A Study On The Characteristics Of Scattering From An Object Submerged In A Shallow-water Waveguide

The shallow water, as an important region in underwater activities, is drawing more and more attention. In this paper, the scattering of an object submerged in a shallow water waveguide is discussed.The normal mode formulation developed by F. Ingenito and the spectral formulation by N. C. Makris for calculating the scattered field of an object submerged in a waveguide are adopted , and the detailed derivations of the modal formula and the spectral formula of the scattered field from the original Kirchhoff's integral equation are given. Through comparison, the similarity and unity of the two deriving method is discussed..The two formulations are then numerically implemented for calculating the scattered field of an object submerged in a shallow water waveguide. The modal formulation is successfully implemented. In the implementation of the spectral formulation, the FFP technology is used to avoid the mixing-up effect introduced by discretization, the core function of wave number integrals of the scattered field is discussed and some interesting properties are detected, and the improvement scheme for the implementation of the spectral formulation is proposed.Finally, the scattered fields of rigid and soft spheres submerged in a shallow water waveguide with different waveguide conditions, such as various boundary conditions, different depths of the waveguide, various media properties, different sound speed profiles, are computed by the modal formula. The scattering characteristics of an object submerged in a shallow water waveguide are then revealed. The coherence of the scattered field is founded. The property that the beginning range of the coherence becomes far with the increasing of the depth of the waveguide isobserved. In the r-φ horizontal slice, the scattered fields alternate with the highand low SPL; in the r-z vertical slice, the scattered fields form obvious coherent wave beams, which turn to the low sound velocity when there is a certain sound profile and show good symmetry in waveguide when the sound velocity is constant.