The 3-D finite elements are hexagonal prisms centered on the nodes of the mesh. Basis functions are Cartesian products of piecewise linear spherical barycentric functions for the tangential directions and normal piecewise linear functions for the radial direction. The dynamical equations are written in terms of the primitive variables of velocity, temperature, and pressure. In the infinite Prandtl number limit, appropriate for creeping flow of silicate rock in planetary mantles, the momentum equation reduces to a balance among buoyancy forces, viscous forces, and the pressure gradient. The time step is adjusted dynamically such that only one or two V-cycles are required per step.
Eulerian advection is utilized in advancing the temperature equation.
Global simulations with resolution on the order of 50 km are now practical on parallel machines.