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1

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

SciTech Connect

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

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

1999-10-01

2

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

Microsoft Academic Search

About five centuries ago, Leonardo da Vinci described the sinuous motion of gas bubbles rising in water. We have attempted to simulate the rise trajectories of bubbles of 4, 5, 7, 8, 9, 12 and 20 mm in diameter rising in a 2D rectangular column filled with water. The simulations were carried out using the volume-of-fluid (VOF) technique developed by

R. Krishna; J. M. van Baten

1999-01-01

3

Simulations of Rising Hydrodynamic and Magnetohydrodynamic Bubbles  

NASA Astrophysics Data System (ADS)

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

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

4

Significance of viscoelastic effects on the rising of a bubble and bubble-to-bubble interaction  

NASA Astrophysics Data System (ADS)

Numerical results for the rising of a bubble and the interaction between two bubbles in non-Newtonian fluids will be discussed. The computations are carried out using a multiscale method combining front-tracking with Brownian dynamics simulations. The evaluation of the material properties for the non-Newtonian fluid will be discussed firstly. The results from the computations of a single bubble show how elastic effects modify the deformation and rising of the bubble by pulling the tail of it. The relationship between the strength of the elastic forces and the discontinuity in the bubble terminal velocity, when plotted versus bubble volume, is also observed in the computations. The bubble-to-bubble interaction is dominated not only by elastic effects but also by the shear-thinning caused by the leading bubble, which leads the trailing bubble to accelerate faster and coalesce with the leading bubble.

Fernandez, Arturo

2011-11-01

5

Contemporary Mathematics Numerical Simulation of Gas Bubbles Rising in Viscous  

E-print Network

Contemporary Mathematics Numerical Simulation of Gas Bubbles Rising in Viscous Liquids at High- duced in the context of gas bubbles rising in viscous liquids, e.g. air bubbles rising in water. Key on a supercomputer. Finally, the use of a non-inertial, moving reference frame attached to the rising bubble

Lin, Ping

6

Liquid jet pumped by rising gas bubbles  

NASA Technical Reports Server (NTRS)

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

Hussain, N. A.; Siegel, R.

1975-01-01

7

Rising Jet-Inflated Bubbles in Clusters of Galaxies  

E-print Network

We conduct two-dimensional axisymmetric (referred to as 2.5D) hydrodynamical numerical simulations of bubble evolution in clusters of galaxies. We inflate bubbles using slow, massive jets with a wide opening angle, and follow their evolution as they rise through the intra-cluster medium (ICM). We find that these jet-inflated bubbles are quite stable, and can reach large distances in the cluster while still maintaining their basic structure. The stability of the jet-inflated bubble comes mainly from the dense shell that forms around it during it's inflation stage, and from the outward momentum of the bubble and the shell. On the contrary, bubbles that are inserted by hand onto the grid and not inflated by a jet, i.e., an artificial bubble, lack these stabilizing factors, therefore, they are rapidly destroyed. The stability of the jet-inflated bubble removes the demand for stabilizing magnetic fields in the bubble.

Assaf Sternberg; Noam Soker

2008-05-15

8

Modelling of bubble rising by smoothed particle hydrodynamics method  

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

9

Steady bubble rise and deformation in Newtonian and viscoplastic fluids and conditions for bubble entrapment  

Microsoft Academic Search

We examine the buoyancy-driven rise of a bubble in a Newtonian or a viscoplastic fluid assuming axial symmetry and steady flow. Bubble pressure and rise velocity are determined, respectively, by requiring that its volume remains constant and its centre of mass remains fixed at the centre of the coordinate system. The continuous constitutive model suggested by Papanastasiou is used to

J. Tsamopoulos; Y. Dimakopoulos; N. Chatzidai; G. Karapetsas; M. Pavlidis

2008-01-01

10

Correlation of bubble rise velocity and volume  

SciTech Connect

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

Burge, C.

1991-01-01

11

Correlation of bubble rise velocity and volume  

SciTech Connect

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

Burge, C.

1991-12-31

12

Analysis of bubble rise using the VOF method. 1: Isolated bubbles  

SciTech Connect

The motion of a gas bubble in an otherwise stationary liquid contained in a closed, right vertical cylinder is investigated using a modified Volume-of-Fluid (VOF) method incorporating surface tension stresses. Starting from a perfectly spherical bubble which is initially at rest, the upward motion of the bubble in a gravitational field is accurately determined by tracking the liquid-gas interface. The initial radius of the bubble is small compared to the cylinder radius so that the influence of the container walls on the bubble motion is negligible. The gas in the bubble can be treated as incompressible. The problem is simulated using primitive variables in a control-volume formulation in conjunction with the interpolation technique of Rhie and Chow (1983), to avoid oscillations in the pressure and velocity fields. The pressure-velocity coupling is based on the SIMPLE algorithm. The modified VOF method used in this study is able to identify and physically treat features such as bubble deformation, cuspformation, breakup and joining. Results in a two-dimensional as well as a three-dimensional coordinate framework are presented. The bubble deformation and its motion are characterized by the Reynolds number, the Bond number, the density ratio, the viscosity ratio, and the ratio of the cylinder radius to that of the initial bubble. The effects of these parameters on the bubble rise are discussed. Physical mechanisms for the computational results obtained are presented. The results agree with experiments reported in the literature.

Chen, L.; Leonardi, E. [Univ. of New South Wales, Sydney, New South Wales (Australia). School of Mechanical and Manufacturing Engineering; Reizes, J.A. [Univ. of Technology, Sydney, New South Wales (Australia); Garimella, S.V. [Univ. of Wisconsin, Milwaukee, WI (United States). Dept. of Mechanical Engineering

1996-12-31

13

The velocity of gas bubble rise in a tube  

NASA Astrophysics Data System (ADS)

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

Zudin, Yu. B.

2013-03-01

14

Steady bubble rise and deformation in Newtonian and viscoplastic fluids and conditions for bubble entrapment  

NASA Astrophysics Data System (ADS)

We examine the buoyancy-driven rise of a bubble in a Newtonian or a viscoplastic fluid assuming axial symmetry and steady flow. Bubble pressure and rise velocity are determined, respectively, by requiring that its volume remains constant and its centre of mass remains fixed at the centre of the coordinate system. The continuous constitutive model suggested by Papanastasiou is used to describe the viscoplastic behaviour of the material. The flow equations are solved numerically using the mixed finite-element/Galerkin method. The nodal points of the computational mesh are determined by solving a set of elliptic differential equations to follow the often large deformations of the bubble surface. The accuracy of solutions is ascertained by mesh refinement and predictions are in very good agreement with previous experimental and theoretical results for Newtonian fluids. We determine the bubble shape and velocity and the shape of the yield surfaces for a wide range of material properties, expressed in terms of the Bingham Bn=tau_y(*}/rho({*}g^{*)) R_b(*) Bond Bo =rho(*}g({*)) R_b({*) 2}/gamma(*) and Archimedes Ar=rho(*2}g({*)) R_b(*3}/mu_o({*2)) numbers, where *o the viscosity, *y the yield stress of the material, g* the gravitational acceleration and R*b the radius of a spherical bubble of the same volume. If the fluid is viscoplastic, the material will not be deforming outside a finite region around the bubble and, under certain conditions, it will not be deforming either behind it or around its equatorial plane in contact with the bubble. As Bn increases, the yield surfaces at the bubble equatorial plane and away from the bubble merge and the bubble becomes entrapped. When Bo is small and the bubble cannot deform from the spherical shape the critical Bn is 0.143, i.e. it is a factor of 3/2 higher than the critical Bn for the entrapment of a solid sphere in a Bingham fluid, in direct correspondence with the 3/2 higher terminal velocity of a bubble over that of a sphere under the same buoyancy force in Stokes flow. As Bo increases allowing the bubble to squeeze through the material more easily, the critical Bingham number increases as well, but eventually it reaches an asymptotic value. Ar affects the critical Bn value much less.

Tsamopoulos, J.; Dimakopoulos, Y.; Chatzidai, N.; Karapetsas, G.; Pavlidis, M.

15

Numerical Simulation of 3D Bubbles Rising in Viscous Liquids using a Front Tracking Method  

E-print Network

Numerical Simulation of 3D Bubbles Rising in Viscous Liquids using a Front Tracking Method Jinsong Simulation of 3D Bubbles Rising in Viscous Liquids using a Front Tracking Method Jinsong Hua a , Jan F, Singapore 117543 Abstract The rise of bubbles in viscous liquids is not only a very common process in many

Lin, Ping

16

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

E-print Network

Force measurements on rising bubbles Woodrow L. Shew, Sebastien Poncet, and Jean-Fran¸cois Pinton sized air bubbles rising through still water are investigated using precise ultrasound velocity deduce the forces on the bubble which give rise to planar zigzag and spiraling motion. I. BACKGROUND

Boyer, Edmond

17

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

Microsoft Academic Search

This investigation presents an experimental study of a system for which the bubble size is not monodisperse. In this work an experimental equipment was designed to study the behaviour of a bidisperse suspension of bubbles rising in a vertical channel, in which the dual limit of small Weber and large Reynolds number is satisfied. Bubbles were produced using capillaries of

J. C. Serrano-Garcia; R. Zenit

2008-01-01

18

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

Microsoft Academic Search

The present study aims at providing insight into the acceleration mechanism of a bubble chain rising in shear-thinning viscoelastic fluids. The experimental investigation by the Particle Image Velocimetry (PIV), birefringence visualisation and rheological simulation shows that two aspects are central to bubble interactions in such media: the stress creation by the passage of bubbles, and their relaxation due to the

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

2005-01-01

19

Radiation Characteristics of Glass Containing Gas Bubbles Laurent Pilon*  

E-print Network

Radiation Characteristics of Glass Containing Gas Bubbles Laurent Pilon* Mechanical and Aerospace, ceramics, and glass, gas bubbles can form in liquid and solid phases. The presence of such bubbles affects media containing large gas bubbles (bubble radius is much larger than the wavelength of radiation

Pilon, Laurent

20

Complex flow around a bubble rising in a non-Newtonian fluid.  

PubMed

Our experimental investigation by both particle image velocimetry and birefringence modulation method shows very complex flow features around a bubble rising in a non-Newtonian fluid. We model this two-phase flow by coupling the free-energy-based lattice Boltzmann scheme and the fluid rheology in the framework of the sixth-order Maxwell model with shear thinning effects. A Newtonian low viscosity drop is used to simulate the rising bubble. Numerical results including noticeably negative wake behind the bubble, stress field, as well as the bubble's teardrop shape are obtained, and compare satisfactorily with our experiments. PMID:15903576

Frank, Xavier; Li, Huai Z

2005-03-01

21

Origin of the negative wake behind a bubble rising in non-Newtonian fluids  

Microsoft Academic Search

The present work aims at understanding the behavior of individual bubbles in non-Newtonian fluids. By means of a Particle Image Velocimetry (PIV) device, the complete flow field around either a single non-spherical bubble rising in polyacrylamide (PAAm) solutions or a solid sphere settling down in the same fluids shows for the first time the similar coexistence of three distinct zones:

M. Kemiha; X. Frank; S. Poncin; H. Z. Li

2006-01-01

22

Forces on aligned rising spherical bubbles at low-to-moderate Reynolds number  

NASA Astrophysics Data System (ADS)

In this paper, the dynamic of a pair of equal-sized spherical gas bubbles rising in vertical line within a Newtonian liquid at low-to-moderate Reynolds numbers (Re ? 50) is studied. The dynamic momentum balance includes buoyancy, quasi-steady, and unsteady (history) drag, as well as inertial and added-mass body acceleration forces acting on the trailing bubble. This equation has been obtained under the following assumptions: (i) the bubble interaction occurs through the steady non-uniform wake induced by the leading bubble and (ii) the flow structure behind the leading bubble is known, so that proper expressions for the trailing bubble hydrodynamic force and its rising velocity can be derived. We propose an approximate analytical model for predicting the hydrodynamic force and the rise velocity of the trailing bubble. For this aim, we first use the well-known asymptotic far wake velocity solution (AWVS) for an axisymmetric body complementing it with an adequate drag expression. Then, the AWVS is modified via a Galilean transformation by introducing an artificial origin whose position is determined by fitting numerical data of known velocity profiles. Comparisons between the proposed models predictions with those reported experimental and numerical data for dimensionless distance between bubbles s/d in the interval 2 ? s/d ? 12.5 are presented. The results show that the added-mass body acceleration and the history forces are negligible compared to the other considered forces.

Ramírez-Muñoz, J.; Baz-Rodríguez, S.; Salinas-Rodríguez, E.; Castellanos-Sahagún, E.; Puebla, H.

2013-09-01

23

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

SciTech Connect

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

Chen, L.; Leonardi, E. [Univ. of New South Wales, Sydney, New South Wales (Australia). School of Mechanical and Manufacturing Engineering; Reizes, J.A. [Univ. of Technology, Sydney, New South Wales (Australia); Garimella, S.V. [Univ. of Wisconsin, Milwaukee, WI (United States). Dept. of Mechanical Engineering

1996-12-31

24

Trajectories of air bubbles rising in dense suspensions in a Hele-Shaw cell  

NASA Astrophysics Data System (ADS)

The motion of bubbles rising in a glass bead-water suspension is investigated experimentally. Observations have been conducted in a suspension confined between two vertical glass plates separated 3 mm. We report experimental results of the velocity and the path of air bubbles rising with various equivalent diameters in the range 1 to 4 mm and generation frequencies in the range 1 to 10 bubbles/s. The glass spheres in the suspension have diameters in the range 5 ? m to 100? m and are hollowed with an effective density of 1.05 g/cm^3. Suspension concentrations used are up to 55% by weight. Observations indicate that bubble trajectories for concentrations of 30% and higher are composed by the general ascending trend plus rapid zigzagging displacements superimposed to a relative slow horizontal oscillation. This dynamics contrasts with the almost rectilinear paths of bubbles of the same diameter rising in pure water. We have also observed that for low concentrations, the bubble rising velocity depends on the departing frequency at the bottom of the cell.

Sanchez, Ramon; Ramos, Eduardo

2005-11-01

25

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

26

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

PubMed

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

Interaction between Taylor bubbles rising in stagnant non-Newtonian fluids  

Microsoft Academic Search

The interaction between Taylor bubbles rising in stagnant non-Newtonian solutions was studied. Aqueous solutions of carboxymethylcellulose (CMC) and polyacrylamide (PAA) polymers were used to study the effect of different rheological properties: shear viscosity and viscoelasticity. The solutions studied covered a range of Reynolds numbers between 10 and 714, and Deborah numbers up to 14. The study was performed with pairs

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

2007-01-01

28

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

NASA Astrophysics Data System (ADS)

This investigation presents an experimental study of a system for which the bubble size is not monodisperse. In this work an experimental equipment was designed to study the behaviour of a bidisperse suspension of bubbles rising in a vertical channel, in which the dual limit of small Weber and large Reynolds number is satisfied. Bubbles were produced using capillaries of two distinct inner diameters. Using water and water-glycerin mixtures, the range of Reynolds numbers was extended from 50 to 500, approximately. To avoid coalescence, a small amount of salt was added to the interstitial fluid, which did not affect the fluid properties significantly. Measurements of the size, bubble velocity, aspect ratio as well the equivalent diameter of the bubbles were obtained as a function of gas volume fraction. We found that the bidisperse nature of the flow changes the dynamics in a significant manner. We observed a modification of the flow agitation, characterized by the liquid velocity variance. Although the decrease of the mean velocity with gas volume fraction is similar to that observed for monodisperse flows (Martínez et. al. 2007), a general increase of the magnitude of fluctuations is observed for certain combinations of bubble size and gas fraction ratios.

Serrano-Garcia, J. C.; Zenit, R.

2008-11-01

29

Heart-shaped bubbles rising in anisotropic liquids Chunfeng Zhou1, Pengtao Yue1,2, James J. Feng1,2 , Chun Liu3, Jie Shen4  

E-print Network

Heart-shaped bubbles rising in anisotropic liquids Chunfeng Zhou1, Pengtao Yue1,2, James J. Feng1-heart shape for bubbles rising in an anisotropic micellar solution. We explain the bubble shape by assuming that the micelles are aligned into a nematic phase, whose anchoring energy on the bubble competes

Shen, Jie

30

Direct calculation of bubble growth, departure, and rise in nucleate pool boiling  

Microsoft Academic Search

A mesh-free numerical method (MPS–MAFL) is presented for the analysis of gas–liquid two-phase flows. In this method, a particle method (MPS) is combined with a gridless method (MAFL) for an arbitrary-Lagrangian–Eulerian calculation. Gas–liquid two-phase flows are calculated directly by the present method with and without the phase change. As an isothermal flow, a gas bubble rising in viscous liquids is

Han Young Yoon; Seiichi Koshizuka; Yoshiaki Oka

2001-01-01

31

Bursting the Bubble of Doom and Adapting to Sea Level Rise Randall W. Parkinson, Ph.D., P.G.  

E-print Network

of Geological Sciences Florida State University Tallahassee, Florida Introduction Late Holocene sea level riseMarch 2010 Bursting the Bubble of Doom and Adapting to Sea Level Rise Randall W. Parkinson, Ph to adapt to sea level rise or for that matter any of the other elements of climate change. In light

Donoghue, Joseph

32

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

33

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.

34

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

PubMed Central

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

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

2009-01-01

35

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

NASA Astrophysics Data System (ADS)

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 bubbles coalescence is in reasonable agreement with experimental and numerical results obtained by other authors.

Merrouche, Djemai; Mohammedi, Kamal; Belaidi, Idir; Mabrouki, Bachir

2007-04-01

36

Three-dimensional ptv study of the surrounding flow and wake of a bubble rising in a stagnant liquid  

NASA Astrophysics Data System (ADS)

The particle tracking velocimetry measurement technique was used to measure the whole-volume, three-dimensional, transient velocity field generated by a single air bubble rising in stagnant water in a small diameter pipe. The three-dimensional flow field was reconstructed using a stereoscopic technique. Conditional averages of the velocity fields for the situations when the bubble rises at the center of the pipe, and close to the pipe wall, were determined. The turbulent motion generated in the continuous liquid phase for both situations was studied.

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

2000-12-01

37

Three-dimensional ptv study of the surrounding flow and wake of a bubble rising in a stagnant liquid  

NASA Astrophysics Data System (ADS)

The particle tracking velocimetry measurement technique was used to measure the whole-volume, three-dimensional, transient velocity field generated by a single air bubble rising in stagnant water in a small diameter pipe. The three-dimensional flow field was reconstructed using a stereoscopic technique. Conditional averages of the velocity fields for the situations when the bubble rises at the center of the pipe, and close to the pipe wall, were determined. The turbulent motion generated in the continuous liquid phase for both situations was studied.

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

38

Characteristics for 4Mb ion-implanted bubble memory modules  

Microsoft Academic Search

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

Y. Kato

1987-01-01

39

Propagation through nonlinear time-dependent bubble clouds and the estimation of bubble populations from measured acoustic characteristics  

Microsoft Academic Search

For several decades the propagation characteristics of acoustic pulses (attenuation and sound speed) have been inverted in attempts to measure the size distributions of gas bubbles in liquids. While this has biomedical and industrial applications, most notably it has been attempted in the ocean for defence and environmental purposes, where the bubbles are predominantly generated by breaking waves. Such inversions

T. G. Leighton; S. D. Meers; P. R. White

2004-01-01

40

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

41

Modeling of Taylor bubble rising in a vertical mini noncircular channel filled with a stagnant liquid  

E-print Network

by the interfacial curvature variations along bubble length, gravity, and viscous force. The interfacial profiles behavior of Taylor bubbles in circular tubes have been reported. Zukoski (1966) conducted an experimental investigation of the motion of long bubbles in a closed tube and clarified the influence of viscosity

Zhao, Tianshou

42

Bubbles  

NASA Astrophysics Data System (ADS)

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

Prosperetti, Andrea

2004-06-01

43

Volume-of-fluid (VOF) simulations of rise of single\\/multiple bubbles in sheared liquids  

Microsoft Academic Search

The understanding of the lift force, which governs the lateral migration of bubbles, is important to improve closures for continuum flow models that are used to simulate large-scale dispersed gas–liquid flows. In the present work, the effect of bubble size\\/shape and more importantly the effect of neighboring bubbles on the magnitude and direction of the lift force were investigated. The

Swapna S. Rabha; Vivek V. Buwa

2010-01-01

44

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

Microsoft Academic Search

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

C. Zhang; S. Eckert; G. Gerbeth

45

Effect of gas expansion on the velocity of individual Taylor bubbles rising in vertical columnswithwater:Experimentalstudiesatatmosphericpressureandundervacuum  

Microsoft Academic Search

This study was designed to determine the effect of gas expansion on the velocity of Taylor bubbles rising individually in a vertical column of water. This experimental study was conducted at atmospheric pressure or under vacuum (33.3 and 20.0kNm ?2 ) using three different acrylic columns with internal diameters of 0.022, 0.032, and 0.052m, and more than 4.0m high. A

L. M. T. Santos; Sena Esteves; M. N. Coelho Pinheiro

46

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

NASA Astrophysics Data System (ADS)

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

Ortiz-Villafuerte, Javier

47

Bubbles  

NASA Astrophysics Data System (ADS)

``Vanitas vanitatum et omnia vanitas": bubbles are emptiness, non-liquid, a tiny cloud shielding a mathematical singularity. Born from chance, a violent and brief life ending in the union with the (nearly) infinite. But a wealth of phenomena spring forth from this nothingness: underwater noise, sonoluminescence, boiling, many others. Ultimately, diffusive processes govern much of the physics, and the difference between the diffusivity of heat and dissolved gases in ordinary liquids holds the key to the striking differences between gas and vapor bubbles.

Prosperetti, Andrea

2002-11-01

48

Characteristics and solar activity dependence of equatorial plasma bubbles detected by the C/NOFS satellite  

NASA Astrophysics Data System (ADS)

Equatorial plasma bubbles are the primary disturbances in the night-time low-latitude ionosphere and cause significant radio scintillation. In this paper, we address the following outstanding problems: What is the threshold vertical plasma drift velocity necessary for the generation of plasma bubbles? How does the threshold plasma drift vary with longitude? How do the occurrence and characteristics of plasma bubbles depend on solar activity? We present observations of plasma bubbles by the C/NOFS satellite between solar minimum and solar maximum. During solar minimum, plasma bubbles often originate in the evening sector and become fully developed after midnight. The plasma flow inside the bubbles is always upward throughout the entire night time. A series of plasma bubbles merge and form broad plasma depletions over a very large longitudinal range (up to 3800 km) near dawn. During solar maximum, C/NOFS is often below the F peak, and this allows us to examine the early phase of irregularity formation. It is found that plasma bubbles are continuously generated near the sunset terminator over 12 hours and that the critical upward ion drift necessary for the generation of plasma bubbles determined from the C/NOFS measurements is 40-70 m/s. The plasma drift at the prereversal enhancement is large at the American-African longitudes but smaller at the Asian longitudes. Significant differences in the characteristics of plasma bubbles between solar minimum and solar maximum are identified. Large plasma bubbles occur in the midnight-dawn sector during solar minimum but in the evening sector during solar maximum. The lifetime of plasma bubbles is long (7 hours or longer) during solar minimum but is short (~3 hours) during solar maximum. The different behaviors of plasma bubbles between solar minimum and solar maximum are related to the F-peak height, the upward plasma drift, and the atmospheric profile that are controlled by solar activity.

Huang, C.; de la Beaujardiere, O.; Roddy, P.; Hunton, D.; Ballenthin, J.; Pfaff, R. F.; Hairston, M. R.

2012-12-01

49

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

50

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

51

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

52

Measurements of the fluctuating liquid velocity of a bidisperse suspension of bubbles rising in a vertical channel  

Microsoft Academic Search

Experiments were performed in a vertical channel to study the behaviour of a bidisperse suspension of bubbles. Bubbles were produced using capillaries of two distinct inner diameters. The capillaries are small enough to generate bubbles in the range of 1 to 6 mm in diameter. Using water and water-glycerin mixtures, the vertical component of the fluctuating liquid velocity was obtained

Juan Carlos Serrano; Santos Mendez; Roberto Zenit

2009-01-01

53

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

PubMed

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

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

2011-12-01

54

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

55

Stream function, flow separation and force equation for stagnation flow passing a small solid sphere touching a rising gas bubble  

Microsoft Academic Search

This paper considers an axisymmetric stagnation flow past a small solid sphere touching an air bubble, which is significantly larger than the particle but smaller than the capillary length so that the deformation can be neglected. The disturbed flow due to the presence of the particle at the bubble surface was modelled by considering an axisymmetric stagnation point flow about

Anh V. Nguyen; Geoffrey M. Evans

2003-01-01

56

Effect of gas expansion on the velocity of individual Taylor bubbles rising in vertical columns with water: Experimental studies at atmospheric pressure and under vacuum  

Microsoft Academic Search

This study was designed to determine the effect of gas expansion on the velocity of Taylor bubbles rising individually in a vertical column of water. This experimental study was conducted at atmospheric pressure or under vacuum (33.3 and 20.0kNm-2) using three different acrylic columns with internal diameters of 0.022, 0.032, and 0.052m, and more than 4.0m high. A non-intrusive optical

L. M. T. Santos; M. T. M. Sena Esteves; M. N. Coelho Pinheiro

2008-01-01

57

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

58

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

PubMed

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

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

1991-01-01

59

CONDENSED MATTER: STRUCTURE, THERMAL AND MECHANICAL PROPERTIES: Numerical investigation of the deformation mechanism of a bubble or a drop rising or falling in another fluid  

NASA Astrophysics Data System (ADS)

A numerical method for simulating the motion and deformation of an axisymmetric bubble or drop rising or falling in another infinite and initially stationary fluid is developed based on the volume of fluid (VOF) method in the frame of two incompressible and immiscible viscous fluids under the action of gravity, taking into consideration of surface tension effects. A comparison of the numerical results by this method with those by other works indicates the validity of the method. In the frame of inviscid and incompressible fluids without taking into consideration of surface tension effects, the mechanisms of the generation of the liquid jet and the transition from spherical shape to toroidal shape during the bubble or drop deformation, the increase of the ring diameter of the toroidal bubble or drop and the decrease of its cross-section area during its motion, and the effects of the density ratio of the two fluids on the deformation of the bubble or drop are analysed both theoretically and numerically.

Wang, Han; Zhang, Zhen-Yu; Yang, Yong-Ming; Hu, Yüe; Zhang, Hui-Sheng

2008-10-01

60

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

Microsoft Academic Search

Breaking waves on the ocean surface produce bubbles that, upon bursting, inject seawater constituents into the atmosphere. Nascent aerosols were generated by bubbling zero-air through flowing seawater within an RH-controlled chamber deployed at Bermuda and analyzed for major chemical and physical characteristics. The composition of feed seawater was representative of the surrounding ocean. Relative size distributions of inorganic aerosol constituents

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

2007-01-01

61

Measurements of the fluctuating liquid velocity of a bidisperse 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 bidisperse suspension of bubbles. Bubbles were produced using capillaries of two distinct inner diameters. The capillaries are small enough to generate bubbles in the range of 1 to 6 mm in diameter. Using water and water-glycerin mixtures, the vertical component of the fluctuating liquid velocity was obtained using a flying hot wire anemometer technique. The system is characterized by the dimensionless Reynolds and Weber numbers in the range of 22bubble concentration. We also found that the variance, normalized with the mean bubble velocity squared, Tf% =Uf^^'2/Ub^2, increased as the Reynolds number decreased. Bidisperse flows, in general, show larger values of fluctuation.

Serrano, Juan Carlos; Mendez, Santos; Zenit, Roberto

2009-11-01

62

Do Bubble Characteristics Affect Recanalization in Stroke Patients Treated with Microbubble-Enhanced Sonothrombolysis?  

Microsoft Academic Search

Administration of microbubbles (MB) may augment the effect of ultrasound-enhanced systemic thrombolysis in acute stroke. Bubble structural characteristics may influence the effect of MB on sonothrombolysis. We aimed to compare the effects of galactose-based air-filled MB (Levovist) and sulphur hexafluoride-filled MB (Sonovue) on recanalization and clinical outcome. One hundred thirty-eight i.v. recombinant tissue plasminogen activator-(tPA-) treated patients with middle cerebral

Marta Rubiera; Marc Ribo; Raquel Delgado-Mederos; Estevo Santamarina; Olga Maisterra; Pilar Delgado; Joan Montaner; José Alvarez-Sabín; Carlos A. Molina

2008-01-01

63

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)

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

64

Flow and heat transfer characteristics of laminar mixed convection of water with sub-millimeter bubbles in a vertical channel  

NASA Astrophysics Data System (ADS)

Laminar mixed-convection heat transfer is widely seen in compact heat exchangers. Injection of sub-millimeter bubbles is considered as one of the efficient techniques for enhancing laminar mixed-convection heat transfer for liquids. However, the effects of sub-millimeter-bubble injection on the laminar mixed-convection heat transfer are poorly understood. In this study, we experimentally investigate flow and heat transfer characteristics of the laminar mixed-convection of water with sub-millimeter bubbles in a vertical channel. The thermocouples and a PTV (Particle Tracking Velocimetry) technique are used for the temperature and velocity measurements, respectively. Tap water is used for working fluid and hydrogen bubbles generated by electrolysis of water are used as the sub-millimeter bubbles. The Reynolds number of the main flow ranges from 100 to 150. Our results show that the ratio of the heat transfer coefficient with sub-millimeter-bubble injection to that without injection decreases as the Reynolds number increases. It is found from the liquid velocity measurements that this decrease is mainly due to a decrease in the "bubble advection effect".

Kitagawa, A.; Kimura, K.; Endo, H.; Hagiwara, Y.

2009-02-01

65

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

NASA Astrophysics Data System (ADS)

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

Chen, Sining; He, Xuechao; Sun, Jinhua

2008-11-01

66

Bubble characteristics in a high-intensity gas\\/liquid contactor  

Microsoft Academic Search

Experimental studies on bubble sizes in a high-intensity gas\\/liquid contactor are described. The contactor utilizes cross flow of liquid at high velocities to generate small bubbles. The relatively limited previous literature on bubble formation in cross flow is first reviewed. Measurements using a video technique at the exit of a short version of the contactor and on a section of

B. Waldie; T. Johnston; W. K. Harris; C. Bell

1999-01-01

67

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

SciTech Connect

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

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

1987-01-01

68

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.

69

About possible mechanisms of influence of gas bubbles on characteristics of turbulent boundary layer  

Microsoft Academic Search

Two different mechanisms responsible for the were revealed impact of gas bubbl injected into a boundary layer on the shear\\u000a stress on the wetted surfaces. Both mechanisms exist due to extremely high sensitivity of bubbles even to very low pressure\\u000a gradients and due to a high value of the virtual mass and coefficient of viscous drag for bubbles. The first

L. I. Maltsev; A. G. Malyuga; B. G. Novikov

2006-01-01

70

Prediction of the bubble-hole size of a cap bubble in a bubble swarm  

Microsoft Academic Search

A phenomenological, semi-theoretical model is proposed for predicting the size or thickness of the bubble-depleted region, or ‘bubble hole’, in the frontal vicinity of a larg cap bubble rising through a swarm of otherwise uniformly dispersed small bubbles. The model lays its theoretical basis on the axial pressure distribution in the very front of the cap nose which modifies the

Katsumi Tsuchiya; Kazutomo Ohsaki

1997-01-01

71

Study on Flow Characteristics of Micro-Bubble Two-Phase Flow  

Microsoft Academic Search

Experimental study was carried out on micro-bubble containing bubbly two-phase flow in a circular pipe. Flow resistance in\\u000a a pipe reduces relative to single-phase flow, especially in the transient region from laminar to turbulent flow. Local velocity\\u000a profile shows increase of liquid velocity near the wall, and overall velocity profile is planarized with it. Visual observation\\u000a with high-speed imaging system

Zensaku Kawara; Hiromasa Yanagisawa; Tomoaki Kunugi; Akimi Serizawa

2007-01-01

72

Effects of hydrodynamics and Lagrangian transport on chemically reacting bubble flows  

Microsoft Academic Search

The objective of this study is to investigate the dynamics of flows occurring in the wakes of rising bubbles of different shapes and sizes. Different wake dynamics can result in qualitatively different mixing characteristics. In the case of fast gas–liquid reaction networks, reactions occur almost exclusively in the bubble wake. Thus, wake mixing can have a strong impact on the

Athanas Koynov; Johannes G. Khinast

2004-01-01

73

Comparative characteristics of strong shock and detonation waves in bubble media by an electrical wire explosion  

NASA Astrophysics Data System (ADS)

Strong shock and detonation waves in inert and chemically active bubble media, which are generated by a wire explosion initiated by a capacitor with a stored energy W_0 =12.3-1,600 J, is experimentally studied. The measurements are performed near the wire and far from the wire in a vertical shock tube 4.5 m long with a volume fraction of the gas in the medium ? _0 =1-4 %. It is shown that in inert bubble medium, a short intensely decaying shock wave (SW) with intense pressure oscillations is formed in the vicinity of wire explosion point; near the explosion point at ? _0 le 2 % the SW propagates with the velocity of sound in a liquid. In chemically active bubble medium, an unsteady detonation wave generated by a wire explosion is formed. The pressure amplitude and the velocity of this wave are greater and the length is smaller than those of SW in an inert bubble medium in the same range of explosion energy. It is found that in the interval of low energy explosion from {˜ }12 to 64 J, the formation of the bubble detonation wave occurs faster than that at high energies (3× 102-103 J).

Kochetkov, I. I.; Pinaev, A. V.

2013-03-01

74

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

75

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

NASA Astrophysics Data System (ADS)

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

Meng, M.; Peng, X. F.

2010-03-01

76

Large and small bubble interaction patterns in a bubble column  

Microsoft Academic Search

A visual analysis is made on the fate of a large (or “cap”) bubble injected into a swarm of otherwise uniformly dispersed small bubbles; experiments, covering gas holdups for the swarm bubbles as high as 6%, are conducted in a two-dimensional column to ensure the distinct appearance of a single cap throughout its rise in the swarm. Specific focus is

K. Tsuchiya; K. Ohsaki; K. Taguchi

1996-01-01

77

Unsteady forces on spherical bubbles  

Microsoft Academic Search

An experimental investigation of freely rising spherical bubbles through a quiescent liquid is presented. The objective of the experiments is to examine the validity of a recently proposed history force expression for clean, spherical bubbles at finite Reynolds number (Mei et al. 1994). Excellent agreement between the measured and predicted bubble trajectory is obtained when using the proposed history force

W. C. Park; J. F. Klausner; R. Mei

1995-01-01

78

Bubble convection within magma reservoirs  

NASA Astrophysics Data System (ADS)

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

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

2008-11-01

79

Period-adding route in sparkling bubbles  

Microsoft Academic Search

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

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

2005-01-01

80

Leverage bubble  

NASA Astrophysics Data System (ADS)

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

Yan, Wanfeng; Woodard, Ryan; Sornette, Didier

2012-01-01

81

A Study of the Optical Characteristics of the Suspended Particles in the Benthic Nepheloid Layer of the Scotian Rise  

Microsoft Academic Search

Light transmission profiles have been used to study the optical properties of the suspended particles which are characteristic of the area of the Scotian Rise in the North Atlantic Ocean. This area is typified by very strong bottom currents and a highly variable bedform morphology. A good correlation (r = 0.96) has been found between the suspended volume and the

Richard W. Spinrad; J. Ronald V. Zaneveld; James C. Kitchen

1983-01-01

82

Experimental investigations of the kinetico-energetic characteristics of a collapsing bubble produced by laser breakdown in viscous fluids  

Microsoft Academic Search

The collapse kinetics of bubbles produced in water, glycerin, and vaseline oil by focusing a single pulse of radiation from a ruby laser was investigated. The parameters of pulses of acoustic emission from the collapsing bubbles were recorded. It was found that about 90% of the energy stored in a bubble in water can be emitted in sound if collapse

V. S. Teslenko

1976-01-01

83

A single bubble path transition from spiral to zigzag in dilute surfactant solution  

Microsoft Academic Search

The surfactant effect on a single bubble motion is so important that it changes whole bubbly flow structures. One of the surfactant key effects is to decrease bubble rise velocity. This phenomenon is described as Marangoni effect which is quantitatively investigated by many experiments and numerical calculations of straight rising bubbles. Some other previous researches studied a bubble trajectory transition

Yoshiyuki Tagawa; Wataru Kawaguchi; Ami Funakubo; Shu Takagi; Yoichiro Matsumoto

2007-01-01

84

Mean velocity and turbulence characteristics of water flow in the bubble dispersion region induced by plunging water jet  

Microsoft Academic Search

Water was injected vertically downward through a straight circular pipe onto a water bath contained in a cylindrical vessel. Three types of bubble dispersion patterns were observed with respect to the distance from the pipe exit to the undisturbed bath surface. When the distance was short, small bubbles were generated at the bath surface and they dispersed in the whole

M. Iguchi; K. Okita; F. Yamamoto

1998-01-01

85

Possible applications of bubble acoustics in Nature  

Microsoft Academic Search

Gas bubbles are the most potent naturally-occurring entities that influence the acoustic environment in liquids. Upon entrainment under breaking waves, waterfalls, or rainfall over water, each bubble undergoes small amplitude decaying pulsations with a natural frequency that varies approximately inversely with the bubble radius, giving rise to the 'plink' of a dripping tap or the roar of a cataract. When

T. G. Leighton; D. C. Finfer

86

Compact bubble clusters in Newtonian and non-Newtonian liquids  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

87

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

88

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

89

Period-adding route in sparkling bubbles.  

PubMed

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

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

2005-09-01

90

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

91

In vitro air removal characteristics of two neonatal cardiopulmonary bypass systems: filtration may lead to fractionation of bubbles.  

PubMed

Introduction of gaseous microemboli (GME) into the arterial line of a pediatric cardiopulmonary bypass (CPB) circuit may lead to cognitive decline and adverse outcomes of the pediatric patient.Arterial filters are incorporated into CPB circuits as a safeguard for gross air and to reduce GME. Recently, arterial filters were integrated in two neonatal oxygenators to reduce volume and foreign surface area.In this study a clinical CPB scenario was simulated. The oxygenators, the corresponding venous reservoirs and the complete CPB circuits were compared regarding air removal and bubble size distribution after the introduction of an air bolus or GME.During a GME challenge, the Capiox FX05 oxygenator removed a significantly higher volume of GME than the QUADROX-i Neonatal oxygenator (97% vs. 86%). Detailed air removal characteristics showed that more GME in the range of 20-50 µm were leaving the devices than were entering. This phenomenon seems to be more present in the Capiox FX05. The circuits were also challenged with an air bolus. Each individual component tested removed 99.9%, which resulted in an air volume reduction of 99.99% by either complete CBP circuit.Overall, we conclude that both CPB systems were very adequate in removing GME and gross air. The air removal properties of both systems are considered safe and reliable.Detailed GME distribution data show that the Capiox FX05 showed more small GME (<50 µm) due to fractionation of larger GME when compared to the QUADROX-i Neonatal. We may conclude that filtration may lead to fractionation. PMID:25262633

Stehouwer, Marco C; Kelder, Johannes C; van Oeveren, Willem; de Vroege, Roel

2014-10-01

92

Bubble Puzzles  

NASA Astrophysics Data System (ADS)

Bubbles are fascinating. With their ubiquitous occurrence in a multitude of fluid systems bubbles occupy a very important place in contemporary science and technology. In many applications, bubble control is crucial. I will demonstrate that bubble nucleation at surfaces, which always has been associated with randomness, can be perfectly controlled both in space and time. This new technique allows to quantitatively study bubble-bubble and bubble-surface interaction and reveals a shielding effect in bubble clusters [1]. -- In a second example for the importance of bubble control I will discuss their disturbing effect in piezo-acoustic ink-jet printing: I will show how bubbles are entrained, grow by rectified diffusion, and finally seriously disturb the jetting process by counteracting the pressure build-up at the nozzle [2]. [1] N. Bremond, M. Arora, C. D. Ohl, and D. Lohse, Phys. Rev. Lett. 96, 224501 (2006). [2] J. de Jong, H. Reinten, M. van den Berg, H. Wijshoff, M. Versluis, G. de Bruin, and D. Lohse, J. Acoust. Soc. Am., (August 2006).

Lohse, Detlef

2006-11-01

93

Bubble-wall interactions in a vertical gas–liquid flow: Bouncing, sliding and bubble deformations  

Microsoft Academic Search

The paper presents the results of a study on the motion of single (individual) bubbles rising in upward shear liquid flow in the vicinity of a vertical wall. Bubbles were found to slide along the wall when their diameter is small. Bubbles could also experience multiple collisions with the wall at certain experimental parameters (geometry of a channel, range of

Alexander Zaruba; Dirk Lucas; Horst-Michael Prasser; Thomas Höhne

2007-01-01

94

Low-Reynolds-number gravity-driven migration and deformation of bubbles near a free surface  

E-print Network

Low-Reynolds-number gravity-driven migration and deformation of bubbles near a free surface Franck 6 September 2011) We investigate numerically the axisymmetric migration of bubbles toward a free the bubble(s) deformation and film drainage; it is benchmarked against several tests. The rise of one bubble

Boyer, Edmond

95

Bubble Baryogenesis  

E-print Network

We propose an alternative mechanism of baryogenesis in which a scalar baryon undergoes a percolating first-order phase transition in the early Universe. The potential barrier that divides the phases contains explicit B and CP violation and the corresponding instanton that mediates decay is therefore asymmetric. The nucleation and growth of these asymmetric bubbles dynamically generates baryons, which thermalize after percolation; bubble collision dynamics can also add to the asymmetry yield. We present an explicit toy model that undergoes bubble baryogenesis, and numerically study the evolution of the baryon asymmetry through bubble nucleation and growth, bubble collisions, and washout. We discuss more realistic constructions, in which the scalar baryon and its potential arise amongst the color-breaking minima of the MSSM, or in the supersymmetric neutrino seesaw mechanism. Phenomenological consequences, such as gravitational waves, and possible applications to asymmetric dark-matter generation are also discussed.

Clifford Cheung; Alex Dahlen; Gilly Elor

2012-05-15

96

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

97

Bubbles and Wormholes: Analytic Models  

E-print Network

The first junction conditions of spherically symmetric bubbles are solved for some cases, and whereby analytic models to the Einstein field equations are constructed. The effects of bubbles on the spacetime structure are studied and it is found that in some cases bubbles can close the spatial sector of the spacetime and turn it into a compact one, while in other cases they can give rise to wormholes. One of the most remarkable features of these wormholes is that they do not necessarily violate the weak and dominant energy condition even at the classical level.

Anzhong Wang; Patricio S. Letelier

1995-05-31

98

Exploring Bubbles  

NASA Astrophysics Data System (ADS)

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

O'Geary, Melissa A.

99

Interaction mechanism of double bubbles in hydrodynamic cavitation  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

100

Analysis of the behavior of bubbles and droplets in isotropic turbulence  

NASA Astrophysics Data System (ADS)

The behavior and scale-dependent dispersion of small air bubbles, and the rise of slightly buoyant oil droplets in water under isotropic turbulence conditions, are analyzed computationally. The flow field is simulated using a pseudo-spectral code, while the bubble dynamics are analyzed by integration of a Lagrangian equation of motion with buoyancy, virtual mass, pressure, drag and lift forces. Consistent with experimental data, bubble rise velocities are increasingly suppressed with increasing turbulence intensity. The role of the lift force in moving the bubbles to the down-flow side of turbulent eddies, and consequently retarding their rise, is observed. Analysis also reveals that the vertical bubble velocities are characterized by asymmetric probability density functions that are positive or negative-skewed dependent upon the non-dimensional turbulence intensity and the Taylor length scale. Lagrangian bubble trajectories are used to determine dispersion characteristics, following the theoretical development of Cushman and Moroni (2001). The dispersion of 40 mum bubbles exhibits transition to Fickian behavior, and the process is weakly affected by the turbulence level for the entire range considered. Larger, 400 mum bubbles are shown to be more sensitive to turbulence level, with transition to Fickian behavior delayed in low turbulence fields. Computations are also performed to investigate the puzzling behavior observed by Friedman and Katz (2002), that the rise velocity of slightly buoyant droplets smaller than 800 mum in diameter is enhanced by turbulence whereas the rise of larger droplets is retarded. Using the quasi-steady, empirically-determined drag and lift coefficients, the observed experimental behavior could not be reproduced. Further, analysis of the effect of lift and history forces also indicates that, within a broad range of uncertainty, these forces do not account for the experimentally observed mean droplet rise. Guided by correlations obtained for the settling of heavy particles under high turbulence intensities, suppression of the drag and virtual mass coefficients for droplet diameters smaller than ten times the Kolmogorov lengthscale was postulated, with enhancement of the drag coefficient postulated for larger droplet diameters. Based on these postulates, the model is able to recover the observed preferential enhancement and retardation of the mean rise of small droplets.

Snyder, Murray R.

101

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

102

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

103

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

104

The sedimentological and geotechnical characteristics of the lower continental slope and rise of the Mississippi Fan fold belt  

E-print Network

salt diapir, exposed at the seafloor, with over 400 meters relief above the flat-lying Gulf bottom. The dome is seaward of the Sigsbee Escarpment. Sediment evacuation scars, gullies, shattered and deformed sediment masses, vent-like dewatering... the entire Upper Continental Rise within the study area. Watkins and Kraft (1978) present that relief features, turbidity flows, squeezing and diapiric action, gas vents, and salt domes are some of the natural forces that might cause seafloor instability...

Ramazanova, Rahila

2012-06-07

105

Bubble - Crystal Interactions in Magmatic Three-Phase Systems  

NASA Astrophysics Data System (ADS)

The influence of crystals on the movement of bubbles through basaltic magmas is poorly understood. We study the interaction of bubbles with a suspension of crystals in a viscous fluid through analog experiments. In our experiments, an air bubble rises through a suspension of plastic beads in a viscous corn syrup - water mixture; we vary bubble volumes, crystal spacings and fluid viscosities. We observe the following change in interaction styles with increasing bubble volume: (1) bubble migration through the crystal network with little bubble deformation, (2) bubble movement through the crystal network with deformation (and sometimes bubble splitting), and (3) displacement of the liquid-crystal mixture by the rising bubble. Interactions change from type (1) to (2) when the bubble is approximately the same size as the crystals forming the network. Transition to type (3) behavior depends on both bubble volume and the thickness of the crystal-liquid layer. In all cases, bubble rise is impeded by the presence of crystals. Preliminary results suggest that impedance is most pronounced for bubbles slightly larger than the crystals (a condition that promotes the maximum bubble deformation). Additionally, very small bubbles may be trapped for long times in the crystal network, suggesting that a shallow reservoir of crystal-rich magma may actually trap rising bubbles from below. These observations provide an alternative interpretation to that of small undeformed bubbles representing late-stage bubble nucleation and large irregularly shaped bubbles forming by coalescence of smaller bubbles (e.g. Lautze and Houghton, 2006). Furthermore, we observe in our experiments that large bubbles can spread out and move laterally underneath a crystal layer. This is not usually considered in models of bubble migration and may explain focusing of gas escape from magma reservoirs and volcanic vents. We apply our experimental results to analysis of bubble populations at Stromboli volcano, Italy, where gases rising from a deep crystal-poor magma reservoir travel through, and entrain, shallow crystal-rich magma. Preliminary results from image analysis on SEM and optical microscope images suggest that the smallest bubbles are most abundant and that their sizes are within the modal size range of the crystals. This can mean that (i) smaller bubbles were initially more abundant or (ii) bigger bubbles have deformed and split into smaller bubbles, which would confirm our conclusion from the analog experiments that interactions change from type (1) to (2) when the bubbles reach the size of the crystals in the network. In addition, the abundance of crystal-size bubbles in these samples suggests relative accumulation, possibly through trapping or extreme impedance, of the bubbles within the crystal-rich layer. Combined with our observation (from the analog experiments) that most bubbles are indeed significantly slowed within the crystal layer, this could suggest that bubble number densities are not direct reflections of bubble nucleation rates.

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

2007-12-01

106

Slowing down bubbles with sound  

NASA Astrophysics Data System (ADS)

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 even for moderate acoustic pressure. 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. We render the bubble's oscillations and translational movements using high speed video. We show that radial oscillations (Rayleigh-Plesset type) have no effect on the mean velocity, while above a critical pressure, a parametric type instability (Faraday waves) is triggered and gives rise to nonlinear surface oscillations. We evidence that these surface waves are subharmonic and responsible for the bubble's drag increase. When the acoustic intensity is increased, Faraday modes interact and the strongly nonlinear oscillations behave randomly, leading to a random behavior of the bubble's trajectory and consequently to a higher slow down. Our observations may suggest new strategies for bubbly flow control, or two-phase microfluidic devices. It might also be applicable to other elastic objects, such as globules, cells or vesicles, for medical applications such as elasticity-based sorting.

Poulain, Cedric; Dangla, Remie; Guinard, Marion

2009-11-01

107

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

SciTech Connect

Inverted annular flow can be visualized as a liquid jet-like core surrounded by a vapor annulus. While many analytical and experimental studies of heat transfer in this regime have been performed, there is very little understanding of the basic hydrodynamics of the post-CHF flow field. However, a recent experimental study was done that was able to successfully investigate the effects of various steady-state inlet flow parameters on the post-CHF hydrodynamics of the film boiling of a single phase liquid jet. This study was carried out by means of a visual photographic analysis of an idealized single phase core inverted annular flow initial geometry (single phase liquid jet core surrounded by a coaxial annulus of gas). In order to extend this study, a subsequent flow visualization of an idealized two-phase core inverted annular flow geometry (two-phase central jet core, surrounded by a coaxial annulus of gas) was carried out. The objective of this second experimental study was to investigate the effect of steady-state inlet, pre-CHF two-phase jet core parameters on the hydrodynamics of the post-CHF flow field. In actual film boiling situations, two-phase flows with net positive qualities at the CHF point are encountered. Thus, the focus of the present experimental study was on the inverted bubbly, slug, and annular flow fields in the post dryout film boiling region. Observed post dryout hydrodynamic behavior is reported. A correlation for the axial extent of the transition flow pattern between inverted annular and dispersed droplet flow (the agitated regime) is developed. It is shown to depend strongly on inlet jet core parameters and jet void fraction at the dryout point. 45 refs., 9 figs., 4 tabs.

Ishii, M.; Denten, J.P.

1988-01-01

108

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

109

Experimental study on turbulent natural convection heat transfer in water with sub-millimeter-bubble injection  

NASA Astrophysics Data System (ADS)

Using thermocouples and a particle tracking velocimetry technique, temperature and velocity measurements are conducted to investigate flow and heat transfer characteristics of turbulent natural convection from a vertical heated plate in water with sub-millimeter-bubble injection. Hydrogen-bubbles generated by the electrolysis of water are used as the sub-millimeter-bubbles. In the turbulent region, the heat transfer deterioration occurs for a bubble flow rate Q = 33 mm3/s, while the heat transfer enhancement occurs for Q = 56 mm3/s. Temperature and velocity measurements suggest that the former is caused by a delay of the transition due to the bubble-induced upward flow. On the other hand, the latter is mainly due to two factors: one is the enhancement of the rotation of eddies in the outer layer, and the other is the increase in the gradient of the streamwise liquid velocity at the heated wall. These are caused by bubbles, which are located in the inner layer, rising at high speed.

Kitagawa, Atsuhide; Kitada, Kenji; Hagiwara, Yoshimichi

2010-09-01

110

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

111

Champagne experiences various rhythmical bubbling regimes in a flute.  

PubMed

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

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

2006-09-20

112

Dynamics of Bubble Ascent in Mud Volcanoes  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

113

Turbulent flow characteristics and bedload sediment transport during the rising limb of hydrographs in a gravel-bed river  

NASA Astrophysics Data System (ADS)

The relationships between flow turbulence and bedload sediment transport in rivers remain poorly understood. This is partly explained by the difficulties of collecting flow and bedload sediment transport measurements simultaneously at a temporal scale that is compatible with turbulence during floods when sediment transport occurs. This study reports on the scales of turbulent coherent flow structures at a range of discharges and on the effects of flow changes on bedload transport variables in a gravel-bed creek. The links between turbulence and bedload transport are also examined. The experiments were conducted at Béard creek (Québec, Canada) and are based on the measurements at high temporal resolution of bedload transport rates using a loadcell in a pit trap and of the near-bed streamwise (U) and vertical (W) flow velocity components using an electromagnetic current meter (ECM). Sampling during high flows was done from a temporary bridge over the 6.8 m wide creek and the sediments were collected with a trap installed in the thalweg immediately downstream from the bridge. The vertical array of four ECMs was placed 13 cm upstream from the trap. Velocity and bedload data were recorded at 10 Hz with the same data logger to ensure the simultaneity of measurements. Data were collected on the rising limb of the hydrograph during a small (1.5 m3.s-1) and a large (5.5 m3.s-1) flood. The analysis rests on the detection of individual bedload transport events and of the properties of the mean and macroturbulent components of the flow. The detection of individual bedload transport event was based on an algorithm developed from the insertion of known bed material quantities in the trap. Frequency distributions of the mean sediment transport rate, duration of sediment transport events and of the waiting time between consecutive events are strongly right skewed and are generally well represented by Gamma distributions. The shape of the frequency distributions of the mean transport rate and the duration of transport events flattens as discharge increases while it narrows for the waiting time between successive events. Sediment transport intermittency reduces for the largest flood as the ratio of mean event duration over total time changed from 5% to 25%. We also observed an increase of the pressure on the bed through the increase of the Reynolds normal (-?, -?) and shear stresses (-?) and a reduction in the duration of macroturbulent events with an increase in discharge. Strong longitudinal and vertical instantaneous flow acceleration plays a role in the displacement of sediment particles. These results support recent observations on the role of flow acceleration on bedload sediment transport.

Roy, A.; Chaput-Desrochers, L.

2013-12-01

114

Collapse of cavitation bubbles in blood  

NASA Astrophysics Data System (ADS)

The behaviour of a single bubble in blood and in water is studied by using a non-Newtonian model of spherical bubble dynamics. This model considers the compressibility of the liquid surrounding the bubble, the shear-thinning characteristic of liquid viscosity, liquid density and surface tension. It was found that, for values of the maximum bubble radius larger than 10-1 mm, the collapse of a bubble in a constant pressure field in blood is more violent than in water. It suggests that the amount of collateral damage of the biological tissue induced by bubble collapse during high-speed rotational angioplasty and laser-induced angioplasty can be underestimated by experiments in vitro using water as ambient liquid.

Brujan, E.-A.

2000-04-01

115

Cavitation and bubble collapse in hot asymmetric nuclear matter  

SciTech Connect

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

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

2004-10-01

116

Acoustic bubble removal method  

NASA Technical Reports Server (NTRS)

A method is described for removing bubbles from a liquid bath such as a bath of molten glass to be used for optical elements. Larger bubbles are first removed by applying acoustic energy resonant to a bath dimension to drive the larger bubbles toward a pressure well where the bubbles can coalesce and then be more easily removed. Thereafter, submillimeter bubbles are removed by applying acoustic energy of frequencies resonant to the small bubbles to oscillate them and thereby stir liquid immediately about the bubbles to facilitate their breakup and absorption into the liquid.

Trinh, E. H.; Elleman, D. D.; Wang, T. G. (inventors)

1983-01-01

117

Bubbles and Superbubbles  

E-print Network

An isolated massive star can blow a bubble, while a group of massive stars can blow superbubbles. In this paper, we examine three intriguing questions regarding bubbles and superbubbles: (1) why don't we see interstellar bubbles around every O star? (2) how hot are the bubble interiors? and (3) what is going on at the hot/cold gas interface in a bubble?

Y. -H. Chu; M. A. Guerrero; R. A. Gruendl

2003-10-10

118

Cosmic ray confinement in fossil cluster bubbles  

E-print Network

Most cool core clusters of galaxies possess active galactic nuclei (AGN) in their centers. These AGN inflate buoyant bubbles containing non-thermal radio emitting particles. If such bubbles efficiently confine cosmic rays (CR) then this could explain ``radio ghosts'' seen far from cluster centers. We simulate the diffusion of cosmic rays from buoyant bubbles inflated by AGN. Our simulations include the effects of the anisotropic particle diffusion introduced by magnetic fields. Our models are consistent with the X-ray morphology of AGN bubbles, with disruption being suppressed by the magnetic draping effect. We conclude that for such magnetic field topologies, a substantial fraction of cosmic rays can be confined inside the bubbles on buoyant rise timescales even when the parallel diffusivity coefficient is very large. For isotropic diffusion at a comparable level, cosmic rays would leak out of the bubbles too rapidly to be consistent with radio observations. Thus, the long confinement times associated with the magnetic suppression of CR diffusion can explain the presence of radio ghosts. We show that the partial escape of cosmic rays is mostly confined to the wake of the rising bubbles, and speculate that this effect could: (1) account for the excitation of the H$\\alpha$ filaments trailing behind the bubbles in the Perseus cluster, (2) inject entropy into the metal enriched material being lifted by the bubbles and, thus, help to displace it permanently from the cluster center and (3) produce observable $\\gamma$-rays via the interaction of the diffusing cosmic rays with the thermal intracluster medium (ICM).

M. Ruszkowski; T. A. Ensslin; M. Bruggen; M. C. Begelman; E. Churazov

2007-05-22

119

Buoyant Bubbles in a Cooling Intracluster Medium I. Hydrodynamic Bubbles  

E-print Network

Over the past several years, numerous examples of X-ray cavities coincident with radio sources have been observed in so-called "cool core" clusters of galaxies. Motivated by these observations, we explore the evolution and the effect of cavities on a cooling intracluster medium (ICM) numerically, adding relevant physics step by step. In this paper we present a first set of hydrodynamical, high resolution (1024^3 effective grid elements), three-dimensional simulations, together with two-dimensional test cases. The simulations follow the evolution of radio cavities, modeled as bubbles filled by relativistic plasma, in the cluster atmosphere while the ICM is subject to cooling. We find that the bubble rise retards the development of a cooling flow by inducing motions in the ICM which repeatedly displace the material in the core. Even bubbles initially set significantly far from the cluster center affect the cooling flow, although much later than the beginning of the simulation. The effect is, however, modest: the cooling time is increased by at most only 25%. As expected, the overall evolution of pure hydrodynamic bubbles is at odds with observations, showing that some additional physics has to be considered in order to match the data.

A. Gardini

2006-11-14

120

The Influence of Solid Particles on Bubble Size Distributions in Magma  

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

121

Hydrodynamic Simulation of Gas-Solid Bubbling Fluidized Bed Containing Horizontal Tubes  

NASA Astrophysics Data System (ADS)

Hydrodynamic simulation of 2-D gas-solid bubbling fluidized bed containing staggered horizontal tubes was performed. The bubble hydrodynamics, bubble diameter and bubble rise velocity, were investigated and compared with experimental results elsewhere in the literature (Hull et al., 1999, Influence of Horizontal tube Banks on the Bubbling and Solids Mixing Behavior of Fluidized Beds. 15th Int. FBC Conference). The Eulerian-Eulerian Two Fluid Model (TFM) implemented in Fluent, version 6.3, was used for the governing equations with closure equations based on the Kinetic Theory of Granular Flow (KTGF). The numerical simulation showed that the horizontal tubes were the main source of bubble break up where bubbles break when they interact with the tubes and grew by coalescence until they reach the next row of tubes. Quantitative investigation of the bubble hydrodynamics also revealed that the predicted average bubble diameter and bubble rise velocity were in good agreement with the experimental results reported in the literature. It was observed that there were small bubbles formed on the lower-half part of the tubes which were usually interacted with an incoming bubble from below and the tube after coalescence. As a result, the numerical simulation predicted a lower average bubble diameter and bubble rise velocity at the bottom of the tube banks than that reported in the literature.

Asegehegn, Teklay Weldeabzgi; Krantz, Hans Joachim

122

Plasma bubble phenomenon in the topside ionosphere  

NASA Astrophysics Data System (ADS)

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

Sidorova, L. N.

123

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

124

Operating Bias Field Adjustment of Bubble Propagation Tracks on Ion-Implanted Permalloy Hybrid Type Magnetic Bubble Memory Devices  

Microsoft Academic Search

Reductions in cell size of ion-implanted Permalloy hybrid magnetic bubble memory devices give rise to large differences in operating bias field regions of ion-implanted and Permalloy propagation tracks. Attempting to utilize the dependence of the operating bias field on the thickness of the bubble garnet film, the authors ion-milled films to reduce their thicknesses, thereby lowering the bubble collapse field

M. Takeshita; T. Ikeda; R. Suzuki; T. Takeuchi; N. Kodama

1985-01-01

125

Davies-Taylor Equation for the Fluidization Bubble.  

National Technical Information Service (NTIS)

The Davies-Taylor equations is justified for the steady rise of a spherical cap gas bubble in a gas - fluidized bed. Starting from the jump conditions at the bubble surface, it is shown that both the fluid and the total pressures should be constant there....

S. Kinrys, R. Y. Qassim

1981-01-01

126

Evolution of bubble size distribution in baked foods  

Microsoft Academic Search

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

Prashant Deshlahra; Anurag Mehra; Debjani Ghosal

2009-01-01

127

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

128

Simulation of Bubbles in Foam With The Volume Control Method Byungmoon Kim  

E-print Network

Simulation of Bubbles in Foam With The Volume Control Method Byungmoon Kim Georgia Tech, NVIDIA the level set is advected by the BFECC [Dupont and Liu 2003] method, the simulation of a rising bubble produces volume loss (top). When the proposed volume control method is used, the volume of bubble

Rossignac, Jarek

129

A force balance model for the motion, impact and bounce of bubbles Evert Klaseboer1  

E-print Network

1 A force balance model for the motion, impact and bounce of bubbles Evert Klaseboer1 , Rogerio@ihpc.a-star.edu.sg A force balance model has been developed to predict the terminal velocity of a sub- millimetric bubble as its rises in water under buoyancy. The dynamics of repeated collisions and rebounds of the bubble

Chan, Derek Y C

130

Duality of the gas-liquid flow regimes in bubble column reactors  

Microsoft Academic Search

The purpose of the present work was to examine the effect of design and working parameters of bubble column reactors on the formation and stability of the homogeneous and the heterogeneous bubbling regimes and to demonstrate the effect of bubbling regime transition on the hydrodynamic and mass transfer characteristics of gas-liquid beds in bubble column reactors. The factors determining the

J. Zahradník; M. Fialová; M. R?ži?ka; J. Drahoš; F. Kaštánek; N. H. Thomas

1997-01-01

131

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

132

Tubes form in the wake of bubbles http://www.rsc.org/chemistryworld/Issues/2005/July/chem_sci/Tubes.asp 1 of 1 7/5/2005 12:31 PM  

E-print Network

Tubes form in the wake of bubbles http://www.rsc.org/chemistryworld/Issues/2005/July/chem_sci/Tubes.asp 1 of 1 7/5/2005 12:31 PM Chemistry World Tubes form in the wake of bubbles Rising gas bubbles that rise with the bubbles out of the precipitation reaction solutions of sodium silicate and copper sulfate

Steinbock, Oliver

133

Soap-bubble growth  

Microsoft Academic Search

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

M. Marder

1987-01-01

134

Soap Bubbles and Logic.  

ERIC Educational Resources Information Center

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

Levine, Shellie-helane; And Others

1986-01-01

135

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

136

Brut: Automatic bubble classifier  

NASA Astrophysics Data System (ADS)

Brut, written in Python, identifies bubbles in infrared images of the Galactic midplane; it uses a database of known bubbles from the Milky Way Project and Spitzer images to build an automatic bubble classifier. The classifier is based on the Random Forest algorithm, and uses the WiseRF implementation of this algorithm.

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

2014-07-01

137

Oscillations of soap bubbles  

Microsoft Academic Search

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

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

2010-01-01

138

Soap Bubbles in Reverse  

Microsoft Academic Search

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

Leslie Rose

1946-01-01

139

Soap Films and Bubbles.  

ERIC Educational Resources Information Center

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

Rice, Karen

1986-01-01

140

Stable Coulomb bubbles ?  

E-print Network

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

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

1996-12-12

141

Cavitation Bubble Dynamics in Liquids of Different Viscosity  

Microsoft Academic Search

A single bubble in liquids is produced by using a high-intensity laser pulse and the dynamic characteristics of the oscillating bubble in glycerin-water mixtures with different viscosity are investigated by a sensitive fiber-optic sensors based on optical beam deflection (OBD). By analyzing the characteristic signals, the bubble radii and the oscillation times are determined. The experimental results show that Cavitation

Xiu-Mei Liu; Xin-Hua Liu; Jie He; You-Fu Hou; Jian Lu; Xiao-Wu Ni

2010-01-01

142

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.

143

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

PubMed

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

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

2011-08-15

144

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

Microsoft Academic Search

CO2 capture from flue gas using a sodium-based solid sorbent was investigated in a bubbling fluidized-bed reactor. Carbonation and regeneration temperature on CO2 removal was determined. The extent of the chemical reactivity after carbonation or regeneration was characterized via 13C NMR. In addition, the physical properties of the sorbent such as pore size, pore volume, and surface area after carbonation

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

2007-01-01

145

Motion and drag of a single bubble in super-purified water  

Microsoft Academic Search

We experimentally study the motion and shape of a single rising bubble in super-purified water. We develop an apparatus that is equipped with a measurement system for monitoring both the resistivity and amount of total organic carbon of water in order to evaluate the purity of water. We investigate the critical Reynolds number above which the rising bubble motion changes

Toshiyuki Sanada; Keiji Sugihara; Minori Shirota; Masao Watanabe

2008-01-01

146

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

147

Lifetime of bubble rafts: cooperativity and avalanches.  

PubMed

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

Ritacco, Hernán; Kiefer, Flavien; Langevin, Dominique

2007-06-15

148

Lifetime of Bubble Rafts: Cooperativity and Avalanches  

NASA Astrophysics Data System (ADS)

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

Ritacco, Hernán; Kiefer, Flavien; Langevin, Dominique

2007-06-01

149

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

150

Europa Rising  

NASA Technical Reports Server (NTRS)

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

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

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

2007-01-01

151

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

152

Shock wave propagation and bubble collapse in liquids containing gas bubbles  

Microsoft Academic Search

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

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

2005-01-01

153

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

154

Bubble Colloidal AFM Probes Formed from Ultrasonically Generated Bubbles  

E-print Network

Letters Bubble Colloidal AFM Probes Formed from Ultrasonically Generated Bubbles Ivan U. Vakarelski forces between two small bubbles (80-140 µm) in aqueous solution during controlled collisions) was extended to measure interaction forces between a cantilever-attached bubble and surface-attached bubbles

Chan, Derek Y C

155

MHD Simulations of Relic Radio Bubbles in Clusters  

E-print Network

In order to better understand the origin and evolution of relic radio bubbles in clusters of galaxies, we report on an extensive set of 2D MHD simulations of hot buoyant bubbles evolving in a realistic intracluster medium. Our bubbles are inflated near the base of the ICM over a finite time interval from a region whose magnetic field is isolated from the ICM. We confirm both the early conjecture from linear analysis and the later results based on preformed MHD bubbles; namely, that very modest ICM magnetic fields can stabilize the rising bubbles against disruption by Rayleigh-Taylor and Kelvin-Helmholtz instabilities. We find in addition that amplification of the ambient fields as they stretch around the bubbles can be sufficient to protect the bubbles or their initial fragments even if the fields are initially much too weak to play a significant role early in the evolution of the bubbles. Indeed, even with initial fields less than a micro-Gauss and values of $\\beta = P_g/P_b$ approaching $10^5$, magnetic stresses in our simulations eventually became large enough to influence the bubble evolution. Magnetic field influence also depends significantly on the geometry of the ICM field and on the topology of the field at the bubble/ICM interface. For example, reconnection of anti-parallel fields across the bubble top greatly reduced the ability of the magnetic field to inhibit disruptive instabilities. Our results confirm earlier estimates of $10^8$ yr for relic radio bubble lifetimes and show that magnetic fields can account for the long term stability of these objects against disruption by surface instabilities. In addition these calculations show that lifting and mixing of the ambient ICM may be a critical function of field geometries in both the ICM and in the bubble interior.

T. W. Jones; D. S. DeYoung

2005-02-07

156

Chaotic bubbling and nonstagnant foams.  

PubMed

We present an experimental investigation of the agglomeration of bubbles obtained from a nozzle working in different bubbling regimes. This experiment consists of a continuous production of bubbles from a nozzle at the bottom of a liquid column, and these bubbles create a two-dimensional (2D) foam (or a bubble raft) at the top of this column. The bubbles can assemble in various dynamically stable arrangement, forming different kinds of foams in a liquid mixture of water and glycerol, with the effect that the bubble formation regimes influence the foam obtained from this agglomeration of bubbles. The average number of bubbles in the foam is related to the bubble formation frequency and the bubble mean lifetime. The periodic bubbling can generate regular or irregular foam, while a chaotic bubbling only generates irregular foam. PMID:17677349

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

2007-06-01

157

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

158

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

E-print Network

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

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

2014-01-01

159

Planar Soap Bubbles  

Microsoft Academic Search

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

RICHARD PAUL; DEVEREAUX VAUGHN

1998-01-01

160

Radio Bubbles in Clusters  

E-print Network

We extend our earlier work on cluster cores with distinct radio bubbles, adding more active bubbles, i.e. those with Ghz radio emission, to our sample, and also investigating ``ghost bubbles,'' i.e. those without GHz radio emission. We have determined k, which is the ratio of the total particle energy to that of the electrons radiating between 10 MHz and 10 GHz. Constraints on the ages of the active bubbles confirm that the ratio of the energy factor, k, to the volume filling factor, f lies within the range 1 bubbles present in the current sample to be able to determine the shape of the population. An analysis of the ghost bubbles in our sample showed that on the whole they have higher upper limits on k/f than the active bubbles, especially when compared to those in the same cluster. A study of the Brightest 55 cluster sample shows that 17, possibly 20, clusters required some form of heating as they have a short central cooling time, t_cool bubbles. This indicates that the duty cycle of bubbles is large in such clusters and that they can play a major role in the heating process.

R. J. H. Dunn; A. C. Fabian; G. B. Taylor

2005-10-06

161

Gas bubbles in simulation and experiment.  

PubMed

An experimental setup for the examination of single bubbles, rising in a liquid, is presented. Its main part is a rotating chamber, in which the bubble is spatially stabilized by a balance of buoyancy, drag, and lift forces. This allows for long observation periods in time. Experimental results are presented for air bubbles in silicone oil. The experimental results are validated by a comparison with numerical simulations. A modified, mass-conserving level-set method is used for the representation of the free interface, while an immersed-boundary formulation is engaged for the conservation equations. The agreement between experiment and simulation, and to available correlations from literature, is found to be perfect. It is shown that the influence of the liquid shear due to the rotation is negligible. Also, for the presented liquid system, no influence by Marangoni stresses could be found, which makes the system of air and silicone oil a good choice for validation purposes. PMID:21084092

Lakshmanan, Peter; Peters, Franz; Fries, Nicolas; Ehrhard, Peter

2011-02-01

162

Bubble dynamics in a compressible shear-thinning liquid  

Microsoft Academic Search

The radial dynamics of a spherical gas bubble in a compressible shear-thinning liquid is studied by means of a singular perturbation method to first order in the bubble-wall Mach number. The Williamson rheological model is adopted to describe the shear-thinning characteristic of liquid viscosity. The equation of motion for the bubble radius, the equation of the natural frequency of the

E.-A. Brujan

1998-01-01

163

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

164

A Bubble Full of Sunshine  

NSF Publications Database

... Release 05-030A Bubble Full of Sunshine Temperatures inside bursting bubbles can be four times ... University of Illinois have determined that temperatures inside gas bubbles collapsing in a liquid ...

165

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

166

Soap bubbles. 1  

Microsoft Academic Search

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

A. Glassner

2000-01-01

167

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

168

Explosion of chaotic bubbling  

NASA Astrophysics Data System (ADS)

We have studied a saddle-node bifurcation/explosion of air bubble formation driven by a sound wave, whose amplitude is the control parameter. The bubbles are formed in a nozzle submerged in a water/glycerol solution inside a cylindrical tube, and the sound wave is tuned to the air column above the fluid. The nonlinear interaction between sound wave and the fluid oscillations, caused by the air bubbles passage through the liquid, results in a route to chaos via quasi-periodicity, with some resonant states characterized by the rational winding numbers W= fs/ fb, where fs is the sound wave frequency and fb is the bubbling rate. We also have shown that the bubble dynamics is similar to the one observed in the two-dimensional circle map.

Tufaile, A.; Reyes, M. B.; Sartorelli, J. C.

2002-05-01

169

The latency reduction of bidirectional magnetic bubble memories  

Microsoft Academic Search

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

C. Naranong; D. Hammerstrom

1979-01-01

170

Equatorial plasma bubbles with enhanced ion and electron temperatures  

Microsoft Academic Search

While the ion and electron temperatures inside equatorial plasma bubbles (EPBs) are normally lower than those in an ambient plasma, bubbles with enhanced temperatures (BETs) are found occasionally in the topside ionosphere. Here we report the characteristics of BETs identified from observations of the first Republic of China Satellite (ROCSAT-1), the first Korea Multi-purpose Satellite (KOMPSAT-1), and the Defense Meteorological

Kyoung Wook Min; Vitaly P. Kim; Hyosub Kil; Shin-Yi Su; Chi Kuang Chao; Jae-Jin Lee

2008-01-01

171

Modeling bubbles and droplets in magnetic fluids.  

PubMed

We develop, test and apply a volume of fluid (VOF) type code for the direct numerical simulation of two-fluid configurations of magnetic fluids with dynamic interfaces. Equilibrium magnetization and linear magnetic material are assumed and uniform imposed magnetic fields are considered, although extensions to nonlinear materials and to fields with spatio-temporal variability are possible. Models are computed for configurations of bubbles of non-magnetic fluid rising in ferrofluid and droplets of ferrofluid falling through non-magnetic fluid. Bubbles and droplets exhibit similar changes of shape in the presence of vertical fields, due to a combination of elongation along the field lines and the fluid dynamics of ordinary rising or falling at small Bond number. Bubbles become more prolate than droplets under the same parameters and are accordingly found to break up more readily than droplets in stronger fields. Indirect effects are observed, such as the change in rise time and the consequent changes in the flow due to increased Reynolds number. PMID:21694272

Korlie, Mark S; Mukherjee, Arup; Nita, Bogdan G; Stevens, John G; Trubatch, A David; Yecko, Philip

2008-05-21

172

Mechanisms of in-line coalescence of two-unequal bubbles in a non-Newtonian fluid  

Microsoft Academic Search

The coalescing mechanism of in-line two-unequal bubbles rising in a bubble column with a non-Newtonian fluid has been experimentally studied. The non-Newtonian fluid is the 1.5wt% polyacryamide in demineralized water and the bubble gas is air. Both qualitative flow visualization and quantitative full-field measurements using particle image analyzer have been conducted for two examples of two-unequal bubble coalescences. The instantaneous

Tsao-Jen Lin; Gen-Ming Lin

2009-01-01

173

Mounting and application of bubble display system: bubble cosmos  

Microsoft Academic Search

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

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

2006-01-01

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

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

PubMed

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

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

2007-10-01

176

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

SciTech Connect

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

Wu, Wen; Chen, Peipei; Jones, Barclay G. [Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign Urbana, IL 61801 (United States); Newell, Ty A. [Department of Mechanical and Industrial Engineering, University of Illinois at Urbana-Champaign Urbana, IL 61801 (United States)

2006-07-01

177

Viscosity destabilizes sonoluminescing bubbles.  

PubMed

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

Toegel, Ruediger; Luther, Stefan; Lohse, Detlef

2006-03-24

178

Charged vacuum bubble stability  

NASA Astrophysics Data System (ADS)

A type of scenario is considered where electrically charged vacuum bubbles, formed from degenerate or nearly degenerate vacua separated by a thin domain wall, are cosmologically produced due to the breaking of a discrete symmetry, with the bubble charge arising from fermions residing within the domain wall. Stability issues associated with wall tension, fermion gas, and Coulombic effects for such configurations are examined. The stability of a bubble depends upon parameters such as the symmetry breaking scale and the fermion coupling. A dominance of either the Fermi gas or the Coulomb contribution may be realized under certain conditions, depending upon parameter values.

Morris, J. R.

1999-01-01

179

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

180

Speculations on Nonlinear Speculative Bubbles  

Microsoft Academic Search

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

J. Barkley Rosser

1997-01-01

181

Computational investigation on bubble detachment from submerged orifice in quiescent liquid under normal and reduced gravity  

NASA Astrophysics Data System (ADS)

In this work numerical simulations have been carried out to study the problem of dynamic air bubble formation from a submerged orifice in quiescent liquid, under constant inflow condition, at normal and reduced gravity levels. A coupled level-set and volume-of-fluid method is used to simulate the bubble formation, bubble detachment, and the bubble rise above the orifice. For the described study, the authors have mainly focused on low and medium air flow rate for simulation of bubble formation at the orifice. The employed gravity levels g /ge are in the range of 100, 10-1, and 10-2. The influence of buoyancy on the bubble shape has been studied. The study includes the bubble volume, formation frequency, pinch-off rate, detached bubble diameter, and the bubble growth history for different air flow rates. Even for the static contact angle ?s=00, it is observed that at low gravity levels the bubble base spreads along the surface of the orifice plate away from the orifice rim during the expansion stage, and during the detachment stage the bubble base again comes back to the orifice rim. As the air flow rate is increased under normal and low gravity conditions, coalescence between the rising bubbles or between the detached bubble and the forming bubble at the orifice is observed. It is shown that the increasing trend of bubble size at detachment, with increasing air flow rate under normal gravity is reversed in the case of reduced gravity (g /ge=10-2).

Chakraborty, I.; Ray, B.; Biswas, G.; Durst, F.; Sharma, A.; Ghoshdastidar, P. S.

2009-06-01

182

Suratman number in bubble-to-slug flow pattern transition under microgravity  

NASA Astrophysics Data System (ADS)

It has been established through the evaluation of characteristic forces active in two-phase flow field and consideration of bubble coalescence in the bubbly flow regime that Suratman number is the key dimensionless group in bubble-slug flow pattern transition under microgravity.

Sen, Nilava

2009-08-01

183

Using bubbles to transform medicine, develop ultrasonic cleaning and learn more about whales and dolphins  

E-print Network

Using bubbles to transform medicine, develop ultrasonic cleaning and learn more about whales and dolphins Pioneering research into bubble acoustics is developing exciting applications in several fields of the world's problems need new solutions. Examining how bubbles work and exploiting their characteristics

Anderson, Jim

184

Effect of Liquid Surface Tension and Viscosity on Micro-Bubble Induced by External Electric Field  

Microsoft Academic Search

\\u000a In present work, different liquids with various surface tension and viscosities were chosen to study the micro-bubble emergence\\u000a and bubble shape. Moreover, the bubbles’ moving characteristics was investigated, and the electric current in the circuit\\u000a was monitored. Different mechanisms of these experimental phenomena will be discussed in the paper.

Xie Guoxin; Luo Jianbin

185

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

186

Colloquium: Soap bubble clusters  

NASA Astrophysics Data System (ADS)

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

Morgan, Frank

2007-07-01

187

Bubble coalescence in magmas  

NASA Technical Reports Server (NTRS)

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

Herd, Richard A.; Pinkerton, Harry

1993-01-01

188

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

Microsoft Academic Search

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

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

1999-01-01

189

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

190

Melting Ice, Rising Seas  

NASA Video Gallery

Sea level rise is an indicator that our planet is warming. Much of the world's population lives on or near the coast, and rising seas are something worth watching. Sea level can rise for two reason...

191

Gas separation and bubble behavior at a woven screen  

NASA Astrophysics Data System (ADS)

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

Conrath, Michael; Dreyer, Michael E.

192

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

193

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

194

Heat transport in bubbling turbulent convection.  

PubMed

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

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

2013-06-01

195

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

196

Impact of tangled magnetic fields on AGN-blown bubbles  

E-print Network

There is growing consensus that feedback from AGN is the main mechanism responsible for stopping cooling flows in clusters of galaxies. AGN are known to inflate buoyant bubbles that supply mechanical power to the intracluster gas (ICM). High Reynolds number hydrodynamical simulations show that such bubbles get entirely disrupted within 100 Myr, as they rise in cluster atmospheres, which is contrary to observations. This artificial mixing has consequences for models trying to quantify the amount of heating and star formation in cool core clusters of galaxies. It has been suggested that magnetic fields can stabilize bubbles against disruption. We perform MHD simulations of fossil bubbles in the presence of tangled magnetic fields using the high order PENCIL code. We focus on the physically-motivated case where thermal pressure dominates over magnetic pressure and consider randomly oriented fields with and without maximum helicity and a case where large scale external fields drape the bubble.We find that helicity has some stabilizing effect. However, unless the coherence length of magnetic fields exceeds the bubble size, the bubbles are quickly shredded. As observations of Hydra A suggest that lengthscale of magnetic fields may be smaller then typical bubble size, this may suggest that other mechanisms, such as viscosity, may be responsible for stabilizing the bubbles. However, since Faraday rotation observations of radio lobes do not constrain large scale ICM fields well if they are aligned with the bubble surface, the draping case may be a viable alternative solution to the problem. A generic feature found in our simulations is the formation of magnetic wakes where fields are ordered and amplified. We suggest that this effect could prevent evaporation by thermal conduction of cold Halpha filaments observed in the Perseus cluster.

M. Ruszkowski; T. A. Ensslin; M. Bruggen; S. Heinz; C. Pfrommer

2007-03-30

197

The dynamics of histotripsy bubbles  

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

198

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

199

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

200

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

201

Dispersed Multiphase Flow: From Micro-to Macro-Scale Numerical Modelling Direct numerical simulation of high Schmidt number mass transfer from air bubbles  

E-print Network

simulation of high Schmidt number mass transfer from air bubbles rising in liquids using the Volume, and a local mesh refinement around the bubble. Furthermore, we show a first result employing so in bubble column reactors, especially for performing chemical reactions like hydrogenations, oxidations

Bothe, Dieter

202

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

NASA Astrophysics Data System (ADS)

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

Zhang, Jie; Ni, Ming-Jiu

2014-10-01

203

Gas Bubble Growth Dynamics in a Supersaturated Solution: Henry's and Sievert's Solubility Laws  

E-print Network

Theoretical description of diffusion growth of a gas bubble after its nucleation in supersaturated liquid solution is presented. We study the influence of Laplace pressure on the bubble growth. We consider two different solubility laws: Henry's law, which is fulfilled for the systems where no gas molecules dissociation takes place and Sievert's law, which is fulfilled for the systems where gas molecules completely dissociate in the solvent into two parts. We show that the difference between Henry's and Sievert's laws for chemical equilibrium conditions causes the difference in bubble growth dynamics. Assuming that diffusion flux of dissolved gas molecules to the bubble is steady we obtain differential equations on bubble radius for both solubility laws. For the case of homogeneous nucleation of a bubble, which takes place at a significant pressure drop bubble dynamics equations for Henry's and Sievert's laws are solved analytically. For both solubility laws three characteristic stages of bubble growth are mar...

Gor, Gennady Yu; Kuni, Fedor M

2012-01-01

204

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

205

Gravitational wave production by collisions: more bubbles  

SciTech Connect

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

Huber, Stephan J [Department of Physics and Astronomy, Sussex, Falmer, Brighton BN1 9QH (United Kingdom)] [Department of Physics and Astronomy, Sussex, Falmer, Brighton BN1 9QH (United Kingdom); Konstandin, Thomas, E-mail: s.huber@sussex.ac.uk, E-mail: konstand@ifae.es [IFAE, Universitat Autonoma de Barcelona, E-08193 Bellaterra, Barcelona (Spain)] [IFAE, Universitat Autonoma de Barcelona, E-08193 Bellaterra, Barcelona (Spain)

2008-09-15

206

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 of electrochemically generated bubble valves were studied. By generating electrochemical bubbles as valves directly

Sachs, Frederick

207

Bubbles and Biosensors  

NSDL National Science Digital Library

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

Vu Bioengineering Ret Program

208

Magnetic-bubble conservative logic  

Microsoft Academic Search

Among integrated-circuit devices, magnetic bubbles are a particularly interesting candidate to implement the Fredkin gate and conservative logic. The magnetostatic repulsion of magnetic bubbles simulates the bouncing-ball model of conservative logic.

Hsu Chang

1982-01-01

209

Axial summit trough of the East Pacific Rise 9L - 10LN: Geolo - gical characteristics and evolution of the axial zone on fast spreading mid - ocean ridges  

Microsoft Academic Search

The nature and morphological characteristics of axial summit troughs on fast (-90- 130 mm\\/yr 'l full spreading rate) and superfast spreading (> 130 mm\\/yr 'l) mid-ocean ridge crests reflect the time-integrated effects of long-term magmatic cycles, short-term volcanic episodicity, and the tensional stress regime imposed on young ocean crust. Two principal types of axial trough morphology have been identified and

Daniel J. Fornari; Rachel M. Haymon; Michael R. Perfit; T. K. Gregg

1998-01-01

210

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

211

The Home Zone: Bubble Shapes  

NSDL National Science Digital Library

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

Damonte, Kathleen

2003-05-01

212

Bubbles Unbound: Bubbles of Nothing Without Kaluza-Klein  

E-print Network

I present analytic time symmetric initial data for five dimensions describing ``bubbles of nothing'' which are asymptotically flat in the higher dimensional sense, i.e. there is no Kaluza-Klein circle asymptotically. The mass and size of these bubbles may be chosen arbitrarily and in particular the solutions contain bubbles of any size which are arbitrarily light. This suggests the solutions may be important phenomenologically and in particular I show that at low energy there are bubbles which expand outwards, suggesting a new possible instability in higher dimensions. Further, one may find bubbles of any size where the only region of high curvature is confined to an arbitrarily small volume.

Keith Copsey

2006-10-05

213

Bubble Chamber Site  

NSDL National Science Digital Library

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

2006-06-19

214

The Bubble N10  

NASA Astrophysics Data System (ADS)

We studied the environment surrounding the infrared bubble N10 in molecular and infrared emission. There is an HII region at the center of this bubble. We investigated J=1-0 transitions of molecules ^{12}CO, ^{13}CO and C^{18}O towards N10. This object was detected by GLIMPSE, a survey carried out between 3.6 and 8.0 ? m. We also analyzed the emission at 24 ? m, corresponding to the emission of hot dust, with a contribution of small grains heated by nearby O stars. Besides, the contribution at 8 ? m is dominated by PAHs (polycyclic aromatic hydrocarbons) excited by radiation from the PDRs of bubbles. In the case of N10, it is proposed that the excess at 4.5 ? m IRAC band indicate an outflow, a signature of early stages of massive star formation. This object was the target of observations at the PMO 13.7 m radio telescope. The bubble N10 presents clumps, from which we can derive physical features through the observed parameters. We also intended to discuss the evolutionary stage of the clumps and their distribution. It can lead us to understand the triggered star formation scenario in this region.

Gama, D.; Lepine, J.; Wu, Y.; Yuan, J.

2014-10-01

215

Soap bubbles and crystals  

Microsoft Academic Search

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

Jean E. Taylor

2006-01-01

216

Oscillations of soap bubbles  

NASA Astrophysics Data System (ADS)

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

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

2010-07-01

217

Colloquium: Soap bubble clusters  

Microsoft Academic Search

Soap bubble clusters and froths model biological cells, metallurgical structures, magnetic domains, liquid crystals, fire-extinguishing foams, bread, cushions, and many other materials and structures. Despite the simplicity of the governing principle of energy or area minimization, the underlying mathematical theory is deep and still not understood, even for rather simple, finite clusters. Only with the advent of geometric measure theory

Frank Morgan

2007-01-01

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

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

220

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

221

Combined in-situ and top-side remote observations of evolution of plasma bubbles  

NASA Astrophysics Data System (ADS)

Ionospheric plasma bubbles in the nighttime are known to cause interference with GPS navigation and trans-ionospheric RF propagation in general. The characteristics of these bubbles have been studied extensively through observations via TIMED GUVI instrument, ground-based imagers, and the C/NOFS mission, but the production and especially the evolution of the bubbles is not adequately understood. We present here a small satellite mission concept that attempts to do combined in-situ and top-side remote observations of the bubbles to better understand their evolution. The mission aims to specifically address key questions about ionospheric bubbles: What are the characteristics of bubbles and how do these characteristics evolve? Does bubble evolution vary with longitude and/or latitude? How do the bubble occurrence rates at the F-region peak and higher altitudes differ? The proposed mission will carry a 135.6 nm photometer to measure the recombination emission from oxygen ions and a Langmuir probe to measure in-situ plasma density. Topside remote sensing using the photometer allows for observations of bubbles near and below the F-region peak while the Langmuir probe gives in situ measurements necessary to characterize the plasma fluctuations and thereby infer the RF scintillation characteristics. Comparison of such coincident measurements will provide a unique insight into bubble formation and evolution.

Barjatya, A.; Eastes, R.; Dymond, K.

2010-12-01

222

Bubble kinetics in a steady-state column of aqueous foam  

E-print Network

We measure the liquid content, the bubble speeds, and the distribution of bubble sizes, in a vertical column of aqueous foam maintained in steady-state by continuous bubbling of gas into a surfactant solution. Nearly round bubbles accumulate at the solution/foam interface, and subsequently rise with constant speed. Upon moving up the column, they become larger due to gas diffusion and more polyhedral due to drainage. The size distribution is monodisperse near the bottom and polydisperse near the top, but there is an unexpected range of intermediate heights where it is bidisperse with small bubbles decorating the junctions between larger bubbles. We explain the evolution in both bidisperse and polydisperse regimes, using Laplace pressure differences and taking the liquid fraction profile as a given.

K. Feitosa; Olivia L. Halt; Randall D. Kamien; D. J. Durian

2006-09-19

223

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

NASA Technical Reports Server (NTRS)

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

Azuma, H.

1993-01-01

224

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

NASA Astrophysics Data System (ADS)

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.

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

2008-12-01

225

DNA denaturation bubbles at criticality  

E-print Network

The equilibrium statistical properties of DNA denaturation bubbles are examined in detail within the framework of the Peyrard-Bishop-Dauxois model. Bubble formation in homogeneous DNA is found to depend crucially on the presence of nonlinear base-stacking interactions. Small bubbles extending over less than 10 base pairs are associated with much larger free energies of formation per site than larger bubbles. As the critical temperature is approached, the free energy associated with further bubble growth becomes vanishingly small. An analysis of average displacement profiles of bubbles of varying sizes at different temperatures reveals almost identical scaled shapes in the absence of nonlinear stacking; nonlinear stacking leads to distinct scaled shapes of large and small bubbles.

Theodorakopoulos, Nikos

2008-01-01

226

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

227

Dynamics of the gas flux from shallow gas hydrate deposits: interaction between oily hydrate bubbles and the oceanic environment  

NASA Astrophysics Data System (ADS)

Decomposition of methane hydrates on the continental margins is a potentially significant source of atmospheric methane, but the input depends upon the poorly understood fate of the hydrocarbon bubbles rising from the sea floor. During a field trip to the Gulf of Mexico, three different seepages were imaged and analyzed. Three different imaging techniques were tried (side, front, and back illumination), of which back illumination produced the best results. The images were analyzed and the size-dependent bubble distribution, mass flux, and rise speeds determined. The total observed gas flux was 62.3×10 -3 mol s -1, primarily methane, of which a single vent produced seven times the next largest vent. Of this major vent, 50% of the bubble mass was contained in the largest bubbles, r>5500 ?m. The vertical velocities demonstrated that these bubbles were heavily contaminated with oil, which was also corroborated by bubble shape and oscillation observations.

Leifer, Ira; MacDonald, Ian

2003-05-01

228

Ion-Implanted Magnetic Bubble Memory Devices  

Microsoft Academic Search

High-density magnetic bubble memory devices have been developed by using ion-implanted tracks. Hybrid type devices, composed of ion-implanted tracks for high-density data storage and Permalloy tracks for write and read functions, have an advantage in compatibility with Permalloy devices in commercial use. The characteristics of junctions connecting the two type tracks are improved by a new design in which both

T. Toyooka

1988-01-01

229

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

230

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

231

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

232

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

233

PIV velocity measurements in the wake of an obstruction simulating a Taylor bubble in a duct  

Microsoft Academic Search

Mean velocity measurements in the wake of an obstruction simulating a Taylor bubble (or slug) have been obtained using Particle Image Velocimetry (PIV) in a duct. Two flow rates were established: one represented the flow behind a large gas slug rising in quiescent fluid and the other represented an idealized slug rising with a higher relative velocity, as typically found

P. Vassallo; R. Kumar

1997-01-01

234

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

SciTech Connect

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

Wu, Wen; Jones, Barclay G. [University of Illinois at Urbana-Champaign, 104 South Wright Street, Urbana, IL 61801 (United States)

2002-07-01

235

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

236

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

237

Negative wake behind a sphere rising in viscoelastic fluids: A lattice Boltzmann investigation  

Microsoft Academic Search

We investigate the complex flow field around a sphere rising in a Maxwell fluid by means of the lattice Boltzmann simulation to provide insights into the strange negative wake experimentally observed behind a bubble or particle in non Newtonian fluids. The influence of the rise velocity, sphere diameter, and fluid's rheology is considered through two dimensionless numbers: the Deborah number

Xavier Frank; Huai Z. Li

2006-01-01

238

Collapse of large vapor bubbles  

NASA Technical Reports Server (NTRS)

The refilling of propellant tanks while in a low-gravity environment requires that entrapped vapor bubbles be collapsed by increasing the system pressure. Tests were performed to verify the mechanism of collapse for these large vapor bubbles with the thermodynamic conditions, geometry, and boundary conditions being those applicable to propellant storage systems. For these conditions it was found that conduction heat transfer determined the collapse rate, with the specific bubble geometry having a significant influence.

Tegart, J.; Dominick, S.

1982-01-01

239

Colliding Kaluza-Klein Bubbles  

E-print Network

We construct an exact solution describing the collision of two Kaluza-Klein "bubbles of nothing" in 3+1 dimensions. When the bubbles collide, a curvature singularity forms which is hidden inside an event horizon. However, unlike the formation of ordinary black holes, in this case the spacetime resembles the entire maximally extended Schwarzschild solution. We also point out that there are inequivalent bubbles that can be constructed from Kerr black holes.

Gary T. Horowitz; Kengo Maeda

2002-07-30

240

Acronical Risings and Settings  

NASA Astrophysics Data System (ADS)

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

Hockey, Thomas A.

2012-01-01

241

Electron Bubbles in Liquid Helium  

E-print Network

When an electron (or positronium atom) is injected into liquid helium with nearly zero energy, a bubble quickly forms around it. This phenomenon (which also occurs in liquid hydrogen, liquid neon and possibly in solid helium) lowers the mobility of the electron to a value similar to that for a positive ion. We estimate the radius of the bubble at zero pressure and temperature based on the zero point energy of the electron. If the liquid is held in a state of negative pressure, the bubble will expand beyond the radius at zero pressure. We also estimate the negative pressure such that a bubble once formed will grow without limit.

Kirk T. McDonald

2003-12-03

242

Detecting bubbles in exotic nuclei  

E-print Network

The occurrence of a bubble, due to an inversion of s$_{1/2}$ state with the state usually located above, is investigated. Proton bubbles in neutron-rich Argon isotopes are optimal candidates. Pairing effects which can play against the bubble formation are evaluated. They cannot prevent bubble formation in very neutron-rich argon isotopes such as $^{68}$Ar. This pleads for a measurement of the charge density of neutron-rich argon isotopes in the forthcoming years, with the advent of electron scattering experiments in next generation exotic beam facilities such as FAIR or RIBF.

E. Khan; M. Grasso; J. Margueron; N. Van Giai

2007-07-03

243

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

2010-01-21

244

Domain Walls and Double Bubbles  

E-print Network

We study configurations of intersecting domain walls in a Wess-Zumino model with three vacua. We introduce a volume-preserving flow and show that its static solutions are configurations of intersecting domain walls that form double bubbles, that is, minimal area surfaces which enclose and separate two prescribed volumes. To illustrate this field theory approach to double bubbles, we use domain walls to reconstruct the phase diagram for double bubbles in the flat square two-torus and also construct all known examples of double bubbles in the flat cubic three-torus.

Mike Gillard; Paul Sutcliffe

2009-03-30

245

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

246

Particle image velocimetry studies of bubble growth and detachment by high-speed photography  

NASA Astrophysics Data System (ADS)

An understanding of bubble flows is important in the design of process equipment, particularly in the chemical and power industries. In vapor-liquid processes the mass and heat transfer between the phases is dominated by the liquid-vapor interface and is determined by the number, size, and shape of the bubbles. For bubble flows these characteristics are often controlled by the generation mechanisms and, since bubble flows are often generated at an orifice, it is important to determine the controlling parameters which dictate how bubbles grow and detach. For bubbles growing at orifices the liquid displacement is an important feature and affects the pressure distribution acting on the bubble and the heat and mass transfer that may occur at the bubble interface. Therefore, in this study, the characteristics of the liquid velocity field are studied experimentally using Particle image Velocimetry (PIV) during growth, detachment and translation of a bubble being generated at an orifice supplied with a constant mass flow rate of air. The process is transient and occurs over a period of approximately 50 msecs. In order to map the transient flow field a combination of high speed cine and cross correlation PIV image processing has been used to determine the liquid velocity vector field during the bubble growth process. The paper contains details of the PIV technique and presents several of the velocity vector maps calculated.

Stickland, Mathew; Dempster, William; Lothian, Lee; Oldroyd, Andrew

1997-05-01

247

Modeling of bubble coalescence in bubbly co-current flows restricted by confined geometry  

Microsoft Academic Search

Principles of kinetic theory are used to model the coalescence of bubbles in horizontal and vertical upflows where bubble movements are restricted by channel geometry. There are four critical variables that determine the rate at which a swarm of small bubbles will coalesce: the initial bubble population, the average initial bubble diameter, the average relative velocity of the bubbles, and

Michael D. Lundin; Mark J. McCready

2009-01-01

248

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.

Fairbanks, Geophysical I.

249

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

NASA Astrophysics Data System (ADS)

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

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

250

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

NASA Technical Reports Server (NTRS)

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

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

1953-01-01

251

Effect of bubble size on micro-bubble drag reduction  

NASA Astrophysics Data System (ADS)

The effect of bubble size on micro-bubble drag reduction was investigated experimentally in a high-speed turbulent channel flow of water. A variety of near-wall injection techniques were used to create a bubbly turbulent boundary layer. The resulting wall friction force was measured directly by a floating element force balance. The bubble size was determined from photographic imaging. Using compressed nitrogen to force flow through a slot injector located in the plate beneath the boundary layer of the tunnel test section, a surfactant solution (Triton X-100, 19ppm) and salt water solution (35ppt) generated bubbles of average size between ˜500 microns and ˜200 microns and ˜100 microns, respectively (40 < d^+ < 200). In addition hollow spherical glass beads (˜75 microns (d^+ = 30) and specific gravity 0.18) and previously prepared lipid stabilized gas bubbles of ˜ 30 micron (d^+ =12) were injected. The results indicate that the drag reduction is related strongly to the injected gas volume flux and the static pressure in the boundary layer. Changing bubble size had essentially no influence on the measured friction drag, suggesting that friction drag is not a strong function of bubble size. [Sponsored by the Office of Naval Research.

Shen, Xiaochun

2005-11-01

252

The colour of bubbles  

NASA Astrophysics Data System (ADS)

Students of General Physics often complain that the course is too abstract and remote from daily life. As teachers, we emphasize that the abstract concepts of physics are indispensable for understanding our daily experiences, and we try to give the impression that quantitative descriptions can be achieved by adopting concrete mathematical expressions. Thus the abstract formulation is not to make physics more difficult, but to make it easier to grasp. We expect the students to learn to describe phenomena qualitatively using the concepts of physics, and to provide a quantitative description by manipulating the mathematical formulation. Here we supply one such example to calculate the colour of bubble films.

Huang, Ding-wei; Huang, Wei-neng; Tseng, Hsiang-chi

2005-11-01

253

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

254

A bubbling bolt  

NASA Astrophysics Data System (ADS)

We present a new solvable system, solving the equations of five-dimensional ungauged = 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.

Bossard, Guillaume; Katmadas, Stefanos

2014-07-01

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

Triangular bubble spline surfaces  

PubMed Central

We present a new method for generating a Gn-surface from a triangular network of compatible surface strips. The compatible surface strips are given by a network of polynomial curves with an associated implicitly defined surface, which fulfill certain compatibility conditions. Our construction is based on a new concept, called bubble patches, to represent the single surface patches. The compatible surface strips provide a simple Gn-condition between two neighboring bubble patches, which are used to construct surface patches, connected with Gn-continuity. For n?2, we describe the obtained Gn-condition in detail. It can be generalized to any n?3. The construction of a single surface patch is based on Gordon–Coons interpolation for triangles. Our method is a simple local construction scheme, which works uniformly for vertices of arbitrary valency. The resulting surface is a piecewise rational surface, which interpolates the given network of polynomial curves. Several examples of G0, G1 and G2-surfaces are presented, which have been generated by using our method. The obtained surfaces are visualized with reflection lines to demonstrate the order of smoothness. PMID:22267872

Kapl, Mario; Byrtus, Marek; Juttler, Bert

2011-01-01

257

Bubbles under stress.  

PubMed

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

Bohn, S

2003-06-01

258

Radiolytic Bubble Gas Hydrogen Compositions  

SciTech Connect

Radioactive waste solids can trap bubbles containing hydrogen that may pose a flammability risk if they are disturbed and hydrogen is released. Whether a release is a problem or not depends, among other things, on the hydrogen composition of the gas. This report develops a method for estimating the hydrogen composition of trapped bubbles based on waste properties.

Hester, J.R.

2003-02-05

259

Radiolytic Bubble Gas Hydrogen Compositions  

SciTech Connect

Radioactive waste solids can trap bubbles containing hydrogen that may pose a flammability risk if they are disturbed and hydrogen is released. Whether a release is a problem or not depends, among other things, on the hydrogen composition of the gas. This report develops a method for estimating the hydrogen composition of trapped bubbles based on waste properties.

Hester, J.R.

2001-08-28

260

Gas bubbles in shaped sapphire  

Microsoft Academic Search

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

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

2010-01-01

261

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

262

Taxing the rich: recombinations and bubble growth during reionization  

NASA Astrophysics Data System (ADS)

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

Furlanetto, Steven R.; Oh, S. Peng

2005-11-01

263

On the structure of shock waves in liquid-bubble mixtures  

Microsoft Academic Search

Asbtract  The structure of shock waves in liquids containing gas bubbles is investigated theoretically. The mechanisms taken into account\\u000a are the steepening of compression waves in the mixture by convection and the effects due to the motion of the bubbles with\\u000a respect to the surrounding fluid. This relative motion, radial and translational, gives rise to dissipation and to dispersion\\u000a caused by

L. van Wijngaarden

1970-01-01

264

Global sea level rise  

Microsoft Academic Search

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

Bruce C. Douglas

1991-01-01

265

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

266

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

267

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

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

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

270

Anatomy of bubbling solutions  

E-print Network

We present a comprehensive analysis of holography for the bubbling solutions of Lin-Lunin-Maldacena. These solutions are uniquely determined by a coloring of a 2-plane, which was argued to correspond to the phase space of free fermions. We show that in general this phase space distribution does not determine fully the 1/2 BPS state of N=4 SYM that the gravitational solution is dual to, but it does determine it enough so that vevs of all single trace 1/2 BPS operators in that state are uniquely determined to leading order in the large N limit. These are precisely the vevs encoded in the asymptotics of the LLM solutions. We extract these vevs for operators up to dimension 4 using holographic renormalization and KK holography and show exact agreement with the field theory expressions.

Kostas Skenderis; Marika Taylor

2007-06-02

271

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

NASA Astrophysics Data System (ADS)

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

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

2006-11-01

272

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

273

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

274

Bubble Growth in Lunar Basalts  

NASA Astrophysics Data System (ADS)

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

Zhang, Y.

2009-05-01

275

On Charged Mesoscopic Metallic Bubbles  

E-print Network

We investigate the existence of stable charged metallic bubbles using the shell correction method. We find that for a given mesoscopic system of n atoms of a given metal and q less n (positive) elementary charges, a metallic bubble turns out to have a lower total energy than a compact spherical cluster, whenever the charge number q is larger than acritical charge number q_c. For a magic number (n-q) of free electrons, the spherical metallic bubble may become stable against fission.

Krzysztof Pomorski; Klaus Dietrich

1997-11-14

276

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

277

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

278

Terminating marine methane bubbles by superhydrophobic sponges.  

PubMed

Marine methane bubbles are absorbed, steadily stored, and continuously transported based on the employment of superhydrophobic sponges. Antiwetting sponges are water-repellent in the atmosphere and absorb gas bubbles under water. Their capacity to store methane bubbles increases with enhanced submerged depth. Significantly, trapped methane bubbles can be continuously transported driven by differential pressure. PMID:22945667

Chen, Xiao; Wu, Yuchen; Su, Bin; Wang, Jingming; Song, Yanlin; Jiang, Lei

2012-11-14

279

Statistical equilibrium of bubble oscillations in dilute bubbly flows Tim Colonius,1  

E-print Network

of bubbles with a given radius and radial velocity.2 For spherical bubbles ini- tially in static equilibriumStatistical equilibrium of bubble oscillations in dilute bubbly flows Tim Colonius,1 Rob Hagmeijer statistical equilibrium, whereby phase cancellations among bubbles with different sizes lead to time

Dabiri, John O.

280

Oceanic Gas Bubble Measurements Using an Acoustic Bubble Spectrometer  

NASA Astrophysics Data System (ADS)

Gas bubble injection by breaking waves contributes significantly to the exchange of gases between atmosphere and ocean at high wind speeds. In this respect, CO2 is primarily important for the global ocean and climate, while O2 is especially relevant for ecosystems in the coastal ocean. For measuring oceanic gas bubble size distributions, a commercially available Dynaflow Acoustic Bubble Spectrometer (ABS) has been modified. Two hydrophones transmit and receive selected frequencies, measuring attenuation and absorption. Algorithms are then used to derive bubble size distributions. Tank test were carried out in order to test the instrument performance.The software algorithms were compared with Commander and Prosperetti's method (1989) of calculating sound speed ratio and attenuation for a known bubble distribution. Additional comparisons with micro-photography were carried out in the lab and will be continued during the SPACE '08 experiment in October 2008 at Martha's Vineyard Coastal Observatory. The measurements of gas bubbles will be compared to additional parameters, such as wind speed, wave height, white cap coverage, or dissolved gases.

Wilson, S. J.; Baschek, B.; Deane, G.

2008-12-01

281

Power induced by bubbles of different sizes and frequencies on to hollow fibers in submerged membrane systems.  

PubMed

To shed light onto the relationship between sparging conditions and fouling control in submerged hollow fiber membranes, the effects of bubble size and frequency on the hydrodynamic conditions induced in membrane system were studied. Two general classes of bubbles were considered: coarse (0.75-2.5 mL) and pulse (100-500 mL). The power transferred (P(trans)) onto membranes could be used to characterise the multiple effects induced under different sparging conditions. P(trans) is proportional to root mean square of shear stress (?(rms)), the area of zone of influence (i.e. the fraction in the system where high velocity and high vorticity (turbulence) are induced by the bubble) and their rise velocity. At a given sparging rate, the power transferred onto membranes was less with coarse bubble sparging than pulse bubble sparging and increased with the size of pulse bubbles. For all cases, the power transfer efficiency was consistently higher for pulse bubble sparging than for coarse bubble sparging. The power transfer efficiency to the system was greatest for the small pulse bubbles considered when a small amount of power is required for fouling control. However, when fouling is extensive, large pulse bubbles may be required to generate the required amount of power for fouling control. PMID:24074817

Jankhah, Sepideh; Bérubé, Pierre R

2013-11-01

282

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

283

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

284

Bubbles created from vacuum fluctuation  

E-print Network

We show that the bubbles $S^2\\times S^2$can be created from vacuum fluctuation in certain De Sitter universe, so the space-time foam-like structure might really be constructed from bubbles of $S^2\\times S^2$ in the very early inflating phase of our universe. But whether such foam-like structure persisted during the later evolution of the universe is a problem unsolved now.

Liao Liu; Feng He

2001-01-05

285

Holographic description of vacuum bubbles  

E-print Network

We discuss a holographic description of vacuum bubbles, with possible implications for a consistent description of the multiverse. In particular, we elaborate on the recent observation by Maldacena, that the interior of AdS bubbles can be described in terms of CFT degrees of freedom living on the worldsheet of the bubble wall. We consider the scattering of bulk gravitons in the ambient parent vacuum, off the bubble wall. In the dual description, the transmission coefficient is interpreted as the probability that a graviton is absorbed by the worldsheet CFT degrees of freedom. The result is in agreement with intuitive expectations. Conformal invariance is not exact in this setup, and the leading corrections due to the IR and UV cut-offs are displayed. Aside from bulk scattering states, we find that when a bubble nucleates within a parent dS vacuum, there is a zero mode of the graviton which describes lower dimensional gravity with a finite Newton's constant. This massless graviton lives within one Hubble radius away from the bubble wall. Possible implications for a fully holographic description of the inflating multiverse are briefly discussed.

Jaume Garriga

2010-12-29

286

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

NASA Astrophysics Data System (ADS)

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

Stephens, James

2006-11-01

287

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

288

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

NASA Astrophysics Data System (ADS)

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

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

289

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

2005-05-03

290

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

NASA Astrophysics Data System (ADS)

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

Schipper, C.; Burgisser, A.

2010-12-01

291

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

292

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

Microsoft Academic Search

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

Yoshinori Kawase; Murray Moo-Young

1987-01-01

293

If initially the free surface is almost flat with 10 bubbles and spikes is determined by the  

E-print Network

in experiments [3,4,6,7], then, the structure of bubbles and spikes is determined by the velocity field ( )0 a characteristic time-scale kv01~ in system (1) (see (4,10), Fig.3). Bubbles are regular points of the free surface: for such a flow (flow in a tube or periodic flow with hexagonal or square symmetry) bubbles and spikes have a near

New York at Stoney Brook, State University of

294

Initial conditions for bubble universes  

SciTech Connect

The ''bubble universes'' of Coleman and De Luccia play a crucial role in string cosmology. Since our own Universe is supposed to be of this kind, bubble cosmology should supply definite answers to the long-standing questions regarding cosmological initial conditions. In particular, it must explain how an initial singularity is avoided, and also how the initial conditions for inflation were established. I argue that the simplest nonanthropic approach to these problems involves a requirement that the spatial sections defined by distinguished bubble observers should not be allowed to have arbitrarily small volumes. Casimir energy is a popular candidate for a quantum effect which can ensure this, but (because it violates energy conditions) there is a danger that it could lead to nonperturbative instabilities in string theory. I make a simple proposal for the initial conditions of a bubble universe, and show that my proposal ensures that the system is nonperturbatively stable. Thus, low-entropy conditions can be established at the beginning of a bubble universe without violating the second law of thermodynamics and without leading to instability in string theory. These conditions are inherited from the ambient spacetime.

McInnes, Brett [Department of Mathematics, National University of Singapore, 2 Science Drive 2, Singapore 117543 (Singapore)

2008-06-15

295

Holographic description of vacuum bubbles  

E-print Network

We discuss a holographic description of vacuum bubbles, with possible implications for a consistent description of the multiverse. In particular, we elaborate on the recent observation by Maldacena, that the interior of AdS bubbles can be described in terms of CFT degrees of freedom living on the worldsheet of the bubble wall. We consider the scattering of bulk gravitons in the ambient parent vacuum, off the bubble wall. In the dual description, the transmission coefficient is interpreted as the probability that a graviton is absorbed by the worldsheet CFT degrees of freedom. The result is in agreement with intuitive expectations. Conformal invariance is not exact in this setup, and the leading corrections due to the IR and UV cut-offs are displayed. Aside from bulk scattering states, we find that when a bubble nucleates within a parent dS vacuum, there is a zero mode of the graviton which describes lower dimensional gravity with a finite Newton's constant. This massless graviton lives within one Hubble radiu...

Garriga, Jaume

2010-01-01

296

Hot bubbles in a magnetic interstellar medium - Another look at the soft X-ray background  

NASA Technical Reports Server (NTRS)

An attempt is made to understand the origin and properties of an isolated local bubble of hot gas using models of explosive events in a magnetic interstellar medium which mimic the local bubble in terms of the C band X-ray surface brightness and radius. The residual bubble of hot gas reaches a maximum size with an internal pressure below ambient, and then shrinks to smaller volume and a pressure nearly equal to ambient. The X-ray brightness reaches its minimum at the time of maximum radius and rises thereafter. It is found that the bubble growth must have been confined by a probably unacceptably large external pressure in order for the hot gas in the maximally extended cavity to radiate at a rate like that observed in the soft X-ray background.

Edgar, Richard J.; Cox, Donald P.

1993-01-01

297

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

SciTech Connect

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

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

2006-10-01

298

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

299

Birth and growth of cavitation bubbles within water under tension  

E-print Network

Water under tension, such as the water rising in tree vessels, is in a metastable state. Water cavitates spontaneously when the tension is high enough, as observed at equilibrium in the water filled holes of a drying hydrogel, called artifical trees. Here, in order to understand the dynamics of cavitation in tensed water, we directly trigger cavitation events, taking advantage of the disturbance generated by a focused laser pulse. We find that the inception of a bubble progresses in two stages. The first stage is ultra-fast, lasting less than microseconds, during which a bubble with a finite volume suddenly appears. This event relaxes the water tension, that we can therefore estimate. A second, slower stage follows when water diffuses into the surrounding medium.

Vincent, Olivier; Quinto-Su, Pedro A; Ohl, Claus-Dieter

2011-01-01

300

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

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

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

1999-03-01

302

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, Michal; Schmitz, Georg; Lewin, Peter A.

2012-01-01

303

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.

304

Interchange Instability and "Bubbles" Gravitational Rayleigh-Taylor  

E-print Network

Interchange Instability and "Bubbles" Linear Nonlinear: Bubbles, fingers, vortices Magnetosphere #12;Jovian Magnetosphere #12;Interchange Bubbles should Propagate Inward through the Io Plasma al., JGR (1994) Jovian day is 11 hours! #12;Interchange Bubble seen in Jovian Magnetosphere? B. H

Mauel, Michael E.

305

From rational bubbles to crashes  

NASA Astrophysics Data System (ADS)

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

Sornette, D.; Malevergne, Y.

2001-10-01

306

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

307

Collapsing Sub-Critical Bubbles  

E-print Network

In the standard scenario, the electroweak phase transition is a first order phase transition which completes by the nucleation of critical bubbles. Recently, there has been speculation that the standard picture of the electroweak phase transition is incorrect. Instead, it has been proposed that throughout the phase transition appreciable amounts of both broken and unbroken phases of $SU(2)$ coexist in equilibrium. I argue that this can not be the case. General principles insure that the universe will remain in a homogenous state of unbroken $SU(2)$ until the onset of critical bubble production.

Greg W. Anderson

1992-09-20

308

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

309

Electric field observations of equatorial bubbles  

NASA Technical Reports Server (NTRS)

Results from the double floating probe experiment performed on the San Marco D satellite are presented, with emphasis on the observation of large incremental changes in the convective electric field vector at the boundary of equatorial plasma bubbles. Attention is given to isolated bubble structures in the upper ionospheric F regions; these observed bubble encounters are divided into two types - type I (live bubbles) and type II (dead bubbles). Type I bubbles show varying degrees of plasma depletion and large upward velocities range up to 1000 km/s. The geometry of these bubbles is such that the spacecraft orbit may cut them where they are tilting either eastward or (more often) westward. Type II bubbles exhibit plasma density depletion but no appreciable upward convection. Both types of events are usually surrounded by a halo of plasma turbulence, which can extend considerably beyond the region of plasma depletion.

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

1992-01-01

310

Soap Bubbles on a Cold Day.  

ERIC Educational Resources Information Center

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

Waiveris, Charles

1994-01-01

311

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

312

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...

313

Experimental characterisation of bubbly flow using MRI  

E-print Network

This thesis describes the first application of ultra-fast magnetic resonance imaging (MRI) towards the characterisation of bubbly flow systems. The principle goal of this study is to provide a hydrodynamic characterisation of a model bubble column...

Tayler, Alexander B.

2011-11-08

314

Detonation wave phenomena in bubbled liquid  

Microsoft Academic Search

Shock wave propagation was investigated in two phase media consisting of diluted glycerin (85%) and reactive gas bubbles. To understand these complex phenomena, we first performed a numerical analysis and experimental studies of single bubbles containing a reactive gas-mixture. For the two-phase mixtures, a needle matrix bubble-generator enabled us to produce a homogeneous bubble distribution with a size dispersion less

A. E. Beylich

1990-01-01

315

Detonation wave phenomena in bubbled liquid  

Microsoft Academic Search

Shock wave propagation was investigated in two phase media consisting of diluted glycerin (85%) and reactive gas bubbles. To understand these complex phenomena, we first performed a numerical analysis and experimental studies of single bubbles containing a reactive gas-mixture. For the two-phase mixtures, a needle matrix bubble-generator enabled us to produce a homogeneous bubble distribution with a size dispersion less

A. Gülhan; A. E. Beylich

1990-01-01

316

Lifetime expectancy for a soap bubble  

NASA Astrophysics Data System (ADS)

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

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

2007-11-01

317

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

Microsoft Academic Search

We present some experimental results about the interaction of a pair of bubbles ascending in non-Newtonian fluids. A high speed camera was used to follow in-line and off-line rising motion of two bubbles in a Newtonian fluid (a glycerin-water solution), a Boger fluid (aqueous polyacrylamide solution), and a shear-thinning fluid (aqueous xanthan solution). For the case of shear-thinning fluids, the

Diego Samano; Rodrigo Velez; Roberto Zenit

2009-01-01

318

HIGH QUALITY ANISOTROPIC TETRAHEDRAL MESH GENERATION VIA ELLIPSOIDAL BUBBLE PACKING  

E-print Network

the behavior of soap bubbles in nature. If we pack soap bubbles in a volumetric domain, the bubblesHIGH QUALITY ANISOTROPIC TETRAHEDRAL MESH GENERATION VIA ELLIPSOIDAL BUBBLE PACKING Soji Yamakawa1 through a physically based particle simulation, which we call 'bubble packing.' Ellipsoidal bubbles

Shimada, Kenji

319

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

NASA Astrophysics Data System (ADS)

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

Stephens, James

2005-11-01

320

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

321

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

322

Inverted Soap Bubbles-A Surface Phenomenon  

Microsoft Academic Search

By pouring soap water onto a surface of soap water it is possible to produce thin spherical shells of air in the water (inverted soap bubbles). The largest diameter observed is about 20 mm. Interference colors indicate shell thickness of the order 0.001 mm. Lifetimes of the bubbles of 4-5 minutes have been observed. A connection between the inverted bubbles

N. Skogen

1956-01-01

323

A User's Guide to Bubbles Frdric Gosselin  

E-print Network

A User's Guide to Bubbles Frédéric Gosselin Philippe G. Schyns Correspondence concerning;Abstract This article provides a user's guide to Bubbles, a technique that reveals the information Effect and discuss the six basic decisions that must be made to set up a Bubbles experiment (i

Gosselin, Frédéric

324

Dynamic removal of oral biofilms by bubbles  

Microsoft Academic Search

A novel approach to the removal of biofilms from solid surfaces is to pass large numbers of air bubbles over the surfaces. Such a phenomenon occurs when teeth are brushed with some types of powered toothbrushes that accelerate bubbly fluid against or across teeth surfaces. Video recordings of air bubbles propelled against a mature biofilm of Streptococcus mutans showed that

Michael R. Parini; William G. Pitt

2006-01-01

325

Frictional drag reduction by bubble injection  

NASA Astrophysics Data System (ADS)

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

Murai, Yuichi

2014-07-01

326

Multifractal properties of large bubble paths in a single bubble column  

NASA Astrophysics Data System (ADS)

In the paper the paths of bubbles emitted from the brass nozzle with inner diameter equal to 1.6 mm have been analyzed. The mean frequency of bubble departure was in the range from 2 to 65.1 Hz. Bubble paths have been recorded using a high speed camera. The image analysis technique has been used to obtain the bubble paths for different mean frequencies of bubble departures. The multifractal analysis (WTMM - wavelet transform modulus maxima methodology) has been used to investigate the properties of bubble paths. It has been shown that bubble paths are the multifractals and the influence of previously departing bubbles on bubble trajectory is significant for bubble departure frequency fb > 30 Hz.

Mosdorf, Romuald; Wyszkowski, Tomasz; D?browski, Kamil

2011-04-01

327

The stability of buoyant bubbles in the atmospheres of galaxy clusters  

E-print Network

The buoyant rise of hot plasma bubbles inflated by AGN outflows in galaxy clusters can heat the cluster gas and thereby compensate radiative energy losses of this material. Numerical simulations of this effect often show the complete disruption of the bubbles followed by the mixing of the bubble material with the surrounding cluster gas due to fluid instabilities on the bubble surface. This prediction is inconsistent with the observations of apparently coherent bubble structures in clusters. We derive a general description in the linear regime of the growth of instabilities on the surface between two fluids under the influence of a gravitational field, viscosity, surface tension provided by a magnetic field and relative motion of the two fluids with respect to each other. We demonstrate that Kelvin-Helmholtz instabilities are always suppressed, if the fluids are viscous. They are also suppressed in the inviscid case for fluids of very different mass densities. We show that the effects of shear viscosity as well as a magnetic fields in the cluster gas can prevent the growth of Rayleigh-Taylor instabilities on relevant scale lengths. R-T instabilities on pc-scales are suppressed even if the kinematic viscosity of the cluster gas is reduced by two orders of magnitude compared to the value given by Spitzer for a fully ionised, unmagnetised gas. Similarly, magnetic fields exceeding a few microG result in an effective surface tension preventing the disruption of bubbles. For more massive clusters, instabilities on the bubble surface grow faster. This may explain the absence of thermal gas in the north-west bubble observed in the Perseus cluster compared to the apparently more disrupted bubbles in the Virgo cluster.

C. R. Kaiser; G. Pavlovski; E. C. D. Pope; H. Fangohr

2005-02-08

328

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

Konicek-Moran, Richard

2010-03-12

329

Soap bubbles. 2 [Computer graphics  

Microsoft Academic Search

For pt.1 see ibid., previous issue. Soap bubbles are fragile, beautiful phenomena. They're fun to make and play with, and their geometry is as clean and elegant as anything in nature, which makes them particularly suited to computer graphics. In pt.1 I discussed the nature of soap films. These thin sheets of soapy water have less surface tension than water

A. Glassner

2000-01-01

330

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.

331

Electrino bubbles and relational entanglement  

E-print Network

We argue that the phenomena exhibited by bubbles forming around free electrons in liquid helium and examined by Maris in his controversial 2000 paper point to the experimental relevance of relational entanglement. An experiment to verify/disprove the relevant argument is suggested.

Italo Vecchi

2007-03-26

332

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

333

The dynamics of a vapour bubble growth under the boiling of a subcooled liquid in low volumes  

NASA Astrophysics Data System (ADS)

This paper presents an experimental study of the dynamics of a vapour bubble growth under the boiling of a subcooled liquid in low volumes. The influence of the mode parameters (heat flux and subcooling to the saturation temperature) on the geometric characteristics of the vapour bubble (base diameter and height) has been found.

Orlova, Evgenija; Kuznetsova, Geniy; Feoktistovb, Dmitriy

2014-08-01

334

Mechanisms of bubble coalescence in silicic magmas  

NASA Astrophysics Data System (ADS)

Bubble coalescence is an important process that strongly affects magmatic degassing. Without coalescence, bubbles remain isolated from one another in the melt, severely limiting gas release. Despite this fact, very little has been done to identify coalescence mechanisms from textures of magmatic rocks or to quantify the dynamics of bubble coalescence in melts. In this paper, we present a systematic study of bubble-coalescence mechanisms and dynamics in natural and experimentally produced bubbly rhyolite magma. We have used a combination of natural observations aided by high-resolution X-ray computed tomography, petrological experiments, and physical models to identify different types of bubble-bubble interaction that lead to coalescence on the timescales of magma ascent and eruption. Our observations and calculations suggest that bubbles most efficiently coalesce when inter-bubble melt walls thin by stretching rather than by melt drainage from between converging bubble walls. Orders of magnitude are more rapid than melt drainage, bubble wall stretching produces walls thin enough that inter-bubble pressure gradients may cause the melt wall to dimple, further enhancing coalescence. To put these results into volcanogical context, we have identified magma ascent conditions where each coalescence mechanism should act, and discuss the physical conditions for preserving coalescence structures in natural pumice. The timescales we propose could improve volcanic eruption models, which currently do not account for bubble coalescence. Although we do not address the effect of shear strain on bubble coalescence, the processes discussed here may operate in several different eruption regimes, including vesiculation of lava domes, post-fragmentation frothing of vulcanian bombs, and bubbling of pyroclasts in conduits.

Castro, Jonathan M.; Burgisser, Alain; Schipper, C. Ian; Mancini, Simona

2012-12-01

335

Effectiveness of Measures of Performance During Speculative Bubbles  

E-print Network

Statistical analysis of financial data most focused on testing the validity of Brownian motion (Bm). Analysis performed on several time series have shown deviation from the Bm hypothesis, that is at the base of the evaluation of many financial derivatives. We inquiry in the behavior of measures of performance based on maximum drawdown movements (MDD), testing their stability when the underlying process deviates from the Bm hypothesis. In particular we consider the fractional Brownian motion (fBm), and fluctuations estimated empirically on raw market data. The case study of the rising part of speculative bubbles is reported.

Petroni, Filippo

2007-01-01

336

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

337

Tharsis Rise Graben  

NASA Technical Reports Server (NTRS)

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

2002-01-01

338

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

2013-10-22

339

How long will a bubble be ?  

E-print Network

A soap bubble is a metastable object that eventually breaks. Indeed, the soapy water film thins until rupture, due to drainage and evaporation. In our experimental investigations, floating bubbles at the surface of a liquid bath have been considered. Their lifetime has been measured and reported with respect to their radius. Large bubbles last longer than small ones. Moreover, small bubbles have more predictable lifetimes than large ones. We propose a general equation for that lifetime, based on the lubrication theory. The evaporation is shown to be an essential process which determines the bubble lifetime.

Gilet, T; Reyssat, E; Vandewalle, N; Dorbolo, S

2007-01-01

340

Mesoporous hollow spheres from soap bubbling.  

PubMed

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

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

2012-02-01

341

Bubbles in Anti-de Sitter Space  

E-print Network

We explore the bubble spacetimes which can be obtained from double analytic continuations of static and rotating black holes in anti-de Sitter space. In particular, we find that rotating black holes with elliptic horizon lead to bubble spacetimes only in dimension greater than five. For dimension greater than seven, the topology of the bubble can be non-spherical. However, a bubble spacetime is shown to arise from a rotating de Sitter black hole in four dimensions. In all cases, the evolution of the bubble is of de Sitter type. Double analytic continuations of hyperbolic black holes and branes are also discussed.

Danny Birmingham; Massimiliano Rinaldi

2002-05-23

342

Asymmetric interface temperature during vapor bubble growth  

NASA Astrophysics Data System (ADS)

We investigate the nucleation, growth, and detachment of single vapor bubbles at the interface microscale. Shear flow is used to investigate pool and convective boiling situations using visible and infrared visualizations. We determine a threshold Reynolds number for the onset of asymmetric interfacial temperatures. Below this threshold, bubble growth is geometrically and thermally symmetric, while above, bubbles no longer grow thermally symmetrically. This is explained by the dominance of convective heat transfer removal over viscous effects at the bubble interface. We experimentally demonstrate asymmetric interfacial temperature profiles that should be taken into account for future bubble growth modeling.

Diana, A.; Castillo, M.; Steinberg, T.; Brutin, D.

2013-07-01

343

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

NASA Technical Reports Server (NTRS)

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

Darrozes, J. S.; Ligneul, P.

1982-01-01

344

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

345

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

346

Quantification of gas bubble emissions from submarine hydrocarbon seeps at the Makran continental margin (offshore Pakistan)  

NASA Astrophysics Data System (ADS)

Evidence for twelve sites with gas bubble emissions causing hydroacoustic anomalies in 18 kHz echosounder records (`flares') was obtained at the convergent Makran continental margin. The hydroacoustic anomalies originating from hydrocarbon seeps at water depths between 575 and 2870 m disappeared after rising up to 2000 m in the water column. Dives with the remotely operated vehicle `Quest 4000 m' revealed that several individual bubble vents contributed to one hydroacoustic anomaly. Analyzed gas samples suggest that bubbles were mainly composed of methane of microbial origin. Bubble size distributions and rise velocities were determined and the volume flux was estimated by counting the emitted bubbles and using their average volume. We found that a low volume flux (Flare 1 at 575 mbsl: 90 ml/min) caused a weak hydroacoustic signal in echograms whereas high volume fluxes (Flare 2 at 1027 mbsl: 1590 ml/min; Flare 5 C at 2870 mbsl: 760 ml/min) caused strong anomalies. The total methane bubble flux in the study area was estimated by multiplying the average methane flux causing a strong hydroacoustic anomaly in the echosounder record with the total number of equivalent anomalies. An order-of-magnitude estimate further considers the temporal variability of some of the flares, assuming a constant flux over time, and allows a large range of uncertainty inherent to the method. Our results on the fate of bubbles and the order-of-magnitude estimate suggest that all of the ˜40 ± 32 × 106 mol methane emitted per year within the gas hydrate stability zone remain in the deep ocean.

RöMer, Miriam; Sahling, Heiko; Pape, Thomas; Bohrmann, Gerhard; Spieß, Volkhard

2012-10-01

347

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

NASA Astrophysics Data System (ADS)

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

Sidorova, Larisa; Filippov, Sergey

348

Eulerian simulation strategy for scaling up a bubble column slurry reactor for Fischer-Tropsch synthesis  

Microsoft Academic Search

CFD simulations were carried out in the Eulerian framework using both two-dimensional (2D) axisymmetric and transient three-dimensional (3D) strategies to describe the influence of column diameter on the hydrodynamics and dispersion characteristics of the bubble column slurry reactor for Fischer-Tropsch (FT) synthesis. Interactions between the bubbles and the slurry were taken into account by means of a momentum-exchange, or drag,

Baten van J. M; R. Krishna

2004-01-01

349

On the Rayleigh-Taylor Instability of Radio Bubbles in Galaxy Clusters  

E-print Network

We consider the Rayleigh-Taylor instability in the early evolution of the rarefied radio bubbles (cavities) observed in many cooling flow clusters of galaxies. The top of a bubble becomes prone to the Rayleigh-Taylor instability as the bubble rises through the intra-cluster medium (ICM). We show that while the jet is powering the inflation, the deceleration of the bubble-ICM interface is able to reverse the Rayleigh-Taylor instability criterion. In addition, the inflation introduces a drag effect which increases substantially the instability growth time. The combined action of these two effects considerably delays the onset of the instability. Later on, when the magnitude of the deceleration drops or the jet fades, the Rayleigh-Taylor and the Kelvin-Helmholtz instabilities set in and eventually disrupt the bubble. We conclude that the initial deceleration and drag, albeit unable to prevent the disruption of a bubble, may significantly lengthen its lifetime, removing the need to invoke stabilising magnetic fields.

Fabio Pizzolato; Noam Soker

2006-05-21

350

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...

351

Bubbling the False Vacuum Away  

E-print Network

We investigate the role of nonperturbative, bubble-like inhomogeneities on the decay rate of false-vacuum states in two and three-dimensional scalar field theories. The inhomogeneities are induced by setting up large-amplitude oscillations of the field about the false vacuum as, for example, after a rapid quench or in certain models of cosmological inflation. We show that, for a wide range of parameters, the presence of large-amplitude bubble-like inhomogeneities greatly accelerates the decay rate, changing it from the well-known exponential suppression of homogeneous nucleation to a power-law suppression. It is argued that this fast, power-law vacuum decay -- known as resonant nucleation -- is promoted by the presence of long-lived oscillons among the nonperturbative fluctuations about the false vacuum. A phase diagram is obtained distinguishing three possible mechanisms for vacuum decay: homogeneous nucleation, resonant nucleation, and cross-over. Possible applications are briefly discussed.

Marcelo Gleiser; Barrett Rogers; Joel Thorarinson

2007-08-28

352

Sonoporation from jetting cavitation bubbles.  

PubMed

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

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

2006-12-01

353

An Expanding Bubble in Space  

NASA Technical Reports Server (NTRS)

Astronomers, using the Wide Field Planetary Camera 2 on board NASA's Hubble Space Telescope in October and November 1997 and April 1999, imaged the Bubble Nebula (NGC 7635) with unprecedented clarity. For the first time, they are able to understand the geometry and dynamics of this very complicated system. Earlier pictures taken of the nebula with the Wide Field Planetary Camera 1 left many issues unanswered, as the data could not be fully calibrated for scientific use. In addition, those data never imaged the enigmatic inner structure presented here. The remarkably spherical 'Bubble' marks the boundary between an intense wind of particles from the star and the more quiescent interior of the nebula. Research Team: Donald Walter (South Carolina State University), Paul Scowen, Jeff Hester, Brian Moore (Arizona State University), Reggie Dufour, Patrick Hartigan and Brent Buckalew (Rice University).

2000-01-01

354

Three-dimensional experimental investigation of the two-phase flow structure in a bubbly pipe flow  

NASA Astrophysics Data System (ADS)

An experimental study was performed to investigate the turbulence structure in a bubbly flow. Particle Image Velocimetry (PIV), a whole-field, non-invasive velocity measurement technique, was utilized. PIV is capable of producing an instantaneous velocity map of steady-state and transient flows of a fluid seeded with microscopically small neutral density particles (within either a two-dimensional plane or a three-dimensional volume). Both qualitative and quantitative spatial information about the flow field being studied can be obtained. The quantitative spatial velocity information can be further processed into useful information of different flow parameters such as vorticity, pathlines, velocity distributions, turbulence intensities, and kinetic energies. An experimental test facility was constructed to generate and visualize the bubbles which were studied as they rose vertically in a clear pipe. The study investigated the influence of a bubble on the surrounding flow field (bubble/flow interaction). A stereoscopic reconstruction technique was developed to obtain the three-dimensional velocity vector data from the recorded planar images. Conditional sampling of the fluid velocity components for a fixed (determined) bubble path within the viewing volume was applied. The flow pattern in the wake region produced by the bubble presence was unsteady. The results showed a general agreement with theoretical results and previous studies found in the literature. Oscillations in the flow field downstream (front) of the rising bubble were noted, for a distance of about one to two bubble diameters. Vortex tubes and recirculation regions upstream (back) of the rising bubble were also observed.

Schmidl, William Daniel

355

Computational Study of Adiabatic Bubble Growth Dynamics from Submerged Orifices in Aqueous Solutions of Surfactants  

NASA Astrophysics Data System (ADS)

The growth dynamics of isolated gas bubbles (inception ? growth ? departure) emanating from a capillary-tube orifice submerged in isothermal pools of aqueous solutions of surfactants is computationally investigated. The Navier-Stokes equations are solved in the liquid and the gas phase. The evolution of the gas-liquid interface is tracked using a Volume-of-Fluid (VOF) method. Surfactant molecules in aqueous solutions have a tendency to diffuse towards the gas-liquid interface and are subsequently adsorbed onto it. This time dependent adsorption process gives rise to the dynamic surface tension behavior of the aqueous surfactant solutions. To computationally model this behavior, the species conservation equation for the surfactant is solved in the bulk fluid and is coupled with the dynamic adsorption-desorption of the surfactant on the interface. A new form of the surfactant transport equation is derived that was necessary to incorporate the interfacial transport in the volume-of-fluid method where the interface is spread over multiple grid cells. Computational results were obtained for bubble growth dynamics from a capillary orifice in a pool of pure water and in an aqueous solution of Sodium Dodecyl Sulphate (SDS). The evolving bubble shape and the flow field in the two phases in the pure liquid and in surfactant solution are compared for a variety of air flow rates (from 4 ml/min to 24 ml/min) in the constant bubble regime. To validate the computational model, the results for the transient shape and size of growing bubbles in pure water were compared with available experimental data and were found to be in excellent agreement. Results show that the dynamic surface tension relaxation gives rise to smaller bubble size at departure in aqueous surfactant solution compared to that in pure water. However, this effect is found to be a function of the air flow rate. At high air flow rates (24 ml/min), the short time for bubble growth allows relatively smaller drop in the surface tension and produces departure diameters similar to bubble diameters in water. At low air flow rates (4 ml/min), the departure time is much larger and allows for complete surface tension relaxation. As such the departure diameters at low air flow rates in aqueous surfactant solution are significantly smaller than those predicted in pure water. Also, the flow patterns around a growing bubble in surfactant solution are altered due to the non-uniform surfactant adsorption along the gas-liquid interface. The computational results elucidate the role of surfactant transport on bubble growth dynamics.

Deodhar, Anirudh M.

356

Bioinspired bubble design for particle generation  

PubMed Central

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

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

2012-01-01

357

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

358

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

359

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

360

A new active cavitation mapping technique for pulsed HIFU applications--bubble Doppler.  

PubMed

In this work, a new active cavitation mapping technique for pulsed high-intensity focused ultrasound (pHIFU) applications termed bubble Doppler is proposed and its feasibility is tested in tissue-mimicking gel phantoms. pHIFU therapy uses short pulses, delivered at low pulse repetition frequency, to cause transient bubble activity that has been shown to enhance drug and gene delivery to tissues. The current gold standard for detecting and monitoring cavitation activity during pHIFU treatments is passive cavitation detection (PCD), which provides minimal information on the spatial distribution of the bubbles. B-mode imaging can detect hyperecho formation, but has very limited sensitivity, especially to small, transient microbubbles. The bubble Doppler method proposed here is based on a fusion of the adaptations of three Doppler techniques that had been previously developed for imaging of ultrasound contrast agents-color Doppler, pulse-inversion Doppler, and decorrelation Doppler. Doppler ensemble pulses were interleaved with therapeutic pHIFU pulses using three different pulse sequences and standard Doppler processing was applied to the received echoes. The information yielded by each of the techniques on the distribution and characteristics of pHIFU-induced cavitation bubbles was evaluated separately, and found to be complementary. The unified approach-bubble Doppler-was then proposed to both spatially map the presence of transient bubbles and to estimate their sizes and the degree of nonlinearity. PMID:25265178

Li, Tong; Khokhlova, Tatiana D; Sapozhnikov, Oleg A; O'Donnell, Matthew; Hwang, Joo Ha

2014-10-01

361

The Fermi Bubbles: Supersonic AGN Jets with Anisotropic Cosmic Ray Diffusion  

E-print Network

The Fermi Gamma-ray Space Telescope reveals two large bubbles in the Galaxy, which extend nearly symmetrically ~50 degrees above and below the Galactic center (GC). Using three-dimensional (3D) magnetohydrodynamic (MHD) simulations that self-consistently include the dynamical interaction between cosmic rays (CR) 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 ROSAT 1.5 keV map can be successfully reproduced by a recent jet activity from the central active galactic nucleus (AGN). 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. The 'young' bubbles naturally satisfy the upper limit of bubble ages estimated from the cooling time of high-energy electrons. No additional physical mechanis...

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

2012-01-01

362

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

NASA Astrophysics Data System (ADS)

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

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

2010-03-01

363

BUBBLE DYNAMICS AT GAS-EVOLVING ELECTRODES  

SciTech Connect

Nucleation of bubbles, their growth by diffusion of dissolved gas to the bubble surface and by coalescence, and their detachment from the electrode are all very fast phenomena; furthermore, electrolytically generated bubbles range in size from ten to a few hundred microns; therefore, magnification and high speed cinematography are required to observe bubbles and the phenomena of their growth on the electrode surface. Viewing the action from the front side (the surface on which the bubbles form) is complicated because the most important events occur close to the surface and are obscured by other bubbles passing between the camera and the electrode; therefore, oxygen was evolved on a transparent tin oxide "window" electrode and the events were viewed from the backside. The movies showed that coalescence of bubbles is very important for determining the size of bubbles and in the chain of transport processes; growth by diffusion and by coalescence proceeds in series and parallel; coalescing bubbles cause significant fluid motion close to the electrode; bubbles can leave and reattach; and bubbles evolve in a cycle of growth by diffusion and different modes of coalescence. An analytical solution for the primary potential and current distribution around a spherical bubble in contact with a plane electrode is presented. Zero at the contact point, the current density reaches only one percent of its undisturbed value at 30 percent of the radius from that point and goes through a shallow maximum two radii away. The solution obtained for spherical bubbles is shown to apply for the small bubbles of electrolytic processes. The incremental resistance in ohms caused by sparse arrays of bubbles is given by {Delta}R = 1.352 af/kS where f is the void fraction of gas in the bubble layer, a is the bubble layer thickness, k is the conductivity of gas free electrolyte, and S is the electrode area. A densely populated gas bubble layer on an electrode was modeled as a hexagonal array of dielectric spheres. Accurately machined lucite spheres were placed one at a time in one end of a hexagonal cell which simulated the unit cell of such an array. The resistance as a function of gas bubble layer packing density sharply increased as close packing was approached. Because the interaction of the fields around bubbles closely spaced in the direction perpendicular to the current dominates the added resistance, and because there is a tri-modal distribution of bubble sizes in a bubble layer, the Distribution Model of Meredith and Tobias (16), derived for three dimensional gas dispersions, approximately predicted the conductivity of a bubble layer at void fractions greater than 0.3. At moderate-to-high current densities, the bubble layer in a cell having an interelectrode gap of half a centimeter could increase the ohmic resistance by as much as 20 percent.

Sides, Paul J.

1980-12-01

364

Collapse of Kaluza-Klein Bubbles  

E-print Network

Kaluza-Klein theory admits ``bubble" configurations, in which the circumference of the fifth dimension shrinks to zero on some compact surface. A three parameter family of such bubble initial data at a moment of time-symmetry (some including a magnetic field) has been found by Brill and Horowitz, generalizing the (zero-energy) ``Witten bubble" solution. Some of these data have negative total energy. We show here that all the negative energy bubble solutions start out expanding away from the moment of time symmetry, while the positive energy bubbles can start out either expanding or contracting. Thus it is unlikely that the negative energy bubbles would collapse and produce a naked singularity.

Steven Corley; Ted Jacobson

1994-03-09

365

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

E-print Network

Thermocapillary migration of long bubbles in polygonal tubes. II. Experiments E. Lajeunesse experimentally the thermocapillary migration of a long gas bubble in a horizontal pipe of rectangular cross migration of the bubble towards the hotter region. The bubble velocity is found to be independent of bubble

Lajeunesse, Eric

366

Dynamics of a Single Reactive Gas Bubble  

Microsoft Academic Search

\\u000a The dynamics of a single combustible stoichiometric oxyacetylene gas bubble immersed in glycerine subjected to an impulsive\\u000a pressure wave has been studied experimentally and theoretically. Emphasis is placed on determining the range of bubble sizes\\u000a over which ignition of the gas occurs after the passage of a pressure pulse generated by the impact of a projectile with a\\u000a piston. Bubbles

B. Bruckert; D. L. Frost; A. N. Meidani; R. Chue; M. Brouillette

367

Bubble kinematics in a sheared foam  

E-print Network

We characterize the kinematics of bubbles in a sheared two-dimensional foam using statistical measures. We consider the distributions of both bubble velocities and displacements. The results are discussed in the context of the expected behavior for a thermal system and simulations of the bubble model. There is general agreement between the experiments and the simulation, but notable differences in the velocity distributions point to interesting elements of the sheared foam not captured by prevalent models.

Yuhong Wang; Kapilanjan Krishan; Michael Dennin

2006-07-05

368

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

2008-10-04

369

Bremsstrahlung Radiation At a Vacuum Bubble Wall  

E-print Network

When charged particles collide with a vacuum bubble, they can radiate strong electromagnetic waves due to rapid deceleration. Owing to the energy loss of the particles by this bremsstrahlung radiation, there is a non-negligible damping pressure acting on the bubble wall even when thermal equilibrium is maintained. In the non-relativistic region, this pressure is proportional to the velocity of the wall and could have influenced the bubble dynamics in the early universe.

Jae-Weon Lee; Kyungsub Kim; Chul H. Lee; Ji-ho Jang

2007-04-06

370

Constraining bubbling of methane from thermokarst lakes  

NASA Astrophysics Data System (ADS)

In northern thermokarst lakes, which form in depressions left as permafrost thaws, methane, a greenhouse gas, can be released from lake sediments to the atmosphere through bubbling, or ebullition. Constraining the amount of methane released through bubbling would help scientists understand the role of thawing permafrost in the carbon cycle and global climate change. However, bubbling is highly variable in both space and time and thus difficult to measure accurately, so there are large uncertainties in estimates of methane emissions from northern ecosystems.

Balcerak, Ernie

2013-08-01

371

Bubbling at high flow rates in inviscid and viscous liquids (slags)  

NASA Astrophysics Data System (ADS)

The behavior of gas discharging into melts at high velocities but still in the bubbling regime has been investigated in a laboratory modeling study for constant flow conditions. Air or helium was injected through a vertical tuyere into water, zinc-chloride, and aqueous glycerol solutions. High speed cinematography and pressure measurements in the tuyere have been carried out simultaneously. Pressure fluctuations at the injection point were monitored and correlated to the mode of bubble formation. The effects of high gas flow rates and high liquid viscosities have been examined in particular. Flow rates were employed up to 10-3 m3/s and viscosity to 0.5 Ns/m2. In order to attain a high gas momentum, the tuyere diameter was only 3 x 10-3 m. The experimental conditions and modeling liquids were chosen with special reference to the established practice of submerged gas injection to treat nonferrous slags. Such slags can be highly viscous. Bubble volume is smaller than that calculated from existing models such as those given by Davidson and Schüler10,11 due to the effect of gas momentum elongating the bubbles. On the other hand, viscosity tends to retard the bubble rise velocity, thus increasing volumes. To take elongation into account, a mathematical model is presented that assumes a prolate ellipsoidal shape of the bubbles. The unsteady potential flow equations for the liquid are solved for this case. Viscous effects are taken into account by noting that flow deviates from irrotational motion only in a thin boundary layer along the surface of the bubble. Thus, drag on the bubble can be obtained by calculating the viscous energy dissipation for potential flow past an ellipse. The time-dependent inertia coefficient for the ellipsoid is found by equating the vertical pressure increase inside and outside the bubble. This pressure change in the bubble is obtained by assuming that gas enters as a homogeneous jet and then calculating the stagnation pressure at the apex of the bubble.

Engh, T. Abel; Nilmani, M.

1988-02-01

372

Some problems of the theory of bubble growth and condensation in bubble chambers  

NASA Technical Reports Server (NTRS)

This work is an attempt to explain the reasons for the discrepancies between the theoretical and experimental values of bubble growth rate in an overheated liquid, and to provide a brief formulation of the main premises of the theory on bubble growth in liquid before making a critical analysis. To simplify the problem, the floating upward of bubbles is not discussed; moreover, the study is based on the results of the theory of the behavior of fixed bubbles.

Tkachev, L. G.

1988-01-01

373

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

374

Marangoni bubble motion in zero gravity  

NASA Technical Reports Server (NTRS)

It is shown experimentally that the Marangoni phenomenon is a primary mechanism for the movement of a gas bubble in a nonisothermal liquid in a low-gravity environment. In such two-phase flow systems, local variations in bubble surface tension are caused by a temperature gradient in the liquid. Shearing stresses thus generated at the bubble surface lead to convection in both media, as a result of which the bubble begins to move. A mathematical model consisting of the Navier-Stokes equations and the thermal energy equations, along with the appropriate boundary conditions for both media, is proposed.

Thompson, R. L.; De Witt, K. J.

1979-01-01

375

Multiple Spark-Generated Bubble Interactions  

NASA Astrophysics Data System (ADS)

The complex interactions of two and three spark-generated bubbles are studied using high speed photography. The corresponding simulations are performed using a 3D Boundary Element Method (BEM) code. The bubbles generated are between 3 to 5 mm in radius, and they are either in-phase or out-of-phase with one another. The possible interaction phenomena between two identically sized bubbles are summarized. Depending on their relative distances and phase differences, they can coalesce, jet towards or away from one another, split into smaller bubbles, or 'catapult' away from one another. The 'catapult' effect can be utilized to generated high speed jet in the absence of a solid boundary or shockwave. Also three bubble interactions are highlighted. Complicated phenomena such as bubble forming an elliptical shape and bubble splitting are observed. The BEM simulations provide insight into the physics of the phenomena by providing details such as detailed bubble shape changes (experimental observations are limited by the temporal and spatial resolution), and jet velocity. It is noted that the well-tested BEM code [1,2] utilized here is computationally very efficient as compared to other full-domain methods since only the bubble surface is meshed.

Khoo, Boo Cheong; Adikhari, Deepak; Fong, Siew Wan; Klaseboer, Evert

376

Bubble dynamics in an acoustic flow field  

NASA Astrophysics Data System (ADS)

Dynamics of interaction between cavitational bubbles is investigated when a complex of a compression and a rarefaction pulse passes through a liquid with pre-existing micro bubbles. Cavitation was generated experimentally with the help of electromagnetic generator of a flat and a convergent acoustic pulse (2-mus duration, 1-20 MPa) having the form of a hollow sphere segment. A modeling was performed within the frame of two-dimensional axisymmetric nonstationary approach on the basis of conservation laws for a model of an ideal compressible liquid. A thermodynamic flow field was computed both in liquid and inside bubbles. Behind the rarefaction wave the microbubbles begin to grow and generate secondary compression shocks, the amplitude of which may exceed that of the incident pulse under certain conditions. It is shown that the process of bubble interaction within a cluster is accompanied by bubble coalescence, fragmentation, and collapse of the initial bubble or its fragments. Simultaneously, high temperature spots appear in the bubble compressing by the secondary wave. Adiabatic heating of gas either inside a bubble or near the neck between a bubble and its fragment may result in sonoluminescence, also observed in experiments. [Work supported by ASA, DAAD, and RFBR.

Voronin, Dmitry V.; Sankin, Georgij N.; Mettin, Robert; Teslenko, Vyacheslav S.; Lauterborn, Werner

2002-11-01

377

Bubble and spherical air shell formation dynamics.  

PubMed

We studied the formation dynamics of air bubbles emitted from a nozzle submerged in aqueous glycerol solutions of different viscosities. We describe the evolution of the bubbling regimes by using the air flow rate as a control parameter and the time between successive bubbles as a dynamical variable. Some results concerning bubbling coalescence were emulated with a combination of simple maps. We also observed the formation of air shells surrounding liquid drops inside the liquid, known as antibubbles. The antibubbling conditions were related to an intermittent regime. PMID:12513583

Tufaile, A; Sartorelli, J C

2002-11-01

378

Analysis of a deflating soap bubble  

NASA Astrophysics Data System (ADS)

A soap bubble on the end of a cylindrical tube is seen to deflate as the higher pressure air inside the bubble escapes through a tube. We perform an experiment to measure the radius of the slowly deflating bubble and observe that the radius decreases to a minimum before quickly increasing. This behavior reflects the fact that the bubble ends up as a flat surface over the end of the tube. A theoretical analysis reproduces this behavior and compares favorably with the experimental data.

Jackson, David P.; Sleyman, Sarah

2010-10-01

379

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

380

Flow patterns of bubble nucleation sites (called fliers) freely floating in champagne glasses.  

PubMed

Laser tomography techniques were used to capture the dynamics of bubbles released from particles (arbitrarily called fliers) freely floating in traditional flutes poured with champagne. By use of long exposure time photography, the trajectories of bubbles released by fliers were found to leave very elegant and characteristic "prints" as they crossed a section of champagne illuminated with a 1 mm thick laser sheet. This characteristic print was made with a succession of lighting filaments. Fine analysis of these prints left by fliers enabled us to deduce the bubbling frequency of each flier (which ranged from about 4 bubbles/s up to about 22 bubbles/s a few seconds after pouring), as well as its velocity through the liquid medium (which ranged from about 0.8 mm/s to about 7.6 mm/s). Finally, this flow visualization technique, very recently applied to the science of champagne and sparkling wines, also proved to be a useful technique to underscore fliers' bubbling instabilities along their rather erratic way through the liquid medium. PMID:17902719

Liger-Belair, Gérard; Beaumont, Fabien; Jeandet, Philippe; Polidori, Guillaume

2007-10-23

381

A force balance model for the motion, impact, and bounce of bubbles  

NASA Astrophysics Data System (ADS)

A force balance model has been developed to predict the terminal velocity of a sub-millimetric bubble as its rises in water under buoyancy. The dynamics of repeated collisions and rebounds of the bubble against a horizontal solid surface is modeled quantitatively by including forces due to buoyancy, added mass, drag, and hydrodynamic lubrication—the last arises from the drainage of water trapped in the thin film between the solid surface and the surface of the deformable bubble. The result is a self-contained, parameter-free model that is capable of giving quantitative agreement with measured trajectories and observed collisions and rebounds against a solid surface as well as the spatio-temporal evolution of the thin film during collision as measured by interferometry.

Klaseboer, Evert; Manica, Rogerio; Hendrix, Maurice H. W.; Ohl, Claus-Dieter; Chan, Derek Y. C.

2014-09-01

382

A computational efficient modelling of laminar separation bubbles  

NASA Technical Reports Server (NTRS)

In predicting the aerodynamic characteristics of airfoils operating at low Reynolds numbers, it is often important to account for the effects of laminar (transitional) separation bubbles. Previous approaches to the modelling of this viscous phenomenon range from fast but sometimes unreliable empirical correlations for the length of the bubble and the associated increase in momentum thickness, to more accurate but significantly slower displacement-thickness iteration methods employing inverse boundary-layer formulations in the separated regions. Since the penalty in computational time associated with the more general methods is unacceptable for airfoil design applications, use of an accurate yet computationally efficient model is highly desirable. To this end, a semi-empirical bubble model was developed and incorporated into the Eppler and Somers airfoil design and analysis program. The generality and the efficiency was achieved by successfully approximating the local viscous/inviscid interaction, the transition location, and the turbulent reattachment process within the framework of an integral boundary-layer method. Comparisons of the predicted aerodynamic characteristics with experimental measurements for several airfoils show excellent and consistent agreement for Reynolds numbers from 2,000,000 down to 100,000.

Dini, Paolo; Maughmer, Mark D.

1990-01-01

383

The potential and force law between different-size bubbles in soap bubble rafts  

Microsoft Academic Search

Since the Bragg bubble model continues to be a powerful tool for modelling interatomic binding and inelastic processes in close-packed metals with particularly attractive applications to the mechanism of plastic flow in metallic glasses, the inter-bubble potential previously developed by Nicolson and Lomer has been generalized to cover interactions between bubbles of unequal size. Fitting the binding energy between pairs

L. T. Shi; A. S. Argon

1982-01-01

384

Opposed bubbly jets at different impact angles: Jet structure and bubble properties  

Microsoft Academic Search

The structure of two colliding water jets containing small gas bubbles is studied experimentally. The effects of the separation distance between jets, as well as the orientation angle, on the spatial distribution of bubbles have been considered. Results on the global structure of the final jet and bubble properties have been obtained using a high-speed video camera, and measurements of

Francesc Suñol; Ricard González-Cinca

2010-01-01

385

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

386

Characterization of Silicon and Silicon on Garnet Devices with Applications to the Detection of Magnetic Bubble Domains in AN Ion-Implanted Contiguous-Disk MEMORY  

Microsoft Academic Search

The electrical and macrostructural characterization of silicon devices that are fabricated on silicon and magnetic bubble substrates is the subject of this thesis. The current -voltage characteristics of silicon magnetodiodes are sensitive to magnetic fields, and we will show that these devices can be integrated with ion-implanted contiguous-disk bubble propagation patterns to construct novel self-aligned magnetic -bubble sensors. The results

Paul H. L. Rasky

1990-01-01

387

Effect of various parameters on bubble formation due to a single jet pulse in two-dimensional coarse-particle fluidized beds  

Microsoft Academic Search

A soft-sphere discrete particle model based on re-arrangement of the gas phase governing equations has been developed to investigate the formation of a single bubble due to a central jet pulse in two-dimensional coarse-particle fluidized beds. A comprehensive study is made on the influence of bed width, particle properties and jet velocity on the bubble characteristics. The bubble grows heterogeneously

Liang-wan Rong; Jie-min Zhan; Chun-liang Wu

388

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

NASA Astrophysics Data System (ADS)

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

Samano, Diego; Velez, Rodrigo; Zenit, Roberto

2009-11-01

389

Spherical solid He nanometer bubbles in an anisotropic complex oxide  

NASA Astrophysics Data System (ADS)

We show, using room temperature, high-resolution electron microscopy studies, that implanted He in LiNbO3 nucleates and accumulates as bubbles. These He inclusions are at ˜20GPa pressure and most probably in the solid phase. In addition, the energetically favored shape of the inclusions in their as-implanted form is spherical and not oblate; this spherical shape is due to the fact that their diameter is below a critical radius for balancing the surface and elastic energies as predicted by elastic theory. When annealed, the characteristic length scale of the He inclusions increases, forming faceted bubbles. Annealing also causes the He inclusions to migrate and accumulate into strings due to the preferred {101¯4} -pyramidal-twinning planes.

Ofan, Avishai; Gaathon, Ophir; Zhang, Lihua; Bakhru, Sasha; Bakhru, Hssaram; Zhu, Yimei; Welch, David; Osgood, Richard M., Jr.

2010-09-01

390

An experimental investigation of throughflow velocities in two-dimensional fluidized bed bubbles: Laser Doppler anemometer measurements  

SciTech Connect

Detailed nonintrusive measurements have been made to determine the throughflow velocity in isolated fluidized bed bubbles. In air-fluidized beds, the throughflow component has been rather neglected and measurements of the visible bubbleflow alone have, therefore, failed to clarify the overall distribution of gas flow between the phases. A single component fiber optic laser Doppler anemometer was used to map the fluid flow through a bubble rising in a two-dimensional bed. The bed was fluidized at a superficial velocity slightly than incipient. The conditioned sampling technique developed to characterize the periodic nature of the bubble phase flow revealed that the throughflow velocity in two-dimensional beds increases linearly with increasing distance from the distributor, thereby enhancing the convective component in the interphase mass transfer process. Bubble growth was accounted for and the end-effects were minimized. Dependence of the bubble throughflow on the elongation of the bubble was observed thus confirming the theoretical analysis of some previous investigators. However, experimental evidence presented in this paper showed that the existing models fail to accurately predict the convective component in the bubble phase of two-dimensional fluidized beds.

Gautam, M. (West Virginia Univ., Morgantown, WV (United States). Dept. of Mechanical and Aerospace Engineering); Jurewicz, J.T. (Florida Atlantic Univ., Boca Raton, FL (United States)); Kale, S.R. (Indian Inst. of Technology, New Delhi (India). Dept. of Mechanical Engineering)

1994-09-01

391

Problem Solving: Bubble Gum Contest  

NSDL National Science Digital Library

This professional development video clip presents students engaged in The Common Core Practice Standard #1âMake 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.

Boston, Wghb

2013-01-01

392

DGP with bubble of nothing  

E-print Network

We construct exact solutions with the bubble of nothing in the Dvali-Gabadadze-Porrati braneworld model. The configuration with a single brane can be constructed, unlike in the Randall-Sundrum braneworld model. The geometry on the single brane looks like the Einstein-Rosen bridge. We also discuss the junction of multibranes. Surprisingly, even without any artificial matter fields on the branes such as three-dimensional tension of the codimension-two objects, two branes can be connected in certain configurations. We investigate solutions of multibranes too. The presence of solutions may indicate the semiclassical instability of the models.

Keisuke Izumi; Tetsuya Shiromizu

2014-02-12

393

Plunging jet characteristics of plunging breakers  

Microsoft Academic Search

With plunging breaking waves, air bubble entrainment is caused by the top of the wave forming a plunging jet and entraining air when it impacts the water in front of the wave. The potential for air bubble entrainment is related directly to the plunging jet impact characteristics. New experiments were performed in a two-dimensional wave flume. The breaking process was

Hubert Chanson; Lee Jaw-Fang

1997-01-01

394

THE GEOMETRY OF BUBBLES AND FOAMS JOHN M. SULLIVAN  

E-print Network

, while the second covered the combinatorics of foams. Soap films, bubble clusters, and foams THE GEOMETRY OF BUBBLES AND FOAMS JOHN M. SULLIVAN University consider mathematical models of bubbles, foams and froths, as collections of surfaces which minimize area

Sullivan, John M.

395

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

396

The incorporation of bubbles into a computer graphics fluid simulation  

E-print Network

We present methods for incorporating bubbles into a photorealistc fluid simulation. Previous methods of fluid simulation in computer graphics do not include bubbles. Our system automatically creates bubbles, which are simulated on top of the fluid...

Greenwood, Shannon Thomas

2005-08-29

397

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

398

Experimental investigation of water laminar mixed-convection flow with sub-millimeter bubbles in a vertical channel  

NASA Astrophysics Data System (ADS)

This paper describes flow and heat transfer characteristics of laminar mixed-convection flows of water with sub-millimeter bubbles in a vertical channel. We use thermocouples and a particle tracking velocimetry technique for the temperature and velocity measurements. The working fluid used is tap water, and hydrogen bubbles generated by electrolysis of the water are used as the sub-millimeter bubbles. The Reynolds number of the main flow ranges from 100 to 200. The ratio of the heat transfer coefficient with sub-millimeter-bubble injection to that without injection (the heat transfer coefficient ratio) ranges from 1.24 to 1.38. The heat transfer coefficient ratio decreases with the increase in the Reynolds number. We conclude from velocity measurements that this decrease is mainly caused by a decrease in the advection effect due to sub-millimeter bubbles.

Kitagawa, Atsuhide; Kimura, Katsuya; Hagiwara, Yoshimichi

2010-03-01

399

Vertical Mobilization of a Residual Oil Phase in a Bead Pack Due to Flow of Discrete Gas Bubbles  

Microsoft Academic Search

Mobilization of trapped oil ganglia is of interest in soil and groundwater clean-up and enhanced oil recovery applications. In this work, experiments with glass beads and various oil phase compositions were performed to determine the volumetric fraction of the non-aqueous phase liquid that may be mobilized with rising discrete gas bubbles. Experiments were performed using 6 mm and 2 mm

Konark Pakkala; Kent Udell

2007-01-01

400

Bubbles, Gating, and Anesthetics in Ion Channels  

PubMed Central

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

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

2008-01-01

401

Equatorial bubbles updrafting at supersonic speeds  

Microsoft Academic Search

Plasma and electric field observations from two satellite encounters with equatorial plasma bubbles updrafting at velocities of about 2 km\\/s are presented. These large, upward velocities are consistent with an adaptation of Chandrasekhar's model for the motion of plasma blobs supported against gravity by a magnetic field. Vector magnetic field measurements, available during one of the bubble encounters show a

Thomas L. Aggson; William J. Burke; Nelson C. Maynard; William B. Hanson; Philip C. Anderson; James A. Slavin; Walter R. Hoegy; Jack L. Saba

1992-01-01

402

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

403

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

404

Gravity Wave Seeding of Equatorial Plasma Bubbles  

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

405

Steady Detonation in a Bubbly Medium  

Microsoft Academic Search

It is shown that the Iordanskii–Kogarko model contains a steady-state solution for a detonation wave in chemically active bubbly media under the following minimum requirements to the model: compressibility of the liquid and allowance for acoustic losses. The rule for choosing the velocity is formulated. The wave structure of the reaction zone and the velocity of steady bubble detonation are

S. A. Zhdan

2002-01-01

406

Chaotic behavior in bubble formation dynamics  

Microsoft Academic Search

We constructed an experimental apparatus to study the dynamics of the formation of air bubbles in a submerged nozzle in a water\\/glycerin solution inside a cylindrical tube. The delay time between successive bubbles was measured with a laser-photodiode system. It was observed bifurcations, chaotic behavior, and sudden changes in a periodic regime as a function of the decreasing air pressure

A. Tufaile; J. C Sartorelli

2000-01-01

407

Acoustic emissions associated with single bubble sonoluminescence  

Microsoft Academic Search

Acoustic emission (AE) from a single bubble trapped in a water\\/glycerine mixture by an acoustic standing wave is reported. The AE has been measured by a calibrated needle hydrophone in different regimes of bubble dynamics. The hydrophone response shows a large amplitude AE pulse which corresponds to the principal collapse along with smaller amplitude pulses which can be associated with

M. Dan; J. D. N. Cheeke

1997-01-01

408

The rheology of gravity driven bubbly liquids  

Microsoft Academic Search

Experiments on a vertical channel were performed to to study the behavior of a monodispersed bubble suspension. Using water and water-glycerin mixtures, we were able to obtain measurements for a range of Reynolds and Weber numbers. To generate a uniform stream of bubbles an array of identical capillaries was used. To avoid the coalescence effects, a small amount of salt

Julian Martinez-Mercado; Roberto Zenit

2002-01-01

409

Soap Films and the Joy of Bubbles  

NASA Astrophysics Data System (ADS)

As a celebration of this year's National Chemistry Week theme, the cover of this issue tries to capture the joy of playing with bubbles. There is nothing quite like the kaleidoscopic rainbow of colors and wetly wild elastic behavior of soap films and bubbles for experiencing the pure joy of a "toy".

Saecker, Mary E.

2005-10-01

410

Measuring soap bubble thickness with color matching  

Microsoft Academic Search

This paper describes a laboratory experiment designed to measure thickness variations across a soap bubble. The experiment uses the phenomenon of thin film interference and the principles of color perception to measure the thickness of the soap film at various points across the surface of the bubble. The students review the classical theory of interference and use a digital camera

Y. D. Afanasyev; G. T. Andrews; C. G. Deacon

2011-01-01

411

Videotaping the Lifespan of a Soap Bubble.  

ERIC Educational Resources Information Center

Describes how the use of a videotape to record the history of a soap bubble allows a study of many interesting events in considerable detail including interference fringes, convection and turbulence patterns on the surface, formation of black film, and the ultimate explosion of the bubble. (JRH)

Ramme, Goran

1995-01-01

412

GK Batchelor When bubbles are spikes,  

E-print Network

GK Batchelor Laboratory When bubbles are spikes, it can matter how the heavy stuff falls Explorations into the behaviour of Rayleigh-Taylor instability CAMBRIDGE UNIVERSITY OF #12;GK Batchelor Laboratory what is a spike? Benjamin St Venant St Venant #12;GK Batchelor Laboratory bubbles = spikes

Dalziel, Stuart

413

Bubble nucleation from gas cavities — a review  

Microsoft Academic Search

This review is concerned with the nucleation of bubbles in solutions supersaturated with a gas, in particular the bubble nucleation that occurs at specific sites, as a cycle. A classification system for the kinds of nucleation that occur is defined and discussed in order to place this specific form of nucleation into a better defined context. It is noted that

S. F. Jones; G. M. Evans; K. P. Galvin

1999-01-01

414

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

415

The effect of wind-generated bubbles on sea-surface backscattering at 940 Hz.  

PubMed

Reliable predictions of sea-surface backscattering strength are required for sonar performance modeling. These are, however, difficult to obtain as measurements of sea-surface backscattering are not available at small grazing angles relevant to low-frequency active sonar (1-3 kHz). Accurate theoretical predictions of scattering strength require a good understanding of physical mechanisms giving rise to the scattering and the relative importance of these. In this paper, scattering from individual resonant bubbles is introduced as a potential mechanism and a scattering model is derived that incorporates the contribution from these together with that of rough surface scattering. The model results are fitted to Critical Sea Test (CST) measurements at a frequency of 940 Hz, treating the number of large bubbles, parameterized through the spectral slope of the size spectrum for bubbles whose radii exceed 1 mm, as a free parameter. This procedure illustrates that the CST data can be explained by scattering from a small number of large resonant bubbles, indicating that these provide an alternative mechanism to that of scattering from bubble clouds. PMID:22088015

van Vossen, Robbert; Ainslie, Michael A

2011-11-01

416

Dynamics of charged hemispherical soap bubbles  

NASA Astrophysics Data System (ADS)

Raising the potential of a charged hemispherical soap bubble over a critical limit causes deformation of the bubble into a cone and ejection of a charged liquid jet. This is followed by a mode which has not previously been observed in bubbles, in which a long cylindrical liquid film column is created and collapses due to a Rayleigh-Plateau instability creating child bubbles. We show that the formation of the column and subsequent creation of child bubbles is due to a drop in potential caused by the ejection of charge from the system via the jet. Similar dynamics may occur in microscopic charged liquid droplets (electrospray processes), causing the creation of daughter droplets and long liquid spindles.

Hilton, J. E.; van der Net, A.

2009-04-01

417

Modelling bubble rise and interaction with a glass Rogerio Manica1*  

E-print Network

-speed photography, immobile interfacial boundary condition, lubrication, interferometry Nomenclature CD drag viscosity (Pa s) wavelength of the laser (m) disjoining pressure (Pa) 1. Introduction Interactions of soft

Chan, Derek Y C

418

Primary Particles from different bubble generation techniques  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

419

Interstellar Bubbles in Two Young HII Regions  

E-print Network

Massive stars are expected to produce wind-blown bubbles in the interstellar medium; however, ring nebulae, suggesting the existence of bubbles, are rarely seen around main-sequence O stars. To search for wind-blown bubbles around main-sequence O stars, we have obtained high-resolution Hubble Space Telescope WFPC2 images and high-dispersion echelle spectra of two pristine HII regions, N11B and N180B, in the Large Magellanic Cloud. These HII regions are ionized by OB associations that still contain O3 stars, suggesting that the HII regions are young and have not hosted any supernova explosions. Our observations show that wind-blown bubbles in these HII regions can be detected kinematically but not morphologically because their expansion velocities are comparable to or only slightly higher than the isothermal sound velocity in the HII regions. Bubbles are detected around concentrations of massive stars, individual O stars, and even an evolved red supergiant (a fossil bubble). Comparisons between the observed bubble dynamics and model predictions show a large discrepancy (1--2 orders of magnitude) between the stellar wind luminosity derived from bubble observations and models and that derived from observations of stellar winds. The number and distribution of bubbles in N11B differ from those in N180B, which can be explained by the difference in the richness of stellar content between these two HII regions. Most of the bubbles observed in N11B and N180B show a blister-structure, indicating that the stars were formed on the surfaces of dense clouds. Numerous small dust clouds, similar to Bok globules or elephant trunks, are detected in these HII regions and at least one of them hosts on-going star formation.

Yael Naze; You-Hua Chu; Sean D. Points; Charles W. Danforth; Margarita Rosado; C. -H. Rosie Chen

2001-04-25

420

Serendipitous Chandra X-Ray Detection of a Hot Bubble within the Planetary Nebula NGC 5315  

NASA Astrophysics Data System (ADS)

We report the serendipitous detection of the planetary nebula NGC 5315 by the Chandra X-Ray Observatory. The Chandra imaging spectroscopy results indicate that the X-rays from this PN, which harbors a Wolf-Rayet (W-R) central star, emanate from a TX~2.5×106 K plasma generated via the same wind-wind collisions that have cleared a compact (<~8000 AU radius) central cavity within the nebula. The inferred X-ray luminosity of NGC 5315 is ~2.5×1032 ergs s-1 (0.3-2.0 keV), placing this object among the most luminous such ``hot bubble'' X-ray sources yet detected within PNe. With the X-ray detection of NGC 5315, objects with W-R-type central stars now constitute a clear majority of known examples of diffuse X-ray sources among PNe; all such ``hot bubble'' PN X-ray sources display well-defined, quasi-continuous optical rims. We therefore assert that X-ray-luminous hot bubbles are characteristic of young PNe with large central star wind kinetic energies and closed bubble morphologies. However, the evidence at hand also suggests that processes such as wind and bubble temporal evolution, as well as heat conduction and/or mixing of hot bubble and nebular gas, ultimately govern the luminosity and temperature of superheated plasma within PNe.

Kastner, Joel H.; Montez, Rodolfo, Jr.; Balick, Bruce; De Marco, Orsola

2008-01-01

421

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

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

422

How does interfacial rheology govern soap bubble cluster dynamics?  

NASA Astrophysics Data System (ADS)

Aqueous foams are concentrated dispersions of gas bubbles in a soapy solution. These complex fluids exhibit solid-like or liquid-like mechanical behaviors, depending on the applied shear. When it is increased beyond a yield strain, neighbor switching bubble rearrangements called T1 events are triggered and plastic flow sets in. We study experimentally the dynamics of such strain induced T1s in 3D bubble clusters that we consider as model systems of 3D foams. To determine the hydrodynamics and physico-chemistry that set the duration of T1s, we use foaming solutions of a wide range of well characterized bulk and interfacial rheological properties. At low shear rates, the T1 duration is set by a balance between surface tension and surface viscous forces in qualitative agreement with previous studies of T1s in 2D foams [1] and we present a simple physical model that explains our 3D findings. Moreover, above a characteristic shear rate, rearrangement dynamics are driven by the applied strain. By combining all our results, we link the transition from intermittent to continous flow dynamics in foams to the rheology of the gas-liquid interfaces. [4pt] [1] M. Durand, H. A. Stone, Phys. Rev. Lett. 97, 2226101 (2006).

Cohen-Addad, Sylvie; Biance, Anne-Laure; Hohler, Reinhard

2009-11-01

423

Microwave emission of sonoluminescing bubbles.  

PubMed

Kordomenos et al. have attempted to measure single bubble sonoluminescence (SBSL) emission in the microwave window of water in a band of frequencies ranging from 1.65 GHz to 2.35 GHz [Phys. Rev. E 59, 1781 (1999)]. The sensitivity of the experiment was such that signals greater than 1 nW would have been detected. We show here that this upper bound is compatible with the radiation processes that we think generate significant emission at optical frequencies, electron-neutral and electron-ion bremsstrahlung. In fact, we argue that, almost independently of the specific assumptions concerning the hydrodynamics or the nature of the radiative processes, SBSL intensities exceeding that upper bound can hardly be expected. PMID:12241521

Hammer, Dominik; Frommhold, Lothar

2002-07-01