Acoustic scattering by an air-bubble near the sea surfaceacoustic scattering by an air-bubble near the sea surface

1995 ◽  
Vol 20 (4) ◽  
pp. 285-292 ◽  
Author(s):  
Guillermo C. Gaunaurd ◽  
Hanson Huang
Keyword(s):  
Acoustic Scattering ◽  
Sea Surface ◽  
Air Bubble

Comments on "acoustic scattering by an air bubble near the sea surface" [and reply]

1996 ◽  
Vol 21 (2) ◽  
pp. 233 ◽  
Author(s):  
M. Strasberg ◽  
G.C. Gaunaurd ◽  
H. Huang
Keyword(s):  
Acoustic Scattering ◽  
Sea Surface ◽  
Air Bubble

Propeller Cavitation Induced Hull Pressure Reduction by Air-Bubble Layer

2013 ◽  
Author(s):  
Jeung-Hoon Lee ◽  
Hyoung-Gil Park ◽  
Jin-Hak Kim ◽  
Kyung-Jun Lee ◽  
Jong-Soo Seo
Keyword(s):  
Acoustic Scattering ◽  
Destructive Interference ◽  
Primary Concern ◽  
Pressure Amplitude ◽  
Pressure Reduction ◽  
Noise Sources ◽  
Air Bubble ◽  
Excessive Consumption ◽  
Bubble Layer ◽  
The Cost

Cavitation generated by a marine propeller is a primary concern among the possible vibration- and noise- sources in commercial ships. By exploiting the compressibility of air, there have been many attempts to form an air-bubble layer underneath the stern-hull surface above the propeller, and consequently to isolate the cavity-induced pressure wave across the layer. However, it could not be popularly used because the cost was so expensive to deliver a huge amount of air for a sufficient isolation performance. In this work, full-scale ship measurements reveal that a significant reduction of pressure-amplitude is possible at the outside of an air-bubble layer, where the isolation effect is not involved. Moreover a hull-vibration reduction of approximately 75% was found to be achievable. Instead of excessive consumption of air, considerably small amount is necessary for a reduction of cavity-induced pressure amplitude, which can make the constitution of relevant system simple. Hence the purpose of this study is to provide a physical proof for such a beneficial phenomenon. By approximating the solution of acoustic scattering from a bubble, we find that phase-reversal reflection provoking a destructive interference is the main reason for a pressure reduction outside the layer.

scholarly journals Tunneling effects in resonant acoustic scattering of an air bubble in unbounded water

2016 ◽  
Vol 88 (2) ◽  
pp. 765-790 ◽  
Author(s):  
ANDRÉ G. SIMÃO ◽  
LUIZ G. GUIMARÃES
Keyword(s):  
Physical Model ◽  
Acoustic Scattering ◽  
Natural Oscillation ◽  
Potential Scattering ◽  
Underwater Sound ◽  
Quality Factors ◽  
Partial Wave Expansion ◽  
Storage Mechanism ◽  
Air Bubble ◽  
Oscillation Modes

Abstract The problem of acoustic scattering of a gaseous spherical bubble immersed within unbounded liquid surrounding is considered in this work. The theory of partial wave expansion related to this problem is revisited. A physical model based on the analogy between acoustic scattering and potential scattering in quantum mechanics is proposed to describe and interpret the acoustical natural oscillation modes of the bubble, namely, the resonances. In this context, a physical model is devised in order to describe the air water interface and the implications of the high density contrast on the various regimes of the scattering resonances. The main results are presented in terms of resonance lifetime periods and quality factors. The explicit numerical calculations are undertaken through an asymptotic analysis considering typical bubble dimensions and underwater sound wavelengths. It is shown that the resonance periods are scaled according to the Minnaert’s period, which is the short lived resonance mode, called breathing mode of the bubble. As expected, resonances with longer lifetimes lead to impressive cavity quality Q-factor ranging from 1010 to 105. The present theoretical findings lead to a better understanding of the energy storage mechanism in a bubbly medium.

scholarly journals Sound Scattering Layers Within and Beyond the Seychelles-Chagos Thermocline Ridge in the Southwest Indian Ocean

2021 ◽  
Vol 8 ◽  
Author(s):  
Myounghee Kang ◽  
Jung-Hoon Kang ◽  
Minju Kim ◽  
SungHyun Nam ◽  
Yeon Choi ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Unique Feature ◽  
Acoustic Scattering ◽  
Sea Surface ◽  
Distribution Dynamics ◽  
Sound Scattering ◽  
Southwest Indian Ocean ◽  
Environmental Properties ◽  
Distinct Features ◽  
Global Oceans

In global oceans, ubiquitous and persistent sound scattering layers (SL) are frequently detected with echosounders. The southwest Indian Ocean has a unique feature, a region of significant upwelling known as the Seychelles-Chagos Thermocline Ridge (SCTR), which affects sea surface temperature and marine ecosystems. Despite their importance, sound SL within and beyond the SCTR are poorly understood. This study aimed to compare the characteristics of the sound SL within and beyond the SCTR in connection with environmental properties, and dominant zooplankton. To this end, the region north of the 12°S latitude in the survey area was defined as SCTR, and the region south of 12°S was defined as non-SCTR. The results indicated contrasting oceanographic properties based on the depth layers between SCTR and non-SCTR regions. Distribution dynamics of the sound SL differed between the two regions. In particular, the diel vertical migration pattern, acoustic scattering values, metrics, and positional properties of acoustic scatterers showed two distinct features. In addition, the density of zooplankton sampled was higher in SCTR than in the non-SCTR region. This is the first study to present bioacoustic and hydrographic water properties within and beyond the SCTR in the southwest Indian Ocean.

Source signature determination by inversion

Geophysics ◽  
1992 ◽  
Vol 57 (12) ◽  
pp. 1633-1640 ◽  
Author(s):  
M. Landrø ◽  
R. Sollie
Keyword(s):  
Reflection Coefficient ◽  
Forward Modeling ◽  
Sea Surface ◽  
Inversion Algorithm ◽  
Air Bubble ◽  
Damping Coefficients ◽  
Air Gun ◽  
Marine Air ◽  
Source Array ◽  
Effective Source

A new method for estimating the pressure wavefield generated by a marine air‐gun array is presented. It is assumed that data is acquired at a ministreamer located below the source array. Effective source signatures for each air gun are estimated by an inversion algorithm. The forward modeling scheme used in the inversion algorithm is based upon a physical modeling of the air bubble generated by each air gun. This means that typical inversion parameters are: gun depths, empirical damping coefficients, and reflection coefficient of the sea surface. Variations in streamer depth are also taken into account by the inversion scheme. The algorithm has been successfully tested on examples with unknown streamer positions, gun parameters, reflection coefficient of sea surface, and ministreamer data contaminated with white noise.

Probability distribution of acoustic scattering from slightly rough sea surface

2016 ◽  
Vol 112 ◽  
pp. 134-144 ◽  
Author(s):  
Mohammad Reza Mousavi ◽  
Mahmood Karimi ◽  
Azizollah Jamshidi
Keyword(s):  
Probability Distribution ◽  
Acoustic Scattering ◽  
Sea Surface ◽  
Rough Sea Surface ◽  
Rough Sea
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