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1

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

2

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

3

Zigzagging bubbles rising side by side  

NASA Astrophysics Data System (ADS)

The interaction between zigzagging bubbles (d=2.9mm) rising side by side and its surrounding liquid motion in quiescent water were experimentally investigated. Hypodermic needles and a bubble generator utilizing pressure oscillation were employed to exactly extract and highly reproduce the interaction between the liquid-phase motion and bubble motion at the collision. The recursive cross correlation PIV technique made it possible to obtain the accurate velocity field of the surrounding liquid motion of a pair of bubbles. The experiments were conducted by changing the initial bubble distance. As a result, the two types of velocity fluctuation of bubbles were mainly observed after the collisions. The first case, only the horizontal velocity of each bubbles obviously decreased. The second case, both the horizontal and the vertical velocity decreased. This difference is considered to be due to the different surrounding liquid motion, especially the formation of vorticity.

Sanada, Toshiyuki; Sone, Daiji; Saito, Takayuki

2007-11-01

4

Liquid jet pumped by rising gas bubbles  

NASA Technical Reports Server (NTRS)

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

Hussain, N. A.; Siegel, R.

1975-01-01

5

Evolution of energy in flow driven by rising bubbles.  

PubMed

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. PMID:19658604

Mazzitelli, Irene M; Lohse, Detlef

2009-06-01

6

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

7

Behavior of a pair of bubbles rising side by side at high Reynolds number  

NASA Astrophysics Data System (ADS)

We study experimentally the motion and the wake of a pair of non-spherical bubbles rising side by side at high Reynolds number. The motions of bubbles were recorded by a high-speed video camera. The wakes of bubbles were visualized by using photochromic dye that is colored with UV light irradiation. We observed vortex separation from bubbles' rear surface at their collision, resulting in a great decrease in rising velocity of bubbles. Applying an existing model for spherical bubble-wall interaction by taking into account non-spherical effects on translational velocities and characteristics at the collision, we found that the revised model accurately describes the trajectory of a pair of bouncing-approaching bubbles. On the contrary, in the case of bubbles bouncing repeatedly, the effect of wake instability of a pair of bubbles on the motion of bubbles rather than the effect of bubble-bubble interaction dominates. We clarify that the vortex separation is strongly related with vertical velocity fluctuation.

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

2006-11-01

8

Dynamics of an initially spherical bubble rising in quiescent liquid  

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

9

Dynamics of an initially spherical bubble rising in quiescent liquid.  

PubMed

The beauty and complexity of the shapes and dynamics of bubbles rising in liquid have fascinated scientists for centuries. Here we perform simulations on an initially spherical bubble starting from rest. We report that the dynamics is fully three-dimensional, and provide a broad canvas of behaviour patterns. Our phase plot in the Galilei-Eötvös plane shows five distinct regimes with sharply defined boundaries. Two symmetry-loss regimes are found: one with minor asymmetry restricted to a flapping skirt; and another with marked shape evolution. A perfect correlation between large shape asymmetry and path instability is established. In regimes corresponding to peripheral breakup and toroid formation, the dynamics is unsteady. A new kind of breakup, into a bulb-shaped bubble and a few satellite drops is found at low Morton numbers. The findings are of fundamental and practical relevance. It is hoped that experimenters will be motivated to check our predictions. PMID:25687557

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

2015-01-01

10

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

11

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

12

Rising and descending bubble size distributions in gas–liquid and gas–liquid–solid slurry bubble column reactor  

Microsoft Academic Search

Dual-tip conductivity probe is used to determine distributions of rising and descending bubble size in gas–liquid and gas–liquid–solid bubble column. The column is 100mm in internal diameter and 1500mm in height. The solid particles used are glass beads with average diameter of 17.82?m representing typical particle size for catalytic slurry reactors. Bubbles are categorized to two size classes, small bubbles

Li-juan Zhang; Tao Li; Wei-yong Ying; Ding-ye Fang

2008-01-01

13

Rise of a Dark Bubble through a Quiescent Prominence  

NASA Astrophysics Data System (ADS)

We report on a dynamical event observed in a quiescent prominence on 2007 November 8: a well-formed dark ``bubble'' with a bright core rose vertically through the prominence without causing it to erupt. This event was observed in H? and He I 1083 nm with the instruments of the Mauna Loa Solar Observatory. The dark bubble had a size of over 40'' and rose from the prominence base, at an average speed of ~12 km s-1, forming a bright compression front as it traversed the prominence. It finally assumed a ``keyhole'' shape before fading. The bright core embedded in the dark bubble was observed to rise from the solar limb, accelerating from ~12 to ~20 km s-1, leaving a thin trail of material behind. Subsequent observations indicate that this was not an exceptional event, but rather that similar disturbances do occur occasionally in prominences without disrupting them. In this Letter we present the November 8 observations, and propose a possible interpretation of the physical mechanism behind these dynamic events.

de Toma, G.; Casini, R.; Burkepile, J. T.; Low, B. C.

2008-11-01

14

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

15

Rise velocity of a swarm of large gas bubbles in liquids  

Microsoft Academic Search

This paper develops a procedure for estimation of the rise velocity of a swarm of large gas bubbles in a bubble column operating in the churn-turbulent flow regime. The large bubble swarm velocity is estimated by introducing two correction factors into the classical Davies–Taylor (1950) relation for rise of a single spherical cap bubble in a liquidVb=0.71gdb(SF)(AF).The scale correction factor

R. Krishna; M. I. Urseanu; J. M van Baten; J. Ellenberger

1999-01-01

16

Velocity fluctuations in a homogeneous dilute dispersion of high-Reynolds-number rising bubbles  

NASA Astrophysics Data System (ADS)

An experimental investigation of a homogeneous swarm of rising bubbles is presented. The experimental arrangement ensures that all the bubbles have the same equivalent radius, a = 1.25 mm. This particular size corresponds to high-Reynolds-number ellipsoidal rising bubbles. The gas volume fractions [alpha] is small, ranging from 0.5 to 1.05%. The results are compared with the reference situation of a single rising bubble, which was investigated in a previous work. From the use of conditional statistics, the existence of two regions in which the liquid velocity fluctuations are of a different nature are distinguished. In the vicinity of the bubbles, the liquid fluctuations are the same as those measured close to a single rising bubble. They therefore do not depend on [alpha]. Far from the bubble, the liquid fluctuations are controlled by the nonlinear interactions between the wakes of all the bubbles. Their probability density function scales as [alpha]0.4, exhibiting a self-similar behaviour. The total fluctuation combines the contributions of these two regions weighted by the fraction of the liquid volume they occupy. The contribution of the bubble vicinity is thus shown to vary linearly with [alpha] while the wake contribution does not. Both are non-isotropic since strong upward vertical fluctuations are more probable.

Risso, Frédéric; Ellingsen, Kjetil

2002-02-01

17

Influence of slurry concentrations on bubble population and their rise velocities in a three-phase slurry bubble column  

Microsoft Academic Search

Experiments were performed in air–water and air–water–glass particles systems to study variations in gas holdups, bubble population and their rise velocities. Slurry concentrations up to 40% (v\\/v) and superficial gas velocities up to 0.30 m\\/s were investigated. The measurements were made using fast response pressure transducers and the dynamic gas disengagement (DGD) technique. The gas holdup due to small bubbles

H Li; A Prakash

2000-01-01

18

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

NASA Astrophysics Data System (ADS)

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

Cihan, Abdullah; Corapcioglu, M. Yavuz

2008-04-01

19

Flow field around growing and rising vapour bubble by PIV measurement  

Microsoft Academic Search

A study on flow field measurement around growing and rising vapour bubbles by use of PIV technique is presented. Bubbles were\\u000a generated from single artificial cavities. Experiments have been conducted with saturated boiling of distilled water at atmospheric\\u000a pressure. In the experiment fluid velocity field surrounding the bubbles was visualized by use of polyamide tracer particles\\u000a and a sheet of

J. T. Cieslinski; J. A. Szymczyk

2005-01-01

20

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

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

21

Flow characteristics of bubbly countercurrent flow  

SciTech Connect

Many concepts have been proposed for future LWRs in which passive and simplified safety functions are actively introduced with the aim of enhancing the reliability of their safety features, maintainability and so on. However, since passive safety features are functioned by the law of nature, the driving force induced by them is much smaller than that induced by active ones, e.g. a gravity-driven coolant injection system. Consequently, it is necessary with regard to passive safety features to be able to simulate multi-dimensional dynamics even for the two-phase flow which can be regarded as one dimensional flow for active ones. The authors have developed a measurement system which is composed of an ultrasonic velocity profile monitor and a video data processing unit in order to clarify its multi-dimensional flow characteristics in bubbly flow and to offer a data base to validate numerical codes for multi-dimensional two-phase. In this paper, the measurement system is applied for bubbly countercurrent flows in a vertical rectangular channel. Both bubble and water velocity profiles and void fraction profiles in the channel were investigated statistically. Next, the distribution parameter and drift flux used in the drift flux model were obtained. Finally, the profile of two-phase multiplier of turbulent intensity in the channel was discussed.

Aritomi, Masanori; Zhou, Shirong [Tokyo Inst. of Tech. (Japan); Nakajima, Makoto [Mitsubishi Heavy Industry Co., Kobe (Japan); Mizoguchi, Junji [Shibaura Inst. of Tech., Omiya (Japan); Takeda, Yasushi [Paul Scherrer Inst., Villigen (Switzerland); Mori, Michitugu [Tokyo Electric Power Co. (Japan); Yoshioka, Yuzuru [Japan Atomic Power Co., Tokyo (Japan)

1996-06-01

22

Numerical simulation of 3D bubbles rising in viscous liquids using a front tracking method  

NASA Astrophysics Data System (ADS)

The rise of bubbles in viscous liquids is not only a very common process in many industrial applications, but also an important fundamental problem in fluid physics. An improved numerical algorithm based on the front tracking method, originally proposed by Tryggvason and his co-workers, has been validated against experiments over a wide range of intermediate Reynolds and Bond numbers using an axisymmetric model [J. Hua, J. Lou, Numerical simulation of bubble rising in viscous liquid, J. Comput. Phys. 22 (2007) 769-795]. In the current paper, this numerical algorithm is further extended to simulate 3D bubbles rising in viscous liquids with high Reynolds and Bond numbers and with large density and viscosity ratios representative of the common air-water two-phase flow system. To facilitate the 3D front tracking simulation, mesh adaptation is implemented for both the front mesh on the bubble surface and the background mesh. On the latter mesh, the governing Navier-Stokes equations for incompressible, Newtonian flow are solved in a moving reference frame attached to the rising bubble. Specifically, the equations are solved using a finite volume scheme based on the Semi-Implicit Method for Pressure-Linked Equations (SIMPLE) algorithm, and it appears to be robust even for high Reynolds numbers and high density and viscosity ratios. The 3D bubble surface is tracked explicitly using an adaptive, unstructured triangular mesh. The numerical model is integrated with the software package PARAMESH, a block-based adaptive mesh refinement (AMR) tool developed for parallel computing. PARAMESH allows background mesh adaptation as well as the solution of the governing equations in parallel on a supercomputer. Further, Peskin distribution function is applied to interpolate the variable values between the front and the background meshes. Detailed sensitivity analysis about the numerical modeling algorithm has been performed. The current model has also been applied to simulate a number of cases of 3D gas bubbles rising in viscous liquids, e.g. air bubbles rising in water. Simulation results are compared with experimental observations both in aspect of terminal bubble shapes and terminal bubble velocities. In addition, we applied this model to simulate the interaction between two bubbles rising in a liquid, which illustrated the model's capability in predicting the interaction dynamics of rising bubbles.

Hua, Jinsong; Stene, Jan F.; Lin, Ping

2008-03-01

23

Flow around individual Taylor bubbles rising in stagnant CMC solutions: PIV measurements  

Microsoft Academic Search

The flow around single Taylor bubbles rising in non-Newtonian solutions of Carboxymethylcellulose (CMC) polymer was studied using simultaneously particle image velocimetry (PIV) and shadowgraphy. This technique made it possible to determine the correct position of the bubble interface. Solutions of polymer with weight percentage varying from 0.1 to 1.0wt% were used to cover a wide range of flow regimes. The

R. G. Sousa; M. L. Riethmuller; A. M. F. R. Pinto; J. B. L. M. Campos

2005-01-01

24

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

25

Scattering from bubbles rising in a vertical line-Comparison between theory and experiments  

NASA Astrophysics Data System (ADS)

In this paper, the experimental data from the sound field around similar sized air bubbles rising in a vertical chain are analyzed. The data reveal a strong anisotropy in the acoustic field. The transition from individual to continuum behavior in a bubble chain is not correctly described with classical theory especially when the bubbles are uniformly sized, discretely populated, and the frequency of interest is close to the natural frequency of the individual bubbles. Single compact scatterers initiated at frequencies near their resonant frequency in isolation act preliminarily as monopole sources, amplifying the local pressure field by a factor of order 1/(k*a), a being the scattering radius and k the wave number at the resonant frequency in the surrounding material [Tolstoy, 1986]. A laboratory investigation used air bubbles in fresh water and varied the bubble sizes and separation by carefully controlling bubble production rates. A linear coupled equation method was developed to explain the result. The model reproduced the acoustic pressure anisotropy along the chain and the change in pulse waveform along the chain. The results suggest that the enhancement of sound intensity along the chain can be explained by bubbles acting as resonant scatterers retransmitting the acoustic energy.

Nikolovska, Aneta; Ooi, Andrew; Manasseh, Richard

2001-05-01

26

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. PMID:24759766

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

2014-01-01

27

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

PubMed

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

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

2015-04-01

28

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

2014-07-01

29

Visualization of gas–liquid mass transfer and wake structure of rising bubbles using pH-sensitive PLIF  

E-print Network

A planar laser-induced fluorescence (PLIF) technique for visualizing gas–liquid mass transfer and wake structure of rising gas bubbles is described. The method uses an aqueous solution of the pH-sensitive dye Naphthofluorescein ...

Stohr, M.

30

Bubbles generated from wind-steepened breaking waves: 2. Bubble plumes, bubbles, and wave characteristics  

Microsoft Academic Search

Measurements of breaking-wave-generated bubble plumes were made in fresh (but not clean) water in a large wind-wave tunnel. To preserve diversity, a classification scheme was developed on the basis of plume dimensions and “optical density,” or the plume's ability to obscure the background. Optically dense plumes were due to the presence of a peak at large radius in the plume

Ira Leifer; Guillemette Caulliez; Gerrit de Leeuw

2006-01-01

31

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

32

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

33

Measurements of the average properties of a suspension of bubbles rising in a vertical channel  

NASA Astrophysics Data System (ADS)

Experiments were performed in a vertical channel to study the behaviour of a monodisperse bubble suspension for which the dual limit of large Reynolds number and small Weber number was satisfied. Measurements of the liquid-phase velocity fluctuations were obtained with a hot-wire anemometer. The gas volume fraction, bubble velocity, bubble velocity fluctuations and bubble collision rate were measured using a dual impedance probe. Digital image analysis was performed to quantify the small polydispersity of the bubbles as well as the bubble shape.

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

2001-02-01

34

Flow in the negative wake of a Taylor bubble rising in viscoelastic carboxymethylcellulose solutions: particle image velocimetry measurements  

NASA Astrophysics Data System (ADS)

A simultaneous technique employing particle image velocimetry (PIV) and shadowgraphy was used to study vertical slug flow in non-Newtonian fluids. Two aqueous solutions of 0.8 and 1.0 wt% carboxymethylcellulose (CMC) were studied and the flow field around individual Taylor bubbles fully characterized. The rheological fluid properties and pipe dimension yielded Reynolds numbers of 8 and 4 and Deborah numbers of 0.2 and 0.4. A negative wake was found downstream of the Taylor bubbles in both fluids. Below the bubble trailing edge, along the axis region, the fluid flows in the opposite direction to the bubble (negative wake), originating rotational liquid movements in adjacent regions. Even far downward from the bubble, rotational liquid movements are clearly seen and measured. In the 1.0 wt% CMC solution, the bubble trailing edge has the shape of a two-dimensional cusp. This two-dimensional cusp, of small dimensions, is seen in different orientations during the bubble rise-indicating a fast rotational movement. The asymmetrical shape of the trailing edge is responsible for small asymmetries in the flow in the wake region (three-dimensional flow). The asymmetrical shape associated with the rotational movement is responsible for an unsteady flow of small amplitude. In the 0.8 wt% CMC solution, the shape of the trailing edge changes during the bubble rise. An axisymmetric axial oscillation a continuous expansion and contraction of the trailing edge, is the origin of this behaviour. This oscillatory movement is responsible for an unsteady flow of small amplitude in the wake region.

Sousa, Renato G.; Nogueira, S.; Pinto, A. M. F. R.; Riethmuller, M. L.; Campos, J. B. L. M.

2004-07-01

35

Simulation of the Coalescence of two Bubbles Rising in a Vertical Pipe with VOF Interface Tracking Method  

Microsoft Academic Search

In this paper, we report the computational results of the coalescence of two bubbles rising in a liquid at rest. The calculations where conducted in parallel using the open source code OpenFOAM. The equations of motion where solved using the finite volume method and the interface is advected using the volume of fluid method (VOF). The predicted behavior of two

Djemai Merrouche; Kamal Mohammedi; Idir Belaidi; Bachir Mabrouki

2007-01-01

36

Experimental investigation of the velocity field induced by a Taylor bubble rising in stagnant water  

E-print Network

by Particle Image Velocimetry (PIV). The mean velocity fields in front of the bubble, in the liquid film experimental study of the coalescence mechanism between two consecutive Taylor bubbles was carried out Elsevier Science Ltd. All rights reserved. PII: S0301-9322(01)00082-9 #12;studied bubble coalescence using

Shemer, Lev

37

Characteristics for 4Mb ion-implanted bubble memory modules  

NASA Astrophysics Data System (ADS)

A 4 Mb module with a 4 Mb on-clip-cache ion-implanted bubble memory chip has been developed. Operation temperature characteristics for the module are evaluated for total operation with fully loaded data. A temperature coefficient for the bias field in the module is adjusted to that for the chip by using a pair of rare earth magnets with large and small temperature coefficients. The acceptable high temperature limit for the module operation is obtained by restricting the number of consecutive minor-minor gate operation to 8 pages. Consequently, reasonable total operation margins are confirmed in a temperature range from -10 to 60 C without any modification for operation conditions.

Kato, Y.

1987-09-01

38

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

39

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

40

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

41

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.

Mercer Mayer

2009-11-11

42

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. PMID:22390990

Zhou, Yufeng; Qin, Jun; Zhong, Pei

2013-01-01

43

Radiation Characteristics of Glass Containing Gas Bubbles Laurent Pilon*  

E-print Network

Lafayette, Indiana 47907 In many materials processing and manufacturing situations such as steel, aluminum of the continuous phase are small. I. Introduction IN MANY materials processing and manufacturing situations such as steel, aluminum, ceramics, and glass, gas bubbles can form in liquid and solid phases. The presence

Pilon, Laurent

44

Some characteristics of ion-implanted bubble chips  

Microsoft Academic Search

The relations between the position of charged walls and the bubble motion around propagation circuits are discussed. Long walls which extend between adjacent propagation loops are revealed by the Bitter technique. The examination of the domain structure in the implanted layer shows the existence of a magnetic gradient which is a function of the distance from the propagation circuits. The

H. Jouve; I. Pulchaska

1979-01-01

45

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

46

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

47

BUBBLE CHARACTERISTICS AND CONVECTIVE EFFECTS IN THE FLOW BOILING HEAT TRANSFER OF BINARY MIXTURES  

E-print Network

BUBBLE CHARACTERISTICS AND CONVECTIVE EFFECTS IN THE FLOW BOILING HEAT TRANSFER OF BINARY MIXTURES-mail: SGKEME@RIT.EDU ABSTRACT Binary mixture pool boiling has been extensively studied in literature growth rate under flow conditions are compared with the models developed for binary pool boiling

Kandlikar, Satish

48

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

NASA Astrophysics Data System (ADS)

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

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

2015-03-01

49

Lattice Boltzmann Study of Bubble Dynamics  

Microsoft Academic Search

The purpose of this work is to assess the applicability of a new two-phase immiscible lattice Boltzmann method based on phase-field method to single bubble dynamics over a wide range of flow regimes. In two-dimensional domain, the bubble geometry, the interface deformation, and the bubble rise characteristics, such as terminal velocity, drag coefficient, and wake properties, are investigated and quantified

Ismail Oguz Kurtoglu; Ching-Long Lin

2006-01-01

50

Coupling the VOF and the MHD models for the simulation of bubble rising in a metallic liquid  

Microsoft Academic Search

In the last few decades magnetohy-drodynamic (MHD) effects have attracted growing interest because of its potential impact\\u000a on numerous industrial technologies such as metallurgy, crystal growth, electron or laser beam melting\\/evaporation of surfaces,\\u000a etc… An example of such flow is the Bubble driven flows which have found wide applications in industrial technologies. In\\u000a metallurgical processes gas bubbles are injected into

D. Merrouche; K. Mohammedi; I. Belaidi

2008-01-01

51

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.

WGBH Boston

2003-01-01

52

Effect of pressure fluctuations on the heat transfer characteristics in a pressurized slurry bubble column  

Microsoft Academic Search

The hydrodynamics and heat transfer characteristics were investigated in a slurry bubble column reactor whose diameter was\\u000a 0.0508 m (ID) and 1.5 m in height. Effects of gas velocity (0.025–0.1 m\\/s), pressure (0.1–0.7MPa), solid concentration (0–20\\u000a vol%) and liquid viscosity (1.0–38.0 mPa s) on the hydrodynamics and heat transfer characteristics were examined. The pressure\\u000a difference fluctuations were analyzed by means

Suk-Hwan Kang; Sung-Mo Son; Yong Kang; Jong-Wook Bae; Ki-Won Jun

2008-01-01

53

Dynamic characteristics of heat transfer coefficient in pressurized bubble columns with viscous liquid medium  

Microsoft Academic Search

Dynamic characteristics of heat transfer coefficient have been investigated in a pressurized bubble column (0.152 m, i.d. and 2.0 m in height) by adopting the chaos theory. Effects of gas velocity (0–0.12 m\\/s), pressure (0.1–0.6 MPa) and liquid viscosity (1.0–38.0 mPa s) on the immersed heater-to-column heat transfer characteristics have been examined. The temperature difference fluctuations between the immersed heater

Yong Jun Cho; Kwang Jae Woo; Yong Kang; Sang Done Kim

2002-01-01

54

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

NASA Astrophysics Data System (ADS)

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

Crews, Jackson B.; Cooper, Clay A.

2014-09-01

55

Some hydrodynamic characteristics of bubbly mixtures flowing vertically upward in tubes  

E-print Network

An investigation of bubbly flow has been conducted in vertical plexiglass tubes using air and water at atmospheric pressure. The bubbly flow pattern is an entrance condition or a non-fully developed flow. A spontaneous ...

Rose, Sewell C.

1964-01-01

56

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

Microsoft Academic Search

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

Ji-Hyun Lee; Wan-Kuen Jo

2006-01-01

57

Buoyancy Driven Shear Flows of Bubble Suspensions  

NASA Astrophysics Data System (ADS)

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

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

1998-11-01

58

Controlling bubbles  

NASA Astrophysics Data System (ADS)

In this short overview we report on our ongoing work on the dynamics of bubbles in various flows. Three different situations are explored: the competition between acoustic and hydrodynamics forces in a vertical pipe (Rensen J, Bosman D, Magnaudet J, Ohl C D, Prosperetti A, Tögel R, Versluis M and Lohse D 2001 Phys. Rev. Lett. 86 4819), a rising bubble on which shape oscillations have been induced (de Vries J, Luther S and Lohse D 2002 Eur. J. Phys. B 29 503), and a bubble in a rotating horizontal cylinder. Whereas for the first two situations the standard bubble force models (Magnaudet J and Eames I 2000 Annu. Rev. Fluid Mech. 32 659) are consistent with our measurements, modifications for the lift force model seem to be required in the last case.

Lohse, Detlef; Prosperetti, Andrea

2003-01-01

59

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

NASA Astrophysics Data System (ADS)

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

Crews, Jackson B.

60

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

E-print Network

in the nuclear industry, more than 90% power generated by nuclear is from water-cooled nuclear reactors either the safety of the nuclear reactors. There are many studies of the bubble or water droplet behav- iours under. The process of bubble starting from deformation until break into three small bubbles is clearly shown from

Frey, Pascal

61

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

62

Study on dependence of hydrodynamic characteristics on gravity in a vertical upward channel bubbly flow  

NASA Astrophysics Data System (ADS)

Since the bubbly flow has extensive applications in the space field, it is very necessary to comprehend the dependence of hydrodynamic characteristics on gravity. In this paper, the dependence of the microbubble distribution and the liquid turbulence modulation by the microbubbles on gravity was investigated in detail with the Euler-Lagrange method. The liquid Navier-Stokes equation was solved using direct numerical simulations (DNS), and the microbubble motion was tracked with Newtonian motion equation considering drag force, shear lift force, added mass force, pressure gradient force, and wall lift force. The coupling between the gas and the liquid phases regarded the interphase force as a momentum source term in the momentum equation of the liquid. The results showed that the phase profile and the turbulence modulation by the microbubbles strongly depend on the magnitude of gravity. When the influence of gravity is relatively weak, the microbubbles approximately uniformly disperse in the wide central region of the channel, and the average statistics of the liquid turbulence are almost not influenced due to the addition of the microbubbles. However, when the influence of gravity is comparatively important, the majority of the microbubbles accumulate near the wall of the channel, and the injection of the microbubbles modifies the profiles of the liquid average statistics.

Pang, Mingjun; Wei, Jinjia; Yu, Bo

2011-10-01

63

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.

Glenn Dolphin

64

Unsteady Characteristics of Laminar Separation Bubbles; An Experimental and Numerical Investigation  

Microsoft Academic Search

Laminar separation bubbles may occur in a wide range of engineering applications\\u000asuch as turbomachinery flows, wind turbines, hydrofoils etc. Much attention has been\\u000agiven to their effect on the flow over airfoils because of the importance for an accurate\\u000aprediction of lift, drag and heat transfer.\\u000aIn the aeronautical world, laminar separation bubbles have traditionally been of con-\\u000acern

M. Baragona

2004-01-01

65

Mass transfer characteristics in a large-scale slurry bubble column reactor with organic liquid mixtures  

Microsoft Academic Search

The mass transfer coefficients (kLa) and bubbles size distribution were measured in a large-scale (0.316-m inside diameter, 2.8-m high) slurry bubble column reactor (SBCR) for H2, CO, N2 and CH4 in two organic liquid mixtures (Isopar-M and a hexanes mixture) in the presence and absence of two solids (iron oxides catalyst and glass beads) in a wide range of pressure

Arsam Behkish; Zhuowu Men; Juan R. Inga; Badie I. Morsi

2002-01-01

66

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

67

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

68

Storm-enhanced plasma density (SED) features, auroral and polar plasma enhancements, and rising topside bubbles of the 31 March 2001 superstorm  

Microsoft Academic Search

The significant plasma structuring (due to bubbles) detected over AnconThe TOI feature development in both hemispheres during E-field penetrationThe temporal variations of auroral and polar plasma enhancements

Ildiko Horvath; Brian C. Lovell

2011-01-01

69

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

70

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

71

Three-dimensional simulation of bubble dynamics in a narrow pipe using lattice Boltzmann method  

NASA Astrophysics Data System (ADS)

In the paper, a three-dimensional model of a gravity-driven bubble rising in a narrow pipe filled with viscous liquid is built using the lattice Boltzmann method. On the Cartesian grid, the free-energy multiphase lattice Boltzmann model and the no-slip bounce-back scheme are combined together to implement the bubble interface and the solid boundary treatment, respectively. To start with, the Laplace law for bubble interface is verified with the newly built model in this paper. Then the cases where the pipe with the radius 1.2 to 2.5 times the bubble radius are carried out to investigate the effects of pipe dimension on the bubble motion, including rising velocity, deformation and jet formation. Moreover, the asymmetric characteristics of bubble biases the centre axle are explored further. The results show that the boundary condition effect consisting of the pipe dimension and the offset of bubble biasing the centre axle is of great significance to the bubble dynamics in a narrow pipe. The former factor mostly affect the velocity characteristics of the bubble, while the latter one mostly focuses on the bubble deformation and trajectory.

Shi, D. Y.; Wang, Z. K.; Zhang, A. M.

2015-01-01

72

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

NASA Astrophysics Data System (ADS)

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

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

2015-05-01

73

Effect of bubble deformation on the properties of bubbly flows  

NASA Astrophysics Data System (ADS)

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 are ellipsoidal, and the Galileo number is 900, so that the rise Reynolds number of a single bubble in an unbounded flow is about 26. Three values of the void fraction have been investigated: 2%, 6% and 12%. At 6%, a change in the behaviour of the bubbles is observed. The bubbles are initially dispersed homogeneously throughout the flow field and their average rise Reynolds number is 23. After the bubbles have risen by about 90 bubble diameters, they form a vertical stream and accelerate. The microstructure of the bubble suspension is analysed and an explanation is proposed for the formation of these streams. The results for the ellipsoidal bubbles are compared to the results for nearly spherical bubbles, for which the Eötvös number is 1 and the Galileo number is 900. The dispersion of the bubbles and the velocity fluctuations in the liquid phase are analysed.

Bunner, Bernard; Tryggvason, Grétar

2003-11-01

74

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.

2013-07-30

75

Power Laws in Real Estate Prices during Bubble Periods  

NASA Astrophysics Data System (ADS)

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

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

76

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

77

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

ERIC Educational Resources Information Center

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

Black, Willie James, Jr.

2012-01-01

78

Seismic response characteristics of high-rise RC wall buildings having different irregularities in lower stories  

Microsoft Academic Search

Three 1:12 scale 17-story RC wall building models having different types of irregularity at the bottom two stories were subjected to the same series of simulated earthquake excitations to observe their seismic response characteristics. The first model has a symmetrical moment-resisting frame (Model 1), the second has an infilled shear wall in the central frame (Model 2), and the third

Han-Seon Lee; Dong-Woo Ko

2007-01-01

79

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

Microsoft Academic Search

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

Eizo Sada; Hidehiro Kumazawa; C. H. Lee

1986-01-01

80

Direct numerical simulations of three-dimensional bubbly flows  

NASA Astrophysics Data System (ADS)

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 motion reaches a statistical steady state with a rise Reynolds number of about 25.

Bunner, Bernard; Tryggvason, Grétar

1999-08-01

81

Direct numerical simulations of bidisperse bubbly flows  

NASA Astrophysics Data System (ADS)

Three-dimensional direct numerical simulations of homogeneous bidisperse bubbly flows at finite Reynolds numbers are presented. A front-tracking/finite-difference method is used to accurately follow the motion of N1 large bubbles of volume V1 and N2 small bubbles of volume V_2. Periodic boundary conditions are used to approximate homogeneous flows. The effect of the interaction between the large bubbles and the small bubbles on the statistical properties of the flow is studied. These statistical properties include the rise velocity, fluctuation velocity, and dispersion cofficient of the bubbles as well as the fluctuation velocity and kinetic energy spectrum of the liquid. To characterize the respective position and motion of the bubbles, the pair probability density is examined. The void fraction ranges between 2% and 12%. Two cases are considered. In the first case, V_1=2V2 and N_1=N_2. The results are found to be quantitatively similar to the results of the monodisperse simulations. In the second case, V_1=8V2 and N1 < N_2. The results exhibit strong differences from the monodisperse simulation results. The small bubbles experience much higher fluctuations relative to their rise velocity tham the large bubbles. The liquid kinetic energy is larger than in the monodisperse case. It appears that the small bubbles hinder the motion of the large bubbles and the large bubbles pull the small bubbles along as they rise.

Bunner, Bernard; Göz, Manfred; Sommerfeld, Martin; Tryggvason, Gretar

2001-11-01

82

Fabrication and Operating Characteristics of Ion-Implanted Bubble Memory Chips for a 16M-Bit Device  

Microsoft Academic Search

A test chip using ion-implanted functions for a 16-Mbit bubble memory device has been designed, fabricated and characterized. A new delineation process for ion-implanted tracks using SiO2 ion-implantation masks is effective for reducing defects in minor loops. As a result, a bias margin of 22 Oe was obtained for minor loop bubble propagation. Test chip operation over a wide temperature

M. Ohashi; K. Betsui; Y. Satoh; N. Furukawa; T. Namiki; K. Komenou

1989-01-01

83

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.

2012-06-26

84

Slurry bubble column dynamics  

SciTech Connect

A novel approach utilizing an electrical conductivity twin-probe technique is described for obtaining important gas-phase characteristics such as: bubble size, velocity ad holdup fraction. A 10 cm internal diameter by 310 cm height glass column is employed to investigate the bubble dynamics measured with this probe. The liquid phase is composed of a mixture of ethanol and water that may have substantial ''surface activity'' which results in a dynamic surface tension effect on the rate of bubble coalescence. Measurements of gas holdup, bubble size,and velocity indicate the influence of surface activity onthe gas phase characteristics. Possible implications of these results on the hydrodynamics of Fischer-Tropsch reactors are given. An experimental technique and subsequent analysis have been developed to determine the bubble size and velocity distributions in a slurry bubble column cold model. Dynamic surface tension effects have been observed for a two component liquid mixture. The maximum frothing ability of a ''surface-active'' species qualitatively agrees with a dynamic surface tension model. Increased gas holdup and interfacial area are observed with the addition of a ''surface-active'' component. In addition, increased gas holdup and interfacial area are observed with a sintered plate distributor compared to a perforated plate. The presence of solids reduces the gas holdup and increases the bubble size. 11 refs., 11 figs.

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

1983-01-01

85

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.

2011-12-07

86

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.

Austen Saltz

2010-01-01

87

Bubble Enhanced Heat Transfer from a Vertical Heated Surface  

Microsoft Academic Search

A rising bubble in a liquid can greatly enhance heat transfer from heated surfaces by acting like a bluff body, displacing fluid as it moves and via the wake generated by the bubble, increasing the mixing of the liquid. The current research quantifies the effect a single free rising ellipsoidal air bubble has on heat transfer from a vertical heated

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

2008-01-01

88

Recalcitrant bubbles  

PubMed Central

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

Shanahan, Martin E. R.; Sefiane, Khellil

2014-01-01

89

Four-dimensional visualization of rising microbubbles  

NASA Astrophysics Data System (ADS)

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

2014-05-01

90

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. 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

91

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

92

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...

93

Bubble velocities induced by trailing vortices behind neighbours  

NASA Astrophysics Data System (ADS)

Although potential flow, including viscous dissipation, explains quite well the flow around individual bubbles of about 1mm radius rising in water, and e.g. predicts their drag quite accurately, this model cannot explain the homogeneous rise of a bubbly suspension. From numerical and analytical work it follows that eventually all bubbles cluster together. On the other hand it has been shown that velocity fluctuations of the bubbles of sufficient intensity, expressed in terms of a critical (pseudo) temperature, prevents clustering.

van Wijngaarden, Leen

2005-10-01

94

Mixing and Eddie Currents in a Modified Bubble Column Reactor  

Microsoft Academic Search

A modified bubble column reactor is introduced and compared with existing photobioreactors. The modified bubble column reactor uses a porous membrane as the interface between the air and the liquid. The characteristics of the porous membrane are investigated. Gas transfer characteristics of carbon dioxide and oxygen where investigated for the modified bubble column reactor. Bubble size and gas holdup relationships

Anil Kommareddy; Gary Anderson

2003-01-01

95

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.

2012-06-26

96

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.

2013-07-08

97

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.

The Exploratorium

2012-06-26

98

Bubble, Bubble, Toil and Trouble.  

ERIC Educational Resources Information Center

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

Journal of Chemical Education, 2001

2001-01-01

99

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

100

Shock Pulse from a Sonoluminescing Gas Bubble  

NASA Astrophysics Data System (ADS)

The shock pulse emanating from a sonoluminescing gas bubble was calculated by using the analytical solutions of the conservation equations for the gas inside the bubble and the Kirkwood-Bethe hypothesis for the outgoing wave. The rise time and the magnitude of the pulse signal are in good agreement with the observed values, which may provide the approximate value of the gas pressure at near the collapse of the sonoluminescing gas bubble.

Lee, Yoon-Pyo; Karng, Sarng; Jeon, Jin-Seok; Kwak, Ho-Young

1997-09-01

101

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

2003-01-01

102

Advances in Optical Characterization of Methane Seeps and Bubble Plumes  

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

103

Gas disengagement technique in a slurry bubble column operated in the coalesced bubble regime  

Microsoft Academic Search

The gas disengagement technique is discussed in detail and is applied in a two-dimensional bubble column and slurry bubble column to obtain the bubble size distribution. Flow characteristics including velocities of each phase and dispersed phase size distribution during the gas disengagement process are obtained by using an advanced image analysis tool including a particle image velocimetry technique. It is

D. J. Lee; X. Luo; L.-S. Fan

1999-01-01

104

Model of single bubble sonoluminescence  

SciTech Connect

The temperature within and the sonoluminescence characteristics of a stable inert-gas single bubble grown in water under some given conditions are computed by using a model that is as sufficiently complete as we can manage, except that possible chemical reactions within the bubble are neglected. We work with several different versions of the equation describing the motion of the bubble wall, which are usually considered to give merely slight differences; or vary a parameter in the formula calculating the net increment of the water condensed at the bubble wall. It is found that the final outcomes of the temperature and the sonoluminescence can be significantly different in some cases. This illustration points to the importance of differentiating among the various seemingly similar equations and of adopting the correct value of the parameter used in the computation model of a single bubble.

An Yu; Ying, C.F. [Department of Physics, Tsinghua University, Beijing 100084 (China); Institute of Acoustics, Chinese Academy of Science, Beijing 100080 (China)

2005-03-01

105

Animation of Bubbles in Liquid  

Microsoft Academic Search

We present a new fluid animation technique in which liquid and gas interact with each other, using the example of bubbles rising in water. In contrast to previous studies which only focused on one fluid, our system considers both the liquid and the gas simultaneously. In addition to the flowing motion, the interactions between liquid and gas cause buoyancy, surface

Jeong-mo Hong; Chang-hun Kim

2003-01-01

106

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

107

Bubble departure size in flow boiling  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

108

Hydrodynamic study in a slurry-bubble-column reactor  

Microsoft Academic Search

Local gas holdup, bubble diameter and bubble rise velocity in the nitrogen\\/Drakeol-10 oil system were measured at both laboratory (ambient temperature and pressure) and industrially relevant (high temperature and pressure) conditions using a dual conductivity probe in a slurry-bubble-column reactor. It was found that a constant superficial velocity, the Sauter mean bubble diameter decreases with increasing pressure and temperature. The

Y. Soong; F. W. Harke; I. K. Gamwo; R. R. Schehl; M. F. Zarochak

1997-01-01

109

Motion of a bubble ring in a viscous fluid  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

110

Mercury Bubbles  

Microsoft Academic Search

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

A. T. Hare

1908-01-01

111

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

112

Dynamics of homogeneous bubbly flows Part 2. Velocity fluctuations  

NASA Astrophysics Data System (ADS)

Direct numerical simulations of the motion of up to 216 three-dimensional buoyant bubbles in periodic domains are presented. The bubbles are nearly spherical and have a rise Reynolds number of about 20. The void fraction ranges from 2% to 24%. Part 1 analysed the rise velocity and the microstructure of the bubbles. This paper examines the fluctuation velocities and the dispersion of the bubbles and the ‘pseudo-turbulence’ of the liquid phase induced by the motion of the bubbles. It is found that the turbulent kinetic energy increases with void fraction and scales with the void fraction multiplied by the square of the average rise velocity of the bubbles. The vertical Reynolds stress is greater than the horizontal Reynolds stress, but the anisotropy decreases when the void fraction increases. The kinetic energy spectrum follows a power law with a slope of approximately [minus sign]3.6 at high wavenumbers.

Bunner, Bernard; Tryggvason, Grétar

2002-09-01

113

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

SciTech Connect

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

Arcanjo, Alexandre Alves; Tibirica, Cristiano Bigonha; Ribatski, Gherhardt [Department of Mechanical Engineering, Escola de Engenharia de Sao Carlos (EESC), University of Sao Paulo (USP), Av. Trabalhador SanCarlense 400, Centro, Sao Carlos, SP (Brazil)

2010-09-15

114

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

115

The Isolated Bubble Regime in Pool Nucleate Boiling  

NASA Technical Reports Server (NTRS)

We consider an isolated bubble boiling regime in which vapour bubbles are intermittently produced at a prearranged set of nucleation site on an upward facing overheated wall plane. In this boiling regime, the bubbles depart from the wall and move as separate entities. Except in the matter of rise velocity, the bubbles do not interfere and are independent of one another. However, the rise velocity is dependent on bubble volume concentration in the bulk. Heat transfer properties specific to this regime cannot be described without bubble detachment size, and we apply our previously developed dynamic theory of vapour bubble growth and detachment to determine this size. Bubble growth is presumed to be thermally controlled. Two limiting cases of bubble evolution are considered: the one in which buoyancy prevails in promoting bubble detachment and the one in which surface tension prevails. We prove termination of the isolated regime of pool nucleate boiling to result from one of the four possible causes, depending on relevant parameters values. The first cause consists in the fact that the upward flow of rising bubbles hampers the downward liquid flow, and under certain conditions, prevents the liquid from coming to the wall in an amount that would be sufficient to compensate for vapour removal from the wall. The second cause is due to the lateral coalescence of growing bubbles that are attached to their corresponding nucleation sites, with ensuing generation of larger bubbles and extended vapour patches near the wall. The other two causes involve longitudinal coalescence either 1) immediately in the wall vicinity, accompanied by the establishment of the multiple bubble boiling regime, or 2) in the bulk, with the formation of vapour columns. The longitudinal coalescence in the bulk is shown to be the most important cause. The critical wall temperature and the heat flux density associated with isolated bubble regime termination are found to be functions of the physical and operating parameters and are discussed in detail.

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

1995-01-01

116

Laminar bubbly flow in a vertical channel  

NASA Astrophysics Data System (ADS)

Direct numerical simulations are used to examine the buoyant rise of many nearly spherical bubbles in laminar flows in vertical channels. The lift force on spherical bubbles leads to a very simple flow structure in terms of the void fraction distribution and the average liquid velocity. The numerical results show that at steady state the number density of bubbles in the center of the channel is always such that the fluid mixture there is in hydrostatic equilibrium and the velocity is uniform. For upflow, excess bubbles are pushed to the walls, forming a bubble rich layer, one bubble diameter thick. For downflow, bubbles are drawn into the channel core, leading to a wall layer with no bubbles, of a thickness determined by the pressure gradient and the average void fraction. For the downflow, the void fraction profile and the velocity profile can be predicted analytically, but for upflow the velocity increase across the wall-layer must be obtained from the simulations. The behaviour of the bubbles in the middle of the channel, including the slip velocity and their velocity fluctuations, is well predicted by results for homogeneous flows in fully periodic domains.

Lu, Jiacai

2005-11-01

117

Rising River  

USGS Multimedia Gallery

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

118

Discrete Bubble Modeling for Cavitation Bubbles  

NASA Astrophysics Data System (ADS)

Dynaflow, Inc. has conducted extensive studies on non-spherical bubble dynamics and interactions with solid and free boundaries, vortical flow structures, and other bubbles. From these studies, emerged a simplified Surface Averaged Pressure (SAP) spherical bubble dynamics model and a Lagrangian bubble tracking scheme. In this SAP scheme, the pressure and velocity of the surrounding flow field are averaged on the bubble surface, and then used for the bubble motion and volume dynamics calculations. This model is implemented using the Fluent User Defined Function (UDF) as Discrete Bubble Model (DBM). The Bubble dynamics portion can be solved using an incompressible liquid modified Rayleigh-Plesset equation or a compressible liquid modified Gilmore equation. The Discrete Bubble Model is a very suitable tool for the studies on cavitation inception of foils and turbo machinery, bubble nuclei effects, noise from the bubbles, and can be used in many practical problems in industrial and naval applications associated with flows in pipes, jets, pumps, propellers, ships, and the ocean. Applications to propeller cavitation, wake signatures of waterjet propelled ships, bubble-wake interactions, modeling of cavitating jets, and bubble entrainments around a ship will be presented.

Choi, Jin-Keun; Chahine, Georges; Hsiao, Chao-Tsung

2007-03-01

119

HYDRODYNAMICS AND HEAT-TRANSFER OF BAFFLED AND UNBAFFLED SLURRY BUBBLE-COLUMNS  

Microsoft Academic Search

Summary This review deals with the discussion of various hy drodynamic and heat-transfer characteristics of bubble and slurry bubble columns both for baffled and unbaffled configurations.The hydrodynamic properties include consideration of initial-bubble diameter, bubble growth, bubble size and size distr ibution, bubble velocity, gas-phase holdup, specific gas-liquid interfacial area, mass- transfer coefficients, different fluid- flow regimes, and effects of operating

King Fahd

120

Molecular emission from single-bubble sonoluminescence  

Microsoft Academic Search

Ultrasound can drive a single gas bubble in water into violent\\u000a oscillation; as the bubble is compressed periodically, extremely short\\u000a flashes of light (about 100 ps) are generated with clock-like\\u000a regularity(1-4). This process, known as single-bubble sonoluminescence,\\u000a gives rise to featureless continuum emission(4,5) in water (from 200 to\\u000a 800 nm, with increasing intensity into the ultraviolet). In contrast,\\u000a the emission

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

2000-01-01

121

Gas accumulation in particle-rich suspensions and implications for bubble populations in crystal-rich magma  

E-print Network

in particle-aided bubble coalescence. However, these studies demon- strate that the effect of particles on gasGas accumulation in particle-rich suspensions and implications for bubble populations in crystal between rising bubbles and particles. We observe different interaction styles as the ratio of bubble

Rempel, Alan W.

122

Slurry bubble column hydrodynamics  

NASA Astrophysics Data System (ADS)

Slurry bubble column reactors are presently used for a wide range of reactions in both chemical and biochemical industry. The successful design and scale up of slurry bubble column reactors require a complete understanding of multiphase fluid dynamics, i.e. phase mixing, heat and mass transport characteristics. The primary objective of this thesis is to improve presently limited understanding of the gas-liquid-solid slurry bubble column hydrodynamics. The effect of superficial gas velocity (8 to 45 cm/s), pressure (0.1 to 1.0 MPa) and solids loading (20 and 35 wt.%) on the time-averaged solids velocity and turbulent parameter profiles has been studied using Computer Automated Radioactive Particle Tracking (CARPT). To accomplish this, CARPT technique has been significantly improved for the measurements in highly attenuating systems, such as high pressure, high solids loading stainless steel slurry bubble column. At a similar set of operational conditions time-averaged gas and solids holdup profiles have been evaluated using the developed Computed Tomography (CT)/Overall gas holdup procedure. This procedure is based on the combination of the CT scans and the overall gas holdup measurements. The procedure assumes constant solids loading in the radial direction and axially invariant cross-sectionally averaged gas holdup. The obtained experimental holdup, velocity and turbulent parameters data are correlated and compared with the existing low superficial gas velocities and atmospheric pressure CARPT/CT gas-liquid and gas-liquid-solid slurry data. The obtained solids axial velocity radial profiles are compared with the predictions of the one dimensional (1-D) liquid/slurry recirculation phenomenological model. The obtained solids loading axial profiles are compared with the predictions of the Sedimentation and Dispersion Model (SDM). The overall gas holdup values, gas holdup radial profiles, solids loading axial profiles, solids axial velocity radial profiles and solids shear stress radial profiles are correlated using several widely used empirical correlations that are modified and improved to better represent present data.

Rados, Novica

123

Gunderson RISEs  

ERIC Educational Resources Information Center

Described are efforts of the Gunderson Senior High School (San Jose, California) in developing improved instruction with the aid of active community participation. Relevance of its efforts to the mandate of the California Commission on Reform in Intermediate and Secondary Education (RISE) is noted. (MJB)

Sleight, Ralph H.

1978-01-01

124

A numerical study of the hydrodynamic interaction of bubble pairs ascending in non-Newtonian liquids  

NASA Astrophysics Data System (ADS)

This talk presents computational results on the interaction of a pair of bubbles immersed in non-Newtonian fluids. The Arbitrary Lagrangian-Eulerian (ALE) technique was used to simulate two bubbles rising in tandem or side by side in shear-thinning and Oldroyd-B fluids. In the shear-thinning fluid, the pairwise interaction is affected by the the Eotvos and Reynolds numbers as well as the initial orientation of two bubbles. In particular, two in-line bubbles will rise together and form a doublet as the trailing bubble catches up with the leading one. In a viscoelastic fluid, a negative wake may appear depending on the initial separation between the bubbles. The capillary number, which can be an indicator of the bubble deformability, seems to play a secondary role in the bubble interaction. The numerical simulations complement previous experiments done with bubble swarms by our group.

Velez, Rodrigo; Yue, Pengtao; Feng, James J.; Zenit, Roberto

2009-11-01

125

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

126

Rising equity  

SciTech Connect

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

Burr, M.T.

1992-09-01

127

On the motion of gas bubbles in homogeneous isotropic turbulence  

Microsoft Academic Search

This paper is concerned with the motion of small gas bubbles, equivalent diameter about 1.0 mm, in isotropic turbulent flows. Data on the mean velocity of rise and the dispersion of the bubbles have been obtained numerically by simulating the turbulence as a sum of Fourier modes with random phases and amplitudes determined by the Kraichnan and the von Kármán

P. D. M. Spelt; A. Biesheuvel

1997-01-01

128

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

SciTech Connect

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

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

1994-06-01

129

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

130

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

131

Multiple effects of operating variables on the bubble properties in three-phase slurry bubble columns  

Microsoft Academic Search

Flow properties of gas phase reactants such as size, rising velocity and frequency were investigated in simulated three-phase\\u000a slurry bubble column reactors. Effects of gas velocity, reactor pressure, liquid viscosity, solid content in the slurry phase\\u000a and column diameter on the flow properties of a gas reactant were determined. The multiple effects of operating variables\\u000a on the bubble properties were

Ik Sang Shin; Sung Mo Son; Uk Yeong Kim; Yong Kang; Sang Done Kim; Heon Jung

2009-01-01

132

Mechanism of mass transfer between a bubble initially composed of oxygen and molten glass1  

E-print Network

Mechanism of mass transfer between a bubble initially composed of oxygen and molten glass1 F ­ BP 135, 93303 Aubervilliers Cedex, France Abstract The bubble removal from molten glass is an important problem in glass melting process. In this paper, the mass transfer undergone by a bubble rising

Boyer, Edmond

133

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

134

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

135

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

136

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.

137

INVITED PAPER: Surfactant effect on the bubble motions and bubbly flow structures in a vertical channel  

NASA Astrophysics Data System (ADS)

It is well known that a small amount of surfactant can drastically change the motion of a single bubble and this causes a dramatic change of the whole bubbly flow structure. In our previous studies using upward vertical channel flows, it was shown that surfactant influences the shear-induced lift and the lateral migration of a bubble, which causes bubble accumulation and clustering near the wall. In this paper, the dependence of surfactant concentration on the motions of a 1 mm bubble rising through the laminar shear flow is investigated using 1-, 3-Pentanol and Triton X-100. The results are compared with the numerical ones, which show quantitative agreement on the lift and drag forces. Furthermore, we analyze the experimental data for the condition of bubble clustering in upward channel flows with the consideration of contaminant level in tap water. The results indicate that lower contaminant level and higher shear rate cause the significant bubble migration toward the wall, which leads to the formation of bubble clusters.

Takagi, Shu; Ogasawara, Toshiyuki; Fukuta, Masato; Matsumoto, Yoichiro

2009-12-01

138

Lagrangian statistics for fluid particles and bubbles in turbulence  

NASA Astrophysics Data System (ADS)

The dispersion of bubbles in homogeneous and isotropic turbulence is numerically examined. The fluid velocity field evolves according to the Navier Stokes equations that are solved by direct numerical simulation. The bubble paths are followed by Lagrangian tracking. The aim of the work is to quantify dispersion properties of bubbles in a regime ranging from low- to high-turbulence velocity fluctuations as compared to the bubble velocity scale, and to compare them to those of fluid particles. Moreover, the forces that are relevant for the bubble dispersion are analysed and their probability density functions, as well as their intermittency characteristics, are compared to those of fluid particle accelerations.

Mazzitelli, Irene M.; Lohse, Detlef

2004-12-01

139

Dye-bubble interactions in an open channel flow  

NASA Astrophysics Data System (ADS)

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

Crepeau, John C.; McIlroy, Hugh M.

2005-12-01

140

Some aspects of high-pressure phenomena of bubbles in liquids and liquid–solid suspensions  

Microsoft Academic Search

Some aspects of bubble dynamics and macroscopic hydrodynamic properties in high-pressure bubble columns and three-phase fluidization systems are discussed. Experimental results along with discrete-phase simulations of a single bubble rising in liquids and liquid–solid suspensions at high pressures are presented. A mechanistic model is described, which accounts for the initial size of bubble from a single orifice in liquid–solid suspensions.

L.-S. Fan; G. Q. Yang; D. J. Lee; K. Tsuchiya; X. Luo

1999-01-01

141

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

142

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

143

On the relevance of the lift force in bubbly turbulence  

NASA Astrophysics Data System (ADS)

Microbubble-laden homogeneous and isotropic turbulent flow is investigated by using direct numerical simulation of the three-dimensional Navier Stokes equations and computing the bubble trajectories with Lagrangian tracking. The bubble motion is calculated by taking into account the effect of fluid acceleration plus added mass, drag, gravity, and in particular the lift force, which had been neglected in many previous simulations. By comparing the results from simulations with and without lift, we find the effect of the lift force to be crucial: for passive bubbles, i.e. bubbles without backreaction on the flow (one-way coupling), the lift enhances the accumulation of bubbles on the downward flow side of vortices, resulting in a considerably reduced rise velocity of bubbles in turbulent flow, compared to still water. This also has consequences for the active bubble case, i.e. for bubbles with backreaction on the flow (two-way coupling): the energy spectrum of the turbulence is modified {non-uniformly}. Because of the combined effect of preferential bubble clustering in downflow zones and the local buoyant transfer, which reduces the vertical fluid velocity fluctuations, large-scale motions (small wavenumbers k) are suppressed. In contrast, small-scale motions (large wavenumbers k) are enhanced due to the local bubble forcing. The net effect turns out to be a reduction of the energy dissipation rate.

Mazzitelli, Irene M.; Lohse, Detlef; Toschi, Federico

2003-08-01

144

A model for the oven rise of dough during baking  

Microsoft Academic Search

A model for dough expansion during oven rise, under conditions where the temperature is independent of position, is presented. The growth of a single gas bubble as a result of the generation of carbon dioxide and water vapour from the surrounding viscous dough is considered. The resulting equations were solved using appropriate numerical methods. The predicted results for oven rise

Jintian Fan; J. R. Mitchell; J. M. V. Blanshard

1999-01-01

145

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

146

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

147

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

148

Bubble-Induced Cave Collapse  

PubMed Central

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

Girihagama, Lakshika; Nof, Doron; Hancock, Cathrine

2015-01-01

149

Soap and Bubbles  

NSDL National Science Digital Library

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

Brieske, Joel A.

2002-01-01

150

Simulation of large bubble/molten steel interaction for gas-injected ladle  

NASA Astrophysics Data System (ADS)

A mathematical model has been developed to simulate numerically the interactions between gas bubbles and molten steel during the gas-injection treatment in secondary refining of steel and to experimentally verify the reliability of the model. A marker-and-cell (MAC) technique is employed to simulate the motions of gas bubbles and molten steel. Photographic observation is used to evaluate the reliability of the mathematical model. A two-dimensional ladle with only one bubble was used to test the capability of the model to handle the interaction between the relatively large bubble and the molten steel. The shape of the bubble is initially round. Then it gradually becomes flattened and eventually evolves into a spherical-cap bubble. Molten steel is induced to flow and forms two circulations. The model was then tested on the same ladle with bubbles continuously released. The first bubble rises in a similar way as the previous case. The second bubble is affected by the first bubble and becomes slightly elongated in the vertical direction rather than in the horizontal direction. It also rises faster and later collides with the first bubble. The released bubbles can be grouped in clusters and are repeated cluster after cluster. Water-model experimental observations are consistent with the predicted results.

Pan, S.-M.; Chiang, J.-D.; Hwang, W.-S.

1999-04-01

151

DNS of many three-dimensional bubbles  

NASA Astrophysics Data System (ADS)

Direct numerical simulations of multiphase flows pose a number of conceptual and practical difficulties. The main problem is to accurately represent the interface between the different phases. To that effect, we employ a front-tracking, one-field methodology where the whole incompressible flow field is solved on a three-dimensional static Cartesian grid and the interface, or front, is tracked by a two-dimensional, moving, and deformable grid. To simulate systems containing O(100) bubbles, the method was parallelized according to a distributed memory model. We present results for 1, 8, 64, 512 deformable bubbles in a homogeneous flow at a moderate Reynolds number and explore the effect of scaling on the rise velocity, the velocity fluctuations, and the Reynolds stresses. The spatial distribution of the bubbles is also examined. Supported by NSF.

Bunner, Bernard; Tryggvason, Gretar

1997-11-01

152

Electrowetting of soap bubbles  

NASA Astrophysics Data System (ADS)

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

Arscott, Steve

2013-07-01

153

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

154

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

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

155

Bubbles: Using Controls  

NSDL National Science Digital Library

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

2012-06-26

156

Sonochemistry and bubble dynamics.  

PubMed

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

Mettin, Robert; Cairós, Carlos; Troia, Adriano

2015-07-01

157

Oscillating plasma bubbles. I. Basic properties and instabilities  

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

158

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

SciTech Connect

Synthesis gas can be made from a variety of coal, natural gas, environmentally distressed materials such as petroleum coke and biomass. There are considerable reactor design and scale-up problems associated with synthesis gas conversion technologies which arise due to the special characteristics of these processes. Bubble columns and slurry bubble column reactors (SBCRs), due to their superior heat transfer characteristics, are the contactors of choice for conversion of syngas to fuels and chemicals. The multiphase fluid dynamics in these systems determines the mass and heat transfer and greatly affects reactor volumetric productivity and selectivity. Here the authors show how the recently collected data for liquid velocity, turbulence parameters, and holdup profiles can be used in guiding model development for liquid backmixing and in providing the needed model parameters. Predictions of the two-compartment convective-diffusion model for the residence time distribution of a nonvolatile tracer, which are based on measured liquid recirculation driven by the gas holdup profile and turbulence caused by the rising gas bubbles, are shown to be in good agreement with tracer data. The adaptation of model parameters needed to achieve predictability for industrial tracer data is discussed. The ability of the model to predict the liquid tracer responses at various locations in a SBCR during methanol synthesis is illustrated.

Degaleesan, S.; Dudukovic, M.P. [Washington Univ., St. Louis, MO (United States); Toseland, B.A.; Bhatt, B.L. [Air Products and Chemicals, Inc., Lehigh Valley, PA (United States)

1997-11-01

159

Measurements of rotating bubble shapes in low-gravity environment  

NASA Technical Reports Server (NTRS)

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

Leslie, F.

1985-01-01

160

Original paper Soap Bubble Clusters  

E-print Network

Original paper Soap Bubble Clusters Fred ALMGREN surface, soap bubbles Abstract. This article reviews the theorems from geometric measure theory which guarantee the existence and give the structure of mathematical models of soap bubble clusters. It also

Taylor, Jean

161

Cavitation erosion by single laser-produced bubbles  

Microsoft Academic Search

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

A. Philipp; W. Lauterborn

1998-01-01

162

Prospects for bubble fusion  

SciTech Connect

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

Nigmatulin, R.I. [Tyumen Institute of Mechanics of Multiphase Systems (TIMMS), Marx (Russian Federation); Lahey, R.T. Jr. [Rensselaer Polytechnic Institute, Troy, NY (United States)

1995-09-01

163

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

164

Single-bubble sonoluminescence  

Microsoft Academic Search

Single-bubble sonoluminescence occurs when an acoustically trapped and periodically driven gas bubble collapses so strongly that the energy focusing at collapse leads to light emission. Detailed experiments have demonstrated the unique properties of this system: the spectrum of the emitted light tends to peak in the ultraviolet and depends strongly on the type of gas dissolved in the liquid; small

Michael P. Brenner; Sascha Hilgenfeldt; Detlef Lohse

2002-01-01

165

The Dueling Bubble Experiment  

Microsoft Academic Search

When two drops or bubbles are brought into close proximity to each other, the thin film of the fluid between them drains as they are squeezed together. If the film becomes thin enough that intermolecular forces of attraction overwhelm capillary forces, the drops\\/bubbles coalesce and the time it takes for this to happen, starting from the point of apparent contact

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

2007-01-01

166

Gases in Tektite Bubbles.  

PubMed

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

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

1962-07-20

167

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

168

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

169

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.

170

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

171

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] [ORNL; Abdou, Ashraf A [ORNL] [ORNL; Riemer, Bernie [ORNL] [ORNL; Felde, David K [ORNL] [ORNL

2007-01-01

172

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

173

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

174

Bubble core field modification by residual electrons inside the bubble  

SciTech Connect

Bubble core field modification due to the nondepleted electrons present inside the bubble is investigated theoretically. These residual electrons induce charge and current densities that can induce the bubble core field modification as well as the bubble shape change. It is found that the electrons entering into the bubble move backward at almost light speed and would weaken the transverse bubble fields. This reduces the ratio of longitudinal to transverse radius of the bubble. For the longitudinal bubble field, two effects compensate with each other because of their competition between the enhancement by the shortening of bubble shape and the reduction by the residual electrons. Therefore the longitudinal field is hardly changeable. As a comparison we perform particle-in-cell simulations and it is found that the results from theoretical consideration are consistent with simulation results. Implication of the modification of fields on bubble electron acceleration is also discussed briefly.

Wu Haicheng [College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Center for Applied Physics and Technology, Peking University, Beijing 100084 (China); Xie Baisong; Zhao Xueyan [College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Zhang Shan [College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Department of Mathematics and Physics, Shijiazhuang Railway Institute, Shijiazhuang 050043 (China); Hong Xueren [College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China); Liu Mingping [School of Information Engineering, Nanchang University, Nanchang 330031 (China)

2010-11-15

175

Expendable bubble tiltmeter for geophysical monitoring  

Microsoft Academic Search

An unusually rugged highly sensitive and inexpensive bubble tiltmeter has been designed, tested, and built in quantity. These tiltmeters are presently used on two volcanoes and an Alaskan glacier, where they continuously monitor surface tilts of geological interest. This paper discusses the mechanical, thermal, and electric details of the meter, and illustrates its performance characteristics in both large (>10?4 radian)

J. A. Westphal; M. A. Carr; W. F. Miller; Daniel Dzurisin

1983-01-01

176

Tribonucleation of bubbles  

PubMed Central

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

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

2014-01-01

177

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

178

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

Microsoft Academic Search

Disperse gas bubbles play an important role in many industrial applications. Knowing the rising velocity, the interfacial area, or the critical size for break-up or coalescence in different systems can be crucial for the process design. Hence, knowing the fundamental behaviour of a single bubble appears mandatory for the examination of bubble swarms and for the Euler-Lagrange or Euler--Euler modelling

Peter Lakshmanan; Peter Ehrhard

2008-01-01

179

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

180

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

NASA Astrophysics Data System (ADS)

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 30 for the lowest volume fraction, but decrease as the volume fraction is increased. The rise of a regular array of bubbles, where the relative positions of the bubbles are fixed, is compared with the evolution of a freely evolving array. Generally, the freely evolving array rises slower than the regular one, in contrast to what has been found earlier for low Reynolds number arrays. The structure of the bubble distribution is examined and it is found that while the three-dimensional bubbles show a tendency to line up horizontally, the two-dimensional bubbles are nearly randomly distributed. The effect of the number of bubbles in each period is examined for the two-dimensional system and it is found that although the rise Reynolds number is nearly independent of the number of bubbles, the velocity fluctuations in the liquid (the Reynolds stresses) increase with the size of the system. While some aspects of the fully three-dimensional flows, such as the reduction in the rise velocity, are predicted by results for two-dimensional bubbles, the structure of the bubble distribution is not. The magnitude of the Reynolds stresses is also greatly over-predicted by the two-dimensional results.

Esmaeeli, Asghar; Tryggvason, Grétar

1999-04-01

181

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

182

Simulation of the effect of methane bubble plumes on vertical mixing in Mono Lake  

Microsoft Academic Search

A one-dimensional vertical mixing model modified for application to hypersaline Mono Lake reproduced mixed layer dynamics well but hypolimnetic heating was underestimated. One possible source of increased hypolimnetic heating is vertical mixing caused by bubble plumes of methane rising from the sediments. Estimates of vertical mixing from methane seepage in Mono Lake were made with the inclusion of a bubble

José R. Romero; John C. Patterson; John M. Melack

1996-01-01

183

Single bubble sonoluminescence: Investigations of the emitted pressure wave with a fiber optic probe hydrophone  

Microsoft Academic Search

In single bubble sonoluminescence (SBSL) in addition to the short light pulses, the bubble emits in the collapse phase a pressure wave that can be measured with a fiber optic probe hydrophone with high spatial resolution (100 mum) and a rise time of 5 ns. In a systematic study we have characterized the width and the amplitude of the emitted

Z. Q. Wang; R. Pecha; B. Gompf; W. Eisenmenger

1999-01-01

184

Bubble Augmented Waterjet Propulsion: Two-Phase Model Development and Experimental Validation  

Microsoft Academic Search

The concept of thrust augmentation through bubble injection into a waterjet has been the subject of many patents and publications over the past several decades. Computational and experimental evidences of the augmentation of the jet thrust through bubble growth in the jet stream explain recent rise in interest in the concept. To generalize the idea to practical designs, an adequately

Georges L. Chahine; Chao-Tsung Hsiao; Jin-Keun Choi; Xiongjun Wu

185

A computationally efficient modelling of laminar separation bubbles  

NASA Technical Reports Server (NTRS)

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

Dini, Paolo; Maughmer, Mark D.

1989-01-01

186

Bubble visualization in a simulated hydraulic jump  

E-print Network

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

Witt, Adam; Shen, Lian

2013-01-01

187

What's in a Bubble?  

ERIC Educational Resources Information Center

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

Saunderson, Megan

2000-01-01

188

Bubble impacts with microcantilevers.  

NASA Astrophysics Data System (ADS)

In the current study, we investigate bubbles in laminar channel flows impacting microcantilever obstacles. Static and resonating cantilevers instrumented with integrated strain gages are mounted perpendicular to the mean flow in a vertically-oriented channel with thickness 2mm, span 10mm, and length 585 mm. Steady, fully-developed upward flows with channel Reynolds numbers based on mean fluid velocity and hydraulic diameter of 0-2500 are considered. Bubbles of diameter 200-1000?m are introduced upstream of the test section, and impacts are observed using a microscope equipped with a high frame rate camera. Observations are made along the length of cantilevers backlit with white light. Strain gage signals are monitored and correlated to impact events. The effect of obstacles on bubble motion and deformation as well as the effect of bubble impacts on the cantilever will be discussed. The flow studies are part of a larger research program examining reliability and performance of vibrating microbeams.

Stegmeir, Matthew; Longmire, Ellen; Ali, Mubassar; Mantell, Susan

2006-11-01

189

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

190

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

191

Temperature rise in superfluid helium pumps  

NASA Technical Reports Server (NTRS)

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

Kittel, Peter

1988-01-01

192

The Adaptive Bubble Router  

Microsoft Academic Search

The design of a new adaptive virtual cut-through router for torus networks is presented in this paper. With much lower VLSI costs than adaptive wormhole routers, the adaptive Bubble router is even faster than deterministic wormhole routers based on virtual channels. This has been achieved by combining a low-cost deadlock avoidance mechanism for virtual cut-through networks, called Bubble flow control,

Valentin Puente; Cruz Izu; Ramón Beivide; José A. Gregorio; Fernando Vallejo; J. M. Prellezo

2001-01-01

193

Clustering in Bubble Suspensions  

NASA Astrophysics Data System (ADS)

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

Zenit, Roberto

2000-11-01

194

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. PMID:23696657

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

2013-01-01

195

Bubble-Turbulence Interaction in Binary Fluids  

NASA Astrophysics Data System (ADS)

Multiphase flows represent a central issue in many natural, biological and industrial fields. For instance, liquid jets vaporization, petroleum refining and boiling, emulsions in pharmaceutical applications, are all characterized by a disperse phase, such as solid particles or liquid bubbles, which evolve in a Newtonian carrier fluid. Features such as the global evaporation rates of liquid fuels in air or the homogeneity of the emulsions are controlled by the finest interaction details occurring between the two phases. In this paper we study the rising motion of a bubble induced by buoyancy in a viscous fluid. Usually this issue is tackled by tracking the bubble interface by means of sharp interface methods. However this approach requires "ad hoc" techniques to describe changes in the topological features of the deforming interface and to enforce the mass preservation. Here the problem is addressed by using a different philosophy based on a diffuse interface method, that allows a straightforward analysis of complex phenomena such as bubbles coalescence and break up without any numerical expedient. The model we adopt, funded on a solid thermodynamical and physical base, relies on the Cahn-Hilliard equation for the disperse phase, see Cahn & Hilliard (1958) and Elliott & Songmu (1986).

F, Battista; M, Froio; F, Picano; P, Gualtieri; M, Casciola C.

2011-12-01

196

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

197

Modeling the dynamics of single-bubble sonoluminescence  

E-print Network

Sonoluminescence (SL) is the phenomenon in which acoustic energy is (partially) transformed into light. It may occur by means of many or just one bubble of gas inside a liquid medium, giving rise to the terms multi-bubble- and single-bubble sonoluminescence (MBSL and SBSL). In the last 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 work, we will not address this more complicated particular issue, but only present a simple model describing the dynamical behaviour of the sonoluminescent bubble, in the SBSL case. Using simple numerical techniques within the software Matlab, we discuss solutions considering various possibilities for some of the parameters involved: liquid compressibility, superficial tension, viscosity, and type of gas. The model may be used as an introductory study of sonoluminescence in physics courses at undergraduate or graduate levels, as well as a quite clarifyi...

Vignoli, Lucas L; Thomé, Roberto C A; Nogueira, A L M A; Paschoal, Ricardo C; Rodrigues, Hilario

2014-01-01

198

Moduli vacuum bubbles produced by evaporating black holes  

SciTech Connect

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

Morris, J. R. [Physics Department, Indiana University Northwest, 3400 Broadway, Gary, Indiana 46408 (United States)

2007-10-15

199

Moduli Vacuum Bubbles Produced by Evaporating Black Holes  

E-print Network

We consider a model with a toroidally compactified extra dimension giving rise to a temperature-dependent 4d effective potential with one-loop contributions due to the Casimir effect, along with a 5d cosmological constant. The forms of the effective potential at low and high temperatures indicates a possibility for the formation of a domain wall bubble, formed by the modulus scalar field, surrounding an evaporating black hole. This is viewed as an example of a recently proposed black hole vacuum bubble arising from matter-sourced moduli fields in the vicinity of an evaporating black hole [D. Green, E. Silverstein, and D. Starr, Phys. Rev. D74, 024004 (2006), arXiv:hep-th/0605047]. The black hole bubble can be highly opaque to lower energy particles and photons, and thereby entrap them within. For high temperature black holes, there may also be a symmetry-breaking black hole bubble of false vacuum of the type previously conjectured by Moss [I.G. Moss, Phys. Rev. D32,1333 (1985)], tending to reflect low energy particles from its wall. A double bubble composed of these two different types of bubble may form around the black hole, altering the hole's emission spectrum that reaches outside observers. Smaller mass black holes that have already evaporated away could have left vacuum bubbles behind that contribute to the dark matter.

J. R. Morris

2007-08-14

200

On bubble clustering and energy spectra in pseudo-turbulence  

NASA Astrophysics Data System (ADS)

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

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

2009-11-01

201

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

202

Statistical equilibrium of bubble oscillations in dilute bubbly flows  

PubMed Central

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

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

2008-01-01

203

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

204

Determining the outcome of cosmic bubble collisions in full General Relativity  

E-print Network

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 non-linear 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.

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

2012-04-09

205

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

206

Thermocapillary migration of long bubbles in polygonal tubes. II. Experiments  

E-print Network

experimentally the thermocapillary migration of a long gas bubble in a horizontal pipe of rectangular cross. A simple calculation taking into account the combined effect of buoyant rise and thermocapillary stress tension gradient resulting from an imposed temperature gradient causes interfacial flow from regions

Lajeunesse, Eric

207

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

NASA Astrophysics Data System (ADS)

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

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

2002-06-01

208

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

209

The Fermi Bubbles  

NASA Astrophysics Data System (ADS)

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

Finkbeiner, Douglas P.

2015-01-01

210

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

211

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.

2014-09-18

212

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

Microsoft Academic Search

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

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

1997-01-01

213

Mixture Segregation within Sonoluminescence Bubbles  

Microsoft Academic Search

This paper concerns a relaxation of the assumption of uniform mixture composition in the interior of sonoluminescence bubbles. Intense temperature and pressure gradients within the bubble drive relative mass diffusion which overwhelms diffusion driven by concentration gradients. This thermal and pressure diffusion results in a robust compositional inhomogeneity in the bubble which lasts several orders of magnitude longer than the

Brian D. Storey; Andrew J. Szeri

1999-01-01

214

Bubble shape instability and sonoluminescence  

Microsoft Academic Search

Light from a sonoluminescing bubble is extinguished if the amplitude of the acoustic field that drives the bubble oscillation exceeds a certain threshold. It has been suggested that shape instability of the bubble surface is responsible. The effect of viscosity on such an instability is examined here.

C. C. Wu; P. H. Roberts

1998-01-01

215

Sonoluminescing Air Bubbles Rectify Argon  

Microsoft Academic Search

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

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

1997-01-01

216

Using Bubbles to Explore Membranes  

NSDL National Science Digital Library

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

Sandra Wardell

2009-01-01

217

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

PubMed

A fiber optic reflectometer (FOR) technique featuring a single fiber probe is investigated for its feasibility of measuring the bubble velocity, diameter, and void fraction in a multiphase flow. The method is based on the interference of the scattered signal from the bubble surface with the Fresnel reflection signal from the tip of the optical fiber. Void fraction is obtained with a high accuracy if an appropriate correction is applied to compensate the underestimated measurement value. Velocity information is accurately obtained from the reflected signals before the fiber tip touches the bubble surface so that several factors affecting the traditional dual-tip probes such as blinding, crawling, and drifting effects due to the interaction between the probe and bubbles can be prevented. The coherent signals reflected from both the front and rear ends of a bubble can provide velocity information. Deceleration of rising bubbles and particles due to the presence of the fiber probe is observed when they are very close to the fiber tip. With the residence time obtained, the bubble chord length can be determined by analyzing the coherent signal for velocity determination before the deceleration starts. The bubble diameters are directly obtained from analyzing the signals of the bubbles that contain velocity information. The chord lengths of these bubbles measured by FOR represent the bubble diameters when the bubble shape is spherical or represent the minor axes when the bubble shape is ellipsoidal. The velocity and size of bubbles obtained from the FOR measurements are compared with those obtained simultaneously using a high speed camera. PMID:19123590

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

2008-12-01

218

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

219

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

220

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.

Francis Eberle

2007-01-01

221

Overconfidence and Speculative Bubbles  

Microsoft Academic Search

Motivated by the behavior of asset prices, trading volume, and price volatility during episodes of asset price bubbles, we present a continuous-time equilibrium model in which overconfidence generates disagreements among agents regarding asset fundamentals. With short-sale constraints, an asset buyer acquires an option to sell the asset to other agents when those agents have more optimistic beliefs. As in a

Jose A. Scheinkman; Wei Xiong

2003-01-01

222

Bubble Rings Entrapment  

E-print Network

We show how micro-bubble rings are entrapped under a drop impacting onto a pool surface. This fluid dynamics video is submitted to the APS DFD Gallery of Fluid Motion 2012, part of the 65th Annual Meeting of the American Physical Society's Division of Fluid Dynamics (18-20 November, San Diego, CA, USA).

Thoraval, Marie-Jean; Takehara, Kohsei; Etoh, Takeharu Goji

2012-01-01

223

The rising risks of rising tides  

SciTech Connect

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

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

1996-12-31

224

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

225

Numerical Model of Large Bubble Bursts at Erebus Volcano, Antarctica  

NASA Astrophysics Data System (ADS)

Erebus volcano in Antarctica has been explosively degassing from its active phonolitic lava lake for decades. For at least the past three decades a lava lake has been present in the northeast corner of the inner crater. The lava lake continually convects and large bubbles burst at the surface 2-6 events per day. A geophysical network consisting a video coverage, acoustic sensors and broadband seismometers have been monitoring activity at the lava lake for years. There is remarkable correlation between bubble burst captured on video and infrasonic signals (with maximum excess pressure as much as 100 Pa) recorded on pressure sensors located within 300 m to 800 m from the active lake. Studies of 358 lava lake infrasound sources recorded over a 98 day period in 2006 suggest that bubble rupture location on the surface is distributed over a 40 m by 50 m area of the lava lake. Many of these bubbles are at least 10 m in diameter at rupture. The size and pressurization of the bubble bursts govern the force imparted to the atmosphere and therefore the characteristic features of the infrasonic pressure transients. A series of numerical simulations of bubble bursts from the lava lake at Erebus are performed in which bubble volumes, internal pressure and lava lake temperature are variables. The simulations are conducted with the computer code Sage that is a multi-material, finite-difference code with an adaptive mesh algorithm. Conductive heat transfer (power law temperature dependence), and strength model for wall rock and lava lake crust are considered. The locations of bubble bursts are constrained from mapped locations of bubble bursts recorded in 2006. We present results from these calculations and demonstrate the effects of bubble volume (5-10 m radius), internal pressure (0.5-10 MPa), lava lake temperature (800-1000C) and source location on the infrasonic signal.

Morrissey, M.; Weaver, R.; Gittings, M.; Johnson, J.; Jones, K.

2007-12-01

226

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

227

Bubbly Little Star  

NASA Technical Reports Server (NTRS)

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

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

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

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

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

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

2007-01-01

228

Numerical simulation of three-dimensional bubbly flows.  

NASA Astrophysics Data System (ADS)

Multiphase flow researchers have long recognized the need for direct numerical simulations of the motion of bubbles in order to complement experimental studies, provide insight into the small-scale, short-time phenomena occuring in these flows, and validate engineering models. A finite-difference/front-tracking method for the representation of deformable fluid interfaces is parallelized and large three-dimensional direct numerical simulations of buoyant bubbly flows are conducted. Results are presented for simulations of up to 864 bubbles in a periodic domain at a Reynolds number of about 30 and a volume fraction of 6%. The flow structure is studied to understand the mechanisms that drive the interactions between the bubbles. Nearly spherical bubbles show a weak trend to align themselves horizontally with repect to each other whereas more deformable bubbles move in a tandem configuration. The effects of system size, volume fraction, and interface deformability on the flow structure and the rise velocity, velocity fluctuations, and Reynolds stresses are investigated. Some figures and animations of results can be seen on the author's webpage.

Bunner, Bernard; Tryggvason, Gretar

1998-11-01

229

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

230

Stability of magnetic equilibria in radio bubbles  

NASA Astrophysics Data System (ADS)

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

Benford, Gregory

2006-06-01

231

The Centaurus A Northern Middle Lobe as a Buoyant Bubble  

E-print Network

We model the northern middle radio lobe of Centaurus A (NGC 5128) as a buoyant bubble of plasma deposited by an intermittently active jet. The extent of the rise of the bubble and its morphology imply that the ratio of its density to that of the surrounding ISM is less than 10^{-2}, consistent with our knowledge of extragalactic jets and minimal entrainment into the precursor radio lobe. Using the morphology of the lobe to date the beginning of its rise through the atmosphere of Centaurus A, we conclude that the bubble has been rising for approximately 140Myr. This time scale is consistent with that proposed by Quillen et al. (1993) for the settling of post-merger gas into the presently observed large scale disk in NGC 5128, suggesting a strong connection between the delayed re-establishment of radio emission and the merger of NGC 5128 with a small gas-rich galaxy. This suggests a connection, for radio galaxies in general, between mergers and the delayed onset of radio emission. In our model, the elongated X-ray emission region discovered by Feigelson et al. (1981), part of which coincides with the northern middle lobe, is thermal gas that originates from the ISM below the bubble and that has been uplifted and compressed. The "large-scale jet" appearing in the radio images of Morganti et al. (1999) may be the result of the same pressure gradients that cause the uplift of the thermal gas, acting on much lighter plasma, or may represent a jet that did not turn off completely when the northern middle lobe started to buoyantly rise. We propose that the adjacent emission line knots (the "outer filaments") and star-forming regions result from the disturbance, in particular the thermal trunk, caused by the bubble moving through the extended atmosphere of NGC 5128.

Curtis J. Saxton; Ralph S. Sutherland; Geoffrey V. Bicknell

2001-07-30

232

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

NASA Astrophysics Data System (ADS)

Bubble 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

233

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.

NBC Learn

2010-10-07

234

Sea Level Rise  

NSDL National Science Digital Library

In this activity, students will learn the difference between sea ice and glaciers in relation to sea level rise. They will create and explore topographic maps as a means of studying sea level rise and how it will affect Alaska's coastline.

Geophysical Institute of University of Fairbanks

235

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

236

Polarizing bubble collisions  

SciTech Connect

We predict the polarization of cosmic microwave background (CMB) photons that results from a cosmic bubble collision. The polarization is purely E-mode, symmetric around the axis pointing towards the collision bubble, and has several salient features in its radial dependence that can help distinguish it from a more conventional explanation for unusually cold or hot features in the CMB sky. The anomalous ''cold spot'' detected by the Wilkinson Microwave Anisotropy Probe (WMAP) satellite is a candidate for a feature produced by such a collision, and the Planck satellite and other proposed surveys will measure the polarization on it in the near future. The detection of such a collision would provide compelling evidence for the string theory landscape.

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

2010-12-01

237

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

238

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

239

Local gas hold-up measurements in fluidized bed and slurry bubble column  

Microsoft Academic Search

Fiber optic probes can be used to evaluate flow properties in gas–solid and gas–liquid–solid systems. In this study, the local flow structure of bubbling flow was investigated in a slurry bubble column and in a fluidized bed. The bubble flow characteristics could, therefore, be determined along the bed cross section in various operating conditions. In both systems, the results were

J-M Schweitzer; J Bayle; T Gauthier

2001-01-01

240

Simulation studies of vapor bubble generation by short-pulse lasers  

Microsoft Academic Search

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

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

1998-01-01

241

Bubble dynamics, shock waves and sonoluminescence  

Microsoft Academic Search

Sound and light emission by bubbles is studied experimentally. Single bubbles kept in a bubble trap and single laser-generated bubbles are investigated using ultrafast and high-speed photography in combination with hydrophones. The optical observation at 20 million frames per second of the shock waves emitted has proven instrumental in revealing the dynamic process upon bubble collapse. When jet formation is

C.-D. Ohl; T. Kurz; R. Geisler; O. Lindau; W. Lauterborn

1999-01-01

242

Stable Multibubble Sonoluminescence Bubble Patterns  

SciTech Connect

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

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

2006-06-30

243

Electrowetting of a soap bubble  

E-print Network

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

Arscott, Steve

2013-01-01

244

Electrowetting of a soap bubble  

E-print Network

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

Steve Arscott

2013-04-25

245

Bubbly wake of surface vessels  

NASA Astrophysics Data System (ADS)

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

Caillé, François; Magnaudet, Jacques; Clanet, Christophe

2006-11-01

246

When sound slows down bubbles  

E-print Network

We present experimental evidence that a bubble moving in a fluid in which a well-chosen acoustic noise is superimposed can be significantly slowed down for moderate acoustic pressures. Through mean velocity measurements, we show that a condition for this effect to occur is for the acoustic noise spectrum to match or overlap the bubble's fundamental resonant mode. By rendering the bubble's oscillations and translational movements using high speed video, we evidence that radial oscillations have no effect on the mean velocity, while above a critical sound pressure threshold, Faraday waves are triggered and are responsible for the bubble's drag increase.

Remi Dangla; Cedric Poulain

2010-04-06

247

Fluid Dynamics of Bubbly Liquids  

NASA Astrophysics Data System (ADS)

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 the inertially dominated suspensions of bubbles of about 1.5 mm diameter in vertical and inclined channels. The gradual decrease of bubble velocity as volume fraction increases is in qualitative agreement with the predictions. By inclining the channel, the resulting buoyancy variation drives a shear flow and provides a means of observing the effects of weak shear on a bubbly liquid. The tendency of buoyancy driven motion to cause the bubbles to accumulate on the upper wall is balanced by lift forces and an effective bubble-phase diffusivity in the cross-channel direction. The bubble velocity gradient can be understood in terms of a balance of the component of the buoyancy force parallel to the channel and an effective viscosity associated with the Reynolds stresses produced by bubble-induced liquid velocity fluctuations. The effective viscosity required to explain the measured bubble velocity gradient is about 1000 times that of the suspending liquid. A pipe flow with the liquid being recirculated, which provides a larger range of shear to buoyancy motion, is under construction.

Tsang, Ying H.; Koch, Donald L.; Sangani, Ashok S.

2002-11-01

248

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

249

Helium bubble bursting in tungsten  

SciTech Connect

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 [University of California, Berkeley, California 94720 (United States); Juslin, Niklas [University of Tennessee, Knoxville, Tennessee 37996 (United States); Wirth, Brian D., E-mail: bdwirth@utk.edu [University of Tennessee, Oak Ridge National Laboratory, Knoxville, Tennessee 37996 (United States)

2013-12-28

250

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

251

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

252

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

253

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

PubMed Central

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

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

2013-01-01

254

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

255

Gas accumulation in particle-rich suspensions and implications for bubble populations in crystal-rich magma  

NASA Astrophysics Data System (ADS)

Gas mobility plays an important role in driving volcanic eruptions and controlling eruption style. The explosivity of an eruption depends, among other factors, on how easily gas can escape from the magma. Many magmatic systems have high concentrations of suspended crystals that inhibit gas migration through the melt. We use suspensions of plastic beads in corn syrup to investigate interactions between rising bubbles and particles. We observe different interaction styles as the ratio ? of bubble to particle size is varied. Large bubbles (? > 1) deform and sometimes break up as they move around particles. Small bubbles (? < 1) are frequently trapped within the suspension, increasing the concentration of gas held within the system. We compare our experiments to bubble populations in tephra from Stromboli volcano, Italy. We show that these samples typically have bubbles and crystals of similar sizes and suggest that crystals might play a role in controlling bubble size in this natural system as well as in our experiments. Because small bubbles (? < 1) get trapped within the suspension, and can be formed by breakup of larger bubbles, we expect that an increase in gas flux will result in an increase in the population of small bubbles. Changes in bubble number density and vesicularity in tephra erupted during periods of different eruptive intensity may thus provide a way of tracking changes in gas flux through the magma prior to eruption.

Belien, Isolde B.; Cashman, Katharine V.; Rempel, Alan W.

2010-08-01

256

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

NASA Astrophysics Data System (ADS)

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

Bröder, D.; Sommerfeld, M.

2002-08-01

257

Amplitude- and rise-time-compensated filters  

DOEpatents

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

Nowlin, Charles H. (Oak Ridge, TN)

1984-01-01

258

Microfluidic Actuation Using Electrochemically Generated Bubbles  

E-print Network

Microfluidic Actuation Using Electrochemically Generated Bubbles Susan Z. Hua,*, Frederick Sachs, Buffalo, New York 14260 Bubble-based actuation in microfluidic applications is attractive owing closing) rate increases with applied voltage, small microfluidic dimensions accelerate bubble deflation

Sachs, Frederick

259

Satellites in the inviscid breakup of bubbles J.M. Gordillo  

E-print Network

Satellites in the inviscid breakup of bubbles J.M. Gordillo Departamento de Ingenier the gas to liquid density ratio = g/l is different from zero, tiny satellite bubbles may be formed with a closed expression for the characteristic satellite diameter, which decreases when decreasing and which

Fontelos, Marco

260

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

261

A bubbling bolt  

E-print Network

We present a new solvable system, solving the equations of five-dimensional ungauged N=1 supergravity coupled to vector multiplets, that allows for non-extremal solutions and reduces to a known system when restricted to the floating brane Ansatz. A two-centre globally hyperbolic smooth geometry is obtained as a solution to this system, describing a bubble linking a Gibbons--Hawking centre to a charged bolt. However this solution turns out to violate the BPS bound, and we show that its generalisation to an arbitrary number of Gibbons--Hawking centres never admits a spin structure.

Guillaume Bossard; Stefanos Katmadas

2014-05-16

262

Bubble levitation and translation under single-bubble sonoluminescence conditions.  

PubMed

Bubble levitation in an acoustic standing wave is re-examined for conditions relevant to single-bubble sonoluminescence. Unlike a previous examination [Matula et al., J. Acoust. Soc. Am. 102, 1522-1527 (1997)], the stable parameter space [Pa,R0] is accounted for in this realization. Forces such as the added mass force and drag are included, and the results are compared with a simple force balance that equates the Bjerknes force to the buoyancy force. Under normal sonoluminescence conditions, the comparison is quite favorable. A more complete accounting of the forces shows that a stably levitated bubble does undergo periodic translational motion. The asymmetries associated with translational motion are hypothesized to generate instabilities in the spherical shape of the bubble. A reduction in gravity results in reduced translational motion. It is hypothesized that such conditions may lead to increased light output from sonoluminescing bubbles. PMID:12942960

Matula, Thomas J

2003-08-01

263

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

SciTech Connect

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

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

2013-03-01

264

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

PubMed

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

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

2015-01-01

265

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

266

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

267

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

268

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

269

Simulation studies of vapor bubble generation by short-pulse lasers  

SciTech Connect

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.

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

1997-10-26

270

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

NASA Technical Reports Server (NTRS)

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.

1993-01-01

271

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

272

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.

Optical Society of America

2008-01-01

273

Phase Diagrams for Sonoluminescing Bubbles  

Microsoft Academic Search

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

Sascha Hilgenfeldt; Detlef Lohse; Michael P. Brenner

1996-01-01

274

Sonoluminescing bubbles and mass diffusion  

Microsoft Academic Search

The transduction of sound into light by a pulsating bubble in water occurs when its maximum radius is about ten times greater than its ambient radius. For such high-amplitude motion, the steady-state balance of mass flow between the bubble and gas dissolved in the surrounding fluid can be maintained by diffusion only at low partial pressures, about 3 Torr. The

Ritva Löfstedt; Keith Weninger; Seth Putterman; Bradley P. Barber

1995-01-01

275

Experimental study of bubble plume with CFD benchmarking  

NASA Astrophysics Data System (ADS)

An experiment and simulations were performed to study the characteristics of a bubble plume in water. Important results including experimental data and simulations are summarized. In order to study the bubble plume characteristics, an experiment was designed and carried out. The experiment consisted of a bubble jet being injected into a tank of water at different flow conditions using different injector configurations. In addition to the experimental work, CFD simulations with ANSYS CFX 13.0 were performed. Selected flow conditions were simulated to benchmark the experimental data, and important settings for boundary conditions and simulation strategy were recommended. The CFD analysis focused on the prediction of the recirculation fluid velocity. According to the benchmark results, the CFD simulation can predict the recirculation fluid velocity with an accuracy of +/-26%.

Macke, Christopher J.

276

Bubble formation in microgravity  

NASA Technical Reports Server (NTRS)

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

Antar, Basil N.

1996-01-01

277

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

278

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

279

Bubble Generation in a Continuous Liquid Flow Under Reduced Gravity Conditions  

NASA Technical Reports Server (NTRS)

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

Pais, Salvatore Cezar

1999-01-01

280

A bubble-based microfluidic gas sensor for gas chromatographs.  

PubMed

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

Bulbul, Ashrafuzzaman; Kim, Hanseup

2015-01-01

281

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

282

Perspective Theoretical Neuroscience Rising  

E-print Network

Neuron Perspective Theoretical Neuroscience Rising L.F. Abbott1,* 1Department of Neuroscience *Correspondence: lfabbott@columbia.edu DOI 10.1016/j.neuron.2008.10.019 Theoretical neuroscience has experienced to introduce new ideas and shape directions of neuroscience research. This review presents some

Columbia University

283

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

284

Rise of human intelligence  

Microsoft Academic Search

Based upon the evidence that the best chess players in the world are becoming increasingly represented by relatively young individuals, Howard [Intelligence 27 (1999) 235–250.] claimed that human intelligence is rising over generations. We suggest that this explanation has several difficulties and show that alternative explanations relating to changes in the chess environment, including increased access to chess knowledge, offer

Fernand Gobet; Guillermo Campitelli; Andrew J Waters

2002-01-01

285

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

286

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

287

Numerical simulation of bubble dispersion in turbulent Taylor-Couette flow  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

288

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

289

Colored bubbles: An experiment for triggering equatorial spread F  

Microsoft Academic Search

Barium plasma clouds were released in the post-sunset F region of the equatorial ionosphere. The clouds were characteristically distorted and exhibited the formation of irregularities of various scales. Visible striations, radio wave scintillations, spread echoes on ionograms were noted. Bubble formation was not observed. The origin of distortions and irregularities is related to the combined action of the friction with

G. Haerendel; O. H. Bauer; S. Cakir; H. Foeppl; E. Rieger; A. Valenzuela

1983-01-01

290

Bubble Column Reactors and Fischer-Tropsch Synthesis  

Microsoft Academic Search

Three-phase slurry bubble column reactors have been used extensively in a number of chemical, petrochemical, and biochemical process engineering applications. For the success of these operations and their large scale industrial exploitation, it is essential that their transport and chemical characteristics be adequately understood on a mechanistic basis so that appropriate design criteria and optimum operating conditions can be established.

S. C. SAXENA

1995-01-01

291

Strings on Bubbling Geometries  

E-print Network

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

Hai Lin; Alexander Morisse; Jonathan P. Shock

2011-07-27

292

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

293

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

294

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

NASA Astrophysics Data System (ADS)

Extensive methane release as a free gas phase from cold vents is well known from deep (>2000m) and shallow (10s of meters) water depths. Supposedly, much more methane is transported into the water column by free gas than by dissolved gas, which is oxidized by anaerobic and aerobic processes and partly precipitated as carbonate. Rising gas bubbles are not affected by this 'filter' mechanisms. Because of the strength of the backscattered signal from gas bubbles in the water column, bubbles can be detected by single-beam or multi-beam echosounder systems. Thus, hydroacoustic systems with different frequencies can be used to 1) detect free gas in the water column, 2) map the distribution of active vent sites which release free gas, 3) monitor a possible periodicity in the release of bubbles induced by e.g. tides or currents, 4) quantify the gas volume and gas flux that is released in a local area or larger region. In the German research project LOTUS we use ship- mounted single-beam echosounders to map gas plumes (flares) and investigate their periodicity (Flare Imaging). Using specialized single-beam echosounder systems makes it possible to measure the bubble sizes and their distribution. In combination with the volume of the backscattering strength these measurements can be used to estimate the gas volume in a defined part of the water body. Though gas bubbles rise in the water column, they are - particularly methane - rapidly dissolved and thus become smaller. Their rising speed as well as their diminishing size can be determined, which helps to understand the dissolution behaviour of methane bubbles; they form a hydrate skin at distinct pressure and temperature conditions. For a detailed, long-term observation of active bubble-expulsing areas we developed a lander based 180 kHz multi beam system that 'looks' horizontally (GasQuant). The system records backscatter data from a 75° swath that covers an area of about 5300m2. Via calibration we can quantify the methane flux of every single bubble-vent and calculate the methane flux of a bubble vent area. Both hydroacoustic techniques were used during several cruises in 2002 to investigate bubble vents at Hydrate Ridge (HR), offshore Oregon. Several bubble-vent areas were detected at the northern summit of HR. They are related to carbonate chemoherms and morphological heights but were also found in areas which do not show any of these features. The GasQuant system was successfully deployed at the northern and southern summit. The data processing is currently in progress.

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

2003-04-01

295

Acoustic Propagation Through Clustered Bubble Clouds  

Microsoft Academic Search

One of the underlying assumptions in the effective medium theory describing the propagation of acoustic waves through bubble clouds is that the probability of an individual bubble being located at some position in space is independent of the locations of other bubbles. However, bubbles within naturally occurring clouds may be influenced by the dynamics of the fluids in which they

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

2007-01-01

296

On sonoluminescence of an oscillating gas bubble  

Microsoft Academic Search

It is proposed that shock dynamics within the gas of a small bubble explains sonoluminescence—the emission of visible radiation in response to spherically symmetric, ultrasonic excitation of a gas bubble in a liquid. As the bubble radius oscillates, shock waves develop from spherical sound waves created inside the gas bubble. As any such shock propagates toward the center, it strengthens

Harvey P. Greenspan; Ali Nadim

1993-01-01

297

Physical Processes for Single Bubble Sonoluminescence  

Microsoft Academic Search

Analytic solutions for a sonoluminescing gas bubble have been obtained, which provide density, pressure and temperature distributions for the gas inside bubble oscillating under ultrasonic field. The solutions have revealed that sonoluminescence should occur just prior to the bubble collapse and its duration is less than 300 ps and that increase and subsequent rapid decrease in bubble wall acceleration induce

Ho-Young Kwak; Jung Hee Na

1997-01-01

298

Experiments with electron bubbles in liquid helium  

Microsoft Academic Search

When a free electron is injected into liquid helium, it forms a microscopic bubble essentially free of helium atoms. The electron bubble is an excellent textbook example of a quantum mechanical particle confined in a potential well. The bubble is also a powerful tool to study superfluidity. In this dissertation, we describe various experiments on electron bubbles using standard ultrasonic

Ambarish Ghosh

2005-01-01

299

Hydrodynamic obstruction to bubble expansion  

SciTech Connect

We discuss a hydrodynamic obstruction to bubble wall acceleration during a cosmological first-order phase transition. The obstruction results from the heating of the plasma in the compression wave in front of the phase transition boundary. We provide a simple criterion for the occurrence of the obstruction at subsonic bubble wall velocity in terms of the critical temperature, the phase transition temperature, and the latent heat of the model under consideration. The criterion serves as a sufficient condition of subsonic bubble wall velocities as required by electroweak baryogenesis.

Konstandin, Thomas [CERN Physics Department, Theory Division, CH-1211 Geneva 23 (Switzerland); No, José M., E-mail: tkonstan@cern.ch, E-mail: jose-miguel.no@cea.fr [Institut de Physique Théorique, CEA/Saclay, F-91191 Gif-sur-Yvette Cédex (France)

2011-02-01

300

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

301

Aspherical bubble dynamics and oscillation times  

SciTech Connect

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

Vogel, A.; Noack, J. [Meizinisches Laserzentrum Luebeck (Germany); Chapyak, E.J.; Godwin, R.P. [Los Alamos National Lab., NM (United States)

1999-06-01

302

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

303

Contemporary sea level rise.  

PubMed

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

Cazenave, Anny; Llovel, William

2010-01-01

304

Onset conditions of bubbles and blobs: A case study on 2 March 2009  

NASA Astrophysics Data System (ADS)

The onset conditions for bubbles and blobs are investigated by analyzing the Communication/Navigation Outage Forecasting System satellite/Coupled Ion-Neutral Dynamics Investigation instrument data on 2 March 2009. A series of bubbles and blobs are detected in the longitude regions 180°-240°E and 240°-295°E, respectively. Bubbles are detected at low latitudes before midnight. Blobs are detected at 14°-25° magnetic latitude, between 2300 and 0500 LT in the altitude range of 400-480 km. The distinguishing feature in the longitude region where bubbles are detected is an enhancement in background plasma density with respect to that in the longitude region where bubbles are absent. Blobs are detected in a longitude region where fluctuations in the plasma density exist over a broad latitude range. The total ion density (and O+ density) and H+ density perturbations are in-phase at the locations of bubbles and out of phase at the locations of blobs. Bubbles are not detected in the longitude region where blobs are detected. The different characteristics of bubbles and blobs and their creation under different geophysical conditions indicate that creation of blobs need not be associated with bubbles.

Kil, H.; Choi, H.-S.; Heelis, R. A.; Paxton, L. J.; Coley, W. R.; Miller, E. S.

2011-03-01

305

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

306

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

SciTech Connect

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

Yang, H.-Y. K.; Ruszkowski, M. [Department of Astronomy, University of Michigan, Ann Arbor, MI (United States); Ricker, P. M. [Department of Astronomy, University of Illinois, Urbana, IL (United States); Zweibel, E. [Department of Astronomy and Physics, University of Wisconsin-Madison, Madison, WI (United States); Lee, D., E-mail: hsyang@umich.edu [Flash Center for Computational Science, University of Chicago, Chicago, IL (United States)

2012-12-20

307

The Fermi Bubbles: Supersonic Active Galactic Nucleus Jets with Anisotropic Cosmic-Ray Diffusion  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

308

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

309

Vulnerability of Turkish Low-Rise and Mid-Rise Reinforced Concrete Frame Structures  

Microsoft Academic Search

In this study, seismic safety of low–rise and mid–rise structures, which constitute approximately 75% of the total building stock in Turkey, is investigated by generating fragility curves. The scope is 3, 5, 7, and 9–story reinforced concrete moment resisting frame structures. The uncertainties in material variability and the specific characteristics of construction practice in Turkey are taken into account in

Bekir Özer AY; M. Altu? Erberik

2008-01-01

310

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

311

Oscillation of Droplets and Bubbles  

Microsoft Academic Search

\\u000a A liquid droplet may go through shape oscillation if it is forced out of its equilibrium spherical shape, while gas bubbles\\u000a undergo both shape and volume oscillations because they are compressible. This can happen when droplets and bubbles are exposed\\u000a to an external flow or an external force. Liquid droplet oscillation is observed during the atomization process when a liquid

N. Ashgriz; M. Movassat

312

Modeling the Local Bubble  

NASA Astrophysics Data System (ADS)

Modeling the Local Bubble is one of those activities fraught with danger. It is very easy to be too naive, to fail to consider the dependence of the model on assumptions about the nearby ambient state, or the likelihood of such a structure. It is similarly easy to become so caught up in the details of the vicinity that it is unclear where to begin a necessarily idealized modeling effort. And finally, it is important to remember that the data we have may in some cases be lying to us, and that we have not yet learned to read their facial expressions quite carefully enough. That said, I've tried in this paper to be helpful to those who may wish to take the risks. I surveyed the very most basic stories that the data seem to tell, and pointed out the standard coincidences that may be telling us a lot about what is happening, but may turn out once again to have been just coincidences. I've described 5 distinct conceptions that in one flavor or another pretty well survey the collection of mental images that have so far been carried by those who've attempted models. One may be right, or something entirely different may be more appropriate. It's at least vital to realize that a conception comes first, followed by a simplified model of details. I've also included a long list of questions directed at observers. Some have partial answers, some one wouldn't know today quite how to approach. But it is a list that students of the soft x-ray background, interstellar absorption lines, possible instrumentation, and the heliosphere may wish to review from time to time, just to see whether they can figure out how to be more helpful. There is another list for modelers, things the models must address, however-so-flimsily if necessary, because there are strong observational constraints (and stronger ones coming) on what can and cannot be present in the local ISM. To that I've added a few remarks concerning x-ray emission coming from beyond the Local Bubble, and another few on how x-ray emission from within the solar system might be contaminating what we see. That last bit is new, exciting, and possibly wrong, but it is an example of the ongoing wariness I believe one has to take toward the facts in the case. By the way, Dieter, it really was a great meeting.

Cox, D. P.

313

Bubbles and foams in microfluidics.  

PubMed

Microfluidics offers great tools to produce highly-controlled dispersions of gas into liquid, from isolated bubbles to organized microfoams. Potential technological applications are manifold, from novel materials to scaffolds for tissue engineering or enhanced oil recovery. More fundamentally, microfluidics makes it possible to investigate the physics of complex systems such as foams at scales where the capillary forces become dominant, in model experiments involving few well-controlled parameters. In this context, this review does not have the ambition to detail in a comprehensive manner all the techniques and applications involving bubbles and foams in microfluidics. Rather, it focuses on particular consequences of working at the microscale, under confinement, and hopes to provide insight into the physics of such systems. The first part of this work focuses on bubbles, and more precisely on (i) bubble generation, where the confinement can suppress capillary instabilities while inertial effects may play a role, and (ii) bubble dynamics, paying special attention to the lubrication film between bubble and wall and the influence of confinement. The second part addresses the formation and dynamics of microfoams, emphasizing structural differences from macroscopic foams and the influence of the confinement. PMID:24913678

Huerre, Axel; Miralles, Vincent; Jullien, Marie-Caroline

2014-09-28

314

The Formation of a Bubble from a Submerged Orifice  

E-print Network

The formation of a single bubble from an orifice in a solid surface, submerged in an in- compressible, viscous Newtonian liquid, is simulated. The finite element method is used to capture the multiscale physics associated with the problem and to track the evolution of the free surface explicitly. The results are compared to a recent experimental analysis and then used to obtain the global characteristics of the process, the formation time and volume of the bubble, for a range of orifice radii; Ohnesorge numbers, which combine the material parameters of the liquid; and volumetric gas flow rates. These benchmark calculations, for the parameter space of interest, are then utilised to validate a selection of scaling laws found in the literature for two regimes of bubble formation, the regimes of low and high gas flow rates.

Simmons, Jonathan A; Shikhmurzaev, Yulii D

2015-01-01

315

Wheat Evolution: Dough Rising  

NSDL National Science Digital Library

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

Biotechnology and Biological Sciences Research Council

2012-01-01

316

Taxing the Rich: Recombinations and Bubble Growth During Reionization  

E-print Network

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

Steven R. Furlanetto; S. Peng Oh

2005-08-16

317

Capillary rise kinetics of some building materials.  

PubMed

The presence of water in masonry is one of the main factors in deterioration. Capillary rise is the most usual mechanism of water penetration into building materials. In this study the kinetics of the capillary rise phenomenon was studied for various building materials: four stones, two bricks, and six plasters. A first-order kinetic model was proposed, in which the equilibrium moisture height derived from Darcy law. The capillary height time constant found to be strongly affected by the material characteristics. Moreover, the capillary height time constant can be predicted if the average pore radius of the materials is known. PMID:15752811

Karoglou, M; Moropoulou, A; Giakoumaki, A; Krokida, M K

2005-04-01

318

Powering of cool filaments in cluster cores by buoyant bubbles - I. Qualitative model  

NASA Astrophysics Data System (ADS)

Cool-core clusters (e.g. Perseus or M87) often possess a network of bright gaseous filaments, observed in radio, infrared, optical and X-ray bands. We propose that these filaments are powered by the reconnection of the magnetic field in the wakes of buoyant bubbles. Active galactic nucleus (AGN)-inflated bubbles of relativistic plasma rise buoyantly in the cluster atmosphere, stretching and amplifying the field in the wake to values of ? = 8?Pgas/B2 ˜ 1. The field lines in the wake have opposite directions and are forced together as the bubble motion stretches the filament. This setup bears strong similarity to the coronal loops on the Sun or to the Earth's magnetotail. The reconnection process naturally explains both the required level of local dissipation rate in filaments and the overall luminosity of filaments. The original source of power for the filaments is the potential energy of buoyant bubbles, inflated by the central AGN.

Churazov, E.; Ruszkowski, M.; Schekochihin, A.

2013-11-01

319

Modeling of Vapor Bubble Growth Under Nucleate Boiling Conditions in Reduced Gravity  

NASA Technical Reports Server (NTRS)

A dynamic model is developed to describe the evolution of a vapor bubble growing at a nucleation site on a superheated surface under arbitrary gravity. The bubble is separated from the surface by a thin microlayer and grows due to the evaporation from the microlayer interface. The average thickness of the microlayer increases as the bubble expands along the surface if the evaporation rate is lower than some critical value. The corresponding threshold value of the surface temperature has to be associated with the burn-out crisis. Two main reasons make for bubble separation, which are the buoyancy force and a force caused by the vapor momentum that comes to the bubble with vapor molecules. The latter force is somewhat diminished if condensation takes place at the upper bubble surface in subcooled liquids. The action of the said forces is opposed by inertia of the additional mass of liquid as the bubble center rises above the surface and by inertia of liquid being expelled by the growing bubble in radial directions. An extra pressure force arises due to the liquid inflow into the microlayer with a finite velocity. The last force helps in holding the bubble close to the surface during an initial stage of bubble evolution. Two limiting regimes with distinctly different properties can be singled out, depending on which of the forces that favor bubble detachment dominates. Under conditions of moderately reduced gravity, the situation is much the same as in normal gravity, although the bubble detachment volume increases as gravity diminishes. In microgravity, the buoyancy force is negligible. Then the bubble is capable of staying near the surface for a long time, with intensive evaporation from the microlayer. It suggests a drastic change in the physical mechanism of heat removal as gravity falls below a certain sufficiently low level. Inferences of the model and conclusions pertaining to effects caused on heat transfer processes by changes in bubble hydrodynamics induced by gravity are discussed in connection with experimental evidence, both available in current and in as yet unpublished literature.

Buyevich, Yu A.; Webbon, Bruce W.

1995-01-01

320

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

321

Dynamics of air bubbles passing through a liquid-liquid interface  

NASA Astrophysics Data System (ADS)

The passage of rising air bubbles through an initially flat horizontal liquid-liquid interface is studied using both laboratory experiments and Direct Numerical Simulation. The dynamics of spheroidal, spherical cap and toroidal bubbles near the liquid-liquid interface and subsequently through the upper liquid are investigated by coupling high-speed shadowgraph visualizations and Particle Image Velocimetry techniques. Axisymmetric computations are also carried out to assess the validity of presently available computational approaches in three-phase flows. These computations are based on two distinct approaches, namely a Volume Of Fluid approach without interface reconstruction and a Cahn-Hilliard model coupled with the incompressible Navier-Stokes equations. Experimental and computational results are compared in various configurations, including cases where the bubble is trapped at the liquid-liquid interface or rises in the upper phase while towing a column of the lower liquid that eventually breaks into droplets of various sizes.

Bonhomme, Romain; Magnaudet, Jacques; Piar, Bruno

2011-11-01

322

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

NASA Astrophysics Data System (ADS)

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

Coupez, Thierry

2007-04-01

323

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

NASA Technical Reports Server (NTRS)

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

Herman, Cila; Iacona, Estelle; Chang, Shinan

2002-01-01

324

Influence of Carbon Dioxide Bubble on Pore in Fibrous Structure of Direct Methanol Fuel Cell  

NASA Astrophysics Data System (ADS)

Direct methanol fuel cell (DMFC) is promising as new portable power source in various electronics devises. However, the performance of DMFC decreases by many problems which the factor of the structure and material effects each species concentration in the electrode catalyst layer. The anode reaction in DMFC products carbon dioxide, and CO2 bubbles generate in anode electrode. Diffusion layer in DMFC electrode is made carbon paper. The CO2 bubbles resulted in gas slugs blocking the pores in carbon paper. The CO2 bubble is affected by structure and surface characteristics in the diffusion layer. The behavior of bubble is analyzed some structure. We showed the relationship between bubble effect and contact angle of carbon fiber. And also, the model results indicate that the contact angle can improve the cell performance.

Sugimura, Masahiko; Fujimoto, Kozo

325

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

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

326

Bubble behavior in a Taylor vortex.  

PubMed

We present a study on the behavior of air bubbles captured in a Taylor vortex formed in the annulus between two concentric cylinders. It is found that small bubbles stay either at certain locations near the vortex cores or in the outflow regions along the inner cylinder. If bubbles of the same size are introduced, a variety of bubble structures (such as ring, chain, cluster, etc.) appear due to different mechanisms. For bubbles of nonuniform size, orbit crossing of small and large bubbles is observed. Droplets and particles can also be captured in Taylor vortices, and these exhibit certain unique features. PMID:16605650

Deng, Rensheng; Wang, Chi-Hwa; Smith, Kenneth A

2006-03-01

327

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

E-print Network

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

Han, Ji-seok

2009-05-15

328

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

329

Ground potential rise monitor  

DOEpatents

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

Allen, Zachery Warren; Zevenbergen, Gary Allen

2012-07-17

330

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

331

Ethnic diversity deflates price bubbles  

PubMed Central

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

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

2014-01-01

332

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...

333

Effects of micron-sized particles on hydrodynamics and local heat transfer in a slurry bubble column  

Microsoft Academic Search

Hydrodynamics and heat transfer in an air–water–glass bead system are investigated to study the effects of particle size (11–93 ?m) and slurry concentration (up to 40 vol.%). The effect of particle size on gas holdup is only slight over the range of particle size investigated. This can be attributed to differences in rise velocities of different bubble fractions. Small bubble

H Li; A Prakash; A Margaritis; M. A Bergougnou

2003-01-01

334

Upward vertical two-phase flow through an annulus. Part 2; Modeling bubble, slug, and annular flow  

Microsoft Academic Search

This paper reports that mechanistic models have been developed for each of the existing two-phase flow patterns in an annulus, namely bubble flow, dispersed bubble flow, slug flow, and annular flow. These models are based on two-phase flow physical phenomena and incorporate annulus characteristics such as casing and tubing diameters and degree of eccentricity. The models also apply to the

E. F. Caetano; O. Shoham; J. P. Brill

1992-01-01

335

Gravity driven flows of bubble suspensions.  

NASA Astrophysics Data System (ADS)

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

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

1999-11-01

336

VISUALIZATION OF SOAP BUBBLE GEOMETRIES Fred Almgren (mathematician)  

E-print Network

VISUALIZATION OF SOAP BUBBLE GEOMETRIES Fred Almgren (mathematician) Department of Mathematics ABSTRACT The authors discuss mathematical soap bubble problems and a new technique for generating computer soap bubble possesses an exquisite perfection of form. Soap bubbles are lovely physical manifestations

Sullivan, John M.

337

Bubble Simulation Using Level Set-Boundary Element Method  

E-print Network

In bubble dynamics, an underwater bubble may evolve from being singly-connected to being toroidal. Furthermore, two or more individual bubbles may merge to form a single large bubble. These dynamics involve significant ...

Tan, Kiok Lim

338

Sea Level: On The Rise  

NSDL National Science Digital Library

Learners will understand the relationship between climate change and sea-level rise. In the first activity, they will learn that heated water causes sea level to rise through a process called thermal expansion. They will also perform an experiment to learn that melting land-based ice contributes to greater sea-level rise than melting sea ice.

2013-11-26

339

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

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

340

Vortex Dynamics from 2D PIV Data in a Bubble Plume  

NASA Astrophysics Data System (ADS)

Bubble plumes are commonly used for aeration and destratification in lakes and show potential as a delivery method for carbon sequestration. The need to design bubble plumes for these uses has led to an increase in research and development of models. However, the dynamics of turbulence in bubble plumes has yet to be quantified. Physical experiments were conducted to quantify turbulence in bubble plumes with air flow rates of 0.5, 1.0, and 1.5L/min. A camera imaged the bubble plume illuminated along a plane with an Argon-Ion laser at 250Hz. The images were processed to remove all bubbles resulting in a new image with only seeding particles. These images were processed using Particle Image Velocimetry giving 2D vector fields for the fluid phase. These vector fields were spatially analyzed to identify vortices and their properties in the field of view. The results show that the expected non-dimensional vortex size is the same for all three flow rates. The results also show that when properly non-dimensionalized the time-average vortex properties such as size and circulation across the width of the bubble plume are similar for all three air flow rates. Finally, the data is used to find the turbulent energy spectrum and the characteristic length scale within the plume. These results agree with the identified vortex results and show the modulation of the turbulence due to the presence of bubbles.

Bryant, Duncan; Socolofsky, Scott

2008-11-01

341

Bubbles Responding to Ultrasound Pressure  

NASA Technical Reports Server (NTRS)

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

2003-01-01

342

Bursting Bubbles and Bilayers  

PubMed Central

This paper discusses various interactions between ultrasound, phospholipid monolayer-coated gas bubbles, phospholipid bilayer vesicles, and cells. The paper begins with a review of microbubble physics models, developed to describe microbubble dynamic behavior in the presence of ultrasound, and follows this with a discussion of how such models can be used to predict inertial cavitation profiles. Predicted sensitivities of inertial cavitation to changes in the values of membrane properties, including surface tension, surface dilatational viscosity, and area expansion modulus, indicate that area expansion modulus exerts the greatest relative influence on inertial cavitation. Accordingly, the theoretical dependence of area expansion modulus on chemical composition - in particular, poly (ethylene glyclol) (PEG) - is reviewed, and predictions of inertial cavitation for different PEG molecular weights and compositions are compared with experiment. Noteworthy is the predicted dependence, or lack thereof, of inertial cavitation on PEG molecular weight and mole fraction. Specifically, inertial cavitation is predicted to be independent of PEG molecular weight and mole fraction in the so-called mushroom regime. In the “brush” regime, however, inertial cavitation is predicted to increase with PEG mole fraction but to decrease (to the inverse 3/5 power) with PEG molecular weight. While excellent agreement between experiment and theory can be achieved, it is shown that the calculated inertial cavitation profiles depend strongly on the criterion used to predict inertial cavitation. This is followed by a discussion of nesting microbubbles inside the aqueous core of microcapsules and how this significantly increases the inertial cavitation threshold. Nesting thus offers a means for avoiding unwanted inertial cavitation and cell death during imaging and other applications such as sonoporation. A review of putative sonoporation mechanisms is then presented, including those involving microbubbles to deliver cargo into a cell, and those - not necessarily involving microubbles - to release cargo from a phospholipid vesicle (or reverse sonoporation). It is shown that the rate of (reverse) sonoporation from liposomes correlates with phospholipid bilayer phase behavior, liquid-disordered phases giving appreciably faster release than liquid-ordered phases. Moreover, liquid-disordered phases exhibit evidence of two release mechanisms, which are described well mathematically by enhanced diffusion (possibly via dilation of membrane phospholipids) and irreversible membrane disruption, whereas liquid-ordered phases are described by a single mechanism, which has yet to be positively identified. The ability to tune release kinetics with bilayer composition makes reverse sonoporation of phospholipid vesicles a promising methodology for controlled drug delivery. Moreover, nesting of microbubbles inside vesicles constitutes a truly “theranostic” vehicle, one that can be used for both long-lasting, safe imaging and for controlled drug delivery. PMID:23382772

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

2012-01-01

343

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

344

Bubble memory module for spacecraft application  

NASA Technical Reports Server (NTRS)

Bubble domain technology offers an all-solid-state alternative for data storage in onboard data systems. A versatile modular bubble memory concept was developed. The key module is the bubble memory module which contains all of the storage devices and circuitry for accessing these devices. This report documents the bubble memory module design and preliminary hardware designs aimed at memory module functional demonstration with available commercial bubble devices. The system architecture provides simultaneous operation of bubble devices to attain high data rates. Banks of bubble devices are accessed by a given bubble controller to minimize controller parts. A power strobing technique is discussed which could minimize the average system power dissipation. A fast initialization method using EEPROM (electrically erasable, programmable read-only memory) devices promotes fast access. Noise and crosstalk problems and implementations to minimize these are discussed. Flight memory systems which incorporate the concepts and techniques of this work could now be developed for applications.

Hayes, P. J.; Looney, K. T.; Nichols, C. D.

1985-01-01

345

Behavior of Rapidly Sheared Bubble Suspensions  

NASA Technical Reports Server (NTRS)

An experiment to be carried out aboard the International Space Station is described. A suspension consisting of millimeter-sized bubbles in water containing some dissolved salt, which prevents bubbles from coalescing, will be sheared in a Couette cylindrical cell. Rotation of the outer cylinder will produce centrifugal force which will tend to accumulate the bubbles near the inner wall. The shearing will enhance collisions among bubbles creating thereby bubble phase pressure that will resist the tendency of the bubbles to accumulate near the inner wall. The bubble volume fraction and velocity profiles will be measured and compared with the theoretical predictions. Ground-based research on measurement of bubble phase properties and flow in vertical channel are described.

Sangani, A. S.; Kushch, V. I.; Hoffmann, M.; Nahra, H.; Koch, D. L.; Tsang, Y.

2002-01-01

346

TECHNOLOGY ASSESSMENT OF FINE BUBBLE AERATORS  

EPA Science Inventory

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

347

Unorthodox bubbles when boiling in cold water  

NASA Astrophysics Data System (ADS)

High-speed movies are taken when bubbles grow at gold surfaces heated spotwise with a near-infrared laser beam heating water below the boiling point (60-70 °C) with heating powers spanning the range from very low to so high that water fails to rewet the surface after bubbles detach. Roughly half the bubbles are conventional: They grow symmetrically through evaporation until buoyancy lifts them away. Others have unorthodox shapes and appear to contribute disproportionately to heat transfer efficiency: mushroom cloud shapes, violently explosive bubbles, and cavitation events, probably stimulated by a combination of superheating, convection, turbulence, and surface dewetting during the initial bubble growth. Moreover, bubbles often follow one another in complex sequences, often beginning with an unorthodox bubble that stirs the water, followed by several conventional bubbles. This large dataset is analyzed and discussed with emphasis on how explosive phenomena such as cavitation induce discrepancies from classical expectations about boiling.

Parker, Scott; Granick, Steve

2014-01-01

348

Unorthodox bubbles when boiling in cold water.  

PubMed

High-speed movies are taken when bubbles grow at gold surfaces heated spotwise with a near-infrared laser beam heating water below the boiling point (60-70?°C) with heating powers spanning the range from very low to so high that water fails to rewet the surface after bubbles detach. Roughly half the bubbles are conventional: They grow symmetrically through evaporation until buoyancy lifts them away. Others have unorthodox shapes and appear to contribute disproportionately to heat transfer efficiency: mushroom cloud shapes, violently explosive bubbles, and cavitation events, probably stimulated by a combination of superheating, convection, turbulence, and surface dewetting during the initial bubble growth. Moreover, bubbles often follow one another in complex sequences, often beginning with an unorthodox bubble that stirs the water, followed by several conventional bubbles. This large dataset is analyzed and discussed with emphasis on how explosive phenomena such as cavitation induce discrepancies from classical expectations about boiling. PMID:24580324

Parker, Scott; Granick, Steve

2014-01-01

349

Temperature Nonequilibration during Single-Bubble Sonoluminescence  

E-print Network

Temperature Nonequilibration during Single-Bubble Sonoluminescence David J. Flannigan*, and Kenneth Information ABSTRACT: Single-bubble sonoluminescence (SBSL) spectra from liquids having low vapor pressures the observation and quantification of nonequilibrated temperatures during sonoluminescence. For SBSL from aqueous

Suslick, Kenneth S.

350

Colliding bubble universes in eternal inflation  

E-print Network

We briefly summarize arguments for inflation and discuss eternal inflation. We then discuss the motion of domain walls and null shells that form in two-bubble collision processes in both the global and in-bubble FRW ...

Thomas, Nathaniel C. (Nathaniel Cabot)

2011-01-01

351

Oscillating bubbles in ultrasonic acoustic field  

NASA Astrophysics Data System (ADS)

Behavior of oscillating bubbles is of fundamental study for acoustic cavitations, and is of great importance for medical field. For example, angiographic and diagnosis of cancer of liver. We focused on behavior of multiple air bubbles exposed to ultrasonic wave. The bubbles were injected into the static water from a vertical capillary tube, and then the ultrasonic wave of 20 kHz was applied from above toward the bubbles. Vibrating motion of the bubbles was captured by a high-speed camera at frame rates up to 45000 fps. Excitations of surface wave and shape oscillation with distinct mode number were realized. Correlation between the accelerated bubble behavior and the bubble-bubble distance.

Matsumoto, K.; Ueno, I.

2009-02-01

352

Removal of hydrogen bubbles from nuclear reactors  

NASA Technical Reports Server (NTRS)

Method proposed for removing large hydrogen bubbles from nuclear environment uses, in its simplest form, hollow spheres of palladium or platinum. Methods would result in hydrogen bubble being reduced in size without letting more radioactivity outside reactor.

Jenkins, R. V.

1980-01-01

353

THE YOUNG INTERSTELLAR BUBBLE WITHIN THE ROSETTE NEBULA  

SciTech Connect

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

Bruhweiler, F. C.; Bourdin, M. O. [IACS/Department of Physics, Catholic University of America, Washington, DC 20064 (United States); Freire Ferrero, R. [Observatoire Astronomique de Strasbourg, Universite Louis Pasteur, CNRS 11 rue de l'Universite, 67000 Strasbourg (France); Gull, T. R., E-mail: bruhweiler@cua.ed, E-mail: theodore.r.gull@nasa.go, E-mail: freire@astro.u-strasbg.f [Exploration of the Universe Division, Code 667, Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2010-08-20

354

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

SciTech Connect

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

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

2011-12-01

355

The good, the bad and the bubbly. Micro bubble behavior under ultrasound.  

E-print Network

The good, the bad and the bubbly. Micro bubble behavior under ultrasound. Michael Conneely Division of Physics The good, the bad and the bubbly. Micro bubble behavior under ultrasound. PaLS Open Day 2013 #12] microsecond behaviour of microbubbles in Ultrasound fields. · Direct relevance across therapeutic

Greenaway, Alan

356

Numerical simulations of single bubble sonoluminescence  

SciTech Connect

A higher-order Godunov method is used to solve the spherically symmetric, compressible Euler equations with an ideal gas equation of state as a model for single bubble sonoluminescence. Basic shock physics is discussed in this context, exploring how modeled variations of the bubble interior support or suppress the generation and propagation of shock waves within the bubble as well as the interaction of a shock with the bubble interface. [Work supported by ONR through the ONR/ARL program.

Mourad, P.D. (Appl. Phys. Lab., Univ. of Washington, Seattle, WA 98195 (United States)); Marcus, D.L. (Lawrence Livermore Natl. Lab., Livermore, CA 94551 (United States)); Roy, R.A.; Matula, T.J. (Univ. of Washington, Seattle, WA 98195 (United States))

1994-11-01

357

Multicompartment hydrodynamic model for slurry bubble columns  

Microsoft Academic Search

A core-annulus multicompartment two-dimensional two-bubble class model accounting for slurry recirculation and coupled with catalyst transport was developed as a part and parcel of the analysis of the behavior of slurry bubble column reactors at high gas throughputs corresponding to the churn turbulent flow regime. The model analyzed the contributions of bubble-induced turbulence closures, bubble coalescence and breakup phenomena, and

Ion Iliuta; Damien Desvigne; Jérôme Anfray; Nicolas Dromard; Daniel Schweich

2008-01-01

358

Silent bubbles - Their effects and detection  

NASA Technical Reports Server (NTRS)

This paper discusses the concept of the 'silent bubble' (a phenomenon due to gas phase formation in tissues, which does not lead to frank decompression sickness). Special attention is given to the conditions for silent bubbles formation, the methods of their detecton, and to their pathophysiology. Data relating the gas formation in blood and the symptoms of decompression sickness indicate that the distinction between the silent bubbles and clinical ones is often vague and that a bubble-free decompression never existed.

Powell, Michael R.

1990-01-01

359

Soap bubbles in paintings: Art and science  

Microsoft Academic Search

Soap bubbles became popular in 17th century paintings and prints primarily as a metaphor for the impermanence and fragility of life. The Dancing Couple (1663) by the Dutch painter Jan Steen is a good example which, among many other symbols, shows a young boy blowing soap bubbles. In the 18th century the French painter Jean-Simeon Chardin used soap bubbles not

F. Behroozi

2008-01-01

360

BUBBLE COMPUTATION, GRANULAR TEMPERATURES, AND REYNOLDS STRESSES  

Microsoft Academic Search

Bubbles were simulated in a two-dimensional fluidized bed with a constant inlet velocity using two computer codes, the IIT code and the MFIX code. The computational results were compared to the Jung et al. (2005) experiments in a thin bubbling bed of 530 ?m glass beads. The use of higher order numerics produces better bubble resolution due to smaller numerical diffusion.

Jonghwun Jung; Dimitri Gidaspow; Isaac K. Gamwo

2006-01-01

361

Black hole formation from colliding bubbles  

E-print Network

Some indication of conditions that are necessary for the formation of black holes from the collision of bubbles during a supercooled phase transition in the the early universe are explored. Two colliding bubbles can never form a black hole. Three colliding bubbles can refocus the energy in their walls to the extent that it becomes infinite.

Ian G. Moss

1994-05-21

362

Shock Wave Emissions of a Sonoluminescing Bubble  

Microsoft Academic Search

A single bubble in water is excited by a standing ultrasound wave. At high intensity the bubble starts to emit light. Together with the emitted light pulse, a shock wave is generated in the liquid at collapse time. The time-dependent velocity of the outward-travelling shock is measured with an imaging technique. The pressure in the shock and in the bubble

Joachim Holzfuss; Matthias Ruggeberg; Andreas Billo

1998-01-01

363

25 July 2002 Sonoluminescence: Bubble power  

E-print Network

25 July 2002 Sonoluminescence: Bubble power When a gas bubble in a liquid is excited by ultrasonic. These flashes of light, known as 'sonoluminescence', occur as the bubble implodes, or cavitates. Now Didenko­397 (2002); doi:10.1038/nature00895 | First Paragraph | Full Text (HTML / PDF) | Sonoluminescence: Inside

Suslick, Kenneth S.

364

Alternative model of single-bubble sonoluminescence  

Microsoft Academic Search

A model of single-bubble sonoluminescence (SBSL) is constructed. In the model, the temperature is assumed to be spatially uniform inside the bubble except at the thermal boundary layer near the bubble wall even at the strong collapse based on the theoretical results of Kwak and Na [Phys. Rev. Lett. 77, 4454 (1996)]. In the model, the effect of the kinetic

Kyuichi Yasui

1997-01-01

365

Hydrodynamic Solutions for a Sonoluminescing Gas Bubble  

Microsoft Academic Search

Analytic solutions for a sonoluminescing gas bubble have been obtained, which provide density, pressure, and temperature distributions for the gas inside a bubble oscillating under an ultrasonic field. The solutions show that sonoluminescence occurs due to the increase and subsequent decrease in bubble wall acceleration which induces a thermal spike. It also turns out that the number of electrons ionized,

Ho-Young Kwak; Jung Hee Na

1996-01-01

366

Passive acoustic analysis of complex bubbly flows  

Microsoft Academic Search

A technique for extracting data from a complex bubbly flow is reviewed, beginning with fundamental laboratory and theoretical developments of the method and ending with an illustration of the technique in practice. Passive bubble acoustics involves 'listening' to the sounds naturally emitted by bubbles and exploiting these data to infer properties of the system. In many industrial plants, the multiphase

Richard Manasseh

2004-01-01

367

Tetrad bubble domain chip arrangement for multiplexing  

NASA Technical Reports Server (NTRS)

Rotating magnetic field of bubble domain memory is used to obtain time-division multiplexing of bubble domain circuits into quadrants. Memory bits are assigned on bit-per-chip rather than bit-per-module basis; power is reduced by circulating only portion of bubbles at a time.

Almasi, G. S.

1973-01-01

368

Bubbularium: See the Colors in Bubbles  

NSDL National Science Digital Library

With little more than a flashlight, a straw, and a plastic lid, make an observatory so you can see the amazing colors in bubbles. Learn about how light travels in waves and how the frequency of a light wave determines which color you see. The activity also has a recipe for "bubble juice" so you'll have some bubbles to work with.

2012-06-26

369

Intra-bubble-combustion. Premixed limit, stage I: dynamics of rapid premixed flame propagation inside a bubble  

NASA Astrophysics Data System (ADS)

The propagation of a spherically symmetric premixed thin flame inside an initially centrally ignited bubble in an unconfined viscous, incompressible liquid is theoretically analysed. This model focuses on the dynamical competition between the pressure increase produced by the chemical reaction and the pressure decrease induced by the bubble expansion (a consequence of radial momentum conservation). When a balance between these two processes is achieved an oscillatory response may be observed. The conditions leading to such a response are investigated. The effective inertia (the squared ratio between the characteristic liquid response time and the combustion time) is the main parameter governing this evolution. Two qualitatively different behaviours are encountered for large and small effective inertia-parameter. An approximate analytical solution is provided for each limiting case, as well as a correlation for the gaseous state at the end of the process, based on the former approximate solutions. While the system considered is deliberately highly idealized, some of these quantitative and qualitative results are expected to be helpful in the design of intra-bubble-combustion experiments (Rosner D E, Arias-Zugasti M and La Mantia B 2001 Combustion of individual bubbles and submerged gas jets 6th International Microgravity Combustion Workshop (Cleveland, OH, USA, 22-24 May); Rosner D E, Arias-Zugasti M and La Mantia B 2002 Combustion of individual bubbles and submerged gas jets (poster) 29th Symp. (International) on Combustion (Sapporo, Japan, 21-26 July); Rosner D E 1997 Combustion synthesis and material processing Chem. Eng. Edu (ASEE) 31 228) and, ultimately, bubble reactors.

Arias-Zugasti, Manuel

2003-06-01

370

The ICARUS Liquid Argon TPC: A neutrino "bubble chamber" after Gargamelle  

NASA Astrophysics Data System (ADS)

The success of the bubble chamber in high energy physics was due to two fundamental characteristics: (1) it provided a massive target (2) with complete imaging and reconstruction of the events. In this context, the Liquid Argon Time Projection Chamber can be considered as a modern fully electronic "bubble chamber". In this talk, we review the developments that led to the ICARUS T600 detector.

Rubbia, Carlo

2011-07-01

371

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

NASA Astrophysics Data System (ADS)

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

Lakshmanan, Peter; Ehrhard, Peter

2008-11-01

372

Slurry Bubble Column Reactor Optimization (book chapter)  

SciTech Connect

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

Gamwo, I.K.; Gidaspow, D. (Illinois Inst. of Technology, Chicago, IL); Jung, J. (ANL)

2007-03-01

373

Pulling bubbles from a bath  

E-print Network

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

Kao, Justin C. T.

374

The Coming Law School Bubble  

ERIC Educational Resources Information Center

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

Krauss, Michael I.

2011-01-01

375

Models of cylindrical bubble pulsation  

PubMed Central

Three models are considered for describing the dynamics of a pulsating cylindrical bubble. A linear solution is derived for a cylindrical bubble in an infinite compressible liquid. The solution accounts for losses due to viscosity, heat conduction, and acoustic radiation. It reveals that radiation is the dominant loss mechanism, and that it is 22 times greater than for a spherical bubble of the same radius. The predicted resonance frequency provides a basis of comparison for limiting forms of other models. The second model considered is a commonly used equation in Rayleigh-Plesset form that requires an incompressible liquid to be finite in extent in order for bubble pulsation to occur. The radial extent of the liquid becomes a fitting parameter, and it is found that considerably different values of the parameter are required for modeling inertial motion versus acoustical oscillations. The third model was developed by V. K. Kedrinskii [Hydrodynamics of Explosion (Springer, New York, 2005), pp. 23–26] in the form of the Gilmore equation for compressible liquids of infinite extent. While the correct resonance frequency and loss factor are not recovered from this model in the linear approximation, it provides reasonable agreement with observations of inertial motion. PMID:22978863

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

2012-01-01

376

Electrolysis Bubbles Make Waterflow Visible  

NASA Technical Reports Server (NTRS)

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

Schultz, Donald F.

1990-01-01

377

Bubble-driven inertial micropump  

NASA Astrophysics Data System (ADS)

The fundamental action of the bubble-driven inertial micropump is investigated. The pump has no moving parts and consists of a thermal resistor placed asymmetrically within a straight channel connecting two reservoirs. Using numerical simulations, the net flow is studied as a function of channel geometry, resistor location, vapor bubble strength, fluid viscosity, and surface tension. Two major regimes of behavior are identified: axial and non-axial. In the axial regime, the drive bubble either remains inside the channel, or continues to grow axially when it reaches the reservoir. In the non-axial regime, the bubble grows out of the channel and in all three dimensions while inside the reservoir. The net flow in the axial regime is parabolic with respect to the hydraulic diameter of the channel cross-section, but in the non-axial regime it is not. From numerical modeling, it is determined that the net flow is maximal when the axial regime crosses over to the non-axial regime. To elucidate the basic physical principles of the pump, a phenomenological one-dimensional model is developed and solved. A linear array of micropumps has been built using silicon-SU8 fabrication technology that is used to manufacture thermal inkjet printheads. Semi-continuous pumping across a 2 mm-wide channel has been demonstrated experimentally. Measured net flow with respect to viscosity variation is in excellent agreement with simulation results.

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

2012-12-01

378

Neutron Detection via Bubble Chambers  

SciTech Connect

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

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

2005-10-06

379

The Trouble With Bubble Gum  

NSDL National Science Digital Library

Most students are totally unaware of the amount of sugar in bubble gum and don't know that they are literally eating sugar in huge amounts. In this chapter, the author is concerned with finding out what happens to the weight of gum when it is chewed, whic

Richard Konicek-Moran

2010-03-12

380

Bubble Universe Dynamics After Free Passage  

E-print Network

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

Pontus Ahlqvist; Kate Eckerle; Brian Greene

2014-12-26

381

Bubble Universe Dynamics After Free Passage  

NASA Astrophysics Data System (ADS)

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

Ahlqvist, Pontus; Eckerle, Kate; Greene, Brian

2015-03-01

382

Free falling and rising of spherical and angular particles  

SciTech Connect

Direct numerical simulations of freely falling and rising particles in an infinitely long domain, with periodic lateral boundary conditions, are performed. The focus is on characterizing the free motion of cubical and tetrahedral particles for different Reynolds numbers, as an extension to the well-studied behaviour of freely falling and rising spherical bodies. The vortical structure of the wake, dynamics of particle movement, and the interaction of the particle with its wake are studied. The results reveal mechanisms of path instabilities for angular particles, which are different from those for spherical ones. The rotation of the particle plays a more significant role in the transition to chaos for angular particles. Following a framework similar to that of Mougin and Magnaudet [“Wake-induced forces and torques on a zigzagging/spiralling bubble,” J. Fluid Mech. 567, 185–194 (2006)], the balance of forces and torques acting on particles is discussed to gain more insight into the path instabilities of angular particles.

Rahmani, M., E-mail: mona.rahmani@ifpen.fr; Wachs, A., E-mail: anthony.wachs@ifpen.fr [Fluid Mechanics Department, IFP Energies nouvelles, Etablissement de Lyon, 69360 Solaize (France)

2014-08-15

383

The role of bubble ascent in magma mixing  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

384

Generation of Bubbly Suspensions in Low Gravity  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

385

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

PubMed

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

Ida, Masato; Naoe, Takashi; Futakawa, Masatoshi

2007-10-01

386

3D Modeling of Equatorial Plasma Bubbles  

NASA Astrophysics Data System (ADS)

Post-sunset ionospheric irregularities in the equatorial F region were first observed by Booker and Wells (1938) using ionosondes. This phenomenon has become known as equatorial spread F (ESF). During ESF the equatorial ionosphere becomes unstable because of a Rayleigh-Taylor-like instability: large scale (10s km) electron density ``bubbles'' can develop and rise to high altitudes (1000 km or greater at times). Understanding and modeling ESF is important because of its impact on space weather: it causes radio wave scintillation that degrades communication and navigation systems. In fact, it is the focus of of the Air Force Communications/Navigation Outage Forecast Satellite (C/NOFS) mission. We will describe 3D simulation results from the NRL ionosphere models SAMI3 and SAMI3/ESF of this phenomenon. In particular, we will examine the causes of the day-to-day ariability of ESF which is an unresolved problem at this time. Booker, H.G. and H.G. Wells, Terr. Mag. Atmos. Elec. 43, 249, 1938.

Huba, Joseph; Joyce, Glenn; Krall, Jonathan

2011-11-01

387

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

SciTech Connect

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

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

1984-01-01

388

On Capillary Rise and Nucleation  

ERIC Educational Resources Information Center

A comparison of capillary rise and nucleation is presented. It is shown that both phenomena result from a balance between two competing energy factors: a volume energy and a surface energy. Such a comparison may help to introduce nucleation with a topic familiar to the students, capillary rise. (Contains 1 table and 3 figures.)

Prasad, R.

2008-01-01

389

Slopes To Prevent Trapping of Bubbles in Microfluidic Channels  

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

390

Mass transfer processes across the Capillary Fringe: Quantification of gas-water interface and bubble mediated mass transfer  

NASA Astrophysics Data System (ADS)

The Capillary Fringe (CF) is a highly dynamic zone at the interface between the water-saturated aquifer and the vadose zone, where steep biogeochemical gradients and thus high bioactivities are expected. Mass transfer processes between the unsaturated zone and the atmosphere, like Greenhouse gas emissions and evaporation, are controlled by the highly temporal and spatial variable gas-water interface across the capillary fringe. Due to water table fluctuations, gas phase may be entrapped or released at/from the CF, which extremely affects the hydraulic properties of the porous medium as well as the mass transfer processes in the partially saturated zone. Most of these processes (gas entrapment and bubble mediated mass transfer (BMT)) are governed by the interactions between the interfaces of gas, water and soil phases. Quantification of these parameters requires a pore-scale approach, which can determine the phase volumes and interfaces with high accuracy. For the understanding and prediction of the involved processes, experiments and modeling at the pore scale are the necessary prerequisites for upscaled, effective modeling approaches. To achieve this aim, we conducted a set of column experiments using X-Ray Computed Tomography (CT). Using this technique, we are able to quantitatively analyze the desired variables in 3D inside the actual bulk volume of the porous media. Water table (WT) elevation was raised at different velocities in the column filled with 1mm-glass beads. After each rise, the column was scanned with CT. We used an intelligent multi-phase segmentation method, considering grey value frequency and voxel neighboring, to separate gas, water, and solid phases in the CT images. The saturation of the gas phase, distribution of the trapped gas bubbles and clusters, and their size, shape, and area are quantified and analyzed at pore-scale. We developed a new segmentation algorithm to distinguish the gas/water interface from the gas/solid interface. Only the first plays the key role in BMT. Parallel to the CT-column experiments we measured in the same experimental setup (column, sediment, WT-rise velocity) the dissolution of trapped Oxygen gas bubbles using optode spots along the capillary fringe inside the column. For the first time we quantify BMT based on pore-scale process characteristics of gas phase distribution using two different models: (i) an effective 1D-diffusion model and (ii) a Multisphere diffusion model.

Geistlinger, Helmut; Mohammadian, Sadjad; Schlüter, Steffen; Karimzadeh, Lotfollah; Vogel, Hans-Jörg

2013-04-01

391

Etiology of gas bubble disease  

SciTech Connect

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

Bouck, G.R.

1980-11-01

392

Soap bubbles in paintings: Art and science  

NASA Astrophysics Data System (ADS)

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

Behroozi, F.

2008-12-01

393

Degassing of magma rising in a dyke  

NASA Astrophysics Data System (ADS)

Magma ascent and degassing proceed in markedly different ways in a volcanic conduit and in a dyke due to large differences in the vertical variations of magma pressure. In a propagating dyke, the width of the dyke and the distributions of magma velocity and pressure must be solved for simultaneously, in contrast to magma rising in a conduit, such that the conduit aperture and dimensions are fixed a priori. In these two cases, magma buoyancy is balanced in different ways depending on the magnitude of forces available to drive wall deformation. Numerical calculations of dyke ascent are used to investigate the different dynamics of magma ascent. The mixture of melt and gas is treated as a compressible viscous fluid below the fragmentation level and as a gas phase carrying melt droplets above it. The numerical code solves for elastic deformation of host rocks, the flow of the magmatic mixture and fracturing at the dyke tip. With volatile-free magma, a dyke fed at a constant rate in a uniform medium adopts a constant shape and width and rises at a constant velocity. With volatiles involved, magma expands and hence the volume flux of magma increases. With no fragmentation, the rheological properties of the magmatic mixture also change due to the presence of bubbles and to the increase of melt viscosity induced by degassing. There is still some uncertainty on a proper formulation for these complicated rheological effects. We use several parameterization schemes to show that, in all cases, the enhenced volume flux due to degassing leads to acceleration and thinning of the dyke. This is true even when one does not account for the effect of gas on the mixture viscosity. In this case, viscosity increases dramatically as magma loses its dissolved volatiles, but density variations more than compensate for such changes. Simple scaling laws allow accurate predictions of dyke width and ascent rate for a wide range of conditions. With fragmentation, dyke behaviour is markedly different. Due to the sharp drop of head loss that occurs in gas-rich fragmented material, large internal overpressures develop below the dyke tip and induce dramatic swelling of the nose region, leading to deceleration of the dyke. Thus, the low-viscosity buoyant mixture of gas and magma clasts in fact rises slowly in an expanding fracture. Due to their markedly different dynamic behaviours, gas-poor and gas-rich magmas could be identified by monitoring techniques in the precursory phases of an eruption, with important implications for hazard assessment. We show that model predictions reproduce very well the magma migration patterns in two extreme cases, at Piton de la Fournaise (volatile-poor basalt) and Mount Saint Helens (volatile-rich magma).

Taisne, B.; Jaupart, C. P.

2012-12-01

394

HBT Interferometry for Sonoluminescence Bubble  

E-print Network

The two-photon correlation of the light pulse emitted from a sonoluminescence bubble is discussed. It is shown that several important information about the mechanism of light emission, such as the time-scale and the shape of the emission region could be obtained from the HBT interferometry. We also argue that such a measurement may serve to reject one of the two currently suggested emission mechanisms, i.e., thermal process versus dynamical Casimir effect.

Hama, Y; Padula, S S; Padula, Sandra S.

1996-01-01

395

HBT Interferometry for Sonoluminescence Bubble  

E-print Network

The two-photon correlation of the light pulse emitted from a sonoluminescence bubble is discussed. It is shown that several important information about the mechanism of light emission, such as the time-scale and the shape of the emission region could be obtained from the HBT interferometry. We also argue that such a measurement may serve to reject one of the two currently suggested emission mechanisms, i.e., thermal process versus dynamical Casimir effect.

Y. Hama; T. Kodama; Sandra S. Padula

1996-12-18

396

Transitional Bubble in Periodic Flow Phase Shift  

NASA Technical Reports Server (NTRS)

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

Talan, M.; Hourmouziadis, Jean

2004-01-01

397

Study on development of ejector of Bubble Jet Engine (BJE) - measurement of thrust -  

NASA Astrophysics Data System (ADS)

The AUV (Autonomous Under-water Vehicle), which is used for the present seabed investigations, has obtained the thrust with the screw driven by the battery. However, it has a disadvantage because of its size and cost. Therefore, this research is carried out to propose the Bubble Jet Engine (BJE) as an alternative propulsion device. It can directly transform combustion energy into kinetic energy, so it is expected that BJE can also rise the level of propulsion efficiency. This research aims at measuring exhaled mass flow rate and thrust to design ejectors, which become the core of BJE, and exploring practical possibility of BJE. Vertical type gas-water ejector experimental apparatus for measuring water entrainment was employed in order to understand the characteristics of operation conditions, such as inlet distance, air pressure of nozzle, diameter of nozzle, and so on. In addition, experiments for measuring the thrust in the condition of ejector were executed with horizontal type apparatus in water. However, the influence of the ejector to improve thrust can't have been recognized with high-pressure air at room temperature yet.

Ono, B.; Nakashima, K.; Shigematsu, T.; Morishita, K.

2009-02-01

398

Unsteady thermocapillary migration of bubbles  

NASA Technical Reports Server (NTRS)

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

Dill, Loren H.; Balasubramaniam, R.

1988-01-01

399

Sonoluminescing bubbles and mass diffusion  

SciTech Connect

The transduction of sound into light by a pulsating bubble in water occurs when its maximum radius is about ten times greater than its ambient radius. For such high-amplitude motion, the steady-state balance of mass flow between the bubble and gas dissolved in the surrounding fluid can be maintained by diffusion only at low partial pressures, about 3 Torr. The observation of sonoluminescence (SL) from bubbles in 200 Torr solutions of air in water requires the action of some as yet unknown mass flow mechanism. On the other hand, gas solutions prepared at low partial pressures, in the diffusion-controlled regime, enable one to achieve SL in gases that do not emit light at higher partial pressures. These include hydrogenic gases and gases with a ratio of specific heats close to unity, which hardly heat up upon adiabatic compression. Experiments that probe the role of mass transfer in SL are presented along with the implications of their comparison to a multiple-time-scale analysis of mass diffusion.

Loefstedt, R.; Weninger, K.; Putterman, S.; Barber, B.P. [Department of Physics, University of California, Los Angeles, California 90024 (United States)] [Department of Physics, University of California, Los Angeles, California 90024 (United States)

1995-05-01

400

Numerical study on ring bubble dynamics in a narrow cylinder with a compliant coating  

NASA Astrophysics Data System (ADS)

In this paper, the ring bubble contraction inside a narrow vertical rigid cylinder with a compliant coating filled with water is studied numerically. To simulate ring bubble dynamics numerically, in addition to computing the pressure and velocity fields of the surrounding fluid, an axisymmetric boundary integral equation approach is adopted alongside a finite difference method. The compliant boundary is modeled as a membrane with a spring foundation. During the ring bubble contraction and under the attraction of the cylinder wall due to the Bjerknes force, a horizontal ring jet is initiated and develops towards the cylinder wall. The numerical results represent the effects of the cylinder radius and two compliant coating characteristics, including its mass per unit area and the spring constant, on the ring bubble behavior. This investigation is motivated by the possibility of utilizing the ring jet in therapeutic cardiovascular applications.

Farhangmehr, V.; Shervani-Tabar, M. T.; Parvizi, R.; Ohl, S. W.; Khoo, B. C.

2015-04-01

401

Structural features of the nonionic surfactants stabilizing long-lived bubble nuclei  

NASA Astrophysics Data System (ADS)

The effects of a wide variety of electrolytes (each at 0.4 M), and one selected organic compound, on bubble production in agarose gels has been studied. Several different commercial preparations of ultrapure agarose were compared for each of the 42 different electrolytes tested, and for phenol (1% v/v in H2O), in order to clearly identify reproducible and significant trends in the chemical data on bubble formation. The anion and cation sequences obtained with regard to the extent of bubble suppression contain many similarities with published data in the physicochemical literature for salting out of identified nonionic surfactants. Moreover, the precise pattern of electrolyte effects on bubble formation yields specific clues as to the structural characteristics of the nonionic surfactants stabilizing bubble nuclei present in different agarose gels. Specifically, the pronounced reduction of bubble number by polyvalent anions and by 1% phenol suggest that the polar portions of these nonionic surfactants represent primarily amide groups. This view was supported by the cation bubble-reduction sequence Na+?K+?Li+ consistently observed with the purest agarose preparation tested; this cation sequence indicates that the polar portions of the surfactant molecules are neither weakly acidic nor weakly basic, but essentially neutral as is the dipolar amide group. The above evidence for amide groups is also consistent with the relative position of Mg2+ in all the cation sequences obtained, which repeatedly indicated appreciable (and often strong) salting out in each case. This last result renders it quite unlikely that ether linkages, which commonly occur in artificially produced surfactants, contribute to the hydrophilicity of the nonionic surfactants stabilizing bubble nuclei in the different aqueous (agarose) gels tested. The nonionic surfactants stabilizing long-lived bubble nuclei are probably mostly, if not all, of natural origin.

D'Arrigo, Joseph S.

1980-05-01

402

Mechanism of bubble detachment from vibrating walls  

SciTech Connect

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

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

2013-11-15

403

Ostwald ripening in multiple-bubble nuclei  

NASA Astrophysics Data System (ADS)

The Ostwald ripening of bubbles is studied by molecular dynamics simulations involving up to 679 × 106 Lennard-Jones particles. Many bubbles appear after depressurizing a system that is initially maintained in the pure-liquid phase, and the coarsening of bubbles follows. The self-similarity of the bubble-size distribution function predicted by Lifshitz-Slyozov-Wagner theory is directly confirmed. The total number of bubbles decreases asymptotically as t-x with scaling exponent x. As the initial temperature increases, the exponent changes from x = 3/2 to 1, which implies that the growth of bubbles changes from interface-limited (the t1/2 law) to diffusion-limited (the t1/3 law) growth.

Watanabe, Hiroshi; Suzuki, Masaru; Inaoka, Hajime; Ito, Nobuyasu

2014-12-01

404

Circulation of bubbly magma and gas segregation within tunnels of the potential Yucca Mountain repository  

NASA Astrophysics Data System (ADS)

Following an intersection of rising magma with drifts of the potential Yucca Mountain nuclear waste repository, a pathway is likely to be established to the surface with magma flowing for days to weeks and affecting the performance of engineered structures located along or near the flow path. In particular, convective circulation could occur within magma-filled drifts due to the exsolution and segregation of magmatic gas. We investigate gas segregation in a magma-filled drift intersected by a vertical dyke by means of analogue experiments, focusing on the conditions of sustained magma flow. Degassing is simulated by electrolysis, producing micrometric bubbles in viscous mixtures of water and golden syrup, or by aerating golden syrup, producing polydisperse bubbly mixtures with 40% of gas by volume. The presence of exsolved bubbles induces a buoyancy-driven exchange flow between the dyke and the drift that leads to gas segregation. Bubbles segregate from the magma by rising and accumulating as a foam at the top of the drift, coupled with the accumulation of denser degassed magma at the base of the drift. Steady-state influx of bubbly magma from the dyke into the drift is balanced by outward flux of lighter foam and denser degassed magma. The length and time scales of this gas segregation are controlled by the rise of bubbles in the horizontal drift. Steady-state gas segregation would be accomplished within hours to hundreds of years depending on the viscosity of the degassed magma and the average size of exsolved gas bubbles, and the resulting foam would only be a few cm thick. The exchange flux of bubbly magma between the dyke and the drift that is induced by gas segregation ranges from 1 m3 s-1, for the less viscous magmas, to 10-8 m3 s-1, for the most viscous degassed magmas, with associated velocities ranging from 10-1 to 10-9 m s-1 for the same viscosity range. This model of gas segregation also predicts that the relative proportion of erupted degassed magma, that could potentially carry and entrain nuclear waste material towards the surface, would depend on the value of the dyke magma supply rate relative to the value of the gas segregation flux, with violent eruption of gassy as well as degassed magmas at relatively high magma supply rates, and eruption of mainly degassed magma by milder episodic Strombolian explosions at relatively lower supply rates.

Menand, Thierry; Phillips, Jeremy C.; Sparks, R. Stephen J.

2008-07-01

405

Basaltic scoria plates at Llaima volcano, Chile; preserved bubble walls from large strombolian bubble bursts  

NASA Astrophysics Data System (ADS)

Textural characteristics of tephra provide constraints on both eruptive and degassing processes during explosive volcanic eruptions. Implicit in such studies is the understanding that information regarding the largest bubble populations is usually lost during the eruptive process. This is particularly the case for Strombolian type eruptions where large (>> 1m) gas slugs or coarse foam clots are ruptured during fragmentation and for, which the preserved tephra do not provide much information. The tephra deposit produced during the 2008-2009 violent Strombolian eruption of Llaima volcano, Chile, is characterized by scoria with bimodal densities: a low density, highly-vesicular brown scoria and a higher density, moderately-vesicular black scoria. The deposit also comprises ~ 10-15% vol of unusual basaltic plates. These plates are typically angular tabular pieces of vesicular lava, which apart from their shape, are similar to the dense scoria population in terms of mineralogy (35% plagioclase ± rare olivine). The plates range in size from 2-12 cm and have a relatively uniform thickness of 2-5 mm and are found as far as 9 km from the summit. Plate surface features include striations, pull-apart fractures, and scoriaceous material tacked to the surface. Often the plates are curved and sometimes folded and/or tacked together. Internal fabrics reveal strongly aligned plagioclase crystals and strained enclaves. The small (mostly < 2mm) vesicles do not show evidence of significant strain. Based on the uniformity of plate thickness, plagioclase alignment, and surface features, we propose that these tephra originate during the violent Strombolian phase of the eruption from discrete large bubble bursts and therefore represent remnant bubble films. The concomitant presence of the plates with the scoria at great distances from the vent suggests 1) bubble rupture occurred simultaneously or was followed closely by the fire fountaining that formed the majority of the deposit and 2) they were transported in the volcanic plume alongside the principal scoria and do not represent a separate population of ballistic clasts. Somewhat similar tephra have been observed, though not described in detail, in other deposits from violent Strombolian eruptions, namely the 'cinertic' activity at Paricutin volcano, Mexico and the great fissural eruption of Tolbachick volcano, Kamchatka. The presence of the plate tephra in other deposits suggests that the process by which they form may be important during violent strombolian eruptions in terms of fragmentation mechanisms and plume energetics. For preservation at distal locations from the vent, we infer these bubbles fragmented at significant heights (10-100's m) above the vent, implying especially large bubbles/slugs. Moreover, the plume must be energetic enough to entrain the plates to allow for transport. These distinctive clasts can therefore help to complete our understanding of violent Strombolian activity at basaltic andesite volcanoes.

Ruth, D. C.; Calder, E. S.

2012-12-01

406

Mechanisms for stable single bubble sonoluminescence  

SciTech Connect

A gas bubble trapped in water by an oscillating acoustic field is expected to either shrink or grow on a diffusive time scale, depending on the forcing strength and the bubble size. At high ambient gas concentration this has long been observed. However, recent sonoluminescence experiments show that when the ambient gas concentration is low the bubble can be stable for days. This paper discusses mechanisms leading to stability. {copyright} {ital 1996 The American Physical Society.}

Brenner, M.P. [Department of Mathematics, MIT, Cambridge, Massachusetts 02139 (United States)] [Department of Mathematics, MIT, Cambridge, Massachusetts 02139 (United States); Lohse, D. [Fachbereich Physik der Universitaet Marburg, Renthof 6, 35032 Marburg (Germany)] [Fachbereich Physik der Universitaet Marburg, Renthof 6, 35032 Marburg (Germany); [Department of Mathematics, The University of Chicago, Chicago, Illinois 60637 (United States); Oxtoby, D. [Department of Chemistry and James Franck Institute, The University of Chicago, Chicago, Illinois 60637 (United States)] [Department of Chemistry and James Franck Institute, The University of Chicago, Chicago, Illinois 60637 (United States); Dupont, T.F. [Department of Mathematics, The University of Chicago, Chicago, Illinois 60637 (United States)] [Department of Mathematics, The University of Chicago, Chicago, Illinois 60637 (United States)

1996-02-01

407

Generator for single bubbles of controllable size  

NASA Astrophysics Data System (ADS)

A new type of apparatus for the production of single bubbles of adjustable size is presented. A single bubble is generated by injecting a short burst of gas into a liquid channel flow. The radius of the bubble can be varied continuously from 300 ?m up to a 3 mm by adjusting the timing of a valve injecting the gas. The device works also in liquids with variable pressure and can be microcomputer controlled.

Ohl, C. D.

2001-01-01

408

Collapse of vacuum bubbles in a vacuum  

SciTech Connect

We revisit the dynamics of a false vacuum bubble in a background de Sitter spacetime. We find that there exists a large parameter space that allows the bubble to collapse into a black hole or to form a wormhole. This may have interesting implications for the creation of a baby universe in the laboratory, the string landscape where the bubble nucleation takes place among a plenitude of metastable vacua, and the inflationary physics.

Ng, Kin-Wang; Wang, Shang-Yung [Institute of Physics, Academia Sinica, Taipei, Taiwan 11529 (China); Department of Physics, Tamkang University, Tamsui, Taiwan 25137 (China)

2011-02-15

409

DNA Bubble Life Time in Denaturation  

E-print Network

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

Zh. S. Gevorkian; Chin-Kun Hu

2010-10-11

410

Size, structure and dynamics of “large” bubbles in a two-dimensional slurry bubble column  

Microsoft Academic Search

This paper reports preliminary results of a study on the hydrodynamics of a two-dimensional slurry bubble column. Experiments have been carried out with air\\/paraffin oil slurries with solids concentrations of 0, 28.3 and 38.6 vol% of porous silica particles (mean diameter of 38 ?m). Bubble sizes, bubble coalescence and bubble break-up rates were determined by video image analysis. Increasing slurry

J. W. A. De Swart; R. E. van Vliet; R. Krishna

1996-01-01

411

Moon Rise - Duration: 67 seconds.  

NASA Video Gallery

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

412

Workplace Suicides on The Rise  

MedlinePLUS

... features on this page, please enable JavaScript. Workplace Suicides on the Rise, Study Finds Police officers, firefighters ... March 17, 2015 Related MedlinePlus Pages Occupational Health Suicide TUESDAY, March 17, 2015 (HealthDay News) -- Workplace suicides ...

413

Rising Food Prices: Who's Responsible?  

ERIC Educational Resources Information Center

Rise in food prices can be partially attributed to the high food consumption level throughout Europe and North America, coupled with failure to evolve systems for more production of cattle, soybeans, and fisheries at lower cost. (PS)

Brown, Lester R.

1973-01-01

414

Bubbly wake: the role of the propeller  

NASA Astrophysics Data System (ADS)

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

Caille, Francois

2005-11-01

415

Instability and Subsequent Evolution of Electroweak Bubbles  

E-print Network

Bubbles in a first-order electroweak phase transition are nucleated with radii $R_0$ and expand with velocity $v$. If $v$ is subsonic, a bubble becomes unstable to non-spherical perturbations when its radius is roughly $10^4\\, R_0$. These perturbations accelerate the transition, and the effective velocity of bubble growth rapidly becomes supersonic. The transition should subsequently proceed spherically via detonation. If for some reason the onset of detonation is postponed, the surface area of the bubbles may be enhanced by $10^5$. We discuss consequences for electroweak baryogenesis.

Marc Kamionkowski; Katherine Freese

1992-08-04

416

MF and HF ducting within equatorial bubbles  

NASA Astrophysics Data System (ADS)

MF and HF conjugate ducting is often observed while satellite sounders are within equatorial bubbles. This paper examines two possible forms of this propagation. The first is guiding by the bubble itself, the second is ducting along irregularities of small cross-section embedded in the bubble. One bubble model, based on observations by Dyson and Benson (1978) gives some results at variance with observation. Nevertheless, it is considered that slight changes to the model, such as asymmetries between the conjugate ionospheres, should remove the discrepancies. The results show that both forms of propagation probably occur.

Platt, I. G.; Dyson, P. L.

1989-10-01

417

The universe out of a breathing bubble  

E-print Network

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

Eduardo I. Guendelman; Nobuyuki Sakai

2008-04-14

418

Dynamics of Vapour Bubbles in Nucleate Boiling. 1; Basic Equations of Bubble Evolution  

NASA Technical Reports Server (NTRS)

We consider the behaviour of a vapour bubble formed at a nucleation site on a heated horizontal wall. There is no forced convection of an ambient liquid, and the bubble is presumably separated from the wall by a thin liquid microlayer. The energy conservation law results in a variational equation for the mechanical energy of the whole system consisting of the bubble and liquid. It leads to a set of two strongly nonlinear equations which govern bubble expansion and motion of its centre of mass. A supplementary equation to find out the vapour temperature follows from consideration of heat transfer to the bubble, both from the bulk of surrounding liquid and through the microlayer. The average thickness of the microlayer is shown to increase monotonously with time as the bubble meniscus spreads along the wall. Bubble expansion is driven by the pressure head between vapour inside and liquid far away from the bubble, with due allowance for surface tension and gravity effects. It is resisted by inertia of liquid being placed into motion as the bubble grows. The inertia originates also a force that presses the bubble to the wall. This force is counteracted by the buoyancy and an effective surface tension force that tends to transform the bubble into a sphere. The analysis brings about quite a new formulation of the familiar problem of bubble growth and detachment under conditions of nucleate pool boiling.

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

1995-01-01

419

21 CFR 870.4205 - Cardiopulmonary bypass bubble detector.  

Code of Federal Regulations, 2010 CFR

...false Cardiopulmonary bypass bubble detector. 870.4205 Section 870.4205...4205 Cardiopulmonary bypass bubble detector. (a) Identification. A cardiopulmonary bypass bubble detector is a device used to detect...

2010-04-01

420

Fluid mechanics of bubble capture by the diving bell spider  

E-print Network

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

Brooks, Alice (Alice P.)

2010-01-01

421

Colorful Demos with a Long-Lasting Soap Bubble.  

ERIC Educational Resources Information Center

Describes several demonstrations that feature interaction of light with soap bubbles. Includes directions about how to produce a long-lasting stationary soap bubble with an easily changeable size and describes the interaction of white light with the bubble. (DDR)

Behroozi, F.; Olson, D. W.

1994-01-01

422

BUBBLY: a method for detecting and characterizing interstellar bubbles using Fabry-Perot spectroscopy  

NASA Astrophysics Data System (ADS)

We present a new method for the detection and characterization of expansion in galaxy discs based on H? Fabry-Perot spectroscopy, taking advantage of the high spatial and velocity resolution of our instrument (GH?FaS). The method analyses multipeaked emission line profiles to find expansion along the line of sight on a point-by-point basis. At this stage we have centred our attention on the large-scale structures of expanding gas associated with H II regions which show a characteristic pattern of expansion velocities, of the order of 100 km s-1, as a result of both bubble shape and projection effects. We show an example of the expansion map obtained with our method from a superbubble detected in the Antennae galaxies. We use the information obtained from the method to measure the relevant physical parameters of the superbubbles, including their ages which can be used to date young star clusters.

Camps-Fariña, A.; Zaragoza-Cardiel, J.; Beckman, J. E.; Font, J.; García-Lorenzo, B.; Erroz-Ferrer, S.; Amram, P.

2015-03-01

423

Optical nucleation of bubble clouds in a high pressure spherical resonator.  

PubMed

An experimental setup for nucleating clouds of bubbles in a high-pressure spherical resonator is described. Using nanosecond laser pulses and multiple phase gratings, bubble clouds are optically nucleated in an acoustic field. Dynamics of the clouds are captured using a high-speed CCD camera. The images reveal cloud nucleation, growth, and collapse and the resulting emission of radially expanding shockwaves. These shockwaves are reflected at the interior surface of the resonator and then reconverge to the center of the resonator. As the shocks reconverge upon the center of the resonator, they renucleate and grow the bubble cloud. This process is repeated over many acoustic cycles and with each successive shock reconvergence, the bubble cloud becomes more organized and centralized so that subsequent collapses give rise to stronger, better defined shockwaves. After many acoustic cycles individual bubbles cannot be distinguished and the cloud is then referred to as a cluster. Sustainability of the process is ultimately limited by the detuning of the acoustic field inside the resonator. The nucleation parameter space is studied in terms of laser firing phase, laser energy, and acoustic power used. PMID:22088012

Anderson, Phillip; Sampathkumar, A; Murray, Todd W; Gaitan, D Felipe; Glynn Holt, R

2011-11-01

424

Is the Local Bubble dead?  

E-print Network

We give a summary of the current state of Local Bubble research, resulting from the discussions of a dedicated panel meeting. After more than 25 years of intense observational and theoretical work, we are still far from a coherent picture, although a probable one emerges at the horizon. A multi-supernova origin seems to be the best guess, with non-equilibrium cooling and soft X-ray emission accompanying its expansion. In addition our vantage point may force us to accept a substantial but quantitatively unknown contribution from heliospheric emission.

Dieter Breitschwerdt; Donald P. Cox

2004-01-21

425

Biosynthesis within a bubble architecture  

NASA Astrophysics Data System (ADS)

Sub-cellular compartmentalization is critical to life; it minimizes diffusion effects and enables locally high concentrations of biochemicals for improved reaction kinetics. We demonstrate an example of in vitro biochemical synthesis inside the water channels of foam using engineered artificial organelles (bacteriorhodopsin and F0F1-ATP synthase reconstituted polymer vesicles) as functional units to produce ATP. These results show that the interstitial space of bubbles serves as a metaphor for sub-cellular structure, providing a new platform for both investigating cellular metabolism and the engineering of biofunctional materials and systems.

Choi, Hyo-Jick; Montemagno, Carlo D.

2006-05-01

426

Problem Solving: Bubble Gum Contest  

NSDL National Science Digital Library

This professional development video clip presents students engaged in The Common Core Practice Standard #1—Make sense of problems and persevere in solving them. The learners gather data for a bubble gum contest, as part of a larger activity involving recording data and writing up results. Students understand the problem and persevere with the task as they independently go to other classrooms to conduct their survey. Additional resources include a video transcript, teaching tips, and a link to a professional development reflection activity based upon the video.

WGHB Boston

2013-01-01

427

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

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

428

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

NASA Astrophysics Data System (ADS)

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

Bull, Geoffrey R.

429

The dynamics, structure and signatures of magnetic bubbles in the outer heliosphere  

NASA Astrophysics Data System (ADS)

The sectored magnetic field due to the flapping of the heliospheric current sheet compresses across the termination shock and may reconnect in the heliosheath, driving the anomalous cosmic rays and producing a sea of elongated magnetic bubbles. A number of Voyager observations are consistent with the bubble picture of the heliosheath, including flow enhancements, magnetic field compressions and strongly-altered transport properties. We are exploring the 3-D structure and dynamics of magnetic bubbles with PIC simulations to understand the associated particle acceleration and how the resulting complex magnetic field will impact the transport of energetic particles, including galactic cosmic rays. We find that magnetic bubbles form as fully 3-D rather than 2-D objects. In spite of the 3-D nature of the reconnection process, particle acceleration does not appear to be significantly changed from earlier results in 2-D. The characteristic signatures of magnetic bubbles are being identified for comparison with the magnetic field data from Voyager. Intriguing Voyager 2 magnetic field observations of brief negative polarity excursions during a nominally positive unipolar period 2009.6-2010.3 are being studied as possible evidence that magnetic bubbles from reconnection in the sector zone are being ejected into the nominally unipolar region in a manner analogous to spray from a water/air interface.

Drake, J. F.; Opher, M.; Swisdak, M. M.; Schoeffler, K. M.

2011-12-01

430

Observing Nitrogen Bubbles in Liquid Zinc in a Vertical Hele-Shaw Cell  

NASA Astrophysics Data System (ADS)

Observations of gas bubbles in liquid metal are strongly hindered by the opacity of metals. To circumvent this limitation, the authors recently proposed to study such systems under quasi-2D flow conditions in a Hele-Shaw cell. The current paper presents a successful application of this approach for nitrogen bubbles in liquid zinc at 973 K (700 °C) in a fused quartz cell with a thickness of 1.5 mm. At low oxygen levels, the cell walls are not wetted by the liquid zinc, and bubbles can be observed directly through the transparent cell walls. Furthermore, using a moving high-speed camera that travels upwards with the bubbles, their properties are quantified in detail along the entire trajectory. In the range of equivalent diameters between 5.9 and 9.0 mm, this reveals a single periodic flow regime in which bubbles follow a sinusoidal path with a characteristic frequency of 3.31 Hz. In addition, systematic intermediate accelerations are observed of which the origin remains unexplained. Considering the unprecedented resolution of such observations for bubbles in liquid metals, especially at high temperatures, it is expected that this approach will contribute to a better understanding of the mechanisms that govern gas injection in pyrometallurgy.

Klaasen, Bart; Verhaeghe, Frederik; Blanpain, Bart; Fransaer, Jan

2015-01-01

431

Mechanism of single-bubble sonoluminescence  

Microsoft Academic Search

The mechanism of the light emission of single-bubble sonoluminescence (SBSL) is studied theoretically based on the quasiadiabatic compression model. It is concluded that SBSL is not the blackbody radiation but the thermal radiation. It is clarified that the shape of the spectrum is determined by the temperature inside the bubble and the intensity is determined by the rates of the

Kyuichi Yasui

1999-01-01

432

Computed optical emissions from a sonoluminescing bubble  

Microsoft Academic Search

A sonoluminescing bubble has been modeled as a thermally conducting, partially ionized plasma. The model is more complete than previous models, due to the inclusion of both plasma and normal molecular thermal conduction, vapor pressure, surface tension, the mixing of gas and water vapor in the bubble, and opacities. The model accounts for most of the observed experimental trends, including

William C. Moss; David A. Young; Judith A. Harte; Joanne L. Levatin; Balazs F. Rozsnyai; George B. Zimmerman; I. Harold Zimmerman

1999-01-01

433

Drops and Bubble in Materials Science  

NASA Astrophysics Data System (ADS)

The formation of extended p-n junctions in semiconductors by drop migration, mechanisms and morphologies of migrating drops and bubbles in solids and nucleation and corrections to the Volmer-Weber equations are discussed. Bubble shrinkage in the processing of glass, the formation of glass microshells as laser-fusion targets, and radiation-induced voids in nuclear reactors were examined.

Doremus, R. H.

1982-03-01

434

Drops and Bubble in Materials Science  

NASA Technical Reports Server (NTRS)

The formation of extended p-n junctions in semiconductors by drop migration, mechanisms and morphologies of migrating drops and bubbles in solids and nucleation and corrections to the Volmer-Weber equations are discussed. Bubble shrinkage in the processing of glass, the formation of glass microshells as laser-fusion targets, and radiation-induced voids in nuclear reactors were examined.

Doremus, R. H.

1982-01-01

435

Continuous-data FIFO bubble shift register  

NASA Technical Reports Server (NTRS)

Simple loop first-in-first-out (FIFO) bubble memory shift register has continuous storage capability. Bubble shift register simplifies chip-control electronics by enabling all control functions to be alined at same bit. FIFO shift register is constructed from passive replicator and annihilator combinations.

Chen, T. T.

1977-01-01

436

The Minnaert Bubble: An Acoustic Approach  

ERIC Educational Resources Information Center

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

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

2008-01-01

437

The Physics of Foams, Droplets and Bubbles  

ERIC Educational Resources Information Center

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

Sarker, Dipak K.

2013-01-01

438

Measuring the surface tension of soap bubbles  

NASA Technical Reports Server (NTRS)

The objectives are for students to gain an understanding of surface tension, to see that pressure inside a small bubble is larger than that inside a large bubble. These concepts can be used to explain the behavior of liquid foams as well as precipitate coarsening and grain growth. Equipment, supplies, and procedures are explained.

Sorensen, Carl D.

1992-01-01

439

Oscillating plasma bubbles. II. Pulsed experiments  

SciTech Connect

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

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

2012-08-15

440