On the theory of air‐gun bubble interactions

Geophysics ◽  
1988 ◽  
Vol 53 (2) ◽  
pp. 192-200 ◽  
Author(s):  
R. C. Bailey ◽  
P. B. Garces
Keyword(s):  
Ambient Pressure ◽  
Bubble Radius ◽  
Dynamical Equations ◽  
Local Pressure ◽  
Know How ◽  
R And D ◽  
Bubble Interactions ◽  
Interaction Terms ◽  
Air Gun ◽  
Marine Air

Calculation of the seismic signatures of marine air‐gun arrays often requires that the interactions among the bubbles from air guns be taken into account. The standard method of doing this is to use the Giles‐Johnston approximation in which a time‐dependent effective ambient pressure is calculated for each bubble as the sum of the true ambient pressure and the local pressure signals of all the other bubbles in the array. These effects of interaction have a relative importance in the dynamics proportional to (R/D), where R and D are the typical bubble radius and interbubble separation, respectively. To ensure that current methods of calculating signatures are accurate, it is necessary to know how good this approximation is. This paper shows that there are no interaction terms in the full dynamical equations proportional to [Formula: see text] or [Formula: see text], and that the errors of the Giles‐Johnston approximation are only of order [Formula: see text]. The Giles‐Johnston approximation is therefore justified even for fairly accurate signature calculations for noncoalescing bubbles. The analysis here also shows how to incorporate bubble motions and deformations into the dynamical equations, so that the errors can be reduced to order [Formula: see text] if desired.

Cutting Experiments in Cutting Speeds of up to 200 m/s with a High-Speed Impact Cutting Tester

2012 ◽  
Vol 523-524 ◽  
pp. 1041-1046 ◽  
Author(s):  
Tappei Higashi ◽  
Masato Sando ◽  
Jun Shinozuka
Keyword(s):  
High Speed ◽  
Ambient Pressure ◽  
Orthogonal Cutting ◽  
Cutting Speed ◽  
High Speed Impact ◽  
Air Gun ◽  
Impact Cutting ◽  
Compressed Gas ◽  
Cutting Experiments ◽  
Cutting Speeds

High-speed orthogonal cutting experiments with cutting speeds of up to 200 m/s with a high-speed impact cutting tester of air-gun type are attempted. In this tester, a light projectile with a small built-in cutting tool is loaded into a tube, being accelerated by a compressed gas. The projectile captures the chip that is indispensable to analyze the cutting mechanism. The projectile holding the chip is decelerated by another compressed gas just after finishing the cutting, being stopped without damage in the tube. Successful experiment can be accomplished by setting adequate values of the operation parameters for the experiment, which are the pressure of each gas and the opening and shutting time of the solenoid-controlled valve for each compressed gas. In order to determine the adequate values of these parameters, a ballistic simulator that simulates the velocity and position of the projectile traveling in the tube is developed. By setting the values of these parameters obtained by the simulator, the cutting speed of 200 m/s is achieved when the ambient pressure is set to be a vacuum and helium is used for each compressed gas. This paper describes the ballistic simulator developed and shows the experimental results of the high-speed cutting of aluminum alloy A2017.

scholarly journals A long-offset seismic reflection and refraction study of the Gippsland and Bass Basins from onshore recording of a marine air-gun source

1989 ◽  
Vol 20 (2) ◽  
pp. 293
Author(s):  
C.D.N. Collins ◽  
J.P. Cull ◽  
J.B. Willcox ◽  
J.B. Colwell
Keyword(s):  
Deep Structure ◽  
Seismic Refraction ◽  
Reflection And Refraction ◽  
Air Gun ◽  
Long Offset ◽  
Deep Crustal Structure ◽  
Basin Formation ◽  
Seismic Refraction Data ◽  
Marine Air ◽  
Refraction Data

Seismic refraction data were obtained for the Bass and Gippsland Basins during the 1988 cruise of the BMR research vessell "Rig Seismic". Seismic recorders were deployed on land by BMR and Monash University to record long-offset wide-angle reflection and refraction data using the ship's air-guns as the energy source. Preliminary results have now been obtained from these data providing information on deep crustal structure related to the basin formation. Two crustal layers have been detected with velocities of 4.5 km/s increasing to 7.4 km/s (unreversed) at depths exceeding 20 km. Additional data have now been obtained over a traverse length of 170 km to provide constraints on the deep structure of Bass Strait and the Lachlan Fold Belt in Victoria and Tasmania.

scholarly journals Comparing the broadband acoustic frequency response of single, clustered, and arrays of marine air guns

Geophysics ◽  
2020 ◽  
Vol 85 (3) ◽  
pp. P27-P36
Author(s):  
Martin Landrø ◽  
Jan Langhammer
Keyword(s):  
Acoustic Signal ◽  
High Frequency ◽  
High Speed ◽  
Acoustic Stimulation ◽  
Main Peak ◽  
Water Tank ◽  
High Frequency Signal ◽  
Acoustic Frequency ◽  
Air Gun ◽  
Marine Air

Field data acquired from a seismic vessel by a seabed hydrophone is used to analyze the broadband response (10 Hz to 62.5 kHz) for various source configurations: single air guns, clustered air guns, and a full array consisting of 30 air guns. The various parts of the acoustic signal are analyzed in detail, and it is found that a high-frequency signal arriving prior to the main peak of a single air-gun signal most likely is caused by small vapor cavities collapsing at or close to the surface of the gun. This is confirmed by high-speed photographs taken when a small air gun is fired in a water tank. When the full array is used, a second type of cavitation signal is observed: ghost cavitation caused by acoustic stimulation by the negative pressure that is backscattered from the free surface. As this ghost signal from 30 different guns arrives at a specific location in the water, cavities might be formed, and they create a high-frequency acoustic signal.

scholarly journals Adaptation to 5 weeks of intermittent local vascular pressure increments; mechanisms to be considered in the development of primary hypertension?

2021 ◽  
Author(s):  
Ola Eiken ◽  
Antonis Elia ◽  
Håkan Sköldefors ◽  
Patrik Sundblad ◽  
Michail E. Keramidas ◽  
...  
Keyword(s):  
Ambient Pressure ◽  
The Body ◽  
Primary Hypertension ◽  
Local Pressure ◽  
Vasoactive Substances ◽  
Before And After ◽  
Matrix Metalloproteinase 7 ◽  
Induced Flow ◽  
Local Release ◽  
Intravascular Pressure

The aims were to study effects of iterative exposures to moderate elevations of local intravascular pressure on arterial/arteriolar stiffness and plasma levels of vasoactive substances. Pressures in the vasculature of an arm were increased by 150 mmHg in healthy men (n=11) before and after a 5-wk regimen, during which the vasculature in one arm was exposed to fifteen 40-min sessions of moderately increased transmural pressure (+65 to +105 mmHg). This vascular pressure training and the pressure-distension determinations were conducted by exposing the subjects arm versus remaining part of the body to differential ambient pressure. During the pressure-distension determinations, venous samples were simultaneously obtained from pressurized and unpressurized vessels. Pressure training reduced arterial pressure distension by 40 ± 23% and pressure-induced flow by 33 ± 30% (p<0.01), but only in the pressure-trained arm, suggesting local adaptive mechanisms. The distending pressure-diameter and distending pressure-flow curves, with training-induced increments in pressure thresholds and reductions in response gains, suggest that the increased precapillary stiffness was attributable to increased contractility and structural remodeling of the walls. Acute vascular pressure provocation induced local release of angiotensin-II (Ang-II) and endothelin-1 (ET-1) (p<0.05), suggesting that these vasoconstrictors limited the pressure distension. Pressure training increased basal levels of ET-1 and induced local pressure release of matrix metalloproteinase 7 (p<0.05), suggesting involvement of these substances in vascular remodeling. The findings are compatible with the notion that local intravascular pressure load acts as a prime mover in the development of primary hypertension.

Optimizing spatial distribution to minimize the inline directivity for a marine air-gun source

Geophysics ◽  
2020 ◽  
Vol 85 (3) ◽  
pp. P37-P44
Author(s):  
Honglei Shen ◽  
Chunhui Tao ◽  
Thomas Elboth ◽  
Hanchuang Wang ◽  
Jianping Zhou ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
High Resolution ◽  
Directional Pattern ◽  
Stimulation Mode ◽  
Air Gun ◽  
Air Water Interface ◽  
Seismic Acquisition ◽  
Highly Correlated ◽  
Marine Air ◽  
Mathematical Derivation

The spatial distribution of an air-gun array and the ghost reflection from the air-water interface cause a directional pattern of the source signature and introduce notches at certain frequencies. This significantly limits the bandwidth of the seismic data and the ability to obtain high-resolution subsurface imaging. With mathematical derivation and numerical simulation, we have determined that the inline directivity relies on the number of air guns and their spacing. Furthermore, the effective width of the take-off angles for an air-gun array is highly correlated with the reciprocal of the distance variance along the inline direction, which is subsequently used for optimizing the source design. For a normal horizontal source, one could adjust the distance between two consecutive air guns to improve the source signature. We optimize the spatial distribution for air guns along the inline and depth directions, that is, by using the synchronized multidepth stimulation mode, to minimize the inline directivity. Simulated results show that a six-gun composed multidepth source could be designed to achieve nearly identical energy distribution with up to ±30° take-off angle for the high-frequency end up to 250 Hz. This represents a significant improvement compared to a normal horizontal source and is more suitable for high-resolution seismic acquisition.

Time‐lapse VSP test results demonstrate good repeatability for both land‐vibrator and marine air‐gun VSP surveys in Middle East carbonates

2007 ◽  
Author(s):  
William L. Soroka ◽  
Samer F. Marmash ◽  
Suaad Khouri ◽  
Ahmed Dawoud ◽  
Saleh Barakat ◽  
...  
Keyword(s):  
Middle East ◽  
Time Lapse ◽  
Test Results ◽  
Air Gun ◽  
Good Repeatability ◽  
Marine Air

Experimental and Numerical Investigation of Single Bubble Dynamics in a Two-Phase Bubbly Medium

2011 ◽  
Vol 133 (12) ◽  
Author(s):  
Arvind Jayaprakash ◽  
Sowmitra Singh ◽  
Georges Chahine
Keyword(s):  
Void Fraction ◽  
Compressible Fluid ◽  
High Speed ◽  
Bubble Dynamics ◽  
Ambient Pressure ◽  
Bubble Radius ◽  
Homogeneous Medium ◽  
Two Phase ◽  
Fluid Medium ◽  
Bubbly Medium

The dynamics of a bubble in a dilute bubbly water-air mixture is investigated experimentally and the results compared with a simple homogeneous compressible fluid model in order to elucidate the requirements from a better advanced numerical solution. The experiments are conducted in view of providing input and validation for an advanced bubbly flow numerical model we are developing. Corrections for classical approaches where in the two-phase flow modeling the dynamics of individual bubble is based on spherical isolated bubble dynamics in the liquid or an equivalent homogeneous medium are sought. The main/primary bubble is produced by an underwater spark discharge from charged capacitors, while the bubbly medium is generated using electrolysis. The size of the main bubble is controlled by the discharge voltage, the capacitors size, and the ambient pressure in the container. The size and concentration of the fine bubbles is controlled by the electrolysis voltage, the length, diameter, arrangement, and type of the wires, and also by the pressure imposed in the container. This enables parametric study of the factors controlling the dynamics of the primary bubble and development of relationships between the primary bubble characteristic quantities such as achieved maximum bubble radius and bubble period and the characteristics of the surrounding two-phase medium: micro bubble sizes and void fraction. The dynamics of the main bubble and of the mixture is observed using high speed video photography. The void fraction of the bubbly mixture in the fluid domain is deduced from image analysis of the high speed movies and obtained as a function of time and space. The interaction between the primary bubble and the bubbly medium is analyzed using both field pressure measurements and high-speed videography. Parameters such as the primary bubble energy and the bubble mixture density (void fraction) are varied, and their effects studied. The experimental data is then compared to a simple compressible fluid medium model which accounts for the change in the medium properties in space and time. This helps illustrate where such simple models are valid and where they need improvements. This information is valuable for the parallel development of an Eulerian-Lagrangian code, which accounts for the dynamics of bubbles in the field and their interaction.

Measurement of air‐gun bubble oscillations

Geophysics ◽  
1998 ◽  
Vol 63 (6) ◽  
pp. 2009-2024 ◽  
Author(s):  
Anton Ziolkowski
Keyword(s):  
Acoustic Radiation ◽  
Bubble Radius ◽  
Real Data ◽  
Equation Of Motion ◽  
Smooth Transition ◽  
Bubble Wall ◽  
Wall Velocity ◽  
Pressure Transducers ◽  
Air Gun ◽  
Bubble Oscillations

In this paper, I provide a theoretical basis for a practical approach to measuring the pressure field of an air gun array and present an algorithm for computing its wavefield from pressure measurements made at known positions in the vicinity of the gun ports. The theory for the oscillations of a single bubble is essentially a straight‐forward extension of Lamb’s original paper and provides a continuous, smooth transition from the oscillating wall of the bubble to the far‐field, preserving both the fluid flow and the acoustic radiation, all to the same accuracy and valid for bubbles with initial pressures up to about 200 atm (3000 psi or 20 MPa). The simplifying assumption, based on an argument of Lamb, is that the particle velocity potential obeys the linear acoustic wave equation. This is used then in the basic dynamic and kinematic equations to lead, without further approximations, to the nonlinear equation of motion of the bubble wall and the wavefield in the water. Given the initial bubble radius, the initial bubble wall velocity, and the pressure variation at any point inside or outside the bubble, the algorithm can be used to calculate the bubble motion and the acoustic wavefield. The interaction among air‐gun bubbles and the resultant total wavefield is formulated using the notional source concept, in which each bubble is replaced by an equivalent notional bubble obeying the same equation of motion but oscillating in water of hydrostatic pressure, thus allowing the wavefields of the notional bubbles to be superposed. A separate calibration experiment using the same pressure transducers and firing the guns individually allows the initial values of the bubble radius and bubble wall velocity to be determined for each gun. An appendix to the paper provides a test of the algorithm on real data from a single gun.

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