Temporal and cross-range coherence of sound traveling through shallow-water nonlinear internal wave packets

Duda, Timothy F.

doi:10.1121/1.2200699

Cited by 15 publications

(11 citation statements)

References 19 publications

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“…On the other hand, for the 400 Hz case, the opposite is seen, that is to say the packet has coupled energy into higher mode lossy modes. Such effects of mean attenuation and amplification are consistent with prior model studies (Duda and Preisig, 1999;Duda, 2006).…”

Section: Implication For Interaction With Nonlinear Wavessupporting

confidence: 79%

Statistics of low-frequency normal-mode amplitudes in an ocean with random sound-speed perturbations: Shallow-water environments

Colosi

Duda

Morozov

2012

The Journal of the Acoustical Society of America

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Second-and fourth-moment mode-amplitude statistics for low-frequency ocean sound propagation through random sound-speed perturbations in a shallow-water environment are investigated using Monte Carlo simulations and a transport theory for the cross-mode coherence matrix. The acoustic observables of mean and mean square intensity are presented and the importance of adiabatic effects and cross-mode coherence decay are emphasized. Using frequencies of 200 and 400 Hz, transport theory is compared with Monte Carlo simulations in a canonical shallow-water environment representative of the summer Mid-Atlantic Bight. Except for ranges less than a horizontal coherence length of the sound structure, the intensity moments from the two calculations are in good agreement. Corrections for the short range behavior are presented. For these frequencies the computed mode coupling rates are extremely small, and the propagation is strongly adiabatic with a rapid decay of cross-mode coherence. Coupling effects are predicted to be important at kilohertz frequencies. Decay of cross-mode coherence has important implications for acoustic interactions with nonlinear internal waves: For the case in which the acoustic path is not at glancing incidence with a nonlinear internal-wave front, adiabatic phase randomizing effects lead to a significantly reduced influence of the nonlinear waves on both mean and mean square intensity.

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Section: Implication For Interaction With Nonlinear Wavessupporting

confidence: 79%

Statistics of low-frequency normal-mode amplitudes in an ocean with random sound-speed perturbations: Shallow-water environments

Colosi

Duda

Morozov

2012

The Journal of the Acoustical Society of America

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“…Additional publications covered temporal fluctuations caused by moving nonlinear wave packets (Duda and Preisig, 1999;Rouseff et al, 2002) and fields of waves Headrick et al, 2000b). Follow-on work expanded into analysis of bias effects (net attenuation or amplification) caused by coupled-mode propagation in the presence of two different mode-stripping conditions (Duda, 2004), and into analysis of acoustic field spatial coherence under similar conditions (Duda, 2006;Finette and Oba, 2003;Mignerey and Orr, 2004).…”

Section: B Prior Workmentioning

confidence: 99%

Horizontal coherence of low-frequency fixed-path sound in a continental shelf region with internal-wave activity

Duda

Collis

Lin

et al. 2012

The Journal of the Acoustical Society of America

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Sound at 85 to 450 Hz propagating in approximately 80-m depth water from fixed sources to a joint horizontal/vertical line array (HLA/VLA) is analyzed. The data are from a continental shelf area east of Delaware Bay (USA) populated with tidally generated long-and short-wavelength internal waves. Sound paths are 19 km in the along-shore (along internal-wave crest) direction and 30 km in the cross-shore direction. Spatial statistics of HLA arrivals are computed as functions of beam steering angle and time. These include array gain, horizontally lagged spatial correlation function, and coherent beam power. These quantities vary widely in magnitude, and vary over a broad range of time scales. For example, correlation scale can change rapidly from forty to five wavelengths, and correlation-scale behavior is anisotropic. In addition, the vertical array can be used to predict correlation expected for adiabatic propagation with cylindrical symmetry, forming a benchmark. Observed variations are in concert with internal-wave activity. Temporal variations of three coherence measures, horizontal correlation length, array gain, and ratio of actual correlation length to predicted adiabatic-mode correlation length, are very strong, varying by almost a factor of ten as internal waves pass.

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“…The beams are green, separated by blue areas of energy depletion. This effect is caused by source to internal-wave distance being a function of azimuth, causing azimuthal variations in mode coupling, and subsequent variations in energy loss via bottom interaction [7]. …”

Section: Internal Wave Environmentsmentioning

confidence: 99%

“…The accuracy of N × 2D simulations of propagation through 3D environments, such as in previous work [7], can be evaluated using the 3D model. To avoid discrepancies cause by comparing codes, we perform such an evaluation by comparing results from strongly-varying and weakly azimuthally varying 3D environments that are identical along the line y = 0.…”

Section: -D To 2-d Comparisonmentioning

confidence: 99%

Initial results from a cartesian three-dimensional parabolic equation acoustical propagation code

Duda¹

2006

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A three-dimensional (3D) parabolic equation acoustical propagation code has been developed and run successfully. The code is written in the MATLAB language and runs in the MATLAB environment. The code has been implemented in two versions, applied to (1) Horizontal low-frequency (100 to 500 Hz) propagation through the shallow water waveguide environment; (2) Vertical high-frequency propagation (6 to 15 kHz) to study normal-incidence reflection from the lower side of the ocean surface.The first edition of the code reported on here does not implement refinements that are often found in 2D propagation models, such as allowing density to vary, optimally smoothing soundspeed discontinuities at the water/seabed interface, and allowing an omni-directional source. The code is part of a development effort to test the applicability of 2D (and N by 2D) models, which have more refinements than this model, to the study of fully 3D propagation problems, such as sound transiting steep nonlinear coastal-area internal waves and/or sloping terrain, and to provide a numerical tool when the full 3D solution is needed.

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Temporal and cross-range coherence of sound traveling through shallow-water nonlinear internal wave packets

Cited by 15 publications

References 19 publications

Statistics of low-frequency normal-mode amplitudes in an ocean with random sound-speed perturbations: Shallow-water environments

Statistics of low-frequency normal-mode amplitudes in an ocean with random sound-speed perturbations: Shallow-water environments

Horizontal coherence of low-frequency fixed-path sound in a continental shelf region with internal-wave activity

Initial results from a cartesian three-dimensional parabolic equation acoustical propagation code

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