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1

Measurements of Bubble Rise Characteristics in Various Temperatures and Liquid Velocities  

SciTech Connect

Single bubble rise characteristics in turbulent flow in a vertical circular pipe were experimentally observed. As a result, it was found that bubble rise velocity relative to the time averaged local liquid velocity decreases with the increase of liquid flowrate and that it also decreases with the decrease of the distance between a bubble and wall. Investigating the mechanisms of the reductions of relative velocity, new correlations were developed for accurately evaluating the bubble rise velocities in turbulent flow. Since the predicted bubble rise velocities reasonably agreed with the measured data, the new correlations could contribute to the improvement of bubbly flow calculations in nuclear reactor safety analysis. (authors)

Kazuhiro Torimoto; Masanori Nishiura; Tomoe Tanaka; Tomio Okawa; Isao Kataoka [Osaka University, 1-1, Yamadaoka, Suita-shi, Osaka, 5650871 (Japan)

2002-07-01

2

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

SciTech Connect

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

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

1999-10-01

3

An Experimental Investigation of Bubble Rise Characteristics in a Crystal Suspended Non-Newtonian Fluid  

NASA Astrophysics Data System (ADS)

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.

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

2008-07-01

4

Modelling of Air Bubble Rising in Water and Polymeric Solution  

NASA Astrophysics Data System (ADS)

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.

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

2010-06-01

5

Cusped Bubbles Rising through Polyelectrolyte Solutions  

NASA Astrophysics Data System (ADS)

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.

Belmonte, Andrew; Sostarecz, Michael

2000-11-01

6

Single Rising Bubble Motion in Aqueous Solution of Electrolyte  

NASA Astrophysics Data System (ADS)

Effects of electrolytes on bubble coalescence are investigated experimentally from fluid dynamic point of view. Collisions of a bubble with free surface in two kinds of liquids, namely, ultrapure water and sodium chloride solution, are observed using a high speed camera. It is found that the repetitive number of bubble bounces on a free surface in electrolyte solution is larger than that in ultrapure water when the equivalent bubble radii are the same. This result qualitatively shows that electrolyte works to prevent bubbles from coalescing. It is also revealed that the bubbles can coalesce if their Weber numbers, which are based on the radius of curvature of the front side of the bubble and the approach velocity just before the collision with the free surface, are less than a critical Weber number. Furthermore, the critical Weber number decreases with the increase in the concentration of the electrolyte solutions despite the fluid dynamic characteristics, such as bubble rise velocity and bubble shape, are not affected by the addition of the electrolytes. It is concluded that Weber number is the most important parameter to specify the effects of electrolytes on bubble coalescence.

Sato, Ayaka; Aoki, Masumi; Watanabe, Masao

7

Freon bubble rise measurements in a vertical rectangular duct  

Microsoft Academic Search

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

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

1995-01-01

8

Evolution of energy in flow driven by rising bubbles  

NASA Astrophysics Data System (ADS)

We investigate by direct numerical simulations the flow that rising bubbles cause in an originally quiescent fluid. We employ the Eulerian-Lagrangian method with two-way coupling and periodic boundary conditions. In order to be able to treat up to 288000 bubbles, the following approximations and simplifications had to be introduced, as done before, e.g., by Climent and Magnaudet, Phys. Rev. Lett. 82, 4827 (1999). (i) The bubbles were treated as point particles, thus (ii) disregarding the near-field interactions among them, and (iii) effective force models for the lift and the drag forces were used. In particular, the lift coefficient was assumed to be 1/2, independent of the bubble Reynolds number and the local flow field. The results suggest that large-scale motions are generated, owing to an inverse energy cascade from the small to the large scales. However, as the Taylor-Reynolds number is only in the range of 1, the corresponding scaling of the energy spectrum with an exponent of -5/3 cannot develop over a pronounced range. In the long term, the property of local energy transfer, characteristic of real turbulence, is lost and the input of energy equals the viscous dissipation at all scales. Due to the lack of strong vortices, the bubbles spread rather uniformly in the flow. The mechanism for uniform spreading is as follows. Rising bubbles induce a velocity field behind them that acts on the following bubbles. Owing to the shear, those bubbles experience a lift force, which makes them spread to the left or right, thus preventing the formation of vertical bubble clusters and therefore of efficient forcing. Indeed, when the lift is artificially put to zero in the simulations, the flow is forced much more efficiently and a more pronounced energy that accumulation at large scales (due to the inverse energy cascade) is achieved.

Mazzitelli, Irene M.; Lohse, Detlef

2009-06-01

9

Cell death from bursting bubbles: role of cell attachment to rising bubbles in sparged reactors.  

PubMed

Bursting bubbles are thought to be the dominant cause of cell death in sparged animal or insect cell cultures. Cells that die during the bubble burst can come from three sources: cells suspended near the bubble; cells trapped in the bubble lamella; and cells that attached to the rising bubble. This article examines cell attachment to rising bubbles using a model in which cell attachment depends on cell radius, bubble radius, and cell-bubble attachment time. For bubble columns over 1 m in height and without protective additives, the model predicts significant attachment for 0.5- to 3-mm radius bubbles, but no significant attachment in the presence of protective additives. For bubble columns over 10 cm in height, and without protective additives, the model predicts significant attachment for 50- to 100-micron radius bubbles, but not all protective additives prevent attachment for these bubbles. The model is consistent with three sets of published data and with our experimental results. Using hybridoma cells, serum-free medium with antifoam, and 1.60 +/- 0.05 mm (standard error) radius bubbles, we measured death rates consistent with cell attachment to rising bubbles, as predicted by the model. With 1.40 +/- 0.05 mm (SE) radius bubbles and either 0.1% w/v Pluronic-F68 or 0.1% w/v methylcellulose added to the medium, we measured death rates consistent with no significant cell attachment to rising bubbles, as predicted by the model. PMID:9921156

Meier, S J; Hatton, T A; Wang, D I

1999-02-20

10

Experimental study on wake structure of single rising clean bubble  

NASA Astrophysics Data System (ADS)

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.

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

2007-11-01

11

Freon bubble rise measurements in a vertical rectangular duct  

SciTech Connect

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.

Vassallo, P.F.; Symolon, P.D.; Moore, W.E.; Trabold, T.A. [Knolls Atomic Power Lab., Schenectady, NY (United States)

1995-12-01

12

Correlation of bubble rise velocity and volume  

SciTech Connect

This project was conducted at Westinghouse's Savannah River Laboratories (SRL). The goal of SRL is to make certain that the modifications on the reactor are safe for those working at the plant as well as the general public. One of the steps needed to insure safety is the knowledge of the occurrences that result from a plenum pipe breakage. When a plenum pipe breaks, two things occur: air is sucked into the pipe and is trapped in the cooling water; and water used to cool the fuel rods is lost. As a result of these occurrences, the water is slowed down by both the loss in water pressure and the upward force of air bubbles pushing against the downward force of the water. The project required the conducting of tests to find the bubble velocity in an annular ribbed pipe filled with stagnant water. This document discusses the methodology and results of this testing.

Burge, C.

1991-01-01

13

Correlation of bubble rise velocity and volume  

SciTech Connect

This project was conducted at Westinghouse`s Savannah River Laboratories (SRL). The goal of SRL is to make certain that the modifications on the reactor are safe for those working at the plant as well as the general public. One of the steps needed to insure safety is the knowledge of the occurrences that result from a plenum pipe breakage. When a plenum pipe breaks, two things occur: air is sucked into the pipe and is trapped in the cooling water; and water used to cool the fuel rods is lost. As a result of these occurrences, the water is slowed down by both the loss in water pressure and the upward force of air bubbles pushing against the downward force of the water. The project required the conducting of tests to find the bubble velocity in an annular ribbed pipe filled with stagnant water. This document discusses the methodology and results of this testing.

Burge, C.

1991-12-31

14

Dynamics of single rising bubbles in a liquid-solid system  

NASA Astrophysics Data System (ADS)

While the dynamics of single rising gas bubbles in clear liquids has been studied extensively, the dynamics of bubbles in liquid-solid slurries containing small particles ( ds< 100?m ) is not yet well understood. We have investigated the rise characteristics of single gas bubbles (=3mm) in a neutrally buoyant suspension of Polystyrene particles ( = 78±5.79 ?m) in a glycerol-water mixture. Using a four-point optical probe we have obtained information on the bubble motion and shape in the slurry. The velocity of single bubbles, rising at terminal velocity through the suspension, slightly decreases with increasing solids volume fraction; this was accompanied by a change in the shape of the bubbles from oblate ellipsoidal to nearly spherical. The viscosity and the surface tension of the liquid in the presence of suspended particles were also measured. Our results show that the viscosity was almost doubled with a 20% increase in the solids volume fraction. We found that the rise velocity of a bubble in the slurry is close to that in a pseudo-single phase liquid with the same viscosity and surface tension.

Hooshyar, Nasim; Mudde, Robbert F.; Hamersma, Peter J.; Sundaresan, Sankaran; Ruud van Ommen, J.

2011-11-01

15

Dynamics of homogeneous bubbly flows Part 1. Rise velocity and microstructure of the bubbles  

Microsoft Academic Search

Direct numerical simulations of the motion of up to 216 three-dimensional buoyant bubbles in periodic domains are presented. The full Navier Stokes equations are solved by a parallelized finite-difference\\/front-tracking method that allows a deformable interface between the bubbles and the suspending fluid and the inclusion of surface tension. The governing parameters are selected such that the average rise Reynolds number

Bernard Bunner; Grétar Tryggvason

2002-01-01

16

The velocity of gas bubble rise in a tube  

NASA Astrophysics Data System (ADS)

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

Zudin, Yu. B.

2013-03-01

17

Advances in the Rising Bubble Technique for discharge measurement  

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

18

Effect of rise distance on droplets generated from bubble bursting on the surface of chromic acid solutions.  

PubMed

In the processes of chromium electroplating, bursting bubbles are the major sources of chromium droplets that may lead to nasal septum disorders among workers. The gas bubbles form as a result of electrochemical reactions on the surfaces of pieces being plated, rise through the liquid, and then burst into droplets at liquid surfaces. The dimensions of the pieces being plated differ from piece to piece, and therefore the rise distance of the bubbles varies. This study is aimed at evaluating the effect of rise distance on the characteristics of droplets generated from bubbles bursting on the surface of chromic acid solutions by an experimental bubbling system. Two rise distances, 15 and 30 cm, were tested. An aerodynamic particle sizer was used to determine the droplet size distribution over the range of 0.8-30 microm. A Marple personal impactor was employed to collect droplet samples on polyvinyl chloride filters for Cr(VI) analysis. It was found that the Cr(VI) concentrations in droplets increased when the bubble rise distance increased. The result suggests that soluble ions such as Cr(VI) are scavenged by rising bubbles. PMID:11843427

Kuo, Yu-Mei; Wang, Chiu-Sen

2002-01-01

19

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

Microsoft Academic Search

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

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

2006-01-01

20

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

21

Rise velocities and gas–liquid mass transfer of bubbles in organic solutions  

Microsoft Academic Search

Bubble size, shape, rise velocity and liquid side mass transfer coefficient have been experimentally determined for bubbles rising in organic systems, consisting of single or mutually soluble components, namely: alkanes (n-dodecane, n-hexadecane), alcohols (ethanol, 1-butanol, 1-octanol) and mixtures thereof. For pure solvents (alkanes and alcohols alike), it was found that the bubbles are non-spherical, and that both the rise velocity

Rocio Maceiras; Rui Santana; Sebastião S. Alves

2007-01-01

22

Effects of Turbulence and Containing Wall on Rise Velocities of Single Bubbles in a Vertical Circular Pipe  

SciTech Connect

Experiments were conducted to clarify the single bubble rise characteristics in turbulent flows in vertical flow channels. It was revealed that the rise velocity of a bubble relative to the time-averaged local liquid velocity could be much smaller in turbulent up-flows than in stagnant liquids. The reduction of relative velocity was estimated to be caused by the two factors: turbulence in continuous phase and steep velocity gradient near wall; new correlations for describing these two effects were proposed. The relative velocity between the phases significantly affects the lateral phase distribution in multidimensional simulation of bubbly two-phase flow and the present correlations can give reasonable predictions for the relative velocity in turbulent flow. It is hence expected that the new correlations can contribute to the further improvement of the simulation models of bubbly two-phase flows. (authors)

Tomio Okawa; Kazuhiro Torimoto; Masanori Nishiura; Isao Kataoka [Osaka University, 1-1, Yamadaoka, Suita-shi, Osaka, 5650871 (Japan); Michitsugu Mori [Tokyo Electric Power Company, Incorporated, 1-3, Uchisaiwai-cho 1-chome, Chiyoda-ku, Tokyo, 1008560 (Japan)

2002-07-01

23

Rise velocity of an air bubble in porous media: Theoretical studies  

Microsoft Academic Search

The rise velocity of injected air phase from the injection point toward the vadose zone is a critical factor in in-situ air sparging operations. It has been reported in the literature that air injected into saturated gravel rises as discrete air bubbles in bubbly flow of air phase. The objective of this study is to develop a quantitative technique to

M. Yavuz Corapcioglu; Abdullah Cihan; Mirna Drazenovic

2004-01-01

24

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

Microsoft Academic Search

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

R. M. Davies; Geoffrey Taylor

1950-01-01

25

Mass transfer of a rising bubble in molten glass with instantaneous oxidation–reduction reaction  

Microsoft Academic Search

The mass transfer around a rising bubble has been studied within the field of glass melting processes. Due to the large value of liquid viscosity, creeping flow was used. The rising bubble is assumed to have a clean interface with a total mobility and the exact solution of Hadamard or Rybczynski was used to define the velocity field around the

F. Pigeonneau

2009-01-01

26

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)

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.

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

2010-09-01

27

Behavior of bubbles in glassmelts. III - Dissolution and growth of a rising bubble containing a single gas  

NASA Technical Reports Server (NTRS)

Finite difference solutions of the mass transport equations governing the dissolution (growth) of a rising gas bubble, containing a single gas, in a glassmelt were obtained. These solutions were compared with those obtained from an approximate procedure for a range of the controlling parameters. Applications were made to describe various aspects of O2 and CO2 gas-bubble behavior in a soda-lime-silicate melt.

Onorato, P. I. K.; Weinberg, M. C.; Uhlmann, D. R.

1981-01-01

28

The local measurement of the size and velocity of bubbles rising in liquids  

Microsoft Academic Search

An experimental study of the rise of small air bubbles (0.1 to 1.0 mm in diameter) in a quiescent pool is described. Local measurements of rise velocity were obtained as a function of height above the source nozzle using a laser-Doppler method. In addition, the bubble diameter was determined simultaneously from the same optical signals. Data are presented for various

W. W. Martin; G. M. Chandler

1982-01-01

29

Suspension viscosity and bubble rise velocity in liquid-solid fluidized beds  

Microsoft Academic Search

The effective viscosity which characterizes the pseudo-homogeneous property of the liquid-solid suspension in gas-liquid-solid fluidization is examined in light of the velocity of single bubbles rising through the suspension. Experiments conducted in this study cover a wide range of bubble diameters (2–23 mm) under high solids holdup (0.48 – 0.57) conditions. The study reveals that the liquid-solid medium exhibits a

Katsumi Tsuchiya; Akihiko Furumoto; Liang-Shih Fan; Jianping Zhang

1997-01-01

30

The effect of surfactant on long bubbles rising in vertical capillary tubes  

NASA Astrophysics Data System (ADS)

In this letter we investigate the effect of interfacial surfactant on the motion of an air bubble rising in a vertical capillary tube filled with a viscous fluid and sealed at one end. A thin layer of liquid, with almost constant thickness b, exists between the bubble interface and the tube wall. The fluid displaced by the front meniscus flows down through this layer because the tube is sealed far up at the top. The steady rising velocity U of the bubble is related to the thickness b. An upper bound for U is obtained in terms of b and other physical data of the problem, which is in good agreement with previous experimental results. It is proved here analytically that the presence of surfactant on the bubble interface causes a thinning and a delay effect: the thickness of the liquid layer behind the bubble and the rise velocity of the bubble are smaller than those for the 'clean' case. Exactly the opposite effect of surfactant in the horizontal case has been derived analytically by Daripa and Pasa (2010 J. Stat. Mech. L02002) and numerically by Ratulowski and Chang (1990 J. Fluid Mech. 210 303). These effects of interfacial surfactant are consistent with previous experimental and numerical results.

Daripa, Prabir; Pa?a, Gelu

2011-02-01

31

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

SciTech Connect

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.

Kamath, C; Gezahegne, A; Miller, P

2007-10-30

32

Analytical solution of the problem of the rise of a Taylor bubble  

NASA Astrophysics Data System (ADS)

In the classical works of Prandtl and Taylor devoted to the analysis of the problem of the rise of a Taylor bubble in a round tube, a solution of the Laplace equation is used, which contains divergent infinite series. The present paper outlines a method for the correct analysis of the mentioned problem. Using the method of superposition of ``elementary flows,'' a solution was obtained for flow of an ideal fluid over a body of revolution in a pipe. Satisfying the free surface condition in the vicinity of the stagnation point and using the limiting transition with respect to the main parameter lead to the relation for the rise velocity of a Taylor bubble expressed in terms of the Froude number. In order to validate the method of superposition, it was applied to the problem of the rise of a plane Taylor bubble in a flat gap, which also has an exact analytical solution obtained with the help of the complex variable theory.

Zudin, Yuri B.

2013-05-01

33

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

NASA Technical Reports Server (NTRS)

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.

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

1984-01-01

34

Why a falling drop does not in general behave like a rising bubble  

PubMed Central

Is a settling drop equivalent to a rising bubble? The answer is known to be in general a no, but we show that when the density of the drop is less than 1.2 times that of the surrounding fluid, an equivalent bubble can be designed for small inertia and large surface tension. Hadamard's exact solution is shown to be better for this than making the Boussinesq approximation. Scaling relationships and numerical simulations show a bubble-drop equivalence for moderate inertia and surface tension, so long as the density ratio of the drop to its surroundings is close to unity. When this ratio is far from unity, the drop and the bubble are very different. We show that this is due to the tendency for vorticity to be concentrated in the lighter fluid, i.e. within the bubble but outside the drop. As the Galilei and Bond numbers are increased, a bubble displays underdamped shape oscillations, whereas beyond critical values of these numbers, over-damped behavior resulting in break-up takes place. The different circulation patterns result in thin and cup-like drops but bubbles thick at their base. These shapes are then prone to break-up at the sides and centre, respectively.

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

2014-01-01

35

Why a falling drop does not in general behave like a rising bubble  

NASA Astrophysics Data System (ADS)

Is a settling drop equivalent to a rising bubble? The answer is known to be in general a no, but we show that when the density of the drop is less than 1.2 times that of the surrounding fluid, an equivalent bubble can be designed for small inertia and large surface tension. Hadamard's exact solution is shown to be better for this than making the Boussinesq approximation. Scaling relationships and numerical simulations show a bubble-drop equivalence for moderate inertia and surface tension, so long as the density ratio of the drop to its surroundings is close to unity. When this ratio is far from unity, the drop and the bubble are very different. We show that this is due to the tendency for vorticity to be concentrated in the lighter fluid, i.e. within the bubble but outside the drop. As the Galilei and Bond numbers are increased, a bubble displays underdamped shape oscillations, whereas beyond critical values of these numbers, over-damped behavior resulting in break-up takes place. The different circulation patterns result in thin and cup-like drops but bubbles thick at their base. These shapes are then prone to break-up at the sides and centre, respectively.

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

2014-04-01

36

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

SciTech Connect

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.

Kreischer, B.E.

1989-01-01

37

Modelling of floc-bubble aggregate rise rates in dissolved air flotation.  

PubMed

The use of relatively simple, but conceptually sound mathematical models, is a powerful tool to identify and understand parameters that are critical to a process. In this paper, a model is presented which addresses the rise rate of floc-bubble aggregates in the DAF separation zone. The model uses Stoke's Law as a point of departure, which is then progressively extended to incorporate the non-sphericity of the aggregates, the non-laminar nature of their movement, the fractal nature of the flocs, the physical constraints of attaching bubbles to a floc, and the limit on bubble numbers imposed by a typical air dosing system. The main findings are: There are two distinctly different DAF domains, namely a small floc domain and a large floc domain. In the small floc domain, the bubble size, the air volume, chemical dosing and the degree of flocculation have to be optimized and accurately controlled, while the large floc domain is less sensitive to these parameters. The calculated rise rates are significantly lower than some of the latest pilot testing results reported from the USA; a surprising finding at first. There are, however, numerous modelling simplifications that may explain this discrepancy. The most probable reasons are the further agglomeration of the aggregates in the separation zone due to differential rise rates or the recirculating flow within the white-water blanket, and the complex and poorly understood flow patterns within the separation zone. PMID:11394271

Haarhoff, J; Edzwald, J K

2001-01-01

38

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

NASA Astrophysics Data System (ADS)

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

Zenit, Roberto; Magnaudet, Jacques

2008-06-01

39

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

Microsoft Academic Search

The conditions for which the paths of freely rising bubbles become oscillatory are studied experimentally using silicone oils with viscosities ranging from 0.5 to 9.4 times that of water. Since these fluids are nonpolar, as opposed to water, the gas-liquid interfaces remain clean without the need of an ultrapure environment. We find the Reynolds number at incipient transition to vary

Roberto Zenit; Jacques Magnaudet

2008-01-01

40

The terminal rise velocity of 10–100 ?m diameter bubbles in water  

Microsoft Academic Search

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 ?m. 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.

Luke Parkinson; Rossen Sedev; Daniel Fornasiero; John Ralston

2008-01-01

41

Bubbly flow model for the dynamic characteristics of cavitating pumps  

Microsoft Academic Search

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

Christopher Brennen

1978-01-01

42

Improvement of the Bubble Rise Velocity Model in the Pressurizer Using ALMOD 3 Computer Code to Calculate Evaporation.  

National Technical Information Service (NTIS)

An improvement is studied for the calculation of bubble rise velocity, by adding two different ways to estimate this velocity, one of which is more adequate to pressures normally found in the reactor cooling system. Additionally, a limitation in bubble ri...

A. A. Madeira

1985-01-01

43

A mass-conserving axisymmetric multiphase lattice Boltzmann method and its application in simulation of bubble rising  

NASA Astrophysics Data System (ADS)

In many lattice Boltzmann studies about bubble rising, mass conservation is not satisfactory and the terminal bubble rising shape or velocity is not so consistent with experimental data as those obtained through other CFD techniques. In this paper, based on the multiphase model (He et al., 1999 [1]), a mass-conserving axisymmetric multiphase lattice Boltzmann model is developed. In the model, a mass correction step and an effective surface tension formula are introduced into the model. We demonstrate how the macroscopic axisymmetric Cahn-Hilliard equation and Navier-Stokes equation are recovered from the lattice Boltzmann equations through Chapman-Enskog expansion. The developed model is applied to simulate the bubble rising in viscous fluid. The mass correction step in our scheme significantly improves the bubble mass conservation. The surface tension calculation successfully predicts the terminal bubble shapes and reproduces the effect of initial bubble shape. The terminal bubble rising velocities are very consistent with experimental and numerical data in the literature. Qualitatively, the wakes behind the bubbles also agree well with experimental data. This model is useful for predicting the axisymmetric two-phase flows.

Huang, Haibo; Huang, Jun-Jie; Lu, Xi-Yun

44

Effect of Rise Distance on Droplets Generated from Bubble Bursting on the Surface of Chromic Acid Solutions  

Microsoft Academic Search

In the processes of chromium electroplating, bursting bubbles are the major sources of chromium droplets that may lead to nasal septum disorders among workers. The gas bubbles form as a result of electrochemical reactions on the surfaces of pieces being plated, rise through the liquid, and then burst into droplets at liquid surfaces. The dimensions of the pieces being plated

Yu-Mei Kuo; Chiu-Sen Wang

2002-01-01

45

Studies in vacuum degassing: Mass and momentum transfer to gas bubbles rising in melts, the freeboard of which is evacuated  

Microsoft Academic Search

A mathematical formulation is presented describing the growth of gas bubbles rising in melts, the freeboard of which is evacuated.\\u000a A novel aspect of the paper is that in the statement of the problem account is taken of the role played by liquid inertia\\u000a and surface kinetics in limiting the growth rate and affecting the rising velocity of the bubble.

J. Szekely; S. D. Fang

1974-01-01

46

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

SciTech Connect

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.

Dabas, R.S.; Reddy, B.M. (National Physical Laboratory, New Delhi (India))

1990-04-01

47

Modeling radiation characteristics of semitransparent media containing bubbles or particles.  

PubMed

Modeling of radiation characteristics of semitransparent media containing particles or bubbles in the independent scattering limit is examined. The existing radiative properties models of a single particle in an absorbing medium using the approaches based on (1) the classical Mie theory neglecting absorption by the matrix, (2) the far field approximation, and (3) the near field approximation are reviewed. Comparison between models and experimental measurements are carried out not only for the radiation characteristics but also for hemispherical transmittance and reflectance of porous fused quartz. Large differences are found among the three models predicting the bubble radiative properties when the matrix is strongly absorbing and/or the bubbles are optically large. However, these disagreements are masked by the matrix absorption during calculation of radiation characteristics of the participating medium. It is shown that all three approaches can be used for radiative transfer calculations in an absorbing matrix containing bubbles. PMID:16783428

Randrianalisoa, Jaona; Baillis, Dominique; Pilon, Laurent

2006-07-01

48

REMARKS ABOUT GAS BUBBLE CHAMBER CHARACTERISTICS  

Microsoft Academic Search

The effect of ionizing radiation on strongly supersaturated gas--liquid ; solutions has been observed by the Genoa research group during the Spring of 1958. ; The group established, in a first approximation, the conditions which the gas--; liquid systems must satisfy in order to turn this effect into formation of bubble ; tracks along the ionizing path. Some of the

P. E. Argan; A. Gigli; E. Picasso; G. Tomasini; L. Gonella

1959-01-01

49

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

PubMed Central

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

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

2009-01-01

50

Analysis of Temperature Rise Induced by High-Intensity Focused Ultrasound in Tissue-Mimicking Gel Considering Cavitation Bubbles  

NASA Astrophysics Data System (ADS)

High-intensity focused ultrasound (HIFU) causes a selective temperature rise in tissue and is used as a noninvasive method for tumor treatment. However, there is a problem in that it typically takes several hours to treat a large tumor. The development of a highly efficient method is required to shorten the treatment time. It is known that cavitation bubbles generated by HIFU enhance HIFU heating. In this study, the enhancement of the heating effect by cavitation was estimated in a numerical simulation solving a bio-heat transfer equation (BHTE) by increasing the absorption coefficients in and out of the volume of cavitation bubbles. The absorption coefficients were obtained by a curve fitting the temperature rise near the focal point between experiment and simulation. The results show that cavitation bubbles caused the increase in ultrasonic absorption not only in but also near the volume of cavitation bubbles.

Asai, Ayumu; Okano, Hiroki; Yoshizawa, Shin; Umemura, Shin-ichiro

2013-07-01

51

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

SciTech Connect

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.

Kocamustafaogullari, G.; Chan, S.H.

1980-06-01

52

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

NASA Astrophysics Data System (ADS)

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

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

2006-12-01

53

Use of the Bubble Rise Model in the Simulation of the Pressurizer in ALMOD 3 Computer Code.  

National Technical Information Service (NTIS)

The implementation of the bubble rise model in the ALMOD 3 computer code to simulate the pressurizer of a nuclear power plant is presented. Some transients for Angra I were calculated and results obtained from the original and modified models were compare...

A. A. Madeira C. T. M. Camargo

1984-01-01

54

Prediction of micro-bubble dissolution characteristics in water and seawater  

SciTech Connect

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)

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

2009-07-15

55

Measurements of radiation characteristics of fused quartz containing bubbles.  

PubMed

We report experimental measurement of radiation characteristics of fused quartz containing bubbles over the spectral region from 1.67 to 3.5 microm. The radiation characteristics were retrieved by an inverse method that minimizes the quadratic difference between the measured and the calculated spectral bidirectional transmittance and reflectance for different sample thicknesses. The theoretical spectral transmittances and reflectances were computed by solving the one-dimensional radiative transfer equation by the discrete-ordinates method for a nonemitting, homogeneous, and scattering medium. The results of the inversion were shown to be independent of the sample thickness for samples thicker than 3 mm and clearly demonstrate that bubbles have an effect on the radiation characteristics of fused quartz. PMID:14725407

Baillis, Dominique; Pilon, Laurent; Randrianalisoa, Harifidy; Gomez, Rafael; Viskanta, Raymond

2004-01-01

56

Measurements of the rise velocities of bubbles, slugs and pressure waves in a gas-solid fluidized bed using pressure fluctuation signals  

Microsoft Academic Search

The rise velocities of bubbles, slugs and pressure waves in a fluidized bed have been measured on-line through the use of pressure transducers coupled with the cross-correlation technique. Sand and glass beads with different particle sizes were tested. Effects of the gas flow rate and column diameter on the rise velocities of bubbles and slugs were investigated. The results were

L. T. Fan; Tho-Ching Ho; W. P. Walawender

1983-01-01

57

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

SciTech Connect

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.

Kocamustafaogullari, G.; Chan, S.H.

1980-01-01

58

Study on the viscosity properties of bubbly oil and the static characteristics of journal bearing lubricated with bubbly oil  

Microsoft Academic Search

A new device, rotatory viscometer, for measuring viscosity of bubbly oil was proposed. Using this device, a new viscosity model, which is better than the others in many aspects was established. By the new model, a numerical method for studying the influences of bubbly oil on static characteristics of the journal bearing, which were verified by use of the remade

An Qi; Zhou Yinsheng; Quan Yongxin

1997-01-01

59

Mixing in a swarm of bubbles rising in a confined cell measured by mean of PLIF with two different dyes  

NASA Astrophysics Data System (ADS)

The present contribution reports an experimental study of the mixing of a passive scalar of very low diffusivity in a homogeneous swarm of inertial bubbles rising in a thin gap. A patch of fluorescent dye is injected within the swarm, and we observe the evolution of its mass in a given region of observation. We analyse the effect of the liquid agitation on the mixing mechanisms varying the gas volume fraction from 1.3 to 7.5 %, while the Reynolds number of the bubbles, Re = 450, their Weber number, We = 0.7, and the gap-to-bubble diameter ratio, w/ d = 0.25, are kept approximately constant. Here, the in-plane local mass of dye is measured by using a two-dyes planar laser-induced fluorescence (PLIF) technique that has been adapted to fix the problem of multiple light reflections at the bubble interfaces. Indeed, they induce both temporal and spatial variations of the captured light intensity that are superimposed to the effective fluorescence signal and prevent from using a standard PLIF technique. The analysis of the instantaneous concentration fields reveals the dominant role of the bubble wakes in the scalar transport. It is shown that mixing in this planar confined geometry is very efficient and enhanced by the increasing gas volume fraction. The present study also highlights that the mixing is not governed by a Fickian law of diffusion.

Bouche, Emmanuella; Cazin, Sébastien; Roig, Véronique; Risso, Frédéric

2013-06-01

60

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

NASA Astrophysics Data System (ADS)

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".

Fan, Wenyuan; Yin, XiaoHong

2014-06-01

61

Bubbly flow model for the dynamic characteristics of cavitating pumps  

NASA Technical Reports Server (NTRS)

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.

Brennen, C.

1978-01-01

62

Path instablity of a rising bubble: Shape matters, Reynolds number doesn't!  

NASA Astrophysics Data System (ADS)

The conditions for the transition to zigzagging trajectories for freely ascending bubbles were studied experimentally. To avoid surface contamination, we used silicon oils with shear viscosities ranging from 1.7 to 9.4 times that of water. Since these fluids are non-polar, as opposed to the case of water, the gas-liquid interfaces remain clean without the need of an ultra-pure environment. Using a 30 cm height cylindrical container, the shape and trajectory of millimetric-sized air bubbles were filmed with a high-speed camera. We found that the most important parameter for the transition from a rectilinear to a zigzagging trajectory is the bubble aspect ratio and not so much the Reynolds number. We found that the Reynolds number at incipient transition varied from 85 to 250, for decreasing liquid viscosity. Correspondingly, the bubble aspect ratio remained relatively constant ranging from 2.23 to 2.11 for the same set of conditions. Since vorticity at the bubble surface is almost independant of the Reynolds number and mostly depends on the bubble shape in the parameter range covered by our experiments, these results support the idea that surface vorticity, which in turn causes the wake to become unstable, is the principal cause for the transition to a oscillatory trajectory, as recently discussed by Magnaudet and Mougin (2007).

Zenit, Roberto; Magnaudet, Jacques

2007-11-01

63

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)

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.

Ortiz-Villafuerte, Javier

64

Bubbles  

NSDL National Science Digital Library

Learners engage in a scientific investigation to answer the question, "Are free-floating bubbles always round?" By experimenting with different-shaped bubble wands and then reading a nonfiction book to support their findings, learners collect evidence to answer the question and then share their findings with others by creating a poster.

Morgan, Emily; Ansberry, Karen

2007-01-01

65

Characteristic Timescales of Shoreface Response to Sea-Level Rise  

NASA Astrophysics Data System (ADS)

On open ocean, wave-dominated, sandy coasts, the response of the shore to sea-level rise is dominated not by inundation, but rather by the dynamic response of sediment transport processes to perturbations of the sea level. In a regime of sea level change, the predominant response of the wave-dominated shoreface depends upon the time-dependent response of the shoreface itself to changes in sea level as well as the potential changes to the shoreline. On a barrier coast, persistent, long-term changes to the shoreline are caused by storm overwash, which transports marine sediment landward, moving the shoreline boundary. Raised sea levels increase the impact and frequency of this overwash as relative barrier elevation is reduced. Overall, sediment transport processes on the shoreface remain poorly understood, complicating predictions of equilibrium shoreface shapes and even net sediment transport directions. However, presuming an equilibrium geometry, energetics-based, time-averaged relationships for cross-shore sediment transport provide a framework to understand the characteristic rates and types of shoreface response to perturbations to either the sea level or the shoreline boundary. In the case of a sea-level rise, we find that the dominant perturbation for a barrier system is not the sea-level rise itself, but rather the movement of the shoreline by overwash. The characteristic response time of the shoreface itself increases significantly at depth, suggesting that the lower shoreface response to a sea level change can be significantly delayed. We estimate the importance of extreme events on shoreface evolution by analyzing decade-long data series of wave characteristics along different open ocean coasts with barriers (Florida Gulf Coast, North Carolina, Marthas Vineyard). Analogous to the effect of floods in fluvial systems, although storm events can move significant sediment, the infrequency of the larger events limits their effect on the shoreface-the morphologically significant event for shoreface evolution has a return interval of less than two years. However, numerical simulations of tens of thousands of synthetic storm strikes at the same locations suggest that the return interval of storm events expected to cause significant overwash is longer, on the order of at least 50 years. To study the interactions between the characteristic timescales of shoreface evolution and barrier overwash, we apply a numerical model of barrier profile evolution that couples shoreface evolution with barrier overwash. This integrated model provides a tool to understand the response of barrier systems to changes in sea level over the late Holocene to the modern. The model also investigates the potential behavior of barrier systems as they (and their human occupants) respond to predicted increased rates of sea-level rise over the coming centuries.

Ashton, A. D.; Ortiz, A.; Lane, P.; Donnelly, J. P.

2011-12-01

66

The Characteristics of Steam Bubbles in Subcooled Boiling Flow  

SciTech Connect

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)

Takatoshi Takemoto; Asi Bunyajitradulya [Chulalongkom University, 254 Phyathai Road, Patumwan, Bangkok 10330 (Thailand); Mitsuo Matsuzaki; Hiroshige Kikura; Masanori Aritomi [Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo 152 (Japan)

2002-07-01

67

Path instablity of a rising bubble: Shape matters, Reynolds number doesn't!  

Microsoft Academic Search

The conditions for the transition to zigzagging trajectories for freely ascending bubbles were studied experimentally. To avoid surface contamination, we used silicon oils with shear viscosities ranging from 1.7 to 9.4 times that of water. Since these fluids are non-polar, as opposed to the case of water, the gas-liquid interfaces remain clean without the need of an ultra-pure environment. Using

Roberto Zenit; Jacques Magnaudet

2007-01-01

68

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

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

69

Dynamic characteristics of laser-induced vapor bubble formation in water based on high speed camera  

NASA Astrophysics Data System (ADS)

In clinical practice, laser ablation usually works under liquid environment such as water, blood or their mixture. Laser-induced vapor bubble or bubble formation and its consequent dynamics were believed to have important influence on tissue ablation. In the paper, the dynamic process of vapor bubble formation and consequently collapse induced by pulsed Ho:YAG laser in static water was investigated by using high-speed camera. The results showed that vapor channel / bubble can be produced with pulsed Ho:YAG laser, and the whole dynamic process of vapor bubble formation, pulsation and consequently collapse can be monitored by using high-speed camera. The dynamic characteristics of vapor bubble, such as pulsation period, the maximum depth and width were determined. The dependence of above dynamic parameters on incident radiant exposure was also presented. Based on which, the influence of vapor bubble on hard tissue ablation was discussed.

Zhang, Xian-zeng; Guo, Wenqing; Zhan, Zhenlin; Xie, Shusen

2013-08-01

70

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

SciTech Connect

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.

Tzeng, J.W.; Chen, R.C.; Fan, L.S. (Ohio State Univ., Columbus (United States))

1993-05-01

71

Bubble Bubble  

NSDL National Science Digital Library

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

Mayer, Mercer

2009-11-11

72

Review of bubble detector response characteristics and results from space.  

PubMed

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

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

2012-06-01

73

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

PubMed Central

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.

Zhou, Yufeng; Qin, Jun; Zhong, Pei

2013-01-01

74

Characteristics of Pretreatment Parameters and Bubble Size Influencing DAF Efficiency  

Microsoft Academic Search

This study attempted to investigate the relationship between the floc size and efficiency of a DAF (Dissolved Air Flotation) method using a PDA (Photometric Dispersion Analyzer), which is used to monitor floc generation via on-line access. This study applied actual measurements to investigate how the size of bubbles affected the flotation velocity, and introduced similar results to the theoretical flotation

Byeong-Yong Sohn; Soon-Buhm Kwon; Jin-Hee Min; Joon-Wun Kang

2009-01-01

75

Characteristics of droplets generated by bubble bursting from chromic acid solutions  

Microsoft Academic Search

The effects of electrolyte concentration and gas flow rate on the characteristics of droplets generated from bubbles bursting on the surface of CrO3 solution were studied with an experimental bubbling system. The experimental conditions included two electrolyte concentrations, 125 and 250gl-1 of CrO3, and three flow rates of sparging air in the range of 4–8lmin-1. A cascade impactor collected droplet

Y. M. Kuo; C. S. Wang

1999-01-01

76

Energy effects in bubble nucleation  

SciTech Connect

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.

Jackson, M.L. (Univ. of Idaho, Moscow, ID (United States). Dept. of Chemical Engineering)

1994-04-01

77

Observations of solute effects on bubble formation  

SciTech Connect

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

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

1995-09-01

78

Effects of microgravity on Marangoni convection and growth characteristic of a single bubble  

NASA Astrophysics Data System (ADS)

Based on previous experiments and the volume of fluid (VOF) multiphase model, the growth characteristics of a single bubble have been numerically investigated in a rectangular pool (10×10×25 mm3) under microgravity. The transport of mass and energy during phase change was realized by source terms of the mass and energy equations through user-defined functions (UDF). Under microgravity, the results show that the temperature and the streamline field distribution around the bubble are significantly changed as compared to the ones of terrestrial conditions. The temperature profile at the two-phase interface is no longer a uniform distribution, and the Marangoni flows are more obvious at the two-phase interface. The effects of gravity on the detachment of the bubble are significant: the bubble does not immediately detach from the heating wall under microgravity conditions. The surface tension gradient caused by the Marangoni effect is more significant at lower microgravity. Bubble growth is more complex under microgravity conditions than normal gravity conditions, and it is related to the magnitude of the microgravity: the lower the microgravity, the higher the bubble growth rate. Furthermore, under microgravity, the bubble diameter changes differently, and the fluctuation amplitude of the heat transfer coefficient increases with increasing microgravity.

Yang, Yan; Pan, Liang-ming; Xu, Jian-jun

2014-07-01

79

Cold Heat Release Characteristics of Solidified Oil Droplet-Water Solution Latent Heat Emulsion by Air Bubbles  

NASA Astrophysics Data System (ADS)

The present work investigates the cold heat-release characteristics of the solidified oil droplets (tetradecane, C14H30, freezing point 278.9 K)/water solution emulsion as a latent heat-storage material having a low melting point. An air bubbles-emulsion direct-contact heat exchange method is selected for the cold heat-results from the solidified oil droplet-emulsion layer. This type of direct-contact method results in the high thermal efficiency. The diameter of air bubbles in the emulsion increases as compared with that in the pure water. The air bubbles blown from a nozzle show a strong mixing behavior during rising in the emulsion. The temperature effectiveness, the sensible heat release time and the latent heat release time have been measured as experimental parameters. The useful nondimensional emulsion level equations for these parameters have been derived in terms of the nondimensional emalsion level expressed the emulsion layer dimensions, Reynolds number for air flow, Stefan number and heat capacity ratio.

Inaba, Hideo; Morita, Shin-Ichi

80

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

PubMed

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

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

2011-12-01

81

Bouncing and Coalescence of Bubble Pairs Rising at High Reynolds Number in Pure Water or Aqueous Surfactant Solutions  

Microsoft Academic Search

The encounter of bubble pairs of O(1 mm) in both pure water and aqueous surfactant solutions was studied experimentally. In pure water, two equally sized bubbles were found to coalesce if the Weber number, W = ? V2 R\\/s, based on the velocity of approach, V, was below a critical value, Wcr = 0.18, where ? and s are the

P. C. Duineveld; J. M. Burgers

1997-01-01

82

Measurement of the Resonant Characteristics of a Single Bubble Vibration by Using a Laser Doppler Vibrometer  

Microsoft Academic Search

We constructed the experimental system with a laser Doppler vibrometer (LDV) for measuring the vibration of a single microbubble. It was demonstrated that the system enabled the capture of the vibration with an amplitude of nanometer order. We attempted to experimentally measure the resonant characteristics of a bubble attached to a wall by using the system. As a result, we

Taisuke Yoshikawa; Hironori Kotera; Kenji Yoshida; Daisuke Koyama; Kentaro Nakamura; Yoshiaki Watanabe

2011-01-01

83

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

NASA Astrophysics Data System (ADS)

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

Nikolovska, Aneta; Sahling, Heiko; Bohrmann, Gerhard

2008-10-01

84

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

NASA Astrophysics Data System (ADS)

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

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

2009-06-01

85

Cauldron Bubbles  

NSDL National Science Digital Library

In this activity, learners mix up a bubbly brew and examine density. Learners explore how they can make different materials fall and rise in water using oil, water, and salt. Learners can experiment using other materials like sugar and sand.

Boston, Wgbh

2003-01-01

86

Bubble cells: renal tubular cells in the urinary sediment with characteristics of viability.  

PubMed

The urinary sediment was examined by light microscopy in 65 consecutive inpatients with renal insufficiency (not due to pre- or postrenal factors) referred to a nephrology consult service for evaluation. In the 60 patients in whom a single diagnosis was reached, the sediments of 34 (57%) contained an easily recognized cell, which we have called the "bubble cell". These cells were bizarre, large cells with a single nucleus, which appeared to contain one or more fluid-filled vesicles. Bubble cells were most prevalent in the sediment of patients with acute tubular necrosis but were also seen a variety of other renal diseases. In most patients with acute tubular necrosis, the sediment also contained "normal"-appearing renal tubular cells, muddy brown casts, and oval fat bodies which were indistinguishable from those seen in the nephrotic syndrome. By electron microscopy, the bubble cells appeared to be vacuolated renal tubular epithelial cells, which had characteristics of viable cells. Most bubble cells excluded the vital dye Trypan blue, whereas the normal-appearing renal tubular cells were typically strongly positive. It was concluded that bubble cells, often accompanied by oval fat bodies, are commonly present in the sediment of patients with acute tubular necrosis as well as many other types of renal disease. Most cells which would be classified as "normal" renal tubular cells in these sediments are dead. In contrast, the findings suggest that the bubble cell represents an injured but viable renal tubular cell. The frequent finding of oval fat bodies in the same sediments suggests that the oval fat body is also produced by tubular cell injury. PMID:1883970

Graber, M; Lane, B; Lamia, R; Pastoriza-Munoz, E

1991-01-01

87

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

Microsoft Academic Search

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

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

2007-01-01

88

Characteristic microwave background distortions from collapsing domain wall bubbles  

NASA Technical Reports Server (NTRS)

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.

Goetz, Guenter; Noetzold, Dirk

1990-01-01

89

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

Microsoft Academic Search

The effect of liquid properties on gas bubble growth and motion characteristics in liquid films confined within a nanogap between a highly polished steel ball and a smooth glass disc under an electric field is reported. Experimental results show that the critical voltage for the appearance of bubbles has insignificant dependence on liquid viscosity and surface tension. The bubble size

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

2009-01-01

90

Cap Bubble Drift Velocity in a Confined Test Section  

SciTech Connect

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.

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

2002-10-09

91

Bubble Combustion  

NASA Technical Reports Server (NTRS)

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

Corrigan, Jackie

2004-01-01

92

The influence of bubble evolution on the early characteristics of the boiling liquid expanding vapor explosion  

NASA Astrophysics Data System (ADS)

In the study of boiling liquid expanding vapor explosion (BLEVE), the critical point to interpret the mechanism of the disaster is to analyze the phase transition of the superheated liquid in the container and the motions of the medium during the first several or several tens of milliseconds after the explosion from the microscopic angle of view. In the study recorded in this paper, a BLEVE simulative device was made. Using high-speed camera, the instant explosive boiling in the liquor phase space and the formation and development of the high speed two-phase flow were observed at the moment of the container broken in explosion, the growing and moving speed of the bubble in the liquor phase space were measured, and the influence of the energy released by blasted bubble nucleate in the early stages on the boiling characteristics of the superheated liquid and the overpressure disciplines in the container were analyzed. The study shows that in a BLEVE process, the boiling of superheated liquid does not present in the form of volume boiling, but presents as a progressive process with several steps that starts from the surface and develops over time.

Chen, Sining; He, Xuechao; Sun, Jinhua

2008-11-01

93

Aerator Combined With Bubble Remover  

NASA Technical Reports Server (NTRS)

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

Dreschel, Thomas W.

1993-01-01

94

Measurement of local flow characteristics in buoyancy-driven bubbly flow at high void fraction  

Microsoft Academic Search

The sedimentation of a homogeneous dispersion of gas bubbles in water is studied, using double optical probe and hot-film anemometry, for high bubble Reynolds number (300–500), and high void fraction ? (0–0.3). An experimental device has been specially designed to produce a uniform swarm of monodisperse bubbles without recirculating motions in the liquid phase. It is found that the evolution

C Garnier; M Lance; J. L Marié

2002-01-01

95

Tiny Bubbles  

NSDL National Science Digital Library

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

Dolphin, Glenn

96

Human Liver Cells Expressing Albumin and Mesenchymal Characteristics Give Rise to Insulin-Producing Cells  

PubMed Central

Activation of the pancreatic lineage in the liver has been suggested as a potential autologous cell replacement therapy for diabetic patients. Transcription factors-induced liver-to-pancreas reprogramming has been demonstrated in numerous species both in vivo and in vitro. However, human-derived liver cells capable of acquiring the alternate pancreatic repertoire have never been characterized. It is yet unknown whether hepatic-like stem cells or rather adult liver cells give rise to insulin-producing cells. Using an in vitro experimental system, we demonstrate that proliferating adherent human liver cells acquire mesenchymal-like characteristics and a considerable level of cellular plasticity. However, using a lineage-tracing approach, we demonstrate that insulin-producing cells are primarily generated in cells enriched for adult hepatic markers that coexpress both albumin and mesenchymal markers. Taken together, our data suggest that adult human hepatic tissue retains a substantial level of developmental plasticity, which could be exploited in regenerative medicine approaches.

Meivar-Levy, Irit; Sapir, Tamar; Berneman, Dana; Weissbach, Tal; Polak-Charcon, Sylvie; Ravassard, Philippe; Tzakis, Andreas G.; Mor, Eytan; Ricordi, Camillo; Ferber, Sarah

2011-01-01

97

Aerosolization of Particles from a Bubbling Liquid: Characteristics and Generator Development  

Microsoft Academic Search

A new aerosol generator is introduced in which particles suspended in a liquid are aerosolized by gentle bubble bursting. Tangential injection of dry air to the bubbling surface dries the airborne droplets immediately after aerosolization so that they rapidly shrink in size and are carried out from the generator by inward and upward swirling air motion. The new generator has

Vidmantas Ulevicius; Klaus Willeke; Sergey A. Grinshpun; Jean Donnelly; Xuejun Lin; Gediminas Mainelis

1997-01-01

98

In Search of the Big Bubble  

ERIC Educational Resources Information Center

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…

Simoson, Andrew; Wentzky, Bethany

2011-01-01

99

Gravity-driven bubbly flows  

Microsoft Academic Search

? Abstract Gravity-driven bubbly flows are a specific class of flows, where all action is provided by gravity. An industrial example,is formed,by the so-called bubble column: a vertical cylinder filled with liquid through,which,bubbles,flow that are introduced at the bottom of the cylinder. On the bubble scale, gravity gives rise to buoyancy of individual bubbles. On larger scales, gravity acts on

Robert F. Mudde

2005-01-01

100

Lift force in bubbly suspensions  

Microsoft Academic Search

Closure relations are presented for the lift coefficient for ordered arrays of 2-D and 3-D bubbles at various bubble volume fractions. These were determined via lattice Boltzmann simulations of bubble rise in periodic boxes, where the bubbles were also subjected to shear. The single-bubble lift coefficient, determined by low-shear computational experiments, varies in a systematic manner with the aspect ratio

Krishnan Sankaranarayanan; Sankaran Sundaresan

2002-01-01

101

Heat Storage Characteristics of Latent-Heat Microcapsule Slurry Using Hot Air Bubbles by Direct-Contact Heat Exchange  

Microsoft Academic Search

This study deals with the heat storage characteristics of latent-heat microcapsule slurry consisting of a mixture of fine microcapsules packed with latent-heat storage material and water. The heat storage operation for the latent-heat microcapsules was carried out by the direct-contact heat exchange method using hot air bubbles. The latent-heat microcapsule consisted of n-paraffin as a core latent-heat storage material and

Hideo Inaba; Akihiko Horibe; Myoung-Jun Kim; Hirofumi Tsukamoto

2001-01-01

102

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

PubMed

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

Wyithe, J Stuart B; Loeb, Abraham

2004-11-11

103

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

Microsoft Academic Search

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

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

2010-01-01

104

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

105

Acoustic manifestations of gas hydrate shelled bubbles  

NASA Astrophysics Data System (ADS)

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

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

2009-11-01

106

Study of stream flow effects on bubble motion  

SciTech Connect

The formation of air bubbles at constant-pressure by submerged orifices was investigated in both quiescent and moving streams inside a vertical tube. Parameters affecting the bubble rise velocity, such as bubble generating frequency and diameter, were studied and analyzed for bubbles rising in a chain and homogeneous mixture. A special technique for measuring bubble motion parameters has been developed, tested, and employed throughout the experimental investigation. The method is based on a water-air impedance variation. Results obtained in stagnant liquid show that increasing the bubble diameter serves to increase bubble rise velocity, while an opposite trend has been observed for stream liquid where the bubble diameter increase reduces the bubble rise velocity. The increase of bubble generation frequency generally increases the bubble rise velocity. Experimental data covered with bubble radial distribution showed symmetrical profiles of bubble velocity and frequency, and the radial distribution of the velocity profiles sometimes has two maxima and one minimum depending on the liquid velocity. Finally, in stagnant liquid, a normalized correlation has been developed to predict the terminal rise velocity in terms of bubble generating frequency, bubble diameter, single bubble rise velocity, and conduit dimensions. Another correlation is presented for forced bubbly flow, where the bubble rise velocity is expressed as a function of bubble generating frequency, bubble diameter, and water superficial velocity.

Sami, S.S.

1983-01-01

107

Shock formation within sonoluminescence bubbles  

SciTech Connect

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.}

Vuong, V.Q. [University of California, Irvine, Department of Mechanical and Aerospace Engineering, Irvine, California 92697-3975 (United States)] [University of California, Irvine, Department of Mechanical and Aerospace Engineering, Irvine, California 92697-3975 (United States); Szeri, A.J. [University of California at Berkeley, Department of Mechanical Engineering, Berkeley, California 94720-1740 (United States)] [University of California at Berkeley, Department of Mechanical Engineering, Berkeley, California 94720-1740 (United States); Young, D.A. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)] [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

1999-01-01

108

Bubble Dynamical Behavior and Flow Boiling Characteristics of Slug Flow in Hairpin Tubes  

NASA Astrophysics Data System (ADS)

A series of experiments was conducted to investigate the flow boiling of R141b in hairpin tubes. A focus was addressed on visually observing flow boiling and two-phase flow in U-turn bends of a vertical upward hairpin tube with inner diameter of 6 mm at liquid velocities of 0.098, 0.147 and 0.196 m/s and heat fluxes in the range of 6191 W/m2 to 24763 W/m2, respectively. The bend could break up large vapor slugs in two ways, bubble tail fracture and bubble rupture, which induced significant effects on local heat and mass transfer. Under certain experimental conditions, small bubbles formed in the bend could not coalesce to be large vapor slugs but accumulate to form a unique flow pattern and greatly release thermal non-equilibrium in the rest part of hairpin the tube.

Meng, M.; Peng, X. F.

2010-03-01

109

Building design and energy end-use characteristics of high-rise residential buildings in Hong Kong  

Microsoft Academic Search

Surveys have been conducted to obtain information about the building design and energy end-use characteristics of high-rise residential buildings in Hong Kong. The building design characteristics data obtained include the floor areas of residential flats, the ratios of the areas of bedrooms and living and dining rooms to the total flat area, the window-to-wall area ratios, the types of fenestration,

K. S. Y. Wan; F. W. H. Yik

2004-01-01

110

Magnetic Properties, Self-Temperature Rising Characteristics, and Biocompatibility of NiFe O Nanoparticles for Hyperthermia Applications  

Microsoft Academic Search

This paper reports first on the very promising self-heating and temperature rising characteristics of solid-state NiFe2O4 nanoparticles for hyperthermia applications. NiFe2O4 nanoparticles were prepared by using both the \\

Sang Won Lee; Seongtae Bae; Y. Takemura; E. Yamashita; J. Kunisaki; Shayne Zurn; Chul Sung Kim

2006-01-01

111

The impact of gravity waves rising from convection in the lower atmosphere on the generation and nonlinear evolution of equatorial bubble  

Microsoft Academic Search

The nonlinear evolution of equatorial F-region plasma bubbles under varying ambient ionospheric conditions and gravity wave seeding perturbations in the bottomside F-layer is studied. To do so, the gravity wave propagation from the convective source region in the lower atmosphere to the thermosphere is simulated using a model of gravity wave propagation in a compressible atmosphere. The wind perturbation associated

E. Alam Kherani; M. A. Abdu; E. R. de Paula; D. C. Fritts; J. H. A. Sobral; F. C. de Meneses Jr.

2009-01-01

112

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

NASA Astrophysics Data System (ADS)

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.

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

113

Modeling of mass transfer characteristics of bubble column reactor with surfactant present  

Microsoft Academic Search

Danckwert's method was used to determine the specific interfacial area,a, and the individual mass transfer coefficient,k\\u000a L, during absorption of CO2 in a bubble column with an anionic surfactant in the carbonate-bicarbonate buffer solution and NaAsO2 as catalyst, the presence of which decreases the specific interfacial area and the individual mass transfer coefficient.\\u000a The specific interfacial area and the individual

Zhao Wei-rong; Shi Hui-xiang; Wang Da-hui

2004-01-01

114

Period-adding route in sparkling bubbles  

Microsoft Academic Search

Chains of bubbles are seen rising along the wall whenever champagne is poured into a glass. The careful observation of a given bubble chain often reveals that the interbubble distance suddenly changes during the degassing process, indicating different bubbling regimes in this elusive phenomenon of effervescence. We report the transitions between these different bubbling regimes that present sequences of multiple

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

2005-01-01

115

Dielectrophoresis of bubbles in isomotive electric fields  

Microsoft Academic Search

The behaviour of bubbles rising in AC isomotive electric fields of 50 Hertz frequency was investigated in several dielectric liquids. Isomotive electrodes were immersed in the sample liquids and aligned so that the motion of single bubbles of nitrogen rising in the interelectrode space was opposed by the dielectrophoretic force. The transit time of each bubble was timed over two

C. M. Feeley; F. McGovern

1988-01-01

116

Simulation of the dynamics of decompression sickness bubbles and the generation of new bubbles.  

PubMed

This communication introduces a system of equations for simulating the dynamics of growth and decay of decompression bubbles. The equations are solved by a numerical method and account for gas diffusion, the action of surface tension, tissue N2 washout by blood, and the rate of ascent from depth. The simulations demonstrate how inward diffusion of N2 can generate a persistent gas bubble from a nucleation process or a nucleus (these are provisionally defined as entities that can give rise to a small bubble of a certain size); an explosive positive-feedback loop is set off as the enlarging radius decreases the pressure due to surface tension. Generation of persistent bubbles is most likely during ascent from depth when PN2 inside any gas phase is decreasing rapidly and PN2 outside is still high before appreciable tissue washout has occurred. The "susceptibility" for the generation of a persistent bubble at any time can be defined as the reciprocal of the difference, at that time, between partial pressure of the nitrogen in tissue and in a spherical bubble of the size that is characteristic of the nucleation process or nucleus; susceptibility is less when ascent is slow because PN2 in bubbles stays high while washout removes N2 from the tissue. PMID:1887520

Van Liew, H D

1991-07-01

117

Leverage bubble  

NASA Astrophysics Data System (ADS)

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

Yan, Wanfeng; Woodard, Ryan; Sornette, Didier

2012-01-01

118

Bubble Mania  

NSDL National Science Digital Library

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

Pbs

2012-01-01

119

Direct numerical simulations of three-dimensional bubbly flows  

Microsoft Academic Search

Direct numerical simulations of the motion of many buoyant bubbles are presented. The Navier-Stokes equation is solved by a front tracking\\/finite difference method that allows a fully deformable interface. The evolution of 91 nearly spherical bubbles at a void fraction of 6% is followed as the bubbles rise over 100 bubble diameters. While the individual bubble velocities fluctuate, the average

Bernard Bunner; Grétar Tryggvason

1999-01-01

120

Heat Storage Characteristics of Latent-Heat Microcapsule Slurry Using Hot Air Bubbles by Direct-Contact Heat Exchange  

NASA Astrophysics Data System (ADS)

This study deals with the heat storage characteristics of latent-heat microcapsule slurry consisting of a mixture of fine microcapsules packed with latent-heat storage material and water. The heat storage operation for the latent-heat microcapsules was carried out by the direct-contact heat exchange method using hot air bubbles. The latent-heat microcapsule consisted of n-paraffin as a core latent-heat storage material and melamine resin as a coating substance. The relationship between the completion time of latent-heat storage and some parameters was examined experimentally. The nondimensional correlation equations for temperature efficiency, the completion time period of the latent-heat storage process and variation in the enthalpy of air through the microcapsule slurry layer were derived in terms of the ratio of microcapsule slurry layer height to microcapsule diameter, Reynolds number for airflow, Stefan number and modified Stefan number for absolute humidity of flowing air.

Inaba, Hideo; Horibe, Akihiko; Kim, Myoung-Jun; Tsukamoto, Hirofumi

121

Geochemical characteristics of off-axis lavas from the Chile Rise  

NASA Astrophysics Data System (ADS)

The Chile Rise, a divergent boundary between the Nazca and Antarctic plates, is unique because it is being subducted beneath the South American plate. Even though the ridge is located on the subducting slab, previous studies (e.g. Klein and Karsten, Nature,V374, 1995) of axial lavas have proposed that the easternmost part of ridge (Segment 1) might be contaminated by a young subduction component. The most plausible explanation for this posited subduction component is transport of the subduction components through a “slab window” from the mantle wedge. For this study, off-axis lavas from Segment 1 were obtained on board R/V Mirai, JAMSTEC in 2009. In contrast to axial lavas, which are sediment covered due to the high sedimentation rate of the near shore area, many of the off-axis lava flows were directly exposed on the seafloor, suggesting recent off-axis volcanic activity. These off-axis lavas were analyzed for major and trace element abundances to evaluate both the melting processes involved in this off-axis magmatism and the extent of mantle heterogeneity beneath this ridge-subduction environment. The off-axis lavas are primitive (MgO is 7.5~ 8.4) and similar to N-MORB in their major element compositions. Compared to published on-axis data for the Chile Rise basalts (Klein and Karsten, Nature,V374, 1995), they are slightly higher in TiO2 for a given MgO content, but have similar Na2O. H2O/Ce contents of the lavas are close to the Pacific MORB/OIB maximum (~220), but one sample is higher (>300). These off-axis lavas are also slightly enriched in fluid mobile elements such as K2O, Ba and Pb compared to N-MORB, suggesting their lava source was similarly influenced by subduction components. For example, a diagram of K2O/TiO2 vs. K2O/H2O shows a trend that is oblique to the Pacific MORB trend, but may be going towards a subduction component. Trends towards a subduction component are less pronounced in off-axis lavas than those seen among the axial lavas; none-the-less, a positive correlation between Th/La and H2O/Ce suggests the involvement of sediment melt in the source. Planned measurements of radiogenic isotopes will help to further distinguish different melt and fluid components.

Park, S.; Sims, K. W.; Michael, P. J.; Orihashi, Y.; Plank, T.; Abe, N.

2010-12-01

122

Visualization of bubble-fluid interaction by a moving object flow image analyzer system.  

PubMed

This paper deals with interaction between a bubble and fluid around it, visualized by a moving object flow image analyzer (MOFIA) consisting of a three-dimensional (3D) moving object image analyzer (MOIA) and two-dimensional particle image velocimetry (PIV). The experiments were carried out for rising bubbles of various sizes and shapes in stagnant water in a vertical pipe. In the MOFIA employed, 3D-MOIA was used to measure bubble motion and PIV to measure fluid flow. The 3D position and shape of a bubble and the velocity field were measured simultaneously. The experimental results showed that the interaction was characterized by the shape, size and density of a bubble. Concretely, they showed the characteristics of bubble motion, wake shedding, and flow field. PMID:12496023

Choi, H M; Terauchi, T; Monji, H; Matsui, G

2002-10-01

123

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

Microsoft Academic Search

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

Ira Leifer

2010-01-01

124

Bubble dielectrophoresis  

Microsoft Academic Search

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

T. B. Jones; G. W. Bliss

1977-01-01

125

Compact bubble clusters in Newtonian and non-Newtonian liquids  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

126

Buoyant Bubbles  

NSDL National Science Digital Library

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

Science, Lawrence H.

2009-01-01

127

Modelling of large-scale dense gas–solid bubbling fluidised beds using a novel discrete bubble model  

Microsoft Academic Search

In order to model the complex hydrodynamic phenomena prevailing in industrial scale gas–solid bubbling fluidised bed reactors and especially the macro-scale emulsion phase circulation patterns induced by bubble–bubble interactions and bubble coalescence, a discrete bubble model (DBM) has been developed. In the DBM, the (larger) bubbles are modelled as discrete elements and are tracked individually during their rise through the

G. A. Bokkers; J. A. Laverman; M. van Sint Annaland; J. A. M. Kuipers

2006-01-01

128

Period-adding route in sparkling bubbles.  

PubMed

Chains of bubbles are seen rising along the wall whenever champagne is poured into a glass. The careful observation of a given bubble chain often reveals that the interbubble distance suddenly changes during the degassing process, indicating different bubbling regimes in this elusive phenomenon of effervescence. We report the transitions between these different bubbling regimes that present sequences of multiple periods known as the period-adding route. PMID:16241621

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

2005-09-01

129

Application of neural networks to prediction of phase transport characteristics in high-pressure two-phase turbulent bubbly flows  

Microsoft Academic Search

The phase transport phenomenon of the high-pressure two-phase turbulent bubbly flow involves complicated interfacial interactions of the mass, momentum, and energy transfer processes between phases, revealing that an enormous effort is required in characterizing the liquid–gas flow behavior. Nonetheless, the instantaneous information of bubbly flow properties is often desired for many industrial applications. This investigation aims to demonstrate the successful

An-Shik Yang; Tien-Chuan Kuo; Pou-Hong Ling

2003-01-01

130

Bubble dielectrophoresis  

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

131

Four-dimensional visualization of rising microbubbles  

PubMed Central

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.

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

2014-01-01

132

Four-dimensional visualization of rising microbubbles.  

PubMed

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

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

2014-01-01

133

Soap Bubbles  

NSDL National Science Digital Library

Learners explore three-dimensional geometric frames including cubes and tetrahedrons, as they create bubble wands with pipe cleaners and drinking straws. Then they investigate how soap film flows into a state of minimum energy when they lift the wand up from the bubble solution. Learners also see how light reflection and interference create shimmering colors in the bubbles.

Exploratorium, The

2011-12-07

134

Best Bubbles  

NSDL National Science Digital Library

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

Saltz, Austen

2010-01-01

135

Recalcitrant bubbles  

PubMed Central

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

Shanahan, Martin E. R.; Sefiane, Khellil

2014-01-01

136

Recalcitrant bubbles  

NASA Astrophysics Data System (ADS)

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).

Shanahan, Martin E. R.; Sefiane, Khellil

2014-04-01

137

Toward An Empirical Scaling For Bubble Coalescence Rates  

NASA Astrophysics Data System (ADS)

Bubble coalescence in magma is a consequence of the thinning of the melt film that separates individual bubbles. New experiments on the drainage of such liquid films, to the point of spontaneous rupture, result in empirical equations for film drainage time as a consequence of gravitational and capillary forces. Application to magmatic systems gives estimates of bubble coalescence rates under conditions where bubble growth is negligible. We conducted laboratory experiments of air bubbles suspended in silicone oil and measured the time required for the liquid film that separates bubbles from the free surface to drain and rupture. The experiments spanned a wide range in Bond number (10-2 ? Bo ? 102). Independent of viscosity, our results show that for Bo < 0.25 film drainage was by capillary forces, whereas for Bo > 0.25 gravitational forces dominated. We obtain a scaling relation for film drainage time t = C ln(?o/?f) ?, where C is an empirical constant, ?o is initial film thickness, ?f is final film thickness. ? = ?R/? is the characteristic capillary time scale (Bo<0.25, C=20),and ? = ?/???R is the characteristic buoyancy time scale (Bo>0.25, C=5), where R is bubble radius, ? is fluid viscosity, ? is surface tension and ?? is density contrast between bubble and liquid. The predicted drainage times are 2-3 orders of magnitude shorter than previous estimates [1] and are consistent with film drainage times in silicate melts at 1? Bo ? 10. If our results may also be applicable to silicate melts at smaller Bond numbers, they indicate that bubble coalescence will occur on relatively short time scales, even in magmatic processes where bubble growth is negligible. [1] Proussevitch et al., J. Volcanol. Geotherm. Res., 59, 161-178 (1993). Figure 1. A single bubble rises in silicone oil (left), drains and ruptures (right) at the free surface. Figure 2. Experimental results. (a) Drainage time vs. bubble radius. (b) Dimensionless drainage time for Bo>0.25, and (c) for Bo<0.25.

Nguyen, C. T.; Gonnermann, H. M.; Chen, Y.; Huber, C.

2012-12-01

138

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...

139

Morphologic Characteristics and Global Distribution of Phreato-Volcanic Constructs on Mars as Seen by HiRISE  

NASA Astrophysics Data System (ADS)

We examine the morphology of pristine phreato-volcanic constructs (PVCs) in Athabasca Valles, identify an assemblage of features that is diagnostic of this class of PVC, and study HiRISE images of candidate PVC fields elsewhere on Mars.

Jaeger, W. L.; Keszthelyi, L.; Galuszka, D. M.; Kirk, R. L.; HiRISE Team

2008-03-01

140

Bubble Suspension  

NSDL National Science Digital Library

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

Exploratorium, The

2011-10-11

141

Big Bubbles  

NSDL National Science Digital Library

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

Science, Lawrence H.

2010-01-01

142

Wall Shear Stress Induced by Taylor Bubbles in Inclined Flow Channels  

NASA Astrophysics Data System (ADS)

The motion of single air bubbles in flat channels is experimentally investigated. The electrodiffusion technique of near-wall flow diagnostics is applied to measure the wall shear stress distribution under large rising bubbles. The measurements are synchronized with the visual observation of bubble movement by a high-speed camera. The analysis of video records provides information on the bubble shape and terminal velocity. The experiments are carried out for three different channel configuration (with heights of 1.5, 4, and 8 mm), cover a wide range of channel inclination angles (from horizontal to vertical position), and dealing with both the bubbles in stagnant and in co-flowing water. The directionally sensitive, two-strip electrodiffusion probe is proved to be an effective tool to investigate the near-wall flow response to translating bubbles. It provides information not only on the wall shear rate distribution, but also detects the location of near-wall flow reversal, gives an estimate of the thickness of liquid film separating the large bubble from the wall, and provides also the characteristics of capillary waves appearing in the bubble tail region. The effect of channel inclination angle on the modification of wall shear stress distribution along the upper and bottom wall is also discussed.

Tihon, J.; P?nkavová, V.; Vejražka, J.

2013-04-01

143

Dynamics of gas-liquid flows in bubble column reactors  

Microsoft Academic Search

Wall pressure fluctuations were measured in bubble columns at different locations and for different gas velocities and height to diameter ratios. Non-linear analysis of the acquired data of pressure fluctuations was carried out to quantify dynamic characteristics. A bubble–bubble interaction model was developed to simulate voidage fluctuations in bubble columns. Dynamic characteristics of the simulated voidage fluctuations were compared with

V. V. Ranade; R. P. Utikar

1999-01-01

144

Magnetic Bubbles  

NASA Astrophysics Data System (ADS)

Bubbles in liquids driven by a sound field are used in many disciplines: for example bubbles clean surfaces in ultrasonic water bathes, they catalyze unique chemical reactions in sonochemistry, and under special conditions even create light. However, conventional bubbles have a major limitation when placed in an acoustic field: it is extremely hard to control their position. Here we present a new type of bubble that has permanent magnetization originating from a shell of self-assembled nanoparticles, so that magnetic fields can be used to control the bubble's position independently. We will report on the recipe and the experiment to study bubble oscillations in weak magnetic fields. The magnetic susceptibility of the bubbles is proportional to their surface area,?=(9±3x10-6m)r^2, where r is the radius. Also they are compressible in moderate acoustic fields and induce a microstreaming flow with a toroidal vortex at the upper pole of the bubble. Similar microstreaming flows have been used to transport and rupture cells at small scales. Thus we envision applications in manipulation of biological materials and in microfluidic devices using acoustic and magnetic forces.

Zhao, Xue; Quinto-Su, Pedro; Ohl, Claus-Dieter

2008-11-01

145

Bubble Tray  

NSDL National Science Digital Library

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

Exploratorium, The

2012-06-26

146

Bubble Trouble  

NSDL National Science Digital Library

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

Society, American C.

2011-01-01

147

Bubble dielectrophoresis  

Microsoft Academic Search

The force due to polarization exerted on dielectric particles, vapor or gas bubbles, and voids in insulating dielectric liquids is an example of dielectrophoresis. This force is directly proportional to the gradient of the electric field intensity. Bubbles and voids are attracted into regions of lower electric field intensity, while dielectric particles (with higher relative polarizability) are attracted into regions

T. B. Jones; G. W. Bliss

1977-01-01

148

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

NASA Astrophysics Data System (ADS)

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 coronæ 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 coronæ 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.

Python, Marie; Akizawa, Norikatsu; Godard, Marguerite; Ildefonse, Benoît; Koepke, Jürgen

2014-05-01

149

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

NASA Astrophysics Data System (ADS)

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.

Yamada, Yumi; Akashi, Toyou; Takahashi, Minoru

150

Measurements on Concentration Waves in Bubbly Liquids.  

National Technical Information Service (NTIS)

Gas-liquid two phase flow is studied. Properties of a single rising bubble and a mixture of bubbles under stationary conditions as experienced during experimentation are described. The instruments and the setup of an experimental loop are described. A the...

C. Kapeteijn

1989-01-01

151

Tiny Bubbles.  

National Technical Information Service (NTIS)

SINCE DECOMPRESSION SICKNESS (DCS) was first described, the elusive nature of its pathophysiology has been a challenge. It is generally thought that intravascular and extravascular bubbles arc responsible for a host of downstream effects that cause the co...

R. T. Mahon

2010-01-01

152

Bubble Suspension  

NSDL National Science Digital Library

This activity from the Exploratorium illustrates the principles of buoyancy, semipermeability, and interference as soap bubbles float on a cushion of carbon dioxide gas. Dry ice, gloves, and adult supervision are required to view the beautiful effect. The site also includes an explanation of the physics involved and other quick experiments that can be done with bubbles. This activity is part of Exploratorium's Science Snacks series.

2006-07-16

153

Stereoisomer Bubbles  

NASA Astrophysics Data System (ADS)

Undergraduate organic chemistry students are given a simple method to determine the stereochemical relationships between several molecules with more than one chiral center. The four groups around each chiral center are assigned Cahn-Ingold-Prelog priorities, and these numbers encircled in "bubbles". Subsequent structure manipulations by the allowed Fisher projection rotations involve only these four number bubbles to make R or S assignments. A table of relationships (identical, diastereomer, or enantiomer) between all the molecules is then generated.

Lesko, Melanie J.

1996-05-01

154

Exploring Bubbles  

NASA Astrophysics Data System (ADS)

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

O'Geary, Melissa A.

155

Interaction mechanism of double bubbles in hydrodynamic cavitation  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

156

Bubble diagnostics  

DOEpatents

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.

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

2003-01-01

157

A novel method of measuring electrophoretic mobility of gas bubbles  

Microsoft Academic Search

Accurate measurement of electrophoretic mobility for gas bubbles is a challenging task as it requires the creation of a desired number of very small air bubbles to ensure negligible rise velocities during the course of the measurement. Here, we report a simple and reliable method for generating stable dispersions of “nano-bubbles.” Preparation of such dispersions relies on the nucleation of

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

2007-01-01

158

Theory of Rayleigh-Taylor bubbles in the equatorial ionosphere  

Microsoft Academic Search

A theory of rising bubbles (or sharp density depletions) in the equatorial ionosphere is presented. Both ion inertia and ion-neutral collisions are included. In the collision-dominated case the bubble velocity is independent of its size, while in the collisionless case it is proportional to the square root of the bubble size.

Edward Ott

1978-01-01

159

The rising psoas sign: an analysis of preoperative imaging characteristics of aborted minimally invasive lateral interbody fusions at L4-5.  

PubMed

Minimally invasive lateral interbody fusion for the treatment of degenerative disc disease, spondylolisthesis, or scoliosis is becoming increasingly popular. The approach at L4-5 carries the highest risk of nerve injury given the proximity of the lumbar plexus and femoral nerve. The authors present 3 cases that were aborted during the approach because of pervasive electromyography responses throughout the L4-5 disc space. Preoperative imaging characteristics of psoas muscle anatomy in all 3 cases are analyzed and discussed. In all cases, the psoas muscle on axial views was rising away from the vertebral column as opposed to its typical location lateral to it. Preoperative evaluation of psoas muscle anatomy is important. A rising psoas muscle at L4-5 on axial imaging may complicate a lateral approach. PMID:24606002

Voyadzis, Jean-Marc; Felbaum, Daniel; Rhee, Jay

2014-05-01

160

Affirmative Discrimination and the Bubble  

ERIC Educational Resources Information Center

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…

Clegg, Roger

2011-01-01

161

Study of CO2 bubble dynamics in seawater from QICS field Experiment  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

162

Study of CO2 bubble dynamics in seawater from QICS field Experiment  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

163

Moon Rise  

NASA Video Gallery

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

164

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

SciTech Connect

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)

Yumi Yamada [Advanced Reactor Technology Company, Ltd. (Japan); Toyou Akashi; Minoru Takahashi [Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550 (Japan)

2006-07-01

165

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

Microsoft Academic Search

The aims of the current study were to illustrate figures for the characteristics of oestrous cycles especially on follicular\\u000a dynamics, corpus luteum and changes in progesterone and prostaglandin F2alpha, in the Holstein cross-bred dairy heifers. Twenty\\u000a six healthy and sexual-mature virgin heifers were monitored for signs of oestrus. Their ovaries were sonically examined and\\u000a the numbers and the sizes of

Sudsaijai Kornmatitsuk; Bunlue Kornmatitsuk; Peerasak Chantaraprateep; Birgitta Larsson

2009-01-01

166

Stability of a class of neutral vacuum bubbles  

NASA Astrophysics Data System (ADS)

A model that gives rise to vacuum bubbles is considered where the domain wall field interacts with another real scalar field, resulting in the formation of domain ribbons within the host domain wall. Ribbon-antiribbon annihilations produce elementary bosons whose mass inside the wall is different from the mass in vacuum. Two cases are considered, where the bosons get trapped either within the bubble wall or the bosons get trapped within the vacuum enclosed by the bubble. The bosonic (meta)stabilization effect on the bubble is examined in each case. It is found that when the bosons become trapped within the bubble wall, the stabilization mechanism lasts for only a limited amount of time, and then the bubble undergoes unchecked collapse. However, when the bosons become trapped within the bubble’s interior volume, the bubble can be long-lived, provided that it has a sufficiently thin wall.

Morris, J. R.

2013-04-01

167

Tiny Bubbles.  

ERIC Educational Resources Information Center

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

Kim, Hy

1985-01-01

168

Two-phase flow characteristic of inverted bubbly, slug and annular flow in post-critical heat flux region  

NASA Astrophysics Data System (ADS)

Inverted annular flow can be visualized as a liquid jet-like core surrounded by a vapor annulus. While many analytical and experimental studies of heat transfer in this regime have been performed, there is very little understanding of the basic hydrodynamics of the post-Convective Heat Flux (CHF) flow field. However, a recent experimental study was done that was able to successfully investigate the effects of various steady-state inlet flow parameters on the post-CHF hydrodynamics of the film boiling of a single phase liquid jet. This study was carried out by means of a visual photographic analysis of an idealized single phase core inverted annular flow initial geometry (single phase liquid jet core surrounded by a coaxial annulus of gas). In order to extend this study, a subsequent flow visualization of an idealized two-phase core inverted annular flow geometry (two-phase central jet core, surrounded by a coaxial annulus of gas) was carried out. The objective of this second experimental study was to investigate the effect of steady-state inlet, pre-CHF two-phase jet core parameters on the hydrodynamics of the post-CHF flow field. In actual film boiling situations, two-phase flows with net positive qualities at the CHF point are encountered. Thus, the focus of the present experimental study was on the inverted bubbly, slug, and annular flow fields in the post dryout film boiling region. Observed post dryout hydrodynamic behavior is reported. A correlation for the axial extent of the transition flow pattern between inverted annular and dispersed droplet flow (the agitated regime) is developed. It is shown to depend strongly on inlet jet core parameters and jet void fraction at the dryout point.

Ishii, M.; Denten, James P.

169

Ring Bubbles of Dolphins  

NASA Technical Reports Server (NTRS)

The article discusses how dolphins create and play with three types of air-filled vortices. The underlying physics is discussed. Photographs and sketches illustrating the dolphin's actions and physics are presented. The dolphins engage in this behavior on their own initiative without food reward. These behaviors are done repeatedly and with singleminded effort. The first type is the ejection of bubbles which, after some practice on the part of the dolphin, turn into toroidal vortex ring bubbles by the mechanism of baroclinic torque. These bubbles grow in radius and become thinner as they rise vertically to the surface. One dolphin would blow two in succession and guide them to fuse into one. Physicists call this a vortex reconnection. In the second type, the dolphins first create an invisible vortex ring in the water by swimming on their side and waving their tail fin (also called flukes) vigorously. This vortex ring travels horizontally in the water. The dolphin then turns around, finds the vortex and injects a stream of air into it from its blowhole. The air "fills-out" the core of 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.

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

1996-01-01

170

Performance Characteristics of the Ferilab 15-Foot Bubble Chamber with a 1/3-Scale Internal Picket Fence (IPF) And a Two-Plane External Muon Identifier (EMI).  

National Technical Information Service (NTIS)

The Fermilab 15-foot bubble chamber has been exposed to a quadrupole triplet neutrino beam. During this exposure, a 2-plane EMI and a 1/3-scale IPF, were in operation down-stream of the bubble chamber. The IPF consisted of sixteen 0.1 m exp 2 drift chambe...

M. L. Stevenson

1978-01-01

171

Champagne experiences various rhythmical bubbling regimes in a flute.  

PubMed

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

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

2006-09-20

172

FEASTING BLACK HOLE BLOWS BUBBLES  

NASA Technical Reports Server (NTRS)

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

2002-01-01

173

Burst of Star Formation Drives Galactic Bubble  

NASA Technical Reports Server (NTRS)

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.

2001-01-01

174

Rising Waters  

NSDL National Science Digital Library

Using a computer interactive tool, students investigate the changes in coastline that would result from a change in sea level, and suggest what factors could cause a rise in sea level. The activity asks students to reflect on outcomes of their investigations completed during the Ice Ages and Night Life activities, all of which are part of Space Update, a collection of resources and activities provided to teach about Earth and space. Summary background information, data and images supporting the activity are available on the Earth Update data site. To complete the activity, students will need to access the Space Update multimedia collection, which is available for download and purchase for use in the classroom.

175

Do we understand the bubble formation by a single drop impacting upon liquid surface?  

NASA Astrophysics Data System (ADS)

Large bubble formation by a single drop impacting upon a liquid surface with low impact energy is conventionally considered to be unimportant and not a cause for small bubble(s) generation. Our experiments contradict three widely accepted concepts about bubble formation. First, this paper presents results that give evidence of much wider existence of large bubble entrainment. Second, there is no closed characteristic regime for regular large bubble generation. Third, for the first time, there are results of bubble pair generation in sequence that show the direct formation of smaller bubble(s) due to a single large bubble rupturing without external disturbances. Additionally, this work demonstrates that the shape of an oscillating prolate drop at impact is the missing factor that helps predict large bubble formation. At the end, this paper presents a new characteristic map for large bubble formation that is based on the theoretical oscillation model.

Wang, An-Bang; Kuan, Chen-Chi; Tsai, Pei-Hsun

2013-10-01

176

Dynamics of Bubble Ascent in Mud Volcanoes  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

177

On the 3D-reconstruction of Taylor-like bubbles trapped inside hollow cellulose fibers acting as bubble nucleation sites in supersaturated liquids  

Microsoft Academic Search

Bubble nucleation and rise in liquids have been extensively experimentally, theoretically and numerically studied in the past. In the specific field of heterogeneous bubble nucleation in carbonated beverages, it was recently observed that the birth of bubbles requires a preexisting gas cavity which is mostly trapped during the liquid pouring, in tiny hollow cellulose fibers-made structures adsorbed on the glass

Cédric Voisin; Philippe Jeandet; Gérard Liger-Belair

2005-01-01

178

Europa Rising  

NASA Technical Reports Server (NTRS)

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.

2007-01-01

179

Copernicus Rising  

NASA Astrophysics Data System (ADS)

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.

Rose, Michael A.

2007-08-01

180

The Dynamics Of Multiple Vortex Breakdown Bubbles In Confined Swirling Flows: Quasi-Periodic Order In The Wake Of Chaos  

Microsoft Academic Search

We study numerically and experimentally the Lagrangian characteristics of the flow in the interior of vortex breakdown (VB) bubbles in a closed container with a rotating lid for governing parameters within the steady, two-bubble regime. The dynamics of the first bubble are chaotic and consistent with those previously uncovered for VB bubbles in the single-bubble regime. In striking contrast, however,

Tahirih C. Lackey; Fotis Sotiropoulos; Donald R. Webster

2000-01-01

181

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

NASA Astrophysics Data System (ADS)

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.

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

2010-12-01

182

a Novel Methodology to Measure Mass Transfer around a Bubble  

Microsoft Academic Search

An original approach for accurately measuring the mass transfer of a single bubble rising in a liquid is reported. The approach consists in using PLIF technique (Planar Laser Induced Fluorescence) at micro-scale to capture images of the released oxygen concentration field in the bubble wake. The applicability of the technique for determining mass transfer coefficients in different fluids (1 <

Jessica Francois; Nicolas Dietrich; Arnaud Cockx

2011-01-01

183

Evolution of bubble size distribution in baked foods  

Microsoft Academic Search

A model to predict the bubble size distribution in baked foods and the oven rise during baking process is presented, and the effect of changing various model parameters on the model output is studied. The model incorporates a population balance equation for the formation and expansion of bubbles coupled with reaction kinetics and heat and mass transfer equations. Nucleation and

Prashant Deshlahra; Anurag Mehra; Debjani Ghosal

2009-01-01

184

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

Microsoft Academic Search

Due to decompression when magma flows up the volcanic conduit, bubbles nucleate, coalesce, rise and explode at the surface of the conduit. On the field, one possible tool to investigate this dynamics is to analyze the acoustic signal produced by the explosion of such bubbles. In order to investigate this phenomenon at the laboratory scale, taking into account the complex

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

2009-01-01

185

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

NASA Astrophysics Data System (ADS)

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.

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

2002-11-01

186

The Stability of Sonoluminescing Bubble.  

NASA Astrophysics Data System (ADS)

The stability of the acoustically driven gaseous bubble oscillating in liquid is explored. The surface instabilities might considerably influence the bubble dynamics and the sonoluminescent radiation. We find that the threshold for the onset of the instabilities is strongly dependent on the gas and liquid parameters, especially the surface tension, liquid viscosity and ratio of the heat capacities of the gas. Qualitative explanation of some of the experimentally observed characteristics of the sonoluminescent radiation follow from this analysis. For example, one can understand why is it so much easier to get sonoluminescence in water than in other liquids.

Kondic, Ljubinko; Gersten, Joel

1996-03-01

187

The dependence of the moving sonoluminescing bubble trajectory on the driving pressure.  

PubMed

With a complete accounting of hydrodynamic forces on the translational-radial dynamics of a moving single-bubble sonoluminescence, temporal evolution of the bubble trajectory is investigated. In this paper, by using quasi-adiabatic evolution for the bubble interior, the bubble peak temperature at the bubble collapse is calculated. The peak temperature changes because of the bubble translational motion. The numerical results indicate that the strength of the bubble collapse is affected by its translational movement. At the bubble collapse, translational movement of the bubble is accelerated because of the increase in the added mass force on the bubble. It is shown that the magnitude of the added mass force rises by the increase in the amplitude of the driving pressure. Consequently, the increase in added mass force results in the longer trajectory path and duration. PMID:19894808

Sadighi-Bonabi, Rasoul; Rezaei-Nasirabad, Reza; Galavani, Zeinab

2009-11-01

188

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

NASA Astrophysics Data System (ADS)

MESSENGER Mercury Laser Altimeter (MLA) data has revealed a broad topographic rise ~1000 km across in the northern smooth plains and more than 1.5 km high; we characterize the rise and outline a range of hypotheses for its origin.

Dickson, J. L.; Head, J. W.; Whitten, J. L.; Fassett, C. I.; Neumann, G. A.; Smith, D. E.; Zuber, M. T.; Phillips, R. J.

2012-03-01

189

Direct measurement of mass transfer around a single bubble by micro-PLIFI  

Microsoft Academic Search

In this paper, an original direct and non-intrusive technique using Planar Laser Induced Florescence with Inhibition (PLIFI) is proposed to quantify the local mass transfer around a single spherical bubble rising in a quiescent liquid. The new set-up tracks the mass transferred in the bubble wake for a plane perpendicular to the bubble trajectory instead of a parallel plane as

J. Francois; N. Dietrich; P. Guiraud; A. Cockx

2011-01-01

190

Experiments on Visualizing the pseudo-3D Structure of Bubble Shape and its Surrounding Liquid Motion  

Microsoft Academic Search

The interface motion of a bubble and the structure of the surrounding liquid motion were simultaneously visualized to obtain their relationship. A zigzag rising bubble of 2.66 mm in equivalent diameter was examined in a rest water column. The bubble shape was filmed using illumination imaging technique with a red LED. On the other hand, the structure of the surrounding

YUKI MIYAMOTO; TAKAYUKI SAITO

2005-01-01

191

The effect of magma flow on nucleation of gas bubbles in a volcanic conduit  

Microsoft Academic Search

We solve the dynamics of magma ascent and the kinetics of bubble nucleation and growth simultaneously, which allow us to predict bubble sizes and number densities under ascent conditions. As magma rises toward the surface, the pressure decreases and eventually becomes less than the solubility pressure. When the degree of supersaturation becomes great enough, bubbles nucleate. Nucleation will stop as

Hélène Massol; Takehiro Koyaguchi

2005-01-01

192

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)

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.

Clement, Eugene P.; Daniels, Charles J.

1947-01-01

193

The Carbon Nanotube Based Micro Bubble Generator in Micro Channel with Dynamic Fluid  

Microsoft Academic Search

Based on the previous study of micro bubble generation using carbon nanotube heating elements with uW power input in static droplet of water, the dynamic characteristic of micro bubble generated by CNTs heater draw us much attention. In this summary, the micro bubble transportation, diameter control in micro channel and the departure of micro bubble from CNTs heater by pulse

Peng Xiao; Wai Kit Chan; Ho Shing Poon; Yu Zhang; Wen J. Li; R. Du

2008-01-01

194

MOBI: Microgravity Observations of Bubble Interactions  

NASA Technical Reports Server (NTRS)

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.

Koch, Donald L.; Sangani, Ashok

2004-01-01

195

Buoyancy Driven Shear Flows of Bubble Suspensions  

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

196

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

NASA Astrophysics Data System (ADS)

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

Kodama, T.; Tomita, Y.

197

Financial Bubbles and Business Scandals in History  

Microsoft Academic Search

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

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

2007-01-01

198

GAS TRANSFER FROM SMALL SPHERICAL BUBBLES IN NATURAL AND INDUSTRIAL SYSTEMS  

Microsoft Academic Search

The bubble terminal velocity and the mass transfer behavior of a small (diameter 0.2 cm) spherical bubble rising through stagnant water are reviewed. Equations relating the bubble diameter and gas composition as a function of depth are presented. The gas-liquid mass transfer co-efficient was estimated from observed bubble diameter versus time data reported in the literature. The system of equations

TARIQ AHMED; MICHAEL J. SEMMENS

2003-01-01

199

Soap Bubbles and Logic.  

ERIC Educational Resources Information Center

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

Levine, Shellie-helane; And Others

1986-01-01

200

Soap-bubble growth  

Microsoft Academic Search

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

M. Marder

1987-01-01

201

Bubble breakup phenomena in a venturi tube  

NASA Astrophysics Data System (ADS)

Microbubble has distinguished characteristics of large surface area to unit volume and small buoyancy, and it has advantages in many engineering fields. Recently microbubble generators with low energy and high performance are required to wide applications. In the present study, we propose one new effective technique to generate tiny bubbles with less than 200 ?m diameter utilizing venturi tube under high void fraction condition. The objective of the present study is to elucidate the mechanism of bubble breakup phenomena in the venturi tube and to clarify the effects of parameters which are necessary to realize an optimum system experimentally. Experiment was conducted with void fraction of 4% and variation of liquid velocity from 9 to 26 m/s at the throat. Under low velocity condition, bubbles which were observed with a high speed camera parted gradually in a wide region. On the contrary under high velocity condition, bubbles expanded after passing through the throat and shrank rapidly. Since the speed of sound in gas-liquid system is extremely lower than that of single-phase flow, the bubble breakup phenomenon in the venturi tube is explained as the supersonic flow in a Laval nozzle. By rapid pressure recovery in diverging area, expanding bubbles collapse violently. The tiny bubbles are generated due to the surface instability of shrinking bubbles.

Fujiwara, Akiko

2005-11-01

202

Preheating in bubble collisions  

SciTech Connect

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.

Zhang Jun; Piao Yunsong [College of Physical Sciences, Graduate School of Chinese Academy of Sciences, Beijing 100049 (China)

2010-08-15

203

Air Bubbles in Ice  

Microsoft Academic Search

The opacity of ice formed from water containing dissolved air is due to the presence of bubbles of air in the ice. Both bubble concentration and sizes were found to depend on the rate of freezing. Bulk water saturated with air at 0°C was found to freeze into ice containing about six bubbles per mm3 when freezing proceeded at 0.5

A E Carte

1961-01-01

204

Oscillations of soap bubbles  

Microsoft Academic Search

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

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

2010-01-01

205

Soap Bubbles in Reverse  

Microsoft Academic Search

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

Leslie Rose

1946-01-01

206

Soap Films and Bubbles.  

ERIC Educational Resources Information Center

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

Rice, Karen

1986-01-01

207

Free surface rise and fall due to wall turbulent structures  

SciTech Connect

Turbulent structures near the wall and the the surface have been studied in open channel flows using oxygen bubble visualization techniques. Experiments indicate that the flow is dominated by the generation of wall ejections and interactions of such structures with the free surface. The ejections are seen to evolve near the wall, reach the free surface, form surface patches, roll back and mix into the bulk flow. Furthermore, there are evidence of ``horseshoe`` and ``hockeystick`` type vortices in relation to the bursting events. Measurements of surface characteristics show that the ejection-inflow events are associated with deformation of the free surface. It is seen that as ejections reach the free surface, the surface goes through a rise, whereas the surface falls when the inflowing fluid returns toward the wall. These effects are enhanced as the flow Reynolds number is increased.

Rashidi, M.

1996-12-20

208

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

209

Lifetime of Bubble Rafts: Cooperativity and Avalanches  

NASA Astrophysics Data System (ADS)

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.

Ritacco, Hernán; Kiefer, Flavien; Langevin, Dominique

2007-06-01

210

Lifetime of bubble rafts: cooperativity and avalanches.  

PubMed

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

Ritacco, Hernán; Kiefer, Flavien; Langevin, Dominique

2007-06-15

211

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

SciTech Connect

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.

Millett, P. C.; El-Azab, A.; Wolf, D. (Materials Science Division); (INL); (Florida State Univ.)

2011-01-01

212

The effects of surfactant on the multiscale structure of bubbly flows.  

PubMed

It is well known that a bubble in contaminated water rises much slower than one in purified water, and the rising velocity in a contaminated system can be less than half that in a purified system. This phenomenon is explained by the so-called Marangoni effect caused by surfactant adsorption on the bubble surface. In other words, while a bubble is rising, there exists a surface concentration distribution of surfactant along the bubble surface because the adsorbed surfactant is swept off from the front part and accumulates in the rear part by advection. Owing to this surfactant accumulation in the rear part, a variation of surface tension appears along the surface and this causes a tangential shear stress on the bubble surface. This shear stress results in the decrease in the rising velocity of the bubble in contaminated liquid. More interestingly, this Marangoni effect influences not only the bubble's rising velocity but also its lateral migration in the presence of mean shear. Together, these influences cause a drastic change of the whole bubbly flow structures. In this paper, we discuss some experimental results related to this drastic change in bubbly flow structure. We show that bubble clustering phenomena are observed in an upward bubbly channel flow under certain conditions of surfactant concentrations. This cluster disappears with an increase in the concentration. We explain this phenomenon by reference to the lift force acting on a bubble in aqueous surfactant solutions. It is shown that the shear-induced lift force acting on a contaminated bubble of 1mm size can be much smaller than that on a clean bubble. PMID:18348969

Takagi, Shu; Ogasawara, Toshiyuki; Matsumoto, Yoichiro

2008-06-28

213

Mechanical interactions between bubbles in experimentally decompressed H2O-saturated rhyolite melts  

NASA Astrophysics Data System (ADS)

Bubble coalescence is a fundamental process that controls the explosivity of volcanic eruptions. If bubbles did not coalesce, or buoyantly rise, exsolved gas will remain in bubbles and the magma will not degas until very late in its rise, through explosive fragmentation. If, on the other hand, bubbles do coalesce, pathways can form that allow gas to escape from the magma during its ascent. Despite the obvious importance of coalescence, very little has been done to characterize the mechanisms of coalescence among bubbles in magma. We used high-resolution x-ray tomography to analyze bubble-coalescence structures formed during experimental decompression of natural rhyolite melt (825 C; dP/dt: 0.025-0.5 MPa s-1), and to resolve how coalescence behavior may influence degassing style. As has been observed in previous studies, X-ray tomographic scans show that when two bubbles grow next to each other, one bubble will penetrate the other at the point along the neighboring bubble's wall where the inter-bubble distance is a minimum. The onset of wall deformation is detectable at inter-bubble distances as large as 20 microns, but often it is less, and deformation progresses to form a high-radius-of-curvature reentrant within the neighboring bubble. Wall rupturing follows when the melt thickness diminishes to <1µm (tomographic resolution limit). There appears to be no relationship between bubble size and reentrant behavior; ie., roughly half of the bubbles forming reentrants where smaller than the neighboring bubble. Penetrative coalescence appears to be the dominant mechanism between two or more bubbles undergoing isotropic expansion. Some experiments underwent shear strain. In these experiments, coalescence between non-spherical bubbles is characterized by overlapping, intercalated bubble tips that are two dimensional and flattened. These interlocking structures may connect several bubbles in a row, and when the tips are ruptured, there is clear tomographic evidence that complete evacuation of gas from within the bubbles to the edge of the sampled occurred. Our results contrast previous studies that have proposed bubble coalescence begins by development of a planar inter-bubble wall that later thins and ruptures due to melt drainage. It appears, at least for rhyolite melts, that bubbles begin to coalesce well before there is any flattening of the inter-bubble wall and that the process is directional rather than symmetrical. We are now investigating how the relative pressures and/or growth rates between neighboring bubbles may influence reentrant behavior and coalescence. 3D renderings of bubble coalescence structures (FOV=600 µm)

Castro, J. M.; Burgisser, A.; Gardner, J. E.

2009-12-01

214

Bubbles and droplets in magnetic fluids  

NASA Astrophysics Data System (ADS)

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.

Yecko, Philip

2006-11-01

215

Bubbly flow structure in hydraulic jump  

Microsoft Academic Search

In an open channel, a hydraulic jump is the rapid transition from super- to sub-critical flow associated with strong turbulence and air bubble entrainment in the mixing layer. New experiments were performed at relatively large Reynolds numbers using phase-detection probes. Some new signal analysis provided characteristic air–water time and length scales of the vortical structures advecting the air bubbles in

H. Chanson

2007-01-01

216

Bubble Manipulation by Self Organization of Bubbles inside Ultrasonic Wave  

NASA Astrophysics Data System (ADS)

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.

Yamakoshi, Yoshiki; Koganezawa, Masato

2005-06-01

217

Breaking waves, turbulence and bubbles  

NASA Astrophysics Data System (ADS)

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

Gemmrich, Johannes; Vagle, Svein; Thomson, Jim

2014-05-01

218

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

NASA Astrophysics Data System (ADS)

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.

Wu, Chengtian

219

Acoustical observation of bubble oscillations induced by bubble popping.  

PubMed

Acoustic measurements of aqueous foams show three distinct radiation mechanisms that contribute to the sound pressure field: oscillations of a bubble surface that precede popping due to the instability of thin liquid film, impulsive radiation due to bursts of bubbles, and oscillations from neighboring bubbles excited by a burst bubble. The movies captured by a fast camera confirm that the bubbles adjacent to a breaking bubble oscillate under the influence of the pressure generated by the burst bubble. The spectra of resulting transient sounds fall in the range of 2-8 kHz and those from bubble oscillations correlate well with the bubble size. PMID:17500901

Ding, Junqi; Tsaur, Felicia W; Lips, Alex; Akay, Adnan

2007-04-01

220

Bem Simulations of Potential Flow with Viscous Effects as Applied to AN Acoustic Bubble  

NASA Astrophysics Data System (ADS)

The problem of a rising bubble under acoustic excitation is numerically investigated by means of two boundary element method (BEM) models in this paper. Our approach via BEM is very economical in the requirement of computational resources and yet reasonably accurate. The models have been implemented for the study of a single rising bubble. We now extend our study to introduce acoustic forcing to a bubble whereby the complexity of the problem increases (e.g. inclusion of shape oscillations). We conduct simulations for small to moderate acoustic pressure, driven close to the bubble's resonant frequency and harmonics for a micron-sized bubble for which viscous effects are reported to be of greater significance. Observations are compared with experimental findings with which we attempt to identify and investigate respectively, the associated conditions and mechanisms behind some effects (e.g. influence on rise velocity) on an acoustic bubble.

Goh, Bing Hui Terence; Klaseboer, Evert; Khoo, Boo Cheong

221

In situ study on growth behavior of interfacial bubbles and its effect on interfacial reaction during a soldering process  

NASA Astrophysics Data System (ADS)

The growth behavior of interfacial bubbles and the effect of bubbles on interfacial reaction during a soldering process were in situ studied by the synchrotron radiation real-time imaging technology. It was found that the bubbles at the solid/liquid interface were heterogeneous nucleation. The heterogeneous nucleation energy of bubbles at the interface was one-tenth of the homogeneity nucleation energy at 250 °C. At the interface, each bubble grew into spherical finally and its volume increased with the rise of temperature. Annexations between adjacent bubbles occurred, during which the bigger bubbles moved toward the smaller ones. The bubbles at the solid/liquid interface affected the dissolution behavior of Cu substrate greatly, i.e., the closer to the bubble bottom the less the Cu dissolution was, since the less the solder and the easier the saturation were. Moreover, the effect of bubbles on the growth behavior of interfacial intermetallic compound (IMC) was also discussed.

Qu, L.; Ma, H. T.; Zhao, H. J.; Kunwar, Anil; Zhao, N.

2014-06-01

222

A computationally efficient modelling of laminar separation bubbles  

NASA Technical Reports Server (NTRS)

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.

Dini, Paolo; Maughmer, Mark D.

1989-01-01

223

Microfluidic bubble logic.  

PubMed

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

Prakash, Manu; Gershenfeld, Neil

2007-02-01

224

Microfluidic Bubble Logic  

NASA Astrophysics Data System (ADS)

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

Prakash, Manu; Gershenfeld, Neil

2007-02-01

225

Test and evaluation of bubble memories  

NASA Technical Reports Server (NTRS)

A description is presented of a test program which has shown that well-constructed bubble memories can operate reliably over long periods of time and at low error rates. Even the relatively high error rate of one memory during burn-in can be considered acceptable if compared with tape recorder standards. No wear-out mechanism or aging could be detected. Bubble memories are now considered suitable for long-duration space missions and certainly are suitable for many military and commercial applications. It must be recognized, however, that bubble memories are complex devices and not yet fully understood. While the particular memory tested may never find practical applications, it nevertheless has provided insight into performance characteristics considered typical of bubble memories.

Bahm, E.

1978-01-01

226

Bubble column bioreactors  

Microsoft Academic Search

The present article investigates the behavior of bubble column bioreactors with yeast culture media in the absence of cells.\\u000a To aid in the assessment of these reactors the following properties were estimated and partly theoretically treated: relative\\u000a mean gas hold-up, bubble swarm velocity, bubble size, gas\\/liquid interfacial area, energy requirement for aeration, oxygen\\u000a transfer coefficient across the gas\\/liquid interface and

K. Schügerl; J. Lücke; U. Oels

227

Gas bubble detector  

NASA Technical Reports Server (NTRS)

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.

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

1995-01-01

228

Planar Soap Bubbles  

Microsoft Academic Search

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

RICHARD PAUL; DEVEREAUX VAUGHN

1998-01-01

229

Visualization studies of a freon-113 bubble condensing in water  

SciTech Connect

Several visualization methods have been applied in studies of organic bubbles condensing in water. The results, although qualitative in nature, have furnished an insight into the physical phenomena governing the process. Shadow graphing of the collapsing bubbles has outlined the thermal surroundings of the bubble. Shadowgraphs of a freon-113 bubble recorded in sequence have illustrated the formation of a thermal layer around the injected bubble. The shadowgraphing has reflected the density gradients, i.e., the temperature field, but it has also led to an understanding of the flow phenomena around the bubble. It was almost obvious that the thermal boundary layer and the wake, related also to a viscous boundary layer and a viscous wake, respectively. The thermal shedding of the wake, and further the envelopment of the bubble by the thermal cloud, were understood to correspond to the flow of the water surrounding the bubble. However, all that still remained to be experimentally proved by methods directly related to flow visualization. That goal was achieved by photographing the entrainment of colored water in the wake of a rising freon-113 bubble. These photographs complemented the shadowgraphs previously recorded and qualitatively proved that the thermal phenomena corresponded to the viscous flow.

Kalman, H.; Ullmann, A.; Letan, R. (Ben-Gurion Univ. of the Negev, Beer-Sheva (Israel))

1987-05-01

230

Dissociation characteristic of the inclusion complex of cyclomaltohexaose (alpha-cyclodextrin) with 1-methylcyclopropene in response to stepwise rising relative humidity.  

PubMed

The dissociation of a crystalline complex of cyclomaltohexaose (alpha-cyclodextrin) and 1-methylcyclopropene has been studied in response to stepwise rising relative humidity at 50 degrees C using a dynamic vapor sorption instrument. The dissociation of the inclusion complex was monitored with a proton transfer reaction mass spectrometer. The increase in relative humidity generally triggered the complex dissociation. However, the dissociation was greatly retarded at 80% relative humidity, presumably owing to collapse of the crystalline structure. Abrupt dissociation was observed at 90% relative humidity which corresponded to complex dissolution. The changes in powder X-ray diffraction pattern of the inclusion complex during the storage period were also investigated. PMID:20691430

Neoh, Tze Loon; Koecher, Katie; Reineccius, Gary; Furuta, Takeshi; Yoshii, Hidefumi

2010-09-23

231

Motion of Isotropic Superfluid Bubbles in Solid 4He  

NASA Astrophysics Data System (ADS)

Liquid-like motion of superfluid bubbles (negative crystals) in solid 4He has been observed (K. Yoneyama, R. Nomura and Y. Okuda: Phys. Rev. E 70 (2004) 021606). To understand this peculiar behavior, we study theoretically the motion of a superfluid bubble in bcc solid 4He. We adopt a simple model in which only the interface energy and the gravitational energy are taken into account and dissipation occurs only at the interface. We show that a spherical bubble rises at a constant velocity proportional to its radius, and that there is a critical size above which the bubble is detached from the flat bottom of the container. The radius of the critical bubble is proportional to the contact angle of the solid.

Mukai, Masaki; Uwaha, Makio

2006-05-01

232

Hydrogen Bubbles as PIV/ICV Tracers in Cylinder Shedding  

NASA Astrophysics Data System (ADS)

We examine the behavior of hydrogen bubbles formed by electrolysis of water on a 2.54 mm cylindrical electrode in a water tunnel. The Reynolds Number based on cylinder diameter varies from 400 to 1100, and tunnel velocities range from 17 to 50 cm/s. Time staggered digital photographs were taken to evaluate the use of the bubbles as PIV and ICV (Image Correlation Velocimetry) tracers as in Apps, Chen and Sigurdson, Expts. Fluids, 2003. The fact that the bubbles originate in a sheet precludes the necessity of using laser sheet illumination. PIV/ICV on bubbles driven by their buoyancy only does not work well as the assumed PIV/ICV condition of the tracer being advected by a background velocity field is violated. The bubbles have a distribution of diameters and therefore different rise velocities, creating a distorted pattern which reduces the correlation between interrogation windows.

Gilbert, Stuart; Sigurdson, Lorenz

2004-11-01

233

A Glycerol Drop in Water Boosts Single-Bubble Sonoluminescence  

NASA Astrophysics Data System (ADS)

A glycerol drop injected at the antinode of standing acoustic waves in pure water is found to diffuse nearly isotropically, leaving a stable sonoluminescing bubble. The dynamics of such a bubble is significantly different from that of an ordinary sonoluminescing bubble in pure water. The bubble rebounds are enlarged but the emission intensity becomes approximately 10% stronger if the driving conditions are unaltered. The stability upper threshold is raised by 2%, at which 40% more sonoluminescence is produced during a stable period. The bubble then experiences a jiggling period, giving rise to rebounds with anomalous spikes as revealed by Mie light scattering. The spikes may be accounted for by fragmentation due to parametric instability.

Harba, Naser; Hayashi, Shigeo

2003-02-01

234

Bubbly flow measurement using digital particle image velocimetry  

SciTech Connect

A three-dimensional velocity measurement investigation in a cocurrent, upward bubbly pipe flow was performed by acquiring the instantaneous three-dimensional velocity field distributions of the two-phase flow with the developed three-dimensional particle image velocimetry (PIV) technique. The first stage of this investigation is to study the interaction between a single rising bubble in a pipe flow and its surrounding fluid using a PIV technique.

Schmidl, W.D.; Ortiz-Villafuerte, J.; Hassan, Y.A. [Texas A & M Univ., College Station, TX (United States)

1997-12-01

235

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

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

236

Evaporation, Boiling and Bubbles  

ERIC Educational Resources Information Center

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

Goodwin, Alan

2012-01-01

237

Let Them Blow Bubbles.  

ERIC Educational Resources Information Center

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

Korenic, Eileen

1988-01-01

238

Market bubbles and crashes  

Microsoft Academic Search

Episodes of market crashes have fascinated economists for centuries. Although many academics, practitioners and policy makers have studied questions related to collapsing asset price bubbles, there is little consensus yet about their causes and effects. This review and essay evaluates some of the hypotheses offered to explain the market crashes that often follow asset price bubbles. Starting from historical accounts

Taisei Kaizoji; Didier Sornette

2008-01-01

239

Soap bubbles. 1  

Microsoft Academic Search

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

A. Glassner

2000-01-01

240

The Vacuum Bubble Nucleation  

SciTech Connect

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.

Lee, Bum-Hoon [Department of Physics and Center for Quantum Spacetime, Sogang University Seoul 121-742 (Korea, Republic of); Lee, Wonwoo [Center for Quantum Spacetime, Sogang University, Seoul 121-742 (Korea, Republic of)

2009-07-10

241

The Fermi bubbles revisited  

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

242

Classification of hard domains in garnet bubble films  

Microsoft Academic Search

The ``exercise'' experiment and the substantial difference in static characteristics show that those dumbbell domains, which can eventually contract to circular form and then collapse, should be classified as a kind of dumbbells rather than hard bubbles. Thus it is suggested that dumbbell domains can be divided into two kinds: ID and IID. Ordinary hard bubbles (OHB), ID and IID,

Xiang Fu Nie; Gui de Tang; Xiu de Niu; Bao Shan Han

1991-01-01

243

Marine liquid aerosol production from bursting of air bubbles  

Microsoft Academic Search

The action of wind stress upon the marine surface is responsible for producing air bubbles in seawater through wave breaking. After a given residence time in the sea, bubbles return to the surface, where they burst. The phenomenon of bursting produces two families of droplets: film drops and jet drops. The characteristics of jet drops are far better known than

F. J. Resch; J. S. Darrozes; G. M. Afèeti

1986-01-01

244

The latency reduction of bidirectional magnetic bubble memories  

Microsoft Academic Search

Magnetic bubble memories have a significant advantage over rotating disk memories as they have no angular momentum. This characteristic theoretically allows them to remain in one position and then be started immediately in either direction. Presented are the results of a simulation of a simple magnetic bubble memory system, which demonstrate that an order of magnitude decrease in latency is

C. Naranong; D. Hammerstrom

1979-01-01

245

Experimental investigation of a turbulent bubbly mixing layer  

Microsoft Academic Search

An experimental investigation of a turbulent air-water bubbly flow in a plane vertical mixing layer is presented. An important characteristic of this bubbly flow is that the slip velocity is of the same order of magnitude as the liquid velocity. For various inlet conditions of liquid velocity and void fraction, the distributions of velocity, turbulence intensity and void fraction were

V. Roig; C. Suzanne; L. Masbernat

1998-01-01

246

Scaling model for laser-produced bubbles in soft tissue  

NASA Astrophysics Data System (ADS)

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 and duration of bubbles as functions of the laser energy and initially heated volume.

London, Richard A.; Bailey, David S.; Amendt, Peter A.; Visuri, Steven R.; Esch, Victor C.

1998-05-01

247

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)

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.

Kagumba, Moses Odongo O.

248

A computationally efficient modelling of laminar separation bubbles  

NASA Technical Reports Server (NTRS)

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.

Maughmer, Mark D.

1988-01-01

249

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

SciTech Connect

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.

Paul C Millett; Anter El-Azab

2011-01-01

250

Hydrodynamical similarities between bubble column and bubbly pipe flow  

Microsoft Academic Search

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

Robert F. Mudde; Takayuki Saito

2001-01-01

251

Mounting and application of bubble display system: bubble cosmos  

Microsoft Academic Search

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

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

2006-01-01

252

Gas Bubble Formation in Stagnant and Flowing Mercury  

SciTech Connect

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

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

2007-01-01

253

Bubbles, Bubbles: Integrated Investigations with Floating Spheres  

ERIC Educational Resources Information Center

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…

Reeder, Stacy

2007-01-01

254

Bubbles, Bubbles: Integrated Investigations with Floating Spheres  

Microsoft Academic Search

In this article, the author describes integrated science and mathematics activities developed for fourthgrade 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 also encouraged to use prior knowledge to make conjectures about what they believed would

Stacy Reeder

2007-01-01

255

A generalized bubble diameter correlation for gas-solid fluidized beds  

Microsoft Academic Search

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

Masayuki Horio; Akira Nonaka

1987-01-01

256

Tribonucleation of bubbles.  

PubMed

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

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

2014-07-15

257

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

SciTech Connect

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

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

2011-02-15

258

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

Microsoft Academic Search

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

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

1999-01-01

259

Speculations on Nonlinear Speculative Bubbles  

Microsoft Academic Search

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

J. Barkley Rosser

1997-01-01

260

Rotating bubble membrane radiator  

DOEpatents

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.

Webb, Brent J. (West Richland, WA); Coomes, Edmund P. (West Richland, WA)

1988-12-06

261

Viscosity Destabilizes Sonoluminescing Bubbles  

NASA Astrophysics Data System (ADS)

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

Toegel, Ruediger; Luther, Stefan; Lohse, Detlef

2006-03-01

262

Viscosity destabilizes sonoluminescing bubbles.  

PubMed

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

Toegel, Ruediger; Luther, Stefan; Lohse, Detlef

2006-03-24

263

A heat transfer model for evaporation of coalescing bubbles in micro-channel flow  

Microsoft Academic Search

The current study presents a one-dimensional model of confined coalescing bubble flow for the prediction of micro-channel convective boiling heat transfer. Coalescing bubble flow has recently been identified as one of the characteristic flow patterns to be found in micro-scale systems, occurring at intermediate vapor qualities between the isolated bubble and the fully annular regimes. As two or more bubbles

L. Consolini; J. R. Thome

2010-01-01

264

Optical measurements of small deeply penetrating bubble populations generated by breaking waves in the Southern Ocean  

NASA Astrophysics Data System (ADS)

size distributions ranging from 0.5 to 125 ?m radius were measured optically during high winds of 13 m s-1 and large-scale wave breaking as part of the Southern Ocean Gas Exchange Experiment. Very small bubbles with radii less than 60 µm were measured at 6-9 m depth using optical measurements of the near-forward volume scattering function and critical scattering angle for bubbles (˜80°). The bubble size distributions generally followed a power law distribution with mean slope values ranging from 3.6 to 4.6. The steeper slopes measured here were consistent with what would be expected near the base of the bubble plume. Bubbles, likely stabilized with organic coatings, were present for time periods on the order of 10-100 s at depths of 6-9 m. Here, relatively young seas, with an inverse wave age of approximately 0.88 and shorter characteristic wave scales, produced lower bubble concentrations, shallower bubble penetration depths, and steep bubble size distribution slopes. Conversely, older seas, with an inverse wave age of 0.70 and longer characteristic wave scales, produced relatively higher bubble concentrations penetrating to 15 m depth, larger bubble sizes, and shallower bubble size distribution slopes. When extrapolated to 4 m depth using a previously published bubble size distribution, our estimates suggest that the deeply penetrating small bubbles measured in the Southern Ocean supplied ˜36% of the total void fraction and likely contributed to the transfer and supersaturation of low-solubility gases.

Randolph, Kaylan; Dierssen, Heidi M.; Twardowski, Michael; Cifuentes-Lorenzen, Alejandro; Zappa, Christopher J.

2014-02-01

265

Atomistic simulation of He bubble in Fe as obstacle to dislocation  

NASA Astrophysics Data System (ADS)

Degradation of mechanical properties due to nanometric irradiation induced defects is one of the challenging issues in designing materials for future fusion reactors. Various types of defects such as voids and He bubbles may be produced due to high dose of neutron irradiation due to fusion reaction. We study the influence of He bubble on the mobility of an edge dislocation in pure bcc-Fe using molecular dynamics simulation as a function of bubble size, He density and temperature. It appears that low contents He bubbles are penetrable defects, which size and temperature rise make them harder and softer, respectively. At high He contents a size dependent loop punching is observed, which at larger bubble sizes leads to a multistep dislocation-defect interaction. It also appears that the bubble surface curvature and temperature are the main parameters in the screw segments annihilation needed for the release of the dislocation from the bubble.

Hafez Haghighat, S. M.; Lucas, G.; Schäublin, R.

2009-07-01

266

Gas separation and bubble behavior at a woven screen  

NASA Astrophysics Data System (ADS)

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

Conrath, Michael; Dreyer, Michael E.

267

Direct numerical simulations of bubbly flows Part 2. Moderate Reynolds number arrays  

Microsoft Academic Search

Direct numerical simulations of the motion of two- and three-dimensional finite Reynolds number buoyant bubbles in a periodic domain are presented. The full Navier Stokes equations are solved by a finite difference\\/front tracking method that allows a fully deformable interface between the bubbles and the ambient fluid and the inclusion of surface tension. The rise Reynolds numbers are around 20

Asghar Esmaeeli; Grétar Tryggvason

1999-01-01

268

Direct numerical simulations of bubbly flows. Part 1. Low Reynolds number arrays  

Microsoft Academic Search

Direct numerical simulations of the motion of two- and three-dimensional buoyant bubbles in periodic domains are presented. The full Navier Stokes equations are solved by a finite difference\\/front tracking method that allows a fully deformable interface between the bubbles and the ambient fluid and the inclusion of surface tension. The governing parameters are selected such that the average rise Reynolds

Asghar Esmaeeli; Grétar Tryggvason

1998-01-01

269

Coupled effects of magma flow and nucleation of gas bubbles in a volcanic conduit  

Microsoft Academic Search

We solve the dynamics of magma ascent and the kinetics of bubble nucleation and growth simultaneously, which allow us to predict bubble sizes and number density under ascent conditions. As magma rises toward the surface the pressure decreases and eventually becomes less than the solubility pressure. When the difference between the concentration of volatiles in the melt and the concentration

H. Massol; T. Koyaguchi

2003-01-01

270

Single-bubble sonoluminescence and the diffusive transport of heat and mass  

Microsoft Academic Search

The spherically symmetric Navier-Stokes equations with variable properties are solved together with momentum and energy equations in the liquid. Calculations are presented for bubbles of noble gases in liquid water. A strong case has been made by several authors that strong shock waves converging on the center of a strongly driven bubble give rise to rapid heating and compression leading

Vuong Quang Vi

1997-01-01

271

Chemistry in Soap Bubbles.  

ERIC Educational Resources Information Center

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

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

2002-01-01

272

Visualization of bubble behavior and bubble diameter correlation for NH 3–H 2O bubble absorption  

Microsoft Academic Search

The objectives of this paper are to visualize the bubble behavior for an ammonia–water absorption process, and to study the effect of key parameters on ammonia–water bubble absorption performance. The orifice diameter, orifice number, liquid concentration and vapor velocity are considered as the key parameters. The departing bubbles tend to be spherical for surface tension dominant flow, and the bubbles

Yong Tae Kang; T. Nagano; Takao Kashiwagi

2002-01-01

273

Colloquium: Soap bubble clusters  

NASA Astrophysics Data System (ADS)

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

Morgan, Frank

2007-07-01

274

Bubble coalescence in magmas  

NASA Technical Reports Server (NTRS)

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

Herd, Richard A.; Pinkerton, Harry

1993-01-01

275

Nonlinear ultrasonic propagation in bubbly liquids: a numerical model.  

PubMed

In this paper, we investigate the problem of ultrasonic propagation in liquids with bubbles. A new numerical algorithm is constructed to solve the acoustic field-bubbles vibration coupled system. For this purpose, a second-order equation written in a volume formulation is considered for bubbles vibration and coupled with the linear nondissipative wave equation, i.e., attenuation and nonlinear effects are supposed to occur exclusively because of the presence of bubbles. Nonlinear characteristics of the phenomenon are particularly analyzed and illustrated. Plane harmonic waves are first considered in a mixture of air bubbles in water, and conclusions about changes in the wave speed, attenuation, harmonic distortion, effective nonlinearity parameter and nonlinear effects with distance are given. In particular, a law relating the second-harmonic progression with the density of bubbles is found. The propagation of plane pulses is also analyzed to give results on nonlinear attenuation, changes of frequency, and self-demodulation. The influence of the resonance frequency of bubbles on the nonlinear field is then determined. Differences and similarities with nonlinear acoustics in homogeneous fluid are shown and commented. The possibilities and limits of an equivalent nonlinear fluid are then discussed. The propagation of a high-frequency pulsed signal in a bubbly liquid used in a biological application is also the subject of numerical experiments, for frequencies near and beyond the resonance frequency of the bubbles. PMID:18314254

Vanhille, Christian; Campos-Pozuelo, Cleofé

2008-05-01

276

Evolution and axial symmetry breaking of the toroidal vortex behind a clean bubble  

NASA Astrophysics Data System (ADS)

We experimentally observed the wake structure behind a rising clean bubble by using silicon oil solution of photochromic dye. Clean bubble condition was realized since both the dye and the silicon oil are non-polar. A single bubble was generated just below a colored region where the dye was activated by UV sheet light illumination. Once the bubble passed the colored part of the liquid, the bubble was accompanied by some portion of activated dye. Hence the flow structure in the rear of the single rising bubble was visualized. In this visualization method, we are able to distinguish the liquid portion trapped behind the bubble from the non-colored surrounding liquid that flows in the colored trapped portion. We precisely controlled the size of the bubble in order to observe how the size of the toroidal vortex behind a bubble evolves and the axial symmetry breaks. The relation between the in-flow of the surrounding liquid into the toroidal vortex and the bubble motion was studied in detail.

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

2008-11-01

277

Reduced gradient bubble model.  

PubMed

An approach to decompression modeling, the reduced gradient bubble model (RGBM), is developed from the critical phase hypothesis. The phase limit is introduced, extended, and applied within bubble-nucleation theory proposed by Yount. Much is different in the RGBM algorithm, on both theoretical and applied sides, with a focus on permissible bubble excesses rather than just dissolved gas buildup, something of a departure from traditional models. Overall, the approach is conservative, with changes in parameter settings affording flexibility. Marginal profiles permitted by tables and meters are restricted by the bubble algorithm. Highlighted features of the conservative algorithm include: (1) reduced no-stop time limits from the varying-permeability model (VPM); (2) short safety stops (or shallow swimming ascents) in the 10-20 feet of sea water (fsw) zone; (3) ascent and descent rates of 60 fsw/min, or slower; (4) restricted repetitive exposures, particularly beyond 100 fsw, based on reduced permissible bubble excess; (5) restricted spike (shallow-to-deep) exposures based on excitation of additional micronuclei; (6) restricted multi-day activity based on regeneration of micronuclei; (7) consistent treatment of altitude diving within model framework; (8) algorithm linked to bubble-nucleation theory and experiment. Coupled to medical reports about the long term effects of breathing pressurized gases and shortcomings in dissolved gas models, conservative modeling seems prudent. PMID:2276850

Wienke, B R

1990-11-01

278

Heat transport in bubbling turbulent convection  

PubMed Central

Boiling is an extremely effective way to promote heat transfer from a hot surface to a liquid due to numerous mechanisms, many of which are not understood in quantitative detail. An important component of the overall process is that the buoyancy of the bubble compounds with that of the liquid to give rise to a much-enhanced natural convection. In this article, we focus specifically on this enhancement and present a numerical study of the resulting two-phase Rayleigh–Bénard convection process in a cylindrical cell with a diameter equal to its height. We make no attempt to model other aspects of the boiling process such as bubble nucleation and detachment. The cell base and top are held at temperatures above and below the boiling point of the liquid, respectively. By keeping this difference constant, we study the effect of the liquid superheat in a Rayleigh number range that, in the absence of boiling, would be between 2 × 106 and 5 × 109. We find a considerable enhancement of the heat transfer and study its dependence on the number of bubbles, the degree of superheat of the hot cell bottom, and the Rayleigh number. The increased buoyancy provided by the bubbles leads to more energetic hot plumes detaching from the cell bottom, and the strength of the circulation in the cell is significantly increased. Our results are in general agreement with recent experiments on boiling Rayleigh–Bénard convection.

Lakkaraju, Rajaram; Stevens, Richard J. A. M.; Oresta, Paolo; Verzicco, Roberto; Lohse, Detlef; Prosperetti, Andrea

2013-01-01

279

Heat transport in bubbling turbulent convection.  

PubMed

Boiling is an extremely effective way to promote heat transfer from a hot surface to a liquid due to numerous mechanisms, many of which are not understood in quantitative detail. An important component of the overall process is that the buoyancy of the bubble compounds with that of the liquid to give rise to a much-enhanced natural convection. In this article, we focus specifically on this enhancement and present a numerical study of the resulting two-phase Rayleigh-Bénard convection process in a cylindrical cell with a diameter equal to its height. We make no attempt to model other aspects of the boiling process such as bubble nucleation and detachment. The cell base and top are held at temperatures above and below the boiling point of the liquid, respectively. By keeping this difference constant, we study the effect of the liquid superheat in a Rayleigh number range that, in the absence of boiling, would be between 2 × 10(6) and 5 × 10(9). We find a considerable enhancement of the heat transfer and study its dependence on the number of bubbles, the degree of superheat of the hot cell bottom, and the Rayleigh number. The increased buoyancy provided by the bubbles leads to more energetic hot plumes detaching from the cell bottom, and the strength of the circulation in the cell is significantly increased. Our results are in general agreement with recent experiments on boiling Rayleigh-Bénard convection. PMID:23696657

Lakkaraju, Rajaram; Stevens, Richard J A M; Oresta, Paolo; Verzicco, Roberto; Lohse, Detlef; Prosperetti, Andrea

2013-06-01

280

A Numerical Study of Low-Reynolds-Number Separation Bubbles  

NASA Technical Reports Server (NTRS)

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

Tatineni, Mahidhar; Zhong, Xiao-Lin

1999-01-01

281

Acronical Risings and Settings  

NASA Astrophysics Data System (ADS)

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.

Hockey, Thomas A.

2012-01-01

282

Statistical equilibrium of bubble oscillations in dilute bubbly flows.  

PubMed

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

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

2008-04-01

283

Statistical equilibrium of bubble oscillations in dilute bubbly flows  

PubMed Central

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

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

2008-01-01

284

BURST OF STAR FORMATION DRIVES BUBBLE IN GALAXY'S CORE  

NASA Technical Reports Server (NTRS)

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

2002-01-01

285

High rise buildings  

SciTech Connect

The feasibility of developing new energy conservation standards for high rise residential-type buildings including hotels, motels, apartment houses, and lodging houses is discussed. Differences between the high and low rise residential building energy regulations are summarized. The data collection method and results are presented. (MCW)

Horn, M.

1980-06-01

286

Rising Sea Levels  

NSDL National Science Digital Library

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

Learn, Nbc

2010-10-07

287

Colliding with a crunching bubble  

SciTech Connect

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

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

2007-03-26

288

Determining the outcome of cosmic bubble collisions in full general relativity  

NASA Astrophysics Data System (ADS)

Cosmic bubble collisions provide an important possible observational window on the dynamics of eternal inflation. In eternal inflation, our observable universe is contained in one of many bubbles formed from an inflating metastable vacuum. The collision between bubbles can leave a detectable imprint on the cosmic microwave background radiation. Although phenomenological models of the observational signature have been proposed, to make the theory fully predictive one must determine the bubble collision spacetime, and thus the cosmological observables, from a scalar field theory giving rise to eternal inflation. Because of the intrinsically nonlinear nature of the bubbles and their collision, this requires a numerical treatment incorporating General Relativity. In this paper, we present results from numerical simulations of bubble collisions in full General Relativity. These simulations allow us to accurately determine the outcome of bubble collisions, and examine their effect on the cosmology inside a bubble universe. We confirm the validity of a number of approximations used in previous analytic work, and identify qualitatively new features of bubble collision spacetimes. Both vacuum bubbles and bubbles containing a realistic inflationary cosmology are studied. We identify the constraints on the scalar field potential that must be satisfied in order to obtain collisions that are consistent with our observed cosmology, yet leave detectable signatures.

Johnson, Matthew C.; Peiris, Hiranya V.; Lehner, Luis

2012-04-01

289

Theoretical and experimental investigation of the liquid flow around a gas bubble  

NASA Astrophysics Data System (ADS)

The relation between the shape of gas bubbles and the flow pattern around them is studied in order to improve understanding of the interaction between the gas and liquid phases. The equilibrium shapes of the free surfaces of the bubbles in different liquids are numerically computed. The liquid flow in the region of single rising bubbles with terminal velocities and high Reynolds numbers is investigated. A theoretical model for the shape of the free surface of a gas bubble and the flow field around it is presented. The usefulness and applicability of this model is tested by comparing experimental and calculated results.

van Bekkum, A. J.

290

Bubbles of Metamorphosis  

NASA Astrophysics Data System (ADS)

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

Prakash, Manu

2011-11-01

291

Bubble-induced damping in displacement-driven microfluidic flows.  

PubMed

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

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

2012-08-01

292

Light scattering by a spheroidal bubble with geometrical optics approximation  

NASA Astrophysics Data System (ADS)

This paper proposes the spheroidal model for analyzing the light scattering characteristics of an air bubble. The angular distributions of light scattered by a large spheroidal bubble with end-on incidence are calculated using geometrical optics approximation. The divergence factor, diffraction, and phase shift are considered in the computation. The MATLAB code was developed and verified using the Mie result for a spherical bubble, and the scattering patterns of the two methods agreed well. The effects on the scattering properties are analyzed in terms of the size and shape parameter of the bubble and the incident beam width. The relations between the deviation angle and incident angle, emergent light intensity, and scattering angle are analyzed and used to explain the scattering patterns of a spheroidal bubble.

He, Huiling; Li, Wei; Zhang, Xiaohui; Xia, Min; Yang, Kecheng

2012-08-01

293

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

294

Unsteady Thermocapillary Migration of Bubbles.  

National Technical Information Service (NTIS)

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 bubb...

L. H. Dill R. Balasubramaniam

1988-01-01

295

Bubble Formation at a Submerged Orifice in Reduced Gravity  

NASA Technical Reports Server (NTRS)

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

Buyevich, Yu A.; Webbon, Bruce W.

1994-01-01

296

Bubbles and Biosensors  

NSDL National Science Digital Library

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

Vu Bioengineering Ret Program

297

Fluid Dynamics of Bubbly Liquids  

NASA Technical Reports Server (NTRS)

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.

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

298

Asset Float and Speculative Bubbles  

Microsoft Academic Search

We model the relationship between asset float (tradeable shares) and speculative bubbles. Investors with heterogeneous beliefs and short-sales constraints trade a stock with limited float because of insider lockups. A bubble arises as price overweighs optimists' beliefs and investors anticipate the option to resell to those with even higher valuations. The bubble's size depends on float as investors anticipate an

HARRISON HONG; JOSÉ SCHEINKMAN; WEI XIONG

2006-01-01

299

The Home Zone: Bubble Shapes  

NSDL National Science Digital Library

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

Damonte, Kathleen

2003-05-01

300

Cohesion of Bubbles in Foam  

ERIC Educational Resources Information Center

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)

Ross, Sydney

1978-01-01

301

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

NASA Technical Reports Server (NTRS)

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.

Azuma, H.

1993-01-01

302

What's in the Bubbles?  

NSDL National Science Digital Library

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

Eberle, Francis; Tugel, Joyce; Keeley, Page

2007-01-01

303

Bubble fusion: Preliminary estimates  

SciTech Connect

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

Krakowski, R.A.

1995-02-01

304

Double Bubble? No Trouble!  

ERIC Educational Resources Information Center

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)

Shaw, Mike I.; Smith, Greg F.

1995-01-01

305

Soap bubbles and crystals  

Microsoft Academic Search

The Plateau problem is a famous problem in the shape of bubbles. The author’s solution to this problem by the introduction\\u000a of geometric measure theory is described. The context of Cyril Stanley Smith’s work on the shape of grains and crystals is\\u000a introduced.

Jean E. Taylor

2006-01-01

306

Colloquium: Soap bubble clusters  

Microsoft Academic Search

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

Frank Morgan

2007-01-01

307

Oscillations of soap bubbles  

NASA Astrophysics Data System (ADS)

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

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

2010-07-01

308

The Liberal Arts Bubble  

ERIC Educational Resources Information Center

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

Agresto, John

2011-01-01

309

Bubble nucleation in liquids  

Microsoft Academic Search

A review of theoretical and experimental aspects of homogeneous and heterogeneous bubble nucleation (valuable in LNG studies) covers recent developments in nucleation theory, which include hydrodynamic and diffusion constraints, gas-phase nonidealities, and heterogeneous nucleation. Large superheating may be involved in the dangerous and destructive contact vapor explosions observed in metallurgical and paper smelt processing and pose a potential hazard in

Milton Blander; Joseph L. Katz

1975-01-01

310

Bubble Chamber Site  

NSDL National Science Digital Library

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

2006-06-19

311

Bubble fusion: Preliminary estimates  

NASA Astrophysics Data System (ADS)

The collapse of a gas-filled bubble in disequilibrium (i.e., internal pressure much less than 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(exp -5) to 10(exp -6) are predicted by an idealized bubble-dynamics model as necessary to achieve conditions where nuclear fusion of deuterium-tritium might be observed. Harmonic and aharmonic pressurizations/decompressions are examined as means to achieve the required levels of disequilibrium required to create fusion conditions. A number of phenomena not included in the analysis reported herein could enhance or reduce the small levels of nuclear fusions predicted.

Krakowski, R. A.

312

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

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

313

Signature of anisotropic bubble collisions  

SciTech Connect

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

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

2010-09-15

314

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

315

Characterization of an acoustic cavitation bubble structure at 230 kHz.  

PubMed

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

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

2011-03-01

316

Bubbles in drops: from cavitation to exploding stars  

NASA Astrophysics Data System (ADS)

We performed an experiment to generate single cavitation bubbles inside centimetric quasi-spherical water drops. To produce such drops, our experiment was realized under microgravity conditions (42nd ESA parabolic flight campaign). The ultra-fast recording of the bubble collapse and ensuing dynamics revealed consequences of the unique geometry of the drop's free surface. We obtained the first visualizations of a jet pair escaping the drop after the collapse of eccentrically-placed bubbles. The high quality of the images also disclosed some features of the inner drop dynamics. Due to their confinement within the isolated drop volume, shock waves emitted at the bubble collapse bounce back and forth thereby exciting gas nuclei into sub-millimetric bubbles. When located beneath the free surface, the collapse of these bubbles gives rise to narrow ``hair-like'' jets on the surface. Here we briefly describe the physics underlying these observations while discussing possible analogies with various astrophysical processes from the Sun (spicules) to asymmetric supernovae.

Kobel, Philippe; Obreschkow, Danail; Dorsaz, Nicolas; de Bosset, Aurele; Tinguely, Marc; Farhat, Mohamed

2011-11-01

317

Downward bubbly gas–liquid flow in a vertical pipe  

Microsoft Academic Search

Local characteristics of downward bubbly flow in a 42.3mm i.d. vertical pipe were investigated. An electrochemical technique was used to measure wall shear stress, local void fraction, liquid velocity, wall shear stress and velocity fluctuations. A gas–liquid mixer was used permitting the change in size of gas bubbles for the same gas and liquid flow rates. Special attention was paid

O. N. Kashinsky; V. V. Randin

1999-01-01

318

Bubble Generation in Liquid Hydrocarbon in Divergent Fields  

NASA Astrophysics Data System (ADS)

The conduction current Ic and the photocurrent Ip were measured in hydrocarbon liquids subjected to d.c. divergent fields. Space-charge limited currents were observed in clarified ionic carrier of both polarities produced by electron attachment. The linear relation between Ip and Ic indicated that molecules were excited by injected electrons before the attachment. In liquid methane in negative point electrode, Ip and Ic were reduced by a rise in pressure, giving evidence for the existence of gaseous bubbles during discharge. However in pentane and hexane, both currents were independent of pressure. The difference is probably caused by the bubble growth rate; the rate is probably larger in liquid methane.

Arii, Kiyomitsu; Kitani, Isamu

1984-01-01

319

Multiscale Modeling of Cavitating Bubbly Flows  

NASA Astrophysics Data System (ADS)

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 3DYNAFS^ 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.

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

2013-03-01

320

Micro bubble formation and bubble dissolution in domestic wet central heating systems  

NASA Astrophysics Data System (ADS)

16 % of the carbon dioxide emissions in the UK are known to originate from wet domestic central heating systems. Contemporary systems make use of very efficient boilers known as condensing boilers that could result in efficiencies in the 90-100% range. However, research and development into the phenomenon of micro bubbles in such systems has been practically non-existent. In fact, such systems normally incorporate a passive deaerator that is installed as a `default' feature with no real knowledge as to the micro bubble characteristics and their effect on such systems. High saturation ratios are known to occur due to the widespread use of untreated tap water in such systems and due to the inevitable leakage of air into the closed loop circulation system during the daily thermal cycling. The high temperatures at the boiler wall result in super saturation conditions which consequently lead to micro bubble nucleation and detachment, leading to bubbly two phase flow. Experiments have been done on a test rig incorporating a typical 19 kW domestic gas fired boiler to determine the expected saturation ratios and bubble production and dissolution rates in such systems.

Fsadni, Andrew M.; Ge, Yunting

2012-04-01

321

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

PubMed

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

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

2012-10-01

322

On the effects of scintillation of low-latitude bubbles on transionospheric paths of propagation  

NASA Astrophysics Data System (ADS)

A previously developed scintillation propagation model for L band signals on transionospheric paths has been further extended to describe the effects caused by the localized structure of plasma bubbles in the low-latitude ionosphere. This takes into account quasi-deterministic and random structures typical of bubbles. The model can produce signal statistical moments (power spectra, correlation functions, scintillation index, etc.) and generate random time series including the case of through bubble propagation. The simulated random time series of the field demonstrate the characteristic nonstationary behavior caused by the presence and motion of the bubble structures through the path of propagation, showing that strong enhancements of the scintillation index (S4) can occur depending on the parameters of the bubble and the path. Modeling results are compared with scintillation records due to bubbles passing through GPS signal paths to a receiver at Douala, Cameroon. This shows good agreement providing validation for the bubble and propagation model.

Zernov, Nikolay N.; Gherm, Vadim E.; Strangeways, Hal J.

2009-02-01

323

Iodine Mass Transfer from Xenon-Iodine Mixed Gas Bubble to Liquid Sodium Pool, (II) Development of Analytical Model  

Microsoft Academic Search

Iodine mass transfer in a xenon-iodine mixed gas bubble rising through a liquid sodium pool is analyzed on the basis of a diffusion model applied to the first short stage just after the bubble generation and a convection model applied to the successive stage. In the diffusion model, production of sodium iodide aerosols and generation of the heat caused by

Shinya MIYAHARA; Norihiko SAGAWA

1996-01-01

324

Bubble Eliminator Based on Centrifugal Flow  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

325

Esperanza Rising - Chapter 3  

NSDL National Science Digital Library

Reading Chapter 3 from Esperanza Rising, by Pam Munoz Ryan, students will learn about thirteen year old Esperanza and her newly widowed mother as they are forced to leave their fairy tale existence at a ranch in Mexico, to live and work in a migrant worker camp during the Great Depression. Students will practice answering text dependent questions.

2012-11-15

326

The rise of graphene  

Microsoft Academic Search

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

A. K. Geim; K. S. Novoselov

2007-01-01

327

Global sea level rise  

SciTech Connect

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.

Douglas, B.C. (NOAA, Rockville, MD (USA))

1991-04-15

328

Sonoluminescence, sonochemistry and bubble dynamics of single bubble cavitation  

NASA Astrophysics Data System (ADS)

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.

Hatanaka, Shin-ichi

2012-09-01

329

Effect of surfactants on single-bubble sonoluminescence  

NASA Astrophysics Data System (ADS)

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.

Yasui, Kyuichi

1998-10-01

330

Pulsed Electrical Discharge in a Gas Bubble in Water  

NASA Astrophysics Data System (ADS)

This experiment is an investigation of the electrical and optical characteristics of a pulsed electrical discharge ignited in a gas bubble in water in a needle-to-plane electrode geometry. Argon or oxygen gas is fed through a platinum hypodermic needle that serves as the high voltage electrode. The gas filled bubble forms at the high voltage electrode with the tip of the needle inside the bubble. The discharge in the gas bubble in water is produced by applying 5 -- 15 kV, microsecond long rectangular pulses between the electrodes submerged in water. The voltage across the electrodes and the current are measured as functions of time. Electrical measurements suggest a discharge ignited in the bubble (composed of the bubbled gas and water vapor) without breakdown of the entire water filled electrode gap. Time-resolved optical emission measurements are taken in the areas of the spectrum corresponding to the main reactive species produced in the discharge, e.g. OH 309 nm, Ar 750 nm, and O 777 nm emissions using optical filters. The discharge properties are investigated as a function of the applied voltage, the distance between the electrodes, the gas in the bubble (Ar or O2). Work supported by the US Army, Picatinny Arsenal, NJ and the US DOE (Contract number DE-AC02-76CH03073).

Schaefer, Erica; Gershman, Sophia; Mozgina, Oksana

2005-10-01

331

Anatomy of bubbling solutions  

Microsoft Academic Search

We present a comprehensive analysis of holography for the bubbling solutions of Lin-Lunin-Maldacena. These solutions are uniquely determined by a coloring of a 2-plane, which was argued to correspond to the phase space of free fermions. We show that in general this phase space distribution does not determine fully the 1\\/2 BPS state of N = 4 SYM that the

Kostas Skenderis; Marika Taylor

2007-01-01

332

Bubble dynamics in drinks  

NASA Astrophysics Data System (ADS)

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.

Brou?ková, Zuzana; Trávní?ek, Zden?k; Šafa?ík, Pavel

2014-03-01

333

Effect of bubble deformation on the properties of bubbly flows  

Microsoft Academic Search

Direct numerical simulations of the motion of 27 three-dimensional deformable buoyant bubbles in periodic domains are presented. The full Navier Stokes equations are solved by a parallelized finite-difference\\/front-tracking method that allows a deformable interface between the bubbles and the suspending fluid and the inclusion of surface tension. The Eötvös number is taken as equal to 5, so that the bubbles

Bernard Bunner; Grétar Tryggvason

2003-01-01

334

Dynamic simulation of bubbly flow in bubble columns  

Microsoft Academic Search

Gas–liquid bubbly flow in two-dimensional bubble columns is studied by numerical simulation. An Eulerian–Eulerian two-fluid model is used to describe the time-dependent motion of the liquid driven by small, spherical gas bubbles injected at the bottom of the columns. The simulations are able to capture the large scale structures as observed experimentally in the laboratory. The numerical results, which include

Y. Pan; M. P. Dudukovic; M. Chang

1999-01-01

335

Plasma bubbles in the topside ionosphere: solar activity dependence  

NASA Astrophysics Data System (ADS)

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.

Sidorova, L.

2009-04-01

336

Measurement of Temperature Dependence of Surface Tension of Alcohol Aqueous Solutions by Maximum Bubble Pressure Method  

NASA Astrophysics Data System (ADS)

The surface tension of some high-carbon alcohol aqueous solutions increases as the temperature rises above a certain temperature. There have been attempts to use such special solutions in thermal devices to promote heat transfer. In this study, the authors analyzed the temperature dependence of surface tension of these solutions to investigate this peculiar characteristic in detail. The test fluids were butanol and pentanol aqueous solutions as peculiar solutions, while pure water and ethanol aqueous solution were normal fluids. First, the authors adopted Wilhelmy's method to measure the surface tension during heating, but found that the influence of evaporation of the solution could not be completely eliminated. In this study, the maximum bubble pressure method was employed, which made it possible to isolate the measured solution from ambient air and eliminate the influence of evaporation of the solution. The authors succeeded in measuring the temperature dependence of surface tension, and obtained more reasonable data.

Ono, Naoki; Kaneko, Takahiro; Nishiguchi, Shotaro; Shoji, Masahiro

337

Effect of frothers on bubble size  

Microsoft Academic Search

The size of bubbles in flotation cells was measured using the UCT bubble size meter and the HUT bubble size analyser. While both methods provided similar critical coalescence concentration (CCC) values for the three tested frothers, they also revealed important differences. Using the HUT bubble size analyser, which does not impose any lower bubble size limit, it was possible to

Rodrigo A. Grau; Janusz S. Laskowski; Kari Heiskanen

2005-01-01

338

Acoustic Measurements Bubbles in Biological Tiessure  

Microsoft Academic Search

An acoustic based instrument, the ABS Acoustic Bubble Spectrometer®© (ABS), was investigated for the detection and quantification of bubbles in biological media. These include viscoelastic media (blood), materials of varying density (bone in tissue), non-homogenous distribution of bubbles (intravenous bubbly flow), and bubbles migrating in tissue (decompression sickness, DCS). The performance of the ABS was demonstrated in a series of

Georges L. CHAHINE; Michel TANGUAY; Greg LORAINE

2009-01-01

339

LETTER TO THE EDITOR: Bubble dynamics in DNA  

NASA Astrophysics Data System (ADS)

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.

Hanke, Andreas; Metzler, Ralf

2003-09-01

340

Zeta potential measurement of bubbles in DAF process and its effect on the removal efficiency  

Microsoft Academic Search

Dissolved Air Flotation (DAF) process has proved its efficiency in water treatment process and has gained much interest, however,\\u000a the research to investigate the process from the fundamental characteristics of bubbles and particles has been limited.\\u000a \\u000a In this research, the electrostatic nature of both bubble and particle\\/floc was focused. The zeta potential of bubbles is\\u000a measured by a system composed

Mooyoung Han; Seok Dockko

1998-01-01

341

Bubble Measuring Instrument and Method  

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

342

Bubble Measuring Instrument and Method  

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

343

Bubble measuring instrument and method  

NASA Technical Reports Server (NTRS)

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.

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

2003-01-01

344

Bubble Measuring Instrument and Method  

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

345

Helium bubble bursting in tungsten  

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

346

A discussion on the effect of bubble induced liquid velocity on the mass transfer performance of bubbles in bubble plumes  

Microsoft Academic Search

The effect of the bubble induced liquid velocity on the mass transfer performance of bubbles in bubble plumes has been studied numerically. A two-way coupling Euler-Lagrange method was adopted for the modeling of bubble plumes with mass transfer. The dissolution of air (nitrogen and oxygen, mainly considered) in bubble plumes with micro bubbles, 100mum<=d0<=1mm, was simulated. The results show that

Xiaobo Gong; Shu Takagi; Yoichiro Matsumoto

2006-01-01

347

Bubble domain technology for spacecraft onboard memory  

NASA Technical Reports Server (NTRS)

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.

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

1982-01-01

348

Bubble Formation of Vortices in a Liquid Helium Bubble Chamber.  

National Technical Information Service (NTIS)

It is believed that vorticity was produced in liquid helium II and used to nucleate bubble formation. Most of the bubbles appear to be round, and many have their outer edges near the inside wall of the glass cylinder. Many more vortices are detected at lo...

M. H. Edwards R. M. Cleary W. M. Fairbank

1965-01-01

349

Performance of high pressure COIL with centrifugal bubble singlet oxygen generator  

NASA Astrophysics Data System (ADS)

A centrifugal bubbling SOG is a perspective source of oxygen at high pressure with high depletion of the BHP in the single burn dawn. The theoretical estimations show that at high centrifugal acceleration gas-liquid contact specific surface 30cm -1, frequency of the surface renewal can less than 10 -3s and bubble rise velocity up to 500 cm/s be realized in the bubble SOG. The results of the measurements of O II(1?) yield, chlorine utilization and water fraction at the exit of the centrifugal bubble SOG are presented. A high O II(1?) yield and chlorine utilization higher than 90% have been obtained at chlorine gas loading up to 6 mmole/s per 1 cm2 of the bubbler surface. The ejector COIL powered by centrifugal bubbling SOG demonstrated ~25% of chemical efficiency with specific power 6 kW per 1 litre/s of the BHP volumetric rate.

Zagidullin, Marsel V.; Nikolaev, Valery D.; Khvatov, Nikolay A.; Svistun, Michael I.

2007-05-01

350

Vessel-Spanning Bubble Formation in K-Basin Sludge Stored in Large-Diameter Containers  

SciTech Connect

The K Basin sludge to be retrieved and stored in the large diameter containers (LDCs) contains some fraction of uranium metal that generates hydrogen gas, which introduces potential upset conditions. One postulated upset condition is a rising plug of sludge supported by a hydrogen bubble that is driven into the vent filters at the top of the container. In laboratory testing with actual K Basin sludge, vessel-spanning bubbles that lifted plugs of sludge were observed in 3-inch-diameter graduated cylinders. This report presents a series of analytical assessments performed by the Pacific Northwest National Laboratory to address the potential for the generation of a vessel spanning bubble in the LDCs. The assessments included the development and evaluation of static and dynamic bubble formation models over the projected range of K Basin sludge physical properties. Additionally, the theory of circular plates was extrapolated to examine conditions under which a plug of sludge would collapse and release a spanning bubble.

Terrones, Guillermo; Gauglitz, Phillip A.

2002-03-01

351

Experiments investigating the use of fiber-optic probes for measuring bubble-size distributions  

Microsoft Academic Search

An experimental investigation was conducted in the laboratory in order to evaluate the use of fiber-optic probes for measuring the size distribution of large transient bubbles entrained beneath breaking ocean waves. Measurements were made in a unidirectional flow cell using two-fiber Optoflow fiber-optic probes (Photonetics Inc.). It was found that the rise times of the signal pulses created when bubbles

C. D. Serdula; M. R. Loewen

1998-01-01

352

Modeling the dynamics of single-bubble sonoluminescence  

NASA Astrophysics Data System (ADS)

Sonoluminescence (SL) is the phenomenon in which acoustic energy is (partially) transformed into light. It may occur by means of one bubble or many bubbles of gas inside a liquid medium, giving rise to the terms single-bubble and multi-bubble sonoluminescence (SBSL and MBSL). In recent years some models have been proposed to explain this phenomenon, but there is still no complete theory for the light-emission mechanism (especially in the case of SBSL). In this paper, we do not address this more complicated specific issue, but only present a simple model describing the dynamical behavior of the sonoluminescent bubble in the SBSL case. Using simple numerical techniques within the Matlab software package, we discuss solutions that consider various possibilities for some of the parameters involved: liquid compressibility, surface tension, viscosity and type of gas. The model may be used for an introductory study of SL on undergraduate or graduate physics courses, and as a clarifying example of a physical system exhibiting large nonlinearity.

Vignoli, Lucas L.; de Barros, Ana L. F.; Thomé, Roberto C. A.; Nogueira, A. L. M. A.; Paschoal, Ricardo C.; Rodrigues, Hilário

2013-05-01

353

Bubble levitation and translation under single-bubble sonoluminescence conditions  

NASA Astrophysics Data System (ADS)

Bubble levitation in an acoustic standing wave is re-examined for conditions relevant to single-bubble sonoluminescence. Unlike a previous examination [Matula et al., J. Acoust. Soc. Am. 102, 1522-1527 (1997)], the stable parameter space [Pa,R0] is accounted for in this realization. Forces such as the added mass force and drag are included, and the results are compared with a simple force balance that equates the Bjerknes force to the buoyancy force. Under normal sonoluminescence conditions, the comparison is quite favorable. A more complete accounting of the forces shows that a stably levitated bubble does undergo periodic translational motion. The asymmetries associated with translational motion are hypothesized to generate instabilities in the spherical shape of the bubble. A reduction in gravity results in reduced translational motion. It is hypothesized that such conditions may lead to increased light output from sonoluminescing bubbles.

Matula, Thomas J.

2003-08-01

354

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

SciTech Connect

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.

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

2010-12-07

355

New mechanism for bubble nucleation: Classical transitions  

SciTech Connect

Given a scalar field with metastable minima, bubbles nucleate quantum mechanically. When bubbles collide, energy stored in the bubble walls is converted into kinetic energy of the field. This kinetic energy can facilitate the classical nucleation of new bubbles in minima that lie below those of the 'parent' bubbles. This process is efficient and classical, and changes the dynamics and statistics of bubble formation in models with multiple vacua, relative to that derived from quantum tunneling.

Easther, Richard [Department of Physics, Yale University, New Haven, Connecticut 06520 (United States); Giblin, John T. Jr [Department of Physics, Kenyon College, Gambier, Ohio 43022 (United States); Perimeter Institute for Theoretical Physics, 31 Caroline Street N, Waterloo, ON N2L 2Y5 (Canada); Hui Lam; Lim, Eugene A. [ISCAP and Physics Department, Columbia University, New York, 10027 (United States)

2009-12-15

356

Taxing the rich: recombinations and bubble growth during reionization  

NASA Astrophysics Data System (ADS)

Reionization is inhomogeneous for two reasons: the clumpiness of the intergalactic medium (IGM), and clustering of the discrete ionizing sources. While numerical simulations can in principle take both into account, they are at present limited by small box sizes. On the other hand, analytic models have only examined the limiting cases of a clumpy IGM (with uniform ionizing emissivity) and clustered sources (embedded in a uniform IGM). Here, we present the first analytic model that includes both factors. At first, recombinations can be ignored and ionized bubbles grow primarily through major mergers, because at any given moment the bubbles have a well-defined characteristic size. As a result, reionization resembles `punctuated equilibrium,' with a series of well-separated sharp jumps in the ionizing background. These features are local effects and do not reflect similar jumps in the global ionized fraction. We then combine our bubble model with a simple description of recombinations in the IGM. We show that the bubbles grow until recombinations balance ionizations, when their expansion abruptly halts. If the IGM density structure is similar to that at moderate redshifts, this limits the bubble radii to ~20 comoving Mpc; however, if the IGM is significantly clumpier at higher redshifts (because of minihalo formation, for example), the limit could be much smaller. Once a bubble reaches saturation, that region of the Universe has for all intents and purposes entered the `post-overlap' stage. Because different HII regions saturate over a finite time interval, the overlap epoch actually has a finite width. Our model also predicts a mean recombination rate several times larger than expected for a uniformly illuminated IGM. This picture naturally explains the substantial large-scale variation in Lyman-series opacity along the lines of sight to the known z > 6 quasars. More quasar spectra will shed light on the transition between the `bubble-dominated' topology characteristic of reionization and the `web-dominated' topology characteristic of the later Universe.

Furlanetto, Steven R.; Oh, S. Peng

2005-11-01

357

Asymptotic analysis of the dissolution of a spherical bubble in the case of a fast reaction  

NASA Astrophysics Data System (ADS)

This dissertation analyzes the dissolution of a stationary spherical gas bubble as the gas diffuses out of the hubble into a liquid and is consumed by a fast reaction in the liquid. Due to the fast reaction a small parameter ? appears in the problem formulation which makes the problem singularly perturbed. The Boundary Function method is used to derive uniform asymptotic approximations to the bubble's radius and gas concentration in the liquid. Existence of the solution, as well as the asymptotic correctness of the approximations are shown. Extensions of the model considering the case of multiple species and the case of a bubble rising with constant velocity are discussed.

Long, William M.

1997-11-01

358

Tuning bubbly structures in microchannels.  

PubMed

Foams have many useful applications that arise from the structure and size distribution of the bubbles within them. Microfluidics allows for the rapid formation of uniform bubbles, where bubble size and volume fraction are functions of the input gas pressure, liquid flow rate, and device geometry. After formation, the microchannel confines the bubbles and determines the resulting foam structure. Bubbly structures can vary from a single row ("dripping"), to multiple rows ("alternating"), to densely packed bubbles ("bamboo" and dry foams). We show that each configuration arises in a distinct region of the operating space defined by bubble volume and volume fraction. We describe the boundaries between these regions using geometric arguments and show that the boundaries are functions of the channel aspect ratio. We compare these geometric arguments with foam structures observed in experiments using flow-focusing, T-junction, and co-flow designs to generate stable nitrogen bubbles in aqueous surfactant solution and stable droplets in oil containing dissolved surfactant. The outcome of this work is a set of design parameters that can be used to achieve desired foam structures as a function of device geometry and experimental control parameters. PMID:22655008

Vuong, Sharon M; Anna, Shelley L

2012-06-01

359

Why Are Bubbles So Colorful?  

NSDL National Science Digital Library

In this activity, learners explore why they can see colors in bubbles and why they change. Learners also examine what thin slits do to light and how this phenomenon is similar to that of bubbles and oil slicks. Note: This activity works best outside in the sunlight.

America, Optical S.

2008-01-01

360

Bursting Bubbles and Air Pollution.  

National Technical Information Service (NTIS)

Photographic studies of small bubbles bursting at the surface of fresh and sea water have shown that aersols are produced through the breakup of minute water jets formed by the collapse of the bubble cavities. It is the purpose of the report to show a few...

A. H. Woodcock

1965-01-01

361

Tuning bubbly structures in microchannels  

PubMed Central

Foams have many useful applications that arise from the structure and size distribution of the bubbles within them. Microfluidics allows for the rapid formation of uniform bubbles, where bubble size and volume fraction are functions of the input gas pressure, liquid flow rate, and device geometry. After formation, the microchannel confines the bubbles and determines the resulting foam structure. Bubbly structures can vary from a single row (“dripping”), to multiple rows (“alternating”), to densely packed bubbles (“bamboo” and dry foams). We show that each configuration arises in a distinct region of the operating space defined by bubble volume and volume fraction. We describe the boundaries between these regions using geometric arguments and show that the boundaries are functions of the channel aspect ratio. We compare these geometric arguments with foam structures observed in experiments using flow-focusing, T-junction, and co-flow designs to generate stable nitrogen bubbles in aqueous surfactant solution and stable droplets in oil containing dissolved surfactant. The outcome of this work is a set of design parameters that can be used to achieve desired foam structures as a function of device geometry and experimental control parameters.

Vuong, Sharon M.; Anna, Shelley L.

2012-01-01

362

Acoustic Behavior of Vapor Bubbles  

NASA Technical Reports Server (NTRS)

In a microgravity environment vapor bubbles generated at a boiling surface tend to remain near it for a long time. This affects the boiling heat transfer and in particular promotes an early transition to the highly inefficient film boiling regime. This paper describes the physical basis underlying attempts to remove the bubbles by means of pressure radiation forces.

Prosperetti, Andrea; Oguz, Hasan N.

1996-01-01

363

Bubble nucleation in stout beers  

Microsoft Academic Search

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

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

2011-01-01

364

Gas bubbles in shaped sapphire  

Microsoft Academic Search

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

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

2010-01-01

365

Numerical model for atmospheric contaminant cloud rise scenarios  

NASA Astrophysics Data System (ADS)

Our numerical approach includes fluid mechanical model which is the combination of a compressible GEODYN code and a Low Mach code (LMC). The first one is an explicit code and it is intended to simulate early stages of nuclear explosions up to 15 s. The second one is an implicit code based on a pressure projection method and it is intended to simulate subsequent cloud rise events up to few hours. We perform series of cloud rise scenarios ranging from idealized bubble rise problem to realistic air bursts. We analyze effects of compressible dynamics and different turbulent parameterizations on the cloud evolution. It is found that in a realistic configuration interaction of a reflected shock wave from the ground with a fireball affects significantly cloud evolution in contrast to idealized bubble rise simulations. We show that by providing initial source from compressible GEODYN code, later times flow evolution can be successfully simulated with fast and efficient LMC code. Finally, we develop formalism for tracer particles and their fallout and present some preliminary results.

Kanarska, Yuliya; Lomov, Ilya; Antoun, Tarabay; Glenn, Lewis

2007-11-01

366

Triangular bubble spline surfaces  

PubMed Central

We present a new method for generating a Gn-surface from a triangular network of compatible surface strips. The compatible surface strips are given by a network of polynomial curves with an associated implicitly defined surface, which fulfill certain compatibility conditions. Our construction is based on a new concept, called bubble patches, to represent the single surface patches. The compatible surface strips provide a simple Gn-condition between two neighboring bubble patches, which are used to construct surface patches, connected with Gn-continuity. For n?2, we describe the obtained Gn-condition in detail. It can be generalized to any n?3. The construction of a single surface patch is based on Gordon–Coons interpolation for triangles. Our method is a simple local construction scheme, which works uniformly for vertices of arbitrary valency. The resulting surface is a piecewise rational surface, which interpolates the given network of polynomial curves. Several examples of G0, G1 and G2-surfaces are presented, which have been generated by using our method. The obtained surfaces are visualized with reflection lines to demonstrate the order of smoothness.

Kapl, Mario; Byrtus, Marek; Juttler, Bert

2011-01-01

367

Triangular bubble spline surfaces.  

PubMed

We present a new method for generating a [Formula: see text]-surface from a triangular network of compatible surface strips. The compatible surface strips are given by a network of polynomial curves with an associated implicitly defined surface, which fulfill certain compatibility conditions. Our construction is based on a new concept, called bubble patches, to represent the single surface patches. The compatible surface strips provide a simple [Formula: see text]-condition between two neighboring bubble patches, which are used to construct surface patches, connected with [Formula: see text]-continuity. For [Formula: see text], we describe the obtained [Formula: see text]-condition in detail. It can be generalized to any [Formula: see text]. The construction of a single surface patch is based on Gordon-Coons interpolation for triangles.Our method is a simple local construction scheme, which works uniformly for vertices of arbitrary valency. The resulting surface is a piecewise rational surface, which interpolates the given network of polynomial curves. Several examples of [Formula: see text], [Formula: see text] and [Formula: see text]-surfaces are presented, which have been generated by using our method. The obtained surfaces are visualized with reflection lines to demonstrate the order of smoothness. PMID:22267872

Kapl, Mario; Byrtus, Marek; Jüttler, Bert

2011-11-01

368

Bubbles under stress.  

PubMed

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

Bohn, S

2003-06-01

369

Bubble formation in microgravity  

NASA Technical Reports Server (NTRS)

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.

Antar, Basil N.

1994-01-01

370

Geomechanical problems in high-rise construction  

Microsoft Academic Search

Fundamental and determining geomechanical factors that ensure the safety of high-rise construction are discussed. Characteristics\\u000a used in selecting a geomechanical model for the beds of high-liability structures, and a mechanical model for the bed soils\\u000a and surrounding mass are analyzed.

Z. G. Ter-Martirosyan; M. V. Proshin

2006-01-01

371

A spacecraft mass memory design using self-structured magnetic bubbles  

NASA Technical Reports Server (NTRS)

A self-structured multilayered bubble device developed for spacecraft sensor systems is described. The data link buffer mass memory is analyzed, and system characteristics are estimated based on a nominal 1.6 micron bubble diameter. It is shown that a memory of at least 10 billion bits capacity and 30 megabits per second could be developed with conventional spacecraft constraints.

Stermer, R. L., Jr.

1980-01-01

372

Experimental Investigation of NH3-H2O Bubble Formation with Absorption Process  

NASA Astrophysics Data System (ADS)

The objectives of the paper are to visualize the bubble shape and to investigate the characteristics of the bubble behavior for an1monia-water absorption process. Tbe orifice dian1eter, liquid concentration and vapor velocity are considered as the key parameters. The initial bubble diameter increases with increasing the liquid concentration. A transition vapor Reynolds number is introduced, which is defined as Reynolds number at a sudden change of ratio of the initial bubble diameter to the orifice diameter. The transition Reynolds number increases with increasing the liquid concentration, and it significantly influences the bubble shape. Heat transfer additive (n-octanol) makes bubble more hemispherical. The departing bubbles tend to be spherical for a surface tension dominant flow, and the bubbles tend to be hemispherical for an inertial force dominant flow. This study presents an experimental correlation of initial bubble diameter with &±20% error band. The correlation can be used to calculate the interfacial area in the design of ammonia-water bubble absorber.

Nagano, Tatsuhiko; Kang, Yong Tae; Akisawa, Atsushi; Kashiwagi, Takao

373

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)

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.

Beaubien, Stan; De Vittor, Cinzia; McGinnis, Dan; Bigi, Sabina; Comici, Cinzia; Ingrosso, Gianmarco; Lombardi, Salvatore; Ruggiero, Livio

2014-05-01

374

System for Manipulating Drops and Bubbles Using Acoustic Radiation Pressure  

NASA Technical Reports Server (NTRS)

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.

Oeftering, Richard C. (Inventor)

1999-01-01

375

Simulation studies of vapor bubble generation by short-pulse lasers  

NASA Astrophysics Data System (ADS)

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 [Lin and Kelly, SPIE 2391, 294 (1995)].

Amendt, Peter A.; London, Richard A.; Strauss, Moshe; Glinsky, Michael E.; Maitland, Duncan J.; Celliers, Peter M.; Visuri, Steven R.; Bailey, David S.; Young, David A.; Ho, Darwin; Lin, Charles P.; Kelly, Michael W.

1998-01-01

376

PIV measurement of a contraction flow using micro-bubble tracer  

NASA Astrophysics Data System (ADS)

Recently, a technique using the micro-bubbles is focused. It was applied to many fields such as purification of rivers and lakes, washing the industrial parts, growth of plants and marine products. The characteristics of micro-bubbles are small size, wide surface area, low terminal velocity, and so on. If this micro-bubble is available as tracer of PIV (Particle Image Velocimetry), environment load would become lower because it doesn't need to discard particle. In this paper, we make a micro-bubble generator with Venturi type mechanism. The generated micro-bubbles are applied to a vertical channel flow with contraction. We validate about traceability of the micro-bubble tracer in comparison with the particle tracer.

Ishikawa, Masaaki; Irabu, Kunio; Teruya, Isao; Nitta, Munehiro

2009-02-01

377

Analysis of quasi-static vapour bubble shape during growth and departure  

NASA Astrophysics Data System (ADS)

In an effort to better understand the physical mechanisms responsible for pool boiling heat transfer, a numerical solution to the capillary equation is used to describe bubble shape evolution. Indeed, any analysis of thermal transport due to nucleate pool boiling requires bubble frequency and volume predictions, which are intimately linked to bubble shape. To this end, a numerical treatment of the capillary equation is benchmarked to profiles measured from captured images of vapour bubble formations. The bubble growth is quasi-static in a quiescent liquid with a triple contact line fixed to the perimeter of a needle orifice. This investigation provides insight into the dependence the bubble shape evolution has on the physical mechanisms quantified in the Bond number with characteristic length equal to the cavity radius.

Lesage, Frédéric J.; Cotton, James S.; Robinson, Anthony J.

2013-06-01

378

Electrons trajectories around a bubble regime in intense laser plasma interaction  

SciTech Connect

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.

Lu, Ding; Xie, Bai-Song; Ali Bake, Muhammad; Sang, Hai-Bo [Key Laboratory of Beam Technology and Materials Modification of the Ministry of Education, College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China)] [Key Laboratory of Beam Technology and Materials Modification of the Ministry of Education, College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Zhao, Xue-Yan [Key Laboratory of Beam Technology and Materials Modification of the Ministry of Education, College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China) [Key Laboratory of Beam Technology and Materials Modification of the Ministry of Education, College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Wu, Hai-Cheng [Center for Applied Physics and Technology, Peking University, Beijing 100084 (China)] [Center for Applied Physics and Technology, Peking University, Beijing 100084 (China)

2013-06-15

379

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

NASA Astrophysics Data System (ADS)

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

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

1993-07-01

380

Ground potential rise monitor  

DOEpatents

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.

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

2012-04-03

381

Experimental determination of bubble size distributions in bubble columns: prediction of mean bubble diameter and gas hold up  

Microsoft Academic Search

Bubble diameters were measured photographically in a bubble column, which was operating in the homogeneous regime with air and aqueous isopropanol solutions. The bubble size data were determined for several values of the superficial gas velocity, and used to fit bubble size distributions. The gas hold up was measured under the same conditions and its values were calculated from the

P. L. C. Lage; R. O. Espósito

1999-01-01

382

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

SciTech Connect

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.

Supathorn Phongikaroon; Steve Herrmann; Shelly Li; Michael Simpson

2005-10-01

383

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

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

384

Surface bubble nucleation stability.  

PubMed

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. PMID:21405411

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

2011-02-01

385

Safety Rises to New Levels.  

ERIC Educational Resources Information Center

Explains how high-rise residence halls can provide high-level safety and security at colleges and universities. Boston University is used to illustrate high-rise security and fire protection issues. (GR)

Lafo, Joseph; Robillard, Marc

2001-01-01

386

OH Production Enhancement in Bubbling Pulsed Discharges  

SciTech Connect

The generation of active species, such as H{sub 2}O{sub 2}, O{sup *}, OH*, HO{sub 2}*, O{sub 3}, N{sub 2}{sup *}, etc, produced in aqueous solutions by HV pulsed discharges was studied in order to find the most efficient way in waste water treatment taking into account that these species are almost stronger oxidizers than ozone. Plasma was generated inside gas bubbles formed by the argon, air and oxygen gas flow between the special designed electrodes. The pulse width and pulse frequency influence was studied in order to increase the efficiency of the OH active species formation. The produced active species were investigated by optical emission spectroscopy and correlated with electrical parameters of the discharges (frequency, pulse width, amplitude, and rise and decay time).

Lungu, Cristian P.; Porosnicu, Corneliu; Jepu, Ionut; Chiru, Petrica; Zaroschi, Valentin; Lungu, Ana M. [National Institute for Laser, Plasma and Radiation Physics, Bucharest, 077125 (Romania); Saito, Nagahiro; Bratescu, Maria; Takai, Osamu [Ecotopia Science Institute, Nagoya University, Nagoya, 464-8603 (Japan); Velea, Theodor; Predica, Vasile [R and D National Institute for Nonferous and Rare Metals, Pantelimon, Jud. Ilfov, 077145 (Romania)

2010-10-13

387

Constrained Vapor Bubble  

NASA Technical Reports Server (NTRS)

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.

Huang, J.; Karthikeyan, M.; Plawsky, J.; Wayner, P. C., Jr.

1999-01-01

388

Bubble dispersion and coalescence in turbulent pipe flow  

NASA Astrophysics Data System (ADS)

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.)

Luo, Jianjun

2002-04-01

389

Tharsis Rise Graben  

NASA Technical Reports Server (NTRS)

(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.

2002-01-01

390

Resonance properties of soluble gas bubbles  

Microsoft Academic Search

Soluble gas bubbles in a liquid experiencing radial oscillations created by an acoustic field are considered. It is shown that the resonance frequency of large soluble gas bubbles practically coincides with the natural frequency of gas bubbles as determined by the Minnaert formula. In the case of small gas bubbles, the presence of capillary effects and solubility of the gas

Nail S. Khabeev

2006-01-01

391

Sound Waves in Water Containing Vapor Bubbles  

Microsoft Academic Search

The rapid evaporation or condensation of a vapor bubble when out of equilibrium compared to the slow dissolving or growth of an air bubble results in quite different propagation properties of sound waves through water containing one or the other types of bubbles. Adapting a method developed by Foldy in his treatment of the air bubble case, we derive an

G. T. Trammell

1962-01-01

392

Bubble Growth in Lunar Basalts  

NASA Astrophysics Data System (ADS)

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

Zhang, Y.

2009-05-01

393

Sonoluminescing Air Bubbles Rectify Argon  

NASA Astrophysics Data System (ADS)

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.

Lohse, Detlef; Brenner, Michael P.; Dupont, Todd F.; Hilgenfeldt, Sascha; Johnston, Blaine

1997-02-01

394

Sonoluminescing Air Bubbles Rectify Argon  

SciTech Connect

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}

Lohse, D.; Hilgenfeldt, S. [Fachbereich Physik der Universitaet Marburg, Renthof 6, 35032 Marburg (Germany)] [Fachbereich Physik der Universitaet Marburg, Renthof 6, 35032 Marburg (Germany); Brenner, M.P. [Department of Mathematics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)] [Department of Mathematics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Dupont, T.F. [Department of Computer Science, University of Chicago, Chicago, Illinois 60637 (United States)] [Department of Computer Science, University of Chicago, Chicago, Illinois 60637 (United States); Johnston, B. [Department of Physics, University of Chicago, Chicago, Illinois 60637 (United States)] [Department of Physics, University of Chicago, Chicago, Illinois 60637 (United States)

1997-02-01

395

The rise of graphene.  

PubMed

Graphene is a rapidly rising star on the horizon of materials science and condensed-matter physics. This strictly two-dimensional material exhibits exceptionally high crystal and electronic quality, and, despite its short history, has already revealed a cornucopia of new physics and potential applications, which are briefly discussed here. Whereas one can be certain of the realness of applications only when commercial products appear, graphene no longer requires any further proof of its importance in terms of fundamental physics. Owing to its unusual electronic spectrum, graphene has led to the emergence of a new paradigm of 'relativistic' condensed-matter physics, where quantum relativistic phenomena, some of which are unobservable in high-energy physics, can now be mimicked and tested in table-top experiments. More generally, graphene represents a conceptually new class of materials that are only one atom thick, and, on this basis, offers new inroads into low-dimensional physics that has never ceased to surprise and continues to provide a fertile ground for applications. PMID:17330084

Geim, A K; Novoselov, K S

2007-03-01

396

An experimental investigation on the confined and elongated bubbles in subcooled flow boiling in a single microchannel  

NASA Astrophysics Data System (ADS)

The characteristics of the confined bubble and elongated bubble in subcooled flow boiling in a single horizontal rectangular microchannel with hydraulic diameter Dh=1mm are studied experimentally. The channel with 1 × 1mm cross section is fabricated in a thin copper plate whose confinement number is Co=2.8 and the degassed deionized water is used as the working fluid. Visualization on the confined and elongated bubbles inside the microchannel is carried out by employing a high-speed CCD camera with a microlens. The recorded images are carefully analyzed to illustrate the behaviors of the confinement and elongation processes of the bubble. The boiling number is used as an adjustable parameter to regulate the operating conditions which is eventually found to take a vital role in the bubble elongation process. Two formation patterns of the confined and elongated bubble are identified and the interactions between the neighboring confined and elongated bubbles are elucidated.

Yin, Liaofei; Jia, Li; Guan, Peng; Liu, Fuhao

2012-12-01

397

Micro-Stereoscopic Vision System for the Determination of Air Bubbles and Aqueous Droplets Content within Oil Drops in Simulated Processes of Multiphase Fermentations  

Microsoft Academic Search

Industrial fermentation procedures involve the mixing of multiple phases (solid, liquid, gaseous), where the interfacial area between the phases (air bubbles, oil drops and aqueous medium) determines the nutrients transfer and hence the performance of the culture. Interactions between phases occur, giving rise to the formation of complex structures containing air bubbles and small drops from the aqueous phase, trapped

J. B. Briere; M. S. Cordova; E. Galindo; Gabriel Corkidi

2005-01-01

398

Vapor Bubble Nucleation: A Microscopic Phenomenon  

Microsoft Academic Search

In this article, vapor bubble nucleation in liquid and the evaporation process of a liquid droplet at its superheat limit\\u000a were discussed from the viewpoint of molecular clustering (molecular cluster model for bubble nucleation). For the vapor bubble\\u000a formation, the energy barrier against bubble nucleation was estimated by the molecular interaction due to the London dispersion\\u000a force. Bubble nucleation by

Ho-Young Kwak

2004-01-01

399

Nonclassical Thermomigration of an Air Bubble  

NASA Astrophysics Data System (ADS)

We study air bubbles confined in capillaries with a temperature gradient. Classically, air bubbles move in a temperature gradient due to decreased surface tension at higher temperatures, creating a net surface traction towards the cold pole, pushing the bubble towards the hot pole for mass conservation. Here we report non-classical thermo-migration of confined air bubbles: in the presence of surfactant the bubbles can go the other way.

Michler, Dominik; Sprik, Rudolf; Schall, Peter; Bonn, Daniel

2012-02-01

400

A Bubble Full of Sunshine  

NSF Publications Database

... inside gas bubbles collapsing in a liquid reach roughly 20,000 degrees Kelvin?four times hotter than ... the discovery by blasting the liquid with intense sound waves and measuring "sonoluminescence," the ...

401

Smashing Bubbles and Vanishing Sugar.  

ERIC Educational Resources Information Center

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)

Ward, Alan

1979-01-01

402

Bubbles in Liquid: Euromech 7.  

National Technical Information Service (NTIS)

A convention was held in Grenoble during April 23 to 26, 1968 to discuss the mechanics of liquids containing bubbles. Summaries are given of selected presentations and discussions which have special relevance to problems dealing with adiabatic flow in foa...

C. Reuterswaerd

1975-01-01

403

Bubble nucleation in stout beers.  

PubMed

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

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

2011-05-01

404

Holography in small bubble chambers  

SciTech Connect

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.

Lecoq, P.

1984-01-01

405

Large Volcanic Rises on Venus  

NASA Technical Reports Server (NTRS)

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.

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

1997-01-01

406

Driving bubbles out of glass  

NASA Technical Reports Server (NTRS)

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.

Mattox, D. M.

1981-01-01

407

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

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

408

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

409

Shock Wave Propagation and Bubble Pulsation of TNT Underwater Explosion  

NASA Astrophysics Data System (ADS)

Shock wave and bubbles are basic forms of energy spread and conversion processes for underwater explosion, which is also the fundamental energy for destructive effect on targets. In this paper, the flow-out boundary and variable step-size multi-material Euler algorithm were utilized to analyze numerically the whole process of shock wave generation and propagation, as well as the bubble formation and impulse of underwater explosion. The computed results present the energy output characteristics of underwater explosion by TNT charge, which provide an important scientific basis for formulation design of charge and improvement of damage effects on underwater target.

Liu, Y.; Ding, J.; Zhang, B. L.; Chen, W. H.; He, Z. Q.

2011-09-01

410

The velocity-distance relation for galaxies on a bubble  

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

411

Application of holographic particle image velocimetry in bubbly flow  

NASA Astrophysics Data System (ADS)

Measuring the velocity field of a bubbly flow is of major importance in many industrial applications like, bubble column reactors. Traditional PIV setup is limited to single plane measurements. The present study involved extension of the existing holographic PIV method to two-phase flow velocimetry. The objective of the present study was to conduct velocity measurements using in-line holographic microscopy arrangement to analyze a flow consisting of an air bubble rising through stagnant water in a rectangular column. Neutrally buoyant 8 microm sized hollow glass spheres are scattered uniformly in the continuous phase and are used as seed particles for image analysis. Double-pulsed hologram is taken with a 2K by 2K pixels CCD sensor with 200micros in between the two frames, which allows only a small movement of both the particles (in the continuous phase) and that of the dispersed phase itself. Holograms are reconstructed at different distances to produce images at every millimeter of the measurement volume. An averaging technique is developed to process the images to reduce the noise in reconstructed holographic images and make it useful for cross-correlation analysis. The image pairs are cross correlated and velocity vectors are obtained for the continuous phase. The dispersed phase velocity is measured using the shift in the center of the bubble. After analyses of all the image pairs throughout the measurement volume, a two component three dimensional velocity field is produced for the two-phase flow.

Banerjee, Atanu

412

Optical Measurements of Bubble Injections in the Southern Ocean  

NASA Astrophysics Data System (ADS)

Bubbles, due to their size compared to wavelengths of light and refractive index relative to water, are effective at backscattering light. The magnitude of light reflected from the sea surface (remote sensing reflectance, Rrs) can be significantly enhanced due to bubble entrainment at temporal scales of minutes and the spectral nature of the light field can be shifted towards green wavelengths. Here, we use optical measurements collected during the Southern Ocean Gas Exchange Experiment (SOGasEx, March 10 through April 4, 2007) to address questions related bubble populations and light scattering. Time series measurements of particle size distribution (PSD), volume scattering function, and backscattering measured at high frequency (1-20 Hz) from the surface layer of the Atlantic Sector of the Southern Ocean will be presented. The PSD from 2-1500 ?m, acquired using a LISST-100X and LISST-FLOC (Laser In-Situ Scattering and Transmissiometry, Sequoia Scientific Inc.) shows significant enhancement of particle populations in time periods on the order of minutes that are related to bubble injections. Simultaneous measurements of the full volume scattering function (MASCOT, WET Labs) are used to differentiate bubble particles using a characteristic bubble scattering feature between 60° and 80°. We will also present the depth-dependent relationships between the power-law slope of the PSD, backscattering and physical parameters (i.e. wind speed, whitecap coverage, and significant wave height) in order to assess the intensity of the bubble field in these waters and the potential influence on light scattering in the Southern Ocean.

Randolph, K. L.; Dierssen, H. M.; Buonassissi, C.; Freeman, S.; Twardowski, M. S.

2008-12-01

413

The Heat Release Ratio and Performance Test at a Small-Scale RDF-5 Bubbling Fluidized Bed Boiler  

NASA Astrophysics Data System (ADS)

Design and operation of boilers using biomass or waste present a number of challenges. It is also well known that the flue gas emissions are strongly dependent on the fuel. Consequently, it is a major challenge to be able to control and maintain all emissions and combustion behavior under their designated limits for all fuel combinations required. Lately, the constant substantial rise in the price of fossil fuels has resulted with RDF (refuse derived fuel) technology becoming more valuable for generating heat in various types of boilers. A small-scale bubbling fluidized bed (BFB) RDF-fired boiler with a steam capacity of 4 ton/hr was developed by ITRI. In this paper, heat release in the fluidized bed region was calculated and the performance testing for this demonstration boiler including the items of bed temperature distribution, flue gas emissions, and the ash characteristics is analyzed and discussed. Finally, a series fuel flexibility tests were conducted in the RDF-5 BFBB.

Wan, Hou-Peng; Chyang, Chien-Song; Yang, Chyh-Sen; Juch, Ching-I.; Lo, Kuo-Chao; Lee, Hom-Ti

414

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)

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.

Katsman, Regina

2014-05-01

415

Bursting Bubbles from Combustion of Thermoplastic Materials in Microgravity  

NASA Technical Reports Server (NTRS)

Many thermoplastic materials in common use for a wide range of applications, including spacecraft, develop bubbles internally as they burn due to chemical reactions taking place within the bulk. These bubbles grow and migrate until they burst at the surface, forceably ejecting volatile gases and, occasionally, molten fuel. In experiments in normal gravity, Kashiwagi and Ohlemiller observed vapor jets extending a few centimeters from the surface of a radiatively heated polymethylmethacrylate (PMMA) sample, with some molten material ejected into the gas phase. These physical phenomena complicated the combustion process considerably. In addition to the non-steady release of volatiles, the depth of the surface layer affected by oxygen was increased, attributed to the roughening of the surface by bursting events. The ejection of burning droplets in random directions presents a potential fire hazard unique to microgravity. In microgravity combustion experiments on nylon Velcro fasteners and on polyethylene wire insulation, the presence of bursting fuel vapor bubbles was associated with the ejection of small particles of molten fuel as well as pulsations of the flame. For the nylon fasteners, particle velocities were higher than 30 cm/sec. The droplets burned robustly until all fuel was consumed, demonstrating the potential for the spread of fire in random directions over an extended distance. The sequence of events for a bursting bubble has been photographed by Newitt et al.. As the bubble reaches the fluid surface, the outer surface forms a dome while the internal bubble pressure maintains a depression at the inner interface. Liquid drains from the dome until it breaks into a cloud of droplets on the order of a few microns in size. The bubble gases are released rapidly, generating vortices in the quiescent surroundings and transporting the tiny droplets. The depression left by the escaping gases collapses into a central jet, which rises with a high velocity and may break up, releasing one or more relatively large drops (on the order of a millimeter in these experiments). A better understanding of bubble development and bursting processes, the effects of bursting behavior on burning rate of the bulk material, and the circumstances under which large droplets are expelled, as well as their trajectories, sizes, and burning rates, is sought through computer modeling compared with experiment.

Butler, K. B.

1999-01-01

416

Bubble Gate for In-Plane Flow Control  

NASA Astrophysics Data System (ADS)

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.

Kazemi Oskooei, Ali; Guenther, Axel

2011-11-01

417

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

SciTech Connect

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

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

2006-10-01

418

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

EPA Science Inventory

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

419

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

NASA Astrophysics Data System (ADS)

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

Frouzova, Jaroslava; Tuser, Michal; Stanovsky, Petr

2014-05-01

420

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

PubMed

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

Holt, Fred D; Lee Culver, R

2011-11-01

421

Fragility-based assessment of typical mid-rise and low-rise RC buildings in Turkey  

Microsoft Academic Search

This paper focuses on the seismic fragility assessment of typical low-rise and mid-rise reinforced concrete (RC) buildings in Turkey by considering Düzce Damage database, which was compiled after the two devastating earthquakes in 1999 that affected the Marmara region. A set of fragility curves is developed by making use of the building characteristics in the database. The generated fragility curve

M. Altu? Erberik

2008-01-01

422

Measurement of Bubble Size Distribution Based on Acoustic Propagation in Bubbly Medium  

NASA Astrophysics Data System (ADS)

Acoustic properties are strongly affected by bubble size distribution in a bubbly medium. Measurement of the acoustic transmission becomes increasingly difficulty as the void fraction of the bubbly medium increases due to strong attenuation, while acoustic reflection can be measured more easily with increasing void fraction. The ABS Acoustic Bubble Spectrometer^, an instrument for bubble size measurement that is under development tries to take full advantage of the properties of acoustic propagation in bubbly media to extract bubble size distribution. Properties of both acoustic transmission and reflection in the bubbly medium from a range of short single-frequency bursts of acoustic waves at different frequencies are measu