Finite volume discretization for dynamic viscosities on Voronoi grids

We present a new formulation to discretize the viscous term in the momentum equation of the Navier–Stokes set. A technique based on the finite volume method enables thermal convection models to utilize spatially varying viscosity on a collocated variable arrangement. This technique can be applied to various grids in two or three dimensions with Voronoi properties, either irregular as the spiral grid or regular like the cubed sphere grid, icosahedral or simple boxes. A model for mantle convection implements this discretization and is compared to other published models. Further computational aspects are illuminated to efficiently reduce required resources.