WAVE PROPAGATION IN RANGE-DEPENDENT PORO-ACOUSTIC WAVEGUIDES

The parabolic equation method is extended to handle range-dependent poro-acoustic waveguides. A poro-acoustic medium is the limiting case of a poro-elastic medium in which the shear wave speed vanishes. Recent experiments indicate that this is a relevant limit [Chotiros, “Biot model of sound propagation in water-saturated sand,” J. Acoust. Soc. Am. 97, 199–214 (1995)]. Energy-conserving and single-scattering techniques are developed for handling vertical interfaces. The single-scattering solution is extended to problems involving fluid layers above poro-acoustic sediments. Improved rational function approximations are developed by rotating the branch cut [Milinazzo et al., “Rational square-root approximations for parabolic equation algorithms,” J. Acoust. Soc. Am. 101, 760–766 (1997)].

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