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1

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

SciTech Connect

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

Estevez, L.A. (Univ. of Puerto Rico, Dept. of Chemical Engineering (US)); Saez, E. (Univ. Simon Bolivar, Dept. de Termodinamica); Pachino, J.; Cavicchioli, I. (INTEVEP, S. A., Caracas (VE))

1988-01-01

2

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

3

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

Microsoft Academic Search

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

Yoshinori Kawase; Murray Moo-Young

1987-01-01

4

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

Microsoft Academic Search

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

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

1995-01-01

5

HOLDUP STRUCTURE IN HIGHLY VISCOUS NEWTONIAN AND NON-NEWTONIAN LIQUIDS IN BUBBLE COLUMNS  

Microsoft Academic Search

Gas holdup structures in highly viscous glycerine and CMC solutions are studied in a 0.305 m diameter batch bubble column. The fractional gas holdups are determined using the dynamic gas disengagement method. Empirical correlations for the gas holdup based on data covering wide ranges of viscosities in Newtonian and pseudoplastic non-Newtonian solutions are presented. For highly viscous pseudoplastic solutions in

S. P. GODBOLE; M. F. HONATH; Y. T. SHAH

1982-01-01

6

AN EXPERIMENTAL STUDY OF GAS HOLDUP IN TWO-PHASE BUBBLE COLUMNS WITH FOAMING LIQUIDS  

Microsoft Academic Search

Gas-liquid upward flow experiments have been performed in two bubble columns of different diameters (0.10 and 0.29 m,) using air as gas phase and several liquids: water, aqueous solutions of ethanol and glycerine, kerosene, and a solution of a surfactant in kerosene. The main goal of the study is the analysis of foaming systems, including the comparison of their behavior with

L. Z. PINO; M. M. YÉPEZ; A. E. SÁEZ; G. DE DRAGO

1990-01-01

7

Pressure drop, gas hold-up and heat transfer during single and two-phase flow through porous media  

Microsoft Academic Search

Pressure drop, bubble size, gas hold-up and convective heat transfer have been studied both experimentally and theoretically at constant wall heat flux for single and two-phase flow through unconsolidated porous media. Single-phase pressure drop and heat transfer coefficients have been measured over a wide range of particle size, heat flux and liquid flow rate. The conservation equations and the Kozeny-Carman

M. Jamialahmadi; H. Müller-Steinhagen; M. R. Izadpanah

2005-01-01

8

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

9

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

10

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

11

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

12

EFFECTS OF ALTERNATE ANTIFOAM AGENTS, NOBLE METALS, MIXING SYSTEMS AND MASS TRANSFER ON GAS HOLDUP AND RELEASE FROM NONNEWTONIAN SLURRIES  

Microsoft Academic Search

Gas holdup tests performed in a small-scale mechanically-agitated mixing system at the Savannah River National Laboratory (SRNL) were reported in 2006. The tests were for a simulant of waste from the Hanford Tank 241-AZ-101 and featured additions of DOW Corning Q2-3183A Antifoam agent. Results indicated that this antifoam agent (AFA) increased gas holdup in the waste simulant by about a

H Guerrero; M Mark Fowley; C Charles Crawford; M Michael Restivo; R Robert Leishear

2007-01-01

13

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

14

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.

2001-08-28

15

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

16

Large and small bubble interaction patterns in a bubble column  

Microsoft Academic Search

A visual analysis is made on the fate of a large (or “cap”) bubble injected into a swarm of otherwise uniformly dispersed small bubbles; experiments, covering gas holdups for the swarm bubbles as high as 6%, are conducted in a two-dimensional column to ensure the distinct appearance of a single cap throughout its rise in the swarm. Specific focus is

K. Tsuchiya; K. Ohsaki; K. Taguchi

1996-01-01

17

Circulating fluidized beds — diameter, solids hold-up, axial gas-mixing, and contact efficiency  

Microsoft Academic Search

Circulating fluidized beds (CFB) employed comprised: 0.0158 m riser diameter with 7.2 m height, 0.09 m riser diameter with 7.2 m height or 3.6 m height, and 0.254 m riser diameter with 10.5 m height.Measurements reported here comprise solid hold-up and axial gas-mixing. Solid circulation rates up to 350 kg\\/m2 s and gas velocities of 2, 4, 6, 8 m\\/s

R. Contractor; R. J. Dry; C. White; Q. M. Mao; S. Konstantinidis; O. E. Potter

2000-01-01

18

Gas hold-up and oxygen mass transfer in three pneumatic bioreactors operating with sugarcane bagasse suspensions.  

PubMed

Sugarcane bagasse is a low-cost and abundant by-product generated by the bioethanol industry, and is a potential substrate for cellulolytic enzyme production. The aim of this work was to evaluate the effects of air flow rate (QAIR), solids loading (%S), sugarcane bagasse type, and particle size on the gas hold-up (?G) and volumetric oxygen transfer coefficient (kLa) in three different pneumatic bioreactors, using response surface methodology. Concentric tube airlift (CTA), split-cylinder airlift (SCA), and bubble column (BC) bioreactor types were tested. QAIR and %S affected oxygen mass transfer positively and negatively, respectively, while sugarcane bagasse type and particle size (within the range studied) did not influence kLa. Using large particles of untreated sugarcane bagasse, the loop-type bioreactors (CTA and SCA) exhibited higher mass transfer, compared to the BC reactor. At higher %S, SCA presented a higher kLa value (0.0448 s?1) than CTA, and the best operational conditions in terms of oxygen mass transfer were achieved for %S < 10.0 g L?1 and QAIR > 27.0 L min?1. These results demonstrated that pneumatic bioreactors can provide elevated oxygen transfer in the presence of vegetal biomass, making them an excellent option for use in three-phase systems for cellulolytic enzyme production by filamentous fungi. PMID:24078146

Esperança, M N; Cunha, F M; Cerri, M O; Zangirolami, T C; Farinas, C S; Badino, A C

2014-05-01

19

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

20

Oceanic Gas Bubble Measurements Using an Acoustic Bubble Spectrometer  

NASA Astrophysics Data System (ADS)

Gas bubble injection by breaking waves contributes significantly to the exchange of gases between atmosphere and ocean at high wind speeds. In this respect, CO2 is primarily important for the global ocean and climate, while O2 is especially relevant for ecosystems in the coastal ocean. For measuring oceanic gas bubble size distributions, a commercially available Dynaflow Acoustic Bubble Spectrometer (ABS) has been modified. Two hydrophones transmit and receive selected frequencies, measuring attenuation and absorption. Algorithms are then used to derive bubble size distributions. Tank test were carried out in order to test the instrument performance.The software algorithms were compared with Commander and Prosperetti's method (1989) of calculating sound speed ratio and attenuation for a known bubble distribution. Additional comparisons with micro-photography were carried out in the lab and will be continued during the SPACE '08 experiment in October 2008 at Martha's Vineyard Coastal Observatory. The measurements of gas bubbles will be compared to additional parameters, such as wind speed, wave height, white cap coverage, or dissolved gases.

Wilson, S. J.; Baschek, B.; Deane, G.

2008-12-01

21

Dynamics of a Single Reactive Gas Bubble  

Microsoft Academic Search

\\u000a The dynamics of a single combustible stoichiometric oxyacetylene gas bubble immersed in glycerine subjected to an impulsive\\u000a pressure wave has been studied experimentally and theoretically. Emphasis is placed on determining the range of bubble sizes\\u000a over which ignition of the gas occurs after the passage of a pressure pulse generated by the impact of a projectile with a\\u000a piston. Bubbles

B. Bruckert; D. L. Frost; A. N. Meidani; R. Chue; M. Brouillette

22

Radiation Characteristics of Glass Containing Gas Bubbles Laurent Pilon*  

E-print Network

Radiation Characteristics of Glass Containing Gas Bubbles Laurent Pilon* Mechanical and Aerospace, ceramics, and glass, gas bubbles can form in liquid and solid phases. The presence of such bubbles affects media containing large gas bubbles (bubble radius is much larger than the wavelength of radiation

Pilon, Laurent

23

BUBBLE DYNAMICS AT GAS-EVOLVING ELECTRODES  

SciTech Connect

Nucleation of bubbles, their growth by diffusion of dissolved gas to the bubble surface and by coalescence, and their detachment from the electrode are all very fast phenomena; furthermore, electrolytically generated bubbles range in size from ten to a few hundred microns; therefore, magnification and high speed cinematography are required to observe bubbles and the phenomena of their growth on the electrode surface. Viewing the action from the front side (the surface on which the bubbles form) is complicated because the most important events occur close to the surface and are obscured by other bubbles passing between the camera and the electrode; therefore, oxygen was evolved on a transparent tin oxide "window" electrode and the events were viewed from the backside. The movies showed that coalescence of bubbles is very important for determining the size of bubbles and in the chain of transport processes; growth by diffusion and by coalescence proceeds in series and parallel; coalescing bubbles cause significant fluid motion close to the electrode; bubbles can leave and reattach; and bubbles evolve in a cycle of growth by diffusion and different modes of coalescence. An analytical solution for the primary potential and current distribution around a spherical bubble in contact with a plane electrode is presented. Zero at the contact point, the current density reaches only one percent of its undisturbed value at 30 percent of the radius from that point and goes through a shallow maximum two radii away. The solution obtained for spherical bubbles is shown to apply for the small bubbles of electrolytic processes. The incremental resistance in ohms caused by sparse arrays of bubbles is given by {Delta}R = 1.352 af/kS where f is the void fraction of gas in the bubble layer, a is the bubble layer thickness, k is the conductivity of gas free electrolyte, and S is the electrode area. A densely populated gas bubble layer on an electrode was modeled as a hexagonal array of dielectric spheres. Accurately machined lucite spheres were placed one at a time in one end of a hexagonal cell which simulated the unit cell of such an array. The resistance as a function of gas bubble layer packing density sharply increased as close packing was approached. Because the interaction of the fields around bubbles closely spaced in the direction perpendicular to the current dominates the added resistance, and because there is a tri-modal distribution of bubble sizes in a bubble layer, the Distribution Model of Meredith and Tobias (16), derived for three dimensional gas dispersions, approximately predicted the conductivity of a bubble layer at void fractions greater than 0.3. At moderate-to-high current densities, the bubble layer in a cell having an interelectrode gap of half a centimeter could increase the ohmic resistance by as much as 20 percent.

Sides, Paul J.

1980-12-01

24

Bubble nucleation from gas cavities — a review  

Microsoft Academic Search

This review is concerned with the nucleation of bubbles in solutions supersaturated with a gas, in particular the bubble nucleation that occurs at specific sites, as a cycle. A classification system for the kinds of nucleation that occur is defined and discussed in order to place this specific form of nucleation into a better defined context. It is noted that

S. F. Jones; G. M. Evans; K. P. Galvin

1999-01-01

25

Gas bubbles in shaped sapphire  

Microsoft Academic Search

Shaped sapphire single crystals almost always contain a typical defect: small bubbles also known as “micro-voids”. The goal of this paper is to review the existing literature and give a survey of our recent work on this specific defect. As a conclusion to our review we propose a mechanism for bubble formation and its occurrence and distribution in shaped sapphire.The

O. M. Bunoiu; Th. Duffar; I. Nicoara

2010-01-01

26

Gas bubble dynamics in soft materials  

E-print Network

Epstein and Plesset's seminal work on the rate of gas bubble dissolution and growth in a simple liquid is generalized to render it applicable to a gas bubble embedded in a soft elastic medium. Both the underlying diffusion equation and the expression for the gas bubble pressure were modified to allow for the non-zero shear modulus of the elastic medium. The extension of the diffusion equation results in a trivial shift (by an additive constant) in the value of the diffusion coefficient, and does not change the form of the rate equations. But the use of a Generalized Young-Laplace equation for the bubble pressure resulted in significant differences on the dynamics of bubble dissolution and growth, relative to a simple liquid medium. Depending on whether the salient parameters (solute concentration, initial bubble radius, surface tension, and shear modulus) lead to bubble growth or dissolution, the effect of allowing for a non-zero shear modulus in the Generalized Young-Laplace equation is to speed up the rate ...

Solano-Altamirano, J M; Goldman, Saul

2014-01-01

27

Liquid jet pumped by rising gas bubbles  

NASA Technical Reports Server (NTRS)

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

Hussain, N. A.; Siegel, R.

1975-01-01

28

Gas bubble coalescence in reduced gravity conditions.  

PubMed

The effects of low gravity, as produced by a reduced gravity aircraft, the KC135, on the formation and coalescence of gas bubbles were examined over a range of gas-liquid ratios and with various medium constituents. These effects will influence design considerations of fermentors operating in reduced gravity conditions. PMID:11537386

Thompson, B G; Brooks, W S

1989-01-01

29

Contemporary Mathematics Numerical Simulation of Gas Bubbles Rising in Viscous  

E-print Network

Contemporary Mathematics Numerical Simulation of Gas Bubbles Rising in Viscous Liquids at High- duced in the context of gas bubbles rising in viscous liquids, e.g. air bubbles rising in water. Key on a supercomputer. Finally, the use of a non-inertial, moving reference frame attached to the rising bubble

Lin, Ping

30

Study of coalescence and breakage in bubble columns with fine pore spargers  

Microsoft Academic Search

Bubble columns are widely used in industrial gas-liquid operations because of their simple con- struction, low operating cost and high-energy efficiency. However, their design and scale up is still a difficult task and subject to errors due to the generally complex structure of the multiphase flow en- countered in this type of equipment. Bubble size and gas holdup are the

N. A. Kazakis; A. A. Mouza; S. V. Paras

31

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

32

Mixing of secondary gas injection in a bubbling fluidized bed  

Microsoft Academic Search

In this work, three-dimensional numerical simulations with the aim of investigating the mixing of secondary gas in a bubbling fluidized bed are performed. Single and multiple horizontal gas jet injections into a small scale rectangular bubbling fluidized bed are studied. A tracer gas is introduced through the jet orifice to study the gas mixing in the system. Both transient and

Tingwen Li; Konstantin Pougatch; Martha Salcudean; Dana Grecov

2009-01-01

33

CHARACTERIZATION OF THE DOWNFLOW SECTION OF AN AIRLIFT COLUMN USING BUBBLE SIZE DISTRIBUTION MEASUREMENTS  

Microsoft Academic Search

Bubble size distributions in an airlift column were investigated with an emphasis on the downflow section. Measurements have been made using direct photographic techniques in conjunction with image analysis in a split cylinder airlift column. Information extracted from these measurements includes local gas hold-up, variation of Sauter mean bubble diameter with column length, and liquid circulation velocity. An air-tap water

SNEHAL A. PATEL; L. A. GLASGOW; L. E. ERICKSON; C. H. LEE

1986-01-01

34

Scattering of sound by gas bubbles in water and sediments  

SciTech Connect

In this paper, a self-consistent multiple scattering approach with suitable pair-correlation function is employed to study acoustic wave propagation through water and sediments containing gas bubbles. The effects of surface tension, shear viscosity of the liquid and thermal conduction in the gas bubbles are considered in the analysis. In the Rayleigh limit, closed form expressions are given as a function of concentration of bubbles. Numerical results are presented for both phase velocity and coherent attenuation as a function of frequency near the fundamental resonance of the bubble for various values of concentration of bubbles.

Ma, Y.; Varadan, V.K.; Varadan, V.V.

1983-05-01

35

Stability of an overheated liquid containing vapor-gas bubbles  

NASA Astrophysics Data System (ADS)

The problem of the stability of an overheated liquid containing bubbles of an insoluble gas is considered. The critical conditions for the masses of gas bubbles, their radii, and volume concentrations are determined for the case of the stable state of the system consisting of a liquid and vapor-gas bubbles. Theory of spontaneous solutions is constructed which describes the exit of the overheated vapor-gas bubble system from the unstable state. On the basis of such solutions, the dynamics of transition of the overheated liquid to a stable state is studied.

Shagapov, V. Sh.; Koledin, V. V.; Vakhitova, N. K.

2013-09-01

36

Fluctuation characteristics of gas-liquid two-phase slug flow in horizontal pipeline  

NASA Astrophysics Data System (ADS)

Slug flow was a flow of long bubbles and liquid slugs alternating in space and time, and under flowing conditions, it is intermittent and unstable. The fluctuation characteristics of liquid holdup, pressure and differential pressure of slug flow were investigated in a 40 m long, 50 mm I.D. horizontal pipeline. At the same superficial liquid velocity, the liquid holdup of liquid film both decreased rapidly at first and then decreased slowly with the increase of superficial gas velocity, while the liquid holdup of liquid slug decreased slowly at first and then decreased rapidly. At the same superficial gas velocity, the liquid holdup of liquid slug and liquid film all increased with the increase of superficial liquid velocity. By statistical analysis, it was found that the probability density distribution of the liquid holdup was bimodal distribution. The high liquid holdup peak was in correspondence with liquid holdup of the slug body and the low liquid holdup peak with liquid holdup of the film. The liquid holdup which was in correspondence with the respective peaks of probability density function was consistent with the mean liquid holdup of smooth stratified film and liquid slug. Moreover, the distribution of pressure was unimodal distribution or bimodal distribution, depending on the number of slug units, and the differential pressure distribution was unimodal distribution.

Luo, X. M.; He, L. M.; Lu, Y. L.

2010-03-01

37

Gas separation and bubble behavior at a woven screen  

NASA Astrophysics Data System (ADS)

Gas-liquid two phase flows are widespread and in many applications the separation of both phases is necessary. Chemical reactors, water treatment devices or gas-free delivery of liquids like propellant are only some of them. We study the performance of a woven metal screen in respect to its phase separation behavior under static and dynamic conditions. Beside hydraulic screen resistance and static bubble point, our study also comprises the bubble detachment from the screen upon gas breakthrough. Since a woven screen is essentially an array of identical pores, analogies to bubble detachment from a needle can be established. While the bubble point poses an upper limit for pressurized gas at a wetted screen to preclude gas breakthrough, the necessary pressure for growing bubbles to detach from the screen pores a lower limit when breakthrough is already in progress. Based on that inside, the dynamic bubble point effects were constituted that relate to a trapped bubble at such a screen in liquid flow. A trapped is caused to break through the screen by the flow-induced pressure drop across it. Our model includes axially symmetric bubble shapes, degree of coverage of the screen and bubble pressurization due to hydraulic losses in the rest of the circuit. We have built an experiment that consists of a Dutch Twilled woven screen made of stainless steel in a vertical acrylic glass tube. The liquid is silicon oil SF0.65. The screen is suspended perpendicular to the liquid flow which is forced through it at variable flow rate. Controlled injection of air from a needle allows us to examine the ability of the screen to separate gas and liquid along the former mentioned effects. We present experimental data on static bubble point and detachment pressure for breakthrough at different gas supply rates that suggest a useful criterion for reliable static bubble point measurements. Results for the dynamic bubble point are presented that include i) screen pressure drop for different trapped bubble volumes, liquid flow rates and flow-induced compression, ii) typical breakthrough of a trapped bubble at rising liquid flow rate and iii) steady gas supply in steady liquid flow. It shows that our model can explain the experimental observations. One of the interesting findings for the dynamic bubble point is that hydraulic losses in the rest of the circuit will shift the breakthrough of gas to higher liquid flow rates.

Conrath, Michael; Dreyer, Michael E.

38

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] [ORNL; Abdou, Ashraf A [ORNL] [ORNL; Riemer, Bernie [ORNL] [ORNL; Felde, David K [ORNL] [ORNL

2007-01-01

39

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

40

Bubble formation at a gas-evolving microelectrode.  

PubMed

The electrolytic production of gas bubbles involves three steps-nucleation, growth, and detachment. Here the growth of hydrogen bubbles and their detachment from a platinum microelectrode of diameter 125 ?m are studied using high-speed photography and overpotential frequency spectrum (noise) analysis. The periodic release of large <800 ?m bubbles-gas oscillator behavior-was often observed, with a corresponding periodic oscillation of the overpotential which is reflected as a main peak and a series of harmonics in the power spectral density. The release frequency is inversely correlated with the bubble size and hydrogen production rate. When the coalescence of bubbles at the electrode surface is inhibited, either chemically with a surfactant or ethylene glycol or hydrodynamically by magnetically induced convection, swarms of small ?50 ?m bubbles are released in an aperiodic stream. The abrupt transition from periodic to aperiodic release occurs when the surface tension falls below 70 mN m(-1). Hydrogen bubble growth is also studied on a transparent platinum thin-film electrode, where the bubble coalescence can be observed directly. It leaves sessile droplets of electrolyte within the footprint of the growing bubble, showing that the growth involves scavenging smaller bubbles from solution due to hydrogen generated directly at the electrode. A possible role of nanobubbles in the lift-off process is discussed. PMID:24694174

Fernández, Damaris; Maurer, Paco; Martine, Milena; Coey, J M D; Möbius, Matthias E

2014-11-01

41

Adhesion of solid particles to gas bubbles. Part 1: Modelling  

Microsoft Academic Search

Particle-to-bubble adhesion is important in the areas of anti-foaming, in flotation processes and in multiphase slurry reactors. In the present work we particularly address the latter. The behaviour of fine catalyst particles adhering to gas bubbles in aqueous media is governed by the surface hydrophobicity. This adhesion on its turn influences the G–L mass transfer, bubble coalescence and the particle

Florin Omota; Alexandre C. Dimian; Alfred Bliek

2006-01-01

42

Shape Oscillations of Gas Bubbles With Newtonian Interfacial Rheological Properties  

NASA Technical Reports Server (NTRS)

The oscillation frequency and damping rate for small-amplitude axisymmetric shape modes of a gas bubble in an ideal liquid are obtained, in the limit when the bubble interface possesses Newtonian interfacial rheology with constant surface shear and dilatational viscosities. Such results permit the latter surface properties to be measured by analyzing experimental data on frequency shift and damping rate of specific shape modes of suspended bubbles in the presence of surfactants.

Nadim, Ali

1996-01-01

43

Experimental and numerical studies of the hydrodynamics in a bubble column  

Microsoft Academic Search

The hydrodynamics in a bubble column of 140mm diameter and a height of 650mm was analysed using a phase-Doppler anemometer (PDA). In order to allow the application of PDA, the bubble column was aerated with relatively fine bubbles with a size spectrum between about 0.3 and 1.5mm. The gas hold-up was varied in the range between 0.5 and 3%. The

S. Lain; D. Bröder; M. Sommerfeld

1999-01-01

44

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

45

Production of Gas Bubbles in Reduced Gravity Environments  

NASA Technical Reports Server (NTRS)

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

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

1996-01-01

46

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

PubMed Central

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.

2013-01-01

47

Proton Radiography Experiment to Visualize Gas Bubbles in Mercury  

SciTech Connect

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 mercury flow speeds (0 - 1 m/s) and gas injection rates (0.1 - 500 sccm). Helium was most commonly used but Argon and Xenon were injected for limited test conditions. The smallest discernable bubbles were about 0.24 mm in diameter. Resolution was limited by image contrast which was notably improved with 6 mm of mercury thickness. Analysis of the radiograph images from jet bubbler conditions provided data on bubble size distribution and total bubble void fraction. In a few cases radiographs captured a large fraction of the injected gas, but generally 20 to 90% of injected gas was not captured in the images. In all more than 400 radiographs were made during the experiment in addition to several movies. Sound recordings of needle bubbler operation were also made and used to quantify bubble formation rate and size; these results are compared to theoretical predictions. This paper describes the experiment goals, scope and equipment; key results are presented and discussed.

Riemer, Bernie [ORNL; Felde, David K [ORNL; Wendel, Mark W [ORNL; Mariam, Fesseha G [Los Alamos National Laboratory (LANL); Merrill, Frank E [ORNL

2007-01-01

48

Gas bubbles in simulation and experiment.  

PubMed

An experimental setup for the examination of single bubbles, rising in a liquid, is presented. Its main part is a rotating chamber, in which the bubble is spatially stabilized by a balance of buoyancy, drag, and lift forces. This allows for long observation periods in time. Experimental results are presented for air bubbles in silicone oil. The experimental results are validated by a comparison with numerical simulations. A modified, mass-conserving level-set method is used for the representation of the free interface, while an immersed-boundary formulation is engaged for the conservation equations. The agreement between experiment and simulation, and to available correlations from literature, is found to be perfect. It is shown that the influence of the liquid shear due to the rotation is negligible. Also, for the presented liquid system, no influence by Marangoni stresses could be found, which makes the system of air and silicone oil a good choice for validation purposes. PMID:21084092

Lakshmanan, Peter; Peters, Franz; Fries, Nicolas; Ehrhard, Peter

2011-02-01

49

Phase holdups in three-phase fluidized beds in the presence of disc promoter  

SciTech Connect

Three-phase fluidized beds are found to have wide applications in process industries. The present investigation essentially comprises of the studies on gas holdup, liquid holdup and bed porosity in three-phase fluidized beds with coaxially placed disc promoter. Holdup data were obtained from bed expansion and pressure drop measurements. Analysis of the data was done to elucidate the effects of dynamic and geometric parameters on gas holdup, liquid holdup and bed porosity. Data were correlated and useful equations were obtained from empirical modeling. (author)

Murty, M.S.N. [Department of Chemical Engineering, GVP College of Engineering, Visakhapatnam 530 048 (India); Ramesh, K.V.; Venkateswarlu, P. [Department of Chemical Engineering, Andhra University, Visakhapatnam 530 003 (India); Prabhakar, G. [Department of Chemical Engineering, Sri Venkateswara University, Tirupati 517 502 (India)

2011-02-15

50

Studies on pressure response of gas bubbles contributions of condensed droplets in bubbles generated by a uniform nucleation  

NASA Technical Reports Server (NTRS)

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 follows: (1) at the onset of bubble growth, the gas mixture inside it adiabatically expands and the temperature decreases. Condensed droplets appear inside the gas mixture due to a uniform nucleation and the temperature recovers, thus the motion of the bubble is apparently isothermal; (2) the evaporation and condensation coefficient largely affects bubble motions (maximum radius, period and rate of attenuation of the bubble oscillation) including the uniform contraction; (3) the oscillation period of the bubble is longer as the equilibrium bubble radius is larger when the surrounding pressure decreases stepwise. In this circumstance the temperature inside the bubble is kept constant due to condensation evaporation phenomena and is nearly isothermal; and (4) when the surrounding pressure decreases in a stepwise fashion, the critical pressure bubble radius relation becomes closer to that for the isothermal process if the bubble radius is larger than 8 microns.

Matsumoto, Y.

1988-01-01

51

Collapse of multiple gas bubbles by a shock wave and induced impulsive pressure  

Microsoft Academic Search

The problem of bubble-bubble interaction is studied experimentally. The motions of multiple gas bubbles attached to a solid wall by a shock wave are observed by using a high speed camera, and the induced impulsive pressures are measured. On the basis of these results, the effects of number and configuration of gas bubbles on the collapsing process and the impulsive

Yukio Tomita; Akira Shima; Takashi Ohno

1984-01-01

52

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

53

Can Propagation of Gas Bubbles Lead to Detached Solidification? Experiments on Freezing of Water  

E-print Network

Can Propagation of Gas Bubbles Lead to Detached Solidification? Experiments on Freezing of Water solidify water upward, in the hope that detached solidification would evolve from gas bubbles forming caused gas bubbles or tubes to form only at the ampoule wall, and not in the interior. Gas tubes were

Regel, Liya L.

54

Vibrational spectra of moving gas bubbles in the transition of a liquid-gas system into weightlessness  

Microsoft Academic Search

Capillary jumps of gas bubbles and bubble surface vibrations are studied under surface tension force in the transition of a liquid-gas system into weightlessness. The vibrating motion of the bubbles is observed to occur over a time period during which the velocity of the translational motion decreases to zero. The translational-vibrational motion of the bubble has a complex spatial character,

V. I. Popov

1981-01-01

55

Effect of dense heat exchanging internals on the hydrodynamics of bubble column reactors using non-invasive measurement techniques  

NASA Astrophysics Data System (ADS)

Given their efficiency and capital cost reduction, bubble/slurry bubble column reactors are the reactors of choice for Fischer-Tropsch (FT) synthesis, offering clean alternative fuels and chemicals. FT synthesis is an exothermic process that requires many heat exchanging tubes in order to remove heat efficiently and maintain the desired temperature and isothermal operating condition. The impact of the heat exchanging tubes (internals) on the hydrodynamics is not fully understood. Reliably designing and scaling up bubble column reactors requires proper understanding of hydrodynamics, as well as heat and mass transfer parameters. The main objective of this work is to advance the understanding of the effect of internals (25% covered cross-sectional area to meet FT needs) on hydrodynamics (gas holdup distribution, 3D liquid velocity, Reynolds stresses, turbulent kinetic energy, eddy diffusivity, etc.) in bubble columns. Single-source gamma-ray Computed Tomography (CT) and Radioactive Particle Tracking (RPT) were used for the first time to study the effect of dense internals and gas velocity on the phase holdup distribution and radial profiles, liquid velocity field and turbulent parameter profiles. The main findings obtained for the first time in this study can be summarized as follows: The presence of internals at a given superficial gas velocity causes: An increase in gas holdup and the axial centerline liquid velocity. A sharp decrease in turbulence parmeters. The increase in superficial gas velocity in the presence of internals causes: An increase in gas holdup, axial centerline liquid velocity and turbulent parameters.

Al Mesfer, Mohammed Khloofh

56

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

57

The velocity of gas bubble rise in a tube  

NASA Astrophysics Data System (ADS)

The solutions of the Laplace equation involving the diverging infinite series are used in the classical works at the analysis of the problem of the gravitational rise of a gas bubble in a tube filled with ideal fluid (the Taylor bubble). In the present work, an approximate method is proposed for a correct analysis of the above problem. The ideal fluid flow around a body of revolution in a tube is constructed by the method of the superposition of elementary solutions. The satisfaction of the free surface condition in the critical point neighborhood and the passage of the main parameter to the limit lead to the sought expression for the dimensionless velocity of the gas bubble — Froude number.

Zudin, Yu. B.

2013-03-01

58

Shock wave deformation of a nonspherical gas bubble in liquids  

Microsoft Academic Search

The deformation of a nonspherical gas bubble caused by the incidence of a shock wave is analysed, taking account of both the nonspherical initial shape and the suddenly induced liquid flow, and then compared with the experimental results given in a previous work. The variational calculation of the governing equations shows: (1) The double disc- and triple disc-type instabilities observed

T. Hasegawa; T. Fujiwara; H. Itoh

1982-01-01

59

Gas-bubble enhanced heating in rabbit thigh in vivo  

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. Sokka; R. King; N. McDannold; K. Hynynen

2002-01-01

60

Duality of the gas-liquid flow regimes in bubble column reactors  

Microsoft Academic Search

The purpose of the present work was to examine the effect of design and working parameters of bubble column reactors on the formation and stability of the homogeneous and the heterogeneous bubbling regimes and to demonstrate the effect of bubbling regime transition on the hydrodynamic and mass transfer characteristics of gas-liquid beds in bubble column reactors. The factors determining the

J. Zahradník; M. Fialová; M. R?ži?ka; J. Drahoš; F. Kaštánek; N. H. Thomas

1997-01-01

61

Shock wave deformation of a nonspherical gas bubble in liquids  

NASA Astrophysics Data System (ADS)

The deformation of a nonspherical gas bubble caused by the incidence of a shock wave is analysed, taking account of both the nonspherical initial shape and the suddenly induced liquid flow, and then compared with the experimental results given in a previous work. The variational calculation of the governing equations shows: (1) The double disc- and triple disc-type instabilities observed in the water experiments result from an ellipsoidal initial shape. (2) The jet formation occurs in the downstream direction, as observed in the glycerin experiments. (3) The instability is more easily excited in a prolate bubble. (4) The larger the size of a prolate bubble, and the higher the flow velocity, the more that induced deformation becomes flat-topped in the case of glycerin.

Hasegawa, T.; Fujiwara, T.; Itoh, H.

62

Hot Gas in the Wolf-Rayet Bubble NGC 6888  

NASA Astrophysics Data System (ADS)

The fast stellar winds from Wolf-Rayet (WR) stars sweep up the circumstellar media and form the so-called wind-blown bubbles or WR bubbles. The shock of these fast stellar winds against the dense shells left by previous evolutionary stages is expected to produce gas at X-ray-emitting temperatures. However, diffuse X-ray emission has been detected only inside two WR bubbles: S308 and NGC 6888. Our 100 ks Chandra ACIS-S observation of the northwest quadrant of NGC 6888 presents the first high-resolution image and clean spectrum of its diffuse X-ray emission. To obtain a global view of the physical structure of NGC 688, we here request a 60 ks XMM-Newton observation, which will otherwise take Chandra 300 ks for a similar mapping of the entire nebula.

Toala, Jesus A.

2012-10-01

63

Hydrodynamics and interfacial gas-liquid mass transfer of gas-liquid-solid fluidized beds  

SciTech Connect

Hydrodynamic characteristics of a cocurrent, gas-liquid-solid fluidized bed is studied to simulate the resid hydrotreating reaction conditions using an aqueous surfactant solution. Reaction conditions for hydrotreating of residual oils and coal liquefaction, which uses cylindrical hydrotreating catalysts under conditions of high gas holdup, are simulated using an aqueous t-pentanol (0.5 wt%) solution as the liquid phase. A mathematical model is developed to described the minimum fluidization velocity behavior. Bed voidage, gas holdup and terminal velocity of the particles are analyzed and correlated empirically to investigate the effect of particle shape and liquid surface tension. Systematic effects of particle properties on bubble wake structure as well as bubble rise characteristics for a single rising bubble in a liquid-solid fluidized bed are studied visually. In order to determine the solids holdup in near wake behind a single bubble, an image processing technique is employed. The bubble rise velocity, the volume ratio of primary wake to bubble, the volume ratio of liquid wake to bubble, and the wake solid holdup are strongly dependent on the particle terminal velocity and the bed expansion. A spectrophotometric technique is developed for the measurement of the instantaneous mass transfer coefficient and the interfacial areas of a bubble as well as the local concentration distribution around the bubble-wake. An ozone and starch-potassium iodide reaction is employed to visualize the gas-liquid mass transfer to a single bubble in liquids and liquid-solid fluidized beds. Axial variations of the concentration, bubble volume and the mass transfer rate are studied. The mass transfer coefficient is found to be dependent on bubble size and bed expansion.

Song, Gyung-Ho.

1989-01-01

64

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

65

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

66

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

E-print Network

THE NUCLEATION AND GROWTH OF GAS BUBBLES IN A NEWTONIAN FLUID: AN ENERGETIC VARIATIONAL PHASE FIELD and growth of gas bubbles in a Newtonian fluid. We employ a general energetic variational formulation with those of classical models. The new approach allows the study of bubble nucleation, growth

Feng, James J.

67

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

68

Calculation and Analysis of Liquid Holdup in Lower Blast Furnace by Model Experiments  

NASA Astrophysics Data System (ADS)

A hydromechanics experiment on the countercurrent flow of gas and liquid simulating the flow conditions in the lower blast furnace was carried out. A cold model of a packed bed with various packing materials and liquids was used to study the holdup of liquid. Correlations for static holdup, dynamic holdup, and total holdup were obtained. A good agreement was found between the calculated and experimental data. A mathematical model simulating the flow fields was applied to study the effect of liquid holdup in blast furnace. The results of the model calculation show that static holdup is the determinant of the total holdup of molten materials when the blast furnace works in stable condition. The slag phase generally reaches flooding holdup ahead of the hot metal. The radial distribution of gas flow is almost not influenced by the holdup of molten materials, but it has a greater influence on the pressure drop. The size of coke has far greater influence on static holdup than liquid properties does. The study is useful for acquiring a deeper understanding of the complex phenomena in the blast furnace and for determining appropriate operational actions under different production conditions.

Xiong, Wei; Bi, Xue-Gong; Wang, Guo-Qiang; Yang, Fu

2012-06-01

69

Gas Bubble Growth Dynamics in a Supersaturated Solution: Henry's and Sievert's Solubility Laws  

E-print Network

Theoretical description of diffusion growth of a gas bubble after its nucleation in supersaturated liquid solution is presented. We study the influence of Laplace pressure on the bubble growth. We consider two different solubility laws: Henry's law, which is fulfilled for the systems where no gas molecules dissociation takes place and Sievert's law, which is fulfilled for the systems where gas molecules completely dissociate in the solvent into two parts. We show that the difference between Henry's and Sievert's laws for chemical equilibrium conditions causes the difference in bubble growth dynamics. Assuming that diffusion flux of dissolved gas molecules to the bubble is steady we obtain differential equations on bubble radius for both solubility laws. For the case of homogeneous nucleation of a bubble, which takes place at a significant pressure drop bubble dynamics equations for Henry's and Sievert's laws are solved analytically. For both solubility laws three characteristic stages of bubble growth are mar...

Gor, Gennady Yu; Kuni, Fedor M

2012-01-01

70

Modelling of Spherical Gas Bubble Oscillations and Sonoluminescence  

NASA Technical Reports Server (NTRS)

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

Prosperetti, A.; Hao, Y.

1999-01-01

71

Comparison of Holdup Measurement Techniques  

SciTech Connect

The measurement of uranium holdup, the residual material left in process equipment such as pipes or ducts, is an integral element of material control and accountability. Not only are the measurements important for accountability, they are also important for criticality safety. The goal in measuring holdup is to quantify the amount of material in the pipes to verify that all material is accounted for (inventory in [inventory out + holdup] = 0) and to ensure that the amount of material heldup is not a criticality risk. There are a number of ways to measure holdup in process equipment; however, this paper will evaluate only two methods (i.e., Holdup Measurement System 4 (HMS-4) and In Situ Object Counting Software (ISOCS)) for specific measurement scenarios. The comparison will use measurements of well-known reference materials in various configurations and will examine the results, uncertainties, repeatability, time required, portability, and cost of each system.

Lousteau, Angela L [ORNL] [ORNL; Stooksbury, John C [ORNL] [ORNL; Cleveland, Steven L [ORNL] [ORNL

2012-01-01

72

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

73

In-water gas combustion in linear and annular gas bubbles  

NASA Astrophysics Data System (ADS)

A new pulsed-cyclic method of in-water gas combustion was developed with separate feed of fuel gas and oxygen with the focus on development of new technologies for heat generators and submerged propellers. The results of calorimetric and hydrodynamic measurements are presented. In-water combustion of acetylene, hydrogen, and propane was tested with the operation frequency of 2-2.5 Hz and with a linear injector. The combustion dynamics of combustion of stoichiometric mixture with propane (C3H8+5O2) was studied for a bubble near a solid wall; the produced gas bubble continues expansion and oscillations (for the case of linear and annular bubbles). It was demonstrated that gas combustion in annular bubbles produces two same-magnitude pulses of force acting on the wall. The first pulse is produced due to expansion of combustion products, and the second pulse is produced due to axial cumulative processes after bubble collapse. This process shapes an annular vortex which facilitates high-speed convective processes between combustion products and liquid; and this convection produces small-size bubbles.

Teslenko, V. S.; Drozhzhin, A. P.; Medvedev, R. N.; Batraev, I. S.

2014-08-01

74

Bubble characteristics in a high-intensity gas\\/liquid contactor  

Microsoft Academic Search

Experimental studies on bubble sizes in a high-intensity gas\\/liquid contactor are described. The contactor utilizes cross flow of liquid at high velocities to generate small bubbles. The relatively limited previous literature on bubble formation in cross flow is first reviewed. Measurements using a video technique at the exit of a short version of the contactor and on a section of

B. Waldie; T. Johnston; W. K. Harris; C. Bell

1999-01-01

75

Bubble formation during horizontal gas injection into downward-flowing liquid  

NASA Astrophysics Data System (ADS)

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

Bai, Hua; Thomas, Brian G.

2001-12-01

76

Acoustically coupled gas bubbles in fluids: time-domain phenomena.  

PubMed

In previous work [C. Feuillade, J. Acoust. Soc. Am. 98, 1178-1190 (1995)] a coupled oscillator formalism was introduced for describing collective resonances, scattering, and superresonances, of multiple gas bubbles in a fluid. Subsequently, time-domain investigations of the impulse response of coupled systems have disclosed the exact conditions which determine whether the ensemble scattering behavior should be described using: either (a), a multiple scattering; or (b), a self-consistent methodology. The determining factor is the Q of the individual scatterers, and their typical spatial separations in the medium. For highly damped or sparse systems, e.g., scattering from loose schools of swimbladder fish, or from a gassy seabed containing entrained bubbles, the multiple scatter counting approach should be applicable. For more strongly coupled systems, e.g., a dense cloud of resonating bubbles in the water column, energy exchange may be due primarily to radiative cycling rather than scattering, in which case a self-consistent approach is indicated. The result has implications for both volume and bottom scattering applications. PMID:11425101

Feuillade, C

2001-06-01

77

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

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

78

Experimental techniques for hydrodynamic characterization of multiphase flows in slurry-phase bubble-column reactors  

SciTech Connect

Slurry-phase bubble-column Fischer-Tropsch (FT) reactors are recognized as one of the more promising technologies for converting synthesis gas from coal into liquid fuel products (indirect liquefaction). However, hydrodynamic effects must be considered when attempting to scale these reactors to sizes of industrial interest. The objective of this program is to facilitate characterization of reactor hydrodynamics by developing and applying noninvasive tomographic diagnostics capable of measuring gas holdup spatial distribution in these reactors.

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

1994-09-01

79

Hydrodynamic Simulation of Gas-Solid Bubbling Fluidized Bed Containing Horizontal Tubes  

NASA Astrophysics Data System (ADS)

Hydrodynamic simulation of 2-D gas-solid bubbling fluidized bed containing staggered horizontal tubes was performed. The bubble hydrodynamics, bubble diameter and bubble rise velocity, were investigated and compared with experimental results elsewhere in the literature (Hull et al., 1999, Influence of Horizontal tube Banks on the Bubbling and Solids Mixing Behavior of Fluidized Beds. 15th Int. FBC Conference). The Eulerian-Eulerian Two Fluid Model (TFM) implemented in Fluent, version 6.3, was used for the governing equations with closure equations based on the Kinetic Theory of Granular Flow (KTGF). The numerical simulation showed that the horizontal tubes were the main source of bubble break up where bubbles break when they interact with the tubes and grew by coalescence until they reach the next row of tubes. Quantitative investigation of the bubble hydrodynamics also revealed that the predicted average bubble diameter and bubble rise velocity were in good agreement with the experimental results reported in the literature. It was observed that there were small bubbles formed on the lower-half part of the tubes which were usually interacted with an incoming bubble from below and the tube after coalescence. As a result, the numerical simulation predicted a lower average bubble diameter and bubble rise velocity at the bottom of the tube banks than that reported in the literature.

Asegehegn, Teklay Weldeabzgi; Krantz, Hans Joachim

80

Bubble-wall interactions in a vertical gas–liquid flow: Bouncing, sliding and bubble deformations  

Microsoft Academic Search

The paper presents the results of a study on the motion of single (individual) bubbles rising in upward shear liquid flow in the vicinity of a vertical wall. Bubbles were found to slide along the wall when their diameter is small. Bubbles could also experience multiple collisions with the wall at certain experimental parameters (geometry of a channel, range of

Alexander Zaruba; Dirk Lucas; Horst-Michael Prasser; Thomas Höhne

2007-01-01

81

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

SciTech Connect

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

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

1999-10-01

82

A three-dimensional CFD model for gas–liquid bubble columns  

Microsoft Academic Search

This paper discusses the development of a three-dimensional Euler–Lagrange CFD model for a gas–liquid bubble column. The model resolves the time-dependent, three-dimensional motion of small, spherical gas bubbles in a liquid. Our model incorporates all relevant forces acting on a bubble rising in a liquid, and accounts for two-way momentum coupling between the phases. The liquid-phase hydrodynamics are described using

E. Delnoij; J. A. M. Kuipers; W. P. M. van Swaaij

1999-01-01

83

Phase-field Modeling of Gas Bubbles and Thermal Conductivity Evolution in Nuclear Fuels  

SciTech Connect

The major factors that influence the thermal conductivity of the ceramics and metals are temperature, stoichiometry, microstructure, porosity, and point defects. Nuclear fuels and structure materials are subject to a severe radiation environment and their properties, including thermal conductivity change significantly with time and irradiation level. In particular, the accumulation of fission products and the formation of He bubbles can decrease the heat transfer, leading to overheating of the fuel element. In this work, we use the phase-field method to study the effect of microstructural changes on thermal conductivity. We developed a phase-field model to simulate the He bubble formation and growth in a single/polycrystalline material with defects. The model takes into account the generation of gas atoms and defects, gas atom diffusivity inhomogeneity, gas atom segregation, and gas bubble nucleation. With the model, we simulated the gas bubble and temperature evolution, and calculated the effect of gas bubble volume fraction on effective thermal conductivity.

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

2009-07-15

84

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

NASA Astrophysics Data System (ADS)

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

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

85

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

86

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

87

Quantification of gas saturations during bubbly gas flow using a novel calibration technique  

NASA Astrophysics Data System (ADS)

An understanding of gas dynamics is important during the remediation of contaminated soil and groundwater by techniques such as in situ air sparging (IAS) and in situ thermal treatment (ISTT). For example, mass transfer rates between dissolved contaminants and gases are governed by gas-liquid interfacial area, relative permeability effects reduce aqueous flow through a gas-occupied treatment zone, bubble flow allows gas phase transport at lower gas saturations in coarse material, and the onset of gas connection allows increased capture and recovery of gas-phase mass during vapor extraction. Visualization using light transmission methods (i.e., transmitting light through thin experimental cells and capturing digital images of the media and fluids in the cell over time) can be used to investigate gas dynamics in laboratory experiments. These light transmission methods often require calibration to representative wet and dry or residual transmitted light intensities in order to quantify gas saturations. In this work, a new calibration procedure was developed and used to quantify gas saturations during bubbly gas flow in coarse sand, which only used data from the water-saturated image. A known gas volume was injected at slow flow rates into the bottom of a thin cell (100 mm × 80 mm × 8 mm) containing water and sand, such that bubbly gas flow occurred. Pixel-wise gas saturation values at multiple points in time during the gas injection were integrated over the volume of the cell and calibrated to the total volume of gas injected. This method was able to overcome experimental difficulties associated with obtaining representative dry or residual images for use in calibration, and was able to calibrate directly to the distribution of discontinuous gas, which resulted in low errors in local gas saturation (i.e., standard deviations of 0.5%-2% with a median filter applied). Calibrated images were used to validate results from a numerical model used to simulate bubbly gas flow in two and three dimensions for use in air sparging applications. In addition, the light transmission method was applied to laboratory experiments of ISTT using electrical resistance heating (ERH) to investigate the development of a gas phase during boiling.

Hegele, P. R.; Mumford, K. G.

2012-12-01

88

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

Microsoft Academic Search

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

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

1996-01-01

89

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

PubMed Central

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

de Quiros, Yara Bernaldo; Gonzalez-Diaz, Oscar; Arbelo, Manuel; Sierra, Eva; Sacchini, Simona; Fernandez, Antonio

2012-01-01

90

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

91

Gas Bubbles and Gas Pancakes at Liquid/Solid Interface: A Continuum Theory Incorporated with Molecular Interactions  

E-print Network

The states of gas accumulated at the liquid-solid interface are analyzed based on the continuum theory where the Hamaker constant is used to describe the long-range interaction at the microscopic scale. The Hamaker constant is always negative, whereas the gas spreading coefficient can be either sign. Despite the complexity of gas, including that the density profile may not be uniform due to absorption on both solid and liquid surfaces, we predict three possible gas states at the liquid-solid interface, i.e. complete wetting, partial wetting and pseudopartial wetting. These possible gas states correspond respectively to a gas pancake (or film) surrounded by a wet solid, a gas bubble with a finite contact angle, and a gas bubble(s) coexisting with a gas pancake. Typical thickness of the gas pancakes is at the nanoscale within the force range of the long-range interaction, whereas the radius of the gas bubbles can be large. The state of gas bubble(s) coexisting with a gas film is predicted theoretically for the first time. Our theoretical results can contribute to the development of a unified picture of gas nucleation at the liquid-solid interface.

Zhaoxia Li; Xuehua Zhang; Lijuan Zhang; Xiaocheng Zeng; Jun Hu; Haiping Fang

2006-08-04

92

Prediction of Gas Generation and Bubble Formation in Crystalline Silicotitanate Ion Exchange Columns  

SciTech Connect

Non-elutable ion exchange technology using crystalline silicotitanate (CST) has been studied at the Savannah River Site (SRS) for removing cesium from SRS soluble radioactive waste. The authors developed a transient model to describe the process of gas generation due to radiolysis and bubble formation in 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.

Hang, T.

2000-12-19

93

Direct numerical simulation of single gas bubbles in pure and contaminated liquids  

Microsoft Academic Search

Disperse gas bubbles play an important role in many industrial applications. Knowing the rising velocity, the interfacial area, or the critical size for break-up or coalescence in different systems can be crucial for the process design. Hence, knowing the fundamental behaviour of a single bubble appears mandatory for the examination of bubble swarms and for the Euler-Lagrange or Euler--Euler modelling

Peter Lakshmanan; Peter Ehrhard

2008-01-01

94

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

95

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

96

The role of gas bubbles and liquid slug lengths on mass transport in the Taylor flow through capillaries  

Microsoft Academic Search

Gas-liquid and liquid-solid mass transfer were studied in capillaries under Taylor flow regime. The influence of the capillary diameter, unit cell length and gas hold-up on measured kLa and kSa coefficients was correlated by simple correlation, which showed that in both cases the mass transport is mostly determined by the liquid slug length and velocity. The results demonstrated that the

Gorazd Ber?i?; Albin Pintar

1997-01-01

97

Shock wave propagation and bubble collapse in liquids containing gas bubbles  

Microsoft Academic Search

The large-amplitude shock wave propagation phenomena in air-bubble\\/ water mixtures were investigated using a two-phase shock tube. Effects of incident shock wave strength and initial void fraction on shock wave pressure characteristics were investigated exp erimentally. The frequency characteristic of large-amplitude shock wave pressure was clarified by the joint time-frequency analysis of shock wave pressure histories. Behavior of the bubbles

H. Sugiyama; K. Ohtani; K. Mizobata; H. Ogasawara

2005-01-01

98

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

Microsoft Academic Search

About five centuries ago, Leonardo da Vinci described the sinuous motion of gas bubbles rising in water. We have attempted to simulate the rise trajectories of bubbles of 4, 5, 7, 8, 9, 12 and 20 mm in diameter rising in a 2D rectangular column filled with water. The simulations were carried out using the volume-of-fluid (VOF) technique developed by

R. Krishna; J. M. van Baten

1999-01-01

99

CFD modelling of bubble column reactor including the influence of gas contraction  

Microsoft Academic Search

In this paper a CFD model for a bubble column reactor undergoing a first order reaction A B is developed. The reactor operates in the homogeneous bubbly regime and has a diameter DT = 1 m and height HT = 5 m. The incoming gas stream contains inerts, varying in proportion from 10 % to 90 %. Three-dimensional transient Eulerian

Baten van J. M; R. Krishna

2004-01-01

100

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

101

Motion of gas bubbles in a liquid under the influence of a temperature gradient  

Microsoft Academic Search

This study deals with the motion of a gas bubble developing under the influence of surface-tension forces in an imponderable viscous liquid with a temperature gradient. A theory of steady-state motion of a bubble in a field with constant temperature gradient is given for the case of small Reynolds numbers. Experimental results that show qualitative agreement with the theory are

V. M. Kuznetsov; B. A. Lugovtsov; E. I. Sher

1966-01-01

102

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

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

103

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

NASA Technical Reports Server (NTRS)

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

McQuillen, J.

2000-01-01

104

Radial oscillation of a gas bubble in a fluid as a problem in canonical perturbation theory  

NASA Astrophysics Data System (ADS)

The oscillation of a gas bubble is in a fluid is of interest in many areas of physics and technology. Lord Rayleigh treated the pressure developed in the collapse of cavitation bubbles and developed an expression for the collapse period. Minnaert developed a harmonic oscillator approximation to bubble oscillation in his study of the sound produced by running water. Besides recent interest in bubble oscillation in connection to sonoluminescence, an understanding of oscillating bubbles is of important to oceanographers studying the sound spectrum produced by water waves, geophysicists employing air guns as acoustic probes, mechanical engineers concerned with erosion of turbine blades, and military engineers concerned with the acoustic signatures developed by the propeller screws of ships and submarines. For the oceanographer, Minnaert's approximation is useful, for the latter two examples, Lord Rayleigh's analysis is appropriate. For the case of the airgun, a period of twice Rayleigh's period for the ``total collapse'' of the cavitation bubble is often cited as a good approximation for the period of an air bubble ejected from an air gun port, typically at ˜2000 psi), however for the geophysical example, numerical integration is employed from the outset to determine the dynamics of the bubble and the emitted acoustic energy. On the one hand, a bubble can be treated as a harmonic oscillator in the small amplitude regime, whereas even in the relatively moderate pressure regime characteristic of air guns the oscillation is strongly nonlinear and amplitude dependent. Is it possible to develop an analytic approximation that affords insight into the behavior of a bubble beyond the harmonic approximation of Minnaert? In this spirit, the free radial oscillation of a gas bubble in a fluid is treated as a problem in canonical perturbation theory. Several orders of the expansion are determined in order to explore the dependence of the oscillation frequency with bubble amplitude. The expansion to second order is inverted to express the time dependence of the oscillation.

Stephens, James

2006-11-01

105

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

106

The Effect of Gas Bubble Percolation on the Carbonaceous Mesophase Produced from Acenaphthylene.  

National Technical Information Service (NTIS)

A study of mesophase formation in acenaphthylene was undertaken in an attempt to determine the effect of gas bubble percolation during pyrolysis on the mesophase microstructure. Samples of acenaphythylene approximately 20 g in size were pyrolyzed in test ...

D. O. Rester

1976-01-01

107

Dynamics of the gas flux from shallow gas hydrate deposits: interaction between oily hydrate bubbles and the oceanic environment  

NASA Astrophysics Data System (ADS)

Decomposition of methane hydrates on the continental margins is a potentially significant source of atmospheric methane, but the input depends upon the poorly understood fate of the hydrocarbon bubbles rising from the sea floor. During a field trip to the Gulf of Mexico, three different seepages were imaged and analyzed. Three different imaging techniques were tried (side, front, and back illumination), of which back illumination produced the best results. The images were analyzed and the size-dependent bubble distribution, mass flux, and rise speeds determined. The total observed gas flux was 62.3×10 -3 mol s -1, primarily methane, of which a single vent produced seven times the next largest vent. Of this major vent, 50% of the bubble mass was contained in the largest bubbles, r>5500 ?m. The vertical velocities demonstrated that these bubbles were heavily contaminated with oil, which was also corroborated by bubble shape and oscillation observations.

Leifer, Ira; MacDonald, Ian

2003-05-01

108

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

PubMed

In this paper, we report that nanofiber network structures were constructed from chitin derivatives by gas bubbling and ultrasonic treatments in water. When chitin was first subjected to N2 gas bubbling with ultrasonication in water, the SEM images of the product showed nanofiber network morphology. However, nanofiber network was not re-constructed by the same N2 gas bubbling and ultrasonic treatments after agglomeration. We then have paid attention to an amidine group to provide the agglomeration-nanofibrillation behavior of chitin derivatives. An amidinated chitin was synthesized by the reaction of the amino groups in a partially deacetylated chitin with N,N-dimethylacetamide dimethyl acetal, which was subjected to CO2 gas bubbling and ultrasonic treatments in water to convert into an amidinium chitin by protonation. The SEM images of the product clearly showed nanofiber network morphology. We further examined re-nanofibrillation of the agglomerated material, which was obtained by mixing the nanofibrillated amidinium chitin with water, followed by drying under reduced pressure. Consequently, the material was re-nanofibrillated by N2 gas bubbling with ultrasonication in water owing to electrostatic repulsion between the amidinium groups. Furthermore, deprotonation of the amidinium chitin and re-protonation of the resulting amidinated chitin were conducted by alkaline treatment and CO2 gas bubbling-ultrasonic treatments, respectively. The material showed the agglomeration-nanofibrillation behavior during the processes. PMID:25238127

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

2014-10-29

109

Radial oscillation of a gas bubble in a fluid as a problem in canonical perturbation theory  

NASA Astrophysics Data System (ADS)

The oscillation of a gas bubble is in a fluid is of interest in many areas of physics and technology. Lord Rayleigh treated the pressure developed in the collapse of cavitation bubbles and developed an expression for the collapse period. Minnaert developed a harmonic oscillator approximation to bubble oscillation in his study of the sound produced by running water. Oscillating bubbles are important to oceanographers studying the sound spectrum produced by water waves, geophysicists employing air guns as acoustic probes, mechanical engineers concerned with erosion of turbine blades, and military engineers concerned with the acoustic signatures developed by the propeller screws of ships and submarines. For the oceanographer, Minnaert's approximation is useful, for the latter two examples, Lord Rayleigh's analysis is appropriate. On the one hand, a bubble can be treated as a harmonic oscillator in the small amplitude regime, whereas even in the relatively moderate pressure regime characteristic of air guns the oscillation is strongly nonlinear and amplitude dependent. Is it possible to develop an analytic approximation that affords insight into the behavior of a bubble beyond the harmonic approximation of Minnaert? In this spirit, the free radial oscillation of a gas bubble in a fluid is treated as a problem in canonical perturbation theory. Several orders of the expansion are determined in order to explore the dependence of the oscillation frequency with bubble amplitude. The expansion to second order is inverted to express the time dependence of the oscillation.

Stephens, James

2005-11-01

110

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

111

The formation of gas bubbles at submerged orifices  

E-print Network

or Committee) *___________________ (head' of Department of Chemical Engineering) May 1958 ABSTRACT This investigation deals with the formation of air bubbles at submerged orifices. Five orifices, ranging from 0.0795 cm. to 0.396 cm. in diameter were used.... (10). They investigated the rate and mechanics of the formation of bubbles at horizontal, submerged orifice plates, which were in? stalled in an eight inch column. Although most of their data pertained to the air-water system, they did per? form...

Hayes, William Bell

2013-10-04

112

Discharge mechanisms in liquid nitrogen with thermally induced gas bubbles  

NASA Astrophysics Data System (ADS)

Discharge voltages of a sphere-plane electrode arrangement in subcooled liquid nitrogen stressed with impulse voltages were investigated. Tests were performed with and without thermally generated bubbles between the electrodes. Polarity effects could be observed at higher gaps and lower utilization factors. These effects are explained by the occurrence of positive and negative streamers, which have different propagation mechanisms. The measured discharge voltage with thermally generated bubbles is compared to calculated values using Paschen's law.

Blaz, M.; Kurrat, M.

2014-05-01

113

Measurements and numerical predictions of gas vortices formed by single bubble eruptions in the freeboard of a fluidised bed  

Microsoft Academic Search

Gas vortices generated in the freeboard of a bubbling fluidised bed have become the centre of increasingly more research due to the advances in experimental technology. The behaviour of gas flow in the freeboard of a bubbling fluidised bed is of interest for applications such as the gasification of coal where reactions of gas mixtures, as well as gas–particle heat

S. Vun; J. Naser; P. J. Witt; W. Yang

2010-01-01

114

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

2002-04-01

115

The interaction of two gas bubbles with a planar shock wave  

NASA Astrophysics Data System (ADS)

We consider axisymmetric and fully 3D numerical simulations of the interaction of two gas bubbles with an initially planar shock wave in water. Modelling the fluid in both phases using the compressible Euler equations together with appropriate equations of state, the resultant hyperbolic systems are solved by employing a combination of a third order ENO-Roe scheme for the spatial derivatives and a third order TVD RK scheme for the temporal derivatives. The interfaces between the different phases are tracked with a level set function in conjunction with a Ghost Fluid Method. Test results are shown to compare very well with previous work on a single bubble. The impact of the distortion of the shock front on the resultant dynamics of two bubbles is studied and its dependence on the initial shock wave strength, initial separation distance of the bubbles, and the ratio of the initial bubble radii elucidated.

Shaw, Stephen; Spelt, Peter; Matar, Omar

2007-11-01

116

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

NASA Astrophysics Data System (ADS)

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 wall to channel centerline (nozzle injection). The size, shape, and velocity of the bubbles along with liquid velocity field are measured using a shadow-particle image velocimetry/particle tracking velocimetry system. The process of bubble formation for the wall orifice and the nozzle injection configurations is physically explained. The effect of variation in water and air flow rates on the observed phenomena is also investigated by considering water average velocities of 0.46, 0.65, and 0.83 m/s and also air average velocities of 1.32, 1.97, 2.63, and 3.29 m/s. It was observed that shifting the air injector tip toward the center of the channel resulted in the coalescence of some of the preliminary bubbles and the formation of larger bubbles termed secondary and multiple bubbles. Increase in air flow rate and reduction in water flow rate also intensify the rate of bubble coalescence. A correlation-based model is also suggested to overcome the shortcoming of the available models in the literature which are developed to only estimate the size of the preliminary bubbles. The model predicts the percent of the preliminary, secondary, and multiple bubbles along with the average size of secondary and multiple bubbles as a function of nozzle position within a cross flow.

Ghaemi, Sina; Rahimi, Payam; Nobes, David S.

2010-04-01

117

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

118

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

NASA Technical Reports Server (NTRS)

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

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

2008-01-01

119

An acoustic levitation technique for the study of nonlinear oscillations of gas bubbles in liquids  

NASA Astrophysics Data System (ADS)

A technique of acoustic levitation was developed for the study of individual gas bubbles in a liquid. Isopropyl alcohol and a mixture of glycerine and water (33-1/3% glycerine by volume) were the two liquids used in this research. Bubbles were levitated near the acoustic pressure antinode of an acoustic wave in the range of 20-22 kHz. Measurements were made of the levitation number as a function of the normalized radius of the bubbles. The levitation number is the ratio of the hydrostatic pressure gradient to the acoustic pressure gradient. These values were then compared to a nonlinear theory. Results were very much in agreement except for the region near the n=2 harmonic. An explanation for the discrepancy between theory and experiment appears to lie in the polytropic exponent associated with the gas in the interior of the bubble.

Young, D. A.; Crum, L. A.

1983-08-01

120

Histopathology and ultrastructure of ocular lesions associated with gas bubble disease in salmonids.  

PubMed

Ocular lesions associated with natural and experimental outbreaks of gas bubble disease (GBD) in commercial salmonids were assessed histologically and by scanning electron microscopy. Small gas emboli were first detected in the choroid gland of the posterior uvea. In subacute and chronic cases, bubble size increased markedly and localization in retrobulbar and periocular sites was favoured. During the acute phase of GBD, ocular lesions were limited to anatomical displacement of tissue and local degeneration of compressed tissues around the perimeter of bubbles. Subacute sequelae included the formation of anterior synechia, lens cataract, and suppurative panophthalmitis. During chronic stages, when large retrobulbar bubbles had caused severe exophthalmia, there was stretching of the optic nerve and of retinal blood vessels and severe distortion of the posterior aspects of the globe. The sequential development, pathogenesis and persistence of ocular lesions associated with GBD in fish are discussed. PMID:2079557

Speare, D J

1990-11-01

121

Experimental Investigation of a Strongly Shocked Gas Bubble  

NASA Astrophysics Data System (ADS)

A free-falling, spherical, soap-film bubble filled with argon is subjected to a planar M=2.88 shock in atmospheric nitrogen; vorticity is deposited on the surface of the bubble during shock interaction, and the Richtmyer-Meshkov instability ensues. The geometrical development of the shocked bubble is diagnosed with laser sheet imaging and a planar slice showing two cross sections of both the major vortex ring and a secondary vortex ring is revealed experimentally for the first time. Quantitative measurements of the experimental data include the vortex velocity defect, and subsequent circulation calculations, along with a new set of relevant length scales. The shock wave strength, leading to a post-shock compressible regime, allows the study of the instability development in a regime between low Mach number shock tube experiments and high Mach number laser driven experiments that has not been investigated previously.

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

2005-05-01

122

Experimental investigation of a strongly shocked gas bubble.  

PubMed

A free-falling, spherical, soap-film bubble filled with argon is subjected to a planar M=2.88 shock in atmospheric nitrogen; vorticity is deposited on the surface of the bubble during shock interaction, and the Richtmyer-Meshkov instability ensues. The geometrical development of the shocked bubble is diagnosed with laser sheet imaging and a planar slice showing two cross sections of both the major vortex ring and a secondary vortex ring is revealed experimentally for the first time. Quantitative measurements of the experimental data include the vortex velocity defect, and subsequent circulation calculations, along with a new set of relevant length scales. The shock wave strength, leading to a post-shock compressible regime, allows the study of the instability development in a regime between low Mach number shock tube experiments and high Mach number laser driven experiments that has not been investigated previously. PMID:15904378

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

2005-05-13

123

An acoustic levitation technique for the study of nonlinear oscillations of gas bubbles in liquids  

Microsoft Academic Search

A technique of acoustic levitation was developed for the study of individual gas bubbles in a liquid. Isopropyl alcohol and a mixture of glycerine and water (33-1\\/3% glycerine by volume) were the two liquids used in this research. Bubbles were levitated near the acoustic pressure antinode of an acoustic wave in the range of 20-22 kHz. Measurements were made of

D. A. Young; L. A. Crum

1983-01-01

124

Analytical solutions of the Rayleigh equation for empty and gas-filled bubble  

NASA Astrophysics Data System (ADS)

The Rayleigh equation for bubble dynamics is widely used. However, analytical solutions of this equation have not previously been obtained. Here we find closed-form general solutions of the Rayleigh equation both for an empty and gas-filled spherical bubble. We present an approach allowing us to construct exact solutions of the Rayleigh equation. We show that our solutions are useful for testing numerical algorithms.

Kudryashov, Nikolay A.; Sinelshchikov, Dmitry I.

2014-10-01

125

Analytical solutions of the Rayleigh equation for empty and gas--filled bubble  

E-print Network

The Rayleigh equation for bubble dynamics is widely used. However, analytical solutions of this equation have not been obtained previously. Here we find closed--form general solutions of the Rayleigh equation both for an empty and gas--filled spherical bubble. We present an approach allowing us to construct exact solutions of the Rayleigh equation. We show that our solutions are useful for testing numerical algorithms.

Kudryashov, Nikolay A

2014-01-01

126

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

127

Methanotrophic microbial communities associated with bubble plumes above gas seeps in the Black Sea  

Microsoft Academic Search

Bubbles evolving from active gas seeps can be traced by hydroacoustic imaging up to 1000 m high in the Black Sea water column. Although methane concentrations are not distinguishable between the water column above the deep seep and reference sites, atmospheric noble gas measurements clearly show the constant input of gases (mainly methane) via seepage into the Black Sea. Archaea

Carsten J. Schubert; Edith Durisch-Kaiser; Christian P. Holzner; Lucia Klauser; Bernhard Wehrli; Oliver Schmale; Jens Greinert; Daniel F. McGinnis; Marc De Batist; Rolf Kipfer

2006-01-01

128

Gas Bubble Disease in Resident Fish of the Lower Clark Fork River  

Microsoft Academic Search

Gas bubble disease (GBD) occurs in the resident fish of the lower Clark Fork River that are exposed to total dissolved gas (TDG) supersaturation produced by the spill at upstream hydroelectric projects. This report describes the incidence and severity of GBD observed in fish routinely collected by electrofishing and other techniques during periods of high supersaturation from 1997 to 2000.

Don E. Weitkamp; Robert D. Sullivan; Tim Swant; Joe DosSantos

2003-01-01

129

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  

Microsoft Academic Search

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

DIMITRI GIDASPOW

1997-01-01

130

Simple Microwave Method for Detecting Water Holdup  

E-print Network

Simple Microwave Method for Detecting Water Holdup Sheikh S. I., Alqurashi K. Y., Ragheb H: Microwave, Reflection, Multiphase flow, Water Holdup, Oil pipeline Introduction: Oil production generally manner, although it has little effect on the changes in S11 response with changing oil- water ratio

Iqbal, Sheikh Sharif

131

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

132

Mathematical simulation of gas bubble transport in moving liquids in low gravity environments  

NASA Astrophysics Data System (ADS)

Experimental work and mathematical modeling is carried out to investigate the motion of gas bubbles in moving liquids in low gravity environments typically found in aircraft flying Keplerian parabolas. Experiments are carried out on board the NASA KC-135 and the NAE T-33 in which an aqueous solution of glycerine is stirred in a plexiglass test cell. Air is injected into the moving liquid and the trajectories of the bubbles are recorded using a video camera. Mathematical modeling is also carried out, in which the governing differential equations of the fluid and the bubbles are solved to determine the liquid flowfield and the trajectories of the bubbles. A good qualitative agreement is obtained between the computed results and the experimental data.

Abdullah, Z.; Salcudean, M.

133

Measurement and Analysis of Gas Bubbles near a Reference Electrode in Aqueous Solutions  

SciTech Connect

Bubble size distributions (BSD) near a reference electrode (RE) in aqueous glycerol solutions of an electrolyte NaCl have been investigated under various gas superficial velocities (Us). BSD and RE voltage were measured by using a high-speed digital camera and a pH/voltage meter, respectively. Self-similarity is seen in the normalized cumulative number distribution through BSD. The percent relative difference (PRD) based on the baseline voltage shows that bubble size (b) has a strong impact on PRD at low liquid viscosity and both PRD and b increase at diverging rates as Us increases. An analysis on bubble rising velocity reveals that the system is in an intermediate region. A fundamental equation for spherical bubble formation is developed via Newton’s second law of motion and is linked to an electrochemical principle in the practical application.

Steven D. Herrmann; Shelly X. Li; Michael F. Simpson; Supathorn Phongikaroon

2006-10-01

134

Surface Remobilization of Gas Bubbles in Polymer Solutions Containing Surfactants  

Microsoft Academic Search

In a previous study, Carreau et al. [Rheol. Acta13, 477 (1974)] did not observe a discontinuity in their graphical representation of velocity as a function of volume (0.1–10 cm3) for air bubbles using a 0.5 wt% polyacrylamide solution in a 20\\/80 glycerin\\/water mixture. In this study, we report that such discontinuity is occurring when smaller volumes are used. Furthermore, we

Denis Rodrigue; Jean-François Blanchet

2002-01-01

135

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

136

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

137

Acoustic monitoring of gas emissions from the seafloor. Part I: quantifying the volumetric flow of bubbles  

NASA Astrophysics Data System (ADS)

Three decades of continuous ocean exploration have led us to identify subsurface fluid related processes as a key phenomenon in marine earth science research. The number of seep areas located on the seafloor has been constantly increasing with the use of multi-scale imagery techniques. Due to recent advances in transducer technology and computer processing, multibeam echosounders are now commonly used to detect submarine gas seeps escaping from the seafloor into the water column. A growing number of en- route surveys shows that sites of gas emissions escaping from the seafloor are much more numerous than previously thought. Estimating the temporal variability of the gas flow rate and volumes escaping from the seafloor has thus become a challenge of relevant interest which could be addressed by sea-floor continuous acoustic monitoring. Here, we investigate the feasibility of estimating the volumetric flow rates of gas emissions from horizontal backscattered acoustic signals. Different models based on the acoustic backscattering theory of bubbles are presented. The forward volume backscattering strength and the inversion volumetric flow rate solutions were validated with acoustic measurements from artificial gas flow rates generated in controlled sea-water tank experiments. A sensitivity analysis was carried out to investigate the behavior of the 120-kHz forward solution with respect to model input parameters (horizontal distance between transducer and bubble stream, bubble size distribution and ascent rate). The most sensitive parameter was found to be the distance of the bubble stream which can affect the volume backscattering strength by 20 dB within the horizontal range of 0-200 m. Results were used to derive the detection probability of a bubble stream for a given volume backscattering strength threshold according to different bubble flow rates and horizontal distance.

Leblond, Isabelle; Scalabrin, Carla; Berger, Laurent

2014-09-01

138

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

SciTech Connect

This report summarizes the accomplishment made during the second year of this cooperative research effort between Washington University, Ohio State University and Air Products and Chemicals. The technical difficulties that were encountered in implementing Computer Automated Radioactive Particle Tracking (CARPT) in high pressure SBCR have been successfully resolved. New strategies for data acquisition and calibration procedure have been implemented. These have been performed as a part of other projects supported by Industrial Consortium and DOE via contract DE-2295PC95051 which are executed in parallel with this grant. CARPT and Computed Tomography (CT) experiments have been performed using air-water-glass beads in 6 inch high pressure stainless steel slurry bubble column reactor at selected conditions. Data processing of this work is in progress. The overall gas holdup and the hydrodynamic parameters are measured by Laser Doppler Anemometry (LDA) in 2 inch slurry bubble column using Norpar 15 that mimic at room temperature the Fischer Tropsch wax at FT reaction conditions of high pressure and temperature. To improve the design and scale-up of bubble column, new correlations have been developed to predict the radial gas holdup and the time averaged axial liquid recirculation velocity profiles in bubble columns.

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

2001-07-25

139

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

Microsoft Academic Search

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

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

2008-01-01

140

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

E-print Network

A planar laser-induced fluorescence (PLIF) technique for visualizing gas–liquid mass transfer and wake structure of rising gas bubbles is described. The method uses an aqueous solution of the pH-sensitive dye Naphthofluorescein ...

Stohr, M.

141

Interaction of gas bubbles with a shock wave near a solid boundary  

NASA Astrophysics Data System (ADS)

The interaction of both single and multiple gas bubbles in water with an initially planar shock in the neighbourhood of a solid boundary is considered. The compressible Euler equations in each phase are solved in axisymmetric and 3-D Cartesian geometry using up to a third-order accurate ENO-Roe scheme for the spatial fluxes in characteristics space; the solutions are evolved temporally using a third-order accurate TVD RK method. The interface between the water and gas phases is tracked with a level set function and interfacial boundary conditions are imposed using the Ghost Fluid method. The solid boundary is captured by employing reflection computational boundary conditions. In the case of a single bubble, the effect of the shock strength and of the initial location of the bubble relative to the boundary on the resultant bubble shapes, liquid jet shapes and velocities is assessed. The importance of the shock wave reflection from the boundary on the resultant dynamics is studied, together with incurred modifications due to bubble multiplicity. This work has applications in shock wave lithotripsy, cavitation-induced damage and surface cleaning.

Shaw, Stephen; Spelt, Peter; Matar, Omar

2008-11-01

142

Giant gas bubbles in a rheomorphic vent fill at the Las Cañadas caldera, Tenerife (Canary Islands)  

NASA Astrophysics Data System (ADS)

During rheomorphism subsequent to fallout deposition, a portion of the densely welded fallout of the La Grieta Member flowed back into the vent from where it was erupted, while the rest of it flowed down the outer slopes of the Las Cañadas caldera in Tenerife. The welded fallout and conduit-vent structure are physically connected and constitute a rare example of this type of deposits rooted to its feeder conduit and exposed in the caldera wall. The lower part of the vent-filling rheomorphic rocks shows gas bubbles and cavities that increase in size (up to 4 m) down vent. Bubbles are deformed against other bubbles, against the steep vent walls, flattened parallel to the flow foliation planes, and elongated parallel to the flow lineation and flow fold axes. The preservation of such giant bubbles, rather than their formation, seems to be a pretty unique feature of the phonolitic products investigated here and it is likely the result of the combination of factors that acted to preserve, in the surrounding of the glass transition interval, the sealing and the late stage cooling of a pressurized system. In addition, strain drop at the base of the vent-filling rheomorphic flow caused by flow stopping against vertical vent walls may have promoted rapid gas exsolution and the formation of large bubbles.

Soriano, Carles; Giordano, Daniele; Galindo, Inés; Hürlimann, Marcel; Ardia, Paola

2009-10-01

143

Computation of gas and solid dispersion coefficients in turbulent risers and bubbling beds  

Microsoft Academic Search

A literature review shows that dispersion coefficients in fluidized beds differ by more than five orders of magnitude. To understand the phenomena, two types of hydrodynamics models that compute turbulent and bubbling behavior were used to estimate radial and axial gas and solid dispersion coefficients. The autocorrelation technique was used to compute the dispersion coefficients from the respective computed turbulent

Veeraya Jiradilok; Dimitri Gidaspow; Ronald W. Breault

2007-01-01

144

Mathematical simulation of gas bubble transport in moving liquids in low gravity environments  

Microsoft Academic Search

Experimental work and mathematical modeling is carried out to investigate the motion of gas bubbles in moving liquids in low gravity environments typically found in aircraft flying Keplerian parabolas. Experiments are carried out on board the NASA KC-135 and the NAE T-33 in which an aqueous solution of glycerine is stirred in a plexiglass test cell. Air is injected into

Z. Abdullah; M. Salcudean

1991-01-01

145

Temperature Gradient Induced Migration of Gas-Filled Bubbles in KCl  

Microsoft Academic Search

The temperature gradient induced migration of gas bubbles has been studied in KCl. This material was selected because of its high vapor pressure and transparency. The experimental variables of temperature, temperature gradient, and diffusion coefficient of the vapor species were investigated and the observed velocities were shown to agree with those expected from the theoretically derived model. The ratio of

R. E. Carter; J. H. Rosolowski; J. S. Nadeau

1971-01-01

146

Gas Bubble Disease in Smallmouth Bass and Northern Squawfish from the Snake and Columbia Rivers  

Microsoft Academic Search

In 1975 and 1976, 179 smallmouth bass (Micropterus dolomieui) and 85 northern squawfish (Ptychocheilus oregonensis) were collected by angling from the lower Snake and mid-Columbia rivers, southeastern Washington. All fish were examined externally for gas bubble syndrome. Emboli were found beneath membranes of the opercula, body, and fins of 72% of the smallmouth bass and 84% of the northern squawfish.

Jerry C. Montgomery; C. Dale Becker

1980-01-01

147

6/10/12 UK team advances measurement of gas bubbles in pipelines. | Technology news | Process Engineer... 1/2processengineering.theengineer.co.uk/.../1012631.article  

E-print Network

6/10/12 UK team advances measurement of gas bubbles in pipelines. | Technology news | Process/1012794.article) Patrick Raleigh, Editor UK team advances measurement of gas bubbles in pipelines. 17 May of Southampton has devised a new method to more accurately measure gas bubbles in pipelines ­ an important

Sóbester, András

148

Hydrodynamic simulation of methanol synthesis in gas–liquid slurry bubble column reactors  

Microsoft Academic Search

A transient, two-dimensional hydrodynamic model for the 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 0.7H. The computed temperature variation in the reactor with heat exchangers was only about

Yuanxiang Wu; Dimitri Gidaspow

2000-01-01

149

Helium gas bubble trapped in liquid helium in high magnetic field  

NASA Astrophysics Data System (ADS)

High magnetic field magnets are used widely in the area of the condensed matter physics, material science, chemistry, geochemistry, and biology at the National High Magnetic Field Laboratory. New high field magnets of state-of-the-art are being pursued and developed at the lab, such as the current developing 32 T, 32 mm bore fully superconducting magnet. Liquid Helium (LHe) is used as the coolant for superconducting magnets or samples tested in a high magnetic field. When the magnetic field reaches a relatively high value the boil-off helium gas bubble generated by heat losses in the cryostat can be trapped in the LHe bath in the region where BzdBz/dz is less than negative 2100 T2/m, instead of floating up to the top of LHe. Then the magnet or sample in the trapped bubble region may lose efficient cooling. In the development of the 32 T magnet, a prototype Yttrium Barium Copper Oxide coil of 6 double pancakes with an inner diameter of 40 mm and an outer diameter of 140 mm was fabricated and tested in a resistive magnet providing a background field of 15 T. The trapped gas bubble was observed in the tests when the prototype coil was ramped up to 7.5 T at a current of 200 A. This letter reports the test results on the trapped gas bubble and the comparison with the analytical results which shows they are in a good agreement.

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

2014-03-01

150

Absence of hot gas within the Wolf-Rayet bubble around WR 16  

NASA Astrophysics Data System (ADS)

We present the analysis of XMM-Newton archival observations towards the Wolf-Rayet (WR) bubble around WR 16. Despite the closed bubble morphology of this WR nebula, the XMM-Newton observations show no evidence of diffuse emission in its interior as in the similar WR bubbles NGC 6888 and S 308. We use the present observations to estimate a 3-? upper limit to the X-ray luminosity in the 0.3-1.5 keV energy band equal to 7.4 × 1032 erg s-1 for the diffuse emission from the WR nebula, assuming a distance of 2.37 kpc. The WR nebula around WR 16 is the fourth observed by the current generation of X-ray satellites and the second not detected. We also examine FUSE spectra to search for nebular O vi absorption lines in the stellar continuum of WR 16. The present far-UV data and the lack of measurements of the dynamics of the optical WR bubble do not allow us to confirm the existence of a conductive layer of gas at T ~ 3 × 105 K between the cold nebular gas and the hot gas in its interior. The present observations result in an upper limit of ne < 0.6 cm-3 on the electron density of the X-ray emitting material within the nebula.

Toalá, J. A.; Guerrero, M. A.

2013-11-01

151

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

NASA Technical Reports Server (NTRS)

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

Meyyappan, M.; Shankar Subramanian, R.

1987-01-01

152

On a differential equation for a gas bubbles collapse mathematical model  

E-print Network

In this paper we present a mathematical model for estimate the collapse time of a gas bubble in a vane of a oil gerotor pump. This amount of time cannot be greater of the total time spent by the pump for filling and then emptying out a vane in a single revolution, otherwise there is a loss of lubrication between internal and external gears. We assume that oil is incompressible and viscous, the bubble has a spherical shape and it is not translating into the external fluid. The analytical treatment of the model shows that the Navier-Stokes equations for the velocity field of the oil can be reduced to a single non linear ordinary differential equation for the variation in time of the bubble radius. The collapse time estimated by a numerical resolution of this equation and the collapse time calculated from an analytical resolution of the linearized equation are substantially equal.

Gianluca Argentini

2006-06-19

153

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

PubMed

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

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

2013-01-01

154

Pressure drop and bubble–liquid interfacial shear stress in a modified gas non-Newtonian liquid downflow bubble column  

Microsoft Academic Search

A functional form of equation for predicting pressure drop in a modified non-Newtonian downflow bubble column has been formulated. The equation has been developed based on the bubble formation, drag at interface and the wettability effect of the liquid. Also the bubble–liquid interfacial shear stress in two-phase flow is analyzed and correlated with the dynamic, geometric and physical variables. The

Subrata Kumar Majumder; Gautam Kundu; Dibyendu Mukherjee

2007-01-01

155

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

156

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

PubMed Central

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. PMID:18851139

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

2009-01-01

157

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

PubMed

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=rholUmaxdmicroapp , in the neighborhood of 0.2, 2, and 200 are investigated. Here, rhol is the density of blood, Umax is the centerline velocity of the inlet Casson profile, d is the diameter of the vessel, and microapp 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), lambda , in the range 0.9< or =lambda< or =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. PMID:18851139

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

2008-09-01

158

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

159

Interaction of gas bubbles with a shock wave near a solid boundary  

Microsoft Academic Search

The interaction of both single and multiple gas bubbles in water with an initially planar shock in the neighbourhood of a solid boundary is considered. The compressible Euler equations in each phase are solved in axisymmetric and 3-D Cartesian geometry using up to a third-order accurate ENO-Roe scheme for the spatial fluxes in characteristics space; the solutions are evolved temporally

Stephen Shaw; Peter Spelt; Omar Matar

2008-01-01

160

Experimental study on a plane shock wave accelerating a gas bubble  

NASA Astrophysics Data System (ADS)

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 such as shock wave reflection, refraction and focusing, distortion of the bubble interface, and vortex formation. Based on these sequences, the changes with time in the characteristic bubble sizes were plotted and the results showed that the influence of the shock wave Mach number is significantly greater in the case of light gas bubbles. The displacement of the inhomogeneity relative to the surrounding gas was determined and compared to Rudinger and Somers' model. In all the cases studied, although the measurements were found to agree well with the theoretical predictions, in the initial acceleration phase, the final translational motions of the vortex ring were not accurately predicted by the model. The database obtained was used to estimate the resulting pattern of circulation, which was compared to other existing models. The circulation was found to increase with both the Mach number and the density ratio across the interface and was always overestimated by the models. These differences are probably caused by the presence of pulverized soap film trapped in the vortices, which reduces the motion and the strength of the resulting flow. A large number of tests are performed over a significant range of shock wave Mach numbers and density differences, with the use of high-speed imaging methods to track the vortex evolution during a single test shot. The database obtained should provide a useful tool for checking the validity of many codes and models describing the dynamics of shock/bubble interactions.

Layes, Guillaume; Jourdan, Georges; Houas, Lazhar

2009-07-01

161

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

SciTech Connect

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

Absolon, Randall F.

1999-03-01

162

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

Microsoft Academic Search

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

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

2009-01-01

163

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. PMID:19062841

Johnsen, Eric; Colonius, Tim

2008-01-01

164

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

165

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

166

The effect of crystal structure stability on the mobility of gas bubbles in intermetallic uranium compounds  

SciTech Connect

Irradiation experiments with certain low-enrichment, high-density, uranium-base intermetallic alloys that are candidate reactor fuel materials, such as U/sub 3/Si and U/sub 6/Fe, have revealed extraordinarily large voids at low and medium fuel burnup. This phenomenon of breakaway swelling does not occur in other fuel types, such as U/sub 3/Si/sub 2/ and UAl/sub 3/, where a distribution of relatively small and stable fission gas bubbles forms. In situ transmission electron microscope observations of ion radiation-induced rapid swelling of intermetallic materials are consistent with growth by plastic flow. Large radiation enhancement of plastic flow in amorphous materials has been observed in several independent experiments and is thought to be a general materials phenomenon. The basis for a microscopic theory of fission gas bubble behavior in irradiated amorphous compounds has been formulated. The assumption underlying the overall theory is that the evolution of the porosity from that observed in the crystalline material to that observed in irradiated amorphous U/sub 3/Si as a function of fluence is due to a softening of the irradiated amorphous material. Bubble growth in the low-viscosity material has been approximated by an effective enhanced diffusivity. Mechanisms are included for the radiation-induced softening of the amorphous material, and for a relation between gas atom mobilities and radiation-induced (defect-generated) changes in the material. Results of the analysis indicate that the observed rapid swelling in U/sub 3/Si arises directly from enhanced bubble migration and coalescence due to plastic flow. 34 refs., 11 figs.

Rest, J.; Hofman, G.L.; Birtcher, R.C.

1988-01-01

167

Hydrodynamics of turbulent bed contactors. 1. Operating regimes and liquid holdup  

SciTech Connect

The hydrodynamics of a three-phase turbulent bed contactor with countercurrent flow of gas and liquid has been studied and its performance compared with that of a packed-bed column using a consistent set of data. The first paper of this series deals with the operating regimes and liquid holdup in a bed of spherical particles. Two types of fluidized-bed operation and conventional packed-bed operation were studied, and criteria for identifying each regime are given. Correlations for the liquid holdup are reported for each regime.

Vunjak-Novakovic, G.V.; Vukovic, D.V.; Littman, H.

1987-05-01

168

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

169

Tritium inventory differences. I. Sampling and U-getter pump holdup  

Microsoft Academic Search

Inventory differences (ID) in tritium material balance accounts (MBA) can occur with unmeasured transfers from the process or unmeasured holdup in the system. Small but cumulatively significant quantities of tritium can leave the MBA by normal capillary sampling of process gas operation. A predictor model for estimating the quantity of tritium leaving the MBA by sampling has been developed and

R. E. Ellefson; J. T. Gill

1986-01-01

170

Feasibility study of using microfluidic platforms for visualizing bubble flows in electrolyzer gas diffusion layers  

NASA Astrophysics Data System (ADS)

In this study, microfluidic platforms were used to visualize air bubble transport in two-dimensional (2D) representations of gas diffusion layers (GDLs) to gain insight into how the geometric features of the GDL impact multiphase flow in polymer electrolyte membrane (PEM) electrolyzers. Two-dimensional porous networks were designed using volumetric pore space information, including average porosity and average throat size obtained from micro-computed tomography (micro CT) visualizations. Microfluidic chips were fabricated to represent felt, sintered powder, and foam GDLs and used to simulate the transfer of oxygen bubbles generated at the catalyst layer, through the GDL towards the flow channels of a PEM electrolyzer. The results of this work indicate that the use of microfluidic platforms for evaluating PEM electrolyzer GDLs is highly promising.

Arbabi, F.; Kalantarian, A.; Abouatallah, R.; Wang, R.; Wallace, J. S.; Bazylak, A.

2014-07-01

171

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

E-print Network

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 for by a simple linear model. The acoustic energy exhibits a high sensitivity to the dynamics of the thin film bursting, which demonstrates that, in practice, it is barely possible to deduce from the acoustic measurements the total amount of energy released by the event. Our experimental findings provide clues for the understanding of the signals from either volcanoes or foams, where one observes respectively, the bursting of giant bubbles at the free surface of lava and bubble bursting avalanches.

Thibaut Divoux; Valérie Vidal; Francisco Melo; Jean-Christophe Géminard

2008-07-01

172

The detection of gas bubbles in guinea-pigs after decompression from air saturation dives using ultrasonic imaging.  

PubMed Central

1. Bubble formation in the hind limb of anaesthetized guinea-pigs, after decompression from two different saturation exposures to air, 0.69 and 0.83 MPa gauge, has been studied using an ultrasonic pulse--echo imaging technique. 2. A qualitative analysis of the bubble formation, observed over a 30 min period after decompression, showed that profuse, largely stationary bubble formation occurred within 3 min of the decompression from 0.83 MPa gauge but that extensive stationary bubble formation was not observed until 17 min after decompression from 0.69 MPa gauge. Electrocardiogram changes appeared coincidently with the appearance of major bubble formation after the 0.83 MPa decompression but after the 0.69 MPa decompression changes were not observed until the end of the 30 min surveillance period, considerably later than the occurrence of a large number of bubbles. 3. A quantitative analysis of the echo patterns recorded during the 60 sec decompression and for 60 sec after the decompression demonstrated that the increase in severity of the decompression corresponded to an increase of 152% in the number of bubbles observed. The echoes observed during this period have been identified as either transient or persistent and their distribution of size, location and times of appearance and duration have been described. 4. From the quantitative analysis approximate estimates of the contribution by mobile, intravascular gas bubbles to the elimination of the excess gas have been made. These estimates range from 0.01 to 0.9% after the 0.69 MPa decompression and from 0.06 to 6% after the 0.83 MPa decompression. 5. It is concluded that the pulse--echo ultrasonic imaging technique provides a powerful means of analysing the distributions of bubble formation, both qualitatively and quantitatively, after decompression; it has the important attribute of being able to monitor both moving and stationary bubbles simultaneously in a variety of tissue types. Images Fig. 1 Fig. 7 PMID:7230020

Daniels, S; Davies, J M; Paton, W D; Smith, E B

1980-01-01

173

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

SciTech Connect

This report summarizes the accomplishment made during the third year of this cooperative research effort between Washington University, Ohio State University and Air Products and Chemicals. Data processing of the performed Computer Automated Radioactive Particle Tracking (CARPT) experiments in 6 inch column using air-water-glass beads (150 {micro}m) system has been completed. Experimental investigation of time averaged three phases distribution in air-Therminol LT-glass beads (150 {micro}m) system in 6 inch column has been executed. Data processing and analysis of all the performed Computed Tomography (CT) experiments have been completed, using the newly proposed CT/Overall gas holdup methodology. The hydrodynamics of air-Norpar 15-glass beads (150 {micro}m) have been investigated in 2 inch slurry bubble column using Dynamic Gas Disengagement (DGD), Pressure Drop fluctuations, and Fiber Optic Probe. To improve the design and scale-up of bubble column reactors, a correlation for overall gas holdup has been proposed based on Artificial Neural Network and Dimensional Analysis.

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

2002-07-25

174

Analysis of intergranular fission-gas bubble-size distributions in irradiated uranium-molybdenum alloy fuel  

NASA Astrophysics Data System (ADS)

An analytical model for the nucleation and growth of intra and intergranular fission-gas bubbles is used to characterize fission-gas bubble development in low-enriched U-Mo alloy fuel irradiated in the advanced test reactor in Idaho as part of the Reduced Enrichment for Research and Test Reactor (RERTR) program. Fuel burnup was limited to less than ˜7.8 at.% U in order to capture the fuel-swelling stage prior to irradiation-induced recrystallization. The model couples the calculation of the time evolution of the average intergranular bubble radius and number density to the calculation of the intergranular bubble-size distribution based on differential growth rate and sputtering coalescence processes. Recent results on TEM analysis of intragranular bubbles in U-Mo were used to set the irradiation-induced diffusivity and re-solution rate in the bubble-swelling model. Using these values, good agreement was obtained for intergranular bubble distribution compared against measured post-irradiation examination (PIE) data using grain-boundary diffusion enhancement factors of 15-125, depending on the Mo concentration. This range of enhancement factors is consistent with values obtained in the literature.

Rest, J.; Hofman, G. L.; Kim, Yeon Soo

2009-04-01

175

Sonographic detection of intrapulmonary shunting of venous gas bubbles during exercise after diving in a professional diver.  

PubMed

We report a case of right-to-left intrapulmonary (IP) shunting of venous gas bubbles at a high level of exercise after diving. The diagnosis was made using a 4-chamber view of the heart via echocardiography during exercise. This case is the first in which we could find evidence of IP shunt recruitment during exercise after diving, and the bubble grade was the highest ever seen in our laboratory. Venous bubbles crossing over through IP shunts during exercise after diving is a very rare event. PMID:17676615

Obad, Ante; Palada, Ivan; Ivancev, Vladimir; Valic, Zoran; Fabijanic, Damir; Brubakk, Alf O; Dujic, Zeljko

2007-10-01

176

On the structure of nonlinear waves in liquids with gas bubbles  

NASA Astrophysics Data System (ADS)

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 produced , R0=1.15 and 1.6 mm, with a dispersion in size of less than 5%. The void fraction was varied over one order of magnitude, ?0=0.2%-2%. The measured pressure profiles were averaged by superimposing many shots, typically 20. Speeds and profiles were measured for shock waves and for wave packets. Investigation of the wave structure allows one to approach the fundamental question of how the physics on the level of the microstructure influences the behavior on the macroscale. In the theoretical work, modeling on the basis of a hierarchy of characteristic length scales is developed. Bubble interactions, transient heat transfer, and dissipation due to molecular and bulk viscosities are included. Solutions for small void fractions and moderate amplitudes are obtained for the steady cases of shock waves and solitons and are compared with the experimental results.

Beylich, Alfred E.; Gülhan, Ali

1990-08-01

177

A Study of Vertical Gas Jets in a Bubbling Fluidized Bed  

SciTech Connect

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

Steven Ceccio; Jennifer Curtis

2011-01-18

178

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. PMID:17930342

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

2009-01-01

179

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

180

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. PMID:23372553

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

2013-01-01

181

Bubbles and Superbubbles  

E-print Network

An isolated massive star can blow a bubble, while a group of massive stars can blow superbubbles. In this paper, we examine three intriguing questions regarding bubbles and superbubbles: (1) why don't we see interstellar bubbles around every O star? (2) how hot are the bubble interiors? and (3) what is going on at the hot/cold gas interface in a bubble?

Y. -H. Chu; M. A. Guerrero; R. A. Gruendl

2003-10-10

182

A Bubble Full of Sunshine  

NSF Publications Database

... Release 05-030A Bubble Full of Sunshine Temperatures inside bursting bubbles can be four times ... University of Illinois have determined that temperatures inside gas bubbles collapsing in a liquid ...

183

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

184

Clostridium perfringens septicemia in a long-beaked common dolphin Delphinus capensis: an etiology of gas bubble accumulation in cetaceans.  

PubMed

An adult female long-beaked common dolphin Delphinus capensis live-stranded in La Jolla, California, USA, on July 30, 2012 and subsequently died on the beach. Computed tomography and magnetic resonance imaging revealed gas bubble accumulation in the vasculature, organ parenchyma, mandibular fat pads, and subdermal sheath as well as a gas-filled cavity within the liver, mild caudal abdominal effusion, and fluid in the uterus. Gross examination confirmed these findings and also identified mild ulcerations on the palate, ventral skin, and flukes, uterine necrosis, and multifocal parenchymal cavitations in the brain. Histological review demonstrated necrosis and round clear spaces interpreted as gas bubbles with associated bacterial rods within the brain, liver, spleen, and lymph nodes. Anaerobic cultures of the lung, spleen, liver, bone marrow, and abdominal fluid yielded Clostridium perfringens, which was further identified as type A via a multiplex PCR assay. The gas composition of sampled bubbles was typical of putrefaction gases, which is consistent with the by-products of C. perfringens, a gas-producing bacterium. Gas bubble formation in marine mammals due to barotrauma, and peri- or postmortem off-gassing of supersaturated tissues and blood has been previously described. This case study concluded that a systemic infection of C. perfringens likely resulted in production of gas and toxins, causing tissue necrosis. PMID:25320031

Danil, Kerri; St Leger, Judy A; Dennison, Sophie; Bernaldo de Quirós, Yara; Scadeng, Miriam; Nilson, Erika; Beaulieu, Nicole

2014-10-16

185

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

SciTech Connect

Chum salmon Oncorhynchus keta alevin developing in gravel habitats downstream of Bonneville Dam on the Columbia River are exposed to elevated levels of total dissolved gas (TDG) when water is spilled at the dam to move migrating salmon smolts downstream to the Pacific Ocean. Current water quality criteria for the management of dissolved gas in dam tailwaters were developed primarily to protect salmonid smolts and are assumed to be protective of alevin if adequate depth compensation is provided. We studied whether chum salmon alevin exposed to six levels of dissolved gas ranging from 100% to 130% TDG at three development periods between hatch and emergence (hereafter early, middle, and late stage) suffered differential mortality, growth, gas bubble disease, or seawater tolerance. Each life stage was exposed for 50 d (early stage), 29 d (middle stage), or 16 d (late stage) beginning at 13, 34, and 37 d post-hatch, respectively, through 50% emergence. The mortality for all stages from exposure to emergence was estimated to be 8% (95% confidence interval (CI) of 4% to 12%) when dissolved gas levels were between 100% and 117% TDG. Mortality significantly increased as dissolved gas levels rose above 117% TDG,; with the lethal concentration that produced 50% mortality (LC50 ) was estimated to be 128.7% TDG (95% CI of 127.2% to 130.2% TDG) in the early and middle stages. By contrast, there was no evidence that dissolved gas level significantly affected growth in any life stage except that the mean wet weight at emergence of early stage fish exposed to 130% TDG was significantly less than the modeled growth of unexposed fish. The proportion of fish afflicted with gas bubble disease increased with increasing gas concentrations and occurred most commonly in the nares and gastrointestinal tract. Early stage fish exhibited higher ratios of filament to lamellar gill chloride cells than late stage fish, and these ratios increased and decreased for early and late stage fish, respectively, as gas levels increased; however, there were no significant differences in mortality between life stages after 96 h in seawater. The study results suggest that current water quality guidelines for the management of dissolved gas appear to offer a conservative level of protection to chum salmon alevin incubating in gravel habitat downstream of Bonneville Dam.

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

2013-02-01

186

The effect on recovery of the injection of alternating slugs of gas and water at pressures above the bubble point  

E-print Network

TW EFFECT ON RECOVERY OF THE INJECTION OF ALTERNATING SLUGS OF GAS AND WATER AT PRESSURES ABOVE THE BUBBLE POINT A Thesis by James Wilson Givens Submitted to the Graduate School of the Agricultural and Mechanical College of Texas in partial... fulfillment of the requirements for the d egree of MASTERS OF SCIENCE August, l96t Major Subject; Petroleum Engineering THE EFFECT ON RECOVERY OF THE INJECTION OF ALTERNATING Sj UGS OF GAS AND WATER AT PRESSURES ABOVE THE BUBBLE POINT A Thesis...

Givens, James Wilson

2012-06-07

187

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

188

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

Microsoft Academic Search

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

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

2004-01-01

189

A MODEL TO ESTIMATE VOLUME CHANGE DUE TO RADIOLYTIC GAS BUBBLES AND THERMAL EXPANSION IN SOLUTION REACTORS  

Microsoft Academic Search

Aqueous homogeneous solution reactors have been proposed for the production of medical isotopes. However, the reactivity effects of fuel solution volume change, due to formation of radiolytic gas bubbles and thermal expansion, have to be mitigated to allow steady-state operation of solution reactors. The results of the free run experiments analyzed indicate that the proposed model to estimate the void

F. SOUTO; A HEGER

2001-01-01

190

Vertical Mobilization of a Residual Oil Phase in a Bead Pack Due to Flow of Discrete Gas Bubbles  

Microsoft Academic Search

Mobilization of trapped oil ganglia is of interest in soil and groundwater clean-up and enhanced oil recovery applications. In this work, experiments with glass beads and various oil phase compositions were performed to determine the volumetric fraction of the non-aqueous phase liquid that may be mobilized with rising discrete gas bubbles. Experiments were performed using 6 mm and 2 mm

Konark Pakkala; Kent Udell

2007-01-01

191

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

NASA Technical Reports Server (NTRS)

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

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

1996-01-01

192

6/10/12 UK University discovers new method to measure gas bubbles in pipelines -Hydrocarbons Technology 1/1www.hydrocarbons-technology.com/news/newsuniversity-devises-method  

E-print Network

6/10/12 UK University discovers new method to measure gas bubbles in pipelines - Hydrocarbons method to measure gas bubbles in pipelines 17 May 2012 The University of Southampton in the UK has discovered a new method to measure gas bubbles in pipelines, a technique crucial to preventing a major oil

Sóbester, András

193

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

194

Patent Holdup and Royalty Stacking* Mark A. Lemley**  

E-print Network

Reply Patent Holdup and Royalty Stacking* Mark A. Lemley** & Carl Shapiro*** We argued in our article, Patent Holdup and Royalty Stacking,1 that the threat to obtain a permanent injunction can greatly enhance a patent holder's negotiating power, leading to royalty rates that exceed a benchmark level based

Sadoulet, Elisabeth

195

STANDARD SETTING, PATENTS, AND HOLD-UP JOSEPH FARRELL  

E-print Network

STANDARD SETTING, PATENTS, AND HOLD-UP JOSEPH FARRELL JOHN HAYES CARL SHAPIRO THERESA SULLIVAN* I. STANDARD SETTING, PATENTS, AND HOLD-UP: A TROUBLESOME MIX Standard setting raises a variety of antitrust-setting organizations (SSOs) include patented technology in standards. We focus on the mechanism of, and techniques

Sadoulet, Elisabeth

196

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

197

Storm in a "Teacup": a radio-quiet quasar with ~10kpc radio-emitting bubbles and extreme gas kinematics  

E-print Network

We present multi-frequency (1-8 GHz) VLA data, combined with VIMOS IFU data and HST imaging, of a z=0.085 radio-quiet type 2 quasar (with L(1.4GHz)~5e23 W/Hz and L(AGN)~2e45 erg/s). Due to the morphology of its emission-line region, the target (J1430+1339) has been referred to as the Teacup AGN in the literature. We identify "bubbles" of radio emission that are extended ~10-12 kpc to both the east and west of the nucleus. The edge of the brighter eastern bubble is co-spatial with an arc of luminous ionized gas. We also show that the Teacup AGN hosts a compact radio structure, located ~0.8 kpc from the core position, at the base of the eastern bubble. This radio structure is co-spatial with an ionized outflow with an observed velocity of v=-760 km/s. This is likely to correspond to a jet, or possibly a quasar wind, interacting with the interstellar medium at this position. The large-scale radio bubbles appear to be inflated by the central AGN, which indicates that the AGN can also interact with the gas on >~10...

Harrison, C M; Alexander, D M; Bauer, F E; Edge, A C; Hogan, M T; Mullaney, J R; Swinbank, A M

2014-01-01

198

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

199

Investigation of nonstationary shock waves in gas-liquid mixtures of bubble structure  

Microsoft Academic Search

Consideration is given to the possibility of constructing an adequate model for the dynamic behavior of a two-phase mixture of a liquid with bubbles. A cell representation is used to obtain a precise condition (the generalized Rayleigh-Lamb equation) for the simultaneous deformation of the two phases. In a numerical study of a 50% solution of glycerin in water containing bubbles

A. A. Gubaidullin; A. I. Ivandaev; R. I. Nigmatulin

1978-01-01

200

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

SciTech Connect

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

DeSouza, A.H.G.; Tanner, R.D. [Vanderbilt Univ., Nashville, TN (United States); Effler, W.T. Jr. [Brown-Forman Corp., Louisville, KY (United States)

1991-12-31

201

Effect of gas expansion on the velocity of individual Taylor bubbles rising in vertical columnswithwater:Experimentalstudiesatatmosphericpressureandundervacuum  

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

L. M. T. Santos; Sena Esteves; M. N. Coelho Pinheiro

202

Numerical simulation of gas–liquid–solid fluidization systems using a combined CFD-VOF-DPM method: bubble wake behavior  

Microsoft Academic Search

A new approach that can predict the characteristics of discrete phases of three-phase flows is provided in this study. In this model, the gas–liquid–solid flow in a fluidized bed is simulated by a combined method of the computational fluid dynamics (CFD) with the discrete particle method (DPM) and a volume-tracking represented by the volume-of-fluid (VOF) method. A bubble induced force

Yong Li; Jianping Zhang; Liang-Shih Fan

1999-01-01

203

Influence of argon gas bubbles and non-metallic inclusions on the flow behavior in steel continuous casting  

Microsoft Academic Search

The present study uses an Eulerian–Lagrangian approach to model the 3D turbulence (k–?) flow of the steel melt (continuous phase) and the trajectories of individual non-metallic inclusions and gas bubbles (dispersed phase) in a continuous casting. The dispersed phase is considered as numerous mass-loaded particles with different classes of diameters and densities. To consider the interaction between the continuous and

C. Pfeiler; M. Wu; A. Ludwig

2005-01-01

204

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

SciTech Connect

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

Wendel, Mark W [ORNL] [ORNL; Felde, David K [ORNL] [ORNL; Sangrey, Robert L [ORNL] [ORNL; Abdou, Ashraf A [ORNL] [ORNL; West, David L [ORNL] [ORNL; Shea, Thomas J [ORNL] [ORNL; Hasegawa, Shoichi [Japan Atomic Energy Agency (JAEA)] [Japan Atomic Energy Agency (JAEA); Kogawa, Hiroyuki [Japan Atomic Energy Agency (JAEA)] [Japan Atomic Energy Agency (JAEA); Naoe, Dr. Takashi [Japan Atomic Energy Agency (JAEA)] [Japan Atomic Energy Agency (JAEA); Farny, Dr. Caleb H. [Boston University] [Boston University; Kaminsky, Andrew L [ORNL] [ORNL

2014-01-01

205

Bubble inclusion and removal using PDMS membrane-based gas permeation for applications in pumping, valving and mixing in microfluidic devices  

NASA Astrophysics Data System (ADS)

Several advancements in fluid handling applications of a gas-permeable polydimethylsiloxane (PDMS) membrane are demonstrated. Devices for controlled pumping, bubble injection, bubble removal and mixing are demonstrated using a three-layered fabrication method. The ability of a gas-permeable membrane to control flow in glass channels is determined. Consistent flow rates ranging from approximately 1 to 14 µl min-1 were observed using control pressures from 100 to 700 mbar. Bubble injection and removal from microfluidic channels was performed in monolithic PDMS devices using several bubble trap geometries at fluid flow rates over 100 µl min-1. The rate of removal of the air in the bubble trap was determined as a function of the area of membrane exposed and the applied vacuum. The PDMS membrane was shown to be an effective tool for the injection and removal of air bubbles in a method of enhancing mixing using bubbles and branched microchannels. The amount of mixing was optically determined before and after bubbles entered the fluid channel. The ability to produce all of these compatible components using a single fabrication process is a step toward inexpensive, parallel, highly integrated microfluidic systems with minimal external controls.

Johnson, Michael; Liddiard, Greg; Eddings, Mark; Gale, Bruce

2009-09-01

206

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

207

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

PubMed

In this study, batch experiments were performed to investigate a novel process for high concentration arsenate removal in the presence of air and/or CO(2) bubbling. The pretreatment step, CO(2) bubbling at 300 mL/min for 5 min, was taken to adjust the solution pH to an acidic environment, followed by air bubbling at 300 mL/min for 10 min to increase dissolved oxygen in the solution. In the treatment period, the nano-scale zero-valent iron was applied to remove aqueous arsenate of 3000 ?g/L, while the treatment system was continuously bubbled by 300 mL/min of air. Such a process resulted in outstanding performance in arsenate removal. Furthermore, in the field groundwater application, the arsenate removal rate for the proposed process was 5 times faster than the rate measured when the system was pretreated by acidic chemical species only. PMID:21256674

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

2011-02-28

208

Mass transfer processes across the Capillary Fringe: Quantification of gas-water interface and bubble mediated mass transfer  

NASA Astrophysics Data System (ADS)

The Capillary Fringe (CF) is a highly dynamic zone at the interface between the water-saturated aquifer and the vadose zone, where steep biogeochemical gradients and thus high bioactivities are expected. Mass transfer processes between the unsaturated zone and the atmosphere, like Greenhouse gas emissions and evaporation, are controlled by the highly temporal and spatial variable gas-water interface across the capillary fringe. Due to water table fluctuations, gas phase may be entrapped or released at/from the CF, which extremely affects the hydraulic properties of the porous medium as well as the mass transfer processes in the partially saturated zone. Most of these processes (gas entrapment and bubble mediated mass transfer (BMT)) are governed by the interactions between the interfaces of gas, water and soil phases. Quantification of these parameters requires a pore-scale approach, which can determine the phase volumes and interfaces with high accuracy. For the understanding and prediction of the involved processes, experiments and modeling at the pore scale are the necessary prerequisites for upscaled, effective modeling approaches. To achieve this aim, we conducted a set of column experiments using X-Ray Computed Tomography (CT). Using this technique, we are able to quantitatively analyze the desired variables in 3D inside the actual bulk volume of the porous media. Water table (WT) elevation was raised at different velocities in the column filled with 1mm-glass beads. After each rise, the column was scanned with CT. We used an intelligent multi-phase segmentation method, considering grey value frequency and voxel neighboring, to separate gas, water, and solid phases in the CT images. The saturation of the gas phase, distribution of the trapped gas bubbles and clusters, and their size, shape, and area are quantified and analyzed at pore-scale. We developed a new segmentation algorithm to distinguish the gas/water interface from the gas/solid interface. Only the first plays the key role in BMT. Parallel to the CT-column experiments we measured in the same experimental setup (column, sediment, WT-rise velocity) the dissolution of trapped Oxygen gas bubbles using optode spots along the capillary fringe inside the column. For the first time we quantify BMT based on pore-scale process characteristics of gas phase distribution using two different models: (i) an effective 1D-diffusion model and (ii) a Multisphere diffusion model.

Geistlinger, Helmut; Mohammadian, Sadjad; Schlüter, Steffen; Karimzadeh, Lotfollah; Vogel, Hans-Jörg

2013-04-01

209

The effect of bubble growth dynamics on the performance of a gas evolving electrode  

E-print Network

bubbles to determine the diffusion coefficient (in water) of air, oxygen and hydrogen. The effect of the liquid phase was investigated by measuring the rate of diffusion of air into sodium chloride solution, and sea water. Glas and PJestwater (15... bubbles to determine the diffusion coefficient (in water) of air, oxygen and hydrogen. The effect of the liquid phase was investigated by measuring the rate of diffusion of air into sodium chloride solution, and sea water. Glas and PJestwater (15...

Haque, Mohammad Shamsul

2012-06-07

210

Hold-up power supply for flash memory  

NASA Technical Reports Server (NTRS)

A hold-up power supply for flash memory systems is provided. The hold-up power supply provides the flash memory with the power needed to temporarily operate when a power loss exists. This allows the flash memory system to complete any erasures and writes, and thus allows it to shut down gracefully. The hold-up power supply detects when a power loss on a power supply bus is occurring and supplies the power needed for the flash memory system to temporally operate. The hold-up power supply stores power in at least one capacitor. During normal operation, power from a high voltage supply bus is used to charge the storage capacitors. When a power supply loss is detected, the power supply bus is disconnected from the flash memory system. A hold-up controller controls the power flow from the storage capacitors to the flash memory system. The hold-up controller uses feedback to assure that the proper voltage is provided from the storage capacitors to the flash memory system. This power supplied by the storage capacitors allows the flash memory system to complete any erasures and writes, and thus allows the flash memory system to shut down gracefully.

Ott, William E. (Inventor)

2004-01-01

211

Prospects for bubble fusion  

SciTech Connect

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

Nigmatulin, R.I. [Tyumen Institute of Mechanics of Multiphase Systems (TIMMS), Marx (Russian Federation); Lahey, R.T. Jr. [Rensselaer Polytechnic Institute, Troy, NY (United States)

1995-09-01

212

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

213

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

NASA Astrophysics Data System (ADS)

In the Central North Sea, during drilling operations, a gas blowout accident happened in 1990. Thereafter, natural gas has leaked prodigiously from a 60 m diameter and 20 m deep crater located at 95 m depth into the water column and to the sea surface. A series of field studies was carried out at this site since 2005 evidencing ongoing intense seepage activity. Three gas bubble megaplumes and dozens of minor to major bubble seeps were observed in the crater during a manned submersible dive, ROV mapped hundreds. Analysis of gas bubbles captured at 118 m water depth revealed concentrations between 88-90%Vol CH4 with ? 13C-CH4 values around -74‰ VPDB, consistent with a biogenic origin. Blowout site flux estimates derived from ROV video show the site's emissions are the strongest and most intense marine methane seepage quantified to date with seabed emissions of ~32.6 kt/y. Based on previous research suggesting greater flux correlates with greater transport efficiency, the direct bubble-mediated atmospheric flux to the atmosphere was estimated at a surprisingly low 0.7kt/y. This is orders of magnitude smaller compared to the seabed flux, thus the bulk methane dissolves before reaching the atmosphere, suggesting enhanced bubble dissolution rates for megaplumes. Analysis of more than 120 water samples from near the blowout plume showed dissolved methane concentration distributions consistent with enhanced bubble dissolution at depth. CH4 concentrations ranged from 0.2 µmol/L at 20 m depth to a peak in the crater of an extraordinary 400 µmol/L. To evaluate further the controlling factors on the rising bubble plume, multibeam water column data were analyzed. The bubble plume spatial distribution revealed a horizontal intrusion of gas bubbles just below the thermocline. This pronounced pattern was traced 200 m horizontally with a downflow plume orientation suggesting trapping of methane-enriched fluids at depth. A numerical bubble propagation model was used to simulate the extraordinarily intense Blowout site plume. Simulations that used normal bubble dissolution rates were unable to explain the observed trapping of almost all methane at depth, even when neglecting the observed very strong upwelling flows at the site. Incorporating a hypothesized enhanced bubble gas exchange rate allowed reproduction of observations. Video and multibeam water column analyses revealed significant turbulence in and around the bubble plume on decimeter and meter scale. Moreover 3D water column assessments by multibeam reveal that the gas ebullitions merge into a 20 m wide spiral vortex extending throughout the water column. Spiral vortex formation never has been reported for gas seepage and may be an important process enhancing plume methane dissolution. Numerical simulations incorporating vortical bubble trapping (slow rise) and enhanced bubble gas exchange were able to reproduce observations. Thus, megaplume processes could explain the surprising low surface methane observations, with important implications for understanding the fate of methane from intense seepage and for blowout response.

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

2014-05-01

214

Towards high-precision isotopic analysis of CO2 from ice-core gas bubbles using quantum cascade laser spectroscopy  

NASA Astrophysics Data System (ADS)

The paleo-climate archive provided by gas stored in bubbles in the ice provides a powerful means to study the ~40% increase in the atmospheric CO2 concentration between glacial and interglacial climates, in combination with numerical modeling studies, to elucidate the underlying physical mechanisms. Of particular interest is, considering the strong correlation between the carbon cycle and climate, and in light of the post-industrial revolution anthropogenic increase of the CO2 concentration. The source of the CO2 released into the atmosphere during previous deglaciations can be constrained from 13CO2 isotopic measurements on CO2 gas stored in bubbles in the ice-cores by the fact that the different CO2 reservoirs (terrestrial biosphere, oceans) and associated mechanisms (biological or physical) have different isotopic signatures. Unfortunately, conventional IRMS measurements on the small quantity of gas available are difficult, tedious, and time-consuming. We report here on the design of an alternative method based on Optical Feedback Cavity Enhanced Absorption Spectrometry (OF-CEAS) using a quantum cascade laser operating near 4.36 ?m. The aim of this instrument design is to achieve the measurement of the 13C/12C isotopic ratio (?13C) with a precision better than 0.05 ‰ on small quantities of the trapped atmospheric CO2. We describe the instrument and show preliminary results.

Shah, Miral; Gorrotxategi Carbajo, Paula; Kerstel, Erik; Chappellaz, Jerome

2013-04-01

215

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

216

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

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

217

The accuracy of the bubble meter method for gas flow measurements  

Microsoft Academic Search

The bubble meter technique is an absolute method of measuring the volume flow rate of gases. It requires accurate standards of mass and time only and is simple in application. This paper describes the method, examines its potential accuracy and derives criteria for design. It is found that errors may be kept below ±1% for flows between 0.1 and 1000

A. Levy

1964-01-01

218

Bubble convection within magma reservoirs  

NASA Astrophysics Data System (ADS)

Volcanoes are gas-rich hence small bubbles slowly rise in magma reservoirs. Under certain condition of gas flux, bubble size and reservoir height, the bubble rise is no more homogeneous: the collective buoyancy of the bubbles produces instabilities and the bubble motion becomes driven by convection. If such a convection occurs, the residence time of bubbles in the reservoir is reduced and thus eruptive activity is modified. By analogy with thermal convection, we define Rayleigh (Rab) and Prandtl (Prb) numbers for bubble convection. However, the critical Rab for bubble convection is hardly known from previous studies and its dependence to Prb is ignored. Laboratory experiments are performed with small bubbles rising in a cylindrical tank filled with viscous oils in order to quantify bubble convection and apply it to real volcanoes. Rab and Prb are acurately determined from measurement, via two hydrophones, of bubble size and gas volume fraction. Bubble velocity is obtained by PIV. Experiments show two main regimes: a steady cellular regime at low Rab and a bubble plume regime when Rab is higher. The critical Rab depends on the critical Prb for the two transitions.

Bouche, Emmanuella; Vergniolle, Sylvie; Gamblin, Yves; Vieira, Antonio

2008-11-01

219

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

220

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

PubMed

The coalescence behavior of air bubbles in a dilute aqueous surfactant solution of a polyglycerol fatty acid ester (PGE), a commercial non-ionic surfactant, is investigated in a binary coalescence experiment. The focus is on the influence of the ionic strength of the solution on the rate of coalescence. Results are compared with the adsorption kinetics and surface shear/dilatational rheological properties of the surfactant. Experiments show that the coalescence frequency is significantly lower at low ionic strength, and that bubble stability increases with increasing aging time. Stabilization occurs via surfactant adsorption and a resulting electrostatic and/or steric repulsive force. The electrostatic force presumably originates from small amounts of anionic fatty acid soaps, which are residues from the industrial synthesis. The steric force can be related to the adsorption of visco-elastic layers of PGE at the air-water interface. PMID:19200557

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

2009-05-15

221

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

NASA Astrophysics Data System (ADS)

12 August 2004 ESA’s quartet of space-weather watchers, Cluster, has discovered vortices of ejected solar material high above the Earth. The superheated gases trapped in these structures are probably tunnelling their way into the Earth’s magnetic ‘bubble’, the magnetosphere. This discovery possibly solves a 17-year-mystery of how the magnetosphere is constantly topped up with electrified gases when it should be acting as a barrier. hi-res Size hi-res: 1446 Kb Credits: H. Hasegawa (Dartmouth College) Three-dimensional cut-away view of Earth's magnetosphere This figure shows a three-dimensional cut-away view of Earth' s magnetosphere. The curly features sketched on the boundary layer are the Kelvin-Helmholtz vortices discovered by Cluster. They originate where two adjacent flows travel with different speed. In this case, one of the flows is the heated gas inside the boundary layer of the magnetosphere, the other the solar wind just outside it. The arrows show the direction of the magnetic field, in red that associated with the solar wind and in green the one inside Earth’s magnetosphere. The white dashed arrow shows the trajectory followed by Cluster. High resolution version (JPG format) 1446 Kb High resolution version (TIFF format) 15 365 Kb hi-res Size hi-res: 22 Kb Credits: H. Hasegawa (Dartmouth College) Electrified gas varies across the vortices along Cluster’s trajectory This computer simulation shows how the density of the electrified gas is expected to vary across the vortices along Cluster’s trajectory (white dashed line). The density is lower inside the boundary layer (blue region) and higher outside, in the region dominated by the solar wind (shown in red). The density variations measured by the instruments on board Cluster match those predicted by this model. Low resolution version (JPG format) 22 Kb High resolution version (TIFF format) 3438 Kb The Earth’s magnetic field is our planet’s first line of defence against the bombardment of the solar wind. The solar wind itself is launched from the Sun and carries the Sun’s magnetic field throughout the Solar System. Sometimes this magnetic field is aligned with Earth’s and sometimes it points in the opposite direction. When the two fields point in opposite directions, scientists understand how ‘doors’ in Earth’s field can open. This phenomenon, called ‘magnetic reconnection’, allows the solar wind to flow in and collect in the reservoir known as the boundary layer. On the contrary, when the fields are aligned they should present an impenetrable barrier to the flow. However, spacecraft measurements of the boundary layer, dating back to 1987, present a puzzle because they clearly show that the boundary layer is fuller when the fields are aligned than when they are not. So how is the solar wind getting in? Thanks to the data from the four formation-flying spacecraft of ESA’s Cluster mission, scientists have made a breakthrough. On 20 November 2001, the Cluster flotilla was heading around from behind Earth and had just arrived at the dusk side of the planet, where the solar wind slides past Earth’s magnetosphere. There it began to encounter gigantic vortices of gas at the magnetopause, the outer ‘edge’ of the magnetosphere. “These vortices were really huge structures, about six Earth radii across,” says Hiroshi Hasegawa, Dartmouth College, New Hampshire who has been analysing the data with help from an international team of colleagues. Their results place the size of the vortices at almost 40 000 kilometres each, and this is the first time such structures have been detected. These vortices are known as products of Kelvin-Helmholtz instabilities (KHI). They can occur when two adjacent flows are travelling with different speeds, so one is slipping past the other. Good examples of such instabilities are the waves whipped up by the wind slipping across the surface of the ocean. Although KHI-waves had been observed before, this is the first time that vortices are actually detected. When a KHI-wave rolls up into a vortex, it become

2004-08-01

222

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

223

Bubble columns for condensation at high concentrations of noncondensable gas: Heat-transfer model and experiments  

E-print Network

Carrier gas based thermodynamic cycles are common in water desalination applications. These cycles often require condensation of water vapor out of the carrier gas stream. As the carrier gas is most likely a noncondensable ...

Narayan, G. Prakash

224

Charged vacuum bubble stability  

NASA Astrophysics Data System (ADS)

A type of scenario is considered where electrically charged vacuum bubbles, formed from degenerate or nearly degenerate vacua separated by a thin domain wall, are cosmologically produced due to the breaking of a discrete symmetry, with the bubble charge arising from fermions residing within the domain wall. Stability issues associated with wall tension, fermion gas, and Coulombic effects for such configurations are examined. The stability of a bubble depends upon parameters such as the symmetry breaking scale and the fermion coupling. A dominance of either the Fermi gas or the Coulomb contribution may be realized under certain conditions, depending upon parameter values.

Morris, J. R.

1999-01-01

225

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

226

The growth kinetics of hydrate film on the surface of gas bubble suspended in water or aqueous surfactant solution  

NASA Astrophysics Data System (ADS)

A novel experimental method to study the hydrate formation kinetics on the gas/water interface was presented and, using this method, the two-dimensional growth kinetic data of hydrate film on the surface of quiescent methane gas bubble suspended in pure water, natural water and natural water added with different contents of sodium dodecyl sulfate (SDS) were measured and compared. The experimental results showed that the presence of the low dose of ions in natural water appreciably inhibited the hydrate formation; the presence of SDS promoted the hydrate growth when its concentration was lower than 1000 mg/L while it inhibited the hydrate formation beyond this region, the concentration of SDS corresponding to the most efficient promotion was determined to be 500 mg/L or so; the presence of low-dose ions in the natural water has little negative influence upon the promotion efficiency of SDS. A two-parameter kinetic model was developed to correlate the growth rates of hydrate films in different aqueous solutions consistently, where the dimensionless Gibbs free energy difference of hydrate formation reaction was chosen as driving force. Good agreement between calculated results and experimental data was achieved and only one parameter was found to be SDS concentration dependent. The mechanism that the presence of SDS affects the hydrate formation rate was discussed based on the experimental and theoretical results with some new insights. Additionally, the three-dimensional growth of hydrate shell covering the gas bubble was studied morphologically and a series of interesting phenomena were observed and discussed.

Sun, Chang-Yu; Chen, Guang-Jin; Ma, Chang-Feng; Huang, Qiang; Luo, Hu; Li, Qing-Ping

2007-08-01

227

Patent Holdup and Royalty Stacking* Mark A. Lemley**  

E-print Network

Patent Holdup and Royalty Stacking* Mark A. Lemley** & Carl Shapiro*** We study several interconnected problems that arise under the current U.S. patent system when a patent covers one component using bargaining theory that the threat to obtain a permanent injunction greatly enhances the patent

Sadoulet, Elisabeth

228

Terminating marine methane bubbles by superhydrophobic sponges.  

PubMed

Marine methane bubbles are absorbed, steadily stored, and continuously transported based on the employment of superhydrophobic sponges. Antiwetting sponges are water-repellent in the atmosphere and absorb gas bubbles under water. Their capacity to store methane bubbles increases with enhanced submerged depth. Significantly, trapped methane bubbles can be continuously transported driven by differential pressure. PMID:22945667

Chen, Xiao; Wu, Yuchen; Su, Bin; Wang, Jingming; Song, Yanlin; Jiang, Lei

2012-11-14

229

Bubble-induced mixing of two horizontal liquid layers with non-uniform gas injection at the bottom. [LMFBR  

SciTech Connect

During a postulated severe core meltdown accident in an LMFBR, a large amount of sodium coolant may spill into the reactor concrete cavity. A layer of liquid products may form as a result of the sodium-concrete reactions. The liquid product layer, which is highly viscous and much heavier than sodium, separates the concrete from the sodium pool. In general, the downward transport of sodium through the liquid product layer to the unreacted concrete surface, which controls the rate of chemical erosion of the concrete, depends strongly on the agitation induced by gas evolution from the heated concrete. In this study, experiments were conducted to explore the effect of non-uniform gas injection on mixing of two horizontal mutually soluble liquid layers. The liquid in the lower layer was chosen to be more viscous and heavier than the liquid in the upper layer. To simulate the reactor accident situation, gas was injected at the bottom of the liquid-liquid system through a circular hole that covered only the center portion of the bottom surface of the lower liquid layer. The bubble-induced mixing motions were observed and the rate of mixing was measured for different hole sizes and for various gas flow rates.

Cheung, F.B.; Leinweber, G.; Pedersen, D.R.

1984-01-01

230

6/10/12 Technique Devised to Measure Pipeline Gas Bubbles | Science Business 1/2sciencebusiness.technewslit.com/?p=9481  

E-print Network

of the blow out preventer was a key factor in the extensive damage caused by the BP/Deepwater Horizon oil for Oil and Gas Eight Teams Funded for Research on Gulf Oil Spill Impact * * * NEW PRODUCTS ENGINEERING issue in extracting oil with off-shore oil rigs. When these bubbles are brought up from the seabed

Sóbester, András

231

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

232

Thermocapillary migration of long bubbles in polygonal tubes. II. Experiments  

E-print Network

Thermocapillary migration of long bubbles in polygonal tubes. II. Experiments E. Lajeunesse experimentally the thermocapillary migration of a long gas bubble in a horizontal pipe of rectangular cross migration of the bubble towards the hotter region. The bubble velocity is found to be independent of bubble

Lajeunesse, Eric

233

Removal of NO from flue gas by aqueous chlorine-dioxide scrubbing solution in a lab-scale bubbling reactor.  

PubMed

The present study attempts to clean up nitric oxide from the simulated flue gas using aqueous chlorine-dioxide solution in the bubbling reactor. Chlorine-dioxide is generated by chloride-chlorate process. Experiments are carried out to examine the effect of various operating variables like input NO concentration, presence of SO(2), pH of the solution and NaCl feeding rate on the NO(x) removal efficiency at 45 degrees C. Complete oxidation of nitric oxide into nitrogen dioxide occurred on passing sufficient ClO(2) gas into the scrubbing solution. NO is finally converted into nitrate and ClO(2) is reduced into chloride ions. A plausible reaction mechanism concerning NO(x) removal by ClO(2) is suggested. DeNO(x) efficiency increased slightly with the increasing input NO concentration. The presence of SO(2) improved the NO(2) absorption but pH of solution showed marginal effect on NO(2) absorption. NO(x) removal mechanism changed when medium of solution changed from acidic to alkaline. A constant NO(x) removal efficiency of about 60% has been achieved in the wide pH range of 3-11 under optimized conditions. PMID:17583424

Deshwal, Bal Raj; Jin, Dong Seop; Lee, Si Hyun; Moon, Seung Hyun; Jung, Jong Hyeon; Lee, Hyung Keun

2008-02-11

234

Recalcitrant bubbles  

PubMed Central

We demonstrate that thermocapillary forces may drive bubbles against liquid flow in ‘anomalous' mixtures. Unlike ‘ordinary' liquids, in which bubbles migrate towards higher temperatures, we have observed vapour bubbles migrating towards lower temperatures, therefore against the flow. This unusual behaviour may be explained by the temperature dependence of surface tension of these binary mixtures. Bubbles migrating towards their equilibrium position follow an exponential trend. They finally settle in a stationary position just ‘downstream' of the minimum in surface tension. The exponential trend for bubbles in ‘anomalous' mixtures and the linear trend in pure liquids can be explained by a simple model. For larger bubbles, oscillations were observed. These oscillations can be reasonably explained by including an inertial term in the equation of motion (neglected for smaller bubbles). PMID:24740256

Shanahan, Martin E. R.; Sefiane, Khellil

2014-01-01

235

Solid Circulation Rate and Gas Leakage Measurements in an Interconnected Bubbling Fluidized Beds  

Microsoft Academic Search

Two-interconnected fluidized bed systems are widely used in various processes such as Fisher-Tropsch, hot gas desulfurization, CO2 capture-regeneration with dry sorbent, chemical-looping combustion, sorption enhanced steam methane reforming, chemical-looping hydrogen generation system, and so on. However, most of two-interconnected fluidized beds systems require riser and\\/or pneumatic transport line for solid conveying and loopseals or seal-pots for gas sealing, recirculation of

Ho-Jung Ryu; Seung-Yong Lee; Moon-Hee Park

2008-01-01

236

Solid Circulation Rate and Gas Leakage Measurements in an Interconnected Bubbling Fluidized Beds  

Microsoft Academic Search

Two-interconnected fluidized bed systems are widely used in various processes such as Fisher-Tropsch, hot gas desulfurization, CO2 capture-regeneration with dry sorbent, chemical-looping combustion, sorption enhanced steam methane reforming, chemical-looping hydrogen generation system, and so on. However, most of two-interconnected fluidized beds systems require riser and\\/or pneumatic transport line for solid conveying and loopseals or seal-pots for gas sealing, recirculation of

Ho-Jung Ryu; Seung-Yong Lee; Moon-Hee Park

2007-01-01

237

TECHNOLOGY ASSESSMENT OF FINE BUBBLE AERATORS  

EPA Science Inventory

This technology assessment addresses design and evaluation of fine bubble aeration equipment. It discusses the associated gas transfer theory used as the basis for measuring water and wastewater oxygenation efficiency. Mixing requirements are also discussed. While bubble aeration...

238

A three dimensional model of an ultrasound contrast agent gas bubble and its mechanical effects on microvessels  

PubMed Central

Ultrasound contrast agents inside a microvessel, when driven by ultrasound, oscillate and induce mechanical stresses on the vessel wall. These mechanical stresses can produce beneficial therapeutic effects but also induce vessel rupture if the stresses are too high. Therefore, it is important to use sufficiently low pressure amplitudes to avoid rupturing the vessels while still inducing the desired therapeutic effects. In this work, we developed a comprehensive three dimensional model of a confined microbubble inside a vessel while considering the bubble shell properties, blood viscosity, vessel wall curvature and the mechanical properties of the vessel wall. Two bubble models with the assumption of a spherical symmetric bubble and a simple asymmetrical bubble were simulated. This work was validated with previous experimental results and enabled us to evaluate the microbubbles’ behaviour and the resulting mechanical stresses induced on the vessel walls. In this study the fluid shear and circumferential stresses were evaluated as indicators of the mechanical stresses. The effects of acoustical parameters, vessel viscoelasticity and rigidity, vessel/bubble size and off-center bubbles on bubble behaviour and stresses on the vessel were investigated. The fluid shear and circumferential stresses acting on the vessel varied with time and location. As the frequency changed, the microbubble oscillated with the highest amplitude at its resonance frequency which was different from the resonance frequency of an unbound bubble. The bubble resonance frequency increased as the rigidity of a flexible vessel increased. The fluid shear and circumferential stresses peaked at frequencies above the bubble’s resonance frequency. The more rigid the vessels were, the more damped the bubble oscillations. The synergistic effect of acoustic frequency and vessel elasticity had also been investigated, since the circumferential stress showed either an increasing trend or a decreasing one versus the vessel rigidity at difference acoustic frequencies. When the acoustic pressure was increased from 52 kPa to 680 kPa, the maximum bubble radius increase by 2.5 folds and the maximum shear and circumferential stress increased by 15.7 and 18.3 folds respectively. The shear stress was largest when the acoustic frequency was higher (3.25 MHz) and the ratio of the vessel radius to the bubble radius was lower. The circumferential stress was largest when the bubble wall was closer to the vessel wall. An oscillating off-center bubble forms a mushroom shape with the most damping on the points closest to the vessel wall. PMID:22252221

Hosseinkhah, N.; Hynynen, K.

2012-01-01

239

Detonation wave phenomena in bubbled liquid  

Microsoft Academic Search

Shock wave propagation was investigated in two phase media consisting of diluted glycerin (85%) and reactive gas bubbles. To understand these complex phenomena, we first performed a numerical analysis and experimental studies of single bubbles containing a reactive gas-mixture. For the two-phase mixtures, a needle matrix bubble-generator enabled us to produce a homogeneous bubble distribution with a size dispersion less

A. E. Beylich

1990-01-01

240

Detonation wave phenomena in bubbled liquid  

Microsoft Academic Search

Shock wave propagation was investigated in two phase media consisting of diluted glycerin (85%) and reactive gas bubbles. To understand these complex phenomena, we first performed a numerical analysis and experimental studies of single bubbles containing a reactive gas-mixture. For the two-phase mixtures, a needle matrix bubble-generator enabled us to produce a homogeneous bubble distribution with a size dispersion less

A. Gülhan; A. E. Beylich

1990-01-01

241

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

242

Radiometric holdup measurements: Differential mass holdup of americium and plutonium oxides during preparation of traceable non-destructive assay standards  

Microsoft Academic Search

Summary  Traceable non-destructive assay standards containing mixtures of well characterized americium and plutonium oxides were prepared by blending weighed quantities with a diatomaceous earth matrix and encapsulating in welded zirconium cylinders. Am and Pu retained in fabrication process materials (e.g., emptied blend bottles), termed holdup, was quantified by gamma-spectroscopy in order to accurately state the total nuclear material content of the

S. L. Mecklenburg; G. K. Becker

2005-01-01

243

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

244

An energy-efficient process for decomposing perfluorooctanoic and perfluorooctane sulfonic acids using dc plasmas generated within gas bubbles  

NASA Astrophysics Data System (ADS)

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) are environmentally harmful and persistent substances. Their decomposition was investigated using dc plasmas generated within small gas bubbles in a solution. The plasma characteristics including discharge voltage, voltage drop in the liquid, plasma shape and the emission spectrum were examined with different gases. The decomposition rate and energy efficiency were evaluated by measuring the concentration of fluoride and sulfate ions released from PFOA/PFOS molecules. The concentration of fluoride ions and energy efficiency in the treatment of a PFOS solution were 17.7 mg l-1 (54.8% of the initial amount of fluorine atoms) and 26 mg kWh-1, respectively, after 240 min of operation. The addition of scavengers of hydroxyl radicals and hydrated electrons showed little effect on the decomposition. The decomposition processes were analyzed with an assumption that positive species reacted with PFOA/PFOS molecules at the boundary of the plasma-solution surface. This type of plasma showed a much higher decomposition energy efficiency compared with energy efficiencies reported in other studies.

Yasuoka, K.; Sasaki, K.; Hayashi, R.

2011-06-01

245

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

246

Gas Bubble Disease Due to Helicopter Transport of Young Pink Salmon  

Microsoft Academic Search

When 0.2-g pink salmon Oncorhynchus gorbuscha were carried by helicopter in Alaska, total gas pressure in the transport water reached 71.3 mm Hg (109.4% of barometric pressure). Gross and microscopic lesions in swim bladders of fish progressed during transport to tympanitic dilatation, then to separation of laminae and rupture. Other associated signs and lesions were exophthalmos, cranial swelling, edematous gill

A. K. Hauck

1986-01-01

247

Wall-to-bed heat transfer in gas-solid bubbling fluidized beds  

Microsoft Academic Search

The wall-to-bed heat transfer in gas-solid fluidized beds is mainly determined by phenomena prevailing in a thermal boundary layer with a thickness in the order of magnitude of the size of a single particle. In this thermal boundary layer the temperature gradients are very steep and the local porosity profile near the wall strongly influences the heat-transfer rate. A two-fluid

D. J. Patil; J. Smit; Sint Annaland van M; J. A. M. Kuipers

2006-01-01

248

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

2012-02-01

249

Removal of elemental mercury from flue gas by thermally activated ammonium persulfate in a bubble column reactor.  

PubMed

In this article, a novel technique on removal of elemental mercury (Hg(0)) from flue gas by thermally activated ammonium persulfate ((NH4)2S2O8) has been developed for the first time. Some experiments were carried out in a bubble column reactor to evaluate the effects of process parameters on Hg(0) removal. The mechanism and kinetics of Hg(0) removal are also studied. The results show that the parameters, (NH4)2S2O8 concentration, activation temperature and solution pH, have significant impacts on Hg(0) removal. The parameters, Hg(0), SO2 and NO concentration, only have small effects on Hg(0) removal. Hg(0) is removed by oxidations of (NH4)2S2O8, sulfate and hydroxyl free radicals. When (NH4)2S2O8 concentration is more than 0.1 mol/L and solution pH is lower than 9.71, Hg(0) removal by thermally activated (NH4)2S2O8 meets a pseudo-first-order fast reaction with respect to Hg(0). However, when (NH4)2S2O8 concentration is less than 0.1 mol/L or solution pH is higher than 9.71, the removal process meets a moderate speed reaction with respect to Hg(0). The above results indicate that this technique is a feasible method for emission control of Hg(0) from flue gas. PMID:25251199

Liu, Yangxian; Wang, Qian

2014-10-21

250

A Simple Economic Teaching Experiment on the Hold-Up Problem  

ERIC Educational Resources Information Center

The hold-up problem is central to the theory of incomplete contracts. This can occur if, after making a sunk investment in a relationship, one party can be taken advantage of by the other party, leading to inefficient underinvestment. The authors describe a simple teaching experiment that illustrates the hold-up problem, and address how to…

Balkenborg, Dieter; Kaplan, Todd; Miller, Timothy

2012-01-01

251

Bubble Baryogenesis  

E-print Network

We propose an alternative mechanism of baryogenesis in which a scalar baryon undergoes a percolating first-order phase transition in the early Universe. The potential barrier that divides the phases contains explicit B and CP violation and the corresponding instanton that mediates decay is therefore asymmetric. The nucleation and growth of these asymmetric bubbles dynamically generates baryons, which thermalize after percolation; bubble collision dynamics can also add to the asymmetry yield. We present an explicit toy model that undergoes bubble baryogenesis, and numerically study the evolution of the baryon asymmetry through bubble nucleation and growth, bubble collisions, and washout. We discuss more realistic constructions, in which the scalar baryon and its potential arise amongst the color-breaking minima of the MSSM, or in the supersymmetric neutrino seesaw mechanism. Phenomenological consequences, such as gravitational waves, and possible applications to asymmetric dark-matter generation are also discussed.

Clifford Cheung; Alex Dahlen; Gilly Elor

2012-05-15

252

Antitrust Holdup Source, Cross-National Institutional Variation, and Corporate Political Strategy Implications for Domestic Mergers in a Global Context  

Microsoft Academic Search

Managers are increasingly uncertain over the source (home-nation or foreign-nation) of antitrust holdup for domestic mergers with significant international implications. I propose a conceptual framework that predicts the source of antitrust holdup for domestic mergers. Under idealized institutional assumptions, I find an industry's global competitiveness to be the primary driver behind holdup source: a contention supported by empirical tests based

Joseph A. Clougherty

2004-01-01

253

Cumulative Innovation, Experimentation and the Hold-Up Problem  

E-print Network

in 2005 in the United States, the Supreme Court in Merck KGaA v. Integra Life Sciences I, Ltd 10 created a very broad research exemption in relation to pre-clinical R&D. Such a change again corresponds closely in the model to a move towards a weak IP... profit-maximizing royalty rate that excludes some second-stage innovators from licensing. Since, the ‘experimentation’ case we discuss below resembles more closely a traditional ‘hold-up’ situation we prefer to reserve that term for use...

Pollock, Rufus

254

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

255

Bubbly Little Star  

NASA Technical Reports Server (NTRS)

In this processed Spitzer Space Telescope image, baby star HH 46/47 can be seen blowing two massive 'bubbles.' The star is 1,140 light-years away from Earth.

The infant star can be seen as a white spot toward the center of the Spitzer image. The two bubbles are shown as hollow elliptical shells of bluish-green material extending from the star. Wisps of green in the image reveal warm molecular hydrogen gas, while the bluish tints are formed by starlight scattered by surrounding dust.

These bubbles formed when powerful jets of gas, traveling at 200 to 300 kilometers per second, or about 120 to 190 miles per second, smashed into the cosmic cloud of gas and dust that surrounds HH 46/47. The red specks at the end of each bubble show the presence of hot sulfur and iron gas where the star's narrow jets are currently crashing head-on into the cosmic cloud's gas and dust material.

Whenever astronomers observe a star, or snap a stellar portrait, through the lens of any telescope, they know that what they are seeing is slightly blurred. To clear up the blurring in Spitzer images, astronomers at the Jet Propulsion Laboratory developed an image processing technique for Spitzer called Hi-Res deconvolution.

This process reduces blurring and makes the image sharper and cleaner, enabling astronomers to see the emissions around forming stars in greater detail. When scientists applied this image processing technique to the Spitzer image of HH 46/47, they were able to see winds from the star and jets of gas that are carving the celestial bubbles.

This infrared image is a three-color composite, with data at 3.6 microns represented in blue, 4.5 and 5.8 microns shown in green, and 24 microns represented as red.

2007-01-01

256

Enhancing gas-liquid mass transfer rates in non-newtonian fermentations by confining mycelial growth to microbeads in a bubble column  

SciTech Connect

The performance of a penicillin fermentation was assessed in a laboratory-scale bubble column fermentor, with mycelial growth confined to the pore matrix of celite beads. Final cell densities of 29 g/L and penicillin titres of 5.5 g/L were obtained in the confined cell cultures. In comparison, cultures of free mycelial cells grown in the absence of beads experienced dissolved oxygen limitations in the bubble column, giving only 17 g/L final cell concentrations with equally low penicillin titres of 2 g/L. The better performance of the confined cell cultures was attributed to enhanced gas liquid mass transfer rates, with mass transfer coefficients (k /SUB L/ a) two to three times higher than those determined in the free cell cultures. Furthermore, the confined cell cultures showed more efficient utilization of power input for mass transfer, providing up to 50% reduction in energy requirements for aeration.

Gbewonyo, K.; Wang, D.I.C.

1983-12-01

257

Effect of bubble size on micro-bubble drag reduction  

NASA Astrophysics Data System (ADS)

The effect of bubble size on micro-bubble drag reduction was investigated experimentally in a high-speed turbulent channel flow of water. A variety of near-wall injection techniques were used to create a bubbly turbulent boundary layer. The resulting wall friction force was measured directly by a floating element force balance. The bubble size was determined from photographic imaging. Using compressed nitrogen to force flow through a slot injector located in the plate beneath the boundary layer of the tunnel test section, a surfactant solution (Triton X-100, 19ppm) and salt water solution (35ppt) generated bubbles of average size between ˜500 microns and ˜200 microns and ˜100 microns, respectively (40 < d^+ < 200). In addition hollow spherical glass beads (˜75 microns (d^+ = 30) and specific gravity 0.18) and previously prepared lipid stabilized gas bubbles of ˜ 30 micron (d^+ =12) were injected. The results indicate that the drag reduction is related strongly to the injected gas volume flux and the static pressure in the boundary layer. Changing bubble size had essentially no influence on the measured friction drag, suggesting that friction drag is not a strong function of bubble size. [Sponsored by the Office of Naval Research.

Shen, Xiaochun

2005-11-01

258

Exploring Bubbles  

NASA Astrophysics Data System (ADS)

Bubbles provide an enjoyable and festive medium through which to teach many concepts within the science topics of light, color, chemistry, force, air pressure, electricity, buoyancy, floating, density, among many others. In order to determine the nature of children's engagement within a museum setting and the learning opportunities of playing with bubbles, I went to a children's interactive museum located in a metropolitan city in the Northeastern part of the United States.

O'Geary, Melissa A.

259

Design and characterization of bubble phononic crystals Valentin Leroy,  

E-print Network

is the longitudinal modulus of the gas, the mass density of the liquid, and R the radius of the bubble and bubble size can be tuned as wanted in that case. Some authors have in- deed reported a huge decrease of bubbles. The idea is to have bubbles em- bedded in an elastic matrix rather than a liquid. In that case

Paris-Sud XI, Université de

260

Frictional drag reduction by bubble injection  

NASA Astrophysics Data System (ADS)

The injection of gas bubbles into a turbulent boundary layer of a liquid phase has multiple different impacts on the original flow structure. Frictional drag reduction is a phenomenon resulting from their combined effects. This explains why a number of different void-drag reduction relationships have been reported to date, while early works pursued a simple universal mechanism. In the last 15 years, a series of precisely designed experimentations has led to the conclusion that the frictional drag reduction by bubble injection has multiple manifestations dependent on bubble size and flow speed. The phenomena are classified into several regimes of two-phase interaction mechanisms. Each regime has inherent physics of bubbly liquid, highlighted by keywords such as bubbly mixture rheology, the spectral response of bubbles in turbulence, buoyancy-dominated bubble behavior, and gas cavity breakup. Among the regimes, bubbles in some selected situations lose the drag reduction effect owing to extra momentum transfer promoted by their active motions. This separates engineers into two communities: those studying small bubbles for high-speed flow applications and those studying large bubbles for low-speed flow applications. This article reviews the roles of bubbles in drag reduction, which have been revealed from fundamental studies of simplified flow geometries and from development of measurement techniques that resolve the inner layer structure of bubble-mixed turbulent boundary layers.

Murai, Yuichi

2014-07-01

261

Electrowetting-on-dielectrics for manipulation of oil drops and gas bubbles in aqueous-shell compound drops.  

PubMed

We present the manipulation of oil, organic and gaseous chemicals by electrowetting-on-dielectric (EWOD) technology using aqueous-shell compound drops. We demonstrate that the transport and coalescence of viscous oil drops, the reaction of bromine with styrene in benzene solution, and the reaction of red blood cells with carbon monoxide bubbles can be accomplished using this method. PMID:25236507

Li, Jiang; Wang, Yixuan; Chen, Haosheng; Wan, Jiandi

2014-10-14

262

Opposed bubbly jets at different impact angles: Jet structure and bubble properties  

Microsoft Academic Search

The structure of two colliding water jets containing small gas bubbles is studied experimentally. The effects of the separation distance between jets, as well as the orientation angle, on the spatial distribution of bubbles have been considered. Results on the global structure of the final jet and bubble properties have been obtained using a high-speed video camera, and measurements of

Francesc Suñol; Ricard González-Cinca

2010-01-01

263

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

NASA Technical Reports Server (NTRS)

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

Maldarelli, Charles; Papageorgiou, Demetrios

1998-01-01

264

Oscillations of soap bubbles  

NASA Astrophysics Data System (ADS)

Oscillations of droplets or bubbles of a confined fluid in a fluid environment are found in various situations in everyday life, in technological processing and in natural phenomena on different length scales. Air bubbles in liquids or liquid droplets in air are well-known examples. Soap bubbles represent a particularly simple, beautiful and attractive system to study the dynamics of a closed gas volume embedded in the same or a different gas. Their dynamics is governed by the densities and viscosities of the gases and by the film tension. Dynamic equations describing their oscillations under simplifying assumptions have been well known since the beginning of the 20th century. Both analytical description and numerical modeling have made considerable progress since then, but quantitative experiments have been lacking so far. On the other hand, a soap bubble represents an easily manageable paradigm for the study of oscillations of fluid spheres. We use a technique to create axisymmetric initial non-equilibrium states, and we observe damped oscillations into equilibrium by means of a fast video camera. Symmetries of the oscillations, frequencies and damping rates of the eigenmodes as well as the coupling of modes are analyzed. They are compared to analytical models from the literature and to numerical calculations from the literature and this work.

Kornek, U.; Müller, F.; Harth, K.; Hahn, A.; Ganesan, S.; Tobiska, L.; Stannarius, R.

2010-07-01

265

Bubble fusion: Preliminary estimates  

SciTech Connect

The collapse of a gas-filled bubble in disequilibrium (i.e., internal pressure {much_lt} external pressure) can occur with a significant focusing of energy onto the entrapped gas in the form of pressure-volume work and/or acoustical shocks; the resulting heating can be sufficient to cause ionization and the emission of atomic radiations. The suggestion that extreme conditions necessary for thermonuclear fusion to occur may be possible has been examined parametrically in terms of the ratio of initial bubble pressure relative to that required for equilibrium. In this sense, the disequilibrium bubble is viewed as a three-dimensional ``sling shot`` that is ``loaded`` to an extent allowed by the maximum level of disequilibrium that can stably be achieved. Values of this disequilibrium ratio in the range 10{sup {minus}5}--10{sup {minus}6} are predicted by an idealized bubble-dynamics model as necessary to achieve conditions where nuclear fusion of deuterium-tritium might be observed. Harmonic and aharmonic pressurizations/decompressions are examined as means to achieve the required levels of disequilibrium required to create fusion conditions. A number of phenomena not included in the analysis reported herein could enhance or reduce the small levels of nuclear fusions predicted.

Krakowski, R.A.

1995-02-01

266

Experimental evidence for seismically initiated gas bubble nucleation and growth in groundwater as a mechanism for coseismic borehole water level rise and remotely triggered seismicity  

NASA Astrophysics Data System (ADS)

in borehole water levels and remotely triggered seismicity occur in response to near and distant earthquakes at locations around the globe, but the mechanisms for these phenomena are not well understood. Experiments were conducted to show that seismically initiated gas bubble growth in groundwater can trigger a sustained increase in pore fluid pressure consistent in magnitude with observed coseismic borehole water level rise, constituting a physically plausible mechanism for remote triggering of secondary earthquakes through the reduction of effective stress in critically loaded geologic faults. A portion of the CO2 degassing from the Earth's crust dissolves in groundwater where seismic Rayleigh and P waves cause dilational strain, which can reduce pore fluid pressure to or below the bubble pressure, triggering CO2 gas bubble growth in the saturated zone, indicated by a spontaneous buildup of pore fluid pressure. Excess pore fluid pressure was measured in response to the application of 0.1-1.0 MPa, 0.01-0.30 Hz confining stress oscillations to a Berea sandstone core flooded with initially subsaturated aqueous CO2, under conditions representative of a confined aquifer. Confining stress oscillations equivalent to the dynamic stress of the 28 June 1992 Mw 7.3 Landers, California, earthquake Rayleigh wave as it traveled through the Long Valley caldera, and Parkfield, California, increased the pore fluid pressure in the Berea core by an average of 36 ± 15 cm and 23 ± 15 cm of equivalent freshwater head, respectively, in agreement with 41.8 cm and 34 cm rises recorded in wells at those locations.

Crews, Jackson B.; Cooper, Clay A.

2014-09-01

267

Study on the dynamic holdup distribution of the pulsed extraction column  

SciTech Connect

In the study, a CSTR cascade dynamic hydraulic model was developed to investigate the dynamic holdup distribution of the pulsed extraction column. It is assumed that the dynamic process of the dispersed phase holdup of pulsed extraction column has equal effects with the operational process of multiple cascade CSTRs. The process is consistent with the following assumptions: the holdups vary on different stages but maintain uniform on each stage; the changes of the hydraulic parameters have impact initially on the inlet of dispersed phase, and stability will be reached gradually through stage-by-stage blending. The model was tested and verified utilizing time domain response curves of the average holdup. Nearly 150 experiments were carried out with different capillary columns, various feed liquids, and diverse continuous phases and under different operation conditions. The regression curves developed by the model show a good consistency with the experimental results. After linking parameters of the model with operational conditions, the study further found that the parameters are only linearly correlated with pulse conditions and have nothing to do with flow rate for a specific pulsed extraction column. The accuracy of the model is measured by the average holdup, and the absolute error is ±0.01. The model can provide supports for the boundary studies on hydraulics and mass transfer by making simple and reliable prediction of the dynamic holdup distribution, with relatively less accessible hydraulic experimental data. (authors)

Wang, S.; Chen, J.; Wu, Q. [Tsinghua University, Beijing 100084 (China)

2013-07-01

268

Leverage bubble  

NASA Astrophysics Data System (ADS)

Leverage is strongly related to liquidity in a market and lack of liquidity is considered a cause and/or consequence of the recent financial crisis. A repurchase agreement is a financial instrument where a security is sold simultaneously with an agreement to buy it back at a later date. Repurchase agreement (repo) market size is a very important element in calculating the overall leverage in a financial market. Therefore, studying the behavior of repo market size can help to understand a process that can contribute to the birth of a financial crisis. We hypothesize that herding behavior among large investors led to massive over-leveraging through the use of repos, resulting in a bubble (built up over the previous years) and subsequent crash in this market in early 2008. We use the Johansen-Ledoit-Sornette (JLS) model of rational expectation bubbles and behavioral finance to study the dynamics of the repo market that led to the crash. The JLS model qualifies a bubble by the presence of characteristic patterns in the price dynamics, called log-periodic power law (LPPL) behavior. We show that there was significant LPPL behavior in the market before that crash and that the predicted range of times predicted by the model for the end of the bubble is consistent with the observations.

Yan, Wanfeng; Woodard, Ryan; Sornette, Didier

2012-01-01

269

Generator for single bubbles of controllable size C. D. Ohla)  

E-print Network

. A single bubble is generated by injecting a short burst of gas into a liquid channel flow. The radius Figure 1 sketches the bubble generator. The pressure for the gas (Pgas) injection upper valve in Fig. 1Generator for single bubbles of controllable size C. D. Ohla) Department of Applied Physics, TU

Ohl, Claus-Dieter

270

Measurement of hold-up times in a thermal ion source for metallic and monoxide ions of lanthanum and cerium  

Microsoft Academic Search

Hold-up times of ions in a thermal ion source were measured for lanthanum and cerium together with neighboring elements in the periodic table. The hold-up times of metallic and monoxide ions of both lanthanum and cerium were found to be almost the same and much longer than those of cesium, barium, praseodymium and neodymium ions. The observed long hold-up times

S. Ichikawa; T. Sekine; H. Iimura; M. Oshima

1992-01-01

271

Seismically Initiated Carbon Dioxide Gas Bubble Growth in Groundwater: A Mechanism for Co-seismic Borehole Water Level Rise and Remotely Triggered Secondary Seismicity  

NASA Astrophysics Data System (ADS)

Visualization experiments, core-scale laboratory experiments, and numerical simulations were conducted to examine the transient effect of dilational seismic wave propagation on pore fluid pressure in aquifers hosting groundwater that is near saturation with respect to dissolved carbon dioxide (CO2) gas. Groundwater can become charged with dissolved CO2 through contact with gas-phase CO2 in the Earth's crust derived from magma degasing, metamorphism, and biogenic processes. The propagation of dilational seismic waves (e.g., Rayleigh and p-waves) causes oscillation of the mean normal confining stress and pore fluid pressure. When the amplitude of the pore fluid pressure oscillation is large enough to drive the pore fluid pressure below the bubble pressure, an aqueous-to-gas-phase transition can occur in the pore space, which causes a buildup of pore fluid pressure and reduces the inter-granular effective stress under confined conditions. In visualization experiments conducted in a Hele-Shaw cell representing a smooth-walled, vertically oriented fracture, millisecond-scale pressure perturbations triggered bubble nucleation and growth lasting tens of seconds, with resulting pore fluid overpressure proportional to the magnitude of the pressure perturbation. In a Berea sandstone core flooded with initially under-saturated aqueous CO2 under conditions representative of a confined aquifer, rapid reductions in confining stress triggered transient pore pressure rise up to 0.7 MPa (100 psi) overpressure on a timescale of ~10 hours. The rate of pore pressure buildup in the first 100 seconds was proportional to the saturation with respect to dissolved CO 2 at the pore pressure minimum. Sinusoidal confining stress oscillations on a Berea sandstone core produced excess pore fluid pressure after the oscillations were terminated. Confining stress oscillations in the 0.1-0.4 MPa (15-60 psi) amplitude range and 0.05-0.30 Hz frequency band increased the pore fluid pressure by 13-60 cm of freshwater. Co-seismic borehole water level increases of the same magnitude were observed in Parkfield, California, and Long Valley caldera, California, in response to the propagation of a Rayleigh wave in the same amplitude and frequency range produced by the June 28, 1992 MW 7.3 Landers, California, earthquake. Co-seismic borehole water level rise is well documented in the literature, but the mechanism is not well understood, and the results of core-scale experiments indicate that seismically initiated CO2 gas bubble nucleation and growth in groundwater is a reasonable mechanism. Remotely triggered secondary seismicity is also well documented, and the reduction of effective stress due to CO2 bubble nucleation and growth in critically loaded faults may potentially explain how, for example, the June 28, 1992 MW 7.3 Landers, California, earthquake triggered seismicity as far away as Yellowstone, Wyoming, 1250 km from the hypocenter. A numerical simulation was conducted using Euler's method and a first-order kinetic model to compute the pore fluid pressure response to confining stress excursions on a Berea sandstone core flooded with initially under-saturated aqueous CO2. The model was calibrated on the pore pressure response to a rapid drop and later recovery of the confining stress. The model predicted decreasing overpressure as the confining stress oscillation frequency increased from 0.05 Hz to 0.30 Hz, in contradiction with the experimental results and field observations, which exhibit larger excess pore fluid pressure in response to higher frequency oscillations. The limitations of the numerical model point to the important influence of non-ideal behavior arising from a discontinuous gas phase and complex dynamics at the gas-liquid interface.

Crews, Jackson B.

272

Numerical Simulations of Bubble Dynamics and Heat Transfer in Pool Boiling---Including the Effects of Conjugate Conduction, Level of Gravity, and Noncondensable Gas Dissolved in the Liquid  

NASA Astrophysics Data System (ADS)

Due to the complex nature of the subprocesses involved in nucleate boiling, it has not been possible to develop comprehensive models or correlations despite decades of accumulated data and analysis. Complications such as the presence of dissolved gas in the liquid further confound attempts at modeling nucleate boiling. Moreover, existing empirical correlations may not be suitable for new applications, especially with regards to varying gravity level. More recently, numerical simulations of the boiling process have proven to be capable of reliably predicting bubble dynamics and associated heat transfer by showing excellent agreement with experimental data. However, most simulations decouple the solid substrate by assuming constant wall temperature. In the present study complete numerical simulations of the boiling process are performed---including conjugate transient conduction in the solid substrate and the effects of dissolved gas in the liquid at different levels of gravity. Finite difference schemes are used to discretize the governing equations in the liquid, vapor, and solid phases. The interface between liquid and vapor phases is tracked by a level set method. An iterative procedure is used at the interface between the solid and fluid phases. Near the three-phase contact line, temperatures in the solid are observed to fluctuate significantly over short periods. The results show good agreement with the data available in the literature. The results also show that waiting and growth periods can be related directly to wall superheat. The functional relationship between waiting period and wall superheat is found to agree well with empirical correlations reported in the literature. For the case of a single bubble in subcooled nucleate boiling, the presence of dissolved gas in the liquid is found to cause noncondensables to accumulate at the top of the bubble where most condensation occurs. This results in reduced local saturation temperature and condensation rates. The numerical predictions show reasonable agreement with the results from experiments performed at microgravity. For nucleate boiling at microgravity the simulations predict a drastic change in vapor removal pattern when compared to Earth normal gravity. The predictions match well with experimental results. However, simulated heat transfer rates were significantly under-predicted.

Aktinol, Eduardo

273

Mechanisms of bubble coalescence in silicic magmas  

NASA Astrophysics Data System (ADS)

Bubble coalescence is an important process that strongly affects magmatic degassing. Without coalescence, bubbles remain isolated from one another in the melt, severely limiting gas release. Despite this fact, very little has been done to identify coalescence mechanisms from textures of magmatic rocks or to quantify the dynamics of bubble coalescence in melts. In this paper, we present a systematic study of bubble-coalescence mechanisms and dynamics in natural and experimentally produced bubbly rhyolite magma. We have used a combination of natural observations aided by high-resolution X-ray computed tomography, petrological experiments, and physical models to identify different types of bubble-bubble interaction that lead to coalescence on the timescales of magma ascent and eruption. Our observations and calculations suggest that bubbles most efficiently coalesce when inter-bubble melt walls thin by stretching rather than by melt drainage from between converging bubble walls. Orders of magnitude are more rapid than melt drainage, bubble wall stretching produces walls thin enough that inter-bubble pressure gradients may cause the melt wall to dimple, further enhancing coalescence. To put these results into volcanogical context, we have identified magma ascent conditions where each coalescence mechanism should act, and discuss the physical conditions for preserving coalescence structures in natural pumice. The timescales we propose could improve volcanic eruption models, which currently do not account for bubble coalescence. Although we do not address the effect of shear strain on bubble coalescence, the processes discussed here may operate in several different eruption regimes, including vesiculation of lava domes, post-fragmentation frothing of vulcanian bombs, and bubbling of pyroclasts in conduits.

Castro, Jonathan M.; Burgisser, Alain; Schipper, C. Ian; Mancini, Simona

2012-12-01

274

Low-enriched uranium holdup measurements in Kazakhstan  

SciTech Connect

Quantification of the residual nuclear material remaining in process equipment has long been a challenge to those who work with nuclear material accounting systems. Fortunately, nuclear material has spontaneous radiation emissions that can be measured. If gamma-ray measurements can be made, it is easy to determine what isotope a deposit contains. Unfortunately, it can be quite difficult to relate this measured signal to an estimate of the mass of the nuclear deposit. Typically, the measurement expert must work with incomplete or inadequate information to determine a quantitative result. Simplified analysis models, the distribution of the nuclear material, any intervening attenuation, background(s), and the source-to-detector distance(s) can have significant impacts on the quantitative result. This presentation discusses the application of a generalized-geometry holdup model to the low-enriched uranium fuel pellet fabrication plant in Ust-Kamenogorsk, Kazakhstan. Preliminary results will be presented. Software tools have been developed to assist the facility operators in performing and documenting the measurements. Operator feedback has been used to improve the user interfaces.

Barham, M.A.; Ceo, R.N.; Smith, S.E. [Oak Ridge Y-12 Plant, TN (United States)] [and others

1998-12-31

275

Constraining bubbling of methane from thermokarst lakes  

NASA Astrophysics Data System (ADS)

In northern thermokarst lakes, which form in depressions left as permafrost thaws, methane, a greenhouse gas, can be released from lake sediments to the atmosphere through bubbling, or ebullition. Constraining the amount of methane released through bubbling would help scientists understand the role of thawing permafrost in the carbon cycle and global climate change. However, bubbling is highly variable in both space and time and thus difficult to measure accurately, so there are large uncertainties in estimates of methane emissions from northern ecosystems.

Balcerak, Ernie

2013-08-01

276

Investigation of the effects of radiolytic-gas bubbles on the long-term operation of solution reactors for medical-isotope production  

NASA Astrophysics Data System (ADS)

One of the most common and important medical radioisotopes is 99Mo, which is currently produced using the target irradiation technology in heterogeneous nuclear reactors. The medical isotope 99Mo can also be produced from uranium fission using aqueous homogeneous solution reactors. In solution reactors, 99Mo is generated directly in the fuel solution, resulting in potential advantages when compared with the target irradiation process in heterogeneous reactors, such as lower reactor power, less waste heat, and reduction by a factor of about 100 in the generation of spent fuel. The commercial production of medical isotopes in solution reactors requires steady-state operation at about 200 kW. At this power regime, the formation of radiolytic-gas bubbles creates a void volume in the fuel solution that introduces a negative coefficient of reactivity, resulting in power reduction and instabilities that may impede reactor operation for medical-isotope production. A model has been developed considering that reactivity effects are due to the increase in the fuel-solution temperature and the formation of radiolytic-gas bubbles. The model has been validated against experimental results from the Los Alamos National Laboratory uranyl fluoride Solution High-Energy Burst Assembly (SHEBA), and the SILENE uranyl nitrate solution reactor, commissioned at the Commissariat a l'Energie Atomique, in Valduc, France. The model shows the feasibility of solution reactors for the commercial production of medical isotopes and reveals some of the important parameters to consider in their design, including the fuel-solution type, 235U enrichment, uranium concentration, reactor vessel geometry, and neutron reflectors surrounding the reactor vessel. The work presented herein indicates that steady-state operation at 200 kW can be achieved with a solution reactor consisting of 120 L of uranyl nitrate solution enriched up to 20% with 235U and a uranium concentration of 145 kg/m3 in a graphite-reflected cylindrical geometry.

Souto Mantecon, Francisco Javier

277

Achieving Higher Accuracy in the Gamma-Ray Spectrocopic Assay of Holdup  

SciTech Connect

Gamma-ray spectroscopy is an important technique for the measurement of quantities of nuclear material holdup in processing equipment. Because the equipment in large facilities dedicated to uranium isotopic enrichment, uranium/plutonium scrap recovery or various stages of fuel fabrication is extensive, the total holdup may be large by its distribution alone, even if deposit thicknesses are small. Good accountability practices require unbiased measurements with uncertainties that are as small as possible. This paper describes new procedures for use with traditional holdup analysis methods based on gamma-ray spectroscopy. The procedures address the two sources of bias inherent in traditional gamma-ray measurements of holdup. Holdup measurements are performed with collimated, shielded gamma-ray detectors. The measurement distance is chosen to simplify the deposit geometry to that of a point, line or area. The quantitative holdup result is based on the net count rate of a representative gamma ray. This rate is corrected for contributions from room background and for attenuation by the process equipment. Traditional holdup measurements assume that the width of the point or line deposit is very small compared to the measurement distance, and that the self-attenuation effects can be neglected. Because each point or line deposit has a finite width and because self-attenuation affects all measurements, bias is incurred in both assumptions. In both cases the bias is negative, explaining the systematically low results of gamma-ray holdup measurements. The new procedures correct for bias that arises from both the finite-source effects and the gamma-ray self-attenuation. The procedures used to correct for both of these effects apply to the generalized geometries. One common empirical parameter is used for both corrections. It self-consistently limits the total error incurred (from uncertain knowledge of this parameter) in the combined correction process, so that it is compelling to use these procedures. The algorithms and the procedures are simple, general, and easily automated for use plant-wide. This paper shows the derivation of the new, generalized correction algorithms for finite-source and self-attenuation effects. It also presents an analysis of the sensitivity of the holdup result to the uncertainty in the empirical parameter when one or both corrections are made. The paper uses specific examples of the magnitudes of finite-source and self-attenuation corrections to measurements that were made in the field. It discusses the automated implementation of the correction procedure.

Russo, P.A.; Wenz, T.R.; Smith, S.E.; Harris, J.F.

2000-09-01

278

Further experimental study of gas fluidized bed collapse  

NASA Astrophysics Data System (ADS)

Gas fluidized bed collapse is the slumping of the bed immediately following the cessation of gas flow. The collapse process is used in industry to study and measure ``fluidization quality'' of catalysts and other powders. Specifically, one can extrapolate the dense-phase void fraction from the collapse measurements, measure the bed's bubble hold-up, and predict the fluidizability of a bed from a single experiment. However, the physics of the collapse mechanism remains poorly understood. In last year's APS/DFD Meeting [D. J. Goldfarb et al., ND.08 (1998)] we presented results of careful measurements of bed pressure, bed height, and particle-impact-induced vessel wall vibration. We expand on the analysis of these results. In addition to the above vibration measurements, we also recently measured laser scattering off the fluidized catalyst powder sample. Results were in general agreement with the experimental results of Menon and Durian [N. Menon and D.J. Durian, Phys. Rev. Lett. 79, 3407 (1997)]: we also observe no perceived particle motion at gas velocities slightly above the minimum fluidization velocity, where the bed has clearly expanded but is not bubbling.

Goldfarb, David J.; Norris, Andrew N.

1999-11-01

279

Champagne experiences various rhythmical bubbling regimes in a flute.  

PubMed

Bubble trains are seen rising gracefully from a few points on the glass wall (called nucleation sites) whenever champagne is poured into a glass. As time passes during the gas-discharging process, the careful observation of some given bubble columns reveals that the interbubble distance may change suddenly, thus revealing different rhythmical bubbling regimes. Here, it is reported that the transitions between the different bubbling regimes of some nucleation sites during gas discharging is a process which may be ruled by a strong interaction between tiny gas pockets trapped inside the nucleation site and/or also by an interaction between the tiny bubbles just blown from the nucleation site. PMID:16968053

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

2006-09-20

280

Bubble Growth in Lunar Basalts  

NASA Astrophysics Data System (ADS)

Although Moon is usually said to be volatile-"free", lunar basalts are often vesicular with mm-size bubbles. The vesicular nature of the lunar basalts suggests that they contained some initial gas concentration. A recent publication estimated volatile concentrations in lunar basalts (Saal et al. 2008). This report investigates bubble growth on Moon and compares with that on Earth. Under conditions relevant to lunar basalts, bubble growth in a finite melt shell (i.e., growth of multiple regularly-spaced bubbles) is calculated following Proussevitch and Sahagian (1998) and Liu and Zhang (2000). Initial H2O content of 700 ppm (Saal et al. 2008) or lower is used and the effect of other volatiles (such as carbon dioxide, halogens, and sulfur) is ignored. H2O solubility at low pressures (Liu et al. 2005), concentration-dependent diffusivity in basalt (Zhang and Stolper 1991), and lunar basalt viscosity (Murase and McBirney 1970) are used. Because lunar atmospheric pressure is essentially zero, the confining pressure on bubbles is completely supplied by the overlying magma. Due to low H2O content in lunar basaltic melt (700 ppm H2O corresponds to a saturation pressure of 75 kPa), H2O bubbles only grow in the upper 16 m of a basalt flow or lake. A depth of 20 mm corresponds to a confining pressure of 100 Pa. Hence, vesicular lunar rocks come from very shallow depth. Some findings from the modeling are as follows. (a) Due to low confining pressure as well as low viscosity, even though volatile concentration is very low, bubble growth rate is extremely high, much higher than typical bubble growth rates in terrestrial melts. Hence, mm-size bubbles in lunar basalts are not strange. (b) Because the pertinent pressures are so low, bubble pressure due to surface tension plays a main role in lunar bubble growth, contrary to terrestrial cases. (c) Time scale to reach equilibrium bubble size increases as the confining pressure increases. References: (1) Liu Y, Zhang YX (2000) Earth Planet. Sci. Lett. 181, 251. (2) Liu Y, Zhang YX, Behrens H (2005) J. Volcanol. Geotherm. Res. 143, 219. (3) Murase T, McBirney A (1970) Science 167, 1491. (4) Proussevitch AA, Sahagian DL (1998) J. Geophys. Res. 103, 18223. (5) Saal AE, Hauri EH, Cascio ML, et al. (2008) Nature 454, 192. (6) Zhang YX, Stolper EM (1991) Nature 351, 306.

Zhang, Y.

2009-05-01

281

Hydrodynamic and gas phase axial dispersion in an air-molten salt two-phase system (molten salt oxidation reactor)  

Microsoft Academic Search

The effects of the gas velocity (0.05–0.22m\\/s) and temperature (870–970°C) on the gas holdup and the gas phase axial dispersion coefficient have been studied in a molten salt oxidation reactor (0.076m i.d.×0.653m H., air-molten sodium carbonate salt two-phase system). The gas phase holdup and the amount of the axial gas phase dispersion coefficient were experimentally evaluated by means of the

Yong-Jun Cho; Hee-Chul Yang; Hee-Chul Eun; Jae-Hyung Yoo; Joon-Hyung Kim

2005-01-01

282

Analysis of bubble rise using the VOF method. 1: Isolated bubbles  

SciTech Connect

The motion of a gas bubble 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. Starting from a perfectly spherical bubble which is initially at rest, the upward motion of the bubble in a gravitational field is accurately determined by tracking the liquid-gas interface. The initial radius of the bubble is small compared to the cylinder radius so that the influence of the container walls on the bubble motion is negligible. The gas in the bubble can be treated as incompressible. The problem is simulated using primitive variables in a control-volume formulation in conjunction with the interpolation technique of Rhie and Chow (1983), to avoid oscillations in the pressure and velocity fields. The pressure-velocity coupling is based on the SIMPLE algorithm. The modified VOF method used in this study is able to identify and physically treat features such as bubble deformation, cuspformation, breakup and joining. Results in a two-dimensional as well as a three-dimensional coordinate framework are presented. The bubble deformation and its motion are characterized by the Reynolds number, the Bond number, the density ratio, the viscosity ratio, and the ratio of the cylinder radius to that of the initial bubble. The effects of these parameters on the bubble rise are discussed. Physical mechanisms for the computational results obtained are presented. The results agree with experiments reported in the literature.

Chen, L.; Leonardi, E. [Univ. of New South Wales, Sydney, New South Wales (Australia). School of Mechanical and Manufacturing Engineering; Reizes, J.A. [Univ. of Technology, Sydney, New South Wales (Australia); Garimella, S.V. [Univ. of Wisconsin, Milwaukee, WI (United States). Dept. of Mechanical Engineering

1996-12-31

283

Marangoni bubble motion in zero gravity  

NASA Technical Reports Server (NTRS)

It is shown experimentally that the Marangoni phenomenon is a primary mechanism for the movement of a gas bubble in a nonisothermal liquid in a low-gravity environment. In such two-phase flow systems, local variations in bubble surface tension are caused by a temperature gradient in the liquid. Shearing stresses thus generated at the bubble surface lead to convection in both media, as a result of which the bubble begins to move. A mathematical model consisting of the Navier-Stokes equations and the thermal energy equations, along with the appropriate boundary conditions for both media, is proposed.

Thompson, R. L.; De Witt, K. J.

1979-01-01

284

Bubble Evolution and Properties in Homogeneous Nucleation Simulations  

E-print Network

We analyze the properties of naturally formed nano-bubbles in Lennard-Jones molecular dynamics simulations of liquid-to-vapor nucleation in the boiling and the cavitation regimes. The large computational volumes provide a realistic environment at unchanging average temperature and liquid pressure, which allows us to accurately measure properties of bubbles from their inception as stable, critically sized bubbles, to their continued growth into the constant speed regime. Bubble gas densities are up to 50$\\%$ lower than the equilibrium vapor densities at the liquid temperature, yet quite close to the gas equilibrium density at the lower gas temperatures measured in the simulations: The latent heat of transformation results in bubble gas temperatures up to 25$\\%$ below those of the surrounding bulk liquid. In the case of rapid bubble growth - typical for the cavitation regime - compression of the liquid outside the bubble leads to local temperature increases of up to 5$\\%$, likely significant enough to alter the...

Angélil, Raymond; Tanaka, Kyoko; Tanaka, Hidekazu

2014-01-01

285

Bioinspired bubble design for particle generation  

PubMed Central

In this study, we devise a method to generate homogeneous particles from a bubble suspension, with the capability to control loading and the structure of bubbles. Ideally, a process such as this would occur at the interface between daughter bubble formation (instant) and gaseous diffusion (gradual). Interestingly, the budding mechanism in micro-organisms is one that demonstrates features of the desired phenomena (although at a much slower rate), as viruses can eject and evolve structures from their membranes. With these natural concepts, a bubble's surface can also be made to serve as a platform for particle generation, which transfers significant elements from the initial bubble coating to the newly generated structures. Here, we illustrate this by preparing coated bubbles (approx. 150 µm in diameter) using a hydrophobic polymer, which may be comparable to naturally occurring bubble coatings (e.g. organic matter forming part of bubble coatings in the sea), and dye (which can demonstrate entrapment of smaller quantities of a desired moiety) and then observe particle generation (approx. 500 nm). The process, which may be driven by a polymerosome-forming mechanism, also illustrates how additional uniform sub-micrometre-scale structures may form from a bubble's surface, which may have also previously been attributed to gas diffusion. In addition, such methods of particle formation from a bubble structure, the incorporation of chemical or biological media via an in situ process and subsequent release technologies have several areas of interest across the broad scientific community. PMID:22112651

Gunduz, Oguzhan; Ahmad, Zeeshan; Stride, Eleanor; Tamerler, Candan; Edirisinghe, Mohan

2012-01-01

286

Simulation of bubbly flows: Comparison between direct quadrature method of moments (DQMOM) and method of classes (CM)  

Microsoft Academic Search

In typical bubbly flow applications, bubbles can break or coalesce due to bubble–bubble and bubble–fluid interactions in presence of turbulence. Under this assumption, a fixed bubble size model might not be suitable for predicting correct multiphase flow behaviour in the gas–liquid system. For example, breakage and coalescence events produce very different bubble size distribution and then affects the interfacial interactions

B. Selma; R. Bannari; P. Proulx

2010-01-01

287

Homogeneous bubble nucleation in rhyolitic melt: Experiments and nonclassical theory  

E-print Network

Homogeneous bubble nucleation in rhyolitic melt: Experiments and nonclassical theory H. M eruptions. The first and most critical step in degassing is the nucleation of gas bubbles, which requires bubble number densities in pyroclasts. We provide a potential resolution to this problem through

Gonnermann, Helge

288

Express Letter Radial variations of melt viscosity around growing bubbles  

E-print Network

strain rates of the £ow [5,6], the bubble-bearing magma fragments and erupts explosively [7,8]. The gas variations of melt viscosity on the growth of bub- bles. We analyze the hydrodynamic equations of the melt-viscosity rind that forms at the bubble^melt interface. 2. The hydrodynamics of the melt around a growing bubble

Lyakhovsky, Vladimir

289

Bubble Coalescence DOI: 10.1002/anie.201006552  

E-print Network

Bubble Coalescence DOI: 10.1002/anie.201006552 Anomalous Stability of Carbon Dioxide in pH-Controlled Bubble Coalescence** Rico F. Tabor, Derek Y. C. Chan, Franz Grieser, and Raymond R. Dagastine* Gas bubbles are formed as cavities in liquids, their pressure, shape, and deformability determined

Chan, Derek Y C

290

Scaling Laws for Reduced-Scale Tests of Pulse Jet Mixing Systems in Non-Newtonian Slurries: Gas Retention and Release Behavior  

SciTech Connect

The Waste Treatment Plant (WTP) under construction at the Hanford Site will use pulse jet mixer (PJM) technology for mixing and gas retention control applications in tanks expected to contain waste slurries exhibiting a non-Newtonian rheology. This paper presents the results of theoretical and experimental studies performed to establish the methodology to perform reduced-scale gas retention and release tests with PJM systems in non-Newtonian fluids with gas generation. The technical basis for scaled testing with unsteady jet mixing systems in gas-generating non-Newtonian fluids is presented in the form of a bubble migration model that accounts for the gas generation rate, the average bubble rise velocity, and the geometry of the vessel. Scaling laws developed from the model were validated with gas holdup and release tests conducted at three scales: large scale, 1/4 scale, and 1/9 scale. Experiments were conducted with two non-Newtonian simulants with in-situ gas generation by decomposition of hydrogen peroxide. The data were compared non-dimensionally, and the important scale laws were examined. From these results, scaling laws are developed which allow the design of mixing systems at a reduced scale.

Stewart, Charles W.; Meyer, Perry A.; Kurath, Dean E.; Barnes, Steven M.

2006-03-02

291

Parallelization of an Euler Lagrange model using mixed domain decomposition and a mirror domain technique: Application to dispersed gas liquid two-phase flow  

NASA Astrophysics Data System (ADS)

We report a parallel algorithm applicable to a Euler-Lagrange model embedding four-way coupling. The model describing the dispersed phase dynamics accounts for bubble-bubble collisions and is parallelized using a mirror domain technique while the pressure Poisson equation for the continuous phase is solved using a domain decomposition technique implemented in the PETSc library [S. Balay, K. Buschelman, W.D. Gropp, D. Kaushik, M.G. Knepley, L.C. McInnes, B.F. Smith, H. Zhang, PETSc Web page: http://www.mcs.anl.gov/petsc, 2001]. The parallel algorithm is verified and it is found that it gives the same results for both phases as compared to the serial algorithm. Furthermore the algorithm shows good scalability up to 32 processors. Using the proposed method, a homogeneous bubbly flow in a laboratory scale bubble column can be simulated at very high gas hold-up (37%) while consuming a reasonable amount of calculation wall time.

Darmana, D.; Deen, N. G.; Kuipers, J. A. M.

2006-12-01

292

Acoustic bubble removal method  

NASA Technical Reports Server (NTRS)

A method is described for removing bubbles from a liquid bath such as a bath of molten glass to be used for optical elements. Larger bubbles are first removed by applying acoustic energy resonant to a bath dimension to drive the larger bubbles toward a pressure well where the bubbles can coalesce and then be more easily removed. Thereafter, submillimeter bubbles are removed by applying acoustic energy of frequencies resonant to the small bubbles to oscillate them and thereby stir liquid immediately about the bubbles to facilitate their breakup and absorption into the liquid.

Trinh, E. H.; Elleman, D. D.; Wang, T. G. (inventors)

1983-01-01

293

Buoyancy Driven Shear Flows of Bubble Suspensions  

NASA Technical Reports Server (NTRS)

In this work the gas volume fraction and the root-mean-squared fluid velocity are measured in buoyancy driven shear flows of bubble suspensions in a tall, inclined, rectangular channel. The experiments are performed under conditions where We << 1a nd Re >> 1, for which comparisons are made with kinetic theory and numerical simulations. Here Re = gamma(a(exp 2)/nu is the Reynolds number and We = rho(gamma(exp 2))a(exp 3)/sigma is the Weber number; gamma is the shear rate, a is the bubble radius, nu is the kinematic viscosity of the liquid, rho is the density of the liquid, and sigma is the surface tension of the gas/liquid interface. Kang et al. calculated the bubble phase pressure and velocity variance of sheared bubble suspensions under conditions where the bubbles are spherical and the liquid phase velocity field can be approximated using potential flow theory, i.e. We= 0 and Re >> 1. Such conditions can be achieved in an experiment using gas bubbles, with a radius of O(0.5mm), in water. The theory requires that there be no average relative motion of the gas and liquid phases, hence the motivation for an experimental program in microgravity. The necessity of performing preliminary, Earth based experiments, however, requires performing experiments where the gas phase rises in the liquid, which significantly complicates the comparison of experiments with theory. Rather than comparing experimental results with theory for a uniform, homogeneous shear flow, experiments can be compared directly with solutions of the averaged equations of motion for bubble suspensions. This requires accounting for the significant lift force acting on the gas phase when the bubbles rise parallel to the average velocity of the sheared suspension. Shear flows can be produced in which the bubble phase pressure gradient, arising from shear induced collisions amongst the bubbles, balances a body force (centrifugal or gravitational) on the gas phase. A steady, non-uniform gas volume fraction can be measured, from which the bubble phase pressure gradient can be obtained and compared to theory and numerical simulations. The presence of bounding walls further complicates the experiments, since the detailed interactions of the bubbles with bounding walls is not well understood, especially in the presence of gravity, where the momentum and energy exchange depends on the inclination of the wall.

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

1999-01-01

294

Evolution of liquid holdup profile in a standing protein stabilized foam  

Microsoft Academic Search

Evolution of liquid holdup profile in a standing foam formed by whipping and stabilized by sodium caseinate in the presence of xanthan gum when subjected to 16 and 29g centrifugal force fields was measured using magnetic resonance imaging for different pH, ionic strength, protein and xanthan gum concentrations. Drainage resulted in the formation of a separate liquid layer at the

Zebin Wang; Ganesan Narsimhan

2004-01-01

295

Bubble dynamics in an acoustic flow field  

NASA Astrophysics Data System (ADS)

Dynamics of interaction between cavitational bubbles is investigated when a complex of a compression and a rarefaction pulse passes through a liquid with pre-existing micro bubbles. Cavitation was generated experimentally with the help of electromagnetic generator of a flat and a convergent acoustic pulse (2-mus duration, 1-20 MPa) having the form of a hollow sphere segment. A modeling was performed within the frame of two-dimensional axisymmetric nonstationary approach on the basis of conservation laws for a model of an ideal compressible liquid. A thermodynamic flow field was computed both in liquid and inside bubbles. Behind the rarefaction wave the microbubbles begin to grow and generate secondary compression shocks, the amplitude of which may exceed that of the incident pulse under certain conditions. It is shown that the process of bubble interaction within a cluster is accompanied by bubble coalescence, fragmentation, and collapse of the initial bubble or its fragments. Simultaneously, high temperature spots appear in the bubble compressing by the secondary wave. Adiabatic heating of gas either inside a bubble or near the neck between a bubble and its fragment may result in sonoluminescence, also observed in experiments. [Work supported by ASA, DAAD, and RFBR.

Voronin, Dmitry V.; Sankin, Georgij N.; Mettin, Robert; Teslenko, Vyacheslav S.; Lauterborn, Werner

2002-11-01

296

Bubbles, Gating, and Anesthetics in Ion Channels  

PubMed Central

We suggest that bubbles are the bistable hydrophobic gates responsible for the on-off transitions of single channel currents. In this view, many types of channels gate by the same physical mechanism—dewetting by capillary evaporation—but different types of channels use different sensors to modulate hydrophobic properties of the channel wall and thereby trigger and control bubbles and gating. Spontaneous emptying of channels has been seen in many simulations. Because of the physics involved, such phase transitions are inherently sensitive, unstable threshold phenomena that are difficult to simulate reproducibly and thus convincingly. We present a thermodynamic analysis of a bubble gate using morphometric density functional theory of classical (not quantum) mechanics. Thermodynamic analysis of phase transitions is generally more reproducible and less sensitive to details than simulations. Anesthetic actions of inert gases—and their interactions with hydrostatic pressure (e.g., nitrogen narcosis)—can be easily understood by actions on bubbles. A general theory of gas anesthesia may involve bubbles in channels. Only experiments can show whether, or when, or which channels actually use bubbles as hydrophobic gates: direct observation of bubbles in channels is needed. Existing experiments show thin gas layers on hydrophobic surfaces in water and suggest that bubbles nearly exist in bulk water. PMID:18234836

Roth, Roland; Gillespie, Dirk; Nonner, Wolfgang; Eisenberg, Robert E.

2008-01-01

297

A Laboratory Experiment To Measure Henry's Law Constants of Volatile Organic Compounds with a Bubble Column and a Gas  

E-print Network

solubilities of organic compounds that have important implications in atmospheric chemistry and water pollution-phase contaminants to pollute water. Solubility also determines potential health effects of a toxicant. However affect climate, air quality, visibility, and human health. Whether a VOC can participate in gas

Lee, Shan-Hu

298

Shock Initiation of Hydrogen\\/Oxygen\\/Argon Bubbles in a Nonreactive Liquid  

Microsoft Academic Search

The present paper gives a mathematical model for collapse and ignition of reactive gas-filled bubbles. Oxyhydrogen bubbles, which can be formed in high-temperalure reactor water, can present an explosion hazard. In addition to treating the classical features of bubble dynamics, energy balances for the liquid and gas phase, and the heat transfer between the gas and surrounding liquid are included

J. KANG; P B. BUTLER

1993-01-01

299

Satellites in the inviscid breakup of bubbles J.M. Gordillo  

E-print Network

Satellites in the inviscid breakup of bubbles J.M. Gordillo Departamento de Ingenier the essential role played by gas inertia in the breakup of gas bubbles. Our results reveal that, whenever the gas to liquid density ratio = g/l is different from zero, tiny satellite bubbles may be formed

Fontelos, Marco

300

The Effect of Bubbles on Internal Waves R.H.J.Grimshawa  

E-print Network

The Effect of Bubbles on Internal Waves R.H.J.Grimshawa , K.R.Khusnutdinovaa,b March 26, 2002 The influence of gas bubbles on the properties of internal waves in a continuously strati- fied fluid is studied bubbles. The model takes into account surface tension on the walls of the bubbles and an effective

301

Dynamics of detonation waves in a channel with variable cross section and filled with bubbly fluid  

NASA Astrophysics Data System (ADS)

The flow of bubbly fluid comprising a mixture of bubbles filled with explosive and inert gases, which is driven through a converging channel, was studied. Depending on the velocity of the hummer hitting the bubbly fluid boundary, the flow may be accompanied by the development of detonation waves which compress the bubbles with inert gas.

Topolnikov, A. S.; Gimaltdinov, I. K.

2014-08-01

302

Building self-ordered tubular macro- and mesoporous nitridated titania from gas bubbles towards high-performance lithium-ion batteries.  

PubMed

Robust well-defined tubular structural materials based on macro- and mesoporous nitridated titania (TMMN-TiO2) were obtained by a simple solution-phase approach in ammonia solution. In this approach, the gas bubbles derived from ammonia solution play the role of templates that direct the ordered growth in the form of a tubular structure. The results demonstrated that the volume ratio of ammonia to water can be favorable for the formation of TMMN-TiO2, which are characterized by FESEM and FTIR. What is more, ammonia was used not only as the template but also as the nitrogen source. Interestingly, it was found that the TiO2 nanocrystals building blocks were assembled into an interconnected mesoporous skeleton and built in ordered tubular macroporous channels. This unique architecture provides many important features that are required for high-performance anodes, such as fast ion transport, high conductivity, and structure stability, thus enabling an electrode with outstanding lithium storage performance. For example, such an electrode delivers 112 mA h g(-1) capacity at 5100 mA g(-1) (30 C) even after 1200 cycles. PMID:23640367

Wang, Hai; Yang, Hongxing; Lu, Lin; Zhou, Yu; Wang, Yuanhao

2013-06-28

303

The rheology of gravity driven bubbly liquids  

NASA Astrophysics Data System (ADS)

Experiments on a vertical channel were performed to to study the behavior of a monodispersed bubble suspension. Using water and water-glycerin mixtures, we were able to obtain measurements for a range of Reynolds and Weber numbers. To generate a uniform stream of bubbles an array of identical capillaries was used. To avoid the coalescence effects, a small amount of salt was added to the interstitial fluid, which did not affect the fluid properties significantly. Measurements of the bubble phase velocity were obtained using a dual impedance probe and through high speed digital video processing. We also obtained measurements of the bubble size and shape as a function of the gas volume fraction for the different flow regimes. We found that, for all cases, the bubble velocity decreases as mean gas volume fraction increases. The flow agitation, characterized with the bubble velocity variance, increases with bubble concentration. The flow becomes unstable for lower gas concentrations as the viscosity of the interstitial fluid increases.

Martinez-Mercado, Julian; Zenit, Roberto

2002-11-01

304

An Inside Out View of Bubbles  

E-print Network

Fast stellar winds can sweep up ambient media and form bubbles. The evolution of a bubble is largely controlled by the content and physical conditions of the shocked fast wind in its interior. This hot gas was not clearly observed until the recent advent of Chandra and XMM-Newton X-ray observatories. To date, diffuse X-ray emission has been unambiguously detected from two circumstellar bubbles blown by WR stars, four planetary nebulae, and two superbubbles blown by young clusters. Model fits to the X-ray spectra show that the circumstellar bubbles are dominated by hot gas with low temperatures (bubbles contain significant fractions of hotter gas (>= 5x10^6 K). In all cases, large discrepancies in the X-ray luminosity are found between observations and conventional models of bubbles. Future theoretical models of bubbles need to re-examine the validity of heat conduction and take into account realistic microscopic processes such as mass loading from dense clumps/knots and turbulent mixing. Chandra ACIS-S observation of NGC 6888 will shed light on these astrophysical processes.

You-Hua Chu; Robert A. Gruendl; Martin A. Guerrero

2002-12-06

305

Daughter bubble cascades produced by folding of ruptured thin films.  

PubMed

Thin liquid films, such as soap bubbles, have been studied extensively for over a century because they are easily formed and mediate a wide range of transport processes in physics, chemistry and engineering. When a bubble on a liquid-gas or solid-gas interface (referred to herein as an interfacial bubble) ruptures, the general expectation is that the bubble vanishes. More precisely, the ruptured thin film is expected to retract rapidly until it becomes part of the interface, an event that typically occurs within milliseconds. The assumption that ruptured bubbles vanish is central to theories on foam evolution and relevant to health and climate because bubble rupture is a source for aerosol droplets. Here we show that for a large range of fluid parameters, interfacial bubbles can create numerous small bubbles when they rupture, rather than vanishing. We demonstrate, both experimentally and numerically, that the curved film of the ruptured bubble can fold and entrap air as it retracts. The resulting toroidal geometry of the trapped air is unstable, leading to the creation of a ring of smaller bubbles. The higher pressure associated with the higher curvature of the smaller bubbles increases the absorption of gas into the liquid, and increases the efficiency of rupture-induced aerosol dispersal. PMID:20535206

Bird, James C; de Ruiter, Riëlle; Courbin, Laurent; Stone, Howard A

2010-06-10

306

Analysis of bubble rise using the VOF method. 2: Bubble interactions, wall effects and evaporation  

SciTech Connect

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. The theoretical background and the motion of an isolated bubble was considered in a separate paper (Chen et al., 1996) where the initial bubble radius was small compared to that of the cylinder and wall-effects were negligible. In this work, the focus is on the interference effects during the motion of two initially spherical bubbles in a gravitational field, as well as the influence of the container wall on the bubble motion: the initial bubble diameter in the present study is more than half the cylinder diameter. The bubble size is also much larger than that required to satisfy the condition in which the gas can be treated as incompressible. In addition, the effect on bubble motion of the inclusion of evaporation at the gas-liquid interface is considered.

Chen, L.; Leonardi, E. [Univ. of New South Wales, Sydney, New South Wales (Australia). School of Mechanical and Manufacturing Engineering; Reizes, J.A. [Univ. of Technology, Sydney, New South Wales (Australia); Garimella, S.V. [Univ. of Wisconsin, Milwaukee, WI (United States). Dept. of Mechanical Engineering

1996-12-31

307

Phase-Doppler anemometer measurement of bubble concentrations in laboratory-simulated breaking waves  

SciTech Connect

Breaking waves and the bubble plumes they generate are thought to be an important air-sea gas transfer mechanism. In order to compare bubble populations generated by laboratory-simulated breaking waves and model bubble-mediated air-water gas transfer in a whitecap simulation tank (WST), it was necessary to measure bubble sizes and water velocities. The phase-Doppler anemometer (PDA) is well suited for this research because it provides simultaneous measurement of the size and velocity of a bubble. Bubble concentrations can be estimated from PDA data records with an accuracy of 15% ({+-}1{sigma}) for larger bubbles with radii in the range of 50 to 160 {mu}m and 40% ({+-}1 {sigma}) for larger bubbles. However, estimation of bubble concentrations requires knowledge of the instrument-scattering cross section as a function of bubble radius. A procedure for calibrating the scattering cross section of the PDA was developed and tested. The PDA was then used to measured size-segregated bubble concentrations in the WST as a function of depth, water temperature, total concentration of dissolved gas, and surfactant concentration. These measurements show that increases in dissolved gas concentration or decreases in water temperature increase bubble concentrations. Surfactants increased the concentration of small bubbles. Comparison of the WST bubble populations to measurements of oceanic bubbles showed that the two agree within the experimental uncertainty of the PDA. 31 refs., 14 figs., 1 tab.

Asher, W.E.; Farley, P.J. [Pacific Northwest Lab., Sequim, WA (United States)] [Pacific Northwest Lab., Sequim, WA (United States)

1995-04-15

308

Soap-bubble growth  

Microsoft Academic Search

A simple theory describing the dynamics of two-dimensional arrays of soap bubbles is proposed, and compared with a recent experiment. The average area of bubbles scales linearly at late times. Agreement with experiment is satisfactory, although not conclusive.

M. Marder

1987-01-01

309

Soap Bubbles and Logic.  

ERIC Educational Resources Information Center

Introduces questions and activities involving soap bubbles which provide students with experiences in prediction and logic. Examines commonly held false conceptions related to the shapes that bubbles take and provides correct explanations for the phenomenon. (ML)

Levine, Shellie-helane; And Others

1986-01-01

310

Davies-Taylor Equation for the Fluidization Bubble.  

National Technical Information Service (NTIS)

The Davies-Taylor equations is justified for the steady rise of a spherical cap gas bubble in a gas - fluidized bed. Starting from the jump conditions at the bubble surface, it is shown that both the fluid and the total pressures should be constant there....

S. Kinrys, R. Y. Qassim

1981-01-01

311

Detonation wave phenomena in bubbled liquid  

NASA Astrophysics Data System (ADS)

Shock wave propagation was investigated in two phase media consisting of diluted glycerin (85%) and reactive gas bubbles. To understand these complex phenomena, we first performed a numerical analysis and experimental studies of single bubbles containing a reactive gas-mixture. For the two-phase mixtures, a needle matrix bubble-generator enabled us to produce a homogeneous bubble distribution with a size dispersion less than 5%. The void fraction ?0 was varied over one order of magnitude, ?0=0.2-2%. It was found that there exists a critical value of shock strength above which bubble explosion starts. Once a bubble explodes, it stimulates the adjacent bubbles to explode due to emission of a blast wave; this process is followed by a series of similar events. A steady detonationlike wave propagates as a precurser with a constant velocity which is much higher than that of the first wave. To study the structure of the detonation wave the measured pressured profiles were averaged by superimposing 50 shots.

Gülhan, A.; Beylich, A. E.

1990-07-01

312

Bubbles in live-stranded dolphins  

PubMed Central

Bubbles in supersaturated tissues and blood occur in beaked whales stranded near sonar exercises, and post-mortem in dolphins bycaught at depth and then hauled to the surface. To evaluate live dolphins for bubbles, liver, kidneys, eyes and blubber–muscle interface of live-stranded and capture-release dolphins were scanned with B-mode ultrasound. Gas was identified in kidneys of 21 of 22 live-stranded dolphins and in the hepatic portal vasculature of 2 of 22. Nine then died or were euthanized and bubble presence corroborated by computer tomography and necropsy, 13 were released of which all but two did not re-strand. Bubbles were not detected in 20 live wild dolphins examined during health assessments in shallow water. Off-gassing of supersaturated blood and tissues was the most probable origin for the gas bubbles. In contrast to marine mammals repeatedly diving in the wild, stranded animals are unable to recompress by diving, and thus may retain bubbles. Since the majority of beached dolphins released did not re-strand it also suggests that minor bubble formation is tolerated and will not lead to clinically significant decompression sickness. PMID:21993505

Dennison, S.; Moore, M. J.; Fahlman, A.; Moore, K.; Sharp, S.; Harry, C. T.; Hoppe, J.; Niemeyer, M.; Lentell, B.; Wells, R. S.

2012-01-01

313

Bubble - Crystal Interactions in Magmatic Three-Phase Systems  

NASA Astrophysics Data System (ADS)

The influence of crystals on the movement of bubbles through basaltic magmas is poorly understood. We study the interaction of bubbles with a suspension of crystals in a viscous fluid through analog experiments. In our experiments, an air bubble rises through a suspension of plastic beads in a viscous corn syrup - water mixture; we vary bubble volumes, crystal spacings and fluid viscosities. We observe the following change in interaction styles with increasing bubble volume: (1) bubble migration through the crystal network with little bubble deformation, (2) bubble movement through the crystal network with deformation (and sometimes bubble splitting), and (3) displacement of the liquid-crystal mixture by the rising bubble. Interactions change from type (1) to (2) when the bubble is approximately the same size as the crystals forming the network. Transition to type (3) behavior depends on both bubble volume and the thickness of the crystal-liquid layer. In all cases, bubble rise is impeded by the presence of crystals. Preliminary results suggest that impedance is most pronounced for bubbles slightly larger than the crystals (a condition that promotes the maximum bubble deformation). Additionally, very small bubbles may be trapped for long times in the crystal network, suggesting that a shallow reservoir of crystal-rich magma may actually trap rising bubbles from below. These observations provide an alternative interpretation to that of small undeformed bubbles representing late-stage bubble nucleation and large irregularly shaped bubbles forming by coalescence of smaller bubbles (e.g. Lautze and Houghton, 2006). Furthermore, we observe in our experiments that large bubbles can spread out and move laterally underneath a crystal layer. This is not usually considered in models of bubble migration and may explain focusing of gas escape from magma reservoirs and volcanic vents. We apply our experimental results to analysis of bubble populations at Stromboli volcano, Italy, where gases rising from a deep crystal-poor magma reservoir travel through, and entrain, shallow crystal-rich magma. Preliminary results from image analysis on SEM and optical microscope images suggest that the smallest bubbles are most abundant and that their sizes are within the modal size range of the crystals. This can mean that (i) smaller bubbles were initially more abundant or (ii) bigger bubbles have deformed and split into smaller bubbles, which would confirm our conclusion from the analog experiments that interactions change from type (1) to (2) when the bubbles reach the size of the crystals in the network. In addition, the abundance of crystal-size bubbles in these samples suggests relative accumulation, possibly through trapping or extreme impedance, of the bubbles within the crystal-rich layer. Combined with our observation (from the analog experiments) that most bubbles are indeed significantly slowed within the crystal layer, this could suggest that bubble number densities are not direct reflections of bubble nucleation rates.

Belien, I.; Cashman, K.; Rempel, A.; Pioli, L.; Pistolesi, M.

2007-12-01

314

Brut: Automatic bubble classifier  

NASA Astrophysics Data System (ADS)

Brut, written in Python, identifies bubbles in infrared images of the Galactic midplane; it uses a database of known bubbles from the Milky Way Project and Spitzer images to build an automatic bubble classifier. The classifier is based on the Random Forest algorithm, and uses the WiseRF implementation of this algorithm.

Beaumont, Christopher; Goodman, Alyssa; Williams, Jonathan; Kendrew, Sarah; Simpson, Robert

2014-07-01

315

Oscillations of soap bubbles  

Microsoft Academic Search

Oscillations of droplets or bubbles of a confined fluid in a fluid environment are found in various situations in everyday life, in technological processing and in natural phenomena on different length scales. Air bubbles in liquids or liquid droplets in air are well-known examples. Soap bubbles represent a particularly simple, beautiful and attractive system to study the dynamics of a

U. Kornek; F. Müller; K. Harth; A. Hahn; S. Ganesan; L. Tobiska; R. Stannarius

2010-01-01

316

Soap Bubbles in Reverse  

Microsoft Academic Search

WHEN sulphuric acid sodium sulphate solution containing surface-active material is dropped into water, bubbles approximately 5 mm. in diameter sinking through water may be observed. Such bubbles are spherical shells of air, with a sphere of acid sodium sulphate within and water outside. They are, in fact, soap bubbles in reverse. Instead of a two-surfaced film of soapy solution in

Leslie Rose

1946-01-01

317

Soap Films and Bubbles.  

ERIC Educational Resources Information Center

Develops and explains a format for a workshop which focuses on soap films and bubbles. The plan consists of: a discussion to uncover what children know about bubbles; explanations of the demonstration equipment; the presentation itself; the assembly of the workshop kit; and time to play with the bubbles. (ML)

Rice, Karen

1986-01-01

318

Stable Coulomb bubbles ?  

E-print Network

Coulomb bubbles, though stable against monopole displacement, are unstable at least with respect to quadrupole and octupole distortions. We show that there exists a temperature at which the pressure of the vapor filling the bubble stabilizes all the radial modes. In extremely thin bubbles, the crispation modes become unstable due to the surface-surface interaction.

L. G. Moretto; K. Tso; G. J. Wozniak

1996-12-12

319

Regulation and properties of a fungal lipase showing interfacial inactivation by gas bubbles, or droplets of lipid or fatty acid.  

PubMed

Ashbya gossypii can grow on triacyglycerol as carbon source. A degradation rate of 0.05 g x g-1 mycelial dry mass x h-1 was detected for soybean oil. Although this rate was within the sensitivity range of lipase assays no activity was detectable. On the other hand, extracellular lipase activity could be visualized by clearance halos round the growing mycelium when trioleoylglycerol was emulsified as the sole carbon source in agar plates. Variation of the culture conditions revealed that reduced shaking speed and decreased fat content in the medium led to detectable amounts of lipase in the supernatant of flask cultures. A maximal activity of 800 U x l-1 was obtained after 32 h of cultivation in flasks containing 1% yeast extract and incubated at 60 rpm. Because of its pI of 9.0, the enzyme could be purified in a single step by preparative isoelectric focusing. It appeared as a homogeneous protein in analytical isoelectric focusing and SDS/PAGE (M 35,000). The lipase was inactivated within minutes in stirred gas/water, trioleoylglycerol/water or oleic acid/water mixtures. These effects suggested an interface inactivation. This idea was supported by a stability modulation observed with the surfactant Pluronic F-68. Inactivation by oleic acid led to an aggregation of the lipase shown by gel filtration. Growth experiments performed under lipase-stabilizing conditions revealed a negative influence of glucose, glycerol or oleic acid on detectable lipase activity, probably due to a regulation of lipase formation. Inactivation and regulation thus explained the lack of detectable lipase activity in cultures of A. gossypii growing on triacylglycerol. PMID:9063467

Stahmann, K P; Böddecker, T; Sahm, H

1997-02-15

320

Measurements of uranium holdup in an operating gaseous diffusion enrichment plant  

SciTech Connect

Holdup of nuclear material in process equipment is one of the major sources of uncertainty in materials balances, particularly for high-throughput facilities with large equipment and extensive piping, such as gaseous diffusion uranium-enrichment plants. Locating and measuring the holdup while the plant is operating is a challenging problem because of background from the process material and the neighboring equipment. This paper reports NDA measurements performed at the Goodyear Atomic Gaseous Diffusion Plant, Portsmouth, Ohio, on enrichment equipment at the higher enrichment and (>10% /sup 235/U isotopic abundance) of the cascade. Both neutron and gamma-ray measurements were made to locate anomalously large deposits in converters and compressors and, within the limitations of the techniques, to quantify the amount of the deposit.

Augustson, R.H.; Walton, R.B.; Harris, R.; Harbarger, W.; Hicks, J.; Timmons, G.; Shissler, D.; Tayloe, R.; Jones, S.; Fields, L.

1983-01-01

321

Critical comparison of hydrodynamic models for gas–solid fluidized beds—Part I : bubbling gas–solid fluidized beds operated with a jet  

Microsoft Academic Search

In the Eulerian approach to model gas–solid fluidized beds closures are required for the internal momentum transfer in the particulate phase. Firstly, two closure models, one semi-empirical model assuming a constant viscosity of the solid phase (CVM) and a second model based on the kinetic theory of granular flow (KTGF), have been compared in this part in their performance to

D. J. Patil; M. van Sint Annaland; J. A. M. Kuipers

2005-01-01

322

Numerical investigations of shock-bubble interactions in mercury  

NASA Astrophysics Data System (ADS)

The bubble collapse induced by the shock-bubble interactions in mercury is investigated numerically to evaluate the cavitation damage. The ghost fluid method (GFM) is applied to the present analysis. Riemann solutions are utilized to correct the values at boundary nodes to suppress the pressure oscillations near the interface. The interactions between an air bubble and a plane shock wave in mercury with the infinite boundary are compared with those in water. It is shown that the collapse time of a bubble in mercury is longer than that in water. The interaction with the incident shock wave leads to the bubble deformation and the formation of liquid jet in the final stage of collapse. Higher impulsive pressure is generated in the mercury when the jet impacts the bubble surface. Also, the interactions between an air bubble and a plane shock wave in mercury in the vicinity of a glass wall are simulated. The mercury and glass are evaluated by using the stiffened gas equations. The motions of three phases for air, mercury, and glass are solved directly coupling the GFM with the level set method. Since the acoustic impedance of glass is smaller than the mercury, the expansion waves are reflected at the glass wall when the shock wave hits the glass wall. Consequently, the bubble takes a similar motion to that near a compliant wall; the glass wall is attracted toward the bubble during the bubble collapse; the collapse time of a bubble becomes shorter than that of an isolated bubble; the jet impacts the bubble surface in the later stage of collapse. Strong shock waves are formed from the bubble when the bubble rebounds as well as when the jet impacts the bubble surface. The shock waves hit the glass wall and lead to the depression of the glass surface.

Takahira, Hiroyuki; Matsuno, Takahiro; Shuto, Keisuke

2008-07-01

323

Comparison of steam-generator liquid holdup and core uncovery in two facilities of differing scale  

SciTech Connect

This paper reports on Run SB-CL-05, a test similar to Semiscale Run S-UT-8. The test results show that the core was uncovered briefly during the accident and that the rods overheated at certain core locations. Liquid holdup on the upflow side of the steam-generator tubes was observed. After the loop seal cleared, the core refilled and the rods cooled. These behaviors were similar to those observed in the Semiscale run. The Large-Scale Test Facility (LSTF) Run SB-CL-06 is a counterpart test to Semiscale Run S-LH-01. The comparison of the results of both tests shows similar phenomena. The similarity of phenomena in these two facilities build confidence that these results can be expected to occur in a PWR. Similar holdup has now been observed in the 6 tubes of Semiscale and in the 141 tubes of LSTF. It is now more believable that holdup may occur in a full-scale steam generator with 3000 or more tubes. These results confirm the scaling of these phenomena from Semiscale (1/1705) to LSTF (1/48). The TRAC results for SB-CL-05 are in reasonable agreement with the test data. TRAC predicted the core uncovery and resulting rod heatup. The liquid holdup on the upflow side of the steam-generator tubes was also correctly predicted. The clearing of the loop seal allowed core recovery and cooled the overheated rods just as it had in the data. The TRAC analysis results of Run SB-CL-05 are similar to those from Semiscale Run S-UT-8. The ability of the TRAC code to calculate the phenomena equally well in the two experiments of different scales confirms the scalability of the many models in the code that are important in calculating this small break.

Motley, F.; Schultz, R.

1987-01-01

324

PLUTONIUM FINISHING PLANT (PFP) GENERALIZED GEOMETRY HOLDUP CALCULATIONS & TOTAL MEASUREMENT UNCERTAINTY  

SciTech Connect

A collimated portable gamma-ray detector will be used to quantify the plutonium content of items that can be approximated as a point, line, or area geometry with respect to the detector. These items can include ducts, piping, glove boxes, isolated equipment inside of gloveboxes, and HEPA filters. The Generalized Geometry Holdup (GGH) model is used for the reduction of counting data. This document specifies the calculations to reduce counting data into contained plutonium and the associated total measurement uncertainty.

KEELE BD

2005-02-01

325

Deploying Methane Bubble Traps at Varying Lake Depths to Validate Bubble Dissolution Models  

NASA Astrophysics Data System (ADS)

Methane is a potent greenhouse gas, and understanding environmental methane cycles is critical both to developing accurate estimates of current methane emission rates and to modeling how cycles may respond to climate change. While there are many natural sources of methane, bubbling from lake sediments, or ebullition, is considered an important emission pathway. Ebullition can transport methane directly to the atmosphere, bypassing potential chemical or biological degradation in the water column. Existing bubble models predict some methane dissolution from rising bubbles, though dissolution estimates depend on the particular equations chosen to parameterize bubble rise velocity and gas transfer rates. To test current bubble dissolution models we installed a series of bubble traps at multiple depths in Upper Mystic Lake near Boston, Massachusetts. Traps gathered bubbles continuously during the summer of 2013 and were periodically emptied for gas volume measurements and chemical composition analysis. The gathered trap data demonstrated that surface traps have a significantly reduced bubble volume and methane fraction when compared with lake-bottom traps. This difference allows us to quantify the amount of methane dissolved in the water column due to ebullition. Preliminary data suggest that dissolution from bubbles could account for approximately 5% of the previously observed hypolimnetic methane accumulation in Upper Mystic Lake. Bubble methane contents in surface traps are consistent with average bubble sizes in the 3-6 mm diameter range based on the bubble models of McGinnis et al, 2006, and suggest that on the order of 50% of methane released by ebullition in this lake is dissolved before reaching the atmosphere. Data also indicates that careful corrections may be needed to account for small amounts of potential gas losses associated with dissolution at the gas/water interface within the traps. Using the gathered data to understand bubble size distributions, calculate methane dissolution quantities, and to calibrate simultaneous sonar studies of ebullition (Scandella et al) will help us develop a detailed lake-wide methane budget. In turn, understanding how ebullition impacts lake-wide methane cycling can lead to better predictive models of lake methane emissions under different climate change scenarios.

Delwiche, K.; Scandella, B.; Juanes, R.; Ruppel, C. D.; Hemond, H.

2013-12-01

326

Bubbling in a co-flow at high Reynolds numbers  

NASA Astrophysics Data System (ADS)

The physical mechanisms underlying bubble formation from a needle in a co-flowing liquid environment at high Reynolds numbers are studied in detail with the aid of experiments and boundary-integral numerical simulations. To determine the effect of gas inertia the experiments were carried out with air and helium. The influence of the injection system is elucidated by performing experiments using two different facilities, one where the constancy of the gas flow-rate entering the bubble is ensured, and another one where the gas is injected through a needle directly connected to a pressurized chamber. In the case of constant flow-rate injection conditions, the bubbling frequency has been shown to hardly depend on the gas density, with a bubble size given by db/ro?[6U(k*U+k2)/(U-1)]1/3 for U ?2, where U is the gas-to-liquid ratio of the mean velocities, ro is the radius of the gas injection needle, and k*=5.84 and k2=4.29, with db/ro˜3.3U1/3 for U ?1. Nevertheless, in this case the effect of gas density is relevant to describe the final instants of bubble breakup, which take place at a time scale much smaller than the bubbling time, tb. This effect is evidenced by the liquid jets penetrating the gas bubbles upon their pinch-off. Our measurements indicate that the velocity of the penetrating jets is considerably larger in air bubbles than in helium bubbles due to the distinct gas inertia of both situations. However, in the case of constant pressure supply conditions, the bubble size strongly depends on the density of the gas through the pressure loss along the gas injection needle. Furthermore, under the operating conditions reported here, the equivalent diameters of the bubbles are between 10% and 20% larger than their constant flow-rate counterparts. In addition, the experiments and the numerical results show that, under constant pressure supply, helium bubbles are approximately 10% larger than air bubbles due to the gas density effect on the bubbling process.

Gordillo, J. M.; Sevilla, A.; Martínez-Bazán, C.

2007-07-01

327

Soap bubbles in analytical chemistry. Conductometric determination of sub-parts per million levels of sulfur dioxide with a soap bubble.  

PubMed

Soap bubbles provide a fascinating tool that is little used analytically. With a very low liquid volume to surface area ratio, a soap bubble can potentially provide a very useful interface for preconcentration where mass transfer to an interfacial surface is important. Here we use an automated system to create bubbles of uniform size and film thickness. We utilize purified Triton-X 100, a nonionic surfactant, to make soap bubbles. We use such bubbles as a gas-sampling interface. Incorporating hydrogen peroxide into the bubble provides a system where electrical conductance increases as the bubble is exposed to low concentrations of sulfur dioxide gas. We theoretically derive the conductance of a hollow conducting spherical thin film with spherical cap electrodes. We measure the film thickness by incorporating a dye in the bubble making solution and laser transmission photometry and find that it agrees well with the geometrically computed thickness. With the conductance of the bubble-making soap solution being measured by conventional methods, we show that the measured values of the bubble conductance with known bubble and electrode dimensions closely correspond to the theoretically computed value. Finally, we demonstrate that sub-ppm levels of SO(2) can readily be detected by the conductivity change of a hydrogen peroxide-doped soap bubble, measured in situ, when the gas flows around the bubble. PMID:16615794

Kanyanee, Tinakorn; Borst, Walter L; Jakmunee, Jaroon; Grudpan, Kate; Li, Jianzhong; Dasgupta, Purnendu K

2006-04-15

328

Bubble Colloidal AFM Probes Formed from Ultrasonically Generated Bubbles  

E-print Network

Letters Bubble Colloidal AFM Probes Formed from Ultrasonically Generated Bubbles Ivan U. Vakarelski forces between two small bubbles (80-140 µm) in aqueous solution during controlled collisions) was extended to measure interaction forces between a cantilever-attached bubble and surface-attached bubbles

Chan, Derek Y C

329

Nonlinear Photon Bubbles Driven by Buoyancy  

E-print Network

We derive an analytic model for nonlinear "photon bubble" wave trains driven by buoyancy forces in magnetized, radiation pressure-dominated atmospheres. Continuous, periodic wave solutions exist when radiative diffusion is slow compared to the dynamical timescale of the atmosphere. We identify these waves with the saturation of a linear instability discovered by Arons - therefore, these wave trains should develop spontaneously. The buoyancy-driven waves are physically distinct from photon bubbles in the presence of rapid diffusion, which evolve into trains of gas pressure-dominated shocks as they become nonlinear. Like the gas pressure-driven shock trains, buoyancy-driven photon bubbles can exhibit very large density contrasts, which greatly enhance the flow of radiation through the atmosphere. However, steady-state solutions for buoyancy-driven photon bubbles exist only when an extra source of radiation is added to the energy equation, in the form of a flux divergence. We argue that this term is required to compensate for the radiation flux lost via the bubbles, which increases with height. We speculate that an atmosphere subject to buoyancy-driven photon bubbles, but lacking this compensating energy source, would lose pressure support and collapse on a timescale much shorter than the radiative diffusion time in the equivalent homogeneous atmosphere.

Mitchell C. Begelman

2005-09-13

330

Bubble dynamics in a compressible shear-thinning liquid  

Microsoft Academic Search

The radial dynamics of a spherical gas bubble in a compressible shear-thinning liquid is studied by means of a singular perturbation method to first order in the bubble-wall Mach number. The Williamson rheological model is adopted to describe the shear-thinning characteristic of liquid viscosity. The equation of motion for the bubble radius, the equation of the natural frequency of the

E.-A. Brujan

1998-01-01

331

Interaction of two three-dimensional explosion bubbles  

Microsoft Academic Search

The interaction of two underwater explosion bubbles was mathematically analyzed in this paper. Based on the assumption of\\u000a potential flow, high-order curved elements were used to discretize the boundary integral equation and solve it. Assuming that\\u000a gas inside the bubble follows the isentropic rule, the Euler-Lagrange method was used to trace the evolution of the bubble,\\u000a and when calculating the

Xiong-Liang Yao; A-man Zhang; Yu-Chen Liu

2007-01-01

332

O/H in the Local Bubble  

E-print Network

We present new measurements of the oxygen gas-phase abundance along four sightlines probing gas inside the Local Bubble, using data obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) and the Hubble Space Telecope (HST). Combining these with seven previously published N(O I) and N(H I) measurements we determine a mean O/H ratio for the Local Bubble, (O/H) = (3.45 +/- 0.19)x10^(-4) (1 sigma in the mean). Our result is virtually identical to O/H = (3.43 +/- 0.15)x10^(-4) derived from data for sightlines probing gas well outside the Local Bubble. In contrast to the D/O and D/H ratios, which seem to have different values beyond the Local Bubble, our results show that the O/H ratio is constant and single-valued both inside and outside the Local Bubble, for low density sightlines, with column densities up to log N (H) ~ 21. In addition, the similarity of the two values above suggests that the net effect of the uncertain O I f-values in the FUSE bandpass is not significant. Taking into account the latest determinations of the Solar abundance of oxygen, our result implies that ~25% of the oxygen in the Local Bubble is depleted onto dust grains. The similarity of the value for O/H along low average density sightlines in the Local Bubble with that of denser sightlines beyond may permit a limit on the diluting effects of infalling low metallicity gas.

Cristina Oliveira; Jean Dupuis; Pierre Chayer; H. Warren Moos

2005-02-15

333

Chaotic bubbling and nonstagnant foams.  

PubMed

We present an experimental investigation of the agglomeration of bubbles obtained from a nozzle working in different bubbling regimes. This experiment consists of a continuous production of bubbles from a nozzle at the bottom of a liquid column, and these bubbles create a two-dimensional (2D) foam (or a bubble raft) at the top of this column. The bubbles can assemble in various dynamically stable arrangement, forming different kinds of foams in a liquid mixture of water and glycerol, with the effect that the bubble formation regimes influence the foam obtained from this agglomeration of bubbles. The average number of bubbles in the foam is related to the bubble formation frequency and the bubble mean lifetime. The periodic bubbling can generate regular or irregular foam, while a chaotic bubbling only generates irregular foam. PMID:17677349

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

2007-06-01

334

Radio Bubbles in Clusters of Galaxies  

SciTech Connect

We extend our earlier work on cluster cores with distinct radio bubbles, adding more active bubbles, i.e. those with GHz radio emission, to our sample, and also investigating ''ghost bubbles'', i.e. those without GHz radio emission. We have determined k, which is the ratio of the total particle energy to that of the electrons radiating between 10MHz and 10GHz. Constraints on the ages of the active bubbles confirm that the ratio of the energy factor, k, to the volume filling factor, f lies within the range 1 {approx}< k/f {approx}< 1000. In the assumption that there is pressure equilibrium between the radio-emitting plasma and the surrounding thermal X-ray gas, none of the radio lobes has equipartition between the relativistic particles and the magnetic field. A Monte-Carlo simulation of the data led to the conclusion that there are not enough bubbles present in the current sample to be able to determine the shape of the population. An analysis of the ghost bubbles in our sample showed that on the whole they have higher upper limits on k/f than the active bubbles, especially when compared to those in the same cluster. A study of the Brightest 55 cluster sample shows that 17, possibly 20, clusters required some form of heating as they have a short central cooling time, t{sub cool} {approx}< 3 Gyr, and a large central temperature drop, T{sub centre}/T{sub outer} < 1/2. Of these between 12 (70 per cent) and 15 (75 per cent), contain bubbles. This indicates that the duty cycle of bubbles is large in such clusters and that they can play a major role in the heating process.

Dunn, Robert J.H.; Fabian, A.C.; /Cambridge U., Inst. of Astron.; Taylor, G.B.; /NRAO, Socorro /KIPAC, Menlo Park

2005-12-14

335

Electrowetting of soap bubbles  

NASA Astrophysics Data System (ADS)

A proof-of-concept demonstration of the electrowetting-on-dielectric of a sessile soap bubble is reported here. The bubbles are generated using a commercial soap bubble mixture—the surfaces are composed of highly doped, commercial silicon wafers covered with nanometer thick films of Teflon®. Voltages less than 40 V are sufficient to observe the modification of the bubble shape and the apparent bubble contact angle. Such observations open the way to inter alia the possibility of bubble-transport, as opposed to droplet-transport, in fluidic microsystems (e.g., laboratory-on-a-chip)—the potential gains in terms of volume, speed, and surface/volume ratio are non-negligible.

Arscott, Steve

2013-07-01

336

Numerical Simulation of Bubble Formation in Co-Flowing Mercury  

SciTech Connect

In this work, we present computational fluid dynamics (CFD) simulations of helium bubble formation and detachment at a submerged needle in stagnant and co-flowing mercury. Since mercury is opaque, visualization of internal gas bubbles was done with proton radiography (pRad) at the Los Alamos Neutron Science Center (LANSCE2). The acoustic waves emitted at the time of detachment and during subsequent oscillations of the bubble were recorded with a microphone. The Volume of Fluid (VOF) model was used to simulate the unsteady two-phase flow of gas injection in mercury. The VOF model is validated by comparing detailed bubble sizes and shapes at various stages of the bubble growth and detachment, with the experimental measurements at different gas flow rates and mercury velocities. The experimental and computational results show a two-stage bubble formation. The first stage involves growing bubble around the needle, and the second follows as the buoyancy overcomes wall adhesion. The comparison of predicted and measured bubble sizes and shapes at various stages of the bubble growth and detachment is in good agreement.

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

2008-01-01

337

RADIATION SCATTERING: Determination of the microstructure of gas bubbles in highly purified water by measuring the elements of the laser radiation scattering matrix  

NASA Astrophysics Data System (ADS)

Modulation interference microscopy and measurements of the elements of the light scattering matrix showed that doubly distilled water purified from solid impurities contains macroscopic scatterers in the form of micron clusters formed by polydisperse air bubbles with the effective radius 70-90 nm. The fractal dimension of clusters lies within 2.4-2.8 and their concentration is ~106 cm-3.

Bunkin, Nikolai F.; Suyazov, N. V.; Shkirin, A. V.; Ignat'ev, P. S.; Indukaev, K. V.

2009-04-01

338

RADIATION SCATTERING: Determination of the microstructure of gas bubbles in highly purified water by measuring the elements of the laser radiation scattering matrix  

Microsoft Academic Search

Modulation interference microscopy and measurements of the elements of the light scattering matrix showed that doubly distilled water purified from solid impurities contains macroscopic scatterers in the form of micron clusters formed by polydisperse air bubbles with the effective radius 70-90 nm. The fractal dimension of clusters lies within 2.4-2.8 and their concentration is ~106 cm-3.

Nikolai F. Bunkin; N. V. Suyazov; A. V. Shkirin; P. S. Ignat'ev; K. V. Indukaev

2009-01-01

339

Planar Soap Bubbles  

Microsoft Academic Search

The generalized soap bubble problem seeks the least perimeter way to enclose\\u000aand separate n given volumes in R^m. We study the possible configurations for\\u000aperimeter minimizing bubble complexes enclosing more than two regions. We prove\\u000athat perimeter minimizing planar bubble complexes with equal pressure regions\\u000aand without empty chambers must have connected regions. As a consequence, we\\u000ashow that

RICHARD PAUL; DEVEREAUX VAUGHN

1998-01-01

340

Fermi Bubbles and Bubble-like Emission from the Galactic Plane  

NASA Astrophysics Data System (ADS)

The diffuse gamma-ray sky revealed "bubbles" of emission above and below the Galactic plane, symmetric around the center of the Milky Way, with a height of 10 kpc in both directions. At present, there is no convincing explanation for the origin. To understand the role of the Galactic center, one has to study the bubble spectrum inside the disk, a region that has been excluded from previous analyses because of the large foreground. From a novel template fit, which allows a simultaneous determination of the signal and foreground in any direction, we find that bubble-like emission is not only found in the halo, but in the Galactic plane as well, with a width in latitude coinciding with the molecular clouds. The longitude distribution has a width corresponding to the Galactic bar with an additional contribution from the Scutum-Centaurus arm. The energy spectrum of the bubbles coincides with the predicted contribution from CRs trapped in sources (SCRs). Also, the energetics fits well. Hence, we conclude that the bubble-like emission has a hadronic origin that arises from SCRs, and the bubbles in the halo arise from hadronic interactions in advected gas. Evidence for advection is provided by the ROSAT X-rays of hot gas in the bubble region.

de Boer, Wim; Weber, Markus

2014-10-01

341

Radio Bubbles in Clusters  

E-print Network

We extend our earlier work on cluster cores with distinct radio bubbles, adding more active bubbles, i.e. those with Ghz radio emission, to our sample, and also investigating ``ghost bubbles,'' i.e. those without GHz radio emission. We have determined k, which is the ratio of the total particle energy to that of the electrons radiating between 10 MHz and 10 GHz. Constraints on the ages of the active bubbles confirm that the ratio of the energy factor, k, to the volume filling factor, f lies within the range 1 bubbles present in the current sample to be able to determine the shape of the population. An analysis of the ghost bubbles in our sample showed that on the whole they have higher upper limits on k/f than the active bubbles, especially when compared to those in the same cluster. A study of the Brightest 55 cluster sample shows that 17, possibly 20, clusters required some form of heating as they have a short central cooling time, t_cool bubbles. This indicates that the duty cycle of bubbles is large in such clusters and that they can play a major role in the heating process.

R. J. H. Dunn; A. C. Fabian; G. B. Taylor

2005-10-06

342

Interaction of lithotripter shockwaves with single inertial cavitation bubbles.  

PubMed

The dynamic interaction of a shockwave (modelled as a pressure pulse) with an initially spherically oscillating bubble is investigated. Upon the shockwave impact, the bubble deforms non-spherically and the flow field surrounding the bubble is determined with potential flow theory using the boundary-element method (BEM). The primary advantage of this method is its computational efficiency. The simulation process is repeated until the two opposite sides of the bubble surface collide with each other (i.e. the formation of a jet along the shockwave propagation direction). The collapse time of the bubble, its shape and the velocity of the jet are calculated. Moreover, the impact pressure is estimated based on water-hammer pressure theory. The Kelvin impulse, kinetic energy and bubble displacement (all at the moment of jet impact) are also determined. Overall, the simulated results compare favourably with experimental observations of lithotripter shockwave interaction with single bubbles (using laser-induced bubbles at various oscillation stages). The simulations confirm the experimental observation that the most intense collapse, with the highest jet velocity and impact pressure, occurs for bubbles with intermediate size during the contraction phase when the collapse time of the bubble is approximately equal to the compressive pulse duration of the shock wave. Under this condition, the maximum amount of energy of the incident shockwave is transferred to the collapsing bubble. Further, the effect of the bubble contents (ideal gas with different initial pressures) and the initial conditions of the bubble (initially oscillating vs. non-oscillating) on the dynamics of the shockwave-bubble interaction are discussed. PMID:19018296

Klaseboer, Evert; Fong, Siew Wan; Turangan, Cary K; Khoo, Boo Cheong; Szeri, Andrew J; Calvisi, Michael L; Sankin, Georgy N; Zhong, Pei

2007-01-01

343

Interaction of lithotripter shockwaves with single inertial cavitation bubbles  

PubMed Central

The dynamic interaction of a shockwave (modelled as a pressure pulse) with an initially spherically oscillating bubble is investigated. Upon the shockwave impact, the bubble deforms non-spherically and the flow field surrounding the bubble is determined with potential flow theory using the boundary-element method (BEM). The primary advantage of this method is its computational efficiency. The simulation process is repeated until the two opposite sides of the bubble surface collide with each other (i.e. the formation of a jet along the shockwave propagation direction). The collapse time of the bubble, its shape and the velocity of the jet are calculated. Moreover, the impact pressure is estimated based on water-hammer pressure theory. The Kelvin impulse, kinetic energy and bubble displacement (all at the moment of jet impact) are also determined. Overall, the simulated results compare favourably with experimental observations of lithotripter shockwave interaction with single bubbles (using laser-induced bubbles at various oscillation stages). The simulations confirm the experimental observation that the most intense collapse, with the highest jet velocity and impact pressure, occurs for bubbles with intermediate size during the contraction phase when the collapse time of the bubble is approximately equal to the compressive pulse duration of the shock wave. Under this condition, the maximum amount of energy of the incident shockwave is transferred to the collapsing bubble. Further, the effect of the bubble contents (ideal gas with different initial pressures) and the initial conditions of the bubble (initially oscillating vs. non-oscillating) on the dynamics of the shockwave–bubble interaction are discussed. PMID:19018296

Klaseboer, Evert; Fong, Siew Wan; Turangan, Cary K.; Khoo, Boo Cheong; Szeri, Andrew J.; Calvisi, Michael L.; Sankin, Georgy N.; Zhong, Pei

2008-01-01

344

Original paper Soap Bubble Clusters  

E-print Network

Original paper Soap Bubble Clusters Fred ALMGREN surface, soap bubbles Abstract. This article reviews the theorems from geometric measure theory which guarantee the existence and give the structure of mathematical models of soap bubble clusters. It also

Taylor, Jean

345

Bubbles in liquids with phase transition. Part 1. On phase change of a single vapor bubble in liquid water  

NASA Astrophysics Data System (ADS)

In the forthcoming second part of this paper a system of balance laws for a multi-phase mixture with many dispersed bubbles in liquid is derived where phase transition is taken into account. The exchange terms for mass, momentum and energy explicitly depend on evolution laws for total mass, radius and temperature of single bubbles. Therefore in the current paper we consider a single bubble of vapor and inert gas surrounded by the corresponding liquid phase. The creation of bubbles, e.g. by nucleation is not taken into account. We study the behavior of this bubble due to condensation and evaporation at the interface. The aim is to find evolution laws for total mass, radius and temperature of the bubble, which should be as simple as possible but consider all relevant physical effects. Special attention is given to the effects of surface tension and heat production on the bubble dynamics as well as the propagation of acoustic elastic waves by including slight compressibility of the liquid phase. Separately we study the influence of the three phenomena heat conduction, elastic waves and phase transition on the evolution of the bubble. We find ordinary differential equations that describe the bubble dynamics. It turns out that the elastic waves in the liquid are of greatest importance to the dynamics of the bubble radius. The phase transition has a strong influence on the evolution of the temperature, in particular at the interface. Furthermore the phase transition leads to a drastic change of the water content in the bubble. It is shown that a rebounding bubble is only possible, if it contains in addition an inert gas. In Part 2 of the current paper the equations derived are sought in order to close the system of equations for multi-phase mixture balance laws for dispersed bubbles in liquids involving phase change.

Dreyer, Wolfgang; Duderstadt, Frank; Hantke, Maren; Warnecke, Gerald

2012-11-01

346

Magnetite Scavenging and the Buoyancy of Bubbles in Magmas  

Microsoft Academic Search

It is generally assumed that when eruptions are triggered, magmas are bubble-free, and all the vesicularity observed in pumice is due to nucleation and growth during ascent. However, decompression experiments show that bubbles tend to nucleate on magnetite crystals at relatively low supersaturation, and there is convincing evidence that an exsolved gas phase was present during much of the evolution

G. A. Gualda; M. S. Ghiorso

2005-01-01

347

ON THRESHOLDS FOR SURFACE WAVES ON RESONANT BUBBLES  

Microsoft Academic Search

The problem of the stability of gas bubbles in a sound field has been investigated using a model for the motion of a nearly spherical bubble in a slightly viscous liquid. The radial motion amplitude and the pressure amplitude thresholds for the instability of the spherical shape have been obtained by the theory of parametric resonance. The comparison with available

R. NABERGOJ; A. FRANCESCUTTO

1979-01-01

348

Solvent-refined-coal (SRC) process. Hydrodynamics and axial mixing in a three-phase bubble column  

SciTech Connect

The hydrodynamics and the mixing properties in a 15.2 cm diameter x 335.3 cm high stainless steel column with three phases (air, water and coal) in cocurrent upflow were studied. The effect of solids particles size, solids concentration, slurry velocity and gas velocity on gas holdup and heat dispersion coefficients were determined. All the experimental data were correlated empirically and the results were compared with other published literature. Theoretical explanations of some results were provided.

Kara, S.; Kelkar, B.G.; Shah, Y.T.

1982-01-01

349

Shock-wave-induced jetting of micron-size bubbles.  

PubMed

Free gas bubbles in water with radii between 7 and 55 microm subjected to a shock wave exhibit a liquid jetting phenomenon with the jet pointing in the direction of the propagating shock wave. With increasing bubble radius, the length of the jet tip increases and a lower estimate of the averaged jet velocity increases linearly from 20 to 150 m/s. At a later stage, the jet breaks up and releases micron-size bubbles. In the course of shock wave permeabilization and transfection of biological cells, this observation suggests a microinjection mechanism when the cells are near bubbles exposed to a shock wave. PMID:12786557

Ohl, C D; Ikink, R

2003-05-30

350

Soap bubbles. 1  

Microsoft Academic Search

I consider the chemistry, physics, and computer graphics of soap bubbles. I focus on the physics of soap films, which are, after all, what bubbles are made of. I see what happens when soap dissolves in water and discuss some surprising properties of soap films

A. Glassner

2000-01-01

351

Let Them Blow Bubbles.  

ERIC Educational Resources Information Center

Describes a series of activities and demonstrations involving the science of soap bubbles. Starts with a recipe for bubble solution and gives instructions for several activities on topics such as density, interference colors, optics, static electricity, and galaxy formation. Contains some background information to help explain some of the effects.…

Korenic, Eileen

1988-01-01

352

Propagation through nonlinear time-dependent bubble clouds and the estimation of bubble populations from measured acoustic characteristics  

Microsoft Academic Search

For several decades the propagation characteristics of acoustic pulses (attenuation and sound speed) have been inverted in attempts to measure the size distributions of gas bubbles in liquids. While this has biomedical and industrial applications, most notably it has been attempted in the ocean for defence and environmental purposes, where the bubbles are predominantly generated by breaking waves. Such inversions

T. G. Leighton; S. D. Meers; P. R. White

2004-01-01

353

Bubbly flow around an isolated airfoil  

SciTech Connect

Performance of turbopumps under gas/liquid two-phase flow is the origin of the present study. To analyze this problem most fundamentally, bubbly flow around an isolated airfoil is studied experimentally and analytically. First, a test tunnel is built, which enables flow measurement around an isolated airfoil in a uniform bubbly flow. The stress is laid on the measurement of local void fraction using a point electrode probe. The redistribution of bubbles driven by pressure gradient around the airfoil is made clear. Numerical study is carried parallel and the result of numerical simulation is compared with an experimental one. The governing equations of two-phase flow are proposed; and the bubbly two-phase flow around an airfoil is calculated using a method based on the MacCormack method combined with the boundary-fitted curvilinear coordinate system. The results reveal that the slippage between bubble and liquid has a significant influence on the bubbly flow. The numerical results agree qualitatively with the experimental ones.

Ohashi, Hideo [Kogakuin Univ., Tokyo (Japan). Dept. of Mechanical Engineering; Matsumoto, Yoichiro [Univ. of Tokyo (Japan). Dept. of Mechanical Engineering

1994-12-31

354

Dynamics of Bubble Ascent in Mud Volcanoes  

NASA Astrophysics Data System (ADS)

Bubble ascent controls the eruption style of both magmatic and mud volcanoes, and is influenced by the rheology of the continuous phase. Mud and some magmas are non-Newtonian, and bubble ascent in non-Newtonian fluids remains incompletely characterized. We performed laboratory experiments using mud obtained from mud volcanoes adjacent to the Salton Sea, in Southern California. The erupting mud is well-described as a Herschel-Bulkley (shear-thinning, yield stress) fluid. We measured the rise speed of bubbles with volumes between 5 and 20 cc, varied the conduit diameter, and controlled for hysteresis in the mud to estimate upper and lower bounds on terminal velocity. Bubbles smaller than about 6 cc are unable to rise due to the mud's yield strength. We made rheological measurements (power-law exponent, yield strength, and consistency index) of the mud to compare the observed bubble rise speed to several empirical fits to laboratory data. We also quantify the rate of coalescence of bubbles as a function of their concentration and hence gas mass flux.

Tran, A.; Rudolph, M. L.; Manga, M.

2011-12-01

355

Final Report Mechanics of Bubbles in Sludges and Slurries  

SciTech Connect

The Hanford Site has 177 underground waste storage tanks that are known to retain and release bubbles composed of flammable gases. Characterizing and understanding the behavior of these bubbles is important for the safety issues associated with the flammable gases for both ongoing waste storage and future waste-retrieval operations. The retained bubbles are known to respond to small barometric pressure changes, though in a complex manner with unusual hysteresis occurring in some tanks in the relationship between bubble volume and pressure, or V-P hysteresis. With careful analysis, information on the volume of retained gas and the interactions of the waste and the bubbles can be determined. The overall objective of this study is to create a better understanding of the mechanics of bubbles retained in high-level waste sludges and slurries. Significant advancements have been made in all the major areas of basic theoretical and experimental method development. In addition, the relevance of these basic developments to Hanford waste has resulted in an entirely new understanding of bubble mechanics and waste microstructure in Hanford waste tanks. This effort included both experimental and theoretical studies. Experimental developments have provided measurements of V-P hysteresis on a range of simulants. The theoretical approaches included solid-mechanics studies of bubbles in soft solids, fluid-mechanics studies of bubbles in yield stress fluids, and porous-media studies of bubbles in model porous media filled with Newtonian fluids or filled with yield-stress fluids.

Gauglitz, Phillip A.; Terrones, Guillermo; Muller, Susan J.; Denn, Morton M.; Rossen, William R.

2001-12-31

356

Unsteady thermocapillary migration of bubbles  

NASA Technical Reports Server (NTRS)

Upon the introduction of a gas bubble into a liquid possessing a uniform thermal gradient, an unsteady thermo-capillary flow begins. Ultimately, the bubble attains a constant velocity. This theoretical analysis focuses upon the transient period for a bubble in a microgravity environment and is restricted to situations wherein the flow is sufficiently slow such that inertial terms in the Navier-Stokes equation and convective terms in the energy equation may be safely neglected (i.e., both Reynolds and Marangoni numbers are small). The resulting linear equations were solved analytically in the Laplace domain with the Prandtl number of the liquid as a parameter; inversion was accomplished numerically using a standard IMSL routine. In the asymptotic long-time limit, the theory agrees with the steady-state theory of Young, Goldstein, and Block. The theory predicts that more than 90 percent of the terminal steady velocity is achieved when the smallest dimensionless time, i.e., the one based upon the largest time scale-viscous or thermal-equals unity.

Dill, Loren H.; Balasubramaniam, R.

1988-01-01

357

Explosion of chaotic bubbling  

NASA Astrophysics Data System (ADS)

We have studied a saddle-node bifurcation/explosion of air bubble formation driven by a sound wave, whose amplitude is the control parameter. The bubbles are formed in a nozzle submerged in a water/glycerol solution inside a cylindrical tube, and the sound wave is tuned to the air column above the fluid. The nonlinear interaction between sound wave and the fluid oscillations, caused by the air bubbles passage through the liquid, results in a route to chaos via quasi-periodicity, with some resonant states characterized by the rational winding numbers W= fs/ fb, where fs is the sound wave frequency and fb is the bubbling rate. We also have shown that the bubble dynamics is similar to the one observed in the two-dimensional circle map.

Tufaile, A.; Reyes, M. B.; Sartorelli, J. C.

2002-05-01

358

Enhancing gas-liquid mass transfer rates in non-newtonian fermentations by confining mycelial growth to microbeads in a bubble column  

Microsoft Academic Search

The performance of a penicillin fermentation was assessed in a laboratory-scale bubble column fermentor, with mycelial growth confined to the pore matrix of celite beads. Final cell densities of 29 g\\/L and penicillin titres of 5.5 g\\/L were obtained in the confined cell cultures. In comparison, cultures of free mycelial cells grown in the absence of beads experienced dissolved oxygen

K. Gbewonyo; D. I. C. Wang

1983-01-01

359

Exercise and nitric oxide prevent bubble formation: a novel approach to the prevention of decompression sickness?  

Microsoft Academic Search

Nitrogen dissolves in the blood during dives, but comes out of solution if divers return to normal pressure too rapidly. Nitrogen bubbles cause a range of effects from skin rashes to seizures, coma and death. It is believed that these bubbles form from bubble precursors (gas nuclei). Recently we have shown that a single bout of exercise 20 h, but

U. Wisloff; Russell S. Richardson; Alf O. Brubakk

2004-01-01

360

Dynamics of soap bubble bursting and its implications to volcano acoustics  

E-print Network

Dynamics of soap bubble bursting and its implications to volcano acoustics V. Vidal1,2 , M. Ripepe3 Abstract In order to assess the physical mechanisms at stake when giant gas bubbles burst at the top on the overpressure inside the bubble before explosion. This could ex- plain the low energy partitioning between

Paris-Sud XI, Université de

361

Effective Spring Constant of Bubbles and Droplets Phil Attard* and Stan J. Miklavcic  

E-print Network

Effective Spring Constant of Bubbles and Droplets Phil Attard* and Stan J. Miklavcic Ian Wark. In Final Form: October 3, 2001 It is shown that gas bubbles and liquid droplets respond as hookean springs on the lengths (the decay length of the interaction, the radius of the bubble or droplet, and the radius

Attard, Phil

362

Water-Splitting Photoelectrolysis Reaction Rate via Microscopic Imaging of Evolved Oxygen Bubbles  

E-print Network

Water-Splitting Photoelectrolysis Reaction Rate via Microscopic Imaging of Evolved Oxygen Bubbles Institute of Technology, Pasadena, California 91125, USA Bubble formation and growth on a water of the gas-evolving reaction rate. Optical microscopy was used to record the bubble growth on single

Atwater, Harry

363

Real time capacitance imaging of bubble formation at the distributor of a fluidized bed  

Microsoft Academic Search

This paper describes the use of a transputer-based 8-electrode capacitance tomography system for imaging gas bubbles in a fluidized bed in the vicinity of an air distributor plate. The quantitative results show how the solid concentration distribution varies as a function of time for three different flow regimes: bubbling, slugging and the transition to turbulent. Bubble shape, length and coalescence

S. J. Wang; T. Dyakowski; C. G. Xie; R. A. Williams; M. S. Beck

1995-01-01

364

Formation and X-ray emission from hot bubbles in planetary nebulae - I. Hot bubble formation  

NASA Astrophysics Data System (ADS)

We carry out high-resolution two-dimensional radiation-hydrodynamic numerical simulations to study the formation and evolution of hot bubbles inside planetary nebulae. We take into account the evolution of the stellar parameters, wind velocity and mass-loss rate from the final thermal pulses during the asymptotic giant branch (AGB) through to the post-AGB stage for a range of initial stellar masses. The instabilities that form at the interface between the hot bubble and the swept-up AGB wind shell lead to hydrodynamical interactions, photoevaporation flows and opacity variations. We explore the effects of hydrodynamical mixing combined with thermal conduction at this interface on the dynamics, photoionization, and emissivity of our models. We find that even models without thermal conduction mix significant amounts of mass into the hot bubble. When thermal conduction is not included, hot gas can leak through the gaps between clumps and filaments in the broken swept-up AGB shell and this depressurises the bubble. The inclusion of thermal conduction evaporates and heats material from the clumpy shell, which expands to seal the gaps, preventing a loss in bubble pressure. The dynamics of bubbles without conduction is dominated by the thermal pressure of the thick photoionized shell, while for bubbles with thermal conduction it is dominated by the hot, shocked wind.

Toalá, J. A.; Arthur, S. J.

2014-10-01

365

Mounting and application of bubble display system: bubble cosmos  

Microsoft Academic Search

In this paper, we propose the soap bubble display method that the image can be projected to the real soap bubbles that white smoke entered. The position and the size of soap bubbles tossed in the air are detected with the camera. By projecting the image only to the position with the projector, the soap bubble display is realized. And

Masahiro Nakamura; Go Inaba; Jun Tamaoki; Kazuhito Shiratori; Junichi Hoshino

2006-01-01

366

Methods for nondestructive assay holdup measurements in shutdown uranium enrichment facilities  

SciTech Connect

Measurement surveys of uranium holdup using nondestructive assay (NDA) techniques are being conducted for shutdown gaseous diffusion facilities at the Oak Ridge K-25 Site (formerly the Oak Ridge Gaseous Diffusion Plant). When in operation, these facilities processed UF{sub 6} with enrichments ranging from 0.2 to 93 wt % {sup 235}U. Following final shutdown of all process facilities, NDA surveys were initiated to provide process holdup data for the planning and implementation of decontamination and decommissioning activities. A three-step process is used to locate and quantify deposits: (1) high-resolution gamma-ray measurements are performed to generally define the relative abundances of radioisotopes present, (2) sizable deposits are identified using gamma-ray scanning methods, and (3) the deposits are quantified using neutron measurement methods. Following initial quantitative measurements, deposit sizes are calculated; high-resolution gamma-ray measurements are then performed on the items containing large deposits. The quantitative estimates for the large deposits are refined on the basis of these measurements. Facility management is using the results of the survey to support a variety of activities including isolation and removal of large deposits; performing health, safety, and environmental analyses; and improving facility nuclear material control and accountability records. 3 refs., 1 tab.

Hagenauer, R.C.; Mayer, R.L. II.

1991-09-01

367

Bubble flow and the formation of cavity defect in weld pool of vacuum electron beam welding  

Microsoft Academic Search

Seen from gas-liquid two-phase-flow system, the gas phase and liquid phase of bubble flow in weld pool are studied by means of isolated phase based on the conservation of mass and momentum. The two-dimensional fractional flow model of bubble flow in weld pool of vacuum electron beam welding is developed. And the gas distribution and the phenomenon of bubble flow

Yi Luo; Jinhe Liu; Hong Ye

2011-01-01

368

Bubble core field modification by residual electrons inside the bubble  

SciTech Connect

Bubble core field modification due to the nondepleted electrons present inside the bubble is investigated theoretically. These residual electrons induce charge and current densities that can induce the bubble core field modification as well as the bubble shape change. It is found that the electrons entering into the bubble move backward at almost light speed and would weaken the transverse bubble fields. This reduces the ratio of longitudinal to transverse radius of the bubble. For the longitudinal bubble field, two effects compensate with each other because of their competition between the enhancement by the shortening of bubble shape and the reduction by the residual electrons. Therefore the longitudinal field is hardly changeable. As a comparison we perform particle-in-cell simulations and it is found that the results from theoretical consideration are consistent with simulation results. Implication of the modification of fields on bubble electron acceleration is also discussed briefly.

Wu Haicheng [College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Center for Applied Physics and Technology, Peking University, Beijing 100084 (China); Xie Baisong; Zhao Xueyan [College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Zhang Shan [College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Department of Mathematics and Physics, Shijiazhuang Railway Institute, Shijiazhuang 050043 (China); Hong Xueren [College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China); Liu Mingping [School of Information Engineering, Nanchang University, Nanchang 330031 (China)

2010-11-15

369

Measurement of the change in the number of ultrafine bubbles through pressurization  

NASA Astrophysics Data System (ADS)

The present study deals with, for the first time, a measurement of the number of bubbles of submicron in size before and after pressurization. Measurement of ultrafine bubbles of submicron size was conducted and it was clarified that greater number of submicron sized bubbles existed before the pressurization in comparison with that after the pressurization. The application of high pressure of gas for its dissolution into water and the ambient-pressure reduction has a possibility to increase the number of ultrafine bubbles.

Tuziuti, T.; Yasui, K.; Kanematsu, Wataru

2014-08-01

370

The mass and energy of a vapor bubble in a turbulent ideal fluid  

E-print Network

The mass of a bubble in a fluid can be taken as the mass of the vapor in it. The self-energy of the bubble is defined as the work performed against the pressure of the fluid in order to create the bubble. Taking the vapor to be an ideal gas the relationship between the self-energy, the mass of the bubble and the speed of the perturbation wave in a turbulent ideal fluid can be obtained.

Valery P. Dmitriyev

2006-02-21

371

Bubble behavior in molten glass in a temperature gradient. [in reduced gravity rocket experiment  

NASA Technical Reports Server (NTRS)

Gas bubble motion in a temperature gradient was observed in a sodium borate melt in a reduced gravity rocket experiment under the NASA SPAR program. Large bubbles tended to move faster than smaller ones, as predicted by theory. When the bubbles contacted a heated platinum strip, motion virtually ceased because the melt only imperfectly wets platinum. In some cases bubble diameter increased noticeably with time.

Meyyappan, M.; Subramanian, R. S.; Wilcox, W. R.; Smith, H.

1982-01-01

372

Significance of viscoelastic effects on the rising of a bubble and bubble-to-bubble interaction  

NASA Astrophysics Data System (ADS)

Numerical results for the rising of a bubble and the interaction between two bubbles in non-Newtonian fluids will be discussed. The computations are carried out using a multiscale method combining front-tracking with Brownian dynamics simulations. The evaluation of the material properties for the non-Newtonian fluid will be discussed firstly. The results from the computations of a single bubble show how elastic effects modify the deformation and rising of the bubble by pulling the tail of it. The relationship between the strength of the elastic forces and the discontinuity in the bubble terminal velocity, when plotted versus bubble volume, is also observed in the computations. The bubble-to-bubble interaction is dominated not only by elastic effects but also by the shear-thinning caused by the leading bubble, which leads the trailing bubble to accelerate faster and coalesce with the leading bubble.

Fernandez, Arturo

2011-11-01

373

Viscosity destabilizes sonoluminescing bubbles.  

PubMed

In single-bubble sonoluminescence (SBSL) microbubbles are trapped in a standing sound wave, typically in water or water-glycerol mixtures. However, in viscous liquids such as glycol, methylformamide, or sulphuric acid it is not possible to trap the bubble in a stable position. This is very peculiar as larger viscosity normally stabilizes the dynamics. Suslick and co-workers call this new mysterious state of SBSL "moving-SBSL." We identify the history force (a force nonlocal in time) as the origin of this destabilization and show that the instability is parametric. A force balance model quantitatively accounts for the observed quasiperiodic bubble trajectories. PMID:16605826

Toegel, Ruediger; Luther, Stefan; Lohse, Detlef

2006-03-24

374

A modelling and experimental study of the bubble trajectory in a non-Newtonian crystal suspension  

NASA Astrophysics Data System (ADS)

This paper presents an experimental and computational study of air bubbles rising in a massecuite-equivalent non-Newtonian crystal suspension. The bubble trajectory inside the stagnant liquid of a 0.05% xanthan gum crystal suspension was investigated and modelled using the computational fluid dynamics (CFD) model to gain an insight into the bubble flow characteristics. The CFD code FLUENT was used for numerical simulation, and the bubble trajectory calculations were performed through a volume of fluid (VOF) model. The influences of the Reynolds number (Re), the Weber number (We) and the bubble aspect ratio (E) on the bubble trajectory are discussed. The conditions for the bubbles' path oscillations are identified. The experimental results showed that the path instability for the crystal suspension was less rapid than in water. The trajectory analysis indicated that 5.76 mm diameter bubbles followed a zigzag motion in the crystal suspension. Conversely, the smaller bubbles (5.76 mm) followed a path of least horizontal movement and larger bubbles (21.21 mm) produced more spiral motion within the crystal suspension. Path instability occurred for bubbles of 15.63 and 21.21 mm diameter, and they induced both zigzag and spiral trajectories within the crystal suspension. At low Re and We, smaller bubbles (5.76 mm) produced a zigzag trajectory, whereas larger bubbles (15.63 and 21.21 mm) showed both zigzag and spiral trajectories at intermediate and moderately high Re and We in the crystal suspension. The simulation results illustrated that a repeating pattern of swirling vortices was created for smaller bubbles due to the unstable wake and unsteady flow of these bubbles. This is the cause of the smaller bubbles moving in a zigzag way. Larger bubbles showed two counter-rotating trailing vortices at the back of the bubble. These vortices induced a velocity component to the gas-liquid interface and caused a deformation. Hence, the larger bubbles produced a path transition.

Hassan, N. M. S.; Khan, M. M. K.; Rasul, M. G.

2010-12-01

375

Speculations on Nonlinear Speculative Bubbles  

Microsoft Academic Search

This paper reviews a variety of issues related to speculative bubbles, especially those involving nonlinear dynamics. Models of irrational bubbles, rational bubbles, and bubbles arising from heterogeneous agents with varying degrees of knowledge or rationality are examined. The latter are shown to be prone to nonlinear dynamics with catastrophic discontinuities, chaos, and other forms of complex phenomena. Empirical evidence regarding

J. Barkley Rosser

1997-01-01

376

Quantification of Liquid Holdup in the Dropping Zone of a Blast Furnace--A Cold Model Study  

E-print Network

Quantification of Liquid Holdup in the Dropping Zone of a Blast Furnace--A Cold Model Study G.S. GUPTA and K. NAVEEN A two-dimensional cold model study, replicating an ironmaking blast furnace dropping average at a particular flow rate. This may have important implications with respect to blast furnace

377

Chaotic Interaction of Oscillating Bubbles under Forced Vibration in Microgravity  

NASA Astrophysics Data System (ADS)

There are many gas-liquid and liquid-liquid systems used on the International Space Station and, future space exploration activities will require physical separation of gas, liquid, and solid phases. Such systems include materials processing systems, (e.g. protein crystal growth), life support, thermal management, and propulsion systems, among others. Separating immiscible fluid mixtures containing different materials with different densities is difficult in the absence of gravity. A force other than gravity is required to accomplish phase separation. Vibration induced acceleration is one method of phase separation in microgravity in which continuum phase and dispersed phase are subjected to forced vibration. The vibration induces an oscil-latory acceleration. As a result of this acceleration, a time varying oscillatory pressure field is formed which is linear at each time and its magnitude is a function of vibration amplitude and frequency. Oscillatory acceleration results in an oscillatory buoyancy force on the dispersed phase. As a result of this oscillatory buoyancy force, dispersed phase starts an oscillatory translational motion. In addition to the oscillatory translational motion of the dispersed phase, its shape starts changing. The non-uniform pressure distribution around the dispersed phase is responsible for the shape change. Since the change in the shape of the dispersed phase re-distributes the pressure field around it and affects the translational motion, the two nonlinear motions, oscillatory translational motion and shape change, are coupled together. This coupling can make the behavior of dispersed phase unpredictable. In the case of more than one bubble inside the domain, the flow fields developed by the motion of each bubble interact with each other resulting in bubble-bubble interaction. Bubbles can attract or repel each other depending on size, vibration amplitude and frequency, fluid properties, and container configuration. Bub-bles which attract each other form larger bubbles and can be removed from the liquid medium easier comparing to smaller ones. This method can enhance the dispersed phase separation in microgravity. The present work consists of numerical simulation of bubble dynamics in mi-crogravity environment and under forced vibration. Oscillatory translational motion of the bubbles and their shape change are captured simultaneously employing a Volume of Fluid flow solver. The results show that the coupling between the shape change and translational motion of one bubble inside a liquid domain results in chaotic motion of the bubble depending on the applied frequency and amplitude. In the case of two bubbles, the interaction force between the bubbles adds more complexity to the flow field. Bubble-bubble interaction is also studied and the effect of vibration amplitude, vibration frequency, and liquid to gas density ratio on the interaction time is investigated.

Movassat, Mohammad; Ashgriz, Nasser; Bussmann, Markus

378

Dynamics of sonoluminescing bubbles within a liquid hammer device.  

PubMed

We studied the dynamics of a single sonoluminescing bubble (SBSL) in a liquid hammer device. In particular, we investigated the phosphoric acid-xenon system, in which pulses up to four orders of magnitude brighter than SBSL in water systems (about 10;{12} photons per pulse) have been previously reported [Chakravarty, Phys. Rev. E 69, 066317 (2004)]. We used stroboscopic photography and a Mie scattering technique in order to measure the radius evolution of the bubbles. Under adequate conditions we may position a bubble at the bottom of the tube (cavity) and a second bubble trapped at the middle of the tube (upper bubble). During its collapse, the cavity produces the compression of the liquid column. This compression drives impulsively the dynamics of the upper bubble. Our measurements reveal that the observed light emissions produced by the upper bubble are generated at its second collapse. We employed a simple numerical model to investigate the conditions that occur during the upper bubble collapse. We found good agreement between numerical and experimental values for the light intensity (fluence) and light pulse widths. Results from the model show that the light emission is increased mainly due to an increase in noble gas ambient radius and not because the maximum temperature increases. Even for the brightest pulses obtained ( 2x10;{13} photons, about 20W of peak power) the maximum temperatures computed for the upper bubble are always lower than 20000K . PMID:19257138

Urteaga, Raúl; García-Martínez, Pablo Luis; Bonetto, Fabián J

2009-01-01

379

Colloquium: Soap bubble clusters  

NASA Astrophysics Data System (ADS)

Soap bubble clusters and froths model biological cells, metallurgical structures, magnetic domains, liquid crystals, fire-extinguishing foams, bread, cushions, and many other materials and structures. Despite the simplicity of the governing principle of energy or area minimization, the underlying mathematical theory is deep and still not understood, even for rather simple, finite clusters. Only with the advent of geometric measure theory could mathematics treat surfaces which might have unprescribed singularities and topological complexities. In 1884, Schwarz gave a rigorous mathematical proof that a single round soap bubble provides the least-area way to enclose a given volume of air. Similarly, the familiar double bubble provides the absolute least-area way to enclose and separate the two given volumes of air, although the proof did not come until 2000 and has an interesting story, as this Colloquium explains in some detail. Whether a triple soap bubble provides the least-area way to enclose and separate three given volumes of air remains an open conjecture today. Even planar bubble clusters remain mysterious. In about 200 B.C. Zenodorus essentially proved that a circle provides the least-perimeter way to enclose a single given area. The planar double and triple bubbles were proved minimizing recently. The status of the planar four-bubble remains open today. In most spaces other than Euclidean space, even the best single bubble remains unproven. One exception is Gauss space, which is of much interest to probabilists and should be more familiar to physicists. General “isoperimetric” problems of minimizing area for given volume occur throughout mathematics and play an important role in differential geometry and analysis, including Perelman’s proof of the Poincaré conjecture.

Morgan, Frank

2007-07-01

380

Bubble coalescence in magmas  

NASA Technical Reports Server (NTRS)

The most important factors governing the nature of volcanic eruptions are the primary volatile contents, the ways in which volatiles exsolve, and how the resulting bubbles grow and interact. In this contribution we assess the importance of bubble coalescence. The degree of coalescence in alkali basalts has been measured using Image Analysis techniques and it is suggested to be a process of considerable importance. Binary coalescence events occur every few minutes in basaltic melts with vesicularities greater than around 35 percent.

Herd, Richard A.; Pinkerton, Harry

1993-01-01

381

Prediction of the bubble-hole size of a cap bubble in a bubble swarm  

Microsoft Academic Search

A phenomenological, semi-theoretical model is proposed for predicting the size or thickness of the bubble-depleted region, or ‘bubble hole’, in the frontal vicinity of a larg cap bubble rising through a swarm of otherwise uniformly dispersed small bubbles. The model lays its theoretical basis on the axial pressure distribution in the very front of the cap nose which modifies the

Katsumi Tsuchiya; Kazutomo Ohsaki

1997-01-01

382

Investigation of bubbles in arterial heat pipes  

NASA Technical Reports Server (NTRS)

The behavior of gas occlusions in arterial heat pipes has been studied experimentally and theoretically. Specifically, the gas-liquid system properties, solubility and diffusivity, have been measured from -50 to 100 C for helium and argon in ammonia, Freon-21 (CHC12F), and methanol. Properties values obtained were then used to experimentally test models for gas venting from a heat pipe artery under isothermal conditions (i.e., no-heat flow), although the models, as developed, are also applicable to heat pipes operated at power, with some minor modifications. Preliminary calculations indicated arterial bubbles in a stagnant pipe require from minutes to days to collapse and vent. It has been found experimentally that a gas bubble entrapped within an artery structure has a very long lifetime in many credible situations. This lifetime has an approximately inverse exponential dependence on temperature, and is generally considerably longer for helium than for argon. The models postulated for venting under static conditions were in general quantitative agreement with experimental data. Factors of primary importance in governing bubble stability are artery diameter, artery wall thickness, noncondensible gas partial pressure, and the property group (the Ostwald solubility coefficient multiplied by the gas/liquid diffusivity).

Saaski, E. W.

1972-01-01

383

THE AGE OF THE LOCAL INTERSTELLAR BUBBLE  

SciTech Connect

The Local Interstellar Bubble is an irregular region from 50 to 150 pc from the Sun in which the interstellar gas density is 10{sup -2}-10{sup -3} of that outside the bubble and the interstellar temperature is 10{sup 6} K. Evidently most of the gas was swept out by one or more supernovae. I explored the stellar contents and ages of the region from visual double stars, spectroscopic doubles, single stars, open clusters, emission regions, X-ray stars, planetary nebulae, and pulsars. The bubble has three sub-regions. The region toward the galactic center has stars as early as O9.5 V and with ages of 2-4 M yr. It also has a pulsar (PSRJ1856-3754) with a spin-down age of 3.76 Myr. That pulsar is likely to be the remnant of the supernova that drove away most of the gas. The central lobe has stars as early as B7 V and therefore an age of about 160 Myr or less. The Pleiades lobe has stars as early as B3 and therefore an age of about 50 Myr. There are no obvious pulsars that resulted from the supernovae that cleared out those areas. As found previously by Welsh and Lallement, the bubble has five B stars along its perimeter that show high-temperature ions of O VI and C II along their lines of sight, confirming its high interstellar temperature.

Abt, Helmut A., E-mail: abt@noao.edu [Kitt Peak National Observatory, P.O. Box 26732, Tucson, AZ 85726-6732 (United States)

2011-05-15

384

Transformation of deep-water methane bubbles into hydrate  

E-print Network

The paper is dedicated to the mechanics of the methane bubbles in the gas hydrate stability zone of the basin. Transformation of deep-water methane bubbles into solid hydrate was investigated in Lake Baikal in situ. Released from the bottom methane bubbles were caught by different traps with transparent walls. It was observed that when bubbles entered into internal space of the trap, the bubbles could be transformed into two different solid hydrate structures depending on ambient conditions. The first structure is hydrate granular matter consisted of solid fragments with sizes of order of 1 mm. The second structure is high porous solid foam consisted of solid bubbles with sizes of order of 5 mm. The formed granular matter did not change during trap lifting up to top border of gas hydrate stability zone, whereas free methane intensively released from solid foam sample during it lifting. It was concluded that the decrease of the depth of bubble sampling and the decrease of the bubble flux rate assist to formati...

Egorov, Alexander V; Rozhkov, Aleksey N

2013-01-01

385

Characterization of acoustic droplet vaporization for control of bubble generation under flow conditions.  

PubMed

This study investigated the manipulation of bubbles generated by acoustic droplet vaporization (ADV) under clinically relevant flow conditions. Optical microscopy and high-frequency ultrasound imaging were used to observe bubbles generated by 2-MHz ultrasound pulses at different time points after the onset of ADV. The dependence of the bubble population on droplet concentration, flow velocity, fluid viscosity and acoustic parameters, including acoustic pressure, pulse duration and pulse repetition frequency, was investigated. The results indicated that post-ADV bubble growth spontaneously driven by air permeation markedly affected the bubble population after insonation. The bubbles can grow to a stable equilibrium diameter as great as twice the original diameter in 0.5-1 s, as predicted by the theoretical calculation. The growth trend is independent of flow velocity, but dependent on fluid viscosity and droplet concentration, which directly influence the rate of gas uptake by bubbles and the rate of gas exchange across the wall of the semipermeable tube containing the bubbles and, hence, the gas content of the host medium. Varying the acoustic pressure does not markedly change the formation of bubbles as long as the ADV thresholds of most droplets are reached. Varying pulse duration and pulse repetition frequency markedly reduces the number of bubbles. Lengthening pulse duration favors the production of large bubbles, but reduces the total number of bubbles. Increasing the PRF interestingly provides superior performance in bubble disruption. These results also suggest that an ADV bubble population cannot be assessed simply on the basis of initial droplet size or enhancement of imaging contrast by the bubbles. Determining the optimal acoustic parameters requires careful consideration of their impact on the bubble population produced for different application scenarios. PMID:24433748

Kang, Shih-Tsung; Huang, Yi-Luan; Yeh, Chih-Kuang

2014-03-01

386

Bubble production mechanism in a microfluidic foam generator.  

PubMed

We present the design and characterization of a microfluidic bubble generator that has the potential of producing monodisperse bubbles in 256 production channels that can operate in parallel. For a single production channel we demonstrate a production rate of up to 4 kHz with a coefficient of variation of less than 1%. We observe a two-stage bubble production mechanism: initially the gas spreads onto a shallow terrace, and then overflows into a larger foam collection channel; pinning of the liquid-gas meniscus is observed at the terrace edge, the result being an asymmetric pinch-off. A semiempirical physical model predicts the scaling of bubble size with fluid viscosity and gas pressure from measurements of the pinned meniscus width. PMID:23003095

Stoffel, M; Wahl, S; Lorenceau, E; Höhler, R; Mercier, B; Angelescu, D E

2012-05-11

387

Pulsation of a spherical bubble in an incompressible fluid  

Microsoft Academic Search

In this paper we show that the main mechanism of inhibition of the collapsing cavity is the inertia of the gas within the cavity. We consider the pulsation of a spherical cavity in an incompressible fluid, taking into account the inertia of an ideal gas within the bubble. The motion of the gas is represented by the equations of gasdynamics

G. I. Bykovtsev; G. S. Rozarenov

1975-01-01

388

BURST OF STAR FORMATION DRIVES BUBBLE IN GALAXY'S CORE  

NASA Technical Reports Server (NTRS)

These NASA Hubble Space Telescope snapshots reveal dramatic activities within the core of the galaxy NGC 3079, where a lumpy bubble of hot gas is rising from a cauldron of glowing matter. The picture at left shows the bubble in the center of the galaxy's disk. The structure is more than 3,000 light-years wide and rises 3,500 light-years above the galaxy's disk. The smaller photo at right is a close-up view of the bubble. Astronomers suspect that the bubble is being blown by 'winds' (high-speed streams of particles) released during a burst of star formation. Gaseous filaments at the top of the bubble are whirling around in a vortex and are being expelled into space. Eventually, this gas will rain down upon the galaxy's disk where it may collide with gas clouds, compress them, and form a new generation of stars. The two white dots just above the bubble are probably stars in the galaxy. The close-up reveals that the bubble's surface is lumpy, consisting of four columns of gaseous filaments that tower above the galaxy's disk. The filaments disperse at a height of 2,000 light-years. Each filament is about 75 light-years wide. Velocity measurements taken by the Canada-France-Hawaii Telescope in Hawaii show that the gaseous filaments are ascending at more than 4 million miles an hour (6 million kilometers an hour). According to theoretical models, the bubble formed when ongoing winds from hot stars mixed with small bubbles of very hot gas from supernova explosions. Observations of the core's structure by radio telescopes indicate that those processes are still active. The models suggest that this outflow began about a million years ago. They occur about every 10 million years. Eventually, the hot stars will die, and the bubble's energy source will fade away. Astronomers have seen evidence of previous outbursts from radio and X-ray observations. Those studies show rings of dust and gas and long plumes of material, all of which are larger than the bubble. NGC 3079 is 50 million light-years from Earth in the constellation Ursa Major. The colors in this image accentuate important details in the bubble. Glowing gas is red and starlight is blue/green. Hubble's Wide Field and Planetary Camera 2 snapped this picture in 1998. The results appear in the July 1, 2001 issue of the Astrophysical Journal. Credits: NASA, Gerald Cecil (University of North Carolina), Sylvain Veilleux (University of Maryland), Joss Bland-Hawthorn (Anglo-Australian Observatory), and Alex Filippenko (University of California at Berkeley).

2002-01-01

389

6/10/12 The use of acoustic inversion to estimate the bubble size distribution in pipelines 1/2www.sciencedaily.com/releases/2012/05/120515104537.htm  

E-print Network

Physics Acoustics Reference Soap bubble Boiling point Boiling Superheating ScienceDaily (May 15, 20126/10/12 The use of acoustic inversion to estimate the bubble size distribution in pipelines 1/2www gas bubbles in pipelines. The ability to measure gas bubbles in pipelines is vital

Sóbester, András

390

The dynamics of histotripsy bubbles  

NASA Astrophysics Data System (ADS)

Histotripsy describes treatments in which high-amplitude acoustic pulses are used to excite bubbles and erode tissue. Though tissue erosion can be directly attributed to bubble activity, the genesis and dynamics of bubbles remain unclear. Histotripsy lesions that show no signs of thermal coagulative damage have been generated with two different acoustic protocols: relatively long acoustic pulses that produce local boiling within milliseconds and relatively short pulses that are higher in amplitude but likely do not produce boiling. While these two approaches are often distinguished as `boiling' versus `cavitation', such labels can obscure similarities. In both cases, a bubble undergoes large changes in radius and vapor is transported into and out of the bubble as it oscillates. Moreover, observations from both approaches suggest that bubbles grow to a size at which they cease to collapse violently. In order to better understand the dynamics of histotripsy bubbles, a single-bubble model has been developed that couples acoustically excited bubble motions to the thermodynamic state of the surrounding liquid. Using this model for bubbles exposed to histotripsy sound fields, simulations suggest that two mechanisms can act separately or in concert to lead to the typically observed bubble growth. First, nonlinear acoustic propagation leads to the evolution of shocks and an asymmetry in the positive and negative pressures that drive bubble motion. This asymmetry can have a rectifying effect on bubble oscillations whereby the bubble grows on average during each acoustic cycle. Second, vapor transport to/from the bubble tends to produce larger bubbles, especially at elevated temperatures. Vapor transport by itself can lead to rectified bubble growth when the ambient temperature exceeds 100 °C (`boiling') or local heating in the vicinity of the bubble leads to a superheated boundary layer.

Kreider, Wayne; Bailey, Michael R.; Sapozhnikov, Oleg A.; Khokhlova, Vera A.; Crum, Lawrence A.

2011-09-01

391

Mass Transport Phenomena Between Bubbles and Dissolved Gases in Liquids Under Reduced Gravity Conditions  

NASA Technical Reports Server (NTRS)

The long term objective of the experiment is to observe the dissolution of isolated, immobile gas bubbles of specified size and composition in a solvent liquid of known concentration in the reduced gravity environment of earth orbit. Preliminary bubble dissolution experiment conducted both in the NASA Lewis 2.2 sec drop tower and in normal gravity using SO2 - Toluene system were not completely successful in their objective. The method of gas injection and lack of bubble interface stabiliy experienced due to the extreme solubility of SO in Toluene has the effects of changing the problem from that of bubble dissolution to one of bubble formation stability and subsequent dissolution in a liquid of unknown initial solute concentration. Current work involves further experimentation in order to refine the bubble injection system and to investigate the concept of having a bubble with a critical radius in a state of unstable equilibrium.

Dewitt, K. J.; Brockwell, J. L.

1985-01-01

392

Colliding with a crunching bubble  

SciTech Connect

In the context of eternal inflation we discuss the fate of Lambda = 0 bubbles when they collide with Lambda< 0 crunching bubbles. When the Lambda = 0 bubble is supersymmetric, it is not completely destroyed by collisions. If the domain wall separating the bubbles has higher tension than the BPS bound, it is expelled from the Lambda = 0 bubble and does not alter its long time behavior. If the domain wall saturates the BPS bound, then it stays inside the Lambda = 0 bubble and removes a finite fraction of future infinity. In this case, the crunch singularity is hidden behind the horizon of a stable hyperbolic black hole.

Freivogel, Ben; Freivogel, Ben; Horowitz, Gary T.; Shenker, Stephen

2007-03-26

393

Observations of the collapses and rebounds of millimeter-sized lithotripsy bubbles  

PubMed Central

Bubbles excited by lithotripter shock waves undergo a prolonged growth followed by an inertial collapse and rebounds. In addition to the relevance for clinical lithotripsy treatments, such bubbles can be used to study the mechanics of inertial collapses. In particular, both phase change and diffusion among vapor and noncondensable gas molecules inside the bubble are known to alter the collapse dynamics of individual bubbles. Accordingly, the role of heat and mass transport during inertial collapses is explored by experimentally observing the collapses and rebounds of lithotripsy bubbles for water temperatures ranging from 20 to 60 °C and dissolved gas concentrations from 10 to 85% of saturation. Bubble responses were characterized through high-speed photography and acoustic measurements that identified the timing of individual bubble collapses. Maximum bubble diameters before and after collapse were estimated and the corresponding ratio of volumes was used to estimate the fraction of energy retained by the bubble through collapse. The rebounds demonstrated statistically significant dependencies on both dissolved gas concentration and temperature. In many observations, liquid jets indicating asymmetric bubble collapses were visible. Bubble rebounds were sensitive to these asymmetries primarily for water conditions corresponding to the most dissipative collapses. PMID:22088027

Kreider, Wayne; Crum, Lawrence A.; Bailey, Michael R.; Sapozhnikov, Oleg A.

2011-01-01

394

Observations of the collapses and rebounds of millimeter-sized lithotripsy bubbles.  

PubMed

Bubbles excited by lithotripter shock waves undergo a prolonged growth followed by an inertial collapse and rebounds. In addition to the relevance for clinical lithotripsy treatments, such bubbles can be used to study the mechanics of inertial collapses. In particular, both phase change and diffusion among vapor and noncondensable gas molecules inside the bubble are known to alter the collapse dynamics of individual bubbles. Accordingly, the role of heat and mass transport during inertial collapses is explored by experimentally observing the collapses and rebounds of lithotripsy bubbles for water temperatures ranging from 20 to 60 °C and dissolved gas concentrations from 10 to 85% of saturation. Bubble responses were characterized through high-speed photography and acoustic measurements that identified the timing of individual bubble collapses. Maximum bubble diameters before and after collapse were estimated and the corresponding ratio of volumes was used to estimate the fraction of energy retained by the bubble through collapse. The rebounds demonstrated statistically significant dependencies on both dissolved gas concentration and temperature. In many observations, liquid jets indicating asymmetric bubble collapses were visible. Bubble rebounds were sensitive to these asymmetries primarily for water conditions corresponding to the most dissipative collapses. PMID:22088027

Kreider, Wayne; Crum, Lawrence A; Bailey, Michael R; Sapozhnikov, Oleg A

2011-11-01

395

Effect of electrolytes on bubble coalescence in columns observed with visualization techniques.  

PubMed

Bubble coalescence and the effect of electrolytes on this phenomenon have been previously studied. This interfacial phenomenon has attracted attention for reactor design/operation and enhanced oil recovery. Predicting bubble coalescence may help prevent low yields in reactors and predict crude oil recovery. Because of the importance of bubble coalescence, the objectives of this work were to improve the accuracy of measuring the percentage of coalescing bubbles and to observe the interfacial gas-liquid behavior. An experimental setup was designed and constructed. Bubble interactions were monitored with a visualization setup. The percentage of air bubble coalescence was 100% in distilled water, about 50% in 0.1 M sodium chloride (NaCl) aqueous solution, and 0% in 0.145 M NaCl aqueous solution. A reduction of the contact gas-liquid area was observed in distillate water. The volume of the resulting bubble was the sum of the original bubble volumes. Repulsion of bubbles was observed in NaCl solutions exceeding 0.07 M. The percentage of bubble coalescence diminishes as the concentration of NaCl chloride increases. High-speed video recording is an accurate technique to measure the percentage of bubble coalescence, and represents an important advance in gas-liquid interfacial studies. PMID:12496024

Aguilera, María Eugenia; Ojeda, Antonieta; Rondón, Carolina; López De Ramos, Aura

2002-10-01

396

Structure and Dynamics of Anaerobic Bacterial Aggregates in a Gas-Lift Reactor  

PubMed Central

Anaerobic mixed-culture aggregates, which converted glucose to acetic, propionic, butyric, and valeric acids, were formed under controlled conditions of substrate feed (carbon limitation) and hydraulic regimen. The continuous-flow system used (anaerobic gas-lift reactor) was designed to retain bacterial aggregates in a well-mixed reactor. Carrier availability (i.e., liquid-suspended sand grains) proved necessary for bacterial aggregate formation from individual cells during reactor start-up. Electron microscopic examination revealed that incipient colonization of sand grains by bacteria from the bulk liquid occurred in surface irregularities, conceivably reflecting local quiescence. Subsequent confluent biofilm formation on sand grains proved to be unstable, however. Substrate depletion in the bulk liquid is assumed to weaken deeper parts of the biofilm due to cellular lysis, after which production of gas bubbles and liquid shearing forces cause sloughing. The resulting fragments, although sand free, were nevertheless large enough to be retained in the reactor and gradually grew larger through bacterial growth and by clumping together with other fragments. In the final steady state, high cell densities were maintained in the form of aggregates, while sand had virtually disappeared due to sampling losses and wash-out. Numerical cell densities within aggregates ranged from 1012/ml at the periphery to very low values in the center. The cells were enmeshed in a polymer matrix containing polysaccharides; nevertheless, carbon sufficiency was not a prerequisite to sustain high hold-up ratios. Images PMID:16347213

Beeftink, H. H.; Staugaard, P.

1986-01-01

397

Microfluidic Actuation Using Electrochemically Generated Bubbles  

E-print Network

Microfluidic Actuation Using Electrochemically Generated Bubbles Susan Z. Hua,*, Frederick Sachs, Buffalo, New York 14260 Bubble-based actuation in microfluidic applications is attractive owing of electrochemically generated bubble valves were studied. By generating electrochemical bubbles as valves directly

Sachs, Frederick

398

Mechanics of Bubbles in Sludges and Slurries Modeling Studies of Particulate Materials  

SciTech Connect

The Hanford Site has 177 underground waste storage tanks that are known to retain and release bubbles composed of flammable gases. Characterizing and understanding the behavior of these bubbles is important for the safety issues associated with the flammable gases for both ongoing waste storage and future waste-retrieval operations. The retained bubbles are known to respond to small barometric pressure changes, though in a complex manner with unusual hysteresis occurring in some tanks in the relationship between bubble volume and pressure, or V-P hysteresis. With careful analysis, information on the volume of retained gas and the interactions of the waste and the bubbles can be determined.

Phillip A. Gauglitz; Guillermo Terrones; Susan J. Muller; Morton M. Denn; William R. Rossen

2002-01-07

399

Bubble Point Measurements with Liquid Methane of a Screen Channel Capillary Liquid Acquisition Device  

NASA Technical Reports Server (NTRS)

Liquid acquisition devices (LADs) can be utilized within a propellant tank in space to deliver single-phase liquid to the engine in low gravity. One type of liquid acquisition device is a screened gallery whereby a fine mesh screen acts as a 'bubble filter' and prevents the gas bubbles from passing through until a crucial pressure differential condition across the screen, called the bubble point, is reached. This paper presents data for LAD bubble point data in liquid methane (LCH4) for stainless steel Dutch twill screens with mesh sizes of 325 by 2300. These tests represent the first known nonproprietary effort to collect bubble point data for LCH4.

Jurns, John M.; McQuillen, John B.; Gaby, Joseph D., Jr.; Sinacore, Steven A., Jr.

2009-01-01

400

Laboratory air bubble generation of various size distributions  

SciTech Connect

Air bubble size in aqueous environments is an important factor governing natural processes ranging from fluid/atmosphere gas transfer to noise production. Bubbles are also known to affect various scientific instruments. In this study we investigate the production capability of eight inexpensive bubble generators using optical imaging techniques. Specific emphasis is directed towards determining bubble size and distribution for a given device, flow conditions, and type of water used (fresh vs salt). In almost all cases tested here, bubbles produced in salt water were more numerous, and smaller than for the same bubbler and conditions in fresh water. For porous media, the finer the pore size, the smaller the bubble produced with some variation depending on thickness of material containing the pore and water type. While no single generator tested was capable of spanning all the bubble sizes observed (100 to 6000 microns), the data contained herein will enable proper choice of bubbler or combinations thereof for future studies depending on the size and distribution of bubbles required.

Puleo, Jack A.; Johnson, Rex V.; Kooney, Tim N. [Naval Research Laboratory, Marine Geosciences Division, Code 7440.3, Bldg 1005, Stennis Space Center, Mississippi 39529 (United States); University of Washington, Ocean Engineering Sciences, School of Oceanography, Box 367940, Seattle, Washington 98195 (United States); Naval Research Laboratory, Marine Geosciences Division, Code 7440.3, Bldg 1005, Stennis Space Center, Mississippi 39529 (United States)

2004-11-01

401

Bubble translation and deformation induced by ultrasound radiation force  

NASA Astrophysics Data System (ADS)

Measurement of small-bubble dynamics has been proposed for the remote evaluation of tissue elasticity [Erpelding et al., Proc. IEEE Ultrasonics Symp., 554-557, 2003]. For example, a microbubble can be produced within the cornea during femtosecond laser surgery and its response to a pulsed ultrasonic radiation force can be measured. The bubble's translation, deformation, and oscillation can be directly related to the mechanical properties of surrounding tissue information that is required for optimization of the surgical procedure. In the work reported here, a model was developed to predict the translation and deformation of an initially spherical bubble in a soft viscoelastic medium as induced by radiation pressure. The extent of bubble translation and deformation is dictated by the elastic stress and viscous forces that oppose the radiation pressure. Numerical simulations predict static, periodic, and transient translation of the bubble in response to continuous, periodic, and pulsed waveforms, respectively. The model also predicts the deformation of the bubble. The results indicate increased deformations with increased bubble translations. Overall, the model can be used to determine the local shear modulus and viscosity of the medium based on measurements of gas-bubble displacement. [Work supported by ARL:UT IR&D.

Ilinskii, Yurii A.; Meegan, G. Douglas; Zabolotskaya, Evgenia A.; Emelianov, Stanislav Y.

2001-05-01

402

Bubbles and Biosensors  

NSDL National Science Digital Library

Students work in groups to create soap bubbles on a smooth surface, recording their observations from which they formulate theories to explain what they see (color swirls on the bubble surfaces caused by refraction). Then they apply this theory to thin films in general, including porous films used in biosensors, listing factors that could change the color(s) that become visible to the naked eye, and learn how those factors can be manipulated to give information on gene detection. Finally (by experimentation or video), students see what happens when water is dropped onto the surface of a Bragg mirror.

Vu Bioengineering Ret Program

403

Magnetic-bubble conservative logic  

Microsoft Academic Search

Among integrated-circuit devices, magnetic bubbles are a particularly interesting candidate to implement the Fredkin gate and conservative logic. The magnetostatic repulsion of magnetic bubbles simulates the bouncing-ball model of conservative logic.

Hsu Chang

1982-01-01

404

Contact lens wear at altitude: subcontact lens bubble formation.  

PubMed

A concern in the past regarding contact lens wear in aviation has been the fear of subcontact lens bubble formation. Previous reports have documented the occurrence of bubbles with hard (PMMA) lenses. Reported here are the results of contact lens bubble studies with soft hydrophilic and rigid gas-permeable lenses. Testing was accomplished in hypobaric chambers and onboard USAF transport aircraft. Hypobaric chamber flights were of three types: high-altitude flights up to 7,620 m (25,000 ft); explosive rapid decompressions from 2,438.4 m (8,000 ft) to 7,620 m (25,000 ft); and 4-h flights at 3,048 m (10,000 ft). Flights aboard transport aircraft typically had cabin pressures equivalent to 1,524-2,438.4 m (5,000-8,000 ft), and ranged in duration from 3 to 10 h. For subjects wearing rigid gas-permeable lenses, central bubbles were detected in 2 of 10 eyes and occurred at altitudes greater than 6,096 m (20,000 ft). With soft contact lenses, bubble formation was detected in approximately 24% (22 of 92 eyes) of the eyes tested, sometimes occurring at altitudes as low as 1,828.8 m (6,000 ft). Soft lens bubbles were always located at the limbus and were without sequela to vision or corneal epithelial integrity. Bubbles under the rigid lenses were primarily central, with potential adverse effects on vision and the corneal epithelium. PMID:3689277

Flynn, W J; Miller, R E; Tredici, T J; Block, M G; Kirby, E E; Provines, W F

1987-11-01

405

Improving electrokinetic microdevice stability by controlling electrolysis bubbles.  

PubMed

The voltage-operating window for many electrokinetic microdevices is limited by electrolysis gas bubbles that destabilize microfluidic system causing noise and irreproducible responses above ?3 V DC and less than ?1 kHz AC at 3 Vpp. Surfactant additives, SDS and Triton X-100, and an integrated semipermeable SnakeSkin® membrane were employed to control and assess electrolysis bubbles from platinum electrodes in a 180 by 70 ?m, 10 mm long microchannel. Stabilized current responses at 100 V DC were observed with surfactant additives or SnakeSkin® barriers. Electrolysis bubble behaviors, visualized via video microscopy at the electrode surface and in the microchannels, were found to be influenced by surfactant function and SnakeSkin® barriers. Both SDS and Triton X-100 surfactants promoted smaller bubble diameters and faster bubble detachment from electrode surfaces via increasing gas solubility. In contrast, SnakeSkin® membranes enhanced natural convection and blocked bubbles from entering the microchannels and thus reduced current disturbances in the electric field. This data illustrated that electrode surface behaviors had substantially greater impacts on current stability than microbubbles within microchannels. Thus, physically blocking bubbles from microchannels is less effective than electrode functionalization approaches to stabilize electrokinetic microfluidic systems. PMID:24648277

Lee, Hwi Yong; Barber, Cedrick; Minerick, Adrienne R

2014-07-01

406

Bursting Bubbles and Bilayers  

PubMed Central

This paper discusses various interactions between ultrasound, phospholipid monolayer-coated gas bubbles, phospholipid bilayer vesicles, and cells. The paper begins with a review of microbubble physics models, developed to describe microbubble dynamic behavior in the presence of ultrasound, and follows this with a discussion of how such models can be used to predict inertial cavitation profiles. Predicted sensitivities of inertial cavitation to changes in the values of membrane properties, including surface tension, surface dilatational viscosity, and area expansion modulus, indicate that area expansion modulus exerts the greatest relative influence on inertial cavitation. Accordingly, the theoretical dependence of area expansion modulus on chemical composition - in particular, poly (ethylene glyclol) (PEG) - is reviewed, and predictions of inertial cavitation for different PEG molecular weights and compositions are compared with experiment. Noteworthy is the predicted dependence, or lack thereof, of inertial cavitation on PEG molecular weight and mole fraction. Specifically, inertial cavitation is predicted to be independent of PEG molecular weight and mole fraction in the so-called mushroom regime. In the “brush” regime, however, inertial cavitation is predicted to increase with PEG mole fraction but to decrease (to the inverse 3/5 power) with PEG molecular weight. While excellent agreement between experiment and theory can be achieved, it is shown that the calculated inertial cavitation profiles depend strongly on the criterion used to predict inertial cavitation. This is followed by a discussion of nesting microbubbles inside the aqueous core of microcapsules and how this significantly increases the inertial cavitation threshold. Nesting thus offers a means for avoiding unwanted inertial cavitation and cell death during imaging and other applications such as sonoporation. A review of putative sonoporation mechanisms is then presented, including those involving microbubbles to deliver cargo into a cell, and those - not necessarily involving microubbles - to release cargo from a phospholipid vesicle (or reverse sonoporation). It is shown that the rate of (reverse) sonoporation from liposomes correlates with phospholipid bilayer phase behavior, liquid-disordered phases giving appreciably faster release than liquid-ordered phases. Moreover, liquid-disordered phases exhibit evidence of two release mechanisms, which are described well mathematically by enhanced diffusion (possibly via dilation of membrane phospholipids) and irreversible membrane disruption, whereas liquid-ordered phases are described by a single mechanism, which has yet to be positively identified. The ability to tune release kinetics with bilayer composition makes reverse sonoporation of phospholipid vesicles a promising methodology for controlled drug delivery. Moreover, nesting of microbubbles inside vesicles constitutes a truly “theranostic” vehicle, one that can be used for both long-lasting, safe imaging and for controlled drug delivery. PMID:23382772

Wrenn, Steven P.; Dicker, Stephen M.; Small, Eleanor F.; Dan, Nily R.; Mleczko, Michal; Schmitz, Georg; Lewin, Peter A.

2012-01-01

407

Efflux time of soap bubbles and liquid spheres.  

PubMed

The efflux time, T, of gas from soap bubbles of radius, R, through their blow tube of length, 1, and radius, p, is given by the equation see pdf for equation where eta is the viscosity of the gas and omicron the surface tension of the bubble solution, all in centimeter-gram-second units. Similar relations between time and diameter were established for the flow from one bubble to another or from one bubble within another. The same relations hold for the flow of liquid spheres, suspended in another liquid of equal density, following Plateau's classic method. They have been extended to the flow of spheres to cylinders and catenoids of rotation. In all these cases the driving force is the surface or interfacial tension, creating an excess pressure as defined by Laplace's equation. PMID:17792780

Grosse, A V

1967-06-01

408

Modeling the dynamics of single-bubble sonoluminescence  

E-print Network

Sonoluminescence (SL) is the phenomenon in which acoustic energy is (partially) transformed into light. It may occur by means of many or just one bubble of gas inside a liquid medium, giving rise to the terms multi-bubble- and single-bubble sonoluminescence (MBSL and SBSL). In the last years some models have been proposed to explain this phenomenon, but there is still no complete theory for the light emission mechanism (especially in the case of SBSL). In this work, we will not address this more complicated particular issue, but only present a simple model describing the dynamical behaviour of the sonoluminescent bubble, in the SBSL case. Using simple numerical techniques within the software Matlab, we discuss solutions considering various possibilities for some of the parameters involved: liquid compressibility, superficial tension, viscosity, and type of gas. The model may be used as an introductory study of sonoluminescence in physics courses at undergraduate or graduate levels, as well as a quite clarifyi...

Vignoli, Lucas L; Thomé, Roberto C A; Nogueira, A L M A; Paschoal, Ricardo C; Rodrigues, Hilario

2014-01-01

409

Acoustic-wave effects in violent bubble collapse  

NASA Astrophysics Data System (ADS)

The effects of acoustic-wave propagation both outside and inside a radially collapsing and rebounding bubble are examined. This is done by comparing computational results produced by various reduced-model equations with benchmark results produced by numerical solution of the Euler equations under adiabatic conditions. Numerical inaccuracy associated with the moving bubble surface is avoided by means of a coordinate transformation that yields a fixed surface coordinate. Comparisons of calculated bubble-radius histories and peak surface pressures show that, while acoustic-wave effects in the external liquid are important, such effects in the internal gas are not.

Geers, Thomas L.; Lagumbay, Randy S.; Vasilyev, Oleg V.

2012-09-01

410

Effect of bubble frequency on bubble departure diameter in nucleate pool boiling  

SciTech Connect

A remarkably high heat flux can be obtained with a heat source of small temperature difference by generating a small amount of electrolytic hydrogen gas from a heating surface under nucleate boiling conditions. In order to elucidate the mechanisms involved in such a system and also in heat transfer in ordinary nucleate boiling, the diameter of escaping vapor bubble at the time of nucleate boiling under reduced pressure was investigated theoretically and experimentally. It was determined that an analytical model which considered the frequency of vapor bubble generation was able to explain relatively well the experimental values.

Nakayama, A.; Kano, M.

1983-07-01

411

Unsteady forces on spherical bubbles  

Microsoft Academic Search

An experimental investigation of freely rising spherical bubbles through a quiescent liquid is presented. The objective of the experiments is to examine the validity of a recently proposed history force expression for clean, spherical bubbles at finite Reynolds number (Mei et al. 1994). Excellent agreement between the measured and predicted bubble trajectory is obtained when using the proposed history force

W. C. Park; J. F. Klausner; R. Mei

1995-01-01

412

The Home Zone: Bubble Shapes  

NSDL National Science Digital Library

Few can resist a bubble wand and a brightly colored bottle of bubble solution. Although playing with bubbles might seem like just a fun outdoor activity, it is also an opportunity to explore some interesting science concepts related to soap, light, and color.

Damonte, Kathleen

2003-05-01

413

Bubbles Unbound: Bubbles of Nothing Without Kaluza-Klein  

E-print Network

I present analytic time symmetric initial data for five dimensions describing ``bubbles of nothing'' which are asymptotically flat in the higher dimensional sense, i.e. there is no Kaluza-Klein circle asymptotically. The mass and size of these bubbles may be chosen arbitrarily and in particular the solutions contain bubbles of any size which are arbitr