Estimation of bubble time period for air-gun clusters using potential isosurfaces

Barker, Daniel S.; Landrø, Martin

doi:10.1190/geo2012-0344.1

Cited by 4 publications

(2 citation statements)

References 15 publications

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“…In addition, low frequency acoustic waves usually are less harmful to marine mammals 59 . One possible method to reduce the acoustic frequency is to use airgun clusters to cause synchronized individual bubbles to coalesce into a bigger bubble 60,61 , which has a longer period.…”

Section: Introductionmentioning

confidence: 99%

Experimental study on interaction and coalescence of synchronized multiple bubbles

Cui

Wang

et al. 2016

Physics of Fluids

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Experiments are carried out on the interaction and coalescence of two, three and four bubbles with approximately the same sizes, distributed evenly and symmetrically. The bubbles are generated simultaneously by electric discharges, using an in-house designed series circuit, and their interaction is captured using a high-speed camera. Particular attentions are paid to if/when coalescence of bubbles happens, and the motion of the joined bubbles. Some new features are observed, which depend mainly on the dimensionless distance γ bb = d bb /R max , where d bb is the inter-bubble distance and R max is the maximum bubble radius. For γ bb > 2, a jet forms and penetrates each side bubble, directed to the center of the configuration, resulting in a protrusion. Towards the end of collapse, a large portion of bubble gases is compressed into the protrusion from the main part of the toroidal bubble. For γ bb < 2, the bubbles coalesce during expansion, and the part of the joined bubble's surface distal from the center of the configuration collapses faster than elsewhere. The experiments show that the oscillation period of multi-bubbles does not change appreciably without coalescence but increases significantly with coalescence. For three bubbles initiated at collinear positions with γ bb > 2, the jets that form from the side bubbles are towards the middle, and the middle bubble splits into two parts, moving towards the two side bubbles. For γ bb < 2, the side bubbles merge with the middle bubble during expansion, forming an ellipsoid bubble; the joined bubble collapses predominantly from two sides, where two inward jets form towards the end of collapse.

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Section: Introductionmentioning

confidence: 99%

Experimental study on interaction and coalescence of synchronized multiple bubbles

Cui

Wang

et al. 2016

Physics of Fluids

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“…A larger bubble will, all other things equal, oscillate slower. In conjunction with studies of the time interval between underwater explosion bubble oscillations (Willis, 1941;Cole, 1948), this early work formed the basis for the well-known Rayleigh-Willis equation, which is commonly used in the marine seismic exploration community (Hegna and Parkes, 2011;Barker and Landrø, 2013;Watson et al, 2016):…”

Section: Bubble Oscillationsmentioning

confidence: 99%

What controls the initial peak of an air-gun source signature?

2019

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Seismic air guns are broadband sources that generate acoustic waves at many frequencies. The low frequency waves can be used for imaging while the high frequency waves are attenuated and/or scattered before they can reflect from targets of interest in the subsurface. It is desirable to reduce the amplitude of the high frequency acoustic waves as they are thought to be disruptive, and potentially damaging, to marine life and are not useful for geophysical purposes. The high frequency acoustic waves are primarily associated with the initial expansion of the air gun bubble and associated peak in the acoustic pressure time series, which is commonly referred to as the source signature of the air gun. Here, we develop a quasi-one-dimensional model of a seismic air gun coupled to a spherical bubble that accounts for gas dynamics and spatially variable depressurization inside the firing chamber in order to investigate controls on the initial peak of the source signature. The model is validated against data collected during field tests in Lake Seneca, New York. Simulations and field data both show that the initial peak is primarily dependent on the operating pressure. A lower gun pressure results in a smaller peak amplitude and a slower rise time. The slope, the amplitude of the initial peak divided by the rise time, is used as a proxy for environmental impact and can decrease by as much as 50% when the air gun pressure is reduced from 2000 psi to 1000 psi. The low frequencies are controlled by the total discharged mass, which is dependent upon gun volume and pressure. Decreasing the operating pressure while simultaneously increasing the gun volume will reduce the high frequencies while maintaining the desirable low frequency signals.

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An alternative method for modeling close-range interactions between air guns

Barker

Landrø

2014

GEOPHYSICS

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We evaluated the problem of modeling the decay of the primary pulse amplitudes of air-gun clusters caused by the traditional assumption of sphericality. This was done by generalizing the Rayleigh equation to work with arbitrary bubble shapes, while retaining the assumption of incompressibility. To approximate the coalescence of the bubbles, we let the shapes be isosurfaces of the velocity potential. With this method, it is possible to model the firing of clustered air guns at any separation distance, including small distances that would cause two spherical bubbles to overlap. In this way, we obtained results matching the relative decay shown to be present for air-gun clusters. In addition, this method also allowed a way of calibrating the model such that effects created by the presence of the gun, compared to just a single spherical air bubble, may be estimated and included.

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Estimation of bubble time period for air-gun clusters using potential isosurfaces

Cited by 4 publications

References 15 publications

Experimental study on interaction and coalescence of synchronized multiple bubbles

Experimental study on interaction and coalescence of synchronized multiple bubbles

What controls the initial peak of an air-gun source signature?

An alternative method for modeling close-range interactions between air guns

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