Applying a numerical Green's function approach to scattering within complex seafloor environments

Abstract

A numerical approach to solving for Green’s functions allows far-field scattering to be solved within variable seafloor environments. The approach is applicable for both seafloor and buried target scattering problems. A robust near-field model is required for near-field solution evaluation and Green’s function determination. In this work, a 3-D finite element model is used. Far-field scattering results are determined through numerical integration of the Helmholtz-Kirchhoff surface integral within the near-field of the target or interface. This approach has previously been shown to give accurate results within flat sediment interface environments; now the technique is extended to more complex interface structures, in which the benefit of the numerical Green’s function technique is most apparent. For flat interface environments, analytic Green’s functions are known, making numerical approaches redundant. For more complex environments, exact solutions are difficult to come by, and analytic approximations grow in error with increasing environmental complexity. Furthermore, the numerical approach requires only a single field measurement to be made within the near-field model, making the approach computationally efficient and feasible for a wide variety of scattering problems. [Work supported by ONR, Ocean Acoustics.]