Geometric multigrid method for solving Poisson's equation on octree grids with irregular boundaries

A method is presented to include irregular domain boundaries in a geometric multigrid solver. Dirichlet boundary conditions can be imposed on an defined by level set function. Our implementation employs quadtree/octree grids with adaptive refinement, cell-centered discretization and pointwise smoothing. Boundary locations are determined at subgrid resolution performing line searches. For grid blocks near the interface, custom operator stencils stored that take interface into account. block away from boundaries, standard second-order accurate used. The convergence properties, robustness computational cost of illustrated several test cases. Program Title: Afivo CPC Library link program files: https://doi.org/10.17632/5y43rjdmxd.2 Developer's repository link: https://github.com/MD-CWI/afivo Licensing provisions: GPLv3 Programming language: Fortran Journal reference previous version: Comput. Phys. Commun. 233 (2018) 156–166. https://doi.org/10.1016/j.cpc.2018.06.018 Does new version supersede version?: Yes. Reasons for Add support internal Summary revisions: solver was generalized ways: coarse Hypre library used, now per block, methods including via function were added. Nature problem: goal solve Poisson's equation presence not aligned grid. It assumed these function, type condition applied. main applications 2D 3D simulations octree-based mesh which frequently changes but do not. Solution method: compatible octree developed, using point-wise Near stored. Line searches performed locate interfaces sub-grid resolution. To increase robustness, this search modified if otherwise resolved. uses OpenMP parallelization.