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Sample records for bubble rise characteristics

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

    SciTech Connect

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

    1999-10-01

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

  2. An Experimental Investigation of Bubble Rise Characteristics in a Crystal Suspended NonNewtonian 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. Cusped Bubbles Rising through Polyelectrolyte Solutions

    NASA Astrophysics Data System (ADS)

    Belmonte, Andrew; Sostarecz, Michael

    2000-11-01

    It is well known that a bubble rising in a polymer fluid can have a cusp-like tail. We report on an experimental study of bubbles rising through solutions of glycerol/water with the addition of the polymer xanthan gum, a polyelectrolyte which becomes more rigid as the free ion concentration is increased. The addition of salt also decreases the elasticity of the xanthan gum solutions, and we observe its effects on the velocity and shape of the cusped bubble.

  5. Dynamics of Bubbles Rising in Finite and Infinite Media

    SciTech Connect

    C.C. Maneri; P.F. Vassallo

    2000-10-27

    The dynamic behavior of single bubbles rising in quiescent liquid Suva (R134a) in a duct has been examined through the use of a high speed video system. Size, shape and velocity measurements obtained with the video system reveal a wide variety of characteristics for the bubbles as they rise in both finite and infinite media. This data, coupled with previously published data for other working fluids, has been used to assess and extend a rise velocity model given by Fan and Tsuchiya. As a result of this assessment, a new rise velocity model has been developed which maintains the physically consistent characteristics of the surface tension in the distorted bubbly regime. In addition, the model is unique in that it covers the entire range of bubble sizes contained in the spherical, distorted and planar slug regimes.

  6. Liquid jet pumped by rising gas bubbles

    NASA Technical Reports Server (NTRS)

    Hussain, N. A.; Siegel, R.

    1975-01-01

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

  7. Liquid jet pumped by rising gas bubbles

    NASA Technical Reports Server (NTRS)

    Hussain, N. A.; Siegel, R.

    1975-01-01

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

  8. Experimental study on wake structure of single rising clean bubble

    NASA Astrophysics Data System (ADS)

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

    2007-11-01

    Wake structure of clean bubble rising in quiescent silicone oil solution of photochromic dye is experimentally studied. A single bubble is generated, immediately after UV sheet light illuminates the part of the liquid just above the bubble generation nozzle in order to activate photochromic dye. Once the bubble passes across the colored part of the liquid, the bubble is accompanied by some portion of activated dye tracers; hence the flow structure in the rear of the single rising bubble is visualized. We capture stereo images of both wake structure and bubble motion. We study how wake structure changes with the increase in bubble size. We observe the stable axisymmetric wake structure, which is called `standing eddy' when bubble size is relatively small, and then wake structure becomes unstable and starts to oscillate with the increase in bubble size. With further increase in bubble size, a pair of streamwise vortices, which is called `double thread', is observed. We discuss in detail this transition from the steady wake to unsteady wake structure, especially double thread wake development and hairpin vortices shedding, in relation to the transition from rectilinear to spiral or zigzag bubble motions.

  9. Rise of Air Bubbles in Aircraft Lubricating Oils

    NASA Technical Reports Server (NTRS)

    Robinson, J. V.

    1950-01-01

    Lubricating and antifoaming additives in aircraft lubricating oils may impede the escape of small bubbles from the oil by forming shells of liquid with a quasi-solid or gel structure around the bubbles. The rates of rise of small air bubbles, up to 2 millimeters in diameter, were measured at room temperature in an undoped oil, in the same oil containing foam inhibitors, and in an oil containing lubricating additives. The apparent diameter of the air bubbles was measured visually through an ocular micrometer on a traveling telescope. The bubbles in the undoped oil obeyed Stokes' Law, the rate of rise being proportional to the square of the apparent diameter and inversely proportional to the viscosity of the oil. The bubbles in the oils containing lubricating additives or foam inhibitors rose more slowly than the rate predicted by Stokes 1 Law from the apparent diameter, and the rate of rise decreased as the length of path the bubbles traveled increased. A method is derived to calculate the thickness of the liquid shell which would have to move with the bubbles in the doped oils to account for the abnoi'I!l8.lly slow velocity. The maximum thickness of this shell, calculated from the velocities observed, was equal to the bubble radius.

  10. Freon bubble rise measurements in a vertical rectangular duct

    SciTech Connect

    Vassallo, P.F.; Symolon, P.D.; Moore, W.E.; Trabold, T.A.

    1995-12-01

    Isolated bubble rise experiments provide data on bubble drag as a function of size and fluid properties. This data is useful in obtaining drag models for higher void fraction bubbly flows. Previous experiments (Haberman and Morton, 1953) have shown that the purity of the fluid affects the bubble rise velocity, and therefore the drag coefficient. For contaminated systems, impurities collecting at the liquid-vapor interface increase the effective viscous drag and decrease the rise velocity. In the current experimental work, Freon-114 is used to simulate high temperature environments. Freon is chosen as the modeling fluid because it boils at a lower temperature, and may be scaled appropriately. However, if the purity of the Freon test liquid is unknown, using it to model high temperature environments may lead to inaccurate results. The purpose of the bubble rise experiment is then (1) to identify the purity of the Freon test liquid, and (2) understand the bubble drag mechanism for single bubbles as a building block for multiple bubble drag models.

  11. Pointed bubbles rising in a two-dimensional tube

    NASA Astrophysics Data System (ADS)

    vanden-Broeck, J. M.

    1985-12-01

    This document considers a periodic array of plane bubbles rising in a gravity field. This configuration can serve as a model for an advanced stage of Rayleigh-Taylor instability. Vanden-Broeck solved the problem numerically and showed that two classes of solutions are possible. One class is characterized by a bubble profile with a continuous slope at the apex of the bubble whereas the other is characterized by the presence of a cusp at the apex. In a recent paper Garabedian and Modi conjectured that solutions with a 120 deg. angle at the apex might also exist. In this paper a scheme is presented to compute such solutions. It is found that a solution exists at a unique Froude number of 0.36. This result does not support Garabedian's conjecture that bubbles with a 120 deg. angle at the apex exist for all values of F between 0.23 and 0.36.

  12. Dynamics of an initially spherical bubble rising in quiescent liquid

    NASA Astrophysics Data System (ADS)

    Tripathi, Manoj Kumar; Sahu, Kirti Chandra; Govindarajan, Rama

    2015-02-01

    The beauty and complexity of the shapes and dynamics of bubbles rising in liquid have fascinated scientists for centuries. Here we perform simulations on an initially spherical bubble starting from rest. We report that the dynamics is fully three-dimensional, and provide a broad canvas of behaviour patterns. Our phase plot in the Galilei-Etvs plane shows five distinct regimes with sharply defined boundaries. Two symmetry-loss regimes are found: one with minor asymmetry restricted to a flapping skirt; and another with marked shape evolution. A perfect correlation between large shape asymmetry and path instability is established. In regimes corresponding to peripheral breakup and toroid formation, the dynamics is unsteady. A new kind of breakup, into a bulb-shaped bubble and a few satellite drops is found at low Morton numbers. The findings are of fundamental and practical relevance. It is hoped that experimenters will be motivated to check our predictions.

  13. 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.

  14. Stretching of material lines in pseudo-turbulence induced by small rising bubbles

    NASA Astrophysics Data System (ADS)

    Tanaka, M.; Tsujimura, Y.; Kanatani, H.

    2011-12-01

    Direct numerical simulations have been conducted for the stretching of material lines in pseudo-turbulence induced by small rising bubbles in order to understand the mixing characteristics of bubbly flows. Contaminated bubbles are considered and are treated as light solid particles. An immersed boundary method has been used for evaluating the coupling force between the bubbles and the surrounding fluid flows. Numerical results show that the total length of material lines increases exponentially in time as a result of stretching and folding due to the rising bubbles. The material lines tend to accumulate in the wake regions of the bubbles, and they are strongly stretched in the vertical direction there. It is also found that the stretching rate of material lines increases with the mean void fraction when it is normalized by the magnitude of the rate-of-strain tensor of liquid flow in pseudo-turbulence. In the case of high void fractions, material lines tend to align with the direction of maximum stretching, and are effectively stretched.

  15. Parallel lattice Boltzmann simulation of bubble rising and coalescence in viscous flows

    NASA Astrophysics Data System (ADS)

    Shi, Dongyan; Wang, Zhikai

    2015-07-01

    A parallel three-dimensional lattice Boltzmann scheme for multicomponent immiscible fluids is proposed to simulate bubble rising and coalescence process in viscous flows. The lattice Boltzmann scheme is based on the free-energy model and is parallelized in the share-memory model by using the OpenMP. Bubble interface is described by a diffusion interface method solving the Cahn-Hilliard equation and both the surface tension force and the buoyancy are introduced in a form of discrete body force. To avoid the numerical instability caused by the interface deformation, the 18 point finite difference scheme is utilized to calculate the first- and second-order space derivative. The correction of the parallel scheme handling three-dimensional interfaces is verified by the Laplace law and the dynamic characteristics of an isolated bubble in stationary flows. Subsequently, effects of the initially relative position, accompanied by the size ratio on bubble-bubble interaction are studied. The results show that the present scheme can effectively describe the bubble interface dynamics, even if rupture and restructure occurs. In addition to the repulsion and coalescence phenomenon due to the relative position, the size ratio also plays an insignificant role in bubble deformation and trajectory.

  16. On the bubble rise velocity of a continually released bubble chain in still water and with crossflow

    NASA Astrophysics Data System (ADS)

    Wang, Binbin; Socolofsky, Scott A.

    2015-10-01

    The rise velocities of in-chain bubbles continually released from a single orifice in still water with and without crossflow are investigated in a series of laboratory experiments for wobbling ellipsoidal bubbles with moderate Reynolds number. For the limiting case in still water, that is, crossflow velocity = 0, the theoretical turbulent wake model correctly predicts the in-chain bubble rise velocity. In this case, the bubble rise velocities VB are enhanced compared to the terminal velocities of the isolated bubbles V0 due to wake drafting and are scaled with flow rate Q and bubble diameter D. Here, we also derive an updated wake model with consideration of the superposition of multiple upstream bubble wakes, which removes the nonlinear behavior of the non-distant (i.e., local) wake model. For the cases with crossflow, the enhancement of the in-chain bubble rise velocity can be significantly reduced, and imaging of the experiments shows very organized paring and grouping trajectories of rising bubbles not observed in still water under different crossflow velocities. The in-chain bubble rise velocities in crossflow are described by two models. First, an empirical model is used to correct the still-water equation for the crossflow effect. In addition, a semi-theoretical model considering the turbulent wake flow and the crossflow influence is derived and used to develop a theoretical normalization of bubble rise velocity, crossflow velocity, and the released bubble flow rate. The theoretical model suggests there are two different regimes of bubble-bubble interaction, with strong interaction occurring for the non-dimensional crossflow velocity Uc + = π Uc 3 D 3 V 0 / ( 18 g β Q 2 ) less than 0.06 and weaker interaction occurring for Uc + greater than 0.06, where Uc is the crossflow velocity, g is the acceleration of gravity, and β is the mixing length coefficient.

  17. Bubble characteristics in the radial direction of three-phase fluidized beds

    SciTech Connect

    Yu, Y.H.; Kim, S.D. )

    1988-12-01

    Bubble characteristics such as bubble size and rising velocity in three-phase fluidized beds provide the basic information for analyzing phase holdup, axial and radial mixing and heat and mass transfer characteristics. The relationship between the bubble size and its rising velocity and the bubble size distribution in three-phase fluidized beds have been investigated. On the other hand, bubble size reduction has been observed by addition of floating bubble breakers. This paper presents a study on the bubble holdup mean velocity, and mean bubble chord length in a three-phase fluidized bed of 0.254 m-ID with four different particle sizes (0.4--6.0 mm).

  18. Bubble characteristics in gassy aqueous sediments

    SciTech Connect

    Orsi, T.H.; Anderson, A.L.

    1994-09-01

    Although gas bubbles are known to dramatically alter the biogeochemical, geotechnical, and geoacoustic characteristics of bottom sediments in numerous marine, estuarine, and lacustrine sediments worldwide, little is known about their size, shape, or spatial distribution within the sediments. In this study, we describe an approach for quantifying gas bubble characteristics in gassy aqueous sediments using x-ray computed tomography (CT or CAT scanning). By calibrating the CT scanner using a specially machined Plexiglas disk with preformed spheres of different diameters, the proper thresholding technique can be identified for segmenting the CT images into matrix (sediment) and bubble (free gas). To illustrate the approach, we examine a naturally gassy sediment from a shallow water lake near College Station, Texas. Free gas within the sediments occurred as large bubbles with diameters >2 mm, resulting in volume fractions ranging from essentially zero to a high in excess of 0.08. The distinct vertical segregation of bubbles correlated well with sediment structure and water content, but had a nominal effect overall on sediment bulk density. Bubble size and shape were related as bubble shape progressed from spherical to elliptical to amorphous (blobs) in form with increasing size. These results suggest that the assumption of spherical bubbles distributed uniformly throughout a volume of aqueous sediments, as commonly invoked for modeling purposes, may be inaccurate.

  19. 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.

  20. Terminal velocities of pure and hydrate coated CO 2 droplets and CH 4 bubbles rising in a simulated oceanic environment

    NASA Astrophysics Data System (ADS)

    Bigalke, N. K.; Enstad, L. I.; Rehder, G.; Alendal, G.

    2010-09-01

    Understanding the upward motion of CO 2 droplets or CH 4 bubbles in oceanic waters is prerequisite to predict the vertical distribution of the two most important greenhouse gases in the water column after these have been released from the seabed. One of the key parameters governing the fate of droplets or bubbles dissolving into the surrounding seawater as they rise, is the terminal velocity, uT. The latter is strongly influenced by the ability of both compounds to form skins of gas hydrate, if pressure and temperature satisfy thermodynamic framework conditions. Experimental efforts aiming to elucidate the rise properties of CO 2 droplets and CH 4 bubbles and specifically the influence of hydrate skins open the possibility to obtain a parameterization of uT applicable to both hydrate-coated and pure fluid particles of CH 4 and CO 2. With the present study, we report on experimentally determined terminal velocities of single CH 4 bubbles released to pressurized and temperature-regulated seawater. Hydrate skins were identified by high bubble sphericities and changed motion characteristics. Based on these experiments as well as published data on the rise of hydrate-coated and pure liquid CO 2 droplets and physical principles previously successfully used for clean bubbles near atmospheric pressures, a new parameterization of uT is proposed. Model predictions show a good agreement with the data base established from the laboratory-based measurements.

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

    NASA Astrophysics Data System (ADS)

    Cihan, Abdullah; Corapcioglu, M. Yavuz

    2008-04-01

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

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

    PubMed

    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. PMID:26066251

  3. The stability of a two-dimensional rising bubble

    SciTech Connect

    Nie, Q.; Tanveer, S.

    1995-06-01

    The stability of an inviscid two-dimensional bubble subject to two-dimensional disturbances is considered and the bubbles are found to be linearly stable for all Weber numbers, for which a steady solution is known. Certain aspects of the nonlinear initial value problem are also studied. An initial condition that consists of a superposition of a suitable symmetric eigenmode (of the linear stability operator) on a steady state is found to result in pinching of the bubble neck as it tends to oscillate about the steady state. An estimate of the threshold amplitude of such a disturbance needed to cause breakup of a large aspect ratio bubble is obtained. The presence of gravity appears to inhibit this pinching process.

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

    SciTech Connect

    Chen, L.; Leonardi, E.; Reizes, J.A.; Garimella, S.V.

    1996-12-31

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

  5. Open system degassing, bubble rise and flow dynamics within volcanic conduits- an experimental approach

    NASA Astrophysics Data System (ADS)

    Pioli, L.; Azzopardi, B. J.; Bonadonna, C.; Marchetti, E.; Ripepe, M.

    2009-12-01

    Open conduit basaltic volcanoes are characterized by frequent eruptions, usually consisting in mild Strombolian and Hawaiian explosions, alternating years to months of quiescence periods, with degassing activity from the central conduit. Recent improvements of thermal, video, radar and acoustic monitoring techniques have provided new powerful tools for the study of degassing processes and made available geophysical and geochemical datasets for many central volcanoes, such as Stromboli, Etna (Italy), Kilauea (Hawaii), Villarrica (Chile). These studies revealed that degassing is an unsteady, often pulsatory process, characterized by fluctuations in both intensity and composition of the emitted gases. Unambiguous interpretation of monitoring data of surface activity in terms of conduit dynamics and flow processes is, however, not possible, due to partial knowledge of the physical processes controlling the dynamics of two-phase flows in magmas. We performed a series of experiments to gain further insights on the dynamics of the gas-bubble rise in magmas within a cylindrical conduit, their ability to segregate and coalesce and the effect of these processes on the degassing dynamics. The experiments consisted in generating fluxes at variable intensities of air through stagnant water or glucose syrup in a bubble column apparatus 6.5 m high and with a diameter of 24 cm diameter. Glucose syrup and water are Newtonian liquids with viscosity ranging from 2.4 to 204.0 Pa*s and from 1.7 to 0.2 10 -3 Pa*s respectively, depending on temperature. Air was inserted at the base of the column through a variable number (1 to 25) of 5mm-diameter nozzles reaching surficial gas velocities of up to 0.5 m/s. The activity of the bubble column was monitored through temperature, pressure, void fraction and acoustic measurements and filmed by a high-speed camera with maximum resolution of 800x600 pixels. Pressure fluctuations, vesicularity and acoustic signal were then analyzed and correlated to flow conditions and observed regimes. The experiments showed a progressive increase of the average vesicularity of the liquid column with increasing gas flux, but also the onset of pressure and void fraction fluctuations whose amplitude and frequency increases with increasing gas fluxes. In all the experiments, bubble rise generated liquid circulation cells and mixing at the column scale. Gradual variations of flow properties marked the onset of bubbly to intermittent to annular flow regimes. Strong differences in the relative importance of shearing and turbulent effects in the glucose syrup and water experiments generated significant variations in the flow dynamics affecting bubble coalescence and breakup, vesicularity and bubble size. This indicates that the stability and characteristics of the two-phase flow regimes are strongly affected by variations of the liquid viscosity. Finally, acoustic signals were generated at higher gas fluxes in the glucose syrup experiments by bursts of large bubbles at the liquid surface indicating significant overpressure buildup.

  6. Bubble rise velocities and drag coefficients in non-Newtonian polysaccharide solutions.

    PubMed

    Margaritis, A; te Bokkel, D W; Karamanev, D G

    1999-08-01

    Microbially produced polysaccharides have properties which are extremely useful in different applications. Polysaccharide producing fermentations start with liquid broths having Newtonian rheology and end as highly viscous non-Newtonian solutions. Since aerobic microorganisms are used to produce these polysaccharides, it is of great importance to know the mass transfer rate of oxygen from a rising air bubble to the liquid phase, where the microorganisms need the oxygen to grow. One of the most important parameters determining the oxygen transfer rate is the terminal rise velocity of air bubble. The dynamics of the rise of air bubbles in the aqueous solutions of different, mostly microbially produced polysaccharides was studied in this work. Solutions with a wide variety of polysaccharide concentrations and rheological properties were studied. The bubble sizes varied between 0.01 mm3 and 10 cm3. The terminal rise velocities as a function of air bubble volume were studied for 21 different polysaccharide solutions with different rheological properties. It was found that the terminal velocities reached a plateau at higher bubble volumes, and the value of the plateau was nearly constant, between 23 and 27 cm/s, for all solutions studied. The data were analyzed to produce the functional relationship between the drag coefficient and Reynolds number (drag curves). It was found out that all the experimental data obtained from 21 polysaccharide solutions (431 experimental points), can be represented by a new single drag curve. At low values of Reynolds numbers, below 1.0, this curve could be described by the modofoed Hadamard-Rybczynski model, while at Re > 60 the drag coefficient was a constant, equal to 0.95. The latter finding is similar to that observed for bubble rise in Newtonian liquids which was explained on the basis of the "solid bubble" approach. PMID:10397862

  7. 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

  8. Bubble and bubble wake characteristics in a gas-liquid-solid fluidized bed

    SciTech Connect

    Kreischer, B.E.

    1989-01-01

    A light transmittance technique involving a dual optical fiber probe was used to measure the local solids holdup in a three-dimensional gas-liquid-solid fluidized bed. The bubble could be clearly identified in the same signal, thus permitting the simultaneous determination of the local solids holdup profile in the wake of a single bubble and the rise velocity and chord length of the bubble. The solids holdup behavior was studied in the wake of single bubbles rising in a liquid-solid fluidized bed for different liquid velocities, particle sizes, and bubble sizes. The wake solids holdup was found to decrease with decreasing mean solids holdup in the bed, to be essentially independent of the bubble Reynolds number over the range investigated in this study (4000 < Re{sub b} < 8000), and to decrease with increasing particle size. In freely bubbling bed at low gas holdups ({epsilon}{sub g} < 0.03), both the solids holdup in the wake and the particulate phase solids holdup were measured. The light transmittance probe developed for the single bubble system was also used for these measurements. Axial variations in the particulate solids holdup indicated that the relative wake solids holdup increased with axial distance from the distributor. The best agreement between the single bubble measurements and the measurements in the freely bubbling bed occurred in the bubble formation region. And finally, a simple model of the bubble wake was developed based on equations available in the literature for a spherical vortex to predict both the wake size and the relative wake solids holdup. The predictions showed good agreement with the experimentally observed values.

  9. Analysis of Rayleigh-Taylor Instability: Statistics on Rising Bubbles and Falling Spikes

    SciTech Connect

    Kamath, C; Gezahegne, A; Miller, P

    2007-10-30

    The analysis of coherent structures in Rayleigh-Taylor simulations is a challenging task as the lack of a precise definition of these structures is compounded by the massive size of the datasets. In an earlier work, we used techniques from image analysis to count these coherent structures in two high-resolution simulations, one a large-eddy simulation with 30 terabytes of analysis data, and the other a direct numerical simulation with 80 terabytes of analysis data. Our analysis indicated that there were four distinct regimes in the process of the mixing of the two fluids, starting from the initial linear stage, followed by the non-linear stage with weak turbulence, the mixing transition stage, and the final stage of strong turbulence. In this paper, we extend our earlier work to focus on only the rising bubbles and the falling spikes. We first consider different ways in which we can constrain the bubble and spike definitions and then extract various statistics on them. Our results on the rising bubble and falling spike counts again show that there are four regimes in the process of fluid mixing, each characterized by an integer-valued slope. Further, the average bubble heights and spike depths are related to similar results obtained using a threshold-based definition. Finally, the ratio of the rising bubbles to all bubbles is very similar in character to the ratio of the falling spikes to all spikes, with near constant values over part of the simulation.

  10. Oscillatory Rise of Bubbles in Wormlike Micellar Fluids with Different Microstructures

    NASA Astrophysics Data System (ADS)

    Handzy, Nestor Z.; Belmonte, Andrew

    2004-03-01

    Previous observations of the nontransient oscillations of rising bubbles and falling spheres in wormlike micellar fluids were limited to a single surfactant system. We present an extensive survey of rising bubbles in another system, an aqueous solution of cetylpyridinium chloride and sodium salicylate, with and without NaCl, across a range of concentrations and temperatures. Two different types of oscillations are seen in different concentration ranges, each with its own temperature dependence. Rheological data identify these different hydrodynamic states with different fluid microstructures.

  11. A global stability approach to wake and path instabilities of nearly oblate spheroidal rising bubbles

    NASA Astrophysics Data System (ADS)

    Cano-Lozano, José Carlos; Tchoufag, Joël; Magnaudet, Jacques; Martínez-Bazán, Carlos

    2016-01-01

    A global Linear Stability Analysis (LSA) of the three-dimensional flow past a nearly oblate spheroidal gas bubble rising in still liquid is carried out, considering the actual bubble shape and terminal velocity obtained for various sets of Galilei (Ga) and Bond (Bo) numbers in axisymmetric numerical simulations. Hence, this study extends the stability analysis approach of Tchoufag et al. ["Linear stability and sensitivity of the flow past a fixed oblate spheroidal bubble," Phys. Fluids 25, 054108 (2013) and "Linear instability of the path of a freely rising spheroidal bubble," J. Fluid Mech. 751, R4 (2014)] (which considered perfectly spheroidal bubbles with an arbitrary aspect ratio) to the case of bubbles with a realistic fore-aft asymmetric shape (i.e., a flatter front and a more rounded rear). The critical curve separating stable and unstable regimes for the straight vertical path is obtained both in the (Ga,Bo) and the (Re,χ) planes, where Re is the bubble Reynolds number and χ its aspect ratio (i.e., the major-to-minor axes length ratio). This provides new insight into the effect of the shape asymmetry on the wake instability of bubbles held fixed in a uniform stream and on the path instability of freely rising bubbles, respectively. For the range of Ga and Bo explored here, we find that the flow past a bubble with a realistic shape is generally more stable than that past a perfectly spheroidal bubble with the same aspect ratio. This study also provides the first critical curve for the onset of path instability that can be compared with experimental observations. The tendencies revealed by this critical curve agree well with those displayed by available data. The quantitative agreement is excellent for O(1) Bond numbers. However, owing to two simplifying assumptions used in the LSA scheme, namely, the steadiness of the base state and the uncoupling between the bubble shape and the flow disturbances, quantitative discrepancies (up to 20%-30%) with experimental threshold values of the Galilei number remain for both small and large Bond numbers.

  12. Lattice Boltzmann simulation of rising bubble dynamics using an effective buoyancy method

    NASA Astrophysics Data System (ADS)

    Ngachin, Merlin; Galdamez, Rinaldo G.; Gokaltun, Seckin; Sukop, Michael C.

    2015-08-01

    This study describes the behavior of bubbles rising under gravity using the Shan and Chen-type multicomponent multiphase lattice Boltzmann method (LBM) [X. Shan and H. Chen, Phys. Rev. E47, 1815 (1993)]. Two-dimensional (2D) single bubble motions were simulated, considering the buoyancy effect for which the topology of the bubble was characterized by the nondimensional Eötvös (Eo), and Morton (M) numbers. In this study, a new approach based on the "effective buoyancy" was adopted and proven to be consistent with the expected bubble shape deformation. This approach expands the range of effective density differences between the bubble and the liquid that can be simulated. Based on the balance of forces acting on the bubble, it can deform from spherical to ellipsoidal shape with skirts appearing at high Eo number. A benchmark computational case for qualitative and quantitative validation was performed using COMSOL Multiphysics based on the level set method. Simulations were conducted for 1 ≤ Eo ≤ 100 and 3 × 10-6 ≤ M ≤ 2.73 × 10-3. Interfacial tension was checked through simulations without gravity, where Laplace's law was satisfied. Finally, quantitative analyses based on the terminal rise velocity and the degree of circularity was performed for various Eo and M values. Our results were compared with both the theoretical shape regimes given in literature and available simulation results.

  13. Transformer overload characteristics---Bubble evolution

    SciTech Connect

    Woods, E.E.; Wendel, R.C.; Dresser, R.D.

    1988-08-01

    Project RP1289-3 explores significant parameters affecting bubble evolution from transformer oil under high temperature operating conditions to address the question: Does ''real life'' operation of a transformer cause harmful bubbling conditions. Studies outlined in the project are designed to determine when bubbling occurs in transformers and if bubbling can be harmful during the normal operation of these transformers. Data obtained from these studies should provide a basis for utilities to perform risk assessments in relation to their loading practices. The program is designed to demonstrate those conditions under which bubbling occurs in transformers by using controlled models and actual signal phase transformers that were designed to give access to both high and low voltage windings for the purpose of viewing bubble generation. Results and observations from tests on the full-size transformers, thermal models, and electrical models have led to the conclusion that bubbles can occur under operating conditions. The electrical models show that dielectric strength can be reduced by as much as 40 percent due to the presence of bubbles. Because of factory safety considerations, the transformers could not be tested at hot spot temperatures greater than 140/degree/C. Therefore, there is no information on the dielectric strength of the full-size transformers under bubbling conditions. 4 refs., 28 figs., 45 tabs.

  14. Velocity of a freely rising gas bubble in a soda-lime silicate glass melt

    NASA Technical Reports Server (NTRS)

    Hornyak, E. J.; Weinberg, M. C.

    1984-01-01

    A comparison is conducted between measured velocities for the buoyant rise of single bubbles of varying size and composition, in a soda-lime silicate glass melt, with the steady state velocities predicted by the Stokes and Hadamard-Rybczynski formulas. In all cases, the data are noted to fit the Hadamard-Rybczynski expression for steady state rise speed considerably better than the Stokes formula.

  15. The terminal rise velocity of 10-100 microm diameter bubbles in water.

    PubMed

    Parkinson, Luke; Sedev, Rossen; Fornasiero, Daniel; Ralston, John

    2008-06-01

    Single bubbles of very pure N2, He, air and CO2 were formed in a quiescent environment in ultra-clean water, with diameters ranging from 10 to 100 mum. Their terminal rise velocities were measured by high-speed video microscopy. For N2, He and air, excellent agreement with the Hadamard-Rybczynski (H-R) equation was observed, indicating that slip was occurring at the liquid-vapor interface. For CO2 bubbles with diameters less than 60 microm, the terminal rise velocities exceeded those predicted by the H-R equation. This effect was ascribed to the enhanced solubility of CO2 compared with the other gases examined. The presence of a diffusion boundary layer may be responsible for the increased terminal velocity of very small CO2 bubbles. PMID:18405911

  16. Numerical investigation of bubble nonlinear dynamics characteristics

    NASA Astrophysics Data System (ADS)

    Shi, Jie; Yang, Desen; Zhang, Haoyang; Shi, Shengguo; Jiang, Wei; Hu, Bo

    2015-10-01

    The complicated dynamical behaviors of bubble oscillation driven by acoustic wave can provide favorable conditions for many engineering applications. On the basis of Keller-Miksis model, the influences of control parameters, including acoustic frequency, acoustic pressure and radius of gas bubble, are discussed by utilizing various numerical analysis methods, Furthermore, the law of power spectral variation is studied. It is shown that the complicated dynamic behaviors of bubble oscillation driven by acoustic wave, such as bifurcation and chaos, further the stimulated scattering processes are revealed.

  17. Non-linear shape oscillations of rising drops and bubbles: Experiments and simulations

    NASA Astrophysics Data System (ADS)

    Lalanne, Benjamin; Abi Chebel, Nicolas; Vejražka, Jiří; Tanguy, Sébastien; Masbernat, Olivier; Risso, Frédéric

    2015-12-01

    This paper focuses on shape-oscillations of a gas bubble or a liquid drop rising in another liquid. The bubble/drop is initially attached to a capillary and is released by a sudden motion of that capillary, resulting in the rise of the bubble/drop along with the oscillations of its shape. Such experimental conditions make difficult the interpretation of the oscillation dynamics with regard to the standard linear theory of oscillation because (i) amplitude of deformation is large enough to induce nonlinearities, (ii) the rising motion may be coupled with the oscillation dynamics, and (iii) clean conditions without residual surfactants may not be achieved. These differences with the theory are addressed by comparing experimental observation with numerical simulation. Simulations are carried out using Level-Set and Ghost-Fluid methods with clean interfaces. The effect of the rising motion is investigated by performing simulations under different gravity conditions. Using a decomposition of the bubble/drop shape into a series of spherical harmonics, experimental and numerical time evolutions of their amplitudes are compared. Due to large oscillation amplitude, non-linear couplings between the modes are evidenced from both experimental and numerical signals; modes of lower frequency influence modes of higher frequency, whereas the reverse is not observed. Nevertheless, the dominant frequency and overall damping rate of the first five modes are in good agreement with the linear theory. Effect of the rising motion on the oscillations is globally negligible, provided the mean shape of the oscillation remains close to a sphere. In the drop case, despite the residual interface contamination evidenced by a reduction in the terminal velocity, the oscillation dynamics is shown to be unaltered compared to that of a clean drop.

  18. Effect of products of PLA2 catalyzed hydrolysis of DLPC on motion of rising bubbles.

    PubMed

    Krzan, Marcel; Jarek, Ewelina; Warszy?ski, Piotr; Rogalska, Ewa

    2015-04-01

    Local velocities of rising bubbles decrease with the increasing concentration in solution of surface-active, water-soluble species. Therefore, it is possible to use this phenomenon to monitor products of enzymatic reactions, which meet such criteria. In this study, hydrolysis of 1,2-dilauroyl-sn-glycero-3-phosphatidylcholine (DLPC) catalyzed by calcium-dependent phospholipase A2 (PLA2) (EC3.1.1.4) from porcine pancreas was used as model reaction. The products of this reaction are lauric acid (LA) and 1-lauroyl-2-hydroxy-sn-glycero-3-phosphatidylcholine (Lyso-PC). DLPC was dispersed in a chloroform/methanol mixture that was spread on a free PLA2 solution surface. Air bubbles were then formed at a capillary orifice and the local velocity of rising bubbles as a function of the distance from the capillary tip was monitored. Local velocity profiles were compared with profiles recorded for solutions of pure enzymatic reaction products and their mixtures. Our experiments showed that the product, which had a dominating effect on bubble motion retardation, was lyso-phosphatidylcholine. This can be explained by differences in the kinetics of lauric acid and lyso-phosphatidylcholine transfer from the spread layer to the solution. PMID:25724770

  19. The shape of bubbles and Drops rising in a Nematic Liquid Crystal

    NASA Astrophysics Data System (ADS)

    Zhou, Chunfeng; Yue, Pengtao; Feng, James J.; Liu, Chun; Shen, Jie

    2006-11-01

    This work is motivated by recent experimental observation of unusual ``inverted-heart" shapes that a bubble assumes when rising in an anisotropic fluid. A possible explanation is in terms of the molecular orientation of the matrix fluid with respect to the bubble surface. In this work, we use numerical simulations to test such a hypothesis. The moving interface problem is formulated in a diffuse-interface framework. The anisotropic fluid is represented by a simplified Leslie-Ericksen theory for nematic liquid crystals, with director anchoring on the surface of an isotropic drop. The simulations are carried out using axisymmetric finite elements. Results show an array of drop shapes, depending on the interplay among inertial, capillary, anchoring and elastic effects. Drops with sufficiently strong planar anchoring and moderate elasticity rising in a medium with vertical far-field orientation assume the inverted-heart observed in experiments. This is shown to be mainly due to the competition between interfacial tension, anchoring energy and bulk elastic energy. Furthermore, two boojum defects appear on the upper and lower poles. The size of the defects plays an significant role in shaping the rising bubble.

  20. Equatorial plasma bubble rise velocities in the Indian sector determined from multistation scintillation observations

    SciTech Connect

    Dabas, R.S.; Reddy, B.M. )

    1990-04-01

    The velocity of plasma-bubble rise over the magnetic equator is calculated on the basis of simultaneous measurements of the onset times of postsunset VHF scintillations from the Japanese satellite ETS-2, obtained at a meridian array of four Indian stations during February 1980. The data and calculation results are presented in tables and graphs and discussed in detail. It is found that bubble velocities increase with altitude, varying in the ranges 128-416, 38-327, and 15-200 m/sec at altitudes 450-550, 550-1140, and 1140-1270 km, respectively. These results are shown to be in good agreement with satellite and radar measurements and with F-layer vertical drift velocities. 17 refs.

  1. Increased pressure from rising bubbles as a mechanism for remotely triggered seismicity

    USGS Publications Warehouse

    Linde, A.T.; Sacks, I.S.; Johnston, M.J.S.; Hill, D.P.; Bilham, R.G.

    1994-01-01

    Aftershocks of large earthquakes tend to occur close to the main rupture zone, and can be used to constrain its dimensions. But following the 1992 Landers earthquake (magnitude M(w) = 7.3) in southern California, many aftershocks were reported in areas remote from the mainshock. Intriguingly, this remote seismicity occurred in small clusters near active volcanic and geothermal systems. For one of these clusters (Long Valley, about 400 km from the Landers earthquake), crustal deformation associated with the seismic activity was also monitored. Here we argue that advective overpressure provides a viable mechanism for remote seismicity triggered by the Landers earthquake. Both the deformation and seismicity data are consistent with pressure increases owing to gas bubbles rising slowly within a volume of magma. These bubbles may have been shaken loose during the passage of seismic waves generated by the mainshock.

  2. 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. 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).

  3. 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.

  4. Bubbles rising in a tube and jets falling from a nozzle

    NASA Astrophysics Data System (ADS)

    vanden-Broeck, J.-M.

    1984-05-01

    The shape of a two-dimensional bubble rising at a constant velocity U in a tube of width h is computed. The flow is assumed to be inviscid and incompressible. The problem is solved numerically by collocation. The results confirm Garabedian's (1957) findings. There exists a unique solution for each value of the Froude number F = U/(gh) to the 1/2 power smaller than a critical value F(c). Here g denotes the acceleration of gravity. It is found that F(c) = 0.36. In addition, the problem of a jet emerging from a vertical nozzle is considered. It is shown that the slope of the free surface at the separation points is horizontal for F smaller than F(c) and vertical for F greater than F(c). Graphs and tables of the results are included.

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

    SciTech Connect

    Kawahara, Akimaro; Sadatomi, Michio; Matsuura, Hidetoshi; Tominaga, Mayo; Noguchi, Masanori; Matsuyama, Fuminori

    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)

  6. 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 Etvs 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 trajectoriesa damped vibrational motion without changes in the bubble shape, a straight trajectory, and another damped vibrational motion accompanied by changes in the bubble shapeare 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.

  7. ALMA observations of cold molecular gas filaments trailing rising radio bubbles in PKS 0745-191

    NASA Astrophysics Data System (ADS)

    Russell, H. R.; McNamara, B. R.; Fabian, A. C.; Nulsen, P. E. J.; Edge, A. C.; Combes, F.; Murray, N. W.; Parrish, I. J.; Salomé, P.; Sanders, J. S.; Baum, S. A.; Donahue, M.; Main, R. A.; O'Connell, R. W.; O'Dea, C. P.; Oonk, J. B. R.; Tremblay, G.; Vantyghem, A. N.; Voit, G. M.

    2016-02-01

    We present ALMA observations of the CO(1-0) and CO(3-2) line emission tracing filaments of cold molecular gas in the central galaxy of the cluster PKS 0745-191. The total molecular gas mass of 4.6 ± 0.3 × 109 M⊙, assuming a Galactic XCO factor, is divided roughly equally between three filaments each extending radially 3-5 kpc from the galaxy centre. The emission peak is located in the SE filament ˜ 1 arcsec (2 kpc) from the nucleus. The velocities of the molecular clouds in the filaments are low, lying within ± 100 km s-1 of the galaxy's systemic velocity. Their FWHMs are less than 150 km s-1, which is significantly below the stellar velocity dispersion. Although the molecular mass of each filament is comparable to a rich spiral galaxy, such low velocities show that the filaments are transient and the clouds would disperse on <107 yr timescales unless supported, likely by the indirect effect of magnetic fields. The velocity structure is inconsistent with a merger origin or gravitational free-fall of cooling gas in this massive central galaxy. If the molecular clouds originated in gas cooling even a few kpc from their current locations their velocities would exceed those observed. Instead, the projection of the N and SE filaments underneath X-ray cavities suggests they formed in the updraft behind bubbles buoyantly rising through the cluster atmosphere. Direct uplift of the dense gas by the radio bubbles appears to require an implausibly high coupling efficiency. The filaments are coincident with low temperature X-ray gas, bright optical line emission and dust lanes indicating that the molecular gas could have formed from lifted warmer gas that cooled in situ.

  8. Rising motion of a single bubble through a liquid metal in the presence of a horizontal magnetic field

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; Ni, Ming-Jiu; Moreau, René

    2016-03-01

    After a previous investigation of the rising motion of a gas bubble in a liquid metal under the influence of a vertical magnetic field, this new study focuses on the case of a uniform horizontal magnetic field. The numerical code is still the same: it is based on a volume-of-fluid technique and on an unstructured Cartesian adaptive grid system. A consistent and conservative scheme is adopted to compute the induced current density and the Lorentz force. In order to allow a benchmark, most of the parameters selected for this new investigation are the same as in an experiment recently performed in Dresden, Germany. The Ar bubble diameter is either 4.3 mm or 6.4 mm, the liquid metal is GaInSn, resulting in Reynolds numbers (Re) larger than in experiments with water (2000 to 4000, instead of 1000 or less) and allowing significant differences even without any magnetic field. In this paper, the magnetic field strength and therefore the interaction parameter are extended to values higher than in the experiment to provide data on the asymptotic behavior when these parameters get very large. The influence of the horizontal magnetic field on properties as the terminal rising velocity, the observed modifications of the rising paths, the shape of the bubble, and the wake structure is displayed and discussed. It is shown that the unstable bubble trajectory is closely related to the wake instability, which is itself strongly influenced by the horizontal magnetic field. When comparing the results with those obtained in the presence of a vertical magnetic field, significant differences appear together with the lack of axial symmetry, such as a slower rising motion of the bubble and the suppression of the "secondary path instability." Increasing the intensity of the magnetic field results in an approximate exponential law to describe how the terminal rising velocity is reduced. The numerical predictions are interpreted in terms of the predominant physical mechanisms.

  9. 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.

  10. Bubbly flow model for the dynamic characteristics of cavitating pumps

    NASA Technical Reports Server (NTRS)

    Brennen, C.

    1978-01-01

    The recent experimental transfer matrices obtained by Ng and Brennen (1978) for some axial flow pumps revealed some dynamic characteristics which were unaccounted for by any existing theoretical analysis; their visual observations suggested that the bubbly cavitating flow in the blade passages could be responsible for these effects. A theoretical model of the dynamic response of this bubbly blade-passage flow is described in the present paper. Void-fraction fluctuations in this flow result not only from pressure fluctuations but also because the fluctuating angle of attack causes fluctuations in the rate of production of bubbles near the leading edge. The latter causes kinematic waves which interact through the boundary conditions with the dynamic waves caused by pressure fluctuation. The resulting theoretical transfer functions which results are in good qualitative agreement with the experiments; with appropriate choices of two parameters good quantitative agreement is also obtained. The theoretical model also provides one possible explanation of the observation that the pump changes from an essentially passive dynamic element in the absence of cavitation to a progressively more active element as the extent of cavitation increases.

  11. Rising bubbles in a two-dimensional tube with surface tension

    NASA Astrophysics Data System (ADS)

    Vanden-Broeck, Jean-Marc

    1984-11-01

    The motion of a two-dimensional bubble rising at a constant velocity U in a tube of width h is considered. The acceleration of gravity g and the surface tension T are included in the dynamic boundary condition. For T=0, the results of Garabedian and Vanden-Broeck show that a solution exists for all values of the Froude number F=U/(gh)1/2 smaller than a critical value Fc0.36. In this paper accurate numerical solutions with T?0 are computed by series truncations. The results show that for each value of T?0, there exists a countably infinite number of solutions. Each of these solutions corresponds to a different value of F. As T tends to zero, all these solutions approach a unique limiting solution characterized by F=F*0.23. Therefore, the degeneracy associated with T=0 is removed by including the effect of surface tension. In addition, the profile corresponding to F=F* is found to be in good agreement with experimental data.

  12. Bubbles

    NASA Astrophysics Data System (ADS)

    Prosperetti, Andrea

    2004-06-01

    Vanitas vanitatum et omnia vanitas: bubbles are emptiness, non-liquid, a tiny cloud shielding a mathematical singularity. Born from chance, a violent and brief life ending in the union with the (nearly) infinite. But a wealth of phenomena spring forth from this nothingness: underwater noise, sonoluminescence, boiling, and many others. Some recent results on a "blinking bubble" micropump and vapor bubbles in sound fields are outlined. The last section describes Leonardo da Vinci's observation of the non-rectlinear ascent of buoyant bubbles and justifies the name Leonardo's paradox recently attributed to this phenomenon.

  13. On the turbulent structure in the wake of Taylor bubbles rising in vertical pipes

    NASA Astrophysics Data System (ADS)

    Shemer, L.; Gulitski, A.; Barnea, D.

    2007-03-01

    The development of gas-liquid slug flow along pipes is governed by the interaction between consecutive elongated bubbles. It is commonly accepted that the trailing bubble's shape and velocity are affected by the flow field in the liquid phase ahead of it. Particle image velocimetry (PIV) measurements of the velocity field in the wake of an elongated Taylor bubble are performed for different pipe diameters and various Reynolds numbers. Experiments are carried out in both laminar and turbulent background flows. Ensemble-averaged quantities in the frame of reference moving with the Taylor bubble are calculated. Peculiarities regarding the variation of the mean velocity distributions, as well as of the normal and shear Reynolds stresses, with the distance from the Taylor bubble bottom are discussed.

  14. Characteristics of an underwater direct current discharge in bubbles and the temperature distribution in the bubbles

    NASA Astrophysics Data System (ADS)

    Xiong, Ranhua; Nikiforov, Anton Yu.; Vanraes, Patrick; Leys, Christophe

    2012-02-01

    An underwater direct current (DC) discharge in artificially produced air bubbles is investigated. Electrical and optical emission properties of the plasma and temperature distribution in bubbles evaluated by using computational fluid dynamics (CFD) are presented. The behavior of plasma inside a bubble significantly depends on the bubble size. The discharge with water as a cathode is characterized by streamer nature, whereas the plasma with water as an anode appears diffuse and homogenous. The gas temperature is estimated from emission of the plasma, and it is much higher when water is a cathode. Bubble dynamics is investigated by CFD simulation, and results are in good agreement with experimental data. It shows the temperature distribution in bubbles strongly depends on the bubble dynamics, and gas-water interface has a sharp temperature gradient and acts as an efficient heat sink.

  15. 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

  16. 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".

  17. The Characteristics of Steam Bubbles in Subcooled Boiling Flow

    SciTech Connect

    Takatoshi Takemoto; Asi Bunyajitradulya; Mitsuo Matsuzaki; Hiroshige Kikura; Masanori Aritomi

    2002-07-01

    In two-fluid modeling and three-fluid modeling, the accurate prediction of the interfacial area concentration, interfacial heat transfer and interfacial shear stress, were required. In this works, the axial profiles of void fraction, interfacial area concentration and interfacial heat transfer coefficient along the flow direction could be measured. For the steam bubbles whose diameter were less than 8 mm, the interfacial area concentration and the mean bubble diameter had a correlation with void fraction despite the variation of liquid flow rate and subcooling. In case the steam bubble collapse occurred due to an irregular bubble condensation and a turbulence of liquid flow, interfacial heat transfer coefficient with the bubble collapse was about twice of that without a bubble collapse. And the interfacial heat transfer coefficient without bubble collapse showed a good agreement with the correlation proposed by Akiyama. In addition, the supposed image processing method could be applied to the present experimental condition. (authors)

  18. Three-dimensional experimental investigation of the shape and dynamics of a rising bubble in stagnant water with particle tracking velocimetry

    NASA Astrophysics Data System (ADS)

    Ortiz-Villafuerte, Javier

    The Particle Tracking Velocimetry technique has been used for a three-dimensional, transient, experimental study of a single bubble dynamics in a restricted medium. The three-dimensional velocity field was reconstructed via stereoscopic matching of two-dimensional images. A hybrid tracking technique has been used to determine the flow around a bubble. The development of the Shadow Particle Image Velocimetry allowed studying the bubble shape and rotation. An accurate estimate of the bubble dimensions, orientation, trajectory, and velocity and acceleration of a bubble rising in water, was obtained. The flow around and within the wake of the bubble was determined from ensemble averaging instantaneous velocity fields. The ensemble average operation was performed by considering a conditional sampling technique. The conditional ensemble averaging was performed for specified bubble trajectories. It was found that bubbles rising close to the wall generate more turbulence, and the disturbances induced in the liquid reach further downstream, when compared to bubbles rising along the pipe core. The bubble Reynolds number was in the range from 350 to 700. Regarding the bubble motion, it was found that the inclusion of the disturbed flow field in the bubble motion equation generates a scattering of the data for the drag and lift coefficients. The wall influence on these coefficients was introduced through the velocities and accelerations of the liquid and the bubble. The results indicate that the presence of the seed particles in the liquid have an influence on the bubble velocity and bubble shape. The instantaneous drag coefficient did not delineate a trend with respect to the rotation parameter; however, it shows a behavior similar to the standard drag curve as function of the Reynolds number. The average drag coefficient values are 0.90 and 0.98 for the bubble trajectories along the pipe core and close to the pipe wall, respectively. No trend for the instantaneous lift coefficient values as a function of the Reynolds number and rotation parameter was observed. The average lift coefficient for the bubble trajectories rising along the pipe center and close to the pipe wall are of values of 0.37 and 0.44, respectively.

  19. Measurement of bubble characteristics in a scale model of a 70 MWe pressurized fluidized bed combustor

    SciTech Connect

    Farrell, P.A.; Glicksman, L.R.

    1997-12-31

    A one-quarter linear scale model of the Tidd 70 MW{sub e} PFBC was constructed. Studies reported previously have shown that the scale model gives local and overall bed expansion values that closely agree with those measured in the PFBC by means of pressure-drop measurements. The cold-scale model was instrumented with light probes embedded in the dowels used to represent the tubes in the boiler. The light probes were used to measure the bubble mean pierced length, bubble frequency, and bubble rise velocity. A probe was positioned in the open area below the tube bank. Measurements were made at u{sub o}/u{sub mf} values between 2.5 and 3.8. In the open area below the tubes, the bubble size and growth rates are smaller than the values predicted from correlations based on atmospheric bubbling beds. This suggests that in a pressurized bed the bubbles either grow more slowly or split as well as coalesce. The bubble size was found to be limited within the tube bank. The bubble velocity is greater than the velocity of a single bubble in an infinite medium, but the bubble velocity was found to be insensitive to the gas superficial velocity. The gas through-flow is closely approximated by the two-phase hypothesis without any bypass flow. This is confirmed by the absence of closely-spaced bubble chains or vertical voids within the tube bank. The bubble behavior is important as it influences both particle and gas mixing through the bed as well as heat transfer to the in-bed tube bundle.

  20. Visualization of flow characteristics in a 2-D bubble column and three-phase fluidized bed

    SciTech Connect

    Tzeng, J.W.; Chen, R.C.; Fan, L.S. )

    1993-05-01

    Macroscopic flow structures of gas-liquid and gas-liquid-solid fluidization systems are studied through flow visualization using a two-dimensional column under various operating conditions. The gas distributor in the column comprises multiple injectors which are individually regulated to generate desired gas flow rates, bubble injection frequencies, and bubble sizes. Colored bed particles and neutrally buoyant particles as solid and liquid tracers, respectively, are used for flow visualization through video photography. In a gas-liquid system operated under liquid-batch conditions, bubble streams injected near both sidewalls are observed to migrate toward be vertical axis, and vortices appear along the sidewalls when gas velocity exceeds 4-6 mm/s. A considerable amount of liquid descends along the sidewalls in a vortical flow pattern. The gross circulation pattern occurring at high gas velocities is associated closely with induced liquid or liquid-solid flows resulting from rising bubbles and bubble wakes. When the gross circulation occurs, four flow regions can be distinguished. The formation of and mechanism for gross circulations can be interpreted in part based on two simplified flow conditions involving single bubbles rising in a stationary liquid and single chains of bubbles injected in a batch liquid. The effects of particle size, inlet liquid velocity and gas flow distribution on the macroscopic flow structure are also examined.

  1. How sea level rise and storm climate impact the looming morpho-economic bubble in coastal property value.

    NASA Astrophysics Data System (ADS)

    McNamara, D.; Keeler, A.; Smith, M.; Gopalakrishnan, S.; Murray, A.

    2012-12-01

    In the United States, the coastal region is now the most densely populated zone in the country and as a result has become a significant source of tax revenue and has some of the highest property values in the country. The loss of land at the coastline from erosion and damage to property from storms has always been a source of vulnerability to coastal economies. To manage this vulnerability, humans have long engaged in the act of nourishing the coastline - placing sand, typically from offshore sources, onto the beach to widen the beach and increase the height of dunes. As humans alter natural coastal dynamics by nourishing, the altered natural dynamics then influence future beach management decisions. In this way human-occupied coastlines are a strongly coupled dynamical system and because of this coupling, the act of nourishment has become an intrinsic part of the economic value of a coastline. Predictions of increased rates of sea level rise and changing storminess suggest that coastal vulnerability is likely to increase. The evolving vulnerability of the coast has already caused changes to occur in the way humans manage the coastline. For example, the federal government has recently reduced subsidies to help coastal communities nourish their beaches. With a future of changing environmental forcing from sea level and storms, the prospect of changes in nourishment cost could have profound consequences on coastal value and sustainability. We utilize two modeling approaches to investigate how disappearing nourishment subsidies reduce coastal property value and to explore the potential for a bubble and subsequent crash in coastal property value as subsidies dwindle and vulnerability rises. The first model is an optimal control model that couples a cost benefit analysis to coastline dynamics. In the second model, we couple a numerical coastline model with an agent-based model for real estate markets. Results from both models suggest the total present value of coastal property is significantly reduced with the removal of nourishment subsidies, creating a temporary bubble in coastal property value. In both models, results show the extent to which rising sea level and changing storminess impact the size of the property value bubble. The utility of the optimal control model is that it provides an empirically grounded parameterization of the coupled human coastal system. The coupled agent-based physical coastline model is more difficult to constrain with current data, however the model provides insight into the dynamics of subjective beliefs about coastal risk, which depend on the weight agents place on scientific predictions and on the way they process signals from previous climate events. Results from this model illustrate how the dynamics of the property bubble burst depend on agent beliefs about their changing environment.

  2. Characteristics of micro-nano bubbles and potential application in groundwater bioremediation.

    PubMed

    Li, Hengzhen; Hu, Liming; Song, Dejun; Lin, Fei

    2014-09-01

    Content of oxygen in water is a critical factor in increasing bioremediation efficiency for contaminated groundwater. Micro-nano bubbles (MNBs) injection seems to be an effective technique for increasing oxygen in water compared with traditional air sparging technology with macrobubbles. Micro-nano bubbles have larger interfacial area, higher inner pressure and density, and lower rising velocity in water, superior to that of macrobubbles. In this paper, MNBs with diameters ranging from 500 nm to 100 microm are investigated, with a specific focus on the oxygen mass transfer coefficient from inner bubbles to surrounding water. The influence of surfactant on the bubbles formation and dissolution is studied as well. The stability of MNBs is further investigated by means of zeta potential measurements and rising velocity analysis. The results show that MNBs can greatly increase oxygen content in water. Higher surfactant concentration in water will decrease the bubbles size, reduce the dissolution rate, and increase the zeta potential. Moreover, MNBs with greater zeta potential value tend to be more stable. Besides, the low rising velocity of MNBs contributes to the long stagnation in water. It is suggested that micro-nano bubble aeration, a potential in groundwater remediation technology, can largely enhance the bioremediation effect. PMID:25327025

  3. 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

  4. Energy effects in bubble nucleation

    SciTech Connect

    Jackson, M.L. . Dept. of Chemical Engineering)

    1994-04-01

    Bubble size and number produced by desorption are important considerations for certain industrial processes such as flotation, gas stripping, and some types of chemical reactions and mass transfer. The size and number of bubbles produced by the desorption of supersaturated gases from water are shown to be a primary function of the energy available for bubble formation in a flowing system; this energy is that not dissipated in turbulence and friction. The number of nucleation sites is greatly increased when certain impurities are present, particularly surface-active agents. Low saturation pressures can produce very large numbers of very small bubbles when added energy is provided for discharge. High gas concentrations produce excess large bubbles which pass up rapidly through the much slower rising bubble mass. A combination of low saturation pressure followed by higher pressure for flow, such as by liquid pumping, results in bubble characteristics which can be controlled for applications.

  5. Characteristics of carbon nanotubes based micro-bubble generator for thermal jet printing.

    PubMed

    Zhou, Wenli; Li, Yupeng; Sun, Weijun; Wang, Yunbo; Zhu, Chao

    2011-12-01

    We propose a conceptional thermal printhead with dual microbubble generators mounted parallel in each nozzle chamber, where multiwalled carbon nanotubes are adopted as heating elements with much higher energy efficiency than traditional approaches using noble metals or polysilicon. Tailing effect of droplet can be excluded by appropriate control of grouped bubble generations. Characteristics of the corresponding micro-fabricated microbubble generators were comprehensively studied before the formation of printhead. Electrical properties of the microheaters on glass substrate in air and performance of bubble generation underwater focusing on the relationships between input power, device resistance and bubble behavior were probed. Proof-of-concept bubble generations grouped to eliminate the tailing effect of droplet were performed indicating precise pattern with high resolution could be realized by this kind of printhead. Experimental results revealed guidance to the geometric design of the printhead as well as its fabrication margin and the electrical control of the microbubble generators. PMID:22408940

  6. Observations of solute effects on bubble formation

    SciTech Connect

    Hofmeier, U.; Yaminsky, V.V.; Christenson, H.K.

    1995-09-01

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

  7. Effects of system parameters on the physical characteristics of bubbles produced through air sparging.

    PubMed

    Burns, S E; Zhang, M

    2001-01-01

    Air sparging is a relatively new, cost-effective technology for the remediation of soil and groundwater contaminated with volatile organic compounds (VOCs). While the method has met with reasonable success at a large number of field sites, implementation of the technique is restricted to relatively coarse-grained soils with large values of air permeability, which significantly limits its applicability. An understanding of the fundamental parameters that control the formation and distribution of air in the sparging process is useful for optimizing the system implementation and extending its range of applicability. This work presents the results of an experimental investigation into the effect of process control parameters on the size and size distribution of air bubbles produced in aqueous and idealized saturated porous media systems. The experiments used digital image analysis to image and quantify the physical characteristics of the bubbles generated in a bench scale test cell. Results demonstrated that the average bubble size and range of size distribution increased as the injection pressure and size of the injection orifice were increased. Larger diameter bubbles with wider size distributions were produced in the presence of particles when compared to aqueous systems. As the particle size was decreased, the size of bubbles produced increased. Finally, the presence of trace quantities of the surfactant Triton X100 led to uniformly small diameter bubbles under all experimental conditions. The presence of the surfactant coating produced bubbles with physical characteristics that are more suited to in situ stripping of VOCs than the bubbles produced in the absence of a surfactant. PMID:11352012

  8. Vertical, Bubbly, Cross-Flow Characteristics over Tube Bundles

    NASA Astrophysics Data System (ADS)

    Iwaki, C.; Cheong, K. H.; Monji, H.; Matsui, G.

    2005-12-01

    Two-phase flow over tube bundles is commonly observed in shell and tube-type heat exchangers. However, only limited amount of data concerning flow pattern and void fraction exists due to the flow complexity and the difficulties in measurement. The detailed flow structure in tube bundles needs to be understood for reliable and effective design. Therefore, the objective of this study was to clarify the two-phase structure of cross-flow in tube bundles by PIV. Experiments were conducted using two types of models, namely in-line and staggered arrays with a pitch-to-diameter ratio of 1.5. Each test section contains 20 rows of five 15 mm O.D. tubes in each row. The experiments data were obtained under very low void fraction (?<0.02). Liquid and gas velocity data in the whole flow field were measured successfully by optical filtering and image processing. The structures of bubbly flow in the two different configurations of tube bundles were described in terms of the velocity vector field, turbulence intensity and void fraction.

  9. Characteristic microwave background distortions from collapsing domain wall bubbles

    NASA Technical Reports Server (NTRS)

    Goetz, Guenter; Noetzold, Dirk

    1990-01-01

    The magnitude and angular pattern of distortions of the microwave background are analyzed by collapsing spherical domain walls. A characteristic pattern of redshift distortions of red or blue spikes surrounded by blue discs was found. The width and height of a spike is related to the diameter and magnitude of the disc. A measurement of the relations between these quantities thus can serve as an unambiguous indicator for a collapsing spherical domain wall. From the redshift distortion in the blue discs an upper bound was found on the surface energy density of the walls sigma is less than or approximately 8 MeV cubed.

  10. 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.

  11. 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.

  12. The effects of coupling and bubble size on the dynamical-systems behaviour of a small cluster of microbubbles

    NASA Astrophysics Data System (ADS)

    Chong, K. J. Y.; Quek, C. Y.; Dzaharudin, F.; Ooi, A.; Manasseh, R.

    2010-03-01

    This study endeavours to apply a theoretical model for predicting the dynamics of a bubble cluster of various sizes, within which each bubble may assume different initial conditions from other bubbles in the cluster. The resulting system of coupled Keller-Miksis-Parlitz equations are solved numerically, and the effects of coupling and bubble size on bubble cluster dynamics are examined for a given set of ultrasound parameters. It has been found that the effects of coupling are significant, and a bubble cluster's bifurcation characteristics and route to chaos can be altered by inter-bubble interactions. This gives rise to the possibility of suppressing the chaotic oscillations of microbubbles by varying bubble cluster size. Small equilibrium radii bubbles have little influence on the dynamics of neighbouring bubbles in a cluster via coupling. Furthermore, a bubble system consisting of smaller-sized bubbles transitions from order to chaos at lower driving pressure amplitudes.

  13. 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.

  14. Cap Bubble Drift Velocity in a Confined Test Section

    SciTech Connect

    Xiaodong Sun; Seungjin Kim; Mamoru Ishii; Frank W. Lincoln; Stephen G. Beus

    2002-10-09

    In the two-group interfacial area transport equation, bubbles are categorized into two groups, i.e., spherical/distorted bubbles as group 1 and cap/slug/churn-turbulent bubbles as group 2. The bubble rise velocities for both groups of bubbles may be estimated by the drift flux model by applying different distribution parameters and drift velocities for both groups. However, the drift velocity for group 2 bubbles is not always applicable (when the wall effect becomes important) as in the current test loop of interest where the flow channel is confined by two parallel flat walls, with a dimension of 200-mm in width and 10-mm in gap. The previous experiments indicated that no stable slug flow existed in this test section, which was designed to permit visualization of the flow patterns and bubble characteristics without the distortion associated with curved surfaces. In fact, distorted cap bubbly and churn-turbulent flow was observed. Therefore, it is essential to developed a correlation for cap bubble drift velocity in this confined flow channel. Since the rise velocity of a cap bubble depends on its size, a high-speed movie camera is used to capture images of cap bubbles to obtain the bubble size information. Meanwhile, the rise velocity of cap and elongated bubbles (called cap bubbles hereafter) is investigated by examining the captured images frame by frame. As a result, the conventional correlation of drift velocity for slug bubbles is modified and acceptable agreements between the measurements and correlation estimation are achieved.

  15. Study of water hammer due to a sudden steam bubble collapse using the characteristics method

    SciTech Connect

    Davis, F.J. Jr.; Hassan, Y.A.

    1987-01-01

    The water hammer phenomenon, due to a sudden collapsing of steam in a subcooled liquid, may affect the nuclear steam supply system in several adverse ways. The cumulative effects of steam condensation water hammer in steam generator feed lines can degrade the steam generator integrity. This type of water hammer event also occurs in the surge tank of boiling water reactors. Water hammer may also play a limiting role in the reactor vessel pressure during the reflood stages of a loss-of-coolant accident. For these reasons, water hammer continues to be a major issue in the nuclear power industry. It is, therefore, very desirable to demonstrate accurate means of calculating the time-dependent pressure due to water hammer. This study presents a numerical program developed for estimating the time-dependent pressure response to steam bubble collapse. The method of characteristics (MOC) is utilized to determine pressure propagation due to water hammer.

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

    SciTech Connect

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

    1985-04-01

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

  17. Methane bubble growth in fine-grained muddy aquatic sediment: Insight from modeling

    NASA Astrophysics Data System (ADS)

    Katsman, Regina; Ostrovsky, Ilia; Makovsky, Yizhaq

    2013-09-01

    Methane (CH4) is the most abundant hydrocarbon and one of the most important greenhouse gases in the atmosphere. CH4 bubble growth and migration within muddy aquatic sediments are closely associated with sediment fracturing. In this paper we present the modeling of buoyancy-driven CH4 bubble growth in fine-grained muddy aquatic sediment prior to the beginning of its rise. We designed a coupled mechanical/reaction-transport numerical model that enables a differential fracturing over the bubble front (as it occurs in nature), when the fracturing increment stays constant at the bubble head and subsides towards bubble tail during bubble growth. We show that this differential fracturing over the bubble front controls the bubble shape and size temporal evolution, and is significantly affected by the critical stress intensity factor of the muddy sediment. The intercalated stages of elastic expansion and fracturing during the bubble growth shorten with time as the bubble approaches its terminal size (prior to its ascent). Our simulations reveal a high asymmetry in the bubble shape growing with time, with respect to its initial symmetric penny-shaped configuration. It was found that the bubble grows allometrically, while the importance of the bubble surface area growth with time. We also confirmed the earlier predictions about the "inverted tear-drop" bubble cross-section just prior to the beginning of its rise. Modeling of the terminal bubble characteristics will permit prediction of the delivery of gaseous methane from the sediment to the atmosphere via the water column.

  18. Buoyancy Driven Shear Flows of Bubble Suspensions

    NASA Astrophysics Data System (ADS)

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

    1998-11-01

    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 << 1 and Re >> 1 , so that the bubbles are relatively undeformed and the flow is inviscid and approximately irrotational. Nitrogen is introduced through an array of capillaries at the base of a .2x.02x2 m channel filled with an aqueous electrolyte solution (0.06 molL-1 MgSO_4). The rising bubbles generate a unidirectional shear flow, where the denser suspension at the lower surface of the channel falls, while the less dense suspension at the upper surface rises. Hot-film anemometry is used to measure the resulting gas volume fraction and fluid velocity profiles. The bubble collision rate with the sensor is related to the gas volume fraction and the mean and variance of the bubble velocity using an experimentally measured collision surface area for the sensor. Bubble collisions with the sensor are identified by the characteristic slope of the hot-film anemometer signal when bubbles collide with the sensor. It is observed that the steady shear flow develops a bubble phase pressure gradient across the channel gap as the bubbles interchange momentum through direct collisions. The discrete phase presssure gradient balances the buoyancy force driving bubbles toward the upper surface resulting in a steady void fraction profile across the gap width. The strength of the shear flow is controlled by the extent of bubble segregation and by the effective viscosity of the bubble phase. The measurements are compared with solutions of the averaged equations of motion (Kang et al. 1997; Spelt and Sangani, 1998), for a range of gas volume fractions and channel inclination angles.

  19. Methane Bubble Growth in Muddy Aquatic Sediment: Insight from Modeling

    NASA Astrophysics Data System (ADS)

    Katsman, Regina; Ostrovsky, Ilia; Makovsky, Yizhaq

    2013-04-01

    Methane (CH4) is the most abundant hydrocarbon and one of the most important greenhouse gases in the atmosphere. CH4 bubble growth and migration within muddy aquatic sediments are closely associated with sediment fracturing. We present the modeling results of buoyancy-driven CH4 bubble growth in fine-grained muddy aquatic sediment prior to the beginning of the bubble rise. The designed coupled mechanical/reaction-transport numerical model enables a differential fracturing over the bubble front, simulating the dynamics observed in the nature. We show that this differential fracturing over the bubble front controls bubble shape and size temporal evolution. The intercalated stages of elastic expansion and fracturing during the bubble growth subside with time as bubble approaches its terminal size prior to ascend. Our simulations reveal a high asymmetry in the bubble shape growing with time, with respect to its initial symmetric penny-shaped configuration. It is found that the bubble grows allometrically, when the importance of the bubble surface area growth with time, making it more sensitive to the ambient field of methane concentrations. We analyze the affect of the different sediment characteristics on the bubble shape and size evolution. Modeling of the terminal parameters of the mature bubble emitted from the sediment will permit predicting the delivery of gaseous methane to the atmosphere via the water column.

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

    NASA Astrophysics Data System (ADS)

    Crews, Jackson B.

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

  1. The effect of fine bubble aeration intensity on membrane bioreactor sludge characteristics and fouling.

    PubMed

    De Temmerman, L; Maere, T; Temmink, H; Zwijnenburg, A; Nopens, I

    2015-06-01

    While most membrane bioreactor (MBR) research focuses on improving membrane filtration through air scour, backwashing and chemical cleaning to physically counteract fouling, relatively few studies have dealt with fouling prevention, e.g. minimizing the impact of operational settings that negatively impact sludge filterability. To evaluate the importance of those settings, the effects of bioreactor aeration intensity variations on membrane fouling have been studied in a lab-scale MBR setup while simultaneously monitoring a unique set of key sludge parameters. In particular, this paper focuses on the impact of shear dynamics resulting from fine air bubbles on the activated sludge quality and flocculation state, impacting membrane fouling. When augmenting the fine bubble aeration intensity both the total and irreversible fouling rate increased. Major indications for sludge filterability deterioration were found to be a shift in the particle size distribution (PSD) in the 3-300 μm range towards smaller sludge flocs, and increasing concentrations of submicron particles (10-1000 nm), soluble microbial products and biopolymers. When lowering the aeration intensity, both the sludge characteristics and fouling either went back to background values or stabilized, respectively indicating a temporary or more permanent effect, with or without time delay. The shift in PSD to smaller flocs and fragments likely increased the total fouling through the formation of a less permeable cake layer, while high concentrations of submicron particles were likely causing increased irreversible fouling through pore blocking. The insights from the performed fouling experiments can be used to optimize system operation with respect to influent dynamics. PMID:25794465

  2. 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.

  3. The influence of initial pressure on the characteristics of conical bubble sonoluminescence

    NASA Astrophysics Data System (ADS)

    He, Shoujie; Ha, Jing; Duan, Pingguang

    2015-12-01

    Based on a conical bubble U-tube, conical bubble sonoluminescence was investigated by using pure water as the working medium. Intense cavitation luminescence can be obtained. With the decrease in initial pressure inside the bubble, the intensity and duration of light emission increased. The spectrum is mainly composed of the spectral bands of H2O at the initial pressure of 1000 Pa. With the decrease in initial pressure, a broad continuum background spectrum that is well fitted by blackbody radiation can be detected, on which several spectral bands emitted by water molecules are superimposed. A higher temperature inside the bubble can be obtained with the decrease in initial pressure. Moreover, the intensity of the continuum background spectrum becomes more dominant compared with that of H2O emission bands. Finally, we conclude that blackbody radiation and molecular emission contribute to luminescence of conical bubble cavitation. Moreover, the initial pressure inside the conical bubble significantly affects the emission mechanism of conical bubble sonoluminescence.

  4. Understanding the plasma and power characteristics of a self-generated steam bubble discharge

    NASA Astrophysics Data System (ADS)

    Garcia, Maria C.; Gucker, Sarah N.; Foster, John E.

    2015-09-01

    Plasma formation in a self-generated steam bubble is studied using a coaxial discharge tube with an axial powered electrode (nominal peak operating voltage 2000 V) and an external ground lead without any gas flow. The discharge is potentially attractive for water purification applications in that the production of reactive nitrogen species and the associated water acidification is avoided. The discharge was found to form after a finite delay, which is attributed to the vapor bubble formation necessary for plasma ignition. Steam bubble composition was confirmed using emission spectra. Plasma properties and power dissipated in the self-generated steam bubble were characterized using emission spectroscopy and Lissajous methods. Discharge density and gas temperature were found to vary significantly over the applied ac voltage cycle. The power dissipated as inferred from the Lissajous method was found to scale inversely with frequency over the low frequency range investigated (4 kHz and 5 kHz).

  5. 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

  6. 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

  7. 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.

  8. Shock formation within sonoluminescence bubbles

    SciTech Connect

    Vuong, V.Q.; Szeri, A.J.; Young, D.A.

    1999-01-01

    A strong case has been made by several authors that sharp, spherically symmetric shocks converging on the center of a spherical bubble driven by a strong acoustic field give rise to rapid compression and heating that produces the brief flash of light known as sonoluminescence. The formation of such shocks is considered. It is found that, although at the main collapse the bubble wall does indeed launch an inwardly-traveling compression wave, and although the subsequent reflection of the wave at the bubble center produces a very rapid temperature peak, the wave is prevented from steepening into a sharp shock by an adverse gradient in the sound speed caused by heat transfer. It is shown that the mathematical characteristics of the flow can be prevented from accumulating into a shock front by this adverse sound speed gradient. A range of results is presented for a variety of bubble ambient radii and sound field amplitudes suggested by experiments. The time scale of the peak temperature in the bubble is set by the dynamics of the compression wave: this is typically in the range 100{endash}300 ps (FWHM) in concert with recent measurements of the sonoluminescence pulse width. {copyright} {ital 1999 American Institute of Physics.}

  9. Dynamics of Rear Stagnant Cap formation at the surface of spherical bubbles rising in surfactant solutions at large Reynolds numbers under conditions of small Marangoni number and slow sorption kinetics.

    PubMed

    Dukhin, S S; Kovalchuk, V I; Gochev, G G; Lotfi, M; Krzan, M; Malysa, K; Miller, R

    2015-08-01

    On the surface of bubbles rising in a surfactant solution the adsorption process proceeds and leads to the formation of a so called Rear Stagnant Cap (RSC). The larger this RSC is the stronger is the retardation of the rising velocity. The theory of a steady RSC and steady retarded rising velocity, which sets in after a transient stage, has been generally accepted. However, a non-steady process of bubble rising starting from the initial zero velocity represents an important portion of the trajectory of rising, characterized by a local velocity profile (LVP). As there is no theory of RSC growth for large Reynolds numbers Re » 1 so far, the interpretation of LVPs measured in this regime was impossible. It turned out, that an analytical theory for a quasi-steady growth of RSC is possible for small Marangoni numbers Ma « 1, i.e. when the RSC is almost completely compressed, which means a uniform surface concentration Γ(θ)=Γ(∞) within the RSC. Hence, the RSC angle ψ(t) is obtained as a function of the adsorption isotherm parameters and time t. From the steady velocity v(st)(ψ), the dependence of non-steady velocity on time is obtained by employing v(st)[ψ(t)] via a quasi-steady approximation. The measurement of LVP creates a promising new opportunity for investigation of the RSC dynamics and adsorption kinetics. While adsorption and desorption happen at the same localization in the classical methods, in rising bubble experiments desorption occurs mainly within RSC while adsorption on the mobile part of the bubble surface. The desorption flux from RSC is proportional to αΓ(∞), while it is usually αΓ. The adsorption flux at the mobile surface above RSC can be assumed proportional to βC0, while it is usually βC0(1-Γ/Γ(∞)). These simplifications may become favorable in investigations of the adsorption kinetics for larger molecules, in particular for globular proteins, which essentially stay at an interface once adsorbed. PMID:25455807

  10. Chemical and physical characteristics of nascent aerosols produced by bursting bubbles at a model air-sea interface

    NASA Astrophysics Data System (ADS)

    Keene, William C.; Maring, Hal; Maben, John R.; Kieber, David J.; Pszenny, Alexander A. P.; Dahl, Elizabeth E.; Izaguirre, Miguel A.; Davis, Andrew J.; Long, Michael S.; Zhou, Xianliang; Smoydzin, Linda; Sander, Rolf

    2007-11-01

    Breaking waves on the ocean surface produce bubbles that, upon bursting, inject seawater constituents into the atmosphere. Nascent aerosols were generated by bubbling zero-air through flowing seawater within an RH-controlled chamber deployed at Bermuda and analyzed for major chemical and physical characteristics. The composition of feed seawater was representative of the surrounding ocean. Relative size distributions of inorganic aerosol constituents were similar to those in ambient air. Ca2+ was significantly enriched relative to seawater (median factor = 1.2). If in the form of CaCO3, these enrichments would have important implications for pH-dependent processes. Other inorganic constituents were present at ratios indistinguishable from those in seawater. Soluble organic carbon (OC) was highly enriched in all size fractions (median factor for all samples = 387). Number size distributions exhibited two lognormal modes. The number production flux of each mode was linearly correlated with bubble rate. At 80% RH, the larger mode exhibited a volume centroid of 5-?m diameter and included 95% of the inorganic sea-salt mass; water comprised 79% to 90% of volume. At 80% RH, the smaller mode exhibited a number centroid of 0.13-?m diameter; water comprised 87% to 90% of volume. The median mass ratio of organic matter to sea salt in the smallest size fraction (geometric mean diameter = 0.13 ?m) was 4:1. These results support the hypothesis that bursting bubbles are an important global source of CN and CCN with climatic implications. Primary marine aerosols also influence radiative transfer via multiphase processing of sulfur and other climate-relevant species.

  11. Characteristics of the initial rising portion of near and far lightning return stroke electric field waveforms

    NASA Astrophysics Data System (ADS)

    Nag, A.; Rakov, V. A.; Tsalikis, D.; Howard, J. S.; Biagi, C. J.; Hill, J. D.; Uman, M. A.; Jordan, D. M.

    2012-11-01

    We examine initial rising portions of electric field waveforms of negative first return strokes in natural cloud-to-ground lightning recorded simultaneously at near and far distances from the lightning channel. The near and far field-measuring stations are located at Camp Blanding and in Gainesville, Florida, respectively, separated by a distance of about 45 km. A total of five return strokes had been recorded in 2007-2008, four of which were analyzed in detail (one was not suitable for analysis due to saturation of electric field waveform at the far station). Field waveform characteristics, including overall zero-to-peak and 10-to-90% risetimes, duration of slow front, fast transition 10-to-90% risetime, and magnitude of slow front relative to the peak, were found to be similar to those reported from other studies, in which the field propagation path was over ground (as opposed to sea water). It is shown, via modeling, that the slow front in electric field waveforms at far distances is primarily due to the radiation field component, while at near distances it is composed of comparable contributions from all three components of electric field. For both measured and model-predicted waveforms, the durations of the slow front appear to be similar at near and far distances from the lightning channel.

  12. Temperature Rise and Welding Characteristics of Various-Frequency Ultrasonic Plastic Welding Systems

    NASA Astrophysics Data System (ADS)

    Hongoh, Misugi; Miura, Hiroyuki; Ueoka, Tetsugi; Tsujino, Jiromaru

    2006-05-01

    Welding characteristics and temperature increases of ultrasonic plastic welding parts over a frequency range from 27 to 94 kHz are studied. Using 27, 40, 67, and 94 kHz ultrasonic plastic welding systems, temperature increases at welding surfaces of lapped 1.0-, 2.0-, and 3.0-mm-thick polypropylene plates and polymethyl methacrylate plates are measured using 0.1- and 0.2-mm-diameter thermocouples inserted between plates, and temperature distributions at cross sections of lapped plate specimens are measured using a thermotracer. The 94 kHz vibration system used for ultrasonic plastic welding consists of a bolt-clamped Langevin-type longitudinal vibration source using four 30-mm-diameter piezoelectric ceramic (PZT) rings, a stepped horn (vibration velocity transform ratio N=3.0) and a catenoidal horn (N=3.13) with an 8-mm-diameter welding tip. The other vibration systems have similar configurations. In the case of using a higher-frequency system, increases in temperature measured at the welding parts are larger. Temperature rises are larger for lapped plate specimens than that for a one-piece specimen owing to the vibration loss of welding surfaces.

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

    PubMed

    Lee, Ji-Hyun; Jo, Wan-Kuen

    2006-05-01

    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 and the outdoor air were Cladosporium, Penicillium, Aspergillus, and Alternaria. The outdoor bacterial concentrations were significantly higher in the low-floor apartments than in the high-floor apartments. However, the bacterial and fungal concentrations in the interior air of the apartments were not significantly different between the low- and the high-floor apartments. The current bioaerosol concentrations were comparable to those in other reports, with geometric mean (GM) bacterial values between 10 and 10(3) CFU m(-3) and fungal aerosol concentrations in homes ranging also from 10 to 10(3) CFU m(-3). The indoor and outdoor fungal concentrations and the outdoor bacterial concentrations were usually higher in the summer than in the winter. The indoor and outdoor bioaerosol concentrations were both higher for the SRFP than for the NRFP. The difference in the total bacterial concentrations was not significant among the surveyed five rooms. The GM total fungal and Cladosporium concentrations, however, were significantly higher for the kitchen than for the other rooms. PMID:16199028

  14. Bubble convection within magma reservoirs

    NASA Astrophysics Data System (ADS)

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

    2008-11-01

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

  15. Cavitation erosion by single laser-produced bubbles

    NASA Astrophysics Data System (ADS)

    Philipp, A.; Lauterborn, W.

    1998-04-01

    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 recorded with high-speed photography with framing rates of up to one million frames/s. Damage is observed when the bubble is generated at a distance less than twice its maximum radius from a solid boundary ([gamma]=2, where [gamma]=s/Rmax, s is the distance between the boundary and the bubble centre at the moment of formation and Rmax is the maximum bubble radius). The impact of the jet contributes to the damage only at small initial distances ([gamma][less-than-or-eq, slant]0.7). In this region, the impact velocity rises to 83 m s[minus sign]1, corresponding to a water hammer pressure of about 0.1 GPa, whereas at [gamma]>1, the impact velocity is smaller than 25 m s[minus sign]1. The largest erosive force is caused by the collapse of a bubble in direct contact with the boundary, where pressures of up to several GPa act on the material surface. Therefore, it is essential for the damaging effect that bubbles are accelerated towards the boundary during the collapse phases due to Bjerknes forces. The bubble touches the boundary at the moment of second collapse when [gamma]<2 and at the moment of first collapse when [gamma]<1. Indentations on an aluminium specimen are found at the contact locations of the collapsing bubble. In the range [gamma]=1.7 to 2, where the bubble collapses mainly down to a single point, one pit below the bubble centre is observed. At [gamma][less-than-or-eq, slant]1.7, the bubble shape has become toroidal, induced by the jet flow through the bubble centre. Corresponding to the decay of this bubble torus into multiple tiny bubbles each collapsing separately along the circumference of the torus, the observed damage is circular as well. Bubbles in the ranges [gamma][less-than-or-eq, slant]0.3 and [gamma]=1.2 to 1.4 caused the greatest damage. The overall diameter of the damaged area is found to scale with the maximum bubble radius. Owing to the possibility of generating thousands of nearly identical bubbles, the cavitation resistance of even hard steel specimens can be tested.

  16. Growth characteristics of Chlorella sorokiniana in airlift and bubble column photobioreactors.

    PubMed

    Kumar, Kanhaiya; Das, Debabrata

    2012-07-01

    The present study investigated the feasibility of bioCO(2) sequestration using Chlorella sorokiniana. It was found that 5% CO(2) (v/v) in air was the most suitable concentration for the growth of this organism. At this concentration, the maximum rate of CO(2) sequestered and the biomass obtained were found to be 1.21 g L(-1)d(-1) and 4.4 g L(-1) respectively. Modeling and simulation of the growth profile was obtained using the logistic equation. Further, at higher CO(2) concentrations, pH drop in the growth media, TAP [-acetate], was prevented by replacing NH(4)Cl by NaNO(3.) Additionally, the study evaluated the performance of two reactors namely: bubble column and airlift reactor based on their growth profile and transport properties like K(L)a and mixing time. The growth profile was better in airlift reactor and it provides cyclic axial mixing of media. K(L)a of downcomer was significantly lower than the riser in airlift reactor. PMID:22525259

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

    SciTech Connect

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

    2015-05-07

    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.

  18. 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.

  19. Cost versus Enrollment Bubbles

    ERIC Educational Resources Information Center

    Vedder, Richard K.; Gillen, Andrew

    2011-01-01

    The defining characteristic of a bubble is unsustainable growth that eventually reverses. Bubbles typically arise when uncertainty leads to unsustainable trends, and the authors argue that there are two areas in which higher education has experienced what appear to be unsustainable trends, namely, college costs (the costs to students, parents, and

  20. 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.

  1. 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

  2. Numerical simulation of bubble induced flow by vortex method

    NASA Astrophysics Data System (ADS)

    Wang, Z. W.; Uchiyama, T.; Chen, B.

    2011-09-01

    The behavior of air bubbles rising in water and the bubble induced flow field are numerically studied using a three-dimensional two-way coupling algorithm based on Vortex-In-Cell method. A small vortex ring structure is generated with the rising of bubbles and the small vortex ring structure is led by the rising bubble cluster at first. The bubbles are accelerated by the vortex ring structure, and the bubble distribution and the shape of the bubble cluster are transformed by the vortex ring structure at the same time.

  3. 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…

  4. 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

  5. Suite Ventilation Characteristics of Current Canadian Mid-andHigh-Rise Residential Buildings

    SciTech Connect

    Wray, Craig P.

    2000-01-01

    This paper characterizes ventilation in residential suiteslocated in ll buildings were between six and thirty-two stories tall andwere built between 1990 and 1995. The key findings from field performancetests of these buildings were: 1. Corridor supply airflows usually didnot meet design flows.2. Makeup air paths for suite exhaust were notproperly designed.3. Suite access door leakage was highly variable andusually did not meet smoke control requirements.4. Airflow from thecorridor through the suite access door leakage appeared to be the primaryventilation air supply for suites.5. Suites were usually well-ventilated,but some were marginally- or under-ventilated.6. Poor pressure controloften allowed transfer air from one suite to another. Inter-suitetransfer air fractions ranged from 0 to 45 percent, with an average of 19percent. In summary, this work showed suite ventilation can be highlyinfluenced by corridor supply flows, by the treatment of corridor accessdoors, and by transfer airflows. As a result, suite ventilation at anygiven time in current mid- and high-rise residential buildings is verydifficult to predict. To ensure suite ventilation performs as intendedunder all operating conditions, the building industry needs to addressthe identified problems through improved ventilation design, operation,and maintenance practices.

  6. The Temporal and Spectral Characteristics of "Fast Rise and Exponential Decay" Gamma-ray Burst Pulses

    NASA Astrophysics Data System (ADS)

    Peng, Z. Y.; Yin, Y.; Bi, X. W.; Zhao, X. H.; Fang, L. M.; Bao, Y. Y.; Ma, L.

    2010-08-01

    In this paper, we have analyzed the temporal and spectral behavior of 52 fast rise and exponential decay (FRED) pulses in 48 long-duration gamma-ray bursts (GRBs) observed by the CGRO/BATSE, using a pulse model with two shape parameters and the Band model with three shape parameters, respectively. It is found that these FRED pulses are distinguished both temporally and spectrally from those in the long-lag pulses. In contrast to the long-lag pulses, only one parameter pair indicates an evident correlation among the five parameters, which suggests that at least four parameters are needed to model burst temporal and spectral behavior. In addition, our studies reveal that these FRED pulses have the following correlated properties: (1) long-duration pulses have harder spectra and are less luminous than short-duration pulses and (2) the more asymmetric the pulses are, the steeper are the evolutionary curves of the peak energy (Ep ) in the ?f ? spectrum within the pulse decay phase. Our statistical results give some constraints on the current GRB models.

  7. THE TEMPORAL AND SPECTRAL CHARACTERISTICS OF 'FAST RISE AND EXPONENTIAL DECAY' GAMMA-RAY BURST PULSES

    SciTech Connect

    Peng, Z. Y.; Ma, L.; Yin, Y.; Bi, X. W.; Zhao, X. H.; Bao, Y. Y. E-mail: astromali@126.co

    2010-08-01

    In this paper, we have analyzed the temporal and spectral behavior of 52 fast rise and exponential decay (FRED) pulses in 48 long-duration gamma-ray bursts (GRBs) observed by the CGRO/BATSE, using a pulse model with two shape parameters and the Band model with three shape parameters, respectively. It is found that these FRED pulses are distinguished both temporally and spectrally from those in the long-lag pulses. In contrast to the long-lag pulses, only one parameter pair indicates an evident correlation among the five parameters, which suggests that at least four parameters are needed to model burst temporal and spectral behavior. In addition, our studies reveal that these FRED pulses have the following correlated properties: (1) long-duration pulses have harder spectra and are less luminous than short-duration pulses and (2) the more asymmetric the pulses are, the steeper are the evolutionary curves of the peak energy (E{sub p}) in the {nu}f{sub {nu}} spectrum within the pulse decay phase. Our statistical results give some constraints on the current GRB models.

  8. Numerical study of the influence of geometrical characteristics of a vertical helical coil on a bubbly flow

    NASA Astrophysics Data System (ADS)

    Saffari, H.; Moosavi, R.

    2014-11-01

    In this article, turbulent single-phase and two-phase (air-water) bubbly fluid flows in a vertical helical coil are analyzed by using computational fluid dynamics (CFD). The effects of the pipe diameter, coil diameter, coil pitch, Reynolds number, and void fraction on the pressure loss, friction coefficient, and flow characteristics are investigated. The Eulerian-Eulerian model is used in this work to simulate the two-phase fluid flow. Three-dimensional governing equations of continuity, momentum, and energy are solved by using the finite volume method. The k- ? turbulence model is used to calculate turbulence fluctuations. The SIMPLE algorithm is employed to solve the velocity and pressure fields. Due to the effect of a secondary force in helical pipes, the friction coefficient is found to be higher in helical pipes than in straight pipes. The friction coefficient increases with an increase in the curvature, pipe diameter, and coil pitch and decreases with an increase in the coil diameter and void fraction. The close correlation between the numerical results obtained in this study and the numerical and empirical results of other researchers confirm the accuracy of the applied method. For void fractions up to 0.1, the numerical results indicate that the friction coefficient increases with increasing the pipe diameter and keeping the coil pitch and diameter constant and decreases with increasing the coil diameter. Finally, with an increase in the Reynolds number, the friction coefficient decreases, while the void fraction increases.

  9. Blowing magnetic skyrmion bubbles

    NASA Astrophysics Data System (ADS)

    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

    2015-07-01

    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.

  10. IODP Expedition 345: Geochemical Characteristics of Fast Spread Lower East Pacific Rise

    NASA Astrophysics Data System (ADS)

    Meyer, R.; Godard, M.; Saha, A.; Gillis, K. M.; Snow, J. E.; Klaus, A.

    2013-12-01

    Drilling by the Integrated Ocean Drilling Program (IODP) at the Hess Deep Rift recovered young (ca. 1Ma) primitive gabbroic rocks that formed at the fast-spreading East Pacific Rise. Olivine gabbro and troctolite are the dominant rock types recovered at Site U1415, with minor gabbro, clinopyroxene oikocryst-bearing troctolite, clinopyroxene oikocryst-bearing gabbro, and gabbronorite.Two rock series were identified, a layered series with simple layers to diffuse bands of gabbroic rock types and a troctolite series. Olivine gabbros, gabbros and gabbronorites from the layered series have high Mg-numbers (Mg/Mg+Fe) = 79-87), high Ni (130-570 ppm), and low TiO2 (0.1-0.3 wt.%)and incompatible element (e.g., Y <11 ppm) contents. The troctolite series overlaps the gabbroic compositions but are, on average, more primitive with high Mg-numbers (81-89), Ni (260-1500 ppm),and Cr (365-1100 ppm) concentrations,and low TiO2 (<0.1 wt.%)and incompatible element (e.g., Y <3 ppm) contents. The most primitive troctolites sampled have compositions overlapping the field of impregnated mantle peridotites, including those from the Hess Deep Rift. However, these samples are low in Ni relative to their high Mg-number, indicating formation by a dominantly cumulate process. The gabbroic rocks at Site U1415 are far more primitive than the shallow-level gabbros at the Hess Deep Rift and are similar in bulk composition to gabbros from the shallow gabbros from Pito Deep where fast-spreading EPR crust is exposed (Perk et al., 2007). These primitive rock types fall within the range of primitive oceanic gabbros from fast-spreading crust.The preliminary geochemical data are consistent with a petrogenesis as a cumulate sequence from parental mid-ocean ridge basaltic (MORB) melt. However, the occurrence of orthopyroxene in highly primitive rocks challenges current models for melt extraction and MORB crystallization, where orthopyroxene is believed to be only stable within a more evolved MORB crystallization sequence. Perk et al. Contrib. Mineral. Petrol., 154(5):575-590, 2007

  11. Influences of suspended fine particles on gas holdup and mass transfer characteristics in a slurry bubble column

    SciTech Connect

    Sada, E.; Kumazawa, H.; Lee, C.H.

    1986-05-01

    In this work, slurries with suspended fine particles (whose size is smaller than 10 ..mu..m) of lower than 1 wt. % were used to provide an insight into the solid-bubble interaction in a bubble column. The liquid property and the gas sparging system as well as the particle size were varied; the effects of these variables on the gas holdup and the volumetric liquid-side mass transfer coefficient were determined experimentally and are here discussed quantitatively.

  12. Recalcitrant bubbles

    PubMed Central

    Shanahan, Martin E. R.; Sefiane, Khellil

    2014-01-01

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

  13. Recalcitrant bubbles.

    PubMed

    Shanahan, Martin E R; Sefiane, Khellil

    2014-01-01

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

  14. Bubble stimulation efficiency of dinoflagellate bioluminescence.

    PubMed

    Deane, Grant B; Stokes, M Dale; Latz, Michael I

    2016-02-01

    Dinoflagellate bioluminescence, a common source of bioluminescence in coastal waters, is stimulated by flow agitation. Although bubbles are anecdotally known to be stimulatory, the process has never been experimentally investigated. This study quantified the flash response of the bioluminescent dinoflagellate Lingulodinium polyedrum to stimulation by bubbles rising through still seawater. Cells were stimulated by isolated bubbles of 0.3-3 mm radii rising at their terminal velocity, and also by bubble clouds containing bubbles of 0.06-10 mm radii for different air flow rates. Stimulation efficiency, the proportion of cells producing a flash within the volume of water swept out by a rising bubble, decreased with decreasing bubble radius for radii less than approximately 1 mm. Bubbles smaller than a critical radius in the range 0.275-0.325 mm did not stimulate a flash response. The fraction of cells stimulated by bubble clouds was proportional to the volume of air in the bubble cloud, with lower stimulation levels observed for clouds with smaller bubbles. An empirical model for bubble cloud stimulation based on the isolated bubble observations successfully reproduced the observed stimulation by bubble clouds for low air flow rates. High air flow rates stimulated more light emission than expected, presumably because of additional fluid shear stress associated with collective buoyancy effects generated by the high air fraction bubble cloud. These results are relevant to bioluminescence stimulation by bubbles in two-phase flows, such as in ship wakes, breaking waves, and sparged bioreactors. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26061152

  15. Writing bubbles

    NASA Astrophysics Data System (ADS)

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

    2012-11-01

    We report on the nucleation of bubbles under a solid sphere immersed in a supersaturated liquid that is gently rubbed against a surface. For a fixed liquid supersaturation, bubbles are observed only above a certain rubbing velocity threshold. Above this threshold and provided that bubbles adhere better to the surface than to the sphere, a regularly spaced row of growing bubbles is left behind on the surface. Direct observation through a transparent sphere shows that each bubble in the row actually results from the early coalescence of several microscopic bubbles, which nucleate between the sphere and the surface. Together with the influence of the degree of supersaturation and the normal force between sphere and surface, we study the influence of the liquid itself (water or ethanol), the sphere material (glass, metal or Teflon) and of the surface roughness (polished or unpolished). Regardless of its precise origin, this method of ``writing bubbles'' also provides a simple way to spatially and temporally control the nucleation of bubbles on a surface and to study their interactions.

  16. 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.

  17. Magma mixing enhanced by bubble segregation

    NASA Astrophysics Data System (ADS)

    Wiesmaier, S.; Daniele, M.; Renggli, C.; Perugini, D.; De Campos, C.; Hess, K. U.; Ertel-Ingrisch, W.; Lavalle, Y.; Dingwell, D. B.

    2014-12-01

    Rising bubbles may significantly affect magma mixing paths as has been demonstrated by analogue experiments in the past. Here, bubble-advection experiments are performed for the first time employing natural materials at magmatic temperatures. Cylinders of basaltic glass were placed below cylinders of rhyolite glass. Upon melting, interstitial air formed bubbles that rose into the rhyolite melt, thereby entraining tails of basaltic liquid. The formation of plume-like filaments of advected basalt within the rhyolite was characterized by microCT and subsequent high-resolution EMP analyses. Melt entrainment by bubble ascent appears as efficient mechanism to mingle contrasting melt compositions. MicroCT imaging shows bubbles trailing each other and trails of multiple bubbles having converged. Rheological modelling of the filaments yields viscosities of up to 2 orders of magnitude lower than for the surrounding rhyolitic liquid. Such a viscosity contrast implies that subsequent bubbles rising are likely to follow the same pathways that previously ascending bubbles have generated. Filaments formed by multiple bubbles would thus experience episodic replenishment with mafic material. Fundamental implications for the concept of bubble advection in magma mixing are thus a) an acceleration of mixing because of decreased viscous resistance for bubbles inside filaments and b) non-conventional diffusion systematics because of intermittent supply of mafic material (instead of a single pulse) inside a filament. Inside these filaments, the mafic material was variably hybridised to andesitic through rhyolitic composition. Compositional profiles alone are ambiguous, however, to determine whether single or multiple bubbles were involved during formation of a filament. Statistical analysis, employing concentration variance as measure of homogenisation, demonstrates that also filaments appearing as single-bubble filaments are likely to have experienced multiple bubbles passing through. Whenever bubbles were essential for magma mixing, standard diffusion calculus may thus be inapplicable for constraining timescales. However, data analysis employing concentration variance allows distinguishing conventional single-pulse filaments from multiple bubble ascent advection in natural samples.

  18. Bubble, Bubble, Toil and Trouble.

    ERIC Educational Resources Information Center

    Journal of Chemical Education, 2001

    2001-01-01

    Bubbles are a fun way to introduce the concepts of surface tension, intermolecular forces, and the use of surfactants. Presents two activities in which students add chemicals to liquid dishwashing detergent with water in order to create longer lasting bubbles. (ASK)

  19. Droplets, Bubbles and Ultrasound Interactions.

    PubMed

    Shpak, Oleksandr; Verweij, Martin; de Jong, Nico; Versluis, Michel

    2016-01-01

    The interaction of droplets and bubbles with ultrasound has been studied extensively in the last 25 years. Microbubbles are broadly used in diagnostic and therapeutic medical applications, for instance, as ultrasound contrast agents. They have a similar size as red blood cells, and thus are able to circulate within blood vessels. Perfluorocarbon liquid droplets can be a potential new generation of microbubble agents as ultrasound can trigger their conversion into gas bubbles. Prior to activation, they are at least five times smaller in diameter than the resulting bubbles. Together with the violent nature of the phase-transition, the droplets can be used for local drug delivery, embolotherapy, HIFU enhancement and tumor imaging. Here we explain the basics of bubble dynamics, described by the Rayleigh-Plesset equation, bubble resonance frequency, damping and quality factor. We show the elegant calculation of the above characteristics for the case of small amplitude oscillations by linearizing the equations. The effect and importance of a bubble coating and effective surface tension are also discussed. We give the main characteristics of the power spectrum of bubble oscillations. Preceding bubble dynamics, ultrasound propagation is introduced. We explain the speed of sound, nonlinearity and attenuation terms. We examine bubble ultrasound scattering and how it depends on the wave-shape of the incident wave. Finally, we introduce droplet interaction with ultrasound. We elucidate the ultrasound-focusing concept within a droplets sphere, droplet shaking due to media compressibility and droplet phase-conversion dynamics. PMID:26486337

  20. 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...

  1. 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.

  2. Bubble diagnostics

    DOEpatents

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

    2003-01-01

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

  3. 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.

  4. 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

  5. Petrological characteristics of Opx-bearing primitive gabbros from the East Pacific Rise and the Oman ophiolite

    NASA Astrophysics Data System (ADS)

    Python, Marie; Akizawa, Norikatsu; Godard, Marguerite; Ildefonse, Benot; Koepke, Jrgen

    2014-05-01

    The Hess Deep rift is located at the junction between the fast spreading East Pacific Rise and the Cocos-Nazca Ridge. Lower crust is exposed along the southern slope of the intrarift ridge between 4675 and 4800 m depth and was sampled during IODP Expedition 345. Primitive troctolites and olivine-rich gabbros are the dominant recovered lithologies and shipboard data showed a high Mg# whole rock chemistry in concordance with their primitive nature. In a MOR system, olivine is a typical primitive mineral and orthoyroxene (Opx) usually appear late in the crystallisation sequence, when the magma already reached a significant degree of differentiation. In spite Opx is not expected in any primitive lithology, this mineral is commonly present in Hess Deep gabbros and may be associated with olivine. This curious association of cumulate Opx with olivine and other primitive minerals was also observed at a lower extent in some gabbros from ODP/IODP Hole 1256D, in the upper Hess Deep crustal section (ODP Hole 894G), and in the crustal section of the Oman ophiolite (Kahwad massif) where, in particular, Opx-bearing troctolites coexist with clinopyroxene oikocrysts-bearing troctolites and amphibole-bearing primitive olivine gabbros. Three types of Opx textures may be distinguished in Opx-bearing olivine gabbros and troctolites: (1) recrystallised coron around olivine, (2) exsolution within clinopyroxene and (3) large prismatic or poikilitic grains. Prismatic or poikilitic Opx are present at all level of the gabbroic crust, while exsolutions and coron were observed only in the lower crust. The mineral chemical compositions vary more with the structural level than with the lithological type and (Opx-bearing) olivine gabbros from Holes 894G, 1256D and from the upper crust of the Oman ophiolite show more differentiated characteristics than the same lithology in the Site 1415 and in the Oman lower crust. Pyroxenes in all samples from the lower crust show a relatively narrow range of Mg# (from 84 to 86% for Opx and 86 to 89% for Cpx) with large variation of minor elements (Ti, Al, Cr) suggesting a strong influence of melt-rock reaction during their formation. On the other hand, the upper crust samples show a large variation in their ferro-magnesian Mg# (72-87% for Cpx and 70-85% for Opx) together with a relatively weak scatter in minor elements. Magmatic crystallisation were then the dominant event in the upper crust, so that Opx is likely to be directly crystallised from magma. In contrast, in the lower crust, magmatic processes were dominated by melt-rock reaction, and the chemical composition and habitus of Opx show that they have been probably formed by reaction between previously abundant olivine and melt.

  6. Affirmative Discrimination and the Bubble

    ERIC Educational Resources Information Center

    Clegg, Roger

    2011-01-01

    In this essay, the author discusses how affirmative action contributed to an unnatural rise in enrollments in college. In considering the higher education bubble, he makes the case that as the opposition to preferences continues to build, the momentum of this trend will only increase as funding shrinks. He offers some tentative answers to a series

  7. Advances in Optical Characterization of Methane Seeps and Bubble Plumes

    NASA Astrophysics Data System (ADS)

    Pizarro, O.; Farr, N.; Camilli, R.; Whelan, J.; Martens, C.; Goudreau, J.; Mendlovitz, H.; Camilli, L.

    2005-12-01

    Methane seeps are potentially a key contributor to the atmospheric methane reservoir and to the global greenhouse gas budget. Improved estimates of methane flux from ocean floor seeps are required to understand the magnitude and characteristics of this potential source. At less active, deep water seeps a large portion of the migrating gas is dissolved and oxidized before reaching the surface. However, in high-intensity, shallow water methane seeps the bubble density, speed and size are such that a significant fraction of the gas may reach the atmosphere. New types of in-situ chemical sensors are now available to quickly and reliably quantify dissolved methane throughout the water column. However, quantifying methane within the water column in the free gas phase (i.e., in bubbles) remains a challenging problem. Current approaches rely either on indirect acoustic methods or direct collection of bubbles. Acoustic methods have the disadvantage of requiring extensive calibration, and can fail to distinguish the bubble signal from other sources of acoustic noise. Gas-capture techniques are mechanically complex, have a surface expression that introduces some noise, and can potentially alias episodic events. In both cases the fine scale structure such as heterogeneity of the rising bubbling plume is lost. We describe a vision-based system to characterize bubble plumes and the seep features from which they emanate. Video-rate optical imagery from 3 cameras is used to generate precise measurements of the motion of bubbles. Lighting is provided by a distributed array of LED modules synchronized to the cameras. In order to conserve power and extend deployment times the system can be configured to be dormant until triggered by chemical sensors indicating high concentrations of methane. Plume characterization is based on the identification of the individual bubbles (and rejection of other particles). Additional image processing steps are then used to estimate each bubble's volume and velocity. The results are then integrated to produce an estimate of volumetric flux rate. This technique can also reveal fine scale variability in the spatial and temporal structure within the plume. The imaging package was field-tested over shallow, gas emitting coastal sediments on a fixed moorings together with an array of oxygen, methane and other chemical sensors. Preliminary results from the field plus flume tests with ground truthing suggest that vision-based sensing is a viable alternative approach for determining gas bubble fluxes.

  8. Tiny Bubbles.

    ERIC Educational Resources Information Center

    Kim, Hy

    1985-01-01

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

  9. Fuel system bubble dissipation device

    SciTech Connect

    Iseman, W.J.

    1987-11-03

    This patent describes a bubble dissipation device for a fuel system wherein fuel is delivered through a fuel line from a fuel tank to a fuel control with the pressure of the fuel being progressively increased by components including at least one pump stage and an ejector in advance of the pump state. The ejector an ejector casing with a wall defining an elongate tubular flow passage which forms a portion of the fuel line to have all of the fuel flow through the tubular flow passage in flowing from the fuel tank to the fuel control, a nozzle positioned entirely within the tubular flow passage and spaced from the wall to permit fuel flow. The nozzle has an inlet and an outlet with the inlet connected to the pump stage to receive fuel under pressure continuously from the pump stage, a bubble accumulation chamber adjoining and at a level above the ejector casing and operatively connected to the fuel line in advance of the ejector casing. The bubble accumulation chamber is of a size to function as a fuel reservoir and hold an air bubble containing vapor above the level of fuel therein and having an outlet adjacent the bottom thereof operatively connected to the tubular flow passage in the ejector casing at an inlet end, a bubble accumulation chamber inlet above the level of the bubble accumulation chamber outlet whereby fuel can flow through the bubble accumulation chamber from the inlet to the outlet thereof with a bubble in the fuel rising above the fuel level in the bubble accumulation chamber.

  10. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  12. 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

  13. Experiment and Numerical Simulation of Bubble Behaviors in Argon Gas Injection Into Lead-Bismuth Pool

    SciTech Connect

    Yumi Yamada; Toyou Akashi; Minoru Takahashi

    2006-07-01

    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 (400 mm in length, 1500 mm in height, 50 mm in width), and bubble behaviors were investigated experimentally. Bubble sizes, bubble rising velocities and void fractions were measured using void probes. Argon gas was injected through five nozzles of 4 mm in diameter into Pb-Bi at two locations. The experimental conditions are the pressure of atmospheric pressure, Pb-Bi temperatures of 443 K, and the flow rate of injection Ar gas is 10, 20, and 30 NL/min. The measured bubble rising velocities were distributed in the range from 1 to 3 m/s. The average velocity was about 0.6 m/s. The measured bubble chord lengths were distributed from 1 mm up to 30 mm. The average chord length was about 7 mm. 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 for spherical bubbles performed better for simulation of the experimental result because of high surface tension force of Pb-Bi. (authors)

  14. 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.

  15. Motion of a bubble ring in a viscous fluid

    NASA Astrophysics Data System (ADS)

    Cheng, M.; Lou, J.; Lim, T. T.

    2013-06-01

    In this paper, lattice Boltzmann method was undertaken to study the dynamics of a vortex ring bubble (or bubble ring) in a viscous incompressible fluid. The study is motivated partly by our desire to assess whether a bubble ring keeps increasing its radius and decreasing its rise velocity as it rises through fluid as was predicted by Turner ["Buoyant vortex rings," Proc. R. Soc. London, Ser. A 239, 61 (1957)], 10.1098/rspa.1957.0022 and Pedley ["The toroidal bubble," J. Fluid Mech. 32, 97 (1968)], 10.1017/S0022112068000601, or does the ring like a rising bubble, eventually reaches a steady state where its radius and velocity remain constant as was predicted by Joseph et al. [Potential Flows of Viscous and Viscoelastic Fluids (Cambridge University Press, 2008)]. The parameters investigated included ring circulation, Reynolds number, density ratio and Bond number. Our numerical results show that a rising bubble ring increases its radius and decreases its velocity, but the process is interrupted by ring instability that eventually causes it to break up into smaller bubbles. This finding is consistent with the stability analysis by Pedley, who predicted that a bubble ring has a finite lifespan and is ultimately destroyed by surface tension instability. Furthermore, it is found that increasing initial circulation has a stabilizing effect on a bubble ring while increasing Reynolds number or Bond number hastens ring instability, resulting in an earlier break up into smaller bubbles; the number of bubbles depends on the wavenumber of the perturbation.

  16. 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.

  17. Bubbling orientifolds

    NASA Astrophysics Data System (ADS)

    Mukhi, Sunil; Smedbäck, Mikael

    2005-08-01

    We investigate a class of 1/2-BPS bubbling geometries associated to orientifolds of type-IIB string theory and thereby to excited states of the SO(N)/Sp(N) Script N = 4 supersymmetric Yang-Mills theory. The geometries are in correspondence with free fermions moving in a harmonic oscillator potential on the half-line. Branes wrapped on torsion cycles of these geometries are identified in the fermi fluid description. Besides being of intrinsic interest, these solutions may also occur as local geometries in flux compactifications where orientifold planes are present to ensure global charge cancellation. We comment on the extension of this procedure to M-theory orientifolds.

  18. Evaluation of flow patterns and elongated bubble characteristics during the flow boiling of halocarbon refrigerants in a micro-scale channel

    SciTech Connect

    Arcanjo, Alexandre Alves; Tibirica, Cristiano Bigonha; Ribatski, Gherhardt

    2010-09-15

    In the present study, quasi-diabatic two-phase flow pattern visualizations and measurements of elongated bubble velocity, frequency and length were performed. The tests were run for R134a and R245fa evaporating in a stainless steel tube with diameter of 2.32 mm, mass velocities ranging from 50 to 600 kg/m{sup 2} s and saturation temperatures of 22 C, 31 C and 41 C. The tube was heated by applying a direct DC current to its surface. Images from a high-speed video-camera (8000 frames/s) obtained through a transparent tube just downstream the heated sections were used to identify the following flow patterns: bubbly, elongated bubbles, churn and annular flows. The visualized flow patterns were compared against the predictions provided by Barnea et al. (1983), Felcar et al. (2007), Revellin and Thome (2007) and Ong and Thome (2009). From this comparison, it was found that the methods proposed by Felcar et al. (2007) and Ong and Thome (2009) predicted relatively well the present database. Additionally, elongated bubble velocities, frequencies and lengths were determined based on the analysis of high-speed videos. Results suggested that the elongated bubble velocity depends on mass velocity, vapor quality and saturation temperature. The bubble velocity increases with increasing mass velocity and vapor quality and decreases with increasing saturation temperature. Additionally, bubble velocity was correlated as linear functions of the two-phase superficial velocity. (author)

  19. Molecular emission from single-bubble sonoluminescence

    NASA Astrophysics Data System (ADS)

    Didenko, Yuri T.; McNamara, William B., III; Suslick, Kenneth S.

    2000-10-01

    Ultrasound can drive a single gas bubble in water into violent oscillation; as the bubble is compressed periodically, extremely short flashes of light (about 100ps) are generated with clock-like regularity. This process, known as single-bubble sonoluminescence, gives rise to featureless continuum emission in water (from 200 to 800nm, with increasing intensity into the ultraviolet). In contrast, the emission of light from clouds of cavitating bubbles at higher acoustic pressures (multi-bubble sonoluminescence) is dominated by atomic and molecular excited-state emission at much lower temperatures. These observations have spurred intense effort to uncover the origin of sonoluminescence and to generalize the conditions necessary for its creation. Here we report a series of polar aprotic liquids that generate very strong single-bubble sonoluminescence, during which emission from molecular excited states is observed. Previously, single-bubble sonoluminescence from liquids other than water has proved extremely elusive. Our results give direct proof of the existence of chemical reactions and the formation of molecular excited states during single-bubble cavitation, and provide a spectroscopic link between single- and multi-bubble sonoluminescence.

  20. Effect of fine bubbles on electric discharge in water

    NASA Astrophysics Data System (ADS)

    Hayashi, Yui; Takada, Noriharu; Kanda, Hideki; Goto, Motonobu

    2015-10-01

    Ar or O2 fine bubbles of diameter  <80 μm were introduced in water and a pulsed discharge plasma was generated between cylinder electrodes in water. Fine bubbles in water affected discharge ignition and caused low inception voltage and suppression of rising temperature. The contamination from electrodes was suppressed in the case of fine bubbles addition because fine bubbles assisted plasma generation. In addition, discharge with fine bubbles enhanced plasma emission with high electron density compared to the no-bubbling case. Discharge with fine bubbles at low-pH conditions generated intense plasma emission compared to neutral and high-pH conditions owing to the electric charge of the fine bubbles.

  1. Rising River

    USGS Multimedia Gallery

    On April 9, 2014 a visit to the USGS gaging station on Libby Brook near Northfield, Maine showed that while runoff had caused a large rise in the small brook, there still remained a significant snowpack in the area....

  2. Shock induced jetting of micron sized bubbles

    NASA Astrophysics Data System (ADS)

    Ohl, Claus-Dieter; Ikink, Roy; Lohse, Detlef; Prosperetti, Andrea

    2002-11-01

    Gas bubbles having a radius between 10 mum and 100 mum and rising freely in water when being subjected to a shock front exhibit a liquid jetting phenomenon. The jet points in the direction of the propagating shock wave. A linear relationship between the jet length and the bubble radius is found and a lower bound of the averaged velocity of the liquid jet can be estimated to be between 50 m/s and 300 m/s increasing linearly for larger bubbles. In a later stage the jet breaks up and releases micron sized bubbles. In the course of shock wave mediated cell permeabilization this observation suggests a microinjection mechanism responsible for cell transfection when minute gas bubbles are present and exposed together with cells to shock waves.

  3. Bubble mobility in mud and magmatic volcanoes

    NASA Astrophysics Data System (ADS)

    Tran, Aaron; Rudolph, Maxwell L.; Manga, Michael

    2015-03-01

    The rheology of particle-laden fluids with a yield stress, such as mud or crystal-rich magmas, controls the mobility of bubbles, both the size needed to overcome the yield stress and their rise speed. We experimentally measured the velocities of bubbles and rigid spheres in mud sampled from the Davis-Schrimpf mud volcanoes adjacent to the Salton Sea, Southern California. Combined with previous measurements in the polymer gel Carbopol, we obtained an empirical model for the drag coefficient and bounded the conditions under which bubbles overcome the yield stress. Yield stresses typical of mud and basaltic magmas with sub-mm particles can immobilize millimeter to centimeter sized bubbles. At Stromboli volcano, Italy, a vertical yield stress gradient in the shallow conduit may immobilize bubbles with diameter ? 1 cm and hinder slug coalescence.

  4. Magma mixing enhanced by bubble segregation

    NASA Astrophysics Data System (ADS)

    Wiesmaier, S.; Morgavi, D.; Renggli, C.; Perugini, D.; De Campos, C. P.; Hess, K.-U.; Ertel-Ingrisch, W.; Lavalle, Y.; Dingwell, D. B.

    2015-04-01

    That rising bubbles may significantly affect magma mixing paths has already been demon strated by analogue experiments. Here, for the first time, bubble-advection experiments are performed employing volcanic melts at magmatic temperatures. Cylinders of basaltic glass were placed below cylinders of rhyolite glass. Upon melting, interstitial air formed bubbles that rose into the rhyolite melt, thereby entraining tails of basaltic liquid. The formation of plume-like filaments of advected basalt within the rhyolite was characterized by microCT and subsequent high-resolution EMP analyses. Melt entrainment by bubble ascent appears to be an efficient mechanism for mingling volcanic melts of highly contrasting compositions and properties. MicroCT imaging reveals bubbles trailing each other and multiple filaments coalescing into bigger ones. Rheological modelling of the filaments yields viscosities of up to 2 orders of magnitude lower than for the surrounding rhyolitic liquid. Such a viscosity contrast implies that bubbles rising successively are likely to follow this pathway of low resistance that previously ascending bubbles have generated. Filaments formed by multiple bubbles would thus experience episodic replenishment with mafic material. Inevitable implications for the concept of bubble advection in magma mixing include thereby both an acceleration of mixing because of decreased viscous resistance for bubbles inside filaments and non-conventional diffusion systematics because of intermittent supply of mafic material (instead of a single pulse) inside a material. Inside the filaments, the mafic material was variably hybridised to andesitic through rhyolitic composition. Compositional profiles alone are ambiguous, however, to determine whether single or multiple bubbles were involved during formation of a filament. Statistical analysis, employing concentration variance as measure of homogenisation, demonstrates that also filaments appearing as single-bubble filaments are likely to have experienced multiple bubbles passages. In cases where bubbles have been essential for magma mixing, standard diffusion analysis may thus be inadequate for constraining timescales. However, data analysis employing concentration variance relaxation permits the distinction of conventional single-pulse filaments from multiple bubble ascent advection in natural samples, demonstrating yet another powerful application of this novel petrological tool.

  5. 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)

  6. Burst of Star Formation Drives Galactic Bubble

    NASA Technical Reports Server (NTRS)

    2001-01-01

    NASA's Hubble Space Telescope (HST) captures a lumpy bubble of hot gas rising from a cauldron of glowing matter in Galaxy NGC 3079, located 50 million light-years from Earth in the constellation Ursa Major. Astronomers suspect the bubble is being blown by 'winds' or high speed streams of particles, released during a burst of star formation. The bubble's lumpy surface has four columns of gaseous filaments towering above the galaxy's disc that whirl around in a vortex and are expelled into space. Eventually, this gas will rain down on the disc and may collide with gas clouds, compress them, and form a new generation of stars.

  7. Dynamics of Bubble Ascent in Mud Volcanoes

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  8. Magma mixing enhanced by bubble segregation

    NASA Astrophysics Data System (ADS)

    Wiesmaier, S.; Morgavi, D.; Renggli, C. J.; Perugini, D.; De Campos, C. P.; Hess, K.-U.; Ertel-Ingrisch, W.; Lavallée, Y.; Dingwell, D. B.

    2015-08-01

    In order to explore the materials' complexity induced by bubbles rising through mixing magmas, bubble-advection experiments have been performed, employing natural silicate melts at magmatic temperatures. A cylinder of basaltic glass was placed below a cylinder of rhyolitic glass. Upon melting, bubbles formed from interstitial air. During the course of the experimental runs, those bubbles rose via buoyancy forces into the rhyolitic melt, thereby entraining tails of basaltic liquid. In the experimental run products, these plume-like filaments of advected basalt within rhyolite were clearly visible and were characterised by microCT and high-resolution EMP analyses. The entrained filaments of mafic material have been hybridised. Their post-experimental compositions range from the originally basaltic composition through andesitic to rhyolitic composition. Rheological modelling of the compositions of these hybridised filaments yield viscosities up to 2 orders of magnitude lower than that of the host rhyolitic liquid. Importantly, such lowered viscosities inside the filaments implies that rising bubbles can ascend more efficiently through pre-existing filaments that have been generated by earlier ascending bubbles. MicroCT imaging of the run products provides textural confirmation of the phenomenon of bubbles trailing one another through filaments. This phenomenon enhances the relevance of bubble advection in magma mixing scenarios, implying as it does so, an acceleration of bubble ascent due to the decreased viscous resistance facing bubbles inside filaments and yielding enhanced mass flux of mafic melt into felsic melt via entrainment. In magma mixing events involving melts of high volatile content, bubbles may be an essential catalyst for magma mixing. Moreover, the reduced viscosity contrast within filaments implies repeated replenishment of filaments with fresh end-member melt. As a result, complex compositional gradients and therefore diffusion systematics can be expected at the filament-host melt interface, due to the repetitive nature of the process. However, previously magmatic filaments were tacitly assumed to be of single-pulse origin. Consequently, the potential for multi-pulse filaments has to be considered in outcrop analyses. As compositional profiles alone may remain ambiguous for constraining the origin of filaments, and as 3-D visual evidence demonstrates that filaments may have experienced multiple bubbles passages even when featuring standard diffusion gradients, therefore, the calculation of diffusive timescales may be inadequate for constraining timescales in cases where bubbles have played an essential role in magma mixing. Data analysis employing concentration variance relaxation in natural samples can distinguish conventional single-pulse filaments from advection via multiple bubble ascent advection in natural samples, raising the prospect of yet another powerful application of this novel petrological tool.

  9. Cavitation and bubble collapse in hot asymmetric nuclear matter

    SciTech Connect

    Kolomietz, V.M.

    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.

  10. Plasma bubble phenomenon in the topside ionosphere

    NASA Astrophysics Data System (ADS)

    Sidorova, L. N.

    There are the indications that plasma bubbles/flux tube aligned plasma density depletions, produced by Rayleigh-Taylor instability at the bottomside of ionosphere, could rise up to the topside ionosphere and plasmasphere. Maruyama and Matuura [Maruyama, T., Matuura, N. Longitudinal variability of annual changes in activity of equatorial spread-F and plasma bubbles. J. Geophys. Res. 89(A12), 10903-10912, 1984.], using ISS-b satellite data for the high solar activity period, 1978-1979, have seen the plasma bubbles over equator at 1100 km altitudes in 46 cases in 1700 passes. That is 3% only. However, there is distinctly another picture in He + density depletions (subtroughs) according to the ISS-b data for the same period. He + density subtroughs were observed in the topside ionosphere over equatorial and low-latitudinal regions ( L 1.3-3) in 11% of the cases [Karpachev, A.T., Sidorova, L.N. Occurrence probability of the light ion trough and subtrough in He + density on season and local time. Adv. Space Res. 29, 999-108, 2002; Sidorova, L.N., He + density topside modeling based on ISS-b satellite data. Adv. Space Res. 33, 850-854, 2004.]. We have carried out a statistical study of the He + density subtrough characteristics. 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 the AE-E satellite and IS radar (Jicamarca) data. Striking similarity in development dynamics is revealed for the different seasons. It is noted also that the He + density subtroughs are mostly observed in the evening-night sector (18-05 LT) from October till May, which is very similar to the peculiarities of the equatorial spread-F (ESF), usually associated with plasma bubbles. 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 et al. [Abdu, M.A., Sobral, J.H.A., Batista, I.S. Equatorial spread-F statistics in the american longitudes: some problems relevant to ESF description in the IRI scheme. Adv. Space Res. 25, 113-124, 2000.] from ground-based ionograms obtained over Brazilian region for the same years. The comparison shows good enough correlation ( R 0.67). It is concluded that: (a) He + density subtroughs like ESF are controlled by pre-reversal enhancement electric field (vertical drift); (b) He + density subtroughs and ESF/bubble irregularities may be considered as phenomena of the same plasma bubble origin; (c) it seems, plasma bubbles, reaching the topside ionosphere altitudes, are most easily observable in He + density as depletions.

  11. The Influence of Solid Particles on Bubble Size Distributions in Magma

    NASA Astrophysics Data System (ADS)

    Belien, I.; Cashman, K.; Rempel, A.

    2008-12-01

    The shapes and size distributions of bubbles in magma are influenced by their interactions with other bubbles and solid particles in addition to their nucleation and growth rates. In previous studies we have found that solid particles can cause a bubble to deform and split, and that small bubbles can get trapped inside layers with high solids concentrations, thereby accumulating relative to larger bubbles. This implies that the relationship between bubble number density and nucleation rate could be less direct than is often assumed during interpretations of bubble concentrations in solidified magmas. We have found that, for a single bubble in a crystal suspension, the extent of retardation of bubble rise depends on the probability of interaction with particles. At high particle concentrations, all bubbles are slowed down, and the rise rate through the suspension is determined by the pore aperture size. Here, we expand upon our previous work and examine the influence of solid particles on multiple-bubble trains with analog experiments. We focus on the high- crystallinity end member of natural magmas, where the influence of crystals is greatest. Starting from a homogeneous population of spherical bubbles, we study the change in shape and size distribution of the bubbles as they rise through a suspension of plastic beads in corn syrup (simulating magma with crystals). We focus particularly on the influence of particles on bubble coalescence.

  12. Rising equity

    SciTech Connect

    Burr, M.T.

    1992-09-01

    This article reports on the results of a financial rankings survey of the independent energy industry indicating that lenders and investors provided more than five billion dollars in capital for new, private power projects during the first six months of 1992. The topics of the article include rising equity requirements, corporate finance, mergers and acquisitions, project finance investors, revenue bonds, project finance lenders for new projects, project finance lenders for restructurings, and project finance advisors.

  13. Reconstructing Pre-Fragmentation Bubble Size Distributions from Volcanic Ash using Stereo SEM Analysis

    NASA Astrophysics Data System (ADS)

    Sahagian, D. L.; Proussevitch, A. A.; Mulukutla, G. K.; Genareau, K.

    2010-12-01

    We have conducted an analysis of bubble (BSD) and ash particle (PSD) size distributions for ashes from two contrasting eruptions. The first is the May, 1980 eruption of Mt. St. Helens (MSH), a dacitic plinian eruption that spread ash over a large area of the Western U.S. The second is the basaltic sub-plinian 1974 eruption of Fuego (Guatemala), which was confined to local deposition with less variation of ash PSDs. Four successive small explosive eruptions of Fuego produced less than 0.02 km3 of dense rock equivalent (DRE) in a dispersal area of 80 km from the volcano. In contrast, the May 1980 plinian eruption of Mount St. Helens resulted in a distal fallout leading to a large subaerial ash deposit as far away as 325 km from the volcano. Pyroclastic flows added extensive fine material to the eruption column resulting in extensive ash dispersal. MSH samples were collected from a range of distances away from the vent, while collection of samples from Fuego was limited to nearer regions due to the lesser dispersal of the ash. Technique- Stereo SEM analysis of BSD of eruptions products (ash) to determine the pre-fragmentation properties of ash-producing magma bodies. This information is normally considered lost due to fragmentation of bubbles in late stages of eruptions. However, using SSEM, we have devised a technique to determine the pre-fragmentation BSDs that reflect the conduit processes of bubble nucleation and growth, and magma rise history. Using standard off-the-shelf software (Alicona MeX) to create Digital Elevation Models (DEMs) of individual ash particles, we built a database of ash surface characteristics. These surfaces include imprints of bubbles that exploded during fragmentation. We use the curvature of these imprints to reconstruct the complete bubbles, using newly developed software we call Bubblemaker that extrapolates the measured DEMs using best-fit ellipsoids of revolution (not necessarily spherical). We have now reconstructed the bubble volumes. These data are used in turn to characterize the statistical parameters of the bubble population, including size distribution, distribution function type (log-normal), its moments, and bubble number density. Our results show that the silicic energetic MSH eruption ashes contain smaller bubbles and higher number densities than do the ashes collected from the more basaltic Fuego eruption. From these results, it is possible to speculate regarding eruption processes. It appears that within a single eruption, there is relatively little variability of bubble sizes as a function of depositional distance from the vent, although other ash characteristics such as PSD vary more strongly with distance.

  14. Steady State Vapor Bubble in Pool Boiling

    NASA Astrophysics Data System (ADS)

    Zou, An; Chanana, Ashish; Agrawal, Amit; Wayner, Peter C.; Maroo, Shalabh C.

    2016-02-01

    Boiling, a dynamic and multiscale process, has been studied for several decades; however, a comprehensive understanding of the process is still lacking. The bubble ebullition cycle, which occurs over millisecond time-span, makes it extremely challenging to study near-surface interfacial characteristics of a single bubble. Here, we create a steady-state vapor bubble that can remain stable for hours in a pool of sub-cooled water using a femtosecond laser source. The stability of the bubble allows us to measure the contact-angle and perform in-situ imaging of the contact-line region and the microlayer, on hydrophilic and hydrophobic surfaces and in both degassed and regular (with dissolved air) water. The early growth stage of vapor bubble in degassed water shows a completely wetted bubble base with the microlayer, and the bubble does not depart from the surface due to reduced liquid pressure in the microlayer. Using experimental data and numerical simulations, we obtain permissible range of maximum heat transfer coefficient possible in nucleate boiling and the width of the evaporating layer in the contact-line region. This technique of creating and measuring fundamental characteristics of a stable vapor bubble will facilitate rational design of nanostructures for boiling enhancement and advance thermal management in electronics.

  15. Steady State Vapor Bubble in Pool Boiling.

    PubMed

    Zou, An; Chanana, Ashish; Agrawal, Amit; Wayner, Peter C; Maroo, Shalabh C

    2016-01-01

    Boiling, a dynamic and multiscale process, has been studied for several decades; however, a comprehensive understanding of the process is still lacking. The bubble ebullition cycle, which occurs over millisecond time-span, makes it extremely challenging to study near-surface interfacial characteristics of a single bubble. Here, we create a steady-state vapor bubble that can remain stable for hours in a pool of sub-cooled water using a femtosecond laser source. The stability of the bubble allows us to measure the contact-angle and perform in-situ imaging of the contact-line region and the microlayer, on hydrophilic and hydrophobic surfaces and in both degassed and regular (with dissolved air) water. The early growth stage of vapor bubble in degassed water shows a completely wetted bubble base with the microlayer, and the bubble does not depart from the surface due to reduced liquid pressure in the microlayer. Using experimental data and numerical simulations, we obtain permissible range of maximum heat transfer coefficient possible in nucleate boiling and the width of the evaporating layer in the contact-line region. This technique of creating and measuring fundamental characteristics of a stable vapor bubble will facilitate rational design of nanostructures for boiling enhancement and advance thermal management in electronics. PMID:26837464

  16. Steady State Vapor Bubble in Pool Boiling

    PubMed Central

    Zou, An; Chanana, Ashish; Agrawal, Amit; Wayner, Peter C.; Maroo, Shalabh C.

    2016-01-01

    Boiling, a dynamic and multiscale process, has been studied for several decades; however, a comprehensive understanding of the process is still lacking. The bubble ebullition cycle, which occurs over millisecond time-span, makes it extremely challenging to study near-surface interfacial characteristics of a single bubble. Here, we create a steady-state vapor bubble that can remain stable for hours in a pool of sub-cooled water using a femtosecond laser source. The stability of the bubble allows us to measure the contact-angle and perform in-situ imaging of the contact-line region and the microlayer, on hydrophilic and hydrophobic surfaces and in both degassed and regular (with dissolved air) water. The early growth stage of vapor bubble in degassed water shows a completely wetted bubble base with the microlayer, and the bubble does not depart from the surface due to reduced liquid pressure in the microlayer. Using experimental data and numerical simulations, we obtain permissible range of maximum heat transfer coefficient possible in nucleate boiling and the width of the evaporating layer in the contact-line region. This technique of creating and measuring fundamental characteristics of a stable vapor bubble will facilitate rational design of nanostructures for boiling enhancement and advance thermal management in electronics. PMID:26837464

  17. A theoretical model for bubble enhanced ultrasound heating due to time-dependent bubble size distributions

    NASA Astrophysics Data System (ADS)

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

    2002-11-01

    Substantial in vitro and in vivo evidence shows that cavitation activity can affect tissue heating in focused ultrasound surgery and acoustic hemostasis applications. In particular, the heating rate in tissue increases significantly after cavitation sets in. Exploitation of this phenomenon for clinical use requires knowledge of, among other parameters, the time-dependent bubble size distribution sustained during insonation. Difficulties associated with the measurement of bubble sizes during in vitro or in vivo experiments call for a theoretical approach to the problem. We will present a theoretical model that estimates the time-dependent distribution of bubble equilibrium radii. Shape instability thresholds and rectified diffusion thresholds bound asymptotic bubble size distributions, and the instantaneous size distributions are governed by growth rates. The temperature rise caused by such bubble activity is calculated and compared with experimental data. [Work supported by DARPA and the U.S. Army.

  18. Vortex Formation in Ellipsoidal Thermal Bubbles.

    NASA Astrophysics Data System (ADS)

    Shapiro, Alan; Kanak, Katharine M.

    2002-07-01

    The rise of an isolated dry thermal bubble in a quiescent unstratified environment is a prototypical natural convective flow. This study considers the rise of an isolated dry thermal bubble of ellipsoidal shape (elliptical in both horizontal and vertical cross sections). The azimuthal asymmetry of the bubble allows the vorticity tilting mechanism to operate without an environmental wind. The dry Boussinesq equations of motion are solved analytically as a Taylor series in time for the early time behavior of the bubble (involving derivatives of up to the third order in time). The analytic results are supplemented with numerical simulations to examine the longer-time behavior. The first nonzero term in the Taylor expansion for the vertical vorticity is a third-order term, and appears as a four-leaf clover pattern with lobes of alternating sign. The horizontal flow associated with this vorticity pattern first appears as a sheared stagnation point-type flow, but eventually organizes into vertical vortices that fill the bubble. The vortices induce large structural changes to the bubble and eventually reverse the sense of the azimuthal asymmetry.

  19. 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.

  20. 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.

  1. 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.

  2. Calculation of bubble shape and particle transport in a fluidized bed

    SciTech Connect

    Puzyrev, E.M.

    1986-07-01

    A model of bubble formation in a fluidized bed under the action of the return stream of the dense phase penetrating into the trail of an ascending bubble is constructed. The growth of bubbles as they rise and the process of replacement of solid material in the trail are analyzed on the basis of the model.

  3. Ignition modes of nanosecond discharge with bubbles in distilled water

    NASA Astrophysics Data System (ADS)

    Hamdan, Ahmad; Cha, Min Suk

    2015-10-01

    Here, we present the microscopic physical characteristics of nanosecond discharges with an array of bubbles in distilled water. In particular, applying a single high-voltage pulse, four delayed intensified charge-coupled device cameras successfully visualized four successive images during a single discharge event. We identified three distinctive modes of ignition inside a bubble, depending on the relative location of the bubble with respect to pin-to-hollow needle electrodes when a single bubble was located in an inter-electrode gap of 1 mm: anode-driven ignition, cathode-driven ignition, and co-ignition near both electrodes. Anode- and cathode-driven ignitions evolved into either a complete propagation of the streamer or an incomplete propagation, which were limited in location by proximity to an ignition location, while co-ignitions consistently showed complete propagation. When we increased the gap to 2 mm to accommodate multiple bubbles in the gap, an ignited bubble near the cathode was able to cause the ignition of an upper adjacent bubble. Bubble-bubble interface zones can also be spots of ignition, such that we observed simultaneous co-ignitions in the zones of bubble-bubble interfaces and near electrodes with triple bubbles. We compared the experimental results of discharge propagation with different ignition modes between Ar, He, and N2 bubbles. In addition, numerical simulations for static electric fields reasonably supported observed ignition behavior such that field intensity was locally enhanced.

  4. Transformer overload and bubble evolution: Proceedings

    SciTech Connect

    Addis, G.; Lindgren, S.

    1988-06-01

    The EPRI workshop on Transformer Overload Characteristics and Bubble Evolution was held to review the findings of investigations over the past 7-8 years to determine whether enough information is now available for utilities to establish safe loading practices. Sixteen papers were presented, including a utility review, physical and dielectric effects of gas and bubble formation from cellulose insulated transformers, transformer life characteristics, gas bubble studies and impulse test on distribution transformers, mathematical modeling of bubble evolution, transformer overload characteristics, variation of PD-strength for oil-paper insulation, survey on maximum safe operating hot spot temperature, and overload management. The meeting concluded with a general discussion covering the existing state of knowledge and the need for additional research. Sixteen papers have been cataloged separately.

  5. Dissolving Bubbles in Glass

    NASA Technical Reports Server (NTRS)

    Weinberg, M. C.; Oronato, P. I.; Uhlmann, D. R.

    1984-01-01

    Analytical expression used to calculate time it takes for stationary bubbles of oxygen and carbon dioxide to dissolve from glass melt. Technique based on analytical expression for bubble radius as function time, with consequences of surface tension included.

  6. 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)

  7. Preheating in bubble collisions

    SciTech Connect

    Zhang Jun; Piao Yunsong

    2010-08-15

    In a landscape with metastable minima, the bubbles will inevitably nucleate. We show that when the bubbles collide, due to the dramatic oscillation of the field at the collision region, the energy deposited in the bubble walls can be efficiently released by the explosive production of the particles. In this sense, the collision of bubbles is actually highly inelastic. The cosmological implications of this result are discussed.

  8. Soap Films and Bubbles.

    ERIC Educational Resources Information Center

    Rice, Karen

    1986-01-01

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

  9. Stable Coulomb Bubbles?

    SciTech Connect

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

    1997-02-01

    Coulomb bubbles, though stable against monopole displacement, are unstable at least with respect to quadrupole and octupole distortions. We show that there exists a temperature at which the pressure of the vapor filling the bubble stabilizes all the radial modes. In extremely thin bubbles, the crispation modes become unstable due to the surface-surface interaction. {copyright} {ital 1997} {ital The American Physical Society}

  10. Lifetime Characteristics of Evening-Preference and Irregular Bed-Rise Time Are Associated With Lifetime Seasonal Variation of Mood and Behavior: Comparison Between Individuals With Bipolar Disorder and Healthy Controls.

    PubMed

    Baek, Ji Hyun; Kim, Ji Sun; Kim, Mi Jin; Ryu, Seunghyung; Lee, Kounseok; Ha, Kyooseob; Hong, Kyung Sue

    2016-01-01

    Sleep-wake cycle disruption and seasonal variation in mood and behavior have been associated with mood disorders. This study aimed to investigate the lifetime characteristics of the sleep-wake cycle and its association with the lifetime characteristics of seasonality in individuals with bipolar disorder. Circadian preference, regularity of bed-rise time, and seasonality were evaluated on a lifetime basis using the Composite Scale of Morningness, the Sleep Timing Questionnaire, and the Seasonal Pattern Assessment Questionnaire in clinically stable individuals with bipolar I/II disorders (n = 103/97) and healthy controls (n = 270). Bipolar groups were more likely to have evening preference and irregular bed-rise time. These characteristics were interrelated and, particularly, more prevalent in bipolar II disorder. Seasonality, which was also more prevalent in the bipolar groups, was associated with evening preference and irregularity of the weekday bed-rise time. PMID:25384190

  11. Near-wall measurements of the bubble- and Lorentz-force-driven convection at gas-evolving electrodes

    NASA Astrophysics Data System (ADS)

    Baczyzmalski, Dominik; Weier, Tom; Kähler, Christian J.; Cierpka, Christian

    2015-08-01

    Chemical energy storage systems, e.g., in the form of hydrogen or methanol, have a great potential for the establishment of volatile renewable energy sources due to the large energy density. The efficiency of hydrogen production through water electrolysis is, however, limited by gas bubbles evolving at the electrode's surface and can be enhanced by an accelerated bubble detachment. In order to characterize the complex multi-phase flow near the electrode, simultaneous measurements of the fluid velocities and the size and trajectories of hydrogen bubbles were performed in a water electrolyzer. The liquid phase velocity was measured by PIV/PTV, while shadowgraphy was used to determine the bubble trajectories. Special measurement and evaluation techniques had to be applied as the measurement uncertainty is strongly affected by the high void fraction close to the wall. In particular, the application of an advanced PTV scheme allowed for more precise fluid velocity measurements closer to electrode. Based on these data, stability characteristics of the near-wall flow were evaluated and compared to that of a wall jet. PTV was used as well to investigate the effect of Lorentz forces on the near-wall fluid velocities. The results show a significantly increased wall parallel liquid phase velocity with increasing Lorentz forces. It is presumed that this enhances the detachment of hydrogen bubbles from the electrode surface and, consequently, decreases the fractional bubble coverage and improves the efficiency. In addition, the effect of large rising bubbles with path oscillations on the near-wall flow was investigated. These bubbles can have a strong impact on the mass transfer near the electrode and thus affect the performance of the process.

  12. Taylor bubbles in liquid filled annuli: Some new observations

    NASA Astrophysics Data System (ADS)

    Agarwal, V.; Jana, A. K.; Das, G.; Das, P. K.

    2007-10-01

    Taylor bubbles rising through a vertical concentric annulus do not wrap around the inner tube completely. The two edges of the bubble are separated by a liquid bridge which increases with an increase of the inner radius. However, the change in the shape of the Taylor bubbles in annuli with extremely small inner diameter has not yet been reported. In the present investigation, several experiments have been performed in circular and noncircular annuli to understand the influence of the inner and outer wall on the bubble shape. The bubble has been observed to assume a completely different shape in both circular and square annuli with a very thin inner rod. Nevertheless, the rise velocity for such situations agree with the prediction of the model proposed by Das et al. [Chem. Eng. Sci. 53, 977 (1998)] when the outer pipe is circular but fails for a square outer pipe.

  13. Dye-bubble interactions in an open channel flow

    NASA Astrophysics Data System (ADS)

    Crepeau, John C.; McIlroy, Hugh M.

    2005-12-01

    An innovative technique has been developed to visualize the effect that a localized surface reaction has in an open channel flow field. The working fluid is hexanoic acid mixed with mineral oil, and it flows over an aluminum plate embedded with sodium metal. Hexanoic acid and sodium metal react to form hydrogen gas and hexanoic salt. The hydrogen gas forms bubbles that rise to the surface and are convected downstream by the fluid. The rising bubbles induce the formation of counter-rotating vortices that straddle the reaction site. Bubble entrainment stretches and bends the dye filaments, and buoyancy transports the bubbles away from the reaction. The products of the reaction introduce velocity fluctuations into an otherwise laminar flow, inducing what has been described by some researchers as pseudoturbulence. Downstream of the reaction, far away from the disturbances caused by the buoyant bubbles, the velocity fluctuations dampen out and the flow relaminarizes.

  14. Structure and dynamics of the wake of bubbles and its relevance for bubble interaction

    NASA Astrophysics Data System (ADS)

    Brcker, Christoph

    1999-07-01

    The flow in the wake of single and two interacting air bubbles freely rising in water is studied experimentally using digital-particle-image-velocimetry in combination with high-speed recording. The experiments focus on ellipsoidal bubbles of diameter of about 0.4-0.8 cm which show spiraling, zigzagging, and rocking motion during their rise in water, which was seeded with small tracer particles for flow visualization. Under counterflow conditions in the vertical channel, the bubbles are retained in the center of the observation region, which allows the wake oscillations and bubble interaction to be observed over several successive periods. By simultaneous diffuse illumination in addition to the light sheet, we were able to record both the path and shape oscillations of the bubble, as well as the wake structure in a horizontal and vertical cross section. The results show that the zigzagging motion is coupled to a regular generation and discharge of alternate oppositely oriented hairpin-like vortex structures. Associated with the wake oscillation, the bubble experiences a strong asymmetric deformation in the equatorial plane at the inversion points of the zigzag path. The zigzag motion is superimposed on a small lateral drift of the bubble, which implies the existence of a net lift force. This is explained by the observed different strength of the hairpin vortices in the zig and zag path; a seemingly familiar phenomenon was found in recent numerical results of the sphere wake flow. For spiraling bubbles the wake is approximately steady to an observer moving with the bubble. It consists of a twisted pair of streamwise vortex filaments which are wound in a helical path and are attached to the bubble base at an asymmetrical position. The minor axis of the bubble is tilted in the tangential plane as well as in the radial plane toward the spiral center. Due to the pressure field induced by the asymmetrically attached wake two components of the lift force exist, one that causes the lateral motion and the other a centripetal force that keeps the bubble on a circular path. A mechanism is proposed to explain the reason for one bubble to spiral or to zigzag. Experiments with two simultaneous released bubbles show that bubble interaction is strongly triggered by the wake dynamics. Once a bubble is captured in the wake of a rocking bubble, it accelerates and rises via successive jumps until they collide. The jumps are explained by the upwards induction effect of the ring-like heads of the hairpin vortices being shed from the leading bubble. The final collision and repulsion thereafter abruptly enlarges the wake for a short moment, which is suggested to be one major contribution to the amplification of turbulence production in bubbly flows.

  15. New look at wave analogy for prediction of bubble terminal velocities

    SciTech Connect

    Maneri, C.C.

    1995-03-01

    The analogy between waves on the surface of an infinite fluid and bubbles rising in low-viscosity fluids of infinite extent, originally proposed by Mendelson for 3-D bubbles, has been used to predict the terminal velocity, of plane bubbles. In terms of its terminal velocity, a plane bubble rising in a rectangular duct of small aspect (spacing-to-width) ratio behaves as if it were a 3-D bubble rising in an infinite medium as long as the end walls (the walls in the width wise direction) are sufficiently far apart. As the end walls are moved toward each other, a wall effect is found to exist. A general expression for the terminal velocity of a bubble of any size rising in a rectangular duct including this wall effect is also developed based on the wave analogy and shown to compare well with existing data.

  16. Tribonucleation of bubbles

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

    We report on the nucleation of bubbles on solids that are gently rubbed against each other while immersed in a gas-supersaturated liquid. For given supersaturation and surface material, bubble nucleation is only observed beyond a certain threshold for the rubbing force and velocity. Above this threshold, a regularly spaced row of growing bubbles is left behind on the surface. Direct observation through the bottom of a transparent solid shows that each bubble in the row results from the early coalescence of several microscopic bubbles. From a detailed study of the wear tracks it seems that these gas nuclei originate from a local fracturing of the surface asperities in the contact area.

  17. Europa Rising

    NASA Technical Reports Server (NTRS)

    2007-01-01

    New Horizons took this image of the icy moon Europa rising above Jupiter's cloud tops with its Long Range Reconnaissance Imager (LORRI) at 11:48 Universal Time on February 28, 2007, six hours after the spacecraft's closest approach to Jupiter.

    The picture was one of a handful of the Jupiter system that New Horizons took primarily for artistic, rather than scientific, value. This particular scene was suggested by space enthusiast Richard Hendricks of Austin, Texas, in response to an Internet request by New Horizons scientists for evocative, artistic imaging opportunities at Jupiter.

    The spacecraft was 2.3 million kilometers (1.4 million miles) from Jupiter and 3 million kilometers (1.8 million miles) from Europa when the picture was taken. Europa's diameter is 3,120 kilometers (1,939 miles). The image is centered on Europa coordinates 5 degrees south, 6 degrees west. In keeping with its artistic intent - and to provide a more dramatic perspective - the image has been rotated so south is at the top.

  18. 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.

  19. Satellites in the inviscid breakup of bubbles.

    PubMed

    Gordillo, J M; Fontelos, M A

    2007-04-01

    In this Letter, we stress the essential role played by gas inertia in the breakup of gas bubbles. Our results reveal that, whenever the gas to liquid density ratio Lambda=rhog/rhol is different from zero, tiny satellite bubbles may be formed as a result of the large gas velocities that are reached close to pinch-off. Moreover, we provide a closed expression for the characteristic satellite diameter, which decreases when decreasing Lambda and which shows order of magnitude agreement with the micron-sized satellite bubbles observed experimentally. PMID:17501278

  20. Lifetime of bubble rafts: cooperativity and avalanches.

    PubMed

    Ritacco, Hernn; Kiefer, Flavien; Langevin, Dominique

    2007-06-15

    We have studied the collapse of pseudo-bi-dimensional foams. These foams are made of uniformly sized soap bubbles packed in an hexagonal lattice sitting at the top of a liquid surface. The collapse process follows the sequence: (1) rupture of a first bubble, driven by thermal fluctuations and (2) a cascade of bursting bubbles. We present a simple numerical model which captures the main characteristics of the dynamics of foam collapse. We show that in a certain range of viscosities of the foaming solutions, the size distribution of the avalanches follows power laws as in self-organized criticality processes. PMID:17677967

  1. Lifetime of Bubble Rafts: Cooperativity and Avalanches

    NASA Astrophysics Data System (ADS)

    Ritacco, Hernn; Kiefer, Flavien; Langevin, Dominique

    2007-06-01

    We have studied the collapse of pseudo-bi-dimensional foams. These foams are made of uniformly sized soap bubbles packed in an hexagonal lattice sitting at the top of a liquid surface. The collapse process follows the sequence: (1) rupture of a first bubble, driven by thermal fluctuations and (2) a cascade of bursting bubbles. We present a simple numerical model which captures the main characteristics of the dynamics of foam collapse. We show that in a certain range of viscosities of the foaming solutions, the size distribution of the avalanches follows power laws as in self-organized criticality processes.

  2. 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.

  3. 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.

  4. Emergence of Granular-sized Magnetic Bubbles through the Solar Atmosphere. I. Spectropolarimetric Observations and Simulations

    NASA Astrophysics Data System (ADS)

    Ortiz, Ada; Bellot Rubio, Luis R.; Hansteen, Viggo H.; de la Cruz Rodrguez, Jaime; Rouppe van der Voort, Luc

    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-1 and expands at a horizontal speed of 4 km s-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-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.

  5. 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; Bellot Rubio, Luis R.; De la Cruz Rodríguez, Jaime

    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 τ = –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.

  6. Phase-field simulation of irradiated metals Part II : Gas bubble kinetics.

    SciTech Connect

    Millett, P. C.; El-Azab, A.; Wolf, D.

    2011-01-01

    The phase-field model developed in Part I of this work is expanded to include fission gas generation, diffusion, and segregation within bubbles nucleated both homogeneously and heterogeneously along grain boundaries. Illustrative results are presented that characterize bubble growth and shrinkage, as well as the bubble density, size and nucleation rate as a function of the irradiation conditions. Finally, intergranular bubble characteristics such as shape, pinning energy and bubble density are investigated.

  7. Bubble Manipulation by Self Organization of Bubbles inside Ultrasonic Wave

    NASA Astrophysics Data System (ADS)

    Yamakoshi, Yoshiki; Koganezawa, Masato

    2005-06-01

    Microbubble manipulation using ultrasonic waves is a promising technology in the fields of future medicine and biotechnology. For example, it is considered that bubble trapping using ultrasonic waves may play an important role in drug or gene delivery systems in order to trap the drugs or genes in the diseased tissue. Usually, when bubbles are designed so that they carry payloads, such as drug or gene, they tend to be harder than free bubbles. These hard bubbles receive a small acoustic radiation force, which is not sufficient for bubble manipulation. In this paper, a novel method of microbubble manipulation using ultrasonic waves is proposed. This method uses seed bubbles in order to manipulate target bubbles. When the seed bubbles are introduced into the ultrasonic wave field, they start to oscillate to produce a bubble aggregation of a certain size. Then the target bubbles are introduced, the target bubbles attach around the seed bubbles producing a bubble mass with bilayers (inner layer: seed bubbles, outer layer: target bubbles). The target bubbles are manipulated as a bilayered bubble mass. Basic experiments are carried out using polyvinyl chloride (PVC) shell bubbles. No target bubbles are trapped when only the target bubbles are introduced. However, they are trapped if the seed bubbles are introduced in advance.

  8. 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.

  9. 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.

  10. Bubbles and droplets in magnetic fluids

    NASA Astrophysics Data System (ADS)

    Yecko, Philip

    2006-11-01

    In this work, the behavior of ferrofluid droplets and of bubbles rising in a ferrofluid is studied using direct numerical simulations based on a volume of fluid (VOF) method. A ferrofluid is a suspension of small (5--15 nm) magnetic particles in a carrier liquid which may be water or a hydrocarbon oil, stabilized against settling by Brownian motion and against agglomeration by coating each particle with a layer of surfactant. Although their main application is the fluid O-ring found in computer hard disk drives, ferrofluids have been more recently recognized for their use in micro- and nano-fluidic pumping, and applications to drug delivery are under investigation. Because ferrofluids are opaque, numerical simulations offer a unique opportunity to visualize flows that cannot be easily visualized experimentally, yet little effort has been directed to numerical simulations of realistic magnetic fluids. In this work, we develop and test a multiphase simulation code, based on Surfer, which can dynamically follow the behavior of small numbers of droplets, bubbles or layers of ferrofluid and ordinary viscous fluid for so-called linear magnetic material. In the rising bubble tests, we quantify the vertical elongation of the bubble and the resulting reduction in drag and rise time. In the falling droplet experiments, we demonstrate the effect of variable magnetic properties on the shape and trajectory of the droplet, including the instability threshold where droplet fission occurs.

  11. Simulation of a bubble chain in a container of high aspect ratio exposed to a magnetic field

    NASA Astrophysics Data System (ADS)

    Schwarz, Stephan; Frhlich, Jochen

    2013-03-01

    The influence of a homogeneous magnetic field acting in the direction of gravity on a bubble chain is studied with phase-resolving numerical simulations. The bubbles rise in a narrow container filled with liquid metal. Individual bubbles are represented by an immersed boundary method with the bubble shape being described by spherical harmonics and deformed by the surrounding liquid metal. A Gaussian bubble size distribution is realized as suggested by corresponding experiments. Bubble-bubble and bubble-wall interactions are modelled based on a repelling potential. With a magnetic field, the averaged trajectory of the bubble chain becomes more rectilinear, and the transverse dispersion is reduced. The average rise velocity decreases under the impact of the field.

  12. Heat transfer and bubble dynamics in slurry bubble columns for Fischer-Tropsch clean alternative energy

    NASA Astrophysics Data System (ADS)

    Wu, Chengtian

    With the increasing demand for alternative energy resources, the Fischer-Tropsch (FT) process that converts synthesis gas into clean liquid fuels has attracted more interest from the industry. Slurry bubble columns are the most promising reactors for FT synthesis due to their advantages over other reactors. Successful operation, design, and scale-up of such reactors require detailed knowledge of hydrodynamics, bubble dynamics, and transport characteristics. However, most previous studies have been conducted at ambient pressure or covered only low superficial gas velocities. The objectives of this study were to experimentally investigate the heat transfer coefficient and bubble dynamics in slurry bubble columns at conditions that can mimic FT conditions. The air-C9C 11-FT catalysts/glass beads systems were selected to mimic the physical properties of the gas, liquid, and solid phases at commercial FT operating conditions. A heat transfer coefficient measurement technique was developed, and for the first time, this technique was applied in a pilot scale (6-inch diameter) high pressure slurry bubble column. The effects of superficial gas velocity, pressure, solids loading, and liquid properties on the heat transfer coefficients were investigated. Since the heat transfer coefficient can be affected by the bubble properties (Kumar et al., 1992), in this work bubble dynamics (local gas holdup, bubble chord length, apparent bubble frequency, specific interfacial area, and bubble velocity) were studied using the improved four-point optical probe technique (Xue et al., 2003; Xue, 2004). Because the four-point optical technique had only been successfully applied in a churn turbulent flow bubble column (Xue, 2004), this technique was first assessed in a small scale slurry bubble column in this study. Then the bubble dynamics were studied at the same conditions as the heat transfer coefficient investigation in the same pilot scale column. The results from four-point probe bubble dynamics study advanced the understanding of heat transfer in the slurry bubble column. This study also provides important benchmark information for the slurry bubble column design and the evaluation of computational fluid dynamics (CFD) simulations.

  13. Characteristics of equatorial plasma bubble zonal drift velocity and tilt based on Hong Kong GPS CORS network: From 2001 to 2012

    NASA Astrophysics Data System (ADS)

    Ji, Shengyue; Chen, Wu; Weng, Duojie; Wang, Zhenjie

    2015-08-01

    Hong Kong (22.3N, 114.2E, dip: 30.5N; geomagnetic 15.7N, 173.4W, declination: 2.7W) is a low-latitude area, and the Hong Kong Continuously Operating Reference Station (CORS) network has been developed and maintained by Lands Department of Hong Kong government since 2001. Based on the collected GPS observations of a whole solar cycle from 2001 to 2012, a method is proposed to estimate the zonal drift velocity as well as the tilt of the observed plasma bubbles, and the estimated results are statistically analyzed. It is found that although the plasma bubbles are basically vertical within the equatorial plane, the tilt can be as big as more than 60 eastward or westward sometimes. And, the tilt and the zonal drift velocity are correlated. When the velocity is large, the tilt is also large generally. Another finding is that large velocity and tilt generally occur in spring and autumn and in solar active years.

  14. Bubble-induced cave collapse.

    PubMed

    Girihagama, Lakshika; Nof, Doron; Hancock, Cathrine

    2015-01-01

    Conventional wisdom among cave divers is that submerged caves in aquifers, such as in Florida or the Yucatan, are unstable due to their ever-growing size from limestone dissolution in water. Cave divers occasionally noted partial cave collapses occurring while they were in the cave, attributing this to their unintentional (and frowned upon) physical contact with the cave walls or the aforementioned "natural" instability of the cave. Here, we suggest that these cave collapses do not necessarily result from cave instability or contacts with walls, but rather from divers bubbles rising to the ceiling and reducing the buoyancy acting on isolated ceiling rocks. Using familiar theories for the strength of flat and arched (un-cracked) beams, we first show that the flat ceiling of a submerged limestone cave can have a horizontal expanse of 63 meters. This is much broader than that of most submerged Florida caves (~ 10 m). Similarly, we show that an arched cave roof can have a still larger expanse of 240 meters, again implying that Florida caves are structurally stable. Using familiar bubble dynamics, fluid dynamics of bubble-induced flows, and accustomed diving practices, we show that a group of 1-3 divers submerged below a loosely connected ceiling rock will quickly trigger it to fall causing a "collapse". We then present a set of qualitative laboratory experiments illustrating such a collapse in a circular laboratory cave (i.e., a cave with a circular cross section), with concave and convex ceilings. In these experiments, a metal ball represented the rock (attached to the cave ceiling with a magnet), and the bubbles were produced using a syringe located at the cave floor. PMID:25849088

  15. Bubble-Induced Cave Collapse

    PubMed Central

    Girihagama, Lakshika; Nof, Doron; Hancock, Cathrine

    2015-01-01

    Conventional wisdom among cave divers is that submerged caves in aquifers, such as in Florida or the Yucatan, are unstable due to their ever-growing size from limestone dissolution in water. Cave divers occasionally noted partial cave collapses occurring while they were in the cave, attributing this to their unintentional (and frowned upon) physical contact with the cave walls or the aforementioned “natural” instability of the cave. Here, we suggest that these cave collapses do not necessarily result from cave instability or contacts with walls, but rather from divers bubbles rising to the ceiling and reducing the buoyancy acting on isolated ceiling rocks. Using familiar theories for the strength of flat and arched (un-cracked) beams, we first show that the flat ceiling of a submerged limestone cave can have a horizontal expanse of 63 meters. This is much broader than that of most submerged Florida caves (~ 10 m). Similarly, we show that an arched cave roof can have a still larger expanse of 240 meters, again implying that Florida caves are structurally stable. Using familiar bubble dynamics, fluid dynamics of bubble-induced flows, and accustomed diving practices, we show that a group of 1-3 divers submerged below a loosely connected ceiling rock will quickly trigger it to fall causing a “collapse”. We then present a set of qualitative laboratory experiments illustrating such a collapse in a circular laboratory cave (i.e., a cave with a circular cross section), with concave and convex ceilings. In these experiments, a metal ball represented the rock (attached to the cave ceiling with a magnet), and the bubbles were produced using a syringe located at the cave floor. PMID:25849088

  16. Development of bubble tester

    NASA Astrophysics Data System (ADS)

    Yang, Wenzhi; Jing, Hongwei; Wu, Shibin; Cao, Xuedong

    2009-05-01

    A Bubble Tester is developed to do the measurements of bubble classes for optical elements. The tester is composed of illumination system,refractor slot, imaging system,CCD,computer controller and data processor,3D workshop and ground base. The light from the illumination system is refracted by the bubbles and inclosures in the optical elements, the imaging system captured the light and imaged the image to CCD and computer captured the image and did data processing to get the dimension, quantity and distribution of the bubbles and enclosures. The tester can measure bubbles with Φ0.05~Φ5mm in diameter and the accuracy is 5%.The tester can measure bubbles and enclosures of optical elements and welding line of the optics according to GB 7661-87.

  17. Electrowetting of soap bubbles

    NASA Astrophysics Data System (ADS)

    Arscott, Steve

    2013-07-01

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

  18. 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.

  19. Sonochemistry and bubble dynamics.

    PubMed

    Mettin, Robert; Cairs, Carlos; Troia, Adriano

    2015-07-01

    The details of bubble behaviour in chemically active cavitation are still not sufficiently well understood. Here we report on experimental high-speed observations of acoustically driven single-bubble and few-bubble systems with the aim of clarification of the connection of their dynamics with chemical activity. Our experiment realises the sonochemical isomerization reaction of maleic acid to fumaric acid, mediated by bromine radicals, in a bubble trap set-up. The main result is that the reaction product can only be observed in a parameter regime where a small bubble cluster occurs, while a single trapped bubble stays passive. Evaluations of individual bubble dynamics for both cases are given in form of radius-time data and numerical fits to a bubble model. A conclusion is that a sufficiently strong collapse has to be accompanied by non-spherical bubble dynamics for the reaction to occur, and that the reason appears to be an efficient mixing of liquid and gas phase. This finding corroborates previous observations and literature reports on high liquid phase sonochemical activity under distinct parameter conditions than strong sonoluminescence emissions. PMID:25194210

  20. Physics of bubble oscillations

    NASA Astrophysics Data System (ADS)

    Lauterborn, Werner; Kurz, Thomas

    2010-10-01

    Bubbles in liquids, soft and squeezy objects made of gas and vapour, yet so strong as to destroy any material and so mysterious as at times turning into tiny light bulbs, are the topic of the present report. Bubbles respond to pressure forces and reveal their full potential when periodically driven by sound waves. The basic equations for nonlinear bubble oscillation in sound fields are given, together with a survey of typical solutions. A bubble in a liquid can be considered as a representative example from nonlinear dynamical systems theory with its resonances, multiple attractors with their basins, bifurcations to chaos and not yet fully describable behaviour due to infinite complexity. Three stability conditions are treated for stable trapping of bubbles in standing sound fields: positional, spherical and diffusional stability. Chemical reactions may become important in that respect, when reacting gases fill the bubble, but the chemistry of bubbles is just touched upon and is beyond the scope of the present report. Bubble collapse, the runaway shrinking of a bubble, is presented in its current state of knowledge. Pressures and temperatures that are reached at this occasion are discussed, as well as the light emission in the form of short flashes. Aspherical bubble collapse, as for instance enforced by boundaries nearby, mitigates most of the phenomena encountered in spherical collapse, but introduces a new effect: jet formation, the self-piercing of a bubble with a high velocity liquid jet. Examples of this phenomenon are given from light induced bubbles. Two oscillating bubbles attract or repel each other, depending on their oscillations and their distance. Upon approaching, attraction may change to repulsion and vice versa. When being close, they also shoot self-piercing jets at each other. Systems of bubbles are treated as they appear after shock wave passage through a liquid and with their branched filaments that they attain in standing sound fields. The N-bubble problem is formulated in the spirit of the n-body problem of astrophysics, but with more complicated interaction forces. Simulations are compared with three-dimensional bubble dynamics obtained by stereoscopic high speed digital videography.

  1. Scaling model for laser-produced bubbles in soft tissue

    SciTech Connect

    London, R. A., LLNL

    1998-03-12

    The generation of vapor-driven bubbles is common in many emerging laser-medical therapies involving soft tissues. To successfully apply such bubbles to processes such as tissue break-up and removal, it is critical to understand their physical characteristics. To complement previous experimental and computational studies, an analytic mathematical model for bubble creation and evolution is presented. In this model, the bubble is assumed to be spherically symmetric, and the laser pulse length is taken to be either very short or very long compared to the bubble expansion timescale. The model is based on the Rayleigh cavitation bubble model. In this description, the exterior medium is assumed to be an infinite incompressible fluid, while the bubble interior consists of a mixed liquid-gas medium which is initially heated by the laser. The heated interior provides the driving pressure which expands the bubble. The interior region is assumed to be adiabatic and is described by the standard water equation-of-state, available in either tabular, or analytic forms. Specifically, we use adiabats from the equation-of-state to describe the evolution of the interior pressure with bubble volume. Analytic scaling laws are presented for the maximum size, the duration, and the energy of bubbles as functions of the laser energy and initially heated volume. Of particular interest, is the efficiency of converting laser energy into bubble motion.

  2. A computationally efficient modelling of laminar separation bubbles

    NASA Technical Reports Server (NTRS)

    Dini, Paolo; Maughmer, Mark D.

    1989-01-01

    The goal is to accurately predict the characteristics of the laminar separation bubble and its effects on airfoil performance. Toward this end, a computational model of the separation bubble was developed and incorporated into the Eppler and Somers airfoil design and analysis program. Thus far, the focus of the research was limited to the development of a model which can accurately predict situations in which the interaction between the bubble and the inviscid velocity distribution is weak, the so-called short bubble. A summary of the research performed in the past nine months is presented. The bubble model in its present form is then described. Lastly, the performance of this model in predicting bubble characteristics is shown for a few cases.

  3. Bernoulli excitation and detection of gas bubbles.

    PubMed

    Telling, R H; Walton, A J

    2001-10-01

    A simple method is proposed for detecting and sizing bubbles in pipeline fluid flow. This is based on changing the pressure of the fluid, which in turn excites volume oscillations in the bubble. If the change in pressure is of sufficient brevity and magnitude, the transient distortion results in excitation of the bubble into radiative oscillation at its natural frequency. In a moving fluid, the Bernoulli equation predicts that such a pressure change can be achieved through a suitable gradient in the flow velocity. In the experiments described here, this is achieved by altering the cross-sectional area of the pipe in which the fluid is flowing. We demonstrate the efficacy of this excitation method and, by detecting the radiated sound using a nearby hydrophone, determine the size of individual bubbles from their characteristic oscillation frequency. PMID:11775661

  4. Bubble breakup in a turbulent shear layer

    NASA Astrophysics Data System (ADS)

    Brandner, P. A.; Henderson, A. D.; de Graaf, K. L.; Pearce, B. W.

    2015-12-01

    The breakup of a millimetre size buoyantly rising bubble encountering a horizontal plane turbulent jet is experimentally investigated using high-speed shadowgraphy and acoustic techniques. The bubble diameter to jet height ratio is 0.75 and the jet height based Reynolds number is 4000. The high-speed imaging was recorded at 7 kHz simultaneous with hydrophone output at 100 kHz. Bubble breakup events were seen to produce simple binary divisions into products of similar size as well as three products where at least one was much smaller than the other products. Coalescence of products was also observed. In almost all cases time-frequency analysis of the acoustic emissions enabled the products to be identified and sized.

  5. Bubble nonlinear dynamics and stimulated scattering process

    NASA Astrophysics Data System (ADS)

    Jie, Shi; De-Sen, Yang; Sheng-Guo, Shi; Bo, Hu; Hao-Yang, Zhang; Shi-Yong, Hu

    2016-02-01

    A complete understanding of the bubble dynamics is deemed necessary in order to achieve their full potential applications in industry and medicine. For this purpose it is first needed to expand our knowledge of a single bubble behavior under different possible conditions including the frequency and pressure variations of the sound field. In addition, stimulated scattering of sound on a bubble is a special effect in sound field, and its characteristics are associated with bubble oscillation mode. A bubble in liquid can be considered as a representative example of nonlinear dynamical system theory with its resonance, and its dynamics characteristics can be described by the Keller–Miksis equation. The nonlinear dynamics of an acoustically excited gas bubble in water is investigated by using theoretical and numerical analysis methods. Our results show its strongly nonlinear behavior with respect to the pressure amplitude and excitation frequency as the control parameters, and give an intuitive insight into stimulated sound scattering on a bubble. It is seen that the stimulated sound scattering is different from common dynamical behaviors, such as bifurcation and chaos, which is the result of the nonlinear resonance of a bubble under the excitation of a high amplitude acoustic sound wave essentially. The numerical analysis results show that the threshold of stimulated sound scattering is smaller than those of bifurcation and chaos in the common condition. Project supported by the Program for Changjiang Scholars and Innovative Research Team in University, China (Grant No. IRT1228) and the Young Scientists Fund of the National Natural Science Foundation of China (Grant Nos. 11204050 and 11204049).

  6. Prospects for bubble fusion

    SciTech Connect

    Nigmatulin, R.I.; Lahey, R.T. Jr.

    1995-09-01

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

  7. Oscillating plasma bubbles. I. Basic properties and instabilities

    SciTech Connect

    Stenzel, R. L.; Urrutia, J. M.

    2012-08-15

    Plasma bubbles are created in an ambient discharge plasma. A bubble is a plasma volume of typically spherical shape, which is separated from the ambient plasma by a negatively biased grid of high transparency. Ions and electrons from the ambient plasma flow into the bubble volume. In steady state the flow of particles and currents is divergence-free, which is established by the plasma potential inside the bubble. The grid has two sheaths, one facing the ambient plasma, the other the bubble plasma. The inner sheath is observed to become unstable, causing the plasma potential in the bubble to oscillate. The instability arises from an excess of ions and a deficiency of electrons. Its frequency is in the range of the ion plasma frequency but depends on all parameters which influence the charge density in the sheath. When the grid voltage is very negative, electrons cannot enter the outer sheath, and the inner sheath becomes a virtual anode which reflects ions such that the bubble interior is empty. When an electron source is placed into the bubble it can neutralize the ions and the bubble refills. Without plasma sources or sinks the bubble plasma is extremely sensitive to perturbations by probes. Modified current-voltage characteristics of Langmuir and emissive probes are demonstrated. A sequence of papers first describes the basic steady-state properties, then the time evolution of bubbles, the effects of electron sources in bubbles, and the role of the grid and bubble geometry. The physics of plasma bubbles is important to several fields of basic plasma physics such as sheaths, sheath instabilities, diagnostic probes, electrostatic confinement, and current and space charge neutralization of beams.

  8. Let Them Blow Bubbles.

    ERIC Educational Resources Information Center

    Korenic, Eileen

    1988-01-01

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

  9. Acoustical emission from bubbles

    NASA Astrophysics Data System (ADS)

    Longuet-Higgins, Michael S.

    1991-12-01

    The scientific objectives of this report are to investigate the dynamics of bubbles formed from a free surface (particularly the upper surface of the ocean) by breaking waves, and the resulting emission of underwater sound. The chief natural source of underwater sound in the ocean at frequencies from 0.5 to 50 kHz is known to be the acoustical emission from newly-formed bubbles and bubble clouds, particularly those created by breaking waves and rain. Attention has been drawn to the occurrence of high-speed jets directed into the bubble just after bubble closure. They have been observed both in rain-drop impacts and in the release of bubbles from an underwater nozzle. Qualitatively they are similar to the inward jets seen in the collapse of a cavitation bubble. There is also a similarity to the highly-accelerated upward jets in standing water waves (accelerations greater than 20g) or in bubbles bursting at a free surface. We have adopted a theoretical approach based on the dynamics of incompressible fluids with a free surface.

  10. The Vacuum Bubble Nucleation

    SciTech Connect

    Lee, Bum-Hoon; Lee, Wonwoo

    2009-07-10

    We study the nucleation of a vacuum bubble via the vacuum-to-vacuum tunneling transition in curved spacetime. We consider Coleman-de Luccia's semiclassical approximation at zero temperature in pure Einstein theory of gravity and the theory with nonminimal coupling. We discuss the dynamics of a nucleated vacuum bubble.

  11. Gases in Tektite Bubbles.

    PubMed

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

    1962-07-20

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

  12. Evaporation, Boiling and Bubbles

    ERIC Educational Resources Information Center

    Goodwin, Alan

    2012-01-01

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

  13. 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

  14. Hydrological Characteristics of Recurrent Slope Lineae on Mars Based on Time-Resolved HiRISE Analyses and Comparisons with Fluid Flow Through an Antarctic Terrestrial Analog Regolith

    NASA Astrophysics Data System (ADS)

    Levy, J. S.; Fountain, A. G.

    2012-03-01

    We test the "wet" (brine-related) RSL formation mechanism by using repeat HiRISE images to determine whether a simple Darcy flow model can explain the spatial pattern of RSL darkening. This remote hydrogeological tool is verified in Antarctic soil.

  15. 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.

  16. Airflow driven bubble pinch-off

    NASA Astrophysics Data System (ADS)

    Bergmann, Raymond; Andersen, Anders; Bohr, Tomas; van der Meer, Devaraj

    2008-11-01

    We create air bubbles at the tip of a ``bathtub vortex'' which reaches to a finite depth. The bathtub vortex is created by letting water drain through a small hole at the bottom of a rotating cylindrical container. For sufficiently large rotation rates the tip of this needle-like surface depression becomes unstable and emits bubbles. The collapse follows a R(t)&1/3circ; power law for the minimal neck radius which is indicative of the balance between liquid inertia and the under pressure due to the airflow in the neck. In a variety of systems it is the under pressure created by airflow that induces and/or propagates the pinch-off of a bubble. In a co-focused jet, and the equivalent flow-focusing devices, it is the externally induced airflow that breaks up the bubbles. In other systems the collapse itself induces an airflow which becomes dominant in the final stages of bubble pinch-off (Phys. Rev. Lett. 98, 144503 (2007)). Our system illustrates the importance of both contributions to the airflow, i.e., the external airflow induced by surface oscillations of the tip and the airflow induced in the neck by the collapse itself. Both of these contributions are of the same order and in Bernoulli's law the unsteadiness gives rise to terms of similar order. Surprisingly enough, all of these terms contribute with the same scaling exponent to the under pressure.

  17. Mechanics of Bubbles in Sludges and Slurries

    SciTech Connect

    Gauglitz, Phillip A.; Denn, Morton M.; Rossen, William R.

    1999-06-01

    This project is focusing on key issues associated with the flammable gas safety hazard and its role in safe storage and in future waste operations such as salt-well pumping, waste transfers, and sluicing and retrieval of tank waste. The purpose of this project is to develop a basic understanding of how single bubbles (of flammable gases) behave in representative waste simulants and then develop a framework for predicting macroscopic full-tank behavior from the underlying single-bubble behavior. The specific objectives of this research are as follows: 1. quantitatively describe the interaction of bubbles with waste materials (both sludges and slurries) to understand the physical mechanisms by which barometric pressure changes give rise to a hysteresis between level and pressure 2. develop improved methods for estimating retained gas by properly accounting for the interactions of bubbles with the waste 3. determine how to estimate waste physical properties from the observed hysteresis and the limitations of these estimates 4. determine how barometric pressure fluctuations induce slow upward migration and release of gas bubbles.

  18. The Bubbling Galactic Disk

    NASA Astrophysics Data System (ADS)

    Churchwell, E.; Povich, M. S.; Allen, D.; Taylor, M. G.; Meade, M. R.; Babler, B. L.; Indebetouw, R.; Watson, C.; Whitney, B. A.; Wolfire, M. G.; Bania, T. M.; Benjamin, R. A.; Clemens, D. P.; Cohen, M.; Cyganowski, C. J.; Jackson, J. M.; Kobulnicky, H. A.; Mathis, J. S.; Mercer, E. P.; Stolovy, S. R.; Uzpen, B.; Watson, D. F.; Wolff, M. J.

    2006-10-01

    A visual examination of the images from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) has revealed 322 partial and closed rings that we propose represent partially or fully enclosed three-dimensional bubbles. We argue that the bubbles are primarily formed by hot young stars in massive star formation regions. We have found an average of about 1.5 bubbles per square degree. About 25% of the bubbles coincide with known radio H II regions, and about 13% enclose known star clusters. It appears that B4-B9 stars (too cool to produce detectable radio H II regions) probably produce about three-quarters of the bubbles in our sample, and the remainder are produced by young O-B3 stars that produce detectable radio H II regions. Some of the bubbles may be the outer edges of H II regions where PAH spectral features are excited and may not be dynamically formed by stellar winds. Only three of the bubbles are identified as known SNRs. No bubbles coincide with known planetary nebulae or W-R stars in the GLIMPSE survey area. The bubbles are small. The distribution of angular diameters peaks between 1' and 3' with over 98% having angular diameters less than 10' and 88% less than 4'. Almost 90% have shell thicknesses between 0.2 and 0.4 of their outer radii. Bubble shell thickness increases approximately linearly with shell radius. The eccentricities are rather large, peaking between 0.6 and 0.7; about 65% have eccentricities between 0.55 and 0.85.

  19. Empirical fractal geometry analysis of some speculative financial bubbles

    NASA Astrophysics Data System (ADS)

    Redelico, Francisco O.; Proto, Araceli N.

    2012-11-01

    Empirical evidence of a multifractal signature during increasing of a financial bubble leading to a crash is presented. The April 2000 crash in the NASDAQ composite index and a time series from the discrete Chakrabarti-Stinchcombe model for earthquakes are analyzed using a geometric approach and some common patterns are identified. These patterns can be related the geometry of the rising period of a financial bubbles with the non-concave entropy problem.

  20. Explicit characteristics of evolutionary-type plasma bubbles observed from Equatorial Atmosphere Radar during the low to moderate solar activity years 2010-2012

    NASA Astrophysics Data System (ADS)

    Ajith, K. K.; Ram, S. Tulasi; Yamamoto, M.; Yokoyama, T.; Gowtam, V. Sai; Otsuka, Y.; Tsugawa, T.; Niranjan, K.

    2015-02-01

    Using the fan sector backscatter maps of 47 MHz Equatorial Atmosphere Radar (EAR) at Kototabang (0.2S geographic latitude, 100.3E geographic longitude, and 10.4S geomagnetic latitude), Indonesia, the spatial and temporal evolution of equatorial plasma bubbles (EPBs) were examined to classify the evolutionary-type EPBs from those which formed elsewhere and drifted into the field of view of radar. A total of 535 EPBs were observed during the low to moderate solar activity years 2010-2012, out of which about 210 (~39%) are of evolving type and the remaining 325 (~61%) are drifting-in EPBs. In general, both the evolving-type and drifting-in EPBs exhibit predominance during the postsunset hours of equinoxes and December solstices. Interestingly, a large number of EPBs were found to develop even a few minutes prior to the apex sunset during equinoxes. Further, the occurrence of evolving-type EPBs exhibits a clear secondary peak around midnight (2300-0100 LT), primarily, due to higher rate of occurrence during the postmidnight hours of June solstices. A significant number (~33%) of postmidnight EPBs generated during June solstices did not exhibited any clear zonal drift, while about 14% of EPBs drifted westward. Also, the westward drifting EPBs are confined only to June solstices. The responsible mechanisms for the genesis of fresh EPBs during postmidnight hours were discussed in light of equatorward meridional winds in the presence of weak westward electric fields.

  1. Effects of water vapor pretreatment time and reaction temperature on CO(2) capture characteristics of a sodium-based solid sorbent in a bubbling fluidized-bed reactor.

    PubMed

    Seo, Yongwon; Jo, Sung-Ho; Ryu, Chong Kul; Yi, Chang-Keun

    2007-10-01

    CO(2) capture from flue gas using a sodium-based solid sorbent was investigated in a bubbling fluidized-bed reactor. Carbonation and regeneration temperature on CO(2) removal was determined. The extent of the chemical reactivity after carbonation or regeneration was characterized via (13)C NMR. In addition, the physical properties of the sorbent such as pore size, pore volume, and surface area after carbonation or regeneration were measured by gas adsorption method (BET). With water vapor pretreatment, near complete CO(2) removal was initially achieved and maintained for about 1-2min at 50 degrees C with 2s gas residence time, while without proper water vapor pretreatment CO(2) removal abruptly decreased from the beginning. Carbonation was effective at the lower temperature over the 50-70 degrees C temperature range, while regeneration more effective at the higher temperature over the 135-300 degrees C temperature range. To maintain the initial 90% CO(2) removal, it would be necessary to keep the regeneration temperature higher than about 135 degrees C. The results obtained in this study can be used as basic data for designing and operating a large scale CO(2) capture process with two fluidized-bed reactors. PMID:17604081

  2. Bubbles, Bubbles: Integrated Investigations with Floating Spheres

    ERIC Educational Resources Information Center

    Reeder, Stacy

    2007-01-01

    In this article, the author describes integrated science and mathematics activities developed for fourth-grade students to explore and investigate three-dimensional geometric shapes, Bernoulli's principle, estimation, and art with and through bubbles. Students were engaged in thinking and reflection on the questions their teachers asked and were

  3. Shock-Induced Bubble Collapse versus Rayleigh Collapse

    NASA Astrophysics Data System (ADS)

    Kapahi, Anil; Hsiao, Chao-Tsung; Chahine, Georges L.

    2015-12-01

    This paper compares two physical mechanisms for the collapse of a bubble near a rigid wall: a traveling shock-induced collapse and a Rayleigh-like collapse due to a uniform rise of the pressure around the bubble. A multi-material compressible flow solver capable of handling material interfaces under high pressures is used to investigate these two scenarios for different levels of the driving pressure ranging from 1 MPa to 400 MPa. The two mechanisms are differentiated on the basis of the resulting bubble dynamics, the reentrant jet velocity, and the pressures imparted to the wall.

  4. Cavitation inception by the backscattering of pressure waves from a bubble interface

    NASA Astrophysics Data System (ADS)

    Takahira, Hiroyuki; Ogasawara, Toshiyuki; Mori, Naoto; Tanaka, Moe

    2015-10-01

    The secondary cavitation that occurs by the backscattering of focused ultrasound from a primary cavitation bubble caused by the negative pressure part of the ultrasound (Maxwell, et al., 2011) might be useful for the energy exchange due to bubble oscillations in High Intensity Focused Ultrasound (HIFU). The present study is concerned with the cavitation inception by the backscattering of ultrasound from a bubble. In the present experiment, a laser-induced bubble which is generated by a pulsed focused laser beam with high intensity is utilized as a primary cavitation bubble. After generating the bubble, focused ultrasound is emitted to the bubble. The acoustic field and the bubble motion are observed with a high-speed video camera. It is confirmed that the secondary cavitation bubble clouds are generated by the backscattering from the laser-induced bubble. The growth of cavitation bubble clouds is analyzed with the image processing method. The experimental results show that the height and width of the bubble clouds grow in stepwise during their evolution. The direct numerical simulations are also conducted for the backscattering of incident pressure waves from a bubble in order to evaluate a pressure field near the bubble. It is shown that the ratio of a bubble collapse time t0 to a characteristic time of wave propagation tS, η = t0/ts, is an important determinant for generating negative pressure region by backscattering. The minimum pressure location by the backscattering in simulations is in good agreement with the experiment.

  5. Heat transfer and bubble dynamics in bubble and slurry bubble columns with internals for Fischer-Tropsch synthesis of clean alternative fuels and chemicals

    NASA Astrophysics Data System (ADS)

    Kagumba, Moses Odongo O.

    Synthesis gas, a mixture of CO and H2 obtained from coal, natural gas and biomass are increasingly becoming reliable sources of clean synthetic fuels and chemicals and via Fischer-Tropsch (F-T) synthesis process. Slurry bubble column reactor is the reactor of choice for the commercialization of the F-T synthesis. Even though the slurry bubble column reactors and contactors are simple in structures, their design, scale-up, operation, and performance prediction are still challenging and not well understood due to complex interaction of phases. All the studies of heat transfer have been performed without simultaneously investigating the bubble dynamics adjacent to the heat transfer surfaces, particularly in slurry with dense internals. This dissertation focuses on enhancing the understanding of the role of local and overall gas holdup, bubble passage frequency, bubble sizes and bubble velocity on the heat transfer characteristics by means of a hybrid measurement technique comprising an advanced four-point optical probe and a fast response heat transfer probe used simultaneously, in the presence and absence of dense internals. It also seeks to advance a mechanistic approach for estimating the needed parameters for predicting the heat transfer rate in two phase and three phase systems. The results obtained suggest that the smaller diameter internals gives higher heat transfer coefficient, higher local and overall gas holdup, bubble passage frequency and specific interfacial area but smaller bubble sizes and lower axial bubble velocities. The presence of dense internals enhances the heat transfer coefficient in both the large and smaller columns, while increased column diameter increases the heat transfer coefficient, axial bubble velocity, local and overall gas holdup, bubble chord lengths and specific interfacial area. Addition of solids (glass beads) leads to increased bubble chord lengths and increase in axial bubble velocity, but a decrease in local and overall gas holdup, a decrease in bubble passage frequency and decrease in the heat transfer coefficient. Further, a mechanistic assessment of the dependence of the heat transfer coefficient on the bubble dynamics shows that the contact time needed in the heat transfer coefficient estimation is indeed a function of the bubble passage frequency and local gas holdup. Hence the variation of the heat transfer coefficient with contact time is via bubble passage frequency and local gas phase holdup, which are related with sizes and velocity.

  6. Topographic Rise in the Northern Smooth Plains of Mercury: Characteristics from Messenger Image and Altimetry Data and Candidate Modes of Origin

    NASA Technical Reports Server (NTRS)

    Dickson, James L.; Head, James W.; Whitten, Jennifer L.; Fassett, Caleb I.; Neumann, Gregory A.; Smith, David E.; Zuber, Maria T.; Phillips, Roger J.

    2012-01-01

    MESSENGER observations from orbit around Mercury have revealed that a large contiguous area of smooth plains occupies much of the high northern latitudes and covers an area in excess of approx.6% of the surface of the planet [1] (Fig. 1). Smooth surface morphology, embayment relationships, color data, candidate flow fronts, and a population of partly to wholly buried craters provide evidence for the volcanic origin of these plains and their emplacement in a flood lava mode to depths at least locally in excess of 1 km. The age of these plains is similar to that of plains associated with and postdating the Caloris impact basin, confirming that volcanism was a globally extensive process in the post-heavy bombardment history of Mercury [1]. No specific effusive vent structures, constructional volcanic edifices, or lava distributary features (leveed flow fronts or sinuous rilles) have been identified in the contiguous plains, although vent structures and evidence of high-effusion-rate flood eruptions are seen in adjacent areas [1]. Subsequent to the identification and mapping of the extensive north polar smooth plains, data from the Mercury Laser Altimeter (MLA) on MESSENGER revealed the presence of a broad topographic rise in the northern smooth plains that is 1,000 km across and rises more than 1.5 km above the surrounding smooth plains [2] (Fig. 2). The purpose of this contribution is to characterize the northern plains rise and to outline a range of hypotheses for its origin.

  7. A computationally efficient modelling of laminar separation bubbles

    NASA Technical Reports Server (NTRS)

    Maughmer, Mark D.

    1988-01-01

    The goal of this research is to accurately predict the characteristics of the laminar separation bubble and its effects on airfoil performance. To this end, a model of the bubble is under development and will be incorporated in the analysis section of the Eppler and Somers program. As a first step in this direction, an existing bubble model was inserted into the program. It was decided to address the problem of the short bubble before attempting the prediction of the long bubble. In the second place, an integral boundary-layer method is believed more desirable than a finite difference approach. While these two methods achieve similar prediction accuracy, finite-difference methods tend to involve significantly longer computer run times than the integral methods. Finally, as the boundary-layer analysis in the Eppler and Somers program employs the momentum and kinetic energy integral equations, a short-bubble model compatible with these equations is most preferable.

  8. Interfacial structure in an air-water planar bubble jet

    NASA Astrophysics Data System (ADS)

    Sun, X.; Vasavada, S.; Choi, S. W.; Kim, S.; Ishii, M.; Beus, S. G.

    2005-04-01

    The objective of the current study is to better understand the interfacial structure and its development in an air-water planar bubble jet, as well as to provide a unique benchmark data set for a 3D thermal-hydraulic analysis code. Both flow visualization and local measurements were performed in three characteristic flow conditions at four elevations along a test section with a cross section of 200 mm in width and 10 mm in gap. A high-speed digital video camera was applied in the flow visualization study to capture the flow structures and bubble interaction phenomena, while a miniaturized four-sensor conductivity probe was used to acquire the time-averaged local void fraction, interfacial velocity, and bubble number frequency. Also, the interfacial area concentration and the averaged bubble Sauter mean diameter were obtained from the local measurements. The lateral bubble transport and bubble interaction mechanisms were clearly demonstrated in the acquired data.

  9. Tribonucleation of bubbles

    PubMed Central

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

    2014-01-01

    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

  10. Effects of system pressure and heat flux on bubble nucleation and growth

    NASA Astrophysics Data System (ADS)

    Qiu, Chao; Zhang, Huichen

    2015-09-01

    Characteristics of bubble nucleation and growth are critical for its application. It is affected by several factors including viscosity, surface tension and temperature. However, the effect of pressure on bubble nucleation and growth has been underreported, although it processes significant effect on above characteristics. In this work, a micro copper electrode is etched on a slab covered with copper to produce bubble on the surface by current input. The nucleation time of bubble is measured under different heat flux and system pressures. The nucleation and growth processes are recorded with a high speed camera in order to discuss the effects of heat flux and system pressure on bubble characteristics. The experiment results indicate that the micro electrode with higher heat flux produces more thermal energy, which makes the time of bubble nucleation shorter and the speed of bubble growth faster. Higher system pressure causes the increase of the critical nucleation temperature and also baffles the bubble nucleation and growth. Bubble growth includes the stages of rapid growth and dynamic equilibrium, with the speed being from fast to slow. In the former part of rapid growth, heat flux plays a dominant role in bubble growth. While the effect of system pressure on bubble growth becomes significant in the latter part of rapid growth. Both the nucleation time and bubble growth agree well with the theoretical analysis. The obtained results help to accurately control bubble nucleation and growth required in different application.

  11. Monte Carlo simulation of spectral reflectance and BRDF of the bubble layer in the upper ocean.

    PubMed

    Ma, Lanxin; Wang, Fuqiang; Wang, Chengan; Wang, Chengchao; Tan, Jianyu

    2015-09-21

    The presence of bubbles can significantly change the radiative properties of seawater and these changes will affect remote sensing and underwater target detection. In this work, the spectral reflectance and bidirectional reflectance characteristics of the bubble layer in the upper ocean are investigated using the Monte Carlo method. The Hall-Novarini (HN) bubble population model, which considers the effect of wind speed and depth on the bubble size distribution, is used. The scattering coefficients and the scattering phase functions of bubbles in seawater are calculated using Mie theory, and the inherent optical properties of seawater for wavelengths between 300 nm and 800 nm are related to chlorophyll concentration (Chl). The effects of bubble coating, Chl, and bubble number density on the spectral reflectance of the bubble layer are studied. The bidirectional reflectance distribution function (BRDF) of the bubble layer for both normal and oblique incidence is also investigated. The results show that bubble populations in clear waters under high wind speed conditions significantly influence the reflection characteristics of the bubble layer. Furthermore, the contribution of bubble populations to the reflection characteristics is mainly due to the strong backscattering of bubbles that are coated with an organic film. PMID:26406633

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

    SciTech Connect

    Paul C Millett; Anter El-Azab

    2011-01-01

    We present a phase-field model for inert gas bubble formation and evolution in irradiated metals. The model evolves vacancy, self-interstitial, and fission gas atoms through a coupled set of Cahn-Hilliard and Allen-Cahn equations, capturing the processes of defect generation, recombination, annihilation at GB sinks, as well as intragranular and intergranular bubble nucleation and growth in polycrystalline microstructures. Illustrative results are presented that characterize bubble growth and shrinkage, as well as the bubble density, size and nucleation rate as a function of varying irradiation conditions. Finally, intergranular bubble characteristics such as shape, pinning energy on GB motion, and bubble density are investigated.

  13. High resolution bubble chambers

    SciTech Connect

    Bizzarri, R.

    1984-01-01

    This chapter discusses the performances obtained or to be expected from small bubble chambers with ''classical'' optics (i.e. no holography). LEBC and HOLEBC, two hydrogen chambers, are used. The limits on the accessible cross sections, the limits on the accessible life times, the limits on the resolution, and bubble density are considered. In the experiment with the bubble chamber LEBC, two lenses were used of focal length f=180 mm, open at f/11 and with a space to film demagnification m=3.2. In the experiment with HOLBEC, lenses of f=300 mm at f/17 are used with a demagnification m=.9.

  14. Rotating bubble membrane radiator

    DOEpatents

    Webb, Brent J.; Coomes, Edmund P.

    1988-12-06

    A heat radiator useful for expelling waste heat from a power generating system aboard a space vehicle is disclosed. Liquid to be cooled is passed to the interior of a rotating bubble membrane radiator, where it is sprayed into the interior of the bubble. Liquid impacting upon the interior surface of the bubble is cooled and the heat radiated from the outer surface of the membrane. Cooled liquid is collected by the action of centrifical force about the equator of the rotating membrane and returned to the power system. Details regarding a complete space power system employing the radiator are given.

  15. A Study on Bubble Departure and Bubble Lift-Off in Sub-Cooled Nucleate Boiling Flows

    SciTech Connect

    Wu, Wen; Chen, Peipei; Jones, Barclay G.; Newell, Ty A.

    2006-07-01

    This research examines bubble departure and bubble lift-off phenomena under subcooled nucleate boiling condition, using a high fidelity digital imaging apparatus. Refrigerant R- 134a is chosen as a simulant fluid due to its merits of having smaller surface tension, reduced latent heat, and lower boiling temperature than water. Images at frame rates up to 4000 frames/s were obtained with varying experimental parameters e.g. pressure, inlet sub-cooled level, and flow rate, etc., showing characteristics of bubble behavior under different conditions. Bubble size and position information was calculated via Canny's algorithm for edge detection and Fitzgibbon's algorithm for ellipse fitting. Bubble departure and lift-off radiuses were obtained and compared with existing bubble forces and detachment models proposed by Thorncroft et al., with good agreement observed. (authors)

  16. Gas Bubble Formation in Stagnant and Flowing Mercury

    SciTech Connect

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

    2007-01-01

    Investigations in the area of two-phase flow at the Oak Ridge National Laboratory's (ORNL) Spallation Neutron Source (SNS) facility are progressing. It is expected that the target vessel lifetime could be extended by introducing gas into the liquid mercury target. As part of an effort to validate the two-phase computational fluid dynamics (CFD) model, simulations and experiments of gas injection in stagnant and flowing mercury have been completed. The volume of fluid (VOF) method as implemented in ANSYS-CFX, was used to simulate the unsteady two-phase flow of gas injection into stagnant mercury. Bubbles produced at the upwards-oriented vertical gas injector were measured with proton radiography at the Los Alamos Neutron Science Center. The comparison of the CFD results to the radiographic images shows good agreement for bubble sizes and shapes at various stages of the bubble growth, detachment, and gravitational rise. Although several gas flows were measured, this paper focuses on the case with a gas flow rate of 8 cc/min through the 100-micron-diameter injector needle. The acoustic waves emitted due to the detachment of the bubble and during subsequent bubble oscillations were recorded with a microphone, providing a precise measurement of the bubble sizes. As the mercury flow rate increases, the drag force causes earlier bubble detachment and therefore smaller bubbles.

  17. Evidence for liquid phase reactions during single bubble acoustic cavitation.

    PubMed

    Troia, A; Madonna Ripa, D; Lago, S; Spagnolo, R

    2004-07-01

    We extended the recent experiment by Lepoint et al. [Sonochemistry and Sonoluminescence, NATO ASI Series, Series C 524, Kluwer Academic Publishers, Dordrecht/Boston/London, 1999, p. 285], involving a so-called single bubble sonochemistry process, to a three-phase system. We have found experimental evidence that a single cavitating bubble can activate the oxidation of I- ions after the injection of a CCl4 liquid drop in the bubble trapping apparatus. The solvent drop (CCl4 is almost water insoluble) is pushed towards the bubble position and forms a thin film on the bubble surface. When the acoustic pressure drive is increased above 100 kPa, the three-phase system gives rise to a dark filament, indicating the complexation reaction between starch (added to the water phase) and I2. I2 species is the product of surface reactions involving bubble-induced decomposition of CCl4. Further increase of the acoustic drive causes the thin CCl4 film to separate from the bubble and stops I2 production. The study of the chemical activity of this three-phase system could give new advances on dynamics of the bubble collapse. PMID:15157862

  18. 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)

  19. 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)

  20. 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.

  1. Colloquium: Soap bubble clusters

    NASA Astrophysics Data System (ADS)

    Morgan, Frank

    2007-07-01

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

  2. 2012 Problem 8: Bubbles

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  3. Clustering in Bubble Suspensions

    NASA Astrophysics Data System (ADS)

    Zenit, Roberto

    2000-11-01

    A monidisperse bubble suspension is studied experimentally for the limit in which the Weber number is small and the Reynolds number is large. For this regime the suspension can be modeled using potential flow theory to describe the dynamics of the interstitial fluid. Complete theoretical descriptions have been composed (Spelt and Sangani, 1998) to model the behavior of these suspensions. Bubble clustering is a natural instability that arises from the potential flow considerations, in which bubbles tend to align in horizontal rafts as they move upwards. The appearance of bubble clusters was recently corroborated experimentally by Zenit et al. (2000), who found that although clusters did appear, their strength was not as strong as the predictions. Experiments involving gravity driven shear flows are used to explain the nature of the clustering observed in these type of flows. Balances of the bubble phase pressure (in terms of a calculated diffusion coefficient) and the Maxwell pressure (from the potential flow description) are presented to predict the stability of the bubble suspension. The predictions are compared with experimental results.

  4. How many bubbles in your glass of bubbly?

    PubMed

    Liger-Belair, Gérard

    2014-03-20

    The issue about how many carbon dioxide bubbles are likely to nucleate in a glass of champagne (or bubbly) is of concern for sommeliers, wine journalists, experienced tasters, and any open minded physical chemist wondering about complex phenomena at play in a glass of bubbly. The whole number of bubbles likely to form in a single glass is the result of the fine interplay between dissolved CO2, tiny gas pockets trapped within particles acting as bubble nucleation sites, and ascending bubble dynamics. Based on theoretical models combining ascending bubble dynamics and mass transfer equations, the falsely naı̈ve question of how many bubbles are likely to form per glass is discussed in the present work. A theoretical relationship is derived, which provides the whole number of bubbles likely to form per glass, depending on various parameters of both the wine and the glass itself. PMID:24571670

  5. Gas separation and bubble behavior at a woven screen

    NASA Astrophysics Data System (ADS)

    Conrath, Michael; Dreyer, Michael E.

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

  6. A computationally efficient modelling of laminar separation bubbles

    NASA Technical Reports Server (NTRS)

    Dini, Paolo; Maughmer, Mark D.

    1989-01-01

    In order to predict the aerodynamic characteristics of airfoils operating at low Reynolds numbers, it is necessary to accurately account for the effects of laminar (transitional) separation bubbles. Generally, the greatest difficulty comes about when attempting to determine the increase in profile drag that results from the presence of separation bubbles. While a number of empirically based separation bubble models have been introduced in the past, the majority assume that the bubble development is fully predictable from upstream conditions. One way of accounting for laminar separation bubbles in airfoil design is the bubble analog used in the design and analysis program of Eppler and Somers. A locally interactive separation bubble model was developed and incorporated into the Eppler and Somers program. Although unable to account for strong interactions such as the large reduction in suction peak sometimes caused by leading edge bubbles, it is able to predict the increase in drag and the local alteration of the airfoil pressure distribution that is caused by bubbles occurring in the operational range which is of most interest.

  7. The impact and bounce of air bubbles at a flat fluid interface.

    PubMed

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

    2016-04-01

    The rise and impact of bubbles at an initially flat but deformable liquid-air interface in ultraclean liquid systems are modelled by taking into account the buoyancy force, hydrodynamic drag, inertial added mass effect and drainage of the thin film between the bubble and the interface. The bubble-surface interaction is analyzed using lubrication theory that allows for both bubble and surface deformation under a balance of normal stresses and surface tension as well as the long-range nature of deformation along the interface. The quantitative result for collision and bounce is sensitive to the impact velocity of the rising bubble. This velocity is controlled by the combined effects of interfacial tension via the Young-Laplace equation and hydrodynamic stress on the surface, which determine the deformation of the bubble. The drag force that arises from the hydrodynamic stress in turn depends on the hydrodynamic boundary conditions on the bubble surface and its shape. These interrelated factors are accounted for in a consistent manner. The model can predict the rise velocity and shape of millimeter-size bubbles in ultra-clean water, in two silicone oils of different densities and viscosities and in ethanol without any adjustable parameters. The collision and bounce of such bubbles with a flat water/air, silicone oil/air and ethanol/air interface can then be predicted with excellent agreement when compared to experimental observations. PMID:26924623

  8. Fast bubble dynamics and sizing

    NASA Astrophysics Data System (ADS)

    Czarnecki, Krzysztof; Fouan, Damien; Achaoui, Younes; Mensah, Serge

    2015-11-01

    Single bubble sizing is usually performed by measuring the resonant bubble response using the Dual Frequency Ultrasound Method. However, in practice, the use of millisecond-duration chirp-like waves yields nonlinear distortions of the bubble oscillations. In comparison with the resonant curve obtained under harmonic excitation, it was observed that the bubble dynamic response shifted by up to 20 percent of the resonant frequency with bubble radii of less than 100 ?m. In the case of low pressure waves (P < 5 kPa), an approximate formula for the apparent frequency shift is derived. Simulated and experimental bubble responses are analyzed in the time-frequency domain using an enhanced concentrated (reassigned) spectrogram. The difference in the resonant frequency resulted from the persistence of the resonant mode in the bubble response. Numerical simulations in which these findings are extended to pairs of coupled bubbles and to bubble clouds are also presented.

  9. 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.

  10. 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.

  11. 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.

  12. The Dueling Bubble Experiment

    NASA Astrophysics Data System (ADS)

    Roy, Anshuman; Borrell, Marcos; Felts, John; Leal, Gary; Hirsa, Amir

    2007-11-01

    When two drops or bubbles are brought into close proximity to each other, the thin film of the fluid between them drains as they are squeezed together. If the film becomes thin enough that intermolecular forces of attraction overwhelm capillary forces, the drops/bubbles coalesce and the time it takes for this to happen, starting from the point of apparent contact is referred to as the drainage time. One practical version of this scenario occurs during the formation of foams, when the thin film forms between gas bubbles that are growing in volume with time. We performed an experimental study that is intended to mimic this process in which the two drops (or bubbles) in the size range of 50-100 microns diameter are created by oozing a liquid/gas out of two capillaries of diameter less than 100 microns directly facing each other and immersed in a second fluid. We present measurements of drainage times for the cases of very low viscosity ratios PDMS drops in Castor oil (less than 0.05) and bubbles of air in PDMS, and highlight the differences that arise in part due to the different boundary conditions for thin film drainage for liquid-liquid versus gas-liquid systems, and in part due to the different Hamaker constants for the two systems.

  13. Bubble bursting mediated aerosols

    NASA Astrophysics Data System (ADS)

    Lhuissier, Henri; Villermaux, Emmanuel

    2009-11-01

    Wave breaking over the ocean in the surf zone is responsible for a substantial amount of atmospheric aerosols production. The objects mediating their formation are bubbles entrained below breaking waves, and bursting at the sea surface. We describe the mechanisms by which the liquid shell constitutive of a bubble ultimately results into small drops, also called film drops. A bubble bursts when a hole nucleates through the liquid shell. The hole grows at the Culick velocity balancing inertia with surface tension and is bordered by a rim collecting the shell liquid. This initially smooth toroidal rim corrugates when the centripetal acceleration caused by the recession motion is strong enough to trigger a Rayleigh-Taylor destabilization. Ligaments then emerge from corrugations crests and resolve by a Plateau-Rayleigh mechanism into droplets. The final myst properties are thus solely determined by the shell geometry at the bursting onset. It depends on the ratio of the bubble radius to the capillary length, and on the slow gravity drainage of the liquid on which are superimposed rearrangements due to the marginal regeneration at the bubble foot. Our findings will be discussed in connexion with know facts in that context.

  14. Plasma in sonoluminescing bubble.

    PubMed

    An, Yu

    2006-12-22

    With the new accommodation coefficient of water vapor evaluated by molecular dynamics model, the maximum temperature of a sonoluminescing bubble calculated with the full partial differential equations easily reaches few tens of thousands degrees. Though at this temperature the gas is weakly ionized (10% or less), the gas density inside a sonoluminescing bubble at the moment of the bubble's flashing is so high that there still forms a dense plasma. The light emission of the bubble is calculated by the plasma model which is compared with that by the bremsstrahlung (electron-ion, electron-neutral atom) and recombination model. The calculation by the two models shows that for the relatively low maximum temperature (< 30,000 K) of the bubble, the pulse width is independent of the wavelength and the spectrum deviates the black body radiation type; while for the relatively high maximum temperature (approximately 60,000 K), the pulse width is dependent of the wavelength and the spectrum is an almost perfect black body radiation spectrum. The maximum temperature calculated by the gas dynamics equations is much higher than the temperature fitted by the black body radiation formula. PMID:16797657

  15. 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

  16. BLOWING COSMIC BUBBLES

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This NASA Hubble Space Telescope image reveals an expanding shell of glowing gas surrounding a hot, massive star in our Milky Way Galaxy. This shell is being shaped by strong stellar winds of material and radiation produced by the bright star at the left, which is 10 to 20 times more massive than our Sun. These fierce winds are sculpting the surrounding material - composed of gas and dust - into the curve-shaped bubble. Astronomers have dubbed it the Bubble Nebula (NGC 7635). The nebula is 10 light-years across, more than twice the distance from Earth to the nearest star. Only part of the bubble is visible in this image. The glowing gas in the lower right-hand corner is a dense region of material that is getting blasted by radiation from the Bubble Nebula's massive star. The radiation is eating into the gas, creating finger-like features. This interaction also heats up the gas, causing it to glow. Scientists study the Bubble Nebula to understand how hot stars interact with the surrounding material. Credit: Hubble Heritage Team (AURA/STScI/NASA)

  17. 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.

  18. Communications; On the formation of potassium bubbles in tungsten rod

    SciTech Connect

    Briant, C.L. . Corporate Research and Development Center)

    1989-01-01

    The microstructure of tungsten wire that is manufactured for use as lamp filaments has been studied by a number of researchers. The author demonstrates that one of the most important features of the microstructure is the potassium bubbles, approximately 500 A in diameter, that are aligned in rows in the direction of wire drawing. These bubbles pin the grain boundaries as they migrate down the length of the wire, giving rise to an interlocking grain structure in the recrystallized wire. If these bubbles were not present, a bamboo structure would form which would then rapidly fail during operation of the lamp as a result of grain boundary sliding. The potassium which forms these bubbles is incorporated into the tungsten during sintering of the powder metallurgy ingot.

  19. Moduli vacuum bubbles produced by evaporating black holes

    SciTech Connect

    Morris, J. R.

    2007-10-15

    We consider a model with a toroidally compactified extra dimension giving rise to a temperature-dependent 4D effective potential with one-loop contributions due to the Casimir effect, along with a 5D cosmological constant. The forms of the effective potential at low and high temperatures indicate a possibility for the formation of a domain wall bubble, formed by the modulus scalar field, surrounding an evaporating black hole. This is viewed as an example of a recently proposed black hole vacuum bubble arising from matter-sourced moduli fields in the vicinity of an evaporating black hole [D. Green, E. Silverstein, and D. Starr, Phys. Rev. D 74, 024004 (2006)]. The black hole bubble can be highly opaque to lower-energy particles and photons, and thereby entrap them within. For high-temperature black holes, there may also be a symmetry-breaking black hole bubble of false vacuum of the type previously conjectured by Moss [I. G. Moss, Phys. Rev. D 32, 1333 (1985)], tending to reflect low-energy particles from its wall. A double bubble composed of these two different types of bubble may form around the black hole, altering the hole's emission spectrum that reaches outside observers. Smaller mass black holes that have already evaporated away could have left vacuum bubbles behind that contribute to the dark matter.

  20. The Fermi Bubbles

    NASA Astrophysics Data System (ADS)

    Finkbeiner, Douglas P.

    2015-01-01

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

  1. BURST OF STAR FORMATION DRIVES BUBBLE IN GALAXY'S CORE

    NASA Technical Reports Server (NTRS)

    2002-01-01

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

  2. Gravitational wave production by collisions: more bubbles

    SciTech Connect

    Huber, Stephan J; Konstandin, Thomas E-mail: konstand@ifae.es

    2008-09-15

    We re-examine the production of gravitational waves by bubble collisions during a first-order phase transition. The spectrum of the gravitational radiation is determined by numerical simulations using the 'envelope approximation'. We find that the spectrum rises as f{sup 3.0} for small frequencies and decreases as f{sup -1.0} for high frequencies. Thus, the fall-off at high frequencies is significantly slower than previously stated in the literature. This result has direct impact on detection prospects for gravity waves originating from a strong first-order electroweak phase transition at space-based interferometers, such as LISA and BBO. In addition, we observe a slight dependence of the peak frequency on the bubble wall velocity.

  3. Direct simulation of single bubble motion under vertical magnetic field: Paths and wakes

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; Ni, Ming-Jiu

    2014-10-01

    Motion of single Ar bubbles rising in GaInSn under vertical magnetic fields is studied numerically using a volume-of-fluid method and adaptive mesh refinement technique for two-phase interface treatment; a consistent and conservative scheme calculates induced current density and Lorentz force. Numerical results are compared with published experimental data [C. Zhang, S. Eckert, and G. Gerbeth, "Experimental study of single bubble motion in a liquid metal column exposed to a DC magnetic field," Int. J. Multiphase Flow 31, 824-842 (2005)], where bubble diameters range from 2.5 to 6.4 mm, producing Reynolds numbers that vary between 2000 and 4000. Maximum experimental magnetic field strength was set to 0.3 T because of experimental restrictions, although we increased it to 0.5 T for firm conclusions. Apart from terminal rising velocity comparisons, we focused on variations in bubble motion paths and wake structures under magnetic fields, which cannot be observed experimentally because liquid metal is opaque. Magnetic field effects on bubble trajectory are exerted through vortex structure modification, which reinforced the conjecture that path instability is mainly attributed to wake instability. In bubble motion without magnetic fields, vortex threads in the bubble wake wrap around each other while vortex filaments incline parallel to the field with increasing magnetic intensity. Additionally, high magnetic fields will induce secondary bubble path instabilities, which contribute to the high Reynolds number flow that instabilities develop around the bubble, producing an asymmetrical Lorentz force distribution. This instability vanishes under higher magnetic intensities because flow instability is suppressed. Rising bubble aspect ratios decrease considerably under magnetic fields and may also contribute to smaller vorticities at the bubble surface. A close relationship between fluctuations in rising velocity and shape variations is found.

  4. Visualization of bubble detachment and coalescence under the influence of a nonuniform electric field

    SciTech Connect

    Liu, Z.; Herman, C.; Mewes, D.

    2006-11-15

    The effect of a nonuniform electric field on the formation, coalescence and detachment of single bubbles and pairs of air bubbles injected into a stagnant, isothermal liquid through orifices is studied to identify characteristic bubble behavior patterns. The results of the experimental visualization clearly indicate the significant differences in bubble shape, size and trajectory caused by the electric field. The electric field was applied between a flat, circular and horizontal ground electrode and a spherical, off-axis top electrode. In single bubble experiments the bubble was tilted towards or away from the upper electrode under the influence of the electric field. Although the direction of the tilt alternated (even in a single experiment), in the majority of the cases the bubble trajectory tilted towards the top electrode. In bubble pair experiments the bubbles behaved similarly to the single bubble case at larger volume flow rates. In low volume flow rate experiments the bubbles were tilted away from each other. Furthermore, the detachment frequency increased under the influence of the electric field, which indicates decreased bubble volume for lower volume flow rates. The effect of the electric field on vertical and lateral bubble coalescence was analyzed and quantified in terms of the detachment time. (author)

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  6. Gas bubble disease: introduction

    SciTech Connect

    Fickeisen, D.H.; Schneider, M.J.; Wedemeyer, G.A.

    1980-11-01

    In 1970, gas bubble disease was identified as a serious problem affecting salmonids in the Columbia and Snake river systems. The source of supersaturation was entrainment of air into water spilling over hydroelectric dams. Regional research projects focusing on tolerance bioassays were immediately implemented. Since then, the scope of gas bubble disease research has broadened to include problems in other aquatic systems, with other species. Emphasis has shifted from defining tolerance limits in bioassay systems to exploring behavioral and physiological aspects. Various methods of degasifying supersaturated water have been developed.

  7. 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.

  8. Heated Gas Bubbles

    NASA Technical Reports Server (NTRS)

    2004-01-01

    Fluid Physics is study of the motion of fluids and the effects of such motion. When a liquid is heated from the bottom to the boiling point in Earth's microgravity, small bubbles of heated gas form near the bottom of the container and are carried to the top of the liquid by gravity-driven convective flows. In the same setup in microgravity, the lack of convection and buoyancy allows the heated gas bubbles to grow larger and remain attached to the container's bottom for a significantly longer period.

  9. Kinetics of methane bubble growth in a 1020 steel

    SciTech Connect

    Panda, B.; Shewmon, P.

    1984-03-01

    A 1020 carbon steel and a sensitive dilatometer have been used to study the changes in the kinetics, and morphology, of methane bubbles with temperature, methane pressure, and bubble size. The transition from roughly spherical bubbles at low methane pressure to lenticular ones at high pressure, as predicted by theory, has been demonstrated along with the predicted change in pressure exponent and activation energy. That is, at high pressures the rate of bubble growth increases as (P /SUB CH4/ )/sup 3/ and exhibits an activation energy characteristic of surface diffusion, while at quite low pressures th pressure exponent is about 3/2 with an activation energy between that for grain boundary and lattice diffusion. When the lenticular bubbles grow to a diameter roughly equal to that of the grains, their growth kinetics change to be limited by the power law creep of the matrix.

  10. Mechanics of collapsing cavitation bubbles.

    PubMed

    van Wijngaarden, Leen

    2016-03-01

    A brief survey is given of the dynamical phenomena accompanying the collapse of cavitation bubbles. The discussion includes shock waves, microjets and the various ways in which collapsing bubbles produce damage. PMID:25890856

  11. Fluid Dynamics of Bubbly Liquids

    NASA Technical Reports Server (NTRS)

    Tsang, Y. H.; Koch, D. L.; Zenit, R.; Sangani, A.; Kushch, V. I.; Spelt, P. D. M.; Hoffman, M.; Nahra, H.; Fritz, C.; Dolesh, R.

    2002-01-01

    Experiments have been performed to study the average flow properties of inertially dominated bubbly liquids which may be described by a novel analysis. Bubbles with high Reynolds number and low Weber number may produce a fluid velocity disturbance that can be approximated by a potential flow. We studied the behavior of suspensions of bubbles of about 1.5 mm diameter in vertical and inclined channels. The suspension was produced using a bank of 900 glass capillaries with inner diameter of about 100 microns in a quasi-steady fashion. In addition, salt was added to the suspension to prevent bubble-bubble coalescence. As a result, a nearly monodisperse suspension of bubble was produced. By increasing the inclination angle, we were able to explore an increasing amount of shear to buoyancy motion. A pipe flow experiment with the liquid being recirculated is under construction. This will provide an even larger range of shear to buoyancy motion. We are planning a microgravity experiment in which a bubble suspension is subjected to shearing in a couette cell in the absence of a buoyancy-driven relative motion of the two phases. By employing a single-wire, hot film anemometer, we were able to obtain the liquid velocity fluctuations. The shear stress at the wall was measured using a hot film probe flush mounted on the wall. The gas volume fraction, bubble velocity, and bubble velocity fluctuations were measured using a homemade, dual impedance probe. In addition, we also employed a high-speed camera to obtain the bubble size distribution and bubble shape in a dilute suspension. A rapid decrease in bubble velocity for a dilute bubble suspension is attributed to the effects of bubble-wall collisions. The more gradual decrease of bubble velocity as gas volume fraction increases, due to subsequent hindering of bubble motion, is in qualitative agreement with the predictions of Spelt and Sangani for the effects of potential-flow bubble-bubble interactions on the mean velocity. The ratio of the bubble velocity variance to the square of the mean is 0(0.1). For these conditions Spelt and Sangani predicted that the homogeneous suspension would be unstable and clustering into horizontal rafts will take place. Evidence for bubble clustering is obtained by analysis of video images. The liquid velocity variance is larger than would be expected for a homogeneous suspension and the liquid velocity frequency spectrum indicates the presence of velocity fluctuations that are slow compared with the time for the passage of an individual bubble. These observations provide further evidence for bubble clustering.

  12. 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 μg m-3 in HR, and 415 ± 428 and 761 ± 661 μg 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.

  13. Plasma bubble registration at altitudes of the topside ionosphere: Numerical evaluations

    NASA Astrophysics Data System (ADS)

    Sidorova, L. N.; Filippov, S. V.

    2014-05-01

    The possibility of registering a plasma bubble at altitudes of the topside ionosphere based on its minor species He+ were studied. The characteristic times of the main aeronomic and electrodynamic processes, in which a bubble and its ion component He+ are involved, were calculated and compared. The recombination processes of helium ions in a bubble, the vertical transfer of a plasma bubble as a whole, and the diffusion transfer of the plasma bubble minor constituent (He+) were considered. The characteristic times of ambipolar and transverse (Bohm) diffusion were calculated when the diffusion transfer was estimated. The effect of the photoionization processes on plasma bubble dissipation were estimated based on the He+ bubble ion component. It was shown that the bubble filling characteristic time with an average He+ depletion to the He+ ambient density is 24 h. It was concluded that such a prolonged bubble lifetime makes it possible to register a plasma bubble reliably over approximately two days. However, it has been noted that only a residual plasma bubble structure, i.e., its trace visible in He+ ions, will apparently be registered during most prolonged observations.

  14. Temperature rise in superfluid helium pumps

    NASA Technical Reports Server (NTRS)

    Kittel, Peter

    1988-01-01

    The temperature rise of a fountain effect pump (FEP) and of a centrifugal pump (CP) are compared. Calculations and estimates presented here show that under the operating conditions expected during the resupply of superfluid helium in space, a centrifugal pump will produce a smaller temperature rise than will a fountain effect pump. The temperature rise for the FEP is calculated assuming an ideal pump, while the temperature rise of the CP is estimated from the measured performance of a prototype pump. As a result of this smaller temperature rise and of the different operating characteristics of the two types of pumps, transfers will be more effective using a centrifugal pump.

  15. Temperature rise in superfluid helium pumps

    SciTech Connect

    Kittel, P.

    1988-07-01

    The temperature rise of a fountain effect pump (FEP) and of a centrifugal pump (CP) are compared. Calculations and estimates presented here show that under the operating conditions expected during the resupply of superfluid helium in space, a centrifugal pump will produce a smaller temperature rise than will a fountain effect pump. The temperature rise for the FEP is calculated assuming an ideal pump, while the temperature rise of the CP is estimated from the measured performance of a prototype pump. As a result of this smaller temperature rise and of the different operating characteristics of the two types of pumps, transfers will be more effective using a centrifugal pump.

  16. Cohesion of Bubbles in Foam

    ERIC Educational Resources Information Center

    Ross, Sydney

    1978-01-01

    The free-energy change, or binding energy, of an idealized bubble cluster is calculated on the basis of one mole of gas, and on the basis of a single bubble going from sphere to polyhedron. Some new relations of bubble geometry are developed in the course of the calculation. (BB)

  17. A multi-functional bubble-based microfluidic system.

    PubMed

    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

  18. 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

  19. Hadron bubble evolution into the quark sea

    SciTech Connect

    Freese, K. ); Adams, F.C. )

    1990-04-15

    A solution is presented for the evolution of hadron bubbles which nucleate in the quark sea if there is a first-order quark-hadron phase transition at a temperature {ital T}{sub {ital c}} on the order of 100 MeV. We make three assumptions: (1) the dominant mechanism for transport of latent heat is radiative, e.g., neutrinos; (2) the distance between nucleation sites is greater than the neutrino mean free path; and (3) the effects of hydrodynamic flow can be neglected. Bubbles nucleate with a characteristic radius 1 fm/{Delta}, where {Delta} is a dimensionless parameter for the undercooling (we take {Delta}{ge}10{sup {minus}4}, so that the expansion of the Universe can be neglected). We argue that bubbles grow stably and remain spherical until the radius becomes as large as the neutrino mean free path, {ital l}{congruent}10 cm. The growth then becomes diffusion limited and the bubbles become unstable to formation of dendrites, or fingerlike structures, because latent heat can diffuse away more easily from long fingers than from spheres. We study the nonlinear evolution of structure with a geometrical model'' and argue that the hadron bubbles ultimately look like stringy seaweed. The percolation of seaweed-shaped bubbles can leave behind regions of quark phase that are quite small. In fact, one might expect the typical scale to be {ital L}{sub {ital Q}}={ital l}{congruent}10 cm. Protons can easily diffuse out of such small regions (and neutrons back in). Thus, these instabilities can lead to important modifications of inhomogeneous nucleosynthesis, which requires {ital L}{sub {ital Q}}{approx gt}1 m.

  20. Bubble fusion: Preliminary estimates

    SciTech Connect

    Krakowski, R.A.

    1995-02-01

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

  1. Double Bubble? No Trouble!

    ERIC Educational Resources Information Center

    Shaw, Mike I.; Smith, Greg F.

    1995-01-01

    Describes a soap-solution activity involving formation of bubbles encasing the students that requires only readily available materials and can be adapted easily for use with various grade levels. Discusses student learning outcomes including qualitative and quantitative observations and the concept of surface tension. (JRH)

  2. Oscillations of soap bubbles

    NASA Astrophysics Data System (ADS)

    Kornek, U.; Mller, 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.

  3. 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

  4. 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…

  5. Bubble Formation at a Submerged Orifice in Reduced Gravity

    NASA Technical Reports Server (NTRS)

    Buyevich, Yu A.; Webbon, Bruce W.

    1994-01-01

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

  6. Experiments on the motion of gas bubbles in turbulence generated by an active grid

    NASA Astrophysics Data System (ADS)

    Poorte, R. E. G.; Biesheuvel, A.

    2002-06-01

    The random motion of nearly spherical bubbles in the turbulent flow behind a grid is studied experimentally. In quiescent water these bubbles rise at high Reynolds number. The turbulence is generated by an active grid of the design of Makita (1991), and can have turbulence Reynolds number R[lambda] of up to 200. Minor changes in the geometry of the grid and in its mode of operation improves the isotropy of the turbulence, compared with that reported by Makita (1991) and Mydlarski & Warhaft (1996). The trajectory of each bubble is measured with high spatial and temporal resolution with a specially developed technique that makes use of a position-sensitive detector. Bubble statistics such as the mean rise velocity and the root-mean-square velocity fluctuations are obtained by ensemble averaging over many identical bubbles. The resulting bubble mean rise velocity is significantly reduced (up to 35%) compared with the quiescent conditions. The vertical bubble velocity fluctuations are found to be non-Gaussian, whereas the horizontal displacements are Gaussian for all times. The diffusivity of bubbles is considerably less than that of fluid particles. These findings are qualitatively consistent with results obtained through theoretical analysis and numerical simulations by Spelt & Biesheuvel (1997).

  7. Transient Dynamics of Laser-Induced Bubbles in an Ultrasonic Field

    NASA Astrophysics Data System (ADS)

    Kurz, Thomas; Wilken, Tobias; Krninger, Dennis; Wimann, Laurens; Lauterborn, Werner

    2008-06-01

    By combining optical bubble generation with acoustic excitation in a standing ultrasonic field the dynamics and light emission of a single bubble are studied at different conditions with high-speed imaging, optical, and acoustical measurements. In particular, the maximum bubble size and luminescence intensity are recorded for as long as the bubble remains stable. At high driving, luminescence intensity at first collapse increases when raising the driving amplitude or decreasing the water temperature. At suitable gas content and driving pressure the bubble remains stable but changes size by diffusion in a characteristic way, until finally switching on sonoluminescence and remaining stably trapped.

  8. A bubbly universe

    NASA Astrophysics Data System (ADS)

    Occhionero, Franco; Baccigalupi, Carlo; Amendola, Luca; Monastra, Stefano

    1997-12-01

    We propose to explain the present large scale structure of the universe in terms of a first order phase transition in a two field inflation: the seeds of structure are assumed to be the ensuing strong, non-Gaussian, bubblelike inhomogeneities generated by the tunneling field. Along with this, of course, the ordinary zero-point fluctuations of the slow rolling inflaton are also present: they are seen as Gaussian and small perturbations of the microwave background on the large angular scales. We describe a biparametric model of bubbles in the matter dominated era (MDE) in which caustics form at a redshift z* in the surrounding shells and we assume that the caustics themselves are the loci of galaxy formation, i.e., the places where light is turned on. (Most likely z* will then define also the epoch of reionization.) The two parameters are then determined by the bubble's two main features, present depth and z*. The caustics will evolve into the shells of galaxies observed today around the nearly empty and spherical voids. Among the possible scenarios we focus on two that yield late or early caustic formation. In the MDE the shells born with the caustics experience a strong overcomoving growth (the larger the deeper is the central cavity): this phenomenon may turn bubbles substantially subdominant at decoupling (i.e., filling then only a small fraction of the available space) into the dominant features by the present time, as the observations require. For compensated voids, from the Sachs-Wolfe, adiabatic, and Doppler effects, we find that the largest present radii compatible with COBE amount to ~100h-1 Mpc in either scenario. Thus, if the large scale structure were generated by bubbles, the present luminous universe could look bubbly up to scales of the order of one hundred Mpc mimicking a fractal with dimension D~2 without conflicting with the isotropy of the microwave background, because homogeneity is restored thereabove.

  9. 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.

  10. Signature of anisotropic bubble collisions

    SciTech Connect

    Salem, Michael P.

    2010-09-15

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

  11. On dense phase voidage and bubble size in high pressure fluidized beds of fine powders

    SciTech Connect

    Weimer, A.W.; Quarderer, G.J.

    1985-06-01

    Dense phase voidage, epsilon /SUB D/ , dense phase superficial gas velocity, u /SUB Do/ , and absolute bubble rise velocity, u /SUB B/ , were measured at pressures up to 8300 kPa in a pilot-scale, fluidized bed of Group A and boundary Group A/B powders. The mean equivalent bubble diameter, d /SUB b/ , near the top of the bed was inferred from u /SUB B/ and known bed operating conditions. Increased pressure at fixed superficial gas velocity, u /SUB o/ , increased epsilon /SUB D/ and u /SUB Do/ and decreased d /SUB b/ for Group A powders. The marked decrease in inferred maximum bubble size, d /SUB bmax/ , with increased pressure could not be explained by a decrease in gas contributing to bubble flow, u /SUB Bo/ , but rather appeared to be the result of a bubble instability phenomenon limiting bubble growth.

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

    PubMed

    Muleki Seya, Pauline; Desjouy, Cyril; Bra, 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

  13. 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.

  14. 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.

  15. Analysis of the three-dimensional structure of a bubble wake using PIV and Galilean decomposition

    SciTech Connect

    Hassan, Y.A.; Schmidl, W.D.; Ortiz-Villafuerte, J.; Scharf, J.R.

    1999-07-01

    Bubbly flow plays a key role in a variety of natural and industrial processes. An accurate and complete description of the phase interactions in two-phase bubbly flow is not available at this time. These phase interactions are, in general, always three-dimensional and unsteady. Therefore, measurement techniques utilized to obtain qualitative and quantitative data from two-phase flow should be able to acquire transient and three-dimensional data, in order to provide information to test theoretical models and numerical simulations. Even for dilute bubble flows, in which bubble interaction is at a minimum, the turbulent motion of the liquid generated by the bubble is yet to be completely understood. For many years, the design of systems with bubbly flows was based primarily on empiricism. Dilute bubbly flows are an extension of single bubble dynamics, and therefore improvements in the description and modeling of single bubble motion, the flow field around the bubble, and the dynamical interactions between the bubble and the flow will consequently improve bubbly flow modeling. The improved understanding of the physical phenomena will have far-reaching benefits in upgrading the operation and efficiency of current processes and in supporting the development of new and innovative approaches. A stereoscopic particle image velocimetry measurement of the flow generated by the passage of a single air-bubble rising in stagnant water, in a circular pipe is presented. Three-dimensional velocity fields within the measurement zone were obtained. Ensemble-averaged instantaneous velocities for a specific bubble path were calculated and interpolated to obtain mean three-dimensional velocity fields. A Galilean velocity decomposition is used to study the vorticity generated in the flow.

  16. Optical monitoring of bubble size and shape in a pulsating bubble surfactometer.

    PubMed

    Seurynck, Shannon L; Brown, Nathan J; Wu, Cindy W; Germino, Kevin W; Kohlmeir, Ellen K; Ingenito, Edward P; Glucksberg, Matthew R; Barron, Annelise E; Johnson, Mark

    2005-08-01

    The pulsating bubble surfactometer (PBS) is often used for in vitro characterization of exogenous lung surfactant replacements and lung surfactant components. However, the commercially available PBS is not able to dynamically track bubble size and shape. The PBS therefore does not account for bubble growth or elliptical bubble shape that frequently occur during device use. More importantly, the oscillatory volume changes of the pulsating bubble are different than those assumed by the software of the commercial unit. This leads to errors in both surface area and surface tension measurements. We have modified a commercial PBS through the addition of an image-acquisition system, allowing real-time determination of bubble size and shape and hence the accurate tracking of surface area and surface tension. Compression-expansion loops obtained with the commercially available PBS software were compared with those provided by the image-analysis system for dipalmitoylphosphatidylcholine, Infasurf, and Tanaka lipids (dipalmitoylphosphatidylcholine-palmitoyloleoylphosphatidyl-glycerol-palmitic acid, 68:22:9) at concentrations of 0.1 and 1.0 mg/ml and at frequencies of 1 and 20 cycles/min. Whereas minimum surface tension as determined by the image-analysis system is similar to that measured by the commercially available software, the maximum surface tension and the shapes of the interfacial area-surface tension loops are quite different. Differences are attributable to bubble drift, nonsinusoidal volume changes, and variable volume excursions seen with the modified system but neglected by the original system. Image analysis reveals that the extent of loop hysteresis is greatly overestimated by the commercial device and that an apparent, rapid increase in surface tension upon film expansion seen in PBS loops is not observed with the image-analysis system. The modified PBS system reveals new dynamic characteristics of lung surfactant preparations that have not previously been reported. PMID:15790687

  17. Remobilizing the Interfaces of Thermocapillary Driven Bubbles Retarded by the Adsorption of a Surfactant Impurity on the Bubble Surface

    NASA Technical Reports Server (NTRS)

    Palaparthi, Ravi; Maldarelli, Charles; Papageorgiou, Dimitri; Singh, Bhim S. (Technical Monitor)

    2000-01-01

    Thermocapillary migration is a method for moving bubbles in space in the absence of buoyancy. A temperature gradient is applied to the continuous phase in which a bubble is situated, and the applied gradient impressed on the bubble surface causes one pole of the drop to be cooler than the opposite pole. As the surface tension is a decreasing function of temperature, the cooler pole pulls at the warmer pole, creating a flow which propels the bubble in the direction of the warmer fluid. A major impediment to the practical use of thermocapillarity to direct the movement of bubbles in space is the fact that surfactant impurities which are unavoidably present in the continuous phase can significantly reduce the migration velocity. A surfactant impurity adsorbed onto the bubble interface is swept to the trailing end of the bubble. When bulk concentrations are low (which is the case with an impurity), diffusion of surfactant to the front end is slow relative to convection, and surfactant collects at the back end of the bubble. Collection at the back lowers the surface tension relative to the front end setting up a reverse tension gradient. For buoyancy driven bubble motions in the absence of a thermocapillarity, the tension gradient opposes the surface flow, and reduces the surface and terminal velocities (the interface becomes more solid-like). When thermocapillary forces are present, the reverse tension gradient set up by the surfactant accumulation reduces the temperature tension gradient, and decreases to near zero the thermocapillary velocity. The objective of our research is to develop a method for enhancing the thermocapillary migration of bubbles which have been retarded by the adsorption onto the bubble surface of a surfactant impurity, Our remobilization theory proposes to use surfactant molecules which kinetically rapidly exchange between the bulk and the surface and are at high bulk concentrations. Because the remobilizing surfactant is present at much higher concentrations than the impurity, it adsorbs to the bubble much faster than the impurity when the bubble is formed, and thereby prevents the impurity from adsorbing onto the surface. In addition the rapid kinetic exchange and high bulk concentration maintain a saturated surface with a uniform surface concentrations. This prevents retarding surface tension gradients and keeps the velocity high. In our first report last year, we detailed experimental results which verified the theory of remobilization in ground based experiments in which the steady velocity of rising bubbles was measured in a continuous phase consisting of a glycerol/water mixture containing a polyethylene glycol surfactant C12E6 (CH3(CH2)11(OCH2CH2)6OH). In our report this year, we detail our efforts to describe theoretically the remobilization observed. We construct a model in which a bubble rises steadily by buoyancy in a continuous (Newtonian) viscous fluid containing surfactant with a uniform far field bulk concentration. We account for the effects of inertia as well as viscosity in the flow in the continuous phase caused by the bubble motion (order one Reynolds number), and we assume that the bubble shape remains spherical (viscous and inertial forces are smaller than capillary forces, i e. small Weber and capillary numbers). The surfactant distribution is calculated by solving the mass transfer equations including convection and diffusion in the bulk, and finite kinetic exchange the bulk and the surface. Convective effects dominate diffusive mass transfer in the bulk of the liquid (high Peclet numbers) except in a thin boundary layer near the surface. A finite volume method is used to numerically solve the hydrodynamic and mass transfer equations on a staggered grid which accounts specifically for the thin boundary layer. We present the results of the nondimensional drag as a function of the bulk concentration of surfactant for different rates of kinetic exchange, from which we develop criteria for the concentration necessary to develop a prescribed degree of remobilization. The criteria c

  18. 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. DOE-SBIR, ONR (monitored by Dr. Ki-Han Kim)

  19. Characterization of an acoustic cavitation bubble structure at 230 kHz.

    PubMed

    Thiemann, Andrea; Nowak, Till; Mettin, Robert; Holsteyns, Frank; Lippert, Alexander

    2011-03-01

    A generic bubble structure in a 230 kHz ultrasonic field is observed in a partly developed standing wave field in water. It is characterized by high-speed imaging, sonoluminescence recordings, and surface cleaning tests. The structure has two distinct bubble populations. Bigger bubbles (much larger than linear resonance size) group on rings in planes parallel to the transducer surface, apparently in locations of driving pressure minima. They slowly rise in a jittering, but synchronous way, and they can have smaller satellite bubbles, thus resembling the arrays of bubbles observed by Miller [D. Miller, Stable arrays of resonant bubbles in a 1-MHz standing-wave acoustic field, J. Acoust. Soc. Am. 62 (1977) 12]. Smaller bubbles (below and near linear resonance size) show a fast "streamer" motion perpendicular to and away from the transducer surface. While the bigger bubbles do not emit light, the smaller bubbles in the streamers show sonoluminescence when they pass the planes of high driving pressure. Both bubble populations exhibit cleaning potential with respect to micro-particles attached to a glass substrate. The respective mechanisms of particle removal, though, might be different. PMID:21041109

  20. The Compressibility Bubble

    NASA Technical Reports Server (NTRS)

    Stack, John

    1935-01-01

    Simultaneous air-flow photographs and pressure-distribution measurements have been made of the NACA 4412 airfoil at high speeds in order to determine the physical nature of the compressibility bubble. The flow photographs were obtained by the Schlieren method and the pressures were simultaneously measured for 54 stations on the 5-inch-chord wing by means of a multiple-tube photographic manometer. Pressure-measurement results and typical Schlieren photographs are presented. The general nature of the phenomenon called the "compressibility bubble" is shown by these experiments. The source of the increased drag is the compression shock that occurs, the excess drag being due to the conversion of a considerable amount of the air-stream kinetic energy into heat at the compression shock.

  1. Bubble dynamics in drinks

    NASA Astrophysics Data System (ADS)

    Broučková, Zuzana; Trávníček, Zdeněk; Šafařík, Pavel

    2014-03-01

    This study introduces two physical effects known from beverages: the effect of sinking bubbles and the hot chocolate sound effect. The paper presents two simple "kitchen" experiments. The first and second effects are indicated by means of a flow visualization and microphone measurement, respectively. To quantify the second (acoustic) effect, sound records are analyzed using time-frequency signal processing, and the obtained power spectra and spectrograms are discussed.

  2. Sonoluminescence, sonochemistry and bubble dynamics of single bubble cavitation

    NASA Astrophysics Data System (ADS)

    Hatanaka, Shin-ichi

    2012-09-01

    The amount of hydroxyl radicals produced from a single cavitation bubble was quantified by terephthalate dosimetry at various frequencies and pressure amplitudes, while the dynamics of the single bubble was observed by stroboscopic and light-scattering methods. Also, sonoluminescence (SL), sonochemiluminescence (SCL) of luminol, and sodium atom emission (Na*) in the cavitation field were observed. The amount of hydroxyl radicals per cycle as well as the intensity of SL was proportional to pressure amplitude at every frequency performed, and it decreased with increasing frequency. When the single bubble was dancing with a decrease in pressure amplitude, however, the amount of hydroxyl radicals was greater than that for the stable bubble at the higher pressure amplitude and did not significantly decrease with frequency. Furthermore, SCL and Na* were detected only under unstable bubble conditions. These results imply that the instability of bubbles significantly enhances sonochemical efficiency for non-volatile substances in liquid phase.

  3. Mechanisms of gas bubble retention

    SciTech Connect

    Gauglitz, P.A.; Mahoney, L.A.; Mendoza, D.P.; Miller, M.C.

    1994-09-01

    Retention and episodic release of flammable gases are critical safety concerns regarding double-shell tanks (DSTs) containing waste slurries. Previous investigations have concluded that gas bubbles are retained by the slurry that has settled at the bottom of the DST. However, the mechanisms responsible for the retention of these bubbles are not well understood. In addition, the presence of retained gas bubbles is expected to affect the physical properties of the sludge, but essentially no literature data are available to assess the effect of these bubbles. The rheological behavior of the waste, particularly of the settled sludge, is critical to characterizing the tendency of the waste to retain gas bubbles. The objectives of this study are to elucidate the mechanisms contributing to gas bubble retention and release from sludge such as is in Tank 241-SY-101, understand how the bubbles affect the physical properties of the sludge, develop correlations of these physical properties to include in computer models, and collect experimental data on the physical properties of simulated sludges with bubbles. This report presents a theory and experimental observations of bubble retention in simulated sludge and gives correlations and new data on the effect of gas bubbles on sludge yield strength.

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

    PubMed

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

    2012-10-01

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

  5. 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.

  6. Experimental study of nonstationary regimes of ascent of a single bubble

    NASA Astrophysics Data System (ADS)

    Arkhipov, V. A.; Vasenin, I. M.; Usanina, A. S.

    2013-09-01

    Results of experimental study of the dynamics of ascent of a single spherical bubble in a viscous fluid at small Reynolds numbers (Re < 1) have been presented. A refined empirical dependence has been obtained for the resistance coefficient in a stationary regime of motion of the bubble. The influence of nonstationary and "hereditary" effects on the dynamics of ascent of the bubble has been evaluated. A substantial influence of the Basset force on the characteristic of a nonstationary regime of motion of the bubble, in particular, on the characteristic time of dynamic relaxation, in the region of small Reynolds numbers has been shown.

  7. Effect of surfactants on single-bubble sonoluminescence

    NASA Astrophysics Data System (ADS)

    Yasui, Kyuichi

    1998-10-01

    The effect of surfactants on single-bubble sonoluminescence (SBSL) is studied theoretically based on the hot-spot model that a SBSL bubble collapses quasiadiabatically and that the quasi-thermal radiation is the origin of the light emission. Stottlemyer and Apfel [J. Acoust. Soc. Am. 102, 1418 (1997)] reported that the surfactant called Triton X-100, which provides free interfacial motion, reduced the magnitude of the light pulse from the bubble. It is clarified by the present study that the effect of the surfactant is caused by the inhibition of condensation of water vapor at the bubble wall at the collapse, which results in lowering the achieved temperature inside a bubble due to the enhancement of the amount of vapor that undergoes endothermal chemical reactions. It is predicted, based on the hot-spot model, that the radiation is not thermalized inside a bubble in the case of SBSL in a solution of the surfactant in water and that the spectrum of SBSL may deviate from the blackbody spectrum and may have some characteristic lines such as the OH line (310 nm). It is suggested that surfactants can be used to enhance the chemical reactions of vapor in sonochemistry. It is also suggested that some of the surfactants are dissociated by the extremely high temperature at the bubble wall at the collapse.

  8. 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.

  9. Stable Multibubble Sonoluminescence Bubble Patterns

    SciTech Connect

    Posakony, Gerald J.; Greenwood, Lawrence R.; Ahmed, Salahuddin

    2006-06-30

    Multibubble standing wave patterns can be generated from a flat piezoceramic transducer element propagating into water. By adding a second transducer positioned at 90 degrees from the transducer generating the standing wave, a 3-dimensional volume of stable single bubbles can be established. Further, the addition of the second transducer stabilizes the bubble pattern so that individual bubbles may be studied. The size of the bubbles and the separation of the standing waves depend on the frequency of operation. Two transducers, operating at frequencies above 500 kHz, provided the most graphic results for the configuration used in this study. At these frequencies stable bubbles exhibit a bright sonoluminescence pattern. Whereas stable SBSL is well-known, stable MBSL has not been previously reported. This paper includes discussions of the acoustic responses, standing wave patterns, and pictorial results of the separation of individual bubble of sonoluminescence in a multibubble sonoluminescence environment.

  10. Simulation of Bubble Dynamics in Sub-Cooled Boiling on Fuel Clad in PWRs

    SciTech Connect

    Wu, Wen; Jones, Barclay G.

    2002-07-01

    The crud deposition on nuclear fuel assembly cladding generally increases the resistance to heat transfer, which may result in deterioration of thermal performance, degradation of the fuel cladding, and an axial power shift, i.e. Axial Offset Anomaly (AOA). Crud formation continues to elude prediction. An operational difficulty, of not being able to accurately determine power safety margin, then arises. In some cases, this condition has required decreasing the core power by as much as thirty percent, hence, resulting in considerable loss of revenue for the utility. The specific purpose of this study is to examine bubble dynamics, flow characteristics of the surrounding fluid, and its impact on the formation of the curd. The presence of a bubble on the clad surface affects the flow field around it, particularly in forming a stagnant flow region behind the bubble. The temperature difference between the bubble and the bulk coolant surrounding it causes vaporization at the bubble-clad interface and condensation at its apex. Pure water is thereby moved into the bubble through vaporization resulting in the concentration of solutes in the water at the bubble/wall surface region, which may cause their precipitation on and/or attachment to the clad surface, thereby initiating crud deposition. We investigate analytically and numerically, the growth of a bubble in the boundary layer and the influence of the bubble on the flow. Because of the small bubble size, a spherical model of the bubble is selected for our research. A two-step calculation is applied to this model. In the first step, bubble growth is estimated analytically with omission of the effect of the bulk fluid velocity, a reasonable approximation. In the second step, the flow field around the stationary bubble is obtained through numerical methods. Some parameters in PWR operating condition have been determined approximately e.g. size of the bubble, boundary layer thickness, flow velocity and drag forces on the bubble. (authors)

  11. How Bubbly Mixtures Foam and Foam Control Using a Fluidized Bed

    NASA Astrophysics Data System (ADS)

    Guitian, Jose; Joseph, D. D.; Mata, Clara

    1997-11-01

    In hydrocracking and other foaming reactors, the foam rises to the top because it has a higher gas fraction than the bubbly mixture from which it comes. The high gas hold-up in foams is undesirable in chemical reactors. To study foams we built a cold slit bubble reactor which when used with aqueous anionic surfactants gives rise to foam. We discovered a critical condition for foaming; when the gas velocity exceeds a critical value which depends on the liquid velocity, a foam interface appears at the top of the reactor, with foam above and bubbly mixture below. The interface is very sharp and it moves down the reactor as the gas velocity is increased at a constant liquid velocity. The foam may be destroyed by increasing the liquid velocity. The reactor partitions into two phase, two phase flow with bubbly mixture below and foam above. The bubbly mixture is dispersed gas in water plus surfactant; the phase above is a foam through which large gas bubbles rise. Constant state theories and semiempirical correlations are presented. Foaming may be strongly suppressed by fluidizing hydrophilic particles in the bubbly mixture below the foam. The suppression is achieved by increasing the liquid hold-up by bed expansion; by increasing the wetted area of solid surface (walls and particles) and by decreasing the gas hold-up by increasing the effective density of the liquid-solid mixture. Even greater suppression of foaming can be achieved by fluidizing hydrophobic particles.

  12. Thin bubbles at low pressures

    NASA Astrophysics Data System (ADS)

    Kravarik, J.; Kubes, P.; Linhart, J. G.

    1994-03-01

    An interferometric study of very thin soap bubbles at low pressures has been carried out. The bubbles have been drawn, using special techniques, at pressures <25 Torr. The results of evaluation of the bubble film thickness as a function of time are reported. When suitable liquids are used the thickness of the film converges to a limiting value typically around 2000 . The liquid nature of the film changes into that of an elastic membrane.

  13. Plasma bubbles in the topside ionosphere: solar activity dependence

    NASA Astrophysics Data System (ADS)

    Sidorova, L.

    2009-04-01

    The present study deals with the He+ density depletions, observed during a high solar activity at the topside ionosphere heights. 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 spacecraft data (high solar activity - F10.7=200, 1978-80), have seen the plasma bubbles in Ne density over equator at 1100 km heights in 46 cases in 1700 passes (3%). However, there is distinctly another picture in He+ density depletions according to ISS-b spacecraft data for the same period. They occur in the topside ionosphere over low- and middle- latitudinal regions (L=1.3-3) in 11% of the cases (Karpachev, Sidorova, 2002; Sidorova, 2004, 2007). The detailed study of the He+ density depletion characteristics was done. It was noted that the He+ density depletions are mostly seen 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 depletion statistics, plotted in LT versus month, was compared with the similar plots for ESF statistics, obtained by Abdu and colleagues (2000) from ground-based ionograms over Brazilian regions for the period of the same solar activity. It was revealed good enough correlation (R=0.67). Also depletion values as function of LT were compared with the vertical plasma drift velocity variations, obtained for the same period from AE-E spacecraft and IS radar (Jicamarca) data. Striking similarity in development dynamics was revealed for the different seasons. It was concluded, that the He+ density depletions should be considered as originating from equatorial plasma bubbles. It seems the plasma bubbles, reaching the topside ionosphere altitudes, are mostly seen not in electron density but in He+ density as depletions. According to publications, many cases of the He+ density depletions were revealed on OGO-4, OGO-6, Oreol-1 and DE-2 spacecraft data. The most of these cases occur during high and maximal solar activity periods, when the He+ density layer is very well developed at the topside ionosphere heights (Wilford et al., 2003). Using the model of the plasma bubble formation as suggested by Woodman and La Hoz (1976), it was shown that the topside plasma bubbles, seen in He+ density, are rather typical phenomena for the topside ionosphere for high solar activity epoch. REFERENCE Abdu, M.A., J.H.A. Sobral, I.S. Batista, Equatorial spread F statistics in the american longitudes: some problems relevant to ESF description in the IRI scheme, Adv. Space Res., vol. 25, pp. 113-124, 2000. Karpachev, A.T. and L.N. Sidorova, Occurrence probability of the light ion trough and subtrough in ??+ density on season and local time, Adv. Space Res., vol. 29, pp. 999-1008, 2002. Maryama, T. and N. Matuura, Longitudinal variability of annual changes in activity of equatorial spread F and plasma bubbles, J. Geophys. Res., 89(A12), 10,903-10,912, 1984. Sidorova, L.N., He+ density topside modeling based on ISS-b satellite data, Adv. Space Res., vol. 33, pp. 850-854, 2004. Sidorova, L.N., Plasma bubble phenomenon in the topside ionosphere, Adv. Space Res., Special issue (COSPAR), doi: 10.1016/j.asr.2007.03.067, 2007. Wilford, C.R., R.J. Moffett, J.M. Rees, G.J. Bailey, Comparison of the He+ layer observed over Arecibo during solar maximum and solar minimum with CTIP model results, J. Geophys. Res., vol. 108, A12, pp. 1452, doi:10.1029/2003JA009940, 2003. Woodman, R.F. and C. La Hoz, Radar observations of F-region equatorial irregularities, J. Geophys. Res., vol. 81, pp. 5447-5466, 1976.

  14. Gas-rise velocities during kicks

    SciTech Connect

    White, D.B. )

    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.

  15. Flight Investigation of the Stability and Control Characteristics of a 0.13-Scale Model of the Convair XFY-1 Vertically Rising Airplane During Constant-Altitude Transitions, TED No. NACA DE 368

    NASA Technical Reports Server (NTRS)

    Lovell, Powell M., Jr.; Kibry, Robert H.; Smith, Charles C., Jr.

    1953-01-01

    An investigation is being conducted to determine the dynamic stability and control characteristics of a 0.13-scale flying model of the Convair XFY-1 vertically rising airplane. This paper presents the results of flight tests to determine the stability and control characteristics of the model during constant-altitude slow transitions from hovering to normal unstalled forward flight. The tests indicated that the airplane can be flown through the transition range fairly easily although some difficulty will probably encountered in controlling the yawing motions at angles of attack between about 60 and 40. An increase in the size of the vertical tail will not materially improve the controllability of the yawing motions in this range of angle of attack but the use of a yaw damper will make the yawing motions easy to control throughout the entire transitional flight range. The tests also indicated that the airplane can probably be flown sideways satisfactorily at speeds up to approximately 33 knots (full scale) with the normal control system and up to approximately 37 knots (full scale) with both elevons and rudders rigged to move differentially for roll control. At sideways speeds above these values, the airplane will have a strong tendency to diverge uncontrollably in roll.

  16. Mid-Infrared Galactic Bubbles

    NASA Astrophysics Data System (ADS)

    Corn, Tyler; Watson, C.

    2008-03-01

    Using 2MASS, GLIMPSE, MIPSGAL, and MAGPIES surveys, we analyzed three bubbles centered at G8.1238-0.47712, G9.83464-0.71713, and G353.35010-0.14083. Each bubble has a circular PAH emission surrounding hot dust. Two bubbles observed also have PAH emission surrounding ionized gas. Physical properties (stellar mass, accretion rate, disk mass, inclination, etc.) are given for each YSO using a model fitter based on radiative transfer numerical simulations and a chi-squared minimization technique. YSOs are suggestive of triggered star formation in two bubbles. Ionizing stars can also be determined.

  17. Bubbly wake of surface vessels

    NASA Astrophysics Data System (ADS)

    Caillé, François; Magnaudet, Jacques; Clanet, Christophe

    2006-11-01

    We study the length of the bubbly wake of surface vessels. This wake is important for the boat security since it can extend to several ship length and thus increases the detectability of the ship by torpedoes. The image analysis of the wake of real scale ships reveals the sensitivity of the length to propellers. We have thus conducted a systematic study in the laboratory of the interaction bubble/propeller, trying to address several questions:- what is the role of cavitation?- is the propeller able to attract the bubbles present along the ship at the sea surface?- if attracted, can these bubble be broken by the propeller?

  18. Bubble measuring instrument and method

    NASA Technical Reports Server (NTRS)

    Kline-Schoder, Robert (Inventor); Magari, Patrick J. (Inventor)

    2003-01-01

    Method and apparatus are provided for a non-invasive bubble measuring instrument operable for detecting, distinguishing, and counting gaseous embolisms such as bubbles over a selectable range of bubble sizes of interest. A selected measurement volume in which bubbles may be detected is insonified by two distinct frequencies from a pump transducer and an image transducer, respectively. The image transducer frequency is much higher than the pump transducer frequency. The relatively low-frequency pump signal is used to excite bubbles to resonate at a frequency related to their diameter. The image transducer is operated in a pulse-echo mode at a controllable repetition rate that transmits bursts of high-frequency ultrasonic signal to the measurement volume in which bubbles may be detected and then receives the echo. From the echo or received signal, a beat signal related to the repetition rate may be extracted and used to indicate the presence or absence of a resonant bubble. In a preferred embodiment, software control maintains the beat signal at a preselected frequency while varying the pump transducer frequency to excite bubbles of different diameters to resonate depending on the range of bubble diameters selected for investigation.

  19. Bubble Measuring Instrument and Method

    NASA Technical Reports Server (NTRS)

    Kline-Schoder, Robert (Inventor); Magari, Patrick J. (Inventor)

    2002-01-01

    Method and apparatus are provided for a non-invasive bubble measuring instrument operable for detecting, distinguishing, and counting gaseous embolisms such as bubbles over a selectable range of bubble sizes of interest. A selected measurement volume in which bubbles may be detected is insonified by two distinct frequencies from a pump transducer and an image transducer. respectively. The image transducer frequency is much higher than the pump transducer frequency. The relatively low-frequency pump signal is used to excite bubbles to resonate at a frequency related to their diameter. The image transducer is operated in a pulse-echo mode at a controllable repetition rate that transmits bursts of high-frequency ultrasonic signal to the measurement volume in which bubbles may be detected and then receives the echo. From the echo or received signal, a beat signal related to the repetition rate may be extracted and used to indicate the presence or absence of a resonant bubble. In a preferred embodiment, software control maintains the beat signal at a preselected frequency while varying the pump transducer frequency to excite bubbles of different diameters to resonate depending on the range of bubble diameters selected for investigation.

  20. Helium bubble bursting in tungsten

    SciTech Connect

    Sefta, Faiza; Juslin, Niklas; Wirth, Brian D.

    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.

  1. Neutron detection via bubble chambers.

    PubMed

    Jordan, D V; Ely, J H; Peurrung, A J; Bond, L J; Collar, J I; Flake, M; Knopf, M A; Pitts, W K; Shaver, M; Sonnenschein, A; Smart, J E; Todd, L C

    2005-01-01

    Research investigating the application of pressure-cycled bubble chambers to fast neutron detection is described. Experiments with a Halon-filled chamber showed clear sensitivity to an AmBe neutron source and insensitivity to a (137)Cs gamma source. Bubble formation was documented using high-speed photography, and a ceramic piezo-electric transducer element registered the acoustic signature of bubble formation. In a second set of experiments, the bubble nucleation response of a Freon-134a chamber to an AmBe neutron source was documented with high-speed photography. PMID:16005238

  2. Bubble Measuring Instrument and Method

    NASA Technical Reports Server (NTRS)

    Kline-Schoder, Robert (Inventor); Magari, Patrick J. (Inventor)

    2002-01-01

    Method and apparatus are provided for a non-invasive bubble measuring instrument operable for detecting, distinguishing, and counting gaseous embolisms such as bubbles over a selectable range of bubble sizes of interest. A selected measurement volume in which bubbles may be detected is insonified by two distinct frequencies from a pump transducer and an image transducer, respectively. The image transducer frequency is much higher than the pump transducer frequency. The relatively low-frequency pump signal is used to excite bubbles to resonate at a frequency related to their diameter. The image transducer is operated in a pulse-echo mode at a controllable repetition rate that transmits bursts of high-frequency ultrasonic signal to the measurement volume in which bubbles may be detected and then receives the echo. From the echo or received signal, a beat signal related to the repetition rate may be extracted and used to indicate the presence or absence of a resonant bubble. In a preferred embodiment, software control maintains the beat signal at a preselected frequency while varying the pump transducer frequency to excite bubbles of different diameters to resonate depending on the range of bubble diameters selected for investigation.

  3. Bubble Measuring Instrument and Method

    NASA Technical Reports Server (NTRS)

    Kline-Schoder, Robert (Inventor); Magari, Patrick J. (Inventor)

    2002-01-01

    Method and apparatus are provided for a non-invasive bubble measuring instrument operable for detecting. distinguishing, and counting gaseous embolisms such as bubbles over a selectable range of bubble sizes of interest. A selected measurement volume in which bubbles may be detected is insonified by two distinct frequencies from a pump transducer and an image transducer, respectively. The image transducer frequency is much higher than the pump transducer frequency. The relatively low-frequency pump signal is used to excite bubbles to resonate at a frequency related to their diameter. The image transducer is operated in a pulse-echo mode at a controllable repetition rate that transmits bursts of high-frequency ultrasonic signal to the measurement volume in which bubbles may be detected and then receive, the echo. From the echo or received signal, a beat signal related to the repetition rate may be extracted and used to indicate the presence or absence of a resonant bubble. In a preferred embodiment, software control maintains the beat signal at a preselected frequency while varying the pump transducer frequency to excite bubbles of different diameters to resonate depending on the range of bubble diameters selected for investigation.

  4. Vortex motion in the near-wake region behind a single gas bubble in a liquid-solid fluidized bed - The pendulum model for wake size prediction

    SciTech Connect

    Tsuchiya, K.; Fan, L.S.

    1987-01-01

    A mechanistic model, denoted as the pendulum model, which interrelates the frequency of vortex shedding and the size of the bubble wake is developed based on secondary motion of a single gas bubble rising in liquids and/or liquid-solid suspensions. In the model, the bubble and its primary wake are regarded as a single semi-rigid body steadily rocking at the vortex shedding frequency. Inherent model parameters, including bubble geometric parameters, the bubble rise velocity and the vortex shedding frequency, are expressed in terms of the bubble size to permit a priori prediction of the wake size. The predicted wake sizes are compared satisfactorily with the experimental data reported in the literature over a wide range of the bubble Reynolds number.

  5. Scaling law for bubbles induced by different external sources: theoretical and experimental study.

    PubMed

    Gong, S W; Ohl, S W; Klaseboer, E; Khoo, B C

    2010-05-01

    The scaling relations for bubbles induced by different external sources are investigated based on a modified Rayleigh model and experimental observations. The equations derived from the modified Rayleigh model are presented to describe the collapse of bubbles induced by the different external sources such as electrical spark, laser, and underwater explosion. A scaling law is then formulated to establish the scaling relations between the different types of bubbles. The scaling law reveals the fact that the characteristic length scale factor differs from the characteristic time scale factor for the different types of bubbles. It is then validated by our experimental observations of the spark- and laser-generated bubbles as well as the bubbles induced by underwater explosions from previous published reports. With the present scaling law, studies on spark- or laser-generated bubbles as well as their applications (for example, in industrial or biomedical related applications) can benefit from the experiences and information built up over the years in underwater explosion bubbles. Conversely, it is possible to substitute a spark- or laser-generated bubble for an underwater explosion bubble in the study of a large-scale and complex physical problem. PMID:20866332

  6. Scaling law for bubbles induced by different external sources: Theoretical and experimental study

    NASA Astrophysics Data System (ADS)

    Gong, S. W.; Ohl, S. W.; Klaseboer, E.; Khoo, B. C.

    2010-05-01

    The scaling relations for bubbles induced by different external sources are investigated based on a modified Rayleigh model and experimental observations. The equations derived from the modified Rayleigh model are presented to describe the collapse of bubbles induced by the different external sources such as electrical spark, laser, and underwater explosion. A scaling law is then formulated to establish the scaling relations between the different types of bubbles. The scaling law reveals the fact that the characteristic length scale factor differs from the characteristic time scale factor for the different types of bubbles. It is then validated by our experimental observations of the spark- and laser-generated bubbles as well as the bubbles induced by underwater explosions from previous published reports. With the present scaling law, studies on spark- or laser-generated bubbles as well as their applications (for example, in industrial or biomedical related applications) can benefit from the experiences and information built up over the years in underwater explosion bubbles. Conversely, it is possible to substitute a spark- or laser-generated bubble for an underwater explosion bubble in the study of a large-scale and complex physical problem.

  7. LETTER TO THE EDITOR: Bubble dynamics in DNA

    NASA Astrophysics Data System (ADS)

    Hanke, Andreas; Metzler, Ralf

    2003-09-01

    The formation of local denaturation zones (bubbles) in double-stranded DNA is an important example of conformational changes of biological macromolecules. We study the dynamics of bubble formation in terms of a Fokker-Planck equation for the probability density to find a bubble of size n base pairs at time t, on the basis of the free energy in the Poland-Scheraga model. Characteristic bubble closing and opening times can be determined from the corresponding first passage time problem, and are sensitive to the specific parameters entering the model. A multistate unzipping model with constant rates recently applied to DNA breathing dynamics (Altan-Bonnet et al 2003 Phys. Rev. Lett. 90 138101) emerges as a limiting case.

  8. Pulsed plasma bubble located in a water capillary

    NASA Astrophysics Data System (ADS)

    Ceccato, P.; Rousseau, A.

    2007-10-01

    Several studies have investigated water discharges for hydroxyl radical generation and organic compound removal for water cleaning [1]. We report preliminary results concerning the generation of plasma in a water capillary and the influence of rise time, water conductivity on the plasma injected power, using electric measurement probes and on the plasma propagation, using CCD camera. The plasma may be generated directly in the water after the formation of a gas bubble due to the ohmic heating or, it can be created in an pre-injected bubble. Bubble expansion and plasma current is monitored. The plasma formation occurs at the water/plasma interface where the electric field is higher. Streamer length and initiation time lag have been measured. [1] A. T. Sugiartoa et al. Journal of Electrostatics 58 (2003) 135--145.

  9. 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.

  10. Bubble, bubble, flow and Hubble: large scale galaxy flow from cosmological bubble collisions

    SciTech Connect

    Larjo, Klaus; Levi, Thomas S. E-mail: tslevi@phas.ubc.ca

    2010-08-01

    We study large scale structure in the cosmology of Coleman-de Luccia bubble collisions. Within a set of controlled approximations we calculate the effects on galaxy motion seen from inside a bubble which has undergone such a collision. We find that generically bubble collisions lead to a coherent bulk flow of galaxies on some part of our sky, the details of which depend on the initial conditions of the collision and redshift to the galaxy in question. With other parameters held fixed the effects weaken as the amount of inflation inside our bubble grows, but can produce measurable flows past the number of efolds required to solve the flatness and horizon problems.

  11. Interface dynamics and coupled growth in directional solidification in presence of bubbles

    NASA Astrophysics Data System (ADS)

    Jamgotchian, H.; Trivedi, R.; Billia, B.

    1993-12-01

    The formation and dynamics of gas bubbles in Bridgman growth of succinonitrile-acetone alloys is examined. The experimental results show for the first time the rich dynamics that are associated with the formation and propagation of bubbles during directional solidification of alloys. The strong coupling of bubbles with the solid-liquid interface is found to result in the growth of elongated bubbles, either attached to a flat solidification front or forming localized cellular as well as dendritic duplexes (bubbles wrapped by a solid envelope). The coupling of the bubble with the solidification front is shown to cause oscillations in the bubble, which are characterized by fast Fourier transforms. When several duplexes are formed, coupled growth and screening may occur. The basic factors that give rise to oscillations, namely competition between source and sink of acetone assisted by capillary convection at the bubble cap, are discussed qualitatively through the development of an internal oscillator model. Coherent sidebranching observed on dendritic duplexes is shown to be due to resonant modes between the bubble cap and the solid envelope.

  12. 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

  13. 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.

  14. Bubble formation in microgravity

    NASA Technical Reports Server (NTRS)

    Antar, Basil N.

    1996-01-01

    An extensive experimental program was initiated for the purpose of understanding the mechanisms leading to bubble generation during fluid handling procedures in a microgravity environment. Several key fluid handling procedures typical for PCG experiments were identified for analysis in that program. Experiments were designed to specifically understand how such procedures can lead to bubble formation. The experiments were then conducted aboard the NASA KC-135 aircraft which is capable of simulating a low gravity environment by executing a parabolic flight attitude. However, such a flight attitude can only provide a low gravity environment of approximately 10-2go for a maximum period of 30 seconds. Thus all of the tests conducted for these experiments were designed to last no longer than 20 seconds. Several experiments were designed to simulate some of the more relevant fluid handling procedures during protein crystal growth experiments. These include submerged liquid jet cavitation, filling of a cubical vessel, submerged surface scratch, attached drop growth, liquid jet impingement, and geysering experiments. To date, four separate KC-135 flight campaigns were undertaken specifically for performing these experiments. However, different experiments were performed on different flights.

  15. Bubbles under stress.

    PubMed

    Bohn, S

    2003-06-01

    We present an experimental and theoretical investigation of a system composed of two soap bubbles strained between two parallel solid surfaces. The two-bubble cluster can be found in several configurations. The existence and stability of each of these states is studied as a function of the distance between the two facing surfaces. The change of this distance can induce a transition from one configuration to another; we observe that most transitions are subcritical, showing that the system is often trapped in states where the minimum of free energy is only local. The hysteretic transitions are responsible for the dissipation of elastic energy. The existence of more than one stable states for given boundaries conditions combined with the absence of thermalization means that the history of the system has to be taken into account and that there is no unique stress-strain relation. In the present system, because of its simplicity, a complete quantitative analysis of these general processes is obtained. The presented results may contribute to a better understanding of the dynamics of more complex systems such as foams or granular materials where similar processes are at work. PMID:15011058

  16. The roles of particles in multiphase processes: Particles on bubble surfaces.

    PubMed

    Bournival, Ghislain; Ata, Seher; Wanless, Erica J

    2015-11-01

    Particle-stabilised foams (or froths) form the fundamental framework of industrial processes like froth flotation. This review provides an overview of the effects of particles on bubble surfaces. The characteristics of the particles have a profound effect on the stability of the bubbles although the stabilisation mechanisms may differ. It is well known that layers of particles may provide a steric barrier between two interfaces, which prevents the coalescence of bubbles. Although perhaps considered of lesser importance, it is interesting to note that particles may affect the bubble surface and momentarily suppress coalescence despite being absent from the film separating two bubbles. Foams are at best metastable and coalescence occurs to achieve a state of minimum energy. Despite this, particles have been reported to stabilise bubbles for significant periods of time. Bubble coalescence is accompanied by a release of energy triggered by the sudden change in surface area. This produces a distinctive oscillation of the bubble surface, which may be influenced by the presence of incompressible particles yielding unique surface properties. A survey of the literature shows that the properties of these composite materials are greatly affected by the physicochemical characteristics of the particles such as hydrophobicity and size. The intense energy released during the coalescence of bubbles may be sufficient to expel particles from the bubble surface. It is noted that the detachment of particles may preferentially occur from specific locations on the bubble surface. Examination of the research accounts again reveals that the properties of the particles may affect their detachment upon the oscillation of the bubble surface. However, it is believed that most parameters affecting the detachment of particles are in fact modifying the dynamics of the three-phase line of contact. Both the oscillation of a coalescing bubble and the resulting detachment of particles are highly dynamic processes. They would greatly benefit from computer simulation studies. PMID:26344866

  17. Optical behavior of surface bubbles

    NASA Astrophysics Data System (ADS)

    Straulino, Samuele; Gambi, Cecilia M. C.; Molesini, Giuseppe

    2015-11-01

    The observation of diamond-like light spots produced by surface bubbles obliquely illuminated is reported. The phenomenon is discussed in terms of geometrical optics, and an explanation is provided attributing the effect to the astigmatism introduced by the deformation of the liquid surface surrounding the bubble. An essential ray tracing program is outlined and used to reconstruct the observed phenomenon numerically.

  18. Bubbling behavior of a fluidized bed of fine particles caused by vibration-induced air inflow.

    PubMed

    Matsusaka, Shuji; Kobayakawa, Murino; Mizutani, Megumi; Imran, Mohd; Yasuda, Masatoshi

    2013-01-01

    We demonstrate that a vibration-induced air inflow can cause vigorous bubbling in a bed of fine particles and report the mechanism by which this phenomenon occurs. When convective flow occurs in a powder bed as a result of vibrations, the upper powder layer with a high void ratio moves downward and is compressed. This process forces the air in the powder layer out, which leads to the formation of bubbles that rise and eventually burst at the top surface of the powder bed. A negative pressure is created below the rising bubbles. A narrow opening at the bottom allows the outside air to flow into the powder bed, which produces a vigorously bubbling fluidized bed that does not require the use of an external air supply system. PMID:23378921

  19. 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.

  20. 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.

  1. Signature of anisotropic bubble collisions

    NASA Astrophysics Data System (ADS)

    Salem, Michael P.

    2010-09-01

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

  2. 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 Vergaas; 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.

  3. Design of experimental setup for investigation of cavitation bubble collapse close to a solid wall

    NASA Astrophysics Data System (ADS)

    Mller, Milo; Zima, Patrik; Unger, Ji?; ivn, Martin

    2012-04-01

    The article describes experimental setup for investigation of the impact load from collapsing cavitation bubble on a solid wall. A vapour bubble is generated inside a cubic chamber by local heating of water inside a thin channel in a button. The bubble collapse is initiated by a piezoelectric actuator attached to the flexible wall of the chamber. A laser diode with a linear CCD sensor are used to detect the bubble position during its buoyancy-driven rise to the upper wall of the chamber. The bubble collapse impact load is measured using a PVDF piezoelectric transducer glued to the upper wall of the chamber and recorded by high-speed CCD camera illuminated by a high-power LED diode. The pressure inside the chamber is measured by the dynamic pressure transducer. All the system components are controlled and synchronized by an oscilloscope and pulse generator using the LabView software.

  4. 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.

  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.

    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. Micro Bubble Trapping By Acoustic Energy

    NASA Astrophysics Data System (ADS)

    Yoshiki, Yamakoshi

    2005-03-01

    Micro bubble trapping by acoustic energy is a promising technology for a future drug or gene delivery system, because the method can control the bubble dynamics using an applied ultrasonic wave. In this paper, acoustic radiation forces which are applied to the micro bubbles are reviewed as well as their applications for micro bubble manipulation. One of the problems in micro bubble trapping by acoustic energy is that the force applied to the micro bubbles is insufficient for some bubbles. This is severe problem when the bubble has a relatively hard shell. In order to increase the trapping force on the micro bubbles, a novel method is proposed. This method uses seed bubbles in order to manipulate target bubbles.

  7. Strongly interacting bubbles under an ultrasonic horn

    NASA Astrophysics Data System (ADS)

    Yasui, Kyuichi; Iida, Yasuo; Tuziuti, Toru; Kozuka, Teruyuki; Towata, Atsuya

    2008-01-01

    Numerical simulations of bubble pulsations have been performed for a system of two bubble clouds in order to study the experimentally observed bubble motion under an ultrasonic horn by high-speed video camera. The comparison between the calculated results and the experimental observation of the bubble pulsation has indicated that the bubble pulsation is strongly influenced by the interaction with surrounding bubbles. The expansion of a bubble during the rarefaction phase of ultrasound is strongly reduced by the bubble-bubble interaction. Some bubbles move toward the horn tip due to the secondary Bjerknes force acting from the bubbles near the horn tip. It has also been shown that the acoustic amplitude in the liquid is strongly reduced by cavitation due to the decrease in acoustic radiation resistance.

  8. Measurements and Analysis of Oxygen Bubble Distributions in LiCl-KCl Molten Salt

    SciTech Connect

    Ryan W. Bezzant; Supathorn Phongikaroon; Michael F. Simpson

    2013-03-01

    Transparent system experimental studies have been performed to provide measurement and analysis of oxygen bubble distributions and mass transfer coefficients at different sparging rates ranging from 0.05 to 0.20 L/min in LiCl-KCl molten salt at 500 degrees C using a high-speed digital camera and an oxygen sensor. The results reveal that bubble sizes and rise velocities increased with an increase in oxygen sparging rate. The bubbles observed were ellipsoidal in shape, and an equivalent diameter based on the ellipsoid volume was calculated. The average equivalent bubble diameters at 500 degrees C and these oxygen sparging rates range from 2.63 to 4.07 mm. Results show that the bubble equivalent diameters at each respective sparging rate are normally distributed. A Fanning friction factor correlation was produced to predict a bubbles rise velocity based on its equivalent diameter. The oxygen mass transfer coefficients for four sparging rates were calculated using the oxygenation model. These calculated values were within the order of magnitude of 10-2 cm/sec and followed a decreasing trend corresponding to an increasing bubble size and sparging rate. The diffusivities were calculated based on two different types of mechanisms, one based on physics of the bubbles and the other on systematic properties. The results reveal that diffusivity values calculated from bubble physics are 1.65 to 8.40 x 10-5 cm2/sec, which are within the range suggested by literature for gases in liquids of a similar viscosity.

  9. 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.

  10. LET dependence of bubbles evaporation pulses in superheated emulsion detectors

    NASA Astrophysics Data System (ADS)

    Di Fulvio, Angela; Huang, Jean; Staib, Lawrence; d'Errico, Francesco

    2015-06-01

    Superheated emulsion detectors are suspensions of metastable liquid droplets in a compliant inert medium. Upon interaction with ionizing radiation, the droplets evaporate, generating visible bubbles. Bubble expansion associated with the boiling of the droplets is accompanied by pressure pulses in both the sonic and ultrasonic frequency range. In this work, we analyzed the signal generated by bubble evaporation in the frequency and time domain. We used octafluoropropane (R-218) based emulsions, sensitive to both photons and neutrons. The frequency content of the detected pulses appears to extend well into the hundreds of kHz, beyond the range used in commercial devices to count bubbles as they are formed (typically 1-10 kHz). Kilohertz components characterize the early part of the waveforms, potentially containing information about the energetics of the explosive bubble initial growth phase. The power spectral density of the acoustic signal produced by neutron-induced evaporation shows a characteristic frequency pattern in the 200-400 kHz range, which is not observed when bubbles evaporate upon gamma ray-induced irradiation. For practical applications, detection of ultrasonic pulses associated with the boiling of the superheated drops can be exploited as a fast readout method, negligibly affected by mechanical ambient noise.

  11. Modeling and experimental analysis of acoustic cavitation bubbles for Burst Wave Lithotripsy

    NASA Astrophysics Data System (ADS)

    Maeda, Kazuki; Kreider, Wayne; Maxwell, Adam; Cunitz, Bryan; Colonius, Tim; Bailey, Michael

    2015-12-01

    Cavitation bubbles initiated by focused ultrasound waves are investigated through experiments and modeling. Pulses of focused ultrasound with a frequency of 335 kHz and a peak negative pressure of 8 MPa is generated in a water tank by a piezoelectric transducer to initiate cavitation. The pressure field is modeled by solving the Euler equations and used to simulate single bubble oscillation. The characteristics of cavitation bubbles observed by highspeed photography qualitatively agree with the simulation results. Finally, bubble clouds are captured using acoustic B-mode imaging that works synchronized with high-speed photography.

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

    NASA Astrophysics Data System (ADS)

    Beaumont, Christopher N.; Goodman, Alyssa A.; Kendrew, Sarah; Williams, Jonathan P.; Simpson, Robert

    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 searchesparticularly 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.

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

    SciTech Connect

    Beaumont, Christopher N.; Williams, Jonathan P.; Goodman, Alyssa A.; Kendrew, Sarah; Simpson, Robert

    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.

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

    NASA Technical Reports Server (NTRS)

    Weinberg, Michael C.

    1986-01-01

    In this work consideration is given to the problem of the extraction of physical data information from gas bubble dissolution and growth measurements. The discussion is limited to the analysis of the simplest experimental systems consisting of a single, one component gas bubble in a glassmelt. It is observed that if the glassmelt is highly under- (super-) saturated, then surface tension effects may be ignored, simplifying the task of extracting gas diffusivity values from the measurements. If, in addition, the bubble rise velocity is very small (or very large) the ease of obtaining physical property data is enhanced. Illustrations are given for typical cases.

  15. An acoustic estimate of methane concentration in a water column in regions of methane bubble release

    NASA Astrophysics Data System (ADS)

    Salomatin, A. S.; Yusupov, V. I.; Vereshchagina, O. F.; Chernykh, D. V.

    2014-11-01

    A remote acoustic method is presented for estimating the methane flux into water from rising bubbles. With the proposed method and data of hydroacoustic measurements in the Sea of Okhotsk, the dissolved methane concentration profile that forms in the water column in regions of methane bubble release is estimated. Comparison of the aforementioned methane concentration profile with results of direct measurements shows good quantitative and qualitative agreement. This testifies to the fair accuracy of the proposed acoustic method and is indicative of the dominant role of bubble transport in the formation of the concentration of dissolved methane in the water column in such regions.

  16. Model and experimental vizualisation of a bubble interacting with an inclined wall

    NASA Astrophysics Data System (ADS)

    Podvin, Berengere; Khoja, Suleman; Attinger, Daniel; Moraga, Francisco

    2006-11-01

    We describe the motion of an air bubble rising through water as it interacts with a wall of variable inclination. The bubble diameter varies about O(1) mm. We use lubrication theory to determine the modification of the bubble interface and compute the hydrodynamic force exerted by the wall. The present work is an extension of Moraga et al's model [Computers and Fluids 2006], which was devised for a horizontal wall. The predictions of the model are checked against experimental visualizations. The influence of the Weber number, Reynolds number and wall inclination is examined

  17. Strings on bubbling geometries

    NASA Astrophysics Data System (ADS)

    Lin, Hai; Morisse, Alexander; Shock, Jonathan P.

    2010-06-01

    We study gauge theory operators which take the form of a product of a trace with a Schur polynomial, and their string theory duals. These states represent strings excited on bubbling AdS geometries which are dual to the Schur polynomials. These geometries generically take the form of multiple annuli in the phase space plane. We study the coherent state wavefunction of the lattice, which labels the trace part of the operator, for a general Young tableau and their dual description on the droplet plane with a general concentric ring pattern. In addition we identify a density matrix over the coherent states on all the geometries within a fixed constraint. This density matrix may be used to calculate the entropy of a given ensemble of operators. We finally recover the BMN string spectrum along the geodesic near any circle from the ansatz of the coherent state wave-function.

  18. Surface Bubble Nucleation Stability

    NASA Astrophysics Data System (ADS)

    Seddon, James R. T.; Kooij, E. Stefan; Poelsema, Bene; Zandvliet, Harold J. W.; Lohse, Detlef

    2011-02-01

    Recent research has revealed several different techniques for nanoscopic gas nucleation on submerged surfaces, with findings seemingly in contradiction with each other. In response to this, we have systematically investigated the occurrence of surface nanobubbles on a hydrophobized silicon substrate for various different liquid temperatures and gas concentrations, which we controlled independently. We found that nanobubbles occupy a distinct region of this parameter space, occurring for gas concentrations of approximately 100%-110%. Below the nanobubble region we did not detect any gaseous formations on the substrate, whereas micropancakes (micron wide, nanometer high gaseous domains) were found at higher temperatures and gas concentrations. We moreover find that supersaturation of dissolved gases is not a requirement for nucleation of bubbles.

  19. 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.

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

    SciTech Connect

    Amendt, P.; London, R.A.; Strauss, M.

    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.

  1. Electrons trajectories around a bubble regime in intense laser plasma interaction

    SciTech Connect

    Lu, Ding; Xie, Bai-Song; Ali Bake, Muhammad; Sang, Hai-Bo; Zhao, Xue-Yan; Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 ; Wu, Hai-Cheng

    2013-06-15

    Some typical electrons trajectories around a bubble regime in intense laser plasma interaction are investigated theoretically. By considering a modification of the fields and ellipsoid bubble shape due to the presence of residual electrons in the bubble regime, we study in detail the electrons nonlinear dynamics with or without laser pulse. To examine the electron dynamical behaviors, a set of typical electrons, which locate initially at the front of the bubble, on the transverse edge and at the bottom of the bubble respectively, are chosen for study. It is found that the range of trapped electrons in the case with laser pulse is a little narrower than that without laser pulse. The partial phase portraits for electrons around the bubble are presented numerically and their characteristic behaviors are discussed theoretically. Implication of our results on the high quality electron beam generation is also discussed briefly.

  2. 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.

  3. Doughnut-shaped soap bubbles.

    PubMed

    Prve, Deison; Saa, Alberto

    2015-10-01

    Soap bubbles are thin liquid films enclosing a fixed volume of air. Since the surface tension is typically assumed to be the only factor responsible for conforming the soap bubble shape, the realized bubble surfaces are always minimal area ones. Here, we consider the problem of finding the axisymmetric minimal area surface enclosing a fixed volume V and with a fixed equatorial perimeter L. It is well known that the sphere is the solution for V=L^{3}/6?^{2}, and this is indeed the case of a free soap bubble, for instance. Surprisingly, we show that for Vbubble is known to be ultimately unstable and, hence, it will eventually lose its axisymmetry by breaking apart in smaller bubbles. Indisputably, however, the topological transition from spherical to toroidal surfaces is mandatory here for obtaining the global solution for this axisymmetric isoperimetric problem. Our result suggests that deformed bubbles with V

  4. Doughnut-shaped soap bubbles

    NASA Astrophysics Data System (ADS)

    Préve, Deison; Saa, Alberto

    2015-10-01

    Soap bubbles are thin liquid films enclosing a fixed volume of air. Since the surface tension is typically assumed to be the only factor responsible for conforming the soap bubble shape, the realized bubble surfaces are always minimal area ones. Here, we consider the problem of finding the axisymmetric minimal area surface enclosing a fixed volume V and with a fixed equatorial perimeter L . It is well known that the sphere is the solution for V =L3/6 π2 , and this is indeed the case of a free soap bubble, for instance. Surprisingly, we show that for V <α L3/6 π2 , with α ≈0.21 , such a surface cannot be the usual lens-shaped surface formed by the juxtaposition of two spherical caps, but is rather a toroidal surface. Practically, a doughnut-shaped bubble is known to be ultimately unstable and, hence, it will eventually lose its axisymmetry by breaking apart in smaller bubbles. Indisputably, however, the topological transition from spherical to toroidal surfaces is mandatory here for obtaining the global solution for this axisymmetric isoperimetric problem. Our result suggests that deformed bubbles with V <α L3/6 π2 cannot be stable and should not exist in foams, for instance.

  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. 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.

  7. Liquid rising near walls

    NASA Astrophysics Data System (ADS)

    Khorrami, Mohammad; Aghamohammadi, Amir

    2016-03-01

    The rise of a liquid in a region confined with walls is studied. This is done for the case of a liquid between two vertical parallel walls, as well as a liquid rising inside or outside a cylinder of circular cross section. Limiting cases of small distances between the walls, or tubes of small cross sections, as well as large distances between the walls, or tubes of large cross sections, are also investigated. For the limiting cases, tubes of arbitrary (but uniform) cross sections are also studied.

  8. Sonoluminescing Air Bubbles Rectify Argon

    SciTech Connect

    Lohse, D.; Hilgenfeldt, S.; Brenner, M.P.; Dupont, T.F.; Johnston, B.

    1997-02-01

    The dynamics of single bubble sonoluminescence (SBSL) strongly depends on the percentage of inert gas within the bubble. We propose a theory for this dependence, based on a combination of principles from sonochemistry and hydrodynamic stability. The nitrogen and oxygen dissociation and subsequent reaction to water soluble gases implies that strongly forced air bubbles eventually consist of pure argon. Thus it is the partial argon (or any other inert gas) pressure which is relevant for stability. The theory provides quantitative explanations for many aspects of SBSL. {copyright} {ital 1997} {ital The American Physical Society}

  9. Bubble size in horizontal pipelines

    SciTech Connect

    Hesketh, R.P.; Russell, T.W.F.; Etchells, A.W.

    1987-04-01

    Bubble sizes for dilute dispersion in horizontal pipelines under turbulent liquid flow conditions are shown to be predicted by a theory. This theory contains the dependence of dispersed-phase density on the bubble size, which is not included in theories presented by others. Theories are compared using experimental data from both gas-liquid and liquid-liquid dispersions to show that only one theory can predict both gas bubble and liquid drop sizes with a single constant. Additionally, a generalized equation is proposed that includes the effect of the dispersed-phase viscosity.

  10. Bubble Growth in Lunar Basalts

    NASA Astrophysics Data System (ADS)

    Zhang, Y.

    2009-05-01

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

  11. The oscillations of vapor bubbles

    NASA Astrophysics Data System (ADS)

    Prosperetti, Andrea; Yin, Z.; Yang, B.

    2003-04-01

    Bob Apfel had so many interests that it is impossible-however fitting and desirable-to pay homage to his work as a whole. Some of his early studies were devoted to bubble nucleation at high superheats. In the first part of this paper a recent application of this phenomenon is described. Once a vapor bubble is generated, its subsequent oscillations (free and forced) present analogies and differences with those of a gas bubble: the second part of the paper focuses on this topic. [Work supported by NSF and NASA.

  12. The oscillation of vapor bubbles

    NASA Astrophysics Data System (ADS)

    Prosperetti, Andrea; Yin, Zhizhong

    2001-05-01

    Bob Apfel had so many interests that it is impossible-however fitting and desirable-to pay homage to his work as a whole. Some of his early studies were devoted to bubble nucleation at high superheats. In the first part of this paper a recent application of this phenomenon is described. Once a vapor bubble is generated, its subsequent oscillations (free and forced) present analogies and differences with those of a gas bubble: the second part of the paper focuses on this topic. [Work supported by NSF and NASA.

  13. 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.

  14. A bubble-based microfluidic gas sensor for gas chromatographs.

    PubMed

    Bulbul, Ashrafuzzaman; Kim, Hanseup

    2015-01-01

    We report a new proof-of-concept bubble-based gas sensor for a gas chromatography system, which utilizes the unique relationship between the diameters of the produced bubbles with the gas types and mixture ratios as a sensing element. The bubble-based gas sensor consists of gas and liquid channels as well as a nozzle to produce gas bubbles through a micro-structure. It utilizes custom-developed software and an optical camera to statistically analyze the diameters of the produced bubbles in flow. The fabricated gas sensor showed that five types of gases (CO2, He, H2, N2, and CH4) produced (1) unique volumes of 0.44, 0.74, 1.03, 1.28, and 1.42 nL (0%, 68%, 134%, 191%, and 223% higher than that of CO2) and (2) characteristic linear expansion coefficients (slope) of 1.38, 2.93, 3.45, 5.06, and 5.44 nL/(kPa (?L s(-1))(-1)). The gas sensor also demonstrated that (3) different gas mixture ratios of CO2?:?N2 (100?:?0, 80?:?20, 50?:?50, 20?:?80 and 0?:?100) generated characteristic bubble diameters of 48.95, 77.99, 71.00, 78.53 and 99.50 ?m, resulting in a linear coefficient of 10.26 ?m (?L s(-1))(-1). It (4) successfully identified an injection (0.01 ?L) of pentane (C5) into a continuous carrier gas stream of helium (He) by monitoring bubble diameters and creating a chromatogram and demonstrated (5) the output stability within only 5.60% variation in 67 tests over a month. PMID:25350655

  15. Amplitude- and rise-time-compensated filters

    DOEpatents

    Nowlin, Charles H. (Oak Ridge, TN)

    1984-01-01

    An amplitude-compensated rise-time-compensated filter for a pulse time-of-occurrence (TOOC) measurement system is disclosed. The filter converts an input pulse, having the characteristics of random amplitudes and random, non-zero rise times, to a bipolar output pulse wherein the output pulse has a zero-crossing time that is independent of the rise time and amplitude of the input pulse. The filter differentiates the input pulse, along the linear leading edge of the input pulse, and subtracts therefrom a pulse fractionally proportional to the input pulse. The filter of the present invention can use discrete circuit components and avoids the use of delay lines.

  16. Remobilizing the Interface of Thermocapillary Driven Bubbles Retarded By the Adsorption of a Surfactant Impurity on the Bubble Surface

    NASA Technical Reports Server (NTRS)

    Palaparthi, Ravi; Maldarelli, Charles; Papageorgiou, Dimitri; Singh, Bhim (Technical Monitor)

    2001-01-01

    Thermocapillary migration is a method for moving bubbles in space in the absence of buoyancy. A temperature gradient is the continuous phase in which a bubble is situated, and the applied gradient impressed on the bubble surface causes one pole of the drop to be cooler than the opposite pole. As the surface tension is a decreasing function of temperature, the cooler pole pulls at the warmer pole, creating a flow that propels the bubble in the direction of the warmer fluid. A major impediment to the practical use of thermocapillary to direct the movement of bubbles in space is the fact that surfactant impurities, which are unavoidably present in the continuous phase, can significantly reduce the migration velocity. A surfactant impurity adsorbed onto the bubble interface is swept to the trailing end of the bubble. When bulk concentrations are low (which is the case with an impurity), diffusion of surfactant to the front end is slow relative to convection, and surfactant collects at the back end of the bubble. Collection at the back lowers the surface tension relative to the front end setting up a reverse tension gradient. (This can also be the case if kinetic desorption of surfactant at the back end of the bubble is much slower than convection.) For buoyancy driven bubble motions in the absence of a thermocapillarity, the tension gradient opposes the surface flow, and reduces the surface and terminal velocities (the interface becomes more solid-like and bubbles translate as solid particles). When thermocapillary forces are present, the reverse tension gradient set up by the surfactant accumulation reduces the temperature-induced tension gradient, and can decrease to near zero the bubble's thermocapillary velocity. The objective of our research is to develop a method for enhancing the thermocapillary migration of bubbles which have be retarded by the adsorption onto the bubble surface of a surfactant impurity. Our remobilization theory proposes to use surfactant molecules which kinetically rapidly exchange between the bulk and the surface and are at high bulk concentrations. Because the remobilizing surfactant is present at much higher concentrations than the impurity, it adsorbs to the bubble surface much faster than the impurity when the bubble is formed, and thereby prevents the impurity from adsorbing onto the surface. In addition, the rapid kinetic exchange and high bulk concentration maintain a saturated surface with uniform surface concentrations. This prevents retarding surface tension gradients and keeps the thermocapillary velocity high. In our reports over the first 2 years, we presented numerical simulations of the bubble motion and surfactant transport which verified theoretically the concept of remobilization, and the development of an apparatus to track and measure the velocity of rising bubbles in a glycerol/water surfactant solution. This year, we detail experimental observations of remobilization. Two polyethylene oxide surfactants were studied, C12E6 (CH3(CH2)11(OCH2)6OH) and C10E8 (CH3(CH2)4(OCH2CH2)8OH). Measurements of the kinetic exchange for these surfactants show that the one with the longer hydrophobe chain C12E6 has a lower rate of kinetic exchange. In addition, this surfactant is much less soluble in the glycerol/water mixture because of the shorter ethoxylate chain. As a result, we found that C12E6 had only a very limited ability to remobilize rising bubbles because of the limited kinetic exchange and reduced solubility. However, C10E8, with its higher solubility and more rapid exchange was found to dramatically remobilize rising bubbles. We also compared our theoretical calculations to the experimental measurements of velocity for both the non-remobilizing and remobilizing surfactants and found excellent agreement. We further observed that for C10E8 at high concentrations, which exceeded the critical micelle concentrations, additional remobilization was measured. In this case the rapid exchange of monomer between micelle and surfactant provides an additional mechanism for maintaining a uniform

  17. Remobilizing the Interface of Thermocapillary Driven Bubbles Retarded By the Adsorption of a Surfactant Impurity on the Bubble Surface

    NASA Technical Reports Server (NTRS)

    Palaparthi, Ravi; Maldarelli, Charles; Papageorgiou, Dimitri; Singh, Bhim (Technical Monitor)

    2001-01-01

    Thermocapillary migration is a method for moving bubbles in space in the absence of buoyancy. A temperature gradient is the continuous phase in which a bubble is situated, and the applied gradient impressed on the bubble surface causes one pole of the drop to be cooler than the opposite pole. As the surface tension is a decreasing function of temperature, the cooler pole pulls at the warmer pole, creating a flow that propels the bubble in the direction of the warmer fluid. A major impediment to the practical use of thermocapillary to direct the movement of bubbles in space is the fact that surfactant impurities, which are unavoidably present in the continuous phase, can significantly reduce the migration velocity. A surfactant impurity adsorbed onto the bubble interface is swept to the trailing end of the bubble. When bulk concentrations are low (which is the case with an impurity), diffusion of surfactant to the front end is slow relative to convection, and surfactant collects at the back end of the bubble. Collection at the back lowers the surface tension relative to the front end setting up a reverse tension gradient. (This can also be the case if kinetic desorption of surfactant at the back end of the bubble is much slower than convection.) For buoyancy driven bubble motions in the absence of a thermocapillarity, the tension gradient opposes the surface flow, and reduces the surface and terminal velocities (the interface becomes more solid-like and bubbles translate as solid particles). When thermocapillary forces are present, the reverse tension gradient set up by the surfactant accumulation reduces the temperature-induced tension gradient, and can decrease to near zero the bubble's thermocapillary velocity. The objective of our research is to develop a method for enhancing the thermocapillary migration of bubbles which have be retarded by the adsorption onto the bubble surface of a surfactant impurity. Our remobilization theory proposes to use surfactant molecules which kinetically rapidly exchange between the bulk and the surface and are at high bulk concentrations. Because the remobilizing surfactant is present at much higher concentrations than the impurity, it adsorbs to the bubble surface much faster than the impurity when the bubble is formed, and thereby prevents the impurity from adsorbing onto the surface. In addition, the rapid kinetic exchange and high bulk concentration maintain a saturated surface with uniform surface concentrations. This prevents retarding surface tension gradients and keeps the thermocapillary velocity high. In our reports over the first 2 years, we presented numerical simulations of the bubble motion and surfactant transport which verified theoretically the concept of remobilization, and the development of an apparatus to track and measure the velocity of rising bubbles in a glycerol/water surfactant solution. This year, we detail experimental observations of remobilization. Two polyethylene oxide surfactants were studied, C12E6 (CH3(CH2)11(OCH2)6OH) and C10E8 (CH3(CH2)4(OCH2CH2)8OH). Measurements of the kinetic exchange for these surfactants show that the one with the longer hydrophobe chain C12E6 has a lower rate of kinetic exchange. In addition, this surfactant is much less soluble in the glycerol/water mixture because of the shorter ethoxylate chain. As a result, we found that C12E6 had only a very limited ability to remobilize rising bubbles because of the limited kinetic exchange and reduced solubility. However, C10E8, with its higher solubility and more rapid exchange was found to dramatically remobilize rising bubbles. We also compared our theoretical calculations to the experimental measurements of velocity for both the non-remobilizing and remobilizing surfactants and found excellent agreement. We further observed that for C10E8 at high concentrations, which exceeded the critical micelle concentrations, additional remobilization was measured. In this case the rapid exchange of monomer between micelle and surfactant provides an additional mechanism for maintaining a uniform surface concentrations.

  18. Bubble dispersion and coalescence in turbulent pipe flow

    NASA Astrophysics Data System (ADS)

    Luo, Jianjun

    2002-04-01

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

  19. Expendable bubble tiltmeter for geophysical monitoring

    USGS Publications Warehouse

    Westphal, J.A.; Carr, M.A.; Miller, W.F.; Dzurisin, D.

    1983-01-01

    An unusually rugged highly sensitive and inexpensive bubble tiltmeter has been designed, tested, and built in quantity. These tiltmeters are presently used on two volcanoes and an Alaskan glacier, where they continuously monitor surface tilts of geological interest. This paper discusses the mechanical, thermal, and electric details of the meter, and illustrates its performance characteristics in both large (>10-4 radian) and small (<10-6 radian) tilt environments. The meter's ultimate sensitivity is better than 2??10-8 radians rms for short periods (hours), and its useful dynamic range is greater than 10 4. Included is a short description of field use of the instrument for volcano monitoring.

  20. Thermocapillary bubble flow and coalescence in a rotating cylinder: A 3D study

    NASA Astrophysics Data System (ADS)

    Alhendal, Yousuf; Turan, A.; Al-mazidi, M.

    2015-12-01

    The process of thermocapillary bubbles rising in a rotating 3D cylinder in zero gravity was analysed and presented numerically with the aid of computational fluid dynamics (CFD) by means of the volume of fluid (VOF) method. Calculations were carried out to investigate in detail the effect of the rotational speed of the hosted liquid on the trajectory of both single and group bubbles driven by the Marangoni force in zero-gravity conditions. For rotational speeds from 0.25 to 2 rad/s, bubble displacement with angular motion was found to be directed between the hotter surface and the rotational axis. This is contrary to the conventional bubble flow from areas of high pressure to low pressure, radial direction, or from cold to hot regions, axial direction. The results demonstrate that for the ratio of rotational speeds to the thermocapillary bubble velocity larger than unity, the surface tension gradient is the dominant force and the bubble motion towards the hotter. On the other hand, for ratio less than 1, the bubble motion is dominated and is significantly affected by centrifugal force. As rotation speed increases, the amount of deflection increases and the Marangoni effect vanishes. The current study is novel in the sense that single- and multi-bubble motion incorporating thermocapillary forces in a rotating liquid in a zero-gravity environment has never been numerically investigated.

  1. Modeling gas bubbles and dissolved gases in a turbulent ocean boundary layer

    NASA Astrophysics Data System (ADS)

    Liang, J.; McWilliams, J. C.; Sullivan, P. P.; Baschek, B.

    2010-12-01

    Gas bubbles are ubiquitous in the surface ocean boundary layer (OBL). After their injection by breaking surface gravity waves, gas bubbles are mixed by turbulent water flows, rise by buoyancy, change size, and exchange gases with the ambient water. They modify the acoustical and optical properties of the upper ocean, enhance upper ocean stratification, and provide an important pathway for gas exchange between the atmosphere and the ocean. We have developed a coupled OBL-Bubble-Dissolved-Gas model that resolves the bubble behavior and bubble impacts on upper ocean dynamics and dissolved gases (Liang et al. 2010). The model is configured to simulate bubbles and dissolved gases in the turbulent OBL with Langmuir circulations and breaking waves. As a result of bubble injection and evolution, Langmuir circulations are weakened, the gas exchange rate is increased, and the equilibrium gas saturation level is enhanced. REFERENCE: Liang, J.-H., J. C. McWilliams, P. P. Sullivan, and B. Baschek (2010) Modeling bubbles and dissolved gases in the ocean, submitted.

  2. Measurement and Analysis of Gas Bubbles Near a Reference Electrode in Aqueous Solutions

    SciTech Connect

    Supathorn Phongikaroon; Steve Herrmann; Shelly Li; Michael Simpson

    2005-10-01

    Bubble size distributions (BSDs) near a reference electrode (RE) in aqueous glycerol solutions of an electrolyte NaCl have been investigated under various gas superficial velocities (U{sub S}). BSD and voltage reading of the solution were measured by using a high-speed digital camera and a pH/voltage meter, respectively. The results show that bubble size (b) increases with liquid viscosity ({mu}{sub c}) and U{sub S}. Self-similarity is seen and can be described by the log-normal form of the continuous number frequency distribution. The result shows that b controls the voltage reading in each solution. As b increases, the voltage increases because of gas bubbles interrupting their electrolyte paths in the solutions. An analysis of bubble rising velocity reveals that Stokes Law should be used cautiously to describe the system. The fundamental equation for bubble formation was developed via Newton's second law of motion and shown to be the function of three dimensionless groups--Weber number, Bond number, and Capillary number. After linking an electrochemical principle in the practical application, the result indicates that the critical bubble size is {approx}177 {micro}m. Further analysis suggests that there may be 3000 to 70,000 bubbles generated on the anode surface depending on the size of initial bubbles and provides the potential cause of the efficiency drop observed in the practical application.

  3. 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 μl 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

  4. Global sea level rise

    SciTech Connect

    Douglas, B.C. )

    1991-04-15

    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 appear to be in large part due to authors' using data from gauges located at convergent tectonic plate boundaries, where changes of land elevation give fictitious sea level trends. In addition, virtually all gauges undergo subsidence or uplift due to postglacial rebound (PGR) from the last deglaciation at a rate comparable to or greater than the secular rise of sea level. Modeling PGR by the ICE-3G model of Tushingham and Peltier (1991) and avoiding tide gauge records in areas of converging tectonic plates produces a highly consistent set of long sea level records. The value for mean sea level rise obtained from a global set of 21 such stations in nine oceanic regions with an average record length of 76 years during the period 1880-1980 is 1.8 mm/yr {plus minus} 0.1. This result provides confidence that carefully selected long tide gauge records measure the same underlying trend of sea level and that many old tide gauge records are of very high quality.

  5. The rise and fall.

    PubMed

    Japsen, B

    1997-09-01

    By the time the government raided Columbia/HCA Healthcare Corp. facilities this summer, colleagues had been trying for years to warn the company's then-top executive, Richard Scott, about the unnerving arrogance from the executive suite in Nashville. Modern Healthcare explores key events in the rise and fall of Scott and the company he built. PMID:10170124

  6. Aspherical bubble dynamics and oscillation times

    SciTech Connect

    Vogel, A.; Noack, J.; Chapyak, E.J.; Godwin, R.P.

    1999-06-01

    The cavitation bubbles common in laser medicine are rarely perfectly spherical and are often located near tissue boundaries, in vessels, etc., which introduce aspherical dynamics. Here, novel features of aspherical bubble dynamics are explored by time-resolved photography and numerical simulations. The growth-collapse period of cylindrical bubbles of large aspect ratio (length:diameter {approximately}20) differs only slightly from twice the Rayleigh collapse time for a spherical bubble with an equivalent maximum volume. This fact justifies using the temporal interval between the acoustic signals emitted upon bubble creation and collapse to estimate the maximum bubble volume. As a result, hydrophone measurements can provide an estimate of the bubble size and energy even for aspherical bubbles. The change of the oscillation period of bubbles near solid walls and elastic (tissue-like) boundaries relative to that of isolated spherical bubbles is also investigated.

  7. The Bubble Box: Towards an Automated Visual Sensor for 3D Analysis and Characterization of Marine Gas Release Sites

    PubMed Central

    Jordt, Anne; Zelenka, Claudius; Schneider von Deimling, Jens; Koch, Reinhard; Köser, Kevin

    2015-01-01

    Several acoustic and optical techniques have been used for characterizing natural and anthropogenic gas leaks (carbon dioxide, methane) from the ocean floor. Here, single-camera based methods for bubble stream observation have become an important tool, as they help estimating flux and bubble sizes under certain assumptions. However, they record only a projection of a bubble into the camera and therefore cannot capture the full 3D shape, which is particularly important for larger, non-spherical bubbles. The unknown distance of the bubble to the camera (making it appear larger or smaller than expected) as well as refraction at the camera interface introduce extra uncertainties. In this article, we introduce our wide baseline stereo-camera deep-sea sensor bubble box that overcomes these limitations, as it observes bubbles from two orthogonal directions using calibrated cameras. Besides the setup and the hardware of the system, we discuss appropriate calibration and the different automated processing steps deblurring, detection, tracking, and 3D fitting that are crucial to arrive at a 3D ellipsoidal shape and rise speed of each bubble. The obtained values for single bubbles can be aggregated into statistical bubble size distributions or fluxes for extrapolation based on diffusion and dissolution models and large scale acoustic surveys. We demonstrate and evaluate the wide baseline stereo measurement model using a controlled test setup with ground truth information. PMID:26690168

  8. Inferring bubble size distributions from resistance probe measurements in gas-liquid, gas-slurry and three phase systems

    SciTech Connect

    Clark, N.N.; Seiss, R.; Turton, R.

    1988-01-01

    Resistance probes measure the presence or absence of a conducting fluid at a point in multiphase flows. Although resistance probes are often used to determine local gas holdup in gas-liquid, gas-slurry and gas-liquid-solid flows, they are seldom used to find the bubble size distribution in the flow. This is due to the fact that the distribution of time intervals measured by the probe due to the passage of bubbles is not readily translated into a bubble size distribution. Even if a bubble rise velocity is known, the resulting distribution of bubble chord lengths cut by the probe has a lower mean and wider range than the size distribution. However, with enough data and a knowledge of the bubble shape it is possible to back transform to a size distribution. The current work deals with the case when the bubble shape is not a constant but changes with bubble size. Shape descriptors have been obtained from photographs of bubbles in water. Using these descriptors and probability density functions, a forward transform is developed to yield an expected chord length distribution for a given distribution of bubble sizes. The more important backward transform is accomplished numerically through a triangular matrix solution. Monte Carlo simulations demonstrate the correctness of this approach and are also used to show that the back transform can be unstable if too few data or too many size divisions in the matrix are used. 21 refs., 9 figs.

  9. The Bubble Box: Towards an Automated Visual Sensor for 3D Analysis and Characterization of Marine Gas Release Sites.

    PubMed

    Jordt, Anne; Zelenka, Claudius; von Deimling, Jens Schneider; Koch, Reinhard; Köser, Kevin

    2015-01-01

    Several acoustic and optical techniques have been used for characterizing natural and anthropogenic gas leaks (carbon dioxide, methane) from the ocean floor. Here, single-camera based methods for bubble stream observation have become an important tool, as they help estimating flux and bubble sizes under certain assumptions. However, they record only a projection of a bubble into the camera and therefore cannot capture the full 3D shape, which is particularly important for larger, non-spherical bubbles. The unknown distance of the bubble to the camera (making it appear larger or smaller than expected) as well as refraction at the camera interface introduce extra uncertainties. In this article, we introduce our wide baseline stereo-camera deep-sea sensor bubble box that overcomes these limitations, as it observes bubbles from two orthogonal directions using calibrated cameras. Besides the setup and the hardware of the system, we discuss appropriate calibration and the different automated processing steps deblurring, detection, tracking, and 3D fitting that are crucial to arrive at a 3D ellipsoidal shape and rise speed of each bubble. The obtained values for single bubbles can be aggregated into statistical bubble size distributions or fluxes for extrapolation based on diffusion and dissolution models and large scale acoustic surveys. We demonstrate and evaluate the wide baseline stereo measurement model using a controlled test setup with ground truth information. PMID:26690168

  10. Transient bubbles, bublets and breakup

    NASA Astrophysics Data System (ADS)

    Keen, Giles; Blake, John

    1999-11-01

    The non-spherical nature of the collapse of bubbles has important ramifications in many practical situations such as ultrasonic cleaning, tanning of leather, and underwater explosions. In particular the high speed liquid jet that can thread a collapsing bubble is central to the functional performance. An impressive photographic record of a liquid jet was obtained by Crum using a bubble situated in the vicinity of a platform oscillating vertically at a frequency of 60 Hz. A boundary integral method is used to model this situation and is found to closely mimic some of the observations. However, a slight variation of parameters or a change in the phase of the driving frequency can lead to dramatically different bubble behaviour, a feature also observed by Crum.

  11. Holography in small bubble chambers

    SciTech Connect

    Lecoq, P.

    1984-01-01

    This chapter reports on an experiment to determine the total charm cross section at different incident momenta using the small, heavy liquid bubble chamber HOBC. Holography in liquid hydrogen is also tested using the holographic lexan bubble chamber HOLEBC with the aim of preparing a future holographic experiment in hydrogen. The high intensity tests show that more than 100 incident tracks per hologram do not cause a dramatic effect on the picture quality. Hydrogen is more favorable than freon as the bubble growth is much slower in hydrogen. An advantage of holography is to have the maximum resolution in the full volume of the bubble chamber, which allows a gain in sensitivity by a factor of 10 compared to classical optics as 100 tracks per hologram look reasonable. Holograms are not more difficult to analyze than classical optics high-resolution pictures. The results show that holography is a very powerful technique which can be used in very high resolution particle physics experiments.

  12. 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

  13. Smashing Bubbles and Vanishing Sugar.

    ERIC Educational Resources Information Center

    Ward, Alan

    1979-01-01

    Science activities with soap bubbles for primary school children are described in this article. Another activity involves children in determining the whereabouts of sugar as it dissolves in water. (SA)

  14. Phase equilibration in bubble collisions

    NASA Astrophysics Data System (ADS)

    Kibble, T. W. B.; Vilenkin, Alexander

    1995-07-01

    In the context of an Abelian gauge symmetry, spontaneously broken at a first-order transition, we discuss the evolution of the phase difference between the Higgs fields in colliding bubbles. We show that the effect of dissipation, represented by a finite plasma conductivity, is to cause the phases to equilibrate on a time scale, determined by the conductivity, which can be much smaller than the bubble radii at the time of collision. Currents induced during the phase equilibration generate a magnetic flux, which is determined by the initial phase difference. In a three-bubble collision, the fluxes produced by each pair of bubbles combine, and a vortex can be formed. We find that, under most conditions, the probability of trapping magnetic flux to form a vortex is correctly given by the ``geodesic rule.''

  15. 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.

  16. Microstreaming from Sessile Semicylindrical Bubbles

    NASA Astrophysics Data System (ADS)

    Hilgenfeldt, Sascha; Rallabandi, Bhargav; Guo, Lin; Wang, Cheng

    2014-03-01

    Powerful steady streaming flows result from the ultrasonic driving of microbubbles, in particular when these bubbles have semicylindrical cross section and are positioned in contact with a microfluidic channel wall. We have used this streaming in experiment to develop novel methods for trapping and sorting of microparticles by size, as well as for micromixing. Theoretically, we arrive at an analytical description of the streaming flow field through an asymptotic computation that, for the first time, reconciles the boundary layers around the bubble and along the substrate wall, and also takes into account the oscillation modes of the bubble. This approach gives insight into changes in the streaming pattern with bubble size and driving frequency, including a reversal of the flow direction at high frequencies with potentially useful applications. Present address: Mechanical and Aerospace Engineering, Missouri S &T.

  17. 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.

  18. Pulling bubbles from a bath

    NASA Astrophysics Data System (ADS)

    Kao, Justin C. T.; Blakemore, Andrea L.; Hosoi, A. E.

    2010-06-01

    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 industrial processes where uniformity of coating is desirable. We report work on an idealized version of this situation, the drag-out of a single bubble in Landau-Levich-Derjaguin flow. We find that a well-defined critical wall speed exists, separating the two regimes of bubble persistence at the meniscus and bubble deposition on the moving wall. Experiments show that this transition occurs at Ca∗˜Bo0.73. A similar result is obtained theoretically by balancing viscous stresses and gravity.

  19. How does a bubble chamber work?

    SciTech Connect

    Konstantinov, D.; Homsi, W.; Luzuriaga, J.; Su, C.K.; Weilert, M.A.; Maris, H.J.

    1998-11-01

    A charged particle passing through a bubble chamber produces a track of bubbles. The way in which these bubbles are produced has been a matter of some controversy. The authors consider the possibility that in helium and hydrogen bubble chambers the production of bubbles is primarily a mechanical process, rather than a thermal process as has often been assumed. The model the authors propose gives results which are in excellent agreement with experiment.

  20. Driving bubbles out of glass

    NASA Technical Reports Server (NTRS)

    Mattox, D. M.

    1981-01-01

    Surface tension gradient in melt forces gas bubbles to surface, increasing glass strength and transparency. Conventional chemical and buoyant fining are extremely slow in viscous glasses, but tension gradient method moves 250 um bubbles as rapidly as 30 um/s. Heat required for high temperature part of melt is furnished by stationary electrical or natural-gas heater; induction and laser heating are also possible. Method has many applications in industry processes.

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

    NASA Astrophysics Data System (ADS)

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

    2003-04-01

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

  2. Bubble-Pen Lithography.

    PubMed

    Lin, Linhan; Peng, Xiaolei; Mao, Zhangming; Li, Wei; Yogeesh, Maruthi N; Rajeeva, Bharath Bangalore; Perillo, Evan P; Dunn, Andrew K; Akinwande, Deji; Zheng, Yuebing

    2016-01-13

    Current lithography techniques, which employ photon, electron, or ion beams to induce chemical or physical reactions for micro/nano-fabrication, have remained challenging in patterning chemically synthesized colloidal particles, which are emerging as building blocks for functional devices. Herein, we develop a new technique - bubble-pen lithography (BPL) - to pattern colloidal particles on substrates using optically controlled microbubbles. Briefly, a single laser beam generates a microbubble at the interface of colloidal suspension and a plasmonic substrate via plasmon-enhanced photothermal effects. The microbubble captures and immobilizes the colloidal particles on the substrate through coordinated actions of Marangoni convection, surface tension, gas pressure, and substrate adhesion. Through directing the laser beam to move the microbubble, we create arbitrary single-particle patterns and particle assemblies with different resolutions and architectures. Furthermore, we have applied BPL to pattern CdSe/ZnS quantum dots on plasmonic substrates and polystyrene (PS) microparticles on two-dimensional (2D) atomic-layer materials. With the low-power operation, arbitrary patterning and applicability to general colloidal particles, BPL will find a wide range of applications in microelectronics, nanophotonics, and nanomedicine. PMID:26678845

  3. Bubble phenomena in three-phase fluidized beds as viewed by a u-shaped fiber optic probe

    SciTech Connect

    Lee, S.L.P.; de Lasa, H.I.; Bergougnou, M.A.

    1984-01-01

    A novel U-shaped fiber optic probe was applied in the present contribution to the characterization of bubbles in a cylindrical three-phase fluidized bed. Air, water and glass beads (335..mu..m) were used as the gas, liquid and solid phases respectively. Several single core silica fibers were used to guide the helium-neon laser beams into the fluidized bed, each of them constituting a U-probe. The design of the U-probes was based on the difference of refraction indexes between gas and liquid phases. Using the U-shaped probes, bubble characteristics such as shape, included angle, bubble velocity and axial bubble length were systematically measured. In addition, the changes of the bubble frequency with the radial position, the variations of the mean bubble diameter with the liquid superficial velocity, the bubble size distribution and their changes with the fluidized bed operation conditions were also investigated.

  4. Physical modeling studies of electrolyte flow due to gas evolution and some aspects of bubble behavior in advanced Hall cells; Part 1: Flow in cells with a flat anode

    SciTech Connect

    Shekhar, R. . Dept. of Metallurgical Engineering); Evans, J.W. . Dept. of Materials Science and Mineral Engineering)

    1994-06-01

    The need for energy reduction in the electrolytic production of aluminum led to the concept of advanced Hall cells that can be operated at lower interelectrode gaps compared to existing cells. However, gas bubbles generated by the anodic reaction increase the resistivity of electrolyte and cancel out part of the reduction in interelectrode resistance expected from bringing the electrodes closer together. Therefore, the primary objective of this work was to determine a cell design in which flow can be managed to promote the removal of anode gas bubbles from the interelectrode gap. In particular, this article focuses on advanced Hall cells equipped with flat'' anodes, similar to those used in existing cells. The principal experimental tool has been a water'' model consisting of a large tank in which simulated anodes can be suspended in either the horizontal or near-horizontal configurations. Gas was generated by forcing compressed air through porous graphite, and the fine bubbles characteristic of inert anodes used in advanced Hall cells were produced by adding butanol to water. Velocities were measured using a laser-Doppler velocimeter (LDV). This study indicates that the existing cell configuration might not be the optimum configuration for advanced Hall cells. The results also show that operation of an advanced Hall cell with a fully submerged anode should give rise to higher electrolyte velocities and thus rapid removal of bubbles. The bubble effect should be further lowered in a near-horizontal configuration; however, the flow pattern could have an adverse effect on current efficiency and alumina distribution in the cell. It has also been shown that the bubble size, and, therefore, the physical properties of the electrolyte, can have a significant effect on the electrolyte flow pattern in the interelectrode gap.

  5. The velocity-distance relation for galaxies on a bubble

    NASA Technical Reports Server (NTRS)

    Bothun, Gregory D.; Geller, Margaret J.; Kurtz, Michael J.; Huchra, John P.; Schild, Rudolph E.

    1992-01-01

    The characteristic diameter of the most prominent void in the redshift survey of de Lapparent et al. (1986) is measured. Distances and peculiar velocities to individual galaxies are derived, and it is shown that the void is approximately a 'Hubble Bubble' in which the near and far edges are separating with the general expansion of the universe. At the 3 sigma level, infall toward the Coma cluster is detected for a portion of the bubble wall. Limits on the net outflow from the void and infall into Coma are used to estimate Omega.

  6. Contemporary sea level rise.

    PubMed

    Cazenave, Anny; Llovel, William

    2010-01-01

    Measuring sea level change and understanding its causes has considerably improved in the recent years, essentially because new in situ and remote sensing observations have become available. Here we report on most recent results on contemporary sea level rise. We first present sea level observations from tide gauges over the twentieth century and from satellite altimetry since the early 1990s. We next discuss the most recent progress made in quantifying the processes causing sea level change on timescales ranging from years to decades, i.e., thermal expansion of the oceans, land ice mass loss, and land water-storage change. We show that for the 1993-2007 time span, the sum of climate-related contributions (2.85 +/- 0.35 mm year(-1)) is only slightly less than altimetry-based sea level rise (3.3 +/- 0.4 mm year(-1)): approximately 30% of the observed rate of rise is due to ocean thermal expansion and approximately 55% results from land ice melt. Recent acceleration in glacier melting and ice mass loss from the ice sheets increases the latter contribution up to 80% for the past five years. We also review the main causes of regional variability in sea level trends: The dominant contribution results from nonuniform changes in ocean thermal expansion. PMID:21141661

  7. Understanding the relation between pre-eruptive bubble size distribution and observed ash particle sizes

    NASA Astrophysics Data System (ADS)

    Proussevitch, A. A.; Sahagian, D. L.; Mulukutla, G. K.

    2011-12-01

    Recent advances in measuring pre-eruptive bubble size distributions (BSDs) from ash particle surface morphology now make it possible to calibrate ash fragmentation models for prediction of pyroclastic characteristics such as particle size distribution. The same magma bodies can generate various eruption products ranging from course bombs to fine ash, with a wide range of fractionation between these end members that in turn depends on decompression rates and the pre-eruptive bubble size distributions controlled by vesiculation dynamics. We have devised a Monte Carlo method to produce spatial models of bubble textures that match inferred BSDs of pre-fragmentation magma in the eruption column based on conditions of 1-stage bubble nucleation and random nucleation site spacing, with either of two bubble growth schemes applicable for low and high vesicularity volcanic products- (1) unconfined growth in the absence of neighboring bubbles, and (2) limited growth in a melt volume shared with neighboring bubbles. These scenarios lead to different BSDs, thus controlling fragmentation thresholds and patterns. From those alternative BSDs we have calculated the thickness distribution of bubble walls and plateau borders, so we can predict the size distribution of ash particles formed by rupture of thinnest inter-bubble films, as well as the fraction of compound fragments or clasts derived from parcels of magmatic foam containing thicker walls. As such, it is possible to parameterize the magmatic conditions that lead to eruptions with a high fraction of fine ash of concern to volcanic hazards.

  8. Shock wave emission upon spherical bubble collapse during cavitation-induced megasonic surface cleaning.

    PubMed

    Minsier, V; Proost, J

    2008-04-01

    When a gas bubble in a liquid interacts with an acoustic wave near a solid surface, the bubble first expands and then collapses. In this paper, a mathematical framework combining the Gilmore model and the method of characteristics is presented to model the shock wave emitted at the end of the bubble collapse. It allows to describe the liquid velocity at the shock front as a function of the radial distance to the bubble center in the case of spherical bubble collapse. Numerical calculations of the liquid velocity at the shock front have shown that this velocity increases with the acoustic amplitude and goes through a maximum as a function of the initial bubble radius. Calculations for different gas state equations inside the bubble show that the Van der Waals law predicts a slightly higher liquid velocity at the shock front than when considering a perfect gas law. Finally, decreasing the value of the surface tension at the bubble/liquid interface results in an increase of the liquid velocity at the shock front. Our calculations indicate that the strength of the shock waves emitted upon spherical bubble collapse can cause delamination of typical device structures used in microelectronics. PMID:17662636

  9. THE FERMI BUBBLES: SUPERSONIC ACTIVE GALACTIC NUCLEUS JETS WITH ANISOTROPIC COSMIC-RAY DIFFUSION

    SciTech Connect

    Yang, H.-Y. K.; Ruszkowski, M.; Ricker, P. M.; Zweibel, E.; Lee, D.

    2012-12-20

    The Fermi Gamma-Ray Space Telescope reveals two large bubbles in the Galaxy, which extend nearly symmetrically {approx}50 Degree-Sign above and below the Galactic center. Using three-dimensional (3D) magnetohydrodynamic simulations that self-consistently include the dynamical interaction between cosmic rays (CRs) and thermal gas and anisotropic CR diffusion along the magnetic field lines, we show that the key characteristics of the observed gamma-ray bubbles and the spatially correlated X-ray features in the ROSAT 1.5 keV map can be successfully reproduced by recent jet activity from the central active galactic nucleus. We find that after taking into account the projection of the 3D bubbles onto the sky the physical heights of the bubbles can be much smaller than previously thought, greatly reducing the formation time of the bubbles to about a Myr. This relatively small bubble age is needed to reconcile the simulations with the upper limit of bubble ages estimated from the cooling time of high-energy electrons. No additional physical mechanisms are required to suppress large-scale hydrodynamic instabilities because the evolution time is too short for them to develop. The simulated CR bubbles are edge-brightened, which is consistent with the observed projected flat surface brightness distribution. Furthermore, we demonstrate that the sharp edges of the observed bubbles can be due to anisotropic CR diffusion along magnetic field lines that drape around the bubbles during their supersonic expansion, with suppressed perpendicular diffusion across the bubble surface. Possible causes of the slight bends of the Fermi bubbles to the west are also discussed.

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

    NASA Astrophysics Data System (ADS)

    Stephens, James

    2006-11-01

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

  11. Mechanisms of single bubble cleaning.

    PubMed

    Reuter, Fabian; Mettin, Robert

    2016-03-01

    The dynamics of collapsing bubbles close to a flat solid is investigated with respect to its potential for removal of surface attached particles. Individual bubbles are created by nanosecond Nd:YAG laser pulses focused into water close to glass plates contaminated with melamine resin micro-particles. The bubble dynamics is analysed by means of synchronous high-speed recordings. Due to the close solid boundary, the bubble collapses with the well-known liquid jet phenomenon. Subsequent microscopic inspection of the substrates reveals circular areas clean of particles after a single bubble generation and collapse event. The detailed bubble dynamics, as well as the cleaned area size, is characterised by the non-dimensional bubble stand-off γ=d/Rmax, with d: laser focus distance to the solid boundary, and Rmax: maximum bubble radius before collapse. We observe a maximum of clean area at γ≈0.7, a roughly linear decay of the cleaned circle radius for increasing γ, and no cleaning for γ>3.5. As the main mechanism for particle removal, rapid flows at the boundary are identified. Three different cleaning regimes are discussed in relation to γ: (I) For large stand-off, 1.8<γ<3.5, bubble collapse induced vortex flows touch down onto the substrate and remove particles without significant contact of the gas phase. (II) For small distances, γ<1.1, the bubble is in direct contact with the solid. Fast liquid flows at the substrate are driven by the jet impact with its subsequent radial spreading, and by the liquid following the motion of the collapsing and rebounding bubble wall. Both flows remove particles. Their relative timing, which depends sensitively on the exact γ, appears to determine the extension of the area with forces large enough to cause particle detachment. (III) At intermediate stand-off, 1.1<γ<1.8, only the second bubble collapse touches the substrate, but acts with cleaning mechanisms similar to an effective small γ collapse: particles are removed by the jet flow and the flow induced by the bubble wall oscillation. Furthermore, the observations reveal that the extent of direct bubble gas phase contact to the solid is partially smaller than the cleaned area, and it is concluded that three-phase contact line motion is not a major cause of particle removal. Finally, we find a relation of cleaning area vs. stand-off γ that deviates from literature data on surface erosion. This indicates that different effects are responsible for particle removal and for substrate damage. It is suggested that a trade-off of cleaning potential and damage risk for sensible surfaces might be achieved by optimising γ. PMID:26187759

  12. Spark bubble interaction with a suspended particle

    NASA Astrophysics Data System (ADS)

    Ohl, Siew-Wan; Wu, Di Wei; Klaseboer, Evert; Cheong Khoo, Boo

    2015-12-01

    Cavitation bubble collapse is influenced by nearby surfaces or objects. A bubble near a rigid surface will move towards the surface and collapse with a high speed jet. When a hard particle is suspended near a bubble generated by electric spark, the bubble expands and collapses moving the particle. We found that within a limit of stand-off distance, the particle is propelled away from the bubble as it collapses. At a slightly larger stand-off distance, the bubble collapse causes the particle to move towards the bubble initially before moving away. The bubble does not move the particle if it is placed far away. This conclusion is important for applications such as drug delivery in which the particle is to be propelled away from the collapsing bubble.

  13. Nanoscale patterns on micron-sized bubbles in foams

    NASA Astrophysics Data System (ADS)

    Dressaire, Emilie; Bell, David; Bee, Rodney; Lips, Alex; Stone, Howard

    2006-11-01

    The rheology and coarsening of foams is closely related to the microstructural characteristics of the small gas bubbles and their surface properties. We present experimental results of a foam formed upon shearing a mixture composed of glucose syrup and sucrose ester. Transmission Electron Microscopy reveals micron-size bubbles whose surfaces are fully covered with regular nanodimension, generally hexagonal, patterns. The influence of the shear rate during foam generation and the setting time on the development of the nanoscale patterns on the gas microcells are described. Plausible routes, driven by disproportionation of the gas from the small bubbles, for the formation of the nanoscale patterns are considered including a nucleation/crystallization pathway (Kim et al. 2003 Langmuir 19, p. 8455) and the buckling of an elastic insoluble surface film.

  14. Xenon bubble chambers for direct dark matter detection

    NASA Astrophysics Data System (ADS)

    Levy, C.; Fallon, S.; Genovesi, J.; Khaitan, D.; Klimov, K.; Mock, J.; Szydagis, M.

    2016-03-01

    The search for dark matter is one of today's most exciting fields. As bigger detectors are being built to increase their sensitivity, background reduction is an ever more challenging issue. To this end, a new type of dark matter detector is proposed, a xenon bubble chamber, which would combine the strengths of liquid xenon TPCs, namely event by event energy resolution, with those of a bubble chamber, namely insensitivity to electronic recoils. In addition, it would be the first time ever that a dark matter detector is active on all three detection channels, ionization and scintillation characteristic of xenon detectors, and heat through bubble formation in superheated fluids. Preliminary simulations show that, depending on threshold, a discrimination of 99.99% to 99.9999+% can be achieved, which is on par or better than many current experiments. A prototype is being built at the University at Albany, SUNY. The prototype is currently undergoing seals, thermal, and compression testing.

  15. Shape and size of methane bubbles in muddy aquatic sediments and their dependence on sediment fracture toughness: a modeling approach

    NASA Astrophysics Data System (ADS)

    Katsman, Regina

    2014-05-01

    Shallow gassy marine sediments abundantly found on continental margins of Israel and worldwide, are a source of a major concern for their contribution to the destabilization of coastal and marine infrastructure, air pollution, and global warming. Bubbles are different in the different sediment types. Size of the bubbles residing in the fine-grained muddy sediment exceeds significantly the grain size of sediment, and its shape can be approximated by a large oblate spheroid surrounded by sediment saturated with water. Experimental results indicate that bubble growth is accompanied by fracturing of the fine-grained muddy sediment. Modeling reveals that fracture toughness of the muddy sediments significantly affects bubble shape and size evolution prior its ascent. Small fracture toughness is responsible for generation of the small bubbles with highly asymmetric configuration and with fracturing concentrated mostly on the bubble head. In contrast, bigger fracture toughness is responsible for generation of the large, more symmetric bubbles. Moreover, growing bubble demonstrates a positive allometry resulting in a bigger rate of growth of its surface area that is responsible for the effectiveness of the solute supply from pore water to the bubble interior. This scaling demonstrates a strong correlation with sediment fracture toughness as well. Cross-section of the buoyant bubbles evolves from the elliptic profile to the one resembling an 'inverted tear drop'. Calculated bubbles characteristics in different sediments types demonstrate a good agreement with values reported in the literature.

  16. The Dynamics of Vapor Bubbles in Acoustic Pressure Fields

    NASA Technical Reports Server (NTRS)

    Hao, Y.; Prosperetti, A.

    1999-01-01

    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.

  17. Interfacial Force Model Development for Turbulent Bubbly Flows

    NASA Astrophysics Data System (ADS)

    Shaver, Dillon; Bolotnov, Igor; Antal, Steven; Podowski, Michael

    2010-11-01

    Typically, a Reynolds averaged Navier-Stokes (RANS) simulation of turbulent bubbly flows makes use of interfacial force models which represent the interaction between the bubbles and the continuous liquid. The modeled forces include drag, virtual mass, turbulent dispersion, and lift. A direct numerical simulation (DNS) fully resolves turbulent fluctuations in velocity and, when coupled with the level set method, can simulate a two-phase flow without relying on interfacial force models. Results from DNS can provide a level of insight into flow characteristics not easily achievable with traditional experimental methods. This makes DNS ideal for developing interfacial force models for use with RANS codes. Turbulent, air/water, bubbly flows in a channel have been previously simulated using the DNS code, PHASTA. Utilizing the time-averaging concept, average velocities of the two phases, void fraction, turbulent kinetic energy, and turbulence dissipation rate distributions are calculated from the DNS data. This information is then used to develop and calibrate the interfacial force models used in the RANS code, NPHASE-CMFD. Two cases are analyzed. The first is of many small, spherical bubbles of 0.9 mm diameter. The other is of a single, large, cap bubble of 3.625 mm equivalent diameter. Both simulations correspond to the liquid Reynolds number of 11,200, based on the hydraulic diameter.

  18. Bubble Gate for In-Plane Flow Control

    NASA Astrophysics Data System (ADS)

    Kazemi Oskooei, Ali; Guenther, Axel

    2011-11-01

    The ability to control fluid flow is of key importance for microfluidic devices. While a large number of sophisticated solutions have been demonstrated, there is still a great amount of interest in developing simple strategies that do not require complex fabrication steps and electrical connections. A small footprint, compatibility with different substrate materials, working fluids and temperatures are amongst other desirable characteristics. We demonstrate a bubble gate strategy that meets all the above. In this strategy, flow control is achieved using a controlled gas stream that intercepts a liquid stream at a T-junction, forming a gas-liquid interface (i.e. bubble). Closely positioned micropillars are employed to limit the bubble motion to a single degree of freedom. The bubble breaks into the liquid stream and occupies the entire liquid cross-section, when the gas pressure is continued. Hence, the bubble movement is able to stop or manipulate the liquid flow. Several control operations are discussed herein, including, but not limited to, valves, liquid metering and peristaltic pumping. PIV measurements are employed to investigate the transient flow structure.

  19. Bubble rearrangements dynamics in foams

    NASA Astrophysics Data System (ADS)

    Le Merrer, Marie; Costa, Severine; Cohen-Addad, Sylvie; Hoehler, Reinhard

    2011-11-01

    Liquid foams are jammed dispersions of gas bubbles in a surfactant solution. Their structure evolves with time because surface tension drives a diffusive gas exchange between neighboring bubbles. This coarsening leads to a build-up of stresses which are relaxed upon local intermittent bubble rearrangements. These events govern the slow viscoelastic foam response, and similar bubble rearrangements are the elementary processes of plastic flow. Thus, the rearrangement duration is a key parameter describing how the microstructure dynamics control the macroscopic rheological response. We probe the duration of coarsening-induced rearrangements in 3D foams using a multiple light scattering technique (time resolved Diffusing-Wave Spectroscopy) as a function of the surfactant chemistry and the liquid fraction. As the foam becomes wetter, the confinement pressure of the packing goes to zero and the contacts between bubbles vanish. For mobile interfaces, we find that the rearrangements slow down as the jamming point is approached. These findings are compared to scaling laws which reveal an analogy between rearrangements dynamics in foams and granular suspensions.

  20. Ethnic diversity deflates price bubbles.

    PubMed

    Levine, Sheen S; Apfelbaum, Evan P; Bernard, Mark; Bartelt, Valerie L; Zajac, Edward J; Stark, David

    2014-12-30

    Markets are central to modern society, so their failures can be devastating. Here, we examine a prominent failure: price bubbles. Bubbles emerge when traders err collectively in pricing, causing misfit between market prices and the true values of assets. The causes of such collective errors remain elusive. We propose that bubbles are affected by ethnic homogeneity in the market and can be thwarted by diversity. In homogenous markets, traders place undue confidence in the decisions of others. Less likely to scrutinize others' decisions, traders are more likely to accept prices that deviate from true values. To test this, we constructed experimental markets in Southeast Asia and North America, where participants traded stocks to earn money. We randomly assigned participants to ethnically homogeneous or diverse markets. We find a marked difference: Across markets and locations, market prices fit true values 58% better in diverse markets. The effect is similar across sites, despite sizeable differences in culture and ethnic composition. Specifically, in homogenous markets, overpricing is higher as traders are more likely to accept speculative prices. Their pricing errors are more correlated than in diverse markets. In addition, when bubbles burst, homogenous markets crash more severely. The findings suggest that price bubbles arise not only from individual errors or financial conditions, but also from the social context of decision making. The evidence may inform public discussion on ethnic diversity: it may be beneficial not only for providing variety in perspectives and skills, but also because diversity facilitates friction that enhances deliberation and upends conformity. PMID:25404313

  1. Ethnic diversity deflates price bubbles

    PubMed Central

    Levine, Sheen S.; Apfelbaum, Evan P.; Bernard, Mark; Bartelt, Valerie L.; Zajac, Edward J.; Stark, David

    2014-01-01

    Markets are central to modern society, so their failures can be devastating. Here, we examine a prominent failure: price bubbles. Bubbles emerge when traders err collectively in pricing, causing misfit between market prices and the true values of assets. The causes of such collective errors remain elusive. We propose that bubbles are affected by ethnic homogeneity in the market and can be thwarted by diversity. In homogenous markets, traders place undue confidence in the decisions of others. Less likely to scrutinize others’ decisions, traders are more likely to accept prices that deviate from true values. To test this, we constructed experimental markets in Southeast Asia and North America, where participants traded stocks to earn money. We randomly assigned participants to ethnically homogeneous or diverse markets. We find a marked difference: Across markets and locations, market prices fit true values 58% better in diverse markets. The effect is similar across sites, despite sizeable differences in culture and ethnic composition. Specifically, in homogenous markets, overpricing is higher as traders are more likely to accept speculative prices. Their pricing errors are more correlated than in diverse markets. In addition, when bubbles burst, homogenous markets crash more severely. The findings suggest that price bubbles arise not only from individual errors or financial conditions, but also from the social context of decision making. The evidence may inform public discussion on ethnic diversity: it may be beneficial not only for providing variety in perspectives and skills, but also because diversity facilitates friction that enhances deliberation and upends conformity. PMID:25404313

  2. 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.

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

    SciTech Connect

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

    2006-10-01

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

  4. Temperature considerations in non-spherical bubble collapse near a rigid wall

    NASA Astrophysics Data System (ADS)

    Alahyari Beig, Shahaboddin; Johnsen, Eric

    2015-12-01

    The inertial collapse of cavitation bubbles is known to be capable of damaging its surroundings. While significant attention has been dedicated to investigating the pressures produced by this process, less is known about heating of the surrounding medium, which may be important when collapse occurs near objects whose mechanical properties strongly depend on temperature (e.g., polymers). Using a newly developed computational approach that prevents pressure and temperature errors generated by naively implemented shock- and interface-capturing schemes, we investigate the dynamics of shock-induced collapse of gas bubbles near rigid surfaces. We characterize the temperature fields based on the relevant nondimensional parameters entering the problem. In particular, we show that bubble collapse causes temperature rises in neighboring solid objects via two mechanisms: the shock produced at collapse and heat diffusion from the hot bubble close to the object.

  5. Measuring and modeling the bubble population produced by an underwater explosion.

    PubMed

    Holt, Fred D; Lee Culver, R

    2011-11-01

    Underwater explosions have been studied intensively in the United States since 1941 [e.g., R. H. Cole, Underwater Explosions (Princeton University Press, Princeton, NJ, 1945), pp. 3-13]. Research to date has primarily focused on the initial shock and subsequent pressure waves caused by the oscillations of the "gas-globe" resulting from charge detonation. These phenomena have relatively short timescales (typically less than 2 s). However, after the gas-globe rises through the water column and breaks the surface, there remains behind a cloud of bubbles and perhaps debris from the explosion container which has been markedly less studied. A recent experiment measured the spatial and temporal acoustic response of the bubble cloud resulting from a 13.6 kg PBXN-111 charge detonated at 15.2 m (50 ft) depth. A directional projector was used to propagate linear frequency-modulated (5-65 kHz) and 40 kHz tonal pulses through the bubble cloud. Two hydrophone arrays were positioned so as to measure the energy lost in propagating through the bubble cloud. Three methods have been utilized to invert measurements and estimate the bubble population. The bubble population estimates have been used to develop a model for the bubble population resulting from an underwater explosion. PMID:22088003

  6. 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

  7. Quantification of methane bubbles ebullition in freshwater reservoirs of temperate zone using sonar working with 120 kHz frequency

    NASA Astrophysics Data System (ADS)

    Frouzova, Jaroslava; Tuser, Michal; Stanovsky, Petr

    2014-05-01

    During hydroacoustic vertical surveys of fish, an indispensable amount of gas bubbles have been observed rising from the bottom towards the water surface. Unfortunately, the gas ebullition essentially interferes with acoustic detection of fish, thereby biasing an estimate of fish quantity. First, to distinguish between fish and bubble echo, comparing acoustic properties of the echoes (e.g. echo shape, echo width, or phase deviation) seemed to be inapplicable. Nevertheless, the difference in the movement 'behavior' (i.e., direction and speed), looks more promising, but it is necessary to obtain the exact position of a sound beam. Furthermore, in case of shallow waters where a horizontally-oriented beam is usually deployed, the method for distinguishing fish and bubbles with the movement behavior is possible, but more complicated to apply due to the boat motion and a different bubble crossing through a beam (i.e. altering position not in a range domain, but in a phase domain of the beam). Second, when gas bubbles are recognized, a functional regression model of acoustic response to the bubble size can be used to estimate size and volume distribution of bubbles. The experiment with man-made methane bubbles was performed to learn the dependence of acoustic response to the bubble size, and a regression model was created

  8. Gravity driven flows of bubble suspensions.

    NASA Astrophysics Data System (ADS)

    Zenit, Roberto; Koch, Donald L.; Sangani, Ashok K.

    1999-11-01

    Experiments on vertical and inclined channels were performed to study the behavior of a mono-dispersed bubble suspension for which the dual limit of large Reynolds number and small Weber number is satisfied. A uniform stream of 1.5 mm diameter bubbles is produced by a bank of identical capillaries and coalescence is inhibited by addition of salt to the water. Measurements of the liquid velocity and bubble-probe collision rate are obtained with a hot wire anemometer. The gas volume fraction, bubble velocity, velocity variance and chord length are measured using a dual impedance probe. Image analysis is used to quantify the distributions of bubble size and aspect ratio. For vertical channels the bubble velocity is observed to decrease as the bubble concentration increases in accord with the predictions of Spelt and Sangani (1998). The bubble velocity variance arises largely due to bubble-wall and bubble-bubble collisions. For inclined channels, the strength of the shear flow is controlled by the extent of bubble segregation and the effective viscosity of the bubble phase. The measurements are compared with solutions of the averaged equations of motion for a range of gas volume fractions and channel inclination angles.

  9. Aspherical bubble dynamics and oscillation times

    SciTech Connect

    Godwin, R.P.; Chapyak, E.J.; Noack, J.; Vogel, A.

    1999-03-01

    The cavitation bubbles common in laser medicine are rarely perfectly spherical and are often located near tissue boundaries, in vessels, etc., which introduce aspherical dynamics. Here, novel features of aspherical bubble dynamics are explored. Time-resolved experimental photographs and simulations of large aspect ratio (length:diameter {approximately}20) cylindrical bubble dynamics are presented. The experiments and calculations exhibit similar dynamics. A small high-pressure cylindrical bubble initially expands radially with hardly any axial motion. Then, after reaching its maximum volume, a cylindrical bubble collapses along its long axis with relatively little radial motion. The growth-collapse period of these very aspherical bubbles differs only sightly from twice the Rayleigh collapse time for a spherical bubble with an equivalent maximum volume. This fact justifies using the temporal interval between the acoustic signals emitted upon bubble creation and collapse to estimate the maximum bubble volume. As a result, hydrophone measurements can provide an estimate of the bubble energy even for aspherical bubbles. The prolongation of the oscillation period of bubbles near solid boundaries relative to that of isolated spherical bubbles is also discussed.

  10. Bubble Dynamics in Laser Lithotripsy

    NASA Astrophysics Data System (ADS)

    Mohammadzadeh, Milad; Martinez Mercado, Julian; Ohl, Claus-Dieter

    2015-12-01

    Laser lithotripsy is a medical procedure for fragmentation of urinary stones with a fiber guided laser pulse of several hundred microseconds long. Using high-speed photography, we present an in-vitro study of bubble dynamics and stone motion induced by Ho:YAG laser lithotripsy. The experiments reveal that detectable stone motion starts only after the bubble collapse, which we relate with the collapse-induced liquid flow. Additionally, we model the bubble formation and dynamics using a set of 2D Rayleigh-Plesset equations with the measured laser pulse profile as an input. The aim is to reduce stone motion through modification of the temporal laser pulse profile, which affects the collapse scenario and consequently the remnant liquid motion.

  11. Bubbles Responding to Ultrasound Pressure

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The Bubble and Drop Nonlinear Dynamics (BDND) experiment was designed to improve understanding of how the shape and behavior of bubbles respond to ultrasound pressure. By understanding this behavior, it may be possible to counteract complications bubbles cause during materials processing on the ground. This 12-second sequence came from video downlinked from STS-94, July 5 1997, MET:3/19:15 (approximate). The BDND guest investigator was Gary Leal of the University of California, Santa Barbara. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). Advanced fluid dynamics experiments will be a part of investigations plarned for the International Space Station. (435KB, 13-second MPEG, screen 160 x 120 pixels; downlinked video, higher quality not available) A still JPG composite of this movie is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300162.html.

  12. 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 μ<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 μ<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 μ<1 is in disagreement with the usual empirical estimates μ≈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.

  13. Study of Interfacial Structures: Bubbly Flow in 1.27 cm Diameter Pipe

    SciTech Connect

    Paranjape, S.; Kim, S.; Ishii, M.; Uhle, J.

    2002-07-01

    The objective of the present research is to study the flow regime map, the detailed interfacial structures, and the bubble transport in an adiabatic air-water two-phase flow mixture, flowing upward through a vertical round pipe having 1.27 cm. inner diameter. The flow regime map is obtained by processing the characteristic signals acquired from an impedance void meter, using a self-organized neural network. The local two-phase flow parameters are measured by the state-of-the-art four-sensor conductivity probe at three axial locations in the pipe. The measured local parameters include void fraction ({alpha}), interfacial area concentration (a{sub i}), bubble frequency (f{sub b}), bubble velocity (U{sub b}) and bubble Sauter mean diameter (D{sub sm}). The radial profiles of these parameters and their development along the axial direction reveals the structure of the two phase mixture and the bubble interaction mechanisms. (authors)

  14. A generalized bubble diameter correlation for gas-solid fluidized beds

    SciTech Connect

    Horio, M.; Nonaka, A.

    1987-11-01

    A new bubble diameter correlation is derived to predict bubbling characteristics of fluidized beds of varieties of powders. The present model is founded on the postulate that the steady bubble size, which is often called the maximum stable diameter, observed in a bed of Geldart group A powder is formed as a result of an equilibrium of successive coalescence and splitting. For the cases of group B powders the present correlation automatically converges to the conventional correlation. For group A powders the present correlation is validated by comparison with experimental data in the literature. Based on this correlation a theoretical explanation is presented for the fact that the maximum bubble diameters observed were up to 50 to 100 times as large as those from the stable bubble theory.

  15. Bubble Formation and Detachment in Reduced Gravity Under the Influence of Electric Fields

    NASA Technical Reports Server (NTRS)

    Herman, Cila; Iacona, Estelle; Chang, Shinan

    2002-01-01

    The objective of the study is to investigate the behavior of individual air bubbles injected through an orifice into an electrically insulating liquid under the influence of a static electric field. Both uniform and nonuniform electric field configurations were considered. Bubble formation and detachment were recorded and visualized in reduced gravity (corresponding to gravity levels on Mars, on the Moon as well as microgravity) using a high-speed video camera. Bubble volume, dimensions and contact angle at detachment were measured. In addition to the experimental studies, a simple model, predicting bubble characteristics at detachment was developed. The model, based on thermodynamic considerations, accounts for the level of gravity as well as the magnitude of the uniform electric field. Measured data and model predictions show good agreement and indicate that the level of gravity and the electric field magnitude significantly affect bubble shape, volume and dimensions.

  16. Electric Field Effects on an Injected Air Bubble at Detachment in a Low Gravity Environment

    NASA Technical Reports Server (NTRS)

    Iacona, Estelle; Herman, Cila; Chang, Shinan

    2002-01-01

    The objective of the study is to investigate the behavior of individual air bubbles injected through an orifice into an electrically insulating liquid under the influence of a static and uniform electric field. Bubble formation and detachment were visualized and recorded in microgravity using a high-speed video camera. Bubble volume, dimensions and contact angle at detachment were measured. In addition to the experimental studies, a simple model, predicting bubble characteristics at detachment was developed. The model, based on thermodynamic considerations, accounts for the level of gravity as well as the magnitude of the uniform electric field. Measured data and model predictions show good agreement, and indicate that the level of gravity and the electric field magnitude significantly affect bubble shape, volume and dimensions.

  17. Bubble Detachment in Variable Gravity Under the Influence of Electric Fields

    NASA Technical Reports Server (NTRS)

    Herman, Cila; Chang, Shinan; Iacona, Estelle

    2002-01-01

    The objective of the research is to investigate the behavior of individual air bubbles injected through an orifice into an electrically insulating liquid under the influence of a static electric field. Situations were considered with both uniform and nonuniform electric fields. Bubble formation and detachment were visualized in terrestrial gravity as well as for several levels of reduced gravity (lunar, martian and microgravity) using a high-speed video camera. Bubble volume, dimensions and contact angles at detachment were measured. In addition to the experimental studies, a simple model, predicting bubble characteristics at detachment in an initially uniform electric field was developed. The model, based on thermodynamic considerations, accounts for the level of gravity as well as the magnitude of the uniform electric field. The results of the study indicate that the level of gravity and the electric field magnitude significantly affect bubble behavior as well as shape, volume and dimensions.

  18. Phospholipid-coated gas bubble engineering: key parameters for size and stability control, as determined by an acoustical method.

    PubMed

    Rossi, Simona; Waton, Gilles; Krafft, Marie Pierre

    2010-02-01

    We have recently reported the sampling of differently sized monomodal populations of microbubbles from a polydisperse lipid-coated bubble preparation. The microbubbles were coated with dimyristoylphosphatidylcholine (DMPC) and stabilized by perfluorohexane (PFH). Such microbubbles are useful as contrast agents and, potentially, for oxygen, drug, and gene delivery and as therapeutic devices. Monomodal populations of small bubbles (approximately 1.6 microm in radius) and large bubbles (approximately 5.4 microm) have been obtained, as assessed by acoustical measurement, static light scattering, and optical microscopy. In this paper, we have determined the influence of various preparation parameters on the initial size characteristics (mean radius and radii distribution) of the microbubbles and on their stability upon time. The bubble size was determined acoustically, with a homemade acoustic setup equipped with a low-power emitter, to avoid altering the bubble stability. We have focused on the effects of the bubble flotation time during the fractionation process and on the DMPC concentration. PFH was indispensable for obtaining stable bubbles. The nature of the buffer [Isoton II vs N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES)] used as the continuous phase did not significantly impact the bubble characteristics and stability. In both buffers, the half-lives of small bubbles (approximately 1.6 microm in radius in Isoton II and approximately 2.1 microm in HEPES) were found to be longer than those of larger ones (approximately 5.4 and approximately 5.9 microm in Isoton II and HEPES, respectively). The bubble stability study revealed that in both buffers, the average radius of the population of large bubbles progressively increased with time. On the other hand, the average radius of the population of small bubbles decreased slightly in Isoton II and remained constant in HEPES. This suggests that the dissolution behavior of small and large bubbles is governed by different mechanisms. PMID:20099916

  19. Soap Bubbles on a Cold Day.

    ERIC Educational Resources Information Center

    Waiveris, Charles

    1994-01-01

    Discusses the effects of blowing bubbles in extremely cold weather. Describes the freezing conditions of the bubbles and some physical properties. Suggests using the activity with all ages of students. (MVL)

  20. 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.

  1. Interaction of Cavitation Bubbles on Surfaces

    NASA Astrophysics Data System (ADS)

    Arora, Manish

    2005-11-01

    Patterned structures on solid surfaces can be used as controlled nucleation sites for cavitation. Etched micro-pits on hydrophobic solid surfaces trap small amounts of gas during immersion in water, which--when lowering the pressure--serve as bubble nucleus. Using specifically patterned surfaces, the dynamics of a few bubbles with controlled distances is investigated. The temporal evolution of the cavitating bubbles is visualized stroboscopically and with high speed imaging. When the inter-bubble distance is sufficiently small, the bubbles merge through a series of fascinating intermediate 3d shapes. Morover, bubbles on the edge of the pattern `shield' the bubbles inside, thus delaying the collapse of the interior bubbles. The results are reproduced with the help of axis-symmetric boundary integral simulations.

  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. TECHNOLOGY ASSESSMENT OF FINE BUBBLE AERATORS

    EPA Science Inventory

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

  4. 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.

  5. 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.

  6. Ground potential rise monitor

    DOEpatents

    Allen, Zachery W. (Mandan, ND); Zevenbergen, Gary A. (Arvada, CO)

    2012-04-03

    A device and method for detecting ground potential rise (GPR) comprising positioning a first electrode and a second electrode at a distance from each other into the earth. The voltage of the first electrode and second electrode is attenuated by an attenuation factor creating an attenuated voltage. The true RMS voltage of the attenuated voltage is determined creating an attenuated true RMS voltage. The attenuated true RMS voltage is then multiplied by the attenuation factor creating a calculated true RMS voltage. If the calculated true RMS voltage is greater than a first predetermined voltage threshold, a first alarm is enabled at a local location. If user input is received at a remote location acknowledging the first alarm, a first alarm acknowledgment signal is transmitted. The first alarm acknowledgment signal is then received at which time the first alarm is disabled.

  7. Measurement of bubble size in fluidized beds

    SciTech Connect

    Viswanathan, K.; Subba Rao, D.

    1984-07-01

    A simple method is developed to estimate bubble size variation with height in fluidized beds from axial pressure measurements. Experiments are performed and results are presented to indicate the procedure of using the method developed. Bubble sizes thus obtained compare reasonably well with available bubble growth correlations. The present method is expected to be useful for bubble size measurements at high temperatures and pressures and under complex reacting conditions.

  8. Lifetime expectancy for a soap bubble

    NASA Astrophysics Data System (ADS)

    Gilet, Tristan; Scheller, Tom; Vandewalle, Nicolas; Dorbolo, Stephane

    2007-11-01

    Soap bubbles are metastable : drainage and evaporation cause their soapy water skin to thin and eventually to rupture. We have investigated experimentally the maximum lifetime of bubbles as a function of their size. For a large range of sizes, this lifetime is proportional to the bubble radius : small bubbles last shorter than large ones, but their lifetime is more predictable. A model based on lubrication theory is proposed : evaporation is shown to be the key process in determining the maximum lifetime.

  9. Effects of floc and bubble size on the efficiency of the dissolved air flotation (DAF) process.

    PubMed

    Han, Mooyoung; Kim, Tschung-il; Kim, Jinho

    2007-01-01

    Dissolved air flotation (DAF) is a method for removing particles from water using micro bubbles instead of settlement. The process has proved to be successful and, since the 1960s, accepted as an alternative to the conventional sedimentation process for water and wastewater treatment. However, limited research into the process, especially the fundamental characteristics of bubbles and particles, has been carried out. The single collector collision model is not capable of determining the effects of particular characteristics, such as the size and surface charge of bubbles and particles. Han has published a set of modeling results after calculating the collision efficiency between bubbles and particles by trajectory analysis. His major conclusion was that collision efficiency is maximum when the bubbles and particles are nearly the same size but have opposite charge. However, experimental verification of this conclusion has not been carried out yet. This paper describes a new method for measuring the size of particles and bubbles developed using computational image analysis. DAF efficiency is influenced by the effect of the recycle ratio on various average floc sizes. The larger the recycle ratio, the higher the DAF efficiency at the same pressure and particle size. The treatment efficiency is also affected by the saturation pressure, because the bubble size and bubble volume concentration are controlled by the pressure. The highest efficiency is obtained when the floc size is larger than the bubble size. These results, namely that the highest collision efficiency occurs when the particles and bubbles are about the same size, are more in accordance with the trajectory model than with the white water collector model, which implies that the larger the particles, the higher is the collision efficiency. PMID:18048983

  10. Frictional drag reduction by bubble injection

    NASA Astrophysics Data System (ADS)

    Murai, Yuichi

    2014-07-01

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

  11. Acoustic Methods Remove Bubbles From Liquids

    NASA Technical Reports Server (NTRS)

    Trinh, E.; Elleman, D. D.; Wang, T. G.

    1983-01-01

    Two acoustic methods applied to molten glass or other viscous liquids to remove bubbles. Bubbles are either absorbed or brought to surface by applying high-intensity Sonic field at resonant frequency. Sonic oscillation increases surface area of bubbles and causes them to dissipate.

  12. Micro bubble dynamics in DNA solutions

    NASA Astrophysics Data System (ADS)

    Deng, Peigang; Lee, Yi-Kuen; Cheng, Ping

    2004-05-01

    Micro bubble generation and its subsequent dynamic behavior in single-stranded DNA (ssDNA) solutions are presented in this paper. A micro vapor bubble was generated in ssDNA using a micro bubble actuator, which is capable of producing periodic and stable single vapor bubbles under pulse heating. The growth and collapse of the micro vapor bubble were visualized by a high-speed CCD camera, and the bubble dynamics was investigated at different ssDNA concentrations and under various pulse widths. It was observed that an increase in the ssDNA concentration led to an increase of the electric power required for incipient bubble nucleation. Based on thermodynamics considerations and a simple model for nucleus formation in ssDNA solution, an analysis of bubble nucleation work was carried out and the results are consistent with experimental data. It is found that the bubble dynamics in ssDNA solutions is different from that in DI water, and an obvious retardation effect on the motion of the micro bubble was observed at high ssDNA concentrations. Based on Zimm's model, the effect of ssDNA macromolecules on the total viscosity of the solution is revealed. The present study indicates that polymer properties can significantly influence bubble nucleation and the subsequent evolution of bubble dynamics, owing to hydrodynamic intermolecular interactions of polymer macromolecules.

  13. Bubble cluster dynamics in an acoustic field.

    PubMed

    Nasibullaeva, E S; Akhatov, I S

    2013-06-01

    A mathematical model describing dynamics of the cluster of gas bubbles in an acoustic field is presented. According to this model a cluster is considered as a large drop with microbubbles inside. The proposed model is used as a basis (1) for an analytical study of small bubble oscillations in mono- and polydisperse clusters and (2) for numerical investigations of nonlinear bubble oscillations and of the diffusion stability of gas bubbles in the cluster. A synchronization of the collapse phases of bubbles with different radii and collapse intensification for bubbles of one size in the presence of bubbles of other size is found. These effects are explained by the interaction between the bubbles of different radii in the cluster. For the cluster with one radius bubbles the numerical values are obtained for the initial gas concentrations in the liquid at which the bubbles tend to one of two equilibrium states because of rectified diffusion. It is found that the cluster with the bubbles of two different radii tends to become a cluster with the bubbles of one radius due to rectified diffusion. PMID:23742328

  14. Remobilizing the Interfaces of Thermocapillary Driven Bubbles Retarded by the Adsorption of a Surfactant Impurity on the Bubble Surface

    NASA Technical Reports Server (NTRS)

    Palaparthi, Ravi; Maldarelli, Charles; Papageorgiou, Dimitri; Singh, Bhim S. (Technical Monitor)

    2000-01-01

    Thermocapillary migration is a method for moving bubbles in space in the absence of buoyancy. A temperature gradient is applied to the continuous phase in which a bubble is situated, and the applied gradient impressed on the bubble surface causes one pole of the drop to be cooler than the opposite pole. As the surface tension is a decreasing function of temperature, the cooler pole pulls at the warmer pole, creating a flow which propels the bubble in the direction of the warmer fluid. A major impediment to the practical use of thermocapillarity to direct the movement of bubbles in space is the fact that surfactant impurities which are unavoidably present in the continuous phase can significantly reduce the migration velocity. A surfactant impurity adsorbed onto the bubble interface is swept to the trailing end of the bubble. When bulk concentrations are low (which is the case with an impurity), diffusion of surfactant to the front end is slow relative to convection, and surfactant collects at the back end of the bubble. Collection at the back lowers the surface tension relative to the front end setting up a reverse tension gradient. For buoyancy driven bubble motions in the absence of a thermocapillarity, the tension gradient opposes the surface flow, and reduces the surface and terminal velocities (the interface becomes more solid-like). When thermocapillary forces are present, the reverse tension gradient set up by the surfactant accumulation reduces the temperature tension gradient, and decreases to near zero the thermocapillary velocity. The objective of our research is to develop a method for enhancing the thermocapillary migration of bubbles which have been retarded by the adsorption onto the bubble surface of a surfactant impurity, Our remobilization theory proposes to use surfactant molecules which kinetically rapidly exchange between the bulk and the surface and are at high bulk concentrations. Because the remobilizing surfactant is present at much higher concentrations than the impurity, it adsorbs to the bubble much faster than the impurity when the bubble is formed, and thereby prevents the impurity from adsorbing onto the surface. In addition the rapid kinetic exchange and high bulk concentration maintain a saturated surface with a uniform surface concentrations. This prevents retarding surface tension gradients and keeps the velocity high. In our first report last year, we detailed experimental results which verified the theory of remobilization in ground based experiments in which the steady velocity of rising bubbles was measured in a continuous phase consisting of a glycerol/water mixture containing a polyethylene glycol surfactant C12E6 (CH3(CH2)11(OCH2CH2)6OH). In our report this year, we detail our efforts to describe theoretically the remobilization observed. We construct a model in which a bubble rises steadily by buoyancy in a continuous (Newtonian) viscous fluid containing surfactant with a uniform far field bulk concentration. We account for the effects of inertia as well as viscosity in the flow in the continuous phase caused by the bubble motion (order one Reynolds number), and we assume that the bubble shape remains spherical (viscous and inertial forces are smaller than capillary forces, i e. small Weber and capillary numbers). The surfactant distribution is calculated by solving the mass transfer equations including convection and diffusion in the bulk, and finite kinetic exchange the bulk and the surface. Convective effects dominate diffusive mass transfer in the bulk of the liquid (high Peclet numbers) except in a thin boundary layer near the surface. A finite volume method is used to numerically solve the hydrodynamic and mass transfer equations on a staggered grid which accounts specifically for the thin boundary layer. We present the results of the nondimensional drag as a function of the bulk concentration of surfactant for different rates of kinetic exchange, from which we develop criteria for the concentration necessary to develop a prescribed degree of remobilization. The criteria compare favorably with the experimental results.

  15. 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.

  16. The penetration of acoustic cavitation bubbles into micrometer-scale cavities.

    PubMed

    Vaidya, Haresh Anant; Ertunç, Özgür; Lichtenegger, Thomas; Delgado, Antonio; Skupin, Andreas

    2016-04-01

    The penetration of acoustically induced cavitation bubbles in micrometer-scale cavities is investigated experimentally by means of high-speed photography and acoustic measurements. Micrometer-scale cavities of different dimensions (width=40μm, 80μm, 10mm and depth=50μm) are designed to replicate the cross section of microvias in a PCB. The aim here is to present a method for enhancing mass transfer due to the penetration of bubbles in such narrow geometries under the action of ultrasound. The micrometer-scale cavities are placed in a test-cell filled with water and subjected to an ultrasound excitation at 75kHz. A cavitation bubble cluster is generated at the mouth of the cavity which acts as a continuous source of bubbles that penetrate into the cavity. The radial oscillation characteristics and translation of these bubbles are investigated in detail here. It is observed that the bubbles arrange themselves into streamer-like structures inside the cavity. Parameters such as bubble population and size distribution and their correlation with the phase of the incident ultrasound radiation are investigated in detail here. This provides a valuable insight into the dynamics of bubbles in narrow confined spaces. Mass transfer investigations show that fresh liquid can be continuously introduced in the cavities under the action of ultrasound. Our findings may have important consequences in optimizing the filling processes for microvias with high aspect ratios. PMID:26763751

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

    NASA Astrophysics Data System (ADS)

    Stephens, James

    2005-11-01

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

  18. Bubble-crystal aggregates promote magma chamber overturn in arc crust

    NASA Astrophysics Data System (ADS)

    Edmonds, M.; Woods, A. W.; Humphreys, M.

    2014-12-01

    Bubble nucleation in melts occurs preferentially on the surfaces of crystals. Of all phases in oxidized melts, magnetite is most favorable for the heterogeneous nucleation of bubbles owing to the high wetting angles at the bubble-crystal-melt interface. Preservation of such relationships in erupted rocks however, is rare owing to overprinting by decompression-induced degassing, shear and bubble detachment during magma ascent. We present evidence from basaltic enclaves preserved in andesite lavas from Soufriere Hills Volcano, Montserrat, for a spatial association between magnetite and bubbles that we propose is a relict of the bubble nucleation process at depth. The existence of bubble-crystal aggregates means that magnetite crystals will tend to sink more slowly, and bubbles will rise less fast than for the case of single crystals and bubbles. The behavior of bubble-crystal aggregates will be dependent on their bulk density, which depends on the relative proportion by mass of the magnetite and the bubble and the pressure. In deeper chambers, the smaller mass of exsolved volatiles leads to the prediction that many of the bubble-crystal aggregates are dense and so fall to base of the chamber (and the bubbles are wholly or partially resorbed). In shallower chambers, however, the larger volume and mass of exsolved volatiles would tend to promote buoyant aggregate formation. The presence of the aggregates has implications for the mixing/mingling process when mafic magmas underplate crystal-rich evolved magma bodies in the arc crust. For shallow magma chambers the buoyancy of the aggregates in the underplating mafic magma will either cause vapor accumulation at the magma interface and the formation of mafic inclusions rich in magnetite; or the enhanced density of the aggregates may promote magma chamber overturn and mixing of mafic magmas into the andesites bodies. Both processes may be important over different spatial and time-scales. The overturn mechanism may explain the hybrid features of the andesite, including the presence of cryptic mafic components, reverse zoning of phenocrysts and how volatiles might be sourced from the mafic magmas and distributed within andesite bodies.

  19. THE YOUNG INTERSTELLAR BUBBLE WITHIN THE ROSETTE NEBULA

    SciTech Connect

    Bruhweiler, F. C.; Bourdin, M. O.; Gull, T. R. E-mail: theodore.r.gull@nasa.go

    2010-08-20

    We use high-resolution International Ultraviolet Explorer (IUE) data and the interstellar (IS) features of highly ionized Si IV and C IV seen toward the young, bright OB stars of NGC 2244 in the core of the Rosette Nebula to study the physics of young IS bubbles. Two discrete velocity components in Si IV and C IV are seen toward stars in the 6.2 pc radius central cavity, while only a single velocity component is seen toward those stars in the surrounding H II region, at the perimeter and external to this cavity. The central region shows characteristics of a very young, windblown bubble. The shell around the central hot cavity is expanding at 56 km s{sup -1} with respect to the embedded OB stars, while the surrounding H II region of the Rosette is expanding at {approx}13 km s{sup -1}. Even though these stars are quite young ({approx}2-4 Myr), both the radius and expansion velocity of the 6.2 pc inner shell point to a far younger age; t{sub age} {approx} 6.4 x 10{sup 4} years. These results represent a strong contradiction to theory and present modeling, where much larger bubbles are predicted around individual O stars and O associations. Specifically, the results for this small bubble and its deduced age extend the 'missing wind luminosity problem' to young evolving bubbles. These results indicate that OB star winds mix the surrounding H II regions and the wind kinetic energy is converted to turbulence and radiated away in the dense H II regions. These winds do not form hot, adiabatically expanding cavities. True IS bubbles appear only to form at later evolutionary times, perhaps triggered by increased mass loss rates or discrete ejection events. Means for rectifying discrepancies between theory and observations are discussed.

  20. 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. This work was funded by the Los Alamos LDRD program.

  1. Electrolysis Bubbles Make Waterflow Visible

    NASA Technical Reports Server (NTRS)

    Schultz, Donald F.

    1990-01-01

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

  2. 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.

  3. Models of cylindrical bubble pulsation

    PubMed Central

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

    2012-01-01

    Three models are considered for describing the dynamics of a pulsating cylindrical bubble. A linear solution is derived for a cylindrical bubble in an infinite compressible liquid. The solution accounts for losses due to viscosity, heat conduction, and acoustic radiation. It reveals that radiation is the dominant loss mechanism, and that it is 22 times greater than for a spherical bubble of the same radius. The predicted resonance frequency provides a basis of comparison for limiting forms of other models. The second model considered is a commonly used equation in Rayleigh-Plesset form that requires an incompressible liquid to be finite in extent in order for bubble pulsation to occur. The radial extent of the liquid becomes a fitting parameter, and it is found that considerably different values of the parameter are required for modeling inertial motion versus acoustical oscillations. The third model was developed by V. K. Kedrinskii [Hydrodynamics of Explosion (Springer, New York, 2005), pp. 2326] in the form of the Gilmore equation for compressible liquids of infinite extent. While the correct resonance frequency and loss factor are not recovered from this model in the linear approximation, it provides reasonable agreement with observations of inertial motion. PMID:22978863

  4. Bubble-driven inertial micropump

    NASA Astrophysics Data System (ADS)

    Torniainen, Erik D.; Govyadinov, Alexander N.; Markel, David P.; Kornilovitch, Pavel E.

    2012-12-01

    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 principles of the pump, a phenomenological one-dimensional model is developed and solved. A linear array of micropumps has been built using silicon-SU8 fabrication technology that is used to manufacture thermal inkjet printheads. Semi-continuous pumping across a 2 mm-wide channel has been demonstrated experimentally. Measured net flow with respect to viscosity variation is in excellent agreement with simulation results.

  5. The Coming Law School Bubble

    ERIC Educational Resources Information Center

    Krauss, Michael I.

    2011-01-01

    In this article, the author explains how forty years of politicized hiring in the law schools has left its destructive mark. The results are potentially catastrophic: Market forces and internal law school policies may be combining to produce a legal education bubble the likes of which the country has never seen. (Contains 11 footnotes.)

  6. LRL 25-inch Bubble Chamber

    DOE R&D Accomplishments Database

    Alvarez, L. W.; Gow, J. D.; Barrera, F.; Eckman, G.; Shand, J.; Watt, R.; Norgren, D.; Hernandez, H. P.

    1964-07-08

    The recently completed 25-inch hydrogen bubble chamber combines excellent picture quality with a fast operating cycle. The chamber has a unique optical system and is designed to take several pictures each Bevatron pulse, in conjunction with the Bevatron rapid beam ejection system.

  7. Tharsis Rise Graben

    NASA Technical Reports Server (NTRS)

    2002-01-01

    (Released 22 May 2002) The Science This image is located in the northwestern portion of the Tharsis Rise at about 12 N and 125 W (235 E). What is immediately noticeable in this image is the series of linear features that are called graben. These features are associated with crustal extension which results in a series of up and down blocks of crust that run perpendicular to the direction of the extension. Images of Mars have shown a large number of these tectonic features concentrated on or near the Tharsis region. The Tharsis region is an enormous bulge that causes major tectonic disruptions across the planet when it tries to settle down from its height and reach equilibrium with the rest of the planet. The graben in this image display a number of preferential directions indicating that the crustal stresses that caused the graben have changed over time. By examining the cross-cutting relationships between the features, it is possible to reassemble the history of the area. The Story Now, if you thought that Mars was almost perfectly round, think again! The red planet has a large bulge sticking out from it called Tharsis. Almost 3,000 miles across, this enormous region rises almost four miles above the average radius of the planet. That's quite a bulge! Since Tharsis the land of the largest volcanoes in the solar system, it may have been formed by both the uplift of land from tectonic action and the build-up of lava flows. Tharsis can cause some pretty major tectonic disruptions across the planet when it tries to settle down from its height and reach a better equilibrium with the rest of the planet. In this image, located in the northwestern portion of the Tharsis Rise, a whole lot of lowered features stripe the landscape. They are called grabens, and formed when the crust of the planet was stretched tectonically. This kind of crustal extension (or stretching) tends to form a series of up-and-down blocks of crust that run perpendicular to the direction of the crustal extension. And that's what we see here. Since the streaks (or grabens) in this image aren't all perfectly aligned, that means that the crustal stresses and their directions have changed over time. And there's another history to be followed here too. Take a look at how some of the grabens cut across others. Those that cross on top of others had to have formed after the ones underneath. By looking at all of the crosscutting relationships, geologists can build up a pretty accurate record of which stresses happened first, next, and last. On Earth, a similar series of rift valleys (grabens) formed by crustal extension too. The East African Rift System began forming almost 30 million years ago due to volcanic activity that also created most of the high peaks in East Africa, including the famous Kilimanjaro. This African peak is so high it always has snow on top of it, even though it's located right near the equator. That height might remind you of the towering Martian volcanoes in Tharsis. The East African Rift Valley System also formed over large domes that were created as hot molten material beneath the Earth's surface welled up, pushing up the crust and causing it to expand and stretch. This stretching caused the rift valleys (grabens) to appear here on our own planet.

  8. Tiny Bubbles in my BEC

    SciTech Connect

    Blinova, Alina A.

    2012-08-01

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

  9. Bubble-size distributions produced by wall injection of air into flowing freshwater, saltwater and surfactant solutions

    NASA Astrophysics Data System (ADS)

    Winkel, Eric S.; Ceccio, Steven L.; Dowling, David R.; Perlin, Marc

    2004-12-01

    As air is injected into a flowing liquid, the resultant bubble characteristics depend on the properties of the injector, near-wall flow, and flowing liquid. Previous research has shown that near-wall bubbles can significantly reduce skin-friction drag. Air was injected into the turbulent boundary layer on a test section wall of a water tunnel containing various concentrations of salt and surfactant (Triton-X-100, Union Carbide). Photographic records show that the mean bubble diameter decreased monotonically with increasing salt and surfactant concentrations. Here, 33 ppt saltwater bubbles had one quarter, and 20 ppm Triton-X-100 bubbles had one half of the mean diameter of freshwater bubbles.

  10. 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.

  11. Weak waves in multifractional liquids with bubbles

    NASA Astrophysics Data System (ADS)

    Gubaidullin, D. A.; Nikiforov, A. A.; Gafiyatov, R. N.

    2016-01-01

    The propagation of weak waves in multifractional mixtures of liquid with vapor-gas and gas bubbles of different sizes and different compositions with phase transitions is studied. The dispersed phase consists of N+M fractions having various gases in bubbles and different in the bubbles radii. Phase transitions accounted for N fractions. The total bubble volume concentration is small (less than 1%). The dispersion relation is derived and dispersion curves is built. Influence of the mass concentration is shown. It is shown that dispersion and dissipation of acoustic waves depends significantly on presence of different bubbles in fractions of the dispersed phase.

  12. 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.

  13. Mesoporous hollow spheres from soap bubbling.

    PubMed

    Yu, Xianglin; Liang, Fuxin; Liu, Jiguang; Lu, Yunfeng; Yang, Zhenzhong

    2012-02-01

    The smaller and more stable bubbles can be generated from the large parent bubbles by rupture. In the presence of a bubble blowing agent, hollow spheres can be prepared by bubbling a silica sol. Herein, the trapped gas inside the bubble acts as a template. When the porogen, i.e., other surfactant, is introduced, a mesostructured shell forms by the co-assembly with the silica sol during sol-gel process. Morphological evolution emphasizes the prerequisite of an intermediate interior gas flow rate and high exterior gas flow rate for hollow spheres. The method is valid for many compositions from inorganic, polymer to their composites. PMID:22078340

  14. Slurry Bubble Column Reactor Optimization (book chapter)

    SciTech Connect

    Gamwo, I.K.; Gidaspow, D.; Jung, J.

    2007-03-01

    Slurry bubble column reactors (SBCR) are the preferred contactors for the conversion of syngas to fules and chemicals partially due to their superior heat and mass transfer characteristics. The multiphase fluid dynamics in these systems greatly affect the reactor volumetric productivity. Here, we have developed a computational fluid dynamics (CFD) assisted design methodology for searching the optimum particle size for maximum production in a SBCR. Reactor optimization due to heat exchanger configuration was also investigated. We have rearranged the heat exchangers in a SBCR and constructed a CFD model for a baffled reactor. The novel arrangement of the exchangers prevents the unfavorable high catalysts concentration at the lower stage of the reactor. Thus an optimum catalyst concentration is maintained during the course of the production of liquid fuels.

  15. The production of drops by the bursting of a bubble at an air liquid interface

    NASA Technical Reports Server (NTRS)

    Darrozes, J. S.; Ligneul, P.

    1982-01-01

    The fundamental mechanism arising during the bursting of a bubble at an air-liquid interface is described. A single bubble was followed from an arbitrary depth in the liquid, up to the creation and motion of the film and jet drops. Several phenomena were involved and their relative order of magnitude was compared in order to point out the dimensionless parameters which govern each step of the motion. High-speed cinematography is employed. The characteristic bubble radius which separates the creation of jet drops from cap bursting without jet drops is expressed mathematically. The corresponding numerical value for water is 3 mm and agrees with experimental observations.

  16. Analysis of energies of stationary bubbles at liquid pool surfaces and the subsequent droplet release due to bubble burst based on RESUS code calculations

    SciTech Connect

    Starflinger, J.; Koch, M.K.; Brockmeier, U.; Unger, H.; Schuetz, W.

    1996-08-01

    In case of a hypothetical nuclear reactor accident involving a failure of the primary system, a liquid coolant pool may frequently be formed, which may be contaminated by suspended or solved fuel particles and fission products. For many accident sequences, in which gas is injected into the liquid domain or bubbles are generated by means of heating, pressure transients or chemical reactions, the release of low volatile species from liquid surfaces into a gas atmosphere due to bubble burst is identified as a decisive release mechanism. Generally, resuspension of radioactive species is caused by droplets ejected from the pool surface into the atmosphere, either dominated by direct momentum exchange mechanisms between gas flow and liquid for high gas fluxes or by bursting of single bubbles in case of low gas fluxes. In the latter case, the release of droplets containing radionuclides is governed by two mechanisms, namely micro-droplet generation due to bubble film cap collapse and formation and subsequent disintegration of liquid jets producing so-called jet droplets. Jet and jet droplet formation is modeled in the code system RESUS.MOD2 which contains models for the growth of the bubble in the pool, its shape while resting at the liquid surface, and jet and jet-droplet generation after bubble cap rupture. Using the module BUBSHAPE (BUBbleSHAPE) of the RESUS code, the characteristic profile of a bubble resting at the liquid surface as well as the mechanical energies available for droplet formation and consequently droplet- and particle release can be determined. The governing resuspension energies are identified to be the surface energy, the energy stored in the gas within the bubble due to its excess pressure, and the potential energy due to the displacement of liquid.

  17. 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.

  18. Acoustic wave equation in a bubbly liquid

    NASA Astrophysics Data System (ADS)

    Miao, Boya; An, Yu

    2015-10-01

    In certain cases, a bubbly liquid may be treated as a two-phase fluid mixture, in which acoustic waves can be described by a linear wave equation using the speed of sound in the two-phase fluid mixture. However, when there is appreciable acoustically driven bubble oscillation, treatment of the two-phase fluid mixture becomes inaccurate. A more accurate description of acoustic waves in bubbly liquids should combine the nonlinear wave equation with an equation describing the dynamics of bubble oscillation. As an example, we investigate the case of an ultrasonic wave in water passing through a bubbly liquid layer. For intense ultrasonic waves or bubbly liquids with high number density of bubble, significant differences are found between the results obtained with the different methods.

  19. Bidirectional cinematography of steam-bubble growth

    SciTech Connect

    Deason, V.A.; Reynolds, L.D.

    1982-01-01

    Single steam bubbles were generated in superheated water in an optical cell. The growth process of the bubbles was recorded with a high-speed motion picture camera at 5000 and 10,000 frames per second. A technique was developed to simultaneously image two orthogonal views of the bubbles on each frame of film. The vertical and horizontal diameters of the bubbles were measured on a frame-by-frame basis, and the data analyzed to determine oscillatory frequencies. The analysis also attempted to determine whether the bubbles were undergoing volumetric oscillations during early growth or whether simple surface wave/rotational behavior caused the observed periodic variations in bubble dimensions. For the bubbles studied, typical oscillation frequencies for the diameters were in the range of 100 to 500 Hz.

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

    NASA Astrophysics Data System (ADS)

    Lakshmanan, Peter; Ehrhard, Peter

    2008-11-01

    Disperse gas bubbles play an important role in many industrial applications. Knowing the rising velocity, the interfacial area, or the critical size for break-up or coalescence in different systems can be crucial for the process design. Hence, knowing the fundamental behaviour of a single bubble appears mandatory for the examination of bubble swarms and for the Euler-Lagrange or Euler--Euler modelling of disperse systems. In the present work a level--set--based volume--tracking method is implemented into the CFD--code OpenFOAM to follow the free interface of a single bubble. The volume-tracking method is coupled with a transport model for surfactants on the interface, including adsorption and desorption processes. The dependency of surface tension on the local surfactant concentration on the interface is modelled by a non-linear (Langmuir) equation of state. Marangoni forces, resulting from surface tension gradients, are included. The rise of a single air bubble (i) in pure water and (ii) in the presence of surfactants of different strengths is simulated. The results show good agreement with available (experimental and theoretical) correlations from literature.

  1. Generation of Bubbly Suspensions in Low Gravity

    NASA Technical Reports Server (NTRS)

    Nahra, Henry K.; Hoffmann, Monica I.; Hussey, Sam; Bell, Kimberly R.

    2000-01-01

    Generation of a uniform monodisperse bubbly suspension in low gravity is a rather difficult task because bubbles do not detach as easily as on Earth. Under microgravity, the buoyancy force is not present to detach the bubbles as they are formed from the nozzles. One way to detach the bubbles is to establish a detaching force that helps their detachment from the orifice. The drag force, established by flowing a liquid in a cross or co-flow configuration with respect to the nozzle direction, provides this additional force and helps detach the bubbles as they are being formed. This paper is concerned with studying the generation of a bubbly suspension in low gravity in support of a flight definition experiment titled "Behavior of Rapidly Sheared Bubbly Suspension." Generation of a bubbly suspension, composed of 2 and 3 mm diameter bubbles with a standard deviation <10% of the bubble diameter, was identified as one of the most important engineering/science issues associated with the flight definition experiment. This paper summarizes the low gravity experiments that were conducted to explore various ways of making the suspension. Two approaches were investigated. The first was to generate the suspension via a chemical reaction between the continuous and dispersed phases using effervescent material, whereas the second considered the direct injection of air into the continuous phase. The results showed that the reaction method did not produce the desired bubble size distribution compared to the direct injection of bubbles. However, direct injection of air into the continuous phase (aqueous salt solution) resulted in uniform bubble-diameter distribution with acceptable bubble-diameter standard deviation.

  2. Polydispersed solids behavior in a bubble column. [Slurry bubble columns

    SciTech Connect

    Smith, D.N.; Ruether, J.A.; Stiegel, G.J.

    1984-01-01

    New data and theory are presented for describing polydispersed solids in slurry bubble columns. Axial solids concentration distributions were measured in a 0.108-m-ID slurry bubble column apparatus operated at steady-state conditions. Slurry and gas superficial velocities ranged from 0.007 to 0.02 m/s and 0.03 to 0.20 m/s, respectively. The liquid phase was water and the solid phase consisted of binary or ternary mixtures of narrow-sized fractions of glass spheres. The experimental data have been used to develop a method for predicting average solids loadings and axial distributions of solids in a bubble column with a one-dimensional sedmentation-dispersion model. Correlations are given for the hindered settling velocity, the solids dispersion coefficient, and the solids concentration at the top and bottom of the column. The effect of a distribution of particle size is interpreted by summation of the concentration of solids for each discrete particle size fraction. 12 refs., 13 figs.

  3. The role of bubble ascent in magma mixing

    NASA Astrophysics Data System (ADS)

    Wiesmaier, Sebastian; Morgavi, Daniele; Perugini, Diego; De Campos, Cristina; Hess, Kai-Uwe; Lavalle, Yan; Dingwell, Donald B.

    2013-04-01

    Understanding the processes that affect the rate of liquid state homogenization provides fundamental clues on the otherwise inaccessible subsurface dynamics of magmatic plumbing systems. Compositional heterogeneities detected in the matrix of magmatic rocks represent the arrested state of a chemical equilibration. Magmatic homogenization is divided into a) the mechanical interaction of magma batches (mingling) and b) the diffusive equilibration of compositional gradients, where diffusive equilibration is exponentially enhanced by progressive mechanical interaction [1]. The mechanical interaction between two distinct batches of magma has commonly been attributed to shear and folding movements between two distinct liquids. A mode of mechanical interaction scarcely invoked is the advection of mafic material into a felsic one through bubble motion. Yet, experiments with analogue materials demonstrated that bubble ascent has the potential to enhance the fluid mechanical component of magma mixing [2]. Here, we present preliminary results from bubble-advection experiments. For the first time, experiments of this kind were performed using natural materials at magmatic temperatures. Cylinders of Snake River Plain (SRP) basalt were drilled with a cavity of defined volume and placed underneath cylinders of SRP rhyolite. Upon melting, the gas pocket (=bubble) trapped within the cavity, rose into the rhyolite, and thus entraining a portion of basaltic material in the shape of a plume trail. These plume-like structures that the advected basalt formed within the rhyolite were characterized by microCT and subsequent high-resolution EMP analyses. Single protruding filaments at its bottom end show a composite structure of many smaller plume tails, which may indicate the opening of a preferential pathway for bubbles after a first bubble has passed. The diffusional gradient around the plume tail showed a progressive evolution of equilibration from bottom to top of the plume tail. Calculating the normalised variance provides an efficient statistical measure of the diffusion rate of cations at the interface of ambient rhyolite and basaltic plume tail. Bubble ascent provides an efficient mechanism for advection of contrasting melt compositions, independent from Rayleigh-Taylor instabilities [cf. 2], or convection induced by overpressure of rising magma. Interaction of volatile-bearing magmas may thus be enhanced at saturation of one or two end-members by buoyant forces exerted from free fluid phases. Future strategies involve to hone down tolerances in the experimental setup to minimise extraneous bubbles, achieve fluid dynamical constraints on the ascent of bubbles in basalt. [1] De Campos, C., D. Perugini, W. Ertel-Ingrisch, D. Dingwell, and G. Poli (2011), Enhancement of magma mixing efficiency by chaotic dynamics: an experimental study, Contrib. Mineral. Petrol. , 161(6), 863-881. [2] Thomas, N., S. Tait, and T. Koyaguchi (1993), Mixing of stratified liquids by the motion of gas bubbles: application to magma mixing, Earth Planet. Sci. Lett. , 115(1-4), 161-175.

  4. Sensitivity study of Bubble diameter for prediction of flow pattern in homogeneous bubble column regime

    NASA Astrophysics Data System (ADS)

    Pourtousi, M.; Ganesan, P.; Sahu, J. N.; Redzwan, Ghufran

    2015-09-01

    Determining the bubble diameter size in a bubble column rector plays an important role to accurately predict flow pattern in a bubble column reactor. This paper employs the Eulerian-Eulerian method to numerically investigate the sensitivity study of bubble diameter size in a cylindrical bubble column reactor. Existing experimental results in the literature are used to validate the implementation of the proposed numerical method. In our simulation various bubble diameter size (i.e., 35.5mm) are used to find an appropriate bubble size inside the bubble column when the regime is homogeneous (superficial gas velocity = 0.005m/s). The result shows that bubble diameter 4mm is a reasonable size for flow pattern prediction inside the column.

  5. Suppression of cavitation inception by gas bubble injection: a numerical study focusing on bubble-bubble interaction.

    PubMed

    Ida, Masato; Naoe, Takashi; Futakawa, Masatoshi

    2007-10-01

    The dynamic behavior of cavitation and gas bubbles under negative pressure has been studied numerically to evaluate the effect of gas bubble injection into a liquid on the suppression of cavitation inception. In our previous studies, it was demonstrated by direct observation that cavitation occurs in liquid mercury when mechanical impacts are imposed, and this will cause cavitation damage in spallation neutron sources, in which liquid mercury is bombarded by a high-power proton beam. In the present paper, we describe numerical investigations of the dynamics of cavitation bubbles in liquid mercury using a multibubble model that takes into account the interaction of a cavitation bubble with preexisting gas bubbles through bubble-radiated pressure waves. The numerical results suggest that, if the mercury includes gas bubbles whose equilibrium radius is much larger than that of the cavitation bubble, the explosive expansion of the cavitation bubble (i.e., cavitation inception) is suppressed by the positive-pressure wave radiated by the injected bubbles, which decreases the magnitude of the negative pressure in the mercury. PMID:17995108

  6. Plasma bubbles in the topside ionosphere: estimations of the survival possibilities

    NASA Astrophysics Data System (ADS)

    Sidorova, Larisa; Filippov, Sergey

    The study deals with the evaluation of the survival possibilities of the plasma bubbles, seen as He+ density depletions in the topside ionosphere. He+ density depletions (or subtroughs) are usually observed during a high solar activity at the topside ionospheric altitudes ( 1000 km) deeply inside the plasmasphere (L 1.3-3). They are considered as originating from equatorial plasma bubbles phenomena or as possible fossil bubble signatures. The estimation of the characteristic times of a life, diffusion and vertical drift transport of helium ions (He+ ) at the topside ionosphere heights of the low-/mid-latitude region was made. It is revealed, that the diffusion transport process is the fastest one (some minutes). Since the ionosphere plasma is magnetized plasma at the topside ionosphere heights, the diffusion processes are field-aligned. Plasma bubbles spread (due to diffusion processes) along the magnetic tubes. Their spreading becomes more and more significant in process of their uplifting. So extended bubbles look like `banana' with the extremities reaching the ionosphere heights in both the hemispheres. This scheme is also correct if the separate components are under considerations, namely He+ . On the other hand, it is well known, that the magnetic tube, partially "devastated" by a plasma bubble, is replenished extremely slowly. The tube replenishment time is proportionally L4 (i.e. Badin, JATP, 1994). For example, it takes 10 hours for refilling the tube (L=2, 45o INVLAT), partially "devastated" or depleted by plasma bubble. It was concluded, that, if some plasma bubbles can reach the topside and plasmashere heights, they can exist here (may be as "dead" bubbles) during some hours. It was also concluded, that there is enough time to register the plasma bubbles at the topside ionosphere heights.

  7. Analysis of small bubbles in glass by glow discharge--time-of-flight mass spectrometry.

    PubMed

    Gonzlez Gago, C; Pereiro, R; Bordel, N; Mazn Ramos, P; Tempez, A; Sanz-Medel, A

    2009-10-12

    The chemical reactions occurring during the glass manufacturing processes can give rise to small bubbles, damaging the required glass properties. To avoid eventual bubbles formation, the chemical composition of the bubbles should be known to trace back the gas sources and take appropriate corrective actions. Mass spectrometry is a most adequate detection technique for such purpose due to its ability to provide the required information in a short time. Analysis of these small bubbles in glass requires a system incorporating a very small volume (for a fast evacuation of the entire line and low dilution of the analytes) and a fast mass analyser allowing the quasi-simultaneous detection of the whole spectral interval of interest, such as a time-of-flight mass spectrometer (TOFMS). In this work, the analytical potential of a radiofrequency glow discharge (rf-GD) coupled to a TOFMS was evaluated for the first time for the analysis of bubbles in glasses. The operating conditions of the rf-GD (pressure and applied power) were optimized by introducing into the system known volumes of air. Detection limits in the order of nL were obtained for molecular nitrogen, oxygen and carbon dioxide. Finally, a stainless steel bellows valve was modified to serve as glass breaker for the sampling process. This valve was connected on-line to the mass spectrometer inlet line and proved to be most appropriate for the analysis of the gaseous content of bubbles (with diameters below 0.5mm) entrapped in industrial glasses. PMID:19786192

  8. 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.

  9. Sonoporation from Jetting Cavitation Bubbles

    PubMed Central

    Ohl, Claus-Dieter; Arora, Manish; Ikink, Roy; de Jong, Nico; Versluis, Michel; Delius, Michael; Lohse, Detlef

    2006-01-01

    The fluid dynamic interaction of cavitation bubbles with adherent cells on a substrate is experimentally investigated. We find that the nonspherical collapse of bubbles near to the boundary is responsible for cell detachment. High-speed photography reveals that a wall bounded flow leads to the detachment of cells. Cells at the edge of the circular area of detachment are found to be permanently porated, whereas cells at some distance from the detachment area undergo viable cell membrane poration (sonoporation). The wall flow field leading to cell detachment is modeled with a self-similar solution for a wall jet, together with a kinetic ansatz of adhesive bond rupture. The self-similar solution for the ?-type wall jet compares very well with the full solution of the Navier-Stokes equation for a jet of finite thickness. Apart from annular sites of sonoporation we also find more homogenous patterns of molecule delivery with no cell detachment. PMID:16950843

  10. Numerical simulation of dielectric bubbles coalescence under the effects of uniform magnetic field

    NASA Astrophysics Data System (ADS)

    Hadidi, Amin; Jalali-Vahid, Davood

    2015-11-01

    In this research, the co-axial coalescence of a pair of gas bubbles rising in a viscous liquid column under the effects of an external uniform magnetic field is simulated numerically. Considered fluids are dielectric, and applied magnetic field is uniform. Effects of different strengths of magnetic field on the interaction of in-line rising bubbles and coalescence between them were investigated. For numerical modeling of the problem, a computer code was developed to solve the governing equations which are continuity, Navier-Stokes equation, magnetic field equation and level set and reinitialization of level set equations. The finite volume method is used for the discretization of the continuity and momentum equations using SIMPLE scheme where the finite difference method is used to discretization of the magnetic field equations. Also a level set method is used to capture the interface of two phases. The results are compared with available numerical and experimental results in the case of no-magnetic field effect which show a good agreement. It is found that uniform magnetic field accelerates the coalescence of the bubbles in dielectric fluids and enhances the rise velocity of the coalesced bubble.

  11. Origin of Corona-Dominated Topographic Rises on Venus

    NASA Technical Reports Server (NTRS)

    Smrekar, S.; Stofan, E.

    1999-01-01

    Both large-scale mantel upwellings, comparable to terrestrial hotspots on Earth, and smaller scale mantel upwellings, known as coronae, occur on Venus. Corona-dominated rises have many of the characteristics of large scale mantle upwellings, or hotspots, such as broad topographic rises greater than 1000km in diameter and large positive gravity anomalies.

  12. 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.

  13. Bubbling phenomena of biharmonic maps

    NASA Astrophysics Data System (ADS)

    Nakauchi, Nobumitsu; Urakawa, Hajime

    2015-12-01

    In this paper, by using Moser's iteration technique, we will show that every sequence in the totality of biharmonic maps between two compact Riemannian manifolds (M, g) and (N, h) with m-energies (m = dim M ? 3) and L2-norm of the tension fields which are bounded above by any positive constant C, causes the bubbling phenomena, which is a generalization of the one for harmonic maps.

  14. Equations of spatial hydrodynamic interaction of weakly nonspherical gas bubbles in liquid in an acoustic field

    NASA Astrophysics Data System (ADS)

    Davletshin, A. I.; Khalitova, T. F.

    2016-01-01

    A mathematical model of spatial hydrodynamic interaction of gas bubbles in liquid in an acoustic field taking into account small deformations of their surfaces is proposed. It is a system of ordinary differential equations of the second order in radii of the bubbles, the position vectors of their centers and the amplitudes of deviation of their shape from the spherical one in the form of spherical harmonics. The equations derived are of the first order of accuracy in A / R and of the fourth order in R / D, where R is the characteristic radius of the bubbles, A is the amplitude of characteristic deviation of their surface from the spherical one in the form of spherical harmonics, D is the characteristic distance between bubbles. The derivation of the equations is carried out by the method of spherical functions with the use of the Bernoulli integral, the kinematic and dynamic boundary conditions on the surface of the bubbles. The effects of viscosity and compressibility of the liquid are considered approximately, the gas in the bubbles is assumed homobaric.

  15. Unsteady thermocapillary migration of bubbles

    NASA Technical Reports Server (NTRS)

    Dill, Loren H.; Balasubramaniam, R.

    1988-01-01

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

  16. Bioinspired bubble design for particle generation

    PubMed Central

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

    2012-01-01

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

  17. Bioinspired bubble design for particle generation.

    PubMed

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

    2012-02-01

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

  18. Soap bubbles in paintings: Art and science

    NASA Astrophysics Data System (ADS)

    Behroozi, F.

    2008-12-01

    Soap bubbles became popular in 17th century paintings and prints primarily as a metaphor for the impermanence and fragility of life. The Dancing Couple (1663) by the Dutch painter Jan Steen is a good example which, among many other symbols, shows a young boy blowing soap bubbles. In the 18th century the French painter Jean-Simeon Chardin used soap bubbles not only as metaphor but also to express a sense of play and wonder. In his most famous painting, Soap Bubbles (1733/1734) a translucent and quavering soap bubble takes center stage. Chardin's contemporary Charles Van Loo painted his Soap Bubbles (1764) after seeing Chardin's work. In both paintings the soap bubbles have a hint of color and show two bright reflection spots. We discuss the physics involved and explain how keenly the painters have observed the interaction of light and soap bubbles. We show that the two reflection spots on the soap bubbles are images of the light source, one real and one virtual, formed by the curved surface of the bubble. The faint colors are due to thin film interference effects.

  19. Excitation of nanoscale vapor bubbles at the surface of gold nanoparticles in water

    SciTech Connect

    Kotaidis, V.; Dahmen, C.; Plessen, G. von; Springer, F.; Plech, A.

    2006-05-14

    Intense nonequilibrium femtosecond laser excitation of gold nanoparticles in water leads to a transient heating of the nanoparticles, which decays via heat transfer to the water phase. It is shown that the water temperature rises to near the critical temperature and the water undergoes an explosive evaporation in the subnanosecond range. The formation of vapor bubbles shows a threshold dependence on laser fluence. The nascent nanoscale vapor bubbles change the heat dissipation drastically. The nanoscale structure is resolved directly with a combination of