The contribution of a lateral wave in simulating low-frequency sound fields in an irregular waveguide with a liquid bottom

Abstract

For a two-dimensional irregular waveguide with a bottom in the form of a liquid half-space simulating the coastal zone of a sea shelf, we present calculations on sound propagation at certain low frequencies taking into account the contribution of the integral over the Pekeris branch cut approximated according to the Zavadsky-Krupin technique. Calculations were conducted on the basis of causal matrix equations for the modes obtained in previous studies and that are equivalent to the equations of the cross section method. It is shown how, with a lowering of sound frequency, there is an increase in the contribution to the full field of the branch-line integral corresponding to a lateral wave. Features of transformation of the first propagating mode are established as the section of the cutoff is passed; in such a situation, we have an idea of the wave pattern of the exposure region of the waveguide beyond this section, where propagating modes are absent. As earlier, we perform a comparative analysis of the curves of losses during propagation, corresponding to the solution of exact equations and the description of approximating one-way propagation when allowing for and ignoring coupling of modes.