WorldWideScience

Sample records for bubble growth

  1. Bubble Growth in Lunar Basalts

    Science.gov (United States)

    Zhang, Y.

    2009-05-01

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

  2. Growth process of helium bubbles in aluminum

    International Nuclear Information System (INIS)

    The growth process of helium bubbles in α-particle bombarded pure aluminum during isothermal anneal at 200 to 6450C for 1 hr to 100 hr was observed by transmission electronmicroscopy and possible mechanisms are discussed. The effects of helium concentration and cold work were investigated. Helium bubbles are detectable only by annealing above 5500C for 1 hr in both the annealed and cold worked samples. The cold work does not cause any extra coarsening trend of bubbles. The observed types of the bubble distribution are divided into two categories, irrespective of helium concentration and cold work; (1) fine and uniform bubble distribution, in which case the average size is limited to about 200 A or less in diameter even by the anneal just below the melting point, and (2) the coarsened and nonuniform bubble distribution ranging from 500 to 4000 A in diameter. The intermediate size bubbles are scarcely found in any cases. In the above fine bubble distribution, the increase of helium concentration by a factor of two increases the density by the same factor of two, but does not change the mean size of bubbles. From these two characteristic bubble distributions, it is concluded that two different mechanisms are operative in this experiment (1) the growth of bubbles by Brownian motion, in which the growth rate of bubbles is decreased to almost zero by bubble faceting and this results in the bubble size constancy during the prolonged annealing, and (2) the growth of bubbles by the grain boundary sweep-out mechanism, by which the abrupt coarsening of bubbles is caused. The lack of the intermediate size bubble is explained in this way. (auth.)

  3. An equation of motion for bubble growth

    International Nuclear Information System (INIS)

    A mathematical model is developed which describes asymmetric bubble growth, either during boiling or bubble injection from submerged orifices. The model is developed using the integral form of the continuity and momentum equations, resulting in a general expression for the acceleration of the bubble's centre of gravity. The proposed model highlights the need to include acceleration due to an asymmetric gain or loss of mass in order to accurately predict bubble motion. Some scenarios are posed by which the growth of bubbles, particularly idealized bubbles that remain a section of a sphere, must include the fact that bubble growth can be asymmetric. In particular, for approximately hemispherical bubble growth the sum of the forces acting on the bubble is negligible compared with the asymmetric term. Further, for bubble injection from a submerged needle this component in the equation of motion is very significant during the initial rapid growth phase as the bubble issues from the nozzle changing from a near hemisphere to truncated sphere geometry. (author)

  4. Bubble growth and rise in soft sediments

    Science.gov (United States)

    Boudreau, Bernard P.; Algar, Chris; Johnson, Bruce D.; Croudace, Ian; Reed, Allen; Furukawa, Yoko; Dorgan, Kelley M.; Jumars, Peter A.; Grader, Abraham S.; Gardiner, Bruce S.

    2005-06-01

    The mechanics of uncemented soft sediments during bubble growth are not widely understood and no rheological model has found wide acceptance. We offer definitive evidence on the mode of bubble formation in the form of X-ray computed tomographic images and comparison with theory. Natural and injected bubbles in muddy cohesive sediments are shown to be highly eccentric oblate spheroids (disks) that grow either by fracturing the sediment or by reopening preexisting fractures. In contrast, bubbles in soft sandy sediment tend to be spherical, suggesting that sand acts fluidly or plastically in response to growth stresses. We also present bubble-rise results from gelatin, a mechanically similar but transparent medium, that suggest that initial rise is also accomplished by fracture. Given that muddy sediments are elastic and yield by fracture, it becomes much easier to explain physically related phenomena such as seafloor pockmark formation, animal burrowing, and gas buildup during methane hydrate melting.

  5. Bubble growth in decompression fields, 2

    International Nuclear Information System (INIS)

    Numerical analysis was performed for the growth of a vapor bubble in decompression fields of uniformly superheated water. The numerical solution obtained for the bubble growth was compared with experimental data reported in the 1st report. Bubble growth rates calculated were somewhat lower than the experimental data. The present solution was, however, shown to compare more favorably with the experimental bubble growth curves than the previous analytical solutions reported in the 1st report. In addition, existing solutions by other researchers provided that the sphericity correction factor was in agreement. Of course, the previous solutions with the correction factor of π/2 were the best-estimated solutions as reported in 1st report. Transient temperature distributions across the thermal boundary layer surrounding the bubble interface were also analyzed. It was found that, during the very short duration of the earlier bubble growth, the thermal boundary layer developed fully and the interfacial temperature approached that of saturation corresponding to the decompressed liquid pressure. (author)

  6. Bubble growth in a narrow horizontal space

    International Nuclear Information System (INIS)

    The purpose of this work is to develop an axis-symmetric two-phase flow model describing the growth of a single bubble squeezed between a horizontal heated upward-facing disc and an insulating surface placed parallel to the heated surface. Heat transfers at the liquid-vapour interfaces are predicted by the kinetic limit of vaporisation. The depths of the liquid films deposed on the surfaces (heated surface and confinement space) are determined using the Moriyama and Inoue correlation (1996). Transient heat transfers within the heated wall are taken into account. The model is applied to pentane bubble growth. The influence of the gap size, the initial temperature of the system, the thermal effusivity of the heated wall and the kinetic limit of vaporisation are studied. The results show that the expansion of the bubbles strongly depends on the gap size and can be affected by the effusivity of the material. Mechanical inertia effects are mainly dominant at the beginning of the bubble expansion. Pressure drop induced by viscous effects have to be taken into account for high capillary numbers. Heat transfers at the meniscus are negligible except at the early stages of the bubble growth. (author)

  7. Bubble growth in mold cavities during microcellular injection molding processes

    International Nuclear Information System (INIS)

    Bubble nucleation and growth are the key steps in polymer foam generation processes. The mechanical properties of foam polymers are closely related to the size of the bubbles created inside the material, and most existing analysis methods use a constant viscosity and surface tension to predict the size of the bubbles. Under actual situations, however, when the polymer contains gases, changes occur in the viscosity and surface tension that cause discrepancies between the estimated and observed bubble sizes. Therefore, we developed a theoretical framework to improve our bubble growth rate and size predictions, and experimentally verified our theoretical results using an injection molding machine modified to make microcellular foam products

  8. Bubble growth in mold cavities during microcellular injection molding processes

    Energy Technology Data Exchange (ETDEWEB)

    Moon, Yong Rak [University of Toronto, Toronto (Canada); Lee, Kyoung Soo; Cha, Sung W. [Yonsei University, Seoul (Korea, Republic of)

    2009-12-15

    Bubble nucleation and growth are the key steps in polymer foam generation processes. The mechanical properties of foam polymers are closely related to the size of the bubbles created inside the material, and most existing analysis methods use a constant viscosity and surface tension to predict the size of the bubbles. Under actual situations, however, when the polymer contains gases, changes occur in the viscosity and surface tension that cause discrepancies between the estimated and observed bubble sizes. Therefore, we developed a theoretical framework to improve our bubble growth rate and size predictions, and experimentally verified our theoretical results using an injection molding machine modified to make microcellular foam products

  9. Bubble growth rate in water binary systems at subatmospheric pressures

    International Nuclear Information System (INIS)

    The vapor-type bubble growth rate has been experimentally studied during bubble boiling both in water and in the following ''positive'' aqueous, binary systems: water-ethanol, water-1-buthanol, water-2-buthanon at pressures between 2 and 26 kPa, the Jackoby numbers between 2700 and 700, and volatile organic component contents between 2 and 30%. Numerical solutions have been presented for growth and annihilation of spherical and axis-symmetrical vapor-type bubbles during transfer between the isometric and isobaric phases. Occurrence of fluctuations both in bubble radius and bubble surface temperature has been predicted

  10. Bubble growth constants for liquid hydrogen and liquid helium

    International Nuclear Information System (INIS)

    Bubble growth constants are calculated for liquid H2 and liquid He at various pressures and liquid superheats for spherically symmetric growth using Scrivens' solution (Chem. Eng. Sci.; 10 (1959)). The constants are shown to be applicable to bubble growth at a heated wall during boiling of cryogenic liquids. (author)

  11. Experimental study on bubble growth in vertical narrow channel

    International Nuclear Information System (INIS)

    A visual investigation of vapor bubble growth in subcooled upward forced convection boiling in vertical rectangular narrow channel (the gap is 2 mm) was performed. High speed camera was used to record the bubble growth with a speed of 5000 fps (frames per second), and the picture size are 512 x 512 pixel. Experimental results about bubble growth in various work conditions (with variation heat flux and mass flux) were recorded; and based on the regression analysis, the exponential fitting relationship between the mean equivalent bubble diameter (De) and the bubble growth time was revealed. The results show that the exponential fitting can predict the mean bubble growth in narrow channel very well; but the coefficients of K and n, are quite different with that of conventional channel; and the K is less dependent on Ja number other than that of conventional channel, and the n has the value of wider range of 0.339 ∼ 0.914. (authors)

  12. Dynamics of diffusive bubble growth in magmas: Isothermal case

    Science.gov (United States)

    Prousevitch, A. A.; Sahagian, D. L.; Anderson, A. T.

    1993-12-01

    We have conducted a parametric study and developed a new cell model describing diffusion-induced growth of closely spaced bubbles in magmatic sytems. The model accounts for (1) the effects of advection of melt resulting from bubble growth, and its affect on the local concentration profile; (2) dynamic resistence of the viscous melt during diffusive growth; (3) diffusion of volatiles in response to evolving concentration gradients; (4) mass balance between dissolved volatiles and gas inside the bubble; (5) changes in the equilibrium saturation concentration at the bubble-melt interface; (6) total pressure within the bubble consisting of ambient, surface tension, and dynamic pressures. The results of this study reveal that bubble growth depends strongly on ambient pressure, volatile oversaturation in the melt, and diffusivity coefficients, but only weakly on bubble separation and inital bubble radius. Increased volatile oversaturation increases growth rate to the point at which it actually reduces time for complete bubble growth. This counterintuitive result is due to significant advective volatile flux toward the bubble interface during growth. Viscosity controls growth dynamics only for cases of high viscosity (greater than 10(exp 4) Pa s). The documentation of the evolution of gas fraction in the melt and bubble wall thickness as a function of time makes it possible to estimate bubble disruption thresholds which bear on volcanic eruption mechanisms. Model results can be applied to the larger-scale problem of magmatic degassing in terms of bubble coalescence, flotation and the development of foams in magma chambers and vent systems, and ultimately to the dynamics of eruption mechanisms.

  13. Rapid vapor bubble growth during decompression of superheated water

    International Nuclear Information System (INIS)

    Both analytical and experimental investigations are performed for vapor bubble growth in a uniformly superheated water under rapid decompression. Numerical and analytical solutions are obtained by solving a complete set of governing equations for bubble growth, and compared with experimental data obtained in the present experiment and previously by Toda and Kitamura. Bubble growth rates calculated numerically are lower than the experimental data, however, they approach more favorably our experimental data than the analytical solutions without the added correction factor given by Toda and Kitamura. Their solutions with the correction factor of π/2 are the best-fit solutions reported thus far. Available solutions by other researchers are found to underpredict bubble growth rates. Transient temperature distributions across the thermal boundary layer on the bubble interface are also estimsted. It is found that for initial periods thermal boundary layer fully develops and the bubble interface temperature approaches that of saturation corresponding to decompressed liquid pressure. (author)

  14. Effect of temperature on swelling and bubble growth in metals

    International Nuclear Information System (INIS)

    The effect of temperature on the swelling of copper-boron alloys has been studied in the temperature range of 900-1040deg C. It is observed that beyond 1030deg C, swelling as well as the rate of bubble growth decrease. Similar characteristics of the bubble growth have been observed in aluminium-boron alloys also. At 590deg C, the bubble growth in aluminium-boron alloys is faster as compared to that at 640deg C. It thus appears that the swelling as well as the growth of the gas bubble are retarded at temperatures near the melting point in metals. Possible reasons for this kind of behaviour are discussed. (author)

  15. Helium ion implantation in zirconium: Bubble formation and growth

    Science.gov (United States)

    Totemeier, Aaron Robert

    To evaluate the behavior of inert helium gas bubbles in zirconium three variants of the metal were implanted with 140 keV helium ions to a total fluence of 3x1017 cm--2 and characterized in cross-section TEM in their as-implanted state as well as during annealing at different temperatures. The three zirconium alloys included high-purity crystal bar material, Zircaloy-4, and a powder-metallurgically extruded material with high carbon and oxygen concentrations. At a sample depth consistent with a helium concentration of approximately 5 atomic percent, a change in the structure of the zirconium was observed a high density region of small (4nm diameter) bubbles formed at concentrations above 10 atom percent. Initial bubble formation and growth was observed to occurred at a temperature between 400-450 °C and these initial bubbles had a unique planar geometry prior to migration and coalescence into more three-dimensional bubbles. These planar bubbles appear to be aligned with major axes parallel to the TEM specimen surface and their formation and growth is possibly due to an increase in the thermal vacancy flux within the zirconium. The observations of bubble response to high temperature annealing suggest that in zirconium, as in other metals, maximum bubble size is weakly dependent on annealing time, whereas the bubble size distribution is strongly dependent on time. Specimens that underwent a prolonged room temperature aging developed a multimodal bubble size distribution within the high density region of small bubbles, concentrated near the highest helium concentration depth.

  16. PROBLEM OF METAL VAPOUR BUBBLE GROWTH IN MAGNETIC FIELD

    OpenAIRE

    Jerzy Gąsiorowski; Jacek Szypliński; Ryszard Wnuk

    1982-01-01

    Limits influencing on hieat transfer method's choice, in fusion reactors, have been analysed. Structure of nucleate boiling of metal was selected, as a effective way of problem solution. Existence of relation between magnetic field and heat transfer intensity in boiling metal was shown.A part of Lorentz's forces in motion balance of valour bubble rising in liquid metal was evaluated. Magnetic field influence on elipsoidal vapour bubble growth time was estimated.

  17. Simulation of bubble growth and coalescence in reacting polymer foams

    Science.gov (United States)

    Marchisio, Daniele; Karimi, Mohsen

    2015-11-01

    This work concerns with the simulation of reacting polymer foams with computational fluid dynamics (CFD). In these systems upon mixing of different ingredients polymerization starts and some gaseous compounds are produced, resulting in the formation of bubbles that growth and coalesce. As the foam expands, the polymerization proceeds resulting in an increase of the apparent viscosity. The evolution of the collective behavior of the bubbles within the polymer foam is tracked by solving a master kinetic equation, formulated in terms of the bubble size distribution. The rate with which individual bubbles grow is instead calculated by resolving the momentum and concentration boundary layers around the bubbles. Moreover, since it is useful to track the evolution of the interface between the foam and the surrounding air, a volume-of-fluid (VOF) model is adopted. The final computational model is implemented in the open-source CFD code openFOAM by making use of the compressibleInterFoam solver. The master kinetic equation is solved with a quadrature-based moment method (QBMM) directly implemented in openFOAM, whereas the bubble growth model is solved independently and ''called'' from the CFD code by using an unstructured database. Model predictions are validated against experimental data. This work was funded by the European Commission under the grant agreement number 604271 (Project acronym: MoDeNa; call identifier: FP7-NMP-2013-SMALL-7).

  18. Bubbles

    DEFF Research Database (Denmark)

    Dholakia, Nikhilesh; Turcan, Romeo V.

    2013-01-01

    A goal of our ongoing research stream is to develop a multidisciplinary metatheory of bubbles. In this viewpoint paper we put forward a typology of bubbles by comparing four types of assets – entertainment, commodities, financial securities (stocks), and housing properties – where bubbles could and...... do form occasionally. Cutting across and comparing such varied asset types provides some rich insights into the nature of bubbles – and offers an inductive way to arrive at the typology of bubbles....

  19. Dynamic of vapor bubble growth in fields of variable pressure

    International Nuclear Information System (INIS)

    A mathematical model for the description of the growth from an initial nucleus of a vapor bubble imersed in liquid, subjected to a loss of pressure is presented. The model is important for analysing LOCA (Loss of Coolant Acident) in P.W.R. type reactors. Several simplifications were made in the phenomenum governing equations. With such simplifications the heat diffusion equation became the determining factor for the bubble growth, and the problem was reduced to solve the heat diffusion equation for semi infinite solid whose surface temperature is a well known function of time (it is supposed that the surface temperature is equal to the saturation temperature of the liquid at the system pressure at a given moment). The model results in an analytical expression for the bubble radius as a function of time. Comparisons with experimental data and previous models were made, with reasonable agreement. (author)

  20. Dynamics of bubble growth for Rayleigh--Taylor unstable interfaces

    International Nuclear Information System (INIS)

    A statistical model is analyzed for the growth of bubbles in a Rayleigh--Taylor unstable interface. The model is compared to solutions of the full Euler equations for compressible two phase flow, using numerical solutions based on the method of front tracking. The front tracking method has the distinguishing feature of being a predominantly Eulerian method in which sharp interfaces are preserved with zero numerical diffusion. Various regimes in the statistical model exhibiting qualitatively distinct behavior are explored

  1. Effect of the proximity of the external surface on the growth characteristics of inert gas bubbles

    International Nuclear Information System (INIS)

    Experimental evidence is discussed in order to show that the proximity of an external surface has a strong effect on the growth of inert gas bubbles. This effect can be explained as follows: while bubbles act as sinks, the external surface provides a copious source for vacancies. These observations suggest the possibility of the growth of inert gas bubbles through spontaneous vacancy condensation. (orig.)

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

    CERN Document Server

    Gor, Gennady Yu; Kuni, Fedor M

    2012-01-01

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

  3. Simulation of hydrogen bubble growth in tungsten by a hybrid model

    International Nuclear Information System (INIS)

    A two dimensional hybrid code (HIIPC-MC) joining rate-theory and Monte Carlo (MC) methods is developed in this work. We evaluate the cascade-coalescence mechanism contribution to the bubble growth by MC. First, effects of the starting radius and solute deuterium concentration on the bubble growth are studied; then the impacts of the wall temperature and implantation ion flux on the bubble growth are assessed. The simulation indicates that the migration-coalescence of the bubbles and the high pressure inside the bubbles are the main driving forces for the bubble growth, and that neglect of the migration and coalescence would lead to an underestimation of the bubble growth or blistering

  4. Dynamics of gas bubble growth in oil-refrigerant mixtures under isothermal decompression

    Energy Technology Data Exchange (ETDEWEB)

    Dias, Joao Paulo; Barbosa Junior, Jader R.; Prata, Alvaro T. [Federal University of Santa Catarina (UFSC), Florianopolis, SC (Brazil). Dept. of Mechanical Engineering], Emails: jpdias@polo.ufsc.br, jrb@polo.ufsc.br, prata@polo.ufsc.br

    2010-07-01

    This paper proposes a numerical model to predict the growth of gaseous refrigerant bubbles in oil-refrigerant mixtures with high contents of oil subjected to isothermal decompression. The model considers an Elementary Cell (EC) in which a spherical bubble is surrounded by a concentric and spherical liquid layer containing a limited amount of dissolved liquid refrigerant. The pressure reduction in the EC generates a concentration gradient at the bubble interface and the refrigerant is transported to the bubble by molecular diffusion. After a sufficiently long period of time, the concentration gradient in the liquid layer and the bubble internal pressure reach equilibrium and the bubble stops growing, having attained its stable radius. The equations of momentum and chemical species conservation for the liquid layer, and the mass balance at the bubble interface are solved via a coupled finite difference procedure to determine the bubble internal pressure, the refrigerant radial concentration distribution and the bubble growth rate. Numerical results obtained for a mixture of ISO VG10 ester oil and refrigerant HFC-134a showed that bubble growth dynamics depends on model parameters like the initial bubble radius, initial refrigerant concentration in the liquid layer, decompression rate and EC temperature. Despite its simplicity, the model showed to be a potential tool to predict bubble growth and foaming which may result from important phenomena occurring inside refrigeration compressors such as lubrication of sliding parts and refrigerant degassing from the oil stored in oil sump during compressor start-up. (author)

  5. Rating Growth of Scientific Knowledge and Risk from Theory Bubbles

    CERN Document Server

    Loeb, Abraham

    2011-01-01

    In physics the value of a theory is measured by its agreement with experimental data. But how should the physics community gauge the value of an emerging theory that has not been tested experimentally as of yet? With no reality check, a hypothesis like string theory may linger for a while before physicists will know its actual value in describing nature. In this short article, I advocate the need for a website operated by graduate students that will use various measures of publicly available data (such as the growth rate of newly funded experiments, research grants, publications, and faculty jobs) to gauge the future dividends of various research frontiers. The analysis can benefit from past experience (e.g. in research areas that suffered from limited experimental data over long periods of time) and aim to alert the community of the risk from future theory bubbles.

  6. Atomistic modeling of growth and coalescence of helium nano-bubbles in tungsten

    International Nuclear Information System (INIS)

    The mechanisms of growth and coalescence of helium nano-bubbles in tungsten are investigated using molecular dynamics simulations. It is shown that crystal symmetries and governed by them properties of dislocations, generated by the growing nano-bubbles, are responsible for main nano-bubble features revealed, including non-spherical shape and anisotropy of surrounding stress field. The transport of helium atoms in non-uniform stress field is simulated at different temperatures and the transport coefficients are determined. The implications of the considered dislocation and helium dynamics on nucleation and growth of bubbles in tungsten with implanted helium are discussed

  7. Atomistic modeling of growth and coalescence of helium nano-bubbles in tungsten

    Science.gov (United States)

    Smirnov, R. D.; Krasheninnikov, S. I.; Guterl, J.

    2015-08-01

    The mechanisms of growth and coalescence of helium nano-bubbles in tungsten are investigated using molecular dynamics simulations. It is shown that crystal symmetries and governed by them properties of dislocations, generated by the growing nano-bubbles, are responsible for main nano-bubble features revealed, including non-spherical shape and anisotropy of surrounding stress field. The transport of helium atoms in non-uniform stress field is simulated at different temperatures and the transport coefficients are determined. The implications of the considered dislocation and helium dynamics on nucleation and growth of bubbles in tungsten with implanted helium are discussed.

  8. The growth of bubbles in pure aluminum during and after irradiation with 600 MeV

    International Nuclear Information System (INIS)

    Pure aluminum specimens have been irradiated in the Pirex facility installed in a 600 MeV proton accelerator. Proton beams of current densities between 3 and 11 μA/mm2 have been used to obtain doses between 0.9 and 6 dpa at various irradiation temperatures from 390 to 750 K. The specimens were observed after irradiation in a transmission electron microscope (TEM). The helium bubble distributions formed as a function of dose and irradiation temperature have been systematically determined. The bubble growth results are discussed in terms of current models. For in-beam growth, this work shows that up to 520 K, the structure is controlled by nucleation and that the diatomic nucleation model, as proposed by Trinkaus, applies. At higher temperatures, bubble growth is controlling the bubble distribution, but which diffusion mechanism is dominant is not clear. In the case of post-irradiation growth, the results are interpreted in terms of bubble coalescence

  9. Electron irradiation effect on bubble formation and growth in a sodium borosilicate glass

    International Nuclear Information System (INIS)

    In this study, the authors studied simultaneous and intermittent electron irradiation effects on bubble growth in a simple sodium borosilicate glass during Xe ion implantation at 200 C. Simultaneous electron irradiation increases the average bubble size in the glass. This enhanced diffusion is also shown by the migration of Xe from bubbles into the matrix when the sample is irradiated by an electron beam after the Xe implantation

  10. Growth of a bubble at a heated surface in a pool of liquid metal

    International Nuclear Information System (INIS)

    A theoretical investigation of the initial vapor bubble growth from a heated wall in a pool of liquid is reported. The analysis assumes the bubble to have the shape of a spherical sector, at the base of which a thin liquid microlayer is retained on the heating surface. The effects of time-and-space dependent heat conduction in the solid, microlayer vaporization, and non-equilibrium condensation on the bubble upper surface are considered. A two-term expression for the bubble growth rate is obtained by a collocation procedure. Calculated results predict the growth of the bubble on a heated surface as a function of the heat flux, the external pressure and the thermophysical properties of the liquid and solid. An expression due to Ruckenstein, modified to take into account the effective contact angle, is used to determine the departure bubble diameter. This turns out to be sensitive to the contact angle, and less strongly influenced by the bubble drag coefficient. The growth is initially inertia-controlled, but heat-transfer effects become significant before departure. In this pressure range (0.1 to 1 atm) the presence of inert gas, by reducing the effective accommodation coefficient for condensation, increases bubble growth rate moderately. (author)

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

    Energy Technology Data Exchange (ETDEWEB)

    Qu, L.; Ma, H.T., E-mail: htma@dlut.edu.cn; Zhao, H.J.; Kunwar, Anil; Zhao, N.

    2014-06-01

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

  12. Gas-bubble growth mechanisms in the analysis of metal fuel swelling

    International Nuclear Information System (INIS)

    During steady-state irradiation, swelling rates associated with growth of fission-gas bubbles in metallic fast reactor fuels may be expected to remain small. As a consequence, bubble-growth mechanisms are not a major consideration in modeling the steady-state fuel behavior, and it is usually adequate to consider the gas pressure to be in equilibrium with the external pressure and surface tension restraint. On transient time scales, however, various bubble-growth mechanisms become important components of the swelling rate. These mechanisms include growth by diffusion, for bubbles within grains and on grain boundaries; dislocation nucleation at the bubble surface, or ''punchout''; and bubble growth by creep. Analyses of these mechanisms are presented and applied to provide information on the conditions and the relative time scales for which the various processes should dominate fuel swelling. The results are compared to a series of experiments in which the swelling of irradiated metal fuel was determined after annealing at various temperatures and pressures. The diffusive growth of bubbles on grain boundaries is concluded to be dominant in these experiments

  13. Nucleation and growth of helium bubbles in aluminum between 20 and 900 K

    DEFF Research Database (Denmark)

    Rajainmäki, H.; Linderoth, Søren; Hansen, H. E.; Nieminen, R. M.; Bentzon, M. D.

    1988-01-01

    The nucleation and growth of helium bubbles have been monitored in 3implanted aluminum by the positron-lifetime technique and transmission electron microscopy. Helium atoms are mobile during the implantation and are subsequently trapped by vacancies. The annealing stages I and III are observed at...... 40 and 200 K, respectively, in agreement with previous positron annihilation and electrical-resistivity data. The low implantation temperature of 20 K hinders bubble formation during implantation, but during isochronal annealing, around 425 K, helium starts to nucleate into bubbles via substitutional...... migration of the He-vacancy pairs. The migration energy for a He-vacancy pair is estimated to be 1.3±0.1 eV. Above 600 K the He bubbles grow through condensation of thermally produced vacancies, as well as bubble migration and coalescence. The created helium bubbles are extremely stable and survive the...

  14. Growth of a dry spot under a vapor bubble at high heat flux and high pressure

    CERN Document Server

    Nikolayev, Vadim; Lagier, G -L; Hegseth, J

    2016-01-01

    We report a 2D modeling of the thermal diffusion-controlled growth of a vapor bubble attached to a heating surface during saturated boiling. The heat conduction problem is solved in a liquid that surrounds a bubble with a free boundary and in a semi-infinite solid heater by the boundary element method. At high system pressure the bubble is assumed to grow slowly, its shape being defined by the surface tension and the vapor recoil force, a force coming from the liquid evaporating into the bubble. It is shown that at some typical time the dry spot under the bubble begins to grow rapidly under the action of the vapor recoil. Such a bubble can eventually spread into a vapor film that can separate the liquid from the heater thus triggering the boiling crisis (critical heat flux).

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

    OpenAIRE

    Gor, Gennady Yu.; Kuchma, Anatoly E.; Kuni, Fedor M.

    2012-01-01

    Theoretical description of diffusion growth of a gas bubble after its nucleation in supersaturated liquid solution is presented. We study the influence of Laplace pressure on the bubble growth. We consider two different solubility laws: Henry's law, which is fulfilled for the systems where no gas molecules dissociation takes place and Sievert's law, which is fulfilled for the systems where gas molecules completely dissociate in the solvent into two parts. We show that the difference between H...

  16. Taxing the rich: recombinations and bubble growth during reionization

    Science.gov (United States)

    Furlanetto, Steven R.; Oh, S. Peng

    2005-11-01

    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

  17. Taxing the Rich: Recombinations and Bubble Growth During Reionization

    CERN Document Server

    Furlanetto, S R; Furlanetto, Steven R.

    2005-01-01

    Reionization is inhomogeneous for two reasons: the clumpiness of the intergalactic medium (IGM) and clustering of the discrete ionizing sources. While numerical simulations can in principle take both into account, they are at present limited by small box sizes. On the other hand, analytic models have only examined the limiting cases of a clumpy IGM (with uniform ionizing emissivity) and clustered sources (embedded in a uniform IGM). Here, we present an analytic model for the evolving topology of reionization that includes both factors. At first, recombinations can be ignored and ionized bubbles grow primarily through major mergers. As a result, reionization resembles "punctuated equilibrium," with a series of well-separated sharp jumps in the ionizing background. These features are local effects and do not reflect similar jumps in the global ionized fraction. We then combine our bubble model with a simple description of recombinations in the IGM. We show that the bubbles stop growing when recombinations balan...

  18. Computational Model for Determination of Vapor Bubble Growth Speed Maximimum in Superheated Liquids

    OpenAIRE

    Turlajs, D; Grivcovs, V; Jaundālders, S

    2008-01-01

    The article deals with problems of investigation of boiling of liquids - the most intensive heat transfer phenomena. There are a lot of research reports of boiling dynamics and heat transfer studies in micro- and nanoscopic levels, carried out with aim to understund phenomena in whole. Simulation model for vapor bubble growth speed maximum calculations in the region of bubble critical radius is elaborated. Numerical calculations were carried out for water in the region of system p...

  19. Experimental Study of Bubble Growth in Stromboli Basalt Melts at 370 MPa and 1 Atmosphere

    Science.gov (United States)

    Bai, L.; Baker, D. R.; Rivers, M.

    2006-05-01

    Volcanic degassing involves gas bubble formation and growth due to the exsolution of the volatiles dissolved in the melts. Although we know that bubble size distributions in natural rocks are controlled by bubble nucleation and growth processes, we are far from a quantitative understanding of their growth. In order to investigate bubble formation and growth under different pressures, degassing experiments using a Stromboli basalt with dissolved H2O, or H2O+CO2, were conducted in a piston-cylinder at 370 MPa and on the GSECARS (Advanced Photon Source) Synchrotron beamline in a custom furnace at one atmosphere. In the high pressure degassing experiments the melts were synthesized at 1250 ° C and 1000 MPa with either about 3.0, 5.0, or 8.0 % H2O or with mixtures of H2O+CO2: approximately 3.0 % H2O and 440 ppm CO2, 5.0 % H2O and 880 ppm CO2, or 8.0 % H2O and 1480 ppm CO2. After homogenization of the dissolved volatiles in the melt, the samples were isothermally decompressed to a final pressure of 370 MPa. The decompressed samples were held at 370 MPa for 0 to 3600 seconds before quenching. In the one atmosphere experiments, the hydrated, volatile-undersaturated melts of the same compositions as the high pressure experiments were synthesized at 1250 ° C and 1000 MPa and quenched to bubble-free glasses. These glasses were heated in-situ on the Synchrotron X-ray beamline at one atmosphere, and then were quenched from different temperatures. The 3D bubble size distributions in the quenched samples were then studied with synchrotron X-ray microtomography. Bubbles nucleated and grew in all samples, producing bubbles with volumes varying between 10-5 and 10-7 mm3 in the high pressure experiments and between 10-1 and 10-7 mm3 in the one atmosphere experiments. The vesicularities of samples from high pressure degassing experiments vary between 0.1 and 6.6 percent. In the one atmosphere degassing experiments the bubbles grew and coalesced, and occasionally popped when the

  20. Birth and growth of cavitation bubbles within water under tension

    CERN Document Server

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

    2011-01-01

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

  1. Helium bubble nucleation and growth in α-Fe: insights from first–principles simulations

    International Nuclear Information System (INIS)

    We have carried out a first-principles study on the nucleation and early-stage growth of He bubbles in Fe. The energetics, atomic and electronic structure of He-vacancy complexes, involving both a monovacancy and a nine-vacancy cluster, are examined. Based on the energetics, we then perform thermodynamics analysis to gain deeper insights into He bubble nucleation and growth. We have determined the energy cost for the nucleation of He bubbles and found that up to eight He atoms can be trapped at a single vacancy. In order to capture more He atoms, the vacancy has to emit Frenkel pairs to release the substantial stress building on the surrounding Fe lattice. Compared to the monovacancy, the nine-vacancy cluster has a lower energy cost for He bubble nucleation and growth. He atoms at the vacancy repel the surrounding electronic charge and redistribute it on the neighboring Fe atoms. The thermodynamic analysis reveals that He chemical potential provides a driving force for He bubble nucleation and growth. There are two critical He chemical potentials that are of particular importance: one of them marks the transition from single He occupation to multiple He occupation at a monovacancy while the other sets off He-induced superabundant vacancy formation. (paper)

  2. Steam bubble growth in the bulk of overheated N2O4-NO chemically reacting solution

    International Nuclear Information System (INIS)

    A mathematical model and numerical investigation of the vapour bubble growth that begins from the bubble critical size at the positive radius fluctuation during the initial moment in the bulk of the overheated N2O4-NO liquid solution are presented. The mathematical model has been stated under the following assumptions: the movement of a bubble wall and surrounding liquid is spherically symmetrical; thermal parameters in the bubble are distributed uniformly; the vapour phase follows the ideal gas law; heat transfer is not affected by the compressibility of liquid; if dissolution of light components is determined by Henry's law, then Hertz-Knudsen's equation determines the velocity of phase transition for a N2O4 component. The mathematical model presented can be applied to another fluids, including chemically reacting ones

  3. Improving microalgal growth with small bubbles in a raceway pond with swing gas aerators.

    Science.gov (United States)

    Yang, Zongbo; Cheng, Jun; Liu, Jianzhong; Zhou, Junhu; Cen, Kefa

    2016-09-01

    A novel swing gas aerator was developed to generate small bubbles for improving the mass transfer coefficient and microalgal growth rate in a raceway pond. A high-speed photography system (HSP) was used to measure the bubble diameter and generation time, and online precise dissolved oxygen probes and pH probes were used to measure the mass transfer coefficient and mixing time. Bubble generation time and diameter decreased by 21% and 9%, respectively, when rubber gas aerators were swung in the microalgae solution. When water pump power and gas aeration rate increased in a raceway pond with swing gas aerators and oscillating baffles (SGAOB), bubble generation time and diameter decreased but solution velocity and mass transfer coefficient increased. The mass transfer coefficient increased by 25% and the solution velocity increased by 11% when SGAOB was used, and the microalgal biomass yield increased by 18%. PMID:27243604

  4. Energy distribution during cavitation bubble growth and collapse in water

    Czech Academy of Sciences Publication Activity Database

    Müller, M.; Maršík, František; Garen, W.

    Kyoto: Maruzen Co., Ltd, 2005 - (Nakahara, M.; Matubayasi, N.; Ueno, M.; Yasuoka, K.; Watanabe, K.), s. 226-231 ISBN 4-621-07596-9. [International Conference on the Properties of Water and Steam /14./. Kyoto (JP), 29.08.2004-03.09.2004] R&D Projects: GA AV ČR(CZ) IBS2076003; GA ČR(CZ) GA101/02/0364 Institutional research plan: CEZ:AV0Z20760514 Keywords : cavitation * bubble dynamics * optical measurement Subject RIV: BJ - Thermodynamics

  5. A simultaneous observation of bubble growth and microlayer behavior for an isolated boiling regime of saturated water

    International Nuclear Information System (INIS)

    The bubble growth rate and microlayer behavior were simultaneously visualized for an isolated boiling regime of saturated water. The increase rate of the bubble volume dropped sharply when the microlayer was totally depleted. However, the contribution of the superheated liquid layer evaporation to the bubble volume increase was comparable to or even higher than that of the microlayer evaporation during the time when the microlayer evaporation was active. The microlayer under the coalesced bubble was much thicker than that under single isolated bubble. (author)

  6. Growth of oxygen bubbles during recharge process in zinc-air battery

    Science.gov (United States)

    Wang, Keliang; Pei, Pucheng; Ma, Ze; Chen, Huicui; Xu, Huachi; Chen, Dongfang; Xing, Haoqiang

    2015-11-01

    Rechargeable zinc-air battery used for energy storage has a serious problem of charging capacity limited by oxygen bubble coalescence. Fast removal of oxygen bubbles adhered to the charging electrode surface is of great importance for improving the charging performance of the battery. Here we show that the law of oxygen bubble growth can be achieved by means of phase-field simulation, revealing two phenomena of bubble detachment and bubble coalescence located in the charging electrode on both sides. Hydrodynamic electrolyte and partial insulation structure of the charging electrode are investigated to solve the problem of oxygen bubble coalescence during charging. Two types of rechargeable zinc-air battery are developed on the basis of different tri-electrode configurations, demonstrating that the charging performance of the battery with electrolyte flow (Ⅰ) is better than that of the battery with the partially insulated electrode (Ⅱ), while the battery Ⅱ is superior to the battery Ⅰ in the discharging performance, cost and portability. The proposed solutions and results would be available for promoting commercial application of rechargeable zinc-air batteries or other metal-air batteries.

  7. Formation of methane nano-bubbles during hydrate decomposition and their effect on hydrate growth.

    Science.gov (United States)

    Bagherzadeh, S Alireza; Alavi, Saman; Ripmeester, John; Englezos, Peter

    2015-06-01

    Molecular dynamic simulations are performed to study the conditions for methane nano-bubble formation during methane hydrate dissociation in the presence of water and a methane gas reservoir. Hydrate dissociation leads to the quick release of methane into the liquid phase which can cause methane supersaturation. If the diffusion of methane molecules out of the liquid phase is not fast enough, the methane molecules agglomerate and form bubbles. Under the conditions of our simulations, the methane-rich quasi-spherical bubbles grow to become cylindrical with a radius of ∼11 Å. The nano-bubbles remain stable for about 35 ns until they are gradually and homogeneously dispersed in the liquid phase and finally enter the gas phase reservoirs initially set up in the simulation box. We determined that the minimum mole fraction for the dissolved methane in water to form nano-bubbles is 0.044, corresponding to about 30% of hydrate phase composition (0.148). The importance of nano-bubble formation to the mechanism of methane hydrate formation, growth, and dissociation is discussed. PMID:26049510

  8. Experimental study of bubble generation during β-BaB2O4 single crystal growth

    International Nuclear Information System (INIS)

    The generation of bubble-inclusions during BaB2O4 (BBO) crystal growth from high temperature solution has been optically observed by an in situ observation technique. It was found that bubbles are formed from the peripheries of some hexagonal defects in the (0001) plane of the growing crystal, which may be caused by the evaporation of the air-opened interface at the high temperature. In addition, atomic force microscope (AFM) was used to investigate the distribution of bubbles. Results revealed that the bubble generation and distribution depend strongly on the microscopic structure of the interface: on a rough interface, bubbles are easily formed and grow rapidly; however, they are greatly suppressed by step trains on a vicinal interface. In the latter case, the height value of a bubble is close to that of the step, which is in the order of several tens of nanometers. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Bubble rupture in bubble electrospinning

    Directory of Open Access Journals (Sweden)

    Chen Rouxi

    2015-01-01

    Full Text Available As the distinctive properties and different applications of nanofibers, the demand of nanofibers increased sharply in recently years. Bubble electrospinning is one of the most effective and industrialized methods for nanofiber production. To optimize the set-up of bubble electrospinning and improve its mass production, the dynamic properties of un-charged and charged bubbles are studied experimentally, the growth and rupture process of a bubble are also discussed in this paper.

  10. A novel closed system bubble column photobioreactor for detailed characterisation of micro and macroalgal growth

    OpenAIRE

    Holdt, Susan Løvstad; Christensen, L; Iversen, J.J.L.

    2013-01-01

    Growth of the marine microalgae Tetraselmis striata Butcher and macroalgae Chondrus crispus Stackhouse was investigated in batch cultures in a closed system bubble column photobioreactor. A laboratory cultivation system was constructed that allowed on-line monitoring of temperature, pH and dissolved oxygen tension and was intended for characterization of photoautotrophic growth. Regulation of temperature was done by cooling and carbon dioxide additions regulated pH. The carbon dioxide additio...

  11. Numerical Simulation of Vapor Bubble Growth and Heat Transfer in a Thin Liquid Film

    International Nuclear Information System (INIS)

    A mathematical model is developed to investigate the dynamics of vapor bubble growth in a thin liquid film, movement of the interface between two fluids and the surface heat transfer characteristics. The model takes into account the effects of phase change between the vapor and liquid, gravity, surface tension and viscosity. The details of the multiphase now and heat transfer are discussed for two cases: (1) when a water micro-droplet impacts a thin liquid film with a vapor bubble growing and (2) when the vapor bubble grows and merges with the vapor layer above the liquid film without the droplet impacting. The development trend of the interface between the vapor and liquid is coincident qualitatively with the available literature, mostly at the first stage. We also provide an important method to better understand the mechanism of nucleate spray cooling. (fundamental areas of phenomenology (including applications))

  12. Numerical Simulation of Vapor Bubble Growth and Heat Transfer in a Thin Liquid Film

    Institute of Scientific and Technical Information of China (English)

    TAO Yu-Jia; HUAI Xiu-Lan; LI Zhi-Gang

    2009-01-01

    A mathematical model is developed to investigate the dynamics of vapor bubble growth in a thin liquid film,movement of the interface between two fluids and the surface heat transfer characteristics. The model takes into account the effects of phase change between the vapor and liquid, gravity, surface tension and viscosity. The details of the multiphase flow and heat transfer are discussed for two cases: (1) when a water micro-droplet impacts a thin liquid fihn with a vapor bubble growing and (2) when the vapor bubble grows and merges with the vapor layer above the liquid film without the droplet impacting. The development trend of the interface between the vapor and liquid is coincident qualitatively with the available literature, mostly at the first stage. We also provide an important method to better understand the mechanism of nucleate spray cooling.

  13. Using a dynamic point-source percolation model to simulate bubble growth

    International Nuclear Information System (INIS)

    Accurate modeling of nucleation, growth and clustering of helium bubbles within metal tritide alloys is of high scientific and technological importance. Of interest is the ability to predict both the distribution of these bubbles and the manner in which these bubbles interact at a critical concentration of helium-to-metal atoms to produce an accelerated release of helium gas. One technique that has been used in the past to model these materials, and again revisited in this research, is percolation theory. Previous efforts have used classical percolation theory to qualitatively and quantitatively model the behavior of interstitial helium atoms in a metal tritide lattice; however, higher fidelity models are needed to predict the distribution of helium bubbles and include features that capture the underlying physical mechanisms present in these materials. In this work, we enhance classical percolation theory by developing the dynamic point-source percolation model. This model alters the traditionally binary character of site occupation probabilities by enabling them to vary depending on proximity to existing occupied sites, i.e. nucleated bubbles. This revised model produces characteristics for one and two dimensional systems that are extremely comparable with measurements from three dimensional physical samples. Future directions for continued development of the dynamic model are also outlined

  14. Using a dynamic point-source percolation model to simulate bubble growth.

    Energy Technology Data Exchange (ETDEWEB)

    Zimmerman, Jonathan A.; Zeigler, David A.; Cowgill, Donald F.

    2004-05-01

    Accurate modeling of nucleation, growth and clustering of helium bubbles within metal tritide alloys is of high scientific and technological importance. Of interest is the ability to predict both the distribution of these bubbles and the manner in which these bubbles interact at a critical concentration of helium-to-metal atoms to produce an accelerated release of helium gas. One technique that has been used in the past to model these materials, and again revisited in this research, is percolation theory. Previous efforts have used classical percolation theory to qualitatively and quantitatively model the behavior of interstitial helium atoms in a metal tritide lattice; however, higher fidelity models are needed to predict the distribution of helium bubbles and include features that capture the underlying physical mechanisms present in these materials. In this work, we enhance classical percolation theory by developing the dynamic point-source percolation model. This model alters the traditionally binary character of site occupation probabilities by enabling them to vary depending on proximity to existing occupied sites, i.e. nucleated bubbles. This revised model produces characteristics for one and two dimensional systems that are extremely comparable with measurements from three dimensional physical samples. Future directions for continued development of the dynamic model are also outlined.

  15. Enhanced Generic Phase-field Model of Irradiation Materials: Fission Gas Bubble Growth Kinetics in Polycrystalline UO2

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yulan; Hu, Shenyang Y.; Montgomery, Robert O.; Gao, Fei; Sun, Xin

    2012-05-30

    Experiments show that inter-granular and intra-granular gas bubbles have different growth kinetics which results in heterogeneous gas bubble microstructures in irradiated nuclear fuels. A science-based model predicting the heterogeneous microstructure evolution kinetics is desired, which enables one to study the effect of thermodynamic and kinetic properties of the system on gas bubble microstructure evolution kinetics and morphology, improve the understanding of the formation mechanisms of heterogeneous gas bubble microstructure, and provide the microstructure to macroscale approaches to study their impact on thermo-mechanical properties such as thermo-conductivity, gas release, volume swelling, and cracking. In our previous report 'Mesoscale Benchmark Demonstration, Problem 1: Mesoscale Simulations of Intra-granular Fission Gas Bubbles in UO2 under Post-irradiation Thermal Annealing', we developed a phase-field model to simulate the intra-granular gas bubble evolution in a single crystal during post-irradiation thermal annealing. In this work, we enhanced the model by incorporating thermodynamic and kinetic properties at grain boundaries, which can be obtained from atomistic simulations, to simulate fission gas bubble growth kinetics in polycrystalline UO2 fuels. The model takes into account of gas atom and vacancy diffusion, vacancy trapping and emission at defects, gas atom absorption and resolution at gas bubbles, internal pressure in gas bubbles, elastic interaction between defects and gas bubbles, and the difference of thermodynamic and kinetic properties in matrix and grain boundaries. We applied the model to simulate gas atom segregation at grain boundaries and the effect of interfacial energy and gas mobility on gas bubble morphology and growth kinetics in a bi-crystal UO2 during post-irradiation thermal annealing. The preliminary results demonstrate that the model can produce the equilibrium thermodynamic properties and the morphology of gas

  16. Growth of bubbles during annealing of 600 MeV proton irradiated aluminium

    International Nuclear Information System (INIS)

    High purity aluminium foils were irradiated with 600 MeV protons in the cyclotron of the Swiss Institute of Nuclear Research (SIN). In this type of irradiation, helium is produced by nuclear reactions simultaneously with displacement damage. The samples were studied by transmission electron microscopy (TEM) as irradiated and after successive isothermal anneals in vacuum. The bubble structure is found to be very stable, no growth being observed for annealing temperatures below 770 K (0.82 Tm, where Tm is the absolute melting temperature). In the present study, the annealings were performed at 900 K in a sample irradiated to 2.8 dpa at 450 K. Overall statistics were used to study the resulting bubble distributions, bubble diameters varying between 2.5 and 10 nm. Distributions obtained after annealing samples thinned for TEM observations are compared to those observed after annealing 75 μm thick irradiated samples, showing that the loss of information in the thinned sample is limited. Under these conditions it is discussed that the most probable growth mechanism is that of bubble coalescence, but it is not clear yet which is the operating diffusion mechanism. (orig.)

  17. Influence of the nucleation surface inclination on heat transfers and on the growth dynamics of a steam bubble

    International Nuclear Information System (INIS)

    The influence of the inclination of the nucleation surface on heat and mass transfers and on the growth dynamics of a single steam bubble is experimentally studied. The bubble is created beneath a wall with an imposed heating flux. The evolution of geometrical bubble parameters and of the frequency of emission with respect to the inclination angle are presented. The total heat flux measurements are compared to the evaporation fluxes determined by image processing. Contrary to the evaporation flux, the total flux is conditioned by the inclination and thus is correlated to the frequency of bubbles emission. (J.S.)

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

    Energy Technology Data Exchange (ETDEWEB)

    Xie, G X; Luo, J B; Liu, S H; Guo, D; Li, G; Zhang, C H [State Key Laboratory of Tribology, Tsinghua University, Beijing 100084 (China)], E-mail: xie-gx@163.com, E-mail: luojb@tsinghua.edu.cn

    2009-06-07

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

  19. An experimental investigation of bubble growth in water subcooled flow boiling in a vertical narrow rectangular channel

    International Nuclear Information System (INIS)

    The mechanism of the bubble growth has been of particular interest for decades due to its significant contribution to the boiling heat transfer. That is why many industrial applications are very interested in understanding the mechanism of bubble growth. Revealing the bubble growth rate during the time from inception to departure is very important because the heat flux supplied to the bubbles corresponds to that required for the bubbles' volume change. And the bubble growth plays a key role in boiling heat transfer because the motion of the bubbles will disturb the boundary layer significantly. At present work, an experiment rig with visible test section was established, and a visualization experiment was carried out to analyze the bubble growth of forced flow boiling in a vertical narrow channel with cross section of 2 mm x 50 mm. Water was used as working fluid at 1 and 3 bar system pressure. Bubble growth behavior in different working conditions with varying mass flux and heat flux were recorded by a high speed camera with speed of 10000 fps. (film per second). The pictures recorded at different working conditions were analyzed to obtain the bubble growth data. Results show that the bubble growth and bubble size are significantly affected by mass flux, heat flux and system pressure, and also by the nucleation site density at a certain working condition. To reach a well prediction for the current experiment data, a dimensionless dual model is proposed. The dual model comprised by a linear model and a power curve model (corresponding to the inertia stage and the diffusion stage, respectively) is used to predict the dimensionless bubble growth, and the proposed dual model agrees with experimental results very well. The experiment constants, k and n, used in dual model almost keep constant even the working condition changed at wide range. K is about 2.79 in linear model and is approaching 1.02 in power curve model, respectively; and n approaches 0.25 in power curve

  20. First-order description of the mechanical fracture behavior of fine-grained surficial marine sediments during gas bubble growth

    Science.gov (United States)

    Barry, M. A.; Boudreau, B. P.; Johnson, B. D.; Reed, A. H.

    2010-12-01

    Bubbles in sediments, imaged via Computed Tomography (CT) scanning, and in surrogate transparent material (gelatin), are well-described geometrically as eccentric oblate spheroids. While sediments are undoubtedly visco-elasto-plastic solids, only part of that complex behavior appears to influence significantly the formation and shape of gas bubbles. Specifically, the shape of these bubbles can be explained if the mechanical response of fine-grained sediment is approximated by Linear Elastic Fracture Mechanics (LEFM). To determine the adequacy of the LEFM approximation for gas bubble growth in fine-grained sediments, a number of gas bubbles were injected and grown in natural sediments, while monitoring the size and shape using an industrial CT scanner. A comparison of measured inverse aspect ratios (IARs) of the injected bubbles with calculated IARs from pressure records provides support for the LEFM theory. Deviations from LEFM are observable in the data, but as bubbles grow larger they trend more closely toward the theory. The use of LEFM has been shown to describe gas bubble growth in shallow coastal sediments to first order.

  1. A universal bubble-growth equation for pure liquids and binary solutions with a non-volatile solute

    International Nuclear Information System (INIS)

    A simple equation suitable for predicting the growth rate of a vapor bubble in uniformly-superheated pure liquids and in binary solutions with a non-volatile solute was developed. The equation also improves on the popular pure-liquid bubble growth expression of Mikie et al. (1970) in that it is valid throughout the bubble growth history, i.e., in the surface-tension-, inertia-, and heat-transfer-controlled regimes, it accounts for bubble growth acceleration effects, and uses correctly-related and variable fluid properties. It was found to agree very well with experimental data for pure water and for aqueous NaCl solutions. As the bubble growth in superheated solutions with a non-volatile solute was found to be quite insensitive to diffusion and non-equilibrium effects in a broad range of common solution properties, this equation is likely to be universally valid for many liquids and solutions. Bubble growth in superheated fluids is of key interest in boiling phenomena in general and in flash evaporation in particular. Applications include a wide variety of separation processes such as water desalination, and energy conversion processes such as ocean-thermal energy conversion, geothermal power generation, and nuclear reactor safety

  2. Impact vesiculation – a new trigger for volcanic bubble growth and degassing

    Directory of Open Access Journals (Sweden)

    D. B. Dingwell

    2007-11-01

    Full Text Available We highlight a potentially important trigger for bubble growth and degassing in volcanic bombs. We have successfully triggered bubble growth in previously unvesiculated samples of silicate melt during experiments to simulate volcanic bomb impact, by firing pellets at, and dropping weights onto, melt samples. We call this phenomenon "impact vesiculation". Further work is required on real volcanic bombs to establish the extent to which impact vesiculation occurs in nature. However, our experiments are sufficient to demonstrate that impact vesiculation is a viable processes and should be borne in mind in analysis of bubble populations and degassing histories of bombs and spatter-fed lava flows. Degassing caused by impact vesiculation can occur only at ground-level, so any attempt to calculate the amount of erupted gas available for transport high into the atmosphere by convection above the source of a fountain-fed lava flow that is based on subtracting the volatile content of fluid inclusions from the volatile content of the resulting lava flow would be an overestimate if significant impact vesiculation has occurred.

  3. Bubble systems

    CERN Document Server

    Avdeev, Alexander A

    2016-01-01

    This monograph presents a systematic analysis of bubble system mathematics, using the mechanics of two-phase systems in non-equilibrium as the scope of analysis. The author introduces the thermodynamic foundations of bubble systems, ranging from the fundamental starting points to current research challenges. This book addresses a range of topics, including description methods of multi-phase systems, boundary and initial conditions as well as coupling requirements at the phase boundary. Moreover, it presents a detailed study of the basic problems of bubble dynamics in a liquid mass: growth (dynamically and thermally controlled), collapse, bubble pulsations, bubble rise and breakup. Special emphasis is placed on bubble dynamics in turbulent flows. The analysis results are used to write integral equations governing the rate of vapor generation (condensation) in non-equilibrium flows, thus creating a basis for solving a number of practical problems. This book is the first to present a comprehensive theory of boil...

  4. A new model of grain growth kinetics in UO{sub 2} fuel pellets. Part 1: Grain growth kinetics controlled by grain face bubble migration

    Energy Technology Data Exchange (ETDEWEB)

    Veshchunov, M.S. [Russian Academy of Sciences, Nuclear Safety Institute (IBRAE), 52, B. Tulskaya, Moscow 115191 (Russian Federation)]. E-mail: vms@ibrae.ac.ru

    2005-11-15

    A new mechanism of the lenticular grain face bubble migration which controls the bubble mobility and determines the drag force exerted on the grain boundary, is developed. It is shown that besides a more complicated (so called 'lenticular') shape of grain face bubbles, the migration mechanism of these bubbles might be essentially different from the intragranular bubbles, owing to their specific location on and interaction with a grain boundary. The model is validated against tests on grain growth kinetics during steady irradiation exposure and during post-irradiation annealing of UO{sub 2} fuel samples, and allows explanation of a strong retarding effect of irradiation on the grain growth observed in these tests.

  5. Improvement of growth rate of plants by bubble discharge in water

    Science.gov (United States)

    Takahata, Junichiro; Takaki, Koichi; Satta, Naoya; Takahashi, Katsuyuki; Fujio, Takuya; Sasaki, Yuji

    2015-01-01

    The effect of bubble discharge in water on the growth rate of plants was investigated experimentally for application to plant cultivation systems. Spinach (Spinacia oleracea), radish (Raphanus sativus var. sativus), and strawberry (Fragaria × ananassa) were used as specimens to clarify the effect of the discharge treatment on edible parts of the plants. The specimens were cultivated in pots filled with artificial soil, which included chicken manure charcoal. Distilled water was sprayed on the artificial soil and drained through a hole in the pots to a water storage tank. The water was circulated from the water storage tank to the cultivation pots after 15 or 30 min discharge treatment on alternate days. A magnetic compression-type pulsed power generator was used to produce the bubble discharge with a repetition rate of 250 pps. The plant height in the growth phase and the dry weight of the harvested plants were improved markedly by the discharge treatment in water. The soil and plant analyzer development (SPAD) value of the plants also improved in the growth phase of the plants. The concentration of nitrate nitrogen, which mainly contributed to the improvement of the growth rate, in the water increased with the discharge treatment. The Brix value of edible parts of Fragaria × ananassa increased with the discharge treatment. The inactivation of bacteria in the water was also confirmed with the discharge treatment.

  6. Experimental investigation of remote seismic triggering by gas bubble growth in groundwater

    Science.gov (United States)

    Crews, J. B.; Cooper, C. A.

    2014-12-01

    Remotely triggered seismicity is the process by which an earthquake at one location initiates others after a time delay ranging from seconds to days, over distances up to thousands of kilometers. Candidate mechanisms have been proposed, but none specifically address the role of carbon dioxide (CO2) gas bubble growth in groundwater as a driver of remote seismic triggering in active volcanic and geothermal regions, where shallow crustal CO2 gas is abundant. In the present study, we hypothesize that a seismic wave from a distant source can initiate rapid gas bubble growth in CO2-rich groundwater, resulting in a persistent increase in pore fluid pressure and a reduction of effective stress, which can trigger failure on a critically loaded geologic fault. Under conditions representative of a confined aquifer, a Berea sandstone core flooded with an aqueous CO2 solution was subjected to a six-period burst of 0.05-0.3 Hz, 0.1-0.4 MPa confining stress oscillations. After the oscillations were terminated, the pore fluid pressure exceeded its initial value by 13-60 cm equivalent freshwater head, scaling with the amplitude and frequency - a surplus that is consistent with borehole water level changes [Roeloffs et al. (1995) USGS Open File Report, 95-42] observed in response to the June 28 1992 MW 7.3 Landers, California earthquake Rayleigh wave in Parkfield and Long Valley caldera, California, where remotely triggered earthquakes occurred [Hill et al. (1993) Science, 260(5114); Hill et al. (1995) Journal of Geophysical Research, 100(B7)]. Our experimental results indicate that seismically initiated gas bubble growth in groundwater is a physically plausible mechanism for remote seismic triggering in active volcanic and geothermal regions, suggesting that the aqueous CO2 saturation state in a confined aquifer may be used to assess susceptibility to remote seismic triggering.

  7. Nucleation and growth of vapor bubbles in the liquid bulk and at a solid surface

    International Nuclear Information System (INIS)

    The main achievements in the study of the vapor phase origin in liquid and the subsequent growth of the vapor bubbles are presented briefly, and a number of issues on which there is no single opinion as yet are also outlined. The theory of homogeneous nucleation and a great number of experiments make it possible not only to explain qualitatively the causes of spontaneous formation of vapor nucleation centers in the metastable liquid but provides a simple computational relation for the estimating the intensity of this process. None of the existing hypotheses, however, can give a complete answer to the question of the mechanism of the vapor phase nucleation on a solid surface under ''pure conditions'', although this is a more pressing problem. At the same time, the role of cavities of reservoir type (with a narrow orifice) on the surface under heating as reliable stabilizers of the vapor formation (especially in liquid metals) is clarified from the practical point of view. Thus, the identification of technology for production of such cavities would make it possible to increase substantially the efficiency of heat transferring surfaces. Any computational relations for the growth of bubbles on the heating surface also are (and, according to the author, necessarily will be) approximate ones, although considerable success has been achieved in this field

  8. Large-scale atomistic simulations of helium-3 bubble growth in complex palladium alloys.

    Science.gov (United States)

    Hale, Lucas M; Zimmerman, Jonathan A; Wong, Bryan M

    2016-05-21

    Palladium is an attractive material for hydrogen and hydrogen-isotope storage applications due to its properties of large storage density and high diffusion of lattice hydrogen. When considering tritium storage, the material's structural and mechanical integrity is threatened by both the embrittlement effect of hydrogen and the creation and evolution of additional crystal defects (e.g., dislocations, stacking faults) caused by the formation and growth of helium-3 bubbles. Using recently developed inter-atomic potentials for the palladium-silver-hydrogen system, we perform large-scale atomistic simulations to examine the defect-mediated mechanisms that govern helium bubble growth. Our simulations show the evolution of a distribution of material defects, and we compare the material behavior displayed with expectations from experiment and theory. We also present density functional theory calculations to characterize ideal tensile and shear strengths for these materials, which enable the understanding of how and why our developed potentials either meet or confound these expectations. PMID:27208963

  9. Improving microalgal growth with reduced diameters of aeration bubbles and enhanced mass transfer of solution in an oscillating flow field.

    Science.gov (United States)

    Yang, Zongbo; Cheng, Jun; Lin, Richen; Zhou, Junhu; Cen, Kefa

    2016-07-01

    A novel oscillating gas aerator combined with an oscillating baffle was proposed to generate smaller aeration bubbles and enhance solution mass transfer, which can improve microalgal growth in a raceway pond. A high-speed photography system (HSP) was used to measure bubble diameter and generation time, and online precise dissolved oxygen probes and pH probes were used to measure mass-transfer coefficient and mixing time. Bubble diameter and generation time decreased with decreased aeration gas rate, decreased orifice diameter, and increased water velocity in the oscillating gas aerator. The optimized oscillating gas aerator decreased bubble diameter and generation time by 25% and 58%, respectively, compared with a horizontal tubular gas aerator. Using an oscillating gas aerator and an oscillating baffle in a raceway pond increased the solution mass-transfer coefficient by 15% and decreased mixing time by 32%; consequently, microalgal biomass yield increased by 19%. PMID:27035474

  10. Numerical investigation of volume of fluid and level set interface capturing methods for bubble growth and detachment

    International Nuclear Information System (INIS)

    The injection of an air bubble in a liquid at rest is an interface flow problem where surface tension and its modeling at solid boundaries is a key factor. It is the subject of this study. Numerical simulations have been performed to study 3D axi-symmetrical bubble growth from an orifice through a horizontal wall. The gas inflow velocity used was sufficiently small to ensure that the bubble growth is quasi-static so that surface tension and buoyancy forces are dominant. The wall was considered non-wettable to avoid spreading of the interface along the wall. The Navier-Stokes equations were solved with two different interface capturing methods based on Volume of Fluid (VOF) and Level Set (LS) as well as coupled CVOFLS. In the VOF method the bubble interface was tracked using either an algebraic solver which results in some diffusion of the interface (compressive scheme implemented in OpenFOAM), or it was determined using a geometric reconstruction scheme (Geo-Reconstruct Scheme from Fluent). The TransAT code was used for the LS model which captures the interface using signed distance function. The bubble volume and center of gravity have been investigated during the growth using the three solvers and numerical results have been assessed against experimental data. These results have shown that reconstructing the interface using the LS method gives good agreement with the experiments. In VOF (compressive scheme), the bubble detaches at earlier times resulting in a smaller detachment volume. The coupled CVOFLS-GeoReconstruct was found to be more computationally expensive than the VOF-GeoReconstruct and to present bubble oscillation during the growth.

  11. Molecular dynamics simulation of the formation, growth and bursting of bubbles in tungsten exposed to high fluxes of low energy deuterium

    International Nuclear Information System (INIS)

    Molecular dynamics simulations are carried out to investigate the formation, growth and bursting of bubbles in tungsten exposed to the irradiation of an extremely high deuterium flux. It is found that the bubbles form in the region near the location of the implanted ion distribution peaks, and that the effect of the substrate temperature on the bubble formation depth is negligible; it is also found that the percentage of deuterium that is found in D2 molecules increases as the bubble grows, and that the evolution of the bubble’s internal pressure is strongly associated with the properties of its surrounding structure. The simulations display the development of a dome-shaped structure at the tungsten surface during the bubble growth. The merging of two deuterium bubbles is also observed. The present simulations also show that the bubble bursts by generating a partially opened lid, which has already been observed in previous independent experiments

  12. Numerical simulation of the bubble growth due to hydrogen isotopes inventory processes in plasma-irradiated tungsten

    International Nuclear Information System (INIS)

    Hydrogen isotopes (HI) inventory is a key issue for fusion devices like ITER. It is especially urgent to understand how HI are retained in tungsten since it currently is the most important candidate material for the plasma-facing wall. Bubble growth is an important experimental complication that yet prevents a full understanding of HI retention processes in tungsten walls and most critically the divertor elements. In this work, we develop a model based on rate equations, which includes the bubble growth in tungsten being exposed to a HI plasma. In the model, HI molecules can be produced through recombination processes on the inner surface of a bubble, and HI molecules can also dissociate themselves to solute atoms, and the latter diffuse into the bulk wall because of very high pressures inside the bubble. The present model is applied to simulate how HI are retained in plasma-irradiated tungsten in the form of molecules to explain the wall temperature, trap concentration, incident HI flux and fluence dependencies of bubble growth

  13. The growth and collapse of transient bubbles in an inviscid fluid

    Institute of Scientific and Technical Information of China (English)

    Yue-binCAI; Chuan-jingLU; 等

    1996-01-01

    The potential flow problem of transient motion of bubbles is studied using the hydrid boundary-finite element method with the boundary discretized by squadratic elements.The interaction of bubbles with a free surface and the interaction between bubbles are presented.

  14. Growth and Collapse of a Single Bubble near a Plate by Spark Discharge in Water

    Science.gov (United States)

    Akcam, I.; Inaba, K.; Takahashi, K.; Kishimoto, K.

    2015-12-01

    Single bubble dynamics in the vicinity of a solid boundary submerged in water were studied experimentally. Single bubble inside a water tank was generated by a spark discharge of capacitor into a couple of copper wires closing a simple circuit. A circular polycarbonate plate was placed horizontally above the bubble creation site. Polycarbonate plates with two different thicknesses were tested by changing the distance between the plate and the creation site. The effects of distance to the wall and wall thickness on the bubble motion is observed by considering the fluid-structure interaction. It is shown that motion of the two boundaries during the bubble generation differ from each other. Jetting behavior of two cases is also different.

  15. Modeling of helium bubble nucleation and growth in austenitic stainless steels using an Object Kinetic Monte Carlo method

    Energy Technology Data Exchange (ETDEWEB)

    De Backer, A., E-mail: andree.debacker@ccfe.ac.uk [UMET, UMR 8207, Université Lille 1, Villeneuve d’Ascq (France); CCFE, Culham Centre for Fusion Energy, Abingdon, Oxon (United Kingdom); Adjanor, G.; Domain, C.; Lescoat, M.L. [EDF R& D, MMC Centre des Renardières, Moret-sur-Loing (France); Jublot-Leclerc, S.; Fortuna, F.; Gentils, A. [CSNSM, Univ Paris-Sud, CNRS/IN2P3, Orsay (France); Ortiz, C.J. [CIEMAT, Laboratorio Nacional de Fusión por Confinamiento Magnético, Madrid (Spain); Souidi, A. [Université Dr. Tahar Moulay de Saida, Saida (Algeria); Becquart, C.S. [UMET, UMR 8207, Université Lille 1, Villeneuve d’Ascq (France)

    2015-06-01

    Implantation of 10 keV helium in 316L steel thin foils was performed in JANNuS-Orsay facility and modeled using a multiscale approach. Density Functional Theory (DFT) atomistic calculations [1] were used to obtain the properties of He and He-vacancy clusters, and the Binary Collision Approximation based code MARLOWE was applied to determine the damage and He-ion depth profiles as in [2,3]. The processes involved in the homogeneous He bubble nucleation and growth were defined and implemented in the Object Kinetic Monte Carlo code LAKIMOCA [4]. In particular as the He to dpa ratio was high, self-trapping of He clusters and the trap mutation of He-vacancy clusters had to be taken into account. With this multiscale approach, the formation of bubbles was modeled up to nanometer-scale size, where bubbles can be observed by Transmission Electron Microscopy. Their densities and sizes were studied as functions of fluence (up to 5 × 10{sup 19} He/m{sup 2}) at two temperatures (473 and 723 K) and for different sample thicknesses (25–250 nm). It appears that the damage is not only due to the collision cascades but is also strongly controlled by the He accumulation in pressurized bubbles. Comparison with experimental data is discussed and sensible agreement is achieved.

  16. Bubbles and market crashes

    CERN Document Server

    Youssefmir, M; Hogg, T; Youssefmir, Michael; Huberman, Bernardo; Hogg, Tad

    1994-01-01

    We present a dynamical theory of asset price bubbles that exhibits the appearance of bubbles and their subsequent crashes. We show that when speculative trends dominate over fundamental beliefs, bubbles form, leading to the growth of asset prices away from their fundamental value. This growth makes the system increasingly susceptible to any exogenous shock, thus eventually precipitating a crash. We also present computer experiments which in their aggregate behavior confirm the predictions of the theory.

  17. On the driving forces for bubble growth and swelling in MX-type fast breeder fuels

    International Nuclear Information System (INIS)

    After giving a definition of three types of swelling, geometrical, local and microscopic swelling, the in-pile working conditions for MX-type fast breeder fuels are briefly described. The equilibrium and non-equilibrium conditions for fission gas bubbles are summarized and a model for bubble interaction is deduced. On the basis of experimental data a curve Tsub(k)(b) is established. Tsub(k) defines the critical swelling temperature as function of burn-up b at which the transition occurs from microscopic swelling with a low rate of swelling Ssub(M) to local swelling Ssub(Λ) with a high rate. The curve Tsub(k)(b) can be defined as the saturation limit of the fuel matrix with regard to small fission gas bubbles beyond which bubble interaction causes the small bubbles to change into large ones. The implications of the existence of that curve for fuels working under Na-bonding and under He-bonding conditions are briefly discussed. (Auth.)

  18. A mechanical analysis of metallic tritide aging by helium bubble growth

    Energy Technology Data Exchange (ETDEWEB)

    Montheillet, F. [Ecole Nationale Superieure des Mines (SMS), CNRS UMR 5146 (PECM), 158 cours Fauriel, 42023 Saint-Etienne Cedex 2 (France)], E-mail: montheil@emse.fr; Delaplanche, D.; Fabre, A.; Munier, E.; Thiebaut, S. [Commissariat a l' Energie Atomique de Valduc, 21120 Is-sur-Tille (France)

    2008-10-25

    A simple mechanical model is proposed for the aging of a metallic tritide. The material is assumed to be elastic-power law viscoplastic. Part of the helium atoms generated by tritium decay form spherical bubbles that weaken the elastic moduli of the overall material. By contrast, others can be stored in solid solution in the matrix and are likely to increase the moduli. Two variants of the model are compared, assuming either instantaneous or finite rate diffusion of helium. They predict globally similar evolutions of the gas pressure inside the bubbles, the geometrical parameters (bubble radius, overall swelling), as well as the matrix and overall elastic moduli. The results are in good agreement with atomistic calculations of the pressure evolution. Furthermore, recent experimental measurements of the Young modulus changes during aging are better reproduced when He diffusion rate is finite, thus supporting the second variant of the model.

  19. 竖直窄流道内过冷流动沸腾的单汽泡生长模型%Model for single bubble growth of subcooled flow boiling in vertical narrow rectangular channel

    Institute of Scientific and Technical Information of China (English)

    袁德文; 潘良明; 陈德奇

    2009-01-01

    The process of bubble growth on heating wall in subcooled boiling includes the micro-layer evaporation on heating wall and the bubble top coagulation when the bubbles grow to a certain size and emerge into the subcooled mainstream fluid. Based on this consideration, a model for the single bubble growth of subcooled flow boiling in vertical narrow rectangular channel was proposed. Compared with experimental results, the error of the simulation results using the proposed model is less than ?5%. The simulation results indicated that as the wall superheat increases, the bubble growth gets faster, with the subcooled degree of mainstream increases, the bubble growth in later stage would be slowed, with the contact angle increases, the contact radius of the bubble bottom and the wall tension would be strengthened, resulting in faster bubble growth to make the bubble to be flat and more easily exposed to the mainstream. The velocity of mainstream has no significant effects on bubble growth rate.%@@ 引言 沸腾具有极高的换热效率的原因就在于沸腾过程中大量气相对周围液体的扰动.对汽泡形成、生长、脱离等过程机理的了解是理解和优化沸腾换热过程的关键.

  20. Nucleation and growth of hydrogen bubbles on dislocations in tungsten under high flux low energy plasma exposure

    International Nuclear Information System (INIS)

    A new mechanism for the nucleation and growth of hydrogen (H) bubbles on dislocations under plasma exposure of tungsten was recently proposed on the basis of direct ab initio calculations. Density functional theory calculations demonstrated that H atoms are strongly bound to a screw dislocation core and exhibit fast one-dimensional migration along its line. Once the number of hydrogen atoms trapped on a dislocation segment exceeds eight, the emission of a jog occurs thereby converting a pure HN cluster into a HN+1-jog configuration. On the basis of these results a kinetic model was formulated to evaluate the conditions (i.e., range of temperature and flux exposure) for the transformation of pure H clusters into supercritical hydrogen–vacancy clusters attached to the dislocation line. In this work, a parametric study employing the kinetic nucleation model was performed to derive the hydrogen bubble formation energy function that offers the best agreement with available experimental results. The obtained results allow one to rationalize the depth and temperature dependence of the experimentally observed hydrogen deposition after high flux low energy plasma exposure for ITER relevant conditions

  1. Nucleation and growth of hydrogen bubbles on dislocations in tungsten under high flux low energy plasma exposure

    Energy Technology Data Exchange (ETDEWEB)

    Grigorev, Petr [SCK-CEN, Nuclear Materials Science Institute, Boeretang 200, Mol 2400 (Belgium); Ghent University, Department of Applied Physics EA17 FUSION-DC, St. Pietersnieuwstraat, 41 B4, B-9000 Gent (Belgium); Department of Experimental Nuclear Physics K-89, Institute of Physics, Nanotechnology and Telecommunications, St. Petersburg State Polytechnical University, 29 Polytekhnicheskaya Str., 195251 St. Petersburg (Russian Federation); Terentyev, Dmitry [SCK-CEN, Nuclear Materials Science Institute, Boeretang 200, Mol 2400 (Belgium); Dubinko, Vladimir [National Science Center, Kharkov Institute of Physics and Technology, Kharkov 61108 (Ukraine); Bonny, Giovanni [SCK-CEN, Nuclear Materials Science Institute, Boeretang 200, Mol 2400 (Belgium); Van Oost, Guido; Noterdaeme, Jean-Marie [Ghent University, Department of Applied Physics EA17 FUSION-DC, St. Pietersnieuwstraat, 41 B4, B-9000 Gent (Belgium); Zhurkin, Evgeny E. [Department of Experimental Nuclear Physics K-89, Institute of Physics, Nanotechnology and Telecommunications, St. Petersburg State Polytechnical University, 29 Polytekhnicheskaya Str., 195251 St. Petersburg (Russian Federation)

    2015-06-01

    A new mechanism for the nucleation and growth of hydrogen (H) bubbles on dislocations under plasma exposure of tungsten was recently proposed on the basis of direct ab initio calculations. Density functional theory calculations demonstrated that H atoms are strongly bound to a screw dislocation core and exhibit fast one-dimensional migration along its line. Once the number of hydrogen atoms trapped on a dislocation segment exceeds eight, the emission of a jog occurs thereby converting a pure H{sub N} cluster into a H{sub N+1}-jog configuration. On the basis of these results a kinetic model was formulated to evaluate the conditions (i.e., range of temperature and flux exposure) for the transformation of pure H clusters into supercritical hydrogen–vacancy clusters attached to the dislocation line. In this work, a parametric study employing the kinetic nucleation model was performed to derive the hydrogen bubble formation energy function that offers the best agreement with available experimental results. The obtained results allow one to rationalize the depth and temperature dependence of the experimentally observed hydrogen deposition after high flux low energy plasma exposure for ITER relevant conditions.

  2. Science Bubbles

    DEFF Research Database (Denmark)

    Hendricks, Vincent Fella; Pedersen, David Budtz

    2013-01-01

    Much like the trade and trait sof bubbles in financial markets,similar bubbles appear on the science market. When economic bubbles burst, the drop in prices causes the crash of unsustainable investments leading to an investor confidence crisis possibly followed by a financial panic. But when...... bubbles appear in science, truth and reliability are the first victims. This paper explores how fashions in research funding and research management may turn science into something like a bubble economy....

  3. Fuel Performance Experiments and Modeling: Fission Gas Bubble Nucleation and Growth in Alloy Nuclear Fuels

    Energy Technology Data Exchange (ETDEWEB)

    McDeavitt, Sean [Texas A & M Univ., College Station, TX (United States); Shao, Lin [Texas A & M Univ., College Station, TX (United States); Tsvetkov, Pavel [Texas A & M Univ., College Station, TX (United States); Wirth, Brian [Univ. of Tennessee, Knoxville, TN (United States); Kennedy, Rory [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2014-04-07

    Advanced fast reactor systems being developed under the DOE's Advanced Fuel Cycle Initiative are designed to destroy TRU isotopes generated in existing and future nuclear energy systems. Over the past 40 years, multiple experiments and demonstrations have been completed using U-Zr, U-Pu-Zr, U-Mo and other metal alloys. As a result, multiple empirical and semi-empirical relationships have been established to develop empirical performance modeling codes. Many mechanistic questions about fission as mobility, bubble coalescience, and gas release have been answered through industrial experience, research, and empirical understanding. The advent of modern computational materials science, however, opens new doors of development such that physics-based multi-scale models may be developed to enable a new generation of predictive fuel performance codes that are not limited by empiricism.

  4. Fuel Performance Experiments and Modeling: Fission Gas Bubble Nucleation and Growth in Alloy Nuclear Fuels

    International Nuclear Information System (INIS)

    Advanced fast reactor systems being developed under the DOE's Advanced Fuel Cycle Initiative are designed to destroy TRU isotopes generated in existing and future nuclear energy systems. Over the past 40 years, multiple experiments and demonstrations have been completed using U-Zr, U-Pu-Zr, U-Mo and other metal alloys. As a result, multiple empirical and semi-empirical relationships have been established to develop empirical performance modeling codes. Many mechanistic questions about fission as mobility, bubble coalescience, and gas release have been answered through industrial experience, research, and empirical understanding. The advent of modern computational materials science, however, opens new doors of development such that physics-based multi-scale models may be developed to enable a new generation of predictive fuel performance codes that are not limited by empiricism.

  5. Dynamic Bubble Behaviour during Microscale Subcooled Boiling

    Institute of Scientific and Technical Information of China (English)

    WANG Hao; PENG Xiao-Feng; David M.Christopher

    2005-01-01

    @@ Bubble cycles, including initiation, growth and departure, are the physical basis of nucleate boiling. The presentinvestigation, however, reveals unusual bubble motions during subcooled nucleate boiling on microwires 25 orl00μm in diameter. Two types of bubble motions, bubble sweeping and bubble return, are observed in theexperiments. Bubble sweeping describes a bubble moving back and forth along the wire, which is motion parallelto the wire. Bubble return is the bubble moving back to the wire after it has detached or leaping above thewire. Theoretical analyses and numerical simulations are conducted to investigate the driving mechanisms forboth bubble sweeping and return. Marangoni flow from warm to cool regions along the bubble interface is foundto produce the shear stresses needed to drive these unusual bubble movements.

  6. Bubble dielectrophoresis

    Science.gov (United States)

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

    1977-01-01

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

  7. A novel closed system bubble column photobioreactor for detailed characterisation of micro and macroalgal growth

    DEFF Research Database (Denmark)

    Holdt, Susan Løvstad; Christensen, L.; Iversen, J. J.L.

    dissolved oxygen tension and was intended for characterization of photoautotrophic growth. Regulation of temperature was done by cooling and carbon dioxide additions regulated pH. The carbon dioxide addition rate was used to optimize irradiance and thereby optimizing growth conditions. Photosynthetically......La) and fast mixing provided by split and dual sparging. Specific growth rates (SGRs) were measured using both off-line and on-line measurements. The latter was possible, because linear correlation was observed between carbon dioxide addition and optical density, which proves that carbon dioxide addition...... photosynthetic quotients and carbon mass balances were used to validate the system. We have developed a system and presented some data handling tools that provides new information about the growth kinetic of algae....

  8. A novel closed system bubble column photobioreactor for detailed characterisation of micro- and macroalgal growth

    DEFF Research Database (Denmark)

    Holdt, Susan Løvstad; Christensen, L.; Iversen, J. J. L.

    2014-01-01

    was suited for cultivation of algae due to fast gas-to-liquid mass transfer (kLa) and fast mixing provided by split and dual sparging. Specific growth rates (SGRs) were measured using both offline and online measurements. The latter was possible, because rectilinear correlation was observed between...... tools that provide new information about growth kinetics of algae. © 2013 Springer Science+Business Media Dordrecht....

  9. Bubble Combustion

    Science.gov (United States)

    Corrigan, Jackie

    2004-01-01

    A method of energy production that is capable of low pollutant emissions is fundamental to one of the four pillars of NASA s Aeronautics Blueprint: Revolutionary Vehicles. Bubble combustion, a new engine technology currently being developed at Glenn Research Center promises to provide low emissions combustion in support of NASA s vision under the Emissions Element because it generates power, while minimizing the production of carbon dioxide (CO2) and nitrous oxides (NOx), both known to be Greenhouse gases. and allows the use of alternative fuels such as corn oil, low-grade fuels, and even used motor oil. Bubble combustion is analogous to the inverse of spray combustion: the difference between bubble and spray combustion is that spray combustion is spraying a liquid in to a gas to form droplets, whereas bubble combustion involves injecting a gas into a liquid to form gaseous bubbles. In bubble combustion, the process for the ignition of the bubbles takes place on a time scale of less than a nanosecond and begins with acoustic waves perturbing each bubble. This perturbation causes the local pressure to drop below the vapor pressure of the liquid thus producing cavitation in which the bubble diameter grows, and upon reversal of the oscillating pressure field, the bubble then collapses rapidly with the aid of the high surface tension forces acting on the wall of the bubble. The rapid and violent collapse causes the temperatures inside the bubbles to soar as a result of adiabatic heating. As the temperatures rise, the gaseous contents of the bubble ignite with the bubble itself serving as its own combustion chamber. After ignition, this is the time in the bubble s life cycle where power is generated, and CO2, and NOx among other species, are produced. However, the pollutants CO2 and NOx are absorbed into the surrounding liquid. The importance of bubble combustion is that it generates power using a simple and compact device. We conducted a parametric study using CAVCHEM

  10. Bubble puzzles

    NARCIS (Netherlands)

    Lohse, Detlef

    2003-01-01

    With their ubiquitous occurrence in a multitude of fluid systems, bubbles occupy an important place in contemporary science and technology. One can readily cite several examples: the production and transport of oil, in which bubbles are purposely injected to help lift heavy oil to the surface; energ

  11. Bubble, Bubble, Toil and Trouble.

    Science.gov (United States)

    Journal of Chemical Education, 2001

    2001-01-01

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

  12. Cellular Injury of Cardiomyocytes during Hepatocyte Growth Factor Gene Transfection with Ultrasound-Triggered Bubble Liposome Destruction

    Directory of Open Access Journals (Sweden)

    Kazuo Komamura

    2011-01-01

    Full Text Available We transfected naked HGF plasmid DNA into cultured cardiomyocytes using a sonoporation method consisting of ultrasound-triggered bubble liposome destruction. We examined the effects on transfection efficiency of three concentrations of bubble liposome (1×106, 1×107, 1×108/mL, three concentrations of HGF DNA (60, 120, 180 μg/mL, two insonification times (30, 60 sec, and three incubation times (15, 60, 120 min. We found that low concentrations of bubble liposome and low concentrations of DNA provided the largest amount of the HGF protein expression by the sonoporated cardiomyocytes. Variation of insonification and incubation times did not affect the amount of product. Following insonification, cardiomyocytes showed cellular injury, as determined by a dye exclusion test. The extent of injury was most severe with the highest concentration of bubble liposome. In conclusion, there are some trade-offs between gene transfection efficiency and cellular injury using ultrasound-triggered bubble liposome destruction as a method for gene transfection.

  13. Comparison of numerical simulations and laboratory studies of shock waves and cavitation bubble growth produced by optical breakdown in water

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-04-01

    In numerical calculations of idealized bubble dynamics test problems, Los Alamos computational tools perform well. A realistic equation of state must be used and geometrical features must be carefully modeled to simulate experiments accurately. In this work, we compare numerical simulations taking these features into account with experiments performed at the Medizinisches Laserzentrum Lubeck. We compare the measured and calculated positions of the shock front and of the bubble wall as a function of time in the laser optical breakdown of water produced by 30-ps 1-mJ Nd:YAG laser pulses.

  14. Effects of local structure on helium bubble growth in bulk and at grain boundaries of bcc iron: A molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Li [Univ. of Electronic Science and Technology of China, Chengdu (China); Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Gao, Fei [Univ. of Michigan, Ann Arbor, MI (United States); Kurtz, Richard J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Zu, Xiaotao [Univ. of Electronic Science and Technology of China, Chengdu (China); Peng, S. M. [China Academy of Engineering Physics, Mianyang (China); Long, X. G. [China Academy of Engineering Physics, Mianyang (China); Zhou, X. S. [China Academy of Engineering Physics, Mianyang (China)

    2015-07-15

    The nucleation and growth of helium (He) bubbles in the bulk and at Σ3 <110> {112} and Σ73b <110> {661} grain boundaries (GBs) in bcc iron have been investigated using molecular dynamics simulations. The results show that a 1/2 <111> {111} dislocation loop is formed with the sequential collection of <111> interstitial crowdions at the periphery of the He cluster and is eventually emitted from the He cluster. Insertion of 45 He atoms into a He cluster leads to the formation of a 1/2 <111> dislocation loop in Σ3 GB. It is of interest to notice that the transition of a dislocation segment through the GB leads to the formation of a step at the GB plane following the loop formation, accounting for the formation of a residual GB defect. A 1/2 <111> loop, with a {110} habit plane, is emitted with further increase of the He bubble size in the Σ3 GB. In contrast, the sequential insertion of He atoms in Σ73b GB continuously emits self-interstitial atoms (SIAs), but these SIAs rearrange at the core of the inherent GB dislocation, instead of forming a dislocation loop, which leads the GB dislocation to propagate along the [1¯1¯ 1 2] direction. In the bulk and Σ3 GB, the He bubble exhibits three-dimensionally spherical shape, but it forms longitudinal shape along the dislocation line in the Σ73 GB, a shape commonly observed at GBs in experiments.

  15. Exploring Bubbles

    Science.gov (United States)

    O'Geary, Melissa A.

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

  16. Antigravitating bubbles

    CERN Document Server

    Barnaveli, A T; Barnaveli, Andro; Gogberashvili, Merab

    1995-01-01

    We investigate the gravitational behavior of spherical domain walls (bubbles) arising during the phase transitions in the early Universe. In the thin-wall approximation we show the existence of the new solution of Einstein equations with negative gravitational mass of bubbles and the reversed direction of time flow on the shell. This walls exhibit gravitational repulsion just as the planar walls are assumed to do. The equilibrium radius and critical mass of such objects are found for realistic models.

  17. Noise Bubbles

    OpenAIRE

    Mario Forni; Luca Gambetti; Marco Lippi; Luca Sala

    2014-01-01

    We introduce noisy information into a standard present value stock price model. Agents receive a noisy signal about the structural shock driving future dividend variations. The resulting equilibrium stock price includes a transitory component — the "noise bubble" — which can be responsible for boom and bust episodes unrelated to economic fundamentals. We propose a non-standard VAR procedure to estimate the structural shock and the "noise" shock, their impulse response functions and the bubble...

  18. Bubbling away

    International Nuclear Information System (INIS)

    Bubble chambers may have almost vanished from the front line of physics research, but the vivid memory of their intricate and sometimes beautiful patterns of particle tracks lives on, and has greatly influenced the computer graphics of track reconstruction in today's big experiments. 'Seeing' an interaction makes it more understandable. Bubble chambers, with their big collaborations of physicists from many widely scattered research institutes, started another ball rolling. The groups formed are even now only surpassed in size by the big collaborations working on today's major detectors at colliding beam machines. From 14-16 July, about 130 physicists gathered at CERN to commemorate the 40th anniversary of the invention of the bubble chamber by Donald Glaser. The meeting, organized by Derek C. Colley from Birmingham, gave a comprehensive overview of bubble chamber contributions to physics, their challenging technology, and the usefulness of bubble chamber photographs in education, both for physics and the public at large. After opening remarks by CERN Director Carlo Rubbia, Donald Glaser began with a brief review of the work which led to his invention - there was much more to it than idly watching beer bubbles rise up the wall of the glass - before turning to his present line of research, biophysics, also very visually oriented

  19. The Temperature Dependence of Void and Bubble Formation and Growth in Aluminium during 600 MeV Proton Irradiation

    DEFF Research Database (Denmark)

    Victoria, M.; Green, W.V; Singh, Bachu Narain; Leffers, Torben

    observed at temperatures above 160° C. At all temperatures, irradiation induced dislocations have been observed, most of them linked to bubbles. At higher temperatures and doses, clear evidence of irradiation induced precipitation has been observed; the precipitates are normally decorated with helium...

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

    Science.gov (United States)

    Crews, Jackson B.; Cooper, Clay A.

    2014-09-01

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

  1. Aspherical bubble dynamics and oscillation times

    Energy Technology Data Exchange (ETDEWEB)

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

    1999-03-01

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

  2. Bubbling Threat

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    The shift of China’s monetary policy stance from "moderately loose" to "prudent" in 2011 indicates curbing inflation and asset bubbles have become the Central Government’s top priority. But is China’s bubble problem short-term or long-term? Is it only monetary or related to economic structure? Is it the cause of China’s economic imbalance or the result? And what kind of deep-rooted problems in the macro economy does it reflect? All these questions call for deep thought,said Zhang Monan,a

  3. 经济增长泡沫的测度--三变量模型与虚拟经济研究%The Measurement of Bubble Economy Growth--Three Variables Model and the Study in Virtual Economy

    Institute of Scientific and Technical Information of China (English)

    毛善成

    2015-01-01

    虚拟经济对经济增长的贡献率等于经济增长泡沫多少的相对测度。利用三变量模型估算了泰国和中国的经济增长泡沫,从而给出1997年亚洲金融风暴首先在泰国爆发的原因,1986~1998年泰国经济增长中有40%的经济泡沫是发生金融危机的数量基础,接下来泰国经济进入了去泡沫发展周期,1999~2010年经济增长只有不足2%的泡沫。作为比较,美国1992~2001年经济增长有三分之一为泡沫,进入21世纪后泡沫继续扩大终于2007破灭。中国2000~2009年经济增长的24%为增长泡沫,2009年增加4万亿刺激计划,其M2已从2009年的60万亿增加到2014年上半年的120万亿,估计中国2009~2014经济增长的30%~40%为增长泡沫,所以中国发生房地产泡沫破灭的危险已接近40%这根临界线。%Rates of virtual economy’s making a contributions to GDP growth is equal to the measurement of bubble economy growth. By three variables model,we estimated the bubble economy growth in Thailand and China, and we found out the origin of 1997 Asia financial crisis starting in Thailand. There was 40% bubble economy growth in Thailand’s economic growth in1986~1998, being a root of financial crisis occurrence. There was lack 2% bubble economy in Thailand’s economic growth in 1999~2010, an eliminating bubble economy cycle. Moreover, there was 1/3 bubble economy in America’s economic growth in 1992~2001, the bubble kept on enlarging in 21century and broke in 2007. There was 24% bubble economy growth in China’s economic growth in 2000~2009, China increased 4 hundreds of millions to stimulate economic growth in 2009, M2 was 60 hundreds of millions in 2009 to 120 hundreds of millions in six 2014, so we estimated that China’s bubble economy growth was 30%~40% and had approximated the critical line of 40% bubble econo-my, so there is a risk that China’s bubble real estate will break soon.

  4. Bubble drag reduction requires large bubbles

    CERN Document Server

    Verschoof, Ruben A; Sun, Chao; Lohse, Detlef

    2016-01-01

    In the maritime industry, the injection of air bubbles into the turbulent boundary layer under the ship hull is seen as one of the most promising techniques to reduce the overall fuel consumption. However, the exact mechanism behind bubble drag reduction is unknown. Here we show that bubble drag reduction in turbulent flow dramatically depends on the bubble size. By adding minute concentrations (6 ppm) of the surfactant Triton X-100 into otherwise completely unchanged strongly turbulent Taylor-Couette flow containing bubbles, we dramatically reduce the drag reduction from more than 40% to about 4%, corresponding to the trivial effect of the bubbles on the density and viscosity of the liquid. The reason for this striking behavior is that the addition of surfactants prevents bubble coalescence, leading to much smaller bubbles. Our result demonstrates that bubble deformability is crucial for bubble drag reduction in turbulent flow and opens the door for an optimization of the process.

  5. Ostwald ripening in multiple-bubble nuclei

    Science.gov (United States)

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

    2014-12-01

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

  6. Ostwald Ripening in Multiple-Bubble Nuclei

    CERN Document Server

    Watanabe, Hiroshi; Inaoka, Hajime; Ito, Nobuyasu

    2014-01-01

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

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

    Science.gov (United States)

    Crews, Jackson B.

    Visualization experiments, core-scale laboratory experiments, and numerical simulations were conducted to examine the transient effect of dilational seismic wave propagation on pore fluid pressure in aquifers hosting groundwater that is near saturation with respect to dissolved carbon dioxide (CO2) gas. Groundwater can become charged with dissolved CO2 through contact with gas-phase CO2 in the Earth's crust derived from magma degasing, metamorphism, and biogenic processes. The propagation of dilational seismic waves (e.g., Rayleigh and p-waves) causes oscillation of the mean normal confining stress and pore fluid pressure. When the amplitude of the pore fluid pressure oscillation is large enough to drive the pore fluid pressure below the bubble pressure, an aqueous-to-gas-phase transition can occur in the pore space, which causes a buildup of pore fluid pressure and reduces the inter-granular effective stress under confined conditions. In visualization experiments conducted in a Hele-Shaw cell representing a smooth-walled, vertically oriented fracture, millisecond-scale pressure perturbations triggered bubble nucleation and growth lasting tens of seconds, with resulting pore fluid overpressure proportional to the magnitude of the pressure perturbation. In a Berea sandstone core flooded with initially under-saturated aqueous CO2 under conditions representative of a confined aquifer, rapid reductions in confining stress triggered transient pore pressure rise up to 0.7 MPa (100 psi) overpressure on a timescale of ~10 hours. The rate of pore pressure buildup in the first 100 seconds was proportional to the saturation with respect to dissolved CO 2 at the pore pressure minimum. Sinusoidal confining stress oscillations on a Berea sandstone core produced excess pore fluid pressure after the oscillations were terminated. Confining stress oscillations in the 0.1-0.4 MPa (15-60 psi) amplitude range and 0.05-0.30 Hz frequency band increased the pore fluid pressure by 13-60 cm

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

    Science.gov (United States)

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

    1995-01-01

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

  9. Measuring the surface tension of soap bubbles

    Science.gov (United States)

    Sorensen, Carl D.

    1992-01-01

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

  10. Nonlinear bubble nucleation and growth following filament and white-light continuum generation induced by a single-shot femtosecond laser pulse into dielectrics based on consideration of the time scale

    International Nuclear Information System (INIS)

    Bubble nucleation and growth following plasma channeling (filament) and white-light continuum in liquid irradiated by a single-shot fs-pulse were experimentally investigated with close observation of the time scale. Making full use of a new confocal system and time-resolved visualization techniques, we obtained evidence suggestive of a major/minor role of the non-linear/thermal effects during the fs-pulse-induced bubble's fountainhead (10−13 s) and growth (10−7 s), which was never observed with the use of the ns-pulse (i.e., optic cavitation). In this context, the fs-pulse-induced bubble is not an ordinary optic cavitation but rather is nonlinear-optic cavitation. We present the intrinsic differences in the dominant-time domain of the fs-pulse and ns-pulse excitation, and intriguingly, a mere hundred femtoseconds' excitation predetermines the size of the bubble appearing several microseconds after irradiation. That is, the nucleation happens temporally beyond a six-order-of-magnitude difference

  11. Nucleation, growth and transport modelling of helium bubbles under nuclear irradiation in lead–lithium with the self-consistent nucleation theory and surface tension corrections

    Energy Technology Data Exchange (ETDEWEB)

    Fradera, J., E-mail: jfradera@ubu.es; Cuesta-López, S., E-mail: scuesta@ubu.es

    2013-12-15

    Highlights: • The work presented in this manuscript provides a reliable computational tool to quantify the He complex phenomena in a HCLL. • A model based on the self-consistent nucleation theory (SCT) is exposed. It includes radiation induced nucleation modelling and surface tension corrections. • Results informed reinforce the necessity of conducting experiments to determine nucleation conditions and bubble transport parameters in LM breeders. • Our findings and model provide a good qualitative insight into the helium nucleation phenomenon in LM systems for fusion technology and can be used to identify key system parameters. -- Abstract: Helium (He) nucleation in liquid metal breeding blankets of a DT fusion reactor may have a significant impact regarding system design, safety and operation. Large He production rates are expected due to tritium (T) fuel self-sufficiency requirement, as both, He and T, are produced at the same rate. Low He solubility, local high concentrations, radiation damage and fluid discontinuities, among other phenomena, may yield the necessary conditions for He nucleation. Hence, He nucleation may have a significant impact on T inventory and may lower the T breeding ratio. A model based on the self-consistent nucleation theory (SCT) with a surface tension curvature correction model has been implemented in OpenFOAM{sup ®} CFD code. A modification through a single parameter of the necessary nucleation condition is proposed in order to take into account all the nucleation triggering phenomena, specially radiation induced nucleation. Moreover, the kinetic growth model has been adapted so as to allow for the transition from a critical cluster to a macroscopic bubble with a diffusion growth process. Limitations and capabilities of the models are shown by means of zero-dimensional simulations and sensitivity analyses to key parameters under HCLL breeding unit conditions. Results provide a good qualitative insight into the helium

  12. Nucleation, growth and transport modelling of helium bubbles under nuclear irradiation in lead–lithium with the self-consistent nucleation theory and surface tension corrections

    International Nuclear Information System (INIS)

    Highlights: • The work presented in this manuscript provides a reliable computational tool to quantify the He complex phenomena in a HCLL. • A model based on the self-consistent nucleation theory (SCT) is exposed. It includes radiation induced nucleation modelling and surface tension corrections. • Results informed reinforce the necessity of conducting experiments to determine nucleation conditions and bubble transport parameters in LM breeders. • Our findings and model provide a good qualitative insight into the helium nucleation phenomenon in LM systems for fusion technology and can be used to identify key system parameters. -- Abstract: Helium (He) nucleation in liquid metal breeding blankets of a DT fusion reactor may have a significant impact regarding system design, safety and operation. Large He production rates are expected due to tritium (T) fuel self-sufficiency requirement, as both, He and T, are produced at the same rate. Low He solubility, local high concentrations, radiation damage and fluid discontinuities, among other phenomena, may yield the necessary conditions for He nucleation. Hence, He nucleation may have a significant impact on T inventory and may lower the T breeding ratio. A model based on the self-consistent nucleation theory (SCT) with a surface tension curvature correction model has been implemented in OpenFOAM® CFD code. A modification through a single parameter of the necessary nucleation condition is proposed in order to take into account all the nucleation triggering phenomena, specially radiation induced nucleation. Moreover, the kinetic growth model has been adapted so as to allow for the transition from a critical cluster to a macroscopic bubble with a diffusion growth process. Limitations and capabilities of the models are shown by means of zero-dimensional simulations and sensitivity analyses to key parameters under HCLL breeding unit conditions. Results provide a good qualitative insight into the helium nucleation

  13. Influence of the nucleation surface inclination on heat transfers and on the growth dynamics of a steam bubble; Influence de l'inclinaison de la surface de nucleation sur les transferts de chaleur et la dynamique de croissance d'une bulle de vapeur

    Energy Technology Data Exchange (ETDEWEB)

    Barthes, M.; Reynard, Ch.; Santini, R.; Tadrist, L. [Institut Universitaire des Systemes Thermiques Industriels - CNRS UMR 6595, 13 - Marseille (France)

    2006-07-01

    The influence of the inclination of the nucleation surface on heat and mass transfers and on the growth dynamics of a single steam bubble is experimentally studied. The bubble is created beneath a wall with an imposed heating flux. The evolution of geometrical bubble parameters and of the frequency of emission with respect to the inclination angle are presented. The total heat flux measurements are compared to the evaporation fluxes determined by image processing. Contrary to the evaporation flux, the total flux is conditioned by the inclination and thus is correlated to the frequency of bubbles emission. (J.S.)

  14. Modelling of microalgal growth and lipid production in Dunaliella tertiolecta using nitrogen-phosphorus-potassium fertilizer medium in sintered disk chromatographic glass bubble column.

    Science.gov (United States)

    Kumar, Anup; Guria, Chandan; Chitres, G; Chakraborty, Arunangshu; Pathak, A K

    2016-10-01

    A comprehensive mathematical model involving NPK-10:26:26 fertilizer, NaCl, NaHCO3, light and temperature operating variables for Dunaliella tertiolecta cultivation is formulated to predict microalgae-biomass and lipid productivity. Proposed model includes Monod/Andrews kinetics for the absorption of essential nutrients into algae-biomass and Droop model involving internal nutrient cell quota for microalgae growth, assuming algae-biomass is composed of sugar, functional-pool and neutral-lipid. Biokinetic model parameters are determined by minimizing the residual-sum-of-square-errors between experimental and computed microalgae-biomass and lipid productivity using genetic algorithm. Developed model is validated with the experiments of Dunaliella tertiolecta cultivation using air-agitated sintered-disk chromatographic glass-bubble column and the effects of operating variables on microalgae-biomass and lipid productivity is investigated. Finally, parametric sensitivity analysis is carried out to know the sensitivity of model parameters on the obtained results in the input parameter space. Proposed model may be helpful in scale-up studies and implementation of model-based control strategy in large-scale algal cultivation. PMID:27450983

  15. Fama on Bubbles

    DEFF Research Database (Denmark)

    Engsted, Tom

    2016-01-01

    While Eugene Fama has repeatedly expressed his discontent with the notion of an “irrational bubble,” he has never publicly expressed his opinion on “rational bubbles.” On empirical grounds Fama rejects bubbles by referring to the lack of reliable evidence that price declines are predictable....... However, this argument cannot be used to rule out rational bubbles because such bubbles do not necessarily imply return predictability, and return predictability of the kind documented by Fama does not rule out rational bubbles. On data samples that include the 1990s, there is evidence of an explosive...

  16. Fama on bubbles

    DEFF Research Database (Denmark)

    Engsted, Tom

    Eugene Fama has repeatedly expressed his discontent with the notion of an irrational bubble. However, he has never publicly expressed his opinion on rational bubbles. This is peculiar since such bubbles build naturally from the rational efficient markets paradigm that Fama strongly adheres to....... On empirical grounds Fama rejects bubbles by referring to the lack of reliable evidence that price declines are predictable. However, this argument cannot be used to rule out rational bubbles because such bubbles do not necessarily imply return predictability. On data samples that include the 1990s...

  17. Soap Bubbles and Logic.

    Science.gov (United States)

    Levine, Shellie-helane; And Others

    1986-01-01

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

  18. Preheating in Bubble Collision

    CERN Document Server

    Zhang, Jun

    2010-01-01

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

  19. Steady State Vapor Bubble in Pool Boiling

    Science.gov (United States)

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

    2016-02-01

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

  20. Steady State Vapor Bubble in Pool Boiling.

    Science.gov (United States)

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

    2016-01-01

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

  1. A physiological model of the interaction between tissue bubbles and the formation of blood-borne bubbles under decompression

    International Nuclear Information System (INIS)

    Under decompression, bubbles can form in the human body, and these can be found both within the body tissues and the bloodstream. Mathematical models for the growth of both types of bubbles have previously been presented, but they have not been coupled together. This work thus explores the interaction between the growth of tissue and blood-borne bubbles under decompression, specifically looking at the extent to which they compete for the common resource of inert gas held in solution in the tissues. The influence of tissue bubbles is found to be significant for densities as low as 10 ml-1 for tissues which are poorly perfused. However, the effects of formation of bubbles in the blood are not found until the density of bubble production sites reaches 106 ml-1. From comparison of the model predictions with experimental evidence for bubbles produced in animals and man under decompression, it is concluded that the density of tissue bubbles is likely to have a significant effect on the number of bubbles produced in the blood. However, the density of nucleation sites in the blood is unlikely to be sufficiently high in humans for the formation of bubbles in the blood to have a significant impact on the growth of the bubbles in the tissue

  2. Dynamical viscosity of nucleating bubbles

    CERN Document Server

    Alamoudi, S M; Boyanovsky, D; Aragão de Carvalho, C; Fraga, E S; Jorás, S E; Takakura, F I

    1999-01-01

    We study the viscosity corrections to the growth rate of nucleating bubbles in a first order phase transition in scalar field theory. We obtain the non-equilibrium equation of motion of the coordinate that describes small departures from the critical bubble and extract the growth rate consistently in weak coupling and in the thin wall limit. Viscosity effects arise from the interaction of this coordinate with the stable quantum and thermal fluctuations around a critical bubble. In the case of 1+1 dimensions we provide an estimate for the growth rate that depends on the details of the free energy functional. In 3+1 dimensions we recognize robust features that are a direct consequence of the thin wall approximation and give the leading viscosity corrections.These are long-wavelength hydrodynamic fluctuations that describe surface waves, quasi-Goldstone modes which are related to ripples on interfaces in phase ordered Ising-like systems. We discuss the applicability of our results to describe the growth rate of ...

  3. Bubbles tomorrow and bubbles yesterday, but never bubbles today?

    OpenAIRE

    Williams, John C.

    2013-01-01

    Standard asset price models have generally failed to detect bubbles, with enormous costs to the economy. Economists are now creating promising new models that account for bubbles by relaxing the assumption of rational expectations and allowing people’s decisions to be driven by their perceptions of what the future may hold. ; This letter is adapted from a presentation by the president and CEO of the Federal Reserve Bank of San Francisco to the National Association for Business Economics in Sa...

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

    Science.gov (United States)

    Yamakoshi, Yoshiki; Koganezawa, Masato

    2005-06-01

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

  5. Effects of 600 MeV proton irradiation on nucleation and growth of precipitates and helium bubbles in a high-purity Al-Mg-Si alloy

    DEFF Research Database (Denmark)

    Singh, Bachu Narain; Leffers, Torben; Victoria, M.; Green, W. V.; Gavillet, D.

    Solution treated specimens of a high-purity Al-0.75%Mg-0.42%Si alloy were irradiated with 600 MeV protons at 150 and 240°C to a dose level of 0.47 and 0.55 dpa, respectively. Mg2Si-type precipitates formed during irradiation at 150 and 240°C; at 240°C, however, a large number of precipitates seem...... to have dissolved during the later stages of irradiation. Thermally aged reference specimens have also been investigated. The needle-shaped precipitates in the aged and the irradiated specimens lie along the 〈100〉 matrix directions. At 150°C bubbles were observed only at grain boundaries whereas at...... 240°C bubbles were seen in the grain interior as well as at the grain boundaries. Long rows of bubbles were observed with the same orientation in the matrix as the precipitate needles. Grain boundary bubbles were found to grow faster in the Al-Mg-Si alloy than in the high-purity aluminium...

  6. Tribonucleation of bubbles

    CERN Document Server

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

    2016-01-01

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

  7. A critical review of physiological bubble formation in hyperbaric decompression.

    Science.gov (United States)

    Papadopoulou, Virginie; Eckersley, Robert J; Balestra, Costantino; Karapantsios, Thodoris D; Tang, Meng-Xing

    2013-05-01

    Bubbles are known to form in the body after scuba dives, even those done well within the decompression model limits. These can sometimes trigger decompression sickness and the dive protocols should therefore aim to limit bubble formation and growth from hyperbaric decompression. Understanding these processes physiologically has been a challenge for decades and there are a number of questions still unanswered. The physics and historical background of this field of study is presented and the latest studies and current developments reviewed. Heterogeneous nucleation is shown to remain the prime candidate for bubble formation in this context. The two main theories to account for micronuclei stability are then to consider hydrophobicity of surfaces or tissue elasticity, both of which could also explain some physiological observations. Finally the modeling relevance of the bubble formation process is discussed, together with that of bubble growth as well as multiple bubble behavior. PMID:23523006

  8. Inexperienced Investors and Bubbles

    OpenAIRE

    Robin Greenwood; Stefan Nagel

    2008-01-01

    We use mutual fund manager data from the technology bubble to examine the hypothesis that inexperienced investors play a role in the formation of asset price bubbles. Using age as a proxy for managers' investment experience, we find that around the peak of the technology bubble, mutual funds run by younger managers are more heavily invested in technology stocks, relative to their style benchmarks, than their older colleagues. Furthermore, young managers, but not old managers, exhibit trend-ch...

  9. Sonoluminescence and bubble fusion

    OpenAIRE

    Arakeri, Vijay H

    2003-01-01

    Sonoluminescence (SL), the phenomenon of light emission from nonlinear motion of a gas bubble, involves an extreme degree of energy focusing. The conditions within the bubble during the last stages of the nearly catastrophic implosion are thought to parallel the efforts aimed at developing inertial confinement fusion. A limited review on the topic of SL and its possible connection to bubble nuclear fusion is presented here. The emphasis is on looking for a link between the various forms o...

  10. Sonochemistry and bubble dynamics.

    Science.gov (United States)

    Mettin, Robert; Cairós, Carlos; Troia, Adriano

    2015-07-01

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

  11. Bubble and drop interfaces

    CERN Document Server

    Miller

    2011-01-01

    The book aims at describing the most important experimental methods for characterizing liquid interfaces, such as drop profile analysis, bubble pressure and drop volume tensiometry, capillary pressure technique, and oscillating drops and bubbles. Besides the details of experimental set ups, also the underlying theoretical basis is presented in detail. In addition, a number of applications based on drops and bubbles is discussed, such as rising bubbles and the very complex process of flotation. Also wetting, characterized by the dynamics of advancing contact angles is discussed critically. Spec

  12. In Situ Measurement of Local Hydrogen Production Rate by Bubble-Evolved Recording

    OpenAIRE

    Xiaowei Hu; Liejin Guo; Yechun Wang

    2013-01-01

    Hydrogen visibly bubbles during photocatalytic water splitting under illumination with above-bandgap radiation, which provides a direct measurement of local gas-evolving reaction rate. In this paper, optical microscopy of superfield depth was used for recording the hydrogen bubble growth on Cd0.5Zn0.5S photocatalyst in reaction liquid and illuminated with purple light. By analyzing change of hydrogen bubble size as a function of time, we understood that hydrogen bubble growth experienced two ...

  13. Prediction of bubble detachment diameter in flow boiling based on force analysis

    International Nuclear Information System (INIS)

    Highlights: ► All the forces acting on the growing bubbles are taken into account in the model. ► The bubble contact diameter has significant effect on bubble detachment. ► Bubble growth force and surface tension are more significant in narrow channel. ► A good agreement between the predicted and the measured results is achieved. - Abstract: Bubble detachment diameter is one of the key parameters in the study of bubble dynamics and boiling heat transfer, and it is hard to be measured in a boiling system. In order to predict the bubble detachment diameter, a theoretical model is proposed based on forces analysis in this paper. All the forces acting on a bubble are taken into account to establish a model for different flow boiling configurations, including narrow and conventional channels, upward, downward and horizontal flows. A correlation of bubble contact circle diameter is adopted in this study, and it is found that the bubble contact circle diameter has significant effect on bubble detachment. A new correlation taking the bubble contact circle diameter into account for the evaluation of bubble growth force is proposed in this study, and it is found that the bubble growth force and surface tension force are more significant in narrow channel when comparing with that in conventional channel. A visual experiment was carried out in order to verify present model; and the experimental data from published literature are used also. A good agreement between predicted and measured results is achieved.

  14. Prospects for bubble fusion

    Energy Technology Data Exchange (ETDEWEB)

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

    1995-09-01

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

  15. Understanding the bubbles

    DEFF Research Database (Denmark)

    Turcan, Romeo V.

    prospects of a new venture and intended outcomes of that new venture; the higher the residue, the higher the likelihood of the bubble emergence; as residue increases, the likelihood of bubble burst increases. One question that arises is whether one can manage the hype, hence the residue. In this, it is...

  16. Tribonucleation of bubbles

    NARCIS (Netherlands)

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

    2014-01-01

    We report on the nucleation of bubbles on solids that are gently rubbed against each other in a liquid. The phenomenon is found to depend strongly on the material and roughness of the solid surfaces. For a given surface, temperature, and gas content, a trail of growing bubbles is observed if the rub

  17. Bubbles in graphene

    DEFF Research Database (Denmark)

    Settnes, Mikkel; Power, Stephen; Lin, Jun;

    2015-01-01

    Strain-induced deformations in graphene are predicted to give rise to large pseudomagnetic fields. We examine theoretically the case of gas-inflated bubbles to determine whether signatures of such fields are present in the local density of states. Sharp-edged bubbles are found to induce Friedel...

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

    Science.gov (United States)

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

    2015-10-01

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

  19. Assisted heterogeneous multinucleation and bubble growth in semicrystalline ethylene-vinyl acetate copolymer/expanded graphite nanocomposite foams: Control of morphology and viscoelastic properties

    Directory of Open Access Journals (Sweden)

    O. Yousefzade

    2015-10-01

    Full Text Available Nanocomposite foams of ethylene-vinyl acetate copolymer (EVA reinforced by expanded graphite (EG were prepared using supercritical nitrogen in batch foaming process. Effects of EG particle size, crosslinking of EVA chains and foaming temperature on the cell morphology and foam viscoelastic properties were investigated. EG sheet surface interestingly provide multiple heterogeneous nucleation sites for bubbles. This role is considerably intensified by incorporating lower loadings of EG with higher aspect ratio. The amorphous and non-crosslinked domains of EVA matrix constitute denser bubble areas. Higher void fraction and more uniform cell structure is achieved for non-crosslinked EVA/EG nanocomposites foamed at higher temperatures. With regard to the structural variation, the void fraction of foam samples decreases with increasing the EG content. Storage and loss moduli were analyzed to study the viscoelastic properties of nanocomposite foams. Surprisingly, the foaming process of EVA results in a drastic reduction in loss and storage moduli regardless of whether the thermoplastic matrix contains EG nanofiller or not. For the EVA/EG foams with the same composition, the nanocomposite having higher void fraction shows relatively lower loss modulus and more restricted molecular movements. The study findings have verified that the dynamics of polymer chains varies after foaming EVA matrix in the presence of EG.

  20. Rotating bubble membrane radiator

    Science.gov (United States)

    Webb, Brent J.; Coomes, Edmund P.

    1988-12-06

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

  1. Boiling crisis as inhibition of bubble detachment by the vapor recoil force

    International Nuclear Information System (INIS)

    Boiling crisis is a transition between nucleate and film boiling. In this communication we present a physical model of the boiling crisis based on the vapor recoil effect. Our numerical simulations of the thermally controlled bubble growth at high heat fluxes show how the bubble begins to spread over the heater thus forming a germ for the vapor film. The vapor recoil force not only causes the vapor spreading, it also creates a strong adhesion to the heater that prevents the bubble departure, thus favoring the further bubble spreading. Near the liquid-gas critical point, the bubble growth is very slow and allows the kinetics of the bubble spreading to be observed. Since the surface tension is very small in this regime, only microgravity conditions can preserve a convex bubble shape. Under such conditions, we observed an increase of the apparent contact angle and spreading of the dry spot under the bubble, thus confirming our model of the boiling crisis. (authors)

  2. Boiling crisis as inhibition of bubble detachment by the vapor recoil force

    CERN Document Server

    Nikolayev, Vadim; Garrabos, Yves

    2016-01-01

    Boiling crisis is a transition between nucleate and film boiling. In this communication we present a physical model of the boiling crisis based on the vapor recoil effect. Our numerical simulations of the thermally controlled bubble growth at high heat fluxes show how the bubble begins to spread over the heater thus forming a germ for the vapor film. The vapor recoil force not only causes the vapor spreading, it also creates a strong adhesion to the heater that prevents the bubble departure, thus favoring the further bubble spreading. Near the liquid-gas critical point, the bubble growth is very slow and allows the kinetics of the bubble spreading to be observed. Since the surface tension is very small in this regime, only microgravity conditions can preserve a convex bubble shape. Under such conditions, we observed an increase of the apparent contact angle and spreading of the dry spot under the bubble, thus confirming our model of the boiling crisis.

  3. Bubble Collision in Curved Spacetime

    International Nuclear Information System (INIS)

    We study vacuum bubble collisions in curved spacetime, in which vacuum bubbles were nucleated in the initial metastable vacuum state by quantum tunneling. The bubbles materialize randomly at different times and then start to grow. It is known that the percolation by true vacuum bubbles is not possible due to the exponential expansion of the space among the bubbles. In this paper, we consider two bubbles of the same size with a preferred axis and assume that two bubbles form very near each other to collide. The two bubbles have the same field value. When the bubbles collide, the collided region oscillates back-and-forth and then the collided region eventually decays and disappears. We discuss radiation and gravitational wave resulting from the collision of two bubbles

  4. Bubble chamber: antiproton annihilation

    CERN Multimedia

    1971-01-01

    These images show real particle tracks from the annihilation of an antiproton in the 80 cm Saclay liquid hydrogen bubble chamber. A negative kaon and a neutral kaon are produced in this process, as well as a positive pion. The invention of bubble chambers in 1952 revolutionized the field of particle physics, allowing real tracks left by particles to be seen and photographed by expanding liquid that had been heated to boiling point.

  5. A Gold Bubble?

    OpenAIRE

    Dirk G Baur; Kristoffer Glover

    2012-01-01

    In this paper we use a test developed by Phillips et al. (2011) to identify a bubble in the gold market. We find that the price of gold followed an explosive price process between 2002 and 2012 interrupted only briefly by the subprime crisis in 2008. We also provide a theoretical foundation for such bubble tests based on a behavioural model of heterogeneous agents and demonstrate that periods of explosive price behaviour are consistent with increased chartist activity in the gold market. The ...

  6. CONDITIONS FOR BUBBLE FORMATION

    OpenAIRE

    Joffe, M

    2010-01-01

    A bubble is typically defined as ìtrade in high volume at prices that are considerably at variance from intrinsic valueî, which is compatible both with higher or lower prices, whereas the metaphor suggests something asymmetric that gradually inflates rather than deflates. Whether bubbles are symmetric or not is an empirical question; the historical record appears to be that they are asymmetric, but the literature is unclear on this point. In addition, in some types of market such as property,...

  7. Radio Bubbles in Clusters

    CERN Document Server

    Dunn, R J H; Taylor, G B

    2005-01-01

    We extend our earlier work on cluster cores with distinct radio bubbles, adding more active bubbles, i.e. those with Ghz radio emission, to our sample, and also investigating ``ghost bubbles,'' i.e. those without GHz radio emission. We have determined k, which is the ratio of the total particle energy to that of the electrons radiating between 10 MHz and 10 GHz. Constraints on the ages of the active bubbles confirm that the ratio of the energy factor, k, to the volume filling factor, f lies within the range 1 < k/f < 1000. In the assumption that there is pressure equilibrium between the radio-emitting plasma and the surrounding thermal X-ray gas, none of the radio lobes has equipartition between the relativistic particles and the magnetic field. A Monte-Carlo simulation of the data led to the conclusion that there are not enough bubbles present in the current sample to be able to determine the shape of the population. An analysis of the ghost bubbles in our sample showed that on the whole they have high...

  8. Bubble migration in a compacting crystal-liquid mush

    Science.gov (United States)

    Boudreau, Alan

    2016-04-01

    Recent theoretical models have suggested that bubbles are unlikely to undergo significant migration in a compaction crystal mush by capillary invasion while the system remains partly molten. To test this, experiments of bubble migration during compaction in a crystal-liquid mush were modeled using deformable foam crystals in corn syrup in a volumetric burette, compacted with rods of varying weights. A bubble source was provided by sodium bicarbonate (Alka-Seltzer®). Large bubbles (>several crystal sizes) are pinched by the compacting matrix and become overpressured and deformed as the bubbles experience a load change from hydrostatic to lithostatic. Once they begin to move, they move much faster than the compaction-driven liquid. Bubbles that are about the same size as the crystals but larger than the narrower pore throats move by deformation or breaking into smaller bubbles as they are forced through pore restrictions. Bubbles that are less than the typical pore diameter generally move with the liquid: The liquid + bubble mixture behaves as a single phase with a lower density than the bubble-free liquid, and as a consequence it rises faster than bubble-free liquid and allows for faster compaction. The overpressure required to force a bubble through the matrix (max grain size = 5 mm) is modest, about 5 %, and it is estimated that for a grain size of 1 mm, the required overpressure would be about 25 %. Using apatite distribution in a Stillwater olivine gabbro as an analog for bubble nucleation and growth, it is suggested that relatively large bubbles initially nucleate and grow in liquid-rich channels that develop late in the compaction history. Overpressure from compaction allows bubbles to rise higher into hotter parts of the crystal pile, where they redissolve and increase the volatile content of the liquid over what it would have without the bubble migration, leading to progressively earlier vapor saturation during crystallization of the interstitial liquid

  9. Bubble transport in subcooled flow boiling

    Science.gov (United States)

    Owoeye, Eyitayo James

    Understanding the behavior of bubbles in subcooled flow boiling is important for optimum design and safety in several industrial applications. Bubble dynamics involve a complex combination of multiphase flow, heat transfer, and turbulence. When a vapor bubble is nucleated on a vertical heated wall, it typically slides and grows along the wall until it detaches into the bulk liquid. The bubble transfers heat from the wall into the subcooled liquid during this process. Effective control of this transport phenomenon is important for nuclear reactor cooling and requires the study of interfacial heat and mass transfer in a turbulent flow. Three approaches are commonly used in computational analysis of two-phase flow: Eulerian-Lagrangian, Eulerian-Eulerian, and interface tracking methods. The Eulerian- Lagrangian model assumes a spherical non-deformable bubble in a homogeneous domain. The Eulerian-Eulerian model solves separate conservation equations for each phase using averaging and closure laws. The interface tracking method solves a single set of conservation equations with the interfacial properties computed from the properties of both phases. It is less computationally expensive and does not require empirical relations at the fluid interface. Among the most established interface tracking techniques is the volume-of-fluid (VOF) method. VOF is accurate, conserves mass, captures topology changes, and permits sharp interfaces. This work involves the behavior of vapor bubbles in upward subcooled flow boiling. Both laminar and turbulent flow conditions are considered with corresponding pipe Reynolds number of 0 -- 410,000 using a large eddy simulation (LES) turbulence model and VOF interface tracking method. The study was performed at operating conditions that cover those of boiling water reactors (BWR) and pressurized water reactors (PWR). The analysis focused on the life cycle of vapor bubble after departing from its nucleation site, i.e. growth, slide, lift-off, rise

  10. Root Causes of the Housing Bubble

    Science.gov (United States)

    Kaizoji, Taisei

    In this chapter we investigate root causes of the recent US housing bubble which has been caused a serious downturn in US economic growth since autumn of 2008. We propose a simple model of housing markets in order to indicate the possible determinants of recent housing prices. Utilizing the model, we verify a number of hypotheses which have been proposed in the recent literature on the housing bubbles. We suggest that the main causes of the housing bubble from 2000 to 2006 are (1) non-elastic housing supply in the metropolitan areas, and (2) declines in the mortgage loan rate and the housing premium by the massive mortgage credit expansion. We also suggest that these factors were strongly influenced by policies that governments and the Federal Reserve Board performed.

  11. Colliding with a crunching bubble

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-03-26

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

  12. Fermi Bubbles with HAWC

    CERN Document Server

    Solares, H A Ayala; Hüntemeyer, P

    2015-01-01

    The Fermi Bubbles, which comprise two large and homogeneous regions of spectrally hard gamma-ray emission extending up to $55^{o}$ above and below the Galactic Center, were first noticed in GeV gamma-ray data from the Fermi Telescope in 2010. The mechanism or mechanisms which produce the observed hard spectrum are not understood. Although both hadronic and lep- tonic models can describe the spectrum of the bubbles, the leptonic model can also explain similar structures observed in microwave data from the WMAP and Planck satellites. Recent publications show that the spectrum of the Fermi Bubbles is well described by a power law with an exponential cutoff in the energy range of 100MeV to 500GeV. Observing the Fermi Bubbles at higher gamma-ray energies will help constrain the origin of the bubbles. A steeper cutoff will favor a leptonic model. The High Altitude Water Cherenkov (HAWC) Observatory, located 4100m above sea level in Mexico, is designed to measure high-energy gamma rays between 100GeV to 100TeV. With...

  13. Bubbles of Metamorphosis

    Science.gov (United States)

    Prakash, Manu

    2011-11-01

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

  14. MEASUREMENT OF BUBBLE-BUBBLE INTERACTION DEPENDED ON REYNOLDS NUMBER USING STEREOSCOPIC BUBBLE-TRACKING TECHNIQUE

    Institute of Scientific and Technical Information of China (English)

    QU Jian-wu; MURAI Yuichi; YAMAMOTO Fujio

    2005-01-01

    Bubble-bubble interaction in free rising bubbly flows is experimentally investigated in the present study.The velocity vectors of the bubbles are measured by a stereoscopic bubble-tracking technique and then the relative velocity vectors of two nearest-neighbor bubbles are calculated with high statistical reliability.With the measurement data at Reynolds number ranging from 5 to 75, the vertical attraction and the horizontal repulsion are confirmed for Re<10 as known by the past study based on Navier-Stokes simulation.The new finding of the present measurement is that the bubbles of Re>30 have repulsive velocity bothin the horizontal and the vertical directions as those rise closely.Moreover, the three-dimensional structure of the bubble-bubble interaction is discussed with the data analysis of the interaction vector fields.

  15. Insights in hydrodynamics of bubbling fluidized beds at elevated pressure by DEM-CFD approach

    Institute of Scientific and Technical Information of China (English)

    Zahra Mansourpour; Sedighe Karimi; Reza Zarghami; Navid Mostoufi; Rahmat Sotudeh-Gharebagh

    2010-01-01

    A numerical simulation was conducted to study the effect of pressure on bubble dynamics in a gas-solid fluidized bed. The gas flow was modeled using the continuum theory and the solid phase, by the dis-crete element method (DEM). To validate the simulation results, calculated local pressure fluctuations were compared with corresponding experimental data of 1-mm polyethylene particles. It was shown that the model successfully predicts the hydrodynamic features of the fluidized bed as observed in the experiments. Influence of pressure on bubble rise characteristics such as bubble rise path, bubble sta-bility, average bubbles diameter and bubble velocity through the bed was investigated. The simulation results are in conformity with current hydrodynamic theories and concepts for fluidized beds at high pressures. The results show further that elevated pressure reduces bubble growth, velocity and stability and enhances bubble gyration through the bed, leading to change in bed flow structure.

  16. Geometric parameters determination of a single vapor bubble growth and heat transfer associated: non condensable influence on the onset of convective instabilities; Determination des caracteristiques geometriques de la croissance d'une bulle de vapeur et des transferts de chaleur associes: influence des incondensables sur le declenchement d'instabilites convectives

    Energy Technology Data Exchange (ETDEWEB)

    Barthes, M.; Reynard, Ch.; Santini, R.; Tadrist, L. [Laboratoire Institut Universitaire des Systemes Thermiques Industriels (IUSTI), CNRS UMR 6595, DME, 13 - Marseille (France)

    2005-06-01

    We present here an experimental work of a single vapor bubble growth in a subcooled liquid bulk (FC-72) at atmospheric pressure. The vapor bubble grows on a downward facing heating element (at constant heating power) on an artificial nucleation site located in the centre of the heated surface. Bubble dynamics are studied thanks to image proceeding. The temporal evolution of geometric parameters, such as diameter, height, volume and shape, are measured. The analysis of some parameters enables us to determine the influence of the heating power on the heat and mass transfers. Moreover an observation, using a shadowgraphy method, of the different modes of convective instabilities is presented. The non condensable gas influence on the occurrence of the instability is discussed. (authors)

  17. Analyzing Cosmic Bubble Collisions

    CERN Document Server

    Gobbetti, Roberto

    2012-01-01

    We develop a set of controlled, analytic approximations to study the effects of bubble collisions on cosmology. We expand the initial perturbation to the inflaton field caused by the collision in a general power series, and determine its time evolution during inflation in terms of the coefficients in the expansion. In models where the observer's bubble undergoes sufficient slow-roll inflation to solve the flatness problem, in the thin wall limit only one coefficient in the expansion is relevant to observational cosmology, allowing nearly model-independent predictions. We discuss two approaches to determining the initial perturbation to the inflaton and the implications for the sign of the effect (a hot or cold spot on the Cosmic Microwave Background temperature map). Lastly, we analyze the effects of collisions with thick-wall bubbles, i.e. away from the thin-wall limit.

  18. Pseudo-Stable Bubbles

    CERN Document Server

    Gleiser, Marcello

    1994-01-01

    The evolution of spherically symmetric unstable scalar field configurations (``bubbles'') is examined for both symmetric (SDWP) and asymmetric (ADWP) double-well potentials. Bubbles with initial static energies $E_0\\la E_{{\\rm crit}}$, where $E_{{\\rm crit}}$ is some critical value, shrink in a time scale determined by their linear dimension, or ``radius''. Bubbles with $E_0\\ga E_{{\\rm crit}}$ evolve into time-dependent, localized configurations which are {\\it very} long-lived compared to characteristic time-scales in the models examined. The stability of these configurations is investigated and possible applications are briefly discussed.tic time-scales in the models examined. The stability of these configurations is investigated and possible applications are briefly discussed.

  19. Bubble nuclei; Noyaux Bulles

    Energy Technology Data Exchange (ETDEWEB)

    Legoll, F. [Service de Physique Theorique, CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France)

    1998-07-22

    For nuclei with very high electrical charge, the Coulomb field is expected to drive the protons away from the centre to the surface of the nucleus. Such a nucleus would be no more compact but look like a bubble. The goal of this work is to confirm this idea. We are interested in only the ground state of spherical nuclei. We use the Skyrme potential with the Sly4 parametrization to calculate the mean-field Hamiltonian. Paring correlations are described by a surface-active delta paring interaction. In its ground state the nucleus {sup A=900} X{sub Z=274} is shown to be a bubble. Another stable state is found with a little higher energy: it is also a bubble. (author) 11 refs., 18 figs., 33 tabs.

  20. Bubble departure in pool and flow boiling systems: A review and latest developments

    International Nuclear Information System (INIS)

    Many of the vapor bubble departure diameter correlations for pool and flow boiling which have been proposed in the open literature are reviewed. In addition, the recent unified bubble detachment model for pool and flow boiling proposed by Zeng et al. (1992a, 1992b) is discussed. It is demonstrated that the unified model, which requires the vapor bubble growth rate as an input, is the only one which satisfactorily predicts vapor bubble departure diameters over the entire range of boiling conditions for which bubble detachment data exist

  1. Scanning bubble chamber pictures

    CERN Multimedia

    1974-01-01

    These were taken at the 2 m hydrogen bubble chamber. The photo shows an early Shiva system where the pre-measurements needed to qualify the event were done manually (cf photo 7408136X). The scanning tables were located in bld. 12. Gilberte Saulmier sits on foreground, Inge Arents at centre.

  2. Critical scattering by bubbles

    International Nuclear Information System (INIS)

    We apply the complex angular momentum theory to the problem of the critical scattering of light by spherical cavities in the high frequency limit (permittivity greater than the external media) (e.g, air bubble in water) (M.W.O.)

  3. BEBC bubble chamber

    CERN Multimedia

    1972-01-01

    Looking up into the interior of BEBC bubble chamber from the expansion cylinder. At the top of the chamber two fish-eye lenses are installed and three other fish-eye ports are blanked off. In the centre is a heat exchanger.

  4. Inertial confinement fusion based on the ion-bubble trigger

    International Nuclear Information System (INIS)

    Triggering the ion-bubble in an inertial confinement fusion, we have developed a novel scheme for the fast ignition. This scheme relies on the plasma cavitation by the wake of an intense laser pulse to generate an ion-bubble. The bubble acts both as an intense electron accelerator and as an electron wiggler. Consequently, the accelerated electrons trapped in the bubble can emit an intense tunable laser light. This light can be absorbed by an ablation layer on the outside surface of the ignition capsule, which subsequently drills it and thereby produces a guide channel in the pellet. Finally, the relativistic electron beam created in the bubble is guided through the channel to the high density core igniting the fusion fuel. The normalized beam intensity and beam energy required for triggering the ignition have been calculated when core is heated by the e-beam. In addition, through solving the momentum transfer, continuity and wave equations, a dispersion relation for the electromagnetic and space-charge waves has been analytically derived. The variations of growth rate with the ion-bubble density and electron beam energy have been illustrated. It is found that the growth rates of instability are significantly controlled by the ions concentration and the e-beam energy in the bubble

  5. Growing bubbles in a slightly supersaturated liquid solution

    CERN Document Server

    Enríquez, Oscar R; Bruggert, Gert-Wim; Lohse, Detlef; Prosperetti, Andrea; van der Meer, Devaraj; Sun, Chao

    2013-01-01

    We have designed and constructed an experimental system to study gas bubble growth in slightly supersatu- rated liquids. This is achieved by working with carbon dioxide dissolved in water, pressurized at a maximum of 1 MPa and applying a small pressure drop from saturation conditions. Bubbles grow from hydrophobic cavities etched on silicon wafers, which allows us to control their number and position. Hence, the experiment can be used to investigate the interaction among bubbles growing in close proximity when the main mass transfer mechanism is diffusion and there is a limited availability of the dissolved species.

  6. The size of active bubbles for the production of hydrogen in sonochemical reaction field.

    Science.gov (United States)

    Merouani, Slimane; Hamdaoui, Oualid

    2016-09-01

    The sonication of aqueous solution generates microscopic cavitation bubbles that may growth and violently collapse to produce highly reactive species (i.e. OH, HO2 and H2O2), hydrogen and emit light, sonoluminescence. The bubble size is a key parameter that influences the chemical activity of the system. This wok aims to study theoretically the size of active bubbles for the production of hydrogen in ultrasonic cavitation field in water using a single bubble sonochemistry model. The effect of several parameters such as frequency of ultrasound, acoustic intensity and liquid temperature on the range of sonochemically active bubbles for the production of hydrogen was clarified. The numerical simulation results showed that the size of active bubbles is an interval which includes an optimum value at which the production rate of H2 is maximal. It was shown that the range of ambient radius for an active bubble as well as the optimum bubble radius for the production of hydrogen increased with increasing acoustic intensity and decreased with increasing ultrasound frequency and bulk liquid temperature. It was found that the range of ambient bubble radius dependence of the operational conditions followed the same trend as those reported experimentally for sonoluminescing bubbles. Comparison with literature data showed a good agreement between the theoretical determined optimum bubble sizes for the production of hydrogen and the experimental reported sizes for sonoluminescing bubbles. PMID:27150777

  7. Bubble Dynamics and Shock Waves

    CERN Document Server

    2013-01-01

    This volume of the Shock Wave Science and Technology Reference Library is concerned with the interplay between bubble dynamics and shock waves. It is divided into four parts containing twelve chapters written by eminent scientists. Topics discussed include shock wave emission by laser generated bubbles (W Lauterborn, A Vogel), pulsating bubbles near boundaries (DM Leppinen, QX Wang, JR Blake), interaction of shock waves with bubble clouds (CD Ohl, SW Ohl), shock propagation in polydispersed bubbly liquids by model equations (K Ando, T Colonius, CE Brennen. T Yano, T Kanagawa,  M Watanabe, S Fujikawa) and by DNS (G Tryggvason, S Dabiri), shocks in cavitating flows (NA Adams, SJ Schmidt, CF Delale, GH Schnerr, S Pasinlioglu) together with applications involving encapsulated bubble dynamics in imaging (AA Doinikov, A Novell, JM Escoffre, A Bouakaz),  shock wave lithotripsy (P Zhong), sterilization of ships’ ballast water (A Abe, H Mimura) and bubbly flow model of volcano eruptions ((VK Kedrinskii, K Takayama...

  8. Guest investigator program study: Physics of equatorial plasma bubbles

    Science.gov (United States)

    Tsunoda, Roland T.

    1994-01-01

    -shaped plasma bubbles. The second topic was pursued because the inability to predict the day-to-day occurrence of plasma bubbles indicated inadequate knowledge of the physics of plasma bubbles. An understanding of bubble formation requires an understanding of the roles of the various terms in the linearized growth rate of the collisional Rayleigh-Taylor instability. In our study, we examined electric-field perturbations found in SM-D EFI data and found that the seeding is more likely to be produced in the E region rather than the F region. The results of this investigation are presented in the Appendix of this report and will be submitted for publication in the Journal of Geophysical Research.

  9. More bubbling solutions

    International Nuclear Information System (INIS)

    In this note we construct families of asymptotically flat, smooth, horizonless solutions with a large number of non-trivial two-cycles (bubbles) of N = 1 five-dimensional supergravity with an arbitrary number of vector multiplets, which may or may not have the charges of a macroscopic black hole and which contain the known bubbling solutions as a sub-family. We do this by lifting various multi-center BPS states of type IIA compactified on Calabi-Yau three-folds and taking the decompactification (M-theory) limit. We also analyse various properties of these solutions, including the conserved charges, the shape, especially the (absence of) throat and closed timelike curves, and relate them to the various properties of the four-dimensional BPS states. We finish by briefly commenting on their degeneracies and their possible relations to the fuzzball proposal of Mathur et al

  10. Bubble dynamics in drinks

    Czech Academy of Sciences Publication Activity Database

    Broučková, Zuzana; Trávníček, Zdeněk; Šafařík, P.

    Liberec: Technical University of Liberec, 2013 - (Vít, T.; Dančová, P.; Novotný, P.), s. 114-118 ISBN 978-80-260-5375-0. [Experimental Fluid Mechanics 2013. Kutná hora (CZ), 19.11.2013-22.11.2013] R&D Projects: GA ČR(CZ) GCP101/11/J019 Institutional support: RVO:61388998 Keywords : bubbles * hot chocolate effect * visualization Subject RIV: BK - Fluid Dynamics

  11. CRISIS FOCUS Blowing Bubbles

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The Chinese stock and property markets have been outperforming expectations, fueled by an unprecedented surge in bank lending. Xie Guozhong, an economist and board member of Rosetta Stone Advisors, argues the robust Chinese economic figures are only propped up by bubbles, whose bursting will lead to a hard landing for the economy. Xie published his opinion in a related article in Caijing Magazine. Edited excerpts follow:

  12. Gas bubbling cleaning method

    International Nuclear Information System (INIS)

    The present invention concerns a gas bubbling cleaning method for objects to be cleaned having complicate shapes such as reactor equipments. For instance, air is used as the gas, while water is used as the cleaning fluid. A jetting air is jetted out to an object to be cleaned from an air bubbling nozzle disposed below the object. This constitutes air/water two phase flow near the object to be cleaned, to generate a three dimensional circulating flow. The distance between the inner wall surface of a cleaning vessel and the object to be cleaned is set to greater than 5 mm, and the ratio between the air flow rate and the horizontal cross section of the cleaning vessel is set to 0.1 to 0.4m/sec. This enables to enter an appropriate amount of bubbles to the air at the inside of the object to be cleaned having a complicate shape. Accordingly, deposits adhered to the inside of the object to be cleaned can be eliminated and cleaned effectively. (I.N.)

  13. Mechanisms of gas bubble retention

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Takahira, Hiroyuki, E-mail: takahira@me.osakafu-u.ac.jp; Ogasawara, Toshiyuki, E-mail: oga@me.osakafu-u.ac.jp; Mori, Naoto, E-mail: su101064@edu.osakafu-u.ac.jp; Tanaka, Moe [Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai-shi, Osaka 599-8531 (Japan)

    2015-10-28

    The secondary cavitation that occurs by the backscattering of focused ultrasound from a primary cavitation bubble caused by the negative pressure part of the ultrasound (Maxwell, et al., 2011) might be useful for the energy exchange due to bubble oscillations in High Intensity Focused Ultrasound (HIFU). The present study is concerned with the cavitation inception by the backscattering of ultrasound from a bubble. In the present experiment, a laser-induced bubble which is generated by a pulsed focused laser beam with high intensity is utilized as a primary cavitation bubble. After generating the bubble, focused ultrasound is emitted to the bubble. The acoustic field and the bubble motion are observed with a high-speed video camera. It is confirmed that the secondary cavitation bubble clouds are generated by the backscattering from the laser-induced bubble. The growth of cavitation bubble clouds is analyzed with the image processing method. The experimental results show that the height and width of the bubble clouds grow in stepwise during their evolution. The direct numerical simulations are also conducted for the backscattering of incident pressure waves from a bubble in order to evaluate a pressure field near the bubble. It is shown that the ratio of a bubble collapse time t{sub 0} to a characteristic time of wave propagation t{sub S}, η = t{sub 0}/t{sub s}, is an important determinant for generating negative pressure region by backscattering. The minimum pressure location by the backscattering in simulations is in good agreement with the experiment.

  15. Electrowetting of a soap bubble

    CERN Document Server

    Arscott, Steve

    2013-01-01

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

  16. Experimental investigation and mechanistic modelling of dilute bubbly bulk boiling

    International Nuclear Information System (INIS)

    During evaporation the geometric shape of the vapour is not described using thermodynamics. In bubbly flows the bubble shape is considered spheric with small diameters and changing into various shapes upon growth. The heat and mass transfer happens at the interfacial area. The forces acting on the bubbles depend on the bubble diameter and shape. In this work the prediction of the bubble diameter and/or bubble number density in bulk boiling was considered outside the vicinity of the heat input area. Thus the boiling effects that happened inside the nearly saturated bulk were under investigation. This situation is relevant for nuclear safety analysis concerning a stagnant coolant in the spent fuel pool. In this research project a new experimental set-up to investigate was built. The experimental set-up consists of an instrumented, partly transparent, high and slender boiling container for visual observation. The direct visual observation of the boiling phenomena is necessary for the identification of basic mechanisms, which should be incorporated in the simulation model. The boiling process has been recorded by means of video images and subsequently was evaluated by digital image processing methods, and by that data concerning the characteristics of the boiling process were generated for the model development and validation. Mechanistic modelling is based on the derivation of relevant mechanisms concluded from observation, which is in line with physical knowledge. In this context two mechanisms were identified; the growth/-shrink mechanism (GSM) of the vapour bubbles and sudden increases of the bubble number density. The GSM was implemented into the CFD-Code ANSYS-CFX using the CFX Expression Language (CEL) by calculation of the internal bubble pressure using the Young-Laplace-Equation. This way a hysteresis is realised as smaller bubbles have an increased internal pressure. The sudden increases of the bubble number density are explainable by liquid super

  17. Experimental investigation and mechanistic modelling of dilute bubbly bulk boiling

    Energy Technology Data Exchange (ETDEWEB)

    Kutnjak, Josip

    2013-06-27

    During evaporation the geometric shape of the vapour is not described using thermodynamics. In bubbly flows the bubble shape is considered spheric with small diameters and changing into various shapes upon growth. The heat and mass transfer happens at the interfacial area. The forces acting on the bubbles depend on the bubble diameter and shape. In this work the prediction of the bubble diameter and/or bubble number density in bulk boiling was considered outside the vicinity of the heat input area. Thus the boiling effects that happened inside the nearly saturated bulk were under investigation. This situation is relevant for nuclear safety analysis concerning a stagnant coolant in the spent fuel pool. In this research project a new experimental set-up to investigate was built. The experimental set-up consists of an instrumented, partly transparent, high and slender boiling container for visual observation. The direct visual observation of the boiling phenomena is necessary for the identification of basic mechanisms, which should be incorporated in the simulation model. The boiling process has been recorded by means of video images and subsequently was evaluated by digital image processing methods, and by that data concerning the characteristics of the boiling process were generated for the model development and validation. Mechanistic modelling is based on the derivation of relevant mechanisms concluded from observation, which is in line with physical knowledge. In this context two mechanisms were identified; the growth/-shrink mechanism (GSM) of the vapour bubbles and sudden increases of the bubble number density. The GSM was implemented into the CFD-Code ANSYS-CFX using the CFX Expression Language (CEL) by calculation of the internal bubble pressure using the Young-Laplace-Equation. This way a hysteresis is realised as smaller bubbles have an increased internal pressure. The sudden increases of the bubble number density are explainable by liquid super

  18. Rational Bubbles in Stock Prices?

    OpenAIRE

    Behzad T. Diba; Grossman, Herschel I.

    1985-01-01

    This paper reports empirical tests for the existence of rational bubbles in stock prices. The analysis focuses on a familiar model that defines market fundamentals to be the expected present value of dividends, discounted at a constantrate, and defines a rational bubble to be a self-confirming divergence of stock prices from market fundamentals in response to extraneous variables. The tests are based on the theoretical result that, if rational bubbles exist, time series obtained by differenci...

  19. Rational Asset Pricing Bubbles Revisited

    OpenAIRE

    Jan Werner

    2012-01-01

    Price bubble arises when the price of an asset exceeds the asset's fundamental value, that is, the present value of future dividend payments. The important result of Santos and Woodford (1997) says that price bubbles cannot exist in equilibrium in the standard dynamic asset pricing model with rational agents as long as assets are in strictly positive supply and the present value of total future resources is finite. This paper explores the possibility of asset price bubbles when either one of ...

  20. A computational model of gas bubble evolution in liquid filled straight tubes

    Science.gov (United States)

    Himm, Jeff; Halpern, David

    1996-11-01

    Deep sea divers suffer from decompression sickness (DCS) when their rate of ascent to the surface is too quick. When the ambient pressure drops, inert gas bubbles are usually formed in blood vessels and tissues of divers. It is believed that the existence of gas bubbles is the cause of DCS that manifests itself as itching, joint pain, and neurological abnormalities. While models of gas bubbles in tissues are relatively well developed, the mechanism of bubble growth in the circulation is far less well understood. The existence of gas bubbles may affect gas exchange in small blood vessels by blocking the flow of blood. Gas bubble evolution in the circulation is investigated using an analytical method for small bubbles and the boundary element method for bubbles whose effective radius is close to the tube radius. The concentration field for the dissolved gas surrounding the bubble is solved numerically using finite differences. The bubble volume is adjusted over time according to the mass flux at the surface. It is shown that the effect of increasing the flow rate is to enhance bubble evolution, up to a factor of two compared with the evolution in tissue where there is no flow. This work was supported by the Naval Medical Research and Development Command work unit 62233N.MM33P30.0041509.

  1. Mathematical model of diffusion-limited evolution of multiple gas bubbles in tissue

    Science.gov (United States)

    Srinivasan, R. Srini; Gerth, Wayne A.; Powell, Michael R.

    2003-01-01

    Models of gas bubble dynamics employed in probabilistic analyses of decompression sickness incidence in man must be theoretically consistent and simple, if they are to yield useful results without requiring excessive computations. They are generally formulated in terms of ordinary differential equations that describe diffusion-limited gas exchange between a gas bubble and the extravascular tissue surrounding it. In our previous model (Ann. Biomed. Eng. 30: 232-246, 2002), we showed that with appropriate representation of sink pressures to account for gas loss or gain due to heterogeneous blood perfusion in the unstirred diffusion region around the bubble, diffusion-limited bubble growth in a tissue of finite volume can be simulated without postulating a boundary layer across which gas flux is discontinuous. However, interactions between two or more bubbles caused by competition for available gas cannot be considered in this model, because the diffusion region has a fixed volume with zero gas flux at its outer boundary. The present work extends the previous model to accommodate interactions among multiple bubbles by allowing the diffusion region volume of each bubble to vary during bubble evolution. For given decompression and tissue volume, bubble growth is sustained only if the bubble number density is below a certain maximum.

  2. Heat transfer mechanisms in bubbly Rayleigh-Benard convection

    CERN Document Server

    Oresta, Paolo; Lohse, Detlef; Prosperetti, Andrea

    2008-01-01

    The heat transfer mechanism in Rayleigh-Benard convection in a liquid with a mean temperature close to its boiling point is studied through numerical simulations with point-like vapor bubbles, which are allowed to grow or shrink through evaporation and condensation and which act back on the flow both thermally and mechanically. It is shown that the effect of the bubbles is strongly dependent on the ratio of the sensible heat to the latent heat as embodied in the Jacob number Ja. For very small Ja the bubbles stabilize the flow by absorbing heat in the warmer regions and releasing it in the colder regions. With an increase in Ja, the added buoyancy due to the bubble growth destabilizes the flow with respect to single-phase convection and considerably increases the Nusselt number.

  3. Droplets, Bubbles and Ultrasound Interactions.

    Science.gov (United States)

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

    2016-01-01

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

  4. Nucleation, growth and transport modelling of helium bubbles under nuclear irradiation in lead-lithium with the Self-consistent nucleation theory and surface tension corrections

    CERN Document Server

    Fradera, Jorge

    2013-01-01

    Helium (He) nucleation in liquid metal breeding blankets of a DT fusion reactor may have a significant impact regarding system design, safety and operation. Large He production rates are expected due to tritium (T) fuel self-sufficiency requirement, as both, He and T, are produced at the same rate. Low He solubility, local high concentrations, radiation damage and fluid discontinuities, among other phenomena, may yield the necessary conditions for He nucleation. Hence, He nucleation may have a significant impact on T inventory and may lower the T breeding ratio. A model based on the self-consistent nucleation theory (SCT) with a surface tension curvature correction model has been implemented in OpenFoam(r) CFD code. A modification through a single parameter of the necessary nucleation condition is proposed in order to take into account all the nucleation triggering phenomena, specially radiation induced nucleation. Moreover, the kinetic growth model has been adapted so as to allow for the transition from a cr...

  5. Bubble Coalescence: Effect of Bubble Approach Velocity and Liquid Viscosity

    Czech Academy of Sciences Publication Activity Database

    Orvalho, Sandra; Růžička, Marek; Olivieri, G.; Marzocchella, A.

    2015-01-01

    Roč. 134, SEP 29 (2015), s. 205-216. ISSN 0009-2509 R&D Projects: GA MŠk(CZ) LD13018 Institutional support: RVO:67985858 Keywords : bubble coalescence * bubble approach velocity * liquid viscosity Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 2.337, year: 2014

  6. Large amplitude oscillation of a boiling bubble growing at a wall in stagnation flow

    International Nuclear Information System (INIS)

    A boiling bubble is created on an artificial site that is part of a bubble generator that is mounted at the center of a pipe. Downflow of water impinges on the bubble generator and creates a stagnation flow above the artificial cavity. Stable axisymmetric elongation in the direction away from the wall and multiple shape oscillation cycles are observed. The time of growth and attachment is typically of the order of 250 ms. Amongst the length scales that characterize the bubble shape is the radius of curvature of the upper part of the bubble, R. The period of oscillation, T, is strongly dependent on time, as is R. The parameters C and m in the defining equation T = C Rm √(ρL/σ) have been determined by fitting to data of more than 100 bubbles. For each operating condition, the same values of C and m have been found. The value of m is 1.49 ± 0.02, which is explained from the continuous growth of the bubble and from the relation to the period of oscillation of a free bubble deforming in the fundamental mode corresponding to the third Legendre Polynomial. For the latter, R is the radius of the volume-equivalent sphere, R0, and C is √12, while for attached boiling bubbles C is found to amount 1.9√12. The difference is easily explained from the continuous growth, difference in definition, finite amplitude oscillation and proximity of the wall. (author)

  7. Optical behavior of surface bubbles

    Science.gov (United States)

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

    2015-11-01

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

  8. Bubble chamber: colour enhanced tracks

    CERN Multimedia

    1998-01-01

    This artistically-enhanced image of real particle tracks was produced in the Big European Bubble Chamber (BEBC). Liquid hydrogen is used to create bubbles along the paths of the particles as a piston expands the medium. A magnetic field is produced in the detector causing the particles to travel in spirals, allowing charge and momentum to be measured.

  9. Bubble coalescence in breathing DNA

    DEFF Research Database (Denmark)

    Novotný, Tomas; Pedersen, Jonas Nyvold; Ambjörnsson, Tobias; Hansen, Mikael Sonne; Metzler, Ralf

    2007-01-01

    We investigate the coalescence of two DNA bubbles initially located at weak segments and separated by a more stable barrier region in a designed construct of double-stranded DNA. The characteristic time for bubble coalescence and the corresponding distribution are derived, as well as the distribu...

  10. Bubble Formation in Basalt-like Melts

    DEFF Research Database (Denmark)

    Jensen, Martin; Keding, Ralf; Yue, Yuanzheng

    2011-01-01

    The effect of the melting temperature on bubble size and bubble formation in an iron bearing calcium aluminosilicate melt is studied by means of in-depth images acquired by optical microscopy. The bubble size distribution and the total bubble volume are determined by counting the number of bubbles...... species. Mass spectroscopy analysis of gases liberated during heating of the glass reveals that small bubbles contain predominantly CH4, CO and CO2, whereas large bubbles bear N2, SO2 and H2S. The methodology utilised in this work can, besides mapping the bubbles in a glass, be applied to shed light on...

  11. Comparison between Airlift Photobioreactor and Bubble Column for Skeletonema Costatum Cultivation

    OpenAIRE

    Prasert Pavasant; Sorawit Powtongsook; Saranya Monkonsit

    2011-01-01

    The cultivation of diatom Skeletonema costatum was achieved in airlift photobioreactor and the system performance was compared to that of bubble column. The standard F/2 medium (Guillard’s medium) for typical diatom cultivation could only yield the best growth character when the silicon concentration increased 4 times the normal value. In terms of cell growth, the airlift photobioreactor provided better performance than the bubble column where the maximum cell concentration, specific growth r...

  12. THE SEMIEMPIRICAL MODEL OF THE MULTICOMPONENT BUBBLE BEHAVIOUR IN GLASS MELTS

    Directory of Open Access Journals (Sweden)

    LUBOMÍR NĚMEC

    2012-12-01

    Full Text Available A semi-empirical model of the bubble growth and dissolution in glasses with a fining agent has been derived. This model applies the experimental data from bubble observation at melting and fining temperatures. The experimental data needed for the model involved the temperature dependences of the average growth rate of the bubble radius and the average concentration of the fining gas in the bubbles. Both sets of values were measured in the laboratory in the glass of the float type and applied in the model. The measurements of the solubilities and diffusion coefficients of the gases present in the glass – needed for the analytical model of multicomponent bubbles – were thus avoided. The course of the partial bubble absorption with the temperature decreasing was simulated by means of two factors modifying the experimental values of the bubble growth rates at constant temperature. The temperature dependence of the resulting bubble growth rate qualitatively corresponded to the experimental observations in the soda-lime-silica glass, but a more detailed experimental and comparative study has yet to be performed. Such a study is being prepared.

  13. High speed photography study on the repulsion of laser induced cavitation bubble on low density polyethylene material

    International Nuclear Information System (INIS)

    The dynamic growth of bubble induced by laser on polyethylene (a non-metallic material) was studied by utilizing the high-speed photographic system. In the early stage of expansion, the bubble maintained the spherical and localized form as normally occurred near a rigid solid-boundary. However, the bubble started repelling when it began to contract; showing that the bubble acted as a negative charge body. As a result the rest of the physical changes of cavitation bubble including the collapse stage which is known as a high damaging regime took place far way from the solid boundary (author)

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

    Energy Technology Data Exchange (ETDEWEB)

    Di Fulvio, Angela; Huang, Jean; Staib, Lawrence [Yale University, Department of Diagnostic Radiology, TAC N140, New Haven, CT 06520-8043 (United States); D’Errico, Francesco [Yale University, Department of Diagnostic Radiology, TAC N140, New Haven, CT 06520-8043 (United States); Scuola di Ingegneria, Universitá di Pisa, Largo Lucio Lazzarino 1, Pisa (Italy)

    2015-06-01

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

  15. A 3D Bubble Merger Model for RTI Mixing

    Science.gov (United States)

    Cheng, Baolian

    2015-11-01

    In this work we present a model for the merger processes of bubbles at the edge of an unstable acceleration driven mixing layer. Steady acceleration defines a self-similar mixing process, with a time-dependent inverse cascade of structures of increasing size. The time evolution is itself a renormalization group evolution. The model predicts the growth rate of a Rayleigh-Taylor chaotic fluid-mixing layer. The 3-D model differs from the 2-D merger model in several important ways. Beyond the extension of the model to three dimensions, the model contains one phenomenological parameter, the variance of the bubble radii at fixed time. The model also predicts several experimental numbers: the bubble mixing rate, the mean bubble radius, and the bubble height separation at the time of merger. From these we also obtain the bubble height to the radius aspect ratio, which is in good agreement with experiments. Applications to recent NIF and Omega experiments will be discussed. This work was performed under the auspices of the U.S. Department of Energy by the Los Alamos National Laboratory under Contract No. W-7405-ENG-36.

  16. Introductory Applicaton of Defocusing DPIV to the Study of Bubbly Shear Flows

    Science.gov (United States)

    Pereira, Francisco; Gharib, Morteza; Dabiri, Dana; Modarress, Darius

    1999-11-01

    A study of a three-dimensional bubbly flow is presented to demonstrate the applicability of the newly developed defocusing digital particle image velocimetry technique. The DDPIV instrument provides bubble size and location information within a one cubic foot volume. A three-dimensional two-phase flow measurement is performed to obtain a full-field quantitative description of the global dynamics of air bubbles in a vortical shear flow generated by a model boat propeller. Clouds of sub-millimeter air bubbles are injected upstream the propeller. The velocity field is calculated from volumetric cross-correlation of consecutive three-dimensional sets of bubble locations, whereas the bubble size information is estimated from the blurred image of bubbles. Flow analysis is presented in terms of vorticity and bubble trajectory. The bubble size distribution upstream and downstream the propeller is discussed. Growth and collapse of bubbles are detected and related to the respective velocity field in the suction and high-pressure regions of the propeller.

  17. Formation mechanism of gas bubble superlattice in UMo metal fuels: Phase-field modeling investigation

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Shenyang Y.; Burkes, Douglas; Lavender, Curt A.; Senor, David J.; Setyawan, Wahyu; Xu, Zhijie

    2016-07-08

    Nano-gas bubble superlattices are often observed in irradiated UMo nuclear fuels. However, the for- mation mechanism of gas bubble superlattices is not well understood. A number of physical processes may affect the gas bubble nucleation and growth; hence, the morphology of gas bubble microstructures including size and spatial distributions. In this work, a phase-field model integrating a first-passage Monte Carlo method to investigate the formation mechanism of gas bubble superlattices was devel- oped. Six physical processes are taken into account in the model: 1) heterogeneous generation of gas atoms, vacancies, and interstitials informed from atomistic simulations; 2) one-dimensional (1-D) migration of interstitials; 3) irradiation-induced dissolution of gas atoms; 4) recombination between vacancies and interstitials; 5) elastic interaction; and 6) heterogeneous nucleation of gas bubbles. We found that the elastic interaction doesn’t cause the gas bubble alignment, and fast 1-D migration of interstitials along 〈110〉 directions in the body-centered cubic U matrix causes the gas bubble alignment along 〈110〉 directions. It implies that 1-D interstitial migration along [110] direction should be the primary mechanism of a fcc gas bubble superlattice which is observed in bcc UMo alloys. Simulations also show that fission rates, saturated gas concentration, and elastic interaction all affect the morphology of gas bubble microstructures.

  18. Fission gas bubble characterisation in irradiated UO2 fuel by SEM

    International Nuclear Information System (INIS)

    The behaviour of gases produced by fission is of great importance for nuclear fuel operation. The fission gases affect fuel performance in different manners. Retained gas in the form of bubbles may lead to fuel swelling. The released gases reduce the heat transfer between the fuel and clad, leading to increase in the fuel temperature. They also increase the fuel pin pressure which may lead to cladding failure and to the consequent release of fission products to the coolant circuit. The mechanism of fission gas release includes diffusion of gas atoms to grain boundaries, formation of fission gas bubbles, growth of the bubbles and their interlinkage to form channels through which the gas gets released into the free space in the fuel pin. It is important to characterise the fission gas bubbles/channels formed in the fuel, especially under high burnup conditions. Within this context, characterisation of the fission gas bubbles from fractured grains of irradiated UO2 fuels with burnups ranging from 400 MWd/t U to 22,000 z MWd/t U has been carried out under Scanning Electron Microscope (SEM). In low burnup fuels, small bubbles were observed on the grain faces. With increasing burnup, larger bubbles and wide channels were observed in addition to the small bubbles. This paper describes the evolution of grain face bubbles in UO2 and provides the data on gas bubble size and distribution in fuel irradiated to different burnup levels which is an important input for fuel modeling. (author)

  19. ADSORPTION OF NANO-PARTICLES ON BUBBLE SURFACE IN NANO-PARTICLE SUSPENSION

    Institute of Scientific and Technical Information of China (English)

    Buxuan Wang; Chunhui Li; Xiaofeng Peng

    2005-01-01

    The adsorption of nano-particles on bubble surface is discussed for saturated boiling on thin wire of nano-particle suspensions. Owing to the decrease of surface tension for suspensions, the nano-particles tend to adsorb on the bubble surface to decrease the Gibbs free energy for stability, and meanwhile the velocity of nano-particles would be smaller than that of bubble growth. The long-range van der Waals force existing between "water particles" and nano-particles is considered the attractive force between the nano-particles and the bubble surface. Thus, the nano-particles would attach on the bubble surface if the particle-surface distance is smaller than its critical value. The distribution of nano-particles on the bubble surface and in the adjacent region is also investigated.

  20. Directed self-assembly of microcomponents enabled by laser-activated bubble latching.

    Science.gov (United States)

    Jiang, Li; Erickson, David

    2011-09-01

    This article introduces a method for microscale assembly using laser-activated bubble latching. The technique combines the advantages of directed fluidic assembly and surface tension-driven latching to create arbitrarily complex and irregular structures with unique properties. The bubble latches, generated through the laser degradation of the tile material, are created on the fly, reversibly linking components at user-determined locations. Different phases of latching bubble growth are analyzed, and shear force calculations show that each bubble is able to support a tensile force of approximately 0.33 μN. We demonstrate that by exploiting the compressibility of bubbles, assembled objects can be made to switch between rigid and flexible states, facilitating component assembly and transport. Furthermore, we show reconfiguration capabilities through the use of bubble hinging. This novel hybrid approach to the assembly of microscale components offers significant user control while retaining a simplistic design environment. PMID:21793555

  1. Strings on Bubbling Geometries

    CERN Document Server

    Lin, Hai; Shock, Jonathan P

    2010-01-01

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

  2. Anatomy of bubbling solutions

    CERN Document Server

    Skenderis, Kostas

    2007-01-01

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

  3. Use of an ultrasonic reflectance technique to examine bubble size changes in dough

    International Nuclear Information System (INIS)

    Bread quality largely depends on the manner in which bubbles are created and manipulated in the dough during processing. We have developed an ultrasonic reflectance technique to monitor bubbles in dough, even at high volume fractions, where near the bubble resonances it is difficult to make measurements using transmission techniques. A broadband transducer centred at 3.5 MHz in a normal incidence wave reflection set-up is used to measure longitudinal velocity and attenuation from acoustic impedance measurements. The technique is illustrated by examining changes in bubbles in dough due to two very different physical effects. In dough made without yeast, a peak in attenuation due to bubble resonance is observed at approximately 2 MHz. This peak diminishes rapidly and shifts to lower frequencies, indicative of Ostwald ripening of bubbles within the dough. The second effect involves the growth of bubble sizes due to gas generated by yeast during fermentation. This process is experimentally challenging to investigate with ultrasound because of very high attenuation. The reflectance technique allows the changes of the velocity and attenuation during fermentation to be measured as a function of frequency and time, indicating bubble growth effects that can be monitored even at high volume fractions of bubbles.

  4. Hydrodynamics of circulating and bubbling fluidized beds

    International Nuclear Information System (INIS)

    This paper reports that a review of modeling of the hydrodynamics of fluidization of bubbling beds showed that inviscid two-fluid models were able to predict a great deal of the behavior of bubbling beds because the dominant mechanism of energy dissipation is the drag between the particles and the fluid. The formation, the growth and the bursting of bubbles were predicted. Predicted wall-to-bed heat transfer coefficients and velocity profiles of jets agreed with measurements. Time average porosity distributions agreed with measurements done using gamma-ray densitometers without the use of any adjustable parameters. However, inviscid models could not correctly predict rates of erosion around tubes immersed into fluidized beds. To correctly model such behavior, granular stresses involving solids viscosity were added into the computer model. This viscosity arises due to random collision of particles. Several models fro this viscosity were investigated and the results compared to measurements of solids distributions in two-dimensional beds and to particle velocities reported in the literature. While in the case of bubbling beds the solids viscosity plays the role of a correction, modeling of a circulating fluidized bed (CFB) without a viscosity is not possible. Recent experimental data obtained at IIT and at IGT show that in CFB the solids viscous dissipation is responsible for as much as half of the pressure drop. From such measurement, solids viscosities were computed. These were used in the two fluid hydrodynamic model, to predict radial solids distributions and solids velocities which matched the experimental distributions. Most important, the model predicted cluster formation and transient internal circulation which is responsible for the favorable characteristics of CFBs, such as good wall-to-bed heat transfer. Video tape movies of computations compared favorably with high speed movies of the experiments

  5. Doughnut-shaped soap bubbles

    Science.gov (United States)

    Préve, Deison; Saa, Alberto

    2015-10-01

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

  6. Segregating gas from melt: an experimental study of the Ostwald ripening of vapor bubbles in magmas

    Science.gov (United States)

    Lautze, Nicole C.; Sisson, Thomas W.; Mangan, Margaret T.; Grove, Timothy L.

    2011-01-01

    Diffusive coarsening (Ostwald ripening) of H2O and H2O-CO2 bubbles in rhyolite and basaltic andesite melts was studied with elevated temperature–pressure experiments to investigate the rates and time spans over which vapor bubbles may enlarge and attain sufficient buoyancy to segregate in magmatic systems. Bubble growth and segregation are also considered in terms of classical steady-state and transient (non-steady-state) ripening theory. Experimental results are consistent with diffusive coarsening as the dominant mechanism of bubble growth. Ripening is faster in experiments saturated with pure H2O than in those with a CO2-rich mixed vapor probably due to faster diffusion of H2O than CO2 through the melt. None of the experimental series followed the time1/3 increase in mean bubble radius and time-1 decrease in bubble number density predicted by classical steady-state ripening theory. Instead, products are interpreted as resulting from transient regime ripening. Application of transient regime theory suggests that bubbly magmas may require from days to 100 years to reach steady-state ripening conditions. Experimental results, as well as theory for steady-state ripening of bubbles that are immobile or undergoing buoyant ascent, indicate that diffusive coarsening efficiently eliminates micron-sized bubbles and would produce mm-sized bubbles in 102–104 years in crustal magma bodies. Once bubbles attain mm-sizes, their calculated ascent rates are sufficient that they could transit multiple kilometers over hundreds to thousands of years through mafic and silicic melt, respectively. These results show that diffusive coarsening can facilitate transfer of volatiles through, and from, magmatic systems by creating bubbles sufficiently large for rapid ascent.

  7. Direct numerical simulation of bubble dynamics in subcooled and near-saturated convective nucleate boiling

    International Nuclear Information System (INIS)

    Highlights: • We simulate convective nucleate pool boiling with a novel phase-change model. • We simulate four cases at different sub-cooling and wall superheat levels. • We investigate the flow structures around the growing bubble and analyze the accompanying physics. • We accurately simulate bubble shape elongation and enhanced wall cooling due to the sliding and slanting motions of bubbles. • Bubble cycle durations show good agreement with experimental observations. - Abstract: With the long-term objective of Critical Heat Flux (CHF) prediction, bubble dynamics in convective nucleate boiling flows has been studied using a Direct Numerical Simulation (DNS). A sharp-interface phase change model which was originally developed for pool boiling flows is extended to convective boiling flows. For physical scales smaller than the smallest flow scales (smaller than the grid size), a micro-scale model was used. After a grid dependency study and a parametric study for the contact angle, four cases of simulation were carried out with different wall superheat and degree of subcooling. The flow structures around the growing bubble were investigated together with the accompanying physics. The relation between the heat flux evolution and the bubble growth was studied, along with investigations of bubble diameter and bubble base diameter evolutions across the four cases. As a validation, the evolutions of bubble diameter and bubble base diameter were compared to experimental observations. The bubble departure period and the bubble shapes show good agreement between the experiment and the simulation, although the Reynolds number of the simulation cases is relatively low

  8. The microjetting behavior from single laser-induced bubbles generated above a solid boundary with a through hole

    Science.gov (United States)

    Abboud, Jack E.; Oweis, Ghanem F.

    2013-01-01

    An inertial bubble collapsing near a solid boundary generates a fast impulsive microjet directed toward the boundary. The jet impacts the solid boundary at a high velocity, and this effect has been taken advantage of in industrial cleaning such as when tiny bubbles are driven ultrasonically to cavitate around machined parts to produce jets that are believed to induce the cleaning effect. In this experimental investigation, we are interested in the jetting from single cavities near a boundary. By introducing a through hole in the boundary beneath a laser-induced bubble, it is hypothesized that the forming jet, upon bubble implosion, will proceed to penetrate through the hole to the other side and that it may be utilized in useful applications such as precise surgeries. It was found that the growth of the bubble induced a fast flow through the hole and lead to the formation of secondary hydrodynamic cavitation. The experiments also showed the formation of a counter jet directed away from the hole and into the bubble. During the growth phase of the bubble, and near the point of maximum expansion, the bubble wall bulged out toward the hole in a `bulb' like formation, which sometimes resulted in the pinching-off of a secondary small bubble. This was ensued by the inward recoiling of the primary bubble wall near the pinch-off spot, which developed into a counter jet seen to move away from the hole and inward into the bubble.

  9. Sonochemistry and the acoustic bubble

    CERN Document Server

    Grieser, Franz; Enomoto, Naoya; Harada, Hisashi; Okitsu, Kenji; Yasui, Kyuichi

    2015-01-01

    Sonochemistry and the Acoustic Bubble provides an introduction to the way ultrasound acts on bubbles in a liquid to cause bubbles to collapse violently, leading to localized 'hot spots' in the liquid with temperatures of 5000° celcius and under pressures of several hundred atmospheres. These extreme conditions produce events such as the emission of light, sonoluminescence, with a lifetime of less than a nanosecond, and free radicals that can initiate a host of varied chemical reactions (sonochemistry) in the liquid, all at room temperature. The physics and chemistry behind the p

  10. Growing bubbles and freezing drops: depletion effects and tip singularities

    NARCIS (Netherlands)

    Enríquez Paz y Puente, Oscar Raúl

    2015-01-01

    In this thesis, the author investigates the growth of gas bubbles in a supersaturated solution and the freezing of water drops when placed on a cold plate. Supersaturated solutions are common in nature and industry; perhaps the best know examples are carbonated drinks, such as beer or soda. These ar

  11. Nonlinear dynamics of a vapor bubble expanding in a superheated region of finite size

    International Nuclear Information System (INIS)

    Growth of a vapor bubble in a superheated liquid is studied theoretically. Contrary to the typical situation of boiling, when bubbles grow in a uniformly heated liquid, here the superheated region is considered in the form of a millimeter-sized spherical hot spot. An initial micron-sized bubble is positioned at the hot spot center and a theoretical model is developed that is capable of studying bubble growth caused by vapor pressure inside the bubble and corresponding hydrodynamic and thermal processes in the surrounding liquid. Such a situation is relevant to the dynamics of vapor cavities that are created in soft biological tissue in the focal region of a high-intensity focused ultrasound beam with a shocked pressure waveform. Such beams are used in the recently proposed treatment called boiling histotripsy. Knowing the typical behavior of vapor cavities during boiling histotripsy could help to optimize the therapeutic procedure

  12. Nonlinear dynamics of a vapor bubble expanding in a superheated region of finite size

    Energy Technology Data Exchange (ETDEWEB)

    Annenkova, E. A., E-mail: a-a-annenkova@yandex.ru [Physics Faculty, Moscow State University, Leninskie Gory, 119991 Moscow (Russian Federation); Kreider, W. [Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40th St., Seattle, WA 98105 (United States); Sapozhnikov, O. A. [Physics Faculty, Moscow State University, Leninskie Gory, 119991 Moscow (Russian Federation); Center for Industrial and Medical Ultrasound, Applied Physics Laboratory, University of Washington, 1013 NE 40th St., Seattle, WA 98105 (United States)

    2015-10-28

    Growth of a vapor bubble in a superheated liquid is studied theoretically. Contrary to the typical situation of boiling, when bubbles grow in a uniformly heated liquid, here the superheated region is considered in the form of a millimeter-sized spherical hot spot. An initial micron-sized bubble is positioned at the hot spot center and a theoretical model is developed that is capable of studying bubble growth caused by vapor pressure inside the bubble and corresponding hydrodynamic and thermal processes in the surrounding liquid. Such a situation is relevant to the dynamics of vapor cavities that are created in soft biological tissue in the focal region of a high-intensity focused ultrasound beam with a shocked pressure waveform. Such beams are used in the recently proposed treatment called boiling histotripsy. Knowing the typical behavior of vapor cavities during boiling histotripsy could help to optimize the therapeutic procedure.

  13. The Housing Bubble Fact Sheet

    OpenAIRE

    Dean Baker

    2005-01-01

    This paper explains the basic facts about the current housing market. It lays out the evidence that the rise in housing prices constitutes a housing bubble - and explains what can be expected when it inevitably collapses.

  14. Bubble bean bags in shampoo

    OpenAIRE

    Kundu, Anup; Sharma, Chandan; Das, Gargi; Harikrishnan, G.

    2011-01-01

    In these fluid dynamics videos, we, for the first time, show various interactions of a 'Taylor bubble' with their smaller and differently, shaped counterparts, in a shear thinning, non-Newtonian fluid, confined in a narrow channel.

  15. Helium bubbles in UO2

    International Nuclear Information System (INIS)

    A certain part of helium generated in MOX fuel could form additional bubbles in fuel pellets as a result of the combination of radiation defects and high temperature. In the present study, the helium infusion treatments were conducted at high temperature with highly pressurized helium for both polycrystalline UO2 fragments and hyperstoichiometric single crystal UO2+x particles. Annealing tests for polycrystalline UO2 were followed by the helium infusion treatment to evaluate formation of helium bubble. In case of as helium-infused polycrystalline sample, it was confirmed that helium bubbles were formed after slight oxidative annealing at more than 1573K. On the other hand, the cavity observed in as-helium-infused single crystal sample grew up to form a negative crystal. Formation mechanism of helium bubble and negative crystal were discussed. (author)

  16. Transient bubbles, bublets and breakup

    Science.gov (United States)

    Keen, Giles; Blake, John

    1999-11-01

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

  17. Pulling bubbles from a bath

    Science.gov (United States)

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

    2010-06-01

    Deposition of bubbles on a wall withdrawn from a liquid bath is a phenomenon observed in many everyday situations—the foam lacing left behind in an emptied glass of beer, for instance. It is also of importance to the many industrial processes where uniformity of coating is desirable. We report work on an idealized version of this situation, the drag-out of a single bubble in Landau-Levich-Derjaguin flow. We find that a well-defined critical wall speed exists, separating the two regimes of bubble persistence at the meniscus and bubble deposition on the moving wall. Experiments show that this transition occurs at Ca∗˜Bo0.73. A similar result is obtained theoretically by balancing viscous stresses and gravity.

  18. Modeling the Local Bubble

    Science.gov (United States)

    Cox, D. P.

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

  19. Mechanisms of single bubble cleaning.

    Science.gov (United States)

    Reuter, Fabian; Mettin, Robert

    2016-03-01

    The dynamics of collapsing bubbles close to a flat solid is investigated with respect to its potential for removal of surface attached particles. Individual bubbles are created by nanosecond Nd:YAG laser pulses focused into water close to glass plates contaminated with melamine resin micro-particles. The bubble dynamics is analysed by means of synchronous high-speed recordings. Due to the close solid boundary, the bubble collapses with the well-known liquid jet phenomenon. Subsequent microscopic inspection of the substrates reveals circular areas clean of particles after a single bubble generation and collapse event. The detailed bubble dynamics, as well as the cleaned area size, is characterised by the non-dimensional bubble stand-off γ=d/Rmax, with d: laser focus distance to the solid boundary, and Rmax: maximum bubble radius before collapse. We observe a maximum of clean area at γ≈0.7, a roughly linear decay of the cleaned circle radius for increasing γ, and no cleaning for γ>3.5. As the main mechanism for particle removal, rapid flows at the boundary are identified. Three different cleaning regimes are discussed in relation to γ: (I) For large stand-off, 1.8flows touch down onto the substrate and remove particles without significant contact of the gas phase. (II) For small distances, γflows at the substrate are driven by the jet impact with its subsequent radial spreading, and by the liquid following the motion of the collapsing and rebounding bubble wall. Both flows remove particles. Their relative timing, which depends sensitively on the exact γ, appears to determine the extension of the area with forces large enough to cause particle detachment. (III) At intermediate stand-off, 1.1cleaning mechanisms similar to an effective small γ collapse: particles are removed by the jet flow and the flow induced by the bubble wall oscillation. Furthermore, the observations reveal that the extent of direct bubble gas phase contact to the solid is partially

  20. Ostwald Ripening in Multiple-Bubble Nuclei

    OpenAIRE

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

    2014-01-01

    The ostwald ripening of bubbles is studied by molecular dynamics simulations involving up to 679 million Lennard-Jones particles. Many bubbles appear after depressurizing a system that is initially maintained in the pure-liquid phase, and the coarsening of bubbles follows. The self-similarity of the bubble-size distribution function predicted by Lifshitz-Slyozov-Wagner theory is directly confirmed. The total number of bubbles decreases asymptotically as $t^{-x}$ with scaling exponent $x$. As ...

  1. Learning the CAPM through Bubbles

    OpenAIRE

    Haim Kedar-Levy

    2004-01-01

    Bubbles are generally considered the outcome of investor irrationality or informational asymmetry, both objectionable in efficient markets with rational investors. We introduce an Intertemporal-CAPM with market clearing between high- and low-risk-averse rational investors who learn the CAPM under incomplete, yet symmetric information. Periodic equilibrium prices make a lognormal price process that nests the classic CAPM with a potential for endogenous bubbles through learning. The absence of ...

  2. Bubbly-to-cap bubbly flow transition in a long-26 m vertical large diameter pipe at low liquid flow rate

    International Nuclear Information System (INIS)

    monotonously again with axial position in the fully-developed cap bubbly flow. The temporary void fraction decrease phenomenon in the transition region from bubbly to cap bubbly flow can be attributed to the formation of medium to large cap bubbles and their gradual growth into the maximum size of cap bubble and/or cluster of large cap bubbles in the developing cap bubbly flow. In order to predict the N-shaped axial void fraction changing behaviors in the flow regime transition from bubbly to cap bubbly flow, the existing 12 drift flux correlation sets for large diameter pipes are reviewed and their predictabilities are studied against the present experimental data. Although some drift flux correlation sets, such as those of Clark and Flemmer (1986) and Hibiki and Ishii (2003), can predict the present experimental data with reasonable average relative deviations, no drift flux correlation set for distribution parameter and drift velocity can give a reliable prediction for the observed N-shaped axial void fraction changing behaviors in the region from bubbly to cap bubbly flow in a vertical large diameter pipe

  3. Doughnut-shaped soap bubbles

    CERN Document Server

    Preve, Deison

    2015-01-01

    Soap bubbles are thin liquid films enclosing a fixed volume of air. Since the surface tension is typically assumed to be the only responsible for conforming the soap bubble shape, the realized bubble surfaces are always minimal area ones. Here, we consider the problem of finding the axisymmetric minimal area surface enclosing a fixed volume $V$ and with a fixed equatorial perimeter $L$. It is well known that the sphere is the solution for $V=L^3/6\\pi^2$, and this is indeed the case of a free soap bubble, for instance. Surprisingly, we show that for $V<\\alpha L^3/6\\pi^2$, with $\\alpha\\approx 0.21$, such a surface cannot be the usual lens-shaped surface formed by the juxtaposition of two spherical caps, but rather a toroidal surface. Practically, a doughnut-shaped bubble is known to be ultimately unstable and, hence, it will eventually lose its axisymmetry by breaking apart in smaller bubbles. Indisputably, however, the topological transition from spherical to toroidal surfaces is mandatory here for obtainin...

  4. Beyond the gas bubble

    International Nuclear Information System (INIS)

    The deliverability issue currently being discussed within the natural gas industry involves both near-term and long-term questions. In the near-term, over the next two or three years, it is probable that the natural gas industry will need to mobilize for much greater levels of investment than have been the experience over the past few years. In the longer-term, it is expected that new opportunities for gas will arise as the nation seeks to meet increasing energy requirements within new environmental constraints. Methane for emissions control, CNG vehicles, expanded gas-fired electricity generation, and increased efficiency of traditional energy services are just a few examples. The issues in the longer-term center on the ability of the gas industry to meet increasing supply requirements reliably and at cost-competitive prices for these markets. This paper begins by reviewing the historical situation of gas deliverability that is the capability of the gas producing and transportation portions of the industry. The delivery system's ability to handle shifts in the centers of consumption and production is discussed, with an emphasis on regional problems of gas deliverability and potential bottlenecks. On the production side, the paper reviews the capability and the required investment necessary to handle an orderly transition to a stable supply and demand balance once the elusive bubble had finally disappeared

  5. FEASTING BLACK HOLE BLOWS BUBBLES

    Science.gov (United States)

    2002-01-01

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

  6. Bubbles Tomorrow and Bubbles Yesterday, but Never Bubbles Today?

    OpenAIRE

    Williams, John C.

    2013-01-01

    Considering their importance and the amount of effort that has gone into understanding them, asset price bubbles continue to perplex. The evidence of these bubbles seldom squares with what would be expected from standard asset price theory. Unlike the suggestions from theory, expectations of prices of both stocks and houses tend to be procyclical—price expectations are driven by recent price performance. Thus, price expectations are extrapolative rather than rational, as assumed by standard a...

  7. Study of Interfacial Mass Transfer on Vapor Bubbles in Microgravity

    Directory of Open Access Journals (Sweden)

    Johannes Straub

    2005-03-01

    Full Text Available The knowledge of interfacial heat and mass transfer is important for environmental and technical applications, especially nowadays for numerical simulations of two phase problems. However, the data available up to now are inconsistent, because most experiments performed on earth suffer under buoyancy and convection, and thus the boundary conditions at the evaluation could not clearly be defined. Therefore, we seized the opportunity to investigate interfacial heat and mass transfer in microgravity environment. In these experiments the growth and collapse in the overall superheated and subcooled bubles, respectively, liquid or free vapor bubbles were observed at various liquid temperature and pressure states and over periods of from a few seconds up to 300 seconds. It was for the first time that such very long periods of bubble growth could be observed. The experimental set-up allowed the control of the liquid supersaturation before the bubbles were initiated by a short heat pulse at a miniaturized heater. Therefore it was possible to perform a systematic parametric study. The measured curves for vapor bubble growth are in good agreement with our numerical simulation. Based on this model the kinetic coefficients for the evaporation and condensation according to Hertz-Knudsen have been derived from the experimental data.

  8. Effect of oxygen and heliox breathing on air bubbles in adipose tissue during 25-kPa altitude exposures

    DEFF Research Database (Denmark)

    Randsoe, T.; Kvist, T.M.; Hyldegaard, O.

    2008-01-01

    .7) after which they started shrinking or remained stable throughout the observation period. Bubble growth time was significantly longer during oxygen breathing compared with heliox breathing and preoxygenated animals. Significantly more bubbles disappeared in preoxygenated animals compared with oxygen and......At altitude, bubbles are known to form and grow in blood and tissues causing altitude decompression sickness. Previous reports indicate that treatment of decompression sickness by means of oxygen breathing at altitude may cause unwanted bubble growth. In this report we visually followed the in vivo...... changes of micro air bubbles injected into adipose tissue of anesthetized rats at 101.3 kPa (sea level) after which they were decompressed from 101.3 kPa to and held at 25 kPa (10,350 m), during breathing of oxygen or a heliox(34:66) mixture (34% helium and 66% oxygen). Furthermore, bubbles were studied...

  9. Nucleus factory on cavitation bubble for amyloid β fibril

    Science.gov (United States)

    Nakajima, Kichitaro; Ogi, Hirotsugu; Adachi, Kanta; Noi, Kentaro; Hirao, Masahiko; Yagi, Hisashi; Goto, Yuji

    2016-02-01

    Structural evolution from monomer to fibril of amyloid β peptide is related to pathogenic mechanism of Alzheimer disease, and its acceleration is a long-running problem in drug development. This study reveals that ultrasonic cavitation bubbles behave as catalysts for nucleation of the peptide: The nucleation reaction is highly dependent on frequency and pressure of acoustic wave, and we discover an optimum acoustical condition, at which the reaction-rate constant for nucleation is increased by three-orders-of magnitudes. A theoretical model is proposed for explaining highly frequency and pressure dependent nucleation reaction, where monomers are captured on the bubble surface during its growth and highly condensed by subsequent bubble collapse, so that they are transiently exposed to high temperatures. Thus, the dual effects of local condensation and local heating contribute to dramatically enhance the nucleation reaction. Our model consistently reproduces the frequency and pressure dependences, supporting its essential applicability.

  10. Investigation on the mechanisms of bubble lift-off from a vertical heated surface in subcooled pool boiling

    International Nuclear Information System (INIS)

    Experiments were conducted to elucidate the mechanisms of bubble lift-off from a vertical heated surface in subcooled pool boiling. The experiments were carried out at atmospheric pressure and distilled water was used as the test fluid. A high speed camera was used to observe the bubble behavior. Main experimental parameters were the static contact angle of the heated surface, wall heat flux and the liquid subcooling. In order to observe the bubble behavior clearly, the experiments were performed in the isolated bubble regime. In the present work, the following three typical types of bubble behavior were observed: (1) adhesion to the heated surface, (2) sliding along the heated surface, and (3) lift-off from the heated surface. The effects of the above-mentioned experimental parameters on the bubble behavior was clarified. In addition, the bubble diameter and the bubble migration velocity in the lateral direction at the moment of lift-off were investigated in detail. Assuming that the superheated layer thickness and the bubble growth rate are the appropriate scaling factors for the bubble size and the bubble migration velocity, respectively, semi-empirical correlations were developed. (author)

  11. Numerical modeling of bubble dynamics in viscoelastic media with relaxation

    Science.gov (United States)

    Warnez, M. T.; Johnsen, E.

    2015-06-01

    Cavitation occurs in a variety of non-Newtonian fluids and viscoelastic materials. The large-amplitude volumetric oscillations of cavitation bubbles give rise to high temperatures and pressures at collapse, as well as induce large and rapid deformation of the surroundings. In this work, we develop a comprehensive numerical framework for spherical bubble dynamics in isotropic media obeying a wide range of viscoelastic constitutive relationships. Our numerical approach solves the compressible Keller-Miksis equation with full thermal effects (inside and outside the bubble) when coupled to a highly generalized constitutive relationship (which allows Newtonian, Kelvin-Voigt, Zener, linear Maxwell, upper-convected Maxwell, Jeffreys, Oldroyd-B, Giesekus, and Phan-Thien-Tanner models). For the latter two models, partial differential equations (PDEs) must be solved in the surrounding medium; for the remaining models, we show that the PDEs can be reduced to ordinary differential equations. To solve the general constitutive PDEs, we present a Chebyshev spectral collocation method, which is robust even for violent collapse. Combining this numerical approach with theoretical analysis, we simulate bubble dynamics in various viscoelastic media to determine the impact of relaxation time, a constitutive parameter, on the associated physics. Relaxation time is found to increase bubble growth and permit rebounds driven purely by residual stresses in the surroundings. Different regimes of oscillations occur depending on the relaxation time.

  12. Bursting Bubbles and Bilayers

    Directory of Open Access Journals (Sweden)

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

    2012-01-01

    Full Text Available 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

  13. Tohoku one meter bubble chamber

    International Nuclear Information System (INIS)

    At the request of Tohoku University and the National Laboratory for High Energy Physics, IHI has developed a complete freon bubble chamber system successfully, which is used for photo analysis of elementary particles physics. This system will be delivered to Fermi National Accelerator Laboratory (FNAL) in Illinois (U.S.A.) and will be coupled with the superconducting accelerator (TEVATRON) for the study of elementary particles. The total system of the freon bubble chamber is composed of a stainless steel casting spherical bubble chamber with a diameter of about one meter, an expansion system for freon pressure control, hydraulic system for driving an expansion piston, a freon feed system, a temperature control system, an overall control system as well as camera and flashlight for photograph. (author)

  14. Disruption of an Aligned Dendritic Network by Bubbles During Re-Melting in a Microgravity Environment

    Science.gov (United States)

    Grugel, Richard N.; Brush, Lucien N.; Anilkumar, Amrutur V.

    2012-01-01

    The quiescent Microgravity environment can be quite dynamic. Thermocapillary flow about "large" static bubbles on the order of 1mm in diameter was easily observed by following smaller tracer bubbles. The bubble induced flow was seen to disrupt a large dendritic array, effectively distributing free branches about the solid-liquid interface. "Small" dynamic bubbles were observed to travel at fast velocities through the mushy zone with the implication of bringing/detaching/redistributing dendrite arm fragments at the solid-liquid interface. Large and small bubbles effectively re-orient/re-distribute dendrite branches/arms/fragments at the solid liquid interface. Subsequent initiation of controlled directional solidification results in growth of dendrites having random orientations which significantly compromises the desired science.

  15. The stability of buoyant bubbles in the atmospheres of galaxy clusters

    CERN Document Server

    Kaiser, C R; Pope, E C D; Fangohr, H

    2005-01-01

    The buoyant rise of hot plasma bubbles inflated by AGN outflows in galaxy clusters can heat the cluster gas and thereby compensate radiative energy losses of this material. Numerical simulations of this effect often show the complete disruption of the bubbles followed by the mixing of the bubble material with the surrounding cluster gas due to fluid instabilities on the bubble surface. This prediction is inconsistent with the observations of apparently coherent bubble structures in clusters. We derive a general description in the linear regime of the growth of instabilities on the surface between two fluids under the influence of a gravitational field, viscosity, surface tension provided by a magnetic field and relative motion of the two fluids with respect to each other. We demonstrate that Kelvin-Helmholtz instabilities are always suppressed, if the fluids are viscous. They are also suppressed in the inviscid case for fluids of very different mass densities. We show that the effects of shear viscosity as we...

  16. Annealing Behaviour of Helium Bubbles in Titanium Films by Thermal Desorption Spectroscopy and Positron Beam Analysis

    Institute of Scientific and Technical Information of China (English)

    LIU Chao-Zhuo; ZHOU Zhu-Ying; SHI Li-Qun; WANG Bao-Yi; HAO Xiao-Peng; ZHAO Guo-Qing

    2007-01-01

    @@ Helium-containing Ti films are prepared using magnetron sputtering in the helium-argon atmosphere. Isochronal annealing at different temperatures for an hour is employed to reveal the behaviour of helium bubble growth. Ion beam analysis is used to measure the retained helium content. Helium can release largely when annealing above 970 K. A thermal helium desorption spectroscopy system is constructed for assessment of the evolution of helium bubbles in the annealed samples by linear heating (0.4K/s) from room temperature to 1500K. Also, Doppler broadening measurements of positron annihilation radiation spectrum are performed by using changeable energy positron beam. Bubble coarsening evolves gradually below 680K, migration and coalescence of small bubbles dominates in the range of 680-970K, and the Ostwald ripening mechanism enlarges the bubbles with a massive release above 970K.

  17. Reconstructing CO2 concentrations in basaltic melt inclusions using Raman analysis of vapor bubbles

    Science.gov (United States)

    Aster, Ellen M.; Wallace, Paul J.; Moore, Lowell R.; Watkins, James; Gazel, Esteban; Bodnar, Robert J.

    2016-09-01

    Melt inclusions record valuable information about pre-eruptive volatile concentrations of melts. However, a vapor bubble commonly forms in inclusions after trapping, and this decreases the dissolved CO2 concentration in the melt (glass) phase in the inclusion. To quantify CO2 loss to vapor bubbles, Raman spectroscopic analysis was used to determine the density of CO2 in bubbles in melt inclusions from two Cascade cinder cones near Mt. Lassen and two Mexican cinder cones (Jorullo, Parícutin). Using analyses of dissolved CO2 and H2O in the glass in the inclusions, the measured CO2 vapor densities were used to reconstruct the original dissolved CO2 contents of the melt inclusions at the time of trapping. Our results show that 30-90% of the CO2 in a melt inclusion is contained in the vapor bubble, values similar to those found in other recent studies. We developed a model for vapor bubble growth to show how post-entrapment bubbles form in melt inclusions as a result of cooling, crystallization, and eruptive quenching. The model allows us to predict the bubble volume fraction as a function of ΔT (the difference between the trapping temperature and eruptive temperature) and the amount of CO2 lost to a bubble. Comparison of the Raman and modeling methods shows highly variable agreement. For 10 of 17 inclusions, the two methods are within ± 550 ppm CO2 (avg. difference 290 ppm), equivalent to ±~300 bars uncertainty in estimated trapping pressure for restored inclusions. Discrepancies between the two methods occur for inclusions that have been strongly affected by post-entrapment diffusive H+ loss, because this process enhances bubble formation. For our dataset, restoring the CO2 lost to vapor bubbles increases inferred trapping pressures of the inclusions by 600 to as much as 4000 bars, highlighting the importance of accounting for vapor bubble formation in melt inclusion studies.

  18. Photon Number Conserving Models of HII Bubbles during Reionization

    Science.gov (United States)

    Paranjape, Aseem; Choudhury, T. Roy; Padmanabhan, Hamsa

    2016-05-01

    Traditional excursion set based models of HII bubble growth during the epoch of reionization are known to violate photon number conservation, in the sense that the mass fraction in ionized bubbles in these models does not equal the ratio of the number of ionizing photons produced by sources and the number of hydrogen atoms in the intergalactic medium. E.g., for a Planck13 cosmology with electron scattering optical depth τ ≃ 0.066, the discrepancy is ˜15 per cent for xHII = 0.1 and ˜5 per cent for xHII = 0.5. We demonstrate that this problem arises from a fundamental conceptual shortcoming of the excursion set approach (already recognised in the literature on this formalism) which only tracks average mass fractions instead of the exact, stochastic source counts. With this insight, we build an approximately photon number conserving Monte Carlo model of bubble growth based on partitioning regions of dark matter into halos. Our model, which is formally valid for white noise initial conditions (ICs), shows dramatic improvements in photon number conservation, as well as substantial differences in the bubble size distribution, as compared to traditional models. We explore the trends obtained on applying our algorithm to more realistic ICs, finding that these improvements are robust to changes in the ICs. Since currently popular semi-numerical schemes of bubble growth also violate photon number conservation, we argue that it will be worthwhile to pursue new, explicitly photon number conserving approaches. Along the way, we clarify some misconceptions regarding this problem that have appeared in the literature.

  19. Helium bubble evolution in a Zr–Sn–Nb–Fe–Cr alloy during post-annealing: An in-situ investigation

    Energy Technology Data Exchange (ETDEWEB)

    Shen, H.H. [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109 (United States); Peng, S.M.; Chen, B. [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Naab, F.N. [Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI 48109 (United States); Sun, G.A.; Zhou, W. [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Xiang, X. [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Sun, K., E-mail: kaisun@umich.edu [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109 (United States); Zu, X.T., E-mail: xtzu@uestc.edu.cn [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China)

    2015-09-15

    The formation of helium bubbles is considered to be detrimental to the mechanical performance of the nuclear materials. The growth behaviors of helium bubbles in a helium ion implanted Zr–Sn–Nb–Fe–Cr alloy with respect to the helium fluence and subsequently annealing procedure were investigated by in-situ transmission electron microscopy. In the as-implanted sample, the measured size distributions of the helium bubbles are consistent with the simulated helium concentrations. Moreover, the mean size of the helium bubbles increases with the increase of the irradiation temperatures and the helium fluence. The in-situ heating study performed in a transmission electron microscope indicates that the mean size of the helium bubbles increase slowly below 923 K and dramatically above 923 K. The coarsening mechanism of the helium bubbles in the alloy is suggested based on the study. - Highlights: • Helium bubble growth in zirconium with annealing was in-situ investigated in TEM. • The mean helium bubble size increase with helium fluence and annealing temperature. • Helium bubble size distribution is same as that of helium concentration by SRIM. • Mean bubble size increases slowly and quickly with temperature below and above 923 K. • The growth mechanism of the helium bubbles in Zr alloy has been discussed.

  20. Helium bubble evolution in a Zr–Sn–Nb–Fe–Cr alloy during post-annealing: An in-situ investigation

    International Nuclear Information System (INIS)

    The formation of helium bubbles is considered to be detrimental to the mechanical performance of the nuclear materials. The growth behaviors of helium bubbles in a helium ion implanted Zr–Sn–Nb–Fe–Cr alloy with respect to the helium fluence and subsequently annealing procedure were investigated by in-situ transmission electron microscopy. In the as-implanted sample, the measured size distributions of the helium bubbles are consistent with the simulated helium concentrations. Moreover, the mean size of the helium bubbles increases with the increase of the irradiation temperatures and the helium fluence. The in-situ heating study performed in a transmission electron microscope indicates that the mean size of the helium bubbles increase slowly below 923 K and dramatically above 923 K. The coarsening mechanism of the helium bubbles in the alloy is suggested based on the study. - Highlights: • Helium bubble growth in zirconium with annealing was in-situ investigated in TEM. • The mean helium bubble size increase with helium fluence and annealing temperature. • Helium bubble size distribution is same as that of helium concentration by SRIM. • Mean bubble size increases slowly and quickly with temperature below and above 923 K. • The growth mechanism of the helium bubbles in Zr alloy has been discussed

  1. Hydrodynamic Interactions of a Bubble Pair and Bubbles in Clusters

    Czech Academy of Sciences Publication Activity Database

    Stanovský, Petr; Růžička, Marek

    Prague : ICPF ASCR, 2013. s. 122. ISBN N. [Workshop on Smart and Green Interfaces 2013. 20.3.2013-22.03.2013, Prague] Grant ostatní: COST (XE) MP1106 Institutional support: RVO:67985858 Keywords : ultrapure water * bubbles * silicon oils Subject RIV: CI - Industrial Chemistry, Chemical Engineering

  2. Radiation Characteristics of Glass Containing Gas Bubbles

    OpenAIRE

    Pilon, Laurent; Viskanta, Raymond

    2003-01-01

    In many materials processing and manufacturing situations such as steel, aluminum, ceramics and glass, gas bubbles can form in liquid and solid phases. The presence of such bubbles affects the thermophysical properties and radiation characteristics of the two-phase system and hence the transport phenomena. This paper presents a general formulation of the radiation characteristics of semitransparent media containing large gas bubbles (bubble radius is much larger than the wavelength of radiati...

  3. Development of Bubble Lift-off Diameter Model for Subcooled Boiling Flows

    International Nuclear Information System (INIS)

    A lot of models and correlations for predicting the bubble departure/lift-off diameter are available in the literature. Most of them were developed based on a hydrodynamic principle, which balances forces acting on a bubble at the departure/lift-off point. One difficulty of these models is lack of essential information, such as bubble front velocity, liquid velocity, or relative velocity, to estimate the active force elements. Hence, the lift-off bubble diameter predicted by these hydrodynamic-controlled models may be suffered a large uncertainty. In contract to the hydrodynamic approach, there are few models developed based on the heat transfer aspect. By balancing the heat conducted through a microlayer underneath a bubble with the heat taken away by condensation at the upper part of the bubble, Unal derived a heat-controlled model of the bubble lift-off diameter. This model did not consider the role of superheat liquid layer surrounding the bubble as well as the effect of liquid properties on the heat transfer process. Beside these two approaches, several empirical correlations have been proposed based on dimensionless analyses for measured experimental databases. The application of these correlations to different experiments conditions is, of course, questionable because of the lack of physical bases. Regarding the heat transfer accompanied by a vapor bubble, four involved heat transfer regions surrounding this bubble can be defined as in Fig. 1. These are dry region, microlayer, superheated liquid layer (SpLL) and subcooled liquid layer (SbLL). The existing of the microlayer is confirmed by experiments, and it is considered to be very effective in the heat transfer. Sernas and Hoper defined five types of the microlayer and indicated that the microlayer acting as a very thick liquid layer gives a best prediction for the bubble growth. However, beside the microlayer, the SpLL might play an important role in the heat transfer if its effective heat transfer area

  4. Modeling bubbly-cap flows using two-group average bubble number density

    International Nuclear Information System (INIS)

    The basic concept of two-group average bubble number density equations along with three-fluid model has been demonstrated for vertical gas-liquid flow. Specifically, the current study focused on: (i)classification of bubble interaction between spherical bubbles (Group-1) and cap bubbles (Group- 2), (ii) preliminary consideration of source and sink terms in the averaged bubble number density equations via the model of Hibiki and Ishii [1] and (iii) assessment by means of experimental data sets at bubbly-to-cap flow transition. Reasonable agreement was achieved between measured and predicted distributions of void fraction, interfacial area concentration (IAC) and volume equivalent bubble diameter. (author)

  5. Frictional drag reduction by bubble injection

    Science.gov (United States)

    Murai, Yuichi

    2014-07-01

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

  6. Modeling bubble collapse aggressiveness in traveling bubble cavitation using bubble breakup model

    Czech Academy of Sciences Publication Activity Database

    Zima, Patrik; Sedlář, M.

    Singapore : Research Publishing Services, 2012 - (Ohl, C.; Klaseboer, E.; Ohl, S.; Gong, S.; Khoo, B.), s. 182-186 ISBN 978-981-07-2826-7. [International Symposium on Cavitation /8./ CAV 2012. Singapur (SG), 13.08.2012-16.08.2012] R&D Projects: GA ČR GAP101/10/1428 Institutional research plan: CEZ:AV0Z20760514 Keywords : bubble collapse * traveling bubble cavitation * numerical modeling Subject RIV: BK - Fluid Dynamics http://rpsonline.com.sg/proceedings/9789810728267/html/209.xml51.xml

  7. Impurity bubbles in a BEC

    Science.gov (United States)

    Timmermans, Eddy; Blinova, Alina; Boshier, Malcolm

    2013-05-01

    Polarons (particles that interact with the self-consistent deformation of the host medium that contains them) self-localize when strongly coupled. Dilute Bose-Einstein condensates (BECs) doped with neutral distinguishable atoms (impurities) and armed with a Feshbach-tuned impurity-boson interaction provide a unique laboratory to study self-localized polarons. In nature, self-localized polarons come in two flavors that exhibit qualitatively different behavior: In lattice systems, the deformation is slight and the particle is accompanied by a cloud of collective excitations as in the case of the Landau-Pekar polarons of electrons in a dielectric lattice. In natural fluids and gases, the strongly coupled particle radically alters the medium, e.g. by expelling the host medium as in the case of the electron bubbles in superfluid helium. We show that BEC-impurities can self-localize in a bubble, as well as in a Landau-Pekar polaron state. The BEC-impurity system is fully characterized by only two dimensionless coupling constants. In the corresponding phase diagram the bubble and Landau-Pekar polaron limits correspond to large islands separated by a cross-over region. The same BEC-impurity species can be adiabatically Feshbach steered from the Landau-Pekar to the bubble regime. This work was funded by the Los Alamos LDRD program.

  8. Electric fields effect on the rise of single bubbles during boiling

    Energy Technology Data Exchange (ETDEWEB)

    Siedel, Samuel; Cioulachtjian, Serge; Bonjour, Jocelyn [CETHIL - UMR 5008 CNRS INSA-Lyon Univ. Lyon 1, INLSA-Lyon (France)], e-mail: jocelyn.bonjour@insa-lyon.fr

    2009-07-01

    An experimental study of saturated pool boiling on a single artificial nucleation site without and with the application of an electric field on the boiling surface has been conducted. N-pentane is boiling on a copper surface and is recorded with a high speed camera providing high quality pictures and movies. The accuracy of the visualization allowed establishing an experimental bubble growth law from a large number of experiments. This law shows that the evaporation rate is decreasing during the bubble growth, and underlines the importance of liquid motion induced by the preceding bubble. Bubble rise is therefore studied: once detached, bubbles accelerate vertically until reaching a maximum velocity in good agreement with a correlation from literature. The bubbles then turn to another direction. The effect of applying an electric field on the boiling surface in finally studied. In addition to changes of the bubble shape, changes are also shown in the liquid plume and the convective structures above the surface. Lower maximum rising velocities were measured in the presence of electric fields, especially with a negative polarity. (author)

  9. Electric fields effect on the rise of single bubbles during boiling

    International Nuclear Information System (INIS)

    An experimental study of saturated pool boiling on a single artificial nucleation site without and with the application of an electric field on the boiling surface has been conducted. N-pentane is boiling on a copper surface and is recorded with a high speed camera providing high quality pictures and movies. The accuracy of the visualization allowed establishing an experimental bubble growth law from a large number of experiments. This law shows that the evaporation rate is decreasing during the bubble growth, and underlines the importance of liquid motion induced by the preceding bubble. Bubble rise is therefore studied: once detached, bubbles accelerate vertically until reaching a maximum velocity in good agreement with a correlation from literature. The bubbles then turn to another direction. The effect of applying an electric field on the boiling surface in finally studied. In addition to changes of the bubble shape, changes are also shown in the liquid plume and the convective structures above the surface. Lower maximum rising velocities were measured in the presence of electric fields, especially with a negative polarity. (author)

  10. Laser induced bubbles inside liquids: Transient optical properties and effects on a beam propagation

    International Nuclear Information System (INIS)

    Light transmission through a laser formed bubble (LFB) following ablation of a metallic target inside water was studied. During the early expansion and late collapsing phases, the refraction index nb of the hot high-pressure vapor bubble is higher than 1.23 and close to that of the surrounding liquid. The cavity growth lowers nb down to 1.00 and causes strong defocusing of the incident laser beam with consequent enlargement of the ablation crater diameter, here overcoming factor two. Inhomogeneous water vapor clustering inside the cool expanded bubble further perturbs the light transmission and induces irregular ablation by the successive laser pulse.

  11. Experimental study of the interaction between the spark-induced cavitation bubble and the air bubble

    Institute of Scientific and Technical Information of China (English)

    罗晶; 许唯临; 牛志攀; 罗书靖; 郑秋文

    2013-01-01

    Experiments are carried out by using high-speed photography to investigate the interaction between the spark-generated cavitation bubble and the air bubble in its surrounding fluid. Three problems are discussed in detail: the impact of the air bubble upon the development of the cavitation bubble, the evolution of the air bubble under the influence of the cavitation bubble, and the change of the fluid pressure during the development of a micro jet of the cavitation bubble. Based on the experimental results, under the condition of no air bubble present, the lifetime of the cavitation bubble from expansion to contraction increases with the increase of the maximum radius. On the other hand, when there is an air bubble present, different sized cavitation bubbles have similarity with one another generally in terms of the lifetime from expansion to contraction, which does not depend on the maximum radius. Also, with the presence of an air bubble, the lifetime of the smaller cavitation bubble is extended while that of the bigger ones reduced. Furthermore, it is shown in the experiment that the low pressure formed in the opposite direction to the cavitation bubble micro jet makes the air bubble in the low pressure area being stretched into a steplike shape.

  12. Hydrodynamics in a swarm of rising bubbles

    International Nuclear Information System (INIS)

    In many applications, bubbles are used to agitate a liquid in order to enhance mixing and transfer. This work is devoted to the study of the hydrodynamics in a stable bubble column. Experimentally, we have determined the properties of the velocity fluctuations inside and behind a homogeneous swarm of rising bubbles for different bubble sizes and gas volume fractions α: self-similarity in α0,4, spectrum in k-3 and integral length scale controlled by buoyancy. Numerically, we have reproduced these properties by means of large-scale simulations, the bubbles being modeled by volume-forces. This confirms that the dynamics is controlled by wake interactions. (author)

  13. Shell correction energy for bubble nuclei

    CERN Document Server

    Yu, Y; Magierski, P; Bulgac, Aurel; Magierski, Piotr

    2000-01-01

    The positioning of a bubble inside a many fermion system does not affect the volume, surface or curvature terms in the liquid drop expansion of the total energy. Besides possible Coulomb effects, the only other contribution to the ground state energy of such a system arises from shell effects. We show that the potential energy surface is a rather shallow function of the displacement of the bubble from the center and in most cases the preferential position of a bubble is off center. Systems with bubbles are expected to have bands of extremely low lying collective states, corresponding to various bubble displacements.

  14. Digital Microfluidics with Bubble Manipulations by Dielectrophoresis

    Directory of Open Access Journals (Sweden)

    Shih-Kang Fan

    2012-03-01

    Full Text Available This paper presents basic bubble manipulations, including transporting, splitting, and merging, by dielectrophoresis (DEP in an oil environment. In our presented method, bubbles are placed between parallel plates in an oil medium of a low vapor pressure, which eliminates the possibility of changing the gaseous composition of the bubble caused by evaporation of the medium. DEP has been previously investigated to actuate dielectric droplets and is adopted here to drive the oil environment as well as the immersed bubbles between parallel plates. In our experiment, air bubbles of 0.3 ml were successfully transported in a 20 cSt silicone oil medium between a 75 mm-high parallel plate gap. In addition, 0.6 ml air bubbles were successfully split into two 0.3 ml air bubbles, and then merged again by DEP. These successful manipulations make digital gaseous lab-on-a-chip a reality.

  15. A study of gas bubbles in liquid mercury in a vertical Hele-Shaw cell

    International Nuclear Information System (INIS)

    High-quality observations of mesoscopic gas bubbles in liquid metal are vital for a further development of pyrometallurgical gas injection reactors. However, the opacity of metals enforces the use of indirect imaging techniques with limited temporal or spatial resolution. In addition, accurate interface tracking requires tomography which further complicates the design of a high-temperature experimental setup. In this paper, an alternative approach is suggested that circumvents these two main restrictions. By injecting gas in a thin layer of liquid metal entrapped between two flat and closely spaced plates, bubbles in a Hele-Shaw flow regime are generated. The resulting quasi-2D multiphase flow phenomena can be fully captured from a single point of view and, when using a non-wetted transparent plate material, the bubbles can be observed directly. The feasibility of this approach is demonstrated by observations on buoyancy-driven nitrogen bubbles in liquid mercury in a vertical Hele-Shaw cell. By using a moving high-speed camera to make continuous close up recordings of individual bubbles, the position and geometry of these bubbles are quantified with a high resolution along their entire path. After a thorough evaluation of the experimental accuracy, this information is used for a detailed analysis of the bubble expansion along the path. While the observed bubble growth is mainly caused by the hydrostatic pressure gradient, a careful assessment of the volume variations for smaller bubbles shows that an accurate bubble description should account for significant dynamic pressure variations that seem to be largely regime dependent. (orig.)

  16. Numerical simulation of bubble behaviors in subcooled flow boiling under swing motion

    Energy Technology Data Exchange (ETDEWEB)

    Wei Jinghua [Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Ministry of Education, Chongqing University, Chongqing 400044 (China); Pan Liangming, E-mail: cneng@cqu.edu.cn [Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Ministry of Education, Chongqing University, Chongqing 400044 (China); Chen Deqi; Zhang Hui [Key Laboratory of Low-grade Energy Utilization Technologies and Systems, Ministry of Education, Chongqing University, Chongqing 400044 (China); Xu Jianjun; Huang Yanping [CNNC Key Laboratory on Nuclear Reactor Thermal Hydraulics Technology, Nuclear Power Institute of China, Chengdu 6140041 (China)

    2011-08-15

    Highlights: > Secondary flow exists inside bubbles due to the evaporation and condensation. > The relative motion of these two bubbles generates two symmetrical vortexes and a stagnant region. > The supplementary microlayer between the two coalescing bubbles is observed in the simulation. > The additional inertia forces generated by swing are negligible. > The fluctuation of mass flow rate caused by swing motion effects the F{sub sl}, F{sub qs}, F{sub h} and the phase distribution significantly. - Abstract: A numerical investigation of bubble behaviors in subcooled flow boiling of water under the effect of additional inertial forces has been performed considering energy and mass transfer during phase change based on the VOF (volume-of-fluid) method. The pressure ranges from 0.1 to 1.0 MPa, and heat flux from 200 to 500 kW/m{sup 2}. The mass flow rate and inlet subcooling are specified at 320 kg/m{sup 2} s and 10 K, respectively. The liquid-vapor interface is captured using the piecewise linearity interpolation calculation (PLIC) geometry restructuring method. The simulations are carried out on upward water flow in a vertical, rectangular duct with single side heating surface. The pressure, velocity vector and temperature distribution around two isolated bubbles are studied firstly. The behaviors of bubble coalescence, sliding, detachment from the heated wall, and the bubble shape variation during lifetime are further examined. The bubble behaviors in the different pressure and heat flux are investigated. The simulated results of bubble growth rate and wall temperature are agreed well with the correlations in the literatures. The additional inertial forces caused by swing are negligible, but the fluctuation of mass flow rate caused by swing motion influences the forces acting on bubble significantly. Compared with the motionless condition, the pressure drop is increased and the fluctuation becomes acute as heat flux increases under the swing condition.

  17. Mathematical models for tritium permeation analysis in liquid metal flows with helium bubbles

    International Nuclear Information System (INIS)

    Highlights: • Tritium transport in wall-attached He bubbles is studied. • Tritium mainly by-passes the bubble and its partial pressure in the bubble is homogeneous. • The bubble boundary layer depth is about twice the bubble radius. • Simplified tritium transport models are developed and validated. • A preliminary tritium wall function is proposed for wall-attached He bubbles flows. - Abstract: In LIBRETTO-2 test, evidence was obtained that helium bubbles nucleated and grew in the neutron irradiated PbLi probes. If such phenomenon occurs inside liquid metal (LM) breeding blanket channels, the study of its effect on tritium permeation and heat transfer in the near wall region will acquire utmost importance. The T4F research group has developed in the past a nucleation, growth and transport model for helium bubbles in LM flows, as well as a tritium transport model in such a multi-fluid system. In the present study, we are focused on the near-wall region analysis in order to obtain a wall function that allow reproducing the tritium permeation with coarse meshes and, hence, reduce the computational time. First, we perform some detailed CFD simulations of the near-wall region where bubbles might be attached. In these simulations, tritium diffusion processes as well as tritium recombination and dissociation are modelled. The analysis of such simulations allows us to further understand the complex phenomena and justify the use of simplified models. As a result, a new model for tritium transport across a LM–solid interface partially covered by helium bubbles is developed, implemented and validated. This simplified model can be seen as a wall function for the CFD simulation which substantially reduces computational time

  18. Buoyant Bubbles in a Cooling Intracluster Medium I. Hydrodynamic Bubbles

    CERN Document Server

    Gardini, A

    2006-01-01

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

  19. The contribution of bubble chambers to European scientific collaboration

    International Nuclear Information System (INIS)

    We tend to take the organization of bubble chamber experiments for granted today. Yet the schemes put in practice in the early 1960s were innovative at the time. They required breaking with existing habits of mind which were dominated by the so-called truck team system for doing experiments. They required the formulation of new procedures for both the definition and the implementation of an experimental programme, procedures which were to serve as a ''model'' for the organization of experimental work at CERN with other techniques. And they stimulated an impressive growth of physics activities in universities and national institutes in the CERN member states. In short, bubble chamber physics was the avenue through which multinational, multi-institutional collaborative work was initiated at CERN, the means whereby the laboratory fulfilled its mission to rebuild physics on a European scale. If the bubble chamber physicists achieved these objectives it is not simply because they had already developed a tradition of collaboration. It was also because their technique imposed certain forms of organization on them. It was this combination of historical, technical and political factors which ensured that bubble chamber physics played the key role that it did in the early history of CERN and indeed of European high-energy physics as a whole. (orig./HB)

  20. Developed ‘laminar’ bubbly flow with non-uniform bubble sizes

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Bubbles with different sizes have different dynamic and kineticbehavior in a two-phase bubbly flow. A common two-fluid model based on the uniform bubble size assumption is not suitable for a bubbly flow with non-uniform bubble sizes. To deal with non-uniform bubbly flows, a multi-fluid model is established, with which bubbles are divided into several groups according to their sizes and a set of basic equations is derived for each group of bubbles with almost the same size. Through analyzing the bubble-bubble and bubble-pipe wall interactions, two new constitutive laws for the wall-force and pressure difference between the liquid phase and interface are developed to close the averaged basic equations. The respective phase distributions for each group of bubbles measured by a specially designed three-dimensional photographic method are used to check the model. Comparison between model-predicted values and experimental data shows that the model can describe laminar bubbly flow with non-uniform bubble sizes.

  1. Synchrotron quantification of ultrasound cavitation and bubble dynamics in Al-10Cu melts.

    Science.gov (United States)

    Xu, W W; Tzanakis, I; Srirangam, P; Mirihanage, W U; Eskin, D G; Bodey, A J; Lee, P D

    2016-07-01

    Knowledge of the kinetics of gas bubble formation and evolution under cavitation conditions in molten alloys is important for the control casting defects such as porosity and dissolved hydrogen. Using in situ synchrotron X-ray radiography, we studied the dynamic behaviour of ultrasonic cavitation gas bubbles in a molten Al-10 wt%Cu alloy. The size distribution, average radius and growth rate of cavitation gas bubbles were quantified under an acoustic intensity of 800 W/cm(2) and a maximum acoustic pressure of 4.5 MPa (45 atm). Bubbles exhibited a log-normal size distribution with an average radius of 15.3 ± 0.5 μm. Under applied sonication conditions the growth rate of bubble radius, R(t), followed a power law with a form of R(t)=αt(β), and α=0.0021 &β=0.89. The observed tendencies were discussed in relation to bubble growth mechanisms of Al alloy melts. PMID:26964960

  2. Bubbling the False Vacuum Away

    CERN Document Server

    Gleiser, Marcelo; Thorarinson, Joel

    2007-01-01

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

  3. Conformal gravity and "gravitational bubbles"

    CERN Document Server

    Berezin, V A; Eroshenko, Yu N

    2015-01-01

    We describe the general structure of the spherically symmetric solutions in the Weyl conformal gravity. The corresponding Bach equations are derived for the special type of metrics, which can be considered as the representative of the general class. The complete set of the pure vacuum solutions, consisting of two classes, is found. The first one contains the solutions with constant two-dimensional curvature scalar, and the representatives are the famous Robertson--Walker metrics. We called one of them the "gravitational bubbles", which is compact and with zero Weyl tensor. These "gravitational bubbles" are the pure vacuum curved space-times (without any material sources, including the cosmological constant), which are absolutely impossible in General Relativity. This phenomenon makes it easier to create the universe from "nothing". The second class consists of the solutions with varying curvature scalar. We found its representative as the one-parameter family, which can be conformally covered by the thee-para...

  4. Bubble entrapment through topological change

    KAUST Repository

    Thoroddsen, Sigurdur T.

    2010-05-03

    When a viscousdrop impacts onto a solid surface, it entraps a myriad of microbubbles at the interface between liquid and solid. We present direct high-speed video observations of this entrapment. For viscousdrops, the tip of the spreading lamella is separated from the surface and levitated on a cushion of air. We show that the primary mechanism for the bubble entrapment is contact between this precursor sheet of liquid with the solid and not air pulled directly through cusps in the contact line. The sheet makes contact with the solid surface,forming a wetted patch, which grows in size, but only entraps a bubble when it meets the advancing contact line. The leading front of this wet patch can also lead to the localized thinning and puncturing of the liquid film producing strong splashing of droplets.

  5. Cavitation inception from bubble nuclei

    DEFF Research Database (Denmark)

    Mørch, Knud Aage

    2015-01-01

    experimental investigations of bubbles and cavitation inception have been presented. These results suggest that cavitation nuclei in equilibrium are gaseous voids in the water, stabilized by a skin which allows diffusion balance between gas inside the void and gas in solution in the surrounding liquid. The...... cavitation nuclei may be free gas bubbles in the bulk of water, or interfacial gaseous voids located on the surface of particles in the water, or on bounding walls. The tensile strength of these nuclei depends not only on the water quality but also on the pressure-time history of the water. A recent model...... and associated experiments throw new light on the effects of transient pressures on the tensile strength of water, which may be notably reduced or increased by such pressure changes....

  6. BEBC Big European Bubble Chamber

    CERN Multimedia

    1974-01-01

    A view of the dismantling of the magnet of BEBC, the 3.7 m European Bubble Chamber : iron magnetic shielding ; lower and upper parts of the vacuum enclosure of the magnet; turbo-molecular vacuum pumps for the "fish-eye" windows; the two superconducting coils; a handling platform; the two cryostats suspended from the bar of the travelling crane which has a 170 ton carrying capacity. The chamber proper, not dismantled, is inside the shielding.

  7. Bubble-induced cave collapse.

    Directory of Open Access Journals (Sweden)

    Lakshika Girihagama

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

  8. Effect of oxygen breathing on micro oxygen bubbles in nitrogen-depleted rat adipose tissue at sea level and 25 kPa altitude exposures

    DEFF Research Database (Denmark)

    Randsoe, Thomas; Hyldegaard, Ole

    2012-01-01

    The standard treatment of altitude decompression sickness (aDCS) caused by nitrogen bubble formation is oxygen breathing and recompression. However, micro air bubbles (containing 79% nitrogen), injected into adipose tissue, grow and stabilize at 25 kPa regardless of continued oxygen breathing...... at 101.3 kPa (sea level) or at 25 kPa altitude exposures during continued oxygen breathing. In keeping with previous observations and bubble kinetic models, we hypothesize that oxygen breathing may contribute to oxygen bubble growth at altitude. Anesthetized rats were exposed to 3 h of oxygen...... prebreathing at 101.3 kPa (sea level). Micro oxygen bubbles of 500-800 nl were then injected into the exposed abdominal adipose tissue. The oxygen bubbles were studied for up to 3.5 h during continued oxygen breathing at either 101.3 or 25 kPa ambient pressures. At 101.3 kPa, all bubbles shrank consistently...

  9. Effect of Orifice Diameter on Bubble Generation Process in Melt Gas Injection to Prepare Aluminum Foams

    Science.gov (United States)

    Yuan, Jianyu; Li, Yanxiang; Wang, Ningzhen; Cheng, Ying; Chen, Xiang

    2016-06-01

    The bubble generation process in conditioned A356 alloy melt through submerged spiry orifices with a wide diameter range (from 0.07 to 1.0 mm) is investigated in order to prepare aluminum foams with fine pores. The gas flow rate and chamber pressure relationship for each orifice is first determined when blowing gas in atmospheric environment. The effects of chamber pressure ( P c) and orifice diameter ( D o) on bubble size are then analyzed separately when blowing gas in melt. A three-dimensional fitting curve is obtained illustrating both the influences of orifice diameter and chamber pressure on bubble size based on the experimental data. It is found that the bubble size has a V-shaped relationship with orifice diameter and chamber pressure neighboring the optimized parameter ( D o = 0.25 mm, P c = 0.4 MPa). The bubble generation mechanism is proposed based on the Rayleigh-Plesset equation. It is found that the bubbles will not be generated until a threshold pressure difference is reached. The threshold pressure difference is dependent on the orifice diameter, which determines the time span of pre-formation stage and bubble growth stage.

  10. Modeling the impediment of methane ebullition bubbles by seasonal lake ice

    Directory of Open Access Journals (Sweden)

    S. Greene

    2014-07-01

    Full Text Available Microbial methane (CH4 ebullition (bubbling from anoxic lake sediments comprises a globally significant flux to the atmosphere, but ebullition bubbles in temperate and polar lakes can be trapped by winter ice cover and later released during spring thaw. This "ice-bubble storage" (IBS constitutes a novel mode of CH4 emission. Before bubbles are encapsulated by downward-growing ice, some of their CH4 dissolves into the lake water, where it may be subject to oxidation. We present field characterization and a model of the annual CH4 cycle in Goldstream Lake, a thermokarst (thaw lake in interior Alaska. We find that summertime ebullition dominates annual CH4 emissions to the atmosphere. Eighty percent of CH4 in bubbles trapped by ice dissolves into the lake water column in winter, and about half of that is oxidized. The ice growth rate and the magnitude of the CH4 ebullition flux are important controlling factors of bubble dissolution. Seven percent of annual ebullition CH4 is trapped as IBS and later emitted as ice melts. In a future warmer climate, there will likely be less seasonal ice cover, less IBS, less CH4 dissolution from trapped bubbles, and greater CH4 emissions from northern lakes.

  11. Manipulating bubbles with secondary Bjerknes forces

    International Nuclear Information System (INIS)

    Gas bubbles in a sound field are submitted to a radiative force, known as the secondary Bjerknes force. We propose an original experimental setup that allows us to investigate in detail this force between two bubbles, as a function of the sonication frequency, as well as the bubbles radii and distance. We report the observation of both attractive and, more interestingly, repulsive Bjerknes force, when the two bubbles are driven in antiphase. Our experiments show the importance of taking multiple scatterings into account, which leads to a strong acoustic coupling of the bubbles when their radii are similar. Our setup demonstrates the accuracy of secondary Bjerknes forces for attracting or repealing a bubble, and could lead to new acoustic tools for noncontact manipulation in microfluidic devices

  12. The KEK 1 m hydrogen bubble chamber

    International Nuclear Information System (INIS)

    A medium size hydrogen bubble chamber has been constructed at the National Laboratory for High Energy Physics, KEK. The bubble chamber has been designed to be operated with a maximum rate of three times per half a second in every two second repetition time of the accelerator, by utilizing a hydraulic expansion system. The bubble chamber has a one meter diameter and a visible volume of about 280 l. A three-view stereo camera system is used for taking photographic pictures of the chamber. A 2 MW bubble chamber magnet is constructed. The main part of the bubble chamber vessel is supported by the magnet yoke. The magnet gives a maximum field of 18.4 kG at the centre of the fiducial volume of the chamber. The overall system of the KEK 1 m hydrogen bubble chamber facility is described in some detail. Some operational characteristics of the facility are also reported. (auth.)

  13. Mechanism of bubble detachment from vibrating walls

    International Nuclear Information System (INIS)

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

  14. Manipulating bubbles with secondary Bjerknes forces

    Energy Technology Data Exchange (ETDEWEB)

    Lanoy, Maxime [Institut Langevin, ESPCI ParisTech, CNRS (UMR 7587), PSL Research University, 1 rue Jussieu, 75005 Paris (France); Laboratoire Matière et Systèmes Complexes, Université Paris-Diderot, CNRS (UMR 7057), 10 rue Alice Domon et Léonie Duquet, 75013 Paris (France); Derec, Caroline; Leroy, Valentin [Laboratoire Matière et Systèmes Complexes, Université Paris-Diderot, CNRS (UMR 7057), 10 rue Alice Domon et Léonie Duquet, 75013 Paris (France); Tourin, Arnaud [Institut Langevin, ESPCI ParisTech, CNRS (UMR 7587), PSL Research University, 1 rue Jussieu, 75005 Paris (France)

    2015-11-23

    Gas bubbles in a sound field are submitted to a radiative force, known as the secondary Bjerknes force. We propose an original experimental setup that allows us to investigate in detail this force between two bubbles, as a function of the sonication frequency, as well as the bubbles radii and distance. We report the observation of both attractive and, more interestingly, repulsive Bjerknes force, when the two bubbles are driven in antiphase. Our experiments show the importance of taking multiple scatterings into account, which leads to a strong acoustic coupling of the bubbles when their radii are similar. Our setup demonstrates the accuracy of secondary Bjerknes forces for attracting or repealing a bubble, and could lead to new acoustic tools for noncontact manipulation in microfluidic devices.

  15. Single DNA denaturation and bubble dynamics

    International Nuclear Information System (INIS)

    While the Watson-Crick double-strand is the thermodynamically stable state of DNA in a wide range of temperature and salt conditions, even at physiological conditions local denaturation bubbles may open up spontaneously due to thermal activation. By raising the ambient temperature, titration, or by external forces in single molecule setups bubbles proliferate until full denaturation of the DNA occurs. Based on the Poland-Scheraga model we investigate both the equilibrium transition of DNA denaturation and the dynamics of the denaturation bubbles with respect to recent single DNA chain experiments for situations below, at, and above the denaturation transition. We also propose a new single molecule setup based on DNA constructs with two bubble zones to measure the bubble coalescence and extract the physical parameters relevant to DNA breathing. Finally we consider the interplay between denaturation bubbles and selectively single-stranded DNA binding proteins.

  16. Kinetics of hydrate formation using gas bubble suspended in water

    Institute of Scientific and Technical Information of China (English)

    马昌峰; 陈光进; 郭天民

    2002-01-01

    An innovative experimental technique, which was devised to study the effects of temperature and pressure on the rate of hydrate formation at the surface of a gas bubble suspended in a stagnant water phase, was adapted in this work. Under such conditions, the hydrate-growth process is free from dynamic mass transfer factors. The rate of hydrate formation of methane and carbon dioxide has been systematically studied. The measured hydrate-growth data were correlated by using the molar Gibbs free energy as driving force. In the course of the experiments, some interesting surface phenomena were observed.

  17. Remote sensing of bubble clouds in seawater

    OpenAIRE

    Flatau, Piotr J.; Flatau, Maria; Zaneveld, J. R. V.; Mobley, Curtis D.

    2000-01-01

    We report on the influence of submerged bubble clouds on the remote sensing properties of water. We show that the optical effect of bubbles on radiative transfer and on the estimate of the ocean color is significant. We present a global map of the volume fraction of air in water derived from daily wind speed data. This map, together with the parameterization of the microphysical properties, shows the possible significance of bubble clouds on the albedo of incoming solar energy

  18. The economy of "soap bubbles" (continued)

    OpenAIRE

    O. Baranovskyi

    2009-01-01

    The author defines the essence of economic "bubbles". He reveals the peculiar features of "soap bubbles" on the markets of shares and consumer credits, in crediting realty purchases, granting credits to medium-size and small business and on the markets of realty and derivatives, as well as "soap bubbles" as a consequence of overconcentration of market, credit, Interest, and exchange risks and the liquidity risks and analyses their evolution. The article considers the specificity of economic (...

  19. A signature of anisotropic bubble collisions

    OpenAIRE

    Salem, Michael P.

    2010-01-01

    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 aff...

  20. Local measurements in turbulent bubbly flows

    International Nuclear Information System (INIS)

    Local measurements methods in bubbly flows are discussed. Concerning liquid velocity measurement, problems linked to HFA and LDA are first analysed. Then simultaneously recorded velocity signals obtained by both anemometers are compared. New signal processing are developed for the two techniques. Bubble sizes and velocities measurements methods using intrusive double optical sensor probe are presented. Plane bubbly mixing layer has been investigated. Local measurements using the described methods are presented as examples. (author)

  1. On Bubble Rising in Countercurrent Flow

    Czech Academy of Sciences Publication Activity Database

    Večeř, M.; Leštinský, P.; Wichterle, K.; Růžička, Marek

    2012-01-01

    Roč. 10, č. 2012 (2012), A30. ISSN 1542-6580 R&D Projects: GA ČR GA104/09/0972; GA ČR GA104/07/1110 Grant ostatní: GA MŠMT(CZ) CZ.1.05/2.1.00/03.0069 Institutional support: RVO:67985858 Keywords : ellipsoidal bubble * bubble shape * bubble velocity Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 0.790, year: 2011

  2. Bubble Universes With Different Gravitational Constants

    OpenAIRE

    Takamizu, Yu-ichi; Maeda, Kei-ichi

    2015-01-01

    We argue a scenario motivated by the context of string landscape, where our universe is produced by a new vacuum bubble embedded in an old bubble and these bubble universes have not only different cosmological constants, but also their own different gravitational constants. We study these effects on the primordial curvature perturbations. In order to construct a model of varying gravitational constants, we use the Jordan-Brans-Dicke (JBD) theory where different expectation values of scalar fi...

  3. Bremsstrahlung Radiation At a Vacuum Bubble Wall

    CERN Document Server

    Lee, Jae-Weon; Lee, Chul H; Jang, Ji-ho

    2007-01-01

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

  4. Electric field effects on the dynamics of bubble detachment from an inclined surface

    Science.gov (United States)

    Di Marco, P.; Morganti, N.; Saccone, G.

    2015-11-01

    An experimental apparatus to study bubble detachment from an inclined surface under the action of electric forces is described. It consists of a container filled with FC72 at room temperature and pressure where a train of gas bubbles is injected from an orifice. An electrostatic field can be imposed around the bubble, while the cell can be tilted from 0 to 90°. It is possible to study interface growth with the aid of high-speed cinematography. Since the interface is asymmetrical, a mirror system allowed to acquire, in the same frame, two images at 90° of the bubble. Different inclinations, injection rates and voltages were tested in order to couple the effects of shear gravity and electric field. Curvature and contact angles have been derived with appropriate interpolation methods of the profile. Force balances on the bubble were checked, finding an electric force, which, at first pulls the bubbles from the orifice, then pushes it against the surface. The motion of the center of gravity confirms this behaviour. A power balance has been developed to determine the energy contributions, revealing that surface growth incorporates both the effects of inlet power and electric field.

  5. Direct Simulations of Homogeneous Bubble Nucleation: Agreement with CNT and no Local Hot Spots

    CERN Document Server

    Diemand, Jürg; Tanaka, Kyoko K; Tanaka, Hidekazu

    2014-01-01

    We present results from direct, large-scale molecular dynamics (MD) simulations of homogeneous bubble (liquid-to-vapor) nucleation. The simulations contain half a billion Lennard-Jones (LJ) atoms and cover up to 56 million time-steps. The unprecedented size of the simulated volumes allows us to resolve the nucleation and growth of many bubbles per run in simple direct micro-canonical (NVE) simulations while the ambient pressure and temperature remain almost perfectly constant. We find bubble nucleation rates which are lower than in most of the previous, smaller simulations. It is widely believed that classical nucleation theory (CNT) generally underestimates bubble nucleation rates by very large factors. However, our measured rates are within two orders of magnitude of CNT predictions - only at very low temperatures does CNT underestimate the nucleation rate significantly. Introducing a small, positive Tolman length leads to very good agreement at all temperatures, as found in our recent vapor-to-liquid nucle...

  6. Stable bubble oscillations beyond Blake's critical threshold.

    Science.gov (United States)

    Hegedűs, Ferenc

    2014-04-01

    The equilibrium radius of a single spherical bubble containing both non-condensable gas and vapor is determined by the mechanical balance at the bubble interface. This expression highlights the fact that decreasing the ambient pressure below the so called Blake's critical threshold, the bubble has no equilibrium state at all. In the last decade many authors have tried to find evidence for the existence of stable bubble oscillation under harmonic forcing in this regime, that is, they have tried to stabilize the bubble motion applying ultrasonic radiation on the bubble. The available numerical results provide only partial proof for the existence as they are usually based on linearized or weakly nonlinear (higher order approximation) bubble models. Here, based on numerical techniques of the modern nonlinear and bifurcation theory, the existence of stable bubble motion has been proven without any restrictions in nonlinearities. Although the model, applied in this paper, is the rather simple Rayleigh-Plesset equation, the presented technique can be extended to more complex bubble models easily. PMID:24485747

  7. Bubble formation in additive manufacturing of glass

    Science.gov (United States)

    Luo, Junjie; Gilbert, Luke J.; Peters, Daniel C.; Bristow, Douglas A.; Landers, Robert G.; Goldstein, Jonathan T.; Urbas, Augustine M.; Kinzel, Edward C.

    2016-05-01

    Bubble formation is a common problem in glass manufacturing. The spatial density of bubbles in a piece of glass is a key limiting factor to the optical quality of the glass. Bubble formation is also a common problem in additive manufacturing, leading to anisotropic material properties. In glass Additive Manufacturing (AM) two separate types of bubbles have been observed: a foam layer caused by the reboil of the glass melt and a periodic pattern of bubbles which appears to be unique to glass additive manufacturing. This paper presents a series of studies to relate the periodicity of bubble formation to part scan speed, laser power, and filament feed rate. These experiments suggest that bubbles are formed by the reboil phenomena why periodic bubbles result from air being trapped between the glass filament and the substrate. Reboil can be detected using spectroscopy and avoided by minimizing the laser power while periodic bubbles can be avoided by a two-step laser melting process to first establish good contact between the filament and substrate before reflowing the track with higher laser power.

  8. Bubble burst as jamming phase transition

    CERN Document Server

    Nishinari, Katsuhiro; Saito, Yukiko Umeno; Watanabe, Tsutomu

    2010-01-01

    Recently research on bubble and its burst attract much interest of researchers in various field such as economics and physics. Economists have been regarding bubble as a disorder in prices. However, this research strategy has overlooked an importance of the volume of transactions. In this paper, we have proposed a bubble burst model by focusing the transactions incorporating a traffic model that represents spontaneous traffic jam. We find that the phenomenon of bubble burst shares many similar properties with traffic jam formation by comparing data taken from US housing market. Our result suggests that the transaction could be a driving force of bursting phenomenon.

  9. SELF-SIMILARITY OF VERTICAL BUBBLY JETS

    Directory of Open Access Journals (Sweden)

    I. E. Lima Neto

    2015-06-01

    Full Text Available AbstractAn integral model for vertical bubbly jets with nearly monodisperse bubble sizes is presented. The model is based on the Gaussian type self-similarity of mean liquid velocity, bubble velocity and void fraction, as well as on functional relationships for initial liquid jet velocity and radius, bubble diameter and relative velocity. Adjusting the model to experimental data available in the literature for a wide range of densimetric Froude numbers provide constant values for the entrainment coefficient, momentum amplification factor, and spreading ratio of the bubble core for different flow conditions. Consistency and sensitivity of key model parameters are also verified. Overall, the deviations between model predictions and axial/radial profiles of mean liquid velocity, bubble velocity and void fraction are lower than about 20%, which suggests that bubbly jets tend to behave as self-preserving shear flows, similarly to single-phase jets and plumes. Furthermore, model simulations indicate a behavior similar to those of single-phase buoyant jets and slurry jets, but some differences with respect to confined bubbly jets are highlighted. This article provides not only a contribution to the problem of self-similarity in two-phase jets, but also a comprehensive model that can be used for analysis of artificial aeration/mixing systems involving bubbly jets.

  10. Energetic molding of chiral magnetic bubbles

    Science.gov (United States)

    Lau, Derek; Sundar, Vignesh; Zhu, Jian-Gang; Sokalski, Vincent

    2016-08-01

    Topologically protected magnetic structures such as skyrmions and domain walls (DWs) have drawn a great deal of attention recently due to their thermal stability and potential for manipulation by spin current, which is the result of chiral magnetic configurations induced by the interfacial Dzyaloshinskii-Moriya interaction (DMI). Designing devices that incorporate DMI necessitates a thorough understanding of how the interaction presents and can be measured. One approach is to measure growth asymmetry of chiral bubble domains in perpendicularly magnetized thin films, which has been described elsewhere by thermally activated DW motion. Here, we demonstrate that the anisotropic angular dependence of DW energy originating from the DMI is critical to understanding this behavior. Domains in Co/Ni multilayers are observed to preferentially grow into nonelliptical teardrop shapes, which vary with the magnitude of an applied in-plane field. We model the domain profile using energetic calculations of equilibrium shape via the Wulff construction, which serves as a new paradigm for describing chiral domains that explains both the teardrop shape and the reversal of growth symmetry at large fields.

  11. Propagation and Dissolution of CO2 bubbles in Algae Photo-bioreactors

    Science.gov (United States)

    Kosaraju, Srinivas

    2015-11-01

    Research grade photo-bioreactors are used to study and cultivate different algal species for biofuel production. In an attempt to study the growth properties of a local algal species in rain water, a custom made bioreactor is designed and being tested. Bio-algae consumes dissolved CO2 in water and during its growth cycle, the consumed CO2 must be replenished. Conventional methods use supply of air or CO2 bubbles in the growth medium. The propagation and dissolution of the bubbles, however, are strongly dependent on the design parameters of the photo-bioreactor. In this paper, we discuss the numerical modeling of the air and CO2 bubble propagation and dissolution in the photo-bioreactor. Using the results the bioreactor design will be modified for maximum productivity.

  12. Bubbles are more than you think - The Center for Information and Bubble Studies

    DEFF Research Database (Denmark)

    Hendricks, Vincent Fella

    2016-01-01

    dynamics of different bubble phenomena from finance over social media to politics and science in order to (1) formulate intervention strategies for malignant bubbles from “shitstorms” to radicalisation, stimulate possible benign bubbles from climate awareness to democratic initiatives and thus play a...... proactive role promoting scientific social responsibility (SSR)....

  13. Giant bubble pinch-off

    OpenAIRE

    Bergmann, Raymond; Meer, Van Der; Stijnman, Mark; Sandtke, Marijn; Prosperetti, Andrea; Lohse, Detlef

    2006-01-01

    Self-similarity has been the paradigmatic picture for the pinch-off of a drop. Here we will show through high-speed imaging and boundary integral simulations that the inverse problem, the pinch-off of an air bubble in water, is not self-similar in a strict sense: A disk is quickly pulled through a water surface, leading to a giant, cylindrical void which after collapse creates an upward and a downward jet. Only in the limiting case of large Froude numbers does the purely inertial scaling h(-l...

  14. Biosynthesis within a bubble architecture

    Science.gov (United States)

    Choi, Hyo-Jick; Montemagno, Carlo D.

    2006-05-01

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

  15. Stationary bubbles: information loss paradox?

    CERN Document Server

    Domènech, Guillem

    2016-01-01

    The main purpose of this work is to build classically stationary bubbles, within the thin-shell formalism, which are unstable under quantum effects; they either collapse into a black hole or expand. Thus, the final state can be thought of a superposition of geometries. We point out that, from a quantum mechanical point of view, there is no issue with a loss of information in such configuration. A classical observer sees a definite geometry and, hence, finds an effective loss of information. Although it does not cover all possible cases, we emphasise the role of semi-classical gravitational effects, mediated by instatons, in alleviating/solving the information loss paradox.

  16. Scales and structures in bubbly flows. Experimental analysis of the flow in bubble columns and in bubbling fluidized beds

    NARCIS (Netherlands)

    Groen, J.S.

    2004-01-01

    In this project a detailed experimental analysis was performed of the dynamic flow field in bubbly flows, with the purpose of determining local hydrodynamics and scale effects. Measurements were done in gas-liquid systems (air-water bubble columns) and in gas-solid systems (air-sand bubbing fluidize

  17. One meter holographic bubble chamber for TEVATRON neutrino experiments

    International Nuclear Information System (INIS)

    A one meter holographic bubble chamber was constructed for Fermilab TEVATRON neutrino experiments. Bubble chamber and optics are briefly outlined. Developments in holography for this bubble chamber and two types of reconstruction projectors are reported. (orig.)

  18. Giant bubble pinch-off

    CERN Document Server

    Bergmann, R; Prosperetti, A; Sandtke, M; Stijnman, M; Van der Meer, D; Bergmann, Raymond; Lohse, Detlef; Meer, Devaraj van der; Prosperetti, Andrea; Sandtke, Marijn; Stijnman, Mark

    2006-01-01

    Self-similarity has been the paradigmatic picture for the pinch-off of a drop. Here we will show through high-speed imaging and boundary integral simulations that the inverse problem, the pinch-off of an air bubble in water, is not self-similar in a strict sense: A disk is quickly pulled through a water surface, leading to a giant, cylindrical void which after collapse creates an upward and a downward jet. Only in the limiting case of large Froude number the neck radius $h$ scales as $h(-\\log h)^{1/4} \\propto \\tau^{1/2}$, the purely inertial scaling. For any finite Froude number the collapse is slower, and a second length-scale, the curvature of the void, comes into play. Both length-scales are found to exhibit power-law scaling in time, but with different exponents depending on the Froude number, signaling the non-universality of the bubble pinch-off.

  19. Cavitation inception from bubble nuclei.

    Science.gov (United States)

    Mørch, K A

    2015-10-01

    The tensile strength of ordinary water such as tap water or seawater is typically well below 1 bar. It is governed by cavitation nuclei in the water, not by the tensile strength of the water itself, which is extremely high. Different models of the nuclei have been suggested over the years, and experimental investigations of bubbles and cavitation inception have been presented. These results suggest that cavitation nuclei in equilibrium are gaseous voids in the water, stabilized by a skin which allows diffusion balance between gas inside the void and gas in solution in the surrounding liquid. The cavitation nuclei may be free gas bubbles in the bulk of water, or interfacial gaseous voids located on the surface of particles in the water, or on bounding walls. The tensile strength of these nuclei depends not only on the water quality but also on the pressure-time history of the water. A recent model and associated experiments throw new light on the effects of transient pressures on the tensile strength of water, which may be notably reduced or increased by such pressure changes. PMID:26442138

  20. Differential criterion of a bubble collapse in viscous liquids

    CERN Document Server

    Bogoyavlenskiy, V A

    1999-01-01

    The present work is devoted to a model of bubble collapse in a Newtonian viscous liquid caused by an initial bubble wall motion. The obtained bubble dynamics described by an analytic solution significantly depends on the liquid and bubble parameters. The theory gives two types of bubble behavior: collapse and viscous damping. This results in a general collapse condition proposed as the sufficient differential criterion. The suggested criterion is discussed and successfully applied to the analysis of the void and gas bubble collapses.

  1. Galactic Teamwork Makes Distant Bubbles

    Science.gov (United States)

    Kohler, Susanna

    2016-03-01

    During the period of reionization that followed the dark ages of our universe, hydrogen was transformed from a neutral state, which is opaque to radiation, to an ionized one, which is transparent to radiation. But what generated the initial ionizing radiation? The recent discovery of multiple distant galaxies offers evidence for how this process occurred.Two Distant GalaxiesWe believe reionization occurred somewhere between a redshift of z = 6 and 7, because Ly-emitting galaxies drop out at roughly this redshift. Beyond this distance, were generally unable to see the light from these galaxies, because the universe is no longer transparent to their emission. This is not always the case, however: if a bubble of ionized gas exists around a distant galaxy, the radiation can escape, allowing us to see the galaxy.This is true of two recently-discovered Ly-emitting galaxies, confirmed to be at a redshift of z~7 and located near one another in a region known as the Bremer Deep Field. The fact that were able to see the radiation from these galaxies means that they are in an ionized HII region presumably one of the earlier regions to have become reionized in the universe.But on their own, neither of these galaxies is capable of generating an ionized bubble large enough for their light to escape. So what ionized the region around them, and what does this mean for our understanding of how reionization occurred in the universe?A Little Help From FriendsLocation in different filters of the objects in the Hubble Bremer Deep Field catalog. The z~7 selection region is outlined by the grey box. BDF-521 and BDF-3299 were the two originally discovered galaxies; the remaining red markers indicate the additional six galaxies discovered in the same region. [Castellano et al. 2016]A team of scientists led by Marco Castellano (Rome Observatory, INAF) investigated the possibility that there are other, faint galaxies near these two that have helped to ionize the region. Performing a survey

  2. Financial frictions, bubbles, and macroprudential policies

    OpenAIRE

    Derviz, Alexis

    2011-01-01

    Writer explores the ability of a macroprudential policy instrument to dampen the consequences of equity mispricing (a bubble) and the correction thereof (the bubble bursting), as well as the consequences for real activity in a production economy. In the model, producers are financed by both bank debt and equity, and face a mix of systemic and idiosyncratic uncertainty.

  3. Gravity Wave Seeding of Equatorial Plasma Bubbles

    Science.gov (United States)

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

    1997-01-01

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

  4. Laminar separation bubbles: Dynamics and control

    Indian Academy of Sciences (India)

    Sourabh S Diwan; O N Ramesh

    2007-02-01

    This work is an experimental investigation of the dynamics and control of the laminar separation bubbles which are typically present on the suction surface of an aerofoil at a large angle of attack. A separation bubble is produced on the upper surface of a flat plate by appropriately contouring the top wall of the wind tunnel. First, a basic (unforced) separation bubble is obtained to set a benchmark for further experiments. Parametric study is done where the reference velocity is decreased to quantify its effect on the aspect ratio of the bubble. It is found that with decrease in Reynolds number, the height of the bubble increases at a greater rate than the length. This feature could be useful in characterising separation bubbles especially from the point of view of low Reynolds number aerofoil design. Artificial disturbance is introduced at two different initial amplitudes (infinitesimal and finite) upstream of separation location and hotwire anemometry is used to trace the wave packet as it is advected downstream. The evolution of wave packets is seen to take place in two distinct stages. Finite amplitude forcing causes periodic quenching of the bubble. Interestingly, even an infinitesimally small forcing is seen to modify and thereby control the separation bubble.

  5. Test on steam bubble behavior, (4)

    International Nuclear Information System (INIS)

    The experiment simulating the behavior of large steam bubbles generated at the time of core collapse accident was carried out with water, and the method of forecasting the vanishing behavior of large steam bubbles was examined. The results are reported in this paper. First, the reference to the literatures, the analysis with FTAC code and the thermodynamic examination were performed. In the evaluation of the transfer of radioactive substances to the outside of reactors at the time of hypothetic core collapse accident in fast reactors, it is important to grasp the behavior of CDA (core disruptive accident) bubbles. The radius of these bubbles was estimated to be several meter, and it was clarified that the incompressible gas in the bubbles exerted large influence on the vanishing behavior of the bubbles. Using incompressible gas and the system simulating the internal structure of a reactor, experiment was carried out, and the change of shape and the rising behavior of large bubbles were examined. Also the experiment using the mixture of steam and incompressible gas was carried out in a warm water tank, and the data on the effect of incompressible gas to obstruct the condensation of bubbles were obtained. (Kako, I.)

  6. Analytical solutions for problems of bubble dynamics

    CERN Document Server

    Kudryashov, Nikolai A

    2016-01-01

    Recently, an asymptotic solution of the Rayleigh equation for an empty bubble in $N$ dimensions has been obtained. Here we give the closed--from general analytical solution of this equation. We also find the general solution of the Rayleigh equation in $N$ dimensions for the case of a gas--filled hyperspherical bubble. In addition, we include a surface tension into consideration.

  7. Magma mixing enhanced by bubble segregation

    Science.gov (United States)

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

    2015-08-01

    In order to explore the materials' complexity induced by bubbles rising through mixing magmas, bubble-advection experiments have been performed, employing natural silicate melts at magmatic temperatures. A cylinder of basaltic glass was placed below a cylinder of rhyolitic glass. Upon melting, bubbles formed from interstitial air. During the course of the experimental runs, those bubbles rose via buoyancy forces into the rhyolitic melt, thereby entraining tails of basaltic liquid. In the experimental run products, these plume-like filaments of advected basalt within rhyolite were clearly visible and were characterised by microCT and high-resolution EMP analyses. The entrained filaments of mafic material have been hybridised. Their post-experimental compositions range from the originally basaltic composition through andesitic to rhyolitic composition. Rheological modelling of the compositions of these hybridised filaments yield viscosities up to 2 orders of magnitude lower than that of the host rhyolitic liquid. Importantly, such lowered viscosities inside the filaments implies that rising bubbles can ascend more efficiently through pre-existing filaments that have been generated by earlier ascending bubbles. MicroCT imaging of the run products provides textural confirmation of the phenomenon of bubbles trailing one another through filaments. This phenomenon enhances the relevance of bubble advection in magma mixing scenarios, implying as it does so, an acceleration of bubble ascent due to the decreased viscous resistance facing bubbles inside filaments and yielding enhanced mass flux of mafic melt into felsic melt via entrainment. In magma mixing events involving melts of high volatile content, bubbles may be an essential catalyst for magma mixing. Moreover, the reduced viscosity contrast within filaments implies repeated replenishment of filaments with fresh end-member melt. As a result, complex compositional gradients and therefore diffusion systematics can be

  8. Solar prominences: 'double, double ... boil and bubble'

    CERN Document Server

    Keppens, Rony

    2015-01-01

    Observations revealed rich dynamics within prominences, the cool 10,000 K, macroscopic (sizes of order 100 Mm) "clouds" in the million degree solar corona. Even quiescent prominences are continuously perturbed by hot, rising bubbles. Since prominence matter is hundredfold denser than coronal plasma, this bubbling is related to Rayleigh-Taylor instabilities. Here we report on true macroscopic simulations well into this bubbling phase, adopting a magnetohydrodynamic description from chromospheric layers up to 30 Mm height. Our virtual prominences rapidly establish fully non-linear (magneto)convective motions where hot bubbles interplay with falling pillars, with dynamical details including upwelling pillars forming within bubbles. Our simulations show impacting Rayleigh-Taylor fingers reflecting on transition region plasma, ensuring that cool, dense chromospheric material gets mixed with prominence matter up to very large heights. This offers an explanation for the return mass cycle mystery for prominence mater...

  9. Oscillation of large air bubble cloud

    Energy Technology Data Exchange (ETDEWEB)

    Bae, Y.Y.; Kim, H.Y.; Park, J.K. [Korea Atomic Energy Research Inst., Daejeon (Korea, Republic of)

    2001-07-01

    The behavior of a large air bubble cloud, which is generated by the air discharged from a perforated sparger, is analyzed by solving Rayleigh-Plesset equation, energy equations and energy balance equation. The equations are solved by Runge-Kutta integration and MacCormack finite difference method. Initial conditions such as driving pressure, air volume, and void fraction strongly affect the bubble pressure amplitude and oscillation frequency. The pool temperature has a strong effect on the oscillation frequency and a negligible effect on the pressure amplitude. The polytropic constant during the compression and expansion processes of individual bubbles ranges from 1.0 to 1.4, which may be attributed to the fact that small bubbles oscillated in frequencies different from their resonance. The temperature of the bubble cloud rapidly approaches the ambient temperature, as is expected from the polytropic constants being between 1.0 and 1.4. (authors)

  10. Bubble Universes With Different Gravitational Constants

    CERN Document Server

    Takamizu, Yu-ichi

    2015-01-01

    We argue a scenario motivated by the context of string landscape, where our universe is produced by a new vacuum bubble embedded in an old bubble and these bubble universes have not only different cosmological constants, but also their own different gravitational constants. We study these effects on the primordial curvature perturbations. In order to construct a model of varying gravitational constants, we use the Jordan-Brans-Dicke (JBD) theory where different expectation values of scalar fields produce difference of constants. In this system, we investigate the nucleation of bubble universe and dynamics of the wall separating two spacetimes. In particular, the primordial curvature perturbation on superhorizon scales can be affected by the wall trajectory as the boundary effect. We show the effect of gravitational constant in the exterior bubble universe can provide a peak like a bump feature at a large scale in a modulation of power spectrum.

  11. Microwave excitation of submerged plasma bubbles

    International Nuclear Information System (INIS)

    Steady-state models were formulated for spherical plasma bubbles, excited in water by an external microwave radiation source. The bubbles were assumed to be at rest relative to the surrounding water, and the energy absorbed by the plasma was balanced by energy loss through thermal conductance and convection to the surrounding water. Two regimes were considered: (1) bubbles with radii R less than the skin depth δ, i.e. R δ. A self-consistent system of equations was formulated. In the R δ case obtained for strong electric fields was larger than in the R δ bubbles had an isothermal core and power from the microwave field was absorbed in a relatively thin layer in the plasma bubble. (paper)

  12. Primary Particles from different bubble generation techniques

    Science.gov (United States)

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

    2011-12-01

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

  13. Mobile access to the Internet: from personal bubble to satellites

    Science.gov (United States)

    Gerla, Mario

    2001-10-01

    Mobile, wireless access and networking has emerged in the last few years as one of the most important directions of Internet growth. The popularity of mobile, and, more generally, nomadic Internet access is due to many enabling factors including: (a) emergence of meaningful applications tailored to the individual on the move; (b) small form factor and long battery life; (c) efficient middleware designed to support mobility; and, (d) efficient wireless networking technologies. A key player in the mobile Internet access is the nomad, i.e. the individual equipped with various computing and I/O gadgets (cellular phone, earphones, GPS navigator, palm pilot, beeper, portable scanner, digital camera, etc.). These devices form his/her Personal Area Network or PAN or personal bubble. The connectivity within the bubble is wireless (using for example a low cost, low power wireless LAN such as Bluetooth). The bubble can expand and contract dynamically depending on needs. It may temporarily include sensors and actuators as the nomad walks into a new environment. In this paper, we identify the need for the interconnection of the PAN with other wireless networks in order to achieve costeffective mobile access to the Internet. We will overview some key networking technologies required to support the PAN (eg, Bluetooth). We will also discuss an emerging technology, Ad Hoc wireless networking which is the natural complement of the PAN in sparsely populated areas. Finally, we will identify the need for intelligent routers to assist the mobile user in the selection of the best Internet access strategy.

  14. Mass transport phenomena between bubbles and dissolved gases in liquids under reduced gravity conditions

    Science.gov (United States)

    Dewitt, Kenneth J.; Brockwell, Jonathan L.; Yung, Chain-Nan; Chai, An-Ti; Mcquillen, John B.; Sotos, Raymond G.; Neumann, Eric S.

    1988-01-01

    This paper will describe the experimental and analytical work that has been done to establish justification and feasibility for a Shuttle mid-deck experiment involving mass transfer between a gas bubble and a liquid. The experiment involves the observation and measurement of the dissolution of an isolated, immobile gas bubble of specified size and composition in a thermostatted solvent liquid of known concentration in the reduced gravity environment of earth orbit. Methods to generate and deploy the bubble have been successful both in normal gravity using mutually buoyant fluids and under reduced gravity conditions in the NASA Lear Jet. Initialization of the experiment with a bubble of a prescribed size and composition in a liquid of known concentration has been accomplished using the concept of unstable equilibrium. Subsequent bubble dissolution or growth is obtained by a step increase or decrease in the liquid pressure. A numerical model has been developed which simulates the bubble dynamics and can be used to determine molecular parameters by comparison with the experimental data. The primary objective of the experiment is the elimination of convective effects that occur in normal gravity. The results will yield information on transport under conditions of pure diffusion.

  15. Micro-bubble generated by laser irradiation on an individual carbon nanocoil

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Yanming, E-mail: amandaming@mail.dlut.edu.cn [School of Physics and Optoelectronic Technology, DUT, Linggong Road, Dalian 116024 (China); Pan, Lujun, E-mail: lpan@dlut.edu.cn [School of Physics and Optoelectronic Technology, DUT, Linggong Road, Dalian 116024 (China); Liu, Yuli, E-mail: liuyuli2005@163.com [School of Physics and Optoelectronic Technology, DUT, Linggong Road, Dalian 116024 (China); Sun, Tao, E-mail: 332077309@qq.com [School of Energy and Power Engineering, DUT, Linggong Road, Dalian 116024 (China)

    2015-08-01

    Highlights: • We have investigated laser irradiated microbubbles which can be generated at fixed point on surface of an individual carbon nanocoil (CNC) immerged in deionized water. • The microbubble can be operated easily and flexibly. • Based on classical heat and mass transfer theories, the bubble growth data is in good agreement with the simplified model. - Abstract: We have investigated the micro-bubbles generated by laser induction on an individual carbon nanocoil (CNC) immerged in deionized water. The photon energy of the incident focused laser beam is absorbed by CNC and converted to thermal energy, which efficiently vaporizes the surrounding water, and subsequently a micro-bubble is generated at the laser location. The dynamics behavior of bubble generation, including its nucleation, expansion and steady-state, has been studied experimentally and theoretically. We have derived equations to analyze the expansion process of a bubble based on classical heat and mass transfer theories. The conclusion is in good agreement with the experiment. CNC, which acts as a realistic micro-bubble generator, can be operated easily and flexibly.

  16. Analysis of large two phase uranium dioxide bubble behavior in water and sodium pools

    International Nuclear Information System (INIS)

    An understanding of the behavior of large, two-phase UO2 bubbles is important in assessing the consequences of a hypothetical core disruptive accident in a fast reactor. The UVABUBL II computer program was written to study the dynamics and heat and mass transfer in large UO2 bubbles, and the code was used to analyze data from the underwater and undersodium FAST experiments conducted at Oak Ridge National Laboratory in which the behavior of UO2 bubbles under a wide variety of conditions was examined. Significant understanding of the phenomena that govern UO2 bubble behavior in both water and sodium was obtained by matching calculations of pressure, bubble size, and bubble growth and collapse rate to the experimental data. Heat and mass transfer included radiative heat losses and coolant entrainment. Larger heat transfer rates were calculated for the water tests with significant surface vaporization occurring. Because of the high thermal conductivity of sodium, no surface vaporization was calculated for the sodium tests. Entrainment was not found to be necessary for either the water or sodium tests, but calculations that included entrainment implied that it may be occurring. 38 references

  17. Effect of free-air nuclei on fully developed individual bubble cavitation

    International Nuclear Information System (INIS)

    Fully developed individual-bubble cavitation was studied. Nuclei population and pressure distribution at the boundary of a cavitating converging-diverging test section were measured. It was shown that some cavitation tests can only yield valid results if the free air content of the water is known. During the initial stages of bubble growth the wall pressure in the cavitation region is lower than the vapor pressure. Wall pressure rises later. For a given cavitation number and flow velocity, the pressure distribution depends on the number of expanding bubbles on the hydrofoil. Minimum pressure coefficient depends only on the cavitation number, the flow velocity and the number of expanding bubbles present. Bubbles generate pressure pulses at the wall; combined effect of all such pulses is to shift the wall pressure away from the value that would be obtained at the same cavitation number if no cavitation was present. The greater the number of expanding bubbles, the more the wall pressure tends to approach the vapor pressure. An important result of the work is to pin-point free air contents of water tunnel which lead to correct scaling of cavitation flows

  18. Molecular dynamics simulation of helium bubble coalescence in titanium

    International Nuclear Information System (INIS)

    Molecular dynamics simulations were performed to study the helium bubble coalescence in titanium. The influence of helium bubble coalescence on the metal microstructure was analyzed. The bubble coalescences in the bulk metal and near the metal surface were compared. When helium bubbles lie in the bulk metal, a lot of defects are induced around by the bubbles coalescence and extend outward. The coalescence of helium bubbles with 1.77 nm diameter can form a dislocation loop around them. The helium bubbles after coalescence evolve from dumbbell shape toward ellipsoid shape. When helium bubbles lie near the metal surface, the defects induced by bubbles coalescence are likely to move to the top surface, and the metal around bubble tends to restore the crystal structure. The helium bubbles evolve from dumbbell shape toward hemispherical shape. (authors)

  19. Effect of isobaric breathing gas shifts from air to heliox mixtures on resolution of air bubbles in lipid and aqueous tissues of recompressed rats

    DEFF Research Database (Denmark)

    Hyldegaard, Ole; Kerem, Dikla; Melamed, Y

    2011-01-01

    while at 285 kPa or following immediate recompression to either 285 or 405 kPa, breathing 80:20 and 50:50 heliox mixtures. During the isobaric shifts, some bubbles in adipose tissue grew marginally for 10-30 min, subsequently they shrank and disappeared at a rate similar to or faster than during air...... shrinkage of all air bubbles, until they disappeared from view. Deep tissue isobaric counterdiffusion may cause some air bubbles to grow transiently in adipose tissue. The effect is marginal and of no clinical consequence. Bubble disappearance rate is faster with heliox breathing mixtures as compared to air......Deep tissue isobaric counterdiffusion that may cause unwanted bubble formation or transient bubble growth has been referred to in theoretical models and demonstrated by intravascular gas formation in animals, when changing inert breathing gas from nitrogen to helium after hyperbaric air breathing...

  20. Legacies of the bubble chamber

    International Nuclear Information System (INIS)

    Legacies are what we pass on to those who follow us, the foundations on which the next advances in our science are being made; the things by which we shall be remembered, recorded in learned journals, written in the text books -food for the historians of science. This is not a summary, and it will draw no conclusions. It is a personal view which will look a little wider than the main physics results to include a mention of one or two of the technologies and methods handed on to both particle physics and other branches of sciences, a brief reference to bubble chamber pictures as aids in teaching, and a comment on the challenge now increasingly applied in the UK - and perhaps elsewhere -as a criterion for funding research: will it contribute to ''wealth creation''? (orig.)

  1. Bubbles and denaturation in DNA

    CERN Document Server

    Van Erp, T S; Peyrard, M; Erp, Titus S. van; Cuesta-Lopez, Santiago; Peyrard, Michel

    2006-01-01

    The local opening of DNA is an intriguing phenomenon from a statistical physics point of view, but is also essential for its biological function. For instance, the transcription and replication of our genetic code can not take place without the unwinding of the DNA double helix. Although these biological processes are driven by proteins, there might well be a relation between these biological openings and the spontaneous bubble formation due to thermal fluctuations. Mesoscopic models, like the Peyrard-Bishop-Dauxois model, have fairly accurately reproduced some experimental denaturation curves and the sharp phase transition in the thermodynamic limit. It is, hence, tempting to see whether these models could be used to predict the biological activity of DNA. In a previous study, we introduced a method that allows to obtain very accurate results on this subject, which showed that some previous claims in this direction, based on molecular dynamics studies, were premature. This could either imply that the present...

  2. Micro-bubble Enhanced Sonoporation

    Science.gov (United States)

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

    2010-03-01

    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. In vitro, we inducted a GFP-containing plasmid into fibroblast cells (NIH3T3) using an ultrasound contrast agent (Sonazoid®, or micro-bubbles) and piezoelectric transducer. Cells were cultured on 24-well plates. The GFP-containing plasmid (concentration: 15 mg/ml) and Sonazoid® were mixed with the cell suspension. Ultrasound frequency was 2.0 MHz (burst wave, duty cycle: 10%), ultrasound intensity was varied from 0 W/cm2 to 11.0 W/cm2, exposure time ranged from 0 s to 120 s, and burst repetition frequency was varied from 50 Hz to 50000 Hz. Gene induction ratio was higher with stronger or longer ultrasound exposure, and gene induction ratio was affected by ultrasound burst repetition frequency. However, the ratio was less than 1%. We also measured cell survival and visualized cells with holes using propidium iodide. We found that about 80% of cells were alive, and many cells developed holes with ultrasound exposure at a burst repetition frequency of 5 kHz. These results suggest that fewer genes enter the cells or are expressed under these conditions. These problems require further study.

  3. Dynamics of laser-induced bubble and nanoparticles generation during ultra-short laser ablation of Pd in liquid

    International Nuclear Information System (INIS)

    In this work, the dynamics of multiple cavitation bubbles produced by femtosecond laser ablation of a palladium target submerged in acetone is studied by means of time-resolved fast shadowgraphy technique. The data have evidenced the periodic growth and collapse of the bubbles and the consequent emission of material together with the role played by the laser focus position. Comparing the results with the previsions of the Rayleigh–Plesset model a good agreement is found. The nanoparticles obtained under different focusing conditions are characterized by means of TEM analysis. Their dimension and distribution are correlated with the bubbles dynamics. (paper)

  4. Effect of oxygen breathing and perfluorocarbon emulsion treatment on air bubbles in adipose tissue during decompression sickness

    DEFF Research Database (Denmark)

    Randsoe, T; Hyldegaard, O

    2009-01-01

    Decompression sickness (DCS) after air diving has been treated with success by means of combined normobaric oxygen breathing and intravascular perfluorocarbon (PFC) emulsions causing increased survival rate and faster bubble clearance from the intravascular compartment. The beneficial PFC effect...... breathing. The combined effect of oxygen breathing and PFC infusion neither prevented nor increased transient bubble growth time, rate, or growth ratio compared with oxygen breathing alone. We conclude that oxygen breathing in combination with PFC infusion causes faster bubble disappearance and does...... has been explained by the increased transport capacity of oxygen and inert gases in blood. However, previous reports have shown that extravascular bubbles in lipid tissue of rats suffering from DCS will initially grow during oxygen breathing at normobaric conditions. We hypothesize that the combined...

  5. Bubbles in live-stranded dolphins.

    Science.gov (United States)

    Dennison, S; Moore, M J; Fahlman, A; Moore, K; Sharp, S; Harry, C T; Hoppe, J; Niemeyer, M; Lentell, B; Wells, R S

    2012-04-01

    Bubbles in supersaturated tissues and blood occur in beaked whales stranded near sonar exercises, and post-mortem in dolphins bycaught at depth and then hauled to the surface. To evaluate live dolphins for bubbles, liver, kidneys, eyes and blubber-muscle interface of live-stranded and capture-release dolphins were scanned with B-mode ultrasound. Gas was identified in kidneys of 21 of 22 live-stranded dolphins and in the hepatic portal vasculature of 2 of 22. Nine then died or were euthanized and bubble presence corroborated by computer tomography and necropsy, 13 were released of which all but two did not re-strand. Bubbles were not detected in 20 live wild dolphins examined during health assessments in shallow water. Off-gassing of supersaturated blood and tissues was the most probable origin for the gas bubbles. In contrast to marine mammals repeatedly diving in the wild, stranded animals are unable to recompress by diving, and thus may retain bubbles. Since the majority of beached dolphins released did not re-strand it also suggests that minor bubble formation is tolerated and will not lead to clinically significant decompression sickness. PMID:21993505

  6. Surfactants for Bubble Removal against Buoyancy.

    Science.gov (United States)

    Raza, Md Qaisar; Kumar, Nirbhay; Raj, Rishi

    2016-01-01

    The common phenomenon of buoyancy-induced vapor bubble lift-off from a heated surface is of importance to many areas of science and technology. In the absence of buoyancy in zero gravity of space, non-departing bubbles coalesce to form a big dry patch on the heated surface and heat transfer deteriorates despite the high latent heat of vaporization of water. The situation is worse on an inverted heater in earth gravity where both buoyancy and surface tension act upwards to oppose bubble removal. Here we report a robust passive technique which uses surfactants found in common soaps and detergents to avoid coalescence and remove bubbles downwards, away from an inverted heater. A force balance model is developed to demonstrate that the force of repulsion resulting from the interaction of surfactants adsorbed at the neighboring liquid-vapor interfaces of the thin liquid film contained between bubbles is strong enough to overcome buoyancy and surface tension. Bubble removal frequencies in excess of ten Hz resulted in more than twofold enhancement in heat transfer in comparison to pure water. We believe that this novel bubble removal mechanism opens up opportunities for designing boiling-based systems for space applications. PMID:26743179

  7. Surfactants for Bubble Removal against Buoyancy

    Science.gov (United States)

    Raza, Md. Qaisar; Kumar, Nirbhay; Raj, Rishi

    2016-01-01

    The common phenomenon of buoyancy-induced vapor bubble lift-off from a heated surface is of importance to many areas of science and technology. In the absence of buoyancy in zero gravity of space, non-departing bubbles coalesce to form a big dry patch on the heated surface and heat transfer deteriorates despite the high latent heat of vaporization of water. The situation is worse on an inverted heater in earth gravity where both buoyancy and surface tension act upwards to oppose bubble removal. Here we report a robust passive technique which uses surfactants found in common soaps and detergents to avoid coalescence and remove bubbles downwards, away from an inverted heater. A force balance model is developed to demonstrate that the force of repulsion resulting from the interaction of surfactants adsorbed at the neighboring liquid-vapor interfaces of the thin liquid film contained between bubbles is strong enough to overcome buoyancy and surface tension. Bubble removal frequencies in excess of ten Hz resulted in more than twofold enhancement in heat transfer in comparison to pure water. We believe that this novel bubble removal mechanism opens up opportunities for designing boiling-based systems for space applications.

  8. The Minnaert bubble: an acoustic approach

    International Nuclear Information System (INIS)

    We propose an ab initio introduction to the well-known Minnaert pulsating bubble at graduate level. After a brief recall of the standard stuff, we begin with a detailed discussion of the radial movements of an air bubble in water. This discussion is managed from an acoustic point of view, and using the Lagrangian rather than the Eulerian variables. In unbounded water, the air-water system has a continuum of eigenmodes, some of them correspond to regular Fabry-Perot resonances. A singular resonance, the lowest one, is shown to coincide with that of Minnaert. In bounded water, the eigenmodes spectrum is discrete, with a finite fundamental frequency. A spectacular quasi-locking of the latter occurs if it happens to exceed the Minnaert frequency, which provides an unforeseen one-bubble alternative version of the famous 'hot chocolate effect'. In the (low) frequency domain in which sound propagation inside the bubble reduces to a simple 'breathing' (i.e. inflation/deflation), the light air bubble can be 'dressed' by the outer water pressure forces, and is turned into the heavy Minnaert bubble. Thanks to this unexpected renormalization process, we demonstrate that the Minnaert bubble definitely behaves like a true harmonic oscillator of the spring-bob type, but with a damping term and a forcing term in apparent disagreement with those commonly admitted in the literature. Finally, we underline the double role played by the water. In order to tell the water motion associated with water compressibility (i.e. the sound) from the simple incompressible accompaniment of the bubble breathing, we introduce a new picture analogous to the electromagnetic radiative picture in Coulomb gauge, which naturally leads us to split the water displacement in an instantaneous and a retarded part. The Minnaert renormalized mass of the dressed bubble is then automatically recovered

  9. An explanation of how split melt processing can enhance the critical current density of Bi2212 round wires based on examination of bubble size and density formed in the melt

    International Nuclear Information System (INIS)

    The recent discovery that gas bubbles formed in the melt state are a major current-limiting mechanism in Bi2Sr2CaCu2Ox (Bi2212) round wires has prompted explicit examination of the bubble density in split melt processed samples which, under optimized 1 bar processing conditions, can exhibit significant (30–50%) enhancement of critical current density, Jc. By examining quenched and furnace-cooled samples from different points in the split melt processing (SMP), we found that the bubble size correlates well to the Jc. Compared with standard processed samples, the bubble size is smaller in SMP samples which are cooled directly to room temperature by an intermediate cooling from the first melt before being reheated to the second melt. Bubble size and density observations suggest that Jc can only be increased when bubble growth in the second melt is prevented by very tight control of the reheat temperature. Smaller bubble size is favorable for Jc because filament connectivity is determined by the effectiveness of bubble bridging by Bi2212 grain growth on cooling from the second melt. Because SMP appears to allow higher Jc by shrinking bubble size rather than by diminishing the bubble volume fraction, we conclude that SMP is unlikely to offer benefits to newer processes like over-pressure processing which raise Jc much more significantly by full Bi2212 densification and bubble elimination. (paper)

  10. Bubbles, Bubbles, Tremors & Trouble: The Bayou Corne Sinkhole

    Science.gov (United States)

    Nunn, J. A.

    2013-12-01

    In May 2012, thermogenic methane bubbles were first observed in Bayou Corne in Assumption Parish, Louisiana. As of July 2013, ninety one bubbling sites have been identified. Gas was also found in the top of the Mississippi River Alluvial Aquifer (MRAA) about 125 ft below the surface. Vent wells drilled into the MRAA have flared more 16 million SCF of gas. Trace amounts of hydrogen sulfide also have been detected. Bayou Corne flows above the Napoleonville salt dome which has been an active area for oil and gas exploration since the 1920s. The dome is also a site of dissolution salt mining which has produced large caverns with diameters of up to 300 ft and heights of 2000 ft. Some caverns are used for storage of natural gas. Microseismic activity was confirmed by an Earthscope seismic station in White Castle, LA in July 2012. An array of microseismic stations set up in the area recorded more than 60 microseismic events in late July and early August, 2012. These microseismic events were located on the western side of the dome. Estimated focal depths are just above the top of salt. In August 2012, a sinkhole developed overnight just to the northwest of a plugged and abandoned brine filled cavern (see figure below). The sinkhole continues to grow in area to more than 20 acres and has consumed a pipeline right of way. The sinkhole is more than 750 ft deep at its center. Microseismic activity was reduced for several months following the formation of the sinkhole. Microseismic events have reoccurred episodically since then with periods of frequent events preceding slumping of material into the sinkhole or a 'burp' where fluid levels in the sinkhole drop and then rebound followed by a decrease in microseismic activity. Some gas and/or oil may appear at the surface of the sinkhole following a 'burp'. Very long period events also have been observed which are believed to be related to subsurface fluid movement. A relief well drilled into the abandoned brine cavern found that

  11. On thermonuclear processes in cavitation bubbles

    International Nuclear Information System (INIS)

    The theoretical and experimental foundations of so-called bubble nuclear fusion are reviewed. In the nuclear fusion process, a spherical cavitation cluster ∼10−2 m in diameter is produced of spherical bubbles at the center of a cylindrical chamber filled with deuterated acetone using a focused acoustic field having a resonant frequency of about 20 kHz. The acoustically-forced bubbles effectuate volume oscillations with sharp collapses during the compression stage. At the final stages of collapse, the bubble cluster emits 2.5 MeV D-D fusion neutron pulses at a rate of ∼2000 per second. The neutron yield is ∼105 s−1. In parallel, tritium nuclei are produced at the same yield. It is shown numerically that, for bubbles having sufficient molecular mass, spherical shock waves develop in the center of the cluster and that these spherical shock waves (microshocks) produce converging shocks within the interior bubbles, which focus energy on the centers of the bubbles. When these shock waves reflect from the centers of the bubbles, extreme conditions of temperature (∼108 K) and density (∼104 kg m−3) arise in a (nano)spherical region (∼10−7 m in size) that last for ∼10−12 s, during which time about ten D-D fusion neutrons and tritium nuclei are produced in the region. A paradoxical result in our experiments is that it is bubble cluster (not streamer) cavitation and the sufficiently high molecular mass of (and hence the low sound speed in) D-acetone (C3D6O) vapor (as compared, for example, to deuterated water D2O) which are necessary conditions for the formation of convergent spherical microshock waves in central cluster bubbles. It is these waves that allow the energy to be sufficiently focused in the nanospherical regions near the bubble centers for fusion events to occur. The criticism to which the concept of 'bubble fusion' has been subjected in the literature, in particular, most recently in Uspekhi Fizicheskikh Nauk (Physics

  12. Toward a Metatheory of Economic Bubbles

    DEFF Research Database (Denmark)

    Dholakia, Nikhilesh; Turcan, Romeo V.

    original research in Toward a Metatheory of Economic Bubbles have far-reaching implications for the study and practice of entrepreneurship and marketing, public and corporate finance, and public policies towards innovation, economy, and finance. It contributes to the defining issues for economic sociology......Dholakia and Turcan present their interdisciplinary metatheory of bubbles with short case studies of minor and major bubbles. They comprehensively identify and exemplify constructs of the theory, set its temporal and contextual boundaries, and examine the underlying economic, psychological, and...

  13. Numerical investigation of bubble nonlinear dynamics characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Jie, E-mail: shijie@hrbeu.edu.cn; Yang, Desen; Shi, Shengguo; Hu, Bo [Acoustic Science and Technology Laboratory, Harbin Engineering University, Harbin 150001 (China); College of Underwater Acoustic Engineering, Harbin Engineering University, Harbin 150001 (China); Zhang, Haoyang; Jiang, Wei [College of Underwater Acoustic Engineering, Harbin Engineering University, Harbin 150001 (China)

    2015-10-28

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

  14. Analytical solutions for problems of bubble dynamics

    International Nuclear Information System (INIS)

    Recently, an asymptotic solution of the Rayleigh equation for an empty bubble in N dimensions has been obtained. Here we give the closed-form general analytical solution of this equation. We also find the general solution of the Rayleigh equation in N dimensions for the case of a gas-filled hyperspherical bubble. In addition, we include a surface tension into consideration. - Highlights: • The Rayleigh equation for bubble's dynamics is considered. • General analytical solutions of the Rayleigh equation are obtained. • Various types of analytical solutions of the Rayleigh equation are studied

  15. Numerical investigation of bubble nonlinear dynamics characteristics

    Science.gov (United States)

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

    2015-10-01

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

  16. Surfactants for Bubble Removal against Buoyancy

    OpenAIRE

    Md. Qaisar Raza; Nirbhay Kumar; Rishi Raj

    2016-01-01

    The common phenomenon of buoyancy-induced vapor bubble lift-off from a heated surface is of importance to many areas of science and technology. In the absence of buoyancy in zero gravity of space, non-departing bubbles coalesce to form a big dry patch on the heated surface and heat transfer deteriorates despite the high latent heat of vaporization of water. The situation is worse on an inverted heater in earth gravity where both buoyancy and surface tension act upwards to oppose bubble remova...

  17. Numerical investigation of bubble nonlinear dynamics characteristics

    International Nuclear Information System (INIS)

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

  18. A view inside the Gargamelle bubble chamber

    CERN Multimedia

    1970-01-01

    Gargamelle was the name given to a big bubble chamber built at the Saclay Laboratory in France during the late 1960s. It was designed principally for the detection at CERN of the elusive particles called neutrinos. A bubble chamber contains a liquid under pressure, which reveals the tracks of electrically charged particles as trails of tiny bubbles when the pressure is reduced. Neutrinos have no charge, and so leave no tracks, but the aim with Gargamelle was "see neutrinos" by making visible any charged particles set in motion by the interaction of neutrinos in the liquid

  19. Holography in a freon bubble chamber

    International Nuclear Information System (INIS)

    After some tests in a PS beam in the summer of 1981, the run took place in October 1981 in the H2 beam of the SPS. Although some problems of heat dissipation in freon limited the expansion rate of the bubble chamber, more than 11000 holograms were taken, showing 10 μm bubble tracks, with very good image quality and contrast. More than 100 tracks can be stored on a hologram without affecting the quality if all the bubbles are small. In addition, the analysis of the holograms does not look more complex than the exploitation of conventional high-resolution pictures. (orig./HSI)

  20. Mycelia Growth and Production of Total Flavonoids and 4H-pyran-4-one, 2,3-dihydro-3,5-dihydroxy-6-methyl- by Schizophyllum commune Using a Bubble Column Bioreactor Considering Aeration Effect and Mass Transfer Study

    OpenAIRE

    Teoh, Y. P.; Mat Don, M.

    2015-01-01

    Higher fungi are a major source of bioactive secondary metabolites, and Schizophyllum commune secreted Schizophyllan that could possess antifungal activity. 4H-pyran-4-one, 2,3-dihydro-3,5-dihydroxy-6-methyl- (DDMP), a compound with flavonoid fraction, is an important bioactive chemical which exhibited antifungal activity to inhibit growth or spore germination. In view of the potential of DDMP, bench scale production of total flavonoid content (TFC) and DDMP of Schizophyllum commune was carri...

  1. Conservation of bubble size distribution during gas reactive absorption in bubble column reactors

    Directory of Open Access Journals (Sweden)

    P. L.C. LAGE

    1999-12-01

    Full Text Available Conservation of the bubble size distribution function was applied to the reactive absorption of carbon dioxide in a bubble column reactor. The model developed was solved by the method of characteristics and by a Monte Carlo method. Simulations were carried out using simplified models for the liquid phase and for the gas-liquid mass transfer. Predictions of gas holdup and outlet gas composition showed that the concept of a mean bubble diameter is not applicable when the bubble size distribution is reasonably polydispersed. In these cases, the mass mean velocity and the numerical mean velocity of the bubbles are very different. Therefore, quantification of the polydispersion of bubbles was shown to be essential to gas-phase hydrodynamics modeling.

  2. Interactions of multiple spark-generated bubbles with phase differences

    Science.gov (United States)

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

    2009-04-01

    This paper aims to study the complex interaction between multiple bubbles, and to provide a summary and physical explanation of the phenomena observed during the interaction of two bubbles. High-speed photography is utilized to observe the experiments involving multiple spark-generated bubbles. Numerical simulations corresponding to the experiments are performed using the Boundary Element Method (BEM). The bubbles are typically between 3 and 5 mm in radius and are generated either in-phase (at the same time) or with phase differences. Complex phenomena are observed such as bubble splitting, and high-speed jetting inside a bubble caused by another collapsing bubble nearby (termed the ‘catapult’ effect). The two-bubble interactions are broadly classified in a graph according to two parameters: the relative inter-bubble distance and the phase difference (a new parameter introduced). The BEM simulations provide insight into the physics, such as bubble shape changes in detail, and jet velocities. Also presented in this paper are the experimental results of three bubble interactions. The interesting and complex observations of multiple bubble interaction are important for a better understanding of real life applications in medical ultrasonic treatment and ultrasonic cleaning. Many of the three bubble interactions can be explained by isolating bubble pairs and classifying their interaction according to the graph for the two bubble case. This graph can be a useful tool to predict the behavior of multiple bubble interactions.

  3. MARANGONI CONVECTION AROUND A VENTILATED AIR BUBBLE UNDER MICROGRAVITY CONDITIONS

    NARCIS (Netherlands)

    HOEFSLOOT, HCJ; JANSSEN, LPBM; HOOGSTRATEN, HW

    1994-01-01

    Under microgravity conditions in both parabolic and sounding rocket flights, the mass-transfer-induced Marangoni convection around an air bubble was studied. To prevent the bubble from becoming saturated, the bubble was ventilated. It turned out that the flow rate of the air through the bubble deter

  4. Generation of pulsed discharge plasma in water with fine bubbles

    Science.gov (United States)

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

    2015-09-01

    Recently, some researchers have proposed electric discharge methods with bubbles in water because the discharge plasma inside bubble was easy to be generated compared to that in water. Almost all of these methods introduced bubbles in the order of millimeter size from a nozzle placed in water. In these methods, bubbles rose one after another owing to high rising speed of millibubble, leading to inefficient gas consumption. We proposed fine bubbles introduction at the discharge area in water. A fine bubble is determined a bubble with less than 100 μm in a diameter. Fine bubbles exhibit extremely slow rising speed. Fine bubbles decrease in size during bubble rising and subsequently collapse in water with OH radical generation. Therefore, combining the discharge plasma with fine bubbles is expected to generate more active species with small amount of gas consumption. In this work, fine bubbles were introduced in water and pulsed discharge plasma was generated between two cylindrical electrodes which placed in water. We examined effects of fine bubbles on electric discharge in water when argon or oxygen gas was utilized as feed gas. Fine bubbles enhanced optical emission of hydrogen and oxygen atoms from H2O molecules, but that of feed gas was not observed. The formation mechanism of H2O2 by electric discharge was supposed to be different from that with no bubbling. Dissolved oxygen in water played a role in H2O2 formation by the discharge with fine bubbles.

  5. Time-Dependent Changes in a Shampoo Bubble

    Science.gov (United States)

    Chattopadhyay, Arun

    2000-10-01

    This article demonstrates the fascinating phenomenon of time evolution of a shampoo bubble through experiments that can be performed by undergraduate students. The changes in thickness of the bubble films with time are followed by UV-vis spectroscopy. The change in chemical composition as a bubble film evolves is monitored by FTIR spectroscopy. It is observed that the change in thickness of a typical shampoo bubble film enclosed in a container is gradual and slow, and the hydrocarbon components of the bubble drain from the bubble much more slowly than water. An additional agent, such as acetonitrile, strikingly alters the dynamics of evolution of such a bubble.

  6. Wetting of soap bubbles on hydrophilic, hydrophobic and superhydrophobic surfaces

    CERN Document Server

    Arscott, Steve

    2013-01-01

    Wetting of sessile bubbles on solid and liquid surfaces has been studied. A model is presented for the contact angle of a sessile bubble based on a modified Young equation - the experimental results agree with the model. A hydrophilic surface results in a bubble contact angle of 90 deg whereas on a superhydrophobic surface one observes 134 deg. For hydrophilic surfaces, the bubble angle diminishes with bubble radius - whereas on a superhydrophobic surface, the bubble angle increases. The size of the Plateau borders governs the bubble contact angle - depending on the wetting of the surface.

  7. Thermodynamic property of gases in the sonoluminescing bubble

    Institute of Scientific and Technical Information of China (English)

    AN Yu; LI Guiqin; ZHOU Tieying

    2001-01-01

    With the theory of statistical physics dealing with chemical reaction (the law of mass action), the different thermodynamic property of noble gases (mono-atomic gases) in a small bubble and diatomic gases in a small bubble semi-quantitatively are analyzed. As bubbles of the mono-atomic and the diatomic gases are compressed, shock waves are produced in both bubbles. Though shock wave leads to sharp increase of pressure and temperature of gases in the bubble, diatomic gas will excitated vibrations and dissociate themselves to mono-atomic gas,these processes will consume many accumulated heat energy and block the further increase of the temperature. Therefore, compare with the mono-atomic gases in the bubble, there will be no enough charged particles ionized to flash for diatomic gases in the bubble, this may be the reason why a bubble of diatomic gases has no single bubble sonoluminescence while a bubble of noble gases has.

  8. Effects of Ambient Pressure on Bubble Characteristics

    Institute of Scientific and Technical Information of China (English)

    卢新培; 刘明海; 江中和; 潘垣

    2002-01-01

    The effects of the ambient pressure Pambient on the bubble characteristics of pulsed discharge in water are investigated. The simulation results show that, when Pambient increases from 1 atm to 100 atm, the bubble radius R decreases from 4cma to 7mm, and its pulsation period decreases frown 8ms to 0.2ms. The results also show that the peak pressure of the first shock wave is independent of Pambient, but the peak pressure of the second shock wave caused by the bubble re-expansion decreases when Pambient increases. On the other hand, the larger the ambient pressure, the larger the peak pressure of the plasma in the bubble, while the plasma temperature is independent of Pambient.

  9. Stretching cells and delivering drugs with bubbles

    Science.gov (United States)

    Ohl, Claus-Dieter; Li, Fenfang; Chon U, Chan; Gao, Yu; Xu, Chenjie

    2015-11-01

    In this talk we'll review our work on impulsive cell stretching using cavitation bubbles and magnetic microbubbles for drug delivery. For sufficient short times cells can sustain a much larger areal strain than the yield strain obtained from quasi-static stretching. Experiments with red blood cells show that even then the rupture of the cell is slow process; it is caused by diffusive swelling rather than mechanical violation of the plasma membrane. In the second part we'll discuss bubbles coated with magnetic and drug loaded particles. These bubbles offer an interesting vector for on demand delivery of drugs using mild ultrasound and magnetic fields. We report on basic experiments in microfluidic channels revealing the release of the agent during bubble oscillations and first in vivo validation with a mouse tumor model. Singapore National Research Foundations Competitive Research Program funding (NRF-CRP9-2011-04).

  10. Observable effects of anisotropic bubble nucleation

    CERN Document Server

    Blanco-Pillado, Jose J

    2010-01-01

    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. Then the reduced symmetry of the background is equivalent to anisotropic initial conditions in our bubble universe. We compute the inflationary spectrum in such a scenario and, as a first step toward understanding the effects of anisotropy, project it onto spherical harmonics. The resulting spectrum exhibits anomalous multipole correlations, their relative amplitude set by the present curvature parameter, which extend to arbitrarily large multipole moments. This raises the possibility of future detection, if slow-roll inflation does not last too long within our bubble. A full understanding of the observational signal must account for the effects of background anisotropy on photon free streaming, and is left...

  11. The 2008 oil bubble: Causes and consequences

    International Nuclear Information System (INIS)

    We argue that 'the 2008 Oil Bubble' was directly and indirectly created by the Federal Reserve in response to deflationary risks that resurfaced after the housing bubble burst and the resulting credit crisis of 2008. Deflationary risks first appeared after the dot.com bubble burst in 2000 and after the terrorist attacks on September 11, 2001. Manipulation of the US dollar value has been one of the key emergency tools in the Fed's arsenal. During the entire period from 2000 to 2008, the US dollar has been falling, while the price of crude oil has been rising, with the culmination in July 2008. If other global central banks embrace the Fed's anti-deflationary strategies, the consequences could be dire for the global economy, potentially resulting in an ultimate gold bubble.

  12. The 2008 oil bubble. Causes and consequences

    International Nuclear Information System (INIS)

    We argue that 'the 2008 Oil Bubble' was directly and indirectly created by the Federal Reserve in response to deflationary risks that resurfaced after the housing bubble burst and the resulting credit crisis of 2008. Deflationary risks first appeared after the dot.com bubble burst in 2000 and after the terrorist attacks on September 11, 2001. Manipulation of the US dollar value has been one of the key emergency tools in the Fed's arsenal. During the entire period from 2000 to 2008, the US dollar has been falling, while the price of crude oil has been rising, with the culmination in July 2008. If other global central banks embrace the Fed's anti-deflationary strategies, the consequences could be dire for the global economy, potentially resulting in an ultimate gold bubble. (author)

  13. Shapes of Bubbles and Drops in Motion.

    Science.gov (United States)

    O'Connell, James

    2000-01-01

    Explains the shape distortions that take place in fluid packets (bubbles or drops) with steady flow motion by using the laws of Archimedes, Pascal, and Bernoulli rather than advanced vector calculus. (WRM)

  14. Simulations of Buoyant Bubbles in Galaxy Clusters

    CERN Document Server

    Brüggen, M

    2003-01-01

    It is generally argued that most clusters of galaxies host cooling flows in which radiative cooling in the centre causes a slow inflow. However, recent observations by Chandra and XMM conflict with the predicted cooling flow rates. Here we report highly resolved hydrodynamic simulations which show that buoyant bubbles can offset the cooling in the inner regions of clusters and can significantly delay the deposition of cold gas. The subsonic rise of bubbles uplifts colder material from the central regions of the cluster. This colder material appears as bright rims around the bubbles. The bubbles themselves appear as depressions in the X-ray surface brightness as observed in a growing number of clusters.

  15. Sonochemical effects on single-bubble sonoluminescence

    CERN Document Server

    Yuan, L

    2005-01-01

    A refined hydro-chemical model for single-bubble sonoluminescence is presented. The processes of water vapor evaporation and condensation, mass diffusion, and chemical reactions are taken into account. Numerical simulations of Xe-, Ar- and He-filled bubbles are carried out. The results show that the trapped water vapor in conjunction with its endothermic chemical reactions significantly reduces the temperature within the bubble so that the degrees of ionization are generally very low. The chemical radicals generated from water vapor are shown to play an increasingly important role in the light emission from Xe to He bubbles. Light spectra and pulses computed from an optically thin model and from an essentially blackbody model are compared with recent experimental results. It is found that the results of the blackbody model generally match better with the experiment ones than those of the optically thin model. Suggestions on how to reconcile the conflict are given.

  16. Using sound to study bubble coalescence.

    Science.gov (United States)

    Kracht, W; Finch, J A

    2009-04-01

    Frothers are surfactants used in flotation to aid generation of small bubbles, an effect attributed to coalescence prevention. Studying coalescence at the moment of bubble creation is a challenge because events occur over a time frame of milliseconds. This communication introduces a novel acoustic technique to study coalescence as bubbles are generated at a capillary. The sound signal was linked to bubble formation and coalescence events using high-speed cinematography. The technique has the resolution to detect events that occur within 1-2 ms. The results show that for common flotation frothers and n-alcohols (C(4)-C(8)) coalescence prevention is not simply related to surface activity. A total stress model is used to give a qualitative explanation to the action observed. Results for salt (sodium chloride) are included for comparison. PMID:19128806

  17. Methane bubbling: from speculation to quantification

    Science.gov (United States)

    Grinham, A. R.; Dunbabin, M.; Yuan, Z.

    2013-12-01

    Rates of methane bubbling (ebullition) represent a notoriously difficult emission pathway to quantify with highly variable spatial and temporal changes. However, the importance of bubbling fluxes in terms of total emissions is increasingly recognised from a number of different globally relevant natural systems including lakes, reservoirs and wetlands. This represents a critical challenge to current survey efforts to quantify greenhouse gas emissions and reduce the uncertainty associated with bubbling fluxes. A number of different methods have been proposed to overcome this challenge including bubble traps, floating chambers, echo sounders, laser spectrography and camera systems. Each method has relative merits and deficiencies with all trading-off the ability to directly quantify methane and provide spatial and temporal coverage. Here we present a novel method that allows direct measurement of methane bubble concentration as well as the ability to persistently monitor a wide spatial area. Central to the monitoring system is an Autonomous Surface Vessel (ASV) and an Optical Methane Detector (OMD). The ASV is equipped with solar panels and uses electric motors for propulsion to allow persistent environmental monitoring. The OMD has a path length of 1.3 m and 7 Hz sampling so a typical mission of 3 hours at 1 m s-1 covers an area in excess of 10 000 m2 and over 65 000 data points. The system was assessed on four sub-tropical freshwater reservoirs of varying surface area (0.5 to 100 km2), age (2 to 65 y) and catchment land use (40 to 90% natural vegetation cover). Each reservoir had unique challenges in terms of navigation and field conditions to test feasibility of this method. Deployment length varied from a single day to over 4 months to test method durability. In addition to ASV bubble surveys, floating static chambers were deployed to determine diffusive fluxes. Localised instantaneous bubble flux rates within a single reservoir ranged over three orders of

  18. Hydrodynamics, Acoustics and Scaling of Traveling Bubble Cavitation

    OpenAIRE

    Kuhn de Chizelle, Yan P.

    1994-01-01

    Recent observations of the geometries of growing and collapsing bubbles over axisymmetric headforms have revealed the complexity of the "microfluidmechanics" associated with these flows (Hamilton et al., 1982, Briançon Marjollet and Franc, 1990, Ceccio and Brennen, 1991). Among the complex features observed were bubble to bubble interaction, cavitation noise generation and bubble interaction with the boundary layer which leads to the shearing of the underside of the bubble and ...

  19. Effects of Gas Dynamics on Rapidly Collapsing Bubbles

    OpenAIRE

    Bauman, Spenser; Fomitchev-Zamilov, Max

    2013-01-01

    The dynamics of rapidly collapsing bubbles are of great interest due to the high degree of energy focusing that occurs withing the bubble. Molecular dynamics provides a way to model the interior of the bubble and couple the gas dynamics with the equations governing the bubble wall. While much theoretical work has been done to understand how a bubble will respond to an external force, the internal dynamics of the gas system are usually simplified greatly in such treatments. This paper shows ho...

  20. Bubble chamber: Omega production and decay

    CERN Multimedia

    1973-01-01

    This image is taken from one of CERN's bubble chambers and shows the decay of a positive kaon in flight. The decay products of this kaon can be seen spiraling in the magnetic field of the chamber. The invention of bubble chambers in 1952 revolutionized the field of particle physics, allowing real tracks left by particles to be seen and photographed by expanding liquid that has been heated to boiling point.

  1. Brexit or Bremain ? Evidence from bubble analysis

    OpenAIRE

    Bianchetti, Marco; Galli, Davide; Ricci, Camilla; Salvatori, Angelo; Scaringi, Marco

    2016-01-01

    We applied the Johansen-Ledoit-Sornette (JLS) model to detect possible bubbles and crashes related to the Brexit/Bremain referendum scheduled for 23rd June 2016. Our implementation includes an enhanced model calibration using Genetic Algorithms. We selected a few historical financial series sensitive to the Brexit/Bremain scenario, representative of multiple asset classes. We found that equity and currency asset classes show no bubble signals, while rates, credit and real estate show super-ex...

  2. Topological vacuum bubbles by anyon braiding

    OpenAIRE

    Han, Cheolhee; Park, Jinhong; Gefen, Yuval; Sim, H.-S.

    2016-01-01

    According to a basic rule of fermionic and bosonic many-body physics, known as the linked cluster theorem, physical observables are not affected by vacuum bubbles, which represent virtual particles created from vacuum and self-annihilating without interacting with real particles. Here we show that this conventional knowledge must be revised for anyons, quasiparticles that obey fractional exchange statistics intermediate between fermions and bosons. We find that a certain class of vacuum bubbl...

  3. Wall slip of bubbles in foams

    OpenAIRE

    WEAIRE, DENIS LAWRENCE

    2006-01-01

    PUBLISHED We present a computational analysis of the flow of liquid foam along a smooth wall, as encountered in the transport of foams in vessels and pipes. We concentrate on the slip of the bubbles at the wall and present some novel finite element calculations of this motion for the case of fully mobile gas/liquid interfaces. Our two-dimensional simulations provide for the first time the bubble shapes and entire flow field, giving detailed insight into the distribution of stre...

  4. Test ventilation with smoke, bubbles, and balloons

    Energy Technology Data Exchange (ETDEWEB)

    Pickering, P.L.; Cucchiara, A.L.; McAtee, J.L.; Gonzales, M.

    1987-01-01

    The behavior of smoke, bubbles, and helium-filled balloons was videotaped to demonstrate the mixing of air in the plutonium chemistry laboratories, a plutonium facility. The air-distribution patterns, as indicated by each method, were compared. Helium-filled balloons proved more useful than bubbles or smoke in the visualization of airflow patterns. The replay of various segments of the videotape proved useful in evaluating the different techniques and in identifying airflow trends responsible for air mixing. 6 refs.

  5. Electrospun jets launched from polymeric bubbles

    OpenAIRE

    J.S. Varabhas; G.G. Chase; S. Tripatanasuwan; D.H. Reneker

    2009-01-01

    In this paper the launching of liquid polymer jetsfrom the apex of gas bubbles on thepolyvinylpyrrolidone in ethanol (PVP) solutionsurface due to an applied electrical potential isinvestigated. Jets of polymer launched from bubbleprovide an alternative method for electrospinningpolymer nanofibers that may be scalable forcommercial production. Bubbles were experimentallycreated on the surface of a polymer solution byforcing air through a syringe into the polymersolution. An electric potential ...

  6. The prediction of bubble defects in castings

    OpenAIRE

    Lawrence, James Andrew

    2004-01-01

    Objective of this research was to develop models that capture the entrainment, breakup and transport of gas bubbles in solidifying TiAl castings. The candidate has reviewed the literature, programmed in FORTRAN code, and validated a number of competing techniques for two phase flow relevant to the filling of moulds. He has developed a hybrid (Donor-acceptor/ Level Set) method, which captures the characteristics of gas bubbles based on the surface tension —fluid inertia balance on the free sur...

  7. Beer tapping: dynamics of bubbles after impact

    Science.gov (United States)

    Mantič-Lugo, V.; Cayron, A.; Brun, P.-T.; Gallaire, F.

    2015-12-01

    Beer tapping is a well known prank where a bottle of beer is impacted from the top by a solid object, usually another bottle, leading to a sudden foam overflow. A description of the shock-driven bubble dynamics leading to foaming is presented based on an experimental and numerical study evoking the following physical picture. First, the solid impact produces a sudden downwards acceleration of the bottle creating a strong depression in the liquid bulk. The existing bubbles undergo a strong expansion and a sudden contraction ending in their collapse and fragmentation into a large amount of small bubbles. Second, the bubble clouds present a large surface area to volume ratio, enhancing the CO2 diffusion from the supersaturated liquid, hence growing rapidly and depleting the CO2. The clouds of bubbles migrate upwards in the form of plumes pulling the surrounding liquid with them and eventually resulting in the foam overflow. The sudden pressure drop that triggers the bubble dynamics with a collapse and oscillations is modelled by the Rayleigh-Plesset equation. The bubble dynamics from impact to collapse occurs over a time (tb ≃ 800 μs) much larger than the acoustic time scale of the liquid bulk (tac = 2H/c ≃ 80 μs), for the experimental container of height H = 6 cm and a speed of sound around c ≃ 1500 m/s. This scale separation, together with the comparison of numerical and experimental results, suggests that the pressure drop is controlled by two parameters: the acceleration of the container and the distance from the bubble to the free surface.

  8. Bubble nonlinear dynamics and stimulated scattering process

    Science.gov (United States)

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

    2016-02-01

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

  9. Water temperature dependence of single bubble sonoluminescence

    OpenAIRE

    Hilgenfeldt, Sascha; Lohse, Detlef; Moss, William C.

    1998-01-01

    The strong dependence of the intensity of single bubble sonoluminescence (SBSL) on water temperature observed in experiment can be accounted for by the temperature dependence of the material constants of water, most essentially of the viscosity, of the argon solubility in water, and of the vapor pressure. The strong increase of light emission at low water temperatures is due to the possibility of applying higher driving pressures, caused by increased bubble stability. The presented calculatio...

  10. Gravity waves from cosmic bubble collisions

    Science.gov (United States)

    Salem, Michael P.; Saraswat, Prashant; Shaghoulian, Edgar

    2013-02-01

    Our local Hubble volume might be contained within a bubble that nucleated in a false vacuum with only two large spatial dimensions. We study bubble collisions in this scenario and find that they generate gravity waves, which are made possible in this context by the reduced symmetry of the global geometry. These gravity waves would produce B-mode polarization in the cosmic microwave background, which could in principle dominate over the inflationary background.

  11. Gravity waves from cosmic bubble collisions

    CERN Document Server

    Salem, Michael P; Shaghoulian, Edgar

    2012-01-01

    Our local Hubble volume might be contained within a bubble that nucleated in a false vacuum with only two large spatial dimensions. We study bubble collisions in this scenario and find that they generate gravity waves, which are made possible in this context by the reduced symmetry of the global geometry. These gravity waves would produce B-mode polarization in the cosmic microwave background, which could in principle dominate over the inflationary background.

  12. Gravity waves from cosmic bubble collisions

    International Nuclear Information System (INIS)

    Our local Hubble volume might be contained within a bubble that nucleated in a false vacuum with only two large spatial dimensions. We study bubble collisions in this scenario and find that they generate gravity waves, which are made possible in this context by the reduced symmetry of the global geometry. These gravity waves would produce B-mode polarization in the cosmic microwave background, which could in principle dominate over the inflationary background

  13. Interstellar Bubbles in Two Young HII Regions

    CERN Document Server

    Naze, Y; Points, S D; Danforth, C W; Rosado, M; Chen, C H R; Naze, Yael; Chu, You-Hua; Points, Sean D.; Danforth, Charles W.; Rosado, Margarita

    2001-01-01

    Massive stars are expected to produce wind-blown bubbles in the interstellar medium; however, ring nebulae, suggesting the existence of bubbles, are rarely seen around main-sequence O stars. To search for wind-blown bubbles around main-sequence O stars, we have obtained high-resolution Hubble Space Telescope WFPC2 images and high-dispersion echelle spectra of two pristine HII regions, N11B and N180B, in the Large Magellanic Cloud. These HII regions are ionized by OB associations that still contain O3 stars, suggesting that the HII regions are young and have not hosted any supernova explosions. Our observations show that wind-blown bubbles in these HII regions can be detected kinematically but not morphologically because their expansion velocities are comparable to or only slightly higher than the isothermal sound velocity in the HII regions. Bubbles are detected around concentrations of massive stars, individual O stars, and even an evolved red supergiant (a fossil bubble). Comparisons between the observed bu...

  14. Fluid dynamics of bubbles in liquid

    Directory of Open Access Journals (Sweden)

    SCHEID C.M.

    1999-01-01

    Full Text Available Results gathered from the literature on the dynamics of bubbles in liquid are correlated by means of a formulation traditionally employed to describe the dynamics of isometric solid particles. It is assumed that the shape of the bubble depends, by means of the Eotvos number, on its diameter and on the gas-liquid surface tension. The analysis reported herein includes the dynamics of the isolated bubble along with wall and concentration effects. However, the effects of gas circulation in the bubble, which result in terminal velocities higher than those of a rigid sphere, are not being considered. A limited number of experimental points are obtained employing a modified version of the Mariotte flask which permits the precise measure of bubble volume. A classic bubble column is also employed in order to measure gas holdup in the continuous phase. Experiments were carried out employing air, with distilled water, potable water, water with variable amounts of surfactant and glycerin as the liquid phase.

  15. Intensely oscillating cavitation bubble in microfluidics

    Science.gov (United States)

    Siew-Wan, Ohl; Tandiono; Klaseboer, Evert; Dave, Ow; Choo, Andre; Claus-Dieter, Ohl

    2015-12-01

    This study reports the technical breakthrough in generating intense ultrasonic cavitation in the confinement of a microfluidics channel [1], and applications that has been developed on this platform for the past few years [2,3,4,5]. Our system consists of circular disc transducers (10-20 mm in diameter), the microfluidics channels on PDMS (polydimethylsiloxane), and a driving circuitry. The cavitation bubbles are created at the gas- water interface due to strong capillary waves which are generated when the system is driven at its natural frequency (around 100 kHz) [1]. These bubbles oscillate and collapse within the channel. The bubbles are useful for sonochemistry and the generation of sonoluminescence [2]. When we add bacteria (Escherichia coli), and yeast cells (Pichia pastoris) into the microfluidics channels, the oscillating and collapsing bubbles stretch and lyse these cells [3]. Furthermore, the system is effective (DNA of the harvested intracellular content remains largely intact), and efficient (yield reaches saturation in less than 1 second). In another application, human red blood cells are added to a microchamber. Cell stretching and rapture are observed when a laser generated cavitation bubble expands and collapses next to the cell [4]. A numerical model of a liquid pocket surrounded by a membrane with surface tension which was placed next to an oscillating bubble was developed using the Boundary Element Method. The simulation results showed that the stretching of the liquid pocket occurs only when the surface tension is within a certain range.

  16. Magnetic susceptibility based magnetic resonance estimation of micro-bubble size for the vertically upward bubbly flow.

    Science.gov (United States)

    Arbabi, A; Mastikhin, I V

    2012-12-01

    The approach originally developed for the Nuclear Magnetic Resonance analysis of stable micro-bubbles is applied to studies of vertical bubbly flows. A very fast dispersion (diffusion) of water in bubbly flows extends the fast diffusion limit down to short (2-10 ms) measurement times, permitting the use of the simplified analytical expression to extract the micro-bubble size information both in bulk and spatially resolved. The observed strong bubble-induced reduction in T(2)(*) necessitates the use of very short encoding times and pure phase encoding methods to accurately measure the void fraction. There was an expected underestimation of bubble sizes at faster flow rates due to the limitations of the theory derived for small bubble sizes and non-interacting spherical bubbles (low void fractions and slow flow rates). This approach lends itself to studies of bubbly flows and cavitating media characterized by small bubble sizes and low void fractions. PMID:23117260

  17. Neutron spectrometry with bubble detectors

    International Nuclear Information System (INIS)

    The use of linear accelerators with photon energies above 10 MV is becoming more common for therapeutical purposes. Although these beams have some clinical advantages over low energies ones, they have neutrons as an additional component to the radiation field, due to the interaction of the high energy photons with the high Z materials which form the head and other accelerator components. The neutrons which cross the accelerator head are emitted almost isotropically, in an energy range which varies from a few keV (thermal) up to some MeV. The evaluation of neutron equivalent doses in radiotherapy facilities is relevant not only for patient protection but also for shielding purposes. In this paper we present results of neutron dose measurements and spectra evaluation, with the use of a neutron bubble spectrometer, performed in some points of a facility which has a 15 MV Varian Clinac linear accelerator. The measured values, when compared with reported in the literature, shows a fairly good agreement. (author)

  18. CFD simulation of bubble column

    Energy Technology Data Exchange (ETDEWEB)

    Ekambara, K., E-mail: ekambara@ualberta.c [Department of Chemical and Materials Engineering, University of Alberta, 536 CME Building, Edmonton, AB, T6G 2G6 (Canada); Dhotre, M.T. [Thermal-Hydraulics Laboratory, Nuclear Energy and Safety Department, Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland)

    2010-05-15

    Three-dimensional simulations of gas-liquid flow in the bubble column using the Euler-Euler approach is presented. The attempt is made to assess the performance and applicability of different turbulence models namely, k-epsilon, k-epsilon RNG, k-omega, Reynolds stress model (RSM) and large eddy simulation (LES) using a commercial code (ANSYS-CFX). For this purpose, the predictions are compared against the experimental data of . Performance of the turbulence models is assessed on basis of comparison of axial liquid velocity, fractional gas hold-up, turbulent kinetic energy and turbulent eddy dissipation rate. All the non-drag (turbulent dispersion, virtual mass and lift force) and drag force were incorporated in the model. The low-Reynolds number treatment of the k-omega yields a better qualitative prediction than the k-epsilon model. The RSM predictions are comparable with LES results and seemed to give better prediction near the sparger, where the flow is more anisotropic and gives a clue why RANS approaches fails to predict the flow in this region. However, the large eddy simulations showed good agreement with the experimental data, but requires higher computational time than RSM.

  19. The Scientometric Bubble Considered Harmful.

    Science.gov (United States)

    Génova, Gonzalo; Astudillo, Hernán; Fraga, Anabel

    2016-02-01

    This article deals with a modern disease of academic science that consists of an enormous increase in the number of scientific publications without a corresponding advance of knowledge. Findings are sliced as thin as salami and submitted to different journals to produce more papers. If we consider academic papers as a kind of scientific 'currency' that is backed by gold bullion in the central bank of 'true' science, then we are witnessing an article-inflation phenomenon, a scientometric bubble that is most harmful for science and promotes an unethical and antiscientific culture among researchers. The main problem behind the scenes is that the impact factor is used as a proxy for quality. Therefore, not only for convenience, but also based on ethical principles of scientific research, we adhere to the San Francisco Declaration on Research Assessment when it emphasizes "the need to eliminate the use of journal-based metrics in funding, appointment and promotion considerations; and the need to assess research on its own merits rather on the journal in which the research is published". Our message is mainly addressed to the funding agencies and universities that award tenures or grants and manage research programmes, especially in developing countries. The message is also addressed to well-established scientists who have the power to change things when they participate in committees for grants and jobs. PMID:25689931

  20. Bubble Divergences from Twisted Cohomology

    Science.gov (United States)

    Bonzom, Valentin; Smerlak, Matteo

    2012-06-01

    We consider a class of lattice topological field theories, among which are the weak-coupling limit of 2d Yang-Mills theory and 3d Riemannian quantum gravity, whose dynamical variables are flat discrete connections with compact structure group on a cell 2-complex. In these models, it is known that the path integral measure is ill-defined because of a phenomenon known as `bubble divergences'. In this paper, we extend recent results of the authors to the cases where these divergences cannot be understood in terms of cellular cohomology. We introduce in its place the relevant twisted cohomology, and use it to compute the divergence degree of the partition function. We also relate its dominant part to the Reidemeister torsion of the complex, thereby generalizing previous results of Barrett and Naish-Guzman. The main limitation to our approach is the presence of singularities in the representation variety of the fundamental group of the complex; we illustrate this issue in the well-known case of two-dimensional manifolds.

  1. Bubbles Pose The Biggest Threat

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    @@ The fast economic growth China has experienced in the past three decades is mainly attributed to dividends of production elements (including labor force and resources), market-oriented reform and globalization. Today, the contribution of the three major dividends is weakening and the growth model built on low-cost advantages can no longer be sustained.

  2. Bubble dynamics in metal nanoparticle formation by laser ablation in liquid studied through high-speed laser stroboscopic videography

    Energy Technology Data Exchange (ETDEWEB)

    Tanabe, Rie; Nguyen, Thao T.P.; Sugiura, Takahiro; Ito, Yoshiro, E-mail: itoy@vos.nagaokaut.ac.jp

    2015-10-01

    Highlights: • Observations at 1 μs interval were carried out for laser ablation in water. • Laser-induced shock wave and cavitation bubble are dynamically observed. • Jet-like shadows are observed during LAL in water after multiple-pulse irradiation. • Cloudlike-shadow moving away from the irradiated copper surface was observed. - Abstract: Laser ablation in liquid (LAL) is utilized in many applications, such as the fabrication of nanoparticles, laser cleaning and laser peening. We have developed a high-speed laser stroboscopic videography system that enables observations at intervals of 1 μs. Using this imaging system, we investigated the dynamics of cavitation bubbles induced by LAL to elucidate the timing and location of nanoparticle formation and dispersion into the surrounding liquid. The initial bubble demonstrated a well-defined, smooth boundary during its growth and shrinkage. Although previous studies have reported the ejection of particles at the boundary of the bubble, this was not observed in our images. Intermixing between the gas phase of the bubble and the surrounding liquid occurred when the first bubble collapsed. Jet-like shadows were recorded during LAL in water after multiple-pulse irradiation, but were not observed in freshly filled water that had not yet been irradiated. These shadows disappeared within 10 μs and are postulated to be micro-bubbles induced by interactions between nanoparticles suspended in the water and the incoming laser beam.

  3. Bubble dynamics in metal nanoparticle formation by laser ablation in liquid studied through high-speed laser stroboscopic videography

    International Nuclear Information System (INIS)

    Highlights: • Observations at 1 μs interval were carried out for laser ablation in water. • Laser-induced shock wave and cavitation bubble are dynamically observed. • Jet-like shadows are observed during LAL in water after multiple-pulse irradiation. • Cloudlike-shadow moving away from the irradiated copper surface was observed. - Abstract: Laser ablation in liquid (LAL) is utilized in many applications, such as the fabrication of nanoparticles, laser cleaning and laser peening. We have developed a high-speed laser stroboscopic videography system that enables observations at intervals of 1 μs. Using this imaging system, we investigated the dynamics of cavitation bubbles induced by LAL to elucidate the timing and location of nanoparticle formation and dispersion into the surrounding liquid. The initial bubble demonstrated a well-defined, smooth boundary during its growth and shrinkage. Although previous studies have reported the ejection of particles at the boundary of the bubble, this was not observed in our images. Intermixing between the gas phase of the bubble and the surrounding liquid occurred when the first bubble collapsed. Jet-like shadows were recorded during LAL in water after multiple-pulse irradiation, but were not observed in freshly filled water that had not yet been irradiated. These shadows disappeared within 10 μs and are postulated to be micro-bubbles induced by interactions between nanoparticles suspended in the water and the incoming laser beam

  4. Single cell membrane poration by bubble-induced microjets in a microfluidic chip.

    Science.gov (United States)

    Li, Z G; Liu, A Q; Klaseboer, E; Zhang, J B; Ohl, C D

    2013-03-21

    This paper demonstrates membrane poration of a single suspension cell due to a fast liquid microjet. The jet is formed during the collapse of a laser induced bubble created at a variable stand-off distance from the target cell. The cell is trapped by a converging structure within a microfluidic chip. The asymmetrical growth and collapse of the cavitation bubble next to the cell lead to the microjetting, which deforms and porates the cell membrane. In the experiments, the membrane porations of myeloma cells are probed with the uptake of trypan blue. Time-resolved studies of the diffusion of trypan blue show a marked dependency on the bubble dynamics, i.e. the stand-off distance. The penetration length of the dye increases with shorter distances. Numerical simulations of the diffusion process agree with larger pores formed on the cell membrane. This method allows for a fast, repeatable, and localized rupture of membranes of individual cells in suspension. PMID:23364762

  5. Acoustic and Visul Study of Bubble Formation Processes in Bubble Columns Staged with Fibrous Catalytic Layers

    Czech Academy of Sciences Publication Activity Database

    Höller, V.; Růžička, Marek; Drahoš, Jiří; Kiwi-Minsker, L.; Renken, A.

    79-80, - (2003), s. 151-157. ISSN 0920-5861 Institutional research plan: CEZ:AV0Z4072921 Keywords : bubble formation * fibrous catalytic layers * staged bubble column Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 2.627, year: 2003

  6. A novel approach to prevent bubble coalescence during measurement of bubble size in flotation

    Institute of Scientific and Technical Information of China (English)

    张炜

    2014-01-01

    Effect of frothers in preventing bubble coalescence during flotation of minerals has long been investigated. To evaluate the performance of a frother, an apparatus to measure the bubble size is a basic necessity. McGill Bubble Size Analyzer (MBSA) or bubble viewer that has been developed and completed by McGill University’s Mineral Processing Group during the last decade is a unique instrument to serve this purpose. Two parameters which are thought to influence the bubble size measurements by McGill bubble viewer include water quality and frother concentration in the chamber. Results show that there is no difference in Sauter mean (D32) when tap or de-ionized water was used instead of process water. However, the frother concentration, in this research DowFroth 250 (DF250), inside the chamber exhibited a pronounced effect on bubble size. Frother concentration below a certain point can not prevent coalescence inside the chamber and therefore caution must be taken in plant applications. It was also noted that the frother concentration which has been so far practiced in plant measurements (CCC75-CCC95) is high enough to prevent coalescence with the bubble viewer.

  7. Financial Bubbles, Real Estate Bubbles, Derivative Bubbles, and the Financial and Economic Crisis

    Science.gov (United States)

    Sornette, Didier; Woodard, Ryan

    The financial crisis of 2008, which started with an initially well-defined epicenter focused on mortgage backed securities (MBS), has been cascading into a global economic recession, whose increasing severity and uncertain duration has led and is continuing to lead to massive losses and damage for billions of people. Heavy central bank interventions and government spending programs have been launched worldwide and especially in the USA and Europe, with the hope to unfreeze credit and bolster consumption. Here, we present evidence and articulate a general framework that allows one to diagnose the fundamental cause of the unfolding financial and economic crisis: the accumulation of several bubbles and their interplay and mutual reinforcement have led to an illusion of a "perpetual money machine" allowing financial institutions to extract wealth from an unsustainable artificial process. Taking stock of this diagnostic, we conclude that many of the interventions to address the so-called liquidity crisis and to encourage more consumption are ill-advised and even dangerous, given that precautionary reserves were not accumulated in the "good times" but that huge liabilities were. The most "interesting" present times constitute unique opportunities but also great challenges, for which we offer a few recommendations.

  8. Rest frame of bubble nucleation

    Energy Technology Data Exchange (ETDEWEB)

    Garriga, Jaume [Departament de Física Fondamental i Institut de Ciencies del Cosmos, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona (Spain); Kanno, Sugumi [Institute of Cosmology, Department of Physics and Astronomy, Tufts University, Medford, Massachusetts 02155 (United States); Tanaka, Takahiro, E-mail: jaume.garriga@ub.edu, E-mail: sugumi@cosmos.phy.tufts.edu, E-mail: tanaka@yukawa.kyoto-u.ac.jp [Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502 (Japan)

    2013-06-01

    Vacuum bubbles nucleate at rest with a certain critical size and subsequently expand. But what selects the rest frame of nucleation? This question has been recently addressed in [1] in the context of Schwinger pair production in 1+1 dimensions, by using a model detector in order to probe the nucleated pairs. The analysis in [1] showed that, for a constant external electric field, the adiabatic ''in'' vacuum of charged particles is Lorentz invariant, (and in this) case pairs tend to nucleate preferentially at rest with respect to the detector. Here, we sharpen this picture by showing that the typical relative velocity between the frame of nucleation and that of the detector is at most of order Δv ∼ S{sub E}{sup −1/3} << 1. Here, S{sub E} >> 1 is the action of the instanton describing pair creation. The bound Δv coincides with the minimum uncertainty in the velocity of a non-relativistic charged particle embedded in a constant electric field. A velocity of order Δv is reached after a time interval of order Δt ∼ S{sub E}{sup −1/3}r{sub 0} << r{sub 0} past the turning point in the semiclassical trajectory, where r{sub 0} is the size of the instanton. If the interaction takes place in the vicinity of the turning point, the semiclassical description of collision does not apply. Nonetheless, we find that even in this case there is still a strong asymmetry in the momentum transferred from the nucleated particles to the detector, in the direction of expansion after the turning point. We conclude that the correlation between the rest frame of nucleation and that of the detector is exceedingly sharp.

  9. Molecular dynamics study of helium bubble pressure in titanium

    Institute of Scientific and Technical Information of China (English)

    Zhang Bao-Ling; Wang Jun; Hou Qing

    2011-01-01

    In this paper, the pressure state of the helium bubble in titanium is simulated by a molecular dynamics (MD) method. First, the possible helium/vacancy ratio is determined according to therelation between the bubble pressure and helium/vacancy ratio; then the dependences of the helium bubble pressure on the bubble radius at different temperatures are studied. It is shown that the product of the bubble pressure and the radius is approximately a constant, a result justifying the pressure-radius relation predicted by thermodynamics-based theory for gas bubble. Furthermore, a state equation of the helium bubble is established based on the MD calculations. Comparison between the results obtained by the state equation and corresponding experimental data shows that the state equation can describe reasonably the state of helium bubble and thus could be used for Monte Carlo simulations of the evolution of helium bubble in metals.

  10. Helium bubble kinetics during laser welding of helium-doped stainless steel

    International Nuclear Information System (INIS)

    Helium is generated within neutron-irradiated reactor components and entrapped in the stainless steel components. The repair of the components using conventional GTA welding practices is then exceedingly difficult, because of the creation of helium bubbles and weld cracking. In this research, the behavior of helium bubbles in austenitic stainless steel weldments was investigated using stainless steel helium ion-implanted and then welded using YAG Laser apparatus. Helium ion implanting of the sample was carried out using 8MeV implantation apparatus, the sample being doped 2.45χ1019/m2 at 6MeV and then doped 1χ1019/m2 at 5MeV. Helium bubbles are present at the bond region, heat-affected zone and weld metal. An increase of weld heat input causes the growth of helium bubbles and produce toe cracks and cracks along the dendrite cell boundary in the weld metal. The helium bubble phenomena can be simulated in the weld metal and in the heat-affected zone during repair welding using helium ion implanting technique. (author)

  11. Dimensionless analysis of bubble departure frequency in forced convective subcooled boiling flow

    International Nuclear Information System (INIS)

    Forced convective subcooled boiling flow experiments were conducted in a vertical upward annular channel. Water was used as the testing fluid, and the tests were performed at atmospheric pressure. A high-speed digital video camera was applied to capture the dynamics of the bubble nucleation process. Bubble departure frequencies were obtained from the video for a total of 58 test conditions. The non-dimensional analysis was performed on the current data as well as available data from literature. Existing models and correlations were compared with the experimental data of bubble waiting time, growth time, and departure frequency. The correlations developed for pool boiling flow do not work well for forced convective subcooled boiling flow, while the models proposed for subcooled boiling flow can not predict the bubble departure frequency in wide experimental ranges. Dimensionless bubble departure frequency is correlated with non-dimensional nucleate boiling heat flux. The new correlation agrees reasonably well with existing experimental data at lower wall superheat. (author)

  12. Constraining Quasar Parameters Through Bubble Detection in Redshifted 21-cm Maps

    CERN Document Server

    Majumdar, Suman; Bharadwaj, Somnath

    2011-01-01

    A growing bubble of ionized hydrogen (HII) around a very high redshift quasar will have many anisotropic features in its shape mainly due to finite light travel time (FLTT), neutral hydrogen density fluctuations in the IGM and clustering of stellar sources. Detection of such a bubble in redshifted 21-cm observations, will not only be a direct probe to the epoch of reionization but will also provide us insight about the quasars' luminosity and age. We simulate a growing HII bubble around a quasar at z ~ 8 in an IGM with mean neutral fraction x_HI = 0.5, using a semi-numerical formalism. A targeted matched filter bubble search on this simulated visibility data is performed with spherical and anisotropic filters, considering 1000 hrs of GMRT observation. We simulate our search at five different stage of growth of the target HII bubble. We find that, in almost all realizations of our simulations the search results over estimate the photon emission rate (N_phs) and the age (tau_Q) of the quasar, due to the effect ...

  13. Bubble spreading during the boiling crisis: modelling and experimenting in microgravity

    CERN Document Server

    Nikolayev, Vadim; Garrabos, Y; Lecoutre, C; Chatain, D

    2016-01-01

    Boiling is a very efficient way to transfer heat from a heater to the liquid carrier. We discuss the boiling crisis, a transition between two regimes of boiling: nucleate and film boiling. The boiling crisis results in a sharp decrease in the heat transfer rate, which can cause a major accident in industrial heat exchangers. In this communication, we present a physical model of the boiling crisis based on the vapor recoil effect. Under the action of the vapor recoil the gas bubbles begin to spread over the heater thus forming a germ for the vapor film. The vapor recoil force not only causes its spreading, it also creates a strong adhesion to the heater that prevents the bubble departure, thus favoring the further spreading. Near the liquid-gas critical point, the bubble growth is very slow and allows the kinetics of the bubble spreading to be observed. Since the surface tension is very small in this regime, only microgravity conditions can preserve a convex bubble shape. In the experiments both in the Mir spa...

  14. The thermodynamic and kinetic interactions of He interstitial clusters with bubbles in W

    Science.gov (United States)

    Perez, Danny; Sandoval, Luis; Uberuaga, Blas P.; Voter, Arthur F.

    2016-05-01

    Due to its enviable properties, tungsten is a leading candidate plasma facing material in nuclear fusion reactors. However, like many other metals, tungsten is known to be affected by the high doses of helium atoms incoming from the plasma. Indeed, the implanted interstitial helium atoms cluster together and, upon reaching a critical cluster size, convert into substitutional nanoscale He bubbles. These bubbles then grow by absorbing further interstitial clusters from the matrix. This process can lead to deleterious changes in microstructure, degradation of mechanical properties, and contamination of the plasma. In order to better understand the growth process, we use traditional and accelerated molecular dynamics simulations to investigate the interactions between interstitial He clusters and pre-existing bubbles. These interactions are characterized in terms of thermodynamics and kinetics. We show that the proximity of the bubble leads to an enhancement of the trap mutation rate and, consequently, to the nucleation of satellite bubbles in the neighborhood of existing ones. We also uncover a number of mechanisms that can lead to the subsequent annihilation of such satellite nanobubbles.

  15. Validation of Bubble Dynamics Equation for a Nano-scale Bubble via Molecular Dynamics Simulation

    Science.gov (United States)

    Tsuda, S.; Hyodo, H.; Watanabe, S.

    2015-12-01

    For a validation of the application of conventional bubble dynamics to a nano-scale bubble behaviour, we simulated a nano-scale bubble collapsing or vibration by Molecular Dynamics (MD) method and compared the result with the solution of Rayleigh-Plesset (RP) equation and that of Confined RP (CRP) equation, whose boundary condition was corrected to be consistent with that of MD simulation. As a result, a good coincidence was obtained between MD, RP, and CRP in the case of one-component fluid. In addition, also a good correspondence was obtained particularly in the comparison between MD and CRP in the case of two-component fluid containing non-condensable gas. The present results indicate that conventional bubble dynamics equation can be applied even to a nano-scale tiny bubble.

  16. Particle-bubble aggregate stability on static bubble generated by single nozzle on flotation process

    Science.gov (United States)

    Warjito, Harinaldi, Setyantono, Manus; Siregar, Sahala D.

    2016-06-01

    There are three sub-processes on flotation. These processes are intervening liquid film into critical thickness, rupture of liquid film forming three phase contact line, and expansion three phase contact line forming aggregate stability. Aggregate stability factor contribute to determine flotation efficiency. Aggregate stability has some important factors such as reagent and particle geometry. This research focussed on to understand effect of particle geometry to aggregate stability. Experimental setup consists of 9 x 9 x26 cm flotation column made of glass, bubble generator, particle feeding system, and high speed video camera. Bubble generator made from single nozzle with 0.3 mm diameter attached to programmable syringe pump. Particle feeding system made of pipette. Particle used in this research is taken from open pit Grasberg in Timika, Papua. Particle has sub-angular geometry and its size varies from 38 to 300 µm. Bubble-particle interaction are recorded using high speed video camera. Recordings from high speed video camera analyzed using image processing software. Experiment result shows that aggregate particle-bubble and induction time depends on particle size. Small particle (38-106 µm) has long induction time and able to rupture liquid film and also forming three phase contact line. Big particle (150-300 µm) has short induction time, so it unable to attach with bubble easily. This phenomenon is caused by apparent gravity work on particle-bubble interaction. Apparent gravity worked during particle sliding on bubble surface experience increase and reached its maximum magnitude at bubble equator. After particle passed bubble equator, apparent gravity force experience decrease. In conclusion particle size from 38-300 µm can form stable aggregate if particle attached with bubble in certain condition.

  17. Nonlinear Rayleigh-Taylor growth in convergine geometry

    International Nuclear Information System (INIS)

    The early nonlinear phase of Rayleigh-Taylor growth is typically described in terms of the classic Layzer model in which bubbles of light fluid rise into the heavy fluid at a constant rate determined by the bubble radius and the gravitational acceleration. However, this model is strictly valid only for planar interfaces and hence ignores any effects which might be introduced by the spherically converging interfaces of interest in inertial confinement fusion. Here a generalization of the Layzer nonlinear bubble rise rate is given for a self-similar spherically converging flow of the type studied by Kidder. A simple formula for the bubble amplitude is found showing that, while the bubble initially rises with a constant velocity similar to the Layzer result, during the late phase of the implosion, an acceleration of the bubble rise rate occurs. The bubble rise rate is verified by comparison with numerical hydrodynamics simulations

  18. Herds of methane chambers grazing bubbles

    Science.gov (United States)

    Grinham, Alistair; Dunbabin, Matthew

    2014-05-01

    Water to air methane emissions from freshwater reservoirs can be dominated by sediment bubbling (ebullitive) events. Previous work to quantify methane bubbling from a number of Australian sub-tropical reservoirs has shown that this can contribute as much as 95% of total emissions. These bubbling events are controlled by a variety of different factors including water depth, surface and internal waves, wind seiching, atmospheric pressure changes and water levels changes. Key to quantifying the magnitude of this emission pathway is estimating both the bubbling rate as well as the areal extent of bubbling. Both bubbling rate and areal extent are seldom constant and require persistent monitoring over extended time periods before true estimates can be generated. In this paper we present a novel system for persistent monitoring of both bubbling rate and areal extent using multiple robotic surface chambers and adaptive sampling (grazing) algorithms to automate the quantification process. Individual chambers are self-propelled and guided and communicate between each other without the need for supervised control. They can maintain station at a sampling site for a desired incubation period and continuously monitor, record and report fluxes during the incubation. To exploit the methane sensor detection capabilities, the chamber can be automatically lowered to decrease the head-space and increase concentration. The grazing algorithms assign a hierarchical order to chambers within a preselected zone. Chambers then converge on the individual recording the highest 15 minute bubbling rate. Individuals maintain a specified distance apart from each other during each sampling period before all individuals are then required to move to different locations based on a sampling algorithm (systematic or adaptive) exploiting prior measurements. This system has been field tested on a large-scale subtropical reservoir, Little Nerang Dam, and over monthly timescales. Using this technique

  19. Drop impact entrapment of bubble rings

    KAUST Repository

    Thoraval, M.-J.

    2013-04-29

    We use ultra-high-speed video imaging to look at the initial contact of a drop impacting on a liquid layer. We observe experimentally the vortex street and the bubble-ring entrapments predicted numerically, for high impact velocities, by Thoraval et al. (Phys. Rev. Lett., vol. 108, 2012, article 264506). These dynamics mainly occur within 50 -s after the first contact, requiring imaging at 1 million f.p.s. For a water drop impacting on a thin layer of water, the entrapment of isolated bubbles starts through azimuthal instability, which forms at low impact velocities, in the neck connecting the drop and pool. For Reynolds number Re above -12 000, up to 10 partial bubble rings have been observed at the base of the ejecta, starting when the contact is -20% of the drop size. More regular bubble rings are observed for a pool of ethanol or methanol. The video imaging shows rotation around some of these air cylinders, which can temporarily delay their breakup into micro-bubbles. The different refractive index in the pool liquid reveals the destabilization of the vortices and the formation of streamwise vortices and intricate vortex tangles. Fine-scale axisymmetry is thereby destroyed. We show also that the shape of the drop has a strong influence on these dynamics. 2013 Cambridge University Press.

  20. Detecting dark matter with scintillating bubble chambers

    Science.gov (United States)

    Zhang, Jianjie; Dahl, C. Eric; Jin, Miaotianzi; Baxter, Daniel

    2016-03-01

    Threshold based direct WIMP dark matter detectors such as the superheated bubble chambers developed by the PICO experiment have demonstrated excellent electron-recoil and alpha discrimination, excellent scalability, ease of change of target fluid, and low cost. However, the nuclear-recoil like backgrounds have been a limiting factor in their dark matter sensitivity. We present a new type of detector, the scintillating bubble chamber, which reads out the scintillation pulse of the scattering events as well as the pressure, temperature, acoustic traces, and bubble images as a conventional bubble chamber does. The event energy provides additional handle to discriminate against the nuclear-recoil like backgrounds. Liquid xenon is chosen as the target fluid in our prototyping detector for its high scintillation yield and suitable vapor pressure which simplifies detector complexity. The detector can be used as an R&D tool to study the backgrounds present in the current PICO bubble chambers or as a prototype for standalone dark matter detectors in the future. Supported by DOE Grant DE-SC0012161.

  1. Large-Scale Clustering in Bubble Models

    CERN Document Server

    Borgani, S

    1993-01-01

    We analyze the statistical properties of bubble models for the large-scale distribution of galaxies. To this aim, we realize static simulations, in which galaxies are mostly randomly arranged in the regions surrounding bubbles. As a first test, we realize simulations of the Lick map, by suitably projecting the three-dimensional simulations. In this way, we are able to safely compare the angular correlation function implied by a bubbly geometry to that of the APM sample. We find that several bubble models provide an adequate amount of large-scale correlation, which nicely fits that of APM galaxies. Further, we apply the statistics of the count-in-cell moments to the three-dimensional distribution and compare them with available observational data on variance, skewness and kurtosis. Based on our purely geometrical constructions, we find that a well defined hierarchical scaling of higher order moments up to scales $\\sim 70\\hm$. The overall emerging picture is that the bubbly geometry is well suited to reproduce ...

  2. Sonoluminescence: Why fiery bubbles have eternal life

    Science.gov (United States)

    Lohse, Detlef; Brenner, Michael; Hilgenfeldt, Sascha

    1996-11-01

    Sound driven gas bubbles in water can emit light pulses. This phenomenon is called sonoluminescence (SL). Two different phases of single bubble SL have been proposed: diffusively stable and diffusively unstable SL. Phase diagrams are presented in the gas concentration vs forcing pressure state space and also in the ambient radius vs forcing pressure state space. These phase diagrams are based on the thresholds for energy focusing in the bubble and on those for (i) shape instabilities and (ii) diffusive instabilities. Stable SL only occurs in a tiny parameter window of large forcing pressure amplitude Pa ~ 1.2 - 1.5atm and low gas concentration of less than 0.4% of saturation. The results quantitatively agree with experimental results of Putterman's UCLA group on argon, but not on air. However, air bubbles and other gas mixtures can also successfully be treated in this approach if in addition (iii) chemical instabilities are considered. The essential feature is the removal of almost all nitrogen and oxygen from the bubble through reaction to soluble compounds (i.e. NOx or NH_3).

  3. On the dynamics of moving single bubble sonoluminescence

    Energy Technology Data Exchange (ETDEWEB)

    Galavani, Zeinab, E-mail: z_galavani@sina.kntu.ac.i [Department of Physics, K. N. Toosi University of Technology, P.O. Box: 16315-1618, Tehran (Iran, Islamic Republic of); Rezaei-Nasirabad, Reza, E-mail: rezanuc_83@ph.iut.ac.i [Department of Physics, Isfahan University of Technology, P.O. Box: 84154, Isfahan (Iran, Islamic Republic of); Bhattarai, Suresh [Department of Physics, St. Xavier' s College, P.O. Box: 7437, Kathmandu (Nepal)

    2010-10-04

    It is well known that the primary Bjerknes force is the origin of the trapping of sonoluminescing bubble in the sound field in liquid. In the present Letter, the quantitative investigation of the behavior of hydrodynamic force on the moving sonoluminescing (SL) bubble introduces the new role of stabilizing the trajectory motion of the bubble for primary Bjerknes force. Using a complete force balanced radial-translational dynamics, it is analytically discussed that by increasing the bubble distance from the antinode of the sound field the increase of the magnitude of inward Bjerknes force, controls the size of the domain of the bubble trajectory. At this time the wake produced by the rapid variation of the bubble's relative translational velocity to the surrounding liquid, changes the bubble direction of motion through the effect of history force. The required momentum for accelerating the SL bubble around the central antinode is produced by the added mass force at the bubble collapse. It is revealed in a re-examination of the coupled radial-translational dynamics for a trapping bubble that because of the bubble lower translational acceleration caused due to the lower added mass force and the bubble attraction towards the acoustic antinodes in presence of inward Bjerknes force, the small bubble will be trapped at the antinode of the sound field.

  4. Modelling of boiling bubbly flows using a polydisperse approach

    International Nuclear Information System (INIS)

    The objective of this work was to improve the modelling of boiling bubbly flows.We focused on the modelling of the polydisperse aspect of a bubble population, i.e. the fact that bubbles have different sizes and different velocities. The multi-size aspect of a bubble population can originate from various mechanisms. For the bubbly flows we are interested in, bubble coalescence, bubble break-up, phase change kinematics and/or gas compressibility inside the bubbles can be mentioned. Since, bubble velocity depends on bubble size, the bubble size spectrum also leads to a bubble velocity spectrum. An averaged model especially dedicated to dispersed flows is introduced in this thesis. Closure of averaged interphase transfer terms are written in a polydisperse framework, i.e. using a distribution function of the bubble sizes and velocities. A quadratic law and a cubic law are here proposed for the modelling of the size distribution function, whose evolution in space and time is then obtained with the use of the moment method. Our averaged model has been implemented in the NEPTUNE-CFD computation code in order to simulate the DEBORA experiment. The ability of our model to deal with sub-cooled boiling flows has therefore been evaluated. (author)

  5. Topological vacuum bubbles by anyon braiding

    Science.gov (United States)

    Han, Cheolhee; Park, Jinhong; Gefen, Yuval; Sim, H.-S.

    2016-03-01

    According to a basic rule of fermionic and bosonic many-body physics, known as the linked cluster theorem, physical observables are not affected by vacuum bubbles, which represent virtual particles created from vacuum and self-annihilating without interacting with real particles. Here we show that this conventional knowledge must be revised for anyons, quasiparticles that obey fractional exchange statistics intermediate between fermions and bosons. We find that a certain class of vacuum bubbles of Abelian anyons does affect physical observables. They represent virtually excited anyons that wind around real anyonic excitations. These topological bubbles result in a temperature-dependent phase shift of Fabry-Perot interference patterns in the fractional quantum Hall regime accessible in current experiments, thus providing a tool for direct and unambiguous observation of elusive fractional statistics.

  6. Bubbles of Nothing and Supersymmetric Compactifications

    CERN Document Server

    Blanco-Pillado, Jose J; Sousa, Kepa; Urrestilla, Jon

    2016-01-01

    We investigate the non-perturbative stability of supersymmetric compactifications with respect to decay via a bubble of nothing. We show examples where this kind of instability is not prohibited by the spin structure, i.e., periodicity of fermions about the extra dimension. However, such "topologically unobstructed" cases do exhibit an extra-dimensional analog of the well-known Coleman-De Luccia suppression mechanism, which prohibits the decay of supersymmetric vacua. We demonstrate this explicitly in a four dimensional Abelian-Higgs toy model coupled to supergravity. The compactification of this model to $M_3 \\times S_1$ presents the possibility of vacua with different windings for the scalar field. Away from the supersymmetric limit, these states decay by the formation of a bubble of nothing, dressed with an Abelian-Higgs vortex. We show how, as one approaches the supersymmetric limit, the circumference of the topologically unobstructed bubble becomes infinite, thereby preventing the realization of this dec...

  7. Refraction by a spherical nematic bubble

    Science.gov (United States)

    Sherman, Richard David

    1989-08-01

    A formalism is developed to study refraction by a spherical nematic bubble. It is applicable to bubbles that are larger than light wavelengths, but smaller than the dimensions for excitation of director-fluctuation-induced scattering. The technique yields a nonlinear differential equation and an associated integral which govern the trajectory of a ray inside a nematic region for an arbitrary director configuration. Explicit solutions are provided for five simple interior arrangements-isotropic, onion skin, radial star, horizontal (bottle brush), and vertical. It is then demonstrated that for extraordinary-ordinary refractive-index difference small compared to either, interfacial refraction at the bubble surface is the dominant contribution; deviations from a rectilinear path are small. When ranked in terms of decreasing scattering effectiveness, the sequence is horizontal, onion, isotropic, radial, and vertical if the light is linearly polarized and coupling optimally to the extraordinary index component; for unpolarized incoherent light the order becomes isotropic, horizontal, onion, radial, and vertical.

  8. Pattern Generation by Bubble Packing Method

    Directory of Open Access Journals (Sweden)

    Goel V.K.

    2013-06-01

    Full Text Available This paper presents a new computational method forornamental Pattern design. The work is a concerted effort ofevaluation of various methods and the comparatively betterprocess is used for designing keeping in mind the accuracyrequirement for such Indian traditional ethnic designs. The firststep in the process to apply the CAD tools to design the patterns.Small semantics (profile are made using the mathematicalmodelling to make different pattern. Geometric constraints suchas scaling, rotation, transformation etc. are applied to make andmodify the profiles. To create patterns, obtains node locationsthrough a physically based particle simulation, which we call'bubble packing. Bubbles are closely packed on the corners,edges and on the surface domain, and nodes are placed at thecenters of the bubbles. Experimental results show that ourmethod can create high quality ornamental patterns. Thefabrication of the ornaments is on rapid prototype machine.

  9. ON THE ANALYSIS OF BUBBLE CHAMBER TRACKS

    International Nuclear Information System (INIS)

    Since its invention by Glaser in 1953, the bubble chamber has become a most valuable tool in high-energy physics. It combines a number of advantages of various older methods of particle detection: it offers high spatial resolution, rapid accumulation of data, some time resolution, and some choice of the nucleus whose interaction one wants to study (bubble chambers have been made to operate with a large number of different liquids, including H2, D2, He, Xe, and several hydrocarbons). In order to exploit the advantages of spatial resolution and rapid data accumulation, high-speed high-precision analysis procedures must be developed. In this article they discuss some of the problems posed by such analysis. The discussion is based largely on experience gained in performing hydrogen bubble chamber experiments with the University of California's Bevatron (6-Bev proton synchrotron)

  10. Bubbles, shocks and elementary technical trading strategies

    Science.gov (United States)

    Fry, John

    2014-01-01

    In this paper we provide a unifying framework for a set of seemingly disparate models for bubbles, shocks and elementary technical trading strategies in financial markets. Markets operate by balancing intrinsic levels of risk and return. This seemingly simple observation is commonly over-looked by academics and practitioners alike. Our model shares its origins in statistical physics with others. However, under our approach, changes in market regime can be explicitly shown to represent a phase transition from random to deterministic behaviour in prices. This structure leads to an improved physical and econometric model. We develop models for bubbles, shocks and elementary technical trading strategies. The list of empirical applications is both interesting and topical and includes real-estate bubbles and the on-going Eurozone crisis. We close by comparing the results of our model with purely qualitative findings from the finance literature.

  11. One Bubble to Rule Them All

    CERN Document Server

    Hartle, James

    2016-01-01

    We apply the principles of quantum mechanics and quantum cosmology to predict probabilities for our local observations of a universe undergoing false vacuum eternal inflation. At a sufficiently fine-grained level, histories of the universe describe a mosaic of bubble universes separated by inflationary regions. We show that predictions for local observations can be obtained directly from sets of much coarser grained histories which only follow a single bubble. These coarse-grained histories contain neither information about our unobservable location nor about the unobservable large-scale structure outside our own bubble. Applied to a landscape of false vacua in the no-boundary state we predict our local universe emerged from the dominant decay channel of the lowest energy false vacuum. We compare and contrast this framework for prediction based on quantum cosmology with traditional approaches to the measure problem in cosmology.

  12. Photon Bubble Turbulence in Cold Atomic Gases

    CERN Document Server

    Rodrigues, João D; Ferreira, António V; Terças, Hugo; Kaiser, Robin; Mendonça, José T

    2016-01-01

    Turbulent radiation flow is ubiquitous in many physical systems where light-matter interaction becomes relevant. Photon bubbling, in particular, has been identified as the main source of turbulent radiation transport in many astrophysical objects, such as stars and accretion disks. This mechanism takes place when radiation trapping in optically dense media becomes unstable, leading to the energy dissipation from the larger to the smaller bubbles. Here, we report on the observation of photon bubble turbulence in cold atomic gases in the presence of multiple scattering of light. The instability is theoretically explained by a fluid description for the atom density coupled to a diffusive transport equation for the photons, which is known to be accurate in the multiple scattering regime investigated here. We determine the power spectrum of the atom density fluctuations, which displays an unusual $\\sim k^{-4}$ scaling, and entails a complex underlying turbulent dynamics resulting from the formation of dynamical bu...

  13. Bubbles, sparks, and the postwar laboratory

    International Nuclear Information System (INIS)

    The development and use of bubble chambers and spark chambers in the 1950s form the main thrust of this article, the bubble chamber as an example of ''image-producing'' instruments and the spark chamber as a ''logic'' device. Work on a cloud chamber by Glaser led to the development of the bubble chamber detector using liquid hydrogen, which was later linked to a computer for accurate automatic track analysis. It made possible demonstrations of the existence of a particle or interaction. Spark chambers were easier to build and so soon became common, various types being developed across the world. The development of spark chambers originated in the need for timing devices for the Manhattan Project, but work on their design occurred in a number of units worldwide. (UK)

  14. Trapping of helium in nano-bubbles in euxenite: Positive identification and implications

    Science.gov (United States)

    Seydoux-Guillaume, Anne-Magali; David, Marie-Laure; Alix, Kevin; Datas, Lucien; Bingen, Bernard

    2016-08-01

    The (Y,REE,U,Th)-(Nb,Ta,Ti) oxides, like euxenite, fergusonite, pyrochlore, zirconolite, are known to contain nanometric spherical cavities or bubbles, interpreted to contain radiogenic helium. In-situ analyses by Scanning Transmission Electron Microscopy (STEM) coupled with Electron Energy Loss Spectroscopy (EELS) inside nano-bubbles from an euxenite crystal, sampled in its host c. 920 Ma old pegmatite in Norway, deliver, for the first time, a positive identification of helium and an estimation of helium pressure in such bubbles. The chemically unaltered euxenite crystal proves amorphous and homogeneously speckled with bubbles ranging from 5 to 68 nm in diameter, around a log-normal distribution centered at 19 nm. The euxenite contains 9.87 wt% UO2 and 3.15 wt% ThO2. It accumulated a theoretical alpha-decay dose of 3.46 ×1020 α / g (i.e. 170 He/nm3), at a dose rate of 11 926 α / g / s. This corresponds to production of 0.23 wt% He. The density of helium inside the bubbles, estimated from EELS data, ranges from 2 to 45 He/nm3, leading to a pressure of 8 to 500 MPa. The proportion of produced helium trapped in bubbles is about 10%. Helium bubbles clearly influence helium diffusion. They may contribute to the swelling of euxenite during amorphization and to the fracturing of the host rock. Our results suggest that dose, dose rate and structural state seem to be important parameters for the nucleation, growth and coalescence of helium bubbles but also demonstrate the crucial need of experimental studies to be able to develop a predictive model of the long term behavior of materials in response to helium irradiation. Furthermore, chemical alteration of euxenite, here materialized by fluid driven dissolution-precipitation towards silica bearing euxenite, removes the bubbles and mobilizes helium into the rock via cracks and grain boundaries. It is then suggested that helium-rich fluid released from such U-Th rich sources may percolate into surrounding rock units

  15. Large-scale Generation of Patterned Bubble Arrays on Printed Bi-functional Boiling Surfaces

    Science.gov (United States)

    Choi, Chang-Ho; David, Michele; Gao, Zhongwei; Chang, Alvin; Allen, Marshall; Wang, Hailei; Chang, Chih-Hung

    2016-04-01

    Bubble nucleation control, growth and departure dynamics is important in understanding boiling phenomena and enhancing nucleate boiling heat transfer performance. We report a novel bi-functional heterogeneous surface structure that is capable of tuning bubble nucleation, growth and departure dynamics. For the fabrication of the surface, hydrophobic polymer dot arrays are first printed on a substrate, followed by hydrophilic ZnO nanostructure deposition via microreactor-assisted nanomaterial deposition (MAND) processing. Wettability contrast between the hydrophobic polymer dot arrays and aqueous ZnO solution allows for the fabrication of heterogeneous surfaces with distinct wettability regions. Heterogeneous surfaces with various configurations were fabricated and their bubble dynamics were examined at elevated heat flux, revealing various nucleate boiling phenomena. In particular, aligned and patterned bubbles with a tunable departure frequency and diameter were demonstrated in a boiling experiment for the first time. Taking advantage of our fabrication method, a 6 inch wafer size heterogeneous surface was prepared. Pool boiling experiments were also performed to demonstrate a heat flux enhancement up to 3X at the same surface superheat using bi-functional surfaces, compared to a bare stainless steel surface.

  16. CRISIS FOCUS: Bubbles Pose The Biggest Threat

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The shift of China’s monetary policy stance from "moderately loose" to "prudent" next year indicates curbing inflation and asset bubbles have become the Central Government’s top priority. But is China’s bubble problem short-term or long-term? Is it only monetary or related to economic structure? Is it the cause of China’s economic imbalance or the result? And what kind of deep-rooted problems in the macro economy does it reflect? All these questions call for deep thought, said Zhang Monan, a researcher with the State Information Center, in a recent article for The Beijing News. Edited excerpt follows:

  17. Bubble chamber: Omega production and decay

    CERN Multimedia

    1973-01-01

    This image is of real particle tracks taken from the CERN 2 m liquid hydrogen bubble chamber and shows the production and decay of a negative omega particle. A negative kaon enters the chamber which decays into many particles, including a negative omega that travels a short distance before decaying into more particles. The invention of bubble chambers in 1952 revolutionized the field of particle physics, allowing real tracks left by particles to be seen and photographed by expanding liquid that had been heated to boiling point.

  18. Bubbles in live-stranded dolphins

    OpenAIRE

    Dennison, S; Moore, M J; Fahlman, A.; Moore, K.; Sharp, S.; Harry, C. T.; Hoppe, J.; NIEMEYER, M.; Lentell, B.; Wells, R. S.

    2011-01-01

    Bubbles in supersaturated tissues and blood occur in beaked whales stranded near sonar exercises, and post-mortem in dolphins bycaught at depth and then hauled to the surface. To evaluate live dolphins for bubbles, liver, kidneys, eyes and blubber–muscle interface of live-stranded and capture-release dolphins were scanned with B-mode ultrasound. Gas was identified in kidneys of 21 of 22 live-stranded dolphins and in the hepatic portal vasculature of 2 of 22. Nine then died or were euthanized ...

  19. Bubble visualization in a simulated hydraulic jump

    CERN Document Server

    Witt, Adam; Shen, Lian

    2013-01-01

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

  20. Bubbles in sheared two-dimensional foams

    OpenAIRE

    Quilliet, C.; Idiart, M. A. P.; Dollet, B.; Berthier, L.; Yekini, A.

    2005-01-01

    Oscillatory shear on two-dimensional monodisperse liquid foams was performed. We show that the effect of the oscillatory shear is to cause the migration of bubbles which size is greater than that of a typical bubble of the foam. These so-called flaws move towards the periphery of the foam in a non random motion, thus realizing size segregation in a system which is by construction gravity insensitive. We also show that elongated cavities in the foam could be relaxed towards a more isotropic fo...

  1. On the maximum drawdown during speculative bubbles

    CERN Document Server

    Rotundo, G; Navarra, Mauro; Rotundo, Giulia

    2006-01-01

    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.

  2. Long-lived oscillons from asymmetric bubbles

    CERN Document Server

    Adib, A B; Almeida, C A S; Adib, Artur B.; Gleiser, Marcelo; Almeida, Carlos A. S.

    2002-01-01

    The possibility that extremely long-lived, time-dependent, and localized field configurations (``oscillons'') arise during the collapse of asymmetrical bubbles in 2+1 dimensional \\phi^4 models is investigated. It is found that oscillons can develop from a large spectrum of elliptically deformed bubbles. Moreover, it is found that such oscillons are: a) circularly symmetric; and b) stable against small arbitrary radial and angular perturbations. They may thus play an important role in the study of time-dependent nonperturbative configurations in field theory, with applications ranging from nonequilibrium statistical physics to early universe cosmology.

  3. Innovative bubble method and means of control

    Directory of Open Access Journals (Sweden)

    Maksim Lynin

    2014-04-01

    Full Text Available A new principle of measuring the viscosity of the fluid based on the control parameters of motion of a gas bubble in a viscous medium. A mathematical model and a measurement tool to monitor the dynamics of changes in the viscosity-temperature parameter bubble environment. An experimental study of the changes in the rheological properties of the process of development of lactic acid bacteria Lactobacillus plantarum on a nutrient medium. The experimental dependence of the viscosity of the medium on the concentration of the aqueous solution of sugar.

  4. A large bubble around the Crab Nebula

    International Nuclear Information System (INIS)

    IRAS and 21 cm observations of the interstellar medium around the Crab nebula show evidence of a large bubble surrounded by a partial shell. If located at the canonical 2 kpc distance of the Crab pulsar, the shell is estimated to have a radius of about 90 pc and to contain about 50,000 solar masses of swept-up gas. The way in which interior conditions of this bubble can have important implications for observations of the Crab are described, and the fashion in which presupernova evolution of the pulsar progenitor has affected its local environment is described. 22 refs

  5. The condensation of sodium vapour bubbles

    International Nuclear Information System (INIS)

    This is a preliminary analytic study of the violent collapse of a vapour bubble by condensation in cold liquid. A calculation method is described and is applied to the condensation of sodium vapour bubbles such as might be formed in an overheating accident in a fast reactor. The method is not satisfactory, and a more thorough study of the problem is needed, but these preliminary results suggest that while the violent collapse is unlikely to do much mechanical damage, it produces a considerable amount of acoustic energy. (author)

  6. Bubble Content in Air/Hydro System--Part 2:Factors Influencing Bubble Content

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A new method for measuring bubble content of two-phase fluids in complex systems such as air/hydro systems has been designed and verified. Some new results of the study on the factors influencing bubble content using this new method are given in this paper, including the results of the experiments in the SKIP-valve system and long-tube system. Results indicate that the operating time, opening of the control-valve, air supply pressure, mass of the load, speed ratio, and the length of the tube all affect bubble content.

  7. Free Surface Lattice Boltzmann with Enhanced Bubble Model

    CERN Document Server

    Anderl, Daniela; Rauh, Cornelia; Rüde, Ulrich; Delgado, Antonio

    2016-01-01

    This paper presents an enhancement to the free surface lattice Boltzmann method (FSLBM) for the simulation of bubbly flows including rupture and breakup of bubbles. The FSLBM uses a volume of fluid approach to reduce the problem of a liquid-gas two-phase flow to a single-phase free surface simulation. In bubbly flows compression effects leading to an increase or decrease of pressure in the suspended bubbles cannot be neglected. Therefore, the free surface simulation is augmented by a bubble model that supplies the missing information by tracking the topological changes of the free surface in the flow. The new model presented here is capable of handling the effects of bubble breakup and coalesce without causing a significant computational overhead. Thus, the enhanced bubble model extends the applicability of the FSLBM to a new range of practically relevant problems, like bubble formation and development in chemical reactors or foaming processes.

  8. Bubble of Real Estate Does Not Appear in Beijing

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    @@ The report newly issued by Citigroup enables the people in Beijing to feel consoling that Beijing does not appear bubble in real estate. But the bubble of real estate has appeared only in Shanghai, Tianjin,Shenyang and Ningbo.

  9. On the (im)possibility of warp bubbles

    OpenAIRE

    Broeck, Chris Van Den

    1999-01-01

    Various objections against Alcubierre's warp drive geometry are reviewed. Superluminal warp bubbles seem an unlikey possibility within the framework of general relativity and quantum field theory, although subluminal bubbles may still be possible.

  10. Introduction to the Workshop "30 years of bubble chamber physics"

    OpenAIRE

    Giorgio GiacomelliUniversity of Bologna and INFN, Bologna, Italy

    2014-01-01

    After some recollections of the early bubble chamber times, a brief overview of the golden age of the field is made, including its legacy and the use of bubble chamber events for the popularization of science.

  11. Bubble Dynamics in a Two-Phase Medium

    CERN Document Server

    Jayaprakash, Arvind; Chahine, Georges

    2010-01-01

    The spherical dynamics of a bubble in a compressible liquid has been studied extensively since the early work of Gilmore. Numerical codes to study the behavior, including when large non-spherical deformations are involved, have since been developed and have been shown to be accurate. The situation is however different and common knowledge less advanced when the compressibility of the medium surrounding the bubble is provided mainly by the presence of a bubbly mixture. In one of the present works being carried out at DYNAFLOW, INC., the dynamics of a primary relatively large bubble in a water mixture including very fine bubbles is being investigated experimentally and the results are being provided to several parallel on-going analytical and numerical approaches. The main/primary bubble is produced by an underwater spark discharge from two concentric electrodes placed in the bubbly medium, which is generated using electrolysis. A grid of thin perpendicular wires is used to generate bubble distributions of vary...

  12. Do unbounded bubbles ultimately become fenced inside a black hole?

    International Nuclear Information System (INIS)

    We examine the dynamical behavior of recently introduced bubbles in asymptotically flat, five-dimensional spacetimes. Using numerical methods, we find that even bubbles that initially start expanding eventually collapse to a Schwarzschild-Tangherlini black hole

  13. Effect of Water Vapour to Temperature Inside Sonoluminescing Bubble

    Institute of Scientific and Technical Information of China (English)

    安宇; 谢崇国; 应崇福

    2003-01-01

    Using the model based on the homo-pressure approximation, we explain why the maximum temperature is sensitive to the ambient temperature in the single bubble sonoluminescence. The numerical simulation shows that the maximum temperature inside a sonoluminescing bubble depends on how much water vapour evaporates or coagulates at the bubble wall during the bubble shrinking to its minimum size. While the amount of water vapour inside the bubble at the initial and the final state of the compression depends on the saturated water vapour pressure which is sensitive to the ambient temperature. The lower the saturated vapour pressure is, the higher the maximum temperature is. This may lead to more general conclusion that those liquids with lower saturated vapour pressure are more favourable for the single bubble sonoluminescence. We also compare those bubbles with different noble gases, the result shows that the maximum temperatures in the different gas bubbles are almost the same for those with the same ambient temperature.

  14. Growth Laws and Self-Similar Growth Regimes of Coarsening Two-Dimensional Foams: Transition from Dry to Wet Limits

    Science.gov (United States)

    Fortuna, Ismael; Thomas, Gilberto L.; de Almeida, Rita M. C.; Graner, François

    2012-06-01

    We study the topology and geometry of two-dimensional coarsening foam with an arbitrary liquid fraction. To interpolate between the dry limit described by von Neumann’s law and the wet limit described by Marqusee’s equation, the relevant bubble characteristics are the Plateau border radius and a new variable: the effective number of sides. We propose an equation for the individual bubble growth rate as the weighted sum of the growth through bubble-bubble interfaces and through bubble-Plateau border interfaces. The resulting prediction is successfully tested, without an adjustable parameter, using extensive bidimensional Potts model simulations. The simulations also show that a self-similar growth regime is observed at any liquid fraction, and they also determine how the average size growth exponent, side number distribution, and relative size distribution interpolate between the extreme limits. Applications include concentrated emulsions, grains in polycrystals, and other domains with coarsening that is driven by curvature.

  15. Mass transport by buoyant bubbles in galaxy clusters

    Science.gov (United States)

    Pope, Edward C. D.; Babul, Arif; Pavlovski, Georgi; Bower, Richard G.; Dotter, Aaron

    2010-08-01

    We investigate the effect of three important processes by which active galactic nuclei (AGN)-blown bubbles transport material: drift, wake transport and entrainment. The first of these, drift, occurs because a buoyant bubble pushes aside the adjacent material, giving rise to a net upward displacement of the fluid behind the bubble. For a spherical bubble, the mass of upwardly displaced material is roughly equal to half the mass displaced by the bubble and should be ~ 107-9 Msolar depending on the local intracluster medium (ICM) and bubble parameters. We show that in classical cool-core clusters, the upward displacement by drift may be a key process in explaining the presence of filaments behind bubbles. A bubble also carries a parcel of material in a region at its rear, known as the wake. The mass of the wake is comparable to the drift mass and increases the average density of the bubble, trapping it closer to the cluster centre and reducing the amount of heating it can do during its ascent. Moreover, material dropping out of the wake will also contribute to the trailing filaments. Mass transport by the bubble wake can effectively prevent the buildup of cool material in the central galaxy, even if AGN heating does not balance ICM cooling. Finally, we consider entrainment, the process by which ambient material is incorporated into the bubble. Studies of observed bubbles show that they subtend an opening angle much larger than predicted by simple adiabatic expansion. We show that bubbles that entrain ambient material as they rise will expand faster than the adiabatic prediction; however, the entrainment rate required to explain the observed opening angle is large enough that the density contrast between the bubble and its surroundings would disappear rapidly. We therefore conclude that entrainment is unlikely to be a dominant mass transport process. Additionally, this also suggests that the bubble surface is much more stable against instabilities that promote

  16. Closure relations for CFD simulation of bubble columns

    OpenAIRE

    Ziegenhein, Thomas; Lucas, Dirk; Rzehak, Roland; Krepper, Eckhard

    2014-01-01

    This paper describes the modelling of bubbly flow in a bubble column considering non-drag forces, polydispersity and bubble induced turbulence using the Eulerian two-fluid approach. The set of used closure models describing the momentum exchange between the phases was chosen on basis of broad experiences in modelling bubbly flows at the Helmholtz-Zentrum Dresden-Rossendorf. Polydispersity is modeled using the inhomogeneous multiple size group (iMUSIG) model, which was developed...

  17. Boundary curvature effects on gas bubble oscillations in underwater explosion

    OpenAIRE

    MATSUMOTO, KAZUHIRO

    1996-01-01

    The oscillation of a gas bubble produced as a result of underwater explosion could cause the severe whipping damage on nearby marine vehicle. The effects of rigid boundary curvatures to explosive gas bubble oscillation behavior in underwater were investigated. The analyses were conducted using a multimaterial Lagrangian-Eulerian finite element code, MSC/DYTRAN. The incident shock wave pressure, bubble pulse pressure, gas bubble radius and period were calculated for the case of detonation of a...

  18. The interaction between multiple bubbles and the free surface

    Institute of Scientific and Technical Information of China (English)

    Zhang A-Man; Yao Xiong-Liang

    2008-01-01

    The flow is assumed to be potential, and a boundary integral method is used to solve the Laplace equation for the velocity potential to investigate the shape and the position of the bubble. A 3D code to study the bubble dynamics is developed, and the calculation results agree well with the experimental data. Numerical analyses are carried out for the interaction between multiple bubbles near the free surface including in-phase and out-of-phase bubbles. The calculation result shows that the bubble period increases with the decrease of the distance between bubble centres because of the depression effect between multiple bubbles. The depression has no relationship with the free surface and it is more apparent for out-of-phase bubbles. There are great differences in dynamic behaviour between the in-phase bubbles and the out-of-phase bubbles due to the depression effect. Furthermore, the interaction among eight bubbles is simulated with a three-dimensional model, and the evolving process and the relevant physical phenomena are presented. These phenomena can give a reference to the future work on the power of bubbles induced by multiple charges exploding simultaneously or continuously.

  19. Cavitation and bubble collapse in hot asymmetric nuclear matter

    CERN Document Server

    Kolomietz, V M

    2004-01-01

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

  20. On the formation of narrow bubble tracks by laser beam in argon, nitrogen and hydrogen bubble chambers

    International Nuclear Information System (INIS)

    Long bubble tracks, < 1 mm in diameter, have been produced in liquid argon and nitrogen with a nitrogen laser beam (lambda = 337 mm), offering subnanosecond pulses with small beam divergence. Bubble formation was observed over a wide range of operating conditions, including those for ordinary bubble chamber operation, with a laser pulse of 10 μJ. Typical bubble densities obtained were 4-8 bubbles/cm, with maximum densities of 20 bubbles/cm. In liquid hydrogen, tracks of 3 m visible length were observed with track diameters from 1.5 to 6 mm and bubble densities from 2 to 25 bubbles/cm. Results and applications will be discussed. (orig.)

  1. Dose dependence of helium bubble formation in nano-engineered SiC at 700 °C

    Science.gov (United States)

    Chen, C.-H.; Zhang, Y.; Wang, Y.; Crespillo, M. L.; Fontana, C. L.; Graham, J. T.; Duscher, G.; Shannon, S. C.; Weber, W. J.

    2016-04-01

    Knowledge of radiation-induced helium bubble nucleation and growth in SiC is essential for applications in fusion and fission environments. Here we report the evolution of microstructure in nano-engineered (NE) 3C SiC, pre-implanted with helium, under heavy ion irradiation at 700 °C up to doses of 30 displacements per atom (dpa). Elastic recoil detection analysis confirms that the as-implanted helium depth profile does not change under irradiation to 30 dpa at 700 °C. While the helium bubble size distribution becomes narrower with increasing dose, the average size of bubbles remains unchanged and the density of bubbles increases somewhat with dose. These results are consistent with a long helium bubble incubation process under continued irradiation at 700 °C up to 30 dpa, similar to that reported under dual and triple beam irradiation at much higher temperatures. The formation of bubbles at this low temperature is enhanced by the nano-layered stacking fault structure in the NE SiC, which enhances point defect mobility parallel to the stacking faults. This stacking fault structure is stable at 700 °C up to 30 dpa and suppresses the formation of dislocation loops normally observed under these irradiation conditions.

  2. Direct Measurement of the Bubble Nucleation Energy Threshold in a CF3I Bubble Chamber

    CERN Document Server

    Behnke, E; Brice, S J; Broemmelsiek, D; Collar, J I; Cooper, P S; Crisler, M; Dahl, C E; Fustin, D; Hall, J; Harnish, C; Levine, I; Lippincott, W H; Moan, T; Nania, T; Neilson, R; Ramberg, E; Robinson, A E; Sonnenschein, A; Vázquez-Jáuregui, E; Rivera, R A; Uplegger, L

    2013-01-01

    We have directly measured the energy threshold and efficiency for bubble nucleation from iodine recoils in a CF3I bubble chamber in the energy range of interest for a dark matter search. These interactions cannot be probed by standard neutron calibration methods, so we develop a new technique by observing the elastic scattering of 12 GeV/c negative pions. The pions are tracked with a silicon pixel telescope and the reconstructed scattering angle provides a measure of the nuclear recoil kinetic energy. The bubble chamber was operated with a nominal threshold of (13.6+-0.6) keV. Interpretation of the results depends on the response to fluorine and carbon recoils, but in general we find agreement with the predictions of the classical bubble nucleation theory. This measurement confirms the applicability of CF3I as a target for spin-independent dark matter interactions and represents a novel technique for calibration of superheated fluid detectors.

  3. BUBBLE - an urban boundary layer meteorology project

    DEFF Research Database (Denmark)

    Rotach, M.W.; Vogt, R.; Bernhofer, C.;

    2005-01-01

    The Basel urban Boundary Layer Experiment (BUBBLE) was a year-long experimental effort to investigate in detail the boundary layer structure in the City of Basel, Switzerland. At several sites over different surface types (urban, sub-urban and rural reference) towers up to at least twice the main...

  4. Making continuous bubble type polyethylene foam incombustible

    International Nuclear Information System (INIS)

    Since continuous bubble type plastic foam has excellent compression characteristics and sound absorption characteristics, it has been widely used as cushion material, sealing material, sound insulating material and so on. However, the most part of plastic foam is taken by air, therefore at the time of fires, it becomes a very dangerous material. At present, the material used mostly as the seat cushions for airliners, railroad coaches, automobiles and others is polyurethane foam, but since it contains C-N couples in its molecules, it is feared to generate cyanic gas according to the condition of combustion. As the plastic foam that does not generate harmful gas at the time of fires, there is continuous bubble type polyethylene which is excellent in its weathering property and chemical resistance. A reactive, phosphorus-containing oligomer has large molecular weight and two or more double couplings in a molecule, therefore, it does not enter the inside of polyethylene, and polymerizes and crosslinks on the surfaces of bubble walls in the foam, accordingly it is expected that the apparent graft polymerization is carried out, and it is very effective for making polyethylene foam incombustible. The method of making graft foam, the properties of graft foam and so on are reported. When the graft polymerization of this oligomer to continuous bubble type polyethylene foam was tried, highly incombustible polyethylene foam was obtained. (K.I.)

  5. Bubble bath burns: an unusual case.

    Science.gov (United States)

    Nizamoglu, Metin; Tan, Alethea; El-Muttardi, Naguib

    2016-01-01

    We present an unusual case of flash burn injury in an adolescent following accidental combination of foaming bath bubbles and tea light candle flame. There has not been any reported similar case described before. This serves as a learning point for public prevention and clinicians managing burn injuries. PMID:27583271

  6. On the Chinese House-Price Bubble

    Institute of Scientific and Technical Information of China (English)

    Christian Dreger; Yanqun Zhang

    2011-01-01

    @@ For many observers, the Chinese economy has been spurred by a bubble in the real-estate market, probably driven by the fiscal stimulus package and massive credit expansion.For example, the stock of loans increased by more than 50% since the end of 2008.

  7. Heat transport in bubbling turbulent convection

    NARCIS (Netherlands)

    Lakkaraju, R.; Stevens, R.J.A.M.; Oresta, P.; Verzicco, R.; Lohse, D.; Prosperetti, A.

    2013-01-01

    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 giv

  8. Oscillations of Bubbles in Surfactant Solutions

    Czech Academy of Sciences Publication Activity Database

    Vejražka, Jiří; Vobecká, Lucie; Tihon, Jaroslav

    - : -, 2012, s. 119 /og3.5/. ISBN N. [European Conference on Foams, Emulsions and Applications EUFOAM 2012 /9./. Lisbon (PT), 08.07.2012-11.07.2012] Institutional support: RVO:67985858 Keywords : bubbles * surfactant * concentration Subject RIV: CI - Industrial Chemistry, Chemical Engineering http://www.demat.ist.utl.pt/eufoam2012/book_of_abstracts.pdf.

  9. Progress of Neutron Bubble Detectors in CIAE

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Neutron bubble detector is the only personal neutron dosimeter which has adequate neutronsensitivity to meet the implications of the ICRP 60 recommendations for neutron dosimetry. It canmonitor the wide range of neutron energy, for example 100 eV to 10 MeV And it becomes a significanttool for neutron dose monitoring at the environment of nuclear energy.

  10. Opposite expansion system of fast bubble chambers

    International Nuclear Information System (INIS)

    Pneumatic opposite expansion system, operating on frequency up to 100 Hz and minimal cycle duration up to 3 ms, is created for accomplishingh expansion working cycle of a precision liquid-hydrogen fast bubble chamber. Fast-action hydraulic servo slide valves with electric control are used as command and control elements

  11. Argonne Bubble Experiment Thermal Model Development II

    Energy Technology Data Exchange (ETDEWEB)

    Buechler, Cynthia Eileen [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-07-01

    This report describes the continuation of the work reported in “Argonne Bubble Experiment Thermal Model Development”. The experiment was performed at Argonne National Laboratory (ANL) in 2014. A rastered 35 MeV electron beam deposited power in a solution of uranyl sulfate, generating heat and radiolytic gas bubbles. Irradiations were performed at three beam power levels, 6, 12 and 15 kW. Solution temperatures were measured by thermocouples, and gas bubble behavior was observed. This report will describe the Computational Fluid Dynamics (CFD) model that was developed to calculate the temperatures and gas volume fractions in the solution vessel during the irradiations. The previous report described an initial analysis performed on a geometry that had not been updated to reflect the as-built solution vessel. Here, the as-built geometry is used. Monte-Carlo N-Particle (MCNP) calculations were performed on the updated geometry, and these results were used to define the power deposition profile for the CFD analyses, which were performed using Fluent, Ver. 16.2. CFD analyses were performed for the 12 and 15 kW irradiations, and further improvements to the model were incorporated, including the consideration of power deposition in nearby vessel components, gas mixture composition, and bubble size distribution. The temperature results of the CFD calculations are compared to experimental measurements.

  12. Bubble oscillations and motion under vibration

    CERN Document Server

    O'Hern, Tim; Torczynski, John

    2011-01-01

    Bubbles under vibration can behave in unusual ways, e.g., moving downward against the force of buoyancy. While the bubble downward motion due to the Bjerknes force is well known at acoustic frequencies close to the bubble resonant frequency, these experiments demonstrate that these effects can be observed at relatively low frequencies as well. Experiments were performed in a thin, quasi-two-dimensional rectangular acrylic box partially filled with 20-cSt PDMS silicone oil with overlying ambient air. The apparatus was subjected to sinusoidal axial vibration that produced breakup of the gas-liquid free surface, producing liquid jets into the air, droplets pinching off from these jets, gas cavities in the liquid from impacts of these droplets, and bubble transport below the interface. Vibration conditions for the attached videos are 280 Hz frequency, 15 g acceleration, and 94 micron peak-to-peak displacement. Behaviors shown in the videos include the following. 1. Free surface breakup into jets and droplets, and...

  13. Inversion of Intensity Profiles for Bubble Emissivity

    OpenAIRE

    Ignace, R.; Toalá, J. A.; Oskinova, L.M.

    2015-01-01

    Under the assumption of spherical symmetry, the run of intensity with impact parameter for a spatially resolved and optically thin bubble can be inverted for an "effective emissivity" as a function of radius. The effective emissivity takes into account instrumental sensitivity and even interstellar absorption. This work was supported by a grant from NASA (G03-14008X).

  14. Drop impact entrapment of bubble rings

    CERN Document Server

    Thoraval, M -J; Etoh, T G; Thoroddsen, S T

    2012-01-01

    We use ultra-high-speed video imaging to look at the initial contact of a drop impacting onto a liquid layer. We observe experimentally the vortex street and the bubble-ring entrapments predicted numerically, for high impact velocities, by Thoraval et al. [Phys. Rev. Lett. 108, 264506 (2012)]. These dynamics occur mostly within 50 {\\mu}s after the first contact, requiring imaging at 1 million frames/sec. For a water drop impacting onto a thin layer of water, the entrapment of isolated bubbles starts through azimuthal instability, which forms at low impact velocities, in the neck connecting the drop and pool. For Re above about 12 000, up to 10 partial bubble-rings have been observed at the base of the ejecta, starting when the contact is about 20% of the drop size. More regular bubble rings are observed for a pool of ethanol or methanol. The video imaging shows rotation around some of these air cylinders, which can temporarily delay their breakup into microbubbles. The different refractive index in the pool l...

  15. Bubble models, data acquisition and model applicability

    Czech Academy of Sciences Publication Activity Database

    Jebavá, Marcela; Kloužek, Jaroslav; Němec, Lubomír

    Vsetín : GLASS SERVICE ,INC, 2005, s. 182-191. ISBN 80-239-4687-0. [International Seminar on Mathematical Modeling and Advanced Numerical Methods in Furnace Design and Operation /8./. Velké Karlovice (CZ), 19.05.2005-20.05.2005] Institutional research plan: CEZ:AV0Z40320502 Keywords : bubble models Subject RIV: CA - Inorganic Chemistry

  16. Bubble interactions in liquid/gas flows

    NARCIS (Netherlands)

    Wijngaarden, van L.

    1982-01-01

    The system of equations, usually employed for unsteady liquid/gas flows, has complex characteristics. This as well as other facts have led to the search for a more accurate description of effects associated with relative motion. For liquid/bubble systems the fluctuations resulting from hydrodynamic

  17. Bubble-Turbulence Interaction in Binary Fluids

    International Nuclear Information System (INIS)

    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 and Hilliard (1958) and Elliott and Songmu (1986).

  18. Bubble-Turbulence Interaction in Binary Fluids

    Science.gov (United States)

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

    2011-12-01

    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).

  19. Bubbles and droplets in magnetic fluids

    Science.gov (United States)

    Yecko, Philip

    2006-11-01

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

  20. Black holes as bubble nucleation sites

    International Nuclear Information System (INIS)

    We consider the effect of inhomogeneities on the rate of false vacuum decay. Modelling the inhomogeneity by a black hole, we construct explicit Euclidean instantons which describe the nucleation of a bubble of true vacuum centred on the inhomogeneity. We find that inhomogeneity significantly enhances the nucleation rate over that of the Coleman-de Luccia instanton — the black hole acts as a nucleation site for the bubble. The effect is larger than previously believed due to the contributions to the action from conical singularities. For a sufficiently low initial mass, the original black hole is replaced by flat space during this process, as viewed by a single causal patch observer. Increasing the initial mass, we find a critical value above which a black hole remnant survives the process. This resulting black hole can have a higher mass than the original black hole, but always has a lower entropy. We compare the process to bubble-to-bubble transitions, where there is a semi-classical Lorentzian description in the WKB approximation

  1. On Stability of a Bubble Column

    Czech Academy of Sciences Publication Activity Database

    Růžička, Marek

    2013-01-01

    Roč. 91, č. 2 (2013), s. 191-203. ISSN 0263-8762 R&D Projects: GA ČR GA104/07/1110 Institutional support: RVO:67985858 Keywords : bubble column * flow regimes * steady solution Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 2.281, year: 2013

  2. Characterization of polymers by bubble inflation

    DEFF Research Database (Denmark)

    Christensen, Jens Horslund; Rasmussen, Henrik K.; Kjær, Erik Michael;

    1999-01-01

    In order to characterise materials using a simple and relative inexpensive method, the bubble inflation technique was modified. A polymer plate is clamped between a Teflon coated heating plate and a heated cylinder. By applying air through the heating plate the polymer membrane deforms into the...

  3. Multi-Dimensional Analysis of the Forced Bubble Dynamics Associated with Bubble Fusion Phenomena. Final Topical Report

    Energy Technology Data Exchange (ETDEWEB)

    Lahey, Jr., Richard T. [Rensselaer Polytechnic Inst., Troy, NY (United States). Center for Multiphase Research and Dept. of Mechanical, Aeronautical and Nuclear Engineering; Jansen, Kenneth E. [Rensselaer Polytechnic Inst., Troy, NY (United States). Center for Multiphase Research and Dept. of Mechanical, Aeronautical and Nuclear Engineering; Nagrath, Sunitha [Rensselaer Polytechnic Inst., Troy, NY (United States). Center for Multiphase Research and Dept. of Mechanical, Aeronautical and Nuclear Engineering

    2002-12-02

    A new adaptive grid, 3-D FEM hydrodynamic shock (ie, HYDRO )code called PHASTA-2C has been developed and used to investigate bubble implosion phenomena leading to ultra-high temperatures and pressures. In particular, it was shown that nearly spherical bubble compressions occur during bubble implosions and the predicted conditions associated with a recent ORNL Bubble Fusion experiment [Taleyarkhan et al, Science, March, 2002] are consistent with the occurrence of D/D fusion.

  4. Cavitation Bubble Nucleation by Energetic Particles

    Energy Technology Data Exchange (ETDEWEB)

    West, C.D.

    1998-12-01

    In the early sixties, experimental measurements using a bubble chamber confirmed quantitatively the thermal spike theory of bubble nucleation by energetic particles: the energy of the slow, heavy alpha decay recoils used in those experiments matched the calculated bubble nucleation energy to within a few percent. It was a triumph, but was soon to be followed by a puzzle. Within a couple of years, experiments on similar liquids, but well below their normal boiling points, placed under tensile stress showed that the calculated bubble nucleation energy was an order of magnitude less than the recoil energy. Why should the theory work so well in the one case and so badly in the other? How did the liquid, or the recoil particle, "know" the difference between the two experiments? Another mathematical model of the same physical process, introduced in 1967, showed qualitatively why different analyses would be needed for liquids with high and low vapor pressures under positive or negative pressures. But, the quantitative agreement between the calculated nucleation energy and the recoil energy was still poor--the former being smaller by a factor of two to three. In this report, the 1967 analysis is extended and refined: the qualitative understanding of the difference between positive and negative pressure nucleation, "boiling" and "cavitation" respectively, is retained, and agreement between the negative pressure calculated to be needed for nucleation and the energy calculated to be available is much improved. A plot of the calculated negative pressure needed to induce bubble formation against the measured value now has a slope of 1.0, although there is still considerable scatter in the individual points.

  5. Study of droplet entrainment from bubbling surface in a bubble column

    International Nuclear Information System (INIS)

    In a bubble column droplets are ejected from the free surface by bubble bursting or splashing. Depending on their size, the droplets are partly carried away by the streaming gas or fall back to the bubbling surface by gravity force. Experiments have been carried out to determine the void fraction in the column by means of an optical probe. In the interfacial zone the bubble bursting process was captured with a high-speed video camera. Simultaneous measurements were made of size and velocity of droplets at several distances from the bubbling surface with a Phase-Doppler Anemometry. The bubble column can be divided into three regions: A lower zone with a flat profile of the local void fraction, a central zone where the flow regime is steady and an upper zone where the local void fraction grows rapidly. A two-parameter log-normal distribution function was proposed in order to describe the polydisperse distribution of droplet-size. Results were obtained concerning the entrainment, concentration, volume fraction and interfacial area of droplets. Finally, it was found that the turbulence intensity affects the droplet terminal velocity for droplets smaller than the Kolmogorov microscale

  6. Bubbles with shock waves and ultrasound: a review.

    Science.gov (United States)

    Ohl, Siew-Wan; Klaseboer, Evert; Khoo, Boo Cheong

    2015-10-01

    The study of the interaction of bubbles with shock waves and ultrasound is sometimes termed 'acoustic cavitation'. It is of importance in many biomedical applications where sound waves are applied. The use of shock waves and ultrasound in medical treatments is appealing because of their non-invasiveness. In this review, we present a variety of acoustics-bubble interactions, with a focus on shock wave-bubble interaction and bubble cloud phenomena. The dynamics of a single spherically oscillating bubble is rather well understood. However, when there is a nearby surface, the bubble often collapses non-spherically with a high-speed jet. The direction of the jet depends on the 'resistance' of the boundary: the bubble jets towards a rigid boundary, splits up near an elastic boundary, and jets away from a free surface. The presence of a shock wave complicates the bubble dynamics further. We shall discuss both experimental studies using high-speed photography and numerical simulations involving shock wave-bubble interaction. In biomedical applications, instead of a single bubble, often clouds of bubbles appear (consisting of many individual bubbles). The dynamics of such a bubble cloud is even more complex. We shall show some of the phenomena observed in a high-intensity focused ultrasound (HIFU) field. The nonlinear nature of the sound field and the complex inter-bubble interaction in a cloud present challenges to a comprehensive understanding of the physics of the bubble cloud in HIFU. We conclude the article with some comments on the challenges ahead. PMID:26442143

  7. Electronic structure of multielectron bubbles in liquid helium

    International Nuclear Information System (INIS)

    A quantum-statistical generalized Thomas-Fermi model is presented for the structure of multielectron bubbles observed in liquid helium-4 at low temperatures. The authors estimate bubbles with more than about 20 electrons to be stable against fissioning to single-electron bubbles. Electrons inside multielectron bubbles are found to concentrate in a narrow layer on the liquid helium surface. It is suggested that large bubbles in liquid helium constitute a new system and regime for testing electron density profiles; one which is quite clean from impurities, band structure effects and the background charge, all of which usually complicate the treatment of the electron density profile of metal surfaces. (Auth.)

  8. Bubble breakup in two-dimensional Stokes flow

    International Nuclear Information System (INIS)

    A new class of exact solutions is reported for an evolving bubble in a two-dimensional slow viscous flow. It is observed that for an expanding bubble the interface grows smoother with time, whereas the contracting-bubble solutions display a tendency to form sharp corners (''near cusps'') for small values of surface tension. In the latter case, we also obtain analytic solutions that describe bubble breakup: For a large class of initial shapes, the interface will eventually develop a thin ''neck'' whose width goes to zero before the bubble is completely removed from the liquid

  9. Fundamental of Inclusion Removal from Molten Steel by Rising Bubble

    Institute of Scientific and Technical Information of China (English)

    WANG Li-tao; ZHANG Qiao-ying; LI Zheng-bang; XUE Zheng-liang

    2004-01-01

    The mechanism of inclusion removal by attachment to rising bubble was analyzed, and the movement behavior of inclusion, the mechanism of bubbles/inclusion interaction, collision probability and adhesion probability were discussed. A mathematical model of inclusion removal from molten steel by attachment to fine bubble was developed. The results of theoretical analysis and mathematical model showed that the optimum bubble diameter for inclusion removal is 1 to 2 mm. A new method that argon is injected into the shroud from ladle to tundish during continuous casting has been proposed to produce fine bubble. It provides theoretical guides for production of super clean steel.

  10. Modeling Space-Time Dependent Helium Bubble Evolution in Tungsten Armor under IFE Conditions

    International Nuclear Information System (INIS)

    The High Average Power Laser (HAPL) program is a coordinated effort to develop Laser Inertial Fusion Energy. The implosion of the D-T target produces a spectrum of neutrons, X-rays, and charged particles, which arrive at the first wall (FW) at different times within about 2.5 μs at a frequency of 5 to 10 Hz. Helium is one of several high-energy charged particle constituents impinging on the candidate tungsten armored low activation ferritic steel First Wall. The spread of the implanted debris and burn helium energies results in a unique space-time dependent implantation profile that spans about 10 μm in tungsten. Co-implantation of X-rays and other ions results in spatially dependent damage profiles and rapid space-time dependent temperature spikes and gradients. The rate of helium transport and helium bubble formation will vary significantly throughout the implanted region. Furthermore, helium will also be transported via the migration of helium bubbles and non-equilibrium helium-vacancy clusters. The HEROS code was developed at UCLA to model the spatial and time-dependent helium bubble nucleation, growth, coalescence, and migration under transient damage rates and transient temperature gradients. The HEROS code is based on kinetic rate theory, which includes clustering of helium and vacancies, helium mobility, helium-vacancy cluster stability, cavity nucleation and growth and other microstructural features such as interstitial loop evolution, grain boundaries, and precipitates. The HEROS code is based on space-time discretization of reaction-diffusion type equations to account for migration of mobile species between neighboring bins as single atoms, clusters, or bubbles. HAPL chamber FW implantation conditions are used to model helium bubble evolution in the implanted tungsten. Helium recycling rate predictions are compared with experimental results of helium ion implantation experiments. (author)

  11. Post-midnight occurrence of equatorial plasma bubbles

    Science.gov (United States)

    Ajith, K. K.; Otsuka, Yuichi; Yamamoto, Mamoru; Yokoyama, Tatsuhiro; Tulasiram, S.

    2016-07-01

    The equatorial plasma bubbles (EPBs)/equatorial spread F (ESF) irregularities are an important topic of space weather interest because of their impact on transionospheric radio communications, satellite-based navigation and augmentation systems. This local plasma depleted structures develop at the bottom side F layer through Rayleigh-Taylor instability and rapidly grow to topside ionosphere via polarization electric fields within them. The steep vertical gradients due to quick loss of bottom side ionization and rapid uplift of equatorial F layer via prereversal enhancement (PRE) of zonal electric field makes the post-sunset hours as the most preferred local time for the formation of EPBs. However, there is a different class of irregularities that occurs during the post-midnight hours of June solstice reported by the previous studies. The occurrence of these post-midnight EPBs maximize during the low solar activity periods. The growth characteristics and the responsible mechanism for the formation of these post-midnight EPBs are not yet understood. Using the rapid beam steering ability of 47 MHz Equatorial Atmosphere Radar (EAR) at Kototabang (0.2°S geographic latitude, 100.3°E geographic longitude, and 10.4°S geomagnetic latitude), Indonesia, the spatial and temporal evolution of equatorial plasma bubbles (EPBs) were examined to classify the evolutionary-type EPBs from those which formed elsewhere and drifted into the field of view of radar. The responsible mechanism for the genesis of summer time post-midnight EPBs were discussed in light of growth rate of Rayleigh-Taylor instability using SAMI2 model.

  12. Effect of metabolic gases and water vapor, perfluorocarbon emulsions, and nitric oxide on tissue bubbles during decompression sickness.

    Science.gov (United States)

    Randsøe, Thomas

    2016-05-01

    In aviation and diving, fast decrease in ambient pressure, such as during accidental loss of cabin pressure or when a diver decompresses too fast to sea level, may cause nitrogen (N2) bubble formation in blood and tissue resulting in decompression sickness (DCS). Conventional treatment of DCS is oxygen (O2) breathing combined with recompression.  However, bubble kinetic models suggest, that metabolic gases, i.e. O2 and carbon dioxide (CO2), and water vapor contribute significantly to DCS bubble volume and growth at hypobaric altitude exposures. Further, perfluorocarbon emulsions (PFC) and nitric oxide (NO) donors have, on an experimental basis, demonstrated therapeutic properties both as treatment and prophylactic intervention against DCS. The effect was ascribed to solubility of respiratory gases in PFC, plausible NO elicited nuclei demise and/or N2 washout through enhanced blood flow rate. Accordingly, by means of monitoring injected bubbles in exposed adipose tissue or measurements of spinal evoked potentials (SEPs) in anaesthetized rats, the aim of this study was to: 1) evaluate the contribution of metabolic gases and water vapor to bubble volume at different barometrical altitude exposures, 2) clarify the O2 contribution and N2 solubility from bubbles during administration of PFC at normo- and hypobaric conditions and, 3) test the effect of different NO donors on SEPs during DCS upon a hyperbaric air dive and, to study the influence of  NO on tissue bubbles at high altitude exposures. The results support the bubble kinetic models and indicate that metabolic gases and water vapor contribute significantly to bubble volume at 25 kPa (~10,376 m above sea level) and constitute a threshold for bubble stabilization or decay at the interval of 47-36 kPa (~6,036 and ~7,920 m above sea level). The effect of the metabolic gases and water vapor seemed to compromise the therapeutic properties of both PFC and NO at altitude, while PFC significantly increased bubble

  13. A comparison study of experimental and direct numerical simulation results associated with dynamics and heat transfer of a boiling bubble

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Satbyoul; Kim, Hyungdae [Kyung Hee Univ., Yongin (Korea, Republic of); Ose, Yasuo [Yamato System Engineer Co., Ltd., Yamato (Japan); Kunugi, Tomoaki [Kyoto Univ., Kyoto (Japan)

    2014-05-15

    In the experiment, by applying both a total reflection technique which consisted of a coherent laser and an infrared thermometry to a boiling surface with high spatial and temporal resolution, the liquid-vapor phase and the heat transfer distributions underneath a growing bubble were simultaneously measured. In the simulation, nucleate boiling process of a single bubble was simulated by using the MARS (Multi-interface Advection and Reconstruction Solver) including a non-empirical boiling and condensation model. The experimental measurement and numerical simulation data of a boiling bubble on a heated wall were presented and compared in detail with focus on liquid-vapor phase and heat transfer distributions on the boiling surface. In the experiment, the technique is based on spatial and temporal synchronization of an infrared thermometry technique for the local heat transfer measurement, a total reflection technique for the liquid-vapor phase detection, and a laser interferometry technique for detection of the microlayer geometry. In the simulation, a single bubble nucleate boiling was simulated by using the MARS including a non-empirical boiling and condensation model. The major findings from the present comparison study are following: - The microlayer evaporation could affect the characteristics of heat transfer for a bubble growth cycle. At the beginning of bubble growth, the effective heat transfer from a heated wall occurs due to microlayer evaporation, which impeded the local wall superheated in the dry region. Ad-hoc experiments to obtain the velocity and temperature field before a bubble nucleation, such as using PIV (particle image velocimetry) and LIF (laser induced fluorescence) techniques, are ongoing in our laboratory.

  14. Modelling for three dimensional coalescence of two bubbles

    Science.gov (United States)

    Han, R.; Li, S.; Zhang, A. M.; Wang, Q. X.

    2016-06-01

    This paper is concerned with the three dimensional (3D) interaction and coalescence of two bubbles subject to buoyancy and the dynamics of the subsequent joined bubble using the boundary integral method (BIM). An improved density potential method is implemented to control the mesh quality. It helps to avoid the numerical instabilities, which occur after coalescence. Numerical convergence tests are conducted in terms of mesh sizes and time steps. The 3D numerical model agrees well with an axisymmetric BIM model for axisymmetric cases as well as experimental results captured by high-speed camera. The bubble jetting, interaction, and coalescence of the two bubbles depend on the maximum bubble radii, the centre distance between two bubbles at inception, and the angle β between the centre line and the direction of buoyancy. We investigate coalescence of two bubbles for β = 0, π/4, and π/2, respectively, and at various centre distances at inception. Numerical results presented include the bubble and jet shapes, the velocity, and pressure fields surrounding the bubbles, as well as the time histories of bubble volumes, jet velocities, and positions of centroid of the bubble system.

  15. Predawn plasma bubble cluster observed in Southeast Asia

    Science.gov (United States)

    Watthanasangmechai, Kornyanat; Yamamoto, Mamoru; Saito, Akinori; Tsunoda, Roland; Yokoyama, Tatsuhiro; Supnithi, Pornchai; Ishii, Mamoru; Yatini, Clara

    2016-06-01

    Predawn plasma bubble was detected as deep plasma depletion by GNU Radio Beacon Receiver (GRBR) network and in situ measurement onboard Defense Meteorological Satellite Program F15 (DMSPF15) satellite and was confirmed by sparse GPS network in Southeast Asia. In addition to the deep depletion, the GPS network revealed the coexisting submesoscale irregularities. A deep depletion is regarded as a primary bubble. Submesoscale irregularities are regarded as secondary bubbles. Primary bubble and secondary bubbles appeared together as a cluster with zonal wavelength of 50 km. An altitude of secondary bubbles happened to be lower than that of the primary bubble in the same cluster. The observed pattern of plasma bubble cluster is consistent with the simulation result of the recent high-resolution bubble (HIRB) model. This event is only a single event out of 76 satellite passes at nighttime during 3-25 March 2012 that significantly shows plasma depletion at plasma bubble wall. The inside structure of the primary bubble was clearly revealed from the in situ density data of DMSPF15 satellite and the ground-based GRBR total electron content.

  16. Rising motion of a bubble layer near a vertical wall

    Science.gov (United States)

    Dabiri, Sadegh; Bhuvankar, Pramod

    2015-11-01

    Bubbly flows in vertical pipes and channels form a wall-peak distribution of bubbles under certain conditions. The dynamics of the bubbles near the wall is different than in an unbounded liquid. Here we report the rising motion of bubbles in a liquid near a vertical wall. In a simulation of a bubbly flow in a periodic domain with a vertical wall on one side, an average pressure gradient is applied to the domain that balances the weight of the liquid phase. The upward flow is created by the rising motion of the bubbles. The bubbles are kept near the wall by the lateral lift force acting on them as a result of rising in a shear flow which is in turn generated by rising motion of bubbles. The rise velocity of the bubbles on the wall and the average rise velocity of the liquid depend on three dimensionless parameters, Archimedes number, Eotvos number, and the average volume fraction of bubbles near the wall. In the limit of small Eo, bubbles are nearly spherical and the dependency on Eo becomes negligible. In this limit, the scaling of the liquid Reynolds number with Archimedes number and the void fraction is presented.

  17. Nucleation of Helium Bubbles on Dislocations, Dislocation Networks and Dislocation in Grain Boundaries during 600 MeV Proton Irradiation of Aluminium

    DEFF Research Database (Denmark)

    Singh, Bachu Narain; Leffers, Torben; Green, W.V.; ; Victoria, M.

    1984-01-01

    Samples of high-purity aluminium were irradiated with 600 MeV protons at temperatures in the range 130 to 433°C; in these experiments 615 and 125 appm of hydrogen and helium, respectively, are produced per dpa. Bubble formation and growth at grain boundaries and in the zone adjacent to the bubble......-denuded zone are described. Precipitation at grain boundaries and migration of grain boundaries during irradiation are also reported....

  18. Eternal inflation, bubble collisions, and the persistence of memory

    International Nuclear Information System (INIS)

    A 'bubble universe' nucleating in an eternally inflating false vacuum will experience, in the course of its expansion, collisions with an infinite number of other bubbles. In an idealized model, we calculate the rate of collisions around an observer inside a given reference bubble. We show that the collision rate violates both the homogeneity and the isotropy of the bubble universe. Each bubble has a center which can be related to 'the beginning of inflation' in the parent false vacuum, and any observer not at the center will see an anisotropic bubble collision rate that peaks in the outward direction. Surprisingly, this memory of the onset of inflation persists no matter how much time elapses before the nucleation of the reference bubble

  19. Orbital motions of bubbles in an acoustic field

    Science.gov (United States)

    Shirota, Minori; Yamashita, Ko; Inamura, Takao

    2012-09-01

    This experimental study aims to clarify the mechanism of orbital motion of two oscillating bubbles in an acoustic field. Trajectory of the orbital motion on the wall of a spherical levitator was observed using a high-speed video camera. Because of a good repeatability in volume oscillation of bubbles, we were also able to observe the radial motion driven at 24 kHz by stroboscopic like imaging technique. The orbital motions of bubbles raging from 0.13 to 0.18 mm were examined with different forcing amplitude and in different viscous oils. As a result, we found that pairs of bubbles revolve along an elliptic orbit around the center of mass of the bubbles. We also found that the two bubbles perform anti-phase radial oscillation. Although this radial oscillation should result in a repulsive secondary Bjerknes force, the bubbles kept a constant separate distance of about 1 mm, which indicates the existence of centripetal primary Bjerknes force.

  20. Precise measurement technique for the stable acoustic cavitation bubble

    Institute of Scientific and Technical Information of China (English)

    HUANG Wei; CHEN Weizhong; LIU Yanan; GAO Xianxian; JIANG Lian; XU Junfeng; ZHU Yifei

    2005-01-01

    Based on the periodic oscillation of the stable acoustic cavitation bubble, we present a precise measurement technique for the bubble evolution. This technique comprises the lighting engineering of pulsing laser beam whose phase can be digitally shifted, and the long distance microphotographics. We used a laser, an acousto-optic modulator, a pulse generator, and a long distance microscope. The evolution of a levitated bubble can be directly shown by a series of bubble's images at different phases. Numerical simulation in the framework of the Rayleigh-Plesset bubble dynamics well supported the experimental result, and the ambient radius of the bubble, an important parameter related to the mass of the gas inside the bubble, was obtained at the same time.

  1. Numerical simulation of high Reynolds number bubble motion

    International Nuclear Information System (INIS)

    This paper presents the results of numerical simulations of bubble motion. All the results are for single bubbles in unbounded fluids. The liquid phase is quiescent except for the motion created by the bubble, which is axisymmetric. The main focus of the paper is on bubbles that are of order 1 mm in diameter in water. Of particular interest is the effect of surfactant molecules on bubble motion. Results for the open-quotes insoluble surfactantclose quotes model will be presented. These results extend research by other investigators to finite Reynolds numbers. The results indicate that, by assuming complete coverage of the bubble surface, one obtains good agreement with experimental observations of bubble motion in tap water. The effect of surfactant concentration on the separation angle is discussed

  2. Morphology of Two-Phase Layers with Large Bubbles

    Science.gov (United States)

    Vékony, Klára; Kiss, László I.

    2010-10-01

    The understanding of formation and movement of bubbles nucleated during aluminum reduction is essential for a good control of the electrolysis process. In our experiments, we filmed and studied the formation of a bubble layer under the anode in a real-size air-water electrolysis cell model. The maximum height of the bubbles was found to be up to 2 cm because of the presence of the so-called Fortin bubbles. Also, the mean height of the bubble layer was found to be much higher than published previously. The Fortin bubbles were investigated more closely, and their shape was found to be induced by a gravity wave formed at the gas-liquid interface. In addition, large bubbles were always observed to break up into smaller parts right before escaping from under the anode. This breakup and escape led to a large momentum transfer in the bath.

  3. Rise velocities of large bubbles in viscous Newtonian liquids

    International Nuclear Information System (INIS)

    The behavior of gas bubbles in molten glass has been widely investigated in the past because of the importance of the refining process in the glass industry. Due to the difficulties in measuring bubble rise velocity in an opaque glass melt, the experimental data are limited. Jucha et.al. and Hornyak and Weinberg found that the bubble motion was governed by the Hadamard-Rybczynski formula for bubbles with diameters up to 1.6mm. However, Nemec found that the Stokes formula to be applicable for his experimental results for bubbles with diameters up to 1.2mm. In this study, rise velocities for large gas bubbles (0.7 cm b -4 to 0.6, the experimental data for steady-state bubble rise velocities agreed better with the Hadamard-Rybcznski formula than with the Stokes formula

  4. Effect of internal bubbly flow on pipe vibrations

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    This paper presents an experimental investigation on wall vibrations of a pipe due to injection of a uniform bubble cloud into the pipe flow. For different bubble void fractions and averaged bubble sizes, the vibrations were measured using accelerometers. To understand the underlying physics, the evolution of the vibration spectra along the streamwise direction was examined. Results showed that wall vibrations were greatly enhanced up to 25 dB, compared with no bubble case. The characteristics of the vibration were mainly dependent on void fraction. These vibrations were believed to be caused by two mechanisms: acoustic resonance and normal modes of the bubble cloud. The former, originating from the interaction between the first mode of the bubble cloud and the first acoustic mode of the pipe, persisted along the entire pipe to enhance the vibration over a broad band frequency range, while the later, due to the process of bubble formation, successively decayed in the streamwise direction.

  5. Flow Structures Around Micro-bubbles During Subcooled Nucleate Boiling

    Institute of Scientific and Technical Information of China (English)

    WANG Hao; PENG Xiao-Feng; David M. Christopher; WANG Bu-Xuan

    2005-01-01

    The flow structures were investigated around micro bubbles on extremely thin wires during subcooled nucleate boiling. Jet flows emanating from the bubbles were observed visually with the fluid field measurement using high-speed photography and a PIV system. The jet flows induced a strong pumping effect around a bubble. The multi-jet structure was further observed experimentally, indicating the evolution of flow structure around micro bubbles. Numerical simulations explore that the jet flows were induced by a strong Marangoni effect due to high temperature gradients near the wire. The bubble interface with multi-jet structure has abnormal temperature distribution such that the coolest parts were observed at two sides of a bubble extending into the subcooled bulk liquid rather than at the top. Evaporation and condensation on the bubble interface play important roles not only in controlling the intensity of the jet flow, but also in bringing out the multi-jet structure.

  6. Numerical simulation of high Reynolds number bubble motion

    Energy Technology Data Exchange (ETDEWEB)

    McLaughlin, J.B. [Clarkson Univ., Potsdam, NY (United States)

    1995-12-31

    This paper presents the results of numerical simulations of bubble motion. All the results are for single bubbles in unbounded fluids. The liquid phase is quiescent except for the motion created by the bubble, which is axisymmetric. The main focus of the paper is on bubbles that are of order 1 mm in diameter in water. Of particular interest is the effect of surfactant molecules on bubble motion. Results for the {open_quotes}insoluble surfactant{close_quotes} model will be presented. These results extend research by other investigators to finite Reynolds numbers. The results indicate that, by assuming complete coverage of the bubble surface, one obtains good agreement with experimental observations of bubble motion in tap water. The effect of surfactant concentration on the separation angle is discussed.

  7. Dynamics of micro-bubble sonication inside a phantom vessel

    KAUST Repository

    Qamar, Adnan

    2013-01-10

    A model for sonicated micro-bubble oscillations inside a phantom vessel is proposed. The model is not a variant of conventional Rayleigh-Plesset equation and is obtained from reduced Navier-Stokes equations. The model relates the micro-bubble oscillation dynamics with geometric and acoustic parameters in a consistent manner. It predicts micro-bubble oscillation dynamics as well as micro-bubble fragmentation when compared to the experimental data. For large micro-bubble radius to vessel diameter ratios, predictions are damped, suggesting breakdown of inherent modeling assumptions for these cases. Micro-bubble response with acoustic parameters is consistent with experiments and provides physical insight to the micro-bubble oscillation dynamics.

  8. Comparison between Airlift Photobioreactor and Bubble Column for Skeletonema Costatum Cultivation

    Directory of Open Access Journals (Sweden)

    Prasert Pavasant

    2011-10-01

    Full Text Available The cultivation of diatom Skeletonema costatum was achieved in airlift photobioreactor and the system performance was compared to that of bubble column. The standard F/2 medium (Guillard’s medium for typical diatom cultivation could only yield the best growth character when the silicon concentration increased 4 times the normal value. In terms of cell growth, the airlift photobioreactor provided better performance than the bubble column where the maximum cell concentration, specific growth rate, and productivity in the airlift were 4.6 x 106 cell mL-1, 0.07 h-1, and 6.4 x 104 cell s-1 compared with 1.8 x 106 cell mL-1, 0.04 h-1, and 2.2 x 104 cell s-1 in the bubble column of the same size (3L and operated at the same aeration rate (superficial velocity = 1.5 cm s-1 and light intensity (34 μmol photons m−2 s−1. This was because the airlift photobioreactor allowed circulatory flow in the system which helps prevent cell precipitation and enhance light utilization efficiency. The optimal operating conditions in the airlift system which was found most optimal to cell growth were: the ratio between downcomer and riser cross sectional area (Ad:Ar of 3.27, superficial gas velocity 1.5 cm s−1 and the light intensity 34 μmol photons m−2 s−1. Preliminary economical assessment on the cultivation of S. costatum in airlift system compared with that in bubble column was carried out, whereas the analysis for nutritional values of the obtained biomass indicated relatively high protein content.

  9. Measurements of fast neutrons by bubble detectors

    International Nuclear Information System (INIS)

    Neutron bubble detectors have been studied using Am-Be and D-D neuron sources, which give limited energy information. The Bubble Detector Spectrometer (BDS) have six different energy thresholds ranging from 10 KeV to 10 Mev. The number of bubbles obtained in each measurement is related to the dose (standardized response R) equivalent neutrons through sensitivity (b / μSv) and also with the neutron flux (neutrons per unit area) through a relationship that provided by the manufacturer. Bubble detectors were used with six different answers (0.11 b/ μSv, 0093 b/μSv, 0.14 b/μSv, 0.17 b/μSv, 0051 b/μSv). To test the response of the detectors (BDS) radiate a set of six of them with different energy threshold, with a source of Am-Be, placing them at a distance of one meter from it for a few minutes. Also, exposed to dense plasma focus Fuego Nuevo II (FN-II FPD) of ICN-UNAM, apparatus which produces fusion plasma, generating neutrons by nuclear reactions of neutrons whose energy emitting is 2.45 MeV. In this case the detectors were placed at a distance of 50 cm from the pinch at 90° this was done for a certain number of shots. In both cases, the standard response is reported (Dose in μSv) for each of the six detectors representing an energy range, this response is given by the expression Ri= Bi / Si where Bi is the number of bubbles formed in each and the detector sensitivity (Si) is given for each detector in (b / μSv). Also, reported for both cases, the detected neutron flux (n cm−2), by a given ratio and the response involves both standardized R, as the average cross section sigma. The results obtained have been compared with the spectrum of Am-Be source. From these measurements it can be concluded that with a combination of bubble detectors, with different responses is possible to measure the equivalent dose in a range of 10 to 100 μSv fields mixed neutron and gamma, and pulsed generated fusion devices

  10. Tests of Bubble Damage Detectors in a Heavy Ion Beam from the SPS

    CERN Multimedia

    2002-01-01

    This experiment is designed to investigate the properties of a bubble damage polymer (BDP) using ion beams from the SPS. These polymers are already used commercially for making neutron and gamma-ray dosimeters. \\\\ \\\\ An attractive feature of BDP detectors is the ability to ``design'' a material to have a particular dE/dx threshold which can be used to detect such objects as monopoles and heavy ions as well as relativistic, singly charged tracks originating f particle interactions. \\\\ \\\\ The BDP detector is a polymer which holds droplets of super-heated liquid in suspension. The droplet size is typically a few microns and the droplet density is normally between 10|5 and 10|7 droplets/cm|3. The passage of a particle with a dE/dx exceeding the threshold of the material will cause the droplets with a sufficiently s parameter to change state, giving rise to bubbles. The dE/dx threshold of the BDP varies with pressure and temperature. The growth of bubbles in the bubble trail is limited by the polymer matrix and th...

  11. Hydrodynamics of ultra-relativistic bubble walls

    CERN Document Server

    Leitao, Leonardo

    2015-01-01

    In cosmological first-order phase transitions, gravitational waves are generated by the collisions of bubble walls and by the bulk motions caused in the fluid. A sizeable signal may result from fast-moving walls. In this work we study the hydrodynamics associated to the fastest propagation modes, namely, ultra-relativistic detonations and runaway solutions. We compute the energy injected by the phase transition into the fluid and the energy which accumulates in the bubble walls. We provide analytic approximations and fits as functions of the net force acting on the wall, which can be readily evaluated for specific models. We also study the back-reaction of hydrodynamics on the wall motion, and we discuss on the extrapolation of the friction force away from the ultra-relativistic limit.

  12. Correlation of bubble rise velocity and volume

    International Nuclear Information System (INIS)

    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

  13. Computational analysis of ozonation in bubble columns

    International Nuclear Information System (INIS)

    This paper presents a new computational ozonation model based on the principle of computational fluid dynamics along with the kinetics of ozone decay and microbial inactivation to predict the performance of ozone disinfection in fine bubble columns. The model can be represented using a mixture two-phase flow model to simulate the hydrodynamics of the water flow and using two transport equations to track the concentration profiles of ozone and microorganisms along the height of the column, respectively. The applicability of this model was then demonstrated by comparing the simulated ozone concentrations with experimental measurements obtained from a pilot scale fine bubble column. One distinct advantage of this approach is that it does not require the prerequisite assumptions such as plug flow condition, perfect mixing, tanks-in-series, uniform radial or longitudinal dispersion in predicting the performance of disinfection contactors without carrying out expensive and tedious tracer studies. (author)

  14. Optimal filters for detecting cosmic bubble collisions

    CERN Document Server

    McEwen, J D; Johnson, M C; Peiris, H V

    2012-01-01

    A number of well-motivated extensions of the LCDM concordance cosmological model postulate the existence of a population of sources embedded in the cosmic microwave background (CMB). One such example is the signature of cosmic bubble collisions which arise in models of eternal inflation. The most unambiguous way to test these scenarios is to evaluate the full posterior probability distribution of the global parameters defining the theory; however, a direct evaluation is computationally impractical on large datasets, such as those obtained by the Wilkinson Microwave Anisotropy Probe (WMAP) and Planck. A method to approximate the full posterior has been developed recently, which requires as an input a set of candidate sources which are most likely to give the largest contribution to the likelihood. In this article, we present an improved algorithm for detecting candidate sources using optimal filters, and apply it to detect candidate bubble collision signatures in WMAP 7-year observations. We show both theoreti...

  15. The Recent Financial Bubble: an Overview

    Directory of Open Access Journals (Sweden)

    Thalassinos E.

    2009-12-01

    Full Text Available The main aim of this paper is to analyse the recent financial crisis and to make recommendations how to handle it in the best possible way. Financial bubbles, since the great depression, have been analysed and some recommendations have been made taking into account the internationalization of the world economy which behaves like a domino. The recent financial crisis in the sub-prime mortgage market creates new problems in the world market with unforeseen continuances. Deflation has been referred to as a possible continuance after a financial bubble because often but not always deflation follows. Deflation often results in financial and economic crises. Financial and economic crises affect the architecture of the monetary system, while a change in the system may affect the role of the dollar, the euro and the yen.

  16. Metastability in bubbling AdS space

    Science.gov (United States)

    Massai, Stefano; Pasini, Giulio; Puhm, Andrea

    2015-02-01

    We study the dynamics of probe M5 branes with dissolved M2 charge in bubbling geometries with SO(4) × SO(4) symmetry. These solutions were constructed by Bena-Warner and Lin-Lunin-Maldacena and correspond to the vacua of the maximally supersymmetric mass-deformed M2 brane theory. We find that supersymmetric probe M2 branes polarize into M5 brane shells whose backreaction creates an additional bubble in the geometry. We explicitly check that the supersymmetric polarization potential agrees with the one found within the Polchinski-Strassler approximation. The main result of this paper is that probe M2 branes whose orientation is opposite to the background flux can polarize into metastable M5 brane shells. These decay to a supersymmetric configuration via brane-flux annihilation. Our findings suggest the existence of metastable states in the mass-deformed M2 brane theory.

  17. Metastability in Bubbling AdS Space

    CERN Document Server

    Massai, Stefano; Puhm, Andrea

    2014-01-01

    We study the dynamics of probe M5 branes with dissolved M2 charge in bubbling geometries with SO(4) x SO(4) symmetry. These solutions were constructed by Bena-Warner and Lin-Lunin-Maldacena and correspond to the vacua of the maximally supersymmetric mass-deformed M2 brane theory. We find that supersymmetric probe M2 branes polarize into M5 brane shells whose backreaction creates an additional bubble in the geometry. We explicitly check that the supersymmetric polarization potential agrees with the one found within the Polchinski-Strassler approximation. The main result of this paper is that probe M2 branes whose orientation is opposite to the background flux can polarize into metastable M5 brane shells. These decay to a supersymmetric configuration via brane-flux annihilation. Our findings suggest the existence of metastable states in the mass-deformed M2 brane theory.

  18. Hydrodynamic models for slurry bubble column reactors

    Energy Technology Data Exchange (ETDEWEB)

    Gidaspow, D. [IIT Center, Chicago, IL (United States)

    1995-12-31

    The objective of this investigation is to convert a {open_quotes}learning gas-solid-liquid{close_quotes} fluidization model into a predictive design model. This model is capable of predicting local gas, liquid and solids hold-ups and the basic flow regimes: the uniform bubbling, the industrially practical churn-turbulent (bubble coalescence) and the slugging regimes. Current reactor models incorrectly assume that the gas and the particle hold-ups (volume fractions) are uniform in the reactor. They must be given in terms of empirical correlations determined under conditions that radically differ from reactor operation. In the proposed hydrodynamic approach these hold-ups are computed from separate phase momentum balances. Furthermore, the kinetic theory approach computes the high slurry viscosities from collisions of the catalyst particles. Thus particle rheology is not an input into the model.

  19. The Distribution of Bubble Sizes During Reionization

    CERN Document Server

    Lin, Yin; Furlanetto, Steven R; Sutter, P M

    2015-01-01

    A key physical quantity during reionization is the size of HII regions. Previous studies found a characteristic bubble size which increases rapidly during reionization, with apparent agreement between simulations and analytic excursion set theory. Using four different methods, we critically examine this claim. In particular, we introduce the use of the watershed algorithm -- widely used for void finding in galaxy surveys -- which we show to be an unbiased method with the lowest dispersion and best performance on Monte-Carlo realizations of a known bubble size PDF. We find that a friends-of-friends algorithm declares most of the ionized volume to be occupied by a network of volume-filling regions connected by narrow tunnels. For methods tuned to detect those volume-filling regions, previous apparent agreement between simulations and theory is spurious, and due to a failure to correctly account for the window function of measurement schemes. The discrepancy is already obvious from visual inspection. Instead, HI...

  20. CS emission near MIR-bubbles

    CERN Document Server

    Watson, C; Quintanar, N; Candelaria, T

    2016-01-01

    We survey 44 young stellar objects located near the edges of mid-IR-identified bubbles in CS (1-0) using the Green Bank Telescope. We detect emission in 18 sources, indicating young protostars that are good candidates for being triggered by the expansion of the bubble. We calculate CS column densities and abundances. Three sources show evidence of infall through non-Gaussian line-shapes. Two of these sources are associated with dark clouds and are promising candidates for further exploration of potential triggered star formation. We obtained on-the-fly maps in CS (1-0) of three sources, showing evidence of significant interactions between the sources and the surrounding environment.