GVOF: An open-source package for unsplit geometric volume of fluid methods on arbitrary grids

Abstract

The gVOF package implements several accurate and efficient geometric volume of fluid (VOF) methods on arbitrary grids, either structured or unstructured with convex or non-convex cells, based on multidimensional unsplit advection and piecewise linear interface calculation (PLIC) schemes, with the purpose of facilitating and extending the use of advanced unsplit geometric VOF methods in new or existing computational fluid dynamics codes. The package includes a complete and self-contained set of routines for VOF initialization, interface reconstruction and fluid advection, and uses as external libraries a set of publicly available in-house tools to perform several analytical and geometrical operations. These operations may involve handling of high-complex non-convex flux polyhedra, even with self-intersecting faces, which are robustly and efficiently treated in this work without the need of costly techniques based on convex decomposition. Results for the accuracy, computational efficiency, and volume (local and global) conservation properties of different combinations of the implemented advection and reconstruction methods are presented for several numerical tests on structured and unstructured grids. An extensive comparison with results obtained by other authors using advanced geometric VOF methods shows the outstanding performance of the gVOF package in terms of efficiency and accuracy. To demonstrate the performance of the package in solving complex two-phase flow problems, the implemented methods are combined with an existing in-house code to simulate the impact of a water drop on a free surface. Program summaryProgram Title:gVOFCPC Library link to program files:https://doi.org/10.17632/9gmn6gsb6p.1Licensing provisions: GPLv3Programming language:FORTRAN and C, with C interfacesExternal routines/libraries:VOFTools (https://doi.org/10.17632/brrgt645bh.3) and isoap (https://doi.org/10.17632/4rcf98s74c.1) librariesNature of problem: The software package includes efficient and accurate routines for volume of fluid initialization, reconstruction of interfaces and fluid advection on arbitrary grids, either structured or unstructured with convex or non-convex cells, which are used to implement advanced unsplit geometric VOF methods. In particular, the package includes a fluid volume fraction initialization method, six PLIC reconstruction methods and three multidimensional unsplit advection methods. Routines to visualize interfaces and compute reconstruction errors; tests to assess the accuracy, computational efficiency, and volume conservation of the implemented methods for the reconstruction and advection of complex interfaces on arbitrary grids; and a user manual have also been included in the supplied package.Solution method: Basically, the implemented methods, which can be used on grids with polyhedral cells of arbitrary geometry, have the following general characteristics. The methods implemented for fluid volume fraction initialization and reconstruction error calculation are based on a recursive grid refinement procedure to compute the fluid volume bounded by cell edges and an implicitly-defined fluid interface. The six implemented interface reconstruction methods are the following: a least-squares gradient interface reconstruction method; three isosurface-based interface reconstruction methods; an extension to 3D of the iterative Swartz interface reconstruction; and a least-squares fit interface reconstruction method. Three unsplit advection methods, which are based on edge-matched, face-matched and non-matched flux polyhedra and are valid for 3D arbitrary grids, are implemented. All the implemented methods can be combined by the user to solve different tests on arbitrary grids. The implemented routines can be used in FORTRAN or C. The OpenMP application programming interface is used to improve the computational efficiency.