A model for variations in the range and depth dependence of the sound speed and attenuation induced by bubble clouds under wind-driven sea surfaces

Novarini, Jorge C.; Keiffer, Richard S.; Norton, Guy V.

doi:10.1109/48.725236

Cited by 40 publications

(17 citation statements)

References 28 publications

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“…Also, for both the ␥ plumes and background layer the slope for large radii becomes depth dependent. For each class the bubble concentration at a given radius and the overall void fraction of the plume are different ͑for a detailed description of the spectral forms see Novarini et al, 1998͒. Because of the lack of sufficient information on bubbles in shallow water, we adopted this model for the bubbly environment in the region of interest, which under the oceanographic viewpoint can be classified as intermediate water ͑Kinsman, 1965͒.…”

Section: The Range-dependent Bubbly Environmentmentioning

confidence: 99%

On the relative role of sea-surface roughness and bubble plumes in shallow-water propagation in the low-kilohertz region

Norton

Novarini

2001

The Journal of the Acoustical Society of America

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In the low-kilohertz frequency range, acoustic transmission in shallow water deteriorates as wind speed increases. Although the losses can be attributed to two environmental factors, the rough sea surface and the bubbles produced when breaking-or spilling waves are present, the relative role of each is still uncertain. For simplicity, in terms of an average bubble population, the time-and space-varying assemblage of microbubbles is usually assumed to be uniform in range and referred to as ''the subsurface bubble layer.'' However the bubble population is range-and depth-dependent. In this article, results of an experiment ͓Weston et al., Philos. Trans. R. Soc. London, Ser. A 265, 507-606 ͑1969͔͒ involving fixed source and receivers, and observations during an extended period of time under varying weather conditions are re-examined by exercising a numerical model that allows for the dissection of the problem. Calculations are made at 2-and 4-kHz. It is shown that at these frequencies and at wind speeds capable of generating breaking waves the main mechanism responsible for the excess loss in the shallow-water waveguide is the patchy nature of the subsurface bubble field. Refraction and attenuation within the pockets of high void fraction are minor contributors to the losses.

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Section: The Range-dependent Bubbly Environmentmentioning

confidence: 99%

On the relative role of sea-surface roughness and bubble plumes in shallow-water propagation in the low-kilohertz region

Norton

Novarini

2001

The Journal of the Acoustical Society of America

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“…The evolution of a bubble cloud can be separated into different stages: the first second or so after breaking where the void fraction of air can reach as high as 10 −1 , the subsequent few seconds after breaking where the bubble plume is being advected downward by the jet associated with the breaking wave with void fractions as high as 10 −3 -10 −4 , the final stage where the breaking wave energy has largely decayed and the cloud of bubbles is more strongly affected by local currents and processes such as Langmuir circulation, where void fractions are O͑10 −6 ͒, and the eventual decay into a background population of bubbles that has a very long lifetime ͑Monahan and Lu, 1990;Novarini et al, 1998͒. The bubble clouds associated with a particular breaking wave have been defined as ␣-, ␤-, and ␥-plumes, reflecting the changes in the cloud as it ages to 1 s, 3 -4 s, and beyond ͑Monahan and Lu, 1990͒.…”

Section: A Environmental Conditionsmentioning

confidence: 99%

Observations of clustering inside oceanic bubble clouds and the effect on short-range acoustic propagation

Weber

2008

The Journal of the Acoustical Society of America

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It has recently been shown [Weber, T. C. et al. (2007). "Acoustic propagation through clustered bubble clouds," IEEE J. Ocean. Eng. 32, 513-523] that gas bubble clustering plays a role in determining the acoustic field characteristics of bubbly fluids. In particular, it has been shown that clustering changes the bubble-induced attenuation as well as the ping-to-ping variability in the acoustic field. The degree to which bubble clustering exists in nature, however, is unknown. This paper describes a method for quantifying bubble clustering using a high frequency (400 kHz) multibeam sonar, and reports on observations of near-surface bubble clustering during a storm (14.6 m/s wind speed) in the Gulf of Maine. The multibeam sonar data are analyzed to estimate the pair correlation function, a measure of bubble clustering. In order to account for clustering in the mean acoustic field, a modification to the effective medium wave number is made. With this modification, the multibeam sonar observations are used to predict the effect of clustering on the attenuation of the mean field for short-range propagation (1 m) at frequencies between 10 and 350 kHz. Results for this specific case show that clustering can cause the attenuation to change by 20%-80% over this frequency range.

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“…As a bubble moves upward, it dissolves into the water. While the surface tension pressure results in faster dissolution of very small bubbles [35]. Bubbles will continue to shrink until they become so small to be removed from the water column.…”

Section: Bubble Plume Updatermentioning

confidence: 99%

A Model for Variations of Sound Speed and Attenuation from Seabed Gas Emissions

White

Bull

et al. 2019

Oceans 2019 MTS/Ieee Seattle

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The release of greenhouse gas, such as carbon dioxide (CO2) and methane (CH4) into the atmosphere, is a major source of global warming. As such a large emphasis has been placed on developing methods of measuring the amount of gas escaping from natural seep sites, particularly in the marine environment. Fortunately, gaseous bubbles crossing the seabed interface into the water column are relatively easily detected and quantified by passive acoustics. Here we design an active acoustic model to determine the frequency dependent changes in sound speed and attenuation in the water column due to gaseous CO2. Our approach is to formulate a numerical model simulating the propagation of sound energy at different frequencies through a mixed media incorporating a gas bubble plume with detection on a hydrophone.

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A model for variations in the range and depth dependence of the sound speed and attenuation induced by bubble clouds under wind-driven sea surfaces

Cited by 40 publications

References 28 publications

On the relative role of sea-surface roughness and bubble plumes in shallow-water propagation in the low-kilohertz region

On the relative role of sea-surface roughness and bubble plumes in shallow-water propagation in the low-kilohertz region

Observations of clustering inside oceanic bubble clouds and the effect on short-range acoustic propagation

A Model for Variations of Sound Speed and Attenuation from Seabed Gas Emissions

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