Generalized Form of the Invariant Imbedding Method and Its Application to the Study of Back-Scattering in Shallow-Water Acoustics

• Main Authors: Mikhail Kazak, Konstantin Koshel, Pavel Petrov
• Format: Article
• Language: English
• Published: MDPI AG 2021-09-01
• Series: Journal of Marine Science and Engineering
• Subjects: ocean acoustics; normal modes; back-scattering; invariant imbedding method
• Online Access: https://www.mdpi.com/2077-1312/9/9/1033

A generalized form of the matrix-invariant imbedding method was developed to solve boundary-value problems for coupled systems of Helmholtz-type equations. Within this approach, a boundary-value problem solution can be obtained by solving evolutionary first-order imbedding equations for a matrix-valued function. The proposed method is applied to the solution of coupled equations for mode amplitudes describing the propagation of acoustic waves in a range-dependent shallow-water waveguide. The back-scattering of modes by bathymetry features is investigated, and the coefficients of the modal expansion of the wave reflected by an inhomogeneity in the bottom relief are computed. It is demonstrated that back-scattering is strongly connected with the modal interactions and that the back-scattered field consists of modes with numbers different from the number of the incident mode.