Coupling Finite Element and Finite Volume within the Plasma Fluid Code: Zapdos

This work focuses on adding capability to couple finite element (FE) variables into finite volume (FV) physics for the open-source multi-fluid plasma code, Zapdos, within INL's Multiphysics Object-Oriented Simulation Environment (MOOSE). This coupling can allow for improvement of multiphysics simulations where one set of physics is best suited for an FE discretization, while another set is best suited for an FV discretization. Plasma dynamics is a fitting example where the electromagnetic field equations are solved with FE and the fluid flow is solved with FV. The new FE to FV coupling method can be summarized as taking the element or face average of the FE variable value or gradient and applying that quantity directly in the FV equation objects. Verification and validation (V&V) were conducted based on Zapdos FE-only V&V efforts. Verification included method of manufactured solutions (MMS) with spatial and temporal convergence studies. These MMS studies were modularized, such that simple decoupled physics to fully coupled multi-fluid problems were studied. Validation included benchmarking with FE-only simulations to investigate the benefits of FE-FV coupling over the traditional FE-only simulations. Initial V&V studies show good alignment to theory and previous simulation.