GRINS: A Multiphysics Framework Based on the libMesh Finite Element Library.

This paper describes a flexible C++ software framework, called GRINS, for simulating complex multiphysics systems of partial differential equations using the finite element method. GRINS is designed to facilitate the rapid development and reuse of finite element formulation code as well as other features of complex simulations, including quantity-of-interest functionals, solvers, boundary conditions, initial conditions, and postprocessing. GRINS is built on the FEMSystem framework that is part of the libMesh finite element library. GRINS, through FEMSystem and libMesh, supports a number of contemporary algorithms and computing features including hybrid distributed and shared memory parallelism, parallel adaptive mesh refinement on unstructured grids, goal-oriented refinement driven by dual-weighted residual error estimates in quantities of interest, and adjoint-based parameter sensitivities. GRINS is deployed both as an application binary, allowing immediate use of existing features, and as a library to which the user may build and link a stand-alone application, extending the framework to their needs. Several examples demonstrate the effectiveness of the design, including uncertainty quantification applications. Planned developments are also discussed.