自由面流动在工程问题中经常遇到。为研究半无限长柱体出水过程中 ,不同的 We和 Fr对自由面的影响 ,基于VOF(volume of fluid)的基本思想 ,使用改进的 Youngs算法实现体积分数的近似和推进 ,对问题进行了数值研究 ,分别得到了该问题的 We和 Fr临界值 :当 We大于临界值时 ,可以忽略表面张力的作用 ;当 Fr大于临界值时 ,可以忽略重力的影响 Free surface flow is often encountered in engineering problems. In order to study the effect of different We and Fr on the free surface in the process of semi-infinite long column, based on the basic idea of ​​volume of fluid (VOF), the Youngs algorithm is used to approximate and promote the volume fraction, We study the numerical values ​​of We and Fr respectively. When We is larger than the critical value, the effect of surface tension can be neglected. When Fr is larger than the critical value, the effect of gravity can be neglected