亚网格内两相流动界面位置的精确定位算法

A Sub-Grid Interface Locating Algorithm for Free Surface Two-Phase Flows

针对流体体积(VOF)法处理两相流动界面张力的虚拟流体方法无法准确确定亚网格内界面位置点的问题,提出了一种高精度的界面位置定位算法。该方法根据界面两侧单元界面曲度在亚网格内构建变曲度弧线,实现了两相界面的高精度近似,完成了网格单元中心连线和界面交点位置以及该位置的曲度的准确求取,成功地考虑了界面曲度对亚网格内界面位置的影响,同时方法本身不受网格类型及空间维度的限制。针对毛细管上升、静态液滴、二维气泡上升以及三维气泡上升等物理过程进行了模拟,结果表明:界面曲度对亚网格界面位置可产生显著影响;亚网格内界面位置的准确捕捉以及该位置点界面曲度的准确求取可以显著改善VOF方法的预测精度,模拟结果显示最好可提高3.5倍。该方法可为复杂结构内高表面张力驱动流提供新的预测手段。

In ghost fluid method,for treating surface tension under the framework of volume of fluid（VOF）,the exact location of fluid interface cannot be easily determined.In order to resolve such a problem,a new sub-grid interface locating algorithm is proposed in this work.In the new algorithm,a variable curvature curve,used to approximate the interface in sub-grid,is constructed based on the curvature of the two grid cells on both sides of the interface.As a result,the intersection point of the connection line of centers of interfacial cells and the interface is calculated accurately.The influence of the curvature on the interface location is taken into account.Moreover,this algorithm is independent on mesh type and space dimension.Numerical tests,including capillary rise,static droplet,bubble rise in two-dimensions and threedimensions,show that interface curvature has a significant influence on the sub-grid interface location.Calculating the sub-grid interface location and the curvature at such a location with high accuracy can improve the numerical prediction of VOF method significantly,and by 3.5times at the best.This method can provide a new tool for predicting physical behaviors of high surface tension driven flow in complex geometrical structures.