Finite-difference time-domain modeling of low to moderate frequency sea-surface reverberation in the presence of a near-surface bubble layer

Keiffer, Richard S.; Novarini, Jorge C.; Zingarelli, Robert A.

doi:10.1121/1.1383769

Cited by 7 publications

(2 citation statements)

References 7 publications

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“…16 In our treatment, the upper bound of the first water layer is a pressure release surface wave and the lower bound is located just below the lowest point of the surface wave. The sound speed can be assumed constant owing to a uniform void fraction due to small bubbles, 17 and the ray trajectory is linear in the first layer.…”

Section: Ray Tracing With a Rough Surfacementioning

confidence: 99%

Emergence of striation patterns in acoustic signals reflected from dynamic surface waves

Choo

Seong

Song

2014

The Journal of the Acoustical Society of America

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A striation pattern can emerge in high-frequency acoustic signals interacting with dynamic surface waves. The striation pattern is analyzed using a ray tracing algorithm for both a sinusoidal and a rough surface. With a source or receiver close to the surface, it is found that part of the surface on either side of the specular reflection point can be illuminated by rays, resulting in time-varying later arrivals in channel impulse response that form the striation pattern. In contrast to wave focusing associated with surface wave crests, the striation occurs due to reflection off convex sections around troughs. Simulations with a sinusoidal surface show both an upward (advancing) and downward (retreating) striation patterns that depend on the surface-wave traveling direction and the location of the illuminated area. In addition, the striation length is determined mainly by the depth of the source or receiver, whichever is closer in range to the illuminated region. Even with a rough surface, the striation emerges in both directions. However, broadband (7-13 kHz) simulations in shallow water indicate that the longer striation in one direction is likely pronounced against a quiet noise background, as observed from at-sea experimental data.

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Section: Ray Tracing With a Rough Surfacementioning

confidence: 99%

Emergence of striation patterns in acoustic signals reflected from dynamic surface waves

Choo

Seong

Song

2014

The Journal of the Acoustical Society of America

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“…FIDO solves the two-dimensional linear acoustic wave equation in a second order accurate algorithm assuming a nondispersive, non-attenuating medium. In previous studies [13], FIDO was tested (with excellent agreement) for backscattering from impenetrable wedge shaped boundaries using exact wedge diffraction theory and other FDTD results as benchmarks. Figure 1 shows a sketch of one of the numerical experiments.…”

Section: Numerical Experiments and Data Characterizationmentioning

confidence: 99%

A wedge diffraction based scattering model for acoustic scattering from rough littoral seafloors

Keiffer

Zingarelli

2008

Oceans 2008

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Models for acoustic scattering from rough surfaces based on Biot and Tolstoy's (BT) exact wedge diffraction theory have proven accurate and useful in a number of experimental and numerical studies [1]. Because the BT solution is restricted to impenetrable wedges (acoustically hard or soft boundary conditions), scattering models based on the BT solution have thus far been limited to the rough air/sea interface where the actual boundary conditions are very nearly pressure-release (soft). Recently, important theoretical work [2,3] has extended the exact BT theory to density-contrast but isospeed wedges. This new development makes possible the application of wedge diffraction based scattering models to the roughness at the sea floor where the change in the acoustic impedance at the boundary is dominated by changes in density and only weakly affected by changes in sound speed. However, it is important to confirm that small amounts of sound speed contrast do not perturb the diffraction too much. To contribute to the understanding of how the diffracted wave is affected by sound speed contrast and get some idea as to the practical limitations of wedgediffraction based scattering models for littoral seafloors, a simple numerical experiment involving a highly accurate Finite-Difference Time-Domain (FDTD) solution to the acoustic wave equation and a wedge-shaped boundary has been explored. This paper presents the results of FDTD experiments designed to quantify any changes in the diffracted field brought about by sound speed contrast. An ad hoc treatment of sound speed contrast is developed based on the requirement that the diffracted wave must smooth out the reflection discontinuity and preserve the continuity of the total field.

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Sound scattering from rough bubbly ocean surface based on modified sea surface acoustic simulator and consideration of various incident angles and sub-surface bubbles’ radii

Bolghasi

Ghadimi

Chekab

2016

J. Marine. Sci. Appl.

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Finite-difference time-domain modeling of low to moderate frequency sea-surface reverberation in the presence of a near-surface bubble layer

Cited by 7 publications

References 7 publications

Emergence of striation patterns in acoustic signals reflected from dynamic surface waves

Emergence of striation patterns in acoustic signals reflected from dynamic surface waves

A wedge diffraction based scattering model for acoustic scattering from rough littoral seafloors

Sound scattering from rough bubbly ocean surface based on modified sea surface acoustic simulator and consideration of various incident angles and sub-surface bubbles’ radii

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