基于VOF方法的可调参数对气泡聚并过程计算精度与成本的影响  

The influence of adjustable parameters based on VOF method on the computational accuracy and cost of bubble coalescence process

作　　者：周萍[1] 蒋怡 廖义香 李家栋[1] ZHOU Ping;JIANG Yi;LIAO Yixiang;LI Jiadong(School of Energy Science and Engineering,Central South University,Changsha 410083,China;Helmholtz Dresden-Rosendorf Research Center,Dresden 01328,Germany)

机构地区：[1]中南大学能源科学与工程学院,湖南长沙410083 [2]亥姆霍茨德累斯顿−罗森多夫研究中心,德国德累斯顿01328

出　　处：《中南大学学报（自然科学版）》2023年第7期2867-2877,共11页Journal of Central South University:Science and Technology

基　　金：国家自然科学基金资助项目(51676211)。

摘　　要：气泡聚并通过改变气液两相间界面面积,影响相间的传热和传质,而聚并时间和液膜厚度是描述2个气泡聚并过程的重要物理参数。采用流体体积(VOF)方法对气泡聚并过程进行数值模拟时,合理设置计算流程中可调参数(例如网格尺寸、最大库朗数以及方程循环次数等),有助于提高求解过程的收敛性、节省计算时间。因此,本文基于OpenFOAM开源软件,采用VOF方法与自适应网格相结合的方法,以同轴两气泡聚并过程为例,探究最大库朗数Co_(max)、相方程循环次数nα和控制方程循环次数n_(pimple)这3个参数对气泡聚并过程数值模拟的计算量与计算精度的影响,同时,得到气泡间液膜厚度在可调参数不同取值时随时间的变化规律。研究结果表明:气泡间液膜的变薄速度与最大库朗数Co_(max)成反比,与相方程循环次数nα和控制方程循环次数n_(pimple)成正比,这主要是由于减小最大库朗数Co_(max)以及增大相方程循环次数nα和控制方程循环次数n_(pimple)提高了计算精度,改善了流体在网格单元上移动滞后的现象,加快了两气泡聚并以及液膜减薄过程;综合考虑计算精度与计算成本,得到了基于VOF方法的气泡聚并数值模拟较优的可调参数组合,即(Co_(max),nα,n_(pimple))=(0.05,3,8)。Bubble coalescence affects the interphase heat and mass transfer by changing the interfacial area of gas and liquid phases.The coalescence time and liquid film thickness are important physical parameters to describe the bubble coalescence process.When simulating the bubble coalescence with volume of fluid(VOF)method,reasonable settings of adjustable parameters(such as mesh size,maximum Courant number and equation cycle times,etc.)can improve the convergence of the solution and save the computational time.The aim of this paper is to investigate the coalescence process of two coaxial bubbles combining the VOF method with the adaptive mesh refinement technology based on OpenFOAM.The influence of the maximum Courant number Co_(max),the cycle times of phase equation nαand the cycle times of governing equation n_(pimple)on the computational efficiency and accuracy of numerical simulation of bubble coalescence process was explored.Meanwhile,the time evolution of the liquid film thickness among bubbles was obtained for different adjustable parameters.The results show that the thinning speed of the liquid film between two bubbles is proportional to nαand n_(pimple),while is inversely proportional to Co_(max).This is because the computational accuracy is promoted by the decrease of Co_(max)and the increase of nαand n_(pimple).The transport lag of the fluid on the grid element is therefore improved,and the bubble coalescence and liquid film thinning is accelerated.Considering the computational accuracy and cost,a set of better adjustable parameters for simulating bubble coalescence with VOF method is obtained,i.e.,(Co_(max),nα,n_(pimple))=(0.05,3,8).

关 键 词：OPENFOAM 气泡聚并 流体体积方法 自适应网格 可调参数 计算精度 计算成本 

分 类 号：TP391.9[自动化与计算机技术—计算机应用技术]