The behavior of vapor bubbles during boiling enhanced with acoustics and open microchannels

NASA Astrophysics Data System (ADS)

Boziuk, Thomas; Smith, Marc K.; Glezer, Ari

2012-11-01

Boiling heat transfer on a submerged heated surface is enhanced by combining a grid of surface micromachined open channels and ultrasonic acoustic actuation to control the formation and evolution of vapor bubbles and to inhibit the instability that leads to film boiling at the critical heat flux (CHF). The microchannels provide nucleation sites for vapor bubble formation and enable the entrainment of bulk subcooled fluid to these sites for sustained evaporation. Acoustic actuation excites interfacial oscillations of the detached bubbles and leads to accelerated condensation in the bulk fluid, thereby limiting the formation of vapor columns that precede the CHF instability. The combined effects of microchannels and acoustic actuation are investigated experimentally with emphasis on bubble nucleation, growth, detachment, and condensation. It is shown that this hybrid approach leads to a significant increase in the critical heat flux, a reduction of the vapor mass above the surface, and the breakup of low-frequency vapor slug formation. A large-scale model of the microchannel grid reveals details of the flow near the nucleation site and shows that the presence of the microchannels decreases the surface superheat at a given heat flux. Supported by ONR.

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.

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

Dynamics of vapor bubbles growth at boiling resulting from enthalpy excess of the surrounding superheated liquid and sound pulses generated by bubbles

NASA Astrophysics Data System (ADS)

Dorofeev, B. M.; Volkova, V. I.

2016-01-01

The results of experiments investigating the exponential dependence of the vapor bubble radius on time at saturated boiling are generalized. Three different methods to obtain this dependence are suggested: (1) by the application of the transient heat conduction equation, (2) by using the correlations of energy conservation, and (3) by solving a similar electrodynamic problem. Based on the known experimental data, the accuracy of the dependence up to one percent and a few percent accuracy of its description based on the sound pressure generated by a vapor bubble have been determined. A significant divergence of the power dependence of the vapor bubble radius on time (with an exponent of 1/2) with the experimental results and its inadequacy for the description of the sound pulse generated by the bubble have been demonstrated.

Motion of liquid plugs between vapor bubbles in capillary tubes: a comparison between fluids

NASA Astrophysics Data System (ADS)

Bertossi, Rémi; Ayel, Vincent; Mehta, Balkrishna; Romestant, Cyril; Bertin, Yves; Khandekar, Sameer

2017-11-01

Pulsating heat pipes (PHP) are now well-known devices in which liquid/vapor slug flow oscillates in a capillary tube wound between hot and cold sources. In this context, this paper focuses on the motion of the liquid plug, trapped between vapor bubbles, moving in capillary tubes, to try to better understand the thermo-physical phenomena involved in such devices. This study is divided into three parts. In the first part, an experimental study presents the evolution of the vapor pressure during the evaporation process of a liquid thin film deposited from a liquid plug flowing in a heated capillary tube: it is found that the behavior of the generated and removed vapor can be very different, according to the thermophysical properties of the fluids. In the second part, a transient model allows to compare, in terms of pressure and duration, the motion of a constant-length liquid plug trapped between two bubbles subjected to a constant difference of vapor pressure: the results highlight that the performances of the four fluids are also very different. Finally, a third model that can be considered as an improvement of the second one, is also presented: here, the liquid slug is surrounded by two vapor bubbles, one subjected to evaporation, the pressure in both bubbles is now a result of the calculation. This model still allows comparing the behaviors of the fluid. Even if our models are quite far from a complete model of a real PHP, results do indicate towards the applicability of different fluids as suitable working fluids for PHPs, particularly in terms of the flow instabilities which they generate.

Numerical study on the splitting of a vapor bubble in the ultrasonic assisted EDM process with the curved tool and workpiece.

PubMed

Shervani-Tabar, M T; Seyed-Sadjadi, M H; Shabgard, M R

2013-01-01

Electrical discharge machining (EDM) is a powerful and modern method of machining. In the EDM process, a vapor bubble is generated between the tool and the workpiece in the dielectric liquid due to an electrical discharge. In this process dynamic behavior of the vapor bubble affects machining process. Vibration of the tool surface affects bubble behavior and consequently affects material removal rate (MRR). In this paper, dynamic behavior of the vapor bubble in an ultrasonic assisted EDM process after the appearance of the necking phenomenon is investigated. It is noteworthy that necking phenomenon occurs when the bubble takes the shape of an hour-glass. After the appearance of the necking phenomenon, the vapor bubble splits into two parts and two liquid jets are developed on the boundaries of the upper and lower parts of the vapor bubble. The liquid jet developed on the upper part of the bubble impinges to the tool and the liquid jet developed on the lower part of the bubble impinges to the workpiece. These liquid jets cause evacuation of debris from the gap between the tool and the workpiece and also cause erosion of the workpiece and the tool. Curved tool and workpiece affect the shape and the velocity of the liquid jets during splitting of the vapor bubble. In this paper dynamics of the vapor bubble after its splitting near the curved tool and workpiece is investigated in three cases. In the first case surfaces of the tool and the workpiece are flat, in the second case surfaces of the tool and the workpiece are convex and in the third case surfaces of the tool and workpiece are concave. Numerical results show that in the third case, the velocity of liquid jets which are developed on the boundaries of the upper and lower parts of the vapor bubble after its splitting have the highest magnitude and their shape are broader than the other cases. Copyright © 2012 Elsevier B.V. All rights reserved.

"Pressure Blocking" Effect in the Growing Vapor Bubble in a Highly Superheated Liquid

NASA Astrophysics Data System (ADS)

Zudin, Yu. B.; Zenin, V. V.

2016-09-01

The problem on the growth of a vapor bubble in a liquid whose superheating enthalpy exceeds the phase transition heat has been considered. A physical model of the "pressure blocking" in the bubble is presented. The problem for the conditions of the experiment on the effervescence of a butane drop has been solved numerically. An algorithm for constructing an analytical solution of the problem on the bubble growth in a highly superheated liquid is proposed.

A Generalized Eulerian-Lagrangian Analysis, with Application to Liquid Flows with Vapor Bubbles

NASA Technical Reports Server (NTRS)

Dejong, Frederik J.; Meyyappan, Meyya

1993-01-01

Under a NASA MSFC SBIR Phase 2 effort an analysis has been developed for liquid flows with vapor bubbles such as those in liquid rocket engine components. The analysis is based on a combined Eulerian-Lagrangian technique, in which Eulerian conservation equations are solved for the liquid phase, while Lagrangian equations of motion are integrated in computational coordinates for the vapor phase. The novel aspect of the Lagrangian analysis developed under this effort is that it combines features of the so-called particle distribution approach with those of the so-called particle trajectory approach and can, in fact, be considered as a generalization of both of those traditional methods. The result of this generalization is a reduction in CPU time and memory requirements. Particle time step (stability) limitations have been eliminated by semi-implicit integration of the particle equations of motion (and, for certain applications, the particle temperature equation), although practical limitations remain in effect for reasons of accuracy. The analysis has been applied to the simulation of cavitating flow through a single-bladed section of a labyrinth seal. Models for the simulation of bubble formation and growth have been included, as well as models for bubble drag and heat transfer. The results indicate that bubble formation is more or less 'explosive'. for a given flow field, the number density of bubble nucleation sites is very sensitive to the vapor properties and the surface tension. The bubble motion, on the other hand, is much less sensitive to the properties, but is affected strongly by the local pressure gradients in the flow field. In situations where either the material properties or the flow field are not known with sufficient accuracy, parametric studies can be carried out rapidly to assess the effect of the important variables. Future work will include application of the analysis to cavitation in inducer flow fields.

Microspectroscopic imaging of solution plasma: How do its physical properties and chemical species evolve in atmospheric-pressure water vapor bubbles?

NASA Astrophysics Data System (ADS)

Yui, Hiroharu; Banno, Motohiro

2018-01-01

In this article, we review the development of scientific instruments for obtaining information on the evolution of physical properties and chemical species of solution plasma (SP). When a pulsed high voltage is applied between electrodes immersed in an aqueous solution, SP is formed in water vapor bubbles transiently generated in the solution under atmospheric pressure. To clarify how SP emerges in water vapor bubbles and is sustained in solutions, an instrument with micrometer spatial resolution and nanosecond temporal resolution is required. To meet these requirements, a microscopic system with a custom-made optical discharge cell was newly developed, where the working distance between the SP and the microscopic objective lens was minimized. A hollow electrode equipped in the discharge cell also enabled us to control the chemical composition in water vapor bubbles. To study the spatial and temporal evolutions of chemical species in micrometer and nano- to microsecond regions, a streak camera with a spectrometer and a CCD detector with a time-gated electronic device were combined with the microscope system. The developed instrument is expected to contribute to providing a new means of developing new schemes for chemical reactions and material syntheses.

Determination of the Accommodation Coefficient Using Vapor/gas Bubble Dynamics in an Acoustic Field

NASA Technical Reports Server (NTRS)

Gumerov, Nail A.; Hsiao, Chao-Tsung; Goumilevski, Alexei G.; Allen, Jeff (Technical Monitor)

2001-01-01

Nonequilibrium liquid/vapor phase transformations can occur in superheated or subcooled liquids in fast processes such as in evaporation in a vacuum. The rate at which such a phase transformation occurs depends on the "condensation" or "accommodation" coefficient, Beta, which is a property of the interface. Existing measurement techniques for Beta are complex and expensive. The development of a relatively inexpensive and reliable technique for measurement of Beta for a wide range of substances and temperatures is of great practical importance. The dynamics of a bubble in an acoustic field strongly depends on the value of Beta. It is known that near the saturation temperature, small vapor bubbles grow under the action of an acoustic field due to "rectified heat transfer." This finding can be used as the basis for an effective measurement technique of Beta. We developed a theory of vapor bubble behavior in an isotropic acoustic wave and in a plane standing acoustic wave. A numerical code was developed which enables simulation of a variety of experimental situations and accurately takes into account slowly evolving temperature. A parametric study showed that the measurement of Beta can be made over a broad range of frequencies and bubble sizes. We found several interesting regimes and conditions which can be efficiently used for measurements of Beta. Measurements of Beta can be performed in both reduced and normal gravity environments.

Near Surface Vapor Bubble Layers in Buoyant Low Stretch Burning of Polymethylmethacrylate

NASA Technical Reports Server (NTRS)

Olson, Sandra L.; Tien, J. S.

1999-01-01

Large-scale buoyant low stretch stagnation point diffusion flames over solid fuel (polymethylmethacrylate) were studied for a range of aerodynamic stretch rates of 2-12/ sec which are of the same order as spacecraft ventilation-induced stretch in a microgravity environment. An extensive layer of polymer material above the glass transition temperature is observed. Unique phenomena associated with this extensive glass layer included substantial swelling of the burning surface, in-depth bubble formation, and migration and/or elongation of the bubbles normal to the hot surface. The bubble layer acted to insulate the polymer surface by reducing the effective conductivity of the solid. The reduced in-depth conduction stabilized the flame for longer than expected from theory neglecting the bubble layer. While buoyancy acts to move the bubbles deeper into the molten polymer, thermocapillary forces and surface regression both act to bring the bubbles to the burning surface. Bubble layers may thus be very important in low gravity (low stretch) burning of materials. As bubbles reached the burning surface, monomer fuel vapors jetted from the surface, enhancing burning by entraining ambient air flow. Popping of these bubbles at the surface can expel burning droplets of the molten material, which may increase the fire propagation hazards at low stretch rates.

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.

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

Simulation and analysis of collapsing vapor-bubble clusters with special emphasis on potentially erosive impact loads at walls

NASA Astrophysics Data System (ADS)

Ogloblina, Daria; Schmidt, Steffen J.; Adams, Nikolaus A.

2018-06-01

Cavitation is a process where a liquid evaporates due to a pressure drop and re-condenses violently. Noise, material erosion and altered system dynamics characterize for such a process for which shock waves, rarefaction waves and vapor generation are typical phenomena. The current paper presents novel results for collapsing vapour-bubble clusters in a liquid environment close to a wall obtained by computational fluid mechanics (CFD) simulations. The driving pressure initially is 10 MPa in the liquid. Computations are carried out by using a fully compressible single-fluid flow model in combination with a conservative finite volume method (FVM). The investigated bubble clusters (referred to as "clouds") differ by their initial vapor volume fractions, initial stand-off distances to the wall and by initial bubble radii. The effects of collapse focusing due to bubble-bubble interaction are analysed by investigating the intensities and positions of individual bubble collapses, as well as by the resulting shock-induced pressure field at the wall. Stronger interaction of the bubbles leads to an intensification of the collapse strength for individual bubbles, collapse focusing towards the center of the cloud and enhanced re-evaporation. The obtained results reveal collapse features which are common for all cases, as well as case-specific differences during collapse-rebound cycles. Simultaneous measurements of maximum pressures at the wall and within the flow field and of the vapor volume evolution show that not only the primary collapse but also subsequent collapses are potentially relevant for erosion.

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

USGS Publications Warehouse

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

2011-01-01

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

High-speed microjet generation using laser-induced vapor bubbles

NASA Astrophysics Data System (ADS)

Oudalov, Nikolai; Tagawa, Yoshiyuki; Peters, Ivo; Visser, Claas-Willem; van der Meer, Devaraj; Prosperetti, Andrea; Sun, Chao; Lohse, Detlef

2011-11-01

The generation and evolution of microjets are studied both experimentally and numerically. The jets are generated by focusing a laser pulse into a microscopic capillary tube (~50 μm) filled with water-based red dye. A vapor bubble is created instantly after shooting the laser (<1 μs), sending out a shockwave towards the curved free surface at which the high-speed microjet forms. The process of jet formation is captured using high-speed recordings at 1.0 × 106 fps. The velocity of the microjets can reach speeds of ~850 m/s while maintaining a very sharp geometry. The high-speed recordings enable us to study the effect of several parameters on the jet velocity, e.g. the absorbed energy and the distance between the laser spot and the free surface.The results show a clear dependence on these variables, even for supersonic speeds. Comparisons with numerical simulations confirm the nature of these dependencies.

Gas embolotherapy: Bubble evolution in acoustic droplet vaporization and design of a benchtop microvascular model

NASA Astrophysics Data System (ADS)

Wong, Zheng Zheng

This work was motivated by an ongoing development of a potential embolotherapy technique to occlude blood flow to tumors using gas bubbles selectively formed by in vivo acoustic droplet vaporization (ADV) of liquid perfluorocarbon droplets. Mechanisms behind the ADV, transport and lodging of emboli need to be understood before gas embolotherapy can translate to the clinic. Evolution of a bubble from acoustic droplet vaporization in a rigid tube, under physiological and room temperature conditions, was observed via ultra-high speed imaging. Effective radii and radial expansion ratios were obtained by processing the images using Image] software. At physiological temperature, a radial expansion ratio of 5.05 was attained, consistent with theoretical prediction. The initial radial growth rate was linear, after which the growth rate increased proportionally with square root of time. Nondimensionalization revealed that the subsequent growth rate also varied inversely with square root of initial radius. Eventually growth became asymptotic. No collapse was observed. A theoretical model derived from a modified Bernoulli equation, and a computational model by Ye & Bull (2004), were compared respectively with experimental results. Initial growth rates were predicted correctly by both models. Experimental results showed heavy damping of growth rate as the bubble grew towards the wall, whereas both models predicted an overshoot in growth followed by multiple oscillations. The theoretical model broke down near the wall; the computational model gave a reasonable bubble shape near the wall but would require correct initial pressure values to be accurate. At room temperature, the expansion ratio shot to 1.43 initially and oscillated down to 1.11, far below the theoretical prediction. Failure of the bubble to expand fully could be due to unconsumed or condensed liquid perfluorocarbon. A new fabrication method via non-lithographic means was devised to make a circular

Observation of vapor bubble of non-azeotropic binary mixture in microgravity with a two-wavelength interferometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abe, Yoshiyuki; Iwasaki, Akira

1999-07-01

Although non-azeotropic mixtures are considered to be promising working fluids in advanced energy conversion systems, the primary technical problems in the heat transfer degradation in phase change processes cause economical handicap to wide-spread applications. The boiling behavior of mixtures still remains a number of basic questions being not answered yet, and the present authors believe that the most essential information for the boiling process in non-azeotropic mixtures is how temperature and concentration profiles are developed around the bubbles. The present study attempts at understanding fundamental heat and mass transfer mechanisms in nucleate pool boiling of non-azeotropic binary mixtures, and withmore » the knowledge to develop a passive boiling heat transfer enhancement eventually. To this end, the authors have employed microgravity environment for rather detailed observation around vapor bubbles in the course of boiling inception and bubble growth. A two-wavelength Mach-Zehnder interferometer has been developed, which withstands mechanical shock caused by gravity change from very low gravity of the order of 10{sup {minus}5} g to relatively high gravity of approximately 8 g exposed during deceleration period. A series of experiments on single vapor bubbles for CFC113 single component and CFC12/CFC112 non-azeotropic binary mixture have been conducted under a high quality microgravity conditions available in 10-second free-fall facility of Japan Microgravity Center (JAMIC). The results for single component liquid showed a strong influence due to Marangoni effect caused by the temperature profile around the bubble. The results for non-azeotropic binary mixture showed, however, considerably different behavior from single component liquid. Both temperature and concentration profiles around a single vapor bubble were evaluated from the interferograms. The temperature and concentration layers established around the bubbles were nearly one order of

CVB: The Constrained Vapor Bubble 40 mm Capillary Experiment on the ISS

NASA Technical Reports Server (NTRS)

Wayner, Peter C., Jr.; Kundan, Akshay; Plawsky, Joel

2013-01-01

Discuss the Constrained Vapor Bubble (CVB) 40mm Fin experiment on the ISS and how it aims to achieve a better understanding of the physics of evaporation and condensation and how they affect cooling processes in microgravity using a remotely controlled microscope and a small cooling device

Effect of metabolic gases and water vapor, perfluorocarbon emulsions, and nitric oxide on tissue bubbles during decompression sickness.

PubMed

Randsøe, Thomas

2016-05-01

In aviation and diving, fast decrease in ambient pressure, such as during accidental loss of cabin pressure or when a diver decompresses too fast to sea level, may cause nitrogen (N2) bubble formation in blood and tissue resulting in decompression sickness (DCS). Conventional treatment of DCS is oxygen (O2) breathing combined with recompression.  However, bubble kinetic models suggest, that metabolic gases, i.e. O2 and carbon dioxide (CO2), and water vapor contribute significantly to DCS bubble volume and growth at hypobaric altitude exposures. Further, perfluorocarbon emulsions (PFC) and nitric oxide (NO) donors have, on an experimental basis, demonstrated therapeutic properties both as treatment and prophylactic intervention against DCS. The effect was ascribed to solubility of respiratory gases in PFC, plausible NO elicited nuclei demise and/or N2 washout through enhanced blood flow rate. Accordingly, by means of monitoring injected bubbles in exposed adipose tissue or measurements of spinal evoked potentials (SEPs) in anaesthetized rats, the aim of this study was to: 1) evaluate the contribution of metabolic gases and water vapor to bubble volume at different barometrical altitude exposures, 2) clarify the O2 contribution and N2 solubility from bubbles during administration of PFC at normo- and hypobaric conditions and, 3) test the effect of different NO donors on SEPs during DCS upon a hyperbaric air dive and, to study the influence of  NO on tissue bubbles at high altitude exposures. The results support the bubble kinetic models and indicate that metabolic gases and water vapor contribute significantly to bubble volume at 25 kPa (~10,376 m above sea level) and constitute a threshold for bubble stabilization or decay at the interval of 47-36 kPa (~6,036 and ~7,920 m above sea level). The effect of the metabolic gases and water vapor seemed to compromise the therapeutic properties of both PFC and NO at altitude, while PFC significantly increased bubble

Corrosion casts of big bubbles formed during deep anterior lamellar keratoplasty.

PubMed

Feizi, Sepehr; Kanavi, Mozhgan Rezaei; Kharaghani, Davood; Balagholi, Sahar; Meskinfam, Masoumeh; Javadi, Mohammad Ali

2016-11-01

To characterize the walls of big bubbles formed during deep anterior lamellar keratoplasty (DALK) using the corrosion casting technique. Fresh corneoscleral buttons with normal transparency and without any known eye diseases (n = 11) were obtained from 11 human donors. A 20-gauge needle was used to inject a solution of 20 % polyvinyl alcohol (PVA) immediately beneath the corneal endothelium to form big bubbles in eight corneoscleral buttons. In the second experiment on three corneoscleral buttons, a big bubble was first formed by air injection beneath the endothelium. Thereafter, 20 % PVA was injected into the bubble space. Scanning electron microscopy was used to characterize the surfaces of the casts, which replicated the walls of the big bubbles. A type-1 bubble was formed in all corneas. In one cornea, one type-1 bubble was initially formed centrally, and while it was enlarged, an eccentric type-2 bubble appeared. Scanning electron microscopy showed that the casts of type-1 bubbles had two distinct surfaces. The anterior surface demonstrated several holes or pits, depending on the material used for the bubble formation, whereas the posterior surface exhibited an uneven surface. The anterior and posterior surfaces of the type-2 cast were more or less similar. A communication measuring 531.9 µm in length and 171.4 µm in diameter was found between the two bubbles. The corrosion casting technique provides a permanent three-dimensional record of the potential spaces and barriers in the posterior corneal stroma, which explains several features associated with big-bubble DALK.

Thulium fiber laser induced vapor bubbles using bare, tapered, ball, hollow steel, and muzzle brake fiber optic tips

NASA Astrophysics Data System (ADS)

Gonzalez, David A.; Hardy, Luke A.; Hutchens, Thomas C.; Irby, Pierce B.; Fried, Nathaniel M.

2018-02-01

This study characterizes laser-induced vapor bubbles for five distal fiber optic tip configurations, to provide insight into stone retropulsion experienced during laser ablation of kidney stones. A TFL with 1908-nm wavelength delivered 34 mJ energy per pulse at 500-μs pulse duration through five different fibers: 100-μm-core/170-μm-OD bare fiber tip, 150-μm- to 300-μm-core tapered fiber tip, 100-μm-core/300-μm-OD ball tip fiber, 100-μm-core/340- μm-OD hollow steel tip fiber, and 100-μm-core/560-μm-OD muzzle brake fiber tip. A high speed camera with 10- μm spatial and 9.5-μs temporal resolution imaged vapor bubble dynamics. A needle hydrophone measured pressure transients in forward (0°) and side (90°) directions while placed at a 6.8 +/- 0.4 mm distance from fiber tip. Maximum bubble dimensions (width/length) averaged 0.7/1.5, 1.0/1.6, 0.5/1.1, 0.8/1.9, and 0.7/1.5 mm, for bare, tapered, ball, hollow steel, and muzzle tips, respectively (n=5). The hollow steel tip exhibited the most elongated vapor bubble shape, translating into increased forward pressure in this study and consistent with higher stone retropulsion in previous reports. Relative pressures (a.u.) in (forward/side) directions averaged 1.7/1.6, 2.0/2.0, 1.4/1.2, 6.8/1.1, and 0.3/1.2, for each fiber tip (n=5). For hollow steel tip, forward pressure was 4× higher than for bare fiber. For the muzzle brake fiber tip, forward pressure was 5× lower than for bare fiber. Bubble dimensions and pressure measurements demonstrated that the muzzle tip reduced forward pressure by partially venting vapors through side holes, consistent with lower stone retropulsion observed in previous reports.

Influence of the Fluid on the Parameters and Limits of Bubble Detonation

NASA Astrophysics Data System (ADS)

Pinaev, A. V.; Prokhorov, E. S.

2017-12-01

The compression and inflammation of reactive gas bubbles in bubble detonation waves have been studied, and the considerable influence of the fluid (liquid or vapor) on the detonation parameters has been found. It has been shown numerically that the final values of the pressure and temperature significantly decrease if the temperature dependence of the adiabatic index is taken into account at the compression stage. The parameters of reactive gas combustion products in the bubble have been calculated in terms of an equilibrium model, and the influence of the fluid that remains in the bubble in the form of microdroplets and vapor on these parameters has been investigated.

Characterization of Acoustic Droplet Vaporization Using MRI

NASA Astrophysics Data System (ADS)

Li, David; Allen, Steven; Hernandez-Garcia, Luis; Bull, Joseph

2013-11-01

Acoustic droplet vaporization (ADV) is the selective vaporization of liquid droplets to form larger gas bubbles. The ADV process is currently being researched for biomedical applications such as gas embolotherapy, drug delivery, and phase-change contrast agents. In this study an albumin encapsulated dodecafluoropentane (DDFP, CAS: 678-26-2) microdroplet suspension was vaporized using a single element focused (f/2, D = 19 mm) 3.5 MHz transducer (Panametrics A321S, Olympus, Waltham, MA). The resulting DDFP bubble clouds were imaged using both bright field microscopy and MRI (Varian 7T, Agilent Technologies Inc., Santa Clara, CA). Field distortions due to DDFP bubble generation were characterized against the bright field images as a function of acoustic power and bubble cloud size. Experimentally a direct correlation between bubble cloud dimensions generated and field distortions seen in the MRI was observed. Additionally, MR velocimetry was used to measure the flow field resulting from ADV. The field distortions due to the bubbles were further characterized by modeling Maxwell's equations using COMSOL (COMSOL Inc., Burlington, MA). The ability to characterize ADV with alternative imaging modalities may prove useful in further development of ADV based biomedical therapies.

Thulium fiber laser-induced vapor bubble dynamics using bare, tapered, ball, hollow steel, and muzzle brake fiber optic tips

NASA Astrophysics Data System (ADS)

Gonzalez, David A.; Hardy, Luke A.; Hutchens, Thomas C.; Irby, Pierce B.; Fried, Nathaniel M.

2018-03-01

This study characterizes laser-induced vapor bubble dynamics for five different distal fiber optic tip configurations, to provide insight into stone retropulsion commonly experienced during laser ablation of kidney stones. A thulium fiber laser with 1908-nm wavelength delivered 34-mJ energy per pulse at 500-μs pulse duration through five different fibers such as 100-μm-core / 170-μm-OD bare fiber tip, 150- to 300-μm-core tapered fiber tip, 100-μm-core / 300-μm-OD ball tip fiber, 100-μm-core / 340-μm-OD hollow steel tip fiber, and 100-μm-core / 560-μm-OD muzzle brake fiber tip. A high-speed camera with 10-μm-spatial and 9.5-μs-temporal resolution was used to image the vapor bubble dynamics. A needle hydrophone measured pressure transients in the forward (0 deg) and side (90 deg) directions while placed at a 6.8 ± 0.4 mm distance from the distal fiber tip. Maximum bubble dimensions (width/length) averaged 0.7/1.5, 1.0/1.6, 0.5/1.1, 0.8/1.9, and 0.7 / 1.5 mm, for bare, tapered, ball, hollow steel, and muzzle brake fiber tips, respectively (n = 5). The hollow steel tip exhibited the most elongated vapor bubble shape, translating into increased forward pressure in this study and consistent with higher stone retropulsion in previous reports. Relative pressures (a.u.) in (forward/side) directions averaged 1.7/1.6, 2.0/2.0, 1.4/1.2, 6.8/1.1, and 0.3/1.2, for each fiber tip (n = 5). For the hollow steel tip, forward pressure was 4 × higher than for the bare fiber. For the muzzle brake fiber tip, forward pressure was 5 × lower than the bare fiber. Bubble dimensions and pressure measurements demonstrated that the muzzle brake fiber tip reduced forward pressure by partially venting vapors through the portholes, which is consistent with the observation of lower stone retropulsion in previous reports.

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.

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.

Bubble transport in bifurcations

NASA Astrophysics Data System (ADS)

Bull, Joseph; Qamar, Adnan

2017-11-01

Motivated by a developmental gas embolotherapy technique for cancer treatment, we examine the transport of bubbles entrained in liquid. In gas embolotherapy, infarction of tumors is induced by selectively formed vascular gas bubbles that originate from acoustic vaporization of vascular droplets. In the case of non-functionalized droplets with the objective of vessel occlusion, the bubbles are transported by flow through vessel bifurcations, where they may split prior to eventually reach vessels small enough that they become lodged. This splitting behavior affects the distribution of bubbles and the efficacy of flow occlusion and the treatment. In these studies, we investigated bubble transport in bifurcations using computational and theoretical modeling. The model reproduces the variety of experimentally observed splitting behaviors. Splitting homogeneity and maximum shear stress along the vessel walls is predicted over a variety of physical parameters. Maximum shear stresses were found to decrease with increasing Reynolds number. The initial bubble length was found to affect the splitting behavior in the presence of gravitational asymmetry. This work was supported by NIH Grant R01EB006476.

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.

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.

Experimental study of flash boiling spray vaporization through quantitative vapor concentration and liquid temperature measurements

NASA Astrophysics Data System (ADS)

Zhang, Gaoming; Hung, David L. S.; Xu, Min

2014-08-01

Flash boiling sprays of liquid injection under superheated conditions provide the novel solutions of fast vaporization and better air-fuel mixture formation for internal combustion engines. However, the physical mechanisms of flash boiling spray vaporization are more complicated than the droplet surface vaporization due to the unique bubble generation and boiling process inside a superheated bulk liquid, which are not well understood. In this study, the vaporization of flash boiling sprays was investigated experimentally through the quantitative measurements of vapor concentration and liquid temperature. Specifically, the laser-induced exciplex fluorescence technique was applied to distinguish the liquid and vapor distributions. Quantitative vapor concentration was obtained by correlating the intensity of vapor-phase fluorescence with vapor concentration through systematic corrections and calibrations. The intensities of two wavelengths were captured simultaneously from the liquid-phase fluorescence spectra, and their intensity ratios were correlated with liquid temperature. The results show that both liquid and vapor phase of multi-hole sprays collapse toward the centerline of the spray with different mass distributions under the flash boiling conditions. Large amount of vapor aggregates along the centerline of the spray to form a "gas jet" structure, whereas the liquid distributes more uniformly with large vortexes formed in the vicinity of the spray tip. The vaporization process under the flash boiling condition is greatly enhanced due to the intense bubble generation and burst. The liquid temperature measurements show strong temperature variations inside the flash boiling sprays with hot zones present in the "gas jet" structure and vortex region. In addition, high vapor concentration and closed vortex motion seem to have inhibited the heat and mass transfer in these regions. In summary, the vapor concentration and liquid temperature provide detailed information

Volumes of critical bubbles from the nucleation theorem

NASA Astrophysics Data System (ADS)

Wilemski, Gerald

2006-09-01

A corollary of the nucleation theorem due to Kashchiev [Nucleation: Basic Theory with Applications (Butterworth-Heinemann, Oxford, 2000)] allows the volume V* of a critical bubble to be determined from nucleation rate measurements. The original derivation was limited to one-component, ideal gas bubbles with a vapor density much smaller than that of the ambient liquid. Here, an exact result is found for multicomponent, nonideal gas bubbles. Provided a weak density inequality holds, this result reduces to Kashchiev's simple form which thus has a much broader range of applicability than originally expected. Limited applications to droplets are also mentioned, and the utility of the pT,x form of the nucleation theorem as a sum rule is noted.

Bioeffects due to acoustic droplet vaporization

NASA Astrophysics Data System (ADS)

Bull, Joseph

2015-11-01

Encapsulated micro- and nano-droplets can be vaporized via ultrasound, a process termed acoustic droplet vaporization. Our interest is primarily motivated by a developmental gas embolotherapy technique for cancer treatment. In this methodology, infarction of tumors is induced by selectively formed vascular gas bubbles that arise from the acoustic vaporization of vascular microdroplets. Additionally, the microdroplets may be used as vehicles for localized drug delivery, with or without flow occlusion. In this talk, we examine the dynamics of acoustic droplet vaporization through experiments and theoretical/computational fluid mechanics models, and investigate the bioeffects of acoustic droplet vaporization on endothelial cells and in vivo. Early timescale vaporization events, including phase change, are directly visualized using ultra-high speed imaging, and the influence of acoustic parameters on droplet/bubble dynamics is discussed. Acoustic and fluid mechanics parameters affecting the severity of endothelial cell bioeffects are explored. These findings suggest parameter spaces for which bioeffects may be reduced or enhanced, depending on the objective of the therapy. This work was supported by NIH grant R01EB006476.

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

NASA Astrophysics Data System (ADS)

Lazic, V.; Jovicevic, S.; Carpanese, M.

2012-07-01

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

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

Dynamics of acoustic droplet vaporization in gas embolotherapy

NASA Astrophysics Data System (ADS)

Qamar, Adnan; Wong, Zheng Z.; Fowlkes, J. Brian; Bull, Joseph L.

2010-04-01

Acoustic droplet vaporization is investigated in a theoretical model. This work is motivated by gas embolotherapy, a developmental cancer treatment involving tumor infarction with gas microbubbles that are selectively formed from liquid droplets. The results indicate that there exists a threshold value for initial droplet size below which the bubble evolution is oscillatory and above which it is smooth and asymptotic, and show that the vaporization process affects the subsequent microbubble expansion. Dampening of the bubble expansion is observed for higher viscosity and surface tension, with effects more pronounced for droplet size less than 6 μm in radius.

The collapse of a cavitation bubble in a corner

NASA Astrophysics Data System (ADS)

Peters, Ivo; Tagawa, Yoshiyuki

2017-11-01

The collapse of cavitation bubbles is influenced by the surrounding geometry. A classic example is the collapse of a bubble near a solid wall, where a fast jet is created towards the wall. The addition of a second wall creates a non-axisymmetric flow field, which influences the displacement and jet formation during the collapse of a bubble. In this experimental study we generate mm-sized vapor bubbles using a focused pulsed laser, giving us full control over the position of the bubble. The corner geometry is formed by two glass slides. High-speed imaging reveals the directional motion of the bubble during the collapse. We find that the bubble displacement cannot be fully described by a simple superposition of the bubble dynamics of the two walls individually. Comparison of our experimental results to a model based on potential flow shows a good agreement for the direction of displacement.

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.

Modeling of bubble dynamics in relation to medical applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amendt, P.A.; London, R.A.; Strauss, M.

1997-03-12

In various pulsed-laser medical applications, strong stress transients can be generated in advance of vapor bubble formation. To better understand the evolution of stress transients and subsequent formation of vapor bubbles, two-dimensional simulations are presented in channel or cylindrical geometry with the LATIS (LAser TISsue) computer code. Differences with one-dimensional modeling are explored, and simulated experimental conditions for vapor bubble generation are presented and compared with data. 22 refs., 8 figs.

Effects of non-condensable gas on the dynamic oscillations of cavitation bubbles

NASA Astrophysics Data System (ADS)

Zhang, Yuning

2016-11-01

Cavitation is an essential topic of multiphase flow with a broad range of applications. Generally, there exists non-condensable gas in the liquid and a complex vapor/gas mixture bubble will be formed. A rigorous prediction of the dynamic behavior of the aforementioned mixture bubble is essential for the development of a complete cavitation model. In the present paper, effects of non-condensable gas on the dynamic oscillations of the vapor/gas mixture bubble are numerically investigated in great detail. For the completeness, a large parameter zone (e.g. bubble radius, frequency and ratio between gas and vapor) is investigated with many demonstrating examples. The mechanisms of mass diffusion are categorized into different groups with their characteristics and dominated regions given. Influences of non-condensable gas on the wave propagation (e.g. wave speed and attenuation) in the bubbly liquids are also briefly discussed. Specifically, the minimum wave speed is quantitatively predicted in order to close the pressure-density coupling relationship usually employed for the cavitation modelling. Finally, the application of the present finding on the development of cavitation model is demonstrated with a brief discussion of its influence on the cavitation dynamics. This work was financially supported by the National Natural Science Foundation of China (Project No.: 51506051).

"Immortal" liquid film formed by colliding bubble at oscillating solid substrates

NASA Astrophysics Data System (ADS)

Zawala, Jan

2016-05-01

This paper presents an experimental study of the behavior of an ascending air bubble (equivalent radius 0.74 mm) colliding with a solid substrate. The substrate is either motionless or oscillating with a precisely adjusted acceleration, slightly higher than gravity. It is shown that the stability of the liquid film formed between the striking bubble and the solid surface depends not only on the hydrophobic/hydrophilic properties of the solid but also on the energetic interrelations in the system. The results indicate that the rupture of the bubble and its attachment at a smooth hydrophobic solid surface are related to the viscous dissipation of energy, leading to a gradual decrease in the bubble deformation, and in consequence in the radius of the formed separating liquid film. When the film radius is small enough, the bubble ruptures and attaches to the hydrophobic solid surface. Moreover, it is shown that when the bubble deformations are forced to be constant, by applying properly adjusted oscillations of the solid substrate (energy supply conditions), bubble rupture can be prevented and a constant bubble bouncing is observed, irrespective of the hydrophobic/hydrophilic properties of the solid substrate. Under such energy supply conditions, the liquid film can be considered "immortal." The numerical calculations performed for the respective system, in which constant kinetic energy is induced, confirm that the liquid film can persist indefinitely owing to its constant radius, which is too large to reach the critical thickness for rupture during the collision time.

Determining the Enthalpy of Vaporization of Salt Solutions Using the Cooling Effect of a Bubble Column Evaporator

ERIC Educational Resources Information Center

Fan, Chao; Pashley, Richard M.

2016-01-01

The enthalpy of vaporization (?H[subscript vap]) of salt solutions is not easily measured, as a certain quantity of pure water has to be evaporated from a solution, at constant composition, and at a fixed temperature and pressure; then the corresponding heat input has to be measured. However, a simple bubble column evaporator (BCE) was used as a…

Optical shielding of nickel nanoparticle by a bubble: Optical limiting gets limited

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shukla, Vijay; Jayabalan, J., E-mail: jjaya@rrcat.gov.in; Chari, Rama

2016-06-13

We have demonstrated that in a nickel nanoparticle colloid, the optical limiting action reduces if a vapor bubble forms around the nanoparticle. The energy-dependent transmission and z-scan measurements on nickel nanoparticles in toluene show the onset of an additional process. At high fluence excitation, the particle becomes less visible to the later part of the incoming pulse due to the heat generated bubble formed around it. We have proposed a simple “particle-in-bubble” model which fits the optical limiting and z-scan curves quite well. Using this model, we have also estimated that the bubble radius increases at a rate of 4.5 m/s.

Bubbles

NASA Astrophysics Data System (ADS)

Prosperetti, Andrea

2002-11-01

``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, many others. Ultimately, diffusive processes govern much of the physics, and the difference between the diffusivity of heat and dissolved gases in ordinary liquids holds the key to the striking differences between gas and vapor bubbles.

Novel approach to Zr powder production by smooth ZrCl4 bubbling through molten salt

NASA Astrophysics Data System (ADS)

Bae, Hyun-Na; Choi, Mi-Seon; Lee, Go-Gi; Kim, Seon-Hyo

2016-01-01

A reduction process using ZrCl4 bubbles as a reactant was investigated to produce zirconium metals. ZrCl4 vapor was bubbled through the lance in the bath, in which Mg melt and MgCl2 salt were separated. Zr powder was formed by a reduction of ZrCl4 bubbles in magnesium layer. However, the lance was clogged by the aggregate of zirconium occurred during ZrCl4 vapor injecting leading to interruption of ZrCl4 supply into the bath. This phenomenon could be caused by the presence of magnesium at the lance tip, which passes through MgCl2 salt during bubbling, and then zirconium was formed in the forms of intermetallic compounds with aluminum. In this study, the effect of molten salt on the troubled phenomena was investigated and it was verified that CaCl2 with relatively low Weber number meaning relatively high surface tension as molten salt is effective in inhibiting the lance clogging phenomena. Then, a few micrometer-sized Zr powder with the high purity of 91.6 wt% was obtained smoothly without the formation of intermetallic compound.

The energy balance within a bubble column evaporator

NASA Astrophysics Data System (ADS)

Fan, Chao; Shahid, Muhammad; Pashley, Richard M.

2018-05-01

Bubble column evaporator (BCE) systems have been studied and developed for many applications, such as thermal desalination, sterilization, evaporative cooling and controlled precipitation. The heat supplied from warm/hot dry bubbles is to vaporize the water in various salt solutions until the solution temperature reaches steady state, which was derived into the energy balance of the BCE. The energy balance and utilization involved in each BCE process form the fundamental theory of these applications. More importantly, it opened a new field for the thermodynamics study in the form of heat and vapor transfer in the bubbles. In this paper, the originally derived energy balance was reviewed on the basis of its physics in the BCE process and compared with new proposed energy balance equations in terms of obtained the enthalpy of vaporization (Δ H vap) values of salt solutions from BCE experiments. Based on the analysis of derivation and Δ H vap values comparison, it is demonstrated that the original balance equation has high accuracy and precision, within 2% over 19-55 °C using improved systems. Also, the experimental and theoretical techniques used for determining Δ H vap values of salt solutions were reviewed for the operation conditions and their accuracies compared to the literature data. The BCE method, as one of the most simple and accurate techniques, offers a novel way to determine Δ H vap values of salt solutions based on its energy balance equation, which had error less than 3%. The thermal energy required to heat the inlet gas, the energy used for water evaporation in the BCE and the energy conserved from water vapor condensation were estimated in an overall energy balance analysis. The good agreement observed between input and potential vapor condensation energy illustrates the efficiency of the BCE system. Typical energy consumption levels for thermal desalination for producing pure water using the BCE process was also analyzed for different inlet air

[The development of vaporizers. A question of precise dose].

PubMed

Petermann, Heike

2009-05-01

Since the beginning of anaesthesia it was well known that anaesthetic agents administered by inhalation must be capable of existing in gaseous form. For vaporization various types tried to work accurately. Since oxygen was available there could be realized new concepts like the principles of injection or bubble through. With Copper Kettle (1948) for ether and chloroform and Draeger Vapor (1958) for Halothane accurate administration of volatile anaesthetics was available. Today vaporizers are part of anaesthetic machines.

Molecular Dynamics Investigation of Each Bubble Behavior in Coarsening of Cavitation Bubbles in a Finite Space

NASA Astrophysics Data System (ADS)

Tsuda, Shin-Ichi; Nakano, Yuta; Watanabe, Satoshi

2017-11-01

Recently, several studies using Molecular Dynamics (MD) simulation have been conducted for investigation of Ostwald ripening of cavitation bubbles in a finite space. The previous studies focused a characteristic length of bubbles as one of the spatially-averaged quantities, but each bubble behavior was not been investigated in detail. The objective of this study is clarification of the characteristics of each bubble behavior in Ostwald ripening, and we conducted MD simulation of a Lennard-Jones fluid in a semi-confined space. As a result, the time dependency of the characteristic length of bubbles as a spatially-averaged quantity suggested that the driving force of the Ostwald ripening is Evaporation/Condensation (EC) across liquid-vapor surface, which is the same result as the previous works. The radius change of the relatively larger bubbles also showed the same tendency to a classical EC model. However, the sufficiently smaller bubbles than the critical size, e.g., the bubbles just before collapsing, showed a different characteristic from the classical EC model. Those smaller bubbles has a tendency to be limited by mechanical non-equilibrium in which viscosity of liquid is dominant rather than by EC across liquid-vapor surface. This work was supported by JSPS KAKENHI Grant Number JP16K06085.

Determination of the dispersion constant in a constrained vapor bubble thermosyphon

NASA Technical Reports Server (NTRS)

Dasgupta, Sunando; Plawsky, Joel L.; Wayner, Peter C., Jr.

1995-01-01

The isothermal profiles of the extended meniscus in a quartz cuvette were measured in a gravitational field using an image analyzing interferometer which is based on computer enhanced video microscopy of the naturally occurring interference fringes. The experimental results for heptane and pentane menisci were analyzed using the extended Young Laplace Equation. These isothermal results characterized the interfacial force field in-siru at the start of the heat transfer experiments by quantifying the dispersion constant, which is a function of the liquid-solid system and cleaning procedures. The experimentally obtained values of the disjoining pressure and the dispersion constants were compared to that predicted from the DLP theory and good agreements were obtained. The measurements are critical to the subsequent non-isothermal experiments because one of the major variables in the heat sink capability of the Constrained Vapor Bubble Thermosyphon, CVBT, is the dispersion constant. In all previous studies of micro heat pipes the value of the dispersion constant has been 'estimated'. One of the major advantages of the current glass cell is the ability to view the extended meniscus at all times. Experimentally, we find that the extended Young-Laplace Equation is an excellent model for the force field at the solid-liquid-vapor interfaces.

MR-based detection of individual histotripsy bubble clouds formed in tissues and phantoms.

PubMed

Allen, Steven P; Hernandez-Garcia, Luis; Cain, Charles A; Hall, Timothy L

2016-11-01

To demonstrate that MR sequences can detect individual histotripsy bubble clouds formed inside intact tissues. A line-scan and an EPI sequence were sensitized to histotripsy by inserting a bipolar gradient whose lobes bracketed the lifespan of a histotripsy bubble cloud. Using a 7 Tesla, small-bore scanner, these sequences monitored histotripsy clouds formed in an agar phantom and in vitro porcine liver and brain. The bipolar gradients were adjusted to apply phase with k-space frequencies of 10, 300 or 400 cm -1 . Acoustic pressure amplitude was also varied. Cavitation was simultaneously monitored using a passive cavitation detection system. Each image captured local signal loss specific to an individual bubble cloud. In the agar phantom, this signal loss appeared only when the transducer output exceeded the cavitation threshold pressure. In tissues, bubble clouds were immediately detected when the gradients created phase with k-space frequencies of 300 and 400 cm -1 . When the gradients created phase with a k-space frequency of 10 cm -1 , individual bubble clouds were not detectable until many acoustic pulses had been applied to the tissue. Cavitation-sensitive MR-sequences can detect single histotripsy bubble clouds formed in biologic tissue. Detection is influenced by the sensitizing gradients and treatment history. Magn Reson Med 76:1486-1493, 2016. © 2015 International Society for Magnetic Resonance in Medicine. © 2015 International Society for Magnetic Resonance in Medicine.

Bubble formation during pulsed laser ablation: mechanism and implications

NASA Astrophysics Data System (ADS)

van Leeuwen, Ton G. J. M.; Jansen, E. Duco; Motamedi, Massoud; Welch, Ashley J.; Borst, Cornelius

1993-07-01

Holmium ((lambda) equals 2.09 micrometers ) and excimer ((lambda) equals 308 nm) lasers are used for ablation of tissue. In a previous study it was demonstrated that both excimer and holmium laser pulses produce fast expanding and collapsing vapor bubbles. To investigate whether the excimer induced bubble is caused by vaporization of water, the threshold fluence for bubble formation at a bare fiber tip in water was compared between the excimer laser (pulse length 115 ns) and the Q-switched and free-running holmium lasers (pulse length 1 microsecond(s) to 250 microsecond(s) , respectively). To induce bubble formation by excimer laser light in water, the absorber oxybuprocaine-hydrochloride (OBP-HCl) was added to the water. Fast flash photography was used to measure the threshold fluence as a function of the water temperature (6 - 90 degree(s)C) at environmental pressure. The ultraviolet excimer laser light is strongly absorbed by blood. Therefore, to document the implications of bubble formation at fluences above the tissue ablation threshold, excimer laser pulses were delivered in vitro in hemoglobin solution and in vivo in the femoral artery of the rabbit. We conclude that the principal content of the fast bubble induced by a 308 nm excimer laser pulse is water vapor. Therefore, delivery of excimer laser pulses in a water or blood environment will cause fast expanding water vapor bubbles, which may induce mechanical damage to adjacent tissue.

The impact of vaporized nanoemulsions on ultrasound-mediated ablation.

PubMed

Zhang, Peng; Kopechek, Jonathan A; Porter, Tyrone M

2013-01-01

The clinical feasibility of using high-intensity focused ultrasound (HIFU) for ablation of solid tumors is limited by the high acoustic pressures and long treatment times required. The presence of microbubbles during sonication can increase the absorption of acoustic energy and accelerate heating. However, formation of microbubbles within the tumor tissue remains a challenge. Phase-shift nanoemulsions (PSNE) have been developed as a means for producing microbubbles within tumors. PSNE are emulsions of submicron-sized, lipid-coated, and liquid perfluorocarbon droplets that can be vaporized into microbubbles using short (<1 ms), high-amplitude (>5 MPa) acoustic pulses. In this study, the impact of vaporized phase-shift nanoemulsions on the time and acoustic power required for HIFU-mediated thermal lesion formation was investigated in vitro. PSNE containing dodecafluoropentane were produced with narrow size distributions and mean diameters below 200 nm using a combination of sonication and extrusion. PSNE was dispersed in albumin-containing polyacrylamide gel phantoms for experimental tests. Albumin denatures and becomes opaque at temperatures above 58°C, enabling visual detection of lesions formed from denatured albumin. PSNE were vaporized using a 30-cycle, 3.2-MHz, at an acoustic power of 6.4 W (free-field intensity of 4,586 W/cm(2)) pulse from a single-element, focused high-power transducer. The vaporization pulse was immediately followed by a 15-s continuous wave, 3.2-MHz signal to induce ultrasound-mediated heating. Control experiments were conducted using an identical procedure without the vaporization pulse. Lesion formation was detected by acquiring video frames during sonication and post-processing the images for analysis. Broadband emissions from inertial cavitation (IC) were passively detected with a focused, 2-MHz transducer. Temperature measurements were acquired using a needle thermocouple. Bubbles formed at the HIFU focus via PSNE vaporization

How many bubbles in your glass of bubbly?

PubMed

Liger-Belair, Gérard

2014-03-20

The issue about how many carbon dioxide bubbles are likely to nucleate in a glass of champagne (or bubbly) is of concern for sommeliers, wine journalists, experienced tasters, and any open minded physical chemist wondering about complex phenomena at play in a glass of bubbly. The whole number of bubbles likely to form in a single glass is the result of the fine interplay between dissolved CO2, tiny gas pockets trapped within particles acting as bubble nucleation sites, and ascending bubble dynamics. Based on theoretical models combining ascending bubble dynamics and mass transfer equations, the falsely naı̈ve question of how many bubbles are likely to form per glass is discussed in the present work. A theoretical relationship is derived, which provides the whole number of bubbles likely to form per glass, depending on various parameters of both the wine and the glass itself.

Liquid phase stabilization versus bubble formation at a nanoscale curved interface

NASA Astrophysics Data System (ADS)

Schiffbauer, Jarrod; Luo, Tengfei

2018-03-01

We investigate the nature of vapor bubble formation near a nanoscale-curved convex liquid-solid interface using two models: an equilibrium Gibbs model for homogenous nucleation, and a nonequilibrium dynamic van der Waals-diffuse-interface model for phase change in an initially cool liquid. Vapor bubble formation is shown to occur for sufficiently large radius of curvature and is suppressed for smaller radii. Solid-fluid interactions are accounted for and it is shown that liquid-vapor interfacial energy, and hence Laplace pressure, has limited influence over bubble formation. The dominant factor is the energetic cost of creating the solid-vapor interface from the existing solid-liquid interface, as demonstrated via both equilibrium and nonequilibrium arguments.

A Tissue-Mimicking Ultrasound Test Object Using Droplet Vaporization to Create Point Targets

PubMed Central

Carneal, Catherine M.; Kripfgans, Oliver D.; Krücker, Jochen; Carson, Paul L.; Fowlkes, J. Brian

2012-01-01

Ultrasound test objects containing reference point targets could be useful for evaluating ultrasound systems and phase aberration correction methods. Polyacrylamide gels containing albumin-stabilized droplets (3.6 µm mean diameter) of dodecafluoropentane (DDFP) are being developed for this purpose. Perturbation by ultrasound causes spontaneous vaporization of the superheated droplets to form gas bubbles, a process termed acoustic droplet vaporization (ADV). The resulting bubbles (20 to 160 µm diameter) are small compared with acoustic wavelengths in diagnostic ultrasound and are theoretically suitable for use as point targets (phase errors <20° for typical f-numbers). Bubbles distributed throughout the material are convenient for determining the point spread function in an imaging plane or volume. Cooling the gel causes condensation of the DDFP droplets, which may be useful for storage. Studying ADV in such viscoelastic media could provide insight into potential bioeffects from rapid bubble formation. PMID:21937339

Bubble formation during drop impact on a heated pool

NASA Astrophysics Data System (ADS)

Tian, Yuansi; Alhazmi, Muath; Kouraytem, Nadia; Thoroddsen, Sigurdur

2017-11-01

Ultra high-speed video imaging, at up to 200 kfps, is used to investigate a drop impinging onto a high temperature pool. The room-temperature perfluorohexane drop, which has a boiling temperature as low as 56 °C impacts on the soybean oil pool heated up to around 200 °C, which is overwhelmingly higher than the boiling temperature of the drop. The bottom of the drop is therefore covered by a layer of vapor which prevents contact between the two immiscible liquid surfaces, akin to the Leidenfrost effect However, as the pool temperature is reduced, one starts seeing contact and the dynamics transition into the vapor explosion regime. At the boundary of this regime we observe some entrapment of scattered or a toroidal ring of small bubbles. Experimental video data will be presented to show this novel phenomenon and explain how these bubbles are formed and evolve.

Freezing Bubbles

NASA Astrophysics Data System (ADS)

Kingett, Christian; Ahmadi, Farzad; Nath, Saurabh; Boreyko, Jonathan

2017-11-01

The two-stage freezing process of a liquid droplet on a substrate is well known; however, how bubbles freeze has not yet been studied. We first deposited bubbles on a silicon substrate that was chilled at temperatures ranging from -10 °C to -40 °C, while the air was at room temperature. We observed that the freeze front moved very slowly up the bubble, and in some cases, even came to a complete halt at a critical height. This slow freezing front propagation can be explained by the low thermal conductivity of the thin soap film, and can be observed more clearly when the bubble size or the surface temperature is increased. This delayed freezing allows the frozen portion of the bubble to cool the air within the bubble while the top part is still liquid, which induces a vapor pressure mismatch that either collapses the top or causes the top to pop. In cases where the freeze front reaches the top of the bubble, a portion of the top may melt and slowly refreeze; this can happen more than just once for a single bubble. We also investigated freezing bubbles inside of a freezer where the air was held at -20 °C. In this case, the bubbles freeze quickly and the ice grows radially from nucleation sites instead of perpendicular to the surface, which provides a clear contrast with the conduction limited room temperature bubbles.

Bubble Dynamics in Polymer Solutions Undergoing Shear.

DTIC Science & Technology

1985-04-01

cavitation bubble in water has been established as the fundamental theoretical approach to understanding this phenomenon. LA_ Laser -induced...cavitation inception. 1-2 Polymer effects on cavity appearance. 2-1 Spherical laser -induced bubble dynamics. 2-2 Vapor cavity jet formation. 2-3 Bubble...distilled water. 2-6B Nonspherical bubble dynamics in dilute polymer. 3-1 Closed-loop hydraulic cavitation tunnel. 3-2 Laser system optical components. 3-3

Bubble formation in water with addition of a hydrophobic solute.

PubMed

Okamoto, Ryuichi; Onuki, Akira

2015-07-01

We show that phase separation can occur in a one-component liquid outside its coexistence curve (CX) with addition of a small amount of a solute. The solute concentration at the transition decreases with increasing the difference of the solvation chemical potential between liquid and gas. As a typical bubble-forming solute, we consider O2 in ambient liquid water, which exhibits mild hydrophobicity and its critical temperature is lower than that of water. Such a solute can be expelled from the liquid to form gaseous domains while the surrounding liquid pressure is higher than the saturated vapor pressure p cx. This solute-induced bubble formation is a first-order transition in bulk and on a partially dried wall, while a gas film grows continuously on a completely dried wall. We set up a bubble free energy ΔG for bulk and surface bubbles with a small volume fraction ϕ. It becomes a function of the bubble radius R under the Laplace pressure balance. Then, for sufficiently large solute densities above a threshold, ΔG exhibits a local maximum at a critical radius and a minimum at an equilibrium radius. We also examine solute-induced nucleation taking place outside CX, where bubbles larger than the critical radius grow until attainment of equilibrium.

Bubble transport and sticking in gas embolotherapy

NASA Astrophysics Data System (ADS)

Bull, Joseph

2002-11-01

Pressure-driven bubble transport in a two-dimensional, bifurcating channel is investigated as a model of gas emboli transport in the microcirculation. Gas emboli are relevant to a number of clinical situations, and our particular interest is a novel gas embolotherapy technique, which involves using gas bubbles to occlude blood flow to tumors. This minimally invasive treatment modality allows selective delivery of emboli. The bubbles originate as 6 micron-diameter liquid droplets of perfluorocarbon (PFC), mixed in saline, and are injected into the vascular system. The droplet forms are small enough to pass through capillary beds, so they can circulate until the next stage of the therapy. By strategically placing an ultrasound source over the artery feeding the tumor, the droplets may be vaporized at that location. Our model is developed using the Stokes equation subject to interfacial and wall boundary conditions, and is solved using the boundary element method. The conditions under which bubbles 'stick' to the channel walls and occlude flow are investigated. Clinically, these results are important because the location and homogeneity of bubble sticking determines the degree of tumor necrosis and the efficacy of the treatment.

Acoustic Droplet Vaporization for the Enhancement of Ultrasound Thermal Therapy.

PubMed

Zhang, Man; Fabiilli, Mario; Carson, Paul; Padilla, Frederic; Swanson, Scott; Kripfgans, Oliver; Fowlkes, Brian

2010-10-11

Acoustic droplet vaporization (ADV) is an ultrasound method for converting biocompatible microdroplets into microbubbles. The objective is to demonstrate that ADV bubbles can enhance high intensity focused ultrasound (HIFU) therapy by controlling and increasing energy absorption at the focus. Thermal phantoms were made with or without droplets. Compound lesions were formed in the phantoms by 5-second exposures with 5-second delays. Center to center spacing of individual lesions was 5.5 mm in either a linear pattern or a spiral pattern. Prior to the HIFU, 10 cycle tone bursts with 0.25% duty cycle were used to vaporize the droplets, forming an "acoustic trench" within 30 seconds. The transducer was then focused in the middle of the back bubble wall to form thermal lesions in the trench. All lesions were imaged optically and with 2T MRI. With the use of ADV and the acoustic trench, a uniform thermal ablation volume of 15 cm(3) was achieved in 4 minutes; without ADV only less than 15% of this volume was filled. The commonly seen tadpole shape characteristic of bubble-enhanced HIFU lesions was not evident with the acoustic trench. In conclusion, ADV shows promise for the spatial control and dramatic acceleration of thermal lesion production by HIFU.

Vortex shedding within laminar separation bubbles forming over an airfoil

NASA Astrophysics Data System (ADS)

Kirk, Thomas M.; Yarusevych, Serhiy

2017-05-01

Vortex shedding within laminar separation bubbles forming over the suction side of a NACA 0018 airfoil is studied through a combination of high-speed flow visualization and boundary layer measurements. Wind tunnel experiments are performed at a chord-based Reynolds number of 100,000 and four angles of attack. The high-speed flow visualization is complemented by quantitative velocity and surface pressure measurements. The structures are shown to originate from the natural amplification of small-amplitude disturbances, and the shear layer roll-up is found to occur coherently across the span. However, significant cycle-to-cycle variations are observed in vortex characteristics, including shedding period and roll-up location. The formation of the roll-up vortices precedes the later stages of transition, during which these structures undergo significant deformations and breakdown to smaller scales. During this stage of flow development, vortex merging is also observed. The results provide new insight into the development of coherent structures in separation bubbles and their relation to the overall bubble dynamics and mean bubble topology.

In vivo droplet vaporization for occlusion therapy and phase aberration correction.

PubMed

Kripfgans, Oliver D; Fowlkes, J Brian; Woydt, Michael; Eldevik, Odd P; Carson, Paul L

2002-06-01

The objective was to determine whether a transpulmonary droplet emulsion (90%, <6 microm diameter) could be used to form large gas bubbles (>30 microm) temporarily in vivo. Such bubbles could occlude a targeted capillary bed when used in a large number density. Alternatively, for a very sparse population of droplets, the resulting gas bubbles could serve as point beacons for phase aberration corrections in ultrasonic imaging. Gas bubbles can be made in vivo by acoustic droplet vaporization (ADV) of injected, superheated, dodecafluoropentane droplets. Droplets vaporize in an acoustic field whose peak rarefactional pressure exceeds a well-defined threshold. In this new work, it has been found that intraarterial and intravenous injections can be used to introduce the emulsion into the blood stream for subsequent ADV (B- and M-mode on a clinical scanner) in situ. Intravenous administration results in a lower gas bubble yield, possibly because of filtering in the lung, dilution in the blood volume, or other circulatory effects. Results show that for occlusion purposes, a reduction in regional blood flow of 34% can be achieved. Individual point beacons with a +24 dB backscatter amplitude relative to white matter were created by intravenous injection and ADV.

The impact of vaporized nanoemulsions on ultrasound-mediated ablation

PubMed Central

2013-01-01

Background The clinical feasibility of using high-intensity focused ultrasound (HIFU) for ablation of solid tumors is limited by the high acoustic pressures and long treatment times required. The presence of microbubbles during sonication can increase the absorption of acoustic energy and accelerate heating. However, formation of microbubbles within the tumor tissue remains a challenge. Phase-shift nanoemulsions (PSNE) have been developed as a means for producing microbubbles within tumors. PSNE are emulsions of submicron-sized, lipid-coated, and liquid perfluorocarbon droplets that can be vaporized into microbubbles using short (<1 ms), high-amplitude (>5 MPa) acoustic pulses. In this study, the impact of vaporized phase-shift nanoemulsions on the time and acoustic power required for HIFU-mediated thermal lesion formation was investigated in vitro. Methods PSNE containing dodecafluoropentane were produced with narrow size distributions and mean diameters below 200 nm using a combination of sonication and extrusion. PSNE was dispersed in albumin-containing polyacrylamide gel phantoms for experimental tests. Albumin denatures and becomes opaque at temperatures above 58°C, enabling visual detection of lesions formed from denatured albumin. PSNE were vaporized using a 30-cycle, 3.2-MHz, at an acoustic power of 6.4 W (free-field intensity of 4,586 W/cm2) pulse from a single-element, focused high-power transducer. The vaporization pulse was immediately followed by a 15-s continuous wave, 3.2-MHz signal to induce ultrasound-mediated heating. Control experiments were conducted using an identical procedure without the vaporization pulse. Lesion formation was detected by acquiring video frames during sonication and post-processing the images for analysis. Broadband emissions from inertial cavitation (IC) were passively detected with a focused, 2-MHz transducer. Temperature measurements were acquired using a needle thermocouple. Results Bubbles formed at the HIFU focus via

Bubble induced flow field modulation for pool boiling enhancement over a tubular surface

NASA Astrophysics Data System (ADS)

Raghupathi, P. A.; Joshi, I. M.; Jaikumar, A.; Emery, T. S.; Kandlikar, S. G.

2017-06-01

We demonstrate the efficacy of using a strategically placed enhancement feature to modify the trajectory of bubbles nucleating on a horizontal tubular surface to increase both the critical heat flux (CHF) and the heat transfer coefficient (HTC). The CHF on a plain tube is shown to be triggered by a local dryout at the bottom of the tube due to vapor agglomeration. To mitigate this effect and delay CHF, the nucleating bubble trajectory is modified by incorporating a bubble diverter placed axially at the bottom of the tube. The nucleating bubble at the base of the diverter experiences a tangential evaporation momentum force (EMF) which causes the bubble to grow sideways away from the tube and avoid localized bubble patches that are responsible for CHF initiation. High speed imaging confirmed the lateral displacement of the bubbles away from the diverter closely matched with the theoretical predictions using EMF and buoyancy forces. Since the EMF is stronger at higher heat fluxes, bubble displacement increases with heat flux and results in the formation of separate liquid-vapor pathways wherein the liquid enters almost unobstructed at the bottom and the vapor bubble leaves sideways. Experimental results yielded CHF and HTC enhancements of ˜60% and ˜75%, respectively, with the diverter configuration when compared to a plain tube. This work can be used for guidance in developing enhancement strategies to effectively modulate the liquid-vapor flow around the heater surface at various locations to enhance HTC and CHF.

A novel bubble-forming material for preparing hydrophobic-agent-loaded bubbles with theranostic functionality.

PubMed

Yang, Pei-Sin; Tung, Fu-I; Chen, Hsiao-Ping; Liu, Tse-Ying; Lin, Yi-Ying

2014-08-01

In the present study, a new bubble-forming material (carboxymethyl hexanoyl chitosan, CHC), together with superparamagnetic iron oxide (SPIO) nanoparticles, was employed to prepare image-guided bubbles for efficiently encapsulating and delivering hydrophobic agents to kill tumor cells. The results showed that CHC could be used for preparing not only micronized bubbles (CHC/SPIO MBs) to exhibit ultrasound imaging functionality but also nanosized bubbles (CHC/SPIO NBs) to exhibit magnetic resonance T2 image contrast. It was found that the amounts of SPIO nanoparticles and hexane during preparation process were the key factors to obtaining CHC/SPIO NBs. Most importantly, under in vitro cell culture conditions with the same amount of camptothecin (CPT) and therapeutic sonication, CPT-loaded CHC/SPIO NBs demonstrated more significant transcellular delivery and cytotoxicity than free CPT. Subsequently, an intratumoral injection was proposed for the in vivo administration of hydrophobic-agent-loaded CHC/SPIO NBs. After injection, the distribution of a hydrophobic dye (DiR, an agent with near-infrared (NIR) fluorescence used as a model drug) released from the CHC/SPIO NBs was tracked by an NIR imaging technique. A significant tumor-specific accumulation was observed in the mouse that received the DiR-loaded CHC/SPIO NBs; the same was not observed in the mouse that received the free dye (without incorporating with CHC/SPIO NBs). It is expected, in the future, both the dose of the therapeutic agent administered and its side effects can be significantly lowered by using novel CHC/SPIO NBs together with local delivery (intratumoral injection), targeted imaging and enhanced cellular uptake of the drug. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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.

Non-equilibrium phase stabilization versus bubble nucleation at a nanoscale-curved Interface

NASA Astrophysics Data System (ADS)

Schiffbauer, Jarrod; Luo, Tengfei

Using continuum dynamic van der Waals theory in a radial 1D geometry with a Lennard-Jones fluid model, we investigate the nature of vapor bubble nucleation near a heated, nanoscale-curved convex interface. Vapor bubble nucleation and growth are observed for interfaces with sufficiently large radius of curvature while phase stabilization of a superheated fluid layer occurs at interfaces with smaller radius. The hypothesis that the high Laplace pressure required for stable equilibrium of very small bubbles is responsible for phase stability is tested by effectively varying the parameter which controls liquid-vapor surface tension. In doing so, the liquid-vapor surface tension- hence Laplace pressure-is shown to have limited effect on phase stabilization vs. bubble nucleation. However, the strong dependence of nucleation on leading-order momentum transport, i.e. viscous dissipation, near the heated inner surface is demonstrated. We gratefully acknowledge ND Energy for support through the ND Energy Postdoctoral Fellowship program and the Army Research Office, Grant No. W911NF-16-1-0267, managed by Dr. Chakrapani Venanasi.

Investigation of chemical vapor deposition of garnet films for bubble domain memories

NASA Technical Reports Server (NTRS)

Besser, P. J.; Hamilton, T. N.

1973-01-01

The important process parameters and control required to grow reproducible device quality ferrimagnetic films by chemical vapor deposition (CVD) were studied. The investigation of the critical parameters in the CVD growth process led to the conclusion that the required reproducibility of film properties cannot be achieved with individually controlled separate metal halide sources. Therefore, the CVD growth effort was directed toward replacement of the halide sources with metallic sources with the ultimate goal being the reproducible growth of complex garnet compositions utilizing a single metal alloy source. The characterization of the YGdGaIG films showed that certain characteristics of this material, primarily the low domain wall energy and the large temperature sensitivity, severely limited its potential as a useful material for bubble domain devices. Consequently, at the time of the change from halide to metallic sources, the target film compositions were shifted to more useful materials such as YGdTmGaIG, YEuGaIG and YSmGaIG.

Shock wave interaction with laser-generated single bubbles.

PubMed

Sankin, G N; Simmons, W N; Zhu, S L; Zhong, P

2005-07-15

The interaction of a lithotripter shock wave (LSW) with laser-generated single vapor bubbles in water is investigated using high-speed photography and pressure measurement via a fiber-optic probe hydrophone. The interaction leads to nonspherical collapse of the bubble with secondary shock wave emission and microjet formation along the LSW propagation direction. The maximum pressure amplification is produced during the collapse phase of the bubble oscillation when the compressive pulse duration of the LSW matches with the forced collapse time of the bubble.

Bursting Bubbles from Combustion of Thermoplastic Materials in Microgravity

NASA Technical Reports Server (NTRS)

Butler, K. B.

1999-01-01

Many thermoplastic materials in common use for a wide range of applications, including spacecraft, develop bubbles internally as they burn due to chemical reactions taking place within the bulk. These bubbles grow and migrate until they burst at the surface, forceably ejecting volatile gases and, occasionally, molten fuel. In experiments in normal gravity, Kashiwagi and Ohlemiller observed vapor jets extending a few centimeters from the surface of a radiatively heated polymethylmethacrylate (PMMA) sample, with some molten material ejected into the gas phase. These physical phenomena complicated the combustion process considerably. In addition to the non-steady release of volatiles, the depth of the surface layer affected by oxygen was increased, attributed to the roughening of the surface by bursting events. The ejection of burning droplets in random directions presents a potential fire hazard unique to microgravity. In microgravity combustion experiments on nylon Velcro fasteners and on polyethylene wire insulation, the presence of bursting fuel vapor bubbles was associated with the ejection of small particles of molten fuel as well as pulsations of the flame. For the nylon fasteners, particle velocities were higher than 30 cm/sec. The droplets burned robustly until all fuel was consumed, demonstrating the potential for the spread of fire in random directions over an extended distance. The sequence of events for a bursting bubble has been photographed by Newitt et al.. As the bubble reaches the fluid surface, the outer surface forms a dome while the internal bubble pressure maintains a depression at the inner interface. Liquid drains from the dome until it breaks into a cloud of droplets on the order of a few microns in size. The bubble gases are released rapidly, generating vortices in the quiescent surroundings and transporting the tiny droplets. The depression left by the escaping gases collapses into a central jet, which rises with a high velocity and may

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.

Bubble generation during transformer overload

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oommen, T.V.

1990-03-01

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

Theranostic Performance of Acoustic Nanodroplet Vaporization-Generated Bubbles in Tumor Intertissue.

PubMed

Ho, Yi-Ju; Yeh, Chih-Kuang

2017-01-01

Solid tumors with poorly perfused regions reveal some of the treatment limitations that restrict drug delivery and therapeutic efficacy. Acoustic droplet vaporization (ADV) has been applied to directly disrupt vessels and release nanodroplets, ADV-generated bubbles (ADV-Bs), and drugs into tumor tissue. In this study, we investigated the in vivo behavior of ADV-Bs stimulated by US, and evaluated the possibility of moving intertissue ADV-Bs into the poorly perfused regions of solid tumors. Intravital imaging revealed intertissue ADV-B formation, movement, and cavitation triggered by US, where the distance of intertissue ADV-B movement was 33-99 µm per pulse. When ADV-Bs were applied to tumor cells, the cell membrane was damaged, increasing cellular permeability or inducing cell death. The poorly perfused regions within solid tumors show enhancement due to ADV-B accumulation after application of US-triggered ADV-B. The intratumoral nanodroplet or ADV-B distribution around the poorly perfused regions with tumor necrosis or hypoxia were demonstrated by histological assessment. ADV-B formation, movement and cavitation could induce cell membrane damage by mechanical force providing a mechanism to overcome treatment limitations in poorly perfused regions of tumors.

Theranostic Performance of Acoustic Nanodroplet Vaporization-Generated Bubbles in Tumor Intertissue

PubMed Central

Ho, Yi-Ju; Yeh, Chih-Kuang

2017-01-01

Solid tumors with poorly perfused regions reveal some of the treatment limitations that restrict drug delivery and therapeutic efficacy. Acoustic droplet vaporization (ADV) has been applied to directly disrupt vessels and release nanodroplets, ADV-generated bubbles (ADV-Bs), and drugs into tumor tissue. In this study, we investigated the in vivo behavior of ADV-Bs stimulated by US, and evaluated the possibility of moving intertissue ADV-Bs into the poorly perfused regions of solid tumors. Intravital imaging revealed intertissue ADV-B formation, movement, and cavitation triggered by US, where the distance of intertissue ADV-B movement was 33-99 µm per pulse. When ADV-Bs were applied to tumor cells, the cell membrane was damaged, increasing cellular permeability or inducing cell death. The poorly perfused regions within solid tumors show enhancement due to ADV-B accumulation after application of US-triggered ADV-B. The intratumoral nanodroplet or ADV-B distribution around the poorly perfused regions with tumor necrosis or hypoxia were demonstrated by histological assessment. ADV-B formation, movement and cavitation could induce cell membrane damage by mechanical force providing a mechanism to overcome treatment limitations in poorly perfused regions of tumors. PMID:28529631

Linear Stability Analysis of an Acoustically Vaporized Droplet

NASA Astrophysics Data System (ADS)

Siddiqui, Junaid; Qamar, Adnan; Samtaney, Ravi

2015-11-01

Acoustic droplet vaporization (ADV) is a phase transition phenomena of a superheat liquid (Dodecafluoropentane, C5F12) droplet to a gaseous bubble, instigated by a high-intensity acoustic pulse. This approach was first studied in imaging applications, and applicable in several therapeutic areas such as gas embolotherapy, thrombus dissolution, and drug delivery. High-speed imaging and theoretical modeling of ADV has elucidated several physical aspects, ranging from bubble nucleation to its subsequent growth. Surface instabilities are known to exist and considered responsible for evolving bubble shapes (non-spherical growth, bubble splitting and bubble droplet encapsulation). We present a linear stability analysis of the dynamically evolving interfaces of an acoustically vaporized micro-droplet (liquid A) in an infinite pool of a second liquid (liquid B). We propose a thermal ADV model for the base state. The linear analysis utilizes spherical harmonics (Ynm, of degree m and order n) and under various physical assumptions results in a time-dependent ODE of the perturbed interface amplitudes (one at the vapor/liquid A interface and the other at the liquid A/liquid B interface). The perturbation amplitudes are found to grow exponentially and do not depend on m. Supported by KAUST Baseline Research Funds.

Exploding and Imaging of Electron Bubbles in Liquid Helium

NASA Astrophysics Data System (ADS)

Yadav, Neha; Vadakkumbatt, Vaisakh; Maris, Humphrey J.; Ghosh, Ambarish

2017-06-01

An electron bubble in liquid helium-4 under the saturated vapor pressure becomes unstable and explodes if the pressure becomes more negative than -1.9 bars. In this paper, we use focused ultrasound to explode electron bubbles. We then image at 30,000 frames per second the growth and subsequent collapse of the bubbles. We find that bubbles can grow to as large as 1 mm in diameter within 2 ms after the cavitation event. We examine the relation between the maximum size of the bubble and the lifetime and find good agreement with the experimental results.

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

NASA Astrophysics Data System (ADS)

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), 10.1103/PhysRevE.75.036304], 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), 10.1016/j.ijheatmasstransfer.2012.10.080]. 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.

Acoustic droplet vaporization of vascular droplets in gas embolotherapy

NASA Astrophysics Data System (ADS)

Bull, Joseph

2016-11-01

This work is primarily motivated by a developmental gas embolotherapy technique for cancer treatment. In this methodology, infarction of tumors is induced by selectively formed vascular gas bubbles that arise from the acoustic vaporization of vascular droplets. Additionally, micro- or nano-droplets may be used as vehicles for localized drug delivery, with or without flow occlusion. In this talk, we examine the dynamics of acoustic droplet vaporization through experiments and theoretical/computational fluid mechanics models, and investigate the bioeffects of acoustic droplet vaporization on endothelial cells and in vivo. Functionalized droplets that are targeted to tumor vasculature are examined. The influence of fluid mechanical and acoustic parameters, as well as droplet functionalization, is explored. This work was supported by NIH Grant R01EB006476.

Vapor pressure and vapor fractionation of silicate melts of tektite composition

USGS Publications Warehouse

Walter, Louis S.; Carron, M.K.

1964-01-01

The total vapor pressure of Philippine tektite melts of approximately 70 per cent silica has been determined at temperatures ranging from 1500 to 2100??C. This pressure is 190 ?? 40 mm Hg at 1500??C, 450 ?? 50 mm at 1800??C and 850 ?? 70 mm at 2100?? C. Determinations were made by visually observing the temperature at which bubbles began to form at a constant low ambient pressure. By varying the ambient pressure, a boiling point curve was constructed. This curve differs from the equilibrium vapor pressure curve due to surface tension effects. This difference was evaluated by determining the equilibrium bubble size in the melt and calculating the pressure due to surface tension, assuming the latter to be 380 dyn/cm. The relative volatility from tektite melts of the oxides of Na, K, Fe, Al and Si has been determined as a function of temperature, total pressure arid roughly, of oxygen fugacity. The volatility of SiO2 is decreased and that of Na2O and K2O is increased in an oxygen-poor environment. Preliminary results indicate that volatilization at 2100??C under atmospheric pressure caused little or no change in the percentage Na2O and K2O. The ratio Fe3 Fe2 of the tektite is increased in ambient air at a pressure of 9 ?? 10-4 mm Hg (= 106.5 atm O2, partial pressure) at 2000??C. This suggests that tektites were formed either at lower oxygen pressures or that they are a product of incomplete oxidation of parent material with a still lower ferricferrous ratio. ?? 1964.

Bubble formed as a result of a Zeolite Crystal Growth experiment in the U.S. Laboratory

NASA Image and Video Library

2002-12-14

ISS006-E-08835 (14 December 2002) --- View of a bubble formed as a result of a Zeolite Crystal Growth (ZCG) experiment in the Destiny laboratory on the International Space Station (ISS). Expedition Six Commander Kenneth D. Bowersox used a Space Station drill to mix 12 Zeolite samples in clear tubes. Scientists on the ground watching on TV noticed bubbles in the samples. Bowersox used a modified mixing procedure to process autoclaves to isolate bubbles. He re-inserted the samples in the ZCG furnace in Express Rack 2 in the U.S. laboratory/Destiny. This experiment has shown that the bubbles could cause larger number of smaller deformed crystals to grow. Bowersox rotated the samples so that the heavier fluid was thrown to the outside while the lighter bubbles stayed on the inside.

Bubble formed as a result of a Zeolite Crystal Growth experiment in the U.S. Laboratory

NASA Image and Video Library

2002-12-14

ISS006-E-08778 (14 December 2002) --- View of a bubble formed as a result of a Zeolite Crystal Growth (ZCG) experiment in the Destiny laboratory on the International Space Station (ISS). Expedition Six Commander Kenneth D. Bowersox used a Space Station drill to mix 12 Zeolite samples in clear tubes. Scientists on the ground watching on TV noticed bubbles in the samples. Bowersox used a modified mixing procedure to process autoclaves to isolate bubbles. He re-inserted the samples in the ZCG furnace in Express Rack 2 in the U.S. laboratory/Destiny. This experiment has shown that the bubbles could cause larger number of smaller deformed crystals to grow. Bowersox rotated the samples so that the heavier fluid was thrown to the outside while the lighter bubbles stayed on the inside.

Bubble formed as a result of a Zeolite Crystal Growth experiment in the U.S. Laboratory

NASA Image and Video Library

2002-12-14

ISS006-E-08775 (14 December 2002) --- View of a bubble formed as a result of a Zeolite Crystal Growth (ZCG) experiment in the Destiny laboratory on the International Space Station (ISS). Expedition Six Commander Kenneth D. Bowersox used a Space Station drill to mix 12 Zeolite samples in clear tubes. Scientists on the ground watching on TV noticed bubbles in the samples. Bowersox used a modified mixing procedure to process autoclaves to isolate bubbles. He re-inserted the samples in the ZCG furnace in Express Rack 2 in the U.S. laboratory/Destiny. This experiment has shown that the bubbles could cause larger number of smaller deformed crystals to grow. Bowersox rotated the samples so that the heavier fluid was thrown to the outside while the lighter bubbles stayed on the inside.

Bubble formed as a result of a Zeolite Crystal Growth experiment in the U.S. Laboratory

NASA Image and Video Library

2002-12-14

ISS006-E-08773 (14 December 2002) --- View of a bubble formed as a result of a Zeolite Crystal Growth (ZCG) experiment in the Destiny laboratory on the International Space Station (ISS). Expedition Six Commander Kenneth D. Bowersox used a Space Station drill to mix 12 Zeolite samples in clear tubes. Scientists on the ground watching on TV noticed bubbles in the samples. Bowersox used a modified mixing procedure to process autoclaves to isolate bubbles. He re-inserted the samples in the ZCG furnace in Express Rack 2 in the U.S. laboratory/Destiny. This experiment has shown that the bubbles could cause larger number of smaller deformed crystals to grow. Bowersox rotated the samples so that the heavier fluid was thrown to the outside while the lighter bubbles stayed on the inside.

Bubble formed as a result of a Zeolite Crystal Growth experiment in the U.S. Laboratory

NASA Image and Video Library

2002-12-14

ISS006-E-08822 (14 December 2002) --- View of a bubble formed as a result of a Zeolite Crystal Growth (ZCG) experiment in the Destiny laboratory on the International Space Station (ISS). Expedition Six Commander Kenneth D. Bowersox used a Space Station drill to mix 12 Zeolite samples in clear tubes. Scientists on the ground watching on TV noticed bubbles in the samples. Bowersox used a modified mixing procedure to process autoclaves to isolate bubbles. He re-inserted the samples in the ZCG furnace in Express Rack 2 in the U.S. laboratory/Destiny. This experiment has shown that the bubbles could cause larger number of smaller deformed crystals to grow. Bowersox rotated the samples so that the heavier fluid was thrown to the outside while the lighter bubbles stayed on the inside.

Bubble formed as a result of a Zeolite Crystal Growth experiment in the U.S. Laboratory

NASA Image and Video Library

2002-12-14

ISS006-E-08831 (14 December 2002) --- View of a bubble formed as a result of a Zeolite Crystal Growth (ZCG) experiment in the Destiny laboratory on the International Space Station (ISS). Expedition Six Commander Kenneth D. Bowersox used a Space Station drill to mix 12 Zeolite samples in clear tubes. Scientists on the ground watching on TV noticed bubbles in the samples. Bowersox used a modified mixing procedure to process autoclaves to isolate bubbles. He re-inserted the samples in the ZCG furnace in Express Rack 2 in the U.S. laboratory/Destiny. This experiment has shown that the bubbles could cause larger number of smaller deformed crystals to grow. Bowersox rotated the samples so that the heavier fluid was thrown to the outside while the lighter bubbles stayed on the inside.

Bubble formed as a result of a Zeolite Crystal Growth experiment in the U.S. Laboratory

NASA Image and Video Library

2002-12-14

ISS006-E-08805 (14 December 2002) --- View of a bubble formed as a result of a Zeolite Crystal Growth (ZCG) experiment in the Destiny laboratory on the International Space Station (ISS). Expedition Six Commander Kenneth D. Bowersox used a Space Station drill to mix 12 Zeolite samples in clear tubes. Scientists on the ground watching on TV noticed bubbles in the samples. Bowersox used a modified mixing procedure to process autoclaves to isolate bubbles. He re-inserted the samples in the ZCG furnace in Express Rack 2 in the U.S. laboratory/Destiny. This experiment has shown that the bubbles could cause larger number of smaller deformed crystals to grow. Bowersox rotated the samples so that the heavier fluid was thrown to the outside while the lighter bubbles stayed on the inside.

Bubble formed as a result of a Zeolite Crystal Growth experiment in the U.S. Laboratory

NASA Image and Video Library

2002-12-14

ISS006-E-08784 (14 December 2002) --- View of a bubble formed as a result of a Zeolite Crystal Growth (ZCG) experiment in the Destiny laboratory on the International Space Station (ISS). Expedition Six Commander Kenneth D. Bowersox used a Space Station drill to mix 12 Zeolite samples in clear tubes. Scientists on the ground watching on TV noticed bubbles in the samples. Bowersox used a modified mixing procedure to process autoclaves to isolate bubbles. He re-inserted the samples in the ZCG furnace in Express Rack 2 in the U.S. laboratory/Destiny. This experiment has shown that the bubbles could cause larger number of smaller deformed crystals to grow. Bowersox rotated the samples so that the heavier fluid was thrown to the outside while the lighter bubbles stayed on the inside.

Bubble formed as a result of a Zeolite Crystal Growth experiment in the U.S. Laboratory

NASA Image and Video Library

2002-12-14

ISS006-E-08836 (14 December 2002) --- View of a bubble formed as a result of a Zeolite Crystal Growth (ZCG) experiment in the Destiny laboratory on the International Space Station (ISS). Expedition Six Commander Kenneth D. Bowersox used a Space Station drill to mix 12 Zeolite samples in clear tubes. Scientists on the ground watching on TV noticed bubbles in the samples. Bowersox used a modified mixing procedure to process autoclaves to isolate bubbles. He re-inserted the samples in the ZCG furnace in Express Rack 2 in the U.S. laboratory/Destiny. This experiment has shown that the bubbles could cause larger number of smaller deformed crystals to grow. Bowersox rotated the samples so that the heavier fluid was thrown to the outside while the lighter bubbles stayed on the inside.

Bubble formed as a result of a Zeolite Crystal Growth experiment in the U.S. Laboratory

NASA Image and Video Library

2002-12-14

ISS006-E-08799 (14 December 2002) --- View of a bubble formed as a result of a Zeolite Crystal Growth (ZCG) experiment in the Destiny laboratory on the International Space Station (ISS). Expedition Six Commander Kenneth D. Bowersox used a Space Station drill to mix 12 Zeolite samples in clear tubes. Scientists on the ground watching on TV noticed bubbles in the samples. Bowersox used a modified mixing procedure to process autoclaves to isolate bubbles. He re-inserted the samples in the ZCG furnace in Express Rack 2 in the U.S. laboratory/Destiny. This experiment has shown that the bubbles could cause larger number of smaller deformed crystals to grow. Bowersox rotated the samples so that the heavier fluid was thrown to the outside while the lighter bubbles stayed on the inside.

Heterogeneously entrapped, vapor-rich melt inclusions record pre-eruptive magmatic volatile contents

NASA Astrophysics Data System (ADS)

Steele-MacInnis, Matthew; Esposito, Rosario; Moore, Lowell R.; Hartley, Margaret E.

2017-04-01

Silicate melt inclusions (MI) commonly provide the best record of pre-eruptive H2O and CO2 contents of subvolcanic melts, but the concentrations of CO2 and H2O in the melt (glass) phase within MI can be modified by partitioning into a vapor bubble after trapping. Melt inclusions may also enclose vapor bubbles together with the melt (i.e., heterogeneous entrapment), affecting the bulk volatile composition of the MI, and its post-entrapment evolution. In this study, we use numerical modeling to examine the systematics of post-entrapment volatile evolution within MI containing various proportions of trapped vapor from zero to 95 volume percent. Modeling indicates that inclusions that trap only a vapor-saturated melt exhibit significant decrease in CO2 and moderate increase in H2O concentrations in the melt upon nucleation and growth of a vapor bubble. In contrast, inclusions that trap melt plus vapor exhibit subdued CO2 depletion at equivalent conditions. In the extreme case of inclusions that trap mostly the vapor phase (i.e., CO2-H2O fluid inclusions containing trapped melt), degassing of CO2 from the melt is negligible. In the latter scenario, the large fraction of vapor enclosed in the MI during trapping essentially serves as a buffer, preventing post-entrapment modification of volatile concentrations in the melt. Hence, the glass phase within such heterogeneously entrapped, vapor-rich MI records the volatile concentrations of the melt at the time of trapping. These numerical modeling results suggest that heterogeneously entrapped MI containing large vapor bubbles represent amenable samples for constraining pre-eruptive volatile concentrations of subvolcanic melts.

A numerical framework for bubble transport in a subcooled fluid flow

NASA Astrophysics Data System (ADS)

Jareteg, Klas; Sasic, Srdjan; Vinai, Paolo; Demazière, Christophe

2017-09-01

In this paper we present a framework for the simulation of dispersed bubbly two-phase flows, with the specific aim of describing vapor-liquid systems with condensation. We formulate and implement a framework that consists of a population balance equation (PBE) for the bubble size distribution and an Eulerian-Eulerian two-fluid solver. The PBE is discretized using the Direct Quadrature Method of Moments (DQMOM) in which we include the condensation of the bubbles as an internal phase space convection. We investigate the robustness of the DQMOM formulation and the numerical issues arising from the rapid shrinkage of the vapor bubbles. In contrast to a PBE method based on the multiple-size-group (MUSIG) method, the DQMOM formulation allows us to compute a distribution with dynamic bubble sizes. Such a property is advantageous to capture the wide range of bubble sizes associated with the condensation process. Furthermore, we compare the computational performance of the DQMOM-based framework with the MUSIG method. The results demonstrate that DQMOM is able to retrieve the bubble size distribution with a good numerical precision in only a small fraction of the computational time required by MUSIG. For the two-fluid solver, we examine the implementation of the mass, momentum and enthalpy conservation equations in relation to the coupling to the PBE. In particular, we propose a formulation of the pressure and liquid continuity equations, that was shown to correctly preserve mass when computing the vapor fraction with DQMOM. In addition, the conservation of enthalpy was also proven. Therefore a consistent overall framework that couples the PBE and two-fluid solvers is achieved.

A numerical simulation of the water vapor bubble rising in ferrofluid by volume of fluid model in the presence of a magnetic field

NASA Astrophysics Data System (ADS)

Shafiei Dizaji, A.; Mohammadpourfard, M.; Aminfar, H.

2018-03-01

Multiphase flow is one of the most complicated problems, considering the multiplicity of the related parameters, especially the external factors influences. Thus, despite the recent developments more investigations are still required. The effect of a uniform magnetic field on the hydrodynamics behavior of a two-phase flow with different magnetic permeability is presented in this article. A single water vapor bubble which is rising inside a channel filled with ferrofluid has been simulated numerically. To capture the phases interface, the Volume of Fluid (VOF) model, and to solve the governing equations, the finite volume method has been employed. Contrary to the prior anticipations, while the consisting fluids of the flow are dielectric, uniform magnetic field causes a force acting normal to the interface toward to the inside of the bubble. With respect to the applied magnetic field direction, the bubble deformation due to the magnetic force increases the bubble rising velocity. Moreover, the higher values of applied magnetic field strength and magnetic permeability ratio resulted in the further increase of the bubble rising velocity. Also it is indicated that the flow mixing and the heat transfer rate is increased by a bubble injection and applying a magnetic field. The obtained results have been concluded that the presented phenomenon with applying a magnetic field can be used to control the related characteristics of the multiphase flows. Compared to the previous studies, implementing the applicable cases using the common and actual materials and a significant reduction of the CPU time are the most remarkable advantages of the current study.

Vapor Cavitation in Dynamically Loaded Journal Bearings

NASA Technical Reports Server (NTRS)

Jacobson, B. O.; Hamrock, B. J.

1983-01-01

High speed motion camera experiments were performed on dynamically loaded journal bearings. The length to diameter ratio of the bearing, the speed of the roller and the tube, the surface material of the roller, and the static and dynamic eccentricity of the bearing were varied. One hundred and thirty-four cases were filmed. The occurrence of vapor cavitation was clearly evident in the films and figures presented. Vapor cavitation was found to occur when the tensile stress applied to the oil exceeded the tensile strength of the oil or the binding of the oil to the surface. The physical situation in which vapor cavitation occurs is during the squeezing and sliding motion within a bearing. Besides being able to accurately capture the vapor cavitation on film, an analysis of the formation and collapse of the cavitation bubbles and characteristics of the bubble content are presented.

CVB: the Constrained Vapor Bubble Capillary Experiment on the International Space Station MARANGONI FLOW REGION

NASA Technical Reports Server (NTRS)

Wayner, Peter C., Jr.; Kundan, Akshay; Plawsky, Joel

2014-01-01

The Constrained Vapor Bubble (CVB) is a wickless, grooved heat pipe and we report on a full- scale fluids experiment flown on the International Space Station (ISS). The CVB system consists of a relatively simple setup a quartz cuvette with sharp corners partially filled with either pentane or an ideal mixture of pentane and isohexane as the working fluids. Along with temperature and pressure measurements, the two-dimensional thickness profile of the menisci formed at the corners of the quartz cuvette was determined using the Light Microscopy Module (LMM). Even with the large, millimeter dimensions of the CVB, interfacial forces dominate in these exceedingly small Bond Number systems. The experiments were carried out at various power inputs. Although conceptually simple, the transport processes were found to be very complex with many different regions. At the heated end of the CVB, due to a high temperature gradient, we observed Marangoni flow at some power inputs. This region from the heated end to the central drop region is defined as a Marangoni dominated region. We present a simple analysis based on interfacial phenomena using only measurements from the ISS experiments that lead to a predictive equation for the thickness of the film near the heated end of the CVB. The average pressure gradient for flow in the film is assumed due to the measured capillary pressure at the two ends of the liquid film and that the pressure stress gradient due to cohesion self adjusts to a constant value over a distance L. The boundary conditions are the no slip condition at the wall interface and an interfacial shear stress at the liquid- vapor interface due to the Marangoni stress, which is due to the high temperature gradient. Although the heated end is extremely complex, since it includes three- dimensional variations in radiation, conduction, evaporation, condensation, fluid flow and interfacial forces, we find that using the above simplifying assumptions, a simple successful

Numerical Analysis of the Influence of Low Frequency Vibration on Bubble Growth

PubMed Central

Han, D.; Kedzierski, Mark A.

2017-01-01

Numerical simulation of bubble growth during pool boiling under the influence of low frequency vibration was performed to understand the influence of common vibrations such as those induced by wind, highway transportation, and nearby mechanical devices on the performance of thermal systems that rely on boiling. The simulations were done for saturated R123 boiling at 277.6 K with a 15 K wall superheat. The numerical volume-of-fluid method (fixed grid) was used to define the liquid-vapor interface. The basic bubble growth characteristics including the bubble departure diameter and the bubble departure time were determined as a function of the bubble contact angle (20°–80°), the vibration displacement (10 µm–50 µm), the vibration frequency (5 Hz–25 Hz), and the initial vibration direction (positive or negative). The bubble parameters were shown to be strongly dependent on the bubble contact angle at the surface. For example, both the bubble departure diameter and the bubble departure time increased with the contact angle. At the same vibration frequency and the initial vibration direction, the bubble departure diameter and the bubble departure time both decreased with increasing vibration displacement. In addition, the vibration frequency had a greater effect on the bubble growth characteristics than did the vibration displacement. The vibration frequency effect was strongly influenced by the initial vibration direction. The pressure contour, the volume fraction of vapor phase, the temperature profile, and the velocity vector were investigated to understand these dynamic bubble behaviors. The limitation of the computational fluid dynamics approach was also described. PMID:28747812

Experimental and numerical study of the effects of a wall on the coalescence and collapse of bubble pairs

NASA Astrophysics Data System (ADS)

Han, Rui; Zhang, A.-Man; Li, Shuai; Zong, Zhi

2018-04-01

Two-bubble interaction is the most fundamental problem in multi-bubbles dynamics, which is crucial in many practical applications involving air-gun arrays and underwater explosions. In this paper, we experimentally and numerically investigate coalescence, collapse, and rebound of non-buoyant bubble pairs below a rigid wall. Two oscillating vapor bubbles with similar size are generated simultaneously near a rigid wall in axisymmetric configuration using the underwater electric discharge method, and the physical process is captured by a high-speed camera. Numerical simulations are conducted based on potential flow theory coupled with the boundary integral method. Our numerical results show excellent agreement with the experimental data until the splashing of the jet impact sets in. With different ranges of γbw (the dimensionless distance between the rigid wall and the nearest bubble center), the interaction between the coalesced bubble and the rigid wall is divided into three types, i.e., "weak," "intermediate," and "strong." As γbw decreases, the contact point of the two axial jets migrates toward the wall. In "strong interaction" cases, only an upward jet towards the upper rigid wall forms and a secondary jet with a larger width appears at the base of the first jet. The collapsing coalesced bubble in a toroidal form splits into many smaller bubbles due to the instabilities and presents as bubble clouds during the rebounding phase, which may lead to a weakened pressure wave because the focusing energy associated with the collapsing bubble is disintegrated.

Challenges in the Structure Determination of Self-Assembled Metallacages: What Do Cage Cavities Contain, Internal Vapor Bubbles or Solvent and/or Counterions?

PubMed

Givelet, Cecile C; Dron, Paul I; Wen, Jin; Magnera, Thomas F; Zamadar, Matibur; Čépe, Klára; Fujiwara, Hiroki; Shi, Yue; Tuchband, Michael R; Clark, Noel; Zbořil, Radek; Michl, Josef

2016-05-25

Proving the structures of charged metallacages obtained by metal ion coordination-driven solution self-assembly is challenging, and the common use of routine NMR spectroscopy and mass spectrometry is unreliable. Carefully determined diffusion coefficients from diffusion-ordered proton magnetic resonance (DOSY NMR) for six cages of widely differing sizes lead us to propose a structural reassignment of two molecular cages from a previously favored trimer to a pentamer or hexamer, and another from a trimer to a much higher oligomer, possibly an intriguing tetradecamer. In the former case, strong support for the reassignment to a larger cage is provided by an observation of a slow reversible transformation of the initially formed cage into a smaller but spectrally very similar one upon dilution. In the latter case, freeze-fracture transmission electron micrographs demonstrate that at least some of the solutions are colloidal, and high-resolution electron transmission and atomic force microscopy images are compatible with a tetradecamer but not a trimer. Comparison of solute partial molar volumes deduced from measurement of solution density with volumes anticipated from molecular models argues strongly against the presence of large voids (solvent vapor bubbles) in cages dissolved in nitromethane. The presence of bubbles was previously proposed in an attempt to account for the bilinear nature of the Eyring plot of the rate constant for pyridine ligand edge exchange reaction in one of the cages and for the unusual activation parameters in the high-temperature regime. An alternative interpretation is proposed now.

Numerical simulation and experimental validation of the dynamics of multiple bubble merger during pool boiling under microgravity conditions.

PubMed

Abarajith, H S; Dhir, V K; Warrier, G; Son, G

2004-11-01

Numerical simulation and experimental validation of the growth and departure of multiple merging bubbles and associated heat transfer on a horizontal heated surface during pool boiling under variable gravity conditions have been performed. A finite difference scheme is used to solve the equations governing mass, momentum, and energy in the vapor liquid phases. The vapor-liquid interface is captured by a level set method that is modified to include the influence of phase change at the liquid-vapor interface. Water is used as test liquid. The effects of reduced gravity condition and orientation of the bubbles on the bubble diameter, interfacial structure, bubble merger time, and departure time, as well as local heat fluxes, are studied. In the experiments, multiple vapor bubbles are produced on artificial cavities in the 2-10 micrometer diameter range, microfabricated on the polished silicon wafer with given spacing. The wafer was heated electrically from the back with miniature strain gage type heating elements in order to control the nucleation superheat. The experiments conducted in normal Earth gravity and in the low gravity environment of KC-135 aircraft are used to validate the numerical simulations.

Bubble nucleation in simple and molecular liquids via the largest spherical cavity method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gonzalez, Miguel A., E-mail: m.gonzalez12@imperial.ac.uk; Department of Chemistry, Imperial College London, London SW7 2AZ; Abascal, José L. F.

2015-04-21

In this work, we propose a methodology to compute bubble nucleation free energy barriers using trajectories generated via molecular dynamics simulations. We follow the bubble nucleation process by means of a local order parameter, defined by the volume of the largest spherical cavity (LSC) formed in the nucleating trajectories. This order parameter simplifies considerably the monitoring of the nucleation events, as compared with the previous approaches which require ad hoc criteria to classify the atoms and molecules as liquid or vapor. The combination of the LSC and the mean first passage time technique can then be used to obtain themore » free energy curves. Upon computation of the cavity distribution function the nucleation rate and free-energy barrier can then be computed. We test our method against recent computations of bubble nucleation in simple liquids and water at negative pressures. We obtain free-energy barriers in good agreement with the previous works. The LSC method provides a versatile and computationally efficient route to estimate the volume of critical bubbles the nucleation rate and to compute bubble nucleation free-energies in both simple and molecular liquids.« less

Walks of bubbles on a hot wire in a liquid bath

NASA Astrophysics Data System (ADS)

Duchesne, A.; Caps, H.

2017-05-01

When a horizontal resistive wire is heated up to the boiling point in a subcooled liquid bath, some vapor bubbles nucleate on its surface. The traditional nucleate boiling theory predicts that bubbles generated from active nucleate sites grow up and depart from the heating surface due to buoyancy and inertia. However, we observed here a different behavior: the bubbles slide along the heated wire. In this situation, unexpected regimes are observed; from the simple sliding motion to bubble clustering. We noticed that bubbles could rapidly change their moving direction and may also interact. Finally, we propose an interpretation for both the attraction between the bubbles and the wire and for the motion of the bubbles on the wire in terms of Marangoni effects.

Anti-Bubbles

NASA Astrophysics Data System (ADS)

Tufaile, Alberto; Sartorelli, José Carlos

2003-08-01

An anti-bubble is a striking kind of bubble in liquid that seemingly does not comply the buoyancy, and after few minutes it disappears suddenly inside the liquid. Different from a simple air bubble that rises directly to the liquid surface, an anti-bubble wanders around in the fluid due to its slightly lesser density than the surrounding liquid. In spite of this odd behavior, an anti-bubble can be understood as the opposite of a conventional soap bubble in air, which is a shell of liquid surrounding air, and an anti-bubble is a shell of air surrounding a drop of the liquid inside the liquid. Two-phase flow has been a subject of interest due to its relevance to process equipment for contacting gases and liquids applied in industry. A chain of bubbles rising in a liquid formed from a nozzle is a two-phase flow, and there are certain conditions in which spherical air shells, called anti-bubbles, are produced. The purpose of this work is mainly to note the existence of anti-bubbling regime as a sequel of a bubbling system. We initially have presented the experimental apparatus. After this we have described the evolution of the bubbling regimes, and emulated the effect of bubbling coalescence with simple maps. Then is shown the inverted dripping as a consequence of the bubble coalescence, and finally the conditions for anti-bubble formation.

Double bubble with the big-bubble technique during deep anterior lamellar keratoplasty.

PubMed

Wise, Stephanie; Dubord, Paul; Yeung, Sonia N

2017-04-28

To report a case of intraoperative double bubble that formed during big-bubble DALK surgery in a patient with corneal scarring secondary to herpetic stromal keratitis. Case report. A 22 year old woman presented with a large corneal scar, likely secondary to previous herpetic stromal keratitis. She underwent big-bubble DALK surgery for visual rehabilitation. Intraoperatively, a mixed bubble with persistent type 2 bubble postoperatively was noted. The second bubble resorbed with clearance of the graft and good visual outcome after 6 weeks. This case report describes the unusual development of a mixed bubble during big-bubble DALK surgery. This graft cleared with resolution of the second bubble postoperatively without further surgical intervention.

Systems and methods for generation of hydrogen peroxide vapor

DOEpatents

Love, Adam H; Eckels, Joel Del; Vu, Alexander K; Alcaraz, Armando; Reynolds, John G

2014-12-02

A system according to one embodiment includes a moisture trap for drying air; at least one of a first container and a second container; and a mechanism for at least one of: bubbling dried air from the moisture trap through a hydrogen peroxide solution in the first container for producing a hydrogen peroxide vapor, and passing dried air from the moisture trap into a headspace above a hydrogen peroxide solution in the second container for producing a hydrogen peroxide vapor. A method according one embodiment includes at least one of bubbling dried air through a hydrogen peroxide solution in a container for producing a first hydrogen peroxide vapor, and passing dried air from the moisture trap into a headspace above the hydrogen peroxide solution in a container for producing a second hydrogen peroxide vapor. Additional systems and methods are also presented.

Vapor segregation and loss in basaltic melts

NASA Astrophysics Data System (ADS)

Edmonds, Marie; Gerlach, Terrence M.

2007-08-01

Measurements of volcanic gases at Pu'u‘Ō’ō, Kilauea Volcano, Hawai'i, reveal distinct degassing regimes with respect to vapor segregation and loss during effusive activity in 2004-2005. Three styles of vapor loss are distinguished by the chemical character of the emitted volcanic gases, measured by open path Fourier transform infrared spectroscopy: (1) persistent continuous gas emission, (2) gas piston events, and (3) lava spattering. Persistent continuous gas emission is associated with magma ascent and degassing beneath the crater vents, then eruption of the degassed magma from flank vents. Gas piston events are the result of static gas accumulation at depths of 400-900 m beneath Pu'u‘Ō’ō. A CO2-rich gas slug travels up the conduit at a few meters per second, displacing magma as it expands. Lava spattering occurs due to dynamic bubble coalescence in a column of relatively stagnant magma. The large gas bubbles are H2O rich and are generated by open-system degassing at depths of <150 m. Static gas accumulation and dynamic bubble coalescence are both manifestations of vapor segregation in basaltic melts, but their implications differ. Accumulation and segregation of CO2-rich vapor at depth does not deplete the melt of H2O (required to drive lava fountains near to the surface) and therefore gas piston events can occur interspersed with lava fountaining activity. Lava spattering, however, efficiently strips H2O-rich vapor from magma beneath the crater vents; the magma must then erupt effusively from vents on the flank of the cone.

Acoustic Droplet Vaporization in Biology and Medicine

PubMed Central

Pitt, William G.

2013-01-01

This paper reviews the literature regarding the use of acoustic droplet vaporization (ADV) in clinical applications of imaging, embolic therapy, and therapeutic delivery. ADV is a physical process in which the pressure waves of ultrasound induce a phase transition that causes superheated liquid nanodroplets to form gas bubbles. The bubbles provide ultrasonic imaging contrast and other functions. ADV of perfluoropentane was used extensively in imaging for preclinical trials in the 1990s, but its use declined rapidly with the advent of other imaging agents. In the last decade, ADV was proposed and explored for embolic occlusion therapy, drug delivery, aberration correction, and high intensity focused ultrasound (HIFU) sensitization. Vessel occlusion via ADV has been explored in rodents and dogs and may be approaching clinical use. ADV for drug delivery is still in preclinical stages with initial applications to treat tumors in mice. Other techniques are still in preclinical studies but have potential for clinical use in specialty applications. Overall, ADV has a bright future in clinical application because the small size of nanodroplets greatly reduces the rate of clearance compared to larger contrast agent bubbles and yet provides the advantages of ultrasonographic contrast, acoustic cavitation, and nontoxicity of conventional perfluorocarbon contrast agent bubbles. PMID:24350267

Nonspherical laser-induced cavitation bubbles

NASA Astrophysics Data System (ADS)

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

2010-01-01

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

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

Effects of free-stream turbulence intensity on transition in a laminar separation bubble formed over an airfoil

NASA Astrophysics Data System (ADS)

Istvan, Mark S.; Yarusevych, Serhiy

2018-03-01

The laminar-to-turbulent transition process in a laminar separation bubble formed over a NACA 0018 airfoil is investigated experimentally. All experiments are performed for an angle of attack of 4°, chord Reynolds numbers of 80,000 and 125,000, and free-stream turbulence intensities between 0.06 and 1.99%. The results show that increasing the level of free-stream turbulence intensity leads to a decrease in separation bubble length, attributed to a downstream shift in mean separation and an upstream shift in mean reattachment, the later ascribed to an upstream shift in mean transition. Maximum spatial amplification rates of disturbances in the separated shear layer decrease with increasing free-stream turbulence intensity, implying that the larger initial amplitudes of disturbances are solely responsible for the upstream shift in mean transition and as a result mean reattachment. At the baseline level of turbulence intensity, coherent structures forming in the aft portion of the bubble are characterized by strong spanwise coherence at formation, and undergo spanwise deformations leading to localized breakup in the vicinity of mean reattachment. As the level of free-stream turbulence intensity is increased, the spanwise coherence of the shear layer rollers is reduced, and spanwise undulations in the vortex filaments start to take place at the mean location of roll-up. At the highest level of turbulence intensity investigated, streamwise streaks originating in the boundary layer upstream of the separation bubble are observed within the bubble. These streaks signify an onset of bypass transition upstream of the separation bubble, which gives rise to a highly three-dimensional shear layer roll-up. A quantitative analysis of the associated changes in salient characteristics of the coherent structures is presented, connecting the effect of elevated free-stream turbulence intensity on the time-averaged and dynamic characteristics of the separation bubble.

Effect of vibration amplitude on vapor cavitation in journal bearings

NASA Astrophysics Data System (ADS)

Brewe, D. E.; Jacobson, B. O.

Computational movies were used to analyze the formation and collapse of vapor cavitation bubbles in a submerged journal bearing. The effect of vibration amplitude on vapor cavitation was studied for a journal undergoing circular whirl. The boundary conditions were implemented using Elrod's algorithm, which conserves mass flow through the cavitation bubble as well as through the oil-film region of the bearing. The vibration amplitudes for the different cases studied resulted in maximum eccentricity ratios ranging from 0.4 to 0.9. The minimum eccentricity ratio reached in each case was 0.1. For the least vibration amplitude studied in which the eccentricity ratio varied between 0.1 and 0.4, no vapor cavitation occurred. The largest vibration amplitude (i.e., eccentricity ratios of 0.1 to 0.9) resulted in vapor cavitation present 76 percent of one complete orbit.

Effect of vibration amplitude on vapor cavitation in journal bearings

NASA Technical Reports Server (NTRS)

Brewe, D. E.; Jacobson, B. O.

1986-01-01

Computational movies were used to analyze the formation and collapse of vapor cavitation bubbles in a submerged journal bearing. The effect of vibration amplitude on vapor cavitation was studied for a journal undergoing circular whirl. The boundary conditions were implemented using Elrod's algorithm, which conserves mass flow through the cavitation bubble as well as through the oil-film region of the bearing. The vibration amplitudes for the different cases studied resulted in maximum eccentricity ratios ranging from 0.4 to 0.9. The minimum eccentricity ratio reached in each case was 0.1. For the least vibration amplitude studied in which the eccentricity ratio varied between 0.1 and 0.4, no vapor cavitation occurred. The largest vibration amplitude (i.e., eccentricity ratios of 0.1 to 0.9) resulted in vapor cavitation present 76 percent of one complete orbit.

Vapor segregation and loss in basaltic melts

USGS Publications Warehouse

Edmonds, M.; Gerlach, T.M.

2007-01-01

Measurements of volcanic gases at Pu'u'O??'o??, Kilauea Volcano, Hawai'i, reveal distinct degassing regimes with respect to vapor segregation and loss during effusive activity in 2004-2005. Three styles of vapor loss are distinguished by the chemical character of the emitted volcanic gases, measured by open path Fourier transform infrared spectroscopy: 1 persistent continuous gas emission, 2 gas piston events, and 3 lava spattering. Persistent continuous gas emission is associated with magma ascent and degassing beneath the crater vents, then eruption of the degassed magma from flank vents. Gas piston events are the result of static gas accumulation at depths of 400-900 m beneath Pu'u'O??'o??. A CO2-rich gas slug travels up the conduit at a few meters per second, displacing magma as it expands. Lava spattering occurs due to dynamic bubble coalescence in a column of relatively stagnant magma. The Large gas bubbles are H2O rich and are generated by open-system degassing at depths of <150 m. Static gas accumulation and dynamic bubble coalescence are both manifestations of vapor segregation in basaltic melts, but their implications differ. Accumulation and segregation of CO2-rich vapor at depth does not deplete the melt of H2O (required to drive lava fountains near to the surface) and therefore gas piston events can occur interspersed with lava fountaining activity. Lava spattering, however, efficiently strips H2O-rich vapor from magma beneath the crater vents; the magma must then erupt effusively from vents on the flank of the cone. ?? 2007 The Geological Society of America.

Inertial collapse of bubble pairs near a solid surface

NASA Astrophysics Data System (ADS)

Alahyari Beig, Shahaboddin; Johnsen, Eric

2017-11-01

Cavitation occurs in a variety of applications ranging from naval structures to biomedical ultrasound. One important consequence is structural damage to neighboring surfaces following repeated inertial collapse of vapor bubbles. Although the mechanical loading produced by the collapse of a single bubble has been widely investigated, less is known about the detailed dynamics of the collapse of multiple bubbles. In such a problem, the bubble-bubble interactions typically affect the dynamics, e.g., by increasing the non-sphericity of the bubbles and amplifying/hindering the collapse intensity depending on the flow parameters. Here, we quantify the effects of bubble-bubble interactions on the bubble dynamics, as well as the pressures/temperatures produced by the collapse of a pair of gas bubbles near a rigid surface. We perform high-resolution simulations of this problem by solving the three-dimensional compressible Navier-Stokes equations for gas/liquid flows. The results are used to investigate the non-spherical bubble dynamics and characterize the pressure and temperature fields based on the relevant parameters entering the problem: stand-off distance, geometrical configuration (angle, relative size, distance), collapse strength. This research was supported in part by ONR Grant N00014-12-1-0751 and NSF Grant CBET 1253157.

Plasmonic nanoparticle-generated photothermal bubbles and their biomedical applications

PubMed Central

Lapotko, Dmitri

2009-01-01

This article is focused on the optical generation and detection of photothermal vapor bubbles around plasmonic nanoparticles. We report physical properties of such plasmonic nanobubbles and their biomedical applications as cellular probes. Our experimental studies of gold nanoparticle-generated photothermal bubbles demonstrated the selectivity of photothermal bubble generation, amplification of optical scattering and thermal insulation effect, all realized at the nanoscale. The generation and imaging of photothermal bubbles in living cells (leukemia and carcinoma culture and primary cancerous cells), and tissues (atherosclerotic plaque and solid tumor in animal) demonstrated a noninvasive highly sensitive imaging of target cells by small photothermal bubbles and a selective mechanical, nonthermal damage to the individual target cells by bigger photothermal bubbles due to a rapid disruption of cellular membranes. The analysis of the plasmonic nanobubbles suggests them as theranostic probes, which can be tuned and optically guided at cell level from diagnosis to delivery and therapy during one fast process. PMID:19839816

Interfacial bubbles formed by plunging thin liquid films in a pool

NASA Astrophysics Data System (ADS)

Salkin, Louis; Schmit, Alexandre; David, Richard; Delvert, Alexandre; Gicquel, Eric; Panizza, Pascal; Courbin, Laurent

2017-06-01

We show that the immersion of a horizontally suspended thin film of liquid in a pool of the same fluid creates an interfacial bubble, that is, a bubble at the liquid-air interface. Varying the fluid properties, the film's size, and its immersion velocity, our experiments unveil two formation regimes characterized by either a visco-capillary or an inertio-capillary mechanism that controls the size of a produced bubble. To rationalize these results, we compare the pressure exerted by the air flow under a plunging film with the Laplace pressure needed to generate film dimpling, which subsequently yields air entrapment and the production of a bubble. This physical model explains the power-law variations of the bubble size with the governing dimensionless number for each regime.

Chaotic bubbling and nonstagnant foams.

PubMed

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

2007-06-01

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

STEAM FORMING NEUTRONIC REACTOR AND METHOD OF OPERATING IT

DOEpatents

Untermyer, S.

1960-05-10

The heterogeneous reactor is liquid moderated and cooled by a steam forming coolant and is designed to produce steam from the coolant directly within the active portion of the reactor while avoiding the formation of bubbles in the liquid moderator. This reactor achieves inherent stability as a result of increased neutron leakage and increased neutron resonance absorption in the U/sup 238/ fuel with the formation of bubbles. The invention produces certain conditions under which the formation of vapor bubbles as a result of a neutron flux excursion from the injection of a reactivity increment into the reactor will operate to nullify the reactivity increment within a sufficiently short period of time to prevent unsafe reactor operating conditions from developing. This is obtained by disposing a plurality of fuel elements within a mass of steam forming coolant in the core with the ratio of the volume of steam forming coolant to the volume of fissionable isotopes being within the range yielding a multiplication factor greater than unity and a negative reactivity to core void coefficient at the boiling temperature of the coolant.

Bubble-facilitated VOC transport: Laboratory experiments and numerical modelling

NASA Astrophysics Data System (ADS)

Mumford, K. G.; Soucy, N. C.

2017-12-01

Most conceptual and numerical models of vapor intrusion assume that the transport of volatile organic compounds (VOCs) from the source to near the building foundation is a diffusion-limited processes. However, the transport of VOCs by mobilized gas bubbles through the saturated zone could lead to increased rates of transport and advection through the unsaturated zone, thereby increasing mass flux and risks associated with vapor intrusion. This mobilized gas could be biogenic (methanogenic) but could also result from the partitioning of VOC to trapped atmospheric gases in light non-aqueous phase liquid (LNAPL) smear zones. The potential for bubble-facilitated VOC transport to increase mass flux was investigated in a series of 1D and 2D laboratory experiments. Pentane source zones were emplaced in sand using sequential drainage and imbibition steps to mimic a water table fluctuation and trap air alongside LNAPL residual. This source was placed below an uncontaminated, water saturated sand (occlusion zone) and a gravel-sized (glass beads) unsaturated zone. Water was pumped laterally through the source zone and occlusion zone to deliver the dissolved gases (air) that are required for the expansion of trapped gas bubbles. Images from 2D flow cell experiments were used to demonstrate fluid rearrangement in the source zone and gas expansion to the occlusion zone, and 1D column experiments were used to measure gas-phase pentane mass flux. This flux was found to be 1-2 orders of magnitude greater than that measured in diffusion-dominated control columns, and showed intermittent behavior consistent with bubble transport by repeated expansion, mobilization, coalescence and trapping. Numerical simulation results under a variety of conditions using an approach that couples macroscopic invasion percolation with mass transfer (MIP-MT) between the aqueous and gas phases will also be presented. The results of this study demonstrate the potential for bubble-facilitated transport to

On the shape of giant soap bubbles.

PubMed

Cohen, Caroline; Darbois Texier, Baptiste; Reyssat, Etienne; Snoeijer, Jacco H; Quéré, David; Clanet, Christophe

2017-03-07

We study the effect of gravity on giant soap bubbles and show that it becomes dominant above the critical size [Formula: see text], where [Formula: see text] is the mean thickness of the soap film and [Formula: see text] is the capillary length ([Formula: see text] stands for vapor-liquid surface tension, and [Formula: see text] stands for the liquid density). We first show experimentally that large soap bubbles do not retain a spherical shape but flatten when increasing their size. A theoretical model is then developed to account for this effect, predicting the shape based on mechanical equilibrium. In stark contrast to liquid drops, we show that there is no mechanical limit of the height of giant bubble shapes. In practice, the physicochemical constraints imposed by surfactant molecules limit the access to this large asymptotic domain. However, by an exact analogy, it is shown how the giant bubble shapes can be realized by large inflatable structures.

Observations of the collapses and rebounds of millimeter-sized lithotripsy bubbles

PubMed Central

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

2011-01-01

Bubbles excited by lithotripter shock waves undergo a prolonged growth followed by an inertial collapse and rebounds. In addition to the relevance for clinical lithotripsy treatments, such bubbles can be used to study the mechanics of inertial collapses. In particular, both phase change and diffusion among vapor and noncondensable gas molecules inside the bubble are known to alter the collapse dynamics of individual bubbles. Accordingly, the role of heat and mass transport during inertial collapses is explored by experimentally observing the collapses and rebounds of lithotripsy bubbles for water temperatures ranging from 20 to 60 °C and dissolved gas concentrations from 10 to 85% of saturation. Bubble responses were characterized through high-speed photography and acoustic measurements that identified the timing of individual bubble collapses. Maximum bubble diameters before and after collapse were estimated and the corresponding ratio of volumes was used to estimate the fraction of energy retained by the bubble through collapse. The rebounds demonstrated statistically significant dependencies on both dissolved gas concentration and temperature. In many observations, liquid jets indicating asymmetric bubble collapses were visible. Bubble rebounds were sensitive to these asymmetries primarily for water conditions corresponding to the most dissipative collapses. PMID:22088027

Dynamics of gas bubble growth in a supersaturated solution with Sievert's solubility law.

PubMed

Gor, G Yu; Kuchma, A E

2009-07-21

This paper presents a theoretical description of diffusion growth of a gas bubble after its nucleation in supersaturated liquid solution. We study systems where gas molecules completely dissociate in the solvent into two parts, thus making Sievert's solubility law valid. We show that the difference between Henry's and Sievert's laws for chemical equilibrium conditions causes the difference in bubble growth dynamics. Assuming that diffusion flux is steady we obtain a differential equation on bubble radius. Bubble dynamics equation is solved analytically for the case of homogeneous nucleation of a bubble, which takes place at a significant pressure drop. We also obtain conditions of diffusion flux steadiness. The fulfillment of these conditions is studied for the case of nucleation of water vapor bubbles in magmatic melts.

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.

Somma-Vesuvius Plinian Eruptions fed by mafic magma: insights from bubbles in melt inclusions

NASA Astrophysics Data System (ADS)

Esposito, R.; Redi, D.; Cannatelli, C.; Danyushevsky, L. V.; Lima, A.; Bodnar, R. J.; De Vivo, B.

2014-12-01

Mt. Somma-Vesuvius Plinian eruptions were first described by Pliny the younger in 79 AD during the infamous eruption that destroyed Pompeii. Today, such eruptions are still a concern to the nearly 3 million people living in the Naples metropolitan area. Understanding the source for Mt. Somma-Vesuvius magma and the coexisting volatile phase is vital to better constrain the long-term eruptive behavior of this volcano. In the present study, ~ 50 olivine phenocrysts were selected from lavas and pumices produced during mild effusive events referred to as inter-Plinian eruptions, and from highly explosive Plinian eruptions that occurred at Mt. Somma-Vesuvius between 33000 ka and 1631 AD. Selected olivine phenocrysts containing MI were examined petrographically and analyzed for Fo content. Fo varies from 69 to 73 mole% for inter-Plinian olivine crystals and from 84 to 90 mole% with one zoned olivine containing 76-81 mole% Fo, for Plinian olivine crystals. Investigated MI vary from slightly crystallized to highly crystallized. Selected crystallized MI were reheated using the Vernadsky stage, and quenched to a homogeneous glass (Group 1) or glass plus a vapor bubble (Group 2). On one hand, MI of Group 1 are hosted in olivine ranging from Fo72 to Fo76 and were all erupted from the Pompeii eruption (white pumice deposit). On the other hand, MI of Group 2 are trapped in olivine ranging from Fo69 to Fo81 and from Fo84 to Fo90, and the hosts are representative of both Plinian and inter-Plinian events. The only eruption where Group-1 and Group-2 MI coexist is the Pompeii eruption. Group 2 MIs were further analyzed by Raman to test for the presence of volatiles (CO2 or H2O) in the vapor bubbles. CO2 was detected in all MI analyzed. CO2 density was determined using the distance between the two Fermi-diad peaks, and ranges between 0.14 and 0.55 g/cm3. Six MI also showed evidence for H2O in the vapor bubble. In addition, carbonates were detected at the glass-vapor interface of five

Bubble migration in a compacting crystal-liquid mush

NASA Astrophysics Data System (ADS)

Boudreau, Alan

2016-04-01

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

Thermodynamic and kinetic considerations of nucleation and stabilization of acoustic cavitation bubbles in water.

PubMed

Bapat, Pratap S; Pandit, Aniruddha B

2008-01-01

Qualitative explanation for a homogeneous nucleation of acoustic cavitation bubbles in the incompressible liquid water with simple phenomenological approach has been provided via the concept of the desorbtion of the dissolved gas and the vaporization of local liquid molecules. The liquid medium has been viewed as an ensemble of lattice structures. Validity of the lattice structure approach against the Brownian motion of molecules in the liquid state has been discussed. Criterion based on probability for nucleus formation has been defined for the vaporization of local liquid molecules. Energy need for the enthalpy of vaporization has been considered as an energy criterion for the formation of a vaporous nucleus. Sound energy, thermal energy of the liquid bulk (Joule-Thomson effect) and free energy of activation, which is associated with water molecules in the liquid state (Brownian motion) as per the modified Eyring's kinetic theory of liquid are considered as possible sources for the enthalpy of vaporization of water molecules forming a single unit lattice. The classical nucleation theory has then been considered for expressing further growth of the vaporous nucleus against the surface energy barrier. Effect of liquid property (temperature), and effect of an acoustic parameter (frequency) on an acoustic cavitation threshold pressure have been discussed. Kinetics of nucleation has been considered.

Contact bubble bilayers with flush drainage.

PubMed

Iwamoto, Masayuki; Oiki, Shigetoshi

2015-03-16

Planar lipid bilayers have been used to form stable bilayers into which membrane proteins are reconstituted for measurements of their function under an applied membrane potential. Recently, a lipid bilayer membrane is formed by the apposition of two monolayers that line an oil-electrolyte interface. Here, a bilayer membrane system is developed with picoliter bubbles under mechanically and chemically manipulable conditions. A water bubble lined with a phospholipid monolayer is blown from a glass pipette into an oil phase. Two blowing pipettes are manipulated, and bubbles (each with a diameter of ~ 50 μm) are held side by side to form a bilayer, which is termed a contact bubble bilayer. With the electrode implemented in the blowing pipette, currents through the bilayer are readily measured. The intra-bubble pressure is varied with the pressure-controller, leading to various sizes of the bubble and the membrane area. A rapid solution exchange system is developed by introducing additional pressure-driven injection pipettes, and the blowing pipette works as a drain. The solution is exchanged within 20 ms. Also, an asymmetric membrane with different lipid composition of each leaflet is readily formed. Example applications of this versatile method are presented to characterize the function of ion channels.

Contact Bubble Bilayers with Flush Drainage

PubMed Central

Iwamoto, Masayuki; Oiki, Shigetoshi

2015-01-01

Planar lipid bilayers have been used to form stable bilayers into which membrane proteins are reconstituted for measurements of their function under an applied membrane potential. Recently, a lipid bilayer membrane is formed by the apposition of two monolayers that line an oil-electrolyte interface. Here, a bilayer membrane system is developed with picoliter bubbles under mechanically and chemically manipulable conditions. A water bubble lined with a phospholipid monolayer is blown from a glass pipette into an oil phase. Two blowing pipettes are manipulated, and bubbles (each with a diameter of ~ 50 μm) are held side by side to form a bilayer, which is termed a contact bubble bilayer. With the electrode implemented in the blowing pipette, currents through the bilayer are readily measured. The intra-bubble pressure is varied with the pressure-controller, leading to various sizes of the bubble and the membrane area. A rapid solution exchange system is developed by introducing additional pressure-driven injection pipettes, and the blowing pipette works as a drain. The solution is exchanged within 20 ms. Also, an asymmetric membrane with different lipid composition of each leaflet is readily formed. Example applications of this versatile method are presented to characterize the function of ion channels. PMID:25772819

Luminescence from cavitation bubbles deformed in uniform pressure gradients

NASA Astrophysics Data System (ADS)

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

2017-09-01

Presented here are observations that demonstrate how the deformation of millimetric cavitation bubbles by a uniform pressure gradient quenches single-collapse luminescence. Our innovative measurement system captures a broad luminescence spectrum (wavelength range, 300-900 nm) from the individual collapses of laser-induced bubbles in water. By varying the bubble size, driving pressure, and perceived gravity level aboard parabolic flights, we probed the limit from aspherical to highly spherical bubble collapses. Luminescence was detected for bubbles of maximum radii within the previously uncovered range, R0=1.5 -6 mm, for laser-induced bubbles. The relative luminescence energy was found to rapidly decrease as a function of the bubble asymmetry quantified by the anisotropy parameter ζ , which is the dimensionless equivalent of the Kelvin impulse. As established previously, ζ also dictates the characteristic parameters of bubble-driven microjets. The threshold of ζ beyond which no luminescence is observed in our experiment closely coincides with the threshold where the microjets visibly pierce the bubble and drive a vapor jet during the rebound. The individual fitted blackbody temperatures range between Tlum=7000 and Tlum=11 500 K but do not show any clear trend as a function of ζ . Time-resolved measurements using a high-speed photodetector disclose multiple luminescence events at each bubble collapse. The averaged full width at half-maximum of the pulse is found to scale with R0 and to range between 10 and 20 ns.

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.

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.

Proposed method to estimate the liquid-vapor accommodation coefficient based on experimental sonoluminescence data.

PubMed

Puente, Gabriela F; Bonetto, Fabián J

2005-05-01

We used the temporal evolution of the bubble radius in single-bubble sonoluminescence to estimate the water liquid-vapor accommodation coefficient. The rapid changes in the bubble radius that occur during the bubble collapse and rebounds are a function of the actual value of the accommodation coefficient. We selected bubble radius measurements obtained from two different experimental techniques in conjunction with a robust parameter estimation strategy and we obtained that for water at room temperature the mass accommodation coefficient is in the confidence interval [0.217,0.329].

Lava bubble-wall fragments formed by submarine hydrovolcanic explosions on Lo'ihi Seamount and Kilauea Volcano

USGS Publications Warehouse

Clague, D.A.; Davis, A.S.; Bischoff, J.L.; Dixon, J.E.; Geyer, R.

2000-01-01

Glassy bubble-wall fragments, morphologically similar to littoral limu o Pele, have been found in volcanic sands erupted on Lo'ihi Seamount and along the submarine east rift zone of Kilauea Volcano. The limu o Pele fragments are undegassed with respect to H2O and S and formed by mild steam explosions. Angular glass sand fragments apparently form at similar, and greater, depths by cooling-contraction granulation. The limu o Pele fragments from Lo'ihi Seamount are dominantly tholeiitic basalt containing 6.25-7.25% MgO. None of the limu o Pele samples from Lo'ihi Seamount contains less than 5.57% MgO, suggesting that higher viscosity magmas do not form lava bubbles. The dissolved CO2 and H2O contents of 7 of the limu o Pele fragments indicate eruption at 1200??300 m depth (120??30 bar). These pressures exceed that generally thought to limit steam explosions. We conclude that hydrovolcanic eruptions are possible, with appropriate pre-mixing conditions, at pressures as great as 120 bar.

Cavitation in confined water: ultra-fast bubble dynamics

NASA Astrophysics Data System (ADS)

Vincent, Olivier; Marmottant, Philippe

2012-02-01

In the hydraulic vessels of trees, water can be found at negative pressure. This metastable state, corresponding to mechanical tension, is achieved by evaporation through a porous medium. It can be relaxed by cavitation, i.e. the sudden nucleation of vapor bubbles. Harmful for the tree due to the subsequent emboli of sap vessels, cavitation is on the contrary used by ferns to eject spores very swiftly. We will focus here on the dynamics of the cavitation bubble, which is of primary importance to explain the previously cited natural phenomena. We use the recently developed method of artificial tress, using transparent hydrogels as the porous medium. Our experiments, on water confined in micrometric hydrogel cavities, show an extremely fast dynamics: bubbles are nucleated at the microsecond timescale. For cavities larger than 100 microns, the bubble ``rings'' with damped oscillations at MHz frequencies, whereas for smaller cavities the oscillations become overdamped. This rich dynamics can be accounted for by a model we developed, leading to a modified Rayleigh-Plesset equation. Interestingly, this model predicts the impossibility to nucleate bubbles above a critical confinement that depends on liquid negative pressure and corresponds to approximately 100 nm for 20 MPa tensions.

Star formation in shells of colliding multi-SNe bubbles

NASA Astrophysics Data System (ADS)

Vasiliev, Evgenii O.; Shchekinov, Yuri A.

2017-12-01

It is believed that when bubbles formed by multiple supernovae explosions interact with one another, they stimulate star formation in overlapping shells. We consider the evolution of a shocked layer formed by the collision of two identical bubbles each of which originated from OB clusters of ˜ 50 members and ˜ 50 pc. The clusters are separated by 200-400 pc.We found that depending on evolutionary status of colliding bubbles the shocked layer can either be destroyed into diffuse lumps, or be fragmented into dense clumps: the former occurs in collisions of young bubbles with continuing supernovae explosions, and the latter occurs in older bubble interactions.We argue that fragmentation efficiency in shells depends on external heating: for a heating rate <˜ 1.7×10-24 erg s-1 the number of fragments formed in a collision of two old bubbles reaches several tens at t ˜ 4 Myr, while a heating rate >˜ 7 × 10-24 erg s-1 prevents fragmentation. The clumps formed in freely expanding parts of bubbles are gradually destroyed and disappear on t <˜ 1 Myr,whereas those formed in the overlapping shells survive much longer. Because of this the number of fragments in an isolated bubble begins to decrease after reaching a maximum, while in collision of two old bubbles it fluctuates around 60-70 until longer than t ˜ 5 Myr.

Numerical and experimental study of dissociation in an air-water single-bubble sonoluminescence system.

PubMed

Puente, Gabriela F; Urteaga, Raúl; Bonetto, Fabián J

2005-10-01

We performed a comprehensive numerical and experimental analysis of dissociation effects in an air bubble in water acoustically levitated in a spherical resonator. Our numerical approach is based on suitable models for the different effects considered. We compared model predictions with experimental results obtained in our laboratory in the whole phase parameter space, for acoustic pressures from the bubble dissolution limit up to bubble extinction. The effects were taken into account simultaneously to consider the transition from nonsonoluminescence to sonoluminescence bubbles. The model includes (1) inside the bubble, transient and spatially nonuniform heat transfer using a collocation points method, dissociation of O2 and N2, and mass diffusion of vapor in the noncondensable gases; (2) at the bubble interface, nonequilibrium evaporation and condensation of water and a temperature jump due to the accommodation coefficient; (3) in the liquid, transient and spatially nonuniform heat transfer using a collocation points method, and mass diffusion of the gas in the liquid. The model is completed with a Rayleigh-Plesset equation with liquid compressible terms and vapor mass transfer. We computed the boundary for the shape instability based on the temporal evolution of the computed radius. The model is valid for an arbitrary number of dissociable gases dissolved in the liquid. We also obtained absolute measurements for R(t) using two photodetectors and Mie scattering calculations. The robust technique used allows the estimation of experimental results of absolute R0 and P(a). The technique is based on identifying the bubble dissolution limit coincident with the parametric instability in (P(a),R0) parameter space. We take advantage of the fact that this point can be determined experimentally with high precision and replicability. We computed the equilibrium concentration of the different gaseous species and water vapor during collapse as a function of P(a) and R0. The

Compressible bubbles in Stokes flow

NASA Astrophysics Data System (ADS)

Crowdy, Darren G.

2003-02-01

The problem of a two-dimensional inviscid compressible bubble evolving in Stokes flow is considered. By generalizing the work of Tanveer & Vasconcelos (1995) it is shown that for certain classes of initial condition the quasi-steady free boundary problem for the bubble shape evolution is reducible to a finite set of coupled nonlinear ordinary differential equations, the form of which depends on the equation of state governing the relationship between the bubble pressure and its area. Recent numerical calculations by Pozrikidis (2001) using boundary integral methods are retrieved and extended. If the ambient pressures are small enough, it is shown that bubbles can expand significantly. It is also shown that a bubble evolving adiabatically is less likely to expand than an isothermal bubble.

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.

Bubble nucleation and inflationary perturbations

NASA Astrophysics Data System (ADS)

Firouzjahi, Hassan; Jazayeri, Sadra; Karami, Asieh; Rostami, Tahereh

2017-12-01

In this work we study the imprints of bubble nucleation on primordial inflationary perturbations. We assume that the bubble is formed via the tunneling of a spectator field from the false vacuum of its potential to its true vacuum. We consider the configuration in which the observable CMB sphere is initially outside of the bubble. As the bubble expands, more and more regions of the exterior false vacuum, including our CMB sphere, fall into the interior of the bubble. The modes which leave the horizon during inflation at the time when the bubble wall collides with the observable CMB sphere are affected the most. The bubble wall induces non-trivial anisotropic and scale dependent corrections in the two point function of the curvature perturbation. The corrections in the curvature perturbation and the diagonal and off-diagonal elements of CMB power spectrum are estimated.

Vapor-phase cristobalite as a durable indicator of magmatic pore structure and halogen degassing: an example from White Island volcano (New Zealand)

NASA Astrophysics Data System (ADS)

Ian Schipper, C.; Mandon, Céline; Maksimenko, Anton; Castro, Jonathan M.; Conway, Chris E.; Hauer, Peter; Kirilova, Martina; Kilgour, Geoff

2017-10-01

Vesicles in volcanic rocks are physical records of magmatic degassing; however, the interpretation of their textures is complicated by resorption, coalescence, and collapse. We discuss the textural significance of vesicle-hosted vapor-phase cristobalite (high-T, low-P SiO2 polymorph), and its utility as a complement to textural assessments of magmatic degassing, using a representative dacite bomb erupted from White Island volcano (New Zealand) in 1999. Imaging in 2D (SEM) and 3D (CT) shows the bomb to have 56% bulk porosity, almost all of which is connected ( 99%) and devoid of SiO2 phases. The remaining ( 1%) of porosity is in isolated, sub-spherical vesicles that have corroded walls and contain small (< 30 μm across) prismatic vapor-phase cristobalite crystals (98.4 ± 0.4 wt.% SiO2 with diagnostic laser Raman spectra). Halogen degassing models show vapor-phase cristobalite to be indicative of closed-system chlorine and fluorine partitioning into H2O-rich fluid in isolated pores. At White Island, this occurred during shallow (< 100s of meters) ascent and extensive ( 50%) groundmass crystallization associated with slow cooling in a volcanic plug. Pristine textures in this White Island bomb demonstrate the link between pore isolation and vapor-phase cristobalite deposition. We suggest that because these crystals have higher preservation potential than the bubbles in which they form, they can serve as durable, qualitative textural indicators of halogen degassing and pre-quench bubble morphologies in slowly cooled volcanic rocks (e.g., lava flows and domes), even where emplacement mechanisms have overprinted original bubble textures.

Removal of nanoaerosol during the bubbling of the salt melt of beryllium and lithium fluorides for the preparation of reactor radioisotopes

NASA Astrophysics Data System (ADS)

Zagnit'ko, A. V.; Chuvilin, D. Yu.

2010-06-01

The parameters of aerosol particles formed in the course of the spontaneous thermal condensation of vapors and bubbling a 66LiF-34BeF2 (mol %) eutectic salt mixture with helium have been studied. For this purpose, a vertical bubbling mode at T ≈ 900 K and an ampule device for obtaining reactor radioisotopes for medical applications were used. The rate of the bulk removal and the chemical composition of aerosols were measured. The size distribution of the aerosol particles was bimodal, and the mass concentration of the particles exceeded by far the maximum permissible concentration (MPC). The characteristics of regenerated nickel multilayer nanofilters for ultrahigh filtration of aerosols from the salt liquid melt were analyzed.

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.

Dynamic behaviors of cavitation bubble for the steady cavitating flow

NASA Astrophysics Data System (ADS)

Cai, Jun; Huai, Xiulan; Li, Xunfeng

2009-12-01

In this paper, by introducing the flow velocity item into the classical Rayleigh-Plesset dynamic equation, a new equation, which does not involve the time term and can describe the motion of cavitation bubble in the steady cavitating flow, has been obtained. By solving the new motion equation using Runge-Kutta fourth order method with adaptive step size control, the dynamic behaviors of cavitation bubble driven by the varying pressure field downstream of a venturi cavitation reactor are numerically simulated. The effects of liquid temperature (corresponding to the saturated vapor pressure of liquid), cavitation number and inlet pressure of venturi on radial motion of bubble and pressure pulse due to the radial motion are analyzed and discussed in detail. Some dynamic behaviors of bubble different from those in previous papers are displayed. In addition, the internal relationship between bubble dynamics and process intensification is also discussed. The simulation results reported in this work reveal the variation laws of cavitation intensity with the flow conditions of liquid, and will lay a foundation for the practical application of hydrodynamic cavitation technology.

Vaporization dynamics of volatile perfluorocarbon droplets: A theoretical model and in vitro validation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Doinikov, Alexander A., E-mail: doinikov@bsu.by; Bouakaz, Ayache; Sheeran, Paul S.

2014-10-15

Purpose: Perfluorocarbon (PFC) microdroplets, called phase-change contrast agents (PCCAs), are a promising tool in ultrasound imaging and therapy. Interest in PCCAs is motivated by the fact that they can be triggered to transition from the liquid state to the gas state by an externally applied acoustic pulse. This property opens up new approaches to applications in ultrasound medicine. Insight into the physics of vaporization of PFC droplets is vital for effective use of PCCAs and for anticipating bioeffects. PCCAs composed of volatile PFCs (with low boiling point) exhibit complex dynamic behavior: after vaporization by a short acoustic pulse, a PFCmore » droplet turns into a vapor bubble which undergoes overexpansion and damped radial oscillation until settling to a final diameter. This behavior has not been well described theoretically so far. The purpose of our study is to develop an improved theoretical model that describes the vaporization dynamics of volatile PFC droplets and to validate this model by comparison with in vitro experimental data. Methods: The derivation of the model is based on applying the mathematical methods of fluid dynamics and thermodynamics to the process of the acoustic vaporization of PFC droplets. The used approach corrects shortcomings of the existing models. The validation of the model is carried out by comparing simulated results with in vitro experimental data acquired by ultrahigh speed video microscopy for octafluoropropane (OFP) and decafluorobutane (DFB) microdroplets of different sizes. Results: The developed theory allows one to simulate the growth of a vapor bubble inside a PFC droplet until the liquid PFC is completely converted into vapor, and the subsequent overexpansion and damped oscillations of the vapor bubble, including the influence of an externally applied acoustic pulse. To evaluate quantitatively the difference between simulated and experimental results, the L2-norm errors were calculated for all cases where

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.

Corner-transport-upwind lattice Boltzmann model for bubble cavitation

NASA Astrophysics Data System (ADS)

Sofonea, V.; Biciuşcǎ, T.; Busuioc, S.; Ambruş, Victor E.; Gonnella, G.; Lamura, A.

2018-02-01

Aiming to study the bubble cavitation problem in quiescent and sheared liquids, a third-order isothermal lattice Boltzmann model that describes a two-dimensional (2D) fluid obeying the van der Waals equation of state, is introduced. The evolution equations for the distribution functions in this off-lattice model with 16 velocities are solved using the corner-transport-upwind (CTU) numerical scheme on large square lattices (up to 6144 ×6144 nodes). The numerical viscosity and the regularization of the model are discussed for first- and second-order CTU schemes finding that the latter choice allows to obtain a very accurate phase diagram of a nonideal fluid. In a quiescent liquid, the present model allows us to recover the solution of the 2D Rayleigh-Plesset equation for a growing vapor bubble. In a sheared liquid, we investigated the evolution of the total bubble area, the bubble deformation, and the bubble tilt angle, for various values of the shear rate. A linear relation between the dimensionless deformation coefficient D and the capillary number Ca is found at small Ca but with a different factor than in equilibrium liquids. A nonlinear regime is observed for Ca≳0.2 .

Single-bubble boiling under Earth's and low gravity

NASA Astrophysics Data System (ADS)

Khusid, Boris; Elele, Ezinwa; Lei, Qian; Tang, John; Shen, Yueyang

2017-11-01

Miniaturization of electronic systems in terrestrial and space applications is challenged by a dramatic increase in the power dissipation per unit volume with the occurrence of localized hot spots where the heat flux is much higher than the average. Cooling by forced gas or liquid flow appears insufficient to remove high local heat fluxes. Boiling that involves evaporation of liquid in a hot spot and condensation of vapor in a cold region can remove a significantly larger amount of heat through the latent heat of vaporization than force-flow cooling can carry out. Traditional methods for enhancing boiling heat transfer in terrestrial and space applications focus on removal of bubbles from the heating surface. In contrast, we unexpectedly observed a new boiling regime of water under Earth's gravity and low gravity in which a bubble was pinned on a small heater up to 270°C and delivered a heat flux up to 1.2 MW/m2 that was as high as the critical heat flux in the classical boiling regime on Earth .Low gravity measurements conducted in parabolic flights in NASA Boeing 727. The heat flux in flight and Earth's experiments was found to rise linearly with increasing the heater temperature. We will discuss physical mechanisms underlying heat transfer in single-bubble boiling. The work supported by NASA Grants NNX12AM26G and NNX09AK06G.

Bubble nucleation in stout beers

NASA Astrophysics Data System (ADS)

Lee, W. T.; McKechnie, J. S.; Devereux, M. G.

2011-05-01

Bubble nucleation in weakly supersaturated solutions of carbon dioxide—such as champagne, sparkling wines, and carbonated beers—is well understood. Bubbles grow and detach from nucleation sites: gas pockets trapped within hollow cellulose fibers. This mechanism appears not to be active in stout beers that are supersaturated solutions of nitrogen and carbon dioxide. In their canned forms these beers require additional technology (widgets) to release the bubbles which will form the head of the beer. We extend the mathematical model of bubble nucleation in carbonated liquids to the case of two gases and show that this nucleation mechanism is active in stout beers, though substantially slower than in carbonated beers and confirm this by observation. A rough calculation suggests that despite the slowness of the process, applying a coating of hollow porous fibers to the inside of a can or bottle could be a potential replacement for widgets.

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.

Microjet Penetrator - medical use of laser induced shock waves and bubbles

NASA Astrophysics Data System (ADS)

Yoh, Jack

2013-06-01

The laser-driven microjet penetrator system accelerates liquids drug and delivers them without a needle, which is shown to overcome the weaknesses of existing piston-driven jet injectors. The system consists of two back-to-back chambers separated by a rubber membrane, one containing ``driving'' water behind another of the liquid drug to be delivered. The laser pulse is sent once, and a bubble forms in the water chamber, which puts elastic strain on the membrane, causing the drug to be forcefully ejected from a miniature nozzle in a narrow jet of 150 micron in diameter. The impacting jet pressure is higher than the skin tensile strength and thus causes the jet to penetrate into the targeted depth underneath the skin. Multiple pulses of the laser increase the desired dosage. The experiments are performed with commercially available Nd:YAG and Er:YAG lasers for clinical applications in laser dermatology and dentistry. The difference in bubble behavior within the water chamber comes from pulse duration and wavelength. For Nd:YAG laser, the pulse duration is very short relative to the bubble lifetime making the bubble behavior close to that of a cavitation bubble (inertial), while in Er:YAG case the high absorption in water and the longer pulse duration change the initial behavior of the bubble making it close to a vapor bubble (thermal). The contraction and subsequent rebound for both cases were seen typical of cavitation bubble. The laser-induced microjet penetrators generate velocities which are sufficient for delivery of drug into a guinea-pig skin for both laser beams of different pulse duration and wavelength. We estimate the typical velocity within 30-80 m/s range and the breakup length to be larger than 1 mm, thus making it a contamination-free medical procedure. Hydrodynamic theory confirms the nozzle exit jet velocity obtained by the microjet system. A significant increase in the delivered dose of drugs is achieved with multiple pulses of a 2.9 μm Er

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.

Modelling chemical reactions in dc plasma inside oxygen bubbles in water

NASA Astrophysics Data System (ADS)

Takeuchi, N.; Ishii, Y.; Yasuoka, K.

2012-02-01

Plasmas generated inside oxygen bubbles in water have been developed for water purification. Zero-dimensional numerical simulations were used to investigate the chemical reactions in plasmas driven by dc voltage. The numerical and experimental results of the concentrations of hydrogen peroxide and ozone in the solution were compared with a discharge current between 1 and 7 mA. Upon increasing the water vapour concentration inside bubbles, we saw from the numerical results that the concentration of hydrogen peroxide increased with discharge current, whereas the concentration of ozone decreased. This finding agreed with the experimental results. With an increase in the discharge current, the heat flux from the plasma to the solution increased, and a large amount of water was probably vaporized into the bubbles.

An acoustical bubble counter for superheated drop detectors.

PubMed

Taylor, Chris; Montvila, Darius; Flynn, David; Brennan, Christopher; d'Errico, Francesco

2006-01-01

A new bubble counter has been developed based on the well-established approach of detecting vaporization events acoustically in superheated drop detectors (SDDs). This counter is called the Framework Scientific ABC 1260, and it represents a major improvement over prior versions of this technology. By utilizing advanced acoustic pattern recognition software, the bubble formation event can be differentiated from ambient background noise, as well as from other acoustic signatures. Additional structural design enhancements include a relocation of the electronic components to the bottom of the device; thus allowing for greater stability, easier access to vial SDDs without exposure to system electronics. Upgrades in the electronics permit an increase in the speed of bubble detection by almost 50%, compared with earlier versions of the counters. By positioning the vial on top of the device, temperature and sound insulation can be accommodated for extreme environments. Lead shells can also be utilized for an enhanced response to high-energy neutrons.

Electrical Breakdown in Water Vapor

NASA Astrophysics Data System (ADS)

Škoro, N.; Marić, D.; Malović, G.; Graham, W. G.; Petrović, Z. Lj.

2011-11-01

In this paper investigations of the voltage required to break down water vapor are reported for the region around the Paschen minimum and to the left of it. In spite of numerous applications of discharges in biomedicine, and recent studies of discharges in water and vapor bubbles and discharges with liquid water electrodes, studies of the basic parameters of breakdown are lacking. Paschen curves have been measured by recording voltages and currents in the low-current Townsend regime and extrapolating them to zero current. The minimum electrical breakdown voltage for water vapor was found to be 480 V at a pressure times electrode distance (pd) value of around 0.6 Torr cm (˜0.8 Pa m). The present measurements are also interpreted using (and add additional insight into) the developing understanding of relevant atomic and particularly surface processes associated with electrical breakdown.

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. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

Infinite stream of Hele--Shaw bubbles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burgess, D.; Tanveer, S.

1991-03-01

Exact solutions are presented for a steady stream of bubbles in a Hele--Shaw cell when the effect of surface tension is neglected. These solutions form a three-parameter family. For specified area and distance between bubbles, the speed of the bubble remains arbitrary when surface tension is neglected. However, numerical and analytical evidence indicates that this arbitrariness is removed by the effect of surface tension. The branch of solutions that corresponds to the McLean--Saffman finger solution were primarily studied. A dramatic increase was observed in bubble speeds when the distance between bubbles is on the order of a bubble diameter, whichmore » may have relevance to experiments done by Maxworthy (J. Fluid Mech. {bold 173}, 95 (1986)).« less

An experimental investigation of bubble splitting through multiple bifurcations

NASA Astrophysics Data System (ADS)

Bull, Joseph L.; Eshpuniyani, Brijesh; Fowlkes, J. Brian

2004-11-01

A bench top vascular bifurcation model is used to investigate the splitting of long bubbles in a series of liquid-filled bifurcations. These experiments are motivated by a gas embolotherapy technique for the potential treatment of cancer by using gas emboli to infarct tumors. The gas bubbles originate as perfluorocarbon droplets that are small enough to pass through capillaries and are injected into the bloodstream. Low intensity ultrasound is used to track their motion, and they are vaporized at the desired location for treatment via high intensity ultrasound to produce gas bubbles whose volumes are approximately 125 to 150 times the droplet volume. Achieving complete tumor necrosis requires infarction of most of the tumor. Understanding the transport and splitting of the gas bubbles, which can be long enough to extend through more than one bifurcation, is necessary to design delivery strategies. The current experiments investigate the behavior of a bubble as it passes through a series of two geometrically symmetric bifurcations, for different values of effective Bond number, which depends on gravity and the positioning of the bifurcation, capillary number, and bubble volume. The experiments are designed to match the Reynolds, Bond and capillary numbers to the physiological values for arterioles, and to provide guidance in achieving uniform tumor infarction. This work is supported by NSF grant BES-0301278 and NIH grant EB003541-01.

Focus Article: Theoretical aspects of vapor/gas nucleation at structured surfaces

NASA Astrophysics Data System (ADS)

Meloni, Simone; Giacomello, Alberto; Casciola, Carlo Massimo

2016-12-01

Heterogeneous nucleation is the preferential means of formation of a new phase. Gas and vapor nucleation in fluids under confinement or at textured surfaces is central for many phenomena of technological relevance, such as bubble release, cavitation, and biological growth. Understanding and developing quantitative models for nucleation is the key to control how bubbles are formed and to exploit them in technological applications. An example is the in silico design of textured surfaces or particles with tailored nucleation properties. However, despite the fact that gas/vapor nucleation has been investigated for more than one century, many aspects still remain unclear and a quantitative theory is still lacking; this is especially true for heterogeneous systems with nanoscale corrugations, for which experiments are difficult. The objective of this focus article is analyzing the main results of the last 10-20 years in the field, selecting few representative works out of this impressive body of the literature, and highlighting the open theoretical questions. We start by introducing classical theories of nucleation in homogeneous and in simple heterogeneous systems and then discuss their extension to complex heterogeneous cases. Then we describe results from recent theories and computer simulations aimed at overcoming the limitations of the simpler theories by considering explicitly the diffuse nature of the interfaces, atomistic, kinetic, and inertial effects.

Numerical Modeling of Liquid-Vapor Phase Change

NASA Technical Reports Server (NTRS)

Esmaeeli, Asghar; Arpaci, Vedat S.

2001-01-01

We implemented a two- and three-dimensional finite difference/front tracking technique to solve liquid-vapor phase change problems. The mathematical and the numerical features of the method were explained in great detail in our previous reports, Briefly, we used a single formula representation which incorporated jump conditions into the governing equations. The interfacial terms were distributed as singular terms using delta functions so that the governing equations would be the same as conventional conservation equations away from the interface and in the vicinity of the interface they would provide correct jump conditions. We used a fixed staggered grid to discretize these equations and an unstructured grid to explicitly track the front. While in two dimensions the front was simply a connection of small line segments, in three dimensions it was represented by a connection of small triangular elements. The equations were written in conservative forms and during the course of computations we used regriding to control the size of the elements of the unstructured grid. Moreover, we implemented a coalescence in two dimensions which allowed the merging of different fronts or two segments of the same front when they were sufficiently close. We used our code to study thermocapillary migration of bubbles, burst of bubbles at a free surface, buoyancy-driven interactions of bubbles, evaporation of drops, rapid evaporation of an interface, planar solidification of an undercooled melt, dendritic solidification, and a host of other problems cited in the reference.

Effects of viscosity on endothelial cell damage under acoustic droplet vaporization

NASA Astrophysics Data System (ADS)

Seda, Robinson; Singh, Rahul; Li, David; Pitre, John; Putnam, Andrew; Fowlkes, J. Brian; Bull, Joseph

2014-11-01

Acoustic droplet vaporization (ADV) is a process by which stabilized superheated microdroplets are able to undergo phase transition with the aid of focused ultrasound. Gas bubbles resulting from ADV can provide local occlusion of the blood vessels supplying diseased tissue, such as tumors. The ADV process can also induce bioeffects that increase vessel permeability, which is beneficial for localized drug delivery. Previous in vitro studies have demonstrated that vaporization at the endothelial layer will affect cell attachment and viability. Several hypotheses have been proposed to elucidate the mechanism of damage including the generation of normal and shear stresses during bubble expansion. A single 3.5 MHz ultrasound pulse consisting of 8 cycles (~2.3 μs) and a 6 MPa peak rarefactional pressure was used to induce ADV on endothelial cells in media of different viscosities. Carboxylmethyl cellulose was added to the cell media to increase the viscosity up to 300 cP to and aid in the reduction of stresses during bubble expansion. The likelihood of cell damage was decreased when compared to our control (~1 cP), but it was still present in some cases indicating that the mechanism of damage does not depend entirely on viscous stresses associated with bubble expansion. This work was supported by NIH Grant R01EB006476.

Convective mass transfer around a dissolving bubble

NASA Astrophysics Data System (ADS)

Duplat, Jerome; Grandemange, Mathieu; Poulain, Cedric

2017-11-01

Heat or mass transfer around an evaporating drop or condensing vapor bubble is a complex issue due to the interplay between the substrate properties, diffusion- and convection-driven mass transfer, and Marangoni effects, to mention but a few. In order to disentangle these mechanisms, we focus here mainly on the convective mass transfer contribution in an isothermal mass transfer problem. For this, we study the case of a millimetric carbon dioxide bubble which is suspended under a substrate and dissolved into pure liquid water. The high solubility of CO2 in water makes the liquid denser and promotes a buoyant-driven flow at a high (solutal) Rayleigh number (Ra˜104 ). The alteration of p H allows the concentration field in the liquid to be imaged by laser fluorescence enabling us to measure both the global mass flux (bubble volume, contact angle) and local mass flux around the bubble along time. After a short period of mass diffusion, where the boundary layer thickens like the square root of time, convection starts and the CO2 is carried by a plume falling at constant velocity. The boundary layer thickness then reaches a plateau which depends on the bubble cross section. Meanwhile the plume velocity scales like (dV /d t )1 /2 with V being the volume of the bubble. As for the rate of volume loss, we recover a constant mass flux in the diffusion-driven regime followed by a decrease in the volume V like V2 /3 after convection has started. We present a model which agrees well with the bubble dynamics and discuss our results in the context of droplet evaporation, as well as high Rayleigh convection.

Between soap bubbles and vesicles: The dynamics of freely floating smectic bubbles

NASA Astrophysics Data System (ADS)

Stannarius, Ralf; May, Kathrin; Harth, Kirsten; Trittel, Torsten

2013-03-01

The dynamics of droplets and bubbles, particularly on microscopic scales, are of considerable importance in biological, environmental, and technical contexts. We introduce freely floating bubbles of smectic liquid crystals and report their unique dynamic properties. Smectic bubbles can be used as simple models for dynamic studies of fluid membranes. In equilibrium, they form minimal surfaces like soap films. However, shape transformations of closed smectic membranes that change the surface area involve the formation and motion of molecular layer dislocations. These processes are slow compared to the capillary wave dynamics, therefore the effective surface tension is zero like in vesicles. Freely floating smectic bubbles are prepared from collapsing catenoid films and their dynamics is studied with optical high-speed imaging. Experiments are performed under normal gravity and in microgravity during parabolic flights. Supported by DLR within grant OASIS-Co.

Doughnut-shaped soap bubbles.

PubMed

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=L(3)/6π(2), and this is indeed the case of a free soap bubble, for instance. Surprisingly, we show that for V<αL(3)/6π(2), 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<αL(3)/6π(2) cannot be stable and should not exist in foams, for instance.

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.

Primordial black hole formation by vacuum bubbles

NASA Astrophysics Data System (ADS)

Deng, Heling; Vilenkin, Alexander

2017-12-01

Vacuum bubbles may nucleate during the inflationary epoch and expand, reaching relativistic speeds. After inflation ends, the bubbles are quickly slowed down, transferring their momentum to a shock wave that propagates outwards in the radiation background. The ultimate fate of the bubble depends on its size. Bubbles smaller than certain critical size collapse to ordinary black holes, while in the supercritical case the bubble interior inflates, forming a baby universe, which is connected to the exterior region by a wormhole. The wormhole then closes up, turning into two black holes at its two mouths. We use numerical simulations to find the masses of black holes formed in this scenario, both in subcritical and supercritical regime. The resulting mass spectrum is extremely broad, ranging over many orders of magnitude. For some parameter values, these black holes can serve as seeds for supermassive black holes and may account for LIGO observations.

Theoretical and experimental comparison of vapor cavitation in dynamically loaded journal bearings

NASA Astrophysics Data System (ADS)

Brewe, D. E.; Hamrock, B. J.; Jacobson, B. A.

Vapor cavitation for a submerged journal bearing under dynamically loaded conditions was investigated. The observation of vapor cavitation in the laboratory was done by high-speed photography. It was found that vapor cavitation occurs when the tensile stress applied to the oil exceeded the tensile strength of the oil or the binding of the oil to the surface. The theoretical solution to the Reynolds equation is determined numerically using a moving boundary algorithm. This algorithm conserves mass throughout the computational domain including the region of cavitation and its boundaries. An alternating direction implicit (MDI) method is used to effect the time march. A rotor undergoing circular whirl was studied. Predicted cavitation behavior was analyzed by three-dimensional computer graphic movies. The formation, growth, and collapse of the bubble in response to the dynamic conditions is shown. For the same conditions of dynamic loading, the cavitation bubble was studied in the laboratory using high-speed photography.

Theoretical and experimental comparison of vapor cavitation in dynamically loaded journal bearings

NASA Technical Reports Server (NTRS)

Brewe, D. E.; Hamrock, B. J.; Jacobson, B. A.

1985-01-01

Vapor cavitation for a submerged journal bearing under dynamically loaded conditions was investigated. The observation of vapor cavitation in the laboratory was done by high-speed photography. It was found that vapor cavitation occurs when the tensile stress applied to the oil exceeded the tensile strength of the oil or the binding of the oil to the surface. The theoretical solution to the Reynolds equation is determined numerically using a moving boundary algorithm. This algorithm conserves mass throughout the computational domain including the region of cavitation and its boundaries. An alternating direction implicit (MDI) method is used to effect the time march. A rotor undergoing circular whirl was studied. Predicted cavitation behavior was analyzed by three-dimensional computer graphic movies. The formation, growth, and collapse of the bubble in response to the dynamic conditions is shown. For the same conditions of dynamic loading, the cavitation bubble was studied in the laboratory using high-speed photography.

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

Occlusion and rupture of ex vivo capillary bifurcation due to acoustic droplet vaporization

NASA Astrophysics Data System (ADS)

Feng, Yi; Qin, Dui; Zhang, Jun; Zhang, Lei; Bouakaz, Ayache; Wan, Mingxi

2018-06-01

Gas embolotherapy (GE) consists in the occlusion of tumor blood vessels using gas emboli induced by acoustic droplet vaporization (ADV), to create tumor starvation and localized drug delivery. Therefore, the occlusion and rupture of capillary bifurcation due to ADV was investigated in an ex vivo rat mesentery model using a confocal acousto-optical high-speed microscope system. Following ADV bubble formation, coalescence, and translational movement, the growing bubbles lodged in and then occluded two different capillary bifurcations. Capillary rupture was induced at the bubble lodging area, immediately followed by gas extravasation and bubble dislodging. Before and after bubble lodgment/occlusion, a local microvessel invagination was observed due to the interactions between ADV bubbles and the microvessel itself, indicating a contribution to the capillary rupture. Understanding the transient dynamics of ADV bubble, the bubble-microvessel interaction and the consequent mechanical bio-effects in GE is of the paramount importance for developing and applying this approach in clinical practice.

Mesoporous hollow spheres from soap bubbling.

PubMed

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

2012-02-01

The smaller and more stable bubbles can be generated from the large parent bubbles by rupture. In the presence of a bubble blowing agent, hollow spheres can be prepared by bubbling a silica sol. Herein, the trapped gas inside the bubble acts as a template. When the porogen, i.e., other surfactant, is introduced, a mesostructured shell forms by the co-assembly with the silica sol during sol-gel process. Morphological evolution emphasizes the prerequisite of an intermediate interior gas flow rate and high exterior gas flow rate for hollow spheres. The method is valid for many compositions from inorganic, polymer to their composites. Copyright © 2011 Elsevier Inc. All rights reserved.

Vapor nucleation paths in lyophobic nanopores.

PubMed

Tinti, Antonio; Giacomello, Alberto; Casciola, Carlo Massimo

2018-04-19

In recent years, technologies revolving around the use of lyophobic nanopores gained considerable attention in both fundamental and applied research. Owing to the enormous internal surface area, heterogeneous lyophobic systems (HLS), constituted by a nanoporous lyophobic material and a non-wetting liquid, are promising candidates for the efficient storage or dissipation of mechanical energy. These diverse applications both rely on the forced intrusion and extrusion of the non-wetting liquid inside the pores; the behavior of HLS for storage or dissipation depends on the hysteresis between these two processes, which, in turn, are determined by the microscopic details of the system. It is easy to understand that molecular simulations provide an unmatched tool for understanding phenomena at these scales. In this contribution we use advanced atomistic simulation techniques in order to study the nucleation of vapor bubbles inside lyophobic mesopores. The use of the string method in collective variables allows us to overcome the computational challenges associated with the activated nature of the phenomenon, rendering a detailed picture of nucleation in confinement. In particular, this rare event method efficiently searches for the most probable nucleation path(s) in otherwise intractable, high-dimensional free-energy landscapes. Results reveal the existence of several independent nucleation paths associated with different free-energy barriers. In particular, there is a family of asymmetric transition paths, in which a bubble forms at one of the walls; the other family involves the formation of axisymmetric bubbles with an annulus shape. The computed free-energy profiles reveal that the asymmetric path is significantly more probable than the symmetric one, while the exact position where the asymmetric bubble forms is less relevant for the free energetics of the process. A comparison of the atomistic results with continuum models is also presented, showing how, for simple

Plasmonic Nanobubbles as Transient Vapor Nanobubbles Generated Around Plasmonic Nanoparticles

PubMed Central

Lukianova-Hleb, Ekaterina; Hu, Ying; Latterini, Loredana; Tarpani, Luigi; Lee, Seunghyun; Drezek, Rebekah A.; Hafner, Jason H.; Lapotko, Dmitri O.

2010-01-01

We have used short laser pulses to generate transient vapor nanobubbles around plasmonic nanoparticles. The photothermal, mechanical and optical properties of such bubbles were found to be different from those of plasmonic nanoparticle and vapor bubbles as well. This phenomena was considered as a new complex nanosystem – plasmonic nanobubble (PNB). Mechanical and optical scattering properties of PNB depended upon the nanoparticle surface and heat capacity, clusterization state, and the optical pulse length. The generation of the PNB required much higher laser pulse fluence thresholds than the explosive boiling level, and was characterized by the relatively high lower threshold of the minimal size (lifetime) of PNB. Optical scattering by PNB and its diameter (measured as the lifetime) has been varied with the fluence of laser pulse and this has demonstrated the tunable nature of PNB. PMID:20307085

Evolution of spherical cavitation bubbles: Parametric and closed-form solutions

NASA Astrophysics Data System (ADS)

Mancas, Stefan C.; Rosu, Haret C.

2016-02-01

We present an analysis of the Rayleigh-Plesset equation for a three dimensional vacuous bubble in water. In the simplest case when the effects of surface tension are neglected, the known parametric solutions for the radius and time evolution of the bubble in terms of a hypergeometric function are briefly reviewed. By including the surface tension, we show the connection between the Rayleigh-Plesset equation and Abel's equation, and obtain the parametric rational Weierstrass periodic solutions following the Abel route. In the same Abel approach, we also provide a discussion of the nonintegrable case of nonzero viscosity for which we perform a numerical integration.

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

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

Effects of fluid viscosity on a moving sonoluminescing bubble.

PubMed

Sadighi-Bonabi, Rasoul; Mirheydari, Mona; Rezaee, Nastaran; Ebrahimi, Homa

2011-08-01

Based on the quasi-adiabatic model, the parameters of the bubble interior for a moving single bubble sonoluminescence in water, adiponitrile, and N-methylformamide are calculated for various fluid viscosities. By using a complete form of the hydrodynamic force, the bubble trajectory is calculated for a moving single bubble sonoluminescence (m-SBSL). It is found that as the fluid viscosity increases, the unique circular path changes to an ellipsoidal and then linear form and along this incrementally increase of viscosity the light intensity increases. By using the Bremsstrahlung model to describe the bubble radiation, gradual increase of the viscosity results in brighter emissions. It is found that in fluids with higher viscosity the light intensity decreases as time passes.

Analysis of cavitation bubble dynamics in a liquid

NASA Technical Reports Server (NTRS)

Fontenot, L. L.; Lee, Y. C.

1971-01-01

General differential equations governing the dynamics of the cavitation bubbles in a liquid were derived. With the assumption of spherical symmetry the governing equations were simplified. Closed form solutions were obtained for simple cases, and numerical solutions were calculated for complicated ones. The growth and the collapse of the bubble were analyzed, oscillations of the bubbles were studied, and the stability of the cavitation bubbles were investigated. The results show that the cavitation bubbles are unstable, and the oscillation is not sinusoidal.

Moduli vacuum bubbles produced by evaporating black holes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morris, J. R.

2007-10-15

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

Laser-induced microjet: wavelength and pulse duration effects on bubble and jet generation for drug injection

NASA Astrophysics Data System (ADS)

Jang, Hun-jae; Park, Mi-ae; Sirotkin, Fedir V.; Yoh, Jack J.

2013-12-01

The expansion of the laser-induced bubble is the main mechanism in the developed microjet injector. In this study, Nd:YAG and Er:YAG lasers are used as triggers of the bubble formation. The impact of the laser parameters on the bubble dynamics is studied and the performance of the injector is evaluated. We found that the main cause of the differences in the bubble behavior comes from the pulse duration and wavelength. For Nd:YAG laser, the pulse duration is very short relative to the bubble lifetime making the behavior of the bubble close to that of the cavitation bubble, while in Er:YAG case, the high absorption in the water and long pulse duration change the initial behavior of the bubble making it close to a vapor bubble. The contraction and subsequent rebound are typical for cavitation bubbles in both cases. The results show that the laser-induced microjet injector generates velocity which is sufficient for the drug delivery for both laser beams of different pulse duration. We estimate the typical velocity within 30-80 m/s range and the breakup length to be larger than 1 mm suitable for trans-dermal drug injection.

Isotopic fractionation of volatile species during bubble growth in magmas

NASA Astrophysics Data System (ADS)

Watson, E. B.

2016-12-01

Bubbles grow in decompressing magmas by simple expansion and also by diffusive supply of volatiles to the bubble/melt interface. The latter phenomenon is of significant geochemical interest because diffusion can fractionate isotopes, raising the possibility that the isotopic character of volatile components in bubbles may not reflect that of volatiles dissolved in the host melt over the lifetime of a bubble—even in the complete absence of equilibrium vapor/melt isotopic fractionation. None of the foregoing is conceptually new, but recent experimental studies have established the existence of isotope mass effects on diffusion in silicate melts for several elements (Li, Mg, Ca, Fe), and this finding has now been extended to the volatile (anionic) element chlorine (Fortin et al. 2016; this meeting). Knowledge of isotope mass effects on diffusion of volatile species opens the way for quantitative models of diffusive fractionation during bubble growth. Significantly different effects are anticipated for "passive" volatiles (e.g., noble gases and Cl) that are partitioned into existing bubbles but play little role in nucleation and growth, as opposed to "active" volatiles whose limited solubilities lead to bubble nucleation during magma decompression. Numerical solution of the appropriate diffusion/mass-conservation equations reveals that the isotope effect on passive volatiles partitioned into bubbles growing at a constant rate in a static system depends (predictably) upon R/D, Kd and D1/D2 (R = growth rate; D = diffusivity; Kd = bubble/melt partition coefficient; D1/D2 = diffusivity ratio of the isotopes of interest). Constant R is unrealistic, but other scenarios can be explored by including the solubility and EOS of an "active" volatile (e.g., CO2) in numerical simulations of bubble growth. For plausible decompression paths, R increases exponentially with time—leading, potentially, to larger isotopic fractionation of species partitioned into the growing bubble.

Hubble's Cosmic Bubbles

NASA Image and Video Library

2017-12-08

This entrancing image shows a few of the tenuous threads that comprise Sh2-308, a faint and wispy shell of gas located 5,200 light-years away in the constellation of Canis Major (The Great Dog). Sh2-308 is a large bubble-like structure wrapped around an extremely large, bright type of star known as a Wolf-Rayet Star — this particular star is called EZ Canis Majoris. These type of stars are among the brightest and most massive stars in the Universe, tens of times more massive than our own sun, and they represent the extremes of stellar evolution. Thick winds continually poured off the progenitors of such stars, flooding their surroundings and draining the outer layers of the Wolf-Rayet stars. The fast wind of a Wolf-Rayet star therefore sweeps up the surrounding material to form bubbles of gas. EZ Canis Majoris is responsible for creating the bubble of Sh2-308 — the star threw off its outer layers to create the strands visible here. The intense and ongoing radiation from the star pushes the bubble out farther and farther, blowing it bigger and bigger. Currently the edges of Sh2-308 are some 60 light-years apart! Beautiful as these cosmic bubbles are, they are fleeting. The same stars that form them will also cause their death, eclipsing and subsuming them in violent supernova explosions. Credit: ESA/Hubble & NASA NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Studies on the Tempo of Bubble Formation in Recently Cavitated Vessels: A Model to Predict the Pressure of Air Bubbles1

PubMed Central

Wang, Yujie; Pan, Ruihua; Tyree, Melvin T.

2015-01-01

A cavitation event in a vessel replaces water with a mixture of water vapor and air. A quantitative theory is presented to argue that the tempo of filling of vessels with air has two phases: a fast process that extracts air from stem tissue adjacent to the cavitated vessels (less than 10 s) and a slow phase that extracts air from the atmosphere outside the stem (more than 10 h). A model was designed to estimate how water tension (T) near recently cavitated vessels causes bubbles in embolized vessels to expand or contract as T increases or decreases, respectively. The model also predicts that the hydraulic conductivity of a stem will increase as bubbles collapse. The pressure of air bubbles trapped in vessels of a stem can be predicted from the model based on fitting curves of hydraulic conductivity versus T. The model was validated using data from six stem segments each of Acer mono and the clonal hybrid Populus 84K (Populus alba × Populus glandulosa). The model was fitted to results with root mean square error less than 3%. The model provided new insight into the study of embolism formation in stem tissue and helped quantify the bubble pressure immediately after the fast process referred to above. PMID:25907963

Size limits the formation of liquid jets during bubble bursting

PubMed Central

Lee, Ji San; Weon, Byung Mook; Park, Su Ji; Je, Jung Ho; Fezzaa, Kamel; Lee, Wah-Keat

2011-01-01

A bubble reaching an air–liquid interface usually bursts and forms a liquid jet. Jetting is relevant to climate and health as it is a source of aerosol droplets from breaking waves. Jetting has been observed for large bubbles with radii of R≫100 μm. However, few studies have been devoted to small bubbles (R<100 μm) despite the entrainment of a large number of such bubbles in sea water. Here we show that jet formation is inhibited by bubble size; a jet is not formed during bursting for bubbles smaller than a critical size. Using ultrafast X-ray and optical imaging methods, we build a phase diagram for jetting and the absence of jetting. Our results demonstrate that jetting in bubble bursting is analogous to pinching-off in liquid coalescence. The coalescence mechanism for bubble bursting may be useful in preventing jet formation in industry and improving climate models concerning aerosol production. PMID:21694715

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.

Development of bubble microstructure in ErT2 films during aging

NASA Astrophysics Data System (ADS)

Bond, Gillian M.; Browning, James F.; Snow, Clark S.

2010-04-01

Helium bubbles form in metal tritide films as tritium decays into H3e, influencing mechanical properties and long-term film stability. The bubble nucleation and growth mechanisms comprise an active research area, but there has been only one previous systematic experimental study of helium bubble growth in metal tritides, on zirconium tritides. There have been no such studies on tritides such as ErT2 that form platelike bubbles and lack a secondary bubble population on a network of line dislocations, and yet such a study is needed to inform the modeling of helium bubble microstructure development in a broader range of metal tritides. Transmission electron microscopy has been used to study the growth and evolution of helium bubbles in ErT2 films over a four-year period. The results have been used to test the present models of helium bubble nucleation and growth in metal tritides, particularly those forming platelike bubbles. The results support the models of Trinkaus and Cowgill. The observations of nonuniform bubble thicknesses and the pattern of grain-boundary bubble formation, however, indicate that these models could be strengthened by closer attention to details of interfacial energy. It is strongly recommended that efforts be made (either experimentally or by calculation) to determine anisotropy of tritide/helium interfacial energy, both for clean, stoichiometric interfaces, and also allowing for such factors as nonstoichiometry and segregation.

Evidence for extreme partitioning of copper into a magmatic vapor phase.

PubMed

Lowenstern, J B; Mahood, G A; Rivers, M L; Sutton, S R

1991-06-07

The discovery of copper sulfides in carbon dioxide- and chlorine-bearing bubbles in phenocryst-hosted melt inclusions shows that copper resides in a vapor phase in some shallow magma chambers. Copper is several hundred times more concentrated in magmatic vapor than in coexisting pantellerite melt. The volatile behavior of copper should be considered when modeling the volcanogenic contribution of metals to the atmosphere and may be important in the formation of copper porphyry ore deposits.

A study of the laminar separation bubble on an airfoil at low Reynolds numbers using flow visualization techniques

NASA Technical Reports Server (NTRS)

Schmidt, Gordon S.; Mueller, Thomas J.

1987-01-01

The use of flow visualization to study separation bubbles is evaluated. The wind tunnel, two NACA 66(3)-018 airfoil models, and kerosene vapor, titanium tetrachloride, and surface flow visualizations techniques are described. The application of the three visualization techniques to the two airfoil models reveals that the smoke and vapor techniques provide data on the location of laminar separation and the onset of transition, and the surface method produces information about the location of turbulent boundary layer separation. The data obtained with the three flow visualization techniques are compared to pressure distribution data and good correlation is detected. It is noted that flow visualization is an effective technique for examining separation bubbles.

Computational investigations of streamers in a single bubble suspended in distilled water under atmospheric pressure conditions

NASA Astrophysics Data System (ADS)

Sharma, Ashish; Levko, Dmitry; Raja, Laxminarayan

2016-09-01

We present a computational model of nanosecond streamers generated in helium bubbles immersed in distilled water at the atmospheric pressure conditions. The model is based on the self-consistent, multispecies and the continuum description of plasma and takes into account the presence of water vapor in the gas bubble for a more accurate description of the kinetics of the discharge. We find that the dynamic characteristics of the streamer discharge are completely different at low and high over voltages. We observe that the polarity of the trigger voltage has a substantial effect on initiation, transition and evolution stages of streamers with the volumetric distribution of species in the streamer channel much more uniform for negative trigger voltages due to the presence of multiple streamers. We also find that the presence of water vapor significantly influences the distribution of the dominant species in the streamer trail and has a profound effect on the flux of the dominant species to the bubble wall. The research reported in this publication was supported by Competitive Research Funding from King Abdullah University of Science and Technology (KAUST).

Numerical Modeling of the Photothermal Processing for Bubble Forming around Nanowire in a Liquid

PubMed Central

Chaari, Anis; Giraud-Moreau, Laurence

2014-01-01

An accurate computation of the temperature is an important factor in determining the shape of a bubble around a nanowire immersed in a liquid. The study of the physical phenomenon consists in solving a photothermic coupled problem between light and nanowire. The numerical multiphysic model is used to study the variations of the temperature and the shape of the created bubble by illumination of the nanowire. The optimization process, including an adaptive remeshing scheme, is used to solve the problem through a finite element method. The study of the shape evolution of the bubble is made taking into account the physical and geometrical parameters of the nanowire. The relation between the sizes and shapes of the bubble and nanowire is deduced. PMID:24795538

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.

Studies on the tempo of bubble formation in recently cavitated vessels: a model to predict the pressure of air bubbles.

PubMed

Wang, Yujie; Pan, Ruihua; Tyree, Melvin T

2015-06-01

A cavitation event in a vessel replaces water with a mixture of water vapor and air. A quantitative theory is presented to argue that the tempo of filling of vessels with air has two phases: a fast process that extracts air from stem tissue adjacent to the cavitated vessels (less than 10 s) and a slow phase that extracts air from the atmosphere outside the stem (more than 10 h). A model was designed to estimate how water tension (T) near recently cavitated vessels causes bubbles in embolized vessels to expand or contract as T increases or decreases, respectively. The model also predicts that the hydraulic conductivity of a stem will increase as bubbles collapse. The pressure of air bubbles trapped in vessels of a stem can be predicted from the model based on fitting curves of hydraulic conductivity versus T. The model was validated using data from six stem segments each of Acer mono and the clonal hybrid Populus 84 K (Populus alba × Populus glandulosa). The model was fitted to results with root mean square error less than 3%. The model provided new insight into the study of embolism formation in stem tissue and helped quantify the bubble pressure immediately after the fast process referred to above. © 2015 American Society of Plant Biologists. All Rights Reserved.

Evaluation of Apical Vapor Lock Formation and comparative Evaluation of its Elimination using Three different Techniques: An in vitro Study.

PubMed

Agarwal, Anand; Deore, Rahul B; Rudagi, Kavitarani; Nanda, Zinnie; Baig, Mirza Osman; Fareez, Md Adil

2017-09-01

The aim of this study was (i) to evaluate the formation of air bubbles in the apical region of root canal (apical vapor lock) during syringe irrigation, using cone beam computed tomography (CBCT) and (ii) comparative evaluation of the elimination of an established vapor lock by EndoActivator, ultrasonics, and manual dynamic agitation (MDA), using CBCT. A total of 60 extracted human single-rooted teeth were equally divided into three groups of 20 teeth each. The samples were decoronated 17 mm from the apex, cleaned, and shaped to size F4 Protaper using 3% sodium hypochlorite. Samples were irrigated with 3% sodium hypochlorite + cesium chloride radiopaque dye, and preoperative CBCT images were obtained. After formation of apical vapor lock in the scanned teeth, EndoActivator (group I), passive ultrasonic irrigation (group II), and MDA with K-file (group III) were performed and the teeth were again placed in CBCT scanner and results analyzed using the chi-square test. The apical vapor lock was formed in all the samples. Out of the 20 teeth in each group, the apical vapor lock was eliminated in 18 samples of EndoActivator group (90%), 16 samples of ultrasonic group (80%), while it was eliminated in 10 samples by MDA (50%). It is concluded that (1) apical vapor lock is consistently formed during endodontic irrigation in closed canal systems and (2) sonic activation performs better than the ultrasonics and MDA in eliminating the apical vapor lock, with statistically significant difference between all the three groups (p < 0.05). The results suggest that the apical vapor lock (dead water zone) is consistently formed during routine endodontic irrigation which impedes irrigant penetration till the working length, thereby leading to inefficient debridement. Hence, to eliminate this vapor lock, techniques, such as sonics or ultrasonics should be used along with the irrigant after shaping and cleaning of the root canal.

Jumping acoustic bubbles on lipid bilayers.

PubMed

Der Loughian, Christelle; Muleki Seya, Pauline; Pirat, Christophe; Inserra, Claude; Béra, Jean-Christophe; Rieu, Jean-Paul

2015-05-07

In the context of sonoporation, we use supported lipid bilayers as a model for biological membranes and investigate the interactions between the bilayer and microbubbles induced by ultrasound. Among the various types of damage caused by bubbles on the surface, our experiments exhibit a singular dynamic interaction process where bubbles are jumping on the bilayer, forming a necklace pattern of alteration on the membrane. This phenomenon was explored with different time and space resolutions and, based on our observations, we propose a model for a microbubble subjected to the combined action of van der Waals, acoustic and hydrodynamic forces. Describing the repeated jumps of the bubble, this model explains the lipid exchanges between the bubble and bilayer.

Physics of lithium bromide (LiBr) solution dewatering through vapor venting membranes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Isfahani, RN; Fazeli, A; Bigham, S

2014-01-01

The physics of water desorption from a lithium bromide (LiBr) solution flow through an array of microchannels capped by a porous membrane is studied. The membrane allows the vapor to exit the flow and retains the liquid. Effects of different parameters such as wall temperature, solution and vapor pressures, and solution mass flux on the desorption rate were studied. Two different mechanisms of desorption are analyzed. These mechanisms consisted of: (1) direct diffusion of water molecules out of the solution and their subsequent flow through the membrane and (2) formation of water vapor bubbles within the solution and their ventingmore » through the membrane. Direct diffusion was the dominant desorption mode at low surface temperatures and its magnitude was directly related to the vapor pressure, the solution concentration, and the heated wall temperature. Desorption at the boiling regime was predominantly controlled by the solution flow pressure and mass flux. Microscale visualization studies suggested that at a critical mass flux, some bubbles are carried out of the desorber through the solution microchannels rather than being vented through the membrane. Overall, an order of magnitude higher desorption rate compare to a previous study on a membrane-based desorber was achieved. Published by Elsevier Ltd.« less

Laser induced explosive vapor and cavitation resulting in effective irrigation of the root canal. Part 1: a visualization study.

PubMed

Blanken, Jan; De Moor, Roeland Jozef Gentil; Meire, Maarten; Verdaasdonk, Rudolf

2009-09-01

Limited information exists regarding the induction of explosive vapor and cavitation bubbles in an endodontic rinsing solution. It is also not clear whether a fiber has to be moved in the irrigation solution or can be kept stationary. No information is available on safe power settings for the use of cavitation in the root canal. This study investigates the fluid movements and the mechanism of action caused by an Er,Cr:YSGG laser in a transparent root model. Glass models with an artificial root canal (15 mm long, with a 0.06 taper and apical diameter of 400 microm) were used for visualization and registration with a high-speed imaging technique (resolution in the microsecond range) of the creation of explosive vapor bubbles with an Er,Cr:YSGG laser at pulse energies of 75, 125, and 250 mJ at 20 Hz using a 200 microm fiber (Z2 Endolase). Fluid movement was investigated by means of dyes and visualization of the explosive vapor bubbles, and as a function of pulse energy and distance of the fiber tip to the apex. The recordings in the glass model show the creation of expanding and imploding vapor bubbles with secondary cavitation effects. Dye is flushed out of the canal and replaced by surrounding fluid. It seems not necessary to move the fiber close to the apex. Imaging suggests that the working mechanism of an Er,Cr:YSGG laser in root canal treatment in an irrigation solution can be attributed to cavitation effects inducing high-speed fluid motion into and out the canal.

Raman Spectral Band Oscillations in Large Graphene Bubbles

NASA Astrophysics Data System (ADS)

Huang, Yuan; Wang, Xiao; Zhang, Xu; Chen, Xianjue; Li, Baowen; Wang, Bin; Huang, Ming; Zhu, Chongyang; Zhang, Xuewei; Bacsa, Wolfgang S.; Ding, Feng; Ruoff, Rodney S.

2018-05-01

Raman spectra of large graphene bubbles showed size-dependent oscillations in spectral intensity and frequency, which originate from optical standing waves formed in the vicinity of the graphene surface. At a high laser power, local heating can lead to oscillations in the Raman frequency and also create a temperature gradient in the bubble. Based on Raman data, the temperature distribution within the graphene bubble was calculated, and it is shown that the heating effect of the laser is reduced when moving from the center of a bubble to its edge. By studying graphene bubbles, both the thermal conductivity and chemical reactivity of graphene were assessed. When exposed to hydrogen plasma, areas with bubbles are found to be more reactive than flat graphene.

A computationally efficient modelling of laminar separation bubbles

NASA Technical Reports Server (NTRS)

Dini, Paolo; Maughmer, Mark D.

1989-01-01

The goal is to accurately predict the characteristics of the laminar separation bubble and its effects on airfoil performance. Toward this end, a computational model of the separation bubble was developed and incorporated into the Eppler and Somers airfoil design and analysis program. Thus far, the focus of the research was limited to the development of a model which can accurately predict situations in which the interaction between the bubble and the inviscid velocity distribution is weak, the so-called short bubble. A summary of the research performed in the past nine months is presented. The bubble model in its present form is then described. Lastly, the performance of this model in predicting bubble characteristics is shown for a few cases.

Comparison of cavitation bubbles evolution in viscous media

NASA Astrophysics Data System (ADS)

Jasikova, Darina; Schovanec, Petr; Kotek, Michal; Kopecky, Vaclav

2018-06-01

There have been tried many types of liquids with different ranges of viscosity values that have been tested to form a single cavitation bubble. The purpose of these experiments was to observe the behaviour of cavitation bubbles in media with different ranges of absorbance. The most of the method was based on spark to induced superheat limit of liquid. Here we used arrangement of the laser-induced breakdown (LIB) method. There were described the set cavitation setting that affects the size bubble in media with different absorbance. We visualized the cavitation bubble with a 60 kHz high speed camera. We used here shadowgraphy setup for the bubble visualization. There were observed time development and bubble extinction in various media, where the size of the bubble in the silicone oil was extremely small, due to the absorbance size of silicon oil.

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).

Formation of soap bubbles by gas jet

NASA Astrophysics Data System (ADS)

Zhou, Maolei; Li, Min; Chen, Zhiyuan; Han, Jifeng; Liu, Dong

2017-12-01

Soap bubbles can be easily generated by various methods, while their formation process is complicated and still worth studying. A model about the bubble formation process was proposed in the study by Salkin et al. [Phys. Rev. Lett. 116, 077801 (2016)] recently, and it was reported that the bubbles were formed when the gas blowing velocity was above one threshold. However, after a detailed study of these experiments, we found that the bubbles could be generated in two velocity ranges which corresponded to the laminar and turbulent gas jet, respectively, and the predicted threshold was only effective for turbulent gas flow. The study revealed that the bubble formation was greatly influenced by the aerodynamics of the gas jet blowing to the film, and these results will help to further understand the formation mechanism of the soap bubble as well as the interaction between the gas jet and the thin liquid film.

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.

Magnetite Scavenging and the Buoyancy of Bubbles in Magmas

NASA Astrophysics Data System (ADS)

Gualda, G. A.; Ghiorso, M. S.

2005-12-01

below which the adhesion force will be strong enough to keep the pair together. Using the available experimental data, we show that crystals as large as 1 mm in diameter could be attached to bubbles and form neutrally buoyant pairs. The presence of multiple crystals in a single bubble would allow bubbles larger than the critical size to become neutrally buoyant. Under the limiting assumption that all magnetite crystals form neutrally buoyant pairs with bubbles, it is possible to compute the maximum gas volume fraction that can be stored as neutrally buoyant bubble-magnetite aggregates. The total abundance of magnetite is only ca. 0.1 vol. %, which yields maximum gas volume fractions on the order of 0.1-0.2 vol. %. About 2-3 vol % of gas can be accounted for if all minerals form neutrally-buoyant aggregates. These values are orders of magnitude lower than the abundance of exsolved gas inferred from melt inclusions in the Bishop magma. Nonetheless, our recent observation of one such aggregate in the early-erupted Bishop Tuff suggests that this is indeed a viable mechanism for storing exsolved gas in magmas. The inevitable conclusion is that a range of pre-eruptive bubbles existed, from magnetite-free, but only a very small fraction of them could have magnetite crystals attached to them. Our treatment shows that there should be an intrinsic association between magnetite crystals and bubbles. However, study our tomography datasets shows that most magnetite crystals are free of bubbles. Not only is this surprising; the puzzling conclusion is that nucleation away from crystals (homogeneous nucleation?) is favored over heterogeneous nucleation on crystal substrates.

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

PubMed

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

2007-10-01

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

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.

Morphology of Two-Phase Layers with Large Bubbles

NASA Astrophysics Data System (ADS)

Vékony, Klára; Kiss, László I.

2010-10-01

The understanding of formation and movement of bubbles nucleated during aluminum reduction is essential for a good control of the electrolysis process. In our experiments, we filmed and studied the formation of a bubble layer under the anode in a real-size air-water electrolysis cell model. The maximum height of the bubbles was found to be up to 2 cm because of the presence of the so-called Fortin bubbles. Also, the mean height of the bubble layer was found to be much higher than published previously. The Fortin bubbles were investigated more closely, and their shape was found to be induced by a gravity wave formed at the gas-liquid interface. In addition, large bubbles were always observed to break up into smaller parts right before escaping from under the anode. This breakup and escape led to a large momentum transfer in the bath.

Targeted Nanoparticle Thermometry: A Method to Measure Local Temperature at the Nanoscale Point Where Water Vapor Nucleation Occurs.

PubMed

Alaulamie, Arwa A; Baral, Susil; Johnson, Samuel C; Richardson, Hugh H

2017-01-01

An optical nanothermometer technique based on laser trapping, moving and targeted attaching an erbium oxide nanoparticle cluster is developed to measure the local temperature. The authors apply this new nanoscale temperature measuring technique (limited by the size of the nanoparticles) to measure the temperature of vapor nucleation in water. Vapor nucleation is observed after superheating water above the boiling point for degassed and nondegassed water. The average nucleation temperature for water without gas is 560 K but this temperature is lowered by 100 K when gas is introduced into the water. The authors are able to measure the temperature inside the bubble during bubble formation and find that the temperature inside the bubble spikes to over 1000 K because the heat source (optically-heated nanorods) is no longer connected to liquid water and heat dissipation is greatly reduced. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of van der Waals forces and salt ions on the growth of water films on ice and the detachment of CO2 bubbles

NASA Astrophysics Data System (ADS)

Thiyam, P.; Lima, E. R. A.; Malyi, O. I.; Parsons, D. F.; Buhmann, S. Y.; Persson, C.; Boström, M.

2016-02-01

We study the effect of salts on the thickness of wetting films on melting ice and interactions acting on CO2 bubble near ice-water and vapor-water interfaces. Governing mechanisms are the Lifshitz and the double-layer interactions in the respective three-layer geometries. We demonstrate that the latter depend on the Casimir-Polder interaction of the salt ions dissolved in water with the respective ice, vapor and CO2 interfaces, as calculated using different models for their effective polarizability in water. Significant variation in the predicted thickness of the equilibrium water film is observed for different salt ions and when using different models for the ions' polarizabilities. We find that CO2 bubbles are attracted towards the ice-water interface and repelled from the vapor-water interface.

Scaling and Instabilities in Bubble Pinch-Off

NASA Astrophysics Data System (ADS)

Burton, J. C.; Waldrep, R.; Taborek, P.

2005-05-01

We have used a 100 000 frame-per-second video to analyze the pinch-off of nitrogen gas bubbles in fluids with a wide range of viscosity. If the external fluid is highly viscous (ηext>100 cP), the bubble neck radius is proportional to the time before break, τ, and decreases smoothly to zero. If the external fluid has low viscosity (ηext<10 cP), the radius scales as τ1/2 until an instability develops in the gas bubble, which causes the neck to rupture and tear apart. Finally, if the viscosity of the external fluid is in an intermediate range, an elongated thread is formed, which breaks apart into micron-sized bubbles.

The elasticity of soap bubbles containing wormlike micelles.

PubMed

Sabadini, Edvaldo; Ungarato, Rafael F S; Miranda, Paulo B

2014-01-28

Slow-motion imaging of the rupture of soap bubbles generally shows the edges of liquid films retracting at a constant speed (known as the Taylor-Culick velocity). Here we investigate soap bubbles formed from simple solutions of a cationic surfactant (cetyltrimethylammonium bromide - CTAB) and sodium salicylate. The interaction of salicylate ions with CTAB leads to the formation of wormlike micelles (WLM), which yield a viscoelastic behavior to the liquid film of the bubble. We demonstrate that these elastic bubbles collapse at a velocity up to 30 times higher than the Taylor-Culick limit, which has never been surpassed. This is because during the bubble inflation, the entangled WLM chains stretch, storing elastic energy. This extra energy is then released during the rupture of the bubble, yielding an additional driving force for film retraction (besides surface tension). This new mechanism for the bursting of elastic bubbles may have important implications to the breakup of viscoelastic sprays in industrial applications.

Cavitation Bubble Cluster Activity in the Breakage of Kidney Stones by Lithotripter Shock Waves

PubMed Central

Pishchalnikov, Yuriy A.; Sapozhnikov, Oleg A.; Bailey, Michael R.; Williams, James C.; Cleveland, Robin O.; Colonius, Tim; Crum, Lawrence A.; Evan, Andrew P.; McAteer, James A.

2008-01-01

High-speed photography was used to analyze cavitation bubble activity at the surface of artificial and natural kidney stones during exposure to lithotripter shock waves in vitro. Numerous individual bubbles formed at the surface of stones, but these bubbles did not remain independent and combined with one another to form bubble clusters. Bubble clusters formed at the proximal end, the distal end, and at the sides of stones. Each cluster collapsed to a narrow point of impact. Collapse of the proximal cluster caused erosion at the leading face of the stone and the collapse of clusters at the sides of stones appeared to contribute to the growth of cracks. Collapse of the distal cluster caused minimal damage. We conclude that cavitation-mediated damage to stones was due not to the action of solitary bubbles, but to the growth and collapse of bubble clusters. PMID:14565872

Helium Bubble Injection Solution To The Cavitation Damage At The Spallation Neutron Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Francis, M. W.; Ruggles, A. E.

2009-03-10

The Spallation Neutron Source (SNS) is one of the largest science projects in the United States, with total cost near 1.4 Billion Dollars. The limiting factor of the facility had always been assumed to be the lifetime of the target window due to radiation damage. After further investigation, the lifetime of the target was determined not to be limited by radiation damage but by cavitation damage. The cavitation damage derives from pressure waves caused by the beam energy deposition. Vapor bubbles form when low to negative pressures occur in the mercury near the stainless steel target window due to wavemore » interaction with the structure. Collapse of these bubbles can focus wave energy in small liquid jets that erode the window surface. Compressibility of the mercury can be enhanced to reduce the amplitude of the pressure wave caused by the beam energy deposition. To enhance compressibility, small (10 to 30 micron diameter) gas bubbles could be injected into the bulk of the mercury. Solubility and diffusivity parameters of inert gas in mercury are required for a complete mechanical simulation and engineering of these strategies. Using current theoretical models, one obtains a theoretical Henry coefficient of helium in mercury on the order of 3.9E15 Pa-molHg/molHe at 300 K. This low solubility was confirmed by a direct, offline experimental method. Mercury was charged with helium and any pressure change was recorded. Any pressure change was attributed to gas going into solution. Therefore, with the sensitivity of the experiment, a lower limit of 9E12 Pa-molHg/molHe was placed on the mercury-helium system. These values guarantee a stable bubble lifetime needed within the SNS mercury target to mitigate cavitation issues.« less

Bubble Dynamics on a Heated Surface

NASA Technical Reports Server (NTRS)

Kassemi, M.; Rashidnia, N.

1999-01-01

In this work, we study steady and oscillatory thermocapillary and natural convective flows 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. A combined numerical-experimental approach is adopted here. The temperature field is visualized using Mach-Zehnder and/or Wollaston Prism Interferometry and the flow field is observed by a laser sheet flow visualization technique. A finite element numerical model is developed which solves the transient two-dimensional continuity, momentum, and energy equations and includes the effects of temperature-dependent surface tension and bubble surface deformation. Below the critical Marangoni number, the steady state low-g and 1-g temperature and velocity fields predicted by the finite element model are in excellent agreement with both the visualization experiments in our laboratory and recently published experimental results in the literature. Above the critical Marangoni number, the model predicts an oscillatory flow which is also closely confirmed by experiments. It is shown that the dynamics of the oscillatory flow are directly controlled by the thermal and hydrodynamic interactions brought about by combined natural and thermocapillary convection. Therefore, as numerical simulations show, there are considerable differences between the 1-g and low-g temperature and flow fields at both low and high Marangoni numbers. This has serious implications for both materials processing and fluid management in space.

Rod-shaped cavitation bubble structure in ultrasonic field.

PubMed

Bai, Lixin; Wu, Pengfei; Liu, Huiyu; Yan, Jiuchun; Su, Chang; Li, Chao

2018-06-01

Rod-shaped cavitation bubble structure in thin liquid layers in ultrasonic field is investigated experimentally. It is found that cavitation structure successively experiences several stages with the change of the thickness of the thin liquid layer. Rod-shaped structure is a stable structure of the boundary between the cavitation cloud region and the non-cavitation liquid region, which can be formed in two different ways. Cavitation bubbles in a thin liquid layer have a distribution in the thickness direction. The rod-shaped structures tend to crosslink with each other to form stable Y-branch structures. The angle of the Y-branch structure is Gauss distribution with mathematical expectation μ = 119.93. A special rod-shaped cavitation structure with source is also investigated in detail. Due to the pressure gradient in the normal direction, the primary Bjerknes force causes the bubbles in the rod-shaped structure on both sides to converge to the axis. The secondary Bjerknes forces between the bubbles also make the cluster converge, so the large bubbles which are attached to the radiating surface tend to align themselves along the central line. According to the formula deduced in this paper, the variation of curvature of curved rod-shaped structure is qualitatively analyzed. The Y-branch structure of cavitation cloud and Plateau boundary of soap bubbles are compared. Copyright © 2018 Elsevier B.V. All rights reserved.

Phase-transition thresholds and vaporization phenomena for ultrasound phase-change nanoemulsions assessed via high speed optical microscopy

PubMed Central

Sheeran, Paul S.; Matsunaga, Terry O.; Dayton, Paul A.

2015-01-01

Ultrasonically activated phase-change contrast agents (PCCAs) based on perfluorocarbon droplets have been proposed for a variety of therapeutic and diagnostic clinical applications. When generated at the nanoscale, droplets may be small enough to exit the vascular space and then be induced to vaporize with high spatial and temporal specificity by externally-applied ultrasound. The use of acoustical techniques for optimizing ultrasound parameters for given applications can be a significant challenge for nanoscale PCCAs due to the contributions of larger outlier droplets. Similarly, optical techniques can be a challenge due to the sub-micron size of nanodroplet agents and resolution limits of optical microscopy. In this study, an optical method for determining activation thresholds of nanoscale emulsions based on the in vitro distribution of bubbles resulting from vaporization of PCCAs after single, short (<10 cycles) ultrasound pulses is evaluated. Through ultra-high-speed microscopy it is shown that the bubbles produced early in the pulse from vaporized droplets are strongly affected by subsequent cycles of the vaporization pulse, and these effects increase with pulse length. Results show that decafluorobutane nanoemulsions with peak diameters on the order of 200 nm can be optimally vaporized with short pulses using pressures amenable to clinical diagnostic ultrasound machines. PMID:23760161

Natural oscillations of a gas bubble in a liquid-filled cavity located in a viscoelastic medium

NASA Astrophysics Data System (ADS)

Doinikov, Alexander A.; Marmottant, Philippe

2018-04-01

The present study is motivated by cavitation phenomena that occur in the stems of trees. The internal pressure in tree conduits can drop down to significant negative values. This drop gives rise to cavitation bubbles, which undergo high-frequency eigenmodes. The aim of the present study is to determine the parameters of the bubble natural oscillations. To this end, a theory is developed that describes the pulsation of a spherical bubble located at the center of a spherical cavity surrounded by an infinite solid medium. It is assumed that the medium inside the bubble is a gas-vapor mixture, the cavity is filled with a compressible viscous liquid, and the medium surrounding the cavity behaves as a viscoelastic solid. The theoretical solution takes into account the outgoing acoustic wave produced by the bubble pulsation, the incoming wave caused by reflection from the liquid-solid boundary, and the outgoing wave propagating in the solid. A dispersion equation for the calculation of complex wavenumbers of the bubble eigenmodes is derived. Approximate analytical solutions to the dispersion equation are found. Numerical simulations are performed to reveal the effect of different physical parameters on the resonance frequency and the attenuation coefficient of the bubble oscillations.

Killing effect of peppermint vapor against pink-slime forming microorganisms.

PubMed

Ihara, Nozomi; Sakamoto, Jin; Yoshida, Munehiro; Tsuchido, Tetsuaki

2015-01-01

The killing effect of peppermint vapor (PMV) against pink-slime forming microorganisms, Methylobacterium mesophilicum as a bacterium and Rhodotorula mucilaginosa as a yeast, was investigated by the agar vapor assay. In this method, microbial cells were spread over the agar surface exposed to PMV in a petri dish, and then transferred into a recovery liquid. When 60μl of the peppermint liquid was added to a paper disc, a marked killing effect of PMV was observed after 48h against M. mesophilicum and after 168h against R. mucilaginosa. M. mesophilicum and R. mucilaginosa were found to be more resistant to PMV than Escherichia coli and Candida albicans, used as reference microorganisms, respectively. With the addition of 0.03% sodium pyruvate as a hydrogen peroxide scavenger in agar, the killing effect of PMV against E. coli and C. albicans was decreased, whereas it was little changed against M. mesophilicum and R. mucilaginosa. In fact, the properties of the killing effect of hydrogen peroxide solution at 0.2-1.0mM was in accord with those of PMV. M. mesophilicum and R. mucilaginosa were more resistant to the oxidant than E. coli and C. albicans, respectively. Results obtained suggested that reactive oxygen species (ROS) may be involved in the killing action of PMV and therefore pink-slime formers are more resistant to PMV than non-pink-slime formers because of the presence of carotenoids as an antioxidant in cells. We also suggest that the use of PMV appeared to be a potential tool for the control of pink-slime forming microorganisms occurring in wet areas of houses such as the bathroom and washing room.

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)

Rise of Air Bubbles in Aircraft Lubricating Oils

NASA Technical Reports Server (NTRS)

Robinson, J. V.

1950-01-01

Lubricating and antifoaming additives in aircraft lubricating oils may impede the escape of small bubbles from the oil by forming shells of liquid with a quasi-solid or gel structure around the bubbles. The rates of rise of small air bubbles, up to 2 millimeters in diameter, were measured at room temperature in an undoped oil, in the same oil containing foam inhibitors, and in an oil containing lubricating additives. The apparent diameter of the air bubbles was measured visually through an ocular micrometer on a traveling telescope. The bubbles in the undoped oil obeyed Stokes' Law, the rate of rise being proportional to the square of the apparent diameter and inversely proportional to the viscosity of the oil. The bubbles in the oils containing lubricating additives or foam inhibitors rose more slowly than the rate predicted by Stokes 1 Law from the apparent diameter, and the rate of rise decreased as the length of path the bubbles traveled increased. A method is derived to calculate the thickness of the liquid shell which would have to move with the bubbles in the doped oils to account for the abnoi'I!l8.lly slow velocity. The maximum thickness of this shell, calculated from the velocities observed, was equal to the bubble radius.

Detecting vapour bubbles in simulations of metastable water

DOE Office of Scientific and Technical Information (OSTI.GOV)

González, Miguel A.; Abascal, Jose L. F.; Valeriani, Chantal, E-mail: christoph.dellago@univie.ac.at, E-mail: cvaleriani@quim.ucm.es

2014-11-14

The investigation of cavitation in metastable liquids with molecular simulations requires an appropriate definition of the volume of the vapour bubble forming within the metastable liquid phase. Commonly used approaches for bubble detection exhibit two significant flaws: first, when applied to water they often identify the voids within the hydrogen bond network as bubbles thus masking the signature of emerging bubbles and, second, they lack thermodynamic consistency. Here, we present two grid-based methods, the M-method and the V-method, to detect bubbles in metastable water specifically designed to address these shortcomings. The M-method incorporates information about neighbouring grid cells to distinguishmore » between liquid- and vapour-like cells, which allows for a very sensitive detection of small bubbles and high spatial resolution of the detected bubbles. The V-method is calibrated such that its estimates for the bubble volume correspond to the average change in system volume and are thus thermodynamically consistent. Both methods are computationally inexpensive such that they can be used in molecular dynamics and Monte Carlo simulations of cavitation. We illustrate them by computing the free energy barrier and the size of the critical bubble for cavitation in water at negative pressure.« less

Bubble dynamics in a standing sound field: the bubble habitat.

PubMed

Koch, P; Kurz, T; Parlitz, U; Lauterborn, W

2011-11-01

Bubble dynamics is investigated numerically with special emphasis on the static pressure and the positional stability of the bubble in a standing sound field. The bubble habitat, made up of not dissolving, positionally and spherically stable bubbles, is calculated in the parameter space of the bubble radius at rest and sound pressure amplitude for different sound field frequencies, static pressures, and gas concentrations of the liquid. The bubble habitat grows with static pressure and shrinks with sound field frequency. The range of diffusionally stable bubble oscillations, found at positive slopes of the habitat-diffusion border, can be increased substantially with static pressure.

Regimes of Micro-bubble Formation Using Gas Injection into Ladle Shroud

NASA Astrophysics Data System (ADS)

Chang, Sheng; Cao, Xiangkun; Zou, Zongshu

2018-03-01

Gas injection into a ladle shroud is a practical approach to produce micro-bubbles in tundishes, to promote inclusion removal from liquid steel. A semi-empirical model was established to characterize the bubble formation considering the effect of shearing action combined with the non-fully bubble break-up by turbulence. The model shows a good accuracy in predicting the size of bubbles formed in complex flow within the ladle shroud.

Regimes of Micro-bubble Formation Using Gas Injection into Ladle Shroud

NASA Astrophysics Data System (ADS)

Chang, Sheng; Cao, Xiangkun; Zou, Zongshu

2018-06-01

Gas injection into a ladle shroud is a practical approach to produce micro-bubbles in tundishes, to promote inclusion removal from liquid steel. A semi-empirical model was established to characterize the bubble formation considering the effect of shearing action combined with the non-fully bubble break-up by turbulence. The model shows a good accuracy in predicting the size of bubbles formed in complex flow within the ladle shroud.

Simple improvements to classical bubble nucleation models.

PubMed

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 ≃0.3σ 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.

Properties of vapor detector arrays formed through plasticization of carbon black-organic polymer composites.

PubMed

Koscho, Michael E; Grubbs, Robert H; Lewis, Nathan S

2002-03-15

Arrays of vapor detectors have been formed through addition of varying mass fractions of the plasticizer diethylene glycol dibenzoate to carbon black-polymer composites of poly(vinyl acetate) (PVAc) or of poly(N-vinylpyrrolidone). Addition of plasticizer in 5% mass fraction increments produced 20 compositionally different detectors from each polymer composite. Differences in vapor sorption and permeability that effected changes in the dc electrical resistance response of these compositionally different detectors allowed identification and classification of various test analytes using standard chemometric methods. Glass transition temperatures, Tg, were measured using differential scanning calorimetry for plasticized polymers having a mass fraction of 0, 0.10, 0.20, 0.30, 0.40, or 0.50 of plasticizer in the composite. The plasticized PVAc composites with Tg < 25 degrees C showed rapid responses at room temperature to all of the test analyte vapors studied in this work, whereas composites with Tg > 25 degrees C showed response times that were highly dependent on the polymer/analyte combination. These composites showed a discontinuity in the temperature dependence of their resistance, and this discontinuity provided a simple method for determining the Tg of the composite and for determining the temperature or plasticizer mass fraction above which rapid resistance responses could be obtained for all members of the test set of analyte vapors. The plasticization approach provides a method for achieving rapid detector response times as well as for producing a large number of chemically different vapor detectors from a limited number of initial chemical feedstocks.

Time-resolved imaging of electrical discharge development in underwater bubbles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tu, Yalong; Xia, Hualei; Yang, Yong, E-mail: yangyong@hust.edu.cn, E-mail: luxinpei@hust.edu.cn

2016-01-15

The formation and development of plasma in single air bubbles submerged in water were investigated. The difference in the discharge dynamics and the after-effects on the bubble were investigated using a 900 000 frame per second high-speed charge-coupled device camera. It was observed that depending on the position of the electrodes, the breakdown could be categorized into two modes: (1) direct discharge mode, where the high voltage and ground electrodes were in contact with the bubble, and the streamer would follow the shortest path and propagate along the axis of the bubble and (2) dielectric barrier mode, where the groundmore » electrode was not in touch with the bubble surface, and the streamer would form along the inner surface of the bubble. The oscillation of the bubble and the development of instabilities on the bubble surface were also discussed.« less

Radiation-pressure-driven dust waves inside bursting interstellar bubbles

NASA Astrophysics Data System (ADS)

Ochsendorf, B. B.; Verdolini, S.; Cox, N. L. J.; Berné, O.; Kaper, L.; Tielens, A. G. G. M.

2014-06-01

Massive stars drive the evolution of the interstellar medium through their radiative and mechanical energy input. After their birth, they form "bubbles" of hot gas surrounded by a dense shell. Traditionally, the formation of bubbles is explained through the input of a powerful stellar wind, even though direct evidence supporting this scenario is lacking. Here we explore the possibility that interstellar bubbles seen by the Spitzer- and Herschel space telescopes, blown by stars with log (L/L⊙) ≲ 5.2, form and expand because of the thermal pressure that accompanies the ionization of the surrounding gas. We show that density gradients in the natal cloud or a puncture in the swept-up shell lead to an ionized gas flow through the bubble into the general interstellar medium, which is traced by a dust wave near the star, which demonstrates the importance of radiation pressure during this phase. Dust waves provide a natural explanation for the presence of dust inside H II bubbles, offer a novel method to study dust in H II regions and provide direct evidence that bubbles are relieving their pressure into the interstellar medium through a champagne flow, acting as a probe of the radiative interaction of a massive star with its surroundings. We explore a parameter space connecting the ambient density, the ionizing source luminosity, and the position of the dust wave, while using the well studied H II bubbles RCW 120 and RCW 82 as benchmarks of our model. Finally, we briefly examine the implications of our study for the environments of super star clusters formed in ultraluminous infrared galaxies, merging galaxies, and the early Universe, which occur in very luminous and dense environments and where radiation pressure is expected to dominate the dynamical evolution.

Vapor bridges between solid substrates in the presence of the contact line pinning effect: Stability and capillary force

NASA Astrophysics Data System (ADS)

Liu, Yawei; Zhang, Xianren

2016-12-01

In this work, we focus on investigating how nanobubbles mediate long-range interaction between neighboring solid substrates in the presence of the contact line pinning effect caused by surface heterogeneities. Using the constrained lattice density functional theory (LDFT), we prove that the nanobubbles, which take the form of vapor bridges here, are stabilized by the pinning effect if the separation between two substrates is less than a critical distance. The critical distance strongly depends on the chemical potential (i.e., the degree of saturation) and could become extremely long at a special chemical potential. Moreover, under the pinning effect, the substrate chemistry only determines the stability of the vapor bridges and the range of the capillary force, but has less influences on the magnitude of the capillary force, indicating that the substrate chemistry or the apparent contact angle for droplets or bubbles on the substrates is no longer a direct parameter to determine the magnitude of capillary force. A qualitative analysis for the two dimensional vapor bridges by considering the feedback mechanism can explain the results from the LDFT calculations.

Electron self-injection in the donut bubble wakefield

NASA Astrophysics Data System (ADS)

Firouzjaei, Ali Shekari; Shokri, Babak

2018-05-01

We investigate electron self-injection in a donut bubble wakefield driven by a Laguerre-Gauss laser pulse. The present work discusses the electron capture by modeling the analytical donut bubble field. We discuss the self-injection of the electrons from plasma for various initial conditions and then compare the results. We show that the donut bubble can trap plasma electrons forming a hollow beam. We present the phase spaces and longitudinal momentum evolution for the trapped electrons in the bubble and discuss their characteristic behaviors and stability. It will be shown that the electrons self-injected in the front are ideal for applications in which a good stability and low energy spread are essential.

Bubble clustering in a glass of stout beer

NASA Astrophysics Data System (ADS)

Iwatsubo, Fumiya; Watamura, Tomoaki; Sugiyama, Kazuyasu

2017-11-01

To clarify why the texture in stout beer poured into a pint glass descends, we investigated local time development of the void fraction and velocity of bubbles. The propagation of the number density distribution, i.e. the texture, appearing near the inclined wall is observed. We visualized individual advective bubbles near the inclined wall by microscope and measured the local void fraction using brightness of images while the velocity of bubbles by means of Particle Tracking Velocimetry. As the result of measurements, we found the local void fraction and the bubbles advection velocity increase and decrease repeatedly with a time delay. We conclude the texture pattern is composed of fluid blobs which contain less bubbles; extruding and suction flows respectively toward and from the interior of the container form respectively in front and back of the blobs.

Bubble fusion: Preliminary estimates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krakowski, R.A.

1995-02-01

The collapse of a gas-filled bubble in disequilibrium (i.e., internal pressure {much_lt} external pressure) can occur with a significant focusing of energy onto the entrapped gas in the form of pressure-volume work and/or acoustical shocks; the resulting heating can be sufficient to cause ionization and the emission of atomic radiations. The suggestion that extreme conditions necessary for thermonuclear fusion to occur may be possible has been examined parametrically in terms of the ratio of initial bubble pressure relative to that required for equilibrium. In this sense, the disequilibrium bubble is viewed as a three-dimensional ``sling shot`` that is ``loaded`` tomore » an extent allowed by the maximum level of disequilibrium that can stably be achieved. Values of this disequilibrium ratio in the range 10{sup {minus}5}--10{sup {minus}6} are predicted by an idealized bubble-dynamics model as necessary to achieve conditions where nuclear fusion of deuterium-tritium might be observed. Harmonic and aharmonic pressurizations/decompressions are examined as means to achieve the required levels of disequilibrium required to create fusion conditions. A number of phenomena not included in the analysis reported herein could enhance or reduce the small levels of nuclear fusions predicted.« less

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.

The effects of water vapor on the oxidation behavior of alumina forming austenitic stainless steels

DOE PAGES

Yanar, N. M.; Lutz, B. S.; Garcia-Fresnillo, L.; ...

2015-08-19

The isothermal oxidation behavior of three alumina forming austenitic (AFA) stainless steels with varying composition was studied at 650 and 800 °C in dry air and gases which contained water vapor. The AFA alloys exhibited better oxidation resistance than a “good chromia former” at 650 °C, particularly in H 2O-containing atmospheres by virtue of alumina-scale formation. Although the AFA alloys were more resistant than chromia formers, their oxidation resistance was degraded at 650 °C in the presence of water vapor. In dry air the AFA alloys formed, thin continuous alumina scales, whereas in Ar–4%H 2–3%H 2O the areas of continuousmore » alumina were reduced and Fe oxide-rich nodules and regions of Cr, Mn-rich oxides formed. In some regions internal oxidation of the aluminum occurred in the H 2O-containing gas. The alloy OC8 had slightly better resistance than OC4 or OC5 in this atmosphere. The alumina-forming capability of the AFA alloys decreases with increasing temperature and, at 800 °C, they are borderline alumina formers, even in dry air. The oxidation resistance of all three alloys was degraded at 800 °C in atmospheres, which contained water vapor (Air–10%H 2O, Ar–3%H 2O and Ar–4%H 2–3%H 2O). The areas, which formed continuous alumina, were reduced in these atmospheres and areas of internal oxidation occurred. However, as a result of the borderline alumina-forming capability of the AFA alloys it was not possible to determine which of the H2O-containing atmospheres was more severe or to rank the alloys in terms of their performance. The experimental results indicate that the initial microstructure of the AFA alloys also plays a role in their oxidation performance. Less protective oxides formed at 800 °C when alloy OC8 was equilibrated before exposure rather than being exposed in the as-processed condition. As a result, the reason for this is the presence of different phases in the bulk of the two specimens.« less

The effects of water vapor on the oxidation behavior of alumina forming austenitic stainless steels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yanar, N. M.; Lutz, B. S.; Garcia-Fresnillo, L.

The isothermal oxidation behavior of three alumina forming austenitic (AFA) stainless steels with varying composition was studied at 650 and 800 °C in dry air and gases which contained water vapor. The AFA alloys exhibited better oxidation resistance than a “good chromia former” at 650 °C, particularly in H 2O-containing atmospheres by virtue of alumina-scale formation. Although the AFA alloys were more resistant than chromia formers, their oxidation resistance was degraded at 650 °C in the presence of water vapor. In dry air the AFA alloys formed, thin continuous alumina scales, whereas in Ar–4%H 2–3%H 2O the areas of continuousmore » alumina were reduced and Fe oxide-rich nodules and regions of Cr, Mn-rich oxides formed. In some regions internal oxidation of the aluminum occurred in the H 2O-containing gas. The alloy OC8 had slightly better resistance than OC4 or OC5 in this atmosphere. The alumina-forming capability of the AFA alloys decreases with increasing temperature and, at 800 °C, they are borderline alumina formers, even in dry air. The oxidation resistance of all three alloys was degraded at 800 °C in atmospheres, which contained water vapor (Air–10%H 2O, Ar–3%H 2O and Ar–4%H 2–3%H 2O). The areas, which formed continuous alumina, were reduced in these atmospheres and areas of internal oxidation occurred. However, as a result of the borderline alumina-forming capability of the AFA alloys it was not possible to determine which of the H2O-containing atmospheres was more severe or to rank the alloys in terms of their performance. The experimental results indicate that the initial microstructure of the AFA alloys also plays a role in their oxidation performance. Less protective oxides formed at 800 °C when alloy OC8 was equilibrated before exposure rather than being exposed in the as-processed condition. As a result, the reason for this is the presence of different phases in the bulk of the two specimens.« less

Dynamics of glass-forming liquids. XV. Dynamical features of molecular liquids that form ultra-stable glasses by vapor deposition

NASA Astrophysics Data System (ADS)

Chen, Zhen; Richert, Ranko

2011-09-01

The dielectric relaxation behavior of ethylbenzene (EBZ) in its viscous regime is measured, and the glass transition temperature (Tg = 116 K) as well as fragility (m = 98) are determined. While the Tg of EBZ from this work is consistent with earlier results, the fragility is found much higher than what has been assumed previously. Literature data is supplemented by the present results on EBZ to compile the dynamic behavior of those glass formers that are known to form ultra-stable glasses by vapor deposition. These dynamics are contrasted with those of ethylcyclohexane, a glass former for which a comparable vapor deposition failed to produce an equally stable glassy state. In a graph that linearizes Vogel-Fulcher-Tammann behavior, i.e., the derivative of -logτ with respect to T/Tg raised to the power of -1/2 versus T/Tg, all ultra-stable glass formers fall onto one master curve in a wide temperature range, while ethylcyclohexane deviates for T ≫ Tg. This result suggests that ultra-stable glass formers share common behavior regarding the dynamics of their supercooled liquid state if scaled to their respective Tg values, and that fragility and related features are linked to the ability to form ultra-stable materials.

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.

Shock-wave generation and bubble formation in the retina by lasers

NASA Astrophysics Data System (ADS)

Sun, Jinming; Gerstman, Bernard S.; Li, Bin

2000-06-01

The generation of shock waves and bubbles has been experimentally observed due to absorption of sub-nanosecond laser pulses by melanosomes, which are found in retinal pigment epithelium cells. Both the shock waves and bubbles may be the cause of retinal damage at threshold fluence levels. The theoretical modeling of shock wave parameters such as amplitude, and bubble size, is a complicated problem due to the non-linearity of the phenomena. We have used two different approaches for treating pressure variations in water: the Tait Equation and a full Equation Of State (EOS). The Tait Equation has the advantage of being developed specifically to model pressure variations in water and is therefore simpler, quicker computationally, and allows the liquid to sustain negative pressures. Its disadvantage is that it does not allow for a change of phase, which prevents modeling of bubbles and leads to non-physical behavior such as the sustaining of ridiculously large negative pressures. The full EOS treatment includes more of the true thermodynamic behavior, such as phase changes that produce bubbles and avoids the generation of large negative pressures. Its disadvantage is that the usual stable equilibrium EOS allows for no negative pressures at all, since tensile stress is unstable with respect to a transition to the vapor phase. In addition, the EOS treatment requires longer computational times. In this paper, we compare shock wave generation for various laser pulses using the two different mathematical approaches and determine the laser pulse regime for which the simpler Tait Equation can be used with confidence. We also present results of our full EOS treatment in which both shock waves and bubbles are simultaneously modeled.

Light generated bubble for microparticle propulsion.

PubMed

Frenkel, Ido; Niv, Avi

2017-06-06

Light activated motion of micron-sized particles with effective forces in the range of micro-Newtons is hereby proposed and demonstrated. Our investigation shows that this exceptional amount of force results from accumulation of light-generated heat by a micron-sized particle that translates into motion due to a phase transition in the nearby water. High-speed imagery indicates the role of bubble expansion and later collapse in this event. Comparing observations with known models reveals a dynamic behavior controlled by polytropic trapped vapor and the inertia of the surrounding liquid. The potential of the proposed approach is demonstrated by realization of disordered optical media with binary light-activated switching from opacity to high transparency.

Electrically driven rapidly vaporizing foils, wires and strips used for collision welding and sheet metal forming

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vivek, Anupam; Daehn, Glenn S; Taber, Geoffrey A

2015-05-05

A method for forming a piece of a sheet metal is performed by positioning a consumable body, made of metal, proximate to the piece of the sheet metal. The consumable body is rapidly vaporized, and the gas pressure generated thereby is directed into the piece of the sheet metal. This results in acceleration of the piece of sheet metal, and it is collided into a stationary body at a velocity, generally in excess of 200 m/s. Depending upon the type of stationary body, the piece of sheet metal is deformed into a predetermined shape or is welded onto the stationarymore » body. The vaporization is accomplished by passing a high current of electricity into the consumable body. The effect of the vaporized metal may be augmented by additional components in the consumable body.« less

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.

CONTINUOUSLY SENSITIVE BUBBLE CHAMBER

DOEpatents

Good, R.H.

1959-08-18

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

Dynamic Bubble Surface Tension Measurements in Northwest Atlantic Seawater

NASA Astrophysics Data System (ADS)

Kieber, D. J.; Long, M. S.; Keene, W. C.; Kinsey, J. D.; Frossard, A. A.; Beaupre, S. R.; Duplessis, P.; Maben, J. R.; Lu, X.; Chang, R.; Zhu, Y.; Bisgrove, J.

2017-12-01

Numerous reports suggest that most organic matter (OM) associated with newly formed primary marine aerosol (PMA) originates from the sea-surface microlayer. However, surface-active OM rapidly adsorbs onto bubble surfaces in the water column and is ejected into the atmosphere when bubbles burst at the air-water interface. Here we present dynamic surface tension measurements of bubbles produced in near surface seawater from biologically productive and oligotrophic sites and in deep seawater collected from 2500 m in the northwest Atlantic. In all cases, the surface tension of bubble surfaces decreased within seconds after the bubbles were exposed to seawater. These observations demonstrate that bubble surfaces are rapidly saturated by surfactant material scavenged from seawater. Spatial and diel variability in bubble surface evolution indicate corresponding variability in surfactant concentrations and/or composition. Our results reveal that surface-active OM is found throughout the water column, and that at least some surfactants are not of recent biological origin. Our results also support the hypothesis that the surface microlayer is a minor to negligible source of OM associated with freshly produced PMA.

Bubble gate for in-plane flow control.

PubMed

Oskooei, Ali; Abolhasani, Milad; Günther, Axel

2013-07-07

We introduce a miniature gate valve as a readily implementable strategy for actively controlling the flow of liquids on-chip, within a footprint of less than one square millimetre. Bubble gates provide for simple, consistent and scalable control of liquid flow in microchannel networks, are compatible with different bulk microfabrication processes and substrate materials, and require neither electrodes nor moving parts. A bubble gate consists of two microchannel sections: a liquid-filled channel and a gas channel that intercepts the liquid channel to form a T-junction. The open or closed state of a bubble gate is determined by selecting between two distinct gas pressure levels: the lower level corresponds to the "open" state while the higher level corresponds to the "closed" state. During closure, a gas bubble penetrates from the gas channel into the liquid, flanked by a column of equidistantly spaced micropillars on each side, until the flow of liquid is completely obstructed. We fabricated bubble gates using single-layer soft lithographic and bulk silicon micromachining procedures and evaluated their performance with a combination of theory and experimentation. We assessed the dynamic behaviour during more than 300 open-and-close cycles and report the operating pressure envelope for different bubble gate configurations and for the working fluids: de-ionized water, ethanol and a biological buffer. We obtained excellent agreement between the experimentally determined bubble gate operational envelope and a theoretical prediction based on static wetting behaviour. We report case studies that serve to illustrate the utility of bubble gates for liquid sampling in single and multi-layer microfluidic devices. Scalability of our strategy was demonstrated by simultaneously addressing 128 bubble gates.

Lowering of acoustic droplet vaporization threshold via aggregation

NASA Astrophysics Data System (ADS)

Guo, Shifang; Shi, Aiwei; Xu, Shanshan; Du, Xuan; Wang, Xin; Zong, Yujin; Bouakaz, Ayache; Wan, Mingxi

2017-12-01

Acoustically sensitive emulsion nanodroplets composed of perfluorocarbon have shown great potential for advanced medical diagnosis and therapy but are limited by the required high acoustic droplet vaporization (ADV) threshold for clinical applications. This study investigates the use of an ultrasonic standing wave to lower the ADV threshold while maintaining the generated bubble size in the required size range, ensuring the generation of inertial cavitation and corresponding physical effects. The results showed that disperse nanodroplets were manipulated to form micron-sized aggregations, and the required ADV threshold was significantly lowered, while a similar size range of the microbubbles generated by disperse nanodroplets was maintained. The threshold could be further regulated by adjusting the aggregation size via controlling the concentration of the disperse nanodroplets. Furthermore, the internal pressures in the aggregations with different sizes were calculated to determine their ADV thresholds theoretically, which were shown to be in good agreement with the experimental results.

Laser diagnostics for characterization of sprays formed by a collapsing non-equilibrium bubble

NASA Astrophysics Data System (ADS)

Kannan, Y. S.; Balusamy, S.; Karri, B.

2015-12-01

In this paper, we investigate the use of laser diagnostic tools for in-plane imaging of bubble induced spray using a laser sheet and Mie scattering technique. A perspex plate of thickness 10 mm with a hole of diameter 1 mm in the center is placed in the middle of a glass tank filled with water such that the top surface of the plate coincides with the water surface. A bubble is created just below the hole using a low-voltage spark circuit such that it expands against the hole. This leads to the formation of two jets which impact leading to a spray and break-up into droplets. The spray evolution is observed using a laser sheet directed in a plane through the center of the hole. The illuminated plane is imaged using a high-speed camera based on the Mie scattering from glass beads suspended in the liquid. Results show that Mie scattering technique has potential in studying bubble-induced sprays with applications such as in fuel sprays, drug-delivery etc, and also for validation of numerical codes. We present results from our ongoing experiments in this paper.

Bubble evolution in Kr-irradiated UO2 during annealing

NASA Astrophysics Data System (ADS)

He, L.; Bai, X. M.; Pakarinen, J.; Jaques, B. J.; Gan, J.; Nelson, A. T.; El-Azab, A.; Allen, T. R.

2017-12-01

Transmission electron microscopy observation of Kr bubble evolution in polycrystalline UO2 annealed at high temperature was conducted in order to understand the inert gas behavior in oxide nuclear fuel. The average diameter of intragranular bubbles increased gradually from 0.8 nm in as-irradiated sample at room temperature to 2.6 nm at 1600 °C and the bubble size distribution changed from a uniform distribution to a bimodal distribution above 1300 °C. The size of intergranular bubbles increased more rapidly than intragranular ones and bubble denuded zones near grain boundaries formed in all the annealed samples. It was found that high-angle grain boundaries held bigger bubbles than low-angle grain boundaries. Complementary atomistic modeling was conducted to interpret the effects of grain boundary character on the Kr segregation. The area density of strong segregation sites in the high-angle grain boundaries is much higher than that in the low angle grain boundaries.

Trapping of water vapor from an atmosphere by condensed silicate matter formed by high-temperature pulse vaporization

NASA Technical Reports Server (NTRS)

Gerasimov, M. V.; Dikov, Yu. P.; Yakovlev, O. I.; Wlotzka, F.

1993-01-01

The origin of planetary atmospheres is thought to be the result of bombardment of a growing planet by massive planetesimals. According to some models, the accumulation of released water vapor and/or carbon dioxide can result in the formation of a dense and hot primordial atmosphere. Among source and sink processes of atmospheric water vapor the formation of hydroxides was considered mainly as rehydration of dehydrated minerals (foresterite and enstatite). From our point of view, the formation of hydroxides is not limited to rehydration. Condensation of small silicate particles in a spreading vapor cloud and their interaction with a wet atmosphere can also result in the origin of hydrated phases which have no genetic connections with initial water bearing minerals. We present results of two experiments of a simulated interaction of condensed silicate matter which originated during vaporization of dry clinopyroxene in a wet helium atmosphere.

The bubble method of water purification

NASA Astrophysics Data System (ADS)

Smirnov, B. M.; Babaeva, N. Yu.; Naidis, G. V.; Panov, V. A.; Saveliev, A. S.; Son, E. E.; Tereshonok, D. V.

2018-02-01

The processes of water purification from admixture molecules are analyzed. The purification rate is limited due to a low diffusion coefficient of the admixture molecules in water. At non-small concentrations of the admixture molecules, the water purication can proceed through association of molecules in condensed nanoparticles which fall on the bottom of the water volume. The rate of association may be increased in an external electric field, but in reality this cannot change significantly the rate of the purification process. The bubble method of water purification is considered, where air bubbles formed at the bottom of the water volume, transfer admixture molecules to the interface. This method allows one to clean small water volumes fast. This mechanism of water purification is realized experimentally and exhibits the promises of the bubble purification method.

Generating Soap Bubbles by Blowing on Soap Films

NASA Astrophysics Data System (ADS)

Salkin, Louis; Schmit, Alexandre; Panizza, Pascal; Courbin, Laurent

2016-02-01

Making soap bubbles by blowing air on a soap film is an enjoyable activity, yet a poorly understood phenomenon. Working either with circular bubble wands or long-lived vertical soap films having an adjustable steady state thickness, we investigate the formation of such bubbles when a gas is blown through a nozzle onto a film. We vary film size, nozzle radius, space between the film and nozzle, and gas density, and we measure the gas velocity threshold above which bubbles are formed. The response is sensitive to containment, i.e., the ratio between film and jet sizes, and dissipation in the turbulent gas jet, which is a function of the distance from the film to the nozzle. We rationalize the observed four different regimes by comparing the dynamic pressure exerted by the jet on the film and the Laplace pressure needed to create the curved surface of a bubble. This simple model allows us to account for the interplay between hydrodynamic, physicochemical, and geometrical factors.

Generating Soap Bubbles by Blowing on Soap Films.

PubMed

Salkin, Louis; Schmit, Alexandre; Panizza, Pascal; Courbin, Laurent

2016-02-19

Making soap bubbles by blowing air on a soap film is an enjoyable activity, yet a poorly understood phenomenon. Working either with circular bubble wands or long-lived vertical soap films having an adjustable steady state thickness, we investigate the formation of such bubbles when a gas is blown through a nozzle onto a film. We vary film size, nozzle radius, space between the film and nozzle, and gas density, and we measure the gas velocity threshold above which bubbles are formed. The response is sensitive to containment, i.e., the ratio between film and jet sizes, and dissipation in the turbulent gas jet, which is a function of the distance from the film to the nozzle. We rationalize the observed four different regimes by comparing the dynamic pressure exerted by the jet on the film and the Laplace pressure needed to create the curved surface of a bubble. This simple model allows us to account for the interplay between hydrodynamic, physicochemical, and geometrical factors.

Final bubble lengths for aqueous foam coarsened in a horizontal cylinder

NASA Astrophysics Data System (ADS)

Sebag, V.; Roth, A. E.; Durian, D. J.

2011-12-01

We report on length statistics measured for bubbles in the equilibrium bamboo state, achieved by the coarsening of aqueous foam in long cylindrical tubes, such that the soap films are all flat and perpendicular to the axis of the tube. The average bubble length is found to be 0.88 times the tube diameter, independent of variation of the liquid filling fraction by a factor of nearly three. The actual distribution is well-approximated by a shifted Rayleigh form, with a minimum bubble size of 0.28 tube diameters. And, perhaps surprisingly, no correlations are found in the lengths of neighboring bubbles. The observed length distribution agrees with that of Fortes et al. for short bubbles, but not for long bubbles.

Supernova remnant evolution in wind bubbles: A closer look at Kes 27

NASA Astrophysics Data System (ADS)

Dwarkadas, V. V.; Dewey, D.

2013-03-01

Massive Stars (>8M⊙) lose mass in the form of strong winds. These winds accumulate around the star, forming wind-blown bubbles. When the star explodes as a supernova (SN), the resulting shock wave expands within this wind-blown bubble, rather than the interstellar medium. The properties of the resulting remnant, its dynamics and kinematics, the morphology, and the resulting evolution, are shaped by the structure and properties of the wind-blown bubble. In this article we focus on Kes 27, a supernova remnant (SNR) that has been proposed by [1] to be evolving in a wind-blown bubble, explore its properties, and investigate whether the X-Ray properties could be ascribed to evolution of a SNR in a wind-blown bubble. Our initial model does not support the scenario proposed by [1], due to the fact that the reflected shock is expanding into much lower densities.

How are soap bubbles blown? Fluid dynamics of soap bubble blowing

NASA Astrophysics Data System (ADS)

Davidson, John; Lambert, Lori; Sherman, Erica; Wei, Timothy; Ryu, Sangjin

2013-11-01

Soap bubbles are a common interfacial fluid dynamics phenomenon having a long history of delighting not only children and artists but also scientists. In contrast to the dynamics of liquid droplets in gas and gas bubbles in liquid, the dynamics of soap bubbles has not been well documented. This is possibly because studying soap bubbles is more challenging due to there existing two gas-liquid interfaces. Having the thin-film interface seems to alter the characteristics of the bubble/drop creation process since the interface has limiting factors such as thickness. Thus, the main objective of this study is to determine how the thin-film interface differentiates soap bubbles from gas bubbles and liquid drops. To investigate the creation process of soap bubbles, we constructed an experimental model consisting of air jet flow and a soap film, which consistently replicates the conditions that a human produces when blowing soap bubbles, and examined the interaction between the jet and the soap film using the high-speed videography and the particle image velocimetry.

A Study of Heat Transfer and Flow Characteristics of Rising Taylor Bubbles

NASA Technical Reports Server (NTRS)

Scammell, Alexander David

2016-01-01

Practical application of flow boiling to ground- and space-based thermal management systems hinges on the ability to predict the systems heat removal capabilities under expected operating conditions. Research in this field has shown that the heat transfer coefficient within two-phase heat exchangers can be largely dependent on the experienced flow regime. This finding has inspired an effort to develop mechanistic heat transfer models for each flow pattern which are likely to outperform traditional empirical correlations. As a contribution to the effort, this work aimed to identify the heat transfer mechanisms for the slug flow regime through analysis of individual Taylor bubbles.An experimental apparatus was developed to inject single vapor Taylor bubbles into co-currently flowing liquid HFE 7100. The heat transfer was measured as the bubble rose through a 6 mm inner diameter heated tube using an infrared thermography technique. High-speed flow visualization was obtained and the bubble film thickness measured in an adiabatic section. Experiments were conducted at various liquid mass fluxes (43-200 kgm2s) and gravity levels (0.01g-1.8g) to characterize the effect of bubble drift velocityon the heat transfer mechanisms. Variable gravity testing was conducted during a NASA parabolic flight campaign.Results from the experiments showed that the drift velocity strongly affects the hydrodynamics and heat transfer of single elongated bubbles. At low gravity levels, bubbles exhibited shapes characteristic of capillary flows and the heat transfer enhancement due to the bubble was dominated by conduction through the thin film. At moderate to high gravity, traditional Taylor bubbles provided small values of enhancement within the film, but large peaks in the wake heat transfer occurred due to turbulent vortices induced by the film plunging into the trailing liquid slug. Characteristics of the wake heat transfer profiles were analyzed and related to the predicted velocity field

Method of forming ultra thin film devices by vacuum arc vapor deposition

NASA Technical Reports Server (NTRS)

Schramm, Harry F. (Inventor)

2005-01-01

A method for providing an ultra thin electrical circuit integral with a portion of a surface of an object, including using a focal Vacuum Arc Vapor Deposition device having a chamber, a nozzle and a nozzle seal, depressing the nozzle seal against the portion of the object surface to create an airtight compartment in the chamber and depositing one or more ultra thin film layer(s) only on the portion of the surface of the object, the layers being of distinct patterns such that they form the circuit.

Computer modeling movement of biomass in the bioreactors with bubbling mixing

NASA Astrophysics Data System (ADS)

Kuschev, L. A.; Suslov, D. Yu; Alifanova, A. I.

2017-01-01

Recently in the Russian Federation there is an observation of the development of biogas technologies which are used in organic waste conversion of agricultural enterprises, consequently improving the ecological environment. To intensify the process and effective outstanding performance of the acquisition of biogas the application of systems of mixing of bubbling is used. In the case of bubbling mixing of biomass in the bioreactor two-phase portions consisting of biomass and bubbles of gas are formed. The bioreactor computer model with bubble pipeline has been made in a vertical spiral form forming a cone type turned upside down. With the help of computing program of OpenFVM-Flow, an evaluation experiment was conducted to determine the key technological parameters of process of bubbling mixing and to get a visual picture of biomass flows distribution in the bioreactor. For the experimental bioreactor the following equation of V=190 l, speed level, the biomass circulation, and the time of a single cycle of uax =0,029 m/s; QC =0,00087 m3/s, Δtbm .=159 s. In future, we plan to conduct a series of theoretical and experimental researches into the mixing frequency influence on the biogas acquisition process effectiveness.

Formation and evolution of bubbly screens in confined oscillating bubbly liquids.

PubMed

Shklyaev, Sergey; Straube, Arthur V

2010-01-01

We consider the dynamics of dilute monodisperse bubbly liquid confined by two plane solid walls and subject to small-amplitude high-frequency oscillations normal to the walls. The initial state corresponds to the uniform distribution of bubbles and motionless liquid. The period of external driving is assumed much smaller than typical relaxation times for a single bubble but larger than the period of volume eigenoscillations. The time-averaged description accounting for the two-way coupling between the liquid and the bubbles is applied. We show that the model predicts accumulation of bubbles in thin sheets parallel to the walls. These singular structures, which are formally characterized by infinitely thin width and infinitely high concentration, are referred to as bubbly screens. The formation of a bubbly screen is described analytically in terms of a self-similar solution, which is in agreement with numerical simulations. We study the evolution of bubbly screens and detect a one-dimensional stationary state, which is shown to be unconditionally unstable.

Formation and evolution of bubbly screens in confined oscillating bubbly liquids

NASA Astrophysics Data System (ADS)

Shklyaev, Sergey; Straube, Arthur V.

2010-01-01

We consider the dynamics of dilute monodisperse bubbly liquid confined by two plane solid walls and subject to small-amplitude high-frequency oscillations normal to the walls. The initial state corresponds to the uniform distribution of bubbles and motionless liquid. The period of external driving is assumed much smaller than typical relaxation times for a single bubble but larger than the period of volume eigenoscillations. The time-averaged description accounting for the two-way coupling between the liquid and the bubbles is applied. We show that the model predicts accumulation of bubbles in thin sheets parallel to the walls. These singular structures, which are formally characterized by infinitely thin width and infinitely high concentration, are referred to as bubbly screens. The formation of a bubbly screen is described analytically in terms of a self-similar solution, which is in agreement with numerical simulations. We study the evolution of bubbly screens and detect a one-dimensional stationary state, which is shown to be unconditionally unstable.

A hydrodynamical model of the circumstellar bubble created by two massive stars

NASA Astrophysics Data System (ADS)

van Marle, A. J.; Meliani, Z.; Marcowith, A.

2012-05-01

Context. Numerical models of the wind-blown bubble of massive stars usually only account for the wind of a single star. However, since massive stars are usually formed in clusters, it would be more realistic to follow the evolution of a bubble created by several stars. Aims: We develop a two-dimensional (2D) model of the circumstellar bubble created by two massive stars, a 40 M⊙ star and a 25 M⊙ star, and follow its evolution. The stars are separated by approximately 16 pc and surrounded by a cold medium with a density of 20 particles per cm3. Methods: We use the MPI-AMRVAC hydrodynamics code to solve the conservation equations of hydrodynamics on a 2D cylindrical grid using time-dependent models for the wind parameters of the two stars. At the end of the stellar evolution (4.5 and 7.0 million years for the 40 and 25 M⊙ stars, respectively), we simulate the supernova explosion of each star. Results: Each star initially creates its own bubble. However, as the bubbles expand they merge, creating a combined, aspherical bubble. The combined bubble evolves over time, influenced by the stellar winds and supernova explosions. Conclusions: The evolution of a wind-blown bubble created by two stars deviates from that of the bubbles around single stars. In particular, once one of the stars has exploded, the bubble is too large for the wind of the remaining star to maintain and the outer shell starts to disintegrate. The lack of thermal pressure inside the bubble also changes the behavior of circumstellar features close to the remaining star. The supernovae are contained inside the bubble, which reflects part of the energy back into the circumstellar medium. Movies are available in electronic form at http://www.aanda.org

Unstable 3D phenomena: Dynamic interactions of a cavitation bubble and Richtmyer-Meshkov unstable divot

NASA Astrophysics Data System (ADS)

Buttler, William; Renner, Dru; Morris, Chris; Manzanares, Ruben; Heidemann, Joel; Kalas, Ryan; Llobet, Anna; Martinez, John; Payton, Jeremy; Saunders, Andy; Schmidt, Derek; Tainter, Amy; Vincent, Samuel; Vogan-McNeil, Wendy

2017-06-01

We radiographically explore a shock-induced Sn cavitation bubble as it interacts with a transverse cavitation wave caused by a Richtmyer-Meshkov unstable spike from a divot. The cavitation bubble forms as two shockwaves collide under the divot, as the shockwaves release to ambient pressure at the surface. The divot inverts and unstably grows, as expected and predicted, but the release waves that form the cavitation bubble reflect from and constrain the cavitation wave growth. As the cavitation wave grows it pierces the cavitation bubble, deflating it onto the unstable transverse cavitation wave.

Lattice diffusion and vapor solid growths forming nanoarchitectures on ZnO nanowires

NASA Astrophysics Data System (ADS)

Sombrio, Guilherme; Rivaldo-Gómez, C. M.; Pomar, Cesar A. D.; Souza, Jose A.

2017-12-01

We report hierarchical nanoarchitectures formed on the tips and sidewalls of ZnO nanowires which is formed on the top of microtubes. The whole growth process of these micro/nanostructures during thermal oxidation combines lattice/grain/surface ionic diffusion along with vapor solid mechanism. All the process takes place along with the presence of an electric current, which plays an important role forming the ZnO molecules due to Zn metal evaporation and attracting them to condense into nanostructures of several morphologies. The observation of a very long needle-like nanowire reveals the stack nature of the growth. These nanoarchitectures are rarely observed experimentally. Raman scattering confirms phonon confinement in the nanostructures. Photoluminescence measurements indicate a route for engineering defects on the surface of ZnO microtubes after the complete coalescence of the nanostructures through heat treatment. This experiment would be useful for improving nanostructure organization which could provide an impact in the manufacturability of nanostructure-based systems.

Momentum effects in steady nucleate pool boiling during microgravity.

PubMed

Merte, Herman

2004-11-01

Pool boiling experiments were conducted in microgravity on five space shuttle flights, using a flat plate heater consisting of a semitransparent thin gold film deposited on a quartz substrate that also acted as a resistance thermometer. The test fluid was R-113, and the vapor bubble behavior at the heater surface was photographed from beneath as well as from the side. Each flight consisted of a matrix of three levels of heat flux and three levels of subcooling. In 26 of the total of 45 experiments conditions of steady-state pool boiling were achieved under certain combinations of heat flux and liquid subcooling. In many of the 26 cases, it was observed from the 16-mm movie films that a large vapor bubble formed, remaining slightly removed from the heater surface, and that subsequent vapor bubbles nucleate and grow on the heater surface. Coalescence occurs upon making contact with the large bubble, which thus acts as a vapor reservoir. Recently, measurements of the frequencies and sizes of the small vapor bubbles as they coalesced with the large bubble permitted computation of the associated momentum transfer. The transient forces obtained are presented here. Where these arise from the conversion of the surface energy in the small vapor bubble to kinetic energy acting away from the solid heater surface, they counter the Marangoni convection due to the temperature gradients normal to the heater surface. This Marangoni convection would otherwise impel the large vapor bubble toward the heater surface and result in dryout and unsteady heat transfer.

Beer tapping: dynamics of bubbles after impact

NASA Astrophysics Data System (ADS)

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

2015-12-01

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

Bubble number saturation curve and asymptotics of hypobaric and hyperbaric exposures.

PubMed

Wienke, B R

1991-12-01

Within bubble number limits of the varying permeability and reduced gradient bubble models, it is shown that a linear form of the saturation curve for hyperbaric exposures and a nearly constant decompression ratio for hypobaric exposures are simultaneously recovered from the phase volume constraint. Both limits are maintained within a single bubble number saturation curve. A bubble term, varying exponentially with inverse pressure, provides closure. Two constants describe the saturation curve, both linked to seed numbers. Limits of other decompression models are also discussed and contrasted for completeness. It is suggested that the bubble number saturation curve thus provides a consistent link between hypobaric and hyperbaric data, a link not established by earlier decompression models.

Measurements of CO{sub 2} fluxes and bubbles from a tower during ASGASEX

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leeuw, G. de; Kunz, G.J.; Larsen, S.E.

1994-12-31

The Air-Sea Gas Exchange experiment ASGASEX was conducted from August 30 until October 1st from the Meetpost Noordwijk (MPN), a research tower in the North Sea at 9 km from the Dutch coast. The objective of ASGASEX was a study of parameters affecting the air-sea exchange of gases, and a comparison of experimental methods to derive the exchange coefficient for CO{sub 2}. A detailed description of the ASGASEX experiment is presented in Oost. The authors` contribution to ASGASEX was a micro-meteorological package to measure the fluxes of CO{sub 2}, momentum, heat and water vapor, and an instrument to measure themore » size distribution of bubbles just below the sea surface. In this contribution the authors report preliminary results from the CO{sub 2} flux measurements and the bubble measurements. The latter was made as part of a larger study on the influence of bubbles on gas exchange in cooperation with the University of Southampton and the University of Galway.« less

Oceanic Gas Bubble Measurements Using an Acoustic Bubble Spectrometer

NASA Astrophysics Data System (ADS)

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

2008-12-01

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

Bubble performance of a novel dissolved air flotation(DAF) unit.

PubMed

Chen, Fu-tai; Peng, Feng-xian; Wu, Xiao-qing; Luan, Zhao-kun

2004-01-01

ES-DAF, a novel DAF with low cost, high reliability and easy controllability, was studied. Without a costly air saturator, ES-DAF consists of an ejector and a static mixer between the pressure side and suction side of the recycle rotary pump. The bubble size distribution in this novel unit was studied in detail by using a newly developed CCD imagination through a microscope. Compared with M-DAF under the same saturation pressure, ES-DAF can produce smaller bubble size and higher bubble volume concentration, especially in lower pressure. In addition, the bubble size decreases with the increase of reflux ratio or decrease of superficial air-water ratio. These results suggested that smaller bubbles will be formed when the initial number of nucleation sites increases by enhancing the turbulence intensity in the saturation system.

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.

New solutions for steady bubbles in a Hele-Shaw cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tanveer, S.

1987-03-01

Exact solutions are presented for steadily moving bubbles in a Hele--Shaw cell when the effect of surface tension is neglected. These solutions form a three-parameter family. For specified area, both the speed of the bubble and the distance of its centroid from the channel centerline remain arbitrary when surface tension is ignored. However, numerical evidence suggests that this twofold arbitrariness is removed by the effect of surface tension, i.e., for given bubble area and surface tension, solutions exist only when the bubble velocity and the centroid distance from the channel centerline attain one or more isolated values. From a limitedmore » numerical search, no nonsymmetric solutions could be found; however, a branch of symmetric bubble solutions that was not found in earlier work was found. This branch corresponds to one of the Romero-Vanden-Broeck branch of finger solutions when the bubble size is large. A new procedure for numerical calculations of bubble solutions in the presence of surface tension is presented and is found to work very well for reasonably large bubbles, unlike the previous method of Tanveer (Phys. Fluids 29, 3537 (1986)). The precise power law dependence of bubble velocity on surface tension for small surface tension is explored for bubbles of different area. Agreement is noted with recent analytical results for a finger.« less

Net vapor generation point in boiling flow of trichlorotrifluoroethane at high pressures

NASA Technical Reports Server (NTRS)

Dougall, R. S.; Lippert, T. E.

1973-01-01

The conditions at which the void in subcooled boiling starts to undergo a rapid increase were studied experimentally. The experiments were performed in a 12.7 x 9.5 mm rectangular channel. Heating was from a 3.2 mm wide strip embedded in one wall. The pressure ranged from 9.45 to 20.7 bar, mass velocity from 600 to 7000 kg/sq m sec, and subcooling from 16 to 67 C. Photographs were used to determine when detached bubbles first appeared in the bulk flow. Measurements of bubble layer thickness along the wall were also made. Results showed that the point of net vapor generation is close to the occurrence of fully-developed boiling.

Fabrication of magnetic bubble memory overlay

NASA Technical Reports Server (NTRS)

1973-01-01

Self-contained magnetic bubble memory overlay is fabricated by process that employs epitaxial deposition to form multi-layered complex of magnetically active components on single chip. Overlay fabrication comprises three metal deposition steps followed by subtractive etch.

Scoping studies of vapor behavior during a severe accident in a metal-fueling reactor

NASA Astrophysics Data System (ADS)

Spencer, B. W.; Marchaterre, J. F.

1985-04-01

The consequences of fuel melting and pin failures for a reactivity-insertion type accident in a sodium-cooled, pool-type reactor fueled with a metal alloy fuel were examined. The principal gas and vapor species released are shown to be Xe, Cs, and bond sodium contained within the fuel porosity. Condensation of sodium vapor as it expands into the upper sodium pool in a jet mixing regime may occur as rapidly as the vapor emerges from the disrupted core. If the predictions of rapid direct-contact condensation can be verified experimentally for the sodium system, the ability of vapor expansion to perform appreciable work on the system and the ability of an expanding vapor bubble to transport fuel and fission produce species to the cover gas region where they may be released to the containment are largely eliminated. The radionuclide species except for fission gas are largely retained within the core and sodium pool.

Giant frequency down-conversion of the dancing acoustic bubble

PubMed Central

Deymier, P. A.; Keswani, M.; Jenkins, N.; Tang, C.; Runge, K.

2016-01-01

We have demonstrated experimentally the existence of a giant frequency down-conversion of the translational oscillatory motion of individual submillimeter acoustic bubbles in water in the presence of a high frequency (500 kHz) ultrasonic standing wave. The frequency of the translational oscillations (~170 Hz) is more than three orders of magnitude smaller than that of the driving acoustic wave. We elucidate the mechanism of this very slow oscillation with an analytical model leading to an equation of translational motion of a bubble taking the form of Mathieu’s equation. This equation illuminates the origin of the giant down conversion in frequency as arising from an unstable equilibrium. We also show that bubbles that form chains along the direction of the acoustic standing wave due to radiation interaction forces exhibit also translation oscillations that form a spectral band. This band extends approximately from 130 Hz up to nearly 370 Hz, a frequency range that is still at least three orders of magnitude lower than the frequency of the driving acoustic wave. PMID:27857217

Giant frequency down-conversion of the dancing acoustic bubble

NASA Astrophysics Data System (ADS)

Deymier, P. A.; Keswani, M.; Jenkins, N.; Tang, C.; Runge, K.

2016-11-01

We have demonstrated experimentally the existence of a giant frequency down-conversion of the translational oscillatory motion of individual submillimeter acoustic bubbles in water in the presence of a high frequency (500 kHz) ultrasonic standing wave. The frequency of the translational oscillations (~170 Hz) is more than three orders of magnitude smaller than that of the driving acoustic wave. We elucidate the mechanism of this very slow oscillation with an analytical model leading to an equation of translational motion of a bubble taking the form of Mathieu’s equation. This equation illuminates the origin of the giant down conversion in frequency as arising from an unstable equilibrium. We also show that bubbles that form chains along the direction of the acoustic standing wave due to radiation interaction forces exhibit also translation oscillations that form a spectral band. This band extends approximately from 130 Hz up to nearly 370 Hz, a frequency range that is still at least three orders of magnitude lower than the frequency of the driving acoustic wave.

BURST OF STAR FORMATION DRIVES BUBBLE IN GALAXY'S CORE

NASA Technical Reports Server (NTRS)

2002-01-01

These NASA Hubble Space Telescope snapshots reveal dramatic activities within the core of the galaxy NGC 3079, where a lumpy bubble of hot gas is rising from a cauldron of glowing matter. The picture at left shows the bubble in the center of the galaxy's disk. The structure is more than 3,000 light-years wide and rises 3,500 light-years above the galaxy's disk. The smaller photo at right is a close-up view of the bubble. Astronomers suspect that the bubble is being blown by 'winds' (high-speed streams of particles) released during a burst of star formation. Gaseous filaments at the top of the bubble are whirling around in a vortex and are being expelled into space. Eventually, this gas will rain down upon the galaxy's disk where it may collide with gas clouds, compress them, and form a new generation of stars. The two white dots just above the bubble are probably stars in the galaxy. The close-up reveals that the bubble's surface is lumpy, consisting of four columns of gaseous filaments that tower above the galaxy's disk. The filaments disperse at a height of 2,000 light-years. Each filament is about 75 light-years wide. Velocity measurements taken by the Canada-France-Hawaii Telescope in Hawaii show that the gaseous filaments are ascending at more than 4 million miles an hour (6 million kilometers an hour). According to theoretical models, the bubble formed when ongoing winds from hot stars mixed with small bubbles of very hot gas from supernova explosions. Observations of the core's structure by radio telescopes indicate that those processes are still active. The models suggest that this outflow began about a million years ago. They occur about every 10 million years. Eventually, the hot stars will die, and the bubble's energy source will fade away. Astronomers have seen evidence of previous outbursts from radio and X-ray observations. Those studies show rings of dust and gas and long plumes of material, all of which are larger than the bubble. NGC 3079 is 50

Plasma bubble monitoring by TEC map and 630 nm airglow image

NASA Astrophysics Data System (ADS)

Takahashi, H.; Wrasse, C. M.; Otsuka, Y.; Ivo, A.; Gomes, V.; Paulino, I.; Medeiros, A. F.; Denardini, C. M.; Sant'Anna, N.; Shiokawa, K.

2015-08-01

Equatorial ionosphere plasma bubbles over the South American continent were successfully observed by mapping the total electron content (TECMAP) using data provided by ground-based GNSS receiver networks. The TECMAP could cover almost all of the continent within ~4000 km distance in longitude and latitude, monitoring TEC variability continuously with a time resolution of 10 min. Simultaneous observations of OI 630 nm all-sky image at Cachoeira Paulista (22.7°S, 45.0°W) and Cariri (7.4°S, 36.5°W) were used to compare the bubble structures. The spatial resolution of the TECMAP varied from 50 km to 1000 km, depending on the density of the observation sites. On the other hand, optical imaging has a spatial resolution better than 15 km, depicting the fine structure of the bubbles but covering a limited area (~1600 km diameter). TECMAP has an advantage in its spatial coverage and the continuous monitoring (day and night) form. The initial phase of plasma depletion in the post-sunset equatorial ionization anomaly (PS-EIA) trough region, followed by development of plasma bubbles in the crest region, could be monitored in a progressive way over the magnetic equator. In December 2013 to January 2014, periodically spaced bubble structures were frequently observed. The longitudinal spacing between the bubbles was around 600-800 km depending on the day. The periodic form of plasma bubbles may suggest a seeding process related to the solar terminator passage in the ionosphere.

Quasi-stokeslet induced by thermoplasmonic Marangoni effect around a water vapor microbubble

PubMed Central

Namura, Kyoko; Nakajima, Kaoru; Suzuki, Motofumi

2017-01-01

Rapid Marangoni flows around a water vapor microbubble (WVMB) is investigated using the thermoplasmonic effect of a gold nanoisland film (GNF). By focusing a laser onto the GNF, a stable WVMB with a diameter of ~10 μm is generated in degassed water, while an air bubble generated in non-degassed water is larger than 40 μm. Under continuous heating, the WVMB involves significantly rapid Marangoni flow. This flow is well-described by a stokeslet sat ~10 μm above the surface of GNF, from which the maximum flow speed around the WVMB is estimated to exceed 1 m/s. This rapid flow generation is attributed to the small bubble size, over which the temperature is graded, and the superheat at the bubble surface in contact with the GNF. It is expected to be useful not only for microfluidic mixing but also for fundamental research on viscous flow induced by a single stokeslet. PMID:28361949

Bubble levitation and translation under single-bubble sonoluminescence conditions.

PubMed

Matula, Thomas J

2003-08-01

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

Cavitation bubble nucleation induced by shock-bubble interaction in a gelatin gel

NASA Astrophysics Data System (ADS)

Oguri, Ryota; Ando, Keita

2018-05-01

An optical visualization technique is developed to study cavitation bubble nucleation that results from interaction between a laser-induced shock and a preexisting gas bubble in a 10 wt. % gelatin gel; images of the nucleated cavitation bubbles are captured and the cavitation inception pressure is determined based on Euler flow simulation. A spherical gas cavity is generated by focusing an infrared laser pulse into a gas-supersaturated gel and the size of the laser-generated bubble in mechanical equilibrium is tuned via mass transfer of the dissolved gas into the bubble. A spherical shock is then generated, through rapid expansion of plasma induced by the laser focusing, in the vicinity of the gas bubble. The shock-bubble interaction is recorded by a CCD camera with flash illumination of a nanosecond green laser pulse. The observation captures cavitation inception in the gel under tension that results from acoustic impedance mismatching at the bubble interface interacting with the shock. We measure the probability of cavitation inception from a series of the repeated experiments, by varying the bubble radius and the standoff distance. The threshold pressure is defined at the cavitation inception probability equal to one half and is calculated, through comparisons to Euler flow simulation, at -24.4 MPa. This threshold value is similar to that from shock-bubble interaction experiments using water, meaning that viscoelasticity of the 10 wt. % gelatin gel has a limited impact on bubble nucleation dynamics.

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.

Is it really important to form a big bubble in DALK to enhance the visual acuity?

PubMed

Acar, Banu Torun; Vural, Ece Turan; Acar, Suphi

2012-09-01

The aim of this study was to investigate the prognosis of visual acuity (VA) in the patients with keratoconus, who underwent deep anterior lamellar keratoplasty (DALK) with a successful big bubble or lamellar dissection. Sixty-eight eyes of 60 patients with keratoconus, who underwent DALK using the big-bubble technique, were enrolled in this retrospective comparative study. The VA and refractive errors were assessed before the operation and, thereafter, at months 1, 3, 6, and 12 after the operation (1) in the patients who achieved a big-bubble formation, and in those who required layer-by-layer lamellar dissection (2) to reach the Descemet membrane. Successful big bubble was achieved in 50 eyes (73.5 %) (group 1), and lamellar dissection was performed in 18 eyes (26.5 %) (group 2). The mean follow-up period was 22.4±6.2 months in group 1 and 23.7±7.8 months in group 2 (P=0.562). Although best-corrected visual acuity (BCVA) values observed at months 1 and 3 were significantly higher in group 1 than in group 2 (P=0.016 and P=0.024, respectively), there was no statistically significant difference between the two groups for BCVA values observed at months 6 and 12 (P=0.412 and P=0.528, respectively). Although the visual recovery was delayed in the early postoperative follow-up because of residual stroma in lamellar dissection, the final results were comparable between the achievement of big-bubble formation and lamellar dissection.

Influence of alkane and perfluorocarbon vapors on adsorbed surface layers and spread insoluble monolayers of surfactants, proteins and lipids.

PubMed

Fainerman, V B; Aksenenko, E V; Miller, R

2017-06-01

The influence of hexane vapor in the air atmosphere on the surface tension of water and solutions of C 10 EO 8 , C n TAB and proteins are presented. For dry air, a fast and strong decrease of surface tension of water was observed. In humid air, the process is slower and the surface tension higher. There are differences between the results obtained by the maximum bubble pressure, pendant drop and emerging bubble methods, which are discussed in terms of depletion and initial surface load. The surface tension of aqueous solutions of β-сasein (BCS), β-lactoglobulin (BLG) and human serum albumin (HSA) at the interfaces with air and air-saturated hexane vapor were measured. The results indicate that the equilibrium surface tension in the hexane vapor atmosphere is considerably lower (at 13-20mN/m) as compared to the values at the interface with pure air. A reorientation model is proposed assuming several states of adsorbed molecules with different molar area values. The newly developed theoretical model is used to describe the effect of alkane vapor in the gas phase on the surface tension. This model assumes that the first layer is composed of surfactant (or protein) molecules mixed with alkane, and the second layer is formed by alkane molecules only. The processing of the experimental data for the equilibrium surface tension for the C 10 EO 8 and BCS solutions results in a perfect agreement between the observed and calculated values. The co-adsorption mechanism of dipalmitoyl phosphatidyl choline (DPPC) and the fluorocarbon molecules leads to remarkable differences in the surface pressure term of cohesion Π coh . This in turn leads to a very efficient fluidization of the monolayer. It was found that the adsorption equilibrium constant for dioctanoyl phosphatidyl choline is increased in the presence of perfluorohexane, and the intermolecular interaction of the components is strong. Copyright © 2015 Elsevier B.V. All rights reserved.

Wind bubbles within H ii regions around slowly moving stars

NASA Astrophysics Data System (ADS)

Mackey, Jonathan; Gvaramadze, Vasilii V.; Mohamed, Shazrene; Langer, Norbert

2015-01-01

Interstellar bubbles around O stars are driven by a combination of the star's wind and ionizing radiation output. The wind contribution is uncertain because the boundary between the wind and interstellar medium is difficult to observe. Mid-infrared observations (e.g., of the H ii region RCW 120) show arcs of dust emission around O stars, contained well within the H ii region bubble. These arcs could indicate the edge of an asymmetric stellar wind bubble, distorted by density gradients and/or stellar motion. We present two-dimensional, radiation-hydrodynamics simulations investigating the evolution of wind bubbles and H ii regions around massive stars moving through a dense (nH = 3000 cm-3), uniform medium with velocities ranging from 4 to 16 km s-1. The H ii region morphology is strongly affected by stellar motion, as expected, but the wind bubble is also very aspherical from birth, even for the lowest space velocity considered. Wind bubbles do not fill their H ii regions (we find filling factors of 10-20 per cent), at least for a main sequence star with mass M⋆ ~ 30 M⊙. Furthermore, even for supersonic velocities the wind bow shock does not significantly trap the ionization front. X-ray emission from the wind bubble is soft, faint, and comes mainly from the turbulent mixing layer between the wind bubble and the H ii region. The wind bubble radiates <1 per cent of its energy in X-rays; it loses most of its energy by turbulent mixing with cooler photoionized gas. Comparison of the simulations with the H ii region RCW 120 shows that its dynamical age is ≲0.4 Myr and that stellar motion ≲4 km s-1 is allowed, implying that the ionizing source is unlikely to be a runaway star but more likely formed in situ. The region's youth, and apparent isolation from other O or B stars, makes it very interesting for studies of massive star formation and of initial mass functions. Movies are available in electronic form at http://www.aanda.org

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. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Pump-probe imaging of nanosecond laser-induced bubbles in agar gel.

PubMed

Evans, R; Camacho-López, S; Pérez-Gutiérrez, F G; Aguilar, G

2008-05-12

In this paper we show results of Nd:YAG laser-induced bubbles formed in a one millimeter thick agar gel slab. The nine nanosecond duration pulse with a wave length of 532 nm was tightly focused inside the bulk of the gel sample. We present for the first time a pump-probe laser-flash shadowgraphy system that uses two electronically delayed Nd:YAG lasers to image the the bubble formation and shock wave fronts with nanosecond temporal resolution and up to nine seconds of temporal range. The shock waves generated by the laser are shown to begin at an earlier times within the laser pulse as the pulse energy increases. The shock wave velocity is used to infer a shocked to unshocked material pressure difference of up to 500 MPa. The bubble created settles to a quasi-stable size that has a linear relation to the maximum bubble size. The energy stored in the bubble is shown to increase nonlinearly with applied laser energy, and corresponds in form to the energy transmission in the agar gel. We show that the interaction is highly nonlinear, and most likely is plasma-mediated.

Compression-induced stacking fault tetrahedra around He bubbles in Al

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shao, Jian-Li, E-mail: shao-jianli@iapcm.ac.cn; Wang, Pei; He, An-Min

Classic molecular dynamics methods are used to simulate the uniform compression process of the fcc Al containing He bubbles. The formation of stacking fault tetrahedra (SFTs) during the collapse of He bubbles is found, and their dependence on the initial He bubble size (0.6–6 nm in diameter) is presented. Our simulations indicate only elastic deformation in the samples for the He bubble size not more than 2 nm. Instead, increasing the He bubble size, we detect several small SFTs forming on the surface of the He bubble (3 nm), as well as the two intercrossed SFTs around the He bubbles (4–6 nm). All thesemore » SFTs are observed to be stable under further compression, though there may appear some SF networks outside the SFTs (5–6 nm). Furthermore, the dynamic analysis on the SFTs shows that the yield pressure keeps a near-linear increase with the initial He bubble pressure, and the potential energy of Al atoms inside the SFTs is lower than outside because of their gliding inwards. In addition, the pressure increments of 2–6 nm He bubbles with strain are less than that of Al, which just provides the opportunity for the He bubble collapse and the SFTs formation. Note that the current work only focuses on the case that the number ratio between He atoms and Al vacancies is 1:1.« less

Design, fabrication and testing of porous tungsten vaporizers for mercury ion thrusters

NASA Technical Reports Server (NTRS)

Zavesky, R.; Kroeger, E.; Kami, S.

1983-01-01

The dispersions in the characteristics, performance and reliability of vaporizers for early model 30-cm thrusters were investigated. The purpose of the paper is to explore the findings and to discuss the approaches that were taken to reduce the observed dispersion and present the results of a program which validated those approaches. The information that is presented includes porous tungsten materials specifications, a discussion of assembly procedures, and a description of a test program which screens both material and fabrication processes. There are five appendices providing additional detail in the areas of vaporizer contamination, nitrogen flow testing, bubble testing, porosimeter testing, and mercury purity. Four neutralizers, seven cathodes and five main vaporizers were successfully fabricated, tested, and operated on thrusters. Performance data from those devices is presented and indicates extremely repeatable results from using the design and fabrication procedures.

Bubble Proliferation in Shock Wave Lithotripsy Occurs during Inertial Collapse

NASA Astrophysics Data System (ADS)

Pishchalnikov, Yuri A.; McAteer, James A.; Pishchalnikova, Irina V.; Williams, James C.; Bailey, Michael R.; Sapozhnikov, Oleg A.

2008-06-01

In shock wave lithotripsy (SWL), firing shock pulses at slow pulse repetition frequency (0.5 Hz) is more effective at breaking kidney stones than firing shock waves (SWs) at fast rate (2 Hz). Since at fast rate the number of cavitation bubbles increases, it appears that bubble proliferation reduces the efficiency of SWL. The goal of this work was to determine the basis for bubble proliferation when SWs are delivered at fast rate. Bubbles were studied using a high-speed camera (Imacon 200). Experiments were conducted in a test tank filled with nondegassed tap water at room temperature. Acoustic pulses were generated with an electromagnetic lithotripter (DoLi-50). In the focus of the lithotripter the pulses consisted of a ˜60 MPa positive-pressure spike followed by up to -8 MPa negative-pressure tail, all with a total duration of about 7 μs. Nonlinear propagation steepened the shock front of the pulses to become sufficiently thin (˜0.03 μm) to impose differential pressure across even microscopic bubbles. High-speed camera movies showed that the SWs forced preexisting microbubbles to collapse, jet, and break up into daughter bubbles, which then grew rapidly under the negative-pressure phase of the pulse, but later coalesced to re-form a single bubble. Subsequent bubble growth was followed by inertial collapse and, usually, rebound. Most, if not all, cavitation bubbles emitted micro-jets during their first inertial collapse and re-growth. After jetting, these rebounding bubbles could regain a spherical shape before undergoing a second inertial collapse. However, either upon this second inertial collapse, or sometimes upon the first inertial collapse, the rebounding bubble emerged from the collapse as a cloud of smaller bubbles rather than a single bubble. These daughter bubbles could continue to rebound and collapse for a few cycles, but did not coalesce. These observations show that the positive-pressure phase of SWs fragments preexisting bubbles but this initial

Diffusive counter dispersion of mass in bubbly media.

PubMed

Goldobin, Denis S; Brilliantov, Nikolai V

2011-11-01

We consider a liquid bearing gas bubbles in a porous medium. When gas bubbles are immovably trapped in a porous matrix by surface-tension forces, the dominant mechanism of transfer of gas mass becomes the diffusion of gas molecules through the liquid. Essentially, the gas solution is in local thermodynamic equilibrium with vapor phase all over the system, i.e., the solute concentration equals the solubility. When temperature and/or pressure gradients are applied, diffusion fluxes appear and these fluxes are faithfully determined by the temperature and pressure fields, not by the local solute concentration, which is enslaved by the former. We derive the equations governing such systems, accounting for thermodiffusion and gravitational segregation effects, which are shown not to be neglected for geological systems-marine sediments, terrestrial aquifers, etc. The results are applied for the treatment of non-high-pressure systems and real geological systems bearing methane or carbon dioxide, where we find a potential possibility of the formation of gaseous horizons deep below a porous medium surface. The reported effects are of particular importance for natural methane hydrate deposits and the problem of burial of industrial production of carbon dioxide in deep aquifers.

Molten silicate mantle during a giant impact. Speciation from vapor to supercritical state

NASA Astrophysics Data System (ADS)

Caracas, R.; Stewart, S. T.

2017-12-01

We employ large-scale first-principles molecular dynamics simulations to understand the physical and chemical behavior of the molten protolunar disk, at the atomic level. We consider the average composition of the Earth's mantle as proposed by Sun and McDonough (1995). We cover the 0.75 - 7.5 g/cm3 density range and 2000 - 10000 K temperature range. This allows us to investigate the entire disk, from the interior of the molten core to the outer regions of the vaporized disk. At high density, the liquid is highly polymerized and viscous, consistent with previous studies. At low density and low temperatures, in the 2000 to 4000 K range, we capture the nucleation of bubbles. The bubbles contain a low-density gas phase rich in individual alkaline and calc-alkaline cations and SiOx groups. When volatiles are present in the system, such molecular species are the first ones to evaporate and be present in these bubbles. We propose numerical tools to detect the liquid-vapor equilibrium. The critical curves are reached consistently regardless of the thermodynamic path we chose to obtain the low densities. We analyze the equilibrium between the gas of the bubbles and the liquid. At high temperature, we identify the supercritical region characterized by one homogeneous fluid, rich in ionic species. We show that the chemical speciation is very different from the one obtained at ambient pressure conditions. Critical curves are necessary to understand the separation and degassing of volatiles during the recovery from a giant impact. Acknowledgements: This research was supported by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement n°681818 - IMPACT). The ab initio simulations were performed on the GENCI supercomputers, under eDARI/CINES grants x106368.

Acoustic trapping in bubble-bounded micro-cavities

NASA Astrophysics Data System (ADS)

O'Mahoney, P.; McDougall, C.; Glynne-Jones, P.; MacDonald, M. P.

2016-12-01

We present a method for controllably producing longitudinal acoustic trapping sites inside microfluidic channels. Air bubbles are injected into a micro-capillary to create bubble-bounded `micro-cavities'. A cavity mode is formed that shows controlled longitudinal acoustic trapping between the two air/water interfaces along with the levitation to the centre of the channel that one would expect from a lower order lateral mode. 7 μm and 10 μm microspheres are trapped at the discrete acoustic trapping sites in these micro-cavities.We show this for several lengths of micro-cavity.

Recovering hydrocarbons from hydrocarbon-containing vapors

DOEpatents

Mirza, Zia I.; Knell, Everett W.; Winter, Bruce L.

1980-09-30

Values are recovered from a hydrocarbon-containing vapor by contacting the vapor with quench liquid consisting essentially of hydrocarbons to form a condensate and a vapor residue, the condensate and quench fluid forming a combined liquid stream. The combined liquid stream is mixed with a viscosity-lowering liquid to form a mixed liquid having a viscosity lower than the viscosity of the combined liquid stream to permit easy handling of the combined liquid stream. The quench liquid is a cooled portion of the mixed liquid. Viscosity-lowering liquid is separated from a portion of the mixed liquid and cycled to form additional mixed liquid.

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.

Bubble Dynamics and Resulting Noise from Traveling Bubble Cavitation.

DTIC Science & Technology

1982-04-13

proportional to the gas content. The subjectivity of visual cavitation determination is evidenced by the maximum standard deviation. As mentioned before...bubble radii at the maximum radius position on the model. The point on the model where the bubble will be at its maximum volume was determined by...48 3.7 Recording Bubble Dynamics . • . * . . . . 52 3.8 Measurement of Gas Nuclei in Water 0 • 52 3 TABLE OF CONTENTS (continued) Paqe

Evolution of Helium Bubbles and Discs in Irradiated 6H-SiC during Post-Implantation Annealing.

PubMed

Shen, Qiang; Zhou, Wei; Ran, Guang; Li, Ruixiang; Feng, Qijie; Li, Ning

2017-01-24

The single crystal 6H-SiC with [0001] crystal direction irradiated by 400 keV He⁺ ions with 1 × 10 17 ions/cm² fluence at 400 °C were annealed at 600, 900, 1200 and 1400 °C for different durations. The evolution of helium bubbles and discs was investigated by transmission electron microscopy. An irradiated layer distributed with fine helium bubbles was formed with a width of ~170 nm after helium ion irradiation. The size of gas bubbles increased with increasing annealing time and temperature and finally reached stable values at a given annealing temperature. According to the relationship between the bubble radii and annealing time, an empirical formula for calculating the bubble radii at the annealing temperature ranged from 600 to 1400 °C was given by fitting the experiment data. Planar bubble clusters (discs) were found to form on (0001) crystal plane at both sides of the bubble layer when the annealing temperature was at the range of 800-1200 °C. The mechanism of bubble growth during post-implantation annealing and the formation of bubble discs were also analyzed and discussed.

Electrochemistry of single nanobubbles. Estimating the critical size of bubble-forming nuclei for gas-evolving electrode reactions.

PubMed

German, Sean R; Edwards, Martin A; Chen, Qianjin; Liu, Yuwen; Luo, Long; White, Henry S

2016-12-12

In this article, we address the fundamental question: "What is the critical size of a single cluster of gas molecules that grows and becomes a stable (or continuously growing) gas bubble during gas evolving reactions?" Electrochemical reactions that produce dissolved gas molecules are ubiquitous in electrochemical technologies, e.g., water electrolysis, photoelectrochemistry, chlorine production, corrosion, and often lead to the formation of gaseous bubbles. Herein, we demonstrate that electrochemical measurements of the dissolved gas concentration, at the instant prior to nucleation of an individual nanobubble of H 2 , N 2 , or O 2 at a Pt nanodisk electrode, can be analyzed using classical thermodynamic relationships (Henry's law and the Young-Laplace equation - including non-ideal corrections) to provide an estimate of the size of the gas bubble nucleus that grows into a stable bubble. We further demonstrate that this critical nucleus size is independent of the radius of the Pt nanodisk employed (<100 nm radius), and weakly dependent on the nature of the gas. For example, the measured critical surface concentration of H 2 of ∼0.23 M at the instant of bubble formation corresponds to a critical H 2 nucleus that has a radius of ∼3.6 nm, an internal pressure of ∼350 atm, and contains ∼1700 H 2 molecules. The data are consistent with stochastic fluctuations in the density of dissolved gas, at or near the Pt/solution interface, controlling the rate of bubble nucleation. We discuss the growth of the nucleus as a diffusion-limited process and how that process is affected by proximity to an electrode producing ∼10 11 gas molecules per second. Our study demonstrates the advantages of studying a single-entity, i.e., an individual nanobubble, in understanding and quantifying complex physicochemical phenomena.

Growth behavior of LiMn{sub 2}O{sub 4} particles formed by solid-state reactions in air and water vapor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kozawa, Takahiro, E-mail: t-kozawa@jwri.osaka-u.ac.jp; Yanagisawa, Kazumichi; Murakami, Takeshi

Morphology control of particles formed during conventional solid-state reactions without any additives is a challenging task. Here, we propose a new strategy to control the morphology of LiMn{sub 2}O{sub 4} particles based on water vapor-induced growth of particles during solid-state reactions. We have investigated the synthesis and microstructural evolution of LiMn{sub 2}O{sub 4} particles in air and water vapor atmospheres as model reactions; LiMn{sub 2}O{sub 4} is used as a low-cost cathode material for lithium-ion batteries. By using spherical MnCO{sub 3} precursor impregnated with LiOH, LiMn{sub 2}O{sub 4} spheres with a hollow structure were obtained in air, while angulated particlesmore » with micrometer sizes were formed in water vapor. The pore structure of the particles synthesized in water vapor was found to be affected at temperatures below 700 °C. We also show that the solid-state reaction in water vapor is a simple and valuable method for the large-scale production of particles, where the shape, size, and microstructure can be controlled. - Graphical abstract: This study has demonstrated a new strategy towards achieving morphology control without the use of additives during conventional solid-state reactions by exploiting water vapor-induced particle growth. - Highlights: • A new strategy to control the morphology of LiMn{sub 2}O{sub 4} particles is proposed. • Water vapor-induced particle growth is exploited in solid-state reactions. • The microstructural evolution of LiMn{sub 2}O{sub 4} particles is investigated. • The shape, size and microstructure can be controlled by solid-state reactions.« less

Phenomenological theory of laser-plasma interaction in ``bubble'' regime

NASA Astrophysics Data System (ADS)

Kostyukov, I.; Pukhov, A.; Kiselev, S.

2004-11-01

The electron trapping in the "bubble" regime of laser-plasma interaction as proposed by Pukhov and Meyer-ter-Vehn [A. Pukhov and J. Meyer-ter-Vehn, Appl. Phys. B 74, 355 (2002)] is studied. In this regime the laser pulse generates a solitary plasma electron cavity: the bubble. It is free from the cold plasma electrons and runs with nearly light velocity. The present work discusses the form of the bubble and the spatial distribution of electromagnetic fields within the cavity. We extend the one-dimensional electron capture theory to the three-dimensional case. It is shown that the bubble can trap plasma electrons. The trapping condition is derived and the trapping cross section is estimated. Electron motion in the self-generated electron bunch is investigated. Estimates for the maximum of electron bunch energy and the bunch density are provided.

Numerical study of the impact of a drop containing a bubble

NASA Astrophysics Data System (ADS)

Wei, Yu; Thoraval, Marie-Jean

2017-11-01

The impact of a drop has many applications from inkjet printing to the spreading of crops diseases. This fundamental phenomenon has therefore attracted a lot of interest from different fields. However, they have mostly focused on the simplest case of a drop containing a single fluid. In inkjet printing and in the deposition process of thermal barrier coatings, some bubbles can be present in the drop when it impacts on the solid surface. The presence of the bubble can produce some additional splashing, and affect the quality of the deposited material. Only a few studies have looked at this problem, and many questions still need to be investigated. Generally, there are three possibilities when a drop containing a bubble impacts onto a solid surface, namely the bubble stays in drop, the bubble bursts and a counter jet forms. We have performed axisymmetric numerical simulations with the open source code Gerris to study this vertical jet. We have systematically varied several parameters, including the impact velocity, the bubble size, the vertical position of the bubble, and the liquid properties. We were thus able to characterize under which condition the bubble leads to splashing and the velocity of the produced jet.

Developing a bubble number-density paleoclimatic indicator for glacier ice

USGS Publications Warehouse

Spencer, M.K.; Alley, R.B.; Fitzpatrick, J.J.

2006-01-01

Past accumulation rate can be estimated from the measured number-density of bubbles in an ice core and the reconstructed paleotemperature, using a new technique. Density increase and grain growth in polar firn are both controlled by temperature and accumulation rate, and the integrated effects are recorded in the number-density of bubbles as the firn changes to ice. An empirical model of these processes, optimized to fit published data on recently formed bubbles, reconstructs accumulation rates using recent temperatures with an uncertainty of 41% (P < 0.05). For modern sites considered here, no statistically significant trend exists between mean annual temperature and the ratio of bubble number-density to grain number-density at the time of pore close-off; optimum modeled accumulation-rate estimates require an eventual ???2.02 ?? 0.08 (P < 0.05) bubbles per close-off grain. Bubble number-density in the GRIP (Greenland) ice core is qualitatively consistent with independent estimates for a combined temperature decrease and accumulation-rate increase there during the last 5 kyr.

FERMI BUBBLES AND BUBBLE-LIKE EMISSION FROM THE GALACTIC PLANE

DOE Office of Scientific and Technical Information (OSTI.GOV)

De Boer, Wim; Weber, Markus, E-mail: wim.de.boer@kit.edu, E-mail: markus.weber2@kit.edu

2014-10-10

The diffuse gamma-ray sky revealed ''bubbles'' of emission above and below the Galactic plane, symmetric around the center of the Milky Way, with a height of 10 kpc in both directions. At present, there is no convincing explanation for the origin. To understand the role of the Galactic center, one has to study the bubble spectrum inside the disk, a region that has been excluded from previous analyses because of the large foreground. From a novel template fit, which allows a simultaneous determination of the signal and foreground in any direction, we find that bubble-like emission is not only found inmore » the halo, but in the Galactic plane as well, with a width in latitude coinciding with the molecular clouds. The longitude distribution has a width corresponding to the Galactic bar with an additional contribution from the Scutum-Centaurus arm. The energy spectrum of the bubbles coincides with the predicted contribution from CRs trapped in sources (SCRs). Also, the energetics fits well. Hence, we conclude that the bubble-like emission has a hadronic origin that arises from SCRs, and the bubbles in the halo arise from hadronic interactions in advected gas. Evidence for advection is provided by the ROSAT X-rays of hot gas in the bubble region.« less

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

PubMed

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

2015-06-07

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

Bubble-free on-chip continuous-flow polymerase chain reaction: concept and application.

PubMed

Wu, Wenming; Kang, Kyung-Tae; Lee, Nae Yoon

2011-06-07

Bubble formation inside a microscale channel is a significant problem in general microfluidic experiments. The problem becomes especially crucial when performing a polymerase chain reaction (PCR) on a chip which is subject to repetitive temperature changes. In this paper, we propose a bubble-free sample injection scheme applicable for continuous-flow PCR inside a glass/PDMS hybrid microfluidic chip, and attempt to provide a theoretical basis concerning bubble formation and elimination. Highly viscous paraffin oil plugs are employed in both the anterior and posterior ends of a sample plug, completely encapsulating the sample and eliminating possible nucleation sites for bubbles. In this way, internal channel pressure is increased, and vaporization of the sample is prevented, suppressing bubble formation. Use of an oil plug in the posterior end of the sample plug aids in maintaining a stable flow of a sample at a constant rate inside a heated microchannel throughout the entire reaction, as compared to using an air plug. By adopting the proposed sample injection scheme, we demonstrate various practical applications. On-chip continuous-flow PCR is performed employing genomic DNA extracted from a clinical single hair root sample, and its D1S80 locus is successfully amplified. Also, chip reusability is assessed using a plasmid vector. A single chip is used up to 10 times repeatedly without being destroyed, maintaining almost equal intensities of the resulting amplicons after each run, ensuring the reliability and reproducibility of the proposed sample injection scheme. In addition, the use of a commercially-available and highly cost-effective hot plate as a potential candidate for the heating source is investigated.

Electrowetting of soap bubbles

NASA Astrophysics Data System (ADS)

Arscott, Steve

2013-07-01

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

Investigation of hydrogen bubbles behavior in tungsten by high-flux hydrogen implantation

NASA Astrophysics Data System (ADS)

Zhao, Jiangtao; Meng, Xuan; Guan, Xingcai; Wang, Qiang; Fang, Kaihong; Xu, Xiaohui; Lu, Yongkai; Gao, Jun; Liu, Zhenlin; Wang, Tieshan

2018-05-01

Hydrogen isotopes retention and bubbles formation are critical issues for tungsten as plasma-facing material in future fusion reactors. In this work, the formation and growing up behavior of hydrogen bubbles in tungsten were investigated experimentally. The planar TEM samples were implanted by 6.0keV hydrogens to a fluence of 3.38 ×1018 H ṡ cm-2 at room temperature, and well-defined hydrogen bubbles were observed by TEM. It was demonstrated that hydrogen bubbles formed when exposed to a fluence of 1.5 ×1018 H ṡ cm-2 , and the hydrogen bubbles grew up with the implantation fluence. In addition, the bubbles' size appeared larger with higher beam flux until saturated at a certain flux, even though the total fluence was kept the same. Finally, in order to understand the thermal annealing effect on the bubbles behavior, hydrogen-implanted samples were annealed at 400, 600, 800, and 1000 °C for 3 h. It was obvious that hydrogen bubbles' morphology changed at temperatures higher than 800 °C.

Hubble's Blue Bubble

NASA Image and Video Library

2017-12-08

A large blue bubble with a bright star in the center on a black background filled with stars Sparkling at the center of this beautiful NASA/ESA Hubble Space Telescope image is a Wolf–Rayet star known as WR 31a, located about 30,000 light-years away in the constellation of Carina (The Keel). The distinctive blue bubble appearing to encircle WR 31a is a Wolf–Rayet nebula — an interstellar cloud of dust, hydrogen, helium and other gases. Created when speedy stellar winds interact with the outer layers of hydrogen ejected by Wolf–Rayet stars, these nebulae are frequently ring-shaped or spherical. The bubble — estimated to have formed around 20,000 years ago — is expanding at a rate of around 220,000 kilometers (136,700 miles) per hour! Unfortunately, the lifecycle of a Wolf–Rayet star is only a few hundred thousand years — the blink of an eye in cosmic terms. Despite beginning life with a mass at least 20 times that of the sun, Wolf–Rayet stars typically lose half their mass in less than 100,000 years. And WR 31a is no exception to this case. It will, therefore, eventually end its life as a spectacular supernova, and the stellar material expelled from its explosion will later nourish a new generation of stars and planets. Image credi: ESA/Hubble & NASA, Acknowledgement: Judy Schmidt

Plasma Discharges in Gas Bubbles in Liquid Water: Breakdown Mechanisms and Resultant Chemistry

NASA Astrophysics Data System (ADS)

Gucker, Sarah M. N.

The use of atmospheric pressure plasmas in gases and liquids for purification of liquids has been investigated by numerous researchers, and is highly attractive due to their strong potential as a disinfectant and sterilizer. However, the fundamental understanding of plasma production in liquid water is still limited. Despite the decades of study dedicated to electrical discharges in liquids, many physical aspects of liquids, such as the high inhomogeneity of liquids, complicate analyses. For example, the complex nonlinearities of the fluid have intricate effects on the electric field of the propagating streamer. Additionally, the liquid material itself can vaporize, leading to discontinuous liquid-vapor boundaries. Both can and do often lead to notable hydrodynamic effects. The chemistry of these high voltage discharges on liquid media can have circular effects, with the produced species having influence on future discharges. Two notable examples include an increase in liquid conductivity via charged species production, which affects the discharge. A second, more complicated scenario seen in some liquids (such as water) is the doubling or tripling of molecular density for a few molecule layers around a high voltage electrode. These complexities require technological advancements in optical diagnostics that have only recently come into being. This dissertation investigates several aspects of electrical discharges in gas bubbles in liquids. Two primary experimental configurations are investigated: the first allows for single bubble analysis through the use of an acoustic trap. Electrodes may be brought in around the bubble to allow for plasma formation without physically touching the bubble. The second experiment investigates the resulting liquid phase chemistry that is driven by the discharge. This is done through a dielectric barrier discharge with a central high voltage surrounded by a quartz discharge tube with a coil ground electrode on the outside. The plasma

Water bubble in front of JEM window

NASA Image and Video Library

2015-03-20

View of water bubble formed in front of the Japanese Experiment Module (JEM) window. The JEM Exposed Facility (JEF) is visible in the background through the window and reflected in the water. Scratches visible on the window.

Effect of Micro-Bubbles in Water on Beam Patterns of Parametric Array

NASA Astrophysics Data System (ADS)

Hashiba, Kunio; Masuzawa, Hiroshi

2003-05-01

The improvement in efficiency of a parametric array by nonlinear oscillation of micro-bubbles in water is studied in this paper. The micro-bubble oscillation can increase the nonlinear coefficient of the acoustic medium. The amplitude of the difference-frequency wave along the longitudinal axis and its beam patterns in the field including the layer with micro-bubbles were analyzed using a Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation. As a result, the largest improvement in efficiency was obtained and a narrow parametric beam was formed by forming a layer with micro-bubbles in front of a parametric sound radiator as thick as about the shock formation distance. If the layer becomes significantly thicker than the distance, the beam of the difference-frequency wave in the far-field will become broader. If the layer is significantly thinner than the distance, the intensity level of the wave in the far-field will be too low.

Nonlinear Bubble Dynamics And The Effects On Propagation Through Near-Surface Bubble Layers

NASA Astrophysics Data System (ADS)

Leighton, Timothy G.

2004-11-01

Nonlinear bubble dynamics are often viewed as the unfortunate consequence of having to use high acoustic pressure amplitudes when the void fraction in the near-surface oceanic bubble layer is great enough to cause severe attenuation (e.g. >50 dB/m). This is seen as unfortunate since existing models for acoustic propagation in bubbly liquids are based on linear bubble dynamics. However, the development of nonlinear models does more than just allow quantification of the errors associated with the use of linear models. It also offers the possibility of propagation modeling and acoustic inversions which appropriately incorporate the bubble nonlinearity. Furthermore, it allows exploration and quantification of possible nonlinear effects which may be exploited. As a result, high acoustic pressure amplitudes may be desirable even in low void fractions, because they offer opportunities to gain information about the bubble cloud from the nonlinearities, and options to exploit the nonlinearities to enhance communication and sonar in bubbly waters. This paper presents a method for calculating the nonlinear acoustic cross-sections, scatter, attenuations and sound speeds from bubble clouds which may be inhomogeneous. The method allows prediction of the time dependency of these quantities, both because the cloud may vary and because the incident acoustic pulse may have finite and arbitrary time history. The method can be readily adapted for bubbles in other environments (e.g. clouds of interacting bubbles, sediments, structures, in vivo, reverberant conditions etc.). The possible exploitation of bubble acoustics by marine mammals, and for sonar enhancement, is explored.

Laser irradiated fluorescent perfluorocarbon microparticles in 2-D and 3-D breast cancer cell models

NASA Astrophysics Data System (ADS)

Niu, Chengcheng; Wang, Long; Wang, Zhigang; Xu, Yan; Hu, Yihe; Peng, Qinghai

2017-03-01

Perfluorocarbon (PFC) droplets were studied as new generation ultrasound contrast agents via acoustic or optical droplet vaporization (ADV or ODV). Little is known about the ODV irradiated vaporization mechanisms of PFC-microparticle complexs and the stability of the new bubbles produced. In this study, fluorescent perfluorohexane (PFH) poly(lactic-co-glycolic acid) (PLGA) particles were used as a model to study the process of particle vaporization and bubble stability following excitation in two-dimensional (2-D) and three-dimensional (3-D) cell models. We observed localization of the fluorescent agent on the microparticle coating material initially and after vaporization under fluorescence microscopy. Furthermore, the stability and growth dynamics of the newly created bubbles were observed for 11 min following vaporization. The particles were co-cultured with 2-D cells to form 3-D spheroids and could be vaporized even when encapsulated within the spheroids via laser irradiation, which provides an effective basis for further work.

A precursor of market crashes: Empirical laws of Japan's internet bubble

NASA Astrophysics Data System (ADS)

Kaizoji, T.

2006-03-01

In this paper, we quantitatively investigate the properties of a statistical ensemble of stock prices. We focus attention on the relative price defined as X(t) = S(t)/S(0), where S(0), is the stock price for an onset time of the bubble. We selected approximately 3200 stocks traded on the Japanese Stock Exchange, and formed a statistical ensemble of daily relative prices for each trading day in the 3-year period from January 4, 1999 to December 28, 2001, corresponding to the period in which internet Bubble formed and crashed in the Japanese stock market. We found that the upper tail of the complementary cumulative distribution function of the ensemble of the relative prices in the high value of the price is well described by a power-law distribution, P(S>x) ˜x-α , with an exponent that moves over time. Furthermore we found that as the power-law exponents α approached two, the bubble burst. It is reasonable to suppose that it indicates that internet bubble is about to burst.

Shear Stress induced Stretching of Red Blood Cells by Oscillating Bubbles within a Narrow Gap

NASA Astrophysics Data System (ADS)

Li, Fenfang; Mohammadzadeh, Milad; Ohl, Claus-Dieter; Claus-Dieter Ohl Team

2013-11-01

The flow pattern, especially the boundary layer caused by the expanding/contracting bubble in a narrow gap (15 μm) and the resultant stretching of red blood cells is investigated in this work. High speed recordings show that a red blood cell (biconcave shape, thickness of 1-2 μm) can be elongated to five times its original length by a laser-induced cavitation bubble within the narrow gap. However, flexible cancer cells in suspension (RKO, spherical shape, diameter of 10-15 μm) are hardly elongated under the same experimental condition. We hypothesize that the shear stress at the boundary layer is crucial for this elongation to occur. Therefore, in order to resolve the related fluid dynamics, we conducted numerical simulations using the finite element method (Fluent). The rapidly expanding/contracting vapor bubble is successfully modeled by employing viscosity and surface tension. The transient pressure inside the bubble and the velocity profile of the flow is obtained. We observe strong shear near the upper and lower boundary during the bubble oscillation. The flow fields are compared with analytical solutions to transient and pulsating flows in 2D. In the experiment the red blood cells sit within the lower boundary layer, thus are probably elongated by this strong shear flow. In contrast, the spherical cancer cells are of comparable size to the gap height so that they are lesser affected by this boundary layer flow.

The geophysical importance of bubbles in the sea

NASA Technical Reports Server (NTRS)

Cirpriano, R. J.

1982-01-01

Present knowledge of the mechanisms for production and enrichment and film drops by bursting bubbles is summarized, with particular emphasis on the unsolved problems. Sea salt is by far the major constituent cycled through the Earth's atmosphere each year. Bursting bubbles in the oceans appear to be primarily responsible. These salt particles play a role in the formation of maritime clouds, which in turn affect the Earth's radiation budget. Along with the salt are carried various chemical pollutants and potentially pathogenic microorganisms, often in highly enriched form.

Letter: Entrapment and interaction of an air bubble with an oscillating cavitation bubble

NASA Astrophysics Data System (ADS)

Kannan, Y. S.; Karri, Badarinath; Sahu, Kirti Chandra

2018-04-01

The mechanism of the formation of an air bubble due to an oscillating cavitation bubble in its vicinity is reported from an experimental study using high-speed imaging. The cavitation bubble is created close to the free surface of water using a low-voltage spark circuit comprising two copper electrodes in contact with each other. Before the bubble is created, a third copper wire is positioned in contact with the free surface of water close to the two crossing electrodes. Due to the surface tension at the triple point (wire-water-air) interface, a small dip is observed in the free surface at the point where the wire is immersed. When the cavitation bubble is created, the bubble pushes at the dip while expanding and pulls at it while collapsing. The collapse phase leads to the entrapment of an air bubble at the wire immersion point. During this phase, the air bubble undergoes a "catapult" effect, i.e., it expands to a maximum size and then collapses with a microjet at the free surface. To the best of our knowledge, this mechanism has not been reported so far. A parametric study is also conducted to understand the effects of wire orientation and bubble distance from the free surface.

Bubble coalescence in a power-law fluid

NASA Astrophysics Data System (ADS)

Kamat, Pritish; Thete, Sumeet; Basaran, Osman

2015-11-01

As two spherical gas bubbles in a liquid are slowly brought together, the liquid film or sheet between them drains and ultimately ruptures, forming a circular hole that connects them. The high curvature near the edge of the liquid sheet drives flow radially outward, causing the film to retract and the radius of the hole to increase with time. Recent experimental and theoretical work in this area has uncovered self-similarity and universal scaling regimes when two bubbles coalesce in a Newtonian fluid. Motivated by applications such as polymer and composites processing, food and drug manufacture, and aeration/deaeration systems where the liquids often exhibit deformation-rate thinning rheology, we extend the recent Newtonian studies to bubble coalescence in power-law fluids. In our work, we use a combination of thin-film theory and full 3D, axisymmetric computations to probe the dynamics in the aftermath of the singularity.

Acoustic bubble sorting for ultrasound contrast agent enrichment.

PubMed

Segers, Tim; Versluis, Michel

2014-05-21

An ultrasound contrast agent (UCA) suspension contains encapsulated microbubbles with a wide size distribution, with radii ranging from 1 to 10 μm. Medical transducers typically operate at a single frequency, therefore only a small selection of bubbles will resonate to the driving ultrasound pulse. Thus, the sensitivity can be improved by narrowing down the size distribution. Here, we present a simple lab-on-a-chip method to sort the population of microbubbles on-chip using a traveling ultrasound wave. First, we explore the physical parameter space of acoustic bubble sorting using well-defined bubble sizes formed in a flow-focusing device, then we demonstrate successful acoustic sorting of a commercial UCA. This novel sorting strategy may lead to an overall improvement of the sensitivity of contrast ultrasound by more than 10 dB.

Analytical and numerical investigations of bubble behavior in electric fields

NASA Astrophysics Data System (ADS)

Vorreiter, Janelle Orae

The behavior of gas bubbles in liquids is important in a wide range of applications. This study is motivated by a desire to understand the motion of bubbles in the absence of gravity, as in many aerospace applications. Phase-change devices, cryogenic tanks and life-support systems are some of the applications where bubbles exist in space environments. One of the main difficulties in employing devices with bubbles in zero gravity environments is the absence of a buoyancy force. The use of an electric field is found to be an effective means of replacing the buoyancy force, improving the control of bubbles in space environments. In this study, analytical and numerical investigations of bubble behavior under the influence of electric fields are performed. The problem is a difficult one in that the physics of the liquid and the electric field need to be considered simultaneously to model the dynamics of the bubble. Simplifications are required to reduce the problem to a tractable form. In this work, for the liquid and the electric field, assumptions are made which reduce the problem to one requiring only the solution of potentials in the domain of interest. Analytical models are developed using a perturbation analysis applicable for small deviations from a spherical shape. Numerical investigations are performed using a boundary integral code. A number of configurations are found to be successful in promoting bubble motion by varying properties of the electric fields. In one configuration, the natural frequencies of a bubble are excited using time-varying electric and pressure fields. The applied electric field is spatially uniform with frequencies corresponding to shape modes of the bubble. The resulting bubble velocity is related to the strength of the electric field as well as the characteristics of the applied fields. In another configuration, static non-uniform fields are used to encourage bubble motion. The resulting motion is related to the degree of non

Optimal conditions for particle-bubble attachment in flotation: an experimental study

NASA Astrophysics Data System (ADS)

Sanchez Yanez, Aaron; Hernandez Sanchez, Jose Federico; Thoroddsen, Sigurdur T.

2017-11-01

Mineral flotation is a process used in the mining industry for separating solid particles of different sizes and densities. The separation is done by injecting bubbles into a slurry where the particles attach to them, forming floating aggregates. The attachment depends mainly on the bubbles and particles sizes as well as the hydrophobicity and roughness of the particles. We simplified the collective behavior in the industrial process to a single free particle-bubble collision, in contrast with previous studies where one of the two was kept fixed. We experimentally investigated the collision of spherical solid particles of a fixed diameter with bubbles of different sizes. By controlling the initial relative offset of the bubble and the particle, we conducted experiments observing their interaction. Recording with two synchronized high-speed cameras, perpendicular to each other, we can reconstruct the tridimensional trajectories of the bubble, the solid particle, and the aggregate. We describe the conditions for which the attachment happens in terms of dimensionless parameters such as the Ohnesorge number, the relative particle-bubble offset and the hydrophobicity of the particle surface. We furthermore investigate the role of the surface roughness in the attachment.

Remobilizing the Interface of Thermocapillary Driven Bubbles Retarded By the Adsorption of a Surfactant Impurity on the Bubble Surface

NASA Technical Reports Server (NTRS)

Palaparthi, Ravi; Maldarelli, Charles; Papageorgiou, Dimitri; Singh, Bhim (Technical Monitor)

2001-01-01

molecules which kinetically rapidly exchange between the bulk and the surface and are at high bulk concentrations. Because the remobilizing surfactant is present at much higher concentrations than the impurity, it adsorbs to the bubble surface much faster than the impurity when the bubble is formed, and thereby prevents the impurity from adsorbing onto the surface. In addition, the rapid kinetic exchange and high bulk concentration maintain a saturated surface with uniform surface concentrations. This prevents retarding surface tension gradients and keeps the thermocapillary velocity high. In our reports over the first 2 years, we presented numerical simulations of the bubble motion and surfactant transport which verified theoretically the concept of remobilization, and the development of an apparatus to track and measure the velocity of rising bubbles in a glycerol/water surfactant solution. This year, we detail experimental observations of remobilization. Two polyethylene oxide surfactants were studied, C12E6 (CH3(CH2)11(OCH2)6OH) and C10E8 (CH3(CH2)4(OCH2CH2)8OH). Measurements of the kinetic exchange for these surfactants show that the one with the longer hydrophobe chain C12E6 has a lower rate of kinetic exchange. In addition, this surfactant is much less soluble in the glycerol/water mixture because of the shorter ethoxylate chain. As a result, we found that C12E6 had only a very limited ability to remobilize rising bubbles because of the limited kinetic exchange and reduced solubility. However, C10E8, with its higher solubility and more rapid exchange was found to dramatically remobilize rising bubbles. We also compared our theoretical calculations to the experimental measurements of velocity for both the non-remobilizing and remobilizing surfactants and found excellent agreement. We further observed that for C10E8 at high concentrations, which exceeded the critical micelle concentrations, additional remobilization was measured. In this case the rapid exchange of

Bubble bath soap poisoning

MedlinePlus

... medlineplus.gov/ency/article/002762.htm Bubble bath soap poisoning To use the sharing features on this page, please enable JavaScript. Bubble bath soap poisoning occurs when someone swallows bubble bath soap. ...

Self-assembling bubble carriers for oral protein delivery.

PubMed

Chuang, Er-Yuan; Lin, Kun-Ju; Lin, Po-Yen; Chen, Hsin-Lung; Wey, Shiaw-Pyng; Mi, Fwu-Long; Hsiao, Hsu-Chan; Chen, Chiung-Tong; Sung, Hsing-Wen

2015-09-01

Successful oral delivery of therapeutic proteins such as insulin can greatly improve the quality of life of patients. This study develops a bubble carrier system by loading diethylene triamine pentaacetic acid (DTPA) dianhydride, a foaming agent (sodium bicarbonate; SBC), a surfactant (sodium dodecyl sulfate; SDS), and a protein drug (insulin) in an enteric-coated gelatin capsule. Following oral administration to diabetic rats, the intestinal fluid that has passed through the gelatin capsule saturates the mixture; concomitantly, DTPA dianhydride produces an acidic environment, while SBC decomposes to form CO2 bubbles at acidic pH. The gas bubbles grow among the surfactant molecules (SDS) owing to the expansion of the generated CO2. The walls of the CO2 bubbles consist of a self-assembled film of water that is in nanoscale and may serve as a colloidal carrier to transport insulin and DTPA. The grown gas bubbles continue to expand until they bump into the wall and burst, releasing their transported insulin, DTPA, and SDS into the mucosal layer. The released DTPA and SDS function as protease inhibitors to protect the insulin molecules as well as absorption enhancers to augment their epithelial permeability and eventual absorption into systemic circulation, exerting their hypoglycemic effects. Copyright © 2015 Elsevier Ltd. All rights reserved.

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

Rigorous buoyancy driven bubble mixing for centrifugal microfluidics.

PubMed

Burger, S; Schulz, M; von Stetten, F; Zengerle, R; Paust, N

2016-01-21

We present batch-mode mixing for centrifugal microfluidics operated at fixed rotational frequency. Gas is generated by the disk integrated decomposition of hydrogen peroxide (H2O2) to liquid water (H2O) and gaseous oxygen (O2) and inserted into a mixing chamber. There, bubbles are formed that ascent through the liquid in the artificial gravity field and lead to drag flow. Additionaly, strong buoyancy causes deformation and rupture of the gas bubbles and induces strong mixing flows in the liquids. Buoyancy driven bubble mixing is quantitatively compared to shake mode mixing, mixing by reciprocation and vortex mixing. To determine mixing efficiencies in a meaningful way, the different mixers are employed for mixing of a lysis reagent and human whole blood. Subsequently, DNA is extracted from the lysate and the amount of DNA recovered is taken as a measure for mixing efficiency. Relative to standard vortex mixing, DNA extraction based on buoyancy driven bubble mixing resulted in yields of 92 ± 8% (100 s mixing time) and 100 ± 8% (600 s) at 130g centrifugal acceleration. Shake mode mixing yields 96 ± 11% and is thus equal to buoyancy driven bubble mixing. An advantage of buoyancy driven bubble mixing is that it can be operated at fixed rotational frequency, however. The additional costs of implementing buoyancy driven bubble mixing are low since both the activation liquid and the catalyst are very low cost and no external means are required in the processing device. Furthermore, buoyancy driven bubble mixing can easily be integrated in a monolithic manner and is compatible to scalable manufacturing technologies such as injection moulding or thermoforming. We consider buoyancy driven bubble mixing an excellent alternative to shake mode mixing, in particular if the processing device is not capable of providing fast changes of rotational frequency or if the low average rotational frequency is challenging for the other integrated fluidic operations.

Formation of Nitrogen Bubbles During Solidification of Duplex Stainless Steels

NASA Astrophysics Data System (ADS)

Dai, Kaiju; Wang, Bo; Xue, Fei; Liu, Shanshan; Huang, Junkai; Zhang, Jieyu

2018-04-01

The nucleation and growth of nitrogen bubbles for duplex stainless steels are of great significance for the formation mechanism of bubbles during solidification. In the current study, numerical method and theoretical analysis of formula derivation were used to study the formation of nitrogen bubbles during solidification. The critical sizes of the bubble for homogeneous nucleation and heterogeneous nucleation at the solid-liquid interface during solidification were derived theoretically by the classical nucleation theory. The results show that the calculated values for the solubility of nitrogen in duplex stainless steel are in good agreement with the experimental values which are quoted by references: for example, when the temperature T = 1823 K and the nitrogen partial pressure P_{{N2 }} = 40P^{Θ} , the calculated value (0.8042 wt pct) for the solubility of Fe-12Cr alloy nitrogen in molten steel is close to the experimental value (0.780 wt pct). Moreover, the critical radii for homogeneous nucleation and heterogeneous nucleation are identical during solidification. On the one hand, with the increasing temperature or the melt depth, the critical nucleation radius of bubbles at the solid-liquid interface increases, but the bubble growth rate decreases. On the other hand, with the decreasing initial content of nitrogen or the cooling rate, the critical nucleation radius of bubbles at the solid-liquid interface increases, but the bubble growth rate decreases. Furthermore, when the melt depth is greater than the critical depth, which is determined by the technological conditions, the change in the Gibbs free energy for the nucleation is not conducive enough to form new bubbles.

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

PubMed

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

2005-01-01

The present study aims at providing insight into the acceleration mechanism of a bubble chain rising in shear-thinning viscoelastic fluids. The experimental investigation by the Particle Image Velocimetry (PIV), birefringence visualisation and rheological simulation shows that two aspects are central to bubble interactions in such media: the stress creation by the passage of bubbles, and their relaxation due to the fluid's memory forming an evanescent corridor of reduced viscosity. Interactions between bubbles were taken into account mainly through a linear superposition of the stress evolution behind each bubble. An analytical approach together with the rheological consideration was developed to compute the rise velocity of a bubble chain in function of the injection period and bubble volume. The model predictions compare satisfactorily with the experimental investigation.

Thermocapillary Migration and Interactions of Bubbles and Drops

NASA Technical Reports Server (NTRS)

Subramaniam, R. Shankar; Balasubramaniam, R.; Wozniak, G.; Hadland, P. H.

1999-01-01

Experiments were performed aboard the LMS mission of the Space Shuttle in summer 1996 in the BDPU on isolated air bubbles and Fluorinert FC-75 drops as well as on interacting bubbles/drops migrating in a temperature gradient in a Dow-Corning DC-200 series silicone oil of nominal viscosity 10 centistokes. The data, recorded in the form of videotape images as well as cine images in selected runs, have been analyzed. The behavior of the isolated objects is consistent with earlier observations made aboard the IML-2 mission while the range of Reynolds and Marangoni numbers has been extended substantially over that in the IML-2 experiments. Large bubbles were found to be slightly deformed to an oblate shape while no deformation could be detected in the case of similarly large drops. Results on interacting drops and bubbles display interesting and unanticipated features. In some experiments, drops are found to follow a three-dimensional trajectory. In others, trailing drops and bubbles are found to move off the axis of the cell when migrating behind a leading drop or bubble which moves along the axis. In this type of run, if the trailing drop is sufficiently large, it is found to pass the leading drop. Finally, behavior similar to that observed in IML-2, namely that a small leading drop slows the movement of a larger trailing drop moving along the cell axis, was observed as well.

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.

Eternal inflation, bubble collisions, and the disintegration of the persistence of memory

NASA Astrophysics Data System (ADS)

Freivogel, Ben; Kleban, Matthew; Nicolis, Alberto; Sigurdson, Kris

2009-08-01

We compute the probability distribution for bubble collisions in an inflating false vacuum which decays by bubble nucleation. Our analysis generalizes previous work of Guth, Garriga, and Vilenkin to the case of general cosmological evolution inside the bubble, and takes into account the dynamics of the domain walls that form between the colliding bubbles. We find that incorporating these effects changes the results dramatically: the total expected number of bubble collisions in the past lightcone of a typical observer is N ~ γ Vf/Vi , where γ is the fastest decay rate of the false vacuum, Vf is its vacuum energy, and Vi is the vacuum energy during inflation inside the bubble. This number can be large in realistic models without tuning. In addition, we calculate the angular position and size distribution of the collisions on the cosmic microwave background sky, and demonstrate that the number of bubbles of observable angular size is NLS ~ (Ωk)1/2N, where Ωk is the curvature contribution to the total density at the time of observation. The distribution is almost exactly isotropic.

Modeling DNA bubble formation at the atomic scale

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beleva, V; Rasmussen, K. O.; Garcia, A. E.

We describe the fluctuations of double stranded DNA molecules using a minimalist Go model over a wide range of temperatures. Minimalist models allow us to describe, at the atomic level, the opening and formation of bubbles in DNA double helices. This model includes all the geometrical constraints in helix melting imposed by the 3D structure of the molecule. The DNA forms melted bubbles within double helices. These bubbles form and break as a function of time. The equilibrium average number of broken base pairs shows a sharp change as a function of T. We observe a temperature profile of sequencemore » dependent bubble formation similar to those measured by Zeng et al. Long nuclei acid molecules melt partially through the formations of bubbles. It is known that CG rich sequences melt at higher temperatures than AT rich sequences. The melting temperature, however, is not solely determined by the CG content, but by the sequence through base stacking and solvent interactions. Recently, models that incorporate the sequence and nonlinear dynamics of DNA double strands have shown that DNA exhibits a very rich dynamics. Recent extensions of the Bishop-Peyrard model show that fluctuations in the DNA structure lead to opening in localized regions, and that these regions in the DNA are associated with transcription initiation sites. 1D and 2D models of DNA may contain enough information about stacking and base pairing interactions, but lack the coupling between twisting, bending and base pair opening imposed by the double helical structure of DNA that all atom models easily describe. However, the complexity of the energy function used in all atom simulations (including solvent, ions, etc) does not allow for the description of DNA folding/unfolding events that occur in the microsecond time scale.« less

Simulation of gas bubbles in hypobaric decompressions: roles of O2, CO2, and H2O.

PubMed

Van Liew, H D; Burkard, M E

1995-01-01

To gain insight into the special features of bubbles that may form in aviators and astronauts, we simulated the growth and decay of bubbles in two hypobaric decompressions and a hyperbaric one, all with the same tissue ratio (TR), where TR is defined as tissue PN2 before decompression divided by barometric pressure after. We used an equation system which is solved by numerical methods and accounts for simultaneous diffusion of any number of gases as well as other major determinants of bubble growth and absorption. We also considered two extremes of the number of bubbles which form per unit of tissue. A) Because physiological mechanisms keep the partial pressures of the "metabolic" gases (O2, CO2, and H2O) nearly constant over a range of hypobaric pressures, their fractions in bubbles are inversely proportional to pressure and their large volumes at low pressure add to bubble size. B) In addition, the large fractions facilitate the entry of N2 into bubbles, and when bubble density is low, enhance an autocatalytic feedback on bubble growth due to increasing surface area. C) The TR is not closely related to bubble size; that is when two different decompressions have the same TR, metabolic gases cause bubbles to grow larger at lower hypobaric pressures. We conclude that the constancy of partial pressures of metabolic gases, unimportant in hyperbaric decompressions, affects bubble size in hypobaric decompressions in inverse relation to the exposure pressure.

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.

Vapor-fed bio-hybrid fuel cell.

PubMed

Benyamin, Marcus S; Jahnke, Justin P; Mackie, David M

2017-01-01

Concentration and purification of ethanol and other biofuels from fermentations are energy-intensive processes, with amplified costs at smaller scales. To circumvent the need for these processes, and to potentially reduce transportation costs as well, we have previously investigated bio-hybrid fuel cells (FCs), in which a fermentation and FC are closely coupled. However, long-term operation requires strictly preventing the fermentation and FC from harming each other. We introduce here the concept of the vapor-fed bio-hybrid FC as a means of continuously extracting power from ongoing fermentations at ambient conditions. By bubbling a carrier gas (N 2 ) through a yeast fermentation and then through a direct ethanol FC, we protect the FC anode from the catalyst poisons in the fermentation (which are non-volatile), and also protect the yeast from harmful FC products (notably acetic acid) and from build-up of ethanol. Since vapor-fed direct ethanol FCs at ambient conditions have never been systematically characterized (in contrast to vapor-fed direct methanol FCs), we first assess the effects on output power and conversion efficiency of ethanol concentration, vapor flow rate, and FC voltage. The results fit a continuous stirred-tank reactor model. Over a wide range of ethanol partial pressures (2-8 mmHg), power densities are comparable to those for liquid-fed direct ethanol FCs at the same temperature, with power densities >2 mW/cm 2 obtained. We then demonstrate the continuous operation of a vapor-fed bio-hybrid FC with fermentation for 5 months, with no indication of performance degradation due to poisoning (of either the FC or the fermentation). It is further shown that the system is stable, recovering quickly from disturbances or from interruptions in maintenance. The vapor-fed bio-hybrid FC enables extraction of power from dilute bio-ethanol streams without costly concentration and purification steps. The concept should be scalable to both large and small

Inhibition of bubble coalescence: effects of salt concentration and speed of approach.

PubMed

Del Castillo, Lorena A; Ohnishi, Satomi; Horn, Roger G

2011-04-01

Bubble coalescence experiments have been performed using a sliding bubble apparatus, in which mm-sized bubbles in an aqueous electrolyte solution without added surfactant rose toward an air meniscus at different speeds obtained by varying the inclination of a closed glass cylinder containing the liquid. The coalescence times of single bubbles contacting the meniscus were monitored using a high speed camera. Results clearly show that stability against coalescence of colliding air bubbles is influenced by both the salt concentration and the approach speed of the bubbles. Contrary to the widespread belief that bubbles in pure water are unstable, we demonstrate that bubbles formed in highly purified water and colliding with the meniscus at very slow approach speeds can survive for minutes or even hours. At higher speeds, bubbles in water only survive for a few seconds, and at still higher speeds they coalesce instantly. Addition of a simple electrolyte (KCl) removes the low-speed stability and shifts the transition between transient stability and instant coalescence to higher approach speeds. At high electrolyte concentration no bubbles were observed to coalesce instantly. These observations are consistent with recent results of Yaminsky et al. (Langmuir 26 (2010) 8061) and the transitions between different regions of behavior are in semi-quantitative agreement with Yaminsky's model. Copyright © 2010 Elsevier Inc. All rights reserved.

A derivation of the stable cavitation threshold accounting for bubble-bubble interactions.

PubMed

Guédra, Matthieu; Cornu, Corentin; Inserra, Claude

2017-09-01

The subharmonic emission of sound coming from the nonlinear response of a bubble population is the most used indicator for stable cavitation. When driven at twice their resonance frequency, bubbles can exhibit subharmonic spherical oscillations if the acoustic pressure amplitude exceeds a threshold value. Although various theoretical derivations exist for the subharmonic emission by free or coated bubbles, they all rest on the single bubble model. In this paper, we propose an analytical expression of the subharmonic threshold for interacting bubbles in a homogeneous, monodisperse cloud. This theory predicts a shift of the subharmonic resonance frequency and a decrease of the corresponding pressure threshold due to the interactions. For a given sonication frequency, these results show that an optimal value of the interaction strength (i.e. the number density of bubbles) can be found for which the subharmonic threshold is minimum, which is consistent with recently published experiments conducted on ultrasound contrast agents. Copyright © 2017 Elsevier B.V. All rights reserved.

Magnetic bubbles and domain evolution in Fe/Gd multilayer nanodots

NASA Astrophysics Data System (ADS)

Wang, T. T.; Liu, W.; Dai, Z. M.; Zhao, X. T.; Zhao, X. G.; Zhang, Z. D.

2018-04-01

The formation of magnetic bubbles and the domain-evolution processes, induced by a perpendicular magnetic field in Fe/Gd multilayer films and nanodots, have been investigated. At room temperature, the stripe domains in a continuous film transform into magnetic bubbles in an external field, while bubbles form spontaneously in nanodots due to the existence of shape anisotropy. When the temperature decreases to 20 K, the enhancement of the perpendicular magnetic anisotropy of the samples results in an increase of the domain size in the continuous film and the magnetization-reversal behavior of each nanodot becomes independent, and most reversed dots do not depend on each other, indicating the magnetic characteristics of a single domain. The present research provides further understanding of the evolution of magnetic bubbles in the Fe/Gd system and suggests their promising applications in patterned recording materials.

Modeling bubble dynamics and radical kinetics in ultrasound induced microalgal cell disruption.

PubMed

Wang, Meng; Yuan, Wenqiao

2016-01-01

Microalgal cell disruption induced by acoustic cavitation was simulated through solving the bubble dynamics in an acoustical field and their radial kinetics (chemical kinetics of radical species) occurring in the bubble during its oscillation, as well as calculating the bubble wall pressure at the collapse point. Modeling results indicated that increasing ultrasonic intensity led to a substantial increase in the number of bubbles formed during acoustic cavitation, however, the pressure generated when the bubbles collapsed decreased. Therefore, cumulative collapse pressure (CCP) of bubbles was used to quantify acoustic disruption of a freshwater alga, Scenedesmus dimorphus, and a marine alga, Nannochloropsis oculata and compare with experimental results. The strong correlations between CCP and the intracellular lipid fluorescence density, chlorophyll-a fluorescence density, and cell particle/debris concentration were found, which suggests that the developed models could accurately predict acoustic cell disruption, and can be utilized in the scale up and optimization of the process. Copyright © 2015 Elsevier B.V. All rights reserved.

Power Laws and Market Crashes ---Empirical Laws on Bursting Bubbles---

NASA Astrophysics Data System (ADS)

Kaizoji, T.

In this paper, we quantitatively investigate the statistical properties of a statistical ensemble of stock prices. We selected 1200 stocks traded on the Tokyo Stock Exchange, and formed a statistical ensemble of daily stock prices for each trading day in the 3-year period from January 4, 1999 to December 28, 2001, corresponding to the period of the forming of the internet bubble in Japn, and its bursting in the Japanese stock market. We found that the tail of the complementary cumulative distribution function of the ensemble of stock prices in the high value of the price is well described by a power-law distribution, P (S > x) ˜ x^{-α}, with an exponent that moves in the range of 1.09 < α < 1.27. Furthermore, we found that as the power-law exponents α approached unity, the bubbles collapsed. This suggests that Zipf's law for stock prices is a sign that bubbles are going to burst.

Spontaneous and Directional Bubble Transport on Porous Copper Wires with Complex Shapes in Aqueous Media.

PubMed

Li, Wenjing; Zhang, Jingjing; Xue, Zhongxin; Wang, Jingming; Jiang, Lei

2018-01-24

Manipulation of gas bubble behaviors is crucial for gas bubble-related applications. Generally, the manipulation of gas bubble behaviors generally takes advantage of their buoyancy force. It is very difficult to control the transportation of gas bubbles in a specific direction. Several approaches have been developed to collect and transport bubbles in aqueous media; however, most reliable and effective manipulation of gas bubbles in aqueous media occurs on the interfaces with simple shapes (i.e., cylinder and cone shapes). Reliable strategies for spontaneous and directional transport of gas bubbles on interfaces with complex shapes remain enormously challenging. Herein, a type of 3D gradient porous network was constructed on copper wire interfaces, with rectangle, wave, and helix shapes. The superhydrophobic copper wires were immersed in water, and continuous and stable gas films then formed on the interfaces. With the assistance of the Laplace pressure gradient between two bubbles, gas bubbles (including microscopic gas bubbles) in the aqueous media were subsequently transported, continuously and directionally, on the copper wires with complex shapes. The small gas bubbles always moved to the larger ones.

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

Disproportionate emission of bubble streams with killer whale biphonic calls: perspectives on production and function.

PubMed

Bowles, Ann E; Grebner, Dawn M; Musser, Whitney B; Nash, Juliette S; Crance, Jessica L

2015-02-01

Stereotyped pulsed calls were attributed to 11 killer whales (Orcinus orca) with and without synchronous bubble streams in three datasets collected from two facilities from 1993 to 2012. Calls with and without synchronous bubble streams and divergent overlapping high frequency components ("biphonic" vs "monophonic") were compared. Subjects produced bubbles significantly more often when calls had divergent high frequency components. However, acoustic features in one biphonic call shared by five subjects provided little evidence for an acoustic effect of synchronous bubble flow. Disproportionate bubbling supported other evidence that biphonic calls form a distinct category, but suggested a function in short-range communication.

Treatment of micro air bubbles in rat adipose tissue at 25 kPa altitude exposures with perfluorocarbon emulsions and nitric oxide.

PubMed

Randsøe, Thomas; Hyldegaard, O

2014-01-01

Perfluorocarbon emulsions (PFC) and nitric oxide (NO) releasing agents have on experimental basis demonstrated therapeutic properties in treating and preventing the formation of venous gas embolism as well as increased survival rate during decompression sickness from diving. The effect is ascribed to an increased solubility and transport capacity of respiratory gases in the PFC emulsion and possibly enhanced nitrogen washout through NO-increased blood flow rate and/or the removal of endothelial micro bubble nuclei precursors. Previous reports have shown that metabolic gases (i.e., oxygen in particular) and water vapor contribute to bubble growth and stabilization during altitude exposures. Accordingly, we hypothesize that the administration of PFC and NO donors upon hypobaric pressure exposures either (1) enhance the bubble disappearance rate through faster desaturation of nitrogen, or in contrast (2) promote bubble growth and stabilization through an increased oxygen supply. In anesthetized rats, micro air bubbles (containing 79% nitrogen) of 4-500 nl were injected into exposed abdominal adipose tissue. Rats were decompressed in 36 min to 25 kPa (~10,376 m above sea level) and bubbles studied for 210 min during continued oxygen breathing (FIO2 = 1). Rats were administered PFC, NO, or combined PFC and NO. In all groups, most bubbles grew transiently, followed by a stabilization phase. There were no differences in the overall bubble growth or decay between groups or when compared with previous data during oxygen breathing alone at 25 kPa. During extreme altitude exposures, the contribution of metabolic gases to bubble growth compromises the therapeutic effects of PFC and NO, but PFC and NO do not induce additional bubble growth.

Gas Bubble Pinch-off in Viscous and Inviscid Liquids

NASA Astrophysics Data System (ADS)

Taborek, P.

2005-11-01

We have used high-speed video to analyze pinch-off of nitrogen gas bubbles in fluids with a wide range of viscosity. If the external fluid is highly viscous (ηext>100 cP), the radius is proportional to the time before break, τ, and decreases smoothly to zero. If the external fluid has low viscosity (ηext<10 cP), the neck radius scales as &1/2circ; until an instability develops in the gas bubble which causes the neck to rupture and tear apart. Finally, if the viscosity of the external fluid is in an intermediate range, an elongated thread is formed which breaks apart into micron-sized bubbles. 100,000 frame-per-second videos will be presented which illustrate each of these flow regimes.

Vaporization and atomization of uranium in a graphite tube electrothermal vaporizer: a mechanistic study using electrothermal vaporization inductively coupled plasma mass spectrometry and graphite furnace atomic absorption spectrometry

NASA Astrophysics Data System (ADS)

Goltz, D. M.; Grégoire, D. C.; Byrne, J. P.; Chakrabarti, C. L.

1995-07-01

The mechanism of vaporization and atomization of U in a graphite tube electrothermal vaporizer was studied using graphite furnace atomic absorption spectrometry (GFAAS) and electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS). Graphite furnace AAS studies indicate U atoms are formed at temperatures above 2400°C. Using ETV-ICP-MS, an appearance temperature of 1100°C was obtained indicating that some U vaporizes as U oxide. Although U carbides form at temperatures above 2000°C, ETV-ICP-MS studies show that they do not vaporize until 2600°C. In the temperature range between 2200°C and 2600°C, U atoms in GFAAS are likely formed by thermal dissociation of U oxide, whereas at higher temperatures, U atoms are formed via thermal dissociation of U carbide. The origin of U signal suppression in ETV-ICP-MS by NaCl was also investigated. At temperatures above 2000°C, signal suppression may be caused by the accelerated rate of formation of carbide species while at temperatures below 2000°C, the presence of NaCl may cause intercalation of the U in the graphite layers resulting in partial retention of U during the vaporization step. The use of 0.3% freon-23 (CHF 3) mixed with the argon carrier gas was effective in preventing the intercalation of U in graphite and U carbide formation at 2700°C.

High-speed off-axis holographic cinematography with a copper-vapor-pumped dye laser.

PubMed

Lauterborn, W; Judt, A; Schmitz, E

1993-01-01

A series of coherent light pulses is generated by pumping a dye laser with the pulsed output of a copper-vapor laser at rates of as much as 20 kHz. Holograms are recorded at this pulse rate on a rotating holographic plate. This technique of high-speed holographic cinematography is demonstrated by viewing the bubble filaments that appear in water under the action of a sound field of high intensity.

Variable-gravity anti-vortex and vapor-ingestion-suppression device

NASA Technical Reports Server (NTRS)

Grayson, Gary D. (Inventor)

2003-01-01

A liquid propellant management device for placement in a liquid storage tank adjacent an outlet of the storage tank to substantially reduce or eliminate the formation of a dip and vortex in the liquid of the tank, as well as prevent vapor ingestion into the outlet, as the liquid drains out through the outlet. The liquid propellant management device has a first member adapted to suppress the formation of a vortex of a liquid exiting the storage tank. A plate is affixed generally perpendicular to the first member, wherein the plate is adapted to suppress vapor ingestion into the outlet by reducing a dip in a surface level of the liquid leaving the tank. A second member is affixed to the second side of the plate. The second member ensures that the plate is wet with liquid and assists in positioning bubbles away from the outlet.

STABILITY OF AQUEOUS FILMS BETWEEN BUBBLES

PubMed Central

Ohnishi, Satomi; Vogler, Erwin A.; Horn, Roger G.

2010-01-01

Film thinning experiments have been conducted with aqueous films between two air phases in a thin film pressure balance. The films are free of added surfactant but simple NaCl electrolyte is added in some experiments. Initially the experiments begin with a comparatively large volume of water in a cylindrical capillary tube a few mm in diameter, and by withdrawing water from the center of the tube the two bounding menisci are drawn together at a prescribed rate. This models two air bubbles approaching at a controlled speed. In pure water the results show three regimes of behavior depending on the approach speed: at slow speed (<1 µm/s) it is possible to form a flat film of pure water, ~100 nm thick, that is stabilised indefinitely by disjoining pressure due to repulsive double-layer interactions between naturally-charged air/water interfaces. The data are consistent with a surface potential of −57 mV on the bubble surfaces. At intermediate approach speed (~1 – 150 µm/s) the films are transiently stable due to hydrodynamic drainage effects, and bubble coalescence is delayed by ~10 – 100 s. At approach speeds greater than ~150 µm/s the hydrodynamic resistance appears to become negligible, and the bubbles coalesce without any measurable delay. Explanations for these observations are presented that take into account DLVO and Marangoni effects entering through disjoining pressure, surface mobility and hydrodynamic flow regimes in thin film drainage. In particular, it is argued that the dramatic reduction in hydrodynamic resistance is a transition from viscosity-controlled drainage to inertia-controlled drainage associated with a change from immobile to mobile air/water interfaces on increasing the speed of approach of two bubbles. A simple model is developed that accounts for the boundaries between different film stability or coalescence regimes. Predictions of the model are consistent with the data, and the effects of adding electrolyte can be explained. In

Aspherical bubble dynamics and oscillation times

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

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 sightlymore » 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.« less

Effect of polymer additives on hydrodynamics and oxygen transfer in a bubble column bioreactor.

PubMed

Kawase, Y

1993-01-01

The influence of polymer additives (polyethylene oxide and polyacrylamide) on the hydrodynamics and oxygen transfer in a bubble column bioreactor was examined. The addition of small amounts of these polymers has been known to cause significant drag reduction in turbulent flow circumstances. The gas hold-up was slightly decreased and the liquid-phase mixing was somewhat enhanced due to the addition of the polymers. The addition of polymer additives brought about a reduction of the volumetric oxygen transfer coefficient by about 40%. In dilute polymer solutions, large bubbles formed by bubble coalescence moved with high rise velocities in the presence of many small bubbles and the bubble size distributions were less uniform compared with those in water. The complicated changes in bubble hydrodynamic characteristics were examined to give possible explanations for oxygen transfer reduction.

Laboratory Experiments on Propagating Plasma Bubbles into Vacuum, Vacuum Magnetic Field, and Background Plasmas

NASA Astrophysics Data System (ADS)

Lynn, Alan G.; Zhang, Yue; Gilmore, Mark; Hsu, Scott

2014-10-01

We discuss the dynamics of plasma ``bubbles'' as they propagate through a variety of background media. These bubbles are formed by a pulsed coaxial gun with an externally applied magnetic field. Bubble parameters are typically ne ~1020 m-3, Te ~ 5 - 10 eV, and Ti ~ 10 - 15 eV. The structure of the bubbles can range from unmagnetized jet-like structures to spheromak-like structures with complex magnetic flux surfaces. Some of the background media the bubbles interact with are vacuum, vacuum with magnetic field, and other magnetized plasmas. These bubbles exhibit different qualitative behavior depending on coaxial gun parameters such as gas species, gun current, and gun bias magnetic field. Their behavior also depends on the parameters of the background they propagate through. Multi-frame fast camera imaging and magnetic probe data are used to characterize the bubble evolution under various conditions.

Combustion of Biosolids in a Bubbling Fluidized Bed, Part 1: Main Ash-Forming Elements and Ash Distribution with a Focus on Phosphorus.

PubMed

Skoglund, Nils; Grimm, Alejandro; Ohman, Marcus; Boström, Dan

2014-02-20

This is the first in a series of three papers describing combustion of biosolids in a 5-kW bubbling fluidized bed, the ash chemistry, and possible application of the ash produced as a fertilizing agent. This part of the study aims to clarify whether the distribution of main ash forming elements from biosolids can be changed by modifying the fuel matrix, the crystalline compounds of which can be identified in the raw materials and what role the total composition may play for which compounds are formed during combustion. The biosolids were subjected to low-temperature ashing to investigate which crystalline compounds that were present in the raw materials. Combustion experiments of two different types of biosolids were conducted in a 5-kW benchscale bubbling fluidized bed at two different bed temperatures and with two different additives. The additives were chosen to investigate whether the addition of alkali (K 2 CO 3 ) and alkaline-earth metal (CaCO 3 ) would affect the speciation of phosphorus, so the molar ratios targeted in modified fuels were P:K = 1:1 and P:K:Ca = 1:1:1, respectively. After combustion the ash fractions were collected, the ash distribution was determined and the ash fractions were analyzed with regards to elemental composition (ICP-AES and SEM-EDS) and part of the bed ash was also analyzed qualitatively using XRD. There was no evidence of zeolites in the unmodified fuels, based on low-temperature ashing. During combustion, the biosolid pellets formed large bed ash particles, ash pellets, which contained most of the total ash content (54%-95% (w/w)). This ash fraction contained most of the phosphorus found in the ash and the only phosphate that was identified was a whitlockite, Ca 9 (K,Mg,Fe)(PO 4 ) 7 , for all fuels and fuel mixtures. With the addition of potassium, cristobalite (SiO 2 ) could no longer be identified via X-ray diffraction (XRD) in the bed ash particles and leucite (KAlSi 2 O 6 ) was formed. Most of the alkaline-earth metals

Combustion of Biosolids in a Bubbling Fluidized Bed, Part 1: Main Ash-Forming Elements and Ash Distribution with a Focus on Phosphorus

PubMed Central

2014-01-01

This is the first in a series of three papers describing combustion of biosolids in a 5-kW bubbling fluidized bed, the ash chemistry, and possible application of the ash produced as a fertilizing agent. This part of the study aims to clarify whether the distribution of main ash forming elements from biosolids can be changed by modifying the fuel matrix, the crystalline compounds of which can be identified in the raw materials and what role the total composition may play for which compounds are formed during combustion. The biosolids were subjected to low-temperature ashing to investigate which crystalline compounds that were present in the raw materials. Combustion experiments of two different types of biosolids were conducted in a 5-kW benchscale bubbling fluidized bed at two different bed temperatures and with two different additives. The additives were chosen to investigate whether the addition of alkali (K2CO3) and alkaline-earth metal (CaCO3) would affect the speciation of phosphorus, so the molar ratios targeted in modified fuels were P:K = 1:1 and P:K:Ca = 1:1:1, respectively. After combustion the ash fractions were collected, the ash distribution was determined and the ash fractions were analyzed with regards to elemental composition (ICP-AES and SEM-EDS) and part of the bed ash was also analyzed qualitatively using XRD. There was no evidence of zeolites in the unmodified fuels, based on low-temperature ashing. During combustion, the biosolid pellets formed large bed ash particles, ash pellets, which contained most of the total ash content (54%–95% (w/w)). This ash fraction contained most of the phosphorus found in the ash and the only phosphate that was identified was a whitlockite, Ca9(K,Mg,Fe)(PO4)7, for all fuels and fuel mixtures. With the addition of potassium, cristobalite (SiO2) could no longer be identified via X-ray diffraction (XRD) in the bed ash particles and leucite (KAlSi2O6) was formed. Most of the alkaline-earth metals calcium and

Late-Holocene climate evolution at the WAIS Divide site, West Antarctica: Bubble number-density estimates

USGS Publications Warehouse

Fegyveresi, John M.; Alley, R.B.; Spencer, M.K.; Fitzpatrick, J.J.; Steig, E.J.; White, J.W.C.; McConnell, J.R.; Taylor, K.C.

2011-01-01

A surface cooling of ???1.7??C occurred over the ???two millennia prior to ???1700 CE at the West Antarctic ice sheet (WAIS) Divide site, based on trends in observed bubble number-density of samples from the WDC06A ice core, and on an independently constructed accumulation-rate history using annual-layer dating corrected for density variations and thinning from ice flow. Density increase and grain growth in polar firn are both controlled by temperature and accumulation rate, and the integrated effects are recorded in the number-density of bubbles as the firn changes to ice. Numberdensity is conserved in bubbly ice following pore close-off, allowing reconstruction of either paleotemperature or paleo-accumulation rate if the other is known. A quantitative late-Holocene paleoclimate reconstruction is presented for West Antarctica using data obtained from the WAIS Divide WDC06A ice core and a steady-state bubble number-density model. The resultant temperature history agrees closely with independent reconstructions based on stable-isotopic ratios of ice. The ???1.7??C cooling trend observed is consistent with a decrease in Antarctic summer duration from changing orbital obliquity, although it remains possible that elevation change at the site contributed part of the signal. Accumulation rate and temperature dropped together, broadly consistent with control by saturation vapor pressure.

Multifocal laser surgery: cutting enhancement by hydrodynamic interactions between cavitation bubbles.

PubMed

Toytman, I; Silbergleit, A; Simanovski, D; Palanker, D

2010-10-01

Transparent biological tissues can be precisely dissected with ultrafast lasers using optical breakdown in the tight focal zone. Typically, tissues are cut by sequential application of pulses, each of which produces a single cavitation bubble. We investigate the hydrodynamic interactions between simultaneous cavitation bubbles originating from multiple laser foci. Simultaneous expansion and collapse of cavitation bubbles can enhance the cutting efficiency, by increasing the resulting deformations in tissue, and the associated rupture zone. An analytical model of the flow induced by the bubbles is presented and experimentally verified. The threshold strain of the material rupture is measured in a model tissue. Using the computational model and the experimental value of the threshold strain one can compute the shape of the rupture zone in tissue resulting from application of multiple bubbles. With the threshold strain of 0.7 two simultaneous bubbles produce a continuous cut when applied at the distance 1.35 times greater than that required in sequential approach. Simultaneous focusing of the laser in multiple spots along the line of intended cut can extend this ratio to 1.7. Counterpropagating jets forming during collapse of two bubbles in materials with low viscosity can further extend the cutting zone-up to approximately a factor of 1.5.

Hubble Sees a Star ‘Inflating’ a Giant Bubble

NASA Image and Video Library

2017-12-08

For the 26th birthday of NASA’s Hubble Space Telescope, astronomers are highlighting a Hubble image of an enormous bubble being blown into space by a super-hot, massive star. The Hubble image of the Bubble Nebula, or NGC 7635, was chosen to mark the 26th anniversary of the launch of Hubble into Earth orbit by the STS-31 space shuttle crew on April 24, 1990 “As Hubble makes its 26th revolution around our home star, the sun, we celebrate the event with a spectacular image of a dynamic and exciting interaction of a young star with its environment. The view of the Bubble Nebula, crafted from WFC-3 images, reminds us that Hubble gives us a front row seat to the awe inspiring universe we live in,” said John Grunsfeld, Hubble astronaut and associate administrator of NASA’s Science Mission Directorate at NASA Headquarters, in Washington, D.C. The Bubble Nebula is seven light-years across—about one-and-a-half times the distance from our sun to its nearest stellar neighbor, Alpha Centauri, and resides 7,100 light-years from Earth in the constellation Cassiopeia. The seething star forming this nebula is 45 times more massive than our sun. Gas on the star gets so hot that it escapes away into space as a “stellar wind” moving at over four million miles per hour. This outflow sweeps up the cold, interstellar gas in front of it, forming the outer edge of the bubble much like a snowplow piles up snow in front of it as it moves forward. As the surface of the bubble's shell expands outward, it slams into dense regions of cold gas on one side of the bubble. This asymmetry makes the star appear dramatically off-center from the bubble, with its location in the 10 o’clock position in the Hubble view. Dense pillars of cool hydrogen gas laced with dust appear at the upper left of the picture, and more “fingers” can be seen nearly face-on, behind the translucent bubble. The gases heated to varying temperatures emit different colors: oxygen is hot enough to emit blue

A model for acoustic vaporization dynamics of a bubble/droplet system encapsulated within a hyperelastic shell.

PubMed

Lacour, Thomas; Guédra, Matthieu; Valier-Brasier, Tony; Coulouvrat, François

2018-01-01

Nanodroplets have great, promising medical applications such as contrast imaging, embolotherapy, or targeted drug delivery. Their functions can be mechanically activated by means of focused ultrasound inducing a phase change of the inner liquid known as the acoustic droplet vaporization (ADV) process. In this context, a four-phases (vapor + liquid + shell + surrounding environment) model of ADV is proposed. Attention is especially devoted to the mechanical properties of the encapsulating shell, incorporating the well-known strain-softening behavior of Mooney-Rivlin material adapted to very large deformations of soft, nearly incompressible materials. Various responses to ultrasound excitation are illustrated, depending on linear and nonlinear mechanical shell properties and acoustical excitation parameters. Different classes of ADV outcomes are exhibited, and a relevant threshold ensuring complete vaporization of the inner liquid layer is defined. The dependence of this threshold with acoustical, geometrical, and mechanical parameters is also provided.

Bubble migration inside a liquid drop in a space laboratory

NASA Technical Reports Server (NTRS)

Annamalai, P.; Shankar, N.; Cole, R.; Subramanian, R. S.

1982-01-01

The design of experiments in materials processing for trials on board the Shuttle are described. Thermocapillary flows will be examined as an aid to mixing in the formation of glasses. Acoustically levitated molten glass spheres will be spot heated to induce surface flow away from the hot spot to induce mixing. The surface flows are also expected to cause internal convective motion which will drive entrained gas bubbles toward the hot spot, a process also enhanced by the presence of thermal gradients. The method is called fining, and will be augmented by rotation of the sphere to cause bubble migration toward the axes of rotation to form one large bubble which is more easily removed. Centering techniques to fix the maximum centering accuracy will also be tried. Ground-based studies of bubble migration in a rotating liquid and in a temperature gradient in a liquid drop are reviewed.

Stationary bubble formation and cavity collapse in wedge-shaped hoppers

PubMed Central

Yagisawa, Yui; Then, Hui Zee; Okumura, Ko

2016-01-01

The hourglass is one of the apparatuses familiar to everyone, but reveals intriguing behaviors peculiar to granular materials, and many issues are remained to be explored. In this study, we examined the dynamics of falling sand in a special form of hourglass, i.e., a wedge-shaped hopper, when a suspended granular layer is stabilized to a certain degree. As a result, we found remarkably different dynamic regimes of bubbling and cavity. In the bubbling regime, bubbles of nearly equal size are created in the sand at a regular time interval. In the cavity regime, a cavity grows as sand beads fall before a sudden collapse of the cavity. Bubbling found here is quite visible to a level never discussed in the physics literature and the cavity regime is a novel phase, which is neither continuous, intermittent nor completely blocked phase. We elucidate the physical conditions necessary for the bubbling and cavity regimes and develop simple theories for the regimes to successfully explain the observed phenomena by considering the stability of a suspended granular layer and clogging of granular flow at the outlet of the hopper. The bubbling and cavity regimes could be useful for mixing a fluid with granular materials. PMID:27138747

Fermi Bubble: Giant Gamma-Ray Bubbles in the Milky Way

NASA Astrophysics Data System (ADS)

Su, Meng

Data from the Fermi-LAT reveal two gigantic gamma-ray emitting bubble structures (known as the Fermibubbles), extending˜50° above and below the Galactic center symmetric about the Galactic plane, with a width of˜40∘ in longitude. The gamma-ray emission associated with these bubbles has a significantly harder spectrum ({dN}/{dE} ˜ {E}^{-2}) than the inverse Compton emission from known cosmic ray electrons in the Galactic disk, or the gamma-rays produced by decay of pions from proton-ISM collisions. The bubbles are spatially correlated with the hard-spectrum microwave excess known as the WMAPhaze; the edges of the bubbles also line up with features in the ROSATsoft X-ray maps at 1.5-2keV. The Fermibubble is most likely created by some large episode of energy injection in the Galactic center, such as past accretion events onto the central massive black hole, or a nuclear starburst in the last˜10Myr. Study of the origin and evolution of the bubbles also has the potential to improve our understanding of recent energetic events in the inner Galaxy and the high-latitude cosmic ray population.

Bubble measuring instrument and method

NASA Technical Reports Server (NTRS)

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

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.

Growth and detachment of single hydrogen bubbles in a magnetohydrodynamic shear flow

NASA Astrophysics Data System (ADS)

Baczyzmalski, Dominik; Karnbach, Franziska; Mutschke, Gerd; Yang, Xuegeng; Eckert, Kerstin; Uhlemann, Margitta; Cierpka, Christian

2017-09-01

This study investigates the effect of a magnetohydrodynamic (MHD) shear flow on the growth and detachment of single sub-millimeter-sized hydrogen gas bubbles. These bubbles were electrolytically generated at a horizontal Pt microelectrode (100 μ m in diameter) in an acidic environment (1 M H2SO4 ). The inherent electric field was superimposed by a homogeneous electrode-parallel magnetic field of up to 700 mT to generate Lorentz forces in the electrolyte, which drive the MHD flow. The growth and motion of the hydrogen bubble was analyzed by microscopic high-speed imaging and measurements of the electric current, while particle tracking velocimetry (μ PTV ) and particle image velocimetry (μ PIV ) were applied to measure the surrounding electrolyte flow. In addition, numerical flow simulations were performed based on the experimental conditions. The results show a significant reduction of the bubble growth time and detachment diameter with increasing magnetic induction, which is known to improve the efficiency of water electrolysis. In order to gain further insight into the bubble detachment mechanism, an analysis of the forces acting on the bubble was performed. The strong MHD-induced drag force causes the bubble to slowly slide away from the center of the microelectrode before its detachment. This motion increases the active electrode area and enhances the bubble growth rate. The results further indicate that at large current densities the coalescence of tiny bubbles formed at the foot of the main bubble might play an important role for the bubble detachment. Moreover, the occurrence of Marangoni stresses at the gas-liquid interface is discussed.

Guest investigator program study: Physics of equatorial plasma bubbles

NASA Technical Reports Server (NTRS)

Tsunoda, Roland T.

1994-01-01

Plasma bubbles are large-scale (10 to 100 km) depletions in plasma density found in the night-time equatorial ionosphere. Their formation has been found to entail the upward transport of plasma over hundreds of kilometers in altitude, suggesting that bubbles play significant roles in the physics of many of the diverse and unique features found in the low-latitude ionosphere. In the simplest scenario, plasma bubbles appear first as perturbations in the bottomside F layer, which is linearly unstable to the gravitationally driven Rayleigh-Taylor instability. Once initiated, bubbles develop upward through the peak of the F layer into its topside (sometimes to altitudes in excess of 1000 km), a behavior predicted by the nonlinear form of the same instability. While good general agreement has been found between theory and observations, little is known about the detailed physics associated with plasma bubbles. Our research activity centered around two topics: the shape of plasma bubbles and associated electric fields, and the day-to-day variability in the occurrence of plasma bubbles. The first topic was pursued because of a divergence in view regarding the nonlinear physics associated with plasma bubble development. While the development of perturbations in isodensity contours in the bottomside F layer into plasma bubbles is well accepted, some believed bubbles to be cylinder-like closed regions of depleted plasma density that floated upward leaving a turbulent wake behind them (e.g., Woodman and LaHoz, 1976; Ott, 1978; Kelley and Ott, 1978). Our results, summarized in a paper submitted to the Journal of Geophysical Research, consisted of incoherent scatter radar measurements that showed unambiguously that the depleted region is wedgelike and not cylinderlike, and a case study and modeling of SM-D electric field instrument (EFI) measurements that showed that the absence of electric-field perturbations outside the plasma-depleted region is a distinct signature of wedge

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

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

BLOWING COSMIC BUBBLES

NASA Technical Reports Server (NTRS)

2002-01-01

This NASA Hubble Space Telescope image reveals an expanding shell of glowing gas surrounding a hot, massive star in our Milky Way Galaxy. This shell is being shaped by strong stellar winds of material and radiation produced by the bright star at the left, which is 10 to 20 times more massive than our Sun. These fierce winds are sculpting the surrounding material - composed of gas and dust - into the curve-shaped bubble. Astronomers have dubbed it the Bubble Nebula (NGC 7635). The nebula is 10 light-years across, more than twice the distance from Earth to the nearest star. Only part of the bubble is visible in this image. The glowing gas in the lower right-hand corner is a dense region of material that is getting blasted by radiation from the Bubble Nebula's massive star. The radiation is eating into the gas, creating finger-like features. This interaction also heats up the gas, causing it to glow. Scientists study the Bubble Nebula to understand how hot stars interact with the surrounding material. Credit: Hubble Heritage Team (AURA/STScI/NASA)

Remobilizing the Interfaces of Thermocapillary Driven Bubbles Retarded by the Adsorption of a Surfactant Impurity on the Bubble Surface

NASA Technical Reports Server (NTRS)

Palaparthi, Ravi; Maldarelli, Charles; Papageorgiou, Dimitri; Singh, Bhim S. (Technical Monitor)

2000-01-01

concentrations than the impurity, it adsorbs to the bubble much faster than the impurity when the bubble is formed, and thereby prevents the impurity from adsorbing onto the surface. In addition the rapid kinetic exchange and high bulk concentration maintain a saturated surface with a uniform surface concentrations. This prevents retarding surface tension gradients and keeps the velocity high. In our first report last year, we detailed experimental results which verified the theory of remobilization in ground based experiments in which the steady velocity of rising bubbles was measured in a continuous phase consisting of a glycerol/water mixture containing a polyethylene glycol surfactant C12E6 (CH3(CH2)11(OCH2CH2)6OH). In our report this year, we detail our efforts to describe theoretically the remobilization observed. We construct a model in which a bubble rises steadily by buoyancy in a continuous (Newtonian) viscous fluid containing surfactant with a uniform far field bulk concentration. We account for the effects of inertia as well as viscosity in the flow in the continuous phase caused by the bubble motion (order one Reynolds number), and we assume that the bubble shape remains spherical (viscous and inertial forces are smaller than capillary forces, i e. small Weber and capillary numbers). The surfactant distribution is calculated by solving the mass transfer equations including convection and diffusion in the bulk, and finite kinetic exchange the bulk and the surface. Convective effects dominate diffusive mass transfer in the bulk of the liquid (high Peclet numbers) except in a thin boundary layer near the surface. A finite volume method is used to numerically solve the hydrodynamic and mass transfer equations on a staggered grid which accounts specifically for the thin boundary layer. We present the results of the nondimensional drag as a function of the bulk concentration of surfactant for different rates of kinetic exchange, from which we develop criteria for the

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

NASA Technical Reports Server (NTRS)

Azuma, H.

1993-01-01

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

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.

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.

Vapor purification with self-cleaning filter

DOEpatents

Josephson, Gary B.; Heath, William O.; Aardahl, Christopher L.

2003-12-09

A vapor filtration device including a first electrode, a second electrode, and a filter between the first and second electrodes is disclosed. The filter is formed of dielectric material and the device is operated by applying a first electric potential between the electrodes to polarize the dielectric material such that upon passing a vapor stream through the filter, particles from the vapor stream are deposited onto the filter. After depositing the particles a second higher voltage is applied between the electrodes to form a nonthermal plasma around the filter to vaporize the collected particles thereby cleaning the filter. The filter can be a packed bed or serpentine filter mat, and an optional upstream corona wire can be utilized to charge airborne particles prior to their deposition on the filter.

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

PubMed

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

2016-07-01

Knowledge of the kinetics of gas bubble formation and evolution under cavitation conditions in molten alloys is important for the control casting defects such as porosity and dissolved hydrogen. Using in situ synchrotron X-ray radiography, we studied the dynamic behaviour of ultrasonic cavitation gas bubbles in a molten Al-10 wt%Cu alloy. The size distribution, average radius and growth rate of cavitation gas bubbles were quantified under an acoustic intensity of 800 W/cm(2) and a maximum acoustic pressure of 4.5 MPa (45 atm). Bubbles exhibited a log-normal size distribution with an average radius of 15.3 ± 0.5 μm. Under applied sonication conditions the growth rate of bubble radius, R(t), followed a power law with a form of R(t)=αt(β), and α=0.0021 &β=0.89. The observed tendencies were discussed in relation to bubble growth mechanisms of Al alloy melts. Copyright © 2016 Elsevier B.V. All rights reserved.

Measurements in a separation bubble on an airfoil using laser velocimetry

NASA Technical Reports Server (NTRS)

Fitzgerald, Edward J.; Mueller, Thomas J.

1990-01-01

An experimental investigation was conducted to measure the reverse flow within the transitional separation bubble that forms on an airfoil at low Reynolds numbers. Measurements were used to determine the effect of the reverse flow on integrated boundary-layer parameters often used to model the bubble. Velocity profile data were obtained on an NACA 663-018 airfoil at angle of attack of 12 deg and a chord Reynolds number of 140,000 using laser Doppler and single-sensor hot-wire anemometry. A new correlation is proposed based on zero velocity position, since the Schmidt (1986) correlations fail in the turbulent portion of the bubble.

Bubble statistics in aged wet foams and the Fokker-Planck equation

NASA Astrophysics Data System (ADS)

Zimnyakov, D. A.; Yuvchenko, S. A.; Tzyipin, D. V.; Samorodina, T. V.

2018-04-01

Results of the experimental study of changes in the bubble size statistics during aging of wet foams are discussed. It is proposed that the evolution of the bubble radii distributions can be described in terms of the one dimensional Fokker- Planck equation. The empirical distributions of the bubble radii exhibit a self-similarity of their shapes and can be transformed to a time-independent form using the radius renormalization. Analysis of obtained data allows us to suggest that the drift term of the Fokker-Planck equation dominates in comparison with the diffusion term in the case of aging of isolated quasi-stable wet foams.

Electron beam-induced radiation damage: the bubbling response in amorphous dried sodium phosphate buffer.

PubMed

Massover, William H

2010-06-01

Irradiation of an amorphous layer of dried sodium phosphate buffer (pH = 7.0) by transmission electron microscopy (100-120 kV) causes rapid formation of numerous small spherical bubbles [10-100 A (= 1-10 nm)] containing an unknown gas. Bubbling is detected even with the first low-dose exposure. In a thin layer (ca. 100-150 A), bubbling typically goes through nucleation, growth, possible fusion, and end-state, after which further changes are not apparent; co-irradiated adjacent areas having a slightly smaller thickness never develop bubbles. In moderately thicker regions (ca. over 200 A), there is no end-state. Instead, a complex sequence of microstructural changes is elicited during continued intermittent high-dose irradiation: nucleation, growth, early simple fusions, a second round of extensive multiple fusions, general reduction of matrix thickness (producing flattening and expansion of larger bubbles, occasional bubble fission, and formation of very large irregularly-shaped bubbles by a third round of compound fusion events), and slow shrinkage of all bubbles. The ongoing lighter appearance of bubble lumens, maintenance of their rounded shape, and extensive changes in size and form indicate that gas content continues throughout their surprisingly long lifetime; the thin dense boundary layer surrounding all bubbles is proposed to be the main mechanism for their long lifetime.

Poynting-Flux-Driven Bubbles and Shocks Around Merging Neutron Star Binaries

NASA Astrophysics Data System (ADS)

Medvedev, M. V.; Loeb, A.

2013-04-01

Merging binaries of compact relativistic objects are thought to be progenitors of short gamma-ray bursts. Because of the strong magnetic field of one or both binary members and high orbital frequencies, these binaries are strong sources of energy in the form of Poynting flux. The steady injection of energy by the binary forms a bubble filled with matter with the relativistic equation of state, which pushes on the surrounding plasma and can drive a shock wave in it. Unlike the Sedov-von Neumann-Taylor blast wave solution for a point-like explosion, the shock wave here is continuously driven by the ever-increasing pressure inside the bubble. We calculate from the first principles the dynamics and evolution of the bubble and the shock surrounding it, demonstrate that it exhibits finite time singularity and find the corresponding analytical solution. We predict that such binaries can be observed as radio sources a few hours before and after the merger.

In situ observation of single cell response to acoustic droplet vaporization: Membrane deformation, permeabilization, and blebbing.

PubMed

Qin, Dui; Zhang, Lei; Chang, Nan; Ni, Pengying; Zong, Yujin; Bouakaz, Ayache; Wan, Mingxi; Feng, Yi

2018-02-06

In this study, the bioeffects of acoustic droplet vaporization (ADV) on adjacent cells were investigated by evaluating the real-time cell response at the single-cell level in situ, using a combined ultrasound-exposure and optical imaging system. Two imaging modalities, high-speed and fluorescence imaging, were used to observe ADV bubble dynamics and to evaluate the impact on cell membrane permeabilization (i.e., sonoporation) using propidium iodide (PI) uptake as an indicator. The results indicated that ADV mainly led to irreversible rather than reversible sonoporation. Further, the rate of irreversible sonoporation significantly increased with increasing nanodroplet concentration, ultrasound amplitude, and pulse duration. The results suggested that sonoporation is correlated to the rapid formation, expansion, and contraction of ADV bubbles near cells, and strongly depends on ADV bubble size and bubble-to-cell distance when subjected to short ultrasound pulses (1 μs). Moreover, the displacement of ADV bubbles was larger when using a long ultrasound pulse (20 μs), resulting in considerable cell membrane deformation and a more irreversible sonoporation rate. During sonoporation, cell membrane blebbing as a recovery manoeuvre was also investigated, indicating the essential role of Ca 2+ influx in the membrane blebbing response. This study has helped us gain further insights into the dynamic behavior of ADV bubbles near cells, ADV bubble-cell interactions, and real-time cell response, which are invaluable in the development of optimal approaches for ADV-associated theranostic applications. Copyright © 2018 Elsevier B.V. All rights reserved.

Method of varying a characteristic of an optical vertical cavity structure formed by metalorganic vapor phase epitaxy

DOEpatents

Hou, Hong Q.; Coltrin, Michael E.; Choquette, Kent D.

2001-01-01

A process for forming an array of vertical cavity optical resonant structures wherein the structures in the array have different detection or emission wavelengths. The process uses selective area growth (SAG) in conjunction with annular masks of differing dimensions to control the thickness and chemical composition of the materials in the optical cavities in conjunction with a metalorganic vapor phase epitaxy (MOVPE) process to build these arrays.

Neutron imaging with bubble chambers for inertial confinement fusion

NASA Astrophysics Data System (ADS)

Ghilea, Marian C.

One of the main methods to obtain energy from controlled thermonuclear fusion is inertial confinement fusion (ICF), a process where nuclear fusion reactions are initiated by heating and compressing a fuel target, typically in the form of a pellet that contains deuterium and tritium, relying on the inertia of the fuel mass to provide confinement. In inertial confinement fusion experiments, it is important to distinguish failure mechanisms of the imploding capsule and unambiguously diagnose compression and hot spot formation in the fuel. Neutron imaging provides such a technique and bubble chambers are capable of generating higher resolution images than other types of neutron detectors. This thesis explores the use of a liquid bubble chamber to record high yield 14.1 MeV neutrons resulting from deuterium-tritium fusion reactions on ICF experiments. A design tool to deconvolve and reconstruct penumbral and pinhole neutron images was created, using an original ray tracing concept to simulate the neutron images. The design tool proved that misalignment and aperture fabrication errors can significantly decrease the resolution of the reconstructed neutron image. A theoretical model to describe the mechanism of bubble formation was developed. A bubble chamber for neutron imaging with Freon 115 as active medium was designed and implemented for the OMEGA laser system. High neutron yields resulting from deuterium-tritium capsule implosions were recorded. The bubble density was too low for neutron imaging on OMEGA but agreed with the model of bubble formation. The research done in here shows that bubble detectors are a promising technology for the higher neutron yields expected at National Ignition Facility (NIF).

Bubble dynamics in a compressible liquid in contact with a rigid boundary

PubMed Central

Wang, Qianxi; Liu, Wenke; Zhang, A. M.; Sui, Yi

2015-01-01

A bubble initiated near a rigid boundary may be almost in contact with the boundary because of its expansion and migration to the boundary, where a thin layer of water forms between the bubble and the boundary thereafter. This phenomenon is modelled using the weakly compressible theory coupled with the boundary integral method. The wall effects are modelled using the imaging method. The numerical instabilities caused by the near contact of the bubble surface with the boundary are handled by removing a thin layer of water between them and joining the bubble surface with its image to the boundary. Our computations correlate well with experiments for both the first and second cycles of oscillation. The time history of the energy of a bubble system follows a step function, reducing rapidly and significantly because of emission of shock waves at inception of a bubble and at the end of collapse but remaining approximately constant for the rest of the time. The bubble starts being in near contact with the boundary during the first cycle of oscillation when the dimensionless stand-off distance γ = s/Rm < 1, where s is the distance of the initial bubble centre from the boundary and Rm is the maximum bubble radius. This leads to (i) the direct impact of a high-speed liquid jet on the boundary once it penetrates through the bubble, (ii) the direct contact of the bubble at high temperature and high pressure with the boundary, and (iii) the direct impingement of shock waves on the boundary once emitted. These phenomena have clear potential to damage the boundary, which are believed to be part of the mechanisms of cavitation damage. PMID:26442148

Ultrasound-triggered drug delivery using acoustic droplet vaporization

NASA Astrophysics Data System (ADS)

Fabiilli, Mario Leonardo

The goal of targeted drug delivery is the spatial and temporal localization of a therapeutic agent and its associated bioeffects. One method of drug localization is acoustic droplet vaporization (ADV), whereby drug-laden perfluorocarbon (PFC) emulsions are vaporized into gas bubbles using ultrasound, thereby releasing drug locally. Transpulmonary droplets are converted into bubbles that occlude capillaries, sequestering the released drug within an organ or tumor. This research investigates the relationship between the ADV and inertial cavitation (IC) thresholds---relevant for drug delivery due to the bioffects generated by IC---and explores the delivery of lipophilic and hydrophilic compounds using PFC double emulsions. IC can positively and negatively affect ultrasound mediated drug delivery. The ADV and IC thresholds were determined for various bulk fluid, droplet, and acoustic parameters. At 3.5 MHz, the ADV threshold occurred at a lower rarefactional pressure than the IC threshold. The results suggest that ADV is a distinct phenomenon from IC, the ADV nucleus is internal to the droplet, and the IC nucleus is the bubble generated by ADV. The ADV triggered release of a lipophilic chemotherapeutic agent, chlorambucil (CHL), from a PFC-in-oil-in-water emulsion was explored using plated cells. Cells exposed to a CHL-loaded emulsion, without ADV, displayed 44% less growth inhibition than cells exposed to an equal concentration of CHL in solution. Upon ADV of the CHL-loaded emulsion, the growth inhibition increased to the same level as cells exposed to CHL in solution. A triblock copolymer was synthesized which enabled the formulation of stable water-in-PFC-in-water (W1/PFC/W2) emulsions. The encapsulation of fluorescein in the W1 phase significantly decreased the mass flux of fluorescein; ADV was shown to completely release the fluorescein from the emulsions. ADV was also shown to release thrombin, dissolved in the W1 phase, which could be used in vivo to extend

Bubble Generation in a Continuous Liquid Flow Under Reduced Gravity Conditions

NASA Technical Reports Server (NTRS)

Pais, Salvatore Cezar

1999-01-01

The present work reports a study of bubble generation under reduced gravity conditions for both co-flow and cross-flow configurations. Experiments were performed aboard the DC-9 Reduced Gravity Aircraft at NASA Glenn Research Center, using an air-water system. Three different flow tube diameters were used: 1.27, 1.9, and 2.54 cm. Two different ratios of air injection nozzle to tube diameters were considered: 0.1 and 0.2. Gas and liquid volumetric flow rates were varied from 10 to 200 ml/s. It was experimentally observed that with increasing superficial liquid velocity, the bubbles generated decreased in size. The bubble diameter was shown to increase with increasing air injection nozzle diameters. As the tube diameter was increased, the size of the detached bubbles increased. Likewise, as the superficial liquid velocity was increased, the frequency of bubble formation increased and thus the time to detach forming bubbles decreased. Independent of the flow configuration (for either single nozzle or multiple nozzle gas injection), void fraction and hence flow regime transition can be controlled in a somewhat precise manner by solely varying the gas and liquid volumetric flow rates. On the other hand, it is observed that uniformity of bubble size can be controlled more accurately by using single nozzle gas injection than by using multiple port injection, since this latter system gives rise to unpredictable coalescence of adjacent bubbles. A theoretical model, based on an overall force balance, is employed to study single bubble generation in the dynamic and bubbly flow regime. Under conditions of reduced gravity, the gas momentum flux enhances bubble detachment; however, the surface tension forces at the nozzle tip inhibits bubble detachment. Liquid drag and inertia can act either as attaching or detaching force, depending on the relative velocity of the bubble with respect to the surrounding liquid. Predictions of the theoretical model compare well with performed

Geyser preplay and eruption in a laboratory model with a bubble trap

NASA Astrophysics Data System (ADS)

Adelstein, Esther; Tran, Aaron; Saez, Carolina Muñoz; Shteinberg, Alexander; Manga, Michael

2014-09-01

We present visual observations and temperature measurements from a laboratory model of a geyser. Our model incorporates a bubble trap, a zone in which vapor can accumulate in the geyser's subsurface plumbing, in a vertical conduit connected to a basal chamber. Analogous features have been identified at several natural geysers. We observe three types of eruptions: 1) rising bubbles eject a small volume of liquid in a weak spout (small eruption); 2) boiling occurs in the conduit above the bubble trap (medium eruption); and 3) boiling occurs in the conduit and chamber (large eruption). In the last two cases, boiling in the conduit causes a rapid hydrostatic pressure drop that allows for the rise and eruption of liquid water in a vigorous spout. Boiling initiates at depth rather than propagating downward from the surface. In a single eruption cycle, multiple small eruptions precede every medium and large eruption. At least one eruption cycle that culminates in a medium eruption (i.e., a quiescent period followed by a series of small eruptions leading up to a medium eruption) precedes every eruption cycle that culminates in a large eruption. We find that the transfer of fluid with high enthalpy to the upper conduit during small and medium eruptions is necessary to heat the upper conduit and prepare the system for the full boiling required for a large eruption. The placement of the bubble trap midway up the conduit allows for more efficient heating of the upper conduit. Our model provides insight into the influence of conduit geometry on eruption style and the importance of heat transfer by smaller events in preparing the geyser system for eruption.

Bubble propagation on a rail: a concept for sorting bubbles by size

NASA Astrophysics Data System (ADS)

Franco-Gómez, Andrés; Thompson, Alice B.; Hazel, Andrew L.; Juel, Anne

We demonstrate experimentally that the introduction of a rail, a small height constriction, within the cross-section of a rectangular channel could be used as a robust passive sorting device in two-phase fluid flows. Single air bubbles carried within silicone oil are generally transported on one side of the rail. However, for flow rates marginally larger than a critical value, a narrow band of bubble sizes can propagate (stably) over the rail, while bubbles of other sizes segregate to the side of the rail. The width of this band of bubble sizes increases with flow rate and the size of the most stable bubble can be tuned by varying the rail width. We present a complementary theoretical analysis based on a depth-averaged theory, which is in qualitative agreement with the experiments. The theoretical study reveals that the mechanism relies on a non-trivial interaction between capillary and viscous forces that is fully dynamic, rather than being a simple modification of capillary static solutions.