Modes selection based on holographic interferometry in presence of intense internal waves in shallow water

Abstract

A holographic method is proposed for sound field modes selection and estimating their parameters (amplitude, horizontal wavenumber, group velocity, absorption coefficient) in shallow water by single scalar receiver in presence of intense internal waves (IIW). It is taken into account that IIW leads to horizontal refraction and modes coupling. The offered holographic method is based on the two-dimensional Fourier transform (2D-FT) of the real part of the moving-source sound field in time–frequency domain. It is shown in the paper that different sound field modes create different focal spots in the hologram domain in presence of IIW. The relationship of the mode phases and group velocities with the coordinates of focal-spot peaks is derived. The hologram domain allows to reconstruct the selected mode field and mode parameters in presence of IIW. The results of modes selection within framework of the numerical experiments are presented in the paper. The modal parameters are estimated. Analysis of influence of IIW on mode selection and mode parameters estimations is performed. It is shown that the effects of horizontal refraction and modes coupling do not lead to loss of the identity of mode parameters of the received signal. [This study was supported by Russian Science Foundation grant no. 22-79-10233. E.S. Kaznacheeva’s numerical experiment was supported grant no. МК-6144.2021.4]