Comparison of hybrid and fully implicit time domain finite element solvers for transient electromagnetic simulation

The paper compares two finite element time domain solvers for transient electromagnetic simulation of multiscale structures. The first solver is based on a dual-field implicit-explicit formulation. By limiting the number of implicit elements, the solver closely resembles nodal discontinuous Galerkin and has better scalability in memory requirement and multithreading for solving large-scale problems. However, when the structures and features to be solved are electrically small, the explicit part of the hybrid solver is limited by the stability condition and becomes inefficient in passing low-frequency signals through the structures. We will demonstrate that the second solver based on a single-variable fully implicit formulation can better handle low-frequency applications such as electrostatic discharge and lightning strikes. It is also immune to bad meshes with extremely small or ill-shaped elements.