#### Sample records for gas bubbles rising

1. Liquid jet pumped by rising gas bubbles

NASA Technical Reports Server (NTRS)

Hussain, N. A.; Siegel, R.

1975-01-01

A two-phase mathematical model is proposed for calculating the induced turbulent vertical liquid flow. Bubbles provide a large buoyancy force and the associated drag on the liquid moves the liquid upward. The liquid pumped upward consists of the bubble wakes and the liquid brought into the jet region by turbulent entrainment. The expansion of the gas bubbles as they rise through the liquid is taken into account. The continuity and momentum equations are solved numerically for an axisymmetric air jet submerged in water. Water pumping rates are obtained as a function of air flow rate and depth of submergence. Comparisons are made with limited experimental information in the literature.

2. Liquid jet pumped by rising gas bubbles

NASA Technical Reports Server (NTRS)

Hussain, N. A.; Siegel, R.

1975-01-01

From observations of a stream of gas bubbles rising through a liquid, a two-phase mathematical model is proposed for calculating the induced turbulent vertical liquid flow. The bubbles provide a large buoyancy force and the associated drag on the liquid moves the liquid upward. The liquid pumped upward consists of the bubble wakes and the liquid brought into the jet region by turbulent entrainment. The expansion of the gas bubbles as they arise through the liquid is taken into account. The continuity and momentum equations are solved numerically for an axisymmetric air jet submerged in water. Water pumping rates are obtained as a function of air flow rate and depth of submergence. Comparisons are made with limited experimental information in the literature.

3. Rise characteristics of gas bubbles in a 2D rectangular column: VOF simulations vs experiments

SciTech Connect

Krishna, R.; Baten, J.M. van

1999-10-01

About five centuries ago, Leonardo da Vinci described the sinuous motion of gas bubbles rising in water. The authors have attempted to simulate the rise trajectories of bubbles of 4, 5, 7, 8, 9, 12, and 20 mm in diameter rising in a 2D rectangular column filled with water. The simulations were carried out using the volume-of-fluid (VOF) technique developed by Hirt and Nichols (J. Computational Physics, 39, 201--225 (1981)). To solve the Navier-Stokes equations of motion the authors used a commercial solver, CFX 4.1c of AEA Technology, UK. They developed their own bubble-tracking algorithm to capture sinuous bubble motions. The 4 and 5 mm bubbles show large lateral motions observed by Da Vinci. The 7, 8 and 9 mm bubble behave like jellyfish. The 12 mm bubble flaps its wings like a bird. The extent of lateral motion of the bubbles decreases with increasing bubble size. Bubbles larger than 20 mm in size assume a spherical cap form and simulations of the rise characteristics match experiments exactly. VOF simulations are powerful tools for a priori determination of the morphology and rise characteristics of bubbles rising in a liquid. Bubble-bubble interactions are also properly modeled by the VOF technique.

4. Behavior of bubbles in glassmelts. III - Dissolution and growth of a rising bubble containing a single gas

NASA Technical Reports Server (NTRS)

Onorato, P. I. K.; Weinberg, M. C.; Uhlmann, D. R.

1981-01-01

Finite difference solutions of the mass transport equations governing the dissolution (growth) of a rising gas bubble, containing a single gas, in a glassmelt were obtained. These solutions were compared with those obtained from an approximate procedure for a range of the controlling parameters. Applications were made to describe various aspects of O2 and CO2 gas-bubble behavior in a soda-lime-silicate melt.

5. The effect of thixotropy on a rising gas bubble: A numerical study

2016-08-01

The deformation of a single, two-dimensional, circular gas bubble rising in an otherwise stationary thixotropic liquid in a confined rectangular vessel is numerically studied using the smoothed particle hydrodynamics method (SPH). The thixotropic liquid surrounding the bubble is assumed to obey the Moore model. The main objective of the work is to investigate the effect of the destruction-to-rebuild ratio (referred to by the thixotropy number in dimensionless form) in this model on the bubble's shape, velocity, and center-ofmass during its rise in the liquid. Based on the numerical results obtained in this work, it is found that the bubble moves faster in the Moore fluid as compared with its Newtonian counterpart. An increase in the thixotropy number is also shown to increase the bubble's speed at any given instant of time. The effect of thixotropy number is found to be noticeable only when it is large. For Moore fluid, a large thixotropy number means that the fluid is basically a shear-thinning fluid. Therefore, it is concluded that the shear-thinning behavior of the Moore model easily masks its thixotropic behavior in the bubble rise problem. The effect of thixotropy number is weakened when the Reynolds number is increased.

6. Instability of two rising bubbles

Galper, Alexander; Miloh, Touvia

1999-11-01

We consider the stability of two rising ideal gas spherical bubbles subject of an intrinsic dynamics. The dynamics is prescribed or governed by the Rayleigh-Plesset equation adjusted for the pressure field induced by the other bubble in the center of each. Hence, each bubble exhibits linear (nonlinear) oscillations about a stable equilibrium. In order to treat the Liapunov stability problem of bubbles spatial motion we develop the corresponding Hamiltonian formalism. Thus, we find that the oscillations can stabilize the side-by-side and one-below-the-other bubbles translation. These types of translation are known to be asymptotically stable (unstable) for the motion of a pair of purely spherical rigid bubbles. The stabilization phenomenon depends on the frequency and phase difference in the bubbles fast oscillations. The rigid'' bubbles theory of the motion is known to have certain discrepancies with the relevant experiments. In order to remove them it is proposed to account for the vorticity wake behind each bubble. Nevertheless, we are able to explain the experiments remaining within the potential framework. Finally, we consider the case of chaotic pulsations. The motion of the two bubbles can also inherit a chaotic character. It results, in turn, in a certain strange attractor for the spatial motion of a pair.

7. Visualization of gas-liquid mass transfer and wake structure of rising bubbles using pH-sensitive PLIF

Stöhr, M.; Schanze, J.; Khalili, A.

2009-07-01

A planar laser-induced fluorescence (PLIF) technique for visualizing gas-liquid mass transfer and wake structure of rising gas bubbles is described. The method uses an aqueous solution of the pH-sensitive dye Naphthofluorescein and CO2 as a tracer gas. It features a high spatial resolution and frame rates of up to 500 Hz, providing the ability to capture cinematographic image sequences. By steering the laser beam with a set of two programmable scanning mirrors, sequences of three-dimensional LIF images can be recorded. The technique is applied to freely rising bubbles with diameters between 0.5 and 5 mm, which perform rectilinear, oscillatory or irregular motions. The resulting PLIF image sequences reveal the evolution of characteristic patterns in the near and far wake of the bubbles and prove the potential of the technique to provide new and detailed insights into the spatio-temporal dynamics of mass transfer of rising gas bubbles. The image sequences further allow the estimation of bubble size and rise velocity. The analysis of bubble rise velocities in the Naphthofluorescein solution indicates that surfactant-contaminated conditions are encountered.

8. Velocity of a freely rising gas bubble in a soda-lime silicate glass melt

NASA Technical Reports Server (NTRS)

Hornyak, E. J.; Weinberg, M. C.

1984-01-01

A comparison is conducted between measured velocities for the buoyant rise of single bubbles of varying size and composition, in a soda-lime silicate glass melt, with the steady state velocities predicted by the Stokes and Hadamard-Rybczynski formulas. In all cases, the data are noted to fit the Hadamard-Rybczynski expression for steady state rise speed considerably better than the Stokes formula.

9. Universal correlation for the rise velocity of long gas bubbles in round pipes

Viana, Flavia; Pardo, Raimundo; Yánez, Rodolfo; Trallero, José L.; Joseph, Daniel D.

2003-11-01

We collected all of the published data we could find on the rise velocity of long gas bubbles in stagnant fluids contained in circular tubes. Data from 255 experiments from the literature and seven new experiments at PDVSA Intevep for fluids with viscosities ranging from 1 mPa s up to 3900 mPa s were assembled on spread sheets and processed in log log plots of the normalized rise velocity, Fr {=} U/(gD)(1/2) Froude velocity vs. buoyancy Reynolds number, R {=} (D(3) g (rho_{l}-rho_{g}) rho_{l})(1/2) /mu for fixed ranges of the Eötvös number, Eo {=} grho_{l}D(2) /sigma where D is the pipe diameter, rho_{l}, rho_{g} and sigma are densities and surface tension. The plots give rise to power laws in Eo; the composition of these separate power laws emerge as bi-power laws for two separate flow regions for large and small buoyancy Reynolds. For large R (>200) we find [hboxFr = {0.34}/(1+3805/hboxEo^{3.06})^{0.58}.] For small R (<10) we find [ hboxFr = frac{9.494times 10^{-3}}{({1+{6197}/hboxEo^{2.561}})^{0.5793}}R^{1.026}.] The flat region for high buoyancy Reynolds number and sloped region for low buoyancy Reynolds number is separated by a transition region (10 {<} R {<} 200) which we describe by fitting the data to a logistic dose curve. Repeated application of logistic dose curves leads to a composition of rational fractions of rational fractions of power laws. This leads to the following universal correlation: [ hboxFr = L[{R;A,B,C,G}] equiv frac{A}{({1+({{R}/{B}})^C})^G} ] where [ A = L[hboxEo;a,b,c,d],quad B = L[hboxEo;e,f,g,h],quad C = L[hboxEo;i,j,k,l],quad G = m/C ] and the parameters (a, b,...,l) are begin{eqnarray*} &&hspace*{-5pt}a hspace*{-0.8pt} {=} hspace*{-0.8pt} 0.34;quad bhspace*{-0.8pt} {=} hspace*{-0.8pt} 14.793;quad chspace*{-0.8pt} {=} hspace*{-0.6pt}{-}3.06;quad dhspace*{-0.6pt} {=} hspace*{-0.6pt}0.58;quad ehspace*{-0.6pt} {=} hspace*{-0.6pt} 31.08;quad fhspace*{-0.6pt} {=} hspace*{-0.6pt}29.868;quad ghspace*{-0.6pt} { =} hspace*{-0.6pt}{ -}1

10. Bubbles Rising Through a Soft Granular Material

Le Mestre, Robin; MacMinn, Chris; Lee, Sungyon

2016-11-01

Bubble migration through a soft granular material involves a strong coupling between the bubble dynamics and the deformation of the material. This is relevant to a variety of natural processes such as gas venting from sediments and gas exsolution from magma. Here, we study this process experimentally by injecting air bubbles into a quasi-2D packing of soft hydrogel beads and measuring the size, speed, and morphology of the bubbles as they rise due to buoyancy. Whereas previous work has focused on deformation resisted by intergranular friction, we focus on the previously inaccessible regime of deformation resisted by elasticity. At low confining stress, the bubbles are irregular and rounded, migrating via local rearrangement. At high confining stress, the bubbles become unstable and branched, migrating via pathway opening. The authors thank The Royal Society for support (International Exchanges Ref IE150885).

11. Self-organization of hydrogen gas bubbles rising above laser-etched metallic aluminum in a weakly basic aqueous solution.

PubMed

Barmina, E V; Kuzmin, P G; Shafeev, G A

2011-10-01

Self-organization of hydrogen bubbles is reported under etching of metallic Aluminum in a weakly basic solution. The ascending gas bubbles drift to the areas with higher density of bubbles. As a result, ascending bubbles form various stationary structures whose symmetry is determined by the symmetry of the etched area. Bubbles are aligned along the bisectors of the contour of the etched area. The special laser-assisted profiling of the etched area in shape of a vortex induces a torque in the fluid above the etched area. The process is interpreted on the basis of Bernoulli equation.

12. Gas bubble detector

NASA Technical Reports Server (NTRS)

Mount, Bruce E. (Inventor); Burchfield, David E. (Inventor); Hagey, John M. (Inventor)

1995-01-01

A gas bubble detector having a modulated IR source focused through a bandpass filter onto a venturi, formed in a sample tube, to illuminate the venturi with modulated filtered IR to detect the presence of gas bubbles as small as 0.01 cm or about 0.004 in diameter in liquid flowing through the venturi. Means are provided to determine the size of any detected bubble and to provide an alarm in the absence of liquid in the sample tube.

13. Scaling law for bubbles rising near vertical walls

2016-06-01

This paper examines the rising motion of a layer of gas bubbles next to a vertical wall in a liquid in the presence of an upward flow parallel to the wall to help with the understanding of the fluid dynamics in a bubbly upflow in vertical channels. Only the region near the wall is simulated with an average pressure gradient applied to the domain that balances the weight of the liquid phase. The upward flow is created by the rising motion of the bubbles. The bubbles are kept near the wall by the lateral lift force acting on them as a result of rising in the shear layer near the wall. The rise velocity of the bubbles sliding on the wall and the average rise velocity of the liquid depend on three dimensionless parameters, Archimedes number, Ar, Eötvös number, Eo, and the average volume fraction of bubbles on the wall. In the limit of small Eo, bubbles are nearly spherical and the dependency on Eo becomes negligible. In this limit, the scaling of the liquid Reynolds number with Archimedes number and the void fraction is presented. A scaling argument is presented based on viscous dissipation analysis that matches the numerical findings. Viscous dissipation rates are found to be high in a thin film region between the bubble and the wall. A scaling of the viscous dissipation and steady state film thickness between the bubble and the wall with Archimedes number is presented.

14. Initial rise of bubbles in cohesive sediments by a process of viscoelastic fracture

Algar, C. K.; Boudreau, B. P.; Barry, M. A.

2011-04-01

An understanding of the mechanics of bubble rise in sediments is essential because of the role of bubbles in releasing methane to the atmosphere and the formation and melting of gas hydrates. Past models to describe and predict the rise of other buoyant geological bodies through a surrounding solid (e.g., magmas and hydrofractures) appear not to be applicable to bubbles in soft sediments, and this paper presents a new model for gas bubble rise in soft, fine-grained, cohesive sediments. Bubbles in such sediments are essentially "dry" (little if any free water) and grow through a process of elastic expansion and fracture that can be described using the principles of linear elastic fracture mechanics, which assume the existence of a spectrum of flaws within the sediment fabric. By extending this theory, we predict that bubbles initially rise by preferential propagation of a fracture in a (sub) vertical direction. We present a criterion for initial bubble rise. Once rise is initiated, the speed of rise is controlled by the viscoelastic response of the sediments to stress. Using this new bubble rise model, we estimate rise velocities to be of the order of centimeters per second. We again show that capillary pressure plays no substantive role in controlling bubble growth or rise.

15. A computational study of the dynamic motion of a bubble rising in Carreau model fluids

Ohta, Mitsuhiro; Yoshida, Yutaka; Sussman, Mark

2010-04-01

We present the results of three-dimensional direct numerical simulations of the dynamic motion of a gas bubble rising in Carreau model fluids. The simulations are carried out by a coupled level-set/volume-of-fluid (CLSVOF) method, which combines some of the advantages of the volume-of-fluid (VOF) method with the level-set (LS) method. In our study, it is shown that the motion of a rising gas bubble largely depends on the Carreau model parameters, n and B (n, the slope of decreasing viscosity and B, time constant). Both the model parameters, n and B, have considerable influence on the bubble rise motion. Using numerical analysis, we can understand in detail the bubble morphology for non-Newtonian two-phase flow systems. We also discuss bubble rise motion in shear-thinning fluids in terms of the effective viscosity, ηeff, the effective Reynolds number, Reeff and the effective Morton number, Meff.

16. The shape of bubbles rising near the nozzle exit in molten metal baths

Iguchi, Manabu; Nakatani, Tadatoshi; Tokunaga, Hirohiko

1997-06-01

A previously developed multineedle electroresistivity probe was used to investigate the shape of bubbles generated at the exit of a central single-hole bottom nozzle in molten Wood’s metal and mercury baths. This probe is capable of detecting the vertical cross section of rising bubbles. The shape of bubbles just after the detachment from the nozzle exit was correlated as a function of a modified Reynolds number and a modified Weber number. Furthermore, the relations between the shape of bubbles and the radial distributions of bubble characteristics specified by gas holdup, bubble frequency, etc. were derived. As a result, it is possible to predict the shape of the bubbles by measuring the bubble characteristics with a conventional two-needle electroresistivity probe.

17. Experimental study on wake structure of single rising clean bubble

Sato, Ayaka; Takedomi, Yuta; Shirota, Minori; Sanada, Toshiyuki; Watanabe, Masao

2007-11-01

Wake structure of clean bubble rising in quiescent silicone oil solution of photochromic dye is experimentally studied. A single bubble is generated, immediately after UV sheet light illuminates the part of the liquid just above the bubble generation nozzle in order to activate photochromic dye. Once the bubble passes across the colored part of the liquid, the bubble is accompanied by some portion of activated dye tracers; hence the flow structure in the rear of the single rising bubble is visualized. We capture stereo images of both wake structure and bubble motion. We study how wake structure changes with the increase in bubble size. We observe the stable axisymmetric wake structure, which is called standing eddy' when bubble size is relatively small, and then wake structure becomes unstable and starts to oscillate with the increase in bubble size. With further increase in bubble size, a pair of streamwise vortices, which is called double thread', is observed. We discuss in detail this transition from the steady wake to unsteady wake structure, especially double thread wake development and hairpin vortices shedding, in relation to the transition from rectilinear to spiral or zigzag bubble motions.

18. On the deformation of gas bubbles in liquids

Legendre, Dominique; Zenit, Roberto; Velez-Cordero, J. Rodrigo

2012-04-01

We consider the deformation of gas bubbles rising in different liquids over a wide range of Morton numbers, from O(10-11) to O(1), and bubble diameters. We have collected data from the literature and performed new experiments for relatively large Morton numbers. A simple expression is proposed to describe the evolution of the bubble deformation, which is consistent with the analytical solution of Moore ["The rise of a gas bubble in a viscous liquid," J. Fluid Mech. 6, 113 (1959)]. It appears that deformation can be predicted correctly by considering the Morton and Weber numbers. The variation of the bubble interfacial area is also analyzed; this quantity is very important for the case of bubbly flow modeling but has not been measured directly to date.

19. Rise of an argon bubble in liquid steel in the presence of a transverse magnetic field

Jin, K.; Kumar, P.; Vanka, S. P.; Thomas, B. G.

2016-09-01

The rise of gaseous bubbles in viscous liquids is a fundamental problem in fluid physics, and it is also a common phenomenon in many industrial applications such as materials processing, food processing, and fusion reactor cooling. In this work, the motion of a single argon gas bubble rising in quiescent liquid steel under an external magnetic field is studied numerically using a Volume-of-Fluid method. To mitigate spurious velocities normally generated during numerical simulation of multiphase flows with large density differences, an improved algorithm for surface tension modeling, originally proposed by Wang and Tong ["Deformation and oscillations of a single gas bubble rising in a narrow vertical tube," Int. J. Therm. Sci. 47, 221-228 (2008)] is implemented, validated and used in the present computations. The governing equations are integrated by a second-order space and time accurate numerical scheme, and implemented on multiple Graphics Processing Units with high parallel efficiency. The motion and terminal velocities of the rising bubble under different magnetic fields are compared and a reduction in rise velocity is seen in cases with the magnetic field applied. The shape deformation and the path of the bubble are discussed. An elongation of the bubble along the field direction is seen, and the physics behind these phenomena is discussed. The wake structures behind the bubble are visualized and effects of the magnetic field on the wake structures are presented. A modified drag coefficient is obtained to include the additional resistance force caused by adding a transverse magnetic field.

20. Rise of Air Bubbles in Aircraft Lubricating Oils

NASA Technical Reports Server (NTRS)

Robinson, J. V.

1950-01-01

Lubricating and antifoaming additives in aircraft lubricating oils may impede the escape of small bubbles from the oil by forming shells of liquid with a quasi-solid or gel structure around the bubbles. The rates of rise of small air bubbles, up to 2 millimeters in diameter, were measured at room temperature in an undoped oil, in the same oil containing foam inhibitors, and in an oil containing lubricating additives. The apparent diameter of the air bubbles was measured visually through an ocular micrometer on a traveling telescope. The bubbles in the undoped oil obeyed Stokes' Law, the rate of rise being proportional to the square of the apparent diameter and inversely proportional to the viscosity of the oil. The bubbles in the oils containing lubricating additives or foam inhibitors rose more slowly than the rate predicted by Stokes 1 Law from the apparent diameter, and the rate of rise decreased as the length of path the bubbles traveled increased. A method is derived to calculate the thickness of the liquid shell which would have to move with the bubbles in the doped oils to account for the abnoi'I!l8.lly slow velocity. The maximum thickness of this shell, calculated from the velocities observed, was equal to the bubble radius.

1. Etiology of gas bubble disease

SciTech Connect

Bouck, G.R.

1980-11-01

Gas bubble disease is a noninfectious, physically induced process caused by uncompensated hyperbaric pressure of total dissolved gases. When pressure compensation is inadequate, dissolved gases may form emboli (in blood) and emphysema (in tissues). The resulting abnormal physical presence of gases can block blood vessels (hemostasis) or tear tissues, and may result in death. Population mortality is generally skewed, in that the median time to death occurs well before the average time to death. Judged from mortality curves, three stages occur in gas bubble disease: (1) a period of gas pressure equilibrium, nonlethal cavitation, and increasing morbidity; (2) a period of rapid and heavy mortality; and (3) a period of protracted survival, despite lesions, and dysfunction that eventually terminates in total mortality. Safe limits for gas supersaturation depend on species tolerance and on factors that differ among hatcheries and rivers, between continuous and intermittent exposures, and across ranges of temperature and salinity.

2. Gas-rise velocities during kicks

SciTech Connect

White, D.B. )

1991-12-01

This paper reports on experiments to examine gas migration rates in drilling muds that were performed in a 15-m-long, 200-mm-ID inclinable flow loop where air injection simulates gas entry during a kick. These tests were conducted using a xanthum gum (a common polymer used in drilling fluids) solution to simulate drilling muds as the liquid phase and air as the gas phase. This work represents a significant extension of existing correlations for gas/liquid flows in large pipe diameters with non- Newtonian fluids. Bubbles rise faster in drilling muds than in water despite the increased viscosity. This surprising result is caused by the change in the flow regime, with large slug-type bubbles forming at lower void fractions. The gas velocity is independent of void fraction, thus simplifying flow modeling. Results show that a gas influx will rise faster in a well than previously believed. This has major implications for kick simulation, with gas arriving at the surface earlier than would be expected and the gas outflow rate being higher than would have been predicted. A model of the two-phase gas flow in drilling mud, including the results of this work, has been incorporated into the joint Schlumberger Cambridge Research (SCR)/BP Intl. kick model.

3. Correlation of bubble rise velocity and volume

SciTech Connect

Burge, C.

1991-01-01

This project was conducted at Westinghouse's Savannah River Laboratories (SRL). The goal of SRL is to make certain that the modifications on the reactor are safe for those working at the plant as well as the general public. One of the steps needed to insure safety is the knowledge of the occurrences that result from a plenum pipe breakage. When a plenum pipe breaks, two things occur: air is sucked into the pipe and is trapped in the cooling water; and water used to cool the fuel rods is lost. As a result of these occurrences, the water is slowed down by both the loss in water pressure and the upward force of air bubbles pushing against the downward force of the water. The project required the conducting of tests to find the bubble velocity in an annular ribbed pipe filled with stagnant water. This document discusses the methodology and results of this testing.

4. Correlation of bubble rise velocity and volume

SciTech Connect

Burge, C.

1991-12-31

This project was conducted at Westinghouses Savannah River Laboratories (SRL). The goal of SRL is to make certain that the modifications on the reactor are safe for those working at the plant as well as the general public. One of the steps needed to insure safety is the knowledge of the occurrences that result from a plenum pipe breakage. When a plenum pipe breaks, two things occur: air is sucked into the pipe and is trapped in the cooling water; and water used to cool the fuel rods is lost. As a result of these occurrences, the water is slowed down by both the loss in water pressure and the upward force of air bubbles pushing against the downward force of the water. The project required the conducting of tests to find the bubble velocity in an annular ribbed pipe filled with stagnant water. This document discusses the methodology and results of this testing.

5. A novel method of measuring electrophoretic mobility of gas bubbles.

PubMed

Najafi, Aref Seyyed; Drelich, Jaroslaw; Yeung, Anthony; Xu, Zhenghe; Masliyah, Jacob

2007-04-15

Accurate measurement of electrophoretic mobility for gas bubbles is a challenging task as it requires the creation of a desired number of very small air bubbles to ensure negligible rise velocities during the course of the measurement. Here, we report a simple and reliable method for generating stable dispersions of "nano-bubbles." Preparation of such dispersions relies on the nucleation of nano-bubbles in solutions supersaturated with gas. Electrophoretic mobility of these nano-bubbles is determined by the ZetaPALS technique (Brookhaven Instruments) using Uzgiris electrodes coated with palladium. The Smoluchowski limit is assumed in the calculation of zeta potentials. In regard to reproducibility and reliability, this novel method shows a clear advantage over other existing techniques of zeta potential measurement for bubbles.

6. Exploring the mechanisms of rising bubbles in marine biofouling prevention

Menesses, Mark; Belden, Jesse; Dickenson, Natasha; Bird, James

2015-11-01

Fluid motion, such as flow past a ship, is known to inhibit the growth of marine biofouling. Bubbles rising along a submerged structure also exhibit this behavior, which is typically attributed to buoyancy induced flow. However, the bubble interface may also have a direct influence on inhibiting growth that is independent of the surrounding flow. Here we aim to decouple these two mechanisms through a combination of field and laboratory experiments. In this study, a wall jet and a stream of bubbles are used to create two flows near a submerged solid surface where biofouling occurs. The flow structure characteristics were recorded using PIV. This experimental analysis allows for us to compare the efficacy of each flow relative to its flow parameters. Exploration of the mechanisms at play in the prevention of biofouling by use of rising bubbles provides a foundation to predict and optimize this antifouling technique under various conditions.

7. Gas Bubble Formation in Stagnant and Flowing Mercury

SciTech Connect

Wendel, Mark W; Abdou, Ashraf A; Riemer, Bernie; Felde, David K

2007-01-01

Investigations in the area of two-phase flow at the Oak Ridge National Laboratory's (ORNL) Spallation Neutron Source (SNS) facility are progressing. It is expected that the target vessel lifetime could be extended by introducing gas into the liquid mercury target. As part of an effort to validate the two-phase computational fluid dynamics (CFD) model, simulations and experiments of gas injection in stagnant and flowing mercury have been completed. The volume of fluid (VOF) method as implemented in ANSYS-CFX, was used to simulate the unsteady two-phase flow of gas injection into stagnant mercury. Bubbles produced at the upwards-oriented vertical gas injector were measured with proton radiography at the Los Alamos Neutron Science Center. The comparison of the CFD results to the radiographic images shows good agreement for bubble sizes and shapes at various stages of the bubble growth, detachment, and gravitational rise. Although several gas flows were measured, this paper focuses on the case with a gas flow rate of 8 cc/min through the 100-micron-diameter injector needle. The acoustic waves emitted due to the detachment of the bubble and during subsequent bubble oscillations were recorded with a microphone, providing a precise measurement of the bubble sizes. As the mercury flow rate increases, the drag force causes earlier bubble detachment and therefore smaller bubbles.

8. Evolution of energy in flow driven by rising bubbles.

PubMed

Mazzitelli, Irene M; Lohse, Detlef

2009-06-01

We investigate by direct numerical simulations the flow that rising bubbles cause in an originally quiescent fluid. We employ the Eulerian-Lagrangian method with two-way coupling and periodic boundary conditions. In order to be able to treat up to 288000 bubbles, the following approximations and simplifications had to be introduced, as done before, e.g., by Climent and Magnaudet, Phys. Rev. Lett. 82, 4827 (1999). (i) The bubbles were treated as point particles, thus (ii) disregarding the near-field interactions among them, and (iii) effective force models for the lift and the drag forces were used. In particular, the lift coefficient was assumed to be 1/2, independent of the bubble Reynolds number and the local flow field. The results suggest that large-scale motions are generated, owing to an inverse energy cascade from the small to the large scales. However, as the Taylor-Reynolds number is only in the range of 1, the corresponding scaling of the energy spectrum with an exponent of -5/3 cannot develop over a pronounced range. In the long term, the property of local energy transfer, characteristic of real turbulence, is lost and the input of energy equals the viscous dissipation at all scales. Due to the lack of strong vortices, the bubbles spread rather uniformly in the flow. The mechanism for uniform spreading is as follows. Rising bubbles induce a velocity field behind them that acts on the following bubbles. Owing to the shear, those bubbles experience a lift force, which makes them spread to the left or right, thus preventing the formation of vertical bubble clusters and therefore of efficient forcing. Indeed, when the lift is artificially put to zero in the simulations, the flow is forced much more efficiently and a more pronounced energy that accumulation at large scales (due to the inverse energy cascade) is achieved.

9. Gas separation and bubble behavior at a woven screen

Conrath, Michael; Dreyer, Michael E.

trapped bubble volumes, liquid flow rates and flow-induced compression, ii) typical breakthrough of a trapped bubble at rising liquid flow rate and iii) steady gas supply in steady liquid flow. It shows that our model can explain the experimental observations. One of the interesting findings for the dynamic bubble point is that hydraulic losses in the rest of the circuit will shift the breakthrough of gas to higher liquid flow rates.

10. Mechanics of gas-vapor bubbles

Hao, Yue; Zhang, Yuhang; Prosperetti, Andrea

2017-03-01

Most bubbles contain a mixture of vapor and incondensible gases. While the limit cases of pure vapor and pure gas bubbles are well studied, much less is known about the more realistic case of a mixture. The bubble contents continuously change due to the combined effects of evaporation and condensation and of gas diffusion in the liquid and in the bubble. This paper presents a model for this situation and illustrates by means of examples several physical processes that can occur: a bubble undergoing a temporary pressure reduction, which makes the liquid temporarily superheated; a bubble subjected to a burst of sound; and a bubble continuously growing by rectified diffusion of heat in the presence of an incondensible gas.

11. A numerical simulation of flows around a deformable gas bubble

Sugano, Minoru; Ishii, Ryuji; Morioka, Shigeki

1991-12-01

A numerical simulation of flows around a (deformable) gas bubble rising through an incompressible viscous fluid was carried out on a supercomputer Fujitsu VP2600 at Data Processing Center of Kyoto University. The solution algorithm is a modified Marker And Cell (MAC) method. For the grid generation, an orthogonal mapping proposed by Ryskin and Leal was applied. it is assumed that the shape of the bubble and the flow field are axisymmetric.

12. Finger evolution of a gas bubble driven by atmospheric pressure plasma

Shiu, Jia-Hau; Chu, Hong-Yu

2016-12-01

We report the generation and evolution of a finger-shaped bubble in liquid by dielectric discharge setup. The spherical gas bubble is deformed into a finger-shaped bubble after the ignition of plasma. The presence of the filamentary discharge in the bubble not only provides the local heating to the bubble, it also changes the distribution of the electric field in the bubble and the bubble mutually provides the pathway to the discharge. The reduced surface tension on the liquid-gas interface due to the rise of temperature by plasma heating and the nonuniform electric field caused by the presence of filamentary discharge might induce the concave-shaped bubble. We also observe the formation of the quasi-two-dimensional bubble, which is generated from the bubble and attached on one side of the electrodes. It is found that the discharge induces the growth of the periodic fluctuations in the thin layer of gas.

13. Dynamics of an initially spherical bubble rising in quiescent liquid

Tripathi, Manoj Kumar; Sahu, Kirti Chandra; Govindarajan, Rama

2015-02-01

The beauty and complexity of the shapes and dynamics of bubbles rising in liquid have fascinated scientists for centuries. Here we perform simulations on an initially spherical bubble starting from rest. We report that the dynamics is fully three-dimensional, and provide a broad canvas of behaviour patterns. Our phase plot in the Galilei-Eötvös plane shows five distinct regimes with sharply defined boundaries. Two symmetry-loss regimes are found: one with minor asymmetry restricted to a flapping skirt; and another with marked shape evolution. A perfect correlation between large shape asymmetry and path instability is established. In regimes corresponding to peripheral breakup and toroid formation, the dynamics is unsteady. A new kind of breakup, into a bulb-shaped bubble and a few satellite drops is found at low Morton numbers. The findings are of fundamental and practical relevance. It is hoped that experimenters will be motivated to check our predictions.

14. A global stability approach to wake and path instabilities of nearly oblate spheroidal rising bubbles

Cano-Lozano, José Carlos; Tchoufag, Joël; Magnaudet, Jacques; Martínez-Bazán, Carlos

2016-01-01

A global Linear Stability Analysis (LSA) of the three-dimensional flow past a nearly oblate spheroidal gas bubble rising in still liquid is carried out, considering the actual bubble shape and terminal velocity obtained for various sets of Galilei (Ga) and Bond (Bo) numbers in axisymmetric numerical simulations. Hence, this study extends the stability analysis approach of Tchoufag et al. ["Linear stability and sensitivity of the flow past a fixed oblate spheroidal bubble," Phys. Fluids 25, 054108 (2013) and "Linear instability of the path of a freely rising spheroidal bubble," J. Fluid Mech. 751, R4 (2014)] (which considered perfectly spheroidal bubbles with an arbitrary aspect ratio) to the case of bubbles with a realistic fore-aft asymmetric shape (i.e., a flatter front and a more rounded rear). The critical curve separating stable and unstable regimes for the straight vertical path is obtained both in the (Ga,Bo) and the (Re,χ) planes, where Re is the bubble Reynolds number and χ its aspect ratio (i.e., the major-to-minor axes length ratio). This provides new insight into the effect of the shape asymmetry on the wake instability of bubbles held fixed in a uniform stream and on the path instability of freely rising bubbles, respectively. For the range of Ga and Bo explored here, we find that the flow past a bubble with a realistic shape is generally more stable than that past a perfectly spheroidal bubble with the same aspect ratio. This study also provides the first critical curve for the onset of path instability that can be compared with experimental observations. The tendencies revealed by this critical curve agree well with those displayed by available data. The quantitative agreement is excellent for O(1) Bond numbers. However, owing to two simplifying assumptions used in the LSA scheme, namely, the steadiness of the base state and the uncoupling between the bubble shape and the flow disturbances, quantitative discrepancies (up to 20%-30%) with

15. BUBBLE DYNAMICS AT GAS-EVOLVING ELECTRODES

SciTech Connect

Sides, Paul J.

1980-12-01

Nucleation of bubbles, their growth by diffusion of dissolved gas to the bubble surface and by coalescence, and their detachment from the electrode are all very fast phenomena; furthermore, electrolytically generated bubbles range in size from ten to a few hundred microns; therefore, magnification and high speed cinematography are required to observe bubbles and the phenomena of their growth on the electrode surface. Viewing the action from the front side (the surface on which the bubbles form) is complicated because the most important events occur close to the surface and are obscured by other bubbles passing between the camera and the electrode; therefore, oxygen was evolved on a transparent tin oxide "window" electrode and the events were viewed from the backside. The movies showed that coalescence of bubbles is very important for determining the size of bubbles and in the chain of transport processes; growth by diffusion and by coalescence proceeds in series and parallel; coalescing bubbles cause significant fluid motion close to the electrode; bubbles can leave and reattach; and bubbles evolve in a cycle of growth by diffusion and different modes of coalescence. An analytical solution for the primary potential and current distribution around a spherical bubble in contact with a plane electrode is presented. Zero at the contact point, the current density reaches only one percent of its undisturbed value at 30 percent of the radius from that point and goes through a shallow maximum two radii away. The solution obtained for spherical bubbles is shown to apply for the small bubbles of electrolytic processes. The incremental resistance in ohms caused by sparse arrays of bubbles is given by {Delta}R = 1.352 af/kS where f is the void fraction of gas in the bubble layer, a is the bubble layer thickness, k is the conductivity of gas free electrolyte, and S is the electrode area. A densely populated gas bubble layer on an electrode was modeled as a hexagonal array of

16. Structure of nanoscale gas bubbles in metals

SciTech Connect

Caro, A. Schwen, D.; Martinez, E.

2013-11-18

A usual way to estimate the amount of gas in a bubble inside a metal is to assume thermodynamic equilibrium, i.e., the gas pressure P equals the capillarity force 2γ/R, with γ the surface energy of the host material and R the bubble radius; under this condition there is no driving force for vacancies to be emitted or absorbed by the bubble. In contrast to the common assumption that pressure inside a gas or fluid bubble is constant, we show that at the nanoscale this picture is no longer valid. P and density can no longer be defined as global quantities determined by an equation of state (EOS), but they become functions of position because the bubble develops a core-shell structure. We focus on He in Fe and solve the problem using both continuum mechanics and empirical potentials to find a quantitative measure of this effect. We point to the need of redefining an EOS for nanoscale gas bubbles in metals, which can be obtained via an average pressure inside the bubble. The resulting EOS, which is now size dependent, gives pressures that differ by a factor of two or more from the original EOS for bubble diameters of 1 nm and below.

17. Evolution of bubble size distribution from gas blowout in shallow water

Zhao, Lin; Boufadel, Michel C.; Lee, Kenneth; King, Thomas; Loney, Norman; Geng, Xiaolong

2016-03-01

Gas is often emanated from the sea bed during a subsea oil and gas blowout. The size of a gas bubble changes due to gas dissolution in the ambient water and expansion as a result of a decrease in water pressure during the rise. It is important to understand the fate and transport of gas bubbles for the purpose of environmental and safety concerns. In this paper, we used the numerical model, VDROP-J to simulate gas formation in jet/plume upon release, and dissolution and expansion while bubble rising during a relatively shallow subsea gas blowout. The model predictions were an excellent match to the experimental data. Then a gas dissolution and expansion module was included in the VDROP-J model to predict the fate and transport of methane bubbles rising due to a blowout through a 0.10 m vertical orifice. The numerical results indicated that gas bubbles would increase the mixing energy in released jets, especially at small distances and large distances from the orifice. This means that models that predict the bubble size distribution (BSD) should account for this additional mixing energy. It was also found that only bubbles of certain sizes would reach the water surfaces; small bubbles dissolve fast in the water column, while the size of the large bubbles decreases. This resulted in a BSD that was bimodal near the orifice, and then became unimodal.

18. The hydrodynamics of bubble rise and impact with solid surfaces.

PubMed

Manica, Rogerio; Klaseboer, Evert; Chan, Derek Y C

2016-09-01

A bubble smaller than 1mm in radius rises along a straight path in water and attains a constant speed due to the balance between buoyancy and drag force. Depending on the purity of the system, within the two extreme limits of tangentially immobile or mobile boundary conditions at the air-water interface considerably different terminal speeds are possible. When such a bubble impacts on a horizontal solid surface and bounces, interesting physics can be observed. We study this physical phenomenon in terms of forces, which can be of colloidal, inertial, elastic, surface tension and viscous origins. Recent advances in high-speed photography allow for the observation of phenomena on the millisecond scale. Simultaneous use of such cameras to visualize both rise/deformation and the dynamics of the thin film drainage through interferometry are now possible. These experiments confirm that the drainage process obeys lubrication theory for the spectrum of micrometre to millimetre-sized bubbles that are covered in this review. We aim to bridge the colloidal perspective at low Reynolds numbers where surface forces are important to high Reynolds number fluid dynamics where the effect of the surrounding flow becomes important. A model that combines a force balance with lubrication theory allows for the quantitative comparison with experimental data under different conditions without any fitting parameter.

19. On the bubble rise velocity of a continually released bubble chain in still water and with crossflow

Wang, Binbin; Socolofsky, Scott A.

2015-10-01

The rise velocities of in-chain bubbles continually released from a single orifice in still water with and without crossflow are investigated in a series of laboratory experiments for wobbling ellipsoidal bubbles with moderate Reynolds number. For the limiting case in still water, that is, crossflow velocity = 0, the theoretical turbulent wake model correctly predicts the in-chain bubble rise velocity. In this case, the bubble rise velocities VB are enhanced compared to the terminal velocities of the isolated bubbles V0 due to wake drafting and are scaled with flow rate Q and bubble diameter D. Here, we also derive an updated wake model with consideration of the superposition of multiple upstream bubble wakes, which removes the nonlinear behavior of the non-distant (i.e., local) wake model. For the cases with crossflow, the enhancement of the in-chain bubble rise velocity can be significantly reduced, and imaging of the experiments shows very organized paring and grouping trajectories of rising bubbles not observed in still water under different crossflow velocities. The in-chain bubble rise velocities in crossflow are described by two models. First, an empirical model is used to correct the still-water equation for the crossflow effect. In addition, a semi-theoretical model considering the turbulent wake flow and the crossflow influence is derived and used to develop a theoretical normalization of bubble rise velocity, crossflow velocity, and the released bubble flow rate. The theoretical model suggests there are two different regimes of bubble-bubble interaction, with strong interaction occurring for the non-dimensional crossflow velocity Uc + = π Uc 3 D 3 V 0 / ( 18 g β Q 2 ) less than 0.06 and weaker interaction occurring for Uc + greater than 0.06, where Uc is the crossflow velocity, g is the acceleration of gravity, and β is the mixing length coefficient.

20. Gas transfer in a bubbly wake flow

Karn, A.; Gulliver, J. S.; Monson, G. M.; Ellis, C.; Arndt, R. E. A.; Hong, J.

2016-05-01

The present work reports simultaneous bubble size and gas transfer measurements in a bubbly wake flow of a hydrofoil, designed to be similar to a hydroturbine blade. Bubble size was measured by a shadow imaging technique and found to have a Sauter mean diameter of 0.9 mm for a reference case. A lower gas flow rate, greater liquid velocities, and a larger angle of attack all resulted in an increased number of small size bubbles and a reduced weighted mean bubble size. Bubble-water gas transfer is measured by the disturbed equilibrium technique. The gas transfer model of Azbel (1981) is utilized to characterize the liquid film coefficient for gas transfer, with one scaling coefficient to reflect the fact that characteristic turbulent velocity is replaced by cross-sectional mean velocity. The coefficient was found to stay constant at a particular hydrofoil configuration while it varied within a narrow range of 0.52-0.60 for different gas/water flow conditions.

1. Numerical study of a Taylor bubble rising in stagnant liquids.

PubMed

Kang, Chang-Wei; Quan, Shaoping; Lou, Jing

2010-06-01

The dynamics of a Taylor bubble rising in stagnant liquids is numerically investigated using a front tracking coupled with finite difference method. Parametric studies on the dynamics of the rising Taylor bubble including the final shape, the Reynolds number (Re(T)), the Weber number (We(T)), the Froude number (Fr), the thin liquid film thickness (w/D), and the wake length (l(w)/D) are carried out. The effects of density ratio (η), viscosity ratio (λ), Eötvös number (Eo), and Archimedes number (Ar) are examined. The simulations demonstrate that the density ratio and the viscosity ratio under consideration have minimal effect on the dynamics of the Taylor bubble. Eötvös number and Archimedes number influence the elongation of the tail and the wake structures, where higher Eo and Ar result in longer wake. To explain the sudden extension of the tail, a Weber number (We(l)) based on local curvature and velocity is evaluated and a critical We(l) is detected around unity. The onset of flow separation at the wake occurs in between Ar=2×10(3) and Ar=1×10(4), which corresponds to Re(T) between 13.39 and 32.55. Archimedes number also drastically affects the final shape of Taylor bubble, the terminal velocity, the thickness of thin liquid film, as well as the wall shear stress. It is found that w/D=0.32 Ar(-0.1).

2. Experimental Study on Rising Velocity of Different Nitrogen Bubbles in of Circular Pipe

Zhang, Hua; Liu, Yiping; Wang, Jing

2007-06-01

Nitrogen bubble rising velocity in bottom of circular pipe has been studied by virtual experiment with high-speed camera. The obtained images are processed systematically. Based on Cole's and Mendelson's empirical formula of bubble rising velocity, fitting formula of nitrogen bubble rising velocity in bottom of circular pipe has been acquired through analyzing nitrogen bubble rising velocity. The treatment results of experimental data show that the rising velocity is related with the diameter of bubbles. And rising velocity of slug bubble is relative to L/D and change law is found. Through this experiment, we research rising velocity's change law, which is the spade work to study propagation mechanism of nitrogen slug bubble in circular pipe.

3. Development and interactions of two inert gas bubbles during decompression.

PubMed

Jiang, Y; Homer, L D; Thalmann, E D

1996-09-01

A mathematical model has been developed to simulate the evolution of two inert gas bubbles in tissue. This is useful for understanding the dynamics of bubbles that presumably arise during decompression. It is assumed that they are spherical and that the tissue volume surrounding them is infinite. The total pressure in each bubble is determined by the barometric and metabolic gas pressures as well as the pressure due to surface tension. Bipolar coordinates are employed to determine the inert gas pressure distribution. Two coupled governing equations for bubble radii are then derived and solved numerically. The results demonstrate how bubble evolution is affected by the distance between bubbles and the initial bubble radii. The existence time and bubble surface flux of two equal-sized bubbles are calculated and compared with those of a single gas bubble model. The results indicate that when two bubbles are very close, it takes 20% more time for two bubbles to dissolve than for a single one, and the total surface flux of two bubbles is nearly 20% less than twice of a single bubble. When the center-to-center distance is 10 times of bubble radius, the effect of bubble interaction on bubble existence time and surface flux are about 6 and 9% changes, respectively. We conclude that if bubbles are not too small, the interactions among bubbles should be included in inert gas bubble models predicting bubble evolution.

4. Ripples on a rising bubble through an immiscible two-liquid interface generate numerous micro droplets

Uemura, T.; Ueda, Y.; Iguchi, M.

2010-11-01

The mass transfer between immiscible two liquid phases can be greatly accelerated by bubbling gas through a reactor (Bird R. B., Stewart W. E. and Lightfoot E. N., Transport Phenomena, 2nd edition (John Wiley and Sons) 2002). Therefore, the physical phenomenon occurring during the passage of a rising bubble through an immiscible two-liquid interface is of particular interest. The passage of the bubble through the oil (upper phase)/water (lower phase) interface starts with an upward lifting of the interface, and the bubble attracts a column of the water phase upwards keeping a film of the water phase around itself. In the present study, a particular remark is given to the influence of different interface tensions retracting the water film, after the water film ruptured, which lays on the interface between air and silicone oil. Unlike the previous studies on the rupture of a single liquid film in a gas which is pulled due to the identical surface tension, this system can form concentric ripples on the outer interface of the water film (oil/water interface) around the bubble due to the weak interface tension. Then, numerous micro water droplets break out from the fully grown ripples.

5. Inert gas bubbles in bcc Fe

Gai, Xiao; Smith, Roger; Kenny, S. D.

2016-03-01

The properties of inert gas bubbles in bcc Fe is examined using a combination of static energy minimisation, molecular dynamics and barrier searching methods with empirical potentials. Static energy minimisation techniques indicate that for small Ar and Xe bubbles, the preferred gas to vacancy ratio at 0 K is about 1:1 for Ar and varies between 0.5:1 and 0.9:1 for Xe. In contrast to interstitial He atoms and small He interstitial clusters, which are highly mobile in the lattice, Ar and Xe atoms prefer to occupy substitutional sites and any interstitials present in the lattice soon displace Fe atoms and become substitutional. If a pre-existing bubble is present then there is a capture radius around a bubble which extends up to the 6th neighbour position. Collision cascades can also enlarge an existing bubble by the capture of vacancies. Ar and Xe can diffuse through the lattice through vacancy driven mechanisms but with relatively high energy barriers of 1.8 and 2.0 eV respectively. This indicates that Ar and Xe bubbles are much harder to form than bubbles of He and that such gases produced in a nuclear reaction would more likely be dispersed at substitutional sites without the help of increased temperature or radiation-driven mechanisms.

6. Hydrodynamic interaction of a pair of bubbles rising in a quiescent liquid.

2005-11-01

Interaction effects on the motions of a pair of bubbles, which either rose in vertical line or side by side, in silicon oil pool were experimentally studied. A pair of bubbles rising in vertical line was generated by releasing bubbles successively from a single nozzle, while one rising side by side was generated, by releasing bubble simultaneously from a pair of horizontally placed orifices. Bubble diameter and liquid kinematic viscosity were taken as the experimental parameters. The motions of bubbles were recorded by a high-speed camera with 2000 fps. We observed that Reynolds number significantly affected the motions of a pair of bubbles rising both in vertical line and side by side. When a pair of bubbles rose in vertical line, the trailing bubble was attracted by the leading bubble wake, and then it collided with leading bubble, in the case of low Re, while a pair of bubbles kept a mutual equilibrium distance due to the balance between the leading bubble wake attractive force and potential repulsive force, in the case of intermediate Re. As Re further increased, the trailing bubble oscillated and then escaped from the vertical line. When a pair of bubbles rose side by side, they separated from each other as they rose in the case of low Re, while they attracted each other and then collided if the initial bubble horizontal distance was smaller than a critical value, in the case of large Re.

7. Gas Bubble Growth in Muddy Sediments

DTIC Science & Technology

2016-06-07

it is fairly easy to show that R ~ eat (a = S/ρg), i.e. exponential growth , which is a far faster than has been suggested previously. We expect this...Gas Bubble Growth in Muddy Sediments Bernard P. Boudreau Department of Oceanography Dalhousie University Halifax, Nova Scotia B3H 4J1, Canada phone...objective is a working model for the growth of a single, isolated bubble in a marine sediment, validated with bubble growth data obtained in laboratory

8. Non-linear shape oscillations of rising drops and bubbles: Experiments and simulations

Lalanne, Benjamin; Abi Chebel, Nicolas; Vejražka, Jiří; Tanguy, Sébastien; Masbernat, Olivier; Risso, Frédéric

2015-12-01

This paper focuses on shape-oscillations of a gas bubble or a liquid drop rising in another liquid. The bubble/drop is initially attached to a capillary and is released by a sudden motion of that capillary, resulting in the rise of the bubble/drop along with the oscillations of its shape. Such experimental conditions make difficult the interpretation of the oscillation dynamics with regard to the standard linear theory of oscillation because (i) amplitude of deformation is large enough to induce nonlinearities, (ii) the rising motion may be coupled with the oscillation dynamics, and (iii) clean conditions without residual surfactants may not be achieved. These differences with the theory are addressed by comparing experimental observation with numerical simulation. Simulations are carried out using Level-Set and Ghost-Fluid methods with clean interfaces. The effect of the rising motion is investigated by performing simulations under different gravity conditions. Using a decomposition of the bubble/drop shape into a series of spherical harmonics, experimental and numerical time evolutions of their amplitudes are compared. Due to large oscillation amplitude, non-linear couplings between the modes are evidenced from both experimental and numerical signals; modes of lower frequency influence modes of higher frequency, whereas the reverse is not observed. Nevertheless, the dominant frequency and overall damping rate of the first five modes are in good agreement with the linear theory. Effect of the rising motion on the oscillations is globally negligible, provided the mean shape of the oscillation remains close to a sphere. In the drop case, despite the residual interface contamination evidenced by a reduction in the terminal velocity, the oscillation dynamics is shown to be unaltered compared to that of a clean drop.

9. Gas Bubble Growth in Muddy Sediments

DTIC Science & Technology

2000-09-30

the ebullitive flux of methane, an important “greenhouse gas”, to the atmosphere. OBJECTIVES The immediate objective is a working model for the growth...OMB control number. 1. REPORT DATE SEP 2000 2. REPORT TYPE 3. DATES COVERED 00-00-2000 to 00-00-2000 4. TITLE AND SUBTITLE Gas Bubble Growth in...N is the porosity, D is the tortuosity-corrected diffusivity, cg is the concentration of gas in the bubble, S is the local rate of methanogenesis, R1

10. Terminal velocities of pure and hydrate coated CO 2 droplets and CH 4 bubbles rising in a simulated oceanic environment

Bigalke, N. K.; Enstad, L. I.; Rehder, G.; Alendal, G.

2010-09-01

Understanding the upward motion of CO 2 droplets or CH 4 bubbles in oceanic waters is prerequisite to predict the vertical distribution of the two most important greenhouse gases in the water column after these have been released from the seabed. One of the key parameters governing the fate of droplets or bubbles dissolving into the surrounding seawater as they rise, is the terminal velocity, uT. The latter is strongly influenced by the ability of both compounds to form skins of gas hydrate, if pressure and temperature satisfy thermodynamic framework conditions. Experimental efforts aiming to elucidate the rise properties of CO 2 droplets and CH 4 bubbles and specifically the influence of hydrate skins open the possibility to obtain a parameterization of uT applicable to both hydrate-coated and pure fluid particles of CH 4 and CO 2. With the present study, we report on experimentally determined terminal velocities of single CH 4 bubbles released to pressurized and temperature-regulated seawater. Hydrate skins were identified by high bubble sphericities and changed motion characteristics. Based on these experiments as well as published data on the rise of hydrate-coated and pure liquid CO 2 droplets and physical principles previously successfully used for clean bubbles near atmospheric pressures, a new parameterization of uT is proposed. Model predictions show a good agreement with the data base established from the laboratory-based measurements.

11. The effect of surfactants on path instability of a rising bubble

Tagawa, Yoshiyuki; Takagi, Shu; Matsumoto, Yoichiro

2013-11-01

We experimentally investigate the surfactant effect on path instability of an air bubble rising in quiescent water. An addition of surfactant varies the gas-water boundary condition from zero shear stress to non-zero shear stress. We report three main findings: firstly, while the drag force acting on the bubble increases with the surfactant concentration as expected, the lift force shows a non-monotonic behavior; secondly, the transient trajectory starting from helical to zigzag is observed, which has never been reported in the case of purified water; lastly, a bubble with the intermediate slip conditions between free-slip and no-slip show a helical motion for a broad range of the Reynolds number. Aforementioned results are rationalized by considering the adsorption-desorption kinetics of the surfactants on gas-water interface and the wake dynamics. Y.T. thanks for financial support from Grant-in-Aid for JSPS Fellows (20-10701). We also thank for Grant-in-Aid for Scientific Research (B) (21360079).

12. Gas Bubble Growth In Muddy Sediments

DTIC Science & Technology

2002-09-30

1 Gas Bubble Growth In Muddy Sediments Bruce D . Johnson Department of Oceanography, Dalhousie University Halifax, Nova Scotia, Canada B3H 4J1 phone...that this information can be used to improve and test acoustic backscatter models for sediments and to better understand the ebullitive flux of...currently valid OMB control number. 1. REPORT DATE 30 SEP 2002 2. REPORT TYPE 3. DATES COVERED 00-00-2002 to 00-00-2002 4. TITLE AND SUBTITLE

13. Gas Bubble Growth in Muddy Sediments

DTIC Science & Technology

2001-09-30

1 Gas Bubble Growth In Muddy Sediments Bruce D . Johnson Department of Oceanography, Dalhousie University Halifax, Nova Scotia, Canada B3H 4J1 phone...that this information can be used to improve and test acoustic backscatter models for sediments and to better understand the ebullitive flux of...currently valid OMB control number. 1. REPORT DATE 30 SEP 2001 2. REPORT TYPE 3. DATES COVERED 00-00-2001 to 00-00-2001 4. TITLE AND SUBTITLE

14. Gas depletion through single gas bubble diffusive growth and its effect on subsequent bubbles

Moreno Soto, Alvaro; Prosperetti, Andrea; Lohse, Detlef; van der Meer, Devaraj; Physics of Fluid Group Collaboration; MCEC Netherlands CenterMultiscale Catalytic Energy Conversion Collaboration

2016-11-01

In weakly supersaturated mixtures, bubbles are known to grow quasi-statically as diffusion-driven mass transfer governs the process. In the final stage of the evolution, before detachment, there is an enhancement of mass transfer, which changes from diffusion to natural convection. Once the bubble detaches, it leaves behind a gas-depleted area. The diffusive mass transfer towards that region cannot compensate for the amount of gas which is taken away by the bubble. Consequently, the consecutive bubble will grow in an environment which contains less gas than for the previous one. This reduces the local supersaturation of the mixture around the nucleation site, leading to a reduced bubble growth rate. We present quantitative experimental data on this effect and the theoretical model for depletion during the bubble growth rate. This work was supported by the Netherlands Center for Multiscale Catalytic Energy Conversion (MCEC), an NWO Gravitation programme funded by the Ministry of Education, Culture and Science of the government of the Netherlands.

15. Suppression of cavitation inception by gas bubble injection: a numerical study focusing on bubble-bubble interaction.

PubMed

Ida, Masato; Naoe, Takashi; Futakawa, Masatoshi

2007-10-01

The dynamic behavior of cavitation and gas bubbles under negative pressure has been studied numerically to evaluate the effect of gas bubble injection into a liquid on the suppression of cavitation inception. In our previous studies, it was demonstrated by direct observation that cavitation occurs in liquid mercury when mechanical impacts are imposed, and this will cause cavitation damage in spallation neutron sources, in which liquid mercury is bombarded by a high-power proton beam. In the present paper, we describe numerical investigations of the dynamics of cavitation bubbles in liquid mercury using a multibubble model that takes into account the interaction of a cavitation bubble with preexisting gas bubbles through bubble-radiated pressure waves. The numerical results suggest that, if the mercury includes gas bubbles whose equilibrium radius is much larger than that of the cavitation bubble, the explosive expansion of the cavitation bubble (i.e., cavitation inception) is suppressed by the positive-pressure wave radiated by the injected bubbles, which decreases the magnitude of the negative pressure in the mercury.

16. Pseudo-Steady Diffusional Growth or Collapse of Bubbles Rising in Time Dependent Pressure Fields

DTIC Science & Technology

1990-03-13

et al. [12], Ishikawa, et al. [13] and Payvar [14] to name a few. Brankovic, et al. collected data for air and carbon dioxide bubbles with a triple...hydrostatic pressure field. Payvar [141 examined the effects, both experimentally and analytically, of a rapid de- compression on bubble growth for C0 2...Furthermore, bubble experimental rise data have only been obtained for a static hydrostatic head, with the exception of Payvar [14], but that was for a

17. How does gas pass? Bubble transport through sediments

Fauria, K. E.; Rempel, A. W.

2009-12-01

The transport of gas through marine sediments is critical for both the formation and the ultimate fate of gas that is housed temporarily within hydrates. We monitored the gas flux produced by repeated bubble injections into a particle layer that was initially saturated with liquid. The size of ejected bubbles and the period between ejection events were different from the input size and period. Our observations clearly demonstrate bubble break-up as well as coalescence and the formation of preferred bubble migration pathways. We develop an elementary, semi-empirical model to interpret aspects of these results and predict the gas flux expected from a given size distribution of bubble inputs as a function of basic host sediment characteristics. Models of gas transport that use simple modifications to Darcy's law are not adequate to cope with bubble dynamics in the parameter regime that we observe.

18. Morphology of Gas Bubbles in Mud: A Microcomputed Tomographic Evaluation

DTIC Science & Technology

2005-07-01

valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT DATE (DD-MM-YYYYI 2. REPORT TYPE 3. DATES COVERED (From - To) 01...oxidation of organic matter is ubiquitous in marine sediments [1,2] and when supersaturated produces gas bubbles. Ebullition of methane gas bubbles from...cycle [10]. Pressure changes during a tidal cycle have also been correlated with bubble migration/ ebullition [11]. The relationship between pressure

19. Methane rising from the Deep: Hydrates, Bubbles, Oil Spills, and Global Warming

Leifer, I.; Rehder, G. J.; Solomon, E. A.; Kastner, M.; Asper, V. L.; Joye, S. B.

2011-12-01

Elevated methane concentrations in near-surface waters and the atmosphere have been reported for seepage from depths of nearly 1 km at the Gulf of Mexico hydrate observatory (MC118), suggesting that for some methane sources, deepsea methane is not trapped and can contribute to atmospheric greenhouse gas budgets. Ebullition is key with important sensitivity to the formation of hydrate skins and oil coatings, high-pressure solubility, bubble size and bubble plume processes. Bubble ROV tracking studies showed survival to near thermocline depths. Studies with a numerical bubble propagation model demonstrated that consideration of structure I hydrate skins transported most methane only to mid-water column depths. Instead, consideration of structure II hydrates, which are stable to far shallower depths and appropriate for natural gas mixtures, allows bubbles to survive to far shallower depths. Moreover, model predictions of vertical methane and alkane profiles and bubble size evolution were in better agreement with observations after consideration of structure II hydrate properties as well as an improved implementation of plume properties, such as currents. These results demonstrate the importance of correctly incorporating bubble hydrate processes in efforts to predict the impact of deepsea seepage as well as to understand the fate of bubble-transported oil and methane from deepsea pipeline leaks and well blowouts. Application to the DWH spill demonstrated the importance of deepsea processes to the fate of spilled subsurface oil. Because several of these parameters vary temporally (bubble flux, currents, temperature), sensitivity studies indicate the importance of real-time monitoring data.

20. Force Balance Model for Bubble Rise, Impact, and Bounce from Solid Surfaces.

PubMed

Manica, Rogerio; Klaseboer, Evert; Chan, Derek Y C

2015-06-23

A force balance model for the rise and impact of air bubbles in a liquid against rigid horizontal surfaces that takes into account effects of buoyancy and hydrodynamic drag forces, bubble deformation, inertia of the fluid via an added mass force, and a film force between the bubble and the rigid surface is proposed. Numerical solution of the governing equations for the position and velocity of the center of mass of the bubbles is compared against experimental data taken with ultraclean water. The boundary condition at the air-water interface is taken to be stress free, which is consistent for bubbles in clean water systems. Features that are compared include bubble terminal velocity, bubbles accelerating from rest to terminal speed, and bubbles impacting and bouncing off different solid surfaces for bubbles that have already or are yet to attain terminal speed. Excellent agreement between theory and experiments indicates that the forces included in the model constitute the main physical ingredients to describe the bouncing phenomenon.

1. Measurement and Analysis of Gas Bubbles Near a Reference Electrode in Aqueous Solutions

SciTech Connect

Supathorn Phongikaroon; Steve Herrmann; Shelly Li; Michael Simpson

2005-10-01

Bubble size distributions (BSDs) near a reference electrode (RE) in aqueous glycerol solutions of an electrolyte NaCl have been investigated under various gas superficial velocities (U{sub S}). BSD and voltage reading of the solution were measured by using a high-speed digital camera and a pH/voltage meter, respectively. The results show that bubble size (b) increases with liquid viscosity ({mu}{sub c}) and U{sub S}. Self-similarity is seen and can be described by the log-normal form of the continuous number frequency distribution. The result shows that b controls the voltage reading in each solution. As b increases, the voltage increases because of gas bubbles interrupting their electrolyte paths in the solutions. An analysis of bubble rising velocity reveals that Stokes Law should be used cautiously to describe the system. The fundamental equation for bubble formation was developed via Newton's second law of motion and shown to be the function of three dimensionless groups--Weber number, Bond number, and Capillary number. After linking an electrochemical principle in the practical application, the result indicates that the critical bubble size is {approx}177 {micro}m. Further analysis suggests that there may be 3000 to 70,000 bubbles generated on the anode surface depending on the size of initial bubbles and provides the potential cause of the efficiency drop observed in the practical application.

2. Three-dimensional numerical simulations of a bubble rising in an unbounded weakly viscous fluid

Cano-Lozano, Jose Carlos; Martínez-Bazán, Carlos; Tchoufag, Joel; Magnaudet, Jacques

2015-11-01

Direct Numerical Simulations (DNS) of a freely rising bubble in an unbounded low-viscosity fluid are performed to analyze the bubble trajectory for values of Galileo and Bond numbers close to the transition between vertical and non-vertical paths. The simulations are performed with the Gerris Flow Solver, based on the Volume of Fluid technique to track the interface, allowing deformations of the bubble during its rising motion. We find the existence of novel regimes of the bubble rise which we describe by tracking the bubble shape, path geometry and wake vortical structures, as well as the temporal evolution of the instantaneous Reynolds number. Besides the traditional rectilinear, zigzag and spiral paths, we observe chaotic, reflectional-symmetry-breaking or reflectional-symmetry-preserving regimes previously reported for axisymmetric solid bodies. The DNS results also allow us to check the accuracy of the neutral curve defining the region of the parameter space within which the vertical path of a buoyancy-driven bubble with fore-and-aft asymmetric shape is linearly stable. Supported by the Spanish MINECO, Junta de Andalucía and EU Funds under projects DPI 2014-59292-C3-3-P and P11-TEP7495.

3. Analytical solution of the problem of the rise of a Taylor bubble

Zudin, Yuri B.

2013-05-01

In the classical works of Prandtl and Taylor devoted to the analysis of the problem of the rise of a Taylor bubble in a round tube, a solution of the Laplace equation is used, which contains divergent infinite series. The present paper outlines a method for the correct analysis of the mentioned problem. Using the method of superposition of "elementary flows," a solution was obtained for flow of an ideal fluid over a body of revolution in a pipe. Satisfying the free surface condition in the vicinity of the stagnation point and using the limiting transition with respect to the main parameter lead to the relation for the rise velocity of a Taylor bubble expressed in terms of the Froude number. In order to validate the method of superposition, it was applied to the problem of the rise of a plane Taylor bubble in a flat gap, which also has an exact analytical solution obtained with the help of the complex variable theory.

4. Measurement Of Gas Bubbles In Mercury Using Proton Radiography

SciTech Connect

Riemer, Bernie; Bingham, Philip R; Mariam, Fesseha G; Merrill, Frank E

2007-01-01

An experiment using proton radiography on a small mercury loop for testing gas bubble injection was conducted at the Los Alamos Neutron Science Center (LANSCE) in December 2006. Small gas bubble injection is one of the approaches under development to reduce cavitation damage in the U.S. Spallation Neutron Source mercury target vessel. Several hundred radiograph images were obtained as the test loop was operated over range of conditions that included two jet type bubble generators, two needle type bubble generators, various mercury flow speeds and gas injection rates, and use of helium, argon and xenon. This paper will describe the analysis of the radiograph images and present the obtained bubble measurement data.

5. Pulsed Electrical Discharge in a Gas Bubble in Water

Schaefer, Erica; Gershman, Sophia; Mozgina, Oksana

2005-10-01

This experiment is an investigation of the electrical and optical characteristics of a pulsed electrical discharge ignited in a gas bubble in water in a needle-to-plane electrode geometry. Argon or oxygen gas is fed through a platinum hypodermic needle that serves as the high voltage electrode. The gas filled bubble forms at the high voltage electrode with the tip of the needle inside the bubble. The discharge in the gas bubble in water is produced by applying 5 -- 15 kV, microsecond long rectangular pulses between the electrodes submerged in water. The voltage across the electrodes and the current are measured as functions of time. Electrical measurements suggest a discharge ignited in the bubble (composed of the bubbled gas and water vapor) without breakdown of the entire water filled electrode gap. Time-resolved optical emission measurements are taken in the areas of the spectrum corresponding to the main reactive species produced in the discharge, e.g. OH 309 nm, Ar 750 nm, and O 777 nm emissions using optical filters. The discharge properties are investigated as a function of the applied voltage, the distance between the electrodes, the gas in the bubble (Ar or O2). Work supported by the US Army, Picatinny Arsenal, NJ and the US DOE (Contract number DE-AC02-76CH03073).

6. Lattice Boltzmann simulation of rising bubble dynamics using an effective buoyancy method

Ngachin, Merlin; Galdamez, Rinaldo G.; Gokaltun, Seckin; Sukop, Michael C.

2015-08-01

This study describes the behavior of bubbles rising under gravity using the Shan and Chen-type multicomponent multiphase lattice Boltzmann method (LBM) [X. Shan and H. Chen, Phys. Rev. E47, 1815 (1993)]. Two-dimensional (2D) single bubble motions were simulated, considering the buoyancy effect for which the topology of the bubble was characterized by the nondimensional Eötvös (Eo), and Morton (M) numbers. In this study, a new approach based on the "effective buoyancy" was adopted and proven to be consistent with the expected bubble shape deformation. This approach expands the range of effective density differences between the bubble and the liquid that can be simulated. Based on the balance of forces acting on the bubble, it can deform from spherical to ellipsoidal shape with skirts appearing at high Eo number. A benchmark computational case for qualitative and quantitative validation was performed using COMSOL Multiphysics based on the level set method. Simulations were conducted for 1 ≤ Eo ≤ 100 and 3 × 10-6 ≤ M ≤ 2.73 × 10-3. Interfacial tension was checked through simulations without gravity, where Laplace's law was satisfied. Finally, quantitative analyses based on the terminal rise velocity and the degree of circularity was performed for various Eo and M values. Our results were compared with both the theoretical shape regimes given in literature and available simulation results.

7. Acoustic observations of gas bubble streams in the NW Black Sea as a method for estimation of gas flux from vent sites

Artemov, Yu. G.

2003-04-01

Relatively recent discovery of the natural CH_4 gas seepage from the sea bed had action upon the philosophy of CH_4 contribution to global budgets. So far as numerous gas vent sites are known, an acceptable method for released gas quantification is required. In particular, the questions should be answered as follows: 1) how much amount of gas comes into the water column due to a certain bubble stream, 2) how much amount of gas comes into the water column due to a certain seepage area of the see floor, 3) how much amount of gas diffuses into the water and how much gas phase enters the atmosphere. Echo-sounder is the habitual equipment for detecting gas plumes (flares) in the water column. To provide observations of gas seeps with bubbles tracking, single target and volume backscattering strength measurements, we use installed on board the R/V "Professor Vodyanitskiy" dual frequency (38 and 120 kHz) split-beam scientific echo-sounder SIMRAD EK-500. Dedicated software is developed to extract from the raw echo data and to handle the definite information for analyses of gas bubble streams features. This improved hydroacoustic techniques allows to determine gas bubbles size spectrum at different depths through the water column as well as rise velocity of bubbles of different sizes. For instance, bubble of 4.5 mm diameter has rising speed of 25.8 cm/sec at 105 m depth, while bubble of 1.7 mm diameter has rising speed of 16.3 cm/sec at 32 m depth. Using volume backscattering measurements in addition, it is possible to evaluate flux of the gas phase produced by methane bubble streams and to learn of its fate in the water column. Ranking of various gas plumes by flux rate value is available also. In this presentation results of acoustic observations at the shallow NW Black Sea seepage area are given.

8. Why a falling drop does not in general behave like a rising bubble

PubMed Central

Tripathi, Manoj Kumar; Sahu, Kirti Chandra; Govindarajan, Rama

2014-01-01

Is a settling drop equivalent to a rising bubble? The answer is known to be in general a no, but we show that when the density of the drop is less than 1.2 times that of the surrounding fluid, an equivalent bubble can be designed for small inertia and large surface tension. Hadamard's exact solution is shown to be better for this than making the Boussinesq approximation. Scaling relationships and numerical simulations show a bubble-drop equivalence for moderate inertia and surface tension, so long as the density ratio of the drop to its surroundings is close to unity. When this ratio is far from unity, the drop and the bubble are very different. We show that this is due to the tendency for vorticity to be concentrated in the lighter fluid, i.e. within the bubble but outside the drop. As the Galilei and Bond numbers are increased, a bubble displays underdamped shape oscillations, whereas beyond critical values of these numbers, over-damped behavior resulting in break-up takes place. The different circulation patterns result in thin and cup-like drops but bubbles thick at their base. These shapes are then prone to break-up at the sides and centre, respectively. PMID:24759766

9. Linear stability of the wake and path of a rising bubble with a realistic shape

Cano-Lozano, José Carlos; Tchoufag, Joel; Magnaudet, Jacques; Fabre, David; Martínez-Bazán, Carlos

2014-11-01

A global linear stability analysis of the flow past a bubble rising in still liquid is carried out using the real bubble shape and the terminal velocity obtained for various sets of Galileo (Ga) and Bond (Bo) numbers in axisymmetric simulations performed with the multiphase software Gerris Flow Solver. Once the bubble shape is known, the axisymmetric, steady base flow is computed by means of an iterative Newton method with the finite element software FreeFem++, and the eigenvalue problem is solved with the shift-invert Arnoldi technique implemented in the SLEPc library. The critical curve separating stable and unstable regimes is obtained in the (Ga, Bo) and (Reynolds number, aspect ratio) spaces. This allows us to discuss the effect of the bubble shape and aspect ratio on the wake and path instabilities. We observe that the fore-and-aft asymmetry of the bubble has some influence on the stability since, for a given aspect ratio, bubbles with a realistic shape (i.e. a flatter front and a more rounded rear) are more stable that perfectly spheroidal bubbles. Supported by the Spanish MINECO, Junta de Andalucía and EU Funds under Projects DPI2011-28356-C03-03 and P11-TEP7495.

10. Parallel lattice Boltzmann simulation of bubble rising and coalescence in viscous flows

Shi, Dongyan; Wang, Zhikai

2015-07-01

A parallel three-dimensional lattice Boltzmann scheme for multicomponent immiscible fluids is proposed to simulate bubble rising and coalescence process in viscous flows. The lattice Boltzmann scheme is based on the free-energy model and is parallelized in the share-memory model by using the OpenMP. Bubble interface is described by a diffusion interface method solving the Cahn-Hilliard equation and both the surface tension force and the buoyancy are introduced in a form of discrete body force. To avoid the numerical instability caused by the interface deformation, the 18 point finite difference scheme is utilized to calculate the first- and second-order space derivative. The correction of the parallel scheme handling three-dimensional interfaces is verified by the Laplace law and the dynamic characteristics of an isolated bubble in stationary flows. Subsequently, effects of the initially relative position, accompanied by the size ratio on bubble-bubble interaction are studied. The results show that the present scheme can effectively describe the bubble interface dynamics, even if rupture and restructure occurs. In addition to the repulsion and coalescence phenomenon due to the relative position, the size ratio also plays an insignificant role in bubble deformation and trajectory.

11. Simulation Studies on Cooling of Cryogenic Propellant by Gas Bubbling

Sandilya, Pavitra; Saha, Pritam; Sengupta, Sonali

Injection cooling was proposed to store cryogenic liquids (Larsen et al. [1], Schmidt [2]). When a non-condensable gas is injected through a liquid, the liquid component would evaporate into the bubble if its partial pressure in the bubble is lower than its vapour pressure. This would tend to cool the liquid. Earlier works on injection cooling was analysed by Larsen et al. [1], Schmidt [2], Cho et al. [3] and Jung et al. [4], considering instantaneous mass transfer and finite heat transfer between gas bubble and liquid. It is felt that bubble dynamics (break up, coalescence, deformation, trajectory etc.) should also play a significant role in liquid cooling. The reported work are based on simple assumptions like single bubble, zero bubble deformation, and no inter-bubble interactions. Hence in this work, we propose a lumped parameter model considering both heat and mass interactions between bubble and the liquid to gain a preliminary insight into the cooling phenomenon during gas injection through a liquid.

12. Bubble coalescence dynamics and supersaturation in electrolytic gas evolution

SciTech Connect

Stover, R.L. |

1996-08-01

The apparatus and procedures developed in this research permit the observation of electrolytic bubble coalescence, which heretofore has not been possible. The influence of bubble size, electrolyte viscosity, surface tension, gas type, and pH on bubble coalescence was examined. The Navier-Stokes equations with free surface boundary conditions were solved numerically for the full range of experimental variables that were examined. Based on this study, the following mechanism for bubble coalescence emerges: when two gas bubbles coalesce, the surface energy decreases as the curvature and surface area of the resultant bubble decrease, and the energy is imparted into the surrounding liquid. The initial motion is driven by the surface tension and slowed by the inertia and viscosity of the surrounding fluid. The initial velocity of the interface is approximately proportional to the square root of the surface tension and inversely proportional to the square root of the bubble radius. Fluid inertia sustains the oblate/prolate oscillations of the resultant bubble. The period of the oscillations varies with the bubble radius raised to the 3/2 power and inversely with the square root of the surface tension. Viscous resistance dampens the oscillations at a rate proportional to the viscosity and inversely proportional to the square of the bubble radius. The numerical simulations were consistent with most of the experimental results. The differences between the computed and measured saddle point decelerations and periods suggest that the surface tension in the experiments may have changed during each run. By adjusting the surface tension in the simulation, a good fit was obtained for the 150-{micro}m diameter bubbles. The simulations fit the experiments on larger bubbles with very little adjustment of surface tension. A more focused analysis should be done to elucidate the phenomena that occur in the receding liquid film immediately following rupture.

13. The preparation and characterization of gas bubble containing liposomes.

PubMed

Liu, Rui; Wei, Xiaohui; Yao, Yanbin; Chai, Qiliang; Chen, Yue; Xu, Yuhong

2005-01-01

Liposomes and lipid nano-particles containing gas bubbles have great potentials to be used as ultrasound contrast agents or as drug and gene delivery vehicles. We developed a method to enable in situ CO2gas bubbles formation inside liposomes. The resulted bubbles containing liposomes were shown to be able to effectively echo ultrasound. Their acoustic properties were assessed by ultrasound imaging and intensity analysis. Compared to most other echogenic liposome formulations reported, our method is easier, faster, and more economical. It would be useful for many applications with improvements and optimization.

14. Production of Gas Bubbles in Reduced Gravity Environments

NASA Technical Reports Server (NTRS)

Oguz, Hasan N.; Takagi, Shu; Misawa, Masaki

1996-01-01

In a wide variety of applications such as waste water treatment, biological reactors, gas-liquid reactors, blood oxygenation, purification of liquids, etc., it is necessary to produce small bubbles in liquids. Since gravity plays an essential role in currently available techniques, the adaptation of these applications to space requires the development of new tools. Under normal gravity, bubbles are typically generated by forcing gas through an orifice in a liquid. When a growing bubble becomes large enough, the buoyancy dominates the surface tension force causing it to detach from the orifice. In space, the process is quite different and the bubble may remain attached to the orifice indefinitely. The most practical approach to simulating gravity seems to be imposing an ambient flow to force bubbles out of the orifice. In this paper, we are interested in the effect of an imposed flow in 0 and 1 g. Specifically, we investigate the process of bubble formation subject to a parallel and a cross flow. In the case of parallel flow, we have a hypodermic needle in a tube from which bubbles can be produced. On the other hand, the cross flow condition is established by forcing bubbles through an orifice on a wall in a shear flow. The first series of experiments have been performed under normal gravity conditions and the working fluid was water. A high quality microgravity facility has been used for the second type and silicone oil is used as the host liquid.

15. Interaction of a shock with elliptical gas bubbles

Georgievskiy, P. Yu.; Levin, V. A.; Sutyrin, O. G.

2015-07-01

The interaction of a shock with spherical and elliptical bubbles of light or heavy gas is numerically studied using the axisymmetric Euler equations. A model with a single heat capacity ratio is implemented, where bubbles are modeled by areas of the same gas with lower or higher density. Details of the general shock refraction patterns—diverging and converging—are described. The formation and development of secondary, focusing shocks are discussed. A computational parameter study for different Atwood numbers , shock strengths , where is the Mach number, and bubble geometries is performed. A basic classification for the shock focusing (cumulation) regimes is suggested, with the division of the internal, external and transitional focusing regimes determined by the position of the shock focusing point relative to the bubble. It is shown that the focusing pattern is governed not only by the Atwood number but also heavily by the Mach number and bubble shape. The qualitative dependence of cumulative intensity on bubble geometry is determined. The theoretical possibility of realizing an extremely intense shock collapse with a relatively small variation in bubble shape is demonstrated for the heavy-bubble scenario.

16. The role of gas in ultrasonically driven vapor bubble growth

Shpak, Oleksandr; Stricker, Laura; Versluis, Michel; Lohse, Detlef

2013-04-01

In this paper we study both experimentally and theoretically the dynamics of an ultrasound-driven vapor bubble of perfluoropentane (PFP) inside a droplet of the same liquid, immersed in a water medium superheated with respect to the PFP boiling point. We determine the temporal evolution of the bubble radius with ultra-high speed imaging at 20 million frames per second. In addition, we model the vapor-gas bubble dynamics, based on a Rayleigh-Plesset-type equation, including thermal and gas diffusion inside the liquid. We compare the numerical results with the experimental data and find good agreement. We underline the fundamental role of gas diffusion in order to prevent total recondensation of the bubble at collapse.

17. Quantification of gas bubble emissions from submarine hydrocarbon seeps at the Makran continental margin (offshore Pakistan)

RöMer, Miriam; Sahling, Heiko; Pape, Thomas; Bohrmann, Gerhard; Spieß, Volkhard

2012-10-01

Evidence for twelve sites with gas bubble emissions causing hydroacoustic anomalies in 18 kHz echosounder records (flares') was obtained at the convergent Makran continental margin. The hydroacoustic anomalies originating from hydrocarbon seeps at water depths between 575 and 2870 m disappeared after rising up to 2000 m in the water column. Dives with the remotely operated vehicle Quest 4000 m' revealed that several individual bubble vents contributed to one hydroacoustic anomaly. Analyzed gas samples suggest that bubbles were mainly composed of methane of microbial origin. Bubble size distributions and rise velocities were determined and the volume flux was estimated by counting the emitted bubbles and using their average volume. We found that a low volume flux (Flare 1 at 575 mbsl: 90 ml/min) caused a weak hydroacoustic signal in echograms whereas high volume fluxes (Flare 2 at 1027 mbsl: 1590 ml/min; Flare 5 C at 2870 mbsl: 760 ml/min) caused strong anomalies. The total methane bubble flux in the study area was estimated by multiplying the average methane flux causing a strong hydroacoustic anomaly in the echosounder record with the total number of equivalent anomalies. An order-of-magnitude estimate further considers the temporal variability of some of the flares, assuming a constant flux over time, and allows a large range of uncertainty inherent to the method. Our results on the fate of bubbles and the order-of-magnitude estimate suggest that all of the ˜40 ± 32 × 106 mol methane emitted per year within the gas hydrate stability zone remain in the deep ocean.

18. Three-dimensional simulations of a rising bubble in a self-rewetting fluid

Premlata, Amarnath; Tripathi, Manoj; Sahu, Kirti; Karapetsas, George; Sefiane, Khellil; Matar, Omar

2015-11-01

The motion of a gas bubble in a square channel with linearly increasing temperature in the vertical direction is investigated via 3D numerical simulations. The channel contains a so-called self-rewetting'' fluid whose surface tension exhibits a parabolic dependence on temperature with a well-defined minimum. An open-source finite-volume fluid flow solver, Gerris, is used with a dynamic adaptive grid refinement technique, based on the vorticity magnitude and position of the interface. We find that in self-rewetting fluids, the buoyancy-induced upward motion of the bubble is retarded by a thermocapillary-driven flow, which occurs as the bubble crosses the location at which the surface tension is minimum. The bubble then migrates downwards when thermocapillarity exceeds buoyancy. In its downward path, the bubble encounters regions of horizontal temperature gradients, which lead to bubble motion towards one of the channel walls. These phenomena are observed at sufficiently small Bond numbers and have no analogue for fluids whose surface tension decreases linearly with temperature. The mechanisms underlying these phenomena are elucidated by considering how the surface tension dependence on temperature affects the thermocapillary stresses in the flow. EPSRC Programme Grant, MEMPHIS, EP/K0039761/1.

19. Paths and wakes of deformable nearly spheroidal rising bubbles close to the transition to path instability

Cano-Lozano, José Carlos; Martínez-Bazán, Carlos; Magnaudet, Jacques; Tchoufag, Joël

2016-09-01

We report on a series of results provided by three-dimensional numerical simulations of nearly spheroidal bubbles freely rising and deforming in a still liquid in the regime close to the transition to path instability. These results improve upon those of recent computational studies [Cano-Lozano et al., Int. J. Multiphase Flow 51, 11 (2013), 10.1016/j.ijmultiphaseflow.2012.11.005; Phys. Fluids 28, 014102 (2016), 10.1063/1.4939703] in which the neutral curve associated with this transition was obtained by considering realistic but frozen bubble shapes. Depending on the dimensionless parameters that characterize the system, various paths geometries are observed by letting an initially spherical bubble starting from rest rise under the effect of buoyancy and adjust its shape to the surrounding flow. These include the well-documented rectilinear axisymmetric, planar zigzagging, and spiraling (or helical) regimes. A flattened spiraling regime that most often eventually turns into either a planar zigzagging or a helical regime is also frequently observed. Finally, a chaotic regime in which the bubble experiences small horizontal displacements (typically one order of magnitude smaller than in the other regimes) is found to take place in a region of the parameter space where no standing eddy exists at the back of the bubble. The discovery of this regime provides evidence that path instability does not always result from a wake instability as previously believed. In each regime, we examine the characteristics of the path, bubble shape, and vortical structure in the wake, as well as their couplings. In particular, we observe that, depending on the fluctuations of the rise velocity, two different vortex shedding modes exist in the zigzagging regime, confirming earlier findings with falling spheres. The simulations also reveal that significant bubble deformations may take place along zigzagging or spiraling paths and that, under certain circumstances, they dramatically alter

20. Investigating the role of gas bubble formation and entrapment in contaminated aquifers: Reactive transport modelling

Amos, Richard T.; Ulrich Mayer, K.

2006-09-01

In many natural and contaminated aquifers, geochemical processes result in the production or consumption of dissolved gases. In cases where methanogenesis or denitrification occurs, the production of gases may result in the formation and growth of gas bubbles below the water table. Near the water table, entrapment of atmospheric gases during water table rise may provide a significant source of O 2 to waters otherwise depleted in O 2. Furthermore, the presence of bubbles will affect the hydraulic conductivity of an aquifer, resulting in changes to the groundwater flow regime. The interactions between physical transport, biogeochemical processes, and gas bubble formation, entrapment and release is complex and requires suitable analysis tools. The objective of the present work is the development of a numerical model capable of quantitatively assessing these processes. The multicomponent reactive transport code MIN3P has been enhanced to simulate bubble growth and contraction due to in-situ gas production or consumption, bubble entrapment due to water table rise and subsequent re-equilibration of the bubble with ambient groundwater, and permeability changes due to trapped gas phase saturation. The resulting formulation allows for the investigation of complex geochemical systems where microbially mediated redox reactions both produce and consume gases as well as affect solution chemistry, alkalinity, and pH. The enhanced model has been used to simulate processes in a petroleum hydrocarbon contaminated aquifer where methanogenesis is an important redox process. The simulations are constrained by data from a crude oil spill site near Bemidji, MN. Our results suggest that permeability reduction in the methanogenic zone due to in-situ formation of gas bubbles, and dissolution of entrapped atmospheric bubbles near the water table, both work to attenuate the dissolved gas plume emanating from the source zone. Furthermore, the simulations demonstrate that under the given

1. Investigating the role of gas bubble formation and entrapment in contaminated aquifers: Reactive transport modelling

USGS Publications Warehouse

Amos, Richard T.; Mayer, K. Ulrich

2006-01-01

In many natural and contaminated aquifers, geochemical processes result in the production or consumption of dissolved gases. In cases where methanogenesis or denitrification occurs, the production of gases may result in the formation and growth of gas bubbles below the water table. Near the water table, entrapment of atmospheric gases during water table rise may provide a significant source of O2 to waters otherwise depleted in O2. Furthermore, the presence of bubbles will affect the hydraulic conductivity of an aquifer, resulting in changes to the groundwater flow regime. The interactions between physical transport, biogeochemical processes, and gas bubble formation, entrapment and release is complex and requires suitable analysis tools. The objective of the present work is the development of a numerical model capable of quantitatively assessing these processes. The multicomponent reactive transport code MIN3P has been enhanced to simulate bubble growth and contraction due to in-situ gas production or consumption, bubble entrapment due to water table rise and subsequent re-equilibration of the bubble with ambient groundwater, and permeability changes due to trapped gas phase saturation. The resulting formulation allows for the investigation of complex geochemical systems where microbially mediated redox reactions both produce and consume gases as well as affect solution chemistry, alkalinity, and pH. The enhanced model has been used to simulate processes in a petroleum hydrocarbon contaminated aquifer where methanogenesis is an important redox process. The simulations are constrained by data from a crude oil spill site near Bemidji, MN. Our results suggest that permeability reduction in the methanogenic zone due to in-situ formation of gas bubbles, and dissolution of entrapped atmospheric bubbles near the water table, both work to attenuate the dissolved gas plume emanating from the source zone. Furthermore, the simulations demonstrate that under the given

2. Effervescence in champagne and sparkling wines: From grape harvest to bubble rise

Liger-Belair, Gérard

2017-01-01

Bubbles in a glass of champagne may seem like the acme of frivolity to most of people, but in fact they may rather be considered as a fantastic playground for any fluid physicist. Under standard tasting conditions, about a million bubbles will nucleate and rise if you resist drinking from your flute. The so-called effervescence process, which enlivens champagne and sparkling wines tasting, is the result of the complex interplay between carbon dioxide (CO2) dissolved in the liquid phase, tiny air pockets trapped within microscopic particles during the pouring process, and some both glass and liquid properties. In this tutorial review, the journey of yeast-fermented CO2 is reviewed (from its progressive dissolution in the liquid phase during the fermentation process, to its progressive release in the headspace above glasses). The most recent advances about the physicochemical processes behind the nucleation, and rise of gaseous CO2 bubbles, under standard tasting conditions, have been gathered hereafter. Let's hope that your enjoyment of champagne will be enhanced after reading this tutorial review dedicated to the unsuspected physics hidden right under your nose each time you enjoy a glass of bubbly.

3. Rising Bubbles.

DTIC Science & Technology

1982-12-01

2. National Science Foundation; 3. Army Research Office; 4. Air Force Office of Scientific Research ; 5. Stanford University. The personnel...Mathematics Department, Stanford University. This group began functioning officially on September 1, 1979, and is supported by: 1. Office of Naval Research ...Stanford University; 13. Stephanos Venakides, Assistant Professor, Stanford University; 14. Margaret Cheney, Research Associate, Stanford University; 15

4. Transient Flow Dynamics in Optical Micro Well Involving Gas Bubbles

NASA Technical Reports Server (NTRS)

Johnson, B.; Chen, C. P.; Jenkins, A.; Spearing, S.; Monaco, L. A.; Steele, A.; Flores, G.

2006-01-01

The Lab-On-a-Chip Application Development (LOCAD) team at NASA s Marshall Space Flight Center is utilizing Lab-On-a-Chip to support technology development specifically for Space Exploration. In this paper, we investigate the transient two-phase flow patterns in an optic well configuration with an entrapped bubble through numerical simulation. Specifically, the filling processes of a liquid inside an expanded chamber that has bubbles entrapped. Due to the back flow created by channel expansion, the entrapped bubbles tend to stay stationary at the immediate downstream of the expansion. Due to the huge difference between the gas and liquid densities, mass conservation issues associated with numerical diffusion need to be specially addressed. The results are presented in terms of the movement of the bubble through the optic well. Bubble removal strategies are developed that involve only pressure gradients across the optic well. Results show that for the bubble to be moved through the well, pressure pulsations must be utilized in order to create pressure gradients across the bubble itself.

5. Bubble and bubble cloud dynamics

Matsumoto, Yoichiro

2000-07-01

Cavitation bubbles are formed from small air bubbles, so-called nuclei, with the surrounding pressure reduction caused by the flow, and then, the bubbles shrink and collapse with the surrounding pressure rise. Such volumetric changes of bubbles are calculated in detail and it is found that they are significantly influenced by the internal phenomena, such as thermal diffusion, mist formation due to a homogeneous condensation, mass diffusion between vapor and noncondensable gas, heat and mass transfer through the bubble wall. The structure in cavitating flow interacts with the cavitation bubbles, and those bubbles form a cloud cavitation. It is well known that cloud cavitation is one of the most destructive forms. The behavior of bubble clouds is simulated numerically. An inward propagating shock wave is formed during the collapse of the bubble cloud, and the shock wave and its precursor are focused at the cloud center area. These phenomena associate high frequency pressure oscillations and violent bubble collapses. Those bubble collapses emit high pressure peaks, which are several hundreds times larger than that of a single bubble collapse.

6. The Bubble Box: Towards an Automated Visual Sensor for 3D Analysis and Characterization of Marine Gas Release Sites

PubMed Central

Jordt, Anne; Zelenka, Claudius; Schneider von Deimling, Jens; Koch, Reinhard; Köser, Kevin

2015-01-01

Several acoustic and optical techniques have been used for characterizing natural and anthropogenic gas leaks (carbon dioxide, methane) from the ocean floor. Here, single-camera based methods for bubble stream observation have become an important tool, as they help estimating flux and bubble sizes under certain assumptions. However, they record only a projection of a bubble into the camera and therefore cannot capture the full 3D shape, which is particularly important for larger, non-spherical bubbles. The unknown distance of the bubble to the camera (making it appear larger or smaller than expected) as well as refraction at the camera interface introduce extra uncertainties. In this article, we introduce our wide baseline stereo-camera deep-sea sensor bubble box that overcomes these limitations, as it observes bubbles from two orthogonal directions using calibrated cameras. Besides the setup and the hardware of the system, we discuss appropriate calibration and the different automated processing steps deblurring, detection, tracking, and 3D fitting that are crucial to arrive at a 3D ellipsoidal shape and rise speed of each bubble. The obtained values for single bubbles can be aggregated into statistical bubble size distributions or fluxes for extrapolation based on diffusion and dissolution models and large scale acoustic surveys. We demonstrate and evaluate the wide baseline stereo measurement model using a controlled test setup with ground truth information. PMID:26690168

7. CFD-informed unified closure relation for the rise velocity of Taylor bubbles in pipes

Lizarraga-Garcia, Enrique; Buongiorno, Jacopo; Al-Safran, Eissa; Lakehal, Djamel

2015-11-01

Two-phase slug flow commonly occurs in gas and oil systems. Current predictive methods are based on the mechanistic models, which require the use of closure relations to complement the conservation equations to predict integral flow parameters such as liquid holdup (or void fraction) and pressure gradient. Taylor bubble velocity in slug flow is one of these closure relations which has been determined to significantly affect the calculation of these parameters. In this work, Computational Fluid Dynamics (CFD) with Level-Set as the Interface Tracking Method (ITM) are employed to simulate the motion of Taylor bubbles in slug flow, for which the commercial code TransAT is used. A large numerical database with stagnant and flowing liquid for various Reynolds numbers is being generated from which a unified Taylor bubble velocity correlation in stagnant liquids for an ample range of fluid properties and pipe geometries is proposed (Mo ∈ [ 1 .10-6 , 5 .103 ] , Eo ∈ [ 10 , 700 ]). Furthermore, it is found that the velocity of Taylor bubbles in inclined pipes is greatly affected by the presence of a lubricating thin film between the bubble and the pipe wall. An analytical and experimentally validated criterion, which predicts the film existence, draiage and breakup, is presented.

8. Measurements of Gas Bubble Size Distributions in Flowing Liquid Mercury

SciTech Connect

Wendel, Mark W; Riemer, Bernie; Abdou, Ashraf A

2012-01-01

ABSTRACT Pressure waves created in liquid mercury pulsed spallation targets have been shown to induce cavitation damage on the target container. One way to mitigate such damage would be to absorb the pressure pulse energy into a dispersed population of small bubbles, however, measuring such a population in mercury is difficult since it is opaque and the mercury is involved in a turbulent flow. Ultrasonic measurements have been attempted on these types of flows, but the flow noise can interfere with the measurement, and the results are unverifiable and often unrealistic. Recently, a flow loop was built and operated at Oak Ridge National Labarotory to assess the capability of various bubbler designs to deliver an adequate population of bubbles to mitigate cavitation damage. The invented diagnostic technique involves flowing the mercury with entrained gas bubbles in a steady state through a horizontal piping section with a glass-window observation port located on the top. The mercury flow is then suddenly stopped and the bubbles are allowed to settle on the glass due to buoyancy. Using a bright-field illumination and a high-speed camera, the arriving bubbles are detected and counted, and then the images can be processed to determine the bubble populations. After using this technique to collect data on each bubbler, bubble size distributions were built for the purpose of quantifying bubbler performance, allowing the selection of the best bubbler options. This paper presents the novel procedure, photographic technique, sample visual results and some example bubble size distributions. The best bubbler options were subsequently used in proton beam irradiation tests performed at the Los Alamos National Laboratory. The cavitation damage results from the irradiated test plates in contact with the mercury are available for correlation with the bubble populations. The most effective mitigating population can now be designed into prototypical geometries for implementation into

9. Preliminary study of the effects of a reversible chemical reaction on gas bubble dissolution. [for space glass refining

NASA Technical Reports Server (NTRS)

Weinberg, M. C.

1982-01-01

A preliminary investigation is carried out of the effects of a reversible chemical reaction on the dissolution of an isolated, stationary gas bubble in a glass melt. The exact governing equations for the model system are formulated and analyzed. The approximate quasi-steady-state version of these equations is solved analytically, and a calculation is made of bubble dissolution rates. The results are then compared with numerical solutions obtained from the finite difference form of the exact governing equations. It is pointed out that in the microgravity condition of space, the buoyant rise of a gas bubble in a glass melt will be negligible on the time scale of most experiments. For this reason, a determination of the behavior of a stationary gas bubble in a melt is relevant for an understanding of glass refining in space.

10. A mass-conserving axisymmetric multiphase lattice Boltzmann method and its application in simulation of bubble rising

Huang, Haibo; Huang, Jun-Jie; Lu, Xi-Yun

2014-07-01

In many lattice Boltzmann studies about bubble rising, mass conservation is not satisfactory and the terminal bubble rising shape or velocity is not so consistent with experimental data as those obtained through other CFD techniques. In this paper, based on the multiphase model (He et al., 1999 [1]), a mass-conserving axisymmetric multiphase lattice Boltzmann model is developed. In the model, a mass correction step and an effective surface tension formula are introduced into the model. We demonstrate how the macroscopic axisymmetric Cahn-Hilliard equation and Navier-Stokes equation are recovered from the lattice Boltzmann equations through Chapman-Enskog expansion. The developed model is applied to simulate the bubble rising in viscous fluid. The mass correction step in our scheme significantly improves the bubble mass conservation. The surface tension calculation successfully predicts the terminal bubble shapes and reproduces the effect of initial bubble shape. The terminal bubble rising velocities are very consistent with experimental and numerical data in the literature. Qualitatively, the wakes behind the bubbles also agree well with experimental data. This model is useful for predicting the axisymmetric two-phase flows.

11. Behavior of bubbles in glassmelts. II - Dissolution of a stationary bubble containing a diffusing and a nondiffusing gas

NASA Technical Reports Server (NTRS)

Weinberg, M. C.; Onorato, P. I. K.; Uhlmann, D. R.

1980-01-01

The effect of a foreign nondiffusing gas on the rate of shrinkage of an oxygen bubble in a soda-lime-silica melt was studied. The rate of change of bubble radius with time was computed using the quasi-stationary approximation. The effects of melt undersaturation and initial fraction of foreign gas in the bubble are considered and compared with those calculated using previously derived expressions.

12. Spread F plasma bubble vertical rise velocities determined from spaced ionosonde observations

SciTech Connect

Abdu, M.A.; de Medeiros, R.T.; Sobral, J.H.A.; Bittencourt, J.A.

1983-11-01

Systematic time differences in the onsets of spread F events in the ionograms are observed between the magnetic equatorial station Fortaleza (4/sup 0/S, 38/sup 0/W, dip latitude 1.8/sup 0/S) and the low-latitude station Cachoeira Paulista (23/sup 0/S, 45/sup 0/W, dip latitude 14/sup 0/S), two stations in Brazil, located at close-by magnetic meridional planes (actually some 12/sup 0/ of magnetic longitude apart). On the assumption, justified from different experimental observations, that the spread F irregularities occur in strongly field-aligned plasma bubbles that extend several degrees on either side of the magnetic equator, and rise up in vertically elongated columns over the magnteic equator, we have related the observed time differences in the onsets of spread F events at the two stations to the plasma bubble vertical rise velocities of the plasma bubbles so determined are found to be well within the values measured by VHF radar and satellite techniques, and further show, at times, good correlations with the amplitude of the prereversal peak in the vertical drift velocities and the heights of the evening equatorial F layer. Possible implications of these results are discussed.

13. Step-Wise Velocity of an Air Bubble Rising in a Vertical Tube Filled with a Liquid Dispersion of Nanoparticles.

PubMed

Cho, Heon Ki; Nikolov, Alex D; Wasan, Darsh T

2017-03-21

The motion of air bubbles in tubes filled with aqueous suspensions of nanoparticles (nanofluids) is of practical interest for bubble jets, lab-on-a-chip, and transporting media. Therefore, the focus of this study is the dynamics of air bubbles rising in a tube in a nanofluid. Many authors experimentally and analytically proposed that the velocity of rising air bubbles is constant for long air bubbles suspended in a vertical tube in common liquids (e.g. an aqueous glycerol solution) when the capillary number is larger than 10(-4). For the first time, we report here a systematic study of an air bubble rising in a vertical tube in a nanofluid (e.g. an aqueous silica dioxide nanoparticle suspension, nominal particle size, 19 nm). We varied the bubble length scaled by the diameter of the tubes (L/D), the concentration of the nanofluid (10 and 12.5 v %), and the tube diameter (0.45, 0.47, and 0.50 cm). The presence of the nanoparticles creates a significant change in the bubble velocity compared with the bubble rising in the common liquid with the same bulk viscosity. We observed a novel phenomenon of a step-wise increase in the air bubble rising velocity versus bubble length for small capillary numbers less than 10(-7). This step-wise velocity increase versus the bubble length was not observed in a common fluid. The step-wise velocity increase is attributed to the nanoparticle self-layering phenomenon in the film adjacent to the tube wall. To elucidate the role of the nanoparticle film self-layering on the bubble rising velocity, the effect of the capillary number, the tube diameter (e.g. the capillary pressure), and nanofilm viscosity are investigated. We propose a model that takes into consideration the nanoparticle layering in the film confinement to explain the step-wise velocity phenomenon versus the length of the bubble. The oscillatory film interaction energy isotherm is calculated and the Frenkel approach is used to estimate the film viscosity.

14. Blind Deconvolution on Underwater Images for Gas Bubble Measurement

Zelenka, C.; Koch, R.

2015-04-01

Marine gas seeps, such as in the Panarea area near Sicily (McGinnis et al., 2011), emit large amounts of methane and carbon-dioxide, greenhouse gases. Better understanding their impact on the climate and the marine environment requires precise measurements of the gas flux. Camera based bubble measurement systems suffer from defocus blur caused by a combination of small depth of field, insufficient lighting and from motion blur due to rapid bubble movement. These adverse conditions are typical for open sea underwater bubble images. As a consequence so called 'bubble boxes' have been built, which use elaborate setups, specialized cameras and high power illumination. A typical value of light power used is 1000W (Leifer et al., 2003). In this paper we propose the compensation of defocus and motion blur in underwater images by using blind deconvolution techniques. The quality of the images can be greatly improved, which will relax requirements on bubble boxes, reduce their energy consumption and widen their usability.

15. Dynamic morphology of gas hydrate on a methane bubble in water: Observations and new insights for hydrate film models

Warzinski, Robert P.; Lynn, Ronald; Haljasmaa, Igor; Leifer, Ira; Shaffer, Frank; Anderson, Brian J.; Levine, Jonathan S.

2014-10-01

Predicting the fate of subsea hydrocarbon gases escaping into seawater is complicated by potential formation of hydrate on rising bubbles that can enhance their survival in the water column, allowing gas to reach shallower depths and the atmosphere. The precise nature and influence of hydrate coatings on bubble hydrodynamics and dissolution is largely unknown. Here we present high-definition, experimental observations of complex surficial mechanisms governing methane bubble hydrate formation and dissociation during transit of a simulated oceanic water column that reveal a temporal progression of deep-sea controlling mechanisms. Synergistic feedbacks between bubble hydrodynamics, hydrate morphology, and coverage characteristics were discovered. Morphological changes on the bubble surface appear analogous to macroscale, sea ice processes, presenting new mechanistic insights. An inverse linear relationship between hydrate coverage and bubble dissolution rate is indicated. Understanding and incorporating these phenomena into bubble and bubble plume models will be necessary to accurately predict global greenhouse gas budgets for warming ocean scenarios and hydrocarbon transport from anthropogenic or natural deep-sea eruptions.

16. Investigation of Gas Holdup in a Vibrating Bubble Column

Mohagheghian, Shahrouz; Elbing, Brian

2015-11-01

Synthetic fuels are part of the solution to the world's energy crisis and climate change. Liquefaction of coal during the Fischer-Tropsch process in a bubble column reactor (BCR) is a key step in production of synthetic fuel. It is known from the 1960's that vibration improves mass transfer in bubble column. The current study experimentally investigates the effect that vibration frequency and amplitude has on gas holdup and bubble size distribution within a bubble column. Air (disperse phase) was injected into water (continuous phase) through a needle shape injector near the bottom of the column, which was open to atmospheric pressure. The air volumetric flow rate was measured with a variable area flow meter. Vibrations were generated with a custom-made shaker table, which oscillated the entire column with independently specified amplitude and frequency (0-30 Hz). Geometric dependencies can be investigated with four cast acrylic columns with aspect ratios ranging from 4.36 to 24, and injector needle internal diameters between 0.32 and 1.59 mm. The gas holdup within the column was measured with a flow visualization system, and a PIV system was used to measure phase velocities. Preliminary results for the non-vibrating and vibrating cases will be presented.

17. Gamma densitometry tomography of gas holdup spatial distribution in industrial scale bubble columns

SciTech Connect

Shollenberger, K.A.; Torczynski, J.R.; Adkins, D.R.; OHern, T.J.; Jackson, N.B.

1995-12-31

Gamma-densitometry tomography (GDT) experiments have been performed to measure gas holdup spatial variations in two bubble columns: a 0.19 m inside diameter Lucite column and a 0.48 m inside diameter stainless steel vessel. Air and water were used for the measurements. Horizontal scans at one vertical position in each column were made for several air flow rates. An axi-symmetric tomographic reconstruction algorithm based on the Abel transform has been used to calculate the time averaged gas holdup radial variation. Integration of these profiles over the column cross section has yielded area-averaged gas holdup results, which have been compared with volume-averaged gas holdups determined from differential pressure measurements and from the rise in the air/water interface during gas flow. The results agree reasonably well.

18. Modeling biogenic gas bubbles formation and migration in coarse sand

Ye, S.

2011-12-01

Shujun Ye Department of Hydrosciences, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210093, China; sjye@nju.edu.cn Brent E. Sleep Department of Civil Engineering, University of Toronto, Toronto, ON, M5S 1A4 CANADA; sleep@ecf.utoronto.ca Methane gas generation in porous media was investigated in an anaerobic two-dimensional sand-filled cell. Inoculation of the lower portion of the cell with a methanogenic culture and addition of methanol to the bottom of the cell led to biomass growth and formation of a gas phase. The formation, migration, distribution and saturation of gases in the cell were visualized by the charge-coupled device (CCD) camera. Gas generated at the bottom of the cell in the biologically active zone moved upwards in discrete fingers, so that gas phase saturations (gas-filled fraction of void space) in the biologically active zone at the bottom of the cell did not exceed 40-50%, while gas accumulation at the top of the cell produced gas phase saturations as high as 80%. Macroscopic invasion percolation (MIP) at near pore scale[Glass, et al., 2001; Kueper and McWhorter, 1992]was used to model gas bubbles growth in porous media. The nonwetting phase migration pathway can be yielded directly by MIP. MIP was adopted to simulate the expansion, fragmentation, and mobilization of gas clusters in the cell. The production of gas, and gas phash saturations were simulated by a continuum model - compositional simulator (COMPSIM) [Sleep and Sykes, 1993]. So a combination of a continuum model and a MIP model was used to simulate the formation, fragmentation and migration of biogenic gas bubbles. Key words: biogenic gas; two dimensional; porous media; MIP; COMPSIM

19. Formation mechanism of gas bubble superlattice in UMo metal fuels: Phase-field modeling investigation

Hu, Shenyang; Burkes, Douglas E.; Lavender, Curt A.; Senor, David J.; Setyawan, Wahyu; Xu, Zhijie

2016-10-01

Nano-gas bubble superlattices are often observed in irradiated UMo nuclear fuels. However, the formation mechanism of gas bubble superlattices is not well understood. A number of physical processes may affect the gas bubble nucleation and growth; hence, the morphology of gas bubble microstructures including size and spatial distributions. In this work, a phase-field model integrating a first-passage Monte Carlo method to investigate the formation mechanism of gas bubble superlattices was developed. Six physical processes are taken into account in the model: 1) heterogeneous generation of gas atoms, vacancies, and interstitials informed from atomistic simulations; 2) one-dimensional (1-D) migration of interstitials; 3) irradiation-induced dissolution of gas atoms; 4) recombination between vacancies and interstitials; 5) elastic interaction; and 6) heterogeneous nucleation of gas bubbles. We found that the elastic interaction doesn't cause the gas bubble alignment, and fast 1-D migration of interstitials along <110> directions in the body-centered cubic U matrix causes the gas bubble alignment along <110> directions. It implies that 1-D interstitial migration along [110] direction should be the primary mechanism of a fcc gas bubble superlattice which is observed in bcc UMo alloys. Simulations also show that fission rates, saturated gas concentration, and elastic interaction all affect the morphology of gas bubble microstructures.

20. Formation mechanism of gas bubble superlattice in UMo metal fuels: Phase-field modeling investigation

SciTech Connect

Hu, Shenyang; Burkes, Douglas E.; Lavender, Curt A.; Senor, David J.; Setyawan, Wahyu; Xu, Zhijie

2016-07-08

Nano-gas bubble superlattices are often observed in irradiated UMo nuclear fuels. However, the for- mation mechanism of gas bubble superlattices is not well understood. A number of physical processes may affect the gas bubble nucleation and growth; hence, the morphology of gas bubble microstructures including size and spatial distributions. In this work, a phase-field model integrating a first-passage Monte Carlo method to investigate the formation mechanism of gas bubble superlattices was devel- oped. Six physical processes are taken into account in the model: 1) heterogeneous generation of gas atoms, vacancies, and interstitials informed from atomistic simulations; 2) one-dimensional (1-D) migration of interstitials; 3) irradiation-induced dissolution of gas atoms; 4) recombination between vacancies and interstitials; 5) elastic interaction; and 6) heterogeneous nucleation of gas bubbles. We found that the elastic interaction doesn’t cause the gas bubble alignment, and fast 1-D migration of interstitials along $\\langle$110$\\rangle$ directions in the body-centered cubic U matrix causes the gas bubble alignment along $\\langle$110$\\rangle$ directions. It implies that 1-D interstitial migration along [110] direction should be the primary mechanism of a fcc gas bubble superlattice which is observed in bcc UMo alloys. Simulations also show that fission rates, saturated gas concentration, and elastic interaction all affect the morphology of gas bubble microstructures.

1. Progression and severity of gas bubble trauma in juvenile salmonids

USGS Publications Warehouse

Mesa, M.G.; Weiland, L.K.; Maule, A.G.

2000-01-01

We conducted laboratory experiments to assess the progression and to quantify the severity of signs of gas bubble trauma (GBT) in juvenile chinook salmon Oncorhynchus tshawytscha and steelhead Oncorhynchus mykiss exposed to different levels of total dissolved gas (TDG), and we attempted to relate these signs to the likelihood of mortality. When fish were exposed to 110% TDG for up to 22 d, no fish died, and there were few signs of GBT in the lateral line or gills. Bubbles in the fins, however, were relatively common, and they progressively worsened over the experimental period. When fish were exposed to 120% TDG for up to 140 h, chinook salmon had an LT20 (time necessary to kill 20% of the fish) ranging from 40 to 120 h, whereas steelhead had LT20s ranging from 20 to 35 h. In steelhead, bubbles in the lateral line, fins, and gills displayed poor trends of worsening over time, showed substantial interindividual variability, and were poorly related to mortality. In chinook salmon, only bubbles in the lateral line showed a distinct worsening over time, and the severity of bubbles in the lateral line was highly correlated with mortality. When fish were exposed to 130% TDG for up to 11 h, LT20s for chinook salmon ranged from 3 to 6 h, whereas those for steelhead ranged from 5 to 7 h. In chinook salmon, bubbles in the lateral line and fins, but not those in the gills, showed distinct trends of worsening over time. In steelhead, bubbles in the lateral line displayed the most significant trend of progressive severity. In both species at 130% TDG, the severity of all GBT signs was highly correlated with mortality. The progressive nature of GBT and the methods we developed to examine fish for GBT may be useful for monitoring programs that aim to assess the severity of dissolved gas supersaturation exposures experienced by fish in the wild. However, the efficacy of such programs seems substantially hindered by problems associated with (1) the variable persistence of GBT signs

2. Mathematical model of diffusion-limited gas bubble dynamics in unstirred tissue with finite volume

NASA Technical Reports Server (NTRS)

Srinivasan, R. Srini; Gerth, Wayne A.; Powell, Michael R.

2002-01-01

Models of gas bubble dynamics for studying decompression sickness have been developed by considering the bubble to be immersed in an extravascular tissue with diffusion-limited gas exchange between the bubble and the surrounding unstirred tissue. In previous versions of this two-region model, the tissue volume must be theoretically infinite, which renders the model inapplicable to analysis of bubble growth in a finite-sized tissue. We herein present a new two-region model that is applicable to problems involving finite tissue volumes. By introducing radial deviations to gas tension in the diffusion region surrounding the bubble, the concentration gradient can be zero at a finite distance from the bubble, thus limiting the tissue volume that participates in bubble-tissue gas exchange. It is shown that these deviations account for the effects of heterogeneous perfusion on gas bubble dynamics, and are required for the tissue volume to be finite. The bubble growth results from a difference between the bubble gas pressure and an average gas tension in the surrounding diffusion region that explicitly depends on gas uptake and release by the bubble. For any given decompression, the diffusion region volume must stay above a certain minimum in order to sustain bubble growth.

3. Chaotic gas bubble oscillations in a viscoelastic fluid

Jiménez-Fernández, Javier

2008-05-01

Regular and chaotic radial oscillations of an acoustically driven gas bubble in a viscoelastic fluid have been theoretically analyzed. For parameter values usually found in diagnostic ultrasound period-doubling routes to chaos have been identified. Thresholds values of the external pressure amplitude for a first bifurcation in terms of the elasticity and the shear viscosity of the host fluid have also been evaluated. To cite this article: J. Jiménez-Fernández, C. R. Mecanique 336 (2008).

4. Warm Pressurant Gas Effects on the Liquid Hydrogen Bubble Point

NASA Technical Reports Server (NTRS)

Hartwig, Jason W.; McQuillen, John B.; Chato, David J.

2013-01-01

This paper presents experimental results for the liquid hydrogen bubble point tests using warm pressurant gases conducted at the Cryogenic Components Cell 7 facility at the NASA Glenn Research Center in Cleveland, Ohio. The purpose of the test series was to determine the effect of elevating the temperature of the pressurant gas on the performance of a liquid acquisition device. Three fine mesh screen samples (325 x 2300, 450 x 2750, 510 x 3600) were tested in liquid hydrogen using cold and warm noncondensible (gaseous helium) and condensable (gaseous hydrogen) pressurization schemes. Gases were conditioned from 0 to 90 K above the liquid temperature. Results clearly indicate a degradation in bubble point pressure using warm gas, with a greater reduction in performance using condensable over noncondensible pressurization. Degradation in the bubble point pressure is inversely proportional to screen porosity, as the coarsest mesh demonstrated the highest degradation. Results here have implication on both pressurization and LAD system design for all future cryogenic propulsion systems. A detailed review of historical heated gas tests is also presented for comparison to current results.

5. Pulsed electrical discharge in gas bubbles in water

Gershman, Sophia

A phenomenological picture of pulsed electrical discharge in gas bubbles in water is produced by combining electrical, spectroscopic, and imaging methods. The discharge is generated by applying one microsecond long 5 to 20 kilovolt pulses between the needle and disk electrodes submerged in water. A gas bubble is generated at the tip of the needle electrode. The study includes detailed experimental investigation of the discharge in argon bubbles and a brief look at the discharge in oxygen bubbles. Imaging, electrical characteristics, and time-resolved optical emission data point to a fast streamer propagation mechanism and formation of a plasma channel in the bubble. Spectroscopic methods based on line intensity ratios and Boltzmann plots of line intensities of argon, atomic hydrogen, and argon ions and the examination of molecular emission bands from molecular nitrogen and hydroxyl radicals provide evidence of both fast beam-like electrons and slow thermalized ones with temperatures of 0.6 -- 0.8 electron-volts. The collisional nature of plasma at atmospheric pressure affects the decay rates of optical emission. Spectroscopic study of rotational-vibrational bands of hydroxyl radical and molecular nitrogen gives vibrational and rotational excitation temperatures of the discharge of about 0.9 and 0.1 electron-volt, respectively. Imaging and electrical evidence show that discharge charge is deposited on the bubble wall and water serves as a dielectric barrier for the field strength and time scales of this experiment. Comparing the electrical and imaging information for consecutive pulses applied at a frequency of 1 Hz indicates that each discharge proceeds as an entirely new process with no memory of the previous discharge aside from long-lived chemical species, such as ozone and oxygen. Intermediate values for the discharge gap and pulse duration, low repetition rate, and unidirectional character of the applied voltage pulses make the discharge process here unique

6. PHASE-FIELD SIMULATION OF IRRADIATED METALS: PART II: GAS BUBBLE KINETICS

SciTech Connect

Paul C Millett; Anter El-Azab

2011-01-01

We present a phase-field model for inert gas bubble formation and evolution in irradiated metals. The model evolves vacancy, self-interstitial, and fission gas atoms through a coupled set of Cahn-Hilliard and Allen-Cahn equations, capturing the processes of defect generation, recombination, annihilation at GB sinks, as well as intragranular and intergranular bubble nucleation and growth in polycrystalline microstructures. Illustrative results are presented that characterize bubble growth and shrinkage, as well as the bubble density, size and nucleation rate as a function of varying irradiation conditions. Finally, intergranular bubble characteristics such as shape, pinning energy on GB motion, and bubble density are investigated.

7. Modelling of Spherical Gas Bubble Oscillations and Sonoluminescence

NASA Technical Reports Server (NTRS)

Prosperetti, A.; Hao, Y.

1999-01-01

The discovery of single-bubble sonoluminescence has led to a renewed interest in the forced radial oscillations of gas bubbles. Many of the more recent studies devoted to this topic have used several simplifications in the modelling, and in particular in accounting for liquid compressibility and thermal processes in the bubble. In this paper the significance of these simplifications is explored by contrasting the results of Lohse and co-workers with those of a more detailed model. It is found that, even though there may be little apparent difference between the radius-versus time behaviour of the bubble as predicted by the two models, quantities such as the spherical stability boundary and the threshold for rectified diffusion are affected in a quantitatively significant way. These effects are a manifestation of the subtle dependence upon dissipative processes of the phase of radial motion with respect to the driving sound field. The parameter space region, where according to the theory of Lohse and co-workers, sonoluminescence should be observable, is recalculated with the new model and is found to be enlarged with respect to the earlier estimate. The dependence of this parameter region on sound frequency is also illustrated.

8. Bangladesh to prepare for rise in gas demand

SciTech Connect

Not Available

1992-06-01

Bangladesh is moving to expand its natural gas infrastructure in response to rising domestic demand. This paper reports that Bangladesh natural gas demand is expected to rise to 700-850 MMcfd in the next few years from the current level of about 500 MMcfd, the Prime Minister Khaleda Zia.

9. Computation of the Knife-Edge Cusp of a Rising Bubble in a Viscoelastic Fluid

You, Ruobo; Haj-Hariri, Hossein

2006-11-01

We consider the buoyant rise of an originally-spherical bubble through a viscoelastic fluid. Experiments have demonstrated that the sharp trailing edge could develop a three dimensional cusp of knife-like'' shape under certain conditions (high capillary number, large drop size). In order to understand the complex physics of this phenomenon, we have conducted a linear, three-dimensional temporal stability analysis of a computationally-obtained axisymmetric cusped bubble. The in-house time-accurate code is control-volume based and uses a body-fitted grid. Flux-difference splitting is employed to handle large Deborah numbers. Artificial compressibility is used for time marching. The resulting eigenanalysis shows the only linearly-unstable mode to be the one with azimuthal wavenumber of 2. The eigenvalue is real and the nature of instability is an exchange of stability. Thus an axisymmetric cusp can indeed develop into a knife-like shape. An investigation of the energy production and dissipation for the disturbances shows that the normal pressure gradient of the base-state along the free surface plays an important role in the evolution of the instability.

10. Generation and characterization of gas bubbles in liquid metals

SciTech Connect

Eckert, S.; Gerbeth, G.; Witke, W.

1996-06-01

There is an ongoing research performed in the RCR on local transport phenomena in turbulent liquid metal (LM) duct flows exposed to external magnetic fields. In this context so-called MHD flow phenomena can be observed, which are unknown in usual hydraulic engineering. The field of interest covers also the influence of magnetic fields on the behaviour of liquid metal - gas mixtures. Profound knowledge on these LMMHD two-phase flow plays an important role in a variety of technological applications, in particular, in the design of Liquid-Metal MHD generators or for several metallurgical processes employing gas-stirred reactors. However, the highly empirical nature of two-phase flow analysis gives little hope for the prediction of MHD two-phase flows without extensive experimental data. A summary is given about the authors research activities focussing on two directions: (a) Momentum transfer between gas and liquid metal in a bubbly flow regime to investigate the influence of the external magnetic field on the velocity slip ration S (b) Peculiarities of the MHD turbulence to use small gas bubbles as local tracers in order to study the turbulent mass transfer.

11. The effect of flow pattern around a bubble rising near a vertical wall, on the wall to liquid heat transfer

2016-11-01

Two-phase flow is an effective means for heat removal due to the enhanced convective effect caused by bubbly flow and the usually high latent heat of vaporization of the liquid phase. We present a numerical study of the effect of flow patterns around a single bubble rising in shear flow near a vertical wall, on the wall-to-liquid heat transfer. The Navier-Stokes equations are solved in a frame of reference moving with the bubble, by using the front tracking method for interface tracking. Our simulations reveal an enhancement of heat transfer downstream of the bubble, and a less pronounced diminishment of heat transfer upstream of the bubble. We observe that in the range of 5 <= Re <= 40 for Reynolds number based on shear and bubble diameter, heat transfer first increases, attains a maximum and decreases as Re increases. The optimum Re depends on the Archimedes number. The heat transfer enhancement is attributed to flow reversal happening in a confined region of the shear flow, in the presence of a bubble. The analytical solution of 2 - D inviscid shear flow over a cylinder near a wall is used to identify two parameters of flow reversal namely 'reversal height' and 'reversal width'. These parameters are then used to qualitatively explain what we observe in 3 - D simulations.

12. Bubbles

Prosperetti, Andrea

2004-06-01

Vanitas vanitatum et omnia vanitas: bubbles are emptiness, non-liquid, a tiny cloud shielding a mathematical singularity. Born from chance, a violent and brief life ending in the union with the (nearly) infinite. But a wealth of phenomena spring forth from this nothingness: underwater noise, sonoluminescence, boiling, and many others. Some recent results on a "blinking bubble" micropump and vapor bubbles in sound fields are outlined. The last section describes Leonardo da Vinci's observation of the non-rectlinear ascent of buoyant bubbles and justifies the name Leonardo's paradox recently attributed to this phenomenon.

13. Bubble formation during horizontal gas injection into downward-flowing liquid

Bai, Hua; Thomas, Brian G.

2001-12-01

Bubble formation during gas injection into turbulent downward-flowing water is studied using high-speed videos and mathematical models. The bubble size is determined during the initial stages of injection and is very important to turbulent multiphase flow in molten-metal processes. The effects of liquid velocity, gas-injection flow rate, injection hole diameter, and gas composition on the initial bubble-formation behavior have been investigated. Specifically, the bubble-shape evolution, contact angles, size, size range, and formation mode are measured. The bubble size is found to increase with increasing gas-injection flow rate and decreasing liquid velocity and is relatively independent of the gas injection hole size and gas composition. Bubble formation occurs in one of four different modes, depending on the liquid velocity and gas flow rate. Uniform-sized spherical bubbles form and detach from the gas injection hole in mode I for a low liquid speed and small gas flow rate. Modes III and IV occur for high-velocity liquid flows, where the injected gas elongates down along the wall and breaks up into uneven-sized bubbles. An analytical two-stage model is developed to predict the average bubble size, based on realistic force balances, and shows good agreement with measurements. Preliminary results of numerical simulations of bubble formation using a volume-of-fluid (VOF) model qualitatively match experimental observations, but more work is needed to reach a quantitative match. The analytical model is then used to estimate the size of the argon bubbles expected in liquid steel in tundish nozzles for conditions typical of continuous casting with a slide gate. The average argon bubble sizes generated in liquid steel are predicted to be larger than air bubbles in water for the same flow conditions. However, the differences lessen with increasing liquid velocity.

14. Mathematical model of diffusion-limited evolution of multiple gas bubbles in tissue

NASA Technical Reports Server (NTRS)

Srinivasan, R. Srini; Gerth, Wayne A.; Powell, Michael R.

2003-01-01

Models of gas bubble dynamics employed in probabilistic analyses of decompression sickness incidence in man must be theoretically consistent and simple, if they are to yield useful results without requiring excessive computations. They are generally formulated in terms of ordinary differential equations that describe diffusion-limited gas exchange between a gas bubble and the extravascular tissue surrounding it. In our previous model (Ann. Biomed. Eng. 30: 232-246, 2002), we showed that with appropriate representation of sink pressures to account for gas loss or gain due to heterogeneous blood perfusion in the unstirred diffusion region around the bubble, diffusion-limited bubble growth in a tissue of finite volume can be simulated without postulating a boundary layer across which gas flux is discontinuous. However, interactions between two or more bubbles caused by competition for available gas cannot be considered in this model, because the diffusion region has a fixed volume with zero gas flux at its outer boundary. The present work extends the previous model to accommodate interactions among multiple bubbles by allowing the diffusion region volume of each bubble to vary during bubble evolution. For given decompression and tissue volume, bubble growth is sustained only if the bubble number density is below a certain maximum.

15. Modulated single-bubble sonoluminescence: Dependence of phase of flashes, their intensity and rise/decay times on viscosity, the modulation strength, and frequency

Mastikhin, Igor; Djurkovic, Borko

2004-05-01

The single-bubble sonoluminescence (SBSL) signal was studied for the case of driving frequency modulated by lower frequency with an offset. In our work, the driving frequency of 28 kHz and the modulation frequencies of 25-1000 Hz were used. The modulation strength of 0.2, 0.5, and 0.8 was defined as the difference of highest and lowest pressures over modulation period. The measurements were performed for water-glycerol mixtures of various viscosities. The measured SBSL signal appeared as a train of flashes for modulation frequencies below 250 Hz, and as a continuous modulated signal for higher frequencies. At the same frequency, the flashes covered similar phase intervals for different modulation strengths and, accordingly, pressure ranges. At higher glycerol concentrations (up to 24%) both the intensity and the stability of flashes increased, due to damped shape instabilities and reduced dancing; however, the phase interval of flashes remained about the same. Such phase-locked behavior can be explained by translational movements of the bubble due to modulated Bjerknes force and changes in the symmetry of the bubble collapse. The changes in intensities and rise/decay times can serve as a measure of the gas exchange between the bubble and its surroundings during silent and luminescent intervals.

16. Sparger Effects on Gas Volume Fraction Distributions in Vertical Bubble-Column Flows as Measured by Gamma-Densitometry Tomography

SciTech Connect

GEORGE,DARIN L.; SHOLLENBERGER,KIM ANN; TORCZYNSKI,JOHN R.

2000-01-18

Gamma-densitometry tomography is applied to study the effect of sparger hole geometry, gas flow rate, column pressure, and phase properties on gas volume fraction profiles in bubble columns. Tests are conducted in a column 0.48 m in diameter, using air and mineral oil, superficial gas velocities ranging from 5 to 30 cm s{sup -1}, and absolute column pressures from 103 to 517 kPa. Reconstructed gas volume fraction profiles from two sparger geometries are presented. The development length of the gas volume fraction profile is found to increase with gas flow rate and column pressure. Increases in gas flow rate increase the local gas volume fraction preferentially on the column axis, whereas increases in column pressure produce a uniform rise in gas volume fraction across the column. A comparison of results from the two spargers indicates a significant change in development length with the number and size of sparger holes.

17. Bubble Combustion

NASA Technical Reports Server (NTRS)

Corrigan, Jackie

2004-01-01

A method of energy production that is capable of low pollutant emissions is fundamental to one of the four pillars of NASA s Aeronautics Blueprint: Revolutionary Vehicles. Bubble combustion, a new engine technology currently being developed at Glenn Research Center promises to provide low emissions combustion in support of NASA s vision under the Emissions Element because it generates power, while minimizing the production of carbon dioxide (CO2) and nitrous oxides (NOx), both known to be Greenhouse gases. and allows the use of alternative fuels such as corn oil, low-grade fuels, and even used motor oil. Bubble combustion is analogous to the inverse of spray combustion: the difference between bubble and spray combustion is that spray combustion is spraying a liquid in to a gas to form droplets, whereas bubble combustion involves injecting a gas into a liquid to form gaseous bubbles. In bubble combustion, the process for the ignition of the bubbles takes place on a time scale of less than a nanosecond and begins with acoustic waves perturbing each bubble. This perturbation causes the local pressure to drop below the vapor pressure of the liquid thus producing cavitation in which the bubble diameter grows, and upon reversal of the oscillating pressure field, the bubble then collapses rapidly with the aid of the high surface tension forces acting on the wall of the bubble. The rapid and violent collapse causes the temperatures inside the bubbles to soar as a result of adiabatic heating. As the temperatures rise, the gaseous contents of the bubble ignite with the bubble itself serving as its own combustion chamber. After ignition, this is the time in the bubble s life cycle where power is generated, and CO2, and NOx among other species, are produced. However, the pollutants CO2 and NOx are absorbed into the surrounding liquid. The importance of bubble combustion is that it generates power using a simple and compact device. We conducted a parametric study using CAVCHEM

18. Observations on gas-bubble disease of fish

USGS Publications Warehouse

1953-01-01

SOME DIFFICULTY has been experienced in raising fry and young fingerlings at the Puyallup hatchery of the Washington State Department of Game, a hatchery now in its fourth year of operation. There has been evidence of gas in the yolk-sac fry, and the mortality was always excessive among the fingerlings while reared in the hatchery troughs. The mortality rate decreased and evidence of gas-bubble disease disappeared when the fish mere moved to outside ponds. Also, fish seemed less susceptible to parasitic diseases when held in the ponds rather than 1m hatchery troughs. Strains of fish raised at the station were cutthroat trout (Salmo clarkii clarkii and Salmo clarkii lewisi) rainbow trout (Salmo gairdnerii gairdnerii), and steelhead trout (Salmo gairdnerii iriatus)

19. Gas bubble disease in farmed fish in Saudi Arabia.

PubMed

Saeed, M O; al-Thobaiti, S A

1997-06-28

Four outbreaks of gas bubble disease were encountered among farmed fish in Saudi Arabia. Two of them occurred among subadult (52.5 g) saltwater tilapia (Oreochromis spilurus), the first affecting about 50 per cent of the stock and resulting in about 30 per cent mortality, and the second affecting about 25 per cent of the population with about 5 per cent mortality. Another outbreak occurred among adult (270 g) brackish water (0.5 per cent salinity) tilapia (Oreochromis niloticus), affecting about 40 per cent of the population with about 25 per cent mortality. The fourth outbreak occurred among three-month-old (15 g) grouper (Epinephelus fuscogutiatus) and resulted in 10 per cent mortality. In all cases the total water gas pressure ranged between 111.2 and 113.4 per cent saturation and nitrogen was supersaturated while oxygen was undersaturated. The outbreaks were alleviated by reducing the gas pressure by splashing the source water or by switching to a source of water with lower gas pressure. However, in O niloticus the conditions of gas supersaturation resulted in a heavy infection by monogenetic trematodes which was treated with formalin at 40 mg/litre for seven hours on five successive days.

20. Spatio-temporal dynamics of an encapsulated gas bubble in an ultrasound field

PubMed Central

Doinikov, Alexander A.; Dayton, Paul A.

2011-01-01

Coupled equations describing the radial and translational dynamics of an encapsulated gas bubble in an ultrasound field are derived by using the Lagrangian formalism. The equations generalize Church’s theory by allowing for the translation motion of the bubble and radiation losses due to the compressibility of the surrounding liquid. The expression given by Church for the inner bubble radius corresponding to the unstrained state of the bubble shell is also refined, assuming that the shell can be of arbitrary thickness and impermeable to gas. Comparative linear analysis of the radial equation is carried out relative to Church’s theory. It is shown that there are substantial departures from predictions of Church’s theory. The proposed model is applied to evaluate radiation forces exerted on encapsulated bubbles and their translational displacements. It is shown that in the range of relatively high frequencies encapsulated bubbles are able to translate more efficiently than free bubbles of the equivalent size. PMID:21442034

1. Frequency dependence in seismoacoustic imaging of shallow free gas due to gas bubble resonance

Tóth, Zsuzsanna; Spiess, Volkhard; Keil, Hanno

2015-12-01

Shallow free gas is investigated in seismoacoustic data in 10 frequency bands covering a frequency range between 0.2 and 43 kHz. At the edge of a gassy patch in the Bornholm Basin (Baltic Sea), compressional wave attenuation caused by free gas is estimated from reflection amplitudes beneath the gassy sediment layer. Imaging of shallow free gas is considerably influenced by gas bubble resonance, because in the resonance frequency range attenuation is significantly increased. At the resonance frequency of the largest bubbles between 3 and 5 kHz, high scattering causes complete acoustic blanking beneath the top of the gassy sediment layer. In the wider resonance frequency range between 3 and 15 kHz, the effect of smaller bubbles becomes dominant and the attenuation slightly decreases. This allows acoustic waves to be transmitted and reflections can be observed beneath the gassy sediment layer for higher frequencies. Above resonance beginning at ˜19 kHz, attenuation is low and the presence of free gas can be inferred from the decreased reflection amplitudes beneath the gassy layer. Below the resonance frequency range (<1 kHz), attenuation is generally very low and not dependent on frequency. Using the geoacoustic model of Anderson and Hampton, the observed frequency boundaries suggest gas bubble sizes between 1 and 4-6 mm, and gas volume fractions up to 0.02% in a ˜2 m thick sediment layer, whose upper boundary is the gas front. With the multifrequency acoustic approach and the Anderson and Hampton model, quantification of free gas in shallow marine environments is possible if the measurement frequency range allows the identification of the resonance frequency peak. The method presented is limited to places with only moderate attenuation, where the amplitudes of a reflection can be analyzed beneath the gassy sediment layer.

2. Detecting the gas bubbles in a liquid metal coolant by means of magnetic flowmeters

Mogilner, A. I.; Morozov, S. A.; Zakharov, S. O.; Uralets, A. Yu.

Solution of some problems of control and diagnosis of circuits with a liquid-metal coolant (LMC) often requires the detection of gas bubbles penetrating the circulation loop. The sources of gas intake can be presented by failed fuel elements in reactor core, failed heat-exchange surfaces in sodium-water steam generators in the secondary circuits, gas capture by circulating coolant from gas circuits. Sometimes the gas is especially injected into circulating coolant to study the dynamics of accumulation and extraction of gas bubbles and to solve research problems related to simulations of emergency situations. The most commonly used methods for gas bubble detection include methods based on measuring coolant electric conductivity. A method for detecting gas bubbles in LMC, based on revealing the change of its electric conductivity is considered. Magnetic flowmeter is used as a detecting element of these changes. Approximate theory for describing spectral and energy noises in signals of a magnetic flowmeter, controlling the flow rate of LMC with gas bubbles is suggested. A new method for signal reading is suggested. Experimental results illustrating the possibility of using the method for measuring the rate of bubble movement and studying the dependence of gas bubble volume on the flow rate of injected gas are presented.

3. Natural frequency of a gas bubble in a tube: experimental and simulation results.

PubMed

Jang, Neo W; Gracewski, Sheryl M; Abrahamsen, Ben; Buttaccio, Travis; Halm, Robert; Dalecki, Diane

2009-07-01

Use of ultrasonically excited microbubbles within blood vessels has been proposed for a variety of clinical applications. In this paper, an axisymmetric coupled boundary element and finite element code and experiments have been used to investigate the effects of a surrounding tube on a bubble's response to acoustic excitation. A balloon model allowed measurement of spherical gas bubble response. Resonance frequencies match one-dimensional cylindrical model predictions for a bubble well within a rigid tube but deviate for a bubble near the tube end. Simulations also predict bubble translation along the tube axis and aspherical oscillations at higher amplitudes.

4. Near-wall measurements of the bubble- and Lorentz-force-driven convection at gas-evolving electrodes

Baczyzmalski, Dominik; Weier, Tom; Kähler, Christian J.; Cierpka, Christian

2015-08-01

Chemical energy storage systems, e.g., in the form of hydrogen or methanol, have a great potential for the establishment of volatile renewable energy sources due to the large energy density. The efficiency of hydrogen production through water electrolysis is, however, limited by gas bubbles evolving at the electrode's surface and can be enhanced by an accelerated bubble detachment. In order to characterize the complex multi-phase flow near the electrode, simultaneous measurements of the fluid velocities and the size and trajectories of hydrogen bubbles were performed in a water electrolyzer. The liquid phase velocity was measured by PIV/PTV, while shadowgraphy was used to determine the bubble trajectories. Special measurement and evaluation techniques had to be applied as the measurement uncertainty is strongly affected by the high void fraction close to the wall. In particular, the application of an advanced PTV scheme allowed for more precise fluid velocity measurements closer to electrode. Based on these data, stability characteristics of the near-wall flow were evaluated and compared to that of a wall jet. PTV was used as well to investigate the effect of Lorentz forces on the near-wall fluid velocities. The results show a significantly increased wall parallel liquid phase velocity with increasing Lorentz forces. It is presumed that this enhances the detachment of hydrogen bubbles from the electrode surface and, consequently, decreases the fractional bubble coverage and improves the efficiency. In addition, the effect of large rising bubbles with path oscillations on the near-wall flow was investigated. These bubbles can have a strong impact on the mass transfer near the electrode and thus affect the performance of the process.

5. A new pressure formulation for gas-compressibility dampening in bubble dynamics models.

PubMed

Gadi Man, Yezaz Ahmed; Trujillo, Francisco J

2016-09-01

We formulated a pressure equation for bubbles performing nonlinear radial oscillations under ultrasonic high pressure amplitudes. The proposed equation corrects the gas pressure at the gas-liquid interface on inertial bubbles. This pressure formulation, expressed in terms of gas-Mach number, accounts for dampening due to gas compressibility during the violent collapse of cavitation bubbles and during subsequent rebounds. We refer to this as inhomogeneous pressure, where the gas pressure at the gas-liquid interface can differ to the pressure at the centre of the bubble, in contrast to homogenous pressure formulations that consider that pressure inside the bubble is spatially uniform from the wall to the centre. The pressure correction was applied to two bubble dynamic models: the incompressible Rayleigh-Plesset equation and the compressible Keller and Miksis equation. This improved the predictions of the nonlinear radial motion of the bubble vs time obtained with both models. Those simulations were also compared with other bubble dynamics models that account for liquid and gas compressibility effects. It was found that our corrected models are in closer agreement with experimental data than alternative models. It was concluded that the Rayleigh-Plesset family of equations improve accuracy by using our proposed pressure correction.

6. Decompression vs. Decomposition: Distribution, Amount, and Gas Composition of Bubbles in Stranded Marine Mammals

PubMed Central

de Quirós, Yara Bernaldo; González-Diaz, Oscar; Arbelo, Manuel; Sierra, Eva; Sacchini, Simona; Fernández, Antonio

2012-01-01

Gas embolic lesions linked to military sonar have been described in stranded cetaceans including beaked whales. These descriptions suggest that gas bubbles in marine mammal tissues may be more common than previously thought. In this study we have analyzed gas amount (by gas score) and gas composition within different decomposition codes using a standardized methodology. This broad study has allowed us to explore species-specific variability in bubble prevalence, amount, distribution, and composition, as well as masking of bubble content by putrefaction gases. Bubbles detected within the cardiovascular system and other tissues related to both pre- and port-mortem processes are a common finding on necropsy of stranded cetaceans. To minimize masking by putrefaction gases, necropsy, and gas sampling must be performed as soon as possible. Before 24 h post mortem is recommended but preferably within 12 h post mortem. At necropsy, amount of bubbles (gas score) in decomposition code 2 in stranded cetaceans was found to be more important than merely presence vs. absence of bubbles from a pathological point of view. Deep divers presented higher abundance of gas bubbles, mainly composed of 70% nitrogen and 30% CO2, suggesting a higher predisposition of these species to suffer from decompression-related gas embolism. PMID:22675306

7. Generation of pulsed discharge plasma in water with fine bubbles

Hayashi, Yui; Takada, Noriharu; Kanda, Hideki; Goto, Motonobu; Goto laboratory Team

2015-09-01

Recently, some researchers have proposed electric discharge methods with bubbles in water because the discharge plasma inside bubble was easy to be generated compared to that in water. Almost all of these methods introduced bubbles in the order of millimeter size from a nozzle placed in water. In these methods, bubbles rose one after another owing to high rising speed of millibubble, leading to inefficient gas consumption. We proposed fine bubbles introduction at the discharge area in water. A fine bubble is determined a bubble with less than 100 μm in a diameter. Fine bubbles exhibit extremely slow rising speed. Fine bubbles decrease in size during bubble rising and subsequently collapse in water with OH radical generation. Therefore, combining the discharge plasma with fine bubbles is expected to generate more active species with small amount of gas consumption. In this work, fine bubbles were introduced in water and pulsed discharge plasma was generated between two cylindrical electrodes which placed in water. We examined effects of fine bubbles on electric discharge in water when argon or oxygen gas was utilized as feed gas. Fine bubbles enhanced optical emission of hydrogen and oxygen atoms from H2O molecules, but that of feed gas was not observed. The formation mechanism of H2O2 by electric discharge was supposed to be different from that with no bubbling. Dissolved oxygen in water played a role in H2O2 formation by the discharge with fine bubbles.

8. Contribution to irradiation creep arising from gas-driven bubbles

SciTech Connect

Woo, C.H.; Garner, F.A.

1998-03-01

In a previous paper the relationship was defined between void swelling and irradiation creep arising from the interaction of the SIPA and SIG creep-driven deformation and swelling-driven deformation was highly interactive in nature, and that the two contributions could not be independently calculated and then considered as directly additive. This model could be used to explain the recent experimental observation that the creep-swelling coupling coefficient was not a constant as previously assumed, but declined continuously as the swelling rate increased. Such a model thereby explained the creep-disappearance and creep-damping anomalies observed in conditions where significant void swelling occurred before substantial creep deformation developed. At lower irradiation temperatures and high helium/hydrogen generation rates, such as found in light water cooled reactors and some fusion concepts, gas-filled cavities that have not yet exceeded the critical radius for bubble-void conversion should also exert an influence on irradiation creep. In this paper the original concept is adapted to include such conditions, and its predictions then compared with available data. It is shown that a measurable increase in the creep rate is expected compared to the rate found in low gas-generating environments. The creep rate is directly related to the gas generation rate and thereby to the neutron flux and spectrum.

9. Growth and collapse of laser-induced bubbles in gas-supersaturated gelatin gels

2016-11-01

We study, with experiments and theory, the growth and collapse of laser-induced bubbles in a gelatin gel. The gel sample is prepared so as to obtain gas supersaturation, according to a difference between heat and gas diffusion rates. Spherical gas bubbles are created by focusing a nano-second laser pulse at 532 nm into the gas-supersaturated gel. The bubble dynamics are recorded by a high-speed camera. To explore effects of the gel elasticity on the bubble collapse, the experimental observations are compared to an extended Rayleigh-Plesset model that accounts for linear/nonlinear elasticity of the gel surrounding bubbles. This work is supported by JSPS KAKENHI Grant No. 25709008.

10. Experiments on the motion of gas bubbles in turbulence generated by an active grid

Poorte, R. E. G.; Biesheuvel, A.

2002-06-01

The random motion of nearly spherical bubbles in the turbulent flow behind a grid is studied experimentally. In quiescent water these bubbles rise at high Reynolds number. The turbulence is generated by an active grid of the design of Makita (1991), and can have turbulence Reynolds number R[lambda] of up to 200. Minor changes in the geometry of the grid and in its mode of operation improves the isotropy of the turbulence, compared with that reported by Makita (1991) and Mydlarski & Warhaft (1996). The trajectory of each bubble is measured with high spatial and temporal resolution with a specially developed technique that makes use of a position-sensitive detector. Bubble statistics such as the mean rise velocity and the root-mean-square velocity fluctuations are obtained by ensemble averaging over many identical bubbles. The resulting bubble mean rise velocity is significantly reduced (up to 35%) compared with the quiescent conditions. The vertical bubble velocity fluctuations are found to be non-Gaussian, whereas the horizontal displacements are Gaussian for all times. The diffusivity of bubbles is considerably less than that of fluid particles. These findings are qualitatively consistent with results obtained through theoretical analysis and numerical simulations by Spelt & Biesheuvel (1997).

11. Nano bubbles in liquid of a noble-gas mixture.

PubMed

Yamamoto, Takenori; Ohnishi, Shuhei

2010-02-07

Large-scale molecular dynamics (MD) simulations with over one million atoms are used to investigate nano bubbles in Ar-Ne liquid. The simulations demonstrate cavitations in the stretched liquid, and bubble creation and collapse. We find that a small cavity created in the stretched liquid spontaneously transforms into a nano bubble with the homogeneous vapor region. The equilibrium spherical bubble of 11.4 nm in radius is obtained after the long-time MD run. The surface tension of the nano bubble is found to be larger than that of the flat surface.

12. Dynamics of gas bubble growth in a supersaturated solution with Sievert's solubility law.

PubMed

Gor, G Yu; Kuchma, A E

2009-07-21

This paper presents a theoretical description of diffusion growth of a gas bubble after its nucleation in supersaturated liquid solution. We study systems where gas molecules completely dissociate in the solvent into two parts, thus making Sievert's solubility law valid. We show that the difference between Henry's and Sievert's laws for chemical equilibrium conditions causes the difference in bubble growth dynamics. Assuming that diffusion flux is steady we obtain a differential equation on bubble radius. Bubble dynamics equation is solved analytically for the case of homogeneous nucleation of a bubble, which takes place at a significant pressure drop. We also obtain conditions of diffusion flux steadiness. The fulfillment of these conditions is studied for the case of nucleation of water vapor bubbles in magmatic melts.

13. Linear oscillation of gas bubbles in a viscoelastic material under ultrasound irradiation

SciTech Connect

Hamaguchi, Fumiya; Ando, Keita

2015-11-15

Acoustically forced oscillation of spherical gas bubbles in a viscoelastic material is studied through comparisons between experiments and linear theory. An experimental setup has been designed to visualize bubble dynamics in gelatin gels using a high-speed camera. A spherical gas bubble is created by focusing an infrared laser pulse into (gas-supersaturated) gelatin gels. The bubble radius (up to 150 μm) under mechanical equilibrium is controlled by gradual mass transfer of gases across the bubble interface. The linearized bubble dynamics are studied from the observation of spherical bubble oscillation driven by low-intensity, planar ultrasound driven at 28 kHz. It follows from the experiment for an isolated bubble that the frequency response in its volumetric oscillation was shifted to the high frequency side and its peak was suppressed as the gelatin concentration increases. The measurement is fitted to the linearized Rayleigh–Plesset equation coupled with the Voigt constitutive equation that models the behavior of linear viscoelastic solids; the fitting yields good agreement by tuning unknown values of the viscosity and rigidity, indicating that more complex phenomena including shear thinning, stress relaxation, and retardation do not play an important role for the small-amplitude oscillations. Moreover, the cases for bubble-bubble and bubble-wall systems are studied. The observed interaction effect on the linearized dynamics can be explained as well by a set of the Rayleigh–Plesset equations coupled through acoustic radiation among these systems. This suggests that this experimental setup can be applied to validate the model of bubble dynamics with more complex configuration such as a cloud of bubbles in viscoelastic materials.

14. Linear oscillation of gas bubbles in a viscoelastic material under ultrasound irradiation

Hamaguchi, Fumiya; Ando, Keita

2015-11-01

Acoustically forced oscillation of spherical gas bubbles in a viscoelastic material is studied through comparisons between experiments and linear theory. An experimental setup has been designed to visualize bubble dynamics in gelatin gels using a high-speed camera. A spherical gas bubble is created by focusing an infrared laser pulse into (gas-supersaturated) gelatin gels. The bubble radius (up to 150 μm) under mechanical equilibrium is controlled by gradual mass transfer of gases across the bubble interface. The linearized bubble dynamics are studied from the observation of spherical bubble oscillation driven by low-intensity, planar ultrasound driven at 28 kHz. It follows from the experiment for an isolated bubble that the frequency response in its volumetric oscillation was shifted to the high frequency side and its peak was suppressed as the gelatin concentration increases. The measurement is fitted to the linearized Rayleigh-Plesset equation coupled with the Voigt constitutive equation that models the behavior of linear viscoelastic solids; the fitting yields good agreement by tuning unknown values of the viscosity and rigidity, indicating that more complex phenomena including shear thinning, stress relaxation, and retardation do not play an important role for the small-amplitude oscillations. Moreover, the cases for bubble-bubble and bubble-wall systems are studied. The observed interaction effect on the linearized dynamics can be explained as well by a set of the Rayleigh-Plesset equations coupled through acoustic radiation among these systems. This suggests that this experimental setup can be applied to validate the model of bubble dynamics with more complex configuration such as a cloud of bubbles in viscoelastic materials.

15. Gas and liquid measurements in air-water bubbly flows

SciTech Connect

Zhou, X.; Doup, B.; Sun, X.

2012-07-01

Local measurements of gas- and liquid-phase flow parameters are conducted in an air-water two-phase flow loop. The test section is a vertical pipe with an inner diameter of 50 mm and a height of 3.2 m. The measurements are performed at z/D = 10. The gas-phase measurements are performed using a four-sensor conductivity probe. The data taken from this probe are processed using a signal processing program to yield radial profiles of the void fraction, bubble velocity, and interfacial area concentration. The velocity measurements of the liquid-phase are performed using a state-of-the-art Particle Image Velocimetry (PIV) system. The raw PIV images are acquired using fluorescent particles and an optical filtration device. Image processing is used to remove noise in the raw PIV images. The statistical cross correlation is introduced to determine the axial velocity field and turbulence intensity of the liquid-phase. Measurements are currently being performed at z/D = 32 to provide a more complete data set. These data can be used for computational fluid dynamic model development and validation. (authors)

16. The dissolution or growth of a gas bubble inside a drop in zero gravity

NASA Technical Reports Server (NTRS)

Kondos, Pericles A.; Subramanian, R. Shankar; Weinberg, Michael C.

1987-01-01

The radius-time history of a gas bubble located concentrically within a spherical liquid drop in a space laboratory is analyzed within the framework of the quasi-stationary approximation. Illustrative results are calculated from the theory which demonstrate interesting qualitative features. For instance, when a pure gas bubble dissolves within a liquid drop in an environment containing the same gas and some inert species, the dissolution can be more or less rapid than that in an unbounded liquid depending on the initial relative size of the drop. Further, given a similar growth situation, indefinite growth is not possible, and the bubble will initially grow, but always dissolve in the end.

17. Studies of the Hot Gas in the Galactic halo and Local Bubble

NASA Technical Reports Server (NTRS)

Shelton, Robin L.

2003-01-01

This paper presents a report on the progress made on Studies of the Hot Gas in the Galactic halo and Local Bubble at Johns Hopkins University. The broad goals of this project are to determine the physical conditions and history of the hot phase of the Galaxy's interstellar medium. Such gas resides in the Galactic halo, the Local Bubble surrounding the solar neighborhood, other bubbles, and supernova remnants. A better understanding of the hot gas and the processes occurring within it requires several types of work, including ultraviolet and X-ray data analyses and computer modeling.

18. Magnetic field induced motion behavior of gas bubbles in liquid

PubMed Central

Wang, Keliang; Pei, Pucheng; Pei, Yu; Ma, Ze; Xu, Huachi; Chen, Dongfang

2016-01-01

The oxygen evolution reaction generally exists in electrochemical reactions. It is a ubiquitous problem about how to control the motion of oxygen bubbles released by the reaction. Here we show that oxygen bubbles during oxygen evolution reaction exhibit a variety of movement patterns in the magnetic field, including directional migration and rotational motion of oxygen bubbles when the magnet in parallel with the electrode, and exclusion movement of oxygen bubbles when the magnet perpendicular to the electrode. The results demonstrate that the direction of oxygen bubbles movement is dependent upon the magnet pole near the electrode, and the kinetics of oxygen bubbles is mainly proportional to intensity of the electromagnetic field. The magnetic-field induced rotational motion of oxygen bubbles in a square electrolyzer can increase liquid hydrodynamics, thus solve the problems of oxygen bubbles coalescence, and uneven distribution of electrolyte composition and temperature. These types of oxygen bubbles movement will not only improve energy saving and metal deposition for energy storage and metal refinery, but also propel object motion in application to medical and martial fields. PMID:26867515

19. Magnetic field induced motion behavior of gas bubbles in liquid

Wang, Keliang; Pei, Pucheng; Pei, Yu; Ma, Ze; Xu, Huachi; Chen, Dongfang

2016-02-01

The oxygen evolution reaction generally exists in electrochemical reactions. It is a ubiquitous problem about how to control the motion of oxygen bubbles released by the reaction. Here we show that oxygen bubbles during oxygen evolution reaction exhibit a variety of movement patterns in the magnetic field, including directional migration and rotational motion of oxygen bubbles when the magnet in parallel with the electrode, and exclusion movement of oxygen bubbles when the magnet perpendicular to the electrode. The results demonstrate that the direction of oxygen bubbles movement is dependent upon the magnet pole near the electrode, and the kinetics of oxygen bubbles is mainly proportional to intensity of the electromagnetic field. The magnetic-field induced rotational motion of oxygen bubbles in a square electrolyzer can increase liquid hydrodynamics, thus solve the problems of oxygen bubbles coalescence, and uneven distribution of electrolyte composition and temperature. These types of oxygen bubbles movement will not only improve energy saving and metal deposition for energy storage and metal refinery, but also propel object motion in application to medical and martial fields.

20. Natural frequency of a gas bubble in a tube: Experimental and simulation results

PubMed Central

Jang, Neo W.; Gracewski, Sheryl M.; Abrahamsen, Ben; Buttaccio, Travis; Halm, Robert; Dalecki, Diane

2009-01-01

Use of ultrasonically excited microbubbles within blood vessels has been proposed for a variety of clinical applications. In this paper, an axisymmetric coupled boundary element and finite element code and experiments have been used to investigate the effects of a surrounding tube on a bubble’s response to acoustic excitation. A balloon model allowed measurement of spherical gas bubble response. Resonance frequencies match one-dimensional cylindrical model predictions for a bubble well within a rigid tube but deviate for a bubble near the tube end. Simulations also predict bubble translation along the tube axis and aspherical oscillations at higher amplitudes. PMID:19603851

1. Tidal influence on gas bubble emissions from permanent seafloor observations at Ocean Networks Canada's cabled array NEPTUNE

Roemer, M.; Scherwath, M.; Heesemann, M.; Spence, G.; Riedel, M.

2015-12-01

Sonar data from the northern Cascadia margin correlate well with tidal pressure changes and not so well with currents, seafloor shaking from storms or earthquakes, or temperature changes. These data are available from Ocean Networks Canada which operates the NEPTUNE observatory with power and communications to gas hydrate sites on the continental slope, allowing 24/7 monitoring of the dynamic gas hydrate activity. Clayoquot Slope at Cascadia's Bullseye Vent and Bubbly Gulch, is equipped with a variety of sensors including a 270 kHz Imagenex 100 m range multibeam sonar, as well as Conductivity-Temperature-Depth (CTD) sensors, high precision Bottom Pressure Recorders (BPR), current meter and Ocean Bottom Seismograph (OBS). This enables statistically meaningful correlation of these data. Hourly sonar data were collected showing venting activity in the form of gas plumes of various strengths. For four years the sonar was located at what appears to be a transient gas site, with longer periods of absolutely no venting observed activity. Here, the strongest correlation of gas bubbling is with rapid decreasing tidal pressure, where subsequent increasing tidal pressure is shutting down the degassing. In May 2014, the sonar was moved by 500 m to a more actively venting site termed Gastown Alley, over a zone of seismic blanking interpreted as having high subsurface gas content. This site is continuously emitting gas bubbles albeit with varying numbers of plumes and intensities. The strongest correlation of gas discharge is with absolute pressures, with maximum flows at higher tidal pressures, hinting at a steady subsurface rise of gas that is squeezed out stronger at high tides, partially emptying the shallow reservoirs, and with subsiding tidal pressure the venting activity also decreases again. Thus, the two sonar sites, though only 500 m apart, show a different behavior in degassing, however, both reacting most strongly to tidal pressure changes.

2. Coalescence of drops and bubbles rising through a non-Newtonian fluid in a tube.

PubMed

Al-Matroushi, Eisa; Borhan, Ali

2009-04-01

We conducted an experimental study of the interaction and coalescence of two drops (of the same fluid) or bubbles translating under the action of buoyancy in a cylindrical tube. The close approach of two Newtonian fluid particles of different size in a non-Newtonian continuous phase was examined using image analysis, and measurements of the coalescence time are reported for various particle size ratios, Bond numbers, and particle-to-suspending-fluid viscosity ratios. The flow disturbance behind the leading bubble and the viscoelastic nature of the continuous phase seemed to retard bubble coalescence. The time scale for coalescence of liquid drops in highly elastic continuous phase was influenced by the relative motion of the drops and their coalescence behavior.

3. A Study of Bubble and Slug Gas-Liquid Flow in a Microgravity Environment

NASA Technical Reports Server (NTRS)

McQuillen, J.

2000-01-01

The influence of gravity on the two-phase flow dynamics is obvious.As the gravity level is reduced,there is a new balance between inertial and interfacial forces, altering the behavior of the flow. In bubbly flow,the absence of drift velocity leads to spherical-shaped bubbles with a rectilinear trajectory.Slug flow is a succession of long bubbles and liquid slug carrying a few bubbles. There is no flow reversal in the thin liquid film as the long bubble and liquid slug pass over the film. Although the flow structure seems to be simpler than in normal gravity conditions,the models developed for the prediction of flow behavior in normal gravity and extended to reduced gravity flow are unable to predict the flow behavior correctly.An additional benefit of conducting studies in microgravity flows is that these studies aide the development of understanding for normal gravity flow behavior by removing the effects of buoyancy on the shape of the interface and density driven shear flows between the gas and the liquid phases. The proposal calls to study specifically the following: 1) The dynamics of isolated bubbles in microgravity liquid flows will be analyzed: Both the dynamics of spherical isolated bubbles and their dispersion by turbulence, their interaction with the pipe wall,the behavior of the bubbles in accelerated or decelerated flows,and the dynamics of isolated cylindrical bubbles, their deformation in accelerated/decelerated flows (in converging or diverging channels), and bubble/bubble interaction. Experiments will consist of the use of Particle Image Velocimetry (PIV) and Laser Doppler Velocimeters (LDV) to study single spherical bubble and single and two cylindrical bubble behavior with respect to their influence on the turbulence of the surrounding liquid and on the wall 2) The dynamics of bubbly and slug flow in microgravity will be analyzed especially for the role of the coalescence in the transition from bubbly to slug flow (effect of fluid properties and

4. Diffusion-driven growth of a spherical gas bubble in gelatin gels supersaturated with air

Shirota, Eriko; Ando, Keita

2016-11-01

We experimentally and theoretically study diffusion-driven growth of laser-induced gas bubbles in gelatin gels supersaturated with air. The supersaturation in the gels is realized by using a large separation between heat and mass diffusion rates. An optical system is developed to induce bubble nucleation by laser focusing and visualize the subsequent bubble growth. To evaluate the effect of the gel elasticity on the bubble growth rate, we propose the extended Epstein-Plesset theory that considers bubble pressure modifications due to linear/nonlinear elasticity (in addition to Laplace pressure). From comparisons between the experiments and the proposed theory, the bubble growth rate is found to be hindered by the elasticity. This study is supported by JSPS KAKENHI Grant Number 25709008.

5. History effects on the gas exchange between a bubble and a liquid

Chu, Shigan; Prosperetti, Andrea

2016-10-01

Diffusive processes exhibit a strong dependence on history effects. For a gas bubble at rest in a liquid, such effects arise when the concentration of dissolved gas at the bubble surface, dictated by Henry's law, depends on time. In this paper we consider several such situations. An oscillating ambient pressure field causes the occurrence of rectified diffusion of gas into or out of the bubble. Unlike previous investigators, who considered the opposite limit, we study this process for conditions when the diffusion length is larger than the bubble radius. It is found that history effects are important in determining the threshold conditions. Under a static ambient pressure, the time dependence of the gas concentration can arise due to the action of surface tension, which increases the gas pressure as the bubble dissolves or, when the bubble contains a mixture of two or more gases, due to the different rates at which they dissolve. In these latter cases history effects prove mostly negligible for bubbles larger than a few hundred nanometers.

6. Wall effects on the thermocapillary migration of single gas bubbles in stagnant liquids

Alhendal, Yousuf; Turan, Ali; Kalendar, Abdulrahim

2016-09-01

In this paper, the governing continuum conservation equations for two-phase flow are solved using the commercial software package (Ansys-Fluent 1) to investigate the thermocapillary movement of a single bubble in stagnant liquid under zero-gravity condition. The current results show that different temperature gradients lead to different bubble migration velocities, and bubble migration velocity varies linearly with the temperature gradient for the given conditions. Furthermore the inside column diameter was found to have a significant influence on the thermocapillary migration of the bubble. Calculation were made in columns with inside diameters Dr 15, 20, 30, 40, 60, 80, 100 and 120 mm. Reduction on bubble migration velocity only occurred when the ratio of the bubble diameter to the column diameter, db/Dr, is greater than 0.267 due to column wall effect. On the other hand, the influence of the column diameter on the rise velocity is negligible when db/Dr is equal to or smaller than 0.267. No bubble shape deformation were observed and the bubble were spherical in shape for all column width. Present investigation of the shape and trajectory of bubble motion driven by surface tension-gradient in different column width is a new area of study and aims to support research into space applications which can help to determine the new migration time and speed.

7. 900-m high gas plumes rising from marine sediments containing structure II hydrates at Vestnesa Ridge, offshore W-Svalbard

Smith, Andrew J.; Mienert, Jürgen; Bünz, Stefan; Greinert, Jens; Rasmussen, Tine L.

2013-04-01

We study an arctic sediment drift in ~1200 m water depth at Vestnesa Ridge, offshore western Svalbard. The ridge is spotted with pockmarks that range in size from a few meters to hundreds of meters in diameter and centimeters to tens of meters in height (e.g. Vogt et al., 1994). There is a strong negative-polarity seismic reflection below the ridge that is interpreted to record a negative impedance contrast marking the boundary between gas hydrate and water above and free gas and water below: it is the bottom-simulating reflector (BSR). Seismically transparent zones, interpreted as gas chimneys, extend from pockmarks at the seafloor to depths below the BSR (180-220 meters below the seafloor) (Bünz et al., 2012). Gas flares, gas hydrate, and methane-seep-specific biological communities (pogonphora and begiatoa bacterial mats) have been observed adjacent to pockmarks at the ridge (Bünz et al., 2012). We present new single-beam echosounding data that were acquired during 2010 and 2012 cruises on the R/V Helmer Hanssen at Vestnesa Ridge using a Simrad EK60 system that operates at frequencies of 18 and 38 kHz. During both cruises which lasted 3-5 days, we detected continuous bubble release from 4 separate pockmarks in 2010 and 6 separate pockmarks in 2012. There were no noticeable, short-term (hourly or daily) variations in the bubble release from the pockmarks, indicating that the venting from the pockmarks does not undergo rapid changes. Plumes from the pockmarks rise between 875 to 925m above the seafloor to a final water depth of 325 to 275m, respectively. This depth is in excellent agreement with the top of the hydrate stability zone (275 meters below sea level) for the gas composition of hydrate sampled at the ridge (96.31% C1; 3.36% C2; 0.21% C3; 0.11% IC4; 0.01% NC4). This suggests that hydrate skins are forming around the gas bubbles, inhibiting the dissolution of gas, and allowing the bubbles to rise to such great heights in the water column. Our results

8. Alma Observations of Massive Molecular Gas Filaments Encasing Radio Bubbles in the Phoenix Cluster

Russell, H. R.; McDonald, M.; McNamara, B. R.; Fabian, A. C.; Nulsen, P. E. J.; Bayliss, M. B.; Benson, B. A.; Brodwin, M.; Carlstrom, J. E.; Edge, A. C.; Hlavacek-Larrondo, J.; Marrone, D. P.; Reichardt, C. L.; Vieira, J. D.

2017-02-01

We report new ALMA observations of the CO(3-2) line emission from the 2.1+/- 0.3× {10}10 {M}ȯ molecular gas reservoir in the central galaxy of the Phoenix cluster. The cold molecular gas is fueling a vigorous starburst at a rate of 500{--}800 {M}ȯ {{yr}}-1 and powerful black hole activity in the forms of both intense quasar radiation and radio jets. The radio jets have inflated huge bubbles filled with relativistic plasma into the hot, X-ray atmospheres surrounding the host galaxy. The ALMA observations show that extended filaments of molecular gas, each 10{--}20 {kpc} long with a mass of several billion solar masses, are located along the peripheries of the radio bubbles. The smooth velocity gradients and narrow line widths along each filament reveal massive, ordered molecular gas flows around each bubble, which are inconsistent with gravitational free-fall. The molecular clouds have been lifted directly by the radio bubbles, or formed via thermal instabilities induced in low-entropy gas lifted in the updraft of the bubbles. These new data provide compelling evidence for close coupling between the radio bubbles and the cold gas, which is essential to explain the self-regulation of feedback. The very feedback mechanism that heats hot atmospheres and suppresses star formation may also paradoxically stimulate production of the cold gas required to sustain feedback in massive galaxies.

9. Dispersed bubble reactor for enhanced gas-liquid-solids contact and mass transfer

DOEpatents

Vimalchand, Pannalal; Liu, Guohai; Peng, WanWang; Bonsu, Alexander

2016-01-26

An apparatus to promote gas-liquid contact and facilitate enhanced mass transfer. The dispersed bubble reactor (DBR) operates in the dispersed bubble flow regime to selectively absorb gas phase constituents into the liquid phase. The dispersion is achieved by shearing the large inlet gas bubbles into fine bubbles with circulating liquid and additional pumped liquid solvent when necessary. The DBR is capable of handling precipitates that may form during absorption or fine catalysts that may be necessary to promote liquid phase reactions. The DBR can be configured with multistage counter current flow sections by inserting concentric cylindrical sections into the riser to facilitate annular flow. While the DBR can absorb CO.sub.2 in liquid solvents that may lead to precipitates at high loadings, it is equally capable of handling many different types of chemical processes involving solids (precipitates/catalysts) along with gas and liquid phases.

10. Improving microalgal growth with small bubbles in a raceway pond with swing gas aerators.

PubMed

Yang, Zongbo; Cheng, Jun; Liu, Jianzhong; Zhou, Junhu; Cen, Kefa

2016-09-01

A novel swing gas aerator was developed to generate small bubbles for improving the mass transfer coefficient and microalgal growth rate in a raceway pond. A high-speed photography system (HSP) was used to measure the bubble diameter and generation time, and online precise dissolved oxygen probes and pH probes were used to measure the mass transfer coefficient and mixing time. Bubble generation time and diameter decreased by 21% and 9%, respectively, when rubber gas aerators were swung in the microalgae solution. When water pump power and gas aeration rate increased in a raceway pond with swing gas aerators and oscillating baffles (SGAOB), bubble generation time and diameter decreased but solution velocity and mass transfer coefficient increased. The mass transfer coefficient increased by 25% and the solution velocity increased by 11% when SGAOB was used, and the microalgal biomass yield increased by 18%.

11. History effects on the gas exchange between a bubble and a liquid

Chu, Shigan; Prosperetti, Andrea

2016-11-01

History effects are a distinctive feature of diffusive processes. For a diffusing gas bubble at rest in a liquid, such effects arise when the concentration of dissolved gas at the bubble surface, connected to the gas pressure by Henry's law, depends on time. This time dependence can be caused by several factors, such as varying ambient pressure, mole fraction in a multicomponent gas bubble, surface tension and others. In this study we consider history effects in the three situations mentioned above. More specifically, rectified diffusion in an oscillating ambient pressure field is explored under conditions when the diffusion length is larger than the bubble radius. History effects are found to be important in determining the threshold conditions for rectified diffusion. In contrast, history effects are small in the other two cases. Supported by the BP/The Gulf of Mexico Research Initiative through the University of Texas Marine Science Institute (DROPPS II consortium: "Dispersion Research on Oil: Physics and Plankton Studies").

12. Phase-field simulations of intragranular fission gas bubble evolution in UO2 under post-irradiation thermal annealing

SciTech Connect

Li, Yulan; Hu, Shenyang Y.; Montgomery, Robert O.; Gao, Fei; Sun, Xin

2013-05-15

Fission gas bubble is one of evolving microstructures, which affect thermal mechanical properties such as thermo-conductivity, gas release, volume swelling, and cracking, in operating nuclear fuels. Therefore, fundamental understanding of gas bubble evolution kinetics is essential to predict the thermodynamic property and performance changes of fuels. In this work, a generic phasefield model was developed to describe the evolution kinetics of intra-granular fission gas bubbles in UO2 fuels under post-irradiation thermal annealing conditions. Free energy functional and model parameters are evaluated from atomistic simulations and experiments. Critical nuclei size of the gas bubble and gas bubble evolution were simulated. A linear relationship between logarithmic bubble number density and logarithmic mean bubble diameter is predicted which is in a good agreement with experimental data.

13. Two-Dimensional Numerical Simulations of Ultrasound in Liquids with Gas Bubble Agglomerates: Examples of Bubbly-Liquid-Type Acoustic Metamaterials (BLAMMs)

PubMed Central

Vanhille, Christian

2017-01-01

This work deals with a theoretical analysis about the possibility of using linear and nonlinear acoustic properties to modify ultrasound by adding gas bubbles of determined sizes in a liquid. We use a two-dimensional numerical model to evaluate the effect that one and several monodisperse bubble populations confined in restricted areas of a liquid have on ultrasound by calculating their nonlinear interaction. The filtering of an input ultrasonic pulse performed by a net of bubbly-liquid cells is analyzed. The generation of a low-frequency component from a single cell impinged by a two-frequency harmonic wave is also studied. These effects rely on the particular dispersive character of attenuation and nonlinearity of such bubbly fluids, which can be extremely high near bubble resonance. They allow us to observe how gas bubbles can change acoustic signals. Variations of the bubbly medium parameters induce alterations of the effects undergone by ultrasound. Results suggest that acoustic signals can be manipulated by bubbles. This capacity to achieve the modification and control of sound with oscillating gas bubbles introduces the concept of bubbly-liquid-based acoustic metamaterials (BLAMMs). PMID:28106748

14. Acoustic wave propagation in bubbly flow with gas, vapor or their mixtures.

PubMed

Zhang, Yuning; Guo, Zhongyu; Gao, Yuhang; Du, Xiaoze

2017-03-29

Presence of bubbles in liquids could significantly alter the acoustic waves in terms of wave speed and attenuation. In the present paper, acoustic wave propagation in bubbly flows with gas, vapor and gas/vapor mixtures is theoretically investigated in a wide range of parameters (including frequency, bubble radius, void fraction, and vapor mass fraction). Our finding reveals two types of wave propagation behavior depending on the vapor mass fraction. Furthermore, the minimum wave speed (required for the closure of cavitation modelling in the sonochemical reactor design) is analyzed and the influences of paramount parameters on it are quantitatively discussed.

15. A parametric study on the rise of a pair of bubbles using algebraic volume of fluid method: effect of diameter and viscosity ratio

Dalal, Amaresh; Kulkarni, Amol C.; Manik, Jai; Natarajan, Ganesh

2016-11-01

The effect of droplet diameter and viscosity ratio on the coalescence of two bubbles rising in a quiescent liquid has been studied numerically using algebraic volume of fluid (VOF) method. If the upper bubble diameter is 75% of the lower bubble, the time taken for their coalescence increases in comparison with the case of equal bubble diameter. For the case, when the diameter of the upper bubble is reduced, this delay may be attributed to comparatively weaker jet formed behind the leading bubble, ultimately resulting in lesser acceleration of the trailing bubble. While for the other case, when the diameter of the lower bubble is reduced, it is because of a totally different scenario of liquid entrapment observed during coalescence. The effect of viscosity of the surrounding fluid is also noticed separately for the situation when the diameters of the bubbles are equal. It has been observed that, the increase in viscosity of the surrounding fluid will increase the form drag over the bubbles, eventually leading to the delay in their coalescence. This study is funded by a Grant from BRNS, DAE, Government of India.

16. The Interaction of the Fermi Bubbles with the Milky Way’s Hot Gas Halo

Miller, Matthew J.; Bregman, Joel N.

2016-09-01

The Fermi bubbles are two lobes filled with non-thermal particles that emit gamma rays, extend ≈ 10 {{kpc}} vertically from the Galactic center, and formed from either nuclear star formation or accretion activity on Sgr A*. Simulations predict a range of shock strengths as the bubbles expand into the surrounding hot gas halo ({T}{halo}≈ 2× {10}6 K), but with significant uncertainties in the energetics, age, and thermal gas structure. The bubbles should contain thermal gas with temperatures between 106 and 108 K, with potential X-ray signatures. In this work, we constrain the bubbles’ thermal gas structure by modeling O vii and O viii emission line strengths from archival XMM-Newton and Suzaku data. Our emission model includes a hot thermal volume-filled bubble component cospatial with the gamma-ray region, and a shell of compressed material. We find that a bubble/shell model with n≈ 1× {10}-3 cm-3 and with log(T) ≈ 6.60-6.70 is consistent with the observed line intensities. In the framework of a continuous Galactic outflow, we infer a bubble expansion rate, age, and energy injection rate of {490}-77+230 km s-1, {4.3}-1.4+0.8 Myr, and {2.3}-0.9+5.1× {10}42 erg s-1. These estimates are consistent with the bubbles forming from a Sgr A* accretion event rather than from nuclear star formation.

17. Facile nanofibrillation of chitin derivatives by gas bubbling and ultrasonic treatments in water.

PubMed

Tanaka, Kohei; Yamamoto, Kazuya; Kadokawa, Jun-ichi

2014-10-29

In this paper, we report that nanofiber network structures were constructed from chitin derivatives by gas bubbling and ultrasonic treatments in water. When chitin was first subjected to N2 gas bubbling with ultrasonication in water, the SEM images of the product showed nanofiber network morphology. However, nanofiber network was not re-constructed by the same N2 gas bubbling and ultrasonic treatments after agglomeration. We then have paid attention to an amidine group to provide the agglomeration-nanofibrillation behavior of chitin derivatives. An amidinated chitin was synthesized by the reaction of the amino groups in a partially deacetylated chitin with N,N-dimethylacetamide dimethyl acetal, which was subjected to CO2 gas bubbling and ultrasonic treatments in water to convert into an amidinium chitin by protonation. The SEM images of the product clearly showed nanofiber network morphology. We further examined re-nanofibrillation of the agglomerated material, which was obtained by mixing the nanofibrillated amidinium chitin with water, followed by drying under reduced pressure. Consequently, the material was re-nanofibrillated by N2 gas bubbling with ultrasonication in water owing to electrostatic repulsion between the amidinium groups. Furthermore, deprotonation of the amidinium chitin and re-protonation of the resulting amidinated chitin were conducted by alkaline treatment and CO2 gas bubbling-ultrasonic treatments, respectively. The material showed the agglomeration-nanofibrillation behavior during the processes.

18. Enhanced Generic Phase-field Model of Irradiation Materials: Fission Gas Bubble Growth Kinetics in Polycrystalline UO2

SciTech Connect

Li, Yulan; Hu, Shenyang Y.; Montgomery, Robert O.; Gao, Fei; Sun, Xin

2012-05-30

Experiments show that inter-granular and intra-granular gas bubbles have different growth kinetics which results in heterogeneous gas bubble microstructures in irradiated nuclear fuels. A science-based model predicting the heterogeneous microstructure evolution kinetics is desired, which enables one to study the effect of thermodynamic and kinetic properties of the system on gas bubble microstructure evolution kinetics and morphology, improve the understanding of the formation mechanisms of heterogeneous gas bubble microstructure, and provide the microstructure to macroscale approaches to study their impact on thermo-mechanical properties such as thermo-conductivity, gas release, volume swelling, and cracking. In our previous report 'Mesoscale Benchmark Demonstration, Problem 1: Mesoscale Simulations of Intra-granular Fission Gas Bubbles in UO2 under Post-irradiation Thermal Annealing', we developed a phase-field model to simulate the intra-granular gas bubble evolution in a single crystal during post-irradiation thermal annealing. In this work, we enhanced the model by incorporating thermodynamic and kinetic properties at grain boundaries, which can be obtained from atomistic simulations, to simulate fission gas bubble growth kinetics in polycrystalline UO2 fuels. The model takes into account of gas atom and vacancy diffusion, vacancy trapping and emission at defects, gas atom absorption and resolution at gas bubbles, internal pressure in gas bubbles, elastic interaction between defects and gas bubbles, and the difference of thermodynamic and kinetic properties in matrix and grain boundaries. We applied the model to simulate gas atom segregation at grain boundaries and the effect of interfacial energy and gas mobility on gas bubble morphology and growth kinetics in a bi-crystal UO2 during post-irradiation thermal annealing. The preliminary results demonstrate that the model can produce the equilibrium thermodynamic properties and the morphology of gas bubbles at

19. Bioinspired gas bubble spontaneous and directional transportation effects in an aqueous medium.

PubMed

Ma, Rui; Wang, Jingming; Yang, Zhongjia; Liu, Meng; Zhang, Jingjing; Jiang, Lei

2015-04-08

A series of well-ordered, 3D gradient porous interconnected network surfaces composed of micro-nano hierarchical geometries is constructed on a copper wire. A continuous gas film can be trapped around its interface in an aqueous medium acting as an effective channel for gas transportation. Driving by the difference of the Laplace pressure, gas bubbles can be transported spontaneously and directionally.

20. The North Sea Blowout: A gas bubble megaplume with spiral vortex motion and why it might, or might not, contribute much to the atmospheric methane

Schneider von Deimling, Jens; Leifer, Ira; Schmidt, Mark; Rehder, Gregor; Linke, Peter

2014-05-01

In the Central North Sea, during drilling operations, a gas blowout accident happened in 1990. Thereafter, natural gas has leaked prodigiously from a 60 m diameter and 20 m deep crater located at 95 m depth into the water column and to the sea surface. A series of field studies was carried out at this site since 2005 evidencing ongoing intense seepage activity. Three gas bubble megaplumes and dozens of minor to major bubble seeps were observed in the crater during a manned submersible dive, ROV mapped hundreds. Analysis of gas bubbles captured at 118 m water depth revealed concentrations between 88-90%Vol CH4 with δ 13C-CH4 values around -74‰ VPDB, consistent with a biogenic origin. Blowout site flux estimates derived from ROV video show the site's emissions are the strongest and most intense marine methane seepage quantified to date with seabed emissions of ~32.6 kt/y. Based on previous research suggesting greater flux correlates with greater transport efficiency, the direct bubble-mediated atmospheric flux to the atmosphere was estimated at a surprisingly low 0.7kt/y. This is orders of magnitude smaller compared to the seabed flux, thus the bulk methane dissolves before reaching the atmosphere, suggesting enhanced bubble dissolution rates for megaplumes. Analysis of more than 120 water samples from near the blowout plume showed dissolved methane concentration distributions consistent with enhanced bubble dissolution at depth. CH4 concentrations ranged from 0.2 µmol/L at 20 m depth to a peak in the crater of an extraordinary 400 µmol/L. To evaluate further the controlling factors on the rising bubble plume, multibeam water column data were analyzed. The bubble plume spatial distribution revealed a horizontal intrusion of gas bubbles just below the thermocline. This pronounced pattern was traced 200 m horizontally with a downflow plume orientation suggesting trapping of methane-enriched fluids at depth. A numerical bubble propagation model was used to simulate

1. A study of gas bubbles in liquid mercury in a vertical Hele-Shaw cell

Klaasen, B.; Verhaeghe, F.; Blanpain, B.; Fransaer, J.

2014-01-01

High-quality observations of mesoscopic gas bubbles in liquid metal are vital for a further development of pyrometallurgical gas injection reactors. However, the opacity of metals enforces the use of indirect imaging techniques with limited temporal or spatial resolution. In addition, accurate interface tracking requires tomography which further complicates the design of a high-temperature experimental setup. In this paper, an alternative approach is suggested that circumvents these two main restrictions. By injecting gas in a thin layer of liquid metal entrapped between two flat and closely spaced plates, bubbles in a Hele-Shaw flow regime are generated. The resulting quasi-2D multiphase flow phenomena can be fully captured from a single point of view and, when using a non-wetted transparent plate material, the bubbles can be observed directly. The feasibility of this approach is demonstrated by observations on buoyancy-driven nitrogen bubbles in liquid mercury in a vertical Hele-Shaw cell. By using a moving high-speed camera to make continuous close up recordings of individual bubbles, the position and geometry of these bubbles are quantified with a high resolution along their entire path. After a thorough evaluation of the experimental accuracy, this information is used for a detailed analysis of the bubble expansion along the path. While the observed bubble growth is mainly caused by the hydrostatic pressure gradient, a careful assessment of the volume variations for smaller bubbles shows that an accurate bubble description should account for significant dynamic pressure variations that seem to be largely regime dependent.

2. Observation of Brewster Angle Light Scattering from Air Bubbles Rising in Water

DTIC Science & Technology

1988-08-25

At the bottom of this pipe a hollow needle is placed which is connected to an air supply. By regulating the air through the needle bubbles were...back scattering direction a beamsplitter was inserted in the light path. Then a retroreflector was placed behind the beamsplitter. The beam coming...out of the retroreflector is reflected at 45’ off the beamsplitter and then focused to a point. This point now defines the backwards direction. 03 0 t W

3. Lander based hydroacoustic monitoring of marine single bubble releases in Eckernförde Bay utilizing the multibeam based GasQuant II system.

Urban, Peter; Schneider von Deimling, Jens; Greinert, Jens

2015-04-01

The GEOMAR Helmholtz Centre for Ocean Research Kiel is currently developing a Imagenex Delta T based lander system for monitoring and quantifying marine gas release (bubbles). The GasQuant II is built as the successor of the GasQuant I system (Greinert, 2008), that has been successfully used for monitoring tempo-spatial variability of gas release in the past (Schneider von Deimling et al., 2010). The new system is lightweight (40 kg), energy efficient, flexible to use and built for ROV deployment with autonomous operation of up to three days. A prototype has been successfully deployed in Eckernförde Bay during the R/V ALKOR cruise AL447 in October/November 2014 to monitor the tempo-spatial variability of gas bubble seepage and to detect a possible correlation with tidal variations. Two deployments, one in forward- and one in upward looking mode, reveal extensive but scattered single bubble releases rather than distinct and more continuous sources. While these releases are difficult to detect in forward looking mode, they can unambiguously be detected in the upward looking mode even for minor gas releases, bubble rising speeds can be determined. Greinert, J., 2008. Monitoring temporal variability of bubble release at seeps: The hydroacoustic swath system GasQuant. J. Geophys. Res. Oceans Vol. 113 Issue C7 CiteID C07048 113, 7048. doi:10.1029/2007JC004704 Schneider von Deimling, J., Greinert, J., Chapman, N.R., Rabbel, W., Linke, P., 2010. Acoustic imaging of natural gas seepage in the North Sea: Sensing bubbles controlled by variable currents. Limnol. Oceanogr. Methods 8, 155. doi:10.4319/lom.2010.8.155

4. Rate of disappearance of gas bubble trauma signs in juvenile salmonids

USGS Publications Warehouse

Hans, K.M.; Mesa, M.G.; Maule, A.G.

1999-01-01

To assess the rate of disappearance of gas bubble trauma (GBT) signs in juvenile salmonids, we exposed spring chinook salmon Oncorhynchus tshawytscha and steelhead O. mykiss to water containing high levels of dissolved gas supersaturation (DGS) for a time period sufficient to induce signs of GBT, reduced the DGS to minimal levels, and then sampled fish through time to document changes in severity of GBT. Because of the tendency of GBT signs to dissipate at different rates, we conducted trials focusing on emboli (bubbles) in the gill filaments and lateral line and separate trials that focused on bubbles in the external surfaces (fins, eyes, and opercula). Bubbles in gill filaments dissipated almost completely within 2 h after transfer of fish to water of nearly normal DGS (104%), whereas bubbles in the lateral line dissipated to negligible levels within 5 h. Bubbles on external surfaces were more persistent through time than they were in gill filaments and the lateral line. Although typically dissipating to low levels within 48 h, external bubbles sometimes remained for 4 d. Assuming a direct relation exists between easily observable signs and direct mortality, our results suggest that fish can recover quickly from the potentially lethal effects of DGS once they move from water with high DGS to water of almost normal gas saturation. These results should be of fundamental importance to fishery managers interpreting the results of monitoring for the severity and prevalence of GBT in juvenile salmonids in the Columbia River system and perhaps elsewhere.

5. Effect of Orifice Diameter on Bubble Generation Process in Melt Gas Injection to Prepare Aluminum Foams

Yuan, Jianyu; Li, Yanxiang; Wang, Ningzhen; Cheng, Ying; Chen, Xiang

2016-06-01

The bubble generation process in conditioned A356 alloy melt through submerged spiry orifices with a wide diameter range (from 0.07 to 1.0 mm) is investigated in order to prepare aluminum foams with fine pores. The gas flow rate and chamber pressure relationship for each orifice is first determined when blowing gas in atmospheric environment. The effects of chamber pressure ( P c) and orifice diameter ( D o) on bubble size are then analyzed separately when blowing gas in melt. A three-dimensional fitting curve is obtained illustrating both the influences of orifice diameter and chamber pressure on bubble size based on the experimental data. It is found that the bubble size has a V-shaped relationship with orifice diameter and chamber pressure neighboring the optimized parameter ( D o = 0.25 mm, P c = 0.4 MPa). The bubble generation mechanism is proposed based on the Rayleigh-Plesset equation. It is found that the bubbles will not be generated until a threshold pressure difference is reached. The threshold pressure difference is dependent on the orifice diameter, which determines the time span of pre-formation stage and bubble growth stage.

6. How sea level rise and storm climate impact the looming morpho-economic bubble in coastal property value.

McNamara, D.; Keeler, A.; Smith, M.; Gopalakrishnan, S.; Murray, A.

2012-12-01

In the United States, the coastal region is now the most densely populated zone in the country and as a result has become a significant source of tax revenue and has some of the highest property values in the country. The loss of land at the coastline from erosion and damage to property from storms has always been a source of vulnerability to coastal economies. To manage this vulnerability, humans have long engaged in the act of nourishing the coastline - placing sand, typically from offshore sources, onto the beach to widen the beach and increase the height of dunes. As humans alter natural coastal dynamics by nourishing, the altered natural dynamics then influence future beach management decisions. In this way human-occupied coastlines are a strongly coupled dynamical system and because of this coupling, the act of nourishment has become an intrinsic part of the economic value of a coastline. Predictions of increased rates of sea level rise and changing storminess suggest that coastal vulnerability is likely to increase. The evolving vulnerability of the coast has already caused changes to occur in the way humans manage the coastline. For example, the federal government has recently reduced subsidies to help coastal communities nourish their beaches. With a future of changing environmental forcing from sea level and storms, the prospect of changes in nourishment cost could have profound consequences on coastal value and sustainability. We utilize two modeling approaches to investigate how disappearing nourishment subsidies reduce coastal property value and to explore the potential for a bubble and subsequent crash in coastal property value as subsidies dwindle and vulnerability rises. The first model is an optimal control model that couples a cost benefit analysis to coastline dynamics. In the second model, we couple a numerical coastline model with an agent-based model for real estate markets. Results from both models suggest the total present value of coastal

7. N131: A dust bubble was born from the disruption of a gas filament?

Zhang, Chuan-Peng

2017-03-01

N131 is an infrared dust bubble residing in a molecular filament. We aim to study the formation and fragmentation of this bubble with multi-wavelength dust and gas observations. Towards the bubble N131, we analyzed archival multi-wavelength observations including 3.6, 4.5, 5.8, 8.0, 24, 70, 160, 250, 350, 500 μm, 1.1 mm, and 21 cm. In addition, we performed new observations of CO (2-1), CO (1-0), and 13CO (1-0) with the IRAM 30-m telescope. Multi-wavelength dust and gas observations reveal a ringlike shell with compact fragments, two filamentary structures, and a secondary bubble N131-A. The bubble N131 is a rare object with a large hole at 24 μm and 21 cm in the direction of its center. The dust and gas clumps are compact and might have been compressed at the inner edge of the ringlike shell, while they are extended and might be pre-existing at the outer edge. The column density, excitation temperature, and velocity show a potentially hierarchical distribution from the inner to outer edge of the ringlike shell. We also detected the front and back sides of the secondary bubble N131-A in the direction of its center. The derived Lyman-continuum ionizing photon flux within N131-A is equivalent to an O9.5 star. Based on the above, we suggest that the bubble N131 might be triggered by the strong stellar winds from a group of massive stars inside the bubble. We propose a scenario in which the bubble N131 forms from the disruption of a gas filament by expansion of H II region, strong stellar winds, and fragments under self-gravity.

8. Surface Forces and Interaction Mechanisms of Emulsion Drops and Gas Bubbles in Complex Fluids.

PubMed

Xie, Lei; Shi, Chen; Cui, Xin; Zeng, Hongbo

2017-02-22

The interactions of emulsion drops and gas bubbles in complex fluids play important roles in a wide range of biological and technological applications, such as programmable drug and gene delivery, emulsion and foam formation, and froth flotation of mineral particles. In this feature article, we have reviewed our recent progress on the quantification of surface forces and interaction mechanisms of gas bubbles and emulsion drops in different material systems by using several complementary techniques, including the drop/bubble probe atomic force microscope (AFM), surface forces apparatus (SFA), and four-roll mill fluidic device. These material systems include the bubble-self-assembled monolayer (SAM), bubble-polymer, bubble-superhydrophobic surface, bubble-mineral, water-in-oil and oil-in-water emulsions with interface-active components in oil production, and oil/water wetting on polyelectrolyte surfaces. The bubble probe AFM combined with reflection interference contrast microscopy (RICM) was applied for the first time to simultaneously quantify the interaction forces and spatiotemporal evolution of a confined thin liquid film between gas bubbles and solid surfaces with varying hydrophobicity. The nanomechanical results have provided useful insights into the fundamental interaction mechanisms (e.g., hydrophobic interaction in aqueous media) at gas/water/solid interfaces, the stabilization/destabilization mechanisms of emulsion drops, and oil/water wetting mechanisms on solid surfaces. A long-range hydrophilic attraction was found between water and polyelectrolyte surfaces in oil, with the strongest attraction for polyzwitterions, contributing to their superior water wettability in oil and self-cleaning capability of oil contamination. Some remaining challenges and future research directions are discussed and provided.

9. The effect of anaesthesia on the intraocular volume of the C3F8 gas bubble.

PubMed

Briggs, M; Wong, D; Groenewald, C; McGalliard, J; Kelly, J; Harper, J

1997-01-01

Long-acting intraocular gas bubbles are frequently used during vitrectomy to tamponade retinal breaks. The aim of this study was to determine the effect of nitrous oxide anaesthesia on the size and effectiveness of the post-vitrectomy gas bubble. Twenty vitrectomy procedures with injection of 12% perfluoropropane (C3F8) gas were performed. For 10 of the cases routine anaesthesia with nitrous oxide was used and for 10 cases non-nitrous anaesthesia with propofol was used. The volume of the intraocular gas bubble was estimated 24 hours post-operatively using A-scan biometry. At 24 hours the gas bubble occupied a mean of 65.1% of the eye in anaesthesia with nitrous oxide and a mean of 66.1% in anaesthesia with intravenous propofol. The wide range of values of gas-fill recorded at 24 hours makes comparison of the two groups inappropriate. Several factors may account for this spread of values, but in our opinion it is the uncontrolled leakage from the sclerostomies which is the most likely. This study suggests that anaesthesia using nitrous oxide does not adversely affect the size of the C3F8 gas bubble at 24 hours post-vitrectomy when compared with anaesthesia without nitrous oxide.

10. Experimental studies of a strongly shocked gas bubble

Ranjan, Devesh; Oakley, Jason; Anderson, Mark; Bonazza, Riccardo

2004-11-01

The interaction of a planar shock wave (M=1.34, 2.84 and 3.34) propagating in nitrogen with a free-falling spherical soap bubble (5 cm diameter) filled with argon leads initially to the compression of the bubble into a disk-like object and, at later times, to the formation of a vortex ring at the periphery of the disk which entrains outside fluid into the argon. The evolution of some of the relevant geometrical properties of the bubble and the vortex ring are studied in the laboratory with a vertical shock tube with a square internal cross section; a retractable injector releases an argon bubble in the shock tube and a downward-propagating, planar shock wave reaches the bubble within 70 ms of its release from the injector. The flow is imaged with a laser sheet illuminated across the shock-accelerated bubble and collecting the Mie scattering signal from the soap film, which acts as a flow tracer. The planar image represents a 2D slice of the flow, however, the shocked bubble geometry evolution is in fact 3D due to an azimuthal instability (Widnall). The presence of a droplet of film results in additional Rayleigh-Taylor and Kelvin-Helmholtz instabilites due to an observed jet; this may help to explain the jetting observed following core-collapse in a supernova. Experimental results are compared with numerical simulations using the Raptor code (LLNL) which solves the full Navier-Stokes equations using the Piecewise Linear Method (PLM) with Adaptive Mesh Refinement (AMR).

11. A Philippinite with an Unusually Large Bubble: Gas Pressure and Noble Gas Composition

Matsuda, J.; Maruoka, T.; Pinti, D. L.; Koeberl, C.

1995-09-01

Bubbles are common in tektites, but usually their sizes range up to only a few mm. They are most abundant in Muong Nong-type tektites. The gases contained in these bubbles are of terrestrial atmospheric composition, with pressures below 1 atm (e.g., [1]). The abundances of light noble gases (He, Ne) are controlled by diffusion from the atmosphere [2], and noble gases dissolved in tektite glass indicate that the glass solidified at atmospheric pressures equivalent to about 40 km altitude [3]. Large bubbles in splash-form tektites are rather rare. Thus, the finding that a philippinite (size: 6.0 x 4.5 cm; weight: 199.6 g) contains an unusually large bubble justified a detailed study. The volume of the bubble, which was confirmed by X-ray photography, was estimated at 5.4 cm^3, by comparing the density of this tektite (2.288 g/cm^3) to that of normal philippinites (2.438 g/cm^3). A device was specifically constructed for crushing the present sample under vacuum. The 10x10 cm cylindrical device has a piston that allows to gently crush the sample by turning a handle. Various disk spacers can be used to adjust the inner height to that of the sample. The device is made of stainless steel, yielding a low noble gas blank. The crushing device is connected to a purification line and a noble gas sector-type mass spectrometer (VG 5400) [4]. Before crushing, the complete tektite was wrapped in aluminum foil. A first crushing attempt, using stainless steel disk spacers, failed and resulted in damage to the steel spacers, indicating a high strength of the tektite. Using iron disk spacers resulted in an ambient pressure increase (probably due to hydrogen from the Fe) in the sample chamber. However, the noble gas blanks were negligible. The background pressure, at 2 x 10-4 Torr, increased to 3 x 10-4 Torr when the sample was crushed. From the volume of the crushing device and that of the bubble in the tektite, the total gas pressure in the bubble was estimated at about 1 x 10-4 atm

12. Characterization of intergranular fission gas bubbles in U-Mo fuel.

SciTech Connect

Kim, Y. S.; Hofman, G.; Rest, J.; Shevlyakov, G. V.; Nuclear Engineering Division; SSCR RIAR

2008-04-14

This report can be divided into two parts: the first part, which is composed of sections 1, 2, and 3, is devoted to report the analyses of fission gas bubbles; the second part, which is in section 4, is allocated to describe the mechanistic model development. Swelling data of irradiated U-Mo alloy typically show that the kinetics of fission gas bubbles is composed of two different rates: lower initially and higher later. The transition corresponds to a burnup of {approx}0 at% U-235 (LEU) or a fission density of {approx}3 x 10{sup 21} fissions/cm{sup 3}. Scanning electron microscopy (SEM) shows that gas bubbles appear only on the grain boundaries in the pretransition regime. At intermediate burnup where the transition begins, gas bubbles are observed to spread into the intragranular regions. At high burnup, they are uniformly distributed throughout fuel. In highly irradiated U-Mo alloy fuel large-scale gas bubbles form on some fuel particle peripheries. In some cases, these bubbles appear to be interconnected and occupy the interface region between fuel and the aluminum matrix for dispersion fuel, and fuel and cladding for monolithic fuel, respectively. This is a potential performance limit for U-Mo alloy fuel. Microscopic characterization of the evolution of fission gas bubbles is necessary to understand the underlying phenomena of the macroscopic behavior of fission gas swelling that can lead to a counter measure to potential performance limit. The microscopic characterization data, particularly in the pre-transition regime, can also be used in developing a mechanistic model that predicts fission gas bubble behavior as a function of burnup and helps identify critical physical properties for the future tests. Analyses of grain and grain boundary morphology were performed. Optical micrographs and scanning electron micrographs of irradiated fuel from RERTR-1, 2, 3 and 5 tests were used. Micrographic comparisons between as-fabricated and as-irradiated fuel revealed

13. Effects of non-condensable gas on the dynamic oscillations of cavitation bubbles

Zhang, Yuning

2016-11-01

Cavitation is an essential topic of multiphase flow with a broad range of applications. Generally, there exists non-condensable gas in the liquid and a complex vapor/gas mixture bubble will be formed. A rigorous prediction of the dynamic behavior of the aforementioned mixture bubble is essential for the development of a complete cavitation model. In the present paper, effects of non-condensable gas on the dynamic oscillations of the vapor/gas mixture bubble are numerically investigated in great detail. For the completeness, a large parameter zone (e.g. bubble radius, frequency and ratio between gas and vapor) is investigated with many demonstrating examples. The mechanisms of mass diffusion are categorized into different groups with their characteristics and dominated regions given. Influences of non-condensable gas on the wave propagation (e.g. wave speed and attenuation) in the bubbly liquids are also briefly discussed. Specifically, the minimum wave speed is quantitatively predicted in order to close the pressure-density coupling relationship usually employed for the cavitation modelling. Finally, the application of the present finding on the development of cavitation model is demonstrated with a brief discussion of its influence on the cavitation dynamics. This work was financially supported by the National Natural Science Foundation of China (Project No.: 51506051).

14. Vapor-Gas Bubble Evolution and Growth in Extremely Viscous Fluids Under Vacuum

NASA Technical Reports Server (NTRS)

Kizito, John; Balasubramaniam, R.; Nahra, Henry; Agui, Juan; Truong, Duc

2008-01-01

Formation of vapor and gas bubbles and voids is normal and expected in flow processes involving extremely viscous fluids in normal gravity. Practical examples of extremely viscous fluids are epoxy-like filler materials before the epoxy fluids cure to their permanent form to create a mechanical bond between two substrates. When these fluids flow with a free liquid interface exposed to vacuum, rapid bubble expansion process may ensue. Bubble expansion might compromise the mechanical bond strength. The potential sources for the origin of the gases might be incomplete out-gassing process prior to filler application; regasification due to seal leakage in the filler applicator; and/or volatiles evolved from cure reaction products formed in the hardening process. We embarked on a study that involved conducting laboratory experiments with imaging diagnostics in order to deduce the seriousness of bubbling caused by entrained air and volatile fluids under space vacuum and low gravity environment. We used clear fluids with the similar physical properties as the epoxy-like filler material to mimic the dynamics of bubbles. Another aspect of the present study was to determine the likelihood of bubbling resulting from dissolved gases nucleating from solution. These experimental studies of the bubble expansion are compared with predictions using a modified Rayleigh- Plesset equation, which models the bubble expansion.

15. Gas-bubble growth mechanisms in the analysis of metal fuel swelling

SciTech Connect

Gruber, E.E.; Kramer, J.M.

1986-06-01

During steady-state irradiation, swelling rates associated with growth of fission-gas bubbles in metallic fast reactor fuels may be expected to remain small. As a consequence, bubble-growth mechanisms are not a major consideration in modeling the steady-state fuel behavior, and it is usually adequate to consider the gas pressure to be in equilibrium with the external pressure and surface tension restraint. On transient time scales, however, various bubble-growth mechanisms become important components of the swelling rate. These mechanisms include growth by diffusion, for bubbles within grains and on grain boundaries; dislocation nucleation at the bubble surface, or ''punchout''; and bubble growth by creep. Analyses of these mechanisms are presented and applied to provide information on the conditions and the relative time scales for which the various processes should dominate fuel swelling. The results are compared to a series of experiments in which the swelling of irradiated metal fuel was determined after annealing at various temperatures and pressures. The diffusive growth of bubbles on grain boundaries is concluded to be dominant in these experiments.

16. Vapor Bubbles

Prosperetti, Andrea

2017-01-01

This article reviews the fundamental physics of vapor bubbles in liquids. Work on bubble growth and condensation for stationary and translating bubbles is summarized and the differences with bubbles containing a permanent gas stressed. In particular, it is shown that the natural frequency of a vapor bubble is proportional not to the inverse radius, as for a gas bubble, but to the inverse radius raised to the power 2/3. Permanent gas dissolved in the liquid diffuses into the bubble with strong effects on its dynamics. The effects of the diffusion of heat and mass on the propagation of pressure waves in a vaporous bubbly liquid are discussed. Other topics briefly touched on include thermocapillary flow, plasmonic nanobubbles, and vapor bubbles in an immiscible liquid.

17. Gas bubble disease in smallmouth bass and northern squawfish from the Snake and Columbia Rivers

SciTech Connect

Montgomery, J.C.; Becker, C.D.

1980-11-01

In 1975 and 1976, 179 smallmouth bass (Micropterus dolomieui) and 85 northern squawfish (Ptychocheilus oregonensis) were collected by angling from the lower Snake and mid-Columbia rivers, southeastern Washington. All fish were examined externally for gas bubble syndrome. Emboli were found beneath membranes of the opercula, body, and fins of 72% of the smallmouth bass and 84% of the northern squawfish. Hemorrhage was also noted on the caudal, anal, and pectoral fins of several smallmouth bass. Presence of gas bubble syndrome corresponded to the spring runoff when total dissolved gas supersaturations in river water exceeded 115%.

18. Gas pockets in a wastewater rising main: a case study.

PubMed

2012-01-01

This paper presents a case study of an existing wastewater rising main (WWRM) in which an extreme transient event produced by simultaneous power failure of the pumps caused the rupture of a 1.2 m (48 in) prestressed concrete cylinder pipe (PCCP), causing an important leakage of sewage. The event and the methodology followed in order to validate the diagnostics of the failure are described. The detail study included in situ observation of the system, experimental investigation in a setup, hydraulic analysis, as well as details of the structural strength of the WWRM. After the extensive investigation and several simulations of fluid transients for different scenarios and flow conditions, it was found that stationary small gas pockets accumulated at high points of the WWRM were identified as the principal contributory factor of the failure. This case study serves as clear warning of the consequences of operating a WWRM with gas pockets at its high points.

19. Gas Bubble Disease Monitoring and Research of Juvenile Salmonids : Annual Report 1996.

SciTech Connect

Maule, Alec G.; Beeman, John W.; Hans, Karen M.; Mesa, M.G.; Haner, P.; Warren, J.J.

1997-10-01

This document describes the project activities 1996--1997 contract year. This report is composed of three chapters which contain data and analyses of the three main elements of the project: field research to determine the vertical distribution of migrating juvenile salmonids, monitoring of juvenile migrants at dams on the Snake and Columbia rivers, and laboratory experiments to describe the progression of gas bubble disease signs leading to mortality. The major findings described in this report are: A miniature pressure-sensitive radio transmitter was found to be accurate and precise and, after compensation for water temperature, can be used to determine the depth of tagged-fish to within 0.32 m of the true depth (Chapter 1). Preliminary data from very few fish suggest that depth protects migrating juvenile steelhead from total dissolved gas supersaturation (Chapter 1). As in 1995, few fish had any signs of gas bubble disease, but it appeared that prevalence and severity increased as fish migrated downstream and in response to changing gas supersaturation (Chapter 2). It appeared to gas bubble disease was not a threat to migrating juvenile salmonids when total dissolved gas supersaturation was < 120% (Chapter 2). Laboratory studies suggest that external examinations are appropriate for determining the severity of gas bubble disease in juvenile salmonids (Chapter 3). The authors developed a new method for examining gill arches for intravascular bubbles by clamping the ventral aorta to reduce bleeding when arches were removed (Chapter 3). Despite an outbreak of bacterial kidney disease in the experimental fish, the data indicate that gas bubble disease is a progressive trauma that can be monitored (Chapter 3).

20. Sound waves in a liquid with polydisperse vapor-gas bubbles

Gubaidullin, D. A.; Fedorov, Yu. V.

2016-03-01

A mathematical model is presented for the propagation of plane, spherical, and cylindrical sound waves in a liquid containing polydisperse vapor-gas bubbles with allowance for phase transitions. A system of integro-differential equations is constructed to describe perturbed motion of a two-phase mixture, and a dispersion relation is derived. An expression for equilibrium sound velocity is obtained for a gas-liquid or vapor-liquid mixture. The theoretical results agree well with the known experimental data. The dispersion curves obtained for the phase velocity and the attenuation coefficient in a mixture of water with vapor-gas bubbles are compared for various values of vapor concentration in the bubbles and various bubble distributions in size. The evolution of pressure pulses of plane and cylindrical waves is demonstrated for different values of the initial vapor concentration in bubbles. The calculated frequency dependence of the phase sound velocity in a mixture of water with vapor bubbles is compared with experimental data.

1. Nonlinear dynamics of a gas bubble in an incompressible elastic medium.

PubMed

Emelianov, Stanislav Y; Hamilton, Mark F; Ilinskii, Yurii A; Zabolotskaya, Evgenia A

2004-02-01

A nonlinear model in the form of the Rayleigh-Plesset equation is developed for a gas bubble in an essentially incompressible elastic medium such as a tissue or rubberlike medium. Two constitutive laws for the elastic medium are considered: the Mooney potential, and Landau's expansion of the strain energy density. These two constitutive laws are compared at quadratic order to obtain a relation between their respective elastic constants. Attention is devoted to the relative importance of shear stress on the bubble dynamics, allowing for the equilibrium gas pressure in the bubble to differ substantially from the pressure at infinity. The model for the bubble motion is approximated to quadratic order to assess the importance of shear stress in the surrounding medium relative to that of the gas pressure in the bubble. Relations are derived for the value of the shear wave speed at which the two contributions are comparable, which provide an assessment of when shear stress in the surrounding medium must be taken into account when modeling bubble dynamics.

2. Shadow imaging in bubbly gas-liquid two-phase flow in porous structures

Altheimer, Marco; Häfeli, Richard; Wälchli, Carmen; Rudolf von Rohr, Philipp

2015-09-01

Shadow imaging is used for the investigation of bubbly gas-liquid two-phase flow in a porous structure. The porous structure is made of Somos WaterShed XC 11122, a clear epoxy resin used in rapid prototyping. Optical access is provided by using an aqueous solution of sodium iodide and zinc iodide having the same refractive index as the structure material (). Nitrogen is injected into the continuous phase at volumetric transport fractions in the range of resulting in a hold-up of . The obtained images of overlapping bubble shadows are processed to measure the bubble dimensions. Therefore, a new processing sequence is developed to determine bubble dimensions from overlapping bubble shadows by ellipse fitting. The accuracy of the bubble detection and sizing routine is assessed processing synthetic images. It is shown that the developed technique is suitable for volumetric two-phase flow measurements. Important global quantities such as gas hold-up and total interfacial area can be measured with only one camera. Operation parameters for gas-liquid two-phase flows are determined to improve mass and heat transfer between the phases.

3. A physiological model of the release of gas bubbles from crevices under decompression.

PubMed

Chappell, M A; Payne, S J

2006-09-28

Moving bubbles have been observed in the blood during or after decompression using ultrasonic techniques. It has been proposed that these may grow from nuclei housed on the blood vessel wall. One candidate for bubble nucleation is hydrophobic crevices. This work explores the growth of gas pockets that might exist in conical crevices and the release of bubbles from these crevices under decompression. An existing dynamic mathematical model for the stability of gas pockets in crevices [Chappell, M.A., Payne, S.J., in press. A physiological model of gas pockets in crevices and their behavior under compression. Respir. Physiol. Neurobiol.] is extended to include the behavior as the gas pocket reaches the crevice mouth and bubbles seed into the bloodstream. The behavior of the crevice bubble is explored for a single inert gas, both alone and with metabolic gases included. It was found that the presence of metabolic gases has a significant effect on the behavior under decompression and that this appears to be due to the high diffusivity of these gases.

4. Gas holdup in cyclone-static micro-bubble flotation column.

PubMed

Li, Xiaobing; Zhu, Wei; Liu, Jiongtian; Zhang, Jian; Xu, Hongxiang; Deng, Xiaowei

2016-01-01

The present work has been carried out to investigate the effect of process variables on gas holdup and develop an empirical equation and a neural network model for online process control of the gas holdup based on the operating variables. In this study, the effect of process variables (nozzle diameter, circulation pressure, aeration rate, and frother dosage) on gas holdup in a cyclone-static micro-bubble flotation column of an air/oily wastewater system was investigated. Gas holdup was estimated using a pressure difference method and an empirical equation was proposed to predict gas holdup. A general regression neural network (GRNN) model was also introduced to predict gas holdup for the cyclone-static micro-bubble flotation column. The predictions from the empirical equation and the GRNN are in good agreement with the experiment data for gas holdup, while the GRNN provides higher accuracy and stability compared with that of the empirical equation.

5. Random-Walk Monte Carlo Simulation of Intergranular Gas Bubble Nucleation in UO2 Fuel

SciTech Connect

Yongfeng Zhang; Michael R. Tonks; S. B. Biner; D.A. Andersson

2012-11-01

Using a random-walk particle algorithm, we investigate the clustering of fission gas atoms on grain bound- aries in oxide fuels. The computational algorithm implemented in this work considers a planar surface representing a grain boundary on which particles appear at a rate dictated by the Booth flux, migrate two dimensionally according to their grain boundary diffusivity, and coalesce by random encounters. Specifically, the intergranular bubble nucleation density is the key variable we investigate using a parametric study in which the temperature, grain boundary gas diffusivity, and grain boundary segregation energy are varied. The results reveal that the grain boundary bubble nucleation density can vary widely due to these three parameters, which may be an important factor in the observed variability in intergranular bubble percolation among grain boundaries in oxide fuel during fission gas release.

6. Computational modelling of the interaction of shock waves with multiple gas-filled bubbles in a liquid

Betney, M. R.; Tully, B.; Hawker, N. A.; Ventikos, Y.

2015-03-01

This study presents a computational investigation of the interactions of a single shock wave with multiple gas-filled bubbles in a liquid medium. This work illustrates how multiple bubbles may be used in shock-bubble interactions to intensify the process on a local level. A high resolution front-tracking approach is used, which enables explicit tracking of the gas-liquid interface. The collapse of two identical bubbles, one placed behind the other is investigated in detail, demonstrating that peak pressures in a two bubble arrangement can exceed those seen in single bubble collapse. Additionally, a parametric investigation into the effect of bubble separation is presented. It is found that the separation distance has a significant effect on both the shape and velocity of the main transverse jet of the second bubble. Extending this analysis to effects of relative bubble size, we show that if the first bubble is sufficiently small relative to the second, it may become entirely entrained in the second bubble main transverse jet. In contrast, if the first bubble is substantially larger than the second, it may offer it significant protection from the incident shock. This protection is utilised in the study of a triangular array of three bubbles, with the central bubble being significantly smaller than the outer bubbles. It is demonstrated that, through shielding of bubbles until later in the collapse process, pressures over five times higher than the maximum pressure observed in the single bubble case may be achieved. This corresponds to a peak pressure that is approximately 40 times more intense than the incident shock wave. This work has applications in a number of different fields, including cavitation erosion, explosives, targeted drug delivery/intensification, and shock wave lithotripsy.

7. Vapor and Gas-Bubble Growth Dynamics around Laser-Irradiated, Water-Immersed Plasmonic Nanoparticles.

PubMed

Wang, Yuliang; Zaytsev, Mikhail E; The, Hai Le; Eijkel, Jan C T; Zandvliet, Harold J W; Zhang, Xuehua; Lohse, Detlef

2017-02-28

Microbubbles produced by exposing water-immersed metallic nanoparticles to resonant light play an important role in emerging and efficient plasmonic-enhanced processes for catalytic conversion, solar energy harvesting, biomedical imaging, and cancer therapy. How do these bubbles form, and what is their gas composition? In this paper, the growth dynamics of nucleating bubbles around laser-irradiated, water-immersed Au plasmonic nanoparticles are studied to determine the exact origin of the occurrence and growth of these bubbles. The microbubbles' contact angle, footprint diameter, and radius of curvature were measured in air-equilibrated water (AEW) and degassed water (DGW) with fast imaging. Our experimental data reveals that the growth dynamics can be divided into two regimes: an initial bubble nucleation phase (regime I, < 10 ms) and, subsequently a bubble growth phase (regime II). The explosive growth in regime I is identical for AEW and DGW due to the vaporization of water. However, the slower growth in regime II is distinctly different for AEW and DGW, which is attributed to the uptake of dissolved gas expelled from the water around the hot nanoparticle. Our scaling analysis reveals that the bubble radius scales with time as R(t) ∝ t(1/6) for both AEW and DGW in the initial regime I, whereas in the later regime II it scales as R(t) ∝ t(1/3) for AEW and is constant for perfectly degassed water. These scaling relations are consistent with the experiments.

8. Growth of a gas bubble in a supersaturated and slightly compressible liquid at low Mach number

Mohammadein, S. A.; Mohamed, K. G.

2011-12-01

In this paper, the growth of a gas bubble in a supersaturated and slightly compressible liquid is discussed. The mathematical model is solved analytically by using the modified Plesset and Zwick method. The growth process is affected by: sonic speed in the liquid, polytropic exponent, diffusion coefficient, initial concentration difference, surface tension, viscosity, adjustment factor and void fraction. The famous formula of Plesset and Zwick is produced as a special case of the result at some values of the adjustment factor. Moreover, the resultant formula is implemented to the case of the growth of underwater gas bubble.

9. Champagne experiences various rhythmical bubbling regimes in a flute.

PubMed

Liger-Belair, Gérard; Tufaile, Alberto; Jeandet, Philippe; Sartorelli, José-Carlos

2006-09-20

Bubble trains are seen rising gracefully from a few points on the glass wall (called nucleation sites) whenever champagne is poured into a glass. As time passes during the gas-discharging process, the careful observation of some given bubble columns reveals that the interbubble distance may change suddenly, thus revealing different rhythmical bubbling regimes. Here, it is reported that the transitions between the different bubbling regimes of some nucleation sites during gas discharging is a process which may be ruled by a strong interaction between tiny gas pockets trapped inside the nucleation site and/or also by an interaction between the tiny bubbles just blown from the nucleation site.

10. Leak testing of bubble-tight dampers using tracer gas techniques

SciTech Connect

Lagus, P.L.; DuBois, L.J.; Fleming, K.M.

1995-02-01

Recently tracer gas techniques have been applied to the problem of measuring the leakage across an installed bubble-tight damper. A significant advantage of using a tracer gas technique is that quantitative leakage data are obtained under actual operating differential pressure conditions. Another advantage is that leakage data can be obtained using relatively simple test setups that utilize inexpensive materials without the need to tear ducts apart, fabricate expensive blank-off plates, and install test connections. Also, a tracer gas technique can be used to provide an accurate field evaluation of the performance of installed bubble-tight dampers on a periodic basis. Actual leakage flowrates were obtained at Zion Generating Station on four installed bubble-tight dampers using a tracer gas technique. Measured leakage rates ranged from 0.01 CFM to 21 CFM. After adjustment and subsequent retesting, the 21 CFM damper leakage was reduced to a leakage of 3.8 CFM. In light of the current regulatory climate and the interest in Control Room Habitability issues, imprecise estimates of critical air boundary leakage rates--such as through bubble-tight dampers--are not acceptable. These imprecise estimates can skew radioactive dose assessments as well as chemical contaminant exposure calculations. Using a tracer gas technique, the actual leakage rate can be determined. This knowledge eliminates a significant source of uncertainty in both radioactive dose and/or chemical exposure assessments.

11. Estimating Trapped Gas Concentrations as Bubbles Within Lake Ice Using Ground Penetrating Radar

Fantello, N.; Parsekian, A.; Walter Anthony, K. M.

2015-12-01

Climate warming is currently one of the most important issues that we are facing. The degradation of permafrost beneath thermokarst lakes has been associated with enhanced methane emissions and it presents a positive feedback to climate warming. Thermokarst lakes release methane to the atmosphere mainly by ebullition (bubbling) but there are a large number of uncertainties regarding the magnitude and variability of these emissions. Here we present a methodology to estimate the amount of gas released from thermokarst lakes through ebullition using ground-penetrating radar (GPR). This geophysical technique is well suited for this type of problem because it is non-invasive, continuous, and requires less effort and time than the direct visual inspection. We are studying GPR data collected using 1.2 GHz frequency antennas in Brooklyn Lake, Laramie, WY, in order to quantify the uncertainties in the method. Although this is not a thermokarst lake, gas bubbles are trapped in the ice and spatial variability in bubble concentration within the ice is evident. To assess the variability in bulk physical properties of the ice due to bubbles, we gathered GPR data from different types of ice. We compared the velocity of the groundwave and reflection obtained from radargrams, and found on each case a larger value for the groundwave velocity suggesting a non-homogeneous medium and that the concentration of bubbles is prone to be near the surface instead of at greater depths. We use a multi-phase dielectric-mixing model to estimate the amount of gas present in a sample of volume of ice and found an uncertainty in relative permittivity (estimated using reflection velocity) of 0.0294, which translates to an uncertainty of 1.1% in gas content; and employing groundwave velocity we found 0.0712 and 2.9%, respectively. If locations of gas seeps in lakes could be detected and quantified using GPR along with field measurements, this could help to constrain future lake-source carbon gas

12. In situ visualization study of CO 2 gas bubble behavior in DMFC anode flow fields

Yang, H.; Zhao, T. S.; Ye, Q.

This paper reports on a visual study of the CO 2 bubble behavior in the anode flow field of an in-house fabricated transparent Direct Methanol Fuel Cell (DMFC), which consisted of a membrane electrode assembly (MEA) with an active area of 4.0 × 4.0 cm 2, two bipolar plates with a single serpentine channel, and a transparent enclosure. The study reveals that at low current densities, small discrete bubbles appeared in the anode flow field. At moderate current densities, a number of gas slugs formed, in addition to small discrete bubbles. And at high current densities, the flow field was predominated by rather long gas slugs. The experiments also indicate that the cell orientation had a significant effect on the cell performance, especially at low methanol flow rates; for the present flow field design the best cell performance could be achieved when the cell was orientated vertically. It has been shown that higher methanol solution flow rates reduced the average length and the number of gas slugs in the flow field, but led to an increased methanol crossover. In particular, the effect of methanol solution flow rates on the cell performance became more pronounced at low temperatures. The effect of temperature on the bubble behavior and the cell performance was also examined. Furthermore, for the present flow field consisting of a single serpentine channel, the channel-blocking phenomenon caused by CO 2 gas slugs was never encountered under all the test conditions in this work.

13. The effect of gas bubbles on electrical breakdown in transformer oil

Tyuftyaev, A. S.; Gadzhiev, M. Kh; Sargsyan, M. A.; Akimov, P. L.; Demirov, N. A.

2016-11-01

To study the breakdown of transformer oil with gas bubbles an experimental setup was created that allows to determine electrical and optical properties of the discharge. Oil was sparged with air and sulfur hexafluoride gas. It was found that sparging oil with gas lowers the breakdown voltage of the oil. When a gas bubble is present between the electrodes at a considerable distance from the electrodes at first there is a spherically shape flash observed, resulting in the discharge gap overlapping by a conductive channel. These leads to discharges forming in the discharge gap with the frequency of hundreds Hz and higher. Despite the slightly lower breakdown voltage of oil sparged with sulfur hexafluoride the advantage of this medium to clean oil can serve as a two-phase medium damping properties, which may be sufficient to prevent the destruction of the body in the breakdown of oil-filled equipment.

14. Gas-Liquid flow characterization in bubble columns with various gas-liquid using electrical resistance tomography

Jin, Haibo; Yuhuan, Han; Suohe, Yang

2009-02-01

Electrical resistance tomography (ERT) is an advanced and new detecting technique that can measure and monitor the parameters of two-phase flow on line, such as gas-liquid bubble column. It is fit for the industrial process where the conductible medium serves as the disperse phase to present the key bubble flow characteristics in multi-phase medium. Radial variation of the gas holdup and mean holdups are investigated in a 0.160 m i. d. bubble column using ERT with two axial locations (Plane 1 and Plane 2). In all the experiments, air was used as the gas phase, tap water as liquid phase, and a series of experiments were done by adding KCl, ethanol, oil sodium, and glycerol to change liquid conductivity, liquid surface tension and viscosity. The superficial gas velocity was varied from 0.02 to 0.2 m/s. The effect of conductivity, surface tension, viscosity on the mean holdups and radial gas holdup distribution is discussed. The results showed that the gas holdup decrease with the increase of surface tension and increase with the increase of viscosity. Meanwhile, the settings of initial liquid conductivity slightly influence the gas holdup values, and the experimental data increases with the increase of the initial setting values in the same conditions.

15. The effect of exercise and rest duration on the generation of venous gas bubbles at altitude

NASA Technical Reports Server (NTRS)

Dervay, Joseph P.; Powell, Michael R.; Butler, Bruce; Fife, Caroline E.

2002-01-01

BACKGROUND: Decompression, as occurs with aviators and astronauts undergoing high altitude operations or with deep-sea divers returning to surface, can cause gas bubbles to form within the organism. Pressure changes to evoke bubble formation in vivo during depressurization are several orders of magnitude less than those required for gas phase formation in vitro in quiescent liquids. Preformed micronuclei acting as "seeds" have been proposed, dating back to the 1940's. These tissue gas micronuclei have been attributed to a minute gas phase located in hydrophobic cavities, surfactant-stabilized microbubbles, or arising from musculoskeletal activity. The lifetimes of these micronuclei have been presumed to be from a few minutes to several weeks. HYPOTHESIS: The greatest incidence of venous gas emboli (VGE) will be detected by precordial Doppler ultrasound with depressurization immediately following lower extremity exercise, with progressively reduced levels of VGE observed as the interval from exercise to depressurization lengthens. METHODS: In a blinded cross-over design, 20 individuals (15 men, 5 women) at sea level exercised by performing knee-bend squats (150 knee flexes over 10 min, 235-kcal x h(-1)) either at the beginning, middle, or end of a 2-h chair-rest period without an oxygen prebreathe. Seated subjects were then depressurized to 6.2 psia (6,706 m or 22,000 ft altitude equivalent) for 120 min with no exercise performed at altitude. RESULTS: Of the 20 subjects with VGE in the pulmonary artery, 10 demonstrated a greater incidence of bubbles with exercise performed just prior to depressurization, compared with decreasing bubble grades and incidence as the interval of rest increased prior to depressurization. No decompression illness was reported. CONCLUSIONS: There is a significant increase in decompression-induced bubble formation at 6.2 psia when lower extremity exercise is performed just prior to depressurization as compared with longer rest intervals

16. Steady-state composition of a two-component gas bubble growing in a liquid solution: self-similar approach.

PubMed

Gor, G Yu; Kuchma, A E

2009-12-21

The paper presents an analytical description of the growth of a two-component bubble in a binary liquid-gas solution. We obtain asymptotic self-similar time dependence of the bubble radius and analytical expressions for the nonsteady profiles of dissolved gases around the bubble. We show that the necessary condition for the self-similar regime of bubble growth is the constant, steady-state composition of the bubble. The equation for the steady-state composition is obtained. We reveal the dependence of the steady-state composition on the solubility laws of the bubble components. Besides, the universal, independent from the solubility laws, expressions for the steady-state composition are obtained for the case of strong supersaturations, which are typical for the homogeneous nucleation of a bubble.

17. Bacillus cereus panophthalmitis associated with intraocular gas bubble.

PubMed Central

al-Hemidan, A; Byrne-Rhodes, K A; Tabbara, K F

1989-01-01

It has become increasingly apparent that Bacillus cereus can cause a severe and devastating form of endophthalmitis following penetrating trauma by a metallic object. B. cereus is an uncommon aetiological agent in non-clostridial gas-forming infections. The patient studied in this single case report showed evidence of intraocular gas mimicking gas gangrene infection. The physiology of non-clostridial bacteria producing gas from anaerobic metabolic conditions is reviewed. Further intraocular and systemic complications which may be avoided by accurate and early diagnosis and the use of recommended treatment with antibiotics such as clindamycin. Images PMID:2493262

18. Relative acoustic frequency response of induced methane, carbon dioxide and air gas bubble plumes, observed laterally.

PubMed

Kubilius, Rokas; Pedersen, Geir

2016-10-01

There is an increased need to detect, identify, and monitor natural and manmade seabed gas leaks. Fisheries echosounders are well suited to monitor large volumes of water and acoustic frequency response [normalized acoustic backscatter, when a measure at one selected frequency is used as a denominator, r(f)] is commonly used to identify echoes from fish and zooplankton species. Information on gas plume r(f) would be valuable for automatic detection of subsea leaks and for separating bubble plumes from natural targets such as swimbladder-bearing fish. Controlled leaks were produced with a specially designed instrument frame suspended in mid-water in a sheltered fjord. The frame was equipped with echosounders, stereo-camera, and gas-release nozzles. The r(f) of laterally observed methane, carbon dioxide, and air plumes (0.040-29 l/min) were measured at 70, 120, 200, and 333 kHz, with bubble sizes determined optically. The observed bubble size range (1-25 mm) was comparable to that reported in the literature for natural cold seeps of methane. A negative r(f) with increasing frequency was observed, namely, r(f) of about 0.7, 0.6, and 0.5 at 120, 200, and 333 kHz when normalized to 70 kHz. Measured plume r(f) is also compared to resolved, single bubble target strength-based, and modeled r(f).

19. Numerical simulation of ultrasound-induced dynamics of a gas bubble neighboring a rigid wall

Kobayashi, Tatsuya; Ando, Keita

2016-11-01

Cavitation erosion has been a technical issue in ultrasonic cleaning under which cavitation bubbles appear near target surfaces to be cleaned. In the present study, we numerically study the interaction of ultrasonic standing waves with a gas bubble in the neighborhood of a rigid wall. We solve multicomponent Euler equations that ignore surface tension and phase change at interfaces, by the finite-volume WENO scheme with interface capturing. The pressure amplitude of the ultrasound is set at several atmospheres and the ultrasound wavelength is tuned to obtain the situation near resonance. In the simulation, we observe jetting flow toward the rigid wall at violent bubble collapse that may explain cavitation erosion in ultrasonic cleaning.

20. Thermocapillary migration of a gas bubble in an arbitrary direction with respect to a plane surface

NASA Technical Reports Server (NTRS)

Meyyappan, M.; Shankar Subramanian, R.

1987-01-01

The thermocapillary migration of a gas bubble in an unbounded fluid in the presence of a neighboring rigid plane surface is considered in the limit of negligible Reynolds and Marangoni numbers. Results are given for a scalar interaction parameter defined as the ratio of the speed of the bubble in the presence of the plane surface to the speed in its absence. It is suggested that the weaker interaction effects noted for the case of thermocapillary migration relative to the case of motion due to a body force such as that caused by a gravitational field is attributable to the more rapid decay, away from the bubble, of the disturbance velocity and temperature gradient fields. The surface is found to exert the greatest influence in the case of motion normal to it, and the weakest influence in the case of parallel motion.

1. Simulation of Interaction of Strong Shocks with Gas Bubbles using the Direct Simulation Monte Carlo Method

Puranik, Bhalchandra; Watvisave, Deepak; Bhandarkar, Upendra

2016-11-01

The interaction of a shock with a density interface is observed in several technological applications such as supersonic combustion, inertial confinement fusion, and shock-induced fragmentation of kidney and gall-stones. The central physical process in this interaction is the mechanism of the Richtmyer-Meshkov Instability (RMI). The specific situation where the density interface is initially an isolated spherical or cylindrical gas bubble presents a relatively simple geometry that exhibits all the essential RMI processes such as reflected and refracted shocks, secondary instabilities, turbulence and mixing of the species. If the incident shocks are strong, the calorically imperfect nature needs to be modelled. In the present work, we have carried out simulations of the shock-bubble interaction using the DSMC method for such situations. Specifically, an investigation of the shock-bubble interaction with diatomic gases involving rotational and vibrational excitations at high temperatures is performed, and the effects of such high temperature phenomena will be presented.

2. Catalytic microtubular jet engines self-propelled by accumulated gas bubbles.

PubMed

Solovev, Alexander A; Mei, Yongfeng; Bermúdez Ureña, Esteban; Huang, Gaoshan; Schmidt, Oliver G

2009-07-01

Strain-engineered microtubes with an inner catalytic surface serve as self-propelled microjet engines with speeds of up to approximately 2 mm s(-1) (approximately 50 body lengths per second). The motion of the microjets is caused by gas bubbles ejecting from one opening of the tube, and the velocity can be well approximated by the product of the bubble radius and the bubble ejection frequency. Trajectories of various different geometries are well visualized by long microbubble tails. If a magnetic layer is integrated into the wall of the microjet engine, we can control and localize the trajectories by applying external rotating magnetic fields. Fluid (i.e., fuel) pumping through the microtubes is revealed and directly clarifies the working principle of the catalytic microjet engines.

3. Compositional Discrimination of Decompression and Decomposition Gas Bubbles in Bycaught Seals and Dolphins

PubMed Central

Bernaldo de Quirós, Yara; Seewald, Jeffrey S.; Sylva, Sean P.; Greer, Bill; Niemeyer, Misty; Bogomolni, Andrea L.; Moore, Michael J.

2013-01-01

Gas bubbles in marine mammals entangled and drowned in gillnets have been previously described by computed tomography, gross examination and histopathology. The absence of bacteria or autolytic changes in the tissues of those animals suggested that the gas was produced peri- or post-mortem by a fast decompression, probably by quickly hauling animals entangled in the net at depth to the surface. Gas composition analysis and gas scoring are two new diagnostic tools available to distinguish gas embolisms from putrefaction gases. With this goal, these methods have been successfully applied to pathological studies of marine mammals. In this study, we characterized the flux and composition of the gas bubbles from bycaught marine mammals in anchored sink gillnets and bottom otter trawls. We compared these data with marine mammals stranded on Cape Cod, MA, USA. Fresh animals or with moderate decomposition (decomposition scores of 2 and 3) were prioritized. Results showed that bycaught animals presented with significantly higher gas scores than stranded animals. Gas composition analyses indicate that gas was formed by decompression, confirming the decompression hypothesis. PMID:24367623

4. Compositional discrimination of decompression and decomposition gas bubbles in bycaught seals and dolphins.

PubMed

Bernaldo de Quirós, Yara; Seewald, Jeffrey S; Sylva, Sean P; Greer, Bill; Niemeyer, Misty; Bogomolni, Andrea L; Moore, Michael J

2013-01-01

Gas bubbles in marine mammals entangled and drowned in gillnets have been previously described by computed tomography, gross examination and histopathology. The absence of bacteria or autolytic changes in the tissues of those animals suggested that the gas was produced peri- or post-mortem by a fast decompression, probably by quickly hauling animals entangled in the net at depth to the surface. Gas composition analysis and gas scoring are two new diagnostic tools available to distinguish gas embolisms from putrefaction gases. With this goal, these methods have been successfully applied to pathological studies of marine mammals. In this study, we characterized the flux and composition of the gas bubbles from bycaught marine mammals in anchored sink gillnets and bottom otter trawls. We compared these data with marine mammals stranded on Cape Cod, MA, USA. Fresh animals or with moderate decomposition (decomposition scores of 2 and 3) were prioritized. Results showed that bycaught animals presented with significantly higher gas scores than stranded animals. Gas composition analyses indicate that gas was formed by decompression, confirming the decompression hypothesis.

5. A Mathematical Model of Diffusion-Limited Gas Bubble Dynamics in Tissue with Varying Diffusion Region Thickness

NASA Technical Reports Server (NTRS)

Srinivasan, R. Srini; Gerth, Wayne A.; Powell, Michael R.; Paloski, William H. (Technical Monitor)

2000-01-01

A three-region mathematical model of gas bubble dynamics has been shown suitable for describing diffusion-limited dynamics of more than one bubble in a given volume of extravascular tissue. The model is based on the dynamics of gas exchange between a bubble and a well-stirred tissue region through an intervening unperfused diffusion region previously assumed to have constant thickness and uniform gas diffusivity. As a result, the gas content of the diffusion region remains constant as the volume of the region increases with bubble growth, causing dissolved gas in the region to violate Henry's law. Earlier work also neglected the relationship between the varying diffusion region volume and the fixed total tissue volume, because only cases in which the diffusion region volume is a small fraction of the overall tissue volume were considered. We herein extend the three-region model to correct these theoretical inconsistencies by allowing both the thickness and gas content of the diffusion region to vary during bubble evolution. A postulated difference in gas diffusivity between an infinitesimally thin layer at the bubble surface and the remainder of the diffusion region leads to variation in diffusion region gas content and thickness during bubble growth and resolution. This variable thickness, differential diffusivity (VTDD) model can yield bubble lifetimes considerably longer than those yielded by earlier three-region models for given model and decompression parameters, and meets a need for theoretically consistent but relatively simple bubble dynamics models for use in studies of decompression sickness (DCS) in human subjects, Keywords: decompression sickness, gas diffusion in tissue, diffusivity

6. The influence of bubble plumes on air-seawater gas transfer velocities

SciTech Connect

Asher, W.E.; Karle, L.M.; Higgins, B.J.

1995-07-01

Air-sea gas exchange is an important process in the geochemical cycling of carbon dioxide (CO{sub 2}). The air-sea flux of CO{sub 2} is determined in part by the physical forcing functions, which are parameterized in terms of the air-sea transfer velocity, k{sub L}. Past studies have attempted to correlate k{sub L} with wind speed, U. Because strong winds occur in ocean regions thought to be important sources or sinks of CO{sub 2}, accurate knowledge of k{sub L} at high U is important in estimating the global air-sea flux of CO{sub 2}. Better understanding of the physical processes affecting gas transfer at large U will increase the accuracy in estimating k{sub L} in ocean regions with high CO{sub 2}, fluxes. Increased accuracy in estimating k{sub L} will increase the accuracy in calculating the net global air-sea CO{sub 2} flux and provide more accurate boundary and initial conditions for global ocean carbon cycle models. High wind speeds are associated with the presence of whitecaps, which can increase the gas flux by generating turbulence, disrupting surface films, and creating bubble plumes. Bubble plumes will create additional turbulence, prolong the surface disruption, and transfer gas to or from individual bubbles while they are beneath the surface. These turbulence and bubble processes very effectively promote gas transfer. Because of this, it is postulated that breaking waves, if present, will dominate non-whitecap related gas exchange. Under this assumption, k{sub L} Will increase linearly with increasing fractional area whitecap coverage, W{sub c}. In support of this, researchers found k{sub L} measured in a whitecap simulation tank (WSI) was linearly correlated with bubble plume coverage, B{sub c} (the laboratory analog of W{sub c}). However, it is not definitively known how the presence of breaking waves and bubble plumes affect the dependence of k{sub L} on Schmidt number, Sc, and aqueous-phase solubility, {alpha}.

7. Gas bubbles in fossil amber as possible indicators of the major gas composition of ancient air

USGS Publications Warehouse

Berner, R.A.; Landis, G.P.

1988-01-01

Gases trapped in Miocene to Upper Cretaceous amber were released by gently crushing the amber under vacuum and were analyzed by quadrupole mass spectrometry. After discounting the possibility that the major gases N2, O2, and CO2 underwent appreciable diffusion and diagenetic exchange with their surroundings or reaction with the amber, it has been concluded that in primary bubbles (gas released during initial breakage) these gases represent mainly original ancient air modified by the aerobic respiration of microorganisms. Values of N2/(CO2+O2) for each time period give consistent results despite varying O2/CO2 ratios that presumably were due to varying degrees of respiration. This allows calculation of original oxygen concentrations, which, on the basis of these preliminary results, appear to have changed from greater than 30 percent O2 during one part ofthe Late Cretaceous (between 75 and 95 million years ago) to 21 percent during the Eocene-Oligocene and for present-day samples, with possibly lower values during the Oligocene-Early Miocene. Variable O2 levels over time in general confirm theoretical isotope-mass balance calculations and suggest that the atmosphere has evolved over Phanerozoic time.

8. Prospecting for zones of contaminated ground-water discharge to streams using bottom-sediment gas bubbles

USGS Publications Warehouse

Vroblesky, Don A.; Lorah, Michelle M.

1991-01-01

Decomposition of organic-rich bottom sediment in a tidal creek in Maryland results in production of gas bubbles in the bottom sediment during summer and fall. In areas where volatile organic contaminants discharge from ground water, through the bottom sediment, and into the creek, part of the volatile contamination diffuses into the gas bubbles and is released to the atmosphere by ebullition. Collection and analysis of gas bubbles for their volatile organic contaminant content indicate that relative concentrations of the volatile organic contaminants in the gas bubbles are substantially higher in areas where the same contaminants occur in the ground water that discharges to the streams. Analyses of the bubbles located an area of previously unknown ground-water contamination. The method developed for this study consisted of disturbing the bottom sediment to release gas bubbles, and then capturing the bubbles in a polyethylene bag at the water-column surface. The captured gas was transferred either into sealable polyethylene bags for immediate analysis with a photoionization detector or by syringe to glass tubes containing wires coated with an activated-carbon adsorbent. Relative concentrations were determined by mass spectral analysis for chloroform and trichloroethylene.

9. Transmission electron microscopy characterization of the fission gas bubble superlattice in irradiated U-7 wt%Mo dispersion fuels

Miller, B. D.; Gan, J.; Keiser, D. D.; Robinson, A. B.; Jue, J. F.; Madden, J. W.; Medvedev, P. G.

2015-03-01

Transmission electron microscopy characterization of irradiated U-7 wt%Mo dispersion fuel were performed on various U-Mo fuel samples to understand the effect of irradiation parameters (fission density, fission rate, and temperature) on the self-organized fission-gas-bubble superlattice that forms in the irradiated U-Mo fuel. The bubble superlattice was seen to form a face centered cubic structure coherent with the host U-7 wt%Mo body-centered cubic structure. At a fission density between 3.0 and 4.5 × 1021 fiss/cm3, the superlattice bubbles appear to have reached a saturation size with additional fission gas associated with increasing burnup predominately accumulating along grain boundaries. At a fission density of ∼4.5 × 1021 fiss/cm3, the U-7 wt%Mo microstructure starts to undergo grain subdivision and can no longer support the ordered bubble superlattice. The sub-divided fuel grains are less than 500 nm in diameter with what appears to be micron-size fission-gas bubbles present on the grain boundaries. Solid fission products typically decorate the inside surface of the micron-sized fission-gas bubbles. Residual superlattice bubbles are seen in areas where fuel grains remain micron sized. Potential mechanisms of the formation and collapse of the bubble superlattice are discussed.

10. Transmission electron microscopy characterization of the fission gas bubble superlattice in irradiated U-7wt% Mo dispersion fuels

SciTech Connect

B.D. Miller; J. Gan; D.D. Keiser Jr.; A.B. Robinson; J.-F. Jue; J.W. Madden; P.G. Medvedev

2015-03-01

Transmission electron microscopy characterization of irradiated U-7wt% Mo dispersion fuel was performed on various samples to understand the effect of irradiation parameters (fission density, fission rate, and temperature) on the self-organized fission-gas-bubble superlattice that forms in the irradiated U-Mo fuel. The bubble superlattice was seen to form a face-centered cubic structure coherent with the host U-7wt% Mo body centered cubic structure. At a fission density between 3.0 and 4.5 x 1021 fiss/cm3, the superlattice bubbles appear to have reached a saturation size with additional fission gas associated with increasing burnup predominately accumulating along grain boundaries. At a fission density of ~4.5x1021 fiss/cm3, the U-7wt% Mo microstructure undergoes grain subdivision and can no longer support the ordered bubble superlattice. The fuel grains are primarily less than 500 nm in diameter with micron-size fission-gas bubbles present on the grain boundaries. Solid fission products decorate the inside surface of the micron-sized fission-gas bubbles. Residual superlattice bubbles are seen in areas where fuel grains remain micron sized. Potential mechanisms of the formation and collapse of the bubble superlattice are discussed.

11. Lagrangian coherent structures analysis of gas-liquid flow in a bubble column

Wu, Qin; Wang, GuoYu; Huang, Biao; Bai, ZeYu

2014-06-01

The objective of this paper is to apply a new identifying method to investigating the gas-liquid two-phase flow behaviors in a bubble column with air injected into water. In the numerical simulations, the standard k- ɛ turbulence model is employed to describe the turbulence phenomenon occurring in the continuous fluid. The Finite-Time Lyapunov Exponent (FTLE) and Lagrangian Coherent Structures (LCS) are applied to analyze the vortex structures in multiphase flow. Reasonable agreements are obtained between the numerical and experimental data. The numerical results show that the evolution of gas-liquid in the column includes initial and periodical developing stages. During the initial stage, the bubble hose is forming and extending along the vertical direction with the vortex structures formed symmetrically. During the periodical developing stage, the bubble hose starts to oscillate periodically, and the vortexes move along the bubble hose to the bottom of column alternately. Compared to the Euler-system-based identification criterion of a vortex, the FTLE field presents the boundary of a vortex without any threshold defined and the LCS represents the divergence extent of infinite neighboring particles. During the initial stage, the interfaces between the forward and backward flows are highlighted by the LCS. As for the periodical developing stage, the LCS curls near the vortex centers, providing a method of analyzing a flow field from a dynamical system perspective.

12. Effect of surfactants on gas holdup of two-phase bubble columns

SciTech Connect

Estevez, L.A. ); Saez, E.; Pachino, J.; Cavicchioli, I. )

1988-01-01

Two-phase experiments have been carried out using organic liquids with a surfactant and air in a bubble column 30 (cm) inside diameter and 3 (m) tall. Under the presence of the surfactant, two distinct regions are observed: a bubbling region is the lower part, and a froth zone in the upper part of the column. Intrinsic gas holdups were measured in each region. Results showed that intrinsic gas holdup did not change significantly with surfactant concentration. However, the position of the limiting surface separating the two regions varied considerably with surfactant concentration, thus affecting strongly the overall gas holdup. Based on the described experimental observations, correlations for intrinsic and overall gas holdups have been proposed. Intrinsic gas holdups have been correlated and a function of gas and liquid superficial velocities, and not as functions of surfactant concentration. Overall gas holdups have been expressed in terms of intrinsic gas holdup and of the fraction PHI of the column that is occupied by the froth region. The variable PHI is the one that has been correlated in terms of the surfactant concentration.

13. Gas bubble retention and its effect on waste properties: Retention mechanisms, viscosity, and tensile and shear strengths

SciTech Connect

Gauglitz, P.A.; Rassat, S.D.; Powell, M.R.

1995-08-01

Several of the underground nuclear storage tanks at Hanford have been placed on a flammable gas watch list, because the waste is either known or suspected to generate, store, and episodically release flammable gases. Because retention and episodic release of flammable gases from these tanks containing radioactive waste slurries are critical safety concerns, Pacific Northwest Laboratory (PNL) is studying physical mechanisms and waste properties that contribute to the episodic gas release from these storage tanks. This study is being conducted for Westinghouse Hanford Company as part of the PNL Flammable Gas project. Previous investigations have concluded that gas bubbles are retained by the slurry or sludge that has settled at the bottom of the tanks; however, the mechanisms responsible for the retention of these bubbles are not well understood. Understanding the rheological behavior of the waste, particularly of the settled sludge, is critical to characterizing the tendency of the waste to retain gas bubbles and the dynamics of how these bubbles are released from the waste. The presence of gas bubbles is expected to affect the rheology of the sludge, specifically its viscosity and tensile and shear strengths, but essentially no literature data are available to assess the effect of bubbles. The objectives of this study were to conduct experiments and develop theories to understand better how bubbles are retained by slurries and sludges, to measure the effect of gas bubbles on the viscosity of simulated slurries, and to measure the effect of gas bubbles on the tensile and shear strengths of simulated slurries and sludges. In addition to accomplishing these objectives, this study developed correlations, based on the new experimental data, that can be used in large-scale computations of waste tank physical phenomena.

14. Gas Bubble Trauma Monitoring and Research of Juvenile Salmonids, 1994-1995 Progress Report.

SciTech Connect

Hans, Karen M.

1997-07-01

This report describes laboratory and field monitoring studies of gas bubble trauma (GBT) in migrating juvenile salmonids in the Snake and Columbia rivers. The first chapter describes laboratory studies of the progression of GBT signs leading to mortality and the use of the signs for GBT assessment. The progression and severity of GBT signs in juvenile salmonids exposed to different levels of total dissolved gas (TDG) and temperatures was assessed and quantified. Next, the prevalence, severity, and individual variation of GBT signs was evaluated to attempt to relate them to mortality. Finally, methods for gill examination in fish exposed to high TDG were developed and evaluated. Primary findings were: (1) no single sign of GBT was clearly correlated with mortality, but many GBT signs progressively worsened; (2) both prevalence and severity of GBT signs in several tissues is necessary; (3) bubbles in the lateral line were the earliest sign of GBT, showed progressive worsening, and had low individual variation but may develop poorly during chronic exposures; (4) fin bubbles had high prevalence, progressively worsened, and may be a persistent sign of GBT; and (5) gill bubbles appear to be the proximate cause of death but may only be relevant at high TDG levels and are difficult to examine. Chapter Two describes monitoring results of juvenile salmonids for signs of GBT. Emigrating fish were collected and examined for bubbles in fins and lateral lines. Preliminary findings were: (1) few fish had signs of GBT, but prevalence and severity appeared to increase as fish migrated downstream; (2) there was no apparent correlation between GBT signs in the fins, lateral line, or gills; (3) prevalence and severity of GBT was suggestive of long-term, non-lethal exposure to relatively low level gas supersaturated water; and (4) it appeared that GBT was not a threat to migrating juvenile salmonids. 24 refs., 26 figs., 3 tabs.

15. Bubbles Quantified In vivo by Ultrasound Relates to Amount of Gas Detected Post-mortem in Rabbits Decompressed from High Pressure

PubMed Central

Bernaldo de Quirós, Yara; Møllerløkken, Andreas; Havnes, Marianne B.; Brubakk, Alf O.; González-Díaz, Oscar; Fernández, Antonio

2016-01-01

The pathophysiological mechanism of decompression sickness is not fully understood but there is evidence that it can be caused by intravascular and autochthonous bubbles. Doppler ultrasound at a given circulatory location is used to detect and quantify the presence of intravascular gas bubbles as an indicator of decompression stress. In this manuscript we studied the relationship between presence and quantity of gas bubbles by echosonography of the pulmonary artery of anesthetized, air-breathing New Zealand White rabbits that were compressed and decompressed. Mortality rate, presence, quantity, and distribution of gas bubbles elsewhere in the body was examined postmortem. We found a strong positive relationship between high ultrasound bubble grades in the pulmonary artery, sudden death, and high amount of intra and extra vascular gas bubbles widespread throughout the entire organism. In contrast, animals with lower bubble grades survived for 1 h after decompression until sacrificed, and showed no gas bubbles during dissection. PMID:27493634

16. Entrapment of Hydrate-coated Gas Bubbles into Oil and Separation of Gas and Hydrate-film; Seafloor Experiments with ROV

Hiruta, A.; Matsumoto, R.

2015-12-01

We trapped gas bubbles emitted from the seafloor into oil-containing collector and observed an unique phenomena. Gas hydrate formation needs water for the crystal lattice; however, gas hydrates in some areas are associated with hydrophobic crude oil or asphalt. In order to understand gas hydrate growth in oil-bearing sediments, an experiment with cooking oil was made at gas hydrate stability condition. We collected venting gas bubbles into a collector with canola oil during ROV survey at a gas hydrate area in the eastern margin of the Sea of Japan. When the gas bubbles were trapped into collector with oil, gas phase appeared above the oil and gas hydrates, between oil and gas phase. At this study area within gas hydrate stability condition, control experiment with oil-free collector suggested that gas bubbles emitted from the seafloor were quickly covered with gas hydrate film. Therefore it is improbable that gas bubbles entered into the oil phase before hydrate skin formation. After the gas phase formation in oil-containing collector, the ROV floated outside of hydrate stability condition for gas hydrate dissociation and re-dived to the venting site. During the re-dive within hydrate stability condition, gas hydrate was not formed. The result suggests that moisture in the oil is not enough for hydrate formation. Therefore gas hydrates that appeared at the oil/gas phase boundary were already formed before bubbles enter into the oil. Hydrate film is the only possible origin. This observation suggests that hydrate film coating gas hydrate was broken at the sea water/oil boundary or inside oil. Further experiments may contribute for revealing kinetics of hydrate film and formation. This work was a part of METI (Ministry of Economy, Trade and Industry)'s project entitled "FY2014 Promoting research and development of methane hydrate". We also appreciate support of AIST (National Institute of Advanced Industrial Science and Technology).

17. Burst of Star Formation Drives Galactic Bubble

NASA Technical Reports Server (NTRS)

2001-01-01

NASA's Hubble Space Telescope (HST) captures a lumpy bubble of hot gas rising from a cauldron of glowing matter in Galaxy NGC 3079, located 50 million light-years from Earth in the constellation Ursa Major. Astronomers suspect the bubble is being blown by 'winds' or high speed streams of particles, released during a burst of star formation. The bubble's lumpy surface has four columns of gaseous filaments towering above the galaxy's disc that whirl around in a vortex and are expelled into space. Eventually, this gas will rain down on the disc and may collide with gas clouds, compress them, and form a new generation of stars.

18. Molecular gas and star formation toward the IR dust bubble S 24 and its environs

Cappa, C. E.; Duronea, N.; Firpo, V.; Vasquez, J.; López-Caraballo, C. H.; Rubio, M.; Vazzano, M. M.

2016-01-01

Aims: We present a multiwavelength analysis of the infrared dust bubble S 24 and the extended IR sources G341.220-0.213 and G341.217-0.237 located in its environs. We aim to investigate the characteristics of the molecular gas and the interstellar dust linked to them and analyze the evolutionary state of the young stellar objects identified there and the relation of the bubble to S 24 and the IR sources. Methods: Using the APEX telescope, we mapped the molecular emission in the CO(2-1), 13CO(2-1), C18O(2-1), and 13CO(3-2) lines in a region of about 5' × 5' in size around the bubble. The cold dust distribution was analyzed using submillimeter continuum images from ATLASGAL and Herschel. Complementary IR and radio data at different wavelengths were used to complete the study of the interstellar medium in the region. Results: The molecular gas distribution shows that gas linked to the S 24 bubble and to G341.220-0.213 and G341.217-0.237 has velocities of between -48.0 km s-1 and -40.0 km s-1, compatible with the kinematical distance of 3.7 kpc that is generally adopted for the region. The gas distribution reveals a shell-like molecular structure of ~0.8 pc in radius bordering the S 24 bubble. A cold dust counterpart of the shell is detected in the LABOCA and Herschel-SPIRE images. The weak extended emission at 24 μm from warm dust and radio continuum emission projected inside the bubble indicates exciting sources and that the bubble is a compact HII region. Part of the molecular gas bordering the S 24 HII region coincides with the extended infrared dust cloud SDC341.194-0.221. A molecular and cold dust clump is present at the interface between the S 24 HII region and G341.217-0.237, shaping the eastern border of the IR bubble. The arc-like molecular structure encircling the northern and eastern sections of the IR source G341.220-0.213 indicates that the source is interacting with the molecular gas. The analysis of the available IR point source catalogs reveals some

19. Thermal stability of fission gas bubble superlattice in irradiated U–10Mo fuel

SciTech Connect

Gan, J.; Keiser, D. D.; Miller, B. D.; Robinson, A. B.; Wachs, D. M.; Meyer, M. K.

2015-09-01

To investigate the thermal stability of the fission gas bubble superlattice, a key microstructural feature in both irradiated U-7Mo dispersion and U-10Mo monolithic fuel plates, a FIB-TEM sample of the irradiated U-10Mo fuel with a local fission density of 3.5×1021 fissions/cm3 was used for an in-situ heating TEM experiment. The temperature of the heating holder was raised at a ramp rate of approximately 10 ºC/min up to ~700 ºC, kept at that temperature for about 34 min, continued to 850 ºC with a reduced rate of 5 ºC/min. The result shows a high thermal stability of the fission gas bubble superlattice. The implication of this observation on the fuel microstructural evolution and performance under irradiation is discussed.

20. Fission gas bubble identification using MATLAB's image processing toolbox

DOE PAGES

Collette, R.; King, J.; Keiser, Jr., D.; ...

2016-06-08

Automated image processing routines have the potential to aid in the fuel performance evaluation process by eliminating bias in human judgment that may vary from person-to-person or sample-to-sample. In addition, this study presents several MATLAB based image analysis routines designed for fission gas void identification in post-irradiation examination of uranium molybdenum (U–Mo) monolithic-type plate fuels. Frequency domain filtration, enlisted as a pre-processing technique, can eliminate artifacts from the image without compromising the critical features of interest. This process is coupled with a bilateral filter, an edge-preserving noise removal technique aimed at preparing the image for optimal segmentation. Adaptive thresholding provedmore » to be the most consistent gray-level feature segmentation technique for U–Mo fuel microstructures. The Sauvola adaptive threshold technique segments the image based on histogram weighting factors in stable contrast regions and local statistics in variable contrast regions. Once all processing is complete, the algorithm outputs the total fission gas void count, the mean void size, and the average porosity. The final results demonstrate an ability to extract fission gas void morphological data faster, more consistently, and at least as accurately as manual segmentation methods.« less

1. Fission gas bubble identification using MATLAB's image processing toolbox

SciTech Connect

Collette, R.; King, J.; Keiser, Jr., D.; Miller, B.; Madden, J.; Schulthess, J.

2016-06-08

Automated image processing routines have the potential to aid in the fuel performance evaluation process by eliminating bias in human judgment that may vary from person-to-person or sample-to-sample. In addition, this study presents several MATLAB based image analysis routines designed for fission gas void identification in post-irradiation examination of uranium molybdenum (U–Mo) monolithic-type plate fuels. Frequency domain filtration, enlisted as a pre-processing technique, can eliminate artifacts from the image without compromising the critical features of interest. This process is coupled with a bilateral filter, an edge-preserving noise removal technique aimed at preparing the image for optimal segmentation. Adaptive thresholding proved to be the most consistent gray-level feature segmentation technique for U–Mo fuel microstructures. The Sauvola adaptive threshold technique segments the image based on histogram weighting factors in stable contrast regions and local statistics in variable contrast regions. Once all processing is complete, the algorithm outputs the total fission gas void count, the mean void size, and the average porosity. The final results demonstrate an ability to extract fission gas void morphological data faster, more consistently, and at least as accurately as manual segmentation methods.

2. Photosynthesis as a Possible Source of Gas Bubbles in Shallow Sandy Coastal Sediments

DTIC Science & Technology

2010-09-30

gas bubbles can be formed when photosynthesis by benthic microalgae causes pore water to become supersaturated with oxygen. OBJECTIVES The...acoustic reflectivity. We also collected sediment samples from the upper few mm of sand to identify the dominant taxa of benthic microalgae present... microalgae in the samples. Following the untimely death of Dr. D.V. Holliday, the remaining team members are sharing the responsibility of analyzing data and

3. Photosynthesis as a Possible Source of Gas Bubbles in Shallow Sandy Coastal Sediments

DTIC Science & Technology

2012-09-30

clearly demonstrates that gas bubbles can be formed when photosynthesis by benthic microalgae causes pore water to become supersaturated with oxygen...We also collected sediment samples from the upper few mm of sand to identify the dominant taxa of benthic microalgae present. Although benthic...Jan Rines (Graduate School of Oceanography / University of Rhode Island = GSO/URI) to identify the benthic microalgae in the samples. Following the

4. The role of sediment structure in gas bubble storage and release

Liu, L.; Wilkinson, J.; Koca, K.; Buchmann, C.; Lorke, A.

2016-07-01

Ebullition is an important pathway for methane emission from inland waters. However, the mechanisms controlling methane bubble formation and release in aquatic sediments remain unclear. A laboratory incubation experiment was conducted to investigate the dynamics of methane bubble formation, storage, and release in response to hydrostatic head drops in three different types of natural sediment. Homogenized clayey, silty, and sandy sediments (initially quasi-uniform through the depth of the columns) were incubated in chambers for 3 weeks. We observed three distinct stages of methane bubble formation and release: stage I—microbubble formation-displacing mobile water from sediment pores with negligible ebullition; stage II—formation of large bubbles, displacing the surrounding sediment with concurrent increase in ebullition; and stage III—formation of conduits with relatively steady ebullition. The maximum depth-averaged volumetric gas content at steady state varied from 18.8% in clayey to 12.0% in silty and 13.2% in sandy sediment. Gas storage in the sediment columns showed strong vertical stratification: most of the free gas was stored in an upper layer, whose thickness varied with sediment grain size. The magnitude of individual ebullition episodes was linearly correlated to hydrostatic head drop and decreased from clayey to sandy to silty sediment and was in excess of that estimated from gas expansion alone, indicating the release of pore water methane. These findings combined with a hydrodynamic model capable of determining dominant sediment type and depositional zones could help resolve spatial heterogeneities in methane ebullition at medium to larger scales in inland waters.

5. Changes in Gas Bubble Disease Signs for Migrating Juvenile Salmonids Experimentally Exposed to Supersaturated Gasses, 1996-1997 Progress Report.

SciTech Connect

Absolon, Randall F.

1999-03-01

This study was designed to answer the question of whether gas bubble disease (GBD) signs change as a result of the hydrostatic conditions juvenile salmonids encounter when they enter the turbine intake of hydroelectric projects during their downstream migration.

6. Marangoni effect visualized in two-dimensions Optical tweezers for gas bubbles

PubMed Central

Miniewicz, A.; Bartkiewicz, S.; Orlikowska, H.; Dradrach, K.

2016-01-01

In the report we demonstrate how, using laser light, effectively trap gas bubbles and transport them through a liquid phase to a desired destination by shifting the laser beam position. The physics underlying the effect is complex but quite general as it comes from the limited to two-dimension, well-known, Marangoni effect. The experimental microscope-based system consists of a thin layer of liquid placed between two glass plates containing a dye dissolved in a solvent and a laser light beam that is strongly absorbed by the dye. This point-like heat source locally changes surface tension of nearby liquid-air interface. Because of temperature gradients a photo-triggered Marangoni flows are induced leading to self-amplification of the effect and formation of large-scale whirls. The interface is bending toward beam position allowing formation of a gas bubble upon suitable beam steering. Using various techniques (employing luminescent particles or liquid crystals), we visualize liquid flows propelled by the tangential to interface forces. This helped us to understand the physics of the phenomenon and analyze accompanying effects leading to gas bubble trapping. The manipulation of sessile droplets moving on the glass surface induced via controlled with laser light interface bending (i.e. “droplet catapult”) is demonstrated as well. PMID:27713512

7. Marangoni effect visualized in two-dimensions Optical tweezers for gas bubbles

Miniewicz, A.; Bartkiewicz, S.; Orlikowska, H.; Dradrach, K.

2016-10-01

In the report we demonstrate how, using laser light, effectively trap gas bubbles and transport them through a liquid phase to a desired destination by shifting the laser beam position. The physics underlying the effect is complex but quite general as it comes from the limited to two-dimension, well-known, Marangoni effect. The experimental microscope-based system consists of a thin layer of liquid placed between two glass plates containing a dye dissolved in a solvent and a laser light beam that is strongly absorbed by the dye. This point-like heat source locally changes surface tension of nearby liquid-air interface. Because of temperature gradients a photo-triggered Marangoni flows are induced leading to self-amplification of the effect and formation of large-scale whirls. The interface is bending toward beam position allowing formation of a gas bubble upon suitable beam steering. Using various techniques (employing luminescent particles or liquid crystals), we visualize liquid flows propelled by the tangential to interface forces. This helped us to understand the physics of the phenomenon and analyze accompanying effects leading to gas bubble trapping. The manipulation of sessile droplets moving on the glass surface induced via controlled with laser light interface bending (i.e. “droplet catapult”) is demonstrated as well.

8. Marangoni effect visualized in two-dimensions Optical tweezers for gas bubbles.

PubMed

Miniewicz, A; Bartkiewicz, S; Orlikowska, H; Dradrach, K

2016-10-07

In the report we demonstrate how, using laser light, effectively trap gas bubbles and transport them through a liquid phase to a desired destination by shifting the laser beam position. The physics underlying the effect is complex but quite general as it comes from the limited to two-dimension, well-known, Marangoni effect. The experimental microscope-based system consists of a thin layer of liquid placed between two glass plates containing a dye dissolved in a solvent and a laser light beam that is strongly absorbed by the dye. This point-like heat source locally changes surface tension of nearby liquid-air interface. Because of temperature gradients a photo-triggered Marangoni flows are induced leading to self-amplification of the effect and formation of large-scale whirls. The interface is bending toward beam position allowing formation of a gas bubble upon suitable beam steering. Using various techniques (employing luminescent particles or liquid crystals), we visualize liquid flows propelled by the tangential to interface forces. This helped us to understand the physics of the phenomenon and analyze accompanying effects leading to gas bubble trapping. The manipulation of sessile droplets moving on the glass surface induced via controlled with laser light interface bending (i.e. "droplet catapult") is demonstrated as well.

9. Warm Pressurant Gas Effects on the Static Bubble Point Pressure for Cryogenic LADs

NASA Technical Reports Server (NTRS)

Hartwig, Jason W.; McQuillen, John; Chato, Daniel J.

2014-01-01

This paper presents experimental results for the liquid hydrogen and nitrogen bubble point tests using warm pressurant gases conducted at the NASA Glenn Research Center. The purpose of the test series was to determine the effect of elevating the temperature of the pressurant gas on the performance of a liquid acquisition device (LAD). Three fine mesh screen samples (325x2300, 450x2750, 510x3600) were tested in liquid hydrogen and liquid nitrogen using cold and warm non-condensable (gaseous helium) and condensable (gaseous hydrogen or nitrogen) pressurization schemes. Gases were conditioned from 0K - 90K above the liquid temperature. Results clearly indicate degradation in bubble point pressure using warm gas, with a greater reduction in performance using condensable over non-condensable pressurization. Degradation in the bubble point pressure is inversely proportional to screen porosity, as the coarsest mesh demonstrated the highest degradation. Results here have implication on both pressurization and LAD system design for all future cryogenic propulsion systems. A detailed review of historical heated gas tests is also presented for comparison to current results.

10. Warm Pressurant Gas Effects on the Bubble Point Pressure for Cryogenic LADs

NASA Technical Reports Server (NTRS)

Hartwig, Jason W.; McQuillen, John B.; Chato, David J.

2014-01-01

This paper presents experimental results for the liquid hydrogen and nitrogen bubble point tests using warm pressurant gases conducted at the NASA Glenn Research Center. The purpose of the test series was to determine the effect of elevating the temperature of the pressurant gas on the performance of a liquid acquisition device (LAD). Three fine mesh screen samples (325x2300, 450x2750, 510x3600) were tested in liquid hydrogen and liquid nitrogen using cold and warm non-condensable (gaseous helium) and condensable (gaseous hydrogen or nitrogen) pressurization schemes. Gases were conditioned from 0K 90K above the liquid temperature. Results clearly indicate degradation in bubble point pressure using warm gas, with a greater reduction in performance using condensable over non-condensable pressurization. Degradation in the bubble point pressure is inversely proportional to screen porosity, as the coarsest mesh demonstrated the highest degradation. Results here have implication on both pressurization and LAD system design for all future cryogenic propulsion systems. A detailed review of historical heated gas tests is also presented for comparison to current results.

11. Gas Bubbles in the Bone: A Case Report.

PubMed

Abbasi, Bita; Seilanian-Toosi, Farrokh; Nekooei, Sirous; Kakhki, Behrang Rezvani; Akhavan, Reza

2016-07-01

Intraosseous pneumatocysts are benign gas-filled cavities within bones which are most commonly found in ilium, sacrum and vertebrae. The lesions are asymptomatic and found incidentally while evaluating for other injuries. Here, we present an intraosseous pneumatocyst of ilium in a 23-year-old male patient. Although once thought to be rare, intraossseous pneumatocyst are now believed to be more common. Thus, familiarity with their appearance is essential to avoid unnecessary workup. Intraosseous pneumatocysts are differentiated from more clinically significant differential diagnoses like osteonecrosis and osteomyelitis by their characteristic appearance of intraosseous air collections with sclerotic rim.

12. Gas Bubbles in the Bone: A Case Report

PubMed Central

Abbasi, Bita; Seilanian-Toosi, Farrokh; Nekooei, Sirous; Kakhki, Behrang Rezvani

2016-01-01

Intraosseous pneumatocysts are benign gas-filled cavities within bones which are most commonly found in ilium, sacrum and vertebrae. The lesions are asymptomatic and found incidentally while evaluating for other injuries. Here, we present an intraosseous pneumatocyst of ilium in a 23-year-old male patient. Although once thought to be rare, intraossseous pneumatocyst are now believed to be more common. Thus, familiarity with their appearance is essential to avoid unnecessary workup. Intraosseous pneumatocysts are differentiated from more clinically significant differential diagnoses like osteonecrosis and osteomyelitis by their characteristic appearance of intraosseous air collections with sclerotic rim. PMID:27630918

13. Buoyancy Driven Shear Flows of Bubble Suspensions

Hill, R. J.; Zenit, R.; Chellppannair, T.; Koch, D. L.; Spelt, P. D. M.; Sangani, A.

1998-11-01

In this work the gas volume fraction and the root-mean-squared fluid velocity are measured in buoyancy driven shear flows of bubble suspensions in a tall, inclined, rectangular channel. The experiments are performed under conditions where We << 1 and Re >> 1 , so that the bubbles are relatively undeformed and the flow is inviscid and approximately irrotational. Nitrogen is introduced through an array of capillaries at the base of a .2x.02x2 m channel filled with an aqueous electrolyte solution (0.06 molL-1 MgSO_4). The rising bubbles generate a unidirectional shear flow, where the denser suspension at the lower surface of the channel falls, while the less dense suspension at the upper surface rises. Hot-film anemometry is used to measure the resulting gas volume fraction and fluid velocity profiles. The bubble collision rate with the sensor is related to the gas volume fraction and the mean and variance of the bubble velocity using an experimentally measured collision surface area for the sensor. Bubble collisions with the sensor are identified by the characteristic slope of the hot-film anemometer signal when bubbles collide with the sensor. It is observed that the steady shear flow develops a bubble phase pressure gradient across the channel gap as the bubbles interchange momentum through direct collisions. The discrete phase presssure gradient balances the buoyancy force driving bubbles toward the upper surface resulting in a steady void fraction profile across the gap width. The strength of the shear flow is controlled by the extent of bubble segregation and by the effective viscosity of the bubble phase. The measurements are compared with solutions of the averaged equations of motion (Kang et al. 1997; Spelt and Sangani, 1998), for a range of gas volume fractions and channel inclination angles.

14. Acoustical scattering cross section of gas bubbles under dual-frequency acoustic excitation.

PubMed

Zhang, Yuning; Li, Shengcai

2015-09-01

The acoustical scattering cross section is a paramount parameter determining the scattering ability of cavitation bubbles when they are excited by the incident acoustic waves. This parameter is strongly related with many important applications of acoustic cavitation including facilitating the reaction of chemical process, boosting bubble sonoluminescence, and performing non-invasive therapy and drug delivery. In present paper, both the analytical and numerical solutions of acoustical scattering cross section of gas bubbles under dual-frequency excitation are obtained. The validity of the analytical solution is shown with demonstrating examples. The nonlinear characteristics (e.g., harmonics, subharmonics and ultraharmonics) of the scattering cross section curve under dual-frequency approach are investigated. Compared with single-frequency approach, the dual-frequency approach displays more resonances termed as "combination resonances" and could promote the acoustical scattering cross section significantly within a much broader range of bubble sizes due to the generation of more resonances. The influence of several paramount parameters (e.g., acoustic pressure amplitude, power allocations between two acoustic components, and the ratio of the frequencies) in the dual-frequency system on the predictions of scattering cross section has been discussed.

15. Intense gas bubble emissions in the Kerch seep area - A newly discovered high-flux seep site in the Black Sea

Römer, M.; Sahling, H.; Pape, T.; Bahr, A.; Feseker, T.; Wintersteller, P.; Bohrmann, G.

2012-04-01

More than 500 bubble-induced hydroacoustic anomalies (flares) were found in the water column above the seafloor in the study area comprising about 430 km2 at the Don-Kuban paleo-fan (Eastern Black Sea) by using ship mounted single beam and multibeam echosounders. Almost all flares originated from the seafloor above the gas hydrate stability zone (GHSZ), which in that region is located below ~700 m water depth. This observation confirms the sealing mechanism of gas hydrate, which impedes migration of free gas through the GHSZ and subsequent bubble emission from the seafloor. However, an intense seep site, called the "Kerch seep area" was discovered as an exception at 890 m water depth well within the GHSZ. In situ temperature measurements in shallow sediments indicate locally elevated temperatures probably caused by enhanced upward fluid flow. The base of the GHSZ in this region is generally situated at about 150 m below the seafloor. However, the local thermal anomalies result in a thinning of the gas hydrate occurrence zone to only a few meters below the seafloor and allow free gas to reach the seafloor. At sites where gas migrated into near-surface deposits, shallow gas hydrate deposits evolved and up-doming of overlying sediments led to the formation of mounds rising several meters from the surrounding seafloor. Further gas bubbles ascending from greater depth are accumulated below the gas hydrate layer at the base of the mound structures and migrate horizontally to their rims. At the mound edges gas bubbles either might form fresh gas hydrates and increase the extent of the mound structures by pushing up overlying sediments or escape at several sites into the water column. Two mounds were mapped in ultra-high resolution during dives with the autonomous underwater vehicle 'AUV MARUM SEAL 5000'. Several individual flares were detected in the Kerch seep area using hydroacoustic systems. Repeated surveys in that area conducted during three cruises within four years

16. Helium gas bubble trapped in liquid helium in high magnetic field

SciTech Connect

Bai, H. Hannahs, S. T.; Markiewicz, W. D.; Weijers, H. W.

2014-03-31

High magnetic field magnets are used widely in the area of the condensed matter physics, material science, chemistry, geochemistry, and biology at the National High Magnetic Field Laboratory. New high field magnets of state-of-the-art are being pursued and developed at the lab, such as the current developing 32 T, 32 mm bore fully superconducting magnet. Liquid Helium (LHe) is used as the coolant for superconducting magnets or samples tested in a high magnetic field. When the magnetic field reaches a relatively high value the boil-off helium gas bubble generated by heat losses in the cryostat can be trapped in the LHe bath in the region where BzdBz/dz is less than negative 2100 T{sup 2}/m, instead of floating up to the top of LHe. Then the magnet or sample in the trapped bubble region may lose efficient cooling. In the development of the 32 T magnet, a prototype Yttrium Barium Copper Oxide coil of 6 double pancakes with an inner diameter of 40 mm and an outer diameter of 140 mm was fabricated and tested in a resistive magnet providing a background field of 15 T. The trapped gas bubble was observed in the tests when the prototype coil was ramped up to 7.5 T at a current of 200 A. This letter reports the test results on the trapped gas bubble and the comparison with the analytical results which shows they are in a good agreement.

17. Sinking Bubbles

Koch, Jeremy; Ewoldt, Randy

2016-11-01

Intuition tells us that bubbles will rise and steel objects will sink in liquids, though here we describe the opposite. With experimental demonstration and theoretical rationale, we describe how the motion of containers of liquid with immersed solid objects and air bubbles can cause curious behaviors: sinking bubbles and rising high-density particles. Bubbles and solid spheres of diameter on the order of a few millimeters are introduced into fluids with different rheological constitutive behaviors. Imposed motion of the rigid container allows for control of the trajectories of the immersed particles - without the container imparting direct shearing motion on the fluid. Results demonstrate the necessary conditions to prevent or produce net motion of the bubbles and heavy particles, both with and against gravitational expectations.

18. The Answer to Rising Gas Prices...Nitrogen?

ERIC Educational Resources Information Center

Lee, Frank; Batelaan, Herman

2010-01-01

It is claimed by the company NitroFill and the GetNitrogen Institute that filling car tires with nitrogen improves gas mileage considerably. The reason given is that oxygen leaks out of tires so that the increased rolling friction causes a reduced gas mileage. Because it is hard to do an actual road test, we report on a simple visual test of…

19. Kinetics of CH4 and CO2 hydrate dissociation and gas bubble evolution via MD simulation.

PubMed

Uddin, M; Coombe, D

2014-03-20

Molecular dynamics simulations of gas hydrate dissociation comparing the behavior of CH4 and CO2 hydrates are presented. These simulations were based on a structurally correct theoretical gas hydrate crystal, coexisting with water. The MD system was first initialized and stabilized via a thorough energy minimization, constant volume-temperature ensemble and constant volume-energy ensemble simulations before proceeding to constant pressure-temperature simulations for targeted dissociation pressure and temperature responses. Gas bubble evolution mechanisms are demonstrated as well as key investigative properties such as system volume, density, energy, mean square displacements of the guest molecules, radial distribution functions, H2O order parameter, and statistics of hydrogen bonds. These simulations have established the essential similarities between CH4 and CO2 hydrate dissociation. The limiting behaviors at lower temperature (no dissociation) and higher temperature (complete melting and formation of a gas bubble) have been illustrated for both hydrates. Due to the shift in the known hydrate stability curves between guest molecules caused by the choice of water model as noted by other authors, the intermediate behavior (e.g., 260 K) showed distinct differences however. Also, because of the more hydrogen-bonding capability of CO2 in water, as reflected in its molecular parameters, higher solubility of dissociated CO2 in water was observed with a consequence of a smaller size of gas bubble formation. Additionally, a novel method for analyzing hydrate dissociation based on H-bond breakage has been proposed and used to quantify the dissociation behaviors of both CH4 and CO2 hydrates. Activation energies Ea values from our MD studies were obtained and evaluated against several other published laboratory and MD values. Intrinsic rate constants were estimated and upscaled. A kinetic reaction model consistent with macroscale fitted kinetic models has been proposed to

20. The rise of ionized gas in the Magellanic Stream

Hernandez, Michael; Barger, Kathleen; Smart, Brianna; Haffner, L. Matthew

2017-01-01

The Small and Large Magellanic Clouds are a pair of interacting galaxies near the Milky Way. Tidal interactions have stripped gas from these galaxies, leaving behind gaseous debris such as the Magellanic Stream. We explore the morphology and kinematics of the neutral and ionized hydrogen gas in the trailing stream traveling toward the Milky Way. This comparison provides us with insight into the physical processes that are affecting the gas flowing through the Galactic halo. This is done using mapped H-alpha emission-line spectroscopy, obtained with the Wisconsin H-alpha Mapper (WHAM), and archival 21-cm HI observations of the Stream near the Magellanic Clouds. We found that the neutral and ionized gas spatially and kinematically trace each other. With a map of the ionized gas in hand, we will continue to study the survival of this tidal relic.

1. Energy transfer between the shape and volume modes of a nonspherical gas bubble

Harkin, Anthony A.; Kaper, Tasso J.; Nadim, Ali

2013-06-01

A model of a nonspherical gas bubble is developed in which the Rayleigh-Plesset equation is augmented with second order terms that back-couple the volume mode to a single shape mode. These additional terms in the Rayleigh-Plesset equation permit oscillation energy to be transferred back and forth between the shape and volume modes. The parametric stability of the shape mode is analyzed for a driven bubble, and it is seen that the bidirectional coupling yields an enhanced, albeit minor, stabilizing effect on the shape mode when compared with a model where the shape-volume coupling is unidirectional. It is also demonstrated how a pure shape distortion can excite significant volume pulsations when the volume mode is in 2:1 internal resonance with the shape mode.

2. The Effect of Viscosity on the Spherical Stability of Oscillating Gas Bubbles

NASA Technical Reports Server (NTRS)

Hao, Y.; Prosperetti, A.

1999-01-01

Gas bubbles driven in radial oscillations are subject to an instability of the spherical shape that is opposed by surface tension and viscosity. An exact linear formulation for the study of the phenomenon has been available for many years, but its complexity has discouraged a detailed investigation. With the recent theory of sonoluminescence of Lohse and co-workers, there has been a renewed interest in the problem and new data have become available. This paper presents a numerical method for the solution of the pertinent equations and compares the theory with these new data. The coupling of the strong nonlinearity of the bubble radial oscillations with the parametric mechanism of the surface instability results in a very complex structure for the stability boundary. Nevertheless, a good agreement between theory and data is found. A comparison with earlier approximate models is also made.

3. Free gas bubbles in the hydrate stability zone: evidence from CT investigation under in situ conditions

Abegg, F.; Freitag, J.; Bohrmann, G.; Brueckmann, W.; Eisenhauer, A.; Amann, H.; Hohnberg, H.-J.

2003-04-01

Determination of the internal structures and the fabric of natural marine gas hydrate as well as its distribution in shallow subseafloor depth was restricted because of dissociation during recovery. Investigation under in situ conditions becomes possible with a pressure coring device. The newly developed MultiAutoclaveCorer (MAC) can take up to four cores which are housed in a pressure vessel called LabTransferChamber (LTC), which is compatible with CT imaging technology. During a video-guided deployment on Hydrate Ridge, a well known near-surface gas hydrate-rich environment, two LTCs were filled and recovered under pressure. CT imaging was performed four days after retrieval in a medical clinic in Palo Alto/Ca., a second round was run 2 months later in Kiel/Germany, still under pressure. The same type of scanner was used for both rounds of imaging. The function and the pressure preserving capability of the MAC was confirmed. Although only 0.8 m apart, both cores showed different gas hydrate contents, varying between a maximum of 5 vol-% in LTC 3 and 48 vol-% in LTC 4, documenting the high variability of gas hydrate occurrences in near-surface sediments. The uppermost layer of gas hydrate was observed 0.1 m below the seafloor. The high gas hydrate content in LTC 4 is concentrated in a horizon between 0.28 and 0.32 m subseafloor depth. Within this hoizon a significant quantity of bubbles was detected with a free gas content of up to 2.4 vol-%. Bubble sizes reach a maximum of 1.8 x 10-2 m in either x, y or z direction. Integrating across the mentioned core interval, the gas hydrate content is 19 vol-% and the free gas content is 0.8 vol-%. Assuming several simplifications, the normalised calculated methane volume of the gas hydrate is 9.15 x 10-3 m^3 and the amount of methane in the bubbles is 1.49 x 10-4 m^3.

4. Generating Singlet Oxygen Bubbles: A New Mechanism for Gas-Liquid Oxidations in Water

PubMed Central

Bartusik, Dorota; Aebisher, David; Ghafari, BiBi

2012-01-01

Laser-coupled microphotoreactors were developed to bubble singlet oxygen [1O2 (1Δg)] into an aqueous solution containing an oxidizable compound. The reactors consisted of custom-modified SMA fiber-optic receptacles loaded with 150-μm silicon phthalocyanine glass sensitizer particles, where the particles were isolated from direct contact with water by a membrane adhesively bonded to the bottom of each device. A tube fed O2 gas to the reactor chambers. In the presence of O2, singlet oxygen was generated by illuminating the sensitizer particles with 669-nm light from an optical fiber coupled to the top of the reactor. The generated 1O2 was transported through the membrane by the O2 stream and formed bubbles in solution. In solution, singlet oxygen reacted with probe compounds (either 9,10-anthracene dipropionate dianion, trans-2-methyl-2-pentanoate anion, N-benzoyl-D,L-methionine, and N-acetyl-D,L-methionine) to give oxidized products in two stages. The early stage was rapid and showed that 1O2 transfer occurred via bubbles mainly in the bulk water solution. The later stage was slow, it arose only from 1O2-probe molecule contact at the gas/liquid interface. A mechanism is proposed that involves 1O2 mass transfer and solvation, where smaller bubbles provide better penetration of 1O2 into the flowing stream due to higher surface-to-volume contact between the probe molecules and 1O2. PMID:22260325

5. Plasma Discharges in Gas Bubbles in Liquid Water: Breakdown Mechanisms and Resultant Chemistry

Gucker, Sarah M. N.

The use of atmospheric pressure plasmas in gases and liquids for purification of liquids has been investigated by numerous researchers, and is highly attractive due to their strong potential as a disinfectant and sterilizer. However, the fundamental understanding of plasma production in liquid water is still limited. Despite the decades of study dedicated to electrical discharges in liquids, many physical aspects of liquids, such as the high inhomogeneity of liquids, complicate analyses. For example, the complex nonlinearities of the fluid have intricate effects on the electric field of the propagating streamer. Additionally, the liquid material itself can vaporize, leading to discontinuous liquid-vapor boundaries. Both can and do often lead to notable hydrodynamic effects. The chemistry of these high voltage discharges on liquid media can have circular effects, with the produced species having influence on future discharges. Two notable examples include an increase in liquid conductivity via charged species production, which affects the discharge. A second, more complicated scenario seen in some liquids (such as water) is the doubling or tripling of molecular density for a few molecule layers around a high voltage electrode. These complexities require technological advancements in optical diagnostics that have only recently come into being. This dissertation investigates several aspects of electrical discharges in gas bubbles in liquids. Two primary experimental configurations are investigated: the first allows for single bubble analysis through the use of an acoustic trap. Electrodes may be brought in around the bubble to allow for plasma formation without physically touching the bubble. The second experiment investigates the resulting liquid phase chemistry that is driven by the discharge. This is done through a dielectric barrier discharge with a central high voltage surrounded by a quartz discharge tube with a coil ground electrode on the outside. The plasma

6. Effects of Anode Wettability and Slots on Anodic Bubble Behavior Using Transparent Aluminium Electrolytic Cells

Zhao, Zhibin; Gao, Bingliang; Feng, Yuqing; Huang, Yipeng; Wang, Zhaowen; Shi, Zhongning; Hu, Xianwei

2017-02-01

Transparent aluminum electrolytic cells were used to study the effects of anode wettability and slots on bubble behavior in a similar environment to that used in industrial cells. Observations were conducted using two types of transparent cells, one with side-observation and the other with a bottom-observation cell design. Anodic bubbles rising process in the side channel is strongly affected by the wettability of the anode. After rising a short distance, the bubbles detach from the anode vertical surface at good-wetting anode cases, while the bubbles still attach to the vertical surface at poor-wetting anode cases. Anode slots of width of 4 mm are able to prevent smaller bubbles from coalescing into larger bubbles and thus decrease the bubble size and gas coverage on the anode. Anode slots also make a contribution in slightly reducing bubble thickness. With the presence of slots, the bubble-induced cell voltage oscillation decreases as well.

7. Bubble shapes in steady axisymmetric flows at intermediate Reynolds number

NASA Technical Reports Server (NTRS)

Ryskin, G.; Leal, L. G.

1982-01-01

The shape of a gas bubble which rises through a quiescent incompressible, Newtonian fluid at intermediate Reynolds numbers is considered. Exact numerical solutions for the velocity and pressure fields, as well as the bubble shape, are obtained using finite difference techniques and a numerically generated transformation to an orthogonal, boundary-fitted coordinate system. No restriction is placed on the allowable magnitude of deformation.

8. A complementary approach to estimate the internal pressure of fission gas bubbles by SEM-SIMS-EPMA in irradiated nuclear fuels

Cagna, C.; Zacharie-Aubrun, I.; Bienvenu, P.; Barrallier, L.; Michel, B.; Noirot, J.

2016-02-01

The behaviour of gases produced by fission is of great importance for nuclear fuel in operation. Within this context, a decade ago, a general method for the characterisation of the fission gas including gas bubbles in an irradiated UO2 nuclear fuel was developed and applied to determine the bubbles internal pressure. The method consists in the determination of the pressure, over a large population of bubbles, using three techniques: SEM, EPMA and SIMS. In this paper, a complementary approach using the information given by the same techniques is performed on an isolated bubble under the surface and is aiming for a better accuracy compared to the more general measurement of gas content. SEM and EPMA enable the detection of a bubble filled with xenon under the surface. SIMS enables the detection of the gas filling the bubble. The quantification is achieved using the EPMA data as reference at positions where no or nearly no bubbles are detected.

9. Trapped bubbles keep pumice afloat and gas diffusion makes pumice sink

Fauria, Kristen E.; Manga, Michael; Wei, Zihan

2017-02-01

Pumice can float on water for months to years - long enough for pumice to travel across oceans and facilitate the spread of species. Long-lived pumice floatation is unexpected, however, because pumice pores are highly connected and water wets volcanic glass. As a result, observations of long floating times have not been reconciled with predictions of rapid sinking. We propose a mechanism to resolve this paradox - the trapping of gas bubbles by water within the pumice. Gas trapping refers to the isolation of gas by water within pore throats such that the gas becomes disconnected from the atmosphere and unable to escape. We use X-ray microtomography to image partially saturated pumice and demonstrate that non-condensable gas trapping occurs in both ambient temperature and hot (500 °C) pumice. Furthermore, we show that the size distribution of trapped gas clusters matches predictions of percolation theory. Finally, we propose that diffusion of trapped gas determines pumice floatation time. Experimental measurements of pumice floatation support a diffusion control on pumice buoyancy and we find that floatation time τ scales as τ ∝ L2/Dθ2 where L is the characteristic length of pumice, D is the gas-water diffusion coefficient, and θ is pumice water saturation. A mechanistic understanding of pumice floatation is a step towards understanding how pumice is partitioned into floating and sinking components and provides an estimate for the lifetime of pumice rafts in the ocean.

10. Electrochemistry of single nanobubbles. Estimating the critical size of bubble-forming nuclei for gas-evolving electrode reactions.

PubMed

German, Sean R; Edwards, Martin A; Chen, Qianjin; Liu, Yuwen; Luo, Long; White, Henry S

2016-12-12

In this article, we address the fundamental question: "What is the critical size of a single cluster of gas molecules that grows and becomes a stable (or continuously growing) gas bubble during gas evolving reactions?" Electrochemical reactions that produce dissolved gas molecules are ubiquitous in electrochemical technologies, e.g., water electrolysis, photoelectrochemistry, chlorine production, corrosion, and often lead to the formation of gaseous bubbles. Herein, we demonstrate that electrochemical measurements of the dissolved gas concentration, at the instant prior to nucleation of an individual nanobubble of H2, N2, or O2 at a Pt nanodisk electrode, can be analyzed using classical thermodynamic relationships (Henry's law and the Young-Laplace equation - including non-ideal corrections) to provide an estimate of the size of the gas bubble nucleus that grows into a stable bubble. We further demonstrate that this critical nucleus size is independent of the radius of the Pt nanodisk employed (<100 nm radius), and weakly dependent on the nature of the gas. For example, the measured critical surface concentration of H2 of ∼0.23 M at the instant of bubble formation corresponds to a critical H2 nucleus that has a radius of ∼3.6 nm, an internal pressure of ∼350 atm, and contains ∼1700 H2 molecules. The data are consistent with stochastic fluctuations in the density of dissolved gas, at or near the Pt/solution interface, controlling the rate of bubble nucleation. We discuss the growth of the nucleus as a diffusion-limited process and how that process is affected by proximity to an electrode producing ∼10(11) gas molecules per second. Our study demonstrates the advantages of studying a single-entity, i.e., an individual nanobubble, in understanding and quantifying complex physicochemical phenomena.

11. Heat transfer between immiscible liquids enhanced by gas bubbling. [PWR; BWR

SciTech Connect

Greene, G.A.; Schwarz, C.E.; Klages, J.; Klein, J.

1982-08-01

The phenomena of core-concrete interactions impact upon containment integrity of light water reactors (LWR) following postulated complete meltdown of the core by containment pressurization, production of combustible gases, and basemat penetration. Experiments have been performed with non-reactor materials to investigate one aspect of this problem, heat transfer between overlying immiscible liquids whose interface is disturbed by a transverse non-condensable gas flux emanating from below. Hydrodynamic studies have been performed to test a criterion for onset of entrainment due to bubbling through the interface and subsequent heat transfer studies were performed to assess the effect of bubbling on interfacial heat transfer rates, both with and without bubble induced entrainment. Non-entraining interfacial heat transfer data with mercury-water/oil fluid pairs were observed to be bounded from below within a factor of two to three by the Szekeley surface renewal heat transfer model. However heat transfer data for fluid pairs which are found to entrain (water-oil), believed to be characteristic of molten reactor core-concrete conditions, were measured to be up to two orders of magnitude greater than surface renewal predictions and are calculated by a simple entrainment heat transfer model.

12. EXPERIMENTS AND SIMULATIONS WITH LARGE GAS BUBBLES IN MERCURY TOWARDS ESTABLISHING A GAS LAYER TO MITIGATE CAVITATION DAMAGE

SciTech Connect

Wendel, Mark W; Riemer, Bernie; Felde, David K; Ruggles, Arthur; Karnowski, Thomas Paul

2006-01-01

One of several options that shows promise for protecting solid surfaces from cavitation damage in liquid metal spallation targets, involves introducing an interstitial gas layer between the liquid metal and the containment vessel wall. Several approaches toward establishing such a protective gas layer are being investigated at the Oak Ridge National Laboratory including large bubble injection, and methods that involve stabilization of the layer by surface modifications to enhance gas hold-up on the wall or by inserting a porous media. It has previously been reported that using a gas layer configuration in a test target showed an order-of-magnitude decrease in damage for an in-beam experiment. Video images that were taken of the successful gas/mercury flow configuration have been analyzed and correlated. The results show that the success was obtained under conditions where only 60% of the solid wall was covered with gas. Such a result implies that this mitigation scheme may have much more potential. Additional experiments with gas injection into water are underway. Multi-component flow simulations are also being used to provide direction for these new experiments. These simulations have been used to size the gas layer and position multiple inlet nozzles.

13. A Study of Vertical Gas Jets in a Bubbling Fluidized Bed

SciTech Connect

Ceccio, Steven; Curtis, Jennifer

2011-04-15

A detailed experimental study of a vertical gas jet impinging a fluidized bed of particles has been conducted with the help of Laser Doppler Velocimetry measurements. Mean and fluctuating velocity profiles of the two phases have been presented and analyzed for different fluidization states of the emulsion. The results of this work would be greatly helpful in understanding the complex two-phase mixing phenomenon that occurs in bubbling beds, such as in coal and biomass gasification, and also in building more fundamental gas-solid Eulerian/Lagrangian models which can be incorporated into existing CFD codes. Relevant simulations to supplement the experimental findings have also been conducted using the Department of Energy's open source code MFIX. The goal of these simulations was two-fold. One was to check the two-dimensional nature of the experimental results. The other was an attempt to improve the existing dense phase Eulerian framework through validation with the experimental results. In particular the sensitivity of existing frictional models in predicting the flow was investigated. The simulation results provide insight on wall-bounded turbulent jets and the effect frictional models have on gas-solid bubbling flows. Additionally, some empirical minimum fluidization correlations were validated for non-spherical particles with the idea of extending the present study to non-spherical particles which are more common in industries.

14. Gas bubble disease in resident fish below Grand Coulee Dam: final report of research

USGS Publications Warehouse

Beeman, J.W.; Venditti, D.A.; Morris, R.G.; Gadomski, D.M.; Adams, B.J.; Vanderkooi, S.J.; Robinson, T.C.; Maule, A.G.

2003-01-01

Fish kills have occurred in the reservoir below Grand Coulee Dam possibly due to total dissolved gas supersaturation (TDGS), which occurs when water cascades over a dam or waterfall. The highest TDGS below Grand Coulee Dam has occurred after spilling water via the outlet tubes, though TDGS from upstream sources has also been recorded. Exposure to TDGS can cause gas bubble disease in aquatic organisms. This disease, analogous to ‘the bends’ in human divers, can range from mild to fatal depending on the level of supersaturation, species, life cycle stage, condition of the fish, fish depth, and the water temperature. The USGS, Western Fisheries Research Center’s Columbia River Research Laboratory conducted field and laboratory experiments to determine the relative risks of TDGS to various species of fish in the reservoir below the dam (Rufus Woods Lake). Field work included examination of over 8000 resident fish for signs of gas bubble disease, examination of the annual growth increments of several species relative to ambient TDGS, and recording the in-situ depths and temperatures of several species using miniature recorders surgically implanted in both resident fish and triploid steelhead reared in commercial net pens. Laboratory experiments included bioassays of the progression of signs and mortality of several species at various TDGS levels. The overarching objective of these studies was to provide data to enable sound management decisions regarding the effects of TDGS in the reservoir below Grand Coulee Dam, though the data may also be applicable to other locations.

15. Method for gas bubble and void control and removal from metals

DOEpatents

Siclen, C.D. Van; Wright, R.N.

1996-02-06

A method is described for enhancing the diffusion of gas bubbles or voids attached to impurity precipitates, and biasing their direction of migration out of the host metal (or metal alloy) by applying a temperature gradient across the host metal (or metal alloy). In the preferred embodiment of the present invention, the impurity metal is insoluble in the host metal and has a melting point lower than the melting point of the host material. Also, preferably the impurity metal is lead or indium and the host metal is aluminum or a metal alloy. 2 figs.

16. Method for gas bubble and void control and removal from metals

DOEpatents

Van Siclen, Clinton D.; Wright, Richard N.

1996-01-01

A method for enhancing the diffusion of gas bubbles or voids attached to impurity precipitates, and biasing their direction of migration out of the host metal (or metal alloy) by applying a temperature gradient across the host metal (or metal alloy). In the preferred embodiment of the present invention, the impurity metal is insoluble in the host metal and has a melting point lower than the melting point of the host material. Also, preferably the impurity metal is lead or indium and the host metal is aluminum or a metal alloy.

17. Review of Monitoring Plans for Gas Bubble Disease Signs and Gas Supersaturation Levels on the Columbia and Snake Rivers.

SciTech Connect

Fidler, Larry; Elston, Ralph; Colt, John

1994-07-01

Montgomery Watson was retained by the Bonneville Power Administration to evaluate the monitoring program for gas bubble disease signs and dissolved gas supersaturation levels on the Columbia and Snake rivers. The results of this evaluation will provide the basis for improving protocols and procedures for future monitoring efforts. Key study team members were Dr. John Colt, Dr. Larry Fidler, and Dr. Ralph Elston. On the week of June 6 through 10, 1994 the study team visited eight monitoring sites (smolt, adult, and resident fish) on the Columbia and Snake rivers. Additional protocol evaluations were conducted at the Willard Field Station (National Biological Survey) and Pacific Northwest Laboratories at Richland (Battelle). On June 13 and 14, 1994, the study team visited the North Pacific Division office of the U.S. Corps of Engineers and the Fish Passage Center to collect additional information and data on the monitoring programs. Considering the speed at which the Gas Bubble Trauma Monitoring Program was implemented this year, the Fish Passage Center and cooperating Federal, State, and Tribal Agencies have been doing an incredible job. Thirty-one specific recommendations are presented in this report and are summarized in Section 14.

18. Incidence and Outcomes of Anterior Chamber Gas Bubble during Femtosecond Flap Creation for Laser-Assisted In Situ Keratomileusis.

PubMed

Rush, Sloan W; Cofoid, Philip; Rush, Ryan B

2015-01-01

Purpose. To report the incidence and outcomes of anterior chamber gas bubble formation during femtosecond laser flap creation for laser-assisted in situ keratomileusis (LASIK). Methods. The charts of 2,886 consecutive eyes that underwent femtosecond LASIK from May 2011 through August 2014 were retrospectively reviewed. The incidence, preoperative characteristics, intraoperative details, and postoperative outcomes were analyzed in subjects developing anterior chamber gas bubble formation during the procedure. Results. A total of 4 cases (0.14%) developed anterior chamber gas bubble formation during femtosecond laser flap creation. In all four cases, the excimer laser was unable to successfully track the pupil immediately following the anterior chamber bubble formation, temporarily postponing the completion of the procedure. There was an ethnicity predilection of anterior chamber gas formation toward Asians (p = 0.0055). An uncorrected visual acuity of 20/20 was ultimately achieved in all four cases without further complications. Conclusions. Anterior chamber gas bubble formation during femtosecond laser flap creation for LASIK is an uncommon event that typically results in a delay in treatment completion; nevertheless, it does influence final positive visual outcome.

19. Characterization of peat structure using X-ray computed tomography and its control on the ebullition of biogenic gas bubbles

Kettridge, Nicholas; Binley, Andrew

2011-03-01

The structural arrangement of peat constituents controls the hydrological and thermal properties of peat. However, the importance of these structural characteristics on other physical processes within a peatland has not been fully assessed. Here, we evaluate the importance of peat structure on its ability to entrain biogenic gas bubbles and control ebullition, an important transport mechanism for methane. X-ray computed tomography (CT) was applied to characterize the structure of a range of peats at varying levels of decomposition. The structural properties of the peat were quantified from a vector representation of the CT images, and the potential of each sample to entrain biogenic gas bubbles was quantified using a rule-based Monte Carlo model that calculates the tortuosity of bubbles pathways through the peat. Sixty-six percent of the variability in the trapping potential of the peat results from porosity variations and 34% from structural variations between samples. A metric that represents this structural control was not identified for all peat types because of difficulties adequately representing some peats as a vector network. However, for S. magellanicum peat we were able to establish that the influence of peat structure on the entrainment of gas bubbles is characterized by ?v, the average vector length of the stems and branches. Peat characterized by longer structural components (larger ?v) enhances the entrainment of gas bubbles. Our findings demonstrate the need to incorporate some representation of the peat structure in numerical models of biogenic gas transport in peat.

20. Effect of air on energy and rise-time spectra measured by proportional gas counter

SciTech Connect

Kawano, T.; Tanaka, M.; Isozumi, S.; Isozumi, Y.; Tosaki, M.; Sugiyama, T.

2015-03-15

Air exerts a negative effect on radiation detection using a gas counter because oxygen contained in air has a high electron attachment coefficient and can trap electrons from electron-ion pairs created by ionization from incident radiation in counting gas. This reduces radiation counts. The present study examined the influence of air on energy and rise-time spectra measurements using a proportional gas counter. In addition, a decompression procedure method was proposed to reduce the influence of air and its effectiveness was investigated. For the decompression procedure, the counting gas inside the gas counter was decompressed below atmospheric pressure before radiation detection. For the spectrum measurement, methane as well as various methane and air mixtures were used as the counting gas to determine the effect of air on energy and rise-time spectra. Results showed that the decompression procedure was effective for reducing or eliminating the influence of air on spectra measurement using a proportional gas counter. (authors)

1. The effects of total dissolved gas on chum salmon fry survival, growth, gas bubble disease, and seawater tolerance

SciTech Connect

Geist, David R.; Linley, Timothy J.; Cullinan, Valerie I.; Deng, Zhiqun

2013-02-01

Chum salmon Oncorhynchus keta alevin developing in gravel habitats downstream of Bonneville Dam on the Columbia River are exposed to elevated levels of total dissolved gas (TDG) when water is spilled at the dam to move migrating salmon smolts downstream to the Pacific Ocean. Current water quality criteria for the management of dissolved gas in dam tailwaters were developed primarily to protect salmonid smolts and are assumed to be protective of alevin if adequate depth compensation is provided. We studied whether chum salmon alevin exposed to six levels of dissolved gas ranging from 100% to 130% TDG at three development periods between hatch and emergence (hereafter early, middle, and late stage) suffered differential mortality, growth, gas bubble disease, or seawater tolerance. Each life stage was exposed for 50 d (early stage), 29 d (middle stage), or 16 d (late stage) beginning at 13, 34, and 37 d post-hatch, respectively, through 50% emergence. The mortality for all stages from exposure to emergence was estimated to be 8% (95% confidence interval (CI) of 4% to 12%) when dissolved gas levels were between 100% and 117% TDG. Mortality significantly increased as dissolved gas levels rose above 117% TDG,; with the lethal concentration that produced 50% mortality (LC50 ) was estimated to be 128.7% TDG (95% CI of 127.2% to 130.2% TDG) in the early and middle stages. By contrast, there was no evidence that dissolved gas level significantly affected growth in any life stage except that the mean wet weight at emergence of early stage fish exposed to 130% TDG was significantly less than the modeled growth of unexposed fish. The proportion of fish afflicted with gas bubble disease increased with increasing gas concentrations and occurred most commonly in the nares and gastrointestinal tract. Early stage fish exhibited higher ratios of filament to lamellar gill chloride cells than late stage fish, and these ratios increased and decreased for early and late stage fish

2. Laboratory investigation of the factors impact on bubble size, pore blocking and enhanced oil recovery with aqueous Colloidal Gas Aphron.

PubMed

Shi, Shenglong; Wang, Yefei; Li, Zhongpeng; Chen, Qingguo; Zhao, Zenghao

Colloidal Gas Aphron as a mobility control in enhanced oil recovery is becoming attractive; it is also designed to block porous media with micro-bubbles. In this paper, the effects of surfactant concentration, polymer concentration, temperature and salinity on the bubble size of the Colloidal Gas Aphron were studied. Effects of injection rates, Colloidal Gas Aphron fluid composition, heterogeneity of reservoir on the resistance to the flow of Colloidal Gas Aphron fluid through porous media were investigated. Effects of Colloidal Gas Aphron fluid composition and temperature on residual oil recovery were also studied. The results showed that bubble growth rate decreased with increasing surfactant concentration, polymer concentration, and decreasing temperature, while it decreased and then increased slightly with increasing salinity. The obvious increase of injection pressure was observed as more Colloidal Gas Aphron fluid was injected, indicating that Colloidal Gas Aphron could block the pore media effectively. The effectiveness of the best blend obtained through homogeneous sandpack flood tests was modestly improved in the heterogeneous sandpack. The tertiary oil recovery increased 26.8 % by Colloidal Gas Aphron fluid as compared to 20.3 % by XG solution when chemical solution of 1 PV was injected into the sandpack. The maximum injected pressure of Colloidal Gas Aphron fluid was about three times that of the XG solution. As the temperature increased, the Colloidal Gas Aphron fluid became less stable; the maximum injection pressure and tertiary oil recovery of Colloidal Gas Aphron fluid decreased.

3. Experimental formation of massive hydrate deposits from accumulation of CH4 gas bubbles within synthetic and natural sediments

SciTech Connect

Madden, Megan Elwood; Szymcek, Phillip; Ulrich, Shannon M; McCallum, Scott D; Phelps, Tommy Joe

2009-01-01

In order for methane to be economically produced from the seafloor, prediction and detection of massive hydrate deposits will be necessary. In many cases, hydrate samples recovered from seafloor sediments appear as veins or nodules, suggesting that there are strong geologic controls on where hydrate is likely to accumulate. Experiments have been conducted examining massive hydrate accumulation from methane gas bubbles within natural and synthetic sediments in a large volume pressure vessels through temperature and pressure data, as well as visual observations. Observations of hydrate growth suggest that accumulation of gas bubbles within void spaces and at sediment interfaces likely results in the formation of massive hydrate deposits. Methane hydrate was first observed as a thin film forming at the gas/water interface of methane bubbles trapped within sediment void spaces. As bubbles accumulated, massive hydrate growth occurred. These experiments suggest that in systems containing free methane gas, bubble pathways and accumulation points likely control the location and habit of massive hydrate deposits.

4. Gas transport and bubble collapse in rhyolitic magma: an experimental approach

Westrich, Henry R.; Eichelberger, John C.

1994-12-01

A series of experiments was conducted to test concepts of porous flow degassing of rhyolitic magma during ascent and of the subsequent collapse of vesicles in degassed magma to form obsidian. Dense, synthetically hydrated, natural glasses were pressurized under water-saturated conditions and then decompressed to achieve a range of porosities in the presence of a tracer vapor, D2O. Rapid isotopic exchange indicative of vapor transport rather than of simple diffusion occurred at a porosity >60 vol.%, in accord with earlier gas permeability measurements on cold natural samples. In another series of experiments, natural and synthetic pumices, vesiculated by degassing to atmospheric pressure, rapidly collapsed to dense glass on repressurization to the modest pressures prevailing in lava flows. No relict bubble textures remained. These results support the hypothesis that effusive eruptions result from the syneruptive escape of gas from permeable magmatic foam, and that a process analogous to welding yields dense lavas when such foams are extruded.

5. Measurement of Entrapped Biogenic Gas Bubbles in Northern Peat Soils: Application of Resistivity and X-ray Computed Tomography.

Kettridge, N.; Binley, A.; Baird, A.

2008-05-01

Peatlands are the largest natural source per annum of CH4 emissions to the atmosphere. CH4 is lost from peatlands via diffusion or active transport through vascular plants, and as bubbles moving to the peatland surface - ebullition. The build up and ebullition of biogenic gas bubbles within northern peatlands is spatially variable and depends on the rate of CH4 production, the transport of dissolved CH4 to bubbles through pore water, and the physical properties of the peat. Recent measurements suggest a threshold bubble volume must be reached to trigger episodic or cyclic ebullition, which is assumed to be dependent on peat type. However, this threshold theory lacks a secure physical basis and therefore cannot be applied to simulate methane ebullition from northern peatlands with any confidence. We develop an approach to examine the structural attributes of the peat that cause and promote the trapping and release of bubbles by combining resistivity and X-ray computed tomography (CT). The spatial and temporal variation in the biogenic gas content of peat cores are identified from resistivity measurements. Areas of high and low entrapped gas content are subsequently correlated with the pore structure of the peat samples, characterised using CT. The CT images of the peat structure are vectorised to allow them to be analysed for metrics which relate to the ability of the peat to trap bubbles: e.g. stem length and width, number of branches, angle of branches. Difficulties applying these approaches within northern peatlands are examined. The low pore water conductivity of poorly decomposed near surface peat can hamper resistivity measurements at the laboratory scale, and electrolytic reactions induce the development of artificial gas bubbles. The similarity in linear attenuations between poorly decomposed Sphagnum and pore water also makes the peat structure indistinguishable from the pore water within standard CT scans. The peat samples must, therefore, first be doped

6. Does nitrogen gas bubbled through a low density polymer gel dosimeter solution affect the polymerization process?

PubMed Central

2015-01-01

Background: On account of the lower electron density in the lung tissue, the dose distribution in the lung cannot be verified with the existing polymer gel dosimeters. Thus, the aims of this study are to make a low density polymer gel dosimeter and investigate the effect of nitrogen gas bubbles on the R2 responses and its homogeneity. Materials and Methods: Two different types of low density polymer gel dosimeters were prepared according to a composition proposed by De Deene, with some modifications. In the first type, no nitrogen gas was perfused through the gel solution and water. In the second type, to expel the dissolved oxygen, nitrogen gas was perfused through the water and gel solution. The post-irradiation times in the gels were 24 and 5 hours, respectively, with and without perfusion of nitrogen gas through the water and gel solution. Results: In the first type of gel, there was a linear correlation between the doses and R2 responses from 0 to 12 Gy. The fabricated gel had a higher dynamic range than the other low density polymer gel dosimeter; but its background R2 response was higher. In the second type, no difference in R2 response was seen in the dose ranges from 0 to 18 Gy. Both gels had a mass density between 0.35 and 0.45 g.cm-3 and CT values of about -650 to -750 Hounsfield units. Conclusion: It appeared that reactions between gelatin-free radicals and monomers, due to an increase in the gel temperature during rotation in the household mixer, led to a higher R2-background response. In the second type of gel, it seemed that the collapse of the nitrogen bubbles was the main factor that affected the R2-responses. PMID:26015914

7. An experimental verification of the possible influence of gas nano-bubbles on the response of an electrochemical quartz crystal microbalance.

PubMed

2005-04-21

Electrochemical removal of oxygen and hydrogen from aqueous solution in the vicinity of gold electrodes, with simultaneous measurements of the response of the quartz crystal microbalance, show no evidence of gas nano-bubbles attached to the surface, irrespective of its roughness and hydrophobicity. The contact between gold and frozen electrolyte, which forms a liquid-like layer between them, also does not contain gas bubbles. These statements could be extended to nano-bubbles with characteristic dimensions larger than a few nanometers.

8. How man-made interference might cause gas bubble emboli in deep diving whales

PubMed Central

Fahlman, Andreas; Tyack, Peter L.; Miller, Patrick J. O.; Kvadsheim, Petter H.

2014-01-01

Recent cetacean mass strandings in close temporal and spatial association with sonar activity has raised the concern that anthropogenic sound may harm breath-hold diving marine mammals. Necropsy results of the stranded whales have shown evidence of bubbles in the tissues, similar to those in human divers suffering from decompression sickness (DCS). It has been proposed that changes in behavior or physiological responses during diving could increase tissue and blood N2 levels, thereby increasing DCS risk. Dive data recorded from sperm, killer, long-finned pilot, Blainville's beaked and Cuvier's beaked whales before and during exposure to low- (1–2 kHz) and mid- (2–7 kHz) frequency active sonar were used to estimate the changes in blood and tissue N2 tension (PN2). Our objectives were to determine if differences in (1) dive behavior or (2) physiological responses to sonar are plausible risk factors for bubble formation. The theoretical estimates indicate that all species may experience high N2 levels. However, unexpectedly, deep diving generally result in higher end-dive PN2 as compared with shallow diving. In this focused review we focus on three possible explanations: (1) We revisit an old hypothesis that CO2, because of its much higher diffusivity, forms bubble precursors that continue to grow in N2 supersaturated tissues. Such a mechanism would be less dependent on the alveolar collapse depth but affected by elevated levels of CO2 following a burst of activity during sonar exposure. (2) During deep dives, a greater duration of time might be spent at depths where gas exchange continues as compared with shallow dives. The resulting elevated levels of N2 in deep diving whales might also make them more susceptible to anthropogenic disturbances. (3) Extended duration of dives even at depths beyond where the alveoli collapse could result in slow continuous accumulation of N2 in the adipose tissues that eventually becomes a liability. PMID:24478724

9. Buoyancy Driven Shear Flows of Bubble Suspensions

NASA Technical Reports Server (NTRS)

Koch, D. L.; Hill, R. J.; Chellppannair, T.; Zenit, R.; Zenit, R.; Spelt, P. D. M.

1999-01-01

In this work the gas volume fraction and the root-mean-squared fluid velocity are measured in buoyancy driven shear flows of bubble suspensions in a tall, inclined, rectangular channel. The experiments are performed under conditions where We << 1a nd Re >> 1, for which comparisons are made with kinetic theory and numerical simulations. Here Re = gamma(a(exp 2)/nu is the Reynolds number and We = rho(gamma(exp 2))a(exp 3)/sigma is the Weber number; gamma is the shear rate, a is the bubble radius, nu is the kinematic viscosity of the liquid, rho is the density of the liquid, and sigma is the surface tension of the gas/liquid interface. Kang et al. calculated the bubble phase pressure and velocity variance of sheared bubble suspensions under conditions where the bubbles are spherical and the liquid phase velocity field can be approximated using potential flow theory, i.e. We= 0 and Re >> 1. Such conditions can be achieved in an experiment using gas bubbles, with a radius of O(0.5mm), in water. The theory requires that there be no average relative motion of the gas and liquid phases, hence the motivation for an experimental program in microgravity. The necessity of performing preliminary, Earth based experiments, however, requires performing experiments where the gas phase rises in the liquid, which significantly complicates the comparison of experiments with theory. Rather than comparing experimental results with theory for a uniform, homogeneous shear flow, experiments can be compared directly with solutions of the averaged equations of motion for bubble suspensions. This requires accounting for the significant lift force acting on the gas phase when the bubbles rise parallel to the average velocity of the sheared suspension. Shear flows can be produced in which the bubble phase pressure gradient, arising from shear induced collisions amongst the bubbles, balances a body force (centrifugal or gravitational) on the gas phase. A steady, non-uniform gas volume fraction

10. Macro- and microscopic in-situ observation of gas bubbles and sludge particles in a biogas tower reactor.

PubMed

Pietsch, Torsten; Mehrwald, Ralf; Grajetzki, Ralf; Sens, Jan; Pakendorf, Tim; Ulrich, Reinhard; Kumpart, Jörn; Matz, Gerhard; Märkl, Herbert

2002-06-01

Macroscopic and microscopic in-situ observation of particles and gas bubbles are used to get precise impressions of the hydrodynamical characteristics of a biologically active suspension. Moreover, values of in-situ velocities and particle densities can be gained by using these methods. The suspended anaerobic sludge revealed an extensive fibrous structure ('fur') on its surface. The observed microfibers have a profound influence on the settling/flotation behavior of the particles because they increase the effective particle volume, they may trap gas bubbles and they favor agglomeration. The biomass particles do not appear as single spherical objects but due to its fibrous structure on the outside as strongly interacting mass. The compressibility of the bubbles which are entrapped in the sludge agglomerates results in a pressure-dependent density of the sludge particles.

11. 3D mapping of the dense interstellar gas around the Local Bubble

Lallement, R.; Welsh, B. Y.; Vergely, J. L.; Crifo, F.; Sfeir, D.

2003-12-01

We present intermediate results from a long-term program of mapping the neutral absorption characteristics of the local interstellar medium, motivated by the availability of accurate and consistent parallaxes from the Hipparcos satellite. Equivalent widths of the interstellar NaI D-line doublet at 5890 Å are presented for the lines-of-sight towards some 311 new target stars lying within ~ 350 pc of the Sun. Using these data, together with NaI absorption measurements towards a further ~ 240 nearby targets published in the literature (for many of them, in the directions of molecular clouds), and the ~ 450 lines-of-sight already presented by (Sfeir et al. \\cite{sfeir99}), we show 3D absorption maps of the local distribution of neutral gas towards 1005 sight-lines with Hipparcos distances as viewed from a variety of different galactic projections. The data are synthesized by means of two complementary methods, (i) by mapping of iso-equivalent width contours, and (ii) by density distribution calculation from the inversion of column-densities, a method devised by Vergely et al. (\\cite{vergely01}). Our present data confirms the view that the local cavity is deficient in cold and neutral interstellar gas. The closest dense and cold gas wall'', in the first quadrant, is at ~ 55-60 pc. There are a few isolated clouds at closer distance, if the detected absorption is not produced by circumstellar material. The maps reveal narrow or wide interstellar tunnels'' which connect the Local Bubble to surrounding cavities, as predicted by the model of Cox & Smith (1974). In particular, one of these tunnels, defined by stars at 300 to 600 pc from the Sun showing negligible sodium absorption, connects the well known CMa void (Gry et al. \\cite{gry85}), which is part of the Local Bubble, with the supershell GSH 238+00+09 (Heiles \\cite{heiles98}). High latitude lines-of-sight with the smallest absorption are found in two chimneys'', whose directions are perpendicular to the

12. A pilot-scale jet bubbling reactor for wet flue gas desulfurization with pyrolusite.

PubMed

Su, Shi-jun; Zhu, Xiao-fan; Liu, Yong-jun; Jiang, Wen-ju; Jin, Yan

2005-01-01

MnO2 in pyrolusite can react with SO2 in flue gas and obtain by-product MnSO4 x H2O. A pilot scale jet bubbling reactor was applied in this work. Different factors affecting both SO2 absorption efficiency and Mn2+ extraction rate have been investigated, these factors include temperature of inlet gas flue, ration of liquid/solid mass flow rate (L/S), pyrolusite grade, and SO2 concentration in the inlet flue gas. In the meantime, the procedure of purification of absorption liquid was also discussed. Experiment results indicated that the increase of temperature from 30 to 70 K caused the increase of SO2 absorption efficiency from 81.4% to 91.2%. And when SO2 concentration in the inlet flue gas increased from 500 to 3000 ppm, SO2 absorption efficiency and Mn2+ extraction rate decreased from 98.1% to 82.2% and from 82.8% to 61.7%, respectively. The content of MnO2 in pyrolusite had a neglectable effect on SO2 absorption efficiency. Low L/S was good for both removal of SO2 and Mn2+ extraction. The absorption liquid was filtrated and purified to remove Si, Mg, Ca, Fe, Al and heavy metals, last product MnSO4 x H2O was obtained which quality could reach China GB1622-86, the industry grade standards.

13. Gas Bubble Disease in the Brain of a Living California Sea Lion (Zalophus californianus)

PubMed Central

Van Bonn, William; Dennison, Sophie; Cook, Peter; Fahlman, Andreas

2013-01-01

A yearling California sea lion (Zalophus californianus) was admitted into rehabilitation with signs of cerebellar pathology. Diagnostic imaging that included radiography and magnetic resonance imaging (MRI) demonstrated space-occupying lesions predominantly in the cerebellum that were filled partially by CSF-like fluid and partially by gas, and cerebral lesions that were fluid filled. Over a maximum period of 4 months, the brain lesions reduced in size and the gas resorbed and was replaced by CSF-like fluid. In humans, the cerebellum is known to be essential for automating practiced movement patterns (e.g., learning to touch-type), also known as procedural learning or the consolidation of “motor memory.” To test the animal in this study for motor memory deficits, an alternation task in a two-choice maze was utilized. The sea lion performed poorly similar to another case of pneumocerebellum previously reported, and contrary to data acquired from a group of sea lions with specific hippocampal injury. The learning deficits were attributed to the cerebellar injury. These data provide important insight both to the clinical presentation and behavioral observations of cerebellar injury in sea lions, as well as providing an initial model for long-term outcome following cerebellar injury. The specific etiology of the gas could not be determined. The live status of the patient with recovery suggests that the most likely etiologies for the gas are either de novo formation or air emboli secondary to trauma. A small air gun pellet was present within and was removed from soft tissues adjacent to the tympanic bulla. While no evidence to support the pellet striking bone was found, altered dive pattern associated with this human interaction may have provided the opportunity for gas bubble formation to occur. The similarity in distribution of the gas bubble related lesions in this case compared with another previously published case of pneumocerebellum suggests that

14. Fuel Performance Experiments and Modeling: Fission Gas Bubble Nucleation and Growth in Alloy Nuclear Fuels

SciTech Connect

McDeavitt, Sean; Shao, Lin; Tsvetkov, Pavel; Wirth, Brian; Kennedy, Rory

2014-04-07

Advanced fast reactor systems being developed under the DOE's Advanced Fuel Cycle Initiative are designed to destroy TRU isotopes generated in existing and future nuclear energy systems. Over the past 40 years, multiple experiments and demonstrations have been completed using U-Zr, U-Pu-Zr, U-Mo and other metal alloys. As a result, multiple empirical and semi-empirical relationships have been established to develop empirical performance modeling codes. Many mechanistic questions about fission as mobility, bubble coalescience, and gas release have been answered through industrial experience, research, and empirical understanding. The advent of modern computational materials science, however, opens new doors of development such that physics-based multi-scale models may be developed to enable a new generation of predictive fuel performance codes that are not limited by empiricism.

15. Acoustic Characterization of Fluorinert FC-43 Liquid with Helium Gas Bubbles: Numerical Experiments

DOE PAGES

Vanhille, Christian; Pantea, Cristian; Sinha, Dipen N.

2017-01-01

In this work, we define the acoustic characteristics of a biphasic fluid consisting of static helium gas bubbles in liquid Fluorinert FC-43 and study the propagation of ultrasound of finite amplitudes in this medium. Very low sound speed and high sound attenuation are found, in addition to a particularly high acoustic nonlinear parameter. This result suggests the possibility of using this medium as a nonlinear enhancer in various applications. In particular, parametric generation of low ultrasonic frequencies is studied in a resonator cavity as a function of driving pressure showing high conversion efficiency. This work suggests that this medium couldmore » be used for applications such as parametric arrays, nondestructive testing, diagnostic medicine, sonochemistry, underwater acoustics, and ultrasonic imaging and to boost the shock formation in fluids.« less

16. Gas Bubble Trauma Monitoring in the Clearwater River Drainage, Idaho 1998.

SciTech Connect

Cochnauer, Tim

1998-12-01

Select portions of the Clearwater and North Fork of the Clearwater rivers were electroshocked to estimate the incidence of gas bubble trauma (GBT) occurring in resident fish populations for the spring and summer months of 1998. The study area was divided into four sections and sampled weekly during periods of spill and non-spill from Dworshak Dam. Five thousand five hundred and forty one fish, representing 22 different species, were captured and examined for GBT. Two fish were detected with signs of GBT; exhibiting the lowest incidence of GBT in the last four years (0.04%). Reduced discharge and lower levels of total dissolved gases may have resulted in lower incidence of GBT in the 1998 monitoring period.

17. Effects of Gravity on Bubble Formation at a Plate Orifice

NASA Technical Reports Server (NTRS)

Webbon, Bruce W.; Buyevich, Yu A.

1995-01-01

A model of the dynamic regime of gas injection through a submerged plate orifice into an ideally wetting liquid is developed in the circumstance when successively detached bubbles may be regarded as independent objects. Two major factors favor bubble detachment: the buoyancy force and a force due to the momentum inflow into the bubble with injected gas. In normal and moderately reduced gravity, the first factor dominates. At relatively low flow rates, a growing bubble is modeled as a spherical segment touching the orifice perimeter during the whole period of its evolution till detachment. If the flow rate exceeds a critical value, another stage of bubble evolution occurs in which an almost spherical gas envelope is connected with the orifice by a nearly cylindrical gaseous stem that lengthens as the bubble rises above the plate. The bubble continues to grow until the gas supply through the stem is completely cut off, after which back flow of gas into the stem from the bubble becomes possible. In microgravity, the second factor prevails, and the latter stage is always present irrespective of the flow rate. However, the gas envelope rises and the stem lengthens very slowly. This difference in the underlying physical mechanisms provides for key properties of bubble growth and detachment being drastically different in appreciable and sufficiently reduced gravity. The frequency of bubble formation slightly decreases with and the detachment volume is almost proportional to the gas flow rate in the first case, in accordance with familiar relations. In the second case, the first variable is proportional to the flow rate whereas the second one is independent of it. Effects of other parameters, such as the orifice radius, gas and liquid densities, and surface tension are discussed.

18. Passive acoustic derived bubble flux and applications to natural gas seepage in the Mackenzie Delta, NWT, Canada and Coal Oil Point, CA

Culling, D.; Leifer, I.; Dallimore, S.; Alcala, K.

2012-12-01

Methane is a prominent greenhouse gas that escapes naturally from thermogenic reservoirs as seepage from marine and lacustrine biogenic sources as bubble ebullition. Geologic methane emissions are critically important contributors to the global methane budget however, few quantitative flux measurements are available for shallow waters. This gap in knowledge is critical as in these settings gas can easily transit as bubbles through the water column and directly influence global atmospheric budgets. Video and active acoustic (sonar) measurements of bubble flux have spatial limitations requiring predictable bubble emission location. Passive acoustics are less affected by these limitations, in addition, they can provide data in water too shallow for effective sonar bubble observations. Lab tests were undertaken to quantify the acoustic signature of bubbles formed in non-cohesive sediments. specifically focusing on mechanisms that complicate interpretation of acoustic data. Lab tests then were compared to field data to provide measurement calibration/validation. The principles behind the acoustic analysis method are based on the Minnaert equation, which relates a bubble radius and acoustic frequency. Bubble size and the resultant acoustic frequency from known flows and capillary tube diameters are well documented; however changing sediment pathways adds to the complexity of bubble formation and the resultant bubble acoustic signal. These complex signals were investigated in a lab tank with a thick, cohesive fine-grained sediment bed, through which bubbles produced by a syringe pump migrated to the sediment-water interface. Then, the resultant bubbles were diverted into clear water and measured from high speed, high definition video, while the acoustic signature of bubble formation was recorded concurrently by a hydrophone. Bubble formation is influenced by currents, which shifts the acoustical signal towards a higher frequency with a more complex pattern than the

19. An Acoustic Levitation Technique for the Study of Nonlinear Oscillations of Gas Bubbles in Liquids.

DTIC Science & Technology

1983-08-15

alcohol and a mixture of glycerine and water (33-1/3% glycerine by volume) were the two liquids used in this research. Bubbles were levitated near the...bubble can be trapped over a - -range of positions near a pressure antinode as a result of the balancing of these two forces. * The acoustic...then used to investigate the nonlinear oscillations of the bubble over a range of sizes. The bubbles were studied in two liq- uids: isopropyl alcohol

20. Relationship of the time course of venous gas bubbles to altitude decompression illness

NASA Technical Reports Server (NTRS)

Conkin, J.; Foster, P. P.; Powell, M. R.; Waligora, J. M.

1996-01-01

The correlation is low between the occurrence of gas bubbles in the pulmonary artery, called venous gas emboli (VGE), and subsequent decompression illness (DCI). The correlation improves when a "grade" of VGE is considered; a zero to four categorical classification based on the intensity and duration of the VGE signal from a Doppler bubble detector. Additional insight about DCI might come from an analysis of the time course of the occurrence of VGE. Using the NASA Hypobaric Decompression Sickness Databank, we compared the time course of the VGE outcome between 322 subjects who exercised and 133 Doppler technicians who did not exercise to evaluate the role of physical activity on the VGE outcome and incidence of DCI. We also compared 61 subjects with VGE and DCI with 110 subjects with VGE but without DCI to identify unique characteristics about the time course of the VGE outcome to try to discriminate between DCI and no-DCI cases. The VGE outcome as a function of time showed a characteristic short lag, rapid response, and gradual recovery phase that was related to physical activity at altitude and the presence or absence of DCI. The average time for DCI symptoms in a limb occurred just before the time of the highest fraction of VGE in the pulmonary artery. It is likely, but not certain, that an individual will report a DCI symptom if VGE are detected early in the altitude exposure, the intensity or grade of VGE rapidly increases from a limb region, and the intensity or grade of VGE remains high.

1. A deep stop during decompression from 82 fsw (25 m) significantly reduces bubbles and fast tissue gas tensions.

PubMed

Marroni, A; Bennett, P B; Cronje, F J; Cali-Corleo, R; Germonpre, P; Pieri, M; Bonuccelli, C; Balestra, C

2004-01-01

In spite of many modifications to decompression algorithms, the incidence of decompression sickness (DCS) in scuba divers has changed very little. The success of stage, compared to linear ascents, is well described yet theoretical changes in decompression ratios have diminished the importance of fast tissue gas tensions as critical for bubble generation. The most serious signs and symptoms of DCS involve the spinal cord, with a tissue half time of only 12.5 minutes. It is proposed that present decompression schedules do not permit sufficient gas elimination from such fast tissues, resulting in bubble formation. Further, it is hypothesized that introduction of a deep stop will significantly reduce fast tissue bubble formation and neurological DCS risk. A total of 181 dives were made to 82 fsw (25 m) by 22 volunteers. Two dives of 25 min and 20 min were made, with a 3 hr 30 min surface interval and according to 8 different ascent protocols. Ascent rates of 10, 33 or 60 fsw/min (3, 10, 18 m/min) were combined with no stops or a shallow stop at 20 fsw (6 m) or a deep stop at 50 fsw (15 m) and a shallow at 20 fsw (6 m). The highest bubbles scores (8.78/9.97), using the Spencer Scale (SS) and Extended Spencer Scale (ESS) respectively, were with the slowest ascent rate. This also showed the highest 5 min and 10 min tissue loads of 48% and 75%. The lowest bubble scores (1.79/2.50) were with an ascent rate of 33 fsw (10 m/min) and stops for 5 min at 50 fsw (15 m) and 20 fsw (6 m). This also showed the lowest 5 and 10 min tissue loads at 25% and 52% respectively. Thus, introduction of a deep stop significantly reduced Doppler detected bubbles together with tissue gas tensions in the 5 and 10 min tissues, which has implications for reducing the incidence of neurological DCS in divers.

2. Self assembly, mobilization, and flotation of crude oil contaminated sand particles as granular shells on gas bubbles in water.

PubMed

Tansel, Berrin; Boglaienko, Daria

2017-01-01

Contaminant fate and transport studies and models include transport mechanisms for colloidal particles and dissolved ions which can be easily moved with water currents. However, mobilization of much larger contaminated granular particles (i.e., sand) in sediments have not been considered as a possible mechanism due to the relatively larger size of sand particles and their high bulk density. We conducted experiments to demonstrate that oil contaminated granular particles (which exhibit hydrophobic characteristics) can attach on gas bubbles to form granular shells and transfer from the sediment phase to the water column. The interactions and conditions necessary for the oil contaminated granular particles to self assemble as tightly packed granular shells on the gas bubbles which transfer from sediment phase to the water column were evaluated both experimentally and theoretically for South Louisiana crude oil and quartz sand particles. Analyses showed that buoyancy forces can be adequate to move the granular shell forming around the air bubbles if the bubble radius is above 0.001mm for the sand particles with 0.28mm diameter. Relatively high magnitude of the Hamaker constant for the oil film between sand and air (5.81×10(-20)J for air-oil-sand) indicates that air bubbles have high affinity to attach on the oil film that is on the sand particles in comparison to attaching to the sand particles without the oil film in water (1.60×10(-20)J for air-water-sand). The mobilization mechanism of the contaminated granular particles with gas bubbles can occur in natural environments resulting in transfer of granular particles from sediments to the water column.

3. Cluster finds giant gas vortices at the edge of Earth's magnetic bubble

2004-08-01

first time that vortices are actually detected. When a KHI-wave rolls up into a vortex, it becomes known as a ‘Kelvin Cat’s eye’. The data collected by Cluster have shown density variations of the electrified gas, right at the magnetopause, precisely like those expected when travelling through a ‘Kelvin Cat’s eye’. Scientists had postulated that, if these structures were to form at the magnetopause, they might be able to pull large quantities of the solar wind inside the boundary layer as they collapse. Once the solar wind particles are carried into the inner part of the magnetosphere, they can be excited strongly, allowing them to smash into Earth’s atmosphere and give rise to the aurorae. Cluster’s discovery strengthens this scenario but does not show the precise mechanism by which the gas is transported into Earth’s magnetic bubble. Thus, scientists still do not know whether this is the only process to fill up the boundary layer when the magnetic fields are aligned. For those measurements, Hasegawa says, scientists will have to wait for a future generation of magnetospheric satellites. Notes for editors The results of this investigation have appeared in today’s issue of the scientific journal Nature, in a paper entitled ‘Transport of solar wind into Earth's magnetosphere through rolled-up Kelvin-Helmholtz vortices’, by H. Hasegawa, M. Fujimoto, T.D. Phan, H. Reme, A. Balogh, M.W. Dunlop, C. Hashimoto and R. TanDokoro. More about magnetic reconnection Solar wind particles follow ‘magnetic field lines’, rather like beads on a wire. The ‘doors’ that open in Earth’s magnetosphere during oppositely aligned magnetic configurations are caused by a phenomenon called ‘magnetic reconnection‘. During this process, Earth’s field lines spontaneously break and join themselves to the Sun’s, allowing the solar wind to pass freely into Earth’s magnetosphere. Magnetic reconnections are not possible in the aligned case, however, hence the

4. Lateral line pore diameters correlate with the development of gas bubble trauma signs in several Columbia River fishes

USGS Publications Warehouse

Morris, R.G.; Beeman, J.W.; VanderKooi, S.P.; Maule, A.G.

2003-01-01

Gas bubble trauma (GBT) caused by gas supersaturation of river water continues to be a problem in the Columbia River Basin. A common indicator of GBT is the percent of the lateral line occluded with gas bubbles; however, this effect has never been examined in relation to lateral line morphology. The effects of 115, 125 and 130% total dissolved gas levels were evaluated on five fish species common to the upper Columbia River. Trunk lateral line pore diameters differed significantly (P<0.0001) among species (longnose sucker>largescale sucker>northern pikeminnow???chinook salmon???redside shiner). At all supersaturation levels evaluated, percent of lateral line occlusion exhibited an inverse correlation to pore size but was not generally related to total dissolved gas level or time of exposure. This study suggests that the differences in lateral line pore diameters between species should be considered when using lateral line occlusion as an indicator of gas bubble trauma. ?? 2003 Elsevier Science Inc. All rights reserved.

5. Inertial-Fusion-Related Hydrodynamic Instabilities in a Spherical Gas Bubble Accelerated by a Planar Shock Wave

SciTech Connect

Niederhaus, John; Ranjan, Devesh; Anderson, Mark; Oakley, Jason; Bonazza, Riccardo; Greenough, Jeff

2005-05-15

Experiments studying the compression and unstable growth of a dense spherical bubble in a gaseous medium subjected to a strong planar shock wave (2.8 < M < 3.4) are performed in a vertical shock tube. The test gas is initially contained in a free-falling spherical soap-film bubble, and the shocked bubble is imaged using planar laser diagnostics. Concurrently, simulations are carried out using a compressible hydrodynamics code in r-z axisymmetric geometry.Experiments and computations indicate the formation of characteristic vortical structures in the post-shock flow, due to Richtmyer-Meshkov and Kelvin-Helmholtz instabilities, and smaller-scale vortices due to secondary effects. Inconsistencies between experimental and computational results are examined, and the usefulness of the current axisymmetric approach is evaluated.

6. Enriched Air Nitrox Breathing Reduces Venous Gas Bubbles after Simulated SCUBA Diving: A Double-Blind Cross-Over Randomized Trial

PubMed Central

Souday, Vincent; Koning, Nick J.; Perez, Bruno; Grelon, Fabien; Mercat, Alain; Boer, Christa; Seegers, Valérie; Radermacher, Peter; Asfar, Pierre

2016-01-01

Objective To test the hypothesis whether enriched air nitrox (EAN) breathing during simulated diving reduces decompression stress when compared to compressed air breathing as assessed by intravascular bubble formation after decompression. Methods Human volunteers underwent a first simulated dive breathing compressed air to include subjects prone to post-decompression venous gas bubbling. Twelve subjects prone to bubbling underwent a double-blind, randomized, cross-over trial including one simulated dive breathing compressed air, and one dive breathing EAN (36% O2) in a hyperbaric chamber, with identical diving profiles (28 msw for 55 minutes). Intravascular bubble formation was assessed after decompression using pulmonary artery pulsed Doppler. Results Twelve subjects showing high bubble production were included for the cross-over trial, and all completed the experimental protocol. In the randomized protocol, EAN significantly reduced the bubble score at all time points (cumulative bubble scores: 1 [0–3.5] vs. 8 [4.5–10]; P < 0.001). Three decompression incidents, all presenting as cutaneous itching, occurred in the air versus zero in the EAN group (P = 0.217). Weak correlations were observed between bubble scores and age or body mass index, respectively. Conclusion EAN breathing markedly reduces venous gas bubble emboli after decompression in volunteers selected for susceptibility for intravascular bubble formation. When using similar diving profiles and avoiding oxygen toxicity limits, EAN increases safety of diving as compared to compressed air breathing. Trial Registration ISRCTN 31681480 PMID:27163253

7. FEASTING BLACK HOLE BLOWS BUBBLES

NASA Technical Reports Server (NTRS)

2002-01-01

A monstrous black hole's rude table manners include blowing huge bubbles of hot gas into space. At least, that's the gustatory practice followed by the supermassive black hole residing in the hub of the nearby galaxy NGC 4438. Known as a peculiar galaxy because of its unusual shape, NGC 4438 is in the Virgo Cluster, 50 million light-years from Earth. These NASA Hubble Space Telescope images of the galaxy's central region clearly show one of the bubbles rising from a dark band of dust. The other bubble, emanating from below the dust band, is barely visible, appearing as dim red blobs in the close-up picture of the galaxy's hub (the colorful picture at right). The background image represents a wider view of the galaxy, with the central region defined by the white box. These extremely hot bubbles are caused by the black hole's voracious eating habits. The eating machine is engorging itself with a banquet of material swirling around it in an accretion disk (the white region below the bright bubble). Some of this material is spewed from the disk in opposite directions. Acting like high-powered garden hoses, these twin jets of matter sweep out material in their paths. The jets eventually slam into a wall of dense, slow-moving gas, which is traveling at less than 223,000 mph (360,000 kph). The collision produces the glowing material. The bubbles will continue to expand and will eventually dissipate. Compared with the life of the galaxy, this bubble-blowing phase is a short-lived event. The bubble is much brighter on one side of the galaxy's center because the jet smashed into a denser amount of gas. The brighter bubble is 800 light-years tall and 800 light-years across. The observations are being presented June 5 at the American Astronomical Society meeting in Rochester, N.Y. Both pictures were taken March 24, 1999 with the Wide Field and Planetary Camera 2. False colors were used to enhance the details of the bubbles. The red regions in the picture denote the hot gas

8. Combination and simultaneous resonances of gas bubbles oscillating in liquids under dual-frequency acoustic excitation.

PubMed

Zhang, Yuning; Zhang, Yuning; Li, Shengcai

2017-03-01

The multi-frequency acoustic excitation has been employed to enhance the effects of oscillating bubbles in sonochemistry for many years. In the present paper, nonlinear dynamic oscillations of bubble under dual-frequency acoustic excitation are numerically investigated within a broad range of parameters. By investigating the power spectra and the response curves of oscillating bubbles, two unique features of bubble oscillations under dual-frequency excitation (termed as "combination resonance" and "simultaneous resonance") are revealed and discussed. Specifically, the amplitudes of the combination resonances are quantitatively compared with those of other traditional resonances (e.g. main resonances, harmonics). The influences of several paramount parameters (e.g., the bubble radius, the acoustic pressure amplitude, the energy allocation between two component waves) on nonlinear bubble oscillations are demonstrated.

9. Segregating gas from melt: an experimental study of the Ostwald ripening of vapor bubbles in magmas

USGS Publications Warehouse

Lautze, Nicole C.; Sisson, Thomas W.; Mangan, Margaret T.; Grove, Timothy L.

2011-01-01

Diffusive coarsening (Ostwald ripening) of H2O and H2O-CO2 bubbles in rhyolite and basaltic andesite melts was studied with elevated temperature–pressure experiments to investigate the rates and time spans over which vapor bubbles may enlarge and attain sufficient buoyancy to segregate in magmatic systems. Bubble growth and segregation are also considered in terms of classical steady-state and transient (non-steady-state) ripening theory. Experimental results are consistent with diffusive coarsening as the dominant mechanism of bubble growth. Ripening is faster in experiments saturated with pure H2O than in those with a CO2-rich mixed vapor probably due to faster diffusion of H2O than CO2 through the melt. None of the experimental series followed the time1/3 increase in mean bubble radius and time-1 decrease in bubble number density predicted by classical steady-state ripening theory. Instead, products are interpreted as resulting from transient regime ripening. Application of transient regime theory suggests that bubbly magmas may require from days to 100 years to reach steady-state ripening conditions. Experimental results, as well as theory for steady-state ripening of bubbles that are immobile or undergoing buoyant ascent, indicate that diffusive coarsening efficiently eliminates micron-sized bubbles and would produce mm-sized bubbles in 102–104 years in crustal magma bodies. Once bubbles attain mm-sizes, their calculated ascent rates are sufficient that they could transit multiple kilometers over hundreds to thousands of years through mafic and silicic melt, respectively. These results show that diffusive coarsening can facilitate transfer of volatiles through, and from, magmatic systems by creating bubbles sufficiently large for rapid ascent.

10. Dynamics of a Spherical Vapor/Gas Bubble in Varying Pressure Fields

Kawashima, Hisanobu; Kameda, Masaharu

A mathematical model is developed to simulate the radial motion of cavitation bubbles. The heat and mass transports including phase change are formulated precisely. In order to reduce the computational cost without loss of the important thermo-fluid phenomena, two simplifications are employed: time-dependent bubble radius is described using the Rayleigh-Plesset equation; the pressure in the bubble is assumed to be uniform in space. For validation of the model, the transient radial motion of an air bubble in water is observed experimentally. A shock tube is used to make the sudden pressure reduction from atmospheric to below the saturated vapor pressure. The bubble radius is measured by high-speed photography, in which an interferomtric laser imaging technique is used for accurate determination of the initial bubble radius. The radial motion is successfully predicted by using this model. The temperature reduction at the bubble wall is a predominant factor on the bubble growth rate under superheated conditions, even if the liquid temperature is close to room temperature. The numerical result indicates that the growth rate is very sensitive to initial bubble radius, ambient pressure, and liquid temperature.

11. Bubble diagnostics

DOEpatents

Visuri, Steven R.; Mammini, Beth M.; Da Silva, Luiz B.; Celliers, Peter M.

2003-01-01

The present invention is intended as a means of diagnosing the presence of a gas bubble and incorporating the information into a feedback system for opto-acoustic thrombolysis. In opto-acoustic thrombolysis, pulsed laser radiation at ultrasonic frequencies is delivered intraluminally down an optical fiber and directed toward a thrombus or otherwise occluded vessel. Dissolution of the occlusion is therefore mediated through ultrasonic action of propagating pressure or shock waves. A vapor bubble in the fluid surrounding the occlusion may form as a result of laser irradiation. This vapor bubble may be used to directly disrupt the occlusion or as a means of producing a pressure wave. It is desirable to detect the formation and follow the lifetime of the vapor bubble. Knowledge of the bubble formation and lifetime yields critical information as to the maximum size of the bubble, density of the absorbed radiation, and properties of the absorbing material. This information can then be used in a feedback system to alter the irradiation conditions.

12. The effect of pH and gas composition on the bubble fractionation of proteins

SciTech Connect

DeSouza, A.H.G.; Tanner, R.D.; Effler, W.T. Jr.

1991-12-31

Studies were conducted to establish the effect of the variation of environmental factors on the separation occurring in protein systems, resulting from bubble fractionation in a bioreactor. The measure of separation was selected to be the separation ratio. This is defined to be the ratio of either the top or the middle position concentration in the vessel to the bottom concentration of the vessel. Invertase and Ce-amylase were the two {open_quotes}model{close_quotes} enzymes considered. It was observed that, under certain conditions, i.e., a combination of the nature of the sparging gas and the medium pH, varying degrees of protein separation were achieved. The pH of the system dramatically influenced the separation. It was found that the best separation occurred at a certain pH, assumed to be at or close to the pI of the protein in question. Furthermore, it was observed that systems sparged with CO{sub 2} exhibited greater separation than systems sparged with air. In fact, in the case of invertase, almost threefold separation was observed at the top port when the solution was sparged with CO{sub 2}.

13. Effect of Nozzle Geometry on Characteristics of Submerged Gas Jet and Bubble Noise.

PubMed

Bie, Hai-Yan; Ye, Jian-Jun; Hao, Zong-Rui

2016-10-01

Submerged exhaust noise is one of the main noise sources of underwater vehicles. The nozzle features of pipe discharging systems have a great influence on exhaust noise, especially on the noise produced by gas-liquid two-phase flow outside the nozzle. To study the influence of nozzle geometry on underwater jet noises, a theoretical study was performed on the critical weber number at which the jet flow field morphology changes. The underwater jet noise experiments of different nozzles under various working conditions were carried out. The experimental results implied that the critical weber number at which the jet flow transformed from bubbling regime to jetting regime was basically identical with the theoretical analysis. In the condition of jetting regime, the generated cavity of elliptical and triangular nozzles was smaller than that of the circular nozzle, and the middle- and high-frequency bands increased nonlinearly. The radiated noise decreased with the decrease in nozzle diameter. Combined with theoretical analysis and experimental research, three different submerged exhaust noise reduction devices were designed, and the validation tests proved that the noise reduction device with folds and diversion cone was the most effective.

14. Proteomics of juvenile senegal sole (Solea senegalensis) affected by gas bubble disease in hyperoxygenated ponds.

PubMed

Salas-Leiton, E; Cánovas-Conesa, B; Zerolo, R; López-Barea, J; Cañavate, J P; Alhama, J

2009-01-01

Solea senegalensis is a commercial flat fish traditionally farmed in earth ponds in coastal wetlands that might also become important to more intensive aquaculture. Gas bubble disease (GBD) is a potential risk for outdoor fish farming, particularly in certain periods of the year, related to improper management leading to macroalgae blooms. Physical-chemical conditions inducing hyperoxia, including radiation, temperature, and high levels of dissolved oxygen, have been monitored in fish affected by GBD together with observed symptoms. Exophthalmia, subcutaneous emphysemas, obstruction of gill lamellae, hemorrhages, and anomalous swimming were the main effects of oxygen supersaturation. A proteomic study was carried out for the first time under aquaculture conditions and protein expression changes are described for fish that were subject to hyperoxic conditions. Proteins identified in gill of GBD-affected fish are related to oxidative alteration of cytoskeleton structure/function (beta-tubulin, beta-actin), motility (light myosin chain, alpha-tropomyosin), or regulatory pathways (calmodulin, Raf kinase inhibitor protein), reflecting the central role of gill in oxygen exchange. Hepatic proteins identified are related to protein oxidative damages (beta-globin, FABPs), protection from oxidative stress (DCXR, GNMT), and inflammatory response (C3), in agreement with the predominant metabolic role of liver. Comparison of protein expression patterns and protein identification are suggested as potentially specific hyperoxia biomarkers that would facilitate prevention of GBD outbreaks.

15. Small Gas Bubble Experiment for Mitigation of Cavitation Damage and Pressure Waves in Short-pulse Mercury Spallation Targets

SciTech Connect

Wendel, Mark W; Felde, David K; Sangrey, Robert L; Abdou, Ashraf A; West, David L; Shea, Thomas J; Hasegawa, Shoichi; Kogawa, Hiroyuki; Naoe, Dr. Takashi; Farny, Dr. Caleb H.; Kaminsky, Andrew L

2014-01-01

Populations of small helium gas bubbles were introduced into a flowing mercury experiment test loop to evaluate mitigation of beam-pulse induced cavitation damage and pressure waves. The test loop was developed and thoroughly tested at the Spallation Neutron Source (SNS) prior to irradiations at the Los Alamos Neutron Science Center - Weapons Neutron Research Center (LANSCE-WNR) facility. Twelve candidate bubblers were evaluated over a range of mercury flow and gas injection rates by use of a novel optical measurement technique that accurately assessed the generated bubble size distributions. Final selection for irradiation testing included two variations of a swirl bubbler provided by Japan Proton Accelerator Research Complex (J-PARC) collaborators and one orifice bubbler developed at SNS. Bubble populations of interest consisted of sizes up to 150 m in radius with achieved gas void fractions in the 10^-5 to 10^-4 range. The nominal WNR beam pulse used for the experiment created energy deposition in the mercury comparable to SNS pulses operating at 2.5 MW. Nineteen test conditions were completed each with 100 pulses, including variations on mercury flow, gas injection and protons per pulse. The principal measure of cavitation damage mitigation was surface damage assessment on test specimens that were manually replaced for each test condition. Damage assessment was done after radiation decay and decontamination by optical and laser profiling microscopy with damaged area fraction and maximum pit depth being the more valued results. Damage was reduced by flow alone; the best mitigation from bubble injection was between half and a quarter that of flow alone. Other data collected included surface motion tracking by three laser Doppler vibrometers (LDV), loop wall dynamic strain, beam diagnostics for charge and beam profile assessment, embedded hydrophones and pressure sensors, and sound measurement by a suite of conventional and contact microphones.

16. Monodisperse, submicrometer droplets via condensation of microfluidic-generated gas bubbles.

PubMed

Seo, Minseok; Matsuura, Naomi

2012-09-10

Microfluidics (MFs) can produce monodisperse droplets with precise size control. However, the synthesis of monodisperse droplets much smaller than the minimum feature size of the microfluidic device (MFD) remains challenging, thus limiting the production of submicrometer droplets. To overcome the minimum micrometer-scale droplet sizes that can be generated using typical MFDs, the droplet material is heated above its boiling point (bp), and then MFs is used to produce monodisperse micrometer-scale bubbles (MBs) that are easily formed in the size regime where standard MFDs have excellent size control. After MBs are formed, they are cooled, condensing into dramatically smaller droplets that are beyond the size limit achievable using the original MFD, with a size decrease corresponding to the density difference between the gas and liquid phases of the droplet material. Herein, it is shown experimentally that monodisperse, submicrometer droplets of predictable sizes can be condensed from a monodisperse population of MBs as generated by MFs. Using perfluoropentane (PFP) as a representative solvent due to its low bp (29.2 °C), it is demonstrated that monodisperse PFP MBs can be produced at MFD temperatures >3.6 °C above the bp of PFP over a wide range of sizes (i.e., diameters from 2 to 200 μm). Independent of initial size, the generated MBs shrink rapidly in size from about 3 to 0 °C above the bp of PFP, corresponding to a phase change from gas to liquid, after which they shrink more slowly to form fully condensed droplets with diameters 5.0 ± 0.1 times smaller than the initial size of the MBs, even in the submicrometer size regime. This new method is versatile and flexible, and may be applied to any type of low-bp solvent for the manufacture of different submicrometer droplets for which precisely controlled dimensions are required.

17. Tiny Bubbles.

ERIC Educational Resources Information Center

Kim, Hy

1985-01-01

A simple oxygen-collecting device (easily constructed from glass jars and a lid) can show bubbles released by water plants during photosynthesis. Suggestions are given for: (1) testing the collected gas; (2) using various carbon dioxide sources; and (3) measuring respiration. (DH)

18. Controlling the Mobility of the Fluid Interface of Moving Gas Bubbles or Liquid Drops by Using Micellar Solutions of Surfactants

NASA Technical Reports Server (NTRS)

Maldarelli, Charles; Papageorgiou, Demetrios

1998-01-01

Microgravity processes must rely on mechanisms other than buoyancy to move bubbles or droplets from one region to another in a continuous liquid phase. One suggested method is thermocapillary migration in which a temperature gradient is applied to the continuous phase. A significant and as yet unresolved impediment to the use of thermocapillary migration to direct bubble or drop motion is that these migrations can be significantly retarded by the adsorption onto the fluid particle surface of surface active impurities unavoidably present in the continuous or (if the particle is a liquid) droplet phases. The focus of our research was to develop a theory for remobilizing fluid particle interfaces retarded by a surfactant impurity in an effort to make more viable the use of thermocapillary migrations for the management of bubbles and drops in microgravity. We postulated that a surfactant at high bulk concentration which kinetically exchanges rapidly with the surface can restore interface mobility. The scaling arguments along with a discussion of the previous literature is reviewed in the context of the scaling framework. The specific objectives of the research were twofold. The first was to prove the remobilization theory by studying a model problem. As the mechanism for remobilization is independent of the force which drives the particle, the fluid particle shape and the presence of fluid inertia, we chose the simplest model consisting of a spherical bubble rising steadily by buoyancy in creeping flow. We solved the hydrodynamic and surfactant transport equations for rapid kinetic exchange to demonstrate that as the concentration increases, the Marangoni retardation at first increases (the low k behavior) and then decreases (the high k behavior). The second objective was to develop a method to determine the kinetic rate constants of a surfactant molecule, since this information is necessary to select surfactants which will exchange rapidly enough relative to the

19. Effect of grain morphology on gas bubble swelling in UMo fuels - A 3D microstructure dependent Booth model

Hu, Shenyang; Burkes, Douglas; Lavender, Curt A.; Joshi, Vineet

2016-11-01

A three dimensional microstructure dependent swelling model is developed for studying the fission gas swelling kinetics in irradiated nuclear fuels. The model is extended from the Booth model [1] in order to investigate the effect of heterogeneous microstructures on gas bubble swelling kinetics. As an application of the model, the effect of grain morphology, fission gas diffusivity, and spatially dependent fission rate on swelling kinetics are simulated in UMo fuels. It is found that the decrease of grain size, the increase of grain aspect ratio for the grain having the same volume, and the increase of fission gas diffusivity (fission rate) cause the increase of swelling kinetics. Other heterogeneities such as second phases and spatially dependent thermodynamic properties including diffusivity of fission gas, sink and source strength of defects could be naturally integrated into the model to enhance the model capability.

20. Effect of grain morphology on gas bubble swelling in UMo fuels – A 3D microstructure dependent Booth model

SciTech Connect

Hu, Shenyang; Burkes, Douglas; Lavender, Curt A.; Joshi, Vineet

2016-11-01

A three dimensional microstructure dependent swelling model is developed for studying the fission gas swelling kinetics in irradiated nuclear fuels. The model is extended from the Booth model [1] in order to investigate the effect of heterogeneous microstructures on gas bubble swelling kinetics. As an application of the model, the effect of grain morphology, fission gas diffusivity, and spatial dependent fission rate on swelling kinetics are simulated in UMo fuels. It is found that the decrease of grain size, the increase of grain aspect ratio for the grain having the same volume, and the increase of fission gas diffusivity (fission rate) cause the increase of swelling kinetics. Other heterogeneities such as second phases and spatial dependent thermodynamic properties including diffusivity of fission gas, sink and source strength of defects could be naturally integrated into the model to enhance the model capability.

1. In Search of the Big Bubble

ERIC Educational Resources Information Center

Simoson, Andrew; Wentzky, Bethany

2011-01-01

Freely rising air bubbles in water sometimes assume the shape of a spherical cap, a shape also known as the "big bubble". Is it possible to find some objective function involving a combination of a bubble's attributes for which the big bubble is the optimal shape? Following the basic idea of the definite integral, we define a bubble's surface as…

2. A new method for measuring concentration of a fluorescent tracer in bubbly gas-liquid flows

Moghaddas, J. S.; Trägårdh, C.; Kovacs, T.; Östergren, K.

2002-06-01

A new experimental model, the two-tracer method (TTM), based on the planar laser-induced fluorescence technique (PLIF), is presented for the measurement of the local concentration of a fluorescent tracer in the liquid phase of a bubbly two-phase system. Light scattering and shading effects due to the bubbles were compensated for using the new model. The TTM results were found to give more accurate predictions of the local concentration than the normal PLIF method in a bubbly two-phase system.

3. Gas holdup and flow regime transition in spider-sparger bubble column: effect of liquid phase properties

Besagni, G.; Inzoli, F.; De Guido, G.; Pellegrini, L. A.

2017-01-01

This paper discusses the effects of the liquid velocity and the liquid phase properties on the gas holdup and the flow regime transition in a large-diameter and large-scale counter-current two-phase bubble column. In particular, we compared and analysed the experimental data obtained in our previous experimental studies. The bubble column is 5.3 m in height, has an inner diameter of 0.24 m, it was operated with gas superficial velocities in the range of 0.004–0.20 m/s and, in the counter-current mode, the liquid was recirculated up to a superficial velocity of -0.09 m/s. Air was used as the dispersed phase and various fluids (tap water, aqueous solutions of sodium chloride, ethanol and monoethylene glycol) were employed as liquid phases. The experimental dataset consist in gas holdup measurements and was used to investigate the global fluid dynamics and the flow regime transition between the homogeneous flow regime and the transition flow regime. We found that the liquid velocity and the liquid phase properties significantly affect the gas holdup and the flow regime transition. In this respect, a possible relationship (based on the lift force) between the flow regime transition and the gas holdup was proposed.

4. Gas-bubbled nano zero-valent iron process for high concentration arsenate removal.

PubMed

Tanboonchuy, Visanu; Hsu, Jia-Chin; Grisdanurak, Nurak; Liao, Chih-Hsiang

2011-02-28

In this study, batch experiments were performed to investigate a novel process for high concentration arsenate removal in the presence of air and/or CO(2) bubbling. The pretreatment step, CO(2) bubbling at 300 mL/min for 5 min, was taken to adjust the solution pH to an acidic environment, followed by air bubbling at 300 mL/min for 10 min to increase dissolved oxygen in the solution. In the treatment period, the nano-scale zero-valent iron was applied to remove aqueous arsenate of 3000 μg/L, while the treatment system was continuously bubbled by 300 mL/min of air. Such a process resulted in outstanding performance in arsenate removal. Furthermore, in the field groundwater application, the arsenate removal rate for the proposed process was 5 times faster than the rate measured when the system was pretreated by acidic chemical species only.

5. Transmission and reflection of sound wave from a layer of liquid with gas bubbles

Gubaidullin, D. A.; Gubaidullina, D. D.; Fedorov, Yu V.

2017-01-01

The problem of reflection and transmission of sound wave through the two-layer medium containing a layer of bubble liquid is considered. A comparison of the reflection and transmission of wave coefficients with known experimental data is presented.

6. The effect of extended O2 prebreathing on altitude decompression sickness and venous gas bubbles

NASA Technical Reports Server (NTRS)

Waligora, James M.; Horrigan, David J.; Conkin, Johnny

1987-01-01

The purpose of this study was to determine the effect of extended O2 prebreathing on symptom and bubble incidence during decompressions simulating extravehicular activity. The 38 subjects breathed O2 for a 6-hr period prior to decompression to 4.3 psi. The subjects performed upper body exercises for 6 hr. Eight subjects were exposed to the same protocol after an 8-hr prebreathe. Venous bubbles were detected in 18 of 38 subjects decompressed after the 6-hr prebreathe. Four of these subjects reported symptoms of altitude decompression sickness. No symptoms or bubbles were detected in the eight subjects who had prebreathed 8 hr. The incidence of symptoms and bubbles, when combined with prior data on 3.5- and 4.0-hr prebreathes, showed an inverse correlation to prebreathing time. The incidence of symptoms was higher than has been reported for subjects exposed to decompression of shorter duration with less activity.

7. Effect of isobaric breathing gas shifts from air to heliox mixtures on resolution of air bubbles in lipid and aqueous tissues of recompressed rats.

PubMed

Hyldegaard, O; Kerem, D; Melamed, Y

2011-09-01

Deep tissue isobaric counterdiffusion that may cause unwanted bubble formation or transient bubble growth has been referred to in theoretical models and demonstrated by intravascular gas formation in animals, when changing inert breathing gas from nitrogen to helium after hyperbaric air breathing. We visually followed the in vivo resolution of extravascular air bubbles injected at 101 kPa into nitrogen supersaturated rat tissues: adipose, spinal white matter, skeletal muscle or tail tendon. Bubbles were observed during isobaric breathing-gas shifts from air to normoxic (80:20) heliox mixture while at 285 kPa or following immediate recompression to either 285 or 405 kPa, breathing 80:20 and 50:50 heliox mixtures. During the isobaric shifts, some bubbles in adipose tissue grew marginally for 10-30 min, subsequently they shrank and disappeared at a rate similar to or faster than during air breathing. No such bubble growth was observed in spinal white matter, skeletal muscle or tendon. In spinal white matter, an immediate breathing gas shift after the hyperbaric air exposure from air to both (80:20) and (50:50) heliox, coincident with recompression to either 285 or 405 kPa, caused consistent shrinkage of all air bubbles, until they disappeared from view. Deep tissue isobaric counterdiffusion may cause some air bubbles to grow transiently in adipose tissue. The effect is marginal and of no clinical consequence. Bubble disappearance rate is faster with heliox breathing mixtures as compared to air. We see no reason for reservations in the use of heliox breathing during treatment of air-diving-induced decompression sickness.

8. Modelling of bubble trajectories in a pump impeller

Dupoiron, Marine; Linden, Paul

2015-11-01

A vertical rotating flow in an annulus gap with an increasing diameter is used to approximate the flow in a pump impeller. We study a spherical gas bubble released at the flow inlet, subject to turbulent drag and added mass forces. Bubbles trajectories have been computed for different geometries, rotation speeds and bubble size, showing a deviation from the liquid streamlines in the angular and radial directions. This effect is related to the pump performance in multiphase conditions: the velocity difference between the gas and the liquid phases changes the final pressure rise produced by the impeller. In some extreme cases, the centrifugal force can be large enough to prevent bubbles from exiting the impeller at all, leading to an unwanted gas accumulation and the blockage of the pump. We eventually quantify the effects of geometrical and operational parameters on the pump behaviour. Work done in collaboration with Schlumberger Gould Research, Cambridge.

9. Acute and Chronic Outcomes of Gas-Bubble Disease in a Colony of African Clawed Frogs (Xenopus laevis).

PubMed

Tsai, Julia Y; Felt, Stephen A; Bouley, Donna M; Green, Sherril L

2017-02-01

Gas-bubble disease occurs in aquatic species that are exposed to water that is supersaturated with gases. In February 2007, municipal water supersaturated with gas was inadvertently pumped into the vivarium's aquatic housing systems and affected approximately 450 adult female Xenopus laevis. The inflow of supersaturated water was stopped immediately, the holding tanks aggressively aerated, and all experimental manipulations and feeding ceased. Within the first 6 h after the event, morbidity approached 90%, and mortality reached 3.5%. Acutely affected frogs showed clinical signs of gas-bubble disease: buoyancy problems, micro- and macroscopic bubbles in the foot webbing, hyperemia in foot webbing and leg skin, and loss of the mucous slime coat. All of the frogs that died or were euthanized had areas of mesenteric infarction, which resulted in intestinal epithelial necrosis and degeneration of the muscular tunic. Over the subsequent 2 wk, as gas saturation levels returned to normal, the clinical symptoms resolved completely in the remaining frogs. However, 3 mo later, 85% of them failed to lay eggs or produce oocytes, and the remaining 15% produced oocytes of low number and poor quality, yielding cytosolic extracts with poor to no enzymatic activity. Histology of the egg mass from a single 2- to 3-y-old frog at 3 mo after disease resolution revealed irregularly shaped oocytes, few large mature oocytes, and numerous small, degenerating oocytes. At 6 mo after the incident, the remaining frogs continued to fail to produce eggs of sufficient quantity or quality after hormonal priming. The researchers consequently opted to cull the remainder of the colony and repopulate with new frogs.

10. Thermocapillary convection around gas bubbles: an important natural effect for the enhancement of heat transfer in liquids under microgravity.

PubMed

Betz, J; Straub, J

2002-10-01

In the presence of a temperature gradient at a liquid-gas or liquid-liquid interface, thermocapillary or Marangoni convection develops. This convection is a special type of natural convection that was not paid much attention in heat transfer for a long time, although it is strong enough to drive liquids against the direction of buoyancy on Earth. In a microgravity environment, however, it is the remaining mode of natural convection and supports heat and mass transfer. During boiling in microgravity it was observed at subcooled liquid conditions. Therefore, the question arises about its contribution to heat transfer without phase change. Thermocapillary convection was quantitatively studied at single gas bubbles in various liquids, both experimentally and numerically. A two-dimensional mathematical model described in this article was developed. The coupled mechanism of heat transfer and fluid flow in pure liquids around a single gas bubble was simulated with a control-volume FE-method. The simulation was accompanied and compared with experiments on Earth. The numerical results are in good accordance with the experiments performed on Earth at various Marangoni numbers using various alcohols of varying chain length and Prandtl numbers. As well as calculations on Earth, the numerical method also allows simulations at stationary spherical gas bubbles in a microgravity environment. The results demonstrate that thermocapillary convection is a natural heat transfer mechanism that can partially replace the buoyancy in a microgravity environment, if extreme precautions are taken concerning the purity of the liquids, because impurities accumulate predominantly at the interface. Under Earth conditions, an enhancement of the heat transfer in a liquid volume is even found in the case where thermocapillary flow is counteracted by buoyancy. In particular, the obstructing influence of surface active substances could be observed during the experiments on Earth in water and also in

11. Tightrope walking bubbles

de Maleprade, Helene; Clanet, Christophe; Quere, David

2016-11-01

A fiber can hold a certain amount of liquid, which allows us to capture flying drops and control their motion. Immersed in water, a fiber can efficiently capture air bubbles only if it is hydrophobic. Using a superhydrophobic coating on an inclined wire, we experimentally control the rising velocity of air bubbles walking along the tightrope. We discuss the nature of the friction around the walker, and the resulting speed of bubbles.

12. Acoustic monitoring of co-seismic changes in gas bubble rupture rate in a hydrothermal reservoir: field evaluation of a possible precursor and mechanism for remote seismic triggering

Crews, J. B.

2015-12-01

Remotely triggered seismicity is a phenomenon in which an earthquake at one location triggers others over distances up to thousands of kilometers. The mechanism by which low-amplitude dynamic oscillations of the confining stress can produce such an effect, often after a time delay of minutes-to-days, is unclear, but a concentration of remotely triggered seismic events in carbon-dioxide-rich volcanic and geothermal regions suggests that an increase in pore fluid pressure associated with the nucleation and growth of carbon-dioxide gas bubbles may reduce the effective stress in critically loaded geologic faults. While this hypothesis has been tested in bench-scale laboratory experiments, field detection of seismically initiated gas bubble growth in groundwater may provide further evidence for this remote triggering mechanism. In the present study, a hydrophone continuously records the acoustic power spectrum in CH-10B, a hydrothermal well located in Long Valley Caldera, California - a site that is susceptible to remotely seismic triggering. This well exhibits co-seismic changes in water level in response to near and distant earthquakes, including every magnitude-six or greater at any location on Earth. Exploiting the inverse relationship between gas bubble radius and the peak acoustic frequency emitted when a gas bubble ruptures, this investigation seeks to detect changes in the acoustic power spectrum arising from a shift in the size-distribution or count rate of rupturing gas bubbles, coincident with a distant earthquake. By resolving the timing and intensity of the onset of a change in gas bubble rupture rate after the passage of seismic wave from a distant source, it may be possible to establish the extent to which seismically initiated gas bubble growth contributes to co-seismic borehole water level response, pore fluid pressure perturbations, and the onset of remotely triggered seismicity.

13. Bubble Formation at a Submerged Orifice in Reduced Gravity

NASA Technical Reports Server (NTRS)

Buyevich, Yu A.; Webbon, Bruce W.

1994-01-01

The dynamic regime of gas injection through a circular plate orifice into an ideally wetting liquid is considered, when successively detached bubbles may be regarded as separate identities. In normal gravity and at relatively low gas flow rates, a growing bubble is modeled as a spherical segment touching the orifice perimeter during the whole time of its evolution. If the flow rate exceeds a certain threshold value, another stage of the detachment process takes place in which an almost spherical gas envelope is connected with the orifice by a nearly cylindrical stem that lengthens as the bubble rises above the plate. The bubble shape resembles then that of a mushroom and the upper envelope continues to grow until the gas supply through the stem is completely cut off. Such a stage is always present under conditions of sufficiently low gravity, irrespective of the flow rate. Two major reasons make for bubble detachment: the buoyancy force and the force due to the momentum inflow into the bubble with the injected gas. The former force dominates the process at normal gravity whereas the second one plays a key role under negligible gravity conditions. It is precisely this fundamental factor that conditions the drastic influence on bubble growth and detachment that changes in gravity are able to cause. The frequency of bubble formation is proportional to and the volume of detached bubbles is independent of the gas flow rate in sufficiently low gravity, while at normal and moderately reduced gravity conditions the first variable slightly decreases and the second one almost linearly increases as the flow rate grows. Effects of other parameters, such as the orifice radius, gas and liquid densities, and surface tension are discussed.

14. Interaction between a large buoyant bubble and turbulence

Loisy, Aurore; Naso, Aurore

2017-01-01

The free rise of isolated, deformable, finite-size bubbles in otherwise homogeneous isotropic turbulence is investigated by direct numerical simulation. The Navier-Stokes equations are solved in both phases subject to the pertinent velocity and stress conditions at the deformable gas-liquid interface. The bubble rise velocity is found to be drastically reduced by turbulence, as is widely known for microbubbles. The probability distribution functions of the horizontal bubble acceleration component are well fitted by a log-normal distribution. The distributions of the vertical components are negatively skewed, a property related to the fact that bubbles experience on average stronger decelerations than accelerations. An assessment of the correlations of bubble acceleration with properties of the surrounding flow is used to define estimates of the liquid velocity and vorticity entering in liquid acceleration and lift forces. Finally, fast rising bubbles are found to preferentially sample downflow regions of the flow, whereas those subjected to a higher turbulence level have an increased residence time in swirling regions, some features similar to those of small bubbles.

15. Observations of bubbles in natural seep flares at MC 118 and GC 600 using in situ quantitative imaging

Wang, Binbin; Socolofsky, Scott A.; Breier, John A.; Seewald, Jeffrey S.

2016-04-01

This paper reports the results of quantitative imaging using a stereoscopic, high-speed camera system at two natural gas seep sites in the northern Gulf of Mexico during the Gulf Integrated Spill Research G07 cruise in July 2014. The cruise was conducted on the E/V Nautilus using the ROV Hercules for in situ observation of the seeps as surrogates for the behavior of hydrocarbon bubbles in subsea blowouts. The seeps originated between 890 and 1190 m depth in Mississippi Canyon block 118 and Green Canyon block 600. The imaging system provided qualitative assessment of bubble behavior (e.g., breakup and coalescence) and verified the formation of clathrate hydrate skins on all bubbles above 1.3 m altitude. Quantitative image analysis yielded the bubble size distributions, rise velocity, total gas flux, and void fraction, with most measurements conducted from the seafloor to an altitude of 200 m. Bubble size distributions fit well to lognormal distributions, with median bubble sizes between 3 and 4.5 mm. Measurements of rise velocity fluctuated between two ranges: fast-rising bubbles following helical-type trajectories and bubbles rising about 40% slower following a zig-zag pattern. Rise speed was uncorrelated with hydrate formation, and bubbles following both speeds were observed at both sites. Ship-mounted multibeam sonar provided the flare rise heights, which corresponded closely with the boundary of the hydrate stability zone for the measured gas compositions. The evolution of bubble size with height agreed well with mass transfer rates predicted by equations for dirty bubbles.

16. The necking time of gas bubbles in liquids of arbitrary viscosity

Bolaños-Jiménez, R.; Sevilla, A.; Martínez-Bazán, C.

2016-04-01

We report an experimental and theoretical study of the collapse time of a gas bubble injected into an otherwise stagnant liquid under quasi-static conditions and for a wide range of liquid viscosities. The experiments were performed by injecting a constant flow rate of air through a needle with inner radius a into several water/glycerine mixtures, providing a viscosity range of 20 cP ≲ μ ≲ 1500 cP. By analyzing the temporal evolution of the neck radius, R0(t), the collapse time has been extracted for three different stages during the collapse process, namely, Ri/a = 0.6, 0.4, and 0.2, being Ri = R0(t = 0) the initial neck radius. The collapse time is shown to monotonically increase with both Ri/a and with the Ohnesorge number, Oh = μ / √{ ρ σ R i } , where ρ and σ represent the liquid density and the surface tension coefficient, respectively. The theoretical approach is based on the cylindrical Rayleigh-Plesset equation for the radial liquid flow around the neck, which is the appropriate leading-order representation of the collapse dynamics, thanks to the slenderness condition R0(t) r1(t) ≪ 1, where r1(t) is half the axial curvature of the interface evaluated at the neck. The Rayleigh-Plesset equation can be integrated numerically to obtain the collapse time, τcol, which is made dimensionless using the capillary time, t σ = √{ ρ Ri 3 / σ } . We present a novel scaling law for τcol as a function of Ri/a and Oh that closely follows the experimental data for the entire range of both parameters, and provide analytical expressions in the inviscid and Stokes regimes, i.e., τ col ( Oh → 0 ) → √{ 2 ln C } and τcol(Oh → ∞) → 2Oh, respectively, where C is a constant of order unity that increases with Ri/a.

17. What can be Learned from X-ray Spectroscopy Concerning Hot Gas in Local Bubble and Charge Exchange Processes?

NASA Technical Reports Server (NTRS)

Snowden, Steve

2007-01-01

What can be learned from x-ray spectroscopy in observing hot gas in local bubble and charge exchange processes depends on spectral resolution, instrumental grasp, instrumental energy band, signal-to-nose, field of view, angular resolution and observatory location. Early attempts at x-ray spectroscopy include ROSAT; more recently, astronomers have used diffuse x-ray spectrometers, XMM Newton, sounding rocket calorimeters, and Suzaku. Future observations are expected with calorimeters on the Spectrum Roentgen Gamma mission, and the Solar Wind Charge Exchange (SWCX). The Geospheric SWCX may provide remote sensing of the solar wind and magnetosheath and remote observations of solar CMEs moving outward from the sun.

18. Degradation mechanisms of 4-chlorophenol in a novel gas-liquid hybrid discharge reactor by pulsed high voltage system with oxygen or nitrogen bubbling.

PubMed

Zhang, Yi; Zhou, Minghua; Hao, Xiaolong; Lei, Lecheng

2007-03-01

The effect of gas bubbling on the removal efficiency of 4-chlorophenol (4-CP) in aqueous solution has been investigated using a novel pulsed high voltage gas-liquid hybrid discharge reactor, which generates gas-phase discharge above the water surface simultaneously with the spark discharge directly in the liquid. The time for 100% of 4-CP degradation in the case of oxygen bubbling (7 min) was much shorter than that in the case of nitrogen bubbling (25 min) as plenty of hydrogen peroxide and ozone formed in oxygen atmosphere enhanced the removal efficiency of 4-CP. Except for the main similar intermediates (4-chlorocatechol, hydroquinone and 1,4-benzoquinone) produced in the both cases of oxygen and nitrogen bubbling, special intermediates (5-chloro-3-nitropyrocatechol, 4-chloro-2-nitrophenol, nitrate and nitrite ions) were produced in nitrogen atmosphere. The reaction pathway of 4-CP in the case of oxygen bubbling was oxygen/ozone attack on the radical hydroxylated derivatives of 4-CP. However, in the case of nitrogen bubbling, hydroxylation was the main reaction pathway with effect of N atom on degradation of 4-CP.

19. Upper ocean bubble measurements from the NE Pacific and estimates of their role in air-sea gas transfer of the weakly soluble gases nitrogen and oxygen

Vagle, Svein; McNeil, Craig; Steiner, Nadja

2010-12-01

Simultaneous observations of upper-ocean bubble clouds, and dissolved gaseous nitrogen (N2) and oxygen (O2) from three winter storms are presented and analyzed. The data were collected on the Canadian Surface Ocean Lower Atmosphere Study (C-SOLAS) mooring located near Ocean Station Papa (OSP) at 50°N, 145°W in the NE Pacific during winter of 2003/2004. The bubble field was measured using an upward looking 200 kHz echosounder. Direct estimates of bubble mediated gas fluxes were made using assumed bubble size spectra and the upward looking echosounder data. A one-dimensional biogeochemical model was used to help compare data and various existing models of bubble mediated air-sea gas exchange. The direct bubble flux calculations show an approximate quadratic/cubic dependence on mean bubble penetration depth. After scaling from N2/O2 to carbon dioxide, near surface, nonsupersaturating, air-sea transfer rates, KT, for U10 > 12 m s-1 fall between quadratic and cubic relationships. Estimates of the subsurface bubble induced air injection flux, VT, show an approximate quadratic/cubic dependence on mean bubble penetration depth. Both KT and VT are much higher than those measured during Hurricane Frances over the wind speed range 12 < U10 < 23 m s-1. This result implies that over the open ocean and this wind speed range, older and more developed seas which occur during winter storms are more effective in exchanging gases between the atmosphere and ocean than younger less developed seas which occur during the rapid passage of a hurricane.

20. Prospects for bubble fusion

SciTech Connect

Nigmatulin, R.I.; Lahey, R.T. Jr.

1995-09-01

In this paper a new method for the realization of fusion energy is presented. This method is based on the superhigh compression of a gas bubble (deuterium or deuterium/thritium) in heavy water or another liquid. The superhigh compression of a gas bubble in a liquid is achieved through forced non-linear, non-periodic resonance oscillations using moderate amplitudes of forcing pressure. The key feature of this new method is a coordination of the forced liquid pressure change with the change of bubble volume. The corresponding regime of the bubble oscillation has been called {open_quotes}basketball dribbling (BD) regime{close_quotes}. The analytical solution describing this process for spherically symmetric bubble oscillations, neglecting dissipation and compressibility of the liquid, has been obtained. This solution shown no limitation on the supercompression of the bubble and the corresponding maximum temperature. The various dissipation mechanisms, including viscous, conductive and radiation heat losses have been considered. It is shown that in spite of these losses it is possible to achieve very high gas bubble temperatures. This because the time duration of the gas bubble supercompression becomes very short when increasing the intensity of compression, thus limiting the energy losses. Significantly, the calculated maximum gas temperatures have shown that nuclear fusion may be possible. First estimations of the affect of liquid compressibility have been made to determine possible limitations on gas bubble compression. The next step will be to investigate the role of interfacial instability and breaking down of the bubble, shock wave phenomena around and in the bubble and mutual diffusion of the gas and the liquid.

1. Determination of the Accommodation Coefficient Using Vapor/gas Bubble Dynamics in an Acoustic Field

NASA Technical Reports Server (NTRS)

Gumerov, Nail A.; Hsiao, Chao-Tsung; Goumilevski, Alexei G.; Allen, Jeff (Technical Monitor)

2001-01-01

Nonequilibrium liquid/vapor phase transformations can occur in superheated or subcooled liquids in fast processes such as in evaporation in a vacuum. The rate at which such a phase transformation occurs depends on the "condensation" or "accommodation" coefficient, Beta, which is a property of the interface. Existing measurement techniques for Beta are complex and expensive. The development of a relatively inexpensive and reliable technique for measurement of Beta for a wide range of substances and temperatures is of great practical importance. The dynamics of a bubble in an acoustic field strongly depends on the value of Beta. It is known that near the saturation temperature, small vapor bubbles grow under the action of an acoustic field due to "rectified heat transfer." This finding can be used as the basis for an effective measurement technique of Beta. We developed a theory of vapor bubble behavior in an isotropic acoustic wave and in a plane standing acoustic wave. A numerical code was developed which enables simulation of a variety of experimental situations and accurately takes into account slowly evolving temperature. A parametric study showed that the measurement of Beta can be made over a broad range of frequencies and bubble sizes. We found several interesting regimes and conditions which can be efficiently used for measurements of Beta. Measurements of Beta can be performed in both reduced and normal gravity environments.

2. Observation of interaction of shock wave with gas bubble by image converter camera

Yoshii, M.; Tada, M.; Tsuji, T.; Isuzugawa, Kohji

1995-05-01

When a spark discharge occurs at the first focal point of a semiellipsoid or a reflector located in water, a spherical shock wave is produced. A part of the wave spreads without reflecting on the reflector and is called direct wave in this paper. Another part reflects on the semiellipsoid and converges near the second focal point, that is named the focusing wave, and locally produces a high pressure. This phenomenon is applied to disintegrators of kidney stone. But it is concerned that cavitation bubbles induced in the body by the expansion wave following the focusing wave will injure human tissue around kidney stone. In this paper, in order to examine what happens when shock waves strike bubbles on human tissue, the aspect that an air bubble is truck by the spherical shock wave or its behavior is visualized by the schlieren system and its photographs are taken using an image converter camera. Besides,the variation of the pressure amplitude caused by the shock wave and the flow of water around the bubble is measured with a pressure probe.

3. Numerical study of Taylor bubbles with adaptive unstructured meshes

Xie, Zhihua; Pavlidis, Dimitrios; Percival, James; Pain, Chris; Matar, Omar; Hasan, Abbas; Azzopardi, Barry

2014-11-01

The Taylor bubble is a single long bubble which nearly fills the entire cross section of a liquid-filled circular tube. This type of bubble flow regime often occurs in gas-liquid slug flows in many industrial applications, including oil-and-gas production, chemical and nuclear reactors, and heat exchangers. The objective of this study is to investigate the fluid dynamics of Taylor bubbles rising in a vertical pipe filled with oils of extremely high viscosity (mimicking the heavy oils'' found in the oil-and-gas industry). A modelling and simulation framework is presented here which can modify and adapt anisotropic unstructured meshes to better represent the underlying physics of bubble rise and reduce the computational effort without sacrificing accuracy. The numerical framework consists of a mixed control-volume and finite-element formulation, a volume of fluid''-type method for the interface capturing based on a compressive control volume advection method, and a force-balanced algorithm for the surface tension implementation. Numerical examples of some benchmark tests and the dynamics of Taylor bubbles are presented to show the capability of this method. EPSRC Programme Grant, MEMPHIS, EP/K0039761/1.

4. BURST OF STAR FORMATION DRIVES BUBBLE IN GALAXY'S CORE

NASA Technical Reports Server (NTRS)

2002-01-01

These NASA Hubble Space Telescope snapshots reveal dramatic activities within the core of the galaxy NGC 3079, where a lumpy bubble of hot gas is rising from a cauldron of glowing matter. The picture at left shows the bubble in the center of the galaxy's disk. The structure is more than 3,000 light-years wide and rises 3,500 light-years above the galaxy's disk. The smaller photo at right is a close-up view of the bubble. Astronomers suspect that the bubble is being blown by 'winds' (high-speed streams of particles) released during a burst of star formation. Gaseous filaments at the top of the bubble are whirling around in a vortex and are being expelled into space. Eventually, this gas will rain down upon the galaxy's disk where it may collide with gas clouds, compress them, and form a new generation of stars. The two white dots just above the bubble are probably stars in the galaxy. The close-up reveals that the bubble's surface is lumpy, consisting of four columns of gaseous filaments that tower above the galaxy's disk. The filaments disperse at a height of 2,000 light-years. Each filament is about 75 light-years wide. Velocity measurements taken by the Canada-France-Hawaii Telescope in Hawaii show that the gaseous filaments are ascending at more than 4 million miles an hour (6 million kilometers an hour). According to theoretical models, the bubble formed when ongoing winds from hot stars mixed with small bubbles of very hot gas from supernova explosions. Observations of the core's structure by radio telescopes indicate that those processes are still active. The models suggest that this outflow began about a million years ago. They occur about every 10 million years. Eventually, the hot stars will die, and the bubble's energy source will fade away. Astronomers have seen evidence of previous outbursts from radio and X-ray observations. Those studies show rings of dust and gas and long plumes of material, all of which are larger than the bubble. NGC 3079 is 50

5. Gas bubble disease: mortalities of coho salmon, Oncorhynchus kisutch, in water with constant total gas pressure and different oxygen-nitrogen ratios

USGS Publications Warehouse

Rucker, R.R.

1975-01-01

A review of the literature regarding gas-bubble disease can be found in a recent publication by Rucker (1972); one by the National Academy of Science (Anonymous in press); and an unpublished report by Weitkamp and Katz (1973)." Most discussions on gas-bubble disease have dealt with the inert gas, nitrogen-oxygen was given a secondary role. It is important to know the relationship of nitrogen and oxygen when we are concerned with the total gas pressure in water. Where water becomes aerated at dams or falls, oxygen and nitrogen are usually about equally saturated, however, many of the samples analyzed from the Columbia River indicate that nitrogen is often about 7% higher than oxygen when expressed as a percentage. When oxygen is removed from water by metabolic and chemical action, or when oxygen is added to the water by photosynthesis, there is a definite change in the ratio of oxygen and the inert gases (mainly nitrogen with some argon, etc.). This present study shows the effect of varying the oxygen and nitrogen ratio in water on fingerling coho salmon, Oncorh.llnchllS kislltch, while maintaining a constant total gas pressure. The primary purpose of these experiments was to determine differences in lethality of various gas ratios of oxygen and nitrogen at a constant total gas pressure of 119%. I also wished to determine whether there was a difference in susceptibility between sizes and stocks of juvenile coho. Also to be examined was the effect of reducing the oJl:ygen while holding the nitrogen constant.

6. Interfacial Bubble Deformations

Seymour, Brian; Shabane, Parvis; Cypull, Olivia; Cheng, Shengfeng; Feitosa, Klebert

Soap bubbles floating at an air-water experience deformations as a result of surface tension and hydrostatic forces. In this experiment, we investigate the nature of such deformations by taking cross-sectional images of bubbles of different volumes. The results show that as their volume increases, bubbles transition from spherical to hemispherical shape. The deformation of the interface also changes with bubble volume with the capillary rise converging to the capillary length as volume increases. The profile of the top and bottom of the bubble and the capillary rise are completely determined by the volume and pressure differences. James Madison University Department of Physics and Astronomy, 4VA Consortium, Research Corporation for Advancement of Science.

7. Three-dimensional measurement of bubble volume based on dual perspective imaging

Xue, Ting; Zhang, Shao-jie; Wu, Bin

2017-01-01

This paper presents a new three-dimensional (3D) volume measurement approach of bubble in gas-liquid two-phase flow. According to the dual perspective imaging principle, bubble feature images can be captured from two different view angles. The least square ellipse fitting algorithm is used to figure out the feature parameters from the captured images. Then the 3D volume of bubble can be quantitatively measured. Compaerd with the traditional volume estimation methods based on single perspective imaging, it can effectively reduce the loss of bubble feature information. In the experiment, the 3D volume reconstruction of bubbles from dual perspective images is conducted, and the variation of bubble volume in the bubble rising process is studied. The results show that the measurement accuracy based on the proposed 3D method is higher than those based on traditional methods. The volume of rising bubble is periodically changed, which indicates that bubble achieves periodic rotation and deformation in the rising process.

8. Influence of a gas bubble on the dynamical parameters of the slug flow using particle image velocimetry

Siddiqui, M. I.; Heikal, M. R.; Munir, S.; Dass, S. C.; Aziz, A. Rashid A.

2014-10-01

Inlet conditions strongly affect the dynamical parameters of a two-phase slug flow. A series of experiments were carried out, in a 6m long Plexiglas pipe having internal diameter 74 mm, to investigate the influence of gas bubble on the flow dynamics inside the slugy body of a unit slug. The pipe was kept inclined at an elevation of 1.160 to consider the terrain slugging mechanism. An optical diagnostic technique, Particle Image Velocimetry (PIV) was employed at a point 3.5m from the inlet to measure the instantaneous velocity fields of the flow for each case. Single-phase liquid pipe flow and the slugy body of the two-phase slug flow are the targeted sections for study and comparison. Velocity components, turbulence intensity and average volume flux are measured and compared. The effect of gas bubble on the liquid Reynolds number is also considered. It is noticed that by increasing the gas flow rate velocity, average flux and average kinetic energy increases dramatically in a slugy body of a slug flow regime. The results are also compared with the single phase liquid flow having same liquid flow rate. Moreover it is noticed that the increase in average volume flux in a slugy body for lower liquid flow rates are more significant as compared to the higher liquid flow rates by increasing gas rate. This shows that slug can be helpful in oil transportation in terrain oil fields for lower liquid flow rates as it creates more fluctuations and vibrational forces for higher liquid flow.

9. Binary coalescence of gas bubbles in the presence of a non-ionic surfactant.

PubMed

Duerr-Auster, N; Gunde, R; Mäder, R; Windhab, Erich J

2009-05-15

The coalescence behavior of air bubbles in a dilute aqueous surfactant solution of a polyglycerol fatty acid ester (PGE), a commercial non-ionic surfactant, is investigated in a binary coalescence experiment. The focus is on the influence of the ionic strength of the solution on the rate of coalescence. Results are compared with the adsorption kinetics and surface shear/dilatational rheological properties of the surfactant. Experiments show that the coalescence frequency is significantly lower at low ionic strength, and that bubble stability increases with increasing aging time. Stabilization occurs via surfactant adsorption and a resulting electrostatic and/or steric repulsive force. The electrostatic force presumably originates from small amounts of anionic fatty acid soaps, which are residues from the industrial synthesis. The steric force can be related to the adsorption of visco-elastic layers of PGE at the air-water interface.

10. Dissolved and Bubble Gas Concentrations in Sandy Surficial Sediments of the West Florida Sand Sheet

DTIC Science & Technology

2016-06-21

types. In these sandy sediments our focus is on oxygen produced through benthic primary production by algae living in the surface sediments. OBJECTIVES...the proposed sites for the October 1999 experiments of the High Frequency Sound Interaction in Ocean Sediments DRI (Directed Research Initiative...benthic primary production and thus some potential for generation of oxygen bubbles at the sediment-water interface. We planned to characterize

11. Photosynthesis as a Possible Source of Gas Bubbles in Shallow Sandy Coastal Sediments

DTIC Science & Technology

2011-09-30

bubbles can be formed when photosynthesis by benthic microalgae causes pore water to become supersaturated with oxygen. OBJECTIVES The next...reflectivity. We also collected sediment samples from the upper few mm of sand to identify the dominant taxa of benthic microalgae present. After...Graduate School of Oceanography / University of Rhode Island (GSO/URI) to identify the benthic microalgae in the samples. Following the untimely death of

12. Nitrogen-gas bubbling during the cultivation of Clostridium tetani produces a higher yield of tetanus toxin for the preparation of its toxoid.

PubMed

De Luca, M M; Abeiro, H D; Bernagozzi, J A; Basualdo, J A

1997-01-01

We investigated the effect of exposing cultures of Clostridium tetani to nitrogen (N2) gas on the recovery of tetanus toxin to be processed for the preparation of its toxoid. N2 was bubbled through nine 10-liter cultures during the growth of the bacteria, while nine parallel control incubations were maintained without bubbling. We found that treatment of the C. tetani anaerobes with an inert gas in this manner during cultivation produced a highly significant increase in the yield of tetanus toxin from them in comparison with the standard procedure.

13. Mechanism of gas bubble shoot-off and motion during spark discharge in liquid

Yavtushenko, I. O.; Orlov, A. M.; Zharkov, S. V.

2012-07-01

The conditions of the excitation of a pulsed plasma discharge on the surface of a processed metal (copper) sample immersed in a conducting aqueous solution have been studied. Cathode polarization of the metal was provided by a high-voltage capacitor bank (4μF) charged to U = 200-1100 V after each discharge. It is established that electric breakdown with a duration not exceeding 0.1 μs is always preceded by the formation of small hydrogen bubbles (with radii r ≈ 37-40 μm) on the polarized metal surface, which takes about 139-159 μs. A mechanism of passivation of the processed metal surface by these hydrogen bubbles, which are synchronously shot off from the electrode surface under the action of the spark discharge, is proposed. Consistent matching of the experimental data and model calculations is used to estimate the main parameters determining the kinetics of bubble detachment from the electrode surface at various voltages U on the capacitor bank.

14. Influence of infection with Renibacterium salmoninarum on susceptibility of juvenile spring chinook salmon to gas bubble trauma

USGS Publications Warehouse

Weiland, L.K.; Mesa, M.G.; Maule, A.G.

1999-01-01

During experiments in our laboratory to assess the progression and severity of gas bubble trauma (GBT) in juvenile spring chinook salmon Oncorhynchus tshawytscha, we had the opportunity to assess the influence of Renibacterium salmoninarum (Rs), the causative agent of bacterial kidney disease, on the susceptibility of salmon to GBT. We exposed fish with an established infection of Rs to 120% total dissolved gas (TDG) for 96 h and monitored severity of GBT signs in the fins and gills, Rs infection level in kidneys by using an enzyme-linked immunosorbent assay (ELISA), and mortality. Mortality occurred rapidly after exposure to 120% TDG, with a LT20 (time necessary to kill 20% of the population) of about 37 h, which is at a minimum about 16% earlier than other bioassays we have conducted using fish that had no apparent signs of disease. Fish that died early (from 31 to 36 h and from 49 to 52 h) had significantly higher infection levels (mean ?? SE ELISA absorbance = 1.532 ?? 0.108) than fish that survived for 96h (mean ?? SE ELISA absorbance = 0.828 ?? 0.137). Fish that died early also had a significantly greater number of gill filaments occluded with bubbles than those that survived 96 h. Conversely, fish that survived for 96 h had a significantly higher median fin severity ranking than those that died early. Our results indicate that fish with moderate to high levels of Rs infection are more vulnerable to the effects of dissolved gas supersaturation (DGS) and die sooner than fish with lower levels of Rs infection. However, there is a substantial amount of individual variation in susceptibility to the apparent cumulative effects of DGS and Rs infection. Collectively, our findings have important implications to programs designed to monitor the prevalence and severity of GBT in juvenile salmonids in areas like the Columbia River basin and perhaps elsewhere.

15. Visualization of airflow growing soap bubbles

Al Rahbi, Hamood; Bock, Matthew; Ryu, Sangjin

2016-11-01

Visualizing airflow inside growing soap bubbles can answer questions regarding the fluid dynamics of soap bubble blowing, which is a model system for flows with a gas-liquid-gas interface. Also, understanding the soap bubble blowing process is practical because it can contribute to controlling industrial processes similar to soap bubble blowing. In this study, we visualized airflow which grows soap bubbles using the smoke wire technique to understand how airflow blows soap bubbles. The soap bubble blower setup was built to mimic the human blowing process of soap bubbles, which consists of a blower, a nozzle and a bubble ring. The smoke wire was placed between the nozzle and the bubble ring, and smoke-visualized airflow was captured using a high speed camera. Our visualization shows how air jet flows into the growing soap bubble on the ring and how the airflow interacts with the soap film of growing bubble.

16. Sponge Cake or Champagne? Bubbles, Magmatic Degassing and Volcanic Eruptions

Cashman, K.; Pioli, L.; Belien, I.; Wright, H.; Rust, A.

2007-12-01

Vesiculation is an unavoidable consequence of magma decompression; the extent to which bubbles travel with ascending magma or leave the system by separated or permeable flow will determine the nature of the ensuing eruption. Bubbles travel with the melt from which they exsolve if the rise time of bubbles through the melt (the 'drift velocity') is much less than the rise rate of the magma (sponge cake). This condition is most likely to be met in viscous melts (where bubble rise velocities are low) and in melts that experience rapid decompression (high ascent velocities). Under these conditions, bubble expansion within the melt continues until sufficient bubble expansion causes coalescence and the development of a permeable network. Typical pumice vesicularities of 70-80% and permeabilities of 10-12 m2 constrain this limit under conditions appropriate for subplinian to plinian eruptions (mass fluxes > 106 kg/s). Slower rise rates (and lower mass fluxes) that characterize effusive eruptions produce silicic lavas with a wider range of vesicularities. In general, permeability decreases with decreasing sample vesicularity as bubbles deform (as evidenced by anisotropy in permeability and electrical conductivity) and pore apertures diminish. Degassing efficiency (and resulting densification of magma within the conduit) under these conditions is determined by permeability and the time allowed for gas escape. Bubbles rise through the melt if the drift velocity exceeds the velocity of magma ascent (champagne). This condition is most easily met in volatile-rich, low viscosity (mafic) melts at low to moderate fluxes. At very low magma flux, magma eruption rate is determined by the extent to which magma is entrained and ejected by rising gases (strombolian eruptions); when bubbles are too small, or are rising too slowly, they may not break the surface at all, but instead may be concentrated in a near-surface layer (surface foam). As the magma flux increases, segregation of

17. 30 CFR 203.54 - How does my relief arrangement for an oil and gas lease operate if prices rise sharply?

Code of Federal Regulations, 2010 CFR

2010-07-01

... gas lease operate if prices rise sharply? 203.54 Section 203.54 Mineral Resources MINERALS MANAGEMENT... arrangement for an oil and gas lease operate if prices rise sharply? In those months when your current reference price rises by at least 25 percent above your base reference price, you must pay the...

18. 30 CFR 203.54 - How does my relief arrangement for an oil and gas lease operate if prices rise sharply?

Code of Federal Regulations, 2011 CFR

2011-07-01

... gas lease operate if prices rise sharply? 203.54 Section 203.54 Mineral Resources BUREAU OF OCEAN... Leases § 203.54 How does my relief arrangement for an oil and gas lease operate if prices rise sharply? In those months when your current reference price rises by at least 25 percent above your...

19. Bubbly flows around a two-dimensional circular cylinder

Lee, Jubeom; Park, Hyungmin

2016-11-01

Two-phase cross flows around a bluff body occur in many thermal-fluid systems like steam generators, heat exchangers and nuclear reactors. However, our current knowledge on the interactions among bubbles, bubble-induced flows and the bluff body are limited. In the present study, the gas-liquid bubbly flows around a solid circular cylinder are experimentally investigated while varying the mean void fraction from 5 to 27%. The surrounding liquid (water) is initially static and the liquid flow is only induced by the air bubbles. For the measurements, we use the high-speed two-phase particle image velocimetry techniques. First, depending on the mean void fraction, two regimes are classified with different preferential concentration of bubbles in the cylinder wake, which are explained in terms of hydrodynamic force balances acting on rising bubbles. Second, the differences between the two-phase and single-phase flows (while matching their Reynolds numbers) around a circular cylinder will be discussed in relation to effects of bubble dynamics and the bubble-induced turbulence on the cylinder wake. Supported by a Grant (MPSS-CG-2016-02) through the Disaster and Safety Management Institute funded by Ministry of Public Safety and Security of Korean government.

20. Cohesion of Bubbles in Foam

ERIC Educational Resources Information Center

Ross, Sydney

1978-01-01

The free-energy change, or binding energy, of an idealized bubble cluster is calculated on the basis of one mole of gas, and on the basis of a single bubble going from sphere to polyhedron. Some new relations of bubble geometry are developed in the course of the calculation. (BB)

1. Passage of a shock wave through inhomogeneous media and its impact on gas-bubble deformation

Nowakowski, A. F.; Ballil, A.; Nicolleau, F. C. G. A.

2015-08-01

The paper investigates shock-induced vortical flows within inhomogeneous media of nonuniform thermodynamic properties. Numerical simulations are performed using a Eulerian type mathematical model for compressible multicomponent flow problems. The model, which accounts for pressure nonequilibrium and applies different equations of state for individual flow components, shows excellent capabilities for the resolution of interfaces separating compressible fluids as well as for capturing the baroclinic source of vorticity generation. The developed finite volume Godunov type computational approach is equipped with an approximate Riemann solver for calculating fluxes and handles numerically diffused zones at flow component interfaces. The computations are performed for various initial conditions and are compared with available experimental data. The initial conditions promoting a shock-bubble interaction process include weak to high planar shock waves with a Mach number ranging from 1.2 to 3 and isolated cylindrical bubble inhomogeneities of helium, argon, nitrogen, krypton, and sulphur hexafluoride. The numerical results reveal the characteristic features of the evolving flow topology. The impulsively generated flow perturbations are dominated by the reflection and refraction of the shock, the compression, and acceleration as well as the vorticity generation within the medium. The study is further extended to investigate the influence of the ratio of the heat capacities on the interface deformation.

2. High-speed visualization and radiated pressure measurement of a laser-induced gas bubble in glycerin-water solutions

Nakajima, Takehiro; Kondo, Tomoki; Ando, Keita

2016-11-01

We study the dynamics of a spherical gaseous bubble created by focusing a nanosecond laser pulse at 532 nm into a large volume of glycerin-water solutions. Free oscillation of the bubble and shock wave emission from the bubble dynamics are recorded by a high-speed camera together with a pulse laser stroboscope; concurrently, pressure radiated from the oscillating bubble is measured by a hydrophone. The bubble achieves a mechanical equilibrium after free oscillation is damped out; the equilibrium state stays for a while, unlike vapor bubbles. We speculate that the bubble content is mainly gases originally dissolved in the liquid (i.e., air). The bubble dynamics we observed are compared to Rayleigh-Plesset-type calculations that account for diffusive effects; the (unknown) initial pressure just after laser focusing is tuned to obtain agreement between the experiment and the calculation. Moreover, viscous effects on the shock propagation are examined with the aid of compressible Navier-Stokes simulation.

3. Growth of a Gas Bubble in a Supersaturated Liquid Under the Effect of Variant Cases of Surface Tension

Mohammadein, S. A.; Mohamed, K. G.

In this paper, the growth of a gas bubble in a supersaturated liquid is discussed for a constant and variable cases of surface tension effect. The mathematical model is solved analytically by using the method of Plesset and Zwick18 after modified it. The growth process is affected by: diffusion coefficient D, Jacob number Ja, surface tension σ, adjustment factor b and void fraction ϕ0. The famous formula of Plesset and Zwick is produced as a special case of the results at some values of the adjustment factors. Moreover, for some values of the adjustment factors, good approximation is obtained when a comparison between our results and the result that produced by Hashemi et al., 9 who solved the problem with the method of combining variables.

4. Soluble surfactants favorably modify fluid structure and wall shear stress profiles during near-occluding bubble motion in a computational model of intravascular gas embolism

Swaminathan, T. N.; Ayyaswamy, P. S.; Eckmann, D. M.

2009-11-01

Finite sized gas bubble motion in a blood vessel causes temporal and spatial gradients of shear stress at the endothelial cell surface lining the vessel wall as the bubble approaches the cell, moves over it and passes it by. Rapid reversals occur in the sign of the shear stress imparted to the cell surface during this motion. The sign-reversing shear is a potently coupled source of cell surface mechanical stretch, potentiating cell injury. The presence of a suitable soluble surfactant in the bulk medium considerably reduces the level of the shear stress gradients imparted to the cell surface as compared to an equivalent surfactant-free system. The bubble shape and the film thickness between the bubble and the vessel wall are also different. Furthermore, the bubble residence time near the proximity of a cell surface changes in comparison. These results based on our modeling may help explain several phenomena observed in experimental studies related to gas embolism, a significant problem in cardiac surgery and decompression sickness.

5. Pefluorocarbon inhibition of bubble induced Ca2+ transients in an in-vitro model of vascular gas-embolism

PubMed Central

Klinger, Alexandra L.; Kandel, Judith; Pichette, Benjamin; Eckmann, David M.

2014-01-01

Endothelial injury resulting from deleterious interaction of gas microbubbles occurs in many surgical procedures and other medical interventions. The symptoms of vascular air embolism (VAE), while serious, are often difficult to detect, and there are essentially no pharmaceutical preventative or post-event treatments currently available. Perfluorocarbons (PFCs), however, have shown particular promise as a therapeutic option in reducing endothelial injury both in- and ex-vivo. Recently, we demonstrated the effectiveness of Oxycyte, a third-generation PFC formulated in a phosphotidylcholine emulsion, using an in-vitro model of VAE developed in our laboratory. This apparatus allows live cell imaging concurrent with precise manipulation of physiologically sized microbubbles so that they may be brought into individual contact with human umbilical vein endothelial cells dye-loaded with the Ca2+ sensitive Fluo-4. Herein, we expand use of this fluorescence microscopy-based cell culture model. Specifically, we examined the concentration dependence of Oxycyte in reducing both the amplitude and frequency of large intracellular Ca2+ currents that are both a hallmark of bubble contact and a quantifiable indication that abnormal intracellular signaling has been triggered. We measured dose dependence curves and fit the resultant data using a modified Black and Leff operational model of agonism. The half maximal inhibitory concentrations of Oxycyte for i) inhibition of occurrence and ii) amplitude reduction were 229±49 µM and 226±167 µM, respectively. This investigation shows the preferential gas/liquid interface occupancy of the PFC component of Oxycyte over that of mechanosensing glycocalyx components and validates Oxycyte’s specific surfactant mechanism of action. Further, no lethality was observed for any concentration of this bioinert PFC, as it acts as a competitive allosteric inhibitor of syndecan activation to ameliorate cell response to bubble contact. PMID:24131543

6. Performance of high pressure COIL with centrifugal bubble singlet oxygen generator

Zagidullin, Marsel V.; Nikolaev, Valery D.; Khvatov, Nikolay A.; Svistun, Michael I.

2007-05-01

A centrifugal bubbling SOG is a perspective source of oxygen at high pressure with high depletion of the BHP in the single burn dawn. The theoretical estimations show that at high centrifugal acceleration gas-liquid contact specific surface 30cm -1, frequency of the surface renewal can less than 10 -3s and bubble rise velocity up to 500 cm/s be realized in the bubble SOG. The results of the measurements of O II(1Δ) yield, chlorine utilization and water fraction at the exit of the centrifugal bubble SOG are presented. A high O II(1Δ) yield and chlorine utilization higher than 90% have been obtained at chlorine gas loading up to 6 mmole/s per 1 cm2 of the bubbler surface. The ejector COIL powered by centrifugal bubbling SOG demonstrated ~25% of chemical efficiency with specific power 6 kW per 1 litre/s of the BHP volumetric rate.

7. The stability of Taylor bubbles in large-diameter tubes: Linear theory

Abubakar, Habib; Matar, Omar

2015-11-01

Taylor bubbles are a characteristic feature of the slug flow regime in gas-liquid pipe flows. With increasing pipe diameter, previous experimental observations have shown that at sufficiently large diameter (> 0.1 m), the slug flow regime, and hence Taylor bubbles, are not observed in gas-liquid flows in vertical pipes. Numerical simulations of a Taylor bubble rising in a quiescent liquid (see companion talk at this APS/DFD conference) have also shown that the wake of Taylor bubbles rising in a riser of such sizes is turbulent and has great impact on the stability of the subsequent, trailing bubbles. In view of these observations, a linear stability analysis is carried out to establish the stability conditions for a Taylor bubble rising in a turbulent flowing liquid. The stability of an axisymmetric Taylor bubble to a small-amplitude, three dimensional, perturbation is studied and the dimensionless flow parameters of the liquid investigated include the Froude number, the inverse viscosity number, and the Eotvos numbers. Nigerian Government scholarship (for HA).

8. Cardiovascular bubble dynamics.

PubMed

Bull, Joseph L

2005-01-01

Gas bubbles can form in the cardiovascular system as a result of patho-physiological conditions or can be intentionally introduced for diagnostic or therapeutic reasons. The dynamic behavior of these bubbles is caused by a variety of mechanisms, such as inertia, pressure, interfacial tension, viscosity, and gravity. We review recent advances in the fundamental mechanics and applications of cardiovascular bubbles, including air embolism, ultrasound contrast agents, targeted microbubbles for drug delivery and molecular imaging, cavitation-induced tissue erosion for ultrasonic surgery, microbubble-induced angiogenesis and arteriogenesis, and gas embolotherapy.

9. Bubble video experiments in the marine waters off Panarea Island (Italy): real-world data for modelling CO2 bubble dissolution and evolution

Beaubien, Stan; De Vittor, Cinzia; McGinnis, Dan; Bigi, Sabina; Comici, Cinzia; Ingrosso, Gianmarco; Lombardi, Salvatore; Ruggiero, Livio

2014-05-01

Carbon capture and storage is expected to provide an important, short-term contribution to mitigate global climate change due to anthropogenic emissions of CO2. Offshore reservoirs are particularly favourable, however concerns exist regarding the potential for CO2 leakage into the water column (with possible ecosystem impacts) and the atmosphere. Although laboratory experiments and modelling can examine these issues, the study of natural systems can provide a more complete and realistic understanding. For this reason the natural CO2 emission site off the coast of Panarea Island (Italy) was chosen for study within the EC-funded ECO2 project. The present paper discusses the results of field experiments conducted at this site to better understand the fate of CO2 gas bubbles as they rise through the water column, and to use this real-world data as input to test the predictive capabilities of a bubble model. Experiments were conducted using a 1m wide x 1m deep x 3m tall, hollow-tube structure equipped with a vertical guide on the front face and a dark, graduated cloth for contrast and depth reference on the back. A Plexiglas box was filled with the naturally emitted gas and fixed on the seafloor inside the structure. Tubes exit the top of the box to make bubbles of different diameters, while valves on each tube control bubble release rate. Bubble rise velocity was measured by tracking each bubble with a HD video camera mounted in the guide and calculating values over 20 cm intervals. Bubble diameter was measured by filming the bubbles as they collide with a graduated Plexiglas sheet deployed horizontally at the measurement height. Bubble gas was collected at different heights using a funnel and analysed in the laboratory for CO2, O2+Ar, N2, and CH4. Water parameters were measured by performing a CTD cast beside the structure and collecting water samples at four depths using a Niskin bottle; samples were analysed in the laboratory for all carbonate system species, DO

10. A fast rise-rate, adjustable-mass-bit gas puff valve for energetic pulsed plasma experiments

SciTech Connect

Loebner, Keith T. K. Underwood, Thomas C.; Cappelli, Mark A.

2015-06-15

A fast rise-rate, variable mass-bit gas puff valve based on the diamagnetic repulsion principle was designed, built, and experimentally characterized. The ability to hold the pressure rise-rate nearly constant while varying the total overall mass bit was achieved via a movable mechanical restrictor that is accessible while the valve is assembled and pressurized. The rise-rates and mass-bits were measured via piezoelectric pressure transducers for plenum pressures between 10 and 40 psig and restrictor positions of 0.02-1.33 cm from the bottom of the linear restrictor travel. The mass-bits were found to vary linearly with the restrictor position at a given plenum pressure, while rise-rates varied linearly with plenum pressure but exhibited low variation over the range of possible restrictor positions. The ability to change the operating regime of a pulsed coaxial plasma deflagration accelerator by means of altering the valve parameters is demonstrated.

11. Review of Current Literature and Research on Gas Supersaturation and Gas Bubble Trauma: Special Publication Number 1, 1986.

SciTech Connect

Colt, John; Bouck, Gerald R.; Fidler, Larry

1986-12-01

This report presents recently published information and on-going research on the various areas of gas supersaturation. Growing interest in the effects of chronic gas supersaturation on aquatic animals has been due primarily to heavy mortality of salmonid species under hatchery conditions. Extensive examination of affected animals has failed to consistently identify pathogenic organisms. Water quality sampling has shown that chronic levels of gas supersaturation are commonly present during a significant period of the year. Small marine fish larvae are significantly more sensitive to gas supersaturation than salmonids. Present water quality criteria for gas supersaturation are not adequate for the protection of either salmonids under chronic exposure or marine fish larvae, especially in aquaria or hatcheries. To increase communication between interested parties in the field of gas supersaturation research and control, addresses and telephone numbers of all people responding to the questionnaire are included. 102 refs.

12. Terminating marine methane bubbles by superhydrophobic sponges.

PubMed

Chen, Xiao; Wu, Yuchen; Su, Bin; Wang, Jingming; Song, Yanlin; Jiang, Lei

2012-11-14

Marine methane bubbles are absorbed, steadily stored, and continuously transported based on the employment of superhydrophobic sponges. Antiwetting sponges are water-repellent in the atmosphere and absorb gas bubbles under water. Their capacity to store methane bubbles increases with enhanced submerged depth. Significantly, trapped methane bubbles can be continuously transported driven by differential pressure.

13. Removal of elemental mercury from flue gas by thermally activated ammonium persulfate in a bubble column reactor.

PubMed

Liu, Yangxian; Wang, Qian

2014-10-21

In this article, a novel technique on removal of elemental mercury (Hg(0)) from flue gas by thermally activated ammonium persulfate ((NH4)(2)S(2)O(8)) has been developed for the first time. Some experiments were carried out in a bubble column reactor to evaluate the effects of process parameters on Hg(0) removal. The mechanism and kinetics of Hg(0) removal are also studied. The results show that the parameters, (NH4)(2)S(2)O(8) concentration, activation temperature and solution pH, have significant impacts on Hg(0) removal. The parameters, Hg(0), SO2 and NO concentration, only have small effects on Hg(0) removal. Hg(0) is removed by oxidations of (NH4)(2)S(2)O(8), sulfate and hydroxyl free radicals. When (NH4)(2)S(2)O(8) concentration is more than 0.1 mol/L and solution pH is lower than 9.71, Hg(0) removal by thermally activated (NH4)(2)S(2)O(8) meets a pseudo-first-order fast reaction with respect to Hg(0). However, when (NH4)(2)S(2)O(8) concentration is less than 0.1 mol/L or solution pH is higher than 9.71, the removal process meets a moderate speed reaction with respect to Hg(0). The above results indicate that this technique is a feasible method for emission control of Hg(0) from flue gas.

14. Study on bubbly flow behavior in natural circulation reactor by thermal-hydraulic simulation tests with SF6-Gas and ethanol liquid

Kondo, Yoshiyuki; Suga, Keishi; Hibi, Koki; Okazaki, Toshihiko; Komeno, Toshihiro; Kunugi, Tomoaki; Serizawa, Akimi; Yoneda, Kimitoshi; Arai, Takahiro

2009-02-01

An advanced experimental technique has been developed to simulate two-phase flow behavior in a light water reactor (LWR). The technique applies three kinds of methods; (1) use of sulfur-hexafluoride (SF6) gas and ethanol (C2H5OH) liquid at atmospheric temperature and a pressure less than 1.0MPa, where the fluid properties are similar to steam-water ones in the LWR, (2) generation of bubble with a sintering tube, which simulates bubble generation on heated surface in the LWR, (3) measurement of detailed bubble distribution data with a bi-optical probe (BOP), (4) and measurement of liquid velocities with the tracer liquid. This experimental technique provides easy visualization of flows by using a large scale experimental apparatus, which gives three-dimensional flows, and measurement of detailed spatial distributions of two-phase flow. With this technique, we have carried out experiments simulating two-phase flow behavior in a single-channel geometry, a multi-rod-bundle one, and a horizontal-tube-bundle one on a typical natural circulation reactor system. Those experiments have clarified a) a flow regime map in a rod bundle on the transient region between bubbly and churn flow, b) three-dimensional flow behaviour in rod-bundles where inter-subassembly cross-flow occurs, c) bubble-separation behavior with consideration of reactor internal structures. The data have given analysis models for the natural circulation reactor design with good extrapolation.

15. Tribonucleation of bubbles

PubMed Central

Wildeman, Sander; Lhuissier, Henri; Sun, Chao; Lohse, Detlef; Prosperetti, Andrea

2014-01-01

We report on the nucleation of bubbles on solids that are gently rubbed against each other in a liquid. The phenomenon is found to depend strongly on the material and roughness of the solid surfaces. For a given surface, temperature, and gas content, a trail of growing bubbles is observed if the rubbing force and velocity exceed a certain threshold. Direct observation through a transparent solid shows that each bubble in the trail results from the early coalescence of several microscopic bubbles, themselves detaching from microscopic gas pockets forming between the solids. From a detailed study of the wear tracks, with atomic force and scanning electron microscopy imaging, we conclude that these microscopic gas pockets originate from a local fracturing of the surface asperities, possibly enhanced by chemical reactions at the freshly created surfaces. Our findings will be useful either for preventing undesired bubble formation or, on the contrary, for “writing with bubbles,” i.e., creating controlled patterns of microscopic bubbles. PMID:24982169

16. Bubble Generation in a Continuous Liquid Flow Under Reduced Gravity Conditions

NASA Technical Reports Server (NTRS)

Pais, Salvatore Cezar

1999-01-01

The present work reports a study of bubble generation under reduced gravity conditions for both co-flow and cross-flow configurations. Experiments were performed aboard the DC-9 Reduced Gravity Aircraft at NASA Glenn Research Center, using an air-water system. Three different flow tube diameters were used: 1.27, 1.9, and 2.54 cm. Two different ratios of air injection nozzle to tube diameters were considered: 0.1 and 0.2. Gas and liquid volumetric flow rates were varied from 10 to 200 ml/s. It was experimentally observed that with increasing superficial liquid velocity, the bubbles generated decreased in size. The bubble diameter was shown to increase with increasing air injection nozzle diameters. As the tube diameter was increased, the size of the detached bubbles increased. Likewise, as the superficial liquid velocity was increased, the frequency of bubble formation increased and thus the time to detach forming bubbles decreased. Independent of the flow configuration (for either single nozzle or multiple nozzle gas injection), void fraction and hence flow regime transition can be controlled in a somewhat precise manner by solely varying the gas and liquid volumetric flow rates. On the other hand, it is observed that uniformity of bubble size can be controlled more accurately by using single nozzle gas injection than by using multiple port injection, since this latter system gives rise to unpredictable coalescence of adjacent bubbles. A theoretical model, based on an overall force balance, is employed to study single bubble generation in the dynamic and bubbly flow regime. Under conditions of reduced gravity, the gas momentum flux enhances bubble detachment; however, the surface tension forces at the nozzle tip inhibits bubble detachment. Liquid drag and inertia can act either as attaching or detaching force, depending on the relative velocity of the bubble with respect to the surrounding liquid. Predictions of the theoretical model compare well with performed

17. Study of bubble-induced turbulence in upward laminar bubbly pipe flows measured with a two-phase particle image velocimetry

Kim, Minki; Lee, Jun Ho; Park, Hyungmin

2016-04-01

In the present study, focusing on characterizing the bubble-induced agitation (turbulence), spatially varying flow statistics of gas and liquid phases in laminar upward bubbly flows (Reynolds number of 750) with varying mean void fraction are investigated using a two-phase high-speed particle image velocimetry. As the flow develops along the vertical direction, bubbles with small-to-moderate void fractions, which were intentionally distributed asymmetrically at the inlet, migrate fast and show symmetric distributions of wall or intermediate peaking. Meanwhile, the mean liquid velocity saturates relatively slowly to a flat distribution at the core region. Despite small void fractions considered, the bubbles generate a substantial turbulence, which increases with increasing mean void fraction. Interestingly, it is found that the mean vertical velocity, bubble-induced normal stress in radial direction, and Reynolds stress profiles match well with those of a single-phase turbulent flow at a moderate Reynolds number (e.g., 104), indicating the similarity between the bubble-induced turbulence and wall-shear-generated turbulence in a single-phase flow. Previously suggested scaling relations are confirmed such that the mean bubble rise velocity and bubble-induced normal stress (in both vertical and radial directions) scale with mean volume void fraction as a power of -0.1 and 0.4, respectively. Finally, based on the analysis of measured bubble dynamics (rise in an oscillating path), a theoretical model for two-phase turbulent (Reynolds) stress is proposed, which includes the contributions by the non-uniform distributions of local void fraction and relative bubble rise velocity, and is further validated with the present experimental data to show a good agreement with each other.

18. Advances in Optical Characterization of Methane Seeps and Bubble Plumes

Pizarro, O.; Farr, N.; Camilli, R.; Whelan, J.; Martens, C.; Goudreau, J.; Mendlovitz, H.; Camilli, L.

2005-12-01

Methane seeps are potentially a key contributor to the atmospheric methane reservoir and to the global greenhouse gas budget. Improved estimates of methane flux from ocean floor seeps are required to understand the magnitude and characteristics of this potential source. At less active, deep water seeps a large portion of the migrating gas is dissolved and oxidized before reaching the surface. However, in high-intensity, shallow water methane seeps the bubble density, speed and size are such that a significant fraction of the gas may reach the atmosphere. New types of in-situ chemical sensors are now available to quickly and reliably quantify dissolved methane throughout the water column. However, quantifying methane within the water column in the free gas phase (i.e., in bubbles) remains a challenging problem. Current approaches rely either on indirect acoustic methods or direct collection of bubbles. Acoustic methods have the disadvantage of requiring extensive calibration, and can fail to distinguish the bubble signal from other sources of acoustic noise. Gas-capture techniques are mechanically complex, have a surface expression that introduces some noise, and can potentially alias episodic events. In both cases the fine scale structure such as heterogeneity of the rising bubbling plume is lost. We describe a vision-based system to characterize bubble plumes and the seep features from which they emanate. Video-rate optical imagery from 3 cameras is used to generate precise measurements of the motion of bubbles. Lighting is provided by a distributed array of LED modules synchronized to the cameras. In order to conserve power and extend deployment times the system can be configured to be dormant until triggered by chemical sensors indicating high concentrations of methane. Plume characterization is based on the identification of the individual bubbles (and rejection of other particles). Additional image processing steps are then used to estimate each bubble

19. Heat transfer between stratified immiscible liquid layers driven by gas bubbling across the interface

SciTech Connect

Greene, G.A.; Irvine, T.F. Jr.

1988-01-01

The modeling of molten core debris in the CORCON and VANESA computer codes as overlying, immiscible liquid layers is discussed as it relates to the transfer of heat and mass between the layers. This initial structure is identified and possible configurations are discussed. The stratified, gas-sparged configuration that is presently employed in CORCON and VANESA is examined and the existing literature for interlayer heat transfer is assessed. An experiment which was designed to measure interlayer heat transfer with gas sparging is described. The results are presented and compared to previously existing models. A dimensionless correlation for stratified, interlayer heat transfer with gas sparging is developed. This relationship is recommended for inclusion in CORCON-MOD2 for heat transfer between stratified, molten liquid layers. 12 refs., 6 figs., 3 tabs.

20. 30 CFR 203.54 - How does my relief arrangement for an oil and gas lease operate if prices rise sharply?

Code of Federal Regulations, 2012 CFR

2012-07-01

... 30 Mineral Resources 2 2012-07-01 2012-07-01 false How does my relief arrangement for an oil and gas lease operate if prices rise sharply? 203.54 Section 203.54 Mineral Resources BUREAU OF SAFETY AND... operate if prices rise sharply? In those months when your current reference price rises by at least...

1. 30 CFR 203.54 - How does my relief arrangement for an oil and gas lease operate if prices rise sharply?

Code of Federal Regulations, 2013 CFR

2013-07-01

... 30 Mineral Resources 2 2013-07-01 2013-07-01 false How does my relief arrangement for an oil and gas lease operate if prices rise sharply? 203.54 Section 203.54 Mineral Resources BUREAU OF SAFETY AND... operate if prices rise sharply? In those months when your current reference price rises by at least...

2. 30 CFR 203.54 - How does my relief arrangement for an oil and gas lease operate if prices rise sharply?

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 2 2014-07-01 2014-07-01 false How does my relief arrangement for an oil and gas lease operate if prices rise sharply? 203.54 Section 203.54 Mineral Resources BUREAU OF SAFETY AND... operate if prices rise sharply? In those months when your current reference price rises by at least...

3. Modelling of Gas Hydrate Dissociation During The Glacial-Inter-glacial Cycles, Case Study The Chatham Rise, New Zealand

Oluwunmi, P.; Pecher, I. A.; Archer, R.; Moridis, G. J.; Reagan, M. T.

2015-12-01

Seafloor depressions covering an area of >20,000 km2 on the Chatham Rise, south east of New Zealand, have been interpreted as pockmarks which are related to past fluid releases. It is proposed that the seafloor depressions were caused by sudden escape of overpressured gas generated by gas hydrate dissociation during glacial sea-level lowering. We are attempting to simulate the evolution of the gas hydrate system through glacial-interglacial cycles in the study area using TOUGH-Hydrate. The Chatham Rise offers a unique opportunity for studying the effect of depressurization from sealevel lowering to gas hydrate systems because it is a bathymetric barrier preventing the Subtropical Front separating subtropical and subantarctic waters from migrating during glacial-interglacial cycles. Hence, bottom-water temperatures can be assumed to remain constant. Recent results from paleoceanographic studies however, indicate that bottom-temperature may have varied locally. These temperature changes may have a more significant effect on the shallow gas hydrate system in the study area than the relatively gradual decrease of pressure associated with sealevel lowering.

4. Fluid Dynamics of Bubbly Liquids

NASA Technical Reports Server (NTRS)

Tsang, Y. H.; Koch, D. L.; Zenit, R.; Sangani, A.; Kushch, V. I.; Spelt, P. D. M.; Hoffman, M.; Nahra, H.; Fritz, C.; Dolesh, R.

2002-01-01

Experiments have been performed to study the average flow properties of inertially dominated bubbly liquids which may be described by a novel analysis. Bubbles with high Reynolds number and low Weber number may produce a fluid velocity disturbance that can be approximated by a potential flow. We studied the behavior of suspensions of bubbles of about 1.5 mm diameter in vertical and inclined channels. The suspension was produced using a bank of 900 glass capillaries with inner diameter of about 100 microns in a quasi-steady fashion. In addition, salt was added to the suspension to prevent bubble-bubble coalescence. As a result, a nearly monodisperse suspension of bubble was produced. By increasing the inclination angle, we were able to explore an increasing amount of shear to buoyancy motion. A pipe flow experiment with the liquid being recirculated is under construction. This will provide an even larger range of shear to buoyancy motion. We are planning a microgravity experiment in which a bubble suspension is subjected to shearing in a couette cell in the absence of a buoyancy-driven relative motion of the two phases. By employing a single-wire, hot film anemometer, we were able to obtain the liquid velocity fluctuations. The shear stress at the wall was measured using a hot film probe flush mounted on the wall. The gas volume fraction, bubble velocity, and bubble velocity fluctuations were measured using a homemade, dual impedance probe. In addition, we also employed a high-speed camera to obtain the bubble size distribution and bubble shape in a dilute suspension. A rapid decrease in bubble velocity for a dilute bubble suspension is attributed to the effects of bubble-wall collisions. The more gradual decrease of bubble velocity as gas volume fraction increases, due to subsequent hindering of bubble motion, is in qualitative agreement with the predictions of Spelt and Sangani for the effects of potential-flow bubble-bubble interactions on the mean velocity. The

5. Quantification of methane bubbles ebullition in freshwater reservoirs of temperate zone using sonar working with 120 kHz frequency

Frouzova, Jaroslava; Tuser, Michal; Stanovsky, Petr

2014-05-01

During hydroacoustic vertical surveys of fish, an indispensable amount of gas bubbles have been observed rising from the bottom towards the water surface. Unfortunately, the gas ebullition essentially interferes with acoustic detection of fish, thereby biasing an estimate of fish quantity. First, to distinguish between fish and bubble echo, comparing acoustic properties of the echoes (e.g. echo shape, echo width, or phase deviation) seemed to be inapplicable. Nevertheless, the difference in the movement 'behavior' (i.e., direction and speed), looks more promising, but it is necessary to obtain the exact position of a sound beam. Furthermore, in case of shallow waters where a horizontally-oriented beam is usually deployed, the method for distinguishing fish and bubbles with the movement behavior is possible, but more complicated to apply due to the boat motion and a different bubble crossing through a beam (i.e. altering position not in a range domain, but in a phase domain of the beam). Second, when gas bubbles are recognized, a functional regression model of acoustic response to the bubble size can be used to estimate size and volume distribution of bubbles. The experiment with man-made methane bubbles was performed to learn the dependence of acoustic response to the bubble size, and a regression model was created

6. Modelling flow pattern transitions for steady upward gas-liquid flow in vertical tubes. [Bubble, slug, churn and dispersed-annular; also existence regions and transitions

SciTech Connect

Taitel, Y.; Bornea, D.; Dukler, A.E.

1980-05-01

Models for predicting flow patterns in steady upward gas-liquid flow in vertical tubes (such as production-well tubing) delineate the transition boundaries between each of the four basic flow patterns for gas-liquid flow in vertical tubes: bubble, slug, churn, and dispersed-annular. Model results suggest that churn flow is the development region for the slug pattern and that bubble flow can exist in small pipes only at high liquid rates, where turbulent dispersion forces are high. Each transition depends on the flow-rate pair, fluid properties, and pipe size, but the nature of the dependence is different for each transition because of differing control mechanisms. The theoretical predictions are in reasonably good agreement with a variety of published flow maps based on experimental data.

7. Blowing magnetic skyrmion bubbles

Jiang, Wanjun; Upadhyaya, Pramey; Zhang, Wei; Yu, Guoqiang; Jungfleisch, M. Benjamin; Fradin, Frank Y.; Pearson, John E.; Tserkovnyak, Yaroslav; Wang, Kang L.; Heinonen, Olle; te Velthuis, Suzanne G. E.; Hoffmann, Axel

2015-07-01

The formation of soap bubbles from thin films is accompanied by topological transitions. Here we show how a magnetic topological structure, a skyrmion bubble, can be generated in a solid-state system in a similar manner. Using an inhomogeneous in-plane current in a system with broken inversion symmetry, we experimentally “blow” magnetic skyrmion bubbles from a geometrical constriction. The presence of a spatially divergent spin-orbit torque gives rise to instabilities of the magnetic domain structures that are reminiscent of Rayleigh-Plateau instabilities in fluid flows. We determine a phase diagram for skyrmion formation and reveal the efficient manipulation of these dynamically created skyrmions, including depinning and motion. The demonstrated current-driven transformation from stripe domains to magnetic skyrmion bubbles could lead to progress in skyrmion-based spintronics.

8. Comparison of induced damage, range, reflection, and sputtering yield between amorphous, bcc crystalline, and bubble-containing tungsten materials under hydrogen isotope and noble gas plasma irradiations

Saito, Seiki; Nakamura, Hiroaki; Tokitani, Masayuki

2017-01-01

Binary-collision-approximation simulation of hydrogen isotope (i.e., hydrogen, deuterium, and tritium) and noble gas (i.e., helium, neon, and argon) injections into tungsten materials is performed. Three tungsten structures (i.e., amorphous, bcc crystalline, and helium bubble-containing structures) are prepared as target materials. Then, the trajectories of incident atoms, the distribution of recoil atoms, the penetration depth range of incident atoms, the sputtering yield, and the reflection rate are carefully investigated for these target materials.

9. A three dimensional model of an ultrasound contrast agent gas bubble and its mechanical effects on microvessels

PubMed Central

Hosseinkhah, N.; Hynynen, K.

2012-01-01

Ultrasound contrast agents inside a microvessel, when driven by ultrasound, oscillate and induce mechanical stresses on the vessel wall. These mechanical stresses can produce beneficial therapeutic effects but also induce vessel rupture if the stresses are too high. Therefore, it is important to use sufficiently low pressure amplitudes to avoid rupturing the vessels while still inducing the desired therapeutic effects. In this work, we developed a comprehensive three dimensional model of a confined microbubble inside a vessel while considering the bubble shell properties, blood viscosity, vessel wall curvature and the mechanical properties of the vessel wall. Two bubble models with the assumption of a spherical symmetric bubble and a simple asymmetrical bubble were simulated. This work was validated with previous experimental results and enabled us to evaluate the microbubbles’ behaviour and the resulting mechanical stresses induced on the vessel walls. In this study the fluid shear and circumferential stresses were evaluated as indicators of the mechanical stresses. The effects of acoustical parameters, vessel viscoelasticity and rigidity, vessel/bubble size and off-center bubbles on bubble behaviour and stresses on the vessel were investigated. The fluid shear and circumferential stresses acting on the vessel varied with time and location. As the frequency changed, the microbubble oscillated with the highest amplitude at its resonance frequency which was different from the resonance frequency of an unbound bubble. The bubble resonance frequency increased as the rigidity of a flexible vessel increased. The fluid shear and circumferential stresses peaked at frequencies above the bubble’s resonance frequency. The more rigid the vessels were, the more damped the bubble oscillations. The synergistic effect of acoustic frequency and vessel elasticity had also been investigated, since the circumferential stress showed either an increasing trend or a decreasing one

10. Gas-bubble snap-off under pressure driven flow in constricted noncircular capillaries

SciTech Connect

1996-04-01

A model for snap-off of a gas thread in a constricted cornered pore is developed. The time for wetting liquid to accumulate at a pore throat into an unstable collar is examined, as for the resulting pore-spanning lens to be displaced from the pore so that snap-off is the time may repeat. A comer-flow hydrodynamic analysis for the accumulation rate of wetting liquid due to both gradients in interfacial curvature and in applied liquid-phase pressure reveals that wetting-phase pressure gradients significantly increase the frequency of liquid accumulation for snap-off as compared to liquid rearrangement driven only by differences in pore-wall curvature. For moderate and large pressure gradients, the frequency of accumulation increases linearly with pressure gradient because of the increased rate of wetting liquid flow along pore comers. Pore topology is important to the theory, for pores with relatively small throats connected to large bodies demonstrate excellent ability to snapoff gas threads even when the initial capillary pressure is high or equivalently when the liquid saturation is low. A macroscopic momentum balance across the lens resulting from snap-off reveals that lens displacement rates are not linear with the imposed pressure drop. Instead, the frequency of lens displacement scales with powers between 0.5 and 0.6 for pores with dimensionless constriction radii between 0.15 and 0.40. Statistical percolation arguments are employed to form a generation rate expression and connect pore-level foam generation events to macroscopic pressure gradients in porous media. The rate of foam generation by capillary snap-off increases linearly with the liquid-phase pressure gradient and according to a power-law relationship with respect to the imposed gas-phase pressure gradient.

11. Interface dynamics and coupled growth in directional solidification in presence of bubbles

Jamgotchian, H.; Trivedi, R.; Billia, B.

1993-12-01

The formation and dynamics of gas bubbles in Bridgman growth of succinonitrile-acetone alloys is examined. The experimental results show for the first time the rich dynamics that are associated with the formation and propagation of bubbles during directional solidification of alloys. The strong coupling of bubbles with the solid-liquid interface is found to result in the growth of elongated bubbles, either attached to a flat solidification front or forming localized cellular as well as dendritic duplexes (bubbles wrapped by a solid envelope). The coupling of the bubble with the solidification front is shown to cause oscillations in the bubble, which are characterized by fast Fourier transforms. When several duplexes are formed, coupled growth and screening may occur. The basic factors that give rise to oscillations, namely competition between source and sink of acetone assisted by capillary convection at the bubble cap, are discussed qualitatively through the development of an internal oscillator model. Coherent sidebranching observed on dendritic duplexes is shown to be due to resonant modes between the bubble cap and the solid envelope.

12. Bubble Eliminator Based on Centrifugal Flow

NASA Technical Reports Server (NTRS)

Gonda, Steve R.; Tsao, Yow-Min D.; Lee, Wenshan

2004-01-01

The fluid bubble eliminator (FBE) is a device that removes gas bubbles from a flowing liquid. The FBE contains no moving parts and does not require any power input beyond that needed to pump the liquid. In the FBE, the buoyant force for separating the gas from the liquid is provided by a radial pressure gradient associated with a centrifugal flow of the liquid and any entrained bubbles. A device based on a similar principle is described in Centrifugal Adsorption Cartridge System (MSC- 22863), which appears on page 48 of this issue. The FBE was originally intended for use in filtering bubbles out of a liquid flowing relatively slowly in a bioreactor system in microgravity. Versions that operate in normal Earth gravitation at greater flow speeds may also be feasible. The FBE (see figure) is constructed as a cartridge that includes two concentric cylinders with flanges at the ends. The outer cylinder is an impermeable housing; the inner cylinder comprises a gas-permeable, liquid-impermeable membrane covering a perforated inner tube. Multiple spiral disks that collectively constitute a spiral ramp are mounted in the space between the inner and outer cylinders. The liquid enters the FBE through an end flange, flows in the annular space between the cylinders, and leaves through the opposite end flange. The spiral disks channel the liquid into a spiral flow, the circumferential component of which gives rise to the desired centrifugal effect. The resulting radial pressure gradient forces the bubbles radially inward; that is, toward the inner cylinder. At the inner cylinder, the gas-permeable, liquid-impermeable membrane allows the bubbles to enter the perforated inner tube while keeping the liquid in the space between the inner and outer cylinders. The gas thus collected can be vented via an endflange connection to the inner tube. The centripetal acceleration (and thus the radial pressure gradient) is approximately proportional to the square of the flow speed and

13. Mesoscale Benchmark Demonstration Problem 1: Mesoscale Simulations of Intra-granular Fission Gas Bubbles in UO2 under Post-irradiation Thermal Annealing

SciTech Connect

Li, Yulan; Hu, Shenyang Y.; Montgomery, Robert; Gao, Fei; Sun, Xin; Tonks, Michael; Biner, Bullent; Millet, Paul; Tikare, Veena; Radhakrishnan, Balasubramaniam; Andersson , David

2012-04-11

A study was conducted to evaluate the capabilities of different numerical methods used to represent microstructure behavior at the mesoscale for irradiated material using an idealized benchmark problem. The purpose of the mesoscale benchmark problem was to provide a common basis to assess several mesoscale methods with the objective of identifying the strengths and areas of improvement in the predictive modeling of microstructure evolution. In this work, mesoscale models (phase-field, Potts, and kinetic Monte Carlo) developed by PNNL, INL, SNL, and ORNL were used to calculate the evolution kinetics of intra-granular fission gas bubbles in UO2 fuel under post-irradiation thermal annealing conditions. The benchmark problem was constructed to include important microstructural evolution mechanisms on the kinetics of intra-granular fission gas bubble behavior such as the atomic diffusion of Xe atoms, U vacancies, and O vacancies, the effect of vacancy capture and emission from defects, and the elastic interaction of non-equilibrium gas bubbles. An idealized set of assumptions was imposed on the benchmark problem to simplify the mechanisms considered. The capability and numerical efficiency of different models are compared against selected experimental and simulation results. These comparisons find that the phase-field methods, by the nature of the free energy formulation, are able to represent a larger subset of the mechanisms influencing the intra-granular bubble growth and coarsening mechanisms in the idealized benchmark problem as compared to the Potts and kinetic Monte Carlo methods. It is recognized that the mesoscale benchmark problem as formulated does not specifically highlight the strengths of the discrete particle modeling used in the Potts and kinetic Monte Carlo methods. Future efforts are recommended to construct increasingly more complex mesoscale benchmark problems to further verify and validate the predictive capabilities of the mesoscale modeling

14. The Bubble Transport Mechanism: Indications for a bubble-mediated transfer of microorganisms from the sediment into the water column

Schmale, Oliver; Stolle, Christian; Schneider von Deimling, Jens; Leifer, Ira; Kießlich, Katrin; Krause, Stefan; Frahm, Andreas; Treude, Tina

2015-04-01

Gas releasing seep areas are known to impact the methane biogeochemistry in the surrounding sediment and water column. Due to microbial processes most of the methane is oxidized under anaerobic and aerobic conditions before the greenhouse gas can escape into the atmosphere. However, methane gas bubbles can largely bypass this microbial filter mechanism, enabling highly efficient transport of methane from the sediment towards the sea surface. Studies in the water column surrounding hydrocarbon seeps indicated an elevated abundance of methanotrophic microorganism in the near field of gas bubble plumes. The enhanced methane concentration in the seep-affected water column stimulates the activity of methane oxidizers and leads to a rapid rise in the abundance of methane-oxidizing microorganisms in the aging plume water. In our study we hypothesized that a bubble-mediated transport mechanisms between the benthic and pelagic habitats represents an exchange process, which transfers methanotrophic microorganisms from the sediment into the water column, a process we termed the "Bubble Transport Mechanism". This mechanism could eventually influence the pelagic methanotrophic community, thereby indirectly providing feedback mechanisms for dissolved methane concentrations in the water column and thus impacting the sea/atmosphere methane flux. To test our hypothesis, field studies were conducted at the "Rostocker Seep" site (Coal Oil Point seep area, California, USA). Catalyzed Reporter Deposition Fluorescence In Situ Hybridization (CARD-FISH) analyzes were performed to determine the abundance of aerobic and anaerobic methanotrophic microorganisms. Aerobic methane oxidizing bacteria were detected in the sediment and the water column, whereas anaerobic methanotrophs were detected exclusively in the sediment. The key device of the project was a newly developed "Bubble Catcher" used to collect naturally emanating gas bubbles at the sea floor together with particles attached to the

15. Numerical analysis of incompressible viscous flow around a bubble

Sugano, Minoru; Ishii, Ryuji; Morioka, Shigeki

1992-12-01

A numerical simulation of flows around a deformable gas bubble rising through an incompressible viscous fluid is carried out on a supercomputer Fujitsu VP-2600 at the Data Processing Center of Kyoto University. The solution algorithm is a modified MAC (Marker And Cell) method. For the grid generation, an orthogonal mapping proposed by Ryskin and Leal is applied. The numerical results are compared with Ryskin and Leal's results and previous experiments. It will be shown that a good agreement is obtained between them.

16. Growth and setting of gas bubbles in a viscoelastic matrix imaged by X-ray microtomography: the evolution of cellular structures in fermenting wheat flour dough.

PubMed

Turbin-Orger, A; Babin, P; Boller, E; Chaunier, L; Chiron, H; Della Valle, G; Dendievel, R; Réguerre, A L; Salvo, L

2015-05-07

X-ray tomography is a relevant technique for the dynamic follow-up of gas bubbles in an opaque viscoelastic matrix, especially using image analysis. It has been applied here to pieces of fermenting wheat flour dough of various compositions, at two different voxel sizes (15 and 5 μm). The resulting evolution of the main cellular features shows that the creation of cellular structures follows two regimes that are defined by a characteristic time of connectivity, tc [30 and 80 min]: first (t ≤ tc), bubbles grow freely and then (t ≥ tc) they become connected since the percolation of the gas phase is limited by liquid films. During the first regime, bubbles can be tracked and the local strain rate can be measured. Its values (10(-4)-5 × 10(-4) s(-1)) are in agreement with those computed from dough viscosity and internal gas pressure, both of which depend on the composition. For higher porosity, P = 0.64 in our case, and thus occurring in the second regime, different cellular structures are obtained and XRT images show deformed gas cells that display complex shapes. The comparison of these images with confocal laser scanning microscopy images suggests the presence of liquid films that separate these cells. The dough can therefore be seen as a three-phase medium: viscoelastic matrix/gas cell/liquid phase. The contributions of the different levels of matter organization can be integrated by defining a capillary number (C = 0.1-1) that makes it possible to predict the macroscopic dough behavior.

17. Tidally controlled gas bubble emissions: A comprehensive study using long-term monitoring data from the NEPTUNE cabled observatory offshore Vancouver Island

Römer, Miriam; Riedel, Michael; Scherwath, Martin; Heesemann, Martin; Spence, George D.

2016-09-01

Long-term monitoring over 1 year revealed high temporal variability of gas emissions at a cold seep in 1250 m water depth offshore Vancouver Island, British Columbia. Data from the North East Pacific Time series Underwater Networked Experiment observatory operated by Ocean Networks Canada were used. The site is equipped with a 260 kHz Imagenex sonar collecting hourly data, conductivity-temperature-depth sensors, bottom pressure recorders, current meter, and an ocean bottom seismograph. This enables correlation of the data and analyzing trigger mechanisms and regulating criteria of gas discharge activity. Three periods of gas emission activity were observed: (a) short activity phases of few hours lasting several months, (b) alternating activity and inactivity of up to several day-long phases each, and (c) a period of several weeks of permanent activity. These periods can neither be explained by oceanographic conditions nor initiated by earthquakes. However, we found a clear correlation of gas emission with bottom pressure changes controlled by tides. Gas bubbles start emanating during decreasing tidal pressure. Tidally induced pressure changes also influence the subbottom fluid system by shifting the methane solubility resulting in exsolution of gas during falling tides. These pressure changes affect the equilibrium of forces allowing free gas in sediments to emanate into the water column at decreased hydrostatic load. We propose a model for the fluid system at the seep, fueled by a constant subsurface methane flux and a frequent tidally controlled discharge of gas bubbles into the ocean, transferable to other gas emission sites in the world's oceans.

18. Numerical simulaion of dynamics of a gas bubble in liquid near a rigid wall during its growth and collapse

Ilgamov, M. A.; Kosolapova, L. A.; Malakhov, V. G.

2016-11-01

A numerical technique of calculating the dynamics of a cavitation bubble near a plane rigid wall is presented. The bubble at its collapse can become toroidal. The liquid is assumed inviscid and incompressible, its flow being potential. The bubble surface movement is determined by the Euler method, the normal component of the liquid velocity on the bubble surface is found by the boundary element method. The technique also includes an algorithm for calculating the velocity and pressure fields in the liquid. The convergence of the numerical solution with refining the temporal and spatial steps is demonstrated. The results of the present technique are compared with some known numerical and experimental data by other authors, their satisfactory agreement is found. To illustrate the capabilities of the present technique the process of growth and collapse of a bubble in water near a wall is considered. The liquid pressure contours in the stage of the bubble collapse are given and the radial liquid pressure profiles on the wall and at a small distance from the wall where the liquid pressure is maximum are shown.

19. Constructing and dismantling frameworks of disease etiology: the rise and fall of sewer gas in America, 1870-1910.

PubMed

An, Perry G

2004-05-01

For roughly forty years, from 1870 to 1910, Americans recognized and feared gases emanating from sewers, believing that they were responsible for causing an array of diseases. Fears of sewer gas arose from deeper anxieties toward contact with decomposing organic matter and the vapors emitted from such refuse. These anxieties were exacerbated by the construction of sewers across the country during the mid-to-late-nineteenth century, which concentrated waste emanations and connected homes to one another. The result was the birth of sewer gas and the attribution of sickness and death to it, as well as the development of a host of plumbing devices and, especially, bathroom fixtures, to combat sewer gas. The rise of the germ theory, laboratory science, and belief in disease specificity, however, transformed the threat of sewer gas, eventually replacing it (and the larger fear of miasmas) with the threat of germs. The germ theory framework, by 1910, proved more suitable than the sewer gas framework in explaining disease causation; it is this suitability that often shapes the relationship between science and society.

20. Constructing and dismantling frameworks of disease etiology: the rise and fall of sewer gas in America, 1870-1910.

PubMed Central

An, Perry G.

2004-01-01

For roughly forty years, from 1870 to 1910, Americans recognized and feared gases emanating from sewers, believing that they were responsible for causing an array of diseases. Fears of sewer gas arose from deeper anxieties toward contact with decomposing organic matter and the vapors emitted from such refuse. These anxieties were exacerbated by the construction of sewers across the country during the mid-to-late-nineteenth century, which concentrated waste emanations and connected homes to one another. The result was the birth of sewer gas and the attribution of sickness and death to it, as well as the development of a host of plumbing devices and, especially, bathroom fixtures, to combat sewer gas. The rise of the germ theory, laboratory science, and belief in disease specificity, however, transformed the threat of sewer gas, eventually replacing it (and the larger fear of miasmas) with the threat of germs. The germ theory framework, by 1910, proved more suitable than the sewer gas framework in explaining disease causation; it is this suitability that often shapes the relationship between science and society. PMID:15829149

1. Enhancing gas-liquid mass transfer rates in non-newtonian fermentations by confining mycelial growth to microbeads in a bubble column

SciTech Connect

Gbewonyo, K.; Wang, D.I.C.

1983-12-01

The performance of a penicillin fermentation was assessed in a laboratory-scale bubble column fermentor, with mycelial growth confined to the pore matrix of celite beads. Final cell densities of 29 g/L and penicillin titres of 5.5 g/L were obtained in the confined cell cultures. In comparison, cultures of free mycelial cells grown in the absence of beads experienced dissolved oxygen limitations in the bubble column, giving only 17 g/L final cell concentrations with equally low penicillin titres of 2 g/L. The better performance of the confined cell cultures was attributed to enhanced gas liquid mass transfer rates, with mass transfer coefficients (k /SUB L/ a) two to three times higher than those determined in the free cell cultures. Furthermore, the confined cell cultures showed more efficient utilization of power input for mass transfer, providing up to 50% reduction in energy requirements for aeration.

2. A theoretical study of bubble motion in surfactant solutions

Wang, Yanping

1999-08-01

We examine the effect of surfactants on a spherical gas bubble rising steadily in an infinite fluid at low and order one Reynolds number with order one and larger Peclet numbers. Our mathematical model is based on the Navier-Stokes equations coupled with a convection- diffusion equation together with appropriate interfacial conditions. The nonlinearity of the equations and boundary conditions, and the coupling between hydrodynamics and surfactant transport make the problem very challenging. When a bubble rises in a fluid containing surface-active agents, surfactant adsorbs onto the bubble surface at the leading edge, convects to the trailing edge by the surface flow and desorbs into the bulk along the interface. This adsorption develops a surface concentration gradient on the interface that makes the surface tension at the back end relatively lower than that at the front end, and thus retards the bubble velocity. Because of surfactant impurities unavoidably present in materials, this retardation can cause a problem in materials processing in space and glass processing when bubbles are created during chemical reactions. Thus the study of how to remobilize (remove the surfactant gradient on the surface) the bubble surface becomes necessary. Many studies have been done on this retarding effects of the surfactant on a moving bubble. However, most were focused on the retarding effect due to a trace amount of surfactant, in which case the bubble velocity monotonically decreases as the bulk concentration increases. The question of how to remobilize the bubble surface remains unanswered. In this work, we will show that the bubble velocity can be controlled by remobilizing the bubble interface using the surfactant concentration. This technique not only can be used to maximize the bubble velocity, but also can be used to maximize mass transfer on purifying materials and extracting materials from mixtures. In the first part of the work, we illustrate numerically that the

3. Storm in a "Teacup": A Radio-quiet Quasar with ≈10 kpc Radio-emitting Bubbles and Extreme Gas Kinematics

Harrison, C. M.; Thomson, A. P.; Alexander, D. M.; Bauer, F. E.; Edge, A. C.; Hogan, M. T.; Mullaney, J. R.; Swinbank, A. M.

2015-02-01

We present multi-frequency (1-8 GHz) Very Large Array data, combined with VIsible MultiObject Spectrograph integral field unit data and Hubble Space Telescope imaging, of a z = 0.085 radio-quiet type 2 quasar (with L 1.4 GHz ≈ 5 × 1023 W Hz-1 and L AGN ≈ 2 × 1045 erg s-1). Due to the morphology of its emission-line region, the target (J1430+1339) has been referred to as the "Teacup" active galactic nucleus (AGN) in the literature. We identify "bubbles" of radio emission that are extended ≈10-12 kpc to both the east and west of the nucleus. The edge of the brighter eastern bubble is co-spatial with an arc of luminous ionized gas. We also show that the "Teacup" AGN hosts a compact radio structure, located ≈0.8 kpc from the core position, at the base of the eastern bubble. This radio structure is co-spatial with an ionized outflow with an observed velocity of v = -740 km s-1. This is likely to correspond to a jet, or possibly a quasar wind, interacting with the interstellar medium at this position. The large-scale radio bubbles appear to be inflated by the central AGN, which indicates that the AGN can also interact with the gas on >~ 10 kpc scales. Our study highlights that even when a quasar is formally "radio-quiet" the radio emission can be extremely effective for observing the effects of AGN feedback.

4. STORM IN A {sup T}EACUP{sup :} A RADIO-QUIET QUASAR WITH ≈10 kpc RADIO-EMITTING BUBBLES AND EXTREME GAS KINEMATICS

SciTech Connect

Harrison, C. M.; Thomson, A. P.; Alexander, D. M.; Edge, A. C.; Hogan, M. T.; Swinbank, A. M.; Bauer, F. E.; Mullaney, J. R.

2015-02-10

We present multi-frequency (1-8 GHz) Very Large Array data, combined with VIsible MultiObject Spectrograph integral field unit data and Hubble Space Telescope imaging, of a z = 0.085 radio-quiet type 2 quasar (with L {sub 1.4} {sub GHz} ≈ 5 × 10{sup 23} W Hz{sup –1} and L {sub AGN} ≈ 2 × 10{sup 45} erg s{sup –1}). Due to the morphology of its emission-line region, the target (J1430+1339) has been referred to as the ''Teacup'' active galactic nucleus (AGN) in the literature. We identify ''bubbles'' of radio emission that are extended ≈10-12 kpc to both the east and west of the nucleus. The edge of the brighter eastern bubble is co-spatial with an arc of luminous ionized gas. We also show that the ''Teacup'' AGN hosts a compact radio structure, located ≈0.8 kpc from the core position, at the base of the eastern bubble. This radio structure is co-spatial with an ionized outflow with an observed velocity of v = –740 km s{sup –1}. This is likely to correspond to a jet, or possibly a quasar wind, interacting with the interstellar medium at this position. The large-scale radio bubbles appear to be inflated by the central AGN, which indicates that the AGN can also interact with the gas on ≳ 10 kpc scales. Our study highlights that even when a quasar is formally ''radio-quiet'' the radio emission can be extremely effective for observing the effects of AGN feedback.

5. Loss of Homeostatic Gas Exchange in Eastern Hemlock in Response to Pollution and Rising CO2?

Rayback, S. A.; Gagen, M. H.; Lini, A.; Cogbill, C. V.

2014-12-01

In eastern North American, multiple environmental effects, natural and anthropogenic, may impinge upon tree-ring based stable carbon isotope ratios when examined over long time periods. Investigation of relationships between a Vermont (USA) eastern hemlock δ¹³C (1849-2010) chronology and local and regional climate variables, as well as a regional sulfur dioxide time series revealed the decoupling of δ¹³C from significant climate drivers such as May-August maximum temperature (r=0.50, p<0.01) and, raise the possibility that this decoupling can be attributed to foliar and soil leaching of calcium due to acidic deposition since the 1960s. Further, investigation of derived photosynthetic isotope discrimination (Δ¹³C) time series showed an overall decreasing trend in Δ¹³C in response to rising atmospheric carbon dioxide (ca), but with a slight rise in Δ¹³C in the last decade. Comparison of time series of leaf intercellular CO2 concentration (ci), ci/ca, and intrinsic water use efficiency (iWUE) showed homeostatic maintenance of ci levels against ca until 1965 and rising iWUE. Then, ci increased proportional (1965-2000) and later at the same rate as ca (2001-2010) and iWUE leveled off indicating a potential loss of sensitivity to increasing atmospheric carbon dioxide. This more recent passive response may be an indication of a loss of homeostatic maintenance of stomatal control and/or may be linked to changing climate in the region (e.g., wetter conditions).

6. Modeling the dynamics of single-bubble sonoluminescence

Vignoli, Lucas L.; de Barros, Ana L. F.; Thomé, Roberto C. A.; Nogueira, A. L. M. A.; Paschoal, Ricardo C.; Rodrigues, Hilário

2013-05-01

Sonoluminescence (SL) is the phenomenon in which acoustic energy is (partially) transformed into light. It may occur by means of one bubble or many bubbles of gas inside a liquid medium, giving rise to the terms single-bubble and multi-bubble sonoluminescence (SBSL and MBSL). In recent years some models have been proposed to explain this phenomenon, but there is still no complete theory for the light-emission mechanism (especially in the case of SBSL). In this paper, we do not address this more complicated specific issue, but only present a simple model describing the dynamical behavior of the sonoluminescent bubble in the SBSL case. Using simple numerical techniques within the Matlab software package, we discuss solutions that consider various possibilities for some of the parameters involved: liquid compressibility, surface tension, viscosity and type of gas. The model may be used for an introductory study of SL on undergraduate or graduate physics courses, and as a clarifying example of a physical system exhibiting large nonlinearity.

7. The Dueling Bubble Experiment

Roy, Anshuman; Borrell, Marcos; Felts, John; Leal, Gary; Hirsa, Amir

2007-11-01

When two drops or bubbles are brought into close proximity to each other, the thin film of the fluid between them drains as they are squeezed together. If the film becomes thin enough that intermolecular forces of attraction overwhelm capillary forces, the drops/bubbles coalesce and the time it takes for this to happen, starting from the point of apparent contact is referred to as the drainage time. One practical version of this scenario occurs during the formation of foams, when the thin film forms between gas bubbles that are growing in volume with time. We performed an experimental study that is intended to mimic this process in which the two drops (or bubbles) in the size range of 50-100 microns diameter are created by oozing a liquid/gas out of two capillaries of diameter less than 100 microns directly facing each other and immersed in a second fluid. We present measurements of drainage times for the cases of very low viscosity ratios PDMS drops in Castor oil (less than 0.05) and bubbles of air in PDMS, and highlight the differences that arise in part due to the different boundary conditions for thin film drainage for liquid-liquid versus gas-liquid systems, and in part due to the different Hamaker constants for the two systems.

8. Slurry bubble column hydrodynamics

Slurry bubble column reactors are presently used for a wide range of reactions in both chemical and biochemical industry. The successful design and scale up of slurry bubble column reactors require a complete understanding of multiphase fluid dynamics, i.e. phase mixing, heat and mass transport characteristics. The primary objective of this thesis is to improve presently limited understanding of the gas-liquid-solid slurry bubble column hydrodynamics. The effect of superficial gas velocity (8 to 45 cm/s), pressure (0.1 to 1.0 MPa) and solids loading (20 and 35 wt.%) on the time-averaged solids velocity and turbulent parameter profiles has been studied using Computer Automated Radioactive Particle Tracking (CARPT). To accomplish this, CARPT technique has been significantly improved for the measurements in highly attenuating systems, such as high pressure, high solids loading stainless steel slurry bubble column. At a similar set of operational conditions time-averaged gas and solids holdup profiles have been evaluated using the developed Computed Tomography (CT)/Overall gas holdup procedure. This procedure is based on the combination of the CT scans and the overall gas holdup measurements. The procedure assumes constant solids loading in the radial direction and axially invariant cross-sectionally averaged gas holdup. The obtained experimental holdup, velocity and turbulent parameters data are correlated and compared with the existing low superficial gas velocities and atmospheric pressure CARPT/CT gas-liquid and gas-liquid-solid slurry data. The obtained solids axial velocity radial profiles are compared with the predictions of the one dimensional (1-D) liquid/slurry recirculation phenomenological model. The obtained solids loading axial profiles are compared with the predictions of the Sedimentation and Dispersion Model (SDM). The overall gas holdup values, gas holdup radial profiles, solids loading axial profiles, solids axial velocity radial profiles and solids

9. Bubble Transport through Micropillar Arrays

Lee, Kenneth; Savas, Omer

2012-11-01

In current energy research, artificial photosynthetic devices are being designed to split water and harvest hydrogen gas using energy from the sun. In one such design, hydrogen gas bubbles evolve on the catalytic surfaces of arrayed micropillars. If these bubbles are not promptly removed from the surface, they can adversely affect gas evolution rates, water flow rates, sunlight capture, and heat management of the system. Therefore, an efficient method of collecting the evolved gas bubbles is crucial. Preliminary flow visualization has been conducted of bubbles advecting through dense arrays of pillars. Bubbles moving through square and hexagonal arrays are tracked, and the results are qualitatively described. Initial attempts to correlate bubble motion with relevant lengthscales and forces are also presented. These observations suggest how bubble transport within such pillar arrays can be managed, as well as guide subsequent experiments that investigate bubble evolution and collection. This material is based upon work performed by the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy under Award Number DE-SC0004993.

10. Are seafloor pockmarks on the Chatham Rise, New Zealand, linked to CO2 hydrates? Gas hydrate stability considerations.

Pecher, I. A.; Davy, B. W.; Rose, P. S.; Coffin, R. B.

2015-12-01

Vast areas of the Chatham Rise east of New Zealand are covered by seafloor pockmarks. Pockmark occurrence appears to be bathymetrically controlled with a band of smaller pockmarks covering areas between 500 and 700 m and large seafloor depressions beneath 800 m water depth. The current depth of the top of methane gas hydrate stability in the ocean is about 500 m and thus, we had proposed that pockmark formation may be linked to methane gas hydrate dissociation during sealevel lowering. However, while seismic profiles show strong indications of fluid flow, geochemical analyses of piston cores do not show any evidence for current or past methane flux. The discovery of Dawsonite, indicative of significant CO2 flux, in a recent petroleum exploration well, together with other circumstantial evidence, has led us to propose that instead of methane hydrate, CO2 hydrate may be linked to pockmark formation. We here present results from CO2 hydrate stability calculations. Assuming water temperature profiles remain unchanged, we predict the upper limit of pockmark occurrence to coincide with the top of CO2 gas hydrate stability during glacial-stage sealevel lowstands. CO2 hydrates may therefore have dissociated during sealevel lowering leading to gas escape and pockmark formation. In contrast to our previous model linking methane hydrate dissociation to pockmark formation, gas hydrates would dissociate beneath a shallow base of CO2 hydrate stability, rather than on the seafloor following upward "grazing" of the top of methane hydrate stability. Intriguingly, at the water depths of the larger seafloor depressions, the base of gas hydrate stability delineates the phase boundary between CO2 hydrates and super-saturated CO2. We caution that because of the high solubility of CO2, dissociation from hydrate to free gas or super-saturated CO2 would imply high concentrations of CO2 and speculate that pockmark formation may be linked to CO2 hydrate dissolution rather than dissociation

11. Evidence for gas accumulation beneath the surface crust driving cyclic rise and fall of the lava surface at Halemaumau, Kilauea Volcano

Patrick, M. R.; Orr, T. R.; Wilson, D.; Sutton, A. J.; Elias, T.; Fee, D.; Nadeau, P. A.

2010-12-01

The ongoing eruption in Halemaumau crater, at the summit of Kilauea Volcano, has surpassed the two-year mark and is characterized by lava lake activity in the vent. As of August 2010, the lava lake is about 70 m in diameter and 180 m below the rim of a narrow vent cavity. Although the explosive events that typified the first year of activity have abated, episodic rise and fall of the lava surface remains common. Cycles of rise and fall range from several minutes to eight hours in duration and are characterized by a quiescent rise phase and violent, gas-charged fall, spanning a height change of 20-30 m. Several models have been proposed to explain the cyclic rise and fall of lava surfaces at basaltic volcanoes, which in some cases is referred to as “gas pistoning”. In one model, episodic rise and fall is driven by the ascent of gas slugs from depth. In another, the cyclic behavior is driven by gas accumulation beneath the surface crust, with each cycle terminated by an abrupt failure of the crust, resulting in gas release. Seismic and infrasound data, as well as gas and webcam monitoring, at Halemaumau over the past two years strongly support the gas accumulation model, based on several lines of evidence. First, gas emission rates drop significantly below background levels during the rise phase, and increase dramatically during the fall phase, suggesting a process of gas buildup and release as opposed to slug flow. Second, the rise phases can last several hours, which is longer than reasonable slug ascent times. Third, the rise rate decreases over time, and in many cases plateaus, as the lava reaches its high stand, which is contrary to the exponential increase expected for gas slugs. Fourth, webcam video has captured numerous instances where rockfalls piercing the surface crust initiate gas release and lava level drop, suggestive of gas accumulation at shallow levels. Lastly, FTIR (Fourier Transform Infrared Spectroscopy) data reveal changes in gas

12. Methane bubble ascent within muddy aquatic sediments under different ambient methane source strengths

Tarboush Sirhan, Shahrazad; Katsman, Regina; Ten Brink, Uri

2016-04-01

Methane (CH4) is the simplest and, the most common hydrocarbon in nature. It is considered as one of the most adverse greenhouse gases, at least 25 times more potent than carbon dioxide. When concentration of the dissolved methane in pore waters exceeds the solubility of the gas (affected in turn by temperature, pressure, salinity and by other factors) methane bubbles nucleate. Gas migration in fine-grained cohesive muddy aquatic sediments is accompanied by sediment fracturing. When gas pressure is high enough to overcome compression, friction, and cohesion at grain contacts, gas migrates by pushing the grains apart. These sub-vertical fractures provide lowered-resistance conduits for migration of other bubbles that can destabilize sediment structure resulting even in slope failure. Therefore, understanding the processes governing bubble propagation within fine-grained aquatic sediment is important. Previous models showed that bubbles propagation within fine-grained muddy aquatic sediments can be modeled using principles of linear elastic fracture mechanics. Mass transfer between the bubble rising with high velocity and the surrounding sediments was mostly ignored. We use a coupled macroscopic mechanical/reaction-transport numerical model under a variable source strength profile associated with bio-chemical processes of methane production and consumption within the sediment, as it occurs in nature. The model shows that changes in the dissolved methane concentrations strongly affect bubble ascent velocity, sometimes leading to its retardation below the sediment-water interface

13. Analysis of concentration fluctuations in gas dispersion around high-rise building for different incident wind directions.

PubMed

Liu, X P; Niu, J L; Kwok, K C S

2011-09-15

This article presents experimental results that illustrate the unsteady characteristics of gas dispersion around a complex-shaped high-rise building for different incident wind directions. A series of wind tunnel experiments were conducted using a 1:30 scale model that represented the real structures under study. The objective of this paper is to study the behaviour of concentration fluctuations through transient analysis. Tracer gas was continuously released from a point source located at different positions, and a time series of fluctuating concentrations were recorded at a large number of points using fast flame ionization detectors. The experimental data were analysed to provide a comprehensive data set including variances and associated statistical quantities. Both the unsteady characteristics of the system and their potential practical impact are presented and discussed. Under crowd living conditions, the air pollutant exhausted from one household could probably re-enter into the neighbouring households, traveling with ambient airflow. Such pollutant dispersion process is defined as air cross-contamination in this study. The results indicate that the wind-induced cross-contamination around the studied type of high-rise building should not be overlooked, and the fluctuating concentrations should be paid attention to particularly during the evaluation of a potential contamination risk. This study can help deepen our understanding of the mechanisms of air cross-contamination, and will be useful for implementing optimization strategies to improve the built environments in metropolitan cities such as Hong Kong.

14. Bubble Size Distribution in a Vibrating Bubble Column

Mohagheghian, Shahrouz; Wilson, Trevor; Valenzuela, Bret; Hinds, Tyler; Moseni, Kevin; Elbing, Brian

2016-11-01

While vibrating bubble columns have increased the mass transfer between phases, a universal scaling law remains elusive. Attempts to predict mass transfer rates in large industrial scale applications by extrapolating laboratory scale models have failed. In a stationary bubble column, mass transfer is a function of phase interfacial area (PIA), while PIA is determined based on the bubble size distribution (BSD). On the other hand, BSD is influenced by the injection characteristics and liquid phase dynamics and properties. Vibration modifies the BSD by impacting the gas and gas-liquid dynamics. This work uses a vibrating cylindrical bubble column to investigate the effect of gas injection and vibration characteristics on the BSD. The bubble column has a 10 cm diameter and was filled with water to a depth of 90 cm above the tip of the orifice tube injector. BSD was measured using high-speed imaging to determine the projected area of individual bubbles, which the nominal bubble diameter was then calculated assuming spherical bubbles. The BSD dependence on the distance from the injector, injector design (1.6 and 0.8 mm ID), air flow rates (0.5 to 5 lit/min), and vibration conditions (stationary and vibration conditions varying amplitude and frequency) will be presented. In addition to mean data, higher order statistics will also be provided.

15. Use of high frequency acoustics to study the spatial distributions of bubbles

Terrill, Eric; Melville, Ken

2002-11-01

It is well understood that the presence of bubbles in the ocean can dramatically change the sound speed, attenuation, and scattering of underwater sound over a range of frequencies. Over the last few decades, rational theories have been developed and tested that describe the complex dispersion of sound through spatially homogeneous bubbly mixtures as a function of the sizes and densities of bubbles. However, it is clear that in the ocean, the size distribution of the bubbles will evolve with a number of different temporal and spatial scales as a result of both the physics which govern their formation (breaking wind waves, breaking waves in the surf, rain generated bubbles, or ship wakes) and the physical processes which control their lifetimes: turbulent mixing, bubble rise speed, and gas dissolution. One approach to measuring their distribution in space is the application of O(1) MHz range-gated sonars which can resolve scales of O(1) cm. These high frequencies are also advantageous to work with since the scattering cross section of the bubbles is approximately proportional to the second moment of the size distribution. Results of field measurement efforts to characterize the spatial scales of bubbles from O(1) m to O(1) cm will be presented and discussed. [Work supported by the ONR Underwater Acoustics and Marine Optics programs.

16. Characterizing methane ebullition (bubbling) dynamics from aquatic sediments

Del Sontro, T.; Ostrovsky, I.; McGinnis, D. F.; Eugster, W.; Maeck, A.; Lorke, A.; Wehrli, B.

2013-05-01

Ebullition (bubbling) is one of the most efficient, yet understudied, transport pathways of CH4 from aquatic sediments to the atmosphere. The spatiotemporal variability of ebullition has hindered gaining knowledge of the dynamics of this phenomenon as it is quite complex and difficult to measure accurately. Here we discuss the characterization of ebullition in several systems using various techniques, but focusing on the hydroacoustic evaluation of ebullition with an echosounder. The spatial variability of ebullition in a small Swiss hydropower reservoir was explored in detail and revealed that bathymetry, perhaps as a proxy for sedimentation, heavily dictates the variability. Since an echosounder can be calibrated for bubble volume, the importance of bubble size was elucidated, particularly the significance of large bubbles for gas transport. With knowledge of bubble size, atmospheric ebullition fluxes can be estimated from the hydroacoustic ebulltion fluxes near the sediment bottom combined with a discrete bubble model to estimate dissolution of rising bubbles. Explicit hotspots of ebullition emission were thus distinguished using hydroacoustic data. Results from a somewhat similar reservoir system in Germany identified increased sediment accumulation as the most probable cause for locations of ebullition hot spots. The effect river inflow and sedimentation have on ebullition has also been seen in the Rhone River delta of Lake Geneva, Switzerland, where ebullition focused on certain sedimentalogical features characterizing the complex bathymetry of the delta. We propose that areas of intense sediment accumulation are conducive to ebullition formation and release, and that this realization aids in predicting the location of ebullition hot spots. In the future, predicting hotspot locations with knowledge of typical bubble sizes and plume types found in those various environments will help in approximating the atmospheric methane emission due to ebullition within a

17. Kinetics and dynamics of nanosecond streamer discharge in atmospheric-pressure gas bubble suspended in distilled water under saturated vapor pressure conditions

Sharma, Ashish; Levko, Dmitry; Raja, Laxminarayan L.; Cha, Min Suk

2016-10-01

We perform computational studies of nanosecond streamer discharges generated in helium bubbles immersed in distilled water under atmospheric pressure conditions. The model takes into account the presence of water vapor in the gas bubble for an accurate description of the discharge kinetics. We find that the dynamic characteristics of the streamer discharge are different at low and high positive trigger voltages with the axial streamer evolution dominant for low voltages and a surface hugging mode favored for high voltages. We also find a substantial difference in initiation, transition and evolution stages of discharge for positive and negative trigger voltages with the volumetric distribution of species in the streamer channel much more uniform for negative trigger voltages on account of the presence of multiple streamers. We observe that the presence of water vapor does not affect the breakdown voltage even for oversaturated conditions but significantly influences the composition of dominant species in the trail of the streamer as well as the flux of the dominant species on the bubble surface.

18. Measuring and modeling the bubble population produced by an underwater explosion.

PubMed

Holt, Fred D; Lee Culver, R

2011-11-01

Underwater explosions have been studied intensively in the United States since 1941 [e.g., R. H. Cole, Underwater Explosions (Princeton University Press, Princeton, NJ, 1945), pp. 3-13]. Research to date has primarily focused on the initial shock and subsequent pressure waves caused by the oscillations of the "gas-globe" resulting from charge detonation. These phenomena have relatively short timescales (typically less than 2 s). However, after the gas-globe rises through the water column and breaks the surface, there remains behind a cloud of bubbles and perhaps debris from the explosion container which has been markedly less studied. A recent experiment measured the spatial and temporal acoustic response of the bubble cloud resulting from a 13.6 kg PBXN-111 charge detonated at 15.2 m (50 ft) depth. A directional projector was used to propagate linear frequency-modulated (5-65 kHz) and 40 kHz tonal pulses through the bubble cloud. Two hydrophone arrays were positioned so as to measure the energy lost in propagating through the bubble cloud. Three methods have been utilized to invert measurements and estimate the bubble population. The bubble population estimates have been used to develop a model for the bubble population resulting from an underwater explosion.

19. Bubble Size Control to Improve Oxygen-Based Bleaching: Characterization of Flow Regimes in Pulp-Water-Gas Three-Phase Flows

SciTech Connect

S.M. Ghiaasiaan and Seppo Karrila

2006-03-20

Flow characteristics of fibrous paper pulp-water-air slurries were investigated in a vertical circular column 1.8 m long, with 5.08 cm diameter. Flow structures, gas holdup (void fraction), and the geometric and population characteristics of gas bubbles were experimentally investigated, using visual observation, Gamma-ray densitometry, and flash X-ray photography. Five distinct flow regimes could be visually identified: dispersed bubbly, layered bubbly, plug, churn-turbulent, and slug. Flow regime maps were constructed, and the regime transition lines were found to be sensitive to consistency. The feasibility of using artificial neural networks (ANNs) for the identification of the flow regimes, using the statistical characteristics of pressure fluctuations measured by a single pressure sensor, was demonstrated. Local pressure fluctuations at a station were recorded with a minimally-intrusive transducer. Three-layer, feed-forward ANNs were designed that could identify the four major flow patterns (bubbly, plug, churn, and slug) well. The feasibility of a transportable artificial neural network (ANN) - based technique for the classification of flow regimes was also examined. Local pressures were recorded at three different locations using three independent but similar transducers. An ANN was designed, trained and successfully tested for the classification of the flow regimes using one of the normalized pressure signals (from Sensor 1). The ANN trained and tested for Sensor 1 predicted the flow regimes reasonably well when applied directly to the other two sensors, indicating a good deal of transportability. An ANN-based method was also developed, whereby the power spectrum density characteristics of other sensors were adjusted before they were used as input to the ANN that was based on Sensor 1 alone. The method improved the predictions. The gas-liquid interfacial surface area concentration was also measured in the study. The gas absorption technique was applied

20. Bubbly Little Star

NASA Technical Reports Server (NTRS)

2007-01-01

In this processed Spitzer Space Telescope image, baby star HH 46/47 can be seen blowing two massive 'bubbles.' The star is 1,140 light-years away from Earth.

The infant star can be seen as a white spot toward the center of the Spitzer image. The two bubbles are shown as hollow elliptical shells of bluish-green material extending from the star. Wisps of green in the image reveal warm molecular hydrogen gas, while the bluish tints are formed by starlight scattered by surrounding dust.

These bubbles formed when powerful jets of gas, traveling at 200 to 300 kilometers per second, or about 120 to 190 miles per second, smashed into the cosmic cloud of gas and dust that surrounds HH 46/47. The red specks at the end of each bubble show the presence of hot sulfur and iron gas where the star's narrow jets are currently crashing head-on into the cosmic cloud's gas and dust material.

Whenever astronomers observe a star, or snap a stellar portrait, through the lens of any telescope, they know that what they are seeing is slightly blurred. To clear up the blurring in Spitzer images, astronomers at the Jet Propulsion Laboratory developed an image processing technique for Spitzer called Hi-Res deconvolution.

This process reduces blurring and makes the image sharper and cleaner, enabling astronomers to see the emissions around forming stars in greater detail. When scientists applied this image processing technique to the Spitzer image of HH 46/47, they were able to see winds from the star and jets of gas that are carving the celestial bubbles.

This infrared image is a three-color composite, with data at 3.6 microns represented in blue, 4.5 and 5.8 microns shown in green, and 24 microns represented as red.

1. A Bubble Bursts

NASA Technical Reports Server (NTRS)

2005-01-01

RCW 79 is seen in the southern Milky Way, 17,200 light-years from Earth in the constellation Centaurus. The bubble is 70-light years in diameter, and probably took about one million years to form from the radiation and winds of hot young stars.

The balloon of gas and dust is an example of stimulated star formation. Such stars are born when the hot bubble expands into the interstellar gas and dust around it. RCW 79 has spawned at least two groups of new stars along the edge of the large bubble. Some are visible inside the small bubble in the lower left corner. Another group of baby stars appears near the opening at the top.

NASA's Spitzer Space Telescope easily detects infrared light from the dust particles in RCW 79. The young stars within RCW 79 radiate ultraviolet light that excites molecules of dust within the bubble. This causes the dust grains to emit infrared light that is detected by Spitzer and seen here as the extended red features.

2. Electrowetting-on-dielectrics for manipulation of oil drops and gas bubbles in aqueous-shell compound drops.

PubMed

Li, Jiang; Wang, Yixuan; Chen, Haosheng; Wan, Jiandi

2014-11-21

We present the manipulation of oil, organic and gaseous chemicals by electrowetting-on-dielectric (EWOD) technology using aqueous-shell compound drops. We demonstrate that the transport and coalescence of viscous oil drops, the reaction of bromine with styrene in benzene solution, and the reaction of red blood cells with carbon monoxide bubbles can be accomplished using this method.

3. Driving bubbles out of glass

NASA Technical Reports Server (NTRS)

Mattox, D. M.

1981-01-01

Surface tension gradient in melt forces gas bubbles to surface, increasing glass strength and transparency. Conventional chemical and buoyant fining are extremely slow in viscous glasses, but tension gradient method moves 250 um bubbles as rapidly as 30 um/s. Heat required for high temperature part of melt is furnished by stationary electrical or natural-gas heater; induction and laser heating are also possible. Method has many applications in industry processes.

4. Magma mixing enhanced by bubble segregation

Wiesmaier, S.; Daniele, M.; Renggli, C.; Perugini, D.; De Campos, C.; Hess, K. U.; Ertel-Ingrisch, W.; Lavallée, Y.; Dingwell, D. B.

2014-12-01

Rising bubbles may significantly affect magma mixing paths as has been demonstrated by analogue experiments in the past. Here, bubble-advection experiments are performed for the first time employing natural materials at magmatic temperatures. Cylinders of basaltic glass were placed below cylinders of rhyolite glass. Upon melting, interstitial air formed bubbles that rose into the rhyolite melt, thereby entraining tails of basaltic liquid. The formation of plume-like filaments of advected basalt within the rhyolite was characterized by microCT and subsequent high-resolution EMP analyses. Melt entrainment by bubble ascent appears as efficient mechanism to mingle contrasting melt compositions. MicroCT imaging shows bubbles trailing each other and trails of multiple bubbles having converged. Rheological modelling of the filaments yields viscosities of up to 2 orders of magnitude lower than for the surrounding rhyolitic liquid. Such a viscosity contrast implies that subsequent bubbles rising are likely to follow the same pathways that previously ascending bubbles have generated. Filaments formed by multiple bubbles would thus experience episodic replenishment with mafic material. Fundamental implications for the concept of bubble advection in magma mixing are thus a) an acceleration of mixing because of decreased viscous resistance for bubbles inside filaments and b) non-conventional diffusion systematics because of intermittent supply of mafic material (instead of a single pulse) inside a filament. Inside these filaments, the mafic material was variably hybridised to andesitic through rhyolitic composition. Compositional profiles alone are ambiguous, however, to determine whether single or multiple bubbles were involved during formation of a filament. Statistical analysis, employing concentration variance as measure of homogenisation, demonstrates that also filaments appearing as single-bubble filaments are likely to have experienced multiple bubbles passing through

5. Gravity driven flows of bubble suspensions.

Zenit, Roberto; Koch, Donald L.; Sangani, Ashok K.

1999-11-01

Experiments on vertical and inclined channels were performed to study the behavior of a mono-dispersed bubble suspension for which the dual limit of large Reynolds number and small Weber number is satisfied. A uniform stream of 1.5 mm diameter bubbles is produced by a bank of identical capillaries and coalescence is inhibited by addition of salt to the water. Measurements of the liquid velocity and bubble-probe collision rate are obtained with a hot wire anemometer. The gas volume fraction, bubble velocity, velocity variance and chord length are measured using a dual impedance probe. Image analysis is used to quantify the distributions of bubble size and aspect ratio. For vertical channels the bubble velocity is observed to decrease as the bubble concentration increases in accord with the predictions of Spelt and Sangani (1998). The bubble velocity variance arises largely due to bubble-wall and bubble-bubble collisions. For inclined channels, the strength of the shear flow is controlled by the extent of bubble segregation and the effective viscosity of the bubble phase. The measurements are compared with solutions of the averaged equations of motion for a range of gas volume fractions and channel inclination angles.

6. Bubbles, microparticles, and neutrophil activation: changes with exercise level and breathing gas during open-water SCUBA diving.

PubMed

Thom, Stephen R; Milovanova, Tatyana N; Bogush, Marina; Yang, Ming; Bhopale, Veena M; Pollock, Neal W; Ljubkovic, Marko; Denoble, Petar; Madden, Dennis; Lozo, Mislav; Dujic, Zeljko

2013-05-15

The study goal was to evaluate responses in humans following decompression from open-water SCUBA diving with the hypothesis that exertion underwater and use of a breathing mixture containing more oxygen and less nitrogen (enriched air nitrox) would alter annexin V-positive microparticle (MP) production and size changes and neutrophil activation, as well as their relationships to intravascular bubble formation. Twenty-four divers followed a uniform dive profile to 18 m of sea water breathing air or 22.5 m breathing 32% oxygen/68% nitrogen for 47 min, either swimming with moderately heavy exertion underwater or remaining stationary at depth. Blood was obtained pre- and at 15 and 120 min postdive. Intravascular bubbles were quantified by transthoracic echocardiography postdive at 20-min intervals for 2 h. There were no significant differences in maximum bubble scores among the dives. MP number increased 2.7-fold, on average, within 15 min after each dive; only the air-exertion dive resulted in a significant further increase to 5-fold over baseline at 2 h postdive. Neutrophil activation occurred after all dives. For the enriched air nitrox stationary at depth dive, but not for other conditions, the numbers of postdive annexin V-positive particles above 1 μm in diameter were correlated with intravascular bubble scores (correlation coefficients ∼0.9, P < 0.05). We conclude that postdecompression relationships among bubbles, MPs, platelet-neutrophil interactions, and neutrophil activation appear to exist, but more study is required to improve confidence in the associations.

7. Bubble, Bubble, Toil and Trouble.

ERIC Educational Resources Information Center

Journal of Chemical Education, 2001

2001-01-01

Bubbles are a fun way to introduce the concepts of surface tension, intermolecular forces, and the use of surfactants. Presents two activities in which students add chemicals to liquid dishwashing detergent with water in order to create longer lasting bubbles. (ASK)

8. Evidence for the infiltration of gas bubbles into the arterial circulation and neuronal injury following "yo-yo" dives in pigs.

PubMed

Ofir, Dror; Yanir, Yoav; Mullokandov, Michael; Aviner, Ben; Arieli, Yehuda

2016-11-01

"Yo-yo" diving may place divers at a greater risk of neurologic decompression illness (DCI). Using a rat model, we previously demonstrated that "yo-yo" diving has a protective effect against DCI. In the current study, we evaluated the risk of neurologic DCI following "yo-yo" dives in a pig model. Pigs were divided into four groups. The Control group (group A) made a square dive, without excursions to the surface ("peeps"). Group B performed two "peeps," group C performed four "peeps," and group D did not dive at all. All dives were conducted on air to 5 atm absolute, for 30-min bottom time. Echocardiography was performed to detect cardiac gas bubbles before the dive, immediately after, and at 90-min postdive. Motor performance was observed during the 5-h postdive period. Symptoms increased dramatically following a dive with four "peeps." Gas bubbles were detected in the right ventricle of all animals except for the sham group and in the left ventricle only after the four-peep dive. Neuronal cell injury was found in the spinal cord in each of the three experimental groups, tending to decrease with an increase in the number of "peeps." A four-peep "yo-yo" dive significantly increased the risk of neurologic DCI in pigs. Following a four-peep dive, we detected a higher incidence of bubbles in the left ventricle, supporting the common concern regarding an increased risk of neurologic DCI, albeit there was no direct correlation with the frequency of "red neurons" in the spinal cord.

9. Impact of rising greenhouse gas concentrations on future tropical ozone and UV exposure

Meul, Stefanie; Dameris, Martin; Langematz, Ulrike; Abalichin, Janna; Kerschbaumer, Andreas; Kubin, Anne; Oberländer-Hayn, Sophie

2016-03-01

Future projections of tropical total column ozone (TCO) are challenging, as its evolution is affected not only by the expected decline of ozone depleting substances but also by the uncertain increase of greenhouse gas (GHG) emissions. To assess the range of tropical TCO projections, we analyze simulations with a chemistry-climate model forced by three different GHG scenarios (Representative Concentration Pathway (RCP) 4.5, RCP6.0, and RCP8.5). We find that tropical TCO will be lower by the end of the 21st century compared to the 1960s in all scenarios with the largest decrease in the medium RCP6.0 scenario. Uncertainties of the projected TCO changes arise from the magnitude of stratospheric column decrease and tropospheric ozone increase which both strongly vary between the scenarios. In the three scenario simulations the stratospheric column decrease is not compensated by the increase in tropospheric ozone. The concomitant increase in harmful ultraviolet irradiance reaches up to 15% in specific regions in the RCP6.0 scenario.

10. Dissolved methane in rising main sewer systems: field measurements and simple model development for estimating greenhouse gas emissions.

PubMed

Foley, Jeff; Yuan, Zhiguo; Lant, Paul

2009-01-01

At present, the potential generation of methane in wastewater collection systems is ignored under international greenhouse gas (GHG) accounting protocols, despite recent reports of substantial dissolved methane formation in sewers. This suggests that the current national GHG inventories for wastewater handling systems are likely to be underestimated for some situations. This study presents a new catalogue of field data on methane formation in rising main sewerage systems and proposes an empirically-fitted, theoretical model to predict dissolved methane concentrations, based upon the independent variables of pipeline geometry (i.e. surface area to volume ratio, A/V) and hydraulic retention time (HRT). Systems with longer HRT and/or larger A/V ratios are shown to have higher dissolved methane concentrations. This simple predictive model provides a means for water authorities to estimate the methane emissions from other pressurised sewerage systems of similar characteristics.

11. Droplets, Bubbles and Ultrasound Interactions.

PubMed

Shpak, Oleksandr; Verweij, Martin; de Jong, Nico; Versluis, Michel

2016-01-01

The interaction of droplets and bubbles with ultrasound has been studied extensively in the last 25 years. Microbubbles are broadly used in diagnostic and therapeutic medical applications, for instance, as ultrasound contrast agents. They have a similar size as red blood cells, and thus are able to circulate within blood vessels. Perfluorocarbon liquid droplets can be a potential new generation of microbubble agents as ultrasound can trigger their conversion into gas bubbles. Prior to activation, they are at least five times smaller in diameter than the resulting bubbles. Together with the violent nature of the phase-transition, the droplets can be used for local drug delivery, embolotherapy, HIFU enhancement and tumor imaging. Here we explain the basics of bubble dynamics, described by the Rayleigh-Plesset equation, bubble resonance frequency, damping and quality factor. We show the elegant calculation of the above characteristics for the case of small amplitude oscillations by linearizing the equations. The effect and importance of a bubble coating and effective surface tension are also discussed. We give the main characteristics of the power spectrum of bubble oscillations. Preceding bubble dynamics, ultrasound propagation is introduced. We explain the speed of sound, nonlinearity and attenuation terms. We examine bubble ultrasound scattering and how it depends on the wave-shape of the incident wave. Finally, we introduce droplet interaction with ultrasound. We elucidate the ultrasound-focusing concept within a droplets sphere, droplet shaking due to media compressibility and droplet phase-conversion dynamics.

12. Vortex-ring-induced large bubble entrainment during drop impact.

PubMed

Thoraval, Marie-Jean; Li, Yangfan; Thoroddsen, Sigurdur T

2016-03-01

For a limited set of impact conditions, a drop impacting onto a pool can entrap an air bubble as large as its own size. The subsequent rise and rupture of this large bubble plays an important role in aerosol formation and gas transport at the air-sea interface. The large bubble is formed when the impact crater closes up near the pool surface and is known to occur only for drops that are prolate at impact. Herein we use experiments and numerical simulations to show that a concentrated vortex ring, produced in the neck between the drop and the pool, controls the crater deformations and pinchoff. However, it is not the strongest vortex rings that are responsible for the large bubbles, as they interact too strongly with the pool surface and self-destruct. Rather, it is somewhat weaker vortices that can deform the deeper craters, which manage to pinch off the large bubbles. These observations also explain why the strongest and most penetrating vortex rings emerging from drop impacts are not produced by oblate drops but by more prolate drop shapes, as had been observed in previous experiments.

13. Bubbling at high flow rates in inviscid and viscous liquids (slags)

Engh, T. Abel; Nilmani, M.

1988-02-01

The behavior of gas discharging into melts at high velocities but still in the bubbling regime has been investigated in a laboratory modeling study for constant flow conditions. Air or helium was injected through a vertical tuyere into water, zinc-chloride, and aqueous glycerol solutions. High speed cinematography and pressure measurements in the tuyere have been carried out simultaneously. Pressure fluctuations at the injection point were monitored and correlated to the mode of bubble formation. The effects of high gas flow rates and high liquid viscosities have been examined in particular. Flow rates were employed up to 10-3 m3/s and viscosity to 0.5 Ns/m2. In order to attain a high gas momentum, the tuyere diameter was only 3 x 10-3 m. The experimental conditions and modeling liquids were chosen with special reference to the established practice of submerged gas injection to treat nonferrous slags. Such slags can be highly viscous. Bubble volume is smaller than that calculated from existing models such as those given by Davidson and Schüler10,11 due to the effect of gas momentum elongating the bubbles. On the other hand, viscosity tends to retard the bubble rise velocity, thus increasing volumes. To take elongation into account, a mathematical model is presented that assumes a prolate ellipsoidal shape of the bubbles. The unsteady potential flow equations for the liquid are solved for this case. Viscous effects are taken into account by noting that flow deviates from irrotational motion only in a thin boundary layer along the surface of the bubble. Thus, drag on the bubble can be obtained by calculating the viscous energy dissipation for potential flow past an ellipse. The time-dependent inertia coefficient for the ellipsoid is found by equating the vertical pressure increase inside and outside the bubble. This pressure change in the bubble is obtained by assuming that gas enters as a homogeneous jet and then calculating the stagnation pressure at the apex of

14. First-order Description of the Mechanical Fracture Behavior of Fine-Grained Surficial Marine Sediments During Gas Bubble Growth

DTIC Science & Technology

2010-01-01

10 F04O29 BARRY ET AL.: BUBBLE GROWTH BY FRACTURE P04029 Figure 3. Map of field site. Canard, Nova Scotia, Canada. appears to approximate the...Bottinger. and T. Dahm (2005), Buoyancy-driven fracture ascent: Experiments in layered gelatine. J. Volcano!. Geotherm . Res., 144. 273-285. doi...Journal Article 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE First-order description of the mechanical fracture behavior of fine-grained

15. Bubbles of Metamorphosis

Prakash, Manu

2011-11-01

Metamorphosis presents a puzzling challenge where, triggered by a signal, an organism abruptly transforms its entire shape and form. Here I describe the role of physical fluid dynamic processes during pupal metamorphosis in flies. During early stages of pupation of third instar larvae into adult flies, a physical gas bubble nucleates at a precise temporal and spatial location, as part of the normal developmental program in Diptera. Although its existence has been known for the last 100 years, the origin and control of this cavitation'' event has remained completely mysterious. Where does the driving negative pressure for bubble nucleation come from? How is the location of the bubble nucleation site encoded in the pupae? How do molecular processes control such a physical event? What is the role of this bubble during development? Via developing in-vivo imaging techniques, direct bio-physical measurements in live insect pupal structures and physical modeling, here I elucidate the physical mechanism for appearance and disappearance of this bubble and predict the site of nucleation and its exact timing. This new physical insight into the process of metamorphosis also allows us to understand the inherent design of pupal shell architectures in various species of insects. Milton Award, Harvard Society of Fellows; Terman Fellowship, Stanford

16. Frictional drag reduction by bubble injection

Murai, Yuichi

2014-07-01

The injection of gas bubbles into a turbulent boundary layer of a liquid phase has multiple different impacts on the original flow structure. Frictional drag reduction is a phenomenon resulting from their combined effects. This explains why a number of different void-drag reduction relationships have been reported to date, while early works pursued a simple universal mechanism. In the last 15 years, a series of precisely designed experimentations has led to the conclusion that the frictional drag reduction by bubble injection has multiple manifestations dependent on bubble size and flow speed. The phenomena are classified into several regimes of two-phase interaction mechanisms. Each regime has inherent physics of bubbly liquid, highlighted by keywords such as bubbly mixture rheology, the spectral response of bubbles in turbulence, buoyancy-dominated bubble behavior, and gas cavity breakup. Among the regimes, bubbles in some selected situations lose the drag reduction effect owing to extra momentum transfer promoted by their active motions. This separates engineers into two communities: those studying small bubbles for high-speed flow applications and those studying large bubbles for low-speed flow applications. This article reviews the roles of bubbles in drag reduction, which have been revealed from fundamental studies of simplified flow geometries and from development of measurement techniques that resolve the inner layer structure of bubble-mixed turbulent boundary layers.

17. OH Production Enhancement in Bubbling Pulsed Discharges

SciTech Connect

Lungu, Cristian P.; Porosnicu, Corneliu; Jepu, Ionut; Chiru, Petrica; Zaroschi, Valentin; Lungu, Ana M.; Saito, Nagahiro; Bratescu, Maria; Takai, Osamu; Velea, Theodor; Predica, Vasile

2010-10-13

The generation of active species, such as H{sub 2}O{sub 2}, O{sup *}, OH*, HO{sub 2}*, O{sub 3}, N{sub 2}{sup *}, etc, produced in aqueous solutions by HV pulsed discharges was studied in order to find the most efficient way in waste water treatment taking into account that these species are almost stronger oxidizers than ozone. Plasma was generated inside gas bubbles formed by the argon, air and oxygen gas flow between the special designed electrodes. The pulse width and pulse frequency influence was studied in order to increase the efficiency of the OH active species formation. The produced active species were investigated by optical emission spectroscopy and correlated with electrical parameters of the discharges (frequency, pulse width, amplitude, and rise and decay time).

18. Influence of bubble size on effervescent atomization. Part 1: bubble characterization and mean spray features

Lewis, Taylor; Shepard, Thomas; Forliti, David

2016-11-01

In the effervescent atomization process a gas-liquid bubbly mixture is ejected from a nozzle with the goal of enhancing liquid break-up. In this work, high speed images are taken of the bubbly flow inside of an effervescent atomizer as well as downstream of the atomizer exit. The use of varying porous plate media grades and channel inserts at the air injection site of the atomizer permitted independent control of mean bubble size. Digital image analyses were used for bubble characterization and measuring mean spray features. The roles of air injection geometry on bubble population parameters inside of the effervescent atomizer are detailed. The effect of bubble size is examined at multiple gas to liquid flow rate ratios for which the bubbly flow regime was maintained. Results are presented demonstrating the influence of bubble size on the average jet width, jet dark core length, and liquid break-up.

19. First measurements of gas output from bubbling pools in a mud volcano at the periphery of Mt Etna (Italy): methodologies and implications for monitoring purposes

Federico, Cinzia; Giudice, Gaetano; Liuzzo, Marco; Pedone, Maria; Cosenza, Paolo; Riccobono, Giuseppe

2014-05-01

Gases and brines emitted in the southern sector of Mt Etna from mofettes, mud pools and mud volcanoes come from an hydrothermal reservoir hosted within the clayey formations of the sedimentary basement (Chiodini et al., 1996). The gas emitted consists mainly of CO2, with CH4, N2 and He as minor species. CO2 and He stable isotopes indicate a clear magmatic origin for these gases, and their compositional changes during either eruptive or rest periods closely parallel that of crater fumaroles (Paonita et al., 2012). Altough these manifestations are the most significant CO2 emitters outside the crater area, their mass output has never been measured. We present the first measurements of gas flux from several bubbling mud pools in a mud volcano located in the village of Paternò (Lon 14.89° Lat 37.57°), in the southern flank of the volcano. We performed gas measurements using a home-made apparatus, able to capture all the bubbles over an area of 0.4 m2. Over an area of about 7000 m2, we measured the flow rate of every single bubbling pool, providing that it had a minimum flux rate of 0.5 l/min. The maximum measured flow rate for a single pool was 15 l/min. A preliminary estimate of the total CO2 output over the whole mud volcano is in the order of few t/d. At the same time, we measured the chemical composition of emitted gases in various pools, characterised by different gas flow rates, to calculate the output of CO2 and verify the effect of eventual chemical fractionation processes upon gas chemistry. During the same campaign of direct measurements, we also used a commercial infrared laser unit (GasFinder 2.0 from Boreal Laser Ltd) for measurement of volcanic CO2 path-integrated concentrations along cross-sections of the atmospheric plumes in the area. The GasFinder was set as to measure CO2 concentrations at 1 Hz rate. During the field campaigns, the position of the GasFinder unit was sequentially moved so as to scan the plumes from different viewing directions and

20. Numerical Simulations of Bubble Dynamics and Heat Transfer in Pool Boiling---Including the Effects of Conjugate Conduction, Level of Gravity, and Noncondensable Gas Dissolved in the Liquid

Aktinol, Eduardo

Due to the complex nature of the subprocesses involved in nucleate boiling, it has not been possible to develop comprehensive models or correlations despite decades of accumulated data and analysis. Complications such as the presence of dissolved gas in the liquid further confound attempts at modeling nucleate boiling. Moreover, existing empirical correlations may not be suitable for new applications, especially with regards to varying gravity level. More recently, numerical simulations of the boiling process have proven to be capable of reliably predicting bubble dynamics and associated heat transfer by showing excellent agreement with experimental data. However, most simulations decouple the solid substrate by assuming constant wall temperature. In the present study complete numerical simulations of the boiling process are performed---including conjugate transient conduction in the solid substrate and the effects of dissolved gas in the liquid at different levels of gravity. Finite difference schemes are used to discretize the governing equations in the liquid, vapor, and solid phases. The interface between liquid and vapor phases is tracked by a level set method. An iterative procedure is used at the interface between the solid and fluid phases. Near the three-phase contact line, temperatures in the solid are observed to fluctuate significantly over short periods. The results show good agreement with the data available in the literature. The results also show that waiting and growth periods can be related directly to wall superheat. The functional relationship between waiting period and wall superheat is found to agree well with empirical correlations reported in the literature. For the case of a single bubble in subcooled nucleate boiling, the presence of dissolved gas in the liquid is found to cause noncondensables to accumulate at the top of the bubble where most condensation occurs. This results in reduced local saturation temperature and condensation rates

1. Gas bubble nucleation and tritium permeation through metallic walls in a liquid 83Pb-17Li blanket

SciTech Connect

Carta, R.; Dernini, S.; Polcaro, A.M.; Ricci, P.F.; Tola, G.; Pierini, G.

1989-01-01

Recent studies have given lower and lower values for the solubility of hydrogen isotopes in the eutectic 83Pb-17Li alloy, a candidate breeding material for the blanket of fusion machines. Therefore, thermodynamic stability for the gaseous phase under the high pressure reached at the bottom of the alloy containers can be achieved even for very low tritium concentrations in the liquid phase. A mathematical model to determine when tritium bubble nucleation occurs at an appreciable rate is presented. This model is used to predict tritium production behavior in the next European Torus (NET) tokamak.

2. Bubble Dynamics and Resulting Noise from Traveling Bubble Cavitation.

DTIC Science & Technology

1982-04-13

has resulted in models which aqree well with bubble dynamics recorded by high speed film . Chahine, et. al. (23) incorporated asymmetric bubble...recording on the tape soundtrack . 3.8 Measurement of Gas Nuclei in Water The role of nuclei density and size in cavitation inception has been the subject...interference between the coherent background and the particle-diffracted radiation exooses photographic film in the far-field of the nuclei. This

3. Tuning bubbly structures in microchannels

PubMed Central

Vuong, Sharon M.; Anna, Shelley L.

2012-01-01

Foams have many useful applications that arise from the structure and size distribution of the bubbles within them. Microfluidics allows for the rapid formation of uniform bubbles, where bubble size and volume fraction are functions of the input gas pressure, liquid flow rate, and device geometry. After formation, the microchannel confines the bubbles and determines the resulting foam structure. Bubbly structures can vary from a single row (“dripping”), to multiple rows (“alternating”), to densely packed bubbles (“bamboo” and dry foams). We show that each configuration arises in a distinct region of the operating space defined by bubble volume and volume fraction. We describe the boundaries between these regions using geometric arguments and show that the boundaries are functions of the channel aspect ratio. We compare these geometric arguments with foam structures observed in experiments using flow-focusing, T-junction, and co-flow designs to generate stable nitrogen bubbles in aqueous surfactant solution and stable droplets in oil containing dissolved surfactant. The outcome of this work is a set of design parameters that can be used to achieve desired foam structures as a function of device geometry and experimental control parameters. PMID:22655008

4. Getting the gas out - developing gas networks in magmatic systems

Cashman, Katharine; Rust, Alison; Oppenheimer, Julie; Belien, Isolde

2015-04-01

Volcanic eruption style, and explosive potential, are strongly controlled by the pre-eruptive history of the magmatic volatiles: specifically, the more efficient the gas loss prior to eruption, the lower the likelihood of primary (magmatic) explosive activity. Commonly considered gas loss mechanisms include separated flow, where individual bubbles (or bubble clouds) travel at a rate that is faster than the host magma, and permeable flow, where gas escapes through permeable (connected) pathways developed within a (relatively) static matrix. Importantly, gas loss via separated flow is episodic, while gas loss via permeable flow is likely to be continuous. Analogue experiments and numerical models on three phase (solid-liquid-gas) systems also suggest a third mechanism of gas loss that involves the opening and closing of 'pseudo fractures'. Pseudo fractures form at a critical crystallinity that is close to the maximum particle packing. Fractures form by local rearrangement of solid particles and liquid to form a through-going gas fracture; gas escape is episodic, and modulated by the available gas volume and the rate of return flow of interstitial liquid back into the fracture. In all of the gas escape scenarios described above, a fundamental control on gas behaviour is the melt viscosity, which affects the rate of individual bubble rise, the rate of bubble expansion, the rate of film thinning (required for bubble coalescence), and the rate of melt flow into gas-generated fractures. From the perspective of magma degassing, rates of gas expansion and film thinning are key to the formation of an interconnected (permeable) gas pathway. Experiments with both analogue and natural materials show that bubble coalescence is relatively slow, and, in particle-poor melts, does not necessarily create permeable gas networks. As a result, degassing efficiency is modulated by the time scales required either (1) to produce large individual bubbles or bubble clouds (in low viscosity

5. Electrolytic Bubble Growth on Pillared Arrays

Lee, Kenneth; Savas, Omer

2013-11-01

In current energy research, artificial photosynthetic (AP) devices are being designed to split water and harvest hydrogen gas using sunlight. In one such design, hydrogen gas bubbles evolve on catalytic surfaces of arrayed micropillars. If these bubbles are not promptly removed from the surface, they can adversely affect gas evolution rates, water flow rates, sunlight capture, and heat management of the system - all of which deteriorate device performance. Therefore, understanding how to remove evolved gas bubbles from the pillar surfaces is crucial. Flow visualization of electrolytic bubble nucleation and detachment from the catalytic pillar surfaces has been conducted. The bubble departure diameter and lift-off frequency are extracted and compared with known correlations from boiling heat transfer. Bubble tracking indicates that bubble detachment is enhanced by local interactions with neighboring bubbles. These observations suggest how hydrogen gas bubbles can be effectively removed from pillared surfaces to prolong AP device longevity. Joint Center for Artificial Photosynthesis, a U.S. Department of Energy (DOE) Energy Innovations Hub.

6. Bubble-free high-speed UV nanoimprint lithography using condensable gas with very low global warming potential

Suzuki, Kenta; Youn, Sung-Won; Hiroshima, Hiroshi

2016-07-01

Bubble-free filling needs to be achieved to realize high-throughput mass production in ultraviolet nanoimprint lithography (UV-NIL). Although bubble-free filling can be accomplished by performing UV-NIL under vacuum, nonvacuum processes can lower equipment and operation costs. UV-NIL in 1,1,1,3,3-pentafluoropropane (PFP) has been recognized as a promising method of realizing ultrahigh-speed UV-NIL; however, the global warming potential (GWP) of PFP of 1030 might restrict its industrial use. In this work, UV-NIL of a spin-coated UV-curable resin in trans-1-chloro-3,3,3-trifluoropropene (CTFP), which has a low GWP of <5, was studied with the aim of identifying an alternative to PFP. The cavity filling speed of resin and mold release force in CTFP were comparable to those in PFP, and superior to those in helium atmosphere. Sub-100 nm patterns were successfully fabricated by UV-NIL in CTFP, although the line width shrinkage ratio of patterns fabricated in CTFP was slightly larger than that of patterns fabricated in PFP.

7. A Laboratory Experiment To Measure Henry's Law Constants of Volatile Organic Compounds with a Bubble Column and a Gas Chromatography Flame Ionization Detector (GC-FID)

ERIC Educational Resources Information Center

Lee, Shan-Hu; Mukherjee, Souptik; Brewer, Brittany; Ryan, Raphael; Yu, Huan; Gangoda, Mahinda

2013-01-01

An undergraduate laboratory experiment is described to measure Henry's law constants of organic compounds using a bubble column and gas chromatography flame ionization detector (GC-FID). This experiment is designed for upper-division undergraduate laboratory courses and can be implemented in conjunction with physical chemistry, analytical…

8. Towards a universal set of bubble coalescence laws in low viscosity magmas

Schipper, C.; Burgisser, A.

2010-12-01

Bubble nucleation, growth, and coalescence control the ascent, degassing, and eruption of all types of magma. Nucleation and growth are consequences of magma decompression, and are satisfactorily described by solubility and physical models. Coalescence is a more complicated issue, and one that bears heavily on the eruptive fate of an ascending magma. If coalescence is efficient, the resulting permeable networks of interconnected void space may lead to efficient outgassing, and in turn, a reduction in explosive potential. Alternatively, if coalescence is inefficient, bubbles may remain isolated and overpressured, leading to cataclysmic explosive eruptions. Vesicle textures in pyroclasts preserve the only natural evidence of bubble-bubble dynamics. However, most (if not all) pyroclast textures either have lost their gas by bubble collapse, or record syn- to post-fragmentation processes. In both cases, natural products may not always be good indicators of processes at depth. There is thus a gap in our understanding of deep conduit coalescence processes. We present an x-ray computed microtomographic (µ-cT) study of coalescence at the single bubble-bubble pair scale in experimentally and naturally decompressed, low viscosity magmas. Experimentally decompressed phonolites allow us to essentially look “behind” fragmentation, by reproducing deep conduit conditions, and controlling decompression and quenching. Initial results indicate there is no single law of coalescence that can explain all the interactions observed in these low-viscosity magmas, where bubble buoyancy and mobility are key issues. Instead, we identify four different processes, acting concurrently. (1) Traditional capillary +/- gravitational drainage along flattened interbubble films. (2) Static “dimpling,” or penetration of one bubble into an adjacent bubble, driven by growth dispersion-controlled differences in internal bubble pressures. (3) Dynamic “handshaking,” similar to dimpling, but

9. Stable tridimensional bubble clusters in multi-bubble sonoluminescence (MBSL).

PubMed

Rosselló, J M; Dellavale, D; Bonetto, F J

2015-01-01

In the present work, stable clusters made of multiple sonoluminescent bubbles are experimentally and theoretically studied. Argon bubbles were acoustically generated and trapped using bi-frequency driving within a cylindrical chamber filled with a sulfuric acid aqueous solution (SA85w/w). The intensity of the acoustic pressure field was strong enough to sustain, during several minutes, a large number of positionally and spatially fixed (without pseudo-orbits) sonoluminescent bubbles over an ellipsoidally-shaped tridimensional array. The dimensions of the ellipsoids were studied as a function of the amplitude of the applied low-frequency acoustic pressure (PAc(LF)) and the static pressure in the fluid (P0). In order to explain the size and shape of the bubble clusters, we performed a series of numerical simulations of the hydrodynamic forces acting over the bubbles. In both cases the observed experimental behavior was in excellent agreement with the numerical results. The simulations revealed that the positionally stable region, mainly determined by the null primary Bjerknes force (F→Bj), is defined as the outer perimeter of an axisymmetric ellipsoidal cluster centered in the acoustic field antinode. The role of the high-frequency component of the pressure field and the influence of the secondary Bjerknes force are discussed. We also investigate the effect of a change in the concentration of dissolved gas on the positional and spatial instabilities through the cluster dimensions. The experimental and numerical results presented in this paper are potentially useful for further understanding and modeling numerous current research topics regarding multi-bubble phenomena, e.g. forces acting on the bubbles in multi-frequency acoustic fields, transient acoustic cavitation, bubble interactions, structure formation processes, atomic and molecular emissions of equal bubbles and nonlinear or unsteady acoustic pressure fields in bubbly media.

10. Primordial Bubbles within Primordial Bubbles

Occhionero, Franco; Amendola, Luca; Corasaniti, Pier Stefano

The nucleation of primordial bubbles during an inflationary phase transition has been suggested to promote the formation of structure either above or below the horizon, depending on whether the nucleation occurs more or less than 60 e-folds before the end of inflation. Here we propose a mechanism which has both features and produces subhorizon cavities up to hundreds of h-1 Mpc -- where excess power is observed -- inside superhorizon bubbles, i.e. in open universes. For this purpose we build a new inflationary two-field model with two vacuum channels in the potential surface: by modulating the energy difference between these channels, episodes of back and forth transition occur in sequence during inflation. Thus, one physical process may i) reconcile inflation with openness and ii) seed a distribution of observable voids. Bubble spectra are given in terms of phenomenological parameters which in turn are functions of microscopic physical parameters. In principle large scale structure constrains fundamental physics: for example, to account for power at scales of hundreds of h-1 Mpc the singularity in the Euclidean action -- which separates the first from the second phase transition -- must be mild enough. The smoking gun of the process might be the imprint of non-Gaussian, ring-like signals on the microwave background at l > 1000 by the subhorizon bubbles. On the other end of the spectrum, the contribution to l =1,2 from the off-centerness of the observer in the open bubble, is being evaluated.

11. Single-bubble sonoluminescence from noble gases.

PubMed

Yasui, K

2001-03-01

Single-bubble sonoluminescence (SBSL) from noble gases in water is studied theoretically in order to clarify the reason of the distinguished feature that the luminescence is strong for all noble gases, while the other systems of cavitation luminescence are greatly enhanced by the presence of the heavy noble gas(xenon). It is clarified that in spite of the larger thermal conductivity of lighter noble gases the maximum temperature in a SBSL bubble of lighter noble gases is higher due both to the segregation of water vapor and noble gas inside a SBSL bubble and the stronger acoustic drive of a SBSL bubble of lighter noble gases.

12. Single-bubble sonoluminescence from noble gases

Yasui, Kyuichi

2001-03-01

Single-bubble sonoluminescence (SBSL) from noble gases in water is studied theoretically in order to clarify the reason of the distinguished feature that the luminescence is strong for all noble gases, while the other systems of cavitation luminescence are greatly enhanced by the presence of the heavy noble gas(xenon). It is clarified that in spite of the larger thermal conductivity of lighter noble gases the maximum temperature in a SBSL bubble of lighter noble gases is higher due both to the segregation of water vapor and noble gas inside a SBSL bubble and the stronger acoustic drive of a SBSL bubble of lighter noble gases.

13. Sound waves in multifractional liquids with bubbles

Gubaidullin, D. A.; Gafiyatov, R. N.

2017-01-01

The propagation of sound waves in multifractional mixtures of liquid with vapor–gas and gas bubbles of different sizes and different compositions with phase transitions is studied. The dispersed phase consists of N+M fractions having various gases in bubbles and different in the bubbles radii. Phase transitions accounted for N fractions. The total bubble volume concentration is small (less than 1%). The dispersion relation is derived and dispersion curves is built. The evolution of the weak pulsed perturbations of the pressure in this mixture was calculated numerically.

14. Phase diagrams for sonoluminescing bubbles

Hilgenfeldt, Sascha; Lohse, Detlef; Brenner, Michael P.

1996-11-01

Sound driven gas bubbles in water can emit light pulses. This phenomenon is called sonoluminescence (SL). Two different phases of single bubble SL have been proposed: diffusively stable and diffusively unstable SL. We present phase diagrams in the gas concentration versus forcing pressure state space and also in the ambient radius versus gas concentration and versus forcing pressure state spaces. These phase diagrams are based on the thresholds for energy focusing in the bubble and two kinds of instabilities, namely (i) shape instabilities and (ii) diffusive instabilities. Stable SL only occurs in a tiny parameter window of large forcing pressure amplitude Pa˜1.2-1.5 atm and low gas concentration of less than 0.4% of the saturation. The upper concentration threshold becomes smaller with increased forcing. Our results quantitatively agree with experimental results of Putterman's UCLA group on argon, but not on air. However, air bubbles and other gas mixtures can also successfully be treated in this approach if in addition (iii) chemical instabilities are considered. All statements are based on the Rayleigh-Plesset ODE approximation of the bubble dynamics, extended in an adiabatic approximation to include mass diffusion effects. This approximation is the only way to explore considerable portions of parameter space, as solving the full PDEs is numerically too expensive. Therefore, we checked the adiabatic approximation by comparison with the full numerical solution of the advection diffusion PDE and find good agreement.

15. Affirmative Discrimination and the Bubble

ERIC Educational Resources Information Center

Clegg, Roger

2011-01-01

In this essay, the author discusses how affirmative action contributed to an unnatural rise in enrollments in college. In considering the higher education bubble, he makes the case that as the opposition to preferences continues to build, the momentum of this trend will only increase as funding shrinks. He offers some tentative answers to a series…

16. Satellites in the inviscid breakup of bubbles.

PubMed

Gordillo, J M; Fontelos, M A

2007-04-06

In this Letter, we stress the essential role played by gas inertia in the breakup of gas bubbles. Our results reveal that, whenever the gas to liquid density ratio Lambda=rhog/rhol is different from zero, tiny satellite bubbles may be formed as a result of the large gas velocities that are reached close to pinch-off. Moreover, we provide a closed expression for the characteristic satellite diameter, which decreases when decreasing Lambda and which shows order of magnitude agreement with the micron-sized satellite bubbles observed experimentally.

17. Leverage bubble

Yan, Wanfeng; Woodard, Ryan; Sornette, Didier

2012-01-01

Leverage is strongly related to liquidity in a market and lack of liquidity is considered a cause and/or consequence of the recent financial crisis. A repurchase agreement is a financial instrument where a security is sold simultaneously with an agreement to buy it back at a later date. Repurchase agreement (repo) market size is a very important element in calculating the overall leverage in a financial market. Therefore, studying the behavior of repo market size can help to understand a process that can contribute to the birth of a financial crisis. We hypothesize that herding behavior among large investors led to massive over-leveraging through the use of repos, resulting in a bubble (built up over the previous years) and subsequent crash in this market in early 2008. We use the Johansen-Ledoit-Sornette (JLS) model of rational expectation bubbles and behavioral finance to study the dynamics of the repo market that led to the crash. The JLS model qualifies a bubble by the presence of characteristic patterns in the price dynamics, called log-periodic power law (LPPL) behavior. We show that there was significant LPPL behavior in the market before that crash and that the predicted range of times predicted by the model for the end of the bubble is consistent with the observations.

18. Air bubble migration rates as a proxy for bubble pressure distribution in ice cores

Dadic, Ruzica; Schneebeli, Martin; Bertler, Nancy

2015-04-01

Air bubble migration can be used as a proxy to measure the pressure of individual bubbles and can help constrain the gradual close-off of gas bubbles and the resulting age distribution of gases in ice cores. The close-off depth of single bubbles can vary by tens of meters, which leads to a distribution of pressures for bubbles at a given depth. The age distribution of gases (along with gas-age-ice-age differences) decreases the resolution of the gas level reconstructions from ice cores and limits our ability to determine the phase relationship between gas and ice, and thus, the impact of rapid changes of greenhouse gases on surface temperatures. For times of rapid climate change, including the last 150 years, and abrupt climate changes further back in the past, knowledge of the age distribution of the gases trapped in air bubbles will enable us to refine estimates of atmospheric changes. When a temperature gradient is applied to gas bubbles in an ice sample, the bubbles migrate toward warmer ice. This motion is caused by sublimation from the warm wall and subsequent frost deposition on the cold wall. The migration rate depends on ice temperature and bubble pressure and is proportional to the temperature gradient. The spread in migration rates for bubbles in the same samples at given temperatures should therefore reflect the variations in bubble pressures within a sample. Air bubbles with higher pressures would have been closed off higher in the firn column and thus have had time to equilibrate with the surrounding ice pressure, while air bubbles that have been closed off recently would have pressures that are similar to todays atmospheric pressure above the firn column. For ice under pressures up to ~13-16 bar, the pressure distribution of bubbles from a single depth provides a record of the trapping function of air bubbles in the firn column for a certain time in the past. We will present laboratory experiments on air bubble migration, using Antarctic ice core

19. The effects of bubble-bubble interactions on pressures and temperatures produced by bubbles collapsing near a rigid surface

Alahyari Beig, Shahaboddin; Johnsen, Eric

2016-11-01

Cavitation occurs in a wide range of hydraulic applications, and one of its most important consequences is structural damage to neighboring surfaces following repeated bubble collapse. A number of studies have been conducted to predict the pressures produced by the collapse of a single bubble. However, the collapse of multiple bubbles is known to lead to enhanced collapse pressures. In this study, we quantify the effects of bubble-bubble interactions on the bubble dynamics and pressures/temperatures produced by the collapse of a pair of bubbles near a rigid surface. For this purpose, we use an in-house, high-order accurate shock- and interface-capturing method to solve the 3D compressible Navier-Stokes equations for gas/liquid flows. The non-spherical bubble dynamics are investigated and the subsequent pressure and temperature fields are characterized based on the relevant parameters entering the problem: stand-off distance, geometrical configuation, collapse strength. We demonstrate that bubble-bubble interactions amplify/reduce pressures and temperatures produced at the collapse, and increase the non-sphericity of the bubbles and the collapse time, depending on the flow parameters.

20. A model of bubble growth leading to xylem conduit embolism.

PubMed

Hölttä, T; Vesala, T; Nikinmaa, E

2007-11-07

The dynamics of a gas bubble inside a water conduit after a cavitation event was modeled. A distinction was made between a typical angiosperm conduit with a homogeneous pit membrane and a typical gymnosperm conduit with a torus-margo pit membrane structure. For conduits with torus-margo type pits pit membrane deflection was also modeled and pit aspiration, the displacement of the pit membrane to the low pressure side of the pit chamber, was found to be possible while the emboli was still small. Concurrent with pit aspiration, the high resistance to water flow out of the conduit through the cell walls or aspirated pits will make the embolism process slow. In case of no pit aspiration and always for conduits with homogeneous pit membranes, embolism growth is more rapid but still much slower than bubble growth in bulk water under similar water tension. The time needed for the embolism to fill a whole conduit was found to be dependent on pit and cell wall conductance, conduit radius, xylem water tension, pressure rise in adjacent conduits due to water freed from the embolising conduit, and the rigidity and structure of the pits in the case of margo-torus type pit membrane. The water pressure in the conduit hosting the bubble was found to occur almost immediately after bubble induction inside a conduit, creating a sudden tension release in the conduit, which can be detected by acoustic and ultra-acoustic monitoring of xylem cavitation.

1. Motion of a bubble ring in a viscous fluid

Cheng, M.; Lou, J.; Lim, T. T.

2013-06-01

In this paper, lattice Boltzmann method was undertaken to study the dynamics of a vortex ring bubble (or bubble ring) in a viscous incompressible fluid. The study is motivated partly by our desire to assess whether a bubble ring keeps increasing its radius and decreasing its rise velocity as it rises through fluid as was predicted by Turner ["Buoyant vortex rings," Proc. R. Soc. London, Ser. A 239, 61 (1957)], 10.1098/rspa.1957.0022 and Pedley ["The toroidal bubble," J. Fluid Mech. 32, 97 (1968)], 10.1017/S0022112068000601, or does the ring like a rising bubble, eventually reaches a steady state where its radius and velocity remain constant as was predicted by Joseph et al. [Potential Flows of Viscous and Viscoelastic Fluids (Cambridge University Press, 2008)]. The parameters investigated included ring circulation, Reynolds number, density ratio and Bond number. Our numerical results show that a rising bubble ring increases its radius and decreases its velocity, but the process is interrupted by ring instability that eventually causes it to break up into smaller bubbles. This finding is consistent with the stability analysis by Pedley, who predicted that a bubble ring has a finite lifespan and is ultimately destroyed by surface tension instability. Furthermore, it is found that increasing initial circulation has a stabilizing effect on a bubble ring while increasing Reynolds number or Bond number hastens ring instability, resulting in an earlier break up into smaller bubbles; the number of bubbles depends on the wavenumber of the perturbation.

2. Bubble Drag Reduction Requires Large Bubbles

Verschoof, Ruben A.; van der Veen, Roeland C. A.; Sun, Chao; Lohse, Detlef

2016-09-01

In the maritime industry, the injection of air bubbles into the turbulent boundary layer under the ship hull is seen as one of the most promising techniques to reduce the overall fuel consumption. However, the exact mechanism behind bubble drag reduction is unknown. Here we show that bubble drag reduction in turbulent flow dramatically depends on the bubble size. By adding minute concentrations (6 ppm) of the surfactant Triton X-100 into otherwise completely unchanged strongly turbulent Taylor-Couette flow containing bubbles, we dramatically reduce the drag reduction from more than 40% to about 4%, corresponding to the trivial effect of the bubbles on the density and viscosity of the liquid. The reason for this striking behavior is that the addition of surfactants prevents bubble coalescence, leading to much smaller bubbles. Our result demonstrates that bubble deformability is crucial for bubble drag reduction in turbulent flow and opens the door for an optimization of the process.

3. Slowing down bubbles with sound

Poulain, Cedric; Dangla, Remie; Guinard, Marion

2009-11-01

We present experimental evidence that a bubble moving in a fluid in which a well-chosen acoustic noise is superimposed can be significantly slowed down even for moderate acoustic pressure. Through mean velocity measurements, we show that a condition for this effect to occur is for the acoustic noise spectrum to match or overlap the bubble's fundamental resonant mode. We render the bubble's oscillations and translational movements using high speed video. We show that radial oscillations (Rayleigh-Plesset type) have no effect on the mean velocity, while above a critical pressure, a parametric type instability (Faraday waves) is triggered and gives rise to nonlinear surface oscillations. We evidence that these surface waves are subharmonic and responsible for the bubble's drag increase. When the acoustic intensity is increased, Faraday modes interact and the strongly nonlinear oscillations behave randomly, leading to a random behavior of the bubble's trajectory and consequently to a higher slow down. Our observations may suggest new strategies for bubbly flow control, or two-phase microfluidic devices. It might also be applicable to other elastic objects, such as globules, cells or vesicles, for medical applications such as elasticity-based sorting.

4. Simulations of Bubble Motion in an Oscillating Liquid

Kraynik, A. M.; Romero, L. A.; Torczynski, J. R.

2010-11-01

Finite-element simulations are used to investigate the motion of a gas bubble in a liquid undergoing vertical vibration. The effect of bubble compressibility is studied by comparing "compressible" bubbles that obey the ideal gas law with "incompressible" bubbles that are taken to have constant volume. Compressible bubbles exhibit a net downward motion away from the free surface that does not exist for incompressible bubbles. Net (rectified) velocities are extracted from the simulations and compared with theoretical predictions. The dependence of the rectified velocity on ambient gas pressure, bubble diameter, and bubble depth are in agreement with the theory. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

5. Temperature considerations in numerical simulations of collapsing bubbles

Johnsen, Eric; Alahyari Beig, Shahaboddin

2014-11-01

In naval and biomedical engineering applications, the inertial collapse of cavitation bubbles is known to damage its surroundings. While significant attention has been dedicated to investigating the pressures produced by this process, less is known about heating of the surrounding medium, which may be important when collapse occurs near objects whose properties strongly depend on temperature (e.g., polymers). Euler simulations are capable of predicting the high pressures thereby generated. However, numerical errors can occur when solving the Navier-Stokes equations for compressible interface problems. Using a newly developed computational approach that prevents such errors, we investigate the dynamics of shock-induced and Rayleigh collapse of individual and collections of gas bubbles, in a free field and near rigid surfaces. We characterize the temperature rises based on the relevant non-dimensional parameters entering the problem. In particular, we show that the temperature of a neighboring object rises due to two mechanisms: the shock produced at collapse and heat diffusion from the hot bubble as it moves toward the object. This work was supported by ONR Grant N00014-12-1-0751.

6. The Impacts of a 2-Degree Rise in Global Temperatures upon Gas-Phase Air Pollutants in Europe

Watson, Laura; Josse, Béatrice; Marecal, Virginie; Lacressonnière, Gwendoline; Vautard, Robert; Gauss, Michael; Engardt, Magnuz; Nyiri, Agnes; Siour, Guillaume

2014-05-01

The 15th session of the Conference of Parties (COP 15) in 2009 ratified the Copenhagen Accord, which "recognises the scientific view that" global temperature rise should be held below 2 degrees C above pre-industrial levels in order to limit the impacts of climate change. Due to the fact that a 2-degree limit has been frequently referred to by policy makers in the context of the Copenhagen Accord and many other high-level policy statements, it is important that the impacts of this 2-degree increase in temperature are adequately analysed. To this end, the European Union sponsored the project IMPACT2C, which uses a multi-disciplinary international team to assess a wide variety of impacts of a 2-degree rise in global temperatures. For example, this future increase in temperature is expected to have a significant influence upon meteorological conditions such as temperature, precipitation, and wind direction and intensity; which will in turn affect the production, deposition, and distribution of air pollutants. For the first part of the air quality analysis within the IMPACT2C project, the impact of meteorological forcings on gas phase air pollutants over Europe was studied using four offline atmospheric chemistry transport models. Two sets of meteorological forcings were used for each model: reanalysis of past observation data and global climate model output. Anthropogenic emissions of ozone precursors for the year 2005 were used for all simulations in order to isolate the impact of meteorology and assess the robustness of the results across the different models. The differences between the simulations that use reanalysis of past observation data and the simulations that use global climate model output show how global climate models modify climate hindcasts by boundary conditions inputs: information that is necessary in order to interpret simulations of future climate. The baseline results were assessed by comparison with AirBase (Version 7) measurement data, and were

7. Methane gas seepage - Disregard of significant water column filter processes?

Schneider von Deimling, Jens; Schmale, Oliver

2016-04-01

Marine methane seepage represents a potential contributor for greenhouse gas in the atmosphere and is discussed as a driver for climate change. The ultimate question is how much methane is released from the seafloor on a global scale and what fraction may reach the atmosphere? Dissolved fluxes from methane seepage sites on the seabed were found to be very efficiently reduced by benthic microbial oxidation, whereas transport of free gas bubbles from the seabed is considered to bypass the effective benthic methane filter. Numerical models are available today to predict the fate of such methane gas bubble release to the water column in regard to gas exchange with the ambient water column, respective bubble lifetime and rise height. However, the fate of rising gas bubbles and dissolved methane in the water column is not only governed by dissolution, but is also affected by lateral oceanographic currents and vertical bubble-induced upwelling, microbial oxidation, and physico-chemical processes that remain poorly understood so far. According to this gap of knowledge we present data from two study sites - the anthropogenic North Sea 22/4b Blowout and the natural Coal Oil point seeps - to shed light into two new processes gathered with hydro-acoustic multibeam water column imaging and microbial investigations. The newly discovered processes are hereafter termed Spiral Vortex and Bubble Transport Mechanism. Spiral Vortex describes the evolution of a complex vortical fluid motion of a bubble plume in the wake of an intense gas release site (Blowout, North Sea). It appears very likely that it dramatically changes the dissolution kinetics of the seep gas bubbles. Bubble Transport Mechanism prescribes the transport of sediment-hosted bacteria into the water column via rising gas bubbles. Both processes act as filter mechanisms in regard to vertical transport of seep related methane, but have not been considered before. Spiral Vortex and Bubble Transport Mechanism represent the

8. Mechanism of single-bubble sonoluminescence

Yasui, Kyuichi

1999-08-01

The mechanism of the light emission of single-bubble sonoluminescence (SBSL) is studied theoretically based on the quasiadiabatic compression model. It is concluded that SBSL is not the blackbody radiation but the thermal radiation. It is clarified that the shape of the spectrum is determined by the temperature inside the bubble and the intensity is determined by the rates of the microscopic processes of the light emission. For a noble-gas bubble, radiative recombination of electrons and ions and electron-atom bremsstrahlung are the dominant microscopic processes of the light emission, and the intensity is mainly determined by the degree of ionization of the gas inside the bubble. It is also clarified that for a noble-gas bubble the pulse width of the light is nearly independent of wavelength.

9. Mechanism of single-bubble sonoluminescence.

PubMed

Yasui, K

1999-08-01

The mechanism of the light emission of single-bubble sonoluminescence (SBSL) is studied theoretically based on the quasiadiabatic compression model. It is concluded that SBSL is not the blackbody radiation but the thermal radiation. It is clarified that the shape of the spectrum is determined by the temperature inside the bubble and the intensity is determined by the rates of the microscopic processes of the light emission. For a noble-gas bubble, radiative recombination of electrons and ions and electron-atom bremsstrahlung are the dominant microscopic processes of the light emission, and the intensity is mainly determined by the degree of ionization of the gas inside the bubble. It is also clarified that for a noble-gas bubble the pulse width of the light is nearly independent of wavelength.

10. Numerical simulation of dielectric bubbles coalescence under the effects of uniform magnetic field

2016-06-01

In this research, the co-axial coalescence of a pair of gas bubbles rising in a viscous liquid column under the effects of an external uniform magnetic field is simulated numerically. Considered fluids are dielectric, and applied magnetic field is uniform. Effects of different strengths of magnetic field on the interaction of in-line rising bubbles and coalescence between them were investigated. For numerical modeling of the problem, a computer code was developed to solve the governing equations which are continuity, Navier-Stokes equation, magnetic field equation and level set and reinitialization of level set equations. The finite volume method is used for the discretization of the continuity and momentum equations using SIMPLE scheme where the finite difference method is used to discretization of the magnetic field equations. Also a level set method is used to capture the interface of two phases. The results are compared with available numerical and experimental results in the case of no-magnetic field effect which show a good agreement. It is found that uniform magnetic field accelerates the coalescence of the bubbles in dielectric fluids and enhances the rise velocity of the coalesced bubble.

11. Bubble Formation Modeling in IE-911

SciTech Connect

Fondeur, F.F.

2000-09-27

The author used diffusion modeling to determine the hydrogen and oxygen concentration inside IE-911. The study revealed gas bubble nucleation will not occur in the bulk solution inside the pore or on the pore wall. This finding results from the fast oxygen and hydrogen gas molecular diffusion and a very confined pore space. The net steady state concentration of these species inside the pore proves too low to drive bubble nucleation. This study did not investigate other gas bubble nucleating mechanism such as suspended particles in solution.

12. Ring Bubbles of Dolphins

NASA Technical Reports Server (NTRS)

Shariff, Karim; Marten, Ken; Psarakos, Suchi; White, Don J.; Merriam, Marshal (Technical Monitor)

1996-01-01

The article discusses how dolphins create and play with three types of air-filled vortices. The underlying physics is discussed. Photographs and sketches illustrating the dolphin's actions and physics are presented. The dolphins engage in this behavior on their own initiative without food reward. These behaviors are done repeatedly and with singleminded effort. The first type is the ejection of bubbles which, after some practice on the part of the dolphin, turn into toroidal vortex ring bubbles by the mechanism of baroclinic torque. These bubbles grow in radius and become thinner as they rise vertically to the surface. One dolphin would blow two in succession and guide them to fuse into one. Physicists call this a vortex reconnection. In the second type, the dolphins first create an invisible vortex ring in the water by swimming on their side and waving their tail fin (also called flukes) vigorously. This vortex ring travels horizontally in the water. The dolphin then turns around, finds the vortex and injects a stream of air into it from its blowhole. The air "fills-out" the core of the vortex ring. Often, the dolphin would knock-off a smaller ring bubble from the larger ring (this also involves vortex reconnection) and steer the smaller ring around the tank. One other dolphin employed a few other techniques for planting air into the fluke vortex. One technique included standing vertically in the water with tail-up, head-down and tail piercing the free surface. As the fluke is waved to create the vortex ring, air is entrained from above the surface. Another technique was gulping air in the mouth, diving down, releasing air bubbles from the mouth and curling them into a ring when they rose to the level of the fluke. In the third type, demonstrated by only one dolphin, the longitudinal vortex created by the dorsal fin on the back is used to produce 10-15 foot long helical bubbles. In one technique she swims in a curved path. This creates a dorsal fin vortex since

13. Interactions between radio sources and X-ray gas at the centers of cooling core clusters

Sarazin, C. L.; Blanton, E. L.; Clarke, T. E.

Recent Chandra and XMM observations of the interaction of central radio sources and cooling cores in clusters of galaxies will be presented. The clusters studied include A262, A2052, A2626, A113, A2029, A2597, and A4059. The radio sources blow "bubbles" in the X-ray gas, displacing the gas and compressing it into shells around the radio lobes. At the same time, the radio sources are confined by the X-ray gas. At larger radii, "ghost bubbles" are seen which are weak in radio emission except at low frequencies. These may be evidence of previous eruptions of the radio sources. In some cases, buoyantly rising bubbles may entrain cooler X-ray gas from the centers of the cooling cores. Some radio sources previously classified as cluster merger radio relics may actually be displaced radio bubbles from the central radio sources. The relation between the radio bubbles, and cooler gas (<~10e4 K) and star formation in cooling cores will be described. The implications for the energetics of radio jets and the cooling of the X-ray gas are discussed. The minimum-energy or equipartition pressures of the radio plasma in the radio lobes are generally much lower than is required to inflate the bubbles. The nature of the primary form of energy and pressure in the bubbles will be discussed, and arguments will be given suggesting that the lobes are dominated by thermal pressure from very hot gas (>10 keV).

14. Bubble Growth in Lunar Basalts

Zhang, Y.

2009-05-01

Although Moon is usually said to be volatile-"free", lunar basalts are often vesicular with mm-size bubbles. The vesicular nature of the lunar basalts suggests that they contained some initial gas concentration. A recent publication estimated volatile concentrations in lunar basalts (Saal et al. 2008). This report investigates bubble growth on Moon and compares with that on Earth. Under conditions relevant to lunar basalts, bubble growth in a finite melt shell (i.e., growth of multiple regularly-spaced bubbles) is calculated following Proussevitch and Sahagian (1998) and Liu and Zhang (2000). Initial H2O content of 700 ppm (Saal et al. 2008) or lower is used and the effect of other volatiles (such as carbon dioxide, halogens, and sulfur) is ignored. H2O solubility at low pressures (Liu et al. 2005), concentration-dependent diffusivity in basalt (Zhang and Stolper 1991), and lunar basalt viscosity (Murase and McBirney 1970) are used. Because lunar atmospheric pressure is essentially zero, the confining pressure on bubbles is completely supplied by the overlying magma. Due to low H2O content in lunar basaltic melt (700 ppm H2O corresponds to a saturation pressure of 75 kPa), H2O bubbles only grow in the upper 16 m of a basalt flow or lake. A depth of 20 mm corresponds to a confining pressure of 100 Pa. Hence, vesicular lunar rocks come from very shallow depth. Some findings from the modeling are as follows. (a) Due to low confining pressure as well as low viscosity, even though volatile concentration is very low, bubble growth rate is extremely high, much higher than typical bubble growth rates in terrestrial melts. Hence, mm-size bubbles in lunar basalts are not strange. (b) Because the pertinent pressures are so low, bubble pressure due to surface tension plays a main role in lunar bubble growth, contrary to terrestrial cases. (c) Time scale to reach equilibrium bubble size increases as the confining pressure increases. References: (1) Liu Y, Zhang YX (2000) Earth

15. How are soap bubbles blown? Fluid dynamics of soap bubble blowing

Davidson, John; Lambert, Lori; Sherman, Erica; Wei, Timothy; Ryu, Sangjin

2013-11-01

Soap bubbles are a common interfacial fluid dynamics phenomenon having a long history of delighting not only children and artists but also scientists. In contrast to the dynamics of liquid droplets in gas and gas bubbles in liquid, the dynamics of soap bubbles has not been well documented. This is possibly because studying soap bubbles is more challenging due to there existing two gas-liquid interfaces. Having the thin-film interface seems to alter the characteristics of the bubble/drop creation process since the interface has limiting factors such as thickness. Thus, the main objective of this study is to determine how the thin-film interface differentiates soap bubbles from gas bubbles and liquid drops. To investigate the creation process of soap bubbles, we constructed an experimental model consisting of air jet flow and a soap film, which consistently replicates the conditions that a human produces when blowing soap bubbles, and examined the interaction between the jet and the soap film using the high-speed videography and the particle image velocimetry.

16. Bubble-Free Containers For Liquids In Microgravity

NASA Technical Reports Server (NTRS)

Kornfeld, Dale M.; Antar, Basil L.

1995-01-01

Reports discuss entrainment of gas bubbles during handling of liquids in microgravity, and one report proposes containers filled with liquids in microgravity without entraining bubbles. Bubbles are troublesome in low-gravity experiments - particularly in biological experiments. Wire-mesh cage retains liquid contents without solid wall, because in microgravity, surface tension of liquid exerts sufficient confining force.

17. Bubbling orientifolds

Mukhi, Sunil; Smedbäck, Mikael

2005-08-01

We investigate a class of 1/2-BPS bubbling geometries associated to orientifolds of type-IIB string theory and thereby to excited states of the SO(N)/Sp(N) Script N = 4 supersymmetric Yang-Mills theory. The geometries are in correspondence with free fermions moving in a harmonic oscillator potential on the half-line. Branes wrapped on torsion cycles of these geometries are identified in the fermi fluid description. Besides being of intrinsic interest, these solutions may also occur as local geometries in flux compactifications where orientifold planes are present to ensure global charge cancellation. We comment on the extension of this procedure to M-theory orientifolds.

18. Bernoulli Suction Effect on Soap Bubble Blowing?

Davidson, John; Ryu, Sangjin

2015-11-01

As a model system for thin-film bubble with two gas-liquid interfaces, we experimentally investigated the pinch-off of soap bubble blowing. Using the lab-built bubble blower and high-speed videography, we have found that the scaling law exponent of soap bubble pinch-off is 2/3, which is similar to that of soap film bridge. Because air flowed through the decreasing neck of soap film tube, we studied possible Bernoulli suction effect on soap bubble pinch-off by evaluating the Reynolds number of airflow. Image processing was utilized to calculate approximate volume of growing soap film tube and the volume flow rate of the airflow, and the Reynolds number was estimated to be 800-3200. This result suggests that soap bubbling may involve the Bernoulli suction effect.

19. Manipulating bubbles with secondary Bjerknes forces

SciTech Connect

Lanoy, Maxime; Derec, Caroline; Leroy, Valentin; Tourin, Arnaud

2015-11-23

Gas bubbles in a sound field are submitted to a radiative force, known as the secondary Bjerknes force. We propose an original experimental setup that allows us to investigate in detail this force between two bubbles, as a function of the sonication frequency, as well as the bubbles radii and distance. We report the observation of both attractive and, more interestingly, repulsive Bjerknes force, when the two bubbles are driven in antiphase. Our experiments show the importance of taking multiple scatterings into account, which leads to a strong acoustic coupling of the bubbles when their radii are similar. Our setup demonstrates the accuracy of secondary Bjerknes forces for attracting or repealing a bubble, and could lead to new acoustic tools for noncontact manipulation in microfluidic devices.

20. Armoring confined bubbles in concentrated colloidal suspensions

Yu, Yingxian; Khodaparast, Sepideh; Stone, Howard

2016-11-01

Encapsulation of a bubble with microparticles is known to significantly improve the stability of the bubble. This phenomenon has recently gained increasing attention due to its application in a variety of technologies such as foam stabilization, drug encapsulation and colloidosomes. Nevertheless, the production of such colloidal armored bubble with controlled size and particle coverage ratio is still a great challenge industrially. We study the coating process of a long air bubble by microparticles in a circular tube filled with a concentrated microparticles colloidal suspension. As the bubble proceeds in the suspension of particles, a monolayer of micro-particles forms on the interface of the bubble, which eventually results in a fully armored bubble. We investigate the phenomenon that triggers and controls the evolution of the particle accumulation on the bubble interface. Moreover, we examine the effects of the mean flow velocity, the size of the colloids and concentration of the suspension on the dynamics of the armored bubble. The results of this study can potentially be applied to production of particle-encapsulated bubbles, surface-cleaning techniques, and gas-assisted injection molding.

1. Temperature measurements in cavitation bubbles

Coutier-Delgosha, Olivier

2016-11-01

Cavitation is usually a nearly isothermal process in the liquid phase, but in some specific flow conditions like hot water or cryogenic fluids, significant temperature variations are detected. In addition, a large temperature increase happens inside the cavitation bubbles at the very end of their collapse, due to the fast compression of the gas at the bubble core, which is almost adiabatic. This process is of primary interest in various biomedical and pharmaceutical applications, where the mechanisms of bubble collapse plays a major role. To investigate the amplitude and the spatial distribution of these temperature variations inside and outside the cavitation bubbles, a system based on cold wires has been developed. They have been tested in a configuration of a single bubble obtained by submitting a small air bubble to a large amplitude pressure wave. Some promising results have been obtained after the initial validation tests. This work is funded by the Office of Naval Research Global under Grant N62909-16-1-2116, Dr. Salahuddin Ahmed & Ki-Han Kim program managers.

2. Morphology control and mechanisms of CaCO3 crystallization on gas-liquid interfaces of CO2/NH3 bubbles in aqueons-glycine solutions

Guan, Xiaomei; Huang, Fangzhi; Li, Jian; Li, Shikuo; Zhang, Xiuzhen; Guo, Degui; Shen, Yuhua; Xie, Anjian

2015-06-01

As one of the new methods of materials preparing, interface-regulated mineralization, has been developed and used to fabricate the CaCO3 materials with mimetic construction of natural biogenic structures in the present work. Combined with the effect of glycine at different concentrations, novel gas-liquid interfaces of CO2/NH3 bubbles have been substituted for the traditional settled matrix and utilized as new reaction fields of CaCO3. CaCO3 crystals with delicate hierarchical structures and morphologies, such as scallop-shaped, ellipsoidal and spherical structure, have been obtained at the special glycine-mediated gasliquid interfaces. The effect of glycine concentration and the chemical reaction kinetics have been deeply studied. As a result, we have successfully captured in detail the crystallization behaviors of CaCO3 in different stages, which allow us to put forward a general kinetic model to reveal the formation mechanism of CaCO3 and implicate a straightforward mean to control the morphology and structure.

3. The Isolated Bubble Regime in Pool Nucleate Boiling

NASA Technical Reports Server (NTRS)

Buyevich, Y. A.; Webbon, Bruce W.; Callaway, Robert (Technical Monitor)

1995-01-01

We consider an isolated bubble boiling regime in which vapour bubbles are intermittently produced at a prearranged set of nucleation site on an upward facing overheated wall plane. In this boiling regime, the bubbles depart from the wall and move as separate entities. Except in the matter of rise velocity, the bubbles do not interfere and are independent of one another. However, the rise velocity is dependent on bubble volume concentration in the bulk. Heat transfer properties specific to this regime cannot be described without bubble detachment size, and we apply our previously developed dynamic theory of vapour bubble growth and detachment to determine this size. Bubble growth is presumed to be thermally controlled. Two limiting cases of bubble evolution are considered: the one in which buoyancy prevails in promoting bubble detachment and the one in which surface tension prevails. We prove termination of the isolated regime of pool nucleate boiling to result from one of the four possible causes, depending on relevant parameters values. The first cause consists in the fact that the upward flow of rising bubbles hampers the downward liquid flow, and under certain conditions, prevents the liquid from coming to the wall in an amount that would be sufficient to compensate for vapour removal from the wall. The second cause is due to the lateral coalescence of growing bubbles that are attached to their corresponding nucleation sites, with ensuing generation of larger bubbles and extended vapour patches near the wall. The other two causes involve longitudinal coalescence either 1) immediately in the wall vicinity, accompanied by the establishment of the multiple bubble boiling regime, or 2) in the bulk, with the formation of vapour columns. The longitudinal coalescence in the bulk is shown to be the most important cause. The critical wall temperature and the heat flux density associated with isolated bubble regime termination are found to be functions of the physical and

4. It takes three to tango: 2. Bubble dynamics in basaltic volcanoes and ramifications for modeling normal Strombolian activity

Suckale, Jenny; Hager, Bradford H.; Elkins-Tanton, Linda T.; Nave, Jean-Christophe

2010-07-01

This is the second paper of two that examine numerical simulations of buoyancy-driven flow in the presence of large viscosity contrasts. In the first paper, we demonstrated that a combination of three numerical tools, an extended ghost fluid type method, the level set approach, and the extension velocity technique, accurately simulates complex interface dynamics in the presence of large viscosity contrasts. In this paper, we use this threefold numerical method to investigate bubble dynamics in the conduits of basaltic volcanos with a focus on normal Strombolian eruptions. Strombolian type activity, named after the famously episodic eruptions at Stromboli volcano, is characterized by temporally discrete fountains of incandescent clasts. The mildly explosive nature of normal Strombolian activity, as compared to more effusive variants of basaltic volcanism, is related to the presence of dissolved gas in the magma, yielding a complex two-phase flow problem. We present a detailed scaling analysis allowing identification of the pertinent regime for a given flow problem. The dynamic interactions between gas and magma can be classified into three nondimensional regimes on the basis of bubble sizes and magma viscosity. Resolving the fluid dynamics at the scale of individual bubbles is not equally important in all three regimes: As long as bubbles remain small enough to be spherical, their dynamic interactions are limited compared to the rich spectrum of coalescence and breakup processes observed for deformable bubbles, in particular, once inertia ceases to be negligible. One key finding in our simulations is that both large gas bubbles and large conduit-filling gas pockets ("slugs") are prone to dynamic instabilities that lead to their rapid breakup during buoyancy-driven ascent. We provide upper bound estimates for the maximum stable bubble size in a given magmatic system and discuss the ramifications of our results for two commonly used models of normal Strombolian type

5. Interactions of mid-infrared bubbles with the interstellar medium: are bubble rims associated with collapsing cores?

Devine, Kathryn E.; Mori, Johanna; Watson, Christer

2017-01-01

Mid-infrared bubbles expanding into the interstellar medium (ISM) are often proposed as a trigger for subsequent star formation, although the mechanisms of this triggering are not well understood. Better observational data of the ISM near bubbles can elucidate the connection between bubbles and nearby star formation. We used the VEGAS spectrometer on the Green Bank Telescope to simultaneously observe several Q-band emission lines between 45-49 GHz. We detected HC3N, C34S, CH3OH, and CS toward four mid-infrared (MIR) bubbles. Two of the bubbles are spatially coincident with dark filaments. We show that in both of these cases, the bubbles do not appear to be causing infall in the filaments. We also present the gas kinematics toward two gas clumps coincident with bubble rims. Both clumps show evidence of infall. Finally, we present trends seen in the chemical abundances relative to the bubble.

6. Magma mixing enhanced by bubble segregation

Wiesmaier, S.; Morgavi, D.; Renggli, C.; Perugini, D.; De Campos, C. P.; Hess, K.-U.; Ertel-Ingrisch, W.; Lavallée, Y.; Dingwell, D. B.

2015-04-01

That rising bubbles may significantly affect magma mixing paths has already been demon strated by analogue experiments. Here, for the first time, bubble-advection experiments are performed employing volcanic melts at magmatic temperatures. Cylinders of basaltic glass were placed below cylinders of rhyolite glass. Upon melting, interstitial air formed bubbles that rose into the rhyolite melt, thereby entraining tails of basaltic liquid. The formation of plume-like filaments of advected basalt within the rhyolite was characterized by microCT and subsequent high-resolution EMP analyses. Melt entrainment by bubble ascent appears to be an efficient mechanism for mingling volcanic melts of highly contrasting compositions and properties. MicroCT imaging reveals bubbles trailing each other and multiple filaments coalescing into bigger ones. Rheological modelling of the filaments yields viscosities of up to 2 orders of magnitude lower than for the surrounding rhyolitic liquid. Such a viscosity contrast implies that bubbles rising successively are likely to follow this pathway of low resistance that previously ascending bubbles have generated. Filaments formed by multiple bubbles would thus experience episodic replenishment with mafic material. Inevitable implications for the concept of bubble advection in magma mixing include thereby both an acceleration of mixing because of decreased viscous resistance for bubbles inside filaments and non-conventional diffusion systematics because of intermittent supply of mafic material (instead of a single pulse) inside a material. Inside the filaments, the mafic material was variably hybridised to andesitic through rhyolitic composition. Compositional profiles alone are ambiguous, however, to determine whether single or multiple bubbles were involved during formation of a filament. Statistical analysis, employing concentration variance as measure of homogenisation, demonstrates that also filaments appearing as single-bubble filaments

7. The Interaction of Radio Sources and X-Ray-Emitting Gas in Cooling Flows

Blanton, E. L.

Recent observations of the interactions between radio sources and the X-ray-emitting gas in cooling flows in the cores of clusters of galaxies are reviewed. The radio sources inflate bubbles in the X-ray gas, which then rise buoyantly outward in the clusters transporting energy to the intracluster medium (ICM). The bright rims of gas around the radio bubbles are cool, rather than hot, and do not show signs of being strongly shocked. Energy deposited into the ICM over the lifetime of a cluster through several outbursts of a radio source helps to account for at least some of the gas that is missing in cooling flows at low temperatures.

8. Single Bubble Sonoluminescence

Farley, Jennifer; Hough, Shane

2003-05-01

Single Bubble Sonoluminescence is the emission of light from a single bubble suspended in a liquid caused by a continuum of repeated implosions due to pressure waves generated from a maintained ultrasonic sinusoidal wave source. H. Frenzel and H. Schultz first studied it in 1934 at the University of Cologne. It was not until 1988 with D.F. Gaitan that actual research began with single bubble sonoluminescence. Currently many theories exist attempting to explain the observed bubble phenomenon. Many of these theories require spherical behavior of the bubble. Observation of the bubble has shown that the bubble does not behave spherically in most cases. One explanation for this is known as jet theory. A spectrum of the bubble will give us the mean physical properties of the bubble such as temperature and pressure inside the bubble. Eventually, with the aide of fluorocene dye a full spectrum of the bubble will be obtained.

9. Greenhouse gas emissions from solid waste in Beijing: The rising trend and the mitigation effects by management improvements.

PubMed

Yu, Yongqiang; Zhang, Wen

2016-04-01

Disposal of solid waste poses great challenges to city managements. Changes in solid waste composition and disposal methods, alon