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1

GAS HOLDUP IN BAFFLED BUBBLE COLUMNS OF DILUTE SLURRIES OF FINE POWDERS AND VISCOUS LIQUIDS  

Microsoft Academic Search

Experimental gas phase holdup data reported by the authors as taken on two baffled bubble columns and involving slurries of fine powders (average particle diameter ?90 ?m) and dilute suspensions (mass fraction ? 20 percent) in viscous fluids are re-examined after correction for a small calculation error in superficial gas velocity. The two bubble columns are: a Plexiglas bubble column, 0.108 m in

S. C. SAXENA; N. S. RAO; Z. D. CHEN

1992-01-01

2

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

SciTech Connect

The influence of pressure, liquid viscosity, and gas velocity on the gas holdup and specific gas-liquid interfacial area in a bubble column reactor has been studied. The 18.7 L reactor had an inner diameter of 15.6 cm with a dispersion height set equal to 3 times the diameter and was operated at pressures between 0.1 and 6.6 MPa. By means of the chemically enhanced absorption of CO{sub 2} in diethanolamine, the gas-liquid interfacial area in the reactor has been determined. The viscosity has been changed in the range from 1 to 9.4 MPa{center_dot}s by adding ethylene glycol to the mixture. It is determined that pressure has a small effect on the gas holdup in pure water, whereas it shows a pronounced effect for the more viscous liquids. This can be attributed to the influence of the increased pressure on the flow regime transition. For the most viscous liquid all interfacial area data were obtained in the fully heterogeneous regime. Here the interfacial area increased with increasing pressure and was moderately affected by the gas velocity. For the less viscous liquids both pressure and gas velocity affect the interfacial area; this influence depends on the flow regime. Therefore, the state of the flow regime has an important impact on the mode in which the operating parameters affect the interfacial area.

Stegeman, D.; Knop, P.A.; Wijnands, A.J.G.; Westerterp, K.R. [Twente Univ. of Technology, Enschede (Netherlands)] [Twente Univ. of Technology, Enschede (Netherlands)

1996-11-01

3

Gas holdup in pulp fibre suspensions: Gas voidage profiles in a batch-operated sparged tower  

Microsoft Academic Search

Gas holdup in a semi-batch operated slurry (pulp fibre suspension) bubble column was investigated for two pulp types (softwood and hardwood kraft pulps) over a range of suspension mass concentrations (Cm=0–9% by mass) and superficial gas velocities (Ug=0.0027–0.027m\\/s). Three techniques were used: height difference between gassed and ungassed operation; pressure difference as a function column height; and electrical resistance tomography

L. K. Ishkintana; C. P. J. Bennington

2010-01-01

4

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

SciTech Connect

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 factor of four and, counter intuitively, that the holdup increased as the simulant shear strength decreased (apparent viscosity decreased). These results raised questions about how the AFA might affect gas holdup in Hanford Waste Treatment and Immobilization Plant (WTP) vessels mixed by air sparging and pulse-jet mixers (PJMs). And whether the WTP air supply system being designed would have the capacity to handle a demand for increased airflow to operate the sparger-PJM mixing systems should the AFA increase retention of the radiochemically generated flammable gases in the waste by making the gas bubbles smaller and less mobile, or decrease the size of sparger bubbles making them mix less effectively for a given airflow rate. A new testing program was developed to assess the potential effects of adding the DOW Corning Q2-3183A AFA to WTP waste streams by first confirming the results of the work reported in 2006 by Stewart et al. and then determining if the AFA in fact causes such increased gas holdup in a prototypic sparger-PJM mixing system, or if the increased holdup is just a feature of the small-scale agitation system. Other elements of the new program include evaluating effects other variables could have on gas holdup in systems with AFA additions such as catalysis from trace noble metals in the waste, determining mass transfer coefficients for the AZ-101 waste simulant, and determining whether other AFA compositions such as Dow Corning 1520-US could also increase gas holdup in Hanford waste. This new testing program was split into two investigations, prototypic sparger-PJM tests and modeling being conducted at the Pacific Northwest National Laboratory (PNNL), and small-scale agitation tests and evaluations of effects waste and AFA ingredients have on gas retention and mass transfer being conducted at SRNL. Only work conducted at SRNL is reported here. Key results are: (1) The unexpected gas holdup behavior reported in 2006 for a small-scale agitation system is confirmed. The gas holdup data from small-scale and bench-scale impeller-type mixing systems reported herein show very different trends than the behavior exhibited by the prototypic sparger-PJM mixing system tested in the PNNL APEL facility. Results obtained from testing this 1/4-scale prototypic mixing system will be reported by PNNL. The reason for this difference in holdup behavior between the two different mixing systems is not known at this time. Consequently, data from the small mechanical agitation systems should not be extrapolated to prototypic plant conditions. (2) Bench-scale and small-scale tests conducted with Dow Corning 1520-US AFA show it to be a viable replacement to Dow Corning Q2-3183A AFA. This alternative AFA will, however, require significantly higher dosage (concentration) to perform the same antifoam function. (3) Addition of noble metals to the AZ-101 waste simulant does not produce a catalytic gas retention effect with the AFA. The Gas holdup is similar whether or not noble metals are present in the AZ-101 simulant. (4) Mass transfer tests were performed in a large (0.76 m diameter) bubble column filled to 1.3, 3.4, and 7.4 m elevations with water and the AZ-101 waste simulant. Mass transfer coefficients for air bubbles emanating from a prototypic 0.051 m diameter sparger were obtained from the transient decay of dissolved oxygen concentration in the initially saturated fluids. Adding AFA to water reduces the mass transfer coefficient slightly. AFA addition reduces the mass transfer coefficient for AZ-101 simulant more than it does for water because the shear strength of the simulant allows for larger bubble sizes, and larger bubbles have smaller surf

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

2007-12-24

5

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

NASA Astrophysics Data System (ADS)

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

Jin, Haibo; Yuhuan, Han; Suohe, Yang

2009-02-01

6

A NEW EXPERIMENTAL CORRELATION USING A CURVE-SHAPED CAPACITANCE SENSOR TO PREDICT LIQUID HOLDUP IN VERTICAL GAS-CONDENSATE PIPELINES  

Microsoft Academic Search

The performance of a curve-shaped capacitance sensor for measuring the mean liquid holdup of the two-phase mixture of gas-condensate and nitrogen in a vertical pipeline was studied experimentally. The sensor consists of two electrodes placed on the external wall of a cylindrical test duct. The calibration curves for bubble, slug, and plug flow regimes were developed for vertical flow and

F. Esmaielzadeh; M. M. Izady; H. Moazzen J

2007-01-01

7

Field data test new holdup, pressure-loss calculations for gas, condensate pipelines  

Microsoft Academic Search

This second of three articles compares the performance of several pressure loss and holdup correlations, including those proposed in Part 1 (OGJ, Mar. 14, p. 55), against field data taken from three large-diameter gas and gas-condensate pipelines. The conclusion of this series continues these comparisons by presenting field data from two more pipelines.

A. Baker; K. Nielsen; A. Gabb

1988-01-01

8

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

Microsoft Academic Search

Electrical resistance tomography (ERT) is an advanced and new detecting technique that can measure and monitor the parameters of two-phase flow on line, such as gas-liquid bubble column. It is fit for the industrial process where the conductible medium serves as the disperse phase to present the key bubble flow characteristics in multi-phase medium. Radial variation of the gas holdup

Haibo Jin; Han Yuhuan; Yang Suohe

2009-01-01

9

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

10

Bubble columns with fine pore sparger operating in the pseudo-homogeneous regime: Gas hold up prediction and a criterion for the transition to the heterogeneous regime  

Microsoft Academic Search

New experimental data concerning the gas holdup in bubble columns equipped with porous sparger were acquired. The effect of liquid properties and sparger characteristic (i.e., pore size, dimensions) on gas holdup at the pseudo-homogeneous regime has been studied and a correlation regarding the prediction of the transition point from the pseudo-homogeneous to the heterogeneous regime has been proposed and found

N. A. Kazakis; I. D. Papadopoulos; A. A. Mouza

2007-01-01

11

Gas-liquid distribution in a bubble column using industrial gamma-ray computed tomography  

NASA Astrophysics Data System (ADS)

A gas absorption column used as a simulator bubble column for industrial processes was evaluated, using the third-generation industrial computed tomography developed at the IPEN. Gamma ray tomography experiments were carried out, using the simulator column empty and filled with water plus gas bubbling. The tomographic measurements were taken at three positions relative to the point of generation of the bubbles: above 20 mm, 120 mm and 320 mm. The resulting images describe the liquid or gas phase holdup distributions for bubbles generated in a hole of ?=5 mm, located at 15 mm of the column wall. The developed third generation CT had a spatial resolution of 4.5 mm and a temporal resolution around 5 h/image. The trend of bubble dispersions, as they rise in the column, was shown.

de Mesquita, Carlos Henrique; de Sousa Carvalho, Diego Vergaças; Kirita, Rodrigo; Vasquez, Pablo Antonio S.; Hamada, Margarida Mizue

2014-02-01

12

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

Microsoft Academic Search

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,

H Guerrero; C Charles Crawford; M Mark Fowley

2008-01-01

13

Measuring holdup in gas-liquid two-phase flow with ultrasonics  

SciTech Connect

The authors investigated the feasibility of using ultrasonic measurements to determine the volume fraction of gas (void fraction) in vertical upwards gas/liquid bubble flow in pipe. The measurements were performed with standard immersion-type ultrasonic transducers mounted on special traversing arms and facing each other across the inside diameter of the 7.25 in. ID acrylic pipe used in the study. The measurements were observed to be very sensitive to changes in void fraction; the ultrasonic extinction showed an exponential decay with increasing void fraction so that the signal intensity diminished by twelve orders of magnitude as the void fraction increased from 0 to about 13% in flow loop experiments and about five to eight orders of magnitude for the same range of void fractions for air bubbling through a stagnant water column. The change in extinction was found to be systematic and repeatable in both systems, but the rate of change with varying void fraction was different for each system. The different responses for the different systems are attributed to variations in bubble-size distributions and are predicted by the various theories of wave propagation in random media.

Maher, T.F. [Shell Offshore, New Orleans, LA (United States); Hill, A.D.; Morriss, S.L. [Univ. of Texas, Austin, TX (United States). Dept. of Petroleum and Geosystems Engineering

1996-09-01

14

Fission gas bubble behaviour in uranium dioxide  

NASA Astrophysics Data System (ADS)

A theoretical model developed to study the gas bubble evolution in nuclear materials has been used to analyze experiments on uranium dioxide irradiated to low burnups (0.1 and 0.4 at%), in which fission gas bubble size distributions were measured following out-of-pile isothermal anneals. Following irradiation, the UO 2 was annealed for 1 or 6 h each at temperatures between 1303 and 1973 K and then thinned for transmission electron microscopy observation of the bubble size distributions. The model is based on the assumption, that the coalescence of the moving bubbles is the main mechanism defining gas porosity development under these conditions. The gas bubbles are assumed to be in equilibrium and their motion is assumed to be caused by random migration. The calculations show that the observed bubble size distributions may be reproduced on the base of the bubble growth mechanisms considered. The joint action of bubble surface and volume diffusion mechanisms can explain both the general nature of the experimental distributions and their perculiarities, in particularly the bimodal bubble size distribution observed after annealing at 1673 K. The choice of appropriate values as input parameters into the model is discussed.

Chkuaseli, V. F.; Matzke, Hj.

15

Experimental investigation of bubble column hydrodynamics: Effect of elevated pressure and superficial gas velocity  

NASA Astrophysics Data System (ADS)

Bubble column reactors are widely used in the chemical and biochemical industries. They were reactors of choice in syngas conversion to clean fuels and chemicals. Most of the current applications of bubble column reactors in the chemical process industry require operation at high-pressure conditions. Further, to enhance the volumetric productivity, high gas flow rates are employed. The fundamental description of bubble column hydrodynamics under these conditions is very complex and complete understanding has not yet been established in spite of concerted research efforts. In order to improve our ability to quantify phenomena in bubble columns, it is essential that precise and quality experimental information is available to advance the state of the art in bubble column design and operation. In this study, measurements of gas holdup from Computed Tomography, and of time-averaged liquid velocity and turbulence from Computer Automated Radioactive Particle Tracking are obtained in a 6.4? diameter stainless steel bubble column at elevated pressure and at high superficial gas velocity with different gas spargers. It is shown quantitatively that deep in the churn-turbulent regime, gas holdup and liquid recirculation increase with pressure and superficial gas velocity while sparger effects are predominantly confined to the distributor zone. Additionally, an increase in pressure results in the reduction of turbulent normal stresses and eddy diffusivities most likely due to a reduction in bubble size. Based on the experimental data obtained from this study, a correction factor to the correlation of Zehner (1986) for predicting the centerline liquid velocity is developed to account for pressure effect on liquid recirculation. The correction factor indicates an one-eighth power dependency on gas density. Comparison of the experimentally estimated eddy viscosity with the model of Ohnuki and Akimoto (2001) suggests that the contribution of bubble-induced turbulence to the effective eddy viscosity is small as compared to that from the shear-induced turbulence. Though further studies are required to comprehend the pressure effects on larger diameter column, this study provides the first detail hydrodynamic data set at high pressure and very high superficial gas velocity.

Ong, Booncheng

16

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

17

Gas holdup, power consumption, and oxygen absorption coefficient in a stirred-tank fermentor under foam control.  

PubMed

For a laboratory stirred-tank fermentor (STF) with foaming system of 0.5M sulfite solution containing an anionic soft detergent, the performing of a foam-breaking apparatus with a rotating disk (FARD)fitted to the STF was evaluated. The gas holdup in a mechanical foam-control system (MFS), i.e., the stirred-tank fermentor with the rotating disk foambreaker, was confirmed to be larger than that in a nonfoaming system (NS), i.e., the STF with an antifoam agent added. The agitation power in the mechanical foam control system was found to be smaller compared with the agitation power in the nonfoaming system, due to the increased gas holdup. Comparison of the oxygen absorption coefficient between the mechanical foam control system and the nonfoaming system in terms of the specific power input also demonstrated the superiority of the mechanical foam control system, not only in oxygen transfer performance but also in power input economy. PMID:18604881

Yasukawa, M; Onodera, M; Yamagiwa, K; Ohkawa, A

1991-09-01

18

Wall-To-Bulk Mass Transfer in a Gas Liquid Upflow Bubble Column  

NASA Astrophysics Data System (ADS)

Experiments have been carried out to investigate the effect of liquid and gas velocities, viscosity and gas hold-up on wall-to-bulk mass transfer coefficient in a gas-liquid upflow bubble column using limiting current technique. The system chosen was an electrolyte as liquid phase and inert nitrogen as gas phase. The electrolyte was an equimolar solution of potassium ferricyanide and potassium ferrocyanide of 0.01 N with 0.5 N sodium hydroxide as indifferent electrolyte. To vary the viscosity carboxy methyl cellulose sodium salt (CMC) in 0.1, 0.2 and 0.4 wt% was added to the electrolyte. The reaction considered was the reduction of ferricyanide ion. The experiments were carried out at constant temperature of 25 °C at which the physical property values of the electrolyte were known from literature. The mass transfer coefficient was computed from the measured limiting current. It was found that the mass transfer coefficient was relatively independent of liquid velocity with in the range covered in the present experiment. The kL increased with increasing gas velocity and gas holdup. The kL was observed to decrease with increasing CMC concentration. The entire experimental data have been correlated in terms of Colburn j-factor, Reynolds number and modified Froude number.

Raju, G. M. J.; Ramesh, K. V.; Sarma, G. V. S.

2013-09-01

19

Gas bubble dynamics in soft materials.  

PubMed

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 solid. 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 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 an inviscid 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 of bubble growth, or to reduce the rate of bubble dissolution, respectively. The relation to previous work on visco-elastic materials is discussed, as is the connection of this work to the problem of Decompression Sickness (specifically, "the bends"). Examples of tissues to which our expressions can be applied are provided. Also, a new phenomenon is predicted whereby, for some parameter values, a bubble can be metastable and persist for long times, or it may grow, when embedded in a homogeneous under-saturated soft elastic medium. PMID:25382720

Solano-Altamirano, J M; Malcolm, John D; Goldman, Saul

2014-12-01

20

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

21

Performance of baffled bubble blood oxygenators.  

PubMed

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

Ohshima, N; Yoshido, F

1979-05-01

22

Standards for holdup measurement  

SciTech Connect

Holdup measurement, needed for material balance, depend intensively on standards and on interpretation of the calibration procedure. More than other measurements, the calibration procedure using the standard becomes part of the standard. Standards practical for field use and calibration techniques have been developed. While accuracy in holdup measurements is comparatively poor, avoidance of bias is a necessary goal.

Zucker, M.S.

1982-01-01

23

Gas Entrainment at the Bottom of a Taylor Bubble  

NASA Astrophysics Data System (ADS)

Gas entrainment phenomena in gas-liquid slug flows were investigated using a new experimental apparatus with a fixed, large gas bubble in which gas and liquid flow rates could be varied independently. Void fraction in the liquid slug due to small bubble entrainment was measured as were wall shear stress and film thickness. Experiments were performed in which the liquid viscosity was varied by a factor 2 and surface tension by a factor 6. It was found that the flow in the liquid slug consisted of 3 zones: a strongly turbulent mixing zone at the base of the fixed bubble dominated by a large vortical flow structure with a high void fraction and a shedding zone in which small bubbles were transferred down to the fully developed zone with uniform lower void fraction. The void fraction was uniform in the core of the flow, but there was a significant bubble-free wall layer. The PDF of bubble size was strongly dependent on the liquid viscosity and surface tension; decreasing surface tension generated smaller, less buoyant bubbles and consistently lower void fractions, as well as a much thinner void-free layer near the wall. At high liquid viscosity, the gas entrainment mechanism at the base of the fixed bubble was radically altered. These results provide important benchmarks for testing improved models of Taylor bubble slug flows.

Metcalfe, Ralph; Su, Chaoguang

1997-11-01

24

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

Microsoft Academic Search

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

Jr-Hung Tsai; Liwei Lin

2002-01-01

25

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

26

Dust and Gas Emission from MIR Bubble N56  

NASA Astrophysics Data System (ADS)

Mid-infrared (MIR) bubbles, identified in galactic surveys, have been extensively studied with the aim of understanding both their structure and influence on the surrounding interstellar medium. Studies of MIR bubbles aim to explore the relationship between bubble expansion and subsequent star formation. We present observations toward bubble N56 using the Herschel Space Telescope and Green Bank Telescope (GBT). The Herschel continuum observations indicate that N56 may be forming within a high mass-scale environment. The GBT NH3(1,1) and NH3(2,2) spectral line observations indicate evidence of line broadening and velocity changes coincident with the MIR-identified bubble rim. The temperature, density, and kinematics of the gas along the bubble rim are presented. We also discuss the relationship between the kinematics, physical properties, and star formation in N56.

Devine, Kathryn E.; Watson, Christer; Candelaria, Tierra; Rodriguez, Paula; Low, Cassiemarie; Pickett, Joseph

2015-01-01

27

Heat transfer investigations in a slurry bubble column  

Microsoft Academic Search

Slurry bubble columns, for use in Fisher-Tropsch synthesis, have been investigated. Two bubble columns (0.108 and 0.305 m internal diameter) were set up and experiments were conducted to determine gas holdup and heat transfer coefficients. These columns were equipped with either single heat transfer probes of different diameters, or bundles of five-, seven- or thirty-seven tubes. The experiments were conducted

S. C. Saxena; N. S. Rao; R. Vadivel; S. Shrivastav; A. C. Saxena; B. B. Patel; P. R. Thimmapuram; M. Y. Kagzi; I. A. Khan; A. K. Verma

1991-01-01

28

Heat transfer investigations in a slurry bubble column  

Microsoft Academic Search

Slurry bubble columns, for use in Fischer-Tropsch synthesis, have been investigated. Two bubble columns (0.108 and 0.305 m internal diameter) were set up and experiments were conducted to determine gas holdup and heat transfer coefficients. These columns were equipped with either single heat transfer probes of different diameters, or bundles of five-, seven-, or thirty-seven tubes. the experiments were conducted

S. C. Saxena; N. S. Rao; R. Vadivel; S. Shrivastav; A. C. Saxena; B. B. Patel; P. R. Thimmapuram; M. Y. Kagzi; I. A. Khan; A. K. Verma

1991-01-01

29

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

30

The formation of gas bubbles at submerged orifices  

E-print Network

L I B R A R Y A & M COLLEGE OF TEXAS THE FORMATION OF GAS BUBBLES AT SUBMERGED ORIFICES By William Bell Hayes III A Dissertation Submitted to the Graduate School of the Agricultural and Mechanical College of Texas in Partial Fulfillment... of the Requirements for the Degree DOCTOR OF PHILOSOPHY May 1958 Major Subject: Chemical Engineering THE FORMATION OF GAS BUBBLES AT SUBMERGED ORIFICES A Dissertation By William Bell Hayes III Approved as to style and content by: O. ___________ (Chairman...

Hayes, William Bell

2013-10-04

31

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

Microsoft Academic Search

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

G. Kreysa; M. Kuhn

1985-01-01

32

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

33

The role of gas in ultrasonically driven vapor bubble growth.  

PubMed

In this paper we study both experimentally and theoretically the dynamics of an ultrasound-driven vapor bubble of perfluoropentane (PFP) inside a droplet of the same liquid, immersed in a water medium superheated with respect to the PFP boiling point. We determine the temporal evolution of the bubble radius with ultra-high speed imaging at 20 million frames per second. In addition, we model the vapor-gas bubble dynamics, based on a Rayleigh-Plesset-type equation, including thermal and gas diffusion inside the liquid. We compare the numerical results with the experimental data and find good agreement. We underline the fundamental role of gas diffusion in order to prevent total recondensation of the bubble at collapse. PMID:23528293

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

2013-04-21

34

The role of gas in ultrasonically driven vapor bubble growth  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

35

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

36

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

Microsoft Academic Search

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

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

2001-01-01

37

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

38

Transient Flow Dynamics in Optical Micro Well Involving Gas Bubbles  

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

39

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

NASA Astrophysics Data System (ADS)

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

Mata, Clara E.

40

Modeling strong compression of a gas bubble in fluid  

Microsoft Academic Search

A technique for calculating strong adiabatic compression of a gas bubble in fluid is proposed. The compression results from\\u000a the pressure applied to the outer surface of the fluid. The motion of the fluid and gas is described by two-dimensional dynamic\\u000a equations of compressed fluid and gas with realistic equations of its state. The effects of viscosity and thermal conductivity

A. A. Aganin; M. A. Il’gamov; T. F. Khalitova

2009-01-01

41

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 components: The interface between the phases is tracked ex- plicitly by an unstructured, adaptive, triangular. Further, the SIMPLE flow solver is integrated with PARAMESH: a block-based, adaptive mesh refinement (AMR

Lin, Ping

42

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

Microsoft Academic Search

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

Wonyong Jang; Mustafa M. Aral

2003-01-01

43

Porosity formation and gas bubble retention in laser metal deposition  

NASA Astrophysics Data System (ADS)

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

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

2009-11-01

44

Measurement of bubble characteristics in a molten iron bath at 1600 °C using an electroresistivity probe  

NASA Astrophysics Data System (ADS)

A two-needle, electroresistivity probe was developed to measure bubble characteristics such as gas holdup, bubble frequency, and bubble rising velocity in a molten iron bath at 1600 °C. The probe’s electrode was made of a 0.5-mm platinum wire coated with ZrO2 cement and an outer coat of alumina as insulator. The life of this probe at 1600 °C was 15 to 20 minutes, making it possible to systematically measure bubble characteristics. The measured values of the bubble characteristics were compared with their respective empirical correlations derived from cold model experiments. Good agreement between the measured values and the empirical correlations was seen for each bubble characteristic. This electroresistivity probe allows us to measure bubble characteristics in actual metallurgical reactors with gas injection at high bath temperatures.

Iguchi, Manabu; Kawabata, Hirotoshi; Nakajima, Keiji; Morita, Zen-Ichiro

1995-02-01

45

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

46

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

Microsoft Academic Search

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

Bo Jin; Paul Lant

2004-01-01

47

Inert gas clusters ejected from bursting bubbles during sputtering.  

PubMed

Ar(+)(n) cluster ions (ngas bubbles. Subsequent ion formation is shown to take place by resonant charge exchange with incident primary Ar+ ions in the gas phase up to at least 175 microm above the surface. Xe+2 clusters are similarly produced from Xe+-bombarded solids. The ion intensities of Ar+2 and Xe+2 are found to have a characteristic second-order dependence on primary Ar+ or Xe+ current density. PMID:12906546

Franzreb, Klaus; Williams, Peter

2003-07-01

48

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

49

A computational model of gas bubble evolution in liquid filled straight tubes  

NASA Astrophysics Data System (ADS)

Deep sea divers suffer from decompression sickness (DCS) when their rate of ascent to the surface is too quick. When the ambient pressure drops, inert gas bubbles are usually formed in blood vessels and tissues of divers. It is believed that the existence of gas bubbles is the cause of DCS that manifests itself as itching, joint pain, and neurological abnormalities. While models of gas bubbles in tissues are relatively well developed, the mechanism of bubble growth in the circulation is far less well understood. The existence of gas bubbles may affect gas exchange in small blood vessels by blocking the flow of blood. Gas bubble evolution in the circulation is investigated using an analytical method for small bubbles and the boundary element method for bubbles whose effective radius is close to the tube radius. The concentration field for the dissolved gas surrounding the bubble is solved numerically using finite differences. The bubble volume is adjusted over time according to the mass flux at the surface. It is shown that the effect of increasing the flow rate is to enhance bubble evolution, up to a factor of two compared with the evolution in tissue where there is no flow. This work was supported by the Naval Medical Research and Development Command work unit 62233N.MM33P30.0041509.

Himm, Jeff; Halpern, David

1996-11-01

50

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

51

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

52

Characterization of breakdown and sustaining of a discharge in a gas bubble in water  

Microsoft Academic Search

Breakdown mechanism in water are not well understood. In the present study, we focus both on the ignition and propagation of the plasma in a bubble\\/water bi-phasic medium, as well as on the sustaining of DC plasmas in a gas bubble. Two geometries are studied : either the bubble is localized in a water filled capillary, or it is surrounded

P. Ceccato; A. Rousseau

2008-01-01

53

Prediction of radial gas profiles in vertical pipe flow on the basis of bubble size distribution  

Microsoft Academic Search

A method for the prediction of the radial gas profile for a given bubble size distribution is presented. It is based on the assumption of the equilibrium of the forces acting on a bubble perpendicularly to the flow direction. These forces strongly depend on the bubble size [14,18]. For the simulation of transient flow regime effects, the modelling of several

Dirk Lucas; Eckhard Krepper; Horst-Michael Prasser

2001-01-01

54

Characterization of the hydrodynamic flow regime in bubble columns via computed tomography  

Microsoft Academic Search

The current work evaluates the potential of Computed Tomography (CT) measurements for flow regime characterization. Experiments were carried out in a pilot scale (0.162 m diameter) bubble column using an air–Therminol LT system at ambient as well high operating pressures (0.4 and 1 MPa). The superficial gas velocities were varied from 1 to 20 cm\\/s at intervals of 1 cm\\/s. The steepness of the gas holdup

Ashfaq Shaikh; Muthanna Al-Dahhan

2005-01-01

55

Experimental investigation for liquid holdup reduction of subsea riser with surfactant  

Microsoft Academic Search

The principal pressure drop in a subsea riser is generally the gravitational pressure drop component due to liquid holdup. Surfactant is a kind of Chemical compound related to flow improvement. Gas-liquid two-phase flow in subsea riser with zero and small liquid flow rates was simulated in two vertical tubes with diameters of 40 mm and 65 mm, respectively. Liquid holdup

C. Li; L. Liu; Q. B. Bao; F. D. Zhou

2010-01-01

56

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

57

Pressure gradient, liquid hold-up and mass transfer in a graphite fibre bed with cocurrent upward gas–liquid flow  

Microsoft Academic Search

The pressure gradient, total liquid hold-up and overall mass transfer capacity for non-foaming co-current upward flow of oxygen\\/water and oxygen\\/1M NaOH through a bed of graphite felt were measured as part of a study of multiphase fluid dynamics in three-dimensional electrodes. Tests were done at 17–25°C in a bed of compressed graphite felt 356mm long, by 38mm wide by 3mm

I. Hodgson; C. Oloman

1999-01-01

58

Noble gas constraints on air-sea gas exchange and bubble fluxes  

NASA Astrophysics Data System (ADS)

Air-sea gas exchange is an important part of the biogeochemical cycles of many climatically and biologically relevant gases including CO2, O2, dimethyl sulfide and CH4. Here we use a three year observational time series of five noble gases (He, Ne, Ar, Kr, and Xe) at the Bermuda Atlantic Time series Study (BATS) site in tandem with a one-dimensional upper ocean model to develop an improved parameterization for air-sea gas exchange that explicitly includes separate components for diffusive gas exchange and bubble processes. Based on seasonal timescale noble gas data, this parameterization, which has a 1? uncertainty of ±14% for diffusive gas exchange and ±29% for bubble fluxes, is more tightly constrained than previous parameterizations. Although the magnitude of diffusive gas exchange is within errors of that of Wanninkhof (1992), a commonly used parameterization, we find that bubble-mediated exchange, which is not explicitly included by Wanninkhof (1992) or many other formulations, is significant even for soluble gases. If one uses observed saturation anomalies of Ar (a gas with similar characteristics to O2) and a parameterization of gas exchange to calculate gas exchange fluxes, then the calculated fluxes differ by ˜240% if the parameterization presented here is used compared to using the Wanninkhof (1992) parameterization. If instead one includes the gas exchange parameterization in a model, then the calculated fluxes differ by ˜35% between using this parameterization and that of Wanninkhof (1992). These differences suggest that the bubble component should be explicitly included in a range of marine biogeochemical calculations that incorporate air-sea gas fluxes.

Stanley, Rachel H. R.; Jenkins, William J.; Lott, Dempsey E.; Doney, Scott C.

2009-11-01

59

On the possibility of diffusionally driven oscillations in two component gas bubbles in fluids  

NASA Technical Reports Server (NTRS)

The problem of an isolated, stationary, two-component gas bubble in a fluid is analyzed. The appropriate governing equations, and an approximate version of these equations, for this model system are reviewed. The qualitative differences in bubble dissolution behavior between single- and two-component gas bubbles are elucidated. In particular, it is demonstrated that in the latter case the gas bubble radius may exhibit extrema as a function of time for certain values of the controlling parameters. The conditions under which these extrema may occur, and the maximum number of extrema which are permitted are elucidated.

Weinberg, Michael C.

1986-01-01

60

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

61

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

62

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

2012-01-01

63

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

SciTech Connect

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

Hang, T.

2000-07-19

64

Free energy wells for small gas bubbles in soft deformable materials  

NASA Astrophysics Data System (ADS)

Thermodynamic expressions are derived for the system relative Gibbs free energy, and the relative Gibbs free energy per bubble, for all possible equilibrium bubble states that can form in a soft slightly rigid material, initially supersaturated with a dissolved inert gas (N2). While the thermodynamic manipulations are exact, the final expressions are approximate, due to an approximation made in deriving the expression for the elastic free energy of a soft material containing more than a single bubble. The expressions predict that provided the shear modulus of the soft material is not negligibly small, free energy wells which stabilize small gas bubbles for finite periods of time exist in such materials. This is consistent with a previous calculation, based solely on the bubble pressure equation, which resulted in the conjecture that bubbles found in soft materials with some rigidity (or shear resistance) are likely to be small. The possible relevance of this to the field of decompression sickness is outlined.

Goldman, Saul

2010-04-01

65

Bubble Bubble  

NSDL National Science Digital Library

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

Mayer, Mercer

2009-11-11

66

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

NASA Technical Reports Server (NTRS)

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

Shelton, Robin L.

2003-01-01

67

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

Microsoft Academic Search

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

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

2003-01-01

68

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

SciTech Connect

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

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

1996-08-01

69

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

70

A molecular dynamics study of helium bubble formation and gas release near titanium surfaces  

NASA Astrophysics Data System (ADS)

Helium bubble formation and gas release near titanium surfaces have been studied using molecular dynamics. The results show that the formation of helium bubbles near a titanium surface is accompanied by the production of defects and the drift of defects toward the metal surfaces as well as an increase in the number of surface metal atoms. It is also shown that the helium bubbles burst at the mechanical stability limit of the metal. The metal surface morphology is modified by the bursting of the helium bubbles, with an increase in the surface roughness and the formation of surface pores as well as the re-deposition of the helium atoms. In contrast, the subsurface metal will retain its perfect crystal structure. The size of the resultant surface pore depends on the initial bubble diameter. For a small bubble, the pore can be healed by the thermal evolution of the substrate.

Zhang, B. L.; Wang, J.; Li, M.; Hou, Q.

2013-07-01

71

Effect of gas expansion on the front shape of a Taylor bubble: an experimental contribution  

NASA Astrophysics Data System (ADS)

An experimental study where an individual Taylor bubble rises through water with different bubble volume expansion rates is presented with the (front) bubble shape determination as main objective. A combination of two techniques, Particle Image Velocimetry (PIV) and Pulsed Shadowgraphy (PS), was used to collect images for further treatment in order to characterize the liquid flow pattern in front of the bubble and the bubble shape. Processing the images acquired with pulsed illumination from behind the bubble it was possible to define with precision the bubble shape at different stages when it was expanding. The operation conditions used allowed a wide range of volume expansion rates (0 to 28.5 × 10-6 m3/s) with a significant effect on the Taylor bubble velocity; increases in bubble velocity up to 21% were observed relatively to constant volume system condition. Nevertheless, it seems that the front shape of Taylor bubbles does not change significantly with the upward liquid flow rates induced by gas expansion, at least for the volume expansion rates used in the experiments.

Santos, Laura; Esteves, Teresa; Coelho Pinheiro, Nazaré

2014-03-01

72

Application of the boundary integral method to the interaction of rising two-dimensional deformable gas bubbles  

Microsoft Academic Search

The boundary integral method is applied to model the initial motion of two-dimensional or cylindrical deformable gas bubbles in an inviscid, incompressible fluid. Following the success of recent boundary integral studies to predict the qualitative behaviour of a single gas bubble, this numerical study is extended to consider the interaction of several bubbles. Surface tension, relative initial position and volume

P. B. Robinson; J. M. Boulton-Stone; J. R. Blake

1995-01-01

73

Heat transfer investigations in a slurry bubble column  

SciTech Connect

Slurry bubble columns, for use in Fischer-Tropsch synthesis, have been investigated. Two bubble columns (0.108 and 0.305 m internal diameter) were set up and experiments were conducted to determine gas holdup and heat transfer coefficients. These columns were equipped with either single heat transfer probes of different diameters, or bundles of five-, seven-, or thirty-seven tubes. the experiments were conducted for two- and three phase systems; employing for gas phase: air and nitrogen, liquid phase: water and Therminol-66, and solid phase: red iron oxide (1.02, 1.70 and 2.38 {mu}m), glass beads (50.0, 90.0, 119.0 and 143.3 {mu}m), silica sand (65 {mu}m), and magnetite (28.0, 35.7, 46.0, 58.0, 69.0, 90.5, 115.5 and 137.5 {mu}m). The column temperature was varied between 298--523 K, gas velocity between 0--40 cm/s, and solids concentration between 0--50 weight percent. The holdup and heat transfer data as a function of operating and system parameters were employed to assess the available correlations and semitheoretical models, and to develop new correlations. Information concerning the design and scale-up of larger units is presented. Specific research work that need to be undertaken to understand the phenomena of heat transfer and gas holdup is outlined so that efficient gas conversion and catalyst usage may be accomplished in slurry bubble columns. 28 refs., 102 figs., 42 tabs.

Saxena, S.C.; Rao, N.S.; Vadivel, R.; Shrivastav, S.; Saxena, A.C.; Patel, B.B.; Thimmapuram, P.R.; Kagzi, M.Y.; Khan, I.A.; Verma, A.K.

1991-02-01

74

Heat transfer investigations in a slurry bubble column  

SciTech Connect

Slurry bubble columns, for use in Fisher-Tropsch synthesis, have been investigated. Two bubble columns (0.108 and 0.305 m internal diameter) were set up and experiments were conducted to determine gas holdup and heat transfer coefficients. These columns were equipped with either single heat transfer probes of different diameters, or bundles of five-, seven- or thirty-seven tubes. The experiments were conducted for two- and three-phase systems; employing for gas phase: air and nitrogen, liquid phase: water and Therminol-66, and solid phase: red iron oxide (1.02, 1.70 and 2.38 {mu}m), glass beads (50.0, 90.0, 119.0 and 143.3 {mu}m), silica sand (65 {mu}), and magnetite (28.0, 35.7, 46.0, 58.0, 69.0, 90.5, 115.5, and 137.5 {mu}m). The column temperature was varied between 298--523 K, gas velocity between 0--40 cm/s, and solids concentration between 0--50 weight percent. The holdup and heat transfer data as a function of operating and system parameters were employed to assess the available correlations and semitheoretical models, and to develop new correlations. Information concerning the design and scale-up of larger units is presented. Specific research work that need to be undertaken to understand the phenomena of heat transfer and gas holdup is outlined so that efficient gas conversion and catalyst usage may be accomplished in slurry bubble columns. 130 refs., 177 figs., 54 tabs.

Saxena, S.C.; Rao, N.S.; Vadivel, R.; Shrivastav, S.; Saxena, A.C.; Patel, B.B.; Thimmapuram, P.R.; Kagzi, M.Y.; Khan, I.A.; Verma, A.K.

1991-02-01

75

Controlling bubbles using bubbles--microfluidic synthesis of ultra-small gold nanocrystals with gas-evolving reducing agents.  

PubMed

Microfluidic wet-chemical synthesis of nanoparticles is a growing area of research in chemical microfluidics, enabling the development of continuous manufacturing processes that overcome the drawbacks of conventional batch-based synthesis methods. The synthesis of ultra-small (<5 nm) metallic nanocrystals is an interesting area with many applications in diverse fields, but is typically very challenging to accomplish in a microfluidics-based system due to the use of a strong gas-evolving reducing agent, aqueous sodium borohydride (NaBH(4)), which causes uncontrolled out-gassing and bubble formation, flow disruption and ultimately reactor failure. Here we present a simple method, rooted in the concepts of multiphase mass transfer that completely overcomes this challenge-we simply inject a stream of inert gas bubbles into our channels that essentially capture the evolving gas from the reactive aqueous solution, thereby preventing aqueous dissolved gas concentration from reaching the solubility threshold for bubble nucleation. We present a simple model for coupled mass transfer and chemical reaction that adequately captures device behaviour. We demonstrate the applicability of our method by synthesizing ultra-small gold nanocrystals (<5 nm); the quality of nanocrystals thus synthesized is further demonstrated by their use in an off-chip synthesis of high-quality gold nanorods. This is a general approach that can be extended to a variety of metallic nanomaterials. PMID:22456754

Khan, Saif A; Duraiswamy, Suhanya

2012-04-24

76

Effects of different gas phases and gas bubbles on the nucleation kinetics.  

PubMed

In this study, the effects of different gas phases and gas bubbles on the Induction time were investigated. In the first step, the effects of different kinds of gases (N(2), Ar, dry air-N(2) and dry air-Ar) which are fed into solution-gas interphase and into the solution were determined. After determining the most effective gas upon the Induction time, the next step was to use this gas in the presence of the seed crystals, to specify variation in the Induction time. The experimental results show that gassing and the presence of seed crystal tend to shorten the Induction time as compared to the normal crystallization condition. PMID:25125123

Ceyhan, Ayhan Abdullah; Baytar, Orhan; Pehlivan, Erol

2014-01-01

77

Acceleration of Gas Bubble-Free Surface Interaction Computation Using Basis Preconditioners  

E-print Network

The computation of gas bubble-free surface interaction entails a time-stepping algorithm whereby a linear system is solved at each time-iteration. In our investigation, the linear systems are derived from a desingularized ...

Tan, Kiok Lim

78

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

SciTech Connect

Flow characteristics of fibrous paper pulp-water-air slurries were investigated in a vertical circular column 1.8 m long, with 5.08 cm diameter. Flow structures, gas holdup (void fraction), and the geometric and population characteristics of gas bubbles were experimentally investigated, using visual observation, Gamma-ray densitometry, and flash X-ray photography. Five distinct flow regimes could be visually identified: dispersed bubbly, layered bubbly, plug, churn-turbulent, and slug. Flow regime maps were constructed, and the regime transition lines were found to be sensitive to consistency. The feasibility of using artificial neural networks (ANNs) for the identification of the flow regimes, using the statistical characteristics of pressure fluctuations measured by a single pressure sensor, was demonstrated. Local pressure fluctuations at a station were recorded with a minimally-intrusive transducer. Three-layer, feed-forward ANNs were designed that could identify the four major flow patterns (bubbly, plug, churn, and slug) well. The feasibility of a transportable artificial neural network (ANN) - based technique for the classification of flow regimes was also examined. Local pressures were recorded at three different locations using three independent but similar transducers. An ANN was designed, trained and successfully tested for the classification of the flow regimes using one of the normalized pressure signals (from Sensor 1). The ANN trained and tested for Sensor 1 predicted the flow regimes reasonably well when applied directly to the other two sensors, indicating a good deal of transportability. An ANN-based method was also developed, whereby the power spectrum density characteristics of other sensors were adjusted before they were used as input to the ANN that was based on Sensor 1 alone. The method improved the predictions. The gas-liquid interfacial surface area concentration was also measured in the study. The gas absorption technique was applied, using CO2 as the transferred species and sodium hydroxide as the alkaline agent in water. Statistical analysis was performed to identify the parametric dependencies. The experimental data were empirically correlated.

S.M. Ghiaasiaan and Seppo Karrila

2006-03-20

79

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

SciTech Connect

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

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

2013-05-15

80

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

81

Mathematical Model For Bubbly Water-Heavy Oil-Gas Flow in Vertical Pipes  

Microsoft Academic Search

In this work a unidimensional, time-dependent homogeneous mathematical model is presented. The model is able to predict pressure, temperature and velocity profiles of the flow known as bubbly-gas—bubbly-oil, which can be present when water-heavy oil and gas flow simultaneously in vertical pipes. The mathematical model consists of mass, momentum, and energy conservation equations and its numerical solution is based on

O. Cazarez-Candia; D. Montoya-Hernández; A. G. Vital-Ocampo

2009-01-01

82

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

83

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

84

Holdup measurement for nuclear fuel manufacturing plants  

SciTech Connect

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

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

1981-07-13

85

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

Microsoft Academic Search

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

G. K. Westbrook

2009-01-01

86

Effects of Intergranular Gas Bubbles on Thermal Conductivity  

SciTech Connect

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

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

2012-11-01

87

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

88

Secondary Vortex Formation in Bifurcated Submerged Entry Nozzles: Numerical Simulation of Gas Bubble Entrapment  

NASA Astrophysics Data System (ADS)

The submerged entry nozzle (SEN) flow behavior is crucial for continuous casting of slab steel since it controls the mold flow pattern. In this study, we focus on the bottom zone of a bifurcated SEN where the flow deflection determines the port outflow. By applying a hybrid finite volume and lattice Boltzmann-based turbulence model, the dynamic behavior of horizontally orientated secondary vortices is investigated. In addition to the pure liquid metal flow, gas bubbles are traced in both discrete and continuous way. Simulation results indicate the existence of highly turbulent secondary vortices in the deflection zone of a bifurcated SEN, which attract gas bubbles in form of bubble threads or continuous gas volumes at their rotational axes. In addition, cyclically detaching gas volumes are formed at the upper port region at higher gas flow rates. Numerical predictions agree well with observations from physical water-air models.

Pirker, Stefan; Kahrimanovic, Damir; Schneiderbauer, Simon

2014-12-01

89

Development of New Geothermal Wellbore Holdup Correlations Using Flowing Well Data  

SciTech Connect

An ability to predict both the quantity of fluid that can be produced and its thermodynamic state (pressure, temperature, enthalpy, gas content, salinity, etc.) is essential for estimating the total usable energy of a geothermal resource. Numerical reservoir simulators can be utilized to calculate the thermodynamic state of the fluid at the underground feed-zone(s) at which the fluid enters the wellbore. The computation of the well-head fluid properties from a given underground state (or vice-versa) requires the use of a wellbore simulator. The fluid flow in the wellbore is not amenable to strict analytical treatment. Depending upon the relative amounts of gas and liquid, a variety of flow patterns can occur in the pipe. At small gas loadings, bubble flow takes place. An increase in gas flow rate can result in slug, churn or annular flow. Existing methods for treating two-phase flow in a wellbore require use of empirical correlations for action factor and for liquid hold-up.

Garg, S.K.; Pritchett, J.W.; Alexander, J.H.

2004-03-01

90

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

91

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

92

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

SciTech Connect

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

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

1986-06-01

93

Heating the bubbly gas of galaxy clusters with weak shocks and sound waves  

E-print Network

Using hydrodynamic simulations and a technique to extract the rotational component of the velocity field, we show how bubbles of relativistic gas inflated by AGN jets in galaxy clusters act as a catalyst, transforming the energy carried by sound and shock waves to heat. The energy is stored in a vortex field around the bubbles which can subsequently be dissipated. The efficiency of this process is set mainly by the fraction of the cluster volume filled by (sub-)kpc scale filaments and bubbles of relativistic plasma.

S. Heinz; E. Churazov

2005-07-01

94

Gas bubble formation in fused silica generated by ultra-short laser pulses.  

PubMed

During processing of glass using ultra-fast lasers the formation of bubble-like structures can be observed in several glass types such as fused silica. Their formation can be exploited to generate periodic gratings in glasses but for other glass processing techniques such as waveguide-writing or glass welding by ultra-fast lasers the bubble formation proves often detrimental. In this work we present experiments and their results in order to gain understanding of the origins and on the underlying formation and transportation mechanisms of the gas bubbles. PMID:24977843

Cvecek, Kristian; Miyamoto, Isamu; Schmidt, Michael

2014-06-30

95

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

SciTech Connect

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

Paul C. Millett; Michael Tonks

2011-06-01

96

On the forced oscillations of a small gas bubble in a spherical liquid-filled flask  

Microsoft Academic Search

A spherically-symmetric problem is considered in which a small gas bubble at the centre of a spherical flask filled with a compressible liquid is excited by small radial displacements of the flask wall. The bubble may be compressed, expanded and made to undergo periodic radial oscillations. Two asymptotic solutions have been found for the low-Mach-number stage. The first one is

R. I. Nigmatulin; I. Sh. Akhatov; N. K. Vakhitova; R. T. Lahey

2000-01-01

97

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

98

Nonlinear oscillations of gas bubbles submerged in water: implications for plasma breakdown  

NASA Astrophysics Data System (ADS)

Gas bubbles submerged in a dielectric liquid and driven by an electric field can undergo dramatic changes in both shape and volume. In certain cases, this deformation can enhance the distribution of the applied field inside the bubble as well as decrease the internal gas pressure. Both effects will tend to facilitate plasma formation in the gas volume. A practical realization of these two effects could have a broad impact on the viability of liquid plasma technologies, which tend to suffer from high voltage requirements. In this experiment, bubbles of diameter 0.4-0.7 mm are suspended in the node of a 26.4 kHz underwater acoustic standing wave and excited into nonlinear shape oscillations using ac electric fields with amplitudes of 5-15 kV cm-1. Oscillations of the deformed bubble are photographed with a high-speed camera operating at 5130 frames s-1 and the resulting images are decomposed into their axisymmetric spherical harmonic modes, Y_l^0 , using an edge detection algorithm. Overall, the bubble motion is dominated by the first three even modes l = 0, 2 and 4. Electrostatic simulations of the deformed bubble's internal electric field indicate that the applied field is enhanced by as much as a factor of 2.3 above the nominal applied field. Further simulation of both the pure l = 2 and l = 4 modes predicts that with additional deformation, the field enhancement factors could reach as much as 10-50.

Sommers, B. S.; Foster, J. E.

2012-10-01

99

The hydroacoustic method for the quantification of the gas flux from a submersed bubble plume  

NASA Astrophysics Data System (ADS)

This article presents an inverse hydroacoustic method for the remote quantification of the total gas flux transported from an underwater bubble plume. The method includes the surveying of the bubble plume by a vertically looking echo sounder and the calculation of the flux using the spatial distribution of the ultrasound backscattering at a fixed depth. A simplified parameterization containing only a few parameters is introduced to describe the empirical bubble size distribution. The linear correlation between the backscattering cross section of the bubble stream and the vertical gas flux is found. The calculation procedure takes into account the occurrence of a gas hydrate film at the bubble's surface. The influence of different parameters on the accuracy of the method is investigated. The resolution volume of the echo sounder corresponding to the fixed distance is considered as a two-dimensional spatial window. The method was applied to quantify the total convective methane flux at the Haakon-Mosby mud volcano (HMMV) depth 1280 m. The calculated values of the total flux near the bottom (100-400 t/year) are in good agreement with the independently estimated flux for the single bubble jet observed from the ROV (70 t/year). These calculations also show significant temporal variability of the flux at the HMMV. The total flux was found to vary by about a factor of 2-3 within time scales of days.

Muyakshin, S. I.; Sauter, E.

2010-12-01

100

Gas, dust, and star formation in the IR dust bubble S 24  

NASA Astrophysics Data System (ADS)

Based on molecular line and dust continuum data obtained with the APEX telescope, and IR images at different wavelengths, we investigate the gas and dust distributions in the environs of the IR dust bubble S 24 and determine the main physical parameters of the molecular gas.

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

2014-10-01

101

An advanced LIF-PLV system for analysing the hydrodynamics in a laboratory bubble column at higher void fractions  

NASA Astrophysics Data System (ADS)

Bubble columns are widely used in the chemical industry and biotechnology. Flow and turbulence in such an apparatus are induced by the bubble rise, and the bubble behaviour is strongly affected by swarm effects (i.e. the interaction between bubbles). For analysing the bubble swarm behaviour and simultaneously evaluating the flow structure and bubble-induced turbulence, a bubble column of 140 mm diameter and a height of 650 mm or 1,400 mm (initial water level) were considered. The bubble column was aerated with relatively fine bubbles having a mean size between about 0.5 and 4.0 mm. The gas hold-up was varied in the range between 0.5 and 19%. A two-phase pulsed-light velocimetry (PLV) system was developed to evaluate instantaneous flow fields of both rising bubbles and the continuous phase. The measurement of the liquid velocities in the bubble swarm was achieved by adding fluorescing seed particles. Images of bubbles and fluorescing tracer particles were acquired by two CCD cameras. Hence, the images from tracers and bubbles were easily separated by optical interference filters with a bandwidth corresponding to the emitting wavelength of the fluorescing tracer particles and the wavelength of the applied Nd-YAG pulsed laser, respectively. To improve the phase separation of the system, the CCD cameras were additionally placed in a non-perpendicular arrangement with respect to the light sheet. The acquired images were evaluated with the minimum-quadratic-difference algorithm. The potential of this technique for the analysis of bubbly flows with higher void fraction was explored. In order to obtain averaged velocity maps of bubble and fluid within the entire column, about 1,000 image pairs were recorded and evaluated for each phase. In addition, turbulence intensities of the fluid were deduced from the measurements. The turbulence properties were used to characterise bubble-induced turbulence for various bubble mean diameters and gas hold-ups. Moreover, the determination of the average bubble slip velocity within the bubble swarm was possible.

Bröder, D.; Sommerfeld, M.

2002-08-01

102

Modeling the influence of bubble pressure on grain boundary separation and fission gas release  

SciTech Connect

Grain boundary (GB) separation as a mechanism for fission gas release (FGR), complementary to gas bubble interlinkage, has been experimentally observed in irradiated light water reactor fuel. However there has been limited effort to develop physics-based models incorporating this mechanism for the analysis of FGR. In this work, a computational study is carried out to investigate GB separation in UO2 fuel under the effect of gas bubble pressure and hydrostatic stress. A non-dimensional stress intensity factor formula is obtained through 2D axisymmetric analyses considering lenticular bubbles and Mode-I crack growth. The obtained functional form can be used in higher length-scale models to estimate the contribution of GB separation to FGR.

Pritam Chakraborty; Michael R. Tonks; Giovanni Pastore

2014-09-01

103

Creating Small Gas Bubbles in Flowing Mercury Using Turbulence at an Orifice  

SciTech Connect

Pressure waves created in liquid mercury pulsed spallation targets have been shown to create cavitation damage to 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, creating such a population in mercury is difficult due to the high surface tension and particularly the non-wetting behavior of mercury on gas-injection hardware. If the larger injected gas bubbles can be broken down into small bubbles after they are introduced to the flow, then the material interface problem is avoided. Research at the Oak Ridge National Labarotory is underway to develop a technique that has shown potential to provide an adequate population of small-enough bubbles to a flowing spallation target. This technique involves gas injection at an orifice of a geometry that is optimized to the turbulence intensity and pressure distribution of the flow, while avoiding coalescence of gas at injection sites. The most successful geometry thus far can be described as a square-toothed orifice having a 2.5 bar pressure drop in the nominal flow of 12 L/s for one of the target inlet legs. High-speed video and high-resolution photography have been used to quantify the bubble population on the surface of the mercury downstream of the gas injection sight. Also, computational fluid dynamics has been used to optimize the dimensions of the toothed orifice based on a RANS computed mean flow including turbulent energies such that the turbulent dissipation and pressure field are best suited for turbulent break-up of the gas bubbles.

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

2010-01-01

104

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

105

Automated gas bubble imaging at sea floor - a new method of in situ gas flux quantification  

NASA Astrophysics Data System (ADS)

Photo-optical systems are common in marine sciences and have been extensively used in coastal and deep-sea research. However, due to technical limitations in the past photo images had to be processed manually or semi-automatically. Recent advances in technology have rapidly improved image recording, storage and processing capabilities which are used in a new concept of automated in situ gas quantification by photo-optical detection. The design for an in situ high-speed image acquisition and automated data processing system is reported ("Bubblemeter"). New strategies have been followed with regards to back-light illumination, bubble extraction, automated image processing and data management. This paper presents the design of the novel method, its validation procedures and calibration experiments. The system will be positioned and recovered from the sea floor using a remotely operated vehicle (ROV). It is able to measure bubble flux rates up to 10 L/min with a maximum error of 33% for worst case conditions. The Bubblemeter has been successfully deployed at a water depth of 1023 m at the Makran accretionary prism offshore Pakistan during a research expedition with R/V Meteor in November 2007.

Thomanek, K.; Zielinski, O.; Sahling, H.; Bohrmann, G.

2010-02-01

106

Automated gas bubble imaging at sea floor - a new method of in situ gas flux quantification  

NASA Astrophysics Data System (ADS)

Photo-optical systems are common in marine sciences and have been extensively used in coastal and deep-sea research. However, due to technical limitations in the past photo images had to be processed manually or semi-automatically. Recent advances in technology have rapidly improved image recording, storage and processing capabilities which are used in a new concept of automated in situ gas quantification by photo-optical detection. The design for an in situ high-speed image acquisition and automated data processing system is reported ("Bubblemeter"). New strategies have been followed with regards to back-light illumination, bubble extraction, automated image processing and data management. This paper presents the design of the novel method, its validation procedures and calibration experiments. The system will be positioned and recovered from the sea floor using a remotely operated vehicle (ROV). It is able to measure bubble flux rates up to 10 L/min with a maximum error of 33% for worst case conditions. The Bubblemeter has been successfully deployed at a water depth of 1023 m at the Makran accretionary prism offshore Pakistan during a research expedition with R/V Meteor in November 2007.

Thomanek, K.; Zielinski, O.; Sahling, H.; Bohrmann, G.

2010-06-01

107

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

108

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

109

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

SciTech Connect

This report can be divided into two parts: the first part, which is composed of sections 1, 2, and 3, is devoted to report the analyses of fission gas bubbles; the second part, which is in section 4, is allocated to describe the mechanistic model development. Swelling data of irradiated U-Mo alloy typically show that the kinetics of fission gas bubbles is composed of two different rates: lower initially and higher later. The transition corresponds to a burnup of {approx}0 at% U-235 (LEU) or a fission density of {approx}3 x 10{sup 21} fissions/cm{sup 3}. Scanning electron microscopy (SEM) shows that gas bubbles appear only on the grain boundaries in the pretransition regime. At intermediate burnup where the transition begins, gas bubbles are observed to spread into the intragranular regions. At high burnup, they are uniformly distributed throughout fuel. In highly irradiated U-Mo alloy fuel large-scale gas bubbles form on some fuel particle peripheries. In some cases, these bubbles appear to be interconnected and occupy the interface region between fuel and the aluminum matrix for dispersion fuel, and fuel and cladding for monolithic fuel, respectively. This is a potential performance limit for U-Mo alloy fuel. Microscopic characterization of the evolution of fission gas bubbles is necessary to understand the underlying phenomena of the macroscopic behavior of fission gas swelling that can lead to a counter measure to potential performance limit. The microscopic characterization data, particularly in the pre-transition regime, can also be used in developing a mechanistic model that predicts fission gas bubble behavior as a function of burnup and helps identify critical physical properties for the future tests. Analyses of grain and grain boundary morphology were performed. Optical micrographs and scanning electron micrographs of irradiated fuel from RERTR-1, 2, 3 and 5 tests were used. Micrographic comparisons between as-fabricated and as-irradiated fuel revealed that the site of first bubble appearance is the grain boundary. Analysis using a simple diffusion model showed that, although the difference in the Mo-content between the grain boundary and grain interior region decreased with burnup, a complete convergence in the Mo-content was not reached at the end of the test for all RERTR tests. A total of 13 plates from RERTR-1, 2, 3 and 5 tests with different as-fabrication conditions and irradiation conditions were included for gas bubble analyses. Among them, two plates contained powders {gamma}-annealed at {approx}800 C for {approx}100 hours. Most of the plates were fabricated with as-atomized powders except for two as-machined powder plates. The Mo contents were 6, 7 and 10wt%. The irradiation temperature was in the range 70-190 C and the fission rate was in the range 2.4 x 10{sup 14} - 7 x 10{sup 14} f/cm{sup 3}-s. Bubble size for both of the {gamma}-annealed powder plates is smaller than the as-atomized powder plates. The bubble size for the as-atomized powder plates increases as a function of burnup and the bubble growth rate shows signs of slowing at burnups higher than {approx}40 at% U-235 (LEU). The bubble-size distribution for all plates is a quasi-normal, with the average bubble size ranging 0.14-0.18 {micro}m. Although there are considerable errors, after an initial incubation period the average bubble size increases with fission density and shows saturation at high fission density. Bubble population (density) per unit grain boundary length was measured. The {gamma}-annealed powder plates have a higher bubble density per unit grain boundary length than the as-atomized powder plates. The measured bubble number densities per unit grain boundary length for as-atomized powder plates are approximately constant with respect to burnup. Bubble density per unit cross section area was calculated using the density per unit grain boundary length data. The grains were modeled as tetrakaidecahedrons. Direct measurements for some plates were also performed and compared with the calculated quantities. Bubble density per unit

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

2008-04-14

110

Effects of gas bubble production on heat transfer from a volumetrically heated liquid pool  

NASA Astrophysics Data System (ADS)

Aqueous solutions of uranium salts may provide a new supply chain to fill potential shortfalls in the availability of the most common radiopharmaceuticals currently in use worldwide, including Tc99m which is a decay product of Mo99. The fissioning of the uranium in these solutions creates Mo99 but also generates large amounts of hydrogen and oxygen from the radiolysis of the water. When the dissolved gases reach a critical concentration, bubbles will form in the solution. Bubbles in the solution affect both the fission power and the heat transfer out of the solution. As a result, for safety and production calculations, the effects of the bubbles on heat transfer must be understood. A high aspect ratio tank was constructed to simulate a section of an annulus with heat exchangers on the inner and outer steel walls to provide cooling. Temperature measurements via thermocouples inside the tank and along the outside of the steel walls allowed the calculation of overall and local heat transfer coefficients. Different air injection manifolds allowed the exploration of various bubble characteristics and patterns on heat transfer from the pool. The manifold type did not appear to have significant impact on the bubble size distributions in water. However, air injected into solutions of magnesium sulfate resulted in smaller bubble sizes and larger void fractions than those in water at the same injection rates. One dimensional calculations provide heat transfer coefficient values as functions of the superficial gas velocity in the pool.

Bull, Geoffrey R.

111

In vitro surfactant mitigation of gas bubble contact-induced endothelial cell death  

PubMed Central

Interactions of gas embolism bubbles with endothelial cells, as can occur during decompression events or other forms of intravascular gas entry, are poorly characterized. Endothelial cells respond to microbubble contact via mechanotransduction responses that can lead to cell death or aberrant cellular function. Cultured bovine aortic endothelial cells were individually contacted with microbubbles. Cells were loaded with fluorescent dyes indicating calcium- and nitric oxide signaling and cell viability. A surfactant, Pluronic F-127, and/or albumin were added to the culture media. Control experiments utilized calcium-free media as well as probe-poking in place of microbubble contact. We acquired fluorescence microscopy time-lapse images of cell responses to bubble and probe contact and determined contact effects on cell signaling and cell death. Calcium influx was essential for cell death to occur with bubble contact. Bubble contact stimulated extracellular calcium entry without altering nitric oxide levels unless cell death was provoked. Cell responses were independent of bubble contact duration lasting either one or 30 seconds. Microbubble contact provoked cell death over 7 times more frequently than micropipette poking. Albumin and the surfactant each attenuated the calcium response to bubble contact and also reduced the lethality of microbubble contact by 67.4% and 76.0%, respectively, when used alone, and by 91.2% when used together. This suggests that surface interactions between the bubble or probe interface and plasma- and cell surface-borne macromolecules differentially modulate the mechanism of calcium trafficking such that microbubble contact more substantially induces cell death or aberrant cellular function. The surfactant findings provide a cytoprotective approach to mitigate this form of mechanical injury. PMID:21384761

2010-01-01

112

Network simulation method applied to models of diffusion-limited gas bubble dynamics in tissue  

NASA Astrophysics Data System (ADS)

In this work the Network Simulation Method is used to study decompression sickness (DCS) in human subjects after diving and/or flying exposures. Bubble dynamics models suitable for these applications assume the bubble to be either contained in an unstirred tissue (two-region model) or surrounded by a boundary layer within a well stirred tissue (three-region model). The main results are obtained using the three-region model of gas bubble dynamics, which consists of a bubble and a well-stirred tissue region with an intervening unperfused diffusion region previously assumed to have a constant thickness and uniform gas diffusivity. Spatial discretization is used to numerically solve the diffusion equation considering the transitory term, where programming does not involve manipulation of the sophisticated mathematical software that is inherent in other numerical methods. The technique in question is always stable and convergent. Different effects (among them, tissue volume, initial bubble radius, surface tension of intercellular fluid and boundary layer thickness) are studied and plotted.

Zueco, Joaquín; Hernández-González, A.

2010-08-01

113

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

Microsoft Academic Search

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

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

2003-01-01

114

Field nano-localization of gas bubble production from water electrolysis  

NASA Astrophysics Data System (ADS)

Using a tip shaped electrode and ac voltages, we show that the production of micro bubbles of gas from water electrolysis is localized at the tip apex inside a domain in the voltage frequency phase space. A model taking into account the electrode shape and dimensions explains these results which suggest a field effect control of the electrolysis reaction rate at a nanometer scale.

Hammadi, Z.; Morin, R.; Olives, J.

2013-11-01

115

RESEARCH PAPER Use of a porous membrane for gas bubble removal in microfluidic  

E-print Network

heating (Prakash and Gershenfeld 2007) and piezo actuation (Xu and Attinger 2008). Sometimes unwanted gas pockets can form, accidentally due to priming or cavitation. These bubbles are sometimes useful, e.g., enhancing heat and mass transfer (Gunther et al. 2004; Kreutzer et al. 2005; Betz and Attinger 2010

Attinger, Daniel

116

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

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

117

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

SciTech Connect

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

Kuo, J.C.W.

1983-11-01

118

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

119

Removal of dichloromethane from waste gas streams using a hybrid bubble column/biofilter bioreactor  

PubMed Central

The performance of a hybrid bubble column/biofilter (HBCB) bioreactor for the removal of dichloromethane (DCM) from waste gas streams was studied in continuous mode for several months. The HBCB bioreactor consisted of two compartments: bubble column bioreactor removing DCM from liquid phase and biofilter removing DCM from gas phase. Effect of inlet DCM concentration on the elimination capacity was examined in the DCM concentration range of 34–359 ppm with loading rates ranged from 2.2 to 22.8 g/m3.h and constant total empty bed retention time (EBRT) of 200 s. In the equal loading rates, the elimination capacity and removal efficiency of the biofilter were higher than the corresponding values of the bubble column bioreactor. The maximum elimination capacity of the HBCB bioreactor was determined to be 15.7 g/m3.h occurred in the highest loading rate of 22.8 g/m3.h with removal efficiency of 69%. The overall mineralization portion of the HBCB bioreactor was in the range of 72-79%. The mixed liquor acidic pH especially below 5.5 inhibited microbial activity and decreased the elimination capacity. Inhibitory effect of high ionic strength was initiated in the mixed liquor electrical conductivity of 12.2 mS/cm. This study indicated that the HBCB bioreactor could benefit from advantages of both bubble column and biofilter reactors and could remove DCM from waste gas streams in a better manner. PMID:24406056

2014-01-01

120

Removal of dichloromethane from waste gas streams using a hybrid bubble column/biofilter bioreactor.  

PubMed

The performance of a hybrid bubble column/biofilter (HBCB) bioreactor for the removal of dichloromethane (DCM) from waste gas streams was studied in continuous mode for several months. The HBCB bioreactor consisted of two compartments: bubble column bioreactor removing DCM from liquid phase and biofilter removing DCM from gas phase. Effect of inlet DCM concentration on the elimination capacity was examined in the DCM concentration range of 34-359 ppm with loading rates ranged from 2.2 to 22.8 g/m3.h and constant total empty bed retention time (EBRT) of 200 s. In the equal loading rates, the elimination capacity and removal efficiency of the biofilter were higher than the corresponding values of the bubble column bioreactor. The maximum elimination capacity of the HBCB bioreactor was determined to be 15.7 g/m3.h occurred in the highest loading rate of 22.8 g/m3.h with removal efficiency of 69%. The overall mineralization portion of the HBCB bioreactor was in the range of 72-79%. The mixed liquor acidic pH especially below 5.5 inhibited microbial activity and decreased the elimination capacity. Inhibitory effect of high ionic strength was initiated in the mixed liquor electrical conductivity of 12.2 mS/cm. This study indicated that the HBCB bioreactor could benefit from advantages of both bubble column and biofilter reactors and could remove DCM from waste gas streams in a better manner. PMID:24406056

Abtahi, Mehrnoosh; Naddafi, Kazem; Mesdaghinia, Alireza; Yaghmaeian, Kamyar; Nabizadeh, Ramin; Jaafarzadeh, Nematollah; Rastkari, Noushin; Nazmara, Shahrokh; Saeedi, Reza

2014-01-01

121

Helium gas bubble trapped in liquid helium in high magnetic field  

SciTech Connect

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

Bai, H., E-mail: bai@magnet.fsu.edu; Hannahs, S. T.; Markiewicz, W. D.; Weijers, H. W. [National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310 (United States)

2014-03-31

122

Investigation of a method for real time quantification of gas bubbles in pipelines.  

PubMed

The need to measure the dynamic void fraction (the proportion of flowing bubbly liquid that is gas) is common across many power, processing and manufacturing industries. Many such pipelines and liquids are optically opaque, and work on margins that require a low cost solution that is not commensurate with the size of the challenge. Such a solution will therefore be a compromise, and in this paper costs are reduced by using a narrowband acoustic solution that cannot, on its own, contain enough information to characterize the void fraction in real time unambiguously. The ambiguity is reduced using likely estimates of the general shape of the bubble size distribution so that, with a single source-receiver pair attached to the outside of the pipe, the absolute gas content can be estimated. While the data that are required a priori (the general shape of the bubble size distribution) are not identical to the output of the inversion (the absolute void fraction of gas entrained as bubbles in the flow), the requirement for such a priori information could limit the usefulness of the technique in industry. PMID:25096085

Baik, K; Leighton, T G; Jiang, J

2014-08-01

123

Bubble Suspension  

NSDL National Science Digital Library

In this activity, learners observe as soap bubbles float on a cushion of carbon dioxide gas. Learners blow bubbles into an aquarium filled with a slab of dry ice. Learners will be amazed as the bubbles hover on the denser layer of carbon dioxide gas, then begin to expand and sink before freezing on the dry ice. Use this activity to discuss sublimation, density, and osmosis as well as principles of buoyancy, semipermeability, and interference.

Exploratorium, The

2011-10-11

124

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

125

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

PubMed

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

Arieli, R; Marmur, A

2013-08-01

126

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

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

127

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

PubMed Central

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

128

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

Microsoft Academic Search

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

A. A. Aganin; T. S. Guseva

2005-01-01

129

Nanofluidic bubble pump using surface tension directed gas injection  

Microsoft Academic Search

A new concept for liquid manipulation has been developed and implemented in surface-micromachined fluid channels. It is based on the surface tension directed injection of a gas into the liquid flow through micrometer-sized holes in the microchannel wall. The injected gas is directed to an exhaust by a cross-sectional asymmetry of the microchannel and thereby moves minute liquid volumes. Successful

N. R. Tas; J. W. Berenschot; T. S. J. Lammerink; M. Elwenspoek; A. van den Berg

2002-01-01

130

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

PubMed Central

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

Bartusik, Dorota; Aebisher, David; Ghafari, BiBi

2012-01-01

131

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

132

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

NASA Astrophysics Data System (ADS)

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

Artemov, Yu. G.

2003-04-01

133

Nanofluidic bubble pump using surface tension directed gas injection.  

PubMed

A new concept for liquid manipulation has been developed and implemented in surface-micromachined fluid channels. It is based on the surface tension directed injection of a gas into the liquid flow through micrometer-sized holes in the microchannel wall. The injected gas is directed to an exhaust by a cross-sectional asymmetry of the microchannel and thereby moves minute liquid volumes. Successful pumping experiments were performed with single stroke volumes of tens of picoliters at frequencies around 1 Hz. The minimum actuation pressure is 0.6 bar for a 2-microm channel height, in accordance with theoretical predictions. PMID:12033330

Tas, N R; Berenschot, J W; Lammerink, T S J; Elwenspoek, M; van den Berg, A

2002-05-01

134

Multi-fractal signal simulation of local, instantaneous heat transfer in a bubbling gas fluidized bed  

SciTech Connect

Recent investigations suggest that the mechanisms of heat transfer in bubbling gas fluidized beds exhibit characteristics consistent with chaos. Also, methods for simulating fractal time-series data have undergone significant development. In the present work, experimental time-series data were acquired using a constant temperature, platinum film heat flux probe flush mounted on a horizontal cylinder submerged in a bubbling gas fluidized bed. Analysis of the power spectra of the experimental signals suggests the existence of multi-fractal characteristics. Based on the fractal nature of chaotic systems, the multi-fractal Weierstrass-Mandelbrot (WM) function was used to simulate the scale-independent contribution to the local instantaneous heat transfer signals. The number of fractal components, the dimension of each fractal component and the range of frequencies associated with each fractal were determined from the power spectrum of an experimental signal. This information was subsequently used to simulate the multi-fractal contribution of an experimental signal.

Pence, D.V.; Beasley, D.E. [Clemson Univ., SC (United States)

1995-12-31

135

Role of Gas Pressure and Molecular Weight in Bubble Pinch-Off from an Underwater Nozzle  

Microsoft Academic Search

We report on experiments that explore the role of gas pressure and molecular weight near the pinch-off of an air bubble from an nozzle submerged in water. We use high-speed video to image the dynamics close to the singularity occurring at pinch-off. As the neck collapses to a radius of several microns, the effects of the Bernoulli pressure associated with

Nathan C. Keim; Sidney R. Nagel

2008-01-01

136

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

Microsoft Academic Search

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

S. A. Mohammadein; K. G. Mohamed

137

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

NASA Technical Reports Server (NTRS)

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

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

2014-01-01

138

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

NASA Technical Reports Server (NTRS)

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

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

2014-01-01

139

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

140

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

PubMed

Molecular dynamics simulations of gas hydrate dissociation comparing the behavior of CH4 and CO2 hydrates are presented. These simulations were based on a structurally correct theoretical gas hydrate crystal, coexisting with water. The MD system was first initialized and stabilized via a thorough energy minimization, constant volume-temperature ensemble and constant volume-energy ensemble simulations before proceeding to constant pressure-temperature simulations for targeted dissociation pressure and temperature responses. Gas bubble evolution mechanisms are demonstrated as well as key investigative properties such as system volume, density, energy, mean square displacements of the guest molecules, radial distribution functions, H2O order parameter, and statistics of hydrogen bonds. These simulations have established the essential similarities between CH4 and CO2 hydrate dissociation. The limiting behaviors at lower temperature (no dissociation) and higher temperature (complete melting and formation of a gas bubble) have been illustrated for both hydrates. Due to the shift in the known hydrate stability curves between guest molecules caused by the choice of water model as noted by other authors, the intermediate behavior (e.g., 260 K) showed distinct differences however. Also, because of the more hydrogen-bonding capability of CO2 in water, as reflected in its molecular parameters, higher solubility of dissociated CO2 in water was observed with a consequence of a smaller size of gas bubble formation. Additionally, a novel method for analyzing hydrate dissociation based on H-bond breakage has been proposed and used to quantify the dissociation behaviors of both CH4 and CO2 hydrates. Activation energies Ea values from our MD studies were obtained and evaluated against several other published laboratory and MD values. Intrinsic rate constants were estimated and upscaled. A kinetic reaction model consistent with macroscale fitted kinetic models has been proposed to indicate the macroscopic consequences of this analysis. PMID:24571292

Uddin, M; Coombe, D

2014-03-20

141

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

142

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

NASA Technical Reports Server (NTRS)

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

Hao, Y.; Prosperetti, A.

1999-01-01

143

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

144

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

SciTech Connect

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

Gidaspow, D.

1996-04-01

145

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

146

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

147

Periodic Orbit Theory Applied to a Chaotically Oscillating Gas Bubble in Water G. Simon 1 , P. Cvitanovi c 2 , M. T. Levinsen 3 , I. Csabai 4 , and  

E-print Network

. As a result the gas inside the bubble compresses and heats up to the extent that light emission occurs [4 model in the context of acoustic cavitation [14] and showed that the radial oscillations of a gas bubble by the assumptions of ideal gas law, absence of heat transfer, and negligence of surface tension e#11;ects. One

Levinsen, Mogens T.

148

Methodology development for the analysis of velocity particle image velocimetry images of turbulent, bubbly gas-liquid flows  

Microsoft Academic Search

Methods of analysing and interpreting two-dimensional velocity field data in order to understand the scales of turbulence of bubbly two-phase flow were developed. Reynolds decomposition and large eddy simulation (LES) decompositions (low-pass filtering), in conjunction with proper orthogonal decomposition (POD) energy spectra analysis, as well as adjusted convective decomposition (constant convection velocity is gas bubble velocity) were applied to analyse

X. Tu; C. Trägårdh

2002-01-01

149

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

150

Method for gas bubble and void control and removal from metals  

DOEpatents

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

Van Siclen, Clinton D. (Idaho Falls, ID); Wright, Richard N. (Idaho Falls, ID)

1996-01-01

151

Method for gas bubble and void control and removal from metals  

DOEpatents

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

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

1996-02-06

152

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

Microsoft Academic Search

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

Toshinori Makuta; Fumio Takemura

2006-01-01

153

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

154

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

155

Bubble Combustion  

NASA Technical Reports Server (NTRS)

A method of energy production that is capable of low pollutant emissions is fundamental to one of the four pillars of NASA s Aeronautics Blueprint: Revolutionary Vehicles. Bubble combustion, a new engine technology currently being developed at Glenn Research Center promises to provide low emissions combustion in support of NASA s vision under the Emissions Element because it generates power, while minimizing the production of carbon dioxide (CO2) and nitrous oxides (NOx), both known to be Greenhouse gases. and allows the use of alternative fuels such as corn oil, low-grade fuels, and even used motor oil. Bubble combustion is analogous to the inverse of spray combustion: the difference between bubble and spray combustion is that spray combustion is spraying a liquid in to a gas to form droplets, whereas bubble combustion involves injecting a gas into a liquid to form gaseous bubbles. In bubble combustion, the process for the ignition of the bubbles takes place on a time scale of less than a nanosecond and begins with acoustic waves perturbing each bubble. This perturbation causes the local pressure to drop below the vapor pressure of the liquid thus producing cavitation in which the bubble diameter grows, and upon reversal of the oscillating pressure field, the bubble then collapses rapidly with the aid of the high surface tension forces acting on the wall of the bubble. The rapid and violent collapse causes the temperatures inside the bubbles to soar as a result of adiabatic heating. As the temperatures rise, the gaseous contents of the bubble ignite with the bubble itself serving as its own combustion chamber. After ignition, this is the time in the bubble s life cycle where power is generated, and CO2, and NOx among other species, are produced. However, the pollutants CO2 and NOx are absorbed into the surrounding liquid. The importance of bubble combustion is that it generates power using a simple and compact device. We conducted a parametric study using CAVCHEM, a computational model developed at Glenn, that simulates the cavitational collapse of a single bubble in a liquid (water) and the subsequent combustion of the gaseous contents inside the bubble. The model solves the time-dependent, compressible Navier-Stokes equations in one-dimension with finite-rate chemical kinetics using the CHEMKIN package. Specifically, parameters such as frequency, pressure, bubble radius, and the equivalence ratio were varied while examining their effect on the maximum temperature, radius, and chemical species. These studies indicate that the radius of the bubble is perhaps the most critical parameter governing bubble combustion dynamics and its efficiency. Based on the results of the parametric studies, we plan on conducting experiments to study the effect of ultrasonic perturbations on the bubble generation process with respect to the bubble radius and size distribution.

Corrigan, Jackie

2004-01-01

156

Enhancing the efficiency of direct carbon fuel cells by bubbling Ar gas in carbon/carbonate slurry  

NASA Astrophysics Data System (ADS)

This study aims to enhance the direct carbon fuel cell (DCFC) efficiency by bubbling Ar gas in a carbon/carbonate slurry. The current discharge curve and CO and CO2 production rates were measured during discharge at 20 mA cm-2. When carbon content in carbonates (WC/carbonate) was 1.0 wt%, Ar bubbling decreased the CO/CO2 production ratio from 0.16 to 0.051, and increased the CO2 production rate, which approached the theoretical value for complete electrochemical oxidation of carbon. Moreover, bubbling increased the cell voltage by about 0.1 V at steady state. At WC/carbonate = 3.0 wt%, the CO/CO2 production ratio without bubbling increased significantly to 8.5, indicating that partial electrochemical oxidation became dominant. The C/O2- ratio is key for explaining the electrochemical oxidation of the carbon. When the C/O2- ratio was low, such as at WC/carbonate = 1.0 wt%, complete electrochemical oxidation became dominant, and bubbling enhanced the complete electrochemical oxidation. When the C/O2- ratio was high, such as at WC/carbonate = 3.0 wt%, partial electrochemical oxidation became dominant, and bubbling did not inhibit it. For WC/carbonate = 1.0 wt%, bubbling increased both coulombic and voltage efficiencies, resulting in an increase in total efficiency from 52% to 64%.

Watanabe, Hirotatsu; Furuyama, Tomoaki; Okazaki, Ken

2015-01-01

157

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

SciTech Connect

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

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

2009-01-01

158

A Bubble Full of Sunshine  

NSF Publications Database

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

159

Propagation of acoustic waves in a viscoelastic two-phase system: influence of gas bubble concentration  

NASA Astrophysics Data System (ADS)

Volcanic explosions generate pressure perturbations in the atmosphere and a seismic wavefield in the ground. The source is therefore well coupled with the atmosphere and the ground. The acoustic and elastic wavefields reflect dynamical processes at the source and the viscoelastic properties of the magma-gas medium. At low pressure (<10 MPa), magma cannot be considered as a homogeneous medium, and must be treated as a mixture of fluid magma and gas bubbles. Acoustic waves are strongly affected by the transmission properties of the magma-gas medium. We analyze the propagation of the acoustic wavefield in a two-phase medium in which the viscosity and compressibility are spatially inhomogeneous. Gas bubble nucleation starts when the magma pressure drops below the supersaturation level (at a depth of a few hundred m for H 2O in basaltic magmas) and the gas-volume fraction increases toward the surface, reaching its maximum value at the magma-air interface. The variation of gas-volume fraction is non-linear with depth and is particularly strong at shallow depths (<50 m). Density and sound velocity of the mixture drop drastically and the shear viscosity of the mixture increases with decreasing depth. Under these conditions, we tested if the propagation of an acoustic wavefield generated by a source embedded in the magma column can generate an infrasonic wavefield in the atmosphere. The acoustic wavefield in the magma is here modeled as function of the void fraction in the magma and resonance is considered to be induced only by body-wave. Large gas bubble concentrations (>70%) strongly affect the propagation properties of the acoustic wavefield. We found that the amplitude of the infrasonic wavefield in the atmosphere typically recorded in case of strombolian explosions (2×10 5 Pa) can be explained by a deep (>50 m) source embedded in the magma conduit only if a very large unrealistic pressure drop (10 13 Pa) is assumed. The strong damping, linked to the poor elastic properties of the shallow magma-gas mixture, prevents the efficient propagation of the acoustic waves in the magma-gas mixture, and resonance of body waves cannot occur. Infrasonic waves can be transmitted from the magma to the atmosphere only when the source is very shallow (<10 m). In conclusion, we neglect the possibility that resonance of body waves can induce infrasonic waves in the atmosphere. Moreover, we introduce new evidence of a strong attenuation induced by the shear viscosity on the propagation of elastic waves in a gas-rich magma. We believe that this latter result could have also a large impact on all the theories based on the resonance of elastic waves in a conduit as model to explain tremor and/or LP events on volcanoes.

Marchetti, Emanuele; Ichihara, Mie; Ripepe, Maurizio

2004-09-01

160

The two-phase flow at gas-evolving electrodes: Bubble-driven and Lorentz-force-driven convection  

NASA Astrophysics Data System (ADS)

We observe electrolysis with gas evolution, a phenomenon occurring in a number of industrial scale electrochemical processes. Here, water electrolysis takes place in a small undivided electrolysis cell consisting of vertical electrodes embedded in a larger glass vessel which contains a dilute NaOH solution. Fluid flow velocities are measured by particle image velocimetry with fluorescent tracers, while size distribution and velocities of the bubbles are determined from bubble shadow images obtained with a high speed camera. Coalescence phenomena are observed in the flow and explain the relatively wide distribution of bubble sizes. Depending on the gap width and the current density, bubbles ascending near the electrodes form two discernible bubble curtains (low average void fraction, wide gaps) or a flow profile more akin to a channel flow (high average void fraction, small gaps). If the flow consists of separate bubble curtains, instabilities develop not unlike to those of a single phase wall jet. Finally, the influence of different wall parallel Lorentz force configurations on the velocity distribution in the cell is investigated. These Lorentz forces are generated by permanent magnets mounted behind the electrodes. Depending on gap width, current density, and magnet configuration, liquid phase velocities can be increased by several times compared to the baseline case.

Weier, T.; Landgraf, S.

2013-03-01

161

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

NASA Astrophysics Data System (ADS)

Methane is a prominent greenhouse gas that escapes naturally from thermogenic reservoirs as seepage from marine and lacustrine biogenic sources as bubble ebullition. Geologic methane emissions are critically important contributors to the global methane budget however, few quantitative flux measurements are available for shallow waters. This gap in knowledge is critical as in these settings gas can easily transit as bubbles through the water column and directly influence global atmospheric budgets. Video and active acoustic (sonar) measurements of bubble flux have spatial limitations requiring predictable bubble emission location. Passive acoustics are less affected by these limitations, in addition, they can provide data in water too shallow for effective sonar bubble observations. Lab tests were undertaken to quantify the acoustic signature of bubbles formed in non-cohesive sediments. specifically focusing on mechanisms that complicate interpretation of acoustic data. Lab tests then were compared to field data to provide measurement calibration/validation. The principles behind the acoustic analysis method are based on the Minnaert equation, which relates a bubble radius and acoustic frequency. Bubble size and the resultant acoustic frequency from known flows and capillary tube diameters are well documented; however changing sediment pathways adds to the complexity of bubble formation and the resultant bubble acoustic signal. These complex signals were investigated in a lab tank with a thick, cohesive fine-grained sediment bed, through which bubbles produced by a syringe pump migrated to the sediment-water interface. Then, the resultant bubbles were diverted into clear water and measured from high speed, high definition video, while the acoustic signature of bubble formation was recorded concurrently by a hydrophone. Bubble formation is influenced by currents, which shifts the acoustical signal towards a higher frequency with a more complex pattern than the Minnaert equation predicts. Furthermore, bubbles from a cohesive media escaped in pulses of multiple bubbles, which caused significant inter-bubble acoustic coupling and mud-bubble interaction. The acoustic signature of subsurface bubble migration and concurrent sediment movements, including bubble pinch off, presented additional complexities. Use of passive acoustic derived flux was applied to natural gas seepage in the Mackenzie Delta in the North West Territories, Canada as well as offshore Coal Oil Point (COP), CA. Video data were used to calibrate the COP acoustic observations and showed a strong current impact for non-cohesive sediments. Seepage flux in the delta (cohesive sediments) was calibrated using a custom turbine tent that directly measured flux. Further applications of passive acoustic-derived seep fluxes include monitoring of marine pipelines for leaks, and studying biogenic wetlands ebullition as well as thermogenic and hydrate seepage.

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

2012-12-01

162

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

163

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

SciTech Connect

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

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

2014-04-07

164

Lateral motion and interaction of gas bubbles growing over spherical and plate heaters  

Microsoft Academic Search

This work investigates the motion of CO2 bubbles emerging in n-heptane when a heat pulse given to a submerged heater creates local supersaturation. The ensuing slow\\u000a diffusion-induced bubble expansion makes bubble motion easy to observe. The low gravity environment of a parabolic flight\\u000a allows bubbles to reach large sizes without departing from the heater while retaining their spherical shape. A

Nikolaos Divinis; Thodoris D. Karapantsios; Margaritis Kostoglou; Vasilis Bontozoglou; Robert de Bruijn; J. C. Legros

2006-01-01

165

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

166

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

167

Deterministic chaos in the gas inlet pressure of gas–liquid bubbling systems  

Microsoft Academic Search

In an attempt to assess the suggestion that submerged gas injection can under certain conditions be described as exhibiting chaotic dynamics, a short analysis has been undertaken on the results of a set of experiments over a limited set of conditions including the variation of chamber volume, injection nozzle diameter, liquid viscosity, and gas flow rate at a temperature of

Louis John Mittoni; Mark Philip Schwarz; Robert David La Nauze

1995-01-01

168

Generalizations of the Young-Laplace equation for the pressure of a mechanically stable gas bubble in a soft elastic material  

NASA Astrophysics Data System (ADS)

The Young-Laplace equation for the pressure of a mechanically stable gas bubble is generalized to include the effects of both surface tension and elastic forces of its surroundings. The latter are taken to be comprised of a soft isotropic material. Generalizations are derived for conditions of constant external pressure and constant system volume. The derived equations are formally exact for a spherical bubble surrounded by a spherical shell of isotropic material, provided that the bubble is sufficiently large for the surface tension to be treated macroscopically, and that the bubble radius is much larger than the thickness of the bubble/soft material interface. The underlying equations are also used to derive a simple expression for the Gibbs free energy of deformation of an elastic medium that surrounds a gas bubble. The possible relevance of this expression to some recently published ideas on decompression sickness ("the bends") is discussed.

Goldman, Saul

2009-11-01

169

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

NASA Astrophysics Data System (ADS)

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

Westbrook, G. K.

2009-04-01

170

Hydrodynamic characteristics and gas-liquid mass transfer in a biofilm airlift suspension reactor.  

PubMed

The hydrodynamics and mass transfer, specifically the effects of gas velocity and the presence and type of solids on the gas hold-up and volumetric mass transfer coefficient, were studied on a lab-scale airlift reactor with internal draft tube. Basalt particles and biofilm-coated particles were used as solid phase. Three distinct flow regimes were observed with increasing gas flow rate. The influence of the solid phase on the hydrodynamics was a peculiar characteristic of the regimes. The volumetric mass transfer coefficient was found to decrease with increasing solid loading and particle size. This could be predominantly related to the influence that the solid has on gas hold-up. The ratio between gas hold-up and volumetric mass transfer coefficient was found to be independent of solid loading, size, or density, and it was proven that the presence of solids in airlift reactors lowers the number of gas bubbles without changing their size. To evaluate scale effects, experimental results were compared with theoretical and empirical models proposed for similar systems. PMID:10099471

Nicolella, C; van Loosdrecht, M C; van der Lans, R G; Heijnen, J J

1998-12-01

171

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

PubMed

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

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

2010-12-01

172

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

173

Noninvasive evaluation of flow changes and gas bubbles in the circulation by combined use of color-flow-imaging and computer postprocessing.  

PubMed

Significant circulatory changes occur in microgravity and gas bubbles may be present in the circulation as a result of decompression during EVA. A system for the non-invasive evaluation of circulatory changes and gas bubbles in the circulation is described. This system is based on an ultrasonic scanning and Doppler system (CFM 700(750), Vingmed Sound, Horten Norway) together with programs to transmit the data to a Macintosh [correction of Mackintosh] II computer. A method for measuring pulsatile blood pressure non-invasively is also included. On the computer, programs for the calculation of cardiovascular parameters and the analysis of ultrasonic images containing gas bubbles have been developed. PMID:11537142

Brubakk, A O; Torp, H; Angelsen, B A

1991-01-01

174

Real-time measurement of bubbling phenomena in a three-dimensional gas-fluidized bed using ultrafast magnetic resonance imaging.  

PubMed

Ultrafast magnetic resonance imaging has been applied for the first time to measure simultaneously both the rise velocities and coalescence of bubbles, and the dynamics of the solid phase in a gas-solid two-phase flow. Here, we consider the hydrodynamics within a gas-fluidized bed of particles of diameter 0.5 mm contained within a column of internal diameter 50 mm; gas velocities in the range of 0.18-0.54 m/s were studied. The data are of sufficient temporal and spatial resolution that bubble size and the evolution of bubble size and velocity following coalescence events are determined. PMID:16712162

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

2006-04-21

175

Vortex centrifugal bubbling reactor  

Microsoft Academic Search

The vortex centrifugal bubbling apparatus is considered as a basis for a new type of multiphase vortex centrifugal bubbling reactor. In this device, a highly dispersed gas–liquid mixture is produced in the field of centrifugal forces inside the vortex chamber. The operation of the vortex centrifugal bubbling apparatus is based on the rotation of liquid by the tangential entry of

A. O. Kuzmin; M. Kh. Pravdina; A. I. Yavorsky; N. I. Yavorsky; V. N. Parmon

2005-01-01

176

Storm in a "Teacup": A Radio-quiet Quasar with ?10 kpc Radio-emitting Bubbles and Extreme Gas Kinematics  

NASA Astrophysics Data System (ADS)

We present multi-frequency (1-8 GHz) Very Large Array data, combined with VIsible MultiObject Spectrograph integral field unit data and Hubble Space Telescope imaging, of a z = 0.085 radio-quiet type 2 quasar (with L 1.4 GHz ? 5 × 1023 W Hz–1 and L AGN ? 2 × 1045 erg s–1). Due to the morphology of its emission-line region, the target (J1430+1339) has been referred to as the "Teacup" active galactic nucleus (AGN) in the literature. We identify "bubbles" of radio emission that are extended ?10-12 kpc to both the east and west of the nucleus. The edge of the brighter eastern bubble is co-spatial with an arc of luminous ionized gas. We also show that the "Teacup" AGN hosts a compact radio structure, located ?0.8 kpc from the core position, at the base of the eastern bubble. This radio structure is co-spatial with an ionized outflow with an observed velocity of v = –740 km s–1. This is likely to correspond to a jet, or possibly a quasar wind, interacting with the interstellar medium at this position. The large-scale radio bubbles appear to be inflated by the central AGN, which indicates that the AGN can also interact with the gas on >~ 10 kpc scales. Our study highlights that even when a quasar is formally "radio-quiet" the radio emission can be extremely effective for observing the effects of AGN feedback.

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

2015-02-01

177

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

USGS Publications Warehouse

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

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

2011-01-01

178

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

Microsoft Academic Search

A mathematical model is developed to simulate the radial motion of cavitation bubbles. The heat and mass transports including phase change are formulated precisely. In order to reduce the computational cost without loss of the important thermo-fluid phenomena, two simplifications are employed: time-dependent bubble radius is described using the Rayleigh-Plesset equation; the pressure in the bubble is assumed to be

Hisanobu Kawashima; Masaharu Kameda

2008-01-01

179

Deterministic chaos in the gas inlet pressure of gas-liquid bubbling systems  

NASA Astrophysics Data System (ADS)

In an attempt to assess the suggestion that submerged gas injection can under certain conditions be described as exhibiting chaotic dynamics, a short analysis has been undertaken on the results of a set of experiments over a limited set of conditions including the variation of chamber volume, injection nozzle diameter, liquid viscosity, and gas flow rate at a temperature of 20 °C. A convenient noninvasive approach is demonstrated using the upstream pressure signal to reconstruct the return map attractors. The classic period doubling sequence leading to irregular behavior is observed only over certain system parameter ranges. The important parameters believed to be responsible for the deterministic chaotic behavior and their relationship are briefly discussed.

Mittoni, Louis John; Schwarz, Mark Philip; La Nauze, Robert David

1995-04-01

180

Tiny Bubbles.  

ERIC Educational Resources Information Center

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

Kim, Hy

1985-01-01

181

Liquid Holdup Profiles in Structured Packing Determined via Neutron Radiography  

E-print Network

at contact points between corrugated sheets and in sections surrounded by a wiper band. Janzen et al. utilized ultrafast electron beam X-ray tomography to examine dynamic holdup in Montz B1-350NM and Montz B1

Eldridge, R. Bruce

182

Hydrodynamical similarities between bubble column and bubbly pipe flow  

Microsoft Academic Search

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

Robert F. Mudde; Takayuki Saito

2001-01-01

183

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

Microsoft Academic Search

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

M. A. Chappell; S. J. Payne

2005-01-01

184

Influence of gas bubbles on nonlinear dynamic characteristics of the oil film of a tilting pad bearing  

Microsoft Academic Search

The influence of a comparatively low volume concentration of gas microbubbles contained in oil on nonlinear characteristics\\u000a describing the behavior of an oil film in the guide gap of a hydrodynamic tilting pad bearing under action of a low-frequency\\u000a harmonic force is analyzed using a numerical dynamic model of a collar-oil film-pad system. It is shown that bubbles in the

N. Ya. Khlopenko

1996-01-01

185

Influence of gas bubbles on nonlinear dynamic characteristics of the oil film of a tilting pad bearing  

Microsoft Academic Search

The influence of a comparatively low volume concentration of gas microbubbles contained in oil on nonlinear characteristics describing the behavior of an oil film in the guide gap of a hydrodynamic tilting pad bearing under action of a low-frequency harmonic force is analyzed using a numerical dynamic model of a collar-oil film-pad system. It is shown that bubbles in the

N. Ya. Khlopenko

1996-01-01

186

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

187

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

188

A description of bubble growth and gas release during thermal annealing of helium implanted copper  

NASA Astrophysics Data System (ADS)

This paper describes an investigation into the migration and coalescence of equilibrium bubbles in helium implanted copper. Using computer simulation methods, the results indicate that when the swelling averaged over the implant depth approached 12%, the subsequent migration and coalescence leads to the unexpected formation of relatively massive bubbles with radii of the order of the helium range (˜130 nm), some 10 times the average bubble radius. Such behaviour would appear to provide an explanation for the surface pores and the large helium loss during annealing observed in the experimental results of Escobar Galindo et al. [Nucl. Instr. and Meth. B, in press].

Evans, J. H.; Escobar Galindo, R.; van Veen, A.

2004-04-01

189

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

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

190

Dynamics of a Tethered Bubble Alexey O. Maksimov 1  

E-print Network

bubble on a solid surface [3] differs from single-bubble SL. The forced oscillation of a gas bubble can using an acoustically driven tethered gas bubble. Clearly the forced oscillation of a tethered gas Abstract. Small gas bubbles adhering to solids occur in a range of manufacturing processes, including

Sóbester, András

191

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

192

Numerical analysis of a gas bubble near bio-materials in an ultrasound field.  

PubMed

Ultrasonic cavitation bubble phenomena play a key role in numerous medical procedures such as ultrasound-assisted lipoplasty, phacoemulsification, lithotripsy, brain tumor surgery, muscle and bone therapies and intraocular or transdermal drug delivery. This study investigates numerically the interaction of a bubble with a bio-material (fat, skin, cornea, brain, muscle, cartilage or bone) involved in the treatments mentioned when subjected to an ultrasound field. A range of frequencies is used to study the bubble behavior in terms of its growth and collapse shapes, and the maximum jet velocity attained. Simulation results show complex dynamic behaviors of the bubble. In several cases a jet is formed directed away from the bio-material while in others, toward it. In certain cases, the bubble eventually breaks into two, with or without the formation of opposite penetrating jets. Very high maximum velocities of jets directing away or toward the bio-materials can be observed in some cases (700 to 900 ms(-1)). PMID:16785014

Fong, Siew Wan; Klaseboer, Evert; Turangan, Cary K; Khoo, Boo Cheong; Hung, Kin Chew

2006-06-01

193

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

194

Novel techniques for slurry bubble column hydrodynamics  

SciTech Connect

The objective of this cooperative research effort between Washington University, Ohio State University and Exxon Research Engineering Company was to improve the knowledge base for scale-up and operation of slurry bubble column reactors for syngas conversion and other coal conversion processes by increased reliance on experimentally verified hydrodynamic models. During the first year (July 1, 1995--June 30, 1996) of this three year program novel experimental tools (computer aided radioactive particle tracking (CARPT), particle image velocimetry (PIV), heat probe, optical fiber probe and gamma ray tomography) were developed and tuned for measurement of pertinent hydrodynamic quantities, such as velocity field, holdup distribution, heat transfer and bubble size. The accomplishments were delineated in the First Technical Annual Report. The second year (July, 1996--June 30, 1997) was spent on further development and tuning of the novel experimental tools (e.g., development of Monte Carlo calibration for CARPT, optical probe development), building up the hydrodynamic data base using these tools and comparison of the two techniques (PIV and CARPT) for determination of liquid velocities. A phenomenological model for gas and liquid backmixing was also developed. All accomplishments were summarized in the Second Annual Technical Report. During the third and final year of the program (July 1, 1997--June 30, 1998) and during the nine months no cost extension, the high pressure facility was completed and a set of data was taken at high pressure conditions. Both PIV, CT and CARPT were used. More fundamental hydrodynamic modeling was also undertaken and model predictions were compared to data. The accomplishments for this period are summarized in this report.

Dudukovic, M.P.

1999-05-14

195

Uranium dioxide films with xenon filled bubbles for fission gas behavior studies  

NASA Astrophysics Data System (ADS)

Electron beam evaporation and ion beam assisted deposition (IBAD) methods were utilized to fabricate depleted UO2 films and UO2 films with embedded Xe atoms, respectively. The films were fabricated at elevated temperature of 700 °C and also subsequently annealed at 1000 °C to induce grain growth and Xe atom redistribution. The goal of this work was to synthesize reference UO2 samples with controlled microstructures and Xe-filled bubble morphologies, without the effects attendant to rector irradiation-induced fission. Transmission electron microscopy (TEM) microstructural characterization revealed that fine Xe-filled bubbles nucleated in the as grown films and subsequent annealing resulted in noticeable bubble size increase. Reported results demonstrate the great potential IBAD techniques and UO2 films have for various areas of nuclear materials studies.

Usov, I. O.; Dickerson, R. M.; Dickerson, P. O.; Byler, D. D.; McClellan, K. J.

2014-09-01

196

Holdup-related issues in safeguarding of nuclear materials  

SciTech Connect

Residual inventories of special nuclear materials (SNM) remaining in processing facilities (holdup) are recognized as an insidious problem for both safety and safeguards. This paper identifies some of the issues that are of concern to the safeguards community at-large that are related to holdup of SNM in large-scale process equipment. These issues range from basic technologies of SNM production to changing regulatory requirements to meet the needs of safeguarding nuclear materials. Although there are no magic formulas to resolve these issues, there are several initiatives that could be taken in areas of facility design, plant operation, personnel training, SNM monitoring, and regulatory guidelines to minimize the problems of holdup and thereby improve both safety and safeguards at nuclear material processing plants. 8 refs.

Pillay, K.K.S.

1988-03-01

197

Implementation and verification of numerical model for gas bubble dynamics in electroconductive fluid  

NASA Astrophysics Data System (ADS)

Apart from common steam reforming process the thermal decomposition of methane is regarded as an alternate route to producing hydrogen and elemental carbon with out of CO2 emissions. Chemical reaction of decarburation can be ensured by means of methane bubbly flow through a molten metal bath and additionally controlled by external electromagnetic field. This is the initial stage of research and preliminary calculation results for the single bubble rise dynamics in 2D axisymmetric consideration at different flow conditions and 2D planar consideration in the presence of external DC EM field are obtained and compared to experimental and simulation data from literature.

Tucs, A.; Spitans, S.; Jakovics, A.; Baake, E.

2013-10-01

198

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

NASA Astrophysics Data System (ADS)

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

Vagle, Svein; McNeil, Craig; Steiner, Nadja

2010-12-01

199

Use of tracers in materials-holdup study  

SciTech Connect

Holdup measurements of special nuclear materials in large processing facilities offer considerable challenges to conventional nondestructive-assay techniques. The use of judiciously chosen radioactive tracers offer a unique method of overcoming this difficulty. Three examples involving the use of /sup 46/Sc and fission products from activated uranium in large-scale experimental studies of uranium holdup are discussed. A justification for the method and its advantages along with examples of successful applications of this technique for large-sale experimental studies are presented.

Pillay, K.K.S.

1983-01-01

200

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

201

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

202

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

203

Gases in Tektite Bubbles.  

PubMed

Spectroscopic analysis of light produced by electrodeless discharge in a tektite bubble showed the main gases in the bubble to be neon, helium, and oxygen. The neon and helium have probably diffused in from the atmosphere, while the oxygen may be atmospheric gas incorporated in the tektite during its formation. PMID:17801113

O'keefe, J A; Lowman, P D; Dunning, K L

1962-07-20

204

Bubble Mania  

NSDL National Science Digital Library

In this math lesson, learners practice measurement skills as they examine a soap bubble print. Learners follow a recipe to make a soap bubble solution. They use the soapy solution to blow large bubbles with a plastic drinking straw until the bubbles pop, leaving behind circular prints. Learners find the diameter, circumference, and area of the bubble print.

Pbs

2012-01-01

205

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

206

Highway robbery: complementary monopoly and the hold-up problem  

Microsoft Academic Search

We analyze the hold-up problem in the context of the Cournot–Ellet theory of complementary monopoly. The strategic interaction among travelers and two distinct owners of successive segments of a segment road is used as a metaphor for complementary goods that are traded sequentially. It is shown that when trade occurs double marginalization is eliminated. Furthermore, allowing for strategic placement of

Yossi Feinberg; Morton I. Kamien

2001-01-01

207

Interstellar bubbles. II - Structure and evolution. [stellar wind interaction with interstellar gas  

NASA Technical Reports Server (NTRS)

The detailed structure of the interaction of a strong stellar wind with the interstellar medium is presented. First, an adiabatic similarity solution is given which is applicable at early times. Second, a similarity solution is derived which includes the effects of thermal conduction between the hot (about 1 million K) interior and the cold shell of swept-up interstellar matter. This solution is then modified to include the effects of radiative energy losses. The evolution of an interstellar bubble is calculated, including the radiative losses. The quantitative results for the outer-shell radius and velocity and the column density of highly ionized species such as O VI are within a factor 2 of the approximate results of Castor, McCray, and Weaver (1975). The effect of stellar motion on the structure of a bubble, the hydrodynamic stability of the outer shell, and the observable properties of the hot region and the outer shell are discussed.

Weaver, R.; Mccray, R.; Castor, J.; Moore, R.; Shapiro, P.

1977-01-01

208

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

209

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

210

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

211

Soluble surfactants favorably modify fluid structure and wall shear stress profiles during near-occluding bubble motion in a computational model of intravascular gas embolism  

NASA Astrophysics Data System (ADS)

Finite sized gas bubble motion in a blood vessel causes temporal and spatial gradients of shear stress at the endothelial cell surface lining the vessel wall as the bubble approaches the cell, moves over it and passes it by. Rapid reversals occur in the sign of the shear stress imparted to the cell surface during this motion. The sign-reversing shear is a potently coupled source of cell surface mechanical stretch, potentiating cell injury. The presence of a suitable soluble surfactant in the bulk medium considerably reduces the level of the shear stress gradients imparted to the cell surface as compared to an equivalent surfactant-free system. The bubble shape and the film thickness between the bubble and the vessel wall are also different. Furthermore, the bubble residence time near the proximity of a cell surface changes in comparison. These results based on our modeling may help explain several phenomena observed in experimental studies related to gas embolism, a significant problem in cardiac surgery and decompression sickness.

Swaminathan, T. N.; Ayyaswamy, P. S.; Eckmann, D. M.

2009-11-01

212

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

213

The role of particle-particle interactions in bubbling gas-fluidized beds of Geldart A particles: A discrete particle study  

NASA Astrophysics Data System (ADS)

Discrete particle simulations are by now well established as an effective tool to study the mechanics of complex gas-solid flows in gas-fluidized beds. In this study, a state-of-the-art discrete particle model is used to explore the role of particle-particle interactions in bubbling gas-fluidized beds of Geldart A particles. We find that the particle-particle interactions, including inelastic particle-particle collision; inter-particle friction and slightly cohesive forces, only have a negligible effect on the hydrodynamics of bubbling gas-fluidized beds of Geldart A particles. This is due to the fact that only a very small fraction of the energy input is dissipated during the non-ideal particle-particle interaction. We finally show that the selected drag correlation model significantly affects the bed hydrodynamics.

Wang, J. W.; van der Hoef, M. A.; Kuipers, J. A. M.

2010-03-01

214

Tribonucleation of bubbles  

PubMed Central

We report on the nucleation of bubbles on solids that are gently rubbed against each other in a liquid. The phenomenon is found to depend strongly on the material and roughness of the solid surfaces. For a given surface, temperature, and gas content, a trail of growing bubbles is observed if the rubbing force and velocity exceed a certain threshold. Direct observation through a transparent solid shows that each bubble in the trail results from the early coalescence of several microscopic bubbles, themselves detaching from microscopic gas pockets forming between the solids. From a detailed study of the wear tracks, with atomic force and scanning electron microscopy imaging, we conclude that these microscopic gas pockets originate from a local fracturing of the surface asperities, possibly enhanced by chemical reactions at the freshly created surfaces. Our findings will be useful either for preventing undesired bubble formation or, on the contrary, for “writing with bubbles,” i.e., creating controlled patterns of microscopic bubbles. PMID:24982169

Wildeman, Sander; Lhuissier, Henri; Sun, Chao; Lohse, Detlef; Prosperetti, Andrea

2014-01-01

215

Continuous Holdup Measurements with Silicon P-I-N Photodiodes  

SciTech Connect

We report on the behavior of silicon P-I-N photodiodes used to perform holdup measurements on plumbing. These detectors differ from traditional scintillation detectors in that no high-voltage is required, no scintillator is used (gamma and X rays are converted directly by the diode), and they are considerably more compact. Although the small size of the diodes means they are not nearly as efficient as scintillation detectors, the diodes' size does mean that a detector module, including one or more diodes, pulse shaping electronics, analog-to-digital converter, embedded microprocessor, and digital interface can be realized in a package (excluding shielding) the size of a pocket calculator. This small size, coupled with only low-voltage power requirement, completely solid-state realization, and internal control functions allows these detectors to be strategically deployed on a permanent basis, thereby reducing or eliminating the need for manual holdup measurements. In this paper, we report on the measurement of gamma and X rays from {sup 235}U and {sup 238}U contained in steel pipe. We describe the features of the spectra, the electronics of the device and show how a network of them may be used to improve estimates of inventory in holdup.

Bell, Z.W.; Oberer, R.B.; Williams, J.A.; Smith, D.E.; Paulus, M.J.

2002-05-01

216

Simple Microwave Method for Detecting Water Holdup  

E-print Network

, resistance and capacitance measurements, which are often incapable of providing accurate concentration) transmission measurements are also used to detect sand, water and gas levels within multiphase flow-phase liquid and observe their complex electrical properties. Since electromagnetic scattering is governed

Iqbal, Sheikh Sharif

217

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

218

Buoyant Bubbles  

NSDL National Science Digital Library

What keeps bubbles and other things, like airplanes, floating or flying in the air? In this activity, learners blow bubbles and wave 3x5 cards above, below and on different sides of the bubbles to keep them afloat as long as possible. The Did You Know section explains the Bernoulli principle: how waving cards above the bubbles helps keep them afloat because faster moving air exerts less pressure to push the bubbles down. The activity can be extended by having learners wave their bubbles through an obstacle course they design themselves.

Science, Lawrence H.

2009-01-01

219

Pulsed electrogeneration of bubbles for electroflotation  

Microsoft Academic Search

Fine bubbles of the size required for many processes such as electroflotation can be generated by electrolysis. A large number of factors such as electrode material, electrode surface\\/morphological properties, pH and current density affect the gas bubble size distribution. This work is aimed at studies on the effect of interrupted current (pulsed) electrolysis on the generation of gas bubbles. A

N. K. Khosla; S. Venkatachalam; P. Somasundaran

1991-01-01

220

Observations of solute effects on bubble formation  

SciTech Connect

The authors have studied the effects of solute, in particular aqueous electrolyte, on bubble formation at capillary orifices and frits at varying gas flow rates. Using a stroboscope, video microscope, and rotating mirror, they have obtained pictures which show how bubble formation involves the interaction of bubbles at the orifice. These interactions depend on the value of the surface elasticity E due to positively (ethanol) or negatively (NaCl) adsorbed solute. At low flow rates consecutive bubbles do not interact. Each bubble detaches and leaves the orifice region before the next one starts forming. A intermediate flow rates the more closely spaced, consecutive bubbles begin to interact. In pure liquids there is no barrier to bubble coalescence and the detached bubble is fed by the subsequent bubble as this starts to grow. The process may be repeated several times before the original bubble has risen out of range. In solutions where E is large enough bubble coalescence is inhibited. Instead of feeding into the detached bubble the following bubble pushes it aside, and the bubbles appear to bounce off each other. Bouncing may give rise to a characteristic sequence of larger and smaller bubbles if the emerging bubbles break off prematurely from the orifice due to the inertia of the original bubble. The transition from feeding to bouncing depends critically on E of the solution and leads to a smaller average bubble size for large E values. At high flow rates detached bubbles are invariably fed by several subsequent ones. At very high flow rates the bubbling becomes chaotic, but the interaction of bubbles after leaving the orifice area produces smaller bubbles in solutions. Bouncing is more likely to occur with narrow and irregular capillaries. The dramatically different appearance of gas-sparged columns in salt water and freshwater has its origin in the difference between assemblies of pores showing mainly feeding (freshwater) or bouncing (salt water).

Hofmeier, U.; Yaminsky, V.V.; Christenson, H.K. [Australian National Univ., Canberra (Australia)] [Australian National Univ., Canberra (Australia)

1995-09-01

221

Radicular Compression by Intraspinal Epidural Gas Bubble Occurred in Distant Two Levels after Lumbar Microdiscectomy  

PubMed Central

The authors report a case of symptomatic epidural gas accumulation 2 weeks after the multi-level lumbar surgery, causing postoperative recurrent radiculopathy. The accumulation of epidural gas compressing the dural sac and nerve root was demonstrated by CT and MRI at the distant two levels, L3-4 and L5-S1, where vacuum in disc space was observed preoperatively and both laminectomy and discectomy had been done. However, postoperative air was not identified at L4-5 level where only laminectomy had been done in same surgical field, which suggested the relationship between postoperative epidural gas and the manipulation of disc structure. Conservative treatment and needle aspiration was performed, but not effective to relieve patient's symptoms. The patient underwent revision surgery to remove the gaseous cyst. Her leg pain was improved after the second operation.

Yoon, Kang-Jun; Ha, Sang-Soo; Kang, Joon-Ki

2014-01-01

222

Modeling of a novel multi-stage bubble column scrubber for flue gas desulfurization  

Microsoft Academic Search

Desulfurization of flue gases from various chemical industries in a techno-econo-enviro manner is a demanding technology. The concentrations of sulfur dioxide in and around these plants overshoot the danger point. In the present investigation, an attempt has been made for wet flue gas desulfurization using water as the absorbing medium in a newly developed scrubber. Prediction of SO2 removal efficiency

B. C. Meikap; G. Kundu; M. N. Biswas

2002-01-01

223

Gas back-mixing studies in membrane assisted bubbling fluidized beds  

Microsoft Academic Search

Fluidized beds employing fine powders are finding increased application in the chemical and petrochemical industry because of their excellent mass and heat transfer characteristics. However, in fluidized bed chemical reactors axial gas back mixing can strongly decrease the conversion and selectivity. By insertion of membranes in fluidized beds large improvements in conversion and selectivity can be achieved, firstly by optimizing

S. A. R. K. Deshmukh; M. van Sint Annaland; J. A. M. Kuipers

2007-01-01

224

Best Bubbles  

NSDL National Science Digital Library

In this activity, learners experiment with creating various types of bubble solutions and testing which ingredients form longer-lasting bubbles. Learners investigate how surface tension works and the importance of using a surfactant to make bubbles. This activity includes a video about NASA astronaut Don Pettit, who used candy corn to conduct science experiments during his stint aboard the International Space Station.

Saltz, Austen

2010-01-01

225

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

226

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

227

A model for simulating gas bubble entrainment in two-phase horizontal slug flow  

Microsoft Academic Search

In an earlier paper it was shown that the basic one-dimensional transient two-fluid model is capable of capturing horizontal and near-horizontal slug flow automatically. However, that work did not account for the effect of gas entrainment into the liquid slug body which is deemed to be an important phenomenon. In this paper, a mathematical model to account for the entrainment

M. Bonizzi; R. I. Issa

2003-01-01

228

Holdup Measures on an SRNL Mossbauer Spectroscopy Instrument  

SciTech Connect

Gamma-ray holdup measurements of a Mossbauer spectroscopy instrument are described and modeled. In the qualitative acquisitions obtained in a low background area of Savannah River National Laboratory, only Am-241 and Np-237 activity were observed. The Am-241 was known to be the instrumental activation source, while the Np-237 is clearly observed as a source of contamination internal to the instrument. The two sources of activity are modeled separately in two acquisition configurations using two separate modeling tools. The results agree well, demonstrating a content of (1980 {+-} 150) {mu}Ci Am-241 and (110 {+-} 50) {mu}Ci of Np-237.

Dewberry, R.; Brown, T.; Salaymeh, S.

2010-05-05

229

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)(2)S(2)O(8)) has been developed for the first time. Some experiments were carried out in a bubble column reactor to evaluate the effects of process parameters on Hg(0) removal. The mechanism and kinetics of Hg(0) removal are also studied. The results show that the parameters, (NH4)(2)S(2)O(8) concentration, activation temperature and solution pH, have significant impacts on Hg(0) removal. The parameters, Hg(0), SO2 and NO concentration, only have small effects on Hg(0) removal. Hg(0) is removed by oxidations of (NH4)(2)S(2)O(8), sulfate and hydroxyl free radicals. When (NH4)(2)S(2)O(8) concentration is more than 0.1 mol/L and solution pH is lower than 9.71, Hg(0) removal by thermally activated (NH4)(2)S(2)O(8) meets a pseudo-first-order fast reaction with respect to Hg(0). However, when (NH4)(2)S(2)O(8) concentration is less than 0.1 mol/L or solution pH is higher than 9.71, the removal process meets a moderate speed reaction with respect to Hg(0). The above results indicate that this technique is a feasible method for emission control of Hg(0) from flue gas. PMID:25251199

Liu, Yangxian; Wang, Qian

2014-10-21

230

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

231

Mesoscale Benchmark Demonstration Problem 1: Mesoscale Simulations of Intra-granular Fission Gas Bubbles in UO2 under Post-irradiation Thermal Annealing  

SciTech Connect

A study was conducted to evaluate the capabilities of different numerical methods used to represent microstructure behavior at the mesoscale for irradiated material using an idealized benchmark problem. The purpose of the mesoscale benchmark problem was to provide a common basis to assess several mesoscale methods with the objective of identifying the strengths and areas of improvement in the predictive modeling of microstructure evolution. In this work, mesoscale models (phase-field, Potts, and kinetic Monte Carlo) developed by PNNL, INL, SNL, and ORNL were used to calculate the evolution kinetics of intra-granular fission gas bubbles in UO2 fuel under post-irradiation thermal annealing conditions. The benchmark problem was constructed to include important microstructural evolution mechanisms on the kinetics of intra-granular fission gas bubble behavior such as the atomic diffusion of Xe atoms, U vacancies, and O vacancies, the effect of vacancy capture and emission from defects, and the elastic interaction of non-equilibrium gas bubbles. An idealized set of assumptions was imposed on the benchmark problem to simplify the mechanisms considered. The capability and numerical efficiency of different models are compared against selected experimental and simulation results. These comparisons find that the phase-field methods, by the nature of the free energy formulation, are able to represent a larger subset of the mechanisms influencing the intra-granular bubble growth and coarsening mechanisms in the idealized benchmark problem as compared to the Potts and kinetic Monte Carlo methods. It is recognized that the mesoscale benchmark problem as formulated does not specifically highlight the strengths of the discrete particle modeling used in the Potts and kinetic Monte Carlo methods. Future efforts are recommended to construct increasingly more complex mesoscale benchmark problems to further verify and validate the predictive capabilities of the mesoscale modeling methods used in this study.

Li, Yulan; Hu, Shenyang Y.; Montgomery, Robert; Gao, Fei; Sun, Xin; Tonks, Michael; Biner, Bullent; Millet, Paul; Tikare, Veena; Radhakrishnan, Balasubramaniam; Andersson , David

2012-04-11

232

Black-hole bubbles  

SciTech Connect

If theories of high-energy physics such as spontaneous symmetry breaking and quantum chromodynamics are correct, then exploding black holes will be surrounded by phase-transition bubbles or fireballs, supported by the pressure of particles trapped inside a high-temperature phase. For quark-gas fireballs, where there is a hadron bag with a hole in it, this enhances the ..gamma..-ray emission by a factor of 69 which could lead to a feature in the ..gamma..-ray background around 200 MeV. For other bubbles there may be detectable electromagnetic pulses produced by the Rees mechanism when the bubble bursts, particularly for the inflated bubbles which result from the models suggested by the inflationary-universe scenario.

Moss, I.G.

1985-09-15

233

Heat transfer and hydrodynamic investigations of a baffled slurry bubble column  

NASA Astrophysics Data System (ADS)

Heat transfer and hydrodynamic investigations have been conducted in a 0.108 m internal diameter bubble column at ambient conditions. The column is equipped with seven 19mm diameter tubes arranged in an equilateral triangular pitch of 36.5 mm. A Monsanto synthetic heat transfer fluid, Therminol-66 having a viscosity of 39.8 cP at 303 K, is used as a liquid medium. Magnetite powders, average diameters 27.7 and 36.6 µm, in five concentrations up to 50 weight percent in the slurry, are used. As a gas phase, industrial grade nitrogen of purity 99.6 percent is employed. Gas holdup in different operating modes and regimes have been measured for the two- and three-phase systems over a superficial gas velocity range up to 0.20 m/s in the semi-batch mode. Heat transfer coefficients are measured at different tube locations in the bundle at different radial and vertical locations over a range of operating conditions. All these data are compared with the existing literature correlations and models. New correlations are proposed.

Saxena, S. C.; Chen, Z. D.

1992-09-01

234

Effect of sodium dodecyl sulfate (SDS) on bubble characteristics and ozone transfer in a bubble column  

Microsoft Academic Search

The rising of ozone?containing bubbles in a bubble column was examined by a high?speed micro video camera. The shape of the bubbles shifted from spherical to ellipsoidal during their rise along the column. The experimental observation indicated that the average diameter at the X?axis of the bubbles was markedly increased after the bubbles left the diffuser because the gas pressure

Young Ku

2007-01-01

235

Noninvasive evaluation of flow changes and gas bubbles in the circulation by combined use of color-flow-imaging and computer postprocessing  

NASA Astrophysics Data System (ADS)

A system for obtaining cardiovascular data by using an ultrasonic scanner combined with a noninvasive method for measuring pulsatile pressure and computer-based postprocessing capabilities has been developed. The system is based on an ultrasonic scanning and Doppler system together with programs to transmit the data to a Macintosh II computer. A system for detecting and counting air bubbles in the circulation system through analysis of ultrasonic images containing gas bubbles has also been developed. The basic instrumentation incorporated in these systems is described and the postprocessing of ultrasound data is discussed in detail. The ability to perform postprocessing of data directly on the spacecraft, thereby making it possible to change experimental setup based on results is cited as one of the primary advantages of this system.

Brubakk, A. O.; Torp, H.; Angelsen, B. A. J.

236

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

237

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

238

Marangoni bubble motion in zero gravity  

Microsoft Academic Search

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

R. L. Thompson; K. J. de Witt

1979-01-01

239

MARANGONI BUBBLE MOTION PHENOMENON IN ZERO GRAVITY  

Microsoft Academic Search

The Marangoni phenomenon is shown to be the primary mechanism for the movement of a gas bubble in a nonisothermal liquid in a low-gravity environment. In such a two-phase system, local variations in surface tension at the bubble surface are caused by a temperature gradient in the liquid. Shearing stresses thus generated at the bubble surface lead to convection in

R. L. THOMPSON; K. J. DeWITT; T. L. LABUS

1980-01-01

240

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

241

Ammonia absorption from a bubble expanding at a submerged orifice into water  

Microsoft Academic Search

To investigate the mechanism of gas absorption from a bubble containing soluble and insoluble components, a gaseous mixture of ammonia and nitrogen was bubbled into water. The growth curve, volume, surface area and shape of the growing bubbles were measured with parameters such as inlet gas composition, gas flow rate and gas chamber volume. The bubble volume decreased with the

Koichi Terasaka; Junko Oka; Hideki Tsuge

2002-01-01

242

Bubble Tray  

NSDL National Science Digital Library

In this activity, learners use simple materials to create giant bubbles. Learners will explore what gives bubbles their shape, what makes them break or last, what causes the colors and patterns in the soap film, and why do they change? Use this activity to introduce the concepts of surface tension and interference.

Exploratorium, The

2012-06-26

243

Sound Propagation in an inhomogeneous two-phase system: the influence of the gas bubble concentration on the sound source model.  

NASA Astrophysics Data System (ADS)

Volcanic explosions produce pressure perturbations in the atmosphere (infrasound) which are not contaminated by path effects as for the seismic wavefield and contain useful and direct informations on the source dynamics. Recently, many dynamical models of the explosive process are based on the analysis of the acoustic field. We have analyzed the acoustic wave field in terms of elastic wave propagation in a two-phase medium where the viscosity and compressibility are spatially inhomogeneous. At low pressure (<10 MPa) the magma can not be considered as an homogeneous medium, but has to be treated as a mixture of fluid magma and gas bubbles. Gas bubble nucleation starts when the pressure of the system drops below the supersaturation level (a few hundreds of meters for H2O in basaltic magmas) and increases towards the surface, reaching its maximum value at the magma-air interface. Such a variation is non-linear with depth and is particularly strong at shallow depth. With the decrease of depth the density of the mixture and the sound velocity drop drastically while the shear viscosity of the mixture increases. We calculated the propagation of an elastic wavefield generated by an explosive source embedded in the magma column as function of the void fraction increase in the magma. Large gas bubble concentrations (>70%) prevent the elastic wavefield to propagate suggesting that or the source is shallow or it is characterized by a high pressure drop. We propose a source model which explain the infrasonic wavefield in terms of a shallow unsteady pressure front.

Marchetti, E.; Ichihara, M.; Ripepe, M.

2001-12-01

244

18. Building L9; view of the relationship between west holdup ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

18. Building L-9; view of the relationship between west holdup kettle and incorporation kettles; mezzanine, looking SE. (Ryan and Harms) - Holston Army Ammunition Plant, RDX-and-Composition-B Manufacturing Line 9, Kingsport, Sullivan County, TN

245

{sup 235}U Holdup Measurement Program in support of facility shutdown  

SciTech Connect

In 1989, the Department of Energy directed shutdown of an enriched uranium processing facility at Savannah River Site. As part of the shutdown requirements, deinventory and cleanout of process equipment and nondestructive measurement of the remaining {sub 235}U holdup were required. The holdup measurements had safeguards, accountability, and nuclear criticality safety significance; therefore, a technically defensible and well-documented holdup measurement program was needed. Appropriate standards were fabricated, measurement techniques were selected, and an aggressive schedule was followed. Early in the program, offsite experts reviewed the measurement program, and their recommendations were adopted. Contact and far-field methods were used for most measurements, but some process equipment required special attention. All holdup measurements were documented, and each report was subjected to internal peer review. Some measured values were checked against values obtained by other methods; agreement was generally good.

Thomason, R.S.; Griffin, J.C.; Lien, O.G.; McElroy, R.D.

1991-12-31

246

sup 235 U Holdup Measurement Program in support of facility shutdown  

SciTech Connect

In 1989, the Department of Energy directed shutdown of an enriched uranium processing facility at Savannah River Site. As part of the shutdown requirements, deinventory and cleanout of process equipment and nondestructive measurement of the remaining {sub 235}U holdup were required. The holdup measurements had safeguards, accountability, and nuclear criticality safety significance; therefore, a technically defensible and well-documented holdup measurement program was needed. Appropriate standards were fabricated, measurement techniques were selected, and an aggressive schedule was followed. Early in the program, offsite experts reviewed the measurement program, and their recommendations were adopted. Contact and far-field methods were used for most measurements, but some process equipment required special attention. All holdup measurements were documented, and each report was subjected to internal peer review. Some measured values were checked against values obtained by other methods; agreement was generally good.

Thomason, R.S.; Griffin, J.C.; Lien, O.G.; McElroy, R.D.

1991-01-01

247

Asymmetric PWM Control Scheme During Hold-Up Time for $LLC$ Resonant Converter  

Microsoft Academic Search

To narrow down the switching-frequency-variation range of an $LLC$ resonant converter, asymmetric pulsewidth modulation (APWM) of the hold-up time is proposed. During the hold-up time, the modulation method of an $LLC$ resonant converter is changed from frequency modulation (FM) to APWM. Since the $LLC$ resonant converter achieves a higher gain with APWM than it does with FM at the same

Bong-Chul Kim; Ki-Bum Park; Gun-Woo Moon

2012-01-01

248

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

249

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

250

Characteristics of three-phase internal loop airlift bioreactors with complete gas recirculation for non-Newtonian fluids  

Microsoft Academic Search

Hydrodynamic and gas–liquid mass transfer characteristics, such as liquid velocity, gas holdup, solid holdup and gas–liquid volumetric mass transfer coefficient, in the riser and downcomer of the gas–liquid-solid three-phase internal loop airlift bioreactors with complete gas recirculation for non-Newtonian fluids, were investigated. A mathematical model for the description of flow behavior and gas–iquid mass transfer of these bioreactors was developed.

Jianping Wen; Xiaoqiang Jia; Xianrui Cheng; Peng Yang

2005-01-01

251

Effects of pulsed ultrasound on the adsorption of n-alkyl anionic surfactants at the gas/solution interface of cavitation bubbles.  

PubMed

Sonolysis of argon-saturated aqueous solutions of the nonvolatile surfactants sodium dodecyl sulfate (SDS) and sodium 1-pentanesulfonate (SPSo) was investigated at three ultrasonic frequencies under both continuous wave (CW) and pulsed ultrasound. Secondary carbon-centered radicals were detected by spin trapping using 3,5-dibromo-4-nitrosobenzenesulfonic acid (DBNBS) and electron paramagnetic resonance (EPR) spectroscopy. Following sonolysis, -*CH- radicals were observed for both surfactants under both sonication modes. Under CW at 354 kHz, the maximum plateau -*CH- radical yield was higher for SPSo than for SDS, indicating that SDS, which is more surface active under equilibrium conditions, accumulates at the gas/solution interface of cavitation bubbles to a lesser degree, compared with the less surface active surfactant, SPSo. However, after sonolysis (354 kHz) under pulsed ultrasound with a pulse length of 100 ms and an interval of 500 ms, the -*CH- radical yield at the plateau concentrations was higher for SDS than for SPSo due to increased amounts of SDS accumulation on the bubble surfaces. In contrast to the findings following sonolysis at 354 kHz, sonolysis of aqueous surfactant solutions at 620 kHz and 803 kHz showed a higher -*CH- radical yield for SDS compared with SPSo under CW but lower -*CH- radical yield with increasing pulsing interval, indicating a frequency dependence on accumulation. Results indicate that pulsing the ultrasonic wave has a significant effect on the relative adsorption ability of n-alkyl surfactants at the gas/solution surface of cavitation bubbles. PMID:17249713

Yang, Limei; Sostaric, Joe Z; Rathman, James F; Kuppusamy, Periannan; Weavers, Linda K

2007-02-15

252

Bubbles of Metamorphosis  

NASA Astrophysics Data System (ADS)

Metamorphosis presents a puzzling challenge where, triggered by a signal, an organism abruptly transforms its entire shape and form. Here I describe the role of physical fluid dynamic processes during pupal metamorphosis in flies. During early stages of pupation of third instar larvae into adult flies, a physical gas bubble nucleates at a precise temporal and spatial location, as part of the normal developmental program in Diptera. Although its existence has been known for the last 100 years, the origin and control of this ``cavitation'' event has remained completely mysterious. Where does the driving negative pressure for bubble nucleation come from? How is the location of the bubble nucleation site encoded in the pupae? How do molecular processes control such a physical event? What is the role of this bubble during development? Via developing in-vivo imaging techniques, direct bio-physical measurements in live insect pupal structures and physical modeling, here I elucidate the physical mechanism for appearance and disappearance of this bubble and predict the site of nucleation and its exact timing. This new physical insight into the process of metamorphosis also allows us to understand the inherent design of pupal shell architectures in various species of insects.

Prakash, Manu

2011-11-01

253

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

254

Squeezing through: capsule or bubble?  

E-print Network

In this fluid dynamics video, we compare the deformation of two flexible particles as they propagate through a sudden constriction of a liquid filled channel under constant-flux flow: a gas bubble, and a capsule formed by encapsulating a liquid droplet in a cross-linked polymeric membrane. Both bubble and capsule adopt highly contorted configurations as they squeeze through the constriction, exhibit broadly similar features over a wide range of flow rates, and rupture for sufficiently high flow rates. However, at flow rates prior to rupture, certain features of the deformation allow bubble and capsule to be distinguished: bubbles exhibit a tip-streaming singularity associated with critical thinning of the rear of the bubble, while the capsule membrane wrinkles under large compressive stresses induced by the constriction.

Dawson, Geoffrey

2013-01-01

255

Development of a membrane-assisted fluidized bed reactor - 1 - Gas phase back-mixing and bubble-to-emulsion phase mass transfer using tracer injection and ultrasound experiments  

Microsoft Academic Search

A small laboratory-scale membrane-assisted fluidized bed reactor (MAFBR) was constructed in order to experimentally demonstrate the benefits of this reactor concept, especially the enhanced bubble-to-emulsion phase mass transfer and the reduced overall axial gas phase back-mixing, due to the presence of the membranes and permeation of gas through the membranes. With steady-state tracer gas injection experiments, it was demonstrated that

S. A. R. K. Deshmukh; J. A. Laverman; A. H. G. Cents; Sint Annaland van M; J. A. M. Kuipers

2005-01-01

256

Water hammer phenomena in gas-water two-phase bubbly flow through a 90° bend tube  

Microsoft Academic Search

Water hammer phenomena of two-phase bubbly flow caused by a rapid valve closure in a 90° bend pipe were investigated experimentally. The experiments were conducted in a horizontal tube of 25.4mm in inner diameter and 1.9~3.8 in ratio of the curvature radius to the inner diameter of the bend tube, in the ranges of superficial velocity from 0.23 to 1.64

Shuli Wang; Qi Sun; Zhi Zheng; Beibei Li; Pei Cai

2008-01-01

257

Bubble structures in He irradiated metals  

Microsoft Academic Search

Transmission electron microscopy is used to investigate the spatial arrangement of gas bubbles produced in the metals, Cu, Ni, Au, stainless steel and Ti irradiated with He at temperatures ? 300 K. For metals having a high degree of crystalline perfection within grains, a gas bubble superlattice is formed at high He doses in every case investigated. A study is

P. B. Johnson; D. J. Mazey; J. H. Evans

1983-01-01

258

Optical detection of gas in producing oil wells  

NASA Astrophysics Data System (ADS)

A new production logging device has been field tested that uses innovative sensing technology to enable the direct detection and quantification of gas in multiphase flows. Four optical probes, deployed 90 degrees apart on the arms of a centralizer-like tool, measure the optical reflectance of the surrounding fluid. The probes are evenly spaced in the pipe cross section, and their orientation in space is accurately known through use of an integrated relative- bearing sensor. In gas-liquid mixtures, the optical signal reflected by the probe is used to determine gas holdup and a gas bubble count, which is related to gas flow rate. In addition, the individual sensor measurements are used to build an image of the gas flow in the well. These images are particularly useful in deviated and horizontal wells for better understanding the multiphase flow patterns and interpreting their inherent phase segregation occurring at such deviations. The new tool has been successfully field tested in wells throughout the world and the tool's capabilities are illustrated by example form both field and laboratory data sets. The new tool has been designed to detect the presence of gas, and hence its major application is to identify gas entries in oil/water wells or water/oil/condensate in gas wells. Because of its high sensitivity to minute amounts of gas, the tool can also be used to locate the bubble point when logging in the tubing. The introduction of optical sensing technology in this new tool represents an innovation in production logging. The provided data enable the direct detection and quantification of gas or liquid in multiphase mixtures, allowing the precise diagnosis of well problems and helping design of production enhancement interventions.

Cens, Fabien; Theron, Bernard; Vuhoang, D.; Faur, Marian; Rezgui, Fadhel; McKeon, D.

2000-12-01

259

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.

260

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

261

Holdup Measurement System II (HMSII): Version 2.1. User`s guide and software documentation  

SciTech Connect

The Holdup Measurement System II (HMSII) software is a database management package for doing Holdup Measurements. It is based on the generalized geometry holdup (GGH) methodology taught in the US Department of Energy Safeguards Technology Training Program, ``Nondestructive Assay of Special Nuclear Materials Holdup.`` This program was developed and taught by Los Alamos National Laboratory (LANL). The HMSII was developed as a joint effort between LANL and the Oak Ridge Y-12 Plant, managed for the US Department of Energy by Lockheed Martin Energy Systems, Inc. The system is designed specifically for use with three types of Multichannel Analyzer (MCA): a Davidson Portable MultiChannel Analyzer (MCA); a EG&G Ortec MicroNOMAD ({mu}NOMAD); or a new Miniature Modular MultiChannel Analyzer (M{sup 3}CA) under development at LANL. It is also designed assuming a 512 channel spectrum from a low resolution (e.g., NaI) detector measuring Uranium or Plutonium. Another important hardware component of the system is a portable bar code reader (also called a DataLogger or Trakker), by Intermec Corporation. The 944X series and the JANUS 2OXX series readers are compatible models with the HMSII. The JANUS series is a bar code reader which is also a 386 compatible palmtop PC with MS-DOS 5.0 built-in. Both series readers are programmable and control all the aspects of field holdup data collection from the MCAs.

Smith, S.E.

1995-05-31

262

Experimental Confirmation of the Oscillating Bubble Technique with Comparison to the Pendant Bubble Method: The Adsorption Dynamics of 1Decanol  

Microsoft Academic Search

A new oscillating bubble method is used to measure surfactant mass transfer kinetics at liquid–gas interfaces. A spherical bubble is formed, equilibrated, and oscillated radially with a small amplitude. The radial oscillations cause the gas-phase pressure to cycle about its equilibrium because of the periodic changes in bubble curvature and surface tension. The phase angle ? between the radial and

David O. Johnson; Kathleen J. Stebe

1996-01-01

263

Stable tridimensional bubble clusters in multi-bubble sonoluminescence (MBSL).  

PubMed

In the present work, stable clusters made of multiple sonoluminescent bubbles are experimentally and theoretically studied. Argon bubbles were acoustically generated and trapped using bi-frequency driving within a cylindrical chamber filled with a sulfuric acid aqueous solution (SA85w/w). The intensity of the acoustic pressure field was strong enough to sustain, during several minutes, a large number of positionally and spatially fixed (without pseudo-orbits) sonoluminescent bubbles over an ellipsoidally-shaped tridimensional array. The dimensions of the ellipsoids were studied as a function of the amplitude of the applied low-frequency acoustic pressure (PAc(LF)) and the static pressure in the fluid (P0). In order to explain the size and shape of the bubble clusters, we performed a series of numerical simulations of the hydrodynamic forces acting over the bubbles. In both cases the observed experimental behavior was in excellent agreement with the numerical results. The simulations revealed that the positionally stable region, mainly determined by the null primary Bjerknes force (F?Bj), is defined as the outer perimeter of an axisymmetric ellipsoidal cluster centered in the acoustic field antinode. The role of the high-frequency component of the pressure field and the influence of the secondary Bjerknes force are discussed. We also investigate the effect of a change in the concentration of dissolved gas on the positional and spatial instabilities through the cluster dimensions. The experimental and numerical results presented in this paper are potentially useful for further understanding and modeling numerous current research topics regarding multi-bubble phenomena, e.g. forces acting on the bubbles in multi-frequency acoustic fields, transient acoustic cavitation, bubble interactions, structure formation processes, atomic and molecular emissions of equal bubbles and nonlinear or unsteady acoustic pressure fields in bubbly media. PMID:24974006

Rosselló, J M; Dellavale, D; Bonetto, F J

2015-01-01

264

A Laboratory Experiment To Measure Henry's Law Constants of Volatile Organic Compounds with a Bubble Column and a Gas Chromatography Flame Ionization Detector (GC-FID)  

ERIC Educational Resources Information Center

An undergraduate laboratory experiment is described to measure Henry's law constants of organic compounds using a bubble column and gas chromatography flame ionization detector (GC-FID). This experiment is designed for upper-division undergraduate laboratory courses and can be implemented in conjunction with physical chemistry, analytical…

Lee, Shan-Hu; Mukherjee, Souptik; Brewer, Brittany; Ryan, Raphael; Yu, Huan; Gangoda, Mahinda

2013-01-01

265

Comparison of electrical capacitance tomography & gamma densitometer measurement in viscous oil-gas flows  

NASA Astrophysics Data System (ADS)

Multiphase flow is a common occurrence in industries such as nuclear, process, oil & gas, food and chemical. A prior knowledge of its features and characteristics is essential in the design, control and management of such processes due to its complex nature. Electrical Capacitance Tomography (ECT) and Gamma Densitometer (Gamma) are two promising approaches for multiphase visualization and characterization in process industries. In two phase oil & gas flow, ECT and Gamma are used in multiphase flow monitoring techniques due to their inherent simplicity, robustness, and an ability to withstand wide range of operational temperatures and pressures. High viscous oil (viscosity > 100 cP) is of interest because of its huge reserves, technological advances in its production and unlike conventional oil (oil viscosity < 100 cP) and gas flows where ECT and Gamma have been previously used, high viscous oil and gas flows comes with certain associated concerns which include; increased entrainment of gas bubbles dispersed in oil, shorter and more frequent slugs as well as oil film coatings on the walls of flowing conduits. This study aims to determine the suitability of both devices in the visualization and characterization of high-viscous oil and gas flow. Static tests are performed with both devices and liquid holdup measurements are obtained. Dynamic experiments were also conducted in a 1 & 3 inch facility at Cranfield University with a range of nominal viscosities (1000, 3000 & 7500 cP). Plug, slug and wavy annular flow patterns were identified by means of Probability Mass Function and time series analysis of the data acquired from Gamma and ECT devices with high speed camera used to validate the results. Measured Liquid holdups for both devices were also compared.

Archibong Eso, A.; Zhao, Yabin; Yeung, Hoi

2014-04-01

266

Comparison of electrical capacitance tomography and gamma densitometer measurement in viscous oil-gas flows  

SciTech Connect

Multiphase flow is a common occurrence in industries such as nuclear, process, oil and gas, food and chemical. A prior knowledge of its features and characteristics is essential in the design, control and management of such processes due to its complex nature. Electrical Capacitance Tomography (ECT) and Gamma Densitometer (Gamma) are two promising approaches for multiphase visualization and characterization in process industries. In two phase oil and gas flow, ECT and Gamma are used in multiphase flow monitoring techniques due to their inherent simplicity, robustness, and an ability to withstand wide range of operational temperatures and pressures. High viscous oil (viscosity > 100 cP) is of interest because of its huge reserves, technological advances in its production and unlike conventional oil (oil viscosity < 100 cP) and gas flows where ECT and Gamma have been previously used, high viscous oil and gas flows comes with certain associated concerns which include; increased entrainment of gas bubbles dispersed in oil, shorter and more frequent slugs as well as oil film coatings on the walls of flowing conduits. This study aims to determine the suitability of both devices in the visualization and characterization of high-viscous oil and gas flow. Static tests are performed with both devices and liquid holdup measurements are obtained. Dynamic experiments were also conducted in a 1 and 3 inch facility at Cranfield University with a range of nominal viscosities (1000, 3000 and 7500 cP). Plug, slug and wavy annular flow patterns were identified by means of Probability Mass Function and time series analysis of the data acquired from Gamma and ECT devices with high speed camera used to validate the results. Measured Liquid holdups for both devices were also compared.

Archibong Eso, A.; Zhao, Yabin; Yeung, Hoi [Department of Offshore Process and Energy Systems Engineering, Cranfield University, Cranfield (United Kingdom)

2014-04-11

267

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

268

Mercury Bubbles  

Microsoft Academic Search

I HAVE on several occasions noticed the beautiful bubbles described by Mr. Wright and Sir William Crookes (pp. 8 and 37). On each occasion I was purifying mercury in the following way. I half filled a rather large Woulffe's bottle with mercury and poured on to it weak nitric acid. Then, in order to keep, the whole in a state

A. T. Hare

1908-01-01

269

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

270

235U Holdup Measurements in Three 321-M Exhaust HEPA Banks  

SciTech Connect

The Analytical Development Section of Savannah River National Laboratory (SRNL) was requested by the Facilities Disposition Division to determine the holdup of enriched uranium in the 321-M facility as part of an overall deactivation project of the facility. The 321-M facility was used to fabricate enriched uranium fuel assemblies, lithium-aluminum target tubes, neptunium assemblies, and miscellaneous components for the production reactors. The results of the holdup assays are essential for determining compliance with the Waste Acceptance Criteria, Material Control & Accountability, and to meet criticality safety controls. This report covers holdup measurements of uranium residue in three HEPA filter exhaust banks of the 321-M facility. Each of the exhaust banks has dimensions near 7' x 14' x 4' and represents a complex holdup problem. A portable HPGe detector and EG&G Dart system that contains the high voltage power supply and signal processing electronics were used to determine highly enriched uranium (HEU) holdup. A personal computer with Gamma-Vision software was used to control the Dart MCA and to provide space to store and manipulate multiple 4096-channel {gamma}-ray spectra. Some acquisitions were performed with the portable detector configured to a Canberra Inspector using NDA2000 acquisition and analysis software. Our results for each component uses a mixture of redundant point source and area source acquisitions that yielded HEU contents in the range of 2-10 grams. This report discusses the methodology, non-destructive assay (NDA) measurements, assumptions, and results of the uranium holdup in these items. This report includes use of transmission-corrected assay as well as correction for contributions from secondary area sources.

Dewberry, R

2005-02-24

271

Bubble kinetics in a steady-state column of aqueous foam  

Microsoft Academic Search

We measure the liquid content, the bubble speeds, and the distribution of bubble sizes, in a vertical column of aqueous foam maintained in steady state by continuous bubbling of gas into a surfactant solution. Nearly round bubbles accumulate at the solution\\/foam interface, and subsequently rise with constant speed. Upon moving up the column, they become larger due to gas diffusion

K. Feitosa; Olivia L. Halt; Randall D. Kamien; D. J. Durian

2006-01-01

272

Bubble effect on Kelvin-Helmholtz' instability  

E-print Network

We derive boundary conditions at interfaces (contact discontinuities) for a class of Lagrangian models describing, in particular, bubbly flows. We use these conditions to study Kelvin-Helmholtz' instability which develops in the flow of two superposed layers of a pure incompressible fluid and a fluid containing gas bubbles, co-flowing with different velocities. We show that the presence of bubbles in one layer stabilizes the flow in some intervals of wave lengths.

Sergey L. Gavrilyuk; Henri Gouin; Vladimir M. Teshukov

2008-01-16

273

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

Microsoft Academic Search

Relatively recent discovery of the natural CH_4 gas seepage from the sea bed had action upon the philosophy of CH_4 contribution to global budgets. So far as numerous gas vent sites are known, an acceptable method for released gas quantification is required. In particular, the questions should be answered as follows: 1) how much amount of gas comes into the

Yu. G. Artemov

2003-01-01

274

Plasticization Effects on Bubble Growth During Polymer Xiaopeng Chen, James J. Feng,  

E-print Network

the melt viscosity, gas diffusivity in the melt, and the gas­melt interfacial tension. In this paper, we incorporating gas diffusion, momentum transfer, melt viscoelasticity, and bubble­bubble interactions via a cell of temperature, the blowing agent separates from the melt and aggregates into gas bubbles. This paper

Feng, James J.

275

FEASTING BLACK HOLE BLOWS BUBBLES  

NASA Technical Reports Server (NTRS)

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

2002-01-01

276

The Behavior of Micro Bubbles and Bubble Cluster in Ultrasound Field  

NASA Astrophysics Data System (ADS)

Ultrasound is widely applied in the clinical field today, such as ultrasound imaging, Extracorporeal Shock Wave Lithotripsy (ESWL) and so on. It is essential to take a real understanding of the dynamics of micro bubbles and bubble cluster in these applications. Thus we numerically simulate them in ultrasound field in this paper. In the numerical simulation, we consider the thermal behavior inside the bubble and the pressure wave phenomena in the bubble cluster in detail, namely, the evaporation and condensation of liquid at the bubble wall, heat transfer through the bubble wall, diffusion of non-condensable gas inside the bubble and the compressibility of liquid. Initial cluster radius is to 0.5[mm], bubble radius is 1.7[mm], void fraction is 0.1[ambient pressure is 101.3[kPa], temperature is 293[K] and the amplitude of ultrasound is 50[kPa]. We simulate bubble cluster in ultrasound field at various frequencies and we obtain the following conclusions. 1) The maximum pressure inside bubble cluster reaches 5[MPa] and this is much higher than that of a bubble. 2) Bubble cluster behaves like a rigid body acoustically when the frequency of ultrasound is much higher than its natural frequency.

Yoshizawa, Shin; Matsumoto, Yoichiro

2001-11-01

277

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

278

Injunctions, Hold-Up, and Patent Royalties Carl Shapiro, University of California at Berkeley  

E-print Network

Injunctions, Hold-Up, and Patent Royalties Carl Shapiro, University of California at Berkeley Send royalty negotiations between a patent holder and a downstream firm whose product is more valuable if it includes a feature cov- ered by the patent. The downstream firm must make specific investments to de- velop

Sadoulet, Elisabeth

279

Experimental Investigation of Taylor bubble acceleration mechanism in slug flow  

Microsoft Academic Search

Measurements of the total drag force on a stationary, solid model of a Taylor bubble placed in a downward flowing liquid stream in a vertical tube have been performed and analyzed using a one-dimensional flow model, in order to study the mechanisms responsible for acceleration of a Taylor bubble in the wake region of a preceding Taylor bubble in gas–liquid

E. T Tudose; M Kawaji

1999-01-01

280

Numerical analysis of the effects of radiation heat transfer and ionization energy loss on the cavitation Bubble?s dynamics  

Microsoft Academic Search

A numerical scheme for simulating the acoustic and hydrodynamic cavitation was developed. Bubble instantaneous radius was obtained using Gilmore equation which considered the compressibility of the liquid. A uniform temperature was assumed for the inside gas during the collapse. Radiation heat transfer inside the bubble and the heat conduction to the bubble was considered. The numerical code was validated with

M. Mahdi; R. Ebrahimi; M. Shams

2011-01-01

281

Laser Doppler velocimetry measurement of turbulent bubbly channel flow  

Microsoft Academic Search

Measurements of the turbulence properties of gas-liquid bubbly flows with mono-dispersed 1-mm-diameter bubbles are reported for upward flow in a rectangular channel. Bubble size and liquid-phase velocity were measured using image-processing and laser Doppler velocimetry (LDV), respectively. A description is given of the special arrangements for two-dimensional LDV needed to obtain reliable bubbly flow data, in particular the configuration of

S. So; H. Morikita; S. Takagi; Y. Matsumoto

2002-01-01

282

Numerical simulations of non-spherical bubble collapse  

Microsoft Academic Search

A high-order accurate shock- and interface-capturing scheme is used to simulate the collapse of a gas bubble in water. In order to better understand the damage caused by collapsing bubbles, the dynamics of the shock-induced and Rayleigh collapse of a bubble near a planar rigid surface and in a free field are analysed. Collapse times, bubble displacements, interfacial velocities and

ERIC J OHNSEN; TIM C OLONIUS

283

Electrolysis Bubbles Make Waterflow Visible  

NASA Technical Reports Server (NTRS)

Technique for visualization of three-dimensional flow uses tiny tracer bubbles of hydrogen and oxygen made by electrolysis of water. Strobe-light photography used to capture flow patterns, yielding permanent record that is measured to obtain velocities of particles. Used to measure simulated mixing turbulence in proposed gas-turbine combustor and also used in other water-table flow tests.

Schultz, Donald F.

1990-01-01

284

Bubble dynamics in structural foam processing  

NASA Astrophysics Data System (ADS)

The stress distribution of viscoelastic polymer melts in a converging channel were determined by measuring wall normal stress and stress birefringence. The Coleman-Noll second order fluid was used to derive theoretical expressions for the wall normal stress, and shear, and shear and normal stresses in the converging flow field. Bubble dynamics in foam extrusion through a converging die was studied by recording bubble dynamics in the flow channel on movie films as a gas charged molten polymer was extruded. A theoretical analysis was made of bubble dynamics in which a threadlike bubble was assumed to flow along the center line of the die and the Coleman-Noll second fluid model was assumed to described the rheological behavior of the gas charged molten polymer. Bubble growth during mold filling was recorded on a movie film as gas charged molten polymer was injected into a mold cavity. A theoretical study of bubble growth in foam injection molding was conducted in which a spherical bubble was assumed to grow after the injection nozzle was closed and the DeWitt models assumed to describe the rheological behavior of gas charged molten polymers. The cell size and distribution of molded specimens as affected by processing variables was investigated by employing short-shot molding process under isothermal conditions.

Yoo, H. J.

1980-03-01

285

Digital image analysis of hydrodynamics two-dimensional bubbling fluidized beds  

Microsoft Academic Search

A new method of digital image analysis has been developed to study the hydrodynamics of two-dimensional bubbling fluidized beds with a digital video camera. The method comprises simultaneous of the size and velocity of gas bubbles, and the axial and radial distribution of bubble voidage. It provides a better estimation of the visible bubble flow than from local probe methods.

Laihong Shen; Filip Johnsson; Bo Leckner

2004-01-01

286

Bubble Characterization in Pressurized Fluidized-Bed Combustors with Bed Internals  

Microsoft Academic Search

Bubble Characterization in Pressurized Fluidized-Bed Combustors with Bed Internals Abstract–Bubble characteristics within a tube bundle of a Pressurized Fluidized Bed Coal Combustor (PFBC) were studied. A model was developed to compute emulsion phase gas velocity, bubble throughflow velocity, and the visible bubble flow coefficient. Experimental data obtained from a PFBC unit were compared with the model prediction and a good

K. M. Sellakumar; V. Zakkay

1988-01-01

287

Breaking Bubble Rafts: Modeling material failure  

NASA Astrophysics Data System (ADS)

Bubble rafts have long been of interest as a model two-dimensional system for the study of general amorphous systems, ranging from metallic glasses to foams and potentially geophysical flows. Consisting of a single layer of gas-bubbles on an aqueous substrate, bubble rafts allow for excellent control over bubble size, size distribution, bubble solution composition, and for the tracking and characterizing of each bubble in the system. The individual bubbles serve as the model for the "particles" in other complex flows, such as molecules or grains. Additionally, bubble rafts have been used in a wide-range of flow geometries and with varied methods of confinement. These features of bubble rafts have provided insight in a range of issues related to the visco-elastic nature of foams and other complex fluids. In this talk, we will present results from a relatively new configuration: uniaxial extension. At relatively low speeds, the system exhibits pinch-off behaviour that is consistent with a fluid-like response. Two types of pinch-off are observed: double-cone and long-thread. The appearance of either mode is dependent on the pulling speed and system size. As the speed of extension is increased, the system exhibits classic fracture behaviour. We will report on our characterization of these transitions, with a focus on connecting to potential microscopic origins of the different modes.

Dennin, M.

2011-12-01

288

Wall-to-Bulk Mass Transfer in Co-current Gas Liquid Upflow Bubble Column Using Hourglass Promoters  

NASA Astrophysics Data System (ADS)

Limiting current measurements made at the point electrodes fixed flush with the inner wall of outer cylinder of an electrochemical cell with co-current gas-liquid upflow. The mass transfer coefficients were computed from the measured limiting currents. The system chosen was an electrolyte as liquid phase and nitrogen as gaseous phase. An equimolar solution of 0.01 N of potassium ferricyanide and ferrocyanide with 0.5 N sodium hydroxide was used as the liquid electrolyte. Data were obtained in the presence of an hourglass promoter internal with varied characteristic length and pitch values. The rod diameter was chosen as 1 cm. A longitudinal variation of mass transfer coefficient has been observed along the length of the test section. Therefore, average values of the kL were obtained and used. The kL values were found to increase with increasing gas and liquid velocities. An increase in pitch decreased the mass transfer coefficient. The characteristic length had no effect of kL. The data were correlated in terms of a jD-Re format of equation using regression analysis.

Suresh, S.; Murty, M. S. N.; Srinivas, B.; Ramesh, K. V.

2013-09-01

289

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

290

Understanding Peat Bubbles: Biogeochemical-Hydrological Linkages  

NASA Astrophysics Data System (ADS)

Decomposition of organic matter in peatland ecosystems produces gaseous end-products that can accumulate at depth and result in the build up of free-phase gas below the water table. This free-phase gas, or bubbles, reduces hydraulic conductivity, alters hydrologic and chemical gradients, and affects productivity surface vegetation through its role in peat buoyancy. In terms of greenhouse gas dynamics, these bubbles are likely the dominant subsurface stock of methane (CH4) and release of this CH4 to the atmosphere via ebullition may account for a significant portion of total efflux. Despite the importance of entrapped bubbles for peatland ecohydrological function there is still little known about how the quantity of bubbles varies between peatland types and at smaller scales within a peatland. Profiles of bubbles collected from several locations within four peatlands reveal that bubble volume varies significant among peatlands, between microforms and with depth. Previous studies also suggest that ebullition is spatially and temporally variable. This spatial variability may have important impacts on system ecohydrology and should be incorporated in models of peatland hydrology and development. This requires the difficult task of mapping bubble volume in three dimensions and over large areas. The potential for geophysical methods and the use of surface features to address this task will be discussed.

Strack, M.

2009-05-01

291

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

Microsoft Academic Search

Simultaneous observations of upper-ocean bubble clouds, and dissolved gaseous nitrogen (N2) and oxygen (O2) from three winter storms are presented and analyzed. The data were collected on the Canadian Surface Ocean Lower Atmosphere Study (C-SOLAS) mooring located near Ocean Station Papa (OSP) at 50°N, 145°W in the NE Pacific during winter of 2003\\/2004. The bubble field was measured using an

Svein Vagle; Craig McNeil; Nadja Steiner

2010-01-01

292

Data Pre-Processing Method to Remove Interference of Gas Bubbles and Cell Clusters During Anaerobic and Aerobic Yeast Fermentations in a Stirred Tank Bioreactor  

NASA Astrophysics Data System (ADS)

One aerobic and four anaerobic batch fermentations of the yeast Saccharomyces cerevisiae were conducted in a stirred bioreactor and monitored inline by NIR spectroscopy and a transflectance dip probe. From the acquired NIR spectra, chemometric partial least squares regression (PLSR) models for predicting biomass, glucose and ethanol were constructed. The spectra were directly measured in the fermentation broth and successfully inspected for adulteration using our novel data pre-processing method. These adulterations manifested as strong fluctuations in the shape and offset of the absorption spectra. They resulted from cells, cell clusters, or gas bubbles intercepting the optical path of the dip probe. In the proposed data pre-processing method, adulterated signals are removed by passing the time-scanned non-averaged spectra through two filter algorithms with a 5% quantile cutoff. The filtered spectra containing meaningful data are then averaged. A second step checks whether the whole time scan is analyzable. If true, the average is calculated and used to prepare the PLSR models. This new method distinctly improved the prediction results. To dissociate possible correlations between analyte concentrations, such as glucose and ethanol, the feeding analytes were alternately supplied at different concentrations (spiking) at the end of the four anaerobic fermentations. This procedure yielded low-error (anaerobic) PLSR models for predicting analyte concentrations of 0.31 g/l for biomass, 3.41 g/l for glucose, and 2.17 g/l for ethanol. The maximum concentrations were 14 g/l biomass, 167 g/l glucose, and 80 g/l ethanol. Data from the aerobic fermentation, carried out under high agitation and high aeration, were incorporated to realize combined PLSR models, which have not been previously reported to our knowledge.

Princz, S.; Wenzel, U.; Miller, R.; Hessling, M.

2014-11-01

293

Modeling of bubble coalescence and disintegration in confined upward two-phase flow  

Microsoft Academic Search

This paper presents the modeling of bubble interaction mechanisms in the two-group interfacial area transport equation (IATE) for confined gas–liquid two-phase flow. The transport equation is applicable to bubbly, cap-turbulent, and churn-turbulent flow regimes. In the two-group IATE, bubbles are categorized into two groups: spherical\\/distorted bubbles as Group 1 and cap\\/slug\\/churn-turbulent bubbles as Group 2. Thus, two sets of equations

Xiaodong Sun; Seungjin Kim; Mamoru Ishii; Stephen G. Beus

2004-01-01

294

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

295

The bubbling galactic plane: fertilization or sterilization?  

NASA Astrophysics Data System (ADS)

Spitzer surveys have revealed that the galactic plane has a high density of bubbles. Many of these show evidence of being associated with star formation. Followup observations collected so far have failed to conclusively determine the relationship (if any) between the bubbles and the triggering of star formation. We propose to obtain MOPRA molecular line pointed observations towards bubbles detected with APEX in the millimeter continuum and with Herschel in the far infrared/submm to reveal the presence and kinematics of dense gas and to search for evidence of the initial phases of star formation.

Testi, Leonardo; Cunningham, Maria; Zavagno, Annie; Deharveng, Lise; Leurini, Silvia; Molinari, Sergio

2010-04-01

296

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

297

Superabsorption of acoustic waves with bubble metascreens  

NASA Astrophysics Data System (ADS)

A bubble metascreen, i.e., a single layer of gas inclusions in a soft solid, can be modeled as an acoustic open resonator, whose behavior is well captured by a simple analytical expression. We show that by tuning the parameters of the metascreen, acoustic superabsorption can be achieved over a broad frequency range, which is confirmed by finite element simulations and experiments. Bubble metascreens can thus be used as ultrathin coatings for turning acoustic reflectors into perfect absorbers.

Leroy, Valentin; Strybulevych, Anatoliy; Lanoy, Maxime; Lemoult, Fabrice; Tourin, Arnaud; Page, John H.

2015-01-01

298

Acoustic waves in polydispersed bubbly liquids  

NASA Astrophysics Data System (ADS)

The propagation of acoustic waves in polydispersed mixtures of liquid with two sorts of gas bubbles each of which has its own bubble size distribution function is studied. The system of the differential equations of the perturbed motion of a mixture is presented, the dispersion relation is obtained. Equilibrium speed of sound, low-frequency and high-frequency asymptotes of the attenuation coefficient are found. Comparison of the developed theory with known experimental data is presented.

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

2014-11-01

299

Formation of toroidal bubbles from acoustic droplet vaporization  

PubMed Central

Acoustic droplet vaporization (ADV) is the selective vaporization of liquid microdroplets using ultrasound to produce stable gas bubbles. ADV is the primary mechanism in an ultrasound based cancer therapy, called gas embolotherapy, where the resulting bubbles are used to create localized occlusions leading to tumor necrosis. In this investigation, early time scale events including phase change are directly visualized using ultra-high speed imaging. Modulating elevated acoustic pressure or pulse length resulted in toroidal bubbles. For sufficiently short pulses (4 cycles at 7.5?MHz), toroidal bubble formation could be avoided, regardless of acoustic pressures tested. PMID:24711672

Li, David S.; Kripfgans, Oliver D.; Fabiilli, Mario L.; Brian Fowlkes, J.; Bull, Joseph L.

2014-01-01

300

Single Bubble Sonoluminescence in Low Gravity and Optical Radiation Pressure Positioning of the Bubble  

NASA Technical Reports Server (NTRS)

Several groups of researchers have demonstrated that high frequency sound in water may be used to cause the regular repeated compression and luminescence of a small bubble of gas in a flask. The phenomenon is known as single bubble sonoluminescence (SBSL). It is potentially important because light emitted by the bubble appears to be associated with a significant concentration of energy within the volume of the bubble. Unfortunately, the detailed physical mechanisms causing the radiation of light by oscillating bubbles are poorly understood and there is some evidence that carrying out experiments in a weightless environment may provide helpful clues. In addition, the radiation pressure of laser beams on the bubble may provide a way of simulating weightless experiments in the laboratory. The standard model of SBSL attributes the light emission to heating within the bubble by a spherically imploding shock wave to achieve temperatures of 50,000 K or greater. In an alternative model, the emission is attributed to the impact of a jet of water which is required to span the bubble and the formation of the jet is linked to the buoyancy of the bubble. The coupling between buoyancy and jet formation is a consequence of the displacement of the bubble from a velocity node (pressure antinode) of the standing acoustic wave that drives the radial bubble oscillations. One objective of this grant is to understand SBSL emission in reduced buoyancy on KC-135 parabolic flights. To optimize the design of those experiments and for other reasons which will help resolve the role of buoyancy, laboratory experiments are planned in simulated low gravity in which the radiation pressure of laser light will be used to position the bubble at the acoustic velocity node of the ultrasonic standing wave. Laser light will also be used to push the bubble away from the velocity node, increasing the effective buoyancy. The original experiments on the optical levitation and radiation pressure on bubbles in water by Unger and Marston noted above were carried out using a continuous wave (CW) beam of an Argon laser. For lateral stability the beam had a intensity minimum along its axis. Calculations of the optical radiation force on an SBSL bubble indicate that ion laser technology is a poor choice for providing the magnitude of the average optical radiation force required. Consequently it is necessary to examine various diode-pumped solid state laser technologies. The approach for this part of the research will be to achieve optical levitation of a quiescent bubble based on contemporary laser technology and then to strobe the laser synchronously with the SBSL bubble oscillations.

Thiessen, D. B.; Young, J. E.; Marr-Lyon, M. J.; Richardson, S. L.; Breckon, C. D.; Douthit, S. G.; Jian, P. S.; Torruellas, W. E.; Marston, P. L.

1999-01-01

301

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

302

Magma mixing enhanced by bubble ascent  

NASA Astrophysics Data System (ADS)

Understanding the processes that affect the rate of liquid state homogenization provides fundamental clues on the otherwise inaccessible subsurface dynamics of magmatic plumbing systems. Compositional heterogeneities detected in the matrix of magmatic rocks represent the arrested state of a chemical equilibration. Magmatic homogenization has been divided into a) the mechanical interaction of magma batches (mingling) and b) the diffusive equilibration of compositional gradients, where diffusive equilibration is exponentially enhanced by progressive mechanical interaction [1]. The mechanical interaction between two distinct batches of magma has commonly been attributed to shear and folding movements between two liquids of distinct viscosities. A mode of mechanical interaction scarcely invoked is the advection of mafic material into a felsic one through bubble motion. Yet, experiments with analogue materials demonstrated that bubble ascent has the potential to enhance the fluid mechanical component of magma mixing [2]. Here, we present preliminary results from bubble-advection experiments. For the first time, experiments of this kind were performed using natural materials at magmatic temperatures. Cylinders of Snake River Plain (SRP) basalt were drilled with a cavity of defined volume and placed underneath cylinders of SRP rhyolite. Upon melting, the gas pocket, or bubble trapped within the cavity, rose into the rhyolite, so entraining a layer of basalt. Successive iterations of the same experiment at progressive intervals ensured a time series of magmatic interaction caused by bubble segregation. Variations in initial bubble size allowed the tracking of bubble volume to advected material ratio at defined viscosity contrast. The resulting plume-like structures that the advected basalt formed within the rhyolite were characterized by microCT and subsequent high-resolution EMP analyses. The mass of advected material per bubble correlated positively with bubble size. The progressive loss of advected basalt during bubble motion was quantified by microCT for defined viscosity couples. The diffusional gradient around the plume tail showed a progressive evolution of equilibration from bottom to top of the plume tail. A future aim is to compute the impact of bubble motion on the efficiency of magma mixing in dependence of volatile solubilities and pressure and viscosity variations. This has implications for the capacity of magma to produce bubbles in e.g. stratified magma chambers. [1] De Campos, C., D. Perugini, W. Ertel-Ingrisch, D. Dingwell, and G. Poli (2011), Enhancement of magma mixing efficiency by chaotic dynamics: an experimental study, Contrib. Mineral. Petrol., 161(6), 863-881. [2] Thomas, N., S. Tait, and T. Koyaguchi (1993), Mixing of stratified liquids by the motion of gas bubbles: application to magma mixing, Earth Planet. Sci. Lett., 115(1-4), 161-175.

Wiesmaier, S.; Morgavi, D.; Perugini, D.; De Campos, C. P.; Hess, K.; Lavallee, Y.; Dingwell, D. B.

2012-12-01

303

Mechanism of single-bubble sonoluminescence.  

PubMed

Considering almost all the effective processes of physics and chemical reaction in our numerical computation model, we investigate the mechanism of single bubble sonoluminescence (SBSL). For those sonoluminescing single bubbles in water at its flashing phase, the numerical simulation reveals that if the temperature inside the bubble is not high enough which may result in the plenty oxygen molecules and OH radicals undissociated, such as the case of a single argon bubble in 20 degrees C or 34 degrees C water, the radiative attachment of electrons to oxygen molecules and OH radicals contributes most to the SBSL; if the temperature inside the bubble is higher which makes most of the water vapor inside the bubble dissociate into oxygen and hydrogen atoms, such as the case of an argon bubble or a helium bubble in 0 degrees C water, the radiative attachment of electrons to oxygen and hydrogen atoms dominates the SBSL; if the temperature is still higher, such as the case of a xenon bubble in 0 degrees C water, the contribution from electron-neutral atom bremsstrahlung and electron-ion bremsstrahlung and recombination would be comparable with the contribution from the radiative attachment of electrons to oxygen and hydrogen atoms, and they together dominate the SBSL. For sonoluminescing single bubbles in those low vapor pressure liquids, such as in 85 wt.% sulphuric acid, the electron-neutral atom bremsstrahlung and the electron-ion bremsstrahlung and recombination contribute most to the continuous spectrum part of SBSL. The present calculation also provides good interpretations to those observed phenomena, such as emitted photon numbers, the width of optical pulses, the blackbody radiation like spectra. The temperature fitted by the blackbody radiation formula is very different from that calculated by the gas dynamics equations. Besides, the effect of chemical dissociation on the shock wave is also discussed. PMID:17025536

An, Yu

2006-08-01

304

Bubble evolution and properties in homogeneous nucleation simulations  

NASA Astrophysics Data System (ADS)

We analyze the properties of naturally formed nanobubbles 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 surface tension as well as the local viscosity. The liquid-vapor bubble interface is thinner than expected from planar coexistence simulations by up to 50 % . Bubbles near the critical size are extremely nonspherical, yet they quickly become spherical as they grow. The Rayleigh-Plesset description of bubble-growth gives good agreement in the cavitation regime.

Angélil, Raymond; Diemand, Jürg; Tanaka, Kyoko K.; Tanaka, Hidekazu

2014-12-01

305

QCL - Optical-Feedback Cavity Enhanced Absorption Spectroscopy For The Analysis Of Atmospheric 13CO2/12CO2 In Ice-Core Gas Bubbles  

NASA Astrophysics Data System (ADS)

In the context of a globally warming climate it is crucial to study the climate variability in the past and to understand the underlying mechanisms. The composition of gas stored in bubbles in polar ice presents a paleo-climate archive that provides a powerful means to study the exact mechanisms involved in the ~40% increase in the atmospheric CO2 concentration between glacial and interglacial climates. It is particularly important to understand such natural coupling between climate and the carbon cycle, as it will partly determine what natural feedback can be expected on the atmospheric CO2 concentration in a future warmer world. The source of the CO2 released into the atmosphere during previous deglaciations can be constrained from isotopic measurements by the fact that the different CO2 reservoirs (terrestrial biosphere, oceans) and associated mechanisms (biological or physical) have different isotopic signatures. Unfortunately, such isotope studies have been seriously hampered by the experimental difficulty of extracting the CO2 without contamination or fractionation, and measuring the isotope signal off-line on an isotope ratio mass spectrometer (IRMS). Here we present an alternative method that leverages the extreme sensitivity afforded by Optical Feedback Cavity Enhanced Absorption Spectroscopy (OF-CEAS) in the Mid-Infrared [1]. This region of the spectrum is accessed by a custom-developed Quantum Cascade Laser operating near 4.35 µm. The feedback to the laser of light that has been spectrally filtered by a high-finesse, V-shaped enhancement cavity has the effect of spectrally narrowing the laser emission and to auto-lock the laser frequency to one of the cavity's longitudinal modes, with clear advantages in terms of acquisition time and signal-to-noise ratio of the measurement. The line strengths in this region are about 5 orders of magnitude higher than in the more easily accessible NIR region near 1.6 µm and about 1000 times higher than at 2 µm. The instrument is temperature stabilization at the mK-level. Together with a small cavity volume of ~20 mL, this enables the analysis of nmol-sized samples with high precision (< 0.05‰) in a fraction of the time required by the conventional IRMS-based technique. We will show preliminary results obtained on synthetic samples. [1] Maisons G., Gorrotxategi Carbajo P., Carras M., Romanini D.: Optical-feedback cavity-enhanced absorption spectroscopy with a quantum cascade laser, Opt. Lett., 35, 3607, 2010. [2] Morville J., Kassi S., Chenevier M., and Romanini D.: Fast, low-noise, mode-by-mode, cavity-enhanced absorption spectroscopy by diode-laser self-locking, Appl. Phys., B 80, 1027-1038, 2005.

Gorrotxategi Carbajo, Paula; Romanini, Daniele; Maisons, Gregory; Carras, Mathieu; Chappellaz, Jerome; Kerstel, Erik

2013-04-01

306

Intragranular Xe bubble population evolution in UO 2: A first passage Monte Carlo simulation approach  

NASA Astrophysics Data System (ADS)

We introduce a first passage based Monte Carlo [1] code to investigate the population evolution of Xe fission gas bubbles in UO 2 fuels. Growth laws are obtained for homogeneous and heterogeneous re-solution models for a wide range of gas and bubble diffusivities. Under certain irradiation conditions, bubble populations find dynamic steady states. Homogeneous re-solution is included using a Monte Carlo binary collision model, while heterogeneous re-solution is modeled as the ad hoc destruction of bubbles.

Schwen, D.; Averback, R. S.

2010-07-01

307

Mechanisms of stability of armored bubbles: FY 1995 progress report  

SciTech Connect

Experimental and theoretical studies of stabilization of liquid films between bubbles were undertaken as part of an effort to model gas release in waste tanks at the Hanford nuclear reservation. Synthetic Hanford waste created here showed solids accumulation at bubble surfaces and some stabilization of bubbles in a froth upon sparging with nitrogen. Dilational interfacial rheological measurements indicate increasing hydrophobicity with increasing EDTA concentration in the wastes. There is greater dilational elasticity of the interface with solid particles present on the interface. Theoretical modeling of a 2D liquid film between bubbles containing one row of solid particles suggests that in 3D such a film would be unstable unless the solids all touch. This hints at a possible mechanism for bubble stabilization, if it can be argued that slowly evolving interfaces, as bubbles grow toward each other in the sludge, have solids closely packed, but that rapid expansion of gas during a rollover event forces the films to expand without additional solids.

Rossen, W.R.; Das, S.K.

1996-04-01

308

Effects of Gravity on Bubble Formation at a Plate Orifice  

NASA Technical Reports Server (NTRS)

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

Webbon, Bruce W.; Buyevich, Yu A.

1995-01-01

309

Metamorphism of stratified firn at Dome Fuji, Antarctica: A mechanism for local insolation modulation of gas transport conditions during bubble close off  

Microsoft Academic Search

The evolution of the structure of a 112.59 m long firn core recovered at Dome Fuji, East Antarctica, was investigated in order to improve understanding of firn densification and bubble formation processes, which are important for interpreting local insolation proxies used for astronomical dating of deep ice cores. Using selected samples, we measured physical properties including (1) the relative dielectric

Shuji Fujita; Junichi Okuyama; Akira Hori; Takeo Hondoh

2009-01-01

310

Modeling the Motion of a Rising Bubble  

NASA Astrophysics Data System (ADS)

It is well known that an air bubble in water with a diameter between 1.3mm and 50mm does not move straight up as might be expected, but instead zigzags or spirals. We have developed an apparatus to study this phenomenon using digital video capture. Air bubbles are formed at the bottom of a rectangular Plexiglas tank three feet high with a base one foot by one foot, filled with water. Bubbles of two different diameters can be formed using either 0.25 inch tubing (bubble diameter 5mm) or a 1cc syringe (bubble diameter 2mm) hooked to an intravenous pump with the rate of gas flow set at 10mL/hr. The motion of the bubbles is recorded using two digital video cameras viewing from the front and side of the tank, operating at 30 frames per second. The position data are obtained from the videos using VideoPoint software and then modeled mathematically. We will present a mathematical model of this motion and compare our data to previous results. We plan to explore the relationships between side-to-side motion and the upward motion of the bubbles.

Greer, Ryan; George, E. A.; Voytas, P. A.

2002-04-01

311

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

312

Circulatory bubble dynamics: from physical to biological aspects.  

PubMed

Bubbles can form in the body during or after decompression from pressure exposures such as those undergone by scuba divers, astronauts, caisson and tunnel workers. Bubble growth and detachment physics then becomes significant in predicting and controlling the probability of these bubbles causing mechanical problems by blocking vessels, displacing tissues, or inducing an inflammatory cascade if they persist for too long in the body before being dissolved. By contrast to decompression induced bubbles whose site of initial formation and exact composition are debated, there are other instances of bubbles in the bloodstream which are well-defined. Gas emboli unwillingly introduced during surgical procedures and ultrasound microbubbles injected for use as contrast or drug delivery agents are therefore also discussed. After presenting the different ways that bubbles can end up in the human bloodstream, the general mathematical formalism related to the physics of bubble growth and detachment from decompression is reviewed. Bubble behavior in the bloodstream is then discussed, including bubble dissolution in blood, bubble rheology and biological interactions for the different cases of bubble and blood composition considered. PMID:24534474

Papadopoulou, Virginie; Tang, Meng-Xing; Balestra, Costantino; Eckersley, Robert J; Karapantsios, Thodoris D

2014-04-01

313

Tiny Bubbles in my BEC  

SciTech Connect

Ultracold atomic gases provide a unique way for exploring many-body quantum phenomena that are inaccessible to conventional low-temperature experiments. Nearly two decades ago the Bose-Einstein condensate (BEC) - an ultracold gas of bosons in which almost all bosons occupy the same single-particle state - became experimentally feasible. Because a BEC exhibits superfluid properties, it can provide insights into the behavior of low-temperature helium liquids. We describe the case of a single distinguishable atom (an impurity) embedded in a BEC and strongly coupled to the BEC bosons. Depending on the strength of impurity-boson and boson-boson interactions, the impurity self-localizes into two fundamentally distinct regimes. The impurity atom can behave as a tightly localized 'polaron,' akin to an electron in a dielectric crystal, or as a 'bubble,' an analog to an electron bubble in superfluid helium. We obtain the ground state wavefunctions of the impurity and BEC by numerically solving the two coupled Gross-Pitaevskii equations that characterize the system. We employ the methods of imaginary time propagation and conjugate gradient descent. By appropriately varying the impurity-boson and boson-boson interaction strengths, we focus on the polaron to bubble crossover. Our results confirm analytical predictions for the polaron limit and uncover properties of the bubble regime. With these results we characterize the polaron to bubble crossover. We also summarize our findings in a phase diagram of the BEC-impurity system, which can be used as a guide in future experiments.

Blinova, Alina A. [Los Alamos National Laboratory

2012-08-01

314

Simulations of Buoyant Bubbles in Galaxy Clusters  

E-print Network

It is generally argued that most clusters of galaxies host cooling flows in which radiative cooling in the centre causes a slow inflow. However, recent observations by Chandra and XMM conflict with the predicted cooling flow rates. Here we report highly resolved hydrodynamic simulations which show that buoyant bubbles can offset the cooling in the inner regions of clusters and can significantly delay the deposition of cold gas. The subsonic rise of bubbles uplifts colder material from the central regions of the cluster. This colder material appears as bright rims around the bubbles. The bubbles themselves appear as depressions in the X-ray surface brightness as observed in a growing number of clusters.

M. Bruggen

2003-01-17

315

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

316

Determination of the radioactive material and plutonium holdup in ducts and piping in the 325 Building  

SciTech Connect

This report describes the measurements performed to determine the radionuclide content and mass of Pu in exposed ducts, filters, and piping in the 325 Building at the Hanford Site. This information is needed to characterize facility radiation levels, to verify compliance with criticality safety specifications, and to allow more accurate nuclear material control using nondestructive assay. Gamma assay was used to determine the gamma-emitting isotopes in ducts, filters, and piping. Passive neutron counting was used to estimate the Pu content. A high-purity Ge detector and a neutron slab detector containing 5 {sup 3}He proportional counters were used. Almost all the gamma activity is from {sup 137}Cs and {sup 60}Co. Estimated Pu mass gram equivalents in the basement ductwork and filters are 31 g; the radioactive liquid waste system (RLWS) line has 12 g; the laboratory vacuum system has 2 g equiv. Pu; the retention process sewer has 3 g. Total Pu mass holdup for basement areas range from 48 to 27 g. Estimated Pu mass gram equivalents for all laboratories range from 385 to 581 g. Individual laboratory estimates are tabulated. Total estimated Pu gram equivalent holdup and material in process for the facility is 410 g. In summary, results indicate that no significant Pu levels, from a criticality safety perspective, reside in the ductwork, laboratory vacuum system lines, RLWS pipes, or any one laboratory in the 325 Building.

Haggard, D.L.; Tanner, J.E.; Tomeraasen, P.L.

1996-08-01

317

Bubble domain circuit organization  

NASA Technical Reports Server (NTRS)

An on-chip bubble domain circuit organization. One or more storage registers are connected to a propagation path whereby data in the form of magnetic bubble domains (bubbles) may be transferred into and out of the storage registers. The propagation path includes a generator for producing the initial bubbles which are expanded into any desired number of new bubbles by a unique multiple output replicator. A unique input decoder is utilized to determine to which storage register the bubbles from the replicator will be directed along the propagation path. Those bubbles not selected may be annihilated. An output decoder utilizing essentially the same decoding scheme as the input decoder, selectively receives bubbles from the storage register. A transfer and replicate switch is utilized between the storage register and output decoder to selectively transfer bubbles to the output decoder. The output decoder may collapse all of the bubbles from certain storage registers so that only the information from the selected storage register reaches the detector. The detectors in turn produce the chip output signal. External control electronics are utilized to control the selective operation of the various devices utilized in the propagation path.

Chen, Thomas T. (Inventor)

1977-01-01

318

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

319

Radiation pressure-driven dust waves inside bursting interstellar bubbles  

E-print Network

Massive stars drive the evolution of the interstellar medium through their radiative and mechanical energy input. After their birth, they form bubbles of hot gas surrounded by a dense shell. Traditionally, the formation of bubbles is explained through the input of a powerful stellar wind, even though direct evidence supporting this scenario is lacking. Here we explore the possibility that interstellar bubbles seen by the Spitzer- and Herschel space telescopes, blown by stars with log(L/L_sun) ionization of the surrounding gas. We show that density gradients in the natal cloud or a puncture in the swept up shell lead to an ionized gas flow through the bubble into the general interstellar medium, which is traced by a dust wave near the star, demonstrating the importance of radiation pressure during this phase. Dust waves provide a natural explanation for the presence of dust inside H II bubbles, offer a novel method to study dust in H II regions...

Ochsendorf, B B; Cox, N L J; Berné, O; Kaper, L; Tielens, A G G M

2014-01-01

320

Soap and Bubbles  

NSDL National Science Digital Library

The first Web site, from The Soap and Detergent Association, is called Soaps and Detergents (1). Visitors learn about the chemistry of soap and detergent, their history, how they're manufactured, and more. The easily read text and fun illustrations make this site a great place to start for this topic. The next site, called Bubble Engineering (2), is provided by Bubble Town. The page describes the physics of a cone-shaped bubble blowing device and how its shape reduces the velocity of air being blown through but not the volume of air moving through it. Other links on the site describe what the contents of the best bubble soap mixture. The third site is provided by Kevin Dunn of Hampden-Sydney College Department of Chemistry called Lye Soap (3). The site describes how soap was invented, the chemistry of lye and soap, how to make your own lye, and more. The fourth site highlighted is part of LessonPlansPage.com called Looking at Bubbles (4). The site, which is a lesson plan, is geared towards students between grades 6 and 8. The main objective of the chemistry activity is to explore what things can be added to soap to make the bubbles last longer. All procedures are provided to view online or to print. The Art and Science of Bubbles (5) Web site is maintained by the Soap and Detergent Association. Many great features can be found on this and other pages within the site, including washing hands with soap, the history and chemistry of soaps and detergents, the environmentally smart way of using and disposing of cleaning products, and more. The sixth site related to soap is entitled Bubble Games (6), which is maintained by bubbles.org. Three free games are offered here including Tic-Tac-Bubble, Bubblechase, and Bubble Wrap, which counts how many bubbles you can pop in twenty seconds. Next, from the Homeschooling page of About.com comes the Soap Power (7) activity. This unique lesson plan details how to power a model boat using soap as a result of its surface tension. Lastly, the Bubble Hydrodynamics (8) Web site is maintained by bubbleology.com. Visitors get an introduction to bubble hydrodynamics and also learn about the relationship between temperature and bubbles, surfactants and bubbles, and even oscillations and bubbles.

Brieske, Joel A.

2002-01-01

321

The control of bubble size in carbonated beverages  

Microsoft Academic Search

The effects on bubble growth dynamics of physically altering the substrate surface on which gas bubbles are nucleated following depressurisation of a saturated solution have been studied. Seven different modified surfaces have been investigated, with modification methods ranging from ageing (by repeated washing) to the production of both random and ordered mechanical abrasions in one, two or four orientations.The main

G. S Barker; B Jefferson; S. J Judd

2002-01-01

322

Forcing of seismic waves travelling through a bubbly magma  

Microsoft Academic Search

The idea of amplification of seismic waves in magma was first introduced by Lensky et al. (2002) who examined the compressibility and the effective bulk viscosity of a bubbly suspension that expands due to the growth of gas bubbles in a supersaturated melt. At the initial stages of growth, when diffusion is efficient and viscous resistance of the melt controls

I. Kurzon; V. Lyakhovsky; N. G. Lensky; O. Navon

2005-01-01

323

Tubular precipitation and redox gradients on a bubbling template  

E-print Network

a gel containing FeSO4. When magnetite forms within the wall, a tube may grow curved in an external). Precipitative film formation on bubbles has also been demonstrated in elec- trodeposition (9). Finally, tree a precipitative film formed at the gas­solution interface; detachment of the bubble leaves a ring of material

Goldstein, Raymond E.

324

Bubble formation in organic light-emitting diodes  

Microsoft Academic Search

Bubbles in organic light-emitting diodes can be formed from gas release due to Joule heating effect at localized electrical shorts during operation, which could be simulated by a rapid thermal annealing. The gases in the bubbles consist of not only adsorbed moistures but also the decomposed organic species, which are detected in situ in an ultrahigh vacuum chamber. In the

L. S. Liao; J. He; X. Zhou; M. Lu; Z. H. Xiong; Z. B. Deng; X. Y. Hou; S. T. Lee

2000-01-01

325

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

326

Atmospheric-pressure microplasma in dielectrophoresis-driven bubbles for optical emission spectroscopy.  

PubMed

The manipulation of bubbles and the ignition of microplasma within a 200 nL bubble at atmospheric pressure and in an inert silicone oil environment were achieved. Driven by dielectrophoresis (DEP), bubble generation, transportation, mixing, splitting, and expelling were demonstrated. This process facilitated the preparation of various bubbles with tuneable gas compositions. Different gas bubbles, including air, argon (Ar), helium (He), and Ar/He mixtures, were manipulated and ignited to the plasma state by dielectric barrier discharge (DBD) within a 50 ?m-high gap between parallel plates. Moving and splitting the atmospheric-pressure microplasma in different gas bubbles were achieved by DEP. The excited light of the microplasma was recorded by an optical spectrometer for the optical emission spectroscopy (OES) analyses. The characteristic peaks of air, Ar, and He were observed in the DEP-driven microplasma. With the capability to manipulate bubbles and microplasma, this platform could be used for gas analyses in the future. PMID:22878730

Fan, Shih-Kang; Shen, Yan-Ting; Tsai, Ling-Pin; Hsu, Cheng-Che; Ko, Fu-Hsiang; Cheng, Yu-Ting

2012-10-01

327

Magnetic bubble materials.  

PubMed

Physicists, materials scientists, and engineers combined to bring solid-state bubble devices into the computer memory and recording marketplace. Devices with smaller bubbles are being developed for increased data capacity and lower cost. Epitaxial garnet films made by isothermal dipping in molten solutions helped put the technology in place and will probably satisfy the material needs of future devices with bubbles scaled down from 2 to 0.5 micrometer in size. PMID:17772820

Giess, E A

1980-05-23

328

The Use of an Ionic Liquid in a Karr Reciprocating Plate Extraction Column: Dispersed Phase Hold-up Prediction  

Microsoft Academic Search

The use of ionic liquids (ILs) as alternatives to volatile organic liquids in solvent extraction is being considered in a number of applications. This study presents data on the dispersed phase holdup of the ionic liquid [bmim][PF6] with water in a Karr extraction column. It was found that this system conforms to the standard slip velocity relationships and that the

Kelly K. L. Yung; Craig D. Smith; Tim A. Bowser; Jilska M. Perera; Geoffrey W. Stevens

2012-01-01

329

The Use of an Ionic Liquid in a Karr Reciprocating Plate Extraction Column: Dispersed Phase Hold-Up Prediction  

Microsoft Academic Search

The use of ionic liquids (ILs) as alternatives to volatile organic liquids in solvent extraction is being considered in a number of applications. This study presents data on the dispersed phase holdup of the ionic liquid [bmim][PF6] with water in a Karr extraction column. It was found that this system conforms to the standard slip velocity relationships and that the

Kelly K. L. Yung; Craig D. Smith; Tim A. Bowser; Jilska M. Perera; Geoffrey W. Stevens

2011-01-01

330

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

331

Bubbles: Using Controls  

NSDL National Science Digital Library

In this experiment, learners use JOY liquid detergent and glycerin to make the largest bubble they can that lasts 15 seconds. They blow the bubbles in a Teaching Tank, a narrow tank that is commercially available, which allows them to easily measure and monitor the bubbles. Results are collected and graphed by learners. Questions and teaching notes are included to encourage learners to consider what the multiple variables are, and what the effects of sugar, corn syrup, or other sweeteners are on their bubbles.

2012-06-26

332

TWO PHASE FLOW : ACCOUNTING FOR THE PRESENCE OF LIQUIDS IN GAS PIPELINE SIMULATION  

Microsoft Academic Search

Multiphase flow of gas and low loads of liquids occurs frequently in natural gas gathering and transmission pipelines for both onshore and offshore operations. Literature and experimental investigations indicate that dispersed droplet and stratified flow patterns are obtained when gas and small quantities of liquids flow concurrently in a pipe. Very few correlations exist for the prediction of holdup and

Ben Asante

333

Multiphase transport of gas and low loads of liquids in pipelines  

Microsoft Academic Search

Multiphase flow of gas and low loads of liquids occurs frequently in natural gas gathering and transmission pipelines for both onshore and offshore operations. Literature and experimental investigations indicate that dispersed droplet and stratified flow patterns are obtained when gas and small quantities of liquids flow concurrently in a pipe. Very few correlations exist for the prediction of holdup and

Ben Asante

2000-01-01

334

Gas/slurry flow in coal-liquefaction processes (fluid dynamics in a three-phase-flow column). Final technical progress report, 1 October 1979-31 March 1982  

SciTech Connect

A commercial coal liquefaction plant will employ vertical tubular reactors feeding slurry and gas concurrently upward through these vessels. In the SRC-I plant design the reactor is essentially an empty vessel with only a distributor plate located near the inlet. Because the commercial plant represents a considerable scale-up over Wilsonville or any pilot plant, this program addressed the need for additional data on behavior of three phase systems in large vessels. Parameters that were investigated in this program were studied at conditions that relate directly to projected plant operating conditions. The fluid dynamic behavior of the three-phase upflow system was studied by measuring gas and slurry holdup, liquid dispersion, solids suspension and solids accumulation. The dependent parameters are gas and liquid velocities, solid particle size, solids concentration, liquid viscosity, liquid surface tension and inlet distributor. Within the range of liquid superficial velocity from 0.0 to 0.5 ft/sec, gas holdup is found to be independent of liquid flow which agrees with other investigators. The results also confirm our previous finding that gas holdup is independent of column diameter when the column diameter is 5 inches or larger. The gas holdup depends strongly on gas flow rate; gas holdup increases with increasing gas velocity. The effect of solids particles on gas holdup depends on the gas flow rate. Increasing liquid viscosity and surface tension reduce gas holdup which agrees with other investigators. Because of the complexity of the system, we could not find a single correlation to best fit all the data. The degree of liquid backmixing markedly affects chemical changes occurring in the dissolver, such as sulfur removal, and oil and distillate formation.

Ying, D.H.S.; Sivasubramanian, R.; Moujaes, S.F.; Givens, E.N.

1982-04-01

335

Terminal Velocity of a Bubble Rise in a Liquid Column  

E-print Network

Abstract—As it is known, buoyancy and drag forces rule bubble’s rise velocity in a liquid column. These forces are strongly dependent on fluid properties, gravity as well as equivalent’s diameter. This study reports a set of bubble rising velocity experiments in a liquid column using water or glycerol. Several records of terminal velocity were obtained. The results show that bubble’s rise terminal velocity is strongly dependent on dynamic viscosity effect. The data set allowed to have some terminal velocities data interval of 8.0 ? 32.9 cm/s with Reynolds number interval 1.3 ? 7490. The bubble’s movement was recorded with a video camera. The main goal is to present an original set data and results that will be discussed based on two-phase flow’s theory. It will also discussed, the prediction of terminal velocity of a single bubble in liquid, as well as the range of its applicability. In conclusion, this study presents general expressions for the determination of the terminal velocity of isolated gas bubbles of a Reynolds number range, when the fluid proprieties are known. Keywords—Bubbles, terminal velocity, two phase-flow, vertical column. I.

Mário A. R. Talaia

336

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

337

Bubble Formation at a Submerged Orifice in Reduced Gravity  

NASA Technical Reports Server (NTRS)

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

Buyevich, Yu A.; Webbon, Bruce W.

1994-01-01

338

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

339

Unsteady thermocapillary migration of bubbles  

NASA Astrophysics Data System (ADS)

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.

340

Dynamics of soap bubble bursting and its implications to volcano acoustics  

E-print Network

the pressure variations, in the magma column, associ- ated with the rise of the gas bubbles toward the surface assert that acoustic waves are generated either by the bursting of the gas bubbles [Ripepe et al. (1996), Johnson (2003)] or by the oscillation of the magma membrane covering the gas slug just before the burst- 1

Paris-Sud XI, Université de

341

Evaporation, Boiling and Bubbles  

ERIC Educational Resources Information Center

Evaporation and boiling are both terms applied to the change of a liquid to the vapour/gaseous state. This article argues that it is the formation of bubbles of vapour within the liquid that most clearly differentiates boiling from evaporation although only a minority of chemistry textbooks seems to mention bubble formation in this context. The…

Goodwin, Alan

2012-01-01

342

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

343

Methane bubbling: from speculation to quantification  

NASA Astrophysics Data System (ADS)

Rates of methane bubbling (ebullition) represent a notoriously difficult emission pathway to quantify with highly variable spatial and temporal changes. However, the importance of bubbling fluxes in terms of total emissions is increasingly recognised from a number of different globally relevant natural systems including lakes, reservoirs and wetlands. This represents a critical challenge to current survey efforts to quantify greenhouse gas emissions and reduce the uncertainty associated with bubbling fluxes. A number of different methods have been proposed to overcome this challenge including bubble traps, floating chambers, echo sounders, laser spectrography and camera systems. Each method has relative merits and deficiencies with all trading-off the ability to directly quantify methane and provide spatial and temporal coverage. Here we present a novel method that allows direct measurement of methane bubble concentration as well as the ability to persistently monitor a wide spatial area. Central to the monitoring system is an Autonomous Surface Vessel (ASV) and an Optical Methane Detector (OMD). The ASV is equipped with solar panels and uses electric motors for propulsion to allow persistent environmental monitoring. The OMD has a path length of 1.3 m and 7 Hz sampling so a typical mission of 3 hours at 1 m s-1 covers an area in excess of 10 000 m2 and over 65 000 data points. The system was assessed on four sub-tropical freshwater reservoirs of varying surface area (0.5 to 100 km2), age (2 to 65 y) and catchment land use (40 to 90% natural vegetation cover). Each reservoir had unique challenges in terms of navigation and field conditions to test feasibility of this method. Deployment length varied from a single day to over 4 months to test method durability. In addition to ASV bubble surveys, floating static chambers were deployed to determine diffusive fluxes. Localised instantaneous bubble flux rates within a single reservoir ranged over three orders of magnitude from 500 to 100 000 mg m-2 d-1 depending on time of day and water depth. Average storage bubble flux rates between reservoirs varied by two orders of magnitude from 1 200 to 15 000 mg m-2 d-1, with the primary driver likely to be catchment forest cover. The relative contribution of bubbling to total fluxes varied from 10% to more than 90% depending on the reservoir and time of sampling. This method was consistently shown to greatly improve the spatial mapping and quantification of methane bubbling rates from reservoir surfaces and reduces the uncertainty associated with the determining the relative contribution of bubbling to total flux.

Grinham, A. R.; Dunbabin, M.; Yuan, Z.

2013-12-01

344

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

345

Measurement of real-time flow structures in gas–liquid and gas–liquid–solid flow systems using electrical capacitance tomography (ECT)  

Microsoft Academic Search

The real-time cross-sectional distributions of the gas holdups in gas–liquid and gas–liquid–solid systems are measured using electrical capacitance tomography. For the gas–liquid system, air as the gas phase and both Norpar 15 (paraffin) and Paratherm as the liquid phases are used. Polystyrene beads whose permittivity is similar to that of Paratherm are used as the solid phase in the gas–liquid–solid

W. Warsito; L.-S. Fan

2001-01-01

346

A large bubble around the Crab Nebula  

NASA Technical Reports Server (NTRS)

IRAS and 21 cm observations of the interstellar medium around the Crab nebula show evidence of a large bubble surrounded by a partial shell. If located at the canonical 2 kpc distance of the Crab pulsar, the shell is estimated to have a radius of about 90 pc and to contain about 50,000 solar masses of swept-up gas. The way in which interior conditions of this bubble can have important implications for observations of the Crab are described, and the fashion in which presupernova evolution of the pulsar progenitor has affected its local environment is described.

Romani, Roger W.; Reach, William T.; Koo, Bon Chul; Heiles, Carl

1990-01-01

347

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

348

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

349

Hydrodynamics of bubble columns with application to Fischer-Tropsch synthesis  

E-print Network

they provided during my graduate studies. v 1 V3 PPR NTS vst TABLE OF CONTENTS CHAPTFR F age INTRODUCTION II LITER ATURF REVIEW A. Gas Flow in Bubbie Colunrns B. Fischer-Tropsch Derived Waxes 1. Efl'ect of Temperature . 2. Efl'ect of Solids . 3. Efi... and Motivation 3 3 7 7 8 9 10 10 11 l2 16 III EXPERIMENT A. Experimental Apparatus 1. Apparatus Description 2. Operation B. Measurements of Average Gas Hold-up 1. Hot-Flov; Runs 2. Cold-Flow Runs C. i&feasurentents of Physical Propertie 1...

Raphael, Matheo Lue

2012-06-07

350

Aerator Combined With Bubble Remover  

NASA Technical Reports Server (NTRS)

System produces bubble-free oxygen-saturated water. Bubble remover consists of outer solid-walled tube and inner hydrophobic, porous tube. Air bubbles pass from water in outer tube into inner tube, where sucked away. Developed for long-term aquaculture projects in space. Also applicable to terrestrial equipment in which entrained bubbles dry membranes or give rise to cavitation in pumps.

Dreschel, Thomas W.

1993-01-01

351

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

352

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

353

Mechanisms of stability of armored bubbles: FY 1996 Final Report  

SciTech Connect

Theoretical and experimental studies examine how a coating, or {open_quotes}armor,{close_quotes} of partially wetted solid particles can stabilize tiny bubbles against diffusion of gas into the surrounding liquid, in spite of the high capillary pressures normally associated with such bubbles. Experiments with polymethylmethacrylate (PNMA) beads and carbonated water demonstrate that armored bubbles can persist for weeks in liquid unsaturated with respect to the gas in the bubbles. This question is of concern regarding gas discharges from waste tanks at the Hanford reservation. The stresses on the solid-solid contacts between particles in such cases is large and could drive sintering of the particles into a rigid framework. Stability analysis suggests that a slightly shrunken bubble would not expel a solid particle from its armor to relieve stress and allow the bubble to shrink further. Expulsion of particles from more stressed bubbles at zero capillary pressure is energetically favored in some cases. It is not clear, however, whether this expulsion would proceed spontaneously from a small perturbation or require a large initial disturbance of the bubble. In some cases, it appears that a bubble would expel some particles and shrink, but the bubble would approach a final, stable size rather than disappear completely. This simplified analysis leaves out several factors. For instance, only one perturbation toward expelling a solid from the armor is considered; perhaps other perturbations would be more energetically favored than that tested. Other considerations (particle deformation, surface roughness, contact-angle hysteresis, and adhesion or physical bonding between adjacent particles) would make expelling solids more difficult than indicated by this theoretical study.

Rossen, W.R.; Kam, S.I.

1996-11-01

354

Acoustofluidic control of bubble size in microfluidic flow-focusing configuration.  

PubMed

This paper reports a method to control the bubble size generated in a microfluidic flow-focusing configuration. With an ultrasonic transducer, we induce acoustic streaming using a forward moving, oscillating gas-liquid interface. The induced streaming substantially affects the formation process of gas bubbles. The oscillating interface acts as a pump that increases the gas flow rate significantly and forms a larger bubble. This method is applicable to a wide range of gas pressure from 30 to 90 kPa and flow rate from 380 to 2700 ?L h(-1). The bubble size can be tuned repeatedly with the response time on the order of seconds. We believe that this method will enhance the capability of a microfluidic bubble generator to produce a tunable bubble size. PMID:25510843

Chong, Zhuang Zhi; Tor, Shu Beng; Loh, Ngiap Hiang; Wong, Teck Neng; Gañán-Calvo, Alfonso M; Tan, Say Hwa; Nguyen, Nam-Trung

2015-02-01

355

Standard test method for nondestructive assay of special nuclear material holdup using Gamma-Ray spectroscopic methods  

E-print Network

1.1 This test method describes gamma-ray methods used to nondestructively measure the quantity of 235U, or 239Pu remaining as holdup in nuclear facilities. Holdup occurs in all facilities where nuclear material is processed, in process equipment, in exhaust ventilation systems and in building walls and floors. 1.2 This test method includes information useful for management, planning, selection of equipment, consideration of interferences, measurement program definition, and the utilization of resources (1, 2, 3, 4). 1.3 The measurement of nuclear material hold up in process equipment requires a scientific knowledge of radiation sources and detectors, transmission of radiation, calibration, facility operations and error analysis. It is subject to the constraints of the facility, management, budget, and schedule; plus health and safety requirements; as well as the laws of physics. The measurement process includes defining measurement uncertainties and is sensitive to the form and distribution of the material...

American Society for Testing and Materials. Philadelphia

2007-01-01

356

The thermodynamics of bubbles  

E-print Network

This paper outlines those concitions annanded by the laws of thermodynamics for equilibriza betwoen the vapor in a bubble and the surrounding liquid and then employs these concepts with a nucleation theory in an atteapt ...

Clark, John A.

1956-01-01

357

Chemistry in Soap Bubbles.  

ERIC Educational Resources Information Center

Describes a laboratory experiment in which common chemical gases are trapped inside soap bubbles. Examines the physical and chemical properties of the gases such as relative density and combustion. (Author/MM)

Lee, Albert W. M.; Wong, A.; Lee, H. W.; Lee, H. Y.; Zhou, Ning-Huai

2002-01-01

358

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

359

2012 Problem 8: Bubbles  

NASA Astrophysics Data System (ADS)

When a large number of bubbles exist in the water, an object may float on the surface or sink. The assumption of equivalent density is proposed in this article to explain the concrete example. According to the assumption, an object is floatable only if its density is less than the equivalent density of the water-bubble mixture. This conclusion is supported by the floating experiment and by measuring the pressure underwater to a satisfactory approximation.

Zhu, Kejing; Xia, Qing; Wang, Sihui; Zhou, Huijun

2015-10-01

360

Bubble gate for in-plane flow control.  

PubMed

We introduce a miniature gate valve as a readily implementable strategy for actively controlling the flow of liquids on-chip, within a footprint of less than one square millimetre. Bubble gates provide for simple, consistent and scalable control of liquid flow in microchannel networks, are compatible with different bulk microfabrication processes and substrate materials, and require neither electrodes nor moving parts. A bubble gate consists of two microchannel sections: a liquid-filled channel and a gas channel that intercepts the liquid channel to form a T-junction. The open or closed state of a bubble gate is determined by selecting between two distinct gas pressure levels: the lower level corresponds to the "open" state while the higher level corresponds to the "closed" state. During closure, a gas bubble penetrates from the gas channel into the liquid, flanked by a column of equidistantly spaced micropillars on each side, until the flow of liquid is completely obstructed. We fabricated bubble gates using single-layer soft lithographic and bulk silicon micromachining procedures and evaluated their performance with a combination of theory and experimentation. We assessed the dynamic behaviour during more than 300 open-and-close cycles and report the operating pressure envelope for different bubble gate configurations and for the working fluids: de-ionized water, ethanol and a biological buffer. We obtained excellent agreement between the experimentally determined bubble gate operational envelope and a theoretical prediction based on static wetting behaviour. We report case studies that serve to illustrate the utility of bubble gates for liquid sampling in single and multi-layer microfluidic devices. Scalability of our strategy was demonstrated by simultaneously addressing 128 bubble gates. PMID:23670058

Oskooei, Ali; Abolhasani, Milad; Günther, Axel

2013-07-01

361

Optimization of bubble column performance for nanoparticle collection.  

PubMed

Fibrous media embody the most effective and widely used method of separating ultrafine particles from a carrier fluid. The main problem associated with them is filter clogging, which induces an increasingly marked pressure drop with time and thus imposes regular media cleaning or replacement. This context has prompted the idea of investigating bubble columns, which operate at constant pressure drop, as alternatives to fibrous filters. This study examines the influence of different operating conditions, such as liquid height, air flow rate, bubble size and presence of granular beds on ultrafine particle collection. Experimental results show that bubble columns are characterised by high collection efficiency, when they feature a large liquid height and small diameter bubbling orifices, while their efficiencies remain lower than those of fibrous filters. Gas velocity does not greatly influence collection efficiency, but the inclusion of a granular bed, composed of beads, increases the bubble residence time in the column, thereby increasing the column collection efficiency. PMID:24584069

Cadavid-Rodriguez, M C; Charvet, A; Bemer, D; Thomas, D

2014-04-30

362

Gas and Shadow Swing  

NASA Astrophysics Data System (ADS)

In our digital art, we design a folding fan as an interactive magic device. You can use it to play with gas around the world of illusions. Although gas could not be seen in our real world, we still want to interact with it in our illusions by the element of bubble shadows. Opening and swinging the folding fan can blow the bubble shadows away; closing and swinging it can break bubbles. If the magic fan touches the shadow of gas, the bubble shadows will explode and release colorful particles to surround you. Those actions are controlled and located by our circuits with Arduino board.

Tsai, Chi-Hung; Lai, Mei-Yi; Liu, Che-Wei; Huang, Shiang-Yin; Lin, Che-Yu; Yeh, Jeng-Sheng

363

Bubble Eliminator Based on Centrifugal Flow  

NASA Technical Reports Server (NTRS)

The fluid bubble eliminator (FBE) is a device that removes gas bubbles from a flowing liquid. The FBE contains no moving parts and does not require any power input beyond that needed to pump the liquid. In the FBE, the buoyant force for separating the gas from the liquid is provided by a radial pressure gradient associated with a centrifugal flow of the liquid and any entrained bubbles. A device based on a similar principle is described in Centrifugal Adsorption Cartridge System (MSC- 22863), which appears on page 48 of this issue. The FBE was originally intended for use in filtering bubbles out of a liquid flowing relatively slowly in a bioreactor system in microgravity. Versions that operate in normal Earth gravitation at greater flow speeds may also be feasible. The FBE (see figure) is constructed as a cartridge that includes two concentric cylinders with flanges at the ends. The outer cylinder is an impermeable housing; the inner cylinder comprises a gas-permeable, liquid-impermeable membrane covering a perforated inner tube. Multiple spiral disks that collectively constitute a spiral ramp are mounted in the space between the inner and outer cylinders. The liquid enters the FBE through an end flange, flows in the annular space between the cylinders, and leaves through the opposite end flange. The spiral disks channel the liquid into a spiral flow, the circumferential component of which gives rise to the desired centrifugal effect. The resulting radial pressure gradient forces the bubbles radially inward; that is, toward the inner cylinder. At the inner cylinder, the gas-permeable, liquid-impermeable membrane allows the bubbles to enter the perforated inner tube while keeping the liquid in the space between the inner and outer cylinders. The gas thus collected can be vented via an endflange connection to the inner tube. The centripetal acceleration (and thus the radial pressure gradient) is approximately proportional to the square of the flow speed and approximately inversely proportional to an effective radius of the annular space. For a given FBE geometry, one could increase the maximum rate at which gas could be removed by increasing the rate of flow to obtain more centripetal acceleration. In experiments and calculations oriented toward the original microgravitational application, centripetal accelerations between 0.001 and 0.012 g [where g normal Earth gravitation (.9.8 m/s2)] were considered. For operation in normal Earth gravitation, it would likely be necessary to choose the FBE geometry and the rate of flow to obtain centripetal acceleration comparable to or greater than g.

Gonda, Steve R.; Tsao, Yow-Min D.; Lee, Wenshan

2004-01-01

364

Electric-field enhanced fluidized beds : a low-energy bubble control method  

Microsoft Academic Search

Reducing the size of gas bubbles can significantly improve the performance of gas-solid fluidized beds one of the most common reactor types in the chemical industry applied for such diverse systems as gasoline and plastics production to foods processing. However, a control of bubbles in these reactors is difficult to realize without measures that either use a lot of energy

F. Kleijn van Willigen

2006-01-01

365

BEM-based numerical study of three-dimensional compressible bubble dynamics in stokes flow  

NASA Astrophysics Data System (ADS)

The dynamics of compressible gas bubbles in a viscous shear flow and an acoustic field at low Reynolds numbers is studied. The numerical approach is based on the boundary element method (BEM), which is effective as applied to the three-dimensional simulation of bubble deformation. However, the application of the conventional BEM to compressible bubble dynamics faces difficulties caused by the degeneration of the resulting algebraic system. Additional relations based on the Lorentz reciprocity principle are used to cope with this problem. Test computations of the dynamics of a single bubble and bubble clusters in acoustic fields and shear flows are presented.

Abramova, O. A.; Akhatov, I. Sh.; Gumerov, N. A.; Itkulova, Yu. A.

2014-09-01

366

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

367

Statistical equilibrium of bubble oscillations in dilute bubbly flows  

PubMed Central

The problem of predicting the moments of the distribution of bubble radius in bubbly flows is considered. The particular case where bubble oscillations occur due to a rapid (impulsive or step change) change in pressure is analyzed, and it is mathematically shown that in this case, inviscid bubble oscillations reach a stationary statistical equilibrium, whereby phase cancellations among bubbles with different sizes lead to time-invariant values of the statistics. It is also shown that at statistical equilibrium, moments of the bubble radius may be computed using the period-averaged bubble radius in place of the instantaneous one. For sufficiently broad distributions of bubble equilibrium (or initial) radius, it is demonstrated that bubble statistics reach equilibrium on a time scale that is fast compared to physical damping of bubble oscillations due to viscosity, heat transfer, and liquid compressibility. The period-averaged bubble radius may then be used to predict the slow changes in the moments caused by the damping. A benefit is that period averaging gives a much smoother integrand, and accurate statistics can be obtained by tracking as few as five bubbles from the broad distribution. The period-averaged formula may therefore prove useful in reducing computational effort in models of dilute bubbly flow wherein bubbles are forced by shock waves or other rapid pressure changes, for which, at present, the strong effects caused by a distribution in bubble size can only be accurately predicted by tracking thousands of bubbles. Some challenges associated with extending the results to more general (nonimpulsive) forcing and strong two-way coupled bubbly flows are briefly discussed. PMID:19547725

Colonius, Tim; Hagmeijer, Rob; Ando, Keita; Brennen, Christopher E.

2008-01-01

368

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

369

TOTAL MEASUREMENT UNCERTAINTY IN HOLDUP MEASUREMENTS AT THE PLUTONIUM FINISHING PLANT (PFP)  

SciTech Connect

An approach to determine the total measurement uncertainty (TMU) associated with Generalized Geometry Holdup (GGH) [1,2,3] measurements was developed and implemented in 2004 and 2005 [4]. This paper describes a condensed version of the TMU calculational model, including recent developments. Recent modifications to the TMU calculation model include a change in the attenuation uncertainty, clarifying the definition of the forward background uncertainty, reducing conservatism in the random uncertainty by selecting either a propagation of counting statistics or the standard deviation of the mean, and considering uncertainty in the width and height as a part of the self attenuation uncertainty. In addition, a detection limit is calculated for point sources using equations derived from summary equations contained in Chapter 20 of MARLAP [5]. The Defense Nuclear Facilities Safety Board (DNFSB) Recommendation 2007-1 to the Secretary of Energy identified a lack of requirements and a lack of standardization for performing measurements across the U.S. Department of Energy (DOE) complex. The DNFSB also recommended that guidance be developed for a consistent application of uncertainty values. As such, the recent modifications to the TMU calculational model described in this paper have not yet been implemented. The Plutonium Finishing Plant (PFP) is continuing to perform uncertainty calculations as per Reference 4. Publication at this time is so that these concepts can be considered in developing a consensus methodology across the complex.

KEELE, B.D.

2007-07-05

370

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

371

FORCED OSCILLATIONS OF NONSPHERICAL BUBBLES Division of Applied Mathematics Brown University, Providence, Rhode Island 02912, U.S.A.  

E-print Network

, subharmonic spherical oscillation can be generated under ex- ternal oscillating pressure. /1,2,3,4/ Although the variational me- thod. 2. GENERAL FORMULATION FOR A BUBBLE IN OSCILLATION. Let us consider a gas bubbleFORCED OSCILLATIONS OF NONSPHERICAL BUBBLES D.Y. Hsieh Division of Applied Mathematics Brown

Paris-Sud XI, Université de

372

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

373

Fission gas detection system  

DOEpatents

A device for collecting fission gas released by a failed fuel rod which device uses a filter to pass coolant but which filter blocks fission gas bubbles which cannot pass through the filter due to the surface tension of the bubble.

Colburn, Richard P. (Pasco, WA)

1985-01-01

374

Holographic Study Of Bubble Dissolution In Human Plasma  

NASA Astrophysics Data System (ADS)

When a deep-sea diver returns to the surface, he may suffer decompression sickness (commonly known as the bends). The disease occurs when the excess inert gas that dissolves in tissues during the dive (N2 or He) forms bubbles. The standard treatment is rapid recompression in order to redissolve the bubbles. The diver is placed in a hyperbaric chamber, which is then pressurized to a point where symptoms are relieved; this pressure is maintained for an arbitrary period presumed adequate to fully dissolve all bubbles. The pressure is then reduced gradually until atomospheric pressure is reached. If all has gone well, the diver experiences no residual effects.

Buckles, Richard G.; Cox, M. E.; Eckenhoff, J. B.

1981-05-01

375

Bubble Formation from Wall Orifice in Liquid Cross-Flow Under Low Gravity  

NASA Technical Reports Server (NTRS)

Two-phase flows present a wide variety of applications for spacecraft thermal control systems design. Bubble formation and detachment is an integral part of the two phase flow science. The objective of the present work is to experimentally investigate the effects of liquid cross-flow velocity, gas flow rate, and orifice diameter on bubble formation in a wall-bubble injection configuration. Data were taken mainly under reduced gravity conditions but some data were taken in normal gravity for comparison. The reduced gravity experiment was conducted aboard the NASA DC-9 Reduced Gravity Aircraft. The results show that the process of bubble formation and detachment depends on gravity, the orifice diameter, the gas flow rate, and the liquid cross-flow velocity. The data are analyzed based on a force balance, and two different detachment mechanisms are identified. When the gas momentum is large, the bubble detaches from the injection orifice as the gas momentum overcomes the attaching effects of liquid drag and inertia. The surface tension force is much reduced because a large part of the bubble pinning edge at the orifice is lost as the bubble axis is tilted by the liquid flow. When the gas momentum is small, the force balance in the liquid flow direction is important, and the bubble detaches when the bubble axis inclination exceeds a certain angle.

Nahra, Henry K.; Kamotani, Y.

2000-01-01

376

The solar wind charge-transfer X-ray emission in the 1/4 keV energy range: inferences on Local Bubble hot gas at low Z  

E-print Network

We present calculations of the heliospheric SWCX emission spectra and their contributions in the ROSAT 1/4 keV band. We compare our results with the soft X-ray diffuse background (SXRB) emission detected in front of 378 identified shadowing regions during the ROSAT All-Sky Survey (Snowden et al. 2000). This foreground component is principally attributed to the hot gas of the so-called Local Bubble (LB), an irregularly shaped cavity of ~50-150 pc around the Sun, which is supposed to contain ~10^6 K plasma. Our results suggest that the SWCX emission from the heliosphere is bright enough to account for most of the foreground emission towards the majority of low galactic latitude directions, where the LB is the least extended. In a large part of directions with galactic latitude above 30deg the heliospheric SWCX intensity is significantly smaller than the measured one. However, the SWCX R2/R1 band ratio differs slightly from the data in the galactic center direction, and more significantly in the galactic anti-centre direction where the observed ratio is the smallest. Assuming that both SWCX and hot gas emission are present and their relative contributions vary with direction, we tested a series of thermal plasma spectra for temperatures ranging from 10^5 to 10^6.5 K and searched for a combination of SWCX spectra and thermal emission matching the observed intensities and band ratios, while simultaneously being compatible with O VI emission measurements. In the frame of collisional equilibrium models and for solar abundances, the range we derive for hot gas temperature and emission measure cannot reproduce the Wisconsin C/B band ratio. We emphasize the need for additional atomic data, describing consistently EUV and X-ray photon spectra of the charge-exchange emission of heavier solar wind ions.

D. Koutroumpa; R. Lallement; J. C. Raymond; V. Kharchenko

2008-12-19

377

Effect of compressibility on the rise velocity of an air bubble in porous media  

NASA Astrophysics Data System (ADS)

The objective of this study is to develop a theoretical model to analyze the effect of air compressibility on air bubble migration in porous media. The model is obtained by combining the Newton's second law of motion and the ideal gas law assuming that the air phase in the bubble behaves as an ideal gas. Numerical and analytical solutions are presented for various cases of interest. The model results compare favorably with both experimental data and analytical solutions reported in the literature obtained for an incompressible air bubble migration. The results show that travel velocity of a compressible air bubble in porous media strongly depends on the depth of air phase injection. A bubble released from greater depths travels with a slower velocity than a bubble with an equal volume injected at shallower depths. As an air bubble rises up, it expands with decreasing bubble pressure with depth. The volume of a bubble injected at a 1-m depth increases 10% as the bubble reaches the water table. However, bubble volume increases almost twofold when it reaches to the surface from a depth of 10 m. The vertical rise velocity of a compressible bubble approaches that of an incompressible one regardless of the injection depth and volume as it reaches the water table. The compressible bubble velocity does not exceed 18.8 cm/s regardless of the injection depth and bubble volume. The results demonstrate that the effect of air compressibility on the motion of a bubble cannot be neglected except when the air is injected at very shallow depths.

Cihan, Abdullah; Corapcioglu, M. Yavuz

2008-04-01

378

Effect of direct bubble-bubble interactions on linear-wave propagation in bubbly liquids  

NASA Astrophysics Data System (ADS)

We study the influence of bubble-bubble interactions on the propagation of linear acoustic waves in bubbly liquids. Using the full model proposed by Fuster and Colonius [J. Fluid Mech. 688, 253 (2011), 10.1017/jfm.2011.380], numerical simulations reveal that direct bubble-bubble interactions have an appreciable effect for frequencies above the natural resonance frequency of the average size bubble. Based on the new results, a modification of the classical wave propagation theory is proposed. The results obtained are in good agreement with previously reported experimental data where the classical linear theory systematically overpredicts the effective attenuation and phase velocity.

Fuster, D.; Conoir, J. M.; Colonius, T.

2014-12-01

379

CFD modeling of bubble columns flows: implementation of population balance  

Microsoft Academic Search

The Bubble Population Balance Equation is implemented both in the two-fluid model and in the Algebraic Slip Mixture Model. Two and three-dimensional numerical simulations of two-phase (air–water) and pseudo-two-phase (air–Therminol-Glass beads) transient flows are performed for laboratory scale bubble columns of two different diameters operated over a range of superficial gas velocities (8 to 20cm\\/s) in the churn turbulent regime.

P. Chen; J. Sanyal; M. P. Dudukovic

2004-01-01

380

Modeling quiescent phase transport of air bubbles induced by breaking waves  

NASA Astrophysics Data System (ADS)

Simultaneous modeling of both the acoustic phase and quiescent phase of breaking wave-induced air bubbles involves a large range of length scales from microns to meters and time scales from milliseconds to seconds, and thus is computational unaffordable in a surfzone-scale computational domain. In this study, we use an air bubble entrainment formula in a two-fluid model to predict air bubble evolution in the quiescent phase in a breaking wave event. The breaking wave-induced air bubble entrainment is formulated by connecting the shear production at the air-water interface and the bubble number intensity with a certain bubble size spectra observed in laboratory experiments. A two-fluid model is developed based on the partial differential equations of the gas-liquid mixture phase and the continuum bubble phase, which has multiple size bubble groups representing a polydisperse bubble population. An enhanced 2-DV VOF (Volume of Fluid) model with a k - ? turbulence closure is used to model the mixture phase. The bubble phase is governed by the advection-diffusion equations of the gas molar concentration and bubble intensity for groups of bubbles with different sizes. The model is used to simulate air bubble plumes measured in laboratory experiments. Numerical results indicate that, with an appropriate parameter in the air entrainment formula, the model is able to predict the main features of bubbly flows as evidenced by reasonable agreement with measured void fraction. Bubbles larger than an intermediate radius of O(1 mm) make a major contribution to void fraction in the near-crest region. Smaller bubbles tend to penetrate deeper and stay longer in the water column, resulting in significant contribution to the cross-sectional area of the bubble cloud. An underprediction of void fraction is found at the beginning of wave breaking when large air pockets take place. The core region of high void fraction predicted by the model is dislocated due to use of the shear production in the algorithm for initial bubble entrainment. The study demonstrates a potential use of an entrainment formula in simulations of air bubble population in a surfzone-scale domain. It also reveals some difficulties in use of the two-fluid model for predicting large air pockets induced by wave breaking, and suggests that it may be necessary to use a gas-liquid two-phase model as the basic model framework for the mixture phase and to develop an algorithm to allow for transfer of discrete air pockets to the continuum bubble phase. A more theoretically justifiable air entrainment formulation should be developed.

Shi, Fengyan; Kirby, James T.; Ma, Gangfeng

381

The Fermi Bubbles  

NASA Astrophysics Data System (ADS)

The Fermi Bubbles are a pair of giant lobes at the heart of the Milky Way, extending roughly 50 degrees north and south of the Galactic Center, and emitting photons with energies up to 100 GeV. This previously unknown structure could be evidence for past activity of the central supermassive black hole, or enhanced star formation towards the inner Galaxy. We will describe the path to discovery of the Bubbles in multiwavelength data, from the first hints in microwave radiation measured by WMAP and X-rays from ROSAT, to the unveiling of their shape and spectrum using public gamma-ray data from the Fermi Gamma-ray Space Telescope, to more recent measurements by Planck and XMM-Newton. We will outline the current state of knowledge of the Bubbles' spectrum, morphology and internal structure, and discuss theoretical proposals and numerical simulations for their nature and origin.

Finkbeiner, Douglas P.

2015-01-01

382

Multivariate bubbles and antibubbles  

NASA Astrophysics Data System (ADS)

In this paper we develop models for multivariate financial bubbles and antibubbles based on statistical physics. In particular, we extend a rich set of univariate models to higher dimensions. Changes in market regime can be explicitly shown to represent a phase transition from random to deterministic behaviour in prices. Moreover, our multivariate models are able to capture some of the contagious effects that occur during such episodes. We are able to show that declining lending quality helped fuel a bubble in the US stock market prior to 2008. Further, our approach offers interesting insights into the spatial development of UK house prices.

Fry, John

2014-08-01

383

Bubbles from nothing  

SciTech Connect

Within the framework of flux compactifications, we construct an instanton describing the quantum creation of an open universe from nothing. The solution has many features in common with the smooth 6d bubble of nothing solutions discussed recently, where the spacetime is described by a 4d compactification of a 6d Einstein-Maxwell theory on S{sup 2} stabilized by flux. The four-dimensional description of this instanton reduces to that of Hawking and Turok. The choice of parameters uniquely determines all future evolution, which we additionally find to be stable against bubble of nothing instabilities.

Blanco-Pillado, Jose J.; Ramadhan, Handhika S.; Shlaer, Benjamin, E-mail: jose@cosmos.phy.tufts.edu, E-mail: handhika@cosmos.phy.tufts.edu, E-mail: shlaer@cosmos.phy.tufts.edu [Institute of Cosmology, Department of Physics and Astronomy, Tufts University, 212 College Ave, Medford, MA 02155 (United States)

2012-01-01

384

Magnetic bubble memories  

NASA Astrophysics Data System (ADS)

The role of magnetic bubble memories in systems is investigated by a review of their functions and construction. Propagation, which is achieved by varying localized magnetic field gradients, and detection, which is achieved by the magnetoresistive effect, are discussed. Board-level products, board or boxed subsystems, and custom designed systems are described, and military applications such as the PBM 90M (1 Mbyte module) for FHD replacement systems are presented. Other applications include security systems, computer terminals, and traffic control. Advantages of bubble systems are also summarized, and include the rugged nonvolatile storage medium, low cost, and high reliability.

Baker, K.

385

Three-Dimensional Magnetohydrodynamic Simulations of Buoyant Bubbles in Galaxy Clusters  

NASA Astrophysics Data System (ADS)

We report results of three-dimensional magnetohydrodynamic simulations of the dynamics of buoyant bubbles in magnetized galaxy cluster media. The simulations are three-dimensional extensions of two-dimensional calculations reported by Jones and De Young. Initially, spherical bubbles and briefly inflated spherical bubbles all with radii a few times smaller than the intracluster medium (ICM) scale height were followed as they rose through several ICM scale heights. Such bubbles quickly evolve into a toroidal form that, in the absence of magnetic influences, is stable against fragmentation in our simulations. This ring formation results from (commonly used) initial conditions that cause ICM material below the bubbles to drive upwards through the bubble, creating a vortex ring; that is, hydrostatic bubbles develop into "smoke rings," if they are initially not very much smaller or very much larger than the ICM scale height. Even modest ICM magnetic fields with ? = P gas/P mag lsim 103 can influence the dynamics of the bubbles, provided the fields are not tangled on scales comparable to or smaller than the size of the bubbles. Quasi-uniform, horizontal fields with initial ? ~ 102 bifurcated our bubbles before they rose more than about a scale height of the ICM, and substantially weaker fields produced clear distortions. These behaviors resulted from stretching and amplification of ICM fields trapped in irregularities along the top surface of the young bubbles. On the other hand, tangled magnetic fields with similar, modest strengths are generally less easily amplified by the bubble motions and are thus less influential in bubble evolution. Inclusion of a comparably strong, tangled magnetic field inside the initial bubbles had little effect on our bubble evolution, since those fields were quickly diminished through expansion of the bubble and reconnection of the initial field.

O'Neill, S. M.; De Young, D. S.; Jones, T. W.

2009-04-01

386

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, Micha?; Schmitz, Georg; Lewin, Peter A.

2012-01-01

387

Bursting bubbles and bilayers.  

PubMed

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, Micha?; Schmitz, Georg; Lewin, Peter A

2012-01-01

388

Drag Reduction by Bubble Oscillations  

E-print Network

Drag reduction in stationary turbulent flows by bubbles is sensitive to the dynamics of bubble oscillations. Without this dynamical effect the bubbles only renormalize the fluid density and viscosity, an effect that by itself can only lead to a small percentage of drag reduction. We show in this paper that the dynamics of bubbles and their effect on the compressibility of the mixture can lead to a much higher drag reduction.

T. S. Lo; Victor S. L'vov; Itamar Procaccia

2005-11-02

389

Bubble size measurement in electroflotation  

Microsoft Academic Search

A feature of electroflotation is the ability to create very fine bubbles, which are known to improve flotation performance of fine particles. This study was aimed at determining the hydrogen bubble size generated as a function ofcurrent density and electrode geometry. Experiments were performed in a viewing cell that allowed direct visualization of hydrogen bubbles being generated and transported away

G. M. Evans; S. W. Donne

2010-01-01

390

Using Bubbles to Explore Membranes  

NSDL National Science Digital Library

In this activity, learners use bubbles to investigate the structure and unique properties of cell membranes. Bubbles serve as macroscopic models that mimic the cells' phospholipid bilayers. Learners also use the bubbles to form prokaryotic cells and eukaryotic cells. This inquiry type lab can be done as a group or cooperative learning experience. Materials listed are designed for a group of 30 learners.

Sandra Wardell

2009-01-01

391

Acoustic bubble sizes, coalescence, and sonochemical activity in aqueous electrolyte solutions saturated with different gases.  

PubMed

Acoustic bubble sizes, coalescence behavior, and sonochemical activity have been investigated in water in the presence of various electrolyte additives (KCl, HCl, and NaNO(3)) and saturating gases-helium, air, and argon. A strong correlation was identified between the bubble radius and the dissolved gas concentration in the cavitation medium. The extent of bubble coalescence for each gas was also studied in different electrolyte solutions. A causal relationship between coalescence and bubble size was inferred. Importantly, the effects of the different electrolytes could be completely attributed to their "salting out" effect on the dissolved gas, providing valuable insight into the contentious issue of ion-specific coalescence inhibition. Extrapolation of the bubble size data to conditions where bubble coalescence is minimal, i.e., zero gas concentration and zero ultrasound exposure time, yielded a bubble radius of 1.5 +/- 0.5 microm at an acoustic frequency of 515 kHz. In addition, the effects of electrolyte concentration and gas type on sonochemical activity were investigated. Sonochemical yields were increased by up to 1 order of magnitude at high electrolyte concentrations. This has been attributed to reduced gas and vapor content in the bubble core prior to collapse and a lower clustering density. PMID:20593787

Brotchie, Adam; Statham, Tom; Zhou, Meifang; Dharmarathne, Leena; Grieser, Franz; Ashokkumar, Muthupandian

2010-08-01

392

The Action of Pressure-Radiation Forces on Pulsating Vapor Bubbles  

NASA Technical Reports Server (NTRS)

The action of pressure-radiation (or Bjerknes) forces on gas bubbles is well understood. This paper studies the analogous phenomenon for vapor bubbles, about which much less is known. A possible practical application is the removal of boiling bubbles from the neighborhood of a heated surface in the case of a downward facing surface or in the absence of gravity. For this reason, the case of a bubble near a plane rigid surface is considered in detail. It is shown that, when the acoustic wave fronts are parallel to the surface, the bubble remains trapped due to secondary Bjerknes force caused by an "image bubble." When the wave fronts are perpendicular to the surface, on the other hand, the bubble can be made to slide laterally.

Hao, Y.; Oguz, N.; Prosperetti, A.

2001-01-01

393

Numerical simulations of bubble formation from submerged needles under non-uniform direct current electric field  

NASA Astrophysics Data System (ADS)

In several chemical and space industries, small bubbles are desired for efficient interaction between the liquid and gas phases. In the present study, we show that non-uniform electric field with appropriate electrode configurations can reduce the volume of the bubbles forming at submerged needles by up to three orders of magnitude. We show that localized high electric stresses at the base of the bubbles result in slipping of the contact line on the inner surface of the needle and subsequent bubble formation occurs with contact line inside the needle. We also show that for bubble formation in the presence of highly non-uniform electric field, due to high detachment frequency, the bubbles go through multiple coalescences and thus increase the apparent volume of the detached bubbles.

Sunder, Shyam; Tomar, Gaurav

2013-10-01

394

Measurements of ultrafine bubbles using different types of particle size measuring instruments  

NASA Astrophysics Data System (ADS)

In 2010, we succeeded in measuring the sizes of bubbles generated by our GALF (GAs Liquid Foam) bubble generating system, using particle tracking analysis for the first time, and quantitatively confirmed the generation and presence of ultrafine bubbles measuring around 100 to 200 nm in diameter. After that, we also developed a new technology to generate a high density of ultrafine bubbles and launched our ultrafine bubble generating system (ultrafineGALF) in 2011. This report details several independent measurements of bubbles generated in water by ultrafineGALF, using dynamic light scattering, laser diffraction scattering, particle tracking analysis, and the electrical sensing zone method. It was found that the presence of ultrafine bubbles with a diameter of about 100 to 200 nm could be determined quantitatively using any of these methods.

Kobayashi, Hideaki; Maeda, Shigeo; Kashiwa, Masakazu; Fujita, Toshihiro

2014-08-01

395

Experimental study of bubble formation at metal porous spargers: Effect of liquid properties and sparger characteristics on the initial bubble size distribution  

Microsoft Academic Search

This work is a study of the effect of liquid properties and pore size on the initial bubble size distribution of a bubble column equipped with fine pore sparger. Various liquids covering a wide range of surface tension and viscosity values are employed, while the gas phase is atmospheric air. A fast video recording technique is used for both the

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

2008-01-01

396

Bubble Dynamics on a Heated Surface  

NASA Technical Reports Server (NTRS)

In this work, we study the combined thermocapillary and natural convective flow generated by a bubble on a heated solid surface. The interaction between gas and vapor bubbles with the surrounding fluid is of interest for both space and ground-based processing. On earth, the volumetric forces are dominant, especially, in apparatuses with large volume to surface ratio. But in the reduced gravity environment of orbiting spacecraft, surface forces become more important and the effects of Marangoni convection are easily unmasked. In order to delineate the roles of the various interacting phenomena, a combined numerical-experimental approach is adopted. The temperature field is visualized using Mach-Zehnder interferometry and the flow field is observed by a laser sheet flow visualization technique. A finite element numerical model is developed which solves the two-dimensional momentum and energy equations and includes the effects of bubble surface deformation. Steady state temperature and velocity fields predicted by the finite element model are in excellent qualitative agreement with the experimental results. A parametric study of the interaction between Marangoni and natural convective flows including conditions pertinent to microgravity space experiments is presented. Numerical simulations clearly indicate that there is a considerable difference between 1-g and low-g temperature and flow fields induced by the bubble.

Kassemi, Mohammad; Rashidnia, Nasser

1996-01-01

397

Methods of Evaluating Bubble Boundary Definition Using Characteristic Parameters of Bubble Boundary  

NASA Astrophysics Data System (ADS)

Taking image with high definition is the basis to study aerated water flow using image measurement method. It was found that gas-water flow have complicated optical properties because both bubbles and water are transparent, and bubbles are featured with continuous deformation. Even under the same illumination conditions, the characteristics of the captured bubble images are very different. By now, human intuition and analysis still play a central role in the choices of the best lighting schemes. Nevertheless, the decision made within a person's mind is not unreliable. In this paper, we presented a series of quantitative evaluation methods to identify the imaging quality of bubble by brightness feature analysis of water, bubbles and interface between them. As an example, an optimized lighting scheme was determined via selection from back-lighting, side-lighting, normal-lighting and other lighting schemes with different angles. It is shown that our method is effective to optimize photography, reduce the number of pictures and obtain high quality images.

Shao, JianBin; Chen, Gang; Li, Guodong

2007-06-01

398

Determination of the radioactive material and plutonium holdup in ducts and piping in the 327 Building  

SciTech Connect

The 327 Building Post Irradiation Testing Laboratory is used for temporary storage and for destructive and nondestructive examination of irradiated reactor fuels and structural materials. The facility contains 12 shielded hot cells, two water-filled basins, and dry storage. This report describes the measurements performed to determine the radionuclide content and mass of Pu in ducts, filters, and piping in the basement of the 327 Building at the Hanford Site in Washington State. This information is needed to characterize facility radiation levels, to verify compliance with criticality safety specifications, and to allow more accurate nuclear material control using nondestructive assay (NDA) methods. Gamma assay techniques typically employed for NDA analysis were used to determine the gamma-emitting isotopes in the ducts, filters, and piping. Passive neutron counting was selected to estimate the Pu content because high gamma levels from fission and activation products effectively mask any gamma emissions from Pu. A high-purity gamma-ray detector was used to measure the mixed fission and activation radionuclides. A slab neutron detector containing five {sup 3}He proportional counters was used to determine the neutron emission rates and estimate the mass of Pu present. Estimated Pu mass in the basement ductwork and filters is 7.2 grams. The radioactive liquid waste system line has 4.2 grams and Special Environmental Radiometallurgy Facility cell recirculating system contains 8.7 grams in the lower filter housing and associated piping. Total Pu mass holdup estimates range from 20.1 grams, assuming that the Pu is weapons-grade Pu, to a best estimate of 11.0 grams Pu, assuming 11% {sup 240}Pu.

Haggard, D.L.; Brackenbush, L.W.

1995-09-01

399

The Liberal Arts Bubble  

ERIC Educational Resources Information Center

The author expresses his doubt that the general higher education bubble will burst anytime soon. Although tuition, student housing, and book costs have all increased substantially, he believes it is still likely that the federal government will continue to pour billions into higher education, largely because Americans have been persuaded that it…

Agresto, John

2011-01-01

400

Bubble Chamber Site  

NSDL National Science Digital Library

This substantial site features a large number of photos of bubble chamber (BC) tracks, many with a discussion of the physics. There is a description of how the BC works and also useful tutorial on reading BC pictures. The high quality of the images and the explanations of the events that are shown make this site especially valuable.

2006-06-19

401

Bubble kinetics in a steady-state column of aqueous foam  

E-print Network

We measure the liquid content, the bubble speeds, and the distribution of bubble sizes, in a vertical column of aqueous foam maintained in steady-state by continuous bubbling of gas into a surfactant solution. Nearly round bubbles accumulate at the solution/foam interface, and subsequently rise with constant speed. Upon moving up the column, they become larger due to gas diffusion and more polyhedral due to drainage. The size distribution is monodisperse near the bottom and polydisperse near the top, but there is an unexpected range of intermediate heights where it is bidisperse with small bubbles decorating the junctions between larger bubbles. We explain the evolution in both bidisperse and polydisperse regimes, using Laplace pressure differences and taking the liquid fraction profile as a given.

K. Feitosa; Olivia L. Halt; Randall D. Kamien; D. J. Durian

2006-09-19

402

Signature of anisotropic bubble collisions  

SciTech Connect

Our universe may have formed via bubble nucleation in an eternally inflating background. Furthermore, the background may have a compact dimension--the modulus of which tunnels out of a metastable minimum during bubble nucleation--which subsequently grows to become one of our three large spatial dimensions. When in this scenario our bubble universe collides with other ones like it, the collision geometry is constrained by the reduced symmetry of the tunneling instanton. While the regions affected by such bubble collisions still appear (to leading order) as disks in an observer's sky, the centers of these disks all lie on a single great circle, providing a distinct signature of anisotropic bubble nucleation.

Salem, Michael P. [Institute of Cosmology, Department of Physics and Astronomy, Tufts University, Medford, Massachusetts 02155 (United States)

2010-09-15

403

A continuum description of wave propagation in bubbly liquids with relative motion  

NASA Astrophysics Data System (ADS)

Bubbly liquids occur in a large number of environmental, naval and industrial settings. From a modeling viewpoint, they present a challenging multi-phase flow problem because the highly compressible bubbles behave nonlinearly in response to large-amplitude acoustic waves, or when excited near their resonance. In this thesis, we study nonlinear wave propagation in liquids containing gas bubbles. We focus on the effect relative motion between the phases has on the wave structure. We begin with a detailed analysis of the fluid mechanics and heat exchange for a single gas bubble. In addition to the standard added-mass and buoyancy-like forces that act on the bubble, our analysis yields the terms which strongly couple its pulsation and translation. We also analyze the heat exchange between the pulsating gas bubble and the surrounding liquid. We exactly invert the Laplace transform solution for the temperature field inside the bubble, and thereby obtain a system of integro-differential equations for the radial oscillations of a bubble. We also present a much simpler but accurate two-point Pade approximation for the thermal damping of a bubble. We incorporate the results from the single-bubble investigation into a continuum-level description of bubbly liquids. The continuum model consists of the standard conservation laws together with a novel nonlinear equation-of-state (EOS). The EOS relates the instantaneous mixture mass and number densities, and their first two material time derivatives, to the instantaneous pressure field. We use our continuum model to study both linear and nonlinear waves (e.g., shocks) in bubbly media. Among other things, we describe exact nonlinear traveling wave solutions to our system of equations, and develop a numerical method, based upon the conservative Godunov scheme, to study transient wave phenomena in bubbly liquids.

Cartmell, Jerome John

404

Simulations of Hot Bubbles in the ICM  

E-print Network

We review the general properties of the intracluster medium (ICM) in clusters that host a cooling flow, and in particular the effects on the ICM of the injection of hot plasma by a powerful active galactic nucleus (AGN). It is observed that, in some cases, the hot plasma produces cavities in the ICM that finally detach and rise, perhaps buoyantly. The gas dynamics induced by the rising bubbles can help explain the absence of a cooled gas component in clusters with a cooling flow. This scenario is explored using numerical simulations.

A. Gardini; P. M. Ricker

2004-09-15

405

DNA denaturation bubbles at criticality  

E-print Network

The equilibrium statistical properties of DNA denaturation bubbles are examined in detail within the framework of the Peyrard-Bishop-Dauxois model. Bubble formation in homogeneous DNA is found to depend crucially on the presence of nonlinear base-stacking interactions. Small bubbles extending over less than 10 base pairs are associated with much larger free energies of formation per site than larger bubbles. As the critical temperature is approached, the free energy associated with further bubble growth becomes vanishingly small. An analysis of average displacement profiles of bubbles of varying sizes at different temperatures reveals almost identical scaled shapes in the absence of nonlinear stacking; nonlinear stacking leads to distinct scaled shapes of large and small bubbles.

Theodorakopoulos, Nikos

2008-01-01

406

On bubble clustering and energy spectra in pseudo-turbulence  

NASA Astrophysics Data System (ADS)

We performed 3D-Particle Tracking (3D-PTV) and Phase Sensitive Constant Temperature Anemometry in pseudo-turbulence to investigate bubble clustering and to obtain the mean bubble rise velocity, distributions of bubble velocities, and energy spectra at dilute gas concentrations. To characterize the clustering the pair correlation function G(r,?) is calculated. The deformable bubbles with equivalent bubble diameter db=4-5 mm are found to cluster within a radial distance of a few bubble radii with a preferred vertical orientation. This vertical alignment is present at both small and large scales. The large number of data-points and the non intrusiveness of PTV allowed to obtain well-converged Probability Density Functions (PDFs) of the bubble velocity. The PDFs have a non-Gaussian form for all velocity components and intermittency effects can be observed. The energy spectrum of the liquid fluctuations decays with a power law of -3.2, different from the -5/3 found for homogeneous isotropic turbulence.

Martinez Mercado, Julian; Chehata Gomez, Daniel; van Gils, Dennis; Sun, Chao; Lohse, Detlef

2009-11-01

407

Black Hole Blows Big Bubble  

NASA Astrophysics Data System (ADS)

Combining observations made with ESO's Very Large Telescope and NASA's Chandra X-ray telescope, astronomers have uncovered the most powerful pair of jets ever seen from a stellar black hole. This object, also known as a microquasar, blows a huge bubble of hot gas, 1000 light-years across, twice as large and tens of times more powerful than other known microquasars. The discovery is reported this week in the journal Nature. "We have been astonished by how much energy is injected into the gas by the black hole," says lead author Manfred Pakull. "This black hole is just a few solar masses, but is a real miniature version of the most powerful quasars and radio galaxies, which contain black holes with masses of a few million times that of the Sun." Black holes are known to release a prodigious amount of energy when they swallow matter. It was thought that most of the energy came out in the form of radiation, predominantly X-rays. However, the new findings show that some black holes can release at least as much energy, and perhaps much more, in the form of collimated jets of fast moving particles. The fast jets slam into the surrounding interstellar gas, heating it and triggering an expansion. The inflating bubble contains a mixture of hot gas and ultra-fast particles at different temperatures. Observations in several energy bands (optical, radio, X-rays) help astronomers calculate the total rate at which the black hole is heating its surroundings. The astronomers could observe the spots where the jets smash into the interstellar gas located around the black hole, and reveal that the bubble of hot gas is inflating at a speed of almost one million kilometres per hour. "The length of the jets in NGC 7793 is amazing, compared to the size of the black hole from which they are launched," says co-author Robert Soria [1]. "If the black hole were shrunk to the size of a soccer ball, each jet would extend from the Earth to beyond the orbit of Pluto." This research will help astronomers understand the similarity between small black holes formed from exploded stars and the supermassive black holes at the centres of galaxies. Very powerful jets have been seen from supermassive black holes, but are thought to be less frequent in the smaller microquasar variety. The new discovery suggests that many of them may simply have gone unnoticed so far. The gas-blowing black hole is located 12 million light-years away, in the outskirts of the spiral galaxy NGC 7793 (eso0914b). From the size and expansion velocity of the bubble the astronomers have found that the jet activity must have been ongoing for at least 200 000 years. Note: [1] Astronomers do not have yet any means of measuring the size of the black hole itself. The smallest stellar black hole discovered so far has a radius of about 15 km. An average stellar black hole of about 10 solar masses has a radius of about 30 km, while a "big" stellar black hole may have a radius of up to 300 km. This is still much smaller than the jets, which extend out to 1000 light-years, or about 9000 million million km! More Information: This result appears in a paper published in this week's issue of the journal Nature (A 300 parsec long jet-inflated bubble around a powerful microquasar in the galaxy NGC 7793, by Manfred W. Pakull, Roberto Soria and Christian Motch). ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world's most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in C

2010-07-01

408

Black Hole Blows Big Bubble  

NASA Astrophysics Data System (ADS)

Combining observations made with ESO's Very Large Telescope and NASA's Chandra X-ray telescope, astronomers have uncovered the most powerful pair of jets ever seen from a stellar black hole. This object, also known as a microquasar, blows a huge bubble of hot gas, 1000 light-years across, twice as large and tens of times more powerful than other known microquasars. The discovery is reported this week in the journal Nature. "We have been astonished by how much energy is injected into the gas by the black hole," says lead author Manfred Pakull. "This black hole is just a few solar masses, but is a real miniature version of the most powerful quasars and radio galaxies, which contain black holes with masses of a few million times that of the Sun." Black holes are known to release a prodigious amount of energy when they swallow matter. It was thought that most of the energy came out in the form of radiation, predominantly X-rays. However, the new findings show that some black holes can release at least as much energy, and perhaps much more, in the form of collimated jets of fast moving particles. The fast jets slam into the surrounding interstellar gas, heating it and triggering an expansion. The inflating bubble contains a mixture of hot gas and ultra-fast particles at different temperatures. Observations in several energy bands (optical, radio, X-rays) help astronomers calculate the total rate at which the black hole is heating its surroundings. The astronomers could observe the spots where the jets smash into the interstellar gas located around the black hole, and reveal that the bubble of hot gas is inflating at a speed of almost one million kilometres per hour. "The length of the jets in NGC 7793 is amazing, compared to the size of the black hole from which they are launched," says co-author Robert Soria [1]. "If the black hole were shrunk to the size of a soccer ball, each jet would extend from the Earth to beyond the orbit of Pluto." This research will help astronomers understand the similarity between small black holes formed from exploded stars and the supermassive black holes at the centres of galaxies. Very powerful jets have been seen from supermassive black holes, but are thought to be less frequent in the smaller microquasar variety. The new discovery suggests that many of them may simply have gone unnoticed so far. The gas-blowing black hole is located 12 million light-years away, in the outskirts of the spiral galaxy NGC 7793 (eso0914b). From the size and expansion velocity of the bubble the astronomers have found that the jet activity must have been ongoing for at least 200 000 years. Notes [1] Astronomers do not have yet any means of measuring the size of the black hole itself. The smallest stellar black hole discovered so far has a radius of about 15 km. An average stellar black hole of about 10 solar masses has a radius of about 30 km, while a "big" stellar black hole may have a radius of up to 300 km. This is still much smaller than the jets, which extend out to several hundreds light years on each side of the black hole, or about several thousand million million km! More information This result appears in a paper published in this week's issue of the journal Nature (A 300 parsec long jet-inflated bubble around a powerful microquasar in the galaxy NGC 7793, by Manfred W. Pakull, Roberto Soria and Christian Motch). ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world's most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO

2010-07-01

409

Ring Bubbles of Dolphins  

NASA Technical Reports Server (NTRS)

The article discusses how dolphins create and play with three types of air-filled vortices. The underlying physics is discussed. Photographs and sketches illustrating the dolphin's actions and physics are presented. The dolphins engage in this behavior on their own initiative without food reward. These behaviors are done repeatedly and with singleminded effort. The first type is the ejection of bubbles which, after some practice on the part of the dolphin, turn into toroidal vortex ring bubbles by the mechanism of baroclinic torque. These bubbles grow in radius and become thinner as they rise vertically to the surface. One dolphin would blow two in succession and guide them to fuse into one. Physicists call this a vortex reconnection. In the second type, the dolphins first create an invisible vortex ring in the water by swimming on their side and waving their tail fin (also called flukes) vigorously. This vortex ring travels horizontally in the water. The dolphin then turns around, finds the vortex and injects a stream of air into it from its blowhole. The air "fills-out" the core of t