An optimized Vofi library to initialize the volume fraction field

The Vofi (Volume Of Fluid Initializer) library has been developed to initialize the volume fraction field determined by implicitly-defined interfaces. The major conceptual changes in the numerical algorithms of the library are discussed and a few new features, including the computation of the reference phase centroid and of the interface length/area, are presented and applied to grid cells that are cuboids. Several numerical tests are considered to demonstrate both the accuracy of the new features, as the grid resolution and the number of integration points are varied, and the considerably improved efficiency of the library with respect to its previous version. A few of these tests are also included in the software distribution written in C, examples of C++ and Fortran interfaces are also provided. The previous version of this program (AEYT_v1_0) may be found here https://doi.org/10.1016/j.cpc.2015.10.026.Vofi（Volume Of Fluid Initializer，流体体积初始化器）库专为初始化由隐式定义界面所确定的体积分数场而开发。本文讨论了该库数值算法中的主要概念性改进，并介绍了若干新特性——包括参考相质心以及界面长度/面积的计算方法——并将其应用于长方体网格单元。通过多组数值测试，验证了新特性在网格分辨率与积分点数变化时的计算精度，同时证明了该库相较于旧版本在效率上的显著提升。该软件的C语言分发包中包含了部分上述测试用例，同时还提供了C++与Fortran接口的示例代码。该程序的旧版本（AEYT_v1_0）可通过以下链接获取：https://doi.org/10.1016/j.cpc.2015.10.026。