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    Entropy and scintillation analysis of acoustical beam propagation through ocean internal waves

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    JASA_Morozov-2005.pdf (2.286Mb)
    Date
    2005-03
    Author
    Morozov, Andrey K.  Concept link
    Colosi, John A.  Concept link
    Metadata
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    Citable URI
    https://hdl.handle.net/1912/2356
    As published
    https://doi.org/10.1121/1.1854571
    DOI
    10.1121/1.1854571
    Keyword
     Underwater acoustic propagation; Acoustic signal processing; Parabolic equations; Entropy; Ocean waves; Chaos 
    Abstract
    Parabolic equation numerical simulations of waveguide acoustical beam propagation in an ocean of Garrett–Munk internal waves are used to examine the range evolution of beam properties such as beamwidth (both spectral and spatial), Shannon entropy, and scintillation index, as a function of beam angle. Simulations are carried out at 250- and 125-Hz acoustic frequencies. The ray trajectories associated with these beams are predominantly chaotic or exponentially sensitive to initial conditions and/or medium perturbations. At long range near saturation, the finite-frequency beams show a constant rate of change of Shannon entropy with range, independent of acoustic frequency. This full-wave rate of entropy is of the same order of magnitude as the average rate of entropy for the ray trajectories associated with this beam. Finite-range Lyapunov exponents provide the estimates of ray entropy rate or Kolmogorov–Siani entropy. The correspondence between full-wave and ray entropies suggests a full-wave manifestation of ray chaos, but only once statistical saturation is obtained. In spite of this correspondence, the simulated acoustical beams expand diffusively not exponentially (or explosively).
    Description
    Author Posting. © Acoustical Society of America, 2005. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 117 (2005): 1611-1623, doi:10.1121/1.1854571.
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    • Applied Ocean Physics and Engineering (AOP&E)
    Suggested Citation
    Journal of the Acoustical Society of America 117 (2005): 1611-1623
     

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