Hybrid FEM-DDM and BEM-BoR for the Analysis of Multiscale Composite Structures

We propose a novel scheme to accelerate the computation of the finite-element method-boundary element method (FEM-BEM) for 3-D electromagnetic scattering. It builds on the FEM-domain decomposition method (FEM-DDM) and the degenerated boundary element method (BEM) developed for the body of revolution (BoR), which is, thus, referred to as BEM-BoR. When coupled with FEM in the framework of domain decomposition, the infinite computational domain is truncated by a closed rotationally symmetric surface enclosing the 3-D scatterer, and BEM-BoR is then applied on this surface as a radiation boundary condition (RBC). The finite-domain interior to this surface is further decomposed into several subdomains, which are connected by the second-order transmission conditions (SOTCs) imposed on nonconformal meshes. We refer to the resultant solver as a hybrid FEM-DDM and BEM-BoR (FEM-BEM-BoR). Since BEM-BoR can be divided into several 2-D problems instead of the original 3-D one, the proposed FEM-BEM-BoR is more efficient than the original FEM-BEM. Numerical examples are presented, and the comparisons of the simulation results with FEM-BEM confirm the accuracy and efficiency improvement of FEM-BEM-BoR. In addition, its practical applicability is demonstrated by modeling large-scale objects.