Fig. 1: Theoretical model that integrates a two-step FEM and a NM algorithm.

a A schematic of the FE model implemented in the proposed two-step FEM scheme for solving the scattering from an arbitrary elastic structure in a two-layered, fluid waveguide. Also shown is the process of computing the scattered field using the coupled FEM/NM method, where the near-field pressures distributed over a vertical line, generated by the two-step FEM solver, are extracted to construct R and T. b A flow chart for the proposed two-step FEM scheme.