Geodynamic Validation and Scalability of TerraNeo: Matrix-Free Mantle Convection Framework

Mantle convection models are of utmost importance in understanding the physics governing major geological processes of our planet such as earthquakes, mountain building, etc. The TerraNeo framework is focussed on creating extreme-scale high-resolution geodynamic models which it achieves
with the massively parallel matrix-free finite element package HyTeG. To handle the Stokes system which arises from the conservation of mass and
momentum equations, a multigrid preconditioned Krylov subspace solver is used, whereas to handle the advection term in the conservation of energy
equation, an operator splitting approach based on the modified method of characteristics (particles) is used.

We first present standard numerical benchmark experiments for geodynamic validation of the framework against other community codes. In addition, we verify order of convergence of error in velocity and pressure against highly accurate solutions for the Stokes system computed with the propagator matrix method for radially varying viscosity and density cases. Next, a mantle circulation model with spatially varying physical parameters (viscosity and density) and assimilated plate velocities is simulated from a past physical state to present day and assessed for geodynamic correctness. Finally, we present scalability studies performed on the supercomputer SuperMUC-NG Phase 1 at LRZ (91st in TOP500, Nov’ 25). In these experiments, we were able to scale the framework to a global model resolution of ≃ 7.5 km on > 300, 000 MPI processes. These results combined with the numerical benchmarking of the framework clearly show that TerraNeo is well suited for creating large-scale geodynamic models.