Broadband enhancement and suppression of backscattering from objects in shallow-sea waveguides through the prescription of incident wavefronts

This paper presents a methodology for enhancing and suppressing backscattering from submerged objects in shallow-water waveguides. A hybrid numerical model is developed that integrates a two-step finite element method (FEM) and a normal mode (NM) algorithm. The FEM scheme computes the near-field scattered field generated by an elastic structure under non-plane-wave incident conditions in a shallow-water environment. A modal filter technique is then applied to construct the modal-domain reflection and transmission matrices of the scattering region using the near-field data derived from the FEM. Scattering enhancement and suppression are achieved by maximizing the Rayleigh quotient of these matrices, with the prescribed incident wavefront determined via singular-value decomposition. The scattered field is subsequently reconstructed using the prescribed wavefront and the NM algorithm. Validation of the hybrid model is performed through comparison with a direct FEM simulation for an elastic spherical shell. Further simulations are conducted for realistic scenarios involving multiple spherical scatterers and a benchmark submarine model. The results demonstrate that the proposed method enables broadband control of backscattering in shallow-water waveguides.