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The presentation describes the theory and implementation issues of modeling of the backscattering from an obstacle immersed in a homogeneous, range-independent waveguide covered with ice. An obstacle is assumed to be spherical, rigid or fluid body. A bottom of the waveguide and an ice cover are fluid, attenuating half-space. The properties of an ice cover and a scatterer may coincide. To calculate the scattering coefficients of a sphere [R. M. Hackman et al., J. Acoust. Soc. Am. 84, 1813–1825 (1988)], the normal mode evaluation is applied. A number of normal modes forming the backscattering field is determined by a given directivity of the source. The obtained analytical expression for the backscattered field is applied to evaluate its dependence on source frequency, depth of a water layer, bottom and ice properties, and distance between the source and obstacle. Two cases are analyzed and compared: when the upper boundary of a waveguide is sound-soft and when a water layer is covered with ice. Computational results are obtained in a wide frequency range 8–12 kHz for conditions of a shallow water testing area. [Work supported by Russian Ministry of Educ. and Sci., Grant 02.G25.31.0058.] |
