小韦伯数下小球入水的数值分析

Numerical Simulation of Hydrophobic Spheres Entering Water at Low Weber Numbers

为了能准确预测壁面湿润性对固体入水的影响,使用二维轴对称模型和动网格技术模拟了疏水小球低速竖直入水实验,使用用户自定义函数(UDF)加入动态接触角模型来处理壁面湿润性.气液界面的捕捉采用流体体积(VOF)法,界面重构应用Compressive方法.首先模拟了小密度超疏水小球入水实验以验证小球受力计算的准确性,然后针对3种不同空泡类型实验进行数值模拟,模拟结果与实验符合较好,并数值分析了入水初速度的改变对入水过程的影响,对于shallowseal空泡,无量纲闭合时间与韦伯数可用二次曲线精确拟合.

In order to analyze the influence of the wetting property on the water entry,a numerical simulation on the vertical water entry of small hydrophobic spheres at low impact speed was performed using the 2D axisymmetric grid and the dynamic mesh model.The dynamic contact angle model with UDFs was applied to handle the wetting property.In the numerical simulation,the VOF method and the compressive scheme were used to track and reconstruct the interfaces,respectively.The accuracy of the force calculation method was validated in the simulation by using a light superhydrophobic sphere.The simulation results for different cavity types agree reasonably with the experimental data.The influence of the impact speed was analyzed based on simulation results.For the shallow seal cavity,the dimensionless pinch-off time could be fitted well by the quadratic functions with an increase in the impact speed.