Razumov D.D., Salin M.B.

The subject of our interest is the sound of the middle-frequency range from 1 to 5 kHz. Its scattering significantly depends on the state of the sea surface: the Rayleigh parameter can range from small numbers for a calm sea to values of the order of one for developed waves. The purpose of this study is to reproduce some of the effects that are observed in experiments on sound scattering on the sea surface using modern numerical methods. To simulate the sea surface we use the direct method for numerical simulation of potential flows with a free surface of a two-dimensional fluid, known as the Zakharov and Dyachenko method. The system of transformed Euler equations is numerically integrated to get how the surface evolves from the initial state. So nonlinear interaction of surface harmonics is taken into the account. We have proposed the original modification of the boundary element method (in 2D), which is suited for studying sound scattering separately on the surface, and it does not impose significant restrictions on the shape of the surface. We calculated the pressure field of the scattered sound wave, the backscattered force, and the Doppler spectrum of the signal depending on the angles of incidence and scattering at different wind speeds. The calculation results are compared with the predictions of classical models.

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