Greenʹs function for a harmonic acoustic point source within seawater overlying a saturated poroelastic seabed

In this paper, Greenʹs function for an acoustic source within half-space seawater overlying a porous seabed is established. The half-space seawater is described using the Helmholtz equation, while the seabed is considered as a saturated porous medium and characterized by Biotʹs theory. Greenʹs function of the half-space seawater has two components: the principal and complementary parts. The principal part of Greenʹs function is the solution for a conventional acoustic point source in an infinite medium, while the complementary part corresponds to the general solution of the Helmholtz equation for the half-space. Greenʹs function of the half-space seabed is obtained by solving Biotʹs dynamic equations via the Hankel transform method. Using the continuity conditions at the interface between the seawater and the seabed, the closed-form Greenʹs functions for the seawater and the seabed in the frequency–wavenumber domain are determined. The frequency domain Greenʹs function is recovered by the inversion of the Hankel transform. A parametric study is carried out for Greenʹs function in the frequency domain, and a time domain example is presented in terms of frequency domain Greenʹs function. Numerical results show that the permeability of the porous seabed has very little influence on the response of the seawater, while Biotʹs modulus has a pronounced influence on the wave field.