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1

Gas hold-up and bubble diameters in a gassed oscillatory baffled column  

Microsoft Academic Search

In this paper attempts are made to address how bubble behaviour in a batch oscillatory baffled column (OBC) contributes to the overall measured enhancement in mass transfer. A CCD camera is used to measure the bubble size distribution and the gas hold-up in the OBC. The experimental results of Sauter mean diameter and gas hold-up are correlated as a function

M. S. N Oliveira; X Ni

2001-01-01

2

Gas hold-up profiles in foaming liquids in bubble columns  

Microsoft Academic Search

Radial variation of gas hold-up was investigated in 0.385m i.d. bubble column using gamma ray tomography. The gas phase was air and the liquid phase comprised of aqueous solutions of n-butanol at different concentrations (0–0.5%v\\/v). These solutions exhibit foaming behaviour at higher concentrations. Radial profiles were measured at three axial locations (HD\\/D=0.259, 3 and 5). The fractional gas hold-up was

U. Parasu Veera; Kamal L Kataria; J. B Joshi

2001-01-01

3

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

SciTech Connect

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.

Shollenberger, K.A.; Torczynski, J.R.; Adkins, D.R.; O`Hern, T.J.; Jackson, N.B.

1995-12-31

4

Gas holdup distributions in large-diameter bubble columns measured by computed tomography  

Microsoft Academic Search

Using the computed tomography (CT) and computer automated radioactive particle tracking (CARPT) facilities at the Chemical Reaction Engineering Laboratory (CREL), time-averaged gas holdup distributions and liquid recirculation velocities were measured in a 44 cm diameter bubble column for air–water and air–drakeoil systems at 2, 5, and 10 cm\\/s superficial gas velocities, which cover bubbly, transition and churn-turbulent flow regimes, respectively.

Jinwen Chen; Puneet Gupta; Sujatha Degaleesan; Muthanna H. Al-Dahhan; Milorad P. Dudukovi?; Bernard A. Toseland

1998-01-01

5

Liquid dispersion, gas holdup and frictional pressure drop in a packed bubble column at elevated pressures  

Microsoft Academic Search

The gas holdup, frictional pressure drop and liquid dispersion have been investigated in a packed bubble column at elevated pressures for the air–water system. The bubble column, which had an internal diameter of 0.15m and which was packed with 15mm plastic Pall rings was operated in the semibatch mode. The operating pressures ranged from 0.1 to 0.66MPa. It was found

Peter Therning; Anders Rasmuson

2001-01-01

6

Effect of superficial gas velocity on gas hold-up profiles in foaming liquids in bubble column reactors  

Microsoft Academic Search

In an extension to our previous work [Chem. Eng. J. 84 (2001) 247], we continue our investigation in the present communication on the effect of superficial gas velocity on radial gas hold-up profiles for air-aqueous solutions of n-butanol. Radial variation of gas hold-up was investigated in 0.385m i.d. bubble column using gamma ray tomography. The gas phase was air and

U. Parasu Veera; K. L. Kataria; J. B. Joshi

2004-01-01

7

Interfacial areas and gas hold-ups in bubble columns and packed bubble columns at elevated pressures  

Microsoft Academic Search

Interfacial areas and gas hold-ups have been determined at pressures up to 1.85 MPa in a bubble column with a diameter of 85.5 mm and for superficial gas velocities between 1 and 10 cm s?1. In some experiments the bubble column was packed with glass cylinders of length 5.0 mm and diameter 4.0 mm. The interfacial areas were determined by

M. H. Oyevaar; T. de la Rie; Sluijs van der C. L; K. R. Westerterp

1989-01-01

8

Interfacial area and gas holdup in a bubble column reactor at elevated pressures  

Microsoft Academic Search

The influence of pressure, liquid viscosity, and gas velocity on the gas holdup and specific gas-liquid interfacial area in a bubble column reactor has been studied. The 18.7 L reactor had an inner diameter of 15.6 cm with a dispersion height set equal to 3 times the diameter and was operated at pressures between 0.1 and 6.6 MPa. By means

D. Stegeman; P. A. Knop; A. J. G. Wijnands; K. R. Westerterp

1996-01-01

9

Liquid dispersion and gas holdup in packed bubble columns at atmospheric pressure  

Microsoft Academic Search

The gas holdup and liquid axial dispersion coefficient are measured in two semibatch packed bubble columns, 0.154 and 0.200m diameter for an air–water system, at atmospheric conditions. It is observed that the one-dimensional dispersion model does not give an accurate description of the tracer concentration profiles from a pulse injection. This is due to convective liquid flows inside the bed

Peter Therning; Anders Rasmuson

2001-01-01

10

Local bubble size distribution, gas–liquid interfacial areas and gas holdups in an up-flow ejector  

Microsoft Academic Search

Particle image velocimetry (PIV) was used to measure local bubble size distributions (BSD), gas–liquid interfacial areas and gas holdups in an up-flow ejector, based on the water–air system with different liquid and gas flow rates under the presence\\/absence of the swirl body. The results show that the bubble flow patterns are different whether to add the swirl body into the

Shi-qing Zheng; Yun Yao; Fang-fei Guo; Rong-shan Bi; Jing-ya Li

2010-01-01

11

Theoretical prediction of gas hold-up in bubble columns with Newtonian and non-Newtonian fluids  

SciTech Connect

A theoretical model for gas hold-up in bubble columns with Newtonian and non-Newtonial fluids has been developed on the basis of the concept of a characteristic turbulent kinematic viscosity in bubble columns. Gas hold-ups in a 40-L bubble column and a 1000-L pilot plant fermenter with Newtonian fluids (water, glycerine, dextrose, and fermentation media) and non-Newtonian fluids((carboxymethyl) cellulose, carboxypolymethylene, and polyacrylamide) were measured. Predictions were compared with the present data and other experimental data and correlations available in the literature, over a wide range of conditions. A satisfactory agreement was found.

Kawase, Y.; Moo-Young, M.

1987-05-01

12

Gas holdup and entrainment characteristics in a modified downflow bubble column with Newtonian and non-Newtonian liquid  

Microsoft Academic Search

Gas entrainment and holdup characteristics have been studied in a downflow bubble column with both Newtonian and non-Newtonian liquid. Aqueous CMC solutions at different concentration were used as a non-Newtonian and water as Newtonian liquid. In the present system, use of plunging liquid jet and ejector were synchronized to obtain significant entrainment and dispersion of gas into liquid. The effects

Ajay Mandal; Gautam Kundu; Dibyendu Mukherjee

2003-01-01

13

Influence of antifoam agents on gas hold-up and mass transfer in bubble columns with non-newtonian fluids  

Microsoft Academic Search

Experimental studies on the effect of antifoam agents on the performance of bubble columns with non-Newtonian fluids have been conducted. It is found that the gas hold-up and volumetric mass transfer coefficient in the case of water were reduced due to the addition of antifoam agents. It was found that this decrease in volumetric mass trasfer coefficient is substantial but

Y. Kawase; M. Moo-Young

1987-01-01

14

Cross-sectional distributions of gas and solid holdups in slurry bubble column investigated by ultrasonic computed tomography  

Microsoft Academic Search

A brief review on recently developed non-invasive techniques for gas–liquid and gas–liquid–solid systems is presented first. The ultrasonic computed tomography (UCT) developed for measuring the time-averaged cross-sectional distributions of gas and solid holdups in a slurry bubble column is then described. The ultrasonic tomography is a coupling of the earlier developed transmission-mode ultrasonic technique with two-parameter sensing (the energy attenuation

M Warsito; M. Ohkawa; N. Kawata; S. Uchida

1999-01-01

15

Impinging-Jet Ozone Bubble Column Modeling: Hydrodynamics, Gas Hold-up, Bubble Characteristics, and Ozone Mass Transfer  

Microsoft Academic Search

A transient back flow cell model was used to model the hydrodynamic behaviour of an impinging-jet ozone bubble column. A steady-state back flow cell model was developed to analyze the dissolved ozone concentration profiles measured in the bubble column. The column-average overall mass transfer coefficient, kLa (s), was found to be dependent on the superficial gas and liquid velocities, uG

Mahad S. Baawain; Mohamed Gamal El-Din; Katie Clarke; Daniel W. Smith

2007-01-01

16

Flow characteristics of gas–liquid two phase plunging jet absorber–gas holdup and bubble penetration depth  

Microsoft Academic Search

A gas-liquid two phase plunging jet is formed through a gas sucking type multi-jet ejector nozzle. In this study, the effects\\u000a of various conditions in the multi-jet ejector nozzle, the column diameter, and the liquid jet length on penetration depth\\u000a of air bubblesl\\u000a \\u000a B\\u000a and gas holdup hG in a gas-liquid two phase plunging jet absorber were studied experimentally. Consequently,

Mitsuharu Ide; Hiroki Uchiyama; Toshifumi Ishikura

1999-01-01

17

Gas-holdup distribution and energy dissipation in an ejector-induced downflow bubble column: the case of non-Newtonian liquid  

Microsoft Academic Search

A precise knowledge of gas-holdup distribution and energy dissipation is essential for designing gas–liquid contactors. A semi-theoretical approach has been presented to obtain the axial distribution of gas holdup through the column for gas-non-Newtonian liquid two-phase flow system. The whole column is distinguished to have three zones based on gas holdup, viz. top, middle and bottom. The middle section where

Ajay Mandal; Gautam Kundu; Dibyendu Mukherjee

2004-01-01

18

Solidification of phase change material on vertical cylindrical surface in holdup air bubbles  

Microsoft Academic Search

Solidification of phase change material around a vertical cylindrical surface was studied to investigate the performance of ice storage system and stored thermal energy. Air bubbles were generated in the phase change material at various air flow rate as a gas holdup to enhance the heat transfer rate and accelerate the ice layer growth at the solid–liquid interface. The test

Mousa M. Mohamed

2005-01-01

19

HOLDUP, INTERFACIAL AREA AND POWER REQUIREMENTS IN TURBINE AGITATED GAS-LIQUID CONTACTORS  

Microsoft Academic Search

This paper reports a detailed study of the hydrodynamic variables involved in the operation of 6-blade (flat) turbine agitated gas-liquid contractors. New information is presented regarding the characteristic velocity of the dispersed gas bubbles. Generalized correlations for prediction of power consumption of impellers under aeration conditions, gas phase holdup, characteristic velocity, mean residence time of gas bubbles, interfacial area of

T. MURUGESAN; T. E. DEGALEESAN

1992-01-01

20

Experimental study of a cocurrent upflow packed bed bubble column reactor: pressure drop, holdup and interfacial area  

Microsoft Academic Search

Gas–liquid interfacial areas have been determined by means of chemically enhanced absorption of CO2 into DEA in a packed bed bubble column reactor with an inner diameter of 156 mm. The influence of the gas velocity and particle diameter on the interfacial areas, pressure drops and liquid holdups has been investigated. For both packings the limiting values of the gas

E. J. Molga; K. R. Westerterp

1997-01-01

21

FISSION GAS HOLDUP TESTS ON HRT CHARCOAL BEDS  

Microsoft Academic Search

Fission gas holdup tests on the HRT charcoal beds under simulated ; operating conditions are complete. A radioactive tracer technique developed for ; use in laboratory absorption studies was utilized. The efficiency of the ; charcoal beds, in regard to holdup of fission gases, exceeds design ; specifications. On the basis of these tests, the charcoal beds should perform ;

R. E. Adams; W. E. Browning

1958-01-01

22

Validation of models of gas holdup in the CORCON code  

SciTech Connect

Gas holdup data for oleci acid at 291 K and for 1018 steel at 1823 K has been taken for nitrogen sparging gas. The liquid levels have been measured using a real time x-ray technique. The data have been compared to correlations from the literature to assess the appropriate correlations for use in calculating gas holdup for molten core debris in reactor accident calculations. A suitable correlation has been determined as well as coefficients for use in a drift flux model. The correlation is in the form {alpha} = 0.128 M{sup -0.0207} jg*{sup 0.584} where {alpha} is holdup, M is the Morton Number and jg* is the dimensionless gas flux through the liquid. 19 refs., 9 figs., 9 tabs.

Brockmann, J.E.; Arellano, F.E.; Lucero, D.A. (Sandia National Labs., Albuquerque, NM (USA))

1989-12-01

23

Static holdup in Gas – Flowing solids – Fixed bed contactors  

Microsoft Academic Search

Static holdup was investigated experimentally and theoretically in gas – flowing solids – fixed bed bench-scale contactors. Diverse packing elements were used: Raschig rings, ceramic beads, crushed stone and glass beads. Four different flowing solids particles were examined: sand, propant, alumina and glass. A wide range of solid fluxes and gas velocities were used in this study.The experimental results showed

Nikola M. Nika?evi?; Zlatica J. Predojevi?; Dragan Lj. Petrovi?; Aleksandar Dudukovi?

2009-01-01

24

Measurement of Gas Hold-up Profiles in Stirred Tank Reactors by Gamma Ray Attenuation Technique  

Microsoft Academic Search

Gas hold-up is one of the most important hydrodynamic characteristics that is needed for performance estimation, design and scale-up of reactors. The performance of large-scale reactors can be reliably evaluated by measuring the gas hold-up in such reactors. In the present work, local gas hold-up in an industrial reactor has been measured with the help of gamma ray tomography. Based

U. Parasu Veera; A. W. Patwardhan; J. B. Joshi

2001-01-01

25

Gamma ray tomography design for the measurement of hold-up profiles in two-phase bubble columns  

Microsoft Academic Search

A gamma ray tomography system was designed, developed and employed for the measurement of radial hold-up profiles in bubble columns. Measurements were of gamma ray attenuation. For the given source strength the collimator designs for both source and detectors were optimized to get the maximum number of counts with the least scattering effects. For the given dwell and scanning times,

U. Parasu Veera

2001-01-01

26

Reduced gas holdup in catalytic reactor  

SciTech Connect

A reactor for refining resid is described, said reactor comprising an elongated vessel containing catalyst particles, means for feeding a mixture of oil and gas into a plenum defined beneath said catalyst particles with enough force to create an ebullated catalyst bed and elutriate said particles, down comer means for recycling said oil through said bed, liquid recycle pan means attached to an upper end of said down comer means, means for withdrawing a gas product from a level in said vessel which is higher than said recycle pan means, and means for substantially precluding passage of said elutriated particles into said down comer means and said product withdrawing means by creating a circulating current around said precluding means in a region surrounding said down comer means and below said recycle pan means, said current redirecting elutriated catalyst downwardly toward said catalyst bed, said precluding means supported below the recycle pan means in proximity to said upper end and surrounding said down comer means.

Buttke, R.D.; Frey, J.R.

1993-06-15

27

GAS INDUCTION AND HOLD-UP CHARACTERISTICS OF LIQUID JET LOOP REACTORS  

Microsoft Academic Search

Gas induction and hold-up characteristics of liquid jet loop reactors (LJLR) have been studied. From the results of these investigations with various diffuser geometries the effect of various parts of the diffuser on the rate of induction, QG, and the gas hold-up, EG, have been discerned. Two different diffuser designs yield highest EG and QG, respectively. The use of draft

S. R. BHUTADA; V. G. PANGARKAR

1987-01-01

28

Flow characteristics near the nozzle of a bubble column with simultaneous gas-liquid injection  

Microsoft Academic Search

Due to their simplicity of construction which precludes the possibility of blockage, simultaneous gas-liquid injectors and liquid ejectors find application to gas-liquid-solid chemical processes such as coal liquefaction. The gas holdup, bubble rising velocity, and bubble diameter near the nozzle in a bubble column with simultaneous gas and liquid injection were measured using an optical fiber probe. A jet-like spouting

Kiyoshi Idogawa; Takashi Fukuda; Hiroshi Nagaishi; Yosuke Maekawa; Tadatoshi Chiba; Shigeharu Morooka

1994-01-01

29

Flow characteristics near the nozzle of a bubble column with simultaneous gas-liquid injection  

SciTech Connect

Due to their simplicity of construction which precludes the possibility of blockage, simultaneous gas-liquid injectors and liquid ejectors find application to gas-liquid-solid chemical processes such as coal liquefaction. The gas holdup, bubble rising velocity, and bubble diameter near the nozzle in a bubble column with simultaneous gas and liquid injection were measured using an optical fiber probe. A jet-like spouting flow was formed around the nozzle; the height of the jet was independent of the diameter of the nozzle. Bubbles were formed near the side wall and near the top of the jet, with their radial dispersion increasing with increasing height. Beyond {approximately}88 cm from the nozzle, the radial distribution of the gas holdup was uniform and independent of the axial height. The radial dispersion and bubble diameter varied with the nozzle diameter. The effects of simultaneous gas-liquid injection on bubble formation were similar to those of an increase in the pressure.

Idogawa, Kiyoshi; Fukuda, Takashi; Nagaishi, Hiroshi; Maekawa, Yosuke [Government Industrial Development Lab., Sapporo (Japan). Resources and Energy Technology Dept.; Chiba, Tadatoshi [Hokkaido Univ., Sapporo (Japan); Morooka, Shigeharu [Kyushu Univ., Fukuoka (Japan)

1994-10-01

30

Experimental studies on a co-current gas-liquid downflow bubble column  

Microsoft Academic Search

Two-phase co-current vertical downflow systems offer some distinct advantages, like uniform and finer bubbles, greater residence time, negligible coalescence of the bubles etc. In the present work the hydrodynamics of a vertical downflow bubble column fitted with an ejector have been evaluated. Experimental studies have been carried out to evaluate the total pressure gradient and gas holdup. Similarity analysis was

G. Kundu; D. Mukherjee; A. K. Mitra

1995-01-01

31

Experimental investigation of bubbling in particle beds with high solid holdup  

SciTech Connect

A series of experiments on bubbling behavior in particle beds was performed to clarify three-phase flow dynamics in debris beds formed after core-disruptive accident (CDA) in sodium-cooled fast breeder reactors (FBRs). Although in the past, several experiments have been performed in packed beds to investigate flow patterns, most of these were under comparatively higher gas flow rate, which may be not expected during an early sodium boiling period in debris beds. The current experiments were conducted under two dimensional (2D) and three dimensional (3D) conditions separately, in which water was used as liquid phase, and bubbles were generated by injecting nitrogen gas from the bottom of the viewing tank. Various particle-bed parameters were varied, including particle-bed height (from 30 mm to 200 mm), particle diameter (from 0.4 mm to 6 mm) and particle type (beads made of acrylic, glass, alumina and zirconia). Under these experimental conditions, three kinds of bubbling behavior were observed for the first time using digital image analysis methods that were further verified by quantitative detailed analysis of bubbling properties including surface bubbling frequency and surface bubble size under both 2D and 3D conditions. This investigation, which hopefully provides fundamental data for a better understanding and an improved estimation of CDAs in FBRs, is expected to benefit future analysis and verification of computer models developed in advanced fast reactor safety analysis codes. (author)

Cheng, Songbai; Hirahara, Daisuke; Tanaka, Youhei; Gondai, Yoji; Zhang, Bin; Matsumoto, Tatsuya; Morita, Koji; Fukuda, Kenji [Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395 (Japan); Yamano, Hidemasa; Suzuki, Tohru; Tobita, Yoshiharu [Advanced Nuclear System R and D Directorate, Japan Atomic Energy Agency, 4002 Narita, O-arai, Ibaraki 311-1393 (Japan)

2011-02-15

32

PARAMETRIC EFFECTS OF ANTI-FOAM COMPOSITION, SIMULANT PROPERTIES AND NOBLE METALS ON THE GAS HOLDUP AND RELEASE OF A NON-NEWTONIAN WASTE SLURRY SIMULANT  

SciTech Connect

Gas holdup tests were performed in bench-scale and small-scale mechanically-agitated mixing systems at the Savannah River National Laboratory (SRNL) for a simulant of waste from the Hanford Tank 241-AZ-101. These featured additions of DOW Corning Q2-3183A anti-foam agent. Results indicated that this anti-foam agent (AFA) increased gas holdup in the waste simulant by about a factor of four and, counter-intuitively, that the holdup increased as the non-newtonian simulant shear strength decreased (apparent viscosity decreased). Such results raised the potential of increased flammable gas retention in Hanford Waste Treatment and Immobilization Plant (WTP) vessels mixed by air sparging and pulse-jet mixers (PJMs) during a Design Basis Event (DBE). Additional testing was performed to determine the effects of simulant properties, composition of alternate AFAs, and presence of trace noble metals. Key results are that: (1) Increased gas holdup resulting from addition of Q2-3183A is due to a decrease in surface tension that supports small bubbles which have low rise velocities. (2) Dow Corning 1520-US AFA shows it to be a viable replacement to Dow Corning Q2-3183A AFA. This alternative AFA, however, requires significantly higher dosage for the same anti-foam function. (3) Addition of noble metals to the AZ-101 waste simulant does not produce a catalytic gas retention effect with the AFA.

Guerrero, H; Charles Crawford, C; Mark Fowley, M

2008-08-07

33

Large-Scale Testing of Effects of Anti-Foam Agent on Gas Holdup in Process Vessels in the Hanford Waste Treatment Plant  

SciTech Connect

The Hanford Waste Treatment and Immobilization Plant (WTP) will vitrify the radioactive wastes stored in underground tanks. These wastes generate and retain hydrogen and other flammable gases that create safety concerns for the vitrification process tanks in the WTP. An anti-foam agent (AFA) will be added to the WTP process streams. Previous testing in a bubble column and a small-scale impeller-mixed vessel indicated that gas holdup in a high-level waste chemical simulant with AFA was as much as 10 times higher than in clay simulant without AFA. This raised a concern that major modifications to the WTP design or qualification of an alternative AFA might be required to satisfy plant safety criteria. However, because the mixing and gas generation mechanisms in the small-scale tests differed from those expected in WTP process vessels, additional tests were performed in a large-scale prototypic mixing system with in situ gas generation. This paper presents the results of this test program. The tests were conducted at Pacific Northwest National Laboratory in a 1/4-scale model of the lag storage process vessel using pulse jet mixers and air spargers. Holdup and release of gas bubbles generated by hydrogen peroxide decomposition were evaluated in waste simulants containing an AFA over a range of Bingham yield stresses and gas generation rates. Results from the 1/4-scale test stand showed that, contrary to the small-scale impeller-mixed tests, holdup in the chemical waste simulant with AFA was not so greatly increased compared to gas holdup in clay without AFA. The test stand, simulants, scaling and data-analysis methods, and results are described in relation to previous tests and anticipated WTP operating conditions. (authors)

Mahoney, L.A.; Alzheimer, J.M.; Arm, S.T.; Guzman-Leong, C.E.; Jagoda, L.K.; Stewart, C.W.; Wells, B.E.; Yokuda, S.T. [Pacific Northwest National Laboratory, Richland, WA (United States)

2008-07-01

34

Flow regimes, gas hold-up and axial gas mixing in the gas-liquid multi-stage agitated contactor  

Microsoft Academic Search

Experimental data are reported on flow regimes, gas hold-up and axial gas mixing of a gas-liquid Multi-stage Agitated Contactor (MAC), consisting of nine compartments [height, H, over diameter, D = 1; D = 0.09 m) separated by horizontal baffles with an opening of 0.04 m and with one centrally positioned impeller per compartment (12-bladed turbine disk; impeller diameter, dI =

B. B. Breman; A. A. C. M. Beenackers; M. J. Bouma

1995-01-01

35

Radiolytic Bubble Gas Hydrogen Compositions  

SciTech Connect

Radioactive waste solids can trap bubbles containing hydrogen that may pose a flammability risk if they are disturbed and hydrogen is released. Whether a release is a problem or not depends, among other things, on the hydrogen composition of the gas. This report develops a method for estimating the hydrogen composition of trapped bubbles based on waste properties.

Hester, J.R.

2003-02-05

36

Large-Scale Testing of Effects of Anti-Foam Agent on Gas Holdup in Process Vessels in the Hanford Waste Treatment Plant - 8280  

SciTech Connect

The Hanford Waste Treatment Plant (WTP) will vitrify the radioactive wastes stored in underground tanks. These wastes generate and retain hydrogen and other flammable gases that create safety concerns for the vitrification process tanks in the WTP. An anti-foam agent (AFA) will be added to the WTP process streams. Prior testing in a bubble column and a small-scale impeller-mixed vessel indicated that gas holdup in a high-level waste chemical simulant with AFA was up to 10 times that in clay simulant without AFA. This raised a concern that major modifications to the WTP design or qualification of an alternative AFA might be required to satisfy plant safety criteria. However, because the mixing and gas generation mechanisms in the small-scale tests differed from those expected in WTP process vessels, additional tests were performed in a large-scale prototypic mixing system with in situ gas generation. This paper presents the results of this test program. The tests were conducted at Pacific Northwest National Laboratory in a ¼-scale model of the lag storage process vessel using pulse jet mixers and air spargers. Holdup and release of gas bubbles generated by hydrogen peroxide decomposition were evaluated in waste simulants containing an AFA over a range of Bingham yield stresses and gas gen geration rates. Results from the ¼-scale test stand showed that, contrary to the small-scale impeller-mixed tests, gas holdup in clay without AFA is comparable to that in the chemical waste simulant with AFA. The test stand, simulants, scaling and data-analysis methods, and results are described in relation to previous tests and anticipated WTP operating conditions.

Mahoney, Lenna A.; Alzheimer, James M.; Arm, Stuart T.; Guzman-Leong, Consuelo E.; Jagoda, Lynette K.; Stewart, Charles W.; Wells, Beric E.; Yokuda, Satoru T.

2008-06-03

37

Effect of the ejector configuration on the gas suction rate and gas hold-up in ejector loop reactors  

Microsoft Academic Search

An experimental study has been aimed at examining the effect of ejector configuration on the rate and energy effectiveness of gas suction and on the values of gas hold-up in ejector loop reactors. Experimental data showed that insertion of a swirl body into the ejector nozzle increased the suction rate and dispersion efficiency of the ejector distributor and significantly improved

P. Havelka; V. Linek; J. Sinkule; J. Zahradník; M. Fialova

1997-01-01

38

Study on bubble sizes in a down-flow liquid jet gas pump  

NASA Astrophysics Data System (ADS)

In this paper the liquid jet gas pump as an important gas-liquid contactor is investigated on bubble sizes. Its internal mixed effect is influenced by gas holdup, bubble size distribution and interfacial area. To improve the mixed effect, experiment investigations have been carried out in a modified down-flow liquid jet gas pump with special emphasis on gas distribution. The mixing tube and diffuser are made of transparent Perspex for visual observation. Bubble diameters in the diffuser have been measured by photographic and capillary method at different operating conditions. Under the same Reynolds number of orifice, about 80% of the bubble diameters range from 0.6 mm to 1.3 mm, which has no obvious effect on the gas-liquid flow rate ratio. The average bubble diameter increases by the decrease of Orifice Reynolds number at the same gas-liquid flow rate ratio (lower gas-liquid rate ratio), the maximal bubble size can reach 3 mm. With the decrease of gas-liquid flow rate ratio, gas gathers together in the wall and the stream appears non uniform, the sampling test shows that the bubble diameters have a small diminution. It is found experimentally that the bubble diameters are strongly dependent on Orifice Reynolds number and the bubble distribution is affected by gas-liquid flow rate ratio

Wu, Y. L.; Xiang, Q. J.; Li, H.; Chen, S. X.

2012-11-01

39

Electrogenerated Gas Bubbles in Flotation  

Microsoft Academic Search

Electrolytic gas evolution plays a very significant part in a number of electrochemical processes. In the electrowinning of metals the evolution of gases at the electrodes is a very important phenonenon. Gas evolution is common in chlorine and water electrolysis and in a number of other processes. Electro-generated gas bubbles have been used in the treatment of waste water and

S. VENKATACHALAM

1992-01-01

40

Gas-bubble formation in liquid layer  

Microsoft Academic Search

The dynamics of bubble formation and breakaway when a gas issues into a liquid is considered. The different modes of gas-bubble formation in a liquid layer are indicated. The results of analytic investigation are compared with experimental data.

A. A. Voloshko; A. V. Vurgaft; V. N. Frolov

1978-01-01

41

CFD SIMULATION AND EXPERIMENTAL STUDY OF FLOW IN PACKED BUBBLE COLUMNS  

Microsoft Academic Search

The gas holdup in a small-scale packed bubble column with dimensions of 35?mm wide and 10?mm deep was measured for air-water system. The effect of gas flow rate on gas holdup was investigated for various packings such as spheres, Berl saddles, and knitted meshes. In all cases it was found that the gas holdup increases with increasing gas flow rate.

F. H. YIN; J. L. MIDGLEY; A. AFACAN; K. NANDAKUMAR; K. T. CHUANG

2004-01-01

42

Etiology of Gas Bubble Disease  

Microsoft Academic Search

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

Gerald R. Bouck

1980-01-01

43

Etiology of gas bubble disease  

Microsoft Academic Search

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

GERALD R. BOUCK

1980-01-01

44

Etiology of gas bubble disease  

SciTech Connect

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.

Bouck, G.R.

1980-11-01

45

Bubble Size Control to Improve Oxygen-Based Bleaching: Characterization of Flow Regimes in Pulp-Water-Gas Three-Phase Flows. Final Report.  

National Technical Information Service (NTIS)

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 w...

S. M. Ghiaasiaan

2006-01-01

46

Heat emission of gas bubbles in a rotating bubbling layer  

Microsoft Academic Search

Based on an experimental study of contact heat transfer between a liquid and a gas in an eddy-generating bubbler and on results processed using the equation of nonstationary heat conduction, we obtained a dimensionless relation for calculating the coefficient that characterizes heat transfer in a gas bubble within the framework of a model based on effective coefficients of heat conduction.

I. I. Borisov; A. A. Khalatov; E. É. Ikonnikova; G. V. Kovalenko; S. V. Shevtsov

1995-01-01

47

Gas bubbles within acute intracranial epidural haematomas  

Microsoft Academic Search

Summary In order to assess the actual incidence of gas bubbles trapped within acute intracranial epidural haematomas, as revealed by computed tomography (CT) of the skull, a series of 204 patients with surgically verified epidural haematomas was retrospectively reviewed. Gas bubbles were observed on CT scan in 22.5% of the cases, with the incidence rising to 37% when CT scanners

M. Cossu; T. Arcuri; B. Cagetti; M. Brambilla Bas; D. Siccardi; A. Pau

1990-01-01

48

Diagnostics of gas bubbles using wavelet transform  

Microsoft Academic Search

Detection of gas bubbles is an important indicator of the process quality in the industrial applications. Gas bubbles in the liquid not only falsify the measurement of the flow rate, but indicate problems like leakage, cavitations, reactions, boiling, etc. Based on electric field simulations and measurement in the flow laboratory, a physical device model has been developed. This paper presents

Abhisek Ukil; Daniel Schrag; Kai Hencken

2010-01-01

49

Studies on impeller type, impeller speed and air flow rate in an industrial scale flotation cell part 2: Effect on gas holdup  

Microsoft Academic Search

Gas holdup was measured at different locations in a 2.8 m3 portable industrial scale subaeration flotation cell, treating zinc cleaner feed at Hellyer Concentrator in Tasmania, Australia. The cell was fitted in turn with four different impeller-stator systems, and operated over a range of air flow rates and impeller speeds. The gas holdup was found to increase with increase in

B. K. Gorain; J.-P. Franzidis; E. V. Manlapig

1995-01-01

50

HYDRODYNAMIC STUDIES IN FISCHER-TROPSCH DERIVED WAXES IN A BUBBLE COLUMN  

Microsoft Academic Search

Gas hold-up and Sauter mean bubble diameter measurements were made in a 0.051 m diameter by 3 m long glass bubble column in the system, nitrogen-molten wax, with three different waxes (paraffin wax FT-300, Sasol's Arge wax and Mobil's reactor wax). Paraffin wax has a tendency to foam and gas hold-up is a strong function of gas distributor type, temperature

DRAGOMIR B. BUKUR; SNEHAL A. PATEL; RAPHAEL MATHEO

1987-01-01

51

Air entrainment rate and holdup in the Jameson cell  

Microsoft Academic Search

Air entrainment rate and holdup are important and potential control parameters in plunging liquid jet bubble columns. In this study, air entrainment and holdup in laboratory Jameson cell downcomer were investigated in an air–water system. Air entrainment flow rates and holdup were quantified experimentally. The effects of various conditions in the nozzle diameter, the downcomer diameter, the free jet length,

T. Ta?demir; B. Öteyaka; A. Ta?demir

2007-01-01

52

Acoustic manifestations of gas hydrate shelled bubbles  

NASA Astrophysics Data System (ADS)

The hydrocarbon seeps emitting buoyant bubble plumes from seafloor vents—gas flares have been actively investigated in different regions of the World Ocean, in particular, on the Sakhalin slope in the Sea of Okhotsk. The gas flares can be easily detected by regular echo sounders, because the scattering cross section of a gas bubble is large. Within the gas-hydrate stability zone—for high hydrostatic pressures and low temperatures, methane-hydrate ice skins are formed on rising seep bubbles which are typically methane. The objective of the present study was to develop a suitable model describing rheological characteristics of gas-hydrate shell and to analyze acoustic manifestations of such bubbles for the frequency range used in marine field experiments.

Maksimov, A. O.; Sosedko, E. V.

2009-11-01

53

Modeling of inclusion removal in a tundish by gas bubbling  

Microsoft Academic Search

Inclusion removal from liquid steel by attachment to rising gas bubbles has been reviewed. A mathematical model of inclusion removal by gas bubbling in a tundish has been developed and it is found that minimization of bubble size is critical to enhance removal. However, small bubble formation in a tundish may be problematic as bubble size is controlled by high

John Patrick Rogler

2004-01-01

54

Bubble coalescence dynamics and supersaturation in electrolytic gas evolution.  

National Technical Information Service (NTIS)

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 coa...

R. L. Stover

1996-01-01

55

Gas bubble formation in nonequilibrium water-gas solutions  

Microsoft Academic Search

This paper concerns the nonequilibrium situation that is created by suddenly reducing the pressure of a liquid which contains a large amount of dissolved gas. A theoretical model for the resulting formation of gas bubbles is presented. For a given temperature, the model predicts the amount of pressure reduction required for the threshold of bubble formation and also the reduction

Ho-Young Kwak; Ronald L. Panton

1983-01-01

56

Fluid inclusions with gas bubbles as geothermometers  

Microsoft Academic Search

Two types of fluid inclusions can be distinguished. The first is based on the assumption of Sorby (1858) that a homogeneous phase, such as water, salt solution, or CO2, is entrapped, meaning that the bubbles result from the gas of the enclosed fluid. The second type includes foreign gas entrapped with the fluid. \\

C. W. Correns; Geol Rundsch

2002-01-01

57

Dissipation of acoustic-wave energy at small gas bubbles  

Microsoft Academic Search

Bubble formation at fission-fragment tracks is one of the major factors which affect the dynamics of homogeneous solution reactors. The rate of bubble growth is also of importance. In the present paper, the behavior of gas bubbles in the field of a sound wave is analyzed. Specifically, the dissipation of acoustic-wave energy at a gas bubble is studied in the

A. N. Sizov

1975-01-01

58

Gas–vapor bubble nucleation—a unified approach  

Microsoft Academic Search

In a solution which is saturated with gas near the superheat limit, one might expect a bubble formed from both dissolved gas and vapor molecules to appear. The integration of the surface-energy concepts, that are postulated on completely different physical bases for gas and vapor bubble formation is a major issue. In this paper, we reformulate gas and vapor bubble

Ho-Young Kwak; Si-Doek Oh

2004-01-01

59

FORMATION AND FLOW OF GAS BUBBLES IN A PRESSURIZED BUBBLE COLUMN WITH A SINGLE ORIFICE OR NOZZLE GAS DISTRIBUTOR  

Microsoft Academic Search

The characteristics of gas bubbles in a 5 cm diameter bubble column equipped with a single orifice of 1,3 or 5 mm diameter were investigated under system pressure of 0.1-15 MPa. The formation of gas bubbles was strongly affected by the system pressure. Under high pressures a dispersed gas jet was formed at gas velocities where spherical gas bubbles would

K. IDOGAWA; K. IKEDA; T. FUKUDA; S. MOROOKA

1987-01-01

60

Ordering of gas bubbles during light ion gas implantation  

Microsoft Academic Search

There have been interesting observations about ordering of microstructures during irradiation. The formation of void lattices\\u000a is amongst the better known examples. Ordering has also been observed in small gas filled bubbles formed during low energy\\u000a light ion implantation in the energy range 30–100 keV.\\u000a \\u000a The basic underlying mechanism for ordering of gas bubbles has not been clearly understood so

H K Sahu; Kanwar Krishan

1992-01-01

61

Influence of pressure on the gas hold-up of aqueous activated carbon slurries in a down flow jet loop reactor  

Microsoft Academic Search

The hydrodynamics of a loop venturi reactor was studied using a down flow liquid jet ejector. The influence of the pressure, P, the superficial gas velocity, Vg,sup, and the presence of small activated carbon particles on the gas hold-up, ?g, of aqueous systems in the main holding vessel was investigated.For the 2-phase system water–N2 gas the influences of Vg,sup (in

J. T. Tinge; A. J. Rodriguez Casado

2002-01-01

62

Resistance due to gas bubbles in aluminum reduction cells  

Microsoft Academic Search

The contribution of gas bubbles to electrical resistance in aluminum reduction cells is becoming increasingly important as smelters attempt to reduce energy consumption. A prime example is the widespread introduction of slotted anodes to encourage faster gas bubble release from under the anodes. However, quantification of the bubble resistance is difficult, which makes evaluation of process changes problematic. Studies of

Mark A. Cooksey; Mark P. Taylor; John J. J. Chen

2008-01-01

63

The preparation and characterization of gas bubble containing liposomes  

Microsoft Academic Search

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 CO2 gas 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

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

2005-01-01

64

Suppression of cavitation inception by gas bubble injection: A numerical study focusing on bubble-bubble interaction  

Microsoft Academic Search

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

Masato Ida; Takashi Naoe; Masatoshi Futakawa

2007-01-01

65

In-Situ Measurements of Low Enrichment Uranium Holdup Process Gas Piping at K-25 - Paper for Waste Management Symposia 2010 East Tennessee Technology Park Oak Ridge, Tennessee  

SciTech Connect

This document is the final version of a paper submitted to the Waste Management Symposia, Phoenix, 2010, abstract BJC/OR-3280. The primary document from which this paper was condensed is In-Situ Measurement of Low Enrichment Uranium Holdup in Process Gas Piping at K-25 Using NaI/HMS4 Gamma Detection Systems, BJC/OR-3355. This work explores the sufficiency and limitations of the Holdup Measurement System 4 (HJVIS4) software algorithms applied to measurements of low enriched uranium holdup in gaseous diffusion process gas piping. HMS4 has been used extensively during the decommissioning and demolition project of the K-25 building for U-235 holdup quantification. The HMS4 software is an integral part of one of the primary nondestructive assay (NDA) systems which was successfully tested and qualified for holdup deposit quantification in the process gas piping of the K-25 building. The initial qualification focused on the measurement of highly enriched UO{sub 2}F{sub 2} deposits. The purpose of this work was to determine if that qualification could be extended to include the quantification of holdup in UO{sub 2}F{sub 2} deposits of lower enrichment. Sample field data are presented to provide evidence in support of the theoretical foundation. The HMS4 algorithms were investigated in detail and found to sufficiently compensate for UO{sub 2}F{sub 2} source self-attenuation effects, over the range of expected enrichment (4-40%), in the North and East Wings of the K-25 building. The limitations of the HMS4 algorithms were explored for a described set of conditions with respect to area source measurements of low enriched UO{sub 2}F{sub 2} deposits when used in conjunction with a 1 inch by 1/2 inch sodium iodide (NaI) scintillation detector. The theoretical limitations of HMS4, based on the expected conditions in the process gas system of the K-25 building, are related back to the required data quality objectives (DQO) for the NBA measurement system established for the K-25 demolition project. The combined review of the HMS software algorithms and supporting field measurements lead to the conclusion that the majority of process gas pipe measurements are adequately corrected for source self-attenuation using HMS4. While there will be instances where the UO{sub 2}F{sub 2} holdup mass presents an infinitely thick deposit to the NaI-HMS4 system these situations are expected to be infrequent. This work confirms that the HMS4 system can quantify UO{sub 2}F{sub 2} holdup, in its current configuration (deposition, enrichment, and geometry), below the DQO levels for the K-25 building decommissioning and demolition project. For an area measurement of process gas pipe in the K-25 building, if an infinitely thick UO{sub 2}F{sub 2} deposit is identified in the range of enrichment of {approx}4-40%, the holdup quantity exceeds the corresponding DQO established for the K-25 building demolition project.

Rasmussen B.

2010-01-01

66

Regimes of formation of gas bubbles in a liquid layer  

Microsoft Academic Search

A theoretical analysis is presented of the dynamics of formation and separation of bubbles during gas injection into a liquid. An equation for the equilibrium of forces acting on a bubble is discussed and used to illustrate the existence of different regimes of bubble formation in a liquid layer. Analytical results agree well with experimental results obtained for water-air, methanol-air,

A. A. Voloshko; A. V. Vurgaft; V. N. Frolov

1978-01-01

67

Helium gas-bubble superlattice formation in molybdenum  

Microsoft Academic Search

The gas-bubble superlattice is a striking phenomenon where small helium bubbles of uniform size are regularly arranged on a space lattice having the same symmetry as the crystal lattice of the host metal but with a lattice spacing some twenty times greater. Typically, bubble diameters are ?2nm and bubble concentrations are ?1×1025m?3. Superlattices have been observed in all three metal

P. B. Johnson; Fenella Lawson

2006-01-01

68

How does gas pass? Bubble transport through sediments  

NASA Astrophysics Data System (ADS)

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.

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

2009-12-01

69

On the possibility to measure volumes of small gas bubbles and the bubble producing gas flow rates acoustically  

Microsoft Academic Search

Using the pulsation properties of gas bubbles it is possible to measure acoustically volumes c.q. equivalent diameters of gas bubbles in the range of 1.8-2.1 mm, produced at low frequencies at capillary tubes in a silent environment. Hence it is possible to measure very low gas flow rates (from 4 up to 100 mm3\\/s). During formation of bubbles at capillary

G. G. Oosterwegel; H. J. de Groot

1980-01-01

70

Performance of baffled bubble blood oxygenators.  

PubMed

Bubble blood oxygenators equipped with baffles of various types in the oxygenating column were studied. The rate of hemolysis, the volumetric coefficient for oxygen absorption into blood, and the fractional gas holdup were found to be affected mainly by the superficial gas velocity. When compared with the conventional bubble blood oxygenator without baffles, the bubble oxygenators equipped with various types of baffles (i.e., horizontal perforated baffles, radial vertical baffles, and a concentric hollow cylinder with and without horizontal perforated baffles) showed less hemolysis, larger gas holdup and higher values of the coefficient for oxygen absorption. Values of the heat transfer coefficient on the surface of the cylindrical baffle, which is useful as a built-in heat exchanger, were several times greater than those for single-phase heat transfer in conventional blood heat exchangers. PMID:533400

Ohshima, N; Yoshido, F

1979-05-01

71

Resistance due to gas bubbles in aluminum reduction cells  

Microsoft Academic Search

The contribution of gas bubbles to electrical resistance in aluminum reduction cells is becoming increasingly important as\\u000a smelters attempt to reduce energy consumption. A prime example is the widespread introduction of slotted anodes to encourage\\u000a faster gas bubble release from under the anodes. However, quantification of the bubble resistance is difficult, which makes\\u000a evaluation of process changes problematic. Studies of

Mark A. Cooksey; Mark P. Taylor; John J. J. Chen

2008-01-01

72

The effect of ion irradiation on inert gas bubble mobility  

SciTech Connect

The effect of Al ion irradiation on the mobility of Xe gas bubbles in Al thin films was investigated. Transmission electron microscopy was used to determine bubble diffusivities in films irradiated and/or annealed at 673K, 723K and 773K. Irradiation increased bubble diffusivity by a factor of 2--9 over that due to thermal annealing alone. The Arrhenius behavior and dose rate dependence of bubble diffusivity are consistent with a radiation enhanced diffusion phenomenon affecting a volume diffusion mechanism of bubble transport. 9 refs., 3 figs., 2 tabs.

Alexander, D.E.; Birtcher, R.C.

1991-09-01

73

Measurement Of Gas Bubbles In Mercury Using Proton Radiography  

Microsoft Academic Search

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

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

2007-01-01

74

Behaviour of inert gas bubbles under chemical concentration gradients  

Microsoft Academic Search

The paper reports on the growth of helium inert gas bubbles in the copper side of the Cu?Ni diffusion couple. A bimodal distribution of the gas bubbles is created through the effect of the surface in the near surface region and diffusion generated excess vacancies in the diffusion zone. The analysis of the results shows that the presence of a

G. P. Tiwari

1996-01-01

75

Preasymptotic development of vapor and vapor-gas bubbles  

Microsoft Academic Search

Using an optical technique, the existence of the minimum growth rate during the initial stage of the development of vapor and vapor-gas bubbles is established. In this paper models of the development of vapor and the vapor- gas bubbles in the preasymptotic and subcritical stages are suggested.

I. N. Ilyin; V. P. Grivtsov; S. R. Yaundalder

1990-01-01

76

The dynamic behavior of a gas bubble near a wall  

Microsoft Academic Search

In this paper, a numerical model based on the potential flow theory is established to simulate the interaction of a gas bubble with a nearby wall. The time-integration boundary integral method is used to solve the dynamics of a gas bubble. With this method the numerical calculations show an excellent agreement with the experimental data. Employing the numerical code based

A. M. Zhang; X. L. Yao; L. H. Feng

2009-01-01

77

Echo effect in a liquid containing gas bubbles  

Microsoft Academic Search

Acoustic echo is considered for a liquid containing gas bubbles, which is analogous to cyclotron echo in plasma. An analytical calculation is performed on the parameters of the entire series of echo pulses for the case where standing-wave pulses are generated. The addition of a small number of randomly distributed gas bubbles to a liquid substantially alters the dispersion behavior

Kotelnikov

1984-01-01

78

Active microfluidic mixer and gas bubble filter driven by thermal bubble micropump  

Microsoft Academic Search

A microfluidic mixer with a gas bubble filter activated by a thermal bubble actuated nozzle-diffuser micropump is successfully demonstrated. The oscillatory flow generated by the micropump can induce wavy interface to increase the contact area of mixing fluids to accelerate the mixing process. The microfluidic mixing channels are 200?m wide, 50?m deep and the speed of the mixing liquids are

Jr-Hung Tsai; Liwei Lin

2002-01-01

79

Studies on Pressure Response of Gas Bubbles Contributions of Condensed Droplets in Bubbles Generated by a Uniform Nucleation.  

National Technical Information Service (NTIS)

The response of a tiny gas bubble under reduced pressure is investigated in its relation to cavitation. Equations of motion are formulated for gas mixtures inside the bubble and numerical calculations performed for several examples. The conclusions are as...

Y. Matsumoto

1988-01-01

80

Fission gas bubbles in uranium-aluminide fuels  

SciTech Connect

Formation of fission gas bubbles heretofore has not been observed in uranium-aluminide fuels. Recent irradiations to record high burnups offered a possibility to determine the onset of fission gas bubble formation in this type of fuel. Present experimental evidence suggests that UAl/sub 2/, UAl/sub 3/, and UAl/sub 4/ do not form fission gas bubbles at fission densities of 7 x 10/sup 21//cm/sup 3/ of fuel (60% depletion of 93% enriched /sup 235/U), and that pure uranium aluminide is likely to remain free of fission gas bubbles to very high /sup 235/U burnup at any enrichment. However, fission gas bubbles were found in these experimental fuels for the first time, but they were without exception associated with uranium-oxide inclusions that were evidently formed during fuel fabrication.

Hofman, G.L.

1987-04-01

81

Gas Bubble Formation in Stagnant and Flowing Mercury  

SciTech Connect

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.

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

2007-01-01

82

Bubbles  

NASA Astrophysics Data System (ADS)

``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, many others. Ultimately, diffusive processes govern much of the physics, and the difference between the diffusivity of heat and dissolved gases in ordinary liquids holds the key to the striking differences between gas and vapor bubbles.

Prosperetti, Andrea

2002-11-01

83

Behavior of a single coherent gas bubble chain and surrounding liquid jet flow structure  

Microsoft Academic Search

The motion of a single nitrogen gas bubble chain and the structure of water flow field surrounding the chain were experimentally studied. We developed a bubble generator that can control both the bubble diameter and the generation frequency independently. Experimental conditions of bubble Reynolds number and bubble distance divided by bubble diameter were from 300 to 650 and from 6.5

Toshiyuki Sanada; Masao Watanabe; Tohru Fukano; Akira Kariyasaki

2005-01-01

84

Gas bubble formation in the cytoplasm of a fermenting yeast  

PubMed Central

Abstract Current paradigms assume that gas bubbles cannot be formed within yeasts although these workhorses of the baking and brewing industries vigorously produce and release CO2 gas. We show that yeasts produce gas bubbles that fill a significant part of the cell. The missing link between intracellular CO2 production by glycolysis and eventual CO2 release from cells has therefore been resolved. Yeasts may serve as model to study CO2 behavior under pressurized conditions that may impact on fermentation biotechnology.

Swart, Chantel W; Dithebe, Khumisho; Pohl, Carolina H; Swart, Hendrik C; Coetsee, Elizabeth; van Wyk, Pieter WJ; Swarts, Jannie C; Lodolo, Elizabeth J; Kock, Johan LF

2012-01-01

85

Measurement Of Gas Bubbles In Mercury Using Proton Radiography  

SciTech Connect

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.

Riemer, Bernie [ORNL; Bingham, Philip R [ORNL; Mariam, Fesseha G [Los Alamos National Laboratory (LANL); Merrill, Frank E [ORNL

2007-01-01

86

The growth of fission gas bubbles in irradiated uranium dioxide  

Microsoft Academic Search

The growth of fission gas bubbles from supersaturated solution in irradiated uranium dioxide has been studied by electron microscopy under isothermal annealing conditions between 1300° and 1500°C. Measurements of the kinetics of bubble growth have enabled the diffusion coefficients of atomic xenon and krypton in irradiated uranium dioxide to be determined. The diffusion coefficients obtained may be expressed by the

R. M. Cornell

1969-01-01

87

Proton Radiography Experiment to Visualize Gas Bubbles in Mercury  

Microsoft Academic Search

An experiment to visualize small gas bubbles injected into mercury flowing in a test loop using proton radiography was conducted at the Los Alamos Neutron Science Center (LANSCE) in December 2006. Radiograph images of bubbles were obtained through two mercury thicknesses: 22 mm and 6 mm. Two jet bubblers and two needle bubblers were operated individually over a range of

Bernie Riemer; David K Felde; Mark W Wendel; Fesseha G Mariam; Frank E Merrill

2007-01-01

88

The formation of gas bubbles synchronised with AC potential  

Microsoft Academic Search

It was found by a new experimental technique that the gas bubbles issuing from a single capillary nozzle were produced exactly synchronously with an AC potential applied between the nozzle and the opposite earth electrode. Each bubble detached from the tip of the nozzle when the applied AC voltage entered the negative peak of each cycle. With this arrangement it

M. Sato

1980-01-01

89

Formation of gas bubbles in liquid flooded nozzles  

Microsoft Academic Search

The presence of liquid downflow through the bed openings, or isolated nozzles, gives rise to certain special conditions for gas bubble formation. According to [2], for nozzle diameters greater than 3 mm, there are variations in the bubble size on account of the flooding of the nozzle by the liquid used, i.e., due to the flow of liquid films on

G. I. Efremov; I. A. Vakhrushev

1968-01-01

90

Dysbaric gas bubble disease in dogs. IV. Acclimatization to diving  

SciTech Connect

Acclimatization to diving was documented to occur in dogs. An increase in the number of repetitive dives which could be tolerated, as well as a decrease in the total number of pulmonary artery venous gas emboli resulting from individual dives were observed. The results from the experimental subject ''Jason'' indicate that acclimatization involves a reduction in the number of bubbles, and not an increase in the ability of the body to tolerate bubbles. Acclimatization is principally a physical rather than a physiological event. Bubbles forming in vivo must grow from nuclei of some sort. If these nuclei are stable, discrete structure that are destroyed when they grow into gross bubbles, then repetitive diving might markedly reduce by attrition the number of such bubble micronuclei. This would result in fewer bubbles being formed during subsequent dives, thus leading to the observed acclimatization effect. 7 refs., 3 figs., 4 tabs.

Kunkle, T.D.; Morita, A.; Beckman, E.L.

1986-01-01

91

Bubble coalescence dynamics and supersaturation in electrolytic gas evolution  

SciTech Connect

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.

Stover, R.L. [Univ. of California, Berkeley, CA (United States). Dept. of Chemical Engineering]|[Lawrence Berkeley National Lab., CA (United States). Energy and Environment Div.

1996-08-01

92

The preparation and characterization of gas bubble containing liposomes.  

PubMed

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. PMID:17281108

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

2005-01-01

93

Natural gas: Life after the bubble  

SciTech Connect

According to the author, the bubble is just about history. The gas supply base shrunk by 6 Tcf to 148 Tcf by year-end 1988 and is expected to fall by another 7 Tcf this year. In 1989, annual deliverability will drop below 19 Tcf or an average of about 1,600 Bcf, which is too close for comfort to the maximum monthly production rate that regularly occurs in winter months. Monthly peaks during severe weather have pushed occasional monthly production to well over 1,700 Bcf. Given any kind of long-lasting cold snap affecting most of the Northeast and Midwest, such peaks could stress the system to the point of random deliverability shortfall this winter. And certainly, if not this winter, shortfall will come earlier and more frequently during the 1989-90 winter season as the deliverability slide goes on. A shortfall will likely be pipeline and/or market area specific, and will result from deliverability as well as operating problems. There are an increasing number of fields in which maximum rates cannot be sustained for any length of time.

Parent, L. (The Gas Price Index, Houston, TX (US))

1989-02-01

94

Gas-vapor bubble dynamics in therapeutic ultrasound  

NASA Astrophysics Data System (ADS)

In applications of therapeutic ultrasound such as shock wave lithotripsy (SWL) and high-intensity focused ultrasound (HIFU), cavitation and the associated bubble dynamics play an important role. Moreover, bubble dynamics have not been fully studied in the context of the large acoustic excitations, elevated temperatures, and gas-saturated conditions that characterize therapeutic ultrasound treatments. Because acoustic cavitation has been typically explored in the context of bubbles containing only non-condensable gases, relatively little is understood about the role of vapor under relevant conditions. Accordingly, the primary goal of this effort is to elucidate the role of vapor in the dynamics of gas-vapor bubbles. Given the large acoustic excitations of SWL and HIFU, the dynamics of violent inertial collapses are of particular interest. To investigate the impact of vapor, both numerical modeling and experiments were utilized. The model was developed for a single, spherical bubble and was designed to capture behavior associated with the collapse and rebound of a gas-vapor bubble. Numerical difficulties in modeling violent collapses were addressed by using scaling principles to approximate the spatial gradients used for estimating heat and mass transport in both liquid and gaseous phases, Model predictions demonstrate thermal effects from vapor transport through the coupling of the saturated vapor pressure to temperature changes in the surrounding liquid. Also, the model suggests that vapor transport affects the dynamics mechanically when vapor is diffusively trapped in the bubble interior. Moreover, predictions imply that the collapses of millimeter-sized lithotripsy bubbles are principally governed by the aforementioned mechanical effects. To test the model, collapses and rebounds of lithotripsy bubbles were experimentally observed using high-speed photography. Although bubble asymmetries added scatter to the data, experimental observations agree very well with the range of model predictions obtained with feasible length scales for mass diffusion in the bubble interior. Statistically significant variations observed in the experimental data imply that both temperature and dissolved gas concentration in the surrounding liquid affect mass diffusion inside the bubble. To complement experimental observations, bubble clusters in an incompressible liquid were modeled; simulations yielded insights related to bubble collapse times.

Kreider, Wayne

95

On the stability of gas bubbles in liquid-gas solutions  

Microsoft Academic Search

It was shown some time ago by use of diffusion theory that a gas bubble in a liquid-gas solution was unstable. This problem has been reconsidered recently in two papers both of which propose to develop a stability analysis solely from thermodynamic considerations. The first of these studies purports to find stability for a gas bubble in a liquid-gas solution.

Milton S. Plesset; Satwindar S. Sadhal

1982-01-01

96

The role of gas in ultrasonically driven vapor bubble growth.  

PubMed

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. PMID:23528293

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

2013-03-26

97

The role of gas in ultrasonically driven vapor bubble growth  

NASA Astrophysics Data System (ADS)

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.

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

2013-04-01

98

The effect of gas bubble flow on ultrafiltration efficiency  

Microsoft Academic Search

We assessed the potentiality of reducing concentration polarization and enhancing ultrafiltration of macromolecules via gas sparging (gas bubbles supplied to the UF system with the feed solution). Consideration was given to the problem of how the quantity of the gas sparged and the duration of the process affect the transport and separation properties of hollow-fibre UF modules. Ultrafiltration tests were

Katarzyna Majewska-Nowak; Ma?gorzata Kabsch-Korbutowicz; Tomasz Winnicki

1999-01-01

99

Liquid recirculation and bubble breakup beneath ventilated gas cavities in downward pipe flow  

Microsoft Academic Search

The dispersion of bubbles into down-flowing liquids is often encountered in a number of industrial applications involving pipe flow, bubble columns and loop reactors. Usually a gas horizontal sparging device is used to generate bubbles that are carried downward with the bulk liquid flow. At low gas flowrates discrete bubbles are formed. However, at higher gas flowrates a ventilated cavity

R. B Thorpe; G. M Evans; K Zhang; P. M Machniewski

2001-01-01

100

Biophysical aspects of gas bubbles in blood.  

PubMed

The widespread use of bubble oxygenators during cardiopulmonary bypass has raised questions concerning the production and introduction of gaseous microemboli (GME) into patients. An understanding of the complications associated with GME requires awareness of the biophysical and biochemical responses that occur between bubbles and blood. The production of GME as well as their interactions with each other and with blood products are examined. These interactions can influence the data collected from Doppler ultrasound devices and the development of organ dysfunction. PMID:3889566

Butler, B D

101

The Influence of Taylor Bubble Length on the Similarity of the Liquid ReCirculation in Turbulent Flow Behind Solid and Gas Bubbles  

Microsoft Academic Search

The similarity between flows induced by a solid Taylor bubble and a gas Taylor bubble is examined numerically using a Finite Volume Method. Although the similarity exists, it happens conditionally. In this work, it is found that the length of bubble plays an important role on the similarity. Short solid bubbles and gas bubbles tend to induce the same flow

Boonchai Lertnuwat

102

Morphology of fission gas bubbles in fissioning uranium metal closely  

NASA Astrophysics Data System (ADS)

We investigate by SEM the micro-structural and basic phenomenological mechanisms governing the fission-gas and fusion-gas behaviour in metals. This comparative study clearly shows the characteristics of fission-gas bubbles (primarily helium and xenon) in uranium fuel metals have the same characteristics as fusion-gas bubbles (helium) in the solid-state fusion metal - palladium. The remarkably similar characteristic morphology clearly identifies the nuclear phenomenological origins of the gas bubbles in the palladium metal which are correllated and explained by the presence of a large amount of DD fusion. Allied evidence of anomalous heat production during cold fusion experiments suggests the nuclear process. Further analysis of these fusion metals by mass spectroscopy clearly identifies anomalous helium isotopes in large quantity were trapped in the palladium metal.

George, Russ

2005-03-01

103

Determination and evaluation of gas holdup time with the quadratic equation model and comparison with nonlinear models for isothermal gas chromatography.  

PubMed

Gas holdup time (tM) is a basic parameter in isothermal gas chromatography (GC). Determination and evaluation of tM and retention behaviors of n-alkanes under isothermal GC conditions have been extensively studied since the 1950s, but still remains unresolved. The difference equation (DE) model [J. Chromatogr. A 1260: 215-223] reveals retention behaviors of n-alkanes excluding tM, while the quadratic equation (QE) model [J. Chromatogr. A 1260: 224-231] including tM is suitable for applications. In the present study, tM values were calculated with the QE model, which is referred to as tMT, evaluated and compared with other three typical nonlinear models. The QE model gives an accurate estimation of tM in isothermal GC. The tMT values are highly accurate, stable, and easy to calculate and use. There is only one tMT value at each GC condition. The proper classification of tM values can clarify their disagreement and facilitate GC retention data standardization for which tMT values are promising reference tM values. PMID:23726077

Wu, Liejun; Chen, Maoxue; Chen, Yongli; Li, Qing X

2013-04-30

104

Plasma formation inside deformed gas bubbles submerged in water  

NASA Astrophysics Data System (ADS)

Plasma formation in liquids produces highly reactive products that may be desirable for a variety of applications, including water purification and waste processing. The direct ignition of plasma in these environments, however, is limited by the large breakdown strength of liquids, which imposes severe voltage and energy requirements on the design of practical devices. One way to address this issue is by first igniting plasma in gas bubbles injected into the water. These bubbles provide an environment with higher reduced electric field (E/N) that is more suitable for plasma formation. If the same bubbles can be excited into strong distortions of their shape and volume, then it is possible to further alter E/N, both by field enhancement at the bubble's highly distorted dielectric interface (via E) and by fluctuations in its internal gas pressure (via N). This principle is investigated by trapping a single bubble at the node of a 26.4 kHz underwater acoustic field and driving it into violent oscillations using an A.C electric field. A third high voltage needle is placed nearby and used to ignite plasma in the bubble at various points during its oscillation. The bubble response is captured using a high speed camera capable of up to 30,000 frames per second.

Sommers, Bradley; Foster, John

2012-10-01

105

Composite power law holdup correlations in horizontal pipes  

Microsoft Academic Search

A wide range of experimental holdup data, from different sources, are analyzed based on a theoretical model proposed in this work to evaluate the holdup in horizontal pipes. 2276 gas–liquid flow experiments in horizontal pipelines with a wide range of operational conditions and fluid properties are included in the database. The experiments are classified by mixture Reynolds number ranges and

F. García; R. García; D. D. Joseph

2005-01-01

106

The Evolution of a Gas Bubble Near an Inclined Wall  

Microsoft Academic Search

:   The nonlinear dynamics of a gas bubble close to an inclined wall is investigated numerically. The fluid is assumed to be\\u000a inviscid and incompressible and the flow irrotational. A time-integration boundary integral method is used to solve the Laplace\\u000a equation for the velocity potential to calculate the shape and position of the bubble. Improvements to the previous research\\u000a on

Q. X. Wang

1998-01-01

107

IMPROVED GAS BUBBLE MOBILITY IN CHIC-TYPE FLOW CHANNELS  

Microsoft Academic Search

Recently the authors have presented an unique solution for preventing clogging of microfluidic channels by gas bubbles (1). It has been shown, that the bubble mobility can be enhanced, if two rectangular channels are nested in a T-shape. This geometrical configuration has been termed channel-in-channel (CHIC) design. In this paper the analytical approach introduced in (1) is enhanced and generalized.

C. Litterst; J. Kohnle; S. Messner; H. Sandmaier; R. Zengerle; P. Koltay

2004-01-01

108

The breakup of bubbles into jets during submerged gas injection  

NASA Astrophysics Data System (ADS)

There has never been any fundamental explanation presented for the transition from the bubbling regime to the jetting regime when gas is injected into liquid at high velocity through submerged tuyeres. This is an important issue in metallurgical processes, since the flow regime is known to influence refining rates, refractory erosion, and the penetration of the liquid into the tuyere. Based on the observation that many small droplets of liquid and gas bubbles are formed to create the jets, a combined Kelvin-Helmholtz and Rayleigh-Taylor instability analysis has been applied to bubbles forming at submerged tuyeres. For particular wavelengths of disturbances, the interface will be unstable and create bubbles and droplets. The critical injection velocity for instability depends on surface tension, tuyere diameter, and the gas-to-liquid density ratio, which can be summarized by We = 10.5(?*)-1/2, where We is the Weber number based on the gas velocity and density and tuyere diameter, and ?* is the gas-to-liquid density ratio. The importance of surface tension had not been appreciated previously for this regime of gas injection. There is considerable controversy in the literature concerning the measurement of the transition from bubbling to jetting. The 70 pct “linking” point, proposed by Ozawa and Mori, describes the situation where 70 pct of the bubbles link with the preceding bubbles and produce a reasonably steady jet. The theoretical correlation developed above predicts the velocity to reach this point ±20 pct (95 pct confidence level) in a variety of systems from six different groups of workers. The theoretical analysis demonstrates that the instabilities are primarily capillary in nature, not gravity waves, which explains the observation that orientation has little effect on the jetting transition.

Zhao, Y.-F.; Irons, G. A.

1990-12-01

109

Gas bubble formation in the cytoplasm of a fermenting yeast.  

PubMed

Current paradigms assume that gas bubbles cannot be formed within yeasts although these workhorses of the baking and brewing industries vigorously produce and release CO(2) gas. We show that yeasts produce gas bubbles that fill a significant part of the cell. The missing link between intracellular CO(2) production by glycolysis and eventual CO(2) release from cells has therefore been resolved. Yeasts may serve as model to study CO(2) behavior under pressurized conditions that may impact on fermentation biotechnology. PMID:23020660

Swart, Chantel W; Dithebe, Khumisho; Pohl, Carolina H; Swart, Hendrik C; Coetsee, Elizabeth; van Wyk, Pieter W J; Swarts, Jannie C; Lodolo, Elizabeth J; Kock, Johan L F

2012-10-01

110

Modelling of gas evolving electrolysis cells. I. The gas voidage problem  

Microsoft Academic Search

A critical review of experimental gas voidage data for gas—liquid mixtures available in the literature yields the result that these data cannot be explained by known theories of the gas hold-up. Based on the empirical experience that bubble coalescence is hindered in electrolyte solutions, new equations are derived for the calculation of the gas voidage as a function of the

G. Kreysa; M. Kuhn

1985-01-01

111

GAS-LIQUID MASS TRANSFER IN JET BUBBLE COLUMN  

Microsoft Academic Search

The jet bubble column consists of a conical entrance section which expands to a cylindrical column. Gas and liquid are co-currently introduced at the bottom of the column by a small diameter inlet pipe which acts like an ejector. The kinetic energy of the gas and liquid jet together with the conical geometry at the lower section of the column

JOSE A. SALAZAR; KEITH D. WISECARVER; Y. T. SHAH; BRUNO SOLARI

1993-01-01

112

Progression and Severity of Gas Bubble Trauma in Juvenile Salmonids  

Microsoft Academic Search

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

Matthew G. Mesa; Lisa K. Weiland; Alec G. Maule

2000-01-01

113

Enhanced diffusion of liquid-coated gas bubbles in solids  

Microsoft Academic Search

Gas bubble diffusion in solids is typically due to surface diffusion of matrix atoms along the gas-solid interface. Insoluble impurities that segregate to the interface tend to suppress surface diffusion by chemically combining with the surface atoms, as in the creation of a metal oxide layer, or by simply presenting a physical barrier to the kinetic jump process. We propose

C. De W. Van Siclen; R. N. Wright

1993-01-01

114

Gas bubble formation and growth processes in thin gold films bombarded by Argon ion beams  

Microsoft Academic Search

Transmission electron microscopy has been applied to the study of gas bubble formation and growth processes in gold irradiated with 25 keV Ar ions to fluences of 10 to 10 ions\\/cm (293 K ? T ? 673 K.) The dependence of main swelling parameters (mean bubble diameter, mean bubble concentration, gas bubble volume fraction) on irradiation temperature and total dose

F. Vasiliu; V. Teodorescu

1975-01-01

115

State of vapor-gas bubbles in the arteries of low-temperature heat pipes  

Microsoft Academic Search

The formation of vapor-gas bubbles during startup and operation of low-temperature arterial heat pipes is studied by a method previously employed for studying boiling on a surface. The size of the bubble, concentration of gas in the bubble, temperature superheat, and the gravitational and circulatory pressure drops in the heat pipe determine the growth, equilibrium, and collapse of a bubble.

M. N. Ivanovskii; V. V. Privezentsev; V. P. Sorokin

1979-01-01

116

Measurements of Gas Bubble Size Distributions in Flowing Liquid Mercury  

SciTech Connect

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 an actual SNS target.

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

2012-01-01

117

Effect of Gas Bubble Mobilization on Contaminant Transport during Thermal Remediation  

Microsoft Academic Search

Discrete gas bubble formation in the subsurface has previously been observed as a result of microbial activity, water table oscillations, and application of direct gas injection and permanganate injection for subsurface remediation. Discrete gas bubble formation could also occur during subsurface thermal remediation, beginning in the heat-up phase and at the edge of the heated zone. Gas bubbles would form

M. M. Krol; K. G. Mumford; R. L. Johnson; B. E. Sleep

2010-01-01

118

The Dynamics of Freely Oscillating Gas-Vapor Bubbles  

NASA Astrophysics Data System (ADS)

This dissertation describes experimental and theoretical studies of the dynamics of freely oscillating gas-vapor bubbles. Longuet-Higgins has predicted that bubble surface modes can produce, through nonlinear coupling, monopole sound radiation. The first part of this dissertation is devoted to an experimental investigation of this phenomenon. A hydrophone and needle were submerged in water in a small sealed cell that was connected to a regulated evacuation system. The sound produced by releasing a bubble from the needle was monitored by a hydrophone and displayed on an oscilloscope. Two high speed video cameras simultaneously recorded the bubble motion and the displayed sound trace. At pressures of a few cm-Hg, it was seen that after the bubble -generation sound died out, there followed a sound of the same frequency but lower magnitude. Because this sound amplitude increased as the ambient pressure decreased and had its maximum value at resonance, it appeared that this sound was evidence for a surface-mode induced volume-mode. Careful data analysis shows that there exists a mutual interaction between these surface and volume modes. The second half of the dissertation contains the development of a theory, in which the resonance frequency omega_{x} and damping constant omega_{y} for free volume oscillations of a spherical bubble in an infinite medium are derived from the linearized, fundamental equations of fluid dynamics. There are three possible wave propagation modes that satisfy the governing equations for the gas-vapor mixture inside the bubble. Outside it, only two modes need be considered because gas diffusion across the bubble surface into the liquid appears negligible for free oscillations. Two parameters omega _{x} and omega_ {y} are values such that the boundary conditions can be satisfied. The dependence of omega_{x} and omega _{y} on many physical parameters is examined. For a bubble containing mostly gas, the values of omega_{x} and omega_{y} agree with previous theories. For a bubble containing mostly vapor, significant additional damping occurs from the effects of vapor evaporation-condensation. We also find that there exists only one resonance frequency for free oscillations, in contrast to the predictions of Finch and Neppiras who suggested that two resonances are possible.

Mao, Yi.

119

Theory of heterogeneous decay of a gas-supersaturated solution on passive gas bubbles  

Microsoft Academic Search

It is shown that there can be barrierless heterogeneous nucleation of bubbles of a mixture of active and passive gases on bubbles of a passive gas in a solution supersaturated with active gas. The threshold solution supersaturation above which barrierless heterogeneous nucleation commences is found. All the thermodynamic data on heterogeneous formation of nucleating centers needed to describe the kinetics

F. M. Kuni; A. A. Melikhov

1993-01-01

120

Experimental characterization of slurry bubble-column reactor hydrodynamics  

SciTech Connect

Sandia`s program to develop, implement, and apply diagnostics for hydrodynamic characterization of slurry bubble column reactors (SBCRs) at industrially relevant conditions is discussed. Gas liquid flow experiments are performed on an industrial scale. Gamma densitometry tomography (GDT) is applied to measure radial variations in gas holdup at one axial location. Differential pressure (DP) measurements are used to calculate volume averaged gas holdups along the axis of the vessel. The holdups obtained from DP show negligible axial variation for water but significant variations for oil, suggesting that the air water flow is fully developed (minimal flow variations in the axial direction) but that the air oil flow is still developing at the GDT measurement location. The GDT and DP gas holdup results are in good agreement for the air water flow but not for the air oil flow. Strong flow variations in the axial direction may be impacting the accuracy of one or both of these techniques. DP measurements are also acquired at high sampling frequencies (250 Hz) and are interpreted using statistical analyses to determine the physical mechanism producing each frequency component in the flow. This approach did not yield the information needed to determine the flow regime in these experiments. As a first step toward three phase material distribution measurements, electrical impedance tomography (EIT) and GDT are applied to a liquid solid flow to measure solids holdup. Good agreement is observed between both techniques and known values.

Shollenberger, K.A.; Torczynski, J.R.; Jackson, N.B.; O`Hern, T.J.

1997-09-01

121

Three-phase gas-liquid-solid foaming bubble reactors and self-lubricated transport of bitumen froth  

NASA Astrophysics Data System (ADS)

Two distinct topics in multi-phase flow of interest of the oil industry are considered in this thesis. Studies of three-phase gas-liquid-solid foaming bubble reactors and self-lubricated transport of bitumen froth are reported. Applications of foams and foaming are found in many industrial processes such as flotation of minerals, enhanced oil recovery, drilling in oil reservoirs, and refining processes. However the physics of foaming and defoaming are not fully understood. Foams trap gas and are not desirable in some processes such as oil refining. Previously, it has been found that foaming may be strongly suppressed in a cold slit bubble reactor by fluidizing hydrophilic particles in the bubbly mixture below the foam. In this work, we fluidized hydrophobic and hydrophilic versions of two different sands in a cold slit foaming bubble reactor. We found that the hydrophobic sands suppress the foam substantially better than their hydrophilic counterparts. To study the capacity of foams to carry particles, we built a new slit foaming bubble reactor, which can be continuously fed with solid particles. Global gas, liquid, and solid holdups were measured for given gas and liquid velocities and solid flow rates. This research provides the fundamental ground work for the identification of flow types in a slit three-phase foaming bubble reactor with continuous injection of particles. Bitumen froth is produced from the oil sands of Athabasca, Canada. When transported in a pipeline, water present in the froth is released in regions of high shear (at the pipe wall). This results in a lubricating layer of water that allows bitumen froth pumping at greatly reduced pressures and hence the potential for savings in pumping energy consumption. Experimental results establishing the features of this self lubrication phenomenon are presented. The pressure gradient of lubricated flows closely follow the empirical law of Blasius for turbulent pipe flow with a constant of proportionality about 10 to 20 times larger than that for water alone. We used Reichardt's model for turbulent Couette flow to predict the effective thickness of the lubricating layer of water. The agreement with direct measurements is satisfactory. Mechanisms for self lubrication are considered.

Mata, Clara E.

122

Effect of Gas Content on the Oscillation of a Laser-Induced Cavitation Bubble  

NASA Astrophysics Data System (ADS)

The oscillation of a cavitation bubble and the effect of gas content inside a cavity on the bubble motion are investigated by theory and experiment. Based on the cavitation model, the numerical study yields the gas content dependence of the amplitude and duration of the bubble oscillation in liquids. In experiment, the temporal oscillation of a single laser-induced cavitation bubble is obtained by means of a sensitive fiber-optic sensor based on optical beam deflection. The characteristic bubble parameters are determined, including the maximum (minimum) radii, oscillation duration and bubble energy, which all decrease with the oscillation. Besides, combining the cavitation theory with experimental data, the variation of gas content within the bubble during each oscillation is estimated, which increases with the oscillation cycle. Our results reveal the competitive interplay of the bubble energy and gas content during the bubble motion and the bubble energy in effect outweighs the latter.

Chen, X.; Xu, R. Q.; Yang, B.; Lu, J.; Ni, X. W.

123

Sandia support for PETC Fischer-Tropsch research: Experimental characterization of slurry-phase bubble-column reactor hydrodynamics  

SciTech Connect

Sandia`s program to develop, implement, and apply diagnostics for hydrodynamic characterization of slurry bubble-column reactors (SBCRs) at industrially relevant conditions is discussed. Gas-liquid flow experiments are performed in an industrial-scale 48 cm ID stainless steel vessel. Gamma-densitometry tomography (GDT) is applied to make spatially resolved gas holdup measurements. Both water and Drakeol 10 with air sparging are examined at ambient and elevated pressures. Gas holdup increases with gas superficial velocity and pressure, and the GDT values are in good agreement with values from differential pressure measurements. Other diagnostic techniques are also discussed.

Jackson, N.B.; Torczynski, J.R.; Shollenberger, K.A.; O`Hern, T.J.; Adkins, D.R.

1996-06-01

124

Eect ofcontaminants on mass transfer coe!cients in bubble column and airlift contactors  

Microsoft Academic Search

In this work, the eects of surface-active contaminants on mass transfer coe!cients kLa and kL were studied in two dierent bubble contactors. The oxygen transfer coe!cient, kL, was obtained from the volumetric oxygen transfer coe!cient, kLa, since the speci7c interfacial area, a, could be determined from the fractional gas holdup, ? , and the average bubble diameter, d32. Water at

J. M. T. Vasconcelos; S. C. P. Orvalho; S. S. Alves; R. L. Mendes; A. Reis

125

The breakup of bubbles into jets during submerged gas injection  

Microsoft Academic Search

There has never been any fundamental explanation presented for the transition from the bubbling regime to the jetting regime when gas is injected into liquid at high velocity through submerged tuyeres. This is an important issue in metallurgical processes, since the flow regime is known to influence refining rates, refractory erosion, and the penetration of the liquid into the tuyere.

Y.-F. Zhao; G. A. Irons

1990-01-01

126

Gas bubble nucleation and growth in cohesive sediments  

Microsoft Academic Search

Sediment often contains a significant amount of organic material, which can be decomposed by bacterial activity. During this process and under anaerobic conditions that prevail in sediments, mainly methane and carbon dioxide are formed. These compounds will dissolve in the pore water, until the level of saturation is attained.Experiments show that gas bubble nucleation occurs already at a small oversaturation

Walther van Kesteren; Thijs van Kessel

2002-01-01

127

Transcillatory heat transfer in a liquid with gas bubbles  

NASA Astrophysics Data System (ADS)

The article describes the model of transcillatory heat transfer induced by gas bubbles buoyant in liquid. The temperature problem is reduced to the equivalent integral equation, and the velocity field in liquid phase is presented as structures of running and stationary waves. The relations for computing the coefficient of transcillatory transfer have been found.

Nigmatulin, R. I.; Filippov, A. I.; Khismatullin, A. S.

2012-12-01

128

Concentration Evolution of Gas Species within a Collapsing Bubble in a Liquid Medium  

Microsoft Academic Search

In this study numerical methods are used to investigate the relationship between chemical concentration of gas species within a cavitating bubble, equilibrium radius of the gas bubble and pressure variations in the ambient liquid. For this purpose, governing equations are developed to describe the dynamic equilibrium of a bubble in a flowing fluid and mass transfer between gas and liquid

Wonyong Jang; Mustafa M. Aral

2003-01-01

129

Micropumping of liquid by directional growth and selective venting of gas bubbles  

Microsoft Academic Search

We introduce a new mechanism to pump liquid in microchannels based on the directional growth and displacement of gas bubbles in conjunction with the non-directional and selective removal of the bubbles. A majority of the existing bubble-driven micropumps employs boiling despite the unfavorable scaling of energy consumption for miniaturization because the vapor bubbles can be easily removed by condensation. Other

Dennis Desheng Meng; Chang-Jin “CJ” Kim

2008-01-01

130

Impedance-based response of an electrolytic gas bubble to pressure in microfluidic channels  

Microsoft Academic Search

In this paper we have electrically measured the response of electrolytic gas bubbles to varying pressures in a microfluidic channel. Impedance measurements were used to monitor either the volume or volume change of an electrolytic bubble. Experimental results show that both the bubble size and bubble dissolution rate are sensitive to the applied pressure, and can be readily measured in

Daniel A. Ateya; Ashish A. Shah; Susan Z. Hua

2005-01-01

131

Experimental study of detonating gas bubble oscillations using a shock tube  

Microsoft Academic Search

Oscillations of bubbles containing a mixture of a detonating gas with argon in their interior are studied. The bubbles are excited for oscillations by a pressure step generated in a shock tube. A bubble wall motion is observed by a rotating mirror camera and a radiated pressure wave by a needle hydrophone. For weak pressure steps the bubble behaves as

K. Vokurka

1993-01-01

132

On the mutual interaction of two gas bubbles in a sound field  

Microsoft Academic Search

The expression for the mutual interaction force between two pulsating gas bubbles immersed in an incompressible and inviscid fluid is derived assuming that the distance between the bubbles is comparable to their sizes. The results of numerical calculations for air bubbles in water are presented. They show that at small distances between the bubbles the interaction force is substantially different

A. A. Doinikov; S. T. Zavtrak

1995-01-01

133

Dynamics of a Gas Bubble during Its Interaction with Compression and Rarefaction Waves  

Microsoft Academic Search

The problem of the passage of acoustic waves in the neighborhood of a gas bubble in a tube is formulated and solved numerically. The main parameters determining the bubble dynamics in a non-stationary field are determined. The mechanism of jet deformation of the bubble followed by jet fragmentation and formation of a secondary small-size bubble fraction is studied. A possible

D. V. Voronin

2005-01-01

134

A Gas-Capture Buoy for Measuring Bubbling Gas Flux in Oceans and Lakes  

Microsoft Academic Search

The design, calibration, and deployment of a buoy and gas-capture assembly for measuring bubbling gas flux in oceans and lakes are described. The assembly collects gas in a chamber while continuously measuring the position of the gas-water interface that forms as gas accumulates. Interface position is determined from the differential pressure between the chamber and ambient seawater. A spar buoy

Libe Washburn; Cyril Johnson; Chris C. Gotschalk; E. Thor Egland

2001-01-01

135

Generation of gas bubbles in microflow using micropipette with ultrasound  

Microsoft Academic Search

Ultrasound was applied to a micropipette micromixer to improve dispersion of gas and liquid in a microchannel. Flow visualization\\u000a using a high-speed camera was performed to examine the effect of ultrasonic irradiation on bubble generation in the microchannel.\\u000a Basically, nitrogen gas was injected using a (0.5 µm ID) glass micropipette into ethanol flowing in a rectangular (100 µm×200\\u000a µm) microchannel

Naoki Ichikawa; Peter M.-Y. Chung; Sohei Matsumoto; Jun-ichi Matsumoto; Naoki Takada

2007-01-01

136

A Theoretical Study of Gas Bubble Dynamics in Tissue  

NASA Astrophysics Data System (ADS)

The behavior of cavitation bubbles in tissue driven by ultrasonic fields is an important problem in biomedical acoustics. The present solution combines the Keller-Miksis equation for nonlinear bubble dynamics with the linear Voigt model for viscoelastic media and experimental values for the model's parameters (rigidity G=0, 0.5 - 2.5 MPa and viscosity ?=0.005 or 0.015 Pa.s). Two and 3-component models are used to study the oscillations of gas bubbles in tissue and in partially digested tissue. Numerical computations are performed for a variety of cases. Inertial cavitation thresholds (Pt) are determined for various equilibrium radii, frequencies and threshold criteria. Bubble-induced tissue displacement and strain is also investigated for several representative tissue types. It is found that: 1) thresholds in tissue are up to 10 times those in liquid, 2) Pt increases nearly linearly with frequency, 3) there is an optimal relation between the microbubble and tissue radii that maximizes the displacement of the tissue adjacent to the bubble and thus the likelihood of tissue damage.

Church, Charles C.; Yang, Xinmai

2006-05-01

137

Bubbles  

NASA Astrophysics Data System (ADS)

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.

Prosperetti, Andrea

2004-06-01

138

Porosity formation and gas bubble retention in laser metal deposition  

NASA Astrophysics Data System (ADS)

One of the inherent problems associated with laser metal deposition using gas-assisted powder transfer is the formation of porosity, which can be detrimental to the mechanical properties of the bulk material. In this work, a comprehensive investigation of porosity is carried out using gas atomised Inconel 718 powder. In the analysis, a clear distinction is made between two types of porosity; namely lack of fusion and gas porosity. The results show that the two types of porosity are attributed by different factors. The gas porosity, which is more difficult to eliminate than the lack of fusion, can be as high as 0.7%. The study shows that the gas porosity is dependent on the process parameters and the melt pool dynamics. The flotation of entrapped gas bubbles was analysed, showing that in a stationary melt pool the gas would be retained by Marangoni-driven flow. The overall Marangoni-driven flow of the melt pool is in the order of five times higher than the flotation effect, and this is the reason why the melt pool geometry would tend to dominate the flow direction of the gas bubbles. Through optimisation, the gas porosity can be reduced to 0.037%.

Ng, G. K. L.; Jarfors, A. E. W.; Bi, G.; Zheng, H. Y.

2009-11-01

139

Influence of high acoustic pressure amplitudes for spherically cavitating gas bubbles in a compressible fluid  

Microsoft Academic Search

In the present paper, a numerical solution is obtained for a nonlinear differential equation describing the radial motion of a pulsating gas bubble in a compressible fluid. The dependence of the erosion and luminescence of activating gas bubbles on the acoustic pressure amplitude is analyzed, and a physical explanation of this effect is proposed. The behavior of the bubble radius

H.-J. Rath

1979-01-01

140

Bubble expansion, gas percolation and preservation of pyroclasts (Invited)  

NASA Astrophysics Data System (ADS)

Prior to eruption, almost all magmas contained enough dissolved water and carbon dioxide to vesiculate at atmospheric pressure into foams with gas volume fractions greater than 95%. However, such high-vesicularity volcanic foams, called reticulite, are rare and form primarily in high lava fountains of crystal-poor basalt. Most eruptions produce pyroclasts of 65-85% vesicularity as well as ash formed by complete fragmentation of magma, often at the scale of individual bubbles. For this reason, the amount of ash produced is commonly taken as a measure of fragmentation efficiency. Here we re-examine this concept by considering the roles of both permeability and isolated bubbles in magma expansion and fragmentation. Syn-eruptive magma expansion requires that gas in the component bubbles expands due to decompression and volatile exsolution faster than it escapes by permeable flow through pathways of interconnected bubbles. Much like a hole in a balloon can make it impossible to inflate, an increase in permeability will halt or drastically slow down magma expansion despite continued decompression and degassing. Evidence for permeability increases ? 2 orders of magnitude across a threshold vesicularity (e.g., Eichelberger et al., 1986) would further suggest that pyroclasts should preserve vesicularities that are close to this threshold. Observed pumice vesicularities of 65-85% are consistent with laboratory studies indicating gas percolation thresholds of ? 60%; however, numerous permeability measurements from other suites of volcanic samples suggest percolation thresholds much lower than 60%. We review these findings in the context of percolation theory, consider reasons for apparent discrepancies in the data, and discuss implications for conditions of vesiculation during volcanic eruptions. We then re-evaluate the conditions required for bubble expansion and reticulite development. In particular, a comparisons of basaltic scoria and reticulite suggests that these two clast types have different vesiculation histories, with proto-reticulite having less-well-connected bubbles than scoria of the same vesicularity. We assess the implications for fragmentation and eruption dynamics, and potential biases in inferring magma properties from studies of relatively large pyroclasts. Central to our argument is that preserved scoria and pumice clasts were too permeable to expand further, and, as suggested by Witham and Sparks (1986) and Klug and Cashman (1996), bubble connectivity is key to the preservation of pumice. In particular, we conclude that reticulite cannot form in explosive rhyolite eruptions because closed-system degassing at the relevant decompression rates leads to stresses sufficient to fragment the magma into ash. This interpretation is consistent with the observed correlation between the intensity of (sub)Plinian eruptions and the proportion of ash relative to pumice erupted (Walker 1973, 1980).

Rust, A.; Cashman, K. V.; Wright, H. M.

2009-12-01

141

Formation of a gas bubble on a vibrating capillary immersed in a liquid  

Microsoft Academic Search

The formation of a train of bubbles in a low-viscosity liquid is investigated. The dependence of the gas flow rate during formation of the bubble train on the vibrational acceleration of the capillary is determined.

I. S. Grachev; D. T. Kokorev; V. F. Yudaev

1976-01-01

142

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

SciTech Connect

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.

Paul C Millett; Anter El-Azab

2011-01-01

143

Acoustic techniques for localizing holdup  

SciTech Connect

Material that does not come out of a process as product or waste is called holdup. When this is fissile material, its location and quantity must be determined to improve safeguards and security as well as safety at the facility. The most common method for detecting and measuring holdup is with radiation based techniques. When using them, one must consider equipment geometry, geometry of holdup, and effects of background radiation when converting the radiation measurement into a fissile material quantity. We are developing complementary techniques that use tiny acoustic transducers, which are unaffected by background radiation, to improve holdup measurements by aiding in determining the above conversion factors for holdup measurements. Thus far, we have applied three techniques, Acoustic Interferometry, Pulse Echo, and bending Wave Propagation, of which the latter appears most effective. This paper will describe each of these techniques and show how they may ultimately reduce costs and personnel radiation exposure while increasing confidence I and accuracy of holdup measurements.

Vnuk, D.

1996-09-01

144

Learning to live with holdup  

SciTech Connect

Holdup of special nuclear materials in processing facilities is recognized by facility operators and regulatory agencies as an insidious materials control and accounting problem. However, there have been few serious efforts to address holdup as a materials accounting problem and to accommodate the legitimate concerns of both groups. This paper reviews past efforts and identifies several key elements relevant to resolving the problem in a pragmatic fashion. These key elements relate to the recognition of holdup as a serious materials accounting problem, innovations in holdup monitoring and their limitations, the role of modeling and sampling in holdup estimation, and the potential value of plant-specific materials accountability requirements. Suggestions are offered for developing cost-effective procedures for holdup measurements/estimation, combining available technologies with properly designed sampling plans.

Pillay, K.K.S.; Picard, R.R.

1986-06-01

145

Modeling biogenic gas bubbles formation and migration in coarse sand  

NASA Astrophysics Data System (ADS)

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

Ye, S.

2011-12-01

146

HYDRODYNAMICS, MIXING AND MASS TRANSFER IN A LARGE DIAMETER JET BUBBLE COLUMN  

Microsoft Academic Search

Experimental measurements for the axial and radial variations in gas holdup, axial and radial dispersion coefficients, volumetric gas-liquid mass transfer coefficient and liquid phase circulation velocity in a cone of a large diameter (122 cm) jet bubble column are presented. Two diameters of the inlet nozzle, namely 10.16 cm and 15.24 cm, three superficial gas velocities (based on cylinder diameter),

Y. T. SHAH; K. WISECARVER; A. BOROLE; A. SALAZAR; B. JOSHI; J. GUITIAN

1995-01-01

147

The breakup of bubbles into jets during submerged gas injection  

Microsoft Academic Search

There has never been any fundamental explanation presented for the transition from the bubbling regime to the jetting regime\\u000a when gas is injected into liquid at high velocity through submerged tuyeres. This is an important issue in metallurgical processes,\\u000a since the flow regime is known to influence refining rates, refractory erosion, and the penetration of the liquid into the\\u000a tuyere.

Y.-F. Zhao; G. A. Irons

1990-01-01

148

Holdup measurements under realistic conditions  

SciTech Connect

This paper reviews the documentation of the precision and bias of holdup (residual nuclear material remaining in processing equipment) measurements and presents previously unreported results. Precision and bias results for holdup measurements are reported from training seminars with simulated holdup, which represent the best possible results, and compared to actual plutonium processing facility measurements. Holdup measurements for plutonium and uranium processing plants are also compared to reference values. Recommendations for measuring holdup are provided for highly enriched uranium facilities and for low enriched uranium facilities. The random error component of holdup measurements is less than the systematic error component. The most likely factor in measurement error is incorrect assumptions about the measurement, such as background, measurement geometry, or signal attenuation. Measurement precision on the order of 10% can be achieved with some difficulty. Bias of poor quality holdup measurement can also be improved. However, for most facilities, holdup measurement errors have no significant impact on inventory difference, sigma, or safety (criticality, radiation, or environmental); therefore, it is difficult to justify the allocation of more resources to improving holdup measurements. 25 refs., 10 tabs.

Sprinkel, J.K. Jr.; Marshall, R.; Russo, P.A.; Siebelist, R. [and others

1997-11-01

149

TOWARDS FIELD MEASUREMENTS OF POPULATIONS OF METHANE GAS BUBBLES IN MARINE SEDIMENT: AN INVERSION METHOD REQUIRED FOR INTERPRETING TWO-FREQUENCY INSONIFICATION DATA FROM SEDIMENT CONTAINING GAS BUBBLES  

Microsoft Academic Search

This paper describes a key stage in the process for developing a new device for the measurement of gas bubbles in sediment. The device is designed to measure gas bubble populations within the top 2 m of marine sediments, and has been deployed at inter-tidal sites along the South coast of England. Acoustic techniques are particularly attractive for such purposes

TIMOTHY LEIGHTON; AGNI MANTOUKA; PAUL WHITE

150

Re-solution of fission gas A review: Part I. Intragranular bubbles  

NASA Astrophysics Data System (ADS)

Theories of fission-fragment-driven re-solution of fission-gas atoms from intragranular bubbles in irradiated UO2 nuclear fuel are reviewed. Two mechanisms of re-solution are generally accepted: the heterogeneous process destroys entire bubbles in the path of fission fragments and returns the gas to the solid as individual atoms; the homogeneous process re-solves fission-gas atoms singly by scattering collisions with fission fragments and uranium recoils whose paths intersect the bubbles. Coupling of these two re-solution models with the bubble nucleation analogs determines the size and number density of the intragranular bubble population. Two approaches are reviewed: the single-size theory, in which all bubbles are accorded one size, and the bubble distribution theory, which seeks to determine the variation of bubble number density with size.

Olander, D. R.; Wongsawaeng, D.

2006-08-01

151

Application of Phase-field Method in Predicting Gas Bubble Microstructure Evolution in Nuclear Fuels  

Microsoft Academic Search

Fission product accumulation and gas bubble microstructure evolution in nuclear fuels strongly affect thermo-mechanical properties such as thermal conductivity, gas release, volumetric swelling and cracking, and hence the fuel performance. In this paper, a general phase-field model is developed to predict gas bubble formation and evolution. Important materials processes and thermodynamic properties including the generation of gas atoms and vacancies,

Shenyang Y. Hu; Yulan Li; Xin Sun; Fei Gao; Ramaswami Devanathan; Charles H. Henager Jr.; Mohammad A. Khaleel

2010-01-01

152

Formation of Gas Bubbles in Gas Supersaturated Water.  

National Technical Information Service (NTIS)

The phenomenon of bubbles formation in supersaturated solutions of gases in water is a transport process, the final result of which is a separation of phases. The objective of the study was to fill the gap, and an extensive experimental work was carried o...

Y. Finkelstein

1984-01-01

153

Flow regime, hydrodynamics, floc size distribution and sludge properties in activated sludge bubble column, air-lift and aerated stirred reactors  

Microsoft Academic Search

This paper presents a comparative study how reactor configuration, sludge loading and air flowrate affect flow regimes, hydrodynamics, floc size distribution and sludge solids–liquid separation properties. Three reactor configurations were studied in bench scale activated sludge bubble column reactor (BCR), air-lift reactor (ALR) and aerated stirred reactor (ASR). The ASR demonstrated the highest capacity of gas holdup and resistance, and

Bo Jin; Paul Lant

2004-01-01

154

Hydrodynamics of Fischer-Tropsch synthesis in slurry bubble column reactors: Final report  

SciTech Connect

This report describes studies on hydrodynamics of bubble columns for Fischer-Tropsch synthesis. These studies were carried out in columns of 0.051 m and 0.229 m in diameter and 3 m tall to determine effects of operating conditions (temperature and gas flow rate), distributor type (sintered metal plate and single and multi-hole perforated plates) and liquid media (paraffin and reactor waxes) on gas hold-up and bubble size distribution. In experiments with the Fischer-Tropsch (F-T) derived paraffin wax (FT-300) for temperatures between 230 and 280/sup 0/C there is a range of gas velocities (transition region) where two values of gas hold-up (i.e., two flow regimes) are possible. Higher hold-ups were accompanied by the presence of foam (''foamy'' regime) whereas lower values were obtained in the absence of foam (''slug flow'' in the 0.051 m column, or ''churn-turbulent'' flow regime in the 0.229 m column). This type of behavior has been observed for the first time in a system with molten paraffin wax as the liquid medium. Several factors which have significant effect on foaming characteristics of this system were identified. Reactor waxes have much smaller tendency to foam and produce lower hold-ups due to the presence of larger bubbles. Finally, new correlations for prediction of the gas hold-up and the specific gas-liquid interfacial area were developed on the basis of results obtained in the present study. 49 refs., 99 figs., 19 tabs.

Bukur, D.B.; Daly, J.G.; Patel, S.A.; Raphael, M.L.; Tatterson, G.B.

1987-06-01

155

Optically actuated thermocapillary movement of gas bubbles on an absorbing substrate  

Microsoft Academic Search

The authors demonstrate an optical manipulation mechanism of gas bubbles for microfluidic applications. Air bubbles in a silicone oil medium are manipulated via thermocapillary forces generated by the absorption of a laser in an amorphous silicon thin film. In contrast to previous demonstrations of optically controlled thermally driven bubble movement, transparent liquids can be used, as the thermal gradient is

Aaron T. Ohta; Arash Jamshidi; Justin K. Valley; Hsan-Yin Hsu; Ming C. Wu

2007-01-01

156

Motion of Interacting Gas Bubbles in a Viscous Liquid Including Wall Effects and Evaporation  

Microsoft Academic Search

The motion of single and multiple gas bubbles in an otherwise stationary liquid contained in a closed right vertical cylinder is investigated using a modified volume-of-fluid (VOF) method incorporating surface tension stresses. An isolated bubble was considered in a separate paper [4], where the initial bubble radius was small in comparison with that of the cylinder and watt effects were

Li Chen; Suresh V. Garimella; John A. Reizes; Eddie Leonardi

1997-01-01

157

On the Formation of Centered Shock Waves in Gas Bubbles under the Conditions of Acoustic Cavitation  

Microsoft Academic Search

The possibility of the formation of centered shock waves in collapsing gas bubbles under the conditions of acoustic cavitation is considered. In this case, the overturning of the front of compression waves occurs at the instant the waves reach the center of the cavitation bubble, resulting in the highest possible temperatures and pressures inside the bubble. Examination of the magnetohydrodynamic

V. S. Malyshevskii

2004-01-01

158

Development of Liposomal Bubbles with Perfluoropropane Gas as Gene Delivery Carriers  

Microsoft Academic Search

Liposomes have some advantages as drug, antigen and gene delivery carriers. Their size can be easily controlled and they can be modified to add a targeting function. Based on liposome technology, we developed novel liposomal bubbles (Bubble liposomes) containing the ultrasound imaging gas, perfluoropropane. We assessed the feasibility of Bubble liposomes as carriers for gene delivery after cavitation induced by

Kazuo Maruyama; Ryo Suzuki; Kaori Sawamura; Tomoko Takizawa; Naoki Utoguchi; Yoichi Negishi

2007-01-01

159

Observation and quantification of gas bubble formation on a mechanical heart valve.  

PubMed

Clinical studies using transcranial Doppler ultrasonography in patients with mechanical heart valves (MHV) have detected gaseous emboli. The relationship of gaseous emboli release and cavitation on MHV has been a subject of debate in the literature. To study the influence of cavitation and gas content on the formation and growth of stable gas bubbles, a mock circulatory loop, which employed a Medtronic-Hall pyrolytic carbon disk valve in the mitral position, was used. A high-speed video camera allowed observation of cavitation and gas bubble release on the inflow valve surfaces as a function of cavitation intensity and carbon dioxide (CO2) concentration, while an ultrasonic monitoring system scanned the aortic outflow tract to quantify gas bubble production by calculating the gray scale levels of the images. In the absence of cavitation, no stable gas bubbles were formed. When gas bubbles were formed, they were first seen a few milliseconds after and in the vicinity of cavitation collapse. The volume of the gas bubbles detected in the aortic track increased with both increased CO2 and increased cavitation intensity. No correlation was observed between O2 concentration and bubble volume. We conclude that cavitation is an essential precursor to stable gas bubble formation, and CO2, the most soluble blood gas, is the major component of stable gas bubbles. PMID:11036552

Lin, H Y; Bianccucci, B A; Deutsch, S; Fontaine, A A; Tarbell, J M

2000-08-01

160

Effect of high pressure operation on overall phase holdups in ebullated-bed reactors  

Microsoft Academic Search

The effect of pressure on basic hydrodynamics of ebullated beds at elevated pressures of up to 15Mpa was studied by measurement of bed profiles by gamma-ray densitometry. For 1.7mm glass beads the bed expansion as well as gas holdup increased with pressure, while liquid and solids holdup decreased. Given the solids holdup is available, it was found that the generalized

R. S. Ruiz; F. Alonso; J. Ancheyta

2004-01-01

161

ADVANCED DIAGNOSTIC TECHNIQUES FOR THREE-PHASE SLURRY BUBBLE COLUMN REACTORS(SBCR)  

SciTech Connect

The objectives set for this cooperative project between Washington University (WU), Ohio State University (OSU), and Air Products and Chemicals, Inc. (APCI) to advance the understanding of the Fischer-Tropsch (FT) slurry bubble column reactor hydrodynamics for proper design and scale-up via advanced diagnostic techniques have been accomplished successfully despite the unexpected challenging technical difficulties in implementing the advanced techniques in high pressure stainless steel slurry bubble column. In this work, a detailed review of the aspects of high pressure phenomena of bubbles in liquids and liquid-solids suspension was performed. All the challenging technical problems mentioned above were resolved and the advanced measurement techniques were successfully used in this project. The effects of reactor pressure, superficial gas velocity, solids loading, and liquid physical properties on the overall gas holdup, holdups distribution, recirculation velocity, turbulent parameters, bubble dynamics (size and rise velocity) were investigated via advanced measurement techniques that includes optical probe, Laser Doppler Anemometry (LDA), Computed Tomography (CT), Computer Automated Radioactive Particle Tracking (CARPT). The findings are discussed and analyzed in this report. In attempt to advance the design and scale-up of bubble columns, new correlations have been developed based on a large bank of data collected at a wide range of operating and design conditions. These correlations are for prediction of radial gas holdup profile, axial liquid velocity profile, overall gas holdup based on Neural Network and gas-liquid mass transfer coefficient. Despite the noticeable advances made on FT SBCR as a part of this project, there are still many parameters and challenging issues that need to be further and properly investigated and understood before this technology will be readily used for alternative fuel development technology.

M.H. Al-Dahhan; L.S. Fan; M.P. Dudukovic

2003-08-01

162

Phase-field modeling of gas bubbles and thermal conductivity evolution in nuclear fuels  

Microsoft Academic Search

A phase-field model was developed to simulate the accumulation and transport of fission products and the evolution of gas bubble microstructures in nuclear fuels. The model takes into account the generation of gas atoms and vacancies, and the elastic interaction between diffusive species and defects as well as the inhomogeneity of elasticity and diffusivity. The simulations show that gas bubble

Shenyang Y. Hu; Charles H. Henager Jr.; Howard L. Heinisch; Marius Stan; Michael I. Baskes; Steven M. Valone

2009-01-01

163

Simulation of large bubble/molten steel interaction for gas-injected ladle  

NASA Astrophysics Data System (ADS)

A mathematical model has been developed to simulate numerically the interactions between gas bubbles and molten steel during the gas-injection treatment in secondary refining of steel and to experimentally verify the reliability of the model. A marker-and-cell (MAC) technique is employed to simulate the motions of gas bubbles and molten steel. Photographic observation is used to evaluate the reliability of the mathematical model. A two-dimensional ladle with only one bubble was used to test the capability of the model to handle the interaction between the relatively large bubble and the molten steel. The shape of the bubble is initially round. Then it gradually becomes flattened and eventually evolves into a spherical-cap bubble. Molten steel is induced to flow and forms two circulations. The model was then tested on the same ladle with bubbles continuously released. The first bubble rises in a similar way as the previous case. The second bubble is affected by the first bubble and becomes slightly elongated in the vertical direction rather than in the horizontal direction. It also rises faster and later collides with the first bubble. The released bubbles can be grouped in clusters and are repeated cluster after cluster. Water-model experimental observations are consistent with the predicted results.

Pan, S.-M.; Chiang, J.-D.; Hwang, W.-S.

1999-04-01

164

Theory of the nonsteady diffusion growth of a gas bubble in a supersaturated solution of gas in liquid  

Microsoft Academic Search

Using a self-similar approach a general nonsteady theory is elaborated for the case of the diffusion growth of a gas bubble in a supersaturated solution of gas in liquid. Due to the fact that the solution and the bubble in it are physically isolated, the self-similar approach accounts for the balance of the number of gas molecules in the solution

A. P. Grinin; F. M. Kuni; G. Yu. Gor

2008-01-01

165

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

PubMed Central

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.

Doinikov, Alexander A.; Dayton, Paul A.

2011-01-01

166

Micropumping of liquid by directional growth and selective venting of gas bubbles.  

PubMed

We introduce a new mechanism to pump liquid in microchannels based on the directional growth and displacement of gas bubbles in conjunction with the non-directional and selective removal of the bubbles. A majority of the existing bubble-driven micropumps employs boiling despite the unfavorable scaling of energy consumption for miniaturization because the vapor bubbles can be easily removed by condensation. Other gas generation methods are rarely suitable for micropumping applications because it is difficult to remove the gas bubbles promptly from a pump loop. In order to eradicate this limitation, the rapid removal of insoluble gas bubbles without liquid leakage is achieved with hydrophobic nanopores, allowing the use of virtually any kind of bubbles. In this paper, electrolysis and gas injection are demonstrated as two distinctively different gas sources. The proposed mechanism is first proved by circulating water in a looped microchannel. Using H(2) and O(2) gas bubbles continuously generated by electrolysis, a prototype device with a looped channel shows a volumetric flow rate of 4.5-13.5 nL s(-1) with a direct current (DC) power input of 2-85 mW. A similar device with an open-ended microchannel gives a maximum flow rate of approximately 65 nL s(-1) and a maximum pressure head of approximately 195 Pa with 14 mW input. The electrolytic-bubble-driven micropump operates with a 10-100 times higher power efficiency than its thermal-bubble-driven counterparts and exhibits better controllability. The pumping mechanism is then implemented by injecting nitrogen gas bubbles to demonstrate the flexibility of bubble sources, which would allow one to choose them for specific needs (e.g., energy efficiency, thermal sensitivity, biocompatibility, and adjustable flow rate), making the proposed mechanism attractive for many applications including micro total analysis systems (microTAS) and micro fuel cells. PMID:18497918

Meng, Dennis Desheng; Kim, Chang-Jin C J

2008-04-24

167

Solvent refined coal (SRC) process. Progress report on the thermal and hydrodynamic behavior of multiphase reactors: A. September 1980April 1981; B. September 1980August 1981; C. August 1981September 30, 1981. [Bubble column reactors  

Microsoft Academic Search

This report summarizes the work carried out at the University of Pittsburgh for the multiphase flow process laboratory supported by Gulf Research and Development Company. The work is divided into three parts. In part A, data on gas holdup and axial dispersion of heat for several liquids other than water for a continuous bubble column are described. The report also

Y. T. Shah; B. G. Kelkar; S. Godbole; M. Honath; R. Albal; A. Kulkarni; S. Phulgaonkar

1982-01-01

168

Bubble Bubble  

NSDL National Science Digital Library

With magic bubble solution, a boy discovers that he can blow any kind of bubble imaginable: a kangaroo, a bird, a car, or a boat. Mercer Mayer's colorful illustrations enliven this engaging tale of mysterious bubbles.

Mayer, Mercer

2009-11-11

169

Dissipation effects with pulsations of gas bubbles in viscoelastic polymeric liquids  

Microsoft Academic Search

result of heat transfer between the gas contained in the bubble and the surrounding medium; acoustical dissipation due to losses for the emission of sound by the oscillating bubbles; viscous dissipation, connected with the irreversible character of processes of the transfer of momentum in the medium and with localization in the case of an incompressible liquid near the gas-liquid interface.

S. P. Levitskii

1979-01-01

170

Influence of gas bubbles on electrical discharges in small working gaps  

Microsoft Academic Search

In the paper the first investigations on gas bubble evolution are presented. The research is based on video recording (VR) and high speed framing camera (HSFC) pictures, as well as theoretical considerations. Violent changes of gas bubbles generated in the consequence of single discharges are analyzed in the time interval of 100 ?s (dissolving time) after the end of the

H.-P. Schulze; K. Mecke; G. Wollenberg

2005-01-01

171

Behavior of Gas Bubbles in Viscoelastic Materials in a Creep Process  

Microsoft Academic Search

This paper investigates the dynamic behavior of a spherical bubble situated in viscoelastic (or elasticoviscous) materials in a creep process. Both the diffusion of the dissolved gas in the material and the thermodynamic behavior of the gas inside the bubble are taken into account. The generalized model of the Kelvin or Maxwell type which consists of the spring, dashpot, and

Wen-Jei Yang; C. Y. Liang

1972-01-01

172

On the Propagation of Sound in a Liquid Containing Gas Bubbles  

Microsoft Academic Search

The theory of the propagation of sound in a homogeneous gas including the effect of heat conduction is presented for the purpose of clarifying the underlying thermodynamic process. The propagation of sound in a liquid with a homogeneous and isotropic distribution of gas bubbles is then considered. The bubbles are assumed to be sufficiently small and numerous so that the

Din-Yu Hsieh; Milton S. Plesset

1961-01-01

173

Stability of Gas Bubbles in a Deformable Material Containing Dissolved Gases  

Microsoft Academic Search

This paper analyzes the stability of gas bubbles in a medium which contains dissolved gases and deforms due to creep. The effects of mass diffusion and surface tension on the dynamic behavior of a gas bubble are taken into account. Asymptotic solutions valid for large times are obtained which predict the radius-time relation, the creep rate, and the rate of

Wen-Jei Yang

1972-01-01

174

MOTION OF SINGLE GAS BUBBLES RISING IN A LIQUID METAL EXPOSED TO A DC MAGNETIC FIELD  

Microsoft Academic Search

Introduction. Bubble driven flows have found wide applications in indus- trial technologies. In metallurgical processes gas bubbles are injected into a bulk liquid metal to drive the liquid into motion, to homogenise the physical and chemi- cal properties of the melt or to refine the melt. For such gas-liquid metal two-phase flows, external magnetic fields provide a possibility to control

C. Zhang; S. Eckert; G. Gerbeth

175

Differently directed motions of gas bubbles in vibrating fluids in the presence of physical inhomogeneities  

Microsoft Academic Search

The dynamic behavior of gas bubbles in vibrating fluid columns has been studied by a number of domestic [i, 4, 9] and foreign [8, i0, ii] authors. The special interest in these investigations is explained primarily by the physics of the detected phenomena: For definite values of the vibration acceleration the gas bubbles in the fluid do not float on

N. A. Pelykh

1985-01-01

176

Physical data measurements and mathematical modelling of simple gas bubble experiments in glass melts  

Microsoft Academic Search

In this work consideration is given to the problem of the extraction of physical data information from gas bubble dissolution and growth measurements. The discussion is limited to the analysis of the simplest experimental systems consisting of a single, one component gas bubble in a glassmelt. It is observed that if the glassmelt is highly under- (super-) saturated, then surface

Michael C. Weinberg

1986-01-01

177

Dynamics of biogenic gas bubbles in peat and their effects on peatland biogeochemistry  

Microsoft Academic Search

Production and emission of peat gas has attracted great interest because substantial amounts of methane (CH4) are emitted to the atmosphere from peat soils. Many studies indicate supersaturation of CH4 in peat water, implying a high potential for gas bubble formation. However, observations of bubbles in peat are often only qualitatively described, and in most cases the presence of entrapped

M. Strack; E. Kellner; J. M. Waddington

2005-01-01

178

The Presence and Dynamics of Entrapped Biogenic Gas Bubbles in Peat I: Biogeochemical Implications  

Microsoft Academic Search

Production and emission of peat gas has attracted great interest since substantial amounts of methane (CH4) are emitted to the atmosphere from peat soils. Many studies indicate supersaturation of methane in peat water indicating a high potential for gas bubble formation. However, observations of bubbles in peat are often only qualitatively described, and as such knowledge of the dynamics of

M. Strack; E. Kellner; J. S. Price; J. Waddington

2004-01-01

179

Exercise during a 3Min Decompression Stop Reduces Postdive Venous Gas Bubbles  

Microsoft Academic Search

DUJIC´, ? Z., I. PALADA, A. OBAD, D. DUPLAN? CIC´, D. BAKOVIC´, and Z. VALIC. Exercise during a 3-Min Decompression Stop Reduces Postdive Venous Gas Bubbles. Med. Sci. Sports Exerc., Vol. 37, No. 8, pp. 1319-1323, 2005. Purpose: Decompression sickness is initiated by the formation of gas bubbles in tissue and blood if the divers return to surface pressure too

IVAN PALADA; ANTE OBAD; ZORAN VALIC

2005-01-01

180

Gas–liquid dispersion in a fibrous fixed bed biofilm reactor at growth and non-growth conditions  

Microsoft Academic Search

There is limited data on gas dispersion characteristics of fixed bed biofilm reactors under growth and non-growth conditions. In this paper, the gas–liquid dispersion of a bubble bed packed with a fibrous structured packing for biofilm application is studied. The reactor is operated with Pseudomonas putida aimed at aniline degradation in wastewater. Gas hold-up and bubble size distribution are determined.

Martin Martinov; Dimiter Hadjiev; Serafim Vlaev

2010-01-01

181

Horizontal drilling in Baldonnel gas reservoirs - a case history of the Jadney - North Bubbles gas pools  

Microsoft Academic Search

The Jedney - North Bubbles gas pools are trapped in anticlinal folds of the host Triassic dolostones against a northern subcrop edge. The pools have been on production since the early 1960`s, with producing wells averaging 45 dam³\\/d and current reserve lives in excess of 10 years. Gross pay thickness of the reservoir is 46m, with the better matrix wells

R. Hill; P. Kubica; G. Tebbutt

1996-01-01

182

Possible high sonic velocity due to the inclusion of gas bubbles in water  

NASA Astrophysics Data System (ADS)

If formation water becomes multi-phase by inclusion of gas bubbles, sonic velocities would be strongly influenced. In general, sonic velocities are knocked down due to low bulk moduli of the gas bubbles. However, sonic velocities may increase depending on the size of gas bubbles, when the bubbles in water or other media oscillate due to incoming sonic waves. Sonic waves are scattered by the bubbles and the superposition of the incoming and the scattered waves result in resonant-frequency-dependent behavior. The phase velocity of sonic waves propagating in fluids containing bubbles, therefore, probably depends on their frequencies. This is a typical phenomenon called “wave dispersion.” So far we have studied about the bubble impact on sonic velocity in bubbly media, such as the formation that contains gas bubbles. As a result, it is shown that the bubble resonance effect is a key to analyze the sonic phase velocity increase. Therefore to evaluate the resonance frequency of bubbles is important to solve the frequency response of sonic velocity in formations having bubbly fluids. There are several analytical solutions of the resonance frequency of bubbles in water. Takahira et al. (1994) derived a equation that gives us the resonance frequency considering bubble - bubble interactions. We have used this theory to calculate resonance frequency of bubbles at the previous work. However, the analytical solution of the Takahira’s equation is based on several assumptions. Therefore we used a numerical approach to calculate the bubble resonance effect more precisely in the present study. We used the boundary element method (BEM) to reproduce a bubble oscillation in incompressible liquid. There are several reasons to apply the BEM. Firstly, it arrows us to model arbitrarily sets and shapes of bubbles. Secondly, it is easy to use the BEM to reproduce a boundary-surface between liquid and gas. The velocity potential of liquid surrounding a bubble satisfies the Laplace equation when the liquid is supposed to be incompressible. We got the boundary integral equation from the Laplace equation and solved the boundary integral equation by the BEM. Then, we got the gradient of the velocity potential from the BEM. We used this gradient to get time derivative of the velocity potential from the Bernouii’s equation. And we used the second order Adams-Bashforth method to execute time integration of the velocity potential. We conducted this scheme iteratively to calculate a bubble oscillation. At each time step, we input a pressure change as a sinusoidal wave. As a result, we observed a bubble oscillation following the pressure frequency. We also evaluated the resonance frequency of a bubble by changing the pressure frequency. It showed a good agreement with the analytical solution described above. Our future work is to extend the calculation into plural bubbles condition. We expect that interaction between bubbles becomes strong and resonance frequency of bubbles becomes small when distance between bubbles becomes small.

Banno, T.; Mikada, H.; Goto, T.; Takekawa, J.

2010-12-01

183

Hydrodynamic studies in both bi-dimensional and three-dimensional bubble columns with a single sparger  

Microsoft Academic Search

Gas holdup in highly viscous fluid in two-phase bubble column with a single sparger operated continuously with respect to the gas flow and batch wise with respect to the liquid was investigated using bed expansion technique. Two- and three-dimensional columns of the same effective cross-sectional area were investigated. Liquid viscosity varied between 0.063 and 0.320 Pa s, static bed heights

M. Z. A. Anabtawi; S. I. Abu-Eishah; N. Hilal; M. B. W. Nabhan

2003-01-01

184

Diffusion of helium gas bubbles in gold and copper foils  

Microsoft Academic Search

Helium bubbles were induced in gold and copper foils by ion bombardment and their diffusion studied by observing the rate at which the bubbles diffuse out of the foil and also by measuring the distance they move in a given annealing time. This is the first time such quantitative comparisons have been made. It was discovered that helium bubbles in

L. E. Willertz; P. G. Shewmon

1970-01-01

185

Gas generation and bubble formation model for crystalline silicotitanate ion exchange columns  

SciTech Connect

The authors developed a transient model to describe the process of gas generation due to radiolysis and bubble formation in crystalline silicotitanate (CST) ion exchange (IX) columns using the Aspen Custom Modeler (ACM) software package. The model calculates gas concentrations and onset of bubble formation for large CST IX columns. The calculations include cesium loading as a function of time, gas generation as a function of cesium loading, and bubble formation as a function of gas solubility. This report summarizes the model development and predictions.

Hang, T.

2000-07-19

186

Gas supersaturation in the surface ocean: The roles of heat flux, gas exchange, and bubbles  

Microsoft Academic Search

In this paper, a one-dimensional model of mixed layer dynamics is used to examine the roles of heat flux, gas exchange, and bubble processes in producing nitrogen and argon gas supersaturation in the surface subtropical Pacific ocean at U.S. JGOFS Station ALOHA during 1989–1990. The N2\\/Ar ratio is measured within a high degree of accuracy by mass spectrometry, and the

Rebecca Schudlich; Steven Emerson

1996-01-01

187

Mass transfer into viscous pseudoplastic liquid in large-diameter bubble columns  

Microsoft Academic Search

In pseudoplastic aqueous solutions of polysaccharides (xanthan, hydroxypropyl guar), hydrodynamics and oxygen mass transfer were studied in bubble columns of 0.19 m, 0.29 m and 0.60 m diameter (0.08 to 1.6 m3 liquid volume). Churn-turbulent flow prevailed; a slight diameter effect on the gas hold-up was observed only at high viscosity in the smaller columns. The volumetric mass transfer coefficients

H. Eickenbusch; P.-O. Brunn; A. Schumpe

1995-01-01

188

Nano bubbles in liquid of a noble-gas mixture.  

PubMed

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. PMID:20094667

Yamamoto, Takenori; Ohnishi, Shuhei

2009-12-01

189

About possible mechanisms of influence of gas bubbles on characteristics of turbulent boundary layer  

Microsoft Academic Search

Two different mechanisms responsible for the were revealed impact of gas bubbl injected into a boundary layer on the shear\\u000a stress on the wetted surfaces. Both mechanisms exist due to extremely high sensitivity of bubbles even to very low pressure\\u000a gradients and due to a high value of the virtual mass and coefficient of viscous drag for bubbles. The first

L. I. Maltsev; A. G. Malyuga; B. G. Novikov

2006-01-01

190

Solid suspension and gas dispersion in gas-solid-liquid agitated systems  

Microsoft Academic Search

The aim of the research work was to investigate the effect of superficial gas velocity and solids concentration on the critical\\u000a agitator speed, gas hold-up and averaged residence time of gas bubbles in an agitated gas-solid-liquid system. Experimental\\u000a studies were conducted in a vessel of the inner diameter of 0.634 m. Different high-speed impellers: Rushton and Smith turbines,\\u000a A 315

Anna Kie?bus-R?pa?a; Joanna Karcz

2010-01-01

191

Hydroacoustic detection and quantification of free gas -methane bubbles- in the ocean  

NASA Astrophysics Data System (ADS)

Extensive methane release as a free gas phase from cold vents is well known from deep (>2000m) and shallow (10s of meters) water depths. Supposedly, much more methane is transported into the water column by free gas than by dissolved gas, which is oxidized by anaerobic and aerobic processes and partly precipitated as carbonate. Rising gas bubbles are not affected by this 'filter' mechanisms. Because of the strength of the backscattered signal from gas bubbles in the water column, bubbles can be detected by single-beam or multi-beam echosounder systems. Thus, hydroacoustic systems with different frequencies can be used to 1) detect free gas in the water column, 2) map the distribution of active vent sites which release free gas, 3) monitor a possible periodicity in the release of bubbles induced by e.g. tides or currents, 4) quantify the gas volume and gas flux that is released in a local area or larger region. In the German research project LOTUS we use ship- mounted single-beam echosounders to map gas plumes (flares) and investigate their periodicity (Flare Imaging). Using specialized single-beam echosounder systems makes it possible to measure the bubble sizes and their distribution. In combination with the volume of the backscattering strength these measurements can be used to estimate the gas volume in a defined part of the water body. Though gas bubbles rise in the water column, they are - particularly methane - rapidly dissolved and thus become smaller. Their rising speed as well as their diminishing size can be determined, which helps to understand the dissolution behaviour of methane bubbles; they form a hydrate skin at distinct pressure and temperature conditions. For a detailed, long-term observation of active bubble-expulsing areas we developed a lander based 180 kHz multi beam system that 'looks' horizontally (GasQuant). The system records backscatter data from a 75° swath that covers an area of about 5300m2. Via calibration we can quantify the methane flux of every single bubble-vent and calculate the methane flux of a bubble vent area. Both hydroacoustic techniques were used during several cruises in 2002 to investigate bubble vents at Hydrate Ridge (HR), offshore Oregon. Several bubble-vent areas were detected at the northern summit of HR. They are related to carbonate chemoherms and morphological heights but were also found in areas which do not show any of these features. The GasQuant system was successfully deployed at the northern and southern summit. The data processing is currently in progress.

Greinert, J.; Artemov, Y.; Gimpel, P.

2003-04-01

192

Chemical and Physical Characteristics of Pulsed Electrical Discharge Within Gas Bubbles in Aqueous Solutions  

Microsoft Academic Search

The chemical and physical characteristics of pulsed electrical discharge within gas bubbles immersed in an aqueous solution\\u000a were investigated using a reactor with long protrusion length high voltage needle electrodes. Argon gas was introduced at\\u000a the base of the needle electrode causing gas bubbles to flow upwards in contact with the needle. The effects of needle protrusion\\u000a length were evaluated

Kai-Yuan Shih; Bruce R. Locke

2010-01-01

193

Growth of Gas Bubbles in Deformable Solids with Time-Dependent Heat and Mass Sources  

Microsoft Academic Search

The equations governing the growth of a spherical inert-gas bubble in a deformable solid resulting from the generation of gas atoms from time-dependent gas sources in the solid matrix are formulated for the general case which includes the effects of surface tension, heat diffusion and time-varying heat sources in the matrix. The dimensionless parameters controlling bubble dynamics are identified. Asymptotic

Wen-Jei Yang

1972-01-01

194

The effect of bubble-mediated gas transfer on purposeful dual-gaseous tracer experiments  

Microsoft Academic Search

For air-water gas exchange across unbroken surfaces, the only gas-dependent parameter affecting the transfer velocity is the molecular diffusivity of the transferring species. In contrast, bubble-mediated transfer processes can cause the transfer velocity to depend on both molecular diffusivity and aqueous-phase solubility. This can complicate the analysis of data from dual-gaseous tracer gas transfer experiments. Bubble effects also complicate the

William E. Asher; Rik Wanninkhof

1998-01-01

195

Modeling discrete gas bubble formation and mobilization during subsurface heating of contaminated zones  

Microsoft Academic Search

During thermal remediation the increase in subsurface temperature can lead to bubble formation and mobilization. In order to investigate the effect of gas formation on resulting aqueous concentrations, a 2D finite difference flow and mass transport model was developed which incorporates a macroscopic invasion percolation (MIP) model to simulate bubble expansion and movement. The model was used to simulate three

Magdalena M. Krol; Kevin G. Mumford; Richard L. Johnson; Brent E. Sleep

2011-01-01

196

Propagation of long waves of finite amplitude in a liquid with polydispersed gas bubbles  

Microsoft Academic Search

In the present paper we consider propagation of long waves of finite amplitude in liquids with a continuous spectrum of gas bubble sizes using the model of a monodispersed medium. It is shown that in general this description is not correct. However, if the surface tension only slightly affects the pressure inside a bubble and the process is nearly isothermal

N. A. Gumerov

1992-01-01

197

Controlled electrochemical gas bubble release from electrodes entirely and partially covered with hydrophobic materials  

Microsoft Academic Search

This paper deals with an experimental study on millimetre-size electrochemically evolved hydrogen bubbles. A method to generate gas bubbles controlled in number, size at detachment and place on a flat electrode is reported. Partially wetted composite islands are implemented on a polished metal substrate. As long as the island size is lower than a limit depending on its wettability, only

C. Brussieux; Ph. Viers; H. Roustan; M. Rakib

2011-01-01

198

Numerical Simulation of Gas Bubbles Rising in Viscous Liquids at High Reynolds Number  

Microsoft Academic Search

A robust algorithm for direct numerical simulation of fully three- dimensional, incompressible two-phase ?ow is presented. The method is intro- duced in the context of gas bubbles rising in viscous liquids, e.g. air bubbles rising in water. Key strengths of the simulation approach include the ability to simulate ?ows in an extended, wide range of Reynolds and Bond numbers and

Jinsong Hua; Ping Lin; Jan F Stene

199

Dissipation of the energy of sound waves in small gas bubbles  

Microsoft Academic Search

One of the main factors affecting the dynamics of homogeneous solution type pulse reactors is the formation of gas bubbles on the fission-fragment tracks [1, 2]. The behavior of the reactor depends very considerably on the size (10-5 cm) and growth rate of these bubbles [2], and it is, accordingly, a very important matter to study these properties. One convenient

A. N. Sizov

1975-01-01

200

Influence of electric field on single gas-bubble growth and detachment in microgravity  

Microsoft Academic Search

The effect of electric and gravitational field on detachment and motion of gas bubbles was studied by injecting nitrogen in a fluoroinert liquid (FC-72) at ambient temperature and pressure through an orifice (about 0.1 mm diameter) drilled in a horizontal tube. In such a way, it was possible to investigate the mechanical effects in bubble dynamics separately from the thermal

P Di Marco; W Grassi; G Memoli; T Takamasa; A Tomiyama; S Hosokawa

2003-01-01

201

On the structure of nonlinear waves in liquids with gas bubbles  

Microsoft Academic Search

Transient wave phenomena in two-phase mixtures with a liquid as the matrix and gas bubbles as the dispersed phase have been studied in a shock tube using glycerine as the liquid and He, N2, and SF6 as gases having a large variation in the ratio of specific heats and the thermal diffusivity. Two different sizes of bubble radii have been

Alfred E. Beylich

1990-01-01

202

The effect of gas-injector location on bubble formation in liquid cross flow  

Microsoft Academic Search

Liquid flows incorporating small-size bubbles play a vital role in many industrial applications. In this work, an experimental investigation is conducted on bubble formation during gas injection from a microtube into the channel of a downward liquid cross flow. The tip of the air injector has been located at the wall (wall orifice) and also at several locations from the

Sina Ghaemi; Payam Rahimi; David S. Nobes

2010-01-01

203

Propagation of Pressure Waves, Caused by a Thermal Shock, in Liquid Metals Containing Gas Bubbles  

Microsoft Academic Search

The propagation of pressure waves caused by a thermal shock in liquid mercury containing micro gas bubbles has been simulated numerically. In the present study, we clarify the influences of the introduced bubble size and void fraction on the absorption of thermal expansion of liquid mercury and attenuation of pressure waves. The mass, momentum and energy conservation equations for both

Kohei Okita; Shu Takagi; Yoichiro Matsumoto

2008-01-01

204

Propagation of Pressure Waves, Caused by a Thermal Shock, in Liquid Metals Containing Gas Bubbles  

Microsoft Academic Search

Propagation of pressure waves caused by a thermal shock in liquid metals containing gas bubbles was investigated numerically, to examine the influences of bubble radius and void fraction on the absorption of thermal expansion of liquid metals and attenuation of the pressure waves. The present approach is to solve the mass, momentum and energy conservation equations with the equation of

Kohei Okita

2005-01-01

205

Laser generation of gas bubbles: Photoacoustic and photothermal effects recorded in transient grating experiments  

SciTech Connect

Absorption of high power laser radiation by colloidal suspensions or solutions containing photoreactive chemicals can result in bubble production. Here, transient grating experiments are reported where picosecond and nanosecond lasers are used to initiate photoinduced processes that lead to bubble formation. Irradiation of colloidal Pt suspensions is found to produce water vapor bubbles that condense back to liquid on a nanosecond time scale. Laser irradiation of Pt suspensions supersaturated with CO{sub 2} liberates dissolved gas to produce bubbles at the sites of the colloidal particles. Laser induced chemical reactions that produce bubbles are found in suspensions of particulate C in water, and in the sensitized decarboxylation of oxalic acid. Theory based on linear acoustics as well as the Rayleigh-Plesset equation is given for description of the bubble motion.

Frez, Clifford; Diebold, Gerald J. [Department of Chemistry, Brown University, Providence, Rhode Island 02912 (United States)

2008-11-14

206

Dynamics of gas micronuclei formed on a flat hydrophobic surface, the predecessors of decompression bubbles.  

PubMed

It is a long-standing hypothesis that the bubbles which evolve as a result of decompression have their origin in stable gas micronuclei. In a previous study (Arieli and Marmur, 2011), we used hydrophilic and monolayer-covered hydrophobic smooth silicon wafers to show that nanobubbles formed on a flat hydrophobic surface may be the gas micronuclei responsible for the bubbles that evolve to cause decompression sickness. On decompression, bubbles appeared only on the hydrophobic wafers. The purpose of the present study was to examine the dynamics of bubble evolution. The numbers of bubbles after decompression were greater with increasing hydrophobicity. Bubbles appeared after decompression from 150 kPa, and their density increased with elevation of the exposure pressure (and supersaturation), up to 400 kPa. The normal force of attraction between the hydrophobic surface and the bubble, as determined from the volume of bubbles leaving the surface of the wafer, was 38×10(-5) N and the tangential force was 20×10(-5) N. We discuss the correlation of these results with previous reports of experimental decompression and bubble formation, and suggest to consider appropriate modification of decompression models. PMID:23246801

Arieli, R; Marmur, A

2012-12-14

207

Hydroacoustic detection and quantification of free gas -methane bubbles in the ocean  

Microsoft Academic Search

Extensive methane release as a free gas phase from cold vents is well known from deep (>2000m) and shallow (10s of meters) water depths. Supposedly, much more methane is transported into the water column by free gas than by dissolved gas, which is oxidized by anaerobic and aerobic processes and partly precipitated as carbonate. Rising gas bubbles are not affected

J. Greinert; Y. Artemov; P. Gimpel

2003-01-01

208

Effect of Gas Bubble Mobilization on Contaminant Transport during Thermal Remediation  

NASA Astrophysics Data System (ADS)

Discrete gas bubble formation in the subsurface has previously been observed as a result of microbial activity, water table oscillations, and application of direct gas injection and permanganate injection for subsurface remediation. Discrete gas bubble formation could also occur during subsurface thermal remediation, beginning in the heat-up phase and at the edge of the heated zone. Gas bubbles would form as soon as total gas pressures from water and volatile contaminants exceed in-situ pressures and then move upwards into cooler regions where they could redissolve into the aqueous phase, or condense as nonaqueous phase liquids. This study examined the behavior of a discontinuous gas phase under non isothermal conditions using a two dimensional electro-thermal model combined with a macroscopic invasion percolation (MIP) model. The effects of various temperatures, different entry pressures and groundwater velocities on the formation, expansion, and mobilization of discrete bubbles were examined for a system contaminated with 1,1,1-TCA. The simulations showed expansion of gas bubbles in the heated subsurface zone at all temperatures for three different soil types, but gas mobilization only occurred at higher temperatures. Soils with lower entry pressures experienced more frequent mobilization events leading to a greater contaminant impacted area. Gas expansion and mobilization in high entry pressure soils led to a significant amount of mass removal from the heated zone, especially at low groundwater velocities, showing that the formation of a discrete gas phase in low permeability soils could be an important mass transport mechanism during thermal remediation. Current conceptual (and computer) models do not include the formation and transport of discrete gas bubbles. However, this study showed that aqueous concentrations could be significantly increased if discrete gas bubble formation and mobilization occurred. This would be especially true for low entry pressure soils where gas mobilization could result in widespread contamination.

Krol, M. M.; Mumford, K. G.; Johnson, R. L.; Sleep, B. E.

2010-12-01

209

ENGINEERING DEVELOPMENT OF SLURRY BUBBLE COLUMN REACTOR (SBCR) TECHNOLOGY  

SciTech Connect

The major technical objectives of this program are threefold: (1) to develop the design tools and a fundamental understanding of the fluid dynamics of a slurry bubble column reactor to maximize reactor productivity, (2) to develop the mathematical reactor design models and gain an understanding of the hydrodynamic fundamentals under industrially relevant process conditions, and (3) to develop an understanding of the hydrodynamics and their interaction with the chemistries occurring in the bubble column reactor. Successful completion of these objectives will permit more efficient usage of the reactor column and tighter design criteria, increase overall reactor efficiency, and ensure a design that leads to stable reactor behavior when scaling up to large diameter reactors. The past three months of research have been focused on two major areas of bubble column hydrodynamics: (1) pressure and temperature effects on gas holdup and (2) region transition using a sparger as a gas distributor.

Bernard A. Toseland, Ph.D.

1999-03-01

210

A Model for Surface Induced Growth of Inert Gas Bubbles in Irradiated Copper-Boron Alloys  

SciTech Connect

A matrix containing inert gas bubbles dilates in direct proportion to the growth experienced by the gas bubbles. This phenomenon is termed as swelling. A model for the swelling induced by the growth of the helium gas bubbles in irradiated copper-boron alloys is presented. The bubbles grow by acquiring vacancies from the external surface, which acts as a source of vacancies. The vacancies reach the surface of the bubbles mainly via lattice diffusion and to a limited extent via diffusion through short-circuiting paths such as grain boundaries and dislocation pipes. The model predicts that overall swelling of the matrix varies as 1.5 power of time. Another consequence of the present model is that the growth rate of a gas bubble varies inversely as the cube of its distance from the external surface. The model has been applied to the data on irradiated copper-boron alloys and found to be in accord with the experimental results. The model is general and can be applied to the growth of all kinds of stationary inert gas bubbles trapped within a crystalline matrix. (authors)

Tiwari, G.P.; Ramadasan, E. [Post Irradiation Examination Division, Bhabha Atomic Research Division (India)

2006-07-01

211

A level set numerical method to determine the dynamics of gas bubbles in inclined channels  

NASA Astrophysics Data System (ADS)

The dynamics of a gas bubble rising in vertical and inclined channels is investigated. The solution of this free boundary problem is determined numerically by using a level set method coupled with a finite difference solution of the Navier-Stokes equations. The numerical method is second order in space. Both two- and three-dimensional results will be discussed as a function of Reynolds number, Bond number, and inclination angle. Steady solutions are found for small values of all these parameters, and path and shape oscillations are observed as these parameters are increased. The effect of inclination angle is investigated for freely rising bubbles and for bubbles initially attached to the channel wall. In the latter case, the contact line problem is solved by introducing a Navier slip boundary condition along with a fixed contact angle. The bubble is observed to rupture at high Bond numbers. At high Reynolds numbers, when the inclination angle is also above a critical value, the steady solution is found to bifurcate into a time-periodic oscillation. The results presented here parallel experimental work that has found a critical inclination angle at which the dynamics changes from steadily rising bubbles to bouncing bubbles. Three-dimensional simulations have been conducted for bubbles in vertical channels. At higher Reynolds number, the initially spherical bubble deforms into an oblate ellipsoidal shape, and a path instability is found when the bubble's aspect ratio exceeds a critical threshold. The density and viscosity ratios between the bubble and the suspending fluid are varied and are found to affect the bubble dynamics. In addition, the bubble's wake is visualized, and a double-threaded wake of counter-rotating vortex filaments is observed behind a zigzagging bubble.

Norman, Catherine Eleanor

212

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

NASA Astrophysics Data System (ADS)

Fission gas bubbles are one of the evolving microstructures that affect thermal mechanical properties, such as thermal 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 phase-field model was developed to describe the evolution kinetics of intragranular 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 nucleus size of gas bubbles and gas bubble evolution were simulated. A linear relationship between logarithmic bubble number density and logarithmic mean bubble diameter was predicted, which is in good agreement with experimental data.

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

2013-05-01

213

Perturbed breakup of gas bubbles in water: Memory, gas flow, and coalescence  

Microsoft Academic Search

The pinch-off of an air bubble from an underwater nozzle ends in a singularity with a remarkable sensitivity to a variety of perturbations. I report on experiments that break both the axial (i.e., vertical) and azimuthal symmetry of the singularity formation. The density of the inner gas influences the axial asymmetry of the neck near pinch-off. For denser gases, flow

Nathan C. Keim

2011-01-01

214

Hydrodynamic characterization of slurry bubble-column reactors for Fischer-Tropsch synthesis  

SciTech Connect

In the Fischer-Tropsch approach to indirect liquefaction, slurry bubble-column reactors (SBCRs) are used to convert coal syngas into the desired product. Sandia`s program to develop, implement, and apply diagnostics for hydrodynamic characterization of SBCRs at industrially relevant conditions is discussed.Gas-liquid flow experiments are performed in an industrial-scale stainless steel vessel. Gamma-densitometry tomography (GDT) is applied to make spatially resolved gas holdup measurements. Both water and Drakeol 10 with air sparging are examined at ambient and elevated pressures. Gas holdup increases with gas superficial velocity and pressure, and the GDT values are in good agreement with values from differential pressure (DP) measurements.

Jackson, N.B.; Torczynski, J.R.; Shollenberger, K.A.; O`Hern, T.J.; Adkins, D.R.

1996-08-01

215

Studies on impeller type, impeller speed and air flow rate in an industrial scale flotation cell. Part 4: Effect of bubble surface area flux on flotation performance  

Microsoft Academic Search

The metallurgical performance of a 2.8m3 portable industrial scale flotation cell was measured when treating zinc cleaner feed at Hellyer concentrator in Tasmania, Australia. The cell was fitted in turn with four different impeller-stator systems and operated over a wide range of air flow rates and impeller speeds. Bubble size, gas holdup and superficial gas velocity were measured at each

B. K. Gorain; J. P. Franzidis; E. V. Manlapig

1997-01-01

216

Self-organization of voids, gas bubbles and dislocation patterns under irradiation  

Microsoft Academic Search

In the present paper three examples of self-organization in solids under irradiation are considered on the basis of original mechanisms, namely, the ordering of voids in void lattices under high temperature irradiation, the alignment of gas bubbles in bubble lattices under low-temperature gas atom implantation, and the formation of superdislocations (one-dimensional pile-ups of dislocation loops) and other dislocation patterns in

V. I. Dubinko; A. A. Turkin

1993-01-01

217

Ebullition of methane-containing gas bubbles from near-surface Sphagnum peat  

Microsoft Academic Search

To date, very little information has been available on the build-up and release of biogenic gas bubbles in poorly-decomposed bog peats near the peatland surface (upper 1 m). We investigated the importance of ebullition of biogenic gas bubbles as a mechanism for the transport of CH4 to the atmosphere in eight cores (24 cm diameter, 22 cm depth) of poorly-decomposed,

Andrew J. Baird; Clive W. Beckwith; Susan Waldron; J. M. Waddington

2004-01-01

218

Inert-gas-bubble formation in the implanted metal\\/Si system  

Microsoft Academic Search

Inert-gas-bubble formation has been observed as a result of ion bombardment of thin metal films (Cr, V, Ni, Ti, or Pd) deposited on Si substrates. Rutherford backscattering measurements and cross-sectional transmission electron microscopic analyses indicated that the gas bubbles were formed predominantly near the interface between the Si substrate and the surface layer. In addition, pronounced mixing between Si and

B. Y. Tsaur; Z. L. Liau; J. W. Mayer; T. T. Sheng

1979-01-01

219

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

SciTech Connect

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 grain boundaries for given grain boundary properties. More validation of the model capability in polycrystalline is underway.

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

2012-05-30

220

Carbonic Anhydrase Activities from the Rainbow Trout Lens Correspond to the Development of Acute Gas Bubble Disease  

Microsoft Academic Search

Dissolved gas supersaturation is hazardous to fish and can result in gas bubble disease (GBD). Signs of GBD typically include bubbles in the eyes, fins, skin, lateral line, and gill filaments. Ocular abnormalities in diseased salmonids typically occur after aberrant gas production in the eyes. In this study, freshwater rainbow trout Oncorhynchus mykiss were exposed experimentally to percent total gas

Nejdet Gültepe; Orhan Ate?; Olcay Hisar; ?ükrü Beydemir

2011-01-01

221

Effects of Intergranular Gas Bubbles on Thermal Conductivity  

SciTech Connect

Model microstructures obtained from phase-field simulations are used to study the effective heat transfer across bicrys- tals with stationary grain boundary bubble populations. We find that the grain boundary coverage, irrespective of the intergranular bubble radii, is the most relevant parameter to the thermal resistance, which we use to derive effec- tive Kapitza resistances that are dependent on the grain boundary coverage and Kaptiza resistance of the intact grain boundary. We propose a model to predict thermal conductivity as a function of porosity, grain-size, Kaptiza resistance of the intact grain boundary, and grain boundary bubble coverage.

K. Chockalingam; Paul C. Millett; M. R. Tonks

2012-11-01

222

Dynamics of biogenic gas bubbles in peat: Potential effects on water storage and peat deformation  

Microsoft Academic Search

Dynamics of biogenic bubbles in peat soils were studied at a field site in southern Québec, Canada. The maximum gas content measured in this study varied spatially with a maximum seasonal increase in volumetric gas content of 0.15. The size of changes in total gas content of a 1 m deep profile was comparable to the seasonal water storage change.

E. Kellner; J. M. Waddington; J. S. Price

2005-01-01

223

Cladding Deformation due to Gas Bubble Swelling of UO2 Pellet in Bump Test  

Microsoft Academic Search

Fission gas release in the bump tests was correlated to the deformations of claddings via mathematical product of the number of gas atoms and their residing time on grain boundaries. A positive correlation of the deformations with the product indicated that gas bubble swelling of pellets contributed to the pellet-cladding mechanical interaction (PCMI).Residual gaps prior to the bump tests turned

Toshiaki KOGAI; Yoshihiko IWANO

1990-01-01

224

Plumes of bubbles release methane gas from the seabed along the West Spitsbergen continental margin  

Microsoft Academic Search

Over 250 plumes of gas bubbles have been discovered emanating from the seabed of the West Spitsbergen continental margin, at and above the upper limit of the gas hydrate stability zone (GHSZ), at depths of 150-400 m. Some plumes extend upward to within 50 m of the sea surface. The gas is predominantly methane, and seismic reflection data indicate free

G. K. Westbrook

2009-01-01

225

Light emission of sonoluminescent bubbles containing a rare gas and water vapor.  

PubMed

We present numerical simulations of sonoluminescent rare-gas bubbles in water, which account for (i) time variations of the water vapor content, (ii) chemical reactions, and (iii) the ionization of the rare gas and the H2O dissociation products. Peak temperatures exceed 10 000 K at densities of a few hundred amagat ( approximately 10(28) particles per m(3)). The gas mixture in the bubble is weakly ionized. Our model accounts for the light emission by electron-atom, electron-ion, and ion-atom bremsstrahlung, recombination radiation, and radiative attachment of electrons to hydrogen and oxygen atoms, which are all more or less important for single bubble sonoluminescence. Spectral shapes, spectral intensities, and durations of the light pulses are computed for helium, argon, and xenon bubbles. We generally obtain good agreement with the observations for photon numbers and pulse durations. Some calculated spectral profiles agree, however, less well with observations, especially in the case of the low water temperature and for helium bubbles. We try to identify the reasons why computed and observed spectral profiles might discernibly differ when all other computed features considered here seem to be quite consistent with observations. We show that by allowing the bubble to heat somewhat nonisotropically, agreement between observed and computed spectral profiles may be obtained, even in the case of helium bubbles at freezing water temperatures. In this case, charge exchange radiation and related processes involving helium atoms and ions become important. PMID:12006015

Hammer, Dominik; Frommhold, Lothar

2002-04-11

226

The Migration and Coalescence of Inert Gas Bubbles in Metals  

Microsoft Academic Search

Thin copper films containing 0.1 atomic percent of helium, introduced by bombardment with 38 MeV alpha-particles, have been pulse-heated at ~ 800 ^circC in the electron microscope and the small helium bubbles which formed were observed and photographed after successive pulses. The bubbles could be seen to move through the copper with velocities ~ 1000 {circ}{ A}, exploding when they

R. S. Barnes; D. J. Mazey

1963-01-01

227

Gas accumulation in particle-rich suspensions and implications for bubble populations in crystal-rich magma  

NASA Astrophysics Data System (ADS)

Gas mobility plays an important role in driving volcanic eruptions and controlling eruption style. The explosivity of an eruption depends, among other factors, on how easily gas can escape from the magma. Many magmatic systems have high concentrations of suspended crystals that inhibit gas migration through the melt. We use suspensions of plastic beads in corn syrup to investigate interactions between rising bubbles and particles. We observe different interaction styles as the ratio ? of bubble to particle size is varied. Large bubbles (? > 1) deform and sometimes break up as they move around particles. Small bubbles (? < 1) are frequently trapped within the suspension, increasing the concentration of gas held within the system. We compare our experiments to bubble populations in tephra from Stromboli volcano, Italy. We show that these samples typically have bubbles and crystals of similar sizes and suggest that crystals might play a role in controlling bubble size in this natural system as well as in our experiments. Because small bubbles (? < 1) get trapped within the suspension, and can be formed by breakup of larger bubbles, we expect that an increase in gas flux will result in an increase in the population of small bubbles. Changes in bubble number density and vesicularity in tephra erupted during periods of different eruptive intensity may thus provide a way of tracking changes in gas flux through the magma prior to eruption.

Belien, Isolde B.; Cashman, Katharine V.; Rempel, Alan W.

2010-08-01

228

Acoustic emission associated with the bursting of a gas bubble at the free surface of a non-Newtonian fluid  

Microsoft Academic Search

We report experimental measurements of the acoustic emission associated with the bursting of a gas bubble at the free surface of a non-Newtonian fluid. On account of the viscoelastic properties of the fluid, the bubble is generally elongated. The associated frequency and duration of the acoustic signal are discussed with regard to the shape of the bubble and successfully accounted

Thibaut Divoux; Valérie Vidal; Francisco Melo; J.-C. Géminard

2008-01-01

229

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

SciTech Connect

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.

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

1986-06-01

230

Experimental studies of a strongly shocked gas bubble  

NASA Astrophysics Data System (ADS)

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).

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

2004-11-01

231

Effects of Ozone-Gas Bubble Size and pH on Ozone\\/UV Treatment  

Microsoft Academic Search

A series of ozone\\/UV treatment under injection of ozone with different ozone-gas bubble sizes was performed at pH 1.7 and 7.4. The increase in the bubble size and the decrease in pH enhanced the ozone utilization efficiency. The enhancement of ozone utilization efficiency was caused by the shift of the production pathway of hydroxyl radical (OH) from the OH production

Naoyuki Kishimoto; Eri Nakamura

2011-01-01

232

Electrical and spectroscopic characterization of underwater plasma discharge inside rising gas bubbles  

Microsoft Academic Search

The generation of high-energetic species in plasma by discharge in liquids makes it suitable for applications such as water treatment. Effective reduction of input power and an increase in the process efficiency can be achieved by externally generated gas bubbles introduced in the liquid. Pulsed discharge in nitrogen, helium and argon bubbles in between a pin-to-plate electrode system submerged in

Patrick Vanraes; Anton Nikiforov; Christophe Leys

2012-01-01

233

MESO-SCALE MODELING OF THE INFLUENCE OF INTERGRANULAR GAS BUBBLES ON EFFECTIVE THERMAL CONDUCTIVITY  

SciTech Connect

Using a mesoscale modeling approach, we have investigated how intergranular fission gas bubbles, as observed in high-burnup nuclear fuel, modify the effective thermal conductivity in a polycrystalline material. The calculations reveal that intergranular porosity has a significantly higher resistance to heat transfer compared to randomly-distributed porosity. A model is developed to describe this conductivity reduction that considers an effective grain boundary Kapitza resistance as a function of the fractional coverage of grain boundaries by bubbles.

Paul C. Millett; Michael Tonks

2011-06-01

234

Holdup measurement for nuclear fuel manufacturing plants  

SciTech Connect

The assay of nuclear material holdup in fuel manufacturing plants is a laborious but often necessary part of completing the material balance. A range of instruments, standards, and a methodology for assaying holdup has been developed. The objectives of holdup measurement are ascertaining the amount, distribution, and how firmly fixed the SNM is. The purposes are reconciliation of material unbalance during or after a manufacturing campaign or plant decommissioning, to decide security requirements, or whether further recovery efforts are justified.

Zucker, M.S.; Degen, M.; Cohen, I.; Gody, A.; Summers, R.; Bisset, P.; Shaub, E.; Holody, D.

1981-07-13

235

Bubble dispersion and coalescence in turbulent pipe flow  

NASA Astrophysics Data System (ADS)

An experiment for investigating bubble coalescence rate in turbulent pipe flow was designed based on measuring evolution of the specific interfacial area at two locations along the pipeline. A broad range of operating conditions (i.e. 0.008 < phiG < 0.5, 4 < epsilonp < 26 w/kg, 25 mum < d32 < 8,700 mum, and sodium dodecyl sulfate (SDS) concentration range of 0--50 ppm) were investigated. Three bubble coalescence rates were developed based on the temporal rate of variation of Sauter mean diameter, specific interfacial area, and bubble population density and the resulting findings were discussed in terms of hydrodynamic factors (including gas hold-up, energy dissipation rate and bubble size) and interfacial properties. The bubble coalescence rate was found to increase as the gas hold-up and the energy dissipation rate increase, and decrease as the bubble size and SAA concentration increase. Compared to tap water, the normalized coalescence rates were found to decrease radically by the presence of minute dosage of SAA due to the decisive role interfacial characteristics play. The exponential format of interfacial parameters can be used to characterize their effect on bubble coalescence processes, which implies that the interfacial characteristics affect the bubble coalescence through influencing coalescence efficiency which leads to decreasing bubble coalescence rate in gas/liquid turbulent flow. A theoretical collision model was adapted to the case of bubble coalescence rate in turbulent two-phase flow in pipes, and the resulting expression was found to apply not only to pure water system but also to contaminated streams displaying surface activity. The use of different interfacial parameters (such as the static surface tension, surface pressure, Gibbs surface excess and surface excess based on long-term approximation) to explain how SAA retards bubble coalescence rate was evaluated and it was found although the dimensionless forms of these interfacial parameters are correlated with bubble coalescence rate for SDS aqueous solutions to the similar degrees, the surface excess based on the long-term approximation could prevail due to its revealing the underlying mechanism of coalescence hindrance. Factors affecting bubble dispersion and sparger performance were systematically investigated though the use of a 25.4 mm pipe loop in which liquid velocities of up to 3.2 m/s, and gas holdup varying between 0.008 and 0.5 were tested. Trace dosage of either MIBC or SDS was added to simulate the industrial streams. The use of novel dynamic spargers results in the formation of large interfacial area of contact (up to 5,400 m2/m3) and small bubbles (d32 down to 25 mum). The efficiency by which dynamic spargers utilize energy for the formation of interfacial area was found to be one order of magnitude higher than that obtained in mechanically-agitated tanks and traditional pipe nozzles, and more efficient than some of the commonly used static mixers operating at the same power input per unit mass of the stream processed. The interfacial area and the Sauter mean bubble size can be predicted by using correlation equations for MIBC and SDS aqueous solutions. (Abstract shortened by UMI.)

Luo, Jianjun

2002-04-01

236

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

SciTech Connect

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).

Maule, Alec G.; Beeman, John W.; Hans, Karen M.; Mesa, M.G.; Haner, P.; Warren, J.J. [Geological Survey, Cook, WA (United States). Columbia River Research Lab.

1997-10-01

237

Characterization of intergranular fission gas bubbles in U-Mo fuel  

Microsoft Academic Search

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

Y. S. Kim; G. Hofman; J. Rest; G. V. Shevlyakov; SSCR RIAR

2008-01-01

238

Numerical simulation of a strongly shocked gas bubble  

NASA Astrophysics Data System (ADS)

Numerical simulations for 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 perifery of the disk which entrains outside fluid into the argon. Computational and experimental studies with strong shocks hope to bridge the gap between traditional shock tube experiments (low M) and laser driven experiments. Computational results in 2D and 3D are compared to planar images from shock tube experiments. The early time epoch of bubble compression is simulated accurately in either 2D or 3D, however, at later stages azimuthal symmetry is lost due to a hydrodynamic instability in the vortex ring (Widnall). Simulations are also performed on a spherical bubble with a ``droplet'' of excess film that results in a strong upstream jet observed experimentally. This jet results in additional Rayleigh-Taylor and Kelvin-Helmholtz instabilites and may help explain the jetting observed following core-collapse in a supernova. The computations are performed using the Raptor code (LLNL) which solves the full Navier-Stokes equations using the Piecewise Linear Method (PLM) with Adaptive Mesh Refinement (AMR).

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

2004-11-01

239

Circulation of bubbly magma and gas segregation within tunnels of the potential Yucca Mountain repository  

NASA Astrophysics Data System (ADS)

Following an intersection of rising magma with drifts of the potential Yucca Mountain nuclear waste repository, a pathway is likely to be established to the surface with magma flowing for days to weeks and affecting the performance of engineered structures located along or near the flow path. In particular, convective circulation could occur within magma-filled drifts due to the exsolution and segregation of magmatic gas. We investigate gas segregation in a magma-filled drift intersected by a vertical dyke by means of analogue experiments, focusing on the conditions of sustained magma flow. Degassing is simulated by electrolysis, producing micrometric bubbles in viscous mixtures of water and golden syrup, or by aerating golden syrup, producing polydisperse bubbly mixtures with 40% of gas by volume. The presence of exsolved bubbles induces a buoyancy-driven exchange flow between the dyke and the drift that leads to gas segregation. Bubbles segregate from the magma by rising and accumulating as a foam at the top of the drift, coupled with the accumulation of denser degassed magma at the base of the drift. Steady-state influx of bubbly magma from the dyke into the drift is balanced by outward flux of lighter foam and denser degassed magma. The length and time scales of this gas segregation are controlled by the rise of bubbles in the horizontal drift. Steady-state gas segregation would be accomplished within hours to hundreds of years depending on the viscosity of the degassed magma and the average size of exsolved gas bubbles, and the resulting foam would only be a few cm thick. The exchange flux of bubbly magma between the dyke and the drift that is induced by gas segregation ranges from 1 m3 s-1, for the less viscous magmas, to 10-8 m3 s-1, for the most viscous degassed magmas, with associated velocities ranging from 10-1 to 10-9 m s-1 for the same viscosity range. This model of gas segregation also predicts that the relative proportion of erupted degassed magma, that could potentially carry and entrain nuclear waste material towards the surface, would depend on the value of the dyke magma supply rate relative to the value of the gas segregation flux, with violent eruption of gassy as well as degassed magmas at relatively high magma supply rates, and eruption of mainly degassed magma by milder episodic Strombolian explosions at relatively lower supply rates.

Menand, Thierry; Phillips, Jeremy C.; Sparks, R. Stephen J.

2008-07-01

240

Bubble Continuous Positive Airway Pressure Enhances Lung Volume and Gas Exchange in Preterm Lambs  

PubMed Central

Rationale: The technique used to provide continuous positive airway pressure (CPAP) to the newborn may influence lung function and breathing efficiency. Objectives: To compare differences in gas exchange physiology and lung injury resulting from treatment of respiratory distress with either bubble or constant pressure CPAP and to determine if the applied flow influences short-term outcomes. Methods: Lambs (133 d gestation; term is 150 d) born via cesarean section were weighed, intubated, and treated with CPAP for 3 hours. Two groups were treated with 8 L/minute applied flow using the bubble (n = 12) or the constant pressure (n = 12) technique. A third group (n = 10) received the bubble method with 12 L/minute bias flow. Measurements at study completion included arterial blood gases, oxygraphy, capnography, tidal flow, multiple breath washout, lung mechanics, static pressure–volume curves, and bronchoalveolar lavage fluid protein. Measurements and Main Results: Birth weight and arterial gas variables at 15 minutes were comparable. Flow (8 or 12 L/min) did not influence the 3-hour outcomes in the bubble group. Bubble technique was associated with a higher pH, PaO2, oxygen uptake, and area under the flow–volume curve, and a decreased alveolar protein, respiratory quotient, PaCO2, and ventilation inhomogeneity compared with the constant pressure group. Conclusions: Compared with constant pressure technique, bubble CPAP promotes enhanced airway patency during treatment of acute postnatal respiratory disease in preterm lambs and may offer protection against lung injury.

Pillow, J. Jane; Hillman, Noah; Moss, Timothy J. M.; Polglase, Graeme; Bold, Geoff; Beaumont, Chris; Ikegami, Machiko; Jobe, Alan H.

2007-01-01

241

Radial variations of melt viscosity around growing bubbles and gas overpressure in vesiculating magmas  

NASA Astrophysics Data System (ADS)

The viscosity of silicic melts depends strongly on their water content. As bubbles grow in a supersaturated melt, water evaporates from the bubble-melt interface. A diffusive profile develops and leads to steep viscosity gradients across the melt shell. Here we investigate the effects of radial viscosity profiles on the dynamics of bubble growth. We find that the effective melt viscosity resisting gas overpressure in the bubbles is close to the viscosity at the dehydrated rind, and may be higher than that of the surrounding melt by more than an order of magnitude. As a result, bubbles may retain pressures that are higher than ambient pressure for longer times, magma degassing is delayed to shallower depth, and fragmentation of magma due to gas overpressure may occur over a wider range of conditions. Measured water content in eruption products yields information on the average melt viscosity, however additional information about the concentration profiles is needed for estimating the effective viscosity that controlled the evolution of bubble growth in the ejecta.

Lensky, Nadav G.; Lyakhovsky, Vladimir; Navon, Oded

2001-03-01

242

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

SciTech Connect

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.

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

2012-11-01

243

Evolution of a gas bubble in porous matrix filled by methane hydrate  

NASA Astrophysics Data System (ADS)

Behavior of a small isolated hydrate-free inclusion (a bubble) within hydrate-bearing porous matrix is studied analytically and numerically. An infinite porous matrix of uniform properties with pores filled by methane hydrates and either water (excessive water situation) or methane gas (excessive gas situation) is considered. A small spherical hydrate-free bubble of radius R0 exists at initial moment within the matrix due to overheating relative to the surrounding medium. There is no continuing heat supply within the bubble, so new hydrate forms on its boundary, and its radius decreases with time. The process is analysed in the framework of the model that takes into account the phase transition and accompanying heat and mass transport processes and assumes spherical symmetry. It is shown that in the case of small (~ 10-2-10-1 m) bubbles, convective fluxes are negligible and the process is fully described by heat conduction and phase change equations. A spherically symmetric Stefan problem for purely conduction-controlled evolution is solved analytically for the case of equilibrium initial temperature and pressure within the bubble. The self-similar solution is verified, with good results, in numerical simulations based on the full filtration and heat transfer model and using the isotherm migration method. Numerical simulations are also conducted for a wide range of cases not amenable to analytical solution. It is found that, except for initial development of an overheated bubble, its radius evolves with time following the self-similar formula: R(t) ( t)1-2 R0-= 1 - tm- , (1) where tm is the life-time of bubble (time of its complete freezing). The analytical solution shows that tm follows 2 tm ~ (R0-?) , (2) where ? is a constant determined by the temperature difference ?T between the bubble's interior and far field. We consider implications for natural hydrate deposits. As an example, for a bubble with R0 = 4 cm and ?T = 0.001 K, we find tm ~ 5.7 ? 106 s (2 months) in a water excess system, and ~ 2.9 ? 107 s (11 months) in a gas excess system. Motion of the bubble is not considered in our study, but it can be estimated that at the typical velocity of buoyancy-driven transport, a small bubble does not move a significant distance over its life-time and, thus, cannot survive filtration through the hydrate stability zone. Work was financially supported by the Civilian Research and Development Foundation (Grant RUP1-2945-PE-09) and the Russian Foundation for Basic Research (Grant 09-01-92505).

Tsiberkin, Kirill; Lyubimov, Dmitry; Lyubimova, Tatyana; Zikanov, Oleg

2013-04-01

244

Model of coupled pulsation and translation of a gas bubble and rigid particle  

PubMed Central

A model of the interaction of a spherical gas bubble and a rigid spherical particle is derived as a coupled system of second-order differential equations using Lagrangian mechanics. The model accounts for pulsation and translation of the bubble as well as translation of the particle in an infinite, incompressible liquid. The model derived here is accurate to order R5?d5, where R is a characteristic radius and d is the separation distance between the bubble and particle. This order is the minimum accuracy required to account for the interaction of the bubble and particle. Dependence on the size and density of the particle is demonstrated through numerical integration of the dynamical equations for both the free and forced response of the system. Numerical results are presented for models accurate to orders higher than R5?d5 to demonstrate the consequences of truncating the equations at order R5?d5.

Hay, Todd A.; Hamilton, Mark F.; Ilinskii, Yurii A.; Zabolotskaya, Evgenia A.

2009-01-01

245

Development of the Liposomes Entrapped Ultrasound Imaging Gas (``Bubble Liposomes'') as Novel Gene Delivery Carriers  

NASA Astrophysics Data System (ADS)

Recently, microbubbles and ultrasound have been investigated with a view to improving the transfection efficiency of nonviral delivery systems for gene by cavitation. However, microbubbles had some problems in terms of stability and targeting ability. To solve these problems, we paid attention to liposomes that had many advantages such as stable and safe in vivo and easy to modify targeting ligand. Previously, we have represented that liposomes are good drug and gene delivery carriers. In addition, we developed that the liposomes (``Bubble liposomes'') were entrapped with perfluoropropane known as ultrasound imaging gas. In this study, we assessed about feasibility of ``Bubble liposomes'' as gene delivery tool utilized cavitation by ultrasound irradiation. ``Bubble liposomes'' could effectively deliver plasmid DNA to cells by combination of ultrasound irradiation without cyototoxicity. This result suggested that ``Bubble liposomes'' might be a new class of tool for gene delivery.

Suzuki, Ryo; Tanaka, Kumiko; Sawamura, Kaori; Takizawa, Tomoko; Utoguchi, Naoki; Negishi, Yoichi; Hagisawa, Kohsuke; Nishioka, Toshihiko; Maruyama, Kazuo

2006-05-01

246

Effects of gas bubbles on the current and potential profiles within porous flow-through electrodes  

Microsoft Academic Search

This paper presents a mathematical model to calculate the distributions of currenti(x), potentialE(x), gas void fraction e(x) and pore electrolyte resistivity ?(x) within porous flow-through electrodes producing hydrogen. It takes into consideration the following effects: (i) the kinetics of the interfacial charge transfer step, (ii) the effect of the non-uniformly generated gas bubbles on the resistivity of the gas-electrolyte dispersion

B. E. El-Anadouli; B. G. Ateya

1992-01-01

247

Promotion of gas bubble formation by ingested nuclei in the ciliate, Tetrahymena pyriformis  

Microsoft Academic Search

Cells of the ciliateTetrahymena pyriformis were suspended with carmine or graphite particles or with Halobacterium gas vesicles, all of which promote bubble formation\\u000a in aqueous suspensions when tested with 10 atm and above (0.1?0.5×107 Pa) (carmine and graphite) or 25 atm and above (gas vesicles) of nitrogen supersaturations. All three particles were ingested,\\u000a but only the gas vesicles promoted intracellular

Barbara B. Hemmingsen

1986-01-01

248

Gas-bubble effects on the formation of colloidal iron oxide nanocrystals.  

PubMed

This paper reports that gas bubbles can be used to tailor the kinetics of the nucleation and growth of inorganic-nanocrystals in a colloidal synthesis. We conducted a mechanistic study of the synthesis of colloidal iron oxide nanocrystals using gas bubbles generated by boiling solvents or artificial Ar bubbling. We identified that bubbling effects take place through absorbing local latent heat released from the exothermic reactions involved in the nucleation and growth of iron oxide nanocrystals. Our results show that gas bubbles display a stronger effect on the nucleation of iron oxide nanocrystals than on their growth. These results indicate that the nucleation and growth of iron oxide nanocrystals may rely on different types of chemical reactions between the iron-oleate decomposition products: the nucleation relies on the strongly exothermic, multiple-bond formation reactions, whereas the growth of iron oxide nanocrystals may primarily depend upon single-bond formation reactions. The identification of exothermic reactions is further consistent with our results in the synthesis of iron oxide nanocrystals with boiling solvents at reaction temperatures ranging from 290 to 365 °C, by which we determined the reaction enthalpy in the nucleation of iron oxide nanocrystals to be -142 ± 12 kJ/mol. Moreover, our results suggest that a prerequisite for effectively suppressing secondary nucleation in a colloidal synthesis is that the primary nucleation must produce a critical amount of nuclei, and this finding is important for a priori design of colloidal synthesis of monodispersed nanocrystals in general. PMID:21702497

Lynch, Jared; Zhuang, Jiaqi; Wang, Tie; LaMontagne, Derek; Wu, Huimeng; Cao, Y Charles

2011-07-22

249

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

NASA Astrophysics Data System (ADS)

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.

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

2012-10-01

250

Enhancement of microplasma-based water-solubilization of single-walled carbon nanotubes using gas bubbling in water  

Microsoft Academic Search

The authors have previously proposed a novel technique for the preparation of water-soluble carbon nanotubes (CNTs) using microplasma generated by a pulsed streamer discharge in water. This paper describes an improvement in the method of the microplasma-based CNT solubilization process by the use of gas bubbling in water. Oxygen, argon and nitrogen were used as bubbling gas in order to

Kiminobu Imasaka; Yuki Kato; Junya Suehiro

2007-01-01

251

Self-Pulsing Regime of DC Electric Discharge in Dielectric Tube Filled With Water Containing Gas Bubble  

Microsoft Academic Search

Effective generation of biochemically active species inside a liquid can be performed by an electric discharge in small gas bubbles admixed from outside into the liquid. In such a case, active species are produced by a gas discharge plasma inside bubbles and then transported due to diffusion into the liquid. This paper presents experimental data of electric discharges in small

Yuri Akishev; Michail Grushin; Vlad Karalnik; Anton Monich; Alex Petryakov; Nikolay Trushkin

2008-01-01

252

Numerical study of wall effects on buoyant gas-bubble rise in a liquid-filled finite cylinder  

Microsoft Academic Search

The wall effects on the axisymmetric rise and deformation of an initially spherical gas bubble released from rest in a liquid-filled, finite circular cylinder are numerically investigated. The bulk and gas phases are considered incompressible and immiscible. The bubble motion and deformation are characterized by the Morton number (Mo), Eötvös number (Eo), Reynolds number (Re), Weber number (We), density ratio,

Karthik Mukundakrishnan; Shaoping Quan; David M. Eckmann; Portonovo S. Ayyaswamy

2007-01-01

253

Effect of viscoelastic properties of a liquid on the dynamics of small oscillations of a gas bubble  

Microsoft Academic Search

A series of papers has been devoted to questions of gas bubble dynamics in viscoeiastic liquids. Of these papers we mention [1 4]. The radial oscillations of a gas bubble in an incompressible viscoeiastic liquid have been studied numerically in [1, 2] using Oldroyd's model [5]. Anexact solution was found in [3], and independently in [4], for the equation of

S. P. Levitskii; A. T. Listrov

1976-01-01

254

Effect of viscoelastic properties of a liquid on the dynamics of small oscillations of a gas bubble  

Microsoft Academic Search

A series of papers has been devoted to questions of gas bubble dynamics in viscoeiastic liquids. Of these papers we mention [1–4]. The radial oscillations of a gas bubble in an incompressible viscoeiastic liquid have been studied numerically in [1, 2] using Oldroyd's model [5]. Anexact solution was found in [3], and independently in [4], for the equation of small

S. P. Levitskii; A. T. Listrov

1976-01-01

255

Effect of Gas Bubbles and Cavity Dimensions on the Local Electrode Potential within Pits, Crevices and Cracks.  

National Technical Information Service (NTIS)

Gas bubbles have been reported to routinely accumulate in cavities during anodic or cathodic polarization in several merals and alloys (Fe, Ni, Cu, Al, stainless steel). These in-place gas bubbles have been found to sharply increase the gradients of poten...

H. W. Pickering

1983-01-01

256

Pressure effects on bubble-column flow characteristics  

SciTech Connect

Bubble-column reactors are used in the chemical processing industry for two-phase and three-phase chemical reactions. Hydrodynamic effects must be considered when attempting to scale these reactors to sizes of industrial interest, and diagnostics are needed to acquire data for the validation of multiphase scaling predictions. This paper discusses the use of differential pressure (DP) and gamma- densitometry tomography (GDT) measurements to ascertain the gas distribution in a two-phase bubble column reactor. Tests were performed on an industrial scale reactor (3-m tall, 0.48-m inside diameter) using a 5-Curie cesium-137 source with a sodium-iodide scintillation detector. GDT results provide information on the time- averaged cross-sectional distribution of gas in the liquid, and DP measurements provide information on the time and volume averaged axial distribution of gas. Close agreement was observed between the two methods of measuring the gas distribution in the bubble column. The results clearly show that, for a fixed volumetric flowrate through the reactor, increasing the system pressure leads to an increase in the gas volume fraction or ``gas holdup`` in the liquid. It is also shown from this work that GDT can provide useful diagnostic information on industrial scale bubble-column reactors.

Adkins, D.R.; Shollenberger, K.A.; O`Hern, T.J.; Torczynski, J.R.

1996-03-01

257

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

NASA Astrophysics Data System (ADS)

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 conditions more than 50% of all produced CH4 partitions to the gas phase or is aerobically oxidised near the water table, suggesting that these processes should be accounted for when assessing the rate and extent of methanogenic degradation of hydrocarbons.

Amos, Richard T.; Ulrich Mayer, K.

2006-09-01

258

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

PubMed

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 conditions more than 50% of all produced CH(4) partitions to the gas phase or is aerobically oxidised near the water table, suggesting that these processes should be accounted for when assessing the rate and extent of methanogenic degradation of hydrocarbons. PMID:16797104

Amos, Richard T; Ulrich Mayer, K

2006-06-22

259

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

SciTech Connect

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 that the site of first bubble appearance is the grain boundary. Analysis using a simple diffusion model showed that, although the difference in the Mo-content between the grain boundary and grain interior region decreased with burnup, a complete convergence in the Mo-content was not reached at the end of the test for all RERTR tests. A total of 13 plates from RERTR-1, 2, 3 and 5 tests with different as-fabrication conditions and irradiation conditions were included for gas bubble analyses. Among them, two plates contained powders {gamma}-annealed at {approx}800 C for {approx}100 hours. Most of the plates were fabricated with as-atomized powders except for two as-machined powder plates. The Mo contents were 6, 7 and 10wt%. The irradiation temperature was in the range 70-190 C and the fission rate was in the range 2.4 x 10{sup 14} - 7 x 10{sup 14} f/cm{sup 3}-s. Bubble size for both of the {gamma}-annealed powder plates is smaller than the as-atomized powder plates. The bubble size for the as-atomized powder plates increases as a function of burnup and the bubble growth rate shows signs of slowing at burnups higher than {approx}40 at% U-235 (LEU). The bubble-size distribution for all plates is a quasi-normal, with the average bubble size ranging 0.14-0.18 {micro}m. Although there are considerable errors, after an initial incubation period the average bubble size increases with fission density and shows saturation at high fission density. Bubble population (density) per unit grain boundary length was measured. The {gamma}-annealed powder plates have a higher bubble density per unit grain boundary length than the as-atomized powder plates. The measured bubble number densities per unit grain boundary length for as-atomized powder plates are approximately constant with respect to burnup. Bubble density per unit cross section area was calculated using the density per unit grain boundary length data. The grains were modeled as tetrakaidecahedrons. Direct measurements for some plates were also performed and compared with the calculated quantities. Bubble density per unit

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

2008-04-14

260

Observation of bubble-involving spontaneous gas dissolution in superheated Al alloy melt  

NASA Astrophysics Data System (ADS)

We present a direct visualization of spontaneous gas dissolution in Al-7.7 mass% Ca eutectic alloy melt during superheating using high-brilliance synchrotron X-ray imaging. A bubble-involving gas dissolution process was observed, which can be understood within the framework of adsorption-diffusion-dissolution mechanism. The heterogenous nucleation and combined effect of hydrogen diffusivity and solubility results in the growth of individual bubbles in a stochastic way with Gaussian distribution. This also applies to the behavior of group bubbles in early stage, while which in final stage can be treated as reverse Ostwald ripening dominated by Lifshitz-Slyozov-Wagner diffusion mechanism when pure diffusive condition is satisfied.

Zhang, S. G.; Zhang, L.; Lu, W. Q.; Zhang, W.; Yu, J. D.; Fu, Y. N.; Li, J. G.

2013-10-01

261

The effect of magma flow on nucleation of gas bubbles in a volcanic conduit  

NASA Astrophysics Data System (ADS)

We solve the dynamics of magma ascent and the kinetics of bubble nucleation and growth simultaneously, which allow us to predict bubble sizes and number densities under ascent conditions. As magma rises toward the surface, the pressure decreases and eventually becomes less than the solubility pressure. When the degree of supersaturation becomes great enough, bubbles nucleate. Nucleation will stop as the concentration of volatiles in the melt decreases due to growth of existing bubbles and hence the degree of supersaturation decreases. We show that a second nucleation event may occur just below the fragmentation level. Near that level, the degree of supersaturation continuously increases as the magma is rapidly decompressed. As a result, nucleation will not stop until fragmentation occurs. This second nucleation event should be taken into account when interpreting bubble size distribution measurements made on natural pumices. The bubbles of the second nucleation event have high internal gas pressures up to 2 MPa greater than the liquid pressure, suggesting that the second nucleation event may enhance fragmentation of magma. We apply the model to the calculation protocol defined at the “Volcanic eruption mechanism modeling workshop, Durham, 2002”. We found that as a result of disequilibrium degassing fragmentation occurs higher in the conduit than under equilibrium degassing.

Massol, Hélène; Koyaguchi, Takehiro

2005-05-01

262

Gas bubbles in rats after heliox saturation and different decompression steps and rates.  

PubMed

Effects of pressure reduction, decompression rate, and repeated exposure on venous gas bubble formation were determined in five groups (GI, GII, GIII, GIV, and GV) of conscious and freely moving rats in a heliox atmosphere. Bubbles were recorded with a Doppler ultrasound probe implanted around the inferior caval vein. Rats were held for 16 h at 0.4 MPa (GI), 0.5 MPa (GII and GIII), 1.7 MPa (GIVa), or 1.9 MPa (GIV and GV), followed by decompression to 0.1 MPa in GI to GIII and to 1.1 MPa in GIV and GV. A greater decompression step, but at the same rate (GII vs. GI and GIVb vs. GIVa), resulted in significantly more bubbles (P < 0.01). A twofold decompression step resulted in equal amount of bubbles when decompressing to 1.1 MPa compared with 0.1 MPa. The faster decompression in GII and GVa (10.0 kPa/s) resulted in significantly more bubbles (P < 0.01) compared with GIII and GVb (2.2 kPa/s). No significant difference was observed in cumulative bubble score when comparing first and second exposure. With the present animal model, different decompression regimes may be evaluated. PMID:12015383

Skogland, Steffen; Segadal, Kåre; Sundland, Harald; Hope, Arvid

2002-06-01

263

The general solution and its analyticity for growth or dissolution of a gas bubble  

Microsoft Academic Search

The isothermal diffusion of a gas bubble in an infinite liquid which is either supersaturated or undersaturated, subject to an arbitrarily prescribed initial condition and the effect of surface tension at the interface, is studied. One of the objectives of the paper is to investigate the analyticity of the solutions. For this purpose, the prescribed initial condition is considered to

L. N. Tao

1979-01-01

264

Detection of small gas bubble using ultrasonic transmission-mode tomography system  

Microsoft Academic Search

This paper presents the development of an ultrasonic transmission-mode tomography system for the detection of small gas bubble using higher frequency ultrasonic sensors. The selection of the sensors is important and must be suitable to the application design. Consideration on the natural limitation of ultrasonic wave is also noted as the higher the frequency of the ultrasonic transducer, the better

N. M. N. Ayob; M. H. F. Rahiman; Z. Zakaria; S. Yaacob; R. A. Rahim

2010-01-01

265

On the stability of gas bubbles oscillating non-spherically in a compressible liquid  

Microsoft Academic Search

This paper describes the non-spherical free and forced oscillations of a gas bubble in a compressible liquid. Generally two different cases of oscillations are possible: spherically radial motion and surface oscillations. The deviation from spherical shape is assumed to be small and is given by a spherical harmonic. Included in the theoretical model are the effect of surface tension, the

H. J. Rath

1981-01-01

266

Multiple voltage electron probe microanalysis of fission gas bubbles in irradiated nuclear fuel  

Microsoft Academic Search

The accurate analysis of locally retained fission gas in nuclear fuel is inherently difficult since the physical form under which it is stored varies from an atomic dispersion to bubbles with a diameter of several hundreds of nanometers. One of the techniques that has been applied since more than 20 yr is electron probe microanalysis (EPMA). This technique, however, is

M. Verwerft

2000-01-01

267

The effect of viscosity on the spherical stability of oscillating gas bubbles  

Microsoft Academic Search

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 @Hilgenfeldt et al.,

Y. Hao; A. Prosperetti

2005-01-01

268

MRI-guided gas bubble enhanced ultrasound heating in in vivo rabbit thigh  

Microsoft Academic Search

In this study, we propose a focused ultrasound surgery protocol that induces and then uses gas bubbles at the focus to enhance the ultrasound absorption and ultimately create larger lesions in vivo. MRI and ultrasound visualization and monitoring methods for this heating method are also investigated. Larger lesions created with a carefully monitored single ultrasound exposure could greatly improve the

S. D. Sokka; R. King; K. Hynynen

2003-01-01

269

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

Microsoft Academic Search

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

Richard T. Amos; K. Ulrich Mayer

2006-01-01

270

Stationary soliton waves in a liquid with heat-conducting gas bubbles  

Microsoft Academic Search

Formation of an undamped soliton wave in the process of propagation of sound perturbations in a liquid with uniformly distributed gas bubbles is first revealed. The stationary soliton wave exists only in the presence of two pairs of competing factors, one of which is a balance between the nonlinearity of the medium and the linear wave dispersion, and another is

D. C. Kim

2006-01-01

271

Fundamental Study of Gas and Vapor Bubble Dynamics in Micro-Channels.  

National Technical Information Service (NTIS)

The aim of this project was to carry out a fundamental study of the basic: Physics underlying the applications of gas and vapor bubbles in heat transfer systems, pumps, actuators, and other small-scale systems. Since these applications require a detailed ...

A. Prosperetti W. N. Sharpe

1999-01-01

272

Friction Drag Reduction of External Flows with Bubble and Gas Injection  

Microsoft Academic Search

The lubrication of external liquid flow with a bubbly mixture or gas layer has been the goal of engineers for many years, and this article presents the underlying principles and recent advances of this technology. It reviews the use of partial and supercavities for drag reduction of axisymmetric objects moving within a liquid. Partial cavity flows can also be used

Steven L. Ceccio

2010-01-01

273

Motion of Spherical Gas Bubbles in a Viscous Liquid at Large Reynolds Numbers  

Microsoft Academic Search

An analysis is made for the motion of a gas bubble rising steadily in a quiescent liquid of infinite extent. The disturbed layer of the fluid, due to viscosity, on either side of the interface is thin when the Reynolds number is sufficiently large and thus makes possible a considerable simplification of the governing equations of motion. Simultaneous solutions of

B. T. Chao

1962-01-01

274

Gas Bubble Trauma Monitoring in the Clearwater River Drainage Idaho 1999.  

National Technical Information Service (NTIS)

A team of two people electroshocked 39 miles of the lower Clearwater River and 1.5 miles of the North Fork Clearwater River below Dworshak Dam during the spring and summer months of 1999. This team monitored gas bubble trauma (GBT) on resident fish specie...

E. Schriever T. Cochnauer T. Feldner

2000-01-01

275

A double layer model of the gas bubble/water interface.  

PubMed

Zeta potential is a physico-chemical parameter of particular importance to describe sorption of contaminants at the surface of gas bubbles. Nevertheless, the interpretation of electrophoretic mobilities of gas bubbles is complex. This is due to the specific behavior of the gas at interface and to the excess of electrical charge at interface, which is responsible for surface conductivity. We developed a surface complexation model based on the presence of negative surface sites because the balance of accepting and donating hydrogen bonds is broken at interface. By considering protons adsorbed on these sites followed by a diffuse layer, the electrical potential at the head-end of the diffuse layer is computed and considered to be equal to the zeta potential. The predicted zeta potential values are in very good agreement with the experimental data of H(2) bubbles for a broad range of pH and NaCl concentrations. This implies that the shear plane is located at the head-end of the diffuse layer, contradicting the assumption of the presence of a stagnant diffuse layer at the gas/water interface. Our model also successfully predicts the surface tension of air bubbles in a KCl solution. PMID:22985594

Leroy, Philippe; Jougnot, Damien; Revil, André; Lassin, Arnault; Azaroual, Mohamed

2012-07-20

276

Experimental simulations of gas-driven eruptions: kinetics of bubble growth and effect of geometry  

Microsoft Academic Search

Simulated gas-driven eruptions using CO2–water-polymer systems are reported. Eruptions are initiated by rapidly decompressing CO2–saturated water containing up to 1.0?wt.% CO2. Both cylindrical test cells and a flask test cell were used to examine the effect of magma chamber\\/conduit geometry on eruption\\u000a dynamics. Bubble-growth kinetics are examined quantitatively in experiments using cylindrical test cells. Uninhibited bubble\\u000a growth can be roughly

Youxue Zhang

1998-01-01

277

Numerical Analysis on the Motion of Gas Bubbles Using Level Set Method  

Microsoft Academic Search

In this paper, we study the behavior of gas bubbles rising through a viscous liquid in a vertical square duct numerically. The level set formulation developed by Sussman et al. is successfully generalized for three-dimensional incompressible two-phase flows including large density and viscosity ratios as well as surface tension effect. Numerical simulations are carried out for gas-liquid flows with different

Hideyuki Oka; Katsuya Ishii

1999-01-01

278

Bubble and bubble cloud dynamics  

NASA Astrophysics Data System (ADS)

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. .

Matsumoto, Yoichiro

2000-07-01

279

Ebullition of methane-containing gas bubbles from near-surface Sphagnum peat  

NASA Astrophysics Data System (ADS)

To date, very little information has been available on the build-up and release of biogenic gas bubbles in poorly-decomposed bog peats near the peatland surface (upper 1 m). We investigated the importance of ebullition of biogenic gas bubbles as a mechanism for the transport of CH4 to the atmosphere in eight cores (24 cm diameter, 22 cm depth) of poorly-decomposed, near-surface bog peat. Ebullition was recorded in all but one sample but varied greatly between samples. Maximum rates of CH4 efflux via ebullition were also highly variable, ranging from 2.2 to 83.0 mg CH4 m-2 day-1. These rates are similar to rates of diffusive CH4 efflux. Our results also show that wetland methane models are likely to need revision because they assume that unrealistically high CH4 pore-water concentrations are required before bubbles can be produced and because, in part, they do not account for gas bubble build-up prior to ebullition.

Baird, Andrew J.; Beckwith, Clive W.; Waldron, Susan; Waddington, J. M.

2004-11-01

280

Evolution of bubbles from gas micronuclei formed on the luminal aspect of ovine large blood vessels.  

PubMed

It has been shown that tiny gas nanobubbles form spontaneously on a smooth hydrophobic surface submerged in water. These nanobubbles were shown to be the source of gas micronuclei from which bubbles evolved during decompression of silicon wafers. We suggest that the hydrophobic inner surface of blood vessels may be a site of nanobubble production. Sections from the right and left atria, pulmonary artery and vein, aorta, and superior vena cava of sheep (n=6) were gently stretched on microscope slides and exposed to 1013 kPa for 18 h. Hydrophobicity was checked in the six blood vessels by advancing contact angle with a drop of saline of 71±19°, with a maximum of about 110±7° (mean±SD). Tiny bubbles ~30 ?m in diameter rose vertically from the blood vessels and grew on the surface of the saline, where they were photographed. All of the blood vessels produced bubbles over a period of 80 min. The number of bubbles produced from a square cm was: in the aorta, 20.5; left atrium, 27.3; pulmonary artery, 17.9; pulmonary vein, 24.3; right atrium, 29.5; superior vena cava, 36.4. More than half of the bubbles were present for less than 2 min, but some remained on the saline-air interface for as long as 18 min. Nucleation was evident in both the venous (superior vena cava, pulmonary artery, right atrium) and arterial (aorta, pulmonary vein, left atrium) blood vessels. This newly suggested mechanism of nucleation may be the main mechanism underlying bubble formation on decompression. PMID:23624230

Arieli, R; Marmur, A

2013-04-25

281

Mass transfer during gas absorption in a vertical gas-liquid slug flow with small bubbles in liquid plugs  

Microsoft Academic Search

A model is developed for the analysis of mass transfer during isothermal absorption in a vertical gas-liquid slug flow at\\u000a large Reynolds numbers with liquid plugs containing small bubbles. Simple formulas for mass flux from the N-th unit cell of gas-liquid slug flow and for total mass flux from N unit cells are derived. In the limiting case the derived

T. Elperin; A. Fominykh

1998-01-01

282

Two-stage process for conversion of synthesis gas to high quality transportation fuels. Quarterly report, 8 June-30 September 1983  

SciTech Connect

The design of two large hot-flow models, to be used for slurry bubble-column hydrodynamic studies, is described. Scoping experiments were performed in smaller models to study the effects of feed-gas distributor type, column diameter, and liquid medium on gas holdup and bubble sizes. In addition, a literature review of bubble-column hydrodynamics is presented. Modifications to improve the operation and flexibility of the existing two stage pilot plant have been designed and construction initiated. Also, a sample of reactor-wax was fractionated under vacuum in a laboratory still. 8 figures, 4 tables.

Kuo, J.C.W.

1983-11-01

283

Sliding of fine particles on the slip surface of rising gas bubbles: Resistance of liquid shear flows  

Microsoft Academic Search

In this paper a model was developed to describe the shear flow resistance force and torque acting on a fine particle as it slides on the slip surface of a rising gas bubble. The shear flow close to the bubble surface was predicted using a Taylor series and the numerical data obtained from the Navier–Stokes equations as a function of

Anh V. Nguyen; Graeme J. Jameson

2005-01-01

284

THE NUCLEATION AND GROWTH OF GAS BUBBLES IN A NEWTONIAN FLUID: AN ENERGETIC VARIATIONAL PHASE FIELD APPROACH  

Microsoft Academic Search

In this paper, we study the nucleation and growth of gas bubbles in a Newtonian fluid. We employ a general energetic variational formulation with a phase-field method, and compare the analytical and numerical predictions of this new formulation with those of classical models. The new approach allows the study of bubble nucleation, growth and coalescence in a unified framework, and

AARON NABER; CHUN LIU; JAMES J. FENG

285

Evolution of a Small Distortion of the Spherical Shape of a Gas Bubble under Strong Expansion-Compression  

Microsoft Academic Search

The evolution of a small distortion of the spherical shape of a gas bubble which undergoes strong radial expansion-compression upon a single oscillation of the ambient liquid pressure under a harmonic law are analyzed by numerical experiments. It is assumed that the distortions of the spherical bubble shape are axisymmetric and have the form of individual spherical surface harmonics with

A. A. Aganin; T. S. Guseva

2005-01-01

286

Gas Injection Into Fractured Reservoirs Above Bubble Point Pressure  

Microsoft Academic Search

Among all enhanced oil recovery (EOR) scenarios, gas injection seems to be promising for implementation in naturally fractured reservoirs. The use of CO2 has received considerable interest as a method of EOR but a major drawback is its availability and increasing cost. Therefore, an alternative gas like CH4 or N2 must be considered to meet the economic considerations. To investigate

P. Heidari; A. Kordestany

2012-01-01

287

Porosity formation and gas bubble retention in laser metal deposition  

Microsoft Academic Search

One of the inherent problems associated with laser metal deposition using gas-assisted powder transfer is the formation of porosity, which can be detrimental to the mechanical properties of the bulk material. In this work, a comprehensive investigation of porosity is carried out using gas atomised Inconel 718 powder. In the analysis, a clear distinction is made between two types of

G. K. L. Ng; A. E. W. Jarfors; G. Bi; H. Y. Zheng

2009-01-01

288

Tracer Techniques in Estimating Nuclear Materials Holdup.  

National Technical Information Service (NTIS)

Residual inventory of nuclear materials remaining in processing facilities (holdup) is recognized as an insidious problem for safety of plant operations and safeguarding of special nuclear materials (SNM). This paper reports on an experimental study where...

K. K. S. Pillay

1987-01-01

289

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

PubMed Central

Laser-coupled microphotoreactors were developed to bubble singlet oxygen [1O2 (1?g)] into an aqueous solution containing an oxidizable compound. The reactors consisted of custom-modified SMA fiber-optic receptacles loaded with 150-?m 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.

Bartusik, Dorota; Aebisher, David; Ghafari, BiBi

2012-01-01

290

Generating singlet oxygen bubbles: a new mechanism for gas-liquid oxidations in water.  

PubMed

Laser-coupled microphotoreactors were developed to bubble singlet oxygen [(1)O(2) ((1)?(g))] into an aqueous solution containing an oxidizable compound. The reactors consisted of custom-modified SMA fiberoptic receptacles loaded with 150 ?m 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 O(2) gas to the reactor chambers. In the presence of O(2), 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 (1)O(2) was transported through the membrane by the O(2) stream and formed bubbles in solution. In solution, singlet oxygen reacted with probe compounds (9,10-anthracene dipropionate dianion, trans-2-methyl-2-pentanoate anion, N-benzoyl-D,L-methionine, or N-acetyl-D,L-methionine) to give oxidized products in two stages. The early stage was rapid and showed that (1)O(2) transfer occurred via bubbles mainly in the bulk water solution. The later stage was slow; it arose only from (1)O(2)-probe molecule contact at the gas/liquid interface. A mechanism is proposed that involves (1)O(2) mass transfer and solvation, where smaller bubbles provide better penetration of (1)O(2) into the flowing stream due to higher surface-to-volume contact between the probe molecules and (1)O(2). PMID:22260325

Bartusik, Dorota; Aebisher, David; Ghafari, BiBi; Lyons, Alan M; Greer, Alexander

2012-01-20

291

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

SciTech Connect

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.

Hans, Karen M.

1997-07-01

292

[Analysis of evolution of the size of decompression gas bubbles in diver tissues during schedules of medical recompression].  

PubMed

The mathematical model of gas bubble dynamics in body tissues was used for the analysis of evolution of their size during the treatment of decompression sickness in divers by means of recompression in accordance with RN table 72 and USN table 6A. It was shown that the duration of the process of bubble dissolution depends on the compression - decompression profile, as well on the initial size of a bubble, the oxygen content in the breathing mixture and the rate of nitrogen diffusion between a bubble and the surrounding tissue. The results of this study give the grounds to assume that the effect of recompression regimes used in the UK, USA and Russia promotes the treatment of DCS as a result of complete dissolution or significant reduction in the bubble sizes as well as due to therapeutic action of moderately hyperoxic breathing mixture on the tissues affected by bubbles. PMID:23814897

Nikolaev, V P

293

Finite-sized gas bubble motion in a blood vessel: Non-Newtonian effects  

NASA Astrophysics Data System (ADS)

We have numerically investigated the axisymmetric motion of a finite-sized nearly occluding air bubble through a shear-thinning Casson fluid flowing in blood vessels of circular cross section. The numerical solution entails solving a two-layer fluid model—a cell-free layer and a non-Newtonian core together with the gas bubble. This problem is of interest to the field of rheology and for gas embolism studies in health sciences. The numerical method is based on a modified front-tracking method. The viscosity expression in the Casson model for blood (bulk fluid) includes the hematocrit [the volume fraction of red blood cells (RBCs)] as an explicit parameter. Three different flow Reynolds numbers, Reapp=?lUmaxd/?app , in the neighborhood of 0.2, 2, and 200 are investigated. Here, ?l is the density of blood, Umax is the centerline velocity of the inlet Casson profile, d is the diameter of the vessel, and ?app is the apparent viscosity of whole blood. Three different hematocrits have also been considered: 0.45, 0.4, and 0.335. The vessel sizes considered correspond to small arteries, and small and large arterioles in normal humans. The degree of bubble occlusion is characterized by the ratio of bubble to vessel radius (aspect ratio), ? , in the range 0.9???1.05 . For arteriolar flow, where relevant, the Fahraeus-Lindqvist effects are taken into account. Both horizontal and vertical vessel geometries have been investigated. Many significant insights are revealed by our study: (i) bubble motion causes large temporal and spatial gradients of shear stress at the “endothelial cell” (EC) surface lining the blood vessel wall as the bubble approaches the cell, moves over it, and passes it by; (ii) rapid reversals occur in the sign of the shear stress (+ ? - ? +) imparted to the cell surface during bubble motion; (iii) large shear stress gradients together with sign reversals are ascribable to the development of a recirculation vortex at the rear of the bubble; (iv) computed magnitudes of shear stress gradients coupled with their sign reversals may correspond to levels that cause injury to the cell by membrane disruption through impulsive compression and stretching; and (v) for the vessel sizes and flow rates investigated, gravitational effects are negligible.

Mukundakrishnan, Karthik; Ayyaswamy, Portonovo S.; Eckmann, David M.

2008-09-01

294

Efficiency of Oil \\/ Water Separation Controlled by Gas Bubble Size and Fluid Dynamics within the Separation Vessel  

Microsoft Academic Search

This paper reviews the current state of gas flotation within the Oil & Gas industry and considers why the industry is now demanding higher efficiency separation than is currently in use. The major principles behind the design of high efficiency gas flotation are discussed and it will be demonstrated that the control of gas bubble size along with fluid dynamics

Douglas W. Lee; J. D Bateman

295

Porosity formation and gas bubble retention in laser metal deposition  

Microsoft Academic Search

One of the inherent problems associated with laser metal deposition using gas-assisted powder transfer is the formation of\\u000a porosity, which can be detrimental to the mechanical properties of the bulk material. In this work, a comprehensive investigation\\u000a of porosity is carried out using gas atomised Inconel 718 powder. In the analysis, a clear distinction is made between two\\u000a types of

G. K. L. Ng; A. E. W. Jarfors; G. Bi; H. Y. Zheng

2009-01-01

296

IR dust bubbles: gas, dust and star formation in the S21-S24 complex  

NASA Astrophysics Data System (ADS)

Churchwell et al. (2006) identified many IR dust bubbles in the GLIMPSE images at 8 ?m. Among these bubbles, S21, S22, S23, and S24 conform a poorly studied complex plenty of small scale bubbles, with IRDCs and signposts of recent star formation, located at about 4.5 kpc. Based on 12CO(2-1), 13CO(2-1), and 13CO(3-2) line observations obtained with the APEX telescope (angular resolution of 20"-30"), LABOCA continuum observations at 870 ?m (angular resolution of 18.5") also from APEX, Spitzer-IRAC and -MIPS images in the near and mid IR (3.6 to 24 ?m, and Herschel-PACS and -SPIRE images in the far infrared (70-500 ?m), we performed an analysis of the characteristics of the gas and dust in this high density complex. This study allowed molecular shells linked to these bubbles to be revealed, and to estimate new distances, excitation conditions, masses, and ambient densities. Cold dust counterparts were revealed by Herschel and LABOCA images, showing the material available for new generations of stars. In addition to the presence of EGOs and methanol masers, a search for young stellar objets in the complex using the available data at several wavelengths in the infrared revealed many active areas of star formation coincident with the densest regions. We compare our results with those for other IR dust bubbles and investigate the possibility that the expansion of the bubbles has triggered the star formation activity.

Cappa, E. C.; Romero, A. G.; Vasquez, J.; Firpo, V.; Dorunea, N.; Rubio, M.; Kobilnicky, C.

2013-06-01

297

Gas Bubbles in Fossil Amber as Possible Indicators of the Major Gas Composition of Ancient Air  

NASA Astrophysics Data System (ADS)

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 of the 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.

Berner, Robert A.; Landis, Gary P.

1988-03-01

298

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

Microsoft Academic Search

In this paper, the growth of a gas bubble in a supersaturated and slightly compressible liquid is discussed. The mathematical\\u000a model is solved analytically by using the modified Plesset and Zwick method. The growth process is affected by: sonic speed\\u000a in the liquid, polytropic exponent, diffusion coefficient, initial concentration difference, surface tension, viscosity, adjustment\\u000a factor and void fraction. The famous

S. A. Mohammadein; K. G. Mohamed

299

Proteomics of Juvenile Senegal Sole ( Solea senegalensis ) Affected by Gas Bubble Disease in Hyperoxygenated Ponds  

Microsoft Academic Search

Solea senegalensis is a commercial flat fish traditionally farmed in earth ponds in coastal wetlands that might also become important to more\\u000a intensive aquaculture. Gas bubble disease (GBD) is a potential risk for outdoor fish farming, particularly in certain periods\\u000a of the year, related to improper management leading to macroalgae blooms. Physical-chemical conditions inducing hyperoxia,\\u000a including radiation, temperature, and high

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

2009-01-01

300

Stationary soliton waves in a liquid with heat-conducting gas bubbles  

Microsoft Academic Search

Formation of an undamped soliton wave in the process of propagation of sound perturbations in a liquid with uniformly distributed\\u000a gas bubbles is first revealed. The stationary soliton wave exists only in the presence of two pairs of competing factors,\\u000a one of which is a balance between the nonlinearity of the medium and the linear wave dispersion, and another is

D. C. Kim

2006-01-01

301

Perturbed breakup of air bubbles in water: Memory, gas flow, and coalescence  

Microsoft Academic Search

The pinch-off of an air bubble from an underwater nozzle ends in a singularity with a remarkable sensitivity to a variety of perturbations. I report on experiments that break both the axial (i.e., vertical) and azimuthal symmetry of the singularity formation. The density of the inner gas influences the axial asymmetry of the neck near pinch-off. For denser gases, flow

Nathan C. Keim

2010-01-01

302

Perturbed breakup of air bubbles in water: Memory, gas flow, and coalescence  

Microsoft Academic Search

The pinch-off of an air bubble from an underwater nozzle ends in a\\u000asingularity with a remarkable sensitivity to a variety of perturbations. I\\u000areport on experiments that break both the axial (i.e., vertical) and azimuthal\\u000asymmetry of the singularity formation. The density of the inner gas influences\\u000athe axial asymmetry of the neck near pinch-off. For denser gases, flow

Nathan C. Keim

2010-01-01

303

Hydrophobic Gas Bubble Formation in Definity: A Freeze Fracture Electron Microscopy Study  

Microsoft Academic Search

Freeze fracture?electron microscopy (FF?EM) was used to study the structure of the colloidal components present in Definity and to determine changes that occur when the pharmaceutical is “activated” by shaking–a process by which the hydrophobic gas present in the headspace of the vial is incorporated into micro?bubbles.Photomicrographs of the initial pharmaceutical show the presence of small colloidal structures which are

Chris Brancewicz; Don H. Rasmussen

2006-01-01

304

Observation of expanding gas bubbles from a pinched electron beam by fast photography  

Microsoft Academic Search

A self-focused electron beam produces a string of hot spots along its path in 0.35 Torr of air. In this communication we report some interesting snap shots on the luminous gas bubbles expanding from the pinched hot spots. The radial speed of expansion is measured to be ~9 mm\\/musec, which corresponds to ~6 eV of kinetic energy per N+ ion.

P. S. P. Wei; J. R. Beymer; J. L. Adamski

1980-01-01

305

Observation of expanding gas bubbles from a pinched electron beam by fast photography  

Microsoft Academic Search

A self-focused electron beam produces a string of hot spots along its path in 0.35 Torr of air. In this communication we report some interesting snap shots on the luminous gas bubbles expanding from the pinched hot spots. The radial speed of expansion is measured to be ?9 mm\\/?sec, which corresponds to ?6 eV of kinetic energy per N+ ion.

P. S. P. Wei; J. R. Beymer; J. L. Adamski

1980-01-01

306

Rise velocities of bubbles and slugs in gas-fluidised beds: Ultra-fast magnetic resonance imaging  

Microsoft Academic Search

Ultra-fast magnetic resonance imaging (MRI) has been applied for the first time to study the rise velocities of bubbles and slugs in a 3-D gas-fluidised bed. Ultra-fast MRI is a non-intrusive technique, providing measurements with both excellent temporal and spatial resolutions. MRI measurements reveal that the excess gas velocity, U-Umf, does not affect the rise velocity of continuously formed bubbles,

C. R. Müller; J. F. Davidson; J. S. Dennis; P. S. Fennell; L. F. Gladden; A. N. Hayhurst; M. D. Mantle; A. C. Rees; A. J. Sederman

2007-01-01

307

Mass Transfer from Gas Bubbles to Impinging Flow of Biological Fluids with Chemical Reaction  

PubMed Central

The rates of mass transfer from a gas bubble to an impinging flow of a biological fluid such as whole blood and plasma are investigated analytically and experimentally. Gases commonly found dissolved in body fluids are included. Consideration is given to the effects of the chemical reaction between the dissolved gas and the liquid on the rate of mass transfer. Through the application of boundary layer theory the over-all transfer is found to be Sh/(Re)1/2 = 0.845 Sc1/3 in the absence of chemical reaction, and Sh/(Re) 1/2 = F? (0) in the presence of chemical reaction, where Sh, Re, and Sc are the Sherwood, Reynolds, and Schmidt numbers, respectively, and F? (0) is a function of Sc and the dimensionless reaction rate constant. Analytical results are also obtained for the bubble lifetime and the bubble radius-time history. These results, which are not incompatible with experimental results, can be applied to predict the dissolution of the entrapped gas emboli in the circulatory system of the human body.

Yang, Wen-Jei; Echigo, R.; Wotton, D. R.; Ou, J. W.; Hwang, J. B.

1972-01-01

308

Friction Drag Reduction of External Flows with Bubble and Gas Injection  

NASA Astrophysics Data System (ADS)

The lubrication of external liquid flow with a bubbly mixture or gas layer has been the goal of engineers for many years, and this article presents the underlying principles and recent advances of this technology. It reviews the use of partial and supercavities for drag reduction of axisymmetric objects moving within a liquid. Partial cavity flows can also be used to reduce the friction drag on the nominally two-dimensional portions of a horizontal surface, and the basic flow features of two-dimensional cavities are presented. Injection of gas can lead to the creation of a bubbly mixture near the flow surface that can significantly modify the flow within the turbulent boundary layer, and there have been significant advances in the understanding of the underlying physical process of drag reduction. Moreover, with sufficient gas flux, the bubbles flowing beneath a solid surface can coalesce to form a thin drag-reducing air layer. The current applications of these techniques to underwater vehicles and surface ships are discussed.

Ceccio, Steven L.

2010-01-01

309

Horizontal drilling in Baldonnel gas reservoirs - a case history of the Jadney - North Bubbles gas pools  

SciTech Connect

The Jedney - North Bubbles gas pools are trapped in anticlinal folds of the host Triassic dolostones against a northern subcrop edge. The pools have been on production since the early 1960`s, with producing wells averaging 45 dam{sup 3}/d and current reserve lives in excess of 10 years. Gross pay thickness of the reservoir is 46m, with the better matrix wells averaging 22m of 9.5% porosity. The reservoir is {open_quote}streaky{close_quote} with lenses of primarily moldic porosity, through dissolution of the shell and crinoid components. Petro-Canada drilled seven horizontal wells into the pools in 1993-1994. Flooding surfaces of {open_quote}high gamma{close_quote} phosphate-rich laminae are correlatable, and allow subdivision of the Baldonnel into five distinctly different units. The middle or {open_quote}C{close_quote} unit porosity was successfully targeted by all seven wells. Well length in the {open_quote}C{close_quote} unit averages 800m, approximately 50% of that being porous. All horizontal wells were evaluated with resistivity and nuclear porosity logs. Porosities calculated from the density log compared favourably with the core porosity. However, in porous intervals the neutron log indicated a large gas effect. In some of the wells, resistivity image logs were run to obtain detailed information on structure; particularly fracture density and orientation. In addition, FMI images also provide valuable information on stratigraphy and reservoir continuity. In one of the wells an ARI resistivity log was run. The drilling program has been economically successful and provided a clearer, albeit more complex, picture of the reservoir.

Hill, R.; Kubica, P.; Tebbutt, G. [Petro-Canada Resources, Calgary (Canada)

1996-06-01

310

Shock-induced collapse of a gas bubble in shockwave lithotripsy.  

PubMed

The shock-induced collapse of a pre-existing nucleus near a solid surface in the focal region of a lithotripter is investigated. The entire flow field of the collapse of a single gas bubble subjected to a lithotripter pulse is simulated using a high-order accurate shock- and interface-capturing scheme, and the wall pressure is considered as an indication of potential damage. Results from the computations show the same qualitative behavior as that observed in experiments: a re-entrant jet forms in the direction of propagation of the pulse and penetrates the bubble during collapse, ultimately hitting the distal side and generating a water-hammer shock. As a result of the propagation of this wave, wall pressures on the order of 1 GPa may be achieved for bubbles collapsing close to the wall. The wall pressure decreases with initial stand-off distance and pulse width and increases with pulse amplitude. For the stand-off distances considered in the present work, the wall pressure due to bubble collapse is larger than that due to the incoming shockwave; the region over which this holds may extend to ten initial radii. The present results indicate that shock-induced collapse is a mechanism with high potential for damage in shockwave lithotripsy. PMID:19062841

Johnsen, Eric; Colonius, Tim

2008-10-01

311

Shock-induced collapse of a gas bubble in shockwave lithotripsy  

PubMed Central

The shock-induced collapse of a pre-existing nucleus near a solid surface in the focal region of a lithotripter is investigated. The entire flow field of the collapse of a single gas bubble subjected to a lithotripter pulse is simulated using a high-order accurate shock- and interface-capturing scheme, and the wall pressure is considered as an indication of potential damage. Results from the computations show the same qualitative behavior as that observed in experiments: a re-entrant jet forms in the direction of propagation of the pulse and penetrates the bubble during collapse, ultimately hitting the distal side and generating a water-hammer shock. As a result of the propagation of this wave, wall pressures on the order of 1 GPa may be achieved for bubbles collapsing close to the wall. The wall pressure decreases with initial stand-off distance and pulse width and increases with pulse amplitude. For the stand-off distances considered in the present work, the wall pressure due to bubble collapse is larger than that due to the incoming shockwave; the region over which this holds may extend to ten initial radii. The present results indicate that shock-induced collapse is a mechanism with high potential for damage in shockwave lithotripsy.

Johnsen, Eric; Colonius, Tim

2008-01-01

312

Dynamics of shock waves in a liquid containing gas bubbles  

Microsoft Academic Search

Results of a numerical solution of the Korteweg-de Vries-Burgers equation describing the process of propagation and buildup of a steady shock-wave structure in a gas-liquid medium. Data are obtained concerning the time required for a steady shock-wave structure to be built up and also concerning the rate of propagation of the shock wave and the occurrence of amplitude oscillations at

S. S. Kutateladze; V. E. Nakoriakov; V. V. Sobolev; I. R. Shreiber

1974-01-01

313

Nucleation stage with nonsteady growth of supercritical gas bubbles in a strongly supersaturated liquid solution and the effect of excluded volume  

Microsoft Academic Search

An approach to the kinetics of barrier formation of supercritical gas bubbles in a strongly supersaturated liquid solution is presented. A common assumption of uniform reduction of a dissolved gas supersaturation in a liquid solution via stationary diffusion to nucleating gas bubbles is shown to be not applicable to the case of high gas supersaturations. The approach recognizes that the

Anatoly E. Kuchma; Fedor M. Kuni; Alexander K. Shchekin

2009-01-01

314

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

USGS Publications Warehouse

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 (Plargescale 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.

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

2003-01-01

315

Two-phase gas bubble-liquid boundary layer flow along vertical and inclined surfaces  

SciTech Connect

The behavior of a two-phase gas bubble-liquid boundary layer along vertical and inclined porous surfaces with uniform gas injection is investigated experimentally and analytically. Using argon gas and water as the working fluids, a photographical study of the two-phase boundary layer flow has been performed for various angles of inclination ranging from 45/sup 0/ to 135/sup 0/ and gas injection rates ranging from 0.01 to 0.1 m/s. An integral method has been employed to solve the system of equations governing the two-phase motion. The effects of the gas injection rate and the angle of inclination on the growth of the boundary layer have been determined. The predicted boundary layer thickness is found to be in good agreement with the experimental results. The calculated axial liquid velocity and the void fraction in the two-phase region are also presented along with the observed flow behavior.

Cheung, F.B.; Epstein, M.

1985-01-01

316

Gas-liquid mass transfer characteristics in a bubble column with suspended sparingly soluble fine particles  

SciTech Connect

(To investigate the influence of suspended particles on mass transfer characteristics in a slurry bubble column, physical and chemical absorptions were performed into aqueous slurries of fine calcium hydroxide particles ca. 7 ..mu..m in average size. Such mass transfer parameters as volumetric liquid-side mass transfer coefficient, specific gas-liquid interfacial area, and hence liquid-side mass transfer coefficient were determined under various electrolyte concentrations, solid concentrations, and gas flow rates.) and K /SUB L/ /SUP o/ a could be correlated by the gas flow rate. (The volumetric gas-side mass transfer coefficient was determined and correlated by the gas flow rate. The enhancement factors during absorption of dilute carbon dioxide into aqueous calcium hydroxide slurries were compared with the theoretical predictions based on the film theoryincorporating a finite slurry concept.)

Sada, E.; Fujiwara, N.; Kumazawa, M.; Lee, C.

1985-04-01

317

The Holdup Measurement System II (HMSII)  

SciTech Connect

A project is in progress that addresses two of problems with existing holdup measurement technology; the need for compact instrumentation and a more efficient means of reducing the massive amounts of data to quantities of Special Nuclear Materials (SNM). The approach taken by the project utilizes the Miniature Modular MultiChannel Analyzer (M{sup 3}CA) a complete and truly portable gamma-ray spectroscopy system, under development at Los Alamos National Laboratory. The hardware is then integrated and automated by the Holdup Measurement System II (HMSII) software being developed by the Oak Ridge Y-12 Plant. Together they provide the hardware components, measurement control in the field, automated data acquisition, data storage and manipulation which simplify holdup measurements.

Finch, T.L.; Gibson, J.S.; Smith, S.E. [Oak Ridge Y-12 Plant, TN (United States); Halbig, J.K.; Klosterbuer, S.F.; Russo, P.A.; Siebelist, R.; Sprinkle, J.K. Jr. [Los Alamos National Lab., NM (United States)

1994-10-04

318

A Next-Generation Automated Holdup Measurement System (HMS5)  

Microsoft Academic Search

Holdup Measurement System 4 software (HMS4) has been in use at facilities to systematically measure and verify the amounts of uranium holdup in process facilities under safeguards since its release in 2004. It is a system for measuring uranium and plutonium and archiving holdup data (via barcoded locations with information) which is essential for any internationally safeguarded facility to monitor

Claudio Andres Gariazzo; Steven E Smith; Alexander A Solodov

2007-01-01

319

Numerical and experimental investigations of gas–liquid dispersion in an ejector  

Microsoft Academic Search

The effects of the ejector geometry (nozzle diameter and mixing chamber) and the operating conditions (liquid circulating rate, liquid level in column) on the hydraulic characteristics in a rectangular bubble column (0.22×0.26×1.3m3) with a horizontal flow ejector were determined. The gas phase holdup increases with increasing liquid circulating rate but decreases with increasing liquid level in the column. In the

Myoung Il Kim; Og Sin Kim; Dong Hyun Lee; Sang Done Kim

2007-01-01

320

Hydrodynamic models for slurry bubble column reactors. Seventh technical progress report, January--March 1996  

SciTech Connect

The objective of this investigation is to convert our ``learning gas solid-liquid`` fluidization model into a predictive design model. The IIT hydrodynamic model computes the phase velocities and the volume fractions of gas, liquid and particulate phase. Model verification involves a comparison of these computed velocities and volume fractions to experimental values. A hydrodynamic model for multiphase flows, based on the principles of mass, momentum and energy conservation for each phase, was developed and applied to model gas-liquid, gas-liquid-solid fluidization and gas-solid-solid separation. To simulate the industrial slurry bubble column reactors, a computer program based on the hydrodynamic model was written with modules for chemical reactions (e.g. the synthesis of methanol), phase changes and heat exchangers. In the simulations of gas-liquid two phases flow system, the gas hold-ups, computed with a variety of operating conditions such as temperature, pressure, gas and liquid velocities, agree well with the measurements obtained at Air Products` pilot plant. The hydrodynamic model has more flexible features than the previous empirical correlations in predicting the gas hold-up of gas-liquid two-phase flow systems. In the simulations of gas-liquid-solid bubble column reactors with and without slurry circulation, the code computes volume fractions, temperatures and velocity distributions for the gas, the liquid and the solid phases, as well as concentration distributions for the species (CO, H{sub 2}, CH{sub 3}0H, ... ), after startup from a certain initial state. A kinetic theory approach is used to compute a solid viscosity due to particle collisions. Solid motion and gas-liquid-solid mixing are observed on a color PCSHOW movie made from computed time series data. The steady state and time average catalyst concentration profiles, the slurry height and the rates of methanol production agree well with the measurements obtained at an Air Products` pilot plant.

Gidaspow, D.

1996-04-01

321

Gas bubbles evolution peculiarities in ferritic–martensitic and austenitic steels and alloys under helium-ion irradiation  

Microsoft Academic Search

Transmission electron microscopy has been used to investigate the gas bubble evolution in model alloys of the Fe–C system, ferritic–martensitic steels of 13Cr type, nickel and austenitic steels under 40-keV helium-ion irradiation up to a fluence of 5×1020 m?2 at the temperature of 920 K. It was shown that helium-ion irradiation at high temperature resulted in formation of bubbles with

I. I Chernov; A. N Kalashnikov; B. A Kalin; S. Yu Binyukova

2003-01-01

322

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

SciTech Connect

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.

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

1982-08-01

323

Numerical study of wall effects on buoyant gas-bubble rise in a liquid-filled finite cylinder  

PubMed Central

The wall effects on the axisymmetric rise and deformation of an initially spherical gas bubble released from rest in a liquid-filled, finite circular cylinder are numerically investigated. The bulk and gas phases are considered incompressible and immiscible. The bubble motion and deformation are characterized by the Morton number (Mo), Eötvös number (Eo), Reynolds number (Re), Weber number (We), density ratio, viscosity ratio, the ratios of the cylinder height and the cylinder radius to the diameter of the initially spherical bubble (H* = H/d0, R* = R/d0). Bubble rise in liquids described by Eo and Mo combinations ranging from (1,0.01) to (277.5,0.092), as appropriate to various terminal state Reynolds numbers (ReT) and shapes have been studied. The range of terminal state Reynolds numbers includes 0.02 < ReT < 70. Bubble shapes at terminal states vary from spherical to intermediate spherical-cap–skirted. The numerical procedure employs a front tracking finite difference method coupled with a level contour reconstruction of the front. This procedure ensures a smooth distribution of the front points and conserves the bubble volume. For the wide range of Eo and Mo examined, bubble motion in cylinders of height H* = 8 and R* ? 3, is noted to correspond to the rise in an infinite medium, both in terms of Reynolds number and shape at terminal state. In a thin cylindrical vessel (small R*), the motion of the bubble is retarded due to increased total drag and the bubble achieves terminal conditions within a short distance from release. The wake effects on bubble rise are reduced, and elongated bubbles may occur at appropriate conditions. For a fixed volume of the bubble, increasing the cylinder radius may result in the formation of well-defined rear recirculatory wakes that are associated with lateral bulging and skirt formation. The paper includes figures of bubble shape regimes for various values of R*, Eo, Mo, and ReT. Our predictions agree with existing results reported in the literature.

Mukundakrishnan, Karthik; Quan, Shaoping; Eckmann, David M.; Ayyaswamy, Portonovo S.

2009-01-01

324

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

NASA Astrophysics Data System (ADS)

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.

Kettridge, Nicholas; Binley, Andrew

2011-03-01

325

Observations of three-dimensional Richtmyer-Meshkov instability on a membraneless gas bubble.  

PubMed

We investigate the three-dimensional evolution of shock impact on a membraneless gas bubble. When a shock wave impacts a gas interface, gas layer is generally perturbed via the Richtmyer-Meshkov instability. We show the vortex structure evolves from the merging process of the extending spikes on the compressed D-shaped surface via the Richtmyer-Meshkov instability. The spikes are found to have a linear growth before 11 ?s (of 1.4 mm). A ripple-typed fluctuating ring structure is observed and discussed with the scaling relation. We also notice that a thin layer exists in the intersection of the counterpropagating shock shells. The superposition of the rarefaction waves from both sides of the intersection is suspected to be responsible for the density change. PMID:23767479

Chu, Hong-Yu; Chen, Dong-Kai

2013-05-17

326

CFD simulation of gas-solid bubbling fluidized bed containing FCC particles  

Microsoft Academic Search

The hydrodynamics of a bubbling gas-solid fluidized bed of 57.4 ?m FCC particles was simulated by using a state-of-the-art\\u000a two-fluid model integrating the kinetic theory of granular flow for particulate phase stresses. The overestimation of the\\u000a bed expansion was resolved by using a suitable scale factor in the drag model as suggested by McKeen and Pugsley (T.R. McKeen,\\u000a T.S. Pugsley,

Seyyed Hossein Hosseini; Rahbar Rahimi; Mortaza Zivdar; Abdolreza Samimi

2009-01-01

327

Noble gas dependence of single-bubble sonoluminescence in phosphoric acid  

NASA Astrophysics Data System (ADS)

Single-bubble sonoluminescence (SL) from a concentrated solution of phosphoric acid doped with various noble gases has been studied using a hydrochemical model. The results indicate that in agreement with experiment, the SL temperature increases with the atomic mass of the noble gases. Also, both the temperature and the intensity of SL are remarkably higher for lower partial pressures of a noble gas. Our calculations show that the maximum acquirable SL intensity from phosphoric acid is considerably greater than that of water. This mainly originates from the lower vapor pressure and the higher viscosity of phosphoric acid relative to water making the instability mechanisms completely different for these liquids.

Faraji, Mehdi; Moshaii, Ahmad

2012-09-01

328

From ordered bubbles to random stripes: Pattern formation in a hydrodynamic lattice gas  

SciTech Connect

A two-component momentum-conserving lattice gas with competing interactions is introduced in two dimensions. One interaction acts at short range and produces interfaces with surface tension. The second interaction, the negative of the first, acts at range a and produces modulated structures with approximate wavelength 2a. Depending on particle density, species concentration, and relative interaction strength, the equilibrium patterns formed by the model range from isotropic mixed and unmixed phases to hexagonally-ordered bubbles to randomly-oriented stripes. A Ginzburg-Landau equation is proposed that qualitatively captures the basic features of the phase transitions. 23 refs., 5 figs.

Rothman, D.H. (Massachusetts Institute of Technology, Cambridge (United States))

1993-05-01

329

Coal gasification by CO 2 gas bubbling in molten salt for solar\\/fossil energy hybridization  

Microsoft Academic Search

Coal gasification with CO2 (the Boudouard reaction: C+CO2=2CO, ?rH°=169.2 kJ\\/mol at 1150 K), which can be applied to a solar thermochemical process to convert concentrated solar heat into chemical energy, was conducted in the molten salt medium (eutectic mixture of Na2CO3 and K2CO3, weight ratio=1\\/1) to provide thermal storage. When CO2 gas was bubbled through the molten salt, higher reaction

Jun Matsunami; Shinya Yoshida; Yoshinori Oku; Osamu Yokota; Yutaka Tamaura; Mitsunobu Kitamura

2000-01-01

330

Simulation of micro gas bubble generation of uniform diameter in an ultrasonic field by a boundary element method  

Microsoft Academic Search

Micro gas bubbles of uniform diameter are generated periodically when liquid under pressure near the tip of a cylindrical needle is oscillated by an ultrasonic wave. Here, using a boundary element method, we simulated this gas-liquid interface behavior previously reported by Makuta et al. [J. Fluid Mech. 548, 113 (2006)]. Although the simulation model is simple because the flow field

Toshinori Makuta; Fumio Takemura

2006-01-01

331

Gas bubbles electrolytically generated at microcavity electrodes used for the measurement of the dynamic surface tension in liquids  

Microsoft Academic Search

A new method is proposed for the measurement of dynamic surface tension in aqueous solutions. The advantage of this method with respect to the classical method based on sparging is that the use of gas pumps is avoided, resulting in a miniaturized system. This method is based on the in situ generation of gas bubbles by means of electrolysis at

A. Volanschi; W. Olthuis; P. Bergveld

1996-01-01

332

DEM-LES of coal combustion in a bubbling fluidized bed. Part I: gas-particle turbulent flow structure  

Microsoft Academic Search

The gas and particle motions in a bubbling fluidized bed both with and without chemical reactions are numerically simulated. The solid phase is modelled as Discrete Element Method (DEM) and the gas phase is modelled as 2-D Navier–Stokes equations for 2-phase flow with fluid turbulence calculated by large Eddy simulation (LES), in which the effect of particles on subgrid scale

Haosheng Zhou; Gilles Flamant; Daniel Gauthier

2004-01-01

333

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

PubMed Central

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 preferential perfusion of the brain, and more specifically the cerebellum, may occur during diving events.

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

2013-01-01

334

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

PubMed

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 preferential perfusion of the brain, and more specifically the cerebellum, may occur during diving events. PMID:23372553

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

2013-01-29

335

Measurement of physical characteristics of bubbles in gas-liquid plumes: Part II. Local properties of turbulent air-water plumes in vertically injected jets  

NASA Astrophysics Data System (ADS)

The structural development of air-water bubble plumes during upward injection into a ladle-shaped vessel has been measured under different conditions of air flow rate, orifice diameter, and bath depth. The measured radial profiles of gas fraction at different axial positions in the plume were found to exhibit good similarity, and the distribution of the phases in the plume was correlated to the modified Froude number. Different regions of flow behavior in the plume were identified by changes in bubble frequency, bubble velocity, and bubble pierced length which occur as bubbles rise in the plume. Measurement of bubble velocity indicates that close to the nozzle the motion of the gas phase is strongly affected by the injection velocity; at injection velocities below 41 m/s, the velocity of the bubbles along the centerline exhibits an increase with height, while above, the tendency reverses. High-speed film observations suggest that this effect is related to the nature of gas discharge, i.e., whether the gas discharge produces single bubbles or short jets. In this region of developing flow, measurement of bubble frequency and pierced length indicates that break-up of the discharging bubbles occurs until a nearly constant bubble-size distribution is established in a region of fully developed flow. In this largest zone of the plume the bubbles influence the flow only through buoyancy, and the spectra of bubble pierced length and diameter can be fitted to a log-normal distribution. Close to the bath surface, a third zone of bubble motion behavior is characterized by a faster decrease in bubble velocity as liquid flows radially outward from the plume.

Castillejos, A. H.; Brimacombe, J. K.

1987-12-01

336

Influence of increased gas density on hydrodynamics of bubble-column reactors  

SciTech Connect

A mechanistic background to the understanding of the hydrodynamics of high-pressure bubble column reactors in both the homogeneous and heterogeneous flow regimes is discussed. An important parameter determining the stability of homogeneous bubbly flow in a bubble column is shown to be the Richardson-Zaki exponent in the bubble swarm velocity relationship V[sub swarm] = [upsilon][sub [infinity

Krishna, R.; Swart, J.W.A. de; Hennephof, D.E.; Ellenberger, J.; Hoefsloot, H.C.J. (Univ. of Amsterdam (Netherlands). Dept. of Chemical Engineering)

1994-01-01

337

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

SciTech Connect

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.

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

2009-01-01

338

Venous gas bubbles while flying with cabin altitudes of airliners or general aviation aircraft 3 hours after diving.  

PubMed

Decompression venous gas bubbles were detected with the precordial Doppler utrasound technique in humans at simulated altitudes of 1,000-3,000 m 3 h after no-stage decompression dives to 15 or 39 m. Bubbles were detected at 3,000 m in a total of 60% of the subjects: in 90% after the 100-min shallow dives to 15 m with some bubbles present in the first minutes (mean onset 12 min), and in only 30% after the 10-min deeper dives to 39 m with later appearances of bubbles (mean onset 28 min). At both 2,000 and 1,000 m bubbles could also be detected, sometimes in the first minutes. The risk of decompression sickness must be considered high with the amount of gas bubbles found, even though only uncertain symptoms appeared in this study. Thus, a safe interval between ordinary SCUBA-diving and flying in airliners or general aviation aircraft seems to be more than 3 h. PMID:7417128

Balldin, U I

1980-07-01

339

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

NASA Astrophysics Data System (ADS)

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 with a solution of lead(II) nitrate which is adsorbed by the peat fibres, making them visible.

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

2008-05-01

340

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

SciTech Connect

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.

Fidler, Larry; Elston, Ralph; Colt, John

1994-07-01

341

A Nonlinear Shallow-Water Model Combined with Gas Bubble Effect for Melt Flows and Interface Instability in Aluminum Reduction Cells  

NASA Astrophysics Data System (ADS)

A nonlinear shallow-water model combined with the effect of anode gas bubbles was derived for the melt flows and interface instability in aluminum reduction cells. Both the electromagnetic forces and the drag forces between the bath and gas bubbles, as the main driven forces for the melt flows, were taken into account in this model. A comparative numerical study was carried out using both the model considering the bubble and the model without considering the bubble. The results show the effect of the bubble cannot be neglected in a fluid dynamics analysis for the aluminum reduction cell. The bath flow, induced by the motion of bubbles, presents a series of small eddies rather than large eddies as the metal flow pattern shows. The horizontal drag forces between the bath and the bubbles in the bath layer enlarge the deformation of the metal-bath interface, to some extent, but have a positive influence on stabilizing the metal-bath interface perturbations.

Xu, Yujie; Zhang, Hongliang; Li, Jie; Lai, Yanqing

2013-10-01

342

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

Microsoft Academic Search

Deep tissue isobaric counterdiffusion that may cause unwanted bubble formation or transient bubble growth has been referred\\u000a to in theoretical models and demonstrated by intravascular gas formation in animals, when changing inert breathing gas from\\u000a nitrogen to helium after hyperbaric air breathing. We visually followed the in vivo resolution of extravascular air bubbles\\u000a injected at 101 kPa into nitrogen supersaturated rat

O. Hyldegaard; D. Kerem; Y. Melamed

343

Experimental Test of a Mechanistic Model of Production, Flux and Gas Bubble Zonation in Non-vegetated Flooded Rice Field Soil  

Microsoft Academic Search

Anoxic wetlands are an important source for the greenhouse gas CH4, much of which is emitted in form of gas bubbles. The conditions for formation of gas bubbles have recently been described\\u000a by an analytical model, which allows the prediction of fluxes by first physical principles using the knowledge of gas concentration\\u000a profiles and\\/or gas production rates. We tested parts

Andre Kusmin; Nikolai M. Bazhin; Ralf Conrad

2006-01-01

344

[Simulation of tissue nitrogen supersaturation and the risk of tissue lesion by gas bubbles at non-stop dives].  

PubMed

The given study shows that a relationship between the coefficients of critical nitrogen supersaturation of theoretical tissues and the values of their nitrogen wash in and washout half-times can be mapped into a curve that goes around the family of curves that define the degree of tissue nitrogen supersaturation after extremely safe non-stop dives from the surface with air as breathing mixture. Our calculations of the growth dynamics of gas bubbles formed in theoretical tissues after these dives indicate that the sizes of tissue bubbles are not in themselves a measure of the risk of developing decompression sickness (DCS). At the same time, the original probabilistic model of the DCS proposed by us previously shows that the risk of lesion of any real tissue by bubbles and appearance of the appropriate DCS symptoms depends on the size of gas bubbles as well on their density and tissue volumes. The theoretical analysis of specific character for the risk of lesion of various body tissues by gas bubbles at equiprobable safe non-stop dives was carried out in the context of this model. PMID:23074951

Nikolaev, V P

345

Hydrodynamics of stirred gas-liquid dispersions  

NASA Astrophysics Data System (ADS)

Results of an investigation of the gas-liquid hydrodynamics of stirred tanks equipped with (profiled) axial flow impellers are reported. Three different flow regimes are distinguished. Only at low gas flow rates, when the gas-liquid flow is dominated by the liquid flow pattern as induced by the impeller, the flow pattern is steady state and the gas well dispersed. The mass transfer performance of these axial flow impellers was compared with that of disc turbines. Results of a computational study on the single phase flow with both radial pumping and axial pumping impellers are described. All computations were carried out with the fluid flow code FLUENT and the results were validated with experimental LDV (Laser Doppler Velocimetry) data. These single phase flow patterns serve as a basis for further study of the gas dispersion process in those hydrodynamic regimes where the flow is stable. The development of a predictive model for the gas-liquid flow in stirred vessels is considered. This model is incorporated in a code named GHOST (Gas Holdup Simulation Tool) which calculates local values of gas holdup, bubble size, and mass transfer rate on the basis of conservation equations and the single phase flow patterns computed earlier. The computational results are validated against experimental data gathered with optical fiber probes. A qualitative description of the spatial distribution of the gas holdup, the bubble size, and the mass transfer rate in stirred mixing vessels is given. This description results from using a combination of experimental data and GHOST results. Conclusions about further possible optimization of gassed stirred tanks are drawn.

Bakker, Andries

346

Experiments on transport of hydrophobic particles and gas bubbles in porous media  

Microsoft Academic Search

Adhesion of hydrophobic colloids (clay minerals) on the surface of bubbles of air and the transport of the composite units formed by bubbles and mineral particles were observed in a glass micro model.

Lior C. Goldenberg; Ian Hutcheon; Norman Wardlaw

1989-01-01

347

Time-Serial analysis on Gas-Liquid Two-Phase Bubbly Flow using POD  

NASA Astrophysics Data System (ADS)

Bubbly flows are complicated flows because bubbles are deformable and the bubble-bubble interactions work in local area including a lot of bubbles. Such flow occurred turbulence in liquid phase by each bubble is called ``pseudo turbulence''. A PIV is most effective to measure complicated bubbly flow because of multi-dimensional measurement. Recently Dynamic PIV system which is consisted of high-speed camera and high-repetition laser is developed, and it is possible to capture time-serial images with higher resolution. In this paper POD (Proper Orthogonal Decomposition) is described as post-processing of bubbly flow. We confirmed it has the effect of temporal-spatio smooth filter.

Ishikawa, Masaaki; Irabu, Kunio; Teruya, Isao

2007-06-01

348

Arterial Gas Bubbles After Decompression in Pigs with Patent Foramen Ovale.  

National Technical Information Service (NTIS)

With patent foramen ovale (PFO), thought to be a risk factor for some forms of decompression sickness (DCS), venous bubbles may pass through the patent opening to become arterial bubbles. We exposed 14 anesthetized, spontaneously breathing pigs to air at ...

A. Vik B. M. Jenssen A. O. Brubakk

1993-01-01

349

Review of scattering and extinction cross-sections, damping factors, and resonance frequencies of a spherical gas bubble.  

PubMed

Perhaps the most familiar concepts when discussing acoustic scattering by bubbles are the resonance frequency for bubble pulsation, the bubbles' damping, and their scattering and extinction cross-sections, all of which are used routinely in oceanography, sonochemistry, and biomedicine. The apparent simplicity of these concepts is illusory: there exist multiple, sometimes contradictory definitions for their components. This paper reviews expressions and definitions in the literature for acoustical cross-sections, resonance frequencies, and damping factors of a spherically pulsating gas bubble in an infinite liquid medium, deriving two expressions for "resonance frequency" that are compared and reconciled with two others from the reviewed literature. In order to prevent errors, care is needed by researchers when combining results from different publications that might have used internally correct but mutually inconsistent definitions. Expressions are presented for acoustical cross-sections associated with forced pulsations damped by liquid shear and (oft-neglected) bulk or dilatational viscosities, gas thermal diffusivity, and acoustic re-radiation. The concept of a dimensionless "damping coefficient" is unsuitable for radiation damping because different cross-sections would require different functional forms for this parameter. Instead, terms based on the ratio of bubble radius to acoustic wavelength are included explicitly in the cross-sections where needed. PMID:22087992

Ainslie, Michael A; Leighton, Timothy G

2011-11-01

350

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

PubMed

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. PMID:16313012

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

2005-01-01

351

Waves in a liquid with gas bubbles in the presence of dilatational viscosity  

Microsoft Academic Search

The propagation of waves in porous solids and bubble-liquid mixtures depends to a great degree on dilatational (or second) viscosity. In the present paper, a computer-aided solution is obtained to the problem of the propagation of a shock- or blast-generated plane wave in a bubble-liquid mixture. The influence of the bubble content, bubble size, and the magnitude and duration of

G. M. Liakhov; V. N. Okhitin

1980-01-01

352

Nonequilibrium behavior of fission gas bubbles with emphasis on the effects of the equation of state. [LMFBR  

Microsoft Academic Search

The paper presents a computer code designed to estimate fission gas behavior during transient fuel conditions, allowing for nonequilibrium bubble states, with emphasis on equation of state sensitivity. The computer code is a modification of the original code by R. G. Esteves, A. R. Wazzan, and D. Okrent, which in its present form includes the following: resolution, coalescence, leakage to

Steele

1976-01-01

353

The Influence of Surface Tension on the Diffusion-Controlled Growth or Dissolution of Spherical Gas Bubbles  

Microsoft Academic Search

Surface tension can markedly affect the growth or dissolution of small gas bubbles but, even when spherical symmetry is maintained and the interfacial concentration assumed constant, generally valid analytical solutions for the change of size with time cannot be obtained; approximations of limited validity are therefore often used. However, accurate and efficient methods for computing the diffusion-controlled growth or dissolution

M. Cable; J. R. Frade

1988-01-01

354

Growth of a Gas Bubble in a Supersaturated Liquid Under the Effect of Variant Cases of Surface Tension  

Microsoft Academic Search

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 sigma, adjustment factor b

S. A. Mohammadein; K. G. Mohamed

2011-01-01

355

Erratum to “Meso-scale modeling of the influence of intergranular gas bubbles on effective thermal conductivity”  

Microsoft Academic Search

Using a mesoscale modeling approach, we have investigated how intergranular fission gas bubbles, as observed in high-burnup nuclear fuel, modify the effective thermal conductivity in a polycrystalline material. The calculations reveal that intergranular porosity has a significantly higher resistance to heat transfer compared to randomly-distributed porosity. A model is developed to describe this conductivity reduction that considers an effective grain

Paul C. Millett; Michael Tonks

2011-01-01

356

Analysis of the formation and removal of gas bubbles in rotationally moulded thermoplastics  

Microsoft Academic Search

The presence of internal bubbles is a characteristic feature of thermoplastic products manufactured by rotational moulding. The bubbles in the mouldings are generally undesirable since they reduce strength and stiffness and impair the appearance of the product if they occur at the surface. The bubbles form as a result of powder particles coalescing during the heating stage of the process

L. Xu; R. J. Crawford

1993-01-01

357

Visibility sizing of 10-100 micron gas bubbles in water  

Microsoft Academic Search

On the basis of the tests described, it is concluded that laser visibility sizing of bubbles is a practical technique. The measurement accuracy is at least as good as the accuracy with which the bubble size distribution was known. Further development of bubble generators with, known, repeatable size distributions would be necessary before a more accurate assessment of the visibility

1985-01-01

358

Effect of Langmuir cells on bubble dissolution and air-sea gas exchange  

Microsoft Academic Search

Gases are exchanged between the atmosphere and ocean by diffusion through the sea surface and by dissolution of air bubbles injected by breaking wind waves. Langmuir cells enhance the contribution from bubbles by keeping them under water for longer thus increasing their dissolution. We determine the importance of Langmuir cells by using a bubble model to calculate the amount of

David Chiba; Burkard Baschek

2010-01-01

359

Laser generation of gas bubbles: Photoacoustic and photothermal effects recorded in transient grating experiments  

Microsoft Academic Search

Absorption of high power laser radiation by colloidal suspensions or solutions containing photoreactive chemicals can result in bubble production. Here, transient grating experiments are reported where picosecond and nanosecond lasers are used to initiate photoinduced processes that lead to bubble formation. Irradiation of colloidal Pt suspensions is found to produce water vapor bubbles that condense back to liquid on a

Clifford Frez; Gerald J. Diebold

2008-01-01

360

Periodic orbit theory applied to a chaotically oscillating gas bubble in water  

Microsoft Academic Search

This study investigates the dynamics of an acoustically driven air bubble in water. Depending on the values of external parameters, the radial oscillations of the bubble can be either stable or chaotic. The necessary condition of chaotic behaviour is identified to be the non-zero amplitude of the bubble's afterbounces at the beginning of the next acoustic cycle, which brings memory

G. Simon; P. Cvitanovic; M. T. Levinsen; I. Csabai; Á. Horváth

2002-01-01

361

Recrystallization and fission-gas-bubble swelling of U-Mo fuel  

NASA Astrophysics Data System (ADS)

At high burnup, U-Mo fuel exhibits some form of recrystallization, by which fuel grains are subdivided. The effect of grain subdivision is to effectively enhance fission gas bubble (FGB) swelling due to increased grain boundaries. Inter-granular FGB swelling, i.e., FGB formation and growth at the grain boundaries, is much larger than the intra-granular FGB swelling. Recrystallized fuel volume fractions of U-Mo fuels irradiated to fission densities reaching 5.7 × 1021 f/cm3 were measured. Analytical expressions of recrystallization kinetics of U-Mo fuel during irradiation have been developed through the usage of the Avrami equation, a phenomenological equation which is also used to describe similar typical transformation reactions, such as new phase formation. In this work, we present a novel FGB swelling model of U-Mo fuel that is expressed in terms of Mo content, extent of cold work (fuel powder fabrication method), and fission density.

Kim, Yeon Soo; Hofman, G. L.; Cheon, J. S.

2013-05-01

362

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

SciTech Connect

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.

Cochnauer, Tim

1998-12-01

363

Use of a porous membrane for gas bubble removal in microfluidic channels: physical mechanisms and design criteria  

Microsoft Academic Search

We demonstrate and explain a simple and efficient way to remove gas bubbles from liquid-filled microchannels, by integrating\\u000a a hydrophobic porous membrane on top of the microchannel. A prototype chip is manufactured in hard, transparent polymer with\\u000a the ability to completely filter gas plugs out of a segmented flow at rates up to 7.4 ?l\\/s\\/mm2 of membrane area. The device involves

Jie Xu; Regis Vaillant; Daniel Attinger

2010-01-01

364

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

SciTech Connect

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.

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

2000-01-18

365

Tiny Bubbles.  

ERIC Educational Resources Information Center

|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)|

Kim, Hy

1985-01-01

366

Can high-frequency sound affect gas-bubble dynamics? A study in the intact prawn Palaemon elegans.  

PubMed

Underwater sound beacons (pingers) are employed in professional and scientific diving for location and navigation. Previous studies have demonstrated that exposure to acoustic fields may lead to the emergence of bubbles and cavities in tissues by rectified diffusion. However, this issue was studied mainly in vitro in various gels and isolated tissues. In the present study, we used the intact prawn Palaemon elegans, whose transparent shell makes it possible to conduct continuous microscopic observation of gas-bubble dynamics in the intact living prawn, to study the effect of high-frequency sound. In a crossover designed experiment, prawns were exposed to hyperbaric pressure of 203 kPa for 10 min, followed by decompression at 40 m/min (control). This procedure was carried out in the study group during transmission of a 37-kHz, 0.25-W, 10-ms pulse width, 1 pulse/s pulse interval. A significant increase was found in the mean volume of bubbles present for a longer period of time, in a higher percentage of the high-frequency sound-exposed prawns. We suggest that this sound exposure causes more gaseous micronuclei to grow into bubbles, and more of the dissolved gas to shift into the gas phase. PMID:11179625

Arieli, Y; Arieli, R; Shupak, A

2000-11-01

367

HYDRODYNAMIC MODELS FOR SLURRY BUBBLE COLUMN REACTORS. FINAL TECHNICAL REPORT ALSO INCLUDES THE QUARTERLY TECHNICAL REPORT FOR THE PERIOD 01/01/1997 - 03/31/1997.  

SciTech Connect

The objective of this study is to develop a predictive experimentally verified computational fluid dynamic (CFD) three phase model. It predicts the gas, liquid and solid hold-ups (volume fractions) and flow patterns in the industrially important bubble-coalesced (churn-turbulent) regime. The input into the model can be either particulate viscosities as measured with a Brookfield viscometer or effective restitution coefficient for particles. A combination of x-ray and {gamma}-ray densitometers was used to measure solid and liquid volume fractions. There is a fair agreement between the theory and the experiment. A CCD camera was used to measure instantaneous particle velocities. There is a good agreement between the computed time average velocities and the measurements. There is an excellent agreement between the viscosity of 800 {micro}m glass beads obtained from measurement of granular temperature (random kinetic energy of particles) and the measurement using a Brookfield viscometer. A relation between particle Reynolds stresses and granular temperature was found for developed flow. Such measurement and computations gave a restitution coefficient for a methanol catalyst to be about 0.9. A transient, two-dimensional hydrodynamic model for production of methanol from syn-gas in an Air Products/DOE LaPorte slurry bubble column reactor was developed. The model predicts downflow of catalyst at the walls and oscillatory particle and gas flow at the center, with a frequency of about 0.7 Hertz. The computed temperature variation in the rector with heat exchangers was only about 5 K, indicating good thermal management. The computed slurry height, the gas holdup and the rate of methanol production agree with LaPorte's reported data. Unlike the previous models in the literature, this model computes the gas and the particle holdups and the particle rheology. The only adjustable parameter in the model is the effective particle restitution coefficient.

DIMITRI GIDASPOW

1997-08-15

368

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

SciTech Connect

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.

Niederhaus, John [University of Wisconsin-Madison (United States); Ranjan, Devesh [University of Wisconsin-Madison (United States); Anderson, Mark [University of Wisconsin-Madison (United States); Oakley, Jason [University of Wisconsin-Madison (United States); Bonazza, Riccardo [University of Wisconsin-Madison (United States); Greenough, Jeff [Lawrence Livermore National Laboratory (United States)

2005-05-15

369

Optical measurements of jet gas and bed particle velocity distributions in a 2D bubbling fluidized bed  

NASA Astrophysics Data System (ADS)

A laser Doppler velocimetry (LDV) measurement technique has been developed to obtain spatially and temporally resolved measurements of jet gas and bed particle velocities in a 2D bubbling fluidized bed. The LDV system was configured to eliminate spurious optical intensity fluctuations, which can contaminate velocity measurements in optically dense flows. The jet gas was seeded with ice crystals, which were formed by rapidly condensing and freezing the moisture in the jet air just prior to injection. LDV bursts from the bed particles and gas tracer ice crystals were simultaneously recorded to obtain the particulate and gas phase velocities at a given location within the jet plume in a non-intrusive manner.

Mychkovsky, Alexander; Ceccio, Steven

2009-11-01

370

Hydrodynamical similarities between bubble column and bubbly pipe flow  

Microsoft Academic Search

The hydrodynamical similarities between the bubbly flow in a bubble column and in a pipe with vertical upward liquid flow are investigated. The system concerns air\\/water bubbly flow in a vertical cylinder of 14.9 cm inner diameter. Measurements of the radial distribution of the liquid velocity, gas fraction and the bubble velocity and size are performed using laser Doppler anemometry

Robert F. Mudde; Takayuki Saito

2001-01-01

371

Measurement of bubble size distribution in a gas-liquid foam using pulsed-field gradient nuclear magnetic resonance.  

PubMed

Pulsed-field gradient nuclear magnetic resonance, previously used for measuring droplet size distributions in emulsions, has been used to measure bubble size distributions in a non-overflowing pneumatic gas-liquid foam that has been created by sparging propane into an aqueous solution of 1.5g/l (5.20mM) SDS. The bubble size distributions measured were reproducible and approximated a Weibull distribution. However, the bubble size distributions did not materially change with position at which they were measured within the froth. An analysis of foam coarsening due to Ostwald ripening in a non-overflowing foam indicates that, for the experimental conditions employed, one would not expect this to be a significant effect. It is therefore apparent that the eventual collapse of the foam is due to bubble bursting (or surface coalescence) rather than Ostwald ripening. This surface coalescence occurs because of evaporation from the free surface of the foam. An analytical solution for the liquid fraction profile for a certain class of non-overflowing pneumatic foam is given, and a mean bubble size that is appropriate for drainage calculations is suggested. PMID:20832808

Stevenson, Paul; Sederman, Andrew J; Mantle, Mick D; Li, Xueliang; Gladden, Lynn F

2010-08-10

372

Plumes of bubbles release methane gas from the seabed along the West Spitsbergen continental margin  

NASA Astrophysics Data System (ADS)

Over 250 plumes of gas bubbles have been discovered emanating from the seabed of the West Spitsbergen continental margin, at and above the upper limit of the gas hydrate stability zone (GHSZ), at depths of 150-400 m. Some plumes extend upward to within 50 m of the sea surface. The gas is predominantly methane, and seismic reflection data indicate free gas beneath the plume field. A 1°C warming of the northward-flowing West Spitsbergen current over the last thirty years is likely to have increased the release of methane from the seabed by reducing the extent of the GHSZ, causing the liberation of methane from decomposing hydrate. If this process is widespread along Arctic continental margins, the methane released could be a large proportion of global methane flux. Methane released from gas hydrate in submarine sediments has been invoked as an agent of past climate change, yet comparatively little is known about methane fluxes in the present-day marine environment. Global atmospheric methane concentration continues to rise, following a period of stability between 1998 and 2006. A multidisciplinary marine geological, geophysical, and geochemical expedition was undertaken with the Royal Research Ship James Clark Ross between 23 August and 24 September 2008, as part of the International Polar Year, to investigate the role of the GHSZ in the release and retention of methane from geological sources along the West Spitsbergen continental margin, between 78° and 80° N. The techniques employed in the expedition included: detailed (10-m resolution) mapping of sea-floor morphology; detailed acoustic imaging of sea-floor stratigraphy and of features extending into the water column; seismic portrayal of geological features to depths of several hundreds of metres beneath the seabed, such as depositional and tectonic structures and the bottom-simulating reflector (BSR, the boundary between free-gas-containing sediment and hydrate-containing sediment); sediment coring to obtain sequences for geochemical and palaeoceanographic investigations; water-column sampling for chemical analyses of the water and dissolved gases; and atmospheric sampling for gas concentration (notably methane). In the Arctic, the GHSZ is especially sensitive to climate-induced changes in temperature, because the degree of temperature change is greater than at lower latitudes. The GHSZ for a specific gas or gases and salinity of water is defined by conditions of temperature and pressure (dependent on water depth plus depth beneath seabed), both of which have varied greatly in this area over the past 15 kyr. At present, the GHSZ (for pure methane gas and water with 3.5 wt % NaCl) is expected to taper out at its landward limit where water temperature is 3°C at a depth of about 396 m. It is in water just shallower than this depth that most of the bubble plumes occur.

Westbrook, G. K.

2009-04-01

373

Tiny Bubbles  

NSDL National Science Digital Library

In this activity, which can be performed as a demonstration by the teacher or by the students themselves, carbon dioxide is generated in a fish tank using sodium bicarbonate and vinegar. The students can observe as the accumulating carbon dioxide extinguishes candles of different heights, marking rising levels of CO2 in the tank. They can also blow soap bubbles (which contain air) into the tank and observe them floating on the denser CO2 at first, then sinking as the gas diffuses through the soap film that forms the bubbles.

Dolphin, Glenn

374

Occupational violence: Armed holdup—A risk management approach  

Microsoft Academic Search

Workplace violence covers a wide spectrum of incidents of aggression that may occur at work. One area of particular concern relates to holdups. This study reviewed all incidents of robbery (holdups and bag snatches) occurring in a quasi-government wagering organization throughout Queensland, Australia between 1990 and August 1993. The study covered 30 robberies, at 28 sites with 34 subjects, 22

Carol Grainger

1995-01-01

375

Gas bubbling-enhanced film boiling of Freon-11 on liquid metal pools. [PWR; BWR  

SciTech Connect

In the analysis of severe core damage accidents in LWRs, a major driving force which must be considered in evaluating containment loading and fission product transport is the ex-vessel interaction between molten core debris and structural concrete. Two computer codes have been developed for this purpose, the CORCON-MOD2 model of ex-vessel, core concrete interactions and the VANESA model for aerosol generation and fission product release as a result of molten core-concrete interactions. Under a wide spectrum of reactor designs and accident sequences, it is possible for water to come into contact with the molten core debris and form a coolant pool overlying the core debris which is attacking the concrete. As the concrete decomposes, noncondensable gases are released, which bubble through the melt and across the boiling interface, affecting the liquid-liquid boiling process. Currently, the CORCON code includes the classical Berenson model for film boiling over a horizontal flat plate for this phenomenon. The objectives of this activity are to investigate the influence of transverse noncondensable gas flux on the magnitude of the stable liquid-liquid film boiling heat flux and develop a gas flux-enhanced, liquid-liquid film boiling model for incorporation into the CORCON-MOD2 computer code to replace or modify the Berenson model.

Greene, G.A.

1985-01-01

376

The effect of dissolved gas concentration on bubble-enhanced heating in tissue-mimetic materials  

NASA Astrophysics Data System (ADS)

Bubble-enhanced heating is a key mechanism to cause tissue damage in ultrasound surgery. We have conducted experiments in an agar-based tissue phantom. We found that the difference of air concentration in the tissue phantom has a small but measurable effect on the enhanced heating. Notably, high air concentration samples exhibit very good repeatability. We have passively monitored broadband acoustic emissions from the bubbles in order to determine if diagnostic information could be gleaned from such signals. Finally we investigate the effect of bubble size distribution on bubble-enhanced heating by employing bubble-based contrast agents to control the initial bubble size distribution. [Work supported by DARPA and the U.S. Army.

Yang, Xinmai; Roy, Ronald A.; Holt, R. Glynn

2002-11-01

377

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

USGS Publications Warehouse

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.

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

2011-01-01

378

Nonlinear oscillations following the Rayleigh collapse of a gas bubble in a linear viscoelastic (tissue-like) medium  

NASA Astrophysics Data System (ADS)

In a variety of biomedical engineering applications, cavitation occurs in soft tissue, a viscoelastic medium. The present objective is to understand the basic physics of bubble dynamics in soft tissue. To gain insights into this problem, theoretical and numerical models are developed to study the Rayleigh collapse and subsequent oscillations of a gas bubble in a viscoelastic material. To account for liquid compressibility and thus accurately model large-amplitude oscillations, the Keller-Miksis equation for spherical bubble dynamics is used. The most basic linear viscoelastic model that includes stress relaxation, viscosity, and elasticity (Zener, or standard linear solid) is considered for soft tissue, thereby adding two ordinary differential equations for the stresses. The present study seeks to advance past studies on cavitation in tissue by determining the basic effects of relaxation and elasticity on the bubble dynamics for situations in which compressibility is important. Numerical solutions show a clear dependence of the oscillations on the viscoelastic properties and compressibility. The perturbation analysis (method of multiple scales) accurately predicts the bubble response given the relevant constraints and can thus be used to investigate the underlying physics. A third-order expansion of the radius is necessary to accurately represent the dynamics. Key quantities of interest such as the oscillation frequency and damping, minimum radius, and collapse time can be predicted theoretically. The damping does not always monotonically decrease with decreasing elasticity: there exists a finite non-zero elasticity for which the damping is minimum; this value falls within the range of reported tissue elasticities. Also, the oscillation period generally changes with time over the first few cycles due to the nonlinearity of the system, before reaching an equilibrium value. The analytical expressions for the key bubble dynamics quantities and insights gained from the analysis may prove valuable in the development and optimization of certain biomedical applications.

Hua, Chengyun; Johnsen, Eric

2013-08-01

379

NUMERICAL STUDY ON THE HYDRODYNAMICAL FORCES ACTING IN A SWARM OF BUOYANCY DRIVEN GAS BUBBLES  

Microsoft Academic Search

Bubble columns are encountered in a large variety of industrial processes, especially as chemical reactors. Detailed process design requires a good understanding of the hydrodynamics which can be obtained using numerical simulation. As in almost all industrial relevant flows, the simulation of the full Navier Stokes equations is a very demanding, if not impossible task. Therefore, in bubble column engineering,

J. J. J. Gillissen

380

Structure of turbulent round bubbling jet generated by premixed gas and liquid injection  

Microsoft Academic Search

An air water mixture was injected into a cylindrical water bath through a single-hole bottom nozzle to generate a vertical turbulent bubbling jet. A parameter called jet volume fraction, defined as the ratio of the air flow rate to the total flow rate of air and water, was introduced to specify the bubbling jet. The jet volume fraction was raised

M. Iguchi; K. Okita; T. Nakatani; N. Kasai

1997-01-01

381

A Method for the Automated Detection of Venous Gas Bubbles in Humans Using Empirical Mode Decomposition  

Microsoft Academic Search

Doppler ultrasound signals are widely used to grade the quantity of circulating venous bubbles in divers. Current techniques rely on trained observers, making the grading process both time-consuming and subjective. The automated detection of bubbles, however, is confounded by the presence of other signals, primarily those arising from blood motion. Empirical Mode Decomposition was used here to calculate the intrinsic

M. A. Chappell; S. J. Payne

2005-01-01

382

Prediction of pressure drop in a modified gas–liquid downflow bubble column  

Microsoft Academic Search

A model for pressure drop in the ejector induced downflow bubble column based on mechanical energy balance within the framework of dynamic interaction of the phases has been formulated. The model includes the effect of bubble formation and form drag at interface on the pressure drop. It provides a functional form of equation for correlating pressure drop. The theoretical model

Subrata Kumar Majumder; Gautam Kundu; Dibyendu Mukherjee

2006-01-01

383

Large eddy simulation of the Gas–Liquid flow in a square cross-sectioned bubble column  

Microsoft Academic Search

In this work the use of large eddy simulations (LES) in numerical simulations of the gas–liquid flow in bubble columns is studied. The Euler–Euler approach is used to describe the equations of motion of the two-phase flow. It is found that, when the drag, lift and virtual mass forces are used, the transient behaviour that was observed in experiments can

N. G. Deen; T. Solberg; B. H. Hjertager

2001-01-01

384

Liquid holdup in columns packed with structured packings: Countercurrent vs. cocurrent operation  

Microsoft Academic Search

An experimental study of the liquid holdup and the liquid holdup axial profile in a square section column with structured packing is carried out. Both cocurrent and countercurrent operations are examined. A conductivity technique to estimate liquid holdups is proposed and calibrated against values measured by the drainage method. Liquid holdups estimated by this technique follow the same trends as

Alejandra Muzen; Miryan C. Cassanello

2005-01-01

385

Venous gas bubble formation and decompression risk after scuba diving in persons with chronic spinal cord injury and able-bodied controls  

Microsoft Academic Search

Study design:Prospective study.Objective:To evaluate the formation of venous gas bubbles following open-sea scuba dives in persons with chronic spinal cord injury (SCI) and in able-bodied diving instructors (C) and to assess the risk for decompression sickness (DCS).Setting:Field study at the Island of Krk, Croatia.Methods:Gas bubbles were monitored with an ultrasound scanner 40 min after surfacing. The probability of DCS (P(DCS))

T Breskovic; P Denoble; I Palada; A Obad; Z Valic; D Glavas; D Bakovic; Z Dujic

2008-01-01

386

Processes of hydrate formation and dissolution behind a shock wave in a liquid containing gas bubbles (mixture of nitrogen and carbon dioxide)  

Microsoft Academic Search

The processes of dissolution and hydrate formation behind a moderate-amplitude shock wave in water containing gas bubbles\\u000a (mixture of nitrogen and carbon dioxide) are studied in experiments with different initial static pressures in the medium\\u000a and concentrations of carbon dioxide in bubbles. An increase in static pressure in the gas-liquid medium is demonstrated to\\u000a enhance the influence of the non-reacting

V. E. Dontsov; V. E. Nakoryakov; E. V. Dontsov

2009-01-01

387

A clinical evaluation of the gas transfer characteristics and gaseous microemboli production of two bubble oxygenators.  

PubMed

The gaseous microemboli (GME) production and gas transfer characteristics of two series of bubble oxygenators (Harvey H-1500 and Bentley BOS-10) were evaluated during clinical perfusion in 33 adult patients during open heart surgery for acquired valvular and ischaemic heart disease. For each oxygenator series, patients were divided into two groups, depending upon the method of measurement (intermittent or continuous) of the arterial PO2(PaO2). Using the data available, the perfusionist altered the gas:blood flow ratio in an attempt to maintain the PaO2 within the normal range. In the first group (I = intermittent), where PaO2 data were available only intermittently, the PaO2 values were well above normal, and large numbers of GME were detected in the arterial blood. In the second group (C = continuous), where the PaO2 data were available continuously, there was significantly better control of the PaO2 (P less than 0.001 and P less than 0.01 for the H-1500 and BOS-10, respectively) and significantly fewer GME (P less than 0.01 and P less than 0.05 for the H-1500 and BOS-10, respectively). The Bentley BOS-10 oxygenator used a lower gas:blood flow ratio to achieve physiological levels (range 9 to 13 kPa at 37 degrees C) of PaO2 than did the Harvey H-1500 oxygenator, but there was no difference in the number of GME detected. The lower gas:blood flow ratios for the BOS-10 oxygenators in group C resulted in significantly higher PaCO2 values well outside the physiological range (4 to 6 kPa at 37 degrees C) during the rewarming phase (mean PaCO2 = 7.6 +/- 0.8 kPa) of cardiopulmonary bypass than did the H-1500 oxygenator (mean PaCO2 = 6.3 +/- 0.7 kPa). Mean values for the PaCO2 for both oxygenators during other phases of bypass (cooling and hypothermia) were within the physiological range. If the CO2 retention was corrected by increasing the gas:blood flow ratio the PaO2 values and GME counts became elevated. PMID:6441873

Pearson, D T; Holden, M P; Poslad, S J; Murray, A; Waterhouse, P S

388

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

PubMed

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. PMID:19101763

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

2008-12-20

389

Intracardial gas bubbles and decompression sickness while flying at 9,000 m within 12-24 h of diving.  

PubMed

Intracardial gas bubbles, detected with Doppler ultrasound, and symptoms of decompression sickness were registered at 9,000 m simulated altitude within 12, 18, and 24 h of exposures to 15 or 39 m simulated water depth allowing no stage decompression. With a time interval of 12 h between diving and flying, the earliest intracardial bubbles were found in some subjects already during the first minutes at altitude, and the earliest symptoms of decompression sickness some minutes afterwards. With an 18-h interval, the earliest bubbles and symptoms as well as their average time onsets appeared somewhat later. With a 24-h interval, the earliest bubbles and symptoms were detected slightly later, i.e. after 17 min and 23 min, respectively. Thus, a safe time interval between no-stage decompression dives and flying at 9,000 m cabin altitude for a maximum of 15 min appears to be 24 h. For prolonged such flights, a longer time interval seems to be necessary. PMID:718575

Balldin, U I

1978-11-01

390

Measurement of interactions between solid particles, liquid droplets, and/or gas bubbles in a liquid using an integrated thin film drainage apparatus.  

PubMed

A novel device was designed to measure drainage dynamics of thin liquid films confined between a solid particle, an immiscible liquid droplet, and/or gas bubble. Equipped with a bimorph force sensor, a computer-interfaced video capture, and a data acquisition system, the newly designed integrated thin film drainage apparatus (ITFDA) allows for the direct and simultaneous measurements of force barrier, true film drainage time, and bubble/droplet deformation under a well-controlled external force, receding and advancing contact angles, capillary force, and adhesion (detachment) force between an air bubble or oil droplet and a solid, a liquid, or an air bubble in an immiscible liquid. Using the diaphragm of a high-frequency speaker as the drive mechanism for the air bubble or oil droplet attached to a capillary tube, this newly designed device is capable of measuring forces over a wide range of hydrodynamic conditions, including bubble approach and retract velocities up to 50 mm/s and displacement range up to 1 mm. The results showed that the ITFDA was capable of measuring hydrodynamic resistance, film drainage time, and other important physical parameters between air bubbles and solid particles in aqueous solutions. As an example of illustrating the versatility, the ITFDA was also applied to other important systems such as interactions between air bubble and oil droplet, two air bubbles, and two oil droplets in an aqueous solution. PMID:23379835

Wang, Louxiang; Sharp, David; Masliyah, Jacob; Xu, Zhenghe

2013-03-07

391

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

PubMed

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 ?m). 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. PMID:22700364

Seo, Minseok; Matsuura, Naomi

2012-06-15

392

SNM holdup assessment of Los Alamos exhaust ducts. Final report  

SciTech Connect

Fissile material holdup in glovebox and fume hood exhaust ducting has been quantified for all Los Alamos duct systems. Gamma-based, nondestructive measurements were used to quantify holdup. The measurements were performed during three measurement campaigns. The first campaign, Phase I, provided foot-by-foot, semiquantitative measurement data on all ducting. These data were used to identify ducting that required more accurate (quantitative) measurement. Of the 280 duct systems receiving Phase I measurements, 262 indicated less than 50 g of fissile holdup and 19 indicated fissile holdup of 50 or more grams. Seven duct systems were measured in a second campaign, called Series 1, Phase II. Holdup estimates on these ducts ranged from 421 g of {sup 235}U in a duct servicing a shut-down uranium-machining facility to 39 g of {sup 239}Pu in a duct servicing an active plutonium-processing facility. Measurements performed in the second campaign proved excessively laborious, so a third campaign was initiated that used more efficient instrumentation at some sacrifice in measurement quality. Holdup estimates for the 12 duct systems measured during this third campaign ranged from 70 g of {sup 235}U in a duct servicing analytical laboratories to 1 g of {sup 235}U and 1 g of {sup 239}Pu in a duct carrying exhaust air to a remote filter building. These quantitative holdup estimates support the conclusion made at the completion of the Phase I measurements that only ducts servicing shut-down uranium operations contain about 400 g of fissile holdup. No ventilation ducts at Los Alamos contain sufficient fissile material holdup to present a criticality safety concern.

Marshall, R.S.

1994-02-01

393

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

PubMed

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. PMID:15485086

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

2004-01-01

394

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

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. PMID:21318313

Hyldegaard, O; Kerem, D; Melamed, Y

2011-02-12

395

Permeabilization of phospholipid bilayer membranes induced by gas-liquid flow in an airlift bubble column.  

PubMed

The permeability of 5(6)-carboxyfluorescein (CF) through the phospholipid bilayer membranes was measured by using the system in which the CF-containing phospholipid vesicles (liposomes) were suspended in the gas-liquid flow in an external loop airlift bubble column. The airlift was operated at various superficial gas velocities UG up to 2.4 cm/s at 25 and 40 degrees C. The CF-containing liposomes composed of POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) had the nominal diameters of 50, 100, and 200 nm. The 50- and 100-nm liposomes were stable at 40 degrees C for 5 h even at a high UG value of 2.4 cm/s based on the observed turbidity of the liposome suspension in the airlift. On the other hand, the 200-nm liposomes were stable at a low UG value of 1.4 cm/s, although a progressive decrease in size of the liposomes was implied at the high UG value of 2.4 cm/s. The permeability coefficient PCF of CF through the lipid membrane of the 100-nm liposomes was significantly increased with increasing UG at a high temperature of 40 degrees C, while at a low temperature of 25 degrees C the PCF value was little dependent on UG. As a typical result on the above liposomes, the PCF value (9.2 x 10(-11) cm/s) at 40 degrees C and UG = 2.4 cm/s in the airlift was more than 15 times larger than that at 25 degrees C in the static liquid corresponding to UG = 0. In addition, the dependence of the PCF value on UG at 40 degrees C became more significant with increasing the size of liposomes suspended. The results obtained revealed that the permeability of the liposome membranes could be regulated by suspending the liposomes in the gas-liquid flow in the airlift without modulating the membrane composition of liposomes. PMID:17975892

Yoshimoto, Makoto; Monden, Miyuki; Jiang, Zhongwei; Nakao, Katsumi

2007-11-02

396

A New Liquid Holdup Correlation for Geothermal Wells  

SciTech Connect

Simulation of two-phase flow in geothermal wellbores requires use of empirical correlations for liquid holdup and for friction factor. Use of currently available correlations often yields widely differing results for geothermal wells. A new liquid holdup correlation is devised for cased wellbores using high-quality discharge and downhold pressure and temperature data from flowing geothermal wells. The latter dataset encompasses a wide range of wellbore diameters, discharge rates and flowing enthalpies. The measured wellhead pressure for wells in the dataset display excellent agreement with the pressures computed by using the new holdup correlation. Finally, an example illustrating the use of the holdup correlation to match downhole pressure and temperature profiles and well characteristic data is given.

Sabodh K. Garg; John W. Pritchett; James H. Alexander; K. Kit Bloomfield

2004-12-01

397

Engineering Development of Slurry Bubble Column Reactor (SBCR) Technology  

SciTech Connect

This report summarizes the procedures used and results obtained in determining radial gas holdup profiles, via gamma ray scanning, and in assessing liquid and gas mixing parameters, via radioactive liquid and gas tracers, during Fischer Tropsch synthesis. The objectives of the study were (i) to develop a procedure for detection of gas holdup radial profiles in operating reactors and (ii) to test the ability of the developed, previously described, engineering models to predict the observed liquid and gas mixing patterns. It was shown that the current scanning procedures were not precise enough to obtain an accurate estimate of the gas radial holdup profile and an improved protocol for future use was developed. The previously developed physically based model for liquid mixing was adapted to account for liquid withdrawal from the mid section of the column. The ability of our engineering mixing models for liquid and gas phase to predict both liquid and gas phase tracer response was established and illustrated.

Puneet Gupta

2002-07-31

398

Dynamics of magma flow inside volcanic conduits with bubble overpressure buildup and gas loss through permeable magma  

NASA Astrophysics Data System (ADS)

Many volcanic eruptions show transitions between extrusive and explosive behaviour. We develop a new generic model that considers concurrence between pressure buildup in the bubbles due to the viscous resistance to their growth and gas escape through the bubble network as they become interconnected. When the pressure difference between bubbles and magma reaches the strength of the material fragmentation occurs. The effect of grain size distribution on the flow in gas-particle dispersion is modelled by two populations of particles which strongly influence the velocity of sound in the mixture. Solutions to the steady-state boundary value problem show non-uniqueness. There are at least two regimes for the fixed parameters in the magma chamber. In the low discharge rate regime, fragmentation does not occur and magma rises with partial gas escape. This regime corresponds to extrusive activity. The upper regime corresponds to explosive activity. The simulations using the parameters defined at the workshop produced the following results for a rhyolitic magma composition: discharge rate 5.5×107 kg/s; fragmentation at depth of 2585 m with magma vesicularity of 0.74; exit gas velocity varies from 200 to 450 m/s depending on the mass fraction of small particles in the fragmented mixture; exit pressure is in the range 1.5 to 3 MPa. Variation of conduit diameter d in the range 40 to 70 m gives a mass flow rate Q which depends on the diameter as d2.8, less strongly than for the case of viscous flow of Newtonian liquid in a cylindrical pipe where Q˜d4. With the increase in conduit diameter, fragmentation happens later in the flow and conduit resistance remains high. Changes in magma temperature from 700 to 950 °C lead to increase in discharge rate only by a factor of 4 whereas viscosity decreases by more then 8000 times.

Melnik, O.; Barmin, A. A.; Sparks, R. S. J.

2005-05-01

399

Large Methane Plumes Formed by Hydrate Coated Gas Bubbles from a Deep-Sea Submarine Mud Volcano  

NASA Astrophysics Data System (ADS)

Submarine mud volcanoes (SMVs) are major methane sources in the marine environment. Worldwide 103-105 SMVs are believed to release in total about 27 Mt CH4 yr-1. Results of the last decade \\'{ } s research suggest, that most of this methane, primarily released diffusively from deep-sea SMVs is immediately oxidised and, thus, has only little climatic impact. Recent hydroacoustic, visual and geochemical observations performed at Haakon Mosby Mud Volcano (HMMV, 1250 meters water depth) reveal that a considerable amount of methane is released by discharge of bubbles and gas hydrate flakes. Gas bubbles withstand dissolution due to the formation of a gas hydrate skin and, thus, are able to ascend several hundred meters through the water column until leaving the temperature-pressure field of gas hydrate stability. Besides, microbial water column methane oxidation was found to be extremely slow, so that methane potentially escapes to the atmosphere, especially during deep winter mixing. We thus propose a much higher environmental relevance of SMVs than previously assumed.

Sauter, E. J.; Muyakshin, S. I.; Charlou, J.; Schlueter, M.; Boetius, A.; Damm, E.; Foucher, J.; Klages, M.

2004-12-01

400

Implementation and verification of numerical model for gas bubble dynamics in electroconductive fluid  

NASA Astrophysics Data System (ADS)

Apart from common steam reforming process the thermal decomposition of methane is regarded as an alternate route to producing hydrogen and elemental carbon with out of CO2 emissions. Chemical reaction of decarburation can be ensured by means of methane bubbly flow through a molten metal bath and additionally controlled by external electromagnetic field. This is the initial stage of research and preliminary calculation results for the single bubble rise dynamics in 2D axisymmetric consideration at different flow conditions and 2D planar consideration in the presence of external DC EM field are obtained and compared to experimental and simulation data from literature.

Tucs, A.; Spitans, S.; Jakovics, A.; Baake, E.

2013-10-01

401

Bubble formation via multidrop impacts  

Microsoft Academic Search

Gas bubbles are often generated when droplets impact a liquid-air interface. For the impact of single droplets, a critical impact velocity must be exceeded for air to be entrained in the form of bubbles. Here we establish that bubbles can be generated at much lower velocities provided that two or more drops impact the liquid-air interface within a sufficiently short

Alexander G. Bick; William D. Ristenpart; Ernst A. van Nierop; Howard A. Stone

2010-01-01

402

Bubbly jets in stagnant water  

Microsoft Academic Search

Air–water bubbly jets are studied experimentally in a relatively large water tank with a gas volume fraction, Co, of up to 80% and nozzle Reynolds number, Re, ranging from 3500 to 17,700. Measurements of bubble properties and mean axial water velocity are obtained and two groups of experiments are identified, one with relatively uniform bubble sizes and another with large

David Z. Zhu; Nallamuthu Rajaratnam

2008-01-01

403

Evaluation of the Integrated Holdup Measurement System with the M3(superscript 3)CA for Assay of Uranium and Plutonium Holdup  

SciTech Connect

Uranium and plutonium holdup that has been simulated by insertion of a variety of sealed, reference samples into pipes, ducts, and other hardware has been measured over a period of six years with an integrated holdup measurement system. The result is a systematic evaluation of the generalized-geometry holdup (GGH) formalism applied to portable gamma-ray holdup measurements with low-resolution detectors. The extended exercise was carried out both with and without automation of the measurements, data reduction/analysis, and holdup evaluation. Automation was accomplished by the software Version 2 for the Holdup Measurement System (HMS2). The purpose of the exercise was to establish reliable benchmarks for GGH measurements and to document the advantages of the automation with actual measurement results. The results presented below demonstrate a factor of 2 improvement in the quantitative reliability of the holdup assay automated by HMS2. The automated results are otherwise identical to the manual measurements. These and similar exercises also show that automation can decrease by a factor of 20 or more the time required to execute a holdup measurement campaign and obtain the holdup quantities for the facility using an integrated holdup measurement system, and that only one person, rather than two, is required to perform the measurements. Enhanced implementation of the integrated holdup measurement system with new software, corrections for systematic effects, and improved room-temperature gamma-ray detectors is planned.

P. A. Russo; J. K. Sprinkle, Jr.; C. W. Bjork; T. O. McKown; G. A. Sheppard; S. E. Smith; J. F. Harris

1999-08-01

404

PROCESS MODEL FOR AMMONIA VOLATILIZATION FROM ANAEROBIC SWINE LAGOONS INCORPORATING VARYING WIND SPEEDS AND GAS BUBBLING  

Microsoft Academic Search

Ammonia volatilization from treatment lagoons varies widely with the total ammonia concentration, pH, temperature, suspended solids, atmospheric ammonia concentration above the water surface, and wind speed. Ammonia emissions were estimated with a process-based mechanistic model integrating ammonia chemistry of the lagoon and interfacial transport characteristics between air and water. This improved model incorporated the effect of internal bubble production and

K. S. Ro; A. A. Szogi; M. B. Vanotti; K. C. Stone

405

Transport evaluation of a gas-liquid scrubber. [Five-tray, single-bubble-cap, single-downcomer, gas liquid contactor  

SciTech Connect

The hydraulics and the mass-transfer behavior of a five-tray, single-bubble-cap, single-downcomer, gas-liquid contactor were studied for use as a gas scrubber. Flooding was not observed at the maximum available liquid and gas flow rates of 0.32 and 464 L/min, respectively. The maximum liquid entrainment was 33% at a gross liquid flow rate of 0.05 L/min. The Murphree-tray efficiencies for absorption of CO/sub 2/ (5000 ppM in air) into demineralized water ranged from 0.14 to 0.74 for volumetric liquid-to-gas ratios of 4 x 10/sup -4/ and 2 x 10/sup -4/, respectively, for k/sub L/a values ranging from 0.088 to 0.36 min/sup -1/. 12 figures, 10 tables.

Brodner, A.J.; Bistline, J.E.; Weber, S.E.

1982-10-01

406

Gas bubbles may not be the underlying cause of decompression illness - The at-depth endothelial dysfunction hypothesis.  

PubMed

Gas formed in tissues and the circulating blood due to decompression is thought to be a significant factor in the progression of decompression illness (DCI). DCI is a potential problem for a growing population of professional and recreational divers. We hypothesise that these gas bubbles are not the causative agent in progression of DCI, rather an exacerbating factor. Endothelial dysfunction caused by a temporary loss of haemostasis due to increased total oxidant status is postulated to be the cause in this at-depth endothelial dysfunction hypothesis. Breathing oxygen at any pressure increases the oxidant status in the circulation causing vasoconstriction; this increase can be prevented by antioxidants, such as Vitamin C, maintaining haemostasis and preventing activation of endothelium, leukocyte recruitment and subsequent localised inflammation. Bubbles have the potential to exacerbate the situation on decompression by damaging the vascular endothelium either through ischemia/reperfusion, physical contact with the endothelium or by an increase in shear stress. Furthermore, this damage may manifest itself in the release of endothelial membrane fragments (microparticles). PMID:19128890

Madden, Leigh A; Laden, Gerard

2009-01-06

407

HEU Holdup Measurements on 321-M A-Lathe  

SciTech Connect

The Analytical Development Section of SRTC was requested by the Facilities Disposition Division (FDD) of the Savannah River Site to determine the holdup of enriched uranium in the 321-M facility as part of an overall deactivation project of the facility. The 321-M facility was used to fabricate enriched uranium fuel assemblies, lithium-aluminum target tubes, neptunium assemblies, and miscellaneous components for the production reactors. The results of the holdup assays are essential for determining compliance with the solid waste Waste Acceptance Criteria, Material Control and Accountability, and to meet criticality safety controls. Three measurement systems were used to determine highly enriched uranium (HEU) holdup. This report covers holdup measurements on the A-Lathe that was used to machine uranium-aluminum-alloy (U-Al). Our results indicated that the lathe contained more than the limits stated in the Waste Acceptance Criteria (WAC) for the solid waste E-Area Vaults. Thus the lathe was decontaminated three times and assayed four times in order to bring the amounts of uranium to an acceptable content. This report will discuss the methodology, Non-Destructive Assay (NDA) measurements, and results of the U-235 holdup on the lathe.

Dewberry, R.A.

2002-04-30

408

Water holdup measurement in kerosene water two-phase flows  

NASA Astrophysics Data System (ADS)

This paper proposes an intrusive method for measurement of water holdup based on water layer thickness in horizontal pipes. Water layer thickness is measured by a capacitance probe, which is made of a metal wire with an insulating film. The capacitance is linearly proportional to the water layer thickness and is independent of water salinity and its distribution. Seven thicknesses over the cross section of the pipe are measured simultaneously to compute water holdup. A curve of water layer thickness as a function of time is compared with a flow structure photo and the measured time-averaged water holdup is compared with that of a quick-closing valve (QCV) system. The experiments were carried out in kerosene-oil two-phase flows with high water fraction in horizontal pipes of 29 mm diameter. Four flow patterns with continuous water are reported, namely wavy stratified flow (WS), three-layer flow (3 L), water and dispersed oil in water flow (W&DO/W) and dispersed oil in water flow (DO/W). The results show that the layer thickness curves are in reasonable agreement with the flow structures to different extents under different flow patterns and that the accuracies of the measured water holdup mainly depend on flow patterns. The relative error limits of water holdup are -15.2% for WS, 12.9% and -14.5% (positive and negative) for 3 L, 34.9% for W&DO/W and 15.8% for DO/W.

Huang, S.-F.; Zhang, X.-G.; Wang, D.; Lin, Z.-H.

2007-12-01

409

Systems-level analysis of AC microfluidics and the problem of trapped gas bubbles  

NASA Astrophysics Data System (ADS)

Using pulsatile pressure and flow rate, we extend the equivalent circuit (EC) approach for systems-level analysis of microfluidic systems to also include dynamic, transient effects such as inertia and compliance. The dynamic time scales of microfluidics are typically on the order of millisecond, or equivalently frequencies in the low kHz regime. A novel pressure source has been developed and successfully tested for the experimental generation of flow under these conditions for two microfluidic setups. Good agreement was found between the experimental observations and the results of corresponding systems-level EC model [1]. Trapped air bubbles in the microfluidic system severely influences its performance, while also leading to erroneous predictions from the systems-level analysis. We present theoretical analysis of the physics of bubble adhesion to the system walls, leading to insights to their removal. [1] S. Vedel, L.H. Olesen, H. Bruus, Lab Chip (submitted 2009), http://arxiv.org/abs/0907.2679

Vedel, S.{O.}Ren; HØJgaard Olesen, Laurits; Bruus, Henrik

2009-11-01

410

Decomposition of Energetic Materials by Pulsed Electrical Discharges in Gas-Bubbled Aqueous Solutions  

Microsoft Academic Search

The application of high-voltage pulsed electrical discharges in bubbled water (PDBWs) for the remediation of solutions containing energetic compounds such as RDX, HMX, and TNT was investigated. Using low-energy pulses ( ~ 300 mJ\\/pulse), it was found that the PDBW was highly selective toward the type of energetic compound. The effects of a catalyst and of the pH value of

O. Mozgina; A. Koutsospyros; S. Gershman; A. Belkind; C. Christodoulatos; K. H. Becker

2009-01-01

411

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

Microsoft Academic Search

This paper reports on a visual study of the CO2 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 × 4.0cm2, two bipolar plates with a single serpentine channel, and a transparent enclosure. The study reveals that at

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

2005-01-01

412

New correlation for liquid hold-up of sodium citrate buffer solution in a Raschig ring packed column  

Microsoft Academic Search

Dynamic liquid hold-up was measured with an air\\/aqueous sodium citrate buffer solution at 20–40 °C, and an air\\/water system at 23 °C, in a 0.1 m diameter\\/1 m high glass column covered by a heat-isolating vacuum jacket and packed with 0.012 m nominal size ceramic Raschig rings. The superficial gas velocity range was extended to 1.2 m s?1. Experimental results

I. Bágyi; E. Márki; E. Békássy-Molnár

1996-01-01

413

Understanding air-gun bubble behavior  

Microsoft Academic Search

An air-gun bubble behaves approximately as a spherical bubble of an ideal gas in an infinite volume of practically incompressible water. With this simplification, the equation of bubble motion and its far-field signature is more understandable than with the more exact theory commonly cited in the literature. The terms of the equation of bubble motion are explained using elementary physics

Daniel T. Johnson

1994-01-01

414

Bubble Tray  

NSDL National Science Digital Library

Bubble Tray from the Exploratorium is an activity about surface tension and constructive or destructive interference observed in soap bubbles. The site provides a soap bubble recipe and suggests common supplies like a coat hanger and pizza pan to produce large, long lasting bubbles. An explanation of the physics involved and other methods of making large bubbles are also supplied. This activity is part of Exploratorium's Science Snacks series.

2006-07-16

415

Centrifugal bubble O{sub 2} ({sup 1{Delta}}) gas generator with a total pressure of 100 Torr  

SciTech Connect

A centrifugal bubbling singlet-oxygen gas generator is developed in which chlorine with helium are injected into the rotating layer of the alkali solution of hydrogen peroxide through cylindrical nozzles directed at an angle of 30{sup 0} to the bubbler surface. The concentrations of water vapour and O{sub 2} ({sup 1{Delta}}) and the gas temperature were determined by using the multichannel recording of the emission bands of oxygen at 634, 703, 762 and 1268 nm. For the chlorine and helium flow rates of 60 and 90 mmol s{sup -1}, respectively, the specific chlorine load of 3.2 mmol cm{sup -2}, a total pressure of 100 Torr in the working region of the gas generator and the oxygen partial pressure of 36 Torr, the chlorine utilisation was 90% and the content of O{sub 2} ({sup 1{Delta}}) was {approx}60%. For the ratio of the flow rates of chlorine and the alkali solution of hydrogen peroxide equal to 1 mol L{sup -1}, the water vapour content was {approx}25%. The chemical efficiency of the oxygen-iodine laser with this gas generator achieved 23% for the specific power of 12.7 W cm per 1 cm{sup 3} s{sup -1} per pass of the solution through the gas generator. (laser applications and other topics in quantum electronics)

Zagidulin, M V; Nikolaev, V D; Svistun, M I; Khvatov, N A [Samara Branch of the P. N. Lebedev Physics Institute, Russian Academy of Sciences, Samara (Russian Federation)

2008-08-31

416

Influence of infection with Renibacterium salmoninarum on susceptibility of juvenile spring chinook salmon to gas bubble trauma  

USGS Publications Warehouse

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.

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

1999-01-01

417

Physics of bubble oscillations  

NASA Astrophysics Data System (ADS)

Bubbles in liquids, soft and squeezy objects made of gas and vapour, yet so strong as to destroy any material and so mysterious as at times turning into tiny light bulbs, are the topic of the present report. Bubbles respond to pressure forces and reveal their full potential when periodically driven by sound waves. The basic equations for nonlinear bubble oscillation in sound fields are given, together with a survey of typical solutions. A bubble in a liquid can be considered as a representative example from nonlinear dynamical systems theory with its resonances, multiple attractors with their basins, bifurcations to chaos and not yet fully describable behaviour due to infinite complexity. Three stability conditions are treated for stable trapping of bubbles in standing sound fields: positional, spherical and diffusional stability. Chemical reactions may become important in that respect, when reacting gases fill the bubble, but the chemistry of bubbles is just touched upon and is beyond the scope of the present report. Bubble collapse, the runaway shrinking of a bubble, is presented in its current state of knowledge. Pressures and temperatures that are reached at this occasion are discussed, as well as the light emission in the form of short flashes. Aspherical bubble collapse, as for instance enforced by boundaries nearby, mitigates most of the phenomena encountered in spherical collapse, but introduces a new effect: jet formation, the self-piercing of a bubble with a high velocity liquid jet. Examples of this phenomenon are given from light induced bubbles. Two oscillating bubbles attract or repel each other, depending on their oscillations and their distance. Upon approaching, attraction may change to repulsion and vice versa. When being close, they also shoot self-piercing jets at each other. Systems of bubbles are treated as they appear after shock wave passage through a liquid and with their branched filaments that they attain in standing sound fields. The N-bubble problem is formulated in the spirit of the n-body problem of astrophysics, but with more complicated interaction forces. Simulations are compared with three-dimensional bubble dynamics obtained by stereoscopic high speed digital videography.

Lauterborn, Werner; Kurz, Thomas

2010-10-01

418

Soluble surfactants favorably modify fluid structure and wall shear stress profiles during near-occluding bubble motion in a computational model of intravascular gas embolism  

NASA Astrophysics Data System (ADS)

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.

Swaminathan, T. N.; Ayyaswamy, P. S.; Eckmann, D. M.

2009-11-01

419

Measurement of physical characteristics of bubbles in gas-liquid plumes: Part II. Local properties of turbulent air-water plumes in vertically injected jets  

Microsoft Academic Search

The structural development of air-water bubble plumes during upward injection into a ladle-shaped vessel has been measured under different conditions of air flow rate, orifice diameter, and bath depth. The measured radial profiles of gas fraction at different axial positions in the plume were found to exhibit good similarity, and the distribution of the phases in the plume was correlated

A. H. Castillejos; J. K. Brimacombe

1987-01-01

420

Generalizations of the Young-Laplace equation for the pressure of a mechanically stable gas bubble in a soft elastic material  

Microsoft Academic Search

The Young-Laplace equation for the pressure of a mechanically stable gas bubble is generalized to include the effects of both surface tension and elastic forces of its surroundings. The latter are taken to be comprised of a soft isotropic material. Generalizations are derived for conditions of constant external pressure and constant system volume. The derived equations are formally exact for

Saul Goldman

2009-01-01

421

The influence of the wall contact angle on gas bubble behaviour in xylem conduits under tension and possible consequences for embolism  

Microsoft Academic Search

Gas-filling of conduits decreases hydraulic conductance of the xylem vessels. Therefo re, embolism formation and reversal is one of the crucial topics in plant water transport. The negative pressure (=tension) in xylem water during plant transpiration may cause embolism in tw o ways: (i) Homogeneous nucleation, the spontaneous formation of a water vapour bubble within the water column due to

Wilfried Konrad; Anita Roth-Nebelsick

2009-01-01

422

Recent developments in modeling gas-phase catalyzed olefin polymerization fluidized-bed reactors: The effect of bubble size variation on the reactor's performance  

Microsoft Academic Search

In the present study recent developments in modeling gas-phase catalyzed olefin polymerization fluidized-bed reactors (FBR) are critically reviewed. A new FBR model is developed to account for the effect of varying bubble size with the bed height on the reactor dynamics and the molecular properties of the polymer product. A comprehensive kinetic model for ethylene copolymerization in the presence of

H. Hatzantonis; H. Yiannoulakis; A. Yiagopoulos; C. Kiparissides

2000-01-01

423

AFM forces between mica and polystyrene surfaces in aqueous electrolyte solutions with and without gas bubbles.  

PubMed

Force curves between a flat mica substrate and a polystyrene microsphere were measured with an atomic force microscope (AFM) in carefully degassed water and aqueous NaCl, CaCl2, and AlCl3 solutions. The pH of the water used does not change significantly with degassing treatment, and its value remains close to 6. Electrolyte concentration ranges from 10-4 to 10-2M and pH from 4.7 to 5.1. We have found that the repulsive long-range electrostatic force between mica and polystyrene is attenuated by the presence of electrolytes and counterbalanced by a long-range attractive force, which we referred to as a hydrophobic force, which is longer-ranged than the ever present attractive van der Waals force. This force, which includes the adhesive bridging of residual air bubbles and newborn vapor cavities, and any other unknown forces, is reasonably well represented by a unique exponential law. Prefactor and decaying length are not very sensitive to electrolyte type, concentration, and pH, suggesting that any new force included in the law, in addition to adhesive bridges, should obey a non-classical electrostatic mechanism. However, we also know that liquid/solid contact angle and liquid/vapor surface tension increase with electrolyte concentration and valence increasing the stability of bubbles and cavities which in turn increase the bridging force. Clearly, these effects are hidden in the empirical force law. PMID:23998373

Saavedra, Jorge H; Acuña, Sergio M; Toledo, Pedro G

2013-08-11

424

Conversion of low H/sub 2//CO ratio synthesis gas to hydrocarbons: Final report, October 1, 1981-September 30, 1986. [Bubble-column reactor  

SciTech Connect

The objectives of this project have been twofold: (1) to develop a theoretical model for designing bubble-column reactors and assessing their performance and (2) to characterize the performance of a laboratory-scale bubble-column reactor. The theoretical part of the project has focused the effects of gas-liquid mass transfer; axial dispersion of gas, liquid, and catalyst; ad the interplay between the kinetics of Fischer-Tropsch synthesis and the water-gas-shift reaction. The experimental portion of the project has focused the effects of reaction conditions on product distribution and, in particular, the conditions under which gas-liquid mass transfer becomes important. Any independent set of experiments was undertaken to investigate the chemistry of carbonaceous deposits formed during Fischer-Tropsch synthesis. 8 refs.

Bell, A.T.; Heinemann, H.

1986-01-01

425

Hold-up Time Measurements for Various Actinide Targets  

Microsoft Academic Search

At Oak Ridge National Laboratory the Holifield Radioactive Ion Beam Facility produces radioactive ion beams (RIBs) by proton-induced fission on an actinide target. The RIB yields depend on the chemical and physical properties of the target used. The rates at which chemical elements are released from the target ion source, called hold-up times, can give information about the movement of

Emily Prettyman; H. K. Carter; Andreas Kronenberg; Eugene Spejewski; Daniel Stracener

2006-01-01

426

Mass flow measurement of gas-liquid bubble flow with the combined use of a Venturi tube and a vortex flowmeter  

Microsoft Academic Search

Development of effective techniques for gas-liquid two-phase flow measurement is of interest to both academic research and industrial applications. This paper presents a novel approach to the measurement of the mass flow rate of homogeneous gas-liquid bubble flow with the combined use of a Venturi tube and a vortex flowmeter. The Venturi tube and the vortex flowmeter were mounted in

Zhiqiang Sun

2010-01-01

427

Mass transfer in bubble column for industrial conditions—effects of organic medium, gas and liquid flow rates and column design  

Microsoft Academic Search

Most of available gas–liquid mass transfer data in bubble column have been obtained in aqueous media and in liquid batch conditions, contrary to industrial chemical reactor conditions. This work provides new data more relevant for industrial conditions, including comparison of water and organic media, effects of large liquid and gas velocities, perforated plates and sparger hole diameter.The usual dynamic O2

H. Chaumat; A. M. Billet-Duquenne; F. Augier; C. Mathieu; H. Delmas

2005-01-01

428

Bubble generation during transformer overload  

SciTech Connect

Bubble generation in transformers has been demonstrated under certain overload conditions. The release of large quantities of bubbles would pose a dielectric breakdown hazard. A bubble prediction model developed under EPRI Project 1289-4 attempts to predict the bubble evolution temperature under different overload conditions. This report details a verification study undertaken to confirm the validity of the above model using coil structures subjected to overload conditions. The test variables included moisture in paper insulation, gas content in oil, and the type of oil preservation system. Two aged coils were also tested. The results indicated that the observed bubble temperatures were close to the predicted temperatures for models with low initial gas content in the oil. The predicted temperatures were significantly lower than the observed temperatures for models with high gas content. Some explanations are provided for the anomalous behavior at high gas levels in oil. It is suggested that the dissolved gas content is not a significant factor in bubble evolution. The dominant factor in bubble evolution appears to be the water vapor pressure which must reach critical levels before bubbles can be released. Further study is needed to make a meaningful revision of the bubble prediction model. 8 refs., 13 figs., 11 tabs.

Oommen, T.V. (Westinghouse ABB Power T and D Co., Sharon, PA (USA). Materials and Mfg. Technology Dept.)

1990-03-01

429

Soap Bubbles  

NSDL National Science Digital Library

Learners explore three-dimensional geometric frames including cubes and tetrahedrons, as they create bubble wands with pipe cleaners and drinking straws. Then they investigate how soap film flows into a state of minimum energy when they lift the wand up from the bubble solution. Learners also see how light reflection and interference create shimmering colors in the bubbles.

Exploratorium, The

2011-12-07

430

Predicting diffused-bubble oxygen transfer rate using the discrete-bubble model  

Microsoft Academic Search

A discrete-bubble model that predicts the rate of oxygen transfer in diffused-bubble systems is evaluated. Key inputs are the applied gas flow rate and the initial bubble size distribution. The model accounts for changes in the volume of individual bubbles due to transfer of oxygen and nitrogen (and hence changing partial pressure), variation in hydrostatic pressure, and changes in temperature.

Daniel F McGinnis; John C Little

2002-01-01

431

Study on bubbly flow behavior in natural circulation reactor by thermal-hydraulic simulation tests with SF6-Gas and ethanol liquid  

NASA Astrophysics Data System (ADS)

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.

Kondo, Yoshiyuki; Suga, Keishi; Hibi, Koki; Okazaki, Toshihiko; Komeno, Toshihiro; Kunugi, Tomoaki; Serizawa, Akimi; Yoneda, Kimitoshi; Arai, Takahiro

2009-02-01

432

Bubble formation at nozzles in pig iron  

Microsoft Academic Search

An experimental study was undertaken to determine how several variables affect the size of gas bubbles formed at nozzles in\\u000a liquid pig iron. The frequency of bubble formation was measured by an acoustic device, which could detect the vibrations produced\\u000a by the bubble release. Accurate knowledge of the gas flow rate then enabled the calculation of bubble volumes. The use

G. A. Irons; R. I. L. Guthrie

1978-01-01

433

Bubble formation resulting from counterdiffusion supersaturation: a possible explanation for isobaric inert gas 'urticaria' and vertigo  

Microsoft Academic Search

In recent simulated diving experiments, subjects have experienced intense itching, confluent maculopapular skin lesions and a severe vestibular derangement with vertigo and nystagmus. These effects have been observed when a gas mixture containing nitrogen or neon is being breathed while a second inert gas, helium, is present in the surrounding environment. Attempts to explain this phenomenon led to a study

D. J. GRAVES; J. IDICULA; C. J. LAMBERTSEN; J. A. QUINN

1973-01-01

434

Experimental study on a plane shock wave accelerating a gas bubble  

Microsoft Academic Search

A detailed experimental study of the interaction between a planar shock wave and an isolated spherical gas inhomogeneity is presented here. Different configurations have been considered: a shock wave moving from one gas into another, of similar density, lower density and one of higher density. Sequences of shadowgraph pictures obtained during the same run provided useful insights into several mechanisms

Guillaume Layes; Georges Jourdan; Lazhar Houas

2009-01-01

435

Nondestructive assay holdup measurements with the Ortec detective  

SciTech Connect

Wing 4 of the Chemistry and Metallurgy Research facility at Los Alamos National Laboratory is to be downgraded from a Hazard Category 2 Nuclear Facility to a Hazard Category 3 Radiological Facility. Survey and holdup measurements are used to ensure that the total contamination levels present in the facility do not contribute enough activity to go above the Hazard Category 3 threshold quantities. Additionally, the measurement information provides an understanding of the cleanup and the equipment removal needs for the next step of decontaminating and decommissioning of the site. The Chemistry and Metallurgy Research (CMR) facility has been housing the research and experimental activities for analytical chemistry, plutonium and uranium chemistry, and metallurgy since the start of the Los Alamos National Laboratory. It is currently being replaced by the new Chemistry and Metallurgy Research Replacement facilities. As a result, the CMR is gradually closing and/or downgrading to a nonnuclear facility. In 2008, the Safeguards Science and Technology group, N-1, was assigned the task of doing survey and holdup measurements of Wing 4 of the CMR. The goal of the measurements is to provide defensible measurement data for Wing 4 of the CMR Building to be downgraded from a Hazard Category 2 Nuclear Facility to below a Hazard Category 3 Radiological Facility. In addition, the measurement information would provide an understanding of the cleanup and the equipment removal needs for the next step of decontaminating and decommissioning the site. The large areal olume of the site and the high intensity of the high-energy gamma rays of thorium, either from the background or the contaminated objects in the measured room or the adjacent rooms, present some challenges in the holdup measurements. Typical holdup techniques of point source, line, or area measurement do not work well. In order to speed up the measurement time and to accuralely account for all the isotopes present in the facility, we used a new technique that we tentatively named 'Room Holdup Measurement' to do holdup measurements of the site. This technique uses the portable, electric-cooled high-purity germanium detectors from Ortec (the Detectives) to measure the activities of the isotopes.

Vo, Duc [Los Alamos National Laboratory; Wenz, Tracy [Los Alamos National Laboratory; Bracken, David [Los Alamos National Laboratory

2009-01-01

436

Review of Current Literature and Research on Gas Supersaturation and Gas Bubble Trauma: Special Publication Number 1, 1986.  

SciTech Connect

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.

Colt, John; Bouck, Gerald R.; Fidler, Larry

1986-12-01

437

Bubble Puzzles  

NASA Astrophysics Data System (ADS)

Bubbles are fascinating. With their ubiquitous occurrence in a multitude of fluid systems bubbles occupy a very important place in contemporary science and technology. In many applications, bubble control is crucial. I will demonstrate that bubble nucleation at surfaces, which always has been associated with randomness, can be perfectly controlled both in space and time. This new technique allows to quantitatively study bubble-bubble and bubble-surface interaction and reveals a shielding effect in bubble clusters [1]. -- In a second example for the importance of bubble control I will discuss their disturbing effect in piezo-acoustic ink-jet printing: I will show how bubbles are entrained, grow by rectified diffusion, and finally seriously disturb the jetting process by counteracting the pressure build-up at the nozzle [2]. [1] N. Bremond, M. Arora, C. D. Ohl, and D. Lohse, Phys. Rev. Lett. 96, 224501 (2006). [2] J. de Jong, H. Reinten, M. van den Berg, H. Wijshoff, M. Versluis, G. de Bruin, and D. Lohse, J. Acoust. Soc. Am., (August 2006).

Lohse, Detlef

2006-11-01

438

A Study of Spouts on Bath Surfaces from Gas Bubbling: Part I. Experimental Investigation  

Microsoft Academic Search

Water model experiments were performed simulating spout formation in a gas-stirred ladle. The height and width of the spout\\u000a region with and without a slag-simulating phase (oil) were obtained using a video technique over a wide range of operating\\u000a conditions. Using the experimental data, the spout dimensions were correlated to the operating variables, namely, the gas\\u000a flow rate and heights

K. Krishnapisharody; G. A. Irons

2007-01-01

439

Holdup correlations in slurry-solid fluidized beds  

SciTech Connect

The use of slurry-solids fluid beds plays an important role in the development of synthetic fuels and the hydrogen processing of petroleum resids. In the H-Coal process in particular, coal oil slurries are processed over extrudates of hydrodesulfurization catalyst. The objective of this note is to present a model which describes the volume fraction occupied by the slurry phase. The accurate prediction of the liquid holdup is important not only for the calculation of the bed height in liquid solid fluidized beds, but also is required for the development of a model predicting the holdup in three-phase fluidized beds. In the present publication, the application of two different correlations is considered: (1) the Richardson and Zaki; and (2) Ramamurthy and Sabbaraju.

Vasalos, I.A.; Rundell, D.N.; Megiris, K.E.; Tjatjopoulos, G.J.

1980-01-01

440

Mesoporous hollow spheres from soap bubbling.  

PubMed

The smaller and more stable bubbles can be generated from the large parent bubbles by rupture. In the presence of a bubble blowing agent, hollow spheres can be prepared by bubbling a silica sol. Herein, the trapped gas inside the bubble acts as a template. When the porogen, i.e., other surfactant, is introduced, a mesostructured shell forms by the co-assembly with the silica sol during sol-gel process. Morphological evolution emphasizes the prerequisite of an intermediate interior gas flow rate and high exterior gas flow rate for hollow spheres. The method is valid for many compositions from inorganic, polymer to their composites. PMID:22078340

Yu, Xianglin; Liang, Fuxin; Liu, Jiguang; Lu, Yunfeng; Yang, Zhenzhong

2011-10-10

441

Application of the ultrasonic technique and high-speed filming for the study of the structure of air-water bubbly flows  

SciTech Connect

Multiphase flows are very common in industry, oftentimes involving very harsh environments and fluids. Accordingly, there is a need to determine the dispersed phase holdup using noninvasive fast responding techniques; besides, knowledge of the flow structure is essential for the assessment of the transport processes involved. The ultrasonic technique fulfills these requirements and could have the capability to provide the information required. In this paper, the potential of the ultrasonic technique for application to two-phase flows was investigated by checking acoustic attenuation data against experimental data on the void fraction and flow topology of vertical, upward, air-water bubbly flows in the zero to 15% void fraction range. The ultrasonic apparatus consisted of one emitter/receiver transducer and three other receivers at different positions along the pipe circumference; simultaneous high-speed motion pictures of the flow patterns were made at 250 and 1000 fps. The attenuation data for all sensors exhibited a systematic interrelated behavior with void fraction, thereby testifying to the capability of the ultrasonic technique to measure the dispersed phase holdup. From the motion pictures, basic gas phase structures and different flows patterns were identified that corroborated several features of the acoustic attenuation data. Finally, the acoustic wave transit time was also investigated as a function of void fraction. (author)

Carvalho, R.D.M.; Venturini, O.J.; Tanahashi, E.I. [Universidade Federal de Itajuba (UNIFEI), Itajuba (Brazil); Neves, F. Jr. [Universidade Tecnologica Federal do Parana (UTFPR), Curitiba (Brazil); Franca, F.A. [Universidade Estadual de Campinas (UNICAMP), Campinas (Brazil)

2009-10-15

442

Transfer Pricing and Hold-Ups in Supply Chains  

Microsoft Academic Search

We reconsider the hold-up problem under symmetric information when more than two parties form a 'supply chain'. The parties are assumed to renegotiate bilaterally and sequentially. Potential trade distortions then arise in addition to the usual investment problem. Following Edlin and Reichelstein (1995, 1996), we consider fixed-quantity contracts. First-best allocations are shown to be attainable if the parties are able

Sabine Böckem; Ulf Schiller

2004-01-01

443

Rarefied gas correction for the bubble entrapment singularity in drop impacts  

NASA Astrophysics Data System (ADS)

We study the non-continuous correction in the dynamics of drop impact on a solid substrate. Close to impact, a thin film of gas is formed beneath the drop so that the local Knudsen number is of order one. We consider the first correction to the dynamics which consists of allowing slip of the gas along the substrate and the interface. We focus on the singular dynamics of entrapment that can be seen when surface tension and liquid viscosity can be neglected. There we show that different dynamical regimes are present that tend to lower the singularity strength. We finally suggest how these effects might be connected to the influence of the gas pressure in the impact dynamics observed in recent experiments.

Duchemin, Laurent; Josserand, Christophe

2012-11-01

444

Big Bubbles  

NSDL National Science Digital Library

How do you measure a bubble when it's floating? You can't really, but in this activity, learners can measure the diameter of the ring of suds a bubble leaves on a flat surface. The fun is blowing up the bubbles as big as possible with a straw. Then comes the measuring. This activity can be used to connect science and math, and makes a great rainy day or indoor lunch activity.

Science, Lawrence H.

2010-01-01

445

Stream function, flow separation and force equation for stagnation flow passing a small solid sphere touching a rising gas bubble  

Microsoft Academic Search

This paper considers an axisymmetric stagnation flow past a small solid sphere touching an air bubble, which is significantly larger than the particle but smaller than the capillary length so that the deformation can be neglected. The disturbed flow due to the presence of the particle at the bubble surface was modelled by considering an axisymmetric stagnation point flow about

Anh V. Nguyen; Geoffrey M. Evans

2003-01-01

446

Measurement of physical characteristics of bubbles in gas-liquid plumes: Part II. Local properties of turbulent air-water plumes in vertically injected jets  

Microsoft Academic Search

The structural development of air-water bubble plumes during upward injection into a ladle-shaped vessel has been measured\\u000a under different conditions of air flow rate, orifice diameter, and bath depth. The measured radial profiles of gas fraction\\u000a at different axial positions in the plume were found to exhibit good similarity, and the distribution of the phases in the\\u000a plume was correlated

A. H. Castillejos; J. K. Brimacombe

1987-01-01

447

Effect of gas expansion on the velocity of individual Taylor bubbles rising in vertical columns with water: Experimental studies at atmospheric pressure and under vacuum  

Microsoft Academic Search

This study was designed to determine the effect of gas expansion on the velocity of Taylor bubbles rising individually in a vertical column of water. This experimental study was conducted at atmospheric pressure or under vacuum (33.3 and 20.0kNm-2) using three different acrylic columns with internal diameters of 0.022, 0.032, and 0.052m, and more than 4.0m high. A non-intrusive optical

L. M. T. Santos; M. T. M. Sena Esteves; M. N. Coelho Pinheiro

2008-01-01

448

Modeling of a novel multi-stage bubble column scrubber for flue gas desulfurization  

Microsoft Academic Search

Desulfurization of flue gases from various chemical industries in a techno-econo-enviro manner is a demanding technology. The concentrations of sulfur dioxide in and around these plants overshoot the danger point. In the present investigation, an attempt has been made for wet flue gas desulfurization using water as the absorbing medium in a newly developed scrubber. Prediction of SO2 removal efficiency

B. C. Meikap; G. Kundu; M. N. Biswas

2002-01-01

449

Dynamic surface tension measured with an integrated sensor–actuator using electrolytically generated gas bubbles  

Microsoft Academic Search

In this paper, a new, simple method to determine dynamic surface tension in aqueous solutions is reported, explained and experimentally verified. By function integration, a small device is obtained. Apart from control and interface electronics no external components or systems are necessary. Instead of the conventional sparging, we use the (cathodic) electrolysis of water at an actuator to produce gas

Wouter Olthuis; Alex Volanschi; Piet Bergveld

1998-01-01

450

Dynamic surface tension measured with an integrated sensor-actuator device using electrolytically generated gas bubbles  

Microsoft Academic Search

In this paper, a new, simple method to determine dynamic surface tension in aqueous solutions is reported, explained and experimentally verified. By function integration, a small device is obtained; apart from control and interface electronics no external components or systems are necessary. Instead of the conventional sparging, we use the (cathodic) electrolysis of water at an actuator to produce gas

Wouter Olthuis; Alex Volanschi; Piet Bergveld

1997-01-01

451

A Next-Generation Automated Holdup Measurement System (HMS-5)  

SciTech Connect

Holdup Measurement System 4 software (HMS4) has been in use at facilities to systematically measure and verify the amounts of uranium holdup in process facilities under safeguards since its release in 2004. It is a system for measuring uranium and plutonium and archiving holdup data (via barcoded locations with information) which is essential for any internationally safeguarded facility to monitor all amounts of residual special nuclear material (SNM). Additionally, HMS4 has been tested by sites in Russia, the United States, South Africa, and China for more effective application. Comments and lessons learned have been received over time and an updated version of the software would enable the international partners to use a wider variety of commercial equipment existing at these facilities. In June 2005, the Oak Ridge National Laboratory (ORNL) and Los Alamos National Laboratory conducted a holdup measurement training course on HMS4 for subject matter experts from the Ulba Metallurgical Facility at Ust-Kamenogorsk, Kazakhstan, which included an additional external software package for improved measurements of low-enriched uranium by using higher energy gamma-rays more readily found. Due to not being currently integrated into HMS4, it would be greatly beneficial to include this application in the next generation HMS software package (HMS-5). This software system upgrade would assist the International Atomic Energy Agency (IAEA) in having a more comprehensive software package and having it tested at several safeguarded locations. When released, HMS4 only supported AMETEK/ORTEC equipment despite many facilities currently utilizing Canberra Industries technology (detectors, multi-channel analyzers, other hardware, and software packages). For HMS-5 to support all available hardware systems and to benefit the majority of international partners and the IAEA, Canberra technology must be integrated because of such widespread use of its hardware. Furthermore, newly developed hardware such as lanthanum halide detectors and digital processing multichannel analyzers will be incorporated into the new HMS-5 system to accommodate the evolving realm of SNM detection and quantification. HMS-5 is the natural progression from the previous incantations of automated special nuclear material holdup measurement systems for process facilities. ORNL is leading this next-generation system with assistance from its foreign partners and past experiences of its Safeguards Laboratory staff.

Gariazzo, Claudio Andres [ORNL; Smith, Steven E [ORNL; Solodov, Alexander A [ORNL

2007-01-01

452

Possible applications of bubble acoustics in Nature  

Microsoft Academic Search

Gas bubbles are the most potent naturally-occurring entities that influence the acoustic environment in liquids. Upon entrainment under breaking waves, waterfalls, or rainfall over water, each bubble undergoes small amplitude decaying pulsations with a natural frequency that varies approximately inversely with the bubble radius, giving rise to the 'plink' of a dripping tap or the roar of a cataract. When

T. G. Leighton; D. C. Finfer

453

Bubble effect on Kelvin-Helmholtz' instability  

Microsoft Academic Search

We derive boundary conditions at interfaces (contact discontinuities) for a class of Lagrangian models describing, in particular, bubbly flows. We use these conditions to study Kelvin-Helmholtz' instability which de- velops in the flow of two superposed layers of a pure incompressible fluid and a fluid containing gas bubbles, co-flowing with different velocities. We show that the presence of bubbles in

454

Bubble effect on Kelvin-Helmholtz instability  

Microsoft Academic Search

We derive boundary conditions at interfaces (contact discontinuities) for a class of Lagrangian models describing, in particular, bubbly flows. We use these conditions to study the Kelvin-Helmholtz instability that develops in the flow of two superposed layers of a pure incompressible fluid and a fluid containing gas bubbles, co-flowing with different velocities. We show that the presence of bubbles in

Sergey L. Gavrilyuk; Henri Gouin; Vladimir M. Teshukov