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1

BUBBLES A ND C RISES  

Microsoft Academic Search

In recent financial crises a bubble, in which asset prices rise, is followed by a collapse and widespread default. Bubbles are caused by agency relationships in the banking sector. Investors use money borrowed from banks to invest in risky assets, which are relatively attractive because investors can avoid losses in low payoff states by defaulting on the loan. This risk

Franklin Allen; Douglas Gale

2000-01-01

2

Path instability of a rising bubble.  

PubMed

We model the problem of path instability of a rising bubble by considering the bubble as a spheroidal body of fixed shape, and we solve numerically the coupled fluid-body problem. Numerical results show that this model exhibits path instability for large enough values of the control parameters. The corresponding characteristics of the zigzag and spiral paths are in good agreement with experimental observations. Analysis of the vorticity field behind the bubble reveals that a wake instability leading to a double threaded wake is the primary cause of the path instability. PMID:11800955

Mougin, Guillaume; Magnaudet, Jacques

2001-12-19

3

Path instability of a rising bubble  

NASA Astrophysics Data System (ADS)

Path instability of a rising bubble is studied by carrying out DNS around a freely moving ellipsoidal bubble with a prescribed aspect ratio. The flow field is obtained by solving the full Navier-Stokes equations and the velocity and rotation rate of the bubble are found by solving the Kirchhoff equations in a form suitable to vortical flows. The problem has two control parameters, ie the aspect ratio K and the Galileo number Ga. Beyond a certain critical value K(Ga) or Ga(K), the path of the bubble first bifurcates towards a plane zigzag whose geometrical characteristics are in good agreement with experimental observations. Detailed examination reveals that the transition to the zigzag path occurs through a supercritical Hopf bifurcation when K is set fixed, while it occurs through a more complex process when Ga is set fixed. Ultimately, the zigzag degenerates into a fully helical trajectory, as observed in experiments. Examining the vorticity field reveals a one-to-one correspondance between the topology of the wake and the nature of the path. The competition between creation of vorticity at the bubble surface and evacuation in the wake allows us to propose a consistent scenario for explaining physically the observed transitions.

Magnaudet, Jacques; Mougin, Guillaume

2001-11-01

4

The rising bubble technique for discharge measurements  

NASA Astrophysics Data System (ADS)

The rising bubble technique is an elegant method to determine the full discharge of a river or a canal in a short moment of time. The method is not new [Sargent, 1982], but hardly applied so far. The method applies air bubbles released from the bottom of a river or canal. While the bubbles rise to the surface they are dragged along by the current. The deeper the stream and the faster the current the longer will be the distance they are dragged along. The horizontal displacement L, of the bubbles can be observed at the surface of the stream. To obtain a discharge, the rising velocity vr, of the bubble is required additionally. When the rising velocity is assumed constant the discharge per unit width amounts to q= Lvr. Placing a tube on the bottom of the stream and releasing bubbles at regular intervals results in a complete discharge profile. The ongoing research is focusing on factors affecting the rising velocity, solving practicalities in applying the method in the field and how modern image processing techniques can enhance determining in a glance the distance travelled by the bubbles. Surfacing of air bubbles in a canal

Luxemburg, W.; Hilgersom, K.; van Eekelen, M.

2010-12-01

5

1300-m-high rising bubbles from mud volcanoes at 2080 m in the Black Sea: Hydroacoustic characteristics and temporal variability  

NASA Astrophysics Data System (ADS)

A mud volcano area in the deep waters (> 2000 m) of the Black Sea was studied by hydroacoustic measurements during several cruises between January 2002 and June 2004. Gas bubbles in the water column give strong backscatter signals and thus can be detected even in great water depths by echosounders as the 38 kHz EK500 scientific split-beam system that was used during the surveys. Because of their shape in echograms and to differentiate against geochemical plumes and real upwelling bubble-water plumes, we call these hydroacoustic manifestations of bubbles in the water column 'flares'. Digital recording and processing of the data allows a 3D visualization and data comparison over the entire observation period, without artefacts caused by changing system settings. During our surveys, we discovered bubble release from three separate mud volcanoes, Dvurechenskiy (DMV), Vodianitskiy (VMV) and the Nameless Seep Site (NSS), in about 2080 m water depth simultaneously. Bubble release was observed between 9 June 2003 and 5 June 2004. The most frequently surveyed, DMV, was found to be inactive during very intensive studies in January 2002. The first activity was observed on 27 June 2002, which finally ceased between 5 and 15 June 2004 after a period of continuously decreasing activity. This observed 2-yr bubble-release period at a mud volcano may give an indication for the duration of active periods. The absence of short-term variations (within days or hours) may indicate that the bubble release from the observed mud volcanoes does not undergo rapid changes. The recorded echograms show that bubbles rise about 1300 m high through the water column, to a final water depth of about 770 m, which is ˜75 m below the phase boundary of pure methane hydrate in the Black Sea. With a release depth from 2068 m and a detected rise height of 1300 m, the flare at VMV is among the deepest and highest reported so far, and gives evidence of highly extended bubble life times (up to 108 min) in deep marine environments. To better understand how a methane bubble (gas analyses of the pore water and gas hydrate gave 99.4% methane) can rise so high without dissolving, we applied a recently developed bubble dissolution model that takes into account a decreased mass transfer due to an immediately formed gas-hydrate rim. Using the hydroacoustically determined bubble rising speeds (19-22 cm/s at the bottom; 12-14 cm/s at the flare top) and the relation between the rising speed of 'dirty'/gas hydrate rimmed bubbles and the bubble size, we could validate that a gas-hydrate-rimmed bubble with a diameter of 9 mm could survive the 1300-m-rise through the water column, before it is finally dissolved. A diameter of about 9 mm is reasonable for bubbles released at seep sites and the coincidence between the observed bubble rising speed and the model approach of a 9-mm bubble supports the assumption of gas-hydrate-rimmed bubbles.

Greinert, Jens; Artemov, Yuriy; Egorov, Viktor; De Batist, Marc; McGinnis, Daniel

2006-04-01

6

A train of rising Bretherton bubbles  

NASA Astrophysics Data System (ADS)

: A closely fitting gas bubble in a vertically aligned capillary tube will rise due to buoyancy when the Bond number exceeds a critical value in the limit of low Capillary number, as shown by Bretherton [J. Fluid Mech. 10, 1961]. We consider a steadily propagating train of such bubbles at various separation distances, and examine the additional influence of a temperature gradient along the walls of the tube. This problem is applicable to processes for manufacturing porous metal solids, where molten foams with low liquid fraction are solidified by an applied temperature drop. We seek to show that gravity can act as a means of control of the porosity of the foam as the liquid is cooled to its melting point.

Davis, Michael J.; Stewart, Peter S.; Davis, Stephen H.

2011-11-01

7

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

8

A Mechanistic Model for Bubble Rise in Soft Sediments  

NASA Astrophysics Data System (ADS)

Wetland and aquatic sediments (marine and freshwater) are significant sources of methane, due to the degradation of organic matter under anoxic conditions. Once produced, methane migrates from the sediments to the overlying water and eventually the atmosphere by diffusion or bubble ebullition. Ebullition is a significant source because it can release methane directly to the water column or atmosphere, bypassing the methane oxidizing zone, that consumes much of the diffusive flux of methane from sediments. Recently it has been shown that bubbles released from thermokarst lakes (lakes formed due to the melting of permafrost) in northern latitudes explain much of the historic glacial/interglacial methane cycle and represent what could be a significant positive feedback mechanism on the Earth's climate system. Therefore a thorough understanding of how bubbles migrate through sediments is necessary. Bubble release is episodic and patchy with periods of release often triggered by decreases in hydrostatic pressure. Here I present a mechanistic model for bubble rise is soft sediments. The model describes the rise of a single isolated bubble through the sediments and therefore describes the initial stages of bubble tube formation. The bubble migrates by propagating a fracture and the rate of rise is controlled by the viscoelastic response of the sediments to stresses induced by the bubble. This model predicts that a bubble will rise under its own weight when the long axis of the fracture reaches a critical length. This length is determined by the strength of the sediment. The model provides insights into the mechanism behind hydrostatic pressure release and predicts rise velocities as a function of measurable sediments properties. This will aid in the prediction of fluxes to the atmospheric from methane producing sediments and increases our understanding of this important link between the aquatic ecosystem and the atmosphere.

Algar, C. K.; Boudreau, B. P.

2009-05-01

9

Mass-transport enhancement by rising bubble curtains  

SciTech Connect

Mass-transport enhancement by rising single and multiple bubble streams was monitored on a vertical electrode incorporating a mosaic of 100 x 100 [mu]m sensing elements. Limiting current measurements of the reduction of ferric to ferrous sulfate revealed the presence of two distinct mechanisms: surface renewal is effective within a swath of five bubble diameters, while macroscopic laminar flows induced by rising bubbles contribute weaker enhancement over a wider path. Enhancement caused by a sheath of multiple side-by-side bubble streams can be well represented by the linear superposition of the effect of single streams. Generally, at equivalent volumetric rates, small bubbles are more effective than larger ones in reducing mass-transfer resistance to the underlying surface.

Sutija, D.P.; Tobias, C.W. (Univ. of California, Berkeley, CA (United States). Dept. of Chemical Engineering Lawrence Berkeley Lab., CA (United States). Chemical Sciences Division)

1994-10-01

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.

1991-12-31

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.

1991-01-01

12

Rising speed and dissolution rate of a carbon dioxide bubble in slightly contaminated water  

Microsoft Academic Search

The rising speed and dissolution rate of a carbon dioxide bubble in slightly contaminated water were investigated experimentally and numerically. We developed an experimental system that uses a charged-coupled device (CCD) camera coupled with a microscope to track the rising bubble. By precisely measuring the bubble size and rising speed, we were able to accurately estimate the drag coefficient and

F. Takemura; A. Yabe

1999-01-01

13

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

Microsoft Academic Search

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

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

2006-01-01

14

Small air bubbles in reagent grade water and seawater 1. rise velocities of 20- to 1000-mum diameter bubbles  

Microsoft Academic Search

The terminal rise velocities of 20- to 1000-mum-diameter air bubbles in water and seawater were measured at atmospheric pressure and room temperature. The velocities were the same in both liquids for bubbles with diameters less than 450 mum. Above 450 mum the rise velocities were higher in water than in seawater. For all diameters tested, the measured velocities fell between

Richard M. Detsch

1991-01-01

15

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

Microsoft Academic Search

An experimental investigation of the flow field around a single Taylor bubble rising in a vertical pipe filled with stagnant water is presented. The Reynolds number of the flow based on the Taylor bubble rise velocity and the pipe diameter is 4350. The velocity field around the bubble was determined by Particle Image Velocimetry (PIV). The mean velocity fields in

R. van Hout; A. Gulitski; D. Barnea; L. Shemer

2002-01-01

16

Bubble characteristics in gassy aqueous sediments  

SciTech Connect

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

Orsi, T.H.; Anderson, A.L. [Texas A& M Univ., College Station, TX (United States)

1994-09-01

17

Initial rise of bubbles in cohesive sediments by a process of viscoelastic fracture  

NASA Astrophysics Data System (ADS)

An understanding of the mechanics of bubble rise in sediments is essential because of the role of bubbles in releasing methane to the atmosphere and the formation and melting of gas hydrates. Past models to describe and predict the rise of other buoyant geological bodies through a surrounding solid (e.g., magmas and hydrofractures) appear not to be applicable to bubbles in soft sediments, and this paper presents a new model for gas bubble rise in soft, fine-grained, cohesive sediments. Bubbles in such sediments are essentially "dry" (little if any free water) and grow through a process of elastic expansion and fracture that can be described using the principles of linear elastic fracture mechanics, which assume the existence of a spectrum of flaws within the sediment fabric. By extending this theory, we predict that bubbles initially rise by preferential propagation of a fracture in a (sub) vertical direction. We present a criterion for initial bubble rise. Once rise is initiated, the speed of rise is controlled by the viscoelastic response of the sediments to stress. Using this new bubble rise model, we estimate rise velocities to be of the order of centimeters per second. We again show that capillary pressure plays no substantive role in controlling bubble growth or rise.

Algar, C. K.; Boudreau, B. P.; Barry, M. A.

2011-04-01

18

On the dynamics and breakup of a bubble rising in a turbulent flow  

Microsoft Academic Search

Experimental investigations of the dynamics of a deformable bubble rising in a uniform turbulent flow are reported. The turbulence is characterized by fast particle image velocimetry. Time-resolved evolutions of bubble translation, rotation, and deformation are determined by three-dimensional shape recognition from three perpendicular camera views. The bubble dynamics involves three mechanisms fairly decoupled: (1) average shape is imposed by the

F. Ravelet; C. Colin; F. Risso

2011-01-01

19

Velocity measurements of liquid and gaseous phase for a system of bubbles rising in water  

Microsoft Academic Search

An experimental procedure for performing simultaneous, phase-separated measurements in a bubbly, two-phase flow is described\\u000a and demonstrated with the application to a system of bubbles rising in water. PIV measurements using a vertical laser light\\u000a sheet are combined with the simultaneous recording of the bubbles' motion by means of a digital high-speed camera viewing\\u000a the bubbles from above. This experimental

R. Lindken; W. Merzkirch

2000-01-01

20

Numerical Simulation of Gas Bubbles Rising in Viscous Liquids at High Reynolds Number  

Microsoft Academic Search

A robust algorithm for direct numerical simulation of fully three- dimensional, incompressible two-phase ?ow is presented. The method is intro- duced in the context of gas bubbles rising in viscous liquids, e.g. air bubbles rising in water. Key strengths of the simulation approach include the ability to simulate ?ows in an extended, wide range of Reynolds and Bond numbers and

Jinsong Hua; Ping Lin; Jan F Stene

21

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

NASA Astrophysics Data System (ADS)

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

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

2010-09-01

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

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

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

24

Bubble and liquid turbulence characteristics of bubbly flow in a large diameter vertical pipe  

Microsoft Academic Search

The bubble and liquid turbulence characteristics of air–water bubbly flow in a 200mm diameter vertical pipe was experimentally investigated. The bubble characteristics were measured using a dual optical probe, while the liquid-phase turbulence was measured using hot-film anemometry. Measurements were performed at six liquid superficial velocities in the range of 0.2–0.68m\\/s and gas superficial velocity from 0.005 to 0.18m\\/s, corresponding

M. E. Shawkat; C. Y. Ching; M. Shoukri

2008-01-01

25

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

26

Technical Note: How image processing facilitates the Rising Bubble Technique for discharge measurement  

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

27

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

Microsoft Academic Search

The rise of bubbles in viscous liquids is not only a very common process in many industrial applications, but also an important fundamental problem in fluid physics. An improved numerical algorithm based on the front tracking method, originally proposed by Tryggvason and his co-workers, has been validated against experiments over a wide range of intermediate Reynolds and Bond numbers using

Jinsong Hua; Jan F. Stene; Ping Lin

2008-01-01

28

A physically based correlation for the effects of power law rheology and inclination on slug bubble rise velocity  

Microsoft Academic Search

A study has been made of the motion of long bubbles in inclined pipes containing viscous Newtonian and non-Newtonian liquids. A semi-theoretical expression for the rise velocity of air bubbles in water is derived on the hypothesis that the dominant factor is the momentum exchange of the bubble underflow, i.e. the bubble nose shape. The correlation calls on empirical inputs

P. S. Carew; N. H. Thomas; A. B. Johnson

1995-01-01

29

Bubble characteristics and aerosol formation in electrowinning cells  

Microsoft Academic Search

The nature of the aerosol emitted from a scale model zinc electrowinning system, operated under industrial conditions, has been established as a function of bubble formation rate, electrode surface characteristics, coalescence of bubbles, and control strategies. The emitted aerosol was collected and characterized using an Andersen Ambient Impactor. The effect of the relative humidity of the ambient air on the

A. Papachristodoulou; F. R. Foulkes; J. W. Smith

1985-01-01

30

Ripples on a rising bubble through an immiscible two-liquid interface generate numerous micro droplets  

NASA Astrophysics Data System (ADS)

The mass transfer between immiscible two liquid phases can be greatly accelerated by bubbling gas through a reactor (Bird R. B., Stewart W. E. and Lightfoot E. N., Transport Phenomena, 2nd edition (John Wiley and Sons) 2002). Therefore, the physical phenomenon occurring during the passage of a rising bubble through an immiscible two-liquid interface is of particular interest. The passage of the bubble through the oil (upper phase)/water (lower phase) interface starts with an upward lifting of the interface, and the bubble attracts a column of the water phase upwards keeping a film of the water phase around itself. In the present study, a particular remark is given to the influence of different interface tensions retracting the water film, after the water film ruptured, which lays on the interface between air and silicone oil. Unlike the previous studies on the rupture of a single liquid film in a gas which is pulled due to the identical surface tension, this system can form concentric ripples on the outer interface of the water film (oil/water interface) around the bubble due to the weak interface tension. Then, numerous micro water droplets break out from the fully grown ripples.

Uemura, T.; Ueda, Y.; Iguchi, M.

2010-11-01

31

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

Microsoft Academic Search

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

Roberto Zenit; Jacques Magnaudet

2008-01-01

32

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

Microsoft Academic Search

Understanding the upward motion of CO2 droplets or CH4 bubbles in oceanic waters is prerequisite to predict the vertical distribution of the two most important greenhouse gases in the water column after these have been released from the seabed. One of the key parameters governing the fate of droplets or bubbles dissolving into the surrounding seawater as they rise, is

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

2010-01-01

33

Sliding of fine particles on the slip surface of rising gas bubbles: Resistance of liquid shear flows  

Microsoft Academic Search

In this paper a model was developed to describe the shear flow resistance force and torque acting on a fine particle as it slides on the slip surface of a rising gas bubble. The shear flow close to the bubble surface was predicted using a Taylor series and the numerical data obtained from the Navier–Stokes equations as a function of

Anh V. Nguyen; Graeme J. Jameson

2005-01-01

34

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

Microsoft Academic Search

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,

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

2007-01-01

35

Spread F plasma bubble vertical rise velocities determined from spaced ionosonde observations  

SciTech Connect

Systematic time differences in the onsets of spread F events in the ionograms are observed between the magnetic equatorial station Fortaleza (4/sup 0/S, 38/sup 0/W, dip latitude 1.8/sup 0/S) and the low-latitude station Cachoeira Paulista (23/sup 0/S, 45/sup 0/W, dip latitude 14/sup 0/S), two stations in Brazil, located at close-by magnetic meridional planes (actually some 12/sup 0/ of magnetic longitude apart). On the assumption, justified from different experimental observations, that the spread F irregularities occur in strongly field-aligned plasma bubbles that extend several degrees on either side of the magnetic equator, and rise up in vertically elongated columns over the magnteic equator, we have related the observed time differences in the onsets of spread F events at the two stations to the plasma bubble vertical rise velocities of the plasma bubbles so determined are found to be well within the values measured by VHF radar and satellite techniques, and further show, at times, good correlations with the amplitude of the prereversal peak in the vertical drift velocities and the heights of the evening equatorial F layer. Possible implications of these results are discussed.

Abdu, M.A.; de Medeiros, R.T.; Sobral, J.H.A.; Bittencourt, J.A.

1983-11-01

36

Rise velocities of bubbles and slugs in gas-fluidised beds: Ultra-fast magnetic resonance imaging  

Microsoft Academic Search

Ultra-fast magnetic resonance imaging (MRI) has been applied for the first time to study the rise velocities of bubbles and slugs in a 3-D gas-fluidised bed. Ultra-fast MRI is a non-intrusive technique, providing measurements with both excellent temporal and spatial resolutions. MRI measurements reveal that the excess gas velocity, U-Umf, does not affect the rise velocity of continuously formed bubbles,

C. R. Müller; J. F. Davidson; J. S. Dennis; P. S. Fennell; L. F. Gladden; A. N. Hayhurst; M. D. Mantle; A. C. Rees; A. J. Sederman

2007-01-01

37

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

Microsoft Academic Search

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

Ira Leifer; Guillemette Caulliez; Gerrit de Leeuw

2006-01-01

38

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

PubMed Central

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

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

2009-01-01

39

Prediction of micro-bubble dissolution characteristics in water and seawater  

SciTech Connect

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

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

2009-07-15

40

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

41

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

NASA Astrophysics Data System (ADS)

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

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

2006-12-01

42

Interaction and coalescence of large bubbles rising in a thin gap.  

PubMed

We present accurate measurements of the relative motion and deformation of two large bubbles released consecutively in a quiescent liquid confined in a thin-gap cell. Although the second injected bubble was smaller, we observed that, in all cases, it accelerated and caught up with the leading bubble. This acceleration is related to the wake of the leading bubble, which also induces significant changes in the width and curvature of the trailing bubble. On the contrary, the velocity of the leading bubble is unaltered during the whole interaction and coalescence process. Shape adaptation of the two bubbles is observed just prior to coalescence. After pinch-off, the liquid film is drained at a constant velocity. PMID:22463363

Huisman, Sander G; Ern, Patricia; Roig, Véronique

2012-02-15

43

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

44

Flow characteristics near the nozzle of a bubble column with simultaneous gas-liquid injection  

Microsoft Academic Search

Due to their simplicity of construction which precludes the possibility of blockage, simultaneous gas-liquid injectors and liquid ejectors find application to gas-liquid-solid chemical processes such as coal liquefaction. The gas holdup, bubble rising velocity, and bubble diameter near the nozzle in a bubble column with simultaneous gas and liquid injection were measured using an optical fiber probe. A jet-like spouting

Kiyoshi Idogawa; Takashi Fukuda; Hiroshi Nagaishi; Yosuke Maekawa; Tadatoshi Chiba; Shigeharu Morooka

1994-01-01

45

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

46

Simulation of AN Axisymmetric Rising Bubble by a Multiple Relaxation Time Lattice Boltzmann Method  

Microsoft Academic Search

In this paper, the lattice Boltzmann method is employed to simulate buoyancy-driven motion of a single bubble. First, an axisymmetric bubble motion under buoyancy force in an enclosed duct is investigated for some range of Eötvös number and a wide range of Archimedes and Morton numbers. Numerical results are compared with experimental data and theoretical predictions, and satisfactory agreement is

Abbas Fakhari; Mohammad Hassan Rahimian

2009-01-01

47

Flow characteristics near the nozzle of a bubble column with simultaneous gas-liquid injection  

SciTech Connect

Due to their simplicity of construction which precludes the possibility of blockage, simultaneous gas-liquid injectors and liquid ejectors find application to gas-liquid-solid chemical processes such as coal liquefaction. The gas holdup, bubble rising velocity, and bubble diameter near the nozzle in a bubble column with simultaneous gas and liquid injection were measured using an optical fiber probe. A jet-like spouting flow was formed around the nozzle; the height of the jet was independent of the diameter of the nozzle. Bubbles were formed near the side wall and near the top of the jet, with their radial dispersion increasing with increasing height. Beyond {approximately}88 cm from the nozzle, the radial distribution of the gas holdup was uniform and independent of the axial height. The radial dispersion and bubble diameter varied with the nozzle diameter. The effects of simultaneous gas-liquid injection on bubble formation were similar to those of an increase in the pressure.

Idogawa, Kiyoshi; Fukuda, Takashi; Nagaishi, Hiroshi; Maekawa, Yosuke [Government Industrial Development Lab., Sapporo (Japan). Resources and Energy Technology Dept.; Chiba, Tadatoshi [Hokkaido Univ., Sapporo (Japan); Morooka, Shigeharu [Kyushu Univ., Fukuoka (Japan)

1994-10-01

48

Differences in Path Instabilities Between a Bubble Rising in Water and in Aqueous Polymer Solution in a Hele-Shaw Cell in the Transient and Steady States  

Microsoft Academic Search

The buoyancy-driven path instabilities of an air bubble rising in a Hele-Shaw cell filled with pure water are examined as a function of the Eötvös number (Eo) in terms of changes in the shape, trajectory, and peripheral length (L) of the bubble in the transient and steady states. The path instabilities in an aqueous solution of hydroxypropyl methyl cellulose (HPMC)

Midori Yamamoto; Masami Kawaguchi

2011-01-01

49

Dependence of the characteristics of bubbles on types of sonochemical reactors.  

PubMed

Computer simulations of bubble oscillations in liquid water irradiated by an ultrasonic wave have revealed that the characteristic of bubbles depends on types of sonochemical reactors: a horn-type reactor and a standing-wave type reactor. When the acoustic amplitude is large at 20 kHz, the bubble content is mostly water vapor even at the end of the bubble collapse and the temperature inside a bubble at the collapse is relatively low. On the other hand, when the acoustic amplitude is relatively low, the bubble content is mostly noncondensable gas at the end of the bubble collapse and the bubble temperature is relatively high. In a horn-type sonochemical reactor, the former type of bubbles are dominant because many bubbles exist near the horn-tip where the acoustic amplitude is large, while in a standing-wave type reactor the latter type of bubbles are dominant because the Bjerknes force gathers bubbles at a region where acoustic amplitude is relatively low. PMID:15474951

Yasui, Kyuichi; Tuziuti, Toru; Iida, Yasuo

2005-01-01

50

Electrical and spectroscopic characterization of underwater plasma discharge inside rising gas bubbles  

Microsoft Academic Search

The generation of high-energetic species in plasma by discharge in liquids makes it suitable for applications such as water treatment. Effective reduction of input power and an increase in the process efficiency can be achieved by externally generated gas bubbles introduced in the liquid. Pulsed discharge in nitrogen, helium and argon bubbles in between a pin-to-plate electrode system submerged in

Patrick Vanraes; Anton Nikiforov; Christophe Leys

2012-01-01

51

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

52

The Characteristics of Steam Bubbles in Subcooled Boiling Flow  

SciTech Connect

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

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

2002-07-01

53

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

54

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

55

Bubble Bubble  

NSDL National Science Digital Library

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

Mayer, Mercer

2009-11-11

56

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

57

Prediction of micro-bubble dissolution characteristics in water and seawater  

Microsoft Academic Search

This paper is concerned with the prediction of micro-bubble dissolution characteristics in water and seawater when microbubbles are generated by a Sadatomi-type micro-bubble generator (2003) with a spherical body in a flowing liquid tube. In the experiments, in order to know the effects of the salinity on the characteristics, tap water and an artificial seawater with different salt concentrations of

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

2009-01-01

58

Crystal Sinking and Bubble Rising in Late-Erupted Bishop Tuff: A Study of Pumice Clasts by X-ray Tomography and Physical Separation  

NASA Astrophysics Data System (ADS)

In this study, we assess relationships between crystal contents, porosity, and density in pumice clasts from late-erupted Bishop Tuff. Relationships between these characteristics influence our understanding of the dynamics and evolution of the magma body. Data employed in this study were obtained both by x-ray tomography and by physical separation. Five late-erupted pumice clasts from the Aeolian Buttes, ranging in bulk density from 0.42-1.18 g/cm3, were studied. Crystal contents and porosities were determined both using the density of the bulk pumice and by tomography. For x-ray tomography, five to seven chips of varying size (2.5-700 mm3) were cut from each pumice clast and imaged at the GSECARS beamline (Advanced Photon Source, Argonne National Lab). Crystals were classified and measured from resulting tomographic images using the software Blob3D and other routines written by us in IDL. For physical separation, one chip was cut from each pumice clast, and crystals were separated by a process of crushing, sieving, and winnowing; at all stages, crystals and pumice were weighed such that cumulative mass fractions could be determined as a function of size. Bulk and matrix porosities were then calculated using these values in conjunction with chip and mineral densities. In general, total crystal contents and bulk density correlate positively. Large crystals (800-3300 ?m diameter) are most abundant in the densest clasts. In this size range, crystal mass fraction increases significantly (from 5-20 wt. %) in high density clasts and remains low (~12 wt. %) in low density clasts. Porosity correlates inversely with clast density and crystal contents. A combination of crystal sinking and bubble rising has been suggested as an important magmatic process for the early-erupted Bishop Tuff. In early-erupted samples, variations in crystal mass fraction from one clast to another are dominated by large crystals. This trend, which is attributed to crystal sinking, is seen similarly in the results of this study. Additionally, for bubble-rising, a negative correlation between porosity and crystal contents is expected. This, too, appears in the late-erupted samples and is similar to that seen in early- erupted Bishop Tuff. Overall, the results of this study are consistent with a crystal sinking-bubble rising process for late-erupted Bishop Tuff.

Pamukcu, A.; Anderson, A. T.; Gualda, G.

2006-12-01

59

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

PubMed Central

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

Zhou, Yufeng; Qin, Jun; Zhong, Pei

2013-01-01

60

Pressure effects on bubble-column flow characteristics  

SciTech Connect

Bubble-column reactors are used in the chemical processing industry for two-phase and three-phase chemical reactions. Hydrodynamic effects must be considered when attempting to scale these reactors to sizes of industrial interest, and diagnostics are needed to acquire data for the validation of multiphase scaling predictions. This paper discusses the use of differential pressure (DP) and gamma- densitometry tomography (GDT) measurements to ascertain the gas distribution in a two-phase bubble column reactor. Tests were performed on an industrial scale reactor (3-m tall, 0.48-m inside diameter) using a 5-Curie cesium-137 source with a sodium-iodide scintillation detector. GDT results provide information on the time- averaged cross-sectional distribution of gas in the liquid, and DP measurements provide information on the time and volume averaged axial distribution of gas. Close agreement was observed between the two methods of measuring the gas distribution in the bubble column. The results clearly show that, for a fixed volumetric flowrate through the reactor, increasing the system pressure leads to an increase in the gas volume fraction or ``gas holdup`` in the liquid. It is also shown from this work that GDT can provide useful diagnostic information on industrial scale bubble-column reactors.

Adkins, D.R.; Shollenberger, K.A.; O`Hern, T.J.; Torczynski, J.R.

1996-03-01

61

The Characteristics of Steam Bubbles in Subcooled Boiling Flow  

Microsoft Academic Search

In two-fluid modeling and three-fluid modeling, the accurate prediction of the interfacial area concentration, interfacial heat transfer and interfacial shear stress, were required. In this works, the axial profiles of void fraction, interfacial area concentration and interfacial heat transfer coefficient along the flow direction could be measured. For the steam bubbles whose diameter were less than 8 mm, the interfacial

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

2002-01-01

62

Chemical and Physical Characteristics of Pulsed Electrical Discharge Within Gas Bubbles in Aqueous Solutions  

Microsoft Academic Search

The chemical and physical characteristics of pulsed electrical discharge within gas bubbles immersed in an aqueous solution\\u000a were investigated using a reactor with long protrusion length high voltage needle electrodes. Argon gas was introduced at\\u000a the base of the needle electrode causing gas bubbles to flow upwards in contact with the needle. The effects of needle protrusion\\u000a length were evaluated

Kai-Yuan Shih; Bruce R. Locke

2010-01-01

63

Flow characteristics in a bubbling fluidized bed at elevated temperature  

Microsoft Academic Search

A bubbling fluidized bed with 0.082 m in diameter and 1.5 m in height was employed to investigate the minimum fluidization velocity and flow dynamics at bed temperature up to 1000°C. Ashes of three sizes (Geldart B) from pressurized fluidized bed boiler were used as fluidization materials. Experiments show that the minimum fluidization velocity decreases with increasing bed temperature. Pressure

Qingjie Guo; Guangxi Yue; Toshiyuki Suda; Junichi Sato

2003-01-01

64

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  

Microsoft Academic Search

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

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

2008-01-01

65

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

66

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

67

Bubble and bubble cloud dynamics  

NASA Astrophysics Data System (ADS)

Cavitation bubbles are formed from small air bubbles, so-called nuclei, with the surrounding pressure reduction caused by the flow, and then, the bubbles shrink and collapse with the surrounding pressure rise. Such volumetric changes of bubbles are calculated in detail and it is found that they are significantly influenced by the internal phenomena, such as thermal diffusion, mist formation due to a homogeneous condensation, mass diffusion between vapor and noncondensable gas, heat and mass transfer through the bubble wall. The structure in cavitating flow interacts with the cavitation bubbles, and those bubbles form a cloud cavitation. It is well known that cloud cavitation is one of the most destructive forms. The behavior of bubble clouds is simulated numerically. An inward propagating shock wave is formed during the collapse of the bubble cloud, and the shock wave and its precursor are focused at the cloud center area. These phenomena associate high frequency pressure oscillations and violent bubble collapses. Those bubble collapses emit high pressure peaks, which are several hundreds times larger than that of a single bubble collapse. .

Matsumoto, Yoichiro

2000-07-01

68

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

69

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

70

Bubble characteristics of steam–water two-phase flow in a large-diameter pipe  

Microsoft Academic Search

Bubble characteristics of steam–water two-phase upward flow were observed in a vertical pipe 155 mm in inner diameter. Experiments were conducted under volumetric flux conditions of JG<0.25 m\\/s and JL<0.6 m\\/s, and three different inlet boundary conditions to investigate the developing state of the flow. The radial distributions of flow structure were obtained by horizontally traversing optical dual void probes

Kimitoshi Yoneda; Akira Yasuo; Tomio Okawa

2002-01-01

71

Impinging-Jet Ozone Bubble Column Modeling: Hydrodynamics, Gas Hold-up, Bubble Characteristics, and Ozone Mass Transfer  

Microsoft Academic Search

A transient back flow cell model was used to model the hydrodynamic behaviour of an impinging-jet ozone bubble column. A steady-state back flow cell model was developed to analyze the dissolved ozone concentration profiles measured in the bubble column. The column-average overall mass transfer coefficient, kLa (s), was found to be dependent on the superficial gas and liquid velocities, uG

Mahad S. Baawain; Mohamed Gamal El-Din; Katie Clarke; Daniel W. Smith

2007-01-01

72

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

NASA Astrophysics Data System (ADS)

This study focuses on the 31 March 2001 superstorm's evening and nighttime sectors. We specified forward fountain circulation and equatorial ionization anomaly (EIA), storm-enhanced density (SED) plume plasma flows, auroral zones, polar cap regions, and traveling ionospheric disturbances (TIDs). These permitted analyzing low-latitude plasma structures, and middle- and high-latitude plasma buildups. Results reveal significant low-latitude plasma structuring around Ancon due to topside rising bubbles during the initial phase under disturbance conditions. The deep equatorial plasma depletion, appearing over the Pacific during the main phase, is an EIA-trough-bubble structure. Topside bubbles and TID-related drift perturbations structured SED plume plasma. Plasma distribution maximized when TIDs were in phase with fountain circulation and SED plume plasma flows, and equatorward wind surges maintained high plasma densities. Plasma density and plasma flow measurements demonstrate the SED plume plasma's poleward migration through the auroral zone into the polar region and the maintenance and increase of auroral and polar enhancements forming a polar tongue of ionization (TOI). Our results contradict previous studies on this superstorm reporting the suppression of bubble formation over Ancon and the absence of TOI and explaining the development of equatorial depletion with no E × B drift action. Our results oppose the current hypothesis that plasma enhancements are transported over many hours into the polar region. Indeed, SED plume plasma (produced by plasmaspheric detachment processes) creates multiple downward plasma flows (stretching from the midlatitude trough's equatorward edge to the polar cap region) that in turn create plasma buildups at various latitudes where flow stagnates.

Horvath, Ildiko; Lovell, Brian C.

2011-04-01

73

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

PubMed Central

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

Fletcher, Madilyn; Marshall, K. C.

1982-01-01

74

Cap Bubble Drift Velocity in a Confined Test Section  

SciTech Connect

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

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

2002-10-09

75

Generation and characteristics of equatorial plasma bubbles detected by the C/NOFS satellite near the sunset terminator  

NASA Astrophysics Data System (ADS)

We present the observations of equatorial plasma bubbles in the evening sector by the Communication/Navigation Outage Forecasting System (C/NOFS) satellite during 2011. We illustrate with a few examples the overall properties of the equatorial ionosphere as the solar activity approached maximum. C/NOFS was often below the F peak and this allowed us to examine the early phases of irregularity formation. We show examples when C/NOFS detected a continuous generation of plasma bubbles near the sunset terminator over eight successive orbits (˜12 h). A clear prereversal enhancement of upward plasma drift occurred between 18:00 and 19:00 LT when plasma bubbles were detected by C/NOFS, and the peak value of the upward ion drift at or near the magnetic equator was 40-70 m s-1. In some cases, C/NOFS was well below the F peak and detected wide regions with very low plasma density over ˜3000 km in longitude in the evening sector, and plasma bubbles were generated within the low-density region. C/NOFS also detected simultaneous existence of plasma bubbles between 19:00 and 03:00 LT, corresponding to a longitudinal coverage of ˜12,000 km. Significant differences in the characteristics of plasma bubbles between periods of low and high solar activity are identified. Large plasma bubbles occur in the midnight-dawn sector at low solar activity but in the evening sector at high solar activity. The lifetime of plasma bubbles is long (7 h or longer) at low solar activity but is short (˜3 h) at high solar activity. Broad plasma depletions occur near dawn at low solar activity, but wide low-density regions with multiple plasma bubbles occur in the evening sector at high solar activity.

Huang, Chao-Song; de La Beaujardiere, O.; Roddy, P. A.; Hunton, D. E.; Ballenthin, J. O.; Hairston, M. R.

2012-11-01

76

Measurement of physical characteristics of bubbles in gas-liquid plumes: Part II. Local properties of turbulent air-water plumes in vertically injected jets  

NASA Astrophysics Data System (ADS)

The structural development of air-water bubble plumes during upward injection into a ladle-shaped vessel has been measured under different conditions of air flow rate, orifice diameter, and bath depth. The measured radial profiles of gas fraction at different axial positions in the plume were found to exhibit good similarity, and the distribution of the phases in the plume was correlated to the modified Froude number. Different regions of flow behavior in the plume were identified by changes in bubble frequency, bubble velocity, and bubble pierced length which occur as bubbles rise in the plume. Measurement of bubble velocity indicates that close to the nozzle the motion of the gas phase is strongly affected by the injection velocity; at injection velocities below 41 m/s, the velocity of the bubbles along the centerline exhibits an increase with height, while above, the tendency reverses. High-speed film observations suggest that this effect is related to the nature of gas discharge, i.e., whether the gas discharge produces single bubbles or short jets. In this region of developing flow, measurement of bubble frequency and pierced length indicates that break-up of the discharging bubbles occurs until a nearly constant bubble-size distribution is established in a region of fully developed flow. In this largest zone of the plume the bubbles influence the flow only through buoyancy, and the spectra of bubble pierced length and diameter can be fitted to a log-normal distribution. Close to the bath surface, a third zone of bubble motion behavior is characterized by a faster decrease in bubble velocity as liquid flows radially outward from the plume.

Castillejos, A. H.; Brimacombe, J. K.

1987-12-01

77

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

78

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

SciTech Connect

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

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

1985-04-01

79

Gas holdup and entrainment characteristics in a modified downflow bubble column with Newtonian and non-Newtonian liquid  

Microsoft Academic Search

Gas entrainment and holdup characteristics have been studied in a downflow bubble column with both Newtonian and non-Newtonian liquid. Aqueous CMC solutions at different concentration were used as a non-Newtonian and water as Newtonian liquid. In the present system, use of plunging liquid jet and ejector were synchronized to obtain significant entrainment and dispersion of gas into liquid. The effects

Ajay Mandal; Gautam Kundu; Dibyendu Mukherjee

2003-01-01

80

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

NASA Astrophysics Data System (ADS)

The fate of marine seep gases in the ocean and atmosphere is intimately connected with bubble and bubble-plume processes, which are strongly size- and depth-dependent. Size-dependent flux distributions, ?, and vertical velocity functions, VZ(r), were measured with a video bubble measurement system in the Santa Barbara Channel, California. Several distinct plume types were identified for which size distributions were measured, major, minor, intermediate, and obstructed. A further vent class is elastic (which was observed but not quantified). In addition, any plume class could be oily. Minor plumes generally produced a lower emission flux, Q, and showed narrow, peaked ? that were well described as Gaussian. The radius of the dominant peak, RP, of minor plumes varied as Q0.40, with correlation coefficient, R2 = 0.84, in agreement with theoretical relationship of RP˜Q0.4 for Q above a critical flow rate. Oil contamination was found to affect RP and was not used in the fit. A probability distribution, ?(RP), for all Gaussian bubble plumes was itself well described by a combination of Gaussian functions, which were different for different seep areas. Major plumes showed a broad distribution including very small and very large bubbles and were well described by a power law with exponent a, which varied with Q according to a = 0.43 + 0.55 log(Q) with R2 = 0.77. One obstructed vent was analyzed and shared characteristics with the minor bubble plumes. Mixed bubble plume size distributions showed characteristics of both major and minor plume classes, i.e., were described by a combination of Gaussian functions and power laws, and were steeper (higher a) than major plumes for the same Q. Oily plumes produced complex, confused bubble size distributions. Upwelling velocities, VUP(r), were derived from VZ(r) and increased as VUP˜Q0.66 (R2 = 0.64); however, consideration of the more intense plumes (Q > 2 cm s-1) showed VUP˜Q0.35 in agreement with other published field measurements. Thus, the weaker bubble plumes were observed during the acceleration phase.

Leifer, Ira

2010-11-01

81

Tiny Bubbles  

NSDL National Science Digital Library

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

Dolphin, Glenn

82

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

83

CONTINUOUSLY SENSITIVE BUBBLE CHAMBER  

DOEpatents

A radiation detector of the bubble chamber class is described which is continuously sensitive and which does not require the complex pressure cycling equipment characteristic of prior forms of the chamber. The radiation sensitive element is a gas-saturated liquid and means are provided for establishing a thermal gradient across a region of the liquid. The gradient has a temperature range including both the saturation temperature of the liquid and more elevated temperatures. Thus a supersaturated zone is created in which ionizing radiations may give rise to visible gas bubbles indicative of the passage of the radiation through the liquid. Additional means are provided for replenishing the supply of gas-saturated liquid to maintaincontinuous sensitivity.

Good, R.H.

1959-08-18

84

In Search of the Big Bubble  

ERIC Educational Resources Information Center

|Freely rising air bubbles in water sometimes assume the shape of a spherical cap, a shape also known as the "big bubble". Is it possible to find some objective function involving a combination of a bubble's attributes for which the big bubble is the optimal shape? Following the basic idea of the definite integral, we define a bubble's surface as…

Simoson, Andrew; Wentzky, Bethany

2011-01-01

85

Gravity-driven bubbly flows  

Microsoft Academic Search

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

Robert F. Mudde

2005-01-01

86

Characteristics of Turbulent Premixed Flames under the Pressure Rising Process in a Closed Vessel  

NASA Astrophysics Data System (ADS)

In a closed vessel such as SI engines, the internal pressure increases due to dilatation during the combustion after the ignition. To clarify quantitative characteristics of turbulent premixed flames under the pressure rising process, direct numerical simulation (DNS) of turbulent premixed flames in a closed vessel at relatively high Reynolds number has been conducted. Detailed kinetic mechanism for hydrogen-air mixtures is used. Because of the local pressure rise, turbulence is enhanced at the unburnt side and flame surface is distorted, which results in increase of the flame surface. Heat release rate of each flame element is augmented since the pressure rise makes flame thickness thin. Under this pressure rising process, the flame thickness, the flame front curvature and the local heat release rate can be scaled by laminar flame thickness and the maximum heat release rate obtained from one dimensional DNS of laminar flame propagation by using averaged temperature in the unburnt region of the vessel as the inlet temperature. The tangential strain rate on the flame front can be scaled by Taylor micro scale averaged in the unburnt side. The local heat release rate is positively correlated with the curvature and the tangential strain. The time evolution of the flame surface area is also investigated quantitatively.

Fukushima, Naoya; Yenerdag, Basmil; Shimura, Masayasu; Tanahashi, Mamoru; Miyauchi, Toshio

2011-11-01

87

Flow structure and bubble characteristics of steam–water two-phase flow in a large-diameter pipe  

Microsoft Academic Search

The flow structure and bubble characteristics of steam–water two-phase upward flow were observed in a vertical pipe 155 mm in inner diameter. Experiments were conducted under volumetric flux conditions of JG<0.25 m s?1 and JL<0.6 m s?1, and three different inlet boundary conditions to investigate the developing state of the flow. The radial distributions of flow structure, such as void

Kimitoshi Yoneda; Akira Yasuo; Tomio Okawa

2002-01-01

88

Acoustic manifestations of gas hydrate shelled bubbles  

NASA Astrophysics Data System (ADS)

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

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

2009-11-01

89

When sound slows down bubbles  

NASA Astrophysics Data System (ADS)

We report experimental observations that a bubble rising in water in the presence of a sound field is significantly slowed down, even at moderate acoustic pressures. We measure the mean rise velocity of bubbles under various acoustic forcings and show this effect occurs if the noise spectrum matches or overlaps bubble resonance. We render surface oscillations and translational movements of bubbles using high speed video imaging and thereby identify Faraday waves on the bubble wall as the cause for the velocity reduction. The associated mechanisms are discussed in terms of induced forces.

Dangla, Rémi; Poulain, Cédric

2010-04-01

90

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

Microsoft Academic Search

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

Javier Ortiz-Villafuerte

1999-01-01

91

A clinical evaluation of the gas transfer characteristics and gaseous microemboli production of two bubble oxygenators.  

PubMed

The gaseous microemboli (GME) production and gas transfer characteristics of two series of bubble oxygenators (Harvey H-1500 and Bentley BOS-10) were evaluated during clinical perfusion in 33 adult patients during open heart surgery for acquired valvular and ischaemic heart disease. For each oxygenator series, patients were divided into two groups, depending upon the method of measurement (intermittent or continuous) of the arterial PO2(PaO2). Using the data available, the perfusionist altered the gas:blood flow ratio in an attempt to maintain the PaO2 within the normal range. In the first group (I = intermittent), where PaO2 data were available only intermittently, the PaO2 values were well above normal, and large numbers of GME were detected in the arterial blood. In the second group (C = continuous), where the PaO2 data were available continuously, there was significantly better control of the PaO2 (P less than 0.001 and P less than 0.01 for the H-1500 and BOS-10, respectively) and significantly fewer GME (P less than 0.01 and P less than 0.05 for the H-1500 and BOS-10, respectively). The Bentley BOS-10 oxygenator used a lower gas:blood flow ratio to achieve physiological levels (range 9 to 13 kPa at 37 degrees C) of PaO2 than did the Harvey H-1500 oxygenator, but there was no difference in the number of GME detected. The lower gas:blood flow ratios for the BOS-10 oxygenators in group C resulted in significantly higher PaCO2 values well outside the physiological range (4 to 6 kPa at 37 degrees C) during the rewarming phase (mean PaCO2 = 7.6 +/- 0.8 kPa) of cardiopulmonary bypass than did the H-1500 oxygenator (mean PaCO2 = 6.3 +/- 0.7 kPa). Mean values for the PaCO2 for both oxygenators during other phases of bypass (cooling and hypothermia) were within the physiological range. If the CO2 retention was corrected by increasing the gas:blood flow ratio the PaO2 values and GME counts became elevated. PMID:6441873

Pearson, D T; Holden, M P; Poslad, S J; Murray, A; Waterhouse, P S

92

Characteristics of Cimex lectularius (Hemiptera: Cimicidae), infestation and dispersal in a high-rise apartment building.  

PubMed

Bed bugs, Cimex lectularius L. (Hemiptera: Cimicidae), are a fast-growing urban pest of significant public health importance in the United States and many other countries. Yet, there is very little field research on the ecology of this pest due to its near absence in the United States and most developed nations for several decades. We investigated characteristics of the bed bug infestation and dispersal in a 223-unit high-rise apartment building through visual inspections, intercepting devices, and resident and staff interviews between December 2008 and April 2009. The following results were obtained: 1) 101 apartments (45% of the high-rise building complex) experienced bed bug infestations (within 41 mo of the first confirmed introduction), 2) 78% of the bed bugs trapped were nymphs, 3) an average of six bed bugs were detected dispersing through apartment entry doors every 4 wk, 4) adult bed bugs were 9 times more likely to disperse than nymphs, 5) 53% of apartments adjacent to infested apartments also were infested, and 6) 50% of the interviewed residents who had infestations were unaware of the bed bugs in their apartments. In addition to active dispersal, several passive bed bug dispersal mechanisms were observed: bringing bed bug-infested furniture into the building, travel, resident turnover, resident visits, and use of a bed bug-infested wheelchair in building common areas. These findings validate an urgent need for public education, early detection, and adoption of more effective bed bug monitoring and intervention programs to curb the exploding problem of bed bug infestations. PMID:20214383

Wang, Changlu; Saltzmann, Kurt; Chin, Eva; Bennett, Gary W; Gibb, Timothy

2010-02-01

93

Energy consumption characteristics of high-rise apartment buildings according to building shape and mixed-use development  

Microsoft Academic Search

Energy management for housing, which is responsible for 70% of the energy consumption by buildings, is increasing in importance. This study identified the characteristics of energy consumption in high-rise apartment buildings through a series of case studies and resident surveys. The results were as follows: (1) high-rise apartment buildings can be classified according to whether they are mixed-use or general

In Young Choi; Sung Heui Cho; Jeong Tai Kim

94

Cavitation erosion by single laser-produced bubbles  

NASA Astrophysics Data System (ADS)

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

Philipp, A.; Lauterborn, W.

1998-04-01

95

Effect of bubble deformation on the properties of bubbly flows  

NASA Astrophysics Data System (ADS)

Direct numerical simulations of the motion of 27 three-dimensional deformable buoyant bubbles in periodic domains are presented. The full Navier Stokes equations are solved by a parallelized finite-difference/front-tracking method that allows a deformable interface between the bubbles and the suspending fluid and the inclusion of surface tension. The Eötvös number is taken as equal to 5, so that the bubbles are ellipsoidal, and the Galileo number is 900, so that the rise Reynolds number of a single bubble in an unbounded flow is about 26. Three values of the void fraction have been investigated: 2%, 6% and 12%. At 6%, a change in the behaviour of the bubbles is observed. The bubbles are initially dispersed homogeneously throughout the flow field and their average rise Reynolds number is 23. After the bubbles have risen by about 90 bubble diameters, they form a vertical stream and accelerate. The microstructure of the bubble suspension is analysed and an explanation is proposed for the formation of these streams. The results for the ellipsoidal bubbles are compared to the results for nearly spherical bubbles, for which the Eötvös number is 1 and the Galileo number is 900. The dispersion of the bubbles and the velocity fluctuations in the liquid phase are analysed.

Bunner, Bernard; Tryggvason, Grétar

2003-11-01

96

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

97

Modeling of inclusion removal in a tundish by gas bubbling  

Microsoft Academic Search

Inclusion removal from liquid steel by attachment to rising gas bubbles has been reviewed. A mathematical model of inclusion removal by gas bubbling in a tundish has been developed and it is found that minimization of bubble size is critical to enhance removal. However, small bubble formation in a tundish may be problematic as bubble size is controlled by high

John Patrick Rogler

2004-01-01

98

Power Laws in Real Estate Prices during Bubble Periods  

NASA Astrophysics Data System (ADS)

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

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

99

Bubble Tray  

NSDL National Science Digital Library

Bubble Tray from the Exploratorium is an activity about surface tension and constructive or destructive interference observed in soap bubbles. The site provides a soap bubble recipe and suggests common supplies like a coat hanger and pizza pan to produce large, long lasting bubbles. An explanation of the physics involved and other methods of making large bubbles are also supplied. This activity is part of Exploratorium's Science Snacks series.

2006-07-16

100

Modeling of a single clean bubble bouncing on a free surface  

NASA Astrophysics Data System (ADS)

Bouncing of a rectilinearly rising bubble on a free surface is modeled with the use of a simple mass-spring system. We use an equation of motion of the system that consists of two springs connected in series, which allows us to account for the restoring forces of both the bubble and free surfaces, and a conservation equation of energy, which allows us to describe an exchange between the surface energy due to deformations of both the bubble and free surfaces and the kinetic energy of the bubble. We can determine that the contact time, i.e. the time duration of a bubble contacting a free surface, should be a half of the characteristic period of the oscillator. We also observe a single clean bubble bouncing on a flat free surface in ultrapure water in order to verify the present model. Analytical and experimental results agree quite well, even in the cases with significant surface deformations. When bubbles are smaller than 0.6 mm in radius, the deformations of both the bubble and free surfaces play important roles in bouncing. In the case of larger bubbles, bouncing is dominated by the free surface deformation since the bubble has already been highly deformed before collision.

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

2011-11-01

101

Effect of bubble deformability in turbulent bubbly upflow in a vertical channel  

NASA Astrophysics Data System (ADS)

As bubbles rising in a vertical channel with upflow become bigger, it is well known that the void fraction distribution changes in a fundamental way, from a wall peak for small bubbles to a maximum void fraction at the channel center for larger bubbles. Here, we use direct numerical simulations of buoyant bubbles in a turbulent flow to show that it is not the size of the bubbles that matters, but their deformability.

Lu, Jiacai; Tryggvason, Gretar

2008-04-01

102

Analyzing sea level rise and tide characteristics change driven by coastal construction at Mokpo Coastal Zone in Korea  

Microsoft Academic Search

This study investigates a construction-induced sea level rise and tide characteristics change, using a regression analysis to separate the local construction effect such as sea-dike\\/seawalls and global warming from total sea level change. The study also makes it clear why and how the extreme high water level has risen just after constructions at Mokpo harbor in Korea. As a result

Ju Whan Kang; Seong-Rok Moon; Seon-Jung Park; Khil-Ha Lee

2009-01-01

103

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

104

Soap Bubbles  

NSDL National Science Digital Library

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

Exploratorium, The

2011-12-07

105

Saturated flow boiling heat transfer and associated bubble characteristics of FC72 on a heated micro-pin-finned silicon chip  

Microsoft Academic Search

An experiment is carried out here to investigate flow boiling heat transfer and associated bubble characteristics of FC-72 on a heated micro-pin-finned silicon chip flush-mounted in the bottom of a horizontal rectangular channel. Besides, three different micro-structures of the chip surface are examined, namely, the smooth, pin-finned 200 and pin-finned 100 surfaces. The pin-finned 200 and 100 surfaces, respectively, contain

Y. M. Lie; J. H. Ke; W. R. Chang; T. C. Cheng; T. F. Lin

2007-01-01

106

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

SciTech Connect

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

Peng, Z. Y.; Ma, L. [Department of Physics, Yunnan Normal University, Kunming 650092 (China); Yin, Y. [Department of Physics, Liupanshui Normal College, Liupanshui 553004 (China); Bi, X. W. [Department of Physics, Honghe University, Mengzi 661100 (China); Zhao, X. H. [National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, P.O. Box 110, Kunming 650011 (China); Fang, L. M. [Department of Physics, Guangdong Institute of Education, Guangzhou 510303 (China); Bao, Y. Y., E-mail: pzy@ynao.ac.c, E-mail: astromali@126.co [Department of Physics, Yuxi Normal College, Yuxi 653100 (China)

2010-08-01

107

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

108

Quantitative measurement of cell-bubble attachment in bubble columns using foam flotation techniques  

Microsoft Academic Search

A simple and convenient system for quantitatively measuring the number of adsorbed animal cells per unit of bubble surface area (G, unit: cells\\/cm2) was developed. The system was successfully applied to recombinant Chinese hamster ovary (r-CHO) suspension cultures to investigate the dynamic cell-bubble attachment in a bubble column. In serum-free medium, G values increased with bubble rising height (H) and

Zhi-You Wen; Wen-Song Tan

1999-01-01

109

Big Bubbles  

NSDL National Science Digital Library

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

Science, Lawrence H.

2010-01-01

110

Can bubbles sink ships?  

NASA Astrophysics Data System (ADS)

I investigate the interplay between the buoyancy force and the upwelling (or drag) force which act on a floating object when bubbles are rising through a body of water. Bubbles reduce the buoyant force by reducing the density of the water, but if they entrain an upwelling flow of water as they rise, they can produce a large upward drag force on the floating object. In an upwelling flow, our model ship (density=0.94 g/cm3) floats in a foam whose density is only 0.75 g/cm3. Comparing results with and without upwelling currents is an interesting demonstration and has real-world applications to ships in the ocean.

Hueschen, Michael A.

2010-02-01

111

Magnetic Bubbles  

NASA Astrophysics Data System (ADS)

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

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

2008-11-01

112

Laboratory-generated primary marine aerosol via bubble-bursting and atomization  

NASA Astrophysics Data System (ADS)

A range of bubble and sea spray aerosol generators has been tested in the laboratory and compared with oceanic measurements from the literature. We have shown that the method of generation has a significant influence on the properties of the aerosol particles produced. Hence, the validity of a generation system to mimic atmospheric aerosol is dependent on its capacity for generating bubbles and particles in a realistic manner. A bubble-bursting aerosol generator which produces bubbles by water impingement was shown to best reproduce the oceanic bubble spectral shapes, which confirms previous findings. Two porous bubblers and a plunging-water jet system were tested as bubble-bursting aerosol generators for comparison with a standard nebulizer. The methods for aerosol production were evaluated by analysing the bubble spectrum generated by the bubble-bursting systems and the submicron size distribution, hygroscopicity and cloud condensation nucleus activity of the aerosols generated by the different techniques. Significant differences in the bubble spectrum and aerosol properties were observed when using different aerosol generators. The aerosols generated by the different methods exhibited similar hygroscopicity and cloud condensation nucleus activity behaviour when a sample of purely inorganic salts was used as a parent seawater solution; however, significant differences in the aerosol properties were found when using samples of filtered natural seawater enriched with biogenic organics. The presence of organics in the aerosol caused suppression of the growth factor at humidities above 75% RH and an increase in the critical supersaturation with respect to the generation from artificial seawater devoid of organics. The extent of the effect of organics on the aerosol properties varied depending on the method of particle production. The results of this work indicate that the aerosol generation mechanism affects the particles organic enrichment, thus the behaviour of the produced aerosols strongly depends on the laboratory aerosol generator employed. Comparison between bubble lifetimes in several laboratory simulations and the oceanic conditions indicated that it would require a considerable extension of the dimensions of the currently used bubble-bursting laboratory systems in order to replicate the characteristic oceanic bubble lifetimes. We analyzed the implications derived from the reduced bubble residence times in scaled systems, regarding marine surfactants adsorption on rising bubbles, and found that adsorption equilibrium is reached on a timescale much shorter than the bubble lifetime in small-scale laboratory generators. This implies that adsorption of marine surface-active material is not limited by surfactant transport to the bubble surface.

Fuentes, E.; Coe, H.; Green, D.; de Leeuw, G.; McFiggans, G.

2010-02-01

113

Bubble, Bubble, Toil and Trouble.  

ERIC Educational Resources Information Center

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

Journal of Chemical Education, 2001

2001-01-01

114

Collapse of cavitation bubbles in blood  

Microsoft Academic Search

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

E.-A. Brujan

2000-01-01

115

Collapse of cavitation bubbles in blood  

Microsoft Academic Search

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

E.-A. Brujan

2000-01-01

116

Soap Bubbles  

NSDL National Science Digital Library

This fun activity from PBS uses simple household items to explore the different shapes a soap bubble can take. It also contains a poll so that visitors can report their results and compare them with those of other visitors.

2010-07-09

117

Gas bubbles within acute intracranial epidural haematomas  

Microsoft Academic Search

Summary In order to assess the actual incidence of gas bubbles trapped within acute intracranial epidural haematomas, as revealed by computed tomography (CT) of the skull, a series of 204 patients with surgically verified epidural haematomas was retrospectively reviewed. Gas bubbles were observed on CT scan in 22.5% of the cases, with the incidence rising to 37% when CT scanners

M. Cossu; T. Arcuri; B. Cagetti; M. Brambilla Bas; D. Siccardi; A. Pau

1990-01-01

118

Propagation and stopping of air bubbles in Carbopol solutions  

Microsoft Academic Search

We present results of an experimental study of the motion of air bubbles rising in a column of Carbopol solution under gravity. In Dubash and Frigaard [N. Dubash, I.A. Frigaard, Conditions for static bubbles in viscoplastic fluids, Phys. Fluids 16 (12) (2004) 4319–4330] we have predicted conditions under which sufficiently small bubbles will not propagate in a yield stress fluid.

N. Dubash; I. A. Frigaard

2007-01-01

119

Anisotropy in the sound field generated by a bubble chain  

Microsoft Academic Search

A vertical chain of rising bubbles represents a transition from individual to continuum behaviour in a compressible gas–liquid flow. Experiments on the distribution of acoustic pressure around a bubble chain revealed a strong anisotropy in the acoustic field in the frequency band generated by individual bubbles. Sound appeared to propagate much more efficiently along the chain than normal to it.

Richard Manasseh; Aneta Nikolovska; Andrew Ooi; Shizuo Yoshida

2004-01-01

120

Anisotropy in the sound field generated by a bubble chain  

Microsoft Academic Search

A vertical chain of rising bubbles represents a transition from individual to contin- uum behaviour in a compressible gas-liquid flow. Experiments on the distribution of acoustic pressure around a bubble chain revealed a strong anisotropy in the acous- tic field in the frequency band generated by individual bubbles. Sound appeared to propagate much more eciently along the chain than normal

Richard Manasseh; Aneta Nikolovska; Andrew Ooi; Shizuo Yoshida

2003-01-01

121

Advances in Optical Characterization of Methane Seeps and Bubble Plumes  

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

122

Affirmative Discrimination and the Bubble  

ERIC Educational Resources Information Center

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

Clegg, Roger

2011-01-01

123

Fuel system bubble dissipation device  

SciTech Connect

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

Iseman, W.J.

1987-11-03

124

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

NASA Astrophysics Data System (ADS)

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

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

2008-03-01

125

Release of multiple bubbles from cohesive sediments  

NASA Astrophysics Data System (ADS)

Methane is a strong greenhouse gas, and marine and wetland sediments constitute significant sources to the atmosphere. This flux is dominated by the release of bubbles, and quantitative prediction of this bubble flux has been elusive because of the lack of a mechanistic model. Our previous work has shown that sediments behave as elastic fracturing solids during bubble growth and rise. We now further argue that bubbles can open previously formed, partially annealed, rise tracts (fractures) and that this mechanism can account for the observed preferential release at low tides in marine settings. When this mechanical model is applied to data from Cape Lookout Bight, NC (USA), the results indicate that methanogenic bubbles released at this site do indeed follow previously formed rise tracts and that the calculated release rates are entirely consistent with the rise of multiple bubbles on tidal time scales. Our model forms a basis for making predictions of future bubble fluxes from warming sediments under the influence of climate change.

Algar, Christopher K.; Boudreau, Bernard P.; Barry, Mark A.

2011-04-01

126

Stability of a class of neutral vacuum bubbles  

NASA Astrophysics Data System (ADS)

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

Morris, J. R.

2013-04-01

127

Oxygen transfer from growing bubbles: Effect of the physical properties of the liquid  

Microsoft Academic Search

Mass transfer from bubbles generated at dispersion devices is a major operation in chemical engineering. Most mass transfer models have focused on the free rising of the bubbles, but the bubbling process plays an important role because it determines the bubbles’ initial volume, surface area and oscillation amplitude. In this work, the mass transfer mechanism and the shape of a

Mariano Martín; Francisco J. Montes; Miguel A. Galán

2007-01-01

128

Tiny Bubbles.  

ERIC Educational Resources Information Center

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

Kim, Hy

1985-01-01

129

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

130

The relationships between the extent of mould problems and physical building characteristics in high-rise apartment buildings  

Microsoft Academic Search

SUMMARY This paper studies the extent of mould problems in a high-rise apartm ent complex with six buildings located in suburban of Seoul, Korea. The complex is composed of 466 households with different stories in buildings. The apartment buildings have occupants' complaints due to mould growth on interior surfaces right after the completion. The research team investigated the sizes of

Hyeun Jun Moon; Hwa-Yong Kim

131

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

132

Quasi-Analytic Models for Density Bubbles and Plasma Clouds in the Equatorial Ionosphere.  

National Technical Information Service (NTIS)

The equatorial ionosphere contains imbedded bubbles that rise though a horizontally stratified plasma. The motion of the bubbles are affect by gravity, neutral winds or external electric fields which produce electric fields in the F-Region density perturb...

P. A. Bernhardt

2006-01-01

133

Forced Aspiration of bubbles into a capillary tube  

NASA Astrophysics Data System (ADS)

One way to remove lodged bubbles in small vena is to force the bubble to be completely aspirated into a fine needle. We study the aspiration of a bubble into a vertical capillary tube, for different bubble size relative to the capillary diameter (i.e. bubble confinement) and low Bond numbers (pipette diameter << capillary length). In this case, there is a critical condition of flow rate depending on the bubble confinement and the capillary number Ca beyond which the bubble is aspirated completely into the capillary. Below this value, the bubble breaks-up forming a liquid slug at the entrance of the tube. A simple model which takes into account the draining time of the annular liquid thin film and the characteristic time of the capillary instability, explains the observed experimental results and establish the characteristic time to aspirate completely the bubble.

Durth, Melanie; Clanet, Christophe; Fernandez, Juan

2009-11-01

134

Influence of Geometrical Characteristics and Operating Conditions on the Effectiveness of Ozone Contacting in Fine-Bubbles Conventional Diffusion Reactors  

Microsoft Academic Search

Ozone contactor hydrodynamics are strongly dependent on the geometry and the operating conditions of the system. In this paper results obtained on a pilot scale reactor showing the relationship between the geometrical characteristics of an ozonation reactor and its hydrodynamic behavior are presented. The validity of the proposed models has been checked on several full-scale reactors for which data were

Zdravka Do-Quang; Clementina Cortina Ramirez; Michel Roustan

2000-01-01

135

In-situ Optical Characterization of Methane Seeps and Bubble Plumes  

NASA Astrophysics Data System (ADS)

Methane seeps are potentially keys contributors to atmospheric methane and to the global greenhouse gas budget. Improved estimates of methane flux from ocean floor seeps are required to understand the magnitude and characteristics of this potential source. In high-intensity methane seeps the bubble density, speed and size may permit a significant fraction of the gas to reach the atmosphere. However, quantifying methane within the water column in the free gas phase (i.e., in bubbles) remains challenging. Current approaches rely either on indirect acoustic methods or direct collection of bubbles. Acoustic methods have the disadvantage of requiring extensive calibration, and can fail to distinguish the bubble signal from other sources of acoustic noise. Gas-capture techniques are mechanically complex and can potentially alias episodic events. In both cases the fine scale structure such as heterogeneity of the rising bubbling plume is lost. We describe a vision-based system to characterize bubble plumes and the seep features from which they emanate. Image data is processed to estimate each bubble's volume and velocity; then integrated to produce an estimate of volumetric flux rate. This technique can reveal fine scale variability in the spatial and temporal structure within the plume. The system can be configured to be dormant until triggered by chemical sensors indicating high concentrations of methane in order to conserve power and extend deployment times. The imaging package was deployed over a methane hydrate site in the Mississippi Canyon for several days on a fixed mooring together with an array of chemical sensors. Preliminary results from field and flume tests suggest that vision-based sensing is a viable approach for determining gas bubble fluxes.

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

2006-12-01

136

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

SciTech Connect

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

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

2010-09-15

137

Bubble cloud depth under a hurricane  

NASA Astrophysics Data System (ADS)

The bubble cloud depth and its correlation with extreme winds are key elements of bubble-mediated gas injection, which are critical to the determination of the global gas budgets. The characteristics of bubble cloud depth were examined from measurements collected during the passage of a category-4 hurricane with winds up to 50 m s-1. The bubble cloud depth increases linearly with wind speed for winds less than 35 m s-1. Our findings are consistent with previous observations at low to moderate wind speeds. However, the rate of increase is reduced significantly at winds higher than 35 m s-1.

Wang, D. W.; Wijesekera, H. W.; Teague, W. J.; Rogers, W. E.; Jarosz, E.

2011-07-01

138

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

139

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

140

Small air bubbles in reagent grade water and seawater 2. Dissolution of 20- to 500-mum-diameter bubbles at atmospheric pressure  

Microsoft Academic Search

The dissolution rates for 20- to 500-mum-diameter air bubbles in water and seawater at 50% and 100% air saturation are presented. The data indicate a dissolution rate that is independent of diameter for bubbles larger than ~70 mum but is strongly dependent on diameter for smaller bubbles. Rise velocity data from a companion study were used in conjunction with Levich's

Isaac A. Harris; Richard M. Detsch

1991-01-01

141

Shock Waves in Bubbly Cavitating Flows: Part I. Shock Waves in Cloud Cavitation. Part II. Bubbly Cavitating Flows Through a Converging-Diverging Nozzle  

Microsoft Academic Search

Two problems are considered in this thesis: the nonlinear dynamics of a cloud of cavitation bubbles, and bubbly cavitating flows through a converging-diverging nozzle. The focus of the first problem is to explore the characteristics of the growth and collapse of a spherical cloud of bubbles. This is typical of the transient behaviour exhibited by a bubble cloud as it

Yi-Chun Wang

1996-01-01

142

Characterization of a Multiple Bubble Jet With a Streamer Discharge  

Microsoft Academic Search

The characteristics of a multiple argon bubble jet in which a streamer is generated by a dc pulsed discharge have been experimentally clarified through discharge visualization in a bubble and decolorization of a methylene blue solution. There are two types of streamer behavior in a bubble jet in which discharge propagation is along the top and bottom interfaces of the

Hideya Nishiyama; Ryosuke Nagai; Hidemasa Takana

2011-01-01

143

Power laws in real estate prices during bubble periods  

Microsoft Academic Search

How can we detect real estate bubbles? In this paper, we propose making use of information on the cross-sectional dispersion of real estate prices. During bubble periods, prices tend to go up considerably for some properties, but less so for others, so that price inequality across properties increases. In other words, a key characteristic of real estate bubbles is not

Takaaki Ohnishi; Takayuki Mizuno; Chihiro Shimizu; Tsutomu Watanabe

2011-01-01

144

POWER LAWS IN REAL ESTATE PRICES DURING BUBBLE PERIODS  

Microsoft Academic Search

How can we detect real estate bubbles? In this paper, we propose making use of information on the cross-sectional dispersion of real estate prices. During bubble periods, prices tend to go up considerably for some properties, but less so for others, so that price inequality across properties increases. In other words, a key characteristic of real estate bubbles is not

T. Mizuno C. Shimizu T. Watanabe T. Ohnishi

2011-01-01

145

Observations of change in surface characteristics of the Louth crater using HiRISE and CTX images  

NASA Astrophysics Data System (ADS)

The study of Martian ice is a critical component in understanding Mars in general; the ice may hold clues to Mars' past climate and the search for life, and to the ultimate goal of human settlement. This case study focuses on the Louth crater (70.1 N, 103.5 E), the southernmost Martian crater which holds a body of ice all year long. High resolution photographs from the HiRISE and CTX cameras on the Mars Reconnaissance Orbiter (MRO) have been used to support previous models of sublimation/deposition and seasonal albedo change of the ice mound in the Louth crater. The photographs were also used to survey geomorphologic features of the ice mound and of the crater, which often resemble terrestrial landforms. The combination of albedo change and landforms helps create an understanding of the dynamic nature of Martian ice, and supports current models of sublimation/deposition and the existence of subsurface ice, which could be vital in the search for life and for manned missions.

Cardenas, B.; Xie, H.

2011-12-01

146

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

147

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

Microsoft Academic Search

This study utilizes a U-shape platform device to generate a single cavitation bubble for a detailed analysis of the flow field\\u000a characteristics and the cause of the counter jet during the process of bubble collapse caused by sending a pressure wave.\\u000a A high speed camera is used to record the flow field of the bubble collapse at different distances from

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

2009-01-01

148

Nonlinear bubble dynamics of cavitation.  

PubMed

For cavitation clouds generated in a standing sound wave driven by an ultrasonic horn, the nonlinear acoustic wave equation governing cavitation dynamics is numerically solved together with the bubble motion equation under an approximation. This conceptual calculation can qualitatively reproduce the observed characteristics of cavitation. PMID:22400656

An, Yu

2012-01-09

149

Buoyant bubbles in a cooling intracluster medium. I. Hydrodynamic bubbles  

NASA Astrophysics Data System (ADS)

Aims: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. Methods: In this paper we present a first set of hydrodynamical, high resolution (10243 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. Results: 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 to match the data.

Gardini, A.

2007-03-01

150

FORMATION AND FLOW OF GAS BUBBLES IN A PRESSURIZED BUBBLE COLUMN WITH A SINGLE ORIFICE OR NOZZLE GAS DISTRIBUTOR  

Microsoft Academic Search

The characteristics of gas bubbles in a 5 cm diameter bubble column equipped with a single orifice of 1,3 or 5 mm diameter were investigated under system pressure of 0.1-15 MPa. The formation of gas bubbles was strongly affected by the system pressure. Under high pressures a dispersed gas jet was formed at gas velocities where spherical gas bubbles would

K. IDOGAWA; K. IKEDA; T. FUKUDA; S. MOROOKA

1987-01-01

151

Microfluidic actuation using electrochemically generated bubbles.  

PubMed

Bubble-based actuation in microfluidic applications is attractive owing to elementary microfabrication requirements. In the present study, the mechanical and chemical characteristics of electrochemically generated bubble valves were studied. By generating electrochemical bubbles as valves directly inside the channel, valves could be closed and opened in milliseconds. Whereas bubble inflation (or valve closing) rate increases with applied voltage, small microfluidic dimensions accelerate bubble deflation rates. It is found that bubbles need not collapse fully to restore full flow, and the channel opens when its hydraulic resistance equals that between the bubble and the wall--a process requiring only milliseconds. Since only picomoles of salt are needed to generate bubbles, pH gradients that are invariably associated with electrochemical reactions were readily suppressed by using a small amount of buffer, as visualized by a pH-sensitive fluorescent dye. A range of common laboratory reagents and electrolytes in varying concentrations, including weak to strong acids and bases, as well as nonaqueous/aqueous mixtures were successfully tested. Using such bubble valves, an eight-way multiplexer was fabricated and tested. PMID:12510764

Hua, Susan Z; Sachs, Frederick; Yang, David X; Chopra, Harsh Deep

2002-12-15

152

Enhanced lifetime of methane bubble streams within the deep ocean  

Microsoft Academic Search

We have made direct comparisons of the dissolution and rise rates of methane and argon bubbles experimentally released in the ocean at depths from 440 to 830 m. The bubbles were injected from the ROV Ventana into a box open at the top and the bottom, and imaged by HDTV while in free motion. The vehicle was piloted upwards at

Gregor Rehder; Peter W. Brewer; Edward T. Peltzer; Gernot Friederich

2002-01-01

153

Formation of gas bubbles in liquid flooded nozzles  

Microsoft Academic Search

The presence of liquid downflow through the bed openings, or isolated nozzles, gives rise to certain special conditions for gas bubble formation. According to [2], for nozzle diameters greater than 3 mm, there are variations in the bubble size on account of the flooding of the nozzle by the liquid used, i.e., due to the flow of liquid films on

G. I. Efremov; I. A. Vakhrushev

1968-01-01

154

Effects of bubble coalescence and breakup on conduit dynamics  

Microsoft Academic Search

Volatiles play a central role in eruption behavior. The ability of an exsolved gas phase to move through, and escape from, ascending magma controls whether an eruption is explosive or effusive. In this study, we investigate the dynamics and interactions of gas bubbles as they rise in a conduit. We focus on the coalescence and breakup dynamics of buoyant bubbles

C. Huber; J. Dufek; A. Parmigiani; M. Manga

2008-01-01

155

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

156

Computational Efficient Modelling of Laminar Separation Bubbles.  

National Technical Information Service (NTIS)

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 ran...

P. Dini M. D. Maughmer

1990-01-01

157

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

PubMed

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

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

2009-11-01

158

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

NASA Astrophysics Data System (ADS)

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

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

2002-11-01

159

Life of thermal bubble on platinum microheater  

NASA Astrophysics Data System (ADS)

When electrical current is supplied to a microline heater immersed in liquid, a microthermal bubble can be formed. The bubble grows until it becomes too large to adhere to a solid surface and finally departs into liquid completing its life. Here we report the experimental results associated with the life of a thermal bubble continuously heated by a platinum microheater. We investigated the effects of the heater dimensions on the nucleation temperature. It was found that a bubble nucleates at lower temperature as the heater gets wider. We also measured the departure diameter and frequency of thermal bubbles depending on the thermal conditions of the microheater and the ambient liquid. As the microheater temperature increases, both the departure diameter and frequency increase, showing different behaviors from those of macroscale boiling. However, as the ambient liquid temperature rises, the departure diameter decreases despite the increase of the departure frequency. Finally, the transient temperature profile of the microheater during bubble formation process was measured. Rapid drop and rise of the temperature were observed, which are attributed to the small-scale convection of cold ambient liquid.

Kim, Ho-Young; Jeong, Kwang-Hun; Ko, Seunghyun; Lee, Heon Ju; Lee, Yoon Pyo; Chang, Young Soo

2007-08-01

160

Bubble formation on a submerged micronozzle.  

PubMed

This work investigates detailed formation of air bubbles on a submerged micrometer-sized nozzle. The experimental study is conducted on a submerged nozzle of radius of 55 microm under low gas flow rate conditions (0.015-0.83 ml/min). The bubble formation is recorded by a high-speed optical camera and detailed characteristics of bubble formation such as the variations of instantaneous contact angles, bubble heights and the radii of contact lines are obtained, which shows a weak dependence on the flow rate under the conditions of current work. Using experimentally captured values of the height of bubble and the radius of contact line, the Young-Laplace equation is solved, which is found to be able to predict the bubble evolution quite well until the last milliseconds before the detachment. A force analysis of bubble formation reveals that the observed variations of contact angles and other characteristics during the bubble growth period are associated with the relative contribution of surface tension, buoyancy force and gravitational force. PMID:20038468

Vafaei, Saeid; Wen, Dongsheng

2009-08-12

161

Design of a bubble-swawm bioreactor for animal cell culture  

Microsoft Academic Search

A stationary bubble-swarm has been used to aerate a mammalian cell culture bioreactor with an extremely low gas flow rate. Prolonging the residence time of the gas bubbles within the medium improved the efficiency of the gas transfer into the liquid phase and suppressed foam formation. An appropriate field of speed gradients prevented the bubbles from rising to the surface.

F. Gudermann; D. Lütkemeyer; J. Lehmann

1994-01-01

162

Calculation of bubble shape and particle transport in a fluidized bed  

SciTech Connect

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

Puzyrev, E.M.

1986-07-01

163

The Art, Craft and Science of Modelling Jet Impact in a Collapsing Cavitation Bubble  

Microsoft Academic Search

One of the key characteristics of the asymmetric collapse of a cavitation bubble near a rigid boundary is the development of a high speed liquid jet that penetrates the interior of the bubble, impacting on the other side to yield a toroidal bubble. After the formation of the toroidal bubble, a vigorous splash may occur that can lead to pressures

J. R. Blake; Y. Tomita; R. P. Tong

1997-01-01

164

Effect of surface active materials on bubble dynamics in two-phase flow  

Microsoft Academic Search

Our goal in this research is to relate bubble performance in processes such as bubble breaking, dissolution, coalescence, and breakup to bubble interfacial characteristics, including surface tension, surface charge, and surface rheological properties. This fiscal year we have studied bubble dissolution rates in clean fresh water and in sea water samples representing a wide range of biological activities. Previous measurements

Bruce D. Johnson

1992-01-01

165

Why do bubbles in Guinness sink?  

NASA Astrophysics Data System (ADS)

Stout beers show the counter-intuitive phenomena of sinking bubbles, while the beer is settling. Previous research suggests that this phenomenon is due to the small size of the bubbles in these beers and the presence of a circulatory current, directed downwards near the side of the wall and upwards in the interior of the glass. The mechanism by which such a circulation is established and the conditions under which it will occur has not been clarified. In this paper, we use simulations and experiments to demonstrate that the flow in a glass of stout beer depends on the shape of the glass. If it narrows downwards (as the traditional stout glass, the pint, does), the flow is directed downwards near the wall and upwards in the interior and sinking bubbles will be observed. If the container widens downwards, the flow is opposite to that described above and only rising bubbles will be seen.

Benilov, E. S.; Cummins, C. P.; Lee, W. T.

2013-02-01

166

Behavior of laser-induced cavitation bubbles in liquid nitrogen  

NASA Astrophysics Data System (ADS)

Initial behavior and the subsequent motion of a bubble in liquid nitrogen are investigated experimentally using high-speed photography. A bubble is generated by focusing a pulsed ruby laser into liquid nitrogen at 78.0 K, changing the ambient pressures up to 253.2 kPa which corresponds to the applied pressure (or overpressure), ?p, being 147.1 kPa. When the energy level of the laser beam at the focus exceeds an irradiance threshold, for instance 5.4×1011 W/cm2 for ?p=4.9 kPa, the optical breakdown occurs in the liquid nitrogen, followed by a series of high-speed phenomena such as plasma formation, shock wave emission, and vapor bubble generation. It is found that during a very short period after the plasma formation a bubble grows nonspherically reflecting from the plasma shape, but the bubble volume itself varies with time in the same way for all cases performed in the present experiment. The liquid inertia is a dominant factor affecting the bubble growth, while the thermal effect becomes remarkable during the bubble collapse, resulting in the retardation of the bubble motion. The characteristic behavior of a laser-induced cavitation bubble in liquid nitrogen is significantly influenced by the phase change of vapor at the bubble surface as well as by the vapor pressure inside the bubble. Immediately after the bubble rebound, instabilities are amplified over the bubble surface similar to those caused in the water case.

Tomita, Y.; Tsubota, M.; Nagane, K.; An-Naka, N.

2000-11-01

167

Moon Rise  

NASA Video Gallery

Aboard the International Space Station in May 2012, Expedition 31 astronaut Don Pettit opened the shutters covering the cupola observation windows in time to watch the moon rise. The time-lapse scene was photographed from the airlock of the Station's Russian segment.

Mark Garcia

2012-05-30

168

Bubble dynamics in a compressible shear-thinning liquid  

NASA Astrophysics Data System (ADS)

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 bubble and the pressure equation are derived. Numerical calculations are presented using the experimental data for two polymer aqueous solutions, viz. HEC and CMC solutions, and water. It is found that the shear-thinning characteristic of liquid viscosity strongly influences only the behaviour of bubbles with initial radii smaller than 10-1 mm and the rheological parameter with the strongest influence on bubble collapse is the infinite-shear viscosity. The effect of polymer additives, including their surfactant properties, on spherical bubble collapse is also discussed.

Brujan, E.-A.

1998-11-01

169

Measurement of physical characteristics of bubbles in gas-liquid plumes: Part II. Local properties of turbulent air-water plumes in vertically injected jets  

Microsoft Academic Search

The structural development of air-water bubble plumes during upward injection into a ladle-shaped vessel has been measured under different conditions of air flow rate, orifice diameter, and bath depth. The measured radial profiles of gas fraction at different axial positions in the plume were found to exhibit good similarity, and the distribution of the phases in the plume was correlated

A. H. Castillejos; J. K. Brimacombe

1987-01-01

170

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

Microsoft Academic Search

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

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

1999-01-01

171

On the Rayleigh-Taylor instability of radio bubbles in galaxy clusters  

Microsoft Academic Search

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 intracluster medium (ICM). We show that while the jet is powering the inflation, the deceleration of the bubble-ICM interface is able

Fabio Pizzolato; Noam Soker

2006-01-01

172

Bubble Dynamics in Double-Stranded DNA  

NASA Astrophysics Data System (ADS)

We report the first measurement of the dynamics of bubble formation in double-stranded DNA. Fluctuations of fluorescence of a synthetic DNA construct, internally tagged with a fluorophore and a quencher, are monitored by fluorescence correlation spectroscopy. The relaxation dynamics follow a multistate relaxation kinetics, with a characteristic time scale of 50 ?s. A simple model of bubble dynamics based on constant zipping-unzipping rates is proposed to account for our experimental data. The role of different secondary structures stabilizing the open bubble is tested.

Altan-Bonnet, Grégoire; Libchaber, Albert; Krichevsky, Oleg

2003-04-01

173

Measurement of physical characteristics of bubbles in gas-liquid plumes: Part II. Local properties of turbulent air-water plumes in vertically injected jets  

Microsoft Academic Search

The structural development of air-water bubble plumes during upward injection into a ladle-shaped vessel has been measured\\u000a under different conditions of air flow rate, orifice diameter, and bath depth. The measured radial profiles of gas fraction\\u000a at different axial positions in the plume were found to exhibit good similarity, and the distribution of the phases in the\\u000a plume was correlated

A. H. Castillejos; J. K. Brimacombe

1987-01-01

174

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

Microsoft Academic Search

In the present study, quasi-diabatic two-phase flow pattern visualizations and measurements of elongated bubble velocity, frequency and length were performed. The tests were run for R134a and R245fa evaporating in a stainless steel tube with diameter of 2.32mm, mass velocities ranging from 50 to 600kg\\/m2s and saturation temperatures of 22°C, 31°C and 41°C. The tube was heated by applying a

Alexandre Alves Arcanjo; Cristiano Bigonha Tibiriçá; Gherhardt Ribatski

2010-01-01

175

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

Microsoft Academic Search

In the present study, quasi-diabatic two-phase flow pattern visualizations and measurements of elongated bubble velocity, frequency and length were performed. The tests were run for R134a and R245fa evaporating in a stainless steel tube with diameter of 2.32 mm, mass velocities ranging from 50 to 600 kg\\/m² s and saturation temperatures of 22 C, 31 C and 41 C. The

Alexandre Alves Arcanjo; Cristiano Bigonha Tibirica; Gherhardt Ribatski

2010-01-01

176

On the maximum drawdown during speculative bubbles  

NASA Astrophysics Data System (ADS)

A taxonomy of large financial crashes proposed in the literature locates the burst of speculative bubbles due to endogenous causes in the framework of extreme stock market crashes, defined as falls of market prices that are outlier with respect to the bulk of drawdown price movement distribution. This paper goes on deeper in the analysis providing a further characterization of the rising part of such selected bubbles through the examination of drawdown and maximum drawdown movement of indices prices. The analysis of drawdown duration is also performed and it is the core of the risk measure estimated here.

Rotundo, Giulia; Navarra, Mauro

2007-08-01

177

Acoustical observation of bubble oscillations induced by bubble popping  

NASA Astrophysics Data System (ADS)

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

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

2007-04-01

178

Acoustical observation of bubble oscillations induced by bubble popping.  

PubMed

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

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

2007-04-03

179

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

SciTech Connect

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

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

1994-06-01

180

Rising seas  

SciTech Connect

Predicting exactly how - or whether - sea level will shift in response to global warming remains a significant challenge. Scientists trained in many separate disciplines are attempting to glean answers using a variety of experimental approaches, ranging from drilling into the Antarctic ice cap to bouncing radar off the ocean from space. With such efforts, investigators have learned a great deal about how sea level has varied in the past and how it is currently changing. For example, most of these scientists agree that the ocean has been creeping upward by two millimeters a year for at least the past several decades. But determining whether a warmer climate will lead to a sudden acceleration in the rate of sea level rise remains an outstanding question. This article discusses the uncertainties, historical data, and possibilities regarding this issue.

Schneider, D.

1997-03-01

181

Effect of Gas Content on the Oscillation of a Laser-Induced Cavitation Bubble  

NASA Astrophysics Data System (ADS)

The oscillation of a cavitation bubble and the effect of gas content inside a cavity on the bubble motion are investigated by theory and experiment. Based on the cavitation model, the numerical study yields the gas content dependence of the amplitude and duration of the bubble oscillation in liquids. In experiment, the temporal oscillation of a single laser-induced cavitation bubble is obtained by means of a sensitive fiber-optic sensor based on optical beam deflection. The characteristic bubble parameters are determined, including the maximum (minimum) radii, oscillation duration and bubble energy, which all decrease with the oscillation. Besides, combining the cavitation theory with experimental data, the variation of gas content within the bubble during each oscillation is estimated, which increases with the oscillation cycle. Our results reveal the competitive interplay of the bubble energy and gas content during the bubble motion and the bubble energy in effect outweighs the latter.

Chen, X.; Xu, R. Q.; Yang, B.; Lu, J.; Ni, X. W.

182

Scaling model for laser-produced bubbles in soft tissue  

SciTech Connect

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

London, R. A., LLNL

1998-03-12

183

Influence of surfactant conditions on the structure of an upward bubbly channel flow  

NASA Astrophysics Data System (ADS)

We investigated an upward bubbly channel flow and the effects of surfactant on its flow structure experimentally. 3-Pentanol and Triton X-100 are used as surfactants. By the addition of small amount of surfactant, bubble coalescences are prevented and mono-dispersed 1mm spherical bubbles are obtained. Under all of our experimental conditions, the added surfactants do not influence the single-phase turbulence. On the other hand, small amount of surfactant drastically changes the whole flow structure of bubbly flow. On the low concentration of 3-Pentanol (21-63ppm), bubbles strongly migrate towards the wall and these highly accumulated bubbles on the wall form crescent-like shaped horizontal bubble clusters of 10-40mm length. However, in 3-Pentanol solution of higher concentration (˜168ppm) or in the 2ppm Triton X-100 solution, the tendency of the lateral migration of bubbles is weaken and the bubbles are distributed uniformly in the channel. In the surfactant solution, the slip velocity on the bubble surface retards and the bubble rising velocity decreases (Marangoni effect). The change of boundary condition on the bubble surface affects not only drag force but shear-induced lift force. It is indicated that this change of shear-induced lift force greatly relates to the lateral migration of bubbles and the disaggregation of the bubble clusters. We also measured the turbulent properties using LDV and discuss the flow structure.

Ogasawara, Toshiyuki

2005-11-01

184

Sponge Cake or Champagne? Bubbles, Magmatic Degassing and Volcanic Eruptions  

NASA Astrophysics Data System (ADS)

Vesiculation is an unavoidable consequence of magma decompression; the extent to which bubbles travel with ascending magma or leave the system by separated or permeable flow will determine the nature of the ensuing eruption. Bubbles travel with the melt from which they exsolve if the rise time of bubbles through the melt (the 'drift velocity') is much less than the rise rate of the magma (sponge cake). This condition is most likely to be met in viscous melts (where bubble rise velocities are low) and in melts that experience rapid decompression (high ascent velocities). Under these conditions, bubble expansion within the melt continues until sufficient bubble expansion causes coalescence and the development of a permeable network. Typical pumice vesicularities of 70-80% and permeabilities of 10-12 m2 constrain this limit under conditions appropriate for subplinian to plinian eruptions (mass fluxes > 106 kg/s). Slower rise rates (and lower mass fluxes) that characterize effusive eruptions produce silicic lavas with a wider range of vesicularities. In general, permeability decreases with decreasing sample vesicularity as bubbles deform (as evidenced by anisotropy in permeability and electrical conductivity) and pore apertures diminish. Degassing efficiency (and resulting densification of magma within the conduit) under these conditions is determined by permeability and the time allowed for gas escape. Bubbles rise through the melt if the drift velocity exceeds the velocity of magma ascent (champagne). This condition is most easily met in volatile-rich, low viscosity (mafic) melts at low to moderate fluxes. At very low magma flux, magma eruption rate is determined by the extent to which magma is entrained and ejected by rising gases (strombolian eruptions); when bubbles are too small, or are rising too slowly, they may not break the surface at all, but instead may be concentrated in a near-surface layer (surface foam). As the magma flux increases, segregation of bubble-rich from bubble-poor melt requires both longer conduits and lateral transport of degassed magma, as seen in violent strombolian eruptions. Flow transitions require coalescence, which is a dynamic process where bubble-bubble interactions are controlled by shear and gravitational (i.e. buoyancy) processes, both of which are strongly dependent on magma rheology. Also common in basaltic magmas that exhibit separated flow are by the simultaneous eruption of crystal-rich (shallow) and crystal-poor (deep) magmas. Upward increases in crystal content within the magma transport system will create rheological changes that may both slow upward bubble migration and change the size and shape of the bubble network (through deformation, coalescence, or bubble splitting). Preliminary experiments further show that abrupt rheological boundaries may concentrate bubbles at the boundary, allowing them to coalesce and move laterally prior to rising through the mush.

Cashman, K.; Pioli, L.; Belien, I.; Wright, H.; Rust, A.

2007-12-01

185

Microfluidic bubble logic.  

PubMed

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

Prakash, Manu; Gershenfeld, Neil

2007-02-01

186

Development of bubble tester  

NASA Astrophysics Data System (ADS)

A Bubble Tester is developed to do the measurements of bubble classes for optical elements. The tester is composed of illumination system,refractor slot, imaging system,CCD,computer controller and data processor,3D workshop and ground base. The light from the illumination system is refracted by the bubbles and inclosures in the optical elements, the imaging system captured the light and imaged the image to CCD and computer captured the image and did data processing to get the dimension, quantity and distribution of the bubbles and enclosures. The tester can measure bubbles with ?0.05~?5mm in diameter and the accuracy is 5%.The tester can measure bubbles and enclosures of optical elements and welding line of the optics according to GB 7661-87.

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

2009-05-01

187

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

NASA Astrophysics Data System (ADS)

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

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

1999-04-01

188

Bubble-Containing Foods  

Microsoft Academic Search

The presence of bubbles in a number of food products, such as bread, champagne, ice cream and beer, has dominated our perception\\u000a of product quality. Novel bubble-containing products occupy a greater proportion of supermarket shelf space. The inclusion\\u000a of bubbles in foods permits the creation of very novel structures while offering lighter alternatives in terms of calories.\\u000a Manufacturers generally find

K. Niranjan; S. F. J. Silva

189

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

190

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

191

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

192

Physics of bubble oscillations  

NASA Astrophysics Data System (ADS)

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

Lauterborn, Werner; Kurz, Thomas

2010-10-01

193

Bubbles: Using Controls  

NSDL National Science Digital Library

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

Products, American E.

2000-01-01

194

A model for the oven rise of dough during baking  

Microsoft Academic Search

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

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

1999-01-01

195

Hydrogen Bubbles as PIV/ICV Tracers in Cylinder Shedding  

NASA Astrophysics Data System (ADS)

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

Gilbert, Stuart; Sigurdson, Lorenz

2004-11-01

196

Mechanics of Bubbles in Sludges and Slurries  

SciTech Connect

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

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

1999-06-01

197

Free surface rise and fall due to wall turbulent structures  

SciTech Connect

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

Rashidi, M.

1996-12-20

198

Evaporation, Boiling and Bubbles  

ERIC Educational Resources Information Center

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

Goodwin, Alan

2012-01-01

199

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…

Korenic, Eileen

1988-01-01

200

Constrained Vapor Bubble Experiment  

Microsoft Academic Search

Microgravity experiments on the Constrained Vapor Bubble Heat Exchanger, CVB, are being developed for the International Space Station. In particular, we present results of a precursory experimental and theoretical study of the vertical Constrained Vapor Bubble in the Earth's environment. A novel non-isothermal experimental setup was designed and built to study the transport processes in an ethanol\\/quartz vertical CVB system.

Shripad Gokhale; Joel Plawsky; Peter C. Wayner Jr.; Ling Zheng; Ying-Xi Wang

2002-01-01

201

The Vacuum Bubble Nucleation  

SciTech Connect

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

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

2009-07-10

202

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

203

How does gas pass? Bubble transport through sediments  

NASA Astrophysics Data System (ADS)

The transport of gas through marine sediments is critical for both the formation and the ultimate fate of gas that is housed temporarily within hydrates. We monitored the gas flux produced by repeated bubble injections into a particle layer that was initially saturated with liquid. The size of ejected bubbles and the period between ejection events were different from the input size and period. Our observations clearly demonstrate bubble break-up as well as coalescence and the formation of preferred bubble migration pathways. We develop an elementary, semi-empirical model to interpret aspects of these results and predict the gas flux expected from a given size distribution of bubble inputs as a function of basic host sediment characteristics. Models of gas transport that use simple modifications to Darcy's law are not adequate to cope with bubble dynamics in the parameter regime that we observe.

Fauria, K. E.; Rempel, A. W.

2009-12-01

204

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

SciTech Connect

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

Paul C Millett; Anter El-Azab

2011-01-01

205

Hydrodynamical similarities between bubble column and bubbly pipe flow  

Microsoft Academic Search

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

Robert F. Mudde; Takayuki Saito

2001-01-01

206

Gas Bubble Formation in Stagnant and Flowing Mercury  

SciTech Connect

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

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

2007-01-01

207

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

208

Analysis of the formation and removal of gas bubbles in rotationally moulded thermoplastics  

Microsoft Academic Search

The presence of internal bubbles is a characteristic feature of thermoplastic products manufactured by rotational moulding. The bubbles in the mouldings are generally undesirable since they reduce strength and stiffness and impair the appearance of the product if they occur at the surface. The bubbles form as a result of powder particles coalescing during the heating stage of the process

L. Xu; R. J. Crawford

1993-01-01

209

Bubbles slowing down economic growth  

Microsoft Academic Search

To analyze the effects of bubbles on economic growth, we study a three-period life overlapping generations economy with accumulation of physical and human capital, using an extension of Azariadis and Drazen (1990). We characterize the balanced growth paths and the local dynamics both in the model without bubbles and with bubbles. Tirole (1985)'s study of bubbles is extended to the

Philippe MICHEL

1992-01-01

210

Bubble generation during transformer overload  

Microsoft Academic Search

Bubble generation in transformers has been demonstrated under certain overload conditions. The release of large quantities of bubbles would pose a dielectric breakdown hazard. A bubble prediction model developed under EPRI Project 1289-4 attempts to predict the bubble evolution temperature under different overload conditions. This report details a verification study undertaken to confirm the validity of the above model using

Oommen

1990-01-01

211

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

212

The stable bubble test.  

PubMed

Idiopathic Respiratory Distress Syndrome (I.R.D.S.) occurs mainly in preterm babies (Halliday and McClure, 1976). The cause of the condition is a deficiency of surfactant in the fetal lung. (Avery and Mead, 1959). The condition, if untreated, is associated with high fetal mortality. A simple test, The Bubble Stability Test, which can predict the possibility of I.R.D.S. occuring is now in use in the University Teaching Hospital, Lusaka. An analysis of the use of the Bubble Stability Test in fifty cases is presented. In our series a positive Bubble Stability Test accurately predicted fetal lung maturity. PMID:878632

O'Dowd, M J; Chikamata, D M

213

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

NASA Astrophysics Data System (ADS)

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

Banerjee, Rahul; Mandal, Labakanta; Roy, S.; Khan, M.; Gupta, M. R.

2011-02-01

214

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

SciTech Connect

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

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

2011-02-15

215

[Cavitation and boiling of bubbles at the focal region during high intensity focused ultrasound exposure].  

PubMed

High intensity focused ultrasound (HIFU) is a very complex transient process and can cause tissue coagulation necrosis. The cavitation and boiling behaviour of bubbles in the focal region play very important roles throughout an injury process. This paper reviews the research done by domestic and foreign scholars on behaviours of bubbles in HIFU irradiation process and summarizes in the focal region bubble cavitation and boiling generation, related detective means and relationships with hyperecho, temperature rise of the focus and injury shape. PMID:23198445

Zhong, Mingsong; Ai, Huijian; Li, Faqi

2012-10-01

216

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

Microsoft Academic Search

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

L. Consolini; J. R. Thome

2010-01-01

217

A level set numerical method to determine the dynamics of gas bubbles in inclined channels  

NASA Astrophysics Data System (ADS)

The dynamics of a gas bubble rising in vertical and inclined channels is investigated. The solution of this free boundary problem is determined numerically by using a level set method coupled with a finite difference solution of the Navier-Stokes equations. The numerical method is second order in space. Both two- and three-dimensional results will be discussed as a function of Reynolds number, Bond number, and inclination angle. Steady solutions are found for small values of all these parameters, and path and shape oscillations are observed as these parameters are increased. The effect of inclination angle is investigated for freely rising bubbles and for bubbles initially attached to the channel wall. In the latter case, the contact line problem is solved by introducing a Navier slip boundary condition along with a fixed contact angle. The bubble is observed to rupture at high Bond numbers. At high Reynolds numbers, when the inclination angle is also above a critical value, the steady solution is found to bifurcate into a time-periodic oscillation. The results presented here parallel experimental work that has found a critical inclination angle at which the dynamics changes from steadily rising bubbles to bouncing bubbles. Three-dimensional simulations have been conducted for bubbles in vertical channels. At higher Reynolds number, the initially spherical bubble deforms into an oblate ellipsoidal shape, and a path instability is found when the bubble's aspect ratio exceeds a critical threshold. The density and viscosity ratios between the bubble and the suspending fluid are varied and are found to affect the bubble dynamics. In addition, the bubble's wake is visualized, and a double-threaded wake of counter-rotating vortex filaments is observed behind a zigzagging bubble.

Norman, Catherine Eleanor

218

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

219

Magnetic Bubble Materials.  

National Technical Information Service (NTIS)

The intent of the study was to define those physical properties of magnetic bubble materials which need to be characterized, to investigate the known methods for making these characterization, and, finally, to recommend those characterization procedures w...

J. W. Moody R. M. Sandfort R. W. Shaw

1972-01-01

220

What's in a Bubble?  

ERIC Educational Resources Information Center

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

Saunderson, Megan

2000-01-01

221

Bubble Domain Structures.  

National Technical Information Service (NTIS)

The patent application provides a film of nickel/iron alloy evaporated onto a substrate at an angle of from 45 degrees to 80 degrees, and having bubble domains formed therein by an applied magnetic field.

I. Puchalska-Hibner

1974-01-01

222

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

223

Modeling of Bubble Oscillations Induced by a Lithotripter Pulse  

NASA Astrophysics Data System (ADS)

In therapeutic applications of biomedical ultrasound, it is important to understand the behavior of cavitation bubbles. Herein, the dynamics of a single, spherical bubble in water are modeled using the Gilmore equation closed by an energy balance on bubble contents for calculation of pressures inside the bubble. Moreover, heat and mass transfer at the bubble wall are incorporated using the Eller-Flynn zeroth-order approximation for gas diffusion, an estimation of non-equilibrium phase change based on the kinetic theory of gases, and assumed shapes for the spatial temperature distribution in the surrounding liquid. Bubble oscillations predicted by this model are investigated in response to a lithotripter shock wave. Model results indicate that vapor trapped inside the bubble during collapse plays a significant role in the afterbounce behavior and is sensitively dependent upon the ambient liquid temperature. Initial experiments have been conducted to quantify the afterbounce behavior of a single bubble as a function of ambient temperature; however, the results imply that many bubbles are present and collectively determine the collapse characteristics.

Kreider, Wayne; Bailey, Michael R.; Crum, Lawrence A.

2006-05-01

224

Bubble formation with electron irradiation in SiC implanted with hydrogen or deuterium  

Microsoft Academic Search

The bubbles were formed and grew when SiC implanted with high fluence of hydrogen ion was irradiated with electron. In this study we tried to inspect the supposition that the energy deposition of the electron beam to hydrogen caused the migration of hydrogen and gave rise to bubble formation and growth. We used hydrogen (H) or deuterium (D) as implanted

J. Aihara; K. Hojou; S. Furuno; M. Ishihara

2002-01-01

225

Dissolution of 100 to 1000 mum diameter air bubbles in reagent grade water and seawater  

Microsoft Academic Search

The dissolution of freely rising, 100 to 1000 mum diameter air bubbles was measured in reagent grade water, seawater, and artificial seawater. Dissolution was studied for samples having varied percent air saturation, and temperature. All data were taken at atmospheric pressure. Bubbles dissolved faster in water and artificial seawater than in seawater and there is less scatter in the dissolution

Richard M. Detsch

1990-01-01

226

Bubble-Turbulence Interaction in Binary Fluids  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

227

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

2013-05-21

228

Impact of tangled magnetic fields on fossil radio bubbles  

NASA Astrophysics Data System (ADS)

There is growing consensus that feedback from active galactic nuclei (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 [intracluster medium (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 magnetohydrodynamical 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 length-scale of magnetic fields may be smaller than 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 H? filaments observed in the Perseus cluster.

Ruszkowski, M.; Enßlin, T. A.; Brüggen, M.; Heinz, S.; Pfrommer, C.

2007-06-01

229

Local bubble distribution in bubbly turbulent Taylor-Couette flow  

NASA Astrophysics Data System (ADS)

In turbulent Taylor-Couette flow, the injection of bubbles reduces the global drag on the cylinder surfaces. The previous bubbly turbulent drag reduction measurements in TC flow were mainly based on the global torque, which is not sufficient to understand the mechanism of bubbly drag reduction. One of the key issues is the actual bubble distribution inside the TC gap. Using optical fibers placed inside the TC gap, we scanned the local bubble distribution in the radial direction. An extension of this technique is a four-point optical fiber probe, which enables to retrieve the bubble velocity vector and aspect ratio.

Narezo, Daniela; van Gils, Dennis; Sun, Chao; Lohse, Detlef

2010-11-01

230

Statistical equilibrium of bubble oscillations in dilute bubbly flows  

PubMed Central

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

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

2008-01-01

231

Communications; On the formation of potassium bubbles in tungsten rod  

SciTech Connect

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

Briant, C.L. (General Electric Co., Schenectady, NY (USA). Corporate Research and Development Center)

1989-01-01

232

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

233

Bubble bursting mediated aerosols  

NASA Astrophysics Data System (ADS)

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

Lhuissier, Henri; Villermaux, Emmanuel

2009-11-01

234

Bubble-induced damping in displacement-driven microfluidic flows.  

PubMed

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

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

2012-08-01

235

Bubble-induced damping in displacement-driven microfluidic flows  

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

236

VLSI intelligent magnetic bubble memories  

SciTech Connect

This thesis presents a systematic exploration of VLSI possibilities for intelligent magnetic bubble memories in which back-end processors and memory elements could be incorporated in bubble VLSI chips. To provide the basis of system designs on bubble chips, a comprehensive library of magnetic bubble logic components was established, with emphasis on standardization in terms of dimensions and I/O to facilitate the chip composition task. These components were designed in current-access perforated-sheet configuration and fabricated on magnetic garnet wafers supporting 2-..mu..m bubbles. Operating margins were studied on 8-..mu..m period devices at 1 MHz by using a high speed magneto-optical sampling camera system. Bubble-to-bubble interaction force was found very reliable in producing successful logic operation with 12% bias field margins equal to 80% of the bubble propagation margin and about 60% of the free bubble bias field margin. An 8.5% overlapped bias margin was obtained for all of the logic components. The established library of bubble logic components was used to design intelligent bubble memories that support string-pattern matching and associative-searching functions. The intrinsic features of bubble logic technology were examined to indicate opportunities for VLSI bubble logic systems on memory chips.

Hwang, J.P.

1985-01-01

237

Bubble Nucleation in Supersaturated Fluids.  

National Technical Information Service (NTIS)

An understanding of the physics of bubble formation is of importance in such diversified endeavors as propeller design, fluid flow, undersea medicine, and the brewing of beer. While the properties of preformed bubbles are well understood, relatively littl...

T. D. Kunkle

1979-01-01

238

Study on Vibration Characteristics of a High-rise Building using results of Microtremor, Manpower Excitation Measurements, Earthquake Observations and Simulations of a 3D Moment-frame structure  

NASA Astrophysics Data System (ADS)

In the Tokyo metropolitan area, high-rise buildings will suffer strong ground motions in near future. In order to estimate damage of the buildings and to carry out counter measures for reducing the damage, it is necessary to know the accurate vibration characteristics of the buildings during the strong ground motions. The purpose of the paper is to investigate vibration characteristics of the Shinjuku Campus building of the 28th floors in Shinjuku, Tokyo, which is a steel structure of moment frames with143 m height. First, we constructed a 3D moment frame model and compared vibration characteristics, such as the natural periods and the corresponding mode shapes, with those obtained by microtremors measurements and manpower excitations. We obtained excellent agreements between them. Second, we compared the observed building response during earthquakes with those of the simulations; we again obtained agreements.

Hoshi, Yukio; Hisada, Yoshiaki; Yamashita, Tetsuo; Masuzawa, Yoe; Shimamura, Kenta

239

Bubble formation via multidrop impacts  

Microsoft Academic Search

Gas bubbles are often generated when droplets impact a liquid-air interface. For the impact of single droplets, a critical impact velocity must be exceeded for air to be entrained in the form of bubbles. Here we establish that bubbles can be generated at much lower velocities provided that two or more drops impact the liquid-air interface within a sufficiently short

Alexander G. Bick; William D. Ristenpart; Ernst A. van Nierop; Howard A. Stone

2010-01-01

240

Bubbly jets in stagnant water  

Microsoft Academic Search

Air–water bubbly jets are studied experimentally in a relatively large water tank with a gas volume fraction, Co, of up to 80% and nozzle Reynolds number, Re, ranging from 3500 to 17,700. Measurements of bubble properties and mean axial water velocity are obtained and two groups of experiments are identified, one with relatively uniform bubble sizes and another with large

David Z. Zhu; Nallamuthu Rajaratnam

2008-01-01

241

Hadron bubble evolution into the quark sea  

SciTech Connect

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

Freese, K. (Physics Department, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (USA)); Adams, F.C. (Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (USA))

1990-04-15

242

Bubbles generated from wind-steepened breaking waves: 1. Bubble plume bubbles  

Microsoft Academic Search

Measurements of bubble plumes from paddle-amplified, wind stress breaking waves were made in a large wind-wave channel during the LUMINY experiment in fresh (but not clean) water. Bubble plumes exhibited considerable variability with respect to dynamics, bubble size distribution, and physical extent. A classification scheme was developed, and time- and size-resolved bubble population distributions were calculated for each plume class.

Ira Leifer; Gerrit de Leeuw

2006-01-01

243

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.

2008-06-11

244

The Liberal Arts Bubble  

ERIC Educational Resources Information Center

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

Agresto, John

2011-01-01

245

Bubbles and steam electricity  

Microsoft Academic Search

Abstract In 1840, Lord Armstrong was the first to study the electrical charge produced as steam escaped from boilers, the phenomenon called steam electricity. In 1969, interest in steam electricity was renewed because of explosions caused by the ignition of chemical vapors during the washing of ship tanks with steam jets. Steam electricity is proposed explained by the bubbles nucleated

T. V. Prevenslik

246

Magnetic Bubble Materials.  

National Technical Information Service (NTIS)

The object of this project is to establish a reliable supply of high quality magnetic bubble materials to support the device work of various Department of Defense agencies. This work encompasses bulk, non-magnetic garnet crystal growth (for use as substra...

J. W. Moody R. J. Janowiecki R. M. Sandfort R. W. Shaw

1973-01-01

247

Magnetic Bubble Materials.  

National Technical Information Service (NTIS)

The object of this project was to establish a reliable supply of high quality magnetic bubble materials to support the device work of various Department of Defense Agencies. Bulk, single crystals of Gd3Ga5O12 were grown by the Czochralski method. Crystals...

J. W. Moody R. M. Sandfort R. W. Shaw

1972-01-01

248

Magnetic bubble computer systems  

Microsoft Academic Search

The purpose of this paper is to extend the work presented earlier on the methods for performing logic on magnetic bubble chips, and to illustrate these techniques by presenting the outline of a design for a general-purpose digital computer.

R. C. Minnick; P. T. Bailey; R. M. Sandfort; W. L. Semon

1972-01-01

249

Magnetic Bubble Materials.  

National Technical Information Service (NTIS)

The Czochralski growth of defect-free, non-magnetic garnet crystals and the preparation of epitaxial magnetic bubble garnet films by liquid phase epitaxy (LPE) and arc-plasma spraying (APS) were investigated. Two garnet systems, Eu-Yb-Y and Sm-Y, were ide...

J. T. Cheng J. W. Moody M. C. Willson R. M. Sandfort R. W. Shaw

1973-01-01

250

Signature of anisotropic bubble collisions  

SciTech Connect

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

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

2010-09-15

251

Temperature rise in superfluid helium pumps  

SciTech Connect

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, P.

1988-07-01

252

Source mechanism regimes for the acoustic signals generated during the expansion of rising and bursting gas slugs in low-viscosity magmas  

Microsoft Academic Search

Strombolian eruptive activity produces gas-rich, magma-poor ejecta suggesting the separation and concentration of volcanic gases within the plumbing system. These gases may then rise as relatively large bubble rafts or individual 'slug' bubbles, and cause detectable seismic activity on interaction with conduit geometry. Rising within a magma column, a gas bubble must expand appreciably in order to maintain magma-static pressure,

S. B. Corder; M. R. James

2010-01-01

253

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

Microsoft Academic Search

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

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

1997-01-01

254

Fluid mechanics of three-dimensional bubbles in fluidized beds  

SciTech Connect

The equations that describe the flow of solids and gas surrounding a single rising stable bubble in a gas particulate fluidized bed were formulated. These equations were integrated using a sixth order Runge-Kutta-Fehlberg method along the centerline of symmetry. It was found that the equations in the region near the bubble surface (the boundary layer region) are singular, and a special treatment is required to complete the integrations. It is shown that the centerline velocity of the gas phase at the bubble surface, measured in a bubble attached frame, must be equal to the terminal velocity of a freely falling particle. A linearized singularity analysis of the equations at the centerline of symmetry indicates a saddle type singularity at both the bubble surface and the edge of the cloud. The conservation equations are transformed into a rectangular stretched domain. In addition, an implicit finite difference scheme was formulated in this transformed plane. The boundary conditions along with the complete flowchart necessary to integrate these equations in the region near the centerline are presented. The method shows that the bubble and cloud shapes, which are not known a-priori, may be determined during the course of the solution.

Ramezan, M.

1984-01-01

255

Bubbles in Foods: Creating Structure out of Thin Air!  

Microsoft Academic Search

Bubbles are always perceived to represent the best in food and drink. Their presence and characteristics have dominated our\\u000a perception of the quality of bread, champagne, ice creams, and let’s not forget the good olde beer! In recent years, there\\u000a has been a constant flow of new bubble-containing snack foods into our supermarkets—whipped cream, chocolate, wafers, cakes,\\u000a meringues, extruded snacks

K. Niranjan; S. F. J. Silva

256

Effects of intermittent entrainment of air bubbles by breaking wind waves on ocean reflectance and underwater light field  

Microsoft Academic Search

Light-scattering properties of air bubbles suspended in water and observational evidence of bubble entrainment by breaking wind waves indicate that bubble clouds may influence ocean reflectance and in-water light field characteristics within the surface layer. We estimate potential changes in remote sensing reflectance and in-water light field associated with a bubble entrainment event observed at a wind speed of 10

Dariusz Stramski; Jaroslaw Tegowski

2001-01-01

257

Multiscale Modeling of Cavitating Bubbly Flows  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

258

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

NASA Astrophysics Data System (ADS)

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

Fsadni, Andrew M.; Ge, Yunting

2012-04-01

259

Computation for angular distribution of scattered light on a coated bubble in water  

NASA Astrophysics Data System (ADS)

The bubbles in sea water are mostly coated with a layer of oil, of which the effect on scattered light has usually been ignored in previous studies. This paper aims to propose an equation of scattering intensity by coated bubbles in water, based on geometrical optics theories. During the research, a PC was used to generate a two-dimensional curve that models the angular distribution of scattered intensity, namely the volume scattering function (VSF), by a coated bubble with a diameter larger than 200 µm. The curve reveals the far-field characteristics of light scattered by the coated bubble, as well as the refractive rays that have the main influence on the scattering intensity. It is seen from the simulation results that the scattering intensity distribution of an uncoated bubble and a coated bubble are very similar. But the oil layer weakens the forward scattering effect of the coated bubble while it strengthens the backward scattering effect.

Li, Wei; Yang, Kecheng; Xia, Min; Tan, Dan; Zhang, Xiaohui; Rao, Jionghui

2006-10-01

260

Mathematical Analysis of Relationship between Land Price and Real Estate Bubbles  

Microsoft Academic Search

In the article, the author studies the relationship between land price and real estate bubbles through mathematical analysis. Firstly, through analyzing the situation in foreign countries, the author points out that the rising price of land makes the price of real estate keep rising because the land price is the most important part of real estate price. This is the

Lv Bo; Zhang Ming-yu

2006-01-01

261

Nonlinear oscillations and collapse of elongated bubbles subject to weak viscous effects  

NASA Astrophysics Data System (ADS)

The weak viscous oscillations of a bubble are examined, in response to an elongation that perturbs the initial spherical shape at equilibrium. The flow field in the surrounding liquid is split in a rotational and an irrotational part. The latter satisfies the Laplacian and can be obtained via an integral equation. A hybrid boundary-finite element method is used in order to solve for the velocity potential and shape deformation of axisymmetric bubbles. Weak viscous effects are included in the computations by retaining first-order viscous terms in the normal stress boundary condition and satisfying the tangential stress balance. An extensive set of simulations was carried out until the bubble either returned to its initial spherical shape, or broke up. For a relatively small initial elongation the bubble returned to its initial spherical state regardless of the size of the Ohnesorge number; Oh=?/(?R?)1/2. For larger initial elongations there is a threshold value in Oh-1 above which the bubble eventually breaks up giving rise to a ``donut'' shaped larger bubble and a tiny satellite bubble occupying the region near the center of the original bubble. The latter is formed as the round ends of the liquid jets that approach each other from opposite sides along the axis of symmetry, coalesce. The size of the satellite bubble decreased as the initial elongation or Oh-1 increased. This pattern persisted for a range of large initial deformations with a decreasing threshold value of the Oh-1 as the initial deformation increased. As its equilibrium radius increases the bubble becomes more susceptible to the above collapse mode. The effect of initial bubble overpressure was also examined and it was seen that small initial overpressures, for the range of initial bubble deformations that was investigated, translate the threshold of Oh-1 to larger values while at the same time increasing the size of the satellite bubble.

Tsiglifis, Kostas; Pelekasis, Nikos A.

2005-10-01

262

Cavitation Bubble in Shear Flow  

NASA Astrophysics Data System (ADS)

In the orifice of liquid injectors at high pressure, cavitation occurs behind the sharp corners, where a strong pressure drop is present due to quick change in the flow direction. In addition, a high level of shear is present inside the boundary layer. Therefore, it is important to understand the influence of the shear on the cavitation. In this study, the deformation of a cavitation bubble in shear and extensional flows is numerically investigated. The Navier-Stokes equations are solved to observe the three-dimensional behavior of the bubble as it grows and collapses. During the collapse phase of the bubble, two re-entrant jets are observed on two sides of the bubble due to interaction of the bubble with the background flow. Re-entrant jets with enough strength could breakup the bubble into smaller bubbles. Post processing of the results is done to cast the disturbance by the bubble on the liquid velocity field in terms of spherical harmonics. It is found that a quadrupole moment is created in addition to the monopole source. As the bubble collapses regions of high vorticity are created near the bubble interface.

Dabiri, Sadegh; Sirignano, William; Joseph, Daniel

2009-11-01

263

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

264

The Fermi Bubbles: Possible Nearby Laboratory for AGN Jet Activity  

NASA Astrophysics Data System (ADS)

The two giant gamma-ray bubbles discovered by the Fermi Gamma-ray Space Telescope are nearly symmetric about the Galactic plane, suggesting some episode of energy injection from the Galactic center, such as a nuclear starburst or active galactic nucleus (AGN) jet activity. Using three-dimensional magnetohydrodynamic simulations that self-consistently include the dynamical interaction between cosmic rays (CR) and thermal gas, and anisotropic CR diffusion along magnetic field lines, we show that the key characteristics of the observed bubbles can be successfully reproduced by a recent jet activity from the central AGN. This implies that the Fermi bubbles could be a unique laboratory for studying AGN jet-inflated bubbles. Our simulations allow us to generate maps of the distribution of the magnetic field, radio polarization, and synchrotron, X-ray, and gamma-ray emission. While the source of pressure support of extragalactic AGN bubbles is still poorly known due to observational limitations, we are able to derive constraints on the composition of the Fermi bubbles by comparing our model predictions with the spatially resolved gamma-ray bubble and microwave haze observations.

Yang, Hsiang-Yi Karen; Ruszkowski, M.; Zweibel, E. G.; Ricker, P. M.

2013-04-01

265

RHIC PRESSURE RISE.  

SciTech Connect

Beam induced pressure rise remains an intensity limit at RHIC for both heavy ion and polarized proton operations. The pressure rises at beam injection, transition, and rebucketing are discussed, where the beam rebucketing pressure rise is probably of most concern for upcoming runs. Counter measures and results of beam studies are presented.

ZHANG,S.Y.ALESSI,J.BAI,M.BLASKIEWICZ,M.ET AL.

2004-07-05

266

Melting Ice Rising Seas  

NSDL National Science Digital Library

This NASA video presents animations, photos and footage of melting polar ice as a result of climate change, the resulting sea-level rise, and selected consequences of that rise. Excellent animations, interviews with scientists, and clear step-by-step explanations provide a solid introduction to one facet of sea level rise and its consequences.

Noaa

267

The magnetooptic bubble display  

Microsoft Academic Search

The various factors that affect the properties of magnetooptic (M\\/O) bubble displays which use bismuth-substituted iron garnets are discussed. A composite bias magnet-ferrite drive-coil assembly is described which allows optical access to the display chip. The drive coils required 300 mW to produce an in-plane field of 30 Oe when operated at 10 kHz, and the bias field was uniform

D. E. Lacklison; G. B. Scott; A. D. Giles; J. A. Clarke; R. F. Pearson; J. L. Page

1977-01-01

268

The magnetooptic bubble display  

Microsoft Academic Search

The various factors that affect the properties of magneto-optic (M\\/O) bubble displays which use bismuth substituted iron garnets are discussed. A composite bias magnet-ferrite drive coil assembly is described which allows optical access to the display chip. The drive coils required 300 mW to produce an in-plane field of 30 Oe when operated at 10 kHz, and the bias field

D. E. LACKLISON; G. B. SCOTT; A. D. GILES; J. Clarke; R. F. PEARSON; J. L. PAGE

1977-01-01

269

Bubble column dynamics with bubble induced turbulence and dispersion  

NASA Astrophysics Data System (ADS)

The paper presents an evolution of developed mathematical model which is devoted to the description of turbulent flows of bubbly media. The model utilizes Euler-Euler approach which is expanded by k-?-SST turbulence model with additional modifications, related to the bubble induced turbulence and bubble path dispersion. Numerical code based on the proposed model was developed to perform computation of bubble column evolution. Good agreement with experimental data was obtained, and necessity of inclusion of both modifications related to the turbulent motion was shown.

Chernyshev, Alexander; Schmidt, Alexander

2013-10-01

270

Experimental study of bubble coalescence in rhyolitic and phonolitic melts  

NASA Astrophysics Data System (ADS)

We have experimentally studied the process of bubble coalescence in rhyolite and phonolite melts of natural composition. The experiments involved decompression of water-saturated melts equilibrated at pressures and temperatures from 100 to 150 MPa and 775 to 840 °C in vertically oriented, rapid-quench capable, cold seal pressure vessels. One type of experiments (rhyolite MCR-100, 120, 150 and phonolite LSP-120 series') approximates a "static" bubble coalescence case, where we held the decompressed samples for ˜5 seconds to 4320 minutes (3 days) before quenching. The second type (rhyolite LPC-100 series) replicates an "expanding" bubble coalescence environment, where we continually decompressed the experiments at a rate of 0.5 MPa/s, examining samples quenched at ending pressures between 10 and 80 MPa. Our "static" case (MCR-100, 120, and 150, and LSP-120) results show significant increases in the modal bubble sizes and in the sizes of the largest bubbles, corresponding to measurable broadening in the size distributions. Their bubble number densities (N V) decrease as a function of hold time at their final pressures (P F), and can be fit well by power law functions. Our "expanding" case experiments (LPC-100) show a significant drop in N V during the duration of the experiments that can be fit by an exponential equation as N V vs. either time or P F. Average estimates of bulk coalescence rates indicate a ˜1 order of magnitude drop in N V for "static" case rhyolites in a 2-3 day period, and ˜2 orders of magnitude for phonolites within a 3 day period. Despite a ˜2 order of magnitude difference in viscosity, coalescene in the phonolite is only slightly faster than the rhyolite. The "expanding" case experiments show a ˜1 order of magnitude drop in N V over 180 seconds. Thus, N V's decrease 4 orders of magnitude faster in expanding vs. static bubbly rhyolite melts. Our results imply that significant bubble coalescence can occur in rhyolite magmas at relatively fast (˜20 m/s) ascent rates in the conduit. Thus, bubble interconnectivity, leading to high permeability, is possible during ascent. Bubble coalescence may occur during second boiling in magma bodies that are stalled in the crust. The timescales over which this occurs is much faster than the estimated rise rates for bubbles to reach the top of the magma chamber.

Larsen, Jessica F.; Denis, Marie-Helene; Gardner, James E.

2004-01-01

271

21 CFR 137.185 - Enriched self-rising flour.  

Code of Federal Regulations, 2010 CFR

...self-rising flour. Enriched self-rising flour conforms to the definition...ingredients, prescribed for self-rising flour by § 137.180, except...technical purposes to give self-rising characteristics to the flour...to meet the 960-milligram level, no claim may be made on...

2010-04-01

272

21 CFR 137.185 - Enriched self-rising flour.  

Code of Federal Regulations, 2010 CFR

...self-rising flour. Enriched self-rising flour conforms to the definition...ingredients, prescribed for self-rising flour by § 137.180, except...technical purposes to give self-rising characteristics to the flour...to meet the 960-milligram level, no claim may be made on...

2009-04-01

273

Bifurcation analysis of bubble dynamics in fluidized beds  

SciTech Connect

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

Blomgren, Peter [San Diego State University; Palacios, Antonio [San Diego State University; Zhu, Bing [San Diego State University; Daw, C Stuart [ORNL; FINNEY, Charles E A [ORNL; Halow, John [Waynesburg University; Pannala, Sreekanth [ORNL

2007-01-01

274

Marine liquid aerosol production from bursting of air bubbles  

NASA Astrophysics Data System (ADS)

The action of wind stress upon the marine surface is responsible for producing air bubbles in seawater through wave breaking. After a given residence time in the sea, bubbles return to the surface, where they burst. The phenomenon of bursting produces two families of droplets: film drops and jet drops. The characteristics of jet drops are far better known than those of film drops. By means of an in-line holographic technique one can obtain experimental results through visualization. One can observe the successive stages of the bursting process of a single bubble in deionized fresh water and in seawater. One visualizes both film drops and jet drops generated by bubbles whose diameter may attain 10 mm. The onset of the bursting phenomenon is clearly shown. Film drop count and size are measurable and may be compared with other available estimates.

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

1986-01-01

275

Energy Measurement of Bubble Bursting Based on Vibration Signals  

NASA Astrophysics Data System (ADS)

An experimental study of the energy of bubble bursting at the surface of a high-viscosity liquid on a cantilever beam is reported. The sudden bursting event of a bubble at the liquid surface can cause a vibration of the cantilever beam besides the acoustic wave and jet wave. The peaks of the vibration signal from the beam slightly lag the peaks of the acoustic signal, and the energy transferred to the vibration is larger than that transferred to the acoustic wave. The amplitude of the jet wave depends on the thickness of the liquid film and the size of the bubble. The results of the investigation can be used to understand the dynamic characteristics of bubble bursting.

Liu, Xiao-Bo; Zhang, Jian-Run; Li, Pu; Le, Van-Quynh

2012-06-01

276

Comprehensive experimental investigation of the hydrodynamics of large-scale, 3D, oscillating bubble plumes  

Microsoft Academic Search

An extensive study of the most important hydrodynamic characteristics of fairly large-scale bubble plumes was conducted using several measurement techniques and a variety of tools to analyze the data. Particle image velocimetry (PIV), double-tip optical probes (OP) and photographic techniques were extensively applied to measure bubble and liquid velocities, void-fraction and bubble sizes. PIV measurements in a vertical plane crossing

M. Simiano; R. Zboray; F. de Cachard; D. Lakehal; G. Yadigaroglu

2006-01-01

277

Bubble generation during transformer overload  

SciTech Connect

Bubble generation in transformers has been demonstrated under certain overload conditions. The release of large quantities of bubbles would pose a dielectric breakdown hazard. A bubble prediction model developed under EPRI Project 1289-4 attempts to predict the bubble evolution temperature under different overload conditions. This report details a verification study undertaken to confirm the validity of the above model using coil structures subjected to overload conditions. The test variables included moisture in paper insulation, gas content in oil, and the type of oil preservation system. Two aged coils were also tested. The results indicated that the observed bubble temperatures were close to the predicted temperatures for models with low initial gas content in the oil. The predicted temperatures were significantly lower than the observed temperatures for models with high gas content. Some explanations are provided for the anomalous behavior at high gas levels in oil. It is suggested that the dissolved gas content is not a significant factor in bubble evolution. The dominant factor in bubble evolution appears to be the water vapor pressure which must reach critical levels before bubbles can be released. Further study is needed to make a meaningful revision of the bubble prediction model. 8 refs., 13 figs., 11 tabs.

Oommen, T.V. (Westinghouse ABB Power T and D Co., Sharon, PA (USA). Materials and Mfg. Technology Dept.)

1990-03-01

278

Distribution of bubble lengths in DNA.  

PubMed

The distribution of bubble lengths in double-stranded DNA is presented for segments of varying guanine-cytosine (GC) content, obtained with Monte Carlo simulations using the Peyrard-Bishop-Dauxois model at 310 K. An analytical description of the obtained distribution in the whole regime investigated, i.e., up to bubble widths of the order of tens of nanometers, is available. We find that the decay lengths and characteristic exponents of this distribution show two distinct regimes as a function of GC content. The observed distribution is attributed to the anharmonic interactions within base pairs. The results are discussed in the framework of the Poland-Scheraga and the Peyrard-Bishop (with linear instead of nonlinear stacking interaction) models. PMID:17243750

Ares, S; Kalosakas, G

2007-01-23

279

Morphology of fission gas bubbles in fissioning uranium metal closely  

NASA Astrophysics Data System (ADS)

We investigate by SEM the micro-structural and basic phenomenological mechanisms governing the fission-gas and fusion-gas behaviour in metals. This comparative study clearly shows the characteristics of fission-gas bubbles (primarily helium and xenon) in uranium fuel metals have the same characteristics as fusion-gas bubbles (helium) in the solid-state fusion metal - palladium. The remarkably similar characteristic morphology clearly identifies the nuclear phenomenological origins of the gas bubbles in the palladium metal which are correllated and explained by the presence of a large amount of DD fusion. Allied evidence of anomalous heat production during cold fusion experiments suggests the nuclear process. Further analysis of these fusion metals by mass spectroscopy clearly identifies anomalous helium isotopes in large quantity were trapped in the palladium metal.

George, Russ

2005-03-01

280

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

281

Shattering a micro-bubble by an expanding bubble  

NASA Astrophysics Data System (ADS)

We investigate the interaction and fragmentation of a pulsed laser induced micro-bubble B1 by another laser induced micro-bubble B2. The high pressure field associated with the expanding B2 compresses B1, associated with an axial jet on B1 through inertia dominated Richtmyer-Meshkov surface instability. The further interplay of the penetrating jet and the pressure field of the forward flow surrounding B1 induce complicated patterns in the next re-expanding stage of B1, which leads to different spherical bubbles of different sizes at the end of the third collapsing phase of B1. The backward interaction from B1 also induces backward jetting and entanglement on B2. For two symmetric bubbles generated at the same time, a thin lubrication liquid layer can be formed between the two bubbles, which can be unstable at the large laser energy. For two bubbles formed at slight phase delay at short distance, the impact of the second expansion bubble leads to the formation of multiple jets on the collapsing bubble B1.

Chen, Yen-Hung; I, Lin

2007-07-01

282

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

PubMed Central

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

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

2013-01-01

283

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

NASA Astrophysics Data System (ADS)

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

Müller, Miloš; Zima, Patrik; Unger, Ji?í; Živný, Martin

2012-04-01

284

Performance of high pressure COIL with centrifugal bubble singlet oxygen generator  

NASA Astrophysics Data System (ADS)

A centrifugal bubbling SOG is a perspective source of oxygen at high pressure with high depletion of the BHP in the single burn dawn. The theoretical estimations show that at high centrifugal acceleration gas-liquid contact specific surface 30cm-1, frequency of the surface renewal can less than 10-3s and bubble rise velocity up to 500 cm/s be realized in the bubble SOG. The results of the measurements of O2(1?) yield, chlorine utilization and water fraction at the exit of the centrifugal bubble SOG are presented. A high O2(1?) yield and chlorine utilization higher than 90% have been obtained at chlorine gas loading up to 6 mmole/s per 1 cm2 of the bubbler surface. The ejector COIL powered by centrifugal bubbling SOG demonstrated ~25% of chemical efficiency with specific power 6 kW per 1 litre/s of the BHP volumetric rate.

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

2007-05-01

285

Gas-rise velocities during kicks  

SciTech Connect

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

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

1991-12-01

286

Vortex ring modelling of toroidal bubbles  

Microsoft Academic Search

During the collapse of a bubble near a surface, a high-speed liquid jet often forms and subsequently impacts upon the opposite\\u000a bubble surface. The jet impact transforms the originally singly-connected bubble to a toroidal bubble, and generates circulation\\u000a in the flow around it. A toroidal bubble simulation is presented by introducing a vortex ring seeded inside the bubble torus\\u000a to

Q. X. Wang; K. S. Yeo; B. C. Khoo; K. Y. Lam

2005-01-01

287

New mechanism for bubble nucleation: Classical transitions  

SciTech Connect

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

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

2009-12-15

288

Bubble levitation and translation under single-bubble sonoluminescence conditions.  

PubMed

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

Matula, Thomas J

2003-08-01

289

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

Microsoft Academic Search

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

C. D. Serdula; M. R. Loewen

1998-01-01

290

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

291

Sonoporation from Jetting Cavitation Bubbles  

Microsoft Academic Search

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

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

2006-01-01

292

Dynamics in reactive bubbly flow  

Microsoft Academic Search

Multiphase flow in microfluidic channels encompasses a rich collection of phenomena of widespread interest in both fundamental and technological context. While studies on non reactive multiphase flow focus on the dynamics of bubble breakup, coalescence and stability, a reactive multiphase flow opens up a broader spectrum of dynamics, like nucleation, growth and detachment of bubbles as well as the secondary

Pavithra Sundararajan; Donald Koch; Abraham Stroock

2010-01-01

293

A bubble domain memory cell  

Microsoft Academic Search

The present conception of a 100 M bit bubble domain digital data recorder for spacecraft applications requires the storage to be compartmentalized in cells containing a group of bubble domain chips. Arranging the memory chips in cells minimizes coil size and power by requiring only a small group of chips to be driven at any given time, and also permits

P. J. Hayes; I. J. Walker

1976-01-01

294

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

295

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

SciTech Connect

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

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

2010-12-07

296

Bubble formation via multidrop impacts  

NASA Astrophysics Data System (ADS)

Gas bubbles are often generated when droplets impact a liquid-air interface. For the impact of single droplets, a critical impact velocity must be exceeded for air to be entrained in the form of bubbles. Here we establish that bubbles can be generated at much lower velocities provided that two or more drops impact the liquid-air interface within a sufficiently short time interval. Using high-speed imaging, we show that bubbles are entrained when a drop lands in the impact crater of a previous drop. We quantify the critical crater depth formed upon impact and the necessary time interval between drop impacts for bubble entrainment to occur. For 1 mm diameter water drops falling at 1 m/s, the critical separation time is approximately 5 ms. This critical time is consistent with a scaling analysis of the time required for an impact crater to close by capillarity.

Bick, Alexander G.; Ristenpart, William D.; van Nierop, Ernst A.; Stone, Howard A.

2010-04-01

297

Bubble dynamics in N dimensions  

NASA Astrophysics Data System (ADS)

Cavitation and bubble dynamics are central concepts in engineering, the natural sciences, and the mathematics of fluid mechanics. Due to the nonlinear nature of their dynamics, the governing equations are not fully solvable. Here, the dynamics of a spherical bubble in an N-dimensional fluid are discussed in the hope that examining bubble behavior in N dimensions will add insight to their behavior in three dimensions. Several canonical results in bubble dynamics are re-derived, including the Rayleigh collapse time, the Rayleigh-Plesset equation, and the Minnaert frequency. Recent analytical approximations to the Rayleigh collapse are discussed, and the N-dimensional generalization is used to resolve a known discrepancy. Numerical simulations are used to examine the onset of nonlinear behavior. Overall, the dynamics of bubbles are faster at higher dimensions, with nonlinear behavior occurring at lower strain. Several features are found to be unique to three dimensions, including the trend of nonlinear behavior and apparent coincidences in timescales.

Klotz, Alexander R.

2013-08-01

298

Rising Sea Levels  

NSDL National Science Digital Library

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

Learn, Nbc

2010-10-07

299

High rise buildings  

SciTech Connect

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

Horn, M.

1980-06-01

300

Oscillations and breakup of a bubble immersed in a turbulent field  

Microsoft Academic Search

This work is an experimental study of the deformation and breakup of a bubble in a turbulent flow. A special facility was designed to obtain intense turbulence without significant mean flow. The experiments were performed under microgravity conditions to ensure that turbulence was the only cause of bubble deformation. A scalar parameter, characteristic of this deformation, was obtained by video

Frédéric Risso; Jean Fabre

1998-01-01

301

Breakdown behavior of cryogenic liquids in the presence of thermal bubbles under ramped voltage  

Microsoft Academic Search

V-t characteristics were measured and the thermal bubble deformation was observed in liquid nitrogen and helium with a ramped voltage, simulating the quenching conditions in large superconducting magnet coils. From the experimental results, the breakdown process of liquid coolants in the presence of thermal bubbles was classified into three categories depending on the voltage slope: (1) breakdown through a composite

Masanori Hara; Hironori Koishihara; K. Saita

1991-01-01

302

Electrons trajectories around a bubble regime in intense laser plasma interaction  

NASA Astrophysics Data System (ADS)

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

Lu, Ding; Zhao, Xue-Yan; Xie, Bai-Song; Ali Bake, Muhammad; Sang, Hai-Bo; Wu, Hai-Cheng

2013-06-01

303

Influence of bubble size on micro-bubble drag reduction  

NASA Astrophysics Data System (ADS)

Micro-bubble drag reduction experiments were conducted in a turbulent water channel flow. Compressed nitrogen was used to force flow through a slot injector located in the plate beneath the boundary layer of the tunnel test section. Gas and bubbly mixtures were injected into a turbulent boundary layer (TBL), and the resulting friction drag was measured downstream of the injector. Injection into tap water, a surfactant solution (Triton X-100, 20 ppm), and a salt-water solution (35 ppt) yielded bubbles of average diameter 476, 322 and 254 ?m, respectively. In addition, lipid stabilized gas bubbles (44 ?m) were injected into the boundary layer. Thus, bubbles with d + values of 200 to 18 were injected. The results indicate that the measured drag reduction by micro-bubbles in a TBL is related strongly to the injected gas volumetric flow rate and the static pressure in the boundary layer, but is essentially independent of the size of the micro-bubbles over the size range tested.

Shen, Xiaochun; Ceccio, Steven L.; Perlin, Marc

2006-09-01

304

Shock Waves in Bubbly Cavitating Flows: Part I. Shock Waves in Cloud Cavitation. Part II. Bubbly Cavitating Flows Through a Converging-Diverging Nozzle.  

NASA Astrophysics Data System (ADS)

Two problems are considered in this thesis: the nonlinear dynamics of a cloud of cavitation bubbles, and bubbly cavitating flows through a converging-diverging nozzle. The focus of the first problem is to explore the characteristics of the growth and collapse of a spherical cloud of bubbles. This is typical of the transient behaviour exhibited by a bubble cloud as it passes a body or the blade of a ship propeller. The simulations employ the fully nonlinear, non-barotropic, homogeneous two-phase flow equations coupled with the Rayleigh-Plesset equation for the dynamics of individual bubbles. It was found that the collapse of the cloud is accompanied by the formation of an inward propagating bubbly shock wave. The focusing of the shock is responsible for the severe noise and damage potential in cloud cavitation. The second problem investigates the nonlinear behavior of bubbly cavitating flows through a converging -diverging nozzle. Two different flow regimes are found from steady state solutions: quasi-steady and quasi-unsteady. Bifurcation occurs as the flow transitions from one regime to the other. Unsteady solutions in a period of consecutive times are also presented. These solutions are characterized by large pressure pulses changing in both magnitude and location with time downstream of the throat. The characteristics of these pulses are similar to the shock pulses of the first problem and are produced by the local violent collapse of the bubbles in the flow.

Wang, Yi-Chun

305

Analysis of throughflow velocity in two-dimensional fluidized bed bubbles  

SciTech Connect

The formation of gas bubbles is one of the most characteristic phenomena of fluidized beds. Many unique properties of fluidized beds can be related directly to the presence of bubbles and are dominated by their behavior. Therefore, accurate prediction of parameters such as bubble shape and size, voidage variation and throughflow are practically important. In the present analysis, an approximate model, based on a strongly idealized picture of the bubble formation has been presented. The bubbling gas fluidized bed has regions of low solids density comprised of gas pockets or voids. The observed voids exhibited a variety of shapes (Halow and Nicoletti, 1992), depending upon the material and fluidization velocity. In the low-velocity experiments with the finer materials, rounded voids are observed. However, with coarser materials, voids were typically large and blunt-nosed. In the image analyses work, reported by Gautam (1989), in a bed operating slightly above the incipient fluidization, elongated bubbles (a > b, as shown in Figure 1) were observed for glass beads (sp. gravity = 2.5) of mean diameter 500 {micro}m and flattened bubbles (a < b) were seen for mean particle diameter of 350 {micro}m. Also, he noticed the dependence of throughflow velocity of the bubble as it traverses up the bed. Additionally, throughflow velocity was found to be independent of the excess gas flow rate through the bed. The digitized image of a typical bubble (refer Gautam et al., 1994) which shows that the bubble were elongated in the vertical direction and were more elliptical than circular. Therefore, description of a bubble on the basis of just one diameter, either the horizontal or the vertical or an equivalent diameter, as has been done by many researchers in the past, is rather incomplete. It is inferred from the present work that the bubble aspect ratio plays an important role in predicting an accurate gas flow through the bubble.

Gera, D.; Gautam, M. [West Virginia Univ., Morgantown, WV (United States). Dept. of Mechanical and Aerospace Engineering

1995-06-01

306

Investigation of Bubble Size Effect on Vertical Upward Bubbly Two-Phase Pipe Flow Consisted With an Abrupt Expansion  

NASA Astrophysics Data System (ADS)

The effects of bubble size on an upward gas-liquid (CO2-water) flow in a vertical pipe after an abrupt expansion is investigated visually and experimentally in the present work. The mean bubble size varies from small scale (db=0.3mm) to relatively large scale (db=4.5mm). Extensive visualization experiments and PIV analysis show different flow patterns downstream of the expansion of flows containing bubbles of different sizes. The effect of bubble size is also investigated measuring the pressure distribution along the pipe and the drag of the expansion and its difference under different bubble sizes is calculated and compared with that of single-phase flow. The fluctuation phenomena occurring downstream are also investigated. The experiments are conducted under constant Reynolds number (Re=1.0×104) and volumetric gas flow rate ratio (?v=0˜10%). The present work gives valuable information about how the bubble size affects the flow characteristics even under steady flow conditions, and explains the differences between results reported by other authors investigating under similar conditions.

Voutsinas, Alexandros; Shakouchi, Toshihiko; Tsujimoto, Koichi; Ando, Toshitake

307

Interacting two-dimensional bubbles and droplets in a yield-stress fluid  

NASA Astrophysics Data System (ADS)

We study the buoyancy-driven motion of two-dimensional bubbles and droplets in a Bingham fluid using a regularization method. The finite-element computations are carried out using the method of level sets to track the interface. We find that multiple bubbles and droplets can move in a body force field under conditions where a single bubble or droplet with the same physical properties would be unable to overcome the integrated yield stress and would be trapped. The finite yielded region around a single bubble or droplet in a Bingham fluid causes a backflow, resulting in unyielded ``ears'' that rotate and exchange material points with the yielded fluid to maintain a fixed position on the equatorial plane as the bubble rises or the droplet falls. The backflow flattens the tail of the trailing bubble or droplet in a pair and, at a sufficiently high level of interfacial tension, causes a splitting of the tail and the creation of a cusp. Three bubbles in a triangular configuration interact in a manner that is qualitatively predictable by considering pair interactions. Despite important differences in detail, the general shape evolution of bubbles and droplets in a Bingham fluid is similar to that in a Newtonian liquid when time scales are considered on a comparable basis.

Singh, John P.; Denn, Morton M.

2008-04-01

308

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 (Ptrans) onto membranes could be used to characterise the multiple effects induced under different sparging conditions. Ptrans 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

2013-09-11

309

Bubble dispersion and coalescence in turbulent pipe flow  

NASA Astrophysics Data System (ADS)

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

Luo, Jianjun

2002-04-01

310

Understanding air-gun bubble behavior  

Microsoft Academic Search

An air-gun bubble behaves approximately as a spherical bubble of an ideal gas in an infinite volume of practically incompressible water. With this simplification, the equation of bubble motion and its far-field signature is more understandable than with the more exact theory commonly cited in the literature. The terms of the equation of bubble motion are explained using elementary physics

Daniel T. Johnson

1994-01-01

311

Measuring bubble distribution with multibeam sonar  

Microsoft Academic Search

Bubbles in water are very efficient scatterers of sound. Depending upon the ratio of acoustic wavelength to bubble radius, the scattering mechanism can be Rayleigh, resonant, or geometric. The strength of the scattered signal depends strongly on this ratio. The strength of the scattered signal can be used to estimate the number of bubbles per unit volume, or bubble density,

R. Lee Culver; David Bradley

2002-01-01

312

Bubble Breakup Caused by Shape Instabilities  

Microsoft Academic Search

The breakup of a bubble is the most intriguing phenomenon in the bubble dynamics to many fluid dynamics researcher. Bubble may break up due to different kinds of mechanisms. However due to the complexity of the system, no general analytical approachis available for studying this breakup phenomenon of a bubble. Hence numerical approach is taken in our current work to

Y.-H. Su; Z. C. Feng

1998-01-01

313

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

314

OH Production Enhancement in Bubbling Pulsed Discharges  

NASA Astrophysics Data System (ADS)

The generation of active species, such as H2O2, O*, OH*, HO2*, O3, N2*, etc, produced in aqueous solutions by HV pulsed discharges was studied in order to find the most efficient way in waste water treatment taking into account that these species are almost stronger oxidizers than ozone. Plasma was generated inside gas bubbles formed by the argon, air and oxygen gas flow between the special designed electrodes. The pulse width and pulse frequency influence was studied in order to increase the efficiency of the OH active species formation. The produced active species were investigated by optical emission spectroscopy and correlated with electrical parameters of the discharges (frequency, pulse width, amplitude, and rise and decay time).

Lungu, Cristian P.; Porosnicu, Corneliu; Jepu, Ionut; Chiru, Petrica; Zaroschi, Valentin; Lungu, Ana M.; Saito, Nagahiro; Bratescu, Maria; Takai, Osamu; Velea, Theodor; Predica, Vasile

2010-10-01

315

Monitoring Sea Level Rise.  

National Technical Information Service (NTIS)

While introducing the GLOSS network and its various engineering applications, the report first briefly summarizes several causes of sea level rise. The authors then discuss several computing methods of monthly and annual mean sea level and their error sou...

X. Peiliang

1990-01-01

316

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

317

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

NASA Astrophysics Data System (ADS)

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

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

2003-04-01

318

Aspherical bubble dynamics and oscillation times  

SciTech Connect

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

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

1999-06-01

319

Vapor Bubble Nucleation: A Microscopic Phenomenon  

Microsoft Academic Search

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

Ho-Young Kwak

2004-01-01

320

Nonclassical Thermomigration of an Air Bubble  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

321

Magnetic Bubble Traveling Wave Tube.  

National Technical Information Service (NTIS)

A device is disclosed for amplifying electromagnetic waves propagating along a meander line slow wave structure by means of magnetic cylindrical domains or bubbles which are propagating at substantially the same velocity as the RF wave in an adjacent plat...

L. J. Jasper

1978-01-01

322

SKAT Bubble Chamber Film Processing.  

National Technical Information Service (NTIS)

The technique of SKAT bubble chamber photographic image processing is briefly described. On the base of the technique 125000 images were processed in neutrino-seances and 182000 images in antineutrino seances. The analysis of geometric reconstruction of t...

D. S. Baranov L. L. Zakamskij A. A. Ivanilov

1984-01-01

323

Nambu bubbles with curvature corrections  

SciTech Connect

A finite-width correction for a two-dimensional membrane described by the Nambu action modified by the addition of the Ricci curvature scalar is studied. The particular case of a spherical bubble is considered in some detail.

Letelier, P.S. (Departamento de Matematica Aplicada, IMECC, Universidade Estadual de Campinas, 13 100 Campinas, Sao Paulo, Brazil (BR))

1990-02-15

324

Transient bubbles, bublets and breakup  

NASA Astrophysics Data System (ADS)

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

Keen, Giles; Blake, John

1999-11-01

325

Snapping shrimp make flashing bubbles.  

PubMed

Snapping shrimp produce a loud crackling noise that is intense enough to disturb underwater communication. This sound originates from the violent collapse of a large cavitation bubble generated under the tensile forces of a high-velocity water jet formed when the shrimp's snapper-claw snaps shut (Fig. 1). Here we show that a short, intense flash of light is emitted as the bubble collapses, indicating that extreme pressures and temperatures of at least 5,000 K (ref. 4) must exist inside the bubble at the point of collapse. We have dubbed this phenomenon 'shrimpoluminescence' - the first observation, to our knowledge, of this mode of light production in any animal - because of its apparent similarity to sonoluminescence, the light emission from a bubble periodically driven by ultrasound. PMID:11586346

Lohse, D; Schmitz, B; Versluis, M

2001-10-01

326

Magnetic bubble memory chip design  

Microsoft Academic Search

The choice and organization of bubble-circuit functions in the design of a magnetic bubble mass memory chip are discussed with emphasis on factors such as circuit function compatibility and performance, circuit density, and processing simplicity. A specific major-minor organized chip design is described which uses rotating field driven propagation, $-sign transfer gates, all T-bar minor loops, a nucleate generator with

PETER I. BONYHARD; J. E. GEUSIC; ANDREW H. BOBECK; Yu-Ssu Chen; PAUL C. MICHAELIS; JAMES L. SMITH

1973-01-01

327

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

328

Evolution of a Collection of Bubbles with Application to Wakes, Bubble Screens, and Cloud Noise.  

National Technical Information Service (NTIS)

Contents: Bubble Dynamics and Cavitation Inception in Non-Uniform Flow Fields; Bubble Interactions with Vortices; Cavitation Dynamics at Microscale Level; Viscous Interaction Between Bubble and Line Vortex; The Motion of a Spherical Body Below a Free Surf...

G. L. Chahine

1994-01-01

329

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

SciTech Connect

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

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

2012-12-20

330

Holographic Description of Vacuum Bubbles  

NASA Astrophysics Data System (ADS)

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.

Garriga, J.

331

Optical Measurements of Bubble Injections in the Southern Ocean  

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

332

Plasma bubble detection in the DEMETER micro-satellite data  

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

333

Interfacial Force Model Development for Turbulent Bubbly Flows  

NASA Astrophysics Data System (ADS)

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

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

2010-11-01

334

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

335

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

336

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

337

Dynamics of a bubbly turbulent boundary layer along a surface piercing flat plate  

NASA Astrophysics Data System (ADS)

The behaviour of a bubble-laden turbulent boundary layer has been studied experimentally in an open channel water flow with Reynolds number up to 10^6. A poly-dispersed bubble cloud with mean diameter around 200 ? m is injected at the leading edge of a vertical, surface piercing flat plate. The high void fraction bubble layer rises along the plate, developing a Kelvin Helmholtz type instability due to the vertical shear. As a result of this instability, streamwise vorticity is generated that combines with the vertical vorticity associated with the boundary layer, tilting the vortex lines. Bubbles are, for the most part, confined to the boundary layer and accumulate as they interact with the turbulent structures present in this type of flows. The flow at the junction between the flat plate and the free surface is also studied in the presence of bubbles. An streamwise submerged vortex is observed, in agreement with previous studies of single phase junction flows. Vorticity originated by the bouyancy-driven instability of the bubbly layer is convected away from the plate when it reaches the surface, and reconects with the streamwise vortex. Thus, the vortex gains strength and starts to accumulate bubbles stripped from the boundary layer, becoming a dominant feature of the flow.

Aliseda, Alberto; Lasheras, Juan C.

2003-11-01

338

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

339

The Rise of the \\  

Microsoft Academic Search

This paper examines the rise of the 'neoconservative' thinkers and policymakers that have exerted such a powerful influence over the foreign policy of the administration of George W. Bush. The paper initially provides a theoretical context for thinking about American power, before detailing the activities and beliefs of some of the most prominent neocon thinkers. The key argument I make

Mark Beeson

340

The rise of graphene  

Microsoft Academic Search

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

A. K. Geim; K. S. Novoselov

2007-01-01

341

Dynamics of air bubbles passing through a liquid-liquid interface  

NASA Astrophysics Data System (ADS)

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

Bonhomme, Romain; Magnaudet, Jacques; Piar, Bruno

2011-11-01

342

Magnetic field generation in first order phase transition bubble collisions  

NASA Astrophysics Data System (ADS)

We consider the formation of a ring-like magnetic field in collisions of bubbles of broken phase in an Abelian Higgs model. Particular attention is paid to multiple collisions. The small collision velocity limit, appropriate to the electroweak phase transition, is discussed. Assuming the relevant features of the Abelian Higgs model are appropriate also to the electroweak case, we argue that after the completion of the electroweak phase transition, when averaged over nucleation center distances, there exists a mean magnetic field B~=2.0×1020 G with a coherence length 9.1×103 GeV-1 (for mH=68 GeV). Because of the ring-like nature of B, the volume average behaves as B~1/L. Taking into account the turbulent enhancement of the field by inverse cascade, we estimate that colliding electroweak bubbles would give rise to a mean field Brms~=10-21 G at 10 Mpc comoving scale today.

Ahonen, Jarkko; Enqvist, Kari

1998-01-01

343

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

344

Bubble-induced acoustic micromixing.  

PubMed

A mixing technique based on the principle of bubble-induced acoustic microstreaming was developed. The mixer consists of a piezoelectric disk that is attached to a reaction chamber, which is designed in such a way that a set of air bubbles with desirable size is trapped in the solution. Fluidic experiments showed that air bubbles resting on a solid surface and set into vibration by the sound field generated steady circulatory flows, resulting in global convection flows and thus rapid mixing. The time to fully mix a 22 microL chamber is significantly reduced from hours (for a pure diffusion-based mixing) to tens of seconds. Numerical simulations showed that the induced flowfield and thus degree of mixing strongly depend on bubble positions. Optimal simulated mixing results were obtained for staggered bubble distribution that minimizes the number of internal flow stagnation regions. Immunomagnetic cell capture experiments showed that acoustic microstreaming provided efficient mixing of bacterial cell (Esherichia coli K12) matrix suspended in blood with magnetic capture beads, resulting in highly effective immunomagnetic cell capture. Bacterial viability assay experiments showed that acoustic microstreaming has a relatively low shear strain field since the blood cells and bacteria remained intact after mixing. Acoustic microstreaming has many advantages over most existing chamber micromixing techniques, including simple apparatus, ease of implementation, low power consumption (2 mW), and low cost. PMID:15100826

Liu, Robin H; Yang, Jianing; Pindera, Maciej Z; Athavale, Mahesh; Grodzinski, Piotr

2002-07-10

345

Dynamics in reactive bubbly flow  

NASA Astrophysics Data System (ADS)

Multiphase flow in microfluidic channels encompasses a rich collection of phenomena of widespread interest in both fundamental and technological context. While studies on non reactive multiphase flow focus on the dynamics of bubble breakup, coalescence and stability, a reactive multiphase flow opens up a broader spectrum of dynamics, like nucleation, growth and detachment of bubbles as well as the secondary mixing in the slugs during these processes. Our interest lies in the flow in an electrochemical microfluidic fuel cell with liquid reactants reacting at catalyst walls producing gaseous products which choke the fuel cell efficiency due to uncontrolled bubbly flow. This challenge is an opportunity in itself provided the multiphase flow dynamics can be characterized to achieve a stable Taylor regime. Taylor regime allows for promisingly high efficiencies due to improved mass transfer of reactants to the concentration boundary layer of the electrodes achieved by the secondary flow in the liquid phase present between bubbles. Here, I will experimentally explore the different regimes of reactive bubbly flow in a microchannel. The phase diagram of the reactive multiphase flows would be used to identify the stable regime for efficient fuel cell operation. Further, I will study the mass transfer in the presence of multiphase flow to regimes of enhanced mass transfer, and compare it with numerical models.

Sundararajan, Pavithra; Koch, Donald; Stroock, Abraham

2010-11-01

346

Coalescence of bubbles translating through a tube.  

PubMed

The results of an experimental study of the interaction and coalescence of two air bubbles translating in a cylindrical tube are presented. Both pressure- and buoyancy-driven motion of the two bubbles in a Newtonian suspending fluid within the tube are considered. The close approach of the two bubbles is examined using image analysis, and measurements of the coalescence time are reported for various bubble size ratios and capillary numbers. For pressure-driven motion of bubbles, coalescence is found to occur in an axisymmetric configuration for all bubble size ratios considered in the experiments. For buoyancy-driven motion, on the other hand, the disturbance flow behind the leading bubble causes the trailing bubble to move radially out toward the tube wall when the trailing bubble size becomes very small compared to the size of the leading bubble. In that case, coalescence occurs in a nonaxisymmetric configuration, with a time scale for coalescence that is substantially larger than that for coalescence in the axisymmetric configuration. When the imposed flow is in the direction of the buoyancy force, coalescence time is independent of bubble size ratio, and decreases as the capillary number increases. Experimental measurements of the radius of the thin liquid film separating the two bubbles are used in conjunction with a simple film drainage model to predict the dependence of the coalescence time on the bubble size ratio. PMID:17124143

Almatroushi, Eisa; Borhan, Ali

2006-09-01

347

Nonspherical laser-induced cavitation bubbles.  

PubMed

The generation of arbitrarily shaped nonspherical laser-induced cavitation bubbles is demonstrated with a optical technique. The nonspherical bubbles are formed using laser intensity patterns shaped by a spatial light modulator using linear absorption inside a liquid gap with a thickness of 40 microm. In particular we demonstrate the dynamics of elliptic, toroidal, square, and V-shaped bubbles. The bubble dynamics is recorded with a high-speed camera at framing rates of up to 300,000 frames per second. The observed bubble evolution is compared to predictions from an axisymmetric boundary element simulation which provides good qualitative agreement. Interesting dynamic features that are observed in both the experiment and simulation include the inversion of the major and minor axis for elliptical bubbles, the rotation of the shape for square bubbles, and the formation of a unidirectional jet for V-shaped bubbles. Further we demonstrate that specific bubble shapes can either be formed directly through the intensity distribution of a single laser focus, or indirectly using secondary bubbles that either confine the central bubble or coalesce with the main bubble. The former approach provides the ability to generate in principle any complex bubble geometry. PMID:20365461

Lim, Kang Yuan; Quinto-Su, Pedro A; Klaseboer, Evert; Khoo, Boo Cheong; Venugopalan, Vasan; Ohl, Claus-Dieter

2010-01-14

348

Nonspherical laser-induced cavitation bubbles  

NASA Astrophysics Data System (ADS)

The generation of arbitrarily shaped nonspherical laser-induced cavitation bubbles is demonstrated with a optical technique. The nonspherical bubbles are formed using laser intensity patterns shaped by a spatial light modulator using linear absorption inside a liquid gap with a thickness of 40?m . In particular we demonstrate the dynamics of elliptic, toroidal, square, and V-shaped bubbles. The bubble dynamics is recorded with a high-speed camera at framing rates of up to 300000 frames per second. The observed bubble evolution is compared to predictions from an axisymmetric boundary element simulation which provides good qualitative agreement. Interesting dynamic features that are observed in both the experiment and simulation include the inversion of the major and minor axis for elliptical bubbles, the rotation of the shape for square bubbles, and the formation of a unidirectional jet for V-shaped bubbles. Further we demonstrate that specific bubble shapes can either be formed directly through the intensity distribution of a single laser focus, or indirectly using secondary bubbles that either confine the central bubble or coalesce with the main bubble. The former approach provides the ability to generate in principle any complex bubble geometry.

Lim, Kang Yuan; Quinto-Su, Pedro A.; Klaseboer, Evert; Khoo, Boo Cheong; Venugopalan, Vasan; Ohl, Claus-Dieter

2010-01-01

349

THE ILLUSION OF STABILITY-LOW INFLATION IN A BUBBLE ECONOMY  

Microsoft Academic Search

Econometric studies show that changes in real house prices are strongly autocorrelated in the UK, giving rise to prolonged departures from equilibrium. What happens when arbitrage is 'broken' and house prices no longer reflect future fundamentals? Adding a bubble to capture the disequilibrium behaviour picked up by econometricians, we show that a narrow focus on consumer price inflation-while neglecting house

MARCUS MILLER; ISHITA MOHANTY; LEI ZHANG

2009-01-01

350

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

Microsoft Academic Search

Extensive methane release as a free gas phase from cold vents is well known from deep (>2000m) and shallow (10s of meters) water depths. Supposedly, much more methane is transported into the water column by free gas than by dissolved gas, which is oxidized by anaerobic and aerobic processes and partly precipitated as carbonate. Rising gas bubbles are not affected

J. Greinert; Y. Artemov; P. Gimpel

2003-01-01

351

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

Microsoft Academic Search

The K Basin sludge to be retrieved and stored in the large diameter containers (LDCs) contains some fraction of uranium metal that generates hydrogen gas, which introduces potential upset conditions. One postulated upset condition is a rising plug of sludge supported by a hydrogen bubble that is driven into the vent filters at the top of the container. In laboratory

Guillermo Terrones; Phillip A. Gauglitz

2002-01-01

352

Investigating the role of gas bubble formation and entrapment in contaminated aquifers: Reactive transport modelling  

Microsoft Academic Search

In many natural and contaminated aquifers, geochemical processes result in the production or consumption of dissolved gases. In cases where methanogenesis or denitrification occurs, the production of gases may result in the formation and growth of gas bubbles below the water table. Near the water table, entrapment of atmospheric gases during water table rise may provide a significant source of

Richard T. Amos; K. Ulrich Mayer

2006-01-01

353

Motion of Spherical Gas Bubbles in a Viscous Liquid at Large Reynolds Numbers  

Microsoft Academic Search

An analysis is made for the motion of a gas bubble rising steadily in a quiescent liquid of infinite extent. The disturbed layer of the fluid, due to viscosity, on either side of the interface is thin when the Reynolds number is sufficiently large and thus makes possible a considerable simplification of the governing equations of motion. Simultaneous solutions of

B. T. Chao

1962-01-01

354

Ozone generation by discharge inside the bubbles in water  

NASA Astrophysics Data System (ADS)

The purpose of this research is an efficient utilization of radicals such as atomic oxygen, ozone and OH radical which are generated in the bubbles and in water by discharge. The bubbles are generated at the discharge region between electrodes by a bubling tube. A pulse-power generator which is able to obtain a rapid rise time of applied voltage between electrodes(typical gap spacing 7.6mm) was used as a power supply. The peak value of output voltage, its pulse width and current are about 100kV, 100ns and 1kA, respectivery. Many small oscillations observed on the waveform of the applied voltage suggest that the discharge occurs in bubbles. The light emission produced by discharge from the bubbles was also observed. The input energy to discharge region was about 1J. Blumlein type of pulse-power source was also used for a pair of disk electrodes(diamater of 30mm, gap spacing of 5mm) at the discharge repetiotion rate of 15 pulse per second. The diamater of bubbles is about 1mm. The maximum applied voltage and discharge current of about 25kV and 150A were measured at the charging voltage of 10kV. The measured ozone which comes from the water was about 43mg/Nm^3 at the oxygen gas flow rate of 0.7l/min and 122mg/Nm^3 at 0.6l/min. In latter case, a TiBaO3 plate(relative dielectric constant of 400 and thickness of 4.5mm) was attached on the surface of the electrode.

Yamabe, C.; Ihara, S.; Miichi, T.; Satoh, S.

1998-10-01

355

The Local Bubble: an update  

NASA Astrophysics Data System (ADS)

Our view of the the Sun's near neighbourhood in space, the "Local Bubble" region, has changed dramatically over the past decade. The interstellar gas inside this rarefied Cavity is character-ized by a surprisingly wide range of temperatures (100K -1,000,000K), densities, and diffuse structures that are all contained within a 150pc diameter region of space whose fragmented neutral boundary has recently been mapped in 3-D. Rather surprisingly, doubts have even been cast on whether the Local Bubble cavity is filled with a hot million degree emitting gas and, much to the bewilderment of many astrophysicists, we still do not know which physical processes are responsible for the observed ionization state of the local interstellar plasma. This short talk will discuss the latest observational results from several recent studies of the Local Bubble region and how current theoretical models seem at odds with empirical evidence.

Welsh, Barry

356

Gas-bubble formation in liquid layer  

Microsoft Academic Search

The dynamics of bubble formation and breakaway when a gas issues into a liquid is considered. The different modes of gas-bubble formation in a liquid layer are indicated. The results of analytic investigation are compared with experimental data.

A. A. Voloshko; A. V. Vurgaft; V. N. Frolov

1978-01-01

357

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

358

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.

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

2012-01-01

359

Predicting diffused-bubble oxygen transfer rate using the discrete-bubble model  

Microsoft Academic Search

A discrete-bubble model that predicts the rate of oxygen transfer in diffused-bubble systems is evaluated. Key inputs are the applied gas flow rate and the initial bubble size distribution. The model accounts for changes in the volume of individual bubbles due to transfer of oxygen and nitrogen (and hence changing partial pressure), variation in hydrostatic pressure, and changes in temperature.

Daniel F McGinnis; John C Little

2002-01-01

360

The Effects of the Bubble size on the Bubble Dispersion and Skin Friction Reduction  

Microsoft Academic Search

The purpose of this study is to elucidate the effects of the bubble size on the skin friction reduction and its persistence. Various bubble injection methods were examined for controlling the bubble size. Measurements of the bubble distribution and skin friction were carried out for a spatially developing boundary layer in a test section and 50 m flat plate ship

Takafumi KAWAMURA; Akiko FUJIWARA; Takahito TAKAHASHI; Hiroharu KATO; Youichiro MATSUMOTO; Yoshiaki KODAMA

361

Bubble formation at nozzles in pig iron  

Microsoft Academic Search

An experimental study was undertaken to determine how several variables affect the size of gas bubbles formed at nozzles in\\u000a liquid pig iron. The frequency of bubble formation was measured by an acoustic device, which could detect the vibrations produced\\u000a by the bubble release. Accurate knowledge of the gas flow rate then enabled the calculation of bubble volumes. The use

G. A. Irons; R. I. L. Guthrie

1978-01-01

362

Heat emission of gas bubbles in a rotating bubbling layer  

Microsoft Academic Search

Based on an experimental study of contact heat transfer between a liquid and a gas in an eddy-generating bubbler and on results processed using the equation of nonstationary heat conduction, we obtained a dimensionless relation for calculating the coefficient that characterizes heat transfer in a gas bubble within the framework of a model based on effective coefficients of heat conduction.

I. I. Borisov; A. A. Khalatov; E. É. Ikonnikova; G. V. Kovalenko; S. V. Shevtsov

1995-01-01

363

Bubble cluster dynamics in an acoustic field.  

PubMed

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

Nasibullaeva, E S; Akhatov, I S

2013-06-01

364

Bubble Dynamics and Breakup in Straining Flows  

Microsoft Academic Search

The dynamics and breakup of a bubble in axisymmetric flow fields has been investigated using numerical and analytical techniques. In particular, the transient bubble deformation, oscillation, and overshoot effects are considered in conjunction with the existence of steady-state solutions. To explore the dynamics of a bubble with a high degree of deformation, a numerical technique suitable for solving axisymmetric, unsteady

1988-01-01

365

Bubble effect on Kelvin-Helmholtz' instability  

Microsoft Academic Search

We derive boundary conditions at interfaces (contact discontinuities) for a class of Lagrangian models describing, in particular, bubbly flows. We use these conditions to study Kelvin-Helmholtz' instability which de- velops in the flow of two superposed layers of a pure incompressible fluid and a fluid containing gas bubbles, co-flowing with different velocities. We show that the presence of bubbles in

366

Bubble effect on Kelvin-Helmholtz instability  

Microsoft Academic Search

We derive boundary conditions at interfaces (contact discontinuities) for a class of Lagrangian models describing, in particular, bubbly flows. We use these conditions to study the Kelvin-Helmholtz instability that develops in the flow of two superposed layers of a pure incompressible fluid and a fluid containing gas bubbles, co-flowing with different velocities. We show that the presence of bubbles in

Sergey L. Gavrilyuk; Henri Gouin; Vladimir M. Teshukov

2004-01-01

367

Chemical Bubble Dynamics and Quantitative Sonochemistry  

Microsoft Academic Search

We model the collapse of a bubble by taking into account all the energy forms involved (i.e., mechanical, thermal, chemical, and radiative) and compare the calculated radical yields with sonochemical data in H 2O. Water decomposition plays a critical role in the energy balance, but trails equilibrium even in bubbles collapsing at subsonic speeds. Integration of the equation of bubble

A. J. Colussi; Linda K. Weavers; Michael R. Hoffmann

1998-01-01

368

ASSET PRICE BUBBLES IN INCOMPLETE MARKETS &ast  

Microsoft Academic Search

This paper studies asset price bubbles in a continuous time model using the local martingale framework. Providing careful definitions of the asset's market and fundamental price, we characterize all possible price bubbles in an incomplete market satisfying the “no free lunch with vanishing risk (NFLVR)” and “no dominance” assumptions. We show that the two leading models for bubbles as either

Robert A. Jarrow; Philip Protter; Kazuhiro Shimbo

2010-01-01

369

Nonequilibrium bubbles in a flowing langmuir monolayer.  

PubMed

We investigate the nonequilibrium behavior of two-dimensional gas bubbles in Langmuir monolayers. A cavitation bubble is induced in liquid expanded phase by locally heating a Langmuir monolayer with an IR-laser. At low IR-laser power the cavitation bubble is immersed in quiescent liquid expanded monolayer. At higher IR-laser power thermo capillary flow around the laser-induced cavitation bubble sets in. The thermo capillary flow is caused by a temperature dependence of the gas/liquid line tension. The slope of the line tension with temperature is determined by measuring the thermo capillary flow velocity. Thermodynamically stable satellite bubbles are generated by increasing the surface area of the monolayer. Those satellite bubbles collide with the cavitation bubble. Upon collision the satellite bubbles either coalesce with the cavitation bubble or slide past the cavitation bubble. Moreover we show that the satellite bubbles can also be produced by the emission from the laser-induced cavitation bubbles. PMID:16853828

Muruganathan, Rm; Khattari, Z; Fischer, Th M

2005-11-24

370

THE YOUNG INTERSTELLAR BUBBLE WITHIN THE ROSETTE NEBULA  

SciTech Connect

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

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

2010-08-20

371

Pyroclastic Eruptions on the Northern East Pacific Rise  

NASA Astrophysics Data System (ADS)

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

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

2004-12-01

372

Buoyancy-driven viscous interaction of a rising drop with a smaller trailing drop  

Microsoft Academic Search

An axisymmetric boundary-integral method was developed and used to study the interaction of two deformable drops (or bubbles) rising (or settling) due to gravity in a viscous medium under conditions of small Reynolds number. The focus is on cases where the smaller drop trails behind the larger drop. When the Bond number is small, interfacial tension keeps the drops nearly

Robert H. Davis

1999-01-01

373

Day-to-day longitudinal variation of bubble occurrence over South America  

NASA Astrophysics Data System (ADS)

VTEC GPS data from LISN Network from 2008 is being analyzed to get the ionospheric conditions that generate spread F irregularities, like bubbles, in the South American (SA) continent. Using Automatic Bubble Detection Algorithm (ABDA), it was possible to find bubble signatures (hundreds of kilometers scale size) between September and December months. The bubble occurrence pattern over SA in general follows the characteristics of bubbles detected previously with digisonde and satellite (e.g. DMSP, CHAMP) that are September-October in the west and November-December in the east. However we have observed bubbles signatures all over the continent among September to December period. Digisonde ionospheric parameters (NmF2, h'F and foF2) were measured to describe the ionospheric local conditions over Fortaleza (Brazil) and Jicamarca (Peru) that can help us to understand the characteristics of the phenomena described here. Digisonde data from Fortaleza located at 3.8S, 38W and 9S dip latitude, and Jicamarca located at 12S, 76.9W and 1N dip latitude were used to measure the day-to-day longitudinal variation. We will show the variation of NmF2, h'F and foF2 in these two stations when spread F (bubble) presence is in the east, in the west and all over the continent.

de La Cruz Cueva, R.; Valladares, C. E.; Batista, I. S.; de Paula, E. R.

2010-12-01

374

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

375

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

2012-12-01

376

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.

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

2012-01-01

377

Micro-bubble Enhanced Sonoporation  

Microsoft Academic Search

A gene transfer system that uses ultrasound, known as sonoporation, has recently been developed, and it is known that micro-bubbles can help gene transfection in this technique. However, the mechanism and optimal induction conditions have not yet been fully clarified. We examined the factors that affect the gene induction rate, and attempted to devise a method for high-efficiency gene induction.

Rie Tachibana; Akio Okamoto; Kiyoshi Yoshinaka; Shu Takagi; Yoichiro Matsumoto

2010-01-01

378

Bubble-driven inertial micropump  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

379

Fine bubble generator and method  

Microsoft Academic Search

This patent describes a method of forming fine gaseous bubbles in a liquid ambient. It comprises: forcing a gas through orifices located in the liquid ambient while simultaneously forcing a liquid through liquid orifices at a velocity sufficient to form jet streams of liquid, the liquid orifices being equal in number to the gas orifices and so oriented that each

P. M. Bhagat; R. M. Koros

1990-01-01

380

Etiology of Gas Bubble Disease  

Microsoft Academic Search

Gas bubble disease is a noninfectious, physically induced process caused by uncompensated hyperbaric pressure of total dissolved gases. When pressure compensation is inadequate, dissolved gases may form emboli (in blood) and emphysema (in tissues). The resulting abnormal physical presence of gases can block blood vessels (hemostasis) or tear tissues, and may result in death. Population mortality is generally skewed, in

Gerald R. Bouck

1980-01-01

381

Electrogenerated Gas Bubbles in Flotation  

Microsoft Academic Search

Electrolytic gas evolution plays a very significant part in a number of electrochemical processes. In the electrowinning of metals the evolution of gases at the electrodes is a very important phenonenon. Gas evolution is common in chlorine and water electrolysis and in a number of other processes. Electro-generated gas bubbles have been used in the treatment of waste water and

S. VENKATACHALAM

1992-01-01

382

Etiology of gas bubble disease  

Microsoft Academic Search

Gas bubble disease is a noninfectious, physically induced process caused by uncompensated hyperbaric pressure of total dissolved gases. When pressure compensation is inadequate, dissolved gases may form emboli (in blood) and emphysema (in tissues). The resulting abnormal physical presence of gases can block blood vessels (hemostasis) or tear tissues, and may result in death. Population mortality is generally skewed, in

GERALD R. BOUCK

1980-01-01

383

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

384

Ice bubbles confirm big chill  

SciTech Connect

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

Kerr, R.A.

1996-06-14

385

The Coming Law School Bubble  

ERIC Educational Resources Information Center

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

Krauss, Michael I.

2011-01-01

386

Bubble bouncing at a clean water surface.  

PubMed

Experiments on the coalescence time of submillimeter bubbles colliding with a distilled water/air interface either being at rest (undisturbed) or vibrating vertically (with controlled amplitude and frequency) were carried out. It was found that the outcome of the bubble collision (coalescence or bounce) depends on impact velocity and size of the bubble, i.e. the parameters determining the bubble deformation degree. With the surface at rest, when the deformation of the bubble was sufficiently high, bubble bouncing was observed. It was caused by the fact that the radius of the intervening liquid film formed between the colliding bubble and water/air interface was large enough to prevent the liquid layer from reaching its thickness of rupture within the time of bubble-interface contact. Coalescence occurred in a consecutive collision if the bubble deformation was below a threshold value, as a result of dissipation of the kinetic energy associated with the bubble motion. The hypothesis about the crucial role of the bubble deformation and size of the liquid film formed in the bouncing mechanism was confirmed in a series of experiments where the bubble collided with a vibrating water/air interface. It was shown that when the kinetic energy was properly re-supplied from an external source (interface vibrations), the spectacular phenomenon of "immortal" bubbles, dancing indefinitely at the water/air interface, was achieved. It was shown that "immortal" bubble formation is a consequence of a similarly high degree of the bubble shape deformation and consequently a large enough radius of the liquid film formed. PMID:24022507

Zawala, Jan; Dorbolo, Stéphane; Vandewalle, Nicolas; Malysa, Kazimierz

2013-09-25

387

Wheat Evolution: Dough Rising  

NSDL National Science Digital Library

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

Council, Biotechnology A.

2012-01-01

388

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

2011-10-10

389

Supercoiling Induces Denaturation Bubbles in Circular DNA  

NASA Astrophysics Data System (ADS)

We present a theoretical framework for the thermodynamic properties of supercoiling-induced denaturation bubbles in circular double-stranded DNA molecules. We explore how DNA supercoiling, ambient salt concentration, and sequence heterogeneity impact on the bubble occurrence. An analytical derivation of the probability distribution to find multiple bubbles is derived and the relevance for supercoiled DNA discussed. We show that in vivo sustained DNA bubbles are likely to occur due to partial twist release in regions rich in weaker AT base pairs. Single DNA plasmid imaging experiments clearly demonstrate the existence of bubbles in free solution.

Jeon, Jae-Hyung; Adamcik, Jozef; Dietler, Giovanni; Metzler, Ralf

2010-11-01

390

Bubbles in an isotropic homogeneous turbulent flow  

NASA Astrophysics Data System (ADS)

Bubbly turbulent flow plays an important role in many engineering applications and natural phenomena. In this kind of flows the bubbles are dispersed in a turbulent flow and they interact with the turbulent structures. The present study focuses on the motion and hydrodynamic interaction of a single bubble in a turbulent environment. In most previous studies, the effect of bubbles on the carrier fluid was analyzed, under the assumption that the bubble size was significantly smaller that the smallest turbulence length scale. An experimental study of the effect of an isotropic and homogeneous turbulent flow on the bubble shape and motion was conducted. Experiments were performed in an isotropic turbulent chamber with nearly zero mean flow, in which a single bubble was injected. The fluid velocity was measured using the Particle Image Velocimetry (PIV) technique. The bubble deformation was determined by video processing of high-speed movies. The fluid disturbances on the bubble shape were studied for bubbles with different sizes. We will present experimental data obtained and discuss the differences among these results to try to understand the bubble - turbulence interaction mechanisms.

Mancilla, F. E.; Martinez, M.; Soto, E.; Ascanio, G.; Zenit, R.

2011-11-01

391

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

392

Conditions for static bubbles in viscoplastic fluids  

NASA Astrophysics Data System (ADS)

We consider the slow motion of a gas bubble in a cylindrical column filled with a viscoplastic fluid, modeled here as a Herschel-Bulkley fluid. Because of the yield stress of the fluid, it is possible that a bubble will remain trapped in the fluid indefinitely. We adapt Prager's two variational principles to our problem. From these variational principles we develop two general stopping conditions, i.e., for a given bubble we can calculate a critical Bingham number above which the bubble will not move. The first condition is derived by bounding the velocity field and the second condition by bounding the stress field. We illustrate these conditions by considering specific bubble shapes, e.g., axisymmetric bubbles. We also develop a condition for bubble motion.

Dubash, Neville; Frigaard, Ian

2004-12-01

393

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

394

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

NASA Astrophysics Data System (ADS)

We solve the dynamics of magma ascent and the kinetics of bubble nucleation and growth simultaneously, which allow us to predict bubble sizes and number densities under ascent conditions. As magma rises toward the surface, the pressure decreases and eventually becomes less than the solubility pressure. When the degree of supersaturation becomes great enough, bubbles nucleate. Nucleation will stop as the concentration of volatiles in the melt decreases due to growth of existing bubbles and hence the degree of supersaturation decreases. We show that a second nucleation event may occur just below the fragmentation level. Near that level, the degree of supersaturation continuously increases as the magma is rapidly decompressed. As a result, nucleation will not stop until fragmentation occurs. This second nucleation event should be taken into account when interpreting bubble size distribution measurements made on natural pumices. The bubbles of the second nucleation event have high internal gas pressures up to 2 MPa greater than the liquid pressure, suggesting that the second nucleation event may enhance fragmentation of magma. We apply the model to the calculation protocol defined at the “Volcanic eruption mechanism modeling workshop, Durham, 2002”. We found that as a result of disequilibrium degassing fragmentation occurs higher in the conduit than under equilibrium degassing.

Massol, Hélène; Koyaguchi, Takehiro

2005-05-01

395

Implementation and verification of numerical model for gas bubble dynamics in electroconductive fluid  

NASA Astrophysics Data System (ADS)

Apart from common steam reforming process the thermal decomposition of methane is regarded as an alternate route to producing hydrogen and elemental carbon with out of CO2 emissions. Chemical reaction of decarburation can be ensured by means of methane bubbly flow through a molten metal bath and additionally controlled by external electromagnetic field. This is the initial stage of research and preliminary calculation results for the single bubble rise dynamics in 2D axisymmetric consideration at different flow conditions and 2D planar consideration in the presence of external DC EM field are obtained and compared to experimental and simulation data from literature.

Tucs, A.; Spitans, S.; Jakovics, A.; Baake, E.

2013-10-01

396

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

397

Safety Rises to New Levels.  

ERIC Educational Resources Information Center

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

Lafo, Joseph; Robillard, Marc

2001-01-01

398

The Sea Level Rise Challenge  

Microsoft Academic Search

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

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

2010-01-01

399

Shock waves in a uniform bubbly flow  

NASA Astrophysics Data System (ADS)

An experimental and numerical study of transient shock wave phenomena in a liquid containing noncondensable gas bubbles is presented. Experiments are done in a shock tube with an upwardly directed bubbly flow to obtain a uniform spatial distribution of bubbles. The bubbly flow has an initial gas volume fraction of 0.2%. The bubbles have a radius of 0.6 mm. The liquid used is a silicone oil whose kinematic viscosity is 50×10-6 m2/s. Nitrogen and SF6 gas bubbles are tested to bring out the thermal effects of the bubble interior. The numerical calculation is performed using a modified mathematical model based on Kameda and Matsumoto [Phys. Fluids 8, 322 (1996)]. The transient pressure profiles determined in the experiment for the upwardly bubbly flow agree well quantitatively with those obtained by the numerical calculation using a uniform spatial distribution of bubbles. The SF6 experiment shows that the radial motion of the bubbles should be estimated by solving an equation in which the liquid compressibility is taken into account.

Kameda, Masaharu; Shimaura, Naoto; Higashino, Fumio; Matsumoto, Yoichiro

1998-10-01

400

Etiology of gas bubble disease  

SciTech Connect

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

Bouck, G.R.

1980-11-01

401

Sonoporation from Jetting Cavitation Bubbles  

PubMed Central

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

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

2006-01-01

402

Effective gene delivery with novel liposomal bubbles and ultrasonic destruction technology.  

PubMed

From the viewpoint of safety, non-viral vector systems represent an attractive gene delivery system for gene therapy. However, the transfection efficiency of non-viral vectors in vivo is generally very low. Previously, it was reported that microbubbles, utilized as imaging agents for diagnostic echocardiography, could promote gene delivery into cells when combined with ultrasound exposure. We therefore developed novel liposomal bubbles (Bubble liposomes) containing the lipid nanobubbles of perfluoropropane which is used as ultrasound imaging agent. These Bubble liposomes were smaller in diameter than conventional microbubbles and induced cavitation upon exposure to ultrasound. These results suggested that cavitation of these Bubble liposomes could be an efficient approach for delivering plasmid DNA into cells. In addition, in in vivo gene delivery, the combination of Bubble liposomes and ultrasound provided more effective gene delivery than conventional lipofection methods, further suggesting that Bubble liposomes could be effective as a non-viral vector system in in vivo gene delivery. In this review, we discuss the characteristics of Bubble liposomes and their potential utility as a gene delivery tool in vitro and in vivo. PMID:18082343

Suzuki, Ryo; Takizawa, Tomoko; Negishi, Yoichi; Utoguchi, Naoki; Maruyama, Kazuo

2007-11-01

403

There is No Housing Bubble  

Microsoft Academic Search

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

James F. Smith

2005-01-01

404

Unsteady thermocapillary migration of bubbles  

NASA Astrophysics Data System (ADS)

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.

405

ORIGIN OF THE FERMI BUBBLE  

SciTech Connect

Fermi has discovered two giant gamma-ray-emitting bubbles that extend nearly 10 kpc in diameter north and south of the Galactic center. The existence of the bubbles was first evidenced in X-rays detected by ROSAT and later WMAP detected an excess of radio signals at the location of the gamma-ray bubbles. We propose that periodic star capture processes by the galactic supermassive black hole, Sgr A*, with a capture rate 3 x 10{sup -5} yr{sup -1} and energy release {approx}3 x 10{sup 52} erg per capture can produce very hot plasma {approx}10 keV with a wind velocity {approx}10{sup 8} cm s{sup -1} injected into the halo and heat up the halo gas to {approx}1 keV, which produces thermal X-rays. The periodic injection of hot plasma can produce shocks in the halo and accelerate electrons to {approx}TeV, which produce radio emission via synchrotron radiation and gamma rays via inverse Compton scattering with the relic and the galactic soft photons.

Cheng, K.-S.; Chernyshov, D. O.; Dogiel, V. A. [Department of Physics, University of Hong Kong, Pokfulam Road, Hong Kong (China); Ko, C.-M.; Ip, W.-H. [Institute of Astronomy, National Central University, Chung-Li 32054, Taiwan (China)

2011-04-10

406

Topside Ionosphere Plasma bubbles seen as He+ Density Depletions: Estimations and Comparisons  

NASA Astrophysics Data System (ADS)

He+ density depletions, considered as originating from equatorial plasma bubbles, were involved in this study. They are usually detected in the topside ionosphere (~1000 km) deeply inside the plasmasphere (L~1.3-3) [1-3]. a) Since there are some questions about the survival possibilities of the topside plasma bubbles, the characteristic times of the main processes, in which plasma bubbles are involved, were compared. It was suggested that the plasma bubbles are produced by Rayleigh-Taylor instability at the bottomside of ionosphere and transported up to the topside ionosphere. It was found that it takes about 3-4 hours for plasma bubbles to reach the topside ionosphere altitudes. It was revealed that ambipolar diffusion transport is the most fast (some minutes). The estimation of the Bohm (cross-field) diffusion time shows that topside plasma bubbles can exist up to 100 hours. It was concluded that there is enough time for the plasma bubbles to survive and to be detected (for example, in minor species of ion composition inside the bubble like He+) at the topside ionosphere altitudes. (b) It was revealed that the topside plasma bubbles can be easily detected as He+ density depletions during high and maximal solar activity. The convenient conditions for observations appear because the strong depleted in He+ density bubbles, reaching the topside ionosphere, most well contrast with the He+ density background layer very well developed in the topside ionosphere during high solar activity [4]. (c) He+ density depletions were considered in connection with equatorial F-region irregularities (EFI), equatorial F-spread (ESF) and equatorial plasma bubbles (EPB). Their longitudinal statistics, calculated for all seasons and both hemispheres (20-50 deg. INVLAT), were compared with EFI statistics taken from AE-E [5], OGO-6 [6], ROCSAT [7] observations. ESF, EPB statistics taken from [8, 9] based on ISS-b and Hinotori spacecraft data were also used for comparison. It was revealed that the main statistical maxima of the equatorial F-region irregularities are well enough reflected in the statistical plots of the He+ density depletions of the both hemispheres. The best conformity was obtained for equinoxes, the worst one was obtained for solstices, when the most dramatic insolation differences take place in the different hemispheres. Hence, it was validated once again that He+ density depletions may be considered as an indicator of topside plasma bubble presence or as fossil bubble signatures.

Sidorova, L.; Filippov, S.

2012-04-01

407

Large Volcanic Rises on Venus  

NASA Astrophysics Data System (ADS)

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

408

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

409

Bubble growth in superheated He-II  

SciTech Connect

Bubble growth in superheated He-II is controlled by the transfer of heat to the surface of the growing bubble by nonlinear Gorter-Mellink counterflow. The present work presents analytic formulas for the bubble radius as a function of time in the limiting cases of small and large superheats. The formulas include the effect of the inertial reaction of the surrounding liquid to the expansion of the bubble. A numerical example shows that bubble velocities of the order of meters per second are possible. A related problem, involving only heat transfer but no movement of the liquid, is the motion of the free surface of superheated He-II in a very long tube. This problem has a similarity solution. The interfacial velocity in the tube is much smaller than the bubble growth velocity. 1 ref.

Dresner, L.

1988-01-01

410

Invention and History of the Bubble Chamber  

ScienceCinema

Don Glaser won the 1960 Nobel Prize for Physics for his 1952 invention of the bubble chamber at Berkeley Lab, a type of particle detector that became the mainstay of high-energy physics research throughout the 1960s and 1970s. He discusses how, inspired by bubbles in a glass of beer, he invented the bubble chamber and detected cosmic-ray muons. His talk was presented July 12, 2006.

411

On the pressure of cavitation bubbles  

Microsoft Academic Search

Shock wave emission upon the collapse of a cavitation bubble attached to a rigid wall is investigated using high-speed photography with 200 million frames\\/s and 5ns exposure time. At a distance of 68?m from the bubble wall, the shock pressure is 1.3±0.3GPa. The shock pressure decays proportionally to r?1.5 with increasing distance from the bubble. An estimation of the peak

E. A. Brujan; T. Ikeda; Y. Matsumoto

2008-01-01

412

Structure of a turbulent separation bubble  

Microsoft Academic Search

Single- and two-point measurements of velocity and surface pressure fluctuations are conducted for the flow in the separation bubble formed along the sides of a blunt, flat plate with right-angled corners, with attention to the bubble's large-scale vortex structure. Large scale vortices are shed downstream from the separation bubble, and on top of this regular vortex shedding, there exists a

Masaru Kiya; Kyuro Sasaki

1983-01-01

413

Collapse of vacuum bubbles in a vacuum  

SciTech Connect

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

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

2011-02-15

414

Aperiodic bubble formation from a submerged orifice  

Microsoft Academic Search

The present work aims at studying the nonlinear behaviors of bubbles, including formation, interference, collision and coalescence, formed from a submerged orifice. The experimental data reveal that the departing periods of successive bubbles evolve regularly from single period to triple periods within the air flow rate regime of 100cc\\/minbubbles. A new comprehensive

Lei Zhang; Masahiro Shoji

2001-01-01

415

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

SciTech Connect

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

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

2011-08-20

416

Model of coupled pulsation and translation of a gas bubble and rigid particle  

PubMed Central

A model of the interaction of a spherical gas bubble and a rigid spherical particle is derived as a coupled system of second-order differential equations using Lagrangian mechanics. The model accounts for pulsation and translation of the bubble as well as translation of the particle in an infinite, incompressible liquid. The model derived here is accurate to order R5?d5, where R is a characteristic radius and d is the separation distance between the bubble and particle. This order is the minimum accuracy required to account for the interaction of the bubble and particle. Dependence on the size and density of the particle is demonstrated through numerical integration of the dynamical equations for both the free and forced response of the system. Numerical results are presented for models accurate to orders higher than R5?d5 to demonstrate the consequences of truncating the equations at order R5?d5.

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

2009-01-01

417

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

NASA Astrophysics Data System (ADS)

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

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

2008-07-01

418

Bubble Motion in a Vibrating Liquid  

NASA Astrophysics Data System (ADS)

Gas bubbles can be forced to move downward, overcoming the buoyancy force, by vertical vibration of the liquid containing the bubble. Bubble motion is controlled by interactions of the oscillating pressure field, and the corresponding bubble volume, with the drag force acting on the bubble. The bubble-drag asymmetry and the oscillating pressure gradient can combine to produce net bubble motion. This is analogous to the Bjerknes force in high-frequency vibrations. Experiments have been conducted demonstrating downward bubble motion over a range of vibration conditions (all less than 300 Hz), liquid properties, and pressure in the air above the free surface. Bubble size and velocity were measured using automated image-processing routines. Comparisons with theory and simulations will be shown. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

O'Hern, T. J.; Shelden, B.; Torczynski, J. R.

2011-11-01

419

Ultrasound-induced nanofragmentation of bubbles  

NASA Astrophysics Data System (ADS)

Micron-sized bubbles are of considerable interest for use in biomedical imaging and drug delivery. Lipid-coated bubbles have been reported to rapidly shrink in the presence of short (3 ?s) ultrasound pulses, purportedly by shedding of the coat during compression. Loss of coat would increase the internal pressure, enhancing diffusive gas loss long after the pulse. Note that during such a short pulse, diffusive gas loss is insignificant. If lipid-shedding is the mechanism for bubble shrinkage, a coated bubble in ultrasound may shrink no faster than a quiescent uncoated bubble; the shrinkage rate is entirely dominated by diffusive loss between pulses. Remarkably, we find that most insonated lipid-coated bubbles do shrink faster than quiescent uncoated bubbles. If bubbles cannot shrink by diffusive gas loss, they must fragment, though no fragmentation was observed. The results are consistent with ``nanofragmentation,'' where sub-micron fragments (which entrap gas) are lost from the bubble. Entrapment of gas in fragments may have important consequences for their efficacy in ultrasound-mediated drug delivery, and could affect their ability to transfer drugs to cells.

Cox, Debra; Thomas, James

2011-10-01

420

Gravity effects to the Vacuum Bubbles  

NASA Astrophysics Data System (ADS)

We study the nucleation process of the vacuum bubbles in curved spacetime. We systematically classify the vacuum bubbles in a de Sitter background and investigate the tunneling between the degenerate vacua in symmetric double-well potential. We also show that the existence of the small false vacuum bubbles within the true vacuum background in the gravity theory with a nonminimally coupled scalar field. We discuss the dynamics of the bubble after its materialization. This article is prepared for the proceedings of Astrophysics And Cosmology After Gamow in Odessa, Ukraine, Aug 2009.

Lee, Bum-Hoon; Lee, Wonwoo

2010-01-01

421

Breaking Bubble Rafts: Modeling material failure  

NASA Astrophysics Data System (ADS)

Bubble rafts have long been of interest as a model two-dimensional system for the study of general amorphous systems, ranging from metallic glasses to foams and potentially geophysical flows. Consisting of a single layer of gas-bubbles on an aqueous substrate, bubble rafts allow for excellent control over bubble size, size distribution, bubble solution composition, and for the tracking and characterizing of each bubble in the system. The individual bubbles serve as the model for the "particles" in other complex flows, such as molecules or grains. Additionally, bubble rafts have been used in a wide-range of flow geometries and with varied methods of confinement. These features of bubble rafts have provided insight in a range of issues related to the visco-elastic nature of foams and other complex fluids. In this talk, we will present results from a relatively new configuration: uniaxial extension. At relatively low speeds, the system exhibits pinch-off behaviour that is consistent with a fluid-like response. Two types of pinch-off are observed: double-cone and long-thread. The appearance of either mode is dependent on the pulling speed and system size. As the speed of extension is increased, the system exhibits classic fracture behaviour. We will report on our characterization of these transitions, with a focus on connecting to potential microscopic origins of the different modes.

Dennin, M.

2011-12-01

422

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

423

Modeling bubble clusters in compressible liquids  

NASA Astrophysics Data System (ADS)

We present a new model to simulate the behaviour of bubble clouds in compressible liquids. The method uses a volume-averaged approach and defines the pressure and void fraction relative to a computational cell. Inside the cell, a generalisation of the Keller-Miksis equation is derived in order to take into account the presence of (one or more) nearby spherical bubbles as well as liquid compressibility effect on the bubble interface motion. The method converges to previous models in two distinct limits. First, it reproduces the bubble radius evolution and pressure disturbances induced by a single bubble subjected to a given far field pressure, irrespective of the relative size of the bubble compared to the grid size. Second, it converges to continuum models based on Ensemble-averaged equations when there are many bubbles in a cell. The main advantage of the model is that it allows to access to the instantaneous pressure profiles in the liquid rather than the averaged behaviour. The local pressures generated and scattered by bubble dynamics is important for predicting the peak pressures that can be locally achieved in some points of the liquid when violent bubble collapses are encountered.

Fuster, Daniel; Colonius, Tim

2010-11-01

424

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

425

Bubble-induced turbulence suppression in Langmuir circulation  

NASA Astrophysics Data System (ADS)

Dissipation rates ? of turbulent kinetic energy and air bubble characteristics were observed within the wave-enhanced near-surface layer in the open ocean. During a period of well developed Langmuir circulation, short periods of increased air fraction and peak bubble radii <150 ?m at 2.5m, indicative of the instrumentation package drifting through convergence zones, coincide with significantly reduced dissipation rates. The rate of turbulence suppression correlates well with the buoyancy frequency inferred from the vertical gradient of air fraction. The Ozmidov scale and turbulent time scales associated with the bubble induced stratification are of O(0.5m) and O(20-60s), respectively. These stratification characteristics are consistent with the suppression of energy containing eddies close to the surface, which in turn results in reduced turbulent dissipation rates. Dissipation rates are observed to decay with depth following a power law ? ? zn, and n = -1, consistent with the theoretical value for constant stress layer scaling, is found within convergence zones, but n ? -3 outside.

Gemmrich, Johannes

2012-05-01

426

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

427

Numerical study of a bubble plume generated by bubble entrainment from an impinging jet  

Microsoft Academic Search

The current paper presents the prediction results of a bubbly flow under plunging jet conditions using multiphase mono- and poly-dispersed approaches. The models consider interfacial momentum transfer terms arising from drag, lift, and turbulent dispersion force for the different bubble sizes. The turbulence is modeled by an extended k–? model which accounts for bubble induced turbulence. Furthermore in case of

Faiza Zidouni Kendil; Eckhard Krepper; Anis Bousbia Salah; Dirk Lucas; Amina Mataoui

2011-01-01

428

Bubble shattering: Differences in bubble formation in fresh water and seawater  

Microsoft Academic Search

Breaking waves result in very different populations of bubbles in fresh water and seawater. The differences in sizes and numbers of bubbles in the two media cause significant differences in many natural processes including gas transfer and generation of aerosols as well as affect sound and light propagation and ambient sound production. Observed differences in bubble populations in seawater and

David E. Slauenwhite; Bruce D. Johnson

1999-01-01

429

Optical absorption properties of electron bubbles and experiments on monitoring individual electron bubbles in liquid helium  

Microsoft Academic Search

When a free electron is injected into liquid helium, it forms a microscopic bubble essentially free of helium atoms, which is referred to as an electron bubble. It represents a fine example of a quantum-mechanical particle confined in a potential well. In this dissertation, we describe our studies on bubble properties, especially the optical absorption properties of ground state electron

Wei Guo

2009-01-01

430

Oscillations and breakup of a bubble immersed in a turbulent field  

NASA Astrophysics Data System (ADS)

This work is an experimental study of the deformation and breakup of a bubble in a turbulent flow. A special facility was designed to obtain intense turbulence without significant mean flow. The experiments were performed under microgravity conditions to ensure that turbulence was the only cause of bubble deformation. A scalar parameter, characteristic of this deformation, was obtained by video processing of high-speed movies. The time evolution and spectral representation of this scalar parameter showed the dynamical characteristics of bubble deformation. The signatures of the eigenmodes of oscillation predicted by the linear theory were clearly observed and the predominance of the second mode was proved. In addition, numerical simulations were performed by computing the response of a damped oscillator to the measured turbulence forcing. Simulations and experiments were found to be in good agreement both qualitatively, from visual inspections of the signals, and quantitatively, from a statistical analysis. The role of bubble dynamics in the deformation process has been clarified. On the one hand, the time response of the bubble controls the maximum amount of energy which can be extracted from each turbulent eddy. On the other hand, the viscous damping limits the energy that the bubble can accumulate during its fluctuating deformation. Moreover, two breakup mechanisms have been identified. One mechanism results from the balance between two opposing dominant forces, and the other from a resonance oscillation. A new parameter, the mean efficiency coefficient, has been introduced to take into account the various aspects of bubble dynamics. Used together with the Weber number, this parameter allows the prediction of the occurrence of these two mechanisms. Finally, the influence of the residence time of the bubble on the statistics of the deformation has been analysed and quantified.

Risso, Frédéric; Fabre, Jean

1998-10-01

431

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

432

Efficient manipulation of microparticles in bubble streaming flows  

PubMed Central

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

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

2012-01-01

433

21 CFR 870.4205 - Cardiopulmonary bypass bubble detector.  

Code of Federal Regulations, 2013 CFR

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

2013-04-01

434

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

435

Bubble coalescence dynamics and supersaturation in electrolytic gas evolution.  

National Technical Information Service (NTIS)

The apparatus and procedures developed in this research permit the observation of electrolytic bubble coalescence, which heretofore has not been possible. The influence of bubble size, electrolyte viscosity, surface tension, gas type, and pH on bubble coa...

R. L. Stover

1996-01-01

436

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

Microsoft Academic Search

The dynamic behavior of cavitation and gas bubbles under negative pressure has been studied numerically to evaluate the effect of gas bubble injection into a liquid on the suppression of cavitation inception. In our previous studies, it was demonstrated by direct observation that cavitation occurs in liquid mercury when mechanical impacts are imposed, and this will cause cavitation damage in

Masato Ida; Takashi Naoe; Masatoshi Futakawa

2007-01-01

437

Interactions of Bubbles in a Temperature Gradient.  

NASA Astrophysics Data System (ADS)

A theoretical and experimental investigation of the hydrodynamic interactions of bubbles in the presence of a temperature gradient has been performed. Both theory and experiment correspond to motion at negligible values of the Reynolds and Peclet numbers so that convective transport of momentum and energy is unimportant. In the theoretical models, the thermocapillary migration of a small chain of spherical bubbles in an unbounded fluid possessing a uniform temperature gradient is investigated. The line of bubble centers is permitted to be either parallel or perpendicular to the direction of the undisturbed temperature gradient. The governing equations are solved by a truncated -series, boundary-collocation technique. Results are presented which demonstrate the impact of the presence of other bubbles on a test bubble. Also, features of the flow topology in the fluid are explored. A pairwise-additive approximation is presented, and is found to perform well except for relatively small separations. The migration of a pair of gas bubbles in an unbounded fluid subject to the combined action of gravity and a downward temperature gradient also is investigated theoretically. The solution for the case when the line-of-centers is oriented arbitrarily with respect to the gravity vector is constructed by superposing solutions of the axisymmetric and asymmetric problems. In the axisymmetric problem, it is found that a pair of unequal bubbles can reach a stable critical separation at which both bubbles move at the same velocity, if the smaller bubble is on top of the larger one; at an appropriate balance of the relative strengths of the gravitational and thermocapillary forces, such a pair of bubbles also can reach a motionless state. Flow structures are illustrated via streamlines. Experiments are performed to measure the velocities of individual members of a pair of air bubbles in a silicone oil under isothermal conditions as well as in a downward temperature gradient. Three situations are investigated: motion driven by buoyancy, motion dominated by thermocapillarity, and motion when the gravitational force and the thermocapillary force on the larger bubble of the pair are comparable. The experimental results are found to be in good agreement with theoretical predictions from the method of reflections which gives the simplest form with results indistinguishable from those based on the boundary collocation technique within the experimental uncertainty. When the gravitational force is slightly smaller than the thermocapillary force on the larger bubble in the pair, the larger bubble moves downward but the smaller bubble nearby is found to move upward. This counter-intuitive behavior is actually consistent with expectation, and an explanation is given.

Wei, Huailiang

438

Statistical characteristics of cavitation noise  

NASA Astrophysics Data System (ADS)

Cavitation noise originates as a superposition of pressure waves emitted during oscillations of individual cavitation bubbles. These pressure waves contain useful information on bubbles generating them and efforts are done to extract it. Unfortunately the pressure waves emitted by different bubbles usually overlap heavily and thus in experiments it makes sense to measure statistical characteristics only. Typical statistical characteristics determined experimentally encompass autospectral densities and instantaneous autospectra. To be able to extract information concerning the oscillating bubbles, suitable models of both cavitation bubbles and cavitation noise are necessary. It has been found out recently that a reasonable insight into the cavitation noise structure may be obtained by simulating cavitation noise on a computer and comparing statistical characteristics of simulated cavitation noise with those determined experimentally. By varying different parameters in theoretical models used to simulate the noise, a good agreement between the simulated and measured cavitation noise statistical characteristics can be obtained. The models parameters thus found may be then analyzed from a physical point of view and conclusions on behavior of cavitation bubbles can be drawn. [Work supported by the Ministry of Education of the Czech Republic as the research Project No. MSM 245100304.

Vokurka, Karel

2002-11-01

439

Linear stability and sensitivity of the flow past a fixed oblate spheroidal bubble  

NASA Astrophysics Data System (ADS)

The stability properties of the wake past an oblate spheroidal bubble held fixed in a uniform stream are studied in the framework of a global linear analysis. In line with previous studies, provided the geometric aspect ratio of the bubble, ?, is large enough, the wake is found to be unstable only within a finite range of Reynolds number, Re. The neutral curves corresponding to the occurrence of the first two unstable modes are determined over a wide range of the (?, Re) domain and the structure of the modes encountered along the two branches of each neutral curve is discussed. Then, using an adjoint-based approach, a series of sensitivity analyses of the flow past the bubble is carried out in the spirit of recent studies devoted to two-dimensional and axisymmetric rigid bodies. The regions of the flow most sensitive to an external forcing are found to be concentrated in the core or at the periphery of the standing eddy, as already observed with bluff bodies at the surface of which the flow obeys a no-slip condition. However, since the shear-free condition allows the fluid to slip along the bubble surface, the rear half of this surface turns out to be also significantly sensitive to disturbances originating in the shear stress, a finding which may be related to the well-known influence of surfactants on the structure and stability properties of the flow past bubbles rising in water.

Tchoufag, J.; Magnaudet, J.; Fabre, D.

2013-05-01

440

Generation and evolution of equatorial ionospheric plasma bubbles and broad plasma depletions measured by the C/NOFS satellite during deep solar minimum  

NASA Astrophysics Data System (ADS)

A spectacular phenomenon in the equatorial ionosphere is the occurrence of broad plasma depletions in which the plasma density is reduced by 1-3 orders of magnitude over thousands of kilometers in longitude near dawn. This phenomenon is observed repeatedly by the Communication/Navigation Outage Forecasting System (C/NOFS) satellite during deep solar minimum. Our purpose is to study where the postmidnight plasma bubbles start to occur, how long they exist, what the maximum size of individual bubbles is, how plasma bubbles are related to broad depletions, and how broad plasma depletions form. The orbit of C/NOFS can be approximately parallel to the geomagnetic equator over a large local time range. If a plasma bubble exists long enough, it may be detected by C/NOFS over successive orbits. The C/NOFS measurements can be used to trace the growth and development of plasma bubbles. In several cases we analyzed, a series of plasma bubbles was first detected by C/NOFS over a longitudinal range of up to 3800 km around midnight. Each of the individual bubbles has a typical width of ~100 km in longitude, and the upward ion drift velocity inside the bubbles is 200-400 m/s. The plasma bubbles rotate to the dawn sector and become broad plasma depletions. The strong upward plasma flow inside the bubbles exist for more than 7 hours, and the bubbles do not become dead/fossil bubbles over the entire night time. The observations clearly show the evolution from multiple plasma bubbles into broad depletions. We propose that the broad plasma depletions with strong upward plasma flow are the result of merging of multiple equatorial plasma bubbles. We will also present the numerical simulations of bubble merging with the physics-based low-latitude ionospheric model (PBMOD). It is found that two separate plasma bubbles join together and form a new single bubble. The simulations demonstrate for the first time that the merging process of plasma bubbles can indeed occur in incompressible ionospheric plasma. The C/NOFS measurements reveal significant new characteristics of equatorial plasma bubbles and broad depletions during deep solar minimum.

Huang, Chaosong; De La Beaujardiere, Odile; Retterer, John; Pfaff, Robert; Roddy, Patrick; Hunton, Donald; Ballenthin, John

2012-07-01