Sample records for bubble rise characteristics

  1. 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

  2. An Experimental Investigation of Bubble Rise Characteristics in a Crystal Suspended Non—Newtonian Fluid

    NASA Astrophysics Data System (ADS)

    Hassan, N. M. S.; Khan, M. M. K.; Rasul, M. G.; Rackemann, D. W.

    2008-07-01

    An experimental study of the bubble rise characteristics in non-Newtonian fluid with crystal suspension is presented in this paper. The suspension was made of different concentration of xanthan gum solutions with 0.23 mm polystyrene crystal particle. Different percentage of crystal content (by weight) was used to vary rheological properties. The effect of crystal particles and bubble volumes on the bubble rise velocity and bubble trajectory is analysed. The results show that the average bubble velocity increases with the increase in bubble volume for crystal suspended xanthan gum solution. In trajectory analysis, it is seen that the small bubbles experienced less horizontal motion in crystal suspended xanthan gum solution while larger bubbles followed a spiral motion. Experimentally determined data for the drag coefficient at high Reynolds number are compared with the results of other analytical and experimental studies available in the literature. The reported experimental data of drag co-efficient increases in crystal suspended xanthan gum solution for corresponding bubble volume and was found to be consistent with published data.

  3. Modelling of Air Bubble Rising in Water and Polymeric Solution

    NASA Astrophysics Data System (ADS)

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

    2010-06-01

    This study investigates a Computational Fluid Dynamics (CFD) model for a single air bubble rising in water and xanthan gum solution. The bubble rise characteristics through the stagnant water and 0.05% xanthan gum solution in a vertical cylindrical column is modelled using the CFD code Fluent. Single air bubble rise dispersed into the continuous liquid phase has been considered and modelled for two different bubble sizes. Bubble velocity and vorticity magnitudes were captured through a surface-tracking technique i.e. Volume of Fluid (VOF) method by solving a single set of momentum equations and tracking the volume fraction of each fluid throughout the domain. The simulated results of the bubble flow contours at two different heights of the cylindrical column were validated by the experimental results and literature data. The model developed is capable of predicting the entire flow characteristics of different sizes of bubble inside the liquid column.

  4. Simulations of Rising Hydrodynamic and Magnetohydrodynamic Bubbles

    NASA Astrophysics Data System (ADS)

    Ricker, P. M.; Robinson, K.; Dursi, L. J.; Rosner, R.; Calder, A. C.; Zingale, M.; Truran, J. W.; Linde, T.; Caceres, A.; Fryxell, B.; Olson, K.; Riley, K.; Siegel, A.; Vladimirova, N.

    Motivated by recent Chandra and XMM-Newton observations of X-ray emission voids in galaxy cluster cooling flows, we have investigated the behavior of rising bubbles in stratified atmospheres using the FLASH adaptive-mesh simulation code. We present results from two-dimensional simulations with and without the effects of magnetic fields, and with varying bubble sizes and background stratifications. We find purely hydrodynamic bubbles to be unstable; a dynamically important magnetic field is required to maintain a bubble's integrity. This suggests that, even absent thermal conduction, for bubbles to be persistent enough to be regularly observed, they must be supported in large part by magnetic fields. We also observe that magnetically supported bubbles leave a tail as they rise. The structure of these tails may provide clues to the bubble's dynamical history.

  5. Simulations of Rising Hydrodynamic and Magnetohydrodynamic Bubbles

    Microsoft Academic Search

    P. M. Ricker; K. Robinson; L. J. Dursi; R. Rosner; A. C. Calder; M. Zingale; J. W. Truran; T. Linde; A. Caceres; B. Fryxell; K. Olson; K. Riley; A. Siegel; N. Vladimirova

    2004-01-01

    Motivated by recent Chandra and XMM-Newton observations of X-ray emission voids in galaxy cluster cooling flows, we have investigated the behavior of rising bubbles in stratified atmospheres using the FLASH adaptive-mesh simulation code. We present results from two-dimensional simulations with and without the effects of magnetic fields, and with varying bubble sizes and background stratifications. We find purely hydrodynamic bubbles

  6. PATH AND WAKE OF A RISING BUBBLE Cover image: Air bubbles from divers rising to the surface, Hawaii.

    E-print Network

    Twente, Universiteit

    PATH AND WAKE OF A RISING BUBBLE #12;Cover image: Air bubbles from divers rising to the surface . . . . . . . . . . . . . . . . . . . . . 19 4 Image analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 4 Free rising bubbles, Hawaii. Photo taken by Ed Robinson, underwater photographer. ISBN 90 365 15262 Copyright c 2001 by A

  7. Modelling of bubble rising by smoothed particle hydrodynamics method

    NASA Astrophysics Data System (ADS)

    Tofighi, N.; Zainali, A.; Yildiz, M.

    2012-09-01

    In this paper, an incompressible smoothed particle hydrodynamics (ISPH) method for two-phase flows with an improved surface treatment using continuum surface force (CSF) approach is proposed. A better surface representation is achieved through using a cubic spline weighting function for discretizing the equations related to interfacial forces while a quintic spline function is used for other equations. In order to demonstrate the effectiveness of the aforementioned method, rising of a Newtonian bubble surrounded by a viscous liquid is simulated. Results obtained from current simulations are in agreement with data available in literature and show the same characteristics.

  8. Morphology of Rising Hydrodynamic and Magnetohydrodynamic Bubbles from Numerical Simulations

    NASA Astrophysics Data System (ADS)

    Robinson, K.; Dursi, L. J.; Ricker, P. M.; Rosner, R.; Calder, A. C.; Zingale, M.; Truran, J. W.; Linde, T.; Caceres, A.; Fryxell, B.; Olson, K.; Riley, K.; Siegel, A.; Vladimirova, N.

    2004-02-01

    Recent Chandra and XMM-Newton observations of galaxy cluster cooling flows have revealed X-ray emission voids of up to 30 kpc in size that have been identified with buoyant, magnetized bubbles. Motivated by these observations, we have investigated the behavior of rising bubbles in stratified atmospheres using the FLASH9 adaptive-mesh simulation code. We present results from two-dimensional simulations with and without the effects of magnetic fields and with varying bubble sizes and background stratifications. We find purely hydrodynamic bubbles to be unstable; a dynamically important magnetic field is required to maintain a bubble's integrity. This suggests that, even absent thermal conduction, for bubbles to be persistent enough to be regularly observed, they must be supported in large part by magnetic fields. Thermal conduction unmitigated by magnetic fields can dissipate the bubbles even faster. We also observe that the bubbles leave a tail as they rise; the structure of these tails can indicate the history of the dynamics of the rising bubble.

  9. Morphology of Rising Hydrodynamic and Magnetohydrodynamic Bubbles from Numerical Simulations

    Microsoft Academic Search

    K. Robinson; L. J. Dursi; P. M. Ricker; R. Rosner; A. C. Calder; M. Zingale; J. W. Truran; T. Linde; A. Caceres; B. Fryxell; K. Olson; K. Riley; A. Siegel; N. Vladimirova

    2003-01-01

    Recent Chandra and XMM-Newton observations of galaxy cluster cooling flows\\u000ahave revealed X-ray emission voids of up to 30 kpc in size that have been\\u000aidentified with buoyant, magnetized bubbles. Motivated by these observations,\\u000awe have investigated the behavior of rising bubbles in stratified atmospheres\\u000ausing the FLASH adaptive-mesh simulation code. We present results from 2-D\\u000asimulations with and without

  10. Morphology of Rising Hydrodynamic and Magnetohydrodynamic Bubbles from Numerical Simulations

    Microsoft Academic Search

    K. Robinson; L. J. Dursi; P. M. Ricker; R. Rosner; A. C. Calder; M. Zingale; J. W. Truran; T. Linde; A. Caceres; B. Fryxell; K. Olson; K. Riley; A. Siegel; N. Vladimirova

    2004-01-01

    Recent Chandra and XMM-Newton observations of galaxy cluster cooling flows have revealed X-ray emission voids of up to 30 kpc in size that have been identified with buoyant, magnetized bubbles. Motivated by these observations, we have investigated the behavior of rising bubbles in stratified atmospheres using the FLASH9 adaptive-mesh simulation code. We present results from two-dimensional simulations with and without

  11. Advances in the Rising Bubble Technique for discharge measurement

    NASA Astrophysics Data System (ADS)

    Hilgersom, Koen; Luxemburg, Willem; Willemsen, Geert; Bussmann, Luuk

    2014-05-01

    Already in the 19th century, d'Auria described a discharge measurement technique that applies floats to find the depth-integrated velocity (d'Auria, 1882). The basis of this technique was that the horizontal distance that the float travels on its way to the surface is the image of the integrated velocity profile over depth. Viol and Semenov (1964) improved this method by using air bubbles as floats, but still distances were measured manually until Sargent (1981) introduced a technique that could derive the distances from two photographs simultaneously taken from each side of the river bank. Recently, modern image processing techniques proved to further improve the applicability of the method (Hilgersom and Luxemburg, 2012). In the 2012 article, controlling and determining the rising velocity of an air bubble still appeared a major challenge for the application of this method. Ever since, laboratory experiments with different nozzle and tube sizes lead to advances in our self-made equipment enabling us to produce individual air bubbles with a more constant rising velocity. Also, we introduced an underwater camera to on-site determine the rising velocity, which is dependent on the water temperature and contamination, and therefore is site-specific. Camera measurements of the rising velocity proved successful in a laboratory and field setting, although some improvements to the setup are necessary to capture the air bubbles also at depths where little daylight penetrates. References D'Auria, L.: Velocity of streams; A new method to determine correctly the mean velocity of any perpendicular in rivers and canals, (The) American Engineers, 3, 1882. Hilgersom, K.P. and Luxemburg, W.M.J.: Technical Note: How image processing facilitates the rising bubble technique for discharge measurement, Hydrology and Earth System Sciences, 16(2), 345-356, 2012. Sargent, D.: Development of a viable method of stream flow measurement using the integrating float technique, Proceedings of the Institution of Civil Engineers (London), Part 2, 71, 1-15, 1981. Viol, V. and Semenov, V.: Experiments in measuring discharges in canals by the photo-integration method, Soviet Hydrol. Selected Pap, 2, 198-199, 1964.

  12. 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

  13. 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

  14. Numerical simulation on single Taylor bubble rising in LBE using moving particle method

    NASA Astrophysics Data System (ADS)

    Li, Xin; Tian, Wen X.; Chen, Rong H.; Su, Guang H.; Qiu, Sui Z.

    2013-07-01

    An improved meshless numerical method (MPS-MAFL) is utilized to simulate single Taylor bubble rising in liquid LBE to study its hydrodynamic characteristics. The computational region is a circular tube in which the liquid is described using discretized particles by un-uniform grid scheme. The gas-liquid interface was approximately treated as a free surface boundary and nonslip conditions are applied on tube wall. Several simulation results and corresponding analysis including Taylor bubble propagation procedure, pressure distribution, velocity profile around bubble nose and in the wake region as well as in the falling film are presented. Some experimental results and CFD numerical simulations from other previous researchers are compared with the present study as validation. The simulation results agree well with both theoretical analysis and experimental results, which demonstrate the reasonable selection of model as well as the accuracy and reliability of moving particle method.

  15. Effects of gravity level on bubble formation and rise in low-viscosity liquids

    NASA Astrophysics Data System (ADS)

    Suñol, Francesc; González-Cinca, Ricard

    2015-05-01

    We present an experimental analysis of the effects of gravity level on the formation and rise dynamics of bubbles. Experiments were carried out with millimeter-diameter bubbles in the hypergravity environment provided by the large-diameter centrifuge of the European Space Agency. Bubble detachment from a nozzle is determined by buoyancy and surface tension forces regardless of the gravity level. Immediately after detachment, bubble trajectory is deviated by the Coriolis force. Subsequent bubble rise is dominated by inertial forces and follows a zig-zag trajectory with amplitude and frequency dependent on the gravity level. Vorticity production is enhanced as gravity increases, which destabilizes the flow and therefore the bubble path.

  16. 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.

  17. CFD simulations of mass transfer from Taylor bubbles rising in circular capillaries

    Microsoft Academic Search

    J. M. van Baten; R. Krishna

    2004-01-01

    Computational Fluid Dynamics (CFD) is used to investigate mass transfer from Taylor bubbles to the liquid phase in circular capillaries. The liquid phase volumetric mass transfer coefficient kLa was determined from CFD simulations of Taylor bubbles in upflow, using periodic boundary conditions. The separate influences of the bubble rise velocity, unit cell length, film thickness, film length, and liquid diffusivity

  18. Experimental studies on the shape and path of small air bubbles rising in clean water

    Microsoft Academic Search

    Mingming Wu; Morteza Gharib

    2002-01-01

    This Letter reports experiments on the shape and path of air bubbles (diameter range 0.1-0.2 cm) rising in clean water. We find that bubbles in this diameter range have two steady shapes, a sphere and an ellipsoid, depending on the size of the capillary tube from which they detach. The spherical bubbles move significantly slower than the ellipsoidal ones of

  19. Morphology of Rising Hydrodynamic and Magneto-hydrodynamic Bubbles from Numerical Simulations

    E-print Network

    Robinson, K; Ricker, P M; Rosner, R; Calder, A C; Zingale, M A; Truran, J W; Linde, T J; Caceres, A; Fryxell, B; Olson, K; Riley, K; Siegel, A; Vladimirova, N

    2004-01-01

    Recent Chandra and XMM-Newton observations of galaxy cluster cooling flows have revealed X-ray emission voids of up to 30 kpc in size that have been identified with buoyant, magnetized bubbles. Motivated by these observations, we have investigated the behavior of rising bubbles in stratified atmospheres using the FLASH adaptive-mesh simulation code. We present results from 2-D simulations with and without the effects of magnetic fields, and with varying bubble sizes and background stratifications. We find purely hydrodynamic bubbles to be unstable; a dynamically important magnetic field is required to maintain a bubble's integrity. This suggests that, even absent thermal conduction, for bubbles to be persistent enough to be regularly observed, they must be supported in large part by magnetic fields. Thermal conduction unmitigated by magnetic fields can dissipate the bubbles even faster. We also observe that the bubbles leave a tail as they rise; the structure of these tails can indicate the history of the dyn...

  20. The Mechanics of Large Bubbles Rising through Extended Liquids and through Liquids in Tubes

    Microsoft Academic Search

    R. M. Davies; Geoffrey Taylor

    1950-01-01

    Part I describes measurements of the shape and rate of rise of air bubbles varying in volume from 1\\\\cdot 5 to 200 cm.3 when they rise through nitrobenzene or water. Measurements of photographs of bubbles formed in nitrobenzene show that the greater part of the upper surface is always spherical. A theoretical discussion, based on the assumption that the pressure

  1. Path instabilities of clean and contaminated air bubbles rising in treated water

    Microsoft Academic Search

    Joshua Alexander Forbes; Mingming Wu

    2002-01-01

    We report experimental results on path instabilities of clean and contaminated air bubbles (diameter range 0.1 - 0.3 cm) rising in treated (distilled and filtered) water. It is known that air bubbles rise via a straight path when its equivalent diameter is less than about 0.13 - 0.18 cm, and via a spiral or zigzag path for larger bubbles. It

  2. Transient and steady state of a rising bubble in a viscoelastic fluid

    NASA Astrophysics Data System (ADS)

    Pillapakkam, Shriram B.; Singh, Pushpendra; Blackmore, Denis; Aubry, Nadine

    A finite element code based on the level-set method is used to perform direct numerical simulations (DNS) of the transient and steady-state motion of bubbles rising in a viscoelastic liquid modelled by the Oldroyd-B constitutive equation. The role of the governing dimensionless parameters, the capillary number (Ca), the Deborah number (De) and the polymer concentration parameter c, in both the rising speed and the deformation of the bubbles is studied. Simulations show that there exists a critical bubble volume at which there is a sharp increase in the terminal velocity with increasing bubble volume, similar to the behaviour observed in experiments, and that the shape of both the bubble and its wake structure changes fundamentally at that critical volume value. The bubbles with volumes smaller than the critical volume are prolate shaped while those with volumes larger than the critical volume have cusp-like trailing ends. In the latter situation, we show that there is a net force in the upward direction because the surface tension no longer integrates to zero. In addition, the structure of the wake of a bubble with a volume smaller than the critical volume is similar to that of a bubble rising in a Newtonian fluid, whereas the wake structure of a bubble with a volume larger than the critical value is strikingly different. Specifically, in addition to the vortex ring located at the equator of the bubble similar to the one present for a Newtonian fluid, a vortex ring is also present in the wake of a larger bubble, with a circulation of opposite sign, thus corresponding to the formation of a negative wake. This not only coincides with the appearance of a cusp-like trailing end of the rising bubble but also propels the bubble, the direction of the fluid velocity behind the bubble being in the opposite direction to that of the bubble. These DNS results are in agreement with experiments.

  3. An analytical approach to the rise velocity of periodic bubble trains in non-Newtonian fluids.

    PubMed

    Frank, X; Li, H Z; Funfschilling, D

    2005-01-01

    The present study aims at providing insight into the acceleration mechanism of a bubble chain rising in shear-thinning viscoelastic fluids. The experimental investigation by the Particle Image Velocimetry (PIV), birefringence visualisation and rheological simulation shows that two aspects are central to bubble interactions in such media: the stress creation by the passage of bubbles, and their relaxation due to the fluid's memory forming an evanescent corridor of reduced viscosity. Interactions between bubbles were taken into account mainly through a linear superposition of the stress evolution behind each bubble. An analytical approach together with the rheological consideration was developed to compute the rise velocity of a bubble chain in function of the injection period and bubble volume. The model predictions compare satisfactorily with the experimental investigation. PMID:15688138

  4. 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.

  5. Morphology of Rising Hydrodynamic and Magneto-hydrodynamic Bubbles from Numerical Simulations

    E-print Network

    K. Robinson; L. J. Dursi; P. M. Ricker; R. Rosner; A. C. Calder; M. Zingale; J. W. Truran; T. Linde; A. Caceres; B. Fryxell; K. Olson; K. Riley; A. Siegel; N. Vladimirova

    2003-10-21

    Recent Chandra and XMM-Newton observations of galaxy cluster cooling flows have revealed X-ray emission voids of up to 30 kpc in size that have been identified with buoyant, magnetized bubbles. Motivated by these observations, we have investigated the behavior of rising bubbles in stratified atmospheres using the FLASH adaptive-mesh simulation code. We present results from 2-D simulations with and without the effects of magnetic fields, and with varying bubble sizes and background stratifications. We find purely hydrodynamic bubbles to be unstable; a dynamically important magnetic field is required to maintain a bubble's integrity. This suggests that, even absent thermal conduction, for bubbles to be persistent enough to be regularly observed, they must be supported in large part by magnetic fields. Thermal conduction unmitigated by magnetic fields can dissipate the bubbles even faster. We also observe that the bubbles leave a tail as they rise; the structure of these tails can indicate the history of the dynamics of the rising bubble.

  6. Modelling bubble rise and interaction with a glass Rogerio Manica1*

    E-print Network

    Chan, Derek Y C

    of the thin water film trapped between the deformed bubble and the glass plate. Our experiments were performedModelling bubble rise and interaction with a glass surface Rogerio Manica1* , Maurice H. W. Hendrix gravity in water and colliding with a horizontal glass plate. Based on lubrication theory, it can account

  7. 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

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

    PubMed

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

    2015-06-23

    A force balance model for the rise and impact of air bubbles in a liquid against rigid horizontal surfaces that takes into account effects of buoyancy and hydrodynamic drag forces, bubble deformation, inertia of the fluid via an added mass force, and a film force between the bubble and the rigid surface is proposed. Numerical solution of the governing equations for the position and velocity of the center of mass of the bubbles is compared against experimental data taken with ultraclean water. The boundary condition at the air-water interface is taken to be stress free, which is consistent for bubbles in clean water systems. Features that are compared include bubble terminal velocity, bubbles accelerating from rest to terminal speed, and bubbles impacting and bouncing off different solid surfaces for bubbles that have already or are yet to attain terminal speed. Excellent agreement between theory and experiments indicates that the forces included in the model constitute the main physical ingredients to describe the bouncing phenomenon. PMID:26035016

  9. Technical Note: How image processing facilitates the rising bubble technique for discharge measurement

    NASA Astrophysics Data System (ADS)

    Hilgersom, K. P.; Luxemburg, W. M. J.

    2012-02-01

    In this article, we rehabilitate the integrating rising bubble technique as an effective means of obtaining discharge measurements. Since Sargent (1981, 1982a), the technique has not been applied widely, mainly as a result of practical difficulties. We hypothesize that modern image processing techniques can greatly improve the rising bubble technique. We applied the technique in both a laboratory setup and a field study, after determining the bubble rising velocity for our nozzles in the specific case. During our measurements, we captured digital photographs of the bubble envelope at the water surface, each picture being a single measurement of the discharge. The photographs were corrected for lens distortion and reprojected so that accurate distances on water surface level could be obtained. This easy digital procedure resulted in accurate discharge measurements, even when turbulence was involved and the averages of multiple image analyses yielded good results. The study shows that the rising bubble technique can be a preferable discharge gauging technique in some situations. Recent developments in image processing facilitate the method substantially.

  10. 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

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

    NASA Astrophysics Data System (ADS)

    Tagawa, Yoshiyuki; Takagi, Shu; Matsumoto, Yoichiro

    2013-11-01

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

  12. Path instability of rising spheroidal air bubbles: A shape-controlled process

    NASA Astrophysics Data System (ADS)

    Zenit, Roberto; Magnaudet, Jacques

    2008-06-01

    The conditions for which the paths of freely rising bubbles become oscillatory are studied experimentally using silicone oils with viscosities ranging from 0.5 to 9.4 times that of water. Since these fluids are nonpolar, as opposed to water, the gas-liquid interfaces remain clean without the need of an ultrapure environment. We find the Reynolds number at incipient transition to vary from 70 to 470, for decreasing liquid viscosity. Correspondingly, the bubble aspect ratio remains almost constant, ranging only from 2.36 to 2.0 for the same set of conditions. Hence, we argue that the dominant parameter to trigger the instability is the bubble shape and not the Reynolds number. Since vorticity generated at the bubble surface is almost independent of the Reynolds number and mostly depends on the bubble aspect ratio in the parameter range covered by our experiments, present results strongly support the view that path instability is a direct consequence of the wake instability that occurs when this surface vorticity exceeds a certain threshold.

  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 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

  15. Prediction of micro-bubble dissolution characteristics in water and seawater

    SciTech Connect

    Kawahara, Akimaro; Sadatomi, Michio; Matsuura, Hidetoshi; Tominaga, Mayo; Noguchi, Masanori [Department of Mechanical System Engineering, Kumamoto University, Kurokami 2-39-1, Kumamoto City 860-8555 (Japan); Matsuyama, Fuminori [Department of Mechanical Engineering, Sasebo National College of Technology (Japan)

    2009-07-15

    This paper is concerned with the prediction of micro-bubble dissolution characteristics in water and seawater when microbubbles are generated by a Sadatomi-type micro-bubble generator (2003) with a spherical body in a flowing liquid tube. In the experiments, in order to know the effects of the salinity on the characteristics, tap water and an artificial seawater with different salt concentrations of 1 and 3 wt% were used as the test liquids. Parameters measured were the Sauter mean diameter of bubbles, d{sub BS}, the void fraction, {alpha}, the rising velocity of bubbles, u{sub G}, the interfacial area concentration, a, the volumetric mass transfer coefficient, K{sub L}a, and the liquid-side mass transfer coefficient, K{sub L}. In the analysis, for predicting {alpha}, K{sub L}a and K{sub L}, some correlations in the literatures were tested against the present data. Furthermore, in order to improve the predictability, new correlations were developed based on the present data. The prediction of K{sub L}a with the new correlation agreed well with Nishino et al.'s [T. Nishino, K. Terasaka, M. Ishida, Application for several micro-bubble generators for gas absorber, in: Proceedings of the Annual Meeting of the Japanese Society for Multiphase Flow, 2006, pp. 276-277 (in Japanese)] and Li and Tsuge's [P. Li, H. Tsuge, Water treatment by induced air flotation using microbubbles, Journal of Chemical Engineering of Japan 39 (2006) 896-903; P. Li, H. Tsuge, Ozone transfer in a new gas-induced contactor with microbubbles, Journal of Chemical Engineering of Japan 39 (2006) 1213-1220] data for different aeration systems using several different micro-bubble generators. (author)

  16. 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.

    1980-06-01

    This report investigates the effect of interfacial nonequilibrium mass transfer and radiative heat transfer on the amount of the fuel vapor condensed before the bubble reaches to the cover-gas region. 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 an Hypothetical Core Disruptive Accident (HCDA). The two-phase bubble mixture as it rises through the sodium pool to the cover-gas region is formulated. 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. The effects of nonequilibrium mass transfer become more meaningful at the later stage of the 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 is found to be possible. As a result, 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 leaking out of the reactor vessel.

  17. Occurrence characteristics of plasma bubble derived from global ground-based GPS receiver networks

    Microsoft Academic Search

    M. Nishioka; A. Saito; T. Tsugawa

    2008-01-01

    Occurrence characteristic of plasma bubble was studied using ground-based GPS receiver networks. The occurrence rate of plasma bubble derived from the global GPS network has higher spatial and temporal resolution than that derived from the other observational techniques because of its wide coverage of the observation. The physical characteristics of plasma bubble occurrence were studied in detail with this novel

  18. Buoyancy-Driven Path Instabilities of Bubble Rising in Simple and Polymer Solutions of Hele-Shaw Cell

    NASA Astrophysics Data System (ADS)

    Kawaguchi, Masami; Niga, Sukehiro; Gou, Nobuaki; Miyake, Kazuo

    2006-12-01

    The buoyancy-driven path instabilities of an air bubble rising in a Hele-Shaw cell are examined as a function of the ratio of the gravitational and the capillary forces, i.e., the Eötvös number (\\mathit{Eo}) of the bubble, for pure water, aqueous isopropyl alcohol (IPA) solutions, and aqueous hydroxypropyl methyl cellulose (HPMC) solutions. In the simple solutions, when \\mathit{Eo} exceeds a threshold value, the motion of the bubble center can be categorized into three regimes: (1) a zigzag path for small \\mathit{Eo}, (2) a straight path for intermediate \\mathit{Eo}, and (3) another zigzag path accompanied by changes in the bubble for larger \\mathit{Eo}; these transitions occur irrespective of the fluid we examined. For HPMC solutions with concentrations lower than 0.001 g/100 mL, three different trajectories—a damped vibrational motion without changes in the bubble shape, a straight trajectory, and another damped vibrational motion accompanied by changes in the bubble shape—are observed as \\mathit{Eo} increases. However, such path instabilities are suppressed for HPMC solutions with concentrations higher than 0.005 g/100 mL. Moreover, path instabilities occur when the Strouhal number exceeds a threshold of 0.2, which leads to the oscillation of the periphery length of the bubble for any of the solutions we studied.

  19. 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

  20. General formulation of an HCDA bubble rising in a sodium pool and the effect of nonequilibrium on fuel transport. [LMFBR

    SciTech Connect

    Kocamustafaogullari, G.; Chan, S.H.

    1980-01-01

    This report which improved the formulation of the previous reports is designed to investigate the effect of the interfacial nonequilibrium mass transfer and the radiative heat transfer on the amount of the fuel vapor condensed before the bubble reaches to the cover-gas region. 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 an Hypothetical Core Disruptive Accident (HCDA). The two-phase bubble mixture as it rises through the sodium pool to the cover-gas region is formulated. 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.

  1. 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.

  2. Influence of characteristics of micro-bubble clouds on backscatter lidar signal.

    PubMed

    Li, Wei; Yang, Kecheng; Xia, Min; Rao, Jionghui; Zhang, Wei

    2009-09-28

    Marine micro-bubbles are one of those important constituents that influence scattering characteristics of water column. Monte Carlo Based simulations show that a water entrained bubble cloud generate a characteristic backscatter of incident laser light [M. Xia, J. Opt. A: Pure Appl. Opt. 8, 350 (2006)]. This characteristic can be used to detect and localize bubble clouds, leading to wide ranging applications, especially in optical remote sensing. This paper describes tests of an underwater lidar system applied to detecting cloud of micro-bubbles. Laboratory experiments demonstrate that the system is capable of detecting bubbles ranging from diameter 10 microm approximately 200 microm, over a distance of 7-12 m from the detector. The dependence of the lidar return signal on size distribution of bubbles, concentration, thickness and location of bubble clouds is studied and compared with simulation results. PMID:19907564

  3. 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.

  4. A laser imaging-LDV coupling measurement of single bubble forming and rising in shear-thinning fluid

    NASA Astrophysics Data System (ADS)

    Fan, Wenyuan; Yin, XiaoHong

    2014-06-01

    The shape evolution of bubble formed in carboxymethylcellulose (CMC) aqueous solution was real-time observed using laser image technique. The flow fields of liquid around growing and rising bubble were measured by laser Doppler velocimetry (LDV), and the liquid mean velocity and its contour curves were obtained. The results show that bubble grows as spherical shape because of the dominant role of surface tension in the early period, and then is stretched gradually as a teardrop shape due to the common effect of buoyancy and shear-thinning of fluid. The axial mean velocity of liquid phase takes on Gaussian distribution with the symmetrical axis passing through orifice center. However, the radial mean velocity increases first and then decreases with the increase of the distance from measured point to the symmetrical axis above. Further, the axial component along symmetrical axis decreases initially and increases with the rise of height, as well as its corresponding contour map diverging gradually. The radial component, yet, decreases steadily with the rise of height, and the maximum value deviates towards the two sides until disappear, as it contour shape of butterfly's "front wing".

  5. 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

  6. Particle Image Velocimetry Measurements of the Mean Flow Characteristics in a Bubble Plume

    Microsoft Academic Search

    Dong-Guan Seol; Tirtharaj Bhaumik; Christian Bergmann; Scott A. Socolofsky

    2007-01-01

    A direct measurement method for the velocity field in multiphase flows using the particle image velocimetry PIV and particle tracking velocimetry PTV methods is developed to study the flow characteristics of an unbounded bubble plume in quiescent, unstrati- fied ambient conditions. A single camera is used to obtain images containing both bubbles and fluid tracer particles. Using gray-scale thresholding, phase-separated

  7. A study of velocity discontinuity for single air bubbles rising in an associative polymer

    Microsoft Academic Search

    E. Soto; C. Goujon; R. Zenit; O. Manero

    2006-01-01

    The motion of air bubbles in aqueous solutions of a hydrophobic alkali-swellable associative polymer is studied in this work. The associative nature of these polymer systems dictates their rheological properties: for moderate values of the shear rate, the formation of structure can lead to a shear-thickening behavior and to the appearance of first normal stress difference. For larger shear rates,

  8. Review of bubble detector response characteristics and results from space.

    PubMed

    Lewis, B J; Smith, M B; Ing, H; Andrews, H R; Machrafi, R; Tomi, L; Matthews, T J; Veloce, L; Shurshakov, V; Tchernykh, I; Khoshooniy, N

    2012-06-01

    A passive neutron-bubble dosemeter (BD), developed by Bubble Technology Industries, has been used for space applications. Both the bubble detector-personal neutron dosemeter and bubble detector spectrometer have been studied at ground-based facilities in order to characterise their response due to neutrons, heavy ion particles and protons. This technology was first used during the Canadian-Russian collaboration aboard the Russian satellite BION-9, and subsequently on other space missions, including later BION satellites, the space transportation system, Russian MIR space station and International Space Station. This paper provides an overview of the experiments that have been performed for both ground-based and space studies in an effort to characterise the response of these detectors to various particle types in low earth orbit and presents results from the various space investigations. PMID:21890528

  9. 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.

  10. CHARACTERISTICS OF THE SECONDARY BUBBLE CLUSTER PRODUCED BY AN ELECTROHYDRAULIC SHOCK WAVE LITHOTRIPTER

    PubMed Central

    Zhou, Yufeng; Qin, Jun; Zhong, Pei

    2013-01-01

    This study investigated the characteristics of the secondary bubble cluster produced by an electrohydraulic lithotripter using high-speed imaging and passive cavitation detection techniques. The results showed that (i) the discrepancy of the collapse time between near a flat rigid boundary and in a free field of the secondary bubble cluster was not as significant as that by the primary one; (ii) the secondary bubble clusters were small but in a high bubble density and nonuniform in distribution, and they did not expand and aggregate significantly near a rigid boundary; and (iii) the corresponding bubble collapse was weaker with few microjet formation and bubble rebound. By applying a strong suction flow near the electrode tip, the production of the secondary shock wave (SW) and induced bubble cluster could be disturbed significantly, but without influence on the primary ones. Consequently, stone fragmentation efficiency was reduced from 41.2 ± 7.1% to 32.2 ± 3.5% after 250 shocks (p <0.05). Altogether, these observations suggest that the secondary bubble cluster produced by an electrohydraulic lithotripter may contribute to its ability for effective stone fragmentation. PMID:22390990

  11. Numerical simulation of the water bubble rising in a liquid column using the combination of level set and moving mesh methods in the collocated grids

    E-print Network

    Frey, Pascal

    of bubble rising in a liquid column is critical in the investigation of the waterevapour two phase flow in the nuclear industry, more than 90% power generated by nuclear is from water-cooled nuclear reactors either Pressurized Water Reactor (PWR) or Boiling Water Reactor (BWR). Water boils inside the BWRs. Although water

  12. Motion characteristics of cavitation bubble near the rigid wall with the driving of acoustic wave

    NASA Astrophysics Data System (ADS)

    Ye, Xi; Zhang, A.-man; Zeng, Dong-rui

    2015-03-01

    The dynamics of cavitation bubble is analyzed in the compressible fluid by use of the boundary integral equation considering the compressibility. After the vertical incidence of plane wave to the rigid wall, the motion characteristics of single cavitation bubble near the rigid wall with initial equilibrium state are researched with different parameters. The results show that after the driving of acoustic wave, the cavitation bubble near the rigid wall will expand or contract, and generate the jet pointing to the wall. Also, the existence of the wall will elongate time for one oscillation. With the compressible model, the oscillation amplitude is reduced, as well as the peak value of inner pressure and jet tip velocity. The effect of the wall on oscillation amplitude is limited. However with the increment of initial vertical distance, the effect of wall on the jet velocity is from acceleration to limitation, and finally to acceleration again.

  13. 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.

  14. Characteristics and detecting of laser-induced single bubble collapse noise

    NASA Astrophysics Data System (ADS)

    Liu, Xiumei; He, Jie; Li, Wenhua; Jiao, Mingli; Liu, Xiaochen; Wang, Haibing; Wang, Bingyang; Li, Beibei

    2015-05-01

    Shock waves emission after collapse of a laser-induced bubble in the liquid was studied experimentally by using a PTZ hydrophone. An experimental method and a Cavitation detection system was designed to investigate bubble collapse noise in this article. When a focused short laser pulse was focused in a liquid near a solid wall, it induced optical breakdown, the emission of shock waves and the generation of cavitation bubbles. A PZT hydrophone was used to detect the shock wave emitted during bubble oscillations. In addition, a software based on MATLAB was designed for analyzing cavitation noise. The software system had multiple functionalities, namely signal reading, noise reduction, signal analysis in frequency domain, and display. The results showed that the software can not only reflect the spectral characteristics of the noise quickly but also can interpret the current cavitation station according to the changing rules of different cavitation station. The results of the research have strong implications for cavitation phenomena analysis and cavitation warning systems in turbines, propellers, and other irrigation machinery.

  15. 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.

  16. Airflow Characteristics of Direct-Type Kitchen Hood Systems in High-Rise Apartment Buildings 

    E-print Network

    Park, M.

    2011-01-01

    Airflow characteristics of direct-type kitchen hood systems in high-rise apartment buildings 1 10.19. 2011 Myungsig Park* , Joseph Jun Kim Innovations Optima LLC Bonggil Jeon Dept of Architectural Engineering, Purdue University Geontae Lee..., Samsung C&T, South Korea 2 Introduction ? Today?s high-rise apartment buildings exhibit high degree of air-tightness. ? They are also subjected to stack effect and seasonal, unpredictable, wind pressure variations. ? Therefore, it is questionable...

  17. Bubble Formation at Metal-Metal Interfaces and its Effect on the Superconducting Characteristics of Aluminum-Indium Laminate Films

    Microsoft Academic Search

    John L. Miles; P. H. Smith

    1963-01-01

    The critical temperature of aluminum-indium laminates was investigated ; in a vacuum of 10⁻⁶ Torr. The transition temperature was found to rise ; upon aging, indicating that a barrier was formed between the films. When the ; aluminumindium laminate was removed from vacuum, bubbles started to form at the ; interface. It was suggested that water vapor oxidizes the top

  18. Bubble Contact Angle Method for Evaluating Substratum Interfacial Characteristics and Its Relevance to Bacterial Attachment

    PubMed Central

    Fletcher, Madilyn; Marshall, K. C.

    1982-01-01

    A bubble contact angle method was used to determine interfacial free-energy characteristics of polystyrene substrata in the presence and absence of potential surface-conditioning proteins (bovine glycoprotein, bovine serum albumin, fatty acid-free bovine serum albumin), a bacterial culture supernatant, and a bacterial exopolymer. Clean petri dish substrata gave a contact angle of 90°, but tissue culture dish substrata were more hydrophilic, giving an angle of 29° or less. Bubble contact angles at the surfaces exposed to the macromolecular solutions varied with the composition and concentration of the solution. Modification by pronase enzymes of the conditioning effect of proteins depended on the nature of both the substratum and the protein, as well as the time of addition of the enzyme relative to the conditioning of the substratum. The effects of dissolved and substratum-adsorbed proteins on the attachment of Pseudomonas sp. strain NCMB 2021 to petri dishes and tissue culture dishes were consistent with changes in bubble contact angles (except when proteins were adsorbed to tissue culture dishes before attachment) as were alterations in protein-induced inhibition of bacterial attachment to petri dishes by treatment with pronase. Differences between the attachment of pseudomonads to petri dishes and tissue culture dishes suggested that different mechanisms of adhesion are involved at the surfaces of these two substrata. PMID:16346054

  19. 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.

  20. Airflow Characteristics of Direct-Type Kitchen Hood Systems in High-Rise Apartment Buildings

    E-print Network

    Park, M.

    2011-01-01

    Airflow characteristics of direct-type kitchen hood systems in high-rise apartment buildings 1 10.19. 2011 Myungsig Park* , Joseph Jun Kim Innovations Optima LLC Bonggil Jeon Dept of Architectural Engineering, Purdue University Geontae Lee... if the adoption of direct- type systems alone in place of the shared-type would yield the level of capture efficiency close to the hood design specification. 3 4 5 6 Figure 1: Layout of apartment used to analyze airflow 7 (a)?24?hour...

  1. Characteristics of indoor and outdoor bioaerosols at Korean high-rise apartment buildings

    Microsoft Academic Search

    Ji-Hyun Lee; Wan-Kuen Jo

    2006-01-01

    This study attempted to evaluate the bioaerosol exposure of apartment residents at high-rise apartment buildings in a Korean city. The characteristics associated with the bioaerosol exposure included the apartment floor, seasonal variation, summer survey period (seasonal rain-front period (SRFP) or no rain-front period (NRFP)), and room location inside an apartment. Four most prevalent fungal genera detected in both the indoor

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. A characteristic size of approximately 10 Mpc for the ionized bubbles at the end of cosmic reionization.

    PubMed

    Wyithe, J Stuart B; Loeb, Abraham

    2004-11-11

    The first galaxies to appear in the Universe at redshifts z > 20 created ionized bubbles in the intergalactic medium of neutral hydrogen left over from the Big Bang. The ionized bubbles grew with time, surrounding clusters of dwarf galaxies and eventually overlapped quickly throughout the Universe over a narrow redshift interval near z approximately 6. This event signalled the end of the reionization epoch when the Universe was a billion years old. Measuring the size distribution of the bubbles at their final overlap phase is a focus of forthcoming programmes to observe highly redshifted radio emission from atomic hydrogen. Here we show that the combined constraints of cosmic variance and light travel time imply an observed bubble size at the end of the overlap epoch of approximately 10 physical Mpc, and a scatter in the observed redshift of overlap along different lines-of-sight of approximately 0.15. This scatter is consistent with observational constraints from recent spectroscopic data on the farthest known quasars. This implies that future radio experiments should be tuned to a characteristic angular scale of 0.5 degrees and have a minimum frequency bandwidth of approximately 8 MHz for an optimal detection of 21-cm flux fluctuations near the end of reionization. PMID:15538361

  7. Simple model of the optical characteristics of bubbles and sediments in seawater of the surf zone.

    PubMed

    Zege, Eleonora P; Katsev, Iosif L; Prikhach, Alexander S; Gilbert, Gary; Witherspoon, Ned

    2006-09-01

    The development of a simple model of the seawater inherent optical properties (IOPs) associated with bubbles and sediments would represent a great advance in surf zone optics. We present one solution for this problem using a combination of geometrical optics and Fraunhofer diffraction. An analytic model of the IOPs of bubbles and sediments (the extinction and absorption coefficients, and phase function) is developed in terms of the moments of the particle size distribution and the complex refractive index of particles. PMID:16912798

  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. 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.

  10. 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.

  11. Seismic characteristics of outer-rise earthquakes in the different seismic coupling subduction zones

    NASA Astrophysics Data System (ADS)

    Lee, Hsin-Hua; Lin, Jing-Yi

    2013-04-01

    Characterizing the seismogenic zone of major subduction plate boundaries provides us a possible to reduce large earthquakes hazard. In the past several decades, many scientists have analyzed various geophysical methods and datasets, such as seismic and geodetic ground motion data, historical tsunami deposits, aftershock distributions, and seafloor bathymetry, trying to understand the mechanisms behind great devastating earthquakes, and to estimate the probability of a major earthquake occurrence in the future. In this study, by using the global earthquake catalog (GCMT) from January 1, 1976 to December 31, 2011. We firstly re-examines the outer-rise earthquake model proposed by the Christensen (1988) at the subduction zones suggested to have different coupling levels. The compressive stress cumulated during the subducting processes are often reflected by the occurrence of compressional outer-rise earthquakes. Thus, in the region where the compressional outer-rise earthquakes take place without any corresponding large underthrusting earthquakes, the seismic potential is usually considered to be high. We re-examined the high seismic potential areas determined by this criteria in Christensen (1988) and confirm that the large underthrusting earthquakes did really occur in the 30 years following the appearance of compressional outer-rise events, such as in Tonga region in the vicinity of 20S, a Mw 8.3 large earthquake occurred in 2006. This result represents that the outer-rise earthquake model could be an indicator for the generation of large earthquakes along subduction zones. In addition, to have a more accurate estimation for the seismic potential, we discuss the relationship between the generation of earthquakes and the change of cumulative gravitational potential energy caused by earthquakes (?GPE) over time. Our result shows an acceleration of ?GPE before large earthquakes. Our result also shows that the extensional outer-rise events for strong seismic coupling subduction zone only presented after the occurrence of earthquakes with magnitude larger than 8, for instance, after the 2012 March Mw 9.0 Tohoku, the 2010 February Mw 8.8 Chili and the 2006 November Mw8.3 Kamchatka earthquakes, which is consistent with the analysis performed by Christensen (1988). Based on our analysis, the outer rise earthquakes occur immediately after the main event which does not coincide with the result stating in Christensen (1988) that they occur in the 30 years after the earthquake. In addition, the duration of the extensional outer-rise earthquakes occurrence appears to be correlated with its magnitude. Meanwhile, for the earthquakes with magnitude smaller than 8, as well as in the weak coupling areas, this observation is not engaged.

  12. Characteristics of temperature rise in variable inductor employing magnetorheological fluid driven by a high-frequency pulsed voltage source

    NASA Astrophysics Data System (ADS)

    Lee, Ho-Young; Kang, In Man; Shon, Chae-Hwa; Lee, Se-Hee

    2015-05-01

    A variable inductor with magnetorheological (MR) fluid has been successfully applied to power electronics applications; however, its thermal characteristics have not been investigated. To evaluate the performance of the variable inductor with respect to temperature, we measured the characteristics of temperature rise and developed a numerical analysis technique. The characteristics of temperature rise were determined experimentally and verified numerically by adopting a multiphysics analysis technique. In order to accurately estimate the temperature distribution in a variable inductor with an MR fluid-gap, the thermal solver should import the heat source from the electromagnetic solver to solve the eddy current problem. To improve accuracy, the B-H curves of the MR fluid under operating temperature were obtained using the magnetic property measurement system. In addition, the Steinmetz equation was applied to evaluate the core loss in a ferrite core. The predicted temperature rise for a variable inductor showed good agreement with the experimental data and the developed numerical technique can be employed to design a variable inductor with a high-frequency pulsed voltage source.

  13. Power Laws in Real Estate Prices during Bubble Periods

    NASA Astrophysics Data System (ADS)

    Ohnishi, Takaaki; Mizuno, Takayuki; Shimizu, Chihiro; Watanabe, Tsutomu

    How can we detect real estate bubbles? In this paper, we propose making use of information on the cross-sectional dispersion of real estate prices. During bubble periods, prices tend to go up considerably for some properties, but less so for others, so that price inequality across properties increases. In other words, a key characteristic of real estate bubbles is not the rapid price hike itself but a rise in price dispersion. Given this, the purpose of this paper is to examine whether developments in the dispersion in real estate prices can be used to detect bubbles in property markets as they arise, using data from Japan and the U.S. First, we show that the land price distribution in Tokyo had a power-law tail during the bubble period in the late 1980s, while it was very close to a lognormal before and after the bubble period. Second, in the U.S. data we find that the tail of the house price distribution tends to be heavier in those states which experienced a housing bubble. We also provide evidence suggesting that the power-law tail observed during bubble periods arises due to the lack of price arbitrage across regions.

  14. Characteristics of air pollutant dispersion around a high-rise building.

    PubMed

    Zhang, Y; Kwok, K C S; Liu, X-P; Niu, J-L

    2015-09-01

    A numerical wind tunnel model was proposed. The computed results of the pollutant diffusion around a typical Hong Kong high-rise building model (at a linear scale of 1:30), were found to show a similar trend to the outcomes of self-conducted experimental measurements that the pathways of pollutant migration for windward and leeward pollutant emission are different. For the case with windward pollutant emission at the 3rd floor within a re-entry, the pollutant migrated downwards due to the downwash created by the wind. In contrast, for the case with leeward pollution emission, dispersion is dominated by intense turbulent mixing in the near wake and characterized by the upward migration of the pollutant in the leeward re-entry. The simulated results of haze-fog (HF) studies confirm that the pathway of pollutant migration is dominated by wind-structure interaction and buoyancy effect only plays a minor role in the dispersion process. PMID:25989454

  15. Characteristics and Obstacles: The Rise of African American Male Principals in Texas

    ERIC Educational Resources Information Center

    Black, Willie James, Jr.

    2012-01-01

    The purpose of this study was to investigate the characteristics of African American males and the obstacles they experience on their path to the principalship. A secondary purpose, but very important as well, was to analyze critically the experiences of successful African American male principals to help inform the preparation of principals who…

  16. Characteristics and scaling of bubble plumes from marine hydrocarbon seepage in the Coal Oil Point seep field

    Microsoft Academic Search

    Ira Leifer

    2010-01-01

    The fate of marine seep gases in the ocean and atmosphere is intimately connected with bubble and bubble-plume processes, which are strongly size- and depth-dependent. Size-dependent flux distributions, ?, and vertical velocity functions, VZ(r), were measured with a video bubble measurement system in the Santa Barbara Channel, California. Several distinct plume types were identified for which size distributions were measured,

  17. Effect of Convex Longitudinal Curvature on the Planing Characteristics of a Surface Without Dead Rise

    NASA Technical Reports Server (NTRS)

    Mottard, Elmo J.

    1959-01-01

    A hydrodynamic investigation was made in Langley tank no. 1 of a planing surface which was curved longitudinally in the shape of a circular arc with the center of curvature above the model and had a beam of inches and a radius of curvature of 20 beams. The planing surface had length-beam ratio of 9 and an angle of dead rise of 0 deg. Wetted length, resistance, and trimming moment were determined for values of load coefficient C(sub Delta) from -4.2 to 63.9 and values of speed coefficient C(sub V) from 6 to 25. The effects of convexity were to increase the wetted length-beam ratio (for a given lift), to decrease the lift-drag ratio, to move the center of pressure forward, and ta increase the trim for maximum lift-drag ratio as compared with values for a flat surface. The effects were greatest at low trims and large drafts. The maximum negative lift coefficient C(sub L,b) obtainable with a ratio of the radius of curvature to the beam of 20 was -0.02. The effects of camber were greater in magnitude for convexity than for the same amount of concavity.

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

    Microsoft Academic Search

    D. Bröder; M. Sommerfeld

    2002-01-01

    Bubble columns are widely used in the chemical industry and biotechnology. Flow and turbulence in such an apparatus are induced by the bubble rise, and the bubble behaviour is strongly affected by swarm effects (i.e. the interaction between bubbles). For analysing the bubble swarm behaviour and simultaneously evaluating the flow structure and bubble-induced turbulence, a bubble column of 140 mm

  19. Compact bubble clusters in Newtonian and non-Newtonian liquids

    NASA Astrophysics Data System (ADS)

    Vélez-Cordero, J. Rodrigo; Lantenet, Johanna; Hernández-Cordero, Juan; Zenit, Roberto

    2014-05-01

    We studied the terminal velocity of a packed array of bubbles, a bubble cluster, rising in different fluids: a Newtonian fluid, an elastic fluid with nearly constant viscosity (Boger fluid), and a viscoelastic fluid with a shear dependent viscosity, for small but finite Reynolds numbers (1 × 10-4 < Re < 4). In all three cases, the cluster velocity increased with the total volume, following the same trend as single bubbles. For the case of clusters in elastic fluids, interestingly, the so-called velocity discontinuity was not observed, unlike the single bubble case. In addition to the absence of jump velocity, the clusters did not show the typical teardrop shape of large bubbles in viscoelastic fluids and the strength of the negative wake is much weaker than the one observed behind single bubbles. Dimensional analysis of the volume-velocity plots allowed us to show that, while the equivalent diameter (obtained from the total cluster volume) is the appropriate length to determine buoyancy forces and characteristic shear rates, the individual bubble size is the appropriate scale to account for surface forces.

  20. 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

  1. 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.

  2. Bubble - Crystal Interactions in Magmatic Three-Phase Systems

    Microsoft Academic Search

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

    2007-01-01

    The influence of crystals on the movement of bubbles through basaltic magmas is poorly understood. We study the interaction of bubbles with a suspension of crystals in a viscous fluid through analog experiments. In our experiments, an air bubble rises through a suspension of plastic beads in a viscous corn syrup - water mixture; we vary bubble volumes, crystal spacings

  3. Bubble — bubbles — 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

  4. 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.

  5. Characteristics of oestrous cycles in Holstein cross-bred dairy heifers: an evidence of delayed post-ovulatory progesterone rise.

    PubMed

    Kornmatitsuk, Sudsaijai; Kornmatitsuk, Bunlue; Chantaraprateep, Peerasak; Larsson, Birgitta

    2009-03-01

    The aims of the current study were to illustrate figures for the characteristics of oestrous cycles especially on follicular dynamics, corpus luteum and changes in progesterone and prostaglandin F2alpha, in the Holstein cross-bred dairy heifers. Twenty six healthy and sexual-mature virgin heifers were monitored for signs of oestrus. Their ovaries were sonically examined and the numbers and the sizes of the follicles as well as of the corpus luteum were documented. In our study, no difference in ratio of the 2-wave and 3-wave patterned cycle was evident. Seasons' change did not affect on characteristics oestrous cycles as well as on dynamics of follicles and corpus luteum. The heifers showed high variation in manifesting oestrus especially on a number of hours. The 'bodily' oestrous signs lasted longer than did 'behavioural' signs and connection of lowering of the back to standing oestrus was established. Certain diversities comparing to of existed dairy breeds were drawn for follicular dynamics, corpus luteum and its progesterone: 1) the 1st an-ovulatory dominant follicles showed higher growth rate and earlier exceeded dominant diameter; 2) the follicle tended to quicker ovulate but with a smaller diameter at ovulation; 3) the corpus luteum exhibited 4-16.5 mm in diameter of central cavity. Connecting to the levels of progesterone, 4) the corpus luteum turned into active, as well as mid-luteal, period quite late, and 5) the duration of the active period of the corpus luteum was shorter, but 6) at the end of the cycle -around the day of oestrus, progesterone remained certain low but significant levels. In conclusion, the Holstein cross-bred dairy heifers in our study faced a problem of delayed post-ovulatory progesterone rise of which underlying causes are needed to be further scrutinised either at endocrine or at cell levels. PMID:18587661

  6. Four-dimensional visualization of rising microbubbles

    NASA Astrophysics Data System (ADS)

    Jung, Ji Won; Jeon, Hyung Min; Pyo, Jaeyeon; Lim, Jae-Hong; Weon, Byung Mook; Kohmura, Yoshiki; Ishikawa, Tetsuya; Je, Jung Ho

    2014-05-01

    Four-dimensional imaging, which indicates imaging in three spatial dimensions as a function of time, provides useful evidence to investigate the interactions of rising bubbles. However, this has been largely unexplored for microbubbles, mostly due to problems associated with strong light scattering and shallow depth of field in optical imaging. Here, tracking x-ray microtomography is used to visualize rising microbubbles in four dimensions. Bubbles are tracked by moving the cell to account for their rise velocity. The sizes, shapes, time-dependent positions, and velocities of individual rising microbubbles are clearly identified, despite substantial overlaps between bubbles in the field of view. Our tracking x-ray microtomography affords opportunities for understanding bubble-bubble (or particle) interactions at microscales - important in various fields such as microfluidics, biomechanics, and floatation.

  7. Four-dimensional visualization of rising microbubbles

    PubMed Central

    Jung, Ji Won; Jeon, Hyung Min; Pyo, Jaeyeon; Lim, Jae-Hong; Weon, Byung Mook; Kohmura, Yoshiki; Ishikawa, Tetsuya; Je, Jung Ho

    2014-01-01

    Four-dimensional imaging, which indicates imaging in three spatial dimensions as a function of time, provides useful evidence to investigate the interactions of rising bubbles. However, this has been largely unexplored for microbubbles, mostly due to problems associated with strong light scattering and shallow depth of field in optical imaging. Here, tracking x-ray microtomography is used to visualize rising microbubbles in four dimensions. Bubbles are tracked by moving the cell to account for their rise velocity. The sizes, shapes, time-dependent positions, and velocities of individual rising microbubbles are clearly identified, despite substantial overlaps between bubbles in the field of view. Our tracking x-ray microtomography affords opportunities for understanding bubble-bubble (or particle) interactions at microscales – important in various fields such as microfluidics, biomechanics, and floatation. PMID:24866552

  8. CHARACTERISTICS OF A FAST RISE TIME POWER SUPPLY FOR A PULSED PLASMA REACTOR FOR CHEMICAL VAPOR DESTRUCTION

    EPA Science Inventory

    Rotating spark gap devices for switching high-voltage direct current (dc) into a corona plasma reactor can achieve pulse rise times in the range of tens of nanoseconds. The fast rise times lead to vigorous plasma generation without sparking at instantaneous applied voltages highe...

  9. Frictional Drag Reduction by Bubbles in Taylor-Couette Flow

    Microsoft Academic Search

    Yuichi Murai; Hiroshi Oiwa; Yasushi Takeda

    2006-01-01

    Frictional drag reduction provided with small bubbles is investigated experimentally using a Couette-Taylor flow system, i.e. shear flow between concentric cylinders. Torque and bubble behavior are measured up to Re=4500 when air bubbles are injected constantly and rise through the cells. Silicone oil is used for avoiding uncertain interfacial property of bubbles as well as for keeping nearly mono-sized bubbles.

  10. Wake bubbles imaging, processing, and simulation of optical properties of bubbles

    NASA Astrophysics Data System (ADS)

    Wu, Ronghua; Wang, Jiang-an; Cao, Jing; Ma, Zhiguo

    2007-11-01

    This paper designed a bubble recognition system which was based on back light-scattering of bubbles in wake of ships, studied imaging characteristics of remote bubbles, and used technologies of imaging processing and target recognition to analyze CCD images of bubbles' back light-scattering so as to study the influence of bubbles and bubble density for back light-scattering. And then, based on scattering theory and theory of multiple light scattering, the light scattering properties of bubbles in wake were analyzed by simulation. Both the results of simulation and imaging processing technology validated that it was feasible to use the light wake homing bombs.

  11. 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.

  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. 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

  14. 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.

  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. 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.

  18. Interaction mechanism of double bubbles in hydrodynamic cavitation

    NASA Astrophysics Data System (ADS)

    Li, Fengchao; Cai, Jun; Huai, Xiulan; Liu, Bin

    2013-06-01

    Bubble-bubble interaction is an important factor in cavitation bubble dynamics. In this paper, the dynamic behaviors of double cavitation bubbles driven by varying pressure field downstream of an orifice plate in hydrodynamic cavitation reactor are examined. The bubble-bubble interaction between two bubbles with different radii is considered. We have shown the different dynamic behaviors between double cavitation bubbles and a single bubble by solving two coupling nonlinear equations using the Runge-Kutta fourth order method with adaptive step size control. The simulation results indicate that, when considering the role of the neighbor smaller bubble, the oscillation of the bigger bubble gradually exhibits a lag in comparison with the single-bubble case, and the extent of the lag becomes much more obvious as time goes by. This phenomenon is more easily observed with the increase of the initial radius of the smaller bubble. In comparison with the single-bubble case, the oscillation of the bigger bubble is enhanced by the neighbor smaller bubble. Especially, the pressure pulse of the bigger bubble rises intensely when the sizes of two bubbles approach, and a series of peak values for different initial radii are acquired when the initial radius ratio of two bubbles is in the range of 0.9˜1.0. Although the increase of the center distance between two bubbles can weaken the mutual interaction, it has no significant influence on the enhancement trend. On the one hand, the interaction between two bubbles with different radii can suppress the growth of the smaller bubble; on the other hand, it also can enhance the growth of the bigger one at the same time. The significant enhancement effect due to the interaction of multi-bubbles should be paid more attention because it can be used to reinforce the cavitation intensity for various potential applications in future.

  19. Surface heat transfer due to sliding bubble motion

    Microsoft Academic Search

    Brian Donnelly; Tadhg S. O’Donovan; Darina B. Murray

    2009-01-01

    The presence of a rising bubble in a fluid can greatly enhance heat transfer from adjacent heated surfaces such as in shell and tube heat exchangers and chemical reactors. One specific case of this is when a bubble impacts and slides along the surface. The result is heat transfer enhancement by two main mechanisms: first, the bubble itself acting as

  20. 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,

  1. Waves of bubbles in basaltic magmas and lavas

    Microsoft Academic Search

    Michael Manga

    1996-01-01

    Initially homogeneous suspensions of bubbles in basaltic magmas and lava flows may become unstable and form rising waves or layers of bubbles. We derive a set of model equations for the two-phase (bubble-liquid) system and present the results of a linear stability analysis and numerical simulations. Periodic vesicle layers are preserved in Columbia River flows with a spacing of ~1

  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. 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.

  4. 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

  5. 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.

  6. Study of CO2 bubble dynamics in seawater from QICS field Experiment

    NASA Astrophysics Data System (ADS)

    Chen, B.; Dewar, M.; Sellami, N.; Stahl, H.; Blackford, J.

    2013-12-01

    One of the concerns of employing CCS at engineering scale is the risk of leakage of storage CO2 on the environment and especially on the marine life. QICS, a scientific research project was launched with an aim to study the effects of a potential leak from a CCS system on the UK marine environment [1]. The project involves the injection of CO2 from a shore-based lab into shallow marine sediments. One of the main objectives of the project is to generate experimental data to be compared with the developed physical models. The results of the models are vital for the biogeochemical and ecological models in order to predict the impact of a CO2 leak in a variety of situations. For the evaluation of the fate of the CO2 bubbles into the surrounding seawater, the physical model requires two key parameters to be used as input which are: (i) a correlation of the drag coefficient as function of the CO2 bubble Reynolds number and (ii) the CO2 bubble size distribution. By precisely measuring the CO2 bubble size and rising speed, these two parameters can be established. For this purpose, the dynamical characteristics of the rising CO2 bubbles in Scottish seawater were investigated experimentally within the QICS project. Observations of the CO2 bubbles plume rising freely in the in seawater column were captured by video survey using a ruler positioned at the leakage pockmark as dimension reference. This observation made it possible, for the first time, to discuss the dynamics of the CO2 bubbles released in seawater. [1] QICS, QICS: Quantifying and Monitoring Potential Ecosystem Impacts of Geological Carbon Storage. (Accessed 15.07.13), http://www.bgs.ac.uk/qics/home.html

  7. 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

  8. Bubble departure size in flow boiling

    NASA Astrophysics Data System (ADS)

    Guan, Peng; Jia, Li; Yin, Liaofei; Tan, Zetao

    2014-12-01

    Flow boiling experiments were conducted in a vertical annular channel to study bubble departure characteristics. Deionized water was used as the working fluid, and the tests were performed at atmospheric pressure. Bubble departure diameters were obtained from the images which were captured by a high-speed digital camera. The relationship between bubble contact diameter and departure diameter was discussed. A new model base on force balance analysis, taking bubble contact diameter into account for predicting bubble departure diameter is proposed in this study. A good agreement between predicted and measured results is achieved.

  9. 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.

  10. High bubble concentrations produced by ultrasounds in binary mixtures.

    PubMed

    Louisnard, O; Lyczko, N; Espitalier, F; Urzedowski, M; Vargas-Hernandez, Y; Sanchez-Romero, C

    2001-07-01

    It was discovered that simultaneous insonification and air blowing of different aqueous binary solutions such as water/sodium-dodecyl-sulphate (SDS), water/methanol or water/potassium-sulphate yields a very concentrated bubble cloud invading the whole vessel in a few seconds. After the end of insonification, this cloudiness remained in the solution for about 1 min. The phenomenon was investigated by computer-treatment of solution pictures recorded every second after the end of insonification. Turbidity appeared to increase with ultrasound power, and also with SDS concentration. During the disappearance of the cloud, a turbidity front appeared rising and spreading upward. This front was studied in the characteristic plane and interpreted as a spatial segregation of different bubble sizes rising with different terminal velocities. The bubble sizes involved were estimated to about 10 microns. Adsorption of surface active species are invoked to explain the cloud formation and its abnormally slow disappearance, but the occurrence of the phenomenon for potassium-sulphate salt remains unexplained. PMID:11441596

  11. Evidence for in-line bubble interactions in non-Newtonian fluids

    Microsoft Academic Search

    H. Z Li; Y Mouline; D Funfschilling; P Marchal; L Choplin; N Midoux

    1998-01-01

    This work reports a study of in-line bubble interactions in non-Newtonian fluids by varying the injection period between bubbles. The experimental data reveal that the bubble rise velocity depends upon the injection period, obviously due to in-line interactions. The original rheological simulation, based on the close relationship between the rise of a chain of bubbles and consecutive shear deformations, proves

  12. Ring Bubbles of Dolphins

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

    The article discusses how dolphins create and play with three types of air-filled vortices. The underlying physics is discussed. Photographs and sketches illustrating the dolphin's actions and physics are presented. The dolphins engage in this behavior on their own initiative without food reward. These behaviors are done repeatedly and with singleminded effort. The first type is the ejection of bubbles which, after some practice on the part of the dolphin, turn into toroidal vortex ring bubbles by the mechanism of baroclinic torque. These bubbles grow in radius and become thinner as they rise vertically to the surface. One dolphin would blow two in succession and guide them to fuse into one. Physicists call this a vortex reconnection. In the second type, the dolphins first create an invisible vortex ring in the water by swimming on their side and waving their tail fin (also called flukes) vigorously. This vortex ring travels horizontally in the water. The dolphin then turns around, finds the vortex and injects a stream of air into it from its blowhole. The air "fills-out" the core of the vortex ring. Often, the dolphin would knock-off a smaller ring bubble from the larger ring (this also involves vortex reconnection) and steer the smaller ring around the tank. One other dolphin employed a few other techniques for planting air into the fluke vortex. One technique included standing vertically in the water with tail-up, head-down and tail piercing the free surface. As the fluke is waved to create the vortex ring, air is entrained from above the surface. Another technique was gulping air in the mouth, diving down, releasing air bubbles from the mouth and curling them into a ring when they rose to the level of the fluke. In the third type, demonstrated by only one dolphin, the longitudinal vortex created by the dorsal fin on the back is used to produce 10-15 foot long helical bubbles. In one technique she swims in a curved path. This creates a dorsal fin vortex since 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.

  13. Single cavitation bubble generation and observation of the bubble collapse flow induced by a pressure wave

    NASA Astrophysics Data System (ADS)

    Yang, Sheng-Hsueh; Jaw, Shenq-Yuh; Yeh, Keh-Chia

    2009-08-01

    This study utilizes a U-shape platform device to generate a single cavitation bubble for a detailed analysis of the flow field characteristics and the cause of the counter jet during the process of bubble collapse caused by sending a pressure wave. A high speed camera is used to record the flow field of the bubble collapse at different distances from a solid boundary. It is found that a Kelvin-Helmholtz vortex is formed when a liquid jet penetrates the bubble surface after the bubble is compressed and deformed. If the bubble center to the solid boundary is within one to three times the bubble’s radius, a stagnation ring will form on the boundary when impinged by the liquid jet. The fluid inside the stagnation ring will be squeezed toward the center of the ring to form a counter jet after the bubble collapses. At the critical position, where the bubble center from the solid boundary is about three times the bubble’s radius, the bubble collapse flow will vary. Depending on the strengths of the pressure waves applied, the collapse can produce a Kelvin-Helmholtz vortex, the Richtmyer-Meshkov instability, or the generation of a counter jet flow. If the bubble surface is in contact with the solid boundary, the liquid jet can only move inside-out without producing the stagnation ring and the counter jet; thus, the bubble collapses along the radial direction. The complex phenomenon of cavitation bubble collapse flows is clearly manifested in this study.

  14. Solar prominences: 'double, double ... boil and bubble'

    E-print Network

    Keppens, Rony

    2015-01-01

    Observations revealed rich dynamics within prominences, the cool 10,000 K, macroscopic (sizes of order 100 Mm) "clouds" in the million degree solar corona. Even quiescent prominences are continuously perturbed by hot, rising bubbles. Since prominence matter is hundredfold denser than coronal plasma, this bubbling is related to Rayleigh-Taylor instabilities. Here we report on true macroscopic simulations well into this bubbling phase, adopting a magnetohydrodynamic description from chromospheric layers up to 30 Mm height. Our virtual prominences rapidly establish fully non-linear (magneto)convective motions where hot bubbles interplay with falling pillars, with dynamical details including upwelling pillars forming within bubbles. Our simulations show impacting Rayleigh-Taylor fingers reflecting on transition region plasma, ensuring that cool, dense chromospheric material gets mixed with prominence matter up to very large heights. This offers an explanation for the return mass cycle mystery for prominence mater...

  15. 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.

  16. 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)

  17. Cavitation and bubble collapse in hot asymmetric nuclear matter

    SciTech Connect

    Kolomietz, V.M. [Physik-Department TU Muenchen, 85747 Garching (Germany)

    2004-10-01

    The dynamics of embryonic bubbles in overheated, viscous, and non-Markovian nuclear matter is studied. We show that the memory and the Fermi surface distortions significantly affect the hindrance of bubble collapse and determine characteristic oscillations of the bubble radius. These oscillations occur due to the additional elastic force induced by the memory integral.

  18. 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

  19. Using X-ray tomography as a tool to better quantify bubble network characteristics in volcanic tephra in three-dimensions

    NASA Astrophysics Data System (ADS)

    Davis, M. A.; Walsh, S. D.; Saar, M. O.; Roberts, J. J.; Proussevitch, A. A.

    2009-12-01

    Eruption-style studies of active volcanoes suggest that volatile pressure build-up and volatile degassing rates in volcano conduit magmas determine volcanic explosivity. Explosive eruptions appear to occur when the viscosity and permeability of the magma are high and low, respectively, leading to gas pressure build up within the magma. Conversely, effusive eruptions tend to occur when gas can more easily escape from magma due to high magma permeabilities and/or low viscosities. Permeabilities and the ability of magma to degas depend on how well-connected and extensive the percolating bubble networks are within the magma. Currently, one method to determine bubble connectivity in the volcano conduit uses quenched volcanic ejecta as an analogue to observe bubble network formation just below the magma fragmentation threshold. We employ X-ray tomography at the Advanced Light Source synchrotron facility at Lawrence Berkeley National Laboratory to obtain high-resolution, three-dimensional (3D) X-ray tomography images of these quenched pumice clasts to then determine pumice permeability numerically. Numerical determinations of permeability, as opposed to measurements using a permeameter, are critical when, for example, numerical upscaling methods are to be applied to the clasts for permeability determinations at the volcano conduit scale. The highest resolution scans we have used at the ALS is 4.1 microns to keep tomography files at a size that are manageable to process. However, some of the inter-bubble walls are thinner than the scanning resolution. If the inter-bubble walls are thinner than the given resolution, tomographic scans will likely not detect these walls. This will result in a misrepresentation of bubble connectivity, macroscopic pumice clast permeabilities, and associated volatile degassing rates. Therefore, for studies of volcanic eruption dynamics, it is critical to accurately define these thin bubble walls in pumice clasts during 3D image post-processing. Here we present a method for re-introducing the thin, undetected bubble walls during post-processing of X-ray tomography scans and how pumice permeability is affected by this method.

  20. {sup 226}Ra and {sup 231}Pa systematics of axial MORB, crustal residence ages, and magma chamber characteristics at 9--10{degree}N East Pacific Rise

    SciTech Connect

    Goldstein, S.J.; Murrell, M.T. [Los Alamos National Lab., NM (United States); Perfit, M.R. [Univ., of Florida, Gainesville, FL (United States). Dept. of Geology; Batiza, R. [Univ., of Hawaii, Honolulu, HI (United States); Fornari, D.J. [Woods Hole Oceanographic Institution, MA (United States). Dept. of Geology and Geophysics

    1994-06-01

    Mass spectrometric measurements of {sup 30}Th-22{sup 226}Ra and {sup 235}-U{sup 231}Pa disequilibria for axial basalts are used to determine crustal residence ages for MORB magma and investigate the temporal and spatial characteristics of axial magma chambers (AMC) at 9--10{degrees}N East Pacific Rise (EPR). Relative crustal residence ages can be calculated from variations in {sup 226}Ra/{sup 230}Th and {sup 231}Pa/{sup 235}U activity ratios for axial lavas, if (1) mantle sources and melting are uniform, and mantle transfer times are constant or rapid for axial N-MORB, and (2) {sup 231}Pa/{sup 235}U and {sup 226}Ra/{sup 230}Th in the melt are unaffected by shallow level fractional crystallization. Uniform Th, Sr, and Nd isotopic systematics and incompatible element ratios for N-MORB along the 9--10{degrees}N segment indicate that mantle sources and transfer times are similar. In addition, estimated bulk solid/melt partition coefficients for U, Th, and Pa are small, hence effects of fractional crystallization on {sup 231}Pa/{sup 235}U ratios for the melt are expected to be negligible. However, fractional crystallization of plagioclase in the AMC would lower {sup 226}Ra/{sup 230}Th ratios in the melt and produce a positive bias in {sup 226}Ra crustal residence ages for fractionated lavas.

  1. Local characteristics of cross-unit contamination around high-rise building due to wind effect: mean concentration and infection risk assessment.

    PubMed

    Liu, X P; Niu, J L; Kwok, K C S; Wang, J H; Li, B Z

    2011-08-15

    In this present work, the characteristics of hazardous gas dispersion and possible cross-unit contamination around a complex-shaped high-rise residential building due to wind effect are thoroughly studied using physical modeling method. Experiments were performed in a boundary layer wind tunnel for a 1:30 scale model that represented a 10-story residential building in prototype. Tracer gas, simulating exhausted room air, was continuously released from different floor levels, and its concentrations on the adjacent envelope surfaces were measured using fast flame ionization detectors. The mean concentration fields were reported and analyzed under different configurations during the experiment to consider the effects on pollutant dispersion behavior due to changes in source position and approaching wind condition, with the main emphasis on the differences between open-window and closed-window conditions. In particular, the measured concentration fields were further examined from a practical point of view, with respect to hazard assessment. Understanding these hazardous plume dispersion features is useful for employing effective intervention strategies in modern residential building environment in case of hazardous substance release. The study on this physical process is not only helpful to reduce the hazardous effect of routine release of harmful pollutant near the building, but also useful for the purpose of prevention and control of accidental infectious diseases outbreak. PMID:21616594

  2. 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

  3. Towards the understanding of bubble interactions and coalescence in non-Newtonian fluids: a cognitive approach

    Microsoft Academic Search

    Huai Z. Li; Xavier Frank; Denis Funfschilling; Youssef Mouline

    2001-01-01

    The present work provides new insights into the behavior of air bubbles in non-Newtonian fluids. The interactions and coalescence between bubbles rising in non-Newtonian fluids were simultaneously investigated by means of birefringence measurements and particle image velocimetry for a chain of bubbles formed from a submerged orifice. Two aspects are identified for the first time as central to interactions and

  4. Effects of Variations in Forebody and Afterbody Dead Rise on the Resistance and Spray Characteristics of the 22ADR Class VPB Airplane: Langley Tank Model 207, TED No. NACA 2361

    NASA Technical Reports Server (NTRS)

    Clement, Eugene P.; Daniels, Charles J.

    1947-01-01

    An investigation was made to determine the effects of changes in the amount and distribution of forebody and afterbody dead rise on the hydrodynamic resistance and spray characteristics of a 1/11-size model of the Bureau of Aeronautics design No. 22ADR class VPB airplane. The variations in dead rise within the range investigated had no significant effects on resistance or trim, free to trim, or on resistance or trimming moment, fixed in trim. The coordinates of the peaks of the bow-spray blisters, with reference to the model, were measured at low speeds, and it was found that the model with the low dead rise at the bow had the lowest blisters. The changes in position of the maximum dead rise of the afterbody had no effect on the bow-spray blister.

  5. 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.

  6. MOBI: Microgravity Observations of Bubble Interactions

    NASA Technical Reports Server (NTRS)

    Koch, Donald L.; Sangani, Ashok

    2004-01-01

    One of the greatest uncertainties affecting the design of multiphase flow technologies for space exploration is the spatial distribution of phases that will arise in microgravity or reduced gravity. On Earth, buoyancy-driven motion predominates whereas the shearing of the bubble suspension controls its behavior in microgravity. We are conducting a series of ground-based experiments and a flight experiment spanning the full range of ratios of buoyancy to shear. These include: (1) bubbles rising in a quiescent liquid in a vertical channel; (2) weak shear flow induced by slightly inclining the channel; (3) moderate shear flow in a terrestrial vertical pipe flow; and (4) shearing of a bubble suspension in a cylindrical Couette cell in microgravity. We consider nearly monodisperse suspensions of 1 to 1.8 mm diameter bubbles in aqueous electrolyte solutions. The liquid velocity disturbance produced by bubbles in this size range can often be described using an inviscid analysis. Electrolytic solutions lead to hydrophilic repulsion forces that stabilize the bubble suspension without causing Marangoni stresses. We will discuss the mechanisms that control the flow behavior and phase distribution in the ground-based experiments and speculate on the factors that may influence the suspension flow and bubble volume fraction distribution in the flight experiment.

  7. 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.

  8. Financial Bubbles and Business Scandals in History

    Microsoft Academic Search

    Kenneth R. Gray; Larry A. Frieder; George W. Clark Jr

    2007-01-01

    This article is a survey of corporate scandals and some of the leading figures associated with them throughout the history of the joint-stock company. We find that great waves of exploration and innovation have been seen to propel speculative ventures that often prove worthless (hence the name “bubble”) and give rise to financial scandal. A look at some of history's

  9. 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.

  10. Emergence of granular-sized magnetic bubbles through the solar atmosphere. I. Spectropolarimetric observations and simulations

    SciTech Connect

    Ortiz, Ada; Hansteen, Viggo H.; Van der Voort, Luc Rouppe [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, N-0315 Oslo (Norway); Bellot Rubio, Luis R. [Instituto de Astrofísica de Andalucía (CSIC), Apdo. 3040, E-18080 Granada (Spain); De la Cruz Rodríguez, Jaime, E-mail: ada@astro.uio.no [Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala (Sweden)

    2014-02-01

    We study a granular-sized magnetic flux emergence event that occurred in NOAA 11024 in 2009 July. The observations were made with the CRISP spectropolarimeter at the Swedish 1 m Solar Telescope achieving a spatial resolution of 0.''14. Simultaneous full Stokes observations of the two photospheric Fe I lines at 630.2 nm and the chromospheric Ca II 854.2 nm line allow us to describe in detail the emergence process across the solar atmosphere. We report here on three-dimensional (3D) semi-spherical bubble events, where instead of simple magnetic footpoints, we observe complex semi-circular feet straddling a few granules. Several phenomena occur simultaneously, namely, abnormal granulation, separation of opposite-polarity legs, and brightenings at chromospheric heights. However, the most characteristic signature in these events is the observation of a dark bubble in filtergrams taken in the wings of the Ca II 854.2 nm line. There is a clear coincidence between the emergence of horizontal magnetic field patches and the formation of the dark bubble. We can infer how the bubble rises through the solar atmosphere as we see it progressing from the wings to the core of Ca II 854.2 nm. In the photosphere, the magnetic bubble shows mean upward Doppler velocities of 2 km s{sup –1} and expands at a horizontal speed of 4 km s{sup –1}. In about 3.5 minutes it travels some 1100 km to reach the mid chromosphere, implying an average ascent speed of 5.2 km s{sup –1}. The maximum separation attained by the magnetic legs is 6.''6. From an inversion of the observed Stokes spectra with the SIR code, we find maximum photospheric field strengths of 480 G and inclinations of nearly 90° in the magnetic bubble interior, along with temperature deficits of up to 250 K at log ? = –2 and above. To aid the interpretation of the observations, we carry out 3D numerical simulations of the evolution of a horizontal, untwisted magnetic flux sheet injected in the convection zone, using the Bifrost code. The computational domain spans from the upper convection zone to the lower corona. In the modeled chromosphere, the rising flux sheet produces a large, cool, magnetized bubble. We compare this bubble with the observed ones and find excellent agreement, including similar field strengths and velocity signals in the photosphere and chromosphere, temperature deficits, ascent speeds, expansion velocities, and lifetimes.

  11. Development and application of an image analysis method for wide bubble size distributions

    Microsoft Academic Search

    M. Bailey; C. O. Gomez; J. A. Finch

    2005-01-01

    The wide bubble size distributions (<2mm to >10mm) generated by jetting spargers have taxed the McGill bubble size analyser methodology. A revised image processing protocol is proposed (“alternative” filter) which includes selecting bubbles on the basis of the holes (bright centres) characteristic of the bubble images in two-phase systems. This allowed for the inclusion of small and large bubbles, while

  12. Copernicus Rising

    NASA Astrophysics Data System (ADS)

    Rose, Michael A.

    2007-08-01

    Copernicus Rising began as a historical biography when it was first conceived, but as the writing progressed it quickly became a rather absurd play that took historical research and twisted it through the lens of my own wit, philosophy and personal affection for the characters. When working with historical figures--characters who existed in a very tangible way in our own history--the playwriting process opens a dialogue between different points in time and space. The difficulty lies in finding a unique and clear voice amongst the discordant personalities involved in this time and space overlap, both in the writing and production processes, in order to get to the heart of what the play is really all about. This thesis follows the journey of the play from its historical roots through the creation of an absurd journey both insides and outside time, space and the human mind. The first part of the thesis explains the beginnings of the concept and outlines much of the research and development that went into the play. The next part outlines the process of production and integrating the world on paper with that of moving bodies on stage. In the final part, post-production discussions and audience feedback sessions shape the play into the draft included in this thesis.

  13. 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)

  14. 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

  15. 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

  16. 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.

  17. 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.

  18. Topics in the Motion of Bubbles in Incompressible Liquids

    NASA Astrophysics Data System (ADS)

    Nie, Qing

    1995-01-01

    In this thesis, the steady states, linear stability and nonlinear dynamics are studied numerically for two dimensional bubbles rising in an inviscid liquid. In particular, two simple models are considered here, a rising bubble without wake and a rising bubble with a closed wake. In the case for the bubble without wake, the steady -state calculation, the linear stability analysis and the calculation of unsteady motion are performed through a conformal mapping formulation. It is found that the bubbles are linearly stable for all the steady states. However, suitable symmetric perturbations result in the pinching of the bubble as it oscillates about a steady state with large aspect ratio. An estimate of the threshold amplitude for a disturbance to cause breakup is obtained. In the second model, the bubble is assumed to have a closed wake represented by a pair of point of vortices. Steady states and unsteady behavior are studied with a boundary integral formulation. A bifurcation study of the steady states shows that the critical Weber number for the existence of the steady-state solutions depends on the strength of the wake. In particular, the larger the strength, the larger the critical Weber number. There is one critical Weber number that agrees with one of the experimental results and some bubble shapes are similar to those computed for Re = 100, 200. In studies of the unsteady motion, the positions of the wake vortices are perturbed initially from the steady states. The consequences show two distinct behaviors. In one case when the strength of the wake is relatively large, the shape of the top of the bubble remains almost unchanged whereas the rear of the bubble develops two "horns" as the bubble surface tries to wrap around the vortices. In the other case when the strength of the wake is relatively small, the bubble exhibits oscillations while the wake vortices move on two almost closed orbits in the moving frame of the centroid of the bubble. In either case, the bubble and its wake vortices preserve symmetry. When the perturbation to the wake is unsymmetric, the bubble develops one horn for a relatively strong wake; while the wake vortices escape when the wake is relatively weak. Also in this thesis, some computational aspects of the boundary integral technique are studied. An analysis distinguishing physical solutions from spurious numerical solutions is performed in the bifurcation study of the bubble with wake. To calculate unsteady free surface motion in the presence of surface tension, an implicit method is developed to weaken substantially the constraint for numerical stability. Moreover, a parallel algorithm is developed and implemented for the computation of boundary integrals during the unsteady calculation.

  19. 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

  20. 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

  1. Breaking waves, turbulence and bubbles

    NASA Astrophysics Data System (ADS)

    Gemmrich, Johannes; Vagle, Svein; Thomson, Jim

    2014-05-01

    The air-sea fluxes of heat, momentum, and gases are to a large extent affected by wave-induced turbulence in the near-surface ocean layer, and are generally increased over the fluxes in a law-of-the-wall type boundary layer. However, air-bubbles generated during the wave breaking process may affect the density stratification and in turn reduce turbulence intensity in the near-surface layer. The turbulence field beneath surface waves is rather complex and provides great challenges for detailed observations. We obtained high resolution near-surface velocity profiles, bubble cloud measurements and video recordings of the breaking activity in a coastal strait. Conditions ranged from moderate to strong wind forcing with wind speed ranging from 5 m/s to 20 m/s. Estimates of the dissipation rates of turbulence kinetic energy are calculated from the in-situ velocity measurements. We find dissipation rates, fluctuating by more than two orders of magnitude, are closely linked to the air-fraction associated with micro-bubbles. Combining these turbulence estimates and the bubble cloud characteristics we infer differences in the strength of wave breaking and its effect on wave-induced mixing and air-sea exchange processes.

  2. 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).

  3. The Milky Way Project: Leveraging Citizen Science and Machine Learning to Detect Interstellar Bubbles

    E-print Network

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

    2014-01-01

    We present Brut, an algorithm to identify bubbles in infrared images of the Galactic midplane. Brut is based on the Random Forest algorithm, and uses bubbles identified by >35,000 citizen scientists from the Milky Way Project to discover the identifying characteristics of bubbles in images from the Spitzer Space Telescope. We demonstrate that Brut's ability to identify bubbles is comparable to expert astronomers. We use Brut to re-assess the bubbles in the Milky Way Project catalog, and find that 10-30% of the objects in this catalog are non-bubble interlopers. Relative to these interlopers, high-reliability bubbles are more confined to the mid plane, and display a stronger excess of Young Stellar Objects along and within bubble rims. Furthermore, Brut is able to discover bubbles missed by previous searches -- particularly bubbles near bright sources which have low contrast relative to their surroundings. Brut demonstrates the synergies that exist between citizen scientists, professional scientists, and machi...

  4. A Study of the Zero-Lift Drag-Rise Characteristics of Wing-Body Combinations Near the Speed of Sound

    NASA Technical Reports Server (NTRS)

    Whitcomb, Richard T

    1956-01-01

    Comparisons have been made of the shock phenomena and drag-rise increments for representative wing and central-body combinations with those for bodies of revolution having the same axial developments of cross-sectional areas normal to the airstream. On the basis of these comparisons, it is concluded that near the speed of sound the zero-lift drag rise of a low-aspect-ratio thin-wing and body combination is primarily dependent on the axial development of the cross-sectional areas normal to the airstream. It follows that the drag rise for any such configuration is approximately the same as that for any other with the same development of cross-sectional areas. Investigations have also been made of representative wing-body combinations with the body so indented that the axial developments of cross-sectional areas for the combinations were the same as that for the original body alone. Such indentations greatly reduced or eliminated the zero-lift drag-rise increments associated with the wings near the speed of sound.

  5. 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.

  6. 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.

  7. Numerical Simulation of Bubble Cluster Induced Flow by Three-Dimensional Vortex-in-Cell Method.

    PubMed

    Chen, Bin; Wang, Zhiwei; Uchiyama, Tomomi

    2014-08-01

    The behavior of air bubble clusters rising in water and the induced flow field are numerically studied using a three-dimensional two-way coupling algorithm based on a vortex-in-cell (VIC) method. In this method, vortex elements are convected in the Lagrangian frame and the liquid velocity field is solved from the Poisson equation of potential on the Eulerian grid. Two-way coupling is implemented by introducing a vorticity source term induced by the gradient of void fraction. Present simulation results are favorably compared with the measured results of bubble plume, which verifies the validity of the proposed VIC method. The rising of a single bubble cluster as well as two tandem bubble clusters are simulated. The mechanism of the aggregation effect in the rising process of bubble cluster is revealed and the transient processes of the generation, rising, strengthening, and separation of a vortex ring structure with bubble clusters are illustrated and analyzed in detail. Due to the aggregation, the average rising velocity increases with void fraction and is larger than the terminal rising velocity of single bubble. For the two tandem bubble cluster cases, the aggregation effect is stronger for smaller initial cluster distance, and both the strength of the induced vortex structure and the average bubble rising velocity are larger. For the 20?mm cluster distance case, the peak velocity of the lower cluster is about 2.7 times that of the terminal velocity of the single bubble and the peak average velocity of two clusters is about 2 times larger. While for the 30?mm cluster distance case, both the peak velocity of the lower cluster and two clusters are about 1.7 times that of the terminal velocity of the single bubble. PMID:24895468

  8. 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.

  9. Frictional Drag Reduction by Bubbles in Taylor-Couette Flow

    NASA Astrophysics Data System (ADS)

    Murai, Yuichi; Oiwa, Hiroshi; Takeda, Yasushi

    2006-11-01

    Frictional drag reduction provided with small bubbles is investigated experimentally using a Couette-Taylor flow system, i.e. shear flow between concentric cylinders. Torque and bubble behavior are measured up to Re=4500 when air bubbles are injected constantly and rise through the cells. Silicone oil is used for avoiding uncertain interfacial property of bubbles as well as for keeping nearly mono-sized bubbles. We assess the effect of drag reduction with two types of evaluation factors, i.e. sensitivity and power gain. The sensitivity exceeds unity at Re<2000, proving that the drag is reduced more than the drop of mixture density. This originates from accumulation of bubbles into the rotating inner cylinder, which is little affected by turbulence. The power gain, which is defined by drag reduction power per bubble injection power, takes the highest value of O(10) at higher Re numbers around 2500. The image processing measurement finds this reason to be disappearance of azimuthal waves when the organized bubbles distribution transits from toroidal to spiral modes. Moreover, the axial spacing of bubble clouds expands during the transition, enforcing the reduction of momentum exchange.

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. Measurements of rotating bubble shapes in low-gravity environment

    NASA Technical Reports Server (NTRS)

    Leslie, F.

    1985-01-01

    Measurements of rotating equilibrium bubble shapes in the low-gravity environment of a free-falling aircraft are presented. Emphasis is placed on bubbles which intersect the container boundaries. These data are compared with theoretical profiles derived from Laplace's formula and are in good agreement with the measurements. The interface shape depends on the contact angle, the radius of intersection with the container, and the parameter F, which is a measure of the relative importance of centrifugal force to surface tension. For isolated bubbles F has a maximum value of 1/2. A further increase in F causes the bubble to break contact with the axis of rotation. For large values of F the bubble becomes more cylindrical and the capillary rise occurs over a thinner layer in order that the small radius of curvature can generate a sufficient pressure drop to account for the increased hydrostatic contribution.

  15. Condensing phenomena of a single vapor bubble into subcooled water

    SciTech Connect

    Kamei, S. (Dept. of Mechanical Engineering, Univ. of Tokyo, Tokyo (JP)); Hirata, M. (Research Center for Advanced Science and Technology, Univ. of Tokyo, Tokyo (JP))

    1990-01-01

    This paper reports on experiments carried out to investigated direct contact condensation of saturated vapor bubbles introduced into a quiescent subcooled water environment. The experiments were performed for a range of pressures from atmospheric to 1 MPa, for subcooling from 10 to 70 K, and for initial bubble diameters of about 10 mm. Flow visualization by high-speed motion pictures was based on a frame-by-frame analysis. The authors show that the successive shapes of the bubbles during their collapse histories proceeded from a sphere to a hemisphere, to an ellipsoid, to a sphere, and finally to collapse. They show that the cavities of the bubbles during their collapse histories proceeded from the bottom to the top. The time to collapse increased with increasing pressure difference. The rising velocities of the bubbles were essentially constant, with an overall range of 20--25 cm/s.

  16. Cavitation erosion by single laser-produced bubbles

    Microsoft Academic Search

    A. Philipp; W. Lauterborn

    1998-01-01

    In order to elucidate the mechanism of cavitation erosion, the dynamics of a single laser-generated cavitation bubble in water and the resulting surface damage on a flat metal specimen are investigated in detail. The characteristic effects of bubble dynamics, in particular the formation of a high-speed liquid jet and the emission of shock waves at the moment of collapse are

  17. Solar Prominences: "Double, Double... Boil and Bubble"

    NASA Astrophysics Data System (ADS)

    Keppens, R.; Xia, C.; Porth, O.

    2015-06-01

    Observations revealed rich dynamics within prominences, the cool (104 K), macroscopic (sizes of order 100 Mm) “clouds” in the million degree solar corona. Even quiescent prominences are continuously perturbed by hot, rising bubbles. Since prominence matter is hundredfold denser than coronal plasma, this bubbling is related to Rayleigh–Taylor instabilities. Here we report on true macroscopic simulations well into this bubbling phase, adopting an MHD description from chromospheric layers up to 30 Mm height. Our virtual prominences rapidly establish fully nonlinear (magneto)convective motions where hot bubbles interplay with falling pillars, with dynamical details including upwelling pillars forming within bubbles. Our simulations show impacting Rayleigh–Taylor fingers reflecting on transition region plasma, ensuring that cool, dense chromospheric material gets mixed with prominence matter up to very large heights. This offers an explanation for the return mass cycle mystery for prominence material. Synthetic views at extreme ultraviolet wavelengths show remarkable agreement with observations, with clear indications of shear-flow induced fragmentations.

  18. Acoustic waveform of continuous bubbling in a non-Newtonian fluid: From laboratory bubbles to quasi-periodic volcanic phenomena

    NASA Astrophysics Data System (ADS)

    Vidal, V.; Ichihara, M.; Ripepe, M.; Kurita, K.

    2009-12-01

    Due to decompression when magma flows up the volcanic conduit, bubbles nucleate, coalesce, rise and explode at the surface of the conduit. On the field, one possible tool to investigate this dynamics is to analyze the acoustic signal produced by the explosion of such bubbles. In order to investigate this phenomenon at the laboratory scale, taking into account the complex lava rheology, we setup the following experiment. A constant air flow-rate is injected at the bottom of a plexiglas cell, filled by a non-Newtonian fluid. Bubbles form, rise, coalesce, and burst at the fluid free surface. A 4-microphones array records the acoustic signal produced by the successive bubble burstings. The bubble rising and explosion dynamics are monitored by both a normal and high-speed video camera. We focus on the acoustic signal associated with the continuous bubble bursting at the fluid surface. Due to the fluid rheological properties, the bubble shape is elongated, and, when bursting at the free surface, acts as a resonator. For a given fluid concentration, at constant flow rate, repetitive bubble bursting occurs at the surface. We report a modulation pattern of the acoustic waveform through time. High-speed images recording shows that the film rupture time directly affects the waveform. Moreover, we point out the existence of a precursor acoustic signal, recorded on the microphone array, previous to each bursting. The time-delay between this precursor and the bursting signal is well correlated with the bursting signal frequency content. Their joint modulation through time is driven by the fluid rheology, which strongly depends on the presence of small, satellite bubbles trapped in the fluid due to the yield stress. Finally, the spectrograms point out a frequency gliding of the harmonics towards higher values, a feature observed on some volcanoes, but still unexplained at present day.

  19. 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…

  20. 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.

  1. MHD Simulations of Relic Radio Bubbles in Clusters

    E-print Network

    Jones, T W

    2005-01-01

    In order to better understand the origin and evolution of relic radio bubbles in clusters of galaxies, we report on an extensive set of 2D MHD simulations of hot buoyant bubbles evolving in a realistic intracluster medium. Our bubbles are inflated near the base of the ICM over a finite time interval from a region whose magnetic field is isolated from the ICM. We confirm both the early conjecture from linear analysis and the later results based on preformed MHD bubbles; namely, that very modest ICM magnetic fields can stabilize the rising bubbles against disruption by Rayleigh-Taylor and Kelvin-Helmholtz instabilities. We find in addition that amplification of the ambient fields as they stretch around the bubbles can be sufficient to protect the bubbles or their initial fragments even if the fields are initially much too weak to play a significant role early in the evolution of the bubbles. Indeed, even with initial fields less than a micro-Gauss and values of $\\beta = P_g/P_b$ approaching $10^5$, magnetic str...

  2. 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

  3. Combined effect of viscosity and vorticity on single mode Rayleigh-Taylor instability bubble growth

    SciTech Connect

    Banerjee, Rahul; Mandal, Labakanta; Roy, S.; Khan, M.; Gupta, M. R. [Department of Instrumentation Science and Centre for Plasma Studies, Jadavpur University, Kolkata 700032 (India)

    2011-02-15

    The combined effect of viscosity and vorticity on the growth rate of the bubble associated with single mode Rayleigh-Taylor instability is investigated. It is shown that the effect of viscosity on the motion of the lighter fluid associated with vorticity accumulated inside the bubble due to mass ablation may be such as to reduce the net viscous drag on the bubble exerted by the upper heavier fluid as the former rises through it.

  4. Bubble materials characterization using spatial filtering techniques

    Microsoft Academic Search

    R. D. HENRY

    1977-01-01

    A technique for utilizing the spatial coding of information in an optical system is applied to the problem of bubble materials characterization. A simple system for static characterization of characteristic length and magnetization is described and the results of measurements presented. This concept is then extended to the measurement of coercivity.

  5. 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

  6. Effective Collecting Method of Volatile Organic Compounds in Water by Bubbling

    NASA Astrophysics Data System (ADS)

    Kida, Hitoshi; Hori, Hayato; Nonoguchi, Yuzo; Kameda, Masaharu; Sato, Ryoichi

    2013-11-01

    A technique is proposed to improve the collection efficiency of a small amount of volatile organic compounds in the gas by impinger, which is generally used as gas collection device for analysis. Eugenol was used as a simulated substance of explosives. The sample gas containing specific amount of eugenol was collected in pure water by the impinger. The concentration of eugenol in water was measured by gas chromatography. The experimental results shows that the collection efficiency of eugenol by the impinger increased as the water level (volume) increased. The bubble motion in the impinger observed by high-speed photography indicates that the averaged values of equivalent diameter and rising velocity of bubbles were reduced as the water level increased. This reduction yields the increase of the resident time of bubble per unit volume of water, which enhances the dissolution of eugenol. On the basis of these characteristics, small glass beads were stuffed into the impimger to increase the resident time per unit volume. The collection efficiency was improved by stuffing the glass beads. Now we test the odorant binding protein as additive for further improvement of collection efficiency.

  7. 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.

  8. Bubble visualization in a simulated hydraulic jump

    E-print Network

    Witt, Adam; Shen, Lian

    2013-01-01

    This is a fluid dynamics video of two- and three-dimensional computational fluid dynamics simulations carried out at St. Anthony Falls Laboratory. A transient hydraulic jump is simulated using OpenFOAM, an open source numerical solver. A Volume of Fluid numerical method is employed with a realizable k-epsilon turbulence model. The goal of this research is to model the void fraction and bubble size in a transient hydraulic jump. This fluid dynamics video depicts the air entrainment characteristics and bubble behavior within a hydraulic jump of Froude number 4.82.

  9. A Numerical Study of Low-Reynolds-Number Separation Bubbles

    NASA Technical Reports Server (NTRS)

    Tatineni, Mahidhar; Zhong, Xiao-Lin

    1999-01-01

    The present study uses two dimensional numerical simulations to study unsteady low-Reynolds-number separation bubbles. The numerical study is in two parts: (1) a two dimensional time-accurate Navier-Stokes solver is used to simulate flows over the APEX airfoil, and (2) a numerical procedure is developed for localized simulations of transitional separation bubbles. The 2-D computations of flow over the APEX airfoil show that the flow is unsteady with periodic vortex shedding. A linear stability analysis of the separated flow shows that the vortex shedding is caused due to the instability of the separated flow. For transonic flows over the APEX airfoil the vortex shedding is additionally influenced by the presence of shocks. The flowfield has two characteristic time scales, one corresponding to the vortex shedding and another corresponding to the movement of the shocks. The two dimensional (2-D) airfoil simulations also showed the presence of nonlinear effects in the separated region. To better understand the characteristics of separation bubbles a numerical procedure has been developed for localized separation bubble calculations. This procedure is used to perform computations for a flat plate separation bubble test case. The separation bubble is induced by specifying a velocity gradient in the freestream. The growth of disturbances in the separation bubble is analyzed by introducing disturbances upstream of the separation bubble.

  10. Bubble stability in vigorous convection: Ramifications for magma-ocean degassing and formation of an early atmosphere

    NASA Astrophysics Data System (ADS)

    Sethian, J.; Suckale, J.; Elkins-Tanton, L. T.

    2009-12-01

    The heat provided by energetic impacts, radioactive decay and core formation during the early stages in terrestrial planet evolution is sufficient to melt a silicate mantle partially or entirely. Thus, magma-ocean models provide an interesting hypothetical starting point for understanding mantle evolution of terrestrial planets. A key constraint in these models is the formation of an early atmosphere, because it exerts a strong control over the heat flux from the planetary surface. One open question in the task of developing a model of early atmosphere formation is related to when volatiles begin to exsolve from the magma ocean and in what quantities. Even magma oceans with initial minute water or carbon contents will eventually, as they solidify, become saturated and begin to exsolve volatiles as gases. The bubble size distribution in the magma is likely to exert a strong control over this process: small gas bubbles will tend to remain entrained in vigorous convection while large bubbles decouple from the surrounding flow field and rise to the surface under their own buoyancy. In this paper, we use numerical simulations of two-phase flow to investigate how the size distribution of gas bubbles in a magma ocean depends on its physical characteristics, such as composition, magma viscosity and volatile content. The numerical technique couples a level-set-based representation of the interface to a Navier-Stokes solver through the construction of extension velocities. Preliminary results indicate that gas bubbles in superliquidus magma oceans with low viscosity remain small. In fact, current estimates of the radius at which gas bubbles cease to be entrained in flow and begin to rise to the free surface under their buoyancy might exceed the radius of stable gas bubbles. This observation implies that the earliest atmospheres might form only during the final stages of magma-ocean solidification and possibly through very rapid degassing of oversaturated magma. Late, rapid degassing from a putative terrestrial magma ocean, for example following a Moon-forming impact, implies that solidification of magma oceans would have been exceptionally fast. Rapid interior cooling in turn makes the time to clement surface conditions rapid, preparing the planetary surface for liquid water.

  11. 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)

  12. 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)

  13. Characteristics of ammonia, hydrogen sulfide, carbon dioxide, and particulate matter concentrations in high-rise and manure-belt layer hen houses

    NASA Astrophysics Data System (ADS)

    Ni, Ji-Qin; Chai, Lilong; Chen, Lide; Bogan, Bill W.; Wang, Kaiying; Cortus, Erin L.; Heber, Albert J.; Lim, Teng-Teeh; Diehl, Claude A.

    2012-09-01

    Indoor air pollutants at high concentrations in poultry houses can potentially affect workers' health, and animal welfare and productivity. This paper presents research results of a 2-year continuous monitoring of ammonia (NH3), carbon dioxide (CO2), hydrogen sulfide (H2S), and particulate matter (PM) concentrations from to date the most comprehensive study on a single farm in two 180,000-bird high-rise (HR) and two 200,000-bird manure-belt (MB) layer hen houses located in Indiana, USA. Air was sampled at ventilation fans of the mechanically-ventilated houses. Concentrations of NH3 and CO2 were measured with photoacoustic multi-gas monitors. Concentrations of H2S and PM10 were monitored with pulsed fluorescence analyzers and Tapered Element Oscillating Microbalances (TEOM), respectively. The 2-year mean ± standard deviation concentrations at ventilation fans of the four layer hen houses were 48.9 ± 39 and 51.9 ± 40.7 ppm in HR, and 13.3 ± 9.1 and 12.9 ± 10.5 ppm in MB for NH3; 26.4 ± 17.6 and 24.9 ± 19 ppb in HR, 40.0 ± 21.1 and 41.2 ± 31.5 ppb in MB for H2S; 1755 ± 848 and 1804 ± 887 ppm in HR, and 2295 ± 871 and 2285 ± 946 ppm in MB for CO2; and 540 ± 303 and 552 ± 338 ?g m-3 in HR, and 415 ± 428 and 761 ± 661 ?g m-3 in MB for PM10. Compared with the MB houses, concentrations of the HR houses were higher for NH3, and lower for CO2, H2S, and PM10 (P < 0.05). High concentrations of NH3 detected in winter represent potential challenges to workers' health and animal welfare. Variations in pollutant concentrations at the exhaust fans were affected by outdoor temperature, ventilation, bird condition, and farm operation. A new weekly variation, characterized by significantly lower PM10 concentrations on Sundays, was identified and was related to the weekly schedule of house operational activities.

  14. Noise from tip vortex and bubble cavitation

    NASA Astrophysics Data System (ADS)

    Sponagle, Neil C.

    1990-03-01

    This paper presents results from experiments designed to study the sound from different types of propeller cavitation. The propellers used in the tests produced tip vortex and travelling bubble cavitation. The spectral content, directivity, and waveform of the far-field sound were measured, in essentially free-field conditions up to 100 kHz. These data were then correlated with information about the cavity dynamics, obtained from visual observations. Vibrational modes on the tip vortex cavities produced sound at characteristic frequencies. Bubble cavitation by itself produced very broadband noise, and strongly affected the vortex cavitation noise mechanisms if the free bubbles entered the tip vortices. The noise from both kinds of cavitation was directional.

  15. 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

  16. 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

  17. 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.

  18. Bubble-induced damping in displacement-driven microfluidic flows.

    PubMed

    Lee, Jongho; Rahman, Faizur; Laoui, Tahar; Karnik, Rohit

    2012-08-01

    Bubble damping in displacement-driven microfluidic flows was theoretically and experimentally investigated for a Y-channel microfluidic network. The system was found to exhibit linear behavior for typical microfluidic flow conditions. The bubbles induced a low-pass filter behavior with a characteristic cutoff frequency that scaled proportionally with flow rate and inversely with bubble volume and exhibited a minimum with respect to the relative resistances of the connecting channels. A theoretical model based on the electrical circuit analogy was able to predict experimentally observed damping of fluctuations with excellent agreement. Finally, a flowmeter with high resolution (0.01 ?L/min) was demonstrated as an application of the bubble-aided stabilization. This study may aid in the design of many other bubble-stabilized microfluidic systems. PMID:23005848

  19. Bubble-induced damping in displacement-driven microfluidic flows

    NASA Astrophysics Data System (ADS)

    Lee, Jongho; Rahman, Faizur; Laoui, Tahar; Karnik, Rohit

    2012-08-01

    Bubble damping in displacement-driven microfluidic flows was theoretically and experimentally investigated for a Y-channel microfluidic network. The system was found to exhibit linear behavior for typical microfluidic flow conditions. The bubbles induced a low-pass filter behavior with a characteristic cutoff frequency that scaled proportionally with flow rate and inversely with bubble volume and exhibited a minimum with respect to the relative resistances of the connecting channels. A theoretical model based on the electrical circuit analogy was able to predict experimentally observed damping of fluctuations with excellent agreement. Finally, a flowmeter with high resolution (0.01 ?L/min) was demonstrated as an application of the bubble-aided stabilization. This study may aid in the design of many other bubble-stabilized microfluidic systems.

  20. 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.

  1. 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

  2. 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.

  3. Multiscale Modeling of Cavitating Bubbly Flows

    NASA Astrophysics Data System (ADS)

    Ma, J.; Hsiao, C.-T.; Chahine, G. L.

    2013-03-01

    Modeling of cavitating bubbly flows is challenging due to the wide range of characteristic lengths of the physics at play: from micrometers (e.g., bubble nuclei radius) to meters (e.g., propeller diameter or sheet cavity length). To address this, we present here a multiscale approach which integrates a Discrete Bubble Model for dispersed microbubbles and a level set N-S solver for macro cavities, along with a mesoscale transition model to bridge the two. This approach was implemented in 3DYNAFScopyright and used to simulate sheet-to-cloud cavitation over a hydrofoil. The hybrid model captures well the full cavitation process starting from free field nuclei and nucleation from solid surfaces. In low pressure region of the foil small nuclei are seen to grow large and eventually merge to form a large scale sheet cavity. A reentrant jet forms under the cavity, travels upstream, and breaks it, resulting in a bubble cloud of a large amount of microbubbles as the broken pockets shrink and travel downstream. This is in good agreement with experimental observations based of sheet lengths and frequency of lift force oscillation. Modeling of cavitating bubbly flows is challenging due to the wide range of characteristic lengths of the physics at play: from micrometers (e.g., bubble nuclei radius) to meters (e.g., propeller diameter or sheet cavity length). To address this, we present here a multiscale approach which integrates a Discrete Bubble Model for dispersed microbubbles and a level set N-S solver for macro cavities, along with a mesoscale transition model to bridge the two. This approach was implemented in 3DYNAFScopyright and used to simulate sheet-to-cloud cavitation over a hydrofoil. The hybrid model captures well the full cavitation process starting from free field nuclei and nucleation from solid surfaces. In low pressure region of the foil small nuclei are seen to grow large and eventually merge to form a large scale sheet cavity. A reentrant jet forms under the cavity, travels upstream, and breaks it, resulting in a bubble cloud of a large amount of microbubbles as the broken pockets shrink and travel downstream. This is in good agreement with experimental observations based of sheet lengths and frequency of lift force oscillation. DOE-SBIR, ONR (monitored by Dr. Ki-Han Kim)

  4. 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

  5. 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.

  6. 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

  7. The motion of a clean bubble confined between two vertical walls

    NASA Astrophysics Data System (ADS)

    Figueroa, B.; Legendre, D.

    2005-11-01

    In nature, as well as in many engineering applications, the effects of confining walls on bubbly flows play an important role. Problems of practical interest where this situation occurs are such as underground water wells and naturally fractured oil reservoirs. Most fundamental studies do not include the effects of walls. The confinement effect on the drag over a bubble was investigated both experimentally and numerically. The experiments were performed with non polar liquids such that the bubble surface could be considered clean. Single bubble experiments and numerical simulations were performed for different Reynolds numbers and dimensionless distances between walls. It was found that the effect of confinement is very strong: the drag can be as much as two times that of a free rising bubble. The comparison between the simulations, performed with the JADIM code, showed good agreement with the experimental results. Both numerical and experimental drag coeficients were found to depend on the dimensionless distance s=(a/R), where a is the bubble radius and R is the distance between walls. The form of this dependency fits closely the form Cd/Cd?[1+8s^3+O(s^4)]. Additionally, it was observed that for large Re the bubble trajectory is unstable, in the sense that it begins to oscillate above certain critical Reynolds; In fact the bubble bounces back and forth from one wall to the other. This instability is different from that observed in freely rising bubbles.

  8. 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,

  9. A novel methodology to measure methane bubble sizes in the water column

    NASA Astrophysics Data System (ADS)

    Hemond, H.; Delwiche, K.; Senft-Grupp, S.; Manganello, T.

    2014-12-01

    The fate of methane ebullition from lake sediments is dependent on initial bubble size. Rising bubbles are subject to dissolution, reducing the fraction of methane that ultimately enters the atmosphere while increasing concentrations of aqueous methane. Smaller bubbles not only rise more slowly, but dissolve more rapidly larger bubbles. Thus, understanding methane bubble size distributions in the water column is critical to predicting atmospheric methane emissions from ebullition. However, current methods of measuring methane bubble sizes in-situ are resource-intensive, typically requiring divers, video equipment, sonar, or hydroacoustic instruments. The complexity and cost of these techniques points to the strong need for a simple, autonomous device that can measure bubble size distributions and be deployed unattended over long periods of time. We describe a bubble sizing device that can be moored in the subsurface and can intercept and measure the size of bubbles as they rise. The instrument uses a novel optical measurement technique with infrared LEDs and IR-sensitive photodetectors combined with a custom-designed printed circuit board. An on-board microcomputer handles raw optical signals and stores the relevant information needed to calculate bubble volume. The electronics are housed within a pressure case fabricated from standard PVC fittings and are powered by size C alkaline batteries. The bill of materials cost is less than $200, allowing us to deploy multiple sensors at various locations within Upper Mystic Lake, MA. This novel device will provide information on how methane bubble sizes may vary both spatially and temporally. We present data from tests under controlled laboratory conditions and from deployments in Upper Mystic Lake.

  10. Hysteresis of inertial cavitation activity induced by fluctuating bubble size distribution.

    PubMed

    Muleki Seya, Pauline; Desjouy, Cyril; Béra, Jean-Christophe; Inserra, Claude

    2015-11-01

    Amongst the variety of complex phenomena encountered in nonlinear physics, a hysteretic effect can be expected on ultrasound cavitation due to the intrinsic nonlinearity of bubble dynamics. When applying successive ultrasound shots for increasing and decreasing acoustic intensities, a hysteretic behaviour is experimentally observed on inertial cavitation activity, with a loop area sensitive to the inertial cavitation threshold. To get a better insight of the phenomena underlying this hysteretic effect, the evolution of the bubble size distribution is studied numerically by implementing rectified diffusion, fragmentation process, rising and dissolution of bubbles from an initial bubble size distribution. When applying increasing and decreasing acoustic intensities, the numerical distribution exhibits asymmetry in bubble number and distribution. The resulting inertial cavitation activity is assessed through the numerical broadband noise of the emitted acoustic radiation of the bubble cloud dynamics. This approach allows obtaining qualitatively the observed hysteretic effect and its interest in terms of control is discussed. PMID:26186844

  11. 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.

  12. 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.

  13. Study of bubble behavior in weightlessness (effects of thermal gradient and acoustic stationary wave) (M-16)

    NASA Technical Reports Server (NTRS)

    Azuma, H.

    1993-01-01

    The aim of this experiment is to understand how bubbles behave in a thermal gradient and acoustic stationary wave under microgravity. In microgravity, bubble or bubbles in a liquid will not rise upward as they do on Earth but will rest where they are formed because there exists no gravity-induced buoyancy. We are interested in how bubbles move and in the mechanisms which support the movement. We will try two ways to make bubbles migrate. The first experiment concerns behavior of bubbles in a thermal gradient. It is well known than an effect of surface tension which is masked by gravity on the ground becomes dominant in microgravity. The surface tension on the side of the bubble at a lower temperature is stronger than at a higher temperature. The bubble migrates toward the higher temperature side due to the surface tension difference. The migration speed depends on the so-called Marangoni number, which is a function of the temperature difference, the bubble diameter, liquid viscosity, and thermal diffusivity. At present, some experimental data about migration speeds in liquids with very small Marangoni numbers were obtained in space experiments, but cases of large Marangoni number are rarely obtained. In our experiment a couple of bubbles are to be injected into a cell filled with silicon oil, and the temperature gradient is to be made gradually in the cell by a heater and a cooler. We will be able to determine migration speeds in a very wide range of Marangoni numbers, as well as study interactions between the bubbles. We will observe bubble movements affected by hydrodynamical and thermal interactions, the two kinds of interactions which occur simultaneously. These observation data will be useful for analyzing the interactions as well as understanding the behavior of particles or drops in materials processing. The second experiment concerns bubble movement in an acoustic stationary wave. It is known that a bubble in a stationary wave moves toward the node or the loop according to whether its diameter is larger or smaller than that of the main resonant radius. In our experiment fine bubbles will be observed to move according to an acoustic field formed in a cylindrical cell. The existence of bubbles varies the acoustic speed, and the interactive force between bubbles will make the bubble behavior collective and complicated. This experiment will be very useful to development of bubble removable technology as well as to the understanding of bubble behavior.

  14. Bubble velocity, diameter, and void fraction measurements in a multiphase flow using fiber optic reflectometer

    NASA Astrophysics Data System (ADS)

    Lim, Ho-Joon; Chang, Kuang-An; Su, Chin B.; Chen, Chi-Yueh

    2008-12-01

    A fiber optic reflectometer (FOR) technique featuring a single fiber probe is investigated for its feasibility of measuring the bubble velocity, diameter, and void fraction in a multiphase flow. The method is based on the interference of the scattered signal from the bubble surface with the Fresnel reflection signal from the tip of the optical fiber. Void fraction is obtained with a high accuracy if an appropriate correction is applied to compensate the underestimated measurement value. Velocity information is accurately obtained from the reflected signals before the fiber tip touches the bubble surface so that several factors affecting the traditional dual-tip probes such as blinding, crawling, and drifting effects due to the interaction between the probe and bubbles can be prevented. The coherent signals reflected from both the front and rear ends of a bubble can provide velocity information. Deceleration of rising bubbles and particles due to the presence of the fiber probe is observed when they are very close to the fiber tip. With the residence time obtained, the bubble chord length can be determined by analyzing the coherent signal for velocity determination before the deceleration starts. The bubble diameters are directly obtained from analyzing the signals of the bubbles that contain velocity information. The chord lengths of these bubbles measured by FOR represent the bubble diameters when the bubble shape is spherical or represent the minor axes when the bubble shape is ellipsoidal. The velocity and size of bubbles obtained from the FOR measurements are compared with those obtained simultaneously using a high speed camera.

  15. 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

  16. 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

  17. The rising risks of rising tides

    SciTech Connect

    Hanson, H.; Lindh, G. [Univ. of Lund (Sweden)

    1996-12-31

    The erosion of beaches, flooding of agricultural land, and intrusion of saltwater into coastal streams could become a reality if temperatures climb. Over the past century, sea levels have risen 4 to 6 inches. Now, the Intergovernmental panel on Climate Change (IPCC) predicts that sea levels will rise between 8 and 28 inches by 2070, say Hans Hanson, associate professor emeritus in the Department of Water Resources Engineering at the University of Lund in Sweden. Coastal communities, which harbor more than half the world`s population, are poorly equipped to combat the threat of encroaching waters. {open_quotes}Few public officials have developed comprehensive strategies to address the potential consequences of sea-level rise,{close_quotes} the authors say. In response to the lack of long-term strategies to address the potential consequences of sea-level rise,{close_quotes} the authors say. In response to the lack of long-term strategies, the IPCC has recommended that coastal nations implement coastal-zone management plans by 2000. {open_quotes}Low-lying islands and high-use, developed coastal areas... face an urgent need to develop strategies for coping with sea-level rise,{close_quotes} the authors conclude.

  18. 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

  19. 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.

  20. Mapping Sea Level Rise

    NSDL National Science Digital Library

    University of Alaska Fairbanks

    2008-01-01

    In this activity related to climate change, learners create and explore topographical maps as a means of studying sea level rise. Learners use various everyday materials including ice and a potato to investigate the difference between sea ice and glaciers in relation to sea level rise, create and use a topographical map to predict sea level rise, and discuss how sea level rise will affect Alaska's coastline. This lesson plan includes detailed activity procedure guidelines, critical thinking questions, an overhead, and handouts. NOTE: material cost does not include cost to purchase DVD since it is not essential to the activity.

  1. 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…

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Acronical Risings and Settings

    NASA Astrophysics Data System (ADS)

    Hockey, Thomas A.

    2012-01-01

    A concept found in historical primary sources, and useful in contemporary historiography, is the acronical rising and setting of stars (or planets). Topocentric terms, they provide information about a star's relationship to the Sun and thus its visibility in the sky. Yet there remains ambiguity as to what these two phrases actually mean. "Acronical” is said to have come from the Greek akros ("point,” "summit,” or "extremity") and nux ("night"). While all sources agree that the word is originally Greek, there are alternate etymologies for it. A more serious difficulty with acronical rising and setting is that there are two competing definitions. One I call the Poetical Definition. Acronical rising (or setting) is one of the three Poetical Risings (or Settings) known to classicists. (The other two are cosmical rising/setting, discussed below, and the more familiar helical rising/setting.) The term "poetical" refers to these words use in classical poetry, e. g., that of Columella, Hesiod, Ovid, Pliny the Younger, and Virgil. The Poetical Definition of "acronical” usually is meant in this context. The Poetical Definition of "acronical” is as follows: When a star rises as the Sun sets, it rises acronically. When a star sets as the Sun sets, it sets acronically. In contrast with the Poetical Definition, there also is what I call the Astronomical Definition. The Astronomical Definition is somewhat more likely to appear in astronomical, mathematical, or navigational works. When the Astronomical Definition is recorded in dictionaries, it is often with the protasis "In astronomy, . . . ." The Astronomical Definition of "acronical” is as follows: When a star rises as the Sun sets, it rises acronically. When a star sets as the Sun rises, it sets acronically. I will attempt to sort this all out in my talk.

  7. Precessing AGN Jets, Bubbles and Cooling Flows

    E-print Network

    Falceta-Goncalves, D; Abraham, Z; Pino, E M de Gouveia Dal; Teixeira, D M

    2011-01-01

    Several galaxy clusters are known to present multiple and misaligned pairs of cavities seen in X-rays, as well as twisted kiloparsec-scale jets at radio wavelengths. It suggests that the AGN precessing jets play a role in the formation of the misaligned bubbles. Also, X-ray spectra reveal that typically these systems are also able to supress cooling flows, predicted theoretically. The absence of cooling flows in galaxy clusters has been a mistery for many years since numerical simulations and analytical studies suggest that AGN jets are highly energetic, but are unable to redistribute it at all directions. We performed 3D hydrodynamical simulations of the interaction between a precessing AGN jet and the warm intracluster medium plasma, which dynamics is coupled to a NFW dark matter gravitational potential. Radiative cooling has been taken into account and the cooling flow problem was studied. We found that precession is responsible for multiple pairs of bubbles, as observed. The misaligned bubbles rise up to ...

  8. Bubble phenomenon in the topside ionosphere

    NASA Astrophysics Data System (ADS)

    Sidorova, L.

    There are the indications that plasma bubbles produced by Rayleigh-Taylor instability at the bottomside of ionosphere could rise up to the topside ionosphere and plasmasphere Maryama and Matuura 1984 using ISS-b satellite data high solar activity period 1978-79 have seen the plasma bubbles in Ne density over equator at 1100 km altitudes in 46 cases in 1700 passes That is sim 3 only However there is distinctly another picture in He density depletions subtroughs According to ISS-b data He density subtroughs occur in the topside ionosphere over equatorial and low-latitudinal regions L sim 1 3-3 in 11 of the cases Karpachev Sidorova 2002 Sidorova 2004 The detailed statistical study of the He density subtrough peculiarities was done The subtrough depth depletion value as function of local time evening--night hours was compared with the vertical plasma drift velocity variations obtained for the same periods from AE-E satellite and IS radar Jicamarca data Striking similarity in development dynamics was revealed for the different seasons It was noted also that the He density subtroughs are mostly observed in the evening-night sector 18-05 LT from October till May It was like to the peculiarities of the equatorial spread-F ESF usually associated with plasma bubble The monthly mean He density subtrough occurrence probability plotted in local time versus month was compared with the similar plots for ESF occurrence probability derived by Abdu and colleagues 2000 from

  9. Stability of magnetic equilibria in radio bubbles

    NASA Astrophysics Data System (ADS)

    Benford, Gregory

    2006-06-01

    Current-carrying flows, in the laboratory and in astrophysical jets, can form remarkably stable magnetic structures. Decades of experience show that such flows often build equilibria that reverse field directions, evolving to a magnetohydrodynamic (MHD) Taylor state, which has remarkable stability properties. We model jets and the magnetic bubbles they build as reversed-field pinch equilibria by assuming the driver current to be stiff in the MHD sense. Taking the jet current as rigid and a fixed function of position, we prove a theorem: that the same, simple MHD stability conditions guarantee stability, even after the jet turns off. This means that magnetic structures harbouring a massive inventory of magnetic energy can persist long after the building jet current has died away. These may be the relic radio `fossils', `ghost bubbles' or `magnetic balloons' found in clusters. These equilibria, which are under magnetic tension, will evolve, retaining the stability properties from that state. The remaining fossil is not a disordered ball of magnetic fields, but a stable structure under tension, able to respond to the slings and arrows of outside forces. Typically their Alfvén speeds greatly exceed the cluster sound speed, and so they can keep out hot cluster plasma, leading to X-ray ghosts. Passing shocks cannot easily destroy them, but can energize and light them up anew at radio frequencies. Bubbles can rise in the hot cluster plasma, perhaps detaching from the parent radio galaxy but stable against Rayleigh-Taylor and other modes.

  10. Gas-rise velocities during kicks

    SciTech Connect

    White, D.B. (Sedco Forex (FR))

    1991-12-01

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

  11. Rising Sea Levels

    NSDL National Science Digital Library

    NBC Learn

    2010-10-07

    In the past century, as the climate has warmed, sea level rise has accelerated. Scientists predict it will only increase, and they're studying changes in the ocean and land to better understand how and why the water is rising. "Changing Planet" is produced in partnership with the National Science Foundation.

  12. Bubble Eliminator Based on Centrifugal Flow

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

  13. Interface shape and Marangoni effect around a bubble within the thermal boundary layer

    NASA Astrophysics Data System (ADS)

    Peng, X. F.; Hu, H. Y.; Ochterbeck, J. M.

    1998-03-01

    The characteristics of a vapor bubble within the thermal boundary layer were theoretically analyzed. The physical models accounting for the variation of interfacial tension and fluid density with temperature were proposed to investigate bubble interface aspects and the fluid flow around the bubble. The analyses demonstrated that the variation in interfacial tension results in variations in the liquid-vapor interface shape and bubble dynamics, which may play a significant role in the departure process of a vapor bubble from a heated wall surface. Increasing temperature gradients in the boundary layer and the gravitational field induce a contact line contraction and correspondingly promotes bubble departure. The simulation of liquid flow around the bubble shows that natural convection dominates the flow for earth conditions; however, the thermocapillary forces provide the principal catalyst for bubble departure in a microgravity environment. The results indicate that both the vapor bubble contraction and the Marangoni flow may increase the heat transfer around the vapor bubble and may cause the bubble to move away from the heating surface, further increasing heat transfer.

  14. 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.

  15. CHARACTERISTICS OF THE CRUSTAL MAGMA BODY IN THE 2005-2006 ERUPTION AREA AT 9°50'N ON THE EAST PACIFIC RISE FROM 3D MULTI-CHANNEL SEISMIC DATA

    NASA Astrophysics Data System (ADS)

    Carton, H. D.; Carbotte, S. M.; Mutter, J. C.; Canales, J.; Nedimovic, M. R.; Marjanovic, M.; Aghaei, O.; Xu, M.; Han, S.; Stowe, L.

    2009-12-01

    In the summer of 2008 a large 3D multi-channel seismic dataset (expedition MGL0812) was collected over the 9°50’N Integrated Study Site at the East Pacific Rise, providing insight into the architecture of the magmatic system and its relationship with hydrothermal activity and volcanic/dyking events associated with the 2005-06 eruption. The main area of 3D coverage is located between 9°42’N and 9°57’N, spanning ~28km along-axis, and was acquired along 94 (1 partial) prime lines shot across-axis and each ~24km-long. Pre-processing of the data acquired in this area is now well under way, with significant efforts targeted at amplitude spike removal. Current work focuses on setting up the 3D processing sequence up to the stack stage for a small group of inlines (axis-perpendicular grid lines spaced 37.5m apart) located over the “bull’s eye” site at 9°50’N, a sequence that will subsequently be applied to the whole dataset. At the meeting we will present stacked and migrated sections - inlines, crosslines, time slices - obtained through 3D processing. We will discuss results focusing on the characteristics of the axial magma body, whose detailed structure and along-axis segmentation will be resolved by the 3D data.

  16. Linearized dynamics of bubbly and cavitating flows in cylindrical ducts

    SciTech Connect

    d`Auria, F.; d`Agostino, L. [Universita degli Studi di Pisa (Italy). Dipartimento di Ingegneria Aerospaziale; Brennen, C.E. [Californai Inst. of Tech., Pasadena, CA (United States). Division of Engineering and Applied Science

    1994-12-31

    The present work investigates the dynamics of the three-dimensional, unsteady flow of a bubbly mixture in a cylindrical duct subject to a periodic pressure excitation at one end. The results are then applied to the case of the idealized pressure excitation generated by the rotor stage of a turbomachine with the objective of understanding the dynamics of an inlet or discharge duct filled with bubbly liquid. The flow displays various regimes (subsonic, supersonic and super-resonant), with radically different propagation characteristics. Depending on the dispersion of the gaseous phase in the bubbly mixture and the angular speed of the turbomachine, the dynamic effects due to the bubble response can be significant, and the flow no longer behaves as a homogeneous barotropic fluid, as is commonly assumed. Examples are presented to illustrate the influence of various flow parameters.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. Bifurcation analysis of bubble dynamics in fluidized beds.

    PubMed

    Blomgren, Peter; Palacios, Antonio; Zhu, Bing; Daw, Stuart; Finney, Charles; Halow, John; Pannala, Sreekanth

    2007-03-01

    We use a low-dimensional, agent-based bubble model to study the changes in the global dynamics of fluidized beds in response to changes in the frequency of the rising bubbles. The computationally based bifurcation analysis shows that at low frequencies, the global dynamics is attracted towards a fixed point since the bubbles interact very little with one another. As the frequency of injection increases, however, the global dynamics undergoes a series of bifurcations to new behaviors that include highly periodic orbits, chaotic attractors, and intermittent behavior between periodic orbits and chaotic sets. Using methods from time-series analysis, we are able to approximate nonlinear models that allow for long-term predictions and the possibility of developing control algorithms. PMID:17411256

  2. 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

  3. Bubble domain technology for spacecraft onboard memory

    NASA Technical Reports Server (NTRS)

    Hayes, P. J.; Stermer, R. L., Jr.

    1982-01-01

    Bubble device technologies for spacecraft onboard memory offer improved reliability and memory functional characteristics. Recent advances include Permalloy gap devices (commercially available) whose improved performance and higher density are attributable to an asymmetric chevron pattern. Secondly, an order of magnitude increase in density at less power than the Permalloy technology is possible with the ion implant technology. A third technology, the self-structured current access system, offers another order of magnitude improvement in density and data rate, and is being studied. Capacity estimates for Permalloy gap, ion implant, and self-structured current access systems are, respectively, 10 to the 8th, 10 to the 9th, and 10 to the 10th bits, and power per unit data rate efficiencies are 140, 60, and 2 W/Mbps. A flexible modular organization system, compatible with all of these device technologies, is analyzed, and, as the system is contained in a bubble, relatively simple retrofitting is foreseen.

  4. Global sea level rise

    Microsoft Academic Search

    Bruce C. Douglas

    1991-01-01

    Published values for the long-term, global mean sea level rise determined from tide gauge records exhibit considerable scatter, from about 1 mm to 3 mm\\/yr. This disparity is not attributable to instrument error; long-term trends computed at adjacent sites often agree to within a few tenths of a millimeter per year. Instead, the differing estimates of global sea level rise

  5. Fragmentation, nucleation and migration of crystals and bubbles in the Bishop Tuff rhyolitic magma

    SciTech Connect

    Gualda, G.; Cook, D.L.; Chopra, R.; Qin, L.; Anderson, A.T.; Rivers, M. (UC)

    2010-12-07

    The Bishop Tuff (USA) is a large-volume, high-silica pyroclastic rhyolite. Five pumice clasts from three early stratigraphic units were studied. Size distributions were obtained using three approaches: (1) crushing, sieving and winnowing (reliable for crystals >100 {micro}m); (2) microscopy of 1 mm{sup 3} fragments (preferable for crystals <100 {micro}m); and (3) computerised X-ray microtomography of {approx}1 cm{sup 3} pumice pieces. Phenocryst fragments coated with glass are common, and the size distributions for all crystals are concave-upward, indicating that crystal fragmentation is an important magmatic process. Three groups are recognised, characterised by: (1) high-density (0.759-0.902 g cm{sup -3}), high-crystal content (14.4-15.3 wt.%) and abundant large crystals (>800 {micro}m); concave-downward size distributions for whole crystals indicate late-stage growth with limited nucleation, compatible with the slow cooling of a large, gas-saturated, stably stratified magma body; (2) low-density (0.499 g cm{sup -3}), low-crystal content (6.63 wt.%) and few large crystals; the approximately linear size distribution reveals that nucleation was locally important, perhaps close to the walls; and (3) intermediate characteristics in all respects. The volumetric fraction of bubbles inversely correlates with the number of large crystals. This is incompatible with isobaric closed-system crystallisation, but can be explained by sinking of large crystals and rise of bubbles in the magma.

  6. Effects of Generated Bubbles Between Electrodes on Efficiency of Alkaline Water Electrolysis

    NASA Astrophysics Data System (ADS)

    Nagai, Niro; Takeuchi, Masanori; Nakao, Motohide

    There is an optimum condition on water electrolysis efficiency due to the effects of generated bubbles between electrodes. In this paper, in order to explain the existence of the optimum condition, a model of alkaline water electrolysis was established. The model can express void fraction and current density profiles along electrodes, and show the existence of the optimum condition. For verification of this model, rising velocity, diameter distribution of bubbles between electrodes and current density profiles along electrodes were measured during water electrolysis of KOH solution. Two-phase flows between electrodes were observed by a still camera and a digital video camera. The results showed that bubble rising velocity ranges from 4-24cm/s and becomes larger as current density increases. Bubble diameter ranges from 0.01-0.8mm, where average diameter becomes large as current density increases. Obtained results showed the sound validity of present model.

  7. 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,

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. Solid phase transition of overpressurised helium bubbles seen from positron annihilation studies

    NASA Astrophysics Data System (ADS)

    Maji, Sanjib; Singh, Amarjeet; Nambissan, P. M. G.

    2001-03-01

    Positron lifetime and Doppler broadening measurements on highly overpressurised ( P?10 Peq) helium bubbles in Al indicated abnormal variations at low temperatures, which is being assigned to the transformation of dense helium bubbles into the solid phase, as expected from the Simon-Glatzel equation. The bubble pressure calculated using separate models for the fluid and solid phases shows consistency with the helium freezing characteristics. The solid phase transition is further confirmed by verifying an exponential variation of the ultrasonic velocity with the solid bubble pressure.

  13. Numerical modeling of bubble dynamics in viscoelastic media with relaxation

    NASA Astrophysics Data System (ADS)

    Warnez, M. T.; Johnsen, E.

    2015-06-01

    Cavitation occurs in a variety of non-Newtonian fluids and viscoelastic materials. The large-amplitude volumetric oscillations of cavitation bubbles give rise to high temperatures and pressures at collapse, as well as induce large and rapid deformation of the surroundings. In this work, we develop a comprehensive numerical framework for spherical bubble dynamics in isotropic media obeying a wide range of viscoelastic constitutive relationships. Our numerical approach solves the compressible Keller-Miksis equation with full thermal effects (inside and outside the bubble) when coupled to a highly generalized constitutive relationship (which allows Newtonian, Kelvin-Voigt, Zener, linear Maxwell, upper-convected Maxwell, Jeffreys, Oldroyd-B, Giesekus, and Phan-Thien-Tanner models). For the latter two models, partial differential equations (PDEs) must be solved in the surrounding medium; for the remaining models, we show that the PDEs can be reduced to ordinary differential equations. To solve the general constitutive PDEs, we present a Chebyshev spectral collocation method, which is robust even for violent collapse. Combining this numerical approach with theoretical analysis, we simulate bubble dynamics in various viscoelastic media to determine the impact of relaxation time, a constitutive parameter, on the associated physics. Relaxation time is found to increase bubble growth and permit rebounds driven purely by residual stresses in the surroundings. Different regimes of oscillations occur depending on the relaxation time.

  14. 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.

  15. THE MILKY WAY PROJECT: LEVERAGING CITIZEN SCIENCE AND MACHINE LEARNING TO DETECT INTERSTELLAR BUBBLES

    SciTech Connect

    Beaumont, Christopher N.; Williams, Jonathan P. [Institute for Astronomy, University of Hawai'i, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Goodman, Alyssa A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Kendrew, Sarah; Simpson, Robert, E-mail: beaumont@ifa.hawaii.edu [Department of Astrophysics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom)

    2014-09-01

    We present Brut, an algorithm to identify bubbles in infrared images of the Galactic midplane. Brut is based on the Random Forest algorithm, and uses bubbles identified by >35,000 citizen scientists from the Milky Way Project to discover the identifying characteristics of bubbles in images from the Spitzer Space Telescope. We demonstrate that Brut's ability to identify bubbles is comparable to expert astronomers. We use Brut to re-assess the bubbles in the Milky Way Project catalog, and find that 10%-30% of the objects in this catalog are non-bubble interlopers. Relative to these interlopers, high-reliability bubbles are more confined to the mid-plane, and display a stronger excess of young stellar objects along and within bubble rims. Furthermore, Brut is able to discover bubbles missed by previous searches—particularly bubbles near bright sources which have low contrast relative to their surroundings. Brut demonstrates the synergies that exist between citizen scientists, professional scientists, and machine learning techniques. In cases where ''untrained' citizens can identify patterns that machines cannot detect without training, machine learning algorithms like Brut can use the output of citizen science projects as input training sets, offering tremendous opportunities to speed the pace of scientific discovery. A hybrid model of machine learning combined with crowdsourced training data from citizen scientists can not only classify large quantities of data, but also address the weakness of each approach if deployed alone.

  16. Measurement of the Bubbles Entrained in a Translating Axisymmetric Plunging Laminar Jet

    NASA Astrophysics Data System (ADS)

    Tavakolinejad, M.; Shakeri, M.; Chang, P.; Duncan, J. H.

    2006-11-01

    Air entrainment induced by a translating axisymmetric laminar vertical water jet as it impinges onto the free surface of a quiescent pool of water is studied experimentally. The experiments are performed in a towing tank that is 24 ft long, 2.5 ft wide and 3 ft deep. When the jet is stationary, the water surface around the jet impact site is smooth and no air is entrained. When the jet is moving horizontally, a depression of the free surface forms directly downstream of the jet. Air is entrained from the cusp formed at the bottom of the leading edge of the depression. Previously presented high-speed flow visualization movies of the entrainment process have show that the bubbles enter the water when vortices from the jet shear layer pass over the cusp and that these bubbles are initially trapped within the vortices. Further downstream, two regions of bubbles are formed. Close behind the jet and near the free surface there is a region of large irregular shaped bubbles with relatively high rise velocity. Deeper in the water and extending further downstream there is a region of small diameter bubbles with lower rise velocity. The results of shadowgraph measurements of the size distributions of the small bubbles in fresh and salt water are presented. In the presence of salt water, a larger number of small diameter bubbles is found.

  17. Simulation studies of vapor bubble generation by short-pulse lasers

    SciTech Connect

    Amendt, P.; London, R.A.; Strauss, M. [and others

    1997-10-26

    Formation of vapor bubbles is characteristic of many applications of short-pulse lasers in medicine. An understanding of the dynamics of vapor bubble generation is useful for developing and optimizing laser-based medical therapies. To this end, experiments in vapor bubble generation with laser light deposited in an aqueous dye solution near a fiber-optic tip have been performed. Numerical hydrodynamic simulations have been developed to understand and extrapolate results from these experiments. Comparison of two-dimensional simulations with the experiment shows excellent agreement in tracking the bubble evolution. Another regime of vapor bubble generation is short-pulse laser interactions with melanosomes. Strong shock generation and vapor bubble generation are common physical features of this interaction. A novel effect of discrete absorption by melanin granules within a melanosome is studied as a possible role in previously reported high Mach number shocks.

  18. The bubbly-slug transition in a boiling two-phase flow under microgravity

    NASA Astrophysics Data System (ADS)

    Kiper, Ali M.; Swanson, T. D.

    1993-07-01

    A theory is presented to describe, in reduced gravity flow boiling, the transition from bubbly two-phase flow to slug flow. It is shown that characteristics of the bubbly flow and the transition were controlled by the mechanism of vapor bubble growth dynamics. By considering in nucleate boiling, behavior of vapor bubbles at departure from a heated surface a condition required for transition was determined. Although required, this condition alone could not ensure coalescence of bubbles to cause the transition to slug two-phase flow. The condition leading to coalescence, therefore, was obtained by examining oscillations of vapor bubbles following their departure from the heated surface. The predicted transition conditions were compared with the prediction and test data reported for adiabatic reduced gravity two-phase flow, and good qualitative agreement was found.

  19. 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

  20. A boiling heat transfer surface for creating a single stream of vapor bubbles.

    NASA Astrophysics Data System (ADS)

    Douglas, Zachary W.; Smith, Marc K.; Glezer, Ari

    2006-11-01

    The high heat transfer rate characteristic of boiling is limited by the vapor-bubble removal rate and a critical transition to film boiling. External forces, such as acoustic waves, can be used to enhance vapor-bubble removal and improve heat transfer. In order to explore such enhanced vapor-bubble removal processes, a boiling heat transfer surface has been designed to control the location, growth, and detachment of a single stream of vapor bubbles. The device consists of an insulating annulus surrounding a thermally conductive pin 1 mm in radius. The upper surfaces of the annulus and the pin have a thin polished electro-plated copper coating. When heated from below, the pin provides a thermal conduit that creates a local hot spot on the copper surface. The majority of all bubble nucleations occur within 3 mm of the center of the pin. A thin hydrophobic coating centered on the hot spot encourages the formation of a single vapor bubble that grows to a size determined by the radius of the hydrophobic coating. When the bubble detaches from the surface, a new vapor bubble forms in the same location. High-speed video and bubble-size and thermal measurements will be presented to document the characteristics and performance of this heat transfer surface.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. The rise of graphene

    Microsoft Academic Search

    A. K. Geim; K. S. Novoselov

    2007-01-01

    Graphene is a rapidly rising star on the horizon of materials science and condensed-matter physics. This strictly two-dimensional material exhibits exceptionally high crystal and electronic quality, and, despite its short history, has already revealed a cornucopia of new physics and potential applications, which are briefly discussed here. Whereas one can be certain of the realness of applications only when commercial

  14. Numerical simulation of bubble dispersion in turbulent Taylor-Couette flow

    NASA Astrophysics Data System (ADS)

    Chouippe, A.; Climent, E.; Legendre, D.; Gabillet, C.

    2014-04-01

    We investigate bubble dispersion in turbulent Taylor-Couette flow. The aim of this study is to describe the main mechanisms yielding preferential bubble accumulation in near-wall structures of the flow. We first proceed to direct numerical simulation of Taylor-Couette flows for three different geometrical configurations (three radius ratios ? = R1/R2: ? = 0.5, ? = 0.72, and ? = 0.91 with the outer cylinder at rest) and Reynolds numbers corresponding to turbulent regime ranging from 3000 to 8000. The statistics of the flow are discussed using two different averaging procedures that permit to characterize the mean azimuthal velocity, the Taylor vortices contribution and the small-scale turbulent fluctuations. The simulations are compared and validated with experimental and numerical data from literature. The second part of this study is devoted to bubble dispersion. Bubble accumulation is analyzed by comparing the dispersion obtained with the full turbulent flow field to bubble dispersion occurring at lower Reynolds numbers in previous works. Several patterns of preferential accumulation of bubbles have been observed depending on bubble size and the effect of gravity. For the smaller size considered, bubbles disperse homogeneously throughout the gap, while for the larger size they accumulate along the inner wall for the large gap width (? = 0.5). Varying the intensity of buoyancy yields complex evolution of the bubble spatial distribution. For low gravity effect, bubble entrapment is strong leading to accumulation along the inner wall in outflow regions (streaks of low wall shear stress). When buoyancy effect dominates on vortex trapping, bubbles rise through the vortices, while spiral patterns stretched along the inner cylinder are clearly identified. Force balance is analyzed to identify dominating forces leading to this accumulation and accumulation patterns are compared with previous experiments.

  15. Bubble chamber spectroscopy for chemical analysis: A new concept

    Microsoft Academic Search

    J. H. Atencio; Xin Luo; E. I. McCreary; A. W. McCown; R. K. Sander

    1995-01-01

    A new technique for the detection of trace concentrations of molecules in solution has been developed. This system utilizes the amplification characteristics of a bubble chamber in which energy deposition from laser absorption is monitored. In the experimental set-up, a trace quantity of solute is introduced into liquid propane that is contained in a small (10 ml) stainless steel cell

  16. Bubble chamber for chemical analysis: a new concept

    Microsoft Academic Search

    Jerry H. Atencio; Xin Luo; Andrew W. McCown; E. Iain McCreary; Robert K. Sander

    1995-01-01

    A new technique for the detection of trace concentrations of molecules in solution has been developed. This system utilizes the amplification characteristics of a bubble chamber in which energy deposition from laser absorption is monitored. In the experimental set-up, a trace quantity of solute is introduced into liquid propane that is contained in a small (10 ml) stainless steel cell

  17. Quantitative consideration of flow structures (bubble swarms and liquid motion) and dissolved CO2 concentration transportation, in a bubbly flow

    NASA Astrophysics Data System (ADS)

    Shinohara, Daisuke; Saito, Takayuki

    2013-11-01

    The objective of the present study is to clarify the relationship between large scale flow structures (: bubble swarm and liquid motion) and dissolved CO2 concentration transportation, in a large-diameter bubble column. For this specific purpose, the time-series void fractions, dissolved CO2 concentration and liquid-phase-velocities were simultaneously measured by using a photoelectric optical fiber probe (POFP) and Laser Doppler Velocimetry. The POFP was newly developed in order to simultaneously measure bubble characteristics and dissolved CO2 concentration. We calculated the spatial scale of the bubble swarms and liquid motion based on the thinking of the integral length scale. The spatial scale of the bubble swarms and liquid motion was large in the bottom zone. Moreover, the size of this spatial scale changed with time; i.e. the flow structures changed with time in the bottom zone. The characteristics of the flow structures in the bottom zone faded out towards the upper zone of the column. The cross-correlation coefficients of dissolved CO2 concentration were calculated at several zones by height. As a result, the relationship between the flow structures and dissolved CO2 concentration transportation was found out.

  18. 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

  19. 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

  20. 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.

  1. 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

  2. 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.

  3. Experimental study on bubble pulse features under the combined action of horizontal and vertical walls

    NASA Astrophysics Data System (ADS)

    Wang, Shi-ping; Chu, Wen-hua; Zhang, A.-man

    2014-06-01

    The pulse features of a bubble have a close connection with the boundary condition. When a bubble moves near a rigid wall, it will be attracted by the Bjerknes force of the wall, and a jet pointing at the wall will be generated. In real application, the bubble may move under the combined action of walls in different directions when it forms at the corner of a pipe or at the bottom of a dam. The motion of the bubble shows complex and nonlinear characteristics under these conditions. In order to investigate the bubble pulse features near complex walls, a horizontal wall and a vertical wall are put into the experimental water tank synchronously, and an electric circuit with 200 voltages is designed to generate discharge bubbles, and then experimental study on the bubble pulse features under the combined action of horizontal and vertical walls is carried out. The influences of the combined action of two walls on the bubble shape, pulse period, moving trace and inside jet are obtained by changing the distances from bubble center to the two walls. It aims at providing references for the relevant theoretical and numerical research.

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. 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

  9. 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.

  10. 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.

  11. Plasma bubble detection in the DEMETER micro-satellite data

    NASA Astrophysics Data System (ADS)

    Onishi, T.; Nguyen, C.-T.; Berthelier, J.-J.

    2012-04-01

    The occurrence of plasma bubbles is the most important phenomenon that affects the night time equatorial ionosphere resulting in strong and localized drops of the plasma density with often very sharp boundaries. Besides its own interest for ionospheric physics this phenomenon is also of significant practical importance since it disrupts HF communication and GPS signal reception. In the frame of a French ANR funded project to model the rise and development of plasma bubbles we have searched for specific disturbances of the low latitude ionosphere that might be considered as "precursors" of plasma bubbles, possibly leading, under favourable conditions, to an instable ionosphere. To this aim, we have manually selected and classified typical events observed on data from two instruments on board the DEMETER satellite, IAP (Plasma analyzer) and ISL (Langmuir probe experiment). We present in this poster the various types of events and show that one of them appears to be associated with the later occurrence of plasma bubbles. From the first list of events recorded during an ~ 18 month period we will discuss in detail the plasma disturbances and present initial results of a statistical study.

  12. 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

  13. Wheat Evolution: Dough Rising

    NSDL National Science Digital Library

    Biotechnology and Biological Sciences Research Council

    2012-01-01

    In this activity (p.6-7 of PDF), learners investigate the evolution of wheat by creating dough from different flours, observing the samples of dough as they rise, and then baking the dough. The evolution of wheat from wild grasses demonstrates the dramatic effect of both natural and directed evolution on the structure of a crop plant and the chemical makeup of the product harvested from it. These activities illustrate the changes to both the structure and the chemistry of the wheat plant.

  14. 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.

  15. Taxing the Rich: Recombinations and Bubble Growth During Reionization

    E-print Network

    Steven R. Furlanetto; S. Peng Oh

    2005-08-16

    Reionization is inhomogeneous for two reasons: the clumpiness of the intergalactic medium (IGM) and clustering of the discrete ionizing sources. While numerical simulations can in principle take both into account, they are at present limited by small box sizes. On the other hand, analytic models have only examined the limiting cases of a clumpy IGM (with uniform ionizing emissivity) and clustered sources (embedded in a uniform IGM). Here, we present an analytic model for the evolving topology of reionization that includes both factors. At first, recombinations can be ignored and ionized bubbles grow primarily through major mergers. As a result, reionization resembles "punctuated equilibrium," with a series of well-separated sharp jumps in the ionizing background. These features are local effects and do not reflect similar jumps in the global ionized fraction. We then combine our bubble model with a simple description of recombinations in the IGM. We show that the bubbles stop growing when recombinations balance ionizations. If the IGM density structure is similar to that at moderate redshifts, this limits the bubble radii to ~20 comoving Mpc; however, it may be much smaller if the IGM is significantly clumpier at higher redshifts. Once a bubble reaches saturation, that region of the universe has for all intents and purposes entered the "post-overlap" stage, so the overlap epoch actually has a finite width. This picture naturally explains the substantial large-scale variation in Lyman-series opacity along the lines of sight to the known z>6 quasars. More quasar spectra will shed light on the transition between the "bubble-dominated" topology characteristic of reionization and the "web-dominated" topology characteristic of the later universe. [Abridged

  16. Pyroclastic Eruptions on the Northern East Pacific Rise

    NASA Astrophysics Data System (ADS)

    Clague, D. A.; Davis, A. S.; Paduan, J. B.

    2004-12-01

    Glass sand-sized fragments were recovered from three sites along the northern East Pacific Rise using the ROV Tiburon. Abundant moderately-vesicular bubble-wall (like limu o Pele) fragments, and rare Pele's hair were recovered near the center of the Alarcon Rise at 2360-2400 m at 23\\deg23'N to 23\\deg26'N and just south of the Tamayo Fracture Zone at 3150-3190 m at 22\\deg50'N. Less abundant, but morphologically similar, fragments were recovered at 2620 m at 20\\deg50'N, near the 21\\deg N hydrothermal vent sites. The samples were recovered in push cores and using a small 29-jar suction sampler designed to collect and filter glass particles. The particles in individual samples include numerous compositional types, suggesting widespread dispersal of the particles after their formation. Many of the bubble-wall fragments enclose abundant (10-15%) spherical to elongate, stretched vesicles. The particles provide stratigraphic information on the sequence of eruptions in an area and can therefore be used to determine eruption compositions in space and time. For example, at the site at 22\\deg50'N, particles with a distinct composition were recovered from the flank of a small cone, establishing that the cone predates an eruption just to the south of the cone. Also at this site, glass particles collected on top of the cone have a range of compositions that, on average, are about 0.3% lower in MgO than pillow rind glasses from the same cone. This compositional difference indicates that the pillow basalt glasses average about 6\\deg C cooler than the particulate glasses. Maicher and White (2002) proposed that bubble-wall fragments form from steam expansion where lava flows cover saturated sediment forming hydroclastic (secondary) eruptions. On the other hand, Clague et al. (2003) proposed that bubble-wall fragments from the Gorda Ridge were formed by discharge of coalesced magmatic gas bubbles through the erupting vent in pyroclastic eruptions. Four lines of evidence support the pyroclastic origin of the glass fragments on the East Pacific Rise: 1) bubble-wall fragments occur with Pele's hair fragments, 2) site at 22\\deg50'N, like the sites on the Gorda Ridge, are at pressures greater than the critical pressure for sea water boiling so no vapor phase is produced upon heating, and 3) bubble-wall fragments occur on top of a monogenetic cone that should have been sediment-free when the glass particles formed, and 4) the abundant vesicles trapped in some bubble-wall fragments are evidence of high concentrations of magmatic gas in these lavas. Pyroclastic eruptions, most likely similar to strombolian eruptions, are ubiquitous along the slow-spreading Gorda Ridge and the fast-spreading northern East Pacific Rise demonstrating similar eruptive processes despite the different spreading rates and ridge morphologies.

  17. 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.

  18. Towards a universal set of bubble coalescence laws in low viscosity magmas

    NASA Astrophysics Data System (ADS)

    Schipper, C.; Burgisser, A.

    2010-12-01

    Bubble nucleation, growth, and coalescence control the ascent, degassing, and eruption of all types of magma. Nucleation and growth are consequences of magma decompression, and are satisfactorily described by solubility and physical models. Coalescence is a more complicated issue, and one that bears heavily on the eruptive fate of an ascending magma. If coalescence is efficient, the resulting permeable networks of interconnected void space may lead to efficient outgassing, and in turn, a reduction in explosive potential. Alternatively, if coalescence is inefficient, bubbles may remain isolated and overpressured, leading to cataclysmic explosive eruptions. Vesicle textures in pyroclasts preserve the only natural evidence of bubble-bubble dynamics. However, most (if not all) pyroclast textures either have lost their gas by bubble collapse, or record syn- to post-fragmentation processes. In both cases, natural products may not always be good indicators of processes at depth. There is thus a gap in our understanding of deep conduit coalescence processes. We present an x-ray computed microtomographic (µ-cT) study of coalescence at the single bubble-bubble pair scale in experimentally and naturally decompressed, low viscosity magmas. Experimentally decompressed phonolites allow us to essentially look “behind” fragmentation, by reproducing deep conduit conditions, and controlling decompression and quenching. Initial results indicate there is no single law of coalescence that can explain all the interactions observed in these low-viscosity magmas, where bubble buoyancy and mobility are key issues. Instead, we identify four different processes, acting concurrently. (1) Traditional capillary +/- gravitational drainage along flattened interbubble films. (2) Static “dimpling,” or penetration of one bubble into an adjacent bubble, driven by growth dispersion-controlled differences in internal bubble pressures. (3) Dynamic “handshaking,” similar to dimpling, but occurring between buoyantly moving bubbles. (4) “Suction,” or entrainment of small trailing bubble into faster-rising larger bubbles. Initial analytical models indicate that in low viscosity magmas, all of these processes act on timescales shorter than the typical timescales of ascent and decompression. Examination of a range of natural submarine and subaerial pyroclasts permits discussion of how each coalescence mechanism is represented in nature, and on the caveats of using textural information in natural pyroclasts to quantify coalescence mechanisms.

  19. Characteristics of Electromagnetic Modes in Nighttime Equatorial Plasma

    NASA Astrophysics Data System (ADS)

    Basu, B.

    2004-05-01

    Unequal electron and ion flow velocities, which can result from the presence of gravity and/or electric field in collisional plasma, give rise to a net current density that provides excitation energy for plasma instabilities. In the presence of density gradient, the instability is of collisional interchange type. The generalized Rayleigh-Taylor instability (GRTI) is an example of such instability and is believed to be responsible for the generation of the so-called bubbles (regions of depleted density) in the nighttime equatorial ionosphere. Scintillation caused by the bubbles can degrade and disrupt the communication and navigation systems that depend on trans-ionospheric radio links. The GRTI has so far been studied only in the electrostatic limit, making the ad hoc assumption that the magnetic field fluctuations are negligible. However, magnetic field data from CHAMP satellite seem to indicate the presence of measurable magnetic fluctuations associated with the bubbles. The magnetometer on C/NOFS satellite will also be sensitive enough to detect any magnetic fluctuation. This prompted us to extend our linear stability analysis of GRTI to include the magnetic fluctuations. The eigenvalue equation for electromagnetic modes driven by the combined effects of the gravity and an eastward electric field has been derived. Analysis of the equation using realistic ionospheric plasma parameters will be presented. In particular, the growth rates and the spectral characteristics of the modes, together with the estimate of the strength of the magnetic field fluctuation relative to that of the electric field fluctuation, will be discussed.

  20. Stabilisation using bubbles in F.E. time dependent problem with application in forming

    NASA Astrophysics Data System (ADS)

    Coupez, Thierry

    2007-04-01

    A simple and unified approach is described to stabilize FE on unstructured meshes for a large panel of problems. A variational multiscale approach may be used as a guideline to obtain stability. The simple P1 continuous approximation is systematically augmented with a bubble function inside elements. The bubble is condensed giving rise to supplementary terms in the varitional formulation. Bubble addition comes from the mixed formulation of incompressible flow problem. It is also introduced to retrieve the SUPG method for convective equation, giving rise also in a more general framework to the RFB methods. Different applications are proposed: the incompressible Navier Stokes equation, the interface capturing by Level set method and also a space time continuous P1 Finite Element method working with a full unstructured mesh both in space and time.

  1. 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.

  2. 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

  3. Quasi-periodic Fast-mode Magnetosonic Wave Trains Inside and Outside CME Bubbles Detected by SDO/AIA

    NASA Astrophysics Data System (ADS)

    Liu, Wei; Ofman, L.; Downs, C.; Title, A. M.

    2013-07-01

    Quasi-periodic fast-mode magnetosonic wave trains both inside and outside expanding CME bubbles have recently been discovered by SDO/AIA (Liu et al. 2011, 2012; Shen & Liu 2012). In general, a wave train inside a CME bubble originates from a flare site and propagates along a funnel of coronal loops at typically 1000-2000 km/s (Ofman et al. 2011). A wave train outside a CME usually originates from a CME flank and propagates in the low corona along the solar surface following the leading front of a global EUV wave at typically 500-1000 km/s. The former is primarily seen in the cooler 171 Angstrom channel with a characteristic temperature of 0.8 MK, while the latter is pronounced in the hotter 193 and 211 Angstrom channels of typically 1.6-2.0 MK. What is the relationship between the two types of wave trains? Why do they appear differently in location and wavelength (temperature)? To answer these questions, we report here for the first time the evidence that the wave train beyond the CME bubble is the continuation of the same wave train along the funnel within the CME. The continuous deceleration of the waves is consistent with the expected decrease of the local fast-mode speed with distance from the active region (e.g., Ofman et al. 2011; Downs et al. 2012). There is an abrupt change of the wave speed at the topological interface where the expanding CME flank is located, indicative of contrasting magnetic and plasma conditions, which can give rise to different (fast-mode) speeds and wavelength (temperature) dependent appearances of these wave trains.Abstract (2,250 Maximum Characters): Quasi-periodic fast-mode magnetosonic wave trains both inside and outside expanding CME bubbles have recently been discovered by SDO/AIA (Liu et al. 2011, 2012; Shen & Liu 2012). In general, a wave train inside a CME bubble originates from a flare site and propagates along a funnel of coronal loops at typically 1000-2000 km/s (Ofman et al. 2011). A wave train outside a CME usually originates from a CME flank and propagates in the low corona along the solar surface following the leading front of a global EUV wave at typically 500-1000 km/s. The former is primarily seen in the cooler 171 Angstrom channel with a characteristic temperature of 0.8 MK, while the latter is pronounced in the hotter 193 and 211 Angstrom channels of typically 1.6-2.0 MK. What is the relationship between the two types of wave trains? Why do they appear differently in location and wavelength (temperature)? To answer these questions, we report here for the first time the evidence that the wave train beyond the CME bubble is the continuation of the same wave train along the funnel within the CME. The continuous deceleration of the waves is consistent with the expected decrease of the local fast-mode speed with distance from the active region (e.g., Ofman et al. 2011; Downs et al. 2012). There is an abrupt change of the wave speed at the topological interface where the expanding CME flank is located, indicative of contrasting magnetic and plasma conditions, which can give rise to different (fast-mode) speeds and wavelength (temperature) dependent appearances of these wave trains.

  4. Dynamic Modeling of Hydro- Formylation of 1-Decene on Rh/C Catalyst in Bubble Column Slurry Reactor

    NASA Astrophysics Data System (ADS)

    Upkare, Makarand M.; Rajurkar, Kalpendra B.; Das, Samir K.; Jaganathan, R.

    2010-10-01

    A dynamic model has been developed for the bubble column slurry reactor operating under non-isothermal conditions. The model consists of mass and heat balance equations for the gas and liquid phases and the catalyst particle. The model equations consisted of partial differential equations (PDE) which were converted to ordinary differential equations (ODE) by using finite difference relationships for the spatial derivatives and the ordinary differential equations for the time derivatives (Numerical Method of Lines-NMoL). The model was applied to describe the dynamic behaviour of bubble column slurry reactor during the hydroformylation of 1-decene on Rh/C catalyst. Model simulations were performed to obtain a meaningful path to steady state and to reproduce the other characteristics of the dynamic behaviour of the reactor. Under given conditions, the reaction required approximately 3750 seconds to reach the steady state concentrations at various reactor positions. It was observed with increase in the fluid velocities, the dynamics of the system was altered to 2500 seconds to reach the steady state condition. The effect of axial dispersion on the substrate concentration and the temperature rise along the reactor was further studied and discussed.

  5. PHYSICAL MODELING OF THE FLOW FIELD AROUND TWIN HIGH-RISE BUILDINGS

    EPA Science Inventory

    A wind tunnel study was conducted to investigate the flow characteristics near three configurations of high-rise buildings - an isolated high-rise building, two high-rise buildings separated in the streamwise direction, and two high-rise buildings separated in the streamwise dire...

  6. The role of colloidal particles on the migration of air bubbles in porous media 

    E-print Network

    Han, Ji-seok

    2009-05-15

    in the presence of colloidal particles captured on the air-water interface. The model was based on the pore-scale balance equation for forces acting on a bubble rising in a porous medium in the presence of colloids. A dimensional analysis of the phenomenon...

  7. 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

  8. Ground potential rise monitor

    DOEpatents

    Allen, Zachery Warren; Zevenbergen, Gary Allen

    2012-07-17

    A device and method for detecting ground potential rise (GPR) comprising a first electrode, a second electrode, and a voltage attenuator. The first electrode and the second electrode are both electrically connected to the voltage attenuator. A means for determining the presence of a dangerous ground potential is connected to the voltage attenuator. The device and method further comprises a means for enabling one or more alarms upon the detection of the dangerous ground potential. Preferably, a first transmitter/receiver is connected to the means for enabling one or more alarms. Preferably, a second transmitter/receiver, comprising a button, is electromagnetically connected to the first transmitter/receiver. Preferably, the means for determining the presence of a dangerous ground potential comprises a means for determining the true RMS voltage at the output of the voltage attenuator, a transient detector connected to the output of the voltage attenuator, or a combination thereof.

  9. Sea Level Rise Media Release

    E-print Network

    Hu, Aixue

    Sea Level Rise Media Release Coverage Report 07/06/2009 Melting Ice Could Lead to Massive Waves 06/11/2009 Rising sea levels could see U.S. Atlantic coast cities make hard choices; Where to let Baltimore Chronicle & Sentinel, The 06/08/2009 Rapid rise in sea levels on East Coast predicted Pittsburgh

  10. The Sea Level Rise Challenge

    Microsoft Academic Search

    W. Abdalati; S. C. Moser; R. W. Schmitt

    2010-01-01

    Recent research on sea level rise suggests that sea level rise by the end of this century may well be significantly larger than those identified in the IPCC AR4 (2007). Whereas in the past, sea level rise was ascribed equally to thermal expansion of a warming ocean and the melting of land-based ice sheets and glaciers, the recent acceleration in

  11. Time and Space Resolved Heat Transfer Measurements Under Nucleate Bubbles with Constant Heat Flux Boundary Conditions

    NASA Technical Reports Server (NTRS)

    Myers, Jerry G.; Hussey, Sam W.; Yee, Glenda F.; Kim, Jungho

    2003-01-01

    Investigations into single bubble pool boiling phenomena are often complicated by the difficulties in obtaining time and space resolved information in the bubble region. This usually occurs because the heaters and diagnostics used to measure heat transfer data are often on the order of, or larger than, the bubble characteristic length or region of influence. This has contributed to the development of many different and sometimes contradictory models of pool boiling phenomena and dominant heat transfer mechanisms. Recent investigations by Yaddanapyddi and Kim and Demiray and Kim have obtained time and space resolved heat transfer information at the bubble/heater interface under constant temperature conditions using a novel micro-heater array (10x10 array, each heater 100 microns on a side) that is semi-transparent and doubles as a measurement sensor. By using active feedback to maintain a state of constant temperature at the heater surface, they showed that the area of influence of bubbles generated in FC-72 was much smaller than predicted by standard models and that micro-conduction/micro-convection due to re-wetting dominated heat transfer effects. This study seeks to expand on the previous work by making time and space resolved measurements under bubbles nucleating on a micro-heater array operated under constant heat flux conditions. In the planned investigation, wall temperature measurements made under a single bubble nucleation site will be synchronized with high-speed video to allow analysis of the bubble energy removal from the wall.

  12. Shrinkage of bubbles and drops in the lattice Boltzmann equation method for nonideal gases.

    PubMed

    Zheng, Lin; Lee, Taehun; Guo, Zhaoli; Rumschitzki, David

    2014-03-01

    One characteristic of multiphase lattice Boltzmann equation (LBE) methods is that the interfacial region has a finite (i.e., noninfinitesimal) thickness known as a diffuse interface. In simulations of, e.g., bubble or drop dynamics, for problems involving nonideal gases, one frequently observes that the diffuse interface method produces a spontaneous, nonphysical shrinkage of the bubble or drop radius. In this paper, we analyze in detail a single-fluid two-phase model and use a LBE model for nonideal gases in order to explain this fundamental problem. For simplicity, we only investigate the static bubble or droplet problem. We find that the method indeed produces a density shift, bubble or droplet shrinkage, as well as a critical radius below which the bubble or droplet eventually vanishes. Assuming that the ratio between the interface thickness D and the initial bubble or droplet radius r0 is small, we analytically show the existence of this density shift, bubble or droplet radius shrinkage, and critical bubble or droplet survival radius. Numerical results confirm our analysis. We also consider droplets on a solid surface with different curvatures, contact angles, and initial droplet volumes. Numerical results show that the curvature, contact angle, and the initial droplet volume have an effect on this spontaneous shrinkage process, consistent with the survival criterion. PMID:24730962

  13. 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.

  14. 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.

  15. Large Volcanic Rises on Venus

    NASA Technical Reports Server (NTRS)

    Smrekar, Suzanne E.; Kiefer, Walter S.; Stofan, Ellen R.

    1997-01-01

    Large volcanic rises on Venus have been interpreted as hotspots, or the surface manifestation of mantle upwelling, on the basis of their broad topographic rises, abundant volcanism, and large positive gravity anomalies. Hotspots offer an important opportunity to study the behavior of the lithosphere in response to mantle forces. In addition to the four previously known hotspots, Atla, Bell, Beta, and western Eistla Regiones, five new probable hotspots, Dione, central Eistla, eastern Eistla, Imdr, and Themis, have been identified in the Magellan radar, gravity and topography data. These nine regions exhibit a wider range of volcano-tectonic characteristics than previously recognized for venusian hotspots, and have been classified as rift-dominated (Atla, Beta), coronae-dominated (central and eastern Eistla, Themis), or volcano-dominated (Bell, Dione, western Eistla, Imdr). The apparent depths of compensation for these regions ranges from 65 to 260 km. New estimates of the elastic thickness, using the 90 deg and order spherical harmonic field, are 15-40 km at Bell Regio, and 25 km at western Eistla Regio. Phillips et al. find a value of 30 km at Atla Regio. Numerous models of lithospheric and mantle behavior have been proposed to interpret the gravity and topography signature of the hotspots, with most studies focusing on Atla or Beta Regiones. Convective models with Earth-like parameters result in estimates of the thickness of the thermal lithosphere of approximately 100 km. Models of stagnant lid convection or thermal thinning infer the thickness of the thermal lithosphere to be 300 km or more. Without additional constraints, any of the model fits are equally valid. The thinner thermal lithosphere estimates are most consistent with the volcanic and tectonic characteristics of the hotspots. Estimates of the thermal gradient based on estimates of the elastic thickness also support a relatively thin lithosphere (Phillips et al.). The advantage of larger estimates of the thermal lithospheric thickness is that they provide an explanation for the apparently modest levels of geologic activity on Venus over the last half billion years.

  16. Cartesian grid simulations of bubbling fluidized beds with a horizontal tube bundle

    SciTech Connect

    Li, Tingwen; Dietiker, Jean-Francois; Zhang, Yongmin; Shahnam, Mehrdad

    2011-12-01

    In this paper, the flow hydrodynamics in a bubbling fluidized bed with submerged horizontal tube bundle was numerically investigated with an open-source code: Multiphase Flow with Interphase eXchange (MFIX). A newly implemented cut-cell technique was employed to deal with the curved surface of submerged tubes. A series of 2D simulations were conducted to study the effects of gas velocity and tube arrangement on the flow pattern. Hydrodynamic heterogeneities on voidage, particle velocity, bubble fraction, and frequency near the tube circumferential surface were successfully predicted by this numerical method, which agrees qualitatively with previous experimental findings and contributes to a sounder understanding of the non-uniform heat transfer and erosion around a horizontal tube. A 3D simulation was also conducted. Significant differences between 2D and 3D simulations were observed with respect to bed expansion, bubble distribution, voidage, and solids velocity profiles. Hence, the 3D simulation is needed for quantitative prediction of flow hydrodynamics. On the other hand, the flow characteristics and bubble behavior at the tube surface are similar under both 2D and 3D simulations as far as the bubble frequency and bubble phase fraction are concerned. Comparison with experimental data showed that qualitative agreement was obtained in both 2D and 3D simulations for the bubble characteristics at the tube surface.

  17. 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.

  18. 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, ...

  19. 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.

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. 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. \\

  5. 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...

  6. 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

  7. 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

  8. From rational bubbles to crashes

    NASA Astrophysics Data System (ADS)

    Sornette, D.; Malevergne, Y.

    2001-10-01

    We study and generalize in various ways the model of rational expectation (RE) bubbles introduced by Blanchard and Watson in the economic literature. Bubbles are argued to be the equivalent of Goldstone modes of the fundamental rational pricing equation, associated with the symmetry-breaking introduced by non-vanishing dividends. Generalizing bubbles in terms of multiplicative stochastic maps, we summarize the result of Lux and Sornette that the no-arbitrage condition imposes that the tail of the return distribution is hyperbolic with an exponent ?<1. We then outline the main results of Malevergne and Sornette, who extend the RE bubble model to arbitrary dimensions d: a number d of market time series are made linearly interdependent via d× d stochastic coupling coefficients. We derive the no-arbitrage condition in this context and, with the renewal theory for products of random matrices applied to stochastic recurrence equations, we extend the theorem of Lux and Sornette to demonstrate that the tails of the unconditional distributions associated with such d-dimensional bubble processes follow power laws, with the same asymptotic tail exponent ?<1 for all assets. The distribution of price differences and of returns is dominated by the same power-law over an extended range of large returns. Although power-law tails are a pervasive feature of empirical data, the numerical value ?<1 is in disagreement with the usual empirical estimates ??3. We then discuss two extensions (the crash hazard rate model and the non-stationary growth rate model) of the RE bubble model that provide two ways of reconciliation with the stylized facts of financial data.

  9. 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

  10. Impurity bubbles in a BEC

    NASA Astrophysics Data System (ADS)

    Timmermans, Eddy; Blinova, Alina; Boshier, Malcolm

    2013-05-01

    Polarons (particles that interact with the self-consistent deformation of the host medium that contains them) self-localize when strongly coupled. Dilute Bose-Einstein condensates (BECs) doped with neutral distinguishable atoms (impurities) and armed with a Feshbach-tuned impurity-boson interaction provide a unique laboratory to study self-localized polarons. In nature, self-localized polarons come in two flavors that exhibit qualitatively different behavior: In lattice systems, the deformation is slight and the particle is accompanied by a cloud of collective excitations as in the case of the Landau-Pekar polarons of electrons in a dielectric lattice. In natural fluids and gases, the strongly coupled particle radically alters the medium, e.g. by expelling the host medium as in the case of the electron bubbles in superfluid helium. We show that BEC-impurities can self-localize in a bubble, as well as in a Landau-Pekar polaron state. The BEC-impurity system is fully characterized by only two dimensionless coupling constants. In the corresponding phase diagram the bubble and Landau-Pekar polaron limits correspond to large islands separated by a cross-over region. The same BEC-impurity species can be adiabatically Feshbach steered from the Landau-Pekar to the bubble regime. Polarons (particles that interact with the self-consistent deformation of the host medium that contains them) self-localize when strongly coupled. Dilute Bose-Einstein condensates (BECs) doped with neutral distinguishable atoms (impurities) and armed with a Feshbach-tuned impurity-boson interaction provide a unique laboratory to study self-localized polarons. In nature, self-localized polarons come in two flavors that exhibit qualitatively different behavior: In lattice systems, the deformation is slight and the particle is accompanied by a cloud of collective excitations as in the case of the Landau-Pekar polarons of electrons in a dielectric lattice. In natural fluids and gases, the strongly coupled particle radically alters the medium, e.g. by expelling the host medium as in the case of the electron bubbles in superfluid helium. We show that BEC-impurities can self-localize in a bubble, as well as in a Landau-Pekar polaron state. The BEC-impurity system is fully characterized by only two dimensionless coupling constants. In the corresponding phase diagram the bubble and Landau-Pekar polaron limits correspond to large islands separated by a cross-over region. The same BEC-impurity species can be adiabatically Feshbach steered from the Landau-Pekar to the bubble regime. This work was funded by the Los Alamos LDRD program.

  11. Bubble-bubble interaction: A potential source of cavitation noise

    NASA Astrophysics Data System (ADS)

    Ida, Masato

    2009-01-01

    The interaction between microbubbles through pressure pulses has been studied to show that it can be a source of cavitation noise. A recent report demonstrated that the acoustic noise generated by a shrimp originates from the collapse of a cavitation bubble produced when the shrimp closes its snapper claw. The recorded acoustic signal contains a broadband noise that consists of positive and negative pulses, but a theoretical model for single bubbles fails to reproduce the negative ones. Using a nonlinear multibubble model, we have shown here that the negative pulses can be explained by considering the interaction of microbubbles formed after the cavitation bubble has collapsed and fragmented: Positive pulses produced at the collapse of the microbubbles hit and impulsively compress neighboring microbubbles to generate reflected pulses whose amplitudes are negative. Discussing the details of the noise generation process, we have found that no negative pulses are generated if the internal pressure of the reflecting bubble is very high when hit by a positive pulse.

  12. 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

  13. 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

  14. 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

  15. Attentive vision, scene representation and bubble space

    Microsoft Academic Search

    O. Erkent; H. I. Bozma

    2010-01-01

    Visual data based environmental representation is crucial for mobile robot applications requiring recognition. Previous work has shown that bubble memory - which is an egocentric approach based on hypothetically surrounding a spherical surface around the robot, to provide a compact representation of the scene from a single viewpoint. This paper proposes bubble space as an extension of bubble model to

  16. Adaptive Bubble Pulse Cancellation and Its Applications

    Microsoft Academic Search

    Feng-Xiang Ge; Yan Zhang; Zheng Lin Li; Renhe Zhang

    2010-01-01

    Explosive sources are widely used as sound sources in underwater acoustics experiments. Unfortunately, the resulting direct pulse is often corrupted by bubble pulses, which has an undesired influence on the observation and its applications. Canceling these bubble pulses will greatly enhance the quality of the observation and will be helpful for its applications. To cancel the bubble pulse, an adaptive

  17. Electric field observations of equatorial bubbles

    Microsoft Academic Search

    T. L. Aggson; N. C. Maynard; W.B. Hanson; Jack L. Saba

    1992-01-01

    The authors present here results from the double floating probe experiment carried on the San Marco D satellite, with emphasis on the observations of large incremental changes in the convective electric field vector at the boundary of equatorial plasma bubbles. This study concentrates on isolated bubble structures in the upper ionospheric F region and divides these observed bubble encounters into

  18. Viscosity of magmas containing highly deformable bubbles

    Microsoft Academic Search

    M. Manga; M. Loewenberg

    2001-01-01

    The shear viscosity of a suspension of deformable bubbles dispersed within a Newtonian fluid is calculated as a function of the shear rate and strain. The relative importance of bubble deformation in the suspension is characterized by the capillary number (Ca), which represents the ratio of viscous and surface tension stresses. For small Ca, bubbles remain nearly spherical, and for

  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. Bubble-Driven Inertial Micropump

    E-print Network

    Torniainen, Erik D; Markel, David P; Kornilovitch, Pavel E

    2012-01-01

    The fundamental action of the bubble-driven inertial micropump is investigated. The pump has no moving parts and consists of a thermal resistor placed asymmetrically within a straight channel connecting two reservoirs. Using numerical simulations, the net flow is studied as a function of channel geometry, resistor location, vapor bubble strength, fluid viscosity, and surface tension. Two major regimes of behavior are identified: axial and non-axial. In the axial regime, the drive bubble either remains inside the channel or continues to grow axially when it reaches the reservoir. In the non-axial regime the bubble grows out of the channel and in all three dimensions while inside the reservoir. The net flow in the axial regime is parabolic with respect to the hydraulic diameter of the channel cross-section but in the non-axial regime it is not. From numerical modeling, it is determined that the net flow is maximal when the axial regime crosses over to the non-axial regime. To elucidate the basic physical princi...

  1. Neutron Detection via Bubble Chambers

    SciTech Connect

    Jordan, David V.; Ely, James H.; Peurrung, Anthony J.; Bond, Leonard J.; Collar, J. I.; Flake, Matthew; Knopf, Michael A.; Pitts, W. K.; Shaver, Mark W.; Sonnenschein, Andrew; Smart, John E.; Todd, Lindsay C.

    2005-10-06

    The results of a Pacific Northwest National Laboratory (PNNL) exploratory research project investigating the feasibility of fast neutron detection using a suitably prepared and operated, pressure-cycled bubble chamber are described. The research was conducted along two parallel paths. Experiments with a slow pressure-release Halon chamber at the Enrico Fermi Institute at the University of Chicago showed clear bubble nucleation sensitivity to an AmBe neutron source and insensitivity to the 662 keV gammas from a 137Cs source. Bubble formation was documented via high-speed (1000 frames/sec) photography, and the acoustic signature of bubble formation was detected using a piezo-electric transducer element mounted on the base of the chamber. The chamber’s neutron sensitivity as a function of working fluid temperature was mapped out. The second research path consisted of the design, fabrication, and testing of a fast pressure-release Freon-134a chamber at PNNL. The project concluded with successful demonstrations of the PNNL chamber’s AmBe neutron source sensitivity and 137Cs gamma insensitivity. The source response tests of the PNNL chamber were documented with high-speed photography.

  2. Ice bubbles confirm big chill

    SciTech Connect

    Kerr, R.A.

    1996-06-14

    Clues buried in Greenland`s icesheet indicate that during the last ice age, the climate repeatedly warmed sharply, only to slide into a renewed chill lasting thousands of years. New indicators derived from trapped bubbles of ancient gases, nitrogen and methane, indicate that these were indeed catastrophic events. This article describes the research and adjunct issues.

  3. Pulling bubbles from a bath

    E-print Network

    Kao, Justin C. T.

    Deposition of bubbles on a wall withdrawn from a liquid bath is a phenomenon observed in many everyday situations—the foam lacing left behind in an emptied glass of beer, for instance. It is also of importance to the many ...

  4. Bubble Universe Dynamics After Free Passage

    NASA Astrophysics Data System (ADS)

    Ahlqvist, Pontus; Eckerle, Kate; Greene, Brian

    2015-03-01

    We consider bubble collisions in single scalar field theories with multiple vacua. Recent work has argued that at sufficiently high impact velocities, collisions between such bubble vacua are governed by `free passage' dynamics in which field interactions can be ignored during the collision, providing a systematic process for populating local minima without quantum nucleation. We focus on the time period that follows the bubble collision and provide evidence that, for certain potentials, interactions can drive significant deviations from the free-passage bubble profile, thwarting the production of bubbles with different field values.

  5. Bubble Universe Dynamics After Free Passage

    E-print Network

    Pontus Ahlqvist; Kate Eckerle; Brian Greene

    2014-12-26

    We consider bubble collisions in single scalar field theories with multiple vacua. Recent work has argued that at sufficiently high impact velocities, collisions between such bubble vacua are governed by 'free passage' dynamics in which field interactions can be ignored during the collision, providing a systematic process for populating local minima without quantum nucleation. We focus on the time period that follows the bubble collision and provide evidence that, for certain potentials, interactions can drive significant deviations from the free-passage bubble profile, thwarting the production of bubbles with different field values.

  6. Lidar signature from bubbles in the sea.

    PubMed

    Churnside, James H

    2010-04-12

    The lidar signature from a collection of bubbles is proportional to the volume backscatter coefficient at a scattering angle of 180 degrees . This quantity, calculated using a combination of geometric optics and diffraction, is proportional to the void fraction of the bubbles in the water for any bubble size distribution. The constant of proportionality is 233 m(-1) sr(-1)for clean bubbles, slightly less for bubbles coated with a thin layer of organic material, and as large as 1445 m(-1) sr(-1) for a thick coating of protein. PMID:20588675

  7. Metaphors and models: the ASR bubble in the Floridan aquifer.

    PubMed

    Vacher, H L; Hutchings, William C; Budd, David A

    2006-01-01

    Studies at the intersection of cognitive science and linguistics have revealed the crucial role that metaphors play in shaping our thoughts about phenomena we cannot see. According to the domains interaction theory of cognition, a metaphoric expression sets up mappings between a target domain that we wish to understand and a familiar source domain. The source domain contains elements ("commonplaces") that we manipulate mentally, like parts of an analogue model, to illuminate the target domain. This paper applies the structure of domains interaction theory to analyze the dynamics of a metaphor in hydrogeology: the so-called bubble formed by water injected into an aquifer during aquifer storage and recovery (ASR). Of the four commonplaces of bubbles--(1) they are discrete; (2) they are geometrically simple; (3) they rise; and (4) they burst--we focus on the first two using both displacement and dispersion (tracer) models for both homogeneous and heterogeneous storage zones patterned from geological studies of the Suwannee Limestone of Sarasota County, Florida. The displacement model easily shows that "bottle brush" better represents the geometric complexity predicted from the known and inferred heterogeneity. There is virtually no difference, however, in the prediction of recovery efficiency using the dispersion model for a bubble (homogeneous flow zone) vs. bottle brush (heterogeneous flow zone). On the other hand, only the bottle brush reveals that unrecovered tracer is located preferentially in the low-permeability layers that lie adjacent to high-permeability channels in the flow zones. PMID:16556197

  8. Numerical simulation of aeration bubble growth in a plug-flow aeration tank used in wastewater treatment

    NASA Astrophysics Data System (ADS)

    Wang, H. R.; Li, Y. P.

    2010-03-01

    The micro-scale hydrodynamics of bubbles growth by aeration is related to the oxygen transfer efficiency and the overall performance of the activated sludge wastewater treatment process. To gain a deeper insight on the micro-scale phenomena of dispersed bubble in this process, a three-dimensional direct simulation method is developed to study the effects of the liquid cross-flow on micro-scale behavior of bubble growth in a plug-flow aeration tank. The numerical simulations are performed using the level set method coupling with the governing equations of a single fluid with variable properties. The governing equations are solved using the finite-volume projection technique. The simulation results are compared with the experimental observations and theoretical relations. The simulated results show that water cross-flow in plug-flow type aeration tank has a strong impact on the bubble growth process. Compared to that generated under quiescent water conditions used in mixing type aeration tank, the bubble under water cross-flow conditions grows downstream along the tilted axis, and the bubble generation time tends to decrease noticeably and the bubble at detachment has significantly smaller size. The dynamic characteristics of the bubble growth through two orifices are also numerically studied. The effect of water cross-flow on the bubbling synchronicity is finally discussed.

  9. 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.

  10. THEMIS observations of plasma bubbles associated with energetic electron acceleration in the inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Tang, C. L.

    2014-12-01

    Using Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations, we study the plasma bubbles associated with a transient increase of the magnetic field Bz component in the inner magnetosphere during the substorm expansion phase. Except small electric field, the main characteristics of these plasma bubbles are similar with those associated with dipolarization front (DF) in the mid-tail and near-Earth tail. Based on the different dipolarization of the magnetic field, we defined the plasma bubble with no dipolarization phenomenon as "no dipolarization bubble" (NDB), the plasma bubble with dipolarization phenomenon as "dipolarization bubble" (DB). We find that these plasma bubbles in the inner magnetosphere accompany the energetic electron acceleration. Some pancake-type distributions of energetic electrons inside the NDB in the inner magnetosphere are caused by drift betatron acceleration, other pancake-type distributions of energetic electrons inside the NDB are caused by gyrobetatron acceleration. For the DB in the inner magnetosphere, the cigar-type distributions of energetic electrons are attributed to Fermi acceleration. Our observations suggest that the inner magnetosphere may be a very important source region for energetic electrons, except for a reconnection site in the mid-tail and the plasma sheet in the near-Earth tail.

  11. Modeling methane bubble growth in fine-grained muddy aquatic sediments: correlation with sediment properties

    NASA Astrophysics Data System (ADS)

    Katsman, Regina

    2015-04-01

    Gassy sediments contribute to destabilization of aquatic infrastructure, air pollution, and global warming. In the current study a precise shape and size of the buoyant mature methane bubble in fine-grained muddy aquatic sediment is defined by numerical and analytical modeling, their results are in a good agreement. A closed-form analytical solution defining the bubble parameters is developed. It is found that the buoyant mature bubble is elliptical in its front view and resembles an inverted tear drop in its cross-section. The size and shape of the mature bubble strongly correlate with sediment fracture toughness. Bubbles formed in the weaker sediments are smaller and characterized by a larger surface-to volume ratio that induces their faster growth and may lead to their faster dissolution below the sediment-water interface. This may prevent their release to the water column and to the atmosphere. Shapes of the bubbles in the weaker sediments deviate further from the spherical configuration, than those in the stronger sediments. Modeled bubble characteristics, important for the acoustic applications, are in a good agreement with field observations and lab experiments.

  12. Slopes To Prevent Trapping of Bubbles in Microfluidic Channels

    NASA Technical Reports Server (NTRS)

    Greer, Harold E.; Lee, Michael C.; Smith, J. Anthony; Willis, Peter A.

    2010-01-01

    The idea of designing a microfluidic channel to slope upward along the direction of flow of the liquid in the channel has been conceived to help prevent trapping of gas bubbles in the channel. In the original application that gave rise to this idea, the microfluidic channels are parts of micro-capillary electrophoresis (microCE) devices undergoing development for use on Mars in detecting compounds indicative of life. It is necessary to prevent trapping of gas bubbles in these devices because uninterrupted liquid pathways are essential for sustaining the electrical conduction and flows that are essential for CE. The idea is also applicable to microfluidic devices that may be developed for similar terrestrial microCE biotechnological applications or other terrestrial applications in which trapping of bubbles in microfluidic channels cannot be tolerated. A typical microCE device in the original application includes, among other things, multiple layers of borosilicate float glass wafers. Microfluidic channels are formed in the wafers, typically by use of wet chemical etching. The figure presents a simplified cross section of part of such a device in which the CE channel is formed in the lowermost wafer (denoted the channel wafer) and, according to the present innovation, slopes upward into a via hole in another wafer (denoted the manifold wafer) lying immediately above the channel wafer. Another feature of the present innovation is that the via hole in the manifold wafer is made to taper to a wider opening at the top to further reduce the tendency to trap bubbles. At the time of reporting the information for this article, an effort to identify an optimum technique for forming the slope and the taper was in progress. Of the techniques considered thus far, the one considered to be most promising is precision milling by use of femtosecond laser pulses. Other similar techniques that may work equally well are precision milling using a focused ion beam, or a small diamond-tipped drill bit.

  13. Direct numerical simulation of ‘short’ laminar separation bubbles with turbulent reattachment

    NASA Astrophysics Data System (ADS)

    Alam, M.; Sandham, N. D.

    2000-01-01

    Direct numerical simulation of the incompressible Navier-Stokes equations is used to study flows where laminar boundary-layer separation is followed by turbulent reattachment forming a closed region known as a laminar separation bubble. In the simulations a laminar boundary layer is forced to separate by the action of a suction profile applied as the upper boundary condition. The separated shear layer undergoes transition via oblique modes and [Lambda]-vortex-induced breakdown and reattaches as turbulent flow, slowly recovering to an equilibrium turbulent boundary layer. Compared with classical experiments the computed bubbles may be classified as ‘short’, as the external potential flow is only affected in the immediate vicinity of the bubble. Near reattachment budgets of turbulence kinetic energy are dominated by turbulence events away from the wall. Characteristics of near-wall turbulence only develop several bubble lengths downstream of reattachment. Comparisons are made with two-dimensional simulations which fail to capture many of the detailed features of the full three-dimensional simulations. Stability characteristics of mean flow profiles are computed in the separated flow region for a family of velocity profiles generated using simulation data. Absolute instability is shown to require reverse flows of the order of 15 20%. The three-dimensional bubbles with turbulent reattachment have maximum reverse flows of less than 8% and it is concluded that for these bubbles the basic instability is convective in nature.

  14. Direct numerical simulation of ‘short’ laminar separation bubbles with turbulent reattachment

    NASA Astrophysics Data System (ADS)

    Alam, M.; Sandham, N. D.

    2000-05-01

    Direct numerical simulation of the incompressible Navier Stokes equations is used to study flows where laminar boundary-layer separation is followed by turbulent reattachment forming a closed region known as a laminar separation bubble. In the simulations a laminar boundary layer is forced to separate by the action of a suction profile applied as the upper boundary condition. The separated shear layer undergoes transition via oblique modes and [Lambda]-vortex-induced breakdown and reattaches as turbulent flow, slowly recovering to an equilibrium turbulent boundary layer. Compared with classical experiments the computed bubbles may be classified as ‘short’, as the external potential flow is only affected in the immediate vicinity of the bubble. Near reattachment budgets of turbulence kinetic energy are dominated by turbulence events away from the wall. Characteristics of near-wall turbulence only develop several bubble lengths downstream of reattachment. Comparisons are made with two-dimensional simulations which fail to capture many of the detailed features of the full three-dimensional simulations. Stability characteristics of mean flow profiles are computed in the separated flow region for a family of velocity profiles generated using simulation data. Absolute instability is shown to require reverse flows of the order of 15 20%. The three-dimensional bubbles with turbulent reattachment have maximum reverse flows of less than 8% and it is concluded that for these bubbles the basic instability is convective in nature.

  15. A breathing wormlike chain model on DNA denaturation and bubble: effects of stacking interactions.

    PubMed

    Kim, Jae-Yeol; Jeon, Jae-Hyung; Sung, Wokyung

    2008-02-01

    DNA stably exists as a double-stranded structure due to hydrogen-bonding and stacking interactions between bases. The stacking interactions are strengthened when DNA is paired, which results in great enhancement of bending rigidity. We study the effects of this stacking-induced stiffness difference on DNA denaturation and bubble formations. To this end, we model double-stranded DNA as a duplex of two semiflexible chains whose persistence length varies depending on the base-pair distance. Using this model, we perform the Langevin dynamics simulation to examine the characteristics of the denaturation transition and the statistics of the bubbles. We find that the inclusion of the stacking interactions causes the denaturation transition to be much sharper than otherwise. At physiological temperature, the stacking interactions prohibit the initiation of bubble formation but promote bubbles, once grown, to retain the large size. PMID:18266461

  16. 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.

  17. Transitional Bubble in Periodic Flow Phase Shift

    NASA Technical Reports Server (NTRS)

    Talan, M.; Hourmouziadis, Jean

    2004-01-01

    One particular characteristic observed in unsteady shear layers is the phase shift relative to the main flow. In attached boundary layers this will have an effect both on the instantaneous skin friction and heat transfer. In separation bubbles the contribution to the drag is dominated by the pressure distribution. However, the most significant effect appears to be the phase shift on the transition process. Unsteady transition behaviour may determine the bursting of the bubble resulting in an un-recoverable full separation. An early analysis of the phase shift was performed by Stokes for the incompressible boundary layer of an oscillating wall and an oscillating main flow. An amplitude overshoot within the shear layer as well as a phase shift were observed that can be attributed to the relatively slow diffusion of viscous stresses compared to the fast change of pressure. Experiments in a low speed facility with the boundary layer of a flat plate were evaluated in respect to phase shift. A pressure distribution similar to that on the suction surface of a turbomachinery aerofoil was superimposed generating a typical transitional separation bubble. A periodically unsteady main flow in the suction type wind tunnel was introduced via a rotating flap downstream of the test section. The experiments covered a range of the three similarity parameters of momentum-loss-thickness Reynolds-number of 92 to 226 and Strouhal-number (reduced frequency) of 0.0001 to 0.0004 at the separation point, and an amplitude range up to 19 %. The free stream turbulence level was less than 1% .Upstream of the separation point the phase shift in the laminar boundary layer does not appear to be affected significantly bay either of the three parameters. The trend perpendicular to the wall is similar to the Stokes analysis. The problem scales well with the wave velocity introduced by Stokes, however, the lag of the main flow near the wall is less than indicated analytically. The separation point comes closest to the Stokes analysis but the phase is still 20 degrees lower at the wall.

  18. 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.

  19. There is No Housing Bubble

    Microsoft Academic Search

    James F. Smith

    2005-01-01

    There is no evidence of a housing “bubble” in the United States and housing demand should stay strong for years to come. Three major factors lead to this conclusion. First, the 77 million baby boomers are approaching the peak home ownership ages of 65-75 (over 83.0 percent versus a national average in 2004 of 69.0 percent). Second, immigrants, a growing

  20. Improved Bubble-Point Test

    NASA Technical Reports Server (NTRS)

    Welch, Peter J.; Rhodes, Russell E.; Aman, Robert; Nagy, Zoltan

    1994-01-01

    Improved bubble-point test devised for large pleated filter elements. Sizes of pores in filters determined more accurately. Test method replaces older test accurate for pore sizes of 20 microns or less, but subject to gross inaccuracy for filter elements with pores of 70 microns or larger. Unlike older test, no measurement of pressure is necessary. Also no need to estimate average depth of filter-element pleats below surface of liquid.

  1. Giant Bubble Pinch-Off

    Microsoft Academic Search

    Raymond Bergmann; Meer van der Devaraj; 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, is not self-similar in a strict sense: A disk is quickly pulled through a water surface, leading to a giant, cylindrical void which after collapse

  2. A Very Deep Chandra Observation of Abell 2052: Bubbles, Shocks, and Sloshing

    E-print Network

    Blanton, E L; Clarke, T E; Sarazin, C L; McNamara, B R; Douglass, E M; McDonald, M

    2011-01-01

    We present first results from a very deep (~650 ksec) Chandra X-ray observation of Abell 2052, as well as archival VLA radio observations. The data reveal detailed structure in the inner parts of the cluster, including bubbles evacuated by the AGN's radio lobes, compressed bubble rims, filaments, and loops. Two concentric shocks are seen, and a temperature rise is measured for the innermost one. On larger scales, we report the first detection of an excess surface brightness spiral feature. The spiral has cooler temperatures, lower entropies, and higher abundances than its surroundings, and is likely the result of sloshing gas initiated by a previous cluster-cluster or sub-cluster merger. Initial evidence for previously unseen bubbles at larger radii related to earlier outbursts from the AGN is presented.

  3. A VERY DEEP CHANDRA OBSERVATION OF A2052: BUBBLES, SHOCKS, AND SLOSHING

    SciTech Connect

    Blanton, E. L.; Douglass, E. M. [Institute for Astrophysical Research and Astronomy Department, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 (United States); Randall, S. W.; McNamara, B. R. [Harvard Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Clarke, T. E. [Naval Research Laboratory, 4555 Overlook Avenue Southwest, Washington, DC 20375 (United States); Sarazin, C. L. [Department of Astronomy, University of Virginia, PO Box 400325, Charlottesville, VA 22904-4325 (United States); McDonald, M., E-mail: eblanton@bu.edu, E-mail: emdoug@bu.edu, E-mail: srandall@head.cfa.harvard.edu, E-mail: tracy.clarke@nrl.navy.mil, E-mail: sarazin@virginia.edu, E-mail: mcnamara@sciborg.uwaterloo.ca, E-mail: mcdonald@astro.umd.edu [Astronomy Department, University of Maryland, College Park, MD 20742 (United States)

    2011-08-20

    We present the first results from a very deep ({approx}650 ks) Chandra X-ray observation of A2052, as well as archival Very Large Array radio observations. The data reveal detailed structure in the inner parts of the cluster, including bubbles evacuated by radio lobes of the active galactic nucleus (AGN), compressed bubble rims, filaments, and loops. Two concentric shocks are seen, and a temperature rise is measured for the innermost one. On larger scales, we report the first detection of an excess surface brightness spiral feature. The spiral has cooler temperatures, lower entropies, and higher abundances than its surroundings, and is likely the result of sloshing gas initiated by a previous cluster-cluster or sub-cluster merger. Initial evidence for previously unseen bubbles at larger radii related to earlier outbursts from the AGN is presented.

  4. Experimental study of the hydrodynamic interaction between a pair of bubbles ascending in a non-Newtonian liquid

    NASA Astrophysics Data System (ADS)

    Samano, Diego; Velez, Rodrigo; Zenit, Roberto

    2009-11-01

    We present some experimental results about the interaction of a pair of bubbles ascending in non-Newtonian fluids. A high speed camera was used to follow in-line and off-line rising motion of two bubbles in a Newtonian fluid (a glycerin-water solution), a Boger fluid (aqueous polyacrylamide solution), and a shear-thinning fluid (aqueous xanthan solution). For the case of shear-thinning fluids, the power index, n, affects the tendency of the bubble pair to aggregate. Therefore, in addition to bubble separation, orientation and Reynolds number, the hydrodynamic force depends strongly on the shear-thinning nature of the fluid. Several examples will be shown. For elastic fluids, the Deborah number affects the hydrodynamic interaction. We found that the appearance of the negative wake changes the nature of the interaction substantially. Some examples and comparisons with numerical results will be presented.

  5. Study of a Novel Method for the Thermolysis of Solutes in Aqueous Solution Using a Low Temperature Bubble Column Evaporator.

    PubMed

    Shahid, Muhammad; Xue, Xinkai; Fan, Chao; Ninham, Barry W; Pashley, Richard M

    2015-06-25

    An enhanced thermal decomposition of chemical compounds in aqueous solution has been achieved at reduced solution temperatures. The technique exploits hitherto unrecognized properties of a bubble column evaporator (BCE). It offers better heat transfer efficiency than conventional heat transfer equipment. This is obtained via a continuous flow of hot, dry air bubbles of optimal (1-3 mm) size. Optimal bubble size is maintained by using the bubble coalescence inhibition property of some salts. This novel method is illustrated by a study of thermal decomposition of ammonium bicarbonate (NH4HCO3) and potassium persulfate (K2S2O8) in aqueous solutions. The decomposition occurs at significantly lower temperatures than those needed in bulk solution. The process appears to work via the continuous production of hot (e.g., 150 °C) dry air bubbles, which do not heat the solution significantly but produce a transient hot surface layer around each rising bubble. This causes the thermal decomposition of the solute. The decomposition occurs due to the effective collision of the solute with the surface of the hot bubbles. The new process could, for example, be applied to the regeneration of the ammonium bicarbonate draw solution used in forward osmosis. PMID:26067442

  6. The rise of blood sugar as an additional parameter in traumatic shock

    Microsoft Academic Search

    D. Holzrichter; L. Meiss; S. Behrens; V. Mickley

    1987-01-01

    Besides the known cardiovascular effects of hemorrhagic shock, regular metabolic consequences can be demonstrated in the rabbit: 1. The rise in blood sugar in hemorrhagic shock increases with the amount of blood withdrawn per unit of time. 2. The characteristic rise in blood sugar lasts longer than the phase of the partial exsanguination. 3. In traumatic shock, the rise in

  7. Efficient manipulation of microparticles in bubble streaming flows.

    PubMed

    Wang, Cheng; Jalikop, Shreyas V; Hilgenfeldt, Sascha

    2012-03-01

    Oscillating microbubbles of radius 20-100??m driven by ultrasound initiate a steady streaming flow around the bubbles. In such flows, microparticles of even smaller sizes (radius 1-5??m) exhibit size-dependent behaviors: particles of different sizes follow different characteristic trajectories despite density-matching. Adjusting the relative strengths of the streaming flow and a superimposed Poiseuille flow allows for a simple tuning of particle behavior, separating the trajectories of particles with a size resolution on the order of 1??m. Selective trapping, accumulation, and release of particles can be achieved. We show here how to design bubble microfluidic devices that use these concepts to filter, enrich, and preconcentrate particles of selected sizes, either by concentrating them in discrete clusters (localized both stream- and spanwise) or by forcing them into narrow, continuous trajectory bundles of strong spanwise localization. PMID:22662069

  8. Bubble chamber spectroscopy for chemical analysis: A new concept

    SciTech Connect

    Atencio, J.H.; Luo, Xin; McCreary, E.I.; McCown, A.W.; Sander, R.K.

    1995-02-01

    A new technique for the detection of trace concentrations of molecules in solution has been developed. This system utilizes the amplification characteristics of a bubble chamber in which energy deposition from laser absorption is monitored. In the experimental set-up, a trace quantity of solute is introduced into liquid propane that is contained in a small (10 ml) stainless steel cell at 120 psi. The propane is superheated by sudden reduction of the cell pressure. Before wall nucleated boiling occurs, target solute molecules are energized by a laser pulse. Absorption of pump laser energy results in the formation of nucleation centers which develop into bubbles and which in turn are detected by CCD camera. Preliminary experiments with crystal violet used as a test absorber have demonstrated detection sensitivity of 10 parts per trillion (ppt).

  9. Scattering measurements from a dissolving bubble.

    PubMed

    Kapodistrias, George; Dahl, Peter H

    2012-06-01

    A laboratory-scale study on acoustic scattering from a single bubble undergoing dissolution in undersaturated fresh water is presented. Several experiments are performed with the acoustic source driven with five-cycle tone bursts, center frequency of 120 kHz, to insonify a single bubble located on axis of the combined beam of the set of transducers. The bubble is placed on a fine nylon thread located in the far field of the transducer set, arranged in bistatic configuration, in a tank filled with undersaturated water. Backscattered waveforms from the bubble target are acquired every few seconds for several hours until the bubble has completely dissolved, and detailed dissolution curves are produced from the acoustic data. The rate of bubble dissolution is calculated using the solution developed by Epstein and Plesset [J. Chem. Phys. 18, 1505-1509 (1950)]. The results of the experiments performed are in agreement with the calculations. PMID:22712899

  10. 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.

  11. Mechanism of bubble detachment from vibrating walls

    SciTech Connect

    Kim, Dongjun; Park, Jun Kwon, E-mail: junkeun@postech.ac.kr; Kang, Kwan Hyoung [Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), San 31, Hyoja-dong, Pohang 790-784 (Korea, Republic of)] [Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), San 31, Hyoja-dong, Pohang 790-784 (Korea, Republic of); Kang, In Seok [Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), San 31, Hyoja-dong, Pohang 790-784 (Korea, Republic of)] [Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), San 31, Hyoja-dong, Pohang 790-784 (Korea, Republic of)

    2013-11-15

    We discovered a previously unobserved mechanism by which air bubbles detach from vibrating walls in glasses containing water. Chaotic oscillation and subsequent water jets appeared when a wall vibrated at greater than a critical level. Wave forms were developed at water-air interface of the bubble by the wall vibration, and water jets were formed when sufficiently grown wave-curvatures were collapsing. Droplets were pinched off from the tip of jets and fell to the surface of the glass. When the solid-air interface at the bubble-wall attachment point was completely covered with water, the bubble detached from the wall. The water jets were mainly generated by subharmonic waves and were generated most vigorously when the wall vibrated at the volume resonant frequency of the bubble. Bubbles of specific size can be removed by adjusting the frequency of the wall's vibration.

  12. Mechanism of bubble detachment from vibrating walls

    NASA Astrophysics Data System (ADS)

    Kim, Dongjun; Park, Jun Kwon; Kang, In Seok; Kang, Kwan Hyoung

    2013-11-01

    We discovered a previously unobserved mechanism by which air bubbles detach from vibrating walls in glasses containing water. Chaotic oscillation and subsequent water jets appeared when a wall vibrated at greater than a critical level. Wave forms were developed at water-air interface of the bubble by the wall vibration, and water jets were formed when sufficiently grown wave-curvatures were collapsing. Droplets were pinched off from the tip of jets and fell to the surface of the glass. When the solid-air interface at the bubble-wall attachment point was completely covered with water, the bubble detached from the wall. The water jets were mainly generated by subharmonic waves and were generated most vigorously when the wall vibrated at the volume resonant frequency of the bubble. Bubbles of specific size can be removed by adjusting the frequency of the wall's vibration.

  13. Equine cortical bone exhibits rising R-curve fracture mechanics

    Microsoft Academic Search

    C. L. Malik; S. M. Stover; R. B. Martin; J. C. Gibeling

    2003-01-01

    Previous studies of the fracture properties of cortical bone have suggested that the fracture toughness increases with crack length, which is indicative of rising R-curve behavior. Based on this indirect evidence and the similarity of bone to ceramic matrix composites, we hypothesized that bone would exhibit rising R-curve behavior in the transverse orientation and that the characteristics of the R-curves

  14. Moon Rise - Duration: 67 seconds.

    NASA Video Gallery

    Aboard the International Space Station in May 2012, Expedition 31 astronaut Don Pettit opened the shutters covering the cupola observation windows in time to watch the moon rise. The time-lapse sce...

  15. DNA Bubble Life Time in Denaturation

    E-print Network

    Zh. S. Gevorkian; Chin-Kun Hu

    2010-10-11

    We have investigated the denaturation bubble life time for a homogeneous as well as for a heterogeneous DNA within a Poland-Scheraga model. It is shown that at criticality the bubble life time for a homogeneous DNA is finite provided that the loop entropic exponent c>2 and has a scaling dependence on DNA length for c<2. Heterogeneity in the thermodynamical limit makes the bubble life time infinite for any entropic exponent.

  16. 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

  17. 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

  18. 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.

  19. Fluid mechanics of bubble capture by the diving bell spider

    E-print Network

    Brooks, Alice (Alice P.)

    2010-01-01

    The water spider, a unique member of its species, is used as inspiration for a bubble capture mechanism. Bubble mechanics are studied in the pursuit of a biomimetic solution for transporting air bubbles underwater. Careful ...

  20. BUBBLY: A method for detecting and characterizing interstellar bubbles using Fabry-Perot spectroscopy

    E-print Network

    Camps-Fariña, Artemi; Beckman, John E; Font, Joan; García-Lorenzo, Begoña; Erroz-Ferrer, Santiago; Amram, Philippe

    2014-01-01

    We present a new method for the detection and characterization of expansion in galaxy discs based on H{\\alpha} Fabry-Perot spectroscopy, taking advantage of the high spatial and velocity resolution of our instrument (GH{\\alpha}FaS). The method analyses multi-peaked emission line profiles to find expansion along the line of sight on a point-by-point basis. At this stage we have centred our attention on the large scale structures of expanding gas associated with HII regions which show a characteristic pattern of expansion velocities, of order 100 km/s, as a result of both bubble shape and projection effects. We show an example of the expansion map obtained with our method from a superbubble detected in the Antennae galaxies. We use the information obtained from the method to measure the relevant physical parameters of the superbubbles, including their ages which can be used to date young star clusters.

  1. Bubbles and denaturation in DNA.

    PubMed

    van Erp, T S; Cuesta-López, S; Peyrard, M

    2006-08-01

    The local opening of DNA is an intriguing phenomenon from a statistical-physics point of view, but is also essential for its biological function. For instance, the transcription and replication of our genetic code cannot take place without the unwinding of the DNA double helix. Although these biological processes are driven by proteins, there might well be a relation between these biological openings and the spontaneous bubble formation due to thermal fluctuations. Mesoscopic models, like the Peyrard-Bishop-Dauxois (PBD) model, have fairly accurately reproduced some experimental denaturation curves and the sharp phase transition in the thermodynamic limit. It is, hence, tempting to see whether these models could be used to predict the biological activity of DNA. In a previous study, we introduced a method that allows to obtain very accurate results on this subject, which showed that some previous claims in this direction, based on molecular-dynamics studies, were premature. This could either imply that the present PBD model should be improved or that biological activity can only be predicted in a more complex framework that involves interactions with proteins and super helical stresses. In this article, we give a detailed description of the statistical method introduced before. Moreover, for several DNA sequences, we give a thorough analysis of the bubble-statistics as a function of position and bubble size and the so-called l-denaturation curves that can be measured experimentally. These show that some important experimental observations are missing in the present model. We discuss how the present model could be improved. PMID:16957832

  2. Assessment of bubble-borne methane emissions in the East Siberian Arctic Shelf via interpretation of sonar data

    NASA Astrophysics Data System (ADS)

    Chernykh, D.; Leifer, I.; Shakhova, N. E.; Semiletov, I. P.

    2014-12-01

    Arctic warming is proposed to increase methane emissions from submerged permafrost driving a positive feedback. Where emissions are from shallow seas, bubbles transport much of the methane directly, while frequent Arctic storms sparge much of the remaining dissolved methane before microbes can oxidize it. Complexity arises where emissions are small bubbles or from deeper water due to dissolution below the storm-mixed layer. Given that these emissions span a wide geographic area, a promising remote sensing technology that has been used to map and estimate emissions; however, significant uncertainties exist in sonar data interpretation due to a range of parameters affecting sonar return including bubble size distribution and spatial distribution, vertical velocity, and temperature all of which are closely inter-related in a complex and at best poorly understood manner, and change as the bubble plume rises. This process was illustrated in a series of in situ calibration experiments in the East Siberian Arctic Sea (ESAS) where controlled air bubble plumes were created and observed with sonar to quantify the relationship between sonar return and bubble plume flux for a first calibration of in situ sonar bubble plume observations in the ESAS. Results highlight the importance of bubble plume dynamics to sonar return and the absence of a simple relationship between sonar return and bubble flux. Instead sonar return related to height above seabed, even accounting for dissolution and changing hydrostatic pressure, confirming earlier laboratory studies for a deeper water column. Calibrations then were applied to field data of an area of ESAS natural seepage.

  3. Morphology study of methane-propane clathrate hydrates on the bubble surface in the presence of SDS or PVCap

    NASA Astrophysics Data System (ADS)

    Lee, So Young; Kim, Hyoung Chan; Lee, Ju Dong

    2014-09-01

    The characteristics of methane-propane hydrate crystal growth on the surface of gas bubble in pure water were investigated using optical microscope and compared with those in aqueous solutions of sodium dodecyl sulfate (SDS) or poly-N-vinylcaprolactam (PVCap). Most of morphology works in literature mainly focused on the hydrate crystal growth at the gas/water interface or surface of water droplets. However, this study monitors crystal growth at the bubble surface. In the case of pure water, smooth hydrate film was formed initially and the film surface on the bubble became rough as experiment proceeded. It was also observed that the hydrate crystals developed as the dendritic shape from the surface of hydrate film. In the presence of SDS, drastic changes in morphology were observed in that smoke-like crystals appeared from the top of the bubble. Besides, the gas bubble was not fully covered by hydrate film when the SDS concentration increased. In the PVCap solution, seed-like or small spot of hydrate crystals occurred sparsely on the bubble surface and spread out the whole surface as experiment progressed. The experimental results showed that the presence of SDS or PVCap affect morphological characteristics of methane-propane hydrate crystal on the surface of gas bubble.

  4. Comparing computational models of slug rise at Stromboli with UV camera measurements of SO2 flux

    NASA Astrophysics Data System (ADS)

    Pering, Tom D.; McGonigle, Andrew J. S.; James, Mike R.; Tamburello, Giancarlo; Aiuppa, Alessandro

    2015-04-01

    Strombolian eruptions, particularly those at the archetypal Stromboli Volcano (Aeolian Islands, Italy) are generally accepted to be caused by the burst of gas slugs. Using computational fluid dynamic models implemented in Ansys Fluent®, with a range of conduit, magma and gas properties appropriate for current observations at Stromboli volcano, we simulate the rise of such gas slugs and demonstrate that during their ascent there is the potential for daughter bubble production from the slug base. These are bubbles which can detach from the influence of a slug to rise and burst at the surface independently. Within the models we can then estimate the amount and temporal pattern of gas released during and following individual slug burst events. This is achieved by integrating gas released near the magma surface. After correcting for atmospheric entrainment and diffusion we can then compare our modelled gas flux to our ultra-violet (UV) camera measurements of SO2 flux at Stromboli (i.e. UV measurement of gas flux is performed at least ? 50 m above point of slug rupture at the magma surface). The UV camera measurements identify a broad range of degassing patterns following bursts, typifying the dynamic nature and the complexities of the system at Stromboli, including a previously identified coda in gas flux spanning tens of seconds to minutes (e.g. Tamburello et al. 2012). Whilst our models only analyse a narrow range of events at Stromboli, they highlight the possibility that the production of daughter bubbles could contribute to the gas flux observed at Stromboli. In some instances, the gas flux created by bursting daughter bubbles following a burst event is of a similar time span and could explain the observed gas flux coda. It is also possible that well documented puffing events could be explained by the bursting of daughter bubbles. Indeed, the larger modelled daughter bubbles, which are apparent as well-defined peaks in gas flux within both the UV camera record and modelled flux, have a total mass of ? 0.3 - 2.8 kg, a similar range to previous observations. The described phenomena is of course not limited to Stromboli and could play a key role in gas release regimes at a variety of volcanic targets where the potential for and rate of daughter bubble production (i.e. the stability and turbulence of a bubble or slug wake) can be estimated using the inverse viscosity parameter Nf (e.g. Nogueira et al. 2006).

  5. Scattering from a single bubble near a roughened air-water interface: laboratory measurements and modeling.

    PubMed

    Dahl, Peter H; Kapodistrias, George

    2003-01-01

    The problem of scattering from a single bubble located close to a slightly roughened, air-water interface is studied both theoretically and experimentally. Two well-controlled laboratory experiments were performed to investigate the effects of surface roughness on the scattering response of the bubble. In the first experiment, a bubble of radius 1200 microm was placed on a fine thread at a variable distance, d, from the mean-still-water level of the surface, which was roughened using a wind source. In the second experiment, a bubble of radius 800 microm was utilized, while the water surface was roughened using a plunger wave-making source. The waveheights and important characteristic length scales associated with each experiment were quantified using digital photography. The wind source produced waveheights that were represented by a Gaussian distribution, while the plunger source produced waveheights that were represented by a bimodal distribution. To model the acoustic measurements, an expression describing the four scattering paths, from source to bubble to receiver, was used. A random phase shift due to the surface roughness was added to the paths that interacted with the surface, and expectations of this phase shift were computed based on the analytical representations for the waveheight distribution. The data show good agreement with the simulations and the sensitivity of scattering from a subsurface bubble to small changes in waveheight is illustrated. The experiments highlight important parametric dependencies, which are summarized here, and the relation between monostatic and bistatic scattering is also discussed. PMID:12558250

  6. Bubble structure evaluation method of sponge cake by using image morphology

    NASA Astrophysics Data System (ADS)

    Kato, Kunihito; Yamamoto, Kazuhiko; Nonaka, Masahiko; Katsuta, Yukiyo; Kasamatsu, Chinatsu

    2007-01-01

    Nowadays, many evaluation methods for food industry by using image processing are proposed. These methods are becoming new evaluation method besides the sensory test and the solid-state measurement that have been used for the quality evaluation recently. The goal of our research is structure evaluation of sponge cake by using the image processing. In this paper, we propose a feature extraction method of the bobble structure in the sponge cake. Analysis of the bubble structure is one of the important properties to understand characteristics of the cake from the image. In order to take the cake image, first we cut cakes and measured that's surface by using the CIS scanner, because the depth of field of this type scanner is very shallow. Therefore the bubble region of the surface has low gray scale value, and it has a feature that is blur. We extracted bubble regions from the surface images based on these features. The input image is binarized, and the feature of bubble is extracted by the morphology analysis. In order to evaluate the result of feature extraction, we compared correlation with "Size of the bubble" of the sensory test result. From a result, the bubble extraction by using morphology analysis gives good correlation. It is shown that our method is as well as the subjectivity evaluation.

  7. Quantitative evaluation method of the bubble structure of sponge cake by using morphology image processing

    NASA Astrophysics Data System (ADS)

    Tatebe, Hironobu; Kato, Kunihito; Yamamoto, Kazuhiko; Katsuta, Yukio; Nonaka, Masahiko

    2005-12-01

    Now a day, many evaluation methods for the food industry by using image processing are proposed. These methods are becoming new evaluation method besides the sensory test and the solid-state measurement that are using for the quality evaluation. An advantage of the image processing is to be able to evaluate objectively. The goal of our research is structure evaluation of sponge cake by using image processing. In this paper, we propose a feature extraction method of the bobble structure in the sponge cake. Analysis of the bubble structure is one of the important properties to understand characteristics of the cake from the image. In order to take the cake image, first we cut cakes and measured that's surface by using the CIS scanner. Because the depth of field of this type scanner is very shallow, the bubble region of the surface has low gray scale values, and it has a feature that is blur. We extracted bubble regions from the surface images based on these features. First, input image is binarized, and the feature of bubble is extracted by the morphology analysis. In order to evaluate the result of feature extraction, we compared correlation with "Size of the bubble" of the sensory test result. From a result, the bubble extraction by using morphology analysis gives good correlation. It is shown that our method is as well as the subjectivity evaluation.

  8. Interaction of two bubbles produced with time difference

    SciTech Connect

    Sato, Kotaro [Osaka Univ., Toyonaka (Japan); Tomita, Yukio [Hokkaido Univ. of Education, Hakodate (Japan); Shima, Akira [Tohoku Univ., Sendai (Japan). Institute of Fluid Science

    1994-12-31

    Some aspects of the bubble-bubble interaction were simulated experimentally. Two cavitation bubbles were generated in water by focusing two beams released from a twin pulsed ruby laser which has a couple of ruby rods. Time deference between the former generated bubble and the latter one was controlled with a delay circuit and their dynamic behaviors were investigated by means of high-speed photography. Consequently, it is found that the bubble-bubble interaction is influenced not only by the relative size of two bubbles but also by the time difference between two bubble generations.

  9. 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.

  10. Dynamics of Vapour Bubbles in Nucleate Boiling. 2; Evolution of Thermally Controlled Bubbles

    NASA Technical Reports Server (NTRS)

    Buyevich, Yu A.; Webbon, Bruce W.; Callaway, Robert (Technical Monitor)

    1995-01-01

    The previously developed dynamic theory of growth and detachment of vapour bubbles under conditions of nucleate pool boiling is applied to study motion and deformation of a bubble evolving at a single nucleation site. The bubble growth is presumed to be thermally controlled, and two components of heat transfer to the bubble are accounted of: the one from the bulk of surrounding liquid and the one due to heat conduction across a liquid microlayer formed underneath the bubble. Bubble evolution is governed by the buoyancy and an effective surface tension force, both the forces making the bubble centre of mass move away from the wall and, thus, assisting its detachment. Buoyancy-controlled and surface-tension-controlled regimes are considered separately in a meticulous way. The duration of the whole process of bubble evolution till detachment, the rate of growth, and the bubble departure size are found as functions of time and physical and operating parameters. Some repeatedly observed phenomena, such as an influence of gravity on the growth rate, are explained. Inferences of the model agree qualitatively with available experimental evidence, and conclusions pertaining to the dependence on gravity of the bubble radius at detachment and the whole time of the bubble development when being attached to the wall are confirmed quantitatively.

  11. The stability of the flow in a laminar separation bubble

    NASA Astrophysics Data System (ADS)

    Niew, Tai Ran

    1993-09-01

    This dissertation reports a study into the underlying concepts used to analyze incompressible laminar separation bubbles. The suggestion that absolute instability could play a role in bubble flows was further developed, and was the focal point of this project. From a review of previous work and preliminary experiments on a backward faxing step, it was suggested that for some bubbles the reattachment region of the flow field could be absolutely unstable. A cornerstone of this view is that the completion of transition is not a prerequisite for the start of reattachment; and that a more fundamental mechanism involves significant interaction between the two processes. This concept was first tested by solving the eigenvalue problem of the Orr-Sommerfeld equation for a family of reverse flow profiles. The results indicated that with sufficient reverse flow, wall-bounded separated shear-layers that are similar to experimentally measured profiles can be absolutely unstable. This is consistent with the hypothesis outlined above. The numerical study also showed that for convectively unstable profiles, the predominant parameter that determines the spatial growth rate of instability waves is the distance of the separated shear layer from the wall. Furthermore, viscosity only has a weak effect on the stability characteristics of both absolutely and convectively unstable profiles at generic bubble Reynolds numbers. Experiments were then carried out on the flow behind a backward facing step using artificially excited instability waves, and the key issues in formulating a conceptually robust experimental method to test the above hypothesis was discussed. If the forcing was carried out with a non-acoustic source, it was shown that the use of impulse excitation could provide a rigorous procedure. Two qualitatively different transition mechanisms, 'wave' and 'spot' type, were also observed in these experiments. A new perspective of bubble behavior was then developed that considered the interaction of turbulent breakdown, reattachment and inducing of reverse flow. The concept of the absolutely unstable reattachment region is an integral part of this view, and the analysis was used to account for the different breakdown processes detected. Based on this alternative framework for analyzing bubble flows, a comprehensive list of fresh areas for future research was also suggested.

  12. Moving with bubbles: a review of the interactions between bubbles and the microorganisms that surround them.

    PubMed

    Walls, Peter L L; Bird, James C; Bourouiba, Lydia

    2014-12-01

    Bubbles are ubiquitous in biological environments, emerging during the complex dynamics of waves breaking in the open oceans or being intentionally formed in bioreactors. From formation, through motion, until death, bubbles play a critical role in the oxygenation and mixing of natural and artificial ecosystems. However, their life is also greatly influenced by the environments in which they emerge. This interaction between bubbles and microorganisms is a subtle affair in which surface tension plays a critical role. Indeed, it shapes the role of bubbles in mixing or oxygenating microorganisms, but also determines how microorganisms affect every stage of the bubble's life. In this review, we guide the reader through the life of a bubble from birth to death, with particular attention to the microorganism-bubble interaction as viewed through the lens of fluid dynamics. PMID:25096288

  13. 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.

  14. 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

  15. Particle Motion Induced by Bubble Cavitation

    NASA Astrophysics Data System (ADS)

    Poulain, Stéphane; Guenoun, Gabriel; Gart, Sean; Crowe, William; Jung, Sunghwan

    2015-05-01

    Cavitation bubbles induce impulsive forces on surrounding substrates, particles, or surfaces. Even though cavitation is a traditional topic in fluid mechanics, current understanding and studies do not capture the effect of cavitation on suspended objects in fluids. In the present work, the dynamics of a spherical particle due to a cavitation bubble is experimentally characterized and compared with an analytical model. Three phases are observed: the growth of the bubble where the particle is pushed away, its collapse where the particle approaches the bubble, and a longer time scale postcollapse where the particle continues to move toward the collapsed bubble. The particle motion in the longer time scale presumably results from the asymmetric cavitation evolution at an earlier time. Our theory considering the asymmetric bubble dynamics shows that the particle velocity strongly depends on the distance from the bubble as an inverse-fourth-power law, which is in good agreement with our experimentation. This study sheds light on how small free particles respond to cavitation bubbles in fluids.

  16. Particle Motion Induced by Bubble Cavitation.

    PubMed

    Poulain, Stéphane; Guenoun, Gabriel; Gart, Sean; Crowe, William; Jung, Sunghwan

    2015-05-29

    Cavitation bubbles induce impulsive forces on surrounding substrates, particles, or surfaces. Even though cavitation is a traditional topic in fluid mechanics, current understanding and studies do not capture the effect of cavitation on suspended objects in fluids. In the present work, the dynamics of a spherical particle due to a cavitation bubble is experimentally characterized and compared with an analytical model. Three phases are observed: the growth of the bubble where the particle is pushed away, its collapse where the particle approaches the bubble, and a longer time scale postcollapse where the particle continues to move toward the collapsed bubble. The particle motion in the longer time scale presumably results from the asymmetric cavitation evolution at an earlier time. Our theory considering the asymmetric bubble dynamics shows that the particle velocity strongly depends on the distance from the bubble as an inverse-fourth-power law, which is in good agreement with our experimentation. This study sheds light on how small free particles respond to cavitation bubbles in fluids. PMID:26066438

  17. The Minnaert Bubble: An Acoustic Approach

    ERIC Educational Resources Information Center

    Devaud, Martin; Hocquet, Thierry; Bacri, Jean-Claude; Leroy, Valentin

    2008-01-01

    We propose an "ab initio" introduction to the well-known Minnaert pulsating bubble at graduate level. After a brief recall of the standard stuff, we begin with a detailed discussion of the radial movements of an air bubble in water. This discussion is managed from an acoustic point of view, and using the Lagrangian rather than the Eulerian…

  18. 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

  19. 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.

  20. 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.

  1. The Minnaert bubble: an acoustic approach

    Microsoft Academic Search

    Martin Devaud; Thierry Hocquet; Jean-Claude Bacri; Valentin Leroy

    2008-01-01

    We propose an ab initio introduction to the well-known Minnaert pulsating bubble at graduate level. After a brief recall of the standard stuff, we begin with a detailed discussion of the radial movements of an air bubble in water. This discussion is managed from an acoustic point of view, and using the Lagrangian rather than the Eulerian variables. In unbounded

  2. Oscillating plasma bubbles. II. Pulsed experiments

    SciTech Connect

    Stenzel, R. L.; Urrutia, J. M. [Department of Physics and Astronomy, University of California, Los Angeles, California 90095-1547 (United States)

    2012-08-15

    Time-dependent phenomena have been investigated in plasma bubbles which are created by inserting spherical grids into an ambient plasma and letting electrons and ions form a plasma of different parameters than the ambient one. There are no plasma sources inside the bubble. The grid bias controls the particle flux. There are sheaths on both sides of the grid, each of which passes particle flows in both directions. The inner sheath or plasma potential develops self consistently to establish charge neutrality and divergence free charge and mass flows. When the electron supply is restricted, the inner sheath exhibits oscillations near the ion plasma frequency. When all electrons are excluded, a virtual anode forms on the inside sheath, reflects all ions such that the bubble is empty. By pulsing the ambient plasma, the lifetime of the bubble plasma has been measured. In an afterglow, plasma electrons are trapped inside the bubble and the bubble decays as slow as the ambient plasma. Pulsing the grid voltage yields the time scale for filling and emptying the bubble. Probes have been shown to modify the plasma potential. Using pulsed probes, transient ringing on the time scale of ion transit times through the bubble has been observed. The start of sheath oscillations has been investigated. The instability mechanism has been qualitatively explained. The dependence of the oscillation frequency on electrons in the sheath has been clarified.

  3. 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

  4. Gravity Wave Seeding of Equatorial Plasma Bubbles

    NASA Technical Reports Server (NTRS)

    Singh, Sardul; Johnson, F. S.; Power, R. A.

    1997-01-01

    Some examples from the Atmosphere Explorer E data showing plasma bubble development from wavy ion density structures in the bottomside F layer are described. The wavy structures mostly had east-west wavelengths of 150-800 km, in one example it was about 3000 km. The ionization troughs in the wavy structures later broke up into either a multiple-bubble patch or a single bubble, depending upon whether, in the precursor wavy structure, shorter wavelengths were superimposed on the larger scale wavelengths. In the multiple bubble patches, intrabubble spacings vaned from 55 km to 140 km. In a fully developed equatorial spread F case, east-west wavelengths from 690 km down to about 0.5 km were present simultaneously. The spacings between bubble patches or between bubbles in a patch appear to be determined by the wavelengths present in the precursor wave structure. In some cases, deeper bubbles developed on the western edge of a bubble patch, suggesting an east-west asymmetry. Simultaneous horizontal neutral wind measurements showed wavelike perturbations that were closely associated with perturbations in the plasma horizontal drift velocity. We argue that the wave structures observed here that served as the initial seed ion density perturbations were caused by gravity waves, strengthening the view that gravity waves seed equatorial spread F irregularities.

  5. Bubble Growth and Detachment from a Needle

    Microsoft Academic Search

    Michael Shusser; Edmond Rambod; Morteza Gharib

    1999-01-01

    The release of bubbles from an underwater nozzle or orifice occurs in large number of applications, such as perforated plate columns, blood oxygenators and various methods of water treatment. It is also a widely used method in laboratory research on multiphase flow and acoustics for generating small bubbles in a controlled fashion. We studied experimentally the growth and pinch-off of

  6. Mixture segregation by an inertial cavitation bubble

    Microsoft Academic Search

    R. Grossier; O. Louisnard; Y. Vargas

    2007-01-01

    Pressure diffusion is a mass diffusion process forced by pressure gradients. It has the ability to segregate two species of a mixture, driving the densest species toward high pressure zones, but requires very large pressure gradients to become noticeable. An inertial cavitation bubble develops large pressure gradients in its vicinity, especially as the bubble rebounds at the end of its

  7. The Physics of Foams, Droplets and Bubbles

    ERIC Educational Resources Information Center

    Sarker, Dipak K.

    2013-01-01

    Foams or bubble dispersions are common to milkshakes, bread, champagne froth, shaving mousse, shampoo, crude oil extraction systems, upholstery packing and bubble wrap, whereas the term droplet is often synonymous with either a small drop of water or a drop of oil--a type of coarse dispersion. The latter are seen in butter and milk, household…

  8. Stock market bubbles in the laboratory

    Microsoft Academic Search

    David P. Porter; Vernon L. Smith

    1994-01-01

    Trading at prices above the fundamental value of an asset, i.e. a bubble, has been verified and replicated in laboratory asset markets for the past seven years. To date, only common group experience provides minimal conditions for common investor sentiment and trading at fundamental value. Rational expectations models do not predict the bubble and crash phenomena found in these experimental

  9. Bottlenecks aggravate rising construction costs

    SciTech Connect

    NONE

    2008-05-15

    Rising demand for power in developing countries combined with concerns about carbon emissions from coal-fired power plants in developed countries have created a bonanza for carbon-light technologies, including nuclear, renewables and natural gas plants. This, in turn, has put upward pressure on the price of natural gas in key markets while resulting in shortages in critical components for building renewables and nuclear reactors. Globalization of the power industry means that pressures in one segment or one region translate into shortages and rising prices everywhere else.

  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. CITY OF SANTA BARBARA SEALEVEL RISE VULNERABILITY

    E-print Network

    communities. This study assesses the vulnerability of the City of Santa Barbara to future sealevel rise storm damage, flooding, inundation, risk assessment, sealevel rise, vulnerability assessment, wave CITY OF SANTA BARBARA SEALEVEL RISE VULNERABILITY STUDY A White Paper from

  12. Wettability dependent bubble dynamics in microfluidic networks

    NASA Astrophysics Data System (ADS)

    Parthiban, Pravien; Khan, Saif A.; Kreutzer, Michiel T.

    2010-11-01

    The routing of bubble or droplet traffic through microfluidic networks depends greatly on the hydrodynamic resistance in the individual branches of that network. We find that a confined bubble translating through a partially wetting liquid experiences significantly more friction than a bubble lubricated by a completely wetting liquid, with important consequences for the dynamic behavior. For our system, we observe symmetric bubble break up and alternating left-right routing at a microfluidic junction, as described previously by Link et al. For partially wetting liquids, we observe a much richer dynamic behavior, with asymmetric splitting and left-right routing with chaotic periodicity. We identify the contact angle as a key control parameter that determines the different regimes and we explore how the transitions between these regimes can be effected by tuning this parameter. The results of this work aid the prediction and control of bubble traffic through complex microfluidic networks. Link et al., Phys. Rev. Lett. 92 (2005) 054503

  13. Giant Bubble Pinch-Off

    NASA Astrophysics Data System (ADS)

    Bergmann, Raymond; van der Meer, Devaraj; Stijnman, Mark; Sandtke, Marijn; Prosperetti, Andrea; Lohse, Detlef

    2006-04-01

    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, is not self-similar in a strict sense: A disk is quickly pulled through a water surface, leading to a giant, cylindrical void which after collapse creates an upward and a downward jet. Only in the limiting case of large Froude numbers does the purely inertial scaling h(-log?h)1/4??1/2 for the neck radius h [J. M. Gordillo , Phys. Rev. Lett.PRLTAO0031-9007 95, 194501 (2005)] become visible. For any finite Froude number the collapse is slower, and a second length scale, the curvature of the void, comes into play. Both length scales are found to exhibit power-law scaling in time, but with different exponents depending on the Froude number, signaling the nonuniversality of the bubble pinch-off.

  14. Primary Particles from different bubble generation techniques

    NASA Astrophysics Data System (ADS)

    Butcher, A. C.; King, S. M.; Rosenoern, T.; Nilsson, E. D.; Bilde, M.

    2011-12-01

    Sea spray aerosols (SSA) are of major interest to global climate models due to large uncertainty in their emissions and ability to form Cloud Condensation Nuclei (CCN). In general, SSA are produced from wind breaking waves that entrain air and cause bubble bursting on the ocean surface. Preliminary results are presented for bubble generation, bubble size distribution, and CCN activity for laboratory generated SSA. In this study, the major processes of bubble formation are examined with respect to particle emissions. It has been suggested that a plunging jet closely resembles breaking wave bubble entrainment processes and subsequent bubble size distributions (Fuentes, Coe et al. 2010). Figure 1 shows the different particle size distributions obtained from the various bubble generation techniques. In general, frits produce a higher concentration of particles with a stronger bimodal particle size distribution than the various jet configurations used. The experiments consist of a stainless steel cylinder closed at both ends with fittings for aerosol sampling, flow connections for the recirculating jet, and air supply. Bubble generation included a recirculating jet with 16 mm or 4 mm nozzles, a stainless steel frit, or a ceramic frit. The chemical composition of the particles produced via bubble bursting processes has been probed using particle CCN activity. The CCN activity of sodium chloride, artificial sea salt purchased from Tropic Marin, and laboratory grade artificial sea salt (Kester, Duedall et al. 1967) has been compared. Considering the the limits of the shape factor as rough error bars for sodium chloride and bubbled sea salt, the CCN activity of artificial sea salt, Tropic Marin sea salt, and sodium chloride are not significantly different. This work has been supported by the Carlsberg Foundation.

  15. Observation of Microhollows Produced by Bubble Cloud Cavitation

    NASA Astrophysics Data System (ADS)

    Yamakoshi, Yoshiki; Miwa, Takashi

    2012-07-01

    When an ultrasonic wave with sound pressure less than the threshold level of bubble destruction irradiates microbubbles, the microbubbles aggregate by an acoustic radiation force and form bubble clouds. The cavitation of bubble clouds produces a large number of microhollows (microdips) on the flow channel wall. In this study, microhollow production by bubble cloud cavitation is evaluated using a blood vessel phantom made of N-isopropylacrylamide (NIPA) gel. Microbubble dynamics in bubble cloud cavitation is observed by a microscope with a short pulse light emitted diode (LED) light source. Microhollows produced on the flow channel wall are evaluated by a confocal laser microscope with a water immersion objective. It is observed that a mass of low-density bubbles (bubble mist) is formed by bubble cloud cavitation. The spatial correlation between the bubble mist and the microhollows shows the importance of the bubble mist in microhollow production by bubble cloud cavitation.

  16. Centrifuge modelling of capillary rise

    Microsoft Academic Search

    N. Depountis; M. C. R. Davies; C. Harris; S. Burkhart; L. Thorel; A. Rezzoug; D. König; C. Merrifield; W. H. Craig

    2001-01-01

    This paper reports results from centrifuge tests designed to investigate capillary rise in soils subjected to different gravitational fields. The experimental programme is part of the EU-funded NECER project (Network of European Centrifuges for Environmental Geotechnic Research), whose objective is to investigate the appropriateness of geotechnical centrifuge modelling for the investigation of geoenvironmental problems, particularly with reference to partially saturated

  17. Probability of sea level rise

    Microsoft Academic Search

    J. G. Titus; V. K. Narayanan

    1995-01-01

    The report develops probability-based projections that can be added to local tide-gage trends to estimate future sea level at particular locations. It uses the same models employed by previous assessments of sea level rise. The key coefficients in those models are based on subjective probability distributions supplied by a cross-section of climatologists, oceanographers, and glaciologists.

  18. Temperature rise of installed FCC

    NASA Technical Reports Server (NTRS)

    Hankins, J. D.

    1976-01-01

    Report discusses temperature profiles of installed FCC for wood and tile surfaces. Three-conductor FCC was tested at twice nominal current-carrying capacity over bare floor and under carpet, with result indicating that temperature rise is not a linear function of current with FCC at this level.

  19. Probability of sea level rise

    SciTech Connect

    Titus, J.G.; Narayanan, V.K.

    1995-10-01

    The report develops probability-based projections that can be added to local tide-gage trends to estimate future sea level at particular locations. It uses the same models employed by previous assessments of sea level rise. The key coefficients in those models are based on subjective probability distributions supplied by a cross-section of climatologists, oceanographers, and glaciologists.

  20. Large Topographic Rises on Venus: Implications for Mantle Upwelling

    NASA Technical Reports Server (NTRS)

    Stofan, Ellen R.; Smrekar, Suzanne E.; Bindschandler, Duane L.; Senske, David A.

    1995-01-01

    Topographic rises on Venus have been identified that are interpreted to be the surface manifestation of mantle upwellings. These features are classified into groups based on their dominant morphology. Atla and Beta Regiones are classified as rift-dominated, Dione, western Eistla, Bell, and Imdr Regiones as volcano-dominated, and Themis, eastern Eistla, and central Eistla Regiones as corona-dominated. At several topographic rises, geologic indicators were identified that may provide evidence of uplifted topography (e.g., volcanic flow features trending upslope). We assessed the minimum contribution of volcanic construction to the topography of each rise, which in general represents less than 5% of the volume of the rise, similar to the volumes of edifices at terrestrial hotspot swells. The total melt volume at each rise is approximated to be 10(exp 4) - 10(exp 6) cu km. The variations in morphology, topography, and gravity signatures at topographic rises are not interpreted to indicate variations in stage of evolution of a mantle upwelling. Instead, the morphologic variations between the three classes of topographic rises are interpreted to indicate the varying influences of lithospheric structure, plume characteristics, and regional tectonic environment. Within each class, variations in topography, gravity, and amount of volcanism may be indicative of differing stages of evolution. The similarity between swell and volcanic volumes for terrestrial and Venusian hotspots implies comparable time-integrated plume strengths for individual upwellings on the two planets.

  1. Applicability of superheated drop (bubble) detectors to reactor dosimetry

    SciTech Connect

    d`Errico, F.; Curzio, G. [Univ. degli Studi di Pisa (Italy). Dipt. di Costruzioni Meccaniche e Nucleari; Alberts, W.G. [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany); Apfel, R.E.; Guldbakke, S. [Yale Univ., New Haven, CT (United States). Dept. of Mechanical Engineering

    1994-12-31

    The characteristics of superheated drop (bubble) detectors (SDD`s) have been reviewed with respect to the possible application of these devices in reactor dosimetry. In particular, their ability to measure neutrons in the presence of a high noise level, elevated temperatures and intense {gamma} background has been investigated. Based on these studies, the use of SDD`s is proposed for the monitoring and analysis of neutron emission from spent fuel assemblies. Finally, the possibility to employ these detectors in radiation protection dosimetry around power plants is discussed.

  2. Light transfer in bubble sparged photobioreactors for H 2 production and CO 2 mitigation

    Microsoft Academic Search

    Halil Berberoglu; Juan Yin; Laurent Pilon

    2007-01-01

    This paper presents a parametric study simulating light transfer in a photobioreactor containing gas bubbles and filamentous cyanobacteria Anabaena variabilis suspended in water. To the best of our knowledge, this paper presents for the first time a model for such system: (i) using a consistent set of radiation characteristics of the medium derived from experimental data and from Mie theory;

  3. High-Rise Residential Building Energy Analysis in Shanghai, China 

    E-print Network

    Zhou, Hongyun

    2014-07-30

    ................................... 55 Figure 5.6 Monthly Energy Use Before and After Calibration Run 5 ............................. 55 Figure 5.7 Monthly Energy Use Before and After Calibration Run 6 ............................. 56 Figure 5.8 Monthly Energy Use Before and After... 2.2 High-Rise Residential Building Characteristics in Shanghai ........................ 6 2.3 Residential Energy Use Characteristics in Shanghai ..................................... 8 2.4 Energy Efficiency Measures...

  4. Clump Development by the Nickel Bubble Effect in Supernovae

    E-print Network

    Chih-Yueh Wang

    2005-02-21

    We used one-dimensional radiative-transport radiation hydrodynamical (RHD) simulations to investigate the formation of clumping in freely-expanding supernova ejecta due to the radioactive heating from the Ni56 -> Co56 -> Fe56 decay sequence. The heating gives rise to an inflated Nickel bubble, which induces a forward shock that compresses the outer ambient gas into a shell. The radiative energy deposited by the radioactivity leaks out across the shock by radiative diffusion, and we investigate its effect on the evolution of the ejecta structure. Compared to the hydrodynamical adiabatic approximation with gamma =4/3, the preshock gas becomes accelerated by the radiation outflow. The shock is thus weakened and the shell becomes broader and less dense. The thickness of the shell takes up <~ 4 % of the radius of the bubble, and the structure of the shell can be approximately described by a self-similar solution. We compared the properties of the shell components with those of the ejecta clumps indicated by our previous hydrodynamical simulations for the later interaction of clumps with the outer supernova remnant. The high density contrast across the shell, chi ~ 100, is compatible with that of ejecta clumps as indicated for Tycho's knots, but there is insufficient dense gas to cause a pronounced protrusion on the outline of a core collapse supernova remnant, like the bullets in the Vela remnant.

  5. Effect of bubble's arrangement on the viscous torque in bubbly Taylor-Couette flow

    NASA Astrophysics Data System (ADS)

    Fokoua, G. Ndongo; Gabillet, C.; Aubert, A.; Colin, C.

    2015-03-01

    An experimental investigation of the interactions between bubbles, coherent motion, and viscous drag in a Taylor-Couette flow with the outer cylinder at rest is presented. The cylinder radii ratio ? is 0.91. Bubbles are injected inside the gap through a needle at the bottom of the apparatus. Different bubbles sizes are investigated (ratio between the bubble diameter and the gap width ranges from 0.05 to 0.125) for very small void fraction (? ? 0.23%). Different flow regimes are studied corresponding to Reynolds number Re based on the gap width and velocity of the inner cylinder, ranging from 6 × 102 to 2 × 104. Regarding these Re values, Taylor vortices are persistent leading to an axial periodicity of the flow. A detailed characterization of the vortices is performed for the single-phase flow. The experiment also develops bubbles tracking in a meridian plane and viscous torque of the inner cylinder measurements. The findings of this study show evidence of the link between bubbles localisation, Taylor vortices, and viscous torque modifications. We also highlight two regimes of viscous torque modification and various types of bubbles arrangements, depending on their size and on the Reynolds number. Bubbles can have a sliding and wavering motion near the inner cylinder and be either captured by the Taylor vortices or by the outflow areas near the inner cylinder. For small buoyancy effect, bubbles are trapped, leading to an increase of the viscous torque. When buoyancy induced bubbles motion is increased by comparison to the coherent motion of the liquid, a decrease in the viscous torque is rather observed. The type of bubble arrangement is parameterized by the two dimensionless parameters C and H introduced by Climent et al. ["Preferential accumulation of bubbles in Couette-Taylor flow patterns," Phys. Fluids 19, 083301 (2007)]. Phase diagrams summarizing the various types of bubbles arrangements, viscous torque modifications, and axial wavelength evolution are built.

  6. 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

  7. Bubbly Suspension Generated in Low Gravity

    NASA Technical Reports Server (NTRS)

    Nahra, Henry K.

    2000-01-01

    Bubbly suspensions are crucial for mass and heat transport processes on Earth and in space. These processes are relevant to pharmaceutical, chemical, nuclear, and petroleum industries on Earth. They are also relevant to life support, in situ resource utilization, and propulsion processes for long-duration space missions such as the Human Exploration and Development of Space program. Understanding the behavior of the suspension in low gravity is crucial because of factors such as bubble segregation, which could result in coalescence and affect heat and mass transport. Professors A. Sangani and D. Koch, principal investigators in the Microgravity Fluid Physics Program managed by the NASA Glenn Research Center at Lewis Field, are studying the physics of bubbly suspension. They plan to shear a bubbly suspension in a couette cell in microgravity to study bubble segregation and compare the bubble distribution in the couette gap with the one predicted by the suspension-averaged equations of motion. Prior to the Requirement Definition Review of this flight experiment, a technology for generating a bubbly suspension in microgravity has to be established, tested, and verified.

  8. Interacting bubble clouds and their sonochemical production.

    PubMed

    Stricker, Laura; Dollet, Benjamin; Fernández Rivas, David; Lohse, Detlef

    2013-09-01

    An acoustically driven air pocket trapped in a pit etched on a surface can emit a bubble cluster. When several pits are present, the resulting bubble clusters interact in a nontrivial way. Ferna?ndez Rivas et al. [Angew. Chem. Int. Ed. 49, 9699-9701 (2010)] observed three different behaviors at increasing driving power: clusters close to their "mother" pits, clusters attracting each other but still well separated, and merging clusters. The last is highly undesirable for technological purposes as it is associated with a reduction of the radical production and an enhancement of the erosion of the reactor walls. In this paper, the conditions for merging to occur are quantified in the case of two clusters, as a function of the following control parameters: driving pressure, distance between the two pits, cluster radius, and number of bubbles within each cluster. The underlying mechanism, governed by the secondary Bjerknes forces, is strongly influenced by the nonlinearity of the bubble oscillations and not directly by the number of nucleated bubbles. The Bjerknes forces are found to dampen the bubble oscillations, thus reducing the radical production. Therefore, the increased number of bubbles at high power could be the key to understanding the experimental observation that, above a certain power threshold, any further increase of the driving does not improve the sonochemical efficiency. PMID:23967919

  9. 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.

  10. Photon Bubbles in Accretion Discs

    E-print Network

    Charles F. Gammie

    1998-02-17

    We show that radiation dominated accretion discs are likely to suffer from a ``photon bubble'' instability similar to that described by Arons in the context of accretion onto neutron star polar caps. The instability requires a magnetic field for its existence. In an asymptotic regime appropriate to accretion discs, we find that the overstable modes obey the remarkably simple dispersion relation \\omega^2 = -i g k F(B,k). Here g is the vertical gravitational acceleration, B the magnetic field, and F is a geometric factor of order unity that depends on the relative orientation of the magnetic field and the wavevector. In the nonlinear outcome it seems likely that the instability will enhance vertical energy transport and thereby change the structure of the innermost parts of relativistic accretion discs.

  11. The Minnaert bubble: an acoustic approach

    NASA Astrophysics Data System (ADS)

    Devaud, Martin; Hocquet, Thierry; Bacri, Jean-Claude; Leroy, Valentin

    2008-11-01

    We propose an ab initio introduction to the well-known Minnaert pulsating bubble at graduate level. After a brief recall of the standard stuff, we begin with a detailed discussion of the radial movements of an air bubble in water. This discussion is managed from an acoustic point of view, and using the Lagrangian rather than the Eulerian variables. In unbounded water, the air-water system has a continuum of eigenmodes, some of them correspond to regular Fabry-Pérot resonances. A singular resonance, the lowest one, is shown to coincide with that of Minnaert. In bounded water, the eigenmodes spectrum is discrete, with a finite fundamental frequency. A spectacular quasi-locking of the latter occurs if it happens to exceed the Minnaert frequency, which provides an unforeseen one-bubble alternative version of the famous 'hot chocolate effect'. In the (low) frequency domain in which sound propagation inside the bubble reduces to a simple 'breathing' (i.e. inflation/deflation), the light air bubble can be 'dressed' by the outer water pressure forces, and is turned into the heavy Minnaert bubble. Thanks to this unexpected renormalization process, we demonstrate that the Minnaert bubble definitely behaves like a true harmonic oscillator of the spring-bob type, but with a damping term and a forcing term in apparent disagreement with those commonly admitted in the literature. Finally, we underline the double role played by the water. In order to tell the water motion associated with water compressibility (i.e. the sound) from the simple incompressible accompaniment of the bubble breathing, we introduce a new picture analogous to the electromagnetic radiative picture in Coulomb gauge, which naturally leads us to split the water displacement in an instantaneous and a retarded part. The Minnaert renormalized mass of the dressed bubble is then automatically recovered.

  12. Magnetic Topology of Bubbles in Quiescent Prominences

    NASA Astrophysics Data System (ADS)

    Dudík, J.; Aulanier, G.; Schmieder, B.; Zapiór, M.; Heinzel, P.

    2012-12-01

    We study a polar-crown prominence with a bubble and its plume observed in several coronal filters by the SDO/AIA and in H? by the MSDP spectrograph in Bia?ków (Poland) to address the following questions: what is the brightness of prominence bubbles in EUV with respect to the corona outside of the prominence and the prominence coronal cavity? What is the geometry and topology of the magnetic field in the bubble? What is the nature of the vertical threads seen within prominences? We find that the brightness of the bubble and plume is lower than the brightness of the corona outside of the prominence, and is similar to that of the coronal cavity. We constructed linear force-free models of prominences with bubbles, where the flux rope is perturbed by inclusion of parasitic bipoles. The arcade field lines of the bipole create the bubble, which is thus devoid of magnetic dips. Shearing the bipole or adding a second one can lead to cusp-shaped prominences with bubbles similar to the observed ones. The bubbles have complex magnetic topology, with a pair of coronal magnetic null points linked by a separator outlining the boundary between the bubble and the prominence body. We conjecture that plume formation involves magnetic reconnection at the separator. Depending on the viewing angle, the prominence can appear either anvil-shaped with predominantly horizontal structures, or cusp-shaped with predominantly vertical structuring. The latter is an artifact of the alignment of magnetic dips with respect to the prominence axis and the line of sight.

  13. Dynamics of two-dimensional bubbles

    NASA Astrophysics Data System (ADS)

    Piedra, Saúl; Ramos, Eduardo; Herrera, J. Ramón

    2015-06-01

    The dynamics of two-dimensional bubbles ascending under the influence of buoyant forces is numerically studied with a one-fluid model coupled with the front-tracking technique. The bubble dynamics are described by recording the position, shape, and orientation of the bubbles as functions of time. The qualitative properties of the bubbles and their terminal velocities are described in terms of the Eötvos (ratio of buoyancy to surface tension) and Archimedes numbers (ratio of buoyancy to viscous forces). The terminal Reynolds number result from the balance of buoyancy and drag forces and, consequently, is not an externally fixed parameter. In the cases that yield small Reynolds numbers, the bubbles follow straight paths and the wake is steady. A more interesting behavior is found at high Reynolds numbers where the bubbles follow an approximately periodic zigzag trajectory and an unstable wake with properties similar to the Von Karman vortex street is formed. The dynamical features of the motion of single bubbles are compared to experimental observations of air bubbles ascending in a water-filled Hele-Shaw cell. Although the comparison is not strictly valid in the sense that the effect of the lateral walls is not incorporated in the model, most of the dynamical properties observed are in good qualitative agreement with the numerical calculations. Hele-Shaw cells with different gaps have been used to determine the degree of approximation of the numerical calculation. It is found that for the relation between the terminal Reynolds number and the Archimedes number, the numerical calculations are closer to the observations of bubble dynamics in Hele-Shaw cells of larger gaps.

  14. 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.

  15. Visualization studies of a freon-113 bubble condensing in water

    Microsoft Academic Search

    H. Kalman; A. Ullmann; R. Letan

    1987-01-01

    Several visualization methods have been applied in studies of organic bubbles condensing in water. The results, although qualitative in nature, have furnished an insight into the physical phenomena governing the process. Shadow graphing of the collapsing bubbles has outlined the thermal surroundings of the bubble. Shadowgraphs of a freon-113 bubble recorded in sequence have illustrated the formation of a thermal

  16. Microfluidics Formation of Bubbles in a Multisection Flow-Focusing

    E-print Network

    Prentiss, Mara

    Microfluidics Formation of Bubbles in a Multisection Flow-Focusing Junction Michinao Hashimoto the stable formation of trains of mono-, bi-, and tri-disperse bubbles in microfluidic flow- focusing (FF-assembly through the patterns of flow created by the bubbles. 1.1 Bubbles and Droplets in Microfluidics

  17. Bubble growth in rhyolitic melt Yang Liu, Youxue Zhang *

    E-print Network

    Zhang, Youxue

    Bubble growth in rhyolitic melt Yang Liu, Youxue Zhang * The Department of Geological Sciences rhyolitic melt with 1.4^2.0 wt% initial total H2O at 0.1 MPa and 500^600³C. Growth of many bubbles. The average growth rate for bubbles growing in an infinite rhyolitic melt at a bubble radius of 25 Wm is V0

  18. 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.

  19. The TAROT archive: rising afterglows

    NASA Astrophysics Data System (ADS)

    Gendre, B.; Corsi, A.; Cutini, S.; Preger, B.; Klotz, A.; Stratta, G.; Atteia, J. L.; Boer, M.; Daigne, F.; Motchkovitch, R.; Piro, L.

    2009-05-01

    The TAROT telescopes (Télescopes à Action Rapide pour les Objets Transitoires) are two robotic observatories designed to observe the prompt optical emission counterpart and the early afterglow of gamma ray bursts (GRBs). We present the multi-wavelength study of those gamma-ray bursts observed by TAROT. These events are characterized by the presence at early time of a rising in their optical light curves lasting a few hundred of seconds. In one case (GRB 060904B), a flare occurs at similar time in the X-ray band, while in the other cases the X-ray light curves appear smooth during the optical rise. We investigate the possible nature of this behavior and conclude that a multi-component emission is mandatory to explain the optical-to-X-ray afterglow.

  20. Density rise experiment on PLT

    SciTech Connect

    Strachan, J.D.; Bretz, N.; Mazzucato, E.

    1982-05-01

    The evolution of the density profile in PLT during intense gas puffing is documented and analyzed. Measurements of the spectrum of low energy edge neutrals and of the change in central neutral density indicate that charge-exchange processes alone cannot account for the central density rise. The transient density profile changes can be reproduced numerically by a diffusivity of approx. 10/sup 4/ cm/sup 2//s, and a spatially averaged inward flow of 10/sup 3/ cm/s. These transport coefficients are 10 ..-->.. 10/sup 2/ times larger than neoclassical. The ion energy confinement is reduced, the small scale density fluctuations are increased, and runaway electrons losses are increased during the density rise.

  1. Co-operative oscillations of bubbles

    NASA Technical Reports Server (NTRS)

    Snyder, H. A.; Mord, A. J.

    1990-01-01

    A closed cryogenic storage tank in space may contain several bubbles. It is shown that these bubbles can oscillate in volume with n-1 resonant frequencies for n bubbles. The resonances can be excited by a sudden change in pressure, such as withdrawing fluid or venting, or by motion of the vehicle. In situations in which the ac accelerations dominate, such as in large space structures, the potential for harmful coupling of these oscillations to the spacecraft structure must be examined. Experimental data are presented which support the theoretical predictions.

  2. Three-dimensional magnetic bubble memory system

    NASA Technical Reports Server (NTRS)

    Stadler, Henry L. (Inventor); Katti, Romney R. (Inventor); Wu, Jiin-Chuan (Inventor)

    1994-01-01

    A compact memory uses magnetic bubble technology for providing data storage. A three-dimensional arrangement, in the form of stacks of magnetic bubble layers, is used to achieve high volumetric storage density. Output tracks are used within each layer to allow data to be accessed uniquely and unambiguously. Storage can be achieved using either current access or field access magnetic bubble technology. Optical sensing via the Faraday effect is used to detect data. Optical sensing facilitates the accessing of data from within the three-dimensional package and lends itself to parallel operation for supporting high data rates and vector and parallel processing.

  3. 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.

  4. Falling and Rising in Water

    ERIC Educational Resources Information Center

    Mohazzabi, Pirooz

    2010-01-01

    When an object is immersed in a liquid and released, it may sink to the bottom or rise to the surface and float. If the object's density is greater than that of the liquid, it sinks. If the object's density is less than the density of the liquid, it floats. In the special case when the object's density matches the density of the liquid, it will…

  5. Correlation of shape and size of methane bubbles in fine-grained muddy aquatic sediments with sediment fracture toughness

    NASA Astrophysics Data System (ADS)

    Katsman, Regina

    2015-01-01

    Gassy sediments contribute to destabilization of aquatic infrastructure, air pollution, and global warming. In the current study a precise shape and size of the buoyant mature methane bubble in fine-grained muddy aquatic sediment is defined by numerical and analytical modeling, their results are in a good agreement. A closed-form analytical solution defining the bubble parameters is developed. It is found that the buoyant mature bubble is elliptical in its front view and resembles an inverted tear drop in its cross-section. The size and shape of the mature bubble strongly correlate with sediment fracture toughness. Bubbles formed in the weaker sediments are smaller and characterized by a larger surface-to-volume ratio that induces their faster growth and may lead to their faster dissolution below the sediment-water interface. This may prevent their release to the water column and to the atmosphere. Shapes of the bubbles in the weaker sediments deviate further from the spherical configuration, than those in the stronger sediments. Modeled bubble characteristics, important for the acoustic applications, are in a good agreement with field observations and lab experiments.

  6. Bubble growth in visco-elastic magma: implications to magma fragmentation and bubble nucleation

    Microsoft Academic Search

    Kurzon Ittai; Lyakhovsky Vladimir; Navon Oded

    2011-01-01

    We present a visco-elastic bubble growth model, accounting for viscous and elastic deformations and for volatile mass transfer\\u000a between bubbles and melt. We define the borders between previous bubble growth models accounting for incompressible viscous\\u000a melt, and our new model accounting also for elastic deformation; this is done by a set of end-member analytical solutions\\u000a and numerical simulations. Elastic deformation

  7. 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.

  8. Wormholes, void bubbles and vacuum energy suppression

    NASA Astrophysics Data System (ADS)

    Rodrigo, Enrico

    2007-07-01

    The gargantuan discrepancy between the value of the observed cosmological constant and that expected from the zero-point energy of known matter fields can be eliminated by supposing that on macroscopic scales, the overwhelming majority of any volume of spacetime is literal nothingness. This nothingness or void results from the proliferative nucleation of tiny void bubbles (a.k.a. 'bubbles of nothing' or 'semi wormholes') that expand until their surfaces, presumed to be 2-branes, collide. This process results in a dense packing of void bubbles of various sizes that leaves only the vanishing interstitial regions between bubbles for spacetime to occupy. This vast reduction in the amount of actual space, contained within any apparent volume, reduces correspondingly the effective zero-point energy density. Unlike previous wormhole-based attempts at vacuum energy suppression, the current approach is entirely Lorentzian and results in a nonzero value for the cosmological constant.

  9. Loop exponent in DNA bubble dynamics

    NASA Astrophysics Data System (ADS)

    Kaiser, Vojt?ch; Novotný, Tomáš

    2014-08-01

    Dynamics of DNA bubbles are of interest for both statistical physics and biology. We present exact solutions to the Fokker-Planck equation governing bubble dynamics in the presence of a long-range entropic interaction. The complete meeting time and meeting position probability distributions are derived from the solutions. Probability distribution functions (PDFs) reflect the value of the loop exponent of the entropic interaction. Our results extend previous results which concentrated mainly on the tails of the PDFs and open a way to determining the strength of the entropic interaction experimentally which has been a matter of recent discussions. Using numerical integration, we also discuss the influence of the finite size of a DNA chain on the bubble dynamics. Analogous results are obtained also for the case of subdiffusive dynamics of a DNA bubble in a heteropolymer, revealing highly universal asymptotics of meeting time and position probability functions.

  10. Scientific Method Lab Using Bubble Gum

    NSDL National Science Digital Library

    This activity is a lab investigation where students gather data which compares 2 types of bubble gum, while learning to use the scientific method to collect qualitative and quantitative data using SI units.

  11. Nucleate boiling bubble growth and departure

    E-print Network

    Staniszewski, Bogumil E.

    1959-01-01

    The vapor bubble formation on the heating surface during pool boiling has been studied experimentally. Experiments were made at the atmospheric pressure 28 psi and 40 psi, using degassed distilled water and ethanol. The ...

  12. Universe out of a breathing bubble

    SciTech Connect

    Guendelman, Eduardo I.; Sakai, Nobuyuki [Physics Department, Ben Gurion University of the Negev, Beer Sheva 84105 (Israel); Department of Education, Yamagata University, Yamagata 990-8560 (Japan)

    2008-06-15

    We consider the model of a false-vacuum bubble with a thin wall where the surface energy density is composed of two different components, 'domain-wall' type and 'dust' type, with opposite signs. We find stably oscillating solutions, which we call 'breathing bubbles'. By decay to a lower mass state, such a breathing bubble could become either (i) a child universe or ii) a bubble that 'eats up' the original universe, depending on the sign of the surface energy of the domain-wall component. We also discuss the effect of the finite-thickness corrections to the thin-wall approximation and possible origins of the energy contents of our model.

  13. 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

  14. Bubble Radiation Detection: Current and Future Capability

    SciTech Connect

    Peurrung, Anthony J.; Craig, Richard A.

    1999-11-15

    This report examines two radiation detection technologies (superheated droplet detectors and bubble chambers) in detail and answers the question of how they can be or should be adapted for use in national security applications.

  15. Fabrication of magnetic bubble memory overlay

    NASA Technical Reports Server (NTRS)

    1973-01-01

    Self-contained magnetic bubble memory overlay is fabricated by process that employs epitaxial deposition to form multi-layered complex of magnetically active components on single chip. Overlay fabrication comprises three metal deposition steps followed by subtractive etch.

  16. 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

  17. 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

  18. 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.

  19. Bubble dynamics induced by YAG laser focusing in liquid nitrogen and cryogenic laser processing for particles

    NASA Astrophysics Data System (ADS)

    Watanabe, Soju; Sirato, Takumi; Ota, Masanori; Maeno, Kazuo

    2007-05-01

    The cryogenic liquid with vapor bubbles is regarded as phase-changing and unsteady field with heat and mass transfer phenomena. The cryogenic liquid has a characteristic feature of the small latent heat, surface tension, and viscosity, as compared with those of normal temperature water. As the cryogenic laser processing technology is still under development and research, there have been few reports on laser-matter interactions, for example, on micro/nano particle production. This paper firstly deals with behavior of a cavitation bubble induced by a pulsed YAG laser in liquid nitrogen. The interaction of the bubble with the solid wall has been studied by flow visualization, and, furthermore, the laser-particle processing in liquid nitrogen has been studied. As our research on cryogenic laser-submicron particle processing is in the first stage of experiment, the paper concentrates mainly on the microscopic observation of the laser-processed holes on Al surface and small particles.

  20. Vibration and Nonlinear Resonance in the Break-up of an Underwater Bubble

    E-print Network

    Lai, Lipeng; Fezzaa, Kamel; Zhang, Wendy W; Nagel, Sidney R

    2013-01-01

    We use high-speed X-ray phase-contrast imaging, weakly nonlinear analysis and boundary integral simulations to characterize the final stage of underwater bubble break-up. The X-ray imaging study shows that an initial azimuthal perturbation to the shape of the bubble neck gives rise to oscillations that increasingly distort the cross-section shape. These oscillations terminate in a pinch-off where the bubble surface develops concave regions that contact similar to what occurs when two liquid drops coalesce. We also present a weakly nonlinear analysis that shows that this coalescence-like mode of pinch-off occurs when the initial shape oscillation interferes constructively with the higher harmonics it generates and thus reinforce each other's effects in bringing about bubble break-up. Finally we present numerical results that confirm the weakly nonlinear analysis scenario as well as provide insight into observed shape reversals. They demonstrate that when the oscillations interfere destructively, a qualitativel...

  1. Gravity waves from cosmic bubble collisions

    SciTech Connect

    Salem, Michael P.; Saraswat, Prashant; Shaghoulian, Edgar, E-mail: mpsalem@stanford.edu, E-mail: ps88@stanford.edu, E-mail: edgars@stanford.edu [Stanford Institute for Theoretical Physics and Department of Physics, Stanford University, Stanford, California 94305 (United States)

    2013-02-01

    Our local Hubble volume might be contained within a bubble that nucleated in a false vacuum with only two large spatial dimensions. We study bubble collisions in this scenario and find that they generate gravity waves, which are made possible in this context by the reduced symmetry of the global geometry. These gravity waves would produce B-mode polarization in the cosmic microwave background, which could in principle dominate over the inflationary background.

  2. Gravity waves from cosmic bubble collisions

    E-print Network

    Michael P. Salem; Prashant Saraswat; Edgar Shaghoulian

    2013-02-13

    Our local Hubble volume might be contained within a bubble that nucleated in a false vacuum with only two large spatial dimensions. We study bubble collisions in this scenario and find that they generate gravity waves, which are made possible in this context by the reduced symmetry of the global geometry. These gravity waves would produce B-mode polarization in the cosmic microwave background, which could in principle dominate over the inflationary background.

  3. Quantum nucleation of false-vacuum bubbles

    SciTech Connect

    Fischler, W.; Morgan, D.; Polchinski, J. (Department of Physics, Theory Group, University of Texas, Austin, Texas 78712 (USA))

    1990-04-15

    We show that a small bubble of false vacuum can tunnel to the critical size for inflation, and calculate the amplitude in leading WKB approximation. An initially nonsingular space becomes an exterior space plus a baby universe (which contains the bubble), joined by a black-hole singularity. We work in a Hamiltonian formalism; the corresponding Euclidean bounce is shown to have a degenerate vierbein.

  4. Test ventilation with smoke, bubbles, and balloons

    SciTech Connect

    Pickering, P.L.; Cucchiara, A.L.; McAtee, J.L.; Gonzales, M.

    1987-01-01

    The behavior of smoke, bubbles, and helium-filled balloons was videotaped to demonstrate the mixing of air in the plutonium chemistry laboratories, a plutonium facility. The air-distribution patterns, as indicated by each method, were compared. Helium-filled balloons proved more useful than bubbles or smoke in the visualization of airflow patterns. The replay of various segments of the videotape proved useful in evaluating the different techniques and in identifying airflow trends responsible for air mixing. 6 refs.

  5. Test ventilation with smoke, bubbles, and balloons

    SciTech Connect

    Pickering, P.L.; Cucchiara, A.L.; Gonzales, M.; McAtee, J.L.

    1987-06-01

    The behavior of smoke, bubbles, and helium-filled balloons was videotaped to demonstrate the mixing of air in the plutonium chemistry laboratories a plutonium facility. The air-distribution patterns, as indicated by each method, were compared. Helium-filled balloons proved more useful than bubbles or smoke in the visualization of airflow patterns. The replay of various segments of the videotape proved useful in evaluating the different techniques and in identifying airflow trends responsible for air mixing.

  6. Bubbling AdS black holes

    Microsoft Academic Search

    James T. Liu; Hong Lü; Christopher N. Pope; Justin F. Vázquez-Poritz

    2007-01-01

    We explore the non-BPS analog of `AdS bubbles', which are regular spherically symmetric 1\\/2 BPS geometries in type IIB supergravity. They have regular horizons and can be thought of as bubbling generalizations of non-extremal AdS black hole solutions in five-dimensional gauged supergravity. Due to the appearance of the Heun equation even at the linearized level, various approximation and numerical methods

  7. Astronaut Pedro Duque Watches A Water Bubble

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Aboard the International Space Station (ISS), European Space Agency astronaut Pedro Duque of Spain watches a water bubble float between a camera and himself. The bubble shows his reflection (reversed). Duque was launched aboard a Russian Soyuz TMA-3 spacecraft from the Baikonur Cosmodrome, Kazakhstan on October 18th, along with expedition-8 crew members Michael C. Foale, Mission Commander and NASA ISS Science Officer, and Cosmonaut Alexander Y. Kaleri, Soyuz Commander and flight engineer.

  8. Accelerated Aging Tests of Bubble Devices

    Microsoft Academic Search

    W. J. Tabor; R. Zappulla; A. W. Anderson

    1980-01-01

    Bubble devices are being manufactured by Western Electric Company, as well as a number of other companies, and have been used in the Bell System since 1978. Accelerated aging tests which include temperature-humidity-voltage bias exposure, temperature cycling, vibration and shock, and electromigration degradation of the Al-4.5% Cu conductors have been performed since the earliest bubble device was constructed. Many of

  9. Bubbles, feedback and the intra-cluster medium: three-dimensional hydrodynamic simulations

    E-print Network

    Vicent Quilis; Richard G. Bower; Michael L. Balogh

    2001-09-03

    We use a three dimensional hydrodynamical code to simulate the effect of energy injection on cooling flows in the intracluster medium. Specifically, we compare a simulation of a 10$^{15}$ $M_\\odot$ cluster with radiative cooling only, with a second simulation in which thermal energy is injected 31 $\\kpc$ off-centre, over 64 kpc$^{3}$ at a rate of $4.9\\times 10^{44} \\ergs$ for 50 Myr. The heat injection forms a hot, low density bubble which quickly rises, dragging behind it material from the cluster core. The rising bubble pushes with it a shell of gas which expands and cools. We find the appearance of the bubble in X-ray temperature and luminosity to be in good qualitative agreement with recent {\\it Chandra} observations of cluster cores. Toward the end of the simulation, at 600 Myr, the displaced gas begins to fall back toward the core, and the subsequent turbulence is very efficient at mixing the low and high entropy gas. The result is that the cooling flow is disrupted for up to $\\sim 50$ Myr after the injection of energy ceases. Thus, this mechanism provides a very efficient method for regulating cooling flows, if the injection events occur with a 1:1 duty cycle.

  10. Contact Bubble Bilayers with Flush Drainage

    PubMed Central

    Iwamoto, Masayuki; Oiki, Shigetoshi

    2015-01-01

    Planar lipid bilayers have been used to form stable bilayers into which membrane proteins are reconstituted for measurements of their function under an applied membrane potential. Recently, a lipid bilayer membrane is formed by the apposition of two monolayers that line an oil-electrolyte interface. Here, a bilayer membrane system is developed with picoliter bubbles under mechanically and chemically manipulable conditions. A water bubble lined with a phospholipid monolayer is blown from a glass pipette into an oil phase. Two blowing pipettes are manipulated, and bubbles (each with a diameter of ~ 50??m) are held side by side to form a bilayer, which is termed a contact bubble bilayer. With the electrode implemented in the blowing pipette, currents through the bilayer are readily measured. The intra-bubble pressure is varied with the pressure-controller, leading to various sizes of the bubble and the membrane area. A rapid solution exchange system is developed by introducing additional pressure-driven injection pipettes, and the blowing pipette works as a drain. The solution is exchanged within 20?ms. Also, an asymmetric membrane with different lipid composition of each leaflet is readily formed. Example applications of this versatile method are presented to characterize the function of ion channels. PMID:25772819

  11. A radio characterization of Galactic compact bubbles

    NASA Astrophysics Data System (ADS)

    Ingallinera, A.; Trigilio, C.; Umana, G.; Leto, P.; Noriega-Crespo, A.; Flagey, N.; Paladini, R.; Agliozzo, C.; Buemi, C. S.

    2014-02-01

    We report the radio observations of a subsample of the 428 Galactic compact bubbles discovered at 24 ?m with the MIPSGAL survey. Pervasive through the entire Galactic plane, these objects are thought to be different kinds of evolved stars. The very large majority of the bubbles (˜70 per cent) are however not yet classified. We conducted radio observations with the Expanded Very Large Array at 6 and 20 cm in order to obtain the spectral index of 55 bubbles. We found that at least 70 per cent of the 31 bubbles for which we were effectively able to compute the spectral index (or its lower limit) are likely to be thermal emitters. We were also able to resolve some bubbles, obtaining that the size of the radio nebula is usually similar to the IR size, although our low resolution (with respect to IR images) did not allow further morphological studies. Comparisons between radio flux densities and IR archive data from Spitzer and IRAS suggest that at least three unclassified bubbles can be treated as planetary nebula candidates.

  12. Sea Level Rise in Tuvalu

    NASA Astrophysics Data System (ADS)

    Lin, C. C.; Ho, C. R.; Cheng, Y. H.

    2012-04-01

    Most people, especially for Pacific Islanders, are aware of the sea level change which may caused by many factors, but no of them has deeper sensation of flooding than Tuvaluan. Tuvalu, a coral country, consists of nine low-lying islands in the central Pacific between the latitudes of 5 and 10 degrees south, has the average elevation of 2 meters (South Pacific Sea Level and Climate Monitoring Project, SPSLCMP report, 2006) up to sea level. Meanwhile, the maximum sea level recorded was 3.44m on February 28th 2006 that damaged Tuvaluan's property badly. Local people called the flooding water oozes up out of the ground "King Tide", that happened almost once or twice a year, which destroyed the plant, polluted their fresh water, and forced them to colonize to some other countries. The predictable but uncontrollable king tide had been observed for a long time by SPSLCMP, but some of the uncertainties which intensify the sea level rise need to be analyzed furthermore. In this study, a span of 18 years of tide gauge data accessed from Sea Level Fine Resolution Acoustic Measuring Equipment (SEAFRAME) are compared with the satellite altimeter data accessed from Archiving Validation and Interpretation of Satellite Data in Oceanography (AVISO). All above are processed under the limitation of same time and spatial range. The outcome revealed a 9.26cm difference between both. After the tide gauge data shifted to the same base as altimeter data, the results showed the unknown residuals are always positive under the circumstances of the sea level rise above 3.2m. Apart from uncertainties in observing, the residual reflected unknown contributions. Among the total case number of sea level rise above 3.2m is 23 times, 22 of which were recorded with oceanic warm eddy happened simultaneously. The unknown residual seems precisely matched with oceanic warm eddies and illustrates a clear future approach for Tuvaluan to care for.

  13. Investigation of hydrophilic modification for bubble-free operation in microfluidic systems and micropump applications

    NASA Astrophysics Data System (ADS)

    Le, N. B.; Hsu, Y. C.

    2010-03-01

    This study developed a bubble-free method for microfluidic devices and micropump applications by modifying the wetting characteristic of their chamber surfaces. Two methods of hydrophilic film formation were investigated, that is, microwave plasma surface modification and TiO2 thin film deposition. The evaluation results indicated that TiO2 thin film deposition showed better stability and it was therefore selected to improve the surface wettability and unify the spreading behavior. Different hydrophilic strip shape and strip numbers were investigated and the results indicated that the vertical design with trisection strip gives the best result and effectively discharges the bubbles of microfluidic devices. The results were then applied to a peristaltic micropump and very good results were obtained. That is, the micropump stability and robustness are enhanced significantly. Furthermore, in the pump operation frequency range (i.e. 75 ±10?Hz), bubbles are discharged effectively. The results show that when the micropump operated at frequencies lower than 100?Hz, air bubbles became insignificant; therefore, operation frequencies lower than 100?Hz are considered to be the micropump's stable performance range. From the results it was concluded that bubble formation is also responsible for the flow rate downhill effect.

  14. Measurement of bubbly flow using spatiotemporal filter velocimetry coupled with molecular tagging

    NASA Astrophysics Data System (ADS)

    Hosokawa, Shigeo; Ikeda, Satoshi; Tomiyama, Akio

    2014-04-01

    Spectrum analysis of fluctuating velocity is one way for understanding turbulence characteristics. It is however not easy to acquire accurate velocity data at high data acquisition rates in LDV measurements due to uncontrollable tracer particles. A molecular tagging method is one of the methods to form controllable tags in flow fields. We also developed spatiotemporal filter velocimetry (SFV) which can measure velocity with spatial resolution and accuracy as high as LDV. In this study, the spatiotemporal filter velocimetry was therefore coupled with a molecular tagging method to obtain time-series velocity data with high spatial resolutions ant high data acquisition rates. Photobleaching reaction was used to form molecular tags in a flow field. The developed system was applied to single-phase and bubbly flows in a vertical square duct to examine its applicability to spectrum analysis of single phase and bubbly flows. As a result, we confirmed that the SFV coupled with molecular tagging was of use for accurate velocity measurements at high data acquisition rates, and therefore, for spectrum analysis of fluctuating velocity of turbulent single phase and bubbly flows. The turbulence spectra in the vicinity of the wall showed that the bubbles traveling in the vicinity of the wall enhance turbulence intensity in the vicinity of the wall and the turbulence generated by the bubbles dissipates through a pseudo cascade process.

  15. 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

  16. 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

  17. Volatile bubble growth in a decompressing magmatic system: A many-bubble model

    Microsoft Academic Search

    Ivan L'Heureux

    2009-01-01

    Recently, a new model of volatile bubble growth in magma with coupling to the melt advection field was proposed. In that model, the competitive effects of the other (randomly located) bubbles on the growth dynamics were treated in a mean-field sense. That model predicts the possibility of dynamical transitions to or from inflationary regimes, whereby the growth rate and the

  18. Single-bubble sonoluminescence in sulfuric acid and water: bubble dynamics, stability, and continuous spectra.

    PubMed

    Puente, Gabriela F; García-Martínez, Pablo; Bonetto, Fabián J

    2007-01-01

    We present theoretical calculations of an argon bubble in a liquid solution of 85%wt sulfuric acid and 15%wt water in single-bubble sonoluminescence. We used a model without free parameters to be adjusted. We predict from first principles the region in parameter space for stable bubble evolution, the temporal evolution of the bubble radius, the maximum temperature, pressures, and the light spectra due to thermal emissions. We also used a partial differential equation based model (hydrocode) to compute the temperature and pressure evolutions at the center of the bubble during maximum compression. We found the behavior of this liquid mixture to be very different from water in several aspects. Most of the models in sonoluminescence were compared with water experimental results. PMID:17358260

  19. Numerical rise time calculations for obliquely propagating HF pulses

    NASA Astrophysics Data System (ADS)

    Grubor, D. P.

    1995-03-01

    For planning spread spectrum communication systems over ionspheric HF channels it is important to determine pulse rise times or dispersive bandwidths which are characteristic for wideband propagation. In this paper a numerical technique for the calculation of pulse rise times is proposed. This technique has been developed on the basis of known theoretical results concerning the pulse propagation through a plane stratified ionosphere. The calculations were carried out for several cases of propagation through the lower E-region, using the Jones-Stephenson three-dimensional ray-tracing program. The obtained rise times are in the range from a few microseconds (for the wave-packet reflected from sporadic-E) to several tens of microseconds (for the wave-packet propagating nearly along the Pedersen path in the lower E-region). The results are shown to be in good agreement with those previously obtained by other authors, either by measurements or theoretical approaches.

  20. The rise of "china threat" arguments

    E-print Network

    Ueki, Chikako

    2006-01-01

    The study seeks to explain the rise of "China threat" arguments in the United States and Japan in the 1990s by using three theories of states behavior- realism, organization theory, and democratic peace theory. The rise ...

  1. The effect of bubble clouds on vortex rings

    SciTech Connect

    Sridhar, G.; Katz, J. [Johns Hopkins Univ., Baltimore, MD (United States). Dept. of Mechanical Engineering

    1994-12-31

    The effect of bubble clouds on the structure and strength of vortex rings is studied experimentally using Particle Image Velocimetry. Clouds of microscopic bubbles are introduced in the path of laminar and turbulent vortices and images are recorded of the rings before and after they interact with the bubbles. Upon passing through the cloud, the rings entrain some of the bubbles into the core. Depending on the strength of the ring, bubble size and void fraction within the cloud, these entrained bubbles may cause enhanced diffusion of vorticity of fragmentation of the core. Possible explanations are explored.

  2. Quasiadiabatic approach for laser-induced single-bubble sonoluminescence

    NASA Astrophysics Data System (ADS)

    Sadighi-Bonabi, Rasoul; Razeghi, Fatemeh; Ebrahimi, Homa; Fallahi, Shadi; Lotfi, Erik

    2012-01-01

    The luminescence parameters of laser-induced bubble in the presence of an acoustic field in water are studied. A comparison is made between parameters such as bubble radius, interior temperature, and pressure of the bubble induced by laser and an acoustic field influenced by different driving pressure amplitudes. It is found that the bubble volume induced by laser at the collapse instant is more than 106 times larger than the one induced by an acoustic field. It is also noticed, by increasing the driving pressure amplitude, the bubble radius decreases in both cases, however, the bubble interior pressure and temperature increase.

  3. The 1916 Rising: Personalities & Perspectives

    NSDL National Science Digital Library

    As a formative and pivotal moment in Irish history, the 1916 Rising has commanded the attention of many historians over the past nine decades. Recently, the National Library of Ireland created this engaging online exhibit about these events. In total, this resource includes over 500 images drawn from the Library's books, newspapers, drawings, and proclamations. The actual exhibit itself moves visitors through sections that provide a basic outline of Irish history, and then move through the events over the following centuries that would lead up to the Uprising itself. Perhaps the finest moments of the collection are contained within the last few sections, where visitors learn about the fate of those who were arrested due to their activities during the Uprising.

  4. Financial Bubbles, Real Estate Bubbles, Derivative Bubbles, and the Financial and Economic Crisis

    NASA Astrophysics Data System (ADS)

    Sornette, Didier; Woodard, Ryan

    The financial crisis of 2008, which started with an initially well-defined epicenter focused on mortgage backed securities (MBS), has been cascading into a global economic recession, whose increasing severity and uncertain duration has led and is continuing to lead to massive losses and damage for billions of people. Heavy central bank interventions and government spending programs have been launched worldwide and especially in the USA and Europe, with the hope to unfreeze credit and bolster consumption. Here, we present evidence and articulate a general framework that allows one to diagnose the fundamental cause of the unfolding financial and economic crisis: the accumulation of several bubbles and their interplay and mutual reinforcement have led to an illusion of a "perpetual money machine" allowing financial institutions to extract wealth from an unsustainable artificial process. Taking stock of this diagnostic, we conclude that many of the interventions to address the so-called liquidity crisis and to encourage more consumption are ill-advised and even dangerous, given that precautionary reserves were not accumulated in the "good times" but that huge liabilities were. The most "interesting" present times constitute unique opportunities but also great challenges, for which we offer a few recommendations.

  5. Superphenix set to rise again

    SciTech Connect

    Dorozynski, A.

    1993-10-15

    Superphenix, France's seemingly jinxed fast breeder reactor, which has not produced a single kilowatt of energy in more than 3 years, looks set to rise up next year like the mythical bird it is named after. The $5 billion reactor, the largest fast breeder in the world, has just been given the seal of approval by a public commission ordered by the government to look at the pros and cons of restarting. It still has hoops to jump through: a safety check and approval from the ministries of industries and environment. But the consortium of French, Italian, and German power utilities that run the plant are confident they can get it running by next summer. The Superphenix that rises out of the ashes will, however, be a different species of bird from the one planned 20 years ago. The consortium plans to turn the reactor into a debreeder, one that will incinerate more plutonium than it produces and so eat into Europe's plutonium stockpile. Calculations by Superphenix staff and the Atomic Energy Commission indicate that a plutonivorous fast breeder could incinerate 15 to 25 kilograms of plutonium while producing 1 billion kilowatt-hours of electricity-scarcely enough to make a dent in the tonnes of plutonium produced by Electricite de France's reactors each year. The Superphenix consortium is anxious to get the reactor back on line. The annual cost of upkeep and repair of the idle plant and salaries for its 700 staff may reach $140 million this year, 20% more than if the plant was running normally. If restarted, the existing core and a second one ready on the shelf will generate electricity worth $1.3 billion.

  6. It takes three to tango: 2. Bubble dynamics in basaltic volcanoes and ramifications for modeling normal Strombolian activity

    NASA Astrophysics Data System (ADS)

    Suckale, Jenny; Hager, Bradford H.; Elkins-Tanton, Linda T.; Nave, Jean-Christophe

    2010-07-01

    This is the second paper of two that examine numerical simulations of buoyancy-driven flow in the presence of large viscosity contrasts. In the first paper, we demonstrated that a combination of three numerical tools, an extended ghost fluid type method, the level set approach, and the extension velocity technique, accurately simulates complex interface dynamics in the presence of large viscosity contrasts. In this paper, we use this threefold numerical method to investigate bubble dynamics in the conduits of basaltic volcanos with a focus on normal Strombolian eruptions. Strombolian type activity, named after the famously episodic eruptions at Stromboli volcano, is characterized by temporally discrete fountains of incandescent clasts. The mildly explosive nature of normal Strombolian activity, as compared to more effusive variants of basaltic volcanism, is related to the presence of dissolved gas in the magma, yielding a complex two-phase flow problem. We present a detailed scaling analysis allowing identification of the pertinent regime for a given flow problem. The dynamic interactions between gas and magma can be classified into three nondimensional regimes on the basis of bubble sizes and magma viscosity. Resolving the fluid dynamics at the scale of individual bubbles is not equally important in all three regimes: As long as bubbles remain small enough to be spherical, their dynamic interactions are limited compared to the rich spectrum of coalescence and breakup processes observed for deformable bubbles, in particular, once inertia ceases to be negligible. One key finding in our simulations is that both large gas bubbles and large conduit-filling gas pockets ("slugs") are prone to dynamic instabilities that lead to their rapid breakup during buoyancy-driven ascent. We provide upper bound estimates for the maximum stable bubble size in a given magmatic system and discuss the ramifications of our results for two commonly used models of normal Strombolian type activity, the rise-speed-dependent model and the collapsing foam model.

  7. Rest frame of bubble nucleation

    SciTech Connect

    Garriga, Jaume [Departament de Física Fondamental i Institut de Ciencies del Cosmos, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona (Spain); Kanno, Sugumi [Institute of Cosmology, Department of Physics and Astronomy, Tufts University, Medford, Massachusetts 02155 (United States); Tanaka, Takahiro, E-mail: jaume.garriga@ub.edu, E-mail: sugumi@cosmos.phy.tufts.edu, E-mail: tanaka@yukawa.kyoto-u.ac.jp [Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502 (Japan)

    2013-06-01

    Vacuum bubbles nucleate at rest with a certain critical size and subsequently expand. But what selects the rest frame of nucleation? This question has been recently addressed in [1] in the context of Schwinger pair production in 1+1 dimensions, by using a model detector in order to probe the nucleated pairs. The analysis in [1] showed that, for a constant external electric field, the adiabatic ''in'' vacuum of charged particles is Lorentz invariant, (and in this) case pairs tend to nucleate preferentially at rest with respect to the detector. Here, we sharpen this picture by showing that the typical relative velocity between the frame of nucleation and that of the detector is at most of order ?v ? S{sub E}{sup ?1/3} << 1. Here, S{sub E} >> 1 is the action of the instanton describing pair creation. The bound ?v coincides with the minimum uncertainty in the velocity of a non-relativistic charged particle embedded in a constant electric field. A velocity of order ?v is reached after a time interval of order ?t ? S{sub E}{sup ?1/3}r{sub 0} << r{sub 0} past the turning point in the semiclassical trajectory, where r{sub 0} is the size of the instanton. If the interaction takes place in the vicinity of the turning point, the semiclassical description of collision does not apply. Nonetheless, we find that even in this case there is still a strong asymmetry in the momentum transferred from the nucleated particles to the detector, in the direction of expansion after the turning point. We conclude that the correlation between the rest frame of nucleation and that of the detector is exceedingly sharp.

  8. Herds of methane chambers grazing bubbles

    NASA Astrophysics Data System (ADS)

    Grinham, Alistair; Dunbabin, Matthew

    2014-05-01

    Water to air methane emissions from freshwater reservoirs can be dominated by sediment bubbling (ebullitive) events. Previous work to quantify methane bubbling from a number of Australian sub-tropical reservoirs has shown that this can contribute as much as 95% of total emissions. These bubbling events are controlled by a variety of different factors including water depth, surface and internal waves, wind seiching, atmospheric pressure changes and water levels changes. Key to quantifying the magnitude of this emission pathway is estimating both the bubbling rate as well as the areal extent of bubbling. Both bubbling rate and areal extent are seldom constant and require persistent monitoring over extended time periods before true estimates can be generated. In this paper we present a novel system for persistent monitoring of both bubbling rate and areal extent using multiple robotic surface chambers and adaptive sampling (grazing) algorithms to automate the quantification process. Individual chambers are self-propelled and guided and communicate between each other without the need for supervised control. They can maintain station at a sampling site for a desired incubation period and continuously monitor, record and report fluxes during the incubation. To exploit the methane sensor detection capabilities, the chamber can be automatically lowered to decrease the head-space and increase concentration. The grazing algorithms assign a hierarchical order to chambers within a preselected zone. Chambers then converge on the individual recording the highest 15 minute bubbling rate. Individuals maintain a specified distance apart from each other during each sampling period before all individuals are then required to move to different locations based on a sampling algorithm (systematic or adaptive) exploiting prior measurements. This system has been field tested on a large-scale subtropical reservoir, Little Nerang Dam, and over monthly timescales. Using this technique, localised bubbling zones on the water storage were found to produce over 50,000 mg m-2 d-1 and the areal extent ranged from 1.8 to 7% of the total reservoir area. The drivers behind these changes as well as lessons learnt from the system implementation are presented. This system exploits relatively cheap materials, sensing and computing and can be applied to a wide variety of aquatic and terrestrial systems.

  9. The dynamics of periodically driven bubble clouds

    NASA Astrophysics Data System (ADS)

    Smereka, P.; Banerjee, S.

    1988-12-01

    An averaged two-fluid model is used to study the motion of a cloud of bubbles. The linearized equations of motion are shown to be a wave equation with both dissipation and dispersion. The fully nonlinear equations are also examined and it is demonstrated that the cutoff frequency of the cloud is equal to the natural frequency of a single bubble. The steady linear response of a periodically driven bubble cloud is then derived. Resonances are seen to arise when the driving frequency is below the cutoff frequency. The inner core of the cloud is shielded by an outer layer when the driving is above the cutoff frequency. The nonlinear dynamics of periodically driven bubble clouds is studied numerically. It is found that the cutoff frequency is crucial in determining whether or not the cloud will behave like a single bubble. Also, under some conditions the cloud is seen to behave like a damped and driven single-degree-of-freedom Hamiltonian system.

  10. 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

  11. First dark matter search results from a 4-kg CF3I bubble chamber operated in a deep underground site

    NASA Astrophysics Data System (ADS)

    Behnke, E.; Behnke, J.; Brice, S. J.; Broemmelsiek, D.; Collar, J. I.; Conner, A.; Cooper, P. S.; Crisler, M.; Dahl, C. E.; Fustin, D.; Grace, E.; Hall, J.; Hu, M.; Levine, I.; Lippincott, W. H.; Moan, T.; Nania, T.; Ramberg, E.; Robinson, A. E.; Sonnenschein, A.; Szydagis, M.; Vázquez-Jáuregui, E.

    2012-09-01

    New data are reported from the operation of a 4.0-kg CF3I bubble chamber in the 6800-foot-deep SNOLAB underground laboratory. The effectiveness of ultrasound analysis in discriminating alpha-decay background events from single nuclear recoils has been confirmed, with a lower bound of >99.3% rejection of alpha-decay events. Twenty single nuclear recoil event candidates and three multiple bubble events were observed during a total exposure of 553 kg-days distributed over three different bubble nucleation thresholds. The effective exposure for single bubble recoil-like events was 437.4 kg-days. A neutron background internal to the apparatus, of known origin, is estimated to account for five single nuclear recoil events and is consistent with the observed rate of multiple bubble events. The remaining excess of single bubble events exhibits characteristics indicating the presence of an additional background. These data provide new direct detection constraints on WIMP-proton spin-dependent scattering for WIMP masses >20GeV/c2 and demonstrate significant sensitivity for spin-independent interactions.

  12. Bubbles in planetary nebulae and clusters of galaxies: instabilities at bubble' fronts

    NASA Astrophysics Data System (ADS)

    Soker, Noam

    2004-05-01

    I study the stability of off-center low-density more or less spherical (fat) bubbles in clusters of galaxies and in planetary nebulae (PNs) to Rayleigh-Taylor (RT) instability. As the bubble expands and decelerates, the interface between the low-density bubble's interior and the dense shell formed from the accreted ambient medium is RT-stable. If, however, in a specific direction the density decreases such that this segment is accelerated by the pressure inside the bubble, then this accelerated region is RT-unstable. The outermost region, relative to the center of the system, is the most likely to become unstable because there the density gradient is the steepest. Using simple analytical analysis, I find that off-center fat bubbles in PNs are much less stable than in clusters. In PNs bubbles become unstable when they are very small relative to their distance from the center; they can be stabilized somewhat if the mass loss rate from the stellar progenitor decreases for a time, such that the negative density gradient is much shallower. In clusters fat bubbles become unstable when their size is comparable to their distance from the center. I discuss some implications of this instability in clusters and in PNs.

  13. Bubble detector characterization for space radiation.

    PubMed

    Green, A R; Andrews, H R; Bennett, L G I; Clifford, E T H; Ing, H; Jonkmans, G; Lewis, B J; Noulty, R A; Ough, E A

    2005-01-01

    In light of the importance of the neutron contribution to the dose equivalent received by space workers in the near-Earth radiation environment, there is an increasing need for a personal dosimeter that is passive in nature and able to respond to this neutron field in real time. Recent Canadian technology has led to the development of a bubble detector, which is sensitive to neutrons, but insensitive to low linear energy transfer (LET) radiation. By changing the composition of the bubble detector fluid (or "superheat"), the detectors can be fabricated to respond to different types of radiation. This paper describes a preliminary ground-based research effort to better characterize the bubble detectors of different compositions at various charged-particle accelerator facilities, which are capable of simulating the space radiation field. PMID:15835053

  14. How Snapping Shrimp Snap: Through Cavitating Bubbles

    NASA Astrophysics Data System (ADS)

    Versluis, Michel; Schmitz, Barbara; von der Heydt, Anna; Lohse, Detlef

    2000-09-01

    The snapping shrimp (Alpheus heterochaelis) produces a loud snapping sound by an extremely rapid closure of its snapper claw. One of the effects of the snapping is to stun or kill prey animals. During the rapid snapper claw closure, a high-velocity water jet is emitted from the claw with a speed exceeding cavitation conditions. Hydrophone measurements in conjunction with time-controlled high-speed imaging of the claw closure demonstrate that the sound is emitted at the cavitation bubble collapse and not on claw closure. A model for the bubble dynamics based on a Rayleigh-Plesset-type equation quantitatively accounts for the time dependence of the bubble radius and for the emitted sound.

  15. Mixture segregation by an inertial cavitation bubble.

    PubMed

    Grossier, R; Louisnard, O; Vargas, Y

    2007-04-01

    Pressure diffusion is a mass diffusion process forced by pressure gradients. It has the ability to segregate two species of a mixture, driving the densest species toward high pressure zones, but requires very large pressure gradients to become noticeable. An inertial cavitation bubble develops large pressure gradients in its vicinity, especially as the bubble rebounds at the end of its collapse, and it is therefore expected that a liquid mixture surrounding such a bubble would become segregated. Theory developed in an earlier paper shows that this is indeed the case for sufficiently large molecules or nano-particles. The main theoretical results are recalled and a possible implication of this segregation phenomenon on the well-known cavitation-enhanced crystals nucleation is proposed. PMID:17208505

  16. When Do Bubbles Cause a Floating Body To Sink?

    ERIC Educational Resources Information Center

    Denardo, Bruce; Pringle, Leonard; DeGrace, Carl; McGuire, Michael

    2001-01-01

    Describes qualitative lecture demonstrations that show that bubbles can indeed sink a body, including the case of ice in water. Presents a quantitative experiment to determine the density of bubbly water required to sink a spherical body. (Author/YDS)

  17. Measurement of bubble velocity using spatial filter velocimetry

    NASA Astrophysics Data System (ADS)

    Hosokawa, Shigeo; Matsumoto, Takaaki; Tomiyama, Akio

    2013-06-01

    Spatial filter velocimetry (SFV) based on spatial filtering of time-series particle images proposed by Hosokawa and Tomiyama is applied to a bubble column to examine its applicability to bubble velocity measurement. The edge detection process is added in the SFV processing to reduce the size of image pattern and to obtain accurate velocity data. It is demonstrated that SFV is able to measure the bubble velocity in various spatial scales with the same accuracy as PTV. The measured mean bubble velocity does not depend on the interrogation size in the measurements. To the contrary, the standard deviation of measured bubble velocity becomes higher as the interrogation size decreases due to the superposition of interfacial wave velocity on the measured velocity. Simultaneous measurement of bubble and liquid velocities is also carried out for a planar bubble plume. The results clearly show that SFV can measure bubble and liquid velocities simultaneously.

  18. Size limits the formation of liquid jets during bubble bursting.

    PubMed

    Lee, Ji San; Weon, Byung Mook; Park, Su Ji; Je, Jung Ho; Fezzaa, Kamel; Lee, Wah-Keat

    2011-01-01

    A bubble reaching an air-liquid interface usually bursts and forms a liquid jet. Jetting is relevant to climate and health as it is a source of aerosol droplets from breaking waves. Jetting has been observed for large bubbles with radii of R?100??m. However, few studies have been devoted to small bubbles (R<100??m) despite the entrainment of a large number of such bubbles in sea water. Here we show that jet formation is inhibited by bubble size; a jet is not formed during bursting for bubbles smaller than a critical size. Using ultrafast X-ray and optical imaging methods, we build a phase diagram for jetting and the absence of jetting. Our results demonstrate that jetting in bubble bursting is analogous to pinching-off in liquid coalescence. The coalescence mechanism for bubble bursting may be useful in preventing jet formation in industry and improving climate models concerning aerosol production. PMID:21694715

  19. Microstructure, morphology and lifetime of armored bubbles exposed to surfactants

    E-print Network

    Anand Bala Subramaniam; Cecile Mejean; Manouk Abkarian; Howard A. Stone

    2006-02-16

    We report the behavior of particle-stabilized bubbles (armored bubbles) when exposed to various classes and concentrations of surfactants. The bubbles are non-spherical due to the jamming of the particles on the interface and are stable to dissolution prior to the addition of surfactant. We find that the dissolving bubbles exhibit distinct morphological, microstructural, and lifetime changes, which correlate with the concentration of surfactant employed. For low concentrations of surfactant an armored bubble remains non-spherical while dissolving, while for concentrations close to and above the surfactant CMC a bubble reverts to a spherical shape before dissolving. We propose a microstructural interpretation, supported by our experimental observations of particle dynamics on the bubble interface, that recognizes the role of interfacial jamming and stresses in particle stabilization and surfactant-mediated destabilization of armored bubbles.

  20. Acoustical bubble trapper applied to hemodialysis.

    PubMed

    Palanchon, P; Birmelé, B; Tranquart, F

    2008-04-01

    Gaseous microemboli can arise in extracorporeal lines and devices such as dialysis machines. They are associated with severe pulmonary side effects in patients undergoing chronic hemodialysis sessions. The goal of this study was to develop a gaseous emboli trapper using ultrasound waves to remove any air bubble from the tubing system before they reach the patient. A homemade bubble trapper, developed in the laboratory, consists of a Perspex block containing a main channel connected to the tubing of a hemodialysis machine and a second subchannel positioned perpendicularly to the main one, used to trap the air microemboli. The microemboli flowing in the main channel were insonified through an acoustic window with an ultrasound wave, at a frequency of 500 kHz and with a maximal acoustic pressure of 500 kPa, generated by a single-element transducer positioned 3 cm away from the main flow. The radiation force induced by the ultrasound beam acts directly on the flowing air emboli, by pushing them into the subchannel. Two Doppler probes operating both at 2 MHz, connected to a DWL Doppler machine were placed before and after the bubble trapper to count sequentially the number of embolic events. The flow of the machine was varied between 200 mL/min and 500 mL/min. Depending on the flow velocity, the number of microembolic signals (MES) detected by the Doppler probes before and after the trapping system was identical and ranged from 5 to 150 MES/min in absence of the ultrasound irradiation. When the air bubble trapper was activated, a reduction of the number of MES, up to 70%, was achieved. Doppler recordings suggest that the circulating bubbles were either fragmented into smaller bubble fragments or directly got pushed into the second subchannel where they were collected. This simple approach using an ultrasound-based trapping system was shown to operate adequately with the current settings and can be used to filter air microemboli. PMID:17996355

  1. The effect of water temperature on air entrainment, bubble plumes, and surface foam in a laboratory breaking-wave analog

    NASA Astrophysics Data System (ADS)

    Callaghan, A. H.; Stokes, M. D.; Deane, G. B.

    2014-11-01

    Air-entraining breaking waves form oceanic whitecaps and play a key role in climate regulation through air-sea bubble-mediated gas transfer, and sea spray aerosol production. The effect of varying sea surface temperature on air entrainment, subsurface bubble plume dynamics, and surface foam evolution intrinsic to oceanic whitecaps has not been well studied. By using a breaking wave analog in the laboratory over a range of water temperatures (Tw = 5°C to Tw = 30°C) and different source waters, we have examined changes in air entrainment, subsurface bubble plumes, and surface foam evolution over the course of a breaking event. For filtered seawater, air entrainment was estimated to increase by 6% between Tw = 6°C and Tw = 30°C, driven by increases of about 43% in the measured surface roughness of the plunging water sheet. After active air entrainment, the rate of loss of air through bubble degassing was more rapid at colder water temperatures within the first 0.5 s of plume evolution. Thereafter, the trend reversed and bubbles degassed more quickly in warmer water. The largest observed temperature-dependent differences in subsurface bubble distributions occurred at radii greater than about 700 ?m. Temperature-dependent trends observed in the subsurface bubble plume were mirrored in the temporal evolution of the surface whitecap foam area demonstrating the intrinsic link between surface whitecap foam and the subsurface bubble plume. Differences in foam and plume characteristics due to different water sources were greater than the temperature dependencies for the filtered seawater examined.

  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. Bubbling in delay-coupled lasers

    E-print Network

    V. Flunkert; O. D'Huys; J. Danckaert; I. Fischer; E. Schoell

    2010-11-19

    We theoretically study chaos synchronization of two lasers which are delay-coupled via an active or a passive relay. While the lasers are synchronized, their dynamics is identical to a single laser with delayed feedback for a passive relay and identical to two delay-coupled lasers for an active relay. Depending on the coupling parameters the system exhibits bubbling, i.e., noise-induced desynchronization, or on-off intermittency. We associate the desynchronization dynamics in the coherence collapse and low frequency fluctuation regimes with the transverse instability of some of the compound cavity's antimodes. Finally, we demonstrate how, by using an active relay, bubbling can be suppressed.

  4. Particle removal by a single cavitation bubble

    NASA Astrophysics Data System (ADS)

    Xu, Ming; Ji, Chen; Zou, Jun; Ruan, XiaoDong; Fu, Xin

    2014-04-01

    In the paper, the behavior of the particle acted by the oscillating bubble is studied using a high-speed video camera. The bubble is generated using a very low voltage of 55 V. Images are captured at a speed of 15000 fps (frames per second). It is found that the velocity of the particle is dependent on the liquid viscosity, particle size, and tube diameter. Particle velocity decreases with the increase of the glycron-water mixture viscosity. A model is presented to predict the velocity and verified by experimental results. These observations may be beneficial for the application in medical treatment.

  5. Weighting bubbles in group field theory

    NASA Astrophysics Data System (ADS)

    Baratin, Aristide; Freidel, Laurent; Gurau, Razvan

    2014-07-01

    Group field theories (GFT) are higher dimensional generalizations of matrix models whose Feynman diagrams are dual to triangulations. Here we propose a modification of GFT models that includes extra field indices keeping track of the bubbles of the graphs in the Feynman evaluations. In dimension three, our model exhibits new symmetries, interpreted as the action of the vertex translations of the triangulation. The extra field indices have an elegant algebraic interpretation: they encode the structure of a semisimple algebra. Remarkably, when the algebra is chosen to be associative, the new structure contributes a topological invariant from each bubble of the graph to the Feynman amplitudes.

  6. Analysis of Strategic Petroleum Reserve bubble point pressure data

    SciTech Connect

    Lott, S.E.

    1996-05-01

    Mathematical models are presented to predict the bubble pressure for 481 cavern oil samples withdrawn from the Bryan Mound, West Hackberry, Big Hill, and Bayou Choctaw Strategic Petroleum Reserve sites. The predicted bubble point pressure is compared to experimentally measured bubble point pressure to resolve potential sources of error introduced to the experimental analysis. In order to gain a higher level of confidence in the measurement of the bubble point pressure, a stochastic analysis of the data is recommended in the future.

  7. Micro bubble manipulation towards single cell handling tool

    Microsoft Academic Search

    Yuejun Zhao; Sung Kwon Cho

    2005-01-01

    We report a series of micro air bubble manipulations (transporting, merging and eliminating of air bubbles) in two-dimensional microchannels filled with a water solution. Air bubbles (~500 nano liters in volume) are driven by electrowetting-on-dielectric (EWOD) principle. By sequentially energizing an array of electrodes covered with dielectric layers, air bubbles can be transported along a programmed path, merged into a

  8. Counting Rises, Levels and Drops in Compositions 1 Counting Rises, Levels and

    E-print Network

    Heubach, Silvia

    Counting Rises, Levels and Drops in Compositions 1 Counting Rises, Levels and Drops in Compositions Mansour Department of Mathematics, Haifa University, Israel #12;Counting Rises, Levels and Drops;Counting Rises, Levels and Drops in Compositions 3 Definitions · A composition = 12 . . . m of n N

  9. Rhetoric, Risk, and Markets: The Dot-Com Bubble

    ERIC Educational Resources Information Center

    Goodnight, G. Thomas; Green, Sandy Edward, Jr.

    2010-01-01

    Post-conventional economic theories are assembled to inquire into the contingent, mimetic, symbolic, and material spirals unfolding the dot-com bubble, 1992-2002. The new technologies bubble is reconstructed as a rhetorical movement across the practices of the hybrid market-industry risk culture of communications. The legacies of the bubble task…

  10. CFD Simulation of Condensing Vapor Bubble using VOF Model

    Microsoft Academic Search

    Seong-Su Jeon; Seong-Jin Kim; Goon-Cherl Park

    2009-01-01

    In this study, direct numerical simulation for the bubble condensation in the subcooled boiling flow was performed. The main goal was to develop the CFD modeling for the bubble condensation and to evaluate the accuracy of the VOF model with the developed CFD modeling. CFD modeling for the bubble condensation was developed by modeling the source terms in the governing

  11. 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

  12. Logistic Growth Models for Analysis of Stocks Markets Bubbles

    Microsoft Academic Search

    Stasys Girdzijauskas; Dalia Streimikiene

    2008-01-01

    The article deals with stock markets bubbles and analyses the ?rigin of their formation. The well-known and widely discussed burbles in assets markets were analysed and compared trying to define the main features, causes and signals of such bubbles creation: Dotcom, Telecom, Health South Corporation, NASDAQ etc. For the analysis of stock market bubbles formation mechanism the logistic growth models

  13. The stability of the flow in a laminar separation bubble

    Microsoft Academic Search

    Tai Ran Niew

    1993-01-01

    This dissertation reports a study into the underlying concepts used to analyze incompressible laminar separation bubbles. The suggestion that absolute instability could play a role in bubble flows was further developed, and was the focal point of this project. From a review of previous work and preliminary experiments on a backward faxing step, it was suggested that for some bubbles

  14. Forces on ellipsoidal bubbles in a turbulent shear layer

    Microsoft Academic Search

    Barry Ford; Eric Loth

    1998-01-01

    The objective of this research was to gain fundamental knowledge of the drag and lift forces on ellipsoidal air bubbles in water in a turbulent flow. This was accomplished by employing a cinematic two-phase particle image velocimetry (PIV) system to evaluate bubbly flow in a two-stream, turbulent, planar free shear layer of filtered tap water. Ellipsoidal air bubbles with nominal

  15. OH 0739-14: an old star blowing bubbles

    Microsoft Academic Search

    B. Reipurth

    1987-01-01

    Two large bipolar bubbles emanating from the OH\\/IR star OH 0739-14 have been discovered. Interference filter images show that the bubbles are emission-line objects, and longslit spectra reveal that the bubbles are expanding, with a radial velocity-difference between the bubblefronts of over 200 km\\/sec.

  16. Adaptive Bubble Pulse Cancellation From Underwater Explosive Charge Acoustic Signals

    Microsoft Academic Search

    Feng-Xiang Ge; Yan Zhang; Zhenglin Li; Renhe Zhang

    2011-01-01

    Explosive charges are widely used as sound sources in underwater acoustic experiments. Unfortunately, the received shock wave in the observation is often corrupted by a series of bubble pulses. Canceling these bubble pulses can greatly enhance thequalityoftheobservationandwillbehelpfulformanypractical applications. A method based on the adaptive filtering is presented to fit the bubble pulses in the observation, in which the filter co-

  17. Use of a bubble tiltmeter as a horizontal seismometer

    Microsoft Academic Search

    W. F. Miller; R. J. Geller; S. Stein

    1978-01-01

    A bubble tiltmeter has been used as a horizontal seismometer. With the appropriate filters, the bubble system has good response for displacement over the passband of conventional seismometers (from about 10 Hz to 200 s), and for tilt from about 1 Hz to DC. The accuracy of the response is confirmed by comparing the filtered bubble output to conventional seismic

  18. Reducing bubbles in glass coatings improves electrical breakdown strength

    NASA Technical Reports Server (NTRS)

    Banks, B.

    1968-01-01

    Helium reduces bubbles in glass coatings of accelerator grids for ion thrustors. Fusing the coating in a helium atmosphere creates helium bubbles in the glass. In an argon atmosphere, entrapped helium diffuses out of the glass and the bubbles collapse. The resultant coating has a substantially enhanced electrical breakdown strength.

  19. Bubble suspension rheology and implications for conduit flow

    Microsoft Academic Search

    E. W. Llewellin; M. Manga

    2005-01-01

    Bubbles are ubiquitous in magma during eruption and influence the rheology of the suspension. Despite this, bubble-suspension rheology is routinely ignored in conduit-flow and eruption models, potentially impairing accuracy and resulting in the loss of important phenomenological richness. The omission is due, in part, to a historical confusion in the literature concerning the effect of bubbles on the rheology of

  20. Bubble development in explosive silicic eruptions: insights from pyroclast vesicularity textures from Raoul volcano (Kermadec arc)

    NASA Astrophysics Data System (ADS)

    Rotella, Melissa D.; Wilson, Colin J. N.; Barker, Simon J.; Cashman, Katharine V.; Houghton, Bruce F.; Wright, Ian C.

    2014-08-01

    Critical to understanding explosive eruptions is establishing how accurately representative pyroclasts are of processes during magma vesiculation and fragmentation. Here, we present data on densities, and vesicle size and number characteristics, for representative pyroclasts from six silicic eruptions of contrasting size and style from Raoul volcano (Kermadec arc). We use these data to evaluate histories of bubble nucleation, coalescence, and growth in explosive eruptions and to provide comparisons with pumiceous dome carapace material. Density/vesicularity distributions show a scarcity of pyroclasts with ˜65-75 % vesicularity; however, pyroclasts closest to this vesicularity range have the highest bubble number density (BND) values regardless of eruptive intensity or style. Clasts with vesicularities greater than this 65-75 % "pivotal" vesicularity range have decreasing BNDs with increasing vesicularities, interpreted to reflect continuing bubble growth and coalescence. Clasts with vesicularities less than the pivotal range have BNDs that decrease with decreasing vesicularity and preserve textures indicative of processes such as stalling and open system degassing prior to vesiculation in a microlite-rich magma, or vesiculation during slow ascent of degassing magma. Bubble size distributions (BSDs) and BNDs show variations consistent with 65-75 % representing the vesicularity at which vesiculating magma is most likely to undergo fragmentation, consistent with the closest packing of spheres. We consider that the observed vesicularity range may reflect the development of permeability in the magma through shearing as it flows through the conduit. These processes can act in concert with multiple nucleation events, generating a situation of heterogeneous bubble populations that permit some regions of the magma to expand and bubbles to coalesce with other regions in which permeable networks are formed. Fragmentation preserves the range in vesicularity seen as well as any post-fragmentation/pre-quenching expansion which may have occurred. We demonstrate that differing density pyroclasts from a single eruption interval can have widely varying BND values corresponding to the degree of bubble maturation that has occurred. The modal density clasts (the usual targets for vesicularity studies) have likely undergone some degree of bubble maturation and are therefore may not be representative of the magma at the onset of fragmentation.