]. 华东理工大学学报(自然科学版), 2012, 38(3): 293-300. (0) [4] 于意奇, 杨燕华, 程旭, 等. 降膜流动行为的数值模拟研究[J]. 原子能科学技术, 2012, 46(10): 1207-1211. (0) [5] 潘新新, 宋春景, 邱健. 水分配围堰的水膜流动特性数值模拟[J]. 核科学与工程, 2016, 36(4): 482-486. DOI:10.3969/j.issn.0258-0918.2016.04.007 (0) [6] HUANG X G, YANG Y H, HU P, et al. Experimental study of water–air countercurrent flow characteristics in large scale rectangular channel[J]. Annals of nuclear energy, 2014, 69: 125-133. DOI:10.1016/j.anucene.2014.02.005 (0) [7] 石玉琦. 降膜吸收传热传质理论与实验研究[D]. 杭州: 浙江大学, 2018. (0) [8] 田瑞峰, 李兆俊, 张庆武. 板壁水膜波动流动数值研究[J]. 核动力工程, 2006, 27(5): 29-32. DOI:10.3969/j.issn.0258-0926.2006.05.006 (0) [9] 黄磊, 李明春, 陈冬, 等. 降膜流动及膜破裂特性的三维数值模拟[J]. 能源工程, 2015(2): 13-20. DOI:10.3969/j.issn.1004-3950.2015.02.003 (0) [10] 卢涛, 张蔷. 非能动安全壳竖直平板降膜流动特性数值模拟[J]. 热科学与技术, 2016, 15(5): 345-351. (0) [11] 赵婵. 垂直降液膜的流体力学研究[D]. 天津: 天津大学, 2014. (0) [12] 于意奇. 大尺度平板水膜流动行为的数值模拟和试验研究[D]. 上海: 上海交通大学, 2012. (0) [13] WALLIS G B. One-dimensional two-phase flow[M]. New York: McGraw-Hill, 1969. (0) [14] STEPHAN M, MAYINGER F. Experimental and analytical study of countercurrent flow limitation in vertical gas/liquid flows[J]. Chemical engineering & technology, 1992, 15(1): 51-62. (0) [15] 尹涌澜. 沉降膜换热器基础研究及其复合源热泵系统应用分析[D]. 长春: 吉林大学, 2012. (0)