Sample records for gas holdup bubble

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

    SciTech Connect

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

    1988-01-01

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

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

    SciTech Connect

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

    1995-12-31

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

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

    Microsoft Academic Search

    Yoshinori Kawase; Murray Moo-Young

    1987-01-01

    A theoretical model for gas hold-up in bubble columns with Newtonian and non-Newtonial fluids has been developed on the basis of the concept of a characteristic turbulent kinematic viscosity in bubble columns. Gas hold-ups in a 40-L bubble column and a 1000-L pilot plant fermenter with Newtonian fluids (water, glycerine, dextrose, and fermentation media) and non-Newtonian fluids((carboxymethyl) cellulose, carboxypolymethylene, and

  4. Influence of coalescence behaviour of the liquid and of gas sparging on hydrodynamics and bubble characteristics in a bubble column

    Microsoft Academic Search

    E Camarasa; C Vial; S Poncin; G Wild; N Midoux; J Bouillard

    1999-01-01

    This experimental study is aimed at investigating the effect of liquid phase properties and gas distribution on bubble and hydrodynamic characteristics in bubble columns. With the various measuring techniques used, systematic measurements of bubble size, velocity and frequency and gas hold-up are possible. Bubble size distribution and shape factors which are rarely found in literature, are also available. Water–alcohol solutions

  5. Hydrodynamic flow regimes, gas holdup, and liquid circulation in airlift reactors

    SciTech Connect

    Abashar, M.E.; Narsingh, U.; Rouillard, A.E.; Judd, R. [Univ. of Durban (South Africa)] [Univ. of Durban (South Africa)

    1998-04-01

    This study reports an experimental investigation into the hydrodynamic behavior of an external-loop airlift reactor (ALR) for the air-water system. Three distinct flow regimes are identified--namely homogeneous, transition, and heterogeneous regimes. The transition between homogeneous and heterogeneous flow is observed to occur over a wide range rather than being merely a single point as has been previously reported in the literature. A gas holdup correlation is developed for each flow regime. The correlations fit the experimental gas holdup data with very good accuracy (within {+-}5%). It would appear, therefore, that a deterministic equation to describe each flow regime is likely to exist in ALRs. This equation is a function of the reactor geometry and the system`s physical properties. New data concerning the axial variation of gas holdup is reported in which a minimum value is observed. This phenomenon is discussed and an explanation offered. Discrimination between two sound theoretical models--namely model 1 (Chisti et al., 1988) and model 2 (Garcia Calvo, 1989)--shows that model 1 predicts satisfactorily the liquid circulation velocity with an error of less than {+-} 10%. The good predictive features of model 1 may be due to the fact that it allows for a significant energy dissipation by wakes behind bubbles. Model 1 is now further improved by the new gas holdup correlations which are derived for the three different flow regimes.

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

    Microsoft Academic Search

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

    2005-01-01

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

  7. Gas bubble detector

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  8. A new production logging method for fullbore gas holdup measurements in cased wells

    SciTech Connect

    Waid, M.C.; Madigan, W.P.; Smith, H.D. Jr. [and others

    1996-12-31

    The measurement of the gas holdup in a flowing cased-hole environment is a fundamentally difficult problem. Gas holdup, the estimate percent of gas in a volume of wellbore, has traditionally been computed from fluid density measurements. These estimates are inadequate for determining gas holdup in deviated or horizontal wells since the fluid density was not a fullbore measurement. A new Gas Holdup Tool (GHT{trademark}) has been developed which provides a more accurate technique for obtaining gas holdup measurements directly. This 1 11/16-inch production logging tool is used to determine the volumetric fraction of gas in horizontal, deviated, and vertical cased wells, and provides a log of the gas holdup fraction (from 0% to 100%) in all flow regimes. Examples are presented for comparing homogeneous and stratified flows. The tool uses a low-energy Co-57 source and NaI detectors with a new backscatter technique to accurately measure density differences of the total fluid and gas in the borehole around the tool. This new measurement provides the gas fraction (holdup) in all flow regimes, and is not affected by the materials outside the casing. Monte Carlo modeling and experimental data over a wide range of cased-hole conditions validate empirical relationships between detector count rates and gas holdup for various casing diameters. The sensitivity of the measurement to other factors, such as pressure, salinity, and fluid type, are also investigated. The new production logging method may be used in determining points of gas and oil entry into deviated or horizontal wells and for quantitative production logging in deviated or horizontal wells with variable or unknown flow regimes.

  9. Sonoluminescing Gas Bubbles

    Microsoft Academic Search

    I. Scott; H.-Th. Elze; T. Kodama; J. Rafelski

    1998-01-01

    We draw attention to the fact that the popular but unproven hypothesis of shock-driven sonoluminescence is incompatible with the reported synchronicity of the single bubble sonoluminescence (SBSL) phenomenon. Moreover, it is not a necessary requirement, since we show that the sub-shock dynamic heating in gas bubble cavitation can lead to conditions required to generate intense 100ps light pulses. To wit

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

    SciTech Connect

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

    2008-08-07

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

  11. Experimental investigation of bubbling in particle beds with high solid holdup

    SciTech Connect

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

    2011-02-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

    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.

  13. Fluid dynamic parameters in bubble columns with internals

    Microsoft Academic Search

    Jinwen Chen; Fan Li; Sujatha Degaleesan; Puneet Gupta; Muthanna H. Al-Dahhan; Milorad P. Dudukovic; Bernard A. Toseland

    1999-01-01

    The knowledge of gas holdup, liquid recirculation and turbulent parameters is important for design and performance calculation of bubble column reactors. Although numerous experimental studies have been reported on this subject, most are point measurements limited to columns without internals operated at low gas velocities. In this study, we present the results obtained for the gas holdup profiles, time-averaged liquid

  14. Etiology of gas bubble disease

    SciTech Connect

    Bouck, G.R.

    1980-11-01

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

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

    NASA Astrophysics Data System (ADS)

    Ong, Booncheng

    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.

  16. Plasma formation in underwater gas bubbles

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

    The generation of plasma in underwater gas bubbles offers the potential to produce large volume plasma in water while minimizing electrode erosion. Such attributes are desirable for the design of plasma-based water purification systems. In this work, gas bubbles of diameter 0.4-0.7 mm were trapped in the node of a 26.4 kHz underwater acoustic standing wave and pulsed with voltages in the range 10-14 kV. Plasma formation in trapped, isolated bubbles was observed to occur through two separate pathways: (1) plasma generated in the bubble through impact by a liquid streamer and (2) plasma generated in the bubble due solely to the applied electric field. The former case demonstrates the mechanism of so-called streamer hopping in which the discharge transitions from a water streamer to a gaseous surface streamer. Perturbations of the bubble's fluid boundary due to the streamer are also discussed.

  17. Structure of nanoscale gas bubbles in metals

    SciTech Connect

    Caro, A., E-mail: caro@lanl.gov; Schwen, D.; Martinez, E. [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87544 (United States)] [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87544 (United States)

    2013-11-18

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

  18. Structure of nanoscale gas bubbles in metals

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

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

  19. Acoustic manifestations of gas hydrate shelled bubbles

    NASA Astrophysics Data System (ADS)

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

    2009-11-01

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

  20. Mobility of fission gas bubbles

    Microsoft Academic Search

    F. A. Nichols; C. Ronchi

    1985-01-01

    The importance of bubble migration in fuel swelling and fission-product release remains a controversial topic in spite of a great deal of research. For steady-state analyses some authors ignore bubble motion totally, whereas others employ mobilities (based on out-of-pile measurements) which are far below the theoretical diffusion-control predictions. Under transient conditions some continue to employ zero or low bubble mobilities,

  1. Nonlinear interaction between gas bubble and free surface

    SciTech Connect

    Wang, Q.X.; Yeo, K.S.; Khoo, B.C.; Lam, K.Y. [National Univ. of Singapore (Singapore). Dept. of Mechanical and Production Engineering

    1994-12-31

    The nonlinear evolution of gas bubbles in the vicinity of a free surface is investigated numerically. The flow is assumed to be potential and a boundary-integral method is used to solve the Laplace equation for the velocity potential. The bubble content is described by an adiabatic gas law. Investigations were carried out for gas bubbles which are injected as close as one maximum bubble radius from the free surface. The relations between bubble jet penetration, bubble rebound and bubble connectedness to bubble strength are discussed. Results are also compared against the prediction of Blake`s Kelvin impulse theory.

  2. Electron bubbles in a dense helium gas

    NASA Astrophysics Data System (ADS)

    Kalia, Rajiv K.; Harris, John

    1990-03-01

    Quantum molecular dynamics simulations show that electrons in a helium gas at 77 K and with densities 1.0 and 1.5 × 10 22 cm -3 self-trap in bubbles that are stable on a time scale of picoseconds. When the density is reduced to 6 × 10 21 cm -3, the electron does not self-trap but percolates through the gas. A signature of bubble formation is a strong peak in the optical absorption spectrum. The peak is due to intra-bobble dipole transitions and shifts to higher energy with increasing gas density.

  3. Residence time distribution and liquid holdup in Kenics ® KMX static mixer with hydrogenated nitrile butadiene rubber solution and hydrogen gas system

    Microsoft Academic Search

    Chandra Mouli R. Madhuranthakam; Qinmin Pan; Garry L. Rempel

    2009-01-01

    A Kenics® KMX static mixer that has curved-open blade internal structure was investigated to study its hydrodynamic performance related to residence time distribution and liquid holdup in a gas\\/liquid system. The static mixer reactor had 24 mixing elements arranged in line along the length of the reactor such that the angle between two neighboring elements is 90°. The length of

  4. Mathematical model of gas bubble evolution in a straight tube.

    PubMed

    Halpern, D; Jiang, Y; Himm, J F

    1999-10-01

    Deep sea divers suffer from decompression sickness (DCS) when their rate of ascent to the surface is too rapid. When the ambient pressure drops, inert gas bubbles may form in blood vessels and tissues. The evolution of a gas bubble in a rigid tube filled with slowly moving fluid, intended to simulate a bubble in a blood vessel, is studied by solving a coupled system of fluid-flow and gas transport equations. The governing equations for the fluid motion are solved using two techniques: an analytical method appropriate for small nondeformable spherical bubbles, and the boundary element method for deformable bubbles of arbitrary size, given an applied steady flow rate. A steady convection-diffusion equation is then solved numerically to determine the concentration of gas. The bubble volume, or equivalently the gas mass inside the bubble for a constant bubble pressure, is adjusted over time according to the mass flux at the bubble surface. Using a quasi-steady approximation, the evolution of a gas bubble in a tube is obtained. Results show that convection increases the gas pressure gradient at the bubble surface, hence increasing the rate of bubble evolution. Comparing with the result for a single gas bubble in an infinite tissue, the rate of evolution in a tube is approximately twice as fast. Surface tension is also shown to have a significant effect. These findings may have important implications for our understanding of the mechanisms of inert gas bubbles in the circulation underlying decompression sickness. PMID:10529918

  5. Gas-bubble lesions in stranded cetaceans

    Microsoft Academic Search

    P. D. Jepson; M. Arbelo; R. Deaville; I. A. P. Patterson; P. Castro; J. R. Baker; E. Degollada; H. M. Ross; P. Herráez; A. M. Pocknell; F. Rodríguez; F. E. Howie; A. Espinosa; R. J. Reid; J. R. Jaber; V. Martin; A. A. Cunningham; A. Fernández

    2003-01-01

    There are spatial and temporal links between some mass strandings of cetaceans - predominantly beaked whales - and the deployment of military sonar. Here we present evidence of acute and chronic tissue damage in stranded cetaceans that results from the formation in vivo of gas bubbles, challenging the view that these mammals do not suffer decompression sickness. The incidence of

  6. Enhancement of oxygen mass transfer and gas holdup using palm oil in stirred tank bioreactors with xanthan solutions as simulated viscous fermentation broths.

    PubMed

    Mohd Sauid, Suhaila; Krishnan, Jagannathan; Huey Ling, Tan; Veluri, Murthy V P S

    2013-01-01

    Volumetric mass transfer coefficient (kLa) is an important parameter in bioreactors handling viscous fermentations such as xanthan gum production, as it affects the reactor performance and productivity. Published literatures showed that adding an organic phase such as hydrocarbons or vegetable oil could increase the kLa. The present study opted for palm oil as the organic phase as it is plentiful in Malaysia. Experiments were carried out to study the effect of viscosity, gas holdup, and kLa on the xanthan solution with different palm oil fractions by varying the agitation rate and aeration rate in a 5?L bench-top bioreactor fitted with twin Rushton turbines. Results showed that 10% (v/v) of palm oil raised the kLa of xanthan solution by 1.5 to 3 folds with the highest kLa value of 84.44?h(-1). It was also found that palm oil increased the gas holdup and viscosity of the xanthan solution. The kLa values obtained as a function of power input, superficial gas velocity, and palm oil fraction were validated by two different empirical equations. Similarly, the gas holdup obtained as a function of power input and superficial gas velocity was validated by another empirical equation. All correlations were found to fit well with higher determination coefficients. PMID:24350269

  7. Enhancement of Oxygen Mass Transfer and Gas Holdup Using Palm Oil in Stirred Tank Bioreactors with Xanthan Solutions as Simulated Viscous Fermentation Broths

    PubMed Central

    Mohd Sauid, Suhaila; Huey Ling, Tan; Veluri, Murthy V. P. S.

    2013-01-01

    Volumetric mass transfer coefficient (kLa) is an important parameter in bioreactors handling viscous fermentations such as xanthan gum production, as it affects the reactor performance and productivity. Published literatures showed that adding an organic phase such as hydrocarbons or vegetable oil could increase the kLa. The present study opted for palm oil as the organic phase as it is plentiful in Malaysia. Experiments were carried out to study the effect of viscosity, gas holdup, and kLa on the xanthan solution with different palm oil fractions by varying the agitation rate and aeration rate in a 5?L bench-top bioreactor fitted with twin Rushton turbines. Results showed that 10% (v/v) of palm oil raised the kLa of xanthan solution by 1.5 to 3 folds with the highest kLa value of 84.44?h?1. It was also found that palm oil increased the gas holdup and viscosity of the xanthan solution. The kLa values obtained as a function of power input, superficial gas velocity, and palm oil fraction were validated by two different empirical equations. Similarly, the gas holdup obtained as a function of power input and superficial gas velocity was validated by another empirical equation. All correlations were found to fit well with higher determination coefficients. PMID:24350269

  8. Active microuidic mixer and gas bubble lter driven by thermal bubble micropump$

    E-print Network

    Lin, Liwei

    Active micro¯uidic mixer and gas bubble ®lter driven by thermal bubble micropump$ Jr-Hung Tsaia-diffuser micropump is successfully demonstrated. The oscillatory ¯ow generated by the micropump can induce wavy B.V. Keywords: Micropump; Bubble; Micro¯uidics; Mixing; Filter 1. Introduction Liquid mixing

  9. New fiber-optic method for measuring velocities of strands and solids hold-up in gas-solids downflow reactors

    Microsoft Academic Search

    D. A. Sobocinski; B. J. Young; H. I. de Lasa

    1995-01-01

    A novel, reflective-type fiber-optic sensor was used to assess the sizes of certain types of clusters, called strands, as well as strand velocity and solids hold-up in gas-solids downward flowing suspensions. This sensor was employed successfully in a series of experiments performed in a downflow, acrylic cold model reactor. Cluster (strand) velocities in the range of 0.6 to 3.9 m

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

    SciTech Connect

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

    2006-01-01

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

  11. Dissolved gas quantification and bubble formation in liquid chemical dispense

    NASA Astrophysics Data System (ADS)

    Tom, Glenn; Liu, Wei

    2009-12-01

    Gas dissolved in liquids such as photoresist comes out of solution as bubbles after the liquid experiences a pressure drop in a dispense train and may cause on-wafer defects. Reservoirs in the dispense train can assist in removing bubbles but are incapable of effectively removing dissolved gas. This study demonstrates the importance of maintaining the amount of dissolved gas in a liquid below a critical value to reduce bubbles generated after a pressure drop in the dispense train occurs. The methodology used to quantify dissolved gas during liquid dispense cycle using gas chromatography is discussed. The amount of dissolved gas is correlated to the amount of bubbles downstream of a pressure drop. This study also analyzes sources of bubbles in the dispense train and techniques to mediate the sources.

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

    Microsoft Academic Search

    Jr-Hung Tsai; Liwei Lin

    2002-01-01

    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

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

    PubMed

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

    2007-04-15

    Accurate measurement of electrophoretic mobility for gas bubbles is a challenging task as it requires the creation of a desired number of very small air bubbles to ensure negligible rise velocities during the course of the measurement. Here, we report a simple and reliable method for generating stable dispersions of "nano-bubbles." Preparation of such dispersions relies on the nucleation of nano-bubbles in solutions supersaturated with gas. Electrophoretic mobility of these nano-bubbles is determined by the ZetaPALS technique (Brookhaven Instruments) using Uzgiris electrodes coated with palladium. The Smoluchowski limit is assumed in the calculation of zeta potentials. In regard to reproducibility and reliability, this novel method shows a clear advantage over other existing techniques of zeta potential measurement for bubbles. PMID:17257614

  14. Standards for holdup measurement

    SciTech Connect

    Zucker, M.S.

    1982-01-01

    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.

  15. Measurement Of Gas Bubbles In Mercury Using Proton Radiography

    SciTech Connect

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

    2007-01-01

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

  16. Gas distribution effects on waste properties: Viscosities of bubbly slurries

    SciTech Connect

    Gauglitz, P.A.; Shah, R.R.; Davis, R.L.

    1994-09-01

    The retention and episodic release of flammable gases are critical safety concerns for double-shell tanks that contain waste slurries. The rheological behavior of the waste, particularly of the settled sludge, is critical to characterizing the tendency of the waste to retain gas bubbles. The presence of gas bubbles is expected to affect the rheology of the sludge, but essentially no literature data are available to assess the effect of bubbles. Accordingly, the objectives of this study are to develop models for the effect of gas bubbles on the viscosity of a particulate slurry, develop an experimental method (capillary rheometer), collect data on the viscosity of a bubbly slurry, and develop a theoretical basis for interpreting the experimental data from the capillary rheometer.

  17. The growth of fission gas bubbles in irradiated uranium dioxide

    Microsoft Academic Search

    R. M. Cornell

    1969-01-01

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

  18. Interaction of a shock with elliptical gas bubbles

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

  19. CFD simulation of bubble column reactors: importance of drag force formulation

    Microsoft Academic Search

    S. S. Thakre; J. B. Joshi

    1999-01-01

    CFD simulation has been presented for the flow in bubble column reactors. Procedure has been given for the specification of the drag force and the radial lift force on the basis of drift flux constants. An excellent agreement has been shown between the experimental and simulated profiles of gas hold-up and axial liquid velocity. Explanation has been provided for the

  20. Progression and Severity of Gas Bubble Trauma in Juvenile Salmonids

    Microsoft Academic Search

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

    2000-01-01

    We conducted laboratory experiments to assess the progression and to quantify the severity of signs of gas bubble trauma (GBT) in juvenile chinook salmon Oncorhynchus tshawytscha and steelhead Oncorhynchus mykiss exposed to different levels of total dissolved gas (TDG), and we attempted to relate these signs to the likelihood of mortality. When fish were exposed to 110% TDG for up

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

    NASA Astrophysics Data System (ADS)

    Al Mesfer, Mohammed Khloofh

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

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

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

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

  3. Gas bubble dynamics model for shallow volcanic tremor at Stromboli

    NASA Astrophysics Data System (ADS)

    Ripepe, Maurizio; Gordeev, Evgenii

    1999-05-01

    Volcanic tremor at Stromboli (Aeolian islands, Italy) is correlated to small infrasonic transients [Ripepe et al., 1996] which repeat almost rhythmically in time in a range between 0.8 and 1.2 s. We demonstrate that infrasonic transients are associated to small gas bubble (˜0.5 m) burstings which produces no transients in the seismic signal. Tremor ground displacement attenuates with the inverse of the distance from the craters indicating that the source is shallow. Short-term energy release shows that infrasonic and seismic signals are linked to the same dynamical process, while at the long-term scale it is evident that the two signals are controlled by two distinctive mechanisms. We suggest that the possible physical model acts in two steps: first, gas coalescence and, then, gas bursting. In our model, the seismic signal is related to the coalescence of a gas bubble from a layer of small bubbles, while the infrasonic signal is linked to the bursting of the bubble when it reaches the magma surface. Gas bubbles could form by free coalescence in magma or could be forced to coalesce by a structural barrier. We calculate that forced coalescence induces in magma a pressure change (˜104 Pa) 2 orders of magnitude higher than free coalescence, and it explains best the tremor ground displacement (10-5 m) recorded at Stromboli. Moreover, forced coalescence evidences the role of a structural barrier, such as a dike, in volcanic tremor source dynamics. In this gas dynamic process, the delay time of 1-2 s between infrasonic pulses could reflect the gas nucleation interval of basaltic magma [Thomas et al., 1993; Manga, 1996]. We propose that the source function for the shallow volcanic tremor at Stromboli could be the viscoelastic reaction of the magma to the pressure decrease induced by gas bubble growth rate under constant depressurization. The spectrum of our source function is controlled by the time duration of the pressure pulse, which represents the viscoelastic relaxation time of the magma and gas bubble growth rate. The predicted asymptotic decay of the frequency contents fits the spectral behavior of the volcanic tremor ground displacement recorded at Stromboli. We show that the same spectral behavior can be found in ground displacement spectra of volcanic tremor recorded on different volcanoes.

  4. Augmentation of filtering blebs with perfluoropropane gas bubble

    Microsoft Academic Search

    Jeffrey K Luttrull; Robert L Avery

    2000-01-01

    The following two letters address an article that appeared in the March 1999 issue of the Journal: Tym WH, Seah SKL. Augmentation of filtering blebs with perfluoropropane gas bubble: an experimental and pilot clinical study. (Ophthalmology 1999;106:545–9)

  5. Breakdown Voltage Scaling in Gas Bubbles Immersed in Liquid Water

    NASA Astrophysics Data System (ADS)

    Gucker, Sarah; Sommers, Bradley; Foster, John

    2013-09-01

    Radicals produced by the interaction of plasma with liquid water have the capacity to rapidly oxidize organic contaminants. This interaction is currently being investigated as a means to purify water. Direct plasma creation in water typically requires very high voltages to achieve breakdown. Igniting plasma in individual gas bubbles in liquid water on the other hand requires much less voltage. Furthermore, the use of an electrode-less plasma initiation in such bubbles is attractive in that it eliminates electrode erosion thereby circumventing the contamination issue. The breakdown physics of isolated bubbles in liquid water is still poorly understood. In this work, we investigate the relationship between applied voltage for breakdown and the associated pd. This is achieved by locating the breakdown voltage over a range of bubble sizes. This approach allows for the generation of a Paschen-type breakdown curve for isolated bubbles. Such a relationship yields insight into breakdown mechanics and even streamer propagation through water. Radicals produced by the interaction of plasma with liquid water have the capacity to rapidly oxidize organic contaminants. This interaction is currently being investigated as a means to purify water. Direct plasma creation in water typically requires very high voltages to achieve breakdown. Igniting plasma in individual gas bubbles in liquid water on the other hand requires much less voltage. Furthermore, the use of an electrode-less plasma initiation in such bubbles is attractive in that it eliminates electrode erosion thereby circumventing the contamination issue. The breakdown physics of isolated bubbles in liquid water is still poorly understood. In this work, we investigate the relationship between applied voltage for breakdown and the associated pd. This is achieved by locating the breakdown voltage over a range of bubble sizes. This approach allows for the generation of a Paschen-type breakdown curve for isolated bubbles. Such a relationship yields insight into breakdown mechanics and even streamer propagation through water. This material is based upon work supported by the National Science Foundation (CBET 1033141) and the National Science Foundation Graduate Student Research Fellowship under Grant No. DGE 0718128.

  6. Holdup measurements under realistic conditions

    SciTech Connect

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

    1997-11-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

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

  8. Gas evolution during water electrolysis: gas bubble behaviour and potential drop measurements

    SciTech Connect

    Sillen, C.W.M.P.; Van Stralen, S.J.D.

    1980-12-01

    The specific resistance of the electrolyte between the two opposite electrodes during alkaline water electrolysis will be increased by the presence of the gas bubbles. As a consequence the energy efficiency of the electrolysis process will be decreased. In order to reduce this negative effect of the bubbles, it is necessary to study the gas bubble behaviour and to investigate, by means of potential drop measurements, their influence on the specific resistance. A combination of the results of these two types of experiments may lead to an optimal cell design with respect to the gas evolution. The oxygen bubble behaviour is studied at flat, vertical, transparent nickel electrodes at free and forced convection. Important quantities such as bubble density, average bubble radius, the gas volume fraction at the electrode surface, etc., are determined at various current densities, flow velocities, electrolyte concentrations and temperatures. The potential drop is measured between working electrode and diaphragm with the current interruptor method, at various current densities, flow velocities, gas to liquid ratio and electrode configurations.

  9. Pulsed electrical discharge in gas bubbles in water

    NASA Astrophysics Data System (ADS)

    Gershman, Sophia

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

  10. Optical measurements of gas bubbles in oil behind a cavitating micro-orifice flow

    NASA Astrophysics Data System (ADS)

    Iben, Uwe; Wolf, Fabian; Freudigmann, Hans-Arndt; Fröhlich, Jochen; Heller, Winfried

    2015-06-01

    In hydraulic systems, it is common for air release to occur behind valves or throttles in the form of bubbles. These air bubbles can affect the behavior and the performance of these systems to a substantial extent. In the paper, gas release in a liquid flow behind an orifice is analyzed by optical methods for various operation points. The bubbles are observed with a digital camera, and a detection algorithm based on the Hough transformation is used to determine their number and size. The appearance of gas bubbles is very sensitive to the inlet and outlet pressure of the orifice. Gas bubbles are only observed if choking cavitation occurs. An empirical relationship between an adjusted cavitation number and the appearance of gas release is presented. It is assumed that the observed bubbles contain mostly air. With the applied pressure differences, up to 30 % of the dissolved air was degassed in the form of bubbles.

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

    PubMed Central

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

    2009-01-01

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

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

    Microsoft Academic Search

    P. Ceccato; A. Rousseau

    2008-01-01

    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

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

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  14. Gas Sloshing and Bubbles in the Galaxy Group NGC 5098

    E-print Network

    Randall, S W; Markevitch, M; Blanton, E L; Nulsen, P E J; Forman, W R

    2009-01-01

    We present results from Chandra observations of the galaxy pair and associated galaxy group NGC 5098, and find evidence for both gas sloshing and AGN heating. The X-ray brightness images show diffuse emission with a spiral structure, centered on NGC 5098a, and a sharp edge in the diffuse emission surrounding much of the galaxy at about 30 kpc. The spiral structure in the X-ray surface brightness and temperature maps, the offset between the peak of the cool gas and the central AGN, and the structure of the cold front edges all suggest gas sloshing in the core. The most likely perturber is the nearby galaxy NGC 5098b, which has been stripped of its gaseous atmosphere. Detailed images of the core reveal several X-ray cavities, two of which, just north and southeast of the central AGN, correlate with radio emission and have bright X-ray rims, similar to buoyant bubbles seen in the ICM of other systems. We estimate the pressures in the bubbles and rims and show that they are roughly equal, consistent with these be...

  15. An estimate of the gas transfer rate from oceanic bubbles derived from multibeam sonar observations of a ship wake

    Microsoft Academic Search

    Thomas C. Weber; Anthony P. Lyons; David L. Bradley

    2005-01-01

    Measurements of gas transfer rates from bubbles have been made in the laboratory, but these are difficult to extrapolate to oceanic bubbles where populations of surfactants and particulate matter that inhibit gas transfer are different. Measurements at sea are complicated by unknown bubble creation rates that make it difficult to uniquely identify and observe the evolution of individual bubble clouds.

  16. GAS SLOSHING AND BUBBLES IN THE GALAXY GROUP NGC 5098

    SciTech Connect

    Randall, S. W.; Jones, C.; Markevitch, M.; Nulsen, P. E. J.; Forman, W. R. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Blanton, E. L. [Institute for Astrophysical Research, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 (United States)], E-mail: srandall@cfa.harvard.edu, E-mail: cjf@cfa.harvard.edu, E-mail: mmarkevitch@cfa.harvard.edu, E-mail: wrf@cfa.harvard.edu, E-mail: eblanton@bu.edu

    2009-08-01

    We present results from Chandra observations of the galaxy pair and associated galaxy group NGC 5098, and find evidence for both gas sloshing and active galactic nucleus (AGN) heating. The X-ray brightness images show diffuse emission with a spiral structure, centered on NGC 5098a, and a sharp edge in the diffuse emission surrounding much of the galaxy at about 30 kpc. The spiral structure in the X-ray surface brightness and temperature maps, the offset between the peak of the cool gas and the central AGN, and the structure of the cold front edges all suggest gas sloshing in the core. The most likely perturber is the nearby galaxy NGC 5098b, which has been stripped of its gaseous atmosphere. Detailed images of the core reveal several X-ray cavities, two of which, just north and southeast of the central AGN, correlate with radio emission and have bright X-ray rims, similar to buoyant bubbles seen in the intracluster medium of other systems. We estimate the pressures in the bubbles and rims and show that they are roughly equal, consistent with these being young features, as suggested by their close proximity to the central AGN. We assume that the other X-ray cavities in the core, which show no correlation with existing radio observations, are ghost cavities from previous AGN outbursts. An estimate of the mechanical energy required to inflate the cavities indicates that it is sufficient to offset radiative cooling of the gas for 15 Myr. Therefore, for a typical cycle time of 10{sup 7} yr, the central AGN energy output is enough to balance cooling over long timescales.

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

    NASA Astrophysics Data System (ADS)

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

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    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.

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

    Microsoft Academic Search

    C. Zhang; S. Eckert; G. Gerbeth

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

  20. On-line ultrasonic gas entrainment monitor. [LMFBR fission gas bubble release

    Microsoft Academic Search

    C. K. Day; H. N. Pedersen

    1978-01-01

    Apparatus employing ultrasonic energy for detecting and measuring the quantity of gas bubbles present in liquids being transported through pipes is described. An ultrasonic transducer is positioned along the longitudinal axis of a fluid duct, oriented to transmit acoustic energy radially of the duct around the circumference of the enclosure walls. The back-reflected energy is received centrally of the duct

  1. Formation of a submillimeter bubble from an orifice using pulsed acoustic pressure waves in gas phase

    NASA Astrophysics Data System (ADS)

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

    2008-04-01

    The mechanism of a bubble production method using pulsed acoustic pressure waves in gas phase is investigated using high-speed photography. The acoustic characteristics of the present bubble generator are also investigated. We found out the optimal acoustic waveform for producing only one bubble per one action; the bubble detachment radius is accurately controlled by first applying the positive onset-assistance acoustic pressure wave and then the negative detachment-assistance acoustic pressure wave with an accurately controlled time lapse. From an orifice with a radius of 0.09mm submerged in water, bubbles with radii in the range of 0.28-0.78mm with an extremely small standard deviation of less than 1?m are obtained. The shrinking and pinch-off motions of a capillary bridge connecting the bubble and orifice at the time of bubble detachment are observed in detail. The balancing force on a growing bubble, which is based on a spherical bubble formation model is also estimated. As a result, we reveal that when the gas pressure is decreased due to a negative pressure wave, the capillary bridge submerges into the orifice and an upward added mass force is applied on the bubble, both of which cause the detachment of the bubble from the orifice.

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

    PubMed

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

    2012-01-01

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

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

    SciTech Connect

    Hang, T.

    2000-07-19

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-04-01

    During thermal remediation the increase in subsurface temperature can lead to bubble formation and mobilization. In order to investigate the effect of gas formation on resulting aqueous concentrations, a 2D finite difference flow and mass transport model was developed which incorporates a macroscopic invasion percolation (MIP) model to simulate bubble expansion and movement. The model was used to simulate three soil scenarios with different permeabilities and entry pressures at various operating temperatures and groundwater velocities. It was observed that discrete bubble formation occurred in all three soils, upward mobility being limited by lower temperatures and higher entry pressures. Bubble mobilization resulted in a different aqueous mass distribution than if no discrete gas formation was modeled, especially at higher temperatures. This was a result of bubbles moving upwards to cooler areas, then collapsing, and contaminating previously clean zones. The cooling effect also led to possible non-aqueous phase liquid (NAPL) formation which was not predicted using a model without discrete bubble formation.

  5. NUMERICAL ANALYSIS OF A GAS BUBBLE FILTER WITH AN APPLICATION IN A MICROCHANNEL

    Microsoft Academic Search

    M. Muradoglu; S. Nas

    Unsteady multiphase flow in a microchannel bubble filter is studied numerically by using a Finite Difference\\/Front Tracking method. In this method, one field formulation of the Navier-Stokes equations is written for the entire computational domain with different fluid properties for the ambient fluid and bubble gas. The surface tension forces acting on the bubble-fluid interface are treated as body forces

  6. Bubble Bubble

    NSDL National Science Digital Library

    Mercer Mayer

    2009-11-11

    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.

  7. INFLUENCE OF VIBRATION ON THE GAS BUBBLE FLOATING UP A CAPILLARY FILLED WITH LIQUID

    Microsoft Academic Search

    N. Novgorod

    2004-01-01

    The report deals with the analysis of the influence of vibration the gas bubble floating up the cylindrical capillary filled with the liquid that moistens its walls. The approximate approach is developed and it allows to write the equation describing the motion of a bubble as a material particle. The capillary forces causing the attachment of the liquid to the

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

    Microsoft Academic Search

    J. Greinert; Y. Artemov; P. Gimpel

    2003-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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.

  10. Variational principles and two-fluid hydrodynamics of bubbly liquid/gas mixtures

    NASA Astrophysics Data System (ADS)

    Geurst, J. A.

    1986-04-01

    In a recent paper the two-phase flow equations for a bubbly liquid/gas mixture were derived by variational methods. Starting point was an Euler form of Hamilton's extended principle of least action. The effect of the virtual mass of the gas bubbles was included. It is demonstrated now that a variational principle in the Langrange form yields the same two-fluid equations. In addition it is shown how the Lagrange form is trandformed in the Euler form by means of a canonical transformation. With regard to a recent discussion in the literature the material frame indifference or objectivity of the virtual-mass terms is investigated. The mutual force between the two-phases which is associated with the virtual mass of the gas bubbles turns out to be objective. In the limit of low bubble concentrations the results of the one-bubble theory are recovered. A corrected value is derived for the lift coefficient of a gas bubble in a rotational flow. It is indicated how a scheme of iterative solutions yields higher order approximations in which the mutual interaction of the gas bubbles is taken into account.

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

    SciTech Connect

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

    2013-05-15

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

  12. Shock wave propagation and bubble collapse in liquids containing gas bubbles

    Microsoft Academic Search

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

    2005-01-01

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

  13. Hydrodynamic and mass transfer parameters in a large-scale slurry bubble column reactor with high solid loading

    SciTech Connect

    Behkish, A.; Men, Z.; Inga, J.R.; Morsi, B.I.

    1999-07-01

    The effects of pressure (P), superficial gas velocity (UG) and solid concentration (CV) on the equilibrium Solubility (C*), gas holdup (eG), volumetric gas-liquid mass transfer coefficient (kLa) and bubble size distribution for methane (CH{sub 4}) in a liquid mixture of decanes were statistically studied in a large-scale (1-ft diameter, 10-ft high) slurry bubble column reactor (SBCR). Glass beads with volumetric concentrations of 0, 7.6%, 18%, 28.4% and 36% were used. The experiments were selected following the central composite statistical design approach. The kLa values were determined using the transient physical absorption technique; the gas holdup was measured using the manometric method and the bubble size distributions were measured using the Dynamic Gas Disengagement technique (DGD). The equilibrium solubility values appeared to follow Henry's Law in the 1--15 bar range. The eG values were found to increase with superficial gas velocity and pressure due to the increase of the volume fraction of the small and large gas bubbles. The eG values, however, decreased with solid concentration due to the increase of slurry viscosity. The kLa values appeared to have the same trend as eG values indicting that the mass transfer behavior in the SBCR was mainly controlled by the gas-liquid interfacial area. Also, statistical correlations relating kLa and eG to the main process variables were proposed.

  14. Ebullition of biogenic gas bubbles from samples of near-surface peat

    Microsoft Academic Search

    A. Baird; S. Waldron

    2004-01-01

    There is evidence that peat soils are not water-saturated below the water table (e.g. Rosenberry et al. 2003; Baird and Waldron, 2003), owing to accumulations of biogenic gas bubbles, consisting of poorly-soluble gases such as CH4. It has been shown that gas bubbles can block pores and reduce rates of water flow in peat soils (Baird and Waldron, 2003). It

  15. Variational principles and two-fluid hydrodynamics of bubbly liquid\\/gas mixtures

    Microsoft Academic Search

    J. A. Geurst

    1986-01-01

    In a recent paper the two-phase flow equations for a bubbly liquid\\/gas mixture were derived by variational methods. Starting point was an Euler form of Hamilton's extended principle of least action. The effect of the virtual mass of the gas bubbles was included. It is demonstrated now that a variational principle in the Langrange form yields the same two-fluid equations.

  16. Effect of biogenic gas bubbles on water flow through poorly decomposed blanket peat

    NASA Astrophysics Data System (ADS)

    Beckwith, Clive W.; Baird, Andrew J.

    2001-03-01

    A laboratory investigation was used to determine whether biogenic gas bubbles accumulate and block water-conducting pores below the water table in poorly decomposed Sphagnum peat. We found that biogenic gas bubbles did accumulate under realistic incubation temperatures. At the end of incubations at 10.5°C, volumetric water contents in two peat samples decreased to between 0.8 and 0.85 (porosity of the samples ranged from 0.96 to 0.97), indicating that the peat was considerably undersaturated with respect to water. Methane was found to be an important constituent of the gas bubbles. The presence of gas bubbles appeared to have a major effect on hydraulic conductivity (K). In control incubations, prior to which the peat had been irradiated and dosed with a biocide, biogenic gas bubbles did not accumulate, and K was 5-8 times higher than at the end of the microbially active incubations. Our results suggest that biogenic gas bubbles have a potentially significant effect on seepage in peat soils.

  17. Gas-liquid heat transfer in a bubble collapsing near a wall

    Microsoft Academic Search

    H. Yuan; A. Prosperetti

    1997-01-01

    The collapse of a gas bubble near a solid wall is studied numerically by assuming the liquid to be incompressible and the Mach number of the gas flow to be small. The liquid motion is simulated by a boundary integral method and the gas thermo-fluid dynamics by finite differences on a boundary-fitted grid. With the physical properties of a liquid

  18. A novel ultrasound based technique for classifying gas bubble sizes in liquids

    NASA Astrophysics Data System (ADS)

    Hussein, Walid; Salman Khan, Muhammad; Zamorano, Juan; Espic, Felipe; Becerra Yoma, Nestor

    2014-12-01

    Characterizing gas bubbles in liquids is crucial to many biomedical, environmental and industrial applications. In this paper a novel method is proposed for the classification of bubble sizes using ultrasound analysis, which is widely acknowledged for being non-invasive, non-contact and inexpensive. This classification is based on 2D templates, i.e. the average spectrum of events representing the trace of bubbles when they cross an ultrasound field. The 2D patterns are obtained by capturing ultrasound signals reflected by bubbles. Frequency-domain based features are analyzed that provide discrimination between bubble sizes. These features are then fed to an artificial neural network, which is designed and trained to classify bubble sizes. The benefits of the proposed method are that it facilitates the processing of multiple bubbles simultaneously, the issues concerning masking interference among bubbles are potentially reduced and using a single sinusoidal component makes the transmitter–receiver electronics relatively simpler. Results from three bubble sizes indicate that the proposed scheme can achieve an accuracy in their classification that is as high as 99%.

  19. Evolution of fission-gas-bubble-size distribution in recrystallized U-10Mo nuclear fuel

    NASA Astrophysics Data System (ADS)

    Rest, J.

    2010-12-01

    An analytical model for the nucleation and growth of intra and intergranular fission-gas bubbles, used to characterize fission-gas bubble development in U-Mo alloy fuel with burnup limited to less than 10 at.% U in order to capture the fuel swelling stage prior to irradiation-induced recrystallization, is extended to recrystallized fuel at a burnup of ˜16 at.% U. During recrystallization the grain size is transformed from micron to sub-micron sizes. The intergranular bubble-size distribution post-recrystallization is found to evolve with similar kinetics and morphology to that pre-recrystallization with any differences primarily due to gas content and initial and/or boundary conditions (e.g., fuel microstructure). The predictions of the theory are compared with measured bubble-size distributions in pre and post recrystallized U-10Mo alloy fuel.

  20. Discharge mechanisms in liquid nitrogen with thermally induced gas bubbles

    NASA Astrophysics Data System (ADS)

    Blaz, M.; Kurrat, M.

    2014-05-01

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

  1. Compositional changes in natural gas bubble plumes: observations from the Coal Oil Point marine hydrocarbon seep field

    Microsoft Academic Search

    Jordan F. Clark; Ira Leifer; Libe Washburn; Bruce P. Luyendyk

    2003-01-01

    Detailed measurements of bubble composition, dissolved gas concentrations, and plume dynamics were conducted during a 9-month period at a very intense, shallow (22-m water depth) marine hydrocarbon seep in the Santa Barbara Channel, California. Methane, carbon dioxide, and heavier hydrocarbons were lost from rising seep bubbles, while nitrogen and oxygen were gained. Within the rising seawater bubble plume, dissolved methane

  2. Growth by rectified diffusion of strongly acoustically forced gas bubbles in nearly saturated liquids.

    PubMed

    Louisnard, Olivier; Gomez, Francisco

    2003-03-01

    The growth or dissolution of small gas bubbles (R0<15 microm) by rectified diffusion in nearly saturated liquids, subject to low frequencies (20 kHzbubble is also an inertially oscillating bubble. On the assumption that such a bubble keeps its integrity up to the shape instability threshold predicted by single-bubble theory, a numerical estimation and a fully analytical approximation of its growth rate are derived. On the one hand, the merging of the two thresholds raises the problem of the construction and self-sustainment of acoustic cavitation fields. On the other hand, the lifetime of the growing inertial bubbles calculated within the present theory is found to be much shorter than the time necessary to rectify argon. This allows an alternative interpretation of the absence of single-bubble sonoluminescence emission in multibubble fields, without resorting to the conventional picture of shape instabilities caused by the presence of other bubbles. PMID:12689182

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

    SciTech Connect

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

    1986-06-01

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

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

    E-print Network

    S. Heinz; E. Churazov

    2005-09-26

    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.

  5. Growth by rectified diffusion of strongly acoustically forced gas bubbles in nearly saturated liquids

    Microsoft Academic Search

    Olivier Louisnard; Francisco Gomez

    2003-01-01

    The growth or dissolution of small gas bubbles (R0<15 mum) by rectified diffusion in nearly saturated liquids, subject to low frequencies (20 kHzbubble is

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

    NASA Technical Reports Server (NTRS)

    Wang, Yazhen; Regel, Liya; Wilcox, William R.

    2002-01-01

    A vertical Bridgman-Stockbarger apparatus was used to directionally solidify water upward, in the hope that detached solidification would evolve from gas bubbles forming on the wall. A large contact angle of the water on the ampoule wall and a high solubility of the dissolved gas caused gas bubbles or tubes to form only at the ampoule wall, and not in the interior. Gas tubes were often nearly periodically spaced around the ampoule wall, with a spacing that increased with ampoule diameter and decreased with freezing rate. The width of the gas tubes was nearly independent of the ampoule diameter and freezing rate. A high degree of detachment was obtained with a rough, nonwetting coating on the ampoule wall, but full detachment was not achieved. This indicates that detachment does not occur by propagation of a single gas bubble around the periphery of the freezing interface. The convection near the freezing interface influenced gas bubble formation, and was outward for a concave freezing interface and inward for a convex interface.

  7. Experiment and Numerical Simulation of Bubble Behavior in Argon Gas Injection into Lead-Bismuth Pool

    NASA Astrophysics Data System (ADS)

    Yamada, Yumi; Akashi, Toyou; Takahashi, Minoru

    In a lead-bismuth alloy (45%Pb-55%Bi) cooled direct contact boiling water fast reactor (PBWFR), steam can be produced by direct contact of feed water with primary Pb-Bi coolant in the upper core plenum, and Pb-Bi coolant can be circulated by buoyancy forces of steam bubbles. As a basic study to investigate the two-phase flow characteristics in the chimneys of PBWFR, a two-dimensional two-phase flow was simulated by injecting argon gas into Pb-Bi pool in a rectangular vessel (400mm in length, 1500mm in height), and bubble behavior were investigated experimentally. Bubble sizes, bubble rising velocities and void fractions were measured using void probes. The experimental conditions are the atmospheric pressure and the flow rate of injection Ar gas is 10, 20, and 30 NL/min. The average of measured bubble rising velocity was about 0.6 m/s. The average chord length was about 7mm. An analysis was performed by two-dimensional and two-fluid model. The experimental results were compared with the analytical results to evaluate the validity of the analytical model. Although large diameter bubbles were observed in the experiment, the drag force model of lower value performed better for simulation of the experimental result.

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

    SciTech Connect

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

    2010-01-01

    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.

  9. Void fraction measurements in bubble columns using computed tomography

    SciTech Connect

    Kumar, S.B.; Dudukovic, M.P. [Washington Univ., St. Louis, MO (United States); Moslemian, D. [Florida Atlantic Univ., Boca Raton, FL (United States). Dept. of Mechanical Engineering

    1995-12-31

    A Computed Tomographic (CT) scanner has been developed for imaging void fraction distributions in two phase flow systems such as bubble columns and fluidized beds. The scanner has been used to study the effects of various operating parameters such as column diameter, superficial gas velocity, distributor type, etc. on the void fraction and its distribution in an air-water bubble column. The results of this experimental investigation are presented and discussed. It was found that the column dimensions have no significant effect on the void fraction when the column diameter is greater than 0.15 m. Differences in the holdup distribution due to the kind of distributor used are significant only at low gas flow rates. Surface tension of the liquid has a profound influence on the void fraction and its distribution.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  11. Numerical simulation of gas-particle flow with a second-order moment method in bubbling fluidized beds

    Microsoft Academic Search

    Sun Dan; Wang Jianzhi; Lu Huilin; Zhao Yunhua; Chen Juhui; Dimitri Gidaspow; Chen Ming

    2010-01-01

    Flow behavior of gas and particles is performed by means of gas–solid two-fluid model with the second-order moment model of particles in the bubbling fluidized bed. The distributions of velocity and moments of particles are predicted in the bubbling fluidized beds. Predictions are compared with experimental data measured by Jung et al. (2005) in a bubbling fluidized bed and Patil

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

    PubMed

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

    2003-01-21

    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 speed of tumour coagulation with focused ultrasound. All experiments were performed under MRI (clinical, 1.5 T) guidance with one of two eight-sector, spherically curved piezoelectric transducers. The transducer, either a 1.1 or 1.7 MHz array, was driven by a multi-channel RF driving system. The transducer was mounted in an MRI-compatible manual positioning system and the rabbit was situated on top of the system. An ultrasound detector ring was fixed with the therapy transducer to monitor gas bubble activity during treatment. Focused ultrasound surgery exposures were delivered to the thighs of seven New Zealand while rabbits. The experimental, gas-bubble-enhanced heating exposures consisted of a high amplitude 300 acoustic watt, half second pulse followed by a 7 W, 14 W or 21 W continuous wave exposure for 19.5 s. The respective control sonications were 20 s exposures of 14 W, 21 W and 28 W. During the exposures, MR thermometry was obtained from the temperature dependency of the proton resonance frequency shift. MRT2-enhanced imaging was used to evaluate the resulting lesions. Specific metrics were used to evaluate the differences between the gas-bubble-enhanced exposures and their respective control sonications: temperatures with respect to time and space, lesion size and shape, and their agreement with thermal dose predictions. The bubble-enhanced exposures showed a faster temperature rise within the first 4 s and higher overall temperatures than the sonications without bubble formation. The spatial temperature maps and the thermal dose maps derived from the MRI thermometry closely correlated with the resulting lesion as examined by T2-weighted imaging. The lesions created with the gas-bubble-enhanced heating exposures were 2-3 times larger by volume, consistently more spherical in shape and closer to the transducer than the control exposures. The study demonstrates that gas bubbles can reliably be used to create significantly larger lesions in vivo. MRI thermometry techniques were successfully used to monitor the thermal effects mediated by the bubble-enhanced exposures. PMID:12587906

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

    SciTech Connect

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

    2001-07-25

    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.

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

    PubMed

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

    2015-04-01

    A series of well-ordered, 3D gradient porous interconnected network surfaces composed of micro-nano hierarchical geometries is constructed on a copper wire. A continuous gas film can be trapped around its interface in an aqueous medium acting as an effective channel for gas transportation. Driving by the difference of the Laplace pressure, gas bubbles can be transported spontaneously and directionally. PMID:25688855

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

    NASA Astrophysics Data System (ADS)

    Leblond, Isabelle; Scalabrin, Carla; Berger, Laurent

    2014-09-01

    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.

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

    E-print Network

    Dabiri, John O.

    Shock-induced collapse of a gas bubble in shockwave lithotripsy Eric Johnsena and Tim Coloniusb Received 23 April 2008; revised 18 July 2008; accepted 21 July 2008 The shock-induced collapse of a pre shock- and interface-capturing scheme, and the wall pressure is considered as an indication of potential

  17. Field nano-localization of gas bubble production from water electrolysis

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

    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.

  18. A Computational Model of Micro-Bubble-Induced Blood Vessel Deformation in Gas Embolotherapy

    NASA Astrophysics Data System (ADS)

    Ye, Tao; Bull, Joseph L.

    2004-11-01

    Gas embolotherapy is a potential cancer treatment modality that involves injecting liquid perfluorocarbon droplets into the vasculature, and using ultrasound to vaporize the droplets to form larger gas bubbles that can then embolize tumors. The rapid volume expansion during the droplet vaporization may potentially rupture blood vessels. In previous work, we have presented results for the wall stresses in the vaporization process assuming the vessel wall is rigid. In this study, we present a computational model of a bubble expansion in a long tube with an elastic wall to model the flexibility of blood vessels. Deformations of the tube wall and the interface are determined as part of the solution. The unsteady Navier-Stokes equations are solved using a sharp-interface, moving boundary, finite-volume method. Tube wall expansion due to the bubble expansion results in an in flow of liquid at the open ends of the tube. The liquid in the vicinity of the bubble, however, moves in the opposite direction because of the bubble expansion. The two counteracting mechanisms create a complex flow pattern in the tube. The time-dependent wall stresses are also investigated to assess the potential for wall damage. This work is supported by NIH grant EB003541-01 and NSF grant BES-0301278.

  19. Technical Note: Detection of gas bubble leakage via correlation of water column multibeam images

    NASA Astrophysics Data System (ADS)

    Schneider von Deimling, J.; Papenberg, C.

    2012-03-01

    Hydroacoustic detection of natural gas release from the seafloor has been conducted in the past by using singlebeam echosounders. In contrast, modern multibeam swath mapping systems allow much wider coverage, higher resolution, and offer 3-D spatial correlation. Up to the present, the extremely high data rate hampers water column backscatter investigations and more sophisticated visualization and processing techniques are needed. Here, we present water column backscatter data acquired with a 50 kHz prototype multibeam system over a period of 75 seconds. Display types are of swath-images as well as of a "re-sorted" singlebeam presentation. Thus, individual and/or groups of gas bubbles rising from the 24 m deep seafloor clearly emerge in the acoustic images, making it possible to estimate rise velocities. A sophisticated processing scheme is introduced to identify those rising gas bubbles in the hydroacoustic data. We apply a cross-correlation technique adapted from particle imaging velocimetry (PIV) to the acoustic backscatter images. Temporal and spatial drift patterns of the bubbles are assessed and are shown to match very well to measured and theoretical rise patterns. The application of this processing to our field data gives clear results with respect to unambiguous bubble detection and remote bubble rise velocimetry. The method can identify and exclude the main source of misinterpretations, i.e. fish-mediated echoes. Although image-based cross-correlation techniques are well known in the field of fluid mechanics for high resolution and non-inversive current flow field analysis, we present the first application of this technique as an acoustic bubble detector.

  20. Technical Note: Detection of gas bubble leakage via correlation of water column multibeam images

    NASA Astrophysics Data System (ADS)

    Schneider von Deimling, J.; Papenberg, C.

    2011-07-01

    Hydroacoustic detection of natural gas release from the seafloor has been conducted in the past by using singlebeam echosounders. In contrast modern multibeam swath mapping systems allow much wider coverage, higher resolution, and offer 3-D spatial correlation. However, up to the present, the extremely high data rate hampers water column backscatter investigations. More sophisticated visualization and processing techniques for water column backscatter analysis are still under development. We here present such water column backscattering data gathered with a 50 kHz prototype multibeam system. Water column backscattering data is presented in videoframes grabbed over 75 s and a "re-sorted" singlebeam presentation. Thus individual gas bubbles rising from the 24 m deep seafloor clearly emerge in the acoustic images and rise velocities can be determined. A sophisticated processing scheme is introduced to identify those rising gas bubbles in the hydroacoustic data. It applies a cross-correlation technique similar to that used in Particle Imaging Velocimetry (PIV) to the acoustic backscatter images. Tempo-spatial drift patterns of the bubbles are assessed and match very well measured and theoretical rise patterns. The application of this processing scheme to our field data gives impressive results with respect to unambiguous bubble detection and remote bubble rise velocimetry. The method can identify and exclude the main driver for misinterpretations, i.e. fish-mediated echoes. Even though image-based cross-correlation techniques are well known in the field of fluid mechanics for high resolution and non-inversive current flow field analysis, this technique was never applied in the proposed sense for an acoustic bubble detector.

  1. Monitoring temporal variability of bubble release at seeps: The hydroacoustic swath system GasQuant

    NASA Astrophysics Data System (ADS)

    Greinert, Jens

    2008-07-01

    A lander-based hydroacoustic swath system, GasQuant, was deployed in an intensely bubbling seep area at the shelf west of the Crimea Peninsula, Black Sea. With its horizontally oriented swath (21 beams, 63° swath angle, 180 kHz) GasQuant operates in a sonar-like mode and monitors bubbles remotely, exploiting their strong backscattering when crossing the swath. All active seep spots were monitored simultaneously within the covered area (2075 m2). Even applying simple processing and visualization techniques (moving average for filtering, FFT for spectrum analyses; swath and trace plots) identified 17 seeps of different activity patterns that have been grouped as follows: (1) sporadically active with one to a few long bursts (up to 18 min) or randomly occurring short bursts (<200 bursts and active for <5% of the observation time); (2) regularly active seeps showing mainly short bursts of less than one minute but also longer burst of a few minutes (200-350 bursts and 5 to 20% active); (3) frequently active spots with sometimes very periodic bubble release (>350 bursts or >20% active). Studying the bubble release variability of single seeps and of the entire area allows speculation about the external and internal processes that modulate the bubble release. In the study area none of the 17 seeps was found to be permanently active. Only one was active for 75% and another one for 45% of the time monitored. The rest only released bubbles during less than 20% of the time with an overall average of only 12%. This would have strong implications for flux extrapolations if these were based on very accurate but few short-term measurements. Both strong overestimates and underestimates are possible. High-resolution monitoring over at least one tidal cycle as with the GasQuant system might help to get an idea of the temporal variability. Thus flux extrapolations can be corrected to better reflect the real seep activity.

  2. Effect of peripheral temperature on the formation of venous gas bubbles.

    PubMed

    Mekjavi?, I B; Kakitsuba, N

    1989-09-01

    Temperature of the tissue affects the many components involved in the formation of tissue gas phase formation: diffusion, perfusion, and inert gas solubility. Since the effects of perfusion and inert gas solubility may be counteracting in terms of enhancing growth of gas bubbles, the optimal thermal status of divers throughout a dive remains unresolved. To elucidate the role of peripheral body temperature on gas phase formation, four subjects were exposed to a 10 degree and 40 degree C environment for 3 h on two separate occasions, after a no-stop decompression from a 12-h dive to 9.14 m (30 fsw) on air. The 3-hour exposures to either a cold or warm air environment resulted in a significant difference in mean skin temperature (P less than or equal to 0.01) with no alteration in rectal temperature. Total peripheral resistance during the 10 degree C exposure was 13.8 +/- 1.9 mmHg.liter-1.min-1 and significantly higher than that observed during the 40 degree C exposure (10.4 +/- 3.5 mmHg.liter-1.min-1). Gas bubbles in the venous return were monitored with a Doppler ultrasonic transducer placed in the precordial region, both at rest and after a deep knee bend. Venous bubbles were only detected in 1 subject following the warm air exposure, whereas 3 of the 4 subjects developed Doppler-detectable bubbles during the cold air exposure. Although both the cold and warm air exposures (3 h postdecompression) were uneventful, a hot shower taken by the subjects on completion of the cold air exposure (6 h postdecompression) precipitated mild type I symptoms of decompression sickness. These symptoms were not present after a hot shower following the warm air exposure. The present results indicate that despite the assumed greater inert gas solubility of tissues expected during cold air exposure, the decrease in the perfusion may have played a more significant role in the observed levels of detectable venous gas bubbles. Development of type I symptoms following a 12-h saturation, a 3-h cold exposure, and a subsequent hot shower suggests that a rapid rise in peripheral temperature may cause a significant rise in tissue gas tension. This increase in tension does not seem to be sufficiently reduced by increased perfusion to the tissues to prevent bubble formation. PMID:2800052

  3. Bubble Suspension

    NSDL National Science Digital Library

    The Exploratorium

    2011-10-11

    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.

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

    NASA Astrophysics Data System (ADS)

    Toalá, J. A.; Guerrero, M. A.

    2013-11-01

    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.

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

    PubMed

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

    2014-01-01

    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

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

    SciTech Connect

    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

    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.

  7. Experimental study of electric discharge propagation in gas bubbles in liquid

    NASA Astrophysics Data System (ADS)

    Faust, Jessica; Gershman, Sophia

    2013-10-01

    The studies of pulsed electrical discharges in gas bubbles in liquids continue to generate interest by their practical applications to the water treatment as well their theoretical significance for the understanding of the discharge propagation along liquid surfaces. Computational models suggest that the discharge path depends on the ratio of the dielectric constant of the liquid and the gas. This study investigates the formation and propagation of the discharge inside a gas bubble in water and glycerin (dielectric constants of approximately 80 and 41, respectively, at 20 C). The discharge is generated by a 1 ?s pulse of 10-15 kV applied between a needle electrode piercing the bubble wall and a disk electrode submerged in the liquid. Time-resolved 5-10 ns exposure ICCD images are used to compare the discharge path in Ar, O2, and air bubbles in the two liquid dielectrics. 10 nm bandpass filters are used to image the behavior of various excited species, ex. Ar +, OH. Experimental results are compared to the previous modeling results.

  8. On a differential equation for a gas bubbles collapse mathematical model

    E-print Network

    Gianluca Argentini

    2006-06-19

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

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

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

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

    PubMed

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

    2013-01-01

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

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

    SciTech Connect

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

    1995-08-01

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

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

    PubMed Central

    Bartusik, Dorota; Aebisher, David; Ghafari, BiBi

    2012-01-01

    Laser-coupled microphotoreactors were developed to bubble singlet oxygen [1O2 (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

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

    PubMed Central

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

    2009-01-01

    We have numerically investigated the axisymmetric motion of a finite-sized nearly occluding air bubble through a shear-thinning Casson fluid flowing in blood vessels of circular cross section. The numerical solution entails solving a two-layer fluid model—a cell-free layer and a non-Newtonian core together with the gas bubble. This problem is of interest to the field of rheology and for gas embolism studies in health sciences. The numerical method is based on a modified front-tracking method. The viscosity expression in the Casson model for blood (bulk fluid) includes the hematocrit [the volume fraction of red blood cells (RBCs)] as an explicit parameter. Three different flow Reynolds numbers, Reapp=?lUmaxd/?app, in the neighborhood of 0.2, 2, and 200 are investigated. Here, ?l is the density of blood, Umax is the centerline velocity of the inlet Casson profile, d is the diameter of the vessel, and ?app is the apparent viscosity of whole blood. Three different hematocrits have also been considered: 0.45, 0.4, and 0.335. The vessel sizes considered correspond to small arteries, and small and large arterioles in normal humans. The degree of bubble occlusion is characterized by the ratio of bubble to vessel radius (aspect ratio), ?, in the range 0.9???1.05. For arteriolar flow, where relevant, the Fahraeus-Lindqvist effects are taken into account. Both horizontal and vertical vessel geometries have been investigated. Many significant insights are revealed by our study: (i) bubble motion causes large temporal and spatial gradients of shear stress at the “endothelial cell” (EC) surface lining the blood vessel wall as the bubble approaches the cell, moves over it, and passes it by; (ii) rapid reversals occur in the sign of the shear stress (+ ? ? ? +) imparted to the cell surface during bubble motion; (iii) large shear stress gradients together with sign reversals are ascribable to the development of a recirculation vortex at the rear of the bubble; (iv) computed magnitudes of shear stress gradients coupled with their sign reversals may correspond to levels that cause injury to the cell by membrane disruption through impulsive compression and stretching; and (v) for the vessel sizes and flow rates investigated, gravitational effects are negligible. PMID:18851139

  14. Gas bubbles in seals, dolphins, and porpoises entangled and drowned at depth in gillnets.

    PubMed

    Moore, M J; Bogomolni, A L; Dennison, S E; Early, G; Garner, M M; Hayward, B A; Lentell, B J; Rotstein, D S

    2009-05-01

    Gas bubbles were found in 15 of 23 gillnet-drowned bycaught harp (Pagophilus groenlandicus), harbor (Phoca vitulina) and gray (Halichoerus grypus) seals, common (Delphinus delphis) and white-sided (Lagenorhyncus acutus) dolphins, and harbor porpoises (Phocaena phocaena) but in only 1 of 41 stranded marine mammals. Cases with minimal scavenging and bloating were chilled as practical and necropsied within 24 to 72 hours of collection. Bubbles were commonly visible grossly and histologically in bycaught cases. Affected tissues included lung, liver, heart, brain, skeletal muscle, gonad, lymph nodes, blood, intestine, pancreas, spleen, and eye. Computed tomography performed on 4 animals also identified gas bubbles in various tissues. Mean +/- SD net lead line depths (m) were 92 +/- 44 and ascent rates (ms(-1)) 0.3 +/- 0.2 for affected animals and 76 +/- 33 and 0.2 +/- 0.1, respectively, for unaffected animals. The relatively good carcass condition of these cases, comparable to 2 stranded cases that showed no gas formation on computed tomography (even after 3 days of refrigeration in one case), along with the histologic absence of bacteria and autolytic changes, indicate that peri- or postmortem phase change of supersaturated blood and tissues is most likely. Studies have suggested that under some circumstances, diving mammals are routinely supersaturated and that these mammals presumably manage gas exchange and decompression anatomically and behaviorally. This study provides a unique illustration of such supersaturated tissues. We suggest that greater attention be paid to the radiology and pathology of bycatch mortality as a possible model to better understand gas bubble disease in marine mammals. PMID:19176498

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

    USGS Publications Warehouse

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

    1988-01-01

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

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

    SciTech Connect

    Absolon, Randall F.

    1999-03-01

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

  17. Ebullition of biogenic gas bubbles from samples of near-surface peat.

    NASA Astrophysics Data System (ADS)

    Baird, A.; Waldron, S.

    2004-05-01

    There is evidence that peat soils are not water-saturated below the water table (e.g. Rosenberry et al. 2003; Baird and Waldron, 2003), owing to accumulations of biogenic gas bubbles, consisting of poorly-soluble gases such as CH4. It has been shown that gas bubbles can block pores and reduce rates of water flow in peat soils (Baird and Waldron, 2003). It has also been shown that, beyond certain levels, biogenic gas bubble accumulations become unstable, giving rise to large but episodic ebullition events, and that ebullition may be an important mechanism of CH4 transfer between peat soils and the atmosphere (e.g. Romanowicz et al., 1995; Rosenberry et al., 2003). However, the studies that have been done on ebullition have looked at relatively deep peat where the bubbles were apparently held below a confining layer of low hydraulic conductivity. Very little is known about the degree to which gas bubbles accumulate in near-surface peat (i.e. the upper 40 cm) and whether they accumulate to such an extent that ebullition and transfer of carbon gases to the atmosphere occur. To address this lack of knowledge we conducted experiments on eight `undisturbed' samples of near-surface (depths of c. 8 cm to 30 cm) peat taken from two lowland raised bogs, one in SW Scotland and one in W Wales. The samples were c. 10 l in volume and were incubated at 12 deg. C with the water table maintained above the sample surface. Water was allowed to flow through the samples periodically for the measurement of hydraulic conductivity (not reported here). Gas traps were fitted to the tops of the samples and the volume of gas in these was measured c. every 2-3 days. Finally, the samples were fitted with TDR probes and gas permeation samplers to measure gas volume and to take gas samples for the measurement of gas content (CH4 and CO2) using a GC. Ebullition was recorded in every sample but only after a build up of biogenic gas bubbles had occurred. We found that ebullition was not episodic and that it appeared to match gas production. The amount of ebullition varied substantially between samples. In two samples from the Scottish bog consisting respectively of Sphagnum papillosum and S. magellanicum litter, over 400 ml of gas per sample was lost over a 90-day period. At the other extreme, virtually no ebullition occurred from one of the Welsh peat samples, with only 14.5 ml being lost in 125 days. Provisional calculations based on CH4 concentrations in our gas permeation samplers suggest that CH4 efflux from the peatland surface via ebullition is potentially as important as that via diffusional transfer. We consider how transportable our data are to field conditions.

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

    SciTech Connect

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

    1987-05-01

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

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

    Microsoft Academic Search

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

    2009-01-01

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

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

    Microsoft Academic Search

    Nathan C. Keim; Sidney R. Nagel

    2008-01-01

    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

  1. Shock Waves in a Liquid Containing Gas Bubbles

    Microsoft Academic Search

    I. J. Campbell; A. S. Pitcher

    1958-01-01

    Considerations of continuity, momentum and energy together with an equation of state are applied to the propagation of plane shock waves in a gas+liquid mixture. The shock-wave relations assume a particularly simple form when the temperature rise across a shock, which is shown to be small for a very wide range of conditions, is neglected. In particular, a simple relation

  2. Novel Application of X-ray Computed Tomography: Determination of Gas/Liquid Contact Area and Liquid Holdup in Structured Packing

    E-print Network

    Eldridge, R. Bruce

    Novel Application of X-ray Computed Tomography: Determination of Gas/Liquid Contact Area and Liquid Company, 1 Neumann Way-M/D Q8, Cincinnati, Ohio 45215 X-ray computed tomography (CT) was utilized Principles of X-ray Computed Tomography. X-ray computed tomography (CT) is used to noninvasively

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

    PubMed

    Uddin, M; Coombe, D

    2014-03-20

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

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

    SciTech Connect

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

    2002-07-25

    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.

  5. Handling of liquid holdup in Duyong two-phase flow pipeline system

    SciTech Connect

    Saad, M.R.; Singh, B. (Petronas Carigali Sdn. Bhd. (MY))

    1988-01-01

    This paper deals with the handling of liquids in the multi-phase flow pipeline system within Carigali's Duyong Offshore Gas Complex and the Onshore Gas Terminal, in Kerteh, Terongganu. The data and operations experience gathered necessitate changes to the operating procedures originally identified during the design phase. This is to ensure more efficient handling of liquid hold-up in the pipeline during low gas flowrates.

  6. A computational model for large eddy simulation of dilute bubbly turbulent flows

    NASA Astrophysics Data System (ADS)

    Hajit, Mohammad; Sotiropoulos, Fotis

    2013-11-01

    A mathematical formulation of filtered equations for two phase bubbly flows based on two-fluid method is presented. To remove high frequencies (noise), we extracted the filtered form of the equations in curvilinear coordinates, converting the microscopic governing equations to macroscopic equations via spatial averaging of solution variables. The set of equations describing the hydrodynamics in a gas-liquid system can be solved effectively if the solution procedure is decoupled so that an efficient iterative scheme can be employed. We propose a formulation for dilute bubbly flows in which the equations are converted to a loosely-coupled form. The resulting mathematical model is based on five distinct sets of equations, namely mixture momentum balance, pressure Poisson equation, Boyle's law and momentum and mass balances of gas phase. This mathematical formulation provides an efficient numerical procedure for two-way coupling of bubbly flows at low gas holdups. The subgrid-scale modeling is based on dynamic procedure of Germano for both phases. The formulation is validated for a fully turbulent bubble column test by comparing to available experimental results. A mathematical formulation of filtered equations for two phase bubbly flows based on two-fluid method is presented. To remove high frequencies (noise), we extracted the filtered form of the equations in curvilinear coordinates, converting the microscopic governing equations to macroscopic equations via spatial averaging of solution variables. The set of equations describing the hydrodynamics in a gas-liquid system can be solved effectively if the solution procedure is decoupled so that an efficient iterative scheme can be employed. We propose a formulation for dilute bubbly flows in which the equations are converted to a loosely-coupled form. The resulting mathematical model is based on five distinct sets of equations, namely mixture momentum balance, pressure Poisson equation, Boyle's law and momentum and mass balances of gas phase. This mathematical formulation provides an efficient numerical procedure for two-way coupling of bubbly flows at low gas holdups. The subgrid-scale modeling is based on dynamic procedure of Germano for both phases. The formulation is validated for a fully turbulent bubble column test by comparing to available experimental results. This work is supported by the US department of energy (DE-EE0005416) and the Minnesota supercomputing institute.

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

    NASA Technical Reports Server (NTRS)

    Hao, Y.; Prosperetti, A.

    1999-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2003-04-01

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

  9. Experimental investigation of remote seismic triggering by gas bubble growth in groundwater

    NASA Astrophysics Data System (ADS)

    Crews, J. B.; Cooper, C. A.

    2014-12-01

    Remotely triggered seismicity is the process by which an earthquake at one location initiates others after a time delay ranging from seconds to days, over distances up to thousands of kilometers. Candidate mechanisms have been proposed, but none specifically address the role of carbon dioxide (CO2) gas bubble growth in groundwater as a driver of remote seismic triggering in active volcanic and geothermal regions, where shallow crustal CO2 gas is abundant. In the present study, we hypothesize that a seismic wave from a distant source can initiate rapid gas bubble growth in CO2-rich groundwater, resulting in a persistent increase in pore fluid pressure and a reduction of effective stress, which can trigger failure on a critically loaded geologic fault. Under conditions representative of a confined aquifer, a Berea sandstone core flooded with an aqueous CO2 solution was subjected to a six-period burst of 0.05-0.3 Hz, 0.1-0.4 MPa confining stress oscillations. After the oscillations were terminated, the pore fluid pressure exceeded its initial value by 13-60 cm equivalent freshwater head, scaling with the amplitude and frequency - a surplus that is consistent with borehole water level changes [Roeloffs et al. (1995) USGS Open File Report, 95-42] observed in response to the June 28 1992 MW 7.3 Landers, California earthquake Rayleigh wave in Parkfield and Long Valley caldera, California, where remotely triggered earthquakes occurred [Hill et al. (1993) Science, 260(5114); Hill et al. (1995) Journal of Geophysical Research, 100(B7)]. Our experimental results indicate that seismically initiated gas bubble growth in groundwater is a physically plausible mechanism for remote seismic triggering in active volcanic and geothermal regions, suggesting that the aqueous CO2 saturation state in a confined aquifer may be used to assess susceptibility to remote seismic triggering.

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

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

    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.

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

    SciTech Connect

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

    1982-08-01

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

  12. Gas-liquid heat transfer in a bubble collapsing near a wall

    NASA Astrophysics Data System (ADS)

    Yuan, H.; Prosperetti, A.

    1997-01-01

    The collapse of a gas bubble near a solid wall is studied numerically by assuming the liquid to be incompressible and the Mach number of the gas flow to be small. The liquid motion is simulated by a boundary integral method and the gas thermo-fluid dynamics by finite differences on a boundary-fitted grid. With the physical properties of a liquid monopropellant, it is found that the liquid heating is essentially localized in the microjet, but is probably not sufficient to cause spontaneous ignition. The reasons for this conclusion — that, while being in general agreement with available experimental evidence, is at variance with deductions from previous spherical collapse calculations — are elucidated.

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

    DOEpatents

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

    1996-02-06

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

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

    DOEpatents

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

    1996-01-01

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

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

    PubMed Central

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

    2009-01-01

    The wall effects on the axisymmetric rise and deformation of an initially spherical gas bubble released from rest in a liquid-filled, finite circular cylinder are numerically investigated. The bulk and gas phases are considered incompressible and immiscible. The bubble motion and deformation are characterized by the Morton number (Mo), Eötvös number (Eo), Reynolds number (Re), Weber number (We), density ratio, viscosity ratio, the ratios of the cylinder height and the cylinder radius to the diameter of the initially spherical bubble (H* = H/d0, R* = R/d0). Bubble rise in liquids described by Eo and Mo combinations ranging from (1,0.01) to (277.5,0.092), as appropriate to various terminal state Reynolds numbers (ReT) and shapes have been studied. The range of terminal state Reynolds numbers includes 0.02 < ReT < 70. Bubble shapes at terminal states vary from spherical to intermediate spherical-cap–skirted. The numerical procedure employs a front tracking finite difference method coupled with a level contour reconstruction of the front. This procedure ensures a smooth distribution of the front points and conserves the bubble volume. For the wide range of Eo and Mo examined, bubble motion in cylinders of height H* = 8 and R* ? 3, is noted to correspond to the rise in an infinite medium, both in terms of Reynolds number and shape at terminal state. In a thin cylindrical vessel (small R*), the motion of the bubble is retarded due to increased total drag and the bubble achieves terminal conditions within a short distance from release. The wake effects on bubble rise are reduced, and elongated bubbles may occur at appropriate conditions. For a fixed volume of the bubble, increasing the cylinder radius may result in the formation of well-defined rear recirculatory wakes that are associated with lateral bulging and skirt formation. The paper includes figures of bubble shape regimes for various values of R*, Eo, Mo, and ReT. Our predictions agree with existing results reported in the literature. PMID:17930342

  16. On sound generated by gas-jet impingement on a bubbly gas-water interface, with application to supercavity self-noise

    NASA Astrophysics Data System (ADS)

    Gilbert, J. B.; Howe, M. S.; Koch, R. M.

    2012-09-01

    An analysis is made of the sound produced when a high speed turbulent gas jet impinges at normal incidence on a planar gas-water interface in the presence of a uniform, thin homogeneous bubble layer between the gas and the water. It is shown that the bubble layer exhibits a behaviour similar to a 'quarter-wave' resonator, storing energy supplied by gas impingement which is subsequently released as high amplitude sound into the water. In the absence of bubbles the radiation into the water has dipole characteristics, peaking strongly in the direction normal to the interface. The bubbles diffuse this sharp dipole lobe, and are predicted to increase the sound power in the water by up to 10 dB or more over a range of intermediate frequencies when the layer properties are similar to those encountered in experiments using a model scale supercavitating vehicle. At higher frequencies, in the range important for vehicle guidance and control, the bubble layer tends to reduce this source of self-noise. The same mechanism of resonant amplification should be effective more generally, when the bubbles lie within a more confined surface envelope, such as the surface 'wake' of the jet impact zone, whose shape defines a different set of interior eigenmodes.

  17. Bubble Combustion

    NASA Technical Reports Server (NTRS)

    Corrigan, Jackie

    2004-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Watanabe, Hirotatsu; Furuyama, Tomoaki; Okazaki, Ken

    2015-01-01

    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%.

  19. Flow of gas and particles in a bubbling fluidized bed with a filtered two-fluid model

    Microsoft Academic Search

    Yin Lijie; Wang Shuyan; Lu Huilin; Wang Shuai; Xu Pengfei; Wei Lixing; He Yurong

    2010-01-01

    Numerical simulations of gas-particles flow in a bubble fluidized bed with two large eddy simulations of gas and solid phases are presented. For gas phase and solid phase, the sub-grid scale model for the viscosity is based on the Smagorinsky form. The sub-grid model for the particle pressure proposed by Igci et al. (2008) is modified by replacing the minimum

  20. Estimation methods for special nuclear materials holdup

    SciTech Connect

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

    1984-01-01

    The potential value of statistical models for the estimation of residual inventories of special nuclear materials was examined using holdup data from processing facilities and through controlled experiments. Although the measurement of hidden inventories of special nuclear materials in large facilities is a challenging task, reliable estimates of these inventories can be developed through a combination of good measurements and the use of statistical models. 7 references, 5 figures.

  1. Interstellar bubbles

    Microsoft Academic Search

    J. I. Castor; R. McCray; R. Weaver

    1975-01-01

    Early-type stars blow bubbles in the interstellar medium. The radii of the bubbles are typically 30 pc. Typical conditions in their interiors are temperatures of about 1 million K and densities of about 0.01 per cu cm. The dense shell of swept-up interstellar gas that surrounds them is likely to trap the ionization front and may also have an outer

  2. 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

    DIMITRI GIDASPOW

    1997-08-15

    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.

  3. Hydrate film growth on the surface of a gas bubble suspended in water.

    PubMed

    Peng, B Z; Dandekar, A; Sun, C Y; Luo, H; Ma, Q L; Pang, W X; Chen, G J

    2007-11-01

    The lateral film growth rate of CH4, C2H4, CO2, CH4 + C2H4, and CH4 + C3H8 hydrates in pure water were measured at four fixed temperatures of 273.4, 275.4, 277.4, and 279.4 K by means of suspending a single gas bubble in water. The results showed that the lateral growth rates of mixed-gas CH4 + C2H4 hydrate films were slower than that of pure gas (CH4 or C2H4) for the same driving force and that of mixed-gas CH4 + C3H8 hydrate film growth was the slowest. The dependence of the thickness of hydrate film on the driving force was investigated, and it was demonstrated that the thickness of hydrate film was inversely proportional to the driving force. It was found that the convective heat transfer control model reported in the literature could be used to formulate the lateral film growth rate v(f) with the driving force DeltaT perfectly for all systems after introduction of the assumption that the thickness of hydrate films is inversely proportional to the driving force DeltaT; i.e., v(f) = psiDeltaT(5/2) is correct and independent of the composition of gas and the type of hydrate. The thicknesses of different gas hydrate films were estimated, and it is demonstrated that the thicknesses of mixed-gas hydrate films were thicker than those of pure gases, which was qualitatively consistent with the experimental result. PMID:17929860

  4. The resonant mechanism of subdivision of a gas bubble in a fluid

    NASA Astrophysics Data System (ADS)

    Vanovskii, V. V.; Petrov, A. G.

    2012-06-01

    Small nonlinear oscillations of a bubble in a fluid at the resonance of the frequencies of the radial mode and an arbitrary deformational mode 2 : 1 are considered. The deformational mode is determined by the associated Legendre polynomial with indices n = 2, 3, …, m = 0, 1, …, n. The energy transfer from the radial mode into the Legendre deformational mode is described by the method of invariant normalization. An analogy is established with oscillations of the material point on the string with the frequency ratio of the vertical mode to the horizontal one of 2. During the transfer, the amplitude of the Legendre mode with indices n, m exceeds the amplitude of radial oscillations by a factor of 3 n at m = 0. As index m increases, the transfer time increases considerably and the maximal amplitude of the Legendre mode increases insignificantly in this case. From here, it is concluded that the deformational Legendre mode with indices n, m = n has the greatest probability to rise. The considered effect can serve as a mechanism of subdivision of gas bubbles under varying the external pressure in the fluid.

  5. Ion-induced density bubble in a strongly correlated one-dimensional gas

    SciTech Connect

    Goold, J. [Department of Physics, University College Cork, Cork (Ireland); Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, 117543 (Singapore); Doerk, H. [Max-Planck-Institut fuer Plasmaphysik, Boltzmannstr. 3, D-85748 Garching (Germany); Idziaszek, Z. [Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, Hoza 69, PL-00681 Warsaw (Poland); Calarco, T. [Institute for Quantum Information Processing, University of Ulm, Albert-Einstein-Allee 11, D-89069 Ulm (Germany); Busch, Th. [Department of Physics, University College Cork, Cork (Ireland)

    2010-04-15

    We consider a harmonically trapped Tonks-Girardeau gas of impenetrable bosons in the presence of a single embedded ion, which is assumed to be tightly confined in an RF trap. In an ultracold ion-atom collision the ion's charge induces an electric dipole moment in the atoms which leads to an attractive r{sup -4} potential asymptotically. We treat the ion as a static deformation of the harmonic trap potential and model its short range interaction with the gas in the framework of quantum defect theory. The molecular bound states of the ionic potential are not populated due to the lack of any possible relaxation process in the Tonks-Girardeau regime. Armed with this knowledge we calculate the density profile of the gas in the presence of a central ionic impurity and show that a density bubble of the order of 1{mu}m occurs around the ion for typical experimental parameters. From these exact results we show that an ionic impurity in a Tonks gas can be described using a pseudopotential approximation, allowing for significantly easier treatment.

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

    E-print Network

    Paris-Sud XI, Université de

    at the free surface of a non-newtonian fluid. On account of the viscoelastic properties of the fluidAcoustic emission associated with the bursting of a gas bubble at the free surface of a non-newtonian experiments have been performed in newtonian fluid [13, 14, 16]. However, departure from this newto- nian

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

    E-print Network

    Lee, Shan-Hu

    /Manipulatives, Atmospheric Chemistry, Equilibrium, Thermodynamics Henry's law constant represents the solubility of a soluteA Laboratory Experiment To Measure Henry's Law Constants of Volatile Organic Compounds experiment is described to measure Henry's law constants of organic compounds using a bubble column and gas

  8. COMPUTATIONAL MODELLING OF COMPLEX PHENOMENA IN BUBBLE DYNAMICS: VORTEX SHEDDING AND BUBBLE SWARMS

    Microsoft Academic Search

    Heikki Haario; Zhanna Korotkaya; Pasi Luukka; Anton Smolianski

    2004-01-01

    We consider the direct numerical simulation of gas bubbles in viscous uid ows. The behaviour of single bubbles and bubble swarms is studied with the particu- lar emphasis on the bubble coalescence and breakage phenomena. For single bubbles, we are able to simulate the bubble dynamics in all relevant ow regimes, including the von Karman type vortex shedding and wobbling-bubble

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

    SciTech Connect

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

    2014-04-07

    Advanced fast reactor systems being developed under the DOE's Advanced Fuel Cycle Initiative are designed to destroy TRU isotopes generated in existing and future nuclear energy systems. Over the past 40 years, multiple experiments and demonstrations have been completed using U-Zr, U-Pu-Zr, U-Mo and other metal alloys. As a result, multiple empirical and semi-empirical relationships have been established to develop empirical performance modeling codes. many 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.

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

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

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

  11. You see what you know … gas bubbles in the inferior vena cava, an unusual presentation of necrotizing soft tissue infection.

    PubMed

    Winter, Thomas C; Rudolf, Lou; Sommers, Daniel N

    2015-06-01

    Gas detected within the systemic circulation as an unexpected finding is a very rare phenomenon. A case of multiple bubbles within the inferior vena cava detected incidentally during a sonogram requested to assess for portal vein thrombosis is presented. These were eventually determined to be sequelae of a fatal, clinically silent necrotizing soft tissue infection. The differential diagnosis for gas within the inferior vena cava is reviewed, and teaching points that may help future patients are presented. PMID:25364965

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

    NASA Astrophysics Data System (ADS)

    Mychkovsky, Alexander; Ceccio, Steven

    2009-11-01

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

  13. STANDARD SETTING, PATENTS, AND HOLD-UP JOSEPH FARRELL

    E-print Network

    Sadoulet, Elisabeth

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

  14. Prediction of minimum bubbling velocity, fluidization index and range of particulate fluidization for gas–solid fluidization in cylindrical and non-cylindrical beds

    Microsoft Academic Search

    R. K. Singh; G. K. Roy

    2005-01-01

    A uniform fluidization exists between minimum fluidization velocity and minimum bubbling velocity. Experimental investigations have been carried out for determination of minimum bubbling velocity and fluidization index for non-spherical particles in cylindrical and non-cylindrical beds. In the present paper equations have been developed for the prediction of minimum bubbling velocity for gas–solid fluidization in cylindrical and non-cylindrical (viz. semi-cylindrical, hexagonal

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

    SciTech Connect

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

    2005-05-15

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

  16. Improved Background Corrections for Uranium Holdup Measurements

    SciTech Connect

    Oberer, R.B.; Gunn, C.A.; Chiang, L.G.

    2004-06-21

    In the original Generalized Geometry Holdup (GGH) model, all holdup deposits were modeled as points, lines, and areas[1, 5]. Two improvements[4] were recently made to the GGH model and are currently in use at the Y-12 National Security Complex. These two improvements are the finite-source correction CF{sub g} and the self-attenuation correction. The finite-source correction corrects the average detector response for the width of point and line geometries which in effect, converts points and lines into areas. The result of a holdup measurement of an area deposit is a density-thickness which is converted to mass by multiplying it by the area of the deposit. From the measured density-thickness, the true density-thickness can be calculated by correcting for the material self-attenuation. Therefore the self-attenuation correction is applied to finite point and line deposits as well as areas. This report demonstrates that the finite-source and self-attenuation corrections also provide a means to better separate the gamma rays emitted by the material from the gamma rays emitted by background sources for an improved background correction. Currently, the measured background radiation is attenuated for equipment walls in the case of area deposits but not for line and point sources. The measured background radiation is not corrected for attenuation by the uranium material. For all of these cases, the background is overestimated which causes a negative bias in the measurement. The finite-source correction and the self-attenuation correction will allow the correction of the measured background radiation for both the equipment attenuation and material attenuation for area sources as well as point and line sources.

  17. Evidence of injury caused by gas bubbles in a live marine mammal: barotrauma in a California sea lion Zalophus californianus.

    PubMed

    Van Bonn, W; Montie, E; Dennison, S; Pussini, N; Cook, P; Greig, D; Barakos, J; Colegrove, K; Gulland, F

    2011-09-01

    A yearling male California sea lion Zalophus californianus with hypermetric ataxia and bilateral negative menace reflexes was brought to The Marine Mammal Center, Sausalito, California, U.S.A., in late 2009 for medical assessment and treatment. The clinical signs were due to multiple gas bubbles within the cerebellum. These lesions were intraparenchymal, multifocal to coalescing, spherical to ovoid, and varied from 0.5 to 2.4 cm diameter. The gas composed 21.3% of the total cerebellum volume. Three rib fractures were also noted during diagnostic evaluation and were presumed to be associated with the gas bubbles in the brain. The progression of clinical signs and lesion appearance were monitored with magnetic resonance imaging, cognitive function testing and computed tomography. Gas filled voids in the cerebellum were filled with fluid on follow up images. Clinical signs resolved and the sea lion was released with a satellite tag attached. Post release the animal travelled approximately 75 km north and 80 km south of the release site and the tag recorded dives of over 150 m depth. The animal re-stranded 25 d following release and died of a subacute bronchopneumonia and pleuritis. This is the first instance of clinical injury due to gas bubble formation described in a living pinniped and the first sea lion with quantifiable cerebellar damage to take part in spatial learning and memory testing. PMID:22013748

  18. HIGH FREQUENCY RESPONSE OF A FLUID-FILLED CYLINDRICAL SHELL WITH AN INTERNAL COLUMN OF GAS BUBBLES: APPLICATION TO ACTIVE ACOUSTIC GAS LEAK DETECTION

    Microsoft Academic Search

    B. J. Brévart; C. Journeau; C. R. Fuller

    1996-01-01

    The high frequency response to a point force excitation of an infinite elastic cylindrical shell, filled with a liquid including a column of gas bubbles, is investigated. A state vector approach is used for the shell theory to include the effects of shear deformation and rotary inertia. The far field mobility of the shell for each propagating circumferential modenis calculated

  19. 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

    Levinsen, Mogens T.

    investigates the dynamics of an acoustically driven air bubble in water. Depending on the values of external of the next acoustic cycle, which brings memory into the system. We show that for some parameter values investigate the convergence of the calculated quantities. I. INTRODUCTION A gas bubble levitated in a liquid

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

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

    E-print Network

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

    2014-01-01

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

  2. Bubble diagnostics

    DOEpatents

    Visuri, Steven R. (Livermore, CA); Mammini, Beth M. (Walnut Creek, CA); Da Silva, Luiz B. (Danville, CA); Celliers, Peter M. (Berkeley, CA)

    2003-01-01

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

  3. SNM holdup assessment of Los Alamos exhaust ducts. Final report

    SciTech Connect

    Marshall, R.S.

    1994-02-01

    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.

  4. Homogeneous and bubbling fluidization regimes in DEM–CFD simulations: Hydrodynamic stability of gas and liquid fluidized beds

    Microsoft Academic Search

    Alberto Di Renzo; Francesco Paolo Di Maio

    2007-01-01

    In recent years coupled DEM–CFD models have been successfully utilized to simulate fluidized particle systems in the bubbling regime. In this paper we report on DEM–CFD simulations of liquid-fluidization of glass beads and gas-fluidization of Geldart's Group A particles carried out to characterize hydrodynamically the stability of the fluidized state, in the absence of cohesive forces. Due to the importance

  5. Spontaneous structures in three-dimensional bubbling gas-fluidized bed by parallel DEM–CFD coupling simulation

    Microsoft Academic Search

    Takuya Tsuji; Keizo Yabumoto; Toshitsugu Tanaka

    2008-01-01

    Flow structures induced by bubbles formed in three-dimensional shallow rectangular gas-fluidized beds are investigated by the DEM–CFD coupling simulation. A numerical code is parallelized and more than 4.5million particles are tracked in the maximum by using 16 CPUs. To investigate the domain-size dependency, the cross-sectional area of beds is enlarged by the factors up to 82 and the results are

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

    PubMed

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

    2009-01-01

    Solea senegalensis is a commercial flat fish traditionally farmed in earth ponds in coastal wetlands that might also become important to more intensive aquaculture. Gas bubble disease (GBD) is a potential risk for outdoor fish farming, particularly in certain periods of the year, related to improper management leading to macroalgae blooms. Physical-chemical conditions inducing hyperoxia, including radiation, temperature, and high levels of dissolved oxygen, have been monitored in fish affected by GBD together with observed symptoms. Exophthalmia, subcutaneous emphysemas, obstruction of gill lamellae, hemorrhages, and anomalous swimming were the main effects of oxygen supersaturation. A proteomic study was carried out for the first time under aquaculture conditions and protein expression changes are described for fish that were subject to hyperoxic conditions. Proteins identified in gill of GBD-affected fish are related to oxidative alteration of cytoskeleton structure/function (beta-tubulin, beta-actin), motility (light myosin chain, alpha-tropomyosin), or regulatory pathways (calmodulin, Raf kinase inhibitor protein), reflecting the central role of gill in oxygen exchange. Hepatic proteins identified are related to protein oxidative damages (beta-globin, FABPs), protection from oxidative stress (DCXR, GNMT), and inflammatory response (C3), in agreement with the predominant metabolic role of liver. Comparison of protein expression patterns and protein identification are suggested as potentially specific hyperoxia biomarkers that would facilitate prevention of GBD outbreaks. PMID:19101763

  7. Tiny Bubbles

    NSDL National Science Digital Library

    Glenn Dolphin

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

  8. Hydroacoustic methodology for detection, localization, and quantification of gas bubbles rising from the seafloor at gas seeps from the eastern Black Sea

    NASA Astrophysics Data System (ADS)

    Nikolovska, Aneta; Sahling, Heiko; Bohrmann, Gerhard

    2008-10-01

    Detailed acoustic investigation of bubble streams rising from the seafloor were conducted during R/V Meteor cruise M72/3a at a deep submarine hydrocarbon seep environment. The area is located offshore Georgia (eastern part of the Black Sea) at a water depth between 840 m and 870 m. The sediment echosounder Parasound DS-3/P70 was used for detecting bubbles in the water column that causes strong backscatter in the echographs ("flares"). Employing the swath echsounder Kongsberg EM710 flares in the water column were mapped along the entire swath width of approximately 1000 m at high spatial resolution. The exact location of the flares could be extracted manually. Subsequently, the horizontally looking sonar Kongsberg digital telemetry MS1000 mounted on a remotely operated vehicle (ROV) was utilized to quantify the flux of bubbles. A model was developed that is based on the principle of finding the "acoustic mass" in order to quantify the bubble flux at various seeps. The acoustic approach from the backscatter data of the ROV sonar resulted in bubble fluxes in the range of 0.01 to 5.5 L/min (corresponding to 0.037 to 20.5 mol CH4/min) at in situ conditions (˜850 m water depth, ˜9°C). Independent flux estimations using a funnel-shaped device showed that the acoustic model consistently produced lower values but the offset is less than 12%. Furthermore, the deviation decreased with increasing flux rates. A field of bubble streams was scanned three times from different directions in order to reveal the reproducibility of the method. Flux estimations yielded consistent fluxes of about 2 l/min (7.4 mol CH4/min) with variations of less than 10%. Although gas emissions have been found at many sites at the seafloor in a range of geological settings, the amount of escaping gas is still largely unknown. With this study presenting a novel method of quantifying bubble fluxes employing a horizontally looking sonar system, it is intended to contribute to the global effort of better constraining bubble fluxes at deep-sea settings.

  9. Testing a simple model of gas bubble dynamics in porous media

    NASA Astrophysics Data System (ADS)

    Ramirez, Jorge A.; Baird, Andy J.; Coulthard, Tom J.; Waddington, J. Michael

    2015-02-01

    Bubble dynamics in porous media are of great importance in industrial and natural systems. Of particular significance is the impact that bubble-related emissions (ebullition) of greenhouse gases from porous media could have on global climate (e.g., wetland methane emissions). Thus, predictions of future changes in bubble storage, movement, and ebullition from porous media are needed. Methods exist to predict ebullition using numerical models, but all existing models are limited in scale (spatial and temporal) by high computational demands or represent porous media simplistically. A suitable model is needed to simulate ebullition at scales beyond individual pores or relatively small collections (<10-4 m3) of connected pores. Here we present a cellular automaton model of bubbles in porous media that addresses this need. The model is computationally efficient, and could be applied over large spatial and temporal extent without sacrificing fine-scale detail. We test this cellular automaton model against a physical model and find a good correspondence in bubble storage, bubble size, and ebullition between both models. It was found that porous media heterogeneity alone can have a strong effect on ebullition. Furthermore, results from both models suggest that the frequency distributions of number of ebullition events per time and the magnitude of bubble loss are strongly right skewed, which partly explains the difficulty in interpreting ebullition events from natural systems.

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

    E-print Network

    Haque, Mohammad Shamsul

    1967-01-01

    : , ) / ( Wch i t' c~itt ()member) AUGUST 1967 CDQP45 111 ACKNDWLEDGhiE", ITS TIIe aut!Ior vIishes to exoress his sincere thanks to Dr. Ronald Darby, Ctla1n~lan of the Grad, Iate Coalslittee? for h'is capa'11e guidance and valuable help in this researc!1... V11 1 16 28 41 58 64 67 73 77 Table LIST OF TABLES Page 1 BUBBLE NO. 1 GROWTH DATA. 2 BUBBLE NO. 2 GROMTH DATA. 3 BUBBLE NO. 3 GROWTH DATA 80 81 82 4 DATA ON SULFURIC ACID AS A FUNCTION OF CONCENTRATION. . . 83 V1 LIST OF FIGURES...

  11. Optical measurements of phase concentration and velocity distributions of a horizontal gas jet in a 2D bubbling fluidized bed

    NASA Astrophysics Data System (ADS)

    Mychkovsky, Alexander; Ceccio, Steven; Sick, Volker

    2008-11-01

    Optical measurement techniques are used for spatially and temporally resolved measurements of phase concentrations and velocities in a horizontal gas jet injected in a 2D bubbling fluidized bed. A fiber optic probe has been developed to measure Laser Induced Fluorescence (LIF) signals from an acetone tracer to quantify jet gas concentration and elastic Mie scatter from the bed particles to determine the solids fraction in a localized region. These two optical signals are spectrally separated and therefore enable simultaneous measurements of the two phases. In addition, jet gas and particles velocities are obtained with a Laser Doppler Velocimetry (LDV) system. These measurements yield phase concentration and velocity profiles necessary to characterize the dynamic behavior of gas jets in fluidized beds.

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

    PubMed

    Betz, J; Straub, J

    2002-10-01

    In the presence of a temperature gradient at a liquid-gas or liquid-liquid interface, thermocapillary or Marangoni convection develops. This convection is a special type of natural convection that was not paid much attention in heat transfer for a long time, although it is strong enough to drive liquids against the direction of buoyancy on Earth. In a microgravity environment, however, it is the remaining mode of natural convection and supports heat and mass transfer. During boiling in microgravity it was observed at subcooled liquid conditions. Therefore, the question arises about its contribution to heat transfer without phase change. Thermocapillary convection was quantitatively studied at single gas bubbles in various liquids, both experimentally and numerically. A two-dimensional mathematical model described in this article was developed. The coupled mechanism of heat transfer and fluid flow in pure liquids around a single gas bubble was simulated with a control-volume FE-method. The simulation was accompanied and compared with experiments on Earth. The numerical results are in good accordance with the experiments performed on Earth at various Marangoni numbers using various alcohols of varying chain length and Prandtl numbers. As well as calculations on Earth, the numerical method also allows simulations at stationary spherical gas bubbles in a microgravity environment. The results demonstrate that thermocapillary convection is a natural heat transfer mechanism that can partially replace the buoyancy in a microgravity environment, if extreme precautions are taken concerning the purity of the liquids, because impurities accumulate predominantly at the interface. Under Earth conditions, an enhancement of the heat transfer in a liquid volume is even found in the case where thermocapillary flow is counteracted by buoyancy. In particular, the obstructing influence of surface active substances could be observed during the experiments on Earth in water and also in some cases with alcohols. PMID:12446327

  13. Evaluation of the Integrated Holdup Measurement System with the M3(superscript 3)CA for Assay of Uranium and Plutonium Holdup

    SciTech Connect

    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

    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.

  14. Gas and particulate phase velocity measurements of a high-speed gas jet into a two-dimensional bubbling fluidized bed

    NASA Astrophysics Data System (ADS)

    Mychkovsky, Alexander; Ceccio, Steven

    2010-11-01

    A Laser Doppler Velocimetry (LDV) technique was implemented to simultaneously measure the gas and particulate phase velocities in a high-speed jet plume in a two-dimensional (2D) bubbling fluidized bed. The gas and particulate phase velocity profiles are presented and analyzed. This includes similarity profile scaling as well as volume fraction, mass flow, and momentum transport calculations for the two phases. Furthermore, applying the Eulerian equation of motion to the particulate phase with the measured velocity profiles, the bed particle drag coefficient is recovered and is found to be consistent with the established empirical value.

  15. Novel techniques for slurry bubble column hydrodynamics

    SciTech Connect

    Dudukovic, M.P.

    1999-05-14

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2003-11-01

    We collected all of the published data we could find on the rise velocity of long gas bubbles in stagnant fluids contained in circular tubes. Data from 255 experiments from the literature and seven new experiments at PDVSA Intevep for fluids with viscosities ranging from 1 mPa s up to 3900 mPa s were assembled on spread sheets and processed in log log plots of the normalized rise velocity, Fr {=} U/(gD)(1/2) Froude velocity vs. buoyancy Reynolds number, R {=} (D(3) g (rho_{l}-rho_{g}) rho_{l})(1/2) /mu for fixed ranges of the Eötvös number, Eo {=} grho_{l}D(2) /sigma where D is the pipe diameter, rho_{l}, rho_{g} and sigma are densities and surface tension. The plots give rise to power laws in Eo; the composition of these separate power laws emerge as bi-power laws for two separate flow regions for large and small buoyancy Reynolds. For large R (>200) we find [hboxFr = {0.34}/(1+3805/hboxEo^{3.06})^{0.58}.] For small R (<10) we find [ hboxFr = frac{9.494times 10^{-3}}{({1+{6197}/hboxEo^{2.561}})^{0.5793}}R^{1.026}.] The flat region for high buoyancy Reynolds number and sloped region for low buoyancy Reynolds number is separated by a transition region (10 {<} R {<} 200) which we describe by fitting the data to a logistic dose curve. Repeated application of logistic dose curves leads to a composition of rational fractions of rational fractions of power laws. This leads to the following universal correlation: [ hboxFr = L[{R;A,B,C,G}] equiv frac{A}{({1+({{R}/{B}})^C})^G} ] where [ A = L[hboxEo;a,b,c,d],quad B = L[hboxEo;e,f,g,h],quad C = L[hboxEo;i,j,k,l],quad G = m/C ] and the parameters (a, b,...,l) are begin{eqnarray*} &&hspace*{-5pt}a hspace*{-0.8pt} {=} hspace*{-0.8pt} 0.34;quad bhspace*{-0.8pt} {=} hspace*{-0.8pt} 14.793;quad chspace*{-0.8pt} {=} hspace*{-0.6pt}{-}3.06;quad dhspace*{-0.6pt} {=} hspace*{-0.6pt}0.58;quad ehspace*{-0.6pt} {=} hspace*{-0.6pt} 31.08;quad fhspace*{-0.6pt} {=} hspace*{-0.6pt}29.868;quad ghspace*{-0.6pt} { =} hspace*{-0.6pt}{ -}1.96; &&hspace*{-5pt}h = -0.49;quad i = -1.45;quad j = 24.867;quad k = -9.93;quad l = -0.094;quad m = -1.0295.end{eqnarray*} The literature on this subject is reviewed together with a summary of previous methods of prediction. New data and photographs collected at PDVSA-Intevep on the rise of Taylor bubbles is presented.

  17. 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)

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

    2014-05-01

    In the Central North Sea, during drilling operations, a gas blowout accident happened in 1990. Thereafter, natural gas has leaked prodigiously from a 60 m diameter and 20 m deep crater located at 95 m depth into the water column and to the sea surface. A series of field studies was carried out at this site since 2005 evidencing ongoing intense seepage activity. Three gas bubble megaplumes and dozens of minor to major bubble seeps were observed in the crater during a manned submersible dive, ROV mapped hundreds. Analysis of gas bubbles captured at 118 m water depth revealed concentrations between 88-90%Vol CH4 with ? 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

    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.

  20. Transport evaluation of a gas-liquid scrubber. [Five-tray, single-bubble-cap, single-downcomer, gas liquid contactor

    SciTech Connect

    Brodner, A.J.; Bistline, J.E.; Weber, S.E.

    1982-10-01

    The hydraulics and the mass-transfer behavior of a five-tray, single-bubble-cap, single-downcomer, gas-liquid contactor were studied for use as a gas scrubber. Flooding was not observed at the maximum available liquid and gas flow rates of 0.32 and 464 L/min, respectively. The maximum liquid entrainment was 33% at a gross liquid flow rate of 0.05 L/min. The Murphree-tray efficiencies for absorption of CO/sub 2/ (5000 ppM in air) into demineralized water ranged from 0.14 to 0.74 for volumetric liquid-to-gas ratios of 4 x 10/sup -4/ and 2 x 10/sup -4/, respectively, for k/sub L/a values ranging from 0.088 to 0.36 min/sup -1/. 12 figures, 10 tables.

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

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

  2. The effect of lattice and grain boundary diffusion on the redistribution of Xe in metallic nuclear fuels: Implications for the use of ion implantation to study fission-gas-bubble nucleation mechanisms

    Microsoft Academic Search

    Wayne E. King; Scott J. Tumey; Jeffrey Rest; George H. Gilmer

    2011-01-01

    A multi-atom gas bubble-nucleation mechanism has been proposed as part of a predictive fission-gas release model for metallic nuclear fuels. Validation of this mechanism requires experimental measurement of fission-gas bubble-size distributions at well-controlled gas concentrations and temperatures. There are advantages to carrying out such a study using ion implantation as the source of gas atoms compared with neutron irradiations. In

  3. Use of tracers in materials-holdup study

    SciTech Connect

    Pillay, K.K.S.

    1983-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

    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.

  6. Comparison of three different ultrasonic methods for quantification of intravascular gas bubbles.

    PubMed

    Brubakk, A O; Eftedal, O

    2001-01-01

    For evaluating different decompression schedules, the use of ultrasound is common. Systems based on the Doppler principle have mostly been used. However, ultrasonic scanners producing images where the bubbles are easily detected, may be an alternative, because analysis of the signals is simpler than when using Doppler methods. In this study, three methods of bubble detection were used following a series of air dives. The divers were investigated using a "blind" Doppler system where only auditory signals were used for positioning the probe. They were also studied using ultrasonic images and finally an "image-assisted" Doppler method was used, where the sample volume of the Doppler system was positioned using the images. Both Doppler systems were pulsed Doppler systems. The agreement between the methods was determined using weighted kappa statistics. The results show that, at rest, the agreement between the images and the blind Doppler method was very good, and between the two Doppler methods and the images and the image-assisted method the agreement was good. Generally, the agreement is better at higher bubble grades. After movement, the agreement was not good. We conclude that grades from the different methods can be directly compared at rest. PMID:12067148

  7. Holdup measurements of the Rocky Flats Plant 371 precipitator canyons

    Microsoft Academic Search

    P. A. Russo; J. K. Jr. Sprinkle; T. H. Elmont

    1987-01-01

    A shielded NaI(Tl) gamma-ray detector with portable electronics and automated data reduction and readout was used to measure the plutonium holdup on the floors of the Rocky Flats Plant Building 371 precipitator canyons. The amount of plutonium on the floors was determined to be 373 +- 84 g. Based on estimates applied to the very high background count rates measured

  8. 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)

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

    2009-11-01

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

  9. Pefluorocarbon inhibition of bubble induced Ca2+ transients in an in-vitro model of vascular gas-embolism

    PubMed Central

    Klinger, Alexandra L.; Kandel, Judith; Pichette, Benjamin; Eckmann, David M.

    2014-01-01

    Endothelial injury resulting from deleterious interaction of gas microbubbles occurs in many surgical procedures and other medical interventions. The symptoms of vascular air embolism (VAE), while serious, are often difficult to detect, and there are essentially no pharmaceutical preventative or post-event treatments currently available. Perfluorocarbons (PFCs), however, have shown particular promise as a therapeutic option in reducing endothelial injury both in- and ex-vivo. Recently, we demonstrated the effectiveness of Oxycyte, a third-generation PFC formulated in a phosphotidylcholine emulsion, using an in-vitro model of VAE developed in our laboratory. This apparatus allows live cell imaging concurrent with precise manipulation of physiologically sized microbubbles so that they may be brought into individual contact with human umbilical vein endothelial cells dye-loaded with the Ca2+ sensitive Fluo-4. Herein, we expand use of this fluorescence microscopy-based cell culture model. Specifically, we examined the concentration dependence of Oxycyte in reducing both the amplitude and frequency of large intracellular Ca2+ currents that are both a hallmark of bubble contact and a quantifiable indication that abnormal intracellular signaling has been triggered. We measured dose dependence curves and fit the resultant data using a modified Black and Leff operational model of agonism. The half maximal inhibitory concentrations of Oxycyte for i) inhibition of occurrence and ii) amplitude reduction were 229±49 µM and 226±167 µM, respectively. This investigation shows the preferential gas/liquid interface occupancy of the PFC component of Oxycyte over that of mechanosensing glycocalyx components and validates Oxycyte’s specific surfactant mechanism of action. Further, no lethality was observed for any concentration of this bioinert PFC, as it acts as a competitive allosteric inhibitor of syndecan activation to ameliorate cell response to bubble contact. PMID:24131543

  10. Tribonucleation of bubbles.

    PubMed

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

    2014-07-15

    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

  11. The effect of high viscosity on the collapse-like chaotic and regular periodic oscillations of a harmonically excited gas bubble.

    PubMed

    Heged?s, Ferenc; Klapcsik, Kálmán

    2015-11-01

    In the last decade many industrial applications have emerged based on the rapidly developing ultrasonic technology such as ultrasonic pasteurization, alteration of the viscosity of food systems, and mixing immiscible liquids. The fundamental physical basis of these applications is the prevailing extreme conditions (high temperature, pressure and even shock waves) during the collapse of acoustically excited bubbles. By applying the sophisticated numerical techniques of modern bifurcation theory, the present study intends to reveal the regions in the excitation pressure amplitude-ambient temperature parameter plane where collapse-like motion of an acoustically driven gas bubble in highly viscous glycerine exists. We report evidence that below a threshold temperature the bubble model, the Keller-Miksis equation, becomes an overdamped oscillator suppressing collapse-like behaviour. In addition, we have found periodic windows interspersed with chaotic regions indicating the presence of transient chaos, which is important from application point of view if predictability is required. PMID:26186832

  12. Nondestructive assay holdup measurements with the Ortec detective

    SciTech Connect

    Vo, Duc [Los Alamos National Laboratory; Wenz, Tracy [Los Alamos National Laboratory; Bracken, David [Los Alamos National Laboratory

    2009-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    More than 500 bubble-induced hydroacoustic anomalies (flares) were found in the water column above the seafloor in the study area comprising about 430 km2 at the Don-Kuban paleo-fan (Eastern Black Sea) by using ship mounted single beam and multibeam echosounders. Almost all flares originated from the seafloor above the gas hydrate stability zone (GHSZ), which in that region is located below ~700 m water depth. This observation confirms the sealing mechanism of gas hydrate, which impedes migration of free gas through the GHSZ and subsequent bubble emission from the seafloor. However, an intense seep site, called the "Kerch seep area" was discovered as an exception at 890 m water depth well within the GHSZ. In situ temperature measurements in shallow sediments indicate locally elevated temperatures probably caused by enhanced upward fluid flow. The base of the GHSZ in this region is generally situated at about 150 m below the seafloor. However, the local thermal anomalies result in a thinning of the gas hydrate occurrence zone to only a few meters below the seafloor and allow free gas to reach the seafloor. At sites where gas migrated into near-surface deposits, shallow gas hydrate deposits evolved and up-doming of overlying sediments led to the formation of mounds rising several meters from the surrounding seafloor. Further gas bubbles ascending from greater depth are accumulated below the gas hydrate layer at the base of the mound structures and migrate horizontally to their rims. At the mound edges gas bubbles either might form fresh gas hydrates and increase the extent of the mound structures by pushing up overlying sediments or escape at several sites into the water column. Two mounds were mapped in ultra-high resolution during dives with the autonomous underwater vehicle 'AUV MARUM SEAL 5000'. Several individual flares were detected in the Kerch seep area using hydroacoustic systems. Repeated surveys in that area conducted during three cruises within four years suggested that gas discharge varied spatially and temporally while the total number of flares remained rather constant. During seafloor inspections with MARU?s remotely operated vehicle 'ROV QUEST 4000 m' gas bubble emission sites were investigated in detail. Gas bubbles collected during the ROV dives mainly consisted of methane predominantly of microbial origin. By analyzing the high-definition video material the gas flux from several bubble emission sites was calculated. In combination with the hydroacoustic results (flare distributions) it is estimated that about 2.2 - 87 × 106 mol CH4/yr are emitted from the seafloor at the Kerch seep area. Despite this high mass of methane injected into the hydrosphere, the peak of the highest flares at ~350 m water depth as revealed by echosounder recording suggest that the ascending methane completely dissolves in the water column and does not pass the sea-atmosphere boundary.

  14. Review of Current Literature and Research on Gas Supersaturation and Gas Bubble Trauma: Special Publication Number 1, 1986.

    SciTech Connect

    Colt, John; Bouck, Gerald R.; Fidler, Larry

    1986-12-01

    This report presents recently published information and on-going research on the various areas of gas supersaturation. Growing interest in the effects of chronic gas supersaturation on aquatic animals has been due primarily to heavy mortality of salmonid species under hatchery conditions. Extensive examination of affected animals has failed to consistently identify pathogenic organisms. Water quality sampling has shown that chronic levels of gas supersaturation are commonly present during a significant period of the year. Small marine fish larvae are significantly more sensitive to gas supersaturation than salmonids. Present water quality criteria for gas supersaturation are not adequate for the protection of either salmonids under chronic exposure or marine fish larvae, especially in aquaria or hatcheries. To increase communication between interested parties in the field of gas supersaturation research and control, addresses and telephone numbers of all people responding to the questionnaire are included. 102 refs.

  15. Application of the ultrasonic technique and high-speed filming for the study of the structure of air-water bubbly flows

    SciTech Connect

    Carvalho, R.D.M.; Venturini, O.J.; Tanahashi, E.I. [Universidade Federal de Itajuba (UNIFEI), Itajuba (Brazil); Neves, F. Jr. [Universidade Tecnologica Federal do Parana (UTFPR), Curitiba (Brazil); Franca, F.A. [Universidade Estadual de Campinas (UNICAMP), Campinas (Brazil)

    2009-10-15

    Multiphase flows are very common in industry, oftentimes involving very harsh environments and fluids. Accordingly, there is a need to determine the dispersed phase holdup using noninvasive fast responding techniques; besides, knowledge of the flow structure is essential for the assessment of the transport processes involved. The ultrasonic technique fulfills these requirements and could have the capability to provide the information required. In this paper, the potential of the ultrasonic technique for application to two-phase flows was investigated by checking acoustic attenuation data against experimental data on the void fraction and flow topology of vertical, upward, air-water bubbly flows in the zero to 15% void fraction range. The ultrasonic apparatus consisted of one emitter/receiver transducer and three other receivers at different positions along the pipe circumference; simultaneous high-speed motion pictures of the flow patterns were made at 250 and 1000 fps. The attenuation data for all sensors exhibited a systematic interrelated behavior with void fraction, thereby testifying to the capability of the ultrasonic technique to measure the dispersed phase holdup. From the motion pictures, basic gas phase structures and different flows patterns were identified that corroborated several features of the acoustic attenuation data. Finally, the acoustic wave transit time was also investigated as a function of void fraction. (author)

  16. Pulsed electrogeneration of bubbles for electroflotation

    Microsoft Academic Search

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

    1991-01-01

    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

  17. Buoyant Bubbles

    NSDL National Science Digital Library

    Lawrence Hall of Science

    2009-01-01

    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.

  18. Continuous Holdup Measurements with Silicon P-I-N Photodiodes

    SciTech Connect

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

    2002-05-01

    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.

  19. Models for gamma-ray holdup measurements at duct contact

    SciTech Connect

    Sheppard, G.A.; Russo, P.A.; Wenz, T.R.; Miller, M.C.; Piquette, E.C. (Los Alamos National Lab., NM (United States)); Haas, F.X.; Glick, J.B.; Garrett, A.G. (EG and G Rocky Flats, Inc., Golden, CO (United States))

    1991-01-01

    The use of gamma-ray measurements to nondestructively assay special nuclear material holdup in DOE processing facilities has increased recently. A measurement approach that is relatively insensitive to deposit geometry involves withdrawing the detector from the holdup-bearing equipment far enough to validate an assumed point-, line-, or area-source deposit geometry. Because of facility constraints, these generalized geometry procedures are not always followed, and some ducts are measured at contact. Quantitative interpretation of contact measurements requires knowledge of the width of the deposit transverse to the duct axis. Rocky Flats personnel have introduced a method to obtain data from which this width can be deduced. It involves taking measurements in pairs, with the detector viewing the holdup deposit at contact from above and below the duct. The interpretation of the top and bottom measurements to give the deposit width at each location requires a model for the detector's response to radial source position and a model for the deposit geometry. We have derived a relationship between the top-to-bottom count rate ratio and the deposit width that approximates the detector response and models the deposit geometry as a uniform strip. The model was validated in controlled experiments that used thin foils of high-enriched uranium metal to simulate duct deposits. 4 refs., 5 figs., 1 tab.

  20. Axial and Radial Solids Holdup Modeling of Circulating Fluidized Bed Risers

    NASA Astrophysics Data System (ADS)

    Miao, Q.; Zhu, J.; Barghl, S.; Wanfi, C.; Yin, X. L.; Wu, C. Z.

    Hydrodynamics plays a crucial role in defining the performance of gas-solid circulating fluidized beds (CFB). A two dimensional model was developed considering the hydrodynamic behavior of CFB gasifiers. In the modeling, the CFB riser was divided into two regions: a dense region at the bottom and a dilute region at the top of the riser. Radial distributions of bed voidage were taken into account in the upper zone by using (1991)'s correlation. For model validation purposes, a cold model CFB was employed, in which sawdust was transported with air as fluidizing agent. The column was 10m in height and 280 mm in diameter, and was equipped with pressure transducers to measure axial pressure profile and with a reflective optical fiber probe to measure local solids holdup. A satisfactory agreement between the model predictions and experimental data was found.

  1. Bubblebubbles — boiling

    Microsoft Academic Search

    Johannes Straub

    2005-01-01

    A short overview of boiling research in microgravity performed during the past two decades is subject of this presentation.\\u000a The research was concentrated on pool boiling without applying any external forces. The objective of this research was to\\u000a answer the questions: Is boiling an appropriate mechanism of heat transfer in space applications, and how do heat transfer\\u000a and bubble dynamics

  2. Bubble dielectrophoresis

    NASA Technical Reports Server (NTRS)

    Jones, T. B.; Bliss, G. W.

    1977-01-01

    The theoretical principles related to bubble dielectrophoresis are examined, taking into account the polarization force, aspects of bubble deformation, the electrostatic bubble levitation theorem, and the equation of motion. The measurement of the dielectrophoretic force on static and dynamic bubbles represents a convenient experimental method for the study of the general problem of dielectrophoresis. The experiments reported include static-force measurements, static-levitation experiments, and dynamic-force measurements.

  3. A second-order moment method of dense gas–solid flow for bubbling fluidization

    Microsoft Academic Search

    Sun Dan; Wang Shuyan; Lu Huilin; Shen Zhiheng; Li Xiang; Wang Shuai; Zhao Yunhua; Wei Lixin

    2009-01-01

    A gas–solid two-fluid model with the second-order moment method is presented to close the set of equations applied to fluidization. With the kinetic theory of granular flow, transport equations for the velocity moments are derived for the particle phase. Closure equations for the third-order moments of velocity and for the fluid–particle velocity correlation are presented. The former is based on

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

    PubMed

    Liu, Yangxian; Wang, Qian

    2014-10-21

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

  5. Heat transfer and hydrodynamic investigations of a baffled slurry bubble column

    NASA Astrophysics Data System (ADS)

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

    1992-09-01

    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.

  6. A Simple Economic Teaching Experiment on the Hold-Up Problem

    ERIC Educational Resources Information Center

    Balkenborg, Dieter; Kaplan, Todd; Miller, Timothy

    2012-01-01

    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…

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

    SciTech Connect

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

    2012-04-11

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

  8. Gas-bubble snap-off under pressure driven flow in constricted noncircular capillaries

    SciTech Connect

    Kovscek, A.R.; Radke, C.J.

    1996-04-01

    A model for snap-off of a gas thread in a constricted cornered pore is developed. The time for wetting liquid to accumulate at a pore throat into an unstable collar is examined, as for the resulting pore-spanning lens to be displaced from the pore so that snap-off is the time may repeat. A comer-flow hydrodynamic analysis for the accumulation rate of wetting liquid due to both gradients in interfacial curvature and in applied liquid-phase pressure reveals that wetting-phase pressure gradients significantly increase the frequency of liquid accumulation for snap-off as compared to liquid rearrangement driven only by differences in pore-wall curvature. For moderate and large pressure gradients, the frequency of accumulation increases linearly with pressure gradient because of the increased rate of wetting liquid flow along pore comers. Pore topology is important to the theory, for pores with relatively small throats connected to large bodies demonstrate excellent ability to snapoff gas threads even when the initial capillary pressure is high or equivalently when the liquid saturation is low. A macroscopic momentum balance across the lens resulting from snap-off reveals that lens displacement rates are not linear with the imposed pressure drop. Instead, the frequency of lens displacement scales with powers between 0.5 and 0.6 for pores with dimensionless constriction radii between 0.15 and 0.40. Statistical percolation arguments are employed to form a generation rate expression and connect pore-level foam generation events to macroscopic pressure gradients in porous media. The rate of foam generation by capillary snap-off increases linearly with the liquid-phase pressure gradient and according to a power-law relationship with respect to the imposed gas-phase pressure gradient.

  9. Bubble effect on Kelvin-Helmholtz' instability

    Microsoft Academic Search

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

  10. Bubble effect on Kelvin-Helmholtz instability

    Microsoft Academic Search

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

    2004-01-01

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

  11. Possible applications of bubble acoustics in Nature

    Microsoft Academic Search

    T. G. Leighton; D. C. Finfer

    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

  12. Big Bubbles

    NSDL National Science Digital Library

    Lawrence Hall of Science

    2010-01-01

    How do you measure a bubble when it's floating? You can't really, but in this activity, learners can measure the diameter of the ring of suds a bubble leaves on a flat surface. The fun is blowing up the bubbles as big as possible with a straw. Then comes the measuring. This activity can be used to connect science and math, and makes a great rainy day or indoor lunch activity.

  13. Bubbly Little Star

    NASA Technical Reports Server (NTRS)

    2007-01-01

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

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

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

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

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

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

  14. A Bubble Bursts

    NASA Technical Reports Server (NTRS)

    2005-01-01

    RCW 79 is seen in the southern Milky Way, 17,200 light-years from Earth in the constellation Centaurus. The bubble is 70-light years in diameter, and probably took about one million years to form from the radiation and winds of hot young stars.

    The balloon of gas and dust is an example of stimulated star formation. Such stars are born when the hot bubble expands into the interstellar gas and dust around it. RCW 79 has spawned at least two groups of new stars along the edge of the large bubble. Some are visible inside the small bubble in the lower left corner. Another group of baby stars appears near the opening at the top.

    NASA's Spitzer Space Telescope easily detects infrared light from the dust particles in RCW 79. The young stars within RCW 79 radiate ultraviolet light that excites molecules of dust within the bubble. This causes the dust grains to emit infrared light that is detected by Spitzer and seen here as the extended red features.

  15. Bubble Tray

    NSDL National Science Digital Library

    The Exploratorium

    2012-06-26

    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.

  16. Bubble Trouble

    NSDL National Science Digital Library

    American Chemical Society

    2011-01-01

    In this activity on page 15 of the PDF, learners measure the amount of bubbles that they make using a detergent. Learners investigate whether adding Epsom salt to the solution affects its "sudsiness"--an important attribute of soap, since sudsy bubbles help soap clean greasy dirt. Use this activity to explore how chemicals can change a material's properties and how substances dissolve.

  17. Bubble migration during hydrate formation

    NASA Astrophysics Data System (ADS)

    Shagapov, V. Sh.; Chiglintseva, A. S.; Rusinov, A. A.

    2015-03-01

    A model of the process of migration of methane bubbles in water under thermobaric conditions of hydrate formation is proposed. The peculiarities of the temperature field evolution, migration rate, and changes in the radius and volume fraction of gas hydrate bubbles are studied. It is shown that, with a constant mass flow of gas from the reservoir bottom, for all parameters of the surfacing gas hydrate disperse system, there is a quasistationary pattern in the form of a "step"-like wave. Depending on the relationship of the initial gas bubble density with the average gas density in the hydrate composition determined by the depth from which bubbles rise to the surface, the final radius of hydrate particles may be larger or smaller than the initial gas bubble radii. It is established that the speed at which gas hydrate inclusions rise to the surface decreases by several times due to an increase in their weight during hydrate formation. The influence of the depth of the water reservoir whose bottom is a gas flow source on the dynamics of hydrate formation is studied.

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

    NASA Astrophysics Data System (ADS)

    Crews, Jackson B.; Cooper, Clay A.

    2014-09-01

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

  19. Nonequilibrium bubbles in a flowing langmuir monolayer.

    PubMed

    Muruganathan, Rm; Khattari, Z; Fischer, Th M

    2005-11-24

    We investigate the nonequilibrium behavior of two-dimensional gas bubbles in Langmuir monolayers. A cavitation bubble is induced in liquid expanded phase by locally heating a Langmuir monolayer with an IR-laser. At low IR-laser power the cavitation bubble is immersed in quiescent liquid expanded monolayer. At higher IR-laser power thermo capillary flow around the laser-induced cavitation bubble sets in. The thermo capillary flow is caused by a temperature dependence of the gas/liquid line tension. The slope of the line tension with temperature is determined by measuring the thermo capillary flow velocity. Thermodynamically stable satellite bubbles are generated by increasing the surface area of the monolayer. Those satellite bubbles collide with the cavitation bubble. Upon collision the satellite bubbles either coalesce with the cavitation bubble or slide past the cavitation bubble. Moreover we show that the satellite bubbles can also be produced by the emission from the laser-induced cavitation bubbles. PMID:16853828

  20. Decommissioning the Fuel Process Building, a Shift in Paradigm for Terminating Safeguards on Process Holdup

    SciTech Connect

    Ivan R. Thomas

    2010-07-01

    INMM Abstract 51st Annual Meeting Decommissioning the Fuel Process Building, a Shift in Paradigm for Terminating Safeguards on Process Holdup The Fuel Process Building at the Idaho Nuclear Technology and Engineering Center (INTEC) is being decommissioned after nearly four decades of recovering high enriched uranium from various government owned spent nuclear fuels. The separations process began with fuel dissolution in one of multiple head-ends, followed by three cycles of uranium solvent extraction, and ending with denitration of uranyl nitrate product. The entire process was very complex, and the associated equipment formed an extensive maze of vessels, pumps, piping, and instrumentation within several layers of operating corridors and process cells. Despite formal flushing and cleanout procedures, an accurate accounting for the residual uranium held up in process equipment over extended years of operation, presented a daunting safeguards challenge. Upon cessation of domestic reprocessing, the holdup remained inaccessible and was exempt from measurement during ensuing physical inventories. In decommissioning the Fuel Process Building, the Idaho Cleanup Project, which operates the INTEC, deviated from the established requirements that all nuclear material holdup be measured and credited to the accountability books and that all nuclear materials, except attractiveness level E residual holdup, be transferred to another facility. Instead, the decommissioning involved grouting the process equipment in place, rather than measuring and removing the contained holdup for subsequent transfer. The grouting made the potentially attractiveness level C and D holdup even more inaccessible, thereby effectually converting the holdup to attractiveness level E and allowing for termination of safeguards controls. Prior to grouting the facility, the residual holdup was estimated by limited sampling and destructive analysis of solutions in process lines and by acceptable knowledge based upon the separations process, plant layout, and operating history. The use of engineering estimates, in lieu of approved measurement methods, was justified by the estimated small quantity of holdup remaining, the infeasibility of measuring the holdup in a highly radioactive background, and the perceived hazards to personnel. The alternate approach to quantifying and terminating safeguards on process holdup was approved by deviation.

  1. Bubbles of Metamorphosis

    NASA Astrophysics Data System (ADS)

    Prakash, Manu

    2011-11-01

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

  2. Nutty Bubbles

    E-print Network

    A. M. Ghezelbash; R. B. Mann

    2002-07-12

    We investigate the various time-dependent bubble spacetimes that can be obtained from double analytic continuation of asymptotically locally flat/AdS spacetimes with NUT charge. We find different time-dependent explicit solutions of general relativity from double analytic continuations of Taub-Nut(-AdS) and Kerr-Nut(-AdS) spacetimes. One solution in particular has Milne-like evolution throughout, and another is a NUT-charged generalization of the AdS soliton. These solutions are all four dimensional. In certain situations the NUT charge induces an ergoregion into the bubble spacetime and in other situations it quantitatively modifies the evolution of the bubble, as when rotation is present. In dimensions greater than four, no consistent bubble solutions are found that have only one timelike direction.

  3. Study on the dynamic holdup distribution of the pulsed extraction column

    SciTech Connect

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

    2013-07-01

    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)

  4. Exploring Bubbles

    NASA Astrophysics Data System (ADS)

    O'Geary, Melissa A.

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

  5. Sonoluminescence: Why fiery bubbles have eternal life

    Microsoft Academic Search

    Detlef Lohse; Michael Brenner; Sascha Hilgenfeldt

    1996-01-01

    Sound driven gas bubbles in water can emit light pulses. This phenomenon is called sonoluminescence (SL). Two different phases of single bubble SL have been proposed: diffusively stable and diffusively unstable SL. Phase diagrams are presented in the gas concentration vs forcing pressure state space and also in the ambient radius vs forcing pressure state space. These phase diagrams are

  6. Capillarity-Driven Bubble Separations

    NASA Astrophysics Data System (ADS)

    Wollman, Andrew; Weislogel, Mark; Dreyer, Michael

    2013-11-01

    Techniques for phase separation in the absence of gravity continue to be sought after 5 decades of space flight. This work focuses on the fundamental problem of gas bubble separation in bubbly flows through open wedge-shaped channel in a microgravity environment. The bubbles appear to rise in the channel and coalesce with the free surface. Forces acting on the bubble are the combined effects of surface tension, wetting conditions, and geometry; not buoyancy. A single dimensionless group is identified that characterizes the bubble behavior and supportive experiments are conducted in a terrestrial laboratory, in a 2.1 second drop tower, and aboard the International Space Station as part of the Capillary Channel Flow (CCF) experiments. The data is organized into regime maps that provide insight on passive phase separations for applications ranging from liquid management aboard spacecraft to lab-on-chip technologies. Techniques for phase separation in the absence of gravity continue to be sought after 5 decades of space flight. This work focuses on the fundamental problem of gas bubble separation in bubbly flows through open wedge-shaped channel in a microgravity environment. The bubbles appear to rise in the channel and coalesce with the free surface. Forces acting on the bubble are the combined effects of surface tension, wetting conditions, and geometry; not buoyancy. A single dimensionless group is identified that characterizes the bubble behavior and supportive experiments are conducted in a terrestrial laboratory, in a 2.1 second drop tower, and aboard the International Space Station as part of the Capillary Channel Flow (CCF) experiments. The data is organized into regime maps that provide insight on passive phase separations for applications ranging from liquid management aboard spacecraft to lab-on-chip technologies. NASA NNX09AP66A, NASA Oregon Space Grant NNX10AK68H, NASA NNX12AO47A, DLR 50WM0535/0845/1145

  7. Oscillations of soap bubbles

    NASA Astrophysics Data System (ADS)

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

    2010-07-01

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

  8. What Can Be Learned from X-Ray Spectroscopy Concerning Hot Gas in the Local Bubble and Charge Exchange Processes?

    NASA Technical Reports Server (NTRS)

    Snowden, S. L.

    2008-01-01

    Both solar wind charge exchange emission and diffuse thermal emission from the Local Bubble are strongly dominated in the soft X-ray band by lines from highly ionized elements. While both processes share many of the same lines, the spectra should differ significantly due to the different production mechanisms, abundances, and ionization states. Despite their distinct spectral signatures, current and past observatories have lacked the spectral resolution to adequately distinguish between the two sources. High-resolution X-ray spectroscopy instrumentation proposed for future missions has the potential to answer fundamental questions such as whether there is any hot plasma in the Local Hot Bubble, and if so, what are the abundances of the emitting plasma and whether the plasma is in equilibrium. Such instrumentation will provide dynamic information about the solar wind including data on ion species which are currently difficult to track. It will also make possible remote sensing of the solar wind.

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

    PubMed

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

    2015-01-01

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

  10. Air bubble migration rates as a proxy for bubble pressure distribution in ice cores

    NASA Astrophysics Data System (ADS)

    Dadic, Ruzica; Schneebeli, Martin; Bertler, Nancy

    2015-04-01

    Air bubble migration can be used as a proxy to measure the pressure of individual bubbles and can help constrain the gradual close-off of gas bubbles and the resulting age distribution of gases in ice cores. The close-off depth of single bubbles can vary by tens of meters, which leads to a distribution of pressures for bubbles at a given depth. The age distribution of gases (along with gas-age-ice-age differences) decreases the resolution of the gas level reconstructions from ice cores and limits our ability to determine the phase relationship between gas and ice, and thus, the impact of rapid changes of greenhouse gases on surface temperatures. For times of rapid climate change, including the last 150 years, and abrupt climate changes further back in the past, knowledge of the age distribution of the gases trapped in air bubbles will enable us to refine estimates of atmospheric changes. When a temperature gradient is applied to gas bubbles in an ice sample, the bubbles migrate toward warmer ice. This motion is caused by sublimation from the warm wall and subsequent frost deposition on the cold wall. The migration rate depends on ice temperature and bubble pressure and is proportional to the temperature gradient. The spread in migration rates for bubbles in the same samples at given temperatures should therefore reflect the variations in bubble pressures within a sample. Air bubbles with higher pressures would have been closed off higher in the firn column and thus have had time to equilibrate with the surrounding ice pressure, while air bubbles that have been closed off recently would have pressures that are similar to todays atmospheric pressure above the firn column. For ice under pressures up to ~13-16 bar, the pressure distribution of bubbles from a single depth provides a record of the trapping function of air bubbles in the firn column for a certain time in the past. We will present laboratory experiments on air bubble migration, using Antarctic ice core samples from a range of depths, to show that air bubble migration is a valid proxy for bubble pressure and can thus be used to determine the trapping function of air bubbles and gas age distribution for past conditions.

  11. Bubble nucleation in stout beers.

    PubMed

    Lee, W T; McKechnie, J S; Devereux, M G

    2011-05-01

    Bubble nucleation in weakly supersaturated solutions of carbon dioxide-such as champagne, sparkling wines, and carbonated beers-is well understood. Bubbles grow and detach from nucleation sites: gas pockets trapped within hollow cellulose fibers. This mechanism appears not to be active in stout beers that are supersaturated solutions of nitrogen and carbon dioxide. In their canned forms these beers require additional technology (widgets) to release the bubbles which will form the head of the beer. We extend the mathematical model of bubble nucleation in carbonated liquids to the case of two gases and show that this nucleation mechanism is active in stout beers, though substantially slower than in carbonated beers and confirm this by observation. A rough calculation suggests that despite the slowness of the process, applying a coating of hollow porous fibers to the inside of a can or bottle could be a potential replacement for widgets. PMID:21728549

  12. Bubble nucleation in stout beers

    NASA Astrophysics Data System (ADS)

    Lee, W. T.; McKechnie, J. S.; Devereux, M. G.

    2011-05-01

    Bubble nucleation in weakly supersaturated solutions of carbon dioxide—such as champagne, sparkling wines, and carbonated beers—is well understood. Bubbles grow and detach from nucleation sites: gas pockets trapped within hollow cellulose fibers. This mechanism appears not to be active in stout beers that are supersaturated solutions of nitrogen and carbon dioxide. In their canned forms these beers require additional technology (widgets) to release the bubbles which will form the head of the beer. We extend the mathematical model of bubble nucleation in carbonated liquids to the case of two gases and show that this nucleation mechanism is active in stout beers, though substantially slower than in carbonated beers and confirm this by observation. A rough calculation suggests that despite the slowness of the process, applying a coating of hollow porous fibers to the inside of a can or bottle could be a potential replacement for widgets.

  13. HEU Holdup Measurements in 321-M B and Spare U-Al Casting Furnaces

    SciTech Connect

    Salaymeh, S.R.

    2002-04-30

    The Analytical Development Section of Savannah River Technology Center (SRTC) was requested by the Facilities Decontamination Division (FDD) 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. This report covers holdup measurements in two uranium aluminum alloy (U-Al) casting furnaces. Our results indicate an upper limit of 235U content for the B and Spare furnaces of 51 and 67 g respectively. This report discusses the methodology, non-destructive assay (NDA) measurements, and results of the uranium holdup on the two furnaces.

  14. FEASTING BLACK HOLE BLOWS BUBBLES

    NASA Technical Reports Server (NTRS)

    2002-01-01

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

  15. The dynamics of single bubble sonoluminescence

    Microsoft Academic Search

    Gerardo Adrian Delgadino

    1999-01-01

    Ultrafast compressions and expansions may occur in microbubbles undergoing forced oscillations. For certain conditions ultra high temperatures are produced. In a spherically symmetric stationary acoustic field, a gas bubble about ten micrometers in diameter was levitated. Bubble volume oscillations caused by the varying pressure field were excited. The non-linear oscillations were characterized by a slow growth, up to ten times

  16. The Behavior of Micro Bubbles and Bubble Cluster in Ultrasound Field

    NASA Astrophysics Data System (ADS)

    Yoshizawa, Shin; Matsumoto, Yoichiro

    2001-11-01

    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.

  17. Characterization of capacitance sensor for the measurement of water droplet in gas

    NASA Astrophysics Data System (ADS)

    Guo, Liye; Yang, Yunjie; Lei, Lei; Peng, Lihui

    2014-04-01

    The measurement of water droplet in gas may play an important role in air-condition, gas delivery under precise instrument environment or other applications. To fulfill the requirement of the detection of water droplet hold-up in gas-liquid two-phase flow, the characterization of capacitance sensor is studied. Two classicalcategories of capacitancesensors, which are capacitance sensors with concave electrode and helical electrode, areinvestigated comparatively by simulation and experiments. The simulation results show that concave capacitance appears better performances in the measurement of water droplet in gas. Droplet near the helical electrode (near the pipe wall) may cause considerably higher capacitance fluctuation than that locates centrally, which would result in high measure error or uncertainty in real applications. On the contract, the concave electrode has less capacitance fluctuation. The spanning angle of concave electrodes is the main factor that influences the sensor sensitivity distribution. To achieve the best angle of concave electrodes, the characterization of concave capacitance sensor is investigated theoretically. The sensitivity distribution is obtained by COMSOL Multiphysics and quantitativelyanalyzed. The sensitivity distribution of concave sensor has the shape of a saddle, high sensitivity in the edge of electrodes and negative sensitivity between the edges of different electrodes. The capacitancesare calculated while water droplet in different positions under different concave electrode angles. By interpolation calculation, the optimal concave capacitance sensor with homogeneous sensitivity distribution is obtained aselectrode spanning angle of 135° and verified by experiments. The test samplesmonitoring water droplet including small rubble bubble with water inside, small wet paper ball, etc., havebeen used to conduct the static experiment. The relationship between the capacitance variation and water droplet hold-up is obtained. The preliminary results show that the designed sensor is able to measure water droplet of 1ml.

  18. Methane emission by bubbling from Gatun Lake, Panama

    Microsoft Academic Search

    Michael Keller; Robert F. Stallard

    1994-01-01

    We studied methane emission by bubbling from Gatun Lake, Panama, at water depths of less than 1 m to about 10 m. Gas bubbles were collected in floating traps deployed during 12- to 60-hour observation periods. Comparison of floating traps and floating chambers showed that about 98% of methane emission occurred by bubbling and only 2% occurred by diffusion. Average

  19. Chaotic bubble coalescence in non-Newtonian fluids

    Microsoft Academic Search

    H. Z. Li; Y. Mouline; L. Choplin; N. Midoux

    1997-01-01

    This work aims at studying in-line bubble coalescence in non-Newtonian fluids. The visualisation and power spectrum of time series data, recorded via an optical sensing device, confirm that the bubble formation at the orifice is perfectly periodic under a constant gas flowrate. However, the separation interval between bubbles becomes irregular during rise, until, at a certain height above the orifice,

  20. How are soap bubbles blown? Fluid dynamics of soap bubble blowing

    NASA Astrophysics Data System (ADS)

    Davidson, John; Lambert, Lori; Sherman, Erica; Wei, Timothy; Ryu, Sangjin

    2013-11-01

    Soap bubbles are a common interfacial fluid dynamics phenomenon having a long history of delighting not only children and artists but also scientists. In contrast to the dynamics of liquid droplets in gas and gas bubbles in liquid, the dynamics of soap bubbles has not been well documented. This is possibly because studying soap bubbles is more challenging due to there existing two gas-liquid interfaces. Having the thin-film interface seems to alter the characteristics of the bubble/drop creation process since the interface has limiting factors such as thickness. Thus, the main objective of this study is to determine how the thin-film interface differentiates soap bubbles from gas bubbles and liquid drops. To investigate the creation process of soap bubbles, we constructed an experimental model consisting of air jet flow and a soap film, which consistently replicates the conditions that a human produces when blowing soap bubbles, and examined the interaction between the jet and the soap film using the high-speed videography and the particle image velocimetry.

  1. COSI's Bubble Recipe

    NSDL National Science Digital Library

    2012-06-26

    Everybody loves bubbles, and this is the best bubble recipe ever! Included as part of one of COSI's Family Science Quests, this COSI favorite invites learners to make bubbles and suggests a variety of ways to explore and experiment.

  2. Hold-Up under Costly Litigation and Imperfect Courts of Law

    Microsoft Academic Search

    C. Manuel Willington

    2004-01-01

    Two main results have been obtained on the literature on contractual solutions to the hold-up problem. First, a contract specifying a price and quantity of the final good to be traded will, fairly generally, induce efficient investments if these are `selfish' in nature, i.e., each party's investment directly affects only his own profit (Edlin and Reichelstein, 1996). Second, and in

  3. Liquid holdup distribution in packed columns: gamma ray tomography and CFD simulation

    Microsoft Academic Search

    Fuhe Yin; Artin Afacan; K Nandakumar; Karl T Chuang

    2002-01-01

    In the present study, the liquid (water) holdup distribution was measured in a large scale packed column (0.6 m diameter) filled with 25.4 mm metal Pall rings using noninvasive gamma ray tomography technique. Horizontal scans, at two vertical positions (400 mm apart), were made for two liquid flow rates. Three different designs of liquid distributor were used to examine the

  4. The Hold-up Problem and Incomplete Contracts: A Survey of Recent Topics in Contract Theory

    Microsoft Academic Search

    Patrick W. Schmitz

    2001-01-01

    This article provides a nontechnical survey on recent topics in the theory of contracts. The hold-up problem is presented and the incomplete contracts approach is discussed. Emphasis is put on conceptual problems and open questions that await further research. Copyright 2001 by Blackwell Publishing Ltd and the Board of Trustees of the Bulletin of Economic Research

  5. Diffusive Accumulation of Methane Bubbles in Seabed

    E-print Network

    Goldobin, D S; Levesley, J; Lovell, M A; Rochelle, C A; Jackson, P; Haywood, A; Hunter, S; Rees, J

    2010-01-01

    We consider seabed bearing methane bubbles. In the absence of fractures the bubbles are immovably trapped in a porous matrix by surface tension forces; therefore the dominant mechanism of transfer of gas mass becomes the diffusion of gas molecules through the liquid. The adequate description of this process requires accounting "other-than-normal" (non-Fickian) diffusion effects, thermodiffusion and gravity action. We evaluate the diffusive flux of aqueous methane and predict the possibility of existence of bubble mass accumulation zones (which can appear independently from the presence/absence of hydrate stability zone) and effect of non-Fickian drift on the capacity of shallow and deep methane-hydrate deposits.

  6. Buoyancy Driven Shear Flows of Bubble Suspensions

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

  7. Detoxification of high-strength liquid pollutants in an ozone bubble column reactor: Gas–liquid flow patterns, interphase mass transfer and chemical depuration

    Microsoft Academic Search

    Rodrigo J. G. Lopes; Rosa M. Quinta-Ferreira

    2011-01-01

    The contemporary status of computational flow modelling is encouraging the application of modern CFD codes to the design and investigation of multiphase reactors. Aiming to accomplish novel and stringent environmental regulations on the decontamination of high-strength wastewaters, here we present a comprehensive discrete bubble model for the ozonation of liquid pollutants. As long as a bubble column reactor can operate

  8. Investigation of the Heat Transfer Coefficient of Liquid and Gas Bubble Train Flow in a Square Mini-channel Using Infra-Red thermography

    E-print Network

    Khandekar, Sameer

    ; aspect ratio = 1.0; Dh = 5 mm, Bo 3.4) in non-boiling horizontal Taylor bubble-train slug flow under the effect of gravity for Bo fluid which/3 , the theory being valid for creeping flows at low Ca ranging from 10 -3 to 10 -2 and bubble Weber number, We

  9. Morphology control and mechanisms of CaCO3 crystallization on gas-liquid interfaces of CO2/NH3 bubbles in aqueons-glycine solutions

    NASA Astrophysics Data System (ADS)

    Guan, Xiaomei; Huang, Fangzhi; Li, Jian; Li, Shikuo; Zhang, Xiuzhen; Guo, Degui; Shen, Yuhua; Xie, Anjian

    2015-06-01

    As one of the new methods of materials preparing, interface-regulated mineralization, has been developed and used to fabricate the CaCO3 materials with mimetic construction of natural biogenic structures in the present work. Combined with the effect of glycine at different concentrations, novel gas-liquid interfaces of CO2/NH3 bubbles have been substituted for the traditional settled matrix and utilized as new reaction fields of CaCO3. CaCO3 crystals with delicate hierarchical structures and morphologies, such as scallop-shaped, ellipsoidal and spherical structure, have been obtained at the special glycine-mediated gasliquid interfaces. The effect of glycine concentration and the chemical reaction kinetics have been deeply studied. As a result, we have successfully captured in detail the crystallization behaviors of CaCO3 in different stages, which allow us to put forward a general kinetic model to reveal the formation mechanism of CaCO3 and implicate a straightforward mean to control the morphology and structure.

  10. Fate of rising methane bubbles in stratified waters: How much methane reaches the atmosphere?

    Microsoft Academic Search

    D. F. McGinnis; J. Greinert; Y. Artemov; S. E. Beaubien; A. Wüest

    2006-01-01

    There is growing concern about the transfer of methane originating from water bodies to the atmosphere. Methane from sediments can reach the atmosphere directly via bubbles or indirectly via vertical turbulent transport. This work quantifies methane gas bubble dissolution using a combination of bubble modeling and acoustic observations of rising bubbles to determine what fraction of the methane transported by

  11. A massive bubble of extremely metal-poor gas around a collapsing Ly? blob at z = 2.54

    NASA Astrophysics Data System (ADS)

    Humphrey, A.; Binette, L.; Villar-Martín, M.; Aretxaga, I.; Papaderos, P.

    2013-01-01

    Using long-slit optical spectroscopy obtained at the 10.4 m Gran Telescopio Canarias, we have examined the gaseous environment of the radio-loud quasar TXS 1436+157 (z = 2.54), previously known to be associated with a large Ly? nebula and a spatially extended Ly?-absorbing structure. From the Ly? nebula, we measure kinematic properties consistent with infall at a rate of ˜10-100 M? yr-1 - more than sufficient to power a quasar at the top of the luminosity function. The absorbing structure lies outside of the Ly? nebula, at a radius of ? 40 kpc from the quasar. Against the bright unresolved continuum and line emission from the quasar, we detect in absorption the N v ??1239, 1241, C iv ??1548, 1551 and Si iv ??1394, 1403 doublets, with no unambiguous detection of absorption lines from any low-ionization species of metal. The metal column densities, taken together with the H i column density measurement from the literature, indicate that the absorbing gas is predominantly ionized by the quasar, has a mass of hydrogen of ? 1.6 × 1011 M?, a gas density of ?18 cm-3, a line-of-sight thickness of ?18 pc and a covering factor approaching unity. While this absorbing structure is clearly not composed of pristine gas, it has an extremely low metallicity, with ionization models providing a 3? limit of 12+log(O/H) ? 7.3. To explain these results, we discuss a scenario involving starburst-driven superbubbles and the creation of infalling filaments of cold gas which fuel/trigger the quasar. We also discuss the possibility of detecting large-scale absorbers such as this in emission when illuminated by a powerful quasar.

  12. Stable bubble oscillations beyond Blake's critical threshold.

    PubMed

    Heged?s, Ferenc

    2014-04-01

    The equilibrium radius of a single spherical bubble containing both non-condensable gas and vapor is determined by the mechanical balance at the bubble interface. This expression highlights the fact that decreasing the ambient pressure below the so called Blake's critical threshold, the bubble has no equilibrium state at all. In the last decade many authors have tried to find evidence for the existence of stable bubble oscillation under harmonic forcing in this regime, that is, they have tried to stabilize the bubble motion applying ultrasonic radiation on the bubble. The available numerical results provide only partial proof for the existence as they are usually based on linearized or weakly nonlinear (higher order approximation) bubble models. Here, based on numerical techniques of the modern nonlinear and bifurcation theory, the existence of stable bubble motion has been proven without any restrictions in nonlinearities. Although the model, applied in this paper, is the rather simple Rayleigh-Plesset equation, the presented technique can be extended to more complex bubble models easily. PMID:24485747

  13. Bubbles, Gating, and Anesthetics in Ion Channels

    PubMed Central

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

    2008-01-01

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

  14. Motion of an intravascular axisymmetric bubble

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; Eckmann, David M.; Ayyaswamy, Portonovo S.

    2003-11-01

    The motion of a gas bubble in an arteriolar blood vessel or microvessel is investigated numerically. An imposed pressure gradient drives blood flow. The full Navier-Stokes equations are solved numerically using a front tracking method. Comparative behaviors of bubbles of various ratios (effective diameter/vessel diameter) are ascertained. Effects of vessel size, magnitude of the applied pressure gradient, presence of a soluble surfactant, variations in the values of the density ratio (?_g/?_l) and viscosity ratio (?_g/?_l) on the motion and interfacial shape of the bubble are determined. The results obtained have significance in the study of activation of blood clotting, initiation of inflammation, cellular injury, and adhesion of gas bubbles to the vessel wall occurring in intravascular gas embolism. Supported by NIH R01 HL67986.

  15. Enhancing acoustic cavitation using artificial crevice bubbles.

    PubMed

    Zijlstra, Aaldert; Fernandez Rivas, David; Gardeniers, Han J G E; Versluis, Michel; Lohse, Detlef

    2015-02-01

    We study the response of pre-defined cavitation nuclei driven continuously in the kHz regime (80, 100 and 200 kHz). The nuclei consist of stabilized gaspockets in cylindrical pits of 30 ?m diameter etched in silicon or glass substrates. It is found that above an acoustic pressure threshold the dynamics of the liquid-gas meniscus switches from a stable drum-like vibration to expansion and deformation, frequently resulting in detachment of microbubbles. Just above this threshold small bubbles are continuously and intermittently ejected. At elevated input powers bubble detachment becomes more frequent and cavitation bubble clouds are formed and remain in the vicinity of the pit bubble. Surprisingly, the resulting loss of gas does not lead to deactivation of the pit which can be explained by a rectified gas diffusion process. PMID:25455191

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

    E-print Network

    Givens, James Wilson

    1961-01-01

    . CONCLUSIONS, 24 6. ACKNOWLEDGEMENT. 7. APPE NDIX. 8. REFERENCES. 25 32 337530 LIST OF FIGURES AND TABLES FIGURES 1. Core Saturating and Flooding Apparatus Page 2. Physical Characteristics of Refined Oil and East Texas Crude Oil at 77'F. 3. Refined... Oil Recovery vs Pore Volumes of Injected Fluid for an Initial Gas Slug. 13 4, Refined Oil Recovery vs Pore Volumes of Injected Fluid for an Initial Water Slug. 14 5. The Effect of Slug Length on Recovery of Refined Oil. 15 6. Recovery of East...

  17. Development of a neural network model for the prediction of liquid holdup in two-phase horizontal flow 

    E-print Network

    Shippen, Mack Edward

    2001-01-01

    on these groups demonstrated improved accuracy and range of application. Eaton used the dimensional groups proposed by Ros to develop correlations for 8 predicting flow pattern, liquid holdup, and pressure gradient in horizontal pipes. Experimental data... data were collected using air and water in 1-in. and 1. 5-in. smooth pipe at inclination angles of + 90 degrees. He concluded that frictional pressure loss is strongly influenced by liquid holdup predictions. Contrary to Eaton, Beggs found...

  18. Cavitation bubble behavior and bubble-shock wave interaction near a gelatin surface as a study of in vivo bubble dynamics

    NASA Astrophysics Data System (ADS)

    Kodama, T.; Tomita, Y.

    The collapse of a single cavitation bubble near a gelatin surface, and the interaction of an air bubble attached to a gelatin surface with a shock wave, were investigated. These events permitted the study of the behavior of in vivo cavitation bubbles and the subsequent tissue damage mechanism during intraocular surgery, intracorporeal and extracorporeal shock wave lithotripsy. Results were obtained with high-speed framing photography. The cavitation bubbles near the gelatin surface did not produce significant liquid jets directed at the surface, and tended to migrate away from it. The period of the motion of a cavitation bubble near the gelatin surface was longer than that of twice the Rayleigh's collapse time for a wide range of relative distance, L/Rmax, excepting for very small L/Rmax values (L was the stand-off distance between the gelatin surface and the laser focus position, and Rmax was the maximum bubble radius). The interaction of an air bubble with a shock wave yielded a liquid jet inside the bubble, penetrating into the gelatin surface. The liquid jet had the potential to damage the gelatin. The results predicted that cavitation-bubble-induced tissue damage was closely related to the oscillatory bubble motion, the subsequent mechanical tissue displacement, and the liquid jet penetration generated by the interaction of the remaining gas bubbles with subsequent shock waves. The characteristic bubble motion and liquid jet formation depended on the tissue's mechanical properties, resulting in different damage mechanisms from those observed on hard materials.

  19. 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)

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

    2014-11-01

    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.

  20. A massive bubble of extremely metal poor gas around a collapsing Ly-alpha blob at z=2.54

    E-print Network

    Humphrey, Andrew; Villar-Martin, Montserrat; Aretxaga, Itziar; Papaderos, Polychronis

    2012-01-01

    Using long-slit optical spectroscopy obtained at the 10.4 m Gran Telescopio Canarias, we have examined the gaseous environment of the radio-loud quasar TXS 1436+157 (z=2.54), previously known to be associated with a large Ly-alpha nebula and a spatially extended Ly-alpha-absorbing structure. From the Ly-alpha nebula we measure kinematic properties consistent with infall at a rate of about 10-100 M./yr - more than sufficient to power a quasar at the top of the luminosity function. The absorbing structure lies outside of the Ly-alpha nebula, at a radius of >40 kpc from the quasar. Against the bright unresolved continuum and line emission from the quasar, we detect in absorption the NV 1239,1241, CIV 1548,1551 and SiIV 1394,1403 doublets, with no unambiguous detection of absorption lines from any low-ionization species of metal. The metal column densities, taken together with the HI column density measurement from the literature, indicate that the absorbing gas is predominantly ionized by the quasar, has a mass ...

  1. Dynamics of diffusive bubble growth and pressure recovery in a bubbly rhyolitic melt embedded in an elastic solid

    Microsoft Academic Search

    Bernard Chouet; Phillip Dawson; Masaru Nakano

    2006-01-01

    We present a model of gas exsolution and bubble expansion in a melt supersaturated in response to a sudden pressure drop. In our model, the melt contains a suspension of gas bubbles of identical sizes and is encased in a penny-shaped crack embedded in an elastic solid. The suspension is modeled as a three-dimensional lattice of spherical cells with slight

  2. Measurements of uranium holdup in an operating gaseous diffusion enrichment plant

    SciTech Connect

    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

    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.

  3. Force measurements on rising bubbles Woodrow L. Shew, Sebastien Poncet, and Jean-Francois Pinton

    E-print Network

    Boyer, Edmond

    An understanding of bubble-fluid interactions is impor- tant in a broad range of natural, engineering, and med- ical settings. Air-sea gas transfer, bubble column reac- tors, oil/natural gas transport, boiling heat of the bub- ble's wake. Lunde and Perkins [15] used dye to ob- serve the wake of ascending bubbles and solid

  4. Sonoluminescence and phase diagrams of single bubbles at low dissolved air concentrations I. Csabai,2

    E-print Network

    Horváth, Ákos

    . INTRODUCTION Single bubble sonoluminescence SBSL is a phenom- enon where an acoustically levitated gas bubble the concentration of dissolved air in water. We also present a new technique to obtain the acoustic pressure (Pa in the acoustic cycle. Using this technique we give phase diagrams of the bubble in the (R0 ,Pa) and (Pa , gas

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

    SciTech Connect

    Motley, F.; Schultz, R.

    1987-01-01

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

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

    SciTech Connect

    KEELE BD

    2005-02-01

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

  7. Bubble Breakup Caused by Shape Instabilities

    NASA Astrophysics Data System (ADS)

    Su, Y.-H.; Feng, Z. C.

    1998-11-01

    The breakup of a bubble is the most intriguing phenomenon in the bubble dynamics to many fluid dynamics researcher. Bubble may break up due to different kinds of mechanisms. However due to the complexity of the system, no general analytical approachis available for studying this breakup phenomenon of a bubble. Hence numerical approach is taken in our current work to investigate the breakup of a single ideal gas bubble oscillating in an infinite region of an inviscid and incompressible fluid due to the one-to two resonance mechanism. Boundary element method combined with 4-th order Runge-Kutta integrator is used to simulate the bubble motion. Several simulations with different time steps are conducted to ensure the convergence of numerical integration. Conservation of energy is used as a measure of justifying the accuracy of our calculation. Our numerical data shows that the velocity of two poles of an axisymmetric bubble starts to vary at a very high frequency before the bubble breaks up. Several flow fields just before the breakup show that the velocity at the two poles is much larger than the velocity elsewhere.

  8. Measuring bubbles in a bubbly wake flow

    NASA Astrophysics Data System (ADS)

    Lee, Seung-Jae; Kawakami, Ellison; Arndt, Roger E. A.

    2012-11-01

    This paper presents measurements of the velocity and size distribution of bubbles in a bubbly wake. This was carried out by utilizing particle shadow velocimetry (PSV). This technique is a non-scattering approach that relies on direct in-line volume illumination by a pulsed source such as a light-emitting diode (LED). A narrow depth-of-field (DoF) is required for imaging a 2-dimensional plane within a flow volume. Shadows of the bubbles were collected by a high-speed camera. Once a reference image, taken when no bubbles were present in the flow, was subtracted from the images, the image was segmented using an edge detection technique. The Canny algorithm was determined to be best suited for this application. A curvature profile method was employed to distinguish individual bubbles within a cluster of highly overlapping bubbles. The utilized algorithm was made to detect partly overlapping bubbles and reconstruct the missing parts. The movement of recognized individual bubbles was tracked on a two dimensional plane within a flow volume. In order to obtain quantitative results, the wake of a ventilated hydrofoil was investigated by applying the shadowgraphy technique and the described bubble detection algorithm. These experiments were carried out in the high speed cavitation tunnel at Saint Anthony Falls Laboratory (SAFL) of the University of Minnesota. This research is jointly sponsored by the Office of Naval Re- search, Dr. Ron Joslin, program manager, and the Department of Energy, Golden Field Office.

  9. Bubble formation in microgravity

    NASA Technical Reports Server (NTRS)

    Antar, Basil N.

    1994-01-01

    Two KC-135 flight campaigns have been conducted to date which are specifically dedicated to study bubble formation in microgravity. The first flight was conducted during March 14-18, 1994, and the other during June 20-24, 1994. The results from the June 1994 flight have not been analyzed yet, while the results from the March flight have been partially analyzed. In the first flight three different experiments were performed, one with the specific aim at determining whether or not cavitation can take place during any of the fluid handling procedures adopted in the shuttle bioprocessing experiments. The other experiments were concerned with duplicating some of the procedures that resulted in bubble formation, namely the NCS filling procedure and the needle scratch of a solid surface. The results from this set of experiments suggest that cavitation did not take place during any of the fluid handling procedures. The results clearly indicate that almost all were generated as a result of the breakup of the gas/liquid interface. This was convincingly demonstrated in the scratch tests as well as in the liquid fill tests.

  10. Measurement of the oil holdup for a two-phase oil-water flow through a sudden contraction in a horizontal pipe

    NASA Astrophysics Data System (ADS)

    Colombo, L. P. M.; Guilizzoni, M.; Sotgia, G. M.; Bortolotti, S.; Pavan, L.

    2014-04-01

    Oil-water two-phase flow experiments were conducted in a horizontal duct made of Plexiglas® to determine the holdup of oil by means of the quick closing valves technique, using mineral oil (viscosity: 0.838 Pa s at 20 °C density: 890 kg m-3) and tap water. The duct presents a sudden contraction, with contraction ratio of 0.64. About 200 tests were performed by varying the flow rates of the phases. Flow patterns were investigated for both the up- and downstream pipe. Due to the relatively high value of the contraction ratio, it was not observed any relevant variation of the flow patterns across the sudden contraction. Data were then compared with predictions of a specific correlation for oil-water flow and some correlations for gas-water flow. A drift-flux model was also applied to determine the distribution parameter. The results agree quite well with flow pattern visualization.

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

    NASA Technical Reports Server (NTRS)

    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

    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.

  12. Computational fluid dynamics modeling of gas dispersion in multi impeller bioreactor.

    PubMed

    Ahmed, Syed Ubaid; Ranganathan, Panneerselvam; Pandey, Ashok; Sivaraman, Savithri

    2010-06-01

    In the present study, experiments have been carried out to identify various flow regimes in a dual Rushton turbines stirred bioreactor for different gas flow rates and impeller speeds. The hydrodynamic parameters like fractional gas hold-up, power consumption and mixing time have been measured. A two fluid model along with MUSIG model to handle polydispersed gas flow has been implemented to predict the various flow regimes and hydrodynamic parameters in the dual turbines stirred bioreactor. The computational model has been mapped on commercial solver ANSYS CFX. The flow regimes predicted by numerical simulations are validated with the experimental results. The present model has successfully captured the flow regimes as observed during experiments. The measured gross flow characteristics like fractional gas hold-up, and mixing time have been compared with numerical simulations. Also the effect of gas flow rate and impeller speed on gas hold-up and power consumption have been investigated. PMID:20471599

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.

  14. Soap Bubbles and Logic.

    ERIC Educational Resources Information Center

    Levine, Shellie-helane; And Others

    1986-01-01

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

  15. Bubble evolution and properties in homogeneous nucleation simulations.

    PubMed

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

    2014-12-01

    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. PMID:25615216

  16. Bubble evolution and properties in homogeneous nucleation simulations

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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.

  17. Bubbles and Market Crashes

    Microsoft Academic Search

    Michael Youssefmir; Bernardo A. Huberman; Tad Hogg

    1998-01-01

    We present a dynamical theory of asset price bubbles that exhibits the appearance of bubbles and their subsequent crashes. We show that when speculative trends dominate over fundamental beliefs, bubbles form, leading to the growth of asset prices away from their fundamental value. This growth makes the system increasingly susceptible to any exogenous shock, thus eventually precipitating a crash. We

  18. Bubbles and Market Crashes

    Microsoft Academic Search

    Michael Youssefmir; Bernardo A. Huberman; Tad Hogg

    1994-01-01

    We present a dynamical theory of asset price bubbles that exhibits the appearance of bubbles and their subsequent crashes. We show that when speculative trends dominate over fundamental beliefs, bubbles form, leading to the growth of asset prices away from their fundamental value. This growth makes the system increasingly susceptible to any exogenous shock, thus eventually precipitating a crash. We

  19. Mechanisms of stability of armored bubbles: FY 1995 progress report

    SciTech Connect

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

    1996-04-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    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.

  1. The flow patterns of bubble plume in an MBBR

    Microsoft Academic Search

    Shi-rong LI; Wen CHENG; Meng WANG; Chen CHEN

    2011-01-01

    The flow patterns of the gas-liquid two-phase flow in a Moving-Bed Biofilm Reactor (MBBR) have a critical effect upon the mass transfer by the convection. Bubble plumes promote unsteadily fluctuating two-phase flows during the aeration. This article studies the unsteady structure of bubble plumes through experiments. The time-serial bubble plume images in various cases of the tank are analyzed. The

  2. The fate of CO 2 bubble leaked from seabed

    Microsoft Academic Search

    Baixin Chen; Masahiro Nishio; Yongchen Song; Makoto Akai

    2009-01-01

    A numerical model of an individual CO2 bubble dissolution and ascent in shallow seawater was developed to simulate the fate of CO2 leaked from seabed naturally or artificially. The model consists of a solubility sub-model of CO2 gas in seawater, a CO2 bubble mass transfer sub-model, and a CO2 bubble momentum transfer sub-model. The model is applied to predict the

  3. Acoustic Bubble Removal from Boiling Surfaces

    NASA Technical Reports Server (NTRS)

    Prosperetti, Andrea

    2002-01-01

    The object of the study was the investigation of the forces generated by standing acoustic waves on vapor bubbles, both far and near boundaries. In order to accomplish this objective, in view of the scarcity of publications on the topic, it has been necessary to build an edifice of knowledge about vapor bubbles in sound and flow fields from the ground up, as it were. We have addressed problems of gradually greater difficulty as follows: 1. In the first place, the physics of an stationary isolated bubble subject to a sound field in an unbounded liquid was addressed; 2. The case of bubbles translating in a stationary pressure field was then considered; 3. This was followed by a study of the combined effects of sound and translation, 4. And of a neighboring boundary 5. Finally, a new method to deal with nonspherical bubbles was developed- In addition to the work on vapor bubbles, some studies on gas bubbles were conducted in view of NASA's interest in the phenomenon of sonoluminescence.

  4. Molecular dynamics simulations of cavitation bubble collapse and sonoluminescence

    NASA Astrophysics Data System (ADS)

    Schanz, Daniel; Metten, Burkhard; Kurz, Thomas; Lauterborn, Werner

    2012-11-01

    The dynamics of the medium within a collapsing and rebounding cavitation bubble is investigated by means of molecular dynamics (MD) simulations adopting a hard sphere model for the species inside the bubble. The dynamics of the surrounding liquid (water) is modelled using a Rayleigh-Plesset (RP)-type equation coupled to the bubble interior by the gas pressure at the wall obtained from the MD calculations. Water vapour and vapour chemistry are included in the RP-MD model as well as mass and energy transfer through the bubble wall. The calculations reveal the evolution of temperature, density and pressure within a bubble at conditions typical of single-bubble sonoluminescence and predict how the particle numbers and densities of different vapour dissociation and reaction products in the bubble develop in space and time. Among the parameters varied are the sound pressure amplitude of a sonoluminescence bubble in water, the noble gas mixture in the bubble and the accommodation coefficients for mass and energy exchange through the bubble wall. Simulation particle numbers up to 10 million are used; most calculations, however, are performed with one million particles to save computer run time. Validation of the MD code was done by comparing MD results with solutions obtained by continuum mechanics calculations for the Euler equations.

  5. Effect of supercritical water shell on cavitation bubble dynamics

    NASA Astrophysics Data System (ADS)

    Shao, Wei-Hang; Chen, Wei-Zhong

    2015-05-01

    Based on reported experimental data, a new model for single cavitation bubble dynamics is proposed considering a supercritical water (SCW) shell surrounding the bubble. Theoretical investigations show that the SCW shell apparently slows down the oscillation of the bubble and cools the gas temperature inside the collapsing bubble. Furthermore, the model is simplified to a Rayleigh–Plesset-like equation for a thin SCW shell. The dependence of the bubble dynamics on the thickness and density of the SCW shell is studied. The results show the bubble dynamics depends on the thickness but is insensitive to the density of the SCW shell. The thicker the SCW shell is, the smaller are the wall velocity and the gas temperature in the bubble. In the authors’ opinion, the SCW shell works as a buffering agent. In collapsing, it is compressed to absorb a good deal of the work transformed into the bubble internal energy during bubble collapse so that it weakens the bubble oscillations. Project supported by the National Natural Science Foundation of China (Grant Nos. 11174145 and 11334005).

  6. Circulatory bubble dynamics: from physical to biological aspects.

    PubMed

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

    2014-04-01

    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

  7. Acoustic bubble traps

    NASA Astrophysics Data System (ADS)

    Geisler, Reinhard; Kurz, Thomas; Lauterborn, Werner

    2000-07-01

    A small, oscillating bubble in a liquid can be trapped in the antinode of an acoustic standing wave field. Bubble stability is required for the study of single bubble sonoluminescence (SBSL). The properties of the acoustic resonator are essential for the stable trapping of sonoluminescing bubbles. Resonators can be chosen according to the intended application: size and geometry can be varied in a wide range. In this work, the acoustic responses of different resonators were measured by means of holographic interferometry, hydrophones and a laser vibrometer. Also, high-speed photography was used to observe the bubble dynamics. Several single, stable sonoluminescent bubbles were trapped simultaneously within an acoustic resonator in the pressure antinodes of a higher harmonic mode (few bubble sonoluminescence, FBSL).

  8. 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

    Shuji Fujita; Junichi Okuyama; Akira Hori; Takeo Hondoh

    2009-01-01

    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

  9. A statistical study of gaseous environment of Spitzer interstellar bubbles

    NASA Astrophysics Data System (ADS)

    Hou, L. G.; Gao, X. Y.

    2014-02-01

    The expansion of interstellar bubbles is suggested to be an important mechanism of triggering material accumulation and star formation. In this work, we investigate the gaseous environment of a large sample of interstellar bubbles identified by the Spitzer space telescope, aiming to explore the possible evidence of triggered gas accumulation and star formation in a statistical sense. By cross-matching 6124 Spitzer interstellar bubbles from the Milky Way Project (MWP) and more than 2500 Galactic H II regions collected by us, we obtain the velocity information for 818 MWP bubbles. To study the gaseous environment of the interstellar bubbles and get rid of the projection effect as much as possible, we constrain the velocity difference between the bubbles and the 13CO(1-0) emission extracted from the Galactic Ring Survey (GRS). Three methods: the mean azimuthally averaged radial profile of 13CO emission, the surface number density of molecular clumps and the angular cross-correlation function of MWP bubbles and the GRS molecular clumps are adopted. Significant over density of molecular gas is found to be close to the bubble rims. 60 per cent of the studied bubbles were found to have associated molecular clumps. By comparing the clump-associated and the clump-unassociated MWP interstellar bubbles, we reveal that the bubbles in associations tend to be larger and thicker in physical sizes. From the different properties shown by the bubble-associated and bubble-unassociated clumps, we speculate that some of the bubble-associated clumps result from the expansion of bubbles. The fraction of the molecular clumps associated with the MWP bubbles is estimated to be about 20 per cent after considering the projection effect. For the bubble-clump complexes, we found that the bubbles in the complexes with associated massive young stellar object(s) (MYSO(s)) have larger physical sizes, hence the complexes tend to be older. We propose that an evolutionary sequence might exist between the relatively younger MYSO-unassociated bubble-clump complexes and the MYSO-associated complexes.

  10. Contribution to complex gas-liquid flows: Development and validation of a mathematical model

    NASA Astrophysics Data System (ADS)

    Selma, Brahim

    This study describes the development and validation of Computational Fluid Dynamics (CFD) model for the simulation of dispersed two-phase flows taking in the account the population balance of particles size distribution. A two-fluid (Euler-Euler) methodology previously developed for complex flows is adapted to the present project. The continuous phase turbulence is represented using a two-equation k --- epsilon turbulence model which contains additional terms to account for the effects of the dispersed on the continuous phase turbulence and the effects of the gas-liquid interface. The inter-phase momentum transfer is determined from the instantaneous forces acting on the dispersed phase, comprising drag, lift, virtual mass and drift velocity. These forces are phase fraction dependent and in this work revised modelling is put forward in order to capture a good accuracy for gas hold-up, liquid velocity profiles and turbulence parameters. Furthermore, a correlation for the effect of the drift velocity on the turbulence behaviour is proposed. The revised modelling is based on an extensive survey of the existing literature. The conservation equations are discretised using the finite-volume method and solved in a solution procedure, which is loosely based on the PISO algorithm. Special techniques are employed to ensure the stability of the procedure when the phase fraction is high or changing rapidely [61]. Finally, assessment of the model is made with reference to experimental data for gas-liquid bubbly flow in a rectangular bubble column [133; 134; 135; 18], in a double-turbine stirred tank reactor [126; 127] and in an air-lift bioreacator [101]. Key words: mathematical modelling, complex flow gas-liquid, turbulence, population balance, computational fluids dynamics CFD, OpenFOAM, moments method, method of classes, QMOM, DQMOM.

  11. Radio Bubbles in Clusters of Galaxies

    SciTech Connect

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

    2005-12-14

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

  12. NUMERICAL SIMULATION OF BUBBLE AND DROPLET DYNAMICS USING PARTITIONED SOLVERS

    Microsoft Academic Search

    J. Degroote; J. Vierendeels; E. Dick

    2006-01-01

    Bubbles and droplets can be simulated as a problem involving Fluid-Structure Interaction (FSI). The interface between the liquid and the gas is then conceived as a zero thickness structure. The position of the interface is determined by the equilibrium between surface tension eects and the pressure jump across the interface. Most techniques frequently used for studying bubble and droplet dynamics,

  13. Electromagnetic ``Bubbles'' and Shock Waves: Unipolar, Nonoscillating EM Solitons

    Microsoft Academic Search

    A. E. Kaplan; P. L. Shkolnikov

    1995-01-01

    We show that atomic gases can support solitary pulses of a unipolar electromagnetic field (``EM bubbles'') with amplitude up to the atomic field ( ~109 V\\/cm) and duration down to ~ 10-16 s. EM bubbles propagate without dispersion, are stable, and are insensitive to the change of gas density. Atomic gasses can also support an EM shock wave forming a

  14. The Dynamics of Bubbles and Bubble Clouds.

    NASA Astrophysics Data System (ADS)

    Smereka, Peter Stenberg

    In an effort to understand acoustic cavitation noise the dynamics of periodically driven single bubbles and bubble clouds are examined. The single bubble equations are written as a perturbation of a Hamiltonian system and the conditions for resonances to occur are found, these can interact with the nonresonant orbit to produce jump and period-doubling bifurcations. To study the chaotic behavior a map which approximates the Poincare map in the resonant band is derived. The Poincare map is computed numerically which shows the formation of strange attractors which suddenly disappear leaving behind Smale horseshoe maps. The bubble cloud is studied using an averaged two-fluid model for bubbly flow with periodic driving at the boundary. The equations are examined both analytically and numerically. Local and global existence of solutions is proved and the existence of an absorbing set is established. An analysis of the linearized equations combined with estimates on the nonlinearity is used to prove the existence of nonlinear periodic orbit. This periodic orbit is a fixed point of the Poincare map and its stability is determined by finding the spectrum of the linearized Poincare map. This calculation combined with the absorbing set proves that the long term dynamics of the bubble cloud is finite dimensional. Numerical computations show the important attractors are a periodic -two orbit and a quasi-periodic orbit.

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

    NASA Astrophysics Data System (ADS)

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

    2012-11-01

    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.

  16. Soap and Bubbles

    NSDL National Science Digital Library

    Brieske, Joel A.

    2002-01-01

    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.

  17. Dynamics of elliptical magnetic bubbles

    Microsoft Academic Search

    M. A. Wanas

    1973-01-01

    Domain-wall anisotropy forces cylindrical domains (magnetic bubbles) to deviate from circular to elliptical geometry. Dynamics of elliptical bubbles are considered. It is found that the magnitude of the damping and coercive forces experienced by a moving eliptical bubble depends upon the direction of bubble motion. Bubbles suffer less damping and less coercion if moved along the wall-preferred direction.

  18. Microfluidic bubble logic.

    PubMed

    Prakash, Manu; Gershenfeld, Neil

    2007-02-01

    We demonstrate universal computation in an all-fluidic two-phase microfluidic system. Nonlinearity is introduced into an otherwise linear, reversible, low-Reynolds number flow via bubble-to-bubble hydrodynamic interactions. A bubble traveling in a channel represents a bit, providing us with the capability to simultaneously transport materials and perform logical control operations. We demonstrate bubble logic AND/OR/NOT gates, a toggle flip-flop, a ripple counter, timing restoration, a ring oscillator, and an electro-bubble modulator. These show the nonlinearity, gain, bistability, synchronization, cascadability, feedback, and programmability required for scalable universal computation. With increasing complexity in large-scale microfluidic processors, bubble logic provides an on-chip process control mechanism integrating chemistry and computation. PMID:17289994

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

    Microsoft Academic Search

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

    2011-01-01

    An understanding of the mechanics of bubble rise in sediments is essential because of the role of bubbles in releasing methane to the atmosphere and the formation and melting of gas hydrates. Past models to describe and predict the rise of other buoyant geological bodies through a surrounding solid (e.g., magmas and hydrofractures) appear not to be applicable to bubbles

  20. Bubble simulations with an interface tracking technique based on a partitioned fluid-structure interaction algorithm

    Microsoft Academic Search

    J. Degroote; P. Bruggeman; R. Haelterman; J. Vierendeels

    2008-01-01

    Numerical techniques frequently used for the simulation of one bubble can be classified as inter- face tracking techniques and interface capturing techniques. Most of these techniques calculate both the flow around the bubble and the shape of the interface between the gas and the liquid with one code. In this paper, a rising axisymmetric bubble is simulated with an interface

  1. A polydisperse twofluid model for surf zone bubble simulation Gangfeng Ma,1

    E-print Network

    Kirby, James T.

    A polydisperse twofluid model for surf zone bubble simulation Gangfeng Ma,1 Fengyan Shi,1 and James 18 May 2011. [1] Wave breaking in the surf zone entrains large volumes of air bubbles into the water representation of the gas phase. Then, it is employed to study the bubbly flow under a laboratory surf zone

  2. Contact time of a pair of bubbles in an acoustic field

    NASA Astrophysics Data System (ADS)

    Shirota, Minori; Miyamae, Hiroki

    2010-11-01

    Contact time of a pair of bubbles in an acoustic field is investigated experimentally. Pairs of bubbles of about 0.1 mm in radius were exposed in an acoustic field of about 30 kHz. The bubbles were generated at T-shaped microfluidic junction in silicone oil of 50 cSt with actively controlled gas pressure change. These bubbles were then introduced into an acoustic levitator commonly used in single bubble sonoluminescence experiment. The contact time of the oscillating bubbles were quantitatively evaluated using high-speed imaging technique. Bubbles with in-phase volume oscillation attracted each other due to secondary Bjerknes force and finally coalesced. We observed bubbles smaller than resonant sizes at large separate distance deforms greatly and coalesced immediately when they touch, while bubbles of the resonant sizes were kept contacting such long time as over 100 periods of forcing.

  3. Methods for nondestructive assay holdup measurements in shutdown uranium enrichment facilities

    SciTech Connect

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

    1991-09-01

    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.

  4. A two-compartment convective-diffusion model for slurry bubble column reactors

    Microsoft Academic Search

    S. Degaleesan; M. P. Dudukovic; B. A. Toseland; B. L. Bhatt

    1997-01-01

    Synthesis gas can be made from a variety of coal, natural gas, environmentally distressed materials such as petroleum coke and biomass. There are considerable reactor design and scale-up problems associated with synthesis gas conversion technologies which arise due to the special characteristics of these processes. Bubble columns and slurry bubble column reactors (SBCRs), due to their superior heat transfer characteristics,

  5. Bubble Expansion and Magma Fragmentation: the Importance of Decompression Rate

    NASA Astrophysics Data System (ADS)

    Namiki, A.; Manga, M.

    2005-12-01

    The occurrence of explosive and effusive volcanic eruptions is often attributed to fragmentation and gas escape by permeable flow, respectively. In Namiki and Manga [ EPSL vol.236, page 269-284 (2005)] , we presented decompression experiments of bubbly fluid and found that for sufficiently large pressure reduction ? P and initial vesicularity ?, the fluid can fragment and make a highly permeable structure caused by rupture of bubble walls. In our previous study, however, the decompression was always instantaneous. In this study, we perform another series of decompression experiments using the same shock-tube apparatus to investigate the effect of decompression rate on the expansion and eruption style of bubbly, viscoelastic fluids. For fast decompression, we again observe fragmentation and rupture of bubble walls for large ? P and large ?. For slow decompression, however, bubbles maintain a spherical shape as the bubbly fluid expands irrespective of ? P and ?. In order to explain the effect of decompression rate on the style of eruption, we compare theoretical models for the expansion of the bubbly fluid with the observed expansion. We consider two theoretical limits for the expansion of bubbles which we refer to as ``equilibrium'' and ``disequilibrium'' expansion. During equilibrium expansion, the pressures inside and outside the bubbles are assumed to be equal throughout the decompression. The height of the expanding bubbly fluid can be calculated using the ideal gas law assuming isothermal expansion of the bubbles is caused by the pressure reduction. For disequilibrium expansion, we calculate the velocity of the expanding bubbly fluid assuming that the enthalpy change caused by the pressure reduction is converted into kinetic energy. When the decompression is fast enough, the calculated expansion rate under the equilibrium assumption is greater than that for disequilibrium expansion, and vice versa for sufficiently slow decompression. In the latter limit, where bubbles expand while maintaining their spherical shape, the measured expansion is well-explained by equilibrium expansion. On the other hand, for fast decompression cases in which we observe the rupture of bubble walls and fragmentation, the expansion follows disequilibrium expansion. We thus conclude that fragmentation and the rupture of bubble walls require disequilibrium expansion so that there is a pressure difference between the gas inside the bubbles and surrounding fluid.

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

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

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

    E-print Network

    Valery P. Dmitriyev

    2006-02-22

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

  8. Migration of a bubble in front of a directionally solidified interface.

    PubMed

    Hadji, Layachi

    2007-04-01

    We examine the quasistatic thermocapillary migration of a gas bubble normal to a solidified interface. The analysis accounts for the deformation of the solid-liquid interface caused by the bubble's presence. An expression for the distance between the bubble surface and the crystal-melt interface is derived, and used to quantify the dependence of the bubble's migration velocity on the processing variables and material properties of the directional solidification process. PMID:17500941

  9. Bubble formation in Rangely Field, Colorado 

    E-print Network

    Wood, J. W

    1953-01-01

    ) '2(l. 417 Schweitzer, P. H. and Szebehely, V. G. : ?Gas Evolution in Liquids and Cavitation" J. Clf A lied Ph s, (Dec. , 1950) 21. 1218 Gersh, I. , Hawkinson, G. E. , and Rathbun, E. N. & "Tissue and Vascular Bubbles after Decompression from High...

  10. MECHANICS OF BUBBLES IN SLUDGES AND SLURRIES

    EPA Science Inventory

    Previous studies have established that the waste level of Hanford tanks responds to barometric pressure changes, the compressibility of retained bubbles accounts for the level changes, and the volume of retained gas can be determined from the measured waste level and barometric p...

  11. Methane bubbling: from speculation to quantification

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.

  12. Evaporation, Boiling and Bubbles

    ERIC Educational Resources Information Center

    Goodwin, Alan

    2012-01-01

    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…

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  14. The Fermi bubbles revisited

    NASA Astrophysics Data System (ADS)

    Yang, Rui-zhi; Aharonian, Felix; Crocker, Roland

    2014-07-01

    We analyze 60 months of all-sky data from the Fermi-LAT. The Fermi bubble structures discovered previously are clearly revealed by our analysis. With more data, hence better statistics, we can now divide each bubble into constant longitude slices to investigate their gross ?-ray spectral morphology. While the detailed spectral behavior of each slice derived in our analysis is somewhat dependent on the assumed background model, we find, robustly, a relative deficit in the flux at low energies (i.e., hardening) toward the top of the south bubble. In neither bubble does the spectrum soften with longitude. The morphology of the Fermi bubbles is also revealed to be energy-dependent: at high energies they are more extended. We conclude from the gamma-ray spectrum at high latitudes that a low energy break in the parent cosmic ray population is required in both leptonic and hadronic models. We briefly discuss possible leptonic and hadronic interpretations of this phenomenology.

  15. A method for bubble volume calculating in vertical two-phase flow

    NASA Astrophysics Data System (ADS)

    Wang, H. Y.; Dong, F.

    2009-02-01

    The movement of bubble is a basic subject in gas-liquid two-phase flow research. A method for calculating bubble volume which is one of the most important characters in bubble motion research was proposed. A suit of visualized experimental device was designed and set up. Single bubble rising in stagnant liquid in a rectangular tank was studied using the high-speed video system. Bubbles generated by four orifice with different diameter (1mm, 2mm, 3mm, 4mm) were recorded respectively. Sequences of recorded high-speed images were processed by digital image processing method, such as image noise remove, binary image transform, bubble filling, and so on. then, Several parameters could be obtained from the processed image. Bubble area, equivalent diameter, bubble velocity, bubble acceleration are all indispensable in bubble volume calculating. In order to get the force balance equation, forces that work on bubble along vertical direction, including drag force, virtual mass force, buoyancy, gravity and liquid thrust, were analyzed. Finally, the bubble volume formula could be derived from the force balance equation and bubble parameters. Examples were given to shown the computing process and results. Comparison of the bubble volume calculated by geomettic method and the present method have shown the superiority of the proposed method in this paper.

  16. Anomalous capillary pressure, stress, and stability of solids-coated bubbles

    SciTech Connect

    Kam, S.I.; Rossen, W.R. [Univ. of Texas, Austin, TX (United States). Dept. of Petroleum and Geosystems Engineering] [Univ. of Texas, Austin, TX (United States). Dept. of Petroleum and Geosystems Engineering

    1999-05-15

    Concern about gas discharges from waste tanks at the Hanford nuclear reservation has led to the study of the mechanisms by which gas is trapped in and then episodically released from these tanks. A two-dimensional theoretical model for solids-coated, or armored, bubbles shows how the armor can support a liquid-vapor interface of reduced or reversed curvature between the particles, giving the bubble zero or even negative capillary pressure. The inward capillary force pulling the particles into the center of the bubble are balanced by large contact forces between the particles in the armor. Thus the bubble is stabilized against dissolution of gas into surrounding liquid, which otherwise would rapidly collapse the bubble. The stresses between particles in such cases are large and could drive sintering of the particles into a rigid framework. Earlier work on solids-coated bubbles assumed that solids can freely enter or leave the bubble surface as the bubble shrinks or expands. In such a case, armored bubbles would not be stable to gas dissolution into surrounding liquid. A new free-energy analysis, however, suggests that a shrunken bubble would not spontaneously expel a solid particle from its armor to relieve stress and allow the bubble to shrink further. Implications and limitations of the theory are discussed.

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

    PubMed

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

    2014-03-01

    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

  18. Modeling of Bubble Oscillations Induced by a Lithotripter Pulse

    NASA Astrophysics Data System (ADS)

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

    2006-05-01

    In therapeutic applications of biomedical ultrasound, it is important to understand the behavior of cavitation bubbles. Herein, the dynamics of a single, spherical bubble in water are modeled using the Gilmore equation closed by an energy balance on bubble contents for calculation of pressures inside the bubble. Moreover, heat and mass transfer at the bubble wall are incorporated using the Eller-Flynn zeroth-order approximation for gas diffusion, an estimation of non-equilibrium phase change based on the kinetic theory of gases, and assumed shapes for the spatial temperature distribution in the surrounding liquid. Bubble oscillations predicted by this model are investigated in response to a lithotripter shock wave. Model results indicate that vapor trapped inside the bubble during collapse plays a significant role in the afterbounce behavior and is sensitively dependent upon the ambient liquid temperature. Initial experiments have been conducted to quantify the afterbounce behavior of a single bubble as a function of ambient temperature; however, the results imply that many bubbles are present and collectively determine the collapse characteristics.

  19. Effects of bubble coalescence and breakup on conduit dynamics

    NASA Astrophysics Data System (ADS)

    Huber, C.; Dufek, J.; Parmigiani, A.; Manga, M.

    2008-12-01

    Volatiles play a central role in eruption behavior. The ability of an exsolved gas phase to move through, and escape from, ascending magma controls whether an eruption is explosive or effusive. In this study, we investigate the dynamics and interactions of gas bubbles as they rise in a conduit. We focus on the coalescence and breakup dynamics of buoyant bubbles in a shear flow (conduit flow) below the fragmentation level. We use a 3D multiphase lattice Boltzmann model to investigate the dynamics at the scale of the bubbles. The net coalescence rate and evolution of the bubble size distribution and number density depend exponentially on the capillary number, Ca (ratio of shear forces to surface tension forces). The Bond number (ratio of buoyancy force to surface tension force) also influences breakup dynamics at large Ca. The results obtained from our 3D lattice Boltzmann model are used to develop a parameterization for the evolution of both bubble size distribution and number density. This parameterization is then used as a model for subgrid scale processes in a 2D conduit model in which the bubbly fluid is treated as a continuum. Our bubble-scale dynamics model can also be used to quantify the development of permeability as bubbles coalesce and connect with the fragmentation surface. We use this multiscale approach to investigate the eruption dynamics of the mafic andesite eruptions that have recently occurred at Tungurahua volcano, Ecuador

  20. THE AGE OF THE LOCAL INTERSTELLAR BUBBLE

    SciTech Connect

    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

    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.

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

    PubMed

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

    2015-02-21

    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

  2. Mechanisms of stability of armored bubbles: FY 1996 Final Report

    SciTech Connect

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

    1996-11-01

    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.

  3. Bubble production mechanism in a microfluidic foam generator.

    PubMed

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

    2012-05-11

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

  4. Shape Oscillations of Rising Bubbles

    Microsoft Academic Search

    Knud Lunde; Richard J. Perkins

    1997-01-01

    The paper details results from an experimental study on bubbles rising in still tap water. Shape and motion parameters of the bubbles were measured using a combination of high speed cinematography and digital image processing. The Reynolds numbers of the bubbles studied ranged from about 700 to 1300, with the bubbles exhibiting all the familiar shape and motion characteristics: oblate

  5. Aerator Combined With Bubble Remover

    NASA Technical Reports Server (NTRS)

    Dreschel, Thomas W.

    1993-01-01

    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.

  6. Bubbling Suppression in Fluidized Beds of Fine and Ultrafine Powders

    Microsoft Academic Search

    Jose Manuel Valverde; Antonio Castellanos

    2008-01-01

    Liquid-fluidized beds of noncohesive beads, gas-fluidized beds of noncohesive light beads, and gas-fluidized beds of fine particles are examples of systems exhibiting nonbubbling fluid-like fluidization. In contrast, stable fluid bubbles have been seen to develop continuously in liquid-fluidized beds of high-density beads, gas-fluidized beds of noncohesive beads, and gas-fluidized beds of fine particles at high gas velocities. On the other

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

    PubMed Central

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

    2011-01-01

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

  8. Gas and Shadow Swing

    NASA Astrophysics Data System (ADS)

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

    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.

  9. Chemistry in Soap Bubbles.

    ERIC Educational Resources Information Center

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

    2002-01-01

    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)

  10. What's in a Bubble?

    ERIC Educational Resources Information Center

    Saunderson, Megan

    2000-01-01

    Describes a unit on detergents and bubbles that establishes an interest in the properties of materials and focuses on active learning involving both hands- and minds-on learning rather than passive learning. (ASK)

  11. Bubble coalescence in magmas

    NASA Technical Reports Server (NTRS)

    Herd, Richard A.; Pinkerton, Harry

    1993-01-01

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

  12. Acoustic Shielding by Cavitation Bubbles in Shock Wave Lithotripsy (SWL)

    NASA Astrophysics Data System (ADS)

    Pishchalnikov, Yuri A.; McAteer, James A.; Bailey, Michael R.; Pishchalnikova, Irina V.; Williams, James C.; Evan, Andrew P.

    2006-05-01

    Lithotripter pulses (˜7-10 ?s) initiate the growth of cavitation bubbles, which collapse hundreds of microseconds later. Since the bubble growth-collapse cycle trails passage of the pulse, and is ˜1000 times shorter than the pulse interval at clinically relevant firing rates, it is not expected that cavitation will affect pulse propagation. However, pressure measurements with a fiber-optic hydrophone (FOPH-500) indicate that bubbles generated by a pulse can, indeed, shield the propagation of the negative tail. Shielding was detected within 1 ?s of arrival of the negative wave, contemporaneous with the first observation of expanding bubbles by high-speed camera. Reduced negative pressure was observed at 2 Hz compared to 0.5 Hz firing rate, and in water with a higher content of dissolved gas. We propose that shielding of the negative tail can be attributed to loss of acoustic energy into the expansion of cavitation bubbles.

  13. Optimization of bubble column performance for nanoparticle collection.

    PubMed

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

    2014-04-30

    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

  14. Time correlated single photon Mie scattering from a sonoluminescing bubble K. R. Weninger,1

    E-print Network

    Evans, Paul G.

    The acoustically driven pulsations of a gas bubble in wa- ter can be so nonlinear as to generate broad band scattering measurements may be due to light scattered by the outgoing acoustic ``shock'' wave around those gleaned from the data. The Mie scattering experiments were conducted on gas bubbles levitated

  15. Bubble dynamics in viscoelastic fluids with application to reacting and non-reacting polymer foams

    Microsoft Academic Search

    S. L. Everitt; O. G. Harlen; H. J. Wilson; D. J. Read

    2003-01-01

    The effects of fluid viscoelasticity on the expansion of gas bubbles in polymer foams for the cases of reactive and non-reactive polymers are investigated. For non-reactive polymers, bubble expansion is controlled by a combination of gas diffusion and fluid rheology. In the diffusion limited case, the initial growth rate is slow due to small surface area, whereas at high diffusivity

  16. DNS of Separation Bubbles

    NASA Astrophysics Data System (ADS)

    Hildings, Casper; Henningson, Dan

    1996-11-01

    Separation bubbles in laminar flow over a flat plate have been investigated using a modified version of the spectral DNS-code developed at FFA/KTH. By prescribing the velocity at the free-stream boundary, a varying pressure gradient was introduced, sufficiently strong to form a separation bubble. The numerical method chosen uses the so called ``fringe region'' technique to damp outflowing disturbances and return the flow to a prescribed inlet state. A detailed investigation of the efficiency of the disturbance damping has been made, since separation bubbles amplify disturbances several orders of magnitude. If these disturbances are not adequately damped they may reenter at the inflow and corrupt the computation. Guidelines to find the most efficient fringe are presented. Initially the 2D separation bubble investigated by Rist and Maucher (Rist, U., Maucher, U. AGARD-Symposium, 1994, Chania, Crete.) was calculated in order to verify the code. The characteristics of this bubble, including length and height as well as the growth rate of small disturbances compare well with those of Rist and Maucher. Presently a corresponding experimental study of separation bubbles is made at KTH. Comparisons between the ongoing numerical work and the experiments will be presented.

  17. Bubble Eliminator Based on Centrifugal Flow

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

    The fluid bubble eliminator (FBE) is a device that removes gas bubbles from a flowing liquid. The FBE contains no moving parts and does not require any power input beyond that needed to pump the liquid. In the FBE, the buoyant force for separating the gas from the liquid is provided by a radial pressure gradient associated with a centrifugal flow of the liquid and any entrained bubbles. A device based on a similar principle is described in Centrifugal Adsorption Cartridge System (MSC- 22863), which appears on page 48 of this issue. The FBE was originally intended for use in filtering bubbles out of a liquid flowing relatively slowly in a bioreactor system in microgravity. Versions that operate in normal Earth gravitation at greater flow speeds may also be feasible. The FBE (see figure) is constructed as a cartridge that includes two concentric cylinders with flanges at the ends. The outer cylinder is an impermeable housing; the inner cylinder comprises a gas-permeable, liquid-impermeable membrane covering a perforated inner tube. Multiple spiral disks that collectively constitute a spiral ramp are mounted in the space between the inner and outer cylinders. The liquid enters the FBE through an end flange, flows in the annular space between the cylinders, and leaves through the opposite end flange. The spiral disks channel the liquid into a spiral flow, the circumferential component of which gives rise to the desired centrifugal effect. The resulting radial pressure gradient forces the bubbles radially inward; that is, toward the inner cylinder. At the inner cylinder, the gas-permeable, liquid-impermeable membrane allows the bubbles to enter the perforated inner tube while keeping the liquid in the space between the inner and outer cylinders. The gas thus collected can be vented via an endflange connection to the inner tube. The centripetal acceleration (and thus the radial pressure gradient) is approximately proportional to the square of the flow speed and 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.

  18. Formation of monodisperse bubbles in a microfluidic flow-focusing device

    NASA Astrophysics Data System (ADS)

    Garstecki, Piotr; Gitlin, Irina; DiLuzio, Willow; Whitesides, George M.; Kumacheva, Eugenia; Stone, Howard A.

    2004-09-01

    This letter describes a method for generating monodisperse gaseous bubbles in a microfluidic flow-focusing device. The bubbles can be obtained in a range of diameters from 10 to 1000?m. The volume Vb of the bubbles scales with the flow rate q and the viscosity ? of the liquid, and the pressure p of the gas stream as Vb?p /q?. This method allows simultaneous, independent control of the size of the individual bubbles and volume fraction of the dispersed phase. Under appropriate conditions, bubbles self-assemble into highly ordered, flowing lattices. Structures of these lattices can be adjusted dynamically by changing the flow parameters.

  19. Bubble Evolution During Acoustic Droplet Vaporization

    NASA Astrophysics Data System (ADS)

    Qamar, Adnan; Bull, Joseph

    2009-11-01

    A first theoretical model of bubble evolution in Acoustic Droplet Vaporization (ADV) inside a circular microchannel is presented. This work is motivated by a novel gas embolotherapy technique, which is intended to treat cancers by occluding blood flow using gas bubbles. The intended therapy involves the injection of superheated Dodecafluoropentane (DDFP, C5F12, boiling point 29 C) droplets, each encapsulated in an albumin shell, into the blood stream. The blood circulation carries these droplets into the tumor region where high-intensity ultrasound is used to trigger ADV to form bubbles near the desired occlusion sites. The proposed model describes the rapid phase transition from highly superheated DDFP droplet to the vapor phase via a homogeneous nucleation within the DDFP droplet. For every time step the radial component of the Navier-Stokes equation is integrated from the nucleated bubble surface to the expanding boundary of the droplet with proper boundary conditions taking into account for the vaporization process. Further from the droplet boundary to the end of microchannel a modified unsteady Bernoulli equation with the head loss term is utilized. Close agreement with experimental data for all the acoustic parameters and different initial droplet sizes is obtained. The proposed model is expected to elucidate the role of different parameters involved in the complex ADV process. This work is supported by NIH grant R01EB006476.

  20. Comparison of two phase liquid holdup and pressure drop correlations across flow regime boundaries for horizontal and inclined pipes

    SciTech Connect

    Arya, A.; Gould, T.L.

    1981-01-01

    During the last decade the interest in two-phase flow through horizontal and inclined pipes has increased considerably,. Design engineers are primarily concerned with the calculation of pressure drop in two-phase lines and prediction of liquid holdup (in-situ liquid volume fraction), in order to size flow lines and calculate slug catcher size. These calculations are also important for the design of surface facilities such as pumps, compressors and separators. The correlations tested in this study first predict the flow pattern in the pipeline at the specified physical conditions with the help of a flow pattern map. After determining the flow pattern, the corresponding holdup and friction factor correlations are used to calculate pressure drop. 7 refs.

  1. Passive gas separator and accumulator device

    Microsoft Academic Search

    H. Choe; T. T. Fallas

    1994-01-01

    A separation device employing a gas separation filter and swirler vanes for separating gas from a gas-liquid mixture is provided. The cylindrical filter utilizes the principle that surface tension in the pores of the filter prevents gas bubbles from passing through. As a result, the gas collects in the interior region of the filter and coalesces to form larger bubbles

  2. Passive gas separator and accumulator device

    Microsoft Academic Search

    Hwang Choe; T. T. Fallas

    1993-01-01

    A separation device employing a gas separation filter and swirler vanes for separating gas from a gas-liquid mixture is provided. The cylindrical filter uses the principle that surface tension in the filter pores prevents gas bubbles from passing through; the gas collects in the interior of the filter to form larger bubbles in the center of the device. The device

  3. Bubbles attenuate elastic waves at seismic frequencies: First experimental evidence

    NASA Astrophysics Data System (ADS)

    Tisato, Nicola; Quintal, Beatriz; Chapman, Samuel; Podladchikov, Yury; Burg, Jean-Pierre

    2015-05-01

    The migration of gases from deep to shallow reservoirs can cause damageable events. For instance, some gases can pollute the biosphere or trigger explosions and eruptions. Seismic tomography may be employed to map the accumulation of subsurface bubble-bearing fluids to help mitigating such hazards. Nevertheless, how gas bubbles modify seismic waves is still unclear. We show that saturated rocks strongly attenuate seismic waves when gas bubbles occupy part of the pore space. Laboratory measurements of elastic wave attenuation at frequencies <100 Hz are modeled with a dynamic gas dissolution theory demonstrating that the observed frequency-dependent attenuation is caused by wave-induced-gas-exsolution-dissolution (WIGED). This result is incorporated into a numerical model simulating the propagation of seismic waves in a subsurface domain containing CO2-gas bubbles. This simulation shows that WIGED can significantly modify the wavefield and illustrates how accounting for this physical mechanism can potentially improve the monitoring and surveying of gas bubble-bearing fluids in the subsurface.

  4. Laboratory air bubble generation of various size distributions

    SciTech Connect

    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

    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.

  5. Cartilage formation in the CELLS 'double bubble' hardware

    NASA Technical Reports Server (NTRS)

    Duke, P. J.; Arizpe, Jorge; Montufar-Solis, Dina

    1991-01-01

    The CELLS experiment scheduled to be flown on the first International Microgravity Laboratory is designed to study the effect of microgravity on the cartilage formation, by measuring parameters of growth in a differentiating cartilage cell culture. This paper investigates the conditions for this experiment by studying cartilage differentiation in the 'bubble exchange' hardware with the 'double bubble' design in which the bubbles are joined by a flange which also overlays the gasket. Four types of double bubbles (or double gas permeable membranes) were tested: injection-molded bubbles 0.01- and 0.005-in. thick, and compression molded bubbles 0.015- and 0.01-in. thick. It was found that double bubble membranes of 0.005- and 0.010-in. thickness supported cartilage differentiation, while the 0.015-in. bubbles did not. It was also found that nodule count, used in this study as a parameter, is not the best measure of the amount of cartilage differentiation.

  6. Laser-induced nucleation of carbon dioxide bubbles

    NASA Astrophysics Data System (ADS)

    Ward, Martin R.; Jamieson, William J.; Leckey, Claire A.; Alexander, Andrew J.

    2015-04-01

    A detailed experimental study of laser-induced nucleation (LIN) of carbon dioxide (CO2) gas bubbles is presented. Water and aqueous sucrose solutions supersaturated with CO2 were exposed to single nanosecond pulses (5 ns, 532 nm, 2.4-14.5 MW cm-2) and femtosecond pulses (110 fs, 800 nm, 0.028-11 GW cm-2) of laser light. No bubbles were observed with the femtosecond pulses, even at high peak power densities (11 GW cm-2). For the nanosecond pulses, the number of bubbles produced per pulse showed a quadratic dependence on laser power, with a distinct power threshold below which no bubbles were observed. The number of bubbles observed increases linearly with sucrose concentration. It was found that filtering of solutions reduces the number of bubbles significantly. Although the femtosecond pulses have higher peak power densities than the nanosecond pulses, they have lower energy densities per pulse. A simple model for LIN of CO2 is presented, based on heating of nanoparticles to produce vapor bubbles that must expand to reach a critical bubble radius to continue growth. The results suggest that non-photochemical laser-induced nucleation of crystals could also be caused by heating of nanoparticles.

  7. A multi-functional bubble-based microfluidic system

    PubMed Central

    Khoshmanesh, Khashayar; Almansouri, Abdullah; Albloushi, Hamad; Yi, Pyshar; Soffe, Rebecca; Kalantar-zadeh, Kourosh

    2015-01-01

    Recently, the bubble-based systems have offered a new paradigm in microfluidics. Gas bubbles are highly flexible, controllable and barely mix with liquids, and thus can be used for the creation of reconfigurable microfluidic systems. In this work, a hydrodynamically actuated bubble-based microfluidic system is introduced. This system enables the precise movement of air bubbles via axillary feeder channels to alter the geometry of the main channel and consequently the flow characteristics of the system. Mixing of neighbouring streams is demonstrated by oscillating the bubble at desired displacements and frequencies. Flow control is achieved by pushing the bubble to partially or fully close the main channel. Patterning of suspended particles is also demonstrated by creating a large bubble along the sidewalls. Rigorous analytical and numerical calculations are presented to describe the operation of the system. The examples presented in this paper highlight the versatility of the developed bubble-based actuator for a variety of applications; thus providing a vision that can be expanded for future highly reconfigurable microfluidics. PMID:25906043

  8. The dynamics of histotripsy bubbles

    NASA Astrophysics Data System (ADS)

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

    2011-09-01

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

  9. Statistical equilibrium of bubble oscillations in dilute bubbly flows.

    PubMed

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

    2008-04-01

    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

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

    NASA Technical Reports Server (NTRS)

    Nahra, Henry K.; Kamotani, Y.

    2000-01-01

    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.

  11. Numerical simulation of the dynamic flow behaviour in a bubble column: comparison of the bubble-induced turbulence models in K-epsilon model

    Microsoft Academic Search

    D. Zhang; JAM Kuipers; J. A. M. Kuipers

    2005-01-01

    Numerical simulations of the gas-liquid bubbly flow in a bubble column were conducted with the commercial CFD package CFX-4.4 to investigate the performance of three models (Pfleger and Becker, 2001; Sato and Sekoguchi, 1975; Troshko and Hassan, 2001) to account for the bubble-induced turbulence in the k-? model. Furthermore, the effect of two different interfacial closure models was investigated. All

  12. Simulation of Micro Bubble in a Narrow Tube

    NASA Astrophysics Data System (ADS)

    Ye, Tao; Bull, Joseph L.

    2003-11-01

    We are investigating a new gas embolotherapy technique that involves acoustically vaporizing perfluorocarbon liquid droplets to form gas bubbles, which are large enough to occlude flow in arterioles and capillaries with the goal of starving tumors. The bubbles typically originate as 6 micrometer, liquid droplets that are small enough to pass through capillaries. These droplets can be observed using ultrasound imaging and then vaporized by a high intensity ultrasound field when they are at the desired location. Vaporization close to the tumor will minimize the infarction of healthy tissue, but poses the risk of vessel rupture and subsequent hemorrhage if the bubbles are formed in too small of vessels. Mechanical stresses induced by bubble growth and collapse need to be determined in order to prevent rupture of the blood vessel or endothelial cell injury. In this study, the physics of the micro-scale bubble growth/collapse in a narrow tube with a flexible wall is investigated using direct numerical simulation. The computational method is a novel shape-interface, moving boundary method for solving full Navier-Stokes equations of multi-phase fluid flows with dynamic interfaces. Dimensionless parameters are varied to examine the effects of viscosity, surface tension, and bubble pressure. Our simulations reveal that normal and shear stress on the vessel wall reach peak values at different stages with peak magnitude of normal stress far greater than that of shear stress. The initial phase of the bubble expansion is the most dangerous period for the vessel in all cases.

  13. Colliding with a crunching bubble

    SciTech Connect

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

    2007-03-26

    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.

  14. Acoustic-wave effects in violent bubble collapse

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

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

  15. Gas-sensing optrode

    DOEpatents

    Hirschfeld, T.B.

    1988-04-12

    An optrode is provided for sensing dissolved gases or volatile components of a solution. A fiber optic is provided through which light from an associated light source is transmitted from a first end to a second end. A bubble forming means, such as a tube, is attached to the second end of the fiber optic, and an indicator material is disposed in cooperation with the bubble forming means adjacent to the second end of the fiber optic such that it is illuminated by light emanating from the second end. The bubble forming means causes a gas bubble to form whenever the optrode is immersed in the fluid. The gas bubble separates the indicator material from the fluid. Gases, or other volatile components, of the fluid are sensed as they diffuse across the gas bubble from the fluid to the indicator material. 3 figs.

  16. 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

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

    2008-12-19

    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.

  17. Study of the behavior of rising bubbles in a Boger-type fluid

    NASA Astrophysics Data System (ADS)

    Velez-Cordero, J. R.; Samano, D.; Zenit, R.

    2011-11-01

    Particle aggregation is a common phenomenon observed in viscoelastic multiphase flows. In this work a new effect has been observed to occur in monodispersed bubbly flows in a Boger-type fluid. It was found that the dispersion of bubble changes dramatically depending on the bubble size: if the diameter of the bubbles is small, large vertical clusters are formed; on the other hand, the bubble assembly rises in a dispersed manner if the bubble size is increased. To understand the condition for which agglomeration occurs two additional experiments were conducted: the interaction of two side-by-side bubble chains was analyzed; and, the unsteady behavior of the first normal stress difference was studied in a rheometric flow. These analyses suggest that there is a process of accumulation of elastic stress; when the accumulated elastic stress surpasses the viscous repulsive stress, aggregation can occur even at supercritical speeds. Interestingly, the two bubble diameters tested in the bubbly flow experiments are above and below the critical diameter for which the velocity of an isolated bubble becomes discontinuous, the so-called bubble velocity discontinuity. This suggests that the bubble dispersion improvement could result from the modification of the gas-liquid interface.

  18. Multivariate bubbles and antibubbles

    NASA Astrophysics Data System (ADS)

    Fry, John

    2014-08-01

    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.

  19. Acoustically Bound Microfluidic Bubble Crystals

    NASA Astrophysics Data System (ADS)

    Rabaud, David; Thibault, Pierre; Mathieu, Mylène; Marmottant, Philippe

    2011-04-01

    Bubbles confined in microchannels self-organize without directly contacting one another when excited by an external acoustic field. The bubbles tend to form periodic “crystal”-like lattices with a finite interbubble distance. This equilibrium distance can be adjusted by simply tuning the acoustic frequency. This new type of crystal is purely mediated by acoustic surface waves emitted by the pulsating bubbles. Because these waves are reflected at the channel boundaries, the bubbles interact with their own images across the boundary.

  20. Laboratory Experiments on Propagating Plasma Bubbles into Vacuum, Vacuum Magnetic Field, and Background Plasmas

    NASA Astrophysics Data System (ADS)

    Lynn, Alan G.; Zhang, Yue; Gilmore, Mark; Hsu, Scott

    2014-10-01

    We discuss the dynamics of plasma ``bubbles'' as they propagate through a variety of background media. These bubbles are formed by a pulsed coaxial gun with an externally applied magnetic field. Bubble parameters are typically ne ~1020 m-3, Te ~ 5 - 10 eV, and Ti ~ 10 - 15 eV. The structure of the bubbles can range from unmagnetized jet-like structures to spheromak-like structures with complex magnetic flux surfaces. Some of the background media the bubbles interact with are vacuum, vacuum with magnetic field, and other magnetized plasmas. These bubbles exhibit different qualitative behavior depending on coaxial gun parameters such as gas species, gun current, and gun bias magnetic field. Their behavior also depends on the parameters of the background they propagate through. Multi-frame fast camera imaging and magnetic probe data are used to characterize the bubble evolution under various conditions.

  1. Bubble dynamics and interactions with a pair of micro pillars in tandem

    SciTech Connect

    D. Elcock; M. Honkanen; C. Kuo; M. Amitay; Y. Peles

    2011-06-01

    This study investigates flow patterns and bubble dynamics of two-phase flow around two 100 µm diameter circular pillars in tandem, which were entrenched inside a horizontal micro channel. Bubble velocity, trajectory, size, and void fraction were measured using a high speed camera and analyzed using a particle tracking velocimetry method. A range of gas and liquid superficial velocities were tested, resulting in different bubbly flow patterns, which were consistent with previous studies. These flow patterns were altered as they interacted with the pillars. Depending on the relative transverse location of bubbles to the pillars, and through bubble–bubble interaction, the flow sometimes returned to its original state. It was also determined that the pillars altered both the bubble trajectory and void fraction, especially in the pillars region.

  2. Bursting Bubbles and Bilayers

    PubMed Central

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

    2012-01-01

    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

  3. Stationary and protable instruments for assay of HEU (highly enriched uranium) solids holdup

    SciTech Connect

    Russo, P.A.; Sprinkle, J.K. Jr.; Stephens, M.M.; Brumfield, T.L.; Gunn, C.S.; Watson, D.R.

    1987-01-01

    Two NaI(Tl)-based instruments, one stationary and one portable, designed for automated assay of highly enriched uranium (HEU) solids holdup, are being evaluated at the scrap recovery facility of the Oak Ridge Y-12 Plant. The stationary instrument, a continuous monitor of HEU within the filters of the chip burner exhaust system, measures the HEU deposits that accumulate erratically and rapidly during chip burner operation. The portable system was built to assay HEU in over 100 m of elevated piping used to transfer UO/sub 3/, UO/sub 2/, and UF/sub 4/ powder to, from, and between the fluid bed conversion furnances and the powder storage hoods. Both instruments use two detector heads. Both provide immediate automatic readout of accumulated HEU mass. The 186-keV /sup 235/U gamma ray is the assay signature, and the 60-keV gamma ray from an /sup 241/Am source attached to each detector is used to normalize the 186-keV rate. The measurement geometries were selected for compatibility with simple calibration models. The assay calibrations were calculated from these models and were verified and normalized with measurements of HEU standards built to match geometries of uniform accumulations on the surfaces of the process equipment. This instrumentation effort demonstrates that simple calibration models can often be applied to unique measurement geometries, minimizing the otherwise unreasonable requirements for calibration standards and allowing extension of the measurements to other process locations.

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

    SciTech Connect

    KEELE, B.D.

    2007-07-05

    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.

  5. Bubble size measurement in electroflotation

    Microsoft Academic Search

    G. M. Evans; S. W. Donne

    2010-01-01

    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

  6. Bubbles in Real Estate Markets

    Microsoft Academic Search

    Richard Herring; Susan Wachter

    2002-01-01

    Real estate bubbles may occur without banking crises. And banking crises may occur without real estate bubbles. But the two phenomena are correlated in a remarkable number of instances. This paper provides a conceptual framework explaining why the banking sector’s importance and link to the real estate sector not only amplifies the real estate bubble but also can have major

  7. The Bubble Transport Mechanism: Indications for a bubble-mediated transfer of microorganisms from the sediment into the water column

    NASA Astrophysics Data System (ADS)

    Schmale, Oliver; Stolle, Christian; Schneider von Deimling, Jens; Leifer, Ira; Kießlich, Katrin; Krause, Stefan; Frahm, Andreas; Treude, Tina

    2015-04-01

    Gas releasing seep areas are known to impact the methane biogeochemistry in the surrounding sediment and water column. Due to microbial processes most of the methane is oxidized under anaerobic and aerobic conditions before the greenhouse gas can escape into the atmosphere. However, methane gas bubbles can largely bypass this microbial filter mechanism, enabling highly efficient transport of methane from the sediment towards the sea surface. Studies in the water column surrounding hydrocarbon seeps indicated an elevated abundance of methanotrophic microorganism in the near field of gas bubble plumes. The enhanced methane concentration in the seep-affected water column stimulates the activity of methane oxidizers and leads to a rapid rise in the abundance of methane-oxidizing microorganisms in the aging plume water. In our study we hypothesized that a bubble-mediated transport mechanisms between the benthic and pelagic habitats represents an exchange process, which transfers methanotrophic microorganisms from the sediment into the water column, a process we termed the "Bubble Transport Mechanism". This mechanism could eventually influence the pelagic methanotrophic community, thereby indirectly providing feedback mechanisms for dissolved methane concentrations in the water column and thus impacting the sea/atmosphere methane flux. To test our hypothesis, field studies were conducted at the "Rostocker Seep" site (Coal Oil Point seep area, California, USA). Catalyzed Reporter Deposition Fluorescence In Situ Hybridization (CARD-FISH) analyzes were performed to determine the abundance of aerobic and anaerobic methanotrophic microorganisms. Aerobic methane oxidizing bacteria were detected in the sediment and the water column, whereas anaerobic methanotrophs were detected exclusively in the sediment. The key device of the project was a newly developed "Bubble Catcher" used to collect naturally emanating gas bubbles at the sea floor together with particles attached to the bubble surface rim. Bubble Catcher experiments were carried out directly above a natural bubble release spot and on a reference site at which artificially released gas bubbles were caught, which had no contact with the sediment. CARD-FISH analyzes showed that aerobic methane oxidizing bacteria were transported by gas bubbles from the sediment into the water column. In contrast anaerobic methanotrophs were not detected in the bubble catcher. Based on our study we hypothesize that the Bubble Shuttle transport mechanism contributes to the pelagic methane sink by a sediment-water column transfer of methane oxidizing microorganisms. Furthermore, this Bubble Shuttle may influence the methanotrophic community in the water column after massive short-term submarine inputs of methane (e.g. release of methane from bore holes). Especially in deep-sea regions, where the abundance of methane oxidizing microorganisms in the water column is low in general, the Bubble Transport Mechanism may inject a relevant amount of methane oxidizing microorganisms into the water column during massive inputs, supporting indirectly the turnover of this greenhouse active trace gas in the submarine environment.

  8. Electrophoresis of surfactant-free bubbles.

    PubMed

    Harper, J F

    2010-10-01

    In 1996 Kelsall et al. [5] reported electrophoretic experiments with oxygen bubbles in dilute solutions of several salts that were remarkably free of surfactants, but the experimental results agree with neither their own theory nor anyone else's known to the present author. This paper assumes a double-layer thickness much smaller than the bubble radius, as it was in the experiments. It redevelops the theory on various hypotheses about the precise location of the free surface charge, and both with and without van der Weg's recently-suggested modification to the electrochemical potential. The results suggest that the free surface charge is at or on the gas side of the change in permittivity at a bubble's surface in a surfactant-free liquid, and that the classical theory for the speed of rise of a bubble is not quite correct in an electrolyte solution, but the correction is too small to measure. However, there are still unresolved difficulties with both theory and experiments, which van der Weg's suggestion does not remove. Nor does it improve the fit between theory and Grahame's [13] experiments on the differential capacitance of a double layer. PMID:20609448

  9. Experimental and Numerical Investigation of Pressure Wave Attenuation due to Bubbly Layers

    NASA Astrophysics Data System (ADS)

    Jayaprakash, Arvind; Fourmeau, Tiffany; Hsiao, Chao-Tsung; Chahine, Georges; Dynaflow Inc. Team

    2013-03-01

    In this work, the effects of dispersed microbubbles on a steep pressure wave and its attenuation are investigated both numerically and experimentally. Numerical simulations were carried out using a compressible Euler equation solver, where the liquid-gas mixture was modeled using direct numerical simulations involving discrete deforming bubbles. To reduce computational costs a 1D configuration is used and the bubbles are assumed distributed in layers and the initial pressure profile is selected similar to that of a one-dimensional shock tube problem. Experimentally, the pressure pulse was generated using a submerged spark electric discharge, which generates a large vapor bubble, while the microbubbles in the bubbly layer are generated using electrolysis. High speed movies were recorded in tandem with high fidelity pressure measurements. The dependence of pressure wave attenuation on the bubble radii, the void fraction, and the bubbly layer thickness were parametrically studied. It has been found that the pressure wave attenuation can be seen as due to waves reflecting and dispersing in the inter-bubble regions, with the energy absorbed by bubble volume oscillations and re-radiation. Layer thickness and small bubble sizes were also seen as having a strong effect on the attenuation with enhanced attenuation as the bubble size is reduced for the same void fraction. In this work, the effects of dispersed microbubbles on a steep pressure wave and its attenuation are investigated both numerically and experimentally. Numerical simulations were carried out using a compressible Euler equation solver, where the liquid-gas mixture was modeled using direct numerical simulations involving discrete deforming bubbles. To reduce computational costs a 1D configuration is used and the bubbles are assumed distributed in layers and the initial pressure profile is selected similar to that of a one-dimensional shock tube problem. Experimentally, the pressure pulse was generated using a submerged spark electric discharge, which generates a large vapor bubble, while the microbubbles in the bubbly layer are generated using electrolysis. High speed movies were recorded in tandem with high fidelity pressure measurements. The dependence of pressure wave attenuation on the bubble radii, the void fraction, and the bubbly layer thickness were parametrically studied. It has been found that the pressure wave attenuation can be seen as due to waves reflecting and dispersing in the inter-bubble regions, with the energy absorbed by bubble volume oscillations and re-radiation. Layer thickness and small bubble sizes were also seen as having a strong effect on the attenuation with enhanced attenuation as the bubble size is reduced for the same void fraction. This study was supported by the Department of Energy, under SBIR Phase II Contract DE-FG02-07ER84839.

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

    NASA Astrophysics Data System (ADS)

    Cartmell, Jerome John

    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.

  11. Effect of liquid properties on the growth and motion characteristics of micro-bubbles induced by electric fields in confined liquid films

    NASA Astrophysics Data System (ADS)

    Xie, G. X.; Luo, J. B.; Liu, S. H.; Guo, D.; Li, G.; Zhang, C. H.

    2009-06-01

    The effect of liquid properties on gas bubble growth and motion characteristics in liquid films confined within a nanogap between a highly polished steel ball and a smooth glass disc under an electric field is reported. Experimental results show that the critical voltage for the appearance of bubbles has insignificant dependence on liquid viscosity and surface tension. The bubble size after detachment increases with liquid viscosity, and bubble instability and coalescence tend to occur when bubbles move some distance away from where they were formed. An increase in liquid surface tension results in larger bubbles at the growth stage. Also, the bubble motion characteristics are greatly influenced by liquid viscosity, and the dielectrophoresis force is demonstrated to be the dominant driving force for bubble movement. Theoretical models and analyses have been used to discuss the bubble formation and describe the bubble movement characteristics.

  12. The Liberal Arts Bubble

    ERIC Educational Resources Information Center

    Agresto, John

    2011-01-01

    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…

  13. What's in the Bubbles?

    NSDL National Science Digital Library

    Francis Eberle

    2007-01-01

    The purpose of this assessment probe is to elicit students' ideas about particles during a change in state. The probe is designed to find out if students recognize that the bubbles formed when water boils are the result of liquid water changing into water vapor. This free selection also includes the Table of Contents, Foreword, Preface, and Index.

  14. 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.

  15. Methane emission by bubbling from Gatun Lake, Panama

    SciTech Connect

    Keller, M. [National Center for Atmospheric Research, Boulder, CO (United States)] [National Center for Atmospheric Research, Boulder, CO (United States); Stallard, R.F. [Geological Survey, Denver, CO (United States)] [Geological Survey, Denver, CO (United States)

    1994-04-20

    We studied methane emission by bubbling from Gatun Lake, Panama, at water depths of less than 1 m to about 10 m. Gas bubbles were collected in floating traps deployed during 12- to 60-hour observation periods. Comparison of floating traps and floating chambers showed that about 98% of methane emission occurred by bubbling and only 2% occurred by diffusion. Average methane concentration of bubbles at our sites varied from 67% to 77%. Methane emission by bubbling occurred episodically, with greatest rates primarily between the hours of 0800 and 1400 LT. Events appear to be triggered by wind. The flux of methane associated with bubbling was strongly anticorrelated with water depth. Seasonal changes in water depth caused seasonal variation of methane emission. Bubble methane fluxes through the lake surface into the atmosphere measured during 24-hour intervals were least (10-200 mg m{sup -2} d{sup -1}) at deeper sites (>7 m) and greatest (300-2000 mg m{sup -2} d{sup -1}) at shallow sites (<2 m). 37 refs., 11 figs., 5 tabs.

  16. Collapsing Bubble in Metal for High Energy Density Physics Study

    SciTech Connect

    Ng, S F; Barnard, J J; Leung, P T; Yu, S S

    2011-04-13

    This paper presents a new idea to produce matter in the high energy density physics (HEDP) regime in the laboratory using an intense ion beam. A gas bubble created inside a solid metal may collapse by driving it with an intense ion beam. The melted metal will compress the gas bubble and supply extra energy to it. Simulations show that the spherical implosion ratio can be about 5 and at the stagnation point, the maximum density, temperature and pressure inside the gas bubble can go up to nearly 2 times solid density, 10 eV and a few megabar (Mbar) respectively. The proposed experiment is the first to permit access into the Mbar regime with existing or near-term ion facilities, and opens up possibilities for new physics gained through careful comparisons of simulations with measurements of quantities like stagnation radius, peak temperature and peak pressure at the metal wall.

  17. Passive gas separator and accumulator device

    Microsoft Academic Search

    Hwang Choe; Thomas T. Fallas

    1994-01-01

    A separation device employing a gas separation filter and swirler vanes for separating gas from a gasliquid mixture is provided. The cylindrical filter utilizes the principle that surface tension in the pores of the filter prevents gas bubbles from passing through. As a result, the gas collects in the interior region of the filter and coalesces to form larger bubbles

  18. Black Hole Blows Big Bubble

    NASA Astrophysics Data System (ADS)

    2010-07-01

    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

  19. Black Hole Blows Big Bubble

    NASA Astrophysics Data System (ADS)

    2010-07-01

    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

  20. System for Manipulating Drops and Bubbles Using Acoustic Radiation Pressure

    NASA Technical Reports Server (NTRS)

    Oeftering, Richard C. (Inventor)

    1999-01-01

    The manipulation and control of drops of liquid and gas bubbles is achieved using high intensity acoustics in the form of and/or acoustic radiation pressure and acoustic streaming. generated by a controlled wave emission from a transducer. Acoustic radiation pressure is used to deploy or dispense drops into a liquid or a gas or bubbles into a liquid at zero or near zero velocity from the discharge end of a needle such as a syringe needle. Acoustic streaming is useful in manipulating the drop or bubble during or after deployment. Deployment and discharge is achieved by focusing the acoustic radiation pressure on the discharge end of the needle, and passing the acoustic waves through the fluid in the needle. through the needle will itself, or coaxially through the fluid medium surrounding the needle. Alternatively, the acoustic waves can be counter-deployed by focusing on the discharge end of the needle from a transducer axially aligned with the needle, but at a position opposite the needle, to prevent premature deployment of the drop or bubble. The acoustic radiation pressure can also be used for detecting the presence or absence of a drop or a bubble at the tip of a needle or for sensing various physical characteristics of the drop or bubble such as size or density.

  1. Bubble formation in water with addition of a hydrophobic solute

    E-print Network

    Ryuichi Okamoto; Akira Onuki

    2015-05-29

    We show that phase separation can occur in a one-component liquid outside its coexistence curve (CX) with addition of a small amount of a solute. The solute concentration at the transition decreases with increasing the difference of the solvation chemical potential between liquid and gas. As a typical bubble-forming solute, we consider ${\\rm O}_2$ in ambient liquid water, which exhibits mild hydrophobicity and its critical temperature is lower than that of water. Such a solute can be expelled from the liquid to form gaseous domains while the surrounding liquid pressure is higher than the saturated vapor pressure $p_{cx}$. This solute-induced bubble formation is a first-order transition in bulk and on a partially dried wall, while a gas film grows continuously on a completely dried wall. We set up a bubble free energy $\\Delta G$ for bulk and surface bubbles with a small volume fraction $\\phi$. It becomes a function of the bubble radius $R$ under the Laplace pressure balance. Then, for sufficiently large solute densities above a threshold, $\\Delta G$ exhibits a local maximum at a critical radius and a minimum at an equilibrium radius. We also examine solute-induced nucleation taking place outside CX, where bubbles larger than the critical radius grow until attainment of equilibrium.

  2. Mechanisms of gas bubble retention and release: results for Hanford Waste Tanks 241-S-102 and 241-SY-103 and single-shell tank simulants

    SciTech Connect

    Gauglitz, P.A.; Rassat, S.D.; Bredt, P.R.; Konynenbelt, J.H.; Tingey, S.M.; Mendoza, D.P.

    1996-09-01

    Research at Pacific Northwest National Laboratory (PNNL) has probed the physical mechanisms and waste properties that contribute to the retention and release of flammable gases from radioactive waste stored in underground tanks at Hanford. This study was conducted for Westinghouse Hanford Company as part of the PNNL Flammable Gas Project. The wastes contained in the tanks are mixes of radioactive and chemical products, and some of these wastes are known to generate mixtures of flammable gases, including hydrogen, nitrous oxide, and ammonia. Because these gases are flammable, their retention and episodic release pose a number of safety concerns.

  3. Segregation in water-based stable single-bubble sonoluminescence

    NASA Astrophysics Data System (ADS)

    Levinsen, Mogens T.

    2012-01-01

    A long-standing issue in the field of long-time-stable, water-based, single-bubble sonoluminescence has been the close similarity of the spectra to that of blackbody radiation, the question being whether the similarity is just a weird coincidence, with the bubbles being, on the whole, transparent to their own radiation. One mechanism that has been suggested is the generation of a shock or, at least, a compression wave in the gas of the bubble. A footprint of such a wave would be segregation of species. We have investigated spectra from bubbles seeded with various mixtures of helium or neon with xenon or argon using a transformation, specific to our experimental setup and spectrometer, that was shown to allow for a single-parameter characterization of the spectra in some simpler situations. The surprising result of this investigation is that although no trace of segregation is found, the radiation seems to be highly thermalized in all cases.

  4. Ring Bubbles of Dolphins

    NASA Technical Reports Server (NTRS)

    Shariff, Karim; Marten, Ken; Psarakos, Suchi; White, Don J.; Merriam, Marshal (Technical Monitor)

    1996-01-01

    The article discusses how dolphins create and play with three types of air-filled vortices. The underlying physics is discussed. Photographs and sketches illustrating the dolphin's actions and physics are presented. The dolphins engage in this behavior on their own initiative without food reward. These behaviors are done repeatedly and with singleminded effort. The first type is the ejection of bubbles which, after some practice on the part of the dolphin, turn into toroidal vortex ring bubbles by the mechanism of baroclinic torque. These bubbles grow in radius and become thinner as they rise vertically to the surface. One dolphin would blow two in succession and guide them to fuse into one. Physicists call this a vortex reconnection. In the second type, the dolphins first create an invisible vortex ring in the water by swimming on their side and waving their tail fin (also called flukes) vigorously. This vortex ring travels horizontally in the water. The dolphin then turns around, finds the vortex and injects a stream of air into it from its blowhole. The air "fills-out" the core of the vortex ring. Often, the dolphin would knock-off a smaller ring bubble from the larger ring (this also involves vortex reconnection) and steer the smaller ring around the tank. One other dolphin employed a few other techniques for planting air into the fluke vortex. One technique included standing vertically in the water with tail-up, head-down and tail piercing the free surface. As the fluke is waved to create the vortex ring, air is entrained from above the surface. Another technique was gulping air in the mouth, diving down, releasing air bubbles from the mouth and curling them into a ring when they rose to the level of the fluke. In the third type, demonstrated by only one dolphin, the longitudinal vortex created by the dorsal fin on the back is used to produce 10-15 foot long helical bubbles. In one technique she swims in a curved path. This creates a dorsal fin vortex since centrifugal force has to be balanced by a lift-like force. She then re-traces her path and injects air into the vortex from her blowhole. She can even make a ring reconnect from the helix. In the second technique, demonstrated a few times, she again swims in a curved path, releases a cloud or group of bubbles from her blowhole and turns sharply away (Which presumably strengthens the vortex). As the bubbles encounter the vortex, they travel to the center of the vortex, merge and, in a flash, elongate along the core of the vortex. In all the three types, the air-water interface is shiny smooth and stable because the pressure gradient in the vortex flow around the bubble stabilizes it. A lot of the interesting physics still remains to be explored.

  5. Bubble Generation in a Continuous Liquid Flow Under Reduced Gravity Conditions

    NASA Technical Reports Server (NTRS)

    Pais, Salvatore Cezar

    1999-01-01

    The present work reports a study of bubble generation under reduced gravity conditions for both co-flow and cross-flow configurations. Experiments were performed aboard the DC-9 Reduced Gravity Aircraft at NASA Glenn Research Center, using an air-water system. Three different flow tube diameters were used: 1.27, 1.9, and 2.54 cm. Two different ratios of air injection nozzle to tube diameters were considered: 0.1 and 0.2. Gas and liquid volumetric flow rates were varied from 10 to 200 ml/s. It was experimentally observed that with increasing superficial liquid velocity, the bubbles generated decreased in size. The bubble diameter was shown to increase with increasing air injection nozzle diameters. As the tube diameter was increased, the size of the detached bubbles increased. Likewise, as the superficial liquid velocity was increased, the frequency of bubble formation increased and thus the time to detach forming bubbles decreased. Independent of the flow configuration (for either single nozzle or multiple nozzle gas injection), void fraction and hence flow regime transition can be controlled in a somewhat precise manner by solely varying the gas and liquid volumetric flow rates. On the other hand, it is observed that uniformity of bubble size can be controlled more accurately by using single nozzle gas injection than by using multiple port injection, since this latter system gives rise to unpredictable coalescence of adjacent bubbles. A theoretical model, based on an overall force balance, is employed to study single bubble generation in the dynamic and bubbly flow regime. Under conditions of reduced gravity, the gas momentum flux enhances bubble detachment; however, the surface tension forces at the nozzle tip inhibits bubble detachment. Liquid drag and inertia can act either as attaching or detaching force, depending on the relative velocity of the bubble with respect to the surrounding liquid. Predictions of the theoretical model compare well with performed experiments. However, at higher superficial,liquid velocities, the bubble neck length begins to significantly deviate from the value of the air injection nozzle diameter and thus the theory no longer predicts the experiment behavior. Effects of fluid properties, injection geometry and flow conditions on generated bubble size are investigated using the theoretical model. It is shown that bubble diameter is larger in a reduced gravity environment than in a normal gravity environment at similar flow condition and flow geometry.

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

    SciTech Connect

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

    1995-09-01

    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.

  7. Numerical simulations of non-spherical bubble collapse

    PubMed Central

    JOHNSEN, ERIC; COLONIUS, TIM

    2009-01-01

    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 surface pressures are quantified as a function of the pressure ratio driving the collapse and of the initial bubble stand-off distance from the wall; these quantities are compared to the available theory and experiments and show good agreement with the data for both the bubble dynamics and the propagation of the shock emitted upon the collapse. Non-spherical collapse involves the formation of a re-entrant jet directed towards the wall or in the direction of propagation of the incoming shock. In shock-induced collapse, very high jet velocities can be achieved, and the finite time for shock propagation through the bubble may be non-negligible compared to the collapse time for the pressure ratios of interest. Several types of shock waves are generated during the collapse, including precursor and water-hammer shocks that arise from the re-entrant jet formation and its impact upon the distal side of the bubble, respectively. The water-hammer shock can generate very high pressures on the wall, far exceeding those from the incident shock. The potential damage to the neighbouring surface is quantified by measuring the wall pressure. The range of stand-off distances and the surface area for which amplification of the incident shock due to bubble collapse occurs is determined. PMID:19756233

  8. Dissolution Arrest and Stability of Armored Bubbles

    E-print Network

    Manouk Abkarian; Anand Bala Subramaniam; Shin-Hyun Kim; Ryan Larsen; Seung-Man Yang; Howard A. Stone

    2007-03-25

    Dissolving armored bubbles stabilize with nonspherical shapes by jamming the initially Brownian particles adsorbed on their interfaces. In a gas-saturated solution, these shapes are characterized by planar facets or folds for decreasing ratios of the particle to bubble radii. We perform numerical simulations that mimic dissolution, and show that the faceted shape represents a local minimum of energy during volume reduction. This minimum is marked by the vanishing of the Laplace overpressure $\\Delta P$, which together with the existence of a $V$-interval where $d\\Delta P/dV>0$ guarantees stability against dissolution. The reduction of $\\Delta P$ is due to the saddle-shape deformation of most of the interface which accompanies the reduction in the mean curvature of the interface.

  9. CFD simulation of bubble column—An analysis of interphase forces and turbulence models

    Microsoft Academic Search

    Mandar V. Tabib; Swarnendu A. Roy; Jyeshtharaj B. Joshi

    2008-01-01

    3D transient CFD simulations of bubble column have been performed for a wide range of superficial gas velocity on an industrially relevant cylindrical column and the CFD predictions have been compared with the experiments of Menzel et al. [T. Menzel, T. Weide, O. Staudacher, U. Onken, Reynolds stress model for bubble column reactor, Ind. Eng. Chem. Res. 29 (1990) 988–994].

  10. Intrapulmonary small-sized bubble formation is governed by solute-liquid density and airspace geometry

    Microsoft Academic Search

    Emile M. Scarpelli

    1988-01-01

    Small bubbles are formed normally at birth from secreted surfactants and from surfactants within fetal pulmonary liquid. Theoretically, the process can be effectuated both during inspiration and expiration, but the mechanism should predictably vary with respiratory phase: during inspiration the bubbles may form by gas dispersion in liquid where the terminal bronchioles serve as regulators or 'spargers'; during expiration the

  11. Physics of diffuse clouds in the Local Bubble , Part I : the CMa tunnel

    Microsoft Academic Search

    Cecile Gry

    1996-01-01

    We propose to study the physical conditions in diffuse clouds in the Local Bubble environment and their interfaces with the hot gas filling the bubble. , The local interstellar medium presents a favourable situation to check the general ISM theories. Particularly helpfull are lines of sight with low column densities and few or well separated velocity components, which are resolved

  12. Physics of diffuse clouds in the Local Bubble , Part I : the CMa tunnel

    Microsoft Academic Search

    Cecile Gry

    1997-01-01

    We propose to study the physical conditions in diffuse clouds in the Local Bubble environment and their interfaces with the hot gas filling the bubble. , The local interstellar medium presents a favourable situation to check the general ISM theories. Particularly helpfull are lines of sight with low column densities and few or well separated velocity components, which are resolved

  13. Dissolution of carbon dioxide bubbles and microfluidic multiphase flows Ruopeng Sun and Thomas Cubaud*

    E-print Network

    Cubaud, Thomas

    Dissolution of carbon dioxide bubbles and microfluidic multiphase flows Ruopeng Sun and Thomas the dissolution of carbon dioxide bubbles into common liquids (water, ethanol, and methanol) using microfluidic. Introduction Carbon dioxide gas is widespread in natural and industrial processes. At the small scale

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

    Microsoft Academic Search

    J. M. Jurns; J. B. McQuillen

    2008-01-01

    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,

  15. Vol. 22, No. 3, Aug. 1, 2002 Scientists measure energy dissipation in a single cavitating bubble

    E-print Network

    Suslick, Kenneth S.

    -Champaign have now quantified those effects in a single bubble. "During compression, the gas inside the bubble is heated, just like the heating when a tire is pumping up. This energy is converted into light emission applications, such as the breakdown of pollutants, development of medical imaging agents, and making catalysts

  16. HYPOTHESES ON THE ACOUSTICS OF WHALES, DOLPHINS AND PORPOISES IN BUBBLY WATER

    Microsoft Academic Search

    Timothy G. Leighton; D. C. Finfer

    The use made of acoustics for communication and echolocation by cetaceans is well-known. We are also familiar with the ability of gas bubbles in the ocean to complicate and confound human attempts to achieve these tasks for ourselves. Some cetaceans must deal with bubbles as a result of their location (for example as occurs with those species restricted to coastal

  17. Damage mechanisms of suspended animal cells in agitated bioreactors with and without bubble entrainment

    Microsoft Academic Search

    Kurt T. Kunas; Eleftherios T. Papoutsakis

    1990-01-01

    We show that when freely suspended hybridoma cells are cultured in an agitated bioreactor, two fluid- mechanical mechanisms can cause cell damage and growth retardation. The first is present only when there is a gas phase, and is associated with vortex formation accompanied by bubble entrainment and breakup. In the absence of a vortex and bubble entrainment, cells can be

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

    E-print Network

    The Effect of Bubbles on Internal Waves R.H.J.Grimshawa , K.R.Khusnutdinovaa,b March 26, 2002 The influence of gas bubbles on the properties of internal waves in a continuously strati- fied fluid is studied the buoyancy frequency, while the other class is a modified internal wave, whose frequency is less than

  19. Polarizing bubble collisions

    SciTech Connect

    Czech, Bart?omiej; Larjo, Klaus; Levi, Thomas S.; Sigurdson, Kris [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1 (Canada); Kleban, Matthew, E-mail: czech@phas.ubc.ca, E-mail: mk161@nyu.edu, E-mail: larjo@phas.ubc.ca, E-mail: tslevi@phas.ubc.ca, E-mail: krs@phas.ubc.ca [CCPP, Department of Physics, New York University, New York, NY 10003 (United States)

    2010-12-01

    We predict the polarization of cosmic microwave background (CMB) photons that results from a cosmic bubble collision. The polarization is purely E-mode, symmetric around the axis pointing towards the collision bubble, and has several salient features in its radial dependence that can help distinguish it from a more conventional explanation for unusually cold or hot features in the CMB sky. The anomalous ''cold spot'' detected by the Wilkinson Microwave Anisotropy Probe (WMAP) satellite is a candidate for a feature produced by such a collision, and the Planck satellite and other proposed surveys will measure the polarization on it in the near future. The detection of such a collision would provide compelling evidence for the string theory landscape.

  20. Magnetic bubble domain memories

    NASA Technical Reports Server (NTRS)

    Ypma, J. E.

    1974-01-01

    Some attractive features of Bubble Domain Memory and its relation to existing technologies are discussed. Two promising applications are block access mass memory and tape recorder replacement. The required chip capabilities for these uses are listed, and the specifications for a block access mass memory designed to fit between core and HPT disk are presented. A feasibility model for a tape recorder replacement is introduced.

  1. Bubble dynamics in drinks

    NASA Astrophysics Data System (ADS)

    Brou?ková, Zuzana; Trávní?ek, Zden?k; Šafa?ík, Pavel

    2014-03-01

    This study introduces two physical effects known from beverages: the effect of sinking bubbles and the hot chocolate sound effect. The paper presents two simple "kitchen" experiments. The first and second effects are indicated by means of a flow visualization and microphone measurement, respectively. To quantify the second (acoustic) effect, sound records are analyzed using time-frequency signal processing, and the obtained power spectra and spectrograms are discussed.

  2. Giant bubble-pinchoff

    Microsoft Academic Search

    Raymond Bergmann; Devaraj van der Meer; Mark Stijnman; Marijn Sandtke; Andrea Prosperetti; Detlef Lohse

    2006-01-01

    Self-similarity has been the paradigmatic picture for the pinch-off of a drop. Here we will show through high-speed imaging and boundary integral simulations that the inverse problem, the pinch-off of an air bubble in water, does not obey self-similarity (of the first kind): A disk is quickly pulled through a water surface, leading to a giant, cylindrical void, which at

  3. Bubble video experiments in the marine waters off Panarea Island (Italy): real-world data for modelling CO2 bubble dissolution and evolution

    NASA Astrophysics Data System (ADS)

    Beaubien, Stan; De Vittor, Cinzia; McGinnis, Dan; Bigi, Sabina; Comici, Cinzia; Ingrosso, Gianmarco; Lombardi, Salvatore; Ruggiero, Livio

    2014-05-01

    Carbon capture and storage is expected to provide an important, short-term contribution to mitigate global climate change due to anthropogenic emissions of CO2. Offshore reservoirs are particularly favourable, however concerns exist regarding the potential for CO2 leakage into the water column (with possible ecosystem impacts) and the atmosphere. Although laboratory experiments and modelling can examine these issues, the study of natural systems can provide a more complete and realistic understanding. For this reason the natural CO2 emission site off the coast of Panarea Island (Italy) was chosen for study within the EC-funded ECO2 project. The present paper discusses the results of field experiments conducted at this site to better understand the fate of CO2 gas bubbles as they rise through the water column, and to use this real-world data as input to test the predictive capabilities of a bubble model. Experiments were conducted using a 1m wide x 1m deep x 3m tall, hollow-tube structure equipped with a vertical guide on the front face and a dark, graduated cloth for contrast and depth reference on the back. A Plexiglas box was filled with the naturally emitted gas and fixed on the seafloor inside the structure. Tubes exit the top of the box to make bubbles of different diameters, while valves on each tube control bubble release rate. Bubble rise velocity was measured by tracking each bubble with a HD video camera mounted in the guide and calculating values over 20 cm intervals. Bubble diameter was measured by filming the bubbles as they collide with a graduated Plexiglas sheet deployed horizontally at the measurement height. Bubble gas was collected at different heights using a funnel and analysed in the laboratory for CO2, O2+Ar, N2, and CH4. Water parameters were measured by performing a CTD cast beside the structure and collecting water samples at four depths using a Niskin bottle; samples were analysed in the laboratory for all carbonate system species, DO, and dissolved gases. An in-house developed GasPro sensor was also mounted on the structure to monitor pCO2 over the entire 2.5 hour duration of the experiment. The obtained data were used as input into the Discrete Bubble Model (DBM) (e.g., McGinnis et al., 2011, doi:10.1029/2010JC006557). The DBM uses mass balance to predict the gas flux across the bubble surface, whereby gas flux direction depends on internal bubble gas concentration and ambient concentration, and considering the Henry's coefficient and partial pressure of the gas. The model uses bubble-size dependent relationships for the mass transfer rate and the bubble rise velocity. Important model input parameters include: bubble size; depth; ambient dissolved gas concentrations, temperature and salinity; and initial bubble gas concentrations. Measured and modelled results are compared, showing good general agreement. Based on the concentrations measured at the lowest level, the modelled and measured bubble concentrations match very closely. Bubble size values do not match as well if this initial concentration is used, however they improve as a value closer to 100% CO2 is applied. This preliminary study has shown promising results and highlight areas where experimental design and data quality should be improved in the next phase of the study.

  4. Radiation-pressure-driven dust waves inside bursting interstellar bubbles

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

    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?) ? 5.2, form and expand because of the thermal pressure that accompanies the 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, which demonstrates 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 and provide direct evidence that bubbles are relieving their pressure into the interstellar medium through a champagne flow, acting as a probe of the radiative interaction of a massive star with its surroundings. We explore a parameter space connecting the ambient density, the ionizing source luminosity, and the position of the dust wave, while using the well studied H II bubbles RCW 120 and RCW 82 as benchmarks of our model. Finally, we briefly examine the implications of our study for the environments of super star clusters formed in ultraluminous infrared galaxies, merging galaxies, and the early Universe, which occur in very luminous and dense environments and where radiation pressure is expected to dominate the dynamical evolution.

  5. Multiwavelength study of the infrared dust bubble S51

    NASA Astrophysics Data System (ADS)

    Zhang, C. P.; Wang, J. J.

    2012-08-01

    Aims: We investigate the environment of the infrared dust bubble S51 and search for evidence of triggered star formation in its surroundings. Methods: We performed a multiwavelength study of the region around S51 with data taken from large-scale surveys: 2MASS, GLIMPSE, MIPSGAL, IRAS, and MALT90. We analyzed the spectral profile and the distribution of the molecular gas (13CO, C18O, HCN, HNC, HCO+, C2H, N2H+, and HC3N), and dust in the environment of S51. We used a mid-infrared emission three-color image to explore the physical environment and GLIMPSE color - color diagram [5.8]-[8.0] versus [3.6]-[4.5] to search for young stellar objects and identify the ionizing star candidates. Results: From a comparison of the morphology of the molecular gas and the Spitzer 8.0 ?m emission, we conclude that the dust bubble is interacting with CO at a kinematic distance of 3.4 kpc. The bubble S51 structure, carried with shell and front side, is exhibited with 13CO and C18O emission. Both outflow and inflow may exist in sources in the shell of bubble S51. We discover a small bubble G332.646-0.606 (Rin = 26'', rin = 15'', Rout = 35'' and rout = 25'') located at the northwest border of S51. A water maser, a methanol maser, and IRAS 16158-5055 are located at the junction of the two bubbles. Several young stellar objects are distributed along an arc-shaped structure near the S51 shell. They may represent a second generation of stars whose formation was triggered by the bubble expanding into the molecular gas.

  6. A mechanics approach for wet gas flow metering, theory and application to flow loop tests

    Microsoft Academic Search

    Cadalen Sébastien; Lance Michel

    2011-01-01

    New technology combined to the rise of the barrel price make wet gas flow metering of primary importance. A Venturi and a multienergy gamma ray hold-up meter provide capital information to estimate gas and liquid flow rates with the required metering accuracy. Starting from Navier–Stokes’ equations, the two-phase flow is modeled with a three 1D equations system for gas, liquid

  7. Liquid/Gas Vortex Separator

    NASA Technical Reports Server (NTRS)

    Morris, B. G.

    1986-01-01

    Liquid/gas separator vents gas from tank of liquid that contains gas randomly distributed in bubbles. Centrifugal force separates liquid and gas, forcing liquid out of vortex tube through venturi tube. Gas vented through exhaust port. When liquid detected in vent tube, exhaust port closed, and liquid/gas mixture in vent tube drawn back into tank through venturi.

  8. In Search of the Big Bubble

    ERIC Educational Resources Information Center

    Simoson, Andrew; Wentzky, Bethany

    2011-01-01

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

  9. Acoustic Measurements Bubbles in Biological Tiessure

    Microsoft Academic Search

    Georges L. CHAHINE; Michel TANGUAY; Greg LORAINE

    2009-01-01

    An acoustic based instrument, the ABS Acoustic Bubble Spectrometer®© (ABS), was investigated for the detection and quantification of bubbles in biological media. These include viscoelastic media (blood), materials of varying density (bone in tissue), non-homogenous distribution of bubbles (intravenous bubbly flow), and bubbles migrating in tissue (decompression sickness, DCS). The performance of the ABS was demonstrated in a series of

  10. Transmission Electron Microscopy Investigation of Krypton Bubbles in Polycrystalline CeO2

    SciTech Connect

    Lingfeng He; Clarissa Yablinsky; Mahima Gupta; Jian Gan; Marquis A. Kirk; Todd R. Allen

    2013-05-01

    To gain an understanding of gas bubble transport in oxide nuclear fuel, this paper uses polycrystalline CeO2, composed of both nanograins and micrograins, as a surrogate material for UO2. The CeO2 was implanted with 150-keV Kr ions up to a dose of 1 x 1016 ions/cm2 at 600 degrees C. Transmission electron microscopy characterizations of small Kr bubbles in nanograin and micrograin regions were compared. The grain boundary acted as an efficient defect sink, as evidenced by smaller bubbles and a lower bubble density in the nanograin region as compared to the micrograin region.

  11. A Comparison of Underwater Bubble Continuous Positive Airway Pressure with Ventilator-Derived Continuous Positive Airway Pressure in Premature Neonates Ready for Extubation

    Microsoft Academic Search

    Kyong-Soon Lee; Michael S. Dunn; Marsha Fenwick; Andrew T. Shennan

    1998-01-01

    Objective and methods: As the result of vigorous bubbling, infants receiving continuous positive airway pressure (CPAP) by an underwater seal (bubble CPAP) were observed to have vibrations of their chests at frequencies similar to high-frequency ventilation (HFV). We performed a randomized crossover study in 10 premature infants ready for extubation to test whether bubble CPAP contributes to gas exchange compared

  12. Fluid bubble eliminator

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

    A gas-liquid separator uses a helical passageway to impart a spiral motion to a fluid passing therethrough. The centrifugal fore generated by the spiraling motion urges the liquid component of the fluid radially outward which forces the gas component radially inward. The gas component is then filtered through a gas-permeable, liquid-impervious membrane and discharged through a central passageway.

  13. Fluid Bubble Eliminator

    NASA Technical Reports Server (NTRS)

    Gonda, Steve R. (Inventor); Tsao, Yow-Min (Inventor); Lee, Wenshan (Inventor)

    2005-01-01

    A gas-liquid separator uses a helical passageway to impart a spiral motion to a fluid passing therethrough. The centrifugal fore generated by the spiraling motion urges the liquid component of the fluid radially outward which forces the gas component radially inward. The gas component is then filtered through a gas-permeable, liquid-impervious membrane and discharged through a central passageway.

  14. SPRITE MRI of bubbly flow in a horizontal pipe

    NASA Astrophysics Data System (ADS)

    Sankey, Mark; Yang, Zhi; Gladden, Lynn; Johns, Michael L.; Lister, Derek; Newling, Benedict

    2009-08-01

    Bubble flow is characterised by numerous phase interfaces and turbulence, leading to fast magnetic resonance signal decay and artefacts in spin-warp imaging. In this paper, the SPRITE MRI pulse sequence, with its potential for very short encoding times, is demonstrated as an ideal technique for studying such dynamic systems. It has been used to acquire liquid velocity and relative intensity maps of two-phase gas-liquid dispersed bubble flow in a horizontal pipe at a liquid Reynolds number of 14,500. The fluids were air and water and a turbulence grid was used to generate a dispersed bubble flow pattern. The SPRITE technique shows promise for future research in gas-liquid flow.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  16. Sounds of marine seeps: a study of bubble activity near a rigid boundary.

    PubMed

    Maksimov, A O; Burov, B A; Salomatin, A S; Chernykh, D V

    2014-09-01

    A passive acoustic method for detecting environmentally dangerous gas leaks from pipelines and methane naturally leaking from the seabed has been investigated. Gas escape involves the formation and release of bubbles of different sizes. Each bubble emits a sound at a specific frequency. Determination of the bubble radius from the frequency of its signature passive acoustic emission by use of so-called Minnaert formula has a restricted area of applicability near the seabed. The point is that the inertial mass and the damping constant of the birthing bubble are markedly different from those of a free bubble. The theoretical model for the bubble volume oscillations near the seabed has been proposed and an analytical solution has been derived. It was shown that the bispherical coordinates provide separation of variables and are more suitable for analysis of the volume oscillations of these constrained bubbles. Explicit formulas have been derived, which describe the dependence of the bubble emission near a rigid wall on its size and the separation distance between the bubble and the boundary. PMID:25190382

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

    NASA Astrophysics Data System (ADS)

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

    2011-04-01

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

  18. Effect of gas liquid separator and liquid height on the global hydrodynamic parameters of an external loop airlift contactor

    Microsoft Academic Search

    Chafaa Bentifraouine; Catherine Xuereb; Jean-Pierre Riba

    1997-01-01

    This study is devoted to the measurement of global hydrodynamic characteristics (gas hold-up and liquid circulating velocity) of an external loop airlift contactor filled with tap water, with different conditions for phase separation and for liquid height. It is shown that these two operating parameters have a great influence on the behaviour of the airlift reactor. These parameters generally are

  19. Effects of liquid helium bubble formation in a superconducting cavity cryogenic system

    SciTech Connect

    Chang, X.; Wang, E.; Xin, T.

    2011-03-01

    We constructed a simple prototype model based on the geometry of the 56 MHz superconducting cavity for RHIC. We studied the formation, in this prototype, of bubbles of liquid helium and their thermal effects on the cavity. We found that due to the low viscosity of the liquid helium, and its small surface tension, no large bubbles formed. The tiny bubbles, generated from most of the area, behaved like light gas travelling in a free space and escaped from the trapping region. The bubbles that were generated in the trapping area, due to its descending geometry, are much bigger than the other bubbles, but due to the liquid flow generated by heating, they still are negligible compared to the size of the trapping region. We expected that the effects of bubbles in our 56 MHz cavity during operation might well be negligible.

  20. Domain Walls and Double Bubbles

    E-print Network

    Mike Gillard; Paul Sutcliffe

    2009-03-30

    We study configurations of intersecting domain walls in a Wess-Zumino model with three vacua. We introduce a volume-preserving flow and show that its static solutions are configurations of intersecting domain walls that form double bubbles, that is, minimal area surfaces which enclose and separate two prescribed volumes. To illustrate this field theory approach to double bubbles, we use domain walls to reconstruct the phase diagram for double bubbles in the flat square two-torus and also construct all known examples of double bubbles in the flat cubic three-torus.

  1. Helium bubble bursting in tungsten

    SciTech Connect

    Sefta, Faiza [University of California, Berkeley, California 94720 (United States); Juslin, Niklas [University of Tennessee, Knoxville, Tennessee 37996 (United States); Wirth, Brian D., E-mail: bdwirth@utk.edu [University of Tennessee, Oak Ridge National Laboratory, Knoxville, Tennessee 37996 (United States)

    2013-12-28

    Molecular dynamics simulations have been used to systematically study the pressure evolution and bursting behavior of sub-surface helium bubbles and the resulting tungsten surface morphology. This study specifically investigates how bubble shape and size, temperature, tungsten surface orientation, and ligament thickness above the bubble influence bubble stability and surface evolution. The tungsten surface is roughened by a combination of adatom “islands,” craters, and pinholes. The present study provides insight into the mechanisms and conditions leading to various tungsten topology changes, which we believe are the initial stages of surface evolution leading to the formation of nanoscale fuzz.

  2. Quenching Cluster Cooling Flows with Recurrent Hot Plasma Bubbles

    E-print Network

    Claudio Dalla Vecchia; Richard Bower; Tom Theuns; Michael Balogh; Pasquale Mazzotta; Carlos S. Frenk

    2004-09-07

    The observed cooling rate of hot gas in clusters is much lower than that inferred from the gas density profiles. This suggests that the gas is being heated by some source. We use an adaptive-mesh refinement code (FLASH) to simulate the effect of multiple, randomly positioned, injections of thermal energy within 50 kpc of the centre of an initially isothermal cluster with mass M_200=3x10^(14) Msol and kT=3.1 keV. We have performed eight simulations with spherical bubbles of energy generated every 10^8 years, over a total of 1.5 Gyr. Each bubble is created by injecting thermal energy steadily for 10^7 years; the total energy of each bubble ranges from 0.1--3x10^(60) erg, depending on the simulation. We find that 2x10^(60) erg per bubble (corresponding to a average power of 6.3x10^(44) erg/s) effectively balances energy loss in the cluster and prevents the accumulation of gas below kT=1 keV from exceeding the observational limits of 30 Msol/yr. This injection rate is comparable to the radiated luminosity of the cluster, and the required energy and periodic timescale of events are consistent with observations of bubbles produced by central AGN in clusters. The effectiveness of this process depends primarily on the total amount of injected energy and the initial location of the bubbles, but is relatively insensitive to the exact duty cycle of events.

  3. Cosmic Bubble Image Wins NRAO Contest

    NASA Astrophysics Data System (ADS)

    2006-10-01

    A striking image of an enormous bubble blown into the dusty gas disk of our own Milky Way galaxy has won first place in the National Radio Astronomy Observatory's second annual Radio Astronomy Image Contest. Dr. Jayanne English of the University of Manitoba led the team that made the winning image using data from the National Science Foundation's Very Large Array (VLA) in New Mexico and Robert C. Byrd Green Bank Telescope (GBT) in West Virginia. Cosmic Bubble Image Giant "Bubble" in Milky Way's Gas CREDIT: English et al., NRAO/AUI/NSF Click on image for large files and full information English and her collaborators Jeroen Stil and Russ Taylor, from the University of Calgary, will share the grand prize of $1,000 from Associated Universities, Inc., the research corporation that operates the observatory for the NSF. "We congratulate Dr. English for producing an outstanding image that beautifully illustrates the power of our radio telescopes," said NRAO Director Fred K.Y. Lo. The image contest is part of a broader NRAO effort to make radio astronomical data and images easily accessible and widely available to scientists, students, teachers, the general public, news media and science-education professionals. That effort includes an expanding image gallery on the observatory's Web site. English's winning image shows a giant bubble in the Milky Way's dusty gas disk. The bubble has been sculpted by the wind and radiation force from a few dozen hot, massive stars along with the explosive force of supernova explosions from dying stars. The bubble, seen in the faint radio glow of hydrogen gas, is some 30,000 light-years from Earth and measures 1,100 by 520 light-years. If the bubble, in the constellation Vulpecula, were visible to human eyes, it would appear to be eight times the diameter of the full Moon in the sky. The image was made using data collected as part of the VLA Galactic Plane Survey (VGPS), a set of systematic observations of the Milky Way. This survey, led by Taylor, required about 3,000 separate VLA observations taking 260 hours, augmented by data from the GBT. The VGPS is part, along with the Canadian Galactic Plane Survey and the Southern Galactic Plane Survey, of an international effort to produce a detailed atlas of our home Galaxy as seen by radio telescopes. Second place in the contest went to Fabian Walter of the Max Planck Institute for Astrophysics in Heidelberg, Germany, for a collection of galaxy images. Honorable Mentions were awarded to Michael Bietenholz of York University in Canada, Joeri van Leeuwen of the University of British Columbia, Neal Miller of NRAO and the Johns Hopkins University, and Yurii Pidopryhora of NRAO and Ohio University. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

  4. Dynamic Bubble Behaviour during Microscale Subcooled Boiling

    NASA Astrophysics Data System (ADS)

    Wang, Hao; Peng, Xiao-Feng; David, Christopher M.

    2005-11-01

    Bubble cycles, including initiation, growth and departure, are the physical basis of nucleate boiling. The present investigation, however, reveals unusual bubble motions during subcooled nucleate boiling on microwires 25 or 100 ?m in diameter. Two types of bubble motions, bubble sweeping and bubble return, are observed in the experiments. Bubble sweeping describes a bubble moving back and forth along the wire, which is motion parallel to the wire. Bubble return is the bubble moving back to the wire after it has detached or leaping above the wire. Theoretical analyses and numerical simulations are conducted to investigate the driving mechanisms for both bubble sweeping and return. Marangoni flow from warm to cool regions along the bubble interface is found to produce the shear stresses needed to drive these unusual bubble movements.

  5. HOLDUP MEASUREMENTS FOR THREE VISUAL EXAMINATION AND TRU REMEDIATION GLOVEBOX FACILITIES AT THE SAVANNAH RIVER SITE

    SciTech Connect

    Dewberry, R; Donald Pak, D

    2007-05-04

    Visual Examination (VE) gloveboxes are used to remediate transuranic waste (TRU) drums at three separate facilities at the Savannah River Site. Noncompliant items are removed before the drums undergo further characterization in preparation for shipment to the Waste Isolation Pilot Plant (WIPP). Maintaining the flow of drums through the remediation process is critical to the program's seven-days-per-week operation. Conservative assumptions are used to ensure that glovebox contamination from this continual operation is below acceptable limits. Holdup measurements using cooled HPGe spectrometers are performed in order to confirm that these assumptions are conservative. {sup 239}Pu is the main nuclide of interest; however, {sup 241}Pu, equilibrium {sup 237}Np/{sup 233}Pa and {sup 238}Pu (if detected) are typically assayed. At the Savannah River National Laboratory (SRNL) facility {sup 243,244,245}Cm are also generally observed and are always reported at either finite levels or at limits of detection. A complete assay at each of the three facilities includes a measure of TRU content in the gloveboxes and HEPA filters in the glovebox exhaust. This paper includes a description of the {gamma}-PHA acquisitions, of the modeling, and of the calculations of nuclide content. Because each of the remediation facilities is unique and ergonomically unfavorable to {gamma}-ray acquisitions, we have constructed custom detector support devices specific to each set of acquisitions. This paper includes a description and photographs of these custom devices. The description of modeling and calculations include determination and application of container and matrix photon energy dependent absorption factors and also determination and application of geometry factors relative to our detector calibration geometry. The paper also includes a discussion of our measurements accuracy using off-line assays of two SRNL HEPA filters. The comparison includes assay of the filters inside of 55-gallon drums using the SRNL Q{sup 2} assay system and separately using off-line assay with an acquisition configuration unique from the original in-situ acquisitions.

  6. Sponge Cake or Champagne? Bubbles, Magmatic Degassing and Volcanic Eruptions

    NASA Astrophysics Data System (ADS)

    Cashman, K.; Pioli, L.; Belien, I.; Wright, H.; Rust, A.

    2007-12-01

    Vesiculation is an unavoidable consequence of magma decompression; the extent to which bubbles travel with ascending magma or leave the system by separated or permeable flow will determine the nature of the ensuing eruption. Bubbles travel with the melt from which they exsolve if the rise time of bubbles through the melt (the 'drift velocity') is much less than the rise rate of the magma (sponge cake). This condition is most likely to be met in viscous melts (where bubble rise velocities are low) and in melts that experience rapid decompression (high ascent velocities). Under these conditions, bubble expansion within the melt continues until sufficient bubble expansion causes coalescence and the development of a permeable network. Typical pumice vesicularities of 70-80% and permeabilities of 10-12 m2 constrain this limit under conditions appropriate for subplinian to plinian eruptions (mass fluxes > 106 kg/s). Slower rise rates (and lower mass fluxes) that characterize effusive eruptions produce silicic lavas with a wider range of vesicularities. In general, permeability decreases with decreasing sample vesicularity as bubbles deform (as evidenced by anisotropy in permeability and electrical conductivity) and pore apertures diminish. Degassing efficiency (and resulting densification of magma within the conduit) under these conditions is determined by permeability and the time allowed for gas escape. Bubbles rise through the melt if the drift velocity exceeds the velocity of magma ascent (champagne). This condition is most easily met in volatile-rich, low viscosity (mafic) melts at low to moderate fluxes. At very low magma flux, magma eruption rate is determined by the extent to which magma is entrained and ejected by rising gases (strombolian eruptions); when bubbles are too small, or are rising too slowly, they may not break the surface at all, but instead may be concentrated in a near-surface layer (surface foam). As the magma flux increases, segregation of bubble-rich from bubble-poor melt requires both longer conduits and lateral transport of degassed magma, as seen in violent strombolian eruptions. Flow transitions require coalescence, which is a dynamic process where bubble-bubble interactions are controlled by shear and gravitational (i.e. buoyancy) processes, both of which are strongly dependent on magma rheology. Also common in basaltic magmas that exhibit separated flow are by the simultaneous eruption of crystal-rich (shallow) and crystal-poor (deep) magmas. Upward increases in crystal content within the magma transport system will create rheological changes that may both slow upward bubble migration and change the size and shape of the bubble network (through deformation, coalescence, or bubble splitting). Preliminary experiments further show that abrupt rheological boundaries may concentrate bubbles at the boundary, allowing them to coalesce and move laterally prior to rising through the mush.

  7. Bubble levitation and translation under single-bubble sonoluminescence conditions.

    PubMed

    Matula, Thomas J

    2003-08-01

    Bubble levitation in an acoustic standing wave is re-examined for conditions relevant to single-bubble sonoluminescence. Unlike a previous examination [Matula et al., J. Acoust. Soc. Am. 102, 1522-1527 (1997)], the stable parameter space [Pa,R0] is accounted for in this realization. Forces such as the added mass force and drag are included, and the results are compared with a simple force balance that equates the Bjerknes force to the buoyancy force. Under normal sonoluminescence conditions, the comparison is quite favorable. A more complete accounting of the forces shows that a stably levitated bubble does undergo periodic translational motion. The asymmetries associated with translational motion are hypothesized to generate instabilities in the spherical shape of the bubble. A reduction in gravity results in reduced translational motion. It is hypothesized that such conditions may lead to increased light output from sonoluminescing bubbles. PMID:12942960

  8. A bubbling bolt

    E-print Network

    Guillaume Bossard; Stefanos Katmadas

    2014-05-16

    We present a new solvable system, solving the equations of five-dimensional ungauged N=1 supergravity coupled to vector multiplets, that allows for non-extremal solutions and reduces to a known system when restricted to the floating brane Ansatz. A two-centre globally hyperbolic smooth geometry is obtained as a solution to this system, describing a bubble linking a Gibbons--Hawking centre to a charged bolt. However this solution turns out to violate the BPS bound, and we show that its generalisation to an arbitrary number of Gibbons--Hawking centres never admits a spin structure.

  9. A bubbling bolt

    E-print Network

    Bossard, Guillaume

    2014-01-01

    We present a new solvable system, solving the equations of five-dimensional ungauged N=1 supergravity coupled to vector multiplets, that allows for non-extremal solutions and reduces to a known system when restricted to the floating brane Ansatz. A two-centre globally hyperbolic smooth geometry is obtained as a solution to this system, describing a bubble linking a Gibbons--Hawking centre to a charged bolt. However this solution turns out to violate the BPS bound, and we show that its generalisation to an arbitrary number of Gibbons--Hawking centres never admits a spin structure.

  10. Bubble Coalescence DOI: 10.1002/anie.201006552

    E-print Network

    Chan, Derek Y C

    H-Controlled Bubble Coalescence** Rico F. Tabor, Derek Y. C. Chan, Franz Grieser, and Raymond R. Dagastine* Gas, due to its high water-solubility and unusual aqueous chemistry, carbon dioxide may be expected are the experimental data, and solid black lines are the model prediction. Dseparation is defined as the change

  11. Bubble breakup from ventilated cavities in multiphase reactors

    Microsoft Academic Search

    G. D. Rigby; G. M. Evans; G. J. Jameson

    1997-01-01

    A study of the small bubbles created by gas dispersion mechanisms at the rear of a ventilated cavity attached to a cylindrical bluff body is presented. A critical Weber number model, which uses a CFD simulation of the continuous-phase flow field to simulate the rate of energy dissipation at the rear of the cavity, is proposed to allow prediction of

  12. In vivo bubble nucleation probability in sheep brain tissue

    Microsoft Academic Search

    J. Gateau; J.-F. Aubry; D. Chauvet; A.-L. Boch; M. Fink; M. Tanter

    2011-01-01

    Gas nuclei exist naturally in living bodies. Their activation initiates cavitation activity, and is possible using short ultrasonic excitations of high amplitude. However, little is known about the nuclei population in vivo, and therefore about the rarefaction pressure required to form bubbles in tissue. A novel method dedicated to in vivo investigations was used here that combines passive and active

  13. Dynamics of a Tethered Bubble Alexey O. Maksimov 1

    E-print Network

    Sóbester, András

    printing, casting, coating and electroplating. The behavior of a gas bubbles tethered to a rigid plane boundary in an oscillatory pressure field is investigated by use conformal symmetry of the problem adhering to solids occur in a range of manufacturing processes, including printing, casting, coating

  14. Self-assembling bubble carriers for oral protein delivery.

    PubMed

    Chuang, Er-Yuan; Lin, Kun-Ju; Lin, Po-Yen; Chen, Hsin-Lung; Wey, Shiaw-Pyng; Mi, Fwu-Long; Hsiao, Hsu-Chan; Chen, Chiung-Tong; Sung, Hsing-Wen

    2015-09-01

    Successful oral delivery of therapeutic proteins such as insulin can greatly improve the quality of life of patients. This study develops a bubble carrier system by loading diethylene triamine pentaacetic acid (DTPA) dianhydride, a foaming agent (sodium bicarbonate; SBC), a surfactant (sodium dodecyl sulfate; SDS), and a protein drug (insulin) in an enteric-coated gelatin capsule. Following oral administration to diabetic rats, the intestinal fluid that has passed through the gelatin capsule saturates the mixture; concomitantly, DTPA dianhydride produces an acidic environment, while SBC decomposes to form CO2 bubbles at acidic pH. The gas bubbles grow among the surfactant molecules (SDS) owing to the expansion of the generated CO2. The walls of the CO2 bubbles consist of a self-assembled film of water that is in nanoscale and may serve as a colloidal carrier to transport insulin and DTPA. The grown gas bubbles continue to expand until they bump into the wall and burst, releasing their transported insulin, DTPA, and SDS into the mucosal layer. The released DTPA and SDS function as protease inhibitors to protect the insulin molecules as well as absorption enhancers to augment their epithelial permeability and eventual absorption into systemic circulation, exerting their hypoglycemic effects. PMID:26132436

  15. Optimization of an augmented Prosperetti-Lezzi bubble model.

    PubMed

    Geers, Thomas L

    2014-07-01

    Three enhancements are introduced for predicting the violent collapse and rebound of a spherical bubble with the matched-asymptotic-expansion model of Prosperetti and Lezzi [(1986). J. Fluid Mech. 168, 457-478]. The first introduces spatial variation of the pressure field inside the bubble. It derives from the perturbation analysis of the interior Euler equations begun by Geers et al. [(2012). J. Appl. Phys. 112, 054910]. The second enhancement augments the Prosperetti and Lezzi equation with a term that accounts for the kinetic energy of the bubble gas, while the third provides an optimum value for the free variable appearing in that equation. The optimum value emerges from a comparison of peak pressures predicted by the augmented equation with corresponding results generated by finite-difference simulations based on transformed Euler equations for both the bubble gas and the surrounding liquid [Geers et al. (2012). J. Appl. Phys. 112, 054910]. The three enhancements considerably extend the range of applicability of a single-degree-of-freedom bubble model. PMID:24993193

  16. HEU Measurements of Holdup and Recovered Residue in the Deactivation and Decommissioning Activities of the 321-M Reactor Fuel Fabrication Facility at the Savannah River Site

    SciTech Connect

    DEWBERRY, RAYMOND; SALAYMEH, SALEEM R.; CASELLA, VITO R.; MOORE, FRANK S.

    2005-03-11

    This paper contains a summary of the holdup and material control and accountability (MC&A) assays conducted for the determination of highly enriched uranium (HEU) in the deactivation and decommissioning (D&D) of Building 321-M at the Savannah River Site (SRS). The 321-M facility was the Reactor Fuel Fabrication Facility at SRS and was used to fabricate HEU fuel assemblies, lithium-aluminum target tubes, neptunium assemblies, and miscellaneous components for the SRS production reactors. The facility operated for more than 35 years. During this time thousands of uranium-aluminum-alloy (U-Al) production reactor fuel tubes were produced. After the facility ceased operations in 1995, all of the easily accessible U-Al was removed from the building, and only residual amounts remained. The bulk of this residue was located in the equipment that generated and handled small U-Al particles and in the exhaust systems for this equipment (e.g., Chip compactor, casting furnaces, log saw, lathes A & B, cyclone separator, Freon{trademark} cart, riser crusher, ...etc). The D&D project is likely to represent an important example for D&D activities across SRS and across the Department of Energy weapons complex. The Savannah River National Laboratory was tasked to conduct holdup assays to quantify the amount of HEU on all components removed from the facility prior to placing in solid waste containers. The U-235 holdup in any single component of process equipment must not exceed 50 g in order to meet the container limit. This limit was imposed to meet criticality requirements of the low level solid waste storage vaults. Thus the holdup measurements were used as guidance to determine if further decontamination of equipment was needed to ensure that the quantity of U-235 did not exceed the 50 g limit and to ensure that the waste met the Waste Acceptance Criteria (WAC) of the solid waste storage vaults. Since HEU is an accountable nuclear material, the holdup assays and assays of recovered residue were also important for material control and accountability purposes. In summary, the results of the holdup assays were essential for determining compliance with the Waste Acceptance Criteria, Material Control & Accountability, and to ensure that administrative criticality safety controls were not exceeded. This paper discusses the {gamma}-ray assay measurements conducted and the modeling of the acquired data to obtain measured holdup in process equipment, exhaust components, and fixed geometry scrap cans. It also presents development work required to model new acquisition configurations and to adapt available instrumentation to perform the assays.

  17. Helium Bubble Behaviour in b.c.c. Metals Below 0.65T_m

    Microsoft Academic Search

    P. J. Goodhew; S. K. Tyler

    1981-01-01

    We have considered the methods available for distinguishing between the rate-controlling mechanisms for gas bubble migration in metals at temperatures below 0.6T_m. We show that several combinations of mechanism, gas behaviour and rate-controlling process give rise to similar power laws describing the rate of growth of populations of bubbles by migration and coalescence. We have therefore extended the model developed

  18. Why Are Bubbles So Colorful?

    NSDL National Science Digital Library

    Optical Society of America

    2008-01-01

    In this activity, learners explore why they can see colors in bubbles and why they change. Learners also examine what thin slits do to light and how this phenomenon is similar to that of bubbles and oil slicks. Note: This activity works best outside in the sunlight.

  19. A prediction for bubbling geometries

    E-print Network

    Takuya Okuda

    2008-02-11

    We study the supersymmetric circular Wilson loops in N=4 Yang-Mills theory. Their vacuum expectation values are computed in the parameter region that admits smooth bubbling geometry duals. The results are a prediction for the supergravity action evaluated on the bubbling geometries for Wilson loops.

  20. Bubble detector investigations in China.

    PubMed

    Guo, Shi-Lun

    2006-01-01

    Investigation on bubble detectors started in China in 1989. Five types of bubble detectors have been developed, with LET thresholds ranging from 0.05 to 6.04 MeV mg(-1) cm(2) at 25 degrees C. The neutron response of bubble detectors made with freon-12 has been investigated with mono-energetic neutrons from 20 keV to 19 MeV. Its effective threshold energy for neutron detection is approximately 100 keV at 28 degrees C. The response above this threshold is approximately 1.5 x 10(-4) (bubble cm(-2))/(n cm(-2)). Bubble detectors are unique not only for neutron dosimetry but also for monitoring and identifying high-energy heavy ions such as cosmic radiation in the space. High-energy heavy ion tracks in large size bubble detectors have been investigated in cooperation with scientists in Japan. The key parameter behind the thresholds of bubble detectors for track registration is the critical rate of energy loss. Three approaches to identify high-energy heavy ions with bubble detectors are suggested. PMID:16782985

  1. X-ray computed tomography of peat soils: measuring gas content and peat structure

    Microsoft Academic Search

    Nicholas Kettridge; Andrew Binley

    2008-01-01

    The potential of using X-ray computed tomography (CT) to (i) analyse individual biogenic gas bubbles entrapped within peats and (ii) produce reliable descriptors of peat structure is examined. Existing approaches used to study biogenic gas bubbles measure the gas content of volumes of peat many orders of magnitude larger than most bubbles, and are, therefore, of little use in helping

  2. Bubble dynamics in N dimensions

    NASA Astrophysics Data System (ADS)

    Klotz, Alexander R.

    2013-08-01

    Cavitation and bubble dynamics are central concepts in engineering, the natural sciences, and the mathematics of fluid mechanics. Due to the nonlinear nature of their dynamics, the governing equations are not fully solvable. Here, the dynamics of a spherical bubble in an N-dimensional fluid are discussed in the hope that examining bubble behavior in N dimensions will add insight to their behavior in three dimensions. Several canonical results in bubble dynamics are re-derived, including the Rayleigh collapse time, the Rayleigh-Plesset equation, and the Minnaert frequency. Recent analytical approximations to the Rayleigh collapse are discussed, and the N-dimensional generalization is used to resolve a known discrepancy. Numerical simulations are used to examine the onset of nonlinear behavior. Overall, the dynamics of bubbles are faster at higher dimensions, with nonlinear behavior occurring at lower strain. Several features are found to be unique to three dimensions, including the trend of nonlinear behavior and apparent coincidences in timescales.

  3. A theoretical model for fragmentation of viscous bubbly magmas in shock tubes

    NASA Astrophysics Data System (ADS)

    Koyaguchi, T.; Mitani, N. K.

    2005-10-01

    A coupled model for one-dimensional time-dependent compressible flow and bubble expansion is developed to investigate fragmentation mechanisms of viscous bubbly magmas in shock tubes. Initially a bubbly magma at a high pressure is separated from air at the atmospheric pressure by a diaphragm. As the diaphragm is ruptured, a shock wave propagates into the air, and a rarefaction wave propagates into the bubbly magma. As a result, the bubbly magma is decompressed and expands. Gas overpressure and hoop stress around expanding bubbles are calculated by applying the cell model. It is assumed that the magma fragments and the flow changes from bubbly flow to gas-pyroclast dispersion when the hoop stress or the gas volume fraction reaches a given threshold. Two types of fragmentation mechanisms are recognized: (1) high-viscosity magma fragments as the hoop stress reaches the tensile strength of the melt (stress fragmentation) and (2) the hoop stress does not grow in low-viscosity magma so that fragmentation occurs after bubble expansion when the gas volume fraction reaches a threshold (expansion fragmentation). During stress fragmentation a zone of steep pressure gradient forms just behind the fragmentation surface, which propagates into the magma together with the fragmentation surface. Analytical considerations suggest that the self-sustained stress fragmentation process can be described by a combination of a traveling-wave-type solution in the bubbly flow region and a self-similar solution in the gas-pyroclast flow region. Some simple formulae to predict the fragmentation speed (downward propagation velocity of the fragmentation surface) are derived on the basis of these solutions. The formulae are applied to recent experimental results using shock tube techniques as well as Vulcanian explosions in nature.

  4. The disappearance of ultrasound contrast bubbles: observations of bubble dissolution and cavitation nucleation.

    PubMed

    Chen, Wen Shiang; Matula, Thomas J; Crum, Lawrence A

    2002-06-01

    The destruction process of biSphere and Optison ultrasound (US) contrast microbubbles were studied at 1.1 MHz. High-amplitude tone bursts caused shell disruption and/or fragmentation of the microbubbles, leading to dissolution of the freed gas. The bubble destruction and subsequent dissolution process was imaged with a high pulse-repetition frequency (PRF) 10-cycle, 5-MHz bistatic transducer configuration. Three types of dissolution profiles were measured: In one case, biSphere microbubbles showed evidence of dissolution through resonance, during which a temporary increase in the scattering amplitude was observed. In another case, both biSphere and Optison microbubbles showed evidence of fragmentation, during which the scattering amplitude decreased rapidly. Finally, in some cases, we observed the impulsive growth and subsequent rapid decay of signals that appear to be due to cavitation nucleation. Simulations of bubble dissolution curves show good agreement with experiments. PMID:12113792

  5. Utilization of minute-bubble technique on crystallization: Application to antisolvent crystallization of sodium chloride

    NASA Astrophysics Data System (ADS)

    Wada, Yoshinari; Matsumoto, Masakazu; Onoe, Kaoru

    2013-06-01

    A crystallization technique to accelerate the nucleation of NaCl crystals utilizing local supersaturation regions around the gas-liquid interfaces of nitrogen (N2) minute-bubbles was developed. The effects of N2 bubble supply and minimizing bubble diameter on antisolvent crystallization phenomena of NaCl were examined. The initial concentration of NaCl in the saturated solution was set at 5.50 mol/l, and ethanol (EtOH) was added as an antisolvent to the saturated NaCl solution where the added volume ratio of EtOH became 10 vol%. N2 minute-bubbles with an average bubble diameter (dbbl) of 40 ?m were continuously supplied to the suspended solution using a self-supporting bubble generator, and NaCl was crystallized. Furthermore, dbbl was varied in the range of 100-2000 ?m by changing the hole size (5-120 ?m) on the gas dispersion plate using a dispersing-type bubble generator. Consequently, the average size of NaCl crystals while supplying N2 minute-bubbles was about 7 ?m at 1 min crystallization and almost same profile in size distribution was obtained independent of the crystallization time. When minute-bubbles were not supplied, the average size was shifted up to 13 ?m and the size distribution width was expanded in comparison with that obtained under supplying N2 minute-bubbles. The supply of minute-bubbles at a dbbl of 40 ?m into antisolvent crystallization of NaCl is effective in obtaining fine crystals with narrow distribution width.

  6. Microgravity Experiments on Bubble Removal in the Hydrodynamic Focusing Bioreactor - Space (HFB-S)

    NASA Technical Reports Server (NTRS)

    Nahra, H. K.; Niederhaus, C. E.; Robinson, S.; Hudson, E.; Geffert, S. K.; Lupo, P. J.; Gonda, S. R.; Kleis, S. J.; Kizito, J. P.

    2005-01-01

    The Hydrodynamic Focusing Bioreactor-Space (HFB-S) is being developed as a possible replacement for the Rotating Wall Perfused Vessel (RWPV) bioreactor currently planned for use on the International Space Station (ISS). The HFB-S is being developed with the ability to remove gas bubbles that may inadvertently enter the system during long duration experiments (approx. 1-3 months). The RWPV has been used in the past with great success on Shuttle flights and Mir missions, but has occasionally experienced problems with gas bubbles entering the fluid-filled vessel. These bubbles are harmful to the cell science, and bubble removal in the RWPV is problematic. The HFB-S has an access port on the rotation axis that allows for bubble removal under specific operating conditions without detrimentally affecting the cell tissue. Experiments on bubble removal with the HFB-S were conducted in the microgravity environment on NASA's KC-135 Reduced Gravity Aircraft. The first set of flights provided useful data on bubble trajectories that are validating computational predictions. The second set of flights free-floated the apparatus and tested the most recent configuration of the bioreactor while focusing on the bubble removal process itself. These experiments have shown that gas bubbles can successfully be driven to the removal port and purged in microgravity. The last day's experiments had an excellent microgravity environment due to calm air, and the experience gained in previous flights allowed successful bubble removal 18 out of 35 tries, remarkable given the microgravity time constraints and g-jitter on the KC-135.

  7. Bubbles in the Pericardium.

    PubMed

    Saini, Aditya; Patel, Brijesh

    2015-01-01

    BACKGROUND Purulent pericarditis is a rare but life-threatening illness. Often, it may be masked by the primary infectious etiology like pneumonia, endocarditis, or CNS infection, leading to a delay in diagnosis and treatment. Echocardiography is the modality of choice for estimating the presence and size of pericardial effusion and detecting presence of tamponade. CASE REPORT We present a case of a young man with acute respiratory illness in whom clinical exam, electrocardiography, and classic echocardiographic findings played a key role in diagnosis. An echo-dense effusion (rather than echo-free space) appearing like "bubbles" within the pericardial space was seen and a purulent nature of the fluid was strongly suspected. Prompt institution of antimicrobial therapy and timely pericardial drainage resulted in complete clinical recovery of the patient. CONCLUSIONS In this case, timely diagnosis and prompt treatment of effusion with pericardial drainage and antibiotics resulted in complete recovery from this otherwise devastating infection. PMID:26134605

  8. UV irradiation/cold shock-mediated apoptosis is switched to bubbling cell death at low temperatures.

    PubMed

    Chen, Szu-Jung; Lin, Pei-Wen; Lin, Hsin-Ping; Huang, Shenq-Shyang; Lai, Feng-Jie; Sheu, Hamm-Ming; Hsu, Li-Jin; Chang, Nan-Shan

    2015-04-10

    When COS7 fibroblasts and other cells were exposed to UVC irradiation and cold shock at 4°C for 5 min, rapid upregulation and nuclear accumulation of NOS2, p53, WWOX, and TRAF2 occurred in 10-30 min. By time-lapse microscopy, an enlarging gas bubble containing nitric oxide (NO) was formed in the nucleus in each cell that finally popped out to cause "bubbling death". Bubbling occurred effectively at 4 and 22°C, whereas DNA fragmentation was markedly blocked at 4°C. When temperature was increased to 37°C, bubbling was retarded and DNA fragmentation occurred in 1 hr, suggesting that bubbling death is switched to apoptosis with increasing temperatures. Bubbling occurred prior to nuclear uptake of propidium iodide and DAPI stains. Arginine analog N?-LAME inhibited NO synthase NOS2 and significantly suppressed the bubbling death. Unlike apoptosis, there were no caspase activation and flip-over of membrane phosphatidylserine (PS) during bubbling death. Bubbling death was significantly retarded in Wwox knockout MEF cells, as well as in cells overexpressing TRAF2 and dominant-negative p53. Together, UV/cold shock induces bubbling death at 4°C and the event is switched to apoptosis at 37°C. Presumably, proapoptotic WWOX and p53 block the protective TRAF2 to execute the bubbling death. PMID:25779665

  9. Rheology of bubble-bearing magmas

    Microsoft Academic Search

    Michael Manga; Jonathan Castro; Katharine V. Cashman; Michael Loewenberg

    1998-01-01

    The rheology of bubble-bearing suspensions is investigated through a series of three-dimensional boundary integral calculations in which the effects of bubble deformation, volume fraction, and shear rate are considered. The behaviour of bubbles in viscous flows is characterized by the capillary number, Ca, the ratio of viscous shear stresses that promote deformation to surface tension stresses that resist bubble deformation.

  10. Interactions between bubbles in magmas and lavas: effects of bubble deformation

    Microsoft Academic Search

    Michael Manga; H. A. Stone

    1994-01-01

    The interactions between two deformable bubbles are studied in order to determine the effects of deformation on bubble dynamics and to determine the limits in which the effects of deformation can be ignored. Deformation due to hydrodynamic interactions with other bubbles leads to alignment of horizontally offset bubbles and thus an enhanced rate of coalescence. Bubble alignment may produce spatial

  11. Constrained Vapor Bubble

    NASA Technical Reports Server (NTRS)

    Huang, J.; Karthikeyan, M.; Plawsky, J.; Wayner, P. C., Jr.

    1999-01-01

    The nonisothermal Constrained Vapor Bubble, CVB, is being studied to enhance the understanding of passive systems controlled by interfacial phenomena. The study is multifaceted: 1) it is a basic scientific study in interfacial phenomena, fluid physics and thermodynamics; 2) it is a basic study in thermal transport; and 3) it is a study of a heat exchanger. The research is synergistic in that CVB research requires a microgravity environment and the space program needs thermal control systems like the CVB. Ground based studies are being done as a precursor to flight experiment. The results demonstrate that experimental techniques for the direct measurement of the fundamental operating parameters (temperature, pressure, and interfacial curvature fields) have been developed. Fluid flow and change-of-phase heat transfer are a function of the temperature field and the vapor bubble shape, which can be measured using an Image Analyzing Interferometer. The CVB for a microgravity environment, has various thin film regions that are of both basic and applied interest. Generically, a CVB is formed by underfilling an evacuated enclosure with a liquid. Classification depends on shape and Bond number. The specific CVB discussed herein was formed in a fused silica cell with inside dimensions of 3x3x40 mm and, therefore, can be viewed as a large version of a micro heat pipe. Since the dimensions are relatively large for a passive system, most of the liquid flow occurs under a small capillary pressure difference. Therefore, we can classify the discussed system as a low capillary pressure system. The studies discussed herein were done in a 1-g environment (Bond Number = 3.6) to obtain experience to design a microgravity experiment for a future NASA flight where low capillary pressure systems should prove more useful. The flight experiment is tentatively scheduled for the year 2000. The SCR was passed on September 16, 1997. The RDR is tentatively scheduled for October, 1998.

  12. Bubble pump: scalable strategy for in-plane liquid routing.

    PubMed

    Oskooei, Ali; Günther, Axel

    2015-07-01

    We present an on-chip liquid routing technique intended for application in well-based microfluidic systems that require long-term active pumping at low to medium flowrates. Our technique requires only one fluidic feature layer, one pneumatic control line and does not rely on flexible membranes and mechanical or moving parts. The presented bubble pump is therefore compatible with both elastomeric and rigid substrate materials and the associated scalable manufacturing processes. Directed liquid flow was achieved in a microchannel by an in-series configuration of two previously described "bubble gates", i.e., by gas-bubble enabled miniature gate valves. Only one time-dependent pressure signal is required and initiates at the upstream (active) bubble gate a reciprocating bubble motion. Applied at the downstream (passive) gate a time-constant gas pressure level is applied. In its rest state, the passive gate remains closed and only temporarily opens while the liquid pressure rises due to the active gate's reciprocating bubble motion. We have designed, fabricated and consistently operated our bubble pump with a variety of working liquids for >72 hours. Flow rates of 0-5.5 ?l min(-1), were obtained and depended on the selected geometric dimensions, working fluids and actuation frequencies. The maximum operational pressure was 2.9 kPa-9.1 kPa and depended on the interfacial tension of the working fluids. Attainable flow rates compared favorably with those of available micropumps. We achieved flow rate enhancements of 30-100% by operating two bubble pumps in tandem and demonstrated scalability of the concept in a multi-well format with 12 individually and uniformly perfused microchannels (variation in flow rate <7%). We envision the demonstrated concept to allow for the consistent on-chip delivery of a wide range of different liquids that may even include highly reactive or moisture sensitive solutions. The presented bubble pump may provide active flow control for analytical and point-of-care diagnostic devices, as well as for microfluidic cells culture and organ-on-chip platforms. PMID:26016773

  13. Temperature-controlled 'breathing' of carbon dioxide bubbles.

    PubMed

    Tumarkin, Ethan; Nie, Zhihong; Park, Jai Il; Abolhasani, Milad; Greener, Jesse; Sherwood-Lollar, Barbara; Günther, Axel; Kumacheva, Eugenia

    2011-10-21

    We report a microfluidic (MF) approach to studies of temperature mediated carbon dioxide (CO(2)) transfer between the gas and the liquid phases. Micrometre-diameter CO(2) bubbles with a narrow size distribution were generated in an aqueous or organic liquid and subsequently were subjected to temperature changes in the downstream channel. In response to the cooling-heating-cooling cycle the bubbles underwent corresponding contraction-expansion-contraction transitions, which we term 'bubble breathing'. We examined temperature-controlled dissolution of CO(2) in four exemplary liquid systems: deionized water, a 0.7 M aqueous solution of NaCl, ocean water extracted from Bermuda coastal waters, and dimethyl ether of poly(ethylene glycol), a solvent used in industry for absorption of CO(2). The MF approach can be extended to studies of other gases with a distinct, temperature-dependent solubility in liquids. PMID:21869987

  14. High-Temporal Resolution Measurement of Methane Bubbling From a Eutrophic, Dimictic, Freshwater Lake

    NASA Astrophysics Data System (ADS)

    Varadharajan, C.; Hemond, H.

    2009-12-01

    Significant amounts of methane can be released to the atmosphere from freshwater lakes, particularly through bubbling. However, spatial and temporal heterogeneity in ebullition has complicated efforts to accurately measure such methane emissions. In investigating the methane cycle at the Upper Mystic Lake in Massachusetts, we hypothesized that ebullition is triggered when the total hydrostatic pressure at a lake bottom falls below a critical value, which is determined by the gas content and gas storage potential of the sediments. Conditions for bubble breakout from sediments should either involve a drop in hydrostatic pressure or/and an increase in the sediment gas phase, with ebullition continuing until hydrostatic pressure rises or sediments are depleted of gas. In 2008, bubbling fluxes at the Upper Mystic Lake were measured over 4-6 months at a resolution of 5-10 minutes using underwater traps equipped with pressure sensors. Total hydrostatic pressure, lake water level and atmospheric pressure were monitored at similar resolutions. The precise timing of bubbling episodes was identified from the automated trap data using a multi-resolution analysis based on the stationary wavelet transform. In addition, conventional statistical methods were used to examine the relationship between ebullition and hydrostatic pressure. Synchronous lake-wide bubbling episodes were triggered when total hydrostatic pressure (sum of atmospheric pressure plus water column depth) fell below a site-dependent threshold. The bubbling episodes occurred about 10% of the time in an aperiodic manner, during which most of the bubbled gas for the study period was released (50-70% depending on the site). The wavelet analysis revealed that some of these episodes, which could last for several days, actually consisted of several short 5-20 minute bubble bursts. The results indicate that sediment gas storage is also important in determining the patterns of methane released through ebullition.

  15. Helium Bubble Behaviour in b.c.c. Metals Below 0.65T_m

    NASA Astrophysics Data System (ADS)

    Goodhew, P. J.; Tyler, S. K.

    1981-06-01

    We have considered the methods available for distinguishing between the rate-controlling mechanisms for gas bubble migration in metals at temperatures below 0.6T_m. We show that several combinations of mechanism, gas behaviour and rate-controlling process give rise to similar power laws describing the rate of growth of populations of bubbles by migration and coalescence. We have therefore extended the model developed by Gruber (1967) to take account of the condition of constant gas pressure in the bubbles, which is likely to obtain at low temperatures in the absence of continuous irradiation damage, and the additional possibility that the nucleation of a surface ledge can control the migration rate of faceted bubbles. The experimental growth rates of helium bubbles, which we have measured in niobium, niobium-zirconium alloys and vanadium, are shown to be consistent with bubble migration by a surface diffusion mechanism controlled by the surface diffusion coefficient for small bubbles but by ledge nucleation for larger bubbles. The bubble size above which the (slow) ledge nucleation process controls growth is sensitively affected by the ledge energy. We show that the addition of zirconium to niobium can alter the ledge energy by an order of magnitude by cleansing the bubble faces of oxygen. Subsequent segregation of Zr-O complexes to the bubbles further alters the ledge energy. The bubble growth rate, and hence the swelling and embrittlement behaviour of the material under these conditions, is therefore very sensitive to the material purity and to segregation effects either induced thermally or accelerated by transmutation and irradiation damage. We find that the ledge energy on the (100) face of pure niobium is ca. 11 x 10-11 J/m, which is decreased to ca. 4 x 10-11 J/m by the segregation of Zr-O to the surfaces. The ledge energy at a similar surface in niobium containing 400/10^6 oxygen is as low as 1.2 x 10-11 J/m. In vanadium we find a ledge energy of 3.4 x 10-11 J/m. These ledge energies result in the effective cessation of bubble growth at bubble sizes in the range 2-20 nm.

  16. Bubble cavitation noise and cavitation noise spectrum

    SciTech Connect

    Latorre, R. [Univ. of New Orleans, LA (United States). School of Naval Architecture and Marine Engineering

    1994-12-31

    Cavitaton noise from collapsing bubbles generates noise pulses and a cavitation noise spectrum. This paper examines the relationship of cavitation bubble noise pulse and the noise spectra. The scaling relationships are developed from the transformation relationships of bubble potential energy into bubble noise. The resulting scaling relationships allow the bubble cavitation noise spectra to be reduced to a single curve. The analysis leads to a second relationship for sheet cavitation noise spectrum.

  17. Thermocapillary Bubble Migration: Thermal Boundary Layers for Large Marangoni Numbers

    NASA Technical Reports Server (NTRS)

    Balasubramaniam, R.; Subramanian, R. S.

    1996-01-01

    The migration of an isolated gas bubble in an immiscible liquid possessing a temperature gradient is analyzed in the absence of gravity. The driving force for the bubble motion is the shear stress at the interface which is a consequence of the temperature dependence of the surface tension. The analysis is performed under conditions for which the Marangoni number is large, i.e. energy is transferred predominantly by convection. Velocity fields in the limit of both small and large Reynolds numbers are used. The thermal problem is treated by standard boundary layer theory. The outer temperature field is obtained in the vicinity of the bubble. A similarity solution is obtained for the inner temperature field. For both small and large Reynolds numbers, the asymptotic values of the scaled migration velocity of the bubble in the limit of large Marangoni numbers are calculated. The results show that the migration velocity has the same scaling for both low and large Reynolds numbers, but with a different coefficient. Higher order thermal boundary layers are analyzed for the large Reynolds number flow field and the higher order corrections to the migration velocity are obtained. Results are also presented for the momentum boundary layer and the thermal wake behind the bubble, for large Reynolds number conditions.

  18. The dynamics of vapor bubbles in acoustic pressure fields

    NASA Astrophysics Data System (ADS)

    Hao, Y.; Prosperetti, A.

    1999-08-01

    In spite of a superficial similarity with gas bubbles, the intimate coupling between dynamical and thermal processes confers to oscillating vapor bubbles some unique characteristics. This paper examines numerically the validity of some asymptotic-theory predictions such as the existence of two resonant radii and a limit size for a given sound amplitude and frequency. It is found that a small vapor bubble in a sound field of sufficient amplitude grows quickly through resonance and continues to grow thereafter at a very slow rate, seemingly indefinitely. Resonance phenomena therefore play a role for a few cycles at most, and reaching a limit size—if one exists at all—is found to require far more than several tens of thousands of cycles. It is also found that some small bubbles may grow or collapse depending on the phase of the sound field. The model accounts in detail for the thermo-fluid-mechanic processes in the vapor. In the second part of the paper, an approximate formulation valid for bubbles small with respect to the thermal penetration length in the vapor is derived and its accuracy examined. The present findings have implications for acoustically enhanced boiling heat transfer and other special applications such as boiling in microgravity.

  19. A PIV\\/PTV system for analysing turbulent bubbly flows

    Microsoft Academic Search

    D. Bröder; M. Sommerfeld

    Bubble columns are widely used in 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 in a bubble column of 140 mm

  20. Magnetism. Blowing magnetic skyrmion bubbles.

    PubMed

    Jiang, Wanjun; Upadhyaya, Pramey; Zhang, Wei; Yu, Guoqiang; Jungfleisch, M Benjamin; Fradin, Frank Y; Pearson, John E; Tserkovnyak, Yaroslav; Wang, Kang L; Heinonen, Olle; te Velthuis, Suzanne G E; Hoffmann, Axel

    2015-07-17

    The formation of soap bubbles from thin films is accompanied by topological transitions. Here we show how a magnetic topological structure, a skyrmion bubble, can be generated in a solid-state system in a similar manner. Using an inhomogeneous in-plane current in a system with broken inversion symmetry, we experimentally "blow" magnetic skyrmion bubbles from a geometrical constriction. The presence of a spatially divergent spin-orbit torque gives rise to instabilities of the magnetic domain structures that are reminiscent of Rayleigh-Plateau instabilities in fluid flows. We determine a phase diagram for skyrmion formation and reveal the efficient manipulation of these dynamically created skyrmions, including depinning and motion. The demonstrated current-driven transformation from stripe domains to magnetic skyrmion bubbles could lead to progress in skyrmion-based spintronics. PMID:26067256

  1. Partial coalescence of soap bubbles

    NASA Astrophysics Data System (ADS)

    Pucci, G.; Harris, D. M.; Bush, J. W. M.

    2015-06-01

    We present the results of an experimental investigation of the merger of a soap bubble with a planar soap film. When gently deposited onto a horizontal film, a bubble may interact with the underlying film in such a way as to decrease in size, leaving behind a smaller daughter bubble with approximately half the radius of its progenitor. The process repeats up to three times, with each partial coalescence event occurring over a time scale comparable to the inertial-capillary time. Our results are compared to the recent numerical simulations of Martin and Blanchette ["Simulations of surfactant effects on the dynamics of coalescing drops and bubbles," Phys. Fluids 27, 012103 (2015)] and to the coalescence cascade of droplets on a fluid bath.

  2. Design of a Gas-Liquid Unbaffled Stirred Tank with a Concave Blade Impeller

    NASA Astrophysics Data System (ADS)

    Devi, T. T.; Kumar, Bimlesh

    2015-01-01

    Experimental investigation of unbaffled multiphase (gas-liquid) stirred tanks is conducted with the use of a concave blade impeller to analyze mass transfer, gassed power, and gas holdup. The experiments are carried out with various impeller diameter to tank diameter ratios and impeller clearances. The design criterion for the mass transfer rate is proposed, and its prediction capability is found to be satisfactory. The results show that the gassed power is dependent on the impeller diameter to tank diameter ratio and impeller clearance. The design criteria for gassed power to ungassed power ratio and gas holdup are also introduced. Multiphase modeling is done by employing the computational fluid dynamics (CFD) techniques to observe the characteristic flow pattern transition and to carry out a qualitative analysis of the mass transfer rate.

  3. An acoustic technique for measurement of bubble solids mass loading (a) Fundamental study of single bubble

    E-print Network

    Zhang, Wen

    of attached solids in industrial flotation cells. It is observed that the coating of solids on a bubble on a bubble surface alters bubble dynamics. As intuitively expected, the added mass causes a decrease

  4. Dynamics of single rising bubbles in neutrally buoyant liquid-solid suspensions.

    PubMed

    Hooshyar, Nasim; van Ommen, J Ruud; Hamersma, Peter J; Sundaresan, Sankaran; Mudde, Robert F

    2013-06-14

    We experimentally investigate the effect of particles on the dynamics of a gas bubble rising in a liquid-solid suspension while the particles are equally sized and neutrally buoyant. Using the Stokes number as a universal scale, we show that when a bubble rises through a suspension characterized by a low Stokes number (in our case, small particles), it will hardly collide with the particles and will experience the suspension as a pseudoclear liquid. On the other hand, when the Stokes number is high (large particles), the high particle inertia leads to direct collisions with the bubble. In that case, Newton's collision rule applies, and direct exchange of momentum and energy between the bubble and the particles occurs. We present a simple theory that describes the underlying mechanism determining the terminal bubble velocity. PMID:25165930

  5. Film drainage of viscous liquids on top of bare bubble: Influence of the Bond number

    NASA Astrophysics Data System (ADS)

    Rouyer, Florence; Ko?árková, Helena; Metallaoui, Salahedine; Pigeonneau, Franck; Lpmdi-Université Paris-Est Marne La Vallée Team; Svi-Saint-Gobain Recherche Team

    2011-11-01

    We present experimental result of film drainage on top of gas bubbles pushed by gravity forces toward the upper surface of a liquid bath for Newtonian liquids with mobile interface (UCON, castor oil and soda-lime-silica melt). The temporal evolution of the thickness of the film between a single bubble and the air/liquid interface is investigated via interference method under various physical conditions, range of viscosities and surface tension of the liquids, and bubble sizes. These experiments evidence the influence of the deformation of the thin film on the thinning rate and confirm the slow down of film drainage with Bond number as previously reported by numerical work. A simple model that considered the liquid flow in the cap squeezed by buoyancy forces of the bubble is in good agreement with experimental and numerical data. Qualitatively, the smaller is the area of the thin film compare to the surface of the bubble, the faster is the drainage.

  6. The importance of bubble deformability for strong drag reduction in bubbly turbulent Taylor-Couette flow

    NASA Astrophysics Data System (ADS)

    Narezo Guzman, Daniela; van Gils, Dennis P. M.; Sun, Chao; Lohse, Detlef

    2012-11-01

    Drag reduction (DR) in two-phase turbulent Taylor-Couette (TC) flow is studied for Reynolds number up to Re = 2 ×106 for pure inner cylinder (IC) rotation, thus extending the previously explored range. DR based on the global torque as a function of the global gas volume fraction (?) over the range 0 % up to 4 % is obtained. We observe two DR regimes: moderate DR up to 7 % for Re = 5 . 1 ×105 and stronger DR for Re = 1 . 0 ×106 and 2 . 0 ×106 , remarkably finding more than 40 % of DR for ? = 4 % at Re = 2 . 0 ×106 . Furthermore, TC flow is locally studied in each regime (Re = 5 . 1 ×105 and 1 . 0 ×106) at a fixed ? = 3 % : statistics of the local liquid flow azimuthal velocity and the local gas concentration are obtained. The local bubble Weber number (We) is computed close to the IC showing that the crossover from the moderate to the strong DR regime occurs roughly at the crossover of We ~ 1 . We find that a larger local gas volume fraction close to the inner wall has a positive effect on the azimuthal velocity decrease, which is responsible for the observed DR. However for strong DR what is more important for the ? values explored here is bubble deformability close to the boundary layer. Supported by the Technology Foundation STW of the Netherlands.

  7. Giant bubble-pinchoff

    NASA Astrophysics Data System (ADS)

    Lohse, Detlef

    2006-03-01

    Self-similarity has been the paradigmatic picture for the pinch-off of a drop. Here we will show through high-speed imaging and boundary integral simulations that the inverse problem, the pinch-off of an air bubble in water, does not obey self-similarity (of the first kind): A disk is quickly pulled through a water surface, leading to a giant, cylindrical void, which at collapse creates an upward and a downward jet. The neck radius h(tau) of the void does NOT scale with the inertial power law exponent 1/2 (i.e., does not obey ``Rayleigh-scaling''). This is due to a second length-scale, the inverse curvature of the void,which follows a power-law scaling with a different exponent. Only for infinite Froude numbers the scaling exponent 1/2 is recovered. In all cases we find the void-profile to be symmetric around the minimal void radius up to the time the airflow in the neck deforms the interface.

  8. Bubbles in the Pericardium

    PubMed Central

    Saini, Aditya; Patel, Brijesh

    2015-01-01

    Patient: Male, 22 Final Diagnosis: Purulent pericardial effusion with tamponade Symptoms: Chest pain • short of breath Medication: None Clinical Procedure: Pericardial drainage Specialty: Cardiology Objective: Rare disease Background: Purulent pericarditis is a rare but life-threatening illness. Often, it may be masked by the primary infectious etiology like pneumonia, endocarditis, or CNS infection, leading to a delay in diagnosis and treatment. Echocardiography is the modality of choice for estimating the presence and size of pericardial effusion and detecting presence of tamponade. Case Report: We present a case of a young man with acute respiratory illness in whom clinical exam, electrocardiography, and classic echocardiographic findings played a key role in diagnosis. An echo-dense effusion (rather than echo-free space) appearing like “bubbles” within the pericardial space was seen and a purulent nature of the fluid was strongly suspected. Prompt institution of antimicrobial therapy and timely pericardial drainage resulted in complete clinical recovery of the patient. Conclusions: In this case, timely diagnosis and prompt treatment of effusion with pericardial drainage and antibiotics resulted in complete recovery from this otherwise devastating infection. PMID:26134605

  9. Global Structure of Isothermal Diffuse X-Ray Emission along the Fermi Bubbles

    NASA Astrophysics Data System (ADS)

    Kataoka, J.; Tahara, M.; Totani, T.; Sofue, Y.; Inoue, Y.; Nakashima, S.; Cheung, C. C.

    2015-07-01

    In our previous works, we found absorbed thermal X-ray plasma with kT ? 0.3 keV observed ubiquitously near the edges of the Fermi bubbles and interpreted this emission as weakly shock-heated Galactic halo gas. Here we present a systematic and uniform analysis of archival Suzaku (29 pointings; 6 newly presented) and Swift (68 pointings; 49 newly presented) data within Galactic longitudes | l| < 20° and latitude 5°? | b| < 60°, covering the whole extent of the Fermi bubbles. We show that the plasma temperature is constant at kT ? 0.30 ± 0.07 keV, while the emission measure (EM) varies by an order of magnitude, increasing toward the Galactic center (i.e., low | b| ) with enhancements at the North Polar Spur (NPS), SE-claw, and NW-clump features. Moreover, the EM distribution of kT ? 0.30 keV plasma is highly asymmetric in the northern and southern bubbles. Although the association of the X-ray emission with the bubbles is not conclusive, we compare the observed EM properties with simple models assuming (i) a filled halo without bubbles, whose gas density follows a hydrostatic isothermal model (King profile), and (ii) a bubble-in-halo in which two identical bubbles expand into the halo, forming thick shells of swept halo gas. We argue that the EM profile in the north (b > 0°) favors (ii), whereas that of the south (b < 0°) is rather close to (i), but a weak excess signature is clearly detected also in the south like NPS (South Polar Spur). Such an asymmetry, if due to the bubbles, cannot be fully understood only by the inclination of bubbles’ axis against the Galactic disk normal, thus suggesting asymmetric outflow due to different environmental/initial conditions.

  10. THE FERMI BUBBLES AS A SCALED-UP VERSION OF SUPERNOVA REMNANTS

    SciTech Connect

    Fujita, Yutaka [Department of Earth and Space Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan)] [Department of Earth and Space Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Ohira, Yutaka; Yamazaki, Ryo, E-mail: fujita@vega.ess.sci.osaka-u.ac.jp [Department of Physics and Mathematics, Aoyama Gakuin University, Fuchinobe, Chuou-ku, Sagamihara 252-5258 (Japan)] [Department of Physics and Mathematics, Aoyama Gakuin University, Fuchinobe, Chuou-ku, Sagamihara 252-5258 (Japan)

    2013-09-20

    In this study, we treat Fermi bubbles as a scaled-up version of supernova remnants (SNRs). The bubbles are created through activities of the super-massive black hole (SMBH) or starbursts at the Galactic center (GC). Cosmic-rays (CRs) are accelerated at the forward shocks of the bubbles like SNRs, which means that we cannot decide whether the bubbles were created by the SMBH or starbursts from the radiation from the CRs. We follow the evolution of CR distribution by solving a diffusion-advection equation, considering the reduction of the diffusion coefficient by CR streaming. In this model, gamma rays are created through hadronic interaction between CR protons and the gas in the Galactic halo. In the GeV band, we can well reproduce the observed flat distribution of gamma-ray surface brightness because some amount of gas is left behind the shock. The edge of the bubbles is fairly sharp owing to the high gas density behind the shock and the reduction of the diffusion coefficient there. The latter also contributes the hard gamma-ray spectrum of the bubbles. We find that the CR acceleration at the shock began when the bubbles were small, and the time scale of the energy injection at the GC was much smaller than the age of the bubbles. We predict that if CRs are accelerated to the TeV regime, the apparent bubble size should be larger in the TeV band, which could be used to discriminate our hadronic model from other leptonic models. We also present neutrino fluxes.

  11. The formation of bubbles in Zr alloys under Kr ion irradiation

    SciTech Connect

    Birtcher, R.C. [Argonne National Lab., IL (United States). Materials Science Div.; Pagano, L. Jr.; Motta, A.T. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Nuclear Engineering

    1996-06-01

    The authors report here a study of Kr ion implantation and the resultant bubble formation in Zr and Zr alloys, including Zircaloy-2 and Zircaloy-4. Implantations into thin foils were performed in the HVEM/Tandem facility at Argonne National Laboratory at temperatures between 300 to 800 C and to doses up to 2 x 10{sup 16} ion.cm{sup {minus}2}. Bulk specimens were implanted in an ion-beam chamber and then thinned for viewing by TEM. In thin foils, only small bubbles (30--100 {angstrom}) were formed at all temperatures with the exception of the Cr-rich V alloy where bubbles of 130 {angstrom} bubbles were formed. Bulk samples implanted at 300 C contained a bubble morphology similar to that observed after implantation into thin foils. However, at high temperatures (500--800 C) large faceted bubbles (up to 300 {angstrom}) were produced in bulk specimens. The results indicate that bubble formation and evolution below 500 C is controlled by gas concentration, while it is controlled by bubble mobility at high temperatures.

  12. Simulations of Images and Optical Spectra of Plasmas Sustained in Bubbles in Water

    NASA Astrophysics Data System (ADS)

    Tian, Wei; Kushner, Mark

    2012-10-01

    Plasmas in bubbles in water are being investigated for their ability to produce chemically reactive species for water purification and medical treatment. The gas in the bubbles is important to the production of these active species. In this paper, we report on a computational investigation of the dynamics of plasmas in bubbles in water. These simulations were performed using nonPDPSIM, in which Poisson's equation, transport equations for charged and neutral species, and electron temperature are integrated in 2-dimensions on an unstructured mesh. Bubbles of specified composition and size ( 3 mm diameter) in water at atmospheric pressure are placed at the tip of the powered electrode and water vapor is allowed to diffuse into the bubble from the vapor-water boundary. Voltage pulses (15-30 kV) produce plasma streamers in the bubble which typically hug the vapor-water boundary. Images, optical spectra and plasma properties will be discussed for bubbles of N2, Ar and He, and compared to experiments [1]. The differences in plasma dynamics and appearance (e.g., volume discharge or surface hugging) depend in large part on the electron energy relaxation length, and the rate of diffusion of water vapor into the interior. Electron impact dissociative excitation of water vapor and excitation transfer processes from injected bubble gases to the water vapor are responsible for differences in the optical spectra and, by inference, differences in radical production. [4pt] [1] K. Tachibana, et al., Plasma Sources Sci. Technol. 20, 034005 (2011).

  13. General formulation of an HCDA bubble rising in a sodium pool and the effect of nonequilibrium on fuel transport

    SciTech Connect

    Kocamustafaogullari, G.; Chan, S.H.

    1983-10-01

    Consideration is given to a fuel-dominated bubble, which is assumed to have just penetrated into the sodium pool in a spherical form subsequent to a hypothetical core disruptive accident. The two-phase bubble mixture is formulated as it rises through the sodium pool to the cover-gas region. The formulation takes into account the effects of the nonequilibrium mass transfer at the interfaces and of the radiative cooling of the bubble as well as the kinematic, dynamic, and thermal effects of the surrounding fields. The results of calculation for the amount of the fuel vapor condensed before the bubble reaches the cover-gas region are presented over a wide possible range of the evaporation coefficient as well as the liquid sodium-bubble interface absorbtivity. It is shown that the effects of nonequilibrium mass transfer become more meaningful at the later stage of bubble rise where the temperature difference between the liquid fuel and the gaseous mixture has been increased. The thermal radiative cooling is found to be very effective in attenuating the fuel content of the bubble; depending on the value of the liquid sodium-bubble absorbtivity, a great reduction of fuel vapor can result. Consequently, if the condensed fuel falls out of the bubble, the thermal radiation, which condenses out most of the fuel vapor, can effectively prevent and eliminate most of the fuel leakage from the reactor vessel.

  14. Numerical investigation of turbulent bubbly wakes created by the ventilated partial cavity

    NASA Astrophysics Data System (ADS)

    Xiang, Min; Zhang, WeiHua; Cheung, S. C. P.; Tu, JiYuan

    2012-02-01

    This paper presents a numerical study on the turbulent bubbly wakes created by the ventilated partial cavity. A semi-empirical approach is introduced to model the discrete interface of the ventilated cavity and its complex gas leakage rate induced by the local turbulent shear stress. Based on the Eulerian-Eulerian two-fluid modeling framework, a population balance approach based on MUltiple-SIze-Group (MUSIG) model is incorporated to simulate the size evolution of the sheared off microbubbles and its complex interactions with the two-phase flow structure in the wake region. Numerical predictions at various axial locations downstream of the test body were in satisfactory agreement with the experimental measurements. The captured bubbly wake structure illustrates that the bubbles may disperse as a twin-vortex tube driven by gravity effect. The predicted Sauter mean bubble diameter has confirmed the dominance of the coleascense process in the axial direction. As the bubbles develop downstream, the coleascense and breakup rate gradually reach balance, resulting in the stable bubble diameter. A close examination of the flow structures, gas void fraction distributions and the bubble size evolution provides valuable insights into the complex physical phenomenon induced by ventilated cavity.

  15. Plasmas sustained in bubbles in water: optical emission and excitation mechanisms

    NASA Astrophysics Data System (ADS)

    Tian, Wei; Tachibana, Kunhide; Kushner, Mark J.

    2014-02-01

    Plasmas in bubbles in water are being investigated for their ability to produce chemically reactive species for water purification and medical treatment. The gas forming the bubble is potentially a design parameter for water purification as the type and rate of production of active species may be controllable by the type of gas in the bubble. In this paper, we report on a computational investigation of the dynamics of plasmas in bubbles in water sustained in different gases. Images, optical spectra and plasma properties are discussed for plasmas in bubbles of N2, Ar and He in water, and compared to experiments. The differences in plasma dynamics and spatial distribution of the plasma (e.g., volume discharge or surface hugging) when using different gases depend in large part on the electron energy relaxation length, and the rate of diffusion of water vapour into the interior of the bubble. Electron impact dissociative excitation of water vapour, electron impact excitation of dissociation products and excitation transfer from the plasma excited injected bubble gases to water vapour all contribute to plasma emission. Variations in the contributions of these processes are responsible for differences in the observed optical spectra and differences in radical production.

  16. Spatial and Temporal Variation in Methane Bubbling From a Stratified, Eutrophic Lake

    NASA Astrophysics Data System (ADS)

    Varadharajan, C.; Borja, E.; Tcaciuc, A. P.; Hemond, H. F.

    2008-12-01

    Recent studies have suggested that significant amounts of methane can be released to the atmosphere from freshwater lakes, particularly through bubbling. However, spatial and temporal heterogeneity in ebullition has complicated efforts to accurately measure methane emissions from aquatic ecosystems. We have hypothesized that bubbling is triggered by variations in absolute water pressure at the lake bottom, and hence should be more or less synchronous from site to site within a small lake. In 2007, most of the bubbling in the eutrophic Upper Mystic Lake in Massachusetts occurred episodically, with peak fluxes approaching 200 ml/m2/d in late summer and early fall (comparable to wetland emissions), while average bubble fluxes were approximately 30-45 ml/m2/d. However the temporal resolution of these measurements was only of the order of a week. In 2008, under-water bubble traps were equipped with pressure sensors that measured the gas collected every 5 minutes, to determine the exact temporal pattern of ebullition. Early results suggest that synchronous lake-wide bubbling occurs during episodes lasting 2 to 4 days, and is in fact strongly linked with changes in the lake's water level, and to a lesser extent with variations in atmospheric pressure. Spatial variability in bubble fluxes was observed during both years, with shallower locations emitting 2 to 20 times less flux than deeper stations. The mixing ratio of methane present in the collected gas varied across stations and ranged from 30% to 90%.

  17. Heating the intra-cluster medium by jet-inflated bubbles

    E-print Network

    Hillel, Shlomi

    2015-01-01

    We examine the heating of the intra-cluster medium (ICM) of cooling flow clusters of galaxies by jet-inflated bubbles and conclude that mixing of hot bubble gas with the ICM is the dominate heating process. We use the PLUTO hydrodynamical code in full 3D to properly account for the inflation of the bubbles and to the multiple vortices induced by the jets and bubbles. The vortices mix some hot shocked jet gas with the ICM. For the parameters used the mixing process accounts for approximately 80% of the energy transferred from the jets to the ICM. Only about 20% of the transferred energy is channelled to the kinetic energy of the ICM. Part of this develops as ICM turbulence. We conclude that turbulent heating plays a smaller role than mixing. Heating by shocks is less efficient even.

  18. The effect of dilution on the quantitative measurement of bubbles in high-density ultrafine bubble-filled water using the light scattering method

    NASA Astrophysics Data System (ADS)

    Maeda, Shigeo; Kobayashi, Hideaki; Ida, Katsuhisa; Kashiwa, Masakazu; Nishihara, Ikkan; Fujita, Toshihiro

    2014-08-01

    We have developed an ultrafine bubble generating system, ultrafineGALF, upgrading the microGALF system to a flow rate of 0.24 m3/h. The ultrafineGALF system can generate a dense population of more than 109 ultrafine bubbles per ml. The density and size distribution of these bubbles have been measured using a NanoSight measuring instrument, but precision measurement of the number density has become difficult because it now extends beyond the measuring range (1×109/ml) of this instrument. Thus far, the number density of the ultrafine bubbles after dilution has been measured, but few reports are available on the effect of dilution on gas particles, which behave differently from solid particles. In this study, the effect of dilution, which is required to measure the density of ultrafine bubbles at ultra-high densities, was investigated. No large differences due to the use of dilution among three types of samples with different concentrations of ultrafine bubbles were found, although the samples did show slightly different rates of change in the concentration of ultrafine bubbles over time.

  19. LOW FREQUENCY SOUND SPEED MEASUREMENTS PAIRED WITH COMPUTED X-RAY TOMOGRAPHY IMAGING IN GAS-

    E-print Network

    Wilson, Preston S.

    LOW FREQUENCY SOUND SPEED MEASUREMENTS PAIRED WITH COMPUTED X-RAY TOMOGRAPHY IMAGING IN GAS the overall void fraction (VF) and the bubble size distribution (BSD), both of which greatly effect varying fractions of biogenic gas bubbles or air bubbles. The acoustic resonator operated between 100

  20. Plasma Turbulence in the Local Bubble

    E-print Network

    Steven R. Spangler

    2008-06-05

    Turbulence in the Local Bubble could play an important role in the thermodynamics of the gas that is there. The best astronomical technique for measuring turbulence in astrophysical plasmas is radio scintillation. Measurements of the level of scattering to the nearby pulsar B0950+08 by Philips and Clegg in 1992 showed a markedly lower value for the line-of-sight averaged turbulent intensity parameter $$ than is observed for other pulsars, consistent with radio wave propagation through a highly rarefied plasma. In this paper, we discuss the observational progress that has been made since that time. At present, there are four pulsars (B0950+08, B1133+16, J0437-4715, and B0809+74) whose lines of sight seem to lie mainly within the local bubble. The mean densities and line of sight components of the interstellar magnetic field along these lines of sight are smaller than nominal values for pulsars, but not by as much expected. Three of the four pulsars also have measurements of interstellar scintillation. The value of the parameter $$ is smaller than normal for two of them, but is completely nominal for the third. This inconclusive status of affairs could be improved by measurements and analysis of ``arcs'' in ``secondary spectra'' of pulsars.

  1. A self-priming and bubble-tolerant piezoelectric silicon micropump for liquids and gases

    Microsoft Academic Search

    R. Linnemann; P. Woias; C.-D. Senfft; J. A. Ditterich

    1998-01-01

    In this paper a novel silicon micropump for liquids and gases is presented, which is tolerant towards gas-bubbles and which is able to prime itself. The micropump is based on a piezoelectrically driven diaphragm actuator, which is combined with a valve unit consisting of two cantilever valves. The self-priming and bubble-tolerant operation mode was achieved by maximizing the compression ratio,

  2. High-frequency sound field and bubble formation in a rat decompression model

    Microsoft Academic Search

    Avi Shupak; Yehuda Arieli; Haim Bitterman; Vera Brod; Ran Arieli; Giora Rosenhause

    2002-01-01

    High-frequency sound might cause bubble enlargement by rectified diffusion. The purpose of the present study was to investigate gas bubble formation in the immersed diving animal during exposure to high-frequency sound. Anaesthetised rats were subjected to a simulated diving profile while immersed inside a hyperbaric chamber. An acoustic beacon (pinger) was placed ventral to the animal’s abdomen, transmitting at an

  3. Bubble nucleation in rhyolite and dacite melts: temperature dependence of surface tension

    Microsoft Academic Search

    James E. GardnerRichard; Richard A. Ketcham

    Surface tension (?) profoundly influences the ability of gas bubbles to nucleate in silicate melts. To determine how temperature impacts ?, experiments were carried out in which high-silica rhyolite melts with 5 wt% dissolved water were decompressed at temperatures\\u000a that ranged from 775 to 1,085°C. Decompressions were also carried out using dacite melts with 4.3 wt% dissolved water at 1,150°C.\\u000a Water bubbles

  4. Frictional drag reduction by wavy advection of deformable bubbles

    NASA Astrophysics Data System (ADS)

    Oishi, Yoshihiko; Murai, Yuichi; Tasaka, Yuji; Yasushi, Takeda

    2009-02-01

    Bubbles can reduce frictional drag in wall turbulence, and its effect is expected to use for ships and pipelines to save their power consumptions. A number of basic experiments have been carried out to date for finding out the best condition for enhancing the drag reduction. One issue that remains at present is the difference of the performance between steady and unsteady status in terms of bubble concentration. All the experiments in the past deal with the steady effect, i.e., the drag reduction is evaluated as a function of mean void fraction or given gas flow rate of continuous injection. Despite to this, the actual phenomena highly depend on local interaction between two phases upon unsteady manner. We focus on this point and elucidate the influence of time-fluctuating void fraction on the total response to the drag reduction. This view is in fact important to estimate the persistency of the bubble-based drag reduction in the flow direction since bubbles formulate wavy advection during their migration. Our experiments are designed to measure the above-mentioned effect from laminar, transitional, and turbulent flows in a horizontal channel. For avoiding the contamination effect that worsens the reproducibility of the experiment, Silicone oil is used as carrier fluid. The oil also simulates the high Weber number bubble condition because of low surface tension. The unsteady interaction between the wavy advection of bubbles and the local skin friction, a synchronized system is constructed to connect the high-speed camera with the shear transducer, which can evaluate the interaction at 1000 fps. From the results, we confirm that the drag reduction is provided at Re>3000 in the turbulent flow regime, and also the total drag reduction is enhanced by the presence of the waves.

  5. Evolution of glass bubbles in VAD sintering process

    Microsoft Academic Search

    Alireza Hassani I; Nosratollah Granpayeh; Faramarz E. Seraji; Mohammad S. Zabihi

    2003-01-01

    Behavior of the bubbles in the fast and slow heating rate of the sintering process is simulated. In fast sintering, bubbles expand and can be joined together to create bigger bubbles. In slow heating rate, bubbles shrink slowly.

  6. Initial conditions for bubble universes

    SciTech Connect

    McInnes, Brett [Department of Mathematics, National University of Singapore, 2 Science Drive 2, Singapore 117543 (Singapore)

    2008-06-15

    The ''bubble universes'' of Coleman and De Luccia play a crucial role in string cosmology. Since our own Universe is supposed to be of this kind, bubble cosmology should supply definite answers to the long-standing questions regarding cosmological initial conditions. In particular, it must explain how an initial singularity is avoided, and also how the initial conditions for inflation were established. I argue that the simplest nonanthropic approach to these problems involves a requirement that the spatial sections defined by distinguished bubble observers should not be allowed to have arbitrarily small volumes. Casimir energy is a popular candidate for a quantum effect which can ensure this, but (because it violates energy conditions) there is a danger that it could lead to nonperturbative instabilities in string theory. I make a simple proposal for the initial conditions of a bubble universe, and show that my proposal ensures that the system is nonperturbatively stable. Thus, low-entropy conditions can be established at the beginning of a bubble universe without violating the second law of thermodynamics and without leading to instability in string theory. These conditions are inherited from the ambient spacetime.

  7. Hanford's Battle with Nuclear Waste Tank SY101: Bubbles, Toils, and Troubles

    Microsoft Academic Search

    Charles W

    2006-01-01

    Radioactive waste tank SY-101 is one of 177 big underground tanks that store waste from decades of plutonium production at the Hanford Nuclear Reservation in central Washington State. The chemical reactions and radioactivity in all the tanks make bubbles of flammable gas, mainly hydrogen along with a little methane and ammonia. But SY-101 was the most potent gas producer of

  8. Liquid backmixing in bubble columns via computer-automated radioactive particle tracking (CARPT)

    Microsoft Academic Search

    Y. B. Yang; N. Devanathan; M. P. Dudukovi?

    1993-01-01

    A single, fully wettable, neutrally buoyant, small radioactive particle and 16 scintillation detectors are utilized to monitor particle motion in gas-liquid bubble columns of different heights and diameters and at different gas superficial velocities. Instantaneous velocities, time-averaged velocities, Reynolds stresses and eddy diffusivities are computed from the particle position versus time data. Anisotropy, indicated by the data, was confirmed by

  9. Electromagnetic bubbles: subcycle near-femtosecond and subfemtosecond field solitons

    Microsoft Academic Search

    A. E. Kaplan; S. F. Straub; P. L. Shkolnikov

    1997-01-01

    We demonstrate the feasibility of strong (up to atomic fields) and supershort (few-femtosecond or even sub- femtosecond) subcycle (nonoscillating) electromagnetic solitons (EM bubbles (EMB's)) in a gas of two-level at- oms as well as EMB's and preionization shock waves in classically nonlinear atoms. We show that EMB's can be generated by existing sources of radiation, including subpicosecond half-cycle pulses and

  10. Bubble memory module for spacecraft application

    NASA Technical Reports Server (NTRS)

    Hayes, P. J.; Looney, K. T.; Nichols, C. D.

    1985-01-01

    Bubble domain technology offers an all-solid-state alternative for data storage in onboard data systems. A versatile modular bubble memory concept was developed. The key module is the bubble memory module which contains all of the storage devices and circuitry for accessing these devices. This report documents the bubble memory module design and preliminary hardware designs aimed at memory module functional demonstration with available commercial bubble devices. The system architecture provides simultaneous operation of bubble devices to attain high data rates. Banks of bubble devices are accessed by a given bubble controller to minimize controller parts. A power strobing technique is discussed which could minimize the average system power dissipation. A fast initialization method using EEPROM (electrically erasable, programmable read-only memory) devices promotes fast access. Noise and crosstalk problems and implementations to minimize these are discussed. Flight memory systems which incorporate the concepts and techniques of this work could now be developed for applications.

  11. A study of bubble wetting on surfaces

    E-print Network

    Day, Julia Katherine

    2010-01-01

    In microfluidics, the formation of bubbles within devices obstructs flow and can damage the microfluidic chip or the samples contained therein. This thesis works toward a better understand of bubble wetting on surfaces, ...

  12. Behavior of Rapidly Sheared Bubble Suspensions

    NASA Technical Reports Server (NTRS)

    Sangani, A. S.; Kushch, V. I.; Hoffmann, M.; Nahra, H.; Koch, D. L.; Tsang, Y.

    2002-01-01

    An experiment to be carried out aboard the International Space Station is described. A suspension consisting of millimeter-sized bubbles in water containing some dissolved salt, which prevents bubbles from coalescing, will be sheared in a Couette cylindrical cell. Rotation of the outer cylinder will produce centrifugal force which will tend to accumulate the bubbles near the inner wall. The shearing will enhance collisions among bubbles creating thereby bubble phase pressure that will resist the tendency of the bubbles to accumulate near the inner wall. The bubble volume fraction and velocity profiles will be measured and compared with the theoretical predictions. Ground-based research on measurement of bubble phase properties and flow in vertical channel are described.

  13. Unorthodox bubbles when boiling in cold water.

    PubMed

    Parker, Scott; Granick, Steve

    2014-01-01

    High-speed movies are taken when bubbles grow at gold surfaces heated spotwise with a near-infrared laser beam heating water below the boiling point (60-70?°C) with heating powers spanning the range from very low to so high that water fails to rewet the surface after bubbles detach. Roughly half the bubbles are conventional: They grow symmetrically through evaporation until buoyancy lifts them away. Others have unorthodox shapes and appear to contribute disproportionately to heat transfer efficiency: mushroom cloud shapes, violently explosive bubbles, and cavitation events, probably stimulated by a combination of superheating, convection, turbulence, and surface dewetting during the initial bubble growth. Moreover, bubbles often follow one another in complex sequences, often beginning with an unorthodox bubble that stirs the water, followed by several conventional bubbles. This large dataset is analyzed and discussed with emphasis on how explosive phenomena such as cavitation induce discrepancies from classical expectations about boiling. PMID:24580324

  14. Electric field observations of equatorial bubbles

    NASA Astrophysics Data System (ADS)

    Aggson, T. L.; Maynard, N. C.; Hanson, W. B.; Saba, Jack L.

    1992-03-01

    Results from the double floating probe experiment performed on the San Marco D satellite are presented, with emphasis on the observation of large incremental changes in the convective electric field vector at the boundary of equatorial plasma bubbles. Attention is given to isolated bubble structures in the upper ionospheric F regions; these observed bubble encounters are divided into two types - type I (live bubbles) and type II (dead bubbles). Type I bubbles show varying degrees of plasma depletion and large upward velocities range up to 1000 km/s. The geometry of these bubbles is such that the spacecraft orbit may cut them where they are tilting either eastward or (more often) westward. Type II bubbles exhibit plasma density depletion but no appreciable upward convection. Both types of events are usually surrounded by a halo of plasma turbulence, which can extend considerably beyond the region of plasma depletion.

  15. Removal of hydrogen bubbles from nuclear reactors

    NASA Technical Reports Server (NTRS)

    Jenkins, R. V.

    1980-01-01

    Method proposed for removing large hydrogen bubbles from nuclear environment uses, in its simplest form, hollow spheres of palladium or platinum. Methods would result in hydrogen bubble being reduced in size without letting more radioactivity outside reactor.

  16. Unorthodox bubbles when boiling in cold water

    NASA Astrophysics Data System (ADS)

    Parker, Scott; Granick, Steve

    2014-01-01

    High-speed movies are taken when bubbles grow at gold surfaces heated spotwise with a near-infrared laser beam heating water below the boiling point (60-70 °C) with heating powers spanning the range from very low to so high that water fails to rewet the surface after bubbles detach. Roughly half the bubbles are conventional: They grow symmetrically through evaporation until buoyancy lifts them away. Others have unorthodox shapes and appear to contribute disproportionately to heat transfer efficiency: mushroom cloud shapes, violently explosive bubbles, and cavitation events, probably stimulated by a combination of superheating, convection, turbulence, and surface dewetting during the initial bubble growth. Moreover, bubbles often follow one another in complex sequences, often beginning with an unorthodox bubble that stirs the water, followed by several conventional bubbles. This large dataset is analyzed and discussed with emphasis on how explosive phenomena such as cavitation induce discrepancies from classical expectations about boiling.

  17. Bubbles and Fads in Asset Prices

    Microsoft Academic Search

    Colin Camerer

    1989-01-01

    The article considers the possibility that asset prices might deviate from intrinsic values based on market fundamentals. Three broad categories of theory are surveyed: (1) growing bubbles, (2) fads, and (3) information bubbles. \\

  18. Experimental characterisation of bubbly flow using MRI

    E-print Network

    Tayler, Alexander B.

    2011-11-08

    This thesis describes the first application of ultra-fast magnetic resonance imaging (MRI) towards the characterisation of bubbly flow systems. The principle goal of this study is to provide a hydrodynamic characterisation of a model bubble column...

  19. STATE ESTIMATION OF BUBBLE FREQUENCY AND VELOCITY IN A BUBBLING FLUIDIZED BED

    Microsoft Academic Search

    DALE C. GYURE; DAVID E. CLOUGH

    1986-01-01

    Bubble frequency and velocity in a bubbling fluidized bed are estimated by combining advanced estimation theory and the cross correlation function of pressure measurements. The cross correlation function is shown to be a mathematical function of bubble frequency and velocity. Sequential weighted least squares and a version of Kalman filtering are used to compute optimal estimates of these bubble parameters

  20. The good, the bad and the bubbly. Micro bubble behavior under ultrasound.

    E-print Network

    Greenaway, Alan

    The good, the bad and the bubbly. Micro bubble behavior under ultrasound. Michael Conneely Division of Physics The good, the bad and the bubbly. Micro bubble behavior under ultrasound. PaLS Open Day 2013 #12] microsecond behaviour of microbubbles in Ultrasound fields. · Direct relevance across therapeutic