Three dimensional finite element modeling of scattering by objects at rough interfaces

Fully three-dimensional finite element models for buried objects and objects at interfaces have been extended to incorporate interface roughness. Near field results are solved using a fully scattered field formulation, in which all fields in the absence of the target are applied and the target scattering is solved. Results are extended to the far field through the Helmholtz-Kirchhoff integral, using a numerically determined Green’s function approach. Interface roughness is applied using a modified power law wavenumber spectrum. Previous model demonstrations evaluated the scattering in the flat interface limit, in which background fields were prescribed analytically. Now, the presence of the surface roughness forces background fields to be evaluated and prescribed numerically. Such models have strong applicability for predicting scattering by objects buried within or resting on a rough seafloor interface. Model results are compared with various experimental and other modeled results, demonstrating model va...