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Sample records for bubble super heated

  1. Compact, super heat exchanger

    NASA Technical Reports Server (NTRS)

    Fortini, A.; Kazaroff, J. M.

    1980-01-01

    Heat exchanger uses porous media to enhance heat transfer through walls of cooling channels, thereby lowering wall temperature. Porous media within cooling channel increases internal surface area from which heat can be transferred to coolant. Comparison data shows wall has lower temperature and coolant has higher temperature when porous medium is used within heat exchanger. Media can be sintered powedered metal, metal fibers, woven wire layers, or any porous metal having desired permeability and porosity.

  2. Operational comparison of bubble (super heated drop) dosimetry with routine albedo TLD for a selected group of Pu-238 workers at Los Alamos National Laboratory

    SciTech Connect

    Romero, L.L.; Hoffman, J.M.; Foltyn, E.M.; Buhl, T.E.

    1998-09-01

    Personnel neutron dosimetry continues to be a difficult science due to the lack of availability of robust passive dosimeters that exhibit tissue- or near-tissue- equivalent response. This paper is an operational study that compares the use of albedo thermoluminescent dosimeters with bubble dosimeters to determine whether bubble dosimeters do provide a useful daily ALARA tool that can yield measurements close to the dose-of-record. A group of workers at Los Alamos National Laboratory (LANL) working on the Radioisotopic Thermoelectric Generators (RTG) for the NASA Cassini space mission wore both bubble dosimeters and albedo dosimeters over a period from 1993 through 1996. The personal albedo dosimeter was processed on a monthly basis and used as the dose-of-record. The results of this study indicated that cumulative daily bubble dosimetry results agreed with whole-body albedo dosimetry results within about 37% on average.

  3. First observations of super plasma bubbles in Europe

    NASA Astrophysics Data System (ADS)

    Cherniak, Iurii; Zakharenkova, Irina

    2016-11-01

    Ionospheric plasma bubbles of equatorial origin have never been registered at midlatitudes in Europe. During the 22-23 June 2015 geomagnetic storm the prompt penetration electric fields caused the occurrence of plasma bite-outs in the postsunset sector over low latitudes of Western Africa and large-scale plasma bubbles extended toward Europe. For the first time, using multisite GPS and Global Navigation Satellite System observations ( 1500 stations), the super plasma bubble signatures were registered in Europe. They were observed more than 8 h (20-04 UT) and covered a broad area within 30°-40°N and 20°W-10°E. These unique results were confirmed by measurements on board Swarm and DMSP satellites and ground-based absolute total electron content observations. Occurrence of the super plasma bubbles in Europe affected Global Navigation Satellite Systems measurements over a number of stations in Spain, Portugal, southern France, and Italy and led to performance degradation of the European Geostationary Navigation Overlay Service.

  4. Bubble heating in Extreme Cooling Clusters

    NASA Astrophysics Data System (ADS)

    Allen, Steven

    2007-09-01

    Our proposal targets `extreme cooling' clusters: those systems with the largest, fastest cooling rates that most severely challenge the AGN-heating paradigm for cluster cores. By targeting two X-ray bright `extreme cooling cluters' with the clearest radio bubbles in their cores, we seek to establish whether it is possible for AGN heating to balance cooling in such systems. If cooling is not balanced by some heat source, then large residual cooling rates should be detectable in the spectral X-ray data. We will measure the bubble properties precisely and map the spatial-spectral structure of the surrounding X-ray gas, searching for ghost bubbles, shocks, ripples, fronts and non-thermal emission.

  5. Expanding Taylor bubble under constant heat flux

    NASA Astrophysics Data System (ADS)

    Voirand, Antoine; Benselama, Adel M.; Ayel, Vincent; Bertin, Yves

    2016-09-01

    Modelization of non-isothermal bubbles expanding in a capillary, as a contribution to the understanding of the physical phenomena taking place in Pulsating Heat Pipes (PHPs), is the scope of this paper. The liquid film problem is simplified and solved, while the thermal problem takes into account a constant heat flux density applied at the capillary tube wall, exchanging with the liquid film surrounding the bubble and also with the capillary tube outside medium. The liquid slug dynamics is solved using the Lucas-Washburn equation. Mass and energy balance on the vapor phase allow governing equations of bubble expansion to be written. The liquid and vapor phases are coupled only through the saturation temperature associated with the vapor pressure, assumed to be uniform throughout the bubble. Results show an over-heating of the vapor phase, although the particular thermal boundary condition used here always ensures an evaporative mass flux at the liquid-vapor interface. Global heat exchange is also investigated, showing a strong decreasing of the PHP performance to convey heat by phase change means for large meniscus velocities.

  6. Heat transport in bubbling turbulent convection

    PubMed Central

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

    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 give rise to a much-enhanced natural convection. In this article, we focus specifically on this enhancement and present a numerical study of the resulting two-phase Rayleigh–Bénard convection process in a cylindrical cell with a diameter equal to its height. We make no attempt to model other aspects of the boiling process such as bubble nucleation and detachment. The cell base and top are held at temperatures above and below the boiling point of the liquid, respectively. By keeping this difference constant, we study the effect of the liquid superheat in a Rayleigh number range that, in the absence of boiling, would be between 2 × 106 and 5 × 109. We find a considerable enhancement of the heat transfer and study its dependence on the number of bubbles, the degree of superheat of the hot cell bottom, and the Rayleigh number. The increased buoyancy provided by the bubbles leads to more energetic hot plumes detaching from the cell bottom, and the strength of the circulation in the cell is significantly increased. Our results are in general agreement with recent experiments on boiling Rayleigh–Bénard convection. PMID:23696657

  7. Heat transport in bubbling turbulent convection.

    PubMed

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

    2013-06-04

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

  8. Investigation of bubbles in arterial heat pipes

    NASA Technical Reports Server (NTRS)

    Saaski, E. W.

    1972-01-01

    The behavior of gas occlusions in arterial heat pipes has been studied experimentally and theoretically. Specifically, the gas-liquid system properties, solubility and diffusivity, have been measured from -50 to 100 C for helium and argon in ammonia, Freon-21 (CHC12F), and methanol. Properties values obtained were then used to experimentally test models for gas venting from a heat pipe artery under isothermal conditions (i.e., no-heat flow), although the models, as developed, are also applicable to heat pipes operated at power, with some minor modifications. Preliminary calculations indicated arterial bubbles in a stagnant pipe require from minutes to days to collapse and vent. It has been found experimentally that a gas bubble entrapped within an artery structure has a very long lifetime in many credible situations. This lifetime has an approximately inverse exponential dependence on temperature, and is generally considerably longer for helium than for argon. The models postulated for venting under static conditions were in general quantitative agreement with experimental data. Factors of primary importance in governing bubble stability are artery diameter, artery wall thickness, noncondensible gas partial pressure, and the property group (the Ostwald solubility coefficient multiplied by the gas/liquid diffusivity).

  9. A genetic algorithm-based optimization model for pool boiling heat transfer on horizontal rod heaters at isolated bubble regime

    NASA Astrophysics Data System (ADS)

    Alavi Fazel, S. Ali

    2017-03-01

    A new optimized model which can predict the heat transfer in the nucleate boiling at isolated bubble regime is proposed for pool boiling on a horizontal rod heater. This model is developed based on the results of direct observations of the physical boiling phenomena. Boiling heat flux, wall temperature, bubble departing diameter, bubble generation frequency and bubble nucleation site density have been experimentally measured. Water and ethanol have been used as two different boiling fluids. Heating surface was made by several metals and various degrees of roughness. The mentioned model considers various mechanisms such as latent heat transfer due to micro-layer evaporation, transient conduction due to thermal boundary layer reformation, natural convection, heat transfer due to the sliding bubbles and bubble super-heating. The fractional contributions of individual mentioned heat transfer mechanisms have been calculated by genetic algorithm. The results show that at wall temperature difference more that about 3 K, bubble sliding transient conduction, non-sliding transient conduction, micro-layer evaporation, natural convection, radial forced convection and bubble super-heating have higher to lower fractional contributions respectively. The performance of the new optimized model has been verified by comparison of the existing experimental data.

  10. Bubble Dynamics on a Heated Surface

    NASA Technical Reports Server (NTRS)

    Kassemi, Mohammad; Rashidnia, Nasser

    1996-01-01

    In this work, we study the combined thermocapillary and natural convective flow generated by a bubble on a heated solid surface. The interaction between gas and vapor bubbles with the surrounding fluid is of interest for both space and ground-based processing. On earth, the volumetric forces are dominant, especially, in apparatuses with large volume to surface ratio. But in the reduced gravity environment of orbiting spacecraft, surface forces become more important and the effects of Marangoni convection are easily unmasked. In order to delineate the roles of the various interacting phenomena, a combined numerical-experimental approach is adopted. The temperature field is visualized using Mach-Zehnder interferometry and the flow field is observed by a laser sheet flow visualization technique. A finite element numerical model is developed which solves the two-dimensional momentum and energy equations and includes the effects of bubble surface deformation. Steady state temperature and velocity fields predicted by the finite element model are in excellent qualitative agreement with the experimental results. A parametric study of the interaction between Marangoni and natural convective flows including conditions pertinent to microgravity space experiments is presented. Numerical simulations clearly indicate that there is a considerable difference between 1-g and low-g temperature and flow fields induced by the bubble.

  11. Potential Temperature Limitations of Bubble-Enhanced Heating during HIFU

    NASA Astrophysics Data System (ADS)

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

    2010-03-01

    During high-intensity focused ultrasound (HIFU) treatments in the absence of bubbles, tissue is heated by absorption of the incident ultrasound. However, bubbles present at the focus can enhance the rate of heating. One mechanism for such enhanced heating involves inertial bubble collapses that transduce incident ultrasound to higher frequencies that are more readily absorbed. Previously, it has been reported that bubble-enhanced heating diminishes as treatments progress. The objective of this effort is to quantify how inertial bubble collapses are affected as the focal temperature rises during treatment. A model of a single, spherical bubble has been developed to couple the thermodynamic state of a strongly driven spherical bubble with the temperature of the surrounding liquid. This model allows for the dynamic transport of heat, vapor, and non-condensable gases to/from the bubble and has been demonstrated to fit experimental data from the collapses and rebounds of millimeter-sized bubbles over a range of temperature conditions. The responses of micron-sized, air-vapor bubbles in water were simulated under exposure to MHz/MPa HIFU excitation at various surrounding liquid temperatures. Each bubble response was characterized by the power spectral density of its radiated pressure in order to emulate a hydrophone measurement. Simulations suggest that bubble collapses are significantly attenuated at temperatures above about 70° C. For instance, the acoustically radiated energy at 80° C is an order of magnitude less than that at 20° C. Simulations that fully include the effect of vapor on bubbles excited during HIFU suggest that the efficacy of bubble-enhanced heating may be limited to temperatures below 70° C.

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

    NASA Astrophysics Data System (ADS)

    Wu, Chengtian

    With the increasing demand for alternative energy resources, the Fischer-Tropsch (FT) process that converts synthesis gas into clean liquid fuels has attracted more interest from the industry. Slurry bubble columns are the most promising reactors for FT synthesis due to their advantages over other reactors. Successful operation, design, and scale-up of such reactors require detailed knowledge of hydrodynamics, bubble dynamics, and transport characteristics. However, most previous studies have been conducted at ambient pressure or covered only low superficial gas velocities. The objectives of this study were to experimentally investigate the heat transfer coefficient and bubble dynamics in slurry bubble columns at conditions that can mimic FT conditions. The air-C9C 11-FT catalysts/glass beads systems were selected to mimic the physical properties of the gas, liquid, and solid phases at commercial FT operating conditions. A heat transfer coefficient measurement technique was developed, and for the first time, this technique was applied in a pilot scale (6-inch diameter) high pressure slurry bubble column. The effects of superficial gas velocity, pressure, solids loading, and liquid properties on the heat transfer coefficients were investigated. Since the heat transfer coefficient can be affected by the bubble properties (Kumar et al., 1992), in this work bubble dynamics (local gas holdup, bubble chord length, apparent bubble frequency, specific interfacial area, and bubble velocity) were studied using the improved four-point optical probe technique (Xue et al., 2003; Xue, 2004). Because the four-point optical technique had only been successfully applied in a churn turbulent flow bubble column (Xue, 2004), this technique was first assessed in a small scale slurry bubble column in this study. Then the bubble dynamics were studied at the same conditions as the heat transfer coefficient investigation in the same pilot scale column. The results from four-point probe

  13. Neutron field parameter measurements on the JET tokamak by means of super-heated fluid detectors

    SciTech Connect

    Gherendi, M.; Craciunescu, T.; Pantea, A.; Zoita, V. L.; Johnson, M. Gatu; Hellesen, C.; Conroy, S.; Baltog, I.; Edlington, T.; Kiptily, V.; Popovichev, S.; Murari, A.; Collaboration: JET EFDA Contributors

    2012-10-15

    The neutron field parameters (fluence and energy distribution) at a specific location outside the JET Torus Hall have been measured by means of super-heated fluid detectors (or 'bubble detectors') in combination with an independent, time-of-flight, technique. The bubble detector assemblies were placed at the end of a vertical line of sight at about 16 m from the tokamak mid plane. Spatial distributions of the neutron fluence along the radial and toroidal directions have been obtained using two-dimensional arrays of bubble detectors. Using a set of three bubble detector spectrometers the neutron energy distribution was determined over a broad energy range, from about 10 keV to above 10 MeV, with an energy resolution of about 30% at 2.5 MeV. The very broad energy response allowed for the identification of energy features far from the main fusion component (around 2.45 MeV for deuterium discharges).

  14. Heat transfer mechanisms in bubbly Rayleigh-Bénard convection.

    PubMed

    Oresta, Paolo; Verzicco, Roberto; Lohse, Detlef; Prosperetti, Andrea

    2009-08-01

    The heat transfer mechanism in Rayleigh-Bénard convection in a liquid with a mean temperature close to its boiling point is studied through numerical simulations with pointlike 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 Jakob 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.

  15. Heat transfer and bubble dynamics in bubble and slurry bubble columns with internals for Fischer-Tropsch synthesis of clean alternative fuels and chemicals

    NASA Astrophysics Data System (ADS)

    Kagumba, Moses Odongo O.

    Synthesis gas, a mixture of CO and H2 obtained from coal, natural gas and biomass are increasingly becoming reliable sources of clean synthetic fuels and chemicals and via Fischer-Tropsch (F-T) synthesis process. Slurry bubble column reactor is the reactor of choice for the commercialization of the F-T synthesis. Even though the slurry bubble column reactors and contactors are simple in structures, their design, scale-up, operation, and performance prediction are still challenging and not well understood due to complex interaction of phases. All the studies of heat transfer have been performed without simultaneously investigating the bubble dynamics adjacent to the heat transfer surfaces, particularly in slurry with dense internals. This dissertation focuses on enhancing the understanding of the role of local and overall gas holdup, bubble passage frequency, bubble sizes and bubble velocity on the heat transfer characteristics by means of a hybrid measurement technique comprising an advanced four-point optical probe and a fast response heat transfer probe used simultaneously, in the presence and absence of dense internals. It also seeks to advance a mechanistic approach for estimating the needed parameters for predicting the heat transfer rate in two phase and three phase systems. The results obtained suggest that the smaller diameter internals gives higher heat transfer coefficient, higher local and overall gas holdup, bubble passage frequency and specific interfacial area but smaller bubble sizes and lower axial bubble velocities. The presence of dense internals enhances the heat transfer coefficient in both the large and smaller columns, while increased column diameter increases the heat transfer coefficient, axial bubble velocity, local and overall gas holdup, bubble chord lengths and specific interfacial area. Addition of solids (glass beads) leads to increased bubble chord lengths and increase in axial bubble velocity, but a decrease in local and overall gas

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

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  17. Faraday Rotation Measurements of the Super Bubble Associated with the Rosette Nebula

    NASA Astrophysics Data System (ADS)

    Savage, Allison H.; Spangler, S. R.; Fischer, P. D.

    2012-01-01

    The Rosette Nebula is an excellent candidate for studies of super bubbles associated with stellar associations. We made linear polarization measurements of background radio sources with the Expanded Very Large Array (EVLA) to explore the properties of the prominent stellar bubble associated with the Rosette Nebula. We report the results of Faraday rotation measurements of 23 extra-galactic radio sources whose lines of sight pass through or close to the Rosette Nebula. The observations were made at 4.4GHz, 4.9GHz, and 7.6GHz. We are able to establish a background rotation measure due to the galactic plane in the vicinity of the Rosette Nebula of 140 rad/m2. Sources whose lines of sight pass through the nebula have an excess rotation measure of 300 -700 rad/m2, which we attribute to the plasma shell of the Rosette Nebula. We discuss two simple plasma shell models that can account for the magnitude of the rotation measure, and its dependence on distance from the center of the nebula. These two models represent different modes of interaction of the Rosette Nebula star cluster with the surrounding interstellar medium. This research was supported at the University of Iowa by grant AST09-56901 from the National Science Foundation.

  18. Ballistic heat transport in laser generated nano-bubbles.

    PubMed

    Lombard, Julien; Biben, Thierry; Merabia, Samy

    2016-08-04

    Nanobubbles generated by laser heated plasmonic nanoparticles are of interest for biomedical and energy harvesting applications. Of utmost importance is the maximal size of these transient bubbles. Here, we report hydrodynamic phase field simulations of the dynamics of laser induced nanobubbles, with the aim to understand which physical processes govern their maximal size. We show that the nanobubble maximal size and lifetime are to a large extent controlled by the ballistic thermal flux which is present inside the bubble. Taking into account this thermal flux, we can reproduce the fluence dependence of the maximal nanobubble radius as reported experimentally. We also discuss the influence of the laser pulse duration on the number of nanobubbles generated and their maximal size. These studies represent a significant step toward the optimization of the nanobubble size, which is of crucial importance for photothermal cancer therapy applications.

  19. Ballistic heat transport in laser generated nano-bubbles

    NASA Astrophysics Data System (ADS)

    Lombard, Julien; Biben, Thierry; Merabia, Samy

    2016-08-01

    Nanobubbles generated by laser heated plasmonic nanoparticles are of interest for biomedical and energy harvesting applications. Of utmost importance is the maximal size of these transient bubbles. Here, we report hydrodynamic phase field simulations of the dynamics of laser induced nanobubbles, with the aim to understand which physical processes govern their maximal size. We show that the nanobubble maximal size and lifetime are to a large extent controlled by the ballistic thermal flux which is present inside the bubble. Taking into account this thermal flux, we can reproduce the fluence dependence of the maximal nanobubble radius as reported experimentally. We also discuss the influence of the laser pulse duration on the number of nanobubbles generated and their maximal size. These studies represent a significant step toward the optimization of the nanobubble size, which is of crucial importance for photothermal cancer therapy applications.Nanobubbles generated by laser heated plasmonic nanoparticles are of interest for biomedical and energy harvesting applications. Of utmost importance is the maximal size of these transient bubbles. Here, we report hydrodynamic phase field simulations of the dynamics of laser induced nanobubbles, with the aim to understand which physical processes govern their maximal size. We show that the nanobubble maximal size and lifetime are to a large extent controlled by the ballistic thermal flux which is present inside the bubble. Taking into account this thermal flux, we can reproduce the fluence dependence of the maximal nanobubble radius as reported experimentally. We also discuss the influence of the laser pulse duration on the number of nanobubbles generated and their maximal size. These studies represent a significant step toward the optimization of the nanobubble size, which is of crucial importance for photothermal cancer therapy applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/C6NR02144A

  20. Vapor bubble evolution on a heated surface containing open microchannels

    NASA Astrophysics Data System (ADS)

    Forster, Christopher J.; Glezer, Ari; Smith, Marc K.

    2011-11-01

    Power electronics require cooling technologies capable of high heat fluxes at or below the operating temperatures of these devices. Boiling heat transfer is an effective choice for such cooling, but it is limited by the critical heat flux (CHF), which is typically near 125 W/cm2 for pool boiling of water on a flat plate at standard pressure and gravity. One method of increasing CHF is to incorporate an array of microchannels into the heated surface. Microchannels have been experimentally shown to improve CHF, and the goal of this study is to determine the primary mechanisms associated with the microchannels that allow for the increased CHF. While the use of various microstructures is not new, the emphasis of previous work has been on heat transfer aspects, as opposed to the fluid dynamics inside and in the vicinity of the microchannels. This work considers the non-isothermal fluid motion during bubble growth and departure by varying channel geometry, spacing, and heat flux input using a level-set method including vaporization and condensation. These results and the study of the underlying mechanisms will aid in the design optimization of microchannel-based cooling devices. Supported by ONR.

  1. Bubble nucleation in superhydrophobic microchannels due to subcritical heating

    NASA Astrophysics Data System (ADS)

    Cowley, Adam; Maynes, Daniel; Crockett, Julie; Iverson, Brian

    2016-11-01

    We report on experiments that investigate the effects of heating on laminar flow in superhydrophobic (SH) microchannels. The parallel plate microchannels (180 μm spacing) consist of two surfaces: a rib/cavity structured SH surface and a smooth glass surface. The back of the SH surface is in contact with an aluminum strip that is heated and a camera is used to image through the glass surface to visualize the flow. Thermocouples embedded in the aluminum obtain the temperature profile along the length of the channel. The friction factor-Reynolds product (fRe) is obtained via pressure drop and volumetric flow rate measurements. Five surface types/configurations are investigated: smooth hydrophilic, smooth hydrophobic, SH with ribs perpendicular to the flow, SH with ribs parallel to the flow, and SH with both ribs parallel to the flow and sparse ribs perpendicular to the flow. Both degassed and air-saturated water are used. When air-saturated water is used, the cavities of the SH surfaces act as nucleation sites and air is desorbed out of the water. Depending on the surface type/configuration, large bubbles can form and result in a large increase in fRe and channel surface temperatures. When degassed water is used no bubble nucleation is observed, however, the air trapped in the cavities of the SH surfaces is quickly absorbed and the surfaces transition to a wetted state. This research was supported by the National Science Foundation (NSF) (Grant No. CBET-1235881).

  2. Bubbles

    NASA Astrophysics Data System (ADS)

    Prosperetti, Andrea

    2004-06-01

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

  3. Interaction of two cavitation bubbles in a tube and its effects on heat transfer

    NASA Astrophysics Data System (ADS)

    Liu, Bin; Cai, Jun; Tao, Yuequn; Huai, Xiulan

    2017-02-01

    When two cavitation bubbles exist in a confined space, the interaction between the bubbles significantly affects the characteristics of bubble dynamic behaviors. In this paper, a three-dimensional (3D) model is established to study the growth and collapse of two cavitation bubbles in a heated tube and its effects on heat transfer. The liquid and gas phases throughout the calculation domain are solved by a set of Navier-Stokes equations. It is assumed that the gas inside the bubble is compressible vapor, and the surrounding liquid is incompressible water. The mass transfer between two phases is ignored. The calculated bubble profiles were compared to the available experimental data, and a good agreement has been achieved. Then, the relationship among the bubble motion, flow field and pressure distributions was analyzed. On this basis, the effects of bubble interaction on the heat transfer between the wall surface and sounding liquid were discussed. It is found that heat transfer in the centre wall region is enhanced owing to the vortex flow and micro-jet induced by the bubble contraction and collapse. In contrast, the highest surface temperature appears in the surrounding region, which is mainly attributed to the thermal resistance induced by the bubble. The present study is helpful to understand the heat transfer phenomenon with cavitation in the liquid.

  4. Bubble Departure from Metal-Graphite Composite Surfaces and Its Effects on Pool Boiling Heat Transfer

    NASA Technical Reports Server (NTRS)

    Chao, David F.; Sankovic, John M.; Motil, Brian J.; Yang, W-J.; Zhang, Nengli

    2010-01-01

    The formation and growth processes of a bubble in the vicinity of graphite micro-fiber tips on metal-graphite composite boiling surfaces and their effects on boiling behavior are investigated. It is discovered that a large number of micro bubbles are formed first at the micro scratches and cavities on the metal matrix in pool boiling. By virtue of the non-wetting property of graphite, once the growing micro bubbles touch the graphite tips, the micro bubbles are sucked by the tips and merged into larger micro bubbles sitting on the end of the tips. The micro bubbles grow rapidly and coalesce to form macro bubbles, each spanning several tips. The necking process of a detaching macro bubble is analyzed. It is revealed that a liquid jet is produced by sudden break-off of the bubble throat. The composite surfaces not only have higher temperatures in micro- and macrolayers but also make higher frequency of the bubble departure, which increase the average heat fluxes in both the bubble growth stage and in the bubble departure period. Based on these analyses, the enhancement mechanism of pool boiling heat transfer on composite surfaces is clearly revealed.

  5. Development of a Parching Machine Using Super-Heated Vapor or Super-Heated High-Moisture Atmosphere

    NASA Astrophysics Data System (ADS)

    Sato, Shoichi; Shinsho, Seiji; Iriki, Hiroyuki; Asai, Junya; Suganuma, Hirofumi; Shibata, Tsutomu

    We developed a new parching machine with super-heated vapor or super-heated highmoisture atmosphere as a heat medium, and investigated the influence exerted on the characteristics of manufactured tea and crude tea quality. (1)We developed machine specifications that improved throughput and allowed us to control stable quality compared with the conventional kamairicha parching machine. (2)The new parching machine could not only manufacture like kamairicha but also achieve various degrees of steaming of products like green tea or heavily steamed sencha. (3)The new parching machine could not only deactivate enzymes but dry leaves. (4)The influence of throughput was great with respect to the grade of pan-parched flavour, which meant that there was a contact opportunity for tea leaves and the surface of machine's wall. (5)Unpleasant smells such as that produced in a summer crop of tea were reduced by the new parching machine.

  6. Cryogenic Liquid Experiments in Orbit. Volume 2. Bubble Mechanics, Boiling Heat Transfer, and Propellant Tank Venting in a Zero-Gravity Environment

    DTIC Science & Technology

    1966-12-01

    Thermophoresis Experimental Apparatus . . . 27 8 Bubble Thermophoresis Lighting and Viewing Schematic ....... ..................... .... 28 9 Bubble... Thermophoresis Experimental Apparatus (with- out bubble holder) ...... ................ ... 29 10 Bubble Force Experiment Bubble Insertion Technique (Expanded View...several interesting and important ef- fects in bubble behavior and boiling heat transfer. These ef- fects are discussed below. 2. Bubble Thermophoresis

  7. Bubbly flow velocity measurements near a heated cylindrical conductor

    SciTech Connect

    Canaan, R.E.; Hassan, Y.A. )

    1990-01-01

    The objective of this study is to apply recent advances and improvements in the digital pulsed laser velocimetry (DPLV) technique to the analysis of two-phase bubbly flow about a cylindrical conductor emitting a constant heat flux within a transparent rectangular enclosure. Pulsed laser velocimetry is a rapidly advancing fluid flow visualization technique that determines full-field instantaneous velocity vectors of a quantitative nature such that the flow field remains undisturbed by the measurement. The DPLV method offers several significant advantages over more traditional fluid velocity measurement techniques such as hot wire/film anemometry and laser Doppler anemometry because reliable instantaneous velocity data may be acquired over substantial flow areas in a single experiment.

  8. Tidal heating of young super-Earth atmospheres

    NASA Astrophysics Data System (ADS)

    Ginzburg, Sivan; Sari, Re'em

    2017-02-01

    Short-period Earth to Neptune-sized exoplanets (super-Earths) with voluminous gas envelopes seem to be very common. These gas atmospheres are thought to have originated from the protoplanetary disc in which the planets were embedded during their first few million years. The accretion rate of gas from the surrounding nebula is determined by the ability of the gas to cool and radiate away its gravitational energy. Here, we demonstrate that heat from the tidal interaction between the star and the young (and therefore inflated) planet can inhibit the gas cooling and accretion. Quantitatively, we find that the growth of super-Earth atmospheres halts for planets with periods of about 10 d, provided that their initial eccentricities are of the order of 0.2. Thus, tidal heating provides a robust and simple mechanism that can simultaneously explain why these planets did not become gas giants and account for the deficit of low-density planets closer to the star, where the tides are even stronger. We suggest that tidal heating may be as important as other factors (such as the nebula's lifetime and atmosphere evaporation) in shaping the observed super-Earth population.

  9. Ultrasonic effect on the bubble nucleation and heat transfer of oscillating nanofluid

    SciTech Connect

    Zhao, Nannan; Fu, Benwei; Ma, H. B.

    2014-06-30

    Ultrasonic sound effect on bubble nucleation, oscillating motion activated by bubble formation, and its heat transfer enhancement of nanofluid was experimentally investigated. Nanofluid consists of distilled water and dysprosium (III) oxide (Dy{sub 2}O{sub 3}) nanoparticles with an average size of 98 nm and a mass ratio of 0.5%. Visualization results demonstrate that when the nanoparticles are added in the fluid influenced by the ultrasonic sound, bubble nucleation can be significantly enhanced. The oscillating motion initiated by the bubble formation of nanofluid under the influence of ultrasonic sound can significantly enhance heat transfer of nanofluid in an interconnected capillary loop.

  10. Atmospheric heating in an irradiated transiting super-Earth and super-Neptune

    NASA Astrophysics Data System (ADS)

    Miller, Brendan

    2014-09-01

    We propose Chandra observations of HD 97658 (13 ks) and HAT-P-11 (8 ks) to determine the high-energy radiation incident upon their short-period transiting planets. HD 97658 b is a hot super-Earth with a density between Earth and ice giants, while HAT-P-11 b is a hot super-Neptune orbiting an active K4 star. Measurement of the stellar X-ray (and UV; we contribute Swift time) luminosities provides a current epoch estimate of atmospheric heating and constrains whether these planets are likely to experience significant mass loss through atmospheric evaporation over their total lifetimes. These observations provide essential empirical input for understanding and modeling the potential evolutionary transformation of hot gas giants into less massive and more dense remnants.

  11. Atmospheric heating in an irradiated transiting super-Earth and super-Neptune

    NASA Astrophysics Data System (ADS)

    Miller, Brendan P.; Gallo, Elena; Wright, Jason; Poppenhaeger, Katja

    2016-01-01

    We present new Chandra observations of HD 97658 (13 ks) and HAT-P-11 (8 ks), obtained to determine the high-energy radiation incident upon their short-period transiting planets. HD 97658 b is a hot super-Earth with a density between Earth and ice giants, while HAT-P-11 b is a hot super-Neptune orbiting an active K4 star. Our measurement of the stellar X-ray (and UV, from Swift) luminosities provides a current epoch estimate of atmospheric heating. We discuss whether these planets are likely to have experienced significant mass loss through atmospheric evaporation over their total lifetimes. These observations provide essential empirical input for understanding and modeling the potential evolutionary transformation of hot gas giants into less massive and more dense remnants.

  12. Heat transfer during bubble shrinking in saturated He II under microgravity condition

    NASA Astrophysics Data System (ADS)

    Takada, S.; Kimura, N.; Murakami, M.; Okamura, T.

    2015-12-01

    Microgravity experiments of He II boiling were carried out using a drop tower. The process of bubble shrinking in He II in microgravity was observed by a high speed camera. The time duration of the microgravity environment less than 1 mg was about 1.3 sec. First, a large spherical bubble of about 10 mm in diameter was created by a short wire heater (Diameter 0.05 x Length 2.82 mm) for a heating time of 0.4 sec. The subsequent bubble shrinking was visualized after the heater was switched off. The time variation of the volume of bubble was estimated by image analysis. The shrinking speed of bubble was calculated from these time variation data. The shrinking speed depends on the heat flux across the liquid-vapor interface. It is found that the heat flux across the interface in microgravity can be explained by the kinetic theory with a pressure difference due to surface tension.

  13. Super-Joule heating in graphene and silver nanowire network

    SciTech Connect

    Maize, Kerry; Das, Suprem R.; Sadeque, Sajia; Mohammed, Amr M. S.; Shakouri, Ali E-mail: alam@purdue.edu; Janes, David B.; Alam, Muhammad A. E-mail: alam@purdue.edu

    2015-04-06

    Transistors, sensors, and transparent conductors based on randomly assembled nanowire networks rely on multi-component percolation for unique and distinctive applications in flexible electronics, biochemical sensing, and solar cells. While conduction models for 1-D and 1-D/2-D networks have been developed, typically assuming linear electronic transport and self-heating, the model has not been validated by direct high-resolution characterization of coupled electronic pathways and thermal response. In this letter, we show the occurrence of nonlinear “super-Joule” self-heating at the transport bottlenecks in networks of silver nanowires and silver nanowire/single layer graphene hybrid using high resolution thermoreflectance (TR) imaging. TR images at the microscopic self-heating hotspots within nanowire network and nanowire/graphene hybrid network devices with submicron spatial resolution are used to infer electrical current pathways. The results encourage a fundamental reevaluation of transport models for network-based percolating conductors.

  14. Bubble dynamics and heat transfer for pool boiling on hydrophilic, superhydrophobic and biphilic surfaces

    NASA Astrophysics Data System (ADS)

    Teodori, E.; Palma, T.; Valente, T.; Moita, A. S.; Moreira, A. L. N.

    2016-09-01

    This paper proposes a detailed analysis of bubble dynamics to describe pool boiling heat transfer in extreme wetting scenarios (superhydrophobic vs hydrophilic). A mechanistic approach, based on extensive post-processing allows quantifying the relative advantage of the superhydrophobic surfaces to endorse the onset of boiling at very low superheats (1-2K) vs their worse heat transfer performance associated to the swift formation of an insulating vapour film. Based on this analysis, a simple biphilic surface is created. The results suggest that for high heat fluxes, bubble dynamics is dominated by the emission of very small bubbles, which seems to affect the interaction mechanisms, precluding the emission of the large bubbles from the surface, thus compromising the good performance of the biphilic surfaces.

  15. Nanoscale dynamics of Joule heating and bubble nucleation in a solid-state nanopore.

    PubMed

    Levine, Edlyn V; Burns, Michael M; Golovchenko, Jene A

    2016-01-01

    We present a mathematical model for Joule heating of an electrolytic solution in a nanopore. The model couples the electrical and thermal dynamics responsible for rapid and extreme superheating of the electrolyte within the nanopore. The model is implemented numerically with a finite element calculation, yielding a time and spatially resolved temperature distribution in the nanopore region. Temperatures near the thermodynamic limit of superheat are predicted to be attained just before the explosive nucleation of a vapor bubble is observed experimentally. Knowledge of this temperature distribution enables the evaluation of related phenomena including bubble nucleation kinetics, relaxation oscillation, and bubble dynamics.

  16. The heat-pipe resembling action of boiling bubbles in endovenous laser ablation.

    PubMed

    van der Geld, Cees W M; van den Bos, Renate R; van Ruijven, Peter W M; Nijsten, Tamar; Neumann, H A Martino; van Gemert, Martin J C

    2010-11-01

    Endovenous laser ablation (EVLA) produces boiling bubbles emerging from pores within the hot fiber tip and traveling over a distal length of about 20 mm before condensing. This evaporation-condensation mechanism makes the vein act like a heat pipe, where very efficient heat transport maintains a constant temperature, the saturation temperature of 100 degrees C, over the volume where these non-condensing bubbles exist. During EVLA the above-mentioned observations indicate that a venous cylindrical volume with a length of about 20 mm is kept at 100 degrees C. Pullback velocities of a few mm/s then cause at least the upper part of the treated vein wall to remain close to 100 degrees C for a time sufficient to cause irreversible injury. In conclusion, we propose that the mechanism of action of boiling bubbles during EVLA is an efficient heat-pipe resembling way of heating of the vein wall.

  17. Study of Critical Heat Flux Mechanism in Flow Boiling Using Bubble Crowding Model

    NASA Astrophysics Data System (ADS)

    Kinoshita, Hidetaka; Nariai, Hideki; Inasaka, Fujio

    Critical heat flux (CHF) of Subcooled Flow Boiling with water in a tube was investigated from the viewpoint of mechanistic models. The Weisman-Pei bubble crowding model was selected to predict CHF in a short tube and in a tube with an internal twisted tape under nonuniform heating conditions, Based on the results of bubble behavior observation and preliminary analysis. The original Weisman-Pei model was modified in order to explain the physical phenomena of CHF. The modified model predicted well CHF in a smooth tube including the very short tube and the tube with an internal twisted tape under uniform and nonuniform heating conditions.

  18. Stationary bubble formation and Marangoni convection induced by CW laser heating of a single gold nanoparticle.

    PubMed

    Setoura, Kenji; Ito, Syoji; Miyasaka, Hiroshi

    2017-01-05

    Gold nanoparticles (Au NPs) efficiently convert incident light into heat under the resonant conditions of localized surface plasmon. Controlling mass transfer through plasmonic heating of Au NPs has potential applications such as manipulation and fabrication within a small space. Here, we describe the formation of stationary microbubbles and subsequent fluid convection induced by CW laser heating of Au NPs in water. Stationary bubbles of about 1-20 μm in diameter were produced by irradiating individual Au NPs with a CW laser. Spatial profiles and velocity distribution of fluid convection around the microbubbles were visualized by the wide-field fluorescence imaging of tracer nanospheres. To evaluate the bubble-induced convection, numerical simulations were performed on the basis of general heat diffusion and Navier-Stokes equations. A comparison between the experimental and computational results revealed that a temperature derivative of surface tension at the bubble surface is a key factor to control the fluid convection. Temperature differences of a few Kelvin at the bubble surface resulted in convective velocities ranging from 10(2) to 10(3) μm s(-1). The convective velocity gradually increased with increasing bubble diameter. This article covers both natural and Marangoni convection induced by plasmonic heating of Au NPs.

  19. A Nonlinear Super-Exponential Rational Model of Speculative Financial Bubbles

    NASA Astrophysics Data System (ADS)

    Sornette, D.; Andersen, J. V.

    Keeping a basic tenet of economic theory, rational expectations, we model the nonlinear positive feedback between agents in the stock market as an interplay between nonlinearity and multiplicative noise. The derived hyperbolic stochastic finite-time singularity formula transforms a Gaussian white noise into a rich time series possessing all the stylized facts of empirical prices, as well as accelerated speculative bubbles preceding crashes. We use the formula to invert the two years of price history prior to the recent crash on the Nasdaq (April 2000) and prior to the crash in the Hong Kong market associated with the Asian crisis in early 1994. These complex price dynamics are captured using only one exponent controlling the explosion, the variance and mean of the underlying random walk. This offers a new and powerful detection tool of speculative bubbles and herding behavior.

  20. Holographic interferometric study of heat transfer to a vapor bubble sliding along a downward facing heater surface

    NASA Astrophysics Data System (ADS)

    Manickam, Sathish Kumar

    Mechanistic modeling of heterogeneous boiling requires understanding of bubble nucleation, growth and departure from the heater surfaces. Often due to the nature of flow or heater geometry, bubbles upon leaving their nucleation sites, slide along the heater surface before eventual lift-off. In such cases understanding of bubble growth and its effect on heat transfer from the surface becomes very important part of mechanistic models. In this work an attempt is made to study the heat transfer associated with single vapor bubbles sliding along downward facing heater surfaces. Heater surface is made of polished silicon wafer, with a set of foil-heaters attached at the back. The surface can be tilted to a required angle of inclination. By controlling the power to these heaters the surface can be maintained at different wall superheats. Experiments were conducted with PF-5060 as test liquid, for liquid subcoolings ranging from 0.2 to 1.2°C and wall superheats from 0.2 to 0.8°C. Single bubbles were generated on an artificial cavity at the lower end of the heater surface. High-speed digital photography was used to measure the size of the bubbles and obtain the bubble growth rate. Temperature field in the liquid around the sliding bubble was measured non-intrusively using holographic interferometry. Heat transfer into the sliding vapor bubble is obtained from the interferometry fringes. Results show that for the range of parameters considered the bubbles continue to grow, with rates of growth decreasing with increasing liquid subcooling. Heat transfer measurements show that condensation occurs on most of the bubble interface away from the wall. Condensation accounts for less than 12% of the heat transfer from the bubble base. Results also show an increase in the area averaged heat flux values of about one to two orders of magnitude, with the presence of the vapor bubbles compared to that of natural convection. The heater surface showed no drop in temperature as a result

  1. Heat transfer between immiscible liquids enhanced by gas bubbling. [PWR; BWR

    SciTech Connect

    Greene, G.A.; Schwarz, C.E.; Klages, J.; Klein, J.

    1982-08-01

    The phenomena of core-concrete interactions impact upon containment integrity of light water reactors (LWR) following postulated complete meltdown of the core by containment pressurization, production of combustible gases, and basemat penetration. Experiments have been performed with non-reactor materials to investigate one aspect of this problem, heat transfer between overlying immiscible liquids whose interface is disturbed by a transverse non-condensable gas flux emanating from below. Hydrodynamic studies have been performed to test a criterion for onset of entrainment due to bubbling through the interface and subsequent heat transfer studies were performed to assess the effect of bubbling on interfacial heat transfer rates, both with and without bubble induced entrainment. Non-entraining interfacial heat transfer data with mercury-water/oil fluid pairs were observed to be bounded from below within a factor of two to three by the Szekeley surface renewal heat transfer model. However heat transfer data for fluid pairs which are found to entrain (water-oil), believed to be characteristic of molten reactor core-concrete conditions, were measured to be up to two orders of magnitude greater than surface renewal predictions and are calculated by a simple entrainment heat transfer model.

  2. Preliminary wall heat transfer measurements and visualization of bubble growth and departure: Saturated nucleate boiling of FC-72

    SciTech Connect

    Bae, S.W.; Kim, J.; Mullen, J.D.; Kim, M.H.

    1999-07-01

    A visualization study of single bubbles growing on a microscale heater array kept at nominally constant temperature was performed. The heater array consisted of 96 heaters each 0.27 mm x 0.27 mm in size. The heater temperatures were kept constant using electronic feedback loops similar to those used in hot-wire anemometry and the power required to do this was measured throughout the bubble departure cycle for each heater in the array. Preliminary data taken at a wall superheat of 29 C resulted in boiling in the isolated bubble regime on the surface. A snapshot of boiling on the surface is seen in Figure A-1. Three types of bubble behavior were observed. The bubbles nucleating in the upper left and lower left corners of the array did not appear to be influenced by bubbles that had departed previously, nor by other bubbles on the heater (Type I behavior). The bubbles nucleating from the single site towards the center of the array were influenced by the wake of the bubble that had departed previously (Type II behavior). The bubbles nucleating in the upper and lower right corners nucleated and grew on separate sites, then merged to form a single large bubble that departed the surface (Type III behavior). Large amounts of heat transfer were associated with three processes during the bubble departure cycle-bubble nucleation, shrinking of the dry spot before departure, and merging of bubbles. The heat transfer mechanisms seen are often not accounted for in many of the current models.

  3. Nanoscale Dynamics of Joule heating and Bubble Nucleation in a Solid-State Nanopore

    PubMed Central

    Levine, Edlyn V.; Burns, Michael M.; Golovchenko, Jene A.

    2016-01-01

    We present a mathematical model for Joule heating of an electrolytic solution in a nanopore. The model couples the electrical and thermal dynamics responsible for rapid and extreme superheating of the electrolyte within the nanopore. The model is implemented numerically with a finite element calculation, yielding a time and spatially resolved temperature distribution in the nanopore region. Temperatures near the thermodynamic limit of superheat are predicted to be attained just before the explosive nucleation of a vapor bubble is observed experimentally. Knowledge of this temperature distribution enables the evaluation of related phenomena including bubble nucleation kinetics, relaxation oscillation, and bubble dynamics. PACS numbers 47.55.dp, 47.55.db, 85.35.-p, 05.70Fh PMID:26871171

  4. Bubble dynamics, two-phase flow, and boiling heat transfer in a microgravity environment

    NASA Technical Reports Server (NTRS)

    Chung, Jacob N.

    1994-01-01

    The two-phase bubbly flow and boiling heat transfer in microgravity represents a substantial challenge to scientists and engineers and yet there is an urgent need to seek fundamental understanding in this area for future spacecraft design and space missions. At Washington State University, we have successfully designed, built and tested a 2.1 second drop tower with an innovation airbag deceleration system. Microgravity boiling experiments performed in our 0.6 second Drop Tower produced data flow visualizations that agree with published results and also provide some new understanding concerning flow boiling and microgravity bubble behavior. On the analytical and numerical work, the edge effects of finite divergent electrode plates on the forces experienced by bubbles were investigated. Boiling in a concentric cylinder microgravity and an electric field was numerically predicted. We also completed a feasibility study for microgravity boiling in an acoustic field.

  5. The effect of flow pattern around a bubble rising near a vertical wall, on the wall to liquid heat transfer

    NASA Astrophysics Data System (ADS)

    Bhuvankar, Pramod; Dabiri, Sadegh

    2016-11-01

    Two-phase flow is an effective means for heat removal due to the enhanced convective effect caused by bubbly flow and the usually high latent heat of vaporization of the liquid phase. We present a numerical study of the effect of flow patterns around a single bubble rising in shear flow near a vertical wall, on the wall-to-liquid heat transfer. The Navier-Stokes equations are solved in a frame of reference moving with the bubble, by using the front tracking method for interface tracking. Our simulations reveal an enhancement of heat transfer downstream of the bubble, and a less pronounced diminishment of heat transfer upstream of the bubble. We observe that in the range of 5 <= Re <= 40 for Reynolds number based on shear and bubble diameter, heat transfer first increases, attains a maximum and decreases as Re increases. The optimum Re depends on the Archimedes number. The heat transfer enhancement is attributed to flow reversal happening in a confined region of the shear flow, in the presence of a bubble. The analytical solution of 2 - D inviscid shear flow over a cylinder near a wall is used to identify two parameters of flow reversal namely 'reversal height' and 'reversal width'. These parameters are then used to qualitatively explain what we observe in 3 - D simulations.

  6. Vapor Bubbles

    NASA Astrophysics Data System (ADS)

    Prosperetti, Andrea

    2017-01-01

    This article reviews the fundamental physics of vapor bubbles in liquids. Work on bubble growth and condensation for stationary and translating bubbles is summarized and the differences with bubbles containing a permanent gas stressed. In particular, it is shown that the natural frequency of a vapor bubble is proportional not to the inverse radius, as for a gas bubble, but to the inverse radius raised to the power 2/3. Permanent gas dissolved in the liquid diffuses into the bubble with strong effects on its dynamics. The effects of the diffusion of heat and mass on the propagation of pressure waves in a vaporous bubbly liquid are discussed. Other topics briefly touched on include thermocapillary flow, plasmonic nanobubbles, and vapor bubbles in an immiscible liquid.

  7. Environmental Forcing of Super Typhoon Paka's (1997) Latent Heat Structure

    NASA Technical Reports Server (NTRS)

    Rodgers, Edward B.; Olson, William; Halverson, Jeff; Simpson, Joanne; Pierce, Harold

    1999-01-01

    The distribution and intensity of total (i.e., combined stratified and convective processes) rainrate/latent heat release (LHR) were derived for tropical cyclone Paka during the period 9-21 December, 1997 from the F-10, F-11, F-13, and F-14 Defense Meteorological Satellite Special Sensor Microwave/Imager and the Tropical Rain Measurement Mission Microwave Imager observations. These observations were frequent enough to capture three episodes of inner core convective bursts that preceded periods of rapid intensification and a convective rainband (CRB) cycle. During these periods of convective bursts, satellite sensors revealed that the rainrates/LHR: 1) increased within the inner eye wall region; 2) were mainly convectively generated (nearly a 65% contribution), 3) propagated inwards; 4) extended upwards within the middle and upper-troposphere, and 5) became electrically charged. These factors may have caused the eye wall region to become more buoyant within the middle and upper-troposphere, creating greater cyclonic angular momentum, and, thereby, warming the center and intensifying the system. Radiosonde measurements from Kwajalein Atoll and Guam, sea surface temperature observations, and the European Center for Medium Range Forecast analyses were used to examine the necessary and sufficient condition for initiating and maintaining these inner core convective bursts. For example, the necessary conditions such as the atmospheric thermodynamics (i.e., cold tropopause temperatures, moist troposphere, and warm SSTs [greater than 26 deg]) suggested that the atmosphere was ideal for Paka's maximum potential intensity (MPI) to approach super-typhoon strength. Further, Paka encountered weak vertical wind shear (less than 15 m/s ) before interacting with the westerlies on 21 December. The sufficient conditions, on the other hand, appeared to have some influence on Paka's convective burst, but the horizontal moisture flux convergence values in the outer core were weaker than

  8. The role of buoyancy orientation on bubble residence times and the related critical heat flux

    SciTech Connect

    Brusstar, M.J.; Merte, H. Jr.; Keller, R.B.

    1995-12-31

    Measurements of the effects of buoyancy orientation on the critical heat flux (CHF) in subcooled forced convection boiling of R113 are presented, examining the motion of the vapor above the heater surface and its possible influence on the feed of liquid to the surface. At the low flow velocity of 4 cm/s used, the buoyancy force acting on the vapor dominates over the flow inertia, and the measured CHF values show a strong dependence on the orientation of the heater surface with respect to gravity. The transient and time-averaged behavior of the vapor above the surface at heat flux levels close to the CHF is characterized using hot wire anemometry. Through this, a description of the behavior of the largest vapor bubbles is obtained, which is considered to be of primary importance to the processes by which liquid is fed to the heater surface at these high heat flux levels. The mean residence time of the largest bubbles above the heater surface at a given heater orientation is also determined from the hot wire data. The reciprocal of the mean residence time is found to correlate directly with the measured CHF values for the different orientations and subcoolings, showing that the amount of energy absorbed in the vapor formation process during the bubble residence time is constant for all heater orientations at a given subcooling, and demonstrates that the motion of the largest bubbles determines the CHF. This suggests that the relative effects of buoyancy orientation on the CHF can be modeled by considering only the motion of the largest bubbles in the immediate vicinity of the heater surface.

  9. The heat-pipe resembling action of boiling bubbles in endovenous laser ablation

    PubMed Central

    van den Bos, Renate R.; van Ruijven, Peter W. M.; Nijsten, Tamar; Neumann, H. A. Martino; van Gemert, Martin J. C.

    2010-01-01

    Endovenous laser ablation (EVLA) produces boiling bubbles emerging from pores within the hot fiber tip and traveling over a distal length of about 20 mm before condensing. This evaporation-condensation mechanism makes the vein act like a heat pipe, where very efficient heat transport maintains a constant temperature, the saturation temperature of 100°C, over the volume where these non-condensing bubbles exist. During EVLA the above-mentioned observations indicate that a venous cylindrical volume with a length of about 20 mm is kept at 100°C. Pullback velocities of a few mm/s then cause at least the upper part of the treated vein wall to remain close to 100°C for a time sufficient to cause irreversible injury. In conclusion, we propose that the mechanism of action of boiling bubbles during EVLA is an efficient heat-pipe resembling way of heating of the vein wall. PMID:20644976

  10. [Influence of infra-red and super high frequency heating on food value of the beef meat].

    PubMed

    Beliaeva, M A

    2005-01-01

    In clause results of research of influence infrared and super high frequency heating on amino acid, fatty fabric and mineral; substances fresh beef are shown meat, after infra-red and the super high frequency of processing, also are shown influence of various modes infra-red heating of processing on amino acid of meat. Advantage of an infra-red way of processing is shown in comparison with super high frequency heating.

  11. Dislocation “Bubble-Like-Effect” and the Ambient Temperature Super-plastic Elongation of Body-centred Cubic Single Crystalline Molybdenum

    PubMed Central

    Lu, Yan; Xiang, Sisi; Xiao, Lirong; Wang, Lihua; Deng, Qingsong; Zhang, Ze; Han, Xiaodong

    2016-01-01

    With our recently developed deformation device, the in situ tensile tests of single crystal molybdenum nanowires with various size and aspect ratio were conducted inside a transmission electron microscope (TEM). We report an unusual ambient temperature (close to room temperature) super-plastic elongation above 127% on single crystal body-centred cubic (bcc) molybdenum nanowires with an optimized aspect ratio and size. A novel dislocation “bubble-like-effect” was uncovered for leading to the homogeneous, large and super-plastic elongation strain in the bcc Mo nanowires. The dislocation bubble-like-effect refers to the process of dislocation nucleation and annihilation, which likes the nucleation and annihilation process of the water bubbles. A significant plastic deformation dependence on the sample’s aspect ratio and size was revealed. The atomic scale TEM observations also demonstrated that a single crystal to poly-crystal transition and a bcc to face-centred cubic phase transformation took place, which assisted the plastic deformation of Mo in small scale. PMID:26956918

  12. Modelling of heat flux received by a bubble pump of absorption-diffusion refrigeration cycles

    NASA Astrophysics Data System (ADS)

    Benhmidene, Ali; Chaouachi, Béchir; Gabsi, Slimane; Bourouis, Mahmoud

    2011-11-01

    In the present study, the heat flux received by a bubble pump, which was simulated to a vertical tube 1 m long and with a variable diameter, was optimized. A numerical study was carried out in order to solve balance equations concerning the water-ammonia mixture in the up flow. The two-fluid model was used to derive the equations. A numerical study was carried out on a heat flux between 1 and 70 kW m-2 and the liquid velocity was determined. The optimum flux was determined for a tube diameter equal to 4, 6, 8 and 10 mm and a mass flow rate ranging from 10 to 90 kg m-2 s-1. The optimum heat flux was correlated as a function of the tube diameter and mass flow rate, while the minimum heat flux required for pumping was correlated as a function of the tube diameter.

  13. Bubble and bubble cloud dynamics

    NASA Astrophysics Data System (ADS)

    Matsumoto, Yoichiro

    2000-07-01

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

  14. Bubble Dynamics, Two-Phase Flow, and Boiling Heat Transfer in Microgravity

    NASA Technical Reports Server (NTRS)

    Chung, Jacob N.

    1998-01-01

    This report contains two independent sections. Part one is titled "Terrestrial and Microgravity Pool Boiling Heat Transfer and Critical heat flux phenomenon in an acoustic standing wave." Terrestrial and microgravity pool boiling heat transfer experiments were performed in the presence of a standing acoustic wave from a platinum wire resistance heater using degassed FC-72 Fluorinert liquid. The sound wave was created by driving a half wavelength resonator at a frequency of 10.15 kHz. Microgravity conditions were created using the 2.1 second drop tower on the campus of Washington State University. Burnout of the heater wire, often encountered with heat flux controlled systems, was avoided by using a constant temperature controller to regulate the heater wire temperature. The amplitude of the acoustic standing wave was increased from 28 kPa to over 70 kPa and these pressure measurements were made using a hydrophone fabricated with a small piezoelectric ceramic. Cavitation incurred during experiments at higher acoustic amplitudes contributed to the vapor bubble dynamics and heat transfer. The heater wire was positioned at three different locations within the acoustic field: the acoustic node, antinode, and halfway between these locations. Complete boiling curves are presented to show how the applied acoustic field enhanced boiling heat transfer and increased critical heat flux in microgravity and terrestrial environments. Video images provide information on the interaction between the vapor bubbles and the acoustic field. Part two is titled, "Design and qualification of a microscale heater array for use in boiling heat transfer." This part is summarized herein. Boiling heat transfer is an efficient means of heat transfer because a large amount of heat can be removed from a surface using a relatively small temperature difference between the surface and the bulk liquid. However, the mechanisms that govern boiling heat transfer are not well understood. Measurements of

  15. Pore-network study of bubble growth in porous media driven by heat transfer

    SciTech Connect

    Satik, C.; Yortsos, Y.C.

    1996-05-01

    We present experimental and theoretical investigations of vapor phase growth in pore-network models of porous media. Visualization experiments of boiling of ethyl alcohol in horizontal etched-glass micromodels were conducted. The vapor phase was observed to grow into a disordered pattern following a sequence of pressurization and pore-filling steps. At sufficiently small cluster sizes, growth occurred `one pore at a time,` leading to invasion percolation patterns. Single-bubble (cluster) growth was next simulated with a pore-network simulator that includes heat transfer (convection and conduction), and capillary and viscous forces, although not gravity. A boundary in the parameter space was delineated that separates patterns of growth dictated solely by capillarity (invasion percolation) from other patterns. The region of validity of invasion percolation was found to decrease as the supersaturation (heat flux), the capillary number, the thermal diffusivity, and the vapor cluster size increase. Implications to continuum models are discussed. 33 refs., 9 figs.

  16. Heat treatment temperature influence on ASTM A890 GR 6A super duplex stainless steel microstructure

    SciTech Connect

    Martins, Marcelo; E-mail: marcelo.martins@sulzer.com; Casteletti, Luiz Carlos

    2005-09-15

    Duplex and super duplex stainless steels are ferrous alloys with up to 26% chromium, 8% nickel, 5% molybdenum and 0.3% nitrogen, which are largely used in applications in media containing ions from the halogen family, mainly the chloride ion (Cl{sup -}). The emergence of this material aimed at substituting Copper-Nickel alloys (Cupro-Nickel) that despite presenting good corrosion resistance, has mechanical properties quite inferior to steel properties. The metallurgy of duplex and super duplex stainless steel is complex due to high sensitiveness to sigma phase precipitation that becomes apparent, due to the temperatures they are exposed on cooling from solidification as well as from heat treatment processes. The objective of this study was to verify the influence of heat treating temperatures on the microstructure and hardness of ASTM A890/A890M Gr 6A super duplex stainless steel type. Microstructure control is of extreme importance for castings, as the chemical composition and cooling during solidification inevitably provide conditions for precipitation of sigma phase. Higher hardness in these materials is directly associated to high sigma phase concentration in the microstructure, precipitated in the ferrite/austenite interface. While heat treatment temperature during solution treatment increases, the sigma phase content in the microstructure decreases and consequently, the material hardness diminishes. When the sigma phase was completely dissolved by the heat treatment, the material hardness was influenced only due to ferrite and austenite contents in the microstructure.

  17. Development of a surface array of microscale heaters to measure wall heat transfer underneath single bubbles in nucleate pool boiling

    SciTech Connect

    Kim, J.; Kalkur, T.S.

    1995-12-31

    A novel array of microscale heaters has been developed to measure the heat transfer coefficient at many points underneath individual bubbles during boiling as a function of space and time. This heater array enables the local heat transfer from a surface during the bubble growth and departure process to be measured with very high temporal and spatial resolution, and should allow better understanding of the boiling heat transfer mechanisms by pinpointing when and where in the bubble departure cycle large amounts of wall heat transfer occur. Such information can provide much needed data regarding the important heat transfer mechanisms during the bubble departure cycle, and can serve as benchmarks to validate many of the analytical and numerical models used to simulate boiling. The current array has 148 heaters within a 3 mm diameter circle. Feedback loops similar to those used in hot-wire anemometry are used to keep each heater at a constant temperature, and the power required to do this is directly related to the heat transfer coefficient. A description of the heater performance and construction, the feedback loops, the computer control circuit, and the calibration rig are described.

  18. The role of the tropical super greenhouse effect in heating the ocean surface

    SciTech Connect

    Lubin, D. )

    1994-07-08

    Measurements made by a Fourier transform infrared (FTIR) spectroradiometer operating in the middle infrared (5 to 20 micrometers, with a spectral resolution of one inverse centimeter) imply that there is an anomalously large greenhouse effect over equatorial oceans that is caused by water vapor. As sea-surface temperature increased from 297 to 303 degrees kelvin, the net infrared cooling at the surface decreased by 30 to 50 watts per square meter. Thus, according to the FTIR data, the super greenhouse effect that has been inferred from satellite measurements contributes directly to radiative heating of the sea surface. The data demonstrate that most of this heating occurs in the middle infrared by means of the continuum emission window of water vapor and that tropical deep convection contributes substantially to this super greenhouse effect.

  19. Plasma Heating to Super-Hot Temperatures (>30 MK) in the August 9, 2011 Solar Flare

    NASA Astrophysics Data System (ADS)

    Sharykin, Ivan; Struminsky, Alexei; Zimovets, Ivan

    2015-08-01

    We investigate the August 9, 2011 solar flare of X-ray class X6.9, the "hottest" flare from 2000 to 2012, with a peak plasma temperature according to GOES data of 33 MK. Our goal is to determine the cause of such an anomalously high plasma temperature and to investigate the energy balance in the flare region with allowance made for the presence of a super-hot plasma (>30 MK). We analyze the RHESSI, GOES, AIA/SDO, and EVE/SDO data and discuss the spatial structure of the flare region and the results of our spectral analysis of its X-ray emission. Our analysis of the RHESSI X-ray spectra is performed in the one-temperature and two-temperature approximations by taking into account the emission of hot (20 MK) and super-hot (45 MK) plasmas. The hard X-ray spectrum in both models is fitted by power laws. The observed peculiarities of the flare are shown to be better explained in terms of the two-temperature model, in which the super-hot plasma is located at the flare loop tops (or in the magnetic cusp region). The formation of the super-hot plasma can be associated with its heating through primary energy release and with the suppression of thermal conduction.

  20. Enhancement of Pool Boiling Heat Transfer and Control of Bubble Motion in Microgravity Using Electric Fields (BCOEL)

    NASA Technical Reports Server (NTRS)

    Herman, Cila; Iacona, Estelle; Acquaviva, Tom; Coho, Bill; Grant, Nechelle; Nahra, Henry; Taylor, Al; Julian, Ed; Robinson, Dale; VanZandt, Dave

    2001-01-01

    The BCOEL project focuses on improving pool boiling heat transfer and bubble control in microgravity by exposing the fluid to electric fields. The electric fields induce a body force that can replace gravity in the low gravity environment, and enhance bubble removal from the heated surface. A better understanding of microgravity effects on boiling with and without electric fields is critical to the proper design of the phase-change-heat-removal equipment for use in spacebased applications. The microgravity experiments will focus on the visualization of bubble formation and shape during boiling. Heat fluxes on the boiling surface will be measured, and, together with the measured driving temperature differences, used to plot boiling curves for different electric field magnitudes. Bubble formation and boiling processes were found to be extremely sensitive to g-jitter. The duration of the experimental run is critical in order to achieve steady state in microgravity experiments. The International Space Station provides conditions suitable for such experiments. The experimental apparatus to be used in the study is described in the paper. The apparatus will be tested in the KC-135 first, and microgravity experiments will be conducted on board of the International Space Station using the Microgravity Science Glovebox as the experimental platform.

  1. Enhancement of Pool Boiling Heat Transfer and Control of Bubble Motion in Microgravity Using Electric Fields - BCOEL

    NASA Technical Reports Server (NTRS)

    Herman, Cila; Iacona, Estelle; Acquaviva, Tom; Coho, Bill; Grant, Nechelle; Nahra, Henry; Sankaran, Subramanian; Taylor, Al; Julian, Ed; Robinson, Dale; VanZandt, Dave

    2001-01-01

    The BCOEL project focuses on improving pool boiling heat transfer and bubble control in microgravity by exposing the fluid to electric fields. The electric fields induce a body force that can replace gravity in the low gravity environment, and enhance bubble removal from thc heated surface. A better understanding of microgravity effects on boiling with and without electric fields is critical to the proper design of the phase-change-heat-removal equipment for use in space-based applications. The microgravity experiments will focus on the visualization of bubble formation and shape during boiling. Heat fluxes on the boiling surface will be measured, and, together with the measured driving temperature differences, used to plot boiling curvcs for different electric field magnitudes. Bubble formation and boiling processes were found to be extremely sensitive to g-jitter. The duration of the experimental run is critical in order to achieve steady state in microgravity experiments. The International Space Station provides conditions suitable for such experiments. The experimental appararus to be used in the study is described in the paper. The apparatus will be tested in the KC-135 first, and microgravity experiments will be conducted on board of the International Space Station using the Microgravity Science Glovebox as the experimental platform.

  2. Disjoining pressure and capillarity in the constrained vapor bubble heat transfer system.

    PubMed

    Chatterjee, Arya; Plawsky, Joel L; Wayner, Peter C

    2011-10-14

    Using the disjoining pressure concept in a seminal paper, Derjaguin, Nerpin and Churaev demonstrated that isothermal liquid flow in a very thin film on the walls of a capillary tube enhances the rate of evaporation of moisture by several times. The objective of this review is to present the evolution of the use of Churaev's seminal research in the development of the Constrained Vapor Bubble (CVB) heat transfer system. In this non-isothermal "wickless heat pipe", liquid and vapor flow results from gradients in the intermolecular force field, which depend on the disjoining pressure, capillarity and temperature. A Kelvin-Clapeyron model allowed the use of the disjoining pressure to be expanded to describe non-isothermal heat, mass and momentum transport processes. The intermolecular force field described by the convenient disjoining pressure model is the boundary condition for "suction" and stability at the leading edge of the evaporating curved flow field. As demonstrated by the non-isothermal results, applications that depend on the characteristics of the evaporating meniscus are legion.

  3. Heat transfer and hydrodynamic investigations of a baffled slurry bubble column

    NASA Astrophysics Data System (ADS)

    Saxena, S. C.; Chen, Z. D.

    1992-09-01

    Heat transfer and hydrodynamic investigations have been conducted in a 0.108 m internal diameter bubble column at ambient conditions. The column is equipped with seven 19mm diameter tubes arranged in an equilateral triangular pitch of 36.5 mm. A Monsanto synthetic heat transfer fluid, Therminol-66 having a viscosity of 39.8 cP at 303 K, is used as a liquid medium. Magnetite powders, average diameters 27.7 and 36.6 µm, in five concentrations up to 50 weight percent in the slurry, are used. As a gas phase, industrial grade nitrogen of purity 99.6 percent is employed. Gas holdup in different operating modes and regimes have been measured for the two- and three-phase systems over a superficial gas velocity range up to 0.20 m/s in the semi-batch mode. Heat transfer coefficients are measured at different tube locations in the bundle at different radial and vertical locations over a range of operating conditions. All these data are compared with the existing literature correlations and models. New correlations are proposed.

  4. Dynamical Behavior of Discrete Bubble and Heat Transfer of Nucleate Pool Boiling in Short-Term Microgravity

    NASA Astrophysics Data System (ADS)

    Zhao, Jian-Fu

    2012-07-01

    Boiling in microgravity is an increasing significant subject of investigation. Motivation for the study comes not only from many potential space applications due to its high efficiency to transfer high heat flux with liquid-vapor phase change, but also from powerful platform of microgravity to reveal the mechanism of heat transfer underneath the phenomenon of boiling. In the present paper, the growth of a discrete bubble during nucleate pool boiling and heat transfer in short-term microgravity is studied experimentally utilizing the drop tower Beijing. A P-doped N-type square silicon chip with the dimensions of 10x10x0.5 mm ^{3} was used as the heater. Two 0.25-mm diameters copper wires for power supply was soldered to the side surfaces of the chip at the opposite ends. The normal resistant of the chip is 75 Ω. The chip was heated by using Joule effect. A D.C. power supply of constant current was used to input energy to the heater element. A 0.12-mm diameter, T-type thermocouple adhered on the centre of the backside of the chip was used for the measurement of wall temperature, while two other T-type thermocouples were used for the bulk liquid temperature. FC-72 was used as working fluid. The concentration of air was determined by using Henry law as 0.0046 moles gas/mole liquid. The pressure and the bulk liquid temperature in the boiling chamber were nominally 102.0 kPa and 12.0 °C, respectively. The shapes of the bubbles were recorded using a high speed camera at a speed of 250 fps with a shutter speed of 1/2000 s. Based on the image manipulation, the effective diameter of the discrete bubble is obtained. The experiments were conducted utilizing the drop tower Beijing, which can provide a short-term microgravity condition. The residual gravity of 10 ^{-2 ... -3} g _{0} can be maintained throughout the short duration of 3.6 s. To avoid the influence of natural convection in normal gravity environment, the heating switched on at the release of the drop capsule

  5. Bubble Combustion

    NASA Technical Reports Server (NTRS)

    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

  6. Bubble Formation on a Wall in Cross-Flowing Liquid and Surrounding Fluid Motion,With and Without Heating

    NASA Technical Reports Server (NTRS)

    Bhunia, Avijit; Kamotani, Yasuhiro; Nahra, Henry K.

    2000-01-01

    Application of gas-liquid two-phase flow systems for space-based thermal management and for the HEDS program demands a precise control of bubble size distribution in liquid. The necessity of bulk liquid motion for controlling bubble size and frequency in the space environment has been suggested by recent studies on pool, forced convection boiling and bubble formation in flowing liquid. The present work, consisting of two parts, explores bubble generation at wall in a cross-flowing liquid, i.e., in a forced convection boiling configuration. A schematic is shown. The first part looks into the bubble formation process under isothermal conditions in a reduced gravity environment, by injecting gas through a hole in the wall of a flowing liquid channel. In the latter part with channel wall heating, flow and temperature fields near a single bubble are studied under normal (1-g) and micro-gravity (mu-g) conditions. The objective of the isothermal experiments is to experimentally investigate the effects of liquid cross-flow velocity, gas flow rate, and orifice diameter on bubble formation. Data were taken mainly under reduced gravity conditions but some data were taken in normal gravity for comparison. The reduced gravity experiment was conducted aboard the NASA DC-9 Reduced Gravity Aircraft. The results show that the process of bubble formation and detachment depends on gravity, the orifice diameter (D(sub N)), the gas flow rate (Q(sub g)), and the liquid cross-flow velocity (U(sub L)). The reduced gravity data are shown. The data are analyzed based on a force balance, and two different detachment mechanisms are identified. When the gas momentum is large, the bubble detaches from the injection orifice as the gas momentum overcomes the attaching effects of liquid drag and inertia. The surface tension force is much reduced because a large part of the bubble pinning edge at the orifice is lost as the bubble axis is tilted by the liquid flow. When the gas momentum is small

  7. Demonstration of Super Cooled Ice as a Phase Change Material Heat Sink for Portable Life Support Systems

    NASA Technical Reports Server (NTRS)

    Leimkuehler, Thomas O.; Bue, Grant C.

    2009-01-01

    A phase change material (PCM) heat sink using super cooled ice as a nontoxic, nonflammable PCM is being developed. The latent heat of fusion for water is approximately 70% larger than most paraffin waxes, which can provide significant mass savings. Further mass reduction is accomplished by super cooling the ice significantly below its freezing temperature for additional sensible heat storage. Expansion and contraction of the water as it freezes and melts is accommodated with the use of flexible bag and foam materials. A demonstrator unit has been designed, built, and tested to demonstrate proof of concept. Both testing and modeling results are presented along with recommendations for further development of this technology.

  8. Assessment of NASA Dual Microstructure Heat Treatment Method Utilizing Ladis SuperCooler(trademark) Cooling Technology

    NASA Technical Reports Server (NTRS)

    Lemsky, Joe; Gayda, John (Technical Monitor)

    2005-01-01

    The intent of this investigation was to demonstrate the NASA DMHT method with a tailored Ladish SuperCool(Trademark) cooling method on a Rolls-Royce AE2100, stage 3 disk shape. One disk each of two alloys, LSHR and ME3, were successfully converted as shown by macrostructure. DMHT heating time selection and cooling rate was aided by finite element modeling analysis. Residual stresses were also predicted and reported. Detailed microstructural analysis was performed by NASA and included in this report. Mechanical property characterization, also planned by NASA, is incomplete at this time and not part of this report.

  9. Plasma heating to super-hot temperatures (>30 MK) in the August 9, 2011 solar flare

    NASA Astrophysics Data System (ADS)

    Sharykin, I. N.; Struminskii, A. B.; Zimovets, I. V.

    2015-01-01

    We investigate the August 9, 2011 solar flare of X-ray class X6.9, the "hottest" flare from 2000 to 2012, with a peak plasma temperature according to GOES data of ≈32.5 MK. Our goal is to determine the cause of such an anomalously high plasma temperature and to investigate the energy balance in the flare region with allowance made for the presence of a super-hot plasma (>30 MK). We analyze the RHESSI, GOES, AIA/SDO, and EVE/SDO data and discuss the spatial structure of the flare region and the results of our spectral analysis of its X-ray emission. Our analysis of the RHESSI X-ray spectra is performed in the one-temperature and two-temperature approximations by taking into account the emission of hot (˜20 MK) and super-hot (˜45 MK) plasmas. The hard X-ray spectrum in both models is fitted by power laws. The observed peculiarities of the flare are shown to be better explained in terms of the two-temperature model, in which the super-hot plasma is located at the flare loop tops (or in the magnetic cusp region). The formation of the super-hot plasma can be associated with its heating through primary energy release and with the suppression of thermal conduction. The anomalously high temperature (33 MK according to GOES) is most likely to be an artefact of the method for calculating the temperature based on two-channel GOES measurements in the one-temperature approximation applied to the emission of a multi-temperature flare plasma with a minor contribution from the low-temperature part of the differential emission measure.

  10. Heating and Burning of Optical Fibers and Cables by Light Scattered from Bubble Train Formed by Optical Fiber Fuse

    NASA Astrophysics Data System (ADS)

    Yamada, Makoto; Tomoe, Akisumi; Kinoshita, Takahiro; Koyama, Osanori; Katuyama, Yutaka; Shibuya, Takashi

    We investigate in detail the scattering properties and heating characteristics in various commercially available optical fibers and fiber cables when a bubble train forms in the middle of the fiber as a result of the fiber fuse phenomenon that occurs when a high power signal is launched into the fiber. We found theoretically and experimentally that almost all the optical light is scattered at the top of the bubble train. The scattered light heats UV coated fiber, nylon jacketed silica fiber, fire-retardant jacketed fiber (PVC or FRPE jacketed fiber) and fire-retardant fiber cable (PVC or FRPE fiber cable), to around 100, over 200 and over 600°C, respectively, and finally the fiber burns and is destroyed at a launched optical power of 3W. Furthermore, it is confirmed that the combustion does not spread when we use fire retardant jacketed fibers.

  11. Exploiting zone trapping to avoid liberation of air bubbles in flow-based analytical procedures requiring heating.

    PubMed

    Vida, Ana C F; Zagatto, Elias A G

    2014-01-01

    In flow-based analytical procedures requiring heating, liberation of air bubbles is avoided by trapping a sample selected portion into a heated hermetic environment. The flow-through cuvette is maintained into a temperature-controlled aluminium block, thus acting as the trapping element and allowing real-time monitoring. The feasibility of the innovation was demonstrated in the spectrophotometric catalytic determination of vanadium in mineral waters. Air bubbles were not released even for temperatures as high as 95°C. The proposed system handles about 25 samples per hour, requires only 3 mg p-anisidine per determination and yields precise results (r.s.d. = 2.1%), in agreement with ICP-MS. Detection limit was evaluated (3.3 σ criterion) as 0.1 μg L(-1) V.

  12. Flow and Heat Flux Behavior of Micro-bubble Jet Flows Observed in Thin, Twisted-Wire, Subcooled Boiling in Microgravity

    NASA Astrophysics Data System (ADS)

    Munro, Troy R.; Ban, Heng

    2015-02-01

    Thin wire, subcooled boiling experiments were performed onboard an aircraft flying a parabolic trajectory to provide microgravity conditions for improved observation of jet flow phenomena and their behavior in the absence of buoyant forces. A new type of nucleation jet flow was observed in microgravity. This new micro-bubble jet flow is seen at medium to high heat fluxes and is characterized by a region of the wire that forms multiple jet columns which contain micro-bubbles. These columns flow together and penetrate tens of millimeters into the bulk fluid. Bubble behavior on the wire was observed to progress from a dominance of larger isolated bubbles on the wire to a dominance of micro-bubble jet flows on the wire as heat flux was increased. There was also a transient transition from a few large isolated bubbles to micro-bubble jet flow dominance for a set heat flux. A cross correlation calculation provided velocities of micro-bubbles in the flow, which were in the range of 4-14 mm/s. These velocities were used with convection correlations to show that fluid flows induced by jet flows are a significant contributor to the subcooled boiling heat transfer in microgravity, but are not the primary contributor. Additionally, a relative bubble area analysis approximates the direct contribution of these jet flows to the overall heat dissipation. These micro-bubble jet flows, which are only observed on thin wires (not flat surfaces), and the convection currents they induce, have the potential to allow for sustained fluid motion to occur in microgravity.

  13. Thermocapillary convection around gas bubbles: an important natural effect for the enhancement of heat transfer in liquids under microgravity.

    PubMed

    Betz, J; Straub, J

    2002-10-01

    In the presence of a temperature gradient at a liquid-gas or liquid-liquid interface, thermocapillary or Marangoni convection develops. This convection is a special type of natural convection that was not paid much attention in heat transfer for a long time, although it is strong enough to drive liquids against the direction of buoyancy on Earth. In a microgravity environment, however, it is the remaining mode of natural convection and supports heat and mass transfer. During boiling in microgravity it was observed at subcooled liquid conditions. Therefore, the question arises about its contribution to heat transfer without phase change. Thermocapillary convection was quantitatively studied at single gas bubbles in various liquids, both experimentally and numerically. A two-dimensional mathematical model described in this article was developed. The coupled mechanism of heat transfer and fluid flow in pure liquids around a single gas bubble was simulated with a control-volume FE-method. The simulation was accompanied and compared with experiments on Earth. The numerical results are in good accordance with the experiments performed on Earth at various Marangoni numbers using various alcohols of varying chain length and Prandtl numbers. As well as calculations on Earth, the numerical method also allows simulations at stationary spherical gas bubbles in a microgravity environment. The results demonstrate that thermocapillary convection is a natural heat transfer mechanism that can partially replace the buoyancy in a microgravity environment, if extreme precautions are taken concerning the purity of the liquids, because impurities accumulate predominantly at the interface. Under Earth conditions, an enhancement of the heat transfer in a liquid volume is even found in the case where thermocapillary flow is counteracted by buoyancy. In particular, the obstructing influence of surface active substances could be observed during the experiments on Earth in water and also in

  14. Interior Dynamics and Outgassing in Tidally-heated Rocky Super-Earths

    NASA Astrophysics Data System (ADS)

    Valencia, D. C.

    2014-12-01

    In the search for a habitable Earth analog it has been recognized that a shortcut is to observe rocky planets around M stars, because their habitable zones are at shorter periods. It is also true that at these distances tidal dissipation raised by the star on the planet becomes critical. Thus, it is important to investigate what are the interior and surface conditions of these tidally heated planets. For low-mass planets, outgassing, which is tied to mantle convection, sets the dominant input component to the atmospheric composition (with atmospheric escape and ingassing the other relevant components), which in turn helps determine the surface temperature and overall habitability profile. We have performed interior dynamic calculations based on [1] tied to a simple outgassing model to investigate the effects of tidal heating in outgassing. I will present results of the effect of planetary mass and tidal heating in outgassing budgets, by taking Earth as the reference state. [1] Tackley, P. J., M. Ammann, J. P. Brodholt, D. P. Dobson and D. Valencia (2013) Mantle dynamics in super-Earths: Post-perovskite rheology and self-regulation of viscosity, Icarus 225(1), 50-61

  15. Subtle Mitsunobu couplings under super-heating: the role of high-throughput continuous flow and microwave strategies.

    PubMed

    Manvar, Atul; Shah, Anamik

    2014-11-07

    Non-conventional heating techniques, high-throughput microwave-assisted synthesis and continuous flow penetrate almost every scientific field. Mitsunobu coupling is a ubiquitous choice for the dehydrative redox condensation of primary or secondary alcohols with (pro)nucleophiles. The aim of this review is to showcase the ease of subtle Mitsunobu coupling under super-heating. Surprisingly, this strategy is rather non-trivial; considering the sensitivity of reagents, Mitsunobu chemistry is typically performed at lower temperatures or under ambient conditions. In view of the absence of any previous work focusing on this topic, the current review considers the utility of super-heating in fragile Mitsunobu reactions. Therefore, we anticipate that this review will also bridge some of the apparent gaps in the extant literature by specifically describing the advances made by non-conventional heating assisted by microwave or continuous flow in one of the most powerful stereochemical transformations.

  16. In-Situ Shipboard Heat Exchanger Cleaning and Maintenance Using Innovative I2 Bubble Infusion Technology

    DTIC Science & Technology

    2014-07-15

    at the Queens Botanical Gardens, Flushing, NY. This facility employed a geothermal system for heating and cooling. Iron reducing bacteria from the...the patented I2 infusion system to reduce the rate of foul within Department of Defense shipboard heat exchangers. Fouling of DoD shipboard heat ...selection of the heat exchangers used in the demonstration and provided invaluable information regarding Navy heat exchanger system construction

  17. Heat transfer from a horizontal finned tube bundle in bubbling fluidized beds of small and large particles

    SciTech Connect

    Devaru, C.B.; Kolar, A.K.

    1995-12-31

    Steady state average heat transfer coefficient measurements were made by the local thermal simulation technique in a cold, square, bubbling air-fluidized bed (0.305 m x 0.305 m) with immersed horizontal finned tube bundles (in-line and staggered) with integral 60{degree} V-thread. Studies were conducted using beds of small (average particle diameter less than 1 mm) sand particles and of large (average particle diameter greater thin 1 mm) particles (raagi, mustard, millet and coriander). The fin pitch varied from 0.8 to 5.0 mm and the fin height varied from 0.69 to 4.4 mm. The tube pitch ratios used were 1.75 and 3.5. The influence of bed particle diameter, fluidizing velocity, fin pitch, and tube pitch ratio on average heat transfer coefficient was studied. Fin pitch and bed particle diameter are the most significant parameters affecting heat transfer coefficient within the range of experimental conditions. Bed pressure drop depends only on static bed height. New direct correlations, incorporating easily measurable quantities, for average heat transfer coefficient for finned tube bundles (in-line and staggered) are proposed.

  18. Rotating bubble membrane radiator

    DOEpatents

    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.

  19. Study of cavitation bubble dynamics during Ho:YAG laser lithotripsy by high-speed camera

    NASA Astrophysics Data System (ADS)

    Zhang, Jian J.; Xuan, Jason R.; Yu, Honggang; Devincentis, Dennis

    2016-02-01

    Although laser lithotripsy is now the preferred treatment option for urolithiasis, the mechanism of laser pulse induced calculus damage is still not fully understood. This is because the process of laser pulse induced calculus damage involves quite a few physical and chemical processes and their time-scales are very short (down to sub micro second level). For laser lithotripsy, the laser pulse induced impact by energy flow can be summarized as: Photon energy in the laser pulse --> photon absorption generated heat in the water liquid and vapor (super heat water or plasma effect) --> shock wave (Bow shock, acoustic wave) --> cavitation bubble dynamics (oscillation, and center of bubble movement , super heat water at collapse, sonoluminscence) --> calculus damage and motion (calculus heat up, spallation/melt of stone, breaking of mechanical/chemical bond, debris ejection, and retropulsion of remaining calculus body). Cavitation bubble dynamics is the center piece of the physical processes that links the whole energy flow chain from laser pulse to calculus damage. In this study, cavitation bubble dynamics was investigated by a high-speed camera and a needle hydrophone. A commercialized, pulsed Ho:YAG laser at 2.1 mu;m, StoneLightTM 30, with pulse energy from 0.5J up to 3.0 J, and pulse width from 150 mu;s up to 800 μs, was used as laser pulse source. The fiber used in the investigation is SureFlexTM fiber, Model S-LLF365, a 365 um core diameter fiber. A high-speed camera with frame rate up to 1 million fps was used in this study. The results revealed the cavitation bubble dynamics (oscillation and center of bubble movement) by laser pulse at different energy level and pulse width. More detailed investigation on bubble dynamics by different type of laser, the relationship between cavitation bubble dynamics and calculus damage (fragmentation/dusting) will be conducted as a future study.

  20. Sliding bubbles on a hot horizontal wire in a subcooled bath

    NASA Astrophysics Data System (ADS)

    Duchesne, Alexis; Dubois, Charles; Caps, Hervé

    2015-11-01

    When a wire is heated up to the boiling point in a liquid bath some bubbles will nucleate on the wire surface. Traditional nucleate boiling theory predicts that bubbles generate from active nucleate site, grow up and depart from the heating surface due to buoyancy and inertia. However, an alternative scenario is presented in the literature for a subcooled bath: bubbles slide along the horizontal wire before departing. New experiments were performed by using a constantan wire and different liquids, varying the injected power. Silicone oil, water and even liquid nitrogen were tested in order to vary wetting conditions, liquid viscosities and surface tensions. We explored the influence of the wire diameter and of the subcooled bath temperature. We observed, of course, sliding motion, but also a wide range of behaviors from bubbles clustering to film boiling. We noticed that bubbles could change moving sense, especially when encountering with another bubble. The bubble speed is carefully measured and can reach more than 100 mm/s for a millimetric bubble. We investigated the dependence of the speed on the different parameters and found that this speed is, for a given configuration, quite independent of the injected power. We understand these phenomena in terms of Marangoni effects. This project has been financially supported by ARC SuperCool contract of the University of Liège.

  1. Heat transfer between stratified immiscible liquid layers driven by gas bubbling across the interface

    SciTech Connect

    Greene, G.A.; Irvine, T.F. Jr.

    1988-01-01

    The modeling of molten core debris in the CORCON and VANESA computer codes as overlying, immiscible liquid layers is discussed as it relates to the transfer of heat and mass between the layers. This initial structure is identified and possible configurations are discussed. The stratified, gas-sparged configuration that is presently employed in CORCON and VANESA is examined and the existing literature for interlayer heat transfer is assessed. An experiment which was designed to measure interlayer heat transfer with gas sparging is described. The results are presented and compared to previously existing models. A dimensionless correlation for stratified, interlayer heat transfer with gas sparging is developed. This relationship is recommended for inclusion in CORCON-MOD2 for heat transfer between stratified, molten liquid layers. 12 refs., 6 figs., 3 tabs.

  2. Experimental study of a constrained vapor bubble fin heat exchanger in the absence of external natural convection.

    PubMed

    Basu, Sumita; Plawsky, Joel L; Wayner, Peter C

    2004-11-01

    In preparation for a microgravity flight experiment on the International Space Station, a constrained vapor bubble fin heat exchanger (CVB) was operated both in a vacuum chamber and in air on Earth to evaluate the effect of the absence of external natural convection. The long-term objective is a general study of a high heat flux, low capillary pressure system with small viscous effects due to the relatively large 3 x 3 x 40 mm dimensions. The current CVB can be viewed as a large-scale version of a micro heat pipe with a large Bond number in the Earth environment but a small Bond number in microgravity. The walls of the CVB are quartz, to allow for image analysis of naturally occurring interference fringes that give the pressure field for liquid flow. The research is synergistic in that the study requires a microgravity environment to obtain a low Bond number and the space program needs thermal control systems, like the CVB, with a large characteristic dimension. In the absence of natural convection, operation of the CVB may be dominated by external radiative losses from its quartz surface. Therefore, an understanding of radiation from the quartz cell is required. All radiative exchange with the surroundings occurs from the outer surface of the CVB when the temperature range renders the quartz walls of the CVB optically thick (lambda > 4 microns). However, for electromagnetic radiation where lambda < 2 microns, the walls are transparent. Experimental results obtained for a cell charged with pentane are compared with those obtained for a dry cell. A numerical model was developed that successfully simulated the behavior and performance of the device observed experimentally.

  3. Heat Transfer Enhancement due to Bubble Pumping in FC-72 Near the Saturation Temperature

    DTIC Science & Technology

    1991-03-01

    Surface Boiling ," Industrial and Engineering Chemistry, vol. 41, No. 9, 1949. Mudawar, I., and D.E. Maddox, Critical Heat Flux in Subcooled Flow Boiling ...BACKGROUND Research on pool boiling in electronic cooling systems has focused on three primary areas: (1) reducing the temperature excursion at incipient...problems: (i) Boiling restricts the- physical design of the system . (ii) A high degree of superheat may be required if the surface is very smooth in order

  4. The dynamics of histotripsy bubbles

    NASA Astrophysics Data System (ADS)

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

    2011-09-01

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

  5. Modification of flow perturbations in a laminar separation bubble by heat transfer

    NASA Astrophysics Data System (ADS)

    Boiko, A. V.; Dovgal, A. V.; Sorokin, A. M.

    2017-02-01

    Laminar boundary layer separation in conditions of localized heat transfer is investigated at low subsonic velocity through wind-tunnel measurements and linear stability analysis. A backward-facing step flow is subjected to a stationary temperature variation generated by Peltier elements installed on the test model directly downstream of the separation line. The experimental and theoretical data clarify the response of velocity disturbances in the separation region to the temperature variation, the latter appearing primarily as a modifier of the initial wave spectrum of the amplifying separated layer oscillations.

  6. Air gasification of rice husk in bubbling fluidized bed reactor with bed heating by conventional charcoal.

    PubMed

    Makwana, J P; Joshi, Asim Kumar; Athawale, Gaurav; Singh, Dharminder; Mohanty, Pravakar

    2015-02-01

    An experimental study of air gasification of rice husk was conducted in a bench-scale fluidized bed gasifier (FBG) having 210 mm diameter and 1600 mm height. Heating of sand bed material was performed using conventional charcoal fuel. Different operating conditions like bed temperature, feeding rate and equivalence ratio (ER) varied in the range of 750-850 °C, 25-31.3 kg/h, and 0.3-0.38, respectively. Flow rate of air was kept constant (37 m(3)/h) during FBG experiments. The carbon conversion efficiencies (CCE), cold gas efficiency, and thermal efficiency were evaluated, where maximum CCE was found as 91%. By increasing ER, the carbon conversion efficiency was decreased. Drastic reduction in electric consumption for initial heating of gasifier bed with charcoal compared to ceramic heater was ∼45%. Hence rice husk is found as a potential candidate to use directly (without any processing) in FBG as an alternative renewable energy source from agricultural field.

  7. Super energy saver heat pump with dynamic hybrid phase change material

    DOEpatents

    Ally, Moonis Raza [Oak Ridge, TN; Tomlinson, John Jager [Knoxville, TN; Rice, Clifford Keith [Clinton, TN

    2010-07-20

    A heat pump has a refrigerant loop, a compressor in fluid communication with the refrigerant loop, at least one indoor heat exchanger in fluid communication with the refrigerant loop, and at least one outdoor heat exchanger in fluid communication with the refrigerant loop. The at least one outdoor heat exchanger has a phase change material in thermal communication with the refrigerant loop and in fluid communication with an outdoor environment. Other systems, devices, and methods are described.

  8. Statistical equilibrium of bubble oscillations in dilute bubbly flows

    PubMed Central

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

    2008-01-01

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

  9. Prospects for bubble fusion

    SciTech Connect

    Nigmatulin, R.I.; Lahey, R.T. Jr.

    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.

  10. Investigation of Third Gyro-harmonic Heating at HAARP Using Stimulated Radio Emissions, the MUIR and SuperDARN Radars

    NASA Astrophysics Data System (ADS)

    Mahmoudian, Alireza; Bernhardt, Paul; Ruohoniemi, J. Michael; Isham, Brett; Watkins, Brenton; Scales, Wayne

    2016-07-01

    Use of high frequency (HF) heating experiments has been extended in recent years as a useful methodology for plasma physicists wishing to remotely study the properties and behavior of the ionosphere as well as nonlinear plasma processes. Our recent work using high latitude heating experiments has lead to several important discoveries that have enabled assessment of active geomagnetic conditions, determination of minor ion species and their densities, ion mass spectrometry, electron temperature measurements in the heating ionosphere, as well a deeper understanding of physical processes associated with electron acceleration and formation of field aligned irregularities. The data recorded during two campaigns at HAARP in 2011 and 2012 will be presented. Several diagnostic instruments have been used to detect HAARP heater-generated ionospheric irregularities and plasma waves. These diagnostics include an ionosonde, MUIR (Modular UHF Ionospheric Radar at 446 MHz), SuperDARN HF backscatter radar and ground-based SEE receivers. Variation of the wideband/ narrowband SEE features, SuperDARN echoes, and enhanced ion lines were studied with pump power variation, pump frequency stepping near 3fce as well as changing beam angle relative to the magnetic zenith. In particular, formation of field-aligned irregularities (FAIs) and upper hybrid (UH) waves through oscillating two-stream instability (OSTI) and resonance instability is studied. During heating, Narrowband SEE (NSEE) showed enhancements that correlated with the enhanced MUIR radar ion lines. IA MSBS (Magnetized Stimulated Brillouin Scatter) lines are much narrower than Wideband SEE (WSEE) lines and as a result electron temperature calculated using NSEE line offset has potential to be more accurate. This technique may therefore complement the electron temperature calculation using ISR spectra. Strength of IA MSBS lines correlate with EHIL in the MUIR spectrum during HF pump frequency variation near 3fce. Therefore, NSEE

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

    SciTech Connect

    Ishii, M.; Denten, J.P.

    1988-01-01

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

  12. Unorthodox bubbles when boiling in cold water

    NASA Astrophysics Data System (ADS)

    Parker, Scott; Granick, Steve

    2014-01-01

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

  13. Unorthodox bubbles when boiling in cold water.

    PubMed

    Parker, Scott; Granick, Steve

    2014-01-01

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

  14. Super-Leidenfrost spray cooling: A solution to the problem of controlled high-temperature, high-flux heat extraction

    NASA Astrophysics Data System (ADS)

    Edwards, C. F.; Hahn, D. W.

    Our interest in spray cooling stems from a problem in high-temperature materials synthesis. Specifically, it is the growth of diamond films by flame chemical vapor deposition (CVD). A high velocity jet of premixed C2H2/O2/H2 is formed into a stagnation point flow over the surface of a molybdenum mandrel causing the formation of a highly strained flame immediately adjacent to the surface. The difficulty that arises is that concomitant with the flux of energetic species to the surface is a large flux of heat which must be removed from the mandrel if control of the growth process is to be maintained. The situation is further complicated by the fact that the deposition surface temperature must be held to a tight tolerance somewhere within the optimal diamond growth range (approximately 1200 K) and the heat extraction must be made in a one-dimensional fashion to preserve the uniform boundary condition on the flame. Since the cooling surface temperature is fixed near the saturation condition by the phase change of the droplets, and the heat flux into the mandrel is imposed by the flame, the only way to achieve a desired deposition surface temperature is to vary the thermal resistance of the mandrel itself. Since the cooling surface is isothermal, uniform temperature at the deposition surface will only result if the heat flux through the mandrel is uniform, that is, if the sides of the mandrel are effectively adiabatic and the flame is uniform over the mandrel surface. If either of these conditions is not met, the deposition surface temperature cannot be made uniform using this method. These limitations could be overcome if it were possible to carry out the spray cooling process without being tied to the isothermal boundary condition inherent in phase-cooling. Such a solution exists for spray cooling above the Leidenfrost temperature; that is the subject of this paper -- super-Leidenfrost spray cooling.

  15. Collapse of large vapor bubbles

    NASA Technical Reports Server (NTRS)

    Tegart, J.; Dominick, S.

    1982-01-01

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

  16. Particle Size of Gamma Prime as a Result of Vacuum Heat Treatment of INCONEL 738 Super Alloy

    NASA Astrophysics Data System (ADS)

    Guzman, I.; Granda, E.; Mendez, R.; Lopez, G.; Acevedo, J.; Gonzalez, D.

    2013-04-01

    In this paper, the influence of the cooling rate and cooling media after a standard solution heat treatment on the size and distribution of the gamma prime phase (γ') in the nickel-based super alloy INCONEL 738 in over-aged conditions is described. The volume fraction of the gamma prime depends on the chemical composition of the alloy, the solution treatment temperature and the cooling rate; in over-aged alloys (i.e., with more than 25,000 h of service) the volume fraction of γ' is about 78.8%. However, it has been demonstrated that in order to maintain excellent creep strength a volume fraction of at least 60% or lower is required. In this work the volume fraction was optimized between 40 and 55% by means of a standard solution heat treatment at 1120 °C using different cooling gases. A γ' volume fraction of 54.8% was obtained by using argon as the cooling medium at a cooling rate of 87 °C/min, producing a precipitate of partial distribution of primary and secondary γ'. Better results were obtained in a nitrogen atmosphere at a cooling rate of 287 °C/min, leading to a volume fraction of 40% and obtaining a total re-precipitation of primary and secondary γ'.

  17. A coupled numerical analysis of shield temperatures, heat losses and residual gas pressures in an evacuated super-insulation using thermal and fluid networks - Part I: Stationary conditions

    NASA Astrophysics Data System (ADS)

    Reiss, H.

    2004-04-01

    This paper describes numerical simulations, using thermal networks, of shield temperatures and radiative and conductive heat losses of a super-insulated cryogenic storage tank operating at 77 K. Interactions between radiation and conductive heat transfer modes in the shields are investigated, by calculation of local shield temperatures. As a new method, fluid networks are introduced for calculation of stationary residual gas pressure distribution in the evacuated multilayer super-insulation. Output from the fluid network is coupled to the iterative thermal network calculations. Parameter tests concern thickness and emissivity of shields, degree of perforation, residual gas sources like desorption from radiation shields, spacers and container walls, and permeation from the inner container to the evacuated insulation space. Variations of either a conductive (thickness of Al-film on Mylar) or a radiative parameter (thermal emissivity) exert crosswise influences on the radiative or conductive heat losses of the tank, respectively.

  18. ON THE HEATING EFFICIENCY DERIVED FROM OBSERVATIONS OF YOUNG SUPER STAR CLUSTERS IN M82

    SciTech Connect

    Silich, Sergiy; Tenorio-Tagle, Guillermo; Torres-Campos, Ana; Munoz-Tunon, Casiana; Monreal-Ibero, Ana; Melo, Veronica E-mail: cmt@ll.iac.es

    2009-08-01

    Here, we discuss the mechanical feedback that massive stellar clusters provide to the interstellar medium of their host galaxy. We apply an analytic theory developed in a previous study for M82-A1 to a sample of 10 clusters located in the central zone of the starburst galaxy M82, all surrounded by compact and dense H II regions. We claim that the only way that such H II regions can survive around the selected clusters, is if they are embedded into a high-pressure ISM and if the majority of their mechanical energy is lost within the star cluster volume via strong radiative cooling. The latter implies that these clusters have a low heating efficiency, {eta}, and evolve in the bimodal hydrodynamic regime. In this regime, the shock-heated plasma in the central zones of a cluster becomes thermally unstable, loses its pressure and is accumulated there, whereas the matter injected by supernovae and stellar winds outside this volume forms a high-velocity outflow-the star cluster wind. We calculated the heating efficiency for each of the selected clusters and found that in all cases it does not exceed 10%. Such low heating efficiency values imply a low mechanical energy output and the impact that the selected clusters provide to the ISM of M82 is thus much smaller than what one would expect using stellar cluster synthetic models.

  19. Subsonic evolution of the radio bubbles in the nearby massive early-type galaxy NGC 4472: uplift, buoyancy, and heating

    NASA Astrophysics Data System (ADS)

    Kraft, Ralph P.; Gendron Marsolais, Marie-Lou; Bogdan, Akos; Su, Yuanyuan; Forman, William R.; Hlavacek-Larrondo, Julie; Jones, Christine; Nulsen, Paul; Randall, Scott W.; Roediger, Elke

    2017-01-01

    We present results from a deep (380 ks) Chandra observation of the hot gas in the nearby massive early-type galaxy NGC 4472. X-ray cavities were previously reported coincident with the radio lobes (Biller et al. 2004). In our deeper observation, we confirm the presence of the cavities and detect rims of enhanced emission surrounding the bubbles. The temperature of the gas in these rims is less than that of the ambient medium, demonstrating that they cold, low entropy material that has been drawn up from the group center by the buoyant rise of the bubbles and not shocks from supersonic inflation of the lobes. Interestingly, the gravitational energy required to lift these lobes from the group center is a significant fraction of the bubble enthalpy. This suggests that uplift by AGN bubbles may play an important role in some cases in offsetting the radiative cooling at cluster and group centers. This uplift also provides an efficient means of transporting enriched material from the group center to large radii.

  20. Rectified growth of histotripsy bubbles

    PubMed Central

    Kreider, Wayne; Maxwell, Adam D.; Khokhlova, Tatiana; Simon, Julianna C.; Khokhlova, Vera A.; Sapozhnikov, Oleg; Bailey, Michael R.

    2015-01-01

    Histotripsy treatments use high-amplitude shock waves to fractionate tissue. Such treatments have been demonstrated using both cavitation bubbles excited with microsecond-long pulses and boiling bubbles excited for milliseconds. A common feature of both approaches is the need for bubble growth, where at 1 MHz cavitation bubbles reach maximum radii on the order of 100 microns and boiling bubbles grow to about 1 mm. To explore how histotripsy bubbles grow, a model of a single, spherical bubble that accounts for heat and mass transport was used to simulate the bubble dynamics. Results suggest that the asymmetry inherent in nonlinearly distorted waveforms can lead to rectified bubble growth, which is enhanced at elevated temperatures. Moreover, the rate of this growth is sensitive to the waveform shape, in particular the transition from the peak negative pressure to the shock front. Current efforts are focused on elucidating this behavior by obtaining an improved calibration of measured histotripsy waveforms with a fiber-optic hydrophone, using a nonlinear propagation model to assess the impact on the focal waveform of higher harmonics present at the source’s surface, and photographically observing bubble growth rates. PMID:26413193

  1. Driving bubbles out of glass

    NASA Technical Reports Server (NTRS)

    Mattox, D. M.

    1981-01-01

    Surface tension gradient in melt forces gas bubbles to surface, increasing glass strength and transparency. Conventional chemical and buoyant fining are extremely slow in viscous glasses, but tension gradient method moves 250 um bubbles as rapidly as 30 um/s. Heat required for high temperature part of melt is furnished by stationary electrical or natural-gas heater; induction and laser heating are also possible. Method has many applications in industry processes.

  2. Sinking Bubbles

    NASA Astrophysics Data System (ADS)

    Koch, Jeremy; Ewoldt, Randy

    2016-11-01

    Intuition tells us that bubbles will rise and steel objects will sink in liquids, though here we describe the opposite. With experimental demonstration and theoretical rationale, we describe how the motion of containers of liquid with immersed solid objects and air bubbles can cause curious behaviors: sinking bubbles and rising high-density particles. Bubbles and solid spheres of diameter on the order of a few millimeters are introduced into fluids with different rheological constitutive behaviors. Imposed motion of the rigid container allows for control of the trajectories of the immersed particles - without the container imparting direct shearing motion on the fluid. Results demonstrate the necessary conditions to prevent or produce net motion of the bubbles and heavy particles, both with and against gravitational expectations.

  3. Experimental magma degassing: The revenge of the deformed bubbles

    NASA Astrophysics Data System (ADS)

    Marxer, H.; Bellucci, P.; Ulmer, S.; Nowak, M.

    2013-12-01

    We performed decompression experiments with a hydrated phonolitic melt at a T of 1323 K in an internally heated pressure vessel to investigate the effect of decompression method and rate on melt degassing. Samples were decompressed from 200 to 75 MPa with step-wise and continuous decompression (SD/CD) at nominal decompression rates (DRs) of 0.0028-1.7 MPa/s. At target P the samples were quenched rapidly under isobaric conditions with 150 K/s. The vesiculated glass products were compared in terms of bubble number density (BND), bubble size distribution (BSD) and residual H2O content. Almost all capsules were deformed after decompression: the initially crimped headspaces were expanded and the walls were inflexed in the capsule center. We postulate that the deformation is primarily due to the change in molar volume V(m) of exsolved H2O during rapid quench. Bubble growth in the melt contributes to the deformation by capsule expansion, but the main problem is the shrinkage and collapse of bubbles during cooling. In first approximation, the texture of the vesiculated melt is not frozen until the glass transition T (~773 K for this composition, [1]) is reached. From 1323 K to T(g) the melt will display viscous behavior. For a final P of 75 MPa, V(m) of the exsolved H2O at T(g) is only ~25% of V(m) at 1323 K [2]. The fluid P in the bubbles is therefore continuously decreasing during quench. In combination with constant external P, the bubbles can either contract isometrically, get deformed (flattened) or even become dented by sucking melt inwards, which can be observed in some glass products. The shrinkage of bigger bubbles in the capsules is sometimes affecting the whole vesicle texture in a sample. FPA-FTIR measurements did not reveal H2O diffusion profiles towards bubbles [3]. H2O concentration gradients around bubbles are expected to be disturbed or annihilated due to melt transport. All derived BSDs of our samples were corrected to resemble the bubble sizes prior to

  4. Alternative model of single-bubble sonoluminescence

    NASA Astrophysics Data System (ADS)

    Yasui, Kyuichi

    1997-12-01

    A model of single-bubble sonoluminescence (SBSL) is constructed. In the model, the temperature is assumed to be spatially uniform inside the bubble except at the thermal boundary layer near the bubble wall even at the strong collapse based on the theoretical results of Kwak and Na [Phys. Rev. Lett. 77, 4454 (1996)]. In the model, the effect of the kinetic energy of gases inside the bubble is taken into account, which heats up the whole bubble when gases stop their motions at the end of the strong collapse. In the model, a bubble in water containing air is assumed to consist mainly of argon based on the hypothesis of Lohse et al. [Phys. Rev. Lett. 78, 1359 (1997)]. Numerical calculations under a SBSL condition reveal that the kinetic energy of gases heats up the whole bubble considerably. It is also clarified that vapor molecules (H2O) undergo chemical reactions in the heated interior of the bubble at the collapse and that chemical reactions decrease the temperature inside the bubble considerably. It is suggested that SBSL originates in thermal radiation from the whole bubble rather than a local point (the bubble center) heated by a converging spherical shock wave widely suggested in the previous theories of SBSL.

  5. Bubble, Bubble, Toil and Trouble.

    ERIC Educational Resources Information Center

    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)

  6. Hubble Sees a Star 'Inflating' a Giant Bubble

    NASA Video Gallery

    A zoom into the Hubble Space Telescope photograph of an enormous, balloon-like bubble being blown into space by a super-hot, massive star. Astronomers trained the iconic telescope on this colorful ...

  7. Bubble diagnostics

    DOEpatents

    Visuri, Steven R.; Mammini, Beth M.; Da Silva, Luiz B.; Celliers, Peter M.

    2003-01-01

    The present invention is intended as a means of diagnosing the presence of a gas bubble and incorporating the information into a feedback system for opto-acoustic thrombolysis. In opto-acoustic thrombolysis, pulsed laser radiation at ultrasonic frequencies is delivered intraluminally down an optical fiber and directed toward a thrombus or otherwise occluded vessel. Dissolution of the occlusion is therefore mediated through ultrasonic action of propagating pressure or shock waves. A vapor bubble in the fluid surrounding the occlusion may form as a result of laser irradiation. This vapor bubble may be used to directly disrupt the occlusion or as a means of producing a pressure wave. It is desirable to detect the formation and follow the lifetime of the vapor bubble. Knowledge of the bubble formation and lifetime yields critical information as to the maximum size of the bubble, density of the absorbed radiation, and properties of the absorbing material. This information can then be used in a feedback system to alter the irradiation conditions.

  8. Numerical Simulations of Bubble Dynamics and Heat Transfer in Pool Boiling---Including the Effects of Conjugate Conduction, Level of Gravity, and Noncondensable Gas Dissolved in the Liquid

    NASA Astrophysics Data System (ADS)

    Aktinol, Eduardo

    Due to the complex nature of the subprocesses involved in nucleate boiling, it has not been possible to develop comprehensive models or correlations despite decades of accumulated data and analysis. Complications such as the presence of dissolved gas in the liquid further confound attempts at modeling nucleate boiling. Moreover, existing empirical correlations may not be suitable for new applications, especially with regards to varying gravity level. More recently, numerical simulations of the boiling process have proven to be capable of reliably predicting bubble dynamics and associated heat transfer by showing excellent agreement with experimental data. However, most simulations decouple the solid substrate by assuming constant wall temperature. In the present study complete numerical simulations of the boiling process are performed---including conjugate transient conduction in the solid substrate and the effects of dissolved gas in the liquid at different levels of gravity. Finite difference schemes are used to discretize the governing equations in the liquid, vapor, and solid phases. The interface between liquid and vapor phases is tracked by a level set method. An iterative procedure is used at the interface between the solid and fluid phases. Near the three-phase contact line, temperatures in the solid are observed to fluctuate significantly over short periods. The results show good agreement with the data available in the literature. The results also show that waiting and growth periods can be related directly to wall superheat. The functional relationship between waiting period and wall superheat is found to agree well with empirical correlations reported in the literature. For the case of a single bubble in subcooled nucleate boiling, the presence of dissolved gas in the liquid is found to cause noncondensables to accumulate at the top of the bubble where most condensation occurs. This results in reduced local saturation temperature and condensation rates

  9. Asymmetric interface temperature during vapor bubble growth

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

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

  10. ALL CURLED UP: A NUMERICAL INVESTIGATION OF SHOCK-BUBBLE INTERACTIONS AND THE ROLE OF VORTICES IN HEATING GALAXY CLUSTERS

    SciTech Connect

    Friedman, Samuel H.; Heinz, Sebastian; Churazov, Eugene

    2012-02-10

    Jets from active galactic nuclei (AGNs) in the centers of galaxy clusters inflate cavities of low-density relativistic plasma and drive shock and sound waves into the intracluster medium. When these waves overrun previously inflated cavities, they form a differentially rotating vortex through the Richtmyer-Meshkov instability (RMI). The dissipation of energy captured in the vortex can contribute to the feedback of energy into the atmospheres of cool core clusters. Using a series of hydrodynamic simulations, we investigate the efficiency of this process: we calculate the kinetic energy in the vortex by decomposing the velocity field into its irrotational and solenoidal parts. Compared to the two-dimensional case, the three-dimensional RMI is about a factor of two more efficient. The energy in the vortex field for weak shocks is E{sub vortex} Almost-Equal-To {rho}{sub ICM}{Delta} v{sup 2}{sub shock} V{sub bubble} (with dependence on the geometry, density contrast, and shock width). For strong shocks, the vortex becomes dynamically unstable, quickly dissipating its energy via a turbulent cascade. We derive a number of diagnostics for observations and laboratory experiments of shock-bubble interactions, like the shock-vortex standoff distance, which can be used to derive lower limits on the Mach number. The differential rotation of the vortex field leads to viscous dissipation, which is sufficiently efficient to react to cluster cooling and to dissipate the vortex energy within the cooling radius of the cluster for a reasonable range of vortex parameters. For sufficiently large filling factors (of order a few percent or larger), this process could thus contribute significantly to AGN feedback in galaxy clusters.

  11. Bubble Transport through Micropillar Arrays

    NASA Astrophysics Data System (ADS)

    Lee, Kenneth; Savas, Omer

    2012-11-01

    In current energy research, artificial photosynthetic devices are being designed to split water and harvest hydrogen gas using energy from the sun. In one such design, hydrogen gas bubbles evolve on the catalytic surfaces of arrayed micropillars. If these bubbles are not promptly removed from the surface, they can adversely affect gas evolution rates, water flow rates, sunlight capture, and heat management of the system. Therefore, an efficient method of collecting the evolved gas bubbles is crucial. Preliminary flow visualization has been conducted of bubbles advecting through dense arrays of pillars. Bubbles moving through square and hexagonal arrays are tracked, and the results are qualitatively described. Initial attempts to correlate bubble motion with relevant lengthscales and forces are also presented. These observations suggest how bubble transport within such pillar arrays can be managed, as well as guide subsequent experiments that investigate bubble evolution and collection. This material is based upon work performed by the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy under Award Number DE-SC0004993.

  12. An analysis of the hydrogen bubble concerns in the three-mile island unit-2 reactor vessel

    NASA Astrophysics Data System (ADS)

    Gordon, S.; Schmidt, K. H.; Honekamp, J. R.

    On 30 March 1979, two days after the accident at the Three-Mile Island Reactor near Harrisburg, Pennsylvania, press reports appeared about a non-condensable bubble in the reactor vessel. This bubble was said to consist mainly of hydrogen, and to grow rapidly, possibly due to the development of oxygen. Danger of explosion was reported to be imminent. We analyzed all possible sources of non-condensable gases, including radiolysis, and determined that a continuing growth of the bubble during several days after the accident was not possible. Our main conclusions were the following: (1) Most of the initial hydrogen in the bubble was produced by the reaction of the Zircalloy cladding with the super-heated water. (2) During the first 16 hr after shutdown, when boiling of the primary coolant water took place, in the worst case stoichiometric amounts of hydrogen and oxygen could have been produced by radiolysis, leading to a maximum amount of oxygen in the bubble, of 0.7% of the hydrogen, which is well below the explosion limit. (3) After this 16 hr period, when boiling had totally ceased, no further oxygen could have been produced by radiolysis of the primary cooling water. On the contrary, oxygen was recombined with hydrogen due to radiolysis at such a rate that the oxygen in the water was completely removed in less than five minutes. The subsequent rate of removal of oxygen from the bubble by dissolution and radiolysis depended essentially on the rate of dissolution.

  13. Primordial Bubbles within Primordial Bubbles

    NASA Astrophysics Data System (ADS)

    Occhionero, Franco; Amendola, Luca; Corasaniti, Pier Stefano

    The nucleation of primordial bubbles during an inflationary phase transition has been suggested to promote the formation of structure either above or below the horizon, depending on whether the nucleation occurs more or less than 60 e-folds before the end of inflation. Here we propose a mechanism which has both features and produces subhorizon cavities up to hundreds of h-1 Mpc -- where excess power is observed -- inside superhorizon bubbles, i.e. in open universes. For this purpose we build a new inflationary two-field model with two vacuum channels in the potential surface: by modulating the energy difference between these channels, episodes of back and forth transition occur in sequence during inflation. Thus, one physical process may i) reconcile inflation with openness and ii) seed a distribution of observable voids. Bubble spectra are given in terms of phenomenological parameters which in turn are functions of microscopic physical parameters. In principle large scale structure constrains fundamental physics: for example, to account for power at scales of hundreds of h-1 Mpc the singularity in the Euclidean action -- which separates the first from the second phase transition -- must be mild enough. The smoking gun of the process might be the imprint of non-Gaussian, ring-like signals on the microwave background at l > 1000 by the subhorizon bubbles. On the other end of the spectrum, the contribution to l =1,2 from the off-centerness of the observer in the open bubble, is being evaluated.

  14. Mechanics of gas-vapor bubbles

    NASA Astrophysics Data System (ADS)

    Hao, Yue; Zhang, Yuhang; Prosperetti, Andrea

    2017-03-01

    Most bubbles contain a mixture of vapor and incondensible gases. While the limit cases of pure vapor and pure gas bubbles are well studied, much less is known about the more realistic case of a mixture. The bubble contents continuously change due to the combined effects of evaporation and condensation and of gas diffusion in the liquid and in the bubble. This paper presents a model for this situation and illustrates by means of examples several physical processes that can occur: a bubble undergoing a temporary pressure reduction, which makes the liquid temporarily superheated; a bubble subjected to a burst of sound; and a bubble continuously growing by rectified diffusion of heat in the presence of an incondensible gas.

  15. Thermal-gravitational modeling and scaling of two-phase heat transport systems from micro-gravity to super-gravity levels

    NASA Astrophysics Data System (ADS)

    Delil, A. A. M.

    2001-02-01

    Earlier publications extensively describe NLR research on thermal-gravitational modeling and scaling of two-phase heat transport systems for spacecraft applications. These publications on mechanically and capillary pumped two-phase loops discuss pure geometric scaling, pure fluid to fluid scaling, and combined (hybrid) scaling of a prototype system by a model at the same gravity level, and of a prototype in micro-gravity environment by a scale-model on earth. More recent publications include the scaling aspects of prototype two-phase loops for Moon or Mars applications by scale-models on earth. Recent work, discussed here, concerns extension of thermal-gravitational scaling to super-g acceleration levels. This turned out to be necessary, since a very promising super-g application for (two-phase) heat transport systems will be cooling of high-power electronics in spinning satellites and in military combat aircraft. In such aircraft, the electronics can be exposed during maneuvres to transient accelerations up to 120 m/s2. The discussions focus on ``conventional'' (capillary) pumped two-phase loops. It can be considered as introduction to the accompanying article, which focuses on pulsating and oscillating devices. .

  16. Leverage bubble

    NASA Astrophysics Data System (ADS)

    Yan, Wanfeng; Woodard, Ryan; Sornette, Didier

    2012-01-01

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

  17. Tiny Bubbles.

    ERIC Educational Resources Information Center

    Kim, Hy

    1985-01-01

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

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

    NASA Technical Reports Server (NTRS)

    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.

  19. Bubble Drag Reduction Requires Large Bubbles

    NASA Astrophysics Data System (ADS)

    Verschoof, Ruben A.; van der Veen, Roeland C. A.; Sun, Chao; Lohse, Detlef

    2016-09-01

    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.

  20. Acoustic-Induced Drag on a Bubble.

    DTIC Science & Technology

    1999-03-01

    possibly controlling bubble migration and heat transfer. 14. SUBJECT TERMS: Drag, bubble dynamics, analog to stochastic electrodynamics 15. NUMBER OF...remains constant. The notion that acoustic noise can test, by analogy, predictions due to stochastic electrodynamics and to ZPF effects has been

  1. Magnetic resonance imaging for the exploitation of bubble-enhanced heating by high-intensity focused ultrasound: a feasibility study in ex vivo liver.

    PubMed

    Elbes, Delphine; Denost, Quentin; Robert, Benjamin; Köhler, Max O; Tanter, Mickaël; Bruno, Quesson

    2014-05-01

    Bubble-enhanced heating (BEH) may be exploited to improve the heating efficiency of high-intensity focused ultrasound in liver and to protect tissues located beyond the focal point. The objectives of this study, performed in ex vivo pig liver, were (i) to develop a method to determine the acoustic power threshold for induction of BEH from displacement images measured by magnetic resonance acoustic radiation force imaging (MR-ARFI), and (ii) to compare temperature distribution with MR thermometry for HIFU protocols with and without BEH. The acoustic threshold for generation of BEH was determined in ex vivo pig liver from MR-ARFI calibration curves of local tissue displacement resulting from sonication at different powers. Temperature distributions (MR thermometry) resulting from "conventional" sonications (20 W, 30 s) were compared with those from "composite" sonications performed at identical parameters, but after a HIFU burst pulse (0.5 s, acoustic power over the threshold for induction of BEH). Displacement images (MR-ARFI) were acquired between sonications to measure potential modifications of local tissue displacement associated with modifications of tissue acoustic characteristics induced by the burst HIFU pulse. The acoustic threshold for induction of BEH corresponded to a displacement amplitude of approximately 50 μm in ex vivo liver. The displacement and temperature images of the composite group exhibited a nearly spherical pattern, shifted approximately 4 mm toward the transducer, in contrast to elliptical shapes centered on the natural focal position for the conventional group. The gains in maximum temperature and displacement values were 1.5 and 2, and the full widths at half-maximum of the displacement data were 1.7 and 2.2 times larger than in the conventional group in directions perpendicular to ultrasound propagation axes. Combination of MR-ARFI and MR thermometry for calibration and exploitation of BEH appears to increase the efficiency and safety

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  3. Electrolytic Bubble Growth on Pillared Arrays

    NASA Astrophysics Data System (ADS)

    Lee, Kenneth; Savas, Omer

    2013-11-01

    In current energy research, artificial photosynthetic (AP) devices are being designed to split water and harvest hydrogen gas using sunlight. In one such design, hydrogen gas bubbles evolve on catalytic surfaces of arrayed micropillars. If these bubbles are not promptly removed from the surface, they can adversely affect gas evolution rates, water flow rates, sunlight capture, and heat management of the system - all of which deteriorate device performance. Therefore, understanding how to remove evolved gas bubbles from the pillar surfaces is crucial. Flow visualization of electrolytic bubble nucleation and detachment from the catalytic pillar surfaces has been conducted. The bubble departure diameter and lift-off frequency are extracted and compared with known correlations from boiling heat transfer. Bubble tracking indicates that bubble detachment is enhanced by local interactions with neighboring bubbles. These observations suggest how hydrogen gas bubbles can be effectively removed from pillared surfaces to prolong AP device longevity. Joint Center for Artificial Photosynthesis, a U.S. Department of Energy (DOE) Energy Innovations Hub.

  4. Surfactants for Bubble Removal against Buoyancy.

    PubMed

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

    2016-01-08

    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.

  5. Surfactants for Bubble Removal against Buoyancy

    PubMed Central

    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

  6. Surfactants for Bubble Removal against Buoyancy

    NASA Astrophysics Data System (ADS)

    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.

  7. Three-Dimensional Metal-Organic Framework as Super Heat-Resistant Explosive: Potassium 4-(5-Amino-3-Nitro-1H-1,2,4-Triazol-1-Yl)-3,5-Dinitropyrazole.

    PubMed

    Li, Chuan; Zhang, Man; Chen, Qishan; Li, Yingying; Gao, Huiqi; Fu, Wei; Zhou, Zhiming

    2017-01-31

    A new super heat-resistant explosive, potassium 4-(5-amino-3-nitro-1H-1,2,4-triazol-1-yl)-3,5-dinitropyrazole (KCPT, 1), featuring a three-dimensional (3D) energetic metal-organic framework (MOF) was synthesized and fully characterized. The new 3D MOF was found to be extremely heat-resistant, having a high decomposition temperature of 323 °C. In addition, KCPT exhibits the best calculated detonation performance (vD =8457 m s(-1) , p=32.5 GPa) among the reported super heat-resistant explosives or energetic potassium salts while retaining a suitable impact sensitivity of 7.5 J, which makes it one of the most promising heat-resistant explosives.

  8. Mass transfer effects on the transmission of bubble screens

    NASA Astrophysics Data System (ADS)

    Fuster, Daniel; Bergamasco, Luca

    2016-11-01

    In this work we investigate, theoretically and numerically, the reflection and transmission properties of bubble screens excited by pressure wave pulses. We use modified expressions for the bubble resonance frequency and the damping factor in order to capture the influence of mass transfer on the reflection-transmission coefficients. In addition to the influence of variables such as the bubble radius and the averaged inter-bubble distance, the analysis reveals that in conditions close to the saturation line there exists a regime where the heat transport surrounding the bubble plays an important role on the bubble's response also influencing the reflection properties of the bubble screen. The linear analysis allows us to predict the critical vapor content beyond which liquid heat's transport controls the dynamic response of the bubbles. Numerical simulations show that these effects become especially relevant in the nonlinear regime. ANR Cachmap.

  9. Bubbling orientifolds

    NASA Astrophysics Data System (ADS)

    Mukhi, Sunil; Smedbäck, Mikael

    2005-08-01

    We investigate a class of 1/2-BPS bubbling geometries associated to orientifolds of type-IIB string theory and thereby to excited states of the SO(N)/Sp(N) Script N = 4 supersymmetric Yang-Mills theory. The geometries are in correspondence with free fermions moving in a harmonic oscillator potential on the half-line. Branes wrapped on torsion cycles of these geometries are identified in the fermi fluid description. Besides being of intrinsic interest, these solutions may also occur as local geometries in flux compactifications where orientifold planes are present to ensure global charge cancellation. We comment on the extension of this procedure to M-theory orientifolds.

  10. Slurry bubble column hydrodynamics

    NASA Astrophysics Data System (ADS)

    Rados, Novica

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

  11. Screening of liquids for thermocapillary bubble movement

    NASA Technical Reports Server (NTRS)

    Wilcox, W. R.; Subramanian, R. S.; Papazian, J. M.; Smith, H. D.; Mattox, D. M.

    1979-01-01

    Ground-based methods for pretesting qualitatively the thermocapillary movement of gas bubbles in a liquid to be used in space processing are discussed. Theoretical considerations are shown to require the use of a thin, enclosed, horizontal liquid film in order that the bubbles move faster than the bulk convection of the liquid, with insulating boundaries to prevent the onset of instabilities. Experimental realizations of horizontal cells in which to test the thermocapillary movement of bubbles in sheets of molten glass heated from below and organic melts in tubes heated from both ends are briefly described and the results of experiments are indicated.

  12. Design and Operation of Experimental System for Studying Heat Transfer in a Smooth Tube at Near and Super Critical Pressure

    NASA Astrophysics Data System (ADS)

    Wenkai, Li; Yuxin, Wu; Yan, Li; Junfu, Lu; Hai, Zhang

    Boilers running at supercritical pressure with large capacity have been widely used in power generation technology. How to keep the safety of heat transfer in the riser system is an important issue. However, it is difficult to study heat transfer for the vertical smooth tubes in a boiler at sub-critical or supercritical pressure since the thermodynamic properties of water is very complex and sensitive to temperature and pressure near the critical point. Hot-state experiment of heat transfer for the tubes of diameter used in a boiler is of great value for the design of membrane wall. In order to study the heat transfer of vertical smooth tubes running at low heat flux and low mass flux for sub-critical CFB boilers, a near-supercritical pressure water test bed was built in Tsinghua University. The designed pressure is 21MPa, the mass flux of water is 550kg/m2s, and the heat flux is 136kW/m. In this paper, the design and structure of the test bed is introduced. The experimental result is analyzed, more experimental work is needed in future research.

  13. Single Bubble Sonoluminescence

    NASA Astrophysics Data System (ADS)

    Farley, Jennifer; Hough, Shane

    2003-05-01

    Single Bubble Sonoluminescence is the emission of light from a single bubble suspended in a liquid caused by a continuum of repeated implosions due to pressure waves generated from a maintained ultrasonic sinusoidal wave source. H. Frenzel and H. Schultz first studied it in 1934 at the University of Cologne. It was not until 1988 with D.F. Gaitan that actual research began with single bubble sonoluminescence. Currently many theories exist attempting to explain the observed bubble phenomenon. Many of these theories require spherical behavior of the bubble. Observation of the bubble has shown that the bubble does not behave spherically in most cases. One explanation for this is known as jet theory. A spectrum of the bubble will give us the mean physical properties of the bubble such as temperature and pressure inside the bubble. Eventually, with the aide of fluorocene dye a full spectrum of the bubble will be obtained.

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

    NASA Astrophysics Data System (ADS)

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

    2007-11-01

    The surfactant effect on a single bubble motion is so important that it changes whole bubbly flow structures. One of the surfactant key effects is to decrease bubble rise velocity. This phenomenon is described as Marangoni effect which is quantitatively investigated by many experiments and numerical calculations of straight rising bubbles. Some other previous researches studied a bubble trajectory transition from a zigzag trajectory to spiral in super purified water (Mougin et al. 2002). However, the surfactant effect on this 3D motion bubbles is not enough investigated. To investigate it in detail, we measured trajectories of single bubbles rising in a tank of 1300mm height filled with dilute surfactant solution. We observed a bubble motion transition from spiral to zigzag, which is just reverse transition of trajectories in super purified water. Considering our other measurement results of bubble trajectories in super purified water, those in different surfactant solution, and a profile of bubble rise velocity, we think this interesting result is explained by surfactant concentration on a bubble surface. We will discuss its mechanism in detail in our presentation.

  15. Bubble nucleation in an explosive micro-bubble actuator

    NASA Astrophysics Data System (ADS)

    van den Broek, D. M.; Elwenspoek, M.

    2008-06-01

    Explosive evaporation occurs when a thin layer of liquid reaches a temperature close to the critical temperature in a very short time. At these temperatures spontaneous nucleation takes place. The nucleated bubbles instantly coalesce forming a vapour film followed by rapid growth due to the pressure impulse. In this paper we take a closer look at the bubble nucleation. The moment of bubble nucleation was determined by both stroboscopic imaging and resistance thermometry. Two nucleation regimes could be distinguished. Several different heater designs were investigated under heat fluxes of hundreds of W mm-2. A close correspondence between current density in the heater and point of nucleation was found. This results in design rules for effective heaters.

  16. Are All Obsidians Super-Heated? Insights from Observations of Crystallization Kinetics in Experiments on Glass Mountain Obsidians (Long Valley, CA)

    NASA Astrophysics Data System (ADS)

    Waters, L.; Andrews, B. J.

    2015-12-01

    The Glass Mountain obsidians (Long Valley, CA) are crystal-poor (<8%) and highly-evolved (high SiO2, low MgO, Sr, Ba) and, therefore, their formation required extremely efficient crystal-liquid separation. Petrologic and experimental investigation of the mineral phases in Glass Mountain lavas may reveal differentiation processes that generated the obsidians, if the mineral assemblage is phenocrystic. Results of high-resolution SEM mapping and electron microprobe analysis of a Glass Mountain sample reveal that the obsidian is saturated in nine phases (sanidine + quartz + plagioclase + ilmenite + titanomagnetite + zircon + apatite + allanite + biotite). Sanidine (Or78-Or35) and quartz occur in the largest abundances, and plagioclase (super-liquidus conditions. Therefore, the Glass Mountain obsidians were super-heated prior to crystallization, achieved either by fluid under-saturated decompression from a crystalline mush or H2O-saturated partial melting.

  17. Acoustic bubble removal method

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

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

  18. A study of laser-induced bubbles in cryogenic fluid - Behavior of bubbles in liquid nitrogen

    NASA Astrophysics Data System (ADS)

    Maeno, Kazuo; Yokoyama, Shingo; Hanaoka, Yutaka

    The dynamics of cavitation vapor bubble in cryogenic liquid nitrogen is investigated experimentally and analytically. The bubbles are produced by focusing a giant pulse of Q-switched ruby laser into the liquid nitrogen in a cryostat, and the dynamics of the laser-induced bubble are studied by means of high-speed photography by using an image converter camera with the framing rates of 100,000 frames/s. A numerical analysis is also performed on the behavior of a bubble in cryogenic liquid. The mathematical formulation takes into account the effect of liquid inertia (incompressible liquid), nonequilibrium condensation of the vapor in the bubble, and the heat transfer at the bubble wall. The experimental data on the bubble motion in liquid nitrogen under the near-equilibrium initial conditions with an atmospheric pressure are compared to the numerical solutions. The bubble motion observed indicates more violent and decaying behavior than the estimated tendency. The heat and mass transfer effects including the evaporation and condensation phenomena have strong influence on the vapor bubble motion in cryogenic liquid. Qualitatively, the numerical analysis can simulate the experimental results.

  19. Fearless versus fearful speculative financial bubbles

    NASA Astrophysics Data System (ADS)

    Andersen, J. V.; Sornette, D.

    2004-06-01

    Using a recently introduced rational expectation model of bubbles, based on the interplay between stochasticity and positive feedbacks of prices on returns and volatility, we develop a new methodology to test how this model classifies nine time series that have been previously considered as bubbles ending in crashes. The model predicts the existence of two anomalous behaviors occurring simultaneously: (i) super-exponential price growth and (ii) volatility growth, that we refer to as the “fearful singular bubble” regime. Out of the nine time series, we find that five pass our tests and can be characterized as “fearful singular bubbles”. The four other cases are the information technology Nasdaq bubble and three bubbles of the Hang Seng index ending in crashes in 1987, 1994 and 1997. According to our analysis, these four bubbles have developed with essentially no significant increase of their volatility. This paper thus proposes that speculative bubbles ending in crashes form two groups hitherto unrecognized, namely those accompanied by increasing volatility (reflecting increasing risk perception) and those without change of volatility (reflecting an absence of risk perception).

  20. Scaling model for laser-produced bubbles in soft tissue

    SciTech Connect

    London, R. A., LLNL

    1998-03-12

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

  1. A coupled numerical analysis of shield temperatures, heat losses and residual gas pressures in an evacuated super-insulation using thermal and fluid networks. Part II: Unsteady-state conditions (cool-down period)

    NASA Astrophysics Data System (ADS)

    Reiss, H.

    2006-12-01

    This paper analyses the cool-down period of a 300 L super-insulated cryogenic storage tank for liquid nitrogen. Storage tank and evacuated shields are the same as described in part I of this paper where stationary states were investigated. The aim of the present paper is to introduce thermal resistance networks as a tool to quantitatively understand and control also unsteady-states like cool-down of super-insulations. Numerical simulations using thermal resistance networks have been performed to determine time dependence of local shield temperatures and heat loss components. Coupling between radiation and solid conduction is investigated under these conditions. Using the numerical results, we have checked an experimental method suggested in the literature to separate heat losses through the insulation from losses through thermal bridges by measurement of unsteady-state evaporation rates. The results of the simulations confirm that it takes the outer shields much longer to reach stationary temperature; cool-down does not proceed uniformly in the super-insulation. Coupling between different heat transfer modes again is obvious. Thermal emissivity is important also during the early phase of cool-down. Using the obtained numerical results, the experimental method to separate heat loss components could only roughly been confirmed for thick metallic foils.

  2. Bubble drag reduction requires large bubbles

    NASA Astrophysics Data System (ADS)

    Verschoof, Ruben; van der Veen, Roeland; Sun, Chao; Lohse, Detlef

    2016-11-01

    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. A few volume percent (<= 4 %) of bubbles can reduce the overall drag up to 40% and beyond. However, the exact mechanism is unknown, thus hindering further progress and optimization. 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. We acknowledge support from STW and FOM.

  3. Constrained Vapor Bubble

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

    The nonisothermal Constrained Vapor Bubble, CVB, is being studied to enhance the understanding of passive systems controlled by interfacial phenomena. The study is multifaceted: 1) it is a basic scientific study in interfacial phenomena, fluid physics and thermodynamics; 2) it is a basic study in thermal transport; and 3) it is a study of a heat exchanger. The research is synergistic in that CVB research requires a microgravity environment and the space program needs thermal control systems like the CVB. Ground based studies are being done as a precursor to flight experiment. The results demonstrate that experimental techniques for the direct measurement of the fundamental operating parameters (temperature, pressure, and interfacial curvature fields) have been developed. Fluid flow and change-of-phase heat transfer are a function of the temperature field and the vapor bubble shape, which can be measured using an Image Analyzing Interferometer. The CVB for a microgravity environment, has various thin film regions that are of both basic and applied interest. Generically, a CVB is formed by underfilling an evacuated enclosure with a liquid. Classification depends on shape and Bond number. The specific CVB discussed herein was formed in a fused silica cell with inside dimensions of 3x3x40 mm and, therefore, can be viewed as a large version of a micro heat pipe. Since the dimensions are relatively large for a passive system, most of the liquid flow occurs under a small capillary pressure difference. Therefore, we can classify the discussed system as a low capillary pressure system. The studies discussed herein were done in a 1-g environment (Bond Number = 3.6) to obtain experience to design a microgravity experiment for a future NASA flight where low capillary pressure systems should prove more useful. The flight experiment is tentatively scheduled for the year 2000. The SCR was passed on September 16, 1997. The RDR is tentatively scheduled for October, 1998.

  4. Finger evolution of a gas bubble driven by atmospheric pressure plasma

    NASA Astrophysics Data System (ADS)

    Shiu, Jia-Hau; Chu, Hong-Yu

    2016-12-01

    We report the generation and evolution of a finger-shaped bubble in liquid by dielectric discharge setup. The spherical gas bubble is deformed into a finger-shaped bubble after the ignition of plasma. The presence of the filamentary discharge in the bubble not only provides the local heating to the bubble, it also changes the distribution of the electric field in the bubble and the bubble mutually provides the pathway to the discharge. The reduced surface tension on the liquid-gas interface due to the rise of temperature by plasma heating and the nonuniform electric field caused by the presence of filamentary discharge might induce the concave-shaped bubble. We also observe the formation of the quasi-two-dimensional bubble, which is generated from the bubble and attached on one side of the electrodes. It is found that the discharge induces the growth of the periodic fluctuations in the thin layer of gas.

  5. Steady State Vapor Bubble in Pool Boiling

    PubMed Central

    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

  6. Steady State Vapor Bubble in Pool Boiling.

    PubMed

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

    2016-02-03

    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.

  7. Bubbly Suspension Generated in Low Gravity

    NASA Technical Reports Server (NTRS)

    Nahra, Henry K.

    2000-01-01

    Bubbly suspensions are crucial for mass and heat transport processes on Earth and in space. These processes are relevant to pharmaceutical, chemical, nuclear, and petroleum industries on Earth. They are also relevant to life support, in situ resource utilization, and propulsion processes for long-duration space missions such as the Human Exploration and Development of Space program. Understanding the behavior of the suspension in low gravity is crucial because of factors such as bubble segregation, which could result in coalescence and affect heat and mass transport. Professors A. Sangani and D. Koch, principal investigators in the Microgravity Fluid Physics Program managed by the NASA Glenn Research Center at Lewis Field, are studying the physics of bubbly suspension. They plan to shear a bubbly suspension in a couette cell in microgravity to study bubble segregation and compare the bubble distribution in the couette gap with the one predicted by the suspension-averaged equations of motion. Prior to the Requirement Definition Review of this flight experiment, a technology for generating a bubbly suspension in microgravity has to be established, tested, and verified.

  8. Experimental study of flow in a channel with a periodically heated wall

    NASA Astrophysics Data System (ADS)

    Inasawa, Ayumu; Taneda, Keinosuke; Floryan, Jerzy M.

    2015-11-01

    Flows in a channel with spatially periodic wall heating are examined experimentally at the Reynolds numbers below Re = 20 and at the Rayleigh number based on the amplitude of the periodic heating and the channel half width Rap = 3500, to realize the super-thermohydrophobic effect leading to a significant drag reduction (Floryan, 2012). The periodic heating is applied at the lower wall while the temperature of the upper wall is uniform and controlled. The results show that steady separation bubbles are created by periodic heating, which separate the main stream from the wall and, thus, the net friction drag is reduced. It is also found that the separation bubbles are strengthened when the average temperature of the lower wall exceeds that of the upper wall. Comparisons between the experiments and the theoretical results are presented.

  9. The Isolated Bubble Regime in Pool Nucleate Boiling

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  10. Scaling model for laser-produced bubbles in soft tissue

    NASA Astrophysics Data System (ADS)

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

    1998-05-01

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

  11. Single Bubble Sonoluminescence in Low Gravity and Optical Radiation Pressure Positioning of the Bubble

    NASA Technical Reports Server (NTRS)

    Thiessen, D. B.; Young, J. E.; Marr-Lyon, M. J.; Richardson, S. L.; Breckon, C. D.; Douthit, S. G.; Jian, P. S.; Torruellas, W. E.; Marston, P. L.

    1999-01-01

    Several groups of researchers have demonstrated that high frequency sound in water may be used to cause the regular repeated compression and luminescence of a small bubble of gas in a flask. The phenomenon is known as single bubble sonoluminescence (SBSL). It is potentially important because light emitted by the bubble appears to be associated with a significant concentration of energy within the volume of the bubble. Unfortunately, the detailed physical mechanisms causing the radiation of light by oscillating bubbles are poorly understood and there is some evidence that carrying out experiments in a weightless environment may provide helpful clues. In addition, the radiation pressure of laser beams on the bubble may provide a way of simulating weightless experiments in the laboratory. The standard model of SBSL attributes the light emission to heating within the bubble by a spherically imploding shock wave to achieve temperatures of 50,000 K or greater. In an alternative model, the emission is attributed to the impact of a jet of water which is required to span the bubble and the formation of the jet is linked to the buoyancy of the bubble. The coupling between buoyancy and jet formation is a consequence of the displacement of the bubble from a velocity node (pressure antinode) of the standing acoustic wave that drives the radial bubble oscillations. One objective of this grant is to understand SBSL emission in reduced buoyancy on KC-135 parabolic flights. To optimize the design of those experiments and for other reasons which will help resolve the role of buoyancy, laboratory experiments are planned in simulated low gravity in which the radiation pressure of laser light will be used to position the bubble at the acoustic velocity node of the ultrasonic standing wave. Laser light will also be used to push the bubble away from the velocity node, increasing the effective buoyancy. The original experiments on the optical levitation and radiation pressure on bubbles

  12. Bubbly Cavitation Flows.

    DTIC Science & Technology

    1991-03-31

    and 12. Comparison is also made with analytical predictions based on the Rayleigh - Plesset equations. In addition to the single bubble studies, the...bubble maximum size distributions and those predicted using the measured nuclei number distribution and the Rayleigh - Plesset model for the bubble dyna...tions 7, 9, 11, 12, 13 examined travelling bubble cavitation on two classic axisymmetric headforms (a Schiebe body and the ITTC headform) and, with the

  13. Radio Bubbles in Clusters of Galaxies

    SciTech Connect

    Dunn, Robert J.H.; Fabian, A.C.; Taylor, G.B.; /NRAO, Socorro /KIPAC, Menlo Park

    2005-12-14

    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 10MHz and 10GHz. 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 {approx}< k/f {approx}< 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 higher upper limits on k/f than the active bubbles, especially when compared to those in the same cluster. A study of the Brightest 55 cluster sample shows that 17, possibly 20, clusters required some form of heating as they have a short central cooling time, t{sub cool} {approx}< 3 Gyr, and a large central temperature drop, T{sub centre}/T{sub outer} < 1/2. Of these between 12 (70 per cent) and 15 (75 per cent), contain bubbles. This indicates that the duty cycle of bubbles is large in such clusters and that they can play a major role in the heating process.

  14. Models of cylindrical bubble pulsation

    PubMed Central

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

    2012-01-01

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

  15. Acoustic bubble traps

    NASA Astrophysics Data System (ADS)

    Geisler, Reinhard; Kurz, Thomas; Lauterborn, Werner

    2000-07-01

    A small, oscillating bubble in a liquid can be trapped in the antinode of an acoustic standing wave field. Bubble stability is required for the study of single bubble sonoluminescence (SBSL). The properties of the acoustic resonator are essential for the stable trapping of sonoluminescing bubbles. Resonators can be chosen according to the intended application: size and geometry can be varied in a wide range. In this work, the acoustic responses of different resonators were measured by means of holographic interferometry, hydrophones and a laser vibrometer. Also, high-speed photography was used to observe the bubble dynamics. Several single, stable sonoluminescent bubbles were trapped simultaneously within an acoustic resonator in the pressure antinodes of a higher harmonic mode (few bubble sonoluminescence, FBSL).

  16. Demonstrating the Importance of Bubbles and Viscosity on Volcanic Eruptions

    NASA Astrophysics Data System (ADS)

    Namiki, A.

    2005-12-01

    The behavior of bubbles (exsolved volatile from magma) and viscosity of magma are important parameters that influence volcanic eruptions. Exsolved volatiles increase the volume of magma and reduce its density so that magma has sufficient volume and buoyancy force to erupt. Volatiles exsolve through nucleation and growth by diffusion and bubbles can expand as pressure is reduced. The time scale of diffusion depends on the viscosity of surrounding magma, and the expansion time scale of a bubble is also depends on the viscosity of magma. These control the time scale for volume change. If bubbles segregate from magma and collapse, the magma might not able to expand sufficiently to erupt violently. Whether a bubble can segregate from the liquid part of magma is also depends on viscosity of magma. In this poster, I introduce a straightforward demonstration to show the importance of bubbles and viscosity of magma on volcanic eruptions. To make bubbles, I use baking soda (NaHCO3) and citric acid. Reaction between them generates carbon dioxide (CO2) to make bubbles. I make citric acid solution gel by using agar at the bottom of a transparent glass and pour baking soda disolved corn syrup on top of the agar. This situation is a model of basally heated magma chamber. When water disolved magma (baking soda disolved corn syrup) receives sufficient heat (citric acid) bubbles are generated. I can change viscosity of corn syrup by varying the concentration of water. This demonstration shows how viscosity controls the time scale of volume change of bubbly magma and the distribution of bubbles in the fluid. In addition it helps to understand the important physical processes in volcanic eruption: bubble nucleation, diffusion grows, expansion, and bubble driving convection. I will perform a live demonstration at the site of the poster.

  17. Bubble transport in subcooled flow boiling

    NASA Astrophysics Data System (ADS)

    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

  18. Bubbles in liquids with phase transition. Part 1. On phase change of a single vapor bubble in liquid water

    NASA Astrophysics Data System (ADS)

    Dreyer, Wolfgang; Duderstadt, Frank; Hantke, Maren; Warnecke, Gerald

    2012-11-01

    In the forthcoming second part of this paper a system of balance laws for a multi-phase mixture with many dispersed bubbles in liquid is derived where phase transition is taken into account. The exchange terms for mass, momentum and energy explicitly depend on evolution laws for total mass, radius and temperature of single bubbles. Therefore in the current paper we consider a single bubble of vapor and inert gas surrounded by the corresponding liquid phase. The creation of bubbles, e.g. by nucleation is not taken into account. We study the behavior of this bubble due to condensation and evaporation at the interface. The aim is to find evolution laws for total mass, radius and temperature of the bubble, which should be as simple as possible but consider all relevant physical effects. Special attention is given to the effects of surface tension and heat production on the bubble dynamics as well as the propagation of acoustic elastic waves by including slight compressibility of the liquid phase. Separately we study the influence of the three phenomena heat conduction, elastic waves and phase transition on the evolution of the bubble. We find ordinary differential equations that describe the bubble dynamics. It turns out that the elastic waves in the liquid are of greatest importance to the dynamics of the bubble radius. The phase transition has a strong influence on the evolution of the temperature, in particular at the interface. Furthermore the phase transition leads to a drastic change of the water content in the bubble. It is shown that a rebounding bubble is only possible, if it contains in addition an inert gas. In Part 2 of the current paper the equations derived are sought in order to close the system of equations for multi-phase mixture balance laws for dispersed bubbles in liquids involving phase change.

  19. Conditions for bubble elongation in cold ice-sheet ice

    USGS Publications Warehouse

    Alley, R.B.; Fitzpatrick, J.J.

    1999-01-01

    Highly elongated bubbles are sometimes observed in ice-sheet ice. Elongation is favored by rapid ice deformation, and opposed by diffusive processes. We use simple models to show that vapor transport dominates diffusion except possibly very close to the melting point, and that latent-heat effects are insignificant. Elongation is favored by larger bubbles at pore close-off, but is nearly independent of bubble compression below close-off. The simple presence of highly elongated bubbles indicates only that a critical ice-strain rate has been exceeded for significant time, and provides no information on possible disruption of stratigraphic continuity by ice deformation.

  20. Gas bubble detector

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    A gas bubble detector having a modulated IR source focused through a bandpass filter onto a venturi, formed in a sample tube, to illuminate the venturi with modulated filtered IR to detect the presence of gas bubbles as small as 0.01 cm or about 0.004 in diameter in liquid flowing through the venturi. Means are provided to determine the size of any detected bubble and to provide an alarm in the absence of liquid in the sample tube.

  1. Tightrope walking bubbles

    NASA Astrophysics Data System (ADS)

    de Maleprade, Helene; Clanet, Christophe; Quere, David

    2016-11-01

    A fiber can hold a certain amount of liquid, which allows us to capture flying drops and control their motion. Immersed in water, a fiber can efficiently capture air bubbles only if it is hydrophobic. Using a superhydrophobic coating on an inclined wire, we experimentally control the rising velocity of air bubbles walking along the tightrope. We discuss the nature of the friction around the walker, and the resulting speed of bubbles.

  2. Non-Abelian bubbles in microstate geometries

    NASA Astrophysics Data System (ADS)

    Ramírez, Pedro F.

    2016-11-01

    We find the first smooth bubbling microstate geometries with non-Abelian fields. The solutions constitute an extension of the BPS three-charge smooth microstates. These consist in general families of regular supersymmetric solutions with non-trivial topology, i.e. bubbles, of {N}=d , d = 5 Super-Einstein-Yang-Mills theory, having the asymptotic charges of a black hole or black ring but with no horizon. The non-Abelian fields make their presence at the very heart of the microstate structure: the physical size of the bubbles is affected by the non-Abelian topological charge they carry, which combines with the Abelian flux threading the bubbles to hold them up. Interestingly the non-Abelian fields carry a set of adjustable continuous parameters that do not alter the asymptotics of the solutions but modify the local geometry. This feature can be used to obtain a classically infinite number of microstate solutions with the asymptotics of a single black hole or black ring.

  3. Photothermally controlled Marangoni flow around a micro bubble

    SciTech Connect

    Namura, Kyoko Nakajima, Kaoru; Kimura, Kenji; Suzuki, Motofumi

    2015-01-26

    We have experimentally investigated the control of Marangoni flow around a micro bubble using photothermal conversion. Using a focused laser spot acting as a highly localized heat source on Au nanoparticles/dielectric/Ag mirror thin film enables us to create a micro bubble and to control the temperature gradient around the bubble at a micrometer scale. When we irradiate the laser next to the bubble, a strong main flow towards the bubble and two symmetric rotation flows on either side of it develop. The shape of this rotation flow shows a significant transformation depending on the relative position of the bubble and the laser spot. Using this controllable rotation flow, we have demonstrated sorting of the polystyrene spheres with diameters of 2 μm and 0.75 μm according to their size.

  4. Bubble behavior in molten glass in a temperature gradient. [in reduced gravity rocket experiment

    NASA Technical Reports Server (NTRS)

    Meyyappan, M.; Subramanian, R. S.; Wilcox, W. R.; Smith, H.

    1982-01-01

    Gas bubble motion in a temperature gradient was observed in a sodium borate melt in a reduced gravity rocket experiment under the NASA SPAR program. Large bubbles tended to move faster than smaller ones, as predicted by theory. When the bubbles contacted a heated platinum strip, motion virtually ceased because the melt only imperfectly wets platinum. In some cases bubble diameter increased noticeably with time.

  5. Formation and X-ray emission from hot bubbles in planetary nebulae - I. Hot bubble formation

    NASA Astrophysics Data System (ADS)

    Toalá, J. A.; Arthur, S. J.

    2014-10-01

    We carry out high-resolution two-dimensional radiation-hydrodynamic numerical simulations to study the formation and evolution of hot bubbles inside planetary nebulae. We take into account the evolution of the stellar parameters, wind velocity and mass-loss rate from the final thermal pulses during the asymptotic giant branch (AGB) through to the post-AGB stage for a range of initial stellar masses. The instabilities that form at the interface between the hot bubble and the swept-up AGB wind shell lead to hydrodynamical interactions, photoevaporation flows and opacity variations. We explore the effects of hydrodynamical mixing combined with thermal conduction at this interface on the dynamics, photoionization, and emissivity of our models. We find that even models without thermal conduction mix significant amounts of mass into the hot bubble. When thermal conduction is not included, hot gas can leak through the gaps between clumps and filaments in the broken swept-up AGB shell and this depressurises the bubble. The inclusion of thermal conduction evaporates and heats material from the clumpy shell, which expands to seal the gaps, preventing a loss in bubble pressure. The dynamics of bubbles without conduction is dominated by the thermal pressure of the thick photoionized shell, while for bubbles with thermal conduction it is dominated by the hot, shocked wind.

  6. Acoustical emission from bubbles

    NASA Astrophysics Data System (ADS)

    Longuet-Higgins, Michael S.

    1991-12-01

    The scientific objectives of this report are to investigate the dynamics of bubbles formed from a free surface (particularly the upper surface of the ocean) by breaking waves, and the resulting emission of underwater sound. The chief natural source of underwater sound in the ocean at frequencies from 0.5 to 50 kHz is known to be the acoustical emission from newly-formed bubbles and bubble clouds, particularly those created by breaking waves and rain. Attention has been drawn to the occurrence of high-speed jets directed into the bubble just after bubble closure. They have been observed both in rain-drop impacts and in the release of bubbles from an underwater nozzle. Qualitatively they are similar to the inward jets seen in the collapse of a cavitation bubble. There is also a similarity to the highly-accelerated upward jets in standing water waves (accelerations greater than 20g) or in bubbles bursting at a free surface. We have adopted a theoretical approach based on the dynamics of incompressible fluids with a free surface.

  7. Evaporation, Boiling and Bubbles

    ERIC Educational Resources Information Center

    Goodwin, Alan

    2012-01-01

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

  8. Let Them Blow Bubbles.

    ERIC Educational Resources Information Center

    Korenic, Eileen

    1988-01-01

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

  9. Simulating Surfzone Bubbles

    DTIC Science & Technology

    2012-09-30

    D (Ripple) and 3-D ( Truchas ) Navier- Stokes solvers. In the continuation of this work, our objectives are to: 1) Implement a physics-based...a bubble phase with multiple bubble size (or, more accurately, mass) bins. The existing 3-D model Truchas has been extended to include Carrica et al

  10. Bubble collision with gravitation

    SciTech Connect

    Hwang, Dong-il; Lee, Bum-Hoon; Lee, Wonwoo; Yeom, Dong-han E-mail: bhl@sogang.ac.kr E-mail: innocent.yeom@gmail.com

    2012-07-01

    In this paper, we study vacuum bubble collisions with various potentials including gravitation, assuming spherical, planar, and hyperbolic symmetry. We use numerical calculations from double-null formalism. Spherical symmetry can mimic the formation of a black hole via multiple bubble collisions. Planar and especially hyperbolic symmetry describes two bubble collisions. We study both cases, when two true vacuum regions have the same field value or different field values, by varying tensions. For the latter case, we also test symmetric and asymmetric bubble collisions, and see details of causal structures. If the colliding energy is sufficient, then the vacuum can be destabilized, and it is also demonstrated. This double-null formalism can be a complementary approach in the context of bubble collisions.

  11. Interfacial Bubble Deformations

    NASA Astrophysics Data System (ADS)

    Seymour, Brian; Shabane, Parvis; Cypull, Olivia; Cheng, Shengfeng; Feitosa, Klebert

    Soap bubbles floating at an air-water experience deformations as a result of surface tension and hydrostatic forces. In this experiment, we investigate the nature of such deformations by taking cross-sectional images of bubbles of different volumes. The results show that as their volume increases, bubbles transition from spherical to hemispherical shape. The deformation of the interface also changes with bubble volume with the capillary rise converging to the capillary length as volume increases. The profile of the top and bottom of the bubble and the capillary rise are completely determined by the volume and pressure differences. James Madison University Department of Physics and Astronomy, 4VA Consortium, Research Corporation for Advancement of Science.

  12. Tribonucleation of bubbles

    PubMed Central

    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 rubbing force and velocity exceed a certain threshold. Direct observation through a transparent solid shows that each bubble in the trail results from the early coalescence of several microscopic bubbles, themselves detaching from microscopic gas pockets forming between the solids. From a detailed study of the wear tracks, with atomic force and scanning electron microscopy imaging, we conclude that these microscopic gas pockets originate from a local fracturing of the surface asperities, possibly enhanced by chemical reactions at the freshly created surfaces. Our findings will be useful either for preventing undesired bubble formation or, on the contrary, for “writing with bubbles,” i.e., creating controlled patterns of microscopic bubbles. PMID:24982169

  13. Bubble core field modification by residual electrons inside the bubble

    SciTech Connect

    Wu Haicheng; Xie Baisong; Zhao Xueyan; Zhang Shan; Hong Xueren; Liu Mingping

    2010-11-15

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

  14. Laser-induced nucleation of carbon dioxide bubbles

    NASA Astrophysics Data System (ADS)

    Ward, Martin R.; Jamieson, William J.; Leckey, Claire A.; Alexander, Andrew J.

    2015-04-01

    A detailed experimental study of laser-induced nucleation (LIN) of carbon dioxide (CO2) gas bubbles is presented. Water and aqueous sucrose solutions supersaturated with CO2 were exposed to single nanosecond pulses (5 ns, 532 nm, 2.4-14.5 MW cm-2) and femtosecond pulses (110 fs, 800 nm, 0.028-11 GW cm-2) of laser light. No bubbles were observed with the femtosecond pulses, even at high peak power densities (11 GW cm-2). For the nanosecond pulses, the number of bubbles produced per pulse showed a quadratic dependence on laser power, with a distinct power threshold below which no bubbles were observed. The number of bubbles observed increases linearly with sucrose concentration. It was found that filtering of solutions reduces the number of bubbles significantly. Although the femtosecond pulses have higher peak power densities than the nanosecond pulses, they have lower energy densities per pulse. A simple model for LIN of CO2 is presented, based on heating of nanoparticles to produce vapor bubbles that must expand to reach a critical bubble radius to continue growth. The results suggest that non-photochemical laser-induced nucleation of crystals could also be caused by heating of nanoparticles.

  15. Simulation Studies on Cooling of Cryogenic Propellant by Gas Bubbling

    NASA Astrophysics Data System (ADS)

    Sandilya, Pavitra; Saha, Pritam; Sengupta, Sonali

    Injection cooling was proposed to store cryogenic liquids (Larsen et al. [1], Schmidt [2]). When a non-condensable gas is injected through a liquid, the liquid component would evaporate into the bubble if its partial pressure in the bubble is lower than its vapour pressure. This would tend to cool the liquid. Earlier works on injection cooling was analysed by Larsen et al. [1], Schmidt [2], Cho et al. [3] and Jung et al. [4], considering instantaneous mass transfer and finite heat transfer between gas bubble and liquid. It is felt that bubble dynamics (break up, coalescence, deformation, trajectory etc.) should also play a significant role in liquid cooling. The reported work are based on simple assumptions like single bubble, zero bubble deformation, and no inter-bubble interactions. Hence in this work, we propose a lumped parameter model considering both heat and mass interactions between bubble and the liquid to gain a preliminary insight into the cooling phenomenon during gas injection through a liquid.

  16. Turning bubbles on and off during boiling using charged surfactants

    NASA Astrophysics Data System (ADS)

    Cho, H. Jeremy; Mizerak, Jordan P.; Wang, Evelyn N.

    2015-10-01

    Boiling--a process that has powered industries since the steam age--is governed by bubble formation. State-of-the-art boiling surfaces often increase bubble nucleation via roughness and/or wettability modification to increase performance. However, without active in situ control of bubbles, temperature or steam generation cannot be adjusted for a given heat input. Here we report the ability to turn bubbles `on and off' independent of heat input during boiling both temporally and spatially via molecular manipulation of the boiling surface. As a result, we can rapidly and reversibly alter heat transfer performance up to an order of magnitude. Our experiments show that this active control is achieved by electrostatically adsorbing and desorbing charged surfactants to alter the wettability of the surface, thereby affecting nucleation. This approach can improve performance and flexibility in existing boiling technologies as well as enable emerging or unprecedented energy applications.

  17. Turning bubbles on and off during boiling using charged surfactants

    PubMed Central

    Cho, H. Jeremy; Mizerak, Jordan P.; Wang, Evelyn N.

    2015-01-01

    Boiling—a process that has powered industries since the steam age—is governed by bubble formation. State-of-the-art boiling surfaces often increase bubble nucleation via roughness and/or wettability modification to increase performance. However, without active in situ control of bubbles, temperature or steam generation cannot be adjusted for a given heat input. Here we report the ability to turn bubbles ‘on and off' independent of heat input during boiling both temporally and spatially via molecular manipulation of the boiling surface. As a result, we can rapidly and reversibly alter heat transfer performance up to an order of magnitude. Our experiments show that this active control is achieved by electrostatically adsorbing and desorbing charged surfactants to alter the wettability of the surface, thereby affecting nucleation. This approach can improve performance and flexibility in existing boiling technologies as well as enable emerging or unprecedented energy applications. PMID:26486275

  18. Turning bubbles on and off during boiling using charged surfactants.

    PubMed

    Cho, H Jeremy; Mizerak, Jordan P; Wang, Evelyn N

    2015-10-21

    Boiling--a process that has powered industries since the steam age--is governed by bubble formation. State-of-the-art boiling surfaces often increase bubble nucleation via roughness and/or wettability modification to increase performance. However, without active in situ control of bubbles, temperature or steam generation cannot be adjusted for a given heat input. Here we report the ability to turn bubbles 'on and off' independent of heat input during boiling both temporally and spatially via molecular manipulation of the boiling surface. As a result, we can rapidly and reversibly alter heat transfer performance up to an order of magnitude. Our experiments show that this active control is achieved by electrostatically adsorbing and desorbing charged surfactants to alter the wettability of the surface, thereby affecting nucleation. This approach can improve performance and flexibility in existing boiling technologies as well as enable emerging or unprecedented energy applications.

  19. Bubble evolution and properties in homogeneous nucleation simulations

    NASA Astrophysics Data System (ADS)

    Angélil, Raymond; Diemand, Jürg; Tanaka, Kyoko K.; Tanaka, Hidekazu

    2014-12-01

    We analyze the properties of naturally formed nanobubbles in Lennard-Jones molecular dynamics simulations of liquid-to-vapor nucleation in the boiling and the cavitation regimes. The large computational volumes provide a realistic environment at unchanging average temperature and liquid pressure, which allows us to accurately measure properties of bubbles from their inception as stable, critically sized bubbles, to their continued growth into the constant speed regime. Bubble gas densities are up to 50 % lower than the equilibrium vapor densities at the liquid temperature, yet quite close to the gas equilibrium density at the lower gas temperatures measured in the simulations: The latent heat of transformation results in bubble gas temperatures up to 25 % below those of the surrounding bulk liquid. In the case of rapid bubble growth—typical for the cavitation regime—compression of the liquid outside the bubble leads to local temperature increases of up to 5 %, likely significant enough to alter the surface tension as well as the local viscosity. The liquid-vapor bubble interface is thinner than expected from planar coexistence simulations by up to 50 % . Bubbles near the critical size are extremely nonspherical, yet they quickly become spherical as they grow. The Rayleigh-Plesset description of bubble-growth gives good agreement in the cavitation regime.

  20. Viscosity Destabilizes Sonoluminescing Bubbles

    NASA Astrophysics Data System (ADS)

    Toegel, Ruediger; Luther, Stefan; Lohse, Detlef

    2006-03-01

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

  1. Viscosity destabilizes sonoluminescing bubbles.

    PubMed

    Toegel, Ruediger; Luther, Stefan; Lohse, Detlef

    2006-03-24

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

  2. Cardiovascular bubble dynamics.

    PubMed

    Bull, Joseph L

    2005-01-01

    Gas bubbles can form in the cardiovascular system as a result of patho-physiological conditions or can be intentionally introduced for diagnostic or therapeutic reasons. The dynamic behavior of these bubbles is caused by a variety of mechanisms, such as inertia, pressure, interfacial tension, viscosity, and gravity. We review recent advances in the fundamental mechanics and applications of cardiovascular bubbles, including air embolism, ultrasound contrast agents, targeted microbubbles for drug delivery and molecular imaging, cavitation-induced tissue erosion for ultrasonic surgery, microbubble-induced angiogenesis and arteriogenesis, and gas embolotherapy.

  3. Photon Bubbles and the Vertical Structure of Accretion Disks

    NASA Astrophysics Data System (ADS)

    Begelman, Mitchell C.

    2006-06-01

    We consider the effects of ``photon bubble'' shock trains on the vertical structure of radiation pressure-dominated accretion disks. These density inhomogeneities are expected to develop spontaneously in radiation-dominated accretion disks where magnetic pressure exceeds gas pressure, even in the presence of magnetorotational instability (MRI). They increase the rate at which radiation escapes from the disk and may allow disks to exceed the Eddington limit by a substantial factor without blowing themselves apart. To refine our earlier analysis of photon bubble transport in accretion disks, we generalize the theory of photon bubbles to include the effects of finite optical depths and radiation damping. Modifications to the diffusion law at low τ tend to ``fill in'' the low-density regions of photon bubbles, while radiation damping inhibits the formation of photon bubbles at large radii, small accretion rates, and small heights above the equatorial plane. Accretion disks dominated by photon bubble transport may reach luminosities from 10 to >100 times the Eddington limit (LEdd), depending on the mass of the central object, while remaining geometrically thin. However, photon bubble-dominated disks with α-viscosity are subject to the same thermal and viscous instabilities that plague standard radiation pressure-dominated disks, suggesting that they may be intrinsically unsteady. Photon bubbles can lead to a ``core-halo'' vertical disk structure. In super-Eddington disks the halo forms the base of a wind, which carries away substantial energy and mass, but not enough to prevent the luminosity from exceeding LEdd. Photon bubble-dominated disks may have smaller color corrections than standard accretion disks of the same luminosity. They remain viable contenders for some ultraluminous X-ray sources and may play a role in the rapid growth of supermassive black holes at high redshift.

  4. Hadron bubble evolution into the quark sea

    SciTech Connect

    Freese, K. ); Adams, F.C. )

    1990-04-15

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

  5. Chemistry in Soap Bubbles.

    ERIC Educational Resources Information Center

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

    2002-01-01

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

  6. What's in a Bubble?

    ERIC Educational Resources Information Center

    Saunderson, Megan

    2000-01-01

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

  7. Blowing magnetic skyrmion bubbles

    NASA Astrophysics Data System (ADS)

    Jiang, Wanjun; Upadhyaya, Pramey; Zhang, Wei; Yu, Guoqiang; Jungfleisch, M. Benjamin; Fradin, Frank Y.; Pearson, John E.; Tserkovnyak, Yaroslav; Wang, Kang L.; Heinonen, Olle; te Velthuis, Suzanne G. E.; Hoffmann, Axel

    2015-07-01

    The formation of soap bubbles from thin films is accompanied by topological transitions. Here we show how a magnetic topological structure, a skyrmion bubble, can be generated in a solid-state system in a similar manner. Using an inhomogeneous in-plane current in a system with broken inversion symmetry, we experimentally “blow” magnetic skyrmion bubbles from a geometrical constriction. The presence of a spatially divergent spin-orbit torque gives rise to instabilities of the magnetic domain structures that are reminiscent of Rayleigh-Plateau instabilities in fluid flows. We determine a phase diagram for skyrmion formation and reveal the efficient manipulation of these dynamically created skyrmions, including depinning and motion. The demonstrated current-driven transformation from stripe domains to magnetic skyrmion bubbles could lead to progress in skyrmion-based spintronics.

  8. Bubble motion and size variation during thermal migration with phase change

    NASA Astrophysics Data System (ADS)

    Nurse, Asha; McFadden, Geoffrey; Coriell, Sam; Mathematical Modeling Group Team

    2011-11-01

    An analysis of the motion of a spherical bubble in a two-phase, single component system with a vertical linear temperature gradient is presented. The model for the migration of an immiscible bubble considered by Young, Goldstein and Block is modified to allow for phase change at the bubble surface, including the possibility of both bubble translation and the change of bubble radius with time. Depending of the material parameters, the thermocapillary effects that normally lead to migration of an immiscible bubble can be overwhelmed by the effects of latent heat generation, resulting in a change in the mechanism driving the motion. For a water-steam system conditions are determined for a stationary bubble in which the the effects of buoyancy and thermal migration are balanced. The stability of the bubble is also considered.

  9. Blowing DNA bubbles.

    PubMed

    Severin, N; Zhuang, W; Ecker, C; Kalachev, A A; Sokolov, I M; Rabe, J P

    2006-11-01

    We report here experimental observations which indicate that topologically or covalently formed polymer loops embedded in an ultrathin liquid film on a solid substrate can be "blown" into circular "bubbles" during scanning force microscopy (SFM) imaging. In particular, supercoiled vector DNA has been unraveled, moved, stretched, and overstretched to two times its B-form length and then torn apart. We attribute the blowing of the DNA bubbles to the interaction of the tapping SFM tip with the ultrathin liquid film.

  10. 2012 Problem 8: Bubbles

    NASA Astrophysics Data System (ADS)

    Zhu, Kejing; Xia, Qing; Wang, Sihui; Zhou, Huijun

    2015-10-01

    When a large number of bubbles exist in the water, an object may float on the surface or sink. The assumption of equivalent density is proposed in this article to explain the concrete example. According to the assumption, an object is floatable only if its density is less than the equivalent density of the water-bubble mixture. This conclusion is supported by the floating experiment and by measuring the pressure underwater to a satisfactory approximation.

  11. Bubble coalescence in magmas

    NASA Technical Reports Server (NTRS)

    Herd, Richard A.; Pinkerton, Harry

    1993-01-01

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

  12. Revealing the Location of the Mixing Layer in a Hot Bubble

    NASA Astrophysics Data System (ADS)

    Guerrero, M. A.; Fang, X.; Chu, Y. H.; Toalá, J. A.; Gruendl, R. A.

    2017-03-01

    The fast stellar winds can blow bubbles in the circumstellar material ejected from previous phases of stellar evolution. These are found at different scales, from planetary nebulae (PNe) around stars evolving to the white dwarf stage, to Wolf-Rayet (WR) bubbles and up to large-scale bubbles around massive star clusters. In all cases, the fast stellar wind is shock-heated and a hot bubble is produced. At the mixing layer between the hot bubble and optical nebula, processes of mass evaporation and mixing of nebular material and heat conduction are key to determine the thermal structure of these bubbles and their evolution. In this contribution we review our current understanding of the X-ray observations of hot bubbles in PNe and present the first spatially-resolved study of a mixing layer in a PN.

  13. Clustering in Bubble Suspensions

    NASA Astrophysics Data System (ADS)

    Zenit, Roberto

    2000-11-01

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

  14. Numerical simulation of shock/bubble-cloud interaction problems

    NASA Astrophysics Data System (ADS)

    Ando, Keita; Colonius, Tim; Brennen, Christopher

    2009-11-01

    The interaction of a shock wave with a dilute bubble cloud is computed using a continuum two-phase model incorporating the effect of a distribution of nuclei sizes. The bubble dynamics are evaluated using a Rayleigh-Plesset-type equation including the effects of heat transfer, liquid viscosity and compressibility. A finite-volume WENO scheme coupled with an approximate HLLC Riemann solver is developed to solve the shock problems. Linear and shock wave propagation through a one-dimensional bubble screen is computed and the effect of phase cancellations among the different-sized bubbles is quantified. The size distribution in the screen is found to increase the cushioning of the shock loading. Computations of shock/bubble-cloud interaction in two dimensions are also presented.

  15. Dynamics of a single cavitating and reacting bubble.

    PubMed

    Hauke, Guillermo; Fuster, Daniel; Dopazo, Cesar

    2007-06-01

    Some of the studies on the dynamics of cavitating bubbles often consider simplified submodels assuming uniform fluid properties within the gas bubbles, ignoring chemical reactions, or suppressing fluid transport phenomena across the bubble interface. Another group of works, to which the present contribution belongs, includes the radial dependence of the fluid variables. Important fluid processes that occur inside the gas bubble, such as chemical reactions, and across the bubble interface, such as heat and mass transfer phenomena, are here considered also. As a consequence, this model should yield more realistic results. In particular, it is found that water evaporation and condensation are fundamental transport phenomena in estimating the dissociation reactions of water into OH. The thermal and mass boundary layers and the radial variation of the chemical concentrations also seem essential for accurate predictions.

  16. Formation and ascent of nonisothermal ionospheric and chromospheric bubbles

    SciTech Connect

    Genkin, L.G.; Erukhimov, L.M.; Myasnikov, E.N.; Shvarts, M.M.

    1987-11-01

    The influences of nonisothermicity on the dynamics of ionospheric and chromospheric bubbles is discussed. The possibility of the existence in the ionosphere of a recombination-thermal instability, arising from the temperature dependence of the coefficient of charge exchange between molecules and atomic ions, is shown, and its influence on the formation and evolution of equatorial bubbles is analyzed. It is shown that the formation and dynamics of bubbles may depend on recombination processes and gravity, while plasma heating (predominantly by vertical electric fields) leads to the deepening and preservation of bubbles as they move to greater altitudes. The hypothesis is advanced that the formation of bubbles may be connected with the ascent of clumps of molecules in ionospheric tornados.

  17. A coupled numerical analysis of shield temperatures, heat losses and residual gas pressures in an evacuated super-insulation using thermal and fluid networks. Part III: Unsteady-state conditions (evacuation period)

    NASA Astrophysics Data System (ADS)

    Reiss, H.

    2006-12-01

    This paper analyses the evacuation period of a 300 L super-insulated cryogenic storage tank for liquid nitrogen. Storage tank and radiation shields are the same as in part I of this paper. The present analysis extends application of stationary fluid networks to unsteady-states to determine local, residual gas pressures between shields and the evacuation time of a multilayer super-insulation. Parameter tests comprise magnitude of desorption from radiation shields, spacers and container walls and their influence on length of the evacuation period. Calculation of the integrals over time-dependent desorption rates roughly confirms weight losses of radiation shields obtained after heating and out-gassing the materials, as reported in the literature. After flooding the insulation space with dry N 2-gas, the evacuation time can enormously be reduced, from 72 to 4 h, to obtain a residual gas pressure of 0.01 Pa in-between shields of this storage tank. Permeation of nitrogen through container walls is of no importance for residual gas pressures. The simulations finally compare freezing H 2O-layers adsorbed on shields, spacers and container walls with flooding of the materials.

  18. Energy cascading by triple-bubble interactions via time-delayed control

    NASA Astrophysics Data System (ADS)

    Lin, Yen-Liang; Chang, Chia-Ming; Yang, I.-Da; Chieng, Ching-Chang; Tseng, Fan-Gang

    2012-01-01

    The triple-bubble interaction controlled by a precise time-delayed technique was investigated in detail with respect to different ignition times, heater spaces and sequential firing modes to promote efficient energy cascading and concentration. The target bubble, which was generated under a specific delay time with two auxiliary bubbles, can have a volume that is two or almost three times larger than that of a single bubble. This result overcomes the limitation of energy usage on an explosive microbubble under a constant heat flux. As the heater space decreases, stronger bubble-bubble interactions were obtained due to the hydrodynamic effect and the intensive pressure wave emission, resulting in highly enhancing and depressing bubble dynamics. Other interesting phenomena, such as bubble shifting, mushroom-shape bubble, rod-shape bubble and bubble extension among heaters, were also recorded by a high-speed phase-averaged stroboscopic technique, displaying special non-spherical bubble dynamics. Artificial manipulation of bubble behavior was further conducted in a two-level sequential firing process. Using various volumetric combinations, the adjustable multi-level fluid transportation can be realized by a digital time-delayed control. The above-mentioned information can be applied to not only the design and operation of inkjet printheads but also cavitation research and fluid pumping in microdevices.

  19. Thermocapillary Flow and Aggregation of Bubbles on a Solid Wall

    NASA Technical Reports Server (NTRS)

    Kasumi, Hiroki; Solomentsev, Yuri E.; Guelcher, Scott A.; Anderson, John L.; Sides, Paul J.

    2000-01-01

    During the electrolytic evolution of oxygen bubbles forming on a vertically oriented transparent tin oxide electrode, bubbles were found to be mutually attractive. The mechanism of the aggregation had never been explained satisfactorily until Guelcher et al. attributed it to thermocapillary flow. The gradient of surface tension of the liquid at the bubble's surface, which was established because of reaction heat and ohmic heat loss at the electrode wall, drives flow of the liquid adjacent to each bubble; the bubble "pumps" fluid along its surface away from the wall. Fluid flows toward the bubble to conserve mass and entrains nearby bubbles in the flow pattern. The same logic would apply when two bubbles of equal size are adjacent to each other on a warm wall. Each bubble drives thermocapillary flow and hence entrains the other in its flow pattern, which drives the aggregation. Our objective here is to perform experiments where the temperature gradient at the wall is well known and controlled. The theory can be quantitatively tested by studying aggregation of bubble pairs of equal size, and by varying system parameters such as temperature gradient, bubble size and fluid viscosity. The results are then compared with the theory in a quantitatively rigorous manner. We demonstrate that the theory without adjustable parameters is capable of quantitatively modeling the rate of aggregation of two bubbles. The equations governing the thermocapillary flow around a single stationary bubble on a heated or cooled wall in a semi-infinite domain were solved. Both Reynolds number and Marangoni number were much less than unity. The critical result is that liquid in the vicinity of a warm wall flows toward a stationary collector bubble. Consequently the thermocapillary flow around the stationary bubble entrains another bubble toward itself. The bubbles undergo hindered translation parallel to the wall with velocity U while the fluid flow field is described with u. Two velocities

  20. Experimental Study on the Effect of Liquid Contact Angle on Bubble Movement under Microgravity

    NASA Astrophysics Data System (ADS)

    Yanjie, Yang; Li, Shiyou; Yiyong, Huang; Guangyu, Li

    2016-07-01

    The experimental study of bubble dynamics under microgravity has been conducted utilizing the Drop Tower Beijing(NMLC). A pottery sized of 20mm in length, 10mm in width and 1.2mm in height was used as the heater. The fluid was HFE7500 and distilled water. During the experiment under microgravity the nucleate boiling and film boiling were observed. At the same heating power the bubble of HFE7500 whose contact angle is smaller grew faster and bigger, moved quickly on the heating surface, combined into center big bubble by colliding and reached its CHF earlier to film boiling. The bubble of distilled water whose contact angle is bigger didn't move obviously on heating surface, and it transferred from nucleate boiling to film boiling at its original place meanwhile it absorbed smaller bubble around. Key words: microgravity; bubble movement; contact angle; drop tower

  1. Bubbly flows around a two-dimensional circular cylinder

    NASA Astrophysics Data System (ADS)

    Lee, Jubeom; Park, Hyungmin

    2016-11-01

    Two-phase cross flows around a bluff body occur in many thermal-fluid systems like steam generators, heat exchangers and nuclear reactors. However, our current knowledge on the interactions among bubbles, bubble-induced flows and the bluff body are limited. In the present study, the gas-liquid bubbly flows around a solid circular cylinder are experimentally investigated while varying the mean void fraction from 5 to 27%. The surrounding liquid (water) is initially static and the liquid flow is only induced by the air bubbles. For the measurements, we use the high-speed two-phase particle image velocimetry techniques. First, depending on the mean void fraction, two regimes are classified with different preferential concentration of bubbles in the cylinder wake, which are explained in terms of hydrodynamic force balances acting on rising bubbles. Second, the differences between the two-phase and single-phase flows (while matching their Reynolds numbers) around a circular cylinder will be discussed in relation to effects of bubble dynamics and the bubble-induced turbulence on the cylinder wake. Supported by a Grant (MPSS-CG-2016-02) through the Disaster and Safety Management Institute funded by Ministry of Public Safety and Security of Korean government.

  2. Interaction of a shock with elliptical gas bubbles

    NASA Astrophysics Data System (ADS)

    Georgievskiy, P. Yu.; Levin, V. A.; Sutyrin, O. G.

    2015-07-01

    The interaction of a shock with spherical and elliptical bubbles of light or heavy gas is numerically studied using the axisymmetric Euler equations. A model with a single heat capacity ratio is implemented, where bubbles are modeled by areas of the same gas with lower or higher density. Details of the general shock refraction patterns—diverging and converging—are described. The formation and development of secondary, focusing shocks are discussed. A computational parameter study for different Atwood numbers , shock strengths , where is the Mach number, and bubble geometries is performed. A basic classification for the shock focusing (cumulation) regimes is suggested, with the division of the internal, external and transitional focusing regimes determined by the position of the shock focusing point relative to the bubble. It is shown that the focusing pattern is governed not only by the Atwood number but also heavily by the Mach number and bubble shape. The qualitative dependence of cumulative intensity on bubble geometry is determined. The theoretical possibility of realizing an extremely intense shock collapse with a relatively small variation in bubble shape is demonstrated for the heavy-bubble scenario.

  3. Colliding with a crunching bubble

    SciTech Connect

    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.

  4. Micro-assembly using optically controlled bubble microrobots

    NASA Astrophysics Data System (ADS)

    Hu, Wenqi; Ishii, Kelly S.; Ohta, Aaron T.

    2011-08-01

    Bubbles controlled by optically induced heating were made to function as novel microrobots for micromanipulation and micro-assembly. Using light patterns generated by a commercial computer projector, bubble microrobots were controlled and used to manipulate glass microbeads and perform the micro-assembly of micro-blocks and cell-encapsulating hydrogel beads. Two manipulation modes, pulling and pushing, were used to move micro-objects into place and manipulate glass beads with a velocity of up to 350 μm/s. The simultaneous independent control of three bubble robots was also demonstrated.

  5. A Bubble Bursts

    NASA Technical Reports Server (NTRS)

    2005-01-01

    RCW 79 is seen in the southern Milky Way, 17,200 light-years from Earth in the constellation Centaurus. The bubble is 70-light years in diameter, and probably took about one million years to form from the radiation and winds of hot young stars.

    The balloon of gas and dust is an example of stimulated star formation. Such stars are born when the hot bubble expands into the interstellar gas and dust around it. RCW 79 has spawned at least two groups of new stars along the edge of the large bubble. Some are visible inside the small bubble in the lower left corner. Another group of baby stars appears near the opening at the top.

    NASA's Spitzer Space Telescope easily detects infrared light from the dust particles in RCW 79. The young stars within RCW 79 radiate ultraviolet light that excites molecules of dust within the bubble. This causes the dust grains to emit infrared light that is detected by Spitzer and seen here as the extended red features.

  6. The Dueling Bubble Experiment

    NASA Astrophysics Data System (ADS)

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

    2007-11-01

    When two drops or bubbles are brought into close proximity to each other, the thin film of the fluid between them drains as they are squeezed together. If the film becomes thin enough that intermolecular forces of attraction overwhelm capillary forces, the drops/bubbles coalesce and the time it takes for this to happen, starting from the point of apparent contact is referred to as the drainage time. One practical version of this scenario occurs during the formation of foams, when the thin film forms between gas bubbles that are growing in volume with time. We performed an experimental study that is intended to mimic this process in which the two drops (or bubbles) in the size range of 50-100 microns diameter are created by oozing a liquid/gas out of two capillaries of diameter less than 100 microns directly facing each other and immersed in a second fluid. We present measurements of drainage times for the cases of very low viscosity ratios PDMS drops in Castor oil (less than 0.05) and bubbles of air in PDMS, and highlight the differences that arise in part due to the different boundary conditions for thin film drainage for liquid-liquid versus gas-liquid systems, and in part due to the different Hamaker constants for the two systems.

  7. Bubbles of Metamorphosis

    NASA Astrophysics Data System (ADS)

    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

  8. Forced convection in the wakes of sliding bubbles

    NASA Astrophysics Data System (ADS)

    Meehan, O'Reilly; Donnelly, B.; Persoons, T.; Nolan, K.; Murray, D. B.

    2016-09-01

    Both vapour and gas bubbles are known to significantly increase heat transfer rates between a heated surface and the surrounding fluid, even with no phase change. However, the complex wake structures means that the surface cooling is not fully understood. The current study uses high speed infra-red thermography to measure the surface temperature and convective heat flux enhancement associated with an air bubble sliding under an inclined surface, with a particular focus on the wake. Enhancement levels of 6 times natural convection levels are observed, along with cooling patterns consistent with a possible hairpin vortex structure interacting with the thermal boundary layer. Local regions of suppressed convective heat transfer highlight the complexity of the bubble wake in two-phase applications.

  9. Robust Acoustic Transducers for Bubble Chambers

    NASA Astrophysics Data System (ADS)

    Wells, Jonathan

    2015-04-01

    The PICO collaboration utilizes bubble chambers filled with various superheated liquids as targets for dark matter. Acoustic sensors have proved able to distinguish nuclear recoils from radioactive background on an event-by-event basis. We have recently produced a more robust transducer which should be able to operate for years, rather than months, in the challenging environment of a heated high pressure hydraulic fluid outside these chambers. Indiana University South Bend.

  10. Single-bubble dynamics in pool boiling of one-component fluids.

    PubMed

    Xu, Xinpeng; Qian, Tiezheng

    2014-06-01

    We numerically investigate the pool boiling of one-component fluids with a focus on the effects of surface wettability on the single-bubble dynamics. We employed the dynamic van der Waals theory [Phys. Rev. E 75, 036304 (2007)], a diffuse-interface model for liquid-vapor flows involving liquid-vapor transition in nonuniform temperature fields. We first perform simulations for bubbles on homogeneous surfaces. We find that an increase in either the contact angle or the surface superheating can enhance the bubble spreading over the heating surface and increase the bubble departure diameter as well and therefore facilitate the transition into film boiling. We then examine the dynamics of bubbles on patterned surfaces, which incorporate the advantages of both hydrophobic and hydrophilic surfaces. The central hydrophobic region increases the thermodynamic probability of bubble nucleation while the surrounding hydrophilic region hinders the continuous bubble spreading by pinning the contact line at the hydrophobic-hydrophilic intersection. This leads to a small bubble departure diameter and therefore prevents the transition from nucleate boiling into film boiling. With the bubble nucleation probability increased and the bubble departure facilitated, the efficiency of heat transfer on such patterned surfaces is highly enhanced, as observed experimentally [Int. J. Heat Mass Transfer 57, 733 (2013)]. In addition, the stick-slip motion of contact line on patterned surfaces is demonstrated in one-component fluids, with the effect weakened by surface superheating.

  11. Bubbles from nothing

    SciTech Connect

    Blanco-Pillado, Jose J.; Ramadhan, Handhika S.; Shlaer, Benjamin E-mail: handhika@cosmos.phy.tufts.edu

    2012-01-01

    Within the framework of flux compactifications, we construct an instanton describing the quantum creation of an open universe from nothing. The solution has many features in common with the smooth 6d bubble of nothing solutions discussed recently, where the spacetime is described by a 4d compactification of a 6d Einstein-Maxwell theory on S{sup 2} stabilized by flux. The four-dimensional description of this instanton reduces to that of Hawking and Turok. The choice of parameters uniquely determines all future evolution, which we additionally find to be stable against bubble of nothing instabilities.

  12. Multivariate bubbles and antibubbles

    NASA Astrophysics Data System (ADS)

    Fry, John

    2014-08-01

    In this paper we develop models for multivariate financial bubbles and antibubbles based on statistical physics. In particular, we extend a rich set of univariate models to higher dimensions. Changes in market regime can be explicitly shown to represent a phase transition from random to deterministic behaviour in prices. Moreover, our multivariate models are able to capture some of the contagious effects that occur during such episodes. We are able to show that declining lending quality helped fuel a bubble in the US stock market prior to 2008. Further, our approach offers interesting insights into the spatial development of UK house prices.

  13. Fluid Dynamics of Bubbly Liquids

    NASA Technical Reports Server (NTRS)

    Tsang, Y. H.; Koch, D. L.; Zenit, R.; Sangani, A.; Kushch, V. I.; Spelt, P. D. M.; Hoffman, M.; Nahra, H.; Fritz, C.; Dolesh, R.

    2002-01-01

    Experiments have been performed to study the average flow properties of inertially dominated bubbly liquids which may be described by a novel analysis. Bubbles with high Reynolds number and low Weber number may produce a fluid velocity disturbance that can be approximated by a potential flow. We studied the behavior of suspensions of bubbles of about 1.5 mm diameter in vertical and inclined channels. The suspension was produced using a bank of 900 glass capillaries with inner diameter of about 100 microns in a quasi-steady fashion. In addition, salt was added to the suspension to prevent bubble-bubble coalescence. As a result, a nearly monodisperse suspension of bubble was produced. By increasing the inclination angle, we were able to explore an increasing amount of shear to buoyancy motion. A pipe flow experiment with the liquid being recirculated is under construction. This will provide an even larger range of shear to buoyancy motion. We are planning a microgravity experiment in which a bubble suspension is subjected to shearing in a couette cell in the absence of a buoyancy-driven relative motion of the two phases. By employing a single-wire, hot film anemometer, we were able to obtain the liquid velocity fluctuations. The shear stress at the wall was measured using a hot film probe flush mounted on the wall. The gas volume fraction, bubble velocity, and bubble velocity fluctuations were measured using a homemade, dual impedance probe. In addition, we also employed a high-speed camera to obtain the bubble size distribution and bubble shape in a dilute suspension. A rapid decrease in bubble velocity for a dilute bubble suspension is attributed to the effects of bubble-wall collisions. The more gradual decrease of bubble velocity as gas volume fraction increases, due to subsequent hindering of bubble motion, is in qualitative agreement with the predictions of Spelt and Sangani for the effects of potential-flow bubble-bubble interactions on the mean velocity. The

  14. Bubble injected hydrocyclone flotation cell

    SciTech Connect

    Stanley, D.A.; Jordon, C.E.

    1990-11-20

    This patent describes an apparatus for selective separation of a mixture of hydrophobic and hydrophilic mineral particles. It comprises: a bubble-injected hydrocyclone flotation cell and a bubble slurry. The cell comprises an enclosed body section; a mineral pulp feed port; a bubble slurry feed port; and a vortex finder.

  15. The Early Years: Blowing Bubbles

    ERIC Educational Resources Information Center

    Ashbrook, Peggy

    2016-01-01

    Blowing bubbles is not only a favorite summer activity for young children. Studying bubbles that are grouped together, or "foam," is fun for children and fascinating to many real-world scientists. Foam is widely used--from the bedroom (mattresses) to outer space (insulating panels on spacecraft). Bubble foam can provide children a…

  16. Cohesion of Bubbles in Foam

    ERIC Educational Resources Information Center

    Ross, Sydney

    1978-01-01

    The free-energy change, or binding energy, of an idealized bubble cluster is calculated on the basis of one mole of gas, and on the basis of a single bubble going from sphere to polyhedron. Some new relations of bubble geometry are developed in the course of the calculation. (BB)

  17. Argonne Bubble Experiment Thermal Model Development II

    SciTech Connect

    Buechler, Cynthia Eileen

    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.

  18. The Action of Pressure-Radiation Forces on Pulsating Vapor Bubbles

    NASA Technical Reports Server (NTRS)

    Hao, Y.; Oguz, N.; Prosperetti, A.

    2001-01-01

    The action of pressure-radiation (or Bjerknes) forces on gas bubbles is well understood. This paper studies the analogous phenomenon for vapor bubbles, about which much less is known. A possible practical application is the removal of boiling bubbles from the neighborhood of a heated surface in the case of a downward facing surface or in the absence of gravity. For this reason, the case of a bubble near a plane rigid surface is considered in detail. It is shown that, when the acoustic wave fronts are parallel to the surface, the bubble remains trapped due to secondary Bjerknes force caused by an "image bubble." When the wave fronts are perpendicular to the surface, on the other hand, the bubble can be made to slide laterally.

  19. The Liberal Arts Bubble

    ERIC Educational Resources Information Center

    Agresto, John

    2011-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  1. Effects of mineral nutrition conditions on heat tolerance of chufa (Сyperus esculentus L.) plant communities to super optimal air temperatures in the BTLSS

    NASA Astrophysics Data System (ADS)

    Shklavtsova, E. S.; Ushakova, S. A.; Shikhov, V. N.; Anishchenko, O. V.

    2014-09-01

    The use of mineralized human wastes as a basis for nutrient solutions will increase the degree of material closure of bio-technical human life support systems. As stress tolerance of plants is determined, among other factors, by the conditions under which they have been grown before exposure to a stressor, the purpose of the study is to investigate the level of tolerance of chufa (Cyperus esculentus L.) plant communities grown in solutions based on mineralized human wastes to a damaging air temperature, 45 °C. Experiments were performed with 30-day-old chufa plant communities grown hydroponically, on expanded clay aggregate, under artificial light, at 690 μmol m-2 s-1 PAR and at a temperature of 25 °C. Plants were grown in Knop’s solution and solutions based on human wastes mineralized according to Yu.A. Kudenko’s method, which contained nitrogen either as ammonium and urea or as nitrates. The heat shock treatment lasted 20 h at 690 and 1150 μmol m-2 s-1 PAR. Chufa heat tolerance was evaluated based on parameters of CO2 gas exchange, the state of its photosynthetic apparatus (PSA), and intensity of peroxidation of leaf lipids. Chufa plants grown in the solutions based on mineralized human wastes that contained ammonium and urea had lower heat tolerance than plants grown in standard mineral solutions. Heat tolerance of the plants grown in the solutions based on mineralized human wastes that mainly contained nitrate nitrogen was insignificantly different from the heat tolerance of the plants grown in standard mineral solutions. A PAR intensity increase from 690 μmol m-2 s-1 to 1150 μmol m-2 s-1 enhanced heat tolerance of chufa plant communities, irrespective of the conditions of mineral nutrition under which they had been grown.

  2. Bubbly Little Star

    NASA Technical Reports Server (NTRS)

    2007-01-01

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

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

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

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

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

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

  3. Heat Pipe With Interrupted Slot

    NASA Technical Reports Server (NTRS)

    Brown, Richard F.; Kosson, Robert L.; Edelstein, Fred

    1994-01-01

    Newer version of heat pipe slot interrupted by plug or, if heat pipe is cast, by bridge of heat-pipe material cast integrally across groove. Small barrier assists in priming heat pipe. Vapor and noncondensible gas still accumulates in liquid channel at evaporator before or during startup, but barrier keeps liquid out of small part of slot at bubble. Dry part of slot allows bubble to escape into vapor channel, making room for liquid to move in during startup.

  4. Bubble dynamics and bubble-induced turbulence of a single-bubble chain

    NASA Astrophysics Data System (ADS)

    Lee, Joohyoung; Park, Hyungmin

    2016-11-01

    In the present study, the bubble dynamics and liquid-phase turbulence induced by a chain of bubbles injected from a single nozzle have been experimentally investigated. Using a high-speed two-phase particle image velociemtry, measurements on the bubbles and liquid-phase velocity field are conducted in a transparent tank filled with water, while varying the bubble release frequency from 0.1 to 35 Hz. The tested bubble size ranges between 2.0-3.2 mm, and the corresponding bubble Reynolds number is 590-1100, indicating that it belongs to the regime of path instability. As the release frequency increases, it is found that the global shape of bubble dispersion can be classified into two regimes: from asymmetric (regular) to axisymmetric (irregular). In particular, at higher frequency, the wake vortices of leading bubbles cause an irregular behaviour of the following bubble. For the liquid phase, it is found that a specific trend on the bubble-induced turbulence appears in a strong relation to the above bubble dynamics. Considering this, we try to provide a theoretical model to estimate the liquid-phase turbulence induced by a chain of bubbles. Supported by a Grant funded by Samsung Electronics, Korea.

  5. Chemical separations by bubble-assisted interphase mass-transfer.

    PubMed

    Boyd, David A; Adleman, James R; Goodwin, David G; Psaltis, Demetri

    2008-04-01

    We show that when a small amount of heat is added close to a liquid-vapor interface of a captive gas bubble in a microchannel, interphase mass-transfer through the bubble can occur in a controlled manner with only a slight change in the temperature of the fluid. We demonstrate that this method, which we refer to as bubble-assisted interphase mass-transfer (BAIM), can be applied to interphase chemical separations, e.g., simple distillation, without the need for high temperatures, vacuum, or active cooling. Although any source of localized heating could be used, we illustrate BAIM with an all-optical technique that makes use of the plasmon resonance in an array of nanoscale metal structures that are incorporated into the channel to produce localized heating of the fluid when illuminated by a stationary low-power laser.

  6. Signature of anisotropic bubble collisions

    SciTech Connect

    Salem, Michael P.

    2010-09-15

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

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

    SciTech Connect

    Jafari, S. Nilkar, M.; Ghasemizad, A.; Mehdian, H.

    2014-10-15

    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.

  8. Microlayer Topology And Bubble Growth In Nucleate Boiling

    NASA Astrophysics Data System (ADS)

    Jawurek, H. H.; Macgregor, H. G.; Bodenheimer, J. S.

    1987-09-01

    During nucleate boiling thin liquid films (nicrolayers) form beneath the base of bubbles and evaporate into the bubble interiors. A technique is presented which permits the simultaneous determination of microlayer topology and the contribution of microlayer evaporation to bubble growth. Isolated-bubble boiling takes place on an electrically heated, transparent tin-oxide coating deposited on a glass plate, the latter forming the floor of a vessel. With coherent Claser) illumination from beneath, the microlayers reflect fringe patterns similar to Newton's rings. Owing to the rapid evaporation of the layers (the process is completed within milliseconds) the fringes are in rapid motion and are recorded by eine photography at some 4 000 frames per second and exposure times of 50 μs. The resulting interferograms provide details of microlayer shape and thickness versus time, and thus evaporation rate. Simultaneously, and on the same film, bubble profiles (and thus volumes) are obtained under white light illumination. The two bubble images are manipulated by mirrors and lenses so as to appear side by side on the same frame of film, the fringes magnified and the profiles reduced. Sample results for methanol boiling at a pressure of 58.5 kPa and with the liquid bulk at saturation temperature, are presented. Under such conditions microlayer evaporation accounts for 37 per cent of the total bubble volume at detachment.

  9. Molecular dynamics simulations of bubble nucleation in dark matter detectors.

    PubMed

    Denzel, Philipp; Diemand, Jürg; Angélil, Raymond

    2016-01-01

    Bubble chambers and droplet detectors used in dosimetry and dark matter particle search experiments use a superheated metastable liquid in which nuclear recoils trigger bubble nucleation. This process is described by the classical heat spike model of F. Seitz [Phys. Fluids (1958-1988) 1, 2 (1958)PFLDAS0031-917110.1063/1.1724333], which uses classical nucleation theory to estimate the amount and the localization of the deposited energy required for bubble formation. Here we report on direct molecular dynamics simulations of heat-spike-induced bubble formation. They allow us to test the nanoscale process described in the classical heat spike model. 40 simulations were performed, each containing about 20 million atoms, which interact by a truncated force-shifted Lennard-Jones potential. We find that the energy per length unit needed for bubble nucleation agrees quite well with theoretical predictions, but the allowed spike length and the required total energy are about twice as large as predicted. This could be explained by the rapid energy diffusion measured in the simulation: contrary to the assumption in the classical model, we observe significantly faster heat diffusion than the bubble formation time scale. Finally we examine α-particle tracks, which are much longer than those of neutrons and potential dark matter particles. Empirically, α events were recently found to result in louder acoustic signals than neutron events. This distinction is crucial for the background rejection in dark matter searches. We show that a large number of individual bubbles can form along an α track, which explains the observed larger acoustic amplitudes.

  10. Molecular dynamics simulations of bubble nucleation in dark matter detectors

    NASA Astrophysics Data System (ADS)

    Denzel, Philipp; Diemand, Jürg; Angélil, Raymond

    2016-01-01

    Bubble chambers and droplet detectors used in dosimetry and dark matter particle search experiments use a superheated metastable liquid in which nuclear recoils trigger bubble nucleation. This process is described by the classical heat spike model of F. Seitz [Phys. Fluids (1958-1988) 1, 2 (1958), 10.1063/1.1724333], which uses classical nucleation theory to estimate the amount and the localization of the deposited energy required for bubble formation. Here we report on direct molecular dynamics simulations of heat-spike-induced bubble formation. They allow us to test the nanoscale process described in the classical heat spike model. 40 simulations were performed, each containing about 20 million atoms, which interact by a truncated force-shifted Lennard-Jones potential. We find that the energy per length unit needed for bubble nucleation agrees quite well with theoretical predictions, but the allowed spike length and the required total energy are about twice as large as predicted. This could be explained by the rapid energy diffusion measured in the simulation: contrary to the assumption in the classical model, we observe significantly faster heat diffusion than the bubble formation time scale. Finally we examine α -particle tracks, which are much longer than those of neutrons and potential dark matter particles. Empirically, α events were recently found to result in louder acoustic signals than neutron events. This distinction is crucial for the background rejection in dark matter searches. We show that a large number of individual bubbles can form along an α track, which explains the observed larger acoustic amplitudes.

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

    NASA Astrophysics Data System (ADS)

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

    1997-05-01

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

  12. Ring Bubbles of Dolphins

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

    The article discusses how dolphins create and play with three types of air-filled vortices. The underlying physics is discussed. Photographs and sketches illustrating the dolphin's actions and physics are presented. The dolphins engage in this behavior on their own initiative without food reward. These behaviors are done repeatedly and with singleminded effort. The first type is the ejection of bubbles which, after some practice on the part of the dolphin, turn into toroidal vortex ring bubbles by the mechanism of baroclinic torque. These bubbles grow in radius and become thinner as they rise vertically to the surface. One dolphin would blow two in succession and guide them to fuse into one. Physicists call this a vortex reconnection. In the second type, the dolphins first create an invisible vortex ring in the water by swimming on their side and waving their tail fin (also called flukes) vigorously. This vortex ring travels horizontally in the water. The dolphin then turns around, finds the vortex and injects a stream of air into it from its blowhole. The air "fills-out" the core of the vortex ring. Often, the dolphin would knock-off a smaller ring bubble from the larger ring (this also involves vortex reconnection) and steer the smaller ring around the tank. One other dolphin employed a few other techniques for planting air into the fluke vortex. One technique included standing vertically in the water with tail-up, head-down and tail piercing the free surface. As the fluke is waved to create the vortex ring, air is entrained from above the surface. Another technique was gulping air in the mouth, diving down, releasing air bubbles from the mouth and curling them into a ring when they rose to the level of the fluke. In the third type, demonstrated by only one dolphin, the longitudinal vortex created by the dorsal fin on the back is used to produce 10-15 foot long helical bubbles. In one technique she swims in a curved path. This creates a dorsal fin vortex since

  13. Supermanifolds and super Riemann surfaces

    SciTech Connect

    Rabin, J.M.

    1986-09-01

    The theory of super Riemann surfaces is rigorously developed using Rogers' theory of supermanifolds. The global structures of super Teichmueller space and super moduli space are determined. The super modular group is shown to be precisely the ordinary modular group. Super moduli space is shown to be the gauge-fixing slice for the fermionic string path integral.

  14. Anodic Bubble Behavior and Voltage Drop in a Laboratory Transparent Aluminum Electrolytic Cell

    NASA Astrophysics Data System (ADS)

    Zhao, Zhibin; Wang, Zhaowen; Gao, Bingliang; Feng, Yuqing; Shi, Zhongning; Hu, Xianwei

    2016-06-01

    The anodic bubbles generated in aluminum electrolytic cells play a complex role to bath flow, alumina mixing, cell voltage, heat transfer, etc., and eventually affect cell performance. In this paper, the bubble dynamics beneath the anode were observed for the first time from bottom view directly in a similar industrial electrolytic environment, using a laboratory-scale transparent aluminum electrolytic cell. The corresponding cell voltage was measured simultaneously for quantitatively investigating its relevance to bubble dynamics. It was found that the bubbles generated in many spots that increased in number with the increase of current density; the bubbles grew through gas diffusion and various types of coalescences; when bubbles grew to a certain size with their surface reaching to the anode edge, they escaped from the anode bottom suddenly; with the increase of current density, the release frequency increases, and the size of these bubbles decreases. The cell voltage was very consistent with bubble coverage, with a high bubble coverage corresponding to a higher cell voltage. At low current density, the curves of voltage and coverage fluctuated in a regularly periodical pattern, while the curves became more irregular at high current density. The magnitude of voltage fluctuation increased with current density first and reached a maximum value at current density of 0.9 A/cm2, and decreased when the current density was further increased. The extra resistance induced by bubbles was found to increase with the bubble coverage, showing a similar trend with published equations.

  15. Bubble dynamics in drinks

    NASA Astrophysics Data System (ADS)

    Broučková, Zuzana; Trávníček, Zdeněk; Šafařík, Pavel

    2014-03-01

    This study introduces two physical effects known from beverages: the effect of sinking bubbles and the hot chocolate sound effect. The paper presents two simple "kitchen" experiments. The first and second effects are indicated by means of a flow visualization and microphone measurement, respectively. To quantify the second (acoustic) effect, sound records are analyzed using time-frequency signal processing, and the obtained power spectra and spectrograms are discussed.

  16. Sonoluminescence, sonochemistry and bubble dynamics of single bubble cavitation

    NASA Astrophysics Data System (ADS)

    Hatanaka, Shin-ichi

    2012-09-01

    The amount of hydroxyl radicals produced from a single cavitation bubble was quantified by terephthalate dosimetry at various frequencies and pressure amplitudes, while the dynamics of the single bubble was observed by stroboscopic and light-scattering methods. Also, sonoluminescence (SL), sonochemiluminescence (SCL) of luminol, and sodium atom emission (Na*) in the cavitation field were observed. The amount of hydroxyl radicals per cycle as well as the intensity of SL was proportional to pressure amplitude at every frequency performed, and it decreased with increasing frequency. When the single bubble was dancing with a decrease in pressure amplitude, however, the amount of hydroxyl radicals was greater than that for the stable bubble at the higher pressure amplitude and did not significantly decrease with frequency. Furthermore, SCL and Na* were detected only under unstable bubble conditions. These results imply that the instability of bubbles significantly enhances sonochemical efficiency for non-volatile substances in liquid phase.

  17. Bubble colloidal AFM probes formed from ultrasonically generated bubbles.

    PubMed

    Vakarelski, Ivan U; Lee, Judy; Dagastine, Raymond R; Chan, Derek Y C; Stevens, Geoffrey W; Grieser, Franz

    2008-02-05

    Here we introduce a simple and effective experimental approach to measuring the interaction forces between two small bubbles (approximately 80-140 microm) in aqueous solution during controlled collisions on the scale of micrometers to nanometers. The colloidal probe technique using atomic force microscopy (AFM) was extended to measure interaction forces between a cantilever-attached bubble and surface-attached bubbles of various sizes. By using an ultrasonic source, we generated numerous small bubbles on a mildly hydrophobic surface of a glass slide. A single bubble picked up with a strongly hydrophobized V-shaped cantilever was used as the colloidal probe. Sample force measurements were used to evaluate the pure water bubble cleanliness and the general consistency of the measurements.

  18. Instability of two rising bubbles

    NASA Astrophysics Data System (ADS)

    Galper, Alexander; Miloh, Touvia

    1999-11-01

    We consider the stability of two rising ideal gas spherical bubbles subject of an intrinsic dynamics. The dynamics is prescribed or governed by the Rayleigh-Plesset equation adjusted for the pressure field induced by the other bubble in the center of each. Hence, each bubble exhibits linear (nonlinear) oscillations about a stable equilibrium. In order to treat the Liapunov stability problem of bubbles spatial motion we develop the corresponding Hamiltonian formalism. Thus, we find that the oscillations can stabilize the side-by-side and one-below-the-other bubbles translation. These types of translation are known to be asymptotically stable (unstable) for the motion of a pair of purely spherical rigid bubbles. The stabilization phenomenon depends on the frequency and phase difference in the bubbles fast oscillations. The ``rigid'' bubbles theory of the motion is known to have certain discrepancies with the relevant experiments. In order to remove them it is proposed to account for the vorticity wake behind each bubble. Nevertheless, we are able to explain the experiments remaining within the potential framework. Finally, we consider the case of chaotic pulsations. The motion of the two bubbles can also inherit a chaotic character. It results, in turn, in a certain strange attractor for the spatial motion of a pair.

  19. The growth of vapor bubble and relaxation between two-phase bubble flow

    NASA Astrophysics Data System (ADS)

    Mohammadein, S. A.; Subba Reddy Gorla, Rama

    2002-10-01

    This paper presents the behavior of the bubble growth and relaxation between vapor and superheated liquid. The growth and thermal relaxation time between the two-phases are obtained for different levels of superheating. The heat transfer problem is solved numerically by using the extended Scriven model. Results are compared with those of Scriven theory and MOBY DICK experiment with reasonably good agreement for lower values of superheating.

  20. SuperPILOT.

    ERIC Educational Resources Information Center

    Weissmann, Stephen M.

    1983-01-01

    SuperPILOT is Apple Computer's new computer assisted instruction authoring language. Provided is a review of SuperPILOT, indicated to be ideally suited for the development of interactive tutorials for the classroom. Includes comments on the language's strengths/weaknesses as well as comments on system requirements and special program features. (JN)

  1. In Search of the Big Bubble

    ERIC Educational Resources Information Center

    Simoson, Andrew; Wentzky, Bethany

    2011-01-01

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

  2. Superheating and Homogeneous Single Bubble Nucleation in a Solid-State Nanopore

    PubMed Central

    Nagashima, Gaku; Levine, Edlyn V.; Hoogerheide, David P.; Burns, Michael M.; Golovchenko, Jene A.

    2014-01-01

    We demonstrate extreme superheating and single bubble nucleation in an electrolyte solution within a nanopore in a thin silicon nitride membrane. The high temperatures are achieved by Joule heating from a highly focused ionic current induced to flow through the pore by modest voltage biases. Conductance, nucleation, and bubble evolution are monitored electronically and optically. Temperatures near the thermodynamic limit of superheat are achieved just before bubble nucleation with the system at atmospheric pressure. Bubble nucleation is homogeneous and highly reproducible. This nanopore approach more generally suggests broad application to the excitation, detection, and characterization of highly metastable states of matter. PMID:25062192

  3. Hydrophilic strips for preventing air bubble formation in a microfluidic chamber.

    PubMed

    Choi, Munseok; Na, Yang; Kim, Sung-Jin

    2015-12-01

    In a microfluidic chamber, unwanted formation of air bubbles is a critical problem. Here, we present a hydrophilic strip array that prevents air bubble formation in a microfluidic chamber. The array is located on the top surface of the chamber, which has a large variation in width, and consists of a repeated arrangement of super- and moderately hydrophilic strips. This repeated arrangement allows a flat meniscus (i.e. liquid front) to form when various solutions consisting of a single stream or two parallel streams with different hydrophilicities move through the chamber. The flat meniscus produced by the array completely prevents the formation of bubbles. Without the array in the chamber, the meniscus shape is highly convex, and bubbles frequently form in the chamber. This hydrophilic strip array will facilitate the use of a microfluidic chamber with a large variation in width for various microfluidic applications.

  4. Neutron detection via bubble chambers.

    PubMed

    Jordan, D V; Ely, J H; Peurrung, A J; Bond, L J; Collar, J I; Flake, M; Knopf, M A; Pitts, W K; Shaver, M; Sonnenschein, A; Smart, J E; Todd, L C

    2005-01-01

    Research investigating the application of pressure-cycled bubble chambers to fast neutron detection is described. Experiments with a Halon-filled chamber showed clear sensitivity to an AmBe neutron source and insensitivity to a (137)Cs gamma source. Bubble formation was documented using high-speed photography, and a ceramic piezo-electric transducer element registered the acoustic signature of bubble formation. In a second set of experiments, the bubble nucleation response of a Freon-134a chamber to an AmBe neutron source was documented with high-speed photography.

  5. Helium bubble bursting in tungsten

    SciTech Connect

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

    2013-12-28

    Molecular dynamics simulations have been used to systematically study the pressure evolution and bursting behavior of sub-surface helium bubbles and the resulting tungsten surface morphology. This study specifically investigates how bubble shape and size, temperature, tungsten surface orientation, and ligament thickness above the bubble influence bubble stability and surface evolution. The tungsten surface is roughened by a combination of adatom “islands,” craters, and pinholes. The present study provides insight into the mechanisms and conditions leading to various tungsten topology changes, which we believe are the initial stages of surface evolution leading to the formation of nanoscale fuzz.

  6. Droplets, Bubbles and Ultrasound Interactions.

    PubMed

    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.

  7. Bubble measuring instrument and method

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

    Method and apparatus are provided for a non-invasive bubble measuring instrument operable for detecting, distinguishing, and counting gaseous embolisms such as bubbles over a selectable range of bubble sizes of interest. A selected measurement volume in which bubbles may be detected is insonified by two distinct frequencies from a pump transducer and an image transducer, respectively. The image transducer frequency is much higher than the pump transducer frequency. The relatively low-frequency pump signal is used to excite bubbles to resonate at a frequency related to their diameter. The image transducer is operated in a pulse-echo mode at a controllable repetition rate that transmits bursts of high-frequency ultrasonic signal to the measurement volume in which bubbles may be detected and then receives the echo. From the echo or received signal, a beat signal related to the repetition rate may be extracted and used to indicate the presence or absence of a resonant bubble. In a preferred embodiment, software control maintains the beat signal at a preselected frequency while varying the pump transducer frequency to excite bubbles of different diameters to resonate depending on the range of bubble diameters selected for investigation.

  8. Bubble Measuring Instrument and Method

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

    Method and apparatus are provided for a non-invasive bubble measuring instrument operable for detecting, distinguishing, and counting gaseous embolisms such as bubbles over a selectable range of bubble sizes of interest. A selected measurement volume in which bubbles may be detected is insonified by two distinct frequencies from a pump transducer and an image transducer. respectively. The image transducer frequency is much higher than the pump transducer frequency. The relatively low-frequency pump signal is used to excite bubbles to resonate at a frequency related to their diameter. The image transducer is operated in a pulse-echo mode at a controllable repetition rate that transmits bursts of high-frequency ultrasonic signal to the measurement volume in which bubbles may be detected and then receives the echo. From the echo or received signal, a beat signal related to the repetition rate may be extracted and used to indicate the presence or absence of a resonant bubble. In a preferred embodiment, software control maintains the beat signal at a preselected frequency while varying the pump transducer frequency to excite bubbles of different diameters to resonate depending on the range of bubble diameters selected for investigation.

  9. Numerical Simulation on Single Bubble Pool Boiling with Influence of Heater Thermal Capacity

    NASA Astrophysics Data System (ADS)

    Zhao, Jian-Fu; Zhang, Liang; Li, Zhen-Dong

    The model of single bubble pool boiling is used to simulate nucleate pool boiling phenomenon in the present paper. Local convection and heat transfer around a single vapour bubble which is growing from a nucleus bubble planted artificially on the surface of heaters with different thicknesses, as well as transient heat conduction inside the heater’s wall, are simulated numerically with sharp interface representation. Multi-cycle simulation is adopted to eliminate the effect of un-physical initial conditions. It’s found that the thermal response of wall is found to affect the bubble growth and boiling heat transfer. During the process of bubble growth, a sharp temperature drop inside the solid wall is evident near the contact line underneath the growing bubble because of the strong evaporation in micro-region. The temperature and heat flux profiles change with the move of the contact line, and twice sharp temperature drops at a certain location are observed, which correspond to the expanding and recoiling processes, respectively. During the waiting period after the bubble detached from the wall, the temperature field is recovered by heat conduction inside the solid wall. As a part of preparation of the SOBER project onboard the Chinese recoverable satellite SJ-10, which will be launched in the end of 2015, the gravity influence is also studied.

  10. Effects of liquid helium bubble formation in a superconducting cavity cryogenic system

    SciTech Connect

    Chang, X.; Wang, E.; Xin, T.

    2011-03-01

    We constructed a simple prototype model based on the geometry of the 56 MHz superconducting cavity for RHIC. We studied the formation, in this prototype, of bubbles of liquid helium and their thermal effects on the cavity. We found that due to the low viscosity of the liquid helium, and its small surface tension, no large bubbles formed. The tiny bubbles, generated from most of the area, behaved like light gas travelling in a free space and escaped from the trapping region. The bubbles that were generated in the trapping area, due to its descending geometry, are much bigger than the other bubbles, but due to the liquid flow generated by heating, they still are negligible compared to the size of the trapping region. We expected that the effects of bubbles in our 56 MHz cavity during operation might well be negligible.

  11. Diffusion-driven growth of a spherical gas bubble in gelatin gels supersaturated with air

    NASA Astrophysics Data System (ADS)

    Shirota, Eriko; Ando, Keita

    2016-11-01

    We experimentally and theoretically study diffusion-driven growth of laser-induced gas bubbles in gelatin gels supersaturated with air. The supersaturation in the gels is realized by using a large separation between heat and mass diffusion rates. An optical system is developed to induce bubble nucleation by laser focusing and visualize the subsequent bubble growth. To evaluate the effect of the gel elasticity on the bubble growth rate, we propose the extended Epstein-Plesset theory that considers bubble pressure modifications due to linear/nonlinear elasticity (in addition to Laplace pressure). From comparisons between the experiments and the proposed theory, the bubble growth rate is found to be hindered by the elasticity. This study is supported by JSPS KAKENHI Grant Number 25709008.

  12. Bubble motion and size variation during thermal migration with phase change

    NASA Astrophysics Data System (ADS)

    Nurse, A. K.; McFadden, G. B.; Coriell, S. R.

    2013-01-01

    An analysis of the motion of a spherical bubble in a two-phase (fluid-fluid), single component system with a vertical linear temperature gradient is presented. The model for the migration of an immiscible bubble under the effects of buoyancy and thermocapillarity, considered by Young et al. ["The motion of bubbles in a vertical temperature gradient," J. Fluid Mech. 6, 350-356 (1959)], is modified to allow for phase change at the bubble surface. We allow the possibility of both translation of the bubble in the vertical direction and the change of bubble radius with time. Depending on the material parameters, the thermocapillary and buoyancy effects that govern the migration of an immiscible bubble can be overwhelmed by the effects of latent heat generation, resulting in a change in the mechanism driving the motion. For a water-steam system, conditions are determined for a stationary bubble in which the effects of buoyancy and thermal migration are balanced. The linear stability of the bubble is considered, and conditions are determined that correspond to small-amplitude oscillations of the position and radius of the bubble. A weakly nonlinear analysis of the solution in the vicinity of the unstable solution is performed, and the results are compared with a numerical solution of the nonlinear equations.

  13. Bubble Size Distribution in a Vibrating Bubble Column

    NASA Astrophysics Data System (ADS)

    Mohagheghian, Shahrouz; Wilson, Trevor; Valenzuela, Bret; Hinds, Tyler; Moseni, Kevin; Elbing, Brian

    2016-11-01

    While vibrating bubble columns have increased the mass transfer between phases, a universal scaling law remains elusive. Attempts to predict mass transfer rates in large industrial scale applications by extrapolating laboratory scale models have failed. In a stationary bubble column, mass transfer is a function of phase interfacial area (PIA), while PIA is determined based on the bubble size distribution (BSD). On the other hand, BSD is influenced by the injection characteristics and liquid phase dynamics and properties. Vibration modifies the BSD by impacting the gas and gas-liquid dynamics. This work uses a vibrating cylindrical bubble column to investigate the effect of gas injection and vibration characteristics on the BSD. The bubble column has a 10 cm diameter and was filled with water to a depth of 90 cm above the tip of the orifice tube injector. BSD was measured using high-speed imaging to determine the projected area of individual bubbles, which the nominal bubble diameter was then calculated assuming spherical bubbles. The BSD dependence on the distance from the injector, injector design (1.6 and 0.8 mm ID), air flow rates (0.5 to 5 lit/min), and vibration conditions (stationary and vibration conditions varying amplitude and frequency) will be presented. In addition to mean data, higher order statistics will also be provided.

  14. Numerical study of Taylor bubbles with adaptive unstructured meshes

    NASA Astrophysics Data System (ADS)

    Xie, Zhihua; Pavlidis, Dimitrios; Percival, James; Pain, Chris; Matar, Omar; Hasan, Abbas; Azzopardi, Barry

    2014-11-01

    The Taylor bubble is a single long bubble which nearly fills the entire cross section of a liquid-filled circular tube. This type of bubble flow regime often occurs in gas-liquid slug flows in many industrial applications, including oil-and-gas production, chemical and nuclear reactors, and heat exchangers. The objective of this study is to investigate the fluid dynamics of Taylor bubbles rising in a vertical pipe filled with oils of extremely high viscosity (mimicking the ``heavy oils'' found in the oil-and-gas industry). A modelling and simulation framework is presented here which can modify and adapt anisotropic unstructured meshes to better represent the underlying physics of bubble rise and reduce the computational effort without sacrificing accuracy. The numerical framework consists of a mixed control-volume and finite-element formulation, a ``volume of fluid''-type method for the interface capturing based on a compressive control volume advection method, and a force-balanced algorithm for the surface tension implementation. Numerical examples of some benchmark tests and the dynamics of Taylor bubbles are presented to show the capability of this method. EPSRC Programme Grant, MEMPHIS, EP/K0039761/1.

  15. Earths, Super-Earths, and Jupiters

    NASA Astrophysics Data System (ADS)

    Chiang, Eugene; Lee, Eve J.

    2015-12-01

    We review and add to the theory of how planets acquire atmospheres from parent circumstellar disks. We derive (in real time) a simple and general analytic expression for how a planet's atmosphere grows with time, as a function of the underlying core mass and nebular conditions, including the gas metallicity. Planets accrete as much gas as can cool: an atmosphere's doubling time is given by its Kelvin-Helmholtz time. The theory can be applied in any number of settings --- gas-rich vs. gas-poor nebulae; dusty vs. dust-free atmospheres; close-in vs. far-out distances --- and is confirmed against detailed numerical models for objects ranging in mass from Mars (0.1 Mearth) to the most extreme super Earths (10--20 Mearth). We explain why heating from planetesimal accretion, commonly invoked in models of core accretion, is irrelevant. This talk sets the stage for another presentation, "Breeding Super-Earths and Birthing Super-Puffs".

  16. Visualization of airflow growing soap bubbles

    NASA Astrophysics Data System (ADS)

    Al Rahbi, Hamood; Bock, Matthew; Ryu, Sangjin

    2016-11-01

    Visualizing airflow inside growing soap bubbles can answer questions regarding the fluid dynamics of soap bubble blowing, which is a model system for flows with a gas-liquid-gas interface. Also, understanding the soap bubble blowing process is practical because it can contribute to controlling industrial processes similar to soap bubble blowing. In this study, we visualized airflow which grows soap bubbles using the smoke wire technique to understand how airflow blows soap bubbles. The soap bubble blower setup was built to mimic the human blowing process of soap bubbles, which consists of a blower, a nozzle and a bubble ring. The smoke wire was placed between the nozzle and the bubble ring, and smoke-visualized airflow was captured using a high speed camera. Our visualization shows how air jet flows into the growing soap bubble on the ring and how the airflow interacts with the soap film of growing bubble.

  17. Formation and Growth of Micro and Macro Bubbles on Copper-Graphite Composite Surfaces

    NASA Technical Reports Server (NTRS)

    Chao, David F.; Sankovic, John M.; Motil, Brian J.; Zhang, Nengli

    2007-01-01

    Micro scale boiling behavior in the vicinity of graphite micro-fiber tips on the coppergraphite composite boiling surfaces is investigated. It is discovered that a large number of micro bubbles are formed first at the micro scratches and cavities on the copper matrix in pool boiling. In virtue of the non-wetting property of graphite, once the growing micro bubbles touch the graphite tips, the micro bubbles are sucked by the tips and merged into larger micro bubbles sitting on the tips. The micro bubbles grow rapidly and coalesce to form macro bubbles, each of which sitting on several tips. The growth processes of the micro and macro bubbles are analyzed and formulated followed by an analysis of bubble departure on the composite surfaces. Based on these analyses, the enhancement mechanism of the pool boiling heat transfer on the composite surfaces is clearly revealed. Experimental results of pool boiling heat transfer both for water and Freon-113 on the composite surfaces convincingly demonstrate the enhancement effects of the unique structure of Cu-Gr composite surfaces on boiling heat transfer.

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

    PubMed

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

    2015-01-01

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

  19. Black Hole Blows Big Bubble

    NASA Astrophysics Data System (ADS)

    2010-07-01

    Combining observations made with ESO's Very Large Telescope and NASA's Chandra X-ray telescope, astronomers have uncovered the most powerful pair of jets ever seen from a stellar black hole. This object, also known as a microquasar, blows a huge bubble of hot gas, 1000 light-years across, twice as large and tens of times more powerful than other known microquasars. The discovery is reported this week in the journal Nature. "We have been astonished by how much energy is injected into the gas by the black hole," says lead author Manfred Pakull. "This black hole is just a few solar masses, but is a real miniature version of the most powerful quasars and radio galaxies, which contain black holes with masses of a few million times that of the Sun." Black holes are known to release a prodigious amount of energy when they swallow matter. It was thought that most of the energy came out in the form of radiation, predominantly X-rays. However, the new findings show that some black holes can release at least as much energy, and perhaps much more, in the form of collimated jets of fast moving particles. The fast jets slam into the surrounding interstellar gas, heating it and triggering an expansion. The inflating bubble contains a mixture of hot gas and ultra-fast particles at different temperatures. Observations in several energy bands (optical, radio, X-rays) help astronomers calculate the total rate at which the black hole is heating its surroundings. The astronomers could observe the spots where the jets smash into the interstellar gas located around the black hole, and reveal that the bubble of hot gas is inflating at a speed of almost one million kilometres per hour. "The length of the jets in NGC 7793 is amazing, compared to the size of the black hole from which they are launched," says co-author Robert Soria [1]. "If the black hole were shrunk to the size of a soccer ball, each jet would extend from the Earth to beyond the orbit of Pluto." This research will help

  20. Black Hole Blows Big Bubble

    NASA Astrophysics Data System (ADS)

    2010-07-01

    Combining observations made with ESO's Very Large Telescope and NASA's Chandra X-ray telescope, astronomers have uncovered the most powerful pair of jets ever seen from a stellar black hole. This object, also known as a microquasar, blows a huge bubble of hot gas, 1000 light-years across, twice as large and tens of times more powerful than other known microquasars. The discovery is reported this week in the journal Nature. "We have been astonished by how much energy is injected into the gas by the black hole," says lead author Manfred Pakull. "This black hole is just a few solar masses, but is a real miniature version of the most powerful quasars and radio galaxies, which contain black holes with masses of a few million times that of the Sun." Black holes are known to release a prodigious amount of energy when they swallow matter. It was thought that most of the energy came out in the form of radiation, predominantly X-rays. However, the new findings show that some black holes can release at least as much energy, and perhaps much more, in the form of collimated jets of fast moving particles. The fast jets slam into the surrounding interstellar gas, heating it and triggering an expansion. The inflating bubble contains a mixture of hot gas and ultra-fast particles at different temperatures. Observations in several energy bands (optical, radio, X-rays) help astronomers calculate the total rate at which the black hole is heating its surroundings. The astronomers could observe the spots where the jets smash into the interstellar gas located around the black hole, and reveal that the bubble of hot gas is inflating at a speed of almost one million kilometres per hour. "The length of the jets in NGC 7793 is amazing, compared to the size of the black hole from which they are launched," says co-author Robert Soria [1]. "If the black hole were shrunk to the size of a soccer ball, each jet would extend from the Earth to beyond the orbit of Pluto." This research will help

  1. Bubble formation in microgravity

    NASA Technical Reports Server (NTRS)

    Antar, Basil N.

    1996-01-01

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

  2. Bubble formation in microgravity

    NASA Technical Reports Server (NTRS)

    Antar, Basil N.

    1994-01-01

    Two KC-135 flight campaigns have been conducted to date which are specifically dedicated to study bubble formation in microgravity. The first flight was conducted during March 14-18, 1994, and the other during June 20-24, 1994. The results from the June 1994 flight have not been analyzed yet, while the results from the March flight have been partially analyzed. In the first flight three different experiments were performed, one with the specific aim at determining whether or not cavitation can take place during any of the fluid handling procedures adopted in the shuttle bioprocessing experiments. The other experiments were concerned with duplicating some of the procedures that resulted in bubble formation, namely the NCS filling procedure and the needle scratch of a solid surface. The results from this set of experiments suggest that cavitation did not take place during any of the fluid handling procedures. The results clearly indicate that almost all were generated as a result of the breakup of the gas/liquid interface. This was convincingly demonstrated in the scratch tests as well as in the liquid fill tests.

  3. Triangular bubble spline surfaces

    PubMed Central

    Kapl, Mario; Byrtus, Marek; Jüttler, Bert

    2011-01-01

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

  4. Tuning bubbly structures in microchannels

    PubMed Central

    Vuong, Sharon M.; Anna, Shelley L.

    2012-01-01

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

  5. Bubble detector investigations in China.

    PubMed

    Guo, Shi-Lun

    2006-01-01

    Investigation on bubble detectors started in China in 1989. Five types of bubble detectors have been developed, with LET thresholds ranging from 0.05 to 6.04 MeV mg(-1) cm(2) at 25 degrees C. The neutron response of bubble detectors made with freon-12 has been investigated with mono-energetic neutrons from 20 keV to 19 MeV. Its effective threshold energy for neutron detection is approximately 100 keV at 28 degrees C. The response above this threshold is approximately 1.5 x 10(-4) (bubble cm(-2))/(n cm(-2)). Bubble detectors are unique not only for neutron dosimetry but also for monitoring and identifying high-energy heavy ions such as cosmic radiation in the space. High-energy heavy ion tracks in large size bubble detectors have been investigated in cooperation with scientists in Japan. The key parameter behind the thresholds of bubble detectors for track registration is the critical rate of energy loss. Three approaches to identify high-energy heavy ions with bubble detectors are suggested.

  6. In situ X-ray tomographic microscopy observations of vesiculation of bubble-free and bubble-bearing magmas

    NASA Astrophysics Data System (ADS)

    Pistone, Mattia; Caricchi, Luca; Fife, Julie L.; Mader, Kevin; Ulmer, Peter

    2015-12-01

    Magma degassing is thought to play a major role in magma fractionation, transport, storage, and volcanic eruption dynamics. However, the conditions that determine when and how magma degassing operates prior to and during an eruption remain poorly constrained. We performed experiments to explore if the initial presence of gas bubbles in magma influences the capability of gas to escape from the magma. Vesiculation of natural H2O-poor (<<1 wt.%) silicic obsidian glasses was investigated by in situ, high-temperature (above the glass transition) experiments using synchrotron-based X-ray tomographic microscopy with high spatial (3 μm/pixel) and temporal resolution (1 second per 3D dataset). As a validation, a second set of experiments was performed on identical starting materials using a Karl-Fisher titration setup to quantify the amount of extracted gas that escapes via volatile diffusion and/or bubble coalescence during vesiculation. In both sets of experiments, vesiculation was triggered by heating the samples at room pressure. Our results suggest that the presence of pre-existing gas bubbles during a nucleation event significantly decreases the tendency of bubbles to coalesce and inhibits magma outgassing. In contrast, in initially bubble-free samples, the nucleation and growth of bubbles is accompanied by significant coalescence and outgassing. We infer that volatile-undersaturated (i.e. bubble-free) magmas in the reservoirs are more likely to erupt effusively, while the presence of excess gas already at depth (i.e. bubble-bearing systems) increases the likelihood of explosive eruptions.

  7. Super Ball Bot

    NASA Video Gallery

    Tensegrity Robot: Child's Play or Space Tech? Super Ball Bot is an all-in-one landing and mobility platform based on tensegrity structures, allowing for lower-cost, and more reliable planetary miss...

  8. Super Thin Ceramic Coatings

    NASA Video Gallery

    New technology being developed at NASA's Glenn Research Center creates super thin ceramic coatings on engine components. The Plasma Spray – Physical Vapor Deposition (PS-PVD) rig uses a powerful ...

  9. Research Program of a Super Fast Reactor

    SciTech Connect

    Oka, Yoshiaki; Ishiwatari, Yuki; Liu, Jie; Terai, Takayuki; Nagasaki, Shinya; Muroya, Yusa; Abe, Hiroaki; Akiba, Masato; Akimoto, Hajime; Okumura, Keisuke; Akasaka, Naoaki; GOTO, Shoji

    2006-07-01

    Research program of a supercritical-pressure light water cooled fast reactor (Super Fast Reactor) is funded by MEXT (Ministry of Education, Culture, Sports, Science and Technology) in December 2005 as one of the research programs of Japanese NERI (Nuclear Energy Research Initiative). It consists of three programs. (1) development of Super Fast Reactor concept; (2) thermal-hydraulic experiments; (3) material developments. The purpose of the concept development is to pursue the advantage of high power density of fast reactor over thermal reactors to achieve economic competitiveness of fast reactor for its deployment without waiting for exhausting uranium resources. Design goal is not breeding, but maximizing reactor power by using plutonium from spent LWR fuel. MOX will be the fuel of the Super Fast Reactor. Thermal-hydraulic experiments will be conducted with HCFC22 (Hydro chlorofluorocarbons) heat transfer loop of Kyushu University and supercritical water loop at JAEA. Heat transfer data including effect of grid spacers will be taken. The critical flow and condensation of supercritical fluid will be studied. The materials research includes the development and testing of austenitic stainless steel cladding from the experience of PNC1520 for LMFBR. Material for thermal insulation will be tested. SCWR (Supercritical-Water Cooled Reactor) of GIF (Generation-4 International Forum) includes both thermal and fast reactors. The research of the Super Fast Reactor will enhance SCWR research and the data base. The research period will be until March 2010. (authors)

  10. Super-Kamiokande

    NASA Astrophysics Data System (ADS)

    Magro, Lluís Martí

    2016-06-01

    The Super-Kamiokande experiment performs a large variety of studies, many of them in the neutrino sector. The archetypes are atmospheric neutrino (recently awarded with the Nobel prize for Mr. T. Kajita) and the solar neutrinos analyses. In these proceedings we report our latest results and present updates to indirect dark matter searches, our solar neutrino analysis and discuss the future upgrade of Super-Kamiokande by loading gadolinium into our ultra-pure water.

  11. Vapor-Resistant Heat-Pipe Artery

    NASA Technical Reports Server (NTRS)

    Dussinger, Peter M.; Shaubach, Robert M.; Buchko, Matt

    1991-01-01

    Vapor lock in heat pipe delayed or prevented. Modifications of wick prevent flow of vapor into, or formation of vapor in, liquid-return artery. Small pores of fine-grained sintered wick help to prevent formation of large bubbles. Slotted tube offers few nucleation sites for bubbles. Improves return of liquid in heat pipe.

  12. Doughnut-shaped soap bubbles

    NASA Astrophysics Data System (ADS)

    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 <α L3/6 π2 , with α ≈0.21 , such a surface cannot be the usual lens-shaped surface formed by the juxtaposition of two spherical 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.

  13. Deforming super Riemann surfaces with gravitinos and super Schottky groups

    NASA Astrophysics Data System (ADS)

    Playle, Sam

    2016-12-01

    The (super) Schottky uniformization of compact (super) Riemann surfaces is briefly reviewed. Deformations of super Riemann surface by gravitinos and Beltrami parameters are recast in terms of super Schottky group cohomology. It is checked that the super Schottky group formula for the period matrix of a non-split surface matches its expression in terms of a gravitino and Beltrami parameter on a split surface. The relationship between (super) Schottky groups and the construction of surfaces by gluing pairs of punctures is discussed in an appendix.

  14. A super-resolution ultrasound method for brain vascular mapping

    PubMed Central

    O'Reilly, Meaghan A.; Hynynen, Kullervo

    2013-01-01

    Purpose: High-resolution vascular imaging has not been achieved in the brain due to limitations of current clinical imaging modalities. The authors present a method for transcranial ultrasound imaging of single micrometer-size bubbles within a tube phantom. Methods: Emissions from single bubbles within a tube phantom were mapped through an ex vivo human skull using a sparse hemispherical receiver array and a passive beamforming algorithm. Noninvasive phase and amplitude correction techniques were applied to compensate for the aberrating effects of the skull bone. The positions of the individual bubbles were estimated beyond the diffraction limit of ultrasound to produce a super-resolution image of the tube phantom, which was compared with microcomputed tomography (micro-CT). Results: The resulting super-resolution ultrasound image is comparable to results obtained via the micro-CT for small tissue specimen imaging. Conclusions: This method provides superior resolution to deep-tissue contrast ultrasound and has the potential to be extended to provide complete vascular network imaging in the brain. PMID:24320408

  15. Thermodynamics and kinetics of vapor bubbles nucleation in one-component liquids.

    PubMed

    Alekseechkin, Nikolay V

    2012-08-09

    The multivariable theory of nucleation (J. Chem. Phys. 2006, 124, 124512) is applied to the problem of vapor bubbles formation in pure liquids. The presented self-consistent macroscopic theory of this process employs thermodynamics (classical, statistical, and linear nonequilibrium), hydrodynamics, and interfacial kinetics. As a result of thermodynamic study of the problem, the work of formation of a bubble is obtained and parameters of the critical bubble are determined. The variables V (the bubble volume), ρ (the vapor density), and T (the vapor temperature) are shown to be natural for the given task. An equation for the dependence of surface tension on bubble state parameters is obtained. An algorithm of writing the equations of motion of a bubble in the space {V, ρ, T}--equations for V, ρ, and T--is offered. This algorithm ensures symmetry of the matrix of kinetic coefficients. The equation for T written on the basis of this algorithm is shown to represent the first law of thermodynamics for a bubble. The negative eigenvalue of the motion equations which alongside with the work of the critical bubble formation determines the stationary nucleation rate of bubbles is obtained. Various kinetic limits are considered. One of the kinetic constraints leads to the fact that the nucleation cannot occur in the whole metastable region; it occurs only in some subregion of the latter. Zeldovich's theory of cavitation is shown to be a limiting case of the theory presented. The limiting effects of various kinetic processes on the nucleation rate of bubbles are shown analytically. These are the inertial motion of a liquid as well as the processes of particles exchange and heat exchange between a bubble and surrounding liquid. The nucleation rate is shown to be determined by the slowest kinetic process at positive and moderately negative pressures in a liquid. The limiting effects of the processes of evaporation-condensation and heat exchange vanish at high negative

  16. Dynamics of a Spherical Vapor/Gas Bubble in Varying Pressure Fields

    NASA Astrophysics Data System (ADS)

    Kawashima, Hisanobu; Kameda, Masaharu

    A mathematical model is developed to simulate the radial motion of cavitation bubbles. The heat and mass transports including phase change are formulated precisely. In order to reduce the computational cost without loss of the important thermo-fluid phenomena, two simplifications are employed: time-dependent bubble radius is described using the Rayleigh-Plesset equation; the pressure in the bubble is assumed to be uniform in space. For validation of the model, the transient radial motion of an air bubble in water is observed experimentally. A shock tube is used to make the sudden pressure reduction from atmospheric to below the saturated vapor pressure. The bubble radius is measured by high-speed photography, in which an interferomtric laser imaging technique is used for accurate determination of the initial bubble radius. The radial motion is successfully predicted by using this model. The temperature reduction at the bubble wall is a predominant factor on the bubble growth rate under superheated conditions, even if the liquid temperature is close to room temperature. The numerical result indicates that the growth rate is very sensitive to initial bubble radius, ambient pressure, and liquid temperature.

  17. Thermocapillary Bubble Migration - An Oseen-Like Analysis of the Energy Equation

    NASA Technical Reports Server (NTRS)

    Balasubramaniam, R.; Dill, L. H.

    1992-01-01

    The thermocapillary migration of a bubble in a liquid possessing a temperature gradient is analyzed in the limit of large Reynolds and Marangoni numbers. Crespo and Manuel (1983) performed an analysis in this limit wherein energy conduction is completely neglected and obtained the bubble migration velocity using energy dissipation arguments. In the present analysis, performed in a coordinate system moving with the bubble, the velocity field in the convection term in the energy equation is approximated in an Oseen-like manner by replacing it with the velocity field far away from the bubble (i.e., the migration velocity of the bubble). Conduction is retained to satisfy the zero conductive heat flux boundary condition on the bubble surface. An approximate solution has been obtained for the Oseen-like energy equation. The bubble velocity obtained using energy dissipation considerations is in agreement with the result of Crespo and Manuel. The solution shows the thermal boundary layer and wake structure in the vicinity of the bubble. The Oseen-like analysis, however, has inherent limitations, as the flow penetrates the bubble surface. These issues are discussed and the result are compared to those in the literature.

  18. Bubble formation in a coflow configuration in normal and reduced gravity

    SciTech Connect

    Bhunia, A.; Pais, S.C.; Kamotani, Yasuhiro; Kim, I.H.

    1998-07-01

    Situations where a gas and a liquid flow together in a pipe occur in various terrestrial applications, such as gas dissolution in liquid in the chemical and pharmaceutical industries, oil and gas pipelines, nuclear power plants, and two-phase flow heat exchangers, to name a few examples. A study of bubble generation for constant gas-flux condition by single-nozzle injection in a coflowing liquid is reported. Focusing on single-bubble generation in the dynamic and bubbly flow regime, the onset condition for bubble coalescence is investigated. The role of various forces involved in the bubble formation process is studied, and an overall force balance describing bubble dynamics is developed. Gas-momentum flux and buoyancy in normal gravity enhance, while the surface-tension force at the nozzle rim inhibits bubble detachment. On the other hand, liquid drag and inertia can act both as attaching or detaching forces, depending on the relative velocity of the bubble with respect to the surrounding liquid. Predictions of the theoretical model compare well with the present reduced-gravity experiment and available normal-gravity experiments. Effects of the fluid properties, injection geometry, and flow conditions on bubble size are investigated.

  19. Bubble Growth in Lunar Basalts

    NASA Astrophysics Data System (ADS)

    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

  20. Partial coalescence of soap bubbles

    NASA Astrophysics Data System (ADS)

    Harris, Daniel M.; Pucci, Giuseppe; Bush, John W. M.

    2015-11-01

    We present the results of an experimental investigation of the merger of a soap bubble with a planar soap film. When gently deposited onto a horizontal film, a bubble may interact with the underlying film in such a way as to decrease in size, leaving behind a smaller daughter bubble with approximately half the radius of its progenitor. The process repeats up to three times, with each partial coalescence event occurring over a time scale comparable to the inertial-capillary time. Our results are compared to the recent numerical simulations of Martin and Blanchette and to the coalescence cascade of droplets on a fluid bath.

  1. THE FERMI BUBBLES AS A SCALED-UP VERSION OF SUPERNOVA REMNANTS

    SciTech Connect

    Fujita, Yutaka; Ohira, Yutaka; Yamazaki, Ryo

    2013-09-20

    In this study, we treat Fermi bubbles as a scaled-up version of supernova remnants (SNRs). The bubbles are created through activities of the super-massive black hole (SMBH) or starbursts at the Galactic center (GC). Cosmic-rays (CRs) are accelerated at the forward shocks of the bubbles like SNRs, which means that we cannot decide whether the bubbles were created by the SMBH or starbursts from the radiation from the CRs. We follow the evolution of CR distribution by solving a diffusion-advection equation, considering the reduction of the diffusion coefficient by CR streaming. In this model, gamma rays are created through hadronic interaction between CR protons and the gas in the Galactic halo. In the GeV band, we can well reproduce the observed flat distribution of gamma-ray surface brightness because some amount of gas is left behind the shock. The edge of the bubbles is fairly sharp owing to the high gas density behind the shock and the reduction of the diffusion coefficient there. The latter also contributes the hard gamma-ray spectrum of the bubbles. We find that the CR acceleration at the shock began when the bubbles were small, and the time scale of the energy injection at the GC was much smaller than the age of the bubbles. We predict that if CRs are accelerated to the TeV regime, the apparent bubble size should be larger in the TeV band, which could be used to discriminate our hadronic model from other leptonic models. We also present neutrino fluxes.

  2. Terminating marine methane bubbles by superhydrophobic sponges.

    PubMed

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

    2012-11-14

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

  3. Bubble Dynamics and Resulting Noise from Traveling Bubble Cavitation.

    DTIC Science & Technology

    1982-04-13

    has resulted in models which aqree well with bubble dynamics recorded by high speed film . Chahine, et. al. (23) incorporated asymmetric bubble...recording on the tape soundtrack . 3.8 Measurement of Gas Nuclei in Water The role of nuclei density and size in cavitation inception has been the subject...interference between the coherent background and the particle-diffracted radiation exooses photographic film in the far-field of the nuclei. This

  4. Nucleus factory on cavitation bubble for amyloid β fibril

    NASA Astrophysics Data System (ADS)

    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.

  5. Nucleus factory on cavitation bubble for amyloid β fibril

    PubMed Central

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

    2016-01-01

    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. PMID:26912021

  6. Xenon bubble chambers for direct dark matter detection

    NASA Astrophysics Data System (ADS)

    Levy, C.; Fallon, S.; Genovesi, J.; Khaitan, D.; Klimov, K.; Mock, J.; Szydagis, M.

    2016-03-01

    The search for dark matter is one of today's most exciting fields. As bigger detectors are being built to increase their sensitivity, background reduction is an ever more challenging issue. To this end, a new type of dark matter detector is proposed, a xenon bubble chamber, which would combine the strengths of liquid xenon TPCs, namely event by event energy resolution, with those of a bubble chamber, namely insensitivity to electronic recoils. In addition, it would be the first time ever that a dark matter detector is active on all three detection channels, ionization and scintillation characteristic of xenon detectors, and heat through bubble formation in superheated fluids. Preliminary simulations show that, depending on threshold, a discrimination of 99.99% to 99.9999+% can be achieved, which is on par or better than many current experiments. A prototype is being built at the University at Albany, SUNY. The prototype is currently undergoing seals, thermal, and compression testing.

  7. Characterization and application of bubbles during thermal blooming

    NASA Astrophysics Data System (ADS)

    Abeywickrema, Ujitha; Banerjee, Neil

    2014-09-01

    When a highly absorbing thermal medium is heated with a focused laser pump beam, diffraction ring patterns can be observed due to self-phase modulation. It is further observed that when the laser power increases, the usual self-phase modulation diffraction patterns change due to formation of a bubble inside the thermal lens created by the focused beam. This phenomenon, called thermal blooming, is the next step to selfphase modulation. A stable bubble is formed using a focused laser beam, and the bubble is characterized using holograms made with a probe beam. A 532 nm Argon-Ion laser is used as the pump and a 633 nm low power He-Ne laser is used as the probe. The thermal medium comprises a mixture of a red dye and isopropyl alcohol. To minimize the optical effects arising from convection, the focused pump is introduced vertically into the liquid sample. The recorded in-line holograms are numerically reconstructed to determine the size and 3d shape of the bubbles. Bubble sizes are monitored as a function of the pump intensity. Once formed, the bubbles can be steered by mechanically deflecting the pump beam or any other laser beam. Finally, Ag nanoparticles are fabricated, examined, and introduced into the thermal medium. The presence of nanoparticle agglomeration around the thermally generated bubbles is tested using a focused probe beam at 405 nm corresponding to the absorption peak of the Ag nanoparticles due to plasmonic resonance. This technique should prove useful in drug delivery systems using nanoparticles agglomerated around microbubbles.

  8. The Super HMS

    SciTech Connect

    Chen Yan

    1998-06-01

    As a part of physics instrumentation development for TJNAF long range institution upgrade plan, a 12 GeV/c Super High Momentum Spectrometer (the Super HMS) has been proposed for high luminosity and high q2 physics in endstation Hall C. The fundamental configuration of Super HMS is QQDD. Two identical quadrupoles are the superconducting HMS Q1s with maximum gradient 8 Tesla/m. Two identical SLAC B202/B203 dipole magnets are considered for the use of dispersive elements with accumulative bending power 18.7 degree at 12 GeV/c while the central field is set to 2.05 Tesla. A sliding mechanism could guide the whole system, including the magnetic elements and detector house, moving forwards and backwards by +/- 100 cm. Under an assumed magnetic structure, the Super HMS optics performance has been studied by using TRANSPORT, TURTLE, and RAYTRACE codes and related reconstruction methods. The applicable solid angle can be adjusted between 1 msr and 2.3 msr. The maximum central momentum is 12 GeV/c. The reconstructed momentum resolution within full momentum range 20% is better than 10-3. The in-plane angle reconstruction accuracy is about 0.5 mr, mainly determined by the local multiple scattering from detector materials. This report also points out the strategy of super HMS optics adapting low rigidity quadrupoles for the use of high momentum operation, and the potential capability of very forward angle operations.

  9. Aspherical bubble dynamics and oscillation times

    SciTech Connect

    Vogel, A.; Noack, J.; Chapyak, E.J.; Godwin, R.P.

    1999-06-01

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

  10. Transient bubbles, bublets and breakup

    NASA Astrophysics Data System (ADS)

    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.

  11. Partial coalescence of soap bubbles

    NASA Astrophysics Data System (ADS)

    Pucci, G.; Harris, D. M.; Bush, J. W. M.

    2015-06-01

    We present the results of an experimental investigation of the merger of a soap bubble with a planar soap film. When gently deposited onto a horizontal film, a bubble may interact with the underlying film in such a way as to decrease in size, leaving behind a smaller daughter bubble with approximately half the radius of its progenitor. The process repeats up to three times, with each partial coalescence event occurring over a time scale comparable to the inertial-capillary time. Our results are compared to the recent numerical simulations of Martin and Blanchette ["Simulations of surfactant effects on the dynamics of coalescing drops and bubbles," Phys. Fluids 27, 012103 (2015)] and to the coalescence cascade of droplets on a fluid bath.

  12. Modelling of single bubble-dynamics and thermal effects

    NASA Astrophysics Data System (ADS)

    Papoulias, D.; Gavaises, M.

    2015-12-01

    This paper evaluates the solution effects of different Rayleigh-Plesset models (R-P) for simulating the growth/collapse dynamics and thermal behaviour of homogeneous gas bubbles. The flow inputs used for the discrete cavitation bubble calculations are obtained from Reynolds-averaged Navier-Stokes simulations (RANS), performed in high-pressure nozzle holes. Parametric 1-D results are presented for the classical thermal R-P equation [1] as well as for refined models which incorporated compressibility corrections and thermal effects [2, 3]. The thermal bubble model is coupled with the energy equation, which provides the temperature of the bubble as a function of conduction/convection and radiation heat-transfer mechanisms. For approximating gas pressure variations a high-order virial equation of state (EOS) was used, based on Helmholtz free energy principle [4]. The coded thermal R-P model was validated against experimental measurements [5] and model predictions [6] reported in single-bubble sonoluminescence (SBSL).

  13. Bubble dynamics in high-amplitude ultrasound therapies

    NASA Astrophysics Data System (ADS)

    Johnsen, Eric; Mancia, Lauren

    2015-11-01

    Cavitation plays an important role in certain therapeutic ultrasound procedures, such as histotripsy in which megahertz pressure pulses are used to destroy tissue. The large tensions (> 25 MPa) nucleate bubbles in the tissue, which rapidly grow to radii on the order of hundreds of microns and subsequently collapse. To better understand potential cavitation-induced damage, we developed a numerical framework for spherical bubble dynamics in soft tissue that includes liquid compressibility and full thermal effects, as well as a comprehensive viscoelastic model with elasticity, relaxation, viscosity and various nonlinearities. This framework has enabled us to understand the effects of the viscoelastic and thermal properties of the tissue on the bubble dynamics, and compute stress and temperature fields in the surroundings. Results indicate that different viscoelastic properties affect the bubble dynamics differently, but that overall the viscoelastic nature of tissue produces larger stresses and increased heating on the surroundings, compared to bubble dynamics in purely viscous liquids. This work was supported by NSF grant number CBET 1253157 and NIH grant number 1R01HL110990-01A1.

  14. The Dynamics of Vapor Bubbles in Acoustic Pressure Fields

    NASA Technical Reports Server (NTRS)

    Hao, Y.; Prosperetti, A.

    1999-01-01

    In spite of a superficial similarity with gas bubbles, the intimate coupling between dynamical and thermal processes confers to oscillating vapor bubbles some unique characteristics. This paper examines numerically the validity of some asymptotic-theory predictions such as the existence of two resonant radii and a limit size for a given sound amplitude and frequency. It is found that a small vapor bubble in a sound field of sufficient amplitude grows quickly through resonance and continues to grow thereafter at a very slow rate, seemingly indefinitely. Resonance phenomena therefore play a role for a few cycles at most, and reaching a limit size-if one exists at all-is found to require far more than several tens of thousands of cycles. It is also found that some small bubbles may grow or collapse depending on the phase of the sound field. The model accounts in detail for the thermo-fluid-mechanic processes in the vapor. In the second part of the paper, an approximate formulation valid for bubbles small with respect to the thermal penetration length in the vapor is derived and its accuracy examined, The present findings have implications for acoustically enhanced boiling heat transfer and other special applications such as boiling in microgravity.

  15. Three-Dimensional Bubble Size Distributions From Growth at High Water Supersaturation: X-ray Microtomographic Investigations

    NASA Astrophysics Data System (ADS)

    Robert, G.; Allard, E.; Jeff, L.; Rivers, M.; Baker, D. R.

    2004-05-01

    The growth of bubbles and exsolution of water from molten rocks is responsible for most volcanic eruptions on Earth. Rapid bubble growth without formation of an interconnected, percolating, cluster of bubbles can create a volcanic eruption, whereas slower bubble growth and a high enough (but still quantitatively unknown) bubble density results in more passive volcanic degassing. Understanding the rates and mechanisms of water exsolution provides better insight into volcanic eruptions and can lead to mitigation of their potentially devastating effects. In order to better understand the mechanisms of volcanic eruptions we are investigating the formation of water bubbles by heating previously hydrated silicate melts at 1 atm pressure and using x-ray microtomography to study the bubble size distribution. Hydrous silicate melts spanning a wide range of composition and physical properties were prepared by dissolving water into silicate melts at high temperatures and high pressure by melting glasses with water in sealed capsules at 500 MPa and 1100 oC in a piston-cylinder apparatus followed by rapid quenching to room temperature and pressure. Chips of these glasses were heated at 1 atm and temperatures up to 1000 oC. Most chips of samples were heated under an optical microscope at 1 atm in the laboratory at McGill University to make bubble-bearing samples, whereas a few chips were degassed a custom-designed, boron-nitride furnace on a bending magnet beamline at the Advanced Photon Source and observed with x-rays during bubble growth. In some cases the chips were heated to sufficiently high temperatures and for durations long enough to grow many large bubbles and convert the sample into a foam; in other cases the samples were only partially degassed so that we could observe the development of bubble formation and possible coalescence prior to foam formation. The bubble-bearing glasses formed during the heating experiment were imaged by x-ray microtomography performed on

  16. Slowing down bubbles with sound

    NASA Astrophysics Data System (ADS)

    Poulain, Cedric; Dangla, Remie; Guinard, Marion

    2009-11-01

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

  17. Temperature measurements in cavitation bubbles

    NASA Astrophysics Data System (ADS)

    Coutier-Delgosha, Olivier

    2016-11-01

    Cavitation is usually a nearly isothermal process in the liquid phase, but in some specific flow conditions like hot water or cryogenic fluids, significant temperature variations are detected. In addition, a large temperature increase happens inside the cavitation bubbles at the very end of their collapse, due to the fast compression of the gas at the bubble core, which is almost adiabatic. This process is of primary interest in various biomedical and pharmaceutical applications, where the mechanisms of bubble collapse plays a major role. To investigate the amplitude and the spatial distribution of these temperature variations inside and outside the cavitation bubbles, a system based on cold wires has been developed. They have been tested in a configuration of a single bubble obtained by submitting a small air bubble to a large amplitude pressure wave. Some promising results have been obtained after the initial validation tests. This work is funded by the Office of Naval Research Global under Grant N62909-16-1-2116, Dr. Salahuddin Ahmed & Ki-Han Kim program managers.

  18. Bubble baths: just splashing around?

    NASA Astrophysics Data System (ADS)

    Robinson, Wesley; Speirs, Nathan; Sharker, Saberul Islam; Hurd, Randy; Williams, Bj; Truscott, Tadd

    2016-11-01

    Soap Bubbles on the water surface would seem to be an intuitive means for splash suppression, but their presence appears to be a double edged sword. We present on the water entry of hydrophilic spheres where the liquid surface is augmented by the presence of a bubble layer, similar to a bubble bath. While the presence of a bubble layer can diminish splashing upon impact at low Weber numbers, it also induces cavity formation at speeds below the critical velocity. The formation of a cavity generally results in larger Worthington jets and thus, larger amounts of ejected liquid. Bubble layers induce cavity formation by wetting the sphere prior to liquid impact, causing them to form cavities similar to those created by hydrophobic spheres. Droplets present on a pre-wetted sphere disrupt the flow of the advancing liquid during entry, pushing it away from the impacting body to form an entrained air cavity. This phenomena was noted by Worthington with pre-wetted stone marbles, and suggests that the application of a bubble layer is generally ineffective as a means of splash suppression.

  19. Bubble-Pen Lithography.

    PubMed

    Lin, Linhan; Peng, Xiaolei; Mao, Zhangming; Li, Wei; Yogeesh, Maruthi N; Rajeeva, Bharath Bangalore; Perillo, Evan P; Dunn, Andrew K; Akinwande, Deji; Zheng, Yuebing

    2016-01-13

    Current lithography techniques, which employ photon, electron, or ion beams to induce chemical or physical reactions for micro/nano-fabrication, have remained challenging in patterning chemically synthesized colloidal particles, which are emerging as building blocks for functional devices. Herein, we develop a new technique - bubble-pen lithography (BPL) - to pattern colloidal particles on substrates using optically controlled microbubbles. Briefly, a single laser beam generates a microbubble at the interface of colloidal suspension and a plasmonic substrate via plasmon-enhanced photothermal effects. The microbubble captures and immobilizes the colloidal particles on the substrate through coordinated actions of Marangoni convection, surface tension, gas pressure, and substrate adhesion. Through directing the laser beam to move the microbubble, we create arbitrary single-particle patterns and particle assemblies with different resolutions and architectures. Furthermore, we have applied BPL to pattern CdSe/ZnS quantum dots on plasmonic substrates and polystyrene (PS) microparticles on two-dimensional (2D) atomic-layer materials. With the low-power operation, arbitrary patterning and applicability to general colloidal particles, BPL will find a wide range of applications in microelectronics, nanophotonics, and nanomedicine.

  20. Thermocapillary Migration of Deformable Bubbles at Moderate to Large Marangoni Number in Microgravity

    NASA Astrophysics Data System (ADS)

    Zhao, Jian-Fu; Li, Zhen-Dong; Li, Hui-Xiong; Li, Jing

    2010-09-01

    Using the level-set method and the continuum interface model, the axisymmetric thermocapillary migration of gas bubbles in an immiscible bulk liquid with a temperature gradient at moderate to large Marangoni number is simulated numerically. Constant material properties of the two phases are assumed. Steady state of the motion can always be reached. The terminal migration velocity decreases monotonously with the increase of the Marangoni number due to the wrapping of isotherms around the front surface of the bubble. Good agreements with space experimental data and previous theoretical and numerical studies in the literature are evident. Slight deformation of bubble is observed, but no distinct influence on the motion occurs. It is also found that the influence of the convective transport of heat inside bubbles cannot be neglected at finite Marangoni number, while the influence of the convective transport of momentum inside bubbles may be actually negligible.

  1. Observation of bubble formation in water during microwave irradiation by dynamic light scattering

    NASA Astrophysics Data System (ADS)

    Asakuma, Yusuke; Munenaga, Takuya; Nakata, Ryosuke

    2016-09-01

    A microwave reactor was designed for in situ observation of nano- and micro-bubbles, and size profiles during and after irradiation were measured with respect to irradiation power and time. Bubble formation in water during irradiation was observed even at temperatures below the boiling point of water. The maximum size strongly depended on radiation power and time, even at a given temperature. Nano-particles in the dispersion medium were found to play an important role in achieving more stable nucleation of bubbles around particles, and stable size distributions were obtained from clear autocorrelation by a dynamic light scattering system. Moreover, a combination of microwave induction heating and the addition of nano-particles to the dispersion medium can prevent heterogeneous nucleation of bubbles on the cell wall. Quantitative nano-bubble size profiles obtained by in situ observation provide useful information regarding microwave-based industrial processes for nano-particle production.

  2. Growth and collapse of laser-induced bubbles in gas-supersaturated gelatin gels

    NASA Astrophysics Data System (ADS)

    Ando, Keita; Nakamura, Nobuyuki

    2016-11-01

    We study, with experiments and theory, the growth and collapse of laser-induced bubbles in a gelatin gel. The gel sample is prepared so as to obtain gas supersaturation, according to a difference between heat and gas diffusion rates. Spherical gas bubbles are created by focusing a nano-second laser pulse at 532 nm into the gas-supersaturated gel. The bubble dynamics are recorded by a high-speed camera. To explore effects of the gel elasticity on the bubble collapse, the experimental observations are compared to an extended Rayleigh-Plesset model that accounts for linear/nonlinear elasticity of the gel surrounding bubbles. This work is supported by JSPS KAKENHI Grant No. 25709008.

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

    NASA Astrophysics Data System (ADS)

    Sun, Yanming; Pan, Lujun; Liu, Yuli; Sun, Tao

    2015-08-01

    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.

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

    SciTech Connect

    Annenkova, E. A.; Kreider, W.; Sapozhnikov, O. A.

    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.

  5. Kr bubble formation and growth in sputtered Au

    SciTech Connect

    Patten, J.W.; Bayne, M.A.; Hays, D.D.; Moss, R.W.

    1980-01-01

    Sputtering parameters were adjusted to produce Kr content up to several atomic percent in sputtered Au. As-sputtered density was approximately 17.5 g/cm/sup 3/ or 91% of theoretical density for a Kr content of approximately 5 at.%. Kr bubble formation and growth behavior was characterized as a function of heat treatment time and temperature (below the melting point) by transmission electron microscopy, optical metallography, and density measurement. Kr bubbles as small as 50 A diameter and densities down to 72% of theoretical (14.0 g/cm/sup 3/) were observed. Larger bubbles in excess of 1 ..mu..m diameter were observed in the lowest density samples. Surface finishes better than 20 ..mu..m were produced on the substrate sides of these sputtered deposits by replication of machined substrate surfaces. However, surface finish was degraded with increasing deposit thickness for deposits containing up to 5 at.% Kr. Surfaces were also degraded by heat treatments sufficiently severe to produce large (1 ..mu..m diameter) Kr bubbles intersecting the deposit surfaces.

  6. A Study of Cavitation-Ignition Bubble Combustion

    NASA Technical Reports Server (NTRS)

    Nguyen, Quang-Viet; Jacqmin, David A.

    2005-01-01

    We present the results of an experimental and computational study of the physics and chemistry of cavitation-ignition bubble combustion (CIBC), a process that occurs when combustible gaseous mixtures are ignited by the high temperatures found inside a rapidly collapsing bubble. The CIBC process was modeled using a time-dependent compressible fluid-dynamics code that includes finite-rate chemistry. The model predicts that gas-phase reactions within the bubble produce CO and other gaseous by-products of combustion. In addition, heat and mechanical energy release through a bubble volume-expansion phase are also predicted by the model. We experimentally demonstrate the CIBC process using an ultrasonically excited cavitation flow reactor with various hydrocarbon-air mixtures in liquid water. Low concentrations (< 160 ppm) of carbon monoxide (CO) emissions from the ultrasonic reactor were measured, and found to be proportional to the acoustic excitation power. The results of the model were consistent with the measured experimental results. Based on the experimental findings, the computational model, and previous reports of the "micro-diesel effect" in industrial hydraulic systems, we conclude that CIBC is indeed possible and exists in ultrasonically- and hydrodynamically-induced cavitation. Finally, estimates of the utility of CIBC process as a means of powering an idealized heat engine are also presented.

  7. Time and Space Resolved Heat Flux Measurements During Nucleate Boiling with Constant Heat Flux Boundary Conditions

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

    The lack of temporally and spatially resolved measurements under nucleate bubbles has complicated efforts to fully explain pool-boiling phenomena. The objective of this current work was to acquire time and space resolved temperature distributions under nucleating bubbles on a constant heat flux surface using a microheater array with 100x 100 square microns resolution, then numerically determine the wall to liquid heat flux. This data was then correlated with high speed (greater than l000Hz) visual recordings of The bubble growth and departure from the heater surface acquired from below and from the side of the heater. The data indicate that microlayer evaporation and contact line heat transfer are not major heat transfer mechanisms for bubble growth. The dominant heat transfer mechanism appears to be transient conduction into the liquid as the liquid rewets the wall during the bubble departure process.

  8. Acoustical Emission from Bubbles and Dynamics of Bubbles and Bubble Clouds.

    DTIC Science & Technology

    1997-01-01

    distribution of bubble sizes from a breaking wave , that is immediately following on the entrainment and disintegration of a given volume of air? In the...experimental confirmation was found by later workers. A simple statistical model has been proposed for the initial bubble sizes from breaking waves ...which also has received experimental support. A direct method of calculating wave -generated ripples has been proposed, which accounts quantitatively

  9. FEASTING BLACK HOLE BLOWS BUBBLES

    NASA Technical Reports Server (NTRS)

    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

  10. Handbook of Super 8 Production.

    ERIC Educational Resources Information Center

    Telzer, Ronnie, Ed.

    This handbook is designed for anyone interested in producing super 8 films at any level of complexity and cost. Separate chapters present detailed discussions of the following topics: super 8 production systems and super 8 shooting and editing systems; budgeting; cinematography and sound recording; preparing to edit; editing; mixing sound tracks;…

  11. Single-bubble sonoluminescence from hydrogen

    NASA Astrophysics Data System (ADS)

    Yasui, Kyuichi

    1999-09-01

    Single-bubble sonoluminescence (SBSL) from a hydrogen bubble is studied theoretically based on a quasiadiabatic compression model of a bubble collapse. It is clarified that the maximum temperature in a hydrogen bubble in 20 °C water under conditions of SBSL is always about 6000 K due to the effect of chemical reactions inside the bubble. It is suggested that the light emission at such temperature is by the transition from the lowest stable triplet state of the H2 molecule to the repulsive state resulting from two normal atoms (H2*→2H+hν). It is shown that the number of hydrogen molecules inside the bubble remains almost constant in spite of the high temperature and pressure inside the bubble at the collapse. It is also shown that the addition of argon to a hydrogen bubble results in the higher maximum temperature inside the bubble.

  12. Optimal Super Dielectric Material

    DTIC Science & Technology

    2015-09-01

    electrically insulating materials filled to the point of incipient wetness (paste consistency) with liquids containing dissolved ions. This work...109. This strongly supports the fundamental hypothesis of SDM: In the presence of an electric field any electrically insulating, porous material...ABSTRACT The results of this study establish that powder-based super dielectric materials (SDM) are a large family of porous electrically

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

    NASA Technical Reports Server (NTRS)

    Buyevich, Yu A.; Webbon, Bruce W.

    1995-01-01

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

  14. Bubble Generation in a Flowing Liquid Medium and Resulting Two-Phase Flow in Microgravity

    NASA Technical Reports Server (NTRS)

    Kamotani, Yasuhiro

    1996-01-01

    An experimental and theoretical research program is described herein to study bubble generation in a liquid flow in a pipe under reduced gravity conditions. The objective of the work is to study the bubble size and frequency of the generation and the resulting two-phase flow but it also concerns the fluid mechanical aspects of boiling in forced flow in microgravity. By injecting a gas into a liquid flow in a pipe through a small hole in the pipe wall we will investigate how the bubble expands and detaches from the wall, without involving the complexities of boiling. The experiments will be conducted both under isothermal conditions and with heat transfer from the wall. In the experiments with heat transfer the effect of thermocapillarity on the bubble formation and detachment will be the main subject.

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

  16. Single-Bubble and Multibubble Sonoluminescence

    NASA Astrophysics Data System (ADS)

    Yasui, Kyuichi

    1999-11-01

    Computer simulations of radiation processes in an air bubble and an argon bubble are performed under a condition of single-bubble sonoluminescence (SBSL) based on a quasiadiabatic compression model of a bubble collapse. It is clarified that emissions from excited molecules are strongly quenched by high pressure and temperature inside a SBSL bubble and SBSL originates in the emissions from plasma. It is pointed out that sonoluminescence from cavitation fields (MBSL) originates in emissions from excited molecules, which is not quenched due to the much lower pressure and temperature inside the MBSL bubbles.

  17. Bright visible emission from carbon nanotubes spatially constrained on a micro-bubble.

    PubMed

    Ramanandan, Gopika; Dharmadhikari, A K; Dharmadhikari, J A; Ramachandran, Hema; Mathur, D

    2009-06-08

    We report emission of broadband light in the spectral range 500 nm - 900 nm from single walled carbon nanotubes (SWNTs) in a liquid environment upon irradiance by a very low power (typically <5 mW), continuous-wave laser source in a tweezers setup. We show (i) formation of micro-bubbles upon irradiation of fluids containing bundles of SWNTs, (ii) optical trapping of such micro-bubbles, (iii) adhesion of SWNTs on the surface of such micro-bubbles, and (iv) bright emission of white light due to tweezer-induced localized heating of spatially-constrained SWNTs.

  18. Phase diagrams for sonoluminescing bubbles

    NASA Astrophysics Data System (ADS)

    Hilgenfeldt, Sascha; Lohse, Detlef; Brenner, Michael P.

    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. We present phase diagrams in the gas concentration versus forcing pressure state space and also in the ambient radius versus gas concentration and versus forcing pressure state spaces. These phase diagrams are based on the thresholds for energy focusing in the bubble and two kinds of instabilities, namely (i) shape instabilities and (ii) diffusive instabilities. Stable SL only occurs in a tiny parameter window of large forcing pressure amplitude Pa˜1.2-1.5 atm and low gas concentration of less than 0.4% of the saturation. The upper concentration threshold becomes smaller with increased forcing. Our 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. All statements are based on the Rayleigh-Plesset ODE approximation of the bubble dynamics, extended in an adiabatic approximation to include mass diffusion effects. This approximation is the only way to explore considerable portions of parameter space, as solving the full PDEs is numerically too expensive. Therefore, we checked the adiabatic approximation by comparison with the full numerical solution of the advection diffusion PDE and find good agreement.

  19. Ethnic diversity deflates price bubbles

    PubMed Central

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

    2014-01-01

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

  20. Valveless pumping using traversing vapor bubbles in microchannels

    NASA Astrophysics Data System (ADS)

    Jun, Thomas K.; Kim, Chang-Jin ``Cj''

    1998-06-01

    Pumping of fluids in microchannels using the movement of a single or multiple vapor bubble(s) is proposed, analyzed, and demonstrated. The pumping mechanism requires no micromechanical moving parts for actuation by utilizing asymmetric heating which creates a variation in vapor pressure and surface tension due to the heater-induced temperature gradient along the channel. A heat and mass transfer analysis was performed to understand the pumping mechanism and estimate the pumping capability of the micropumping device. To verify the concept and our analysis, a pumping device with a transparent microchannel with a hydraulic diameter of 3.4 μm was fabricated on a silicon wafer using surface micromachining. Experimental results with the first generation device have shown pumping of isopropanol at velocities as high as 160 μm/s (0.5 nl/min flow rate) with a pressure head of approximately 800 Pa.

  1. Numerical simulation of bubble departure in subcooled pool boiling based on non-empirical boiling and condensation model

    NASA Astrophysics Data System (ADS)

    Ose, Y.; Kunugi, T.

    2013-07-01

    In this study, in order to clarify the heat transfer characteristics of the subcooled boiling phenomena and to discuss on their mechanism, a non-empirical boiling and condensation model for numerical simulation has been adopted. This model consists of an improved phase-change model and a consideration of a relaxation time based on the quasithermal equilibrium hypothesis. The transient three-dimensional numerical simulations based on the MARS (Multiinterface Advection and Reconstruction Solver) with the non-empirical boiling and condensation model have been conducted for an isolated boiling bubble behavior in a subcooled pool. The subcooled bubble behaviors, such as the growth process of the nucleate bubble on the heating surface, the condensation process and the extinction behaviors after departing from the heating surface were investigated, respectively. In this paper, the bubble departing behavior from the heating surface was discussed in detail. The overall numerical results showed in very good agreement with the experimental results.

  2. Gravity driven flows of bubble suspensions.

    NASA Astrophysics Data System (ADS)

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

    1999-11-01

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

  3. Aspherical bubble dynamics and oscillation times

    SciTech Connect

    Godwin, R.P.; Chapyak, E.J.; Noack, J.; Vogel, A.

    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.

  4. Bubbles & Turbulence in the Ocean Surface Layer & Topographic Interactions in Coastal Waters

    DTIC Science & Technology

    2016-06-07

    have two long term goals relating to this project: (i) To determine processes responsible for vertical transfer of heat, mass and momentum across the...transport of key oceanographic variables such as heat, mass and momentum . Bubble distributions in particular, provide clues as to the character of wave

  5. Bursting Bubbles and Bilayers

    PubMed Central

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

    2012-01-01

    This paper discusses various interactions between ultrasound, phospholipid monolayer-coated gas bubbles, phospholipid bilayer vesicles, and cells. The paper begins with a review of microbubble physics models, developed to describe microbubble dynamic behavior in the presence of ultrasound, and follows this with a discussion of how such models can be used to predict inertial cavitation profiles. Predicted sensitivities of inertial cavitation to changes in the values of membrane properties, including surface tension, surface dilatational viscosity, and area expansion modulus, indicate that area expansion modulus exerts the greatest relative influence on inertial cavitation. Accordingly, the theoretical dependence of area expansion modulus on chemical composition - in particular, poly (ethylene glyclol) (PEG) - is reviewed, and predictions of inertial cavitation for different PEG molecular weights and compositions are compared with experiment. Noteworthy is the predicted dependence, or lack thereof, of inertial cavitation on PEG molecular weight and mole fraction. Specifically, inertial cavitation is predicted to be independent of PEG molecular weight and mole fraction in the so-called mushroom regime. In the “brush” regime, however, inertial cavitation is predicted to increase with PEG mole fraction but to decrease (to the inverse 3/5 power) with PEG molecular weight. While excellent agreement between experiment and theory can be achieved, it is shown that the calculated inertial cavitation profiles depend strongly on the criterion used to predict inertial cavitation. This is followed by a discussion of nesting microbubbles inside the aqueous core of microcapsules and how this significantly increases the inertial cavitation threshold. Nesting thus offers a means for avoiding unwanted inertial cavitation and cell death during imaging and other applications such as sonoporation. A review of putative sonoporation mechanisms is then presented, including those

  6. Bubbles Responding to Ultrasound Pressure

    NASA Technical Reports Server (NTRS)

    2003-01-01

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

  7. How safe is Bubble Soccer?

    PubMed

    Halani, Sameer H; Riley, Jonathan P; Pradilla, Gustavo; Ahmad, Faiz U

    2016-12-01

    Traumatic neurologic injury in contact sports is a rare but serious consequence for its players. These injuries are most commonly associated with high-impact collisions, for example in football, but are found in a wide variety of sports. In an attempt to minimize these injuries, sports are trying to increase safety by adding protection for participants. Most recently is the seemingly 'safe' sport of Bubble Soccer, which attempts to protect its players with inflatable plastic bubbles. We report a case of a 16-year-old male sustaining a cervical spine burst fracture with incomplete spinal cord injury while playing Bubble Soccer. To our knowledge, this is the first serious neurological injury reported in the sport.

  8. From rational bubbles to crashes

    NASA Astrophysics Data System (ADS)

    Sornette, D.; Malevergne, Y.

    2001-10-01

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

  9. Bubble dynamics during the non-isothermal degassing of liquids. Exploiting microgravity conditions.

    PubMed

    Kostoglou, Margaritis; Karapantsios, Thodoris D

    2007-10-31

    This work reviews the up to date state of understanding of dynamic phenomena occurring when gas bubbles grow over submerged heated surfaces. Gas bubbles are produced on hot surfaces because the adjacent liquid layers become superheated causing local desorption of dissolved gases while the liquid far afield remains at low temperatures. Non-isothermal degassing is a very complex process combining heat and mass transport coupled with momentum exchange between the two phases. Difficulties due to buoyancy effects on gas bubbles as well as natural convection of hot liquid layers hindered its thorough investigation in terrestrial conditions and only recent microgravity data allowed serious progress to be made. To reduce the complexity, gas bubble growth on a heated wall was studied here separately from bubble lateral motion and coalescence. A complete mathematical formulation was provided but given the inability to solve the problem numerically with the present resources, a series of approximate solutions were attempted. The comparison between experimental observations and theoretical predictions revealed useful information regarding the governing mechanisms of bubble growth.

  10. Novel techniques for slurry bubble column hydrodynamics

    SciTech Connect

    Dudukovic, M.P.

    1999-05-14

    The objective of this cooperative research effort between Washington University, Ohio State University and Exxon Research Engineering Company was to improve the knowledge base for scale-up and operation of slurry bubble column reactors for syngas conversion and other coal conversion processes by increased reliance on experimentally verified hydrodynamic models. During the first year (July 1, 1995--June 30, 1996) of this three year program novel experimental tools (computer aided radioactive particle tracking (CARPT), particle image velocimetry (PIV), heat probe, optical fiber probe and gamma ray tomography) were developed and tuned for measurement of pertinent hydrodynamic quantities, such as velocity field, holdup distribution, heat transfer and bubble size. The accomplishments were delineated in the First Technical Annual Report. The second year (July, 1996--June 30, 1997) was spent on further development and tuning of the novel experimental tools (e.g., development of Monte Carlo calibration for CARPT, optical probe development), building up the hydrodynamic data base using these tools and comparison of the two techniques (PIV and CARPT) for determination of liquid velocities. A phenomenological model for gas and liquid backmixing was also developed. All accomplishments were summarized in the Second Annual Technical Report. During the third and final year of the program (July 1, 1997--June 30, 1998) and during the nine months no cost extension, the high pressure facility was completed and a set of data was taken at high pressure conditions. Both PIV, CT and CARPT were used. More fundamental hydrodynamic modeling was also undertaken and model predictions were compared to data. The accomplishments for this period are summarized in this report.

  11. Removal of hydrogen bubbles from nuclear reactors

    NASA Technical Reports Server (NTRS)

    Jenkins, R. V.

    1980-01-01

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

  12. Electric field observations of equatorial bubbles

    NASA Astrophysics Data System (ADS)

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

    1992-03-01

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

  13. Soap Bubbles on a Cold Day.

    ERIC Educational Resources Information Center

    Waiveris, Charles

    1994-01-01

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

  14. Electric field observations of equatorial bubbles

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  15. Behavior of Rapidly Sheared Bubble Suspensions

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

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

  16. Bubble memory module for spacecraft application

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

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

  17. British super-shuttle

    NASA Astrophysics Data System (ADS)

    1984-10-01

    British Aerospace, the nationalized aerospace manufacturer, confirmed that a space shuttle of new design is indeed being studied, and that a model of the craft will be displayed. The British television network ITN had announced that secret plans were being prepared for the construction of a reusable horizontal takeoff super-shuttle, which could breathe atmospheric oxygen to supply its propulsion system. Retracting a first denial according to which the project existed merely as scribbles on the back of an envelope, a British Aerospace spokesperson declared that it was in fact a very serious study. The super-shuttle, called HOTOL (horizontal takeoff and landing), would be placed in orbit as a platform for satellite launching. The spokesperson further indicated that with a certain resemblance to the Concorde, it would be pilotless, remote controlled, and would allow frequent operations at short time intervals.

  18. NASA Super Pressure Balloon

    NASA Technical Reports Server (NTRS)

    Fairbrother, Debbie

    2016-01-01

    NASA is in the process of qualifying the mid-size Super Pressure Balloon (SPB) to provide constant density altitude flight for science investigations at polar and mid-latitudes. The status of the development of the 18.8 million cubic foot SPB capable of carrying one-tonne of science to 110,000 feet, will be given. In addition, the operating considerations such as launch sites, flight safety considerations, and recovery will be discussed.

  19. OPE for super loops

    NASA Astrophysics Data System (ADS)

    Sever, Amit; Vieira, Pedro; Wang, Tianheng

    2011-11-01

    We extend the Operator Product Expansion for Null Polygon Wilson loops to the Mason-Skinner-Caron-Huot super loop dual to non MHV gluon amplitudes. We explain how the known tree level amplitudes can be promoted into an infinite amount of data at any loop order in the OPE picture. As an application, we re-derive all one loop NMHV six gluon amplitudes by promoting their tree level expressions. We also present some new all loops predictions for these amplitudes.

  20. Magma mixing enhanced by bubble segregation

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    Rising bubbles may significantly affect magma mixing paths as has been demonstrated by analogue experiments in the past. Here, bubble-advection experiments are performed for the first time employing natural materials at magmatic temperatures. Cylinders of basaltic glass were placed below cylinders of rhyolite glass. Upon melting, interstitial air formed bubbles that rose into the rhyolite melt, thereby entraining tails of basaltic liquid. The formation of plume-like filaments of advected basalt within the rhyolite was characterized by microCT and subsequent high-resolution EMP analyses. Melt entrainment by bubble ascent appears as efficient mechanism to mingle contrasting melt compositions. MicroCT imaging shows bubbles trailing each other and trails of multiple bubbles having converged. Rheological modelling of the filaments yields viscosities of up to 2 orders of magnitude lower than for the surrounding rhyolitic liquid. Such a viscosity contrast implies that subsequent bubbles rising are likely to follow the same pathways that previously ascending bubbles have generated. Filaments formed by multiple bubbles would thus experience episodic replenishment with mafic material. Fundamental implications for the concept of bubble advection in magma mixing are thus a) an acceleration of mixing because of decreased viscous resistance for bubbles inside filaments and b) non-conventional diffusion systematics because of intermittent supply of mafic material (instead of a single pulse) inside a filament. Inside these filaments, the mafic material was variably hybridised to andesitic through rhyolitic composition. Compositional profiles alone are ambiguous, however, to determine whether single or multiple bubbles were involved during formation of a filament. Statistical analysis, employing concentration variance as measure of homogenisation, demonstrates that also filaments appearing as single-bubble filaments are likely to have experienced multiple bubbles passing through

  1. Super-quantum curves from super-eigenvalue models

    NASA Astrophysics Data System (ADS)

    Ciosmak, Paweł; Hadasz, Leszek; Manabe, Masahide; Sułkowski, Piotr

    2016-10-01

    In modern mathematical and theoretical physics various generalizations, in particular supersymmetric or quantum, of Riemann surfaces and complex algebraic curves play a prominent role. We show that such supersymmetric and quantum generalizations can be combined together, and construct supersymmetric quantum curves, or super-quantum curves for short. Our analysis is conducted in the formalism of super-eigenvalue models: we introduce β-deformed version of those models, and derive differential equations for associated α/ β-deformed super-matrix integrals. We show that for a given model there exists an infinite number of such differential equations, which we identify as super-quantum curves, and which are in one-to-one correspondence with, and have the structure of, super-Virasoro singular vectors. We discuss potential applications of super-quantum curves and prospects of other generalizations.

  2. Theory of supercompression of vapor bubbles and nanoscale thermonuclear fusion

    NASA Astrophysics Data System (ADS)

    Nigmatulin, Robert I.; Akhatov, Iskander Sh.; Topolnikov, Andrey S.; Bolotnova, Raisa Kh.; Vakhitova, Nailya K.; Lahey, Richard T.; Taleyarkhan, Rusi P.

    2005-10-01

    This paper provides the theoretical basis for energetic vapor bubble implosions induced by a standing acoustic wave. Its primary goal is to describe, explain, and demonstrate the plausibility of the experimental observations by Taleyarkhan et al. [Science 295, 1868 (2002); Phys. Rev. E 69, 036109 (2004)] of thermonuclear fusion for imploding cavitation bubbles in chilled deuterated acetone. A detailed description and analysis of these data, including a resolution of the criticisms that have been raised, together with some preliminary HYDRO code simulations, has been given by Nigmatulin et al. [Vestnik ANRB (Ufa, Russia) 4, 3 (2002); J. Power Energy 218-A, 345 (2004)] and Lahey et al. [Adv. Heat Transfer (to be published)]. In this paper a hydrodynamic shock (i.e., HYDRO) code model of the spherically symmetric motion for a vapor bubble in an acoustically forced liquid is presented. This model describes cavitation bubble cluster growth during the expansion period, followed by a violent implosion during the compression period of the acoustic cycle. There are two stages of the bubble dynamics process. The first, low Mach number stage, comprises almost all the time of the acoustic cycle. During this stage, the radial velocities are much less than the sound speeds in the vapor and liquid, the vapor pressure is very close to uniform, and the liquid is practically incompressible. This process is characterized by the inertia of the liquid, heat conduction, and the evaporation or condensation of the vapor. The second, very short, high Mach number stage is when the radial velocities are the same order, or higher, than the sound speeds in the vapor and liquid. In this stage high temperatures, pressures, and densities of the vapor and liquid take place. The model presented herein has realistic equations of state for the compressible liquid and vapor phases, and accounts for nonequilibrium evaporation/condensation kinetics at the liquid/vapor interface. There are interacting

  3. Theory of supercompression of vapor bubbles and nanoscale thermonuclear fusion

    SciTech Connect

    Nigmatulin, Robert I.; Akhatov, Iskander Sh.; Topolnikov, Andrey S.; Bolotnova, Raisa Kh.; Vakhitova, Nailya K.; Lahey, Richard T. Jr.; Taleyarkhan, Rusi P.

    2005-10-01

    This paper provides the theoretical basis for energetic vapor bubble implosions induced by a standing acoustic wave. Its primary goal is to describe, explain, and demonstrate the plausibility of the experimental observations by Taleyarkhan et al. [Science 295, 1868 (2002); Phys. Rev. E 69, 036109 (2004)] of thermonuclear fusion for imploding cavitation bubbles in chilled deuterated acetone. A detailed description and analysis of these data, including a resolution of the criticisms that have been raised, together with some preliminary HYDRO code simulations, has been given by Nigmatulin et al. [Vestnik ANRB (Ufa, Russia) 4, 3 (2002); J. Power Energy 218-A, 345 (2004)] and Lahey et al. [Adv. Heat Transfer (to be published)]. In this paper a hydrodynamic shock (i.e., HYDRO) code model of the spherically symmetric motion for a vapor bubble in an acoustically forced liquid is presented. This model describes cavitation bubble cluster growth during the expansion period, followed by a violent implosion during the compression period of the acoustic cycle. There are two stages of the bubble dynamics process. The first, low Mach number stage, comprises almost all the time of the acoustic cycle. During this stage, the radial velocities are much less than the sound speeds in the vapor and liquid, the vapor pressure is very close to uniform, and the liquid is practically incompressible. This process is characterized by the inertia of the liquid, heat conduction, and the evaporation or condensation of the vapor. The second, very short, high Mach number stage is when the radial velocities are the same order, or higher, than the sound speeds in the vapor and liquid. In this stage high temperatures, pressures, and densities of the vapor and liquid take place. The model presented herein has realistic equations of state for the compressible liquid and vapor phases, and accounts for nonequilibrium evaporation/condensation kinetics at the liquid/vapor interface. There are interacting

  4. Measurement of the Shear Lift Force on a Bubble in a Channel Flow

    NASA Technical Reports Server (NTRS)

    Nahra, Henry K.; Motil, Brian; Skor, Mark

    2005-01-01

    Two-phase flow systems play vital roles in the design of some current and anticipated space applications of two-phase systems which include: thermal management systems, transfer line flow in cryogenic storage, space nuclear power facilities, design and operation of thermal bus, life support systems, propulsion systems, In Situ Resource Utilization (ISRU), and space processes for pharmaceutical applications. The design of two-phase flow systems for space applications requires a clear knowledge of the behaviors of the dispersed phase (bubble), its interaction with the continuous phase (liquid) and its effect on heat and mass transfer processes, The need to understand the bubble generation process arises from the fact that for all space applications, the size and distribution of bubbles are extremely crucial for heat and mass transfer control. One important force in two-phase flow systems is the lift force on a bubble or particle in a liquid shear flow. The shear lift is usually overwhelmed by buoyancy in normal gravity, but it becomes an important force in reduced gravity. Since the liquid flow is usually sheared because of the confining wall, the trajectories of bubbles and particles injected into the liquid flow are affected by the shear lift in reduced gravity. A series of experiments are performed to investigate the lift force on a bubble in a liquid shear flow and its effect on the detachment of a bubble from a wall under low gravity conditions. Experiments are executed in a Poiseuille flow in a channel. An air-water system is used in these experiments that are performed in the 2.2 second drop tower. A bubble is injected into the shear flow from a small injector and the shear lift is measured while the bubble is held stationary relative to the fluid. The trajectory of the bubble prior, during and after its detachment from the injector is investigated. The measured shear lift force is calculated from the trajectory of the bubble at the detachment point. These

  5. Frictional drag reduction by bubble injection

    NASA Astrophysics Data System (ADS)

    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. Carbon Film Electrodes For Super Capacitor Applications

    DOEpatents

    Tan, Ming X.

    1999-07-20

    A method for treating an organic polymer material, preferably a vinylidene chloride/vinyl chloride copolymer (Saran) to produce a flat sheet of carbon film material having a high surface area (.apprxeq.1000 m.sup.2 /g) suitable as an electrode material for super capacitor applications. The method comprises heating a vinylidene chloride/vinyl chloride copolymer film disposed between two spaced apart graphite or ceramic plates to a first temperature of about 160.degree. C. for about 14 hours to form a stabilized vinylidene chloride/vinyl chloride polymer film, thereafter heating the stabilized film to a second temperature of about 750.degree. C. in an inert atmosphere for about one hour to form a carbon film; and finally activating the carbon film to increase the surface area by heating the carbon film in an oxidizing atmosphere to a temperature of at least 750-850.degree. C. for between 1-6 hours.

  7. Temperature-dependent biphasic shrinkage of lipid-coated bubbles in ultrasound.

    PubMed

    Cox, Debra J; Thomas, James L

    2013-04-09

    Lipid-coated microbubbles and emulsions are of interest as possible ultrasound-mediated drug delivery vehicles and for their interesting behaviors and fundamental properties. We and others have noted that bubbles coated with the long chain saturated phospholipid distearoylphosphatidylcholine (DSPC) rapidly shrink to a quasistable size when repeatedly insonated with short ultrasound pulses; such stability may adversely affect the bubble's subsequent ability to deliver its pharmacological cargo. Bubbles coated with the unsaturated lipid dioleoylphosphatidylcholine (DOPC) did not show stability but did undergo an abrupt change from rapid initial shrinkage to a slow persistent shrinkage, leading ultimately to dissolution or dispersion. As DOPC and DSPC differ not only in chain saturation but also phase behavior, we performed additional studies using dimyristoyl PC (DMPC) as a coat lipid and controlled the solution temperature to study bubble behavior on exposure to repeated ultrasound pulses for the same coat, in both fluid and gel phases. We find, first, that essentially all bubbles show an initially rapid shrinkage, in which gas loss exceeds the limit imposed by gas diffusion into the surrounding medium; this rapid shrinkage may be evidence of nanoscopic bubble fragmentation. Second, upon reaching a fraction of their initial size, bubbles begin a slower shrinkage with a shrinkage rate that depends on the resting phase state of the coat lipid: fluid DMPC monolayers give a more rapid shrinkage than gel phase. DOPC-coated bubbles showed no temperature-dependent responses in the same temperature range. The results are especially interesting in that bubble compression during the pulse is likely to adiabatically heat the bubble and fluidize the coat, regardless of its initial phase state; thus, some structural feature of the resting coat, such as defect lines in the gel phase, may be important in the subsequent response to the ~3 μs ultrasound pulse.

  8. The collapsing bubble in a liquid by molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Xiao, C.; Heyes, D. M.; Powles, J. G.

    Molecular dynamics simulations have been made of a collapsing bubble or cavity in a simple liquid. Simulations of a Lennard-Jones liquid reveal that the collapsing process takes place in a series of stages. First, the 'hottest' molecules from the high kinetic energy tail in the Maxwell-Boltzmann distribution diffuse into the empty cavity. This is followed by a gradual filling in of the cavity until the density in the centre is a little lower than that of the bulk liquid. The system eventually reaches a final new equilibrium liquid state through a subsequent slower equilibration phase. The bubble fills in an oscillatory manner, by partly filling in, and then partially emptying, and so on, with ever decreasing amplitude towards the final uniform liquid state. These density oscillations are more obvious in systems with a larger bubble. Similar oscillations are observed in the kinetic energy of the molecules at selected radii from the centre of the initial bubble. The maximum temperature occurs typically at the end of the initial fillingin stage during which the density of the core undergoes a vapour-to-liquid phase transition, the released latent heat probably contributing to the temperatures achieved in this region. The average maximum temperature found in the smallest system examined is about nine times the critical temperature, which is about 6000K for water, thus suggesting a simple mechanism for producing molecules with the sorts of kinetic energies and lifetimes required for sonoluminescence.

  9. Effects of FLIRT on bubble growth in man.

    PubMed

    Winkler, B E; Koch, A; Schoeppenthau, H; Ludwig, T; Tetzlaff, K; Hartig, F; Kaehler, W; Koehler, A; Kanstinger, A; Ciscato, W; Muth, C-M

    2012-11-01

    Recompression during decompression has been suggested to possibly reduce the risk of decompression sickness (DCS). The main objective of the current study was to investigate the effects of FLIRT (First Line Intermittent Recompression Technique) on bubble detection in man. 29 divers underwent 2 simulated dives in a dry recompression chamber to a depth of 40 msw (500 kPa ambient pressure) in random order. A Buehlmann-based decompression profile served as control and was compared to an experimental profile with intermittent recompression during decompression (FLIRT). Circulating bubbles in the right ventricular outflow tract (RVOT) were monitored by Doppler ultrasound and quantified using the Spencer scoring algorithm. Heat shock protein 70 (HSP70), thrombocytes, D-Dimers and serum osmolarity were analyzed before and 120 min after the dive. Both dive profiles elicited bubbles in most subjects (range Spencer 0-4). However, no statistically significant difference was found in bubble scores between the control and the experimental dive procedure. There was no significant change in either HSP70, thrombocytes, and D-Dimers. None of the divers had clinical signs or symptoms suggestive of DCS. We conclude that FLIRT did not significantly alter the number of microbubbles and thus may not be considered superior to classical decompression in regards of preventing DCS.

  10. LRL 25-inch Bubble Chamber

    DOE R&D Accomplishments Database

    Alvarez, L. W.; Gow, J. D.; Barrera, F.; Eckman, G.; Shand, J.; Watt, R.; Norgren, D.; Hernandez, H. P.

    1964-07-08

    The recently completed 25-inch hydrogen bubble chamber combines excellent picture quality with a fast operating cycle. The chamber has a unique optical system and is designed to take several pictures each Bevatron pulse, in conjunction with the Bevatron rapid beam ejection system.

  11. Ice bubbles confirm big chill

    SciTech Connect

    Kerr, R.A.

    1996-06-14

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

  12. Bubble-driven inertial micropump

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  13. Bursting the Taylor cone bubble

    NASA Astrophysics Data System (ADS)

    Pan, Zhao; Truscott, Tadd

    2014-11-01

    A soap bubble fixed on a surface and placed in an electric field will take on the shape of a cone rather than constant curvature (dome) when the electrical field is not present. The phenomenon was introduced by J. Zeleny (1917) and studied extensively by C.T. Wilson & G.I. Taylor (1925). We revisit the Taylor cone problem by studying the deformation and bursting of soap bubbles in a point charge electric field. A single bubble takes on the shape of a cone in the electric field and a high-speed camera equipped with a micro-lens is used to observe the unsteady dynamics at the tip. Rupture occurs as a very small piece of the tip is torn away from the bubble toward the point charge. Based on experiments, a theoretical model is developed that predicts when rupture should occur. This study may help in the design of foam-removal techniques in engineering and provide a better understanding of an electrified air-liquid interface.

  14. Impurity bubbles in a BEC

    NASA Astrophysics Data System (ADS)

    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.

  15. Affirmative Discrimination and the Bubble

    ERIC Educational Resources Information Center

    Clegg, Roger

    2011-01-01

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

  16. "Financial Bubbles" and Monetary Policy

    ERIC Educational Resources Information Center

    Tikhonov, Yuriy A.; Pudovkina, Olga E.; Permjakova, Juliana V.

    2016-01-01

    The relevance of this research is caused by the need of strengthening a role of monetary regulators to prevent financial bubbles in the financial markets. The aim of the article is the analysis of a problem of crisis phenomena in the markets of financial assets owing to an inadequate growth of their cost, owing to subjective reasons. The leading…

  17. Neutron Detection via Bubble Chambers

    SciTech Connect

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

    2005-10-06

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

  18. The effects of bubble-bubble interactions on pressures and temperatures produced by bubbles collapsing near a rigid surface

    NASA Astrophysics Data System (ADS)

    Alahyari Beig, Shahaboddin; Johnsen, Eric

    2016-11-01

    Cavitation occurs in a wide range of hydraulic applications, and one of its most important consequences is structural damage to neighboring surfaces following repeated bubble collapse. A number of studies have been conducted to predict the pressures produced by the collapse of a single bubble. However, the collapse of multiple bubbles is known to lead to enhanced collapse pressures. In this study, we quantify the effects of bubble-bubble interactions on the bubble dynamics and pressures/temperatures produced by the collapse of a pair of bubbles near a rigid surface. For this purpose, we use an in-house, high-order accurate shock- and interface-capturing method to solve the 3D compressible Navier-Stokes equations for gas/liquid flows. The non-spherical bubble dynamics are investigated and the subsequent pressure and temperature fields are characterized based on the relevant parameters entering the problem: stand-off distance, geometrical configuation, collapse strength. We demonstrate that bubble-bubble interactions amplify/reduce pressures and temperatures produced at the collapse, and increase the non-sphericity of the bubbles and the collapse time, depending on the flow parameters.

  19. Tiny Bubbles in my BEC

    SciTech Connect

    Blinova, Alina A.

    2012-08-01

    Ultracold atomic gases provide a unique way for exploring many-body quantum phenomena that are inaccessible to conventional low-temperature experiments. Nearly two decades ago the Bose-Einstein condensate (BEC) - an ultracold gas of bosons in which almost all bosons occupy the same single-particle state - became experimentally feasible. Because a BEC exhibits superfluid properties, it can provide insights into the behavior of low-temperature helium liquids. We describe the case of a single distinguishable atom (an impurity) embedded in a BEC and strongly coupled to the BEC bosons. Depending on the strength of impurity-boson and boson-boson interactions, the impurity self-localizes into two fundamentally distinct regimes. The impurity atom can behave as a tightly localized 'polaron,' akin to an electron in a dielectric crystal, or as a 'bubble,' an analog to an electron bubble in superfluid helium. We obtain the ground state wavefunctions of the impurity and BEC by numerically solving the two coupled Gross-Pitaevskii equations that characterize the system. We employ the methods of imaginary time propagation and conjugate gradient descent. By appropriately varying the impurity-boson and boson-boson interaction strengths, we focus on the polaron to bubble crossover. Our results confirm analytical predictions for the polaron limit and uncover properties of the bubble regime. With these results we characterize the polaron to bubble crossover. We also summarize our findings in a phase diagram of the BEC-impurity system, which can be used as a guide in future experiments.

  20. Investigation and experimental analysis of the bubble departure diameter in pure liquids on horizontal cylindrical heater

    NASA Astrophysics Data System (ADS)

    Bovard, Samaneh; Asadinia, Hoda; Hosseini, Goharshad; Alavi Fazel, S. A.

    2016-08-01

    In this study, partial pool boiling heat transfer and bubble departure diameter on horizontal cylindrical heater in heat flux range between 103 and 105 w m-2 were investigated. Pure liquid water, Ethanol and Acetone were utilized as the fluids for the system. Aluminum, stainless steel 316A, copper and brass were considered as the materials for the heater's surface rod. Different degrees of roughness were applied for copper and aluminum surface. Bubble departure diameter and heat transfer coefficients were chosen for the system measurement. The empirical model for bubble departure diameter was estimated by using experimental data. This model is based on dimensionless numbers that through which experimental data are shown from literature and the present the study is in good agreement with the model.

  1. Antioscillons from bubble collisions at finite temperature

    NASA Astrophysics Data System (ADS)

    Mersini-Houghton, Laura

    2014-04-01

    We study the role of the topology of bubbles at finite temperatures plays on collisions and the existence of new field configurations. We show that in the case of false vacuum decay at finite temperature, the cylindrical symmetry of bubbles admits a new exotic field with negative energies, the antiperiodic "twisted" field. New field configurations arise generically, not only at finite temperatures but whenever a cluster of bubbles resulting from collisions form nontrivial topologies. The interaction of both configurations induces instabilites on the bubble. Collisions of bubbles occupied by the new fields can lead to the emergence of new structures, named antioscillons.

  2. Acoustically enhanced heat transport

    NASA Astrophysics Data System (ADS)

    Ang, Kar M.; Yeo, Leslie Y.; Friend, James R.; Hung, Yew Mun; Tan, Ming K.

    2016-01-01

    We investigate the enhancement of heat transfer in the nucleate boiling regime by inducing high frequency acoustic waves (f ˜ 106 Hz) on the heated surface. In the experiments, liquid droplets (deionized water) are dispensed directly onto a heated, vibrating substrate. At lower vibration amplitudes (ξs ˜ 10-9 m), the improved heat transfer is mainly due to the detachment of vapor bubbles from the heated surface and the induced thermal mixing. Upon increasing the vibration amplitude (ξs ˜ 10-8 m), the heat transfer becomes more substantial due to the rapid bursting of vapor bubbles happening at the liquid-air interface as a consequence of capillary waves travelling in the thin liquid film between the vapor bubble and the air. Further increases then lead to rapid atomization that continues to enhance the heat transfer. An acoustic wave displacement amplitude on the order of 10-8 m with 106 Hz order frequencies is observed to produce an improvement of up to 50% reduction in the surface temperature over the case without acoustic excitation.

  3. Acoustically enhanced heat transport

    SciTech Connect

    Ang, Kar M.; Hung, Yew Mun; Tan, Ming K.; Yeo, Leslie Y.

    2016-01-15

    We investigate the enhancement of heat transfer in the nucleate boiling regime by inducing high frequency acoustic waves (f ∼ 10{sup 6} Hz) on the heated surface. In the experiments, liquid droplets (deionized water) are dispensed directly onto a heated, vibrating substrate. At lower vibration amplitudes (ξ{sub s} ∼ 10{sup −9} m), the improved heat transfer is mainly due to the detachment of vapor bubbles from the heated surface and the induced thermal mixing. Upon increasing the vibration amplitude (ξ{sub s} ∼ 10{sup −8} m), the heat transfer becomes more substantial due to the rapid bursting of vapor bubbles happening at the liquid-air interface as a consequence of capillary waves travelling in the thin liquid film between the vapor bubble and the air. Further increases then lead to rapid atomization that continues to enhance the heat transfer. An acoustic wave displacement amplitude on the order of 10{sup −8} m with 10{sup 6} Hz order frequencies is observed to produce an improvement of up to 50% reduction in the surface temperature over the case without acoustic excitation.

  4. Acoustically enhanced heat transport.

    PubMed

    Ang, Kar M; Yeo, Leslie Y; Friend, James R; Hung, Yew Mun; Tan, Ming K

    2016-01-01

    We investigate the enhancement of heat transfer in the nucleate boiling regime by inducing high frequency acoustic waves (f ∼ 10(6) Hz) on the heated surface. In the experiments, liquid droplets (deionized water) are dispensed directly onto a heated, vibrating substrate. At lower vibration amplitudes (ξs ∼ 10(-9) m), the improved heat transfer is mainly due to the detachment of vapor bubbles from the heated surface and the induced thermal mixing. Upon increasing the vibration amplitude (ξs ∼ 10(-8) m), the heat transfer becomes more substantial due to the rapid bursting of vapor bubbles happening at the liquid-air interface as a consequence of capillary waves travelling in the thin liquid film between the vapor bubble and the air. Further increases then lead to rapid atomization that continues to enhance the heat transfer. An acoustic wave displacement amplitude on the order of 10(-8) m with 10(6) Hz order frequencies is observed to produce an improvement of up to 50% reduction in the surface temperature over the case without acoustic excitation.

  5. Detecting the gas bubbles in a liquid metal coolant by means of magnetic flowmeters

    NASA Astrophysics Data System (ADS)

    Mogilner, A. I.; Morozov, S. A.; Zakharov, S. O.; Uralets, A. Yu.

    Solution of some problems of control and diagnosis of circuits with a liquid-metal coolant (LMC) often requires the detection of gas bubbles penetrating the circulation loop. The sources of gas intake can be presented by failed fuel elements in reactor core, failed heat-exchange surfaces in sodium-water steam generators in the secondary circuits, gas capture by circulating coolant from gas circuits. Sometimes the gas is especially injected into circulating coolant to study the dynamics of accumulation and extraction of gas bubbles and to solve research problems related to simulations of emergency situations. The most commonly used methods for gas bubble detection include methods based on measuring coolant electric conductivity. A method for detecting gas bubbles in LMC, based on revealing the change of its electric conductivity is considered. Magnetic flowmeter is used as a detecting element of these changes. Approximate theory for describing spectral and energy noises in signals of a magnetic flowmeter, controlling the flow rate of LMC with gas bubbles is suggested. A new method for signal reading is suggested. Experimental results illustrating the possibility of using the method for measuring the rate of bubble movement and studying the dependence of gas bubble volume on the flow rate of injected gas are presented.

  6. COMPUTATIONAL AND EXPERIMENTAL MODELING OF THREE-PHASE SLURRY-BUBBLE COLUMN REACTOR

    SciTech Connect

    Isaac K. Gamwo; Dimitri Gidaspow

    1999-09-01

    Considerable progress has been achieved in understanding three-phase reactors from the point of view of kinetic theory. In a paper in press for publication in Chemical Engineering Science (Wu and Gidaspow, 1999) we have obtained a complete numerical solution of bubble column reactors. In view of the complexity of the simulation a better understanding of the processes using simplified analytical solutions is required. Such analytical solutions are presented in the attached paper, Large Scale Oscillations or Gravity Waves in Risers and Bubbling Beds. This paper presents analytical solutions for bubbling frequencies and standing wave flow patterns. The flow patterns in operating slurry bubble column reactors are not optimum. They involve upflow in the center and downflow at the walls. It may be possible to control flow patterns by proper redistribution of heat exchangers in slurry bubble column reactors. We also believe that the catalyst size in operating slurry bubble column reactors is not optimum. To obtain an optimum size we are following up on the observation of George Cody of Exxon who reported a maximum granular temperature (random particle kinetic energy) for a particle size of 90 microns. The attached paper, Turbulence of Particles in a CFB and Slurry Bubble Columns Using Kinetic Theory, supports George Cody's observations. However, our explanation for the existence of the maximum in granular temperature differs from that proposed by George Cody. Further computer simulations and experiments involving measurements of granular temperature are needed to obtain a sound theoretical explanation for the possible existence of an optimum catalyst size.

  7. Nucleation of bubbles on a solidification front—experiment and analysis

    NASA Astrophysics Data System (ADS)

    Wei, P. S.; Huang, C. C.; Lee, K. W.

    2003-06-01

    The heterogeneous nucleation of bubbles on an advancing solidification front during the freezing of water containing a dissolved gas has been experimentally and analytically studied. The formation of bubbles resulting from supersaturation of liquids is commonly encountered in different fields such as heat transfer, manufacturing, and bioscience. In this work, the sizes of nucleating bubbles and the concentration profiles of dissolved oxygen and carbon dioxide gases in the water ahead of the solidification front have been measured. From successful comparisons between the measured and predicted critical radii of nucleating bubbles and distributions of dissolved gas content, the phenomena of heterogeneous nucleation in a binary weak solution during the freezing process are quantitatively confirmed. The results show that an increase in gas content at the solidification front in the liquid decreases the free-energy barrier and critical radii of bubbles that are formed on the solidification front. The sizes of the critical radii decrease and the number of nucleating bubbles increase in the early stage of solidification. As the solidification rates decrease at longer times, the content of the dissolved gas in the liquid on the advancing interface decreases and the critical radii of nucleating bubbles increase.

  8. Generation of Bubbly Suspensions in Low Gravity

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  9. Comparison of the bubble size distribution in silicate foams using 2D images and 3D x-ray microtomography

    NASA Astrophysics Data System (ADS)

    Robert, Genevieve; Baker, Don R.; Rivers, Mark L.; Allard, Emilie; Larocque, Jeffery

    2004-10-01

    Three silicate glasses were hydrated at high pressure and then heated at atmospheric pressure to exsolve the water into bubbles and create foams. The bubble size distribution in these foams was measured by x-ray microtomography on the GSECARS BM-13 beamline at the Advanced Photon Source. The bubble area distributions were measured in two dimensions using the image slices produced from the microtomography and the software ImageJ. The bubble volume distributions were measured from the three-dimensional tomographic images with the BLOB3D software. We found that careful analysis of the microtomography data in both two and three dimensions was necessary to avoid the physically unrealistic, experimental artifact of identifying and counting many small bubbles whose surfaces were not defined by a septum of glass. When this artifact was avoided the foams demonstrated power-law distributions of bubble sizes in both two and three dimensions. Conversion of the power-law exponents for bubble areas measured in two dimensions to exponents for bubble volumes usually agreed with the measured three dimensional volume exponents. Furthermore, the power-law distributions for bubble volumes typically agree with multiple theories of bubble growth, all of which yield an exponent of 1 for the cumulative bubble volume distribution. The measured bubble volume distributions with exponents near 0.3 can be explained by diffusive growth as proposed by other authors, but distributions with exponents near 1.4 remain to be explained and are the subject of continuing research on the effects of water concentration and melt viscosity on foaming behavior.

  10. Temperature considerations in numerical simulations of collapsing bubbles

    NASA Astrophysics Data System (ADS)

    Johnsen, Eric; Alahyari Beig, Shahaboddin

    2014-11-01

    In naval and biomedical engineering applications, the inertial collapse of cavitation bubbles is known to damage its surroundings. While significant attention has been dedicated to investigating the pressures produced by this process, less is known about heating of the surrounding medium, which may be important when collapse occurs near objects whose properties strongly depend on temperature (e.g., polymers). Euler simulations are capable of predicting the high pressures thereby generated. However, numerical errors can occur when solving the Navier-Stokes equations for compressible interface problems. Using a newly developed computational approach that prevents such errors, we investigate the dynamics of shock-induced and Rayleigh collapse of individual and collections of gas bubbles, in a free field and near rigid surfaces. We characterize the temperature rises based on the relevant non-dimensional parameters entering the problem. In particular, we show that the temperature of a neighboring object rises due to two mechanisms: the shock produced at collapse and heat diffusion from the hot bubble as it moves toward the object. This work was supported by ONR Grant N00014-12-1-0751.

  11. Investigation of the effect of wall materials and tube diameter by heat transfer from horizontal tubes to boiling liquids

    NASA Astrophysics Data System (ADS)

    Siebert, Matthias

    1987-09-01

    Heating surface materials like copper, brass, and stainless steel are studied for their heat transfer coefficient through tubes of 8 mm diameter. Refrigerants considered are R12, R113, R114, methane, and pentane. Heat transfer measurements are carried out in dependence on boiling pressure, liquid properties, bubble formation, and size and bubble deposit thickness on heat surfaces. Nucleate boiling is visualized and observed.

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

    PubMed

    Ida, Masato; Naoe, Takashi; Futakawa, Masatoshi

    2007-10-01

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

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

    SciTech Connect

    Shen, H.H.; Peng, S.M.; Chen, B.; Naab, F.N.; Sun, G.A.; Zhou, W.; Xiang, X.; Sun, K.; Zu, X.T.

    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.

  14. A model for sound velocity in a two-phase air-water bubbly flow

    SciTech Connect

    Chung, N.M.; Lin, W.K.; Pei, B.S.; Hsu, Y.Y. )

    1992-07-01

    In this paper, wave propagation in a homogeneous, low void fraction, two-phase air-water bubbly flow is analyzed through the compressibility of a single bubble to derive a P({rho}) relation; the dispersion relation is then derived by a homogeneous model. The phase velocity and attenuation calculated from the model are compared with existing data and are in good agreement. The momentum transfer effect is considered through the virtual mass term and is significant at a higher void fraction. The interfacial heat transfer between phases is significant at low frequency, while bubble scattering effects are important at high frequency (near resonance). Bubble behavior at both low and high frequency is derived based on the isothermal and the adiabatic cases, respectively. The phase velocity occurs at the limiting condition in both cases. Furthermore, resonance is present in the model, and the resonant frequency is determined.

  15. Shear-induced bubble coalescence in rhyolitic melts with low vesicularity

    NASA Astrophysics Data System (ADS)

    Okumura, Satoshi; Nakamura, Michihiko; Tsuchiyama, Akira

    2006-10-01

    We have experimentally demonstrated for the first time, shear-induced development of bubble size and shape in a rhyolitic melt. The deformation experiments have been performed by using an externally heated, piston-cylinder type apparatus with a rotational piston. At 975°C, the vesiculated rhyolitic melts having cylindrical shape were twisted at rotational speeds of 0.3, 0.5 and 1.0 rpm. The number, size and shape of bubbles were then measured by using the X-ray computed tomography. The experimental results show that coalescence of bubbles occur even at low vesicularity (20 vol.%) and the degree of coalescence is enhanced with the shear rate. Because the shear-induced deformation seems to be produced for magmas ascending in a volcanic conduit, we propose the possibility of the vesiculated magma undergoing bubble coalescence at a significant depth (low vesicularity), resulting in the formation of permeable magmas, at least near the conduit wall.

  16. Condensing process of a single vapor bubble ejected in subcooled pool

    NASA Astrophysics Data System (ADS)

    Ueno, Ichiro; Arima, Masayuki; Hattori, Yasusuke

    Behavior of growing/collapsing vapor bubble ejected to subcooled liquid bath was focused. Vapor bubble was produced by vapor generate system. With this system, heated container was carried out temperature control with a thermostat. This system enabled the authors to observe interaction between the vapor and the liquid in the condensing process extracted from the boiling phenomenon consisting of liquid-gas-solid interactions. The bubble behavior was detected by employing a high-speed camera with up to 100,000 fps. The instability emerged over the surface of the growing and collapsing vapor are discussed as functions of the degree of subcooling, and the temperature and ejection speed of vapor. The present study aims to understand and control the micro-bubble emission boiling known as MEB.

  17. Three dimensional calculations of the effective Kapitza resistance of UO2 grain boundaries containing intergranular bubbles

    NASA Astrophysics Data System (ADS)

    Millett, Paul C.; Tonks, Michael R.; Chockalingam, K.; Zhang, Yongfeng; Biner, S. B.

    2013-08-01

    A parametric study has been performed that quantifies the effective change in grain boundary Kapitza resistance due to the presence of intergranular bubbles. The steady-state heat conduction equation was solved in three-dimensional space using INL's MOOSE finite element software, with which spacial mesh adaptivity was used to resolve interfacial widths down to several nanometers while investigating bubble sizes up to a micrometer. Three critical parameters were systematically varied: the intergranular bubble radius, the fractional grain boundary bubble coverage, and the Kapitza resistance of the intact grain boundary. Using the simulation results, a mathematical model dependent on each of these parameters was developed to describe the effective Kapitza resistance. Furthermore, we illustrate how this model can be implemented in a fuel performance code to predict the temperature profile of a cylindrical fuel pellet.

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

    PubMed

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

    2011-12-01

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

  19. The effects of geometric, flow, and boiling parameters on bubble growth and behavior in subcooled flow boiling

    NASA Astrophysics Data System (ADS)

    Samaroo, Randy

    Air bubble injection and subcooled flow boiling experiments have been performed to investigate the liquid flow field and bubble nucleation, growth, and departure, in part to contribute to the DOE Nuclear HUB project, Consortium for Advanced Simulation of Light Water Reactors (CASL). The main objective was to obtain quantitative data and compartmentalize the many different interconnected aspects of the boiling process -- from the channel geometry, to liquid and gas interactions, to underlying heat transfer mechanisms. The air bubble injection experiments were performed in annular and rectangular geometries and yielded data on bubble formation and departure from a small hole on the inner tube surface, subsequent motion and deformation of the detached bubbles, and interactions with laminar or turbulent water flow. Instantaneous and ensemble- average liquid velocity profiles have been obtained using a Particle Image Velocimetry technique and a high speed video camera. Reynolds numbers for these works ranged from 1,300 to 7,700. Boiling experiments have been performed with subcooled water at atmospheric pres- sure in the same annular channel geometry as the air injection experiments. A second flow loop with a slightly larger annular channel was constructed to perform further boiling experiments at elevated pressures up to 10 bar. High speed video and PIV measurements of turbulent velocity profiles in the presence of small vapor bubbles on the heated rod are presented. The liquid Reynolds number for this set of experiments ranged from 5,460 to 86,000. It was observed that as the vapor bubbles are very small compared to the injected air bubbles, further experiments were performed using a microscopic objective to obtain higher spatial resolution for velocity fields near the heated wall. Multiple correlations for the bubble liftoff diameter, liftoff time and bub- ble history number were evaluated against a number of experimental datasets from previous works, resulting in a

  20. Intensity of vortices: from soap bubbles to hurricanes.

    PubMed

    Meuel, T; Xiong, Y L; Fischer, P; Bruneau, C H; Bessafi, M; Kellay, H

    2013-12-13

    By using a half soap bubble heated from below, we obtain large isolated single vortices whose properties as well as their intensity are measured under different conditions. By studying the effects of rotation of the bubble on the vortex properties, we found that rotation favors vortices near the pole. Rotation also inhibits long life time vortices. The velocity and vorticity profiles of the vortices obtained are well described by a Gaussian vortex. Besides, the intensity of these vortices can be followed over long time spans revealing periods of intensification accompanied by trochoidal motion of the vortex center, features which are reminiscent of the behavior of tropical cyclones. An analysis of this intensification period suggests a simple relation valid for both the vortices observed here and for tropical cyclones.

  1. Intensity of vortices: from soap bubbles to hurricanes

    NASA Astrophysics Data System (ADS)

    Meuel, T.; Xiong, Y. L.; Fischer, P.; Bruneau, C. H.; Bessafi, M.; Kellay, H.

    2013-12-01

    By using a half soap bubble heated from below, we obtain large isolated single vortices whose properties as well as their intensity are measured under different conditions. By studying the effects of rotation of the bubble on the vortex properties, we found that rotation favors vortices near the pole. Rotation also inhibits long life time vortices. The velocity and vorticity profiles of the vortices obtained are well described by a Gaussian vortex. Besides, the intensity of these vortices can be followed over long time spans revealing periods of intensification accompanied by trochoidal motion of the vortex center, features which are reminiscent of the behavior of tropical cyclones. An analysis of this intensification period suggests a simple relation valid for both the vortices observed here and for tropical cyclones.

  2. Temperature distribution in a mixture surrounding a growing vapour bubble

    NASA Astrophysics Data System (ADS)

    Mohammadein, S. A.; Gouda, Sh. A.

    2006-03-01

    The paper presents temperature distribution of superheated liquid during the growth of spherical vapour bubble between two-phase temperatures. The heat equation is resolved by the modification of similarity parameter method of Screven [Chem Engng Sci 10:1-13(1959)] between two finite boundaries. Under these conditions, the growth of vapour bubble and temperature are obtained analytically in an implicit form which are different than that obtained before. The growth rate is obtained as a generalized formula compared with Plesset amd Zwick and Scriven et al. theories [J Appl Phys 25:493-500(1954);Chem Engng Sci 10:1-13(1959)]. The growth and temperature field affected by the initial superheating and thermal diffusivity.

  3. SuperCam_MastUnit

    NASA Astrophysics Data System (ADS)

    Deleuze, M. D.; Bernardi, P. B.; Caïs, Ph. C.; Perez, R. P.; Rees, J. M. R.; Pares, L. P.; Dubois, B. D.; Parot, Y. P.; Quertier, B. Q.; Maurice, S. M.; Maccabe, K. M.; Wiens, R. W.; Rull, F. R.

    2016-10-01

    This paper will describe and give a development status of SuperCam's mast unit. SuperCam will be carried on the Mars 2020 rover, and consists in an enhanced version of the ChemCam LIBS which is still performing at the surface of Mars, on Curiosity.

  4. Sonoporation from Jetting Cavitation Bubbles

    PubMed Central

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

    2006-01-01

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

  5. Etiology of gas bubble disease

    SciTech Connect

    Bouck, G.R.

    1980-11-01

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

  6. Bubble-induced cave collapse.

    PubMed

    Girihagama, Lakshika; Nof, Doron; Hancock, Cathrine

    2015-01-01

    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.

  7. Bubble-Induced Cave Collapse

    PubMed Central

    Girihagama, Lakshika; Nof, Doron; Hancock, Cathrine

    2015-01-01

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

  8. Development and interactions of two inert gas bubbles during decompression.

    PubMed

    Jiang, Y; Homer, L D; Thalmann, E D

    1996-09-01

    A mathematical model has been developed to simulate the evolution of two inert gas bubbles in tissue. This is useful for understanding the dynamics of bubbles that presumably arise during decompression. It is assumed that they are spherical and that the tissue volume surrounding them is infinite. The total pressure in each bubble is determined by the barometric and metabolic gas pressures as well as the pressure due to surface tension. Bipolar coordinates are employed to determine the inert gas pressure distribution. Two coupled governing equations for bubble radii are then derived and solved numerically. The results demonstrate how bubble evolution is affected by the distance between bubbles and the initial bubble radii. The existence time and bubble surface flux of two equal-sized bubbles are calculated and compared with those of a single gas bubble model. The results indicate that when two bubbles are very close, it takes 20% more time for two bubbles to dissolve than for a single one, and the total surface flux of two bubbles is nearly 20% less than twice of a single bubble. When the center-to-center distance is 10 times of bubble radius, the effect of bubble interaction on bubble existence time and surface flux are about 6 and 9% changes, respectively. We conclude that if bubbles are not too small, the interactions among bubbles should be included in inert gas bubble models predicting bubble evolution.

  9. Armoring confined bubbles in concentrated colloidal suspensions

    NASA Astrophysics Data System (ADS)

    Yu, Yingxian; Khodaparast, Sepideh; Stone, Howard

    2016-11-01

    Encapsulation of a bubble with microparticles is known to significantly improve the stability of the bubble. This phenomenon has recently gained increasing attention due to its application in a variety of technologies such as foam stabilization, drug encapsulation and colloidosomes. Nevertheless, the production of such colloidal armored bubble with controlled size and particle coverage ratio is still a great challenge industrially. We study the coating process of a long air bubble by microparticles in a circular tube filled with a concentrated microparticles colloidal suspension. As the bubble proceeds in the suspension of particles, a monolayer of micro-particles forms on the interface of the bubble, which eventually results in a fully armored bubble. We investigate the phenomenon that triggers and controls the evolution of the particle accumulation on the bubble interface. Moreover, we examine the effects of the mean flow velocity, the size of the colloids and concentration of the suspension on the dynamics of the armored bubble. The results of this study can potentially be applied to production of particle-encapsulated bubbles, surface-cleaning techniques, and gas-assisted injection molding.

  10. Soap bubbles in paintings: Art and science

    NASA Astrophysics Data System (ADS)

    Behroozi, F.

    2008-12-01

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

  11. External artery heat pipe

    NASA Technical Reports Server (NTRS)

    Gernert, Nelson J. (Inventor); Ernst, Donald M. (Inventor); Shaubach, Robert M. (Inventor)

    1989-01-01

    An improved heat pipe with an external artery. The longitudinal slot in the heat pipe wall which interconnects the heat pipe vapor space with the external artery is completely filled with sintered wick material and the wall of the external artery is also covered with sintered wick material. This added wick structure assures that the external artery will continue to feed liquid to the heat pipe evaporator even if a vapor bubble forms within and would otherwise block the liquid transport function of the external artery.

  12. Experimental investigation of undesired stable equilibria in pumpkin shape super-pressure balloon designs

    NASA Astrophysics Data System (ADS)

    Schur, W. W.

    2004-01-01

    Excess in skin material of a pneumatic envelope beyond what is required for minimum enclosure of a gas bubble is a necessary but by no means sufficient condition for the existence of multiple equilibrium configurations for that pneumatic envelope. The very design of structurally efficient super-pressure balloons of the pumpkin shape type requires such excess. Undesired stable equilibria in pumpkin shape balloons have been observed on experimental pumpkin shape balloons. These configurations contain regions with stress levels far higher than those predicted for the cyclically symmetric design configuration under maximum pressurization. Successful designs of pumpkin shape super-pressure balloons do not allow such undesired stable equilibria under full pressurization. This work documents efforts made so far and describes efforts still underway by the National Aeronautics and Space Administration's Balloon Program Office to arrive on guidance on the design of pumpkin shape super-pressure balloons that guarantee full and proper deployment.

  13. Unsteady thermocapillary migration of bubbles

    NASA Technical Reports Server (NTRS)

    Dill, Loren H.; Balasubramaniam, R.

    1988-01-01

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

  14. Magnetars are super hot and super cool

    NASA Astrophysics Data System (ADS)

    Ho, Wynn C. G.; Glampedakis, Kostas; Andersson, Nils

    2013-03-01

    We examine to what extent the inferred surface temperature of magnetars in quiescence can constrain the presence of a superfluid in the neutron star core and the role of magnetic field decay in the core. By performing detailed simulations of neutron star cooling, we show that extremely strong heating from field decay in the core cannot produce the high observed surface temperatures nor delay the onset of neutron superfluidity in the core. We find that it is not possible to conclude that magnetar cores are in a non-superfluid state purely from high surface temperatures. We find that neutron superfluidity in the core occurs less than a few hundred years after neutron star formation for core fields < 1016 G. Thus all known neutron stars, including magnetars, without a core containing exotic particles, should have a core of superfluid neutrons and superconducting protons.

  15. Heat transfer with nucleate boiling of liquids under weak mass force field conditions

    NASA Technical Reports Server (NTRS)

    Kirichenko, Y. A.

    1974-01-01

    The motion is examined of a vapor bubble growing and rising from a flat horizontal heater in the ideal fluid approximation and taking drag into account. Estimates are given of bubble lifetime, bubble radius at detachment, bubble detachment frequency, and time for the bubble to attain a constant rate of rise. The relations obtained for the microcharacteristics of the boiling process are used to determine the coefficients of heat transfer in developed nucleate boiling. A new form of the equations for describing heat transfer in nucleate boiling in dimensionless parameters is proposed.

  16. Marangoni Effects on Near-Bubble Microscale Transport During Boiling of Binary Fluid Mixtures

    NASA Technical Reports Server (NTRS)

    V. Carey; Sun, C.; Carey, V. P.

    2000-01-01

    In earlier investigations, Marangoni effects were observed to be the dominant mechanism of boiling transport in 2-propanol/water mixtures under reduced gravity conditions. In this investigation we have examined the mechanisms of binary mixture boiling by exploring the transport near a single bubble generated in a binary mixture between a heated surface and cold surface. The temperature field created in the liquid around the bubble produces vaporization over the portion of its interface near the heated surface and condensation over portions of its interface near the cold surface. Experiments were conducted using different mixtures of water and 2-propanol under 1g conditions and under reduced gravity conditions aboard the KC135 aircraft. Since 2-propanol is more volatile than water, there is a lower concentration of 2-propanol near the hot surface and a higher concentration of 2-propanol near the cold plate relative to the bulk quantity. This difference in interface concentration gives rise to strong Marangoni effects that move liquid toward the hot plate in the near bubble region for 2-propanol and water mixtures. In the experiments in this study, the pressure of the test system was maintained at about 5 kPa to achieve the full spectrum of boiling behavior (nucleate boiling, critical heat flux and film boiling) at low temperature and heat flux levels. Heat transfer data and visual documentation of the bubble shape were extracted from the experimental results. In the 1-g experiments at moderate to high heat flux levels, the bubble was observed to grow into a mushroom shape with a larger top portion near the cold plate due to the buoyancy effect. The shape of the bubble was somewhat affected by the cold plate subcooling and the superheat of the heated surface. At low superheat levels for the heated surface, several active nucleation sites were observed, and the vapor stems from them merged to form a larger bubble. The generation rate of vapor is moderate in this

  17. Bernoulli Suction Effect on Soap Bubble Blowing?

    NASA Astrophysics Data System (ADS)

    Davidson, John; Ryu, Sangjin

    2015-11-01

    As a model system for thin-film bubble with two gas-liquid interfaces, we experimentally investigated the pinch-off of soap bubble blowing. Using the lab-built bubble blower and high-speed videography, we have found that the scaling law exponent of soap bubble pinch-off is 2/3, which is similar to that of soap film bridge. Because air flowed through the decreasing neck of soap film tube, we studied possible Bernoulli suction effect on soap bubble pinch-off by evaluating the Reynolds number of airflow. Image processing was utilized to calculate approximate volume of growing soap film tube and the volume flow rate of the airflow, and the Reynolds number was estimated to be 800-3200. This result suggests that soap bubbling may involve the Bernoulli suction effect.

  18. Manipulating bubbles with secondary Bjerknes forces

    SciTech Connect

    Lanoy, Maxime; Derec, Caroline; Leroy, Valentin; Tourin, Arnaud

    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.

  19. Bubbles Rising Through a Soft Granular Material

    NASA Astrophysics Data System (ADS)

    Le Mestre, Robin; MacMinn, Chris; Lee, Sungyon

    2016-11-01

    Bubble migration through a soft granular material involves a strong coupling between the bubble dynamics and the deformation of the material. This is relevant to a variety of natural processes such as gas venting from sediments and gas exsolution from magma. Here, we study this process experimentally by injecting air bubbles into a quasi-2D packing of soft hydrogel beads and measuring the size, speed, and morphology of the bubbles as they rise due to buoyancy. Whereas previous work has focused on deformation resisted by intergranular friction, we focus on the previously inaccessible regime of deformation resisted by elasticity. At low confining stress, the bubbles are irregular and rounded, migrating via local rearrangement. At high confining stress, the bubbles become unstable and branched, migrating via pathway opening. The authors thank The Royal Society for support (International Exchanges Ref IE150885).

  20. BUBBLE DYNAMICS AT GAS-EVOLVING ELECTRODES

    SciTech Connect

    Sides, Paul J.

    1980-12-01

    Nucleation of bubbles, their growth by diffusion of dissolved gas to the bubble surface and by coalescence, and their detachment from the electrode are all very fast phenomena; furthermore, electrolytically generated bubbles range in size from ten to a few hundred microns; therefore, magnification and high speed cinematography are required to observe bubbles and the phenomena of their growth on the electrode surface. Viewing the action from the front side (the surface on which the bubbles form) is complicated because the most important events occur close to the surface and are obscured by other bubbles passing between the camera and the electrode; therefore, oxygen was evolved on a transparent tin oxide "window" electrode and the events were viewed from the backside. The movies showed that coalescence of bubbles is very important for determining the size of bubbles and in the chain of transport processes; growth by diffusion and by coalescence proceeds in series and parallel; coalescing bubbles cause significant fluid motion close to the electrode; bubbles can leave and reattach; and bubbles evolve in a cycle of growth by diffusion and different modes of coalescence. An analytical solution for the primary potential and current distribution around a spherical bubble in contact with a plane electrode is presented. Zero at the contact point, the current density reaches only one percent of its undisturbed value at 30 percent of the radius from that point and goes through a shallow maximum two radii away. The solution obtained for spherical bubbles is shown to apply for the small bubbles of electrolytic processes. The incremental resistance in ohms caused by sparse arrays of bubbles is given by {Delta}R = 1.352 af/kS where f is the void fraction of gas in the bubble layer, a is the bubble layer thickness, k is the conductivity of gas free electrolyte, and S is the electrode area. A densely populated gas bubble layer on an electrode was modeled as a hexagonal array of

  1. Super-Hard Superconductivity

    NASA Astrophysics Data System (ADS)

    Adams, Philip; Prozorov, Ruslan

    2005-03-01

    We present the magnetic response of Type-II superconductivity in the extreme pinning limit, where screening currents within an order of magnitude of the Ginzburg-Landau depairing critical current density develop upon the application of a magnetic field. We show that this ``super-hard'' limit is well approximated in highly disordered, cold drawn, Nb wire whose magnetization response is characterized by a cascade of Meissner-like phases, each terminated by a catastrophic collapse of the magnetization. Direct magneto-optic measurements of the flux penetration depth in the virgin magnetization branch are in excellent agreement with the exponential model in which Jc(B)=Jco(-B/Bo), where Jco˜5x10^6 A/cm^2 for Nb. The implications for the fundamental limiting hardness of a superconductor will be discussed.

  2. Influence of bubble size on effervescent atomization. Part 1: bubble characterization and mean spray features

    NASA Astrophysics Data System (ADS)

    Lewis, Taylor; Shepard, Thomas; Forliti, David

    2016-11-01

    In the effervescent atomization process a gas-liquid bubbly mixture is ejected from a nozzle with the goal of enhancing liquid break-up. In this work, high speed images are taken of the bubbly flow inside of an effervescent atomizer as well as downstream of the atomizer exit. The use of varying porous plate media grades and channel inserts at the air injection site of the atomizer permitted independent control of mean bubble size. Digital image analyses were used for bubble characterization and measuring mean spray features. The roles of air injection geometry on bubble population parameters inside of the effervescent atomizer are detailed. The effect of bubble size is examined at multiple gas to liquid flow rate ratios for which the bubbly flow regime was maintained. Results are presented demonstrating the influence of bubble size on the average jet width, jet dark core length, and liquid break-up.

  3. Bursting the bubble of melt inclusions

    USGS Publications Warehouse

    Lowenstern, Jacob B.

    2015-01-01

    Most silicate melt inclusions (MI) contain bubbles, whose significance has been alternately calculated, pondered, and ignored, but rarely if ever directly explored. Moore et al. (2015) analyze the bubbles, as well as their host glasses, and conclude that they often hold the preponderance of CO2 in the MI. Their findings entreat future researchers to account for the presence of bubbles in MI when calculating volatile budgets, saturation pressures, and eruptive flux.

  4. Collapse of vacuum bubbles in a vacuum

    SciTech Connect

    Ng, Kin-Wang; Wang, Shang-Yung

    2011-02-15

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

  5. Detailed Jet Dynamics in a Collapsing Bubble

    NASA Astrophysics Data System (ADS)

    Supponen, Outi; Obreschkow, Danail; Kobel, Philippe; Farhat, Mohamed

    2015-12-01

    We present detailed visualizations of the micro-jet forming inside an aspherically collapsing cavitation bubble near a free surface. The high-quality visualizations of large and strongly deformed bubbles disclose so far unseen features of the dynamics inside the bubble, such as a mushroom-like flattened jet-tip, crown formation and micro-droplets. We also find that jetting near a free surface reduces the collapse time relative to the Rayleigh time.

  6. Buoyancy Driven Shear Flows of Bubble Suspensions

    NASA Astrophysics Data System (ADS)

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

    1998-11-01

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

  7. Bubble, Drop and Particle Unit (BDPU)

    NASA Technical Reports Server (NTRS)

    1998-01-01

    This section of the Life and Microgravity Spacelab (LMS) publication includes the following articles entitled: (1) Oscillatory Thermocapillary Instability; (2) Thermocapillary Convection in Multilayer Systems; (3) Bubble and Drop Interaction with Solidification Front; (4) A Liquid Electrohydrodynamics Experiment; (5) Boiling on Small Plate Heaters under Microgravity and a Comparison with Earth Gravity; (6) Thermocapillary Migration and Interactions of Bubbles and Drops; and (7) Nonlinear Surface Tension Driven Bubble Migration

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

    NASA Technical Reports Server (NTRS)

    Tkachev, L. G.

    1988-01-01

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

  9. Micro-bubble emission boiling with the cavitation bubble blow pit

    PubMed Central

    Inada, Shigeaki; Shinagawa, Kazuaki; Illias, Suhaimi Bin; Sumiya, Hiroyuki; Jalaludin, Helmisyah A.

    2016-01-01

    The miniaturization boiling (micro-bubble emission boiling [MEB]) phenomenon, with a high heat removal capacity that contributes considerably to the cooling of the divertor of the nuclear fusion reactor, was discovered in the early 1980s. Extensive research on MEB has been performed since its discovery. However, the progress of the application has been delayed because the generation mechanism of MEB remains unclear. Reasons for this lack of clarity include the complexity of the phenomenon itself and the high-speed phase change phenomenon in which boiling and condensation are rapidly generated. In addition, a more advanced thermal technique is required to realize the MEB phenomenon at the laboratory scale. To the authors’ knowledge, few studies have discussed the rush mechanism of subcooled liquid to the heating surface, which is critical to elucidating the mechanism behind MEB. This study used photographic images to verify that the cavitation phenomenon spreads to the inside of the superheated liquid on the heating surface and thus clarify the mechanism of MEB. PMID:27628271

  10. Micro-bubble emission boiling with the cavitation bubble blow pit

    NASA Astrophysics Data System (ADS)

    Inada, Shigeaki; Shinagawa, Kazuaki; Illias, Suhaimi Bin; Sumiya, Hiroyuki; Jalaludin, Helmisyah A.

    2016-09-01

    The miniaturization boiling (micro-bubble emission boiling [MEB]) phenomenon, with a high heat removal capacity that contributes considerably to the cooling of the divertor of the nuclear fusion reactor, was discovered in the early 1980s. Extensive research on MEB has been performed since its discovery. However, the progress of the application has been delayed because the generation mechanism of MEB remains unclear. Reasons for this lack of clarity include the complexity of the phenomenon itself and the high-speed phase change phenomenon in which boiling and condensation are rapidly generated. In addition, a more advanced thermal technique is required to realize the MEB phenomenon at the laboratory scale. To the authors’ knowledge, few studies have discussed the rush mechanism of subcooled liquid to the heating surface, which is critical to elucidating the mechanism behind MEB. This study used photographic images to verify that the cavitation phenomenon spreads to the inside of the superheated liquid on the heating surface and thus clarify the mechanism of MEB.

  11. Micro-bubble emission boiling with the cavitation bubble blow pit.

    PubMed

    Inada, Shigeaki; Shinagawa, Kazuaki; Illias, Suhaimi Bin; Sumiya, Hiroyuki; Jalaludin, Helmisyah A

    2016-09-15

    The miniaturization boiling (micro-bubble emission boiling [MEB]) phenomenon, with a high heat removal capacity that contributes considerably to the cooling of the divertor of the nuclear fusion reactor, was discovered in the early 1980s. Extensive research on MEB has been performed since its discovery. However, the progress of the application has been delayed because the generation mechanism of MEB remains unclear. Reasons for this lack of clarity include the complexity of the phenomenon itself and the high-speed phase change phenomenon in which boiling and condensation are rapidly generated. In addition, a more advanced thermal technique is required to realize the MEB phenomenon at the laboratory scale. To the authors' knowledge, few studies have discussed the rush mechanism of subcooled liquid to the heating surface, which is critical to elucidating the mechanism behind MEB. This study used photographic images to verify that the cavitation phenomenon spreads to the inside of the superheated liquid on the heating surface and thus clarify the mechanism of MEB.

  12. Fundamental study of FC-72 pool boiling surface temperature fluctuations and bubble behavior

    NASA Astrophysics Data System (ADS)

    Griffin, Alison R.

    A heater designed to monitor surface temperature fluctuations during pool boiling experiments while the bubbles were simultaneously being observed has been fabricated and tested. The heat source was a transparent indium tin oxide (ITO) layer commercially deposited on a fused quartz substrate. Four copper-nickel thin film thermocouples (TFTCs) on the heater surface measured the surface temperature, while a thin layer of sapphire or fused silica provided electrical insulation between the TFTCs and the ITO. The TFTCs were micro-fabricated using the liftoff process to deposit the nickel and copper metal films. The TFTC elements were 50 mum wide and overlapped to form a 25 mum by 25 mum junction. TFTC voltages were recorded by a DAQ at a sampling rate of 50 kHz. A high-speed CCD camera recorded bubble images from below the heater at 2000 frames/second. A trigger sent to the camera by the DAQ synchronized the bubble images and the surface temperature data. As the bubbles and their contact rings grew over the TFTC junction, correlations between bubble behavior and surface temperature changes were demonstrated. On the heaters with fused silica insulation layers, 1--2°C temperature drops on the order of 1 ms occurred as the contact ring moved over the TFTC junction during bubble growth and as the contact ring moved back over the TFTC junction during bubble departure. These temperature drops during bubble growth and departure were due to microlayer evaporation and liquid rewetting the heated surface, respectively. Microlayer evaporation was not distinguished as the primary method of heat removal from the surface. Heaters with sapphire insulation layers did not display the measurable temperature drops observed with the fused silica heaters. The large thermal diffusivity of the sapphire compared to the fused silica was determined as the reason for the absence of these temperature drops. These findings were confirmed by a comparison of temperature drops in a 2-D simulation of

  13. Single-bubble sonoluminescence from noble gases.

    PubMed

    Yasui, K

    2001-03-01

    Single-bubble sonoluminescence (SBSL) from noble gases in water is studied theoretically in order to clarify the reason of the distinguished feature that the luminescence is strong for all noble gases, while the other systems of cavitation luminescence are greatly enhanced by the presence of the heavy noble gas(xenon). It is clarified that in spite of the larger thermal conductivity of lighter noble gases the maximum temperature in a SBSL bubble of lighter noble gases is higher due both to the segregation of water vapor and noble gas inside a SBSL bubble and the stronger acoustic drive of a SBSL bubble of lighter noble gases.

  14. Single-bubble sonoluminescence from noble gases

    NASA Astrophysics Data System (ADS)

    Yasui, Kyuichi

    2001-03-01

    Single-bubble sonoluminescence (SBSL) from noble gases in water is studied theoretically in order to clarify the reason of the distinguished feature that the luminescence is strong for all noble gases, while the other systems of cavitation luminescence are greatly enhanced by the presence of the heavy noble gas(xenon). It is clarified that in spite of the larger thermal conductivity of lighter noble gases the maximum temperature in a SBSL bubble of lighter noble gases is higher due both to the segregation of water vapor and noble gas inside a SBSL bubble and the stronger acoustic drive of a SBSL bubble of lighter noble gases.

  15. Spectroscopic characteristic of conical bubble luminescence

    NASA Astrophysics Data System (ADS)

    Chen, Qi-Dai; Fu, Li-Min; Ai, Xi-Cheng; Zhang, Jian-Ping; Wang, Long

    2005-04-01

    The conical bubble sonoluminescence (CBSL) from the collapse of the bubble was observed in an improved U-tube apparatus. The emitted light energy of a single CBSL flash was measured to be ~ 1.4mJ. The pulse width was about 100μs. The spectra of luminescence were continuum superimposed with the spectral bands from the excited-state C2, CN and CH. The CBSL provides a link between the light emission of the single-bubble and the multi-bubble sonoluminescence (SBSL and MBSL).

  16. Multiple Spark-Generated Bubble Interactions

    NASA Astrophysics Data System (ADS)

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

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

  17. Analysis of a deflating soap bubble

    NASA Astrophysics Data System (ADS)

    Jackson, David P.; Sleyman, Sarah

    2010-10-01

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

  18. Band gaps in bubble phononic crystals

    NASA Astrophysics Data System (ADS)

    Leroy, V.; Bretagne, A.; Lanoy, M.; Tourin, A.

    2016-12-01

    We investigate the interaction between Bragg and hybridization effects on the band gap properties of bubble phononic crystals. These latter consist of air cavities periodically arranged in an elastomer matrix and are fabricated using soft-lithography techniques. Their transmission properties are affected by Bragg effects due to the periodicity of the structure as well as hybridization between the propagating mode of the embedding medium and bubble resonance. The hybridization gap survives disorder while the Bragg gap requires a periodic distribution of bubbles. The distance between two bubble layers can be tuned to make the two gaps overlap or to create a transmission peak in the hybridization gap.

  19. Sound waves in multifractional liquids with bubbles

    NASA Astrophysics Data System (ADS)

    Gubaidullin, D. A.; Gafiyatov, R. N.

    2017-01-01

    The propagation of sound waves in multifractional mixtures of liquid with vapor–gas and gas bubbles of different sizes and different compositions with phase transitions is studied. The dispersed phase consists of N+M fractions having various gases in bubbles and different in the bubbles radii. Phase transitions accounted for N fractions. The total bubble volume concentration is small (less than 1%). The dispersion relation is derived and dispersion curves is built. The evolution of the weak pulsed perturbations of the pressure in this mixture was calculated numerically.

  20. Bubble formation in additive manufacturing of glass

    NASA Astrophysics Data System (ADS)

    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.

  1. Modeling and optimization of an acoustic diode based on micro-bubble nonlinearity.

    PubMed

    Guo, Xiasheng; Lin, Zhou; Tu, Juan; Liang, Bin; Cheng, Jianchun; Zhang, Dong

    2013-02-01

    The first acoustic diode (AD), which is composed by integrating a super lattice (SL) with a nonlinear medium (NLM), has recently been proposed to make a one-way street for the acoustic energy flux. This device prohibits the acoustic waves from one direction, but allows the transmission of the second harmonic wave (generated from the NLM) from the other direction. To improve its performance, it is crucial to transfer more acoustic energy from the stop-band of the acoustic filter (i.e., the SL) to its pass-band with the help of the NLM. In this work, a finite difference time domain model is developed to study the dynamic behaviors of the AD, in which a micro-bubble suspension takes the role of the NLM. Based on this model, the method of optimizing the nonlinearity-based AD is investigated by examining its performance with respect to several parameters, such as the periodicity number of the SL, the bubble size distribution, the bubble shell parameters, and the bubble concentration. It is also suggested that, instead of the rectification ratio, it might be more reasonable to characterize the performance of the AD with the energy attenuation coefficients (or transmission loss) for both incident directions.

  2. Numerical investigation on boiling flow of liquid nitrogen in a vertical tube using bubble number density approach

    NASA Astrophysics Data System (ADS)

    Shao, Xuefeng; Li, Xiangdong; Wang, Rongshun

    2016-04-01

    An average bubble number density (ABND) model was formulated and numerically resolved for the subcooled flow boiling of liquid nitrogen. The effects of bubble coalescence and breakup were taken into account. Some new closure correlations describing bubble nucleation and departure on the heating surface were selected as well. For the purpose of comparison, flow boiling of liquid nitrogen was also numerically simulated using a modified two-fluid model. The results show that the simulations performed by using the ABND model achieve encouraging improvement in accuracy in predicting heat flux and wall temperature of a vertical tube. Moreover, the influence of the bubble coalescence and breakup is shown to be great on predicting overall pressure beyond the transition point.

  3. SuperB Progress Report: Detector

    SciTech Connect

    Grauges, E.; Donvito, G.; Spinoso, V.; Manghisoni, M.; Re, V.; Traversi, G.; Eigen, G.; Fehlker, D.; Helleve, L.; Carbone, A.; Di Sipio, R.; Gabrielli, A.; Galli, D.; Giorgi, F.; Marconi, U.; Perazzini, S.; Sbarra, C.; Vagnoni, V.; Valentinetti, S.; Villa, M.; Zoccoli, A.; /INFN, Bologna /Bologna U. /Caltech /Carleton U. /Cincinnati U. /INFN, CNAF /INFN, Ferrara /Ferrara U. /UC, Irvine /Taras Shevchenko U. /Orsay, LAL /LBL, Berkeley /UC, Berkeley /Frascati /INFN, Legnaro /Orsay, IPN /Maryland U. /McGill U. /INFN, Milan /Milan U. /INFN, Naples /Naples U. /Novosibirsk, IYF /INFN, Padua /Padua U. /INFN, Pavia /Pavia U. /INFN, Perugia /Perugia U. /INFN, Perugia /Caltech /INFN, Pisa /Pisa U. /Pisa, Scuola Normale Superiore /PNL, Richland /Queen Mary, U. of London /Rutherford /INFN, Rome /Rome U. /INFN, Rome2 /Rome U.,Tor Vergata /INFN, Rome3 /Rome III U. /SLAC /Tel Aviv U. /INFN, Turin /Turin U. /INFN, Padua /Trento U. /INFN, Trieste /Trieste U. /TRIUMF /British Columbia U. /Montreal U. /Victoria U.

    2012-02-14

    This report describes the present status of the detector design for SuperB. It is one of four separate progress reports that, taken collectively, describe progress made on the SuperB Project since the publication of the SuperB Conceptual Design Report in 2007 and the Proceedings of SuperB Workshop VI in Valencia in 2008.

  4. A Study of the Constrained Vapor Bubble Thermosyphon

    NASA Technical Reports Server (NTRS)

    Wayner, Peter C., Jr.; Plawsky, J. L.

    2000-01-01

    The objective of this effort is to better understand the physics of evaporation, condensation, and fluid flow as they affect the heat transfer processes in a constrained vapor bubble heat exchanger (CVBHX). This CVBHX consists of a small enclosed container with a square cross section (inside dimensions. 3 x 3 x 40 mm) partially filled with a liquid. The major portion of the liquid is in the corners, which act as arteries. When a temperature difference is applied to the ends of the CVBHX, evaporation occurs at the hot end and condensation at the cold end resulting in a very effective heat transfer device with great potential in space applications. Liquid is returned by capillary flow in the corners. A complete description of the system and the results obtained to date are given in the papers listed.

  5. A reduced-order, single-bubble cavitation model with applications to therapeutic ultrasound

    PubMed Central

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

    2011-01-01

    Cavitation often occurs in therapeutic applications of medical ultrasound such as shock-wave lithotripsy (SWL) and high-intensity focused ultrasound (HIFU). Because cavitation bubbles can affect an intended treatment, it is important to understand the dynamics of bubbles in this context. The relevant context includes very high acoustic pressures and frequencies as well as elevated temperatures. Relative to much of the prior research on cavitation and bubble dynamics, such conditions are unique. To address the relevant physics, a reduced-order model of a single, spherical bubble is proposed that incorporates phase change at the liquid-gas interface as well as heat and mass transport in both phases. Based on the energy lost during the inertial collapse and rebound of a millimeter-sized bubble, experimental observations were used to tune and test model predictions. In addition, benchmarks from the published literature were used to assess various aspects of model performance. Benchmark comparisons demonstrate that the model captures the basic physics of phase change and diffusive transport, while it is quantitatively sensitive to specific model assumptions and implementation details. Given its performance and numerical stability, the model can be used to explore bubble behaviors across a broad parameter space relevant to therapeutic ultrasound. PMID:22088026

  6. Compressible DNS study of separation bubbles for flow past a low pressure turbine blade

    NASA Astrophysics Data System (ADS)

    Ranjan, Rajesh; Deshpande, Suresh; Narasimha, Roddam

    2014-11-01

    A representative low pressure turbine blade T106A is subjected to a direct numerical simulation (DNS) study for low Reynolds Number (Re = 51831 based on inflow velocity and axial chord) and angle of incidence (45.5 deg from the axial chord). The DNS code used here solves the compressible Navier-Stokes equations and uses a semi-kinetic energy preserving scheme. A hybrid grid is used for the computational domain, with a very fine wall-bounded boundary layer grid near the surface of the blade and an unstructured grid for rest of the domain. Total grid size for the current simulation is around 160 million. In the mean flow, a long but shallow separation bubble is found near the trailing edge. However, the instantaneous flow reveals a train of bubbles at this location. These instantaneous bubbles continually break and merge in time. The presence of these separation bubbles make the flow very complicated, as the bubbles are responsible for tripping the otherwise laminar flow to a transitional state. Skin friction and heat transfer co-efficient are also computed over the blade to understand the effect of these bubbles on parameters of engineering importance. Supported by a GATET funded project on DNS of turbomachinery blading. The Param Yuva-II at CDAC was utilized for the simulations.

  7. Counter-current thermocapilllary migration of bubbles in microchannels using self-rewetting liquids

    NASA Astrophysics Data System (ADS)

    Nazareth, Robson; Saenz, Pedro; Valluri, Prashant; Sefiane, Khellil

    2015-11-01

    The study of bubble transport in microchannels is of great interest in evaporative cooling of microdevices technologies. This is because bubble transport under heat-transfer or phase-change causes several flow instabilities that are less understood and hinder informed design of microcooling devices. Bubble motion in microchannels under temperature gradients is highly influenced by thermocapillary forces due surface tension gradients. Most studies until now so far are mainly based on pure liquids which present a linear temperature (inverse) dependence of surface tension. In this work, we consider motion of a bubble (formed of inert gas) in the so-called self-rewetting fluid that presents a parabolic (quadratic) dependence of surface tension on temperature, in a temperature range that includes a surface tension minimum. We particularly investigate the counter-current thermocapillary migration of bubbles in these liquids, as experimentally depicted by Shanahan and Sefiane (2014), by means of direct numerical simulations. We present a model that solves the 3D governing equations of mass, momentum, interface and energy for the two-phase system composed by incompressible, Newtonian and immiscible fluids. We resolve the deformable interface by means of a Volume-of-Fluid method. Our results indicate that there exists a pressure drop limit beyond which there would be no counter-current migration of bubbles.

  8. Alma Observations of Massive Molecular Gas Filaments Encasing Radio Bubbles in the Phoenix Cluster

    NASA Astrophysics Data System (ADS)

    Russell, H. R.; McDonald, M.; McNamara, B. R.; Fabian, A. C.; Nulsen, P. E. J.; Bayliss, M. B.; Benson, B. A.; Brodwin, M.; Carlstrom, J. E.; Edge, A. C.; Hlavacek-Larrondo, J.; Marrone, D. P.; Reichardt, C. L.; Vieira, J. D.

    2017-02-01

    We report new ALMA observations of the CO(3-2) line emission from the 2.1+/- 0.3× {10}10 {M}ȯ molecular gas reservoir in the central galaxy of the Phoenix cluster. The cold molecular gas is fueling a vigorous starburst at a rate of 500{--}800 {M}ȯ {{yr}}-1 and powerful black hole activity in the forms of both intense quasar radiation and radio jets. The radio jets have inflated huge bubbles filled with relativistic plasma into the hot, X-ray atmospheres surrounding the host galaxy. The ALMA observations show that extended filaments of molecular gas, each 10{--}20 {kpc} long with a mass of several billion solar masses, are located along the peripheries of the radio bubbles. The smooth velocity gradients and narrow line widths along each filament reveal massive, ordered molecular gas flows around each bubble, which are inconsistent with gravitational free-fall. The molecular clouds have been lifted directly by the radio bubbles, or formed via thermal instabilities induced in low-entropy gas lifted in the updraft of the bubbles. These new data provide compelling evidence for close coupling between the radio bubbles and the cold gas, which is essential to explain the self-regulation of feedback. The very feedback mechanism that heats hot atmospheres and suppresses star formation may also paradoxically stimulate production of the cold gas required to sustain feedback in massive galaxies.

  9. Shadow imaging in bubbly gas-liquid two-phase flow in porous structures

    NASA Astrophysics Data System (ADS)

    Altheimer, Marco; Häfeli, Richard; Wälchli, Carmen; Rudolf von Rohr, Philipp

    2015-09-01

    Shadow imaging is used for the investigation of bubbly gas-liquid two-phase flow in a porous structure. The porous structure is made of Somos WaterShed XC 11122, a clear epoxy resin used in rapid prototyping. Optical access is provided by using an aqueous solution of sodium iodide and zinc iodide having the same refractive index as the structure material (). Nitrogen is injected into the continuous phase at volumetric transport fractions in the range of resulting in a hold-up of . The obtained images of overlapping bubble shadows are processed to measure the bubble dimensions. Therefore, a new processing sequence is developed to determine bubble dimensions from overlapping bubble shadows by ellipse fitting. The accuracy of the bubble detection and sizing routine is assessed processing synthetic images. It is shown that the developed technique is suitable for volumetric two-phase flow measurements. Important global quantities such as gas hold-up and total interfacial area can be measured with only one camera. Operation parameters for gas-liquid two-phase flows are determined to improve mass and heat transfer between the phases.

  10. A reduced-order, single-bubble cavitation model with applications to therapeutic ultrasound.

    PubMed

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

    2011-11-01

    Cavitation often occurs in therapeutic applications of medical ultrasound such as shock-wave lithotripsy (SWL) and high-intensity focused ultrasound (HIFU). Because cavitation bubbles can affect an intended treatment, it is important to understand the dynamics of bubbles in this context. The relevant context includes very high acoustic pressures and frequencies as well as elevated temperatures. Relative to much of the prior research on cavitation and bubble dynamics, such conditions are unique. To address the relevant physics, a reduced-order model of a single, spherical bubble is proposed that incorporates phase change at the liquid-gas interface as well as heat and mass transport in both phases. Based on the energy lost during the inertial collapse and rebound of a millimeter-sized bubble, experimental observations were used to tune and test model predictions. In addition, benchmarks from the published literature were used to assess various aspects of model performance. Benchmark comparisons demonstrate that the model captures the basic physics of phase change and diffusive transport, while it is quantitatively sensitive to specific model assumptions and implementation details. Given its performance and numerical stability, the model can be used to explore bubble behaviors across a broad parameter space relevant to therapeutic ultrasound.

  11. Carbon Dioxide Absorption Heat Pump

    NASA Technical Reports Server (NTRS)

    Jones, Jack A. (Inventor)

    2002-01-01

    A carbon dioxide absorption heat pump cycle is disclosed using a high pressure stage and a super-critical cooling stage to provide a non-toxic system. Using carbon dioxide gas as the working fluid in the system, the present invention desorbs the CO2 from an absorbent and cools the gas in the super-critical state to deliver heat thereby. The cooled CO2 gas is then expanded thereby providing cooling and is returned to an absorber for further cycling. Strategic use of heat exchangers can increase the efficiency and performance of the system.

  12. Colorful Demos with a Long-Lasting Soap Bubble.

    ERIC Educational Resources Information Center

    Behroozi, F.; Olson, D. W.

    1994-01-01

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

  13. Plasma quenching by air during single-bubble sonoluminescence.

    PubMed

    Flannigan, David J; Suslick, Kenneth S

    2006-08-03

    We report the observation of sudden and dramatic changes in single-bubble sonoluminescence (SBSL) intensity (i.e., radiant power, phi(SL)) and spectral profiles at a critical acoustic pressure (P(c)) for solutions of sulfuric acid (H2SO4) containing mixtures of air and noble gas. Nitric oxide (NO), nitrogen (N2), and atomic oxygen emission lines are visible just below P(c). At P(c), very bright (factor of 7000 increase in phi(SL)) and featureless SBSL is observed when Ar is present. In addition, Ar lines are observed from a dimmed bubble that has been driven above P(c). These observations suggest that bright SBSL from H2SO4 is due to a plasma, and that molecular components of air suppress the onset of bright light emission through quenching mechanisms and endothermic processes. Determination of temperatures from simulations of the emission lines shows that air limits the heating during single-bubble cavitation. When He is present, phi(SL) increases by only a factor of 4 at P(c), and the SBSL spectrum is not featureless as for Ar, but instead arises from sulfur oxide (SO) and sulfur dioxide (SO2) bands. These differences are attributed to the high thermal conductivity and ionization potential of He compared to Ar.

  14. Warm Pressurant Gas Effects on the Liquid Hydrogen Bubble Point

    NASA Technical Reports Server (NTRS)

    Hartwig, Jason W.; McQuillen, John B.; Chato, David J.

    2013-01-01

    This paper presents experimental results for the liquid hydrogen bubble point tests using warm pressurant gases conducted at the Cryogenic Components Cell 7 facility at the NASA Glenn Research Center in Cleveland, Ohio. The purpose of the test series was to determine the effect of elevating the temperature of the pressurant gas on the performance of a liquid acquisition device. Three fine mesh screen samples (325 x 2300, 450 x 2750, 510 x 3600) were tested in liquid hydrogen using cold and warm noncondensible (gaseous helium) and condensable (gaseous hydrogen) pressurization schemes. Gases were conditioned from 0 to 90 K above the liquid temperature. Results clearly indicate a degradation in bubble point pressure using warm gas, with a greater reduction in performance using condensable over noncondensible pressurization. Degradation in the bubble point pressure is inversely proportional to screen porosity, as the coarsest mesh demonstrated the highest degradation. Results here have implication on both pressurization and LAD system design for all future cryogenic propulsion systems. A detailed review of historical heated gas tests is also presented for comparison to current results.

  15. Magma mixing enhanced by bubble segregation

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    That rising bubbles may significantly affect magma mixing paths has already been demon strated by analogue experiments. Here, for the first time, bubble-advection experiments are performed employing volcanic melts at magmatic temperatures. Cylinders of basaltic glass were placed below cylinders of rhyolite glass. Upon melting, interstitial air formed bubbles that rose into the rhyolite melt, thereby entraining tails of basaltic liquid. The formation of plume-like filaments of advected basalt within the rhyolite was characterized by microCT and subsequent high-resolution EMP analyses. Melt entrainment by bubble ascent appears to be an efficient mechanism for mingling volcanic melts of highly contrasting compositions and properties. MicroCT imaging reveals bubbles trailing each other and multiple filaments coalescing into bigger ones. Rheological modelling of the filaments yields viscosities of up to 2 orders of magnitude lower than for the surrounding rhyolitic liquid. Such a viscosity contrast implies that bubbles rising successively are likely to follow this pathway of low resistance that previously ascending bubbles have generated. Filaments formed by multiple bubbles would thus experience episodic replenishment with mafic material. Inevitable implications for the concept of bubble advection in magma mixing include thereby both an acceleration of mixing because of decreased viscous resistance for bubbles inside filaments and non-conventional diffusion systematics because of intermittent supply of mafic material (instead of a single pulse) inside a material. Inside the filaments, the mafic material was variably hybridised to andesitic through rhyolitic composition. Compositional profiles alone are ambiguous, however, to determine whether single or multiple bubbles were involved during formation of a filament. Statistical analysis, employing concentration variance as measure of homogenisation, demonstrates that also filaments appearing as single-bubble filaments

  16. Neural basis of economic bubble behavior.

    PubMed

    Ogawa, A; Onozaki, T; Mizuno, T; Asamizuya, T; Ueno, K; Cheng, K; Iriki, A

    2014-04-18

    Throughout human history, economic bubbles have formed and burst. As a bubble grows, microeconomic behavior ceases to be constrained by realistic predictions. This contradicts the basic assumption of economics that agents have rational expectations. To examine the neural basis of behavior during bubbles, we performed functional magnetic resonance imaging while participants traded shares in a virtual stock exchange with two non-bubble stocks and one bubble stock. The price was largely deflected from the fair price in one of the non-bubble stocks, but not in the other. Their fair prices were specified. The price of the bubble stock showed a large increase and battering, as based on a real stock-market bust. The imaging results revealed modulation of the brain circuits that regulate trade behavior under different market conditions. The premotor cortex was activated only under a market condition in which the price was largely deflected from the fair price specified. During the bubble, brain regions associated with the cognitive processing that supports order decisions were identified. The asset preference that might bias the decision was associated with the ventrolateral prefrontal cortex and the dorsolateral prefrontal cortex (DLPFC). The activity of the inferior parietal lobule (IPL) was correlated with the score of future time perspective, which would bias the estimation of future price. These regions were deemed to form a distinctive network during the bubble. A functional connectivity analysis showed that the connectivity between the DLPFC and the IPL was predominant compared with other connectivities only during the bubble. These findings indicate that uncertain and unstable market conditions changed brain modes in traders. These brain mechanisms might lead to a loss of control caused by wishful thinking, and to microeconomic bubbles that expand, on the macroscopic scale, toward bust.

  17. What's So Super about Superfoods?

    MedlinePlus

    ... Restaurant Deciphering the Menu Ordering Your Meal Eating Fast Food Dining Out Tips by Cuisine Physical Activity Fitness ... Most myths about super foods are perpetuated by marketing efforts, said Kris-Etherton, which is why most ...

  18. Energy Release and Transport in Super-Hot Solar Flares

    NASA Astrophysics Data System (ADS)

    Caspi, A.; McTiernan, J. M.; Shih, A.; Martinez Oliveros, J. C.; Allred, J. C.; Warren, H. P.

    2015-12-01

    Solar flares efficiently convert the magnetic energy stored in the Sun's complex coronal magnetic field into the kinetic energies of hot plasma, accelerated particles, and bulk flows. In intense flares, up to 10^32-33 ergs can go into heating plasma to tens of MK, accelerating electrons to hundreds of MeV and ions to tens of GeV, and ejecting 10^9-10 kg of coronal material into the heliosphere at thousands of km/s. However, the exact physical mechanisms behind these phenomena are poorly understood. For example, while "super-hot" (T > 30 MK) plasma temperatures appear to be common in the most intense, X-class flares, how that plasma is so efficiently heated remains unknown. Current studies favor an in situ heating process for super-hot plasma, versus chromospheric evaporation for cooler plasma, although the specific mechanism is under debate. X-class flares are also often associated with enhanced photospheric/chromospheric white light emission, which is itself poorly understood, and with fast (>1000 km/s) CMEs; super-hot flares are more commonly observed in eruptive two-ribbon arcade flares than in highly-confined events. These phenomena may well have common underlying drivers. We discuss the current understanding of super-hot plasma in solar flares, its formation, and evolution, based on observations from RHESSI, SDO/EVE, SDO/AIA, and other instruments. We discuss the energetics of these events and their relationship to white light enhancement and fast CMEs. We explore the possibility of energy deposition by accelerated ions as a common driver for super-hot plasmas and white light enhancement, and discuss future instrumentation -- both for CubeSats and Explorers -- that will provide a deeper understanding of these phenomena and their interrelationships.

  19. Global Structure of Isothermal Diffuse X-Ray Emission along the Fermi Bubbles

    NASA Astrophysics Data System (ADS)

    Kataoka, J.; Tahara, M.; Totani, T.; Sofue, Y.; Inoue, Y.; Nakashima, S.; Cheung, C. C.

    2015-07-01

    In our previous works, we found absorbed thermal X-ray plasma with kT ≃ 0.3 keV observed ubiquitously near the edges of the Fermi bubbles and interpreted this emission as weakly shock-heated Galactic halo gas. Here we present a systematic and uniform analysis of archival Suzaku (29 pointings; 6 newly presented) and Swift (68 pointings; 49 newly presented) data within Galactic longitudes | l| < 20° and latitude 5°≲ | b| < 60°, covering the whole extent of the Fermi bubbles. We show that the plasma temperature is constant at kT ≃ 0.30 ± 0.07 keV, while the emission measure (EM) varies by an order of magnitude, increasing toward the Galactic center (i.e., low | b| ) with enhancements at the North Polar Spur (NPS), SE-claw, and NW-clump features. Moreover, the EM distribution of kT ≃ 0.30 keV plasma is highly asymmetric in the northern and southern bubbles. Although the association of the X-ray emission with the bubbles is not conclusive, we compare the observed EM properties with simple models assuming (i) a filled halo without bubbles, whose gas density follows a hydrostatic isothermal model (King profile), and (ii) a bubble-in-halo in which two identical bubbles expand into the halo, forming thick shells of swept halo gas. We argue that the EM profile in the north (b > 0°) favors (ii), whereas that of the south (b < 0°) is rather close to (i), but a weak excess signature is clearly detected also in the south like NPS (South Polar Spur). Such an asymmetry, if due to the bubbles, cannot be fully understood only by the inclination of bubbles’ axis against the Galactic disk normal, thus suggesting asymmetric outflow due to different environmental/initial conditions.

  20. Effects of crystallization and bubble nucleation on the seismic properties of magmas

    NASA Astrophysics Data System (ADS)

    Tripoli, Barbara Andrea; Cordonnier, Benoit; Zappone, Alba; Ulmer, Peter

    2016-02-01

    Seismic tomography of potentially hazardous volcanoes is a prime tool to assess the location and dimensions of magmatic reservoirs. Seismic velocities are strongly affected by processes occurring within the conduit or in the magma chamber, such as crystallization and bubble exsolution. However, the limited number of constrained measurements does not allow yet to link seismic tomography and the textural state of a particular volcanic system. In this study, we investigated a chemically simplified melt in the system CaO-Na2O-Al2O3-SiO2-H2O-CO2, which undergoes plagioclase crystallization and bubble exsolution. A Paterson-type internally heated gas pressure apparatus was employed to measure ultrasonic velocities at a constant pressure of 250 MPa and at temperature from 850 to 700°C. Magmatic processes such as crystallization, bubble nucleation, and coalescence have been recognized throughout the measurements of seismic velocities in the laboratory. Compression and shear wave velocities increase nonlinearly during crystallization. At a crystal fraction exceeding 0.45, the formation of a crystal network favors the propagation of seismic waves through magmatic liquids. However, bubble nucleation induced by crystallization leads to an increase of magma compressibility resulting in a lowering of the wave propagation velocities. These two processes occur simultaneously and have a competing influence on the seismic properties of magmas. In addition, as already observed by previous authors, when the bubble fraction is less than 0.10, the decrease in seismic velocities is more pronounced than for higher bubble fractions. The effect of bubble coalescence on elastic properties is thus lower than the effect of bubble nucleation.

  1. Bubble confinement in flow boiling of FC-72 in a ''rectangular'' microchannel of high aspect ratio

    SciTech Connect

    Barber, Jacqueline; Brutin, David; Tadrist, Lounes; Sefiane, Khellil

    2010-11-15

    Boiling in microchannels remains elusive due to the lack of full understanding of the mechanisms involved. A powerful tool in achieving better comprehension of the mechanisms is detailed imaging and analysis of the two-phase flow at a fundamental level. Boiling is induced in a single microchannel geometry (hydraulic diameter 727 {mu}m), using a refrigerant FC-72, to investigate the effect of channel confinement on bubble growth. A transparent, metallic, conductive deposit has been developed on the exterior of the rectangular microchannel, allowing simultaneous uniform heating and visualisation to be achieved. The data presented in this paper is for a particular case with a uniform heat flux applied to the microchannel and inlet liquid mass flowrate held constant. In conjunction with obtaining high-speed images and videos, sensitive pressure sensors are used to record the pressure drop across the microchannel over time. Bubble nucleation and growth, as well as periodic slug flow, are observed in the microchannel test section. The periodic pressure fluctuations evidenced across the microchannel are caused by the bubble dynamics and instances of vapour blockage during confined bubble growth in the channel. The variation of the aspect ratio and the interface velocities of the growing vapour slug over time, are all observed and analysed. We follow visually the nucleation and subsequent both 'free' and 'confined' growth of a vapour bubble during flow boiling of FC-72 in a microchannel, from analysis of our results, images and video sequences with the corresponding pressure data obtained. (author)

  2. Cavitation inception from bubble nuclei

    PubMed Central

    Mørch, K. A.

    2015-01-01

    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

  3. Cavitation inception from bubble nuclei.

    PubMed

    Mørch, K A

    2015-10-06

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

    Acoustic properties are strongly affected by bubble size distribution in a bubbly medium. Measurement of the acoustic transmission becomes increasingly difficulty as the void fraction of the bubbly medium increases due to strong attenuation, while acoustic reflection can be measured more easily with increasing void fraction. The ABS ACOUSTIC BUBBLE SPECTROMETER®\\copyright, an instrument for bubble size measurement that is under development tries to take full advantage of the properties of acoustic propagation in bubbly media to extract bubble size distribution. Properties of both acoustic transmission and reflection in the bubbly medium from a range of short single-frequency bursts of acoustic waves at different frequencies are measured in an effort to deduce the bubble size distribution. With the combination of both acoustic transmission and reflection, assisted with validations from photography, the ABS ACOUSTIC BUBBLE SPECTROMETER®\\copyright has the potential to measure bubble size distributions in a wider void fraction range. This work was sponsored by Department of Energy SBIR program

  5. New approaches to hard bubble suppression

    NASA Technical Reports Server (NTRS)

    Henry, R. D.; Besser, P. J.; Warren, R. G.; Whitcomb, E. C.

    1973-01-01

    Description of a new double-layer method for the suppression of hard bubbles that is more versatile than previously reported suppression techniques. It is shown that it may be possible to prevent hard bubble generation without recourse to exchange coupling of multilayer films.

  6. Simple improvements to classical bubble nucleation models

    NASA Astrophysics Data System (ADS)

    Tanaka, Kyoko K.; Tanaka, Hidekazu; Angélil, Raymond; Diemand, Jürg

    2015-08-01

    We revisit classical nucleation theory (CNT) for the homogeneous bubble nucleation rate and improve the classical formula using a correct prefactor in the nucleation rate. Most of the previous theoretical studies have used the constant prefactor determined by the bubble growth due to the evaporation process from the bubble surface. However, the growth of bubbles is also regulated by the thermal conduction, the viscosity, and the inertia of liquid motion. These effects can decrease the prefactor significantly, especially when the liquid pressure is much smaller than the equilibrium one. The deviation in the nucleation rate between the improved formula and the CNT can be as large as several orders of magnitude. Our improved, accurate prefactor and recent advances in molecular dynamics simulations and laboratory experiments for argon bubble nucleation enable us to precisely constrain the free energy barrier for bubble nucleation. Assuming the correction to the CNT free energy is of the functional form suggested by Tolman, the precise evaluations of the free energy barriers suggest the Tolman length is ≃0.3 σ independently of the temperature for argon bubble nucleation, where σ is the unit length of the Lennard-Jones potential. With this Tolman correction and our prefactor one gets accurate bubble nucleation rate predictions in the parameter range probed by current experiments and molecular dynamics simulations.

  7. The Minnaert Bubble: An Acoustic Approach

    ERIC Educational Resources Information Center

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

    2008-01-01

    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…

  8. Air bubble bursting effect of lotus leaf.

    PubMed

    Wang, Jingming; Zheng, Yongmei; Nie, Fu-Qiang; Zhai, Jin; Jiang, Lei

    2009-12-15

    In this paper, a phenomenon of air bubbles quickly bursting within several milliseconds on a "self-cleaning" lotus leaf was described. This observation prompted the synthesis of artificial surfaces similar to that of the lotus leaf. The artificial leaf surfaces, prepared by photolithography and wet etching, showed a similar air bubble bursting effect. Smooth and rough silicon surfaces with an ordered nanostructure or patterned microstructure were utilized to study the contribution of the micro/nano hierarchical structures to this phenomenon of air bubble bursting. Air bubbles were found to burst on some superhydrophobic surfaces with microstructure (within 220 ms). However, air bubbles burst much more rapidly (within 13 ms) on similar surfaces with micro/nanostructure. The height, width, and spacing of hierarchical structures could also affect air bubble bursting, and the effect of the height was more obvious. When the height of hierarchical structures was around the height found in natural lotus papillae, the width and spacing were significant for air bubble bursting. An original model was proposed to further evaluate the reason why the micro/nano hierarchical rough structures had an excellent air bubble bursting effect, and the validity of the model was theoretically demonstrated.

  9. Continuous-data FIFO bubble shift register

    NASA Technical Reports Server (NTRS)

    Chen, T. T.

    1977-01-01

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

  10. Videotaping the Lifespan of a Soap Bubble.

    ERIC Educational Resources Information Center

    Ramme, Goran

    1995-01-01

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

  11. Drops and Bubble in Materials Science

    NASA Technical Reports Server (NTRS)

    Doremus, R. H.

    1982-01-01

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

  12. The Physics of Foams, Droplets and Bubbles

    ERIC Educational Resources Information Center

    Sarker, Dipak K.

    2013-01-01

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

  13. Measuring the surface tension of soap bubbles

    NASA Technical Reports Server (NTRS)

    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.

  14. Structure of nanoscale gas bubbles in metals

    SciTech Connect

    Caro, A. Schwen, D.; Martinez, E.

    2013-11-18

    A usual way to estimate the amount of gas in a bubble inside a metal is to assume thermodynamic equilibrium, i.e., the gas pressure P equals the capillarity force 2γ/R, with γ the surface energy of the host material and R the bubble radius; under this condition there is no driving force for vacancies to be emitted or absorbed by the bubble. In contrast to the common assumption that pressure inside a gas or fluid bubble is constant, we show that at the nanoscale this picture is no longer valid. P and density can no longer be defined as global quantities determined by an equation of state (EOS), but they become functions of position because the bubble develops a core-shell structure. We focus on He in Fe and solve the problem using both continuum mechanics and empirical potentials to find a quantitative measure of this effect. We point to the need of redefining an EOS for nanoscale gas bubbles in metals, which can be obtained via an average pressure inside the bubble. The resulting EOS, which is now size dependent, gives pressures that differ by a factor of two or more from the original EOS for bubble diameters of 1 nm and below.

  15. Gravity Wave Seeding of Equatorial Plasma Bubbles

    NASA Technical Reports Server (NTRS)

    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.

  16. Galactic Teamwork Makes Distant Bubbles

    NASA Astrophysics Data System (ADS)

    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

  17. The apparent ``super-Carnot'' efficiency of hurricanes: Nature's steam engine versus the steam locomotive

    NASA Astrophysics Data System (ADS)

    Denur, Jack

    2011-06-01

    The thermodynamics of the hurricane—Nature's steam engine—presents surprising contrasts with that of the steam locomotive. The hurricane rejects not only its waste heat at the lowest available temperature (as all heat engines must do to maximize efficiency), but also its work (that is, the kinetic energy of its winds) via frictional dissipation at the highest available temperature. We show how the hurricane's "super-Carnot" efficiency is consistent with the laws of thermodynamics. We also show that even standard heat engines can achieve "super-Carnot" efficiency, albeit via a different mechanism and to a far inferior degree than the hurricane.

  18. Magma mixing enhanced by bubble segregation

    NASA Astrophysics Data System (ADS)

    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

  19. Mechanism of single-bubble sonoluminescence

    NASA Astrophysics Data System (ADS)

    Yasui, Kyuichi

    1999-08-01

    The mechanism of the light emission of single-bubble sonoluminescence (SBSL) is studied theoretically based on the quasiadiabatic compression model. It is concluded that SBSL is not the blackbody radiation but the thermal radiation. It is clarified that the shape of the spectrum is determined by the temperature inside the bubble and the intensity is determined by the rates of the microscopic processes of the light emission. For a noble-gas bubble, radiative recombination of electrons and ions and electron-atom bremsstrahlung are the dominant microscopic processes of the light emission, and the intensity is mainly determined by the degree of ionization of the gas inside the bubble. It is also clarified that for a noble-gas bubble the pulse width of the light is nearly independent of wavelength.

  20. Mechanism of single-bubble sonoluminescence.

    PubMed

    Yasui, K

    1999-08-01

    The mechanism of the light emission of single-bubble sonoluminescence (SBSL) is studied theoretically based on the quasiadiabatic compression model. It is concluded that SBSL is not the blackbody radiation but the thermal radiation. It is clarified that the shape of the spectrum is determined by the temperature inside the bubble and the intensity is determined by the rates of the microscopic processes of the light emission. For a noble-gas bubble, radiative recombination of electrons and ions and electron-atom bremsstrahlung are the dominant microscopic processes of the light emission, and the intensity is mainly determined by the degree of ionization of the gas inside the bubble. It is also clarified that for a noble-gas bubble the pulse width of the light is nearly independent of wavelength.

  1. A simple collision model for small bubbles

    NASA Astrophysics Data System (ADS)

    Heitkam, Sascha; Sommer, Anna-Elisabeth; Drenckhan, Wiebke; Fröhlich, Jochen

    2017-03-01

    In this work, a model for the interaction force between a small bubble and a wall or another bubble is presented. The formulation is especially designed for Lagrangian calculations of bubble or soft sphere trajectories, with or without resolution of the continuous fluid. The force only relies on position and velocity of the bubble. The model does not include any empirical parameter that would have to be calibrated. Therefore, this force model is easy to implement. The formulation of the force is explicit, which means low computational effort. The collision of a small bubble with an inclined top wall is investigated numerically and experimentally. The computational results achieved with the new collision model show good agreement with the experiment.

  2. Towards observable signatures of other bubble universes

    SciTech Connect

    Aguirre, Anthony; Johnson, Matthew C.; Shomer, Assaf

    2007-09-15

    We evaluate the possibility of observable effects arising from collisions between vacuum bubbles in a universe undergoing false-vacuum eternal inflation. Contrary to conventional wisdom, we find that under certain assumptions most positions inside a bubble should have access to a large number of collision events. We calculate the expected number and angular size distribution of such collisions on an observer's 'sky', finding that for typical observers the distribution is anisotropic and includes many bubbles, each of which will affect the majority of the observer's sky. After a qualitative discussion of the physics involved in collisions between arbitrary bubbles, we evaluate the implications of our results, and outline possible detectable effects. In an optimistic sense, then, the present paper constitutes a first step in an assessment of the possible effects of other bubble universes on the cosmic microwave background and other observables.

  3. Bubble chamber as a trace chemical detector.

    PubMed

    Luo, X; McCreary, E I; Atencio, J H; McCown, A W; Sander, R K

    1998-08-20

    A novel concept for trace chemical analysis in liquids has been demonstrated. The technique utilizes light absorption in a superheated liquid. Although a superheated liquid is thermodynamically unstable, a high degree of superheating can be dynamically achieved for a short period of time. During this time the superheated liquid is extremely sensitive to boiling at nucleation sites produced by energy deposition. Observation of bubbles in the superheated liquid in some sense provides amplification of the initial energy deposition. Bubble chambers containing superheated liquids have been used to detect energetic particles; now a bubble chamber is used to detect a trace chemical in superheated liquid propane by observing bubble formation initiated by optical absorption. Crystal violet is used as a test case and can be detected at the subpart-per-10(12) level by using a Nd:YAG laser. The mechanism for bubble formation and ideas for further improvement are discussed.

  4. Air bubble migration rates as a proxy for bubble pressure distribution in ice cores

    NASA Astrophysics Data System (ADS)

    Dadic, Ruzica; Schneebeli, Martin; Bertler, Nancy

    2015-04-01

    Air bubble migration can be used as a proxy to measure the pressure of individual bubbles and can help constrain the gradual close-off of gas bubbles and the resulting age distribution of gases in ice cores. The close-off depth of single bubbles can vary by tens of meters, which leads to a distribution of pressures for bubbles at a given depth. The age distribution of gases (along with gas-age-ice-age differences) decreases the resolution of the gas level reconstructions from ice cores and limits our ability to determine the phase relationship between gas and ice, and thus, the impact of rapid changes of greenhouse gases on surface temperatures. For times of rapid climate change, including the last 150 years, and abrupt climate changes further back in the past, knowledge of the age distribution of the gases trapped in air bubbles will enable us to refine estimates of atmospheric changes. When a temperature gradient is applied to gas bubbles in an ice sample, the bubbles migrate toward warmer ice. This motion is caused by sublimation from the warm wall and subsequent frost deposition on the cold wall. The migration rate depends on ice temperature and bubble pressure and is proportional to the temperature gradient. The spread in migration rates for bubbles in the same samples at given temperatures should therefore reflect the variations in bubble pressures within a sample. Air bubbles with higher pressures would have been closed off higher in the firn column and thus have had time to equilibrate with the surrounding ice pressure, while air bubbles that have been closed off recently would have pressures that are similar to todays atmospheric pressure above the firn column. For ice under pressures up to ~13-16 bar, the pressure distribution of bubbles from a single depth provides a record of the trapping function of air bubbles in the firn column for a certain time in the past. We will present laboratory experiments on air bubble migration, using Antarctic ice core

  5. Comparative CFD Investigation on the Performance of a New Family of Super-Cavitating Hydrofoils

    NASA Astrophysics Data System (ADS)

    Brizzolara, S.; Bonfiglio, L.

    2015-12-01

    We present a CFD characterization of a new type of super-cavitating hydrofoil section designed to have optimal performance both in super-cavitating conditions and in sub-cavitating conditions (including transitional regime). The basic concepts of the new profile family are first introduced. Lift, drag and cavity shapes at different cavitation numbers are calculated for a new foil and compared with those of conventional sub-cavitating and super-cavitating profiles. Numerical calculations confirm the superior characteristics of the new hydrofoil family, which is able to attain high lift and efficiency both in sub-cavitating and super-cavitating conditions. Numerical calculations are based on a multi-phase fully turbulent URANSE solver with a bubble dynamic cavitation model to follow the generation and evaporation of the vapor phase. The new profile family, initially devised for ultra-high speed hydrofoil crafts, may result useful for diverse applications such as super-cavitating or surface-piercing propellers or high-speed sailing boats.

  6. Supercomputers: Super-polluters?

    SciTech Connect

    Mills, Evan; Mills, Evan; Tschudi, William; Shalf, John; Simon, Horst

    2008-04-08

    Thanks to imperatives for limiting waste heat, maximizing performance, and controlling operating cost, energy efficiency has been a driving force in the evolution of supercomputers. The challenge going forward will be to extend these gains to offset the steeply rising demands for computing services and performance.

  7. /N = 2 super W∞ algebra and its nonlinear realization through super KP formulation

    NASA Astrophysics Data System (ADS)

    Ghosh, Sasanka; Paul, Samir K.

    1995-01-01

    A nonlinear realizations of super W∞ algebra is shown to exist through a consistent superLax formulation of super KP hierarchy. The reduction of the superLax operator gives rise to the Lax operators for N = 2 generalized super KdV hierarchies, proposed by Inami and Kanno. The Lax equations are shown to be Hamiltonian and the associated Poisson bracket algebra among the superfields, consequently, gives rise to a realization of nonlinear super W∞ algebra.

  8. Plasma Turbulence in the Local Bubble

    NASA Astrophysics Data System (ADS)

    Spangler, Steven R.

    Turbulence in the Local Bubble could play an important role in the thermodynamics of the gas that is there. This turbulence could also determine the transport of cosmic rays and perhaps heat flow through this phase of the interstellar medium. The best astronomical technique for measuring turbulence in astrophysical plasmas is radio scintillation. Scintillation measurements yield information on the intensity and spectral characteristics of plasma turbulence between the source of the radio waves and the observer. Measurements of the level of scattering to the nearby pulsar B0950+08 by Philips and Clegg in 1992 showed a markedly lower value for the line-of-sight averaged turbulent intensity parameter than is observed for other pulsars, qualitatively consistent with radio wave propagation through a highly rarefied plasma. In this paper, we discuss the observational progress that has been made since that time. The main development has been improved measurements of pulsar parallaxes with the Very Long Baseline Array. This provides better knowledge of the media along the lines of sight. At present, there are four pulsars (B0950+08, B1133+16, J0437-4715, and B0809+74) whose lines of sight seem to lie mainly within the local bubble. The mean densities and line of sight components of the interstellar magnetic field along these lines of sight are smaller than nominal values for pulsars, but not by as large a factor as might be expected. Three of the four pulsars also have measurements of interstellar scintillation. The value of the parameter is smaller than normal for two of them, but is completely nominal for the third. This inconclusive status of affairs could be improved by measurements and analysis of "arcs" in "secondary spectra" of pulsars, which contain information on the location and intensity of localized screens of turbulence along the lines of sight. Similar data could be obtained from observations of highly compact extragalactic radio sources

  9. Plasma Turbulence in the Local Bubble

    NASA Astrophysics Data System (ADS)

    Spangler, Steven R.

    2009-03-01

    Turbulence in the Local Bubble could play an important role in the thermodynamics of the gas that is there. This turbulence could also determine the transport of cosmic rays and perhaps heat flow through this phase of the interstellar medium. The best astronomical technique for measuring turbulence in astrophysical plasmas is radio scintillation. Scintillation measurements yield information on the intensity and spectral characteristics of plasma turbulence between the source of the radio waves and the observer. Measurements of the level of scattering to the nearby pulsar B0950+08 by Philips and Clegg in 1992 showed a markedly lower value for the line-of-sight averaged turbulent intensity parameter < C {/N 2}> than is observed for other pulsars, qualitatively consistent with radio wave propagation through a highly rarefied plasma. In this paper, we discuss the observational progress that has been made since that time. The main development has been improved measurements of pulsar parallaxes with the Very Long Baseline Array. This provides better knowledge of the media along the lines of sight. At present, there are four pulsars (B0950+08, B1133+16, J0437-4715, and B0809+74) whose lines of sight seem to lie mainly within the local bubble. The mean densities and line of sight components of the interstellar magnetic field along these lines of sight are smaller than nominal values for pulsars, but not by as large a factor as might be expected. Three of the four pulsars also have measurements of interstellar scintillation. The value of the parameter < C {/N 2}> is smaller than normal for two of them, but is completely nominal for the third. This inconclusive status of affairs could be improved by measurements and analysis of “arcs” in “secondary spectra” of pulsars, which contain information on the location and intensity of localized screens of turbulence along the lines of sight. Similar data could be obtained from observations of highly compact extragalactic

  10. Mechanism of single-bubble sonoluminescence

    NASA Astrophysics Data System (ADS)

    An, Yu

    2006-08-01

    Considering almost all the effective processes of physics and chemical reaction in our numerical computation model, we investigate the mechanism of single bubble sonoluminescence (SBSL). For those sonoluminescing single bubbles in water at its flashing phase, the numerical simulation reveals that if the temperature inside the bubble is not high enough which may result in the plenty oxygen molecules and OH radicals undissociated, such as the case of a single argon bubble in 20°C or 34°C water, the radiative attachment of electrons to oxygen molecules and OH radicals contributes most to the SBSL; if the temperature inside the bubble is higher which makes most of the water vapor inside the bubble dissociate into oxygen and hydrogen atoms, such as the case of an argon bubble or a helium bubble in 0°C water, the radiative attachment of electrons to oxygen and hydrogen atoms dominates the SBSL; if the temperature is still higher, such as the case of a xenon bubble in 0°C water, the contribution from electron-neutral atom bremsstrahlung and electron-ion bremsstrahlung and recombination would be comparable with the contribution from the radiative attachment of electrons to oxygen and hydrogen atoms, and they together dominate the SBSL. For sonoluminescing single bubbles in those low vapor pressure liquids, such as in 85wt.% sulphuric acid, the electron-neutral atom bremsstrahlung and the electron-ion bremsstrahlung and recombination contribute most to the continuous spectrum part of SBSL. The present calculation also provides good interpretations to those observed phenomena, such as emitted photon numbers, the width of optical pulses, the blackbody radiation like spectra. The temperature fitted by the blackbody radiation formula is very different from that calculated by the gas dynamics equations. Besides, the effect of chemical dissociation on the shock wave is also discussed.

  11. Mechanism of single-bubble sonoluminescence.

    PubMed

    An, Yu

    2006-08-01

    Considering almost all the effective processes of physics and chemical reaction in our numerical computation model, we investigate the mechanism of single bubble sonoluminescence (SBSL). For those sonoluminescing single bubbles in water at its flashing phase, the numerical simulation reveals that if the temperature inside the bubble is not high enough which may result in the plenty oxygen molecules and OH radicals undissociated, such as the case of a single argon bubble in 20 degrees C or 34 degrees C water, the radiative attachment of electrons to oxygen molecules and OH radicals contributes most to the SBSL; if the temperature inside the bubble is higher which makes most of the water vapor inside the bubble dissociate into oxygen and hydrogen atoms, such as the case of an argon bubble or a helium bubble in 0 degrees C water, the radiative attachment of electrons to oxygen and hydrogen atoms dominates the SBSL; if the temperature is still higher, such as the case of a xenon bubble in 0 degrees C water, the contribution from electron-neutral atom bremsstrahlung and electron-ion bremsstrahlung and recombination would be comparable with the contribution from the radiative attachment of electrons to oxygen and hydrogen atoms, and they together dominate the SBSL. For sonoluminescing single bubbles in those low vapor pressure liquids, such as in 85 wt.% sulphuric acid, the electron-neutral atom bremsstrahlung and the electron-ion bremsstrahlung and recombination contribute most to the continuous spectrum part of SBSL. The present calculation also provides good interpretations to those observed phenomena, such as emitted photon numbers, the width of optical pulses, the blackbody radiation like spectra. The temperature fitted by the blackbody radiation formula is very different from that calculated by the gas dynamics equations. Besides, the effect of chemical dissociation on the shock wave is also discussed.

  12. Primary Particles from different bubble generation techniques

    NASA Astrophysics Data System (ADS)

    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. Microlayer formation characteristics in pool isolated bubble boiling of water

    NASA Astrophysics Data System (ADS)

    Yabuki, Tomohide; Nakabeppu, Osamu

    2016-10-01

    Investigation of microlayer formation characteristics is important for developing a reliable nucleate boiling heat transfer model based on accurate physical mechanisms. Although formation mechanisms of the thin liquid film in two-phase flow of confined spaces, such as micro-tubes and closely positioned parallel plates, have been thoroughly studied, microlayer formation mechanisms of pool boiling have been sparsely studied. In a previous study (Yabuki and Nakabeppu in Int J Heat Mass Transf 76:286-297, 2014; Int J Heat Mass Transf 100:851-860, 2016), the spatial distribution of initial microlayer thickness under pool boiling bubbles was calculated by transient heat conduction analysis using the local wall temperature measured with a MEMS sensor. In this study, the hydrodynamic characteristics of microlayer formation in pool boiling were investigated using the relationship between derived initial microlayer thickness and microlayer formation velocity determined by transient local heat flux data. The trend of microlayer thickness was found to change depending on the thickness of the velocity boundary layer outside the bubble foot. When the boundary layer thickness was thin, the initial microlayer thickness was determined by the boundary layer thickness, and the initial microlayer thickness proportionally increased with increasing boundary layer thickness. On the other hand, when the boundary layer was thick, the initial microlayer thickness decreased with increasing boundary layer thickness. In this thick boundary layer region, the momentum balance in the dynamic meniscus region became important, in addition to the boundary layer thickness, and the microlayer thickness, made dimensionless using boundary layer thickness, correlated with the Bond number.

  14. The application of super wavelet finite element on temperature-pressure coupled field simulation of LPG tank under jet fire

    NASA Astrophysics Data System (ADS)

    Zhao, Bin

    2015-02-01

    Temperature-pressure coupled field analysis of liquefied petroleum gas (LPG) tank under jet fire can offer theoretical guidance for preventing the fire accidents of LPG tank, the application of super wavelet finite element on it is studied in depth. First, review of related researches on heat transfer analysis of LPG tank under fire and super wavelet are carried out. Second, basic theory of super wavelet transform is studied. Third, the temperature-pressure coupled model of gas phase and liquid LPG under jet fire is established based on the equation of state, the VOF model and the RNG k-ɛ model. Then the super wavelet finite element formulation is constructed using the super wavelet scale function as interpolating function. Finally, the simulation is carried out, and results show that the super wavelet finite element method has higher computing precision than wavelet finite element method.

  15. Subcooled Boiling Near a Heated Wall

    SciTech Connect

    T.A. Trabold; C.C. Maneri; P.F. Vassallo; D.M. Considine

    2000-10-27

    Experimental measurements of void fraction, bubble frequency, and velocity are obtained in subcooled R-134a flowing over a heated flat plate near an unheated wall and compared to analytical predictions. The measurements were obtained for a fixed system pressure and mass flow rate (P = 2.4 MPa and w = 106 kg/hr) at various inlet liquid temperatures. During the experiments, electrical power was applied at a constant rate to one side of the test section. The local void fraction data, acquired with a hot-film anemometer probe, showed the existence of a significant peak near the heated wall and a smaller secondary peak near the unheated wall for the larger inlet subcoolings. Local vapor velocity data, taken with the hot-film probe and a laser Doppler velocimeter, showed broad maxima near the centerline between the heated and unheated plates. Significant temperature gradients near the heated wall were observed for large inlet subcooling. Bubble size data, inferred from measurements of void fraction, bubble frequency and vapor velocity, when combined with the measured bubble chord length distributions illustrate the transition from pure three dimensional spherical to two-dimensional planar bubble flow, the latter being initiated when the bubbles fill the gap between the plates. These various two-phase flow measurements were used for development of a multidimensional, four-field calculational method; comparisons of the data to the calculations show reasonable agreement.

  16. Effect of surfactants on single bubble sonoluminescence behavior and bubble surface stability.

    PubMed

    Leong, Thomas; Yasui, Kyuichi; Kato, Kazumi; Harvie, Dalton; Ashokkumar, Muthupandian; Kentish, Sandra

    2014-04-01

    The effect of surfactants on the radial dynamics of a single sonoluminescing bubble has been investigated. Experimentally, it is observed that an increase in the surfactant concentration leads to a decline in the oscillation amplitude and hence light emission intensity. Numerical simulations support this result, showing that under the driving pressures required to achieve single bubble sonoluminescence (SBSL), the surface properties, namely, the surface elasticity and dilatational viscosity, contribute to the damping of the radial amplitude in the bubble oscillation. In most cases this stabilizes the bubble surface, and contributes to a decreased light intensity. A stronger driving pressure is necessary to achieve equivalent light emission to a surfactant-free bubble. However, as the driving pressure is increased, the surface stability also decreases, making it practically very difficult for a bubble to achieve high SBSL intensities in concentrated surfactant solutions. Although more stable owing to more mild pulsations, the instability mechanism for a surfactant-coated bubble at higher ambient radii is more likely to be of the Rayleigh-Taylor type than that of a clean bubble at the same given acoustic parameters, which can lead to bubble disintegration before correcting mechanisms can bring the bubble back into the stable sonoluminescence regime.

  17. Nonlinear ultrasonic waves in bubbly liquids with nonhomogeneous bubble distribution: Numerical experiments.

    PubMed

    Vanhille, Christian; Campos-Pozuelo, Cleofé

    2009-06-01

    This paper deals with the nonlinear propagation of ultrasonic waves in mixtures of air bubbles in water, but for which the bubble distribution is nonhomogeneous. The problem is modelled by means of a set of differential equations which describes the coupling of the acoustic field and bubbles vibration, and solved in the time domain via the use and adaptation of the SNOW-BL code. The attenuation and nonlinear effects are assumed to be due to the bubbles exclusively. The nonhomogeneity of the bubble distribution is introduced by the presence of bubble layers (or clouds) which can act as acoustic screens, and alters the behaviour of the ultrasonic waves. The effect of the spatial distribution of bubbles on the nonlinearity of the acoustic field is analyzed. Depending on the bubble density, dimension, shape, and position of the layers, its effects on the acoustic field change. Effects such as shielding and resonance of the bubbly layers are especially studied. The numerical experiments are carried out in two configurations: linear and nonlinear, i.e. for low and high excitation pressure amplitude, respectively, and the features of the phenomenon are compared. The parameters of the medium are chosen such as to reproduce air bubbly water involved in the stable cavitation process.

  18. Influence of bubble size, diffuser width, and flow rate on the integral behavior of bubble plumes

    NASA Astrophysics Data System (ADS)

    Fraga, Bruño.; Stoesser, Thorsten

    2016-06-01

    A large-eddy simulation based Eulerian-Lagrangian model is employed to quantify the impact of bubble size, diffuser diameter, and gas flow rate on integral properties of bubble plumes, such as the plume's width, centerline velocity, and mass flux. Calculated quantities are compared with experimental data and integral model predictions. Furthermore, the LES data were used to assess the behavior of the entrainment coefficient, the momentum amplification factor, and the bubble-to-momentum spread ratio. It is found that bubble plumes with constant bubble size and smaller diameter behave in accordance with integral plume models. Plumes comprising larger and non-uniform bubble sizes appear to deviate from past observations and model predictions. In multi-diameter bubble plumes, a bubble self-organisation takes place, i.e., small bubbles cluster in the center of the plume whilst large bubbles are found at the periphery of the plume. Multi-diameter bubble plumes also feature a greater entrainment rate than single-size bubble plumes, as well as a higher spread ratio and lower turbulent momentum rate. Once the plume is fully established, the size of the diffuser does not appear to affect integral properties of bubble plumes. However, plume development is affected by the diffuser width, as larger release areas lead to a delayed asymptotic behavior of the plume and consequently to a lower entrainment and higher spread ratio. Finally, the effect of the gas flow rate on the integral plume is studied and is deemed very relevant with regards to most integral plume properties and coefficients. This effect is already fairly well described by integral plume models.

  19. Microwave emission of sonoluminescing bubbles.

    PubMed

    Hammer, Dominik; Frommhold, Lothar

    2002-07-01

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

  20. Numerical Analysis of Nucleate Boiling on High Heat-Flux and High Subcooling Condition for Reactivity Initiation Accident

    SciTech Connect

    Heo, S.; Koshizuka, S.; Oka, Y.

    2002-07-01

    This paper shows the numerical simulation study on the growth of the bubble in the transient pool boiling using MPS-MAFL method. The growth process of a bubble with the different initial radii is calculated in a high heat-flux and high subcooling condition expected in nuclear reactor core during RIA. The smaller initial radius is, the earlier the growth starts. The initial bubble radius has little effect on the growth initiation time and the bubble departure radius. (authors)

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

    PubMed Central

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

    2016-01-01

    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. PMID:27034255

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

    PubMed

    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.

  3. Inert gas bubbles in bcc Fe

    NASA Astrophysics Data System (ADS)

    Gai, Xiao; Smith, Roger; Kenny, S. D.

    2016-03-01

    The properties of inert gas bubbles in bcc Fe is examined using a combination of static energy minimisation, molecular dynamics and barrier searching methods with empirical potentials. Static energy minimisation techniques indicate that for small Ar and Xe bubbles, the preferred gas to vacancy ratio at 0 K is about 1:1 for Ar and varies between 0.5:1 and 0.9:1 for Xe. In contrast to interstitial He atoms and small He interstitial clusters, which are highly mobile in the lattice, Ar and Xe atoms prefer to occupy substitutional sites and any interstitials present in the lattice soon displace Fe atoms and become substitutional. If a pre-existing bubble is present then there is a capture radius around a bubble which extends up to the 6th neighbour position. Collision cascades can also enlarge an existing bubble by the capture of vacancies. Ar and Xe can diffuse through the lattice through vacancy driven mechanisms but with relatively high energy barriers of 1.8 and 2.0 eV respectively. This indicates that Ar and Xe bubbles are much harder to form than bubbles of He and that such gases produced in a nuclear reaction would more likely be dispersed at substitutional sites without the help of increased temperature or radiation-driven mechanisms.

  4. Bubbles in live-stranded dolphins

    PubMed Central

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

    2012-01-01

    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 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

  5. Bubble Growth and Detachment from a Needle

    NASA Astrophysics Data System (ADS)

    Shusser, Michael; Rambod, Edmond; Gharib, Morteza

    1999-11-01

    The release of bubbles from an underwater nozzle or orifice occurs in large number of applications, such as perforated plate columns, blood oxygenators and various methods of water treatment. It is also a widely used method in laboratory research on multiphase flow and acoustics for generating small bubbles in a controlled fashion. We studied experimentally the growth and pinch-off of air bubbles released from a submerged needle into a quiescent liquid or a liquid flowing parallel to the needle. Micron-sized bubbles were generated by an air-liquid dispenser. High-speed imaging was performed to study the formation and detachment of bubbles from the tip of the needle. The impact of the needle diameter was investigated and the size and number of produced bubbles were assessed for different flow rates of air and for different velocities of the imposed upward liquid flow. The results were compared with available theoretical models and numerical computations. The existence of a critical gas flow rate and two regimes of bubble growth were verified.

  6. Bubbles in live-stranded dolphins.

    PubMed

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

    2012-04-07

    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.

  7. Acoustic Bubble Removal from Boiling Surfaces

    NASA Technical Reports Server (NTRS)

    Prosperetti, Andrea

    2002-01-01

    The object of the study was the investigation of the forces generated by standing acoustic waves on vapor bubbles, both far and near boundaries. In order to accomplish this objective, in view of the scarcity of publications on the topic, it has been necessary to build an edifice of knowledge about vapor bubbles in sound and flow fields from the ground up, as it were. We have addressed problems of gradually greater difficulty as follows: 1. In the first place, the physics of an stationary isolated bubble subject to a sound field in an unbounded liquid was addressed; 2. The case of bubbles translating in a stationary pressure field was then considered; 3. This was followed by a study of the combined effects of sound and translation, 4. And of a neighboring boundary 5. Finally, a new method to deal with nonspherical bubbles was developed- In addition to the work on vapor bubbles, some studies on gas bubbles were conducted in view of NASA's interest in the phenomenon of sonoluminescence.

  8. Understanding Peat Bubbles: Biogeochemical-Hydrological Linkages

    NASA Astrophysics Data System (ADS)

    Strack, M.

    2009-05-01

    Decomposition of organic matter in peatland ecosystems produces gaseous end-products that can accumulate at depth and result in the build up of free-phase gas below the water table. This free-phase gas, or bubbles, reduces hydraulic conductivity, alters hydrologic and chemical gradients, and affects productivity surface vegetation through its role in peat buoyancy. In terms of greenhouse gas dynamics, these bubbles are likely the dominant subsurface stock of methane (CH4) and release of this CH4 to the atmosphere via ebullition may account for a significant portion of total efflux. Despite the importance of entrapped bubbles for peatland ecohydrological function there is still little known about how the quantity of bubbles varies between peatland types and at smaller scales within a peatland. Profiles of bubbles collected from several locations within four peatlands reveal that bubble volume varies significant among peatlands, between microforms and with depth. Previous studies also suggest that ebullition is spatially and temporally variable. This spatial variability may have important impacts on system ecohydrology and should be incorporated in models of peatland hydrology and development. This requires the difficult task of mapping bubble volume in three dimensions and over large areas. The potential for geophysical methods and the use of surface features to address this task will be discussed.

  9. The Age of the Local Interstellar Bubble

    NASA Astrophysics Data System (ADS)

    Abt, H. A.

    2011-12-01

    The Local Interstellar Bubble is an irregular-shaped region that happens to be centered on the Sun. It has minimum and maximum radii of 50 and 150 pc. The density inside the bubble is 1/200 of that outside and the temperature is about 1 million K. Therefore the density times the temperature at the borders is constant, so the bubble is stable and can be very old. It was evidently cleared of interstellar gas by one or more supernovae. Because of the low density, no new stars could have been formed in the bubble since the supernovae explosions. We looked for the youngest stars within the bubble. In the central region they are B7 so that region is about 160 million years old. The Pleiades lobe has B3 stars so it is about 60 million years old. The lobe toward the galactic center has O9.5 stars so it is about 4 million years old. In fact, it has a pulsar with a spin-down time of 3.76 million years, so that must be the remnant of the supernova that created that region. The bubble has measureable OVI and CII lines, but no HI, confirming its high temperature. The Sun was probably formed elsewhere and happened to drift into the bubble some millions of years ago. The full text of this talk was published in the Astronomical Journal (Abt 2011).

  10. Mean bubble formation time in DNA denaturation

    NASA Astrophysics Data System (ADS)

    Murthy, K. P. N.; Schütz, G. M.

    2011-12-01

    Using the Poland-Scheraga free energy of the bubble size in a double-stranded DNA we propose a discrete stochastic dynamics for the number of base pairs N of an unzipped bubble. We derive a universal subdiffusive growth TN~A/Γ(b+2)N1+b for the mean formation time (MBFT) TN of a bubble of size N. The amplitude A is determined by the bubble initiation rate and time spent in the denaturated state. We examine critically the significance of these results for experiments. We find: i) Our results provide a new method to determine whether the order of the denaturation transition is discontinuous (b>2) or not. ii) The asymptotic growth law of TN is reached with 10% precision already for small bubbles of sizes >20. However, the amplitude is very sensitive to modeling details for small bubbles. iii) In an equilibrium sample of bubbles up to size N the averaged MBFT grows diffusively, TN*~N2, irrespective of b.

  11. Transition process leading to microbubble emission boiling on horizontal circular heated surface in subcooled pool

    NASA Astrophysics Data System (ADS)

    Ueno, Ichiro; Ando, Jun; Horiuchi, Kazuna; Saiki, Takahito; Kaneko, Toshihiro

    2016-11-01

    Microbubble emission boiling (MEB) produces a higher heat flux than critical heat flux (CHF) and therefore has been investigated in terms of its heat transfer characteristics as well as the conditions under which MEB occurs. Its physical mechanism, however, is not yet clearly understood. We carried out a series of experiments to examine boiling on horizontal circular heated surfaces of 5 mm and of 10 mm in diameter, in a subcooled pool, paying close attention to the transition process to MEB. High-speed observation results show that, in the MEB regime, the growth, condensation, and collapse of the vapor bubbles occur within a very short time. In addition, a number of fine bubbles are emitted from the collapse of the vapor bubbles. By tracking these tiny bubbles, we clearly visualize that the collapse of the vapor bubbles drives the liquid near the bubbles towards the heated surface, such that the convection field around the vapor bubbles under MEB significantly differs from that under nucleate boiling. Moreover, the axial temperature gradient in a heated block (quasi-heat flux) indicates a clear difference between nucleate boiling and MEB. A combination of quasi-heat flux and the measurement of the behavior of the vapor bubbles allows us to discuss the transition to MEB. This work was financially supported by the 45th Research Grant in Natural Sciences from The Mitsubishi Foundation (2014 - 2015), and by Research Grant for Boiler and Pressurized Vessels from The Japan Boiler Association (2016).

  12. Dynamics of two-dimensional bubbles.

    PubMed

    Piedra, Saúl; Ramos, Eduardo; Herrera, J Ramón

    2015-06-01

    The dynamics of two-dimensional bubbles ascending under the influence of buoyant forces is numerically studied with a one-fluid model coupled with the front-tracking technique. The bubble dynamics are described by recording the position, shape, and orientation of the bubbles as functions of time. The qualitative properties of the bubbles and their terminal velocities are described in terms of the Eötvos (ratio of buoyancy to surface tension) and Archimedes numbers (ratio of buoyancy to viscous forces). The terminal Reynolds number result from the balance of buoyancy and drag forces and, consequently, is not an externally fixed parameter. In the cases that yield small Reynolds numbers, the bubbles follow straight paths and the wake is steady. A more interesting behavior is found at high Reynolds numbers where the bubbles follow an approximately periodic zigzag trajectory and an unstable wake with properties similar to the Von Karman vortex street is formed. The dynamical features of the motion of single bubbles are compared to experimental observations of air bubbles ascending in a water-filled Hele-Shaw cell. Although the comparison is not strictly valid in the sense that the effect of the lateral walls is not incorporated in the model, most of the dynamical properties observed are in good qualitative agreement with the numerical calculations. Hele-Shaw cells with different gaps have been used to determine the degree of approximation of the numerical calculation. It is found that for the relation between the terminal Reynolds number and the Archimedes number, the numerical calculations are closer to the observations of bubble dynamics in Hele-Shaw cells of larger gaps.

  13. Pressure waves in a supersaturated bubbly magma

    USGS Publications Warehouse

    Kurzon, I.; Lyakhovsky, V.; Navon, O.; Chouet, B.

    2011-01-01

    We study the interaction of acoustic pressure waves with an expanding bubbly magma. The expansion of magma is the result of bubble growth during or following magma decompression and leads to two competing processes that affect pressure waves. On the one hand, growth in vesicularity leads to increased damping and decreased wave amplitudes, and on the other hand, a decrease in the effective bulk modulus of the bubbly mixture reduces wave velocity, which in turn, reduces damping and may lead to wave amplification. The additional acoustic energy originates from the chemical energy released during bubble growth. We examine this phenomenon analytically to identify conditions under which amplification of pressure waves is possible. These conditions are further examined numerically to shed light on the frequency and phase dependencies in relation to the interaction of waves and growing bubbles. Amplification is possible at low frequencies and when the growth rate of bubbles reaches an optimum value for which the wave velocity decreases sufficiently to overcome the increased damping of the vesicular material. We examine two amplification phase-dependent effects: (1) a tensile-phase effect in which the inserted wave adds to the process of bubble growth, utilizing the energy associated with the gas overpressure in the bubble and therefore converting a large proportion of this energy into additional acoustic energy, and (2) a compressive-phase effect in which the pressure wave works against the growing bubbles and a large amount of its acoustic energy is dissipated during the first cycle, but later enough energy is gained to amplify the second cycle. These two effects provide additional new possible mechanisms for the amplification phase seen in Long-Period (LP) and Very-Long-Period (VLP) seismic signals originating in magma-filled cracks.

  14. Nonlinear Bubble Interactions in Acoustic Pressure Fields

    NASA Technical Reports Server (NTRS)

    Barbat, Tiberiu; Ashgriz, Nasser; Liu, Ching-Shi

    1996-01-01

    The systems consisting of a two-phase mixture, as clouds of bubbles or drops, have shown many common features in their responses to different external force fields. One of particular interest is the effect of an unsteady pressure field applied to these systems, case in which the coupling of the vibrations induced in two neighboring components (two drops or two bubbles) may result in an interaction force between them. This behavior was explained by Bjerknes by postulating that every body that is moving in an accelerating fluid is subjected to a 'kinetic buoyancy' equal with the product of the acceleration of the fluid multiplied by the mass of the fluid displaced by the body. The external sound wave applied to a system of drops/bubbles triggers secondary sound waves from each component of the system. These secondary pressure fields integrated over the surface of the neighboring drop/bubble may result in a force additional to the effect of the primary sound wave on each component of the system. In certain conditions, the magnitude of these secondary forces may result in significant changes in the dynamics of each component, thus in the behavior of the entire system. In a system containing bubbles, the sound wave radiated by one bubble at the location of a neighboring one is dominated by the volume oscillation mode and its effects can be important for a large range of frequencies. The interaction forces in a system consisting of drops are much smaller than those consisting of bubbles. Therefore, as a first step towards the understanding of the drop-drop interaction subject to external pressure fluctuations, it is more convenient to study the bubble interactions. This paper presents experimental results and theoretical predictions concerning the interaction and the motion of two levitated air bubbles in water in the presence of an acoustic field at high frequencies (22-23 KHz).

  15. The Minnaert bubble: an acoustic approach

    NASA Astrophysics Data System (ADS)

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

    2008-11-01

    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-Pérot 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.

  16. Dynamics of two-dimensional bubbles

    NASA Astrophysics Data System (ADS)

    Piedra, Saúl; Ramos, Eduardo; Herrera, J. Ramón

    2015-06-01

    The dynamics of two-dimensional bubbles ascending under the influence of buoyant forces is numerically studied with a one-fluid model coupled with the front-tracking technique. The bubble dynamics are described by recording the position, shape, and orientation of the bubbles as functions of time. The qualitative properties of the bubbles and their terminal velocities are described in terms of the Eötvos (ratio of buoyancy to surface tension) and Archimedes numbers (ratio of buoyancy to viscous forces). The terminal Reynolds number result from the balance of buoyancy and drag forces and, consequently, is not an externally fixed parameter. In the cases that yield small Reynolds numbers, the bubbles follow straight paths and the wake is steady. A more interesting behavior is found at high Reynolds numbers where the bubbles follow an approximately periodic zigzag trajectory and an unstable wake with properties similar to the Von Karman vortex street is formed. The dynamical features of the motion of single bubbles are compared to experimental observations of air bubbles ascending in a water-filled Hele-Shaw cell. Although the comparison is not strictly valid in the sense that the effect of the lateral walls is not incorporated in the model, most of the dynamical properties observed are in good qualitative agreement with the numerical calculations. Hele-Shaw cells with different gaps have been used to determine the degree of approximation of the numerical calculation. It is found that for the relation between the terminal Reynolds number and the Archimedes number, the numerical calculations are closer to the observations of bubble dynamics in Hele-Shaw cells of larger gaps.

  17. MAGNETIC TOPOLOGY OF BUBBLES IN QUIESCENT PROMINENCES

    SciTech Connect

    Dudik, J.; Aulanier, G.; Schmieder, B.; Zapior, M.; Heinzel, P.

    2012-12-10

    We study a polar-crown prominence with a bubble and its plume observed in several coronal filters by the SDO/AIA and in H{alpha} by the MSDP spectrograph in Bialkow (Poland) to address the following questions: what is the brightness of prominence bubbles in EUV with respect to the corona outside of the prominence and the prominence coronal cavity? What is the geometry and topology of the magnetic field in the bubble? What is the nature of the vertical threads seen within prominences? We find that the brightness of the bubble and plume is lower than the brightness of the corona outside of the prominence, and is similar to that of the coronal cavity. We constructed linear force-free models of prominences with bubbles, where the flux rope is perturbed by inclusion of parasitic bipoles. The arcade field lines of the bipole create the bubble, which is thus devoid of magnetic dips. Shearing the bipole or adding a second one can lead to cusp-shaped prominences with bubbles similar to the observed ones. The bubbles have complex magnetic topology, with a pair of coronal magnetic null points linked by a separator outlining the boundary between the bubble and the prominence body. We conjecture that plume formation involves magnetic reconnection at the separator. Depending on the viewing angle, the prominence can appear either anvil-shaped with predominantly horizontal structures, or cusp-shaped with predominantly vertical structuring. The latter is an artifact of the alignment of magnetic dips with respect to the prominence axis and the line of sight.

  18. Gaseous bubble oscillations in anisotropic non-Newtonian fluids under influence of high-frequency acoustic field

    NASA Astrophysics Data System (ADS)

    Golykh, R. N.

    2016-06-01

    Progress of technology and medicine dictates the ever-increasing requirements (heat resistance, corrosion resistance, strength properties, impregnating ability, etc.) for non-Newtonian fluids and materials produced on their basis (epoxy resin, coating materials, liquid crystals, etc.). Materials with improved properties obtaining is possible by modification of their physicochemical structure. One of the most promising approaches to the restructuring of non-Newtonian fluids is cavitation generated by high-frequency acoustic vibrations. The efficiency of cavitation in non-Newtonian fluid is determined by dynamics of gaseous bubble. Today, bubble dynamics in isotropic non-Newtonian fluids, in which cavitation bubble shape remains spherical, is most full investigated, because the problem reduces to ordinary differential equation for spherical bubble radius. However, gaseous bubble in anisotropic fluids which are most wide kind of non-Newtonian fluids (due to orientation of macromolecules) deviates from spherical shape due to viscosity dependence on shear rate direction. Therefore, the paper presents the mathematical model of gaseous bubble dynamics in anisotropic non-Newtonian fluids. The model is based on general equations for anisotropic non-Newtonian fluid flow. The equations are solved by asymptotic decomposition of fluid flow parameters. It allowed evaluating bubble size and shape evolution depending on rheological properties of liquid and acoustic field characteristics.

  19. Current-induced enhancement of DNA bubble creation

    NASA Astrophysics Data System (ADS)

    Gu, Lei; Fu, Hua-Hua

    2016-05-01

    Current-induced heating of short double-stranded DNA chains is studied within a two-probe transport setup by using the Langevin approach. The electrons are modeled by a tight-binding Hamiltonian. The DNA atomic motion is described by the Peyrard-Bishop-Dauxois atomic potential, coupled with electrons through the Holstein interaction. The solvent environment is accounted for as a classical heat bath. Voltage biases of 0.1˜ 0.5 {{V}} can effectively break the base pairs and lead to the melting transition, which can be detected from the resulting significant reduction of the conductance. When the bias increases, the opening of base pairs near the leads with higher chemical potential is suppressed and bubble (localized separation of the double strand) formation becomes asymmetric. Our results suggest that the voltage bias can excite the base pairs, hence increases the chemical activity of DNA.

  20. Three-dimensional magnetic bubble memory system

    NASA Technical Reports Server (NTRS)

    Stadler, Henry L. (Inventor); Katti, Romney R. (Inventor); Wu, Jiin-Chuan (Inventor)

    1994-01-01

    A compact memory uses magnetic bubble technology for providing data storage. A three-dimensional arrangement, in the form of stacks of magnetic bubble layers, is used to achieve high volumetric storage density. Output tracks are used within each layer to allow data to be accessed uniquely and unambiguously. Storage can be achieved using either current access or field access magnetic bubble technology. Optical sensing via the Faraday effect is used to detect data. Optical sensing facilitates the accessing of data from within the three-dimensional package and lends itself to parallel operation for supporting high data rates and vector and parallel processing.