Alternating Direction Explicit-Implicit Computational Method Applied to Low-Frequency Underwater Sound Propagation.

by Myron C. Smith, R. H. Mayall, Sylvia V. Huber

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A new sonar interpretation technique for range determination under conditions in which the usual approximate methods are inadequate. A computer solution of the two-dimensional undamped linearized wave equations is found by using an interlacing explicit-implicit scheme. In the computation, the entire two-dimensional field is found as a function of time. The examples considered involve wave propagation in a homogeneous shallow-water channel, where the effect of superposition of discrete spectra produces characteristic modal patterns. The spatial sound pressure fluctuations are represented as plot-density variations along the two-dimensional channel. Examples of discrete propagated modes as well as evanescent modes are presented. The size of the field that can be presented is limited by the size, accuracy, and speed of the computer. The method is programmed in FORTRAN IV for use on the IBM 7040/44 computer with the S-C 4060 microfilm recorder. The program is appended. 32 pp. Ref.

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