Boundary waves at the water-sea bottom interface

Abstract

991 The theory of wave processes in layered media developed in classical works [1–3] is based on the solution of the key boundary problem of hydroacous tics formulated and solved by Pekeris in [1] for a sys tem homogeneous fluid layer–homogeneous fluid half space. A characteristic peculiarity of the model formulation suggested in [1–3] is the fact that bound ary conditions at the interface waveguide–half space are formulated as conditions of local continuity by pressure and the normal component of oscillation velocity (continuity conditions (p, vz)), while the model formulation appears self conjugated. As a con sequence of the assumed model formulation, the power flux through the impedance interface boundary is zero at all incidence angles including subcritical angles, and the wave motion at the impedance bound ary degenerates at small glancing angles due to a mild screen effect. We suggested in [4] a non self conjugated model formulation of boundary problems for layered media and a generalized theory built on its basis. In this model formulation, continuity conditions (p, vz) are satisfied only on average, but the power flux through the impedance boundary is nonzero. It is positively specified at subcritical incidence angles with an alter nating sign, while at supercritical incidence angles, the flux becomes alternating with zero mean value. A bot tom wave of the boundary type is formed at the imped ance boundary as a sequence of the assumed model formulation, which is absent in the classical solution. In the simplest case of spherical wave reflection at the boundary between two half spaces, the level of sound wave inflow into the lower half space z ≥ 0 is determined by the condition of mild screen compen sation by an outflowing nonuniform wave, whose amplitude increases exponentially to the boundary of Boundary Waves at the Water–Sea Bottom Interface